title: Suppression of methylmercury-induced IL-6 and MCP-1 expressions by N-acetylcysteine in U-87MG human astrocytoma cells.
abstract: OBJECTIVE
  The aim of this study was to clarify the involvement of oxidative stress in methylmercury (MeHg)-induced pro-inflammatory cytokine expressions and the suppressive effects of N-acetylcysteine (NAC) in MeHg-induced cytokine expression.
  
  
  METHODS
  Using U-87-MG human astrocytoma cell line, interleukin (IL)-6 and monocyte chemoattractant protein (MCP)-1 expressions induced by 4 μM MeHg were measured at mRNA and protein levels. Hydrogen peroxide (H2O2) and superoxide anion (O2(-)) were quantified by flow-cytometry analysis. To examine the suppressive effects of NAC on the cytokine expressions among different timing of NAC treatment, cells were treated with 0.5 or 5mM NAC before, simultaneously, or after MeHg administration.
  
  
  RESULTS
  MeHg exposure at 4 μM, a non-cytotoxic concentration, significantly induced MCP-1 and IL-6 expressions at both mRNA and protein levels. A significant increase of H2O2 production but not O2(-) was observed. MeHg-induced expression of MCP-1 and IL-6 mRNA was reduced by 10-20% in the presence of 5mM NAC (co-treatment experiment) compared to cells treated with MeHg only. Pre-treatment of cells with 0.5 or 5mM NAC at 0.5 or 1h and its subsequent washout before MeHg addition suppressed MCP-1 and IL-6 cytokine expressions. Post-treatment of cells with NAC after MeHg addition also suppressed the cytokine induction, but the magnitude of suppression was evidently lower than in co-treated cells even though the H2O2 generation was almost completely suppressed by NAC.
  
  
  CONCLUSIONS
  NAC may effectively suppress the MeHg-induced cytokine production through both, inhibition of reactive oxygen species as well as extracellular chelation of MeHg in astrocytes.
authors.affiliation: Department of Epidemiology and Preventive Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima 890-8520, Japan; Department of Physiology, Faculty of Medicine, Diponegoro University, Tembalang, Semarang 50725, Indonesia.
authors.forename: Muflihatul
authors.initials: M
authors.lastname: Muniroh
authors.affiliation: Department of Epidemiology and Preventive Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima 890-8520, Japan.
authors.forename: Noureen
authors.initials: N
authors.lastname: Khan
authors.affiliation: Department of Epidemiology and Preventive Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima 890-8520, Japan. Electronic address: fiy@m.kufm.kagoshima-u.ac.jp.
authors.forename: Chihaya
authors.initials: C
authors.lastname: Koriyama
authors.affiliation: Department of Epidemiology and Preventive Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima 890-8520, Japan.
authors.forename: Suminori
authors.initials: S
authors.lastname: Akiba
authors.affiliation: Department of Environmental Toxicology and Center for Health and the Environment, University of California, Davis, CA 95616, USA.
authors.forename: Christoph F A
authors.initials: CF
authors.lastname: Vogel
authors.affiliation: Integrated Physiology Section, Department of Basic Medical Science, National Institute for Minamata Disease, 4058-18 Hama, Minamata, Kumamoto 867-0008, Japan.
authors.forename: Megumi
authors.initials: M
authors.lastname: Yamamoto
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology*; D001253:Astrocytes / Q000378:metabolism / Q000473:pathology; D001254:Astrocytoma / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D018932:Chemokine CCL2 / Q000096:biosynthesis*; D016166:Free Radical Scavengers / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D015850:Interleukin-6 / Q000096:biosynthesis*; D008767:Methylmercury Compounds / Q000494:pharmacology*; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D018384:Oxidative Stress / Q000187:drug effects; D013481:Superoxides / Q000378:metabolism
chemical_list: C111835:CCL2 protein, human; D018932:Chemokine CCL2; D016166:Free Radical Scavengers; C508600:IL6 protein, human; D015850:Interleukin-6; D008767:Methylmercury Compounds; D009363:Neoplasm Proteins; D013481:Superoxides; D006861:Hydrogen Peroxide; D000111:Acetylcysteine
keywords: Astrocytes; IL-6; MCP-1; Methylmercury; N-acetylcysteine; Reactive oxygen species