Homocysteine Causes Endothelial Dysfunction via Inflammatory Factor-Mediated Activation of Epithelial Sodium Channel (ENaC)

Abstract

BackgroundHyperhomocysteinemia (HHcy) causes cardiovascular diseases via regulating inflammatory responses. We investigated whether and how the epithelial sodium channel (ENaC), a recently identified ion channel in endothelial cells, plays a role in HHcy-induced endothelial dysfunction.MethodsCell-attached patch-clamp recording in acute split-open aortic endothelial cells, western blot, confocal imaging, and wire myograph combined with pharmacological approaches were used to determine whether HHcy-mediated inflammatory signaling leads to endothelial dysfunction via stimulating ENaC.ResultsThe data showed that 4 weeks after L-methionine diet the levels of plasma Hcy were significantly increased and the ENaC was dramatically activated in mouse aortic endothelial cells. Administration of benzamil, a specific ENaC blocker, ameliorated L-methionine diet-induced impairment of endothelium-dependent relaxation (EDR) and reversed Hcy-induced increase in ENaC activity. Pharmacological inhibition of NADPH oxidase, reactive oxygen species (ROS), cyclooxygenase-2 (COX-2)/thromboxane B2 (TXB2), or serum/glucocorticoid regulated kinase 1 (SGK1) effectively attenuated both the Hcy-induced activation of endothelial ENaC and impairment of EDR. Our in vitro data showed that both NADPH oxidase inhibitor and an ROS scavenger reversed Hcy-induced increase in COX-2 expression in human umbilical vein endothelial cells (HUVECs). Moreover, Hcy-induced increase in expression levels of SGK-1, phosphorylated-SGK-1, and phosphorylated neural precursor cell-expressed developmentally downregulated protein 4-2 (p-Nedd4-2) in HUVECs were significantly blunted by a COX-2 inhibitor.ConclusionWe show that Hcy activates endothelial ENaC and subsequently impairs EDR of mouse aorta, via ROS/COX-2-dependent activation of SGK-1/Nedd4-2 signaling. Our study provides a rational that blockade of the endothelial ENaC could be potential method to prevent and/or to treat Hcy-induced cardiovascular disease.

Homocysteine metabolism as the target for predictive medical approach, disease prevention, prognosis, and treatments tailored to the person

“…Hcy post-translationally downregulates dimethylarginine dimethylaminohydrolase enzyme activity (the enzyme that degrades ADMA), causing asymmetric dimethylarginine (ADMA, an endogenous inhibitor of NO synthase) to accumulate and thus inhibit NO synthesis [84]. Liang et al (2021) described that Hcy activates the epithelial sodium channel and consequently induces endothelial dysfunction via reactive oxygen species (ROS)/COX-2-dependent activation of SGK-1/Nedd4-2 signaling [85]. Additionally, Hcy induced a calcium-mediated disruption of dynamics and mitochondrial function in endothelial cells due to overexpression of the mitochondrial calcium uniporter and the IP3R-Grp75-VDAC complex in mitochondria-associated membranes [86].…”

Deficiency of B vitamins leads to cholesterol-independent atherogenic transformation of the aorta

“…Moreover, our data link VCDD to enhancement of norepinephrineinduced contraction probably due to altered biomechanical properties of the aorta as well as impairment of acetylcholine-relaxation. Supporting this notion, Hcy was shown to be associated with endothelial dysfunction (Liang et al, 2021), and the combination of HCD and methionine, a precursor of Hcy, results in virtually abolished endothelium-dependent relaxation (Zulli et al, 2003). Furthermore, VCDD leads to atherogenic transformation of the aorta already in the absence of HCD.…”

Aldosterone-stimulated endothelial epithelial sodium channel (EnNaC) plays a role in cold exposure–induced hypertension in rats

“…The biophysical features of endothelial EnNaC single-channel current, recorded in split-open MAs and in MAECs shown in this study, are comparable to those described previously in the rat or mouse endothelial cells ( Liu et al, 2015b ; Niu et al, 2021 ). Indeed, EnNaC plays a role in salt overload-, homocysteinmia-, and high-fat diet-induced vascular dysfunction ( Yang et al, 2020b ; Liang et al, 2021 ; Niu et al, 2021 ). In addition, other reports showed that activation of EnNaC is responsible for endothelial stiffness and vascular remodeling ( Guo et al, 2016 ).…”

“…Decreased production of vasodilator NO is tightly linked to endothelial dysfunction, vasoconstriction, and elevation of blood pressure. Previous studies showed that activation of EnNaC in the endothelium contributes to pathological stimuli-induced vascular endothelial dysfunction and hypertension ( Jeggle et al, 2013 ; Wang et al, 2018 ; Yang et al, 2020b ; Liang et al, 2021 ). Augmented EnNaC activity hampered the transportation of L-arginine, resulting in impaired NO generation in human umbilical vein endothelial cells ( Guo et al, 2016 ).…”