Korte Stefanie, Sträter Alexandra S, Drüppel Verena, Oberleithner Hans, Jeggle Pia, Grossmann Claudia, Fobker Manfred, Nofer Jerzy-Roch, Brand Eva, Kusche-Vihrog Kristina
Institute of Physiology II, University of Münster, Münster, Germany;
Julius-Bernstein-Institute of Physiology, University Halle-Wittenberg, Halle, Germany;
FASEB J. 2014 Sep;28(9):4015-25. doi: 10.1096/fj.14-250282. Epub 2014 May 27.
Kidney epithelial sodium channels (ENaCs) are known to be inactivated by high sodium concentrations (feedback inhibition). Recently, the endothelial sodium channel (EnNaC) was identified to control the nanomechanical properties of the endothelium. EnNaC-dependent endothelial stiffening reduces the release of nitric oxide, the hallmark of endothelial dysfunction. To study the regulatory impact of sodium on EnNaC, endothelial cells (EA.hy926 and ex vivo mouse endothelium) were incubated in aldosterone-free solutions containing either low (130 mM) or high (150 mM) sodium concentrations. By applying atomic force microscopy-based nanoindentation, an unexpected positive correlation between increasing sodium concentrations and cortical endothelial stiffness was observed, which can be attributed to functional EnNaC. In particular, an acute rise in sodium concentration (+20 mM) was sufficient to increase EnNaC membrane abundance by 90% and stiffening of the endothelial cortex by 18%. Despite the absence of exogenous aldosterone, these effects were prevented by the aldosterone synthase inhibitor FAD286 (100 nM) or the mineralocorticoid receptor (MR)-antagonist spironolactone (100 nM), indicating endogenous aldosterone synthesis and MR-dependent signaling. Interestingly, in the presence of high-sodium concentrations, FAD286 increased the transcription of the MR by 69%. Taken together, a novel feedforward activation of EnNaC by sodium is proposed that contrasts ENaC feedback inhibition in kidney.
肾上皮钠通道（ENaCs）已知会被高钠浓度（反馈抑制）所失活。最近，内皮钠通道（EnNaC）被确定可控制内皮的纳米力学特性。EnNaC依赖性的内皮硬化会减少一氧化氮的释放，而一氧化氮释放减少是内皮功能障碍的标志。为了研究钠对EnNaC的调节作用，将内皮细胞（EA.hy926和离体小鼠内皮）置于含有低（130 mM）或高（150 mM）钠浓度的无醛固酮溶液中孵育。通过应用基于原子力显微镜的纳米压痕技术，观察到钠浓度升高与皮质内皮硬度之间存在意外的正相关，这可归因于功能性的EnNaC。特别是，钠浓度的急性升高（+20 mM）足以使EnNaC膜丰度增加90%，并使内皮皮质硬度增加18%。尽管没有外源性醛固酮，但醛固酮合酶抑制剂FAD286（100 nM）或盐皮质激素受体（MR）拮抗剂螺内酯（100 nM）可阻止这些作用，表明存在内源性醛固酮合成和MR依赖性信号传导。有趣的是，在高钠浓度存在的情况下，FAD286可使MR的转录增加69%。综上所述，提出了一种由钠对EnNaC进行的新型前馈激活机制，这与肾脏中ENaC的反馈抑制形成对比。
