MicroRNA-21 Overexpression Exacerbates Aldosterone-Mediated Renal Injury

Primary aldosteronism is characterized by excess autonomous secretion of aldosterone (ALDO) independent of the renin‐angiotensin system and accounts for ~10% of hypertensive patients. Excess ALDO causes hypertension and cardio‐renal hypertrophy, inflammation and fibrosis that lead to progressive cardio‐renal dysfunction. The molecular mechanisms involved in target organ injury induced by excess ALDO are poorly understood. MicroRNAs (miRNAs) are endogenous, small, non‐coding RNAs that downregulate the expression levels of specific proteins by translational repression or mRNA degradation. Multiple miRNAs have been implicated in renal physiological and pathological processes. Despite extensive studies, the role of miR‐21 in renal pathophysiology remains controversial. The aim of the present study is to elucidate the role of miR‐21 in excess ALDO/SALT‐mediated renal injury. We have previously shown that miR‐21 is ubiquitously expressed in the kidney parenchyma, and enriched in the renal collecting ducts. To analyze the role of miR‐21 in ALDO/SALT‐mediated renal injury, 8‐week old uninephrectomized male miR‐21 overexpression mice (miR21OE) or their wild type (WT) littermate controls were treated with ALDO (0.15 μg/h delivered by osmotic minipumps) and SALT (1.0 % NaCl + 0.3 % KCl in the drinking water) or vehicle for 8 weeks (n=6/group). miR‐21 overexpression attenuated ALDO/SALT‐mediated increase in blood pressure (123 ± 10 vs. 142 ± 4 mm Hg, p<0.05), but did not modify renal hypertrophy. Analysis of urinary biomarkers of renal injury were performed by colorimetric, enzymatic or ELISA assays. ALDO/SALT treatment exacerbated urinary protein excretion in miR21OE compared to WT mice (65 ± 4 vs. 53 ± 2 mg/day, p<0.05). Urinary creatinine concentration was elevated similarly in both miR21OE and WT mice by ALDO/SALT treatment. Urinary concentration of renal injury markers kidney injury marker 1 (KIM‐1; 32 ± 7 vs. 21 ± 6 ng/day, p<0.05) and neutrophil gelatinase‐associated lipocalin (NGAL; 1025 ± 328 vs. 344 ± 35 ng/day, p<0.05) were higher in miR21OE compared to WT mice. Urinary concentration of renal injury marker N‐acetyl‐β‐D‐glucosaminidase (NAG) was elevated by ALDO/SALT treatment to the same degree in both miR21OE and WT mice. Interestingly, miR21OE mice were protected from ALDO/SALT‐mediated increase in urinary gamma‐glutamyltransferase (GGT) activity (36 ± 12 vs. 99 ± 31 mU/day, p<0.05). Analysis of renal mRNA expression of fibrosis and inflammation markers was performed by RT‐qPCR. miR‐21 overexpression exacerbated ALDO/SALT‐mediated upregulation of the fibrosis marker, fibronectin (7.6 ± 1.8 vs. 3.1 ± 0.3 FC, p<0.05). Similar trends were observed for collagen I and III, connective tissue growth factor (CTGF), and lysyl oxidase (Lox). Expression of inflammation marker interleukin‐6 was upregulated by ALDO/SALT treatment only in miR21OE mice compared to WT (3.3 ± 0.8 vs. 1.7 ± 0.2 FC, p<0.05). Similar trends were observed for renal expression of interleukin‐10, plasminogen activator inhibitor‐1 (PAI‐1), monocyte chemoattractant protein‐1 (MCP‐1), and transforming growth factor β (TGF‐β). Our results suggest that miR‐21 overexpression exacerbates ALDO/SALT‐mediated renal fibrosis, inflammation, and certain urinary renal injury markers. These findings suggest that targeted miR‐21 downregulation may mitigate excess ALDO/SALT‐mediated renal injury in primary aldosteronism patients. Support or Funding Information Supported by American Heart Association Grant 12SDG8980032 (DGR) and NIH grants R21DK113500 (DGR) and R25HL121042 (MJR). This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .