Pathology Colloquium 1 Slides 2022/2023 PDF

Riga Stradins University Department of Pathology 2022 / 2023 Cell Injury and Cell Death Prof. Ilze Strumfa Cellular responses to the injury ◼ All organ injuries and thus all clinical diseases arise from derangements in cell structure and function Rudolf Ludwig Carl Virchow (1821 – 1902) Cellular res...

Riga Stradins University Department of Pathology 2022 / 2023 Cell Injury and Cell Death Prof. Ilze Strumfa Cellular responses to the injury ◼ All organ injuries and thus all clinical diseases arise from derangements in cell structure and function Rudolf Ludwig Carl Virchow (1821 – 1902) Cellular responses to injury Cellular adaptations  Hyperplasia  Hypertrophy  Atrophy  Metaplasia Cell injury: reversible vs. irreversible Intracellular accumulations Calcifications Cellular aging Cellular responses to injury Cellular adaptations  Hyperplasia  Hypertrophy  Atrophy  Metaplasia Cell injury: reversible vs. irreversible Intracellular accumulations Calcifications Cellular aging Cellular responses by nature and severity of injurious stimulus (I) Stimulus Altered physiologic stimuli Increased demand, increased stimulation Decreased demand, lack of nutrients etc. Prolonged physical or chemical irritation Cellular response Cellular adaptation Hyperplasia, hypertrophy Atrophy Metaplasia Cellular responses by nature and severity of injurious stimulus (II) Stimulus Cellular response Pathologic stimuli Cell injury / damage Acute, self-limited Acute reversible cell injury Irreversible cell injury (cell death) Subcellular alterations in the organelles Progressive and severe Mild, but chronic Cellular responses by nature and severity of injurious stimulus (III) Stimulus Inherited or acquired metabolic alterations; chronic injury Cumulative sublethal injury Cellular response Intracellular accumulations (e.g., proteins, lipids, carbohydrates) ◼ Calcification Cellular aging ◼ Cellular responses by nature and severity of injurious stimulus (I) Stimulus Altered physiologic stimuli Increased demand, increased stimulation Decreased demand, lack of nutrients etc. Prolonged physical or chemical irritation Cellular response Cellular adaptation Hyperplasia, hypertrophy Atrophy Metaplasia Cell injury Reversible: ◼ Reduced oxidative phosphorylation; ◼ Cellular swelling. Irreversible = cell death ◼ necrosis ◼ apoptosis The causes of cell injury Ischemia ◼ Hypoxia ◼ Physical damage ◼ Chemicals ◼ Infections ◼ Immune reactions ◼ Disturbances of metabolism ◼ Mechanisms of cell injury Depletion of ATP ◼ Mitochondrial damage ◼ Influx of Ca2+ and loss of calcium homeostasis ◼ Oxidative stress ◼ Defects in membrane permeability ◼ DNA damage ◼ Protein damage ◼ Reversible cell injury: ultrastructural changes ◼ Plasma membrane alterations: blebbing, elongation etc.; ◼ Mitochondrial changes: swelling, appearance of small amorphous densities; ◼ Dilation of the endoplasmic reticulum with detachment of polysomes; ◼ Nuclear alterations: changes of chromatin structure Morphology of reversible cell injury under light microscope Two patterns of reversible cell injury are recognizable under light microscope:  cellular swelling,  fatty change. Irreversible cell injury Necrosis ◼ Cell death in living tissue in the setting of irreversible exogenous injury Apoptosis ◼ Programmed cell death The morphologic characteristics of necrosis Increased cytoplasmic eosinophilia ◼ Nuclear changes: ◼ – decreased basophilia of nucleus due to DNA destruction; Pyknosis – nuclear shrinkage and increased basophilia. Visually similar to apoptosis; Karyorrhexis – fragmentation of pyknotic nucleus Nucleus in a necrotic cell disappears in 1 – 2 days Karyolysis Kidney necrosis Photo: I.Strumfa, l.Feldmane Myocardial infarction: necrosis in the myocardium Photo: I.Strumfa, L.Feldmane Types of necrosis Coagulative necrosis ◼ Liquefactive necrosis ◼ Gangrene ◼ Caseous necrosis ◼ Fat necrosis ◼ Fibrinoid necrosis ◼ Coagulative necrosis The affected tissues are firm ◼ The outlines of the affected cells are preserved for some days ◼ Mechanism involves the inactivation of proteolytic enzymes ◼ Example: myocardial infarction ◼ Liquefactive necrosis Characteristic, if necrosis develop in the setting of bacterial or fungal infections: microbes stimule the accumulation of leukocytes and thus – the proteolysis by leukocytic enzymes ◼ Typical for hypoxic necrosis of brain tissue ◼ The affected tissue is transformed into semi-liquid mass ◼ Gangrene ◼ Typical in limbs, but can occur in the intestines, lungs Can be ◼ Dry: coagulation necrosis ◼ Wet: liquefactive necrosis Dry gangrene: coagulation necrosis Photo: I.Strumfa Wet gangrene Photo: A.Vanags Photo: A.Vanags Caseous necrosis Particular type of coagulative necrosis ◼ Characteristic in the middle of tuberculous foci ◼ Caseous necrosis in lymph node Photo: I.Strumfa, L.Feldmane Fat necrosis ◼ ◼ ◼ Foci of fat necrosis usually occur in the setting of acute pancreatitis Fat destruction occurs due to pancreatic lipases that leak from inflamed pancreatic tissue into peripancreatic fat, abdominal cavity, omentum. The enzymes  split fat cell membranes;  lipases split triglycerid esters;  The released fatty acids bind Ca2+ ions, forming calcium soaps: saponification. Bright, chalky white foci are visible for surgeon during the operation, or for pathologist when examining operation material Fibrinoid necrosis Occurs in immune reactions ◼ Contains immune complexes + fibrin ◼ Brightly eosinophilic by light microscopy ◼ The outcomes of necrosis Destruction and reabsorption of the dead tissue (inflammation) ◼ Scar formation ◼ Dystrophic calcification if the necrotic cells are not destroyed ◼ The death of the whole organism ◼ Apoptosis Programmed cell death ◼ Intact plasma membrane ◼ Does not result in inflammation ◼ Can occur in ◼  Physiologic conditions;  Pathologic conditions. Apoptosis in physiologic situations Embriogenesis, including implantation, organogenesis, developmental involution, metamorphosis ◼ Involution of hormone-dependant tissues upon hormon withdrawal ◼ Cell loss in proliferating cell populations ◼ Elimination of potentially harmful selfreactive lymphocytes ◼ Death of “used” host cells as the function is fulfilled ◼ Apoptosis in pathologic situations ◼ Elimination of cells that are irreversibly injured so that repair is no longer possible. The biological “aim” is to get rid from these cellls without evoking host reaction that might cause damage of collateral tissues:  DNA damage  Accumulation of misfolded proteins  Certain infections  Pathologic atrophy The morphological manifestations of apoptosis Cell shrinkage ◼ Chromatin condensation ◼ Formation of cytoplasmic blebs and apoptotic bodies ◼ Phagocytosis of apoptotic cells, usually by macrophages ◼ Apoptosis ( ) in tumour cell Apoptosis in a hepatocyte (chronic viral hepatitis B) Apoptotic body (in viral hepatitis) Mechanisms of apoptosis Highly conserved during evolution, e.g., from nematode Caenorhabditis elegans to mammals ◼ Phases of apoptosis: ◼  Initiation phase by either ◼ intrinsic / mitochondrial pathway or; ◼ extrinsic death-receptor initiated pathway;  Execution phase. Biochemical manifestations of apoptosis ◼ Activation of caspase family:  “c-” for cystein protease  “-aspase” for cleaving after aspartic acid DNA and protein breakdown ◼ Membrane alteration facilitating the recognition by macrophages ◼ Subcellular responses to injury Caused by mild chronic pathologic stimuli May include: ◼ Lysosomal catabolism ◼ Hypertrophy of smooth endoplasmic reticulum ◼ Mitochondrial alterations ◼ Cytoskeletal abnormalities Intra- and extra-cellular accumulations Lipids ◼ Proteins ◼ Hialinosis s. hyalin change ◼ Glycogen ◼ Pigments ◼ ◼ Accumulations of different substances can be intracellular or extracellular The mechanism of the development of intracellular accumulations Production rate exceeds catabolism rate ◼ Disturbances of catabolism: ◼  Accumulation of abnormal endogenous substance that cannot be destroyed;  Normal endogenous substance cannot be destroyed due to defects in the responsible enzymes ◼ Accumulation of exogenous substance Steatosis: fatty change ◼ ◼ ◼ ◼ Abnormal accumulation of triglycerides within parenchymal cells Frequent in liver Occurs in myocardium, muscle, kidney Causes:  Toxic substances (ethanol)  Infections, e.g, chronic viral hepatitis C  Protein malnutrition  Diabetes mellitus  Adiposity  Hypoxia Liver steatosis Grossly ◼ No visible changes in mild steatosis ◼ Liver becomes increased, smooth and yellow, if steatosis is severe Microscopically ◼ Microvesicular steatosis ◼ Macrovesicular steatosis Liver steatosis Photo: I.Strumfa Macrovesicular steatosis Photo: I.Strumfa Microvesicular steatosis Accumulation of cholesterol and cholesterol esthers: examples Atherosclerosis ◼ Xanthoma ◼ Inflammation and necrosis: foamy macrophages ◼ Intracellular accumulation of proteins Reabsorption droplets in proximal renal tubules ◼ Russell bodies ◼ Defects in protein folding ◼ Amyloidosis in kidney Congo red stain Photo: I.Strumfa, L.Feldmane Amyloidosis in kidney tissue Hyaline change Photo: I.Strumfa, L.Feldmane Mallory hyaline in liver due to ethanol toxicity Glycogen accumulation Diabetes mellitus ◼ Glycogenoses ◼ Pigment accumulation ◼ Exogenous pigments  Anthracosis  Tatooing ◼ Endogenous pigments  Lipofuscin s. lipochrome s. wear-and-tear pigment  Melanin  Haemosiderin Lymph node anthracosis Photo: I.Strumfa, L.Feldmane Anthracosis Photo: I.Strumfa, L.Feldmane Anthracosis Photo: I.Strumfa, L.Feldmane Hemosiderosis Perls’ stain Photo: I.Strumfa, L.Feldmane Hemosiderin deposits in liver / hemochromatosis Perls’ stain Photo: I.Strumfa, L.Feldmane Cholestasis Photo: I.Strumfa, L.Feldmane Pathologic calcification ◼ Abnormal deposition of calcium salts in the tissue ◼ Types:  Dystrophic  Metastatic (not to be confused with metastatic malignancy!!!) Dystrophic calcification Local ◼ In abnormal tissues ◼  Necrotic foci  Atheroslerotic plaques  Calcific valvular heart disease ◼ The calcium level in blood is normal Dystrophic calcification in breast cancer Metastatic calcification Occur in normal tissues ◼ Hypercalcemia ◼  Increased parathyroid hormone (PTH) level  Bone destruction  Vitamin D related disorders  Renal failure Metastatic calcification Occurs in basic (pH) tissues ◼ Interstitium of gastric mucosa ◼ Kidney ◼ Lung ◼ Arteries of systemic circulation ◼ Pulmonary veins Cellular aging (I) ◼ Increasing age is related to physiologic and structural alterations in almost all organs and systems. The course of aging is affected by:  Genetic factors;  Diet;  Social factors;  Age-related diseases (atherosclerosis, Type 2 diabetes mellitus; osteoarthritis) ◼ Cellular aging is related to the aging of whole organism Decreased replication in relation to cellular aging ◼ Telomere length vs. number of cell divisions ◼ Telomerase activity is stable in germ cells and stabilized upon malignant conversion Cellular aging (II) ◼ Cellular aging results from:  Progressive decline in cellular function and viability;  Genetic abnormalities;  Accumulation of cellular and molecular damage due to sublethal exposure to exogenous factors. The aging is regulated genetically ◼ Manifestations of cellular aging: ◼  Decreased replication / telomere shortening;  Accumulation of metabolic and genetic damage / [O]. Experimental studies of life span prolongation Calorie restriction ◼ Sirtuins – protein family: ◼  Histone deacetylase activity  Regulate gene expression proteins Increase metabolic activity ◼ Reduce apoptosis ◼ Stimulate protein folding ◼ Inhibit [O] ◼ Increase insulin sensitivity, glucose metabolism ◼ Photo: I.Strumfa Recommended literature (optional) ◼ ◼ Robbins and Cotran Pathologic Basis of Disease, 8th ed. Ed. by Kumar V, Abbas AK, Fausto N, Aster JC. Saunders