Chen Jing-Yun, Lin Chien-Huang, Chen Bing-Chang
Gradual Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan.
Gradual Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan.
Mol Immunol. 2017 Aug;88:155-163. doi: 10.1016/j.molimm.2017.06.029. Epub 2017 Jun 21.
Hypoxia was identified as a mediator of lung fibrosis in patients with chronic obstructive asthma (COA). Overexpression of a disintegrin and metalloproteinase 17 (ADAM 17) and connective tissue growth factor (CTGF) leads to development of tissue fibrosis. However, the signaling pathway in hypoxia-induced ADAM 17 expression remains poorly defined. In this study, we investigated the roles that ribosomal S-6 kinase 1 (RSK1)/CCAAT/enhancer-binding protein β (C/EBPβ)-dependent ADAM 17 expression plays in hypoxia-induced CTGF expression in human lung fibroblasts. We observed that hypoxia caused increases in ADAM 17 expression and ADAM 17-luciferase activity in WI-38 cells. Hypoxia-induced CTGF-luciferase activity and CTGF expression were reduced in cells transfected with small interfering (si)RNA of ADAM 17 in WI-38 cells. Moreover, hypoxia-induced ADAM 17 expression was reduced by RSK1 siRNA and C/EBPβ siRNA. Hypoxia caused time-dependent increases in RSK1 phosphorylation at Thr359/Ser363. Exposure of cells to hypoxia resulted in increased C/EBPβ phosphorylation at Thr266 and C/EBPβ-luciferase activity in time-dependent manners, and these effects were suppressed by RSK1 siRNA. Hypoxia induced recruitment of C/EBPβ to the ADAM 17 promoter. Furthermore, CTGF-luciferase activity induced by hypoxia was attenuated by RSK1 siRNA and C/EBPβ siRNA. These results suggest that hypoxia instigates the RSK1-dependent C/EBPβ signaling pathway, which in turn initiates binding of C/EBPβ to the ADAM 17 promoter and ultimately induces ADAM 17 expression in human lung fibroblasts. Moreover, RSK1/C/EBPβ-dependent ADAM 17 expression is involved in hypoxia-induced CTGF expression. Our results suggest possible therapeutic approaches for treating hypoxia-mediated lung fibrosis in COA.
缺氧被确定为慢性阻塞性哮喘（COA）患者肺纤维化的一个介导因素。去整合素和金属蛋白酶17（ADAM 17）及结缔组织生长因子（CTGF）的过表达会导致组织纤维化的发展。然而，缺氧诱导ADAM 17表达的信号通路仍不清楚。在本研究中，我们调查了核糖体S-6激酶1（RSK1）/CCAAT增强子结合蛋白β（C/EBPβ）依赖性ADAM 17表达在人肺成纤维细胞缺氧诱导CTGF表达中所起的作用。我们观察到缺氧导致WI-38细胞中ADAM 17表达及ADAM 17荧光素酶活性增加。在WI-38细胞中，用ADAM 17的小干扰（si）RNA转染细胞后，缺氧诱导的CTGF荧光素酶活性和CTGF表达降低。此外，RSK1 siRNA和C/EBPβ siRNA降低了缺氧诱导的ADAM 17表达。缺氧导致RSK1在Thr359/Ser363位点的磷酸化呈时间依赖性增加。细胞暴露于缺氧环境会导致C/EBPβ在Thr266位点的磷酸化及C/EBPβ荧光素酶活性呈时间依赖性增加，而这些效应被RSK1 siRNA抑制。缺氧诱导C/EBPβ募集至ADAM 17启动子。此外，RSK1 siRNA和C/EBPβ siRNA减弱了缺氧诱导的CTGF荧光素酶活性。这些结果表明，缺氧激活了RSK1依赖性C/EBPβ信号通路，进而启动C/EBPβ与ADAM 17启动子的结合，并最终诱导人肺成纤维细胞中ADAM 17的表达。此外，RSK1/C/EBPβ依赖性ADAM 17表达参与了缺氧诱导的CTGF表达。我们的结果提示了治疗COA中缺氧介导的肺纤维化的可能治疗方法。
