CHEMICAL MEDIATORS OF INFLAMMATION: HISTAMINE &SEROTONIN
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This document discusses mediators of inflammation, specifically histamine and serotonin. It notes that mediators can be produced locally by cells or derived from plasma, and act to initiate, regulate and sustain inflammatory reactions. Histamine and serotonin are classified as vasoactive amines that are among the first mediators released during inflammation. Histamine is derived from the amino acid histidine and is stored in mast cells, basophils and platelets. It acts to increase vascular permeability and vasodilation, causing wheal and flare reactions, itching, pain and bronchial asthma. Serotonin has similar but less potent actions than histamine and is stored in platelets and mast cells. Both mediators play important roles in initiating and regulating
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CHEMICAL MEDIATORS OF INFLAMMATION: HISTAMINE &SEROTONIN
- 2. MEDIATORS OF INFLAMMATION Histamine & Serotonin
- 3. Overview • General Properties • Types of mediators • Histamine and Serotonin
- 4. Mediators of inflammation These are the substances that INITIATE REGULATE& Inflammatory reactions
- 5. General properties These mediators can be produced Locally, by the CELLS Derived from inactive precursors present in plasma CELL- DERIVED PLASMA -DERIVED Preformed/ Ready made! Synthesised de novo/ made if needed! 1
- 6. They can be produced only in response to agents that stimulate inflammation They can stimulate the release of another mediator They have short lifespan! They can act on wide variety of cells 2 3 4 5
- 7. Preformed Synthesised de novo • Histamine • Serotonin • Arachidonic acid metabolites • Platelet activating factor • NO • Reactive oxygen species • Cytokines • Chemokines Compliment activation Factor XII activation • C3a • C3b • C5a • Coagulation system • Kinin system Cell - Derived Plasma - Derived CHEMICAL MEDIATORS OF INFLAMMATION
- 8. HISTAMINE & SERATONIN Vasoactive amines Are the first mediators to be released during inflammation Once formed it can be either stored or rapidly inactivated Derived from the decarboxylation of the amino acid histidine
- 9. Sources Mast cells Basophils Platelets Stimulus Substances inducing inflammation like heat,cold, irradiation,trauma etc C3a & C5a: Anaphylatoxins IL-1 & IL8. Histamine releasing factors from cells like neutrophils, monocytes and Platelets.
- 10. ACTIONS Increase in Vascular permeability By Increasing Blood Flow and Endothelial Barrier Disruption Vasodilatation It is responsible for the Wheal & Flare reaction in the skin. Responsible for itching and pain Also mediates bronchial Asthma and anaphylactic shock Resulting from nitric oxide release Contraction of extravascular smooth muscles eg:bronchus By the excitation of a subset of unmyelinated C-fibers which are pruriceptive.
- 11. SEROTONIN 5- Hydroxytryptamine Stored in platelets and mast cells Also in chromaffin cells of GIT, spleen and nervous tissue Actions are similar to Histamine but less potent.
- 12. Summary • General Properties • Types of mediators • Histamine and Serotonin
Editor's Notes
- In bronchial asthma , it results in smooth muscle contraction of bronchioles increased mucus secretion and increases the synthesis of eotaxin Massive release of histamine can result in circulatory collapse ( anyphalyctic shock) ie hypotension, tachycardia and shock. Wheal- red swollen mark, due to increased vascular permeability… Flare
- In bronchial asthma , it results in smooth muscle contraction of bronchioles increased mucus secretion and increases the synthesis of eotaxin Massive release of histamine can result in circulatory collapse ( anyphalyctic shock) ie hypotension, tachycardia and shock.