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PubMed2003

Oxidative DNA damage following exposure to dimethylarsinous iodide: the formation of cis-thymine glycol.

The purpose of the present study was to elucidate the genotoxic mechanism of trivalent dimethylated arsenic, particularly the induction mechanism of oxidative stress in nuclear bases. Cis-thymine glycol was used as a biomarker of DNA oxidation damage. The treatment of thymine with dimethylarsinous iodide (DMI), a model compound of dimethylarsinous acid, induced the formation of cis-thymine glycol. This oxidative damage was induced via the production of dimethylated arsenic peroxide, but not via the production of superoxide anion or hydrogen peroxide. Trivalent dimethylated arsenic may thus play an important role in arsenic carcinogenesis through the induction of oxidative base damage.

Cacodylic Acid↗

PubMed2000

No significant paraquat-induced oxidative DNA damage in rats.

The metabolism of paraquat generates oxygen radicals. Paraquat has thus been suggested as a model compound to induce oxidative damage to DNA, lipids and proteins in different cells and tissues, although experimental data are inconsistent. In order to explore the possibilities for an animal model of oxidative DNA damage in vivo, rats were treated with 20 mg/kg paraquat or vehicle i.p. One and five days later we measured DNA oxidation in terms of 7-hydro-8-oxo-2'-deoxyguanosine (8-oxodG) in the liver and lung as well as the urinary excretion of 8-oxodG. No significant effects on the level of 8-oxodG in the liver, the lung or the urinary excretion, could be distinguished following paraquat treatment. We found, however, a significant correlation (r = 0.69; p<0.0002) between the 8-oxodG level in the lung and the urinary excretion, but no significant correlation between the level in the liver and the urinary excretion or between the levels in the liver and the lung. During the experiment the rats were clearly affected by the paraquat as they were very lethargic compared to the controls. Accordingly, even at toxic doses, paraquat did not cause detectable oxidative damage to DNA. The data do not support the use of paraquat as a model compound in experiments investigating effects or prevention of oxidative damage to DNA.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed1994

Role of oxidative DNA damage in the mechanism of fecapentaene-12 genotoxicity.

Fecapentaene-12 (FP-12), a fecal unsaturated, ether-linked lipid excreted by most human individuals in Western populations, has been found to be a potent genotoxin in mammalian cells. Its mechanism of genotoxicity may be mediated by oxygen radical-induced DNA damage or by direct DNA alkylation, of which the relative importance remains to be determined. In the present study, induction of oxidative genetic damage by FP-12 has been investigated, in combination with the biological inactivation of single-stranded bacteriophage phi X-174 DNA. It was shown that formation of 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxodG), a marker for oxidative DNA damage, is induced dose dependently by FP-12 in 2'-deoxyguanosine (dG). It was demonstrated by application of radical scavengers that production of both the superoxide anion and singlet oxygen may be involved in the induction of 8-oxodG. The effect of OH radical scavenging appeared to be less pronounced. Enzymatic peroxidation of FP-12, which has been demonstrated to stimulate oxygen radical formation, was found to increase the hydroxylation ratio in dG, an effect which was less pronounced in single-stranded DNA and even absent in double-stranded DNA. No induction of 8-oxodG was observed after exposure of human skin fibroblasts to 60 microM FP-12 for 3 h in vitro. It was concluded that the induction of 8-oxodG by FP-12 is determined by the accessibility of the guanine molecule rather than the rate of oxygen radical formation. Although free radical formation is known to be stimulated by enzymatic peroxidation of FP-12, the inactivation of phi X-174 DNA spontaneously induced by FP-12 was found to be reduced by application of peroxidases. This furthermore demonstrates that the increased formation of reactive oxygen species by enzymatic peroxidation of FP-12 does not directly relate to increased induction of genotoxic effects. The fact that addition of radical scavengers shows limited effects on the inactivation of phi X-174 DNA suggests that the contribution of oxidative DNA damage to the genotoxic potential of FP-12 is only of minor importance.

Animals↗

PubMed2000

Effect of thyroid hormones on mitochondrial oxygen free radical production and DNA oxidative damage in the rat heart.

Mitochondria seem to be involved in oxygen radical damage and aging. However, the possible relationships between oxygen consumption and oxygen radical production by functional mitochondria, and oxidative DNA damage, have not been studied previously. In order to analyze these relationships, male Wistar rats of 12 weeks of age were rendered hyper- and hypothyroid by chronic T(3) and 6-n-propyl-2-thiouracil treatments, respectively. Hypothyroidism decreased heart mitochondrial H(2)O(2) production in States 4 (to 51% of controls; P<0.05) and 3 (to 21% of controls; P<0.05). In agreement with this, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) decreased in the heart genomic DNA of hypothyroid animals to 40% of controls (P<0.001). Studies with respiratory inhibitors showed that the decrease in oxygen radical generation observed in hypothyroidism occurred at Complex III (mainly) and at Complex I; that decrease was due to the presence of a lower free radical leak in the respiratory chain (P<0.05). Hyperthyroidism did not significantly change heart mitochondrial H(2)O(2) production since the increase in State 4 oxygen consumption in comparison with control and hypothyroid animals (P<0.05) was compensated by a decrease in the free radical leak in relation to control animals (P<0.05). In agreement with this, heart 8-oxodG was not changed in hyperthyroid animals. The lack of increase in H(2)O(2) production per unit of mitochondrial protein will protect mitochondria themselves against self-inflicted damage during hyperthyroidism.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2001

DNA oxidative damage in leukocytes correlates with the severity of HCV-related liver disease: validation in an open population study.

BACKGROUND/AIMS: Oxidative DNA damage, identifiable in the formation of 8-hydroxydeoxyguanosine (8-OHdG), is relevant in the mutagenesis/carcinogenesis process. The aim of this study was to assess 8-OHdG levels in patients with hepatitis C virus (HCV) infection in relation to extent of liver damage and HCV genotype. METHODS: 8-OHdG levels were measured in DNA from circulating leukocytes of 110 anti-HCV positive subjects belonging to the population of the Dionysos study, subgrouped in: 50 anti-HCV+ with persistently normal ALT, 48 with chronic hepatitis and 12 with cirrhosis. Twenty normal subjects served as Controls. 8-OHdG levels were assayed by HPLC/electrochemical detector. RESULTS: 8-OHdG levels rose (P < 0.00001) from Controls to HCV+; chronic hepatitis and cirrhosis were associated with a further increase (P < 0.02 versus HCV+). Genotype 1 was associated with higher levels of 8-OHdG (P < 0.04). Multiple logistic regression analysis showed that, after correction for potential confoundings, 8-OHdG levels correlated (P < 0.02) with presence and extent of liver damage. CONCLUSIONS: An accumulation of 8-OHdG in circulating leukocytes is a reliable marker of the extent of liver damage in HCV+ patients and is present in particular in genotype 1 infection. This genomic damage may contribute to liver carcinogenesis by causing persistent DNA changes.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed1991

Ascorbic acid protects against endogenous oxidative DNA damage in human sperm.

Damage to the DNA of germ cells can lead to mutation, which may result in birth defects, genetic diseases, and cancer. The very high endogenous rate of oxidative DNA damage and the importance of dietary ascorbic acid (AA) in preventing this damage has prompted an examination of these factors in human sperm DNA. The oxidized nucleoside 8-hydroxy-2'-deoxyguanosine (8-oxo-7,8-dihydro-2'-deoxyguanosine; oxo8dG), 1 of approximately 20 major products of oxidative damage to DNA, was measured in DNA isolated from human sperm provided by healthy subjects and compared to the seminal fluid AA levels. This relationship was studied in two groups. In a group of 24 free-living individuals 20-50 years old high levels of oxo8dG were correlated with low seminal plasma AA. The endogenous level of oxo8dG in this group was 13 fmol per microgram of DNA or approximately 25,000 adducts per sperm cell. The second group of individuals was maintained on a controlled diet that varied only in AA content. When dietary AA was decreased from 250 to 5 mg/day, the seminal fluid AA decreased by half and the level of oxo8dG in sperm DNA increased 91%. Repletion of dietary AA for 28 days (from 5 mg/day to 250 or 60 mg/day) caused a doubling in seminal fluid AA and reduced oxo8dG by 36%. These results indicate that dietary AA protects human sperm from endogenous oxidative DNA damage that could affect sperm quality and increase risk of genetic defects, particularly in populations with low AA such as smokers.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed1994

Substrate specificity of Fpg protein. Recognition and cleavage of oxidatively damaged DNA.

