title: Porphyromonas gingivalis lipopolysaccharide is both agonist and antagonist for p38 mitogen-activated protein kinase activation.
abstract: Lipopolysaccharide (LPS) is a key inflammatory mediator. It has been proposed to function as an important molecule that alerts the host of potential bacterial infection. Although highly conserved, LPS contains important structural differences among different bacterial species that can significantly alter host responses. For example, LPS obtained from Porphyromonas gingivalis, an etiologic agent for periodontitis, evokes a highly unusual host cell response. Human monocytes respond to this LPS by the secretion of a variety of different inflammatory mediators, while endothelial cells do not. In addition, P. gingivalis LPS inhibits endothelial cell expression of E-selectin and interleukin 8 (IL-8) induced by other bacteria. In this report the ability of P. gingivalis LPS to activate p38 mitogen-activated protein (MAP) kinase was investigated. It was found that p38 MAP kinase activation occurred in response to P. gingivalis LPS in human monocytes. In contrast, no p38 MAP kinase activation was observed in response to P. gingivalis LPS in human endothelial cells or CHO cells transfected with human Toll-like receptor 4 (TLR-4). In addition, P. gingivalis LPS was an effective inhibitor of Escherichia coli-induced p38 MAP kinase phosphorylation in both endothelial cells and CHO cells transfected with human TLR-4. These data demonstrate that P. gingivalis LPS activates the LPS-associated p38 MAP kinase in monocytes and that it can be an antagonist for E. coli LPS activation of p38 MAP kinase in endothelial and CHO cells. These data also suggest that although LPS is generally considered a bacterial component that alerts the host to infection, LPS from P. gingivalis may selectively modify the host response as a means to facilitate colonization.
authors.affiliation: Department of Periodontics, University of Washington, Seattle, Washington 98181, USA. rdarveau@u.washington.edu
authors.forename: Richard P
authors.initials: RP
authors.lastname: Darveau
authors.forename: Saman
authors.initials: S
authors.lastname: Arbabi
authors.forename: Iris
authors.initials: I
authors.lastname: Garcia
authors.forename: Brian
authors.initials: B
authors.lastname: Bainbridge
authors.forename: Ronald V
authors.initials: RV
authors.lastname: Maier
mesh_terms: D000818:Animals; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D029721:Drosophila Proteins; D004730:Endothelium, Vascular / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D018950:Lipopolysaccharide Receptors / Q000502:physiology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects* / Q000378:metabolism; D009000:Monocytes / Q000201:enzymology; D010766:Phosphorylation; D016966:Porphyromonas gingivalis / Q000472:pathogenicity*; D011956:Receptors, Cell Surface / Q000502:physiology; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D029721:Drosophila Proteins; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases