Maintenance of normal blood pressure is dependent on IP3R1-mediated regulation of eNOS

Abstract

Endothelial cells (ECs) are critical mediators of blood pressure (BP) regulation, primarily via the generation and release of vasorelaxants, including nitric oxide (NO). NO is produced in ECs by endothelial NO synthase (eNOS), which is activated by both calcium (Ca 2+ )-dependent and independent pathways. Here, we report that intracellular Ca 2+ release from the endoplasmic reticulum (ER) via inositol 1,4,5-trisphosphate receptor (IP3R) is required for Ca 2+ -dependent eNOS activation. EC-specific type 1 1,4,5-trisphosphate receptor knockout (IP3R1 −/− ) mice are hypertensive and display blunted vasodilation in response to acetylcholine (ACh). Moreover, eNOS activity is reduced in both isolated IP3R1-deficient murine ECs and human ECs following IP3R1 knockdown. IP3R1 is upstream of calcineurin, a Ca 2+ /calmodulinactivated serine/threonine protein phosphatase. We show here that the calcineurin/nuclear factor of activated T cells (NFAT) pathway is less active and eNOS levels are decreased in IP3R1-deficient ECs. Furthermore, the calcineurin inhibitor cyclosporin A, whose use has been associated with the development of hypertension, reduces eNOS activity and vasodilation following ACh stimulation. Our results demonstrate that IP3R1 plays a crucial role in the ECmediated vasorelaxation and the maintenance of normal BP.is a major cause of morbidity and mortality affecting millions of adults worldwide (1, 2). Globally, among the ∼17 million deaths caused by cardiovascular diseases, nearly half can be attributed to complications of HTN (3-9). In addition, vasodilator drugs that activate nitric oxide (NO) production have been used to treat HTN for decades (4, 10). Calcineurin (also known as protein phosphatase 2B), is a Ca 2+ /calmodulin-activated serine/ threonine protein phosphatase. Calcineurin inhibitors are first-line immunosuppressants used in organ transplantation (11,12). However, calcineurin inhibition causes HTN in up to 70% of patients (13), and the exact underlying mechanisms are not fully understood.Vascular endothelial cells (ECs), located at the interface between the vessel wall and blood, release vasorelaxants that influence vascular smooth muscle tone in response to mechanical (e.g., shear stress) and biochemical stimuli (14, 15). These stimuli induce a rapid increase in intracellular Ca 2+ ([Ca 2+ ] i ) in ECs activating Ca 2+ -dependent signaling pathways, resulting in release of endothelium-derived relaxing factors, including NO (14,[16][17][18][19]. Mice lacking endothelial nitric oxide synthase (eNOS) develop severe HTN (20). However, how eNOS is regulated in vivo remains essentially unclear. The modulation of both plasma membrane Ca 2+ entry and endoplasmic reticulum (ER) Ca 2+ release is critical in EC function (21,22). Moreover, recent meta-analysis and genome-wide association studies in hypertensive individuals have linked type 1 1,4,5-trisphosphate receptor (IP3R1), a major [Ca 2+ ] i release channel (23,24), to high blood pressure (BP) (25,26). On these grounds, we sought to inve...

Ryanodine Receptor Structure and Function in Health and Disease

“…They are required for excitation-contraction coupling, which translates an electrical signal into a mechanical output via the second messenger Ca 2+ (Santulli and Marks 2015). The closely related inositol 1,4,5-trisphosphate receptors (IP3Rs) are also found in most cell types and require the second messenger IP3 for activation (Harnick et al 1995; Yuan et al 2016; Santulli et al 2017a). In skeletal muscle there is a mechanical interaction between RyR1 on the sarcoplasmic reticulum (SR) membrane and the dihydropyridine receptor (Ca v 1.1) on specialized invaginations of the sarcolemma, called transverse tubules, leading to rapid Ca 2+ release (Rios and Brum 1987; Nelson et al 2013; Santulli et al 2017b).…”

Physiology and pathophysiology of excitation–contraction coupling: the functional role of ryanodine receptor

“…The ER/SR of most cell types contains two types of intracellular Ca 2+ release channels: the ryanodine receptors (RyRs) and the inositol 1,4,5-trisphosphate receptors (IP3Rs) (Santulli and Marks 2015; Go et al 1995; Yuan et al 2016; Santulli 2017). There is ~40% homology between the RyR and lP3R in the putative transmembrane regions (Marks et al 1989, 1990; Santulli 2017), a sequence similarity sufficient to indicate that these two channels evolved from a common ancestral cation release channel in unicellular species.…”

IP3 receptor signaling and endothelial barrier function

“…Interestingly enough, endothelial cell-specific knockout of IP 3 R1 causes high blood pressure in mice due to disruption of NFAT/endothelial nitric oxide synthase (eNOS) signaling [228]. Consistent with this finding, other studies demonstrate that expression of IP 3 R1 in aortic endothelial cell is downregulated in spontaneously hypertensive rats [222].…”

“…It is well-known that fluid shear stress induces intracellular Ca 2+ oscillations through activation of heterotrimeric G q /G 11 proteins, which is coupled to purinergic receptor [231], [232] or bound to the plasma membrane in endothelial cells [233], [234]. Deficiency in IP 3 R1 seems to disrupt these adaptive responses to increased blood flow in arteries of systemic circulation and causes hypertension [228, 235, 236]. Cumulatively, these findings suggest, that IP 3 R1-dependent Ca 2+ handling might play a critical role in regulating myogenic vascular tone in arteries.…”