Combination Effects Of Simvastatin And Losartan In The Experimental Renal Interstitial Fibrosis

Background and Objective: Renal interstitial fibrosis is a common featureof varieties of progressive renal diseases. A lot of clinic and laboratory data demonstrate that the level of interstitial fibrosis can be looked as a more accurate prognosis predictor than the level of glomeruli sclerosis. However, the mechanism of the progressive of renal interstitial fibrosis remains unclear. In recent years, it has been a hot topic about the function of cytokine on fibroblast proliferation, macrophage infiltration and extracellular matrix accumulation and degradation. Connective tissue growth factor(CTGF), found in 1991, has simplex function of delivering fibrosis. Simvastatin and Losartan have been widely used in chronic renal diseases. Recently, Simvastatin-3-hydroxy-3-methylglutary coenzyme A reductase inhibitor (HRI), as a classic drug of lowering-lipid, was proved to be able to protect renal function of independent of lowering-lipid. It was proved that Simvastatin and Losartan both can affect the expression of CTGF. Someone supposed that Rho-signal way affected by HRI and MAPK signal way affected by Ang II had cooperation effect. But it is rarely reported that if the combination of Simvastatin and Losartan can be cumulated on the result of slowing-down renal interstitial fibrosis in vivo. Rat underwent unilateral ureteral obstruction (UUO) is a mature model of tubulointerstitial fibrosis, which has unconspicuous change on glumeruli and no complication of hyperlipidemia. So it can bedirectly investigated the independent renal protective function of HRI. In this experiment, the rat model of UUO was choosed to observe the effect of the combination of Simvastatin and Losartan on the expression of CTGF.Methods1. Healthy female SD rats (BW180~220g) were randomly allocated into five groups as described below: (1) sham-operated group, (C, n=6); (2) unilateral ureteral obstruction group, (UUO, n=6); (3) Losartan treated, (UUO+ARB, n=6); (4) Simvastatin treated, (UUO + HRI, n=6); (5)ARB and HRI treated, (UUO + ARB + HRI, n=6). The dose of Losartan is 50mg · Kg~-1· d~-1, and Simvastatin is 20mg· Kg~-1· d~-1. All the rats were killed at 9th day after operation.2. Biochemical parameters: serum creatinine (sCr) was investigated.3. Histological evaluation: interstitial fibrosis was calculated by Masson's staining.4. Immunohistochemical analysis (IHC): CTGF, a -smooth muscle actin( a -SMA) and fibronectin (FN) were stained with SP kit.Results1. Serum Creatinine: after 9d of operation, the variance of sCr was found no difference between groups (P>0.05).2. Interstitial fibrosis: compared with the shame operation group, Masson staining showed that there was more collagen deposition, fibroblast proliferation in the interstitium of 9d UUO rats. The severity of interstitial fibrosis was significant alleviated by ARB or HRI treatment, and more protection could be observed by HRI +ARB (P<0.05). The increase of protein level of FN was observed in the group of UUO at 9d (P<0.01), when compared with control group. Treatment with ARB or HRI was associated with a drop in FN protein expressions (P<0.01). And the more protection with HRI +ARB could be observed (P<0.05).3. CTGF: compared with control group, the protein expression of CTGF was increased in model group at 9 day (P<0.01). Its expression was reduced by ARB or HRI, compared with model group (P<0.05). And the combination treatment playedmore significant effect than the single treatment did (P<0.01).4. a-SMA: in model group, the expression of a-SMA was markedly evaluated, and was significant different from the control group (?<0.01). Treatment with HRI or ARB could downregulate the expression of a -SMA at 9 day (P<0.01). And the combination of ARB and HRI was more successful in attenuating its staining (/)<0.01), compared with the single treatment of HRI or ARB (P<0.01).Conclusions1. Losartan inhibited the expression of CTGF ^ a -SMA and FN, and ameliorated the renal interstitial fibrosis.2. In the model of Unilateral Ureteral Obstruction , Simvastatin could downregulate the protein expression of CTGF, a -SMA and FN, slow-down the renal fibrosis progression.3. Combination treatment of Losartan and Simvastatin showed better protective effect than single treatment, which probably by inhibiting the expression of CTGF.