Increase In 8-oxodG Research Articles

Overexpression of Insulin Receptor Substrate 1 (IRS1) Relates to Poor Prognosis and Promotes Proliferation, Stemness, Migration, and Oxidative Stress Resistance in Cholangiocarcinoma.

Cholangiocarcinoma (CCA) is one of the oxidative stress-driven carcinogenesis through chronic inflammation. Insulin receptor substrate 1 (IRS1), an adaptor protein of insulin signaling pathways, is associated with the progression of many inflammation-related cancers. This study hypothesized that oxidative stress regulates IRS1 expression and that up-regulation of IRS1 induces CCA progression. The localizations of IRS1 and an oxidative stress marker (8-oxodG) were detected in CCA tissues using immunohistochemistry (IHC). The presence of IRS1 in CCA tissues was confirmed using immortal cholangiocyte cells (MMNK1), a long-term oxidative-stress-induced cell line (ox-MMNK1-L), and five CCA cell lines as cell culture models. IRS1 was overexpressed in tumor cells and this was associated with a shorter patient survival time and an increase in 8-oxodG. IRS1 expression was higher in ox-MMNK1-L cells than in MMNK1 cells. Knockdown of IRS1 by siRNA in two CCA cell lines led to inhibition of proliferation, cell cycle progression, migration, invasion, stemness, and oxidative stress resistance properties. Moreover, a transcriptomics study demonstrated that suppressing IRS1 in the KKU-213B CCA cell line reduced the expression levels of several genes and pathways involved in the cellular functions. The findings indicate that IRS1 is a key molecule in the connection between oxidative stress and CCA progression. Therefore, IRS1 and its related genes can be used as prognostic markers and therapeutic targets for CCA therapy.

Associations between levels of oxidative nucleoside damage and cardiovascular risk in patients newly diagnosed with bipolar disorder and their unaffected relatives

Enhanced oxidative stress-generated nucleoside damage may contribute to the increased cardiovascular disease mortality in patients with bipolar disorder (BD) but the association has never been investigated. We investigated the associations between oxidative stress-generated damage to DNA (8-oxodG) and RNA (8-oxoGuo), respectively, and three measures reflecting cardiovascular risk; namely, the Framingham 30-year risk score of cardiovascular diseases, the metabolic syndrome, and the insulin resistance index in 360 patients newly diagnosed with BD, 102 of their unaffected relatives (UR) and 197 healthy control individuals (HC). In sex- and age-adjusted models, the 30-year cardiovascular risk score increased by 20.8% (CI = 7.4–35.9%, p = 0.002) for every one nM/mM creatinine increase in 8-oxoGuo and by 15.6% (95% CI = 5.8–26.4%, p = 0.001) for every one nM/mM creatinine increase in 8-oxodG, respectively. Further, insulin resistance index increased by 24.1% (95% CI = 6.7–43%, p = 0.005) when 8-oxoGuo increased one nM/mM creatinine. The associations between cardiovascular measures and oxidative nucleoside damage were more pronounced in patients with BD compared with UR, and HC. Metabolic syndrome was not associated with nucleoside damage. Overall, higher oxidative stress-generated nucleoside damage was associated with a higher cardiovascular risk score and a higher degree of insulin resistance index, and having BD impacted the associations. Further, within patients, treatment with psychotropics seemed to enhance the associations between 30-year CVD risk score and insulin resistance index, respectively, and oxidatively stress-generated nucleoside damage. Our findings support enhanced oxidative stress-generated nucleoside damage as a putative pathophysiological mechanism that may mediate the higher cardiovascular risk observed in patients with BD already at the time of diagnosis.

Urinary Polycyclic Aromatic Hydrocarbon Metabolites Are Associated with Biomarkers of Chronic Endocrine Stress, Oxidative Stress, and Inflammation in Adolescents: FLEHS-4 (2016-2020).

