8-hydroxy-2--deoxyguanosine and Glucosephosphate-Dehydrogenase-Deficiency

Glucose-6-phosphate dehydrogenase (G6PD) protects the embryo from endogenous and xenobiotic-enhanced oxidative DNA damage and embryopathies. Here we show in aged mice that G6PD similarly protects against endogenous reactive oxygen species (ROS)-mediated neurodegeneration. In G6PD-normal (G6PD(+/+)) and heterozygous (G6PD(+/def)) and homozygous (G6PD(def/def)) G6PD-deficient male and female mice at about 2 years of age, oxidative DNA damage in various brain regions was assessed by 8-oxo-2'-deoxyguanosine formation using high-performance liquid chromatography and immunohistochemistry. Morphological changes in brain sections were assessed by H&E staining. DNA oxidation was increased in G6PD(def/def) mice in the cortex (p < 0.02), hippocampus (p < 0.01) and cerebellum (p < 0.006) compared to G6PD(+/+) mice, and was localized to distinct cell types. Histologically, in G6PD(+/def) mice, enhanced regionally and cellularly specific neurodegenerative changes were observed in those brain regions exhibiting elevated DNA oxidation, with a 53% reduction in the Purkinje cell count. These results show G6PD is important in protecting against the neurodegenerative effects of endogenous ROS in aging, and suggest that common hereditary G6PD deficiencies may constitute a risk factor for some neurodegenerative diseases.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Aging; Animals; Brain; Chromatography, High Pressure Liquid; Deoxyguanosine; DNA Damage; Female; Glucosephosphate Dehydrogenase; Glucosephosphate Dehydrogenase Deficiency; Male; Mice; Neurodegenerative Diseases; Oxidative Stress; Reactive Oxygen Species

Previous studies have shown that glucose-6-phosphate dehydrogenase (G6PD)-deficient cells are under increased oxidative stress and undergo premature cellular senescence. The present study demonstrates that G6PD-deficient cells cultured under 3% oxygen concentration had an extended replicative lifespan, as compared with those cultured under atmospheric oxygen level. This was accompanied by a reduction in the number of senescence-associated beta-galactosidase (SA-beta-Gal) positive and morphologically senile cells at comparable population doubling levels (PDL). Concomitant with the extension of lifespan was decreased production of reactive oxygen species. Additionally, lifespan extension was paralleled by the greatly abated formation of such oxidative damage markers as 8-hydroxy-deoxyguanosine (8-OHdG) as well as the oxidized and cross-linked proteins. Moreover, the mitochondrial mass increased, but the mitochondrial membrane potential DeltaPsim decreased in cells upon serial propagation. These changes were inhibited by lowering the oxygen tension. Our findings provide additional support to the notion that oxidative damage contributes to replicative senescence of G6PD-deficient cells and reduction of oxidative damage by lowering oxygen tension can delay the onset of cellular senescence.

Topics: 8-Hydroxy-2'-Deoxyguanosine; beta-Galactosidase; Cells, Cultured; Cellular Senescence; Deoxyguanosine; Fibroblasts; Glucosephosphate Dehydrogenase; Glucosephosphate Dehydrogenase Deficiency; Humans; Membrane Potential, Mitochondrial; Oxidative Stress; Oxygen; Skin

CDKN2A is regarded as a major melanoma susceptibility gene. A 19 bp deletion has been detected within Dutch families with familial atypical multiple mole-melanoma syndrome. Genetic analysis revealed two individuals with germline deletions in both copies of CDKN2A. One of them did not develop atypical naevi or melanoma, but died of adenocarcinoma at the age of 54 years. This report describes the results of the investigation of the second p16-null individual, who was also found to have glucose-6-phosphate dehydrogenase (G-6-PD) deficiency and who has developed many atypical naevi and seven melanomas. Using electron microscopic techniques, striking alterations in melanosomal structures and deviations in their sulphur, iron and calcium composition indicating a strong preference for phaeomelanogenesis and increased oxidative stress were found in the naevus cells of the patient. Using an in vitro model, we demonstrated that leaking melanin precursors may strongly enhance oxidative DNA damage through iron release from ferritin. We conclude that the homozygous p16 deletion is not sufficient for the development of a dysplastic naevus phenotype and melanoma. However, when an additional modifying factor, such as G-6-PD deficiency, increases the level of oxidative DNA damage in melanin-producing cells, the risk of developing atypical naevi and their malignant transformation may increase significantly.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Adult; Calcium; Cyclin-Dependent Kinase Inhibitor p16; Deoxyguanosine; DNA; DNA Damage; Ferritins; Gene Deletion; Genes, p16; Germ-Line Mutation; Glucosephosphate Dehydrogenase; Glucosephosphate Dehydrogenase Deficiency; Homozygote; Humans; Iron; Male; Melanoma; Microscopy, Electron; Models, Biological; Mutation; Oxidative Stress; Oxygen; Phenotype; Skin; Tumor Cells, Cultured; X-Rays