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

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.

The TNF-derived TIP peptide activates the epithelial sodium channel and ameliorates experimental nephrotoxic serum nephritis

“…58 However, others have shown that in mesenteric arteries, ENaC mediates vasodilation and increases NO generation 59 and that endothelial ENaC-a knockout mice have decreased vasodilatory capacity. 26 We have previously shown that TIP peptide increases rather than decreases NO generation in pulmonary microvascular endothelial cells in response to bacterial toxins. 19 These findings suggest a context-dependent role of ENaC in endothelial function whereby the effects differ during inflammatory and noninflammatory states.…”

“…We demonstrated that the TIP peptide binds to the a subunit of the epithelial sodium channel (ENaC), 20,22 which can be expressed in both epithelial and endothelial cells. 25,26 Support for this experimental direction is provided by the finding that inhaled TIP peptide (a.k.a. AP301 and solnatide) was recently found to be safe in a phase 1 clinical trial in volunteers 27 and displayed promising activities on lung function in 2 phase 2a clinical trials in patients with acute lung injury 28 and after lung transplantation.…”

Multiorgan Development of Oxidative and Nitrosative Stress in LPS-Induced Endotoxemia in C57Bl/6 Mice: DHE-BasedIn VivoApproach

“…However, with DHE also measured and the 2-OH-E + /DHE ratio unchanged along with reduced E + /DHE ratio (Figure 2(b) and 2(d), respectively), this would rather suggest that during endotoxemia in the lung, the single electron oxidation of DHE might be shifted from disproportionation, which leads to E + formation, towards dimerization, resulting in the formation of dimeric products [14], though verification of this hypothesis remains beyond the scope of this article. A different distribution pattern was observed in the liver where DHE, 2-OH-E + , and E + accumulation did not change upon LPS challenge, despite a systemic increase in vascular permeability in endotoxemia [28] and dysfunctional hepatic circulation post-LPS injection. Nevertheless, the 2-OH-E + /E + ratio increased significantly 12 hours post-LPS challenge (Figure 1(g)), similar to both 2-OH-E + /DHE and E + /DHE ratios (Figure 2(a) and 2(c), respectively), suggesting that the liver is under O 2 ∙- -dependent and O 2 ∙- -independent oxidative stress.…”

“…With no DHE detected in the brain and kidney, the origin of the detected 2-OH-E + and E + remains unclear. These could have accumulated from the circulation, as the blood-brain barrier integrity after LPS is compromised [28]. Importantly, only E + was found in the brain tissue, suggesting that the previously reported oxidative stress using DHE fluorescence in the brain [5–13] may not have been formed in situ .…”

Editorial: Cytokine-Ion Channel Interactions in Pulmonary Inflammation

“…These data thus indicate that the ENaC-α subunit, apart from playing a crucial role in ALC in the alveolar epithelium, can also strengthen barrier function in the capillary endothelium. Recent studies have moreover shown a protective role of this ENaC subunit, as well as of the β1 subunit of the Na-K-ATPase, in LPS-induced ALI in mice ( 9 , 10 ). It is important to note that mechanisms impairing barrier function in alveolar epithelial cell monolayers can also negatively affect ENaC expression, at least partially in a transient receptor potential vanilloid 4 (TRPV4)-dependent manner ( 11 ).…”