IP3 receptors regulate vascular smooth muscle contractility and hypertension
Qingsong Lin, … , Ju Chen, Kunfu Ouyang
Qingsong Lin, … , Ju Chen, Kunfu Ouyang
Published October 20, 2016
Citation Information: JCI Insight. 2016;1(17):e89402. https://doi.org/10.1172/jci.insight.89402.
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Research Article Vascular biology

IP3 receptors regulate vascular smooth muscle contractility and hypertension

Abstract

Inositol 1, 4, 5-trisphosphate receptor–mediated (IP3R-mediated) calcium (Ca2+) release has been proposed to play an important role in regulating vascular smooth muscle cell (VSMC) contraction for decades. However, whether and how IP3R regulates blood pressure in vivo remains unclear. To address these questions, we have generated a smooth muscle–specific IP3R triple-knockout (smTKO) mouse model using a tamoxifen-inducible system. In this study, the role of IP3R-mediated Ca2+ release in adult VSMCs on aortic vascular contractility and blood pressure was assessed following tamoxifen induction. We demonstrated that deletion of IP3Rs significantly reduced aortic contractile responses to vasoconstrictors, including phenylephrine, U46619, serotonin, and endothelin 1. Deletion of IP3Rs also dramatically reduced the phosphorylation of MLC20 and MYPT1 induced by U46619. Furthermore, although the basal blood pressure of smTKO mice remained similar to that of wild-type controls, the increase in systolic blood pressure upon chronic infusion of angiotensin II was significantly attenuated in smTKO mice. Taken together, our results demonstrate an important role for IP3R-mediated Ca2+ release in VSMCs in regulating vascular contractility and hypertension.

Authors

Qingsong Lin, Guiling Zhao, Xi Fang, Xiaohong Peng, Huayuan Tang, Hong Wang, Ran Jing, Jie Liu, W. Jonathan Lederer, Ju Chen, Kunfu Ouyang

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Figure 1

Characterization of IP3R deletion in mouse vascular smooth muscle cells in vitro and in vivo.

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Characterization of IP3R deletion in mouse vascular smooth muscle cells ...
(A and B) Vascular smooth muscle cells (VSMCs) isolated from noninduced smTKO mice were cultured and treated with 1 μM 4-hydroxytamoxifen (4OHT) for 48 and 72 hours to induce IP3R gene deletion. VSMCs treated with vehicle were used as the control (Ctrl). Administration of 4OHT significantly decreased the mRNA (A) and protein (B) levels of each IP3R subtype compared with the vehicle treatment. n = 3 independent cultures per group. (C and D) mRNA (C) and protein (D) levels of each IP3R subtype in aortas were assessed from control and smTKO mice. n = 3 (with vessels from 3 mice pooled as one sample) per group. (E) Representative curves of Ca2+ release induced by 10 μM ATP in cultured VSMCs treated with vehicle (black) or 4OHT for 72 hours (gray). Cells were incubated with 5 μM fluo-4-AM at 37°C for 30 minutes and imaged with confocal microscopy. Cells were perfused in Ca2+-free solution for 1 to 2 minutes to eliminate Ca2+ entry via membrane ionotropic purinergic receptors prior to the administration of ATP. (F) Averaged Ca2+ signal mass calculated from the time course of Ca2+ release induced by ATP in VSMCs. n = 3 independent tests per group, and at least 20 cells per experiment were imaged. Significance was determined by the 2-tailed, unpaired Student’s t test. *P < 0.05, **P < 0.01, ***P < 0.001.Data represent mean ± SEM.