Apoptotic effects of TGFbeta superfamily members in isolated adult rat cardiomyocytes

Abstract

Several TGFbeta family members are upregulated in the heart by increased work load after myocardial infarction. Therefore, their expressions correlate with cardiac apoptosis induction in vivo. I have now tested in this study, if TGFbeta superfamily members induce apoptosis in ventricular cardiomyocytes of rat. Cardiomyocytes were stimulated with TGFbeta, myostatin, BMP-2, activin A or GDF15. Apoptosis was determined by detection of chromatin condensation and DNA laddering. Apoptosis was induced by TGFbeta, myostatin, activin A and BMP-2. A classical signaling molecule of TGF beta family members is the transcription factor SMAD, which is able to interact with AP-1, a factor known to mediate apoptosis in cardiomyocytes after NO stimulation. In retardation assays I have now demonstrated that AP-1 and SMAD binding were activated by TGFbeta, myostatin, BMP-2 or activin A. Intracellular scavenging of SMAD or AP-1 binding activity by transformation of cardiomyocytes with SMAD-decoy oligos or AP-1 decoy oligos inhibited apoptosis induction by TGF beta, myostatin, BMP-2 or activin A.GDF15 stimulates SMAD binding activity similar to the other family members. But in contrast to them GDF15 showed anti-apoptotic effects. It inhibited apoptosis induction by TGFbeta. Conclusions: Most of the investigated TGFbeta-superfamily members activate the transcription factors AP-1 and SMAD and induce apoptosis in cardiomyocytes. For TGFbeta, myostatin, BMP-2 and activin-A SMAD/AP-1 is a common pathway for apoptosis induction in cardiomyocytes. GDF 15 has anti-apoptotic effects and inhibits TGF beta induced apoptosis. Therefore, further investigations on GDF15 signaling may have potential to discover now anti-apoptotic therapies in heart.