The 8-oxoguanine-DNA glycosylase of Escherichia coli, also known as formamidopyrimidine-DNA glycosylase (Fpg protein), has N-glycosylase and AP-lyase activities. This enzyme repairs oxidative DNA damage by efficiently removing formamidopyrimidine lesions and 8-oxoguanine residues from DNA. Defined oligodeoxynucleotides containing various 8-oxopurines were used to examine the substrate specificity of Fpg protein and to establish the role of functional groups in DNA on damage recognition and catalysis. Binding affinities of Fpg protein were established for duplex oligodeoxynucleotides containing 8-oxo-2'-deoxyguanine, 8-oxo-2'-deoxyadenine, 8-oxo-2'-deoxynebularine, 8-oxo-2'-deoxyinosine, abasic sites, and a ring-open adduct of C8-aminofluorene guanine. The C8 keto group of 8-oxodG:dC presents in the major groove and is correlated with tight binding (Kd = 8.9 nM). Binding is much weaker when the C8 keto functional group is in the minor groove, as in 8-oxodG:dA (Kd = 340 nM). Km and Vmax were determined for the cleavage reaction. Specificity constants (Kcat/Km) are consistently higher for oligodeoxynucleotide duplexes containing 8-oxopurines with C6 and C8 keto groups, as in 8-oxodG:dC and 8-oxodI:dC, where Kcat/Km are 9.3 and 18 min-1 nM x 10(-3), respectively. 8-oxodN:dC lacks the C6 keto group; the specificity constant is 0.024 min-1 nM x 10(-3). Taken together, our data suggest that the C8 keto group of 8-oxodeoxyguanine and the carbonyl moiety of formamidopyrimidine enable Fpg protein to recognize and bind duplex DNA containing these modified bases. An enzyme-catalyzed reaction involving the C6 keto group of the substrate leads to removal of these lesions. A mechanism involving protonation at O-6 of 8-oxoguanine is proposed to account for the N-glycosylase activity of this enzyme.

Catalysis↗

PubMed1995

Transcription factor NF-kappa B is activated by photosensitization generating oxidative DNA damages.

Reactive oxygen intermediates like hydrogen peroxide (H2O2) have been shown to serve as messengers in the induction of NF-kappa B and, then, in the activation and replication of human immunodeficiency virus (HIV)-1 in human cells. Because H2O2 can be converted into the highly reactive OH. at various locations inside the cells, we started to investigate the generation of Reactive oxygen intermediates by photosensitization. This technique is based on the use of a photosensitizer which is a molecule absorbing visible light and which can be located at various sites inside the cell depending on its physicochemical properties. In this work, we used proflavine (PF), a cationic molecule having a high affinity for DNA, capable of intercalating between DNA base pairs. Upon visible light irradiation, intercalated PF molecules oxidize guanine residues and generate DNA single-strand breaks. In lymphocytes or monocytes latently infected with HIV-1 (ACH-2 or U1, respectively), this photosensitizing treatment induced a cytotoxicity, an induction of NF-kappa B, and a reactivation of HIV-1 in cells surviving the treatment. NF-kappa B induction by PF-mediated photosensitization was not affected by the presence of N-acetyl-L-cysteine while strong inhibition was recorded when the induction was triggered by H2O2 or by phorbol 12-myristate 13-acetate. Another transcription factor like AP-1 is less activated by this photosensitizing treatment. In comparison with other inducing treatments, such as phorbol 12-myristate 13-acetate or tumor necrosis factor alpha, the activation of NF-kappa B is slow, being optimal 120 min after treatment. These kinetic data were obtained by following, on the same samples, both the appearance of NF-kappa B in the nucleus and the disappearance of I kappa B-alpha in cytoplasmic extracts. These data allow us to postulate that signaling events, initiated by DNA oxidative damages, are transmitted into the cytoplasm where the inactive NF-kappa B factor is resident and allow the translocation of p50/p65 subunits of NF-kappa B to the nucleus leading to HIV-1 gene expression.

Acetylcysteine↗

PubMed2004

Differential effects of Helicobacter pylori eradication on oxidative DNA damage at the gastroesophageal junction and at the gastric antrum.

BACKGROUND AND AIM: Helicobacter pylori-associated gastritis causes accumulation of reactive oxygen species in the mucosal compartment. This prospective study evaluates DNA oxidative damage in biopsy samples obtained from both the antrum and the gastroesophageal junction (GEJ) before and after H. pylori eradication. PATIENTS AND METHODS: Thirty-two consecutive H. pylori-positive patients underwent endoscopy with multiple biopsy sampling (i.e., antrum, incisura angularis, fundus, and cardia at the GEJ). After H. pylori eradication, 32 patients underwent a checkup endoscopy (mean interval, 5.7 months); in a subgroup of 13 subjects, a third endoscopy procedure was also performed (mean interval, 18 months). Additional biopsy samples (two from the antrum and two from the GEJ) were used to assess 8-hydroxydeoxyguanosine (8OHdG) levels using both high-pressure liquid chromatography with electrochemical detector and ELISA. RESULTS: In the antral compartment, no significant modifications of 8OHdG levels were assessed after H. pylori eradication. Conversely, following eradication, 8OHdG levels significantly increased (high-pressure liquid chromatography with electrochemical detector, P = 0.04; ELISA method, P = 0.05) in biopsy samples taken from the GEJ, and a further increase was documented in the subgroup of patients who underwent a third endoscopy (P = 0.01). The increasing trend was more relevant in patients in whom H. pylori-cagA-positive strains were eradicated and in those affected by hiatal hernia. CONCLUSIONS: The levels of DNA adducts in the antral mucosa are not modified by H. pylori eradication; conversely, H. pylori eradication significantly increases the oxidative adducts at the GEJ. The clinical and biological importance of this situation and whether and how it relates to a higher risk of precancerous lesions is open to debate.

Anti-Ulcer Agents↗

PubMed2006

Hydroxytyrosol lipophilic analogues: enzymatic synthesis, radical scavenging activity and DNA oxidative damage protection.

The olive oil phenol hydroxytyrosol (3), as well its metabolite homovanillic alcohol (4), were subjected to chemoselective lipase-catalysed acylations, affording with good yield 10 derivatives (5-14) bearing C(2), C(3), C(4), C(10) and C(18) acyl chains at C-1. Hydroxytyrosol (3) and its lipophilic derivatives showed very good DPPH. radical scavenging activity. Compounds 3, 4 and their lipophilic analogues 5-14 were subjected to the atypical Comet test on whole blood cells: 3 and its analogues 5 and 6, with little hydrophobic character (logP<or=1.20), showed a good protective effect against H(2)O(2) induced oxidative DNA damage. The homovanillic alcohol 4 and its analogues 10-14 resulted scarcely effective both as radical scavengers and antioxidant agents.

Acetylation↗

PubMed1998

Substrate specificity of Schizosaccharomyces pombe Nth protein for products of oxidative DNA damage.

A gene from Schizosaccharomyces pombe, which encodes a protein with a strong sequence similarity to the Nth protein of Escherichia coli, has recently been identified [Roldán-Arjona, T., Anselmino, C., and Lindahl, T. (1996) Nucleic Acids Res. 24, 3307-3312]. The functional analysis of this eukaryotic enzyme indicated that it is a homologue of E. coli Nth protein. The gene has been subcloned and the protein (Nth-Spo) purified to apparent homogeneity. We investigated the substrate specificity of this eukaryotic enzyme for modified bases in oxidatively damaged DNA, using the technique of gas chromatography/isotope-dilution mass spectrometry (GC/IDMS). DNA substrates containing up to 17 types of modified bases were prepared by gamma-irradiation or by treatment with H2O2 in the presence of Fe(III)-EDTA or Cu(II). The results revealed an efficient excision of five pyrimidine-derived lesions, 5-hydroxycytosine, thymine glycol, 5-hydroxy-6-hydrothymine, 5,6-dihydroxycytosine, and 5-hydroxyuracil. None of the other pyrimidine or purine lesions was excised. Excision was measured as a function of enzyme concentration, time, substrate concentration, and temperature. Kinetic constants were determined. Although some DNA base lesions removed by Nth-Spo protein were similar to those previously described for E. coli Nth protein, differences between substrate specificities of these two enzymes were noted.

DNA Damage↗

PubMed1997

Increased oxidative DNA damage and hepatocyte overexpression of specific cytochrome P450 isoforms in hepatitis of mice infected with Helicobacter hepaticus.

