title: Peptidoglycan-mediated IL-8 expression in human alveolar type II epithelial cells requires lipid raft formation and MAPK activation.
abstract: Staphylococcus aureus, a major sepsis-causing Gram-positive bacterium, invades pulmonary epithelial cells and causes lung diseases. In the lung, alveolar type II epithelial cells play an important role in innate immunity by secreting chemokines and antimicrobial peptides upon bacterial infection whereas type I cells mainly function in gas-exchange. In this study, we investigated the ability of S. aureus peptidoglycan (PGN) to induce expression of a chemokine, IL-8, in a human alveolar type II epithelial cell line, A549. PGN induces IL-8 mRNA and protein expression in a dose- and time-dependent manner. Supplementation of soluble CD14 further enhanced the PGN-induced IL-8 expression. Interestingly, PGN-induced IL-8 expression was inhibited by nystatin, a specific inhibitor for lipid rafts, but not by chlorpromazine, a specific inhibitor for clathrin-coated pits. Furthermore, PGN-induced IL-8 expression was attenuated by inhibitors for MAP kinases such as ERK, p38 kinase, and JNK/SAPK, whereas no inhibitory effect was observed by inhibitors for reactive oxygen species or protein kinase C. Electrophoretic mobility shift assay demonstrates that PGN increased the DNA binding of the transcription factors, AP-1 and NF-kappaB while minimally, NF-IL6, all of which are involved in the transcription of IL-8. Taken together, these results suggest that PGN induces IL-8 expression in a CD14-enhanced manner in human alveolar type II epithelial cells, through the formation of lipid rafts and the activation of MAP kinases, which ultimately leads to activation of AP-1, NF-kappaB, and NF-IL6.
authors.affiliation: Department of Oral Microbiology & Immunology and Dental Research Institute, School of Dentistry, Seoul National University, Seoul 110-749, Republic of Korea.
authors.forename: In Su
authors.initials: IS
authors.lastname: Cheon
authors.forename: Sang Su
authors.initials: SS
authors.lastname: Woo
authors.forename: Seok-Seong
authors.initials: SS
authors.lastname: Kang
authors.forename: Jintaek
authors.initials: J
authors.lastname: Im
authors.forename: Cheol-Heui
authors.initials: CH
authors.lastname: Yun
authors.forename: Dae Kyun
authors.initials: DK
authors.lastname: Chung
authors.forename: Dong Ki
authors.initials: DK
authors.lastname: Park
authors.forename: Seung Hyun
authors.initials: SH
authors.lastname: Han
mesh_terms: D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism; D045744:Cell Line, Tumor; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000378:metabolism*; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis*; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D021962:Membrane Microdomains / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D010457:Peptidoglycan / Q000378:metabolism / Q000494:pharmacology*; D011493:Protein Kinase C / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D020545:Respiratory Mucosa / Q000378:metabolism*; D013211:Staphylococcus aureus / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000378:metabolism
chemical_list: D022782:CCAAT-Enhancer-Binding Protein-beta; D016209:Interleukin-8; D018950:Lipopolysaccharide Receptors; D016328:NF-kappa B; D010457:Peptidoglycan; D017382:Reactive Oxygen Species; D018808:Transcription Factor AP-1; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases