Constitutive NADPH oxidase and increased mitochondrial respiratory chain activity regulate chemokine gene expression

• Published in: American journal of physiology. Lung cellular and molecular physiology 2007-11, Vol.293 (5), p.L1143-L1155
• Main Authors: Tephly, Linda A, Carter, A. Brent
• Format: Article
• Language: English
• Subjects: Blotting, Western; Chemokine CXCL2 - metabolism; Chemokines - genetics; Electron Transport; Extracellular Signal-Regulated MAP Kinases - metabolism; Gene expression; Gene Expression Regulation - physiology; Genes; Humans; Hydrogen Peroxide - pharmacology; Interleukin-8 - metabolism; Ions; Leukocytes; Lungs; Macrophages, Alveolar - cytology; Macrophages, Alveolar - drug effects; Macrophages, Alveolar - metabolism; MAP Kinase Kinase 1 - metabolism; Mitochondria - metabolism; NADPH Oxidases - antagonists & inhibitors; NADPH Oxidases - genetics; NADPH Oxidases - metabolism; Oxidants - pharmacology; Oxygen; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics; RNA, Messenger - metabolism; RNA, Small Interfering - pharmacology; Superoxide Dismutase - metabolism; Superoxides - metabolism; Transcription, Genetic; Tumor Necrosis Factor-alpha - pharmacology
• ISSN: 1040-0605; 1522-1504
• DOI: 10.1152/ajplung.00114.2007

1 Department of Medicine, University of Iowa Roy J. and Lucille A. Carver College of Medicine, and 2 Iowa City Veterans Administration Medical Center, Iowa City, Iowa Submitted 23 March 2007 ; accepted in final form 15 August 2007 Alveolar macrophages, which generate high levels of reactive oxygen species, especially O 2 – , are involved in the recruitment of neutrophils to sites of inflammation and injury in the lung, and the generation of chemotactic proteins triggers this cellular recruitment. In this study, we asked whether O 2 – generation in alveolar macrophages had a role in the expression of chemokines. Specifically, we hypothesized that O 2 – generation is necessary for chemokine expression in alveolar macrophages after TNF- stimulation. We found that alveolar macrophages have high constitutive NADPH oxidase activity that was not increased by TNF- , but TNF- increased the activity of the mitochondrial respiratory chain. In addition, the mitochondrial respiratory chain increased O 2 – generation if the NADPH oxidase was inhibited. O 2 – generation was necessary for macrophage inflammatory protein-2 (MIP-2) gene expression, because inhibition of NADPH oxidase or the mitochondrial respiratory chain or overexpression of Cu,Zn-superoxide dismutase significantly inhibited expression of MIP-2. TNF- activated the ERK MAP kinase, and ERK activity was essential for chemokine gene expression. In addition, overexpression of the MEK1 ERK pathway significantly increased IL-8 expression, and a small interfering RNA to the NADPH oxidase inhibited ERK- and TNF- -induced chemokine expression. Collectively, these results suggest that in alveolar macrophages, O 2 – generation mediates chemokine expression after TNF- stimulation in an ERK-dependent manner. macrophages; chemokines; superoxide anion; inflammation; reactive oxygen species Address for reprint requests and other correspondence: A. B. Carter, Division of Pulmonary and Critical Care Medicine, C33 GH, Univ. of Iowa Hospital and Clinics, 200 Hawkins Dr., Iowa City, IA 52242 (e-mail: brent-carter{at}uiowa.edu )