Molecular Immunology 48 (2011) 2019–2026 Contents lists available at ScienceDirect Molecular Immunology jo u rn al hom epa ge: www.elsevier.com/locate/molimm Clearance of Propionibacterium acnes by kupffer cells is regulated by osteopontin through modulating the expression of p47phox Haiou Yang a,b,1 , Huaizu Guo a,b,1 , Kexing Fan b,c , Bo Zhang b , Lei Zhao b,c , Sheng Hou b,c , Weizhu Qian b,c , Dapeng Zhang b,c , Hao Wang b,c , Jianxing Dai b,c,∗ , Yajun Guo a,b,c,d,∗ a School of Medicine, Shanghai Jiao Tong University, 227 South Chongqing Road, Shanghai 200025, People’s Republic of China b International Joint Cancer Institute, The Second Military Medical University, Shanghai 200433, People’s Republic of China c National Engineering Research Center for Antibody Medicine, State Key Laboratory of Antibody Medicine and Targeting Therapy and Shanghai Key Laboratory of Cell Engineering, Shanghai 201203, People’s Republic of China d PLA General Hospital Cancer Center, PLA Graduate School of Medicine, Beijing 100853, People’s Republic of China a r t i c l e i n f o Article history: Received 16 May 2011 Accepted 10 June 2011 Available online 6 July 2011 Keywords: Osteopontin Reactive oxygen species Kupffer cells Bacterial clearance a b s t r a c t Osteopontin (OPN) is a cytokine with multiple functions, including the regulation of innate immune response. However, the detailed function and mechanism of OPN in host defense against invaded microorganisms remain unclear. In this report, we revealed that OPN could affect the clearance of Propionibacterium acnes in kupffer cells. In a murine model of P. acnes induced hepatic granuloma, OPN- deficient mice or wild-type (WT) mice treated with anti-OPN mAb exhibited more hepatic granuloma formation than WT mice. Increased infiltration of intrahepatic leukocytes, higher expression of TLRs, and significantly upregulated level of proinflammatory cytokines of liver tissue were observed in OPN- deficient mice after P. acnes challenge. Moreover, in vitro assay showed that kupffer cells isolated from OPN -/- mice exhibited impairment in clearance of P. acnes. Kupffer cells isolated from OPN -/- mice showed reduced level of NADPH oxidase-mediated reactive oxygen species (ROS) in response to P. acnes, which was regulated by NADPH oxidase subunit p47phox. Further investigation revealed that OPN inter- action with v3 integrin activated PI3K and ERK signal pathways, leading to the expression of p47phox. Taken together, these data demonstrated an important role of OPN in enhancing the antimicrobial innate immune response by modulation of bacterium clearance activity in kupffer cells. © 2011 Elsevier Ltd. All rights reserved. 1. Introduction Liver, an organ with predominant innate immunity, can effi- ciently and quickly defend against potentially toxic agents (such as bacterial products, environmental toxins and food antigens) from blood circulation (Gao et al., 2008). The activation of the liver innate immune system is critical for bacteria eradication in the early phase of antimicrobial infection. In host defense against invasive pathogens in the liver, innate immune cells such as kupffer cells and neutrophils play important roles in engulfing and killing microbes. Kupffer cells and neutrophils sense bacteria or their components via a set of cell surface proteins collectively termed the Toll-like recep- tors (TLRs) (Kawai and Akira, 2006) and then produce a series of ∗ Corresponding author at: International Joint Cancer Institute, The Second Mili- tary Medical University, 800 Xiang Yin Road, Shanghai 200433, People’s Republic of China. Tel.: +86 21 81870801; fax: +86 21 65306667. E-mail addresses: daijx@hotmail.com (J. Dai), yguo smmu@smmu.edu.cn (Y. Guo). 1 These authors contributed equally to this work. pro-inflammatory cytokines, such as tumor necrosis factor  (TNF- ), interleukins (IL-1 and IL-6), chemokines and reactive oxygen species (ROS) (Honda et al., 2006; Sweet and Hume, 1996). Kupf- fer cells compose 80–90% of fixed tissue macrophages and have been demonstrated to play an important role in hepatic antimi- crobial response. Although the role of cytokines, chemokines, and adhesion molecules have been implicated (Jaeschke and Hasegawa, 2006), the precise mechanisms of eradicating pathogens by kupffer cells are not elucidated. Osteopontin (OPN) is a secreted, phosphorylated glycopro- tein that is synthesized by many different cell types including macrophages, neutrophils, dendritic cells, NK cells, T and B cells (Huang et al., 2010; Wang and Denhardt, 2008). OPN interaction with certain integrins and CD44 variants mediates cell adhesion, migration and survival in many physiological and pathological processes including wound healing, inflammation, tumor metas- tasis and immune responses. Numerous studies have also shown that OPN modulates cell-mediated immunity and granulomatous inflammation, such as sarcoidosis, tuberculosis, rheumatoid nod- ules and others diseases (O’Regan and Berman, 2000b). In the liver, OPN is highly expressed in activated kupffer cells in response to 0161-5890/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.molimm.2011.06.435