Elsevier, Philadelphia, 2010. Earlier (6-7) or later (9, 10) editions are suitable as well Rīga Stradiņš University Department of Pathology 2022 / 2023 Cellular Adaptation Reactions Prof. Ilze Strumfa Cellular responses to the injury ◼ All organ injuries and thus all clinical diseases arise from derangements in cell structure and function Rudolf Ludwig Carl Virchow (1821 – 1902) Cellular responses to injury Cellular adaptations  Hyperplasia  Hypertrophy  Atrophy  Metaplasia Cell injury: reversible vs. irreversible Intracellular accumulations Calcifications Cellular aging Cellular responses to injury Cellular adaptations  Hyperplasia  Hypertrophy  Atrophy  Metaplasia Cell injury: reversible vs. irreversible Intracellular accumulations Calcifications Cellular aging Cellular responses by nature and severity of injurious stimulus (I) Stimulus Altered physiologic stimuli Increased demand, increased stimulation Decreased demand, lack of nutrients etc. Prolonged physical or chemical irritation Cellular response Cellular adaptation Hyperplasia, hypertrophy Atrophy Metaplasia Cellular responses by nature and severity of injurious stimulus (II) Stimulus Cellular response Pathologic stimuli Cell injury / damage Acute, self-limited Acute reversible cell injury Irreversible cell injury (cell death) Subcellular alterations in the organelles Progressive and severe Mild, but chronic Cellular responses by nature and severity of injurious stimulus (III) Stimulus Inherited or acquired metabolic alterations; chronic injury Cumulative sublethal injury Cellular response Intracellular accumulations (e.g., proteins, lipids, carbohydrates) ◼ Calcification Cellular aging ◼ Cellular responses by nature and severity of injurious stimulus (I) Stimulus Altered physiologic stimuli Increased demand, increased stimulation Decreased demand, lack of nutrients etc. Prolonged physical or chemical irritation Cellular response Cellular adaptation Hyperplasia, hypertrophy Atrophy Metaplasia Cellular adaptation reactions: definitions ◼ Adaptation: reversible functional and structural response to more severe physiologic stresses and some pathologic stimuli resulting in new but altered steady state ◼ Hyperplasia – increase in the number of cells ◼ Hypertrophy – increase in the size of cells or organ ◼ Atrophy – decrease in size and metabolic activity ◼ Metaplasia – replacement of adult cells by another adult cell type ◼ ◼ Hyperplasia Physiologic  Hormone – induced: increased functional capacity of tissue for periodic requirements, e.g., breast;  Compensatory: increased tissue mass after damage or partial resection, e.g., liver after hemihepatectomy can regain the initial mass Pathologic  Induced by hormone dysbalance, e.g., estrogen and progesterone dysbalance can cause endometrial hyperplasia; androgen disbalance can cause prostatic hyperplasia.  Induced by virus, e.g., papilloma virus can cause warts. Endometrial hyperplasia Endometrium in proliferative phase Photo: I.Strumfa Endometrial hyperplasia Hypertrophy: the basics ◼ Enlargement of cells occurs leading to the increased size of organ; ◼ Synthesis of the structural components of the cell is demanded to ensure the greater mass; ◼ Mostly combined with hyperplasia, except for nondividing cells. Although the cardiac and skeletal muscle in adults is suggested to be non-dividing and respond by hypertrophy only, the concept is changing Hypertrophy: the causes ◼ Increased functional demands, e.g., muscle hypertrophy to ensure greater strength ◼ Stimulation by hormones or growth factors, e.g., hypertrophy of myometrium during pregnancy Hypertrophy: the mechanisms Increased production of cellular proteins is due to: ◼ Mechanical sensors are triggered by increased workload resulting in production of growth factors ◼ Growth factors: TGF-beta; IGF-1; ◼ Vasoactive substances: endothelin-1, angiotensin II. Hypertrophy ◼ Physiologic, e.g.:  Muscle upon training;  Myometrium during pregnancy. ◼ Pathologic, e.g.:  Heart muscle in arterial hypertension or valvular heart disease. Myocardial hypertrophy: a complex event Photo: I.Strumfa Hypertrophy in heart muscle: the intracellular pathogenetic events ◼ ◼ ◼ ◼ Mainly physiologic hypertrophy: phosphoinositide 3kinase / Akt pathway; Mainly pathologic hypertrophy: signaling downstream of G-protein coupled receptors; May be associated with switch of contractile proteins from adult to fetal and neonatal forms: alfa isoform of mysin heavy chain is replaced by beta, having slower and more ergonomical contraction; May be associated with re-expression of some genes: atrial natriuretic factor The outcome of (cardiac) hypertrophy Reversible if the cause can be eliminated; ◼ If the cause is persistent, hypertrophy results in regressive changes and heart failure ensures. ◼ ◼ NB! Adaptation to stress can progress to cell injury if the stress is not relieved. Atrophy Shrinkage of cell or organ ◼ Types: Physiologic Pathologic Photo: I.Strumfa Muscle atrophy Atrophy: the mechanisms (I) ◼ Atrophy is defined as reduced size of an organ or tissue due to decreased cell size and number ◼ The biological aim – to ensure the survival of cell in “difficult”, restricted conditions by reduced metabolic needs The mechanisms of atrophy (continued) ◼ Decreased cell size AND decreased number of organelles Decreased protein synthesis due to reduced metabolic activity ◼ Increased degradation: ◼  ubiquitin-proteasome  autophagy pathway; The mechanisms of atrophy (continued) ◼ Ubiquitin-proteasome pathway:  nutrient deficiency activate ubiquitin ligases;  proteins are marked by small peptin ubiquitin and therefore recognised for degradation in proteasomes; ◼ Autophagy (cell “eats” s. destroys its own components in order to obtain nutrients):  Autophagic vacuoles = membrane-bound vacuoles containing cell components;  Autophagic vacuoles fuse with lysosomes for digestion;  Digestion-resistant debris = membrane-bound residual bodies, e.g., brown lipofuscin related to so-called brown atrophy (atrophy associated with brown discoloration of tissue) The causes of atrophy ◼ ◼ ◼ ◼ ◼ ◼ ◼ Decreased workload: immobilization of an extremity to heal bone fracture results in muscle atrophy. Osteoporosis of disuse can occur upon certain conditions; Denervation; Decreased blood flow; Lack of nutrients; Lack of appropriate endocrine stimuli; Aging; Pressure. Related to compromised blood supply (ischemia) The outcomes of atrophy ◼ The changes can be reversible ◼ If the causative factor act for prolonged time, cell death (irreversible changes) can ensure, frequently by apoptosis, e.g., in muscle subjected to chronically diminished blood flow or in endocrine organs after hormone withdrawal Metaplasia During the metaplastic process, one type of mature tissue becomes replaced by another Biological meaning: ◼ +: improved survival of the tissue -: loss of specific function ◼ -: cancerogenesis may ensure upon definite conditions ◼ Squamous metaplasia (associated with pre-cancerous change) in the bronchial epithelium Photo: I.Strumfa Metaplasia (II) ◼ Epithelial  Squamous metaplasia in the bronchial epithelium of smoker and / or upon conditions of A vitamin deficiency  Barrett’s oesophagus ◼ Mesenhymal  Myositis ossificans Mechanisms of metaplasia Metaplasia is ensured by reprogramming of stem cells present in the normal tissues (NB! Not by direct change of cell type):  Tissue destruction  Activation of stem cells or undifferentiated mesenchymal cells  Cytokines, growth factors and extracellular matrix  Expresion of certain genes  Differentiation of stem cells along new pathway Photo: I.Strumfa Rīga Stradiņš University Department of Pathology 2023 / 2024 HAEMODYNAMIC DISORDERS Disorders of peripheral circulation Prof. Ilze Strumfa Dr. Artjoms Sobolevs Normal fluid homeostasis includes: blood vessel wall integrity; preserved intravascular pressure and osmolarity; maintenance of blood as a liquid until an injury causes clotting. Photo – I.Strumfa The haemodynamic disorders include Oedema ◼ Hyperemia and congestion ◼ Haemorrhage ◼ Thrombosis ◼ Embolism ◼ Infarction ◼ Interstitial fluid circulation: scheme The sum of vectors in arterial end: The sum of vectors in venous end: Pk- capillary hydrostatic pressure Pi – interstitial hydrostatic pressure πk - plasma colloid osmotic (oncotic) pressure πi - interstitial colloid osmotic pressure Scheme – A. Soboļevs Interstitial fluid circulation: definitions ◼ Hydrostatic pressure: presaure, caused by a liquid on the walls of an enclosed space.  ◼ Osmotic pressure: The pressure caused by osmosis – the flow of solute (e.g. water) from a solution of lower concentration across a semi-permeable membrane to a solution of higher concentration.  ◼ Intravascular hydrostatic pressure - the force by which the blood acts on the walls of the blood vessel (e.g. capillary hydrostatic pressure). Plasma colloid osmotic (oncotic) pressure – Intravascular osmotic pressure caused by plasma proteins (especially albumin). ◼ Is directed in the opposite direction to the intravascular hydrostatic pressure. The interstitial fluid also has its own hydrostatic and osmotic pressure. Rosen IM and Manaker S. Oxygen delivery and consumption. In: Post TW, ed. UpToDate.Waltham, MA: UpToDate.https://www.uptodate.com/contents/oxygen-delivery-and-consumption#H4.Last updated May 9, 2019. Physiology of the interstitial fluid circulation ◼ ◼ ◼ Capillaries are the site of fluid exchange because they have the largest total cross-sectional area and the slowest blood flow of all blood vessels. The direction of fluid (water) flow is determined by the vector sum of all forces involved. Fluid filtration from the capillaries to the interstitium takes place at the arterial end of the capillary bed.  ◼ Basically, it is determined by arterial hydrostatic circulation pressure (increased Pk) and low concentration of plasma proteins per unit volume, i.e. the blood is more "diluted" (reduced πk). Fluid reabsorption from the interstitium in the capillaries takes place at the venous end of the capillary bed. Basically, it is determined by the flow resistance caused by the capillaries (reduced Pk) and a high concentration of plasma proteins per unit volume, i.e. the blood is more "concentrated" (increased πk). 90% of the fluid filtered at the arterial end is reabsorbed at the venous end, while the remaining 10% returns to the circulation via the lymphatic system. ◼ ◼ Rosen IM and Manaker S. Oxygen delivery and consumption. In: Post TW, ed. UpToDate.Waltham, MA: UpToDate.https://www.uptodate.com/contents/oxygen-delivery-and-consumption#H4.Last updated May 9, 2019. Causes of oedema Oedema = increased volume of extravascular fluid: Increased hydrostatic pressure in blood vessels ◼ Reduced osmotic pressure of plasma (as in hypoproteinemia) ◼ Lymphatic obstruction ◼ Na+ retention ◼ Inflammation ◼ Oedema by increased hydrostatic pressure (I) ◼ Impaired venous drainage  Congestive heart failure  Constrictive pericarditis  Ascites due to liver cirrhosis (v.portae!!) or other causes  Venous obstruction (thrombosis) or compression, e.g., by tumour ◼ Arteriolar dilation, e.g., due to heat Oedema by increased hydrostatic pressure (II) ◼ Na+ retention → incresed circulating fluid → increased intravascular hydrostatic pressure.  