Gram-negative bacterial outer membrane lipopolysaccharides and phospholipids (LPS/PL)

Gram-negative bacterial outer membrane lipopolysaccharides (LPS) and phospholipids constitute the essential structural and functional components of the outer leaflet and inner leaflet of the Gram-negative bacterial outer membrane, respectively [9][13]. This asymmetric lipid bilayer serves as a critical permeability barrier that protects the bacterium from environmental stressors, including detergents, bile salts, and numerous classes of antibiotics [12][13][17]. LPS, often referred to as endotoxin, is a potent stimulator of the host innate immune system through its interaction with Toll-like receptor 4 (TLR4), and its release during infection can lead to systemic inflammation and septic shock [13][14][15]. Therapeutic agents like polymyxins (polymyxin B and colistin) specifically target these lipids by binding to the negatively charged phosphate groups of lipid A and phospholipids [1][3][6]. This binding displaces stabilizing divalent cations such as calcium and magnesium, leading to the destabilization of the membrane, increased permeability, and the eventual leakage of cytoplasmic contents, resulting in bacterial cell death [1][6][7]. Additionally, some agents can neutralize the toxic effects of circulating LPS, providing a dual therapeutic benefit in treating severe Gram-negative infections [3][7].

Other names

EndotoxinLipid AOuter membrane lipidsBacterial lipoglycansLipopolysaccharide

Drugs targeting these components, such as polymyxins, act by binding electrostatically to the negatively charged phosphate groups of lipopolysaccharides and phospholipids, which leads to the displacement of stabilizing divalent cations (Mg2+ and Ca2+) [1][3][6][7]. This process destabilizes the outer membrane, increases its permeability, and causes the lethal leakage of intracellular contents [1][6][7]. Additionally, these drugs can neutralize the pro-inflammatory endotoxin effects of circulating lipopolysaccharides [3][7].