CYTOTOXICITY OF LINOLEIC-ACID DIOLS TO RENAL PROXIMAL TUBULAR CELLS

Monoepoxides of linoleic acid (leukotoxin and isoleukotoxin) have been associated with a variety of pathophysiological diseases in humans in cluding multiple organ failure. They also have been shown to be toxic when injected into experimental animals. Because leukotoxin and isoleu kotoxin are excellent substrates for epoxide hydrolases, we tested the hypothesis that the diol metabolites are less toxic than the parent m onoepoxides using the rabbit renal proximal tubule (RPT) suspension mo del. An equimolar mixture of the positional isomers of the methyl este rs of leukotoxin and isoleukotoxin did not cause cell death to RPT cel ls at concentrations up to 1 mM using lactate dehydrogenase release as the endpoint. The corresponding diols, however, caused cell death in a time- and concentration-dependent manner beginning at 4 hr and reach ing 42% cell death in 6 hr at 1 mM. Cell death was not due to oxidativ e stress since malondialdehyde content did not increase and the iron c helator deferoxamine and the antioxidant N,N'-diphenyl-1,4-phenylenedi amine were not cytoprotective. In contrast, cell death was associated with mitochondrial dysfunction with respiration decreasing 54% prior t o the onset of cell death. Secondary to the mitochondrial dysfunction, the diols completely inhibited active Na+ transport within 30 min of addition. These results suggest that the in vivo toxicity and pathophy siology previously attributed to the monoepoxides of linoleic acid may be due to the diol metabolites. (C) 1997 Academic Press.