The Deletion of Endothelial Sodium Channel α (αENaC) Impairs Endothelium-Dependent Vasodilation and Endothelial Barrier Integrity in Endotoxemia in Vivo.

Magdalena Sternak,Frederic Jaisser,Antoine Tarjus,Brygida Marczyk,Tasnim Mohaissen,Mateusz G Adamski,Stefan Chlopicki,Anna Bar,Kamil Kus,Marta Stojak,Anna Kieronska

doi:10.3389/fphar.2018.00178

Abstract

The role of epithelial sodium channel (ENaC) activity in the regulation of endothelial function is not clear. Here, we analyze the role of ENaC in the regulation of endothelium-dependent vasodilation and endothelial permeability in vivo in mice with conditional αENaC subunit gene inactivation in the endothelium (endo-αENaCKO mice) using unique MRI-based analysis of acetylcholine-, flow-mediated dilation and vascular permeability. Mice were challenged or not with lipopolysaccharide (LPS, from Salmonella typhosa, 10 mg/kg, i.p.). In addition, changes in vascular permeability in ex vivo organs were analyzed by Evans Blue assay, while changes in vascular permeability in perfused mesenteric artery were determined by a FITC-dextran-based assay. In basal conditions, Ach-induced response was completely lost, flow-induced vasodilation was inhibited approximately by half but endothelial permeability was not changed in endo-αENaCKO vs. control mice. In LPS-treated mice, both Ach- and flow-induced vasodilation was more severely impaired in endo-αENaCKO vs. control mice. There was also a dramatic increase in permeability in lungs, brain and isolated vessels as evidenced by in vivo and ex vivo analysis in endotoxemic endo-αENaCKO vs. control mice. The impaired endothelial function in endotoxemia in endo-αENaCKO was associated with a decrease of lectin and CD31 endothelial staining in the lung as compared with control mice. In conclusion, the activity of endothelial ENaC in vivo contributes to endothelial-dependent vasodilation in the physiological conditions and the preservation of endothelial barrier integrity in endotoxemia.

Highlights

The epithelial sodium channel (ENaC), composed of three subunits, is a member of the epithelial Na(+) channel (ENaC)/degenerin superfamily of cation-selective ion channels (Canessa et al, 1994; Kosari et al, 1998; Alvarez De La Rosa et al, 2000; Warnock et al, 2014)
Using a cell-specific knockout mouse model with deletion of the endothelial sodium channel α (αENaC) subunit in the endothelial cells, we demonstrated in vivo that genetic deletion of the αENaC subunit in the endothelium resulted in blunted Ach- and flow-induced vasodilation in the aorta and femoral artery (FA), respectively, without a major effect on endothelial permeability
In endotoxemia, the absence of endothelial ENaC resulted in a more severe impairment of Ach- and flow-induced vasodilation in conduit vessels, as well as pronounced endothelial barrier dysfunction in conduit and peripheral vessel as well as in the lung and brain microcirculation in comparison with mice with preserved endothelial ENaC expression. This dysregulation of the endothelial barrier was associated with altered glycocalyx in endo-αENaCKO mice as evidenced by the lower expression of lectin and CD31 in lungs Altogether, our comprehensive study using various methods to detect endothelial function and permeability changes in various vascular beds allows us to suggest that endothelial ENaC contributes to endothelialdependent regulation of vascular tone in conduit vessels and to the preservation of the endothelial barrier function in endotoxemia both in conduit vessels, in the peripheral αENaC Activity in the Regulation of Endothelial Function

Summary

Introduction

The epithelial sodium channel (ENaC), composed of three subunits (αENaC, βENaC, and γENaC), is a member of the ENaC/degenerin superfamily of cation-selective ion channels (Canessa et al, 1994; Kosari et al, 1998; Alvarez De La Rosa et al, 2000; Warnock et al, 2014). The expression of ENaC has been described in the vascular smooth muscle and endothelium, pointing to its possible role in the regulation of vascular function. All three subunits of ENaC are present in endothelium (Pérez et al, 2009), and the αENaC was shown to be involved in the regulation of endothelial cortical stiffness (Jeggle et al, 2013). Jeggle et al (2013) claimed a direct correlation between ENaC surface expression and the formation of cortical stiffness in endothelial cells. In a mouse model of Liddle syndrome, an inherited form of hypertension caused by gain-of-function mutations in the epithelial Na(+) channel (ENaC), enhanced ENaC expression and increased cortical stiffness were observed in vascular endothelial cells in situ, suggesting that ENaC in the vascular endothelium determines endothelial mechanics and vascular function

Methods

Results

Discussion

Conclusion