Protection of Taurine Against Arsenic-Induced DNA Damage of Mice Kidneys

The purpose of this study was to explore the protective capacity of taurine on arsenic (As)-induced neurotoxicity. Thirty mice were used and ten rats in each group. We treated the As exposure group with 4 ppm As2O3 for 60 days by drinking water and the protective group with 4 ppm As2O3 and 150 mg/kg taurine. Drinking water was only given in the control group. Pathologic changes and DNA damage in the mice kidney were examined by HE staining, immunohistochemistry and comet assay. Abnormal morphological changes were found in the kidney of As exposed mouse. Moreover, 8-hydroxy-2-deoxyguanosine (8-OHdG) expression and comet number, tail moment, and tail length of comet were markedly elevated in the As intoxication mice. However, histopathological changes and low expression of 8-OHdG were shown in the protective group. Our results indicate that supplementation of taurine protects against the histopathologic changes and DNA damage of mouse kidneys in As exposure group.

Translesion Synthesis of the N(2)-2'-Deoxyguanosine Adduct of the Dietary Mutagen IQ in Human Cells: Error-Free Replication by DNA Polymerase κ and Mutagenic Bypass by DNA Polymerases η, ζ, and Rev1

Translesion synthesis (TLS) of the N(2)-2'-deoxyguanosine (dG-N(2)-IQ) adduct of the carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) was investigated in human embryonic kidney 293T cells by replicating plasmid constructs in which the adduct was individually placed at each guanine (G1, G2, or G3) of the NarI sequence (5'-CG1G2CG3CC-3'). TLS efficiency was 38%, 29%, and 25% for the dG-N(2)-IQ located at G1, G2, and G3, respectively, which suggests that dG-N(2)-IQ is bypassed more efficiently by one or more DNA polymerases at G1 than at either G2 or G3. TLS efficiency was decreased 8-35% in cells with knockdown of pol η, pol κ, pol ι, pol ζ, or Rev1. Up to 75% reduction in TLS occurred when pol η, pol ζ, and Rev1 were simultaneously knocked down, suggesting that these three polymerases play important roles in dG-N(2)-IQ bypass. Mutation frequencies (MFs) of dG-N(2)-IQ at G1, G2, and G3 were 23%, 17%, and 11%, respectively, exhibiting a completely reverse trend of the previously reported MF of the C8-dG adduct of IQ (dG-C8-IQ), which is most mutagenic at G3 ( ( 2015 ) Nucleic Acids Res. 43 , 8340 - 8351 ). The major type of mutation induced by dG-N(2)-IQ was targeted G → T, as was reported for dG-C8-IQ. In each site, knockdown of pol κ resulted in an increase in MF, whereas MF was reduced when pol η, pol ι, pol ζ, or Rev1 was knocked down. The reduction in MF was most pronounced when pol η, pol ζ, and Rev1 were simultaneously knocked down and especially when the adduct was located at G3, where MF was reduced by 90%. We conclude that pol κ predominantly performs error-free TLS of the dG-N(2)-IQ adduct, whereas pols η, pol ζ, and Rev1 cooperatively carry out the error-prone TLS. However, in vitro experiments using yeast pol ζ and κ showed that the former was inefficient in full-length primer extension on dG-N(2)-IQ templates, whereas the latter was efficient in both error-free and error-prone extensions. We believe that the observed differences between the in vitro experiments using purified DNA polymerases, and the cellular results may arise from several factors including the crucial roles played by the accessory proteins in TLS.

Hyperglycemia Induces Cellular Hypoxia through Production of Mitochondrial ROS Followed by Suppression of Aquaporin-1

We previously proposed that hyperglycemia-induced mitochondrial reactive oxygen species (mtROS) generation is a key event in the development of diabetic complications. Interestingly, some common aspects exist between hyperglycemia and hypoxia-induced phenomena. Thus, hyperglycemia may induce cellular hypoxia, and this phenomenon may also be involved in the pathogenesis of diabetic complications. In endothelial cells (ECs), cellular hypoxia increased after incubation with high glucose (HG). A similar phenomenon was observed in glomeruli of diabetic mice. HG-induced cellular hypoxia was suppressed by mitochondria blockades or manganese superoxide dismutase (MnSOD) overexpression, which is a specific SOD for mtROS. Overexpression of MnSOD also increased the expression of aquaporin-1 (AQP1), a water and oxygen channel. AQP1 overexpression in ECs suppressed hyperglycemia-induced cellular hypoxia, endothelin-1 and fibronectin overproduction, and apoptosis. Therefore, hyperglycemia-induced cellular hypoxia and mtROS generation may promote hyperglycemic damage in a coordinated manner.

Expression of age-related factors during the development of renal damage in patients with IgA nephropathy

BACKGROUND

Chronic kidney disease patients share clinical and pathological features with the general aging population. Increased oxidative DNA damage, accumulation of cell cycle-arrested cells and decreased Klotho expression are assumed to be age-related factors that are reportedly linked to kidney disease. This study sought to determine the association between these age-related factors and renal damage in patients with IgA nephropathy (IgAN).

METHODS

We performed a cross-sectional analysis of 71 patients who were diagnosed with IgAN by renal biopsy. Expression of 8-hydroxydeoxyguanosine (8-OHdG, a marker of oxidative DNA damage), p16 (a marker of cell cycle-arrest) and Klotho (an anti-aging protein) were evaluated by immunohistochemical staining of renal biopsy samples. We correlated the changes in expression of these markers with Lee's pathologic grades and the Oxford classification. We also investigated the independent association between these markers and interstitial fibrosis using multiple linear regression analysis.

RESULTS

8-OHdG and p16 increased but Klotho decreased with progression of pathologic grade. Expression of 8-OHdG and p16 increased with the deterioration of mesangial hypercellularity and segmental glomerulosclerosis. In addition, p16 increased but Klotho decreased with progression of tubular atrophy/interstitial fibrosis. In univariate regression analysis, age, body mass index, systolic blood pressure, urinary protein excretion and expression of 8-OHdG, p16 and Klotho showed significant correlations with interstitial fibrosis. Multivariable regression analyses revealed that aging, increased renal expression of p16 and decreased expression of Klotho were independently correlated with interstitial fibrosis.

CONCLUSIONS

The age-related factors might play important roles in the development of IgAN.

In vivo detection of a novel endogenous etheno-DNA adduct derived from arachidonic acid and the effects of antioxidants on its formation

Previous studies showed that 7-(1',2'-dihydroxyheptyl)-substituted etheno DNA adducts are products of reactions with the epoxide of (E)-4-hydroxy-2-nonenal, an oxidation product of ω-6 polyunsaturated fatty acids (PUFAs). In this work, we report the detection of 7-(1',2'-dihydroxyheptyl)-1,N(6)-ethenodeoxyadenosine (DHHedA) in rodent and human tissues by two independent methods: a (32)P-postlabeling/HPLC method and an isotope dilution liquid chromatography-electrospray ionization-tandem mass spectrometry method, demonstrating for the first time that DHHedA is a background DNA lesion in vivo. We showed that DHHedA can be formed upon incubation of arachidonic acid with deoxyadenosine, supporting the notion that ω-6 PUFAs are the endogenous source of DHHedA formation. Because cyclic adducts are derived from the oxidation of PUFAs, we subsequently examined the effects of antioxidants, α-lipoic acid, Polyphenon E, and vitamin E, on the formation of DHHedA and γ-hydroxy-1,N(2)-propanodeoxyguanosine (γ-OHPdG), a widely studied acrolein-derived adduct arising from oxidized PUFAs, in the livers of Long Evans Cinnamon (LEC) rats. LEC rats are afflicted with elevated lipid peroxidation and prone to the development of hepatocellular carcinomas. The results showed that although the survival of LEC rats was increased significantly by α-lipoic acid, none of the antioxidants inhibited the formation of DHHedA, and only Polyphenon E decreased the formation of γ-OHPdG. In contrast, vitamin E caused a significant increase in the formation of both γ-OHPdG and DHHedA in the livers of LEC rats.

Selenium compound protects corneal epithelium against oxidative stress

The ocular surface is strongly affected by oxidative stress, and anti-oxidative systems are maintained in corneal epithelial cells and tear fluid. Dry eye is recognized as an oxidative stress-induced disease. Selenium compound eye drops are expected to be a candidate for the treatment of dry eye. We estimated the efficacy of several selenium compounds in the treatment of dry eye using a dry eye rat model. All of the studied selenium compounds were uptaken into corneal epithelial cells in vitro. However, when the selenium compounds were administered as eye drops in the dry eye rat model, most of the selenium compounds did not show effectiveness except for Se-lactoferrin. Se-lactoferrin is a lactoferrin that we prepared that binds selenium instead of iron. Se-lactoferrin eye drops suppressed the up-regulated expression of heme oxygenase-1, cyclooxygenase-2, matrix metallopeptidase-9, and interleukin-6 and also suppressed 8-OHdG production in the cornea induced by surgical removal of the lacrimal glands. Compared with Se-lactoferrin, apolactoferrin eye drops weakly improved dry eye in high dose. The effect of Se-lactoferrin eye drops on dry eye is possibly due to the effect of selenium and also the effect of apolactoferrin. Se-lactoferrin is a candidate for the treatment of dry eye via regulation of oxidative stress in the corneal epithelium.

