Influence Of Irbesartan On The Expression Of CTGF And ILK And Its Relationship With Epithelial-mesenchymal Transition In Mice With Unilateral Ureteral Obstruction (UUO)

AIM: Recent studies have suggested that activation of intrarenal renin-angiotensin system (RAS) might play an important role in progressive renal fibrosis. Irbesartan (Irb), a new type 1 angiotensisn II receptor blocker (ARB), has been proved effective in both diabetic and non- diabetic nephropathy. However, when people noted its renal protective role through reduction of proteinuria and blood pressure, more attention has been paid to its mechanism on renal structural remodeling, and one of the important points is the influence of angiotensin II (Ang II) on renal tubular epithelial mesenchyal transition (EMT), the later has been largely regarded as an early important step in tubulointerstitial fibrosis (TIF). Recent studies have suggested that EMT is mediated by many factors, such as growth factors and cytokines. Among them, Ang II is one of the important rising stars. However, the exact mechanism for Ang II in mediating renal fibrosis is still unclear. The purpose of this study was to investigate the influence of Irb on the expression of recently recognized connective tissue growth factor (CTGF) and integrin-linked kinase (ILK) and its relationship with EMT in mice with unilateral ureteral obstruction (UUO).METHODS: UUO model was made as previously reported. Mice were randomly divided into three groups, sham operation (C, N=20), UUO (N=40) and UUO with irbesartan treatment (UUO+Irb, N=40). Animals were sacrificed at day 1, 3, 7 and 14 respectively after the surgery. Tubulointerstitial fibrosis (TIF) was graded according to Masson staining. The expression for CTGF and ILK was examined by immunohistochemistry, Western Blot and real time PCR respectively. Expression forα-SMA and E-cadherin were detected by immunohistochemistry and real-time PCR. The mRNA level of fibronectin (Fn) was examined by real time PCR.RESULTS: It was shown by Masson staining that in control, sham operated mice, no histologic abnormalities of the kidneys were observed at the light microscopic level. Cellular swelling could be detected in part of the tubular epithelial cells one day after the surgery. At day 3, vacuole degeneration, tubular expansion, and leucocyte infiltration could be observed. Tubulointerstitial pathological changes were severe with time, at day 7 after the surgery, tubular atrophy, more infiltration of leucocytes, the expanded tubular interstitial volume, and over accumulation of extracellular matrix occurred. Fibrosis could be detected in the renal interstitial area at day 7 and more severe at day 14, when almost all of the tubulars were destroyed. Irbesartan could significantly inhibit renal pathological changes and TIF at different time points . The expression of CTGF and ILK at mRNA and protein levels were significantly increased in UUO group one day after the surgery, which was significantly decreased by treatment with Irb(P<0.01, respectively). At day 3 after the surgery, the expression ofα-SMA and the mRNA level of FN...