Smooth muscle LRRC8A knockout preserves vascular function in AngII hypertension

Abstract

Angiotensin II (AngII) causes hypertension and vascular inflammation both directly and indirectly via cytokines. In vascular smooth muscle cells (VSMCs) AngII and TNF activate NADPH oxidase 1 (Nox1) to produce superoxide. TNF receptors associate with Nox1 and Leucine Rich Repeat Containing 8A (LRRC8A) anion channels to modulate inflammation, as well as contractility in a RhoA-dependent manner. VSMC-specific LRRC8A knockout (KO) mesenteric arteries are protected from TNF-induced injury and vasodilated better. We hypothesized that LRRC8A KO would preserve vascular function and decrease blood pressure (BP) in AngII-infused mice. Wild type (WT) and LRRC8A KO mice received AngII infusions for 14 days. Systolic BP was not different, but KO mice had more BP "dipping" during inactive periods and dipping was preserved after AngII. Contraction of KO mesenteric vessels to AngII itself was not altered, however after AngII exposure the function of KO aortic and mesenteric vessels was less impaired as reflected by less augmented contraction to norepinephrine and serotonin and preserved relaxation to acetylcholine and sodium nitroprusside. Western blotting revealed increased soluble guanylate cyclase alpha and reduced CPI-17 in hypertensive KO aortae. Consistent with the presence of lower Rho kinase activity in KO VSMCs, phosphorylation of Ezrin/Radixin/Moesin (ERM) and Cofilin was reduced. Aortic wall/lumen was not different between hypertensive WT and KO mice, but AngII caused less proliferation (lower PCNA), and less induction of antioxidant enzymes and senescence markers in KO vessels. Thus, while AngII-induced contraction does not require LRRC8A, these channels support the associated inflammatory response which modifies BP dipping.