Biomedical subjects

Steffen Loft

Publications and source records attributed to Steffen Loft.

At least 37 records · Page 2Linked to original sources

PubMed2004

Sucrose and IQ induced mutations in rat colon by independent mechanism.

Sucrose-rich diets have repeatedly been observed to have co-carcinogenic actions in colon and liver of rats and to increase the number of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) induced aberrant crypt foci in rat colon. To investigate a possible interaction between sucrose and IQ on the genotoxicity in rat liver and colon, we gave Big Blue rats a diet containing sucrose (0%, 3.45% or 13.4% w/w) and/or IQ (70 ppm) for a period of 3 weeks. Sucrose and IQ increased the mutation frequency in the colon. The effect of combined treatments with IQ and sucrose on the mutation frequencies was additive indicating that sucrose and IQ act independently. This was supported by the mutation spectra where sucrose expands the background mutations in the colon, whereas IQ, in other studies, more specifically has induced G:C --> T:A transversions. In the liver IQ increased the mutation frequency, whereas addition of sucrose reduced the effect of IQ in a dose-dependent manner. The level of bulky DNA adducts in liver and colon was increased in animals exposed to either sucrose or IQ. In animals exposed to IQ, addition of sucrose had marginal effects on the level of bulky DNA adducts. Markers of oxidative damage and DNA repair were generally unaffected by the treatments. In conclusion, sucrose and IQ in the diet induced mutations in the colon by independent mechanisms, whereas an interaction was observed in liver leading to a decrease in mutations by the combined treatment.

Animals↗

PubMed2004

Inflammatory and genotoxic effects of diesel particles in vitro and in vivo.

Recent studies have identified an indirect genotoxicity pathway involving inflammation as one of the mechanisms underlying the carcinogenic effects of air pollution/diesel exhaust particles (DEP). We investigated the short-term effects of DEP on markers of inflammation and genotoxicity in vitro and in vivo. DEP induced an increase in the mRNA level of pro-inflammatory cytokines and a higher level of DNA strand breaks in the human lung epithelial cell line A549 in vitro. For the in vivo study, mice were exposed by inhalation to 20 or 80 mg/m3 DEP either as a single 90-min exposure or as four repeated 90-min exposures (5 or 20 mg/m3) and the effects in broncho-alveolar lavage (BAL) cells and/or lung tissue were characterized. Inhalation of DEP induced a dose-dependent inflammatory response with infiltration of macrophages and neutrophils and elevated gene expression of IL-6 in the lungs of mice. The inflammatory response was accompanied by DNA strand breaks in BAL cells and oxidative DNA damage and increased levels of bulky DNA adducts in lung tissue, the latter indicative of direct genotoxicity. The effect of a large single dose of DEP was more pronounced and sustained on IL-6 expression and oxidative DNA damage in the lung tissue than the effect of the same dose administered over four days, whereas the reverse pattern was seen in BAL cells. Our results suggest that the effects of DEP depend on the rate of delivery of the particle dose. The mutation frequency (MF), after DEP exposure, was determined using the transgenic Muta Mouse and a similar exposure regimen. No increase was observed in MF in lung tissue 28-days after exposure. In conclusion, short-term exposure to DEP resulted in DNA strand breaks in BAL cells, oxidative DNA damage and DNA adducts in lungs; and suggested that DNA damage in part is a consequence of inflammatory processes. The response was not associated with increased MF, indicating that the host defence mechanisms were sufficient to counteract the adverse effects of inflammation. Thus, there may be thresholds for the inflammation-associated genotoxic effects of DEP inhalation.

Animals↗

PubMed2004

Interventions with antioxidants and nutrients in relation to oxidative DNA damage and repair.

