Spironolactone protects against hypertension-induced renal fibrosis by promoting autophagy and inhibiting the NLRP3 inflammasome

Introduction: We aimed to investigate the mechanism by which spironolactone protects against hypertensive renal fibrosis. Methods: For in-vivo experiments, we established Control, SHR, and SHR+spironolactone (20 mg/kg/day) groups. For in-vitro experiments, we established Control, TGF-β1-induced (10 ng/ml), and spironolactone (1 μmol/l) intervention groups. Renal function and serum potassium, estradiol, testosterone, and plasma aldosterone levels were assessed, along with autophagy indicators LC3 and p62, and NLRP3 inflammasome-related proteins (NLRP3, Caspase-1, IL-1β and IL-18). Additionally, changes in macrophage polarization and T cell and dendritic cell populations were determined. Results: 20 mg/kg/day of spironolactone effectively maintained systolic blood pressure and renal function by lowering aldosterone levels and significantly reducing testosterone levels. Hypertensive renal fibrosis was predominant in the glomeruli, tubules, and interstitium, and was associated with autophagy inhibition in renal tubules, NLRP3 inflammasome activation, both M1 and M2 macrophages polarization, with a predominant effect on M1 polarization, decreased CD4 + T cell population and CD4/CD8 ratio, and increased CD8 + T cell and dendritic cell population. Autophagy negatively regulated the NLRP3 inflammasome. Spironolactone inhibited both M1 and M2 macrophages polarization, mainly M1 macrophage polarization, reduced CD8 + T and dendritic cell population, increased CD4 + T cell population, negatively regulated the release of NLRP3 inflammasome-related proteins in macrophages, and restored autophagy in the glomeruli and renal tubules. Conclusion: Spironolactone acts on sites where the mineralocorticoid receptor is present. A dose of 20 mg/kg/day spironolactone is well tolerated and protects against hypertension-induced renal fibrosis by restoring autophagy and suppressing NLRP3 inflammasome activation.