A recently discovered bacterium, Helicobacter hepaticus, infects the intrahepatic bile canaliculi of mice, causing a severe chronic hepatitis culminating in liver cancer. Thus, it affords an animal model for study of bacteria-associated tumorigenesis including H. pylori-related gastric cancer. Reactive oxygen species are often postulated to contribute to this process. We now report that hepatitis of male mice infected with H. hepaticus show significant increases in the oxidatively damaged DNA deoxynucleoside 8-hydroxydeoxyguanosine, with the degree of damage increasing with progression of the disease. Perfusion of infected livers with nitro blue tetrazolium revealed that superoxide was produced in the cytoplasm of hepatocytes, especially in association with plasmacytic infiltrates near portal triads. Contrary to expectations, Kupffer cells, macrophages, and neutrophils were rarely involved. However, levels of cytochrome P450 (CYP) isoforms 1A2 and 2A5 in hepatocytes appeared to be greatly increased, as indicated by the number of cells positive in immunohistochemistry and the intensity of staining in many cells, concomitant with severe hepatitis. The CYP2A5 immunohistochemical staining co-localized with formazan deposits resulting from nitro blue tetrazolium reduction and occurred in nuclei as well as cytoplasm. These findings suggest that CYP2A5 contributes to the superoxide production and 8-hydroxydeoxyguanosine formation, although reactive oxygen species from an unknown source in the hepatocytes leading to CYP2A5 induction or coincidental occurrence of these events are also possibilities. Three glutathione S-transferase isoforms, mGSTP1-1 (pi), mGSTA1-1 (YaYa), and mGSTA4-4, also showed striking increases evidencing major oxidative stress in these livers.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed1993

Increased formation of 8-hydroxydeoxyguanosine, an oxidative DNA damage, in lymphoblasts from Fanconi's anemia patients due to possible catalase deficiency.

Fanconi's anemia (FA) cells are highly susceptible to both reactive oxygen species and mitomycin C (MMC), a DNA cross-linking agent. In this study we have determined the amounts of 8-hydroxydeoxyguanosine (8OHdG), typical of oxidative DNA damage, in Epstein-Barr virus transformed lymphoblasts from FA patients and normal controls by the use of HPLC combined with electrochemical detection. FA cells (HSC72 and 99 cells being assigned to FA complementation group A) formed 2-3 times more 8OHdG than control cells after incubation with 20 mM H2O2 at 37 degrees C for 30 min. FA cells also formed more 8-hydroxyguanosine, typical of oxidative RNA damage, than control cells. FA cells showed decreased activity to decompose H2O2. Although the activity in FA cells was only 20-30% less than control cells, the remaining, undecomposed H2O2 concentration was almost twice as much in FA cells as in control cells, and the remaining H2O2 concentration correlated well with the amounts of 8OHdG formation. The H2O2 decomposing activity was almost completely inhibited by sodium azide (NaN3) or aminotriazole, both catalase inhibitors. With these inhibitors the amounts of 8OHdG formation were much higher than in those cells without inhibitors, and were almost the same in control cells as in FA cells. Catalase activity in FA cell lysates was 70-80% of controls. MMC also increased 8OHdG formation in FA cells only at ED100 but not at ED50. These results indicate that FA cells, at least FA complementation group A cells, have increased susceptibility to oxidative DNA damage, and that this increased susceptibility is possibly due to decreased catalase activity. These results also suggest that catalase plays an important role in protecting DNA from oxidative damage. However, this increased susceptibility to oxidative DNA damage is considered not to be the major cause of the increased susceptibility to MMC.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2000

Increased levels of oxidatively damaged DNA induced by chromium(III) and H2O2: protection by melatonin and related molecules.

