title: Serine lipids of Porphyromonas gingivalis are human and mouse Toll-like receptor 2 ligands.
abstract: The total cellular lipids of Porphyromas gingivalis, a known periodontal pathogen, were previously shown to promote dendritic cell activation and inhibition of osteoblasts through engagement of Toll-like receptor 2 (TLR2). The purpose of the present investigation was to fractionate all lipids of P. gingivalis and define which lipid classes account for the TLR2 engagement, based on both in vitro human cell assays and in vivo studies in mice. Specific serine-containing lipids of P. gingivalis, called lipid 654 and lipid 430, were identified in specific high-performance liquid chromatography fractions as the TLR2-activating lipids. The structures of these lipids were defined using tandem mass spectrometry and nuclear magnetic resonance methods. In vitro, both lipid 654 and lipid 430 activated TLR2-expressing HEK cells, and this activation was inhibited by anti-TLR2 antibody. In contrast, TLR4-expressing HEK cells failed to be activated by either lipid 654 or lipid 430. Wild-type (WT) or TLR2-deficient (TLR2(-/-)) mice were injected with either lipid 654 or lipid 430, and the effects on serum levels of the chemokine CCL2 were measured 4 h later. Administration of either lipid 654 or lipid 430 to WT mice resulted in a significant increase in serum CCL2 levels; in contrast, the administration of lipid 654 or lipid 430 to TLR2(-/-) mice resulted in no increase in serum CCL2. These results thus identify a new class of TLR2 ligands that are produced by P. gingivalis that likely play a significant role in mediating inflammatory responses both at periodontal sites and, potentially, in other tissues where these lipids might accumulate.
authors.affiliation: Department of Immunology, Department of Pediatrics, and Department of Medicine, University of Connecticut School of Medicine, Farmington, Connecticut, USA.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Clark
authors.forename: Jorge L
authors.initials: JL
authors.lastname: Cervantes
authors.forename: Mark W
authors.initials: MW
authors.lastname: Maciejewski
authors.forename: Vahid
authors.initials: V
authors.lastname: Farrokhi
authors.forename: Reza
authors.initials: R
authors.lastname: Nemati
authors.forename: Xudong
authors.initials: X
authors.lastname: Yao
authors.forename: Emily
authors.initials: E
authors.lastname: Anstadt
authors.forename: Mai
authors.initials: M
authors.lastname: Fujiwara
authors.forename: Kyle T
authors.initials: KT
authors.lastname: Wright
authors.forename: Caroline
authors.initials: C
authors.lastname: Riddle
authors.forename: Carson J
authors.initials: CJ
authors.lastname: La Vake
authors.forename: Juan C
authors.initials: JC
authors.lastname: Salazar
authors.forename: Sydney
authors.initials: S
authors.lastname: Finegold
authors.forename: Frank C
authors.initials: FC
authors.lastname: Nichols
mesh_terms: D000818:Animals; D016866:Bacteroidaceae Infections / Q000378:metabolism*; D002460:Cell Line; D018932:Chemokine CCL2 / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D008024:Ligands; D008055:Lipids; D051379:Mice; D008810:Mice, Inbred C57BL; D016966:Porphyromonas gingivalis / Q000378:metabolism*; D012694:Serine / Q000378:metabolism*; D051195:Toll-Like Receptor 2 / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000378:metabolism
chemical_list: D018932:Chemokine CCL2; D005227:Fatty Acids; D008024:Ligands; D008055:Lipids; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D012694:Serine