| Objective:Immunohistochemical staining, Western Blotting and RT-PCR were usedin this study to observe the changes of extracellular signal regulated kinase(ERK) signaling pathway of streptozotocin (STZ) induced type2diabetic rats’kidney. To further investigate the pathogenesis of diabetic nephropathy (DN)and the protective effect of sericin.Methods:48male SD rats were randomly divided into4groups: normal controlgroup, diabetes model group, sericin treatment group and positive controlgroup, with12rats in each group. The rats in normal control group were bredas normal. The rats in diabetes model group, sericin treatment group andpositive control group were made diabetes model by injecting2%STZ(25mg/kg,3d) into the abdominal cavity continuously and blood glucose (BG)≥16.7mmol/L was taken as standard. After the diabetes model wassuccessfully established, the rats in model group received no more treatment;the rats in sericin treatment group were lavaged with sericin (2.4g/kg/d) for35days; the rats in positive control group were lavaged with metformin(55.33mg/kg/d,35d).The blood glucose (BG),24hours urine protein, creatinine and ureanitrogen content in blood of rats in each group were respectively detected. SPimmunohistochemical staining, Western Blotting and RT-PCR were used todetect the expression of mitogen-activated protein kinase kinase1/2(MEK1/2),phosphorylated ERK1/2(pERK1/2), protooncogene c-fos protein and mRNAin kidney respectively.Results:1. BG: Compared with rats in normal control group, BG of rats in model group increased obviously (P<0.01). BG of rats in sericin treatment group andpositive control group was obviously lower than that of rats in model group (P＜0.01); Moreover, there had no obvious differences between sericin treatmentgroup and positive control group (P＞0.05).2.24hours urine protein:24hours urine protein of rats in model groupincreased significantly compared with rats in normal control group (P<0.01).24hours urine protein of rats in sericin treatment group and positive controlgroup was significantly lower than that of rats in model group (P＜0.01);Moreover, there had no significant differences between sericin treatmentgroup and positive control group (P＞0.05).3. Creatinine and urea nitrogen content in blood: The creatinine and ureanitrogen content in blood of rats in model group was remarkably higher thanthat of rats in normal control group (P＜0.01). The creatinine and ureanitrogen content in blood of rats in sericin treatment group and positivecontrol group were remarkably lower than that of rats in model group (P＜0.01, P＜0.05); Moreover, there had no remarkable differences betweensericin treatment group and positive control group (P＞0.05).4. Expression of MEK1/2in kidney: MEK1/2immunopositive productswere brown weeny granules and mainly located in cytoplasm of renal tubularepithelial cells, especially in dilated renal tubules and epithelium damagingrenal tubules. The cytoplasm of intraglomerular mesangial cells also could beobserved MEK1/2immunopositive products occasionally. Compared withnormal control rats, the expression of MEK1/2protein and mRNA in kidneyof rats in model group increased obviously (P＜0.01). The expression ofMEK1/2protein and mRNA in kidney of rats in sericin treatment group andpositive control group was obviously lower than that of rats in model group (P＜0.01); Moreover, there had no obvious differences between sericin treatmentgroup and positive control group (P＞0.05).5. Expression of pERK1/2in kidney: pERK1/2immunopositive productswere buffy granules and located in cytoplasm. pERK1/2immunopositive cellsincluded intraglomerular mesangial cells, podocytes and renal tubular epithelial cells, especially in dilated renal tubules and epithelium damagingrenal tubules. Compared with normal control rats, the expression of pERK1/2protein and mRNA in kidney of rats in model group increased significantly (P＜0.01). The expression of pERK1/2protein and mRNA in kidney of rats insericin treatment group and positive control group were significantly lowerthan that of rats in model group（P＜0.01，P＜0.05）; Moreover, there had nosignificant differences between sericin treatment group and positive controlgroup (P＞0.05).6. Expression of c-fos in kidney: c-Fos immunopositive products werebuffy granules and mainly located in cytoplasm of epithelial cells of dilatedrenal tubules and epithelium damaging renal tubules. Compared with normalcontrol rats, the expression of c-fos protein and mRNA in kidney of rats inmodel group increased remarkably (P＜0.01). The expression of c-fos proteinand mRNA in kidney of rats in sericin treatment group and positive controlgroup were remarkably lower than that of rats in model group（P＜0.01，P＜0.05）; Moreover, there had no remarkable differences between sericintreatment group and positive control group (P＞0.05).Conclusions:1. Sericin can decrease BG and improve renal function of DN rats.2. Activating of ERK signaling pathway of diabetes rats may involve thedevelopment of kidney injury during diabetes. Sericin can inhibit activation ofERK signal pathway by down-regulating expression of MEK, ERK and c-fosof DN rats; So sericin has protective effects on kidney injury of DN rats. |
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