4-4-difluoro-4-bora-3a-4a-diaza-s-indacene and lipoteichoic-acid

Heparin is one of the most effective drugs for preventing and treating thromboembolic complications in surgical patients. Recent evidence suggests that heparin enhances the proinflammatory responses of human peripheral blood monocytes to Gram-negative endotoxin (LPS). We have identified LPS-binding protein (LBP) as a novel heparin-binding plasma protein. The affinity of LPB to heparin was KD = 55 +/- 8 nM, as measured by surface plasmon resonance. Using a fluorescence-based assay, we showed that clinically used heparin preparations significantly enhance the ability of LBP to catalytically disaggregate and transfer LPS to CD14, the LPS receptor. The presence of clinically relevant heparin concentrations in human whole blood increased LPS-induced production of the proinflammatory cytokine IL-8. Fondaparinux, which is identical with the antithrombin III-binding pentasaccharide in heparin, did not bind to LBP or alter LBP function. Thus, this novel anticoagulant drug is a potential candidate for safe administration to patients who have endotoxemia and require anticoagulation.

Topics: Acute-Phase Proteins; Adjuvants, Immunologic; Antithrombin III; Biological Transport; Boron Compounds; Carrier Proteins; Enoxaparin; Fluorescent Dyes; Heparin; Humans; Interleukin-8; Lipopolysaccharide Receptors; Lipopolysaccharides; Membrane Glycoproteins; Monocytes; Signal Transduction; Solubility; Sulfates; Teichoic Acids; Thrombin

Chylomicrons have been shown to protect against endotoxin-induced lethality. LPS-binding protein (LBP) is involved in the inactivation of bacterial toxin by lipoproteins. The current study examined the interaction among LBP, chylomicrons, and bacterial toxin. LBP was demonstrated to associate with chylomicrons and enhance the amount of LPS binding to chylomicrons in a dose-dependent fashion. In addition, LBP accelerated LPS binding to chylomicrons. This LBP-induced interaction of LPS with chylomicrons prevented endotoxin toxicity, as demonstrated by reduced cytokine secretion by PBMC. When postprandial circulating concentrations of chylomicrons were compared with circulating levels of low density lipoprotein, very low density lipoprotein, and high density lipoprotein, chylomicrons exceeded the other lipoproteins in LPS-inactivating capacity. Furthermore, highly purified lipoteichoic acid, an immunostimulatory component of Gram-positive bacteria, was detoxified by incubation with LBP and chylomicrons. In conclusion, our results indicate that LBP associates with chylomicrons and enables chylomicrons to rapidly bind bacterial toxin, thereby preventing cell activation. Besides a role in the detoxification of bacterial toxin present in the circulation, we believe that LBP-chylomicron complexes may be part of a local defense mechanism of the intestine against translocated bacterial toxin.

Topics: Acute-Phase Proteins; Binding Sites; Biological Transport; Boron Compounds; Carrier Proteins; Chylomicrons; Dose-Response Relationship, Drug; Fluorescent Dyes; Humans; Inactivation, Metabolic; Lipopolysaccharides; Lipoproteins, HDL; Lipoproteins, LDL; Lipoproteins, VLDL; Membrane Glycoproteins; Postprandial Period; Teichoic Acids; Tumor Necrosis Factor-alpha