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TOXICOLOGY

The Anti-Inflammatory Drug, Nimesulide (4-Nitro-2-phenoxymethane-sulfoanilide), Uncouples Mitochondria and Induces Mitochondrial Permeability Transition in Human Hepatoma Cells: Protection by Albumin

Institut National de la Santé et de la Recherche Médicale U773, Centre de Recherche Biomédicale Bichat Beaujon, équipe Mitochondries, Paris, France (A.B., S.C., V.D., M.T., A.G., G.F., D.P.); Université Paris 7 Denis Diderot, Faculté de Médecine Xavier Bichat, Paris, France (A.B., S.C., V.D., M.T., A.G., G.F., D.P.); and Institut National de la Santé et de la Recherche Médicale U538, Faculté de Médecine Saint-Antoine, Paris, France (C.W.)

Like other nonsteroidal anti-inflammatory drugs, nimesulide (4-nitro-2-phenoxymethane-sulfoanilide) triggers hepatitis in a few recipients. Although nimesulide has been shown to uncouple mitochondrial respiration and cause hepatocyte necrosis in the absence of albumin, mechanisms for cell death are incompletely understood, and comparisons with human concentrations are difficult because 99% of nimesulide is albumin-bound. We studied the effects of nimesulide, with or without a physiological concentration of albumin, in isolated rat liver mitochondria or microsomes and in human hepatoma cells. Nimesulide did not undergo monoelectronic nitro reduction in microsomes. In mitochondria incubated without albumin, nimesulide (50 µM) decreased the mitochondrial membrane potential (_m), increased basal respiration, and potentiated the mitochondrial permeability transition (MPT) triggered by calcium preloading. In HUH-7 cells incubated for 24 h without albumin, nimesulide (1 mM) decreased the _m and cell NAD(P)H and increased the glutathione disulfide/reduced glutathione ratio and cell peroxides; nimesulide triggered MPT, ATP depletion, high cell calcium, and caused mostly necrosis, with rare apoptotic cells. Coincubation with either cyclosporin A (an MPT inhibitor) or the combination of fructose-1,6-diphosphate (a glycolysis substrate) and oligomycin (an ATPase inhibitor) prevented the decrease in _m, ATP depletion, and cell death. A physiological concentration of albumin abolished the effects of nimesulide on isolated mitochondria or HUH-7 cells. In conclusion, the weak acid, nimesulide, uncouples mitochondria and triggers MPT and ATP depletion in isolated mitochondria or hepatoma cells incubated without albumin. However, in the presence of albumin, only a fraction of the drug enters cells or organelles, and uncoupling and toxicity are not observed.

Address correspondence to: Dr. Alain Berson, Institut National de la Santé et de la Recherche Médicale U773, Equipe Mitochondries, Faculté deMédecine Xavier Bichat, BP 416, 16 rue Henri Huchard, F-75018 Paris, France. E-mail: aberson{at}bichat.inserm.fr