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants of public health concern. Multiple biological mechanisms have been hypothesized to contribute to PAHs-associated adverse health effects. Little is known about the impact of PAHs on endocrine stress and inflammation in adolescence. We examined 393 Flemish adolescents (14–15 years) cross-sectionally, measured urinary concentrations of hydroxylated naphthalene, fluorene, phenanthrene and pyrene metabolites, and calculated the sum of all measured metabolites. We determined hair cortisol concentration (HCC) as endocrine stress biomarker, leucocyte counts and neutrophil–lymphocyte ratio (NLR) in peripheral blood as inflammatory biomarkers, and urinary 8-oxo-7,8-dihydro-2’-deoxyguanosine (8-oxodG) concentration as oxidative stress biomarker. Exposure–response associations were analyzed by multiple regression, adjusted for a priori selected covariates. A doubling of 1-hydroxypyrene concentration was associated with a factor of 1.13 (95% CI: 1.03, 1.24) increase in HCC and a factor of 1.07 (95% CI: 1.02, 1.13) increase in 8-oxodG. Doublings of 2- and 3-hydroxyphenanthrene concentrations were associated with a factor of 1.08 (95% CI: 1.02, 1.14) and 1.06 (95% CI: 1.00, 1.12) increase in 8-oxodG, respectively. Doubling of 2-hydroxyphenanthrene and of the sum of 2- and 3-hydroxyfluorene was associated with, respectively, a factor of 1.08 (95% CI: 1.02, 1.14) and 1.06 (95% CI: 1.01, 1.13) increase in NLR. Our results indicate the glucocorticoid pathway as a potential target for PAH exposure in adolescents and suggest oxidative stress, endocrine stress, and inflammation in adolescence as underlying mechanisms and early markers for PAH-related adverse health effects.

Characteristic profiles of DNA epigenetic modifications in colon cancer and its predisposing conditions\u2014benign adenomas and inflammatory bowel disease

BackgroundActive demethylation of 5-methyl-2′-deoxycytidine (5-mdC) in DNA occurs by oxidation to 5-(hydroxymethyl)-2′-deoxycytidine (5-hmdC) and further oxidation to 5-formyl-2′-deoxycytidine (5-fdC) and 5-carboxy-2′-deoxycytidine (5-cadC), and is carried out by enzymes of the ten-eleven translocation family (TETs 1, 2, 3). Decreased level of epigenetic DNA modifications in cancer tissue may be a consequence of reduced activity/expression of TET proteins. To determine the role of epigenetic DNA modifications in colon cancer development, we analyzed their levels in normal colon and various colonic pathologies. Moreover, we determined the expressions of TETs at mRNA and protein level.The study included material from patients with inflammatory bowel disease (IBD), benign polyps (AD), and colorectal cancer (CRC). The levels of epigenetic DNA modifications and 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) in examined tissues were determined by means of isotope-dilution automated online two-dimensional ultraperformance liquid chromatography with tandem mass spectrometry (2D-UPLC-MS/MS). The expressions of TET mRNA were measured with RT-qPCR, and the expressions of TET proteins were determined immunohistochemically.ResultsIBD was characterized by the highest level of 8-oxodG among all analyzed tissues, as well as by a decrease in 5-hmdC and 5-mdC levels (at a midrange between normal colon and CRC). AD had the lowest levels of 5-hmdC and 5-mdC of all examined tissues and showed an increase in 8-oxodG and 5-(hydroxymethyl)-2′-deoxyuridine (5-hmdU) levels. CRC was characterized by lower levels of 5-hmdC and 5-mdC, the lowest level of 5-fdC among all analyzed tissues, and relatively high content of 5-cadC. The expression of TET1 mRNA in CRC and AD was significantly weaker than in IBD and normal colon. Furthermore, CRC and AD showed significantly lower levels of TET2 and AID mRNA than normal colonic tissue.ConclusionsOur findings suggest that a complex relationship between aberrant pattern of DNA epigenetic modification and cancer development does not depend solely on the transcriptional status of TET proteins, but also on the characteristics of premalignant/malignant cells. This study showed for the first time that the examined colonic pathologies had their unique epigenetic marks, distinguishing them from each other, as well as from normal colonic tissue. A decrease in 5-fdC level may be a characteristic feature of largely undifferentiated cancer cells.

