Department of General Physiology, St. Petersburg State University, 199034 St. Petersburg, Russia.
Department of Biomedicine, University of Aarhus, C 8000 Aarhus, Denmark.
Int J Mol Sci. 2020 Jul 17;21(14):5067. doi: 10.3390/ijms21145067.
The ability of exogenous low ouabain concentrations to affect claudin expression and therefore epithelial barrier properties was demonstrated previously in cultured cell studies. We hypothesized that chronic elevation of circulating ouabain in vivo can affect the expression of claudins and tight junction permeability in different tissues. We tested this hypothesis in rats intraperitoneally injected with ouabain (1 μg/kg) for 4 days. Rat jejunum, colon and brain frontal lobes, which are variable in the expressed claudins and tight junction permeability, were examined. Moreover, the porcine jejunum cell line IPEC-J2 was studied. In IPEC-J2-cells, ouabain (10 nM, 19 days of incubation) stimulated epithelial barrier formation, increased transepithelial resistance and the level of cSrc-kinase activation by phosphorylation, accompanied with an increased expression of claudin-1, -5 and down-regulation of claudin-12; the expression of claudin-3, -4, -8 and tricellulin was not changed. In the jejunum, chronic ouabain increased the expression of claudin-1, -3 and -5 without an effect on claudin-2 and -4 expression. In the colon, only down-regulation of claudin-3 was observed. Chronic ouabain protected the intestine transepithelial resistance against functional injury induced by lipopolysaccharide treatment or by modeled acute microgravity; this regulation was most pronounced in the jejunum. Claudin-1 was also up-regulated in cerebral blood vessels. This was associated with reduction of claudin-3 expression while the expression of claudin-5 and occludin was not affected. Altogether, our results confirm that circulating ouabain can functionally and tissue-specifically affect barrier properties of epithelial and endothelial tissues via Na,K-ATPase-mediated modulation of claudins expression.
先前的细胞培养研究表明，外源性低哇巴因浓度能够影响 Claudin 的表达，从而影响上皮屏障特性。我们假设，体内循环哇巴因的慢性升高会影响不同组织中 Claudin 的表达和紧密连接的通透性。我们通过给大鼠腹腔注射哇巴因（1μg/kg）4 天来验证这一假设。检测了大鼠空肠、结肠和大脑额叶，这些组织中 Claudin 的表达和紧密连接的通透性存在差异。此外，还研究了猪空肠细胞系 IPEC-J2。在 IPEC-J2 细胞中，哇巴因（10 nM，孵育 19 天）刺激上皮屏障形成，增加跨上皮电阻和 cSrc-激酶磷酸化激活水平，同时增加 Claudin-1、-5 的表达，下调 Claudin-12 的表达；Claudin-3、-4、-8 和三细胞连接蛋白的表达没有变化。在空肠中，慢性哇巴因增加 Claudin-1、-3 和 -5 的表达，但对 Claudin-2 和 -4 的表达没有影响。在结肠中，仅观察到 Claudin-3 的下调。慢性哇巴因能保护肠上皮细胞的跨上皮电阻，使其免受脂多糖处理或模拟急性微重力引起的功能损伤；这种调节在空肠中最为明显。 Claudin-1 在脑血管中也上调。这与 Claudin-3 表达的减少有关，而 Claudin-5 和闭合蛋白的表达不受影响。总之，我们的结果证实，循环哇巴因可以通过 Na,K-ATP 酶介导的 Claudin 表达调节，功能性和组织特异性地影响上皮和内皮组织的屏障特性。
