Graduate Center for Nutritional Sciences, University of Kentucky, 900 S. Limestone Street, Lexington, KY 40536, USA.
Biochem Biophys Res Commun. 2010 Jun 18;397(1):5-11. doi: 10.1016/j.bbrc.2010.04.084. Epub 2010 Apr 23.
Glycated albumin, an early-glycation Amadori-modified protein, stimulates transforming growth factor-beta (TGF-beta) expression and increases the production of the extracellular matrix proteins in mesangial cells, contributing to the pathogenesis of diabetic nephropathy. Glycated albumin has been shown to increase NADPH oxidase-dependent superoxide formation in mesangial cells. However, the mechanisms are not well understood. Therefore, in the present studies, we determined the mechanisms by which glycated albumin activates NADPH oxidase in primary rat mesangial cells and its contribution to glycated albumin-induced TGF-beta expression and extracellular matrix protein production. Our data showed that glycated albumin treatment stimulated NADPH oxidase activity and increased the formation of superoxide formation in rat mesangial cells. Moreover, glycated albumin treatment stimulated the expression and phosphorylation of p47phox, one of the cytosolic regulatory subunits of the NADPH oxidase. However, the levels of other NADPH oxidase subunits including Nox1, Nox2, Nox4, p22phox, and p67phox were not altered by glycated albumin. Moreover, siRNA-mediated knockdown of p47phox inhibited glycated albumin-induced NADPH oxidase activity and superoxide formation. Glycated albumin-induced TGF-beta expression and extracellular matrix production (fibronectin) was also inhibited by p47phox knock down. Taken together, these data suggest that up-regulation of p47phox is involved in glycated albumin-mediated activation of NADPH oxidase, leading to glycated albumin-induced expression of TGF-beta and extracellular matrix proteins in mesangial cells and contributing to the development of diabetic nephropathy.
糖化白蛋白，一种早期糖基化的 Amadori 修饰蛋白，可刺激转化生长因子-β（TGF-β）的表达，并增加系膜细胞中细胞外基质蛋白的产生，从而导致糖尿病肾病的发病机制。糖化白蛋白已被证明可增加系膜细胞中 NADPH 氧化酶依赖性超氧化物的形成。然而，其机制尚不清楚。因此，在本研究中，我们确定了糖化白蛋白在原代大鼠系膜细胞中激活 NADPH 氧化酶的机制及其对糖化白蛋白诱导的 TGF-β表达和细胞外基质蛋白产生的贡献。我们的数据表明，糖化白蛋白处理可刺激 NADPH 氧化酶活性，并增加大鼠系膜细胞中超氧化物的形成。此外，糖化白蛋白处理可刺激 NADPH 氧化酶的细胞溶质调节亚基之一 p47phox 的表达和磷酸化。然而，其他 NADPH 氧化酶亚基（包括 Nox1、Nox2、Nox4、p22phox 和 p67phox）的水平不受糖化白蛋白的影响。此外，p47phox 的 siRNA 介导的敲低可抑制糖化白蛋白诱导的 NADPH 氧化酶活性和超氧化物的形成。p47phox 的敲低也抑制了糖化白蛋白诱导的 TGF-β表达和细胞外基质产物（纤连蛋白）的产生。总之，这些数据表明，p47phox 的上调参与了糖化白蛋白介导的 NADPH 氧化酶的激活，导致糖化白蛋白诱导的系膜细胞中 TGF-β和细胞外基质蛋白的表达，并促进糖尿病肾病的发展。
