The Relationship Between Local Hepcidin And Iron Overload,Oxidative Stress And Renal Fibrosis

Background:Hepcidin is a key regulator of iron homeostasis,and hepcidin regulation disorders can lead to iron overload.Hepcidin is mainly produced by the liver,but it can also be synthesized by the kidney.While the association between iron overload and kidney injury is well established,the regulation of iron metabolism in the kidney by locally synthesized hepcidin remains unknown.This study explored the effects of hepcidin in the kidney.Objectives:The aim of this study was to explore the relationship between renal secretion of hepcidin and iron accumulation in the kidney and renal fibrosis,and the regulation of iron sucrose on the secretion of hepcidin in the kidney.Methods:In in vivo experiments,mice were divided into a unilateral ureter obstruction(UUO)model group and a sham operation group,and mice in the UUO model group were sacrificed on days 1,3,5 and 7.The expression and localization of renal hepcidin were studied with western blotting and immunofluorescence.Renal iron and reactive oxygen species(ROS)were examined by immunofluorescence.The expression of ferroportin(FPN1)and divalent metal transporter(DMT 1)was also detected by western blotting.Histopathology,immunohistochemistry and western blotting were used to assess the extent of renal fibrosis.In the in vitro experiments,we tested the hypothesis that hepcidin contributes to fibrosis in HK-2 cells via the augmentation of iron accumulation-dependent oxidative stress.We stimulated HK-2 cells with iron sucrose(FeS)and observed the expression of hepcidin,FPN1,DMT1,cell fibrosis and the levels of intracellular iron and hydroxyl radicals.Results:Serum hepcidin increased significantly on the first day and returned to baseline on the third day in the UUO model,while renal hepcidin expression was consistently higher in the UUO group than in the sham group from the first day.Theexpression of FPN1 gradually decreased,and the expression of DMT 1 gradually increased in the UUO model.Intracellular ferrous ions and hydroxyl radicals significantly increased on the first day of the UUO model.In addition,the degree and location of kidney iron overload were associated with the extent and localization of renal hepcidin synthesis.The results of histopathology,immunohistochemistry and western blotting showed that renal fibrosis occurred on day 5 in the UUO model.Treatment of HK-2 cells with FeS solution upregulated hepcidin expression levels.The expression of FPN1 was decreased,while the expression of DMT 1 was increased.Production of intracellular ferrous ions and hydroxyl radicals increased.In addition,the expression of a-SMA,fibronectin and collagen IV were increased.Conclusion:The expression of hepcidin secreted by the kidney is associated with iron accumulation in the kidney,oxidative stress and renal fibrosis.Iron accumulation in the kidney may be associated with increased expression of DMT 1 and decreased expression of FPN1.Iron sucrose can up-regulate the expression of hepcidin in HK-2 cells.