Title: Manganese-induced cytotoxicity in dopamine-producing cells.
Authors: Stredrick, Denise L; Stokes, Alan H; Worst, Travis J; Freeman, Willard M; Johnson, Elizabeth A; Lash, Lawrence H; Aschner, Michael; Vrana, Kent E
Published In Neurotoxicology, (2004 Jun)
Abstract: Manganese (Mn) is an essential metal that, at excessive levels in the brain, produces extrapyramidal symptoms similar to those in patients with Parkinson's disease (PD). In the present study, Mn toxicity was characterized in a human neuroblastoma (SK-N-SH) cell line and in a mouse catecholaminergic (CATH.a) cell line. Mn was demonstrated to be more toxic in the catecholamine-producing CATH.a cells (EC50 = 60 microM) than in non-catecholaminergic SK-N-SH cells (EC50 = 200 microM). To test the hypothesis that the sensitivity of CATH.a cells to Mn is associated with their dopamine (DA) content, DA concentrations were suppressed in these cells by pretreatment with alpha-methyl-para-tyrosine (AMPT). Treatment for 24 h with 100 microM AMPT decreased intracellular DA, but offered no significant protection from Mn exposure (EC50 = 60 microM). Additional studies were carried out to assess if Mn toxicity was dependent on glutathione (GSH) levels. CATH.a cells were significantly protected by the addition of 5mM GSH (Mn EC50 = 200 microM) and 10mM N-acetyl cysteine (NAC) (Mn EC50 = 300 microM), therefore, indirectly identifying intracellular ROS formation as a mechanism for Mn neurotoxicity. Finally, apoptotic markers of Mn-induced cell death were investigated. DNA fragmentation, caspase-3 activation, and apoptosis-related gene expression were studied in CATH.a cells. No internucleosomal fragmentation or caspase activation was evident, even in the presence of "supraphysiological" Mn concentrations. cDNA hydridization array analysis with two differing Mn concentrations and time points, identified no noteworthy mRNA inductions of genes associated with programmed cell death. In conclusion, DA content was not responsible for the enhanced sensitivity of CATH.a cells to Mn toxicity, but oxidative stress was implicated as a probable mechanism of cytotoxicity.
PubMed ID: 15183009
MeSH Terms: Animals; Cell Line; Cell Line, Tumor; Cell Survival/drug effects; Cell Survival/physiology; Comparative Study; Dopamine/biosynthesis*; Dose-Response Relationship, Drug; Glutathione/metabolism; Glutathione/pharmacology; Growth Inhibitors/metabolism; Growth Inhibitors/toxicity*; Humans; Manganese/adverse effects*; Mice; Neuroblastoma/metabolism; Neuroblastoma/pathology; Reactive Oxygen Species/metabolism; Reactive Oxygen Species/toxicity; Research Support, U.S. Gov't, P.H.S.