Nox4 Is Required for Maintenance of the Differentiated Vascular Smooth Muscle Cell Phenotype

• Type of Material: Article
• Authors: Roza E. Clempus, Emory University; Dan Sorescu, Emory University; Anna E. Dikalova, Emory University; Lily Pounkova, Emory University; Patricia Jo, Emory University; George P. Sorescu, Emory University; Bernard P Lassegue, Emory University; Kathy Griendling, Emory University
• Language: English
• Date: 2007-01
• Publisher: American Heart Association
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2006 American Heart Association, Inc.
• Final Published Version (URL): http://atvb.ahajournals.org/content/27/1/42
• Title of Journal or Parent Work: Arteriosclerosis, Thrombosis, and Vascular Biology
• ISSN: 1079-5642
• Volume: 27
• Issue: 1
• Start Page: 42
• End Page: 48
• Grant/Funding Information: This work was supported by NIH grants HL38206, HL075209, and HL058000, to K.K.G. and an American Heart Association Scientist Development Award (0335244N) to D.S.; National Heart, Lung, and Blood Institute : NHLBI
• Keywords: gene expression; differentiation; vascular smooth muscle; reactive oxygen species
• Research Categories: Biology, Genetics

Abstract

Objective The mechanisms responsible for maintaining the differentiated phenotype of adult vascular smooth muscle cells (VSMCs) are incompletely understood. Reactive oxygen species (ROS) have been implicated in VSMC differentiation, but the responsible sources are unknown. In this study, we investigated the role of Nox1 and Nox4-derived ROS in this process. Methods and Results Primary VSMCs were used to study the relationship between Nox homologues and differentiation markers such as smooth muscle α-actin (SM α-actin), smooth muscle myosin heavy chain (SM-MHC), heavy caldesmon, and calponin. We found that Nox4 and differentiation marker genes were downregulated from passage 1 to passage 6 to 12, whereas Nox1 was gradually upregulated. Nox4 co-localized with SM α-actin–based stress fibers in differentiated VSMC, and moved into focal adhesions in de-differentiated cells. siRNA against nox4 reduced NADPH-driven superoxide production in serum-deprived VSMCs and downregulated SM-α actin, SM-MHC, and calponin, as well as SM-α actin stress fibers. Nox1 depletion did not decrease these parameters. Conclusion Nox4-derived ROS are critical to the maintenance of the differentiated phenotype of VSMCs. These findings highlight the importance of identifying the specific source of ROS involved in particular cellular functions when designing therapeutic interventions.