title: Interaction of cationic amphiphilic drugs with lipid A: implications for development of endotoxin antagonists.
abstract: This report presents evidence for the interactions of several classes of cationic amphiphilic drugs including the phenothiazines, aminoquinolines, biguanides, and aromatic diamidines, with lipid A, the endotoxic principle of lipopolysaccharides. The interactions of the drugs were quantitatively assessed by fluorescence methods. The affinities of the drugs for lipid A parallel their endotoxin-antagonistic effects in the Limulus gelation assay. Dicationic compounds bind lipid A with greater affinity; the affinity of such molecules increases exponentially as a function of the distance between the basic moieties. The bis-amidine drug--pentamidine--examined in greater detail, binds lipid A with high affinity (apparent Kd: 0.12 microM), and LPS, probably due to simultaneous interactions of the terminal amidine groups with the anionic phosphates on lipid A. The sequestration of endotoxin by pentamidine reduces its propensity to bind to cells, and the complex exhibits attenuated toxicity in biological assays. These results have implications in the development of therapeutic strategies against endotoxin-related disease states.
authors.affiliation: Wellcome Trust Research Laboratory, Christian Medical College Hospital, Vellore, India.
authors.forename: S A
authors.initials: SA
authors.lastname: David
authors.forename: B
authors.initials: B
authors.lastname: Bechtel
authors.forename: C
authors.initials: C
authors.lastname: Annaiah
authors.forename: V I
authors.initials: VI
authors.lastname: Mathan
authors.forename: P
authors.initials: P
authors.lastname: Balaram
mesh_terms: D000634:Aminoquinolines / Q000737:chemistry; D001645:Biguanides / Q000737:chemistry; D001681:Biological Assay; D002413:Cations, Divalent / Q000737:chemistry; D064420:Drug-Related Side Effects and Adverse Reactions; D004731:Endotoxins / Q000037:antagonists & inhibitors*; D005434:Flow Cytometry; D008050:Lipid A / Q000037:antagonists & inhibitors*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D004364:Pharmaceutical Preparations / Q000737:chemistry*; D010640:Phenothiazines / Q000737:chemistry; D013329:Structure-Activity Relationship
chemical_list: D000634:Aminoquinolines; D001645:Biguanides; D002413:Cations, Divalent; D004731:Endotoxins; D008050:Lipid A; D004364:Pharmaceutical Preparations; D010640:Phenothiazines