Intermedin Attenuates Renal Interstitial Fibrosis By Inhibiting Oxidative Stress After Unilateral Ureteral Obstruction

Objective:To explore if intermedin(IMD)reduces renal interstitial fibrosis by inhibiting reactive oxygen species(ROS)after unilateral ureteral obstruction(UUO)in rats.Methods:Male Wistar rats were randomly divided into sham-operated group(n=24),UUO group(n=24),UUO+IMD-pcDNA3.1 group(n=24),UUO+IMDshRNA group(n=24)and UUO+pcDNA3.1 group(n=24).Plasmid transfection was induced 7 days before UUO operation.Groups of 6 animals were killed at 1,3,7 and 14 d after operation,respectively.The obstructed kidneys were harvested for further analysis.For analyzing the degree of tubulointerstitial collagen deposition,sections were stained with Masson trichrome.ROS content in the obstructed kidney was measured by chemiluminescence.Renal superoxide dismutase(SOD)activity and malondialdehyde(MDA)content were evaluated by colorimetry.Expression of heme oxygenase 1(HO-1)was detected by real-time reverse transcription-polymerase chain reaction(RT-PCR)and immunohistochemical staining,respectively.Results:Masson trichrome showed no obvious fibrosis at each time point in the kidney of sham-operational rats.In the UUO group,the degree of renal interstitial fibrosis increased with the time of obstruction.Overexpression of IMD in the kidney by IMD-pcDNA3.1transfer decreased interstitial collagen deposition on each time point compare to the untreated UUO controls(P<0.05),while UUO+IMDshRNA transfection further increased interstitial collagen expansion(P<0.05).Renal fibrosis showed no difference between UUO group and UUO+pcDNA3.1 group(P>0.05).ROS activity and MDA contentincreased obviously in each time point in the obstructed kidney of UUO rats compared with sham controls.IMDshRNA transfection further increased ROS activity and MDA content,whilc IMD-pc DNA3.1 transfer decreased them(P<0.05).SOD activity and HO-1expression increased significantly 1d in after UUO,and then gradually declined.SOD activity was lower than that of the sham at 3,7,14 days after UUO,while HO-1expressions were still higher than that of the sham at each time point(P<0.05).SOD activity and the expression of HO-1 were significantly up-regulated in the kidney of UUO+IMD-pcDNA3.1 group compared to UUO group(P<0.05),while markedly down-regulated in the kidney of UUO+IMDshRNA group(P<0.05).There were no differences in ROS activity,MDA content,SOD activity and HO-1 expression between UUO group and UUO+pcDNA3.1 group(P>0.05).Conclusion :IMD attenuates renal fibrosis induced by UUO by inhibiting oxidative stress.