MicroRNA-324-3p Promotes Renal Fibrosis and Is a Target of ACE Inhibition

Abstract

The contribution of microRNA (miRNA) to the pathogenesis of renal fibrosis is not well understood. Here, we investigated whether miRNA modulates the fibrotic process in Munich Wistar Fromter (MWF) rats, which develop spontaneous progressive nephropathy. We analyzed the expression profile of miRNA in microdissected glomeruli and found that miR-324-3p was the most upregulated. In situ hybridization localized miR-324-3p to glomerular podocytes, parietal cells of Bowman's capsule, and most abundantly, cortical tubules. A predicted target of miR-324-3p is prolyl endopeptidase (Prep), a serine peptidase involved in the metabolism of angiotensins and the synthesis of the antifibrotic peptide N-acetyl-serylaspartyl-lysyl-proline (Ac-SDKP). In cultured tubular cells, transient transfection with a miR-324-3p mimic reduced Prep protein and activity, validating Prep as a target of this miRNA. In MWF rats, upregulation of miR-324-3p associated with markedly reduced expression of Prep in both glomeruli and tubules, low urine Ac-SDKP, and increased deposition of collagen. ACE inhibition downregulated glomerular and tubular miR-324-3p, promoted renal Prep expression, increased plasma and urine Ac-SDKP, and attenuated renal fibrosis. In summary, these results suggest that dysregulation of the miR-324-3p/Prep pathway contributes to the development of fibrosis in progressive nephropathy. The renoprotective effects of ACE inhibitors may result, in part, from modulation of this pathway, suggesting that it may hold other potential therapeutic targets. 23: 149623: -150523: , 201223: . doi: 10.1681 Munich Wistar Fromter (MWF) is an inbred rat strain characterized by inborn nephron deficit, glomerular hypertrophy, and high urinary protein excretion. 1,2 Males develop hypertension and overt proteinuria with age. 3,4 Angiotensin II (Ang II) has a direct role in the pathogenesis of proteinuria and glomerular injury by decreasing the size selectivity of the glomerular capillary barrier against the filtration of plasma proteins 5,6 that is followed by development of glomerulosclerosis. 4 Treatment with an angiotensin-converting enzyme inhibitor (ACEi) protects MWF rats from kidney damage by both preserving and remodeling the glomerular barrier, thus inducing regression of proteinuria and glomerulosclerosis. 7,8 A large body of evidence in this model and other animal models and clinical trials confirms that Ang II is a potential therapeutic target for remission/regression of progressive glomerulopathies. 9,10 In advanced nephropathy, J Am Soc Nephrol

Delivery of microRNA-146a with polyethylenimine nanoparticles inhibits renal fibrosis in vivo

“…14 Several miRs have been reported to suppress transcription of important mRNAs that regulate the development of renal fibrosis. [15][16][17][18][19][20][21][22][23][24] However, few studies have focused on the effects of exogenous miR delivery on renal fibrosis in an in vivo therapeutic setting. [15][16][17][18]24 miR146a has been reported to inhibit inflammation by suppressing target mRNAs, such as those encoding tumor necrosis factor receptor-associated factor 6 (TRAF6), interleukin-1 receptor-associated kinase 1 (IRAK1), and Toll-like receptor 4 (TLR4), resulting in the inhibition of NF-κB in several organs.…”

Post-Transcriptional Gene Regulation Makes Things Clearer in Renal Fibrosis

“…Overexpression of miR-324-3p increased proximal tubular cell (PTC) susceptibility to developing a fibrogenic phenotype in response to TGF-b. 15 In the study by Zhou et al, renal miR-150 expression correlated with the expression of profibrotic molecules like collagen I (COL1), which were significantly increased in the renal tubulointerstitium. Whether the altered expression of miR-150 in LN patients was associated with changes in clinical markers such as proteinuria was not shown, possibly because kidney specimens were retrieved from LN patients enrolled between 1976 and 1999 and no clinical data were available.…”

Angiotensin Converting Enzyme Inhibitor–Modulated MicroRNAs Targeting Renal Fibrosis

“…Treatment of the rats with an ACE inhibitor, lisinopril, significantly raised urine and plasma concentrations of Ac-SDKP and suppressed interstitial collagen deposition in the kidneys with higher Prep expression and less miR-324-3p expression in the tubular epithelia. 15 This study strongly suggests that dysregulation of the miR-324-3p/Prep complex contributes to the progression of spontaneous nephropathy in MWF rats. However, its universal validity remains to be clarified, because miR-324-3p has never been identified in any lists of upregulated miRNAs detected in kidney tissues from either diabetic nephropathy or IgA nephropathy, 14,21,22 in which the profibrotic effects of ACE inhibition have been confirmed.…”

“…20 Delivery of a miR-324-3p mimic into cultured tubular epithelial cells resulted in significant downregulation of mRNA encoding Prep and protein expression and suppressed TGF-b1 induction of a profibrotic marker, a-smooth muscle actin, in those cells. 15 In situ hybridization and immunohistochemistry also demonstrated that upregulation of miR-324-3p expression associates with reduced expression of Prep in both glomeruli and cortical tubular epithelia in fibrotic areas. Treatment of the rats with an ACE inhibitor, lisinopril, significantly raised urine and plasma concentrations of Ac-SDKP and suppressed interstitial collagen deposition in the kidneys with higher Prep expression and less miR-324-3p expression in the tubular epithelia.…”

“…10 Additionally, other miRNAs implicated in renal fibrosis thus far include miR-192, miR200a, and miR-377. [12][13][14] In this issue of JASN, Macconi et al 15 add miR-324-3p into the interesting mix of miR regulators in renal fibrosis. They found miR-324-3p was significantly upregulated in glomeruli from the kidneys of Munich Wistar Fromter (MWF) rats with spontaneous progressive nephropathy.…”