Cigarette smoke condensate-induced oxidative DNA damage and its removal in human cervical cancer cells

Exposure to cigarette smoke is well documented to increase oxidative stress and could account for higher risk of cervical cancer in smokers. Cervical pre-cancerous lesions that are initiated by human papillomavirus (HPV) infection generally regress in the absence of known risk factors such as smoking. 8-oxodeoxyguanosine (8-oxodG) is a highly mutagenic oxidative DNA lesion that is formed by the oxidation of deoxyguanosine. In the present study, we examined: a) the effect of cigarette smoke condensate (CSC) on 8-oxodG formation in and its removal from HPV-transfected (ECT1/E6 E7), HPV-positive (CaSki) and HPV-negative (C33A) human cervical cancer cells, and b) the cell cycle progression and apoptosis in CSC-treated ECT1/E6 E7 cells. CSC induced 8-oxodG in a dose- (p=0.03) and time (p=0.002)-dependent fashion in ECT1/E6 E7 cells as determined by flow cytometry. A 2.4-fold higher level of 8-oxodG was observed in HPV-positive compared with HPV-negative cells. However, 8-oxodG lesions were almost completely removed 72 h post-exposure in all cell lines as determined by ImageStream analysis. This observation correlates with the 2- and 5-fold increase in the p53 levels in ECT1/E6 E7 and CaSki cells with no significant change in C33A cells. We conclude that: a) cigarette smoke constituents induce oxidative stress with higher burden in HPV-positive cervical cancer cells and b) the significant increase observed in p53 levels in wild-type cervical cells (ECT1/E6 E7 and CaSki) may be attributed to the p53-dependent DNA repair pathway while a p53-independent pathway in C33A cells cannot be ruled out.

Reduced DNA oxidation in aged prostaglandin H synthase-1 knockout mice

Prostaglandin H synthase (PHS)-2 (COX-2) is implicated in the neurodegeneration of Alzheimer and Parkinson diseases. Multiple mechanisms may be involved, including PHS-catalyzed bioactivation of neurotransmitters, precursors, and metabolites to neurotoxic free radical intermediates. Herein, in vitro studies with the purified PHS-1 (COX-1) isoform and in vivo studies of aging PHS-1 knockout mice were used to evaluate the potential neurodegenerative role of PHS-1-catalyzed bioactivation of endogenous neurotransmitters to free radical intermediates that enhance reactive oxygen species formation and oxidative DNA damage. The brains of 2-year-old wild-type (+/+) PHS-1 normal and heterozygous (+/-) and homozygous (-/-) PHS-1 knockout mice were analyzed for 8-oxo-2'-deoxyguanosine formation, characterized by high-performance liquid chromatography with electrochemical detection and by immunohistochemistry. Compared to aging PHS-1(+/+) normal mice, aging PHS-1(-/-) knockout mice had less oxidative DNA damage in the cortex, hippocampus, cerebellum, and brain stem. This PHS-1-dependent oxidative damage was not observed in young mice. In vitro incubation of purified PHS-1 and 2'-deoxyguanosine with dopamine, L-DOPA, and epinephrine, but not glutamate or norepinephrine, enhanced oxidative DNA damage. These results suggest that PHS-1-dependent accumulation of oxidatively damaged macromolecules including DNA may contribute to the mechanisms and risk factors of aging-related neurodegeneration.

Increased testicular 8-hydroxy-2'-deoxyguanosine (8-OHdG) and inducible nitric oxide synthetase (iNOS) and nuclear factor κB (NF-κB) expressions in experimental rat varicocele

OBJECTIVES

To assess nuclear factor-kappaB (NF-kappaB), inducible NO synthase (iNOS) immunohistochemically, and 8-hydroxy-2'-deoxyguanosine (8-OHdG) biochemically, which are sensitive biological markers of oxidative damage and stress, in testes with experimental varicocele.

MATERIALS AND METHODS

Adult rats were randomly divided into three groups. Control group (n: 10), sham group (n: 10), varicocele group (n: 10). Of 14 rats undergoing partial ligation of the left renal vein, 10 rats had developed dilation of the left spermatic vein when evaluated 3 months after varicocele-inducing surgery. The rats were sacrificed after 3 months of the varicocele-inducing surgery. Ipsilateral and contralateral testes were examined for 8-hydroxy-2'-deoxyguanosine (8-OHdG) biochemically, inducible NO synthase (iNOS) and nuclear factor-kappaB (NF-kappaB) expression immunohistochemically.

RESULTS

Inducible NO synthase (iNOS), nuclear factor-kappaB (NF-kappaB) expressions and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels in both testes of varicocele group were markedly higher compared with control and sham groups (p < 0.01). There was no difference between control and sham groups (p > 0.05).

CONCLUSIONS

Regarding to our results, we suggest that varicocele may produce oxidative stress in both of testes, and we believe that this stress may play a role in male fertility.

Mycorrhization alleviates benzo[a]pyrene-induced oxidative stress in an in vitro chicory root model

Among chemicals that are widely spread both in terrestrial and aquatic ecosystems, benzo[a]pyrene is a major source of concern. However, little is known about its adverse effects on plants, as well as about the role of mycorrhization in protection of plant grown in benzo[a]pyrene-polluted conditions. Hence, to contribute to a better understanding of the adverse effects of polycyclic aromatic hydrocarbons on the partners of mycorrhizal symbiotic association, benzo[a]pyrene-induced oxidative stress was studied in transformed Cichorium intybus roots grown in vitro and colonized or not by Glomus intraradices. The arbuscular mycorrhizal fungus development (colonization, extraradical hyphae length, and spore formation) was significantly reduced in response to increasing concentrations of benzo[a]pyrene (35-280 microM). The higher length of arbuscular mycorrhizal roots, compared to non-arbuscular mycorrhizal roots following benzo[a]pyrene exposure, pointed out a lower toxicity of benzo[a]pyrene in arbuscular mycorrhizal roots, thereby suggesting protection of the roots by mycorrhization. Accordingly, in benzo[a]pyrene-exposed arbuscular mycorrhizal roots, statistically significant decreases were observed in malondialdehyde concentration and 8-hydroxy-2'-desoxyguanosine formation. The higher superoxide dismutase activity detected in mycorrhizal chicory roots could explain the benzo[a]pyrene tolerance of the colonized roots. Taken together, these results support an essential role of mycorrhizal fungi in protecting plants submitted to polycyclic aromatic hydrocarbon, notably by reducing polycyclic aromatic hydrocarbon-induced oxidative stress damage.

Dual actions involved in arsenite-induced oxidative DNA damage

Arsenic is a recognized human carcinogen, but the mechanism of carcinogenesis is not well understood. Oxidative stress and inhibition of DNA damage repair have been postulated as potential carcinogenic actions of arsenic. The present study tests the hypothesis that arsenite not only induces oxidative stress but also inhibits the activity of the DNA base excision repair protein, poly(ADP-ribose) polymerase-1 (PARP-1), leading to exacerbation of the oxidative DNA damage induced by arsenic. HaCat cells were treated with arsenite for 24 h before measuring 8-hydroxyl-2'-deoxyguanosine (8-OHdG), PARP-1 activity, and reactive oxygen species (ROS). Zinc supplementation and PARP-1 siRNA were used to increase or decrease, respectively, the PARP-1 protein's physiological function. At high concentrations (10 microM or higher), arsenite greatly induced oxidative DNA damage, as indicated by 8-OHdG formation. At lower concentrations (1 microM), arsenite did not produce detectable 8-OHdG, but was still able to effectively inhibit PARP-1 activity. Zinc supplementation reduced the formation of 8-OHdG, restored the PARP-1 activity inhibited by arsenite, but did not decrease ROS production. SiRNA knockdown of PARP-1 did not affect the 8-OHdG level induced by arsenic, while it greatly increased the 8-OHdG level produced by hydrogen peroxide indicating that PARP-1 is a molecular target of arsenite. Our findings demonstrate that in addition to inducing oxidative stress at higher concentrations, arsenite can also inhibit the function of a key DNA repair protein, PARP-1, even at very low concentrations, thus exacerbating the overall oxidative DNA damage produced by arsenite, and potentially, by other oxidants as well.

