Interleukin-17A mediates cardiomyocyte apoptosis through Stat3-iNOS pathway

Interleukin-17A, a pro-inflammatory cytokine, has a direct proapoptotic effect on cardiomyocytes. However, the specific mechanism has not been clarified. In the present study, an in-vitro model of cardiomyocyte apoptosis induced by IL-17A stimulation was employed and the roles of iNOS and Stat3 involved were investigated. Our data showed that the neonatal mouse cardiomyocytes express IL-17 receptors: IL-17RA and IL-17RC, but did not express IL-17A. Exogenous IL-17A significantly induces iNOS expression and hence the cardiomyocyte apoptosis. Moreover, IL-17A-induced cardiomyocyte apoptosis can be achieved directly via iNOS activation. We further showed that exogenous IL-17A simultaneously triggers Stat3 activation, which in turn inhibits IL-17A-induced iNOS expression in cardiomyocytes. And both ChIP and dual-luciferase results confirmed that Stat3 directly inhibits transcriptional activities of iNOS via binding to its specific promoter region. Consistent with these data, silencing of Stat3 in fact can aggravate IL-17A-triggered cardiomyocyte apoptosis. Finally, using an in vivo myocardial ischemia/reperfusion injury model, we verified that Stat3 inhibition increased iNOS expression and exacerbated cardiomyocyte apoptosis. Thus, our data strongly support the notion that Stat3 plays a compensatory anti-apoptotic role in IL-17A/iNOS-mediated cardiomyocyte apoptosis via inhibiting iNOS transcription, providing a novel molecular mechanism of apoptosis regulation and complicated interactions between IL-17A/iNOS and IL-17A/Stat3 signalings.