Intracellular Accumulations

• One manifestation of metabolic pathology is the accumulation of abnormal amounts of various substances.

Objectives for Study

• Overview of intracellular accumulations.
• Details about the accumulation of lipids.
• Details about the accumulation of cholesterol.
• Details about the accumulation of proteins.
• Details about the accumulation of glycogen.
• Information about the accumulation of different types of pigments.
• Pathologic calcification.

Overview

• Cells may accumulate abnormal amounts of various substances under certain circumstances.
• These accumulations can be harmless (reversible) or toxic (irreversible), potentially leading to cell injury.
• Substances can be found in the cytoplasm, within organelles (lysosomes), or in the nucleus.
• The substances originate from synthesis by affected cells, or are produced elsewhere.
• Normal cellular constituents like lipids, proteins, carbohydrates, and water can accumulate in excess.

Pathways of Accumulation

• There may be a normal or increased rate of production of normal substances, but the metabolic rate is inadequate for removal, an example being fatty changes in the liver.
• Genetic or acquired defects in folding, packaging, transport, or secretion can result in a normal or abnormal endogenous substance accumulating, such as in α-1 antitrypsin deficiency.
• α-1 antitrypsin accumulation in the liver can cause liver cirrhosis.
• A failure to degrade a metabolite can result due to an inherited defect in an enzyme, known as storage diseases.
• Abnormal exogenous substances can deposit and accumulate when the cell lacks the enzymatic machinery or the ability to transport them, such as with carbon or silica particles.

Exogenous Substances

• Examples include carbon, silica, viral inclusions, heavy metals (silver, gold, lead), pigments, and urate (uric acid).
• Macroscopic color (anthracosis) and microscopic analysis (Russell bodies) can detect them.
• Staining characteristics include:
  • Pearls Prussian Blue (iron).
  • PAS staining.
• Other detection methods include immunohistochemistry and biochemical/biophysical determinations (melanin, homogentisic acid).

Accumulation of Lipids: Fatty Change (Steatosis)

• Fatty change refers to any abnormal accumulation of triglycerides within parenchymal cells and it typically occurs in the liver, but can also occur in the heart, skeletal muscles, kidney, and other organs.
• Intracellular accumulations of lipids includes: - Liver, Heart, Pancreas, Muscles, Kidneys (eg. Tg), Cholesterol/Cholesterol Ester, Phospholipids

Causes of Fatty Change

• Toxins, especially alcohol abuse.
• Diabetes mellitus.
• Protein malnutrition or starvation.
• Obesity.
• Anoxia.
• Carbon tetrachloride.

Lipid Accumulation Mechanisms

• Hepatotoxins (e.g., alcohol) disrupt mitochondria and the smooth endoplasmic reticulum (SER), causing anoxia.
• Starvation increases adipose tissue mobilization, particularly triglycerides.
• Defects in uptake, catabolism, or secretion steps can lead to lipid accumulation.
• CCl4 and protein malnutrition can also lead to lipid accumulation.

Significance of Fatty Change

• Depends on the cause and severity of the accumulation.
• Mild cases may have no effect on cellular function.
• Severe fatty change may transiently impair cellular function.
• In severe forms, it can precede cell death and may be an early lesion in nonalcoholic steatohepatitis.

Fatty Liver Prognosis

• Mild cases have a benign natural history, with approximately 3% developing cirrhosis.
• Moderate to severe cases can develop inflammation and degeneration in hepatocytes, with +/- fibrosis; 30% develop cirrhosis.
• The 5 to 10 year survival rates are 67% and 59%, respectively.

Other Fatty Liver Condition

• Anoxia inhibits FA oxidation, which can cause anemia
• PCM - Starvation increase adipose tissue mobilization particularly Tg
• Acute Fatty liver of pregnancy & Reyes syndrome are rare fatal conditions
• Acute Fatty liver of pregnancy and Reyes syndrome are rare fatal conditions

Identifing Fatty Change

• In Frozen section = Sudan iv and Oil-Red O tests can be performed - The colour is orange-red
• Glycogen = PAS positive and Best carmine positive
• Water = If neither test stains, sample is assumed to water

Detecting Lipids

• Heart :alternate bands of yellow and brown myocardium (tiggered effect ) also seen in anaemia and anoxia
• Fat infiltration is also seen in pancreas

Morphology of Fatty Change

• The most common sites are the liver and heart.
• With increasing accumulation, the organ enlarges, becomes progressively yellow, soft, and greasy.
• Early changes show small fat vacuoles in the cytoplasm around the nucleus under light microscopy
• In later stages, vacuoles coalesce, creating cleared spaces that displace the nucleus to the cell periphery, and contiguous cells may rupture (fatty cysts).
• Fatty change is reversible unless a vital intracellular process is irreversibly impaired, such as in CCl4 poisoning.