Cells are constantly exposed to oxidants from metabolic and other biochemical reactions as well as external factors, suggesting that DNA repair systems and nutritional antioxidants are important determinants for low levels of DNA damage and cancer risk. The effects of single antioxidants, as well as various vegetables, fruits and carotenoid- and polyphenolic-rich products, have been assessed with biomarkers, mainly including DNA damage in white blood cells (WBC), urinary excretion of oxidized bases and nucleosides and DNA repair capacity. The basal levels of oxidative DNA damage, and effects of the interventions have been rather variable, possibly reflecting differences in the populations, regimens, and the type of assays. In general, single dose antioxidant interventions have shown protective effects with respect to WBC DNA oxidation. Studies with continuous ingestion of antioxidants show mixed results with respect to effects on oxidative DNA damage in WBC, possibly due to various problems with design, statistical power and period effects. Studies with only male subjects appear to show consistent antioxidant effects in terms of reduced levels of oxidized pyrimidines. Investigations of oxidatively stressed subjects, e.g. HIV-infected patients or diabetics, suggest beneficial outcomes in populations with high initial levels of oxidative DNA damage. Recent research on the effect of antioxidants on DNA repair enzymes suggest effects in terms of increased removal of oxidized purines, whereas mRNA levels of the relevant DNA repair genes appears to be unaffected by an antioxidant-rich diet. In the future, care should be taken with respect to design of intervention studies and considerations of gender effect, genotypes of defence enzymes as well as DNA repair capacity.

Antioxidants↗

PubMed2004

Oxidative DNA damage in circulating mononuclear blood cells after ingestion of blackcurrant juice or anthocyanin-rich drink.

Berry extracts possess antioxidant activity in cell free systems, whereas cell culture and animal experimental systems have produced mixed outcomes. Our aim was to investigate the effects of blackcurrant juice and specifically blackcurrant anthocyanins on the steady state level of oxidative DNA damage in mononuclear blood cells (MNBC) of humans, determined as strand breaks (SB) as well as endonuclease III (Endo III) and formamidopyrimidine DNA glycosylase (Fpg) sensitive sites by the comet assay. Fifty-seven healthy humans completed a 3-week controlled parallel intervention study with three groups randomized to supplementation with blackcurrant juice, anthocyanin drink, or a control drink. The daily doses ranged from 475 to 1000ml/d according to body weight (mean anthocyanin intakes in blackcurrant juice and anthocyanin drink groups were 397 and 365g/d, respectively) and they were ingested during three daily meals while all volunteers were on the same strictly controlled low-flavonoid diet. Fasting venous blood samples were obtained at baseline and after 3-week of supplementation. The baseline level of oxidative DNA damage was low (e.g. less than 200 Fpg lesions per diploid cell). Fpg sensitive sites increased during the intervention within the blackcurrant juice group, whereas there were no differences between treatments in any of the DNA damage markers. In conclusion, this study shows that even large amounts of dietary antioxidants did not decrease the already low steady state levels of oxidative DNA damage in healthy adequately nourished humans.

Adult↗

PubMed2004

DNA damage in lung after oral exposure to diesel exhaust particles in Big Blue rats.

Several chemical mutagens and carcinogens, including polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs, are adsorbed to the surface of diesel exhaust particles (DEP). DEP can induce formation of reactive oxygen species and cause oxidative DNA damage as well as bulky carcinogen DNA adducts. Lung tissue is a target organ for DEP induced cancer following inhalation. Recent studies have provided evidence that the lung is also a target organ for DNA damage and cancer after oral exposure to other complex mixtures of PAHs. The genotoxic effect of oral administration of DEP was investigated, in terms of markers of DNA damage, mutations and repair, in the lung of Big Blue rats fed a diet with 0, 0.2, 0.8, 2, 8, 20 or 80 mg DEP/kg feed for 21 days. There was no significant increase in the mutation frequency in the cII gene. However, an increase of DNA damage measured as DNA strand breaks (comet assay) and bulky DNA adducts (32P post labeling) was observed. The level of DNA strand breaks increased significantly at all dose levels while the level of DNA adducts increased significantly only at the intermediate dose levels. Similarly, the number of oxidized DNA bases measured as endonuclease III and fapyguanine glycosylase (FPG) sensitive sites increased at the intermediate dose levels. The induction of DNA damage by DEP exposure did not increase the expression of the repair genes OGG1 and ERCC1 at the mRNA level. The present study indicates that the lung is a target organ for primary DNA damage following oral exposure to DEP. DNA damage was induced following exposure to relatively low levels of DEP, but under the conditions used in the present experiment DNA damage did not result in an increased mutation rate.

Animals↗

PubMed2004

Cell-specific oxidative DNA damage induced by estrogen in rat testicular cells in vitro.

