Department of Medical Engineering, College of Engineering, University of South Florida, Tampa, FL, 33620, USA.
Global Center for Hearing and Speech Research, University of South Florida, Tampa, FL, 33612, USA.
Sci Rep. 2020 Sep 24;10(1):15604. doi: 10.1038/s41598-020-72450-4.
Na-K-2Cl Cotransporter (NKCC1) is a protein that aids in the active transport of sodium, potassium, and chloride ions across cell membranes. It has been shown that long-term systemic treatment with aldosterone (ALD) can enhance NKCC1 protein expression and activity in the aging cochlea resulting in improved hearing. In the present work, we used a cell line with confirmed NKCC1 expression to demonstrate that in vitro application of ALD increased outward voltage-gated potassium currents significantly, and simultaneously upregulated whole lysate and membrane portion NKCC1 protein expression. These ALD-induced changes were blocked by applying the mineralocorticoid receptor antagonist eplerenone. However, application of the NKCC1 inhibitor bumetanide or the potassium channel antagonist Tetraethyl ammonium had no effect. In addition, NKKC1 mRNA levels remained stable, indicating that ALD modulates NKCC1 protein expression via the activation of mineralocorticoid receptors and post-transcriptional modifications. Further, in vitro electrophysiology experiments, with ALD in the presence of NKCC1, K channel and mineralocorticoid receptor inhibitors, revealed interactions between NKCC1 and outward K channels, mediated by a mineralocorticoid receptor-ALD complex. These results provide evidence of the therapeutic potential of ALD for the prevention/treatment of inner ear disorders such as age-related hearing loss.
钠钾 2 氯协同转运蛋白（NKCC1）是一种蛋白，可帮助钠离子、钾离子和氯离子跨细胞膜进行主动运输。研究表明，长期全身性应用醛固酮（ALD）可增强衰老耳蜗中 NKCC1 蛋白的表达和活性，从而改善听力。在本研究中，我们使用经证实表达 NKCC1 的细胞系证明，体外应用 ALD 可显著增加外向电压门控钾电流，同时上调整个裂解物和膜部分 NKCC1 蛋白表达。ALD 诱导的这些变化可被矿物质皮质激素受体拮抗剂螺内酯阻断。但是，NKCC1 抑制剂布美他尼或钾通道拮抗剂四乙铵的应用没有效果。此外，NKKC1 mRNA 水平保持稳定，表明 ALD 通过激活矿物质皮质激素受体和转录后修饰来调节 NKCC1 蛋白表达。此外，在存在 NKCC1、K 通道和矿物质皮质激素受体抑制剂的情况下进行体外电生理学实验，揭示了 NKCC1 和外向 K 通道之间的相互作用，该作用由矿物质皮质激素受体-ALD 复合物介导。这些结果为 ALD 在预防/治疗内耳疾病（如年龄相关性听力损失）方面的治疗潜力提供了证据。
