title: Lipoprotein in the cell wall of Staphylococcus aureus is a major inducer of nitric oxide production in murine macrophages.
abstract: Staphylococcus aureus is a Gram-positive bacterium that causes inflammation at infection sites by inducing various inflammatory mediators such as nitric oxide (NO). To identify the staphylococcal virulence factors contributing to NO production, we compared the ability of ethanol-killed wild-type S. aureus and mutant strains lacking lipoteichoic acid (ΔltaS), lipoproteins (Δlgt), or d-alanine (ΔdltA) to stimulate NO production in a murine macrophage cell line, RAW 264.7, and the primary macrophages derived from C57BL/6 mice. Wild-type, ΔltaS, and ΔdltA strains induced NO production in a dose-dependent manner but this response was not observed when the cells were stimulated with the Δlgt strain. Moreover, purified lipoproteins triggered NO production in macrophages. Coincident with NO induction, the wild-type, ΔltaS, and ΔdltA strains induced expression of inducible NO synthase (iNOS) at both mRNA and protein levels whereas Δlgt failed to induce iNOS protein or mRNA. Transient transfection followed by a reporter gene assay and Western blotting experiments demonstrated that wild-type, ΔltaS, and ΔdltA strains, but not the Δlgt strain, induced substantial activation of NF-κB and STAT1 phosphorylation, both of which are known to be crucial for iNOS expression. Moreover, wild-type, ΔltaS, and ΔdltA strains increased Toll-like receptor 2 (TLR2) activation, which is known to mediate S. aureus-induced innate immunity, whereas the Δlgt strain did not. Collectively, these results suggest that lipoproteins in the cell wall of S. aureus play a major role in the induction of NO production in murine macrophages through activation of the TLR2 receptor.
authors.affiliation: Department of Oral Microbiology and Immunology, DRI, and BK21 Plus Program, School of Dentistry, Seoul National University, Seoul 110-749, Republic of Korea.
authors.forename: Nam Joong
authors.initials: NJ
authors.lastname: Kim
authors.affiliation: Department of Oral Microbiology and Immunology, DRI, and BK21 Plus Program, School of Dentistry, Seoul National University, Seoul 110-749, Republic of Korea.
authors.forename: Ki Bum
authors.initials: KB
authors.lastname: Ahn
authors.affiliation: Division of High-risk Pathogen Research, Center for Infectious Diseases, Korean National Institute of Health, Cheongwon-gun, Chungbuk 363-951, Republic of Korea.
authors.forename: Jun Ho
authors.initials: JH
authors.lastname: Jeon
authors.affiliation: Department of Agricultural Biotechnology and Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Republic of Korea.
authors.forename: Cheol-Heui
authors.initials: CH
authors.lastname: Yun
authors.affiliation: Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: B Brett
authors.initials: BB
authors.lastname: Finlay
authors.affiliation: Department of Oral Microbiology and Immunology, DRI, and BK21 Plus Program, School of Dentistry, Seoul National University, Seoul 110-749, Republic of Korea. Electronic address: shhan-mi@snu.ac.kr.
authors.forename: Seung Hyun
authors.initials: SH
authors.lastname: Han
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D002460:Cell Line; D002473:Cell Wall / Q000276:immunology; D004789:Enzyme Activation; D057809:HEK293 Cells; D006801:Humans; D008074:Lipoproteins / Q000276:immunology*; D008264:Macrophages / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016328:NF-kappa B / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis*; D052247:Nitric Oxide Synthase Type II / Q000096:biosynthesis* / Q000235:genetics; D010766:Phosphorylation; D012333:RNA, Messenger / Q000096:biosynthesis; D050794:STAT1 Transcription Factor / Q000378:metabolism; D013203:Staphylococcal Infections / Q000276:immunology; D013211:Staphylococcus aureus / Q000201:enzymology / Q000276:immunology* / Q000472:pathogenicity; D051195:Toll-Like Receptor 2 / Q000378:metabolism*; D014166:Transferases / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D008074:Lipoproteins; D016328:NF-kappa B; D012333:RNA, Messenger; D050794:STAT1 Transcription Factor; C494080:Stat1 protein, mouse; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D014166:Transferases; C042308:phosphatidylglycerol glyceryl transferase
keywords: Lipoproteins; Macrophage; Nitric oxide; Staphylococcus aureus; TLR2