Abstract 191: Transcriptional Regulation of Renin by Nuclear Receptors Co-regulated With Renin

Abstract

Expression of the renin gene is required to maintain normal morphological and physiological identity of renal juxtaglomerular (JG) cells, yet the mechanisms regulating renin gene transcription remain elusive. We re-examined data from Brunskill et. al (JASN 22:2213, 2011), investigating genome-wide gene expression in JG and other renal cell types. Based on our previous data implicating nuclear receptors (RAR, RXR, VDR, PPARG, Nr2f2 and Nr2f6) in the regulation of mouse and human renin gene expression, we focused our analysis on the expression of genes encoding the 48 nuclear hormone receptors and their co-regulation with renin. Several nuclear receptors have an expression pattern emulating that of renin, that is, they were similarly enriched in JG cells but not in other cell types. These include Esr1, Nr1h4, Ppara, VDR, Nr1i2, Ppard, Hnf4g, Nr1h3, Thrb, Hnf4a, Esrrg, Nr4a3, Nr3c2, and Ar. We tested the hypothesis that a nuclear receptor that is co-regulated with renin may participate in renin gene regulation. To accomplish this, endogenous renin expression was evaluated in renin-expressing As4.1 cells after siRNA-mediated knock down of selected nuclear receptors. Each experiment included a negative control siRNA duplex (NC) that does not target any known genes. By way of example, siRNA-mediated inhibition of estrogen receptor alpha (Esr1) by 70-80% resulted in a 2-fold decrease in renin mRNA (fold change ± SEM: siEsr1: 0.4±0.2, p<0.001 vs NC). Similar results were obtained with a different siRNA targeting Esr1. Interestingly, loss of Esr1 also caused up-regulation of vitamin D receptor (VDR, 2.8±0.7 fold, p<0.001 vs NC) and Nr2f6 (2.0±0.2 fold, p<0.05 vs NC), both of which are known to be negative regulators of renin. Similarly, both renin (0.1±0.02, p<0.001 vs untreated) and Esr1 (0.3±0.1, p<0.05 vs untreated) mRNA were reduced in the kidney from mice treated with deoxycorticosterone acetate (50mg) and receiving 0.15 M NaCl in drinking water for 21 days (DOCA-salt). These data suggest Esr1 may regulate renin expression. Studies are in progress to assess if Esr1 stimulates renin expression on its own or acts by affecting the level of other nuclear receptors; and to determine if other co-regulated nuclear receptors also regulate expression of the renin gene.