Interplay Between Connexin40 and Nitric Oxide Signaling During Hypertension

Abstract

A fter a chronic increase in blood pressure, arteries undergo alterations of endothelial (ECs) and smooth muscle cells (SMCs) because of hemodynamic changes.1 Specifically, hypertension results in the hypertrophic remodeling of arterial walls, 2,3 which associates with altered expression of connexins (Cxs). [4][5][6][7][8] These proteins form channels for the communication of ECs and SMCs, which is needed to coordinate vasoconstriction and vasodilation along the vessels.9 ECs predominantly express Cx37 and Cx40, [5][6][7] whereas SMCs mostly express Cx43 and Cx45. 5,6,10 Mice lacking Cx40 feature hypertension 4,6,11,12 because of increased secretion of renin 4,13 and reduced relaxation of peripheral vessels.14 This effect may be the link to the decreased expression of endothelial nitric oxide synthase (eNOS), 5,15 which impairs the release of NO, whereby ECs usually relax SMCs. [4][5][6]13 Thus, restoration of Cx40 in ECs of Cx40−/− mice normalizes eNOS levels, 8 suggesting an interaction between these proteins. As yet, however, such interaction has not been tested during hypertension.To investigate this question, we have subjected wild-type (WT) and Cx40-null mice (Cx40−/−) 4,13 to conditions inducing hypertension by either volume overload (after a 1-kidney, 1-clip [1K1C] procedure 16,17 ) or renin overproduction (after a 2-kidney, 1-clip [2K1C] procedure 6 ). We show that Cx40 consistently increased in aortic ECs, whereas Cx37 and Cx45 increased in SMCs, irrespective of the mechanism leading to hypertension. In contrast, Cx43 only increased in SMCs during renin-dependent hypertension. The volume-dependent hypertension of WT mice was associated with an increased interaction between Cx40 and Cx37 with eNOS, whereas Cx40−/− null mice featured decreased levels of eNOS and increased phosphorylation of the enzyme. The results provide evidence that Cx40 and Cx37 of ECs activate different signaling mechanisms depending on the cause of hypertension. MethodsSee online-only Data Supplement. Results 1K1C Procedure Induces Volume-Dependent HypertensionCompared with untreated WT controls, WT 1K1C mice featured increased blood pressure, heart weight, kidney index, and thickeness of the aortic media (Tables S2 and S3 in the online-only Data Supplement). These alterations occurred in Abstract-Connexins (Cxs) and endothelial nitric oxide synthase (eNOS) contribute to the adaptation of endothelial and smooth muscle cells to hemodynamic changes. To decipher the in vivo interplay between these proteins, we studied Cx40-null mice, a model of renin-dependent hypertension which displays an altered endothelium-dependent relaxation of the aorta because of reduced eNOS levels. These mice, which were either untreated or subjected to the 1-kidney, 1-clip (1K1C) procedure, a model of volume-dependent hypertension, were compared with control mice submitted to either the 1K1C or the 2-kidney, 1-clip (2K1C) procedure, a model of renin-dependent hypertension. All operated mice became hypertensive and featured hypertrophy and altered Cx express...

Enhanced Function of Induced Pluripotent Stem Cell-Derived Endothelial Cells Through ESM1 Signaling

“…G). This data is in agreement with previous reports showing a role of CX40 in ECs in association with the EC marker eNOS . Therefore, these experiments demonstrate that ESM1 regulates the expression of EC markers such as eNOS and CD144 through an association with CX40, an important EC gap junction channel component, possibly due to increased formation and stability of gap junctions, which are essential functional EC characteristics.…”

The eNOS signalosome and its link to endothelial dysfunction

“…Restoration of Cx40 expression in endothelial cells from Cx40-deficient mice normalizes eNOS levels [93], suggesting a link between these proteins. Volume-dependent hypertension (one kidney, one clip model) promotes the interaction of both Cx40 and Cx37 with eNOS resulting in increased release of NO [93]. Contrary to what was previously shown for Cx37's effect on eNOS function in vitro, vascular reactivity studies demonstrated that basal NO release and the sensitivity to acetylcholine are decreased in aortae from Cx37 −/− and Cx40 −/− mice but not in Cx40 +/− mice [94].…”

“…This effect has been linked to reduced eNOS expression in Cx40-deficient mice [92]. Restoration of Cx40 expression in endothelial cells from Cx40-deficient mice normalizes eNOS levels [93], suggesting a link between these proteins. Volume-dependent hypertension (one kidney, one clip model) promotes the interaction of both Cx40 and Cx37 with eNOS resulting in increased release of NO [93].…”

Interaction Between ALK1 Signaling and Connexin40 in the Development of Arteriovenous Malformations

“…How endothelial Cx40 controls blood pressure remains poorly understood but might be attributable to endothelial nitric oxide synthase activity, an important modulator of vascular tone. 40 Interestingly, both ALK1 and Cx40 interact and regulate the activity of endothelial nitric oxide synthase, 33,41 suggesting that the phenotype of the Acvrl1 +/− ; Gja5 EGFP/+ mice may be at least partially attributable to uncoupled endothelial nitric oxide synthase activity. To support this hypothesis, we have found an increase production of reactive oxygen species in the lung arteries of Acvrl1 +/− ; Gja5 EGFP/+ mice.…”