Chapter 3: Acute Inflammation II Flashcards
What are the four most important mediators of acute inflammation?
1) vasoactive amines 2) lipid products (prostaglandins and leukotrienes) 3) cytokines 4) products of complement activation
what are the two major vasoactive amines?
histamine and serotonin
what are the first mediators to be released during inflammation?
histamine and serotonin
what is the richest source of histamine/ where is histamine stored?
in mast cell granules
how is histamine released from mast cells?
released by mast cell degranulation in response to to a variety of stimuli
what are the different stimuli that can cause release of histamine by mast cell degranulation?
1) physical injury (such as trauma), cold and heat 2) binding of antigen to IgE antibodies displayed on the surfaces of mast cells (hypersensitivity reactions and skin testing) 3) products of complement called anaphylatoxins
what is the function of histamine?
it causes dilation of the arterioles (smooth muscle) and increases the permeability of venules
what is histamine considered to be?
the principal mediator of the immediate transient phase of increased vascular permeability
How are the vasoactive effects of histamine mediated?
mainly via binding to receptors on microvascular endothelial cells
what are the lipid mediators and what are the produced from?
prostaglandins and leukotrienes –> produced from arachidonic acid
when do we produce arachidonic acid?
when you break down cell membranes by phospholipases
what are the two main “arms” of arachidonic acid?
cyclooxygenase and 5-Lipoxygenase
what does cyclooxygenase lead to?
prostaglandin G2, Prostaglandin H2, prostacyclin PGI2, Thromboxane A2, and PGD2/PGE2
what is the effect of prostacyclin/ PGI2?
it causes vasodilation and inhibits platelet aggregation
what is the effect of thromboxane A2?
it causes vasoconstriction and promotes platelet aggregation
what is the effect of PGD2/ PGE2?
it causes vasodilation, increased vascular permeability, and leukocyte chemotaxis
How can you inhibit the cyclooxygenases?
using a COX-1 and COX-2 inhibitor, aspirin, or indomethacin
what comes from 5-Lipoxygenase?
5-HPETE, Leukotriene C4, Leukotriene D4, and Leukotriene E4
What does 5-HPETE lead to?
5-HETE, which leads to chemotaxis
what do leukotrienes C4, D4, and E4 all lead to?
bronchospasm and increased vascular permeability
besides 5-HETE, what else can 5–HPETE lead to?
12-Lipoxygenase
what can 12-lipoxygenase lead to?
Lipoxin A4 and Lipoxin B4
what is the function of lipoxin A4 and B4?
they inhibit neutrophil adhesion and chemotaxis (they are considered the stop signals in inflammation)
how can you inhibit leukotriene production/ 5-lipoxygenase production?
use a 5-lipoxygenase inhibitor (Zileuton)