17 alpha-Ethinylestradiol (EE) can induce oxidative DNA damage in terms of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in rat testicular cells by an apparent estrogen receptor-mediated mechanism. We investigated differential susceptibility to EE in cell sub-populations from rat testes and the role of rat 8-oxo-guanine DNA glycosylase (rOGG1). Isolated rat testicular cells were incubated with EE concentrations ranging from 0.1 to 1000 nM. Single strand DNA breaks and oxidised purines as fapyguanine glycosylase (FPG) sensitive sites were assessed by the comet assay. In the total cell population and in round haploid cells, oxidised purines showed a bell-shaped concentration-response relationship with a maximally increased levels at 10 nM EE, whereas, no significant effects were seen in diploid, S-phase or tetraploid cells. The mRNA level of rOGG1 in testes cells was unaffected by EE, whereas, baseline levels were higher than in liver tissue and similar to colon tissue.

Animals↗

PubMed2004

Low CYP1A2 activity associated with testicular cancer.

The incidence rate of testicular cancer has increased during the last 50 years. An interplay between changing environmental factors and individual susceptibility, e.g. in foreign compound metabolizing enzymes, may have important influences on the risk of testicular cancer. The cytochrome P4501A2 (CYP1A2) enzyme and the bimodally expressed enzyme N-acetyltransferase2 (NAT2) metabolize many procarcinogens/carcinogens. The aim of this population-based case-control study was to investigate if CYP1A2 or NAT2 activity measured as a ratio of urinary metabolites of dietary caffeine is a risk factor in testicular cancer. 378 men participated (80 seminomas, 104 non-seminomas and 194 controls). The CYP1A2 activity was lower in the cases than in the controls [median and 30-70% percentiles: 4.7 (3.9-5.7) and 5.2 (4.4-6.4), respectively]. The subjects were classified in tertiles with low, medium or high CYP1A2 activity. A low CYP1A2 activity was associated with the highest risk of testicular cancer. Including all participants except men using drugs suspected to influence CYP1A2 activity (n = 15), medium and low activity conferred odds ratios (ORs) of 1.54 [confidence intervals of 95% (CI(95%)) 0.93-2.55] and 2.11; CI(95%) (1.23-3.62), respectively, of having testicular cancer. Excluding smokers (n = 157) the ORs of medium and low activity were 3.63; CI(95%) (1.53-8.60) and 4.70; CI(95%) (2.03-10.89), respectively. After further exclusion of cases that had received chemotherapy or radiation (n = 47), similar significant results were achieved. In the groups with the lowest CYP1A2 activity the ORs for seminoma and non-seminoma were 2.12; CI(95%) (0.93-4.81) and 2.10; CI(95%) (1.02-4.32). The phenotype of NAT2 was not associated with testicular cancer. In conclusion, we found no association of NAT2 phenotype to testicular cancer, whereas significant associations between CYP1A2 activity and testicular cancer were shown.

Adult↗

PubMed2004

Urinary 1-hydroxypyrene and mutagenicity in bus drivers and mail carriers exposed to urban air pollution in Denmark.

BACKGROUND: Previous studies in Denmark have shown that bus drivers and tramway employees were at an increased risk for developing several types of cancer and that bus drives from central Copenhagen have high levels of biomarkers of DNA damage. AIMS: The present study evaluates 1-hydroxypyrene concentrations and mutagenic activity in urine as biomarkers of exposure in non-smoking bus drivers in city and rural areas on a work day and a day off and in non-smoking mail carriers working outdoors (in the streets) and indoors (in the office). METHODS: Twenty-four hour urine samples were collected on a working day and a day off from 60 non-smoking bus drivers in city and rural areas and from 88 non-smoking mail carriers working outdoors (in the streets) and indoors (in the office). The concentration of 1-hydroxypyrene was measured by means of HPLC and the mutagenic activity was assessed by the Ames assay with Salmonella tester strain YG1021 and S9 mix. The N-acetyltransferase (NAT2) phenotype was used as a biomarker for susceptibility to mutagenic/carcinogenic compounds. RESULTS: Bus drivers excreted more 1-hydroxypyrene in urine than did mail carriers. The differences were slightly smaller when NAT2 phenotype, cooking at home, exposure to vehicle exhaust, and performing physical exercise after work were included. The NAT2 slow acetylators had 29% (1.29 [CI: 1.15-1.98]) higher 1-hydroxypyrene concentrations in urine than the fast acetylators. Male bus drivers had 0.92 revertants/mol creatinine [CI: 0.37-1.47] and female bus drivers 1.90 revertants/mol creatinine [CI: 1.01-2.79] higher mutagenic activity in urine than mail carriers. CONCLUSION: The present study indicates that bus drivers are more exposed to polycyclic aromatic hydrocarbons (PAH) and mutagens than mail carriers. Mail carriers who worked outdoors had higher urinary concentration of 1-hydroxypyrene, a marker of exposure to PAH, than those working indoors. The individual levels of urinary mutagenic activity were not correlated to excretion of 1-hydroxypyrene. This might be due to the fact that the most potent mutagenic compounds in diesel exhaust are not PAH but dinitro-pyrenes. Among bus drivers, fast NAT2 acetylators had higher mutagenic activity in urine than slow NAT2 acetylators and female bus drivers had higher mutagenic activity than male bus drivers.

