Calcium handling coupled to the endothelin ET and ET receptor-mediated vasoconstriction in resistance arteries: Differential regulation by PI3K, PKC and RhoK.

Abnormal endothelin-1 (ET-1) activity is involved in the pathogenesis of vascular diseases such as essential and pulmonary arterial hypertension, coronary artery disease, and cerebrovascular disease, blockade of ET receptors having shown efficacy in clinical assays and experimental models of hypertension. Augmented Ca influx and changes in Ca sensitization associated with arterial vasoconstriction underlie increased systemic vascular resistance in hypertension. Since peripheral resistance arteries play a key role in blood pressure regulation, we aimed to determine here the specific Ca signaling mechanisms linked to the ET receptor-mediated vasoconstriction in resistance arteries and their selective regulation by protein kinase C (PKC), Rho kinase (RhoK), the phosphatidylinositol 3-kinase (PI3K) and the mitogen-activated protein kinase (MAPK). ET-1-induced contraction was mediated by the endothelin ET receptor with a minor contribution of vascular smooth muscle (VSM) endothelin ET receptors. ET receptor activation elicited Ca mobilization from intracellular stores, extracellular Ca influx and Ca sensitization associated with contraction in resistance arteries. Vasoconstriction induced by ET-1 was largely dependent on activation of canonical transient receptor potential channel 3 (TRPC3) and extracellular Ca influx through nifedipine-sensitive voltage-dependent Ca channels. PI3K inhibition reduced intracellular Ca mobilization and Ca entry without altering vasoconstriction elicited by ET-1, while PKC has dual opposite actions by enhancing Ca influx associated with contraction, and by inhibiting Ca release from intracellular stores. RhoK was a major determinant of the enhanced sensitivity of the contractile filaments underlying ET-1 vasoconstriction, with also a modulatory positive action on Ca influx and intracellular Ca release. Augmented RhoK and PKC activities are involved in vascular dysfunction in hypertension and vascular complications of insulin-resistant states, and these kinases are thus potential pharmacological targets in vascular diseases in which the ET pathway is impaired.