Chromium (Cr) compounds are known occupational and environmental carcinogens. This trace element is found in the workplace primarily in the valence forms Cr(III) and Cr(VI). Cr(III), which was thought originally to be relatively nontoxic, was recently found to be more reactive toward purified DNA than was chromium(VI). Herein, we examined the ability of Cr(III) to induce oxidative DNA damage by measuring the formation of 8-hydroxydeoxyguanosine (8-OH-dG) in purified calf thymus DNA incubated with CrCl3 plus H2O2. In this system we observed that the Cr(III)-induced formation of 8-OH-dG in isolated DNA was both dose- and time-dependent. When melatonin and related molecules, including 6-methoxy-1,2,3,4-tetrahydro-beta-carboline (pinoline), N-acetylserotonin, 6-hydroxymelatonin and indole-3-propionic acid, were co-incubated with CrCl3 plus H2O2, the accumulations of 8-OH-dG in DNA samples were markedly inhibited in a concentration-dependent manner. The concentrations of each indole required to reduce DNA damage by 50%, i.e. the IC50 values, were 0.48, 0.51, 0.88, 1.00 and 3.08 microM for pinoline, melatonin, N-acetylserotonin, 6-hydroxymelatonin and indole-3-propionic acid, respectively. These results suggest that one of the mechanisms by which Cr(III) may induce cancer is via Fenton-type reactions which generate the hydroxyl radical (*OH). The findings also indicate that the protective effects of melatonin and related molecules against Cr(III)-induced carcinogenesis relate to their direct *OH scavenging ability which thereby reduces the formation of the damaged DNA product, 8-OH-dG.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed1995

Exposure of mammalian cell cultures to benzo[a]pyrene and light results in oxidative DNA damage as measured by 8-hydroxydeoxyguanosine formation.

Carcinogenic polycyclic aromatic hydrocarbons induce DNA damage through direct covalent interactions with nucleotides of the DNA in cells in which they are activated to 'ultimate carcinogenic metabolites'. To determine whether they also induce oxidative damage to DNA under the same circumstances, early passage Syrian hamster embryo and human mammary carcinoma cell line MCF-7 cultures were treated for 24 h with 0-5 micrograms/ml benzo[a]pyrene (BaP) or for 1 h with 0-100 microM methylene blue (as a positive control for oxidative damage). The cells were then exposed to fluorescent light for 1 or 4 h or retained in darkness. After cell harvest, DNA isolation and enzymatic digestion of the DNA to deoxyribonucleosides, the amounts of 8-hydroxy-2'deoxyguanosine (8-OH-dGuo) and unmodified deoxyguanosine present were determined by reverse-phase HPLC with electrochemical and UV detection respectively. Cultures treated with methylene blue for 1 h followed by light exposure for 1 h contained 5-fold (10 microM) and 8- to 28-fold (100 microM) higher 8-OH-dGuo levels than cells treated with methylene blue not exposed to light or untreated cells with methylene blue not exposed to light or untreated cells exposed to light. There was no significant change in 8-OH-dGuo levels in cultures treated with 1-5 micrograms/ml BaP for 24 h in the absence of light. However, both the human and hamster cell cultures treated with BaP and then exposed to fluorescent light for 4 h contained 3-fold (1 micrograms/ml) and 8- to 10-fold (5 micrograms/ml) higher 8-OH-dGuo levels than those not exposed to light or not treated with BaP. These results indicate that BaP treatment does not cause 8-OH-dGuo formation in DNA of cells maintained in darkness. Exposure of BaP-treated cells to fluorescent light causes formation of significant amounts of oxidative DNA damage as measured by 8-OH-dGuo formation. These findings suggest that oxidative damage of DNA could be involved in tumor induction by BaP in tissues, such as skin, in which exposure to BaP can occur in the presence of light.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2002

Elevated levels of oxidative DNA damage and DNA repair enzymes in human atherosclerotic plaques.

BACKGROUND: The formation of reactive oxygen species is a critical event in atherosclerosis because it promotes cell proliferation, hypertrophy, growth arrest, and/or apoptosis and oxidation of LDL. In the present study, we investigated whether reactive oxygen species-induced oxidative damage to DNA occurs in human atherosclerotic plaques and whether this is accompanied by the upregulation of DNA repair mechanisms. METHODS AND RESULTS: We observed increased immunoreactivity against the oxidative DNA damage marker 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxo-dG) in plaques of the carotid artery compared with the adjacent inner media and nonatherosclerotic mammary arteries. Strong 8-oxo-dG immunoreactivity was found in all cell types of the plaque including macrophages, smooth muscle cells, and endothelial cells. As shown by competitive ELISA, carotid plaques contained 160+/-29 8-oxo-dG residues/10(5) dG versus 3+/-1 8-oxo-dG residues/10(5) dG in mammary arteries. Single-cell gel electrophoresis showed elevated levels of DNA strand breaks in the plaque. The overall number of apoptotic nuclei was low (1% to 2%) and did not correlate with the amount of 8-oxo-dG immunoreactive cells (>90%). This suggests that initial damage to DNA occurs at a sublethal level. Several DNA repair systems that are involved in base excision repair (redox factor/AP endonuclease [Ref 1] and poly(ADP-ribose) polymerase 1 [PARP-1]) or nonspecific repair pathways (p53, DNA-dependent protein kinase) were upregulated, as shown by Western blotting and immunohistochemistry. Overexpression of DNA repair enzymes was associated with elevated levels of proliferating cell nuclear antigen. CONCLUSIONS: Our findings provide evidence that oxidative DNA damage and repair increase significantly in human atherosclerotic plaques.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2005

