IP₃ receptors regulate vascular smooth muscle contractility and hypertension

Area of Science:

• Cardiovascular Biology
• Cellular Physiology
• Molecular Pharmacology

Background:

• Inositol 1,4,5-trisphosphate receptor (IP3R)-mediated calcium release is implicated in vascular smooth muscle cell (VSMC) contraction.
• The in vivo role of IP3Rs in regulating blood pressure remains largely undetermined.

Purpose of the Study:

• To investigate the role of IP3R-mediated calcium release in VSMCs in regulating vascular contractility and blood pressure in vivo.
• To determine the impact of IP3R deletion on aortic contractility and hypertension.

Main Methods:

• Generation of a smooth muscle-specific IP3R triple-knockout (smTKO) mouse model using a tamoxifen-inducible system.
• Assessment of aortic vascular contractility in response to various vasoconstrictors post-tamoxifen induction.
• Measurement of blood pressure and response to angiotensin II infusion in smTKO and wild-type mice.

Main Results:

• Deletion of IP3Rs significantly impaired aortic contractile responses to phenylephrine, U46619, serotonin, and endothelin 1.
• IP3R deletion markedly reduced the phosphorylation of MLC20 and MYPT1 induced by U46619.
• smTKO mice exhibited attenuated systolic blood pressure increases during chronic angiotensin II infusion compared to controls.

Conclusions:

• IP3R-mediated calcium release in VSMCs is essential for normal vascular contractility.
• IP3Rs play a critical role in the development of hypertension in vivo.