Adult↗

PubMed2004

Vitamin C supplementation decreases oxidative DNA damage in mononuclear blood cells of smokers.

BACKGROUND: Antioxidants, in particular vitamin C, have been suggested to decrease oxidative DNA damage. Such effects have been shown in mononuclear blood cells in the first few hours after ingestion, whereas studies of longer-term effects in well-nourished humans have been mainly negative. AIM: To investigate the antioxidant effect of vitamin C in terms of oxidative DNA damage measured by the comet assay and DNA repair measured by expression of OGG1 mRNA in blood cells of male smokers given 2 x 250 mg vitamin C daily as plain or slow release tablets combined with plain release vitamin E 2 x 91 mg, or placebo for 4 wk. RESULTS: This study showed a difference in DNA protective effects between a slow release and a plain release vitamin C formulation. Ingestion of slow release vitamin C formulation was associated with fewer endonuclease III and formamidopyrimidine DNA glycosylase sensitive sites measured by the comet assay in mononuclear blood cells obtained 4 h and 8 h after a single tablet and 4 wk after two tablets a day. Ingestion of the vitamin formulation with plain release only indicated a damage-reducing effect 4 h after intake of a single tablet, and the effect was more apparent on endonuclease III than formamidopyrimidine DNA glycosylase sites. Overall the slow release tablets of vitamin C formulation had a more pronounced and a sustained protective effect on base damage compared with the plain release tablets. Plasma vitamin E was unaltered in the first 12 h after ingestion of a single tablet, suggesting that the antioxidant effect was mediated by vitamin C. Differences in plasma vitamin C levels at steady state could not explain the difference between the two vitamin C formulations, whereas wider amplitudes of plasma vitamin C were seen after ingestion of plain release formulation compared to slow release formulation. Assessment of OGG1 mRNA levels by RT-PCR did not indicate increased expression of this DNA repair gene after 4 wk of vitamin supplementation. CONCLUSION: This study suggests that long-term vitamin C supplementation at high dose, i. e. 500 mg together with vitamin E in moderate dose, 182 mg, decreases the steady-state level of oxidative DNA damage in mononuclear blood cells of smokers.

Adult↗

PubMed2004

Intra-laboratory comet assay sample scoring exercise for determination of formamidopyrimidine DNA glycosylase sites in human mononuclear blood cell DNA.

Oxidative DNA damage detected by the comet assay as formamidopyrimidine DNA glycosylase (FPG) sensitive sites, almost as a rule is reported as comet assay score rather than numerical sites in the genome, probably because the latter requires X-ray calibration. We compared the ability of five experienced and five inexperienced comet assay investigators to detect a dose-response relationship in irradiated A549 lung epithelial cell culture samples (0, 10 Gy and three samples of 5 Gy), based on an arbitrary five class scoring system. The samples were scored on three different occasions, thus allowing determination of the variation in sample scoring. All investigators qualitatively distinguished between samples in a dose-dependent manner, albeit with large variation in the slope and intercept of dose-response curves. There was a tendency that investigators with experience in scoring A549 cells had more consistent results than experienced investigators who had only scored lymphocytes or inexperienced investigators. The inexperienced investigators improved their scoring ability during the three sessions. Subsequently we showed that the variation in baseline level of FPG modifications in mononuclear blood cells of five healthy humans was lower when investigators used their individual X-ray calibration curve as compared to a common calibration curve. In conclusion, this study showed that comet assay investigators score differently when using a five class scoring system, which indicates that more consistent estimations of FPG sites in the genome are obtained by use of investigators' individual X-ray calibrations.

Calibration↗

PubMed2004

The 6-a-day study: effects of fruit and vegetables on markers of oxidative stress and antioxidative defense in healthy nonsmokers.

