title: NADPH oxidase 4 mediates TGF-β-induced smooth muscle α-actin via p38MAPK and serum response factor.
abstract: In contrast to other cell types, vascular smooth muscle cells modify their phenotype in response to external signals. NADPH oxidase 4 (Nox4) is critical for maintenance of smooth muscle gene expression; however, the underlying mechanisms are incompletely characterized. Using smooth muscle α-actin (SMA) as a prototypical smooth muscle gene and transforming growth factor-β (TGF-β) as a differentiating agent, we examined Nox4-dependent signaling. TGF-β increases Nox4 expression and activity in human aortic smooth muscle cells (HASMC). Transfection of HASMC with siRNA against Nox4 (siNox4) abolishes TGF-β-induced SMA expression and stress fiber formation. siNox4 also significantly inhibits TGF-β-stimulated p38MAPK phosphorylation, as well as that of its substrate, mitogen-activated protein kinase-activated protein kinase-2. Moreover, the p38MAPK inhibitor SB-203580 nearly completely blocks the SMA increase induced by TGF-β. Inhibition of either p38MAPK or NADPH oxidase-derived reactive oxygen species impairs the TGF-β-induced phosphorylation of Ser103 on serum response factor (SRF) and reduces its transcriptional activity. Binding of SRF to myocardin-related transcription factor (MRTF) is also necessary, because downregulation of MRTF by siRNA abolishes TGF-β-induced SMA expression. Taken together, these data suggest that Nox4 regulates SMA expression via activation of a p38MAPK/SRF/MRTF pathway in response to TGF-β.
authors.affiliation: Division of Cardiology, Department of Medicine, Emory University, Atlanta, GA 30322, USA.
authors.forename: Abel
authors.initials: A
authors.lastname: Martin-Garrido
authors.forename: David I
authors.initials: DI
authors.lastname: Brown
authors.forename: Alicia N
authors.initials: AN
authors.lastname: Lyle
authors.forename: Anna
authors.initials: A
authors.lastname: Dikalova
authors.forename: Bonnie
authors.initials: B
authors.lastname: Seidel-Rogol
authors.forename: Bernard
authors.initials: B
authors.lastname: Lassègue
authors.forename: Alejandra
authors.initials: A
authors.lastname: San Martín
authors.forename: Kathy K
authors.initials: KK
authors.lastname: Griendling
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism*; D001011:Aorta / Q000166:cytology / Q000378:metabolism; D015153:Blotting, Western; D002478:Cells, Cultured; D005455:Fluorescent Antibody Technique; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D008156:Luciferases / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D026362:Serum Response Factor / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D022502:Stress Fibers / Q000378:metabolism* / Q000473:pathology; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D007093:Imidazoles; D011725:Pyridines; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D026362:Serum Response Factor; D016212:Transforming Growth Factor beta; D008156:Luciferases; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498910:NOX4 protein, human; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580