title: Oxidative induction of pro-inflammatory cytokine formation by human monocyte-derived macrophages following exposure to manganese in vitro.
abstract: Manganese (as Mn(2+)), a superoxide dismutase mimetic, catalyzes the formation of the relatively stable membrane-permeable reactive oxygen species (ROS) hydrogen peroxide (H2O2), a mediator of intracellular redox signaling in immune and inflammatory cells. The goal of this study was to investigate the potential for Mn(2+), via its pro-oxidative properties, to activate production of pro-inflammatory cytokines/chemokines IL-1β, IL-6, IL-8, IFNγ, TNFα, and G-CSF by human monocyte-derived macrophages in vitro. For these studies, the cells were isolated from peripheral blood mononuclear leukocytes and matured to generate a population of large CD14/CD16 co-expressing cells. The monocyte-derived macrophages were then exposed to bacterial lipopolysaccharide (LPS, 1 μg/ml) or MnCl2 (25-100 μM)-alone or in combination-for 24 h at 37 °C, after which cell-free supernatants were analyzed using a multiplex cytokine assay procedure. Exposure of the cells to LPS caused modest statistically insignificant increases in cytokine production; MnCl2 caused dose-related increases in production of all six cytokines (achieving statistical significance of p < 0.0171- < 0.0005 for IL-1β, IL-6, IL-8, IFNγ, and TNFα). In the case of LPS and MnCl2 combinations, the observed increases in production of IL-1β, IL-6, IL-8, IFNγ, and G-CSF were greater than those seen with cells exposed to the individual agents. The Mn(2+)-mediated induction of cytokine production was associated with increased production of H2O2 and completely attenuated by inclusion of the H2O2-scavenger dithiothreitol, and partially by inhibitors of NF-κB and p38MAP kinase. The findings from the studies here help to further characterize the pro-inflammatory mechanisms that may underpin clinical disorders associated with excess exposure to Mn(2+), particularly those disorders seen in the central nervous and respiratory systems.
authors.affiliation: Medical Research Council Unit for Inflammation and Immunity, Department of Immunology, Faculty of Health Sciences, University of Pretoria , Pretoria , South Africa .
authors.forename: Matlou I
authors.initials: MI
authors.lastname: Mokgobu
authors.forename: Moloko C
authors.initials: MC
authors.lastname: Cholo
authors.forename: Ronald
authors.initials: R
authors.lastname: Anderson
authors.forename: Helen C
authors.initials: HC
authors.lastname: Steel
authors.forename: Maraki P
authors.initials: MP
authors.lastname: Motheo
authors.forename: Thembani N
authors.initials: TN
authors.lastname: Hlatshwayo
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Tintinger
authors.forename: Annette J
authors.initials: AJ
authors.lastname: Theron
mesh_terms: D000328:Adult; D002478:Cells, Cultured; D002712:Chlorides / Q000494:pharmacology*; D016207:Cytokines / Q000378:metabolism*; D004229:Dithiothreitol / Q000494:pharmacology; D005260:Female; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D007093:Imidazoles / Q000494:pharmacology; D018836:Inflammation Mediators / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000276:immunology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008264:Macrophages / Q000187:drug effects* / Q000276:immunology; D008297:Male; D017895:Manganese Compounds / Q000494:pharmacology*; D020149:Manganese Poisoning / Q000276:immunology*; D008875:Middle Aged; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D016273:Occupational Exposure / Q000009:adverse effects; D010084:Oxidation-Reduction / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D012140:Respiratory Tract Diseases / Q000139:chemically induced / Q000276:immunology*; D055815:Young Adult
chemical_list: D002712:Chlorides; D016207:Cytokines; D007093:Imidazoles; D018836:Inflammation Mediators; D008070:Lipopolysaccharides; D017895:Manganese Compounds; D016328:NF-kappa B; D011725:Pyridines; D006861:Hydrogen Peroxide; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole; C025340:manganese chloride; D004229:Dithiothreitol
keywords: Cytokines; H2O2; NF-κB; macrophages; manganese