Caspase activation in a cardiac cell-free model of apoptosis

Abstract

The release of mitochondrial anapoptogenic factors, like cytochrome c, into the cytosol is a fundamental step for caspase activation and induction of apoptosis. In this report it is shown that the polyamine spermine causes the exit of cytochrome c from heart mitochondria. Polyamines are ubiquitous compounds necessary for growth processes, whose excessive accumulation can trigger apoptosis. The release of cytochrome c caused by spermine is a selective process that is independent of mitochondria damage. The cytochrome c-releasing power of spermine is not affected by cyclosporin A, differently from the effect of permeability transition inducers. Addition of cytochrome c to cytosol extracts from chick embryo heart cells (CEHC) or H9C2 ventricular cardiomyoblasts triggers the onset of caspase activity. In a cardiac cell-free model of apoptosis, the latent caspase activity of cytosolic extracts from CEHC can be activated by cytochrome c released from spermine-treated heart mitochondria. The activated caspase activity is inhibited by nitric oxide donor molecules. These data suggest that prolonged and sustained elevation of polyamines, characteristic of heart hypertrophy, could be involved in the development of apoptosis.