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The Protective Effect Of Olmesartan Medoxomil On Human Renal Mesangial Cells Under High Glucose Concentration

Posted on:2010-01-28Degree:MasterType:Thesis
Country:ChinaCandidate:H Y LiuFull Text:PDF
GTID:2144360278953229Subject:Internal Medicine
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Introduction:Diabetic nephropathy (DN) which is one of the most common and severe diabetic microvascular complications is recognized as the leading cause of increasing mortality in diabetic patients. The earliest pathologic changes of DN are characterized in glomerular hypertrophy, thicknening of glomerular basement membrane, and accumulation of extracellular matrix (ECM), which lead to glomerular hyperfiltration and microalbuminuria. Mesangial cells are the major producer of ECM . It plays a key role in the development of glomerulosclerosis in DN. Previous studies have shown that high glucose which leads to oxidative stress is one of the initiating factors of DN. Superoxide dismutase (SOD) and catalase (CAT) are important antioxidase in our body, both of which are factors reflecting the ability of scavenging oxyradical indirectly. Malondialdehyde (MDA) is the production of the lipid peroxidation which reflect the progress and the intensity of lipid peroxidation. The three indexes are used to evaluate the level of oxidative stress synthetically. Recently, research indicates that high glucose and oxidative stress lead to oxidative stress, then stimulate cell proliferation-associated factors such as transforming growth factorsβ1 (TGF-β1) or vascular endothelial growth factor (VEGF), both of which play an important role in the pathogenesis of DN. There is abundant evidence in the literature implicates that TGF-β1 is a major fibrogenic growth factor in pathogenesis of glomerulosclerosis and interstitial fibrosis. VEGF has potent vasopermeability indu- cing properties and may contribute to albuminuria in the pathogenesis of diabetic nephropathy since it induced cells proliferation and ECM accumulation. Olmesartan medoxomil which exerts renal protective effects is a new-type blocker of angiotensinⅡtype 1 (AT1) receptor. This effect and its exact mechanisms in the pathogenesis of DN arouse more and more attention. Objective: In order to explore the possible mechanism of olmesartan medoxomil on the renal protective effects, the cultured human renal mesangial cells (HRMCs) under the stimulation of high concentration of glucose were used to observe the effects of olmesartan medoxomil by testing the indexes of OS and the expressions of its interrelated factors, such as TGF-?1 and VEGF.Methods: Primary normal adult HRMCs purchased from ScienCell company (US) were cultured with high glucose in vitro and 5-8 passage were used for experiment. HRMCs were divided into four groups:1. low glucose group (glucose 5.6 mmol/l).2. high glucose group (glucose 30 mmol/l). 3. low glucose+DMSO group (glucose 5.6 mmol/l+DMSO 2×10-5 mmol/l, LG+DMSO). 4.high glucose + olmesartan medoxomil group. In the concertration control experiment, HRMCs were treated with various concentrations of olmesartan medoxomil (2×10-7, 2×10-6, 2×10-5 mmol/l) for 48 h named HG+L-OLM, HG+M-OLM, HG+H-OLM respectively. In the time control experiment, HRMCs were treated with olmesartan medoxomil at final concentrations of 2×10-6 mmol/l for 24 h and 48 h respectively. The activities of SOD, CAT and the contents of MDA in supernatants were evaluated by spectrophotometry. The cell proliferation of HRMCs was measured by MTT. The protein of TGF-?1 and VEGF in the culture supernatants of HRMCs were determined by ELISA analysis. The mRNA level of TGF-?1 and VEGF were detected by RT-PCR.Results:1. The high level of glucose concentration could promote the cell proliferation of HRMCs. The activities of SOD and CAT obviously decreased, while the contents of MDA increased significantly under high glucose in supernatants of HRMCs. The TGF- 1 and VEGF mRNA and proteins expression were increased significantly under high glucose. The effect above can be observed in 24-hours point, but obviously in 48- hours point.2. There was no significant difference in low glucose group and LG+DMSO between groups at each time point, it suggested DMSO has no side effect on HRMCs survival.3. The cell proliferation of HRMCs was suppressed by olmesartan medoxomil. The effect was concentration dependent.4. Compared with the high glucose group, the activities of SOD and CAT significantly increased, while the contents of MDA decreased greatly in olmesartan medoxomil group. Which was concentration dependent. 5. The up-regution regulation mRNA and proteins expression of TGF-β1 and VEGF induced by high glucose was inhibited by olmesartan medoxomil. Which was marked concentration-dependent.Conclusion: The condition of high glucose concentrations induces ROS increased and the activity of antioxidant enzyme system declined in cultured HRMCs. Olmesartan medoxomil may exert renal function protection through a indirect way of inhibiting the expression of cytokines, such as TGF-?1 and VEGF, which induced by the active oxygen production, or a direct way of inhibiting high glucose-induced cytokines expression.
Keywords/Search Tags:olmesartan medoxomil, diabetic nephropathy, HRMCs, ROS, TGF-β1, VEGF
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