title: Regulation of human beta-defensin-2 in gingival epithelial cells: the involvement of mitogen-activated protein kinase pathways, but not the NF-kappaB transcription factor family.
abstract: Stratified epithelia of the oral cavity are continually exposed to bacterial challenge that is initially resisted by neutrophils and epithelial factors, including antimicrobial peptides of the beta-defensin family. Previous work has shown that multiple signaling pathways are involved in human beta-defensin (hBD)-2 mRNA regulation in human gingival epithelial cells stimulated with a periodontal bacterium, Fusobacterium nucleatum, and other stimulants. The goal of this study was to further characterize these pathways. The role of NF-kappaB in hBD-2 regulation was investigated initially due to its importance in inflammation and infection. Nuclear translocation of p65 and NF-kappaB activation was seen in human gingival epithelial cells stimulated with F. nucleatum cell wall extract, indicating possible involvement of NF-kappaB in hBD-2 regulation. However, hBD-2 induction by F. nucleatum was not blocked by pretreatment with two NF-kappaB inhibitors, pyrrolidine dithiocarbamate and the proteasome inhibitor, MG132. To investigate alternative modes of hBD-2 regulation, we explored involvement of mitogen-activated protein kinase pathways. F. nucleatum activated p38 and c-Jun NH(2)-terminal kinase (JNK) pathways, whereas it had little effect on p44/42. Furthermore, inhibition of p38 and JNK partially blocked hBD-2 mRNA induction by F. nucleatum, and the combination of two inhibitors completely blocked expression. Our results suggest that NF-kappaB is neither essential nor sufficient for hBD-2 induction, and that hBD-2 regulation by F. nucleatum is via p38 and JNK, while phorbol ester induces hBD-2 via the p44/42 extracellular signal-regulated kinase pathway. Studies of hBD-2 regulation provide insight into how its expression may be enhanced to control infection locally within the mucosa and thereby reduce microbial invasion into the underlying tissue.
authors.affiliation: Department of Oral Biology, School of Dentistry, University of Washington, Seattle, WA 98195, USA.
authors.forename: Suttichai
authors.initials: S
authors.lastname: Krisanaprakornkit
authors.forename: Janet R
authors.initials: JR
authors.lastname: Kimball
authors.forename: Beverly A
authors.initials: BA
authors.lastname: Dale
mesh_terms: D021581:Active Transport, Cell Nucleus; D002457:Cell Extracts / Q000494:pharmacology; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D016384:Consensus Sequence; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000276:immunology; D016967:Fusobacterium nucleatum / Q000502:physiology*; D005881:Gingiva / Q000166:cytology / Q000276:immunology*; D006801:Humans; D018928:Immunity, Mucosal; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000502:physiology*; D011759:Pyrrolidines / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D013859:Thiocarbamates / Q000494:pharmacology; D015533:Transcriptional Activation; D023083:beta-Defensins / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D002457:Cell Extracts; C106641:DEFB4A protein, human; D004791:Enzyme Inhibitors; D016328:NF-kappa B; D011759:Pyrrolidines; D012333:RNA, Messenger; D013859:Thiocarbamates; D023083:beta-Defensins; C020972:pyrrolidine dithiocarbamic acid; D020928:Mitogen-Activated Protein Kinases