Regulation of the renal epithelial sodium channel (ENaC) by the vascular endothelial growth factor (VEGF) and the pathogenetic role of renal ENaC for VEGF receptor inhibitor-induced hypertension.

血管内皮生长因子 (VEGF) 对肾上皮钠通道 (ENaC) 的调节以及肾 ENaC 对 VEGF 受体抑制剂诱导的高血压的发病作用。

• 批准号: 288511211
• 负责人: Professor Dr. Olaf Grisk, since 3/2016
• 金额: --
• 依托单位: Institut für Physiologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/288511211?language=en
• 关键词: Regulation; renal; epithelial; sodium; channel

Vascular endothelial growth factor receptor (VEGFR) inhibitors are used in tumor therapy. One therapy-limiting side effect is arterial hypertension. The role of renal mechanisms in VEGFR inhibitor-induced hypertension is currently unclear. In experimental studies in rats, we showed that the VEGFR inhibitor, sunitinib, significantly decreases fractional Na+ excretion while having little effects on vascular function. Fractional Li+ excretion, as a marker for proximal Na+ reabsorption, was unchanged suggesting that Na+ transport was affected at more distal sites. Experiments in murine cortical CD (M1) cells further revealed that VEGF (VEGF-A) significantly decreases epithelial Na+ channel (ENaC) subunit mRNA abundances and that this effect is inhibited by sunitinib. VEGF also significantly reduced alpha-ENaC subunit protein abundance in M1 cells. Again, sunitinib diminished this effect.Our findings suggest that VEGF may be a negative physiological regulator of ENaC in the kidney and that increased ENaC-dependent Na+ reabsorption may contribute to sunitinib-induced hypertension. The first objective of our proposed project is to examine whether VEGF down-regulates ENaC in M1 cells. We will test the hypotheses that VEGF reduces ENaC protein abundances and proteolytic cleavage of gamma-ENaC, activates the VEGFR-2, induces internalization of ENaC and decreases ENaC activity (patch clamp). In addition, we will investigate if the extracellular signal-regulated kinase (ERK1/2)- and the nitric oxide synthase (NOS)-dependent pathways are involved in the VEGF-induced ENaC down-regulation.The second objective is to investigate if the VEGFR inhibitor, sunitinib, increases renal ENaC activity in rats. We will test the hypotheses that sunitinib treatment for 4 days increases renal ENaC expression, enhances proteolytic cleavage of the gamma-ENaC subunit, decreases phosphorylation of beta- and gamma-ENaC subunits or stimulates the insertion of ENaC subunits from the cytoplasm into the apical plasma membrane, leading to enhanced ENaC activity. The third objective is to test if sunitinib reduces renal NO formation in rats. We will test the hypotheses that sunitinib treatment for 4 days decreases renal NOS expression, decreases renal NOS activity and alters the localization of renal NOS isoenzymes. Furthermore, we will treat rats with a combination of sunitinib and the NO donor, nitrate, to test the hypotheses that NO reduces the sunitinib-induced increases in arterial blood pressure and renal sodium reabsorption and reduces the sunitinib-induced increases in renal ENaC expression. Finally, we will perform experiments in CD-specific NOS1 knockout mice to test the hypothesis that sunitinib causes greater elevations in arterial pressure and renal sodium reabsorption in knockout mice than in controls.

血管内皮生长因子受体（VEGFR）抑制剂用于肿瘤治疗。一种限制治疗的副作用是动脉高血压。肾脏机制在VEGFR受体介导的高血压中的作用目前尚不清楚。在大鼠的实验研究中，我们发现VEGFR抑制剂舒尼替尼显著降低Na+排泄分数，而对血管功能几乎没有影响。分数Li+排泄，作为近端Na+重吸收的标志，是不变的，这表明Na+转运在更远的网站受到影响。在小鼠皮质CD（M1）细胞中的实验进一步揭示了VEGF（VEGF-A）显著降低上皮Na+通道（ENaC）亚基mRNA丰度，并且舒尼替尼抑制了该作用。VEGF还显著降低了M1细胞中α-ENaC亚基蛋白的丰度。我们的研究结果表明，VEGF可能是肾脏ENaC的负性生理调节因子，ENaC依赖性Na+重吸收增加可能导致舒尼替尼诱导的高血压。我们提出的项目的第一个目标是检查VEGF是否下调M1细胞中的ENaC。我们将测试以下假设：VEGF降低ENaC蛋白丰度和γ-ENaC的蛋白水解裂解，激活VEGFR-2，诱导ENaC内化并降低ENaC活性（膜片钳）。此外，我们还将研究细胞外信号调节激酶（ERK 1/2）和一氧化氮合酶（NOS）依赖性通路是否参与VEGF诱导的ENaC下调。第二个目的是研究VEGFR抑制剂舒尼替尼是否增加大鼠肾脏ENaC活性。我们将测试舒尼替尼治疗4天增加肾脏ENaC表达，增强γ-ENaC亚基的蛋白水解裂解，降低β-和γ-ENaC亚基的磷酸化或刺激ENaC亚基从细胞质插入顶端质膜，导致ENaC活性增强的假设。第三个目的是测试舒尼替尼是否减少大鼠肾脏NO的形成。我们将检验舒尼替尼治疗4天降低肾NOS表达、降低肾NOS活性和改变肾NOS同工酶定位的假设。此外，我们将用舒尼替尼和NO供体硝酸盐的组合治疗大鼠，以测试NO降低舒尼替尼诱导的动脉血压和肾钠重吸收增加并降低舒尼替尼诱导的肾ENaC表达增加的假设。最后，我们将在CD特异性NOS 1基因敲除小鼠中进行实验，以验证舒尼替尼导致敲除小鼠动脉压和肾钠重吸收升高的假设。