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

Endothelin-l (ET-1) induces cardiac hypertrophy, Because Ca2+ is a major se cond messenger of ET-1, the role of Ca2+ in ET-l-induced hypertrophic respo nses in cultured cardiac myocytes of neonatal rats was examined. ET-I activ ated 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 chela tion 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 a ctivator. beta-MHC promoter activation induced by ET-I was suppressed by pr etreatment with the calmodulin inhibitor, W7, the Ca2+/calmodulin-dependent kinase II (CaMKII) inhibitor, KN62, and the calcineurin inhibitor, cyclosp orin A. P-MHC promoter activation by ET-I was also attenuated by overexpres sion of dominant-negative mutants of CaMKII and calcineurin, ET-1 increased the activity of CaMKII and calcineurin in cardiac myocytes, Pretreatment w ith KN62 and cyclosporin A strongly suppressed ET-l-induced increases in [H -3]phenylalanine uptake and in cell size. These results suggest that Ca2+ p lays a critical role in ET-l-induced cardiomyocyte hypertrophy by activatin g CaMKII- and calcineurin-dependent pathways.