| Background and Objectives:Diabetic Nephropathy (DN) is the highest incidence and the most damaging complication of chronic microvascular complications of diabetes mellitus (DM). Today the leading cause of end-stage renal disease (ESRD) in the world is DN. About 40% of type 1 DM patients and 5%-10% of patients with type 2 DM can develop to DN. DM can involve all the anatomical structures of the kidney (glomeruli, tubules, interstitial, and renal vessel, etc) through a variety of different ways. Lots of recent studies have shown that in a variety of primary and secondary glomerular diseases, renal interstitial fibrosis(RIF) is the one of the best indicators which can reflect the severity of renal function decline and the prognostic of diseases. The existing research suggests, the relevance of the renal interstitial fibrosis and renal dysfunction is more closely than the glomerulosclerosis and renal dysfunction. RIF will be the common pathway of a number of chronic kidney disease through to ESRD. As the two important vasoactive hormones, AngiotensinⅡ(AngⅡ) and endothelin 1 (ET-1) are present in renal tubular epithelial cells, and as the activities of AngⅡand ET-1 increased, cells hyperplasia and hypertrophy occure. Extracellular matrix (ECM) degradation is inhibited, and synthesis increased. AngⅡand ET-1 can mediate inflammatory response, participate in and accelerate the process of RIF. Chronic ischemia and hypoxia widely exists in RIF. Hypoxia inducible factor-la (HIF-1α) can increased as the landmark production when the tissue exists ischemia and hypoxia. The activity of Ang II increased, at the same time, it can stimulate the expression of HIF-la in renal tubular epithelial cells; HIF-la is also the upstream of ET-1 gene,it play the role of regulating synthesis and secretion of ET-1, there's cross-effect between AngⅡand ET-1. AngⅡcan make endothelin converting enzyme activity increased, so that the transcriptional activity of original before endothelin mRNA increased and ultimately synthesis of ET-1 increase. ET-1 can increase the activity of angiotensin converting enzyme, thereby contributing to angiotensin I to the conversion of AngⅡ. In addition, the effects of AngⅡand ET-1 may also play a role by sharing receptors[3]. In short, there is close contact between the three factors Angiotensin II receptor blockors (ARBs) have a negligible effect in the treatment of chronic kidney disease, and ARBs can significantly reduce proteinuria, and does not depend on blood pressure control, it also can effectively reduce blood pressure in DM patients with normal urinary albumin excretion rate[4], thereby reducing glomerular injury caused by the long-term proteinuria. Recently, the role of tubulointerstitial in the development of DN received more attention than before, so the protective effect of ARBs on tubulointerstitial are given gradually attention. ARBs has a highly selective for ATI receptors, and can completely blocked Ang II, thus reduce the production of HIF-1αand ET-1, in order to delay the progression of RIF. AGT is precursor of AngⅡ, if the generation of AngⅡis blocked, the synthesis of AGT will be inhibited. At present, the research about expression of AngⅡ, ET-1 and HIF-la on renal interstitial fibrosis in diabetic nephropathy and relations of them are very few.This study tries to observe the extent of the RIF kidney tissues from two levels of the model of DN rats and DN patients; And measured the expression levels of AngⅡ, ET-1 and HIF-1α, as well as the relationship between them and RIF; and analyze the correlation between clinical indicators and cytokines;and to observe the effects of valsartan as an blocker in the above mentioned processes. From the point of AngⅡ, ET-1 and HIF-1α, and the possible mechanism of RIF, we try to investigate a new method to control the progress of DN.Methods:(1) Animal experiments54 SD male rats were randomly divided into following groups:control group(C, n=18), model group without valsartan (D, n=18), model group with valsartan (T, n=18). After fasting 12 hours, the rats of D group and T group were injected single dose STZ in 0.1 mol/1 citrate buffer, pH 4.4 (60mg/kg), the rats of and C group were injected the same volume of normal saline.72 hours after injection, blood glucose levels were measured, and> 16.7mmol/1 were succeed. After 3 weeks, collecting the urine of 24 hours through metal metabolism cages, and measuring urinary protein of 24 hours. The rats of urine protein of 24 hours≥30mg were succeed. The rats of T group were given valsartan suspension in 40mg·kg-1·d-1,and the others were given distillated water. Six rats of each group were collectted respectively at 4,8,12 weeks. Measuring body weight. Final procedure, the samples of blood were collected for analysis of blood glucose, serum creatinine, albumin; Measuring the left kidney weight; 24 hours urine were collected for measuring the quantity of 24 hours urinary protein. The kidney of rats were harvested, Masson staining was performed, and histological and immunohistochemistry were analyzed. Determine the expression of AGT, ET-1 and HIF-la mRNA by RT-PCR.(2) Clinical trial47 paraffin specimens of DN renal, and 6 controls were enrolled, and all of them were diagnosed by pathology. We observed the level of RIF by Masson staining, and the expressions of AngⅡ, ET-1 and HIF-la by immuno-histochemical staining.(3) results1.Excretion of urinary protein, serum creatine, albumin, area of renal interstitial fibrosis increased markedly in group D and T, compared with group C(P<0.05);the lesions was improved in T group(valsartan treatment).2.Animal immunohistochemical results:no expression of AngⅡ, ET-1 and HIF-la in renal interstitial and renal tubular epithelial cells almost in C group; D group and T group, the expression of them increase by different degrees, and with the time longer and the disease progression, the expression of AngⅡ, ET-1 and HIF-1αgradually increased, in T group the expression of these factors reduced.3.RT-PCR results:Over time, D group, T group, the expression of AGT, ET-1 and HIF-1αmRNA gradually increased; In the same period, the expression of AGT, ET-1 and HIF-1αmRNA in T group have weakened,compared with D group. At 8 and 12 weeks, the difference was significant between D and T group(all P<0.05).4.(1) RIF was existed in DN patient's kidney. (2) The expressions of AngⅡ, ET-1 and HIF-1αwere very low in the control group, but increased significantly in DN group. (3) The expressions of AngⅡ, ET-1 and HIF-1αwere directly correlated with RIF in tubular epithelial cells. (4) The expressions of AngⅡ, ET-1 and HIF-1αwere directly correlated with the level of serum creatinine.,while they have no correlation with 24-hour urinary protein, glucose, and serum albumin.(4) Conclutions1.In the kidney of DN rat model and DN patients, there were exist of RIF, and varying degrees expressions of AngⅡ, ET-1 and HIF-1α, the expression of them were positively correlated with RIF and level of blood creatinine, AngⅡ, ET-1 and HIF-1αpromote the progress of RIF in DN. The increased expression of AngⅡ, ET-1 and HIF-1αmay participate in the progress of renal interstitial fibrosisin in DN.2.Valsartan can reduce the expression of AngⅡ, ET-1 and HIF-1αin DN renal tubular epithelial cells, and reduce renal interstitial damage, and slow down the progress of RIF, finally prevent renal interstitial fibrosis in DN. |
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