Endothelin-1 regulates cardiac L-type calcium channels via NAD(P)H oxidase-derived superoxide

It has been shown that reactive oxygen species (ROS) are involved in the intracellular signaling response to G-protein coupled receptor stimuli in vascular smooth muscle cells and in neurons. In the present study, we tested the hypothesis that NAD(P)H oxidase-derived ROS are involved endothelin-1 (ET-1)-induced L-type calcium channel activation in isolated cardiac myocytes. ET-1 (10 nM) induced a 2-fold increase in L-type calcium channel open-state probability (NPo). This effect of ET-1 was abolished by the ET(A) receptor antagonist cyclo(D-Trp-D-Asp-Pro-D-Val-Leu) [BQ-123 (1 microM)] but was not altered in the presence of an ET(B) receptor antagonist N-cis-2,6-dimethylpiperidinocarbonyl-b-tBu-Ala-D-Trp(1-methoxycarbonyl)-D-Nle-OH [BQ-788 (1 microM)]. Pretreatment of cells with the ROS scavenger tempol (100 microM), polyethylene glycol-superoxide dismutase (SOD, 25 U/ml), or the NAD(P)H-oxidase inhibitor gp91ds-tat ([H]RKKRRQRRR-CSTRIRRQL[NH(3)]) (5 microM) significantly attenuated ET-1-induced increases in calcium channel NPo. Tempol, SOD, and gp91ds-tat alone had no effect on basal calcium channel activity. In addition, ET-1 significantly increased NAD(P)H oxidase activity and elevated intracellular superoxide levels in cultured cardiac myocytes. The superoxide generator, xanthine-xanthine oxidase (10 mM, 20 mU/ml), also increased calcium channel NPo in cardiac myocytes, mimicking the effect of ET-1. These observations provide the first evidence that ET-1 induces the activation of L-type Ca(2+) channels via stimulation of NAD(P)H-derived superoxide production in cardiac myocytes.