Na+ retention can be caused by: Increased NaCl uptake in renal failure (inability to excrete excess Na+) ◼ Increased tubular Na+ reabsorption initiated by:: ❖ Renal hypoperfusion ❖ Activation of the renin-angiotensin-aldosterone system ◼ Oedema by hypoproteinemia ◼ Increased loss of proteins:  Nephrotic syndrome: heavy loss of protein by urine (more than 3.5 g / 24 hrs)  Protein-losing enteropathy ◼ Decreased synthesis of proteins  Liver cirrhosis  Malnutrition or malabsorption Oedema by lymphatic obstruction Inflammatory ◼ Neoplastic ◼ Postsurgical ◼ Postirradiation ◼ Oedema due to inflammation ◼ Occurs due to increased permeability of capillary walls Acute inflammation ◼ Chronic inflammation ◼ Angiogenesis ◼ Oedema: terminology ◼ Peripheral edema – swelling in tissues supplied by the peripheral circulatory system (most often – feet, ankles, lower legs)  Anasarca ◼ – severe generalized peripheral edema. Accumulation of fluid in cavities:  Hydrothorax  Hydropericardium  Ascites Robbin’s and Cotran Pathologic Basis of Disease, 8th edition, 2010; Fluid accumulation in cavities: transudate vs. exudate (I) ◼ ◼ Transudate: Edema fluid with low protein content  Cause: increased intravascular hydrostatic pressure or decreased oncotic pressure  Examples: ◼ Congestive heart failure ◼ Liver cirrhosis with ascites ◼ Kidney failure ◼ Hunger edema, malnutrition Exudate: Edema fluid with a high protein content  Cause: increased permeability of blood vessels or their damage  Examples: inflammation, tumor, metastasis Robbin’s and Cotran Pathologic Basis of Disease, 8th edition, 2010; Fluid accumulation in cavities: transudate vs. exudate (II) ◼ In clinical practice, Light's criteria help to distinguish transudate from exudate: ❖ Exudate has a higher protein and lactate dehydrogenase (LDH) content than transudate: Pleural fluid/serum protein conc. > 0.5 Pleural fluid/serum LDH concn. > 0.6 Pleural fluid LDH concn. > 2/3 of the upper limit of the serum normal range Robbin’s and Cotran Pathologic Basis of Disease, 8th edition, 2010; Oedema: morphology ◼ ◼ ◼ Easily recognized grossly: swelling Microscopically: widening, separation of the extracellular matrix More marked in loose connective tissues Oedema in nasal mucosa Normal tissues Marked oedema Photo – I.Strumfa Oedema Oedema in nasal mucosa No oedema Photo – I.Strumfa Oedema The clinical significance of oedema ◼ Subcutaneous oedema:  Dg: Heart Failure? Kidney failure? Deep vein thrombosis?  Impair wound healing  Impair clearance of the infection ◼ Pulmonary oedema: frequent and significant clinically:  Left ventricular failure;  Renal failure  ARDS  Pulmonary infection ◼ Brain oedema: life-threatening condition Hyperemia and congestion Types of blood flow impairment: Hyperemia and congestion ◼ Increased volume of blood in the vessels of particular tissues:  Hyperemia: an active process due to arteriolar dilation.  Congestion: a passive process: ◼ Often associated with oedema: congestion develops retrogradually from the site of the cause of the congestion → increased hydrostatic pressure → fluid transudation ◼ In the case of a chronic course, it develops:  Hypoxia s. lack of oxygen  Parenchymal cell death, tissue fibrosis;  Capillary ruptures, small haemorrhages, accumulation of haemosiderin (formed by catabolism of RBC) Congestion in gastric veins Photo – Z.Jaunmuktane Examples of congestion  Acute pulmonary congestion  Chronic pulmonary congestion  Acute hepatic congestion  Chronic passive congestion of the liver Blood congestion in the lungs: scheme Cardiac causes of pulmonary edema: Left ventricular systolic and diastolic dysfunction: Acute myocarditis Cardiomyopathy Acute myocardial infarction Heart Failure Dysfunction of left heart valves: Aortic regurgitation/stenosis Mitral regurgitation/ stenosis Arrhythmia: Tachysystolic form of atrial fibrillation Ventricular tachycardia, Third degree AV block, etc. The norm Interstitial Alveolar pulmonary edema pulmonary edema : Blood circulation Scheme – A. Soboļevs : Direction of spread of blood congestion Acute pulmonary congestion: morphological signs Tissues are red, full with fluid ◼ Veins and alveolar capillaries engorged with blood ◼ Interstitial pulmonary edema may occur as fluid is pushed from the capillaries into the alveolar septae ◼ Alveolar pulmonary edema may occur as fluid goes into alveoli from the alveolar septae ◼ Erythrocyte extravasation may occur ◼ Acute blood congestion in the lungs with pulmonary edema Photo – I.Strumfa Chronic pulmonary congestion Veins and capillaries are full-filled with blood ◼ Numerous intraalveolar haemosiderinladed macrophages s. heart-failure cells ◼ Interstitial fibrosis ◼ Chronic pulmonary congestion Photo – I.Strumfa, L.Feldmane Chronic pulmonary congestion Perls’ stain Photo – I.Strumfa, L.Feldmane Blood congestion caused by right-sided heart failure: scheme Blood congestion in the liver Dilated jugular veins Right sided heart failure Ascites The norm Peripheral edema : Blood circulation Scheme – A. Soboļevs : Direction of spread of blood congestion Acute liver congestion Engorged central veins and sinusoids ◼ Irreversible damage to hepatocytes may occur in the center of the lobule centrolobular necrosis ◼ Periportal hepatocytes suffer less from lack of oxygen ◼ Portal tract Centrolobular congestion and necrosis Photo – I.Strumfa Central venule Acute liver congestion Photo – I.Strumfa, L.Feldmane Centrolobular liver necrosis in acute congestion Chronic liver congestion ◼ ◼ ◼ ◼ ◼ Macroscopically «Nutmeg» liver The center of the lobule suffers most from blood congestion (centrolobular congestion), hypoxia and fibrosis: necrosis of hepatocytes Centrolobular congestion: the centrolobular regions are grossly red-brown and depressed on section In the periphery of the lobule, hepatocytes are better preserved, suffer from reversible cell damage, which often manifests as steatosis Fibrosis can progress, usually when chronic blood congestion is caused by severe heart failure - socalled cardiac liver cirrhosis Chronic liver congestion Nutmeg Photo – Z.Jaunmuktane Bleeding Bleeding Haemorrhage – extravasation of blood due to vessel rupture ◼ External ◼ Internal ◼  Hematoma  Accumulation of blood in the body cavities ◼ Haemothorax ◼ Haemopericardium ◼ Haemoperitoneum ◼ Haemarthrosis Patterns of skin / subcutaneous haemorrhage Petechiae: 1 – 2 mm ◼ Purpura: > 3 mm ◼ Ecchymoses: 1 – 2 cm ◼ The outcome of bleeding ◼ Clinical significance is variable:  Possibly little impact on general health status  Hemorrhagic / hypovolemic shock  Death due to shock  Significant local effects, e.g., haemorrhage in brain  Iron-deficiency anaemia due to chronic bleeding ◼ The outcome is influenced by  Volume of lost blood  Rate of blood loss  Site of bleeding Hemostasis and thrombosis Haemostasis and thrombosis ◼ Normally, the blood is liquid. A clot can be formed to stop bleeding: normal haemostasis ◼ Thrombosis represents a pathological process – inappropriate activation of haemostatic process resulting in blood clot (thrombus) formation within intact vessels The main components of adequate haemostasis ◼ Brief arteriolar vasoconstriction due to reflex neurogenic mechanisms, endothelin ◼ Primary haemostasis involving activation and aggregation of platelets ◼ Secondary haemostasis – activation of thrombin that converts soluble fibrinogen to insoluble fibrin ◼ Formation of a thrombus from platelet aggregates and fibrin The pathogenesis of thrombosis Virchow’s triad = three primary abnormalities that lead to thrombus formation: ◼ Endotelial injury ◼ Alterations in normal blood flow ◼ Hypercoagulability Endothelial injury. Thrombus on the surface of ulcerated atherosclerotic plague Photo – I.Strumfa Endotelial injury (I) ◼ Particularly important for thrombus formation in the heart or arteries (sites with high flow rate):  Atherosclerosis  Myocardial  Trauma  Vasculitis infarction Endotelial injury (II) ◼ Spectrum: from physical desquamation to dysfunction as in:  Arterial hypertension  Turbulent blood flow  Bacterial endotoxins in sepsis  Hypercholesterolemia  Smoking  Radiation Alterations in normal blood flow ◼ Turbulence: in arteries and heart  Ulcerated ... atherosclerotic plaques Photo – I.Strumfa Photo – I.Strumfa The alterations in blood flow (continued) ◼ Turbulence: in arteries and heart  Ulcerated atherosclerotic plaques  Aneurisms – pathologic dilations of aorta, other blood vessels or heart ... Photo – I.Strumfa The alterations in blood flow (continued) ◼ Turbulence: in arteries and heart  Ulcerated atherosclerotic plaques  Aneurisms – pathologic dilations of aorta and blood vessels  Myocardial infarction  Atrial dilation ◼ Slow blood flow / stasis in veins Alterations in normal blood flow: the way to thrombosis ◼ Stasis and turbulence:  Promote endothelial activation  Disrupt laminar blood flow and bring platelets into contact with the endothlium  Prevent washout / dilution of activated clotting factors Hypercoagulability ◼ Less frequently becomes the dominant contributor to the Virchow’s triad Primary ◼ Secondary ◼ Hypercoagulability ◼ Primary: genetic  Mutations in the factor V gene 2 – 15% population carry Leiden mutation ◼ The incidence of Leiden mutation in patients with deep venous thrombosis is up to 60% ◼ Leiden mutation results in resistance to Va inactivation and thus promotes unchecked coagulation ◼  Mutations in prothrombin gene  Inherited hyperhomocysteinemia  Inherited deficiencies of anticoagulants Hypercoagulability (II) Secondary – acquired ◼ ◼ ◼ ◼ ◼ ◼ ◼ ◼ Oral contraceptive use Hyperestrogenic state of pregnancy: the synthesis of coagulation factors increases in the liver, the synthesis of anticoagulants decreases Disseminated (widespread in the body) cancers Aging: Thr aggregation capacity increases and PGI2 production in the endothelium decreases Smoking Obesity Heparin-induced thrombocytopenia syndrome (5% of population; solution – low molecular weight heparin preparations) Antiphospholipid antibody syndrome Interaction of the factors of Virchow's triad: scheme Endothelial damage Thrombosis Impaired blood flow Hypercoagulation Scheme – A. Soboļevs Interaction of Virchow's Triad Factors (I) ◼ ◼ The most significant contributor to thrombosis is endothelial damage, which promotes coagulation at the site of damage (local thrombosis). Impaired blood flow (stasis or turbulence) promotes hypercoagulation directly:  Facilitates Thr contact with the endothelium  Prevents flushing of activated clotting factors ◼ and indirectly:  ◼ Causing endothelial damage or dysfunction Circulus vitiosus: Endothelial damage makes the inner surface of the blood vessel rough, thereby disrupting laminar flow and promoting turbulent flow Robbin’s and Cotran Pathologic Basis of Disease, 10th edition, 2017; http://www.medicinehack.com/2011/07/virchows-triad.html Interaction of Virchow's Triad Factors (II) ◼ Procoagulant - anticoagulant imbalances unrelated to endothelial damage or blood flow disturbances (primary and secondary causes of hypercoagulation) also contribute to thrombosis. Robbin’s and Cotran Pathologic Basis of Disease, 8th edition, 2010; Thrombus Photo – I.Strumfa Thrombi ◼ In arteries and heart – in the sites of endothelial damage (atherosclerosis) and turbulence (arterial bifurcation) ◼ On the background of venous congestion ◼ Attached to blood vessell wall ◼ ◼ ◼ Arterial thrombi grow in retrograde direction Venous thrombi grow in the direction of blood flow Presence of Zahn lines – alternating layers of platelets and fibrin / RBCs The thrombus in the vessel wall and Zahn lines Coronary thrombosis RBC Fibrin Photo – I.Strumfa Thrombus Photo – I.Strumfa Types of thrombi Mural vs. occlusive ◼ Arterial vs. venous ◼ Occlusive thrombi Close = occlude the lumen ◼ In arteries or veins ◼ Mural thrombi Located close to the wall, leaving narrowed space for blood flow Formed: ◼ In the heart - in the cases of impaired contractility:  Arrhythmia  Dilation cardiomyopathy  Myocardial infarction ◼ In arteries: atherosclerotic plaques, aneurisms Arterial thrombi Usually occlusive ◼ Locations: Coronary arteries Brain arteries Femoral arteries ◼ Causes: atherosclerosis, trauma, vasculitis etc. ◼ Composition: thrombocytes, fibrin, RBC, WBC ◼ Photo – I.Strumfa Venous thrombi Mostly occlusive ◼ Red ◼ Long ◼ Locations: ◼  veins of lower extremities (90%),  periprostatic venous plexus,  periuterine venous plexus Thrombi on heart valve Photo – I.Strumfa Vegetations – large thrombotic masses of heart valves ◼ Bacterial endocarditis Non-bacterial thrombotic endocarditis in hypercoagulability ◼ Libman – Sacks verrucous endokarditis in systemic lupus erythematosus ◼ Fate of thrombus Propagation ◼ Embolization ◼ Dissolution ◼ Organization and recanalization ◼ Fate of thrombus: sheme Fibrinolysis The norm Thrombus Propagācija Propagation Sheme – A. Soboļevs Embolisation Organisation Recanalization Organized occlusive thrombus 3 2 Photo – I.Strumfa 1 1 The clinical consequences of thrombosis (I) ◼ ◼ Thrombosis is a component of the pathogenesis of many important diseases:  Causes in the veins: ◼ Obstruction, distal edema, hypoxia, possible ulcer ◼ !!! Predisposes to embolism:  In arteries, significant obstruction and distal ischemia, which can lead to tissue death Phlebothrombosis:  Thrombosis of superficial veins, often varicose veins of the legs. ◼ Congestion, pain, swelling, varicose veins ulcers  Deep vein thrombosis ◼ Pain, edema (possible compensation with collaterals), PATE  Migratory thrombophlebitis The clinical correlations of thrombosis (II) ◼ Arterial thrombosis: in atherosclerosis ◼ Clot formation in the heart:  in case of myocardial infarction,  in case of rheumatic heart disease;  In case of bacterial endocarditis. ◼ Formation of emboli from thrombi in the heart, aorta and arteries:  brain, ◼ kidney, spleen damage DIC syndrome Atherosclerosis with superimposed thrombosis Photo – I.Strumfa DIC syndrome ◼ Disseminated intravascular coagulation ◼ Complication of various SERIOUS diseases A clinically significant and pathogenetically complex syndrome The basis of pathogenesis is the formation of many tiny, microscopic fibrin thrombi in the bed of microcirculation vessels. Depletion of thrombocytes and coagulation factors → Activation of fibrinolysis → Bleeding follows Disturbancies of CNS, lung, heart, renal functions ◼ ◼ ◼ ◼ Embolism and embolus Embolus Embolus - detached intravascular solid, liquid, or gaseous mass that is carried by the blood to a site distant from its point of origin ◼ Emboli can consist from: ◼  Mostly detached thrombi: thrombemboli  Fat droplets  Nitrogen bubbles  Air bubbles  Tumour tissues  Small foreign bodies Examples of embolism Pulmonary thrombembolism ◼ Systemic thrombembolism ◼ Fat embolism ◼ Air embolism ◼ Amniotic fluid embolism ◼ Thromboembolism in pulmonary arteries: scheme v.femoralis v.cava inferior Heart: right atrium The right chamber Truncus pulmonalis Scheme – A. Soboļevs Pulmonary thrombembolism ◼ ◼ ◼ ◼ ◼ Pulmonary arterial circulation becomes targeted Incidence: 20 – 25 / 100 000 hospitalised patients Most frequent source of embolus (in case of pulmonary thrombembolism) – deep vein thrombosis above the knee (95%) Frequently recurrent (repeated) Depending on the caliber of the blood vessel occluded, the clinical picture varies from asymptomatic course to sudden death Symptoms of PATE ◼ Sudden onset of symptoms, often provoked by an activity (e.g. sudden physical exertion, getting out of bed in the morning):  Dyspnea and tachypnea (>50% of cases)  Sudden pleuritic pain that worsens during inhalation (about 50% of cases)  Cough and hemoptysis  Tachycardia (about 25% of cases), hypotension  Subfebrile temperature ◼ ◼ Signs of DVT: unilateral painful leg swelling 60 – 80% of PATE are not clinically manifested Agnelli G, Becattini C. Acute Pulmonary Embolism. N Engl J Med.2010; 363(3): p.266-274. doi: 10.1056/nejmra0907731 The outcomes of pulmonary thrombembolism (I) ◼ ◼ Sudden death or acute cor pulmonale if:  Emboli are large (60% occlusion of pulmonary circulation) or  reflectory reaction caused by embolus impacting accross the bifurcation of truncus pulmonalis Lung infarction with possible bleeding  If an embolus closes a medium-caliber artery, the picture of pulmonary bleeding may prevail: vessel rupture; blood enters the necrotic tissue from the anastomoses.  If the embolus closes the terminal branches of the pulmonary arteries and arterioles, tissue necrosis in the form of a hemorrhagic infarction predominates (10% PATE) Haemorrhagic infarction in lung Photo – I.Strumfa, L.Feldmane The outcomes of pulmonary thrombembolism (II) ◼ 60 – 80% clinically silent ◼ Chronic pulmonary hypertension with chronic right-sided heart failure (cor pulmonale) can be caused by multiple emboli over time Systemic thrombembolism: scheme Left atrium/ ventricle of the heart Arcus aortae Aorta abdominalis A. Iliaca communis Leg arteries Abdominal organs (intestines, spleen, kidneys, etc.) Scheme – A. Soboļevs A. brachiocephalica A. carotis communis Cerebral arteries A. subclavia Arm arteries Systemic thrombembolism The source: ◼ 80% intracardiac mural thrombi Myocardial infarction Left atrium dilation/ fibrilation ◼ Aortic atherosclerosis ◼ Aortic aneurysms ◼ Vegetations ◼ Paradoxical ◼ emboli In 10 – 15% cases – cause unknown Systemic thrombembolism Localization of the lesion depends on the site of origin of the thrombus and blood flow ◼ The major sites for systemic arterial embolisation: ◼  75% arteries of the lower extremities  10% brain arteries  Less frequently – arteries of the intestines, kidneys, spleen, upper extremity Systemic thrombembolism The outcome depends on  Collateral circulation  Tissue (sensitivity to ischemia)  The size of embolised vessel Usually – infarction distal to the site of obstruction Fat embolism Problem – microscopic fat globules in the circulation ◼ Cause – ◼  Fractures of long bones  Soft tissue trauma ◼ Frequency:  90% of patients with severe trauma  10% of these patients have clinical manifestations  10% of clinically manifest cases end fatally Manifestations of fat embolism Symptoms develop within 12h - 2 weeks after the traumatic event ◼ The classic triad of symptoms: ◼  Sudden respiratory failure - tachypnea, dyspnea, cyanosis  Neurological manifestations - restlessness, confusion, seizures, neurological deficit, delirium or coma  Petechial rash (up to 50% of cases) ◼ Thrombocytopenia, anemia The pathogenesis of fat embolism Mechanical obstruction of small vessels in lung and brain ◼ Aggregation of RBC and Thr on the fat globules ◼ Thrombocytopenia, anaemia ◼ Haemolysis ◼ Endothelial damage ◼ Fat embolism in lungs Sudan III stain Photo – I.Strumfa, L.Feldmane The pathogenesis of fat embolism Mechanical obstruction (fat, Thr, Er) of small vessels in lungs and brain ◼ Aggregation of RBC and Thr on the fat globules → Thrombocytopenia, anaemia ◼ Haemolysis ◼ Endothelial damage ◼ Air embolism Problem: gas bubbles in the circulation ◼ Causes: Medical manipulations Chest trauma Decompression ◼ Consequences: local lesion or PATE-like clinical picture (100 mL) ◼ Amniotic fluid embolism (I) Cause – infusion of amniotic fluid or fetal tissue into the maternal circulation via a tear in the placental membranes or rupture of uterine veins ◼ In pulmonary capillaries of the mother the following morphologic substrate can be found: ◼  Fetal squamous epithelium  Lanugo  Vernix caseosa  Mucus ◼ Activation of thrombosis Amniotic fluid embolism (II) 1/ 50 000 deliveries ◼ Death rate 20 – 40% ◼ Sudden severe dyspnea, cyanosis, hypotensive shock, seizures, coma ◼ Later – Pulmonary oedema DIC ◼ Infarction ◼ ◼ An infarction is an area of ischemic necrosis caused by occlusion of either the arterial supply or the venous drainage in a particular tissue Clinically very frequent and serious process:  Myocardial infarction  Cerebral infarction (= stroke)  Pulmonary infarction  Intestinal infarction  Gangrene of the legs Photo – I.Strumfa Photo – I.Strumfa Photo – I.Strumfa Photo – I.Strumfa Photo – I.Strumfa The causes of infarction Thrombosis or embolism – 99% Less frequently: ◼ Vasospasm ◼ Haemorrhage within an arterial atheromatous plaque ◼ Compression of the blood vessel  Tumour  Suture  Connective tissue: incarceration / entrapment in hernia sac  Oedema ◼ Twisting of vessels: torsio testis, intestinal volvulus ◼ Trauma The causes of infarction: the affected vessel Mostly – an artery ◼ Rarely - Venous ◼ The classification of infarctions By “colour” – the proportion of haermorrhage in inferction ◼ By type of necrosis – coagulative vs. liquefactive ◼ By presence or absence of infection – septic infarction if associated with infection ◼ Types of infarction White infarction ◼ Red infarction ◼ Septic infarction ◼ White infarction In solid organs with end-arterial circulation: typically in heart, spleen, kidney ◼ Necrosis is marked ◼ Haemorrhage - absent or limited ◼ Photo – I.Strumfa Ischaemic myocardial infarction Photo – I.Strumfa, L.Feldmane Kidney infarctions Photo – Z.Jaunmuktane Wedge-shaped infarction in kidney Photo – Z.Jaunmuktane Kidney infarction Photo – I.Strumfa Red infarction In tissues and organs ◼ With anastomosing blood vessels  E.g., intestinal infarction ◼ Dual blood supply  E.g., pulmonary infarction ◼ Venous infarction ◼ Infarction on the background of congestion ◼ Under the conditions of revascularisation Haemorrhagic pulmonary infarction Photo – I.Strumfa, L.Feldmane Red infarction in torsio testis Photo – Z.Jaunmuktane Red infarction in the bowel Photo – Z.Jaunmuktane The outer view of hernia sac Photo – Z.Jaunmuktane The hernia sac Photo – Z.Jaunmuktane Incarcerated bowel showing red infarction Photo – Z.Jaunmuktane Ischemia and infarction Ischemia – a condition where the current level of blood flow is not sufficient to meet the tissue/organ's O2 needs. Reversible cell damage develops (ion exchange impairment, cell and organelle swelling, etc.) Infarction - a condition when ischemic damage has become irreversible necrosis has developed (rupture of cell plasmatic membranes and organelles, nuclear degradation, etc.) NB! Ischemia (reversible damage) that does not resolve becomes infarction (irreversible damage) Shēma – A. Soboļevs Clinical correlations: the factors that influence the development of infarction Anatomy of blood supply ◼ The rate of thrombosis ◼ Tissue sensitivity to hypoxia ◼ The blood oxygenation ◼ THANKS FOR YOUR ATTENTION! Riga Stradins University Department of Pathology 2022 / 2023 Hypoxia Prof. Ilze Strumfa Dr. Agnese Ūdre Definition Hypoxia is low level of oxygen in body tissues Additional terminology: Hypoxemia – low level of O2 in arterial blood Hypercapnia – increased partial pressure of CO2 in arterial blood Hypocapnia – decreased level of CO2 in arterial blood Clinical significance Although hypoxia is often a pathological condition, variations in arterial oxygen concentrations can be part of the normal physiology. ◼ Hypoxia may be classified as either generalized, affecting the whole body, or local, affecting a region of the body. ◼ Clinical significance II ◼ Severity of hypoxia is determined by: – sudden or gradual;  Duration;  Severity;  Type of hypoxia;  Tissue sensitivity to hypoxia.  Onset ◼ Compensatory capacity is lower if hypoxia develops abruptly, lasts longer and is severe. Classification of hypoxia by onset Acute hypoxia – rapid onset, < 6h Chronic hypoxia – lasting more than 90 days Fulminant hypoxia – lightning-fast Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Acute hypoxia ◼ ◼ ◼ Rapid onset Less frequent compared to chronic hypoxia Examples:  Mountain sickness  Suffocation  Airway obstruction with foreign body  Sudden suppresion of respiratory centre  Acute cardiac failure  Shock – acute circulatory failure Underwood's Pathology: a Clinical Approach, 7th edition, 2019 Chronic hypoxia ◼ ◼ Chronic course Examples:  Chronic heart failure/ Congestive heart failure  Chronic respiratory failure  Chronic anaemia Underwood's Pathology: a Clinical Approach, 7th edition, 2019 Fulminant hypoxia ◼ ◼ ◼ ◼ Rare, occurs mostly in catastrophe medicine Example: an explosive decompression of airplane cabin at high altitude (10 km above sea level) Oxygen is forced out from the lungs due to the rapid expansion of gas during a rapid decompression Severe fatal barotrauma – rapid confusion, drowsiness, death due to respiratory center failure Underwood's Pathology: a Clinical Approach, 7th edition, 2019 Types of hypoxia ◼ ◼ ◼ ◼ ◼ Hypoxic hypoxia Respiratory hypoxia Hemic hypoxia Circulatory hypoxia Histotoxic hypoxia Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Hypoxic hypoxia ◼ ◼ Oxygen pressure (SpO2) in the blood is too low to saturate the hemoglobin Clasification by atmospheric pressure:  Hypobaric hypoxic hypoxia – low atmospheric pressure induces altitude sickness.  