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Bacteria - Endotoxin

Bacteria - Endotoxin

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Endotoxins
Endotoxins are part of the cell wall of Gram-negative bacteria
The lipopolysaccharide endotoxin extends from the outer membrane.
Three important regions of the endotoxin, starting at the cell membrane: Lipid A, Core polysaccharides, and the O-antigen.
They have relatively low toxicity.
Mechanism:
Upon infection and endotoxin release, the Lipid A portion of the lipopolysaccharide interacts with Toll-Like Receptor 4 on macrophage surfaces and triggers cytokine release, potentially inciting cytokine storms.
Four important endotoxin consequences:
Complement activation, which results in neutrophil chemotaxis and inflammation.
Cytokines IL-1 and IL-6 induce fever.
Tissue factor activation leads to coagulation.
Tumor necrosis factor, nitric oxide, and bradykinin induce hypotension (low blood pressure) via vasodilation.
In acute, local conditions, these reactions can protect the host from infection; however, in large quantities, endotoxin can be fatal.
Endotoxin is a major cause of septic shock.

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