title: Signal transduction and nuclear responses in Staphylococcus aureus-induced expression of human beta-defensin 3 in skin keratinocytes.
abstract: The human beta-defensin 3 (hBD-3) is an inducible epithelial peptide antibiotic that has potent antistaphylococcal activity. Infection of skin epithelial cells with viable Staphylococcus aureus, a common skin pathogen, induces increased gene expression of hBD-3 and other antimicrobial peptides. The aim of this study was to identify signaling pathways and nuclear responses that contribute to the gene expression of hBD-3 in primary human keratinocytes upon contact with S. aureus. Increased hBD-3 peptide was observed by immunofluorescence microscopy in keratinocytes exposed to S. aureus and to lipoteichoic acid (LTA). Both are ligands for the cell surface Toll-like receptor 2 (TLR2), and thus the contribution of TLR2 signaling in hBD-3 expression was examined. Functional inhibition of TLR2 prior to S. aureus stimulation significantly decreased hBD-3 mRNA levels by 37%, attesting to the involvement of this surface receptor in the initial recognition and downstream signaling for hBD-3 expression. Treatment of keratinocytes with a p38 mitogen-activated protein kinase (MAPK) inhibitor prior to either S. aureus or LTA stimulation was associated with reduced hBD-3 mRNA transcripts and peptide. We also propose a role for the MAPK-regulated transcriptional activating protein 1 in S. aureus-induced hBD-3 gene expression. Combined, these studies indicate a role for TLR2 signaling and MAPK activation in the upregulation of hBD-3 and demonstrate the innate immune capacity of skin keratinocytes under conditions of S. aureus challenge to enhance the local expression of this antistaphylococcal peptide antibiotic.
authors.affiliation: Department of Veterans Affairs S-111-ID, Puget Sound Health Care System, 1660 S. Columbian Way, Seattle, WA 98108, USA. bmenzies@u.washington.edu
authors.forename: Barbara E
authors.initials: BE
authors.lastname: Menzies
authors.forename: Aimee
authors.initials: A
authors.lastname: Kenoyer
mesh_terms: D002478:Cells, Cultured; D015870:Gene Expression; D006801:Humans; D015603:Keratinocytes / Q000737:chemistry / Q000378:metabolism / Q000382:microbiology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D015398:Signal Transduction; D012867:Skin / Q000166:cytology / Q000378:metabolism / Q000382:microbiology; D013211:Staphylococcus aureus / Q000502:physiology*; D013682:Teichoic Acids / Q000494:pharmacology; D051195:Toll-Like Receptor 2 / Q000819:agonists / Q000037:antagonists & inhibitors / Q000502:physiology*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014158:Transcription, Genetic; D023083:beta-Defensins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: C422950:DEFB103A protein, human; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D013682:Teichoic Acids; D051195:Toll-Like Receptor 2; D018808:Transcription Factor AP-1; D023083:beta-Defensins; C009900:lipoteichoic acid; D048051:p38 Mitogen-Activated Protein Kinases