Katavetin Pisut, Inagi Reiko, Miyata Toshio, Tanaka Tetsuhiro, Sassa Ryoji, Ingelfinger Julie R, Fujita Toshiro, Nangaku Masaomi
Division of Nephrology and Endocrinology, University of Tokyo School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan.
Biochem Biophys Res Commun. 2008 Mar 7;367(2):305-10. doi: 10.1016/j.bbrc.2007.12.086. Epub 2007 Dec 26.
Reduction of vascular endothelial growth factor (VEGF) expression plays a crucial role in chronic kidney disease (CKD). In order to clarify a cause of VEGF suppression in CKD, we examined an interaction between proteinuria and VEGF. Rat proximal tubular cells were subjected to hypoxia with or without albumin to mimic proteinuric conditions, and VEGF expression was assessed by real-time quantitative PCR and enzyme-linked immunosorbent assays. Albumin significantly reduced VEGF expression under hypoxia. Luciferase activity controlled by hypoxia-responsive element (HRE) was suppressed by albumin, demonstrating suppression of the hypoxia-inducible factor (HIF)/HRE pathway. Studies utilizing a proteasome inhibitor and a prolyl hydroxylase inhibitor showed that mechanisms of HIF/HRE pathway suppression by albumin load did not involve degradation of HIF protein levels. Further, albumin did not change HIF mRNA levels. Our data, for the first time, suggest a clear 'link' between proteinuria and hypoxia, the two principal pathogenic factors for CKD progression.
血管内皮生长因子（VEGF）表达的降低在慢性肾脏病（CKD）中起着关键作用。为了阐明CKD中VEGF抑制的原因，我们研究了蛋白尿与VEGF之间的相互作用。将大鼠近端肾小管细胞置于有或无白蛋白的缺氧环境中以模拟蛋白尿状态，并通过实时定量PCR和酶联免疫吸附测定法评估VEGF的表达。白蛋白在缺氧条件下显著降低了VEGF的表达。由缺氧反应元件（HRE）控制的荧光素酶活性受到白蛋白的抑制，表明缺氧诱导因子（HIF）/HRE途径受到抑制。利用蛋白酶体抑制剂和脯氨酰羟化酶抑制剂的研究表明，白蛋白负荷对HIF/HRE途径的抑制机制不涉及HIF蛋白水平的降解。此外，白蛋白并未改变HIF mRNA水平。我们的数据首次表明了蛋白尿与缺氧之间的明确“联系”，这两个因素是CKD进展的主要致病因素。
