The Function and Mechanim of Prorenin Receptor (PRR) in Hypertensive Nephropathy

The Function and Mechanim of Prorenin Receptor (PRR) in Hypertensive Nephropathy

Hypertension is a major independent risk factor for chronic kidney diseases. However, the exact pathologic mechanisms of hypertensive renal fibrosis are still unknown. Our preliminary studies demonstrated that dysregulated activation of the key developmental signaling pathway Wnt/β-catenin controls renin angiotensin system (RAS) expression, which promote the pathogenesis of hypertension and renal fibrosis. Interestingly, we recently identified the positive feedback loop between prorenin receptor (PRR) and Wnt/β-catenin signaling promotes renal fibrosis. Besides, as a component of RAS, PRR plays an important role in activating RAS and regulating hypertension. Here, we evaluated whether PRR mediates hypertension nephropathy progression.

20 male BALB/c mice were implanted subcutaneously for the Ang II infusion model using osmotic mini-pump. And mice were received intravenous injection of pcDNA3 plasmid, PRR expression plasmid or siPRR expression plasmid at 3 days and 8 days after Ang II infusion. The blood pressure of the mice was measured, and mice sacrificed at 14 days post-surgery, blood and kidney tissues were harvested for renal function assay, immunohistochemistry, RT-PCR and WB respectively. In vivo, serum starved HKC-8 cells were pretreated with recombinant Ang II for 24 h. The cells were transfected with PRR plasmid or siPRR plasmid for 6 h before incubated with Ang II. And then cells were collected and subjected to various analyses. In addition, sixty-seven human renal specimens were collected at our center between September 2018 and September 2023, including 38 cases of hypertensive nephropathy, 24 cases of non-hypertensive nephropathy (7 cases of IgA nephropathy, 6 cases of diabetic nephropathy, 5 cases of minimal change disease, and 6 cases of membranous nephropathy) and 5 cases of peritumoral renal tissues. The expression of PRR in renal tissues was detected by immunohistochemistry and semi-quantitatively analyzed by using Image-Pro Plus software. Furthermore, Pearson's correlation analysis was carried out to analyze the correlations between the expression level of PRR and eGFR, serum creatinine, blood urea nitrogen, 24-hour proteinuria, renal fibrosis area and tubular damage.

1). Compared with Ctrl, the blood pressure of AngII group increased significantly; AngII+PRR could further increase the blood pressure; AngII+siPRR can block the increase of blood pressure caused by Ang II infusion. 2). Compared with Ctrl, the ratio of urine microalbumin/urine creatinine (ACR) was increased in AngII group; the AngII+PRR group could further increase ACR than AngII group, and the AngII+siPRR group could reduce the ACR level caused by AngII infusion. 3). Compared with Ctrl, AngII caused β-catenin protein expression; AngII+PRR increased induction of catenin; AngII+siPRR inhibited β-catenin protein expression. 2). Compared with Ctrl, AngII promoted α-SMA, Fibronectin protein and mRNA indction; AngII+PRR group further promoted the expression of above fibrosis; siPRR treatment inhibit α-SMA, fibronectin protein and mRNA expression. 5). Compared with Ctrl, AngII induced the expression TNF-α protein and mRNA; AngII+PRR further increased the expression of TNF-α protein and mRNA; AngII+siPRR down regulates TNF-α protein and mRNA level. 6). Compared with Ctrl group, AngII promoted β-catenin, α- SMA and fibronectin and TNF-α expression in HK-C cells; Overexpression of PRR further promotes β-catenin signal, renal fibrosis and expression of inflammatory factors; Inhibiting PRR can block β-catenin signal activation, and inhibited renal fibrosis and inflammation. 3). Immunohistochemical analysis revealed that PRR was heterogeneously expressed in glomeruli and tubules in CKD patients, while no discernible expression was detected in normal peritumoral tissues. Furthermore, Mann-Whitney test indicated that patients with hypertensive nephropathy had markedly higher PRR expression compared to the non-hypertensive nephropathy cohort (P<0.0001). ROC curve analysis demonstrated PRR expression level yielded an area under the curve (AUC) of 0.872 (95% confidence interval: 0.787-0.957), with an optimal cutoff value of 1.35%, 97% sensitivity, and 66% specificity for predicting hypertensive nephropathy. Additionally, Spearman's correlation coefficient analysis showed that in hypertensive nephropathy patients, PRR expression positively correlated with blood urea nitrogen (P<0.05), serum creatinine (P <0.0001), 24-hour urinary protein excretion (P<0.05), and renal fibrosis area (P<0.05), while negatively correlating with glomerular filtration rate (P<0.0001) and urinary osmolality (P<0.01). However, no significant correlations between PRR expression and renal function in non-hypertensive nephropathy cohort.

1. PRR activation promotes the development of hypertensive nephropathy. 2. Inhibit PRR can reduce the progression of hypertensive renal fibrosis. 3.PRR expression is markedly upregulated in hypertensive nephropathy patients and correlates with renal function and renal fibrosis. Our novel findings suggest PRR as a potential biomarker for hypertensive nephropathy.