Smooth Muscle LRRC8A Anion Channel Knockout Promotes Vasodilation and Protects Against TNFα‐induced Vascular Dysfunction

Abstract

Tumor necrosis factor‐α (TNFα), a pro‐inflammatory cytokine, is associated with cardiovascular risk. Volume‐regulated anion channels (VRACs) are activated by TNFα and are composed of Leucine Rich Repeat Containing 8 (LRRC8) family proteins (LRRC8A, B, C, D and E). LRRC8A is required for all VRACs. We previously determined that VRAC inhibitors or LRRC8A knockdown suppress the inflammatory response to TNFα in cultured vascular smooth muscle cells, however, the role of these channels in vasomotor function has not been studied. We hypothesized that loss of LRRC8A would prevent the impairment of vascular function by TNFα. We created vascular smooth muscle‐specific (Sm22alpha‐Cre) LRRC8A knockout (KO) mice and isolated mesenteric arteries from male mice for wire myograph recording. Vessel segments were incubated with TNFα (10 ng/mL) or vehicle for 2 days in tissue culture. Contractile responses to norepinephrine (NE) were unaltered in LRRC8A KO mice but enhanced by TNFα in wild type (WT) than in KO rings (WT+TNFα 284 ± 18.9 %, KO+TNFα 222 ± 7.1 % of KCl contraction, *p<0.05, n = 5‐6). In the vehicle‐treated group both endothelium‐dependent (acetylcholine, ACh) and ‐independent (sodium nitroprusside, SNP) relaxation were increased in LRRC8A KO compared to WT rings contracted with phenylephrine (PE). Exposure to TNFα impaired relaxation to both ACh and SNP in WT vessels but had no effect on relaxation of LRRC8A KO vessels (black *p<0.05 compared to WT control, red *p<0.05 compared to TNFα‐treated, n = 6‐8). The enhanced relaxation responses of KO vessels were recapitulated in WT rings by 20 min of exposure to a VRAC inhibitor, carbenoxolone (CBX; 100 μM). Thus, in addition to its established role in TNFα signaling, LRRC8A anion channel activity modulates vascular reactivity with loss of function enhancing vasodilator function. VRAC inhibition may provide a novel therapeutic approach to the prevention and treatment of inflammation‐induced vascular dysfunction.