Accumulation of Cholesterol and Cholesteryl Esters

• Cellular cholesterol metabolism is tightly regulated to ensure normal cell membrane synthesis without significant intracellular accumulation.
• The macrophages may be filled with minute, membrane-bound vacuoles of lipid, imparting a foamy appearance to their cytoplasm (foam cells).
• Atherosclerotic plaques their characteristic yellow color helps with pathenogenesis.
• Hereditary & acquired hyperlipidemic syndromes causes macrophages accumulate intracellular cholesterol
• Xanthomas: clusters of foamy macrophages present in the subepithelial connective tissue of skin or in tendons.
• Several different pathologic processes:
  • Macrophages in contact with the lipid debris of necrotic cells
  • Abnormal (e.g., oxidized) forms of lipoproteins can contribute to accumulation.

Accumulation of Proteins

• Morphologically visible protein accumulations are less common than lipid accumulations.
• They occur because excesses are presented to the cells or because the cells synthesize excessive amounts.
• Nephrotic syndrome causes the kidney to filters small amounts of albumin through the glomerulus, and they are normally reabsorbed by pinocytosis in the proximal convoluted tubules.
• Protein leakage and pinocytic vesicles, containing said protein, fuse with lysosomes
• Heavy protein leakage results in histologic appearance of pink, hyaline cytoplasmic droplets.
• If proteinuria stops, the droplets are are metabolized and disappear
• Marked accumulation of newly synthesized immunoglobulins occurs in the RER of some plasma cells which forms rounded, eosinophilic Russell bodies.
• Mallory body, or "alcoholic hyalin," is an eosinophilic cytoplasmic inclusion in liver cells that is highly characteristic of alcoholic liver disease.
  • Mallory Body inclusions are composed predominantly of aggregated intermediate filaments
• The neurofibrillary tangle (found in brains with Alzheimer's) is an aggregated protein inclusion that contains microtubule-associated proteins.

Diseases & Syndromes and Protein Accumulation

• Ehlers-Danlos syndrome.
• Marfan’s syndrome.
• Osteogenesis imperfecta.

Accumulation of Glycogen

• Associated with abnormalities in the metabolism of either glucose or glycogen.
• Causes poorly controlled diabetes mellitus which accumulates in: -renal tubular epithelium. -cardiac myocytes. -β cells of the islets of Langerhans.
• Glycogen accumulates within cells in a group of closely related genetic disorders collectively known as glycogen storage diseases, -glycogenoses.
  • Tay- Sach’s disease
  • Niemman-Pick’s disease
  • Gaucher’s disease
• Glycogen accumulation causes:
  • enzymatic defects that cause injury & cell deal
  • defects in the synthesis or breakdown of glycogen

Identifying Glycogen

• intracellular droplets of glycogen/glucose metabolism
• Clear vacuoles in cytoplasm
• Best fixed in absolute alcohol
• Stained by PAS and Best-carmine tests

Accumulation of Pigments

• Pigments are colored substances that are categorized as either exogenous (coming from outside the body) or endogenous (synthesized within the body itself).

Exogenous Pigment

• The most common is carbon, is phagocytosed by alveolar macrophages when inhaled.
• Following inhalation, it is transported through lymphatic channels to the regional tracheobronchial lymph nodes.
• Aggregates of the pigment blacken the draining lymph nodes and pulmonary parenchyma (anthracosis) and heavy accumulations may induce emphysema or a fibroblastic reaction that can result in coal workers' pneumoconiosis.
• Asbestos bodies are also a type of exogenous pigment.

Endogenous Pigment

• Includes lipofuscin, melanin, and certain derivatives of hemoglobin.

