Cytokines and Inflammation

• Cytokines - part II

Case Scenario

• Ellie (55) is being treated for kidney cancer that has spread.
• Her treatment includes a drug based on interleukin 2 (IL-2) known as aldesleukin.
• Aldesleukin is an immunotherapy drug with the brand name Proleukin.

Inflammatory Cytokines – Definition

• Inflammation is mediated by soluble factors, including secreted polypeptides known as cytokines.
• Inflammatory cytokines can be divided into acute inflammation and chronic inflammation.
• Inflammation is the response of tissue to injury.
• Acute phase inflammation is characterized by increased blood flow, vascular permeability, accumulation of fluid and leukocytes, and inflammatory mediators like cytokines.

Inflammatory Cytokines

• Cytokines mediate acute inflammatory reactions, including IL-1, TNF-a, IL-6, IL-11, IL-8, chemokines, G-CSF, and GM-CSF.
• Cytokines mediate chronic inflammatory processes in humoral inflammation, such as IL-3, IL-4, IL-5, IL-6, IL-7, IL-9, IL-10, IL-13, and transforming growth factor-b (TGF-b).
• Cytokines that contribute to cellular inflammation include IL-1, IL-2, IL-3, IL-4, IL-7, IL-9, IL-10, IL-12, interferons (IFNs), IFN-g-inducing factor (IGIF), TGF-b, TNF-a, and TNF-b.

Proinflammatory Cytokines

• Inflammatory abnormalities are a group of disorders underlying various human diseases.
• Cytokines regulate host responses to infection, immune responses, inflammation, and trauma.
• A proinflammatory cytokine promotes systemic inflammation.
• IL-1 and TNF alpha, (Interleukin (IL)-1 and tumor necrosis factor (TNF)) are examples.
• A proinflammatory cytokine is secreted from immune cells, such as helper T cells (Th) and macrophages and other cell types to promote inflammation.

Proinflammatory Cytokines

• Proinflammatory cytokines produce fever, inflammation, and tissue destruction.
• Biological activities of IL-1 and TNF are reduced by neutralizing antibodies, soluble receptors, receptor antagonists, and inhibitors of proteases that convert inactive precursors to active, mature molecules.
• Blocking IL-1 or TNF is successful in patients with rheumatoid arthritis, inflammatory bowel disease, and graft-vs-host disease.

Anti-Inflammatory Cytokines

• Anti-inflammatory cytokines are immunoregulatory molecules controlling the proinflammatory cytokine response.
• They act in concert with specific cytokine inhibitors and soluble cytokine receptors to regulate the immune response.
• Major anti-inflammatory cytokines include interleukin (IL)-1 receptor antagonist, IL-10, IL-11, IL-13, IL-4, and IL-6.
• Specific cytokine receptors for IL-1, tumor necrosis factor-alpha, and IL-18 function as proinflammatory cytokine inhibitors.

Cytokine Regulation

• Activation by cytokines is antigen-non-specific and must be regulated to avoid inappropriate responses.
• Cytokine action is regulated by transient production in response to antigens or inflammatory stimuli, short half-life in extracellular fluids, and restricted receptor expression profiles on activated and unactivated target cells.
• Cytokine dysregulation examples include the role of tumor necrosis factor alpha (TNFa) in developing rheumatoid arthritis.
• Blockade of TNF’s effect can be achieved through administration of recombinant soluble TNF-receptor or anti-TNF blocking antibody.

Cytokines in Acute Inflammatory Disease

• Cytokines play functions in mediating acute inflammatory reactions, namely IL-1, TNFα, IL-6, IL-11, IL-8, G-CSF, and GM-CSF.
• Leukocyte migration from peripheral blood to extravascular sites is key in the inflammatory response.
• TNFa is secreted by immune and parenchymal cells at inflammatory sites.
• TNFa promotes immune cell extravasation by activating endothelial cells to express adhesion molecules for immune cells.
• TNFa induces the expression of other inflammatory cytokines and chemokines.
• TNFa and IL-1 share pro-inflammatory properties, inducing fever by stimulating PGE2 synthesis in the hypothalamus or inducing release of IL-1.

Cytokines in Acute Inflammatory Disease

• The IL-1 family includes IL-1a and IL-1β, primarily produced by mononuclear phagocytes, fibroblasts, keratinocytes, and T and B lymphocytes.
• Like TNFa, IL-1 plays a function in inflammation.
• IL-1a and IL-1ẞ can trigger fever by enhancing prostaglandin E2 (PGE2) synthesis by the vascular endothelium in the hypothalamus and stimulate T cell proliferation.
• IL-1 elicits histamine release from mast cells at the inflammation site, triggering early vasodilation and increased vascular permeability.
• Neutrophil infiltration into inflammatory sites is one of acute inflammation's hallmarks.
• Local chemotactic factors mediate the sequence of events leading to infiltration at inflammatory sites.
• IL-8 is produced during inflammation and promotes neutrophil chemotaxis to the injury site.