Genetic ablation of NADPH oxidase enhances susceptibility to cigarette smoke-induced lung inflammation and emphysema in mice

Cigarette smoke (CS) induces recruitment of inflammatory cells in the lungs leading to the generation of reactive oxygen species (ROS), which are involved in lung inflammation and injury. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is a multimeric system that is responsible for ROS production in mammalian cells. We hypothesized that NADPH oxidase-derived ROS play an important role in lung inflammation and injury and that targeted ablation of components of NADPH oxidase (p47(phox) and gp91(phox)) would protect lungs against the detrimental effects of CS. To test this hypothesis, we exposed p47(phox-/-) and gp91(phox-/-) mice to CS and examined inflammatory response and injury in the lung. Surprisingly, although CS-induced ROS production was decreased in the lungs of p47(phox-/-) and gp91(phox-/-) mice compared with wild-type mice, the inflammatory response was significantly increased and was accompanied by development of distal airspace enlargement and alveolar destruction. This pathological abnormality was associated with enhanced activation of the TLR4-nuclear factor-kappaB pathway in response to CS exposure in p47(phox-/-) and gp91(phox-/-) mice. This phenomenon was confirmed by in vitro studies in which treatment of peritoneal macrophages with a nuclear factor-kappaB inhibitor reversed the CS-induced release of proinflammatory mediators. Thus, these data suggest that genetic ablation of components of NADPH oxidase enhances susceptibility to the proinflammatory effects of CS leading to airspace enlargement and alveolar damage.

Expression of 8-hydroxydeoxyguanosine in the gastric remnant after distal gastrectomy

BACKGROUND/AIMS

The correlation between remnant gastritis after distal gastrectomy for gastric cancer and expression of 8-hydroxydeoxyguanosine (8-OHdG) and inducible oxide synthase (iNOS) as a marker of oxidative DNA damage was investigated.

METHODOLOGY

Ninety-seven patients who had undergone curative distal gastrectomy for gastric cancer were studied. Reconstructive procedures included Billroth I, Billroth II, and Roux-Y reconstruction in 42, 27, and 28 patients, respectively. Histologic and immunohistochemical analyses were performed on biopsy specimens of the gastric mucosa obtained endoscopically within 2 weeks before and 12 weeks after surgery. The grades of remnant gastritis were evaluated according to the updated Sydney System. 8-OHdG and iNOS expression levels, detected immunohistochemically, were graded.

RESULTS

Neutrophil infiltration correlated with expression of 8-OHdG (p = 0.02). Expression of iNOS also correlated with 8-OHdG (p = 0.02). The ratio of postoperative to preoperative infiltration of neutrophils was less in patients who underwent Roux-Y reconstruction than in others (p = 0.04).

CONCLUSIONS

These results suggest that remnant gastritis possibly causes DNA damage. Excess production of reactive oxygen species correlates with carcinogenic DNA changes. Roux-Y reconstruction may reduce carcinogenesis in the gastric remnant.

Carvedilol, a pharmacological antioxidant, inhibits neointimal matrix metalloproteinase-2 and -9 in experimental atherosclerosis

Matrix metalloproteinase (MMP) is critical to the progression of atherosclerosis and neointima hyperplasia after vascular injury. We investigated the effects of carvedilol, a pharmacological antioxidant with alpha- and beta-adrenergic blocking activity, on MMP-2 and MMP-9 expression. Vascular injury was induced with the balloon catheters on abdominal aortas of high-cholesterol-fed rabbits. On Day 21, there was significant aortic neointima formation with increased oxidative DNA damage by immunostaining with 8-hydroxy-2'-deoxyguanosine and enhanced MMP-2 and MMP-9 expressions by Western blotting, which were significantly reduced by oral administration of carvedilol (20 mg/kg/day) or probucol (100 mg/kg/day). Vascular expression (by Western blot), activity (by gelatin zymography), and mRNA levels of MMP-2 and MMP-9 were also reduced by carvedilol or probucol. Besides, pretreatment with carvedilol or probucol but not propranolol, a beta-blocker, or prazocin, an alpha-blocker, inhibited tumor necrosis factor-alpha-stimulated expressions and activities of MMP-2 and MMP-9 in human aortic smooth muscle cells. On electrophoretic mobility-shift assay, carvedilol inhibited the binding activities of activator protein-1 and specific protein-1, two major transcription factors for MMP promoter regions. Accordingly, carvedilol, a pharmacological antioxidant, inhibited in vivo and in vitro expression of MMP-2 and MMP-9 properly by modulating the redox-related pathways, suggesting its potential clinical implications.

The expression of 8-hydroxydeoxyguanosine in oesophageal tissues and tumours

PURPOSE

The most common marker of oxidative DNA damage is 8-hydroxydeoxyguanosine (8-OHdG), which is linked with several malignancies. In the present study we investigated whether DNA damage linked to oxidative stress (as 8-OHdG) is present in Barrett's mucosa with or without associated adenocarcinoma or high-grade dysplasia and in normal controls' squamous mucosa.

EXPERIMENTAL DESIGN

We measured 8-OHdG in 51 patients (13 Barrett's metaplasia, six Barrett's oesophagus with high-grade dysplasia, 18 adenocarcinoma of the distal oesophagus/oesophagogastric junction and 14 normal controls). The amount of DNA damage was determined by high-performance liquid chromatography in oesophagus samples obtained either from endoscopy or as samples from surgery. The median 8-OHdG concentration was expressed as the ratio of 8-OHdG per 10(5) deoxyguanosine.

RESULTS

Analysis revealed that 8-OHdG was present in both Barrett's metaplasia with and without dysplasia as well as in adenocarcinoma of the oesophagus/oesophagogastric junction. Although the study group was small the amount of 8-OHdG was significantly increased in the distal oesophagus both in Barrett's epithelium 1.26 (0.08-29.47) and in high-grade dysplasia 1.35 (1.04-1.65) as well as in adenocarcinoma of oesophagus/oesophagogastric junction 1.08 (0.59-1.94) compared to controls 0.06 (0-4.08) (p=0.002, p=0.012, p=0.001, respectively). Barrett's patients had no significant difference in 8-OHdG levels between their distal and proximal oesophageal samples.

CONCLUSIONS

Our results show the presence of oxidative DNA damage in the distal oesophagus of patients with Barrett's oesophagus and adenocarcinoma of the oesophagus/oesophagogastric junction. This may have a connection to carcinogenesis in Barrett's oesophagus.

Changes in the antioxidant defense and hepatic drug metabolizing enzyme and isoenzyme levels, 8-hydroxydeoxyguanosine formation and expressions of c-raf.1 and insulin-like growth factor II genes during the stages of development of hepatocellular carcinoma in rats

This is an extensive study in a defined initiation-promotion hepatocellular carcinoma model of hepatocarcinogenesis (in rats) in which many important marker enzymes and isoenzymes and 8-hydroxydeoxyguanosine formation have been studied together with two very important cellular proliferating genes, insulin-like growth factor II and c-raf.1, known for their role in hepatocellular cancer development. Experiments were carried out on hepatic tissues of male Sprague-Dawley rats. Variations in different enzyme/isoenzyme activities/contents/expression pattern and 8-hydroxydeoxyguanosine-positive cells were studied. Insulin-like growth factor II and c-raf.1 gene expressions were monitored. A direct shift with increase in size and numbers of lesions was found to occur in different experimental groups. In this study, glutathione peroxidase (1.14 and 1.46-fold) and reduced triphosphopyridine nucleotide (TPNH)-cytochrome-c-reductase (1.94 and 2.94-fold) activities, cytochrome b5 (1.57 and 3.28-fold) and P-450 contents (1.45 and 1.22-fold), glutathione content (1.27 and 1.45-fold) and superoxide dismutase and catalase (1.16 and 1.39-fold) activities in group A animals were found to be lower than those in initiation and promotion studies, respectively. 8-Hydroxydeoxyguanosine-positive nuclei count showed that oxidative damage of nuclear DNA enhanced with the progress of the disease. The insulin-like growth factor II expression was found to be predominant in hepatocellular carcinoma and in early preneoplastic lesions. Unlike insulin-like growth factor II, c-raf.1 expression was located in the late basophilic lesions associated with hepatocellular carcinoma. During the various stages of the development of hepatocellular carcinoma, the enzymes played a significant role in metabolizing carcinogens and thereby scavenging various toxic metabolites or free radicals produced. A sequence of cellular changes starting from the appearance of glycogen storage foci to basophilic foci leading to hepatocellular carcinoma via mixed cell foci varied the activity/content or expression pattern of the enzymes and isoenzymes and in 8-hydroxydeoxyguanosine formation. It has been established that c-raf.1-induced signaling pathways activated by insulin-like growth factor II is implicated in the late stage of development of cancer.

Prooxidant action of furanone compounds: Implication of reactive oxygen species in the metal-dependent strand breaks and the formation of 8-hydroxy-2′-deoxyguanosine in DNA

Prooxidant properties of furanone compounds including 2,5-furanone (furaneol, 4-hydroxy-2,5-dimethyl-furan-3-one), 4,5-furanone (4,5-dimethyl-3-hydroxy-2(5H)-furanone) (sotolone) and cyclotene (2-hydroxy-3-methyl-2-cyclopenten-1-one) were analyzed in relation to the metal-reducing activity. Only 2.5-furanone known as a "strawberry or pineapple furanone" inactivated aconitase the most sensitive enzyme to active oxygen in the presence of ferrous sulfate, suggesting the furaneol/iron-mediated generation of reactive oxygen species. 2,5-Furanone caused strand scission of pBR322 DNA in the presence of copper. Treatment of calf thymus DNA with 2,5-furanone plus copper produced 8-hydroxy-2'-deoxyguanosine in DNA. 2,5-Furanone showed a potent copper-reducing activity, and thus, DNA strand breaks and the formation of 8-hydroxy-2'-deoxyguanosine by 2,5-furanone can be initiated by the production of superoxide radical through the reduction of cupric ion to cuprous ion, resulting in the conversion to hydrogen peroxide and hydroxyl radical. However, an isomer and analog of 2,5-furanone, 4,5-furanone and cyclotene, respectively, did not show an inactivation of aconitase, DNA injuries including strand breakage and the formation of 8-hydroxy-2'-deoxyguanosine, and copper-reducing activity. Cytotoxic effect of 2,5-furanone with hydroxyketone structure can be explained by its prooxidant properties: furaneol/transition metal complex generates reactive oxygen species causing the inactivation of aconitase and the formation of DNA base damage by hydroxyl radical.

Alterations in manganese superoxide dismutase expression in the progression from reflux esophagitis to esophageal adenocarcinoma

BACKGROUND

Comprehensive understanding of the basic mechanisms in the progression of esophagitis, Barrett esophagus (BE), and esophageal adenocarcinoma (EAC) is urgently needed to develop a management strategy for an effective screening of BE and management of EAC. The aim of this study is to provide a detailed insight of the histology and the cellular and molecular events associated with the genesis of BE and EAC under the esophagoduodenal reflux conditions.

METHODS

Esophagoduodenal anastomosis (EDA) was performed on rats. Animals were weighed weekly and killed after 1, 2, 3, 4, 5, and 6 months. The entire esophagi were examined for macroscopic and microscopic changes and for manganese superoxide dismutase (MnSOD) expression, and TUNEL (terminal deoxynucleotidyl transferase dUTP nick-end labeling) assay was performed.

RESULTS

Morphological transformation from esophagitis (100% of animals) to BE (66% of animals) to EAC was observed after 3 months. There was marked loss of MnSOD expression in animals with esophagitis and BE at 1 and 2 months, with an increase in expression during the transformation to dysplasia and EAC. Increased proliferation and apoptosis was observed and reached a peak at months 1 and 2. Greatly increased levels of 8-hydroxy-deoxyguanosine was found during the progression to EAC.

CONCLUSIONS

The morphological transformation of the esophageal mucosa is an adaptive process, and it is an important foundation for the transdifferentiation of BE and cancer. The significant loss of MnSOD expression to achieve BE and then the adaptive increase in expression to achieve dysplasia and EAC during this transformation may represent a predictive marker in identifying patients who will progress from BE to EAC.

Primary role of superoxide anion generation in the cascade of events leading to endothelial dysfunction and damage in high glucose treated HUVEC

AIM

The aim of the study was to elucidate the chain of events leading to oxidative damage in endothelial cells exposed to high glucose.

METHOD

The nitric oxide synthase (NOS) cofactor tetrahydrobiopterin (BH4), the peroxynitrite decomposition catalyst FP15, the inhibitor of mitochondrial complex II thenoyltrifluoroacetone (TTFA) and the antioxidant superoxide dismutase (SOD) mimetic Mn(III)tetrakis(4-benzoic acid) porphyrin chloride (MnTBAP) were individually added to human umbilical vein endothelial cells (HUVEC) cultured in high glucose. This study was designed to establish the possible sequence of action of NOS, peroxynitrite and superoxide anion in the oxidative damage cascade.

RESULTS

We found that in high glucose, nitrotyrosine, 8OHdG, NO (+40%) and O2- (+300%) production, eNOS and caspase-3 expression increased, while Bcl-2 expression decreased. MnTBAP and TTFA were able to normalize all the parameters assayed. FP15 caused an increase in NO production, did not interfere with eNOS expression and O2- generation, but was able to reduce apoptosis and to normalize nitrotyrosine and 8OHdG formation. BH4 enrichment was able to reduce O2- generation, nitrotyrosine and 8OHdG formation and apoptosis. The addition of this cofactor did not affect eNOS expression, but increased NO formation, more than FP15.

CONCLUSION

These data show the starting role of superoxide anion generated at mitochondrial level in the cascade of events leading to hyperglycemia generated apoptosis.

Lipid peroxidation dominates the chemistry of DNA adduct formation in a mouse model of inflammation

In an effort to define the prevalent DNA damage chemistry-associated chronic inflammation, we have quantified 12 DNA damage products in tissues from the SJL mouse model of nitric oxide (NO) overproduction. Using liquid chromatography-mass spectrometry/MS and immunoblot techniques, we analyzed spleen, liver and kidney from RcsX-stimulated and control mice for the level of the following adducts: the DNA oxidation products 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), guanidinohydantoin (Gh), oxazolone (Ox); 5-guanidino-4-nitroimidazole (NitroIm); spiroiminodihydantoin (Sp) and M(1)dG; the nitrosative deamination products 2'-deoxyxanthosine, 2'-deoxyoxanosine (dO), 2'-deoxyinosine and 2'-deoxyuridine and the lipid peroxidation-derived adducts 1,N(6)-etheno-deoxyadenosine and 1,N(2)-etheno-deoxyguanosine. The levels of dO, Gh, Ox, NitroIm and Sp were all below a detection limit of approximately 1 lesion per 10(7) bases. Whereas there were only modest increases in the spleens of RcsX-treated compared with control mice for the nucleobase deamination products (10-30%) and the DNA oxidation products 8-oxodG (10%) and M(1)dG (50%), there were large (3- to 4-fold) increases in the levels of 1,N(6)-etheno-deoxyadenosine and 1,N(2)-etheno-deoxyguanosine. Similar results were obtained with the liver and with an organ not considered to be a target for inflammation in the SJL mouse, the kidney. This latter observation suggests that oxidative and nitrosative stresses associated with inflammation can affect tissues at a distance from the activated macrophages responsible for NO overproduction during chronic inflammation. These results reveal the complexity of NO chemistry in vivo and support an important role for lipids in the pathophysiology of inflammation.

Oxidative stress contributes to accelerated development of the senescent phenotype in human peritoneal mesothelial cells exposed to high glucose

Increasing evidence indicates that cells exposed to high glucose exhibit shortened proliferative lifespan and enter the state of senescence earlier. However, the contribution of hyperglycemia-induced oxidative stress to premature cell senescence is not entirely clear. In the current study we have examined the role of oxidative stress in cellular senescence of human peritoneal mesothelial cells (HPMC) exposed to high glucose. The experiments were performed on primary omental-derived HPMC grown into senescence in the presence of normal (5 mM) and high (30 mM) glucose. Senescence of HPMC was associated with increased generation of reactive oxygen species (ROS) and decreased cellular glutathione (GSH). Exposure to high glucose significantly exacerbated these effects and increased the level of senescence-associated beta-galactosidase (SA-beta-Gal) and 8-hydroxy-2'-deoxyguanosine (8-OH-dG) expression. Furthermore, high glucose markedly increased senescence-related HPMC hypertrophy. The addition of L-2-oxothiazolidine-4-carboxylic acid, a GSH precursor, restored partially GSH levels and decreased ROS release. This effect was associated with reduced levels of SA-beta-Gal and 8-OH-dG, diminished TGF-beta1 and fibronectin release, and less pronounced hypertrophy of aged HPMC. These results indicate that the accelerated senescence response in HPMC exposed to high glucose is strongly related to oxidative stress.

Hypertension aggravates glomerular dysfunction with oxidative stress in a rat model of diabetic nephropathy

Oxidative stress may contribute to the pathogenesis of diabetic nephropathy (DN), although the detailed mechanism of reactive oxygen species (ROS) regulation is still unclear. This study examined the effect of high-salt diet on ROS production and expression of antioxidant enzymes in control and experimentally diabetic rats. Wistar fatty rats (WFR) as a type 2 diabetes mellitus model and Wistar lean rats (WLR) as a control were fed a normal-salt diet (NS) and high-salt diet (HS) from the age of 6 to 14 weeks. We then examined the blood pressure, urinary albumin excretion (UAE), and urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels. The expression of antioxidant enzymes including alpha-catalase (CAT), Cu-Zn superoxide dismutase (SOD), Mn SOD, and glutathione peroxidase (GPx) were analyzed in the glomeruli of the rats using Western blotting. The expression of NAD(P)H oxidase p47(phox) and NFkappaB p65 was evaluated using immunohistochemical staining. By 14 weeks of age, the WFR-HS group exhibited hypertension and markedly increased UAE. The level of 8-OHdG, a marker of oxidative damage, in the WFR-HS group was also higher than that in the WLR groups or WFR-NS group. The expression of alpha-CAT and Mn SOD proteins was significantly decreased in isolated glomeruli in the WFR-HS group. GPx and Cu-Zn SOD expression did not differ between the WFR and WLR groups. High expression of ROS and decreases in antioxidants were seen in the glomeruli of diabetic rats with hypertension, suggesting that oxidative stress may be involved in the development of DN.

