Chemical Mediators
When injury occur in any part of the body, some chemicals are released in response to acute inflammation from injured area. These chemicals then spread to uninjured area cause immediate transient i.e cause vasodilation, chemotaxis, emigration of neutrophils and increase vascular permeability. These chemicals are called as chemical mediators.
Example of chemical mediators
Some chemicals that are released from injured cells during acute inflammation are listed below:
1. Histamine.
A well-known chemical mediator so far identified is histamine. It is stored in mast cells, basophils, leukocyte and platelets. It causes vascular dilation and release in response to complement system and lysosomal proteins released from neutrophils.
2. Lysosomal compounds
These are positively charged proteins released from neutrophils. It activates complement system and cause vascular permeability.
3. Prostaglandins
These are derived lipids consist of long-chain fatty acids derived from arachidonic acid by the action of cyclooxygenase isoenzymes. It is a family of naturally occurring cyclopentane conatin carboxylic acid of varying degree of unsaturation. These chemicals are potent mediators that cause increased blood flow, chemotaxis (chemical signals that summon white blood cells), and subsequent dysfunction of tissues and organs.
4. Leukotrienes
These are also derivatives of arachidonic acid in neutrophils and possess vasoactive properties. slow reacting substance of anaphylaxis (SRS-A), involved in type I hypersensitivity, is a mixture of leukotrienes. 5-hydroxytryptamine (serotonin). This is present in high concentration in mast cells and platelets. It is a potent vasoconstrictor.
5. Lymphokines
These compounds posses the property of vasoactive or chemotactic attributes.
Plasma factors.
Plasma is composed of:
1. Enzymatic cascade systems complement
2. The kinins
3. Coagulation factors, and
4. Fibrinolytic system
All these are interrelated and produce various inflammatory mediators.
6. Complement system
It is a cascade of enzymatic cascade composed of nine different protein complexes. In necrotic cells enzymes are released from dying cells that activate complement system. However, when infection occurs, and the formation of antigen-antibody complexes establishes it lead to the activation of complement system. Similarly, exogenous pyrogens also activate complement system.
