Department of Nephrology, Affiliated Beijing Friendship Hospital, Faculty of Kidney Diseases, Capital Medical University, Xi Cheng, Beijing 100050, PR China.
Int J Mol Med. 2013 Jan;31(1):67-74. doi: 10.3892/ijmm.2012.1190. Epub 2012 Nov 20.
Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase (NOS) inhibitor, accumulates in plasma during chronic kidney disease (CKD). High plasma levels of ADMA can increase transforming growth factor-β (TGF-β) expression, related to renal fibrosis, but the precise molecular mechanism is not explicit. The present study was designed to determine the mechanism through which long-term low-dose ADMA induces TGF-β expression in endothelial cells and to investigate the molecular mechanism of its action. Human umbilical vein endothelial cells (HUVECs) were exposed to low-dose ADMA (5 and 10 µmol/l) for 7 passages and TGF-β expression was determined. Human renal glomerular endothelial cells (HRGECs) were exposed to high-dose ADMA (100 µmol/l) which were used to clarify the molecular mechanism. The results showed that long-term low-dose ADMA (5 and 10 µmol/l) increases TGF-β production in both mRNA and protein levels in HUVECs in a time-dependent manner. We confirmed that exogenous ADMA (100 µmol/l) significantly enhanced stress fiber formation in HRGECs and upregulated TGF-β expression. Such effects of ADMA in HRGECs were inhibited by pre-treatment with actin depolymerizing agent, actin stabilizing agent, p38 MAPK inhibitor and NADPH oxidase inhibitor. In addition, we demonstrated that ADMA (100 µmol/l) significantly activated nuclear factor-κB (NF-κB) in HRGECs, which was markedly attenuated by actin depolymerizing agent, actin stabilizing agent, p38 MAPK inhibitor and NADPH oxidase inhibitor. In brief, the present study demonstrated that long-term low-dose ADMA induces TGF-β expression in endothelial cells at both the gene and protein levels. The actin cytoskeleton may be involved in modulation of ADMA-induced NF-κB activation and the ensuing TGF-β expression in HRGECs.
不对称二甲基精氨酸（ADMA）是一种内源性一氧化氮合酶（NOS）抑制剂，在慢性肾脏病（CKD）期间会在血浆中积累。高血浆 ADMA 水平可增加转化生长因子-β（TGF-β）的表达，与肾纤维化有关，但确切的分子机制尚不清楚。本研究旨在确定长期低剂量 ADMA 诱导内皮细胞 TGF-β表达的机制，并研究其作用的分子机制。将人脐静脉内皮细胞（HUVEC）暴露于低剂量 ADMA（5 和 10 μmol/l）7 个传代，测定 TGF-β的表达。将人肾小球内皮细胞（HRGEC）暴露于高剂量 ADMA（100 μmol/l），以阐明分子机制。结果表明，长期低剂量 ADMA（5 和 10 μmol/l）可在时间依赖性方式增加 HUVEC 中 TGF-β 的 mRNA 和蛋白水平表达。我们证实外源性 ADMA（100 μmol/l）可显著增强 HRGEC 中的应激纤维形成，并上调 TGF-β表达。ADMA 在 HRGEC 中的这种作用可被肌动蛋白解聚剂、肌动蛋白稳定剂、p38 MAPK 抑制剂和 NADPH 氧化酶抑制剂预处理所抑制。此外，我们证明 ADMA（100 μmol/l）可显著激活 HRGEC 中的核因子-κB（NF-κB），而肌动蛋白解聚剂、肌动蛋白稳定剂、p38 MAPK 抑制剂和 NADPH 氧化酶抑制剂可明显减弱其作用。总之，本研究表明，长期低剂量 ADMA 可在基因和蛋白水平诱导内皮细胞中 TGF-β的表达。肌动蛋白细胞骨架可能参与调节 ADMA 诱导的 NF-κB 激活和随后 HRGEC 中 TGF-β的表达。
