Escherichia coli lipopolysaccharide (LPS) (LPS)

Escherichia coli lipopolysaccharide (LPS) is a fundamental glycolipid component of the outer membrane of Gram-negative bacteria, essential for maintaining cellular structural integrity and providing a permeability barrier against harmful substances [1]. The molecule is composed of three distinct regions: the hydrophobic Lipid A, which anchors the molecule in the membrane; a core oligosaccharide; and the O-antigen polysaccharide chain [2]. LPS is a potent endotoxin and serves as a primary pathogen-associated molecular pattern (PAMP) recognized by the human innate immune system via the Toll-like receptor 4 (TLR4)/MD-2 complex [3]. Upon recognition, it triggers a signaling cascade that leads to the production of pro-inflammatory cytokines, which is vital for clearing infections but can lead to sepsis and septic shock if the response is systemic and uncontrolled [2]. In pharmacology, LPS is the direct target of polymyxin antibiotics, such as Polymyxin B and Colistin, which bind to the Lipid A moiety to disrupt the bacterial membrane [4]. Additionally, therapeutic strategies have explored the use of TLR4 antagonists and LPS-neutralizing agents to mitigate the life-threatening inflammatory effects of endotoxemia during severe infections [3, 4].

Other names

EndotoxinLipid AO-antigenPyrogenBacterial endotoxin

Polymyxin antibiotics bind to the Lipid A component of LPS via electrostatic interactions, displacing divalent cations (Ca2+ and Mg2+) that stabilize the membrane, which leads to increased membrane permeability and bacterial cell death [4]. Other therapeutic approaches involve using TLR4 antagonists like Eritoran to competitively inhibit the binding of LPS to the TLR4/MD-2 complex, thereby preventing the downstream inflammatory cytokine storm [3].