Urinary markers of nucleic acid oxidation and cancer in type 2 diabetes

Aims/hypothesisWe investigated whether urinary markers of nucleic acid oxidation are associated with an increased risk of cancer in type 2 diabetes patients. MethodsUrine samples from 1381 newly diagnosed diabetes patients were assayed for the oxidatively modified guanine nucleosides 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydroguanosine (8-oxoGuo). Cox proportional hazards regression was used to examine the relationship between the urinary markers and cancer incidence. ResultsThe crude analyses showed an association between overall cancer and urinary excretion of the RNA oxidation marker 8-oxoGuo (unadjusted hazard ratio for cancer per natural log increase in 8-oxoGuo 1.35 [95% CI, 1.01–1.81]), however, in the adjusted analyses, no significant associations between 8-oxodG or 8-oxoGuo and overall cancer were found. For site-specific cancers 8-oxodG was associated with breast cancer in the crude analyses (unadjusted hazard ratio for breast cancer per natural log increase in 8-oxodG was 2.37 [95% CI, 1.07–5.26]), although the association was attenuated in the adjusted analyses (sex- and age-adjusted hazard ratio 2.15 [95% CI, 0.92–5.02] and multivariate adjusted hazard ratio1.98 [95% CI, 0.95–4.10]). ConclusionsUrinary excretion of the nucleic acid oxidation markers 8-oxodG and 8-oxoGuo at the time of diagnosis was not associated with cancer overall in type 2 diabetes patients. For site-specific cancers, risk elevations were seen for breast cancer (8-oxodG). These findings should be examined in future and larger studies.

Cerebellar oxidative DNA damage and altered DNA methylation in the BTBR T+tf/J mouse model of autism and similarities with human post mortem cerebellum.

The molecular pathogenesis of autism is complex and involves numerous genomic, epigenomic, proteomic, metabolic, and physiological alterations. Elucidating and understanding the molecular processes underlying the pathogenesis of autism is critical for effective clinical management and prevention of this disorder. The goal of this study is to investigate key molecular alterations postulated to play a role in autism and their role in the pathophysiology of autism. In this study we demonstrate that DNA isolated from the cerebellum of BTBR T+tf/J mice, a relevant mouse model of autism, and from human post-mortem cerebellum of individuals with autism, are both characterized by an increased levels of 8-oxo-7-hydrodeoxyguanosine (8-oxodG), 5-methylcytosine (5mC), and 5-hydroxymethylcytosine (5hmC). The increase in 8-oxodG and 5mC content was associated with a markedly reduced expression of the 8-oxoguanine DNA-glycosylase 1 (Ogg1) and increased expression of de novo DNA methyltransferases 3a and 3b (Dnmt3a and Dnmt3b). Interestingly, a rise in the level of 5hmC occurred without changes in the expression of ten-eleven translocation expression 1 (Tet1) and Tet2 genes, but significantly correlated with the presence of 8-oxodG in DNA. This finding and similar elevation in 8-oxodG in cerebellum of individuals with autism and in the BTBR T+tf/J mouse model warrant future large-scale studies to specifically address the role of OGG1 alterations in pathogenesis of autism.

Association between 8-oxo-7,8-dihydro-2′-deoxyguanosine Excretion and Risk of Postmenopausal Breast Cancer: Nested Case–Control Study

Oxidative stress may be important in carcinogenesis and a possible risk factor for breast cancer. The urinary excretion of oxidatively generated biomolecules, such as 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), represents biomarkers of oxidative stress, reflecting the rate of global damage to DNA in steady state. In a nested case-control design, we examined associations between urinary excretion of 8-oxodG and risk of breast cancer in a population-based cohort of 24,697 postmenopausal women aged 50 to 64 years with 3 to 7 years follow-up. The accruing cases of breast cancer were matched to controls by age at diagnosis, baseline age, and hormone replacement therapy (HRT). Spot urine samples collected at entry was analyzed for 8-oxodG by high-performance liquid chromatography with electrochemical detection. Incidence rate ratio (IRR; 95% confidence intervals) based on 336 matched pairs with all information was estimated per unit increase in 8-oxodG divided by creatinine for all and estrogen receptor (ER) positive and negative breast cancers. There was a borderline significant positive association between 8-oxodG and risk of all breast cancer (IRR: 1.08; 1.00-1.17 per unit increase in nmol/mmol creatinine). This association was significant with respect to the risk of ER-positive cancer (IRR: 1.11; 1.01-1.23) and among women not using HRT (IRR: 1.11; 0.97-1.26) or with low dietary iron intake (IRR: 1.10; 1.06-1.37 per unit increase) for all breast cancer. We observed positive association between 8-oxodG excretion and risk of especially ER-positive breast cancer. Our results suggest that oxidative stress with damage to DNA is important for the development of breast cancer.

