PKCδ mediates anti-proliferative, pro-apoptic effects of testosterone on coronary smooth muscle

PKC delta mediates anti-proliferative, pro-apoptic effects of testosterone on coronary smooth muscle. Am J Physic] Cell Physiol 293: C805-C813, 2007. First published May 16, 2007: doi:10.1152/ajpcell.00127.2007.-Sex hormone status has emerged as an important modulator of coronary physiology and cardiovascular disease risk in both males and females. Our previous studies have demonstrated that testosterone increases protein kinase C (PKC) delta expression and activity in coronary smooth muscle (CSMC). Because PKC delta has been implicated in regulation of proliferation and apoptosis in other cell types, we sought to determine if testosterone modulates CSMC proliferation and/or apoptosis through PKC delta Porcine CSMC cultures (passages 2-6) from castrated males were treated with testosterone for 24 h. Testosterone (20 and 100 nM) decreased [H-3] thymidine incorporation in proliferating CSMC to 59 +/- 5.3 and 33.1 +/- 4.5% of control. Flow cytometric analysis demonstrated that testosterone induced G, arrest in CSMC with a concomitant reduction in the S phase cells. Testosterone reduced protein levels of cyclins D, and E and phosphorylation of retinoblastorna protein while elevating levels of p21(cip1) and p(27kip1),. There were no significant differences in the levels of cyclins D-3, CDK2, CDK4, or CDK6. Testosterone significantly reduced kinase activity of CDK2 and -6, but not CDK4, -7, or -1. PKC delta small interfering RNA (siRNA) prevented testosterone-mediated G, arrest, p(21cip1) upregulation. and cyclin D, and E downregulation. Furthermore, testosterone increased CSMC apoptosis in a dose-dependent manner. which was blocked by either PKC delta siRNA or caspase 3 inhibition. These findings demonstrate that the anti-proliferative, proapoptotic effects of testosterone (in CSMCs are substantially mediated by PKC delta.