Normobaric hypoxic hypoxia – staying in inadequately ventilated room or a place with high CO2 levels. Underwood's Pathology: a Clinical Approach, 7th edition, 2019 Altitude sickness (I)  Hypoxic symptoms in previously healthy mountain climbers.  Pathogenesis: hypobaric hypoxic hypoxia  Symptoms include: ◼ ◼ ◼ ◼ Headache Nausea, vomiting Dyspnoea Sleeping disorders  Typically begins at ~2500 m elevation  3000 m elevation – pulmonary oedema is possible – due to constricted pulmonary arteries  3500 m elevation – cerebral oedema may occur – due to dilated cerebral arteries Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Altitude sickness (II) ◼ High altitude euphoria is possible.  Poor judgement of one’s capacity  Mechanism: during hypoxia, cerebral cortical inhibitory functions are diminished, similarly as in alcohol intoxication ◼ ◼ Subsequently, severe depression and apathy occurs Reaching 5000 – 6000 m altitude, sensory, motor and mental functions deteriorate, leading to reduced awareness of the current situation, coordination difficulties, decreased muscle function Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Hypoxic hypoxia: compensatory mechanisms (I) ◼ ◼ ◼ ◼ Hyperventilation when air has low level of CO2:  Can lower hypoxia but can also cause hypocapnia (decreased level of CO2 in blood);  Hypocapnia can lead to respiratory alcalosis (blood pH deviation to alkalinity);  Hypocapnia lowers activity of respiratory center. Hyperventilation in circumstances when CO2 in air is elevated. Circulatory response Secondary polycytemia Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Hypoxic hypoxia compensatory mechanisms (II) ◼ Hyperventilation in circumstances when CO2 in air is elevated  Can lower hypoxia but lead to hypercapnia (higher blood level of CO2);  Hypercapnia can lead to respiratory acidosis (blood pH decreases);  Hypercapnia increases activity of respiratory center. Circulatory response ◼ Secondary polycythemia ◼ Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Respiratory hypoxia ◼ Caused by decline in respiratory functions in any level:  Hypoventilation;  Impairment of gas diffusion via alveolo-capillary membrane;  Ventilation-perfusion mismatch. ◼ Respiratory hypoxia leads to:  Hypercapnia: elevated CO2 in blood, because CO2 cannot be exchanged via lungs;  Hypercapnia can lead to respiratory acidosis (blood pH decreases). Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Oxyhemoglobin dissociation curve https://rk.md/2017/oxyhemoglobin-dissociation-curve/ Causes of respiratory hypoxia 1. Hypoventilation ◼ Airway obstruction:  Foreign body  Tumor  Inflammatory oedema (bronchitis)  Bronchospasms during bronchial asthma attack ◼ ◼ ◼ ◼ Paralysis of respiratory muscles Skeletal deformations Respiratory center suppression (medications, narcotic abuse, hypocapnia) Superficial breathing due to pain: thoracic trauma, pleuritis, intercostal neuralgia Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Causes of respiratory hypoxia 2. Impairment of gas diffusion via alveolo-capillary membrane ◼ ◼ ◼ Reduction of surface area for gas exchange:  Lung emphysema Decline of functioning alveoli:  Pneumonia;  Lung oedema. Pneumofibrosis: increased thickness of connective tissue in alveolar septum:  Cryptogenic fibrosing alveolitis. Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Causes of respiratory hypoxia 3. Ventilation/perfusion missmatch ◼ Normal ventilation, no blood supply: increased «dead space».    ◼ Pulmonary embolus; Lung emphysema (lots of enlarged alveoli with less surface area and fewer alveolar capillaries); Cardiovascular shock (blood flow to lungs is decreased). Pulmonary shunt – opposite of dead space. Consists of alveoli that are perfused, but not ventilated:      Pneumonia and pulmonary oedema; Tissue trauma – alveolar wall swelling; Atelectasis – collapse of alveoli from failure to expand; Mucous plugging; Pulmonary arteriovenous fistula. Underwood's Pathology: a Clinical Approach, 7th edition, 2019; https://www.osmosis.org/learn/Ventilation-perfusion_ratios_and_VQ_mismatch Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Hemic hypoxia ◼ Lack of oxygen in the blood flowing to the tissues because of decreased haemoglobin level  Anemia – low count of erythrocytes in blood leads to low hemoglobin levels.  Functional hemoglobin defects: inability to transport oxygen molecules: CO intoxication; ◼ Fe oxidation from Fe2+ to Fe3+: methemoglobinemia; severe oxidative stress (smoking etc.). ◼ Increased hemoglobin affinity to oxygen: thalassemia; inherited hemoglobinopathies ◼ Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Oxyhemoglobin dissociation curve https://rk.md/2017/oxyhemoglobin-dissociation-curve/ Circulatory hypoxia ◼ ◼ Decreased cardiac output leads to prolonged systemic transit time The PaO2 in blood can be initially normal.  Cardiovascular failure.  Shock (any etiology). ◼ Can rapidly progress to mixed hypoxia: circulatory + hemic; circulatory + respiratory hypoxia. Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Histotoxic hypoxia ◼ Histotoxic hypoxia refers to a reduction in ATP production by the mitochondria due to a defect in the cellular usage of oxygen.  Cyanide poisoning: cessation of aerobic cell metabolism. Cyanide binds to the enzyme cytochrome C oxidase and blocks the mitochondrial transport chain.  Monobromides, tetrachloromethane: blocks Krebs cycle enzymes.  Anesthetic substance overdose: dehydrogenase blockage. Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Symptoms of hypoxia ◼ ◼ ◼ ◼ Cyanosis Dyspnea – subjective and objective difficulty of breathing (shortness of breath; breathlessness). Hypotension Other symptoms:    ◼ Fatigue Malaise Anxiety, confusion, insomnia Symptoms caused by compensatory mechanisms Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Symptoms of hypoxia: cyanosis (I) ◼ ◼ ◼ Cyanosis is characterized by a blueish discoloration of the skin or mucous membranes. Central cyanosis occurs when the level of deoxygenated hemoglobin in the arteries is above 50 g/L with oxygen saturation below 85%. Cyanosis might not be clinically evident in a patient with severe anemia due to inability to obtain high enough level of reduced hemoglobin. Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Symptoms of hypoxia: cyanosis (II) ◼ Types of cyanosis:  Central/ arterial cyanosis: arterial blood are not enough oxydated and contains reduced hemoglobin: ◼ Tetralogy of Fallot (a type of congenital heart pathologies). ◼ Lung diseases.  Peripheral/ acral/ venous cyanosis: seen in the upper and lower extremities where the blood flow is less rapid. ◼ Low cardiac output; ◼ Venous stasis; ◼ Exposure to extreme cold. Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Symptoms of hypoxia: cyanosis (III) ◼ ◼ The arterial blood gas shows the partial pressure of dissolved oxygen in the blood as well as the saturation of hemoglobin. The pulse oximeter measures the absorption of light at only two wavelengths which correspond to that of oxyhemoglobin and deoxyhemoglobin. Underwood's Pathology: a Clinical Approach, 7th edition, 2019; https://www.ncbi.nlm.nih.gov/books/NBK482247 Hypoxia without cyanosis Hemic hypoxia – due to anemia with total hemoglobin 60 – 90 g/L (normal level 120 – 150 g/L) ◼ CO intoxication: carboxyhemoglobin is lightly red ◼ Histotoxic hypoxia ◼ Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Consequences of hypoxia ◼ Target organs:  Brain!!  Heart  Lungs  Kidneys  Liver  Skeletal muscle Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Compensatory mechanisms (I) ◼ Organs responsible for blood oxygenation and possible compensation are:  Cardiovascular system  Respiratory system  Erythrocytes  Tissue metabolism Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Compensatory mechanisms (II) ◼ Hyperventilation (tachypnoea, hyperpnea):  Hypoxic stimulation leads to hyperventilation in an attempt to correct hypoxia at the expense of a CO2 loss  Hyperventilation can lead to respiratory alkalosis  Hyperventilation is the fastest compensatory mechanism for respiratory acidosis Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Compensatory mechanisms (III) ◼ Tachycardia:  Develops in hypoxic, respiratory, hemic hypoxia  Tachycardia raises myocardial need for oxygen, thus leading to myocardial hypoxic injury  Can result in circulatory hypoxia Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Compensatory mechanisms (IV) ◼ ◼ Centralization of blood circulation Renin-angiotensin-aldosterone system activation:  Activated by hypovolemia, for example, after blood loss  Positive effect, if hypoxia is due to blood loss  Can have negative impact in case of circulatory hypoxia if heart pathology is due to arterial hypertension ◼ Increased erythropoietin synthesis in kidneys:  Secondary polycythemia  Positive effect, if hypoxia is due to blood loss  Negative effect: blood viscosity increases leading to elevated risk for thrombosis Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Oxyhemoglobin dissociation curve ◼ ◼ Describes the relationship between the saturation of hemoglobin and the partial pressure of arterial oxygen. In healthy adults, a PO2 of ~27 mmHg corresponds to ~50% hemoglobin saturation (red curve). This is known as the P50 of hemoglobin. There are many physiologic stressors which can shift the curve rightward or leftward and therefore change hemoglobin’s P50. Underwood's Pathology: a Clinical Approach, 7th edition, 2019; Gould’s Pathophysiology for the Health Professions, 7th edition, 2023 Oxyhemoglobin dissociation curve (ODC) https://rk.md/2017/oxyhemoglobin-dissociation-curve/ Rightward shift of ODC ◼ Rightward shift is caused by:  increased temperature,  increased CO2 production (and therefore decreased pH leading to an acidosis) and increased 2,3-diphosphoglycerate (DPG),  Hypoxia,  Anaemia. ◼ ◼ In these situations, it is important for hemoglobin to unload oxygen to the starved tissues. Additionally, sickle cell hemoglobin (HbSS) and sulfhemoglobin are unable to readily bind oxygen (low affinity) and therefore are right-shifted. Underwood's Pathology: a Clinical Approach, 7th edition, 2019; https://rk.md/2017/oxyhemoglobin-dissociation-curve Leftward shift of ODC ◼ ◼ ◼ ◼ A leftward shift less PO2 can achieve a higher hemoglobin saturation compared to the baseline. Hemoglobin has a higher affinity for oxygen and is less «willing» to give up oxygen molecules to peripheral tissues. Many of the factors which create left shifts are the opposite of those creating right shifts. Additionally, methemoglobinemia (metHb), is unable to accept oxygen like the typical 2+ oxidation state, creates a leftward shift. Carbon monoxide binds hemoglobin ~250x more rapidly than oxygen, so binding spots are reduced and the curve shifts leftward. Fetal hemoglobin is structurally different than adult hemoglobin and adapted to have high affinity for oxygen since the uteroplacental circulation has relatively low partial pressures of oxygen. Underwood's Pathology: a Clinical Approach, 7th edition, 2019; https://rk.md/2017/oxyhemoglobin-dissociation-curve GOOD LUCK