Development of quantitative analysis of 8-nitroguanine concomitant with 8-hydroxydeoxyguanosine formation by liquid chromatography with mass spectrometry and glyoxal derivatization

Under inflammatory conditions, both 8-nitroguanine (NO2Gua) and 8-hydroxydeoxyguanosine (8-OHdG) are found in tissues. Measurements of the two types of damaged bases on nucleotides are expected to provide information pointing to the possible correlation between inflammation and carcinogenesis. For the establishment of an in vivo model, in this study, a sensitive and precise method for the determination of NO2Gua, which uses liquid chromatography with mass spectrometry (LC-MS) and 6-methoxy-2-naphthyl glyoxal (MTNG) derivatization, was developed in vitro. The procedure for DNA digestion in this method is identical to that widely used for 8-OHdG measurement, which enables us to detect the two damaged bases in the same DNA sample. In order to validate our method, we measured NO2Gua levels in DNA sample using LC-MS. A mass spectrometer equipped with an electrospray atmospheric pressure ionization source and operated in the negative ion mode (ESI-) was set up with selective ion monitoring at m/z 391 and 394 for NO2Gua-MTNG and [13C, 15N2]-NO2Gua-MTNG as surrogate standard, respectively. The average recoveries from DNA samples spiked with 25, 50 and 250 nM NO2Gua were 99.4, 99.8 and 99.1% with correction using the added surrogate standard, respectively. The limit of quantification was 3.0 nM for NO2Gua. To ascertain the applicability of our method to DNA samples harboring the two damaged bases, we measured NO2Gua and 8-OHdG levels in calf thymus DNA treated with ONOO-. As a result, both NO2Gua and 8-OHdG levels were clearly increased with ONOO- dose dependency, the amount of NO2Gua at the high dose ONOO- being almost the same as those of 8-OHdG. LC-MS was able to determine NO2Gua in a small amount of DNA sample, and is therefore expected to be a very powerful tool for the evaluation of DNA damage induced by reactive nitrogen species.

Bioavailable flavonoids to suppress the formation of 8-OHdG in HepG2 cells

Antioxidative flavonoids, ubiquitously included in vegetables, fruits and teas, are expected to prevent degenerative diseases. It is unclear, however, whether flavonoids can enter the cellular nuclei and suppress the oxidative damage of DNA. Here, several flavonoids at the physiological concentration of 10 microM were dosed to 2.5x10(7) HepG2 cells. The nuclei were isolated and determined in the incorporated flavonoid levels, and simultaneously exposed to reactive oxygen generated from 25 mM of 2,2'-azobis(2-amidinopropane) dihydrochloride. Most of the tested flavonoids were incorporated into the cells in the range between 1000 and 1600 pmol/10(7) cells, and were in the nuclei at 250-450 pmol/10(7) cells at the maximum incorporation after 30min of cell incubation. In the cells, 23% of quercetin (3,5,7,3',4'-OH) and 8% of luteolin (5,7,3',4'-OH) were the original aglycone forms and the others were the methylated and gulucuronide/sulfate conjugates, while 72% of kaempferol (3,5,7,4'-OH) and 85% of apigenin (5,7,4'-OH) were aglycones and located in the nuclei at the similar ratio of metabolites. Quercetin and luteolin significantly suppressed the formation of 8-oxo-7,8-dihydrodeoxyguanosine by 25% and 15%, respectively, compared to those in 0-time incubated cells with the flavonoids. Under such conditions of low level and hydroxyl-masked in the nuclei, the limited flavonoids were bioavailable antioxidants to prevent genetic damage and they were B-ring catechols such as quercetin and luteolin.

Resveratrol enhances UVA-induced DNA damage in HaCaT human keratinocytes

Resveratrol, a polyphenolic phytoalexin, is a very effective antioxidant that also exhibits strong antiproliferative and anti-inflammatory properties. Recent studies have provided support for the use of resveratrol in human cancer chemoprevention, in combination with either chemotherapeutic drugs or cytotoxic factors for a most efficient treatment of drug refractory tumor cells. Resveratrol is also widely used in topical preparations, as a chemoprotective compound against development of several cutaneous disorders, including skin cancer. Nevertheless, the combined effect of resveratrol and UVA irradiation on cellular toxicity and DNA damage has never been assessed. The aim of this work was to investigate the effect of resveratrol on cell fate in immortalized human keratinocytes HaCaT cells. The results indicated that resveratrol potentiates the production of significant amounts of 8-oxo-7,8-dihydro-2'-deoxyguanosine in UVA-irradiated genomic DNA. Moreover, the combination of resveratrol with UVA significantly enhances the induction of DNA strand breaks and cell death in HaCaT keratinocytes. The conclusion is a potential hazardous effect of topical application of resveratrol, particularly on regions exposed to sunlight.

In vivo mutagenicity and initiation following oxidative DNA lesion in the kidneys of rats given potassium bromate

To clarify the role of 8-OHdG formation as a starting point for carcinogenesis, we examined the dose-dependence and time-course of changes of OGG1 mRNA expression, 8-OHdG levels and in vivo mutations in the kidneys of gpt delta rats given KBrO3 in their drinking water for 13 weeks. There were no remarkable changes in OGG1 mRNA in spite of some increments being statistically significant. Increases of 8-OHdG occurred after 1 week at 500 p.p.m. and after 13 weeks at 250 p.p.m. Elevation of Spi- mutant frequency, suggestive of deletion mutations, occurred after 9 weeks at 500 p.p.m. In a two-stage experiment, F344 rats were given KBrO3 for 13 weeks then, after a 2-week recovery, treated with 1% NTA in the diet for 39 weeks. The incidence and multiplicity of renal preneoplastic lesions in rats given KBrO3 at 500 p.p.m. followed by NTA treatment were significantly higher than in rats treated with NTA alone. Results suggest that a certain period of time might be required for 8-OHdG to cause permanent mutations. The two-step experiment shows that cells exposed to the alteration of the intranuclear status by oxidative stress including 8-OHdG formation might be able to form tumors with appropriate promotion.

Radical production and DNA damage induced by carcinogenic 4-hydrazinobenzoic acid, an ingredient of mushroom Agaricus bisporus

4-Hydrazinobenzoic acid, an ingredient of mushroom Agaricus bisporus, is carcinogenic to rodents. To clarify the mechanism of carcinogenesis, we investigated DNA damage by 4-hydrazinobenzoic acid using (32)P-labeled DNA fragments obtained from the human p53 and p16 tumor suppressor genes. 4-Hydrazinobenzoic acid induced Cu(II)-dependent DNA damage especially piperidine-labile formation at thymine and cytosine residues. Typical hydroxyl radical scavengers showed no inhibitory effects on Cu(II)-mediated DNA damage by 4-hydrazinobenzoic acid. Bathocuproine and catalase inhibited the DNA damage, indicating the participation of Cu(I) and H(2)O(2) in the DNA damage. These findings suggest that H(2)O(2) generated by the autoxidation of 4-hydrazinobenzoic acid reacts with Cu(I) to form reactive oxygen species, capable of causing DNA damage. Interestingly, catalase did not completely inhibit DNA damage caused by a high concentration of 4-hydrazinobenzoic acid (over 50 microM) in the presence of Cu(II). 4-Hydrazinobenzoic acid induced piperidine-labile sites frequently at adenine and guanine residues in the presence of catalase. 4-Hydrazinobenzoic acid increased formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), a characteristic oxidative DNA lesion, in calf thymus DNA, whereas 4-hydrazinobenzoic acid did not increase the formation of 8-oxodG in the presence of catalase. ESR spin-trapping experiments showed that the phenyl radical was formed during the reaction of 4-hydrazinobenzoic acid in the presence of Cu(II) and catalase. Matrix-assisted laser desorption/ionization time-of-flight mass (MALDI-TOF/mass) spectrometry analysis showed that phenyl radical formed adduct with adenosine and guanosine. These results suggested that 4-hydrazinobenzoic acid induced DNA damage via not only H(2)O(2) production but also phenyl radical production. This study suggests that both oxidative DNA damage and DNA adduct formation play important roles in the expression of carcinogenesis of 4-hydrazinobenzoic acid.