BACKGROUND: Fruit and vegetables contain both nutritive and nonnutritive factors that might contribute to redox (antioxidant and prooxidant) actions. OBJECTIVE: We investigated the relative influence of nutritive and nonnutritive factors in fruit and vegetables on oxidative damage and enzymatic defense. DESIGN: A 25-d intervention study with complete control of dietary intake was performed in 43 healthy male and female nonsmokers who were randomly assigned to 1 of 3 groups. In addition to a basic diet devoid of fruit and vegetables, the fruit and vegetables (Fruveg) group received 600 g fruit and vegetables/d; the placebo group received a placebo pill, and the supplement group received a vitamin pill designed to contain vitamins and minerals corresponding to those in 600 g fruit and vegetables. Biomarkers of oxidative damage to protein and lipids and of antioxidant nutrients and defense enzymes were determined before and during intervention. RESULTS: Plasma lipid oxidation lag times increased during intervention in the Fruveg and supplement groups, and the increase was significantly higher in the former. Plasma protein carbonyl formation at lysine residues also increased in both of these groups. Glutathione peroxidase activity increased in the Fruveg group only. Other markers of oxidative damage, oxidative capacity, or antioxidant defense were largely unaffected by the intervention. CONCLUSIONS: Fruit and vegetables increase erythrocyte glutathione peroxidase activity and resistance of plasma lipoproteins to oxidation more efficiently than do the vitamins and minerals that fruit and vegetables are known to contain. Plasma protein carbonyl formation at lysine residues increases because of the vitamins and minerals in fruit and vegetables.

Adult↗

PubMed2004

Benzene exposure assessed by metabolite excretion in Estonian oil shale mineworkers: influence of glutathione s-transferase polymorphisms.

Measurement of urinary excretion of the benzene metabolites S-phenylmercapturic acid (S-PMA) and trans,trans-muconic acid (t,t-MA) has been proposed for assessing benzene exposure, in workplaces with relatively high benzene concentrations. Excretion of S-PMA and t,t-MA in underground workers at an oil shale mine were compared with the excretion in workers engaged in various production assignments above ground. In addition, possible modifying effects of genetic polymorphisms in glutathione S-transferases T1 (GSTT1), M1 (GSTM1), and P1 (GSTP1) on the excretion of S-PMA and t,t-MA were investigated. Fifty underground workers and 50 surface workers participated. Blood samples and three urine samples were collected from each worker: (a) a preshift sample collected the morning after a weekend, (b) a postshift sample 1 collected after the first shift, and (c) a postshift sample 2 collected after the last shift of the week. Personal benzene exposure was 114 +/- 35 mug/m(3) in surface workers (n = 15) and 190 +/- 50 mug/m(3) in underground workers (n = 15) in measurements made prior to the study. We found t,t-MA excretion to be significantly higher in underground workers after the end of shifts 1 and 2 compared with the corresponding surface workers. The same picture, although not significant, was seen for S-PMA excretion. Excretion of S-PMA and t,t-MA was found to increase significantly during the working week in underground workers but not in those employed on the surface. Both t,t-MA and S-PMA excretion were significantly higher in smokers compared with nonsmokers. Subjects carrying the GSTT1 wild-type excreted higher concentrations of S-PMA than subjects carrying the null genotype, suggesting that it is a key enzyme in the glutathione conjugation that leads to S-PMA. The results support the use of benzene metabolites as biomarkers for assessment of exposure at modest levels and warrant for further investigations of health risks of occupational benzene exposure in shale oil mines.

Acetylcysteine↗

PubMed2004

Plasma enterolactone and breast cancer incidence by estrogen receptor status.

The phytoestrogen enterolactone has been hypothesized to prevent breast cancer. Because one of the biological effects of enterolactone is probably estrogenic, it is possible that the preventive effect on breast cancer differs with the estrogen receptor (ER) alpha status of the tumor. The objective of this study was to investigate whether high plasma levels of enterolactone are associated with breast cancer risk and whether the ERalpha status of the tumor influences this relation. The cohort study Diet, Cancer and Health included 29,785 women, ages 50 to 64 years, between 1993 and 1997. Information about diet and life-style factors was obtained by questionnaire, and blood was drawn from each participant. We matched 381 postmenopausal breast cancer cases to 381 controls and analyzed the concentration of enterolactone in plasma with a time-resolved fluoroimmunoassay. Associations between plasma concentrations of enterolactone and breast cancer were analyzed by logistic regression. The incidence rate ratio (IRR) for all breast cancer was 0.93 [95% confidence interval (CI), 0.86-1.01] per 20 nmol/L higher plasma concentration of enterolactone. For ERalpha-positive cancers (n=273) only a weak association was seen (IRR, 0.97; 95% CI, 0.88-1.06), whereas for ERalpha-negative cancers (n = 80; IRR, 0.71; 95% CI, 0.53-0.94) a protective effect was seen per 20 nmol/L higher plasma enterolactone. In accordance with earlier research, we found a tendency toward a lower risk for breast cancer with higher concentrations of enterolactone, which was restricted almost entirely to ERalpha-negative breast cancer.