IN YOUR STUDIES! Rīga Stradiņš University Department of Pathology 2019/ 2020 INFLAMMATION Prof. Ilze Strumfa complex reaction to injurious agents, e.g., microbes, or damaged / necrotic cells Inflammation is a Frequent!! E.g.,  Pneumonia;  Infections: ARVI, gut infections, hepatitis and others;  Appendicitis and many other surgical diseases. Inflammation is connected with repair, regeneration and healing The biological meaning of the inflammation Protective: protects organism against the initial cause of tissue injury (microbes, toxins) and removes the injured, necrotic tisue Harmful: Rheumatoid arthritis Atherosclerosis Life – threatening hypersensitivity Disfiguring scars complex reaction to injurious agents, e.g., microbes, or damaged / necrotic cells Inflammation is a Frequent!! E.g.,  Pneumonia;  Infections: ARVI, gut infections, hepatitis and others;  Appendicitis and many other surgical diseases. The components of inflammation Inflammation consists of:  Vascular reactions  Migration and activation of leukocytes  Systemic reactions The local components of inflammation Vascular reactions  Cellular reactions  The local components in gastritis Chemical gastritis: Mainly vascular reactions Photo: I.Strumfa Helicobacter pylori gastritis: Mainly cellular infiltrate Acute vs. chronic inflammation Acute inflammation  Starts rapidly (in seconds or minutes)  Short – termed (lasting for few days)  Morphologic components:  Exudation of fluid and plasma proteins  Oedema  Reaction / emigration of neutrophils (Neu) Chronic inflammation  Develops after acute inflammation or starts slowly  Long – lasting  Morphological components:  Reactions of lymphocytes and macrophages  Proliferation of blood vessels  Fibrosis  Necrosis, loss of specialised tissues Etiology of acute inflammation Infections (bacterial, viral, fungal, parasitic)  Microbial toxins  Tissue necrosis   Ischemia, e.g., myocardial infarction  Trauma  Physical and chemical factors Foreign bodies  Immune reactions, including allergy  The pathogenesis of acute inflammation The pathogenesis of acute inflammation Leukocyte in capillary Leukocytes in alveolus (pneumonia) Photo – I.Strumfa The pathogenesis of acute inflammation includes: Increased blood flow due to the alterations in vascular caliber: arteriolar dilatation  Structural changes in small blood vessels increasing the permeability (permit the plasma proteins and leukocytes to leave the circulation in the place of inflammation)  Cellular emigration, accumulation and activation  The mechanisms of increased vascular permeability      Formation of intercellular endothelial gaps: retraction of endothelial cells (immediate transient response) Endothelial injury:  Direct endothelial injury  Delayed (2-12 hrs) prolonged leakage: delayed direct endothelial injury (apoptosis) or damage by cytokines Leu-mediated vascular injury Transcytosis Angiogenesis NB! Interstitial fluid circulation Venous end Increased interstitial fluid pressure Increased plasma colloid osmotic pressure Interstitium Lymphatics Hydrostatic pressure Arterial end Response of lymphatic vessels Increased flow to drain the tissue oedema  Movement of leukocytes and cell debris along with the lymph flow  Spread of Ag or inflammation:   Lymphangitis  Lymphadenitis:  Proliferation reactive vs. acute purulent Photo: I.Strumfa Response of lymphatic vessels Increased flow to drain the tissue oedema  Movement of leukocytes and cell debris along with the lymph flow  Spread of Ag or inflammation:   Lymphangitis  Lymphadenitis:  Proliferation reactive vs. acute purulent The cellular components of acute inflammation Leu Leu extravasation:  Marginalization, rolling and adhaesion to the endothelium  Transmigration s. diapedesis  Migration in the interstitium (tissues)  Neu, Mo, Ly, Eo, Ba Rolling and adhaesion Adhaesion Rolling Photo – I.Strumfa Leu adhaesion factors Selectins  Glycoproteins  Integrins  Immunoglobulin superfamily ICAM-1, VCAM-1  Selectins  Family of proteins mediating the rolling interaction between leukocyte and endothelium Ensure low-affinity interactions between Leu (L-selectin), endothelium (E-selectin and P-selectin) and platelets (P-selectin)  Expression is regulated by cytokines (tumour necrosis factor TNF, IL-1)  Integrins Mediate stable adhaesion resulting in Leu stopping and spreading on the endothelium  Integrins are expressed on leukocytes  Endothelium expresses ligands for integrins:   VCAM-1 (vascular cell adhaesion molecule) - the ligand for VLA-4 integrin  ICAM-1(intercellular adhaesion molecule) is the ligand for LFA-1 and Mac-1 integrins  Cytokines convert the expressed integrins from low-affinity to high affinity state Leukocyte diapedesis Occurs in post-capillary venules  Adhaesion factors (CD31) to cross the endothelial layer  Basement membrane destruction by collagenases  Binding to connective tissues by beta1 integrins and CD44  Photo – I.Strumfa Helicobacter pylori Migration in the tissues: active gastritis Photo – I.Strumfa Migration in the tissues: active bronchitis Photo – I.Strumfa The inflammatory cells within the inflammation focus Chemotaxis – locomotion oriented along a chemical gradient: Granulocytes, monocytes (Mo), lymphocytes (Ly) respond to chemotactic stimulus Leukocyte activation by  Microbes,  Necrosis,  Ag-Av,  Cytokines Recognition of microbes and dead tisssues Leukocyte receptors:     Receptors for microbial products: Toll-like receptors (at least 10) G protein-coupled receptors recognize short bacterial peptides Receptors for opsonins (proteins that coat the microbes. These proteins include antibodies, complement proteins and lectins) Receptors for cytokines that are produced in response to microbes Phagocytosis Recognition and attachment  Engulfment: phagosome  Killing and degradation: phagolysosome  Extracellular release of leukocyte products Lysosomal enzymes  Reactive [O] intermediates  Metabolites of arachidonic acid, including prostaglandins un leukotriens  The mechanisms of the extracellular release of leukocyte products  Unusual process! Regurgitation: phagocytic vacuole remains transiently open before closure  Frustrated phagocytosis  Cytotoxic release: after phagocytosis of membranolytic substances  Exocytosis  Termination of the acute inflammatory response The degradation of mediators  Anti-inflammatory mediators:   Lipoxins  TGF beta (transforming groth factor beta) / macrophages and other inflammatory cells  Cholinergic neural impulses The outcomes of acute inflammation Complete resolution  Progression to chronic inflammation  Healing by fibrosis  Death  Photo: I.Strumfa The outcomes of acute inflammation Complete resolution  Progression to chronic inflammation  Healing by fibrosis  Death  The cells in acute inflammation      Neu: dominate 6 – 24 h, disappear by apoptosis in 24 – 48 h Mo: 24 – 48 h Eo: hypersensitivity Ly: viral infections Prolonged predominance of Neu predominance: Pseudomonas 2 – 4 days Photo: I.Strumfa Photo: I.Strumfa Photo: I.Strumfa Allergic sinusitis: eosinophils Photo: I.Strumfa Allergic sinusitis: eosinophils Photo: I.Strumfa Acute respiratory viral infection Photo: I.Strumfa The main morphological patterns of acute inflammation Serous inflammation  Fibrinous inflammation  Purulent inflammation  Inflammatory ulcer  Serous inflammation Marked exudation by relatively thin fluid  Examples:   Skin blister in the site of burn  Acute respiratory viral infections  Serous effusions in body cavities Serous inflammation in nasal mucosa: ARVI Foto – I.Štrumfa Fibrinous inflammation      Exudate rich in fibrinogen due to greater increase of vascular permeability Fibrin formation occurs in the exudate due to local procoagulant (e.g., microbes or cancer cells): fibrinous exudate Typical sites: lining of body cavities Examples:  fibrinous pleurisy,  fibrinous pericarditis Outcomes:  fibrinolysis  fibrosis Fibrinous pericarditis Photo: I.Strumfa Fibrinous pleurisy adjacent to pneumonia Photo: I.Strumfa Organisation of fibrinous exudate over pleural surface: fibrosis Photo: I.Strumfa Purulent inflammation Exudate rich in Neu  Pus  Types: phlegmonous or by abscess formation  Possible outcomes:   Resolution  Healing by fibrosis  Serious systemic effects, even death Purulent peritonitis Lamina muscularis propria Pus Photo: I.Strumfa Purulent meningitis Photo: I.Strumfa Necrotising fasciitis (at grossing of operation material) Photo: I.Strumfa Necrosis Photo: I.Strumfa Purulent inflammation Septic abscesses in kidney Photo: I.Strumfa Septic abscesses in kidney Photo: I.Strumfa Septic abscesses in kidney Photo: I.Strumfa Phlegmonous appendicitis Photo: I.Strumfa Photo: I.Strumfa Photo: I.Strumfa Acute necrotising inflammation Photo: A.Vanags Acute haemorrhagic inflammation: haemorrhagic pneumonia Photo: I.Strumfa, L.Feldmane Inflammatory ulcers  Ulcer – a local defect of the surface of an organ or tissue that is produced by the sloughing of inflamed and / or necrotic tissue, e.g.,  Skin ulcers  Gastric ulcers  Ulcerative destruction of gall bladder in exacerbation of chronic calculous cholecystitis  etc. Inflammatory ulcers Photo: I.Strumfa Inflammatory ulcers Photo: I.Strumfa Inflammatory ( Photo – I.Strumfa )ulcers ( ) Inflammatory ulcers Photo: I.Strumfa, L.Feldmane Inflammatory ulcers Photo: I.Strumfa, l.Feldmane Acute inflammation: the pathogenesis of local clinical signs  Rubor, calor, tumor –  Due  to increased blood flow and oedema Dolor –  Due to tissue damage  Due to production of prostaglandins, neuropeptides and cytokines  Functio laesa Acute inflammation: the therapeutic approach Treat the cause  Depending on the cause, the inflammation can be promoted or decreased  In microbial infections, the inflammation is a useful reaction  In trauma (and several chronic inflammatory diseases) the inflammation has to be reduced  Chronic inflammation  Chronic inflammation is inflammation of prolonged duration (weeks or months) during which  inflammation,  tissue  repair  coexist. injury and The etiology of chronic inflammation Persisting infections: tbc, lues (Treponema pallidum), certain viruses, fungi, parasites Prolonged contact with toxic substances or damaging physical factors Immune-mediated and/ or autoimmune inflammatory disease The morphological components of chronic inflammation Infiltration with mononuclear cells: macrophages, lymphocytes, plasmocytes  Tissue destruction  Fibrosis: healing by connective tissue replacement of damaged tissue + proliferation of new blood vessels (angiogenesis)  Chronic inflammation: cellular composition Photo: I.Strumfa Chronic inflammation: tissue destruction Photo: I.Strumfa Chronic inflammation: tissue destruction Photo: I.Strumfa Chronic inflammation: fibrosis Photo: I.Strumfa Photo: I.Strumfa Macrophage is the dominant cellular player in chronic inflammation The development of macrophage Bone marrow: precursor cell  Circulating monocyte: half-life 24hrs  Tissue macrophage: months or years  Macrophage activation Starts during phase of active inflammation  Activation by  T un NK - Ly cytokines;  Bacterial endotoxins.  In 48 hrs, macrophages acquire dominant status The manifestations of macrophage activation   Morphological: increase in size Functional:  Increased concentration of enzymes in lysosomes  Activated metabolism  Increased ability to perform phagocytosis and killing  Synthesis of biologically active substances enhancing fibrosis and tissue damage The biologically active substances released by macrophages [O]  Proteases  Cytokines un chemotactic factors attracting other cells  Growth factors enhancing   fibroblast proliferation;  collagen synthesis;  angiogenesis The maintenance of the concentration of macrophages Arrival of monocytes  Local proliferation of macrophages  «Immobilization»  Other cells in chronic inflammation Ly: T, B, pc  Lymphoid follicles  Eo  Ba  Granulomatous inflammation  Granuloma – focus of chronic inflammation consisting of microscopic aggregations of  Macrophages that are transformed into epithelioid (epithelium – like) cells  Ly, pc  Giant cells (result of the fusion of epithelioid cells):  Langhans-type GC with peripherally placed nuclei  foreign body type giant cell Granulomas in lung tisue: sarcoidosis Photo: I.Strumfa Granulomas in lung tisue: sarcoidosis Photo: I.Strumfa Granulomas in lung tisue: sarcoidosis Photo: I.Strumfa Types of granulomas Foreign body granuloma: incited by relatively inert foreign bodies that are large enough to preclude phagocytosis by a macrophage and do not provoke specific immune response ...  