Thioredoxin protects against joint destruction in a murine arthritis model

Thioredoxin (TRX) is an oxidative stress-inducible biological antioxidant that is highly expressed in the synoviocytes of rheumatoid arthritis (RA) patients. There is much evidence that oxidative stress plays a key role in the inflammation and destruction of RA joints; the functional relationship between TRX and RA remains unknown, however. We therefore investigated the role played by TRX in the inflammatory and joint-damaging processes of RA using a murine model in which arthritis was induced by administering a mixture of anti-type II collagen monoclonal antibodies (mAb) and lipopolysaccharide (LPS). In Wt mice mAb/LPS injection induced neutrophil infiltration, cartilage destruction, and chondrocyte apoptosis within the joints, all of which were dramatically suppressed in TRX transgenic (TRX-Tg) mice. Moreover, the 8-hydoxy-2'-deoxyguanosine (8-OHdG) expression seen in Wt mice after mAb/LPS injection was almost completely inhibited in TRX-Tg mice. The administration of recombinant TRX also suppressed mAb/LPS-induced joint swelling in Wt mice. Taken together, these results suggest that TRX protects against arthritis and is a plausible candidate with which to develop novel therapies for the treatment of RA.

Formation of 8-hydroxy-2'-deoxyguanosine in the DNA of cultured human keratinocytes by clinically used doses of narrowband and broadband ultraviolet B and psoralen plus ultraviolet A

Psoralen plus ultraviolet A (PUVA) and narrowband ultraviolet B (UVB) are widely used in skin disease phototherapy. Recently, the efficacy of UVB therapy has been greatly improved by narrowband UVB, compared to conventional broadband UVB. The objectives of the current study were to evaluate the influence of UVB-induced and PUVA-induced oxidative stress on cultured keratinocytes. We analyzed 8-hydroxy-2'-deoxyguanosine (8-OH-dG) in human keratinocytes (HaCaT cell line) using a high-performance liquid chromatography system equipped with an electrochemical detector. Non-irradiated human keratinocytes contained a baseline of 1.48 +/- 0.22 (mean +/- SD) 8-OH-dG per 10(6) deoxyguanosine (dG) residues in cellular DNA, which increased linearly with higher doses of UVB. When their abilities to induce 8-OH-dG were compared to each other, based on the minimal erythemal and therapeutically used doses, by irradiating them with broadband UVB at 100 mJ/cm(2), the amount of 8-OH-dG increased to 3.42 +/- 0.46 residues per 10(6) dG, while a narrowband UVB treatment at 1000 mJ/cm(2), with biological effects comparable to those elicited by 100 mJ/cm(2) broadband UVB, increased it to 2.06 +/- 0.31 residues per 10(6) dG. PUVA treatment, with 100 ng/mL 8-methoxypsoralen and 5000 mJ/cm(2) UVA, increased the 8-OH-dG level to 4.52 +/- 0.42 residues per 10(6) dG. When HaCaT cells treated with 2000 mJ/cm(2) narrowband UVB were cultured and the amount of 8-OH-dG was monitored in the living cells, 65.6% of the residues were repaired 24 h after treatment. Our study provides a warning that widely used narrowband UVB and PUVA induce cellular oxidative DNA damage at the therapeutically used doses, although to a lesser degree than broadband UVB with the same clinically effective dose.

Comparison of stable nitroxide, 3-substituted 2,2,5,5-tetramethylpyrrolidine-N-oxyls, with respect to protection from radiation, prevention of DNA damage, and distribution in mice

We compared three 3-substituted 2,2,5,5-tetramethylpyrrolidine-N-oxyls (PROXYLs): carbamoyl-, methoxycarbonyl-, and hydroxymethyl-PROXYL (CM-, MC-, and HM-PROXYL, respectively) with respect to radioprotection, prevention of DNA damage, and in vivo distribution in mice. The PROXYLs provided protection to C3H mice against lethal X-irradiation (8 Gy) with the following order of magnitude, HM- > CM- approximately MC-PROXYL. In contrast, radioprotection at the cellular level assessed by the colony formation of leukemia cell line L5178Y showed no difference among them. The degree of protection from X ray-induced oxidation of DNA bases measured by the formation of 8-hydroxydeoxyguanosine in salmon DNA and the cleavage of DNA measured by electrophoresis of plasmid pBR322 DNA did not differ among the PROXYLs. Redox potentials were also similar for each. However, the blood concentration of the PROXYLs injected ip into the mice showed different maximum concentrations (HM- > CM- approximately MC-PROXYL), although all reached a maximum at around 5-10 min and gradually decreased thereafter. Their concentration in bone marrow showed a similar pattern, suggesting that the difference in in vivo radioprotection among the three PROXYLs is due to the difference in their distribution to bone marrow. In general, the radioprotection provided by stable nitroxides is affected not only by redox potential and reactivity in vitro but also by pharmacokinetics.

DNA damage and apoptosis induction by the pesticide Mancozeb in rat cells: Involvement of the oxidative mechanism

The DNA damaging and proapoptotic effects of Mancozeb, a widely used fungicide of the ethylene-bis-dithiocarbamate (EBDC) group, were studied in RAT-1 fibroblasts cultured in vitro and in peripheral blood mononucleated cells (PBMC) isolated from Wistar rats. After 1 h exposition to Mancozeb (up to 500 ng/ml), cells produced a dose-dependent induction in DNA single strand break (SSB) formation, measured by single cell gel electrophoresis (SCGE). Concomitantly, a concentration-dependent increase in the levels of the oxidative markers of DNA oxidation, the DNA adduct 8-hydroxy-2'-deoxyguanosine (8-OHdG) and of reactive oxygen species (ROS) were observed, suggesting a prooxidant action of Mancozeb. PBMC were less responsive than fibroblasts to the oxidative insult carried out by Mancozeb, as shown by the lower increase in the levels of ROS, 8-OHdG adducts and SSB measured in these cells after exposure to the pesticide. A 4-h treatment with Mancozeb induced also apoptosis in both PBMC and RAT-1 cells, even though leukocytes were less sensitive than fibroblasts to the proapoptotic action. This effect was dose-dependent and was inhibited by the action of the antioxidant alpha-tocopherol. The proapoptotic effect was accompanied by the altered expression of several proteins involved in the regulation of apoptosis, such as the prosurvival protein BCL-2 and the proapoptotic protein c-MYC. Exposition of cells to higher concentrations of Mancozeb or for longer periods (>4 h) caused post-apoptotic, necrotic alterations in cell membrane integrity. The data herein presented demonstrate the oxidative effect of Mancozeb and suggest that its prooxidant action may be involved in the proapoptotic effect exerted by this compound in rat cells. It appears possible that the observed oxidative and genotoxic damage may be involved in the pathogenesis of various pathologies associated with the chronic exposition to Mancozeb, including cancer. On the other hand, the proapoptotic effect of Mancozeb suggests its possible relevance in the pathogenesis of neurodegenerative diseases, often related to the exposition of pesticides.

8-Nitroguanine formation in oral leukoplakia, a premalignant lesion

Oral leukoplakia is a premalignant lesion associated with development of oral cancer. To clarify the mechanism of development of oral carcinogenesis from leukoplakia, we examined DNA damage in oral epithelium of biopsy specimens of patients with leukoplakia by immunohistochemical methods. Histological changes, such as epithelial dysplasia and infiltration of inflammatory cells were observed in oral tissues of leukoplakia patients. A double immunofluorescence labeling study demonstrated that the accumulation of mutagenic 8-nitroguanine, an indicator of nitrative DNA damage, and 8-oxo-7,8-dihydro-2'-deoxyguanosine, an indicator of oxidative DNA damage, was apparently observed in the oral epithelium of patients with leukoplakia, whereas little or no immunoreactivity was observed in normal oral mucosa. Expression of inducible nitric oxide synthase (iNOS) was also observed in oral epithelium of leukoplakia patients. Immunoreactivity of 3-nitrotyrosine, an indicator of nitrative stress, was observed in oral epithelial cells and colocalized with 8-nitroguanine. Moreover, proliferating cell nuclear antigen and p53 were expressed in 8-nitroguanine-positive epithelial cells in the basal layer. These results suggest that iNOS-mediated nitrative stress contributes to development of oral carcinogenesis from leukoplakia through DNA damage as well as oxidative stress.

