STEREOCHEMICAL ANALYSIS AND BIOLOGICAL-ACTIVITY OF 3-HYDROXY-LEUKOTRIENE B-4 - A METABOLITE FROM ETHANOL-TREATED RAT HEPATOCYTES

Leukotriene B-4 (LTB(4)), a biologically active metabolite derived fro m arachidonic acid by the 5-lipoxygenase cascade, is inactivated by cy tochrome P-450-dependent omega-hydroxylation followed by second oxidat ion into a omega-carboxyl group. In many tissues, this second step is mediated by alcohol dehydrogenase. Isolated rat hepatocytes metabolize d LTB(4) in the presence of ethanol and ethoxyresorufin into substanti al quantities of 3-hydroxy-LTB(4) as determined by mass spectrometry. The absolute configuration of this metabolite was found to be greater than 98% 3(S)-hydroxy-LTB(4) by comparison to synthetic standards. Inv estigation of the pharmacologic properties of the 3(S)- and 3(R)-hydro xy-LTB(4) revealed that both caused a significant increase in intracel lular free calcium in human neutrophils at 1 mu M. Both enantiomers al so induced thromboxane A(2) release from the isolated guinea pig lung in a dose-dependent manner. This activity was fully blocked by a speci fic LTB(4) receptor antagonist, LY223982, with an IC50 of 0.21 mu M fo r LTB(4). These results suggested that activation of the LTB(4) recept or does not involve significant recognition of the carbon atoms close to the carboxyl moiety of LTB(4). The failure of the hepatocyte to met abolically inactivate LTB(4) in the presence of ethanol may be of impo rtance to humans, particularly because the bioactive metabolite 3(S)-h ydroxy-LTB(4) was further metabolized by human neutrophils significant ly more slowly than LTB(4).