8-hydroxyguanine and Motor-Neuron-Disease

Mutations in Cu/Zn-superoxide dismutase (SOD1) are associated with some cases of familial amyotrophic lateral sclerosis (ALS). We overexpressed Bcl-2, wild-type SOD1 or mutant SOD1s (G37R and G85R) in NT-2 and SK-N-MC cells. Overexpression of Bcl-2 rendered cells more resistant to apoptosis induced by serum withdrawal, H2O2 or 4-hydroxy-2-trans-nonenal (HNE). Overexpression of Bcl-2 had little effect on levels of protein carbonyls, lipid peroxidation, 8-hydroxyguanine (8-OHG) or 3-nitrotyrosine. Serum withdrawal or H2O2 raised levels of protein carbonyls, lipid peroxidation, 8-OHG and 3-nitrotyrosine, changes that were attenuated in cells overexpressing Bcl-2. Overexpression of either SOD1 mutant tended to increase levels of lipid peroxidation, protein carbonyls, and 3-nitrotyrosine and accelerated viability loss induced by serum withdrawal, H2O2 or HNE, accompanied by greater rises in oxidative damage parameters. The effects of mutant SOD1s were attenuated by Bcl-2. By contrast, expression of wild-type SOD1 rendered cells more resistant to loss of viability induced by serum deprivation, HNE or H2O2. The levels of lipid peroxidation in wild-type SOD1 transfectants were elevated. Overexpression of mutant SOD1s makes cells more predisposed to undergo apoptosis in response to several insults. Our cellular systems appear to mimic events in patients with ALS or transgenic mice overexpressing mutant SOD1.

Topics: Aldehydes; Amino Acid Substitution; Cell Death; Cell Survival; Cross-Linking Reagents; Culture Media, Serum-Free; Genes, bcl-2; Guanine; Humans; Hydrogen Peroxide; Kinetics; Lipid Peroxidation; Motor Neuron Disease; Mutagenesis, Site-Directed; Neuroblastoma; Oxidative Stress; Proto-Oncogene Proteins c-bcl-2; Recombinant Proteins; Superoxide Dismutase; Superoxide Dismutase-1; Teratocarcinoma; Tumor Cells, Cultured; Tyrosine

8-Oxodeoxyguanosine is present in DNA from many tissues. The direct demonstration of 8-oxodeoxyguanosine as a potential biomarker of oxidative DNA damage has implications for the study of mutagenesis, carcinogenesis, and free radical toxicity. Avidin is shown here to bind with high specificity to this potentially mutagenic oxidized nucleoside, 8-oxodeoxyguanosine, and to the oxidatively modified base, 8-oxoguanine. The serendipitous finding that avidin bound to the nuclei of UVA-irradiated cells has led to the development of a technique which allows detection of the damage product in a manner analogous to that of immunological techniques. The technique has been shown to be applicable to isolated DNA and to DNA in fixed cellular material and postmortem tissue. Statistically different levels of damage can be demonstrated in both isolated DNA and cultured cells exposed to free radical generating systems using a 96-well plate-based methodology. The sensitivity of this method allows the detection of 10(-19) mol of 8-oxodeoxyguanosine. This novel usage of avidin conjugates applies also to its bacterial analogue, streptavidin, and to a lesser extent to the monoclonal antibody to biotin (the ligand bound by the parent compound). This finding has tremendous potential as a simple method analogous to immunotechniques for the direct detection of 8-oxodeoxyguanosine. From structural considerations we speculate that avidin would also bind to 8-oxodeoxyadenosine.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Aged; Alkalies; Animals; Avidin; Binding Sites; Biotin; Biotinylation; Cell Nucleus; Deoxyguanosine; DNA; DNA Damage; DNA-Binding Proteins; DNA, Single-Stranded; Dose-Response Relationship, Drug; Female; Fluorescein-5-isothiocyanate; Fluorescent Dyes; Guanine; Humans; Hydrogen Peroxide; Male; Methylene Blue; Motor Neuron Disease; Sensitivity and Specificity; Tumor Cells, Cultured