Site specific synthesis and polymerase bypass of oligonucleotides containing a 6-hydroxy-3,5,6,7-tetrahydro-9H-imidazo[1,2-a]purin-9-one base, an intermediate in the formation of 1,N2-etheno-2'-deoxyguanosine

The reaction of DNA with certain bis-electrophiles such as chlorooxirane and chloroacetaldehyde produces etheno adducts. These lesions are highly miscoding, and some of the chemical agents that produce them have been shown to be carcinogenic in laboratory animals and in humans. An intermediate in the formation of 1,N2-ethenoguanine is 6-hydroxy-3,5,6,7-tetrahydro-9H-imidazo[1,2-a]purin-9-one (6-hydroxyethanoguanine), which undergoes conversion to the etheno adduct. The chemical properties and miscoding potential of the hydroxyethano adduct have not been previously studied. A synthesis of the hydroxyethano-adducted nucleoside was developed, and it was site specifically incorporated into oligonucleotides. This adduct had a half-life of between 24 and 48 h at neutral pH and 25 degrees C at the nucleoside and oligonucleotide levels. The miscoding potential of the hydroxyethano adduct was examined by primer extension reactions with the DNA polymerases Dpo4 and pol T7-, and the results were compared to the corresponding etheno-adducted oligonucleotide. Dpo4 preferentially incorporated dATP opposite the hydroxyethano adduct and dGTP opposite the etheno adduct; pol T7- preferentially incorporated dATP opposite the etheno adduct while dGTP and dATP were incorporated opposite the hydroxyethano adduct with nearly equal catalytic efficiencies. Collectively, these results indicate that the hydroxyethano adduct has a sufficient lifetime and miscoding properties to contribute to the mutagenic spectrum of chlorooxirane and related genotoxic species.

NADPH oxidase is involved in angiotensin II-induced apoptosis in H9C2 cardiac muscle cells: effects of apocynin

Angiotensin II stimulates NADPH oxidase activity in vascular cells. However, it is not fully understood whether angiotensin II, which plays an important role in heart failure, stimulates NADPH oxidase activation and expression in cardiac myocytes. Previous studies have shown that angiotensin II induces myocyte apoptosis, but whether the change is mediated via NADPH oxidase remains to be elucidated. In this study we proposed to determine whether angiotensin II stimulated NADPH oxidase activation and NADPH oxidase subunit p47-phox expression in H9C2 cardiac muscle cells. If so, we would determine whether the NADPH oxidase inhibitor apocynin prevented angiotensin II-induced apoptosis. The results showed that angiotensin II increased NADPH oxidase activity, p47-phox protein and mRNA expression, intracellular reactive oxygen species, and apoptosis in H9C2 cells. Angiotensin II elevated p38 mitogen-activated protein kinase (MAPK) activity, decreased Bcl-2 protein, and increased Bax protein and caspase-3 activity. Apocynin treatment inhibited angiotensin II-induced NADPH oxidase activation and increases in p47-phox expression, intracellular reactive oxygen species, and apoptosis. The effect of apocynin on apoptosis was associated with reduced p38 MAPK activity, increased Bcl-2 protein, and decreased Bax protein and caspase-3 activity. These results suggest that angiotensin II-induced apoptosis is mediated via NADPH oxidase activation probably through p38 MAPK activation, a decrease in Bcl-2 protein, and caspase activation.

Oxidative DNA damage in relation to neurotoxicity in the brain of mice exposed to arsenic at environmentally relevant levels

To clarify the association between oxidative DNA damage and the neurotoxicity of arsenic, the formation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) as an index of oxidative DNA damage in the brain was examined in mice fed with drinking water containing 1 or 2 ppm arsenic, using an HPLC-electrochemical detector and immunohistochemical method. 8-OHdG levels were significantly increased in the brain of mice given arsenic and its immunoreactivity was distributed in the cerebral and cerebellar cortexes. Cerebral cortex neurons and Purkinje cells in the cerebellar cortex showed degenerative changes in accordance with the distribution of 8-OHdG immunoreactivity. The levels of arsenic in this study were lower than those reported in epidemiological studies. Thus, we conclude that environmentally relevant levels of arsenic induce pathological changes through oxidative DNA damage in the brain tissues in vivo and that cerebral and cerebellar cortex neurons seem to be the major targets of arsenic neurotoxicity.

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.

Glycochenodeoxycholate plays a carcinogenic role in immortalized mouse cholangiocytes via oxidative DNA damage

Bile acids have been suggested to be involved in biliary carcinogenesis, although the underlying mechanisms are yet to be established. The aim of this study was to investigate the carcinogenic effect of bile acids in the biliary tract in relation to oxidative stress. Immortalized mouse cholangiocytes were incubated with various bile acids, followed by measurement of reactive oxygen species (ROS) and the glutathione (GSH) level. As a marker of oxidative DNA damage, 8-hydroxydeoxyguanosine (8-OHdG) expression in cholangiocytes was analyzed by flow cytometry. Then the expression of oxidative DNA repair enzymes in cholangiocytes was examined by real-time PCR. In addition, the long-term effect of bile acid-induced oxidative DNA damage on cholangiocytes was investigated using a mouse oligo DNA microarray. It was found that glycochenodeoxycholate (GCDC) induced the generation of ROS and the depletion of GSH. In contrast, no marked changes were induced by the other bile acids. The percentage of 8-OHdG-positive cells was also increased by GCDC, but the expression of oxidative DNA repair enzymes was not up-regulated. DNA microarray analysis showed marked changes of various genes associated with carcinogenesis (genes related to cell proliferation, angiogenesis, invasion, and metastasis). In conclusion, the long-term effect of oxidative DNA damage due to GCDC may promote carcinogenesis in the biliary tract. Furthermore, accumulation of 8-OHdG due to GCDC might contribute to the dysfunction of oxidative DNA repair enzymes.

Antioxidative role of urinary trypsin inhibitor in acute lung injury induced by lipopolysaccharide

We have previously demonstrated the protective role of urinary trypsin inhibitor (UTI) against acute inflammatory lung injury induced by lipopolysaccharide (LPS) using UTI-deficient (-/-) mice and corresponding wild-type (WT) mice. The protection was mediated, at least partly, through inhibition of the enhanced local expression of proinflammatory cytokines, chemokines, and intercellular adhesion molecule-1. In the present study, we addressed whether UTI regulates oxidative stress generated by LPS challenge in the lung. UTI (-/-) and WT mice were treated intratracheally with vehicle or LPS (125 microg/kg). After LPS challenge in both genotypes of mice, the lung levels of mRNA for inducible nitric oxide synthase and hemo oxygenase-1 were elevated, but to a greater extent in UTI (-/-) mice than in WT mice. Immunohistochemistry showed that the formations of 8-hydroxy-2'-deoxyguanosine and nitrotyrosine in the lung were more intense in UTI (-/-) mice than in WT mice after LPS challenge. These results indicate that endogenous UTI is protective against acute lung injury induced by bacterial endotoxin, at least partly, via the antioxidative properties.

Benzo[a]pyrene and its metabolites combined with ultraviolet A synergistically induce 8-hydroxy-2'-deoxyguanosine via reactive oxygen species

We previously reported that benzo[a]pyrene (BaP) and UVA radiation synergistically induced oxidative DNA damage via 8-hydroxy-2'-deoxyguanosine (8-OHdG) formation in vitro. The present study shows that microsomal BaP metabolites and UVA radiation potently enhance 8-OHdG formation in calf thymus DNA about 3-fold over the parent compound BaP. Utilization of various reactive oxygen species scavengers revealed that singlet oxygen and superoxide radical anion were involved in the 8-OHdG formation induced by microsomal BaP metabolites and UVA. Two specific BaP metabolites, benzo[a]pyrene-r-7,t-8-dihydrodiol-t-9,10-epoxide (+/-) (anti) (BPDE) and BaP-7,8-dione, were further tested for synergism with UVA. BaP-7,8-dione showed an effect on 8-OHdG formation induced by UVA radiation that was similar to that of the parent BaP, whereas BPDE exhibited significantly higher induction of 8-OHdG than BaP. At as low as 0.5 microM, BPDE plus UVA radiation substantially increased 8-OHdG levels about 25-fold over the parent BaP. BPDE increased the formation of 8-OHdG levels in both BPDE concentration- and UVA dose-dependent manners. Additionally, singlet oxygen was found to play a major role in 8-OHdG induction by BPDE and UVA. These results suggest that BaP metabolites such as BPDE synergize with UVA radiation to produce ROS, which in turn induce DNA damage.

Formation of M1G-dR from endogenous and exogenous ROS-inducing chemicals

The present study provides fundamental information regarding the production of M1G-dR by ROS. To investigate the production of M1G-dR from deoxyribose damage as caused by ROS, calf thymus DNA (CT-DNA) was incubated with NAD(P)H, CuCl2, and various concentrations of hydrogen peroxide (H2O2). The incubation of CT-DNA with H2O2 resulted in concentration-dependent increases in the number of M1G-dR adducts. In subsequent experiments, 1,4-tetrachlorobenzoquinone or catechol estrogens were evaluated for their effects on M1G-dR formation. In addition, the role of lipid peroxidation in the formation of M1G-dR was verified using an in vitro lipid peroxidation model which consisted of methyl esters of either fish oil or purified fatty acids found in cellular membranes. This experiment confirmed that M1G-dR is a major DNA adduct produced by lipid peroxidation. Furthermore, the number of double bonds in polyunsaturated fatty acids was found to be the key factor in the formation of M1G-dR. The findings obtained from this study provide important information regarding the molecular pathways for M1G-dR formation by ROS, which is an essential element in understanding and evaluating the genotoxicity of a variety of ROS-inducing chemicals.

