The Effect of Voltage‐Sensitive Chloride Channel 6 on Development of Salt‐Sensitive Hypertension

Abstract

Hypertension is currently the number one risk factor for global disease burden. Advancing our knowledge on the underlying mechanisms of blood pressure (BP) control is essential to reduce the incidence of hypertension. Recent human genome‐wide association studies have linked a number of rare coding mutations and intronic single nucleotide polymorphisms in the gene, CLCN6, to lower average systolic and diastolic blood pressure as well as reduced hypertension risk. The voltage‐gated chloride channel 6 (CLC6) is encoded by CLCN6, which is one of 9 voltage‐gated chloride channel (CLC) family members. The functions of CLC6 at molecular, cellular, and physiological levels are largely unknown.We have previously introduced a 5 amino acid deletion into Clcn6 in the Dahl Salt Sensitive (SS) rat background (SS‐Clcn6em2Mcwim (hereafter called CLC6 KO)). These rats demonstrated lower mean arterial pressure (MAP) compared to WT SS rats (Flister et al., Genome Res, 2013) when placed on a high salt (HS, 4% NaCl) diet for 10 days, suggesting these animals might serve as a model system to study the role of CLCN6 in modulating blood pressure. To further test the role of CLC6 on blood pressure and renal function, we placed CLC6 KO or WT SS rats on a HS diet for 3 weeks and recorded their blood pressure using telemetry. Electrolytes and kidney injury were also analyzed. CLC6 KO rats had a significantly lower BP maintaining a MAP about 15 mmHg lower than the WT SS rats. There were no significant differences in plasma Na+, K+, Cl−, or Ca2+ levels between WT SS and CLC6 KO rats on NS diets; however, the plasma K+ levels of the CLC6 KO rats on the HS diet were significantly elevated compared to controls. Immunohistochemical analysis revealed that CLC6 is strongly expressed in blood vessel smooth muscle cells. Therefore, we studied vasodilatory response of isolated mesenteric resistance arteries in response to increasing concentrations of acetylcholine. We found that arteries from the CLC6 KO animals had impaired dilation to 10 μM acetylcholine, and relaxed to 25 ± 2.9 % of their maximal diameter relative to controls (60 ± 13.9 %). Lastly, we measured spontaneous intracellular Ca2+ activity in intact ex vivo mesenteric artery smooth muscle at single cell resolution using event detection analysis of two‐photon microscopy videos. Cells were constricted with phenylephrine then induced to relax with acetylcholine, and Ca2+ cycling was significantly reduced in the CLC6 KO (19.0 ± 1.7 sec vs 93.0 ± 11.3 sec) during relaxation, consistent with the vessel dilation studies.These results suggest that CLC6 KO is protective against development of salt sensitive hypertension by altering the intracellular Ca2+ activity in arterial smooth muscle cells, but additional studies are needed to more fully understand this effect.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.