title: Regulatory effects of AT₁R-TRAF6-MAPKs signaling on proliferation of intermittent hypoxia-induced human umbilical vein endothelial cells.
abstract: Endothelial dysfunction induced by intermittent hypoxia (IH) participates in obstructive sleep apnea syndrome (OSAS)-associated cardiovascular disorders. Myeloid differentiation primary response 88 (MyD88) and tumor necrosis factor receptor-associated factor 6 (TRAF6) regulate numerous downstream adaptors like mitogen-activated protein kinases (MAPKs) and the subsequent oxidative stress and inflammatory responses. This study aimed to characterize the role of MyD88/TRAF6 in IH-treated cell function and its associated signaling. Human umbilical vein endothelial cells (HUVECs) were randomly exposed to IH or normoxia for 0, 2, 4 and 6 h. Western blotting was used to detect the expression pattern of target gene proteins [angiotensin 1 receptor (AT1R), p-ERK1/2, p-p38MAPK, MyD88 and TRAF6], and the relationships among these target genes down-regulated by the corresponding inhibitors were studied. Finally, the influence of these target genes on proliferation of HUVECs was also assessed by EdU analysis. Protein levels of AT1R, TRAF6 and p-ERK1/2 were increased after IH exposure, with a slight rise in MyD88 and a dynamic change in p-p38MAPK. The down-regulation of TRAF6 by siRNA reduced ERK1/2 phosphorylation during IH without any effects on AT1R. Blockade of AT1R with valsartan decreased TRAF6 and p-ERK1/2 protein expression after IH exposure. ERK1/2 inhibition with PD98059 suppressed only AT1R expression. IH promoted HUVECs proliferation, which was significantly suppressed by the inhibition of TRAF6, AT1R and ERK1/2. The findings demonstrate that TRAF6 regulates the proliferation of HUVECs exposed to short-term IH by modulating cell signaling involving ERK1/2 downstream of AT1R. Targeting the AT1R-TRAF6-p-ERK1/2 signaling pathway might be helpful in restoring endothelial function.
authors.affiliation: Department of Respiratory and Critical Care Medicine, Key Laboratory of Respiratory Disease of the Ministry of Health, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Shang
authors.affiliation: Department of Respiratory and Critical Care Medicine, Key Laboratory of Respiratory Disease of the Ministry of Health, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
authors.forename: Xue-Ling
authors.initials: XL
authors.lastname: Guo
authors.affiliation: Department of Respiratory and Critical Care Medicine, Key Laboratory of Respiratory Disease of the Ministry of Health, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Deng
authors.affiliation: Department of Respiratory and Critical Care Medicine, Key Laboratory of Respiratory Disease of the Ministry of Health, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Yuan
authors.affiliation: Department of Respiratory and Critical Care Medicine, Key Laboratory of Respiratory Disease of the Ministry of Health, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China. hgliu@tjh.tjmu.edu.cn.
authors.forename: Hui-Guo
authors.initials: HG
authors.lastname: Liu
mesh_terms: D015687:Cell Hypoxia; D049109:Cell Proliferation; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D061307:Human Umbilical Vein Endothelial Cells / Q000502:physiology*; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D010766:Phosphorylation; D044140:Receptor, Angiotensin, Type 1 / Q000235:genetics / Q000378:metabolism*; D048029:TNF Receptor-Associated Factor 6 / Q000235:genetics / Q000378:metabolism*; D000068756:Valsartan / Q000494:pharmacology
chemical_list: D044140:Receptor, Angiotensin, Type 1; D048029:TNF Receptor-Associated Factor 6; D000068756:Valsartan