Ablation of both Cx40 and Panx1 results in similar cardiovascular phenotypes exhibited in Cx40 knockout mice

Abstract

Connexins (Cxs) and pannexins (Panxs) are highly regulated large-pore channel-forming proteins that participate in cellular communication via small molecular exchange with the extracellular microenvironment, or in the case of connexins, directly between cells. Given the putative functional overlap between single membrane-spanning connexin hemichannels and Panx channels, and cardiovascular system prevalence, we generated the first Cx40−/−Panx1−/− mouse with the anticipation that this genetic modification would lead to a severe cardiovascular phenotype. Mice null for both Cx40 and Panx1 produced litter sizes and adult growth progression similar to wild-type (WT), Cx40−/− and Panx1−/− mice. Akin to Cx40−/− mice, Cx40−/−Panx1−/− mice exhibited cardiac hypertrophy and elevated systolic, diastolic, and mean arterial blood pressure compared with WT and Panx1−/− mice; however assessment of left ventricular ejection fraction and fractional shortening revealed no evidence of cardiac dysfunction between groups. Furthermore, Cx40−/−, Panx1−/−, and Cx40−/−Panx1−/− mice demonstrated impaired endothelial-mediated vasodilation of aortic segments to increasing concentrations of methacholine (MCh) compared with WT, highlighting roles for both Cx40 and Panx1 in vascular endothelial cell (EC) function. Surprisingly, elevated kidney renin mRNA expression, plasma renin activity, and extraglomerular renin-producing cell populations found in Cx40−/− mice was further exaggerated in double knockout mice. Thus, while gestation and gross development were conserved in Cx40−/−Panx1−/− mice, they exhibit cardiac hypertrophy, hypertension, and impaired endothelial-mediated vasodilation that phenocopies Cx40−/− mice. Nevertheless, the augmented renin homeostasis observed in the double knockout mice suggests that both Cx40 and Panx1 may play an integrative role.

Pannexin 1 channels in renin-expressing cells influence renin secretion and blood pressure homeostasis

“…54,55 Global deletion or vascular endothelial Panx1 deletion does not exhibit overt ABP phenotypes. 56,57 Thus, our previous and current studies highlight distinct roles for Panx1 channels in the peripheral and renal vasculature that differentially modulate ABP; these studies demonstrate that cell-type specific knockout animals, especially with Panx1, are essential for dissecting complex physiological mechanisms.…”

Mind the gap: connexins and pannexins in platelet function

“…Despite their structural and functional similarities, there is relatively little data available on the interactions between the pannexins and connexins. Noveielli-Kuntz and colleagues evaluated the cardiovascular phenotype of Cx40 −/- , Panx1 −/- and Cx40 −/- Panx1 −/- mice [ 62 ]. Cx40-deficient mice have impaired vasodilation of aortic segments, leading to hypertension, a phenotype not observed in Panx1 −/- mice.…”

“…Cx40-deficient mice have impaired vasodilation of aortic segments, leading to hypertension, a phenotype not observed in Panx1 −/- mice. This phenotype was explored further with the double knockout and Panx1 depletion could not rescue the vascular phenotype of Cx40 −/- [ 62 ]. However, the impact of this model upon platelet function and thrombus formation was not assessed.…”