title: Effects of melanin and manganese on DNA damage and repair in PC12-derived neurons.
abstract: The mechanism of neurotoxicity produced by the interaction of melanin with manganese was investigated in PC12-derived neuronal cell cultures. The cells were incubated with melanin (25-500 microg/ml), MnCl2 (10 ng/ml-100 microg/ml) and a combination of both substances for 24 and 72 h. Incubation with either toxicant alone resulted in a minimal decrease in cell viability. The combination of melanin and manganese caused significant (up to 60%) decreases in viability of PC12 cells in a dose-dependent manner. Increases in oxidative DNA damage, indicated by levels of 8-hydroxy-2'deoxyguanosine (8-oxodG), was associated with decreased cell viability. Melanin alone, but not manganese alone, resulted in increased oxidative DNA damage. The maximal increase in 8-oxodG caused by melanin was about seven times higher than control after 24 h of exposure. The activity of the DNA repair enzyme, 8-oxoguanine DNA glycosylase (OGG1), was increased in cells incubated with single toxicants and their combinations for 24 h. On the third day of incubation with the toxicants, activity of OGG1 declined below control levels and cell viability significantly decreased. Melanin was observed to have an inhibitory effect on OGG1 activity. Study of the regulation of OGG1 activity in response to melanin and manganese may provide insights into the vulnerability of nigral neurons to oxidative stress in Parkinson's disease.
authors.affiliation: Department of Neurology, University of South Florida, Tampa, FL, USA.
authors.forename: Vasyl
authors.initials: V
authors.lastname: Sava
authors.forename: Diana
authors.initials: D
authors.lastname: Mosquera
authors.forename: Shijie
authors.initials: S
authors.lastname: Song
authors.forename: Fernando
authors.initials: F
authors.lastname: Cardozo-Pelaez
authors.forename: Juan R
authors.initials: JR
authors.lastname: Sánchez-Ramos
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D004247:DNA / Q000032:analysis / Q000737:chemistry; D004249:DNA Damage; D045647:DNA Glycosylases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004260:DNA Repair / Q000187:drug effects*; D006147:Guanine / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry; D015227:Lipid Peroxidation / Q000187:drug effects; D008345:Manganese / Q000494:pharmacology*; D008543:Melanins / Q000378:metabolism / Q000633:toxicity*; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D016716:PC12 Cells; D051381:Rats; D013482:Superoxide Dismutase / Q000378:metabolism; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis
chemical_list: D008543:Melanins; D017392:Thiobarbituric Acid Reactive Substances; D008345:Manganese; C024829:8-hydroxyguanine; D006147:Guanine; D004247:DNA; D013482:Superoxide Dismutase; D045647:DNA Glycosylases; C483741:OGG1 protein, rat