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Title: Metabolism of monoepoxides of methyl linoleate: bioactivation and detoxification.

Authors: Greene, J F; Williamson, K C; Newman, J W; Morisseau, C; Hammock, B D

Published In Arch Biochem Biophys, (2000 Apr 15)

Abstract: Leukotoxin (ltx) and isoleukotoxin (iltx) methyl esters, are metabolites of methyl linoleic acid, an essential fatty acid. They have been associated with acute respiratory distress syndrome. The observed toxicity of ltx and iltx is, in fact, due to the metabolism of the epoxides to their corresponding diols by soluble epoxide hydrolase (sEH). Herein, we demonstrate that ltx/iltx are toxic in a time-dependent manner to human sEH expressing cells with a LT(50) of 10.6 +/- 0.8 h and that ltx and iltx have K(M) of 6.15 +/- 1.0 and 5. 17 +/- 0.56 microM, respectively, and V(max) of 2.67 +/- 0.04 and 1. 86 +/- 0.06 micromol/min/mg, respectively, which can be inhibited by sEH inhibitors. We show that four major metabolites of ltx/iltx are formed in our system, including ltx/iltx free acid, ltxd/iltxd, free acid, and phosphotidylcholine and phosphotidylethanolamine containing the carboxylic acid forms of both ltx/iltx and ltxd/iltxd, but that the only metabolite associated with toxicity is the carboxylic acid form of ltxd/iltxd, suggesting the involvement of cellular esterases. We demonstrate that a serine esterase inhibitor provides some protection from the toxicity of epoxy fatty esters to sEH expressing cells as do intercellular free sulfhydryls, but that this protection is not due to glutathione conjugation. With these data, we have proposed an extension of the metabolic pathway for ltx/iltx in eukaryotic cells.

PubMed ID: 10775430 Exiting the NIEHS site

MeSH Terms: Animals; Carboxylic Acids/metabolism; Cell Line; Cell Survival/drug effects; Epoxide Hydrolases/antagonists & inhibitors; Epoxide Hydrolases/genetics; Epoxide Hydrolases/metabolism; Epoxy Compounds/metabolism*; Epoxy Compounds/toxicity*; Esterases/antagonists & inhibitors; Esterases/metabolism; Glutathione/analogs & derivatives; Glutathione/metabolism; Glutathione/pharmacology; Glycerophospholipids/metabolism; Humans; Kinetics; Linoleic Acids/metabolism*; Linoleic Acids/toxicity*; Metabolic Detoxication, Drug; Models, Biological; Phenylmethylsulfonyl Fluoride/pharmacology; Recombinant Proteins/antagonists & inhibitors; Recombinant Proteins/genetics; Recombinant Proteins/metabolism; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.; Spodoptera; Sulfhydryl Compounds/antagonists & inhibitors; Sulfhydryl Compounds/metabolism

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