title: Serine dipeptide lipids of Porphyromonas gingivalis inhibit osteoblast differentiation: Relationship to Toll-like receptor 2.
abstract: Porphyromonas gingivalis is a periodontal pathogen strongly associated with loss of attachment and supporting bone for teeth. We have previously shown that the total lipid extract of P. gingivalis inhibits osteoblast differentiation through engagement of Toll-like receptor 2 (TLR2) and that serine dipeptide lipids of P. gingivalis engage both mouse and human TLR2. The purpose of the present investigation was to determine whether these serine lipids inhibit osteoblast differentiation in vitro and in vivo and whether TLR2 engagement is involved. Osteoblasts were obtained from calvaria of wild type or TLR2 knockout mouse pups that also express the Col2.3GFP transgene. Two classes of serine dipeptide lipids, termed Lipid 654 and Lipid 430, were tested. Osteoblast differentiation was monitored by cell GFP fluorescence and osteoblast gene expression and osteoblast function was monitored as von Kossa stained mineral deposits. Osteoblast differentiation and function were evaluated in calvarial cell cultures maintained for 21 days. Lipid 654 significantly inhibited GFP expression, osteoblast gene expression and mineral nodule formation and this inhibition was dependent on TLR2 engagement. Lipid 430 also significantly inhibited GFP expression, osteoblast gene expression and mineral nodule formation but these effects were only partially attributed to engagement of TLR2. More importantly, Lipid 430 stimulated TNF-α and RANKL gene expression in wild type cells but not in TLR2 knockout cells. Finally, osteoblast cultures were observed to hydrolyze Lipid 654 to Lipid 430 and this likely occurs through elevated PLA2 activity in the cultured cells. In conclusion, our results show that serine dipeptide lipids of P. gingivalis inhibit osteoblast differentiation and function at least in part through engagement of TLR2. The Lipid 430 serine class also increased the expression of genes that could increase osteoclast activity. We conclude that Lipid 654 and Lipid 430 have the potential to promote TLR2-dependent bone loss as is reported in experimental periodontitis following oral infection with P. gingivalis. These results also support the conclusion that serine dipeptide lipids are involved in alveolar bone loss in chronic periodontitis.
authors.affiliation: Department of Craniofacial Sciences, University of Connecticut School of Dental Medicine, Farmington, CT 06030, USA.
authors.forename: Yu-Hsiung
authors.initials: YH
authors.lastname: Wang
authors.affiliation: From the Department of Chemistry, University of Connecticut, Storrs, CT 06269-3060, USA.
authors.forename: Reza
authors.initials: R
authors.lastname: Nemati
authors.affiliation: Department of Immunology and Medicine, University of Connecticut School of Medicine, Farmington, CT 06030, USA.
authors.forename: Emily
authors.initials: E
authors.lastname: Anstadt
authors.affiliation: Department of Oral Health and Diagnostic Sciences, University of Connecticut School of Dental Medicine, Farmington, CT 06030, USA.
authors.forename: Yaling
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Oral Health and Diagnostic Sciences, University of Connecticut School of Dental Medicine, Farmington, CT 06030, USA.
authors.forename: Young
authors.initials: Y
authors.lastname: Son
authors.affiliation: Department of Oral Health and Diagnostic Sciences, University of Connecticut School of Dental Medicine, Farmington, CT 06030, USA.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhu
authors.affiliation: From the Department of Chemistry, University of Connecticut, Storrs, CT 06269-3060, USA; Institute for Systems Genomics, University of Connecticut, Storrs, CT 06269, USA.
authors.forename: Xudong
authors.initials: X
authors.lastname: Yao
authors.affiliation: Department of Immunology and Medicine, University of Connecticut School of Medicine, Farmington, CT 06030, USA.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Clark
authors.affiliation: Department of Reconstuctive Sciences, University of Connecticut School of Dental Medicine, Farmington, CT 06030, USA.
authors.forename: David W
authors.initials: DW
authors.lastname: Rowe
authors.affiliation: Department of Oral Health and Diagnostic Sciences, University of Connecticut School of Dental Medicine, Farmington, CT 06030, USA. Electronic address: Nichols@nso.uchc.edu.
authors.forename: Frank C
authors.initials: FC
authors.lastname: Nichols
mesh_terms: D016301:Alveolar Bone Loss / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D000818:Animals; D016866:Bacteroidaceae Infections / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D002454:Cell Differentiation / Q000187:drug effects; D055113:Chronic Periodontitis / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D004151:Dipeptides / Q000378:metabolism / Q000633:toxicity; D006801:Humans; D055666:Lipopeptides / Q000378:metabolism / Q000633:toxicity; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010006:Osteoblasts / Q000187:drug effects / Q000382:microbiology* / Q000473:pathology*; D016966:Porphyromonas gingivalis / Q000378:metabolism / Q000472:pathogenicity*; D051195:Toll-Like Receptor 2 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D037521:Virulence Factors / Q000378:metabolism / Q000633:toxicity
chemical_list: D004151:Dipeptides; D055666:Lipopeptides; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2; D037521:Virulence Factors
keywords: Osteoblasts; Porphyromonas gingivalis; Serine lipids and Toll-like receptor 2