The Protective Effects Of Irbesartan On Renal Tubulointerstitial Fibrosis With Unilateral Ureteral Obstruction In Rats

Objective:E26 transformation specific-1(Ets-1) involves in the pathophysiological processes such as development, proliferation and differentiation of cell, angiogenesis, apoptosis, reconstruction of organizations. To investigate the preventive mechanism of Irbesartan and the effect of Ets-1 on the progression of renal interstitial fibrosis with unilateral ureteral obstruction(UUO) in rats.Methods:Forty-five male, Sprague-Dauley (SD) rats, clean animal grade, were randomly divided into the following 3 groups: Sham,UUO,irbesartan (Irb).They were obstructed left ureter through an abdominal incision under sterile conditions and the sham group took the seem opration except for not ligating the left uretera. Irbesartan (50mg·kg-1·d-1) which were dissolved in normal saline were separately administered by gavage once a day from one day before operations. Rats of Sham group and UUO group were administered by gavage by normal saline of equal volume. On the 3rd day, 7th day and 14th day after operation, Left kidney removed after the rats were sacrificed by exsanguinations after left kidney removed. In obstructed kidney, histolgical changes were observed by HE stain, Masson stain and PAS stain. The distribution and expression of E26 transformation specific-1 (Ets-1), transforming growth factor-β1(TGF-β1), matrix metalloproteinase-9(MMP-9) and its main inhibitor tissue inhibitor of metalloproteinase-1(TIMP-1),α-SMA and ColⅠwere measured by routine immunohistochemical method. The results were analyzed semi-quantitatively with the pathological image analysis system. The mRNA of Ets-1 in renal of all 3 groups were measured by RT-PCR.Results:①I rbesartan reduced renal interstitial fibrosis: on the 3rd, 7th and 14th days after UUO, extent of renal interstitial fibrosis of UUO group had statistical significance compared with Sham group at same time point(P<0.05). Irb group reduced the extent of interstitial fibrosis,and had statistical significance compared with UUO group(P<0.05). After UUO, colⅠcontent of renal tissue in UUO group increased compared with Sham group, and reached a peak on 14th day( P<0.05). Irb groups inhibited the increases of colⅠcompared with UUO groups (P<0.05).②T he expression of Ets-1: the expression of Ets-1 was increased in UUO compared with Sham, it reached peak on 7th day then began to decrease from that (P<0.05). In Irb group, Ets-1 level was higher than UUO group at late (P<0.01). The mRNA of Ets-1 reached its peak on 3th day then began to decrease from that in UUO (P<0.05). Ets-1 mRNA level increased at late in Irb compared with UUO group (P<0.05). The expression of Ets-1 protein was positively correlated with Ets-1 mRNA in each group (r=0.832, 0.756, P<0.05).③I rbesartan reduced renal tissue expression of TGF-β1: from the 3rd day, the positive area of TGF-β1 of UUO group increased and were statistically significant, compared with Sham group (P<0.05); the increased trend had been curbed in Irb group, which appeared significant from 7th with UUO Group (P<0.05).④Irbesartan increased the expression of MMP-9 and reduced the TIMP-1: the expression of MMP-9 was increased in UUO, it reached peak on 7th day and then began to decrease, compared with Sham group (P<0.05). In Irb, MMP-9 level was higher than UUO group at late(P<0.01).The expression of TIMP-1 in UUO group increased from the 3rd day, and reached its peak on 14th, compared with Sham group (P<0.05). The increased trend had been curbed in Irb group (P<0.05).⑤I rbesartan inhibited the epithelial-mesenchymal transition (EMT): there's hardly any expression ofα-SMA in the renal tubular epithelial cells of sham group. On the 3rd day, the expression ofα-SMA in the renal tubular epithelial cells in UUO group was increased evidently, and kept increasing until 14th. Meanwhile the expression ofα-SMA in tubular epithelial cells in Irb group was decreased (P<0.05).⑥The correlationship of Ets-1 with other index in UUO group:the expression of Ets-1 was positively correlated remarkably with MMP-9 (r=0.716,P=0.001), and positively correlated with MMP-9/ TIMP-1 (r=0.600,P=0.009). TGF-β1 was positively correlated remarkably with TIMP-1,α-SMA and collagenⅠ(r=0.906, P=0.000;r=0.668,P=0.002;r=0.885,P=0.000)Conclusion: 1.Irbesartan can inhibit proinflammatory factor, EMT and promote the degradation of extracellular matrix to reduce the renal interstitial fibrosis and protect renal function. 2. Ets-1 has involved in the process of renal interstitial fibrosis possibly by adjusting the expression of MMP-9/TIMP-1 and the other fibrogenic cytokine.