Genetic silencing of K _Ca 3.1 inhibits atherosclerosis in ApoE null mice

Increased expression of K_Ca3.1 has been found in vascular smooth muscle cells (SMC), macrophages, and T cells in atherosclerotic lesions from humans and mice. Pharmacological inhibition of K_Ca3.1 in limiting atherosclerosis has been demonstrated in mice and pigs, however direct, loss-of-function, i.e. gene silencing, studies are absent. Therefore, we generated K_Ca3.1^-/-Apoe^-/- (DKO) mice and assessed lesion development in the brachiocephalic artery (BCA) of DKO versus Apoe^-/- mice on a Western diet for 3 months. In BCAs of DKO mice, lesion size and relative stenosis were reduced by ~70% compared to Apoe^-/- mice, with no effect on medial or lumen area. Additionally, DKO mice exhibited a significant reduction in macrophage content within plaques compared to Apoe^-/- mice, independent of sex. <i>In vitro</i> migration assays showed a significant reduction in migration of bone marrow-derived macrophages (BMDMs) from DKO mice compared to those from Apoe^-/- mice. <i>In vitro</i> experiments using rat aortic smooth muscle cells revealed inhibition of PDGF-BB-induced MCP1/Ccl2 expression upon K_Ca3.1 inhibition, while activation of K_Ca3.1 further enhanced MCP1/Ccl2 expression. Both <i>in vivo</i> and <i>in vitro</i> analyses showed that silencing K_Ca3.1 had no significant effect on the collagen content of plaque. RNAseq analysis of BCA samples from DKO and Apoe^-/- mice revealed PPAR-dependent signaling as a potential key mediator of the reduction in atherosclerosis due to K_Ca3.1 silencing. Overall, this study provides the first genetic evidence that K_Ca3.1 is a critical regulator of atherosclerotic lesion development and composition and provides novel mechanistic insight into the link between K_Ca3.1 and atherosclerosis.