Foreign body: breast implant with fibrous capsule Photo: I.Strumfa Foreign body granuloma Polarisation microscopy Photo: I.Strumfa, L.Feldmane Types of granuloma (continued) Foreign body granuloma  Immune granuloma – caused by agents that induce cell-mediated immune response when the inciting agent is poorly degradable   Prototype: tuberculosis Tuberculosis Photo: I.Strumfa Photo: I.Strumfa Photo: I.Strumfa Photo: I.Strumfa Lues Photo: I.Strumfa, L.Feldmane Actinomycosis Photo: I.Strumfa, L.Feldmane Trichinellosis Photo: I.Strumfa, L.Feldmane Echinococcus Photo – I.Strumfa Systemic manifestations of inflammation Acute phase response  SIRS – systemic inflammatory response syndrome  Systemic manifestations of inflammation       Fever Production of acute phase proteins (C-reactive proteins, fibrinogen and serum amyloid A) Leukocytosis Cardiovascular manifestations Anorexia In sepsis  Septic shock: acute vascular insufficiency in septic patient  ARDS: acute respiratory distress syndrome Inappropriate degree of inflammation  Abnormally weak inflammation results in  Increased susceptibility to infections;  Delayed wound healing;  etc.  Excessive inflammation:  Allergy and autoimmunity;  Atherosclerosis;  Alzheimer disease;  etc. Photo: I.Strumfa Inflammation Mediators of inflammation Riga Stradins University, Department of Pathology, D.Balodis, P.Viktorova 2022 Inflammation (inflammatio from Latin inflammare – to manifest) ❑ Inflammatio from Latin in-flammare – manifest ❑ Typical pathological process ❑ How organism respond to various damages tissues ❑ Directed towards isolation, liquidation pathogenic agent and on renewal replacement of damaged tissues to of of or Inflammation Inflammation can cause severe damage; therefore, we must work on preventing damage at any stage of inflammation by stimulating those parts of inflammation which are directed to regeneration. Reasons for inflammation ❑ Any factor, which can cause damages of tissues ❑ Can be divided: ▪ in exogenous (biological, chemical, physical) ▪ in endogenous (immune complexes, necrotised tissues, salt deposits and other) 5 major symptoms of inflammation or local signs of inflammation ❑ Calor (warmth) - ↑blood flow, C3a, C5a ❑ Rubor (redness) - ↑blood flow, C3a, C5a ❑ Tumor (swelling) – inspissation of fluids i/c space, C3a, C5a, C5b67 ❑ Dolor (pain) – oedema, damage of tissues. Cytokines ❑ Functio laesa – disorders of functions The main processes (stages) of inflammation ❑ Alteration (primary and secondary) ❑ Disorders of peripheral blood circulation ❑ Exudation and phagocytosis ❑ Proliferation The main processes (stages) of inflammation Robbins & Cotran Pathologic Basis of Disease, Chapter 3, 71-113, 10th ed., Elsevier, 2021 Consequences of alteration ❑ Damage of tissues ❑ Acidosis ❑ Increase of osmotic pressure ❑ Dysionia Exudation ❑ Transition of liquid part of blood to the inflammatory tissues ❑ Exudate - liquid, which transits to the inflammatory tissues Basic mechanisms which cause exudation ❑  of permeability of capillary and venule walls ❑ Hyperosmia in the focus of inflammation ❑ Changes of filtration in the capillary (changes the effective hydrostatical and oncotic pressure) ❑ Disorders of lymph retention Types of exudate ❑ Serous ❑ Catarrhal ❑ Fibrinous ❑ Haemorrhagic ❑ Purulent Formation of transudates and exudates Robbins & Cotran Pathologic Basis of Disease, Chapter 3, 71113, 10th ed., Elsevier, 2021 Laboratory tests of exudates and transudates Examination (test) Exudate Transudate pH 5,5-7,0 7,4-7,6 Density 1,015-1,027 1,010-1,015 Contents of proteins 3% 3% Types of proteins All possible – albumins, globulins, complement, and other albumins fibrin Is Not Number of blood formelements + amount of died cells in 1 mm3 3000 3000 Albumine/globuline coefficient 0,5-1,0 2-4 Emigration of leukocytes to the focus of inflammation ❑ Is caused by positive haemotaxis ❑ Agents, which cause haemotaxis – haemoattractants: ▪ haemotaxins ▪ haemotaxigens – substances, which promote the formation of haemotaxin ❑ Law on leukocytes emigration ❑ Granulocytes →monocyte → lymphocyte ❑ Sensitivity against haemotaxins diminish Emigration of leukocytes is provided by ❑ Positive haemotaxis ❑  of permeability of walls of blood vessels ❑ Retardation of blood circulation ❑ Flow of exudates The result of local inflammation ❑ Restitutio ad integrum – regeneration of died tissues and renewal of disordered function is complete ❑ Restitutio incompleta – specific tissues are replaced by connective tissues and disordered function renews only partly ❑ Forms scar. What provides all the described processes? Mediators of inflammation ❑ Substances synthesized by different cells, which impact provides development, procedure, regulation and result of all components of inflammation process ❑ Very often activity is characterised by cascade principle ❑ Classification ▪ ▪ Floating: complement system, cytokines, blood coagulation system Cellular: cytokines, eicosanoids, histamine, and other Mediators of inflammation Mediators of inflammation : 4 major groups Metabolites of lipids Cytokines Interleukins Eicosanoids Cascades of 3 soluble proteasis Complement system Interferons PAF Chemokines Growth factors Other Quinine system Blood coagulation system Nitric oxide Complement system Complex, which consists of approximately 20 blood plasma proteins (5% of blood plasma protein mass), which when activated cause lysis of different cells Inhibition of complement activation ❑ Eculizimab – monoclonal antibodies against C5, complement protein, which participate in the late stages of complement activation and launches activity of membrane attack complex (MAC) Cytokines Characteristic features of cytokines (I) ❑ Soluble mediators and regulators of immune and inflammatory reactions ❑ Act autocrine, paracrine and endocrine (systemic) ❑ Forms with interruptions and has short half-life period ❑ Have regulators of lymphocyte activation, growing and differentiation Characteristic features of cytokines (II) ❑ Form complex “net”: ❑ Different cells synthesizes similar cytokines ❑ Pleiotropy ❑ Doubling ❑ Impacts synthesis of other cytokines ❑ Synergism ❑ Antagonism Inflammatory cytokines ❑ Involved in acute inflammation (IL-1 TNF, IL-6, IL-11, IL-8, G-CSF, GM-CSF) ❑ Involved in chronic inflammation : ❑ IL-4,IL-5, IL-6,IL – 7, IL-13 – determine humoral response reactions; ❑ IL-1,IL-2,IL-3,IL-4,IL-7, IL-9,IL-10,IL-12, TNF- and , interferon's – basically determine cellular response reactions IL-1 ❑  and  forms ❑ Form mononuclear phagocytes, fibroblasts, keratinocytes, T and B lymphocytes ❑ Cause fever by activating synthesis of PGE2 in endothelium of hypothalamus blood vessels ❑ Stimulate proliferation of T lymphocytes ❑ Cause excretion of histamine from mast cells in the focus of inflammation ❑ Activity of IL-1 is depressed by IL-1 receptor antagonists IL1Ra (immune complexes, IL-4 stimulated macrophages , TNF- or GM-CSF stimulated neutrophils TNF- and  ❑ TNF- form activated macrophages, monocyte, fibroblasts, mast cells, part of T lymphocytes and NK cells ❑ Cause fever by directly inducing synthesis of PGE2 in endothelium of hypothalamus blood vessels or, indirectly by intensifying formation of IL-1 ❑ Stimulate collagenase, formation of PGE2 in synovial cells by causing damage of joints ❑ Together with IL-1 activate formation of IL-6 TNF- and  (2) ❑ TNF- activate T and B lymphocytes ❑ Induces apoptosis in tumoral cells infected by viruses ❑ TNF -  have systemic activity, especially in cases of bacterial infection (gram negative) IL-6 ❑ Are excreted by mononuclear phagocytes, T lymphocytes, fibroblasts and other ❑ Activate synthesis of acute phase proteins in liver, B lymphocyte growth factor, induces maturing in plasmatic cells. ❑ Activation and differentiation of T lymphocytes ❑ Inhibiting effects of TNF excretion (negative feedback in cases of acute inflammation) ❑ Excessive regulation of IL-6 excretion: chronic inflammation and autoimmune diseases. Effects of cytokines IFN- TNF  IFN- GM-CSF TGF- IL-1 Monocyte/ Macrophage G-CSF GM-CSF TGF- IFN- IL-1 TNF  IP-10 IL-1Ra IL-6 IL-8 RANTES MIG Interferons ❑ Are named after their antiviral effect ❑ IFN- (is produced by leucocytes) and INF- (fibroblasts), are antiviral and anti-proliferative ❑ IFN- or immune interferon, is produced by activated T lymphocytes and NK cells ❑ IFN-, INF- have common receptors on the surface of cell, IFN- - specific receptors of cell surface, stimulate many effector functions of mononuclear phagocytes Schematic action of interferons Cell Virus Cell Virus Functions of interferons ❑ Connect with cells interferons receptors ❑ Stimulate cells produce antiviral proteins ❑ Cellular ability to produce new proteins is inhibited ❑ Act with neutrophils and macrophages IFN- inducing factor (IGIF) Intensify production of IFN- more explicit than IL12 Cytokines: inhibition possibilities ❑ As cytokines have pleiotropy (effect depends on target cell, condition of receptors and activity of other cytokines), then inhibition effect may be difficult to be expected. ❑ Very important role is to inhibition possibilities of proinflammation cytokines (in the future) ❑ TNF- inhibitor: etanercept, infliximab, adalimumab,certolizumab, thalidomide ❑ IL-1 inhibitors: use IL-1ra receptor antagonist -anakinra Eicosanoids ❑ Arachidonic acid derivations ❑ Important role in pathogenesis of inflammation, cardiovascular and reproductive system diseases. ❑ Pharmacological interference in synthesis of eicosanoids (non-steroidal anti-inflammatory medicaments, cyclooxygenase -2 ( COX-2) inhibitors, leukotrienes inhibitors) allow successful treatment of such inflammatory symptoms as pain, fever Metabolism of arachidonic acid Comparison of COX-1 and COX-2 COX-1 COX-2 Manifestation Essential Induced, normally is not in many tissues, but in essential part of nervous system Tissue type Where it is In case of inflammation or in activated tissues In cell Endoplasmatic net Nuclear membrane Role Protection and maintenance of functions Pro-inflammation and mitogenic function Induces Usually is not induced Induce TNF-, IL-1, IL-2 IFN- Inhibits NSAIDs (aspirin) IL-1, IL-4,IL-10,IL-13, GK NSAIDs, COX-2 selective inhibitors Prostaglandins 3 sub-series: PG1 , PG2 , PG3, the most important PG2 Synthesis of prostaglandins , functions, pharmacological inhibition Arachidonic acid Prostacyclin COX-1 COX2 NSAIDs, COX-2 inh PGD2 Cyclooxygenase Vasodilatation Depress aggregation of PLT Synthase of prostacyclin - PGG2 endothelium COX-1 COX2 PGD2 isomerase – cerebrum, mast cells peroxydase PGH2 Synthase of thromboxane -PLT PGE2 isomerase – Thromboxane macrophages mast cells PGF2 reductase – icterus, lungs PGF2 PGE2 Thromboxane antagonists Vasoconstriction PLT activation Depress aggregation of PLT, cause contractions of smooth muscles Vasodilatation, fever, diuresis, immunomodulation hyperalgesia Contractions of smooth muscles Broncho-constriction Abortions Biosynthesis of lipoxyne Arachidonic acid 5-lipoxygenase 15-lipoxygenase 5-HPETE Peroxydase 5-lipoxygenase 15HETE 5-lipoxygenase LTA4 5-lipoxygenase 