| Diabetic nephropathy is one of the most common and severe diabetic microvascular complications and is recognized as a leading cause of increased mortality in diabetic patients.Therefore,it is meaningful to explore potential ways to prevent and treat diabetic nephropathy.Albuminuria,hypertension, progressive renal failure are main clinical manifestations of diabetic nephropathy,and the disease is characterized by an expansion of glomerular mesangium,which is caused by glomerular mesangial cells(GMCs) proliferation and excessive accumulation of extracellular matrix(ECM). Vascular endothelial growth factor(VEGF)has potent vasopermeabilityinducing properties;and there are reports indicating that VEGF can stimulate endothelial cell proliferation and differentiation,change ECM,and play a cardinal role in physiological and pathological angiogenesis.Due to these functions,VEGF may contribute to albuminuria and mesangial expansion in the pathogenesis of diabetic nephropathy and is catching more and more attention.As a new member of the corticotrophin releasing hormone(CRH)peptide family,Urocortin(UCN)has been demonstrated to show various protective effects on cardiovascular system since it was isolated.In addition,treatment with UCN was found to result in reduced VEGF release from rat vascular smooth muscle cells(VSMCs),an inhibition of VSMCs proliferation,and an inhibition of capillary tube formation in collagen gels.Our in vivo results showed that UCN inhibited tumor growth and angiogenesis in hepatocellular carcinoma via down-regulating VEGF expression.The aim of this study is to investigate the effects of UCN on VEGF expression in kidney tissues of diabetic nephropathy rats and the possible mechanisms.In order to establish rat model of diabetic nephropathy,male Wistar Rats were intraperitoneally injected with small dose of STZ-CFA,and were fed with high fat diet.Rats in the UCN group received 6μg·kg-1urocortin and rats in the urocortin+astressin group received 6μg·kg-1urocortin+30μg·kg-1astressin intraperitoneally,from the 7th week of our experiment,daily for 8 weeks.Body weights were weighed weekly.Blood samples from the tail vein were used to determine the non-fasting blood glucose with blood glucose test strips every two weeks.At the end of the experiment,blood samples and urinary samples were collected for biochemical and RIA analysis. Subsequently,renal lesions were evaluated by H-E and PAS staining.The expression of VEGF mRNA in rat kidney tissues were detected by semi-quantitative RT-PCR;and VEGF,transforming growth factor(TGF-β1) proteins in glomeruli were measured by immunohistochemistry.After administration for 8 weeks,UCN significantly decreased kidney weight of UCN-treated rats.However,body weight,plasma glucose levels and renal index remained unaffected.Blood urea nitrogen,creatinine and malondialdehyde(MDA)levels were significantly reduced,whereas creatinine clearance rate and superoxide dismutase(SOD)activity increased markedly in UCN-treated rats.Twenty four hours urinary volume,urinary albumin excretion,urinary microalbumin excretion decreased significantly,whereas urinary urea nitrogen,urinary creatinine increased markedly in UCN-treated rats.UCN significantly decreased glomerular ECM expansion and accumulation in kidney tissues.Moreover,UCN inhibited the overexpression of VEGF and TGF-β1 in glomeruli.The non-selective CRH receptor(CRHR) blocker,astressin,had a marked influence on most of these effects.In the in vitro experiments,rat GMCs were exposed to UCN at different concentrations,and then incubated with exogenous TGF-β1(2 ng/ml)for 12 h. VEGF concentrations in the culture supernatants of GMCs were quantitatively determined by ELISA analysis.Results showed that UCN exerted a concentration-dependent inhibitory effect on VEGF secretion,which can be stimulated by exogenous TGF-β1,while this effect on VEGF was weakened by 5×10-9M astressin.In conclusion,UCN could ameliorate diabetic nephropathy partly because of inhibiting the overexpression of VEGF in vivo and in vitro,and this effect was mediated by the CRHR.Our findings enlarge the knowledge about the pathogenesis of diabetic nephropathy and expand the potential target to this disease.
|
PDF Full Text Request