Wilmer William A, Dixon Cynthia L, Hebert Courtney, Lu Ling, Rovin Brad H
Division of Nephrology, The Department of Internal Medicine, Dorothy M. Davis Heart-Lung Research Institute, The Ohio State University College of Medicine, Columbus, OH 43210, USA.
Antioxid Redox Signal. 2002 Dec;4(6):877-84. doi: 10.1089/152308602762197416.
Transforming growth factor-beta1 (TGF-beta1) mediates the development of glomerulosclerosis by stimulating mesangial cell production of extracellular matrix (ECM) proteins. TGF-beta1 and several ECM genes are regulated by promoter O-tetradecanoylphorbol 13-acetate-responsive elements (TREs) that are transactivated by the activator protein-1 (AP-1) transcription factor complex. AP-1-TRE interactions are regulated by redox changes. Recently, peroxisome proliferator-activated receptors (PPARs) were shown to negatively regulate several transcription factor families. In these studies, we postulated that PPAR-alpha could antagonize TGF-beta1 expression by cultured human mesangial cells (HMC). A TGF-beta1 luciferase expression plasmid was transduced into HMC via recombinant deficient adenoviral vectors. The TGF-beta1 promoter activity increased twofold (209%) following 18-h treatments with H(2)O(2) (1,000 micro M). Using RT-PCR, we demonstrated that HMC possess PPAR-alpha RNA, and PPAR-alpha protein was identified by immunohistochemistry. Pretreatment of cells with the PPAR-alpha ligands WY14643 (100-500 micro M) or clofibrate (100-500 micro M) dose-dependently inhibited oxidant-mediated induction of TGF-beta1. This inhibition occurred without affecting the H(2)O(2)-mediated activation of the mitogen-activated protein kinase (MAPK) pathways extracellular regulated kinase, p38 MAPK, or Jun N-terminal kinase, which are responsible for the regulation of AP-1 phosphorylation. These studies are the first to identify PPAR-alpha expression by HMC. The results of these studies suggest that TGF-beta1 expression mediated by oxidant stress may be suppressible by PPAR-alpha activation.
转化生长因子-β1（TGF-β1）通过刺激系膜细胞产生细胞外基质（ECM）蛋白来介导肾小球硬化的发展。TGF-β1和几个ECM基因受启动子十四烷酰佛波醇-13-乙酸酯反应元件（TREs）调控，这些元件由激活蛋白-1（AP-1）转录因子复合物反式激活。AP-1与TRE的相互作用受氧化还原变化的调节。最近，过氧化物酶体增殖物激活受体（PPARs）被证明对几个转录因子家族具有负调控作用。在这些研究中，我们推测PPAR-α可能拮抗培养的人系膜细胞（HMC）中TGF-β1的表达。通过重组缺陷腺病毒载体将TGF-β1荧光素酶表达质粒转导至HMC中。用H₂O₂（1000 μM）处理18小时后，TGF-β1启动子活性增加了两倍（209%）。通过逆转录-聚合酶链反应（RT-PCR），我们证明HMC含有PPAR-α RNA，并且通过免疫组织化学鉴定出了PPAR-α蛋白。用PPAR-α配体WY14643（100 - 500 μM）或氯贝丁酯（100 - 500 μM）对细胞进行预处理，剂量依赖性地抑制了氧化剂介导的TGF-β1诱导。这种抑制作用的发生并未影响H₂O₂介导的丝裂原活化蛋白激酶（MAPK）途径细胞外调节激酶、p38 MAPK或Jun N末端激酶的激活，这些激酶负责调节AP-1的磷酸化。这些研究首次鉴定出HMC中PPAR-α的表达。这些研究结果表明，PPAR-α激活可能抑制氧化应激介导的TGF-β1表达。
