Regulation of Klotho production by mineralocorticoid receptor signaling in renal cell lines

Abstract

Through the mineralocorticoid receptor, aldosterone controls extracellular volume and arterial blood pressure by stimulating Na⁺ absorption and K⁺ secretion in epithelial cells of the kidney, colon, and several glands. Hyperaldosteronism promotes fibrosis and inflammation in epithelial and non-epithelial tissues, thereby favoring loss of kidney and heart function. Mineralocorticoid receptor blockade therefore gains relevance especially in renal and cardiac disease. Kidney-derived Klotho is a powerful anti-aging protein with anti-fibrosis and anti-inflammatory effects providing cardio- and nephroprotection. We wondered whether Klotho expression and production is influenced by mineralocorticoid receptor agonists and antagonists. Using four renal cell lines, Madin-Darby canine kidney (MDCK), normal rat kidney, subtype 52E (NRK-52E), human kidney 2 (HK2) cells, and primary renal proximal tubule epithelial cells (RPTECs), and the four most frequently prescribed mineralocorticoid receptor blockers, spironolactone, eplerenone, finerenone, and esaxerenone, we assessed Klotho gene expression by qRT-PCR and Klotho protein by Western blotting. Aldosterone and eplerenone did not significantly affect Klotho expression in either cell line. Spironolactone enhanced Klotho expression in MDCK and NRK-52E cells and downregulated Klotho in HK2 cells and RPTECs. Novel non-steroidal mineralocorticoid receptor antagonist finerenone downregulated Klotho expression in MDCK, NRK-52E, and low-dose finerenone in HK2 cells. To conclude, common mineralocorticoid receptor antagonists are characterized by highly diverse effects on Klotho in four renal cell lines. Further studies are needed to define the role of mineralocorticoid receptor blockade for Klotho production.