Gram-negative bacterial outer membrane lipopolysaccharide (LPS)

Gram-negative bacterial outer membrane lipopolysaccharide (LPS), also known as endotoxin, is a complex glycolipid that constitutes the major component of the outer leaflet of the outer membrane in almost all Gram-negative bacteria (Raetz & Whitfield, 2002, Annu Rev Biochem). It is composed of three distinct regions: the hydrophobic Lipid A, a non-repeating core oligosaccharide, and a distal polysaccharide known as the O-antigen. LPS is essential for bacterial viability, providing structural integrity and acting as a potent permeability barrier against toxic compounds, including many antibiotics (Bertani & Ruiz, 2018, Cold Spring Harb Perspect Biol). In the context of human disease, LPS is a primary trigger of the innate immune response; Lipid A is recognized by the Toll-like receptor 4 (TLR4) complex, which can lead to the massive release of pro-inflammatory cytokines (Park & Lee, 2013, Exp Mol Med). This response is a double-edged sword, as excessive LPS-induced signaling can result in life-threatening sepsis and septic shock. Therapeutic strategies targeting LPS include direct membrane disruption by polymyxins, inhibition of LPS assembly/transport pathways such as LptD, and the development of agents designed to neutralize circulating endotoxin or block its interaction with host receptors (Poirel et al., 2017, Clin Microbiol Rev).

Other names

EndotoxinLipoglycanLipid A-core-O-antigen complexBacterial lipopolysaccharide

Drugs targeting lipopolysaccharides (LPS) primarily function through three mechanisms: 1) Direct binding to the Lipid A moiety to displace divalent cations and disrupt the bacterial outer membrane (e.g., polymyxins); 2) Inhibition of the LPS transport machinery, such as the LptD protein, to prevent LPS from reaching the outer membrane (e.g., murepavadin); and 3) Neutralization of circulating LPS or antagonism of the TLR4/MD-2 receptor complex to prevent the systemic inflammatory cascade (e.g., eritoran, alkaline phosphatase).