Molecular mechanisms of butylated hydroxylanisole-induced toxicity: induction of apoptosis through direct release of cytochrome c.

Butylated hydroxyanisole (BHA), a commonly used food preservative, is reported to have anticarcinogenic properties in some animal models. However, the use of BHA as a chemopreventive agent against cancer in human has been challenged by the observation that BHA may exert toxic effect in some tissues of animals. Therefore, it is of great significance to understand the mechanism of BHA-induced toxicity. Here, we report that BHA induces apoptosis in freshly isolated rat hepatocytes. Treatment of hepatocytes with BHA also induced loss of mitochondrial transmembrane potential (Deltapsi(m)), cytochrome c, and activation of caspase-3, -8, and -9 but not caspase-1. Pretreatment with cyclosporin A, an agent that stabilizes mitochondrial permeability transition pore, inhibited BHA-induced loss of Deltapsi(m), cytochrome c release, caspase activation, and apoptosis. Interestingly, benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone failed to prevent these mitochondrial events, although it blocked caspase activation and apoptosis. Furthermore, BHA-induced apoptosis appeared to be independent of formation of reactive intermediates, as evidenced by the lack of effects of antioxidants N-acetyl-L-cysteine and ascorbic acid. Indeed, direct incubation of BHA with isolated mitochondria triggered cytochrome c release. Thus, these results indicate that the cytotoxicity of BHA is due to the induction of apoptosis that is mediated by the direct release of cytochrome c and the subsequent activation of caspases.