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
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
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.
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.