Ca2+/calmodulin-dependent kinase II and calcineurin play critical roles in endothelin-1-induced cardiomyocyte hypertrophy

Endothelin-l (ET-1) induces cardiac hypertrophy, Because Ca2+ is a major second messenger of ET-1, the role of Ca2+ in ET-l-induced hypertrophic responses in cultured cardiac myocytes of neonatal rats was examined. ET-I activated the promoter of the beta-type myosin heavy chain gene (beta-MHC) (-354 to +34 base pairs) by about 4-fold. This activation was inhibited by chelation of Ca2+ and the blocking of protein kinase C activity. Similarly, the beta-MHC promoter was activated by Ca2+ ionophores and a protein kinase C activator. beta-MHC promoter activation induced by ET-I was suppressed by pretreatment with the calmodulin inhibitor, W7, the Ca2+/calmodulin-dependent kinase II (CaMKII) inhibitor, KN62, and the calcineurin inhibitor, cyclosporin A. P-MHC promoter activation by ET-I was also attenuated by overexpression of dominant-negative mutants of CaMKII and calcineurin, ET-1 increased the activity of CaMKII and calcineurin in cardiac myocytes, Pretreatment with KN62 and cyclosporin A strongly suppressed ET-l-induced increases in [H-3]phenylalanine uptake and in cell size. These results suggest that Ca2+ plays a critical role in ET-l-induced cardiomyocyte hypertrophy by activating CaMKII- and calcineurin-dependent pathways.