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Manganese promotes increased formation of hydrogen peroxide by activated human macrophages and neutrophils in vitro.
- Source :
-
Inhalation toxicology [Inhal Toxicol] 2012 Aug; Vol. 24 (10), pp. 634-44. - Publication Year :
- 2012
-
Abstract
- Although pro-inflammatory mechanisms have been implicated in the pathogenesis of manganese (Mn²⁺)-related neurological and respiratory disorders, relatively little is known about the potential of this metal to interact pro-oxidatively with human phagocytes. The primary objective of the current study was to investigate the effects of Mn²⁺ as MnCl₂ (0.5-100 µM) on the generation of the reactive oxygen species (ROS), superoxide, hydrogen peroxide (H₂O₂), and hypohalous acids by isolated human blood neutrophils and monocyte-derived macrophages following activation of these cells with the chemotactic tripeptide, FMLP (1 µM), or the phorbol ester, PMA (25 ng/mL). Generation of ROS was measured using the combination of oxygen consumption, lucigenin/luminol-enhanced chemiluminescence, spectrofluorimetric detection of oxidation of 2,7-dichlorodihydrofluorescein, radiometric assessment of myeloperoxidase (MPO)-mediated protein iodination, release of MPO by ELISA, and spectrophotometric measurement of nitrite formation. Treatment of activated neutrophils with either FMLP or PMA resulted in significantly decreased reactivity of superoxide in the setting of increased formation of H₂O₂ and MPO-mediated iodination, with no detectable effects on either oxygen consumption or MPO release. Similar effects of the metal with respect to superoxide reactivity and H₂O₂ formation were observed with activated macrophages, while generation of NO was unaffected. Taken together with the findings of experiments using cell-free ROS-generating systems, these observations are compatible with a mechanism whereby Mn²⁺, by acting as a superoxide dismutase mimetic, increases the formation of H₂O₂ by activated phagocytes. If operative in vivo, this mechanism may contribute to the toxicity of Mn²⁺.
- Subjects :
- Air Pollutants, Occupational chemistry
Air Pollutants, Occupational toxicity
Catalysis
Cells, Cultured
Chlorides chemistry
Chlorides pharmacology
Free Radical Scavengers chemistry
Free Radical Scavengers pharmacology
Free Radical Scavengers toxicity
Humans
Hydrogen Peroxide chemistry
Macrophage Activation drug effects
Macrophages cytology
Macrophages enzymology
Macrophages immunology
Manganese chemistry
Manganese toxicity
Manganese Compounds chemistry
Manganese Compounds pharmacology
Manganese Poisoning immunology
N-Formylmethionine Leucyl-Phenylalanine pharmacology
Neutrophils cytology
Neutrophils enzymology
Neutrophils immunology
Occupational Exposure adverse effects
Osmolar Concentration
Oxidants chemistry
Oxidants toxicity
Peroxidase metabolism
Reactive Oxygen Species chemistry
Reactive Oxygen Species metabolism
Tetradecanoylphorbol Acetate analogs & derivatives
Tetradecanoylphorbol Acetate pharmacology
Air Pollutants, Occupational pharmacology
Hydrogen Peroxide metabolism
Macrophages drug effects
Manganese pharmacology
Neutrophils drug effects
Oxidants pharmacology
Oxidative Stress drug effects
Subjects
Details
- Language :
- English
- ISSN :
- 1091-7691
- Volume :
- 24
- Issue :
- 10
- Database :
- MEDLINE
- Journal :
- Inhalation toxicology
- Publication Type :
- Academic Journal
- Accession number :
- 22906169
- Full Text :
- https://doi.org/10.3109/08958378.2012.706657