title: Modulation of Ras/Raf/extracellular signal-regulated kinase pathway by reactive oxygen species is involved in cyclic strain-induced early growth response-1 gene expression in endothelial cells.
abstract: Endothelial cells (ECs) exposed to cyclic strain induce gene expression. To elucidate the signaling mechanisms involved, we studied the effects of cyclic strain on ECs by using early growth response-1 (Egr-1) as a target gene. Cyclic strain induced a transient increase of Egr-1 mRNA levels that resulted in an increase of binding of nuclear proteins to the Egr-1 binding sequences in the platelet-derived growth factor-A promoter region. ECs subjected to strain enhanced Egr-1 transcription as revealed by promoter activities. Catalase pretreatment inhibited this induction. ECs, transfected with a dominant positive mutant of Ras (RasL61), increased Egr-1 promoter activities. In contrast, transfection with a dominant negative mutant of Ras (RasN17) attenuated this strain inducibility. ECs transfected with a dominant negative mutant of Raf-1 (Raf301) or the catalytically inactive mutant of extracellular signal-regulated kinase (ERK)-2 (mERK2) diminished strain-induced promoter activities. However, little effect on strain inducibility was observed in ECs transfected with a dominant negative mutant of Rac (RacN17) or a catalytically inactive mutant of JNK (JNK[K-R]). Consistently, strain-induced Egr-1 expression was inhibited after ECs were treated with a specific inhibitor (PD98059) to mitogen-activated protein kinase kinase. Moreover, strain to ECs induced mitogen-activated protein kinase/ERK activity. The activation of the ERK pathway was further substantiated by an increase of strain-induced transcriptional activity of Elk1, an ERK substrate. This strain-induced ERK activity was attenuated after ECs were treated with N-acetylcysteine or catalase. Consequently, this Egr-1 gene induction was abolished after ECs were treated with N-acetylcysteine or catalase. Deletion analyses of the promoter region (-698 bp) indicated that cyclic strain and H2O2 shared a common serum response element. Our data clearly indicate that cyclic strain-induced Egr-1 expression is mediated mainly via the Ras/Raf-1/ERK pathway and that strain-induced reactive oxygen species can modulate Egr-1 expression at least partially via this signaling pathway.
authors: Cardiovascular Division, Institute of Biomedical Sciences, Academia Sinica, and Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan, ROC.
authors: B S
authors: BS
authors: Wung
authors: J J
authors: JJ
authors: Cheng
authors: Y J
authors: YJ
authors: Chao
authors: H J
authors: HJ
authors: Hsieh
authors: D L
authors: DL
authors: Wang
mesh_terms: D000818:Animals; D001011:Aorta / Q000166:cytology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004730:Endothelium, Vascular / Q000737:chemistry / Q000166:cytology / Q000201:enzymology*; D005110:Extracellular Space / Q000502:physiology; D015870:Gene Expression / Q000502:physiology; D017930:Genes, Reporter; D006861:Hydrogen Peroxide / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1; D009687:Nuclear Proteins / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000502:physiology; D019908:Proto-Oncogene Proteins c-raf / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D017382:Reactive Oxygen Species / Q000378:metabolism; D026362:Serum Response Factor; D015398:Signal Transduction / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation / Q000502:physiology; D016335:Zinc Fingers / Q000502:physiology; D018631:ras Proteins / Q000502:physiology*
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D010982:Platelet-Derived Growth Factor; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D026362:Serum Response Factor; D014157:Transcription Factors; C075278:platelet-derived growth factor A; D006861:Hydrogen Peroxide; D019908:Proto-Oncogene Proteins c-raf; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D018631:ras Proteins