A half-marathon and a marathon run induce oxidative DNA damage, reduce antioxidant capacity to protect DNA against damage and modify immune function in hobby runners.

This study investigated whether a 21.1 km (half-marathon) or a 42.195 km (marathon) run modulates DNA damage, antioxidant capacity in lymphocytes and plasma, and the immune system in healthy hobby runners. Ten and 12 volunteers who completed the Baden-Marathon race in Karlsruhe with a running distance of 21.1 km and 41.195 km, respectively, were assessed 10 days before and immediately after the finish. There was no increase in the levels of endogenous DNA strand breaks immediately after half-marathon or marathon races. A statistically significant increase in the levels of oxidative DNA damage in lymphocytes was found using endonuclease III but not formamidopyrimidine glycolase (Fpg). The resistance of DNA to oxidative damage induced by hydrogen peroxide in isolated lymphocytes was significantly decreased after both races. The levels of plasma antioxidants such as alpha-tocopherol, beta-carotene and lycopene were close to, or higher than, those considered optimal for reducing the risk of cardiovascular diseases and there were no significant changes after the races in antioxidant capacity of LDL (lag-time test) or plasma in ORAC, TEAC or paraoxonase assays. The number and percentage of granulocytes and monocytes able to generate oxidative burst were significantly increased after both races, but the lytic activity of NK cells was significantly increased at the end of the half-marathon; no effect was observed in the marathon runners. Thus, oxidative DNA damage in lymphocytes, decreased the antioxidant capacity to protect lymphocytes against DNA strand breaks and increased the formation of reactive species by phagocytes in well-nourished hobby runners indicating moderate oxidative damage during such high-intensity exercise.

Adult↗

PubMed2026

CaCl2 Priming Boosts Salinity-Alkalinity Tolerance in Germinating Soybean by Reducing DNA Oxidative Damage and Enhancing Ca2+ -ROS Signaling Crosstalk.

Soybean (Glycine max) seed germination is highly sensitive to saline-alkaline stress. Seed priming represents an effective strategy to mitigate its detrimental effects. However, the optimal priming conditions (agent, concentration, duration) and the underlying molecular mechanisms remain poorly understood. This study investigated the effects of priming with distilled water (Control), calcium chloride (CaCl2), melatonin (MT), and proline (Pro) under saline-alkaline stress on soybean seed germination and the molecular basis of enhanced tolerance. Evaluation of ten germination-related parameters revealed that priming with 100 mM CaCl2 for 12 h significantly enhanced the germination rate. Physiological analyses demonstrated that CaCl2 priming effectively reduced reactive oxygen species (ROS) accumulation by increasing the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), while decreasing malondialdehyde (MDA) content. Furthermore, CaCl2 priming activated the Ca2+ signaling pathway by increasing radicle Ca2+ content and upregulating the expression levels of Ca2+ signaling-related genes (e.g., GmCAM7, GmCNGC2, GmCNGC19, GmMPK2, and GmMKK2). Additionally, CaCl2 priming significantly enhanced DNA damage repair capacity of soybean cultivars with differing saline-alkaline tolerance. This was manifested by reduced DNA oxidative damage and decreased random amplified polymorphic DNA (RAPD) polymorphism, thereby enhancing genomic stability and alleviating cell cycle arrest. These findings deepen our understanding of the complex regulatory role of calcium signaling in plant abiotic stress responses and provide important novel theoretical insights for improving crop resilience.

Glycine max↗