Prorenin receptor mediates inflammation in renal ischemia

Abstract

We hypothesized that PRR contributes to renal inflammation in the 2-kidney, 1-clip (2K1C) renal ischaemia model. Male Sprague-Dawley rats were fed normal sodium diet. Blood pressure (BP) was obtained on days 0 and 28 after left renal artery clipping that reduced renal blood flow by 40%. Renal expression of TNF-α, COX-2, NF-κB, IL-1β, MCP-1 and collagen type I were assessed in sham and 2K1C rats with or without left renal administration of scramble or PRR shRNA. At baseline, there were no differences in BP. Compared to sham, MAP significantly increased in clipped animals (sham 102 ± 1.9 vs 2K1C 131.8 ± 3.09 mmHg, P < .05) and was not influenced by scramble or PRR shRNA treatment. Compared to sham and contra lateral (non-clipped) kidney, there was upregulation in mRNA and protein expression of PRR (99% and 45%, P < .01), TNF-α (72% and 50%, P < .05), COX-2 (72% and 39%, P < .05), p-NF-κB (92%, P < .05), MCP-1 (87%, P < .05) and immunostaining of collagen type I in the clipped kidney. These increases were not influenced by scramble shRNA. Compared to 2K1C and scramble shRNA, PRR shRNA treatment in the clipped kidney significantly reduced the expression of PRR (62% and 57%, P < .01), TNF-α (51% and 50%, P < .05), COX-2 (50% and 56%, P < .05), p-NF-κB by 68% (P < .05), MCP-1 by 73% (P < .05) and collagen type I respectively. Ang II was increased in both kidneys and did not change in response to scramble or PRR shRNA treatments. We conclude that PRR mediates renal inflammation in renal ischaemia independent of blood pressure and Ang II.

Keywords: (pro)renin receptor; fibrosis; inflammation.

Figure 1

Renal mRNA (A) and protein (B) expressions of (Pro)renin receptor (PRR), mRNA (C) and protein (D) expressions of Tumor necrosis factor- α (TNF-α), mRNA (E) and protein (F) expressions of COX-2, phosphorylation of p-NFκB (G) and total expression of NFκB (H) in Non-clip kidney (NCK, RK) vs clipped kidney (CK, LK) in sham and 2K1C rats following scramble shRNA and PRR shRNA administration in CK. mRNA normalized to β-actin, representative blots (top), quantitative results normalized to β-actin. Data presented as mean ± SEM, *p<0.05 vs sham and ^#p<0.05 vs 2K1C+ scramble shRNA.

Figure 2

Renal interstitial fluid (RIF) (A) expression of interleukine-1β (IL-1β) and (B) angiotensin II in kidneys of sham and 2K1C rats. (C) Urinary albumin to creatinine ratio (UACR) in sham and 2K1C rats following scramble shRNA and PRR shRNA administration in CK. (D) Renal expressions of Monocyte chemotactic protein 1 (MCP-1), in non-clip kidney (NCK, RK) vs clipped kidney (CK, LK) in sham and 2K1C rats following scramble shRNA and PRR shRNA administration in CK. Representative blots (top), quantitative results normalized to β-actin. Data presented as mean ± SEM, *p<0.05 vs sham and ^#p<0.05 vs 2K1C+ scramble shRNA.

Figure 3

Representative images of PRR and Collagen Type I immunostaining in renal cortex and medulla of Clipped Kidney. Cortical (A–D), medullary (E–H) expression of PRR, and Cortical (I–L), medullary (M–P) expression of Collagen Type I in sham, 2K1C+ D5W, 2K1C+ scramble shRNA and 2K1C+ PRR shRNA.