NADPH oxidase 4 mediates TGF-β-induced smooth muscle α-actin via p38MAPK and serum response factor

• Type of Material: Article
• Authors: Abel Martin-Garrido, Emory University; David I. Brown, Emory University; Alicia N. Lyle, Emory University; Anna Dikalova, Emory University; Bonnie Seidel-Rogol, Emory University; Bernard P Lassegue, Emory University; Alejandra San Martin Almeyda, Emory University; Kathy Griendling, Emory University
• Language: English
• Date: 2011-01-15
• Publisher: Elsevier
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2010 Elsevier Inc. All rights reserved.
• License: Creative Commons Attribution-NonCommerical-NoDerivs 3.0 Unported
• Final Published Version (URL): http://dx.doi.org/10.1016/j.freeradbiomed.2010.11.007
• Title of Journal or Parent Work: Free Radical Biology and Medicine
• ISSN: 0891-5849
• Volume: 50
• Issue: 2
• Start Page: 354
• End Page: 362
• Grant/Funding Information: This work was supported by NIH grants HL38206 and HL095070.
• Keywords: serum response factor; reactive oxygen species; Vascular smooth muscle; smooth muscle α-actin; NADPH oxidase 4; transforming growth factor-β; p38 mitogen activated protein kinase
• Research Categories: Health Sciences, Medicine and Surgery

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 (MK-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.