Relationship between Bcl-2/Bax and staurosporine-induced rat cardiomyocyte apoptosis

AIM To explore the changes of Bcl-2/Bax and significance in staurosporine（STS）induced cardiomyocyte apoptosis. METHODS Primary cultured neonatal rat cardiomyocytes were exposed to STS to induce apoptosis. Cell apoptosis was determined by cysteine aspartate specific proteinase(caspase)-3 activity and Hoechst 33258 staining. Bcl-2/Bax expression was measured by Western blot and Bax translocation was assessed by double immunofluorescence labeling as well as Western blot. RESULTS Exposure of cardiomyocytes to STS (4 μmol/L) resulted in an increase of caspase-3 activity in a time-dependent manner with a peak at 8 h. Hoechst 33258 fluorescence staining showed many segmented and irregularly shaped nuclei and STS induction did not alter Bcl-2/Bax levels. In normal cardiomyocytes, a diffuse localization of Bax was primarily found in the cytoplasm. In contrast, exposure of cells to STS resulted in Bax translocation from cytoplasm to mitochondria. Western blot also demonstrated that an increase in mitochondrial Bax level was accompanied by a concomitant decrease in cytosolic Bax level, which provided some direct evidence that a significant increased Bax translocation existed in the STS-induced cell apoptosis. CONCLUSION STS induces a significant pro-apoptotic Bax translocation to mitochondria in cardiomyocyte apoptosis, a mechanism that may be involved in STS-induced cell apoptosis.