title: 3LPS-binding protein and its interactions with P. gingivalis LPS modulate pro-inflammatory response and Toll-like receptor signaling in human oral keratinocytes.
abstract: Lipopolysaccharide (LPS)-binding protein (LBP) as an acute-phase protein plays a crucial role in innate host response to bacterial challenge. Our previous study shows that LBP expression in human gingiva is associated with periodontal status. Porphyromonas gingivalis is a keystone periodontopathogen, and its LPS with lipid A structural heterogeneity critically accounts for periodontal pathogenesis. This study investigated the effects of LBP and its interactions with two featured isoforms of P. gingivalis LPS (tetra-acylated LPS1435/1449 and penta-acylated LPS1690) on the expression of pro-inflammatory cytokines in human oral keratinocytes (HOKs), and the involvement of Toll-like receptor (TLR) signaling. HOKs were pre-incubated with recombinant human LBP (rhLBP) at 10ng/ml, 100ng/ml and 1μg/ml for 1 h, followed by the treatment of P. gingivalis LPS1690 or LPS1435/1449 for 3h or 24h respectively. The expression of IL-6 and IL-8, and involvements of TLR2 and TLR4 were analyzed. The genes associated with TLR signaling were assessed by PCR array. Interestingly, rhLBP per se significantly up-regulated the expression of IL-6 and IL-8 in HOKs (p<0.05), which was blocked by TLR2 antibody (p<0.001). LPS1435/1449 down-regulated more significantly rhLBP-induced IL-6 and IL-8 mRNAs with reference to P. gingivalis LPS1690 (approximately 80% vs. 40%, p<0.05; and 90% vs. 36%, p<0.001, respectively). Moreover, rhLBP markedly down-regulated the gene expression of TLRs and their adaptors such as CD180 (-2.44 folds) and MD-1 (-9.62 folds), while the interaction of P. gingivalis LPS1435/1449 with rhLBP greatly up-regulated both transcripts (7.11 and 4.05 folds, respectively). Notably, P. gingivalis LPS1690-rhLBP interaction dramatically up-regulated CD180 transcript (20.86 folds) and significantly down-regulated MD-1 transcript (-6.93 folds). This pioneering study shows that rhLBP enables to enhance the expression of pro-inflammatory cytokines in HOKs through TLR2 signaling pathway. P. gingivalis LPS with different lipid A structures down-regulates to different extents rhLBP-induced cytokine expression, possibly through fine-tuning of the CD180-MD1 complex and relevant TLRs.
authors.affiliation: Department of Periodontology, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, China.|Discipline of Periodontology, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Pei-Hui
authors.initials: PH
authors.lastname: Ding
authors.affiliation: Department of Periodontics, University of Washington School of Dentistry, D-570 Health Sciences Building, Seattle, WA, United States of America.
authors.forename: Richard P
authors.initials: RP
authors.lastname: Darveau
authors.affiliation: Department of Oral Biology & Medicine, University of California Los Angeles School of Dentistry, CHS, Room 33-030, Los Angeles, CA, United States of America.
authors.forename: Cun-Yu
authors.initials: CY
authors.lastname: Wang
authors.affiliation: Discipline of Periodontology, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Lijian
authors.initials: L
authors.lastname: Jin
mesh_terms: D000209:Acute-Phase Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D006801:Humans; D007249:Inflammation / Q000378:metabolism*; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D016966:Porphyromonas gingivalis / Q000378:metabolism*; D015398:Signal Transduction; D051193:Toll-Like Receptors / Q000378:metabolism*; D000099231:Lipopolysaccharide-Binding Protein
chemical_list: D000209:Acute-Phase Proteins; D002352:Carrier Proteins; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D051193:Toll-Like Receptors; D000099231:Lipopolysaccharide-Binding Protein