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

Abstract

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. Primary cultures of hepatocytes were incubated with CsA, in the range of 0 to 50 microM, in the presence or absence of 50 microM 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. 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 microM and decreasing from 10 to 50 microM. 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. 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.