4-Butyrolactone↗

PubMed2003

Comparison of chlorzoxazone one-sample methods to estimate CYP2E1 activity in humans.

OBJECTIVE: Comparison of a one-sample with a multi-sample method (the metabolic fractional clearance) to estimate CYP2E1 activity in humans. METHODS: Healthy, male Caucasians ( n=19) were included. The multi-sample fractional clearance (Cl(fe)) of chlorzoxazone was compared with one-time-point clearance estimation (Cl(est)) at 3, 4, 5 and 6 h. Furthermore, the metabolite/drug ratios (MRs) estimated from one-time-point samples at 1, 2, 3, 4, 5 and 6 h were compared with Cl(fe). RESULTS: The concordance between Cl(est) and Cl(fe) was highest at 6 h. The minimal mean prediction error (MPE) of Cl(est) as a percentage of actual mean Cl(fe) was -4.2% at 6 h. Furthermore, regarding Cl(fe), there was a negligible difference ( P=0.56) of bias between Cl(est) at 3 h (MPE=-8.9%) and 6 h (MPE=-4.2%). The best concordance between MR and Cl(fe) was found at 3 h (r=0.74; P<0.001). CONCLUSION: All three single-dose-sample estimates, Cl(est) at 3 h or 6 h, and MR at 3 h, can serve as reliable markers of CYP2E1 activity. The one-sample clearance method is an accurate, renal function-independent measure of the intrinsic activity; it is simple to use and easily applicable to humans.

Administration, Oral↗

PubMed2003

Oxidative DNA damage and repair in skeletal muscle of humans exposed to high-altitude hypoxia.

Recent research suggests that high-altitude hypoxia may serve as a model for prolonged oxidative stress in healthy humans. In this study, we investigated the consequences of prolonged high-altitude hypoxia on the basal level of oxidative damage to nuclear DNA in muscle cells, a major oxygen-consuming tissue. Muscle biopsies from seven healthy humans were obtained at sea level and after 2 and 8 weeks of hypoxia at 4100 m.a.s.l. We found increased levels of strand breaks and endonuclease III-sensitive sites after 2 weeks of hypoxia, whereas oxidative DNA damage detected by formamidopyrimidine DNA glycosylase (FPG) protein was unaltered. The expression of 8-oxoguanine DNA glycosylase 1 (OGG1), determined by quantitative RT-PCR of mRNA levels did not significantly change during high-altitude hypoxia, although the data could not exclude a minor upregulation. The expression of heme oxygenase-1 (HO-1) was unaltered by prolonged hypoxia, in accordance with the notion that HO-1 is an acute stress response protein. In conclusion, our data indicate high-altitude hypoxia may serve as a good model for oxidative stress and that antioxidant genes are not upregulated in muscle tissue by prolonged hypoxia despite increased generation of oxidative DNA damage.

Adaptation, Physiological↗

PubMed2003

Dietary elevated sucrose modulation of diesel-induced genotoxicity in the colon and liver of Big Blue rats.

