High Peroxidative Susceptibility of Fish Oil Polyunsaturated Fatty Acid in Cultured Rat Hepatocytes

Abstract

The peroxidative susceptibility in cultured rat hepatocytes of eicosapentaenoic acid (EPA) and other polyunsaturated fatty acids (PUFA) with different numbers of double bonds was examined. Lipid peroxidation was evaluated using a newly developed HPLC procedure which includes the determination of malondialdehyde (MDA). Following exposure to 0.25-1.0 mM EPA adsorbed to BSA (EPA-BSA), cultured hepatocytes produced MDA in the fatty acid concentration- and incubation time-dependent manner. The rate of MDA production by hepatocytes varied greatly with the degree of PUFA unsaturation, and ranked as follows: docosahexaenoic acid > EPA > arachidonic acid > α-linolenic acid = γ-linolenic acid > linoleic acid > oleic acid. Prolonged exposure of cultured hepatocytes to 1.0 mM EPA-BSA resulted in substantial leakage of LDH into the medium. The cell injury was associated with the loss of cellular GSH and protein thiol groups. Cotreatment of the EPA-supplemented hepatocytes with a GSH-depleting agent, diethylmaleate, promoted the cellular protein thiol loss and LDH leakage. An iron chelator, deferoxamine, and other antioxidants such as N,N-diphenyl- p-phenylenediamine and γ-tocopherol efficiently prevented MDA production and consequently LDH leakage in the EPA-supplemented hepatocytes. These results show that peroxidative deterioration in excess of GSH-dependent defense mechanisms may occur in hepatocytes loaded with highly peroxidizable fish oil PUFA.