Protease-activated receptor signaling increases epithelial antimicrobial peptide expression.
Epithelial tissues provide both a physical barrier and an antimicrobial barrier. Antimicrobial peptides of the human beta-defensin (hBD) family are part of the innate immune responses that play a role in mucosal defense. hBDs are made in epithelia including oral epithelium where the bacterial load is particularly great. hBD-2 and hBD-3 are up-regulated in response to bacterial stimuli. Previous studies show that hBD-2 expression in human gingival epithelial cells (GEC) is stimulated by both nonpathogenic and pathogenic bacteria, including Porphyromonas gingivalis, a Gram-negative pathogen associated with periodontitis. Present evidence suggests that hBD-2 expression in GEC uses several signaling pathways, including an NF-kappaB-mediated pathway but without apparent LPS-TLR4 signaling. Protease-activated receptors (PAR) are G-protein-coupled receptors that mediate cellular responses to extracellular proteinases. P. gingivalis secretes multiple proteases that contribute to its virulence mechanisms. To determine whether PAR signaling is used in hBD-2 induction, GEC were stimulated with wild-type P. gingivalis or mutants lacking one or more proteases. hBD-2 mRNA expression was reduced in GEC stimulated with single protease mutants (11-67% compared with wild type), strongly reduced in double mutants (0.1-16%), and restored to wild-type levels (93%) in mutant with restored protease activity. Stimulation by wild type was partially blocked by inhibitors of phospholipase C, a main signaling pathway for PARs. Expression of hBD-3 was unaffected. Peptide agonist of PAR-2, but not PAR-1 activator, also induced hBD-2 in GEC. Thus, P. gingivalis proteases are directly involved in regulation of hBD-2 in cultured GEC, and this induction partially uses the PAR-2 receptor and signaling pathway.
Chung
Whasun O
WO
Department of Oral Biology, University of Washington, Seattle 98195-7132, USA. sochung@u.washington.edu
Hansen
Stephen R
SR
Rao
Divya
D
Dale
Beverly A
BA
D018829:Adhesins, Bacterial; D003546:Cysteine Endopeptidases / Q000502:physiology*; D004847:Epithelial Cells / Q000378:metabolism; D005786:Gene Expression Regulation; D000080867:Gingipain Cysteine Endopeptidases; D005881:Gingiva / Q000378:metabolism*; D006388:Hemagglutinins / Q000502:physiology*; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics; D016133:Polymerase Chain Reaction; D016966:Porphyromonas gingivalis / Q000201:enzymology*; D044463:Receptor, PAR-1 / Q000502:physiology*; D044464:Receptor, PAR-2 / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D023083:beta-Defensins / Q000235:genetics*
D018829:Adhesins, Bacterial; D000080867:Gingipain Cysteine Endopeptidases; D006388:Hemagglutinins; D016209:Interleukin-8; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D023083:beta-Defensins; D003546:Cysteine Endopeptidases