endotoksinet

Endotoxinet, also called lipopolysaccharide, is a large, amphiphilic molecule that constitutes the outer membrane of Gram‑negative bacteria such as Escherichia coli, Salmonella spp. and Pseudomonas aeruginosa. It is composed of three regions: a lipid A moiety that anchors the molecule into the bacterial membrane, a core oligosaccharide and an O‑antigen polysaccharide. The lipid A portion is responsible for the majority of the biological activity of endotoxin and is mainly responsible for its ability to trigger an acute inflammatory response in mammals.

When bacteria die or multiply, endotoxin is released into the environment and can enter the bloodstream through mucosal surfaces or damaged tissues. Once in circulation, endotoxin stimulates immune cells, in particular macrophages, to produce pro‑inflammatory cytokines such as tumor necrosis factor‑α, interleukin‑1 and interleukin‑6. This cytokine cascade can lead to fever, increased vascular permeability, hypotension, and in severe cases septic shock. The clinical diagnosis of an endotoxin‑mediated reaction is usually made by measuring the level of the circulating toxin or its effects on the immune system.

Laboratory detection of endotoxin is commonly performed with the limulus amebocyte lysate (LAL) assay, which relies on a clotting reaction of horseshoe crab amebocytes in the presence of the toxin. Alternative methods include mass spectrometry, high‑performance liquid chromatography and molecular docking approaches. Understanding the structure‑activity relationship of endotoxin has guided the development of polymyxin B and other endotoxin neutralizing agents. Because of its potent immunostimulatory properties, endotoxin is a key factor in the pathogenesis of bacterial infections and is a target for therapeutic intervention in sepsis.