Cross-Talk Between One-Carbon Metabolism and Xenobiotic Metabolism: Implications on Oxidative DNA Damage and Susceptibility to Breast Cancer

The aim of this case-control study is to explore the role of aberrations in xenobiotic metabolism in inducing oxidative DNA damage and altering the susceptibility to breast cancer. Cytochrome P4501A1 (CYP1A1) m1 (OR: 1.41, 95% CI 1.08-1.84), CYP1A1 m4 (OR: 5.13, 95% CI 2.68-9.81), Catecholamine-O-methyl transferase (COMT) H108L (OR: 1.49, 95% CI 1.16-1.92), and glutathione S-transferase (GST) T1 null (OR: 1.68, 95% CI 1.09-2.59) variants showed association with breast cancer risk. Reduced folate carrier 1 (RFC1) 80A/CYP1A1 m1/CYP1A1 m4 and RFC1 80A/thymidylate synthase (TYMS) 5'-UTR 2R/methionine synthase (MTR) 2756G/COMT 108L genetic combinations were found to inflate breast cancer risk under the conditions of low dietary folate (345 ± 110 vs. 379 ± 139 μg/day) and low plasma folate (6.81 ± 1.25 vs. 7.09 ± 1.26 ng/ml) by increasing plasma 8-oxo-2'-deoxyguanosine (8-oxodG). This increase in 8-oxodG is attributed to low methionine (49.38 ± 23.74 vs. 53.90 ± 23.85 μmol/l); low glutathione (378 ± 242 vs. 501 ± 126 μmol/l) and GSTT1 null variant; and hypermethylation of CpG island of extracellular-superoxide dismutase (EC-SOD) (92.78 ± 11.49 vs. 80.45 ± 9.86%), which impair O-methylation of catechol estrogens to methoxy estrogens, conjugation of glutathione to semiquinones/quinones and free radical scavenging respectively. Our results suggest cross-talk between one-carbon metabolism and xenobiotic metabolism influencing oxidative DNA damage and susceptibility to breast cancer.

Methanol exposure does not produce oxidatively damaged DNA in lung, liver or kidney of adult mice, rabbits or primates

In vitro and in vivo genotoxicity tests indicate methanol (MeOH) is not mutagenic, but carcinogenic potential has been claimed in one controversial long-term rodent cancer bioassay that has not been replicated. To determine whether MeOH could indirectly damage DNA via reactive oxygen species (ROS)-mediated mechanisms, we treated male CD-1 mice, New Zealand white rabbits and cynomolgus monkeys with MeOH (2.0 g/kg ip) and 6 h later assessed oxidative damage to DNA, measured as 8-oxo-2′-deoxyguanosine (8-oxodG) by HPLC with electrochemical detection. We found no MeOH-dependent increases in 8-oxodG in lung, liver or kidney of any species. Chronic treatment of CD-1 mice with MeOH (2.0 g/kg ip) daily for 15 days also did not increase 8-oxodG levels in these organs. These results were corroborated in DNA repair-deficient oxoguanine glycosylase 1 ( Ogg1) knockout (KO) mice, which accumulated 8-oxodG in lung, kidney and liver with age, but exhibited no increase following MeOH, despite a 2-fold increase in renal 8-oxodG in Ogg1 KO mice following treatment with a ROS-initiating positive control, the renal carcinogen potassium bromate (KBrO 3; 100 mg/kg ip). These observations suggest that MeOH exposure does not promote the accumulation of oxidatively damaged DNA in lung, kidney or liver, and that environmental exposure to MeOH is unlikely to initiate carcinogenesis in these organs by DNA oxidation.

