Novel Smooth Muscle Ca ²⁺ -Signaling Nanodomains in Blood Pressure Regulation

Abstract

Background: Ca 2+ signals in smooth muscle cells (SMCs) contribute to vascular resistance and control blood pressure. Increased vascular resistance in hypertension has been attributed to impaired SMC Ca 2+ signaling mechanisms. In this regard, transient receptor potential vanilloid 4 (TRPV4 SMC ) ion channels are a crucial Ca 2+ entry pathway in SMCs. However, their role in blood pressure regulation has not been identified. Methods: We used SMC-specific TRPV4 −/− (TRPV4 SMC −/− ) mice to assess the role of TRPV4 SMC channels in blood pressure regulation. We determined the contribution of TRPV4 SMC channels to the constrictor effect of α1 adrenergic receptor (α1AR) stimulation and elevated intraluminal pressure: 2 main physiologic stimuli that constrict resistance-sized arteries. The contribution of spatially separated TRPV4 SMC channel subpopulations to elevated blood pressure in hypertension was evaluated in angiotensin II–infused mice and patients with hypertension. Results: We provide first evidence that TRPV4 SMC channel activity elevates resting blood pressure in normal mice. α1AR stimulation activated TRPV4 SMC channels through PKCα (protein kinase Cα) signaling, which contributed significantly to vasoconstriction and blood pressure elevation. Intraluminal pressure–induced TRPV4 SMC channel activity opposed vasoconstriction through activation of Ca 2+ -sensitive K + (BK) channels, indicating functionally opposite pools of TRPV4 SMC channels. Superresolution imaging of SMCs revealed spatially separated α1AR:TRPV4 and TRPV4:BK nanodomains in SMCs. These data suggest that spatially separated α1AR–TRPV4 SMC and intraluminal pressure–TRPV4 SMC –BK channel signaling have opposite effects on blood pressure, with α1AR–TRPV4 SMC signaling dominating under resting conditions. Furthermore, in patients with hypertension and a mouse model of hypertension, constrictor α1AR–PKCα–TRPV4 signaling was upregulated, whereas dilator pressure–TRPV4–BK channel signaling was disrupted, thereby increasing vasoconstriction and elevating blood pressure. Conclusions: Our data identify novel smooth muscle Ca 2+ -signaling nanodomains that regulate blood pressure and demonstrate their impairment in hypertension.

Vascular smooth muscle cell dysfunction in neurodegeneration

“…Another study found that activated TRPV1 inhibited VSMC proliferation, migration, and ROS production by upregulating the expression of PPARα ( Zhou et al, 2021 ). Additionally, TRPV4 channel activity has been found to increase vasoconstriction and elevate resting blood pressure in mice and patients with hypertension ( Chen et al, 2022 ).…”

Endothelial IK and SK channel activation decreases pulmonary arterial pressure and vascular remodeling in pulmonary hypertension

“…Isolated ECs and SMCs were fixed by incubation with 4% PFA at room temperature for 15 min and then permeabilized by treatment with PBS containing 0.2% Triton‐X for 1 h. The cells were then treated with 5% normal donkey serum for 1 h. ECs were subsequently incubated with monoclonal CD31 antibody (1:100; #RM5201; Invitrogen 18 ) for 1 h at room temperature. SMCs were incubated with FITC‐conjugated anti‐α‐actin antibody (1:500; F3777; Sigma Aldrich 18 , 27 for 1 h at room temperature. After washing the cells three times with PBS, nuclei were stained by incubating with 0.3 μmol/L DAPI (Invitrogen) for 10 min at room temperature in the dark.…”

“…For SMC isolation, 27 arterial segments were transferred to a 12 × 75 mm borosilicate glass culture tube containing 1 ml dissociation solution (145 mmol/L NaCl; 4 mmol/L KCl; 1 mmol/L MgCl 2 ; 10 mmol/L HEPES; 0.05 mmol/L CaCl 2 ,10 mmol/L glucose; pH 7.3) and 0.5 mg/ml bovine serum albumin (BSA) and incubated for 10 min at room temperature (~24°C). The solution was then replaced with 1 ml dissociation solution containing 1 mg/ml papain (Sigma Aldrich) and 0.5 mg/ml dithiothreitol (Sigma Aldrich), and incubation was continued at 37°C for 20 min.…”

TRPV4 Channel–Regulated Microdomains Define a New Paradigm in Hypertension

“…Isoforms of TRPC, TRPV, and TRPM have been identified in the vascular system and are emerging as important regulators of vascular tone and function, particularly TRPC1, TRPC3, TRPC6, TRPC7, TRPV1, TRPV4, and TRPM7. [9][10][11][12] They have also been linked pathological conditions associated with endothelial dysfunction, vascular contraction, and arterial remodeling, processes that characterize the vasculopathy of hypertension. 12 Further developing this notion, Chen and colleagues 10 demonstrate that vascular TRPV4 channels are critically involved in the pathophysiology of hypertension.…”

“…15 Although most previous studies have focused on dysregulation of TRPV4 channels in endothelial cells in hypertension, it is now evident that VSMCs are also important. Using inducible TRPV4 SMC −/− mice, Chen et al 10 show that TRPV4 SMC channels increase blood pressure in basal conditions and contribute to blood pressure elevation in angiotensin II-induced hypertension. The authors go on to unravel underlying molecular mechanisms and demonstrate subpopulations of differentially regulated TRPV4 channels with opposing actions.…”