Role of nucleotide- and base-excision repair in genotoxin-induced neuronal cell death.
Base-excision (BER) and nucleotide-excision ( NER) repair play pivotal roles in protecting the genomes of dividing cells from damage by endogenous and exogenous agents (i.e. environmental genotoxins). However, their role in protecting the genome of post-mitotic neuronal cells from genotoxin-induced damage is less clear. The present study examines the role of the BER enzyme 3-alkyladenine DNA glycosylase (AAG) and the NER protein xeroderma pigmentosum group A (XPA) in protecting cerebellar neurons and astrocytes from chloroacetaldehyde (CAA) or the alkylating agent 3-methyllexitropsin (Me-Lex), which produce ethenobases or 3-methyladenine (3-MeA), respectively. Neuronal and astrocyte cell cultures prepared from the cerebellum of wild type (C57BL/6) mice or Aag(-/-) or Xpa(-/-) mice were treated with 0.1-50 microM CAA for 24h to 7 days and examined for cell viability, DNA fragmentation (TUNEL labeling), nuclear changes, and glutathione levels. Aag(-/-) neurons were more sensitive to the acute (>20 microM) and long-term (>5 microM) effects of CAA than comparably treated wild type neurons and this sensitivity correlated with the extent of DNA fragmentation and nuclear changes. Aag(-/-) neurons were also sensitive to Me-Lex at comparable concentrations of CAA. In contrast, Xpa(-/-) neurons were more sensitive than either wild type or Aag(-/-) neurons to CAA (>10 microM), but less sensitive than Aag(-/-) neurons to Me-Lex. Astrocytes from the cerebellum of wild type, Aag(-/-) or Xpa(-/-) mice were essentially insensitive to CAA at the concentrations tested. These studies demonstrate that BER and NER are required to protect neurons from genotoxin-induced cell death.[1]References
- Role of nucleotide- and base-excision repair in genotoxin-induced neuronal cell death. Kisby, G.E., Lesselroth, H., Olivas, A., Samson, L., Gold, B., Tanaka, K., Turker, M.S. DNA Repair (Amst.) (2004) [Pubmed]
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