Transforming growth factor β1 attenuates ceramide-induced CPP32/Yama activation and apoptosis in human leukaemic HL-60 cells

Ceramide, a product of sphingomyelin turnover, is a novel lipid second messenger that mediates important cellular functions including proliferation, differentiation and apoptosis. This study demonstrates that the CPP32/Yama protease was activated during apoptosis induced by the membrane-permeable second messenger C₂-ceramide in HL-60 cells. We also found that the addition of a specific tetrapeptide inhibitor of CPP32/Yama, Ac-DEVD-CHO, provided an effective protection against ceramide-induced cell death. These results suggested that CPP32/Yama has a central role in ceramide-mediated apoptosis. Furthermore a wide variety of cytokines were examined for their effect on ceramide-induced apoptosis. Only transforming growth factor β1 (TGF-β1) (1 ng/ml) exerted significant prevention of apoptosis induced by C₂-ceramide, or by sphingomyelinase (increases intracellular ceramide). Consistently, TGF-β1 abrogated the cleavage of poly(ADP-ribose) polymerase and the production of the CPP32/Yama active subunit, p17. However, TGF-β1 treatment did not cause growth inhibition or alter the level of cyclin-dependent kinase inhibitor p27. It suggests that the preventive effect of TGF-β1 is not mediated by growth arrest. Interestingly, we found that TGF-β1 prevented the C₂-ceramide-caused decrease of Bcl-2 protein. We thus propose that TGF-β1 rescues ceramide-induced cell death, possibly by maintaining the constant level of Bcl-2, thereby abolishing CPP32/Yama protease activation.