Melanin

• A brown-black pigment produced in melanocytes which can accumulate into adjacent basal keratinocytes.
• Melanomas are skin related conditions

Melanin Production

• Tyrosine can turn into DOPA which then turns into melanin.
• Melanin protects skin from UV-light of sun
• Increased melanin examples:
• Melanoma
• Nevi
• Addisons disease (adrenocortical insufficiency)
• There is loss of adrenocortical hormone which causes a loss of feed back control of ACTH secretion

Hormones & Melanin

• ACTH stimulates melanin production and MSH → ACTH → Melanin
• Lack of melanin can causes Albinism

Alkaptonuria

• Phenylalanine and tyrosine metabolism a condition with a defect due to deficiency of Homogentisic acid oxidase
• Homogentisic acid (methyl acetoacetic acid) increases in the tissues which then causeOchronosis which affects the connective tissue, cartilage and skin

Lipofuscin

• Also known as wear-and-tear pigment or lipochrome.
• It is an insoluble brownish-yellow granular intracellular material seen in a variety of tissues (heart, liver, and brain).
• Has a function of age or atrophy.
• Consists of complexes of lipid and protein and can derive from the free radical-catalyzed peroxidation of polyunsaturated lipids of subcellular membranes.
• Lipofuscin is not injurious to the cell, however important as a marker of past free-radical injury.
• The brown pigment has characteristics can impart an appearance to tissues, known as brown atrophy.
• Insoluble pigment has several mixtures: lipids, Phospholipids and Proteins
• Occurrences:Seen in aging patients, severe malnutrition, cancer cachexia and are Observed in heart, liver, brain

Testing for Lipofuscin

• Test pigment appears as perinuclear electron-dense granules during electron microscopy

Iron Containing Pigments

• A type of Haemoproteins that include Haemoglobin and Porphyrins
• Hb – Increased absorption caused by :
• alcohol
• Vit-C
• Fructose

Factors That Effect Absorption

• Decreased absorption- phytates - phosphates can causes issues with calcium and achlohydria
• Knowledge causes: uptake, metabolism, excretion and storage
• Haemosiderin is and is golden yellow to brown which causes:
  • Haemorrhage - Bruising
    • Blood transfusion
• Seen in heart and spleen as heart failure cells
• Haemosiderosis increases in:
• Fe absorption
• Impaired Fe utilization
• Haemolytic anaemias
• Multiple transfusions
• Haemochromatosis:– caused by Uncotrollable Fe absorption
• Autosomal recessive genetic defect in chromosome 6 Affects:
• Liver cirrhosis
• Carcinoma
• Pancreas - DM
• Carcinoma *Skin – Bronze colour
• Heart → CCF
• Pearls Prussian blue positive

Other Iron Related Pigments

• Haematin causes Brown Black pigment in cytoplasm or Reticuloendothelial cells while associated with with Malaria with Haemolytic crisis as causes Incompatible BT
• Bilirubin can happen while:
• Non-iron yellow pigment
• Haemolytic jaundice
• Primary RBC membrane defect affects
• Autoimmune reaction infections
• severe poisons

Jaundice Subtypes

• Obstructive jaundice and Hepatocellular jaundice are related to glucuronyl-tranferase deficiency's affects to:
  • Glilberts disease
  • Cirgler-Najjer syndrome
• Accumulation of Iron ions of hemoglobin accumulates as golden-yellow hemosiderin, test uses Prussian blue histochemical reaction

Calcium & Disease

• Calcium – that can affect:

Dystophic

   -Dead tissue type

Metastatic

  - hypercalcemic states affect :
    -Hyperparathyroidism
    -Cancer
    -Vit-D toxicity

• Kidney damage affect lead/silver and Uric acid &carrots can affects:
• Purine metabolism and GOUT

Pathologic Calcifications

• dystrophic deposition of calcium and other minerals in injured tissue, includes: (e.g.,atheroma in blood vessels, heart valves in elderly individuals, old tuberculous lesions) with affects normal tissues in hypercalcemic states

Other Inclusions that Occur

• Black hairy tongue due to smoking causes:
• Foods,drinks
• Tropical medicaments
• Betel nuts
• Antibiotics
• FB eg amalgam _ Other inclusions-
• Viral inclusions:
  • Negri bodies ( Rabies) causes: cytoplasm
  • CMV & Herpes simplex _ Other inclusions continues-
• COPPER-Wilson’s disease can turn into Rhodamine caused by Rubeanic acid
• Formalin pigment &Fillamentous inclusions (intermediatefillaments)
• Mallorys –liver cirrhosis and Wilson’s disease

Fibrous Inclusions

• *Cytokeratin filaments - bronchial and trachea - caused by epithelium which happens if: - vit-E deficiency - Grisofulvin - Colchicin - Smoking
• *Enzymes from *Amyloid congored with *Enviromental/occupational factor causes: Acquired Addisons disease and HIV infection -Pulmonary Bronchogenic carcinoma (ACTH)
  • Neurofibromatosis Polyostotic fibrous dysplasia -Lichen planus
• Syndromes affects: Peutz-Jegher’s and Idiopathic oral melanosis