title: The IL-12p70/IL-10 interplay is differentially regulated by free heme and hemozoin in murine bone-marrow-derived macrophages.
abstract: The outcome of malarial anemia is determined by a complex interplay between pro-inflammatory and anti-inflammatory cytokines, its severity associated with accumulation of hemozoin (Hz) in macrophages, elevated IL-10 responses and impaired IL-12 production. Although free heme contributes to malarial anemia by inducing oxidative damage of red blood cells (RBCs) and enhancing their clearance by phagocytes, its impact on IL-12/IL-10 interactions has not been fully characterized. Herein, the effect of hemin (HE) on IL-12 and IL-10 responses was studied in murine bone marrow-derived macrophages (BMDM) and compared with synthetic Hz. Our data reveal that HE induces modest inhibition of IL-12p70 responses to lipopolysaccharide (LPS) whereas Hz significantly impairs IL-12p70 responses to IFNgamma/LPS through down-regulation of IL-12p35 and p40 gene expression. Although reactive oxygen species (ROS) are generated after short-term exposure to HE and Hz, prolonged exposure to these iron protoporphyrins has opposite effects on the cellular redox status, HE being the only compound able to promote persistent ROS production. Accordingly, the inhibitory effect of HE on IL-12p70 seems sustained by redox-dependent induction of IL-10 and is partially controlled by the p38 mitogen-activated protein kinase (MAPK) signalling pathway. Indeed, treatment with n-acetylcysteine (NAC) or with the p38 MAPK inhibitor SB203580 inhibits IL-10 responses and significantly restores IL-12p70 responses to IFNgamma/LPS in HE-conditioned BMDM. Our results suggest that oxidant stress induced by free heme may potentially contribute to sustained production of IL-10 and down-regulation of IL-12 responses in malaria.
authors.affiliation: Department of Biological Sciences, Université du Québec à Montreal, Montreal, Que., Canada.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Cambos
authors.forename: Stefany
authors.initials: S
authors.lastname: Bazinet
authors.forename: Elie
authors.initials: E
authors.lastname: Abed
authors.forename: Jaime
authors.initials: J
authors.lastname: Sanchez-Dardon
authors.forename: Charlotte
authors.initials: C
authors.lastname: Bernard
authors.forename: Robert
authors.initials: R
authors.lastname: Moreau
authors.forename: Martin
authors.initials: M
authors.lastname: Olivier
authors.forename: Tatiana
authors.initials: T
authors.lastname: Scorza
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D005260:Female; D006418:Heme / Q000276:immunology / Q000378:metabolism*; D006420:Hemeproteins / Q000276:immunology / Q000378:metabolism*; D006427:Hemin / Q000378:metabolism; D007371:Interferon-gamma / Q000276:immunology; D016753:Interleukin-10 / Q000276:immunology* / Q000378:metabolism; D018664:Interleukin-12 / Q000037:antagonists & inhibitors / Q000276:immunology* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000276:immunology; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D010084:Oxidation-Reduction; D011485:Protein Binding; D025941:Protein Interaction Mapping; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D006420:Hemeproteins; D008070:Lipopolysaccharides; D017382:Reactive Oxygen Species; D016753:Interleukin-10; D018664:Interleukin-12; C020753:hemozoin; D006418:Heme; D006427:Hemin; D007371:Interferon-gamma; D048051:p38 Mitogen-Activated Protein Kinases