title: Hemoglobin receptor protein from Porphyromonas gingivalis induces interleukin-8 production in human gingival epithelial cells through stimulation of the mitogen-activated protein kinase and NF-κB signal transduction pathways.
abstract: Periodontitis is an inflammatory disease of polymicrobial origin affecting the tissues supporting the tooth. The oral anaerobic bacterium Porphyromonas gingivalis, which is implicated as an important pathogen for chronic periodontitis, triggers a series of host inflammatory responses that promote the destruction of periodontal tissues. Among the virulence factors of P. gingivalis, hemoglobin receptor protein (HbR) is a major protein found in culture supernatants. In this study, we investigated the roles of HbR in the production of inflammatory mediators. We found that HbR induced interleukin-8 (IL-8) production in the human gingival epithelial cell line Ca9-22. p38 mitogen-activated protein kinase (MAPK) and extracellular signal-related kinase 1/2 (Erk1/2) were activated in HbR-stimulated Ca9-22 cells. Inhibitors of p38 MAPK (SB203580) and Erk1/2 (PD98059) blocked HbR-induced IL-8 production. Additionally, HbR stimulated the translocation of NF-κB-p65 to the nucleus, consistent with enhancement of IL-8 expression by activation of the NF-κB pathway. In addition, small interfering RNA (siRNA) targeting activating transcription factor 2 (ATF-2) or cyclic AMP-response element-binding protein (CREB) inhibited HbR-induced IL-8 production. Moreover, pretreatment with SB203580 and PD98059 reduced HbR-induced phosphorylation of CREB and ATF-2, respectively. Combined pretreatment with an inhibitor of NF-κB (BAY11-7082) and SB203580 was more efficient in inhibiting the ability of HbR to induce IL-8 production than pretreatment with either BAY11-7082 or SB203580 alone. Thus, in Ca9-22 cells, the direct activation of p38 MAPK and Erk1/2 by HbR caused the activation of the transcription factors ATF-2, CREB, and NF-κB, thus resulting in the induction of IL-8 production.
authors.affiliation: Department of Oral Microbiology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Fujita
authors.forename: Masaaki
authors.initials: M
authors.lastname: Nakayama
authors.forename: Mariko
authors.initials: M
authors.lastname: Naito
authors.forename: Eiki
authors.initials: E
authors.lastname: Yamachika
authors.forename: Tetsuyoshi
authors.initials: T
authors.lastname: Inoue
authors.forename: Koji
authors.initials: K
authors.lastname: Nakayama
authors.forename: Seiji
authors.initials: S
authors.lastname: Iida
authors.forename: Naoya
authors.initials: N
authors.lastname: Ohara
mesh_terms: D001426:Bacterial Proteins / Q000502:physiology*; D016866:Bacteroidaceae Infections; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology*; D005881:Gingiva / Q000378:metabolism; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis*; D016328:NF-kappa B / Q000502:physiology*; D010518:Periodontitis / Q000382:microbiology; D016966:Porphyromonas gingivalis / Q000502:physiology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011971:Receptors, Immunologic / Q000276:immunology*; D015398:Signal Transduction / Q000502:physiology; D048051:p38 Mitogen-Activated Protein Kinases / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D016209:Interleukin-8; D016328:NF-kappa B; D047428:Protein Kinase Inhibitors; D011971:Receptors, Immunologic; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases