Glutathione depletion induces apoptosis of rat hepatocytes through activation of protein kinase C novel isoforms and dependent increase in AP-1 nuclear binding

Treatment of isolated rat hepatocytes with the glutathione depleting agents L-buthionine-S,R-sulfoximine or diethylmaleate reproduced various cellular conditions of glutathione depletion, from moderate to severe, similar to t hose occurring in a wide spectrum of human liver diseases. To evaluate mole cular changes and possible cellular dysfunction and damage consequent to a pathophysiologic level of GSH depletion, the effects of this condition on p rotein kinase C (PKC) isoforms were investigated, since these are involved in the intracellular specific regulatory processes and are potentially sens itive to redox changes. Moreover, a moderate perturbation of cellular redox state was found to activate novel PKC isoforms, and a clear relationship w as shown between novel kinase activation and nuclear binding of the redox-s ensitive transcription factor, activator protein-1 (AP-1). Apoptotic death of a significant number of cells, confirmed in terms of internucleosomal DN A fragmentation was a possible effect of these molecular reactions, and was triggered by a condition of glutathione depletion usually detected in huma n liver diseases. Finally, the inhibition of novel PKC enzymatic activity i n cells co-treated with rottlerin, a selective novel kinase inhibitor, prev ented glutathione-dependent novel PKC up-regulation, markedly moderated AP- 1 activation, and protected cells against apoptotic death. Taken together, these findings indicate the existence of an apoptotic pathway dependent on glutathione depletion, which occurs through the up-regulation of novel PKCs and AP-1. (C) 2000 Elsevier Science Inc.