Immunobiology 215 (2010) 173–181 Macrophage activation by gastric fluid suggests MMP involvement in aspiration-induced lung disease Chih Mei Cheng a,1 , Chong Chao Hsieh b,1 , Chang Sheng Lin a , Zen Kong Dai c , Pin Keng Shih b , Mary Lou Everett d , Anitra D. Thomas d , William Parker d , R. Duane Davis d , Shu S. Lin d,e,Ã a Faculty of Biomedical and Environmental Biology, Kaohsiung Medical University, Taiwan b Department of Surgery, Chung-Ho Memorial Hospital, Kaohsiung Medical University, Taiwan c Department of Pediatrics, Chung-Ho Memorial Hospital, Kaohsiung Medical University, Taiwan d Department of Surgery, Duke University Medical Center, DUMC Box 2605, NC 27710, USA e Department of Immunology, Duke University Medical Center, DUMC Box 3392, NC 27710, USA Received 2 December 2008; received in revised form 16 February 2009; accepted 16 February 2009 Abstract Asthma occurs in more than 5% of the population in industrialized countries and is now characterized as a chronic inflammatory disease. The chronic aspiration of gastric fluid is considered by many investigators to be a primary inflammatory factor exacerbating or predisposing patients to asthma, with more than 50 medical papers per year linking asthma with gastroesophageal reflux disease (GERD), which can lead to aspiration events. However, the mechanisms involved in the inflammatory effects caused by gastric-fluid aspiration are not clear at the present time. The role of macrophages in the pathogenesis of disease seems likely given the involvement of those cells in a variety of chronic inflammatory diseases. To investigate the potential role of gastric fluid and the mechanisms potentially underlying chronic aspiration-associated pathogenesis, we examined the activation of murine macrophages (Raw 264.7 cell line) with gastric fluid. Inflammatory cytokine production and activation of the NF-kB signaling pathway were observed. Toll-like receptor (TLR)-4-dependent activation was observed under some conditions, indicating that bacterial components within the gastric fluid are involved in macrophage activation. Matrix metalloproteinase-9 (MMP-9) expression by macrophages was enhanced by gastric fluid, suggesting a potential mechanism by which remodeling of airways might be induced by gastric-fluid aspiration. r 2009 Elsevier GmbH. All rights reserved. Keywords: GERD; Asthma; MMP; NF-kB Introduction Airway inflammation is complex and most likely involves a variety of factors associated with both innate and adaptive immunity. Recent work has pointed toward an important role of matrix metalloproteinases (MMPs) in regulation of airway remodeling associated ARTICLE IN PRESS www.elsevier.de/imbio 0171-2985/$ - see front matter r 2009 Elsevier GmbH. All rights reserved. doi:10.1016/j.imbio.2009.02.001 Abbreviations: COPD, chronic obstructive pulmonary disease; GERD, gastroesophageal reflux disease; IL, interleukin; LPS, lipopo- lysaccharide; MMP, matrix metalloprotease; NF-kB, nuclear factor kappa B; TNF, tumor necrosis factor; TLR, toll-like receptor. Ã Corresponding author. Tel.: +1 919 684 4694; fax: +1 919 681 7524. E-mail address: shu.lin@duke.edu (S.S. Lin). 1 These authors contributed equally to this work.