Shimizu Hidehisa, Hirose Yuichi, Nishijima Fuyuhiko, Tsubakihara Yoshiharu, Miyazaki Hitoshi
Graduate School of Life and Environment Sciences, Alliance for Research on North Africa, University of Tsukuba, Ibaraki, Japan.
Am J Physiol Cell Physiol. 2009 Aug;297(2):C389-96. doi: 10.1152/ajpcell.00206.2009. Epub 2009 Jun 3.
Patients with chronic renal failure are at greater risk of developing atherosclerosis than healthy individuals, and recent data suggest that the putative uremic toxin indoxyl sulfate (IS) promotes the pathogenesis of atherosclerosis. The present study examined the effects of IS on vascular smooth muscle cells (VSMCs) with respect to reactive oxygen species (ROS), platelet-derived growth factor (PDGF) receptors, and mitogen-activated protein kinases (MAPKs). IS induced the migration and proliferation of VSMCs and synergistically enhanced their PDGF-induced migration as well as proliferation. The effects of PDGF were promoted after a 24-h incubation with IS despite the absence of IS during PDGF stimulation. Intracellular ROS levels were increased in the presence of IS, and PDGF-dependent ROS production was augmented by a prior 24-h incubation with IS even in the absence of IS during PDGF stimulation. These data suggest that IS increases the sensitivity of VSMCs to PDGF. IS also phosphorylated PDGF-beta-receptors and upregulated PDGF-beta receptor but not alpha-receptor protein expression in the absence of exogenous PDGF. The NADPH oxidase inhibitor diphenylene iodonium blocked IS-dependent increase in receptor expression. Administration of IS to nephrectomized rats also elevated receptor protein expression in arterial VSMCs. Inhibitors of NADPH oxidase, PDGF-beta receptors, extracellular-regulated protein kinase (ERK), and p38 MAPK all inhibited IS-induced VSMCs migration and proliferation. Taken together, these findings indicate that IS induces the migration as well as proliferation of VSMCs through PDGF-beta receptors and that ROS generation is critically involved in this process, which promotes the development of atherosclerosis.
与健康个体相比，慢性肾衰竭患者发生动脉粥样硬化的风险更高，最近的数据表明，假定的尿毒症毒素硫酸吲哚酚（IS）可促进动脉粥样硬化的发病机制。本研究考察了IS对血管平滑肌细胞（VSMC）在活性氧（ROS）、血小板衍生生长因子（PDGF）受体和丝裂原活化蛋白激酶（MAPK）方面的影响。IS诱导VSMC迁移和增殖，并协同增强其由PDGF诱导的迁移及增殖。尽管在PDGF刺激期间不存在IS，但在与IS孵育24小时后，PDGF的作用得到增强。在有IS存在的情况下，细胞内ROS水平升高，即使在PDGF刺激期间不存在IS，预先与IS孵育24小时也会增强PDGF依赖性ROS的产生。这些数据表明，IS增加了VSMC对PDGF的敏感性。在没有外源性PDGF的情况下，IS还使PDGF-β受体磷酸化并上调PDGF-β受体而非α受体的蛋白表达。NADPH氧化酶抑制剂二苯碘鎓可阻断IS依赖性的受体表达增加。对肾切除大鼠给予IS也会升高动脉VSMC中的受体蛋白表达。NADPH氧化酶、PDGF-β受体、细胞外调节蛋白激酶（ERK）和p38 MAPK的抑制剂均抑制IS诱导的VSMC迁移和增殖。综上所述，这些发现表明，IS通过PDGF-β受体诱导VSMC迁移和增殖，并且ROS的产生在此过程中起关键作用，这促进了动脉粥样硬化的发展。