Earlier studies have indicated that sucrose possesses either co-carcinogenic or tumor-promoter effects in colon carcinogenesis induced by genotoxic carcinogens. In this study we investigated the role of sucrose on diesel exhaust particle (DEP)-induced genotoxicity in the colonic mucosa and liver. Big Blue rats were fed with DEP (0.8 ppm in feed) and/or sucrose (3.45% or 6.85% w/w in feed) for 3 weeks. DEP increased both DNA strand breaks and DNA adducts in colon. Interestingly, sucrose also increased the level of bulky DNA adducts in colon. DEP and sucrose had no effect on DNA strand-breaks and DNA adducts in liver. DEP and sucrose treatment did not have any effect on mutation frequency in colon and liver. Oxidative DNA damage detected as 8-oxodG (8-oxo-7,8-dihydro-2'-deoxyguanosine) and endonuclease III or formamidopyrimidine DNA glycosylase sensitive sites was unaltered in colon and liver. The mRNA expression levels of the DNA repair enzymes N-methylpurine DNA glycosylase ( MPG), 8-oxoguanine DNA glycosylase ( OGG1) and ERCC1 (part of the nucleotide excision repair complex) measured by reverse transcription-polymerase chain reaction were increased in liver by DEP feeding. In colon, expression was unaffected by DEP or sucrose feeding. Among biomarkers of oxidative stress, including vitamin C, malondialdehyde and protein oxidations (gamma-glutamyl semialdehyde and 2-amino adipic semialdehyde) in plasma and liver, only malondialdehyde was increased in plasma by sucrose/DEP feeding. In conclusion, sucrose feeding did not increase DEP-induced DNA damage in colon or liver.

Animals↗

PubMed2003

Oxidative DNA damage and defence gene expression in the mouse lung after short-term exposure to diesel exhaust particles by inhalation.

Exposure to diesel exhaust particles (DEP) is suspected to contribute to lung cancer and cardiopulmonary diseases. In recent years generation of reactive oxygen species capable of inducing cellular oxidative stress has been in focus as one of the underlying mechanisms behind the genotoxic effects of particles. However, the role of the antioxidative defence system still needs to be clarified, especially in relation to low-dose DEP exposures. The aim of this study was to characterize the effects of short-term exposure to DEP in terms of DNA damage and expression of key response genes towards oxidative stress in lungs of mice. Mice were exposed by inhalation to 20 or 80 mg/m3 DEP inhaled as either a single dose, or four lower doses (5 and 20 mg/m3) inhaled on four consecutive days. Our results indicate that HO-1 mRNA expression in lung tissue was up-regulated after both types of DEP exposures, whereas OGG1 expression was only up-regulated after repeated exposures. The level of oxidative DNA damage in terms of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) was increased in the lung tissue after a single exposure, whereas increased levels of DNA strand breaks was observed in bronchoalveolar lavage cells after repeated DEP exposures. The levels of 8-oxodG and OGG1 mRNA in lung tissue were mirror images. This suggests that after repeated exposures, up-regulation of DNA repair counteracts an increased rate of 8-oxodG formation leaving the steady state level of 8-oxodG in DNA unchanged. In conclusion, this study indicates that a single high dose of DEP generates 8-oxodG in lung tissue, whereas the same dose inhaled as four low-exposures may up-regulate the antioxidative defence system and protect against generation of 8-oxodG.

Animals↗

PubMed2003

DNA adduct formation and oxidative stress in colon and liver of Big Blue rats after dietary exposure to diesel particles.

Exposure to diesel exhaust particles (DEP) via the gastrointestinal route may impose risk of cancer in the colon and liver. We investigated the effects of DEP given in the diet to Big Blue rats by quantifying a panel of markers of DNA damage and repair, mutation, oxidative damage to proteins and lipids, and antioxidative defence mechanisms in colon mucosa cells, liver tissue and the blood compartment. Seven groups of rats were fed a diet with 0, 0.2, 0.8, 2, 8, 20 or 80 mg DEP/kg feed for 21 days. DEP induced a significant increase in DNA strand breaks in colon and liver. There was no effect on oxidative DNA damage (8-oxodG) in colon or liver DNA or in the urine. However, the mRNA expression of OGG1, encoding an enzyme involved in repair of 8-oxodG, was increased by DEP in both liver and colon. DNA adduct levels measured by 32P-post-labelling were elevated in colon and liver, and the expression of ERCC1 gene was affected in liver, but not in colon. In addition to these effects, DEP exposure induced apoptosis in liver. There was no significant change in mutation frequency in colon or liver. The levels of oxidative protein modifications (oxidized arginine and proline residues) were increased in liver accompanied by enhanced vitamin C levels. In plasma, we found no significant effects on oxidative damage to proteins and lipids, antioxidant enzymes or vitamin C levels. Our data indicate that gastrointestinal exposure to DEP induces DNA adducts and oxidative stress resulting in DNA strand breaks, enhanced repair capacity of oxidative base damage, apoptosis and protein oxidation in colon mucosa cells and liver.

Animals↗