The Effects Of Vascular Endothelial Growth Factor In The Pathogenesis Of Lipid Nephrotoxicity

Objective: Clinical and experimental studies have suggested an important role for hyperlipidemia as a integral factor in modulating the progression of renal disease. LDL and Oxidative modification of LDL are key factors causing atherosclerosis. Recent studies have found that vascular endothelial growth factor(VEGF) have a high level expression in atherosclerotic plaques and may involve in the pathogenesis and progression of atherosclerosis. The pathogenesis of glomerulosclerosis similar to that of atherosclerosis,Therefore,VEGF may also play an important role in the progression of glomerulosclerosis. The aim of this study was to determine the effect of VEGF on the production of extracellular matrix and proliferation of mesangial cells in vitro and in vivo,and probe into the possible associations between VEGF and pathogenesis of glomerulosclerosis.Methods: This study was divided into two parts: in vivo and in vitro. In vivo study was conducted by establishing rat model of diet-induced hypercholesterolemia, sacrifacing the rats at 4,8 and 12weeks. Biochemical changes were studied throughout the course of the investigation. Distributions of VEGF were analyzed in the renal tissues of rats by using immunohistochemical staining technique. Reverse transcription-polymerase chain reaction(RT-PCR) was performed to measured VEGFmRNA level in the renal tissue of rats. In vitro study mesangial cells monolayer grown in serum-free culture medium for 12 hours were incubated with LDL and Ox-LDL( 10-200 H g/ml) for 12-48 hours.Evaluate the proliferative effect of VEGF on cultured rat mesangial cells by cell counting and flow cytometer method. Examine the synthesis of VEGF and distributions of VEGF from mesangial cells stimulated by LDL and Ox-LDL using ELISA and immunohistochemical staining technique. Examine the synthesis of TGF- P i and FN in cultured rat mesangial cells stimulated by LDL and Ox-LDL with ELISA kit. Total RNA was Extracted from mesangial cells and examine expression of VEGFmRNA was examined using RT-PCR method. Examine theproduction of TGF- 3 , and FN in cultured rat mesangial cells stimulated by PhilinopsideA using ELISA method.Results: 1. Serum cholesterol and LDL were elevated at the end of 2 wk in group B, and increased progressively thereafter. Urinary protein excretion was not elevated until 12wk in group B. Serum Cr and BUN were not incresed throughout the course of the study. Hypercellularity and increased mesangial matrix were presant. Immunohistochemical staining showed that few VEGF protein was detected in group A. In group B detections of VEGF was localized mainly within the renal glomerulus, tubules and endomitrium of artery, and raised progressively until 12wk. The expression of VEGFmRNA were increased progressively in the kidneys of group B by RT-PCR. 2. By using cell counting and flow cytometer method.it was suggested that LDL and Ox-LDL stimulated the proliferation of rat mesangial cells in a dose and time-dependent manner. At the concentration of 100-200 j"g/ml,Ox-LDL induced death of cells because of its toxic effects. After mesangial cells were incubated with 10"6g/L PhilinopsideA for 12~48hrs, cell growth were significantly inhibited. LDL and Ox-LDL stimulated the synthesis of VEGF from cultured rat mesangial cells in a dose and time-dependent manner. The level of TGF- P i and FN protein increased greatly after mesangial cells were stimulated by LDL and Ox-LDL with the peak at concentration of 200 n g/ml LDL for 48hrs. PhilinopsideA significantly inhibited the stimulative effect of LDL and Ox-LDL on synthesis of TGF- 3 i and FN. The protein and mRNA levels of VEGF were increased in a dose and time-dependent manner by using immunohistochemical staining technique and RT-PCR method.Conclusion: LDL and Ox-LDL stimulated the proliferation of rat mesangial cells in a dose and time-dependent manner.High concentration of LDL and Ox-LDL induced death of cells because of its toxic effects. LDL and Ox-LDL stimulated the synthesis of VEGF,TGF- 3 i and FN and expression of VEGFmRNA fr...