HSP70 induction by cyclosporine A in cultured rat hepatocytes:: effect of vitamin E succinate

Background/Aims: The effect of vitamin E succinate was studied in vitro against cyclosporine A (CsA) cytotoxicity in reference to the induction of heat shock protein 70 (HSP70) in rat hepatocytes. Methods: Primary cultures of hepatocytes were incubated with CsA, in the range of 0 to 50 mu M, in the presence or absence of 50 mu M vitamin E succinate for 24 h. Peroxides were quantified by using 2',7'-dichlorodihydrofluorescein diacetate, HSP70 levels were measured by Western blot analysis and apoptosis was detected by the hypodiploid peak of propidium iodide stained DNA. Results: At 24 h of incubation with CsA, intracellular peroxide content increased in a dose-dependent manner. HSP70 also increased in parallel to CsA concentration, and apoptosis showed a biphasic change, increasing at concentrations between 0 and 10 mu M and decreasing from 10 to 50 mu M. The effect of vitamin E was studied at 24 h of coincubation with CsA. The values obtained show that vitamin E significantly counteracted the effect of CsA, diminishing the CsA-induced increase in intracellular peroxides and the lysis of cell membrane. These vitamin E effects, were accompanied by a decrease in HSP70 and an enhancement of apoptosis. Conclusions: We conclude that in primary hepatocyte cultures, peroxide generation and cytotoxicity induced by CsA was accompanied by HSP70 induction and that the CsA cytotoxicity significantly decreased in the presence of vitamin E succinate parallel to a disappearance in HSP70 and to an increase in apoptosis.