TMEM16A contributes to angiotensin II-induced cerebral vasoconstriction via the RhoA/ROCK signaling pathway.

Calcium activated chloride channels (CaCCs) are critical in vascular smooth muscle function as they regulate proliferation/apoptosis of smooth muscle cells (SMCs) and vascular tone. Transmembrane protein 16A (TMEM16A) was demonstrated to encode CaCCs in basilar artery SMCs (BASMCs) and participate in basilar artery remodeling during hypertension. In addition, TMEM16A has recently been illustrated to contribute to pressure­induced myogenic response in cerebral vasculature. However, whether TMEM16A is involved in cerebral vasoconstriction that is stimulated by other vasoconstrictors remains unclear. The aim of the present study was to establish whether TMEM16A is involved in the progression of angiotensin II (Ang II)­induced basilar artery constriction and elucidate its potential role during hypertension. The study demonstrated that the specific inhibitor of TMEM16A, T16A­inhA01 attenuated Ang II­induced constriction in rat basilar arteries, and that this effect was weakened in parallel with the decline of TMEM16A expression in basilar arteries of 2­kidney, 2­clip hypertensive rats. Furthermore, it was found that 100 nM Ang II evoked a chloride current in cultured BASMCs with a basal 100­nM intracellular Ca2+ ([Ca2+]i) level. In addition, the current could be abolished by TMEM16A small interfering RNA pretreatment and Ang II receptor type 1 (AT1) receptor blocker, losartan, while Ang II failed to cause a further increase to Ca2+­dependent Cl­ currents activated by 500 nM [Ca2+]i. In addition, in cultured BASMCs, Ang II induced phosphorylation of myosin phosphatase­targeting subunit 1, and myosin light chains were significantly enhanced by TMEM16A overexpression, which were reversed by Rho­associated protein kinase (ROCK) inhibitor, Y­27632, while TMEM16A silencing demonstrated an opposing result. Furthermore, Ang II­induced RhoA activation was enhanced by TMEM16A overexpression. In conclusion, the present study revealed that Ang II elicited a TMEM16A­mediated current and TMEM16A participated in Ang II­induced basilar constriction via the RhoA/ROCK signaling pathway.