Catalpol inhibits apoptosis in hydrogen peroxide-induced cardiac myocytes through a mitochondrial-dependent caspase pathway

Catalpol, an iridoid glucoside, has been reported to inhibit apoptosis of neuron and endothelial cells. In the present study, we investigated the mechanism of catalpol-mediated cardioprotection. The rat embryonic ventricular myocardial cell line (H9c2) cells were first incubated with catalpol, and then exposed to hydrogen peroxide (H2O2). The concentration of malondialdehyde (MDA) and the activity of superoxide dismutase (SOD) were all determined by using commercially available kits. Apoptotic cells were assessed by Hoechst 33258 and Annexin V-fluorescein isothiocyanate binding assay. Synthesis of Bcl-2, Bax, cytochrome c and caspase-3 were analysed by real-time semiquantitative reverse transcription-PCR and Western blotting. We observed that apoptosis in H9c2 was associated with increased Bax, cytochrome c, caspase-3, decreased Bcl-2 activity after 24 h of H2O2 exposure. Catalpol pretreatment afforded a marked protection against the above H2O2-mediated cytotoxicity and apoptosis in H9c2 cells. Moreover, the catalpol pretreatment led to a great reduction in H2O2-induced MDA release and increased SOD. These findings indicated for the first time that pretreatment of H9c2 cells with catalpol can be against H2O2-induced apoptosis, and the protective effect of catalpol involves the mitochondrial-dependent caspase pathway and is associated with increased Bcl-2 and decreased Bax expression.