Transition Metals in Personal Samples of PM2.5 and Oxidative Stress in Human Volunteers

Ambient particulate matter (PM) has been associated with increased risk of lung cancer. One proposed mechanism is that PM induces oxidative stress mediated by transition metals contained within this mixture. We examined the relationship between the personal exposure to water-soluble transition metals in PM(2.5) and oxidative DNA damage. In 49 students from central Copenhagen, we determined PM(2.5) exposure by personal sampling twice in 1 year, and measured in these PM(2.5) samples the concentration of the soluble transition metals vanadium, chromium, iron, nickel, copper, and platinum. Collected lymphocytes and 24-hour urine samples were analyzed for DNA damage in terms of 7-hydro-8-oxo-2'-deoxyguanosine (8-oxodG). We found that the 8-oxodG concentration in lymphocytes was significantly associated with the vanadium and chromium concentrations with a 1.9% increase in 8-oxodG per 1 microg/L increase in the vanadium concentration and a 2.2% increase in 8-oxodG per 1 microg/L increase in the chromium concentration. We have previously reported that in this study population the personal exposure to PM(2.5) was associated with an increase in 8-oxodG in lymphocytes. However, vanadium and chromium were associated with the 8-oxodG concentration in lymphocytes independently of the PM(2.5) mass concentration. The four other transition metals were not associated with 8-oxodG in lymphocytes and none of the transition metals was significantly associated with 8-oxodG in urine. Our results could indicate that vanadium and chromium present in PM(2.5) have an effect on oxidative DNA damage that is independent of particle mass and/or other possible toxic compounds contained within this particulate mixture.

Measurement of 8-oxo-7,8-dihydro-2′-deoxyguanosine in peripheral blood mononuclear cells: Optimisation and application to samples from a case-control study on cancers of the oesophagus and cardia

8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) is a widely used biomarker to evaluate the level of oxidative stress. This study describes in its first part the optimisation of our analytical procedure (HPLC/electrochemical detection). Particular care was exercised to avoid artefactual oxidation and in the precision of measurement, which was evaluated with blood bags from hemochromatosis patients. The best results were obtained with a DNA extraction step using the “chaotropic method” recommended by the European Standards Committee on Oxidative DNA Damage (ESCODD). Other approaches such as anion exchange columns gave ten times as much 8-oxodG as this method. Moreover, a complete DNA hydrolysis using five different enzymes allowed improved precision. The optimised protocol was applied to peripheral blood mononuclear cells (PBMC) sampled during a case-control study on cancers of the oesophagus and cardia. With 7.2±2.6 8-oxodG/106 2′-deoxyguanosines (2′-dG) (mean ± SD), patients (n=17) showed higher levels of 8-oxodG than controls (4.9±1.9 8-oxodG/106 2′-dG, n=43, Student's t-test: p<0.001). This difference remained significant after technical (storage, sampling period, 2′-dG levels) and individual (age, sex, smoking, alcohol) confounding factors were taken into account (p<0.0001, Generalised Linear regression Model). To our knowledge, this is the first report to demonstrate an increase of 8-oxodG in PBMCs of patients suffering from a cancer of the upper digestive tract. This elevated level of DNA damage in patients can raise interesting issues: is oxidative stress the cause or the result of the pathology? Could this biomarker be used to evaluate chemoprevention trials concerning digestive tract cancers?