15-lipoxygenase Epoxytetraen LXA4 LXB4 Active forms of lipoxyne have anti-inflammatory effect, regulate excretion of cytokines and growth factors, as well as functions of leukotrienes Eicosanoids in inflammatory process Action Eicosanoids, which promote the given activity Vasoconstriction PGF2 , TxA2, LTC4, LTD4 , LTE4 Vasodilatation PGI2 , PGE1 , PGE2, PGD2, LXA4, LXB4, LTB4 Oedema PGE2, LTB4 , LTC4, , LTD4 , LTE4 Chemotaxis, Lei adhesion LTB4 , HETE, LXA4, LXB4 permeability of blood vessels LTC4, , LTD4 , LTE4 Pain PGE2, PGI2 , LTB4 Fever PGE2 , PGI2 , LXA4 Response reactions caused by inflammatory mediators Response reaction Inflammatory mediators Vasodilatation PGI2, PGE2, PGE1, PGD2, NO  Permeability of blood vessel wall Histamine. C3a, C5a, bradykinin, LTC4, LTD4, LTE4, PAF (thrombocyte active) substance P, calcitonin gene released peptide (CGRP) Chemotaxis and activation of leucocytes C5a, LBC4, lipoxyne LXA4, LXB4, products of bacteria Damage of tissues Lysosomal fements of neutrophils and macrophages, oxygen radicals, NO Fever IL-1, IL-6, TNF, LXA4, LXB4, LTB4 Pain PGI2, PGE2 , bradykinin, CGRP Acute inflammation ❑ Molecular and cellular interaction which is initialized by different etiological factors ❑ Damage of cell cause activation of inflammation cascade : synthesis of cytokines (IL, TNF), which  level of COX-2 and other enzymes, which cause synthesis of pro-inflammation and vasoactive eicosanoids, excretion of other inflammatory mediators. ❑ Local increased concentration of PGE2, LTB4 and other leukotrienes cause concentration of leucocytes involved in inflammation and increase of permeability of blood vessel walls, activation of neutrophil leucocytes and lymphocytes. Acute inflammation(2) ❑ Inflammatory process is controlled by: lipoxyne, COX-2, ❑ Eicosanoids participate in regeneration processes, ❑ PGE2 depress functions of T and B lymphocytes, NK cells and other Result of acute inflammation ❑ Successful – synthesis of eicosanoids alterate from proinflammation (prostaglandins) to the anti-inflammatory and pro-resolution mediators (lipoxyn, protectin, resolvin). ❑ In tissue leucocytes as well as in other cells involved in inflammation start apoptosis and they as well as other inflammatory cells are phagocyted by macrophages which leave place of inflammation by lymphatic system, the given process is promoted by IL-10, TGF. Chronic inflammation ❑ If apoptosis in inflammatory cells is not activated, inflammatory process lingers and transits into chronic inflammation. ❑ Pathologic condition, which is characterised by lingering and improper response reaction of immune system to the etiological factors of inflammation ❑ Unlike acute inflammation where the dominating role is to neutrophil leukocytes, here dominate macrophages. Chronic inflammation(2) ❑ Macrophages secret inflammatory mediators (protease, eicosanoids, collagenase, growth factors). ❑ Mediators cause damage and renewal of tissues which in the longer period of time re-modulate tissues and cause destruction of structural tissues. ❑ Persistent secretion of chemotactic factors provide migration of monocytes from blood and further transformation of them as macrophages. SIRS – systemic inflammatory reaction syndrome ❑ General syndrome, which is characteristic to systemic activation of mechanisms of hereditary immune system regardless of causative reason ❑ SIRS can be caused by local or generalised infection, trauma, thermal damage, also sterile inflammation (pancreatitis) Trauma Bacteraemia Burn Fungaemia Pancreatitis Parasitaemia SIRS SEPSIS Viraemia Other reasons Other Infection Development of SIRS ❑ Pro-inflammatory cytokines (TNF, IL-1) promote migration of inflammatory cells in the tissues, excretion of other cytokines, eicosanoids, FR of oxygen, activation of adhesion molecules. ❑ Extremely large activity cause changes also in tissues which are not impacted by inflammation ❑ CARS (compensatory anti-inflammatory response) – diminish manifestation of inflammation and renew homeostasis of organism Development of SIRS (2) ❑ CARS participate in IL-10, MIF- macrophage migration inhibiting factor, cholinergic anti-inflammatory reaction (depress synthesis of macrophage cytokines), anergy of lymphocytes (synthesis of Th1 cytokines ) ❑ In norm in the focus of inflammation dominate proinflammatory reactions (mediators), but systemic – antiinflammatory mechanisms ❑ In case of SIRS observe insufficiency of CARS, which is connected with deficiency of normalisation of proinflammatory process Clinical criteria of SIRS ❑ Fever (>380C) ❑ Increased heart rate (> 90 beat/min) ❑ Tachypnoea (>20 breath/min) ❑ Leuokcytosis (> 12000 in 1 mm3 of blood) ❑ If we have only 2 criteria from 4 - it is acute phase response. SIRS and sepsis - criterions 4 clinical criterions of SIRS plus: ▪ Altered mental state ▪ Hypoglycaemia. Systemic effects of cytokines ❑ Induce muscle cells (breakdown!) ❑ Anorexia (loss of appetite) ❑ Lethargy ❑ Malaise ❑ Weakness catabolism Changes in blood test in case of inflammation ❑ Leucocytosis ❑ Shift of neutrophil leucocytes to the left (of amount of new forms or neutrophil leucocytes) ❑ Increase of ESR (aggregation of erythrocytes + changes of contents of blood proteins) ❑  of albumin/globulin coefficient Changes in blood test in case of inflammation ❑ Acute phase proteins (that can be routinely assessed): ❑ CRP - it is considered, that it eliminates product of bacteria by activating alternative way of complement; ❑ fibrinogen (10-fold over baseline); ❑ von Willebrand factor (2-3- fold over baseline). ❑ Procalcitonin – amount correlates with level of proinflammatory cytokines (more higher in case bacterial infection) ❑ TNF, IL-1, IL-6 level , other immunological markers Rīga Stradiņš University Department of Pathology 2022/2023 PATHOLOGY OF THERMOREGULATION Liga Vidusa, Polina Viktorova Ilze Strumfa, Dainis Balodis Pathology of thermoregulation: Contents Revision of physiology Pathology of thermoregulation:  Fever  Set-point change pathway  Clinical signs of stages  Positive and potential negative effects  Cryogens  Hyperthermia  Main clinical forms  Hypothermia  Systemic hypothermia  Artificial hypothermia  Frostbite  Thermoregulation: the definition and normal temperature   Thermoregulation is a process that maintains the body’s core temperature at a constant level, regardless of changes in ambient temperature; The average normal  oral body temperature taken in mid-morning is ~ 36.7°C (36–37.4°C);  rectal or vaginal temperature is 0.5°C higher than the oral temperature;  axillary temperature is 0.5°C lower;  normal diurnal temperature variation is ~1°C. Normal Body Temperature  For healthy individuals 18 to 40 years of age, the mean oral temperature is 36.8° ± 0.4°C  Low levels occur at 6 A.M. and higher levels at 4 to 6 P.M.  The maximum normal oral temperature is 37.2°C at 6 A.M. and 37.7°C at 4 P.M.  These values define the 99% for healthy individuals. Mackowiak, et al., JAMA 1992;268:1578 Core temperature     The core temperature of the human body is 37°C The core of the human body includes the organs of the thorax, abdomen and the head - where the vital organs are located Their enzyme systems must operate in optimal conditions The periphery of the body can withstand some deviation from the core temperature Thermoregulation  To ensure thermoragulation, the balance between heat gain and heat loss by the body is necessary  Metabolic processes produce heat, which must be dissipated  The main kinds of thermoregulation:  Chemical  Physical Chemical thermoregulation    Regulates the heat production (muscles, liver, gut) Is phylogenetically older and more persistent Heat-gain can be achieved as a byproduct of metabolism, contractions of muscle tissue, thermogenesis in brown adipose tissue for neonates Heat production     0,550C increase in body temperature for 7% increase in metabolism Increased production of epinehrine and norepinephrine shifts body metabolism to heat production rather than energy generation Increased level of thyroid hormone → ↑cellular metabolism and heat production (needs 2 weeks for max effects) Shivering – initiated by impulses of hypothalamus and ↑heat production by muscles Physical thermoregulation    Regulates the loss of heat by evaporation, conduction, radiation, convection, perspiratio insensibilis (see the next slide for explanations) Phylogeneticaly newer Heat-loss can be achieved through skin and mucosae, therefore it canbe halted by sympathetically driven skin vasoconstriction and piloerection Heat loss     Radiation – heat radiates from the surface of the body to objects when they are cooler than skin. Conduction – transfer of heat from the skin to cooler air or a cooler object in contact with body Convection – the warmed air moves away from the body by natural convection (heated air rises) or by wind. Evaporation – the water lost from skin surface by diffusion (perspiratio insensibilis) and by neuronactivated sweat glands Revision of physiology  Peripheral thermoreceptors detect environmental and visceral temperatures and report these to the hypothalamus. The thermoregulatory center initiates heat-loss or heatgain responses in effector organs; Figure replicated from Wang, H.; Siemens, J. DOI:10.1080/23328940.2015.1040604 under Creative Commons license, no changes mad e. The system of thermoregulation consists of:  Thermosensors – peripheral (skin, skeletal muscles) and central (core)- spinal cord and CNS  The centre of thermoregulation – hypothalamus  Sympathetic NS mediation:  Sweating, thyroid and adrenal gland production (cholinergic)  The blood flow in the skin and in the organs (1adrenergic)  Child’s thermogenesis - the brown fat - heat production without shivering (3-adrenergic)  Somatic NS  trembling of muscles - cholinergic (segments C6 –TH1 of spinal cord) – heat production by shivering Peripheral (shell) thermosensors (skin) Central (core) thermosensors (CNS) Hypothalamus Somatic nervous system Sympathetic nervous system Cholinergic Alfa1 -adrenergic Beta3-adrenergic Cholinergic Blood vessels Brown fat (non shivering) Skeletal muscles (shivering) Sweat glands Adrenal gland Thyroid gland Fever (febris)  Represents an increase in body temperature that results from a cytokine-induced increase in the set-point of the thermostatic centre in the hypothalamus  Fever is a non-specific response that is mediated by endogenous pyrogens released from host cells in response to infectious or non-infectious disorders. Pyrogens    Pyrogens are exogenous (bacterial products, toxins, whole microorganisms) or endogenous (pyrogenic cytokines – IL1,IL6,TNF) substances that initiate fever. Prostaglandin E2 (PGE2 ) is the final fever mediator in the hypothalamus, induced by cytokines. PGE2 induces changes in the set-point through the second messenger cAMP; hypothalamus initiates shivering and vasoconstriction Pyrogenic cytokines   IL-1 initiates fever, but systemic activity is higher: induces hypotension, increased level of GK, glucose, CRP, ACTH and TSH, but decreased level of testosterone IL-6 – strong pyrogen (apr.50-100 times stronger like IL1β).  Release is activated by IL-1 and TNF-α  Fever induced by IL-6 can be reduced by using COX- inhibitor – e.g., ibuprophen.  In peripheral tissues is not a pro-inflammatory cytokine.  In the brain IL-6 activates COX-3 and increases synthesis of PgE2 (paracetamol effect on temperature, but no effect on COX-2)  TNF-α induces fever by activation of IL-1, which is more effective pyrogen. Causes of fever (classification of fever by the cause)  Infectious   Viral Bacterial Fungi Protozoa          Non-infectious Myocardial infarction Leukemia Neurogenic Surgery Drug-related Allergic Fever Fever is caused by direct or indirect stimulation of prostaglandin E2 (PGE2) production (wh