Cytokine Storm

• Cytokines are involved in producing symptoms of infection like fever, inflammation, runny nose and aches/pains.
• Cytokine production can grow out of control.
• Immune cells release cytokines to produce more immune cells, leading to more pro-inflammatory cytokines.
• This positive feedback loop of cytokine creation can lead to a "cytokine storm.”
• A cytokine storm is an over-activation of immune cells, and over-production of their activating compounds.
• Can damage organs, especially the lungs and kidneys, and even lead to death.
• Severe cases of flu (suspected to be the main cause of death in the 1918 "Spanish Flu” pandemic) and sepsis are examples.

Chronic Inflammatory Disease

• Chronic inflammatory disease has persistent inflammation.
• Patients develop chronic inflammatory disease due to the immune system’s inappropriate response to external stimuli.
• Chronic inflammation causes tissue damage, a progressive shift in cell types, and simultaneous tissue destruction and healing.
• Examples of inflammatory diseases that become chronic: celiac disease, vasculitis, lupus, chronic obstructive pulmonary disease (COPD), irritable bowel disease, atherosclerosis, arthritis, and psoriasis.

Chronic Inflammatory Disease

• Several cytokines are key in mediating chronic inflammatory reactions, including IL3, IL6, TNFẞ, IL4, IL5, IL7, IL9, IL10, IL13, IL14, and IFN.
• IL6 is produced at the inflammation site.
• IL-6 mediates acute phase responses at acute inflammation onset.
• When its activity as a pro-inflammatory cytokine persists, acute inflammation turns into chronic inflammation.
• In chronic inflammation, IL-6 promotes mononuclear cell accumulation at the injury site through continuous MCP-1 secretion, angioproliferation, and anti-apoptotic functions on T cells.
• Continuos expression of IL-6 increases serum levels and it amplifies chronic inflammatory proliferation.
• Plasmacytosis and hyperplasia of synovial cells in the joints of patients with rheumatoid arthritis (RA) are the product of chronic inflammatory proliferation.

Cytokine Inhibitor Drugs

• One aspect of cytokine inhibitor drugs include the:
  • Reduction of cytokine producing cells.
  • This decreases number of cytokine producing cells and inhibits cytokine synthesis.
  • An example is methotrexate - Inhibits activation of T cells, rheumatoid arthritis, PH3113
• Some drugs do not affect viability of cells. Cytokine synthesis can be inhibited without affecting viability of cells.
  • An example is glucocorticoids (e.g., prednisone), which acts as an anti-inflammatory or immunosuppressive by inhibiting interleukin-1, tumor necrosis factor or interleukin-2.
• Monoclonal antibody against cytokines also inhibit function.
  • Infliximab is an example of an antibody directed against TNFa (tumor necrosis factor) for autoimmune disorders.

Therapeutic Uses of Cytokine Blocking Antibodies

• Anti-cytokine antibodies benefit autoimmune diseases and transplant rejection.
  • Anti-TNF-a can treat Rheumatoid Arthritis.
  • Anti-IL-2R can treat Graft rejection
  • Anti-Il-6 antibodies can treat Rheumatoid arthritis and Covid-19.

Cytokine-Based Drugs

• Cytokine-based drugs stimulate the immune response.
• Erythropoietin (EPO) is used to treat anemia.
• Granulocyte colony-stimulating factor (G-CSF) is used to treat neutropenia in cancer patients.
• Interferon alpha (INF-a) is used to treat hepatitis C and multiple sclerosis.
• Interferon beta (INF-b) treats multiple sclerosis.
• Interleukin 11 (IL-11) treats thrombocytopenia in cancer patients.
• Interleukin 2 (IL-2), also known as Aldesleukin, treats cancer.

Therapeutic Uses of Cytokines - Overview

• INT is a therapeutic drug for treating viral diseases, and cancer.
• IL-2, INF-g and TNF-a can enhance T cell activation in immunodeficiency.
• II-2 can treat T-cell proliferation causing Cancer
• GM-CSF induces an increase in leukocyte blood count.
  • It is used to restore leukocyte count after cytotoxic chemotherapy
  • It is also used after bone marrow transplantation to correct AIDS-associated leukopenia

Case Scenario: Aldesleukin

• Aldesleukin is very similar to the cytokine interleukin-2 (IL-2).
• Interleukin-2 is part of the body’s immune system.
• The body normally produces IL-2 which is secreted by T cells, to stimulate growth and differentiation of the T cell response.
• Aldesleukin works by:
  • Induction the enhancement of lymphocyte mitogenesis and stimulation of long-term growth of human interleukin-2 dependent cell lines.
  • Enhancement of lymphocyte cytotoxicity, the induction of killer cell (lymphokine-activated (LAK) and natural (NK)) activity
  • Induction of interferon-gamma production.

Mechanism of Action

• Aldesleukin (high-dose II-2) binds to the IL-2 receptor; this leads to heterodimerization of the cytoplasmic domains of the IL-2R beta and gamma(c) chains.
• Activation of the tyrosine kinase Jak3, and phosphorylation of tyrosine residues on the IL-2R beta chain.
• These events lead to the creation of an activated IL-2R receptor complex.
• IL-2R signalling triggers three distinct pathways.
• These events stimulate growth and differentiation of II-2 dependent T cells.