Effects of melanin and manganese on dna damage and repair in PC12-derived neurons

The mechanism of neurotoxicity produced by the interaction of melanin with manganese was investigated in PC12-derived neuronal cell cultures. The cells were incubated with melanin (25–500 μg/ml), MnCl 2 (10 ng/ml–100 μg/ml) and a combination of both substances for 24 and 72 h. Incubation with either toxicant alone resulted in a minimal decrease in cell viability. The combination of melanin and manganese caused significant (up to 60%) decreases in viability of PC12 cells in a dose-dependent manner. Increases in oxidative DNA damage, indicated by levels of 8-hydroxy-2′deoxyguanosine (8-oxodG), was associated with decreased cell viability. Melanin alone, but not manganese alone, resulted in increased oxidative DNA damage. The maximal increase in 8-oxodG caused by melanin was about seven times higher than control after 24 h of exposure. The activity of the DNA repair enzyme, 8-oxoguanine DNA glycosylase (OGG1), was increased in cells incubated with single toxicants and their combinations for 24 h. On the third day of incubation with the toxicants, activity of OGG1 declined below control levels and cell viability significantly decreased. Melanin was observed to have an inhibitory effect on OGG1 activity. Study of the regulation of OGG1 activity in response to melanin and manganese may provide insights into the vulnerability of nigral neurons to oxidative stress in Parkinson's disease.

OGG1 mRNA expression and incision activity in rats are higher in foetal tissue than in adult liver tissue while 8-oxo-2′-deoxyguanosine levels are unchanged

This study was set up to investigate the relationships between the formation and removal of DNA damage in form of 8-oxodeoxyguanosine (8-oxodG) in neonatal (day 16 of gestation) as compared to adult rats. The hypothesis addressed was whether the rapidly dividing foetal tissue has an enhanced requirement of DNA repair providing protection against potentially mutagenic DNA damages such as 8-oxodG. The activity of the primary 8-oxodG-repair protein OGG1 was measured by a DNA incision assay and the expression of OGG1 mRNA was measured by Real-Time PCR normalised to 18S rRNA. The tissue level of 8-oxodG was measured by HPLC-ECD. We found a 2–3-fold increased incision activity in the foetal control tissue, together with a 3–15-fold increase in mRNA of OGG1 as compared to liver tissue from adult rats. The levels of 8-oxodG in the foetal tissue were unaltered as compared to the adult groups. To increase the levels of 8-oxodG, the rats received an injection (i.p.) of the hepatotoxin 2-nitropropane. The compound induced significant levels of 8-oxodG in male rat livers 5 h after the injection and in the foetuses 24 h after the injection, while the female rats showed no increase in 8-oxodG. The incision activity was slightly depressed in both male and female liver tissue and in the foetal tissue 5 h after the injection, but significantly increased from 5 to 24 h after the injection. However, it did not reach levels significantly above the control levels. In conclusion, this study confirms that foetal tissue has increased levels of OGG1 mRNA and correspondingly an enhanced incision activity on an 8-oxodG substrate in a crude tissue extract.

Iron-induced oxidative DNA damage in rat sperm cells in vivo and in vitro

We investigated whether acute iron intoxication causes oxidative DNA damage, measured in terms of 7-hydro-8-oxo-2′-deoxyguanosine, 8-oxodG, in nuclear DNA in testes and epididymal sperm cells in vivo and in vitro in rats. In addition, we investigated levels of the modified nucleoside in liver and kidney and measured its urinary excretion.Sperm cells were isolated from the epididymides and the testes cells were isolated after homogenisation. In vitro, the sperm and testes cells were incubated with increasing concentrations of FeCl2 ranging from 0 to 600 μM. The median (range) levels of 8-oxodG/105 dG in the epididymal sperm cells increased from 0.48 (0.42–0.90) to 15.1 (11.4–17.6) (p < 0.05), whereas the level rose from 0.63 (0.22–0.81) to 8.8 (4.5–11.6) (p < 0.05) at 0 and 600 μM, respectively, in the testicular cells.In vivo groups of 7–8 rats received 0, 200 or 400 mg iron/kg as dextran i.p. After 24h, epididymal sperm cells, testes, kidneys and liver were collected for analysis. Kidney and sperm DNA showed a significant increase in 8-oxodG in the iron-treated animals. The median (range) values of the 8-oxodG/105 dG in the epididymal sperm cells rose from 0.66 (0.38–1.09) to 1.12 (0.84–5.88) (p < 0.05) at 0 and 400 mg iron/kg, respectively, whereas the values in the testes and liver showed no significant change. In the kidneys the 8-oxodG/105 dG median (range) values were 0.98 (0.73–1.24), 1.21 (1.13–1.69) and 1.34 (1.12–1.66) after 0, 200 and 400 mg iron/kg, respectively (p < 0.05).The 8-oxodG-excretion rate was measured in 24 h urine before and after iron treatment. The rate of urinary 8-oxodG excretion increased from 129 (104–179) pmol/24 h before treatment to 147 (110–239) pmol/24h after treatment in the group receiving 400 mg iron/kg (p < 0.05).The results indicate that acute iron intoxication may increase oxidative damage to sperm and kidney DNA.

