8-hydroxy-2--deoxyguanosine and Ataxia-Telangiectasia

A comparative evaluation is reported of pro-oxidant states in 82 patients with ataxia telangectasia (AT), Bloom syndrome (BS), Down syndrome (DS), Fanconi anemia (FA), Werner syndrome (WS), and xeroderma pigmentosum (XP) vs 98 control donors. These disorders display cancer proneness, and/or early aging, and/or other clinical features. The measured analytes were: (a) leukocyte and urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG), (b) blood glutathione (GSSG and GSH), (c) plasma glyoxal (Glx) and methylglyoxal (MGlx), and (d) some plasma antioxidants [uric acid (UA) and ascorbic acid (AA)]. Leukocyte 8-OHdG levels ranked as follows: WS>BS approximately FA approximately XP>DS approximately AT approximately controls. Urinary 8-OHdG levels were significantly increased in a total of 22 patients with BS, FA, or XP vs 47 controls. The GSSG:GSH ratio was significantly increased in patients with WS and in young (< or =15 years) patients with DS or with FA and decreased in older patients with DS or FA and in AT, BS, and XP patients. The plasma levels of Glx and/or MGlx were significantly increased in patients with WS, FA, and DS. The UA and AA levels were significantly increased in WS and DS patients, but not in AT, FA, BS, nor XP patients. Rationale for chemoprevention trials is discussed.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Adolescent; Adult; Aged; Ataxia Telangiectasia; Bloom Syndrome; Child; Deoxyguanosine; DNA Damage; Down Syndrome; Fanconi Anemia; Female; Glutathione; Glyoxal; Humans; Male; Middle Aged; Pyruvaldehyde; Reactive Oxygen Species; Werner Syndrome; Xeroderma Pigmentosum

Fanconi anemia (FA) and ataxia telangiectasia (AT) share common traits such chromosomal instability and proneness to hematological cancers. Both AT and FA cell lines, and patients, are characterized by abnormally high levels of oxidative stress markers. The key FA protein FANCD2 is phosphorylated on Ser 222 by ATM after ionizing radiation (IR), thus allowing normal activation of the S-phase checkpoint, and ATM cells are known to be hypersensitive to oxidative damage. In this work we show that FANCD2 deficient cells have a defective S-phase checkpoint after Hydrogen Peroxide (H(2)O(2)) induced oxidative damage. ATM dependent phosphorylation of FANCD2 at the S222 residue is necessary for normal S-phase checkpoint activation after oxidative stress, while FANCD2 monoubiquitination at K561 is dispensable. We also show that FANCD2 is not required for base excision repair of 8-oxoG and other DNA lesions (abasic sites, uracils), while treatments that exclusively induce 8-oxoG, but not DNA double strand breaks, fail to activate FANCD2 monoubiquitination, thus indicating that the known accumulation of 8-oxoG in FA cells reflects an overproduction of ROS rather than defective processing of oxidized bases. We conclude that the handling of DNA damage after H(2)O(2)-induced oxidative stress requires the coordinated action of FANCD2 and ATM.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Ataxia Telangiectasia; Ataxia Telangiectasia Mutated Proteins; Bromates; Cell Cycle Proteins; Cell Line; Deoxyguanosine; DNA; DNA Damage; DNA Repair; DNA-Binding Proteins; Fanconi Anemia; Fanconi Anemia Complementation Group D2 Protein; Histones; Humans; Hydrogen Peroxide; Mice; Oxidants; Phosphorylation; Protein Serine-Threonine Kinases; S Phase; Tumor Suppressor Proteins; Ubiquitination

