Inositol 1,4,5-Trisphosphate Receptors in Endothelial Cells Play an Essential Role in Vasodilation and Blood Pressure Regulation

Abstract

Background Endothelial NO synthase plays a central role in regulating vasodilation and blood pressure. Intracellular Ca²⁺ mobilization is a critical modulator of endothelial NO synthase function, and increased cytosolic Ca²⁺ concentration in endothelial cells is able to induce endothelial NO synthase phosphorylation. Ca²⁺ release mediated by 3 subtypes of inositol 1,4,5-trisphosphate receptors ( IP ₃Rs) from the endoplasmic reticulum and subsequent Ca²⁺ entry after endoplasmic reticulum Ca²⁺ store depletion has been proposed to be the major pathway to mobilize Ca²⁺ in endothelial cells. However, the physiological role of IP ₃Rs in regulating blood pressure remains largely unclear. Methods and Results To investigate the role of endothelial IP ₃Rs in blood pressure regulation, we first generated an inducible endothelial cell-specific IP ₃R1 knockout mouse model and found that deletion of IP ₃R1 in adult endothelial cells did not affect vasodilation and blood pressure. Considering all 3 subtypes of IP ₃Rs are expressed in mouse endothelial cells, we further generated inducible endothelial cell-specific IP ₃R triple knockout mice and found that deletion of all 3 IP ₃R subtypes decreased plasma NO concentration and increased basal blood pressure. Furthermore, IP ₃R deficiency reduced acetylcholine-induced vasodilation and endothelial NO synthase phosphorylation at Ser1177. Conclusions Our results reveal that IP ₃R-mediated Ca²⁺ release in vascular endothelial cells plays an important role in regulating vasodilation and physiological blood pressure.

Keywords: blood pressure; calcium; calcium signaling; endothelial cell; hypertension.