A non-toxic heat shock protein 70 inducer, geranylgeranylacetone, suppresses apoptosis of cultured rat hepatocytes caused by hydrogen peroxide and ethanol

Background/Aims: A stress-inducible heat shock protein 70 (HSP70) is one of the best-known endogenous factors protecting cell injury under various pathological conditions. The aim of this study was to examine anti-apoptotic actions of a non-toxic HSP70 inducer, geranylgeranylacetone (GGA), on hepatocytes exposed to hydrogen peroxide (H2O2) or ethanol. Methods: Primary cultures of rat hepatocytes were treated with different concentrations of GGA and exposed to 0.5 mM H2O2 or 100 mM ethanol. The heat shock response was assessed by measuring the activation of heat shock factor 1 (HSF1), HSP70 mRNA expression, and accumulations of HSP70, HSP90, and HSP27. Apoptosis was evaluated by DNA fragmentation. Results: Pretreatment with 1 μM GGA for 2 h enhanced nuclear translocation and phosphorylation of HSF1, HSF1-DNA binding, HSP70 mRNA expression, and its accumulation, when the cells were exposed to H2O2 or ethanol. In association with this accelerated response, GGA suppressed the insult-induced activation of c-Jun N-terminal kinases, caspase 9, and caspase 3-like proteases, leading to significant inhibition of apoptosis. Conclusions: GGA exerted anti-apoptotic actions, at least in part, by priming hepatocytes for enhanced HSP70 induction. Our results suggest that GGA may have a potential benefit for the treatment of alcoholic and ischemia-reperfusion liver injuries.