To evaluate an in vivo pro-oxidant state in patients with ataxia telangiectasia (AT).. A set of oxidative stress endpoints were measured in 9 AT homozygotes, 16 AT heterozygotes (parents) and 83 controls (grouped in age ranges as for patients and parents, respectively). The following analytes were measured: (a) leukocyte 8-hydroxy-2'-deoxyguanosine (8-OHdG); (b) blood glutathione (GSSG and GSH); and (c) plasma levels of glyoxal (Glx) and methylglyoxal (MGlx).. AT patients displayed a significant decrease in blood GSSG (p=0.012) and in MGlx plasma concentrations (p=0.012). A non-significant decrease in the GSSG:GSH ratio (p=0.1) and a non-significant increase in 8-OHdG and Glx levels were observed in AT patients vs. young controls (age range 4-35 years). AT heterozygotes failed to display any significant changes vs. adult controls (age range 36-68 years).. No significant increase in oxidative stress biomarkers was detected in blood from AT patients. The decrease in GSSG and MGlx levels in AT patients may suggest an adaptive response to a pro-oxidant state in AT-related target organs.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Adaptation, Physiological; Adolescent; Adult; Ataxia Telangiectasia; Child; Child, Preschool; Deoxyguanosine; DNA Damage; Female; Glutathione; Glyoxal; Humans; Male; Oxidative Stress; Pyruvaldehyde

Ataxia telangiectasia (AT) is a hereditary human disorder resulting in a wide variety of clinical manifestations, including progressive neurodegeneration, immunodeficiency, and high incidence of lymphoid tumors. Cells from patients with AT show genetic instability, hypersensitivity to radiation, and a continuous state of oxidative stress. Oxidative stress and genetic instability, including DNA deletions, are involved in carcinogenesis. We examined the effect of dietary supplementation with the thiol-containing antioxidant N-acetyl-l-cysteine (NAC) on levels of oxidative DNA damage and the frequency of DNA deletions in Atm-deficient (AT-mutated) mice. We confirmed that Atm-deficient mice display an increased frequency of DNA deletions (Bishop et al., Cancer Res 2000;60:395). Furthermore, we found that Atm-deficient mice have significantly increased levels of 8-OH deoxyguanosine, an indication of oxidative DNA damage. Dietary supplementation with NAC significantly reduced 8-OH deoxyguanosine level and the frequency of DNA deletions in Atm-deficient mice. These levels were similar to the levels in wild-type mice. Our findings demonstrate that NAC counteracts genetic instability and suggest that genetic instability may be a consequence of oxidative stress in Atm-deficient mice.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Acetylcysteine; Animals; Ataxia Telangiectasia; Ataxia Telangiectasia Mutated Proteins; Cell Cycle Proteins; Deoxyguanosine; Dietary Supplements; DNA Damage; DNA-Binding Proteins; Female; Free Radical Scavengers; Genomic Instability; Male; Mice; Mice, Knockout; Optic Nerve; Oxidative Stress; Pigment Epithelium of Eye; Protein Serine-Threonine Kinases; Sequence Deletion; Sulfhydryl Compounds; Tumor Suppressor Proteins

Ataxia telangiectasia (AT) is a pleiotropic genetic disorder characterized by progressive neurodegeneration, especially of cerebellar Purkinje cells, immunodeficiency, increased incidence of cancer, and premature aging. The disease is caused by functional inactivation of the ATM (AT-mutated) gene product, which is thought to act as a sensor of reactive oxygen species and oxidative damage of cellular macromolecules and DNA. The compound phenotype of AT might thus be linked to a continuous state of oxidative stress leading to an increase of programmed cell death (apoptosis). To assess this hypothesis, we analyzed lipid peroxidation products and the oxidative stress associated DNA base damage 8-hydroxy-2-deoxyguanosine in patients with AT. Oxidative damage to lipids and DNA was found to be markedly increased in AT patients. These results indicate that ATM might play an important role in the maintenance of cell homeostasis in response to oxidative damage. In this context, a better control of levels of reactive oxygen species could be a rational foundation of therapeutic intervention to help alleviate some of the symptoms associated with AT.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Adolescent; Adult; Apoptosis; Ataxia Telangiectasia; Ataxia Telangiectasia Mutated Proteins; Cell Cycle Proteins; Child; Child, Preschool; Deoxyguanosine; DNA Damage; DNA-Binding Proteins; Female; Homeostasis; Humans; Lipid Peroxidation; Lymphocytes; Male; Oxidative Stress; Protein Serine-Threonine Kinases; Tumor Suppressor Proteins