RT Journal Article
SR Electronic
T1 Diclofenac Toxicity to Hepatocytes: A Role for Drug Metabolism in Cell Toxicity
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 65
OP 72
VO 288
IS 1
A1 Roque Bort
A1 Xavier Ponsoda
A1 Ramiro Jover
A1 M. José Gómez-Lechón
A1 José V. Castell
YR 1999
UL http://jpet.aspetjournals.org/content/288/1/65.abstract
AB Diclofenac, a 2-arylacetic acid, nonsteroidal anti-inflammatory drug, has been reported to cause adverse hepatic effects in certain individuals. To discriminate among possible mechanisms of hepatotoxicity, we examined the effects of diclofenac on human and rat hepatocytes and hepatic cell lines (HepG2, FaO), investigated the major biochemical events in the course of diclofenac cytotoxicity (calcium homeostasis, lipid peroxidation, and mitochondrial dysfunction), and investigated whether cytotoxicity could be related to drug metabolism by cytochrome P-450. Acute diclofenac-induced toxicity in hepatocytes was preluded by a decrease in ATP levels, whereas no significant oxidative stress (decrease in glutathione and lipid peroxidation) or increase in intracellular calcium concentration could be observed at early incubation stages. Diclofenac was more cytotoxic to drug metabolizing cells (rat and human primary cultured hepatocytes) than to nonmetabolizing cell lines (HepG2, FaO). Despite the fact that diclofenac itself was effective in impairing ATP synthesis by mitochondria, we found evidence that toxicity was also related to drug metabolism and was reduced by the addition of cytochrome P-450 inhibitors (proadifen and ketoconazole) to culture medium. The in vitro cytotoxicity correlated well with the formation by hepatocytes of 5-hydroxydiclofenac and, in particular,N,5-dihydroxydiclofenac, a minor metabolite first characterized in this article. Hepatic microsomes showed the ability to both oxidize 5-hydroxydiclofenac toN,5-dihydroxydiclofenac and back reduce the latter to 5-hydroxydiclofenac with the consumption of NADPH. The experimental results suggest that the toxic effect of diclofenac on hepatocytes may be caused by drug-induced mitochondrial impairment, together with a futile consumption of NADPH. The American Society for Pharmacology and Experimental Therapeutics