Dexamethasone ameliorates oxidative DNA damage induced by benzene and LPS in mouse bone marrow

Mice were grouped to receive vehicle, dexamethasone (DEX), lipopolysaccharide (LPS), benzene (BZ, 200 mg/kg) and combinations: LPS + DEX, BZ + DEX, LPS + BZ, LPS + DEX + BZ. The DNA damage in bone marrow cells from BZ group was enhanced 2.8-fold measured by nuclear 8-hydroxy-2′-deoxyguanosine(8-oxodG) and 1.4-fold measured by Comet score (index of DNA breaks) (p<0.05). In the BZ + DEX group, 8-oxodG level and the Comet score were lowered to 65% and 76% respectively of that in the BZ group (p<0.05). The BZ + LPS caused a 3.9-fold increase in 8-oxodG and a 1.6-fold increase in the Comet score (p<0.05). The LPS + DEX + BZ lowered 8-oxodG level and the Comet score to 50% and 78% of the values in the LPS + BZ group, respectively (p<0.05). Nitrate/nitrite levels in serum were higher after BZ + LPS treatment than after all other treatments. Both 8-oxodG level and the Comet scores were correlated to the serum nitrate/nitrite level across all the treatments (r=0.55, p<0.01 and r=0.69, p<0.01, respectively). In bone marrow cells the 8-oxodG correlated with the Comet scores (r=0.80, p<0.01). We conclude that DEX administration can reduce the DNA damage from BZ treatment and from the combination of BZ and LPS. The correlation of DNA damage with nitrate/nitrite indicates the possible involvement of reactive nitrogen species (RNS) in the interaction between BZ and the inflammatory reaction stimulated by LPS. The 8-oxodG determination is more sensitive than strand break analysis by the Comet assay in bone marrow in vivo in mice for measuring the BZ-induced DNA damage.

Nicotine and smokeless tobacco induced formation of 8-OHdG: [formula omitted], Nuran Ercal, Daniel Armstrong. University of Missouri-Rolla, Chemistry Department, Rolla, MO 65401

We investigated whether urinary markers of nucleic acid oxidation are associated with an increased risk of cancer in type 2 diabetes patients.Urine samples from 1381 newly diagnosed diabetes patients were assayed for the oxidatively modified guanine nucleosides 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydroguanosine (8-oxoGuo). Cox proportional hazards regression was used to examine the relationship between the urinary markers and cancer incidence.The crude analyses showed an association between overall cancer and urinary excretion of the RNA oxidation marker 8-oxoGuo (unadjusted hazard ratio for cancer per natural log increase in 8-oxoGuo 1.35 [95% CI, 1.01–1.81]), however, in the adjusted analyses, no significant associations between 8-oxodG or 8-oxoGuo and overall cancer were found. For site-specific cancers 8-oxodG was associated with breast cancer in the crude analyses (unadjusted hazard ratio for breast cancer per natural log increase in 8-oxodG was 2.37 [95% CI, 1.07–5.26]), although the association was attenuated in the adjusted analyses (sex- and age-adjusted hazard ratio 2.15 [95% CI, 0.92–5.02] and multivariate adjusted hazard ratio1.98 [95% CI, 0.95–4.10]).Urinary excretion of the nucleic acid oxidation markers 8-oxodG and 8-oxoGuo at the time of diagnosis was not associated with cancer overall in type 2 diabetes patients. For site-specific cancers, risk elevations were seen for breast cancer (8-oxodG). These findings should be examined in future and larger studies.