title: Hemoglobin and Streptococcus suis cell wall act in synergy to potentiate the inflammatory response of monocyte-derived macrophages.
abstract: Streptococcus suis, a major swine pathogen world-wide, can trigger macrophages to secrete large amounts of proinflammatory cytokines, which increase the permeability of the blood-brain barrier. In this study, we hypothesized that hemoglobin may potentiate the inflammatory response of human macrophages stimulated with a S. suis cell-wall preparation. Monocyte-derived macrophages were stimulated with the S. suis cell-wall preparation in the presence or absence of human hemoglobin, and the secretion of interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), IL-6, and IL-8 was analyzed by enzyme-linked immunosorbent assays. The cell-wall preparation induced dose-dependent IL-1beta, TNF-alpha, IL-6, and IL-8 responses in macrophages. Hemoglobin potentiated the cell-wall induced inflammatory response, resulting in a significantly higher secretion of all the cytokines. The S. suis cell-wall preparation in combination with hemoglobin activated macrophage intracellular kinases involved in inflammatory signaling pathways. In conclusion, hemoglobin, which may be released in vivo by the action of S. suis suilysin on red blood cells, contributes to raising the levels of pro-inflammatory mediators by acting in synergy with S. suis cell-wall components. This phenomenon may contribute to the development and the severity of meningitis.
authors.affiliation: Groupe de Recherche en Ecologie Buccale, Faculté de Médecine Dentaire, Université Laval, Quebec City, Quebec, Canada.
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Tanabe
authors.forename: Marcelo
authors.initials: M
authors.lastname: Gottschalk
authors.forename: Daniel
authors.initials: D
authors.lastname: Grenier
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology*; D001812:Blood-Brain Barrier / Q000276:immunology; D002460:Cell Line; D002473:Cell Wall / Q000276:immunology / Q000378:metabolism; D016207:Cytokines / Q000276:immunology / Q000378:metabolism; D006454:Hemoglobins / Q000276:immunology* / Q000378:metabolism / Q000494:pharmacology; D006460:Hemolysin Proteins / Q000276:immunology / Q000494:pharmacology; D006801:Humans; D007249:Inflammation / Q000276:immunology; D008262:Macrophage Activation / Q000187:drug effects / Q000276:immunology*; D016920:Meningitis, Bacterial / Q000209:etiology / Q000503:physiopathology; D051379:Mice; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D013290:Streptococcal Infections / Q000276:immunology / Q000503:physiopathology; D017011:Streptococcus suis / Q000737:chemistry / Q000276:immunology*
chemical_list: D000942:Antigens, Bacterial; D016207:Cytokines; D006454:Hemoglobins; D006460:Hemolysin Proteins; C104760:suilysin