Gemfibrozil metabolite inhibits in vitro low-density lipoprotein (LDL) oxidation and diminishes cytotoxicity induced by oxidized LDL

We hypothesized that M1, a metabolite of gemfibrozil, may have antioxidant properties because of its hydroxylated phenol ring, 5-(4-hydroxy-2,5-dimeth yl-phenoxy)-2,2-dimethyl pentanoic acid. The susceptibility of low-density lipoprotein (LDL) to oxidative modification was investigated by a method us ing 2,2-azobis(4-methoxy-2,4-dimethylvaleronitrile [MeO-AMVN]) or Cu2+ as p reviously reported. Conjugated dienes (CDs), lipid hydroperoxide (LPO), and thiobarbituric acid-reactive substances (TBARS) were measured to evaluate the degree of LDL oxidation. Oxidized LDL (OxLDL), which is used for cytoto xicity studies, was prepared by the dialysis method using Cu2+ as the oxida tion inducer. Cytotoxicity induced by OxLDL was studied in J774 macrophages by colorimetric assay using 3-[4,5-dimethyl-thiazol-2-yl]-2,5-diphenyl tet razolium bromide (MTT assay). The oxidative modification of LDL was inhibit ed by M1 in a dose-dependent manner. The antioxidant effect of M1 on LDL ox idation was diminished by dialysis of the LDL incubated with M1 against pho sphate-buffered saline (PBS), suggesting that M1 is hydrophilic rather than lipophilic. M1 diminished the cytotoxicity induced by OxLDL, although it w as milder versus probucol, These data suggest that this gemfibrozil metabol ite has an antioxidant effect on LDL. and thus M1 may contribute to the ant iatherogenic effects of gemfibrozil. Copyright (C) 2000 by W.B. Saunders Co mpany.