A NOVEL SYNTHETIC LIPID-A ANALOG WITH LOW ENDOTOXICITY, DT-5461, PREVENTS LETHAL ENDOTOXEMIA

Bacterial endotoxin (lipopolysaccharide [LPS]) causes severe damage to the host organism as a result of excessive release of inflammatory cy tokines, including interleukin-1 (IL-1) and tumor necrosis factor alph a (TNF-alpha), from mononuclear phagocytes during gram-negative bacter ial infection. We evaluated the ability of a novel synthetic lipid A a nalog with low endotoxicity, DT-5461, to antagonize LPS-induced IL-1 a nd TNF-alpha production in cells of monocyte/macrophage lineage and ex amined the protective effect of DT-5461 against lethal endotoxic shock in mice. The IL-1- or TNF-alpha-inducing activity of DT-5461 is 100,0 00 to 10,000 times less active than that of Escherichia coli LPS (EcLP S) or synthetic lipid A. DT-5461 significantly inhibited EcLPS-induced IL-1 and TNF-alpha release when murine peritoneal macrophages were in cubated with DT-5461 2 h prior to EcLPS stimulation at the same concen tration (1 mu g/ml). The antagonistic effect of DT-5461 on the product ion of IL-1 and TNF-alpha induced by EcLPS occurred in a concentration -dependent manner. DT-5461 also inhibited IL-1 and TNF-alpha induction when murine peritoneal macrophages were stimulated by LPS from Salmon ella typhimurium or synthetic lipid A, as well as by EcLPS, but not by muramyl dipeptides. This indicated that DT-5461 specifically antagoni zed the action of LPS. DT-5461 also antagonized EcLPS-mediated activat ion of human peripheral blood monocytes. DT-5461 blocked the binding o f fluorescein isothiocyanate-labelled LPS to murine peritoneal macroph ages as well as it did the binding of EcLPS and synthetic lipid A, i.e ., in a concentration-dependent fashion. Injection of DT-5461 2 h befo re EcLPS challenge prevented the production of serum IL-1 and TNF-alph a in D-galactosamine-treated mice. Furthermore, this treatment modalit y protected mice against LPS-induced lethal toxicity. This study sugge sts that DT-5461 possesses a potent LPS antagonistic effect and may be useful in a protective strategy against lethal endotoxemia caused by gram-negative bacterial infection.