Procyanidin B2 has anti- and pro-oxidant effects on metal-mediated DNA damage

Procyanidin B2 (epicatechin-(4beta-8)-epicatechin), which is present in grape seeds, apples, and cacao beans, has antioxidant properties. We investigated the mechanism of preventive action of procyanidin B2 against oxidative DNA damage in human cultured cells and isolated DNA. Procyanidin B2 inhibited the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in the human leukemia cell line HL-60 treated with an H2O2-generating system. In contrast, a high concentration of procyanidin B2 increased the formation of 8-oxodG in HL-60 cells. Experiments with calf thymus DNA also revealed that procyanidin B2 decreased 8-oxodG formation by Fe(II)/H2O2, whereas procyanidin B2 induced DNA damage in the presence of Cu(II), and H2O2 extensively enhanced it. An electron spin resonance spin trapping study utilizing 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M4PO) demonstrated that procyanidin B2 decreased the signal of M4PO-OH from H2O2 and Fe(II), whereas procyanidin B2 enhanced the signal from H2O2 and Cu(II). As an antioxidant mechanism, UV-visible spectroscopy showed that procyanidin B2 chelated Fe(II) at equivalent concentrations. As a pro-oxidant property, we examined DNA damage induced by procyanidin B2, using 32P-labeled DNA fragments obtained from genes relevant to human cancer. Our results raise the possibility that procyanidin B2 exerts both antioxidant and pro-oxidant properties by interacting with H2O2 and metal ions.

Up-regulation of telomere-binding TRF1, TRF2 related to reactive oxygen species induced by As(2)O(3) in MGC-803 cells

In this work, our study focused on As(2)O(3) action in view point of telomere. Results showed that treatment of human gastric cancer MGC-803 cells with arsenic trioxide could cause up-regulation of telomeric repeat binding factor TRF1 and TRF2 mRNA and protein levels, and induced G2/M phase arrest and cell apoptosis. At the same time, telomere length shortening and telomerase inhibitory were not obvious. Flow cytometry measurements indicated that the increase of TRF1 and TRF2 proteins is related to oxidative stress by arsenic trioxide. Results also indicate that after arsenic trioxide treatment, p53 protein levels increased significantly and also could bind directly at the telomere t-loop junction. These findings demonstrate arsenic trioxide-induced cell cycle arrest and apoptosis might involve a novel pathway related to TRF1, TRF2 protein.

Nitrative and oxidative DNA damage in intrahepatic cholangiocarcinoma patients in relation to tumor invasion

AIM: Nitrative and oxidative DNA damage such as 8-nitroguanine and 8-oxo-7,8-dihydro-2’-deoxyguanosine (8-oxodG) formation has been implicated in initiation and/ or promotion of inflammation-mediated carcinogenesis. The aim of this study is to clarify whether these DNA lesions participate in the progression of intrahepatic cholangiocarcinoma.

METHODS: We investigated the relation of the formation of 8-nitroguanine and 8-oxodG and the expression of hypoxia-inducible factor-1α (HIF-1α) with tumor invasion in 37 patients with intra-hepatic cholangiocarcinoma.

RESULTS: Immunohistochemical analyses revealed that 8-nitroguanine and 8-oxodG formation occurred to a much greater extent in cancerous tissues than in non-cancerous tissues. HIF-1α could be detected in cancerous tissues in all patients, suggesting low oxygen tension in the tumors. HIF-1α expression was correlated with inducible nitric oxide synthase (iNOS) expression (r = 0.369 and P = 0.025) and 8-oxodG formation (r = 0.398 and P = 0.015). Double immunofluorescence study revealed that iNOS and HIF-1α co-localized in cancerous tissues. Notably, the formation of 8-oxodG was correlated significantly with lymphatic invasion (r = 0.386 and P = 0.018). Moreover, 8-nitroguanine and 8-oxodG in non-cancerous tissues were associated significantly with neural invasion (P = 0.042 and P = 0.026, respectively). These results suggest that reciprocal activation between HIF-1α and iNOS mediates persistent DNA damage, which induces tumor invasiveness via mutations, resulting in poor prognosis.

CONCLUSION: The formation of 8-nitroguanine and 8-oxodG plays an important role in multiple steps of genetic changes leading to tumor progression, including invasiveness.

The Effects of 1‐Nitropyrene on Oxidative DNA Damage and Expression of DNA Repair Enzymes

Nitropyrenes (NPs) present in diesel and gasoline emissions are mutagenic and carcinogenic in experimental animals. Nitro-reduction of 1-NP causes oxidative stress. It is unclear whether 8-hydroxydeoxyguanosine (8-OH-dG) is produced from 1-NP and whether it contributes to the carcinogenic activity of 1-NP. In this study, we measured the level of reactive oxygen species (ROS) in cultured human lung epithelial cells after exposure to 1-NP and the intracellular level of 8-OH-dG and expression level of the 8-OH-dG repair enzymes. As results, 1-NP induced the generation of 8-OH-dG via ROS, but 8-OH-dG repair enzymes prevented an increase of 8-OH-dG formation in cellular DNA of the A549 cell line below 250 microM of 1-NP. These data suggest that 1-NP can induce oxidative DNA damage by generation of ROS, which may play a role in the carcinogenesis induced by 1-NP. These data also suggest that individuals with impaired DNA repair enzymes might be more susceptible to lung cancer induced by 1-NP.

Antioxidant status decreases in children with acute lymphoblastic leukemia during the first six months of chemotherapy treatment

BACKGROUND

Children undergoing treatment for acute lymphoblastic leukemia (ALL) receive combination chemotherapy and many of the components are associated with free radical production.

PROCEDURE

Among 103 children newly diagnosed with ALL, plasma concentrations of antioxidants, total antioxidant capacity (ORAC), and DNA oxidized base 8-oxodeoxyguanosine (8-oxo-dG) were analyzed at baseline and 3 and 6 months after diagnosis.

RESULTS

Plasma vitamin A, antioxidants, 8-oxo-dG, and ORAC changed from diagnosis through the first 6 months of ALL therapy. In patients with higher plasma concentrations of vitamin A, E, total carotenoids, ORAC, and 8-oxo-dG there was a beneficial association with fewer dose reductions, fewer infections, improved quality of life, less delay in chemotherapy treatment schedule, reduced toxicity, and fewer days spent in the hospital. There were also adverse relationships demonstrated.

CONCLUSIONS

Among children with ALL, antioxidant levels and oxidative stress appear to be associated with duration and complications of treatment.

Suppressive Effects of Iron on TGF-β1 Production by Renal Proximal Tubular Epithelial Cells

BACKGROUND

TGF-beta1, which is one of the profibrogenic cytokines, is considered essential for both the tubulointerstitial fibrosis found in chronic kidney diseases and the repair of tissue damage in acute renal injury. Iron plays an important part in inflammatory damage since it supplies cytotoxic hydroxyl radicals. The aim of the present study was to examine the direct effects of iron on TGF-beta1 production and the expression of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidative stress, by human renal proximal tubular epithelial cells (RPTEC).

METHODS

Using human RPTEC, TGF-beta1 expression was studied by immunohistochemical staining, ELISA and RNase protection assays. 8-OHdG expression was evaluated by immunohistochemical staining.

RESULTS

Ferric iron suppressed both TGF-beta1 secretion and mRNA expression, and enhanced 8-OHdG expression in RPTEC in a dose-dependent manner. Desferrioxamine, an iron chelator, eliminated the suppressive effect of ferric citrate on TGF-beta1 production.

CONCLUSIONS

The results suggest that iron may delay the repair of kidney injury during the acute inflammatory phase via a reduction in TGF-beta1 production by RPTEC. Iron chelation may therefore be a useful strategy in the treatment of inflammatory kidney diseases.

Vitamin E protects DNA from oxidative damage in human hepatocellular carcinoma cell lines

Expression of multiple drug resistant (MDR) phenotype and over-expression of P-glycoprotein (P-gp) in the human hepatocellular carcinoma (HCC) cell clone P1(0.5), derived from the PLC/PRF/5 cell line (P5), are associated with strong resistance to oxidative stress and a significant (p < 0.01) increase in intracellular vitamin E content as compared with the parental cell line. This study evaluates the role of vitamin E in conferring resistance to drugs and oxidative stress in P1(0.5) cells. Parental drug-sensitive cells, P5, were incubated in alpha-tocopherol succinate (alpha-TS, 5 microM for 24 h) enriched medium to increase intracellular vitamin E content to levels comparable to those observed in P1(0.5) cells at basal conditions. Susceptibility to lipid peroxidation and oxidative DNA damage were assessed by measuring the concentration of thiobarbituric-reactