Expression Changes Of Methionine Sulfoxide Reductase B1 In The Kidneys Of Instreptozocin-induced Diabetic Mice And Relationships With Oxidative Stress

Background & AimWith the increase of incidence of diabetes, diabetes and its complications have affected human health and existence more and more seriously. Substantial researches have showed that diabetic kidney disease was closely associated with oxidative stress. Methionine (Met) is one of the most easily oxidated amino acids. Reactive oxygen species (ROS) can oxidize Met to methionine sulfoxide (MetO), which affects a multitude of biological functions and fatally injures cells. However, MetO can be reduced to Met by methionine sulfoxide reductase (Msr) and play the positive role on repair process. Mammals have two Msrs, MsrA and MsrB. There is only one gene encoding MsrA, whereas, there are three genes encoding MsrBs (MsrBl, MsrB2 and MsrB3). Among all Msrs, MsrB1 is the only selenoprotein, which plays specialized roles in repairing damaged proteins. Some researches have showed that the expression changes of MsrB1 are associated with aging and many diseases, including neurodegenerative disease, cancer, cataract and so on, but its roles in diabetic nephropathy (DN) are still unclear. The present study was designed to determine the expression changes of methionine sulfoxide reductase B1 (MsrBl) in the kidneys of streptozotocin (STZ)-induced diabetic mice and to investigate their relationships with oxidative stress.MethodsHere, we used STZ-induced and unilaterally nephrectomized C57BL/6 mice as the research objects. Ten-week-old male C57BL/6 mice were randomly divided into four groups:normal control mice group (NC group, n=12), unilaterally nephrectomized mice group (UX group, n=12), STZ-induced diabetic mice group (STZ group, n=12) and STZ mice with unilateral renal ablation group (STZ-UX group, n=14). At the end of the 8th week after the construction of the model, specimens were collected. Biochemical indicators were detected. Renal pathological changes in mice were observed by Periodic Acid Schiff (PAS) and Masson staining. MsrB1 expression and distribution in the kidney tissues were detected by immunohistochemistry. The mRNA and protein levels of MsrB1 were determined by real-time PCR and western blotting respectively. The kits of malondialdehyde (MDA), protein carbonyl (PC) and total sulfhydryl groups (TSH) was used to measure the levels of oxidative stress in the kidneys of the four groups. SPSS 16.0 software was used for statistical analysis.Results1. Biochemical indicators and kidney pathological results proved that the mice suffered from diabetic kidney damages in the STZ group and the STZ-UX group, and mice in the STZ-UX group suffered more.2. The results of immunohistochemistry indicated that MsrB1 specially distributed on renal tubules instead of glomerulars. In the NC group, MsrBl widely located in the nucleus and cytoplasm of the renal tubular epithelial cells in kidney. Compare with the NC group, the distribution of MsrB1 was decreased slightly in the STZ group (P<0.05) and was decreased significantly in the STZ-UX group (P<0.01), but there were no significant changes in the UX group (P>0.05).3. The detection results of the real time PCR and western blotting showed that compare with the NC group, the mRNA and protein levels of MsrB1 were reduced in the kidneys of the STZ group and the STZ-UX group (P<0.05, P<0.01), and the reductions were more significant in the STZ-UX group, but there were no significant changes in the UX group (P>0.05).4. The oxidative stress levels in the mice kidneys of each group:the contents of MDA and PC were higher and TSH was lower in the STZ group and the STZ-UX group than those of the NC group (P<0.05, P<0.01) and STZ-UX group was more significant; there was no significant change in UX group (P>0.05).5. Correlation analysis showed that in the STZ group and STZ-UX group, MsrBl protein expressions were negatively correlated with MDA and PC (P<0.05), and were positively correlated with TSH levels (P<0.05).ConclusionsThe expression of MsrBl decreases significantly in the kidneys of STZ-induced diabetic mice, and was negatively correlated with MDA and PC and positively correlated with TSH, which may play an important role in the oxidative stress of DN. Therefore, further study will be devoted to the molecular mechanism under the MsrB1 downregulation, which may help to seek the molecular target to block the progress of DN.