Events that precede and that follow S-(1,2-dichlorovinyl)- l-cysteine-induced release of mitochondrial Ca 2+ and their association with cytotoxicity to renal cells

Abstract

Previous studies showed that S-(1,2-dichlorovinyl)- l-cysteine perturbs intracellular Ca 2+ homeostasis [Vamvakas et al., Mol Pharmacol 38: 455–461, 1990]. The objective of the present study was to investigate the cellular events that precede and that follow S-(1,2-dichlorovinyl)- l-cysteine-induced mitochondrial Ca 2+ release. In incubations with isolated kidney mitochondria, S-(1,2-dichlorovinyl)- l-cysteine-induced Ca 2+ efflux is preceded by increased oxidation of mitochondrial pyridine nucleotides and is prevented by ATP, an inhibitor of the hydrolysis of pyridine nucleotides, and by meto-iodobenzylguanidine, an acceptor of ADP-ribose moieties. In LLC-PK 1 cells, elevation in the cytosolic Ca 2+ concentration is followed by a several-fold increase in DNA double-strand breaks which is attributed to the activation of Ca 2+- and Mg 2+-dependent endonucleases. The formation of DNA double-strand breaks is followed by increased poly(ADP-ribosylation) of nuclear proteins. S-(1,2-Dichlorovinyl)- l-cysteine-induced cytotoxicity in LLC-PKin1 cells is blocked by chelation of cytosolic Ca 2+ with Quin-2, by inhibition of DNA fragmentation with aurintricarboxylic acid and by inhibition of increased poly(ADP-ribosyl)transferase activity by 3-aminobenzamide. These findings indicate that 5-(1,2-dichlorovinyl)- l-cysteine bioactivation in renal cells may initiate the following cascade of events: increased oxidation and hydrolysis of mitochondrial pyridine nucleotides resulting in the modification of mitochondrial membrane proteins by pyridine nucleotide-derived ADP-ribose moieties, followed by Ca 2+ release. Elevated Ca 2+ concentrations may activate Ca 2+-dependent endonucleases, which leads to DNA fragmentation followed by increased poly(ADP-ribosylation) of nuclear proteins and, finally, cytotoxicity.