Role of AIF in cardiac apoptosis in hypertrophic cardiomyocytes from Dahl salt-sensitive rats

Aims The caspases are thought to be central mediators of the apoptotic program, but recent data indicate that apoptosis may also be mediated by caspase-independent mechanisms such as apoptosis-inducing factor (AIF). The role of AIF-induced apoptosis in heart, however, is currently not well understood. The aim of this study was to investigate the presence of and conditions for AIF-induced cardiac apoptosis in vitro. Methods and results Hypertrophic cardiomyocyte (H-CM) cultures were prepared from the hearts of Dahl salt-sensitive rats fed a high salt diet. Apoptotic stimulation induced by hypoxia/reoxygenation or staurosporine (1 mu M) enhanced AIF release in H-CMs compared with non-hypertrophic cardiomyocytes (N-CMs). Caspase inhibition using zVAD. fmk (25 mu M) or overexpression of CrmA using recombinant adenovirus only partially protected N-CMs from apoptosis (63 +/- 0.93%) and provided no significant protection against apoptosis in hypertrophic cells (23 +/- 1.03%). On the other hand, poly-ADP-ribose polymerase inhibition using 4-AN (20 mu M) during apoptotic stimulation blocked the release of AIF from mitochondria and significantly improved cell viability in hypertrophied cardiomyocytes (74 +/- 1.18%). Conclusion A caspase-dependent, apoptotic pathway is important for N-CM death, whereas a caspase-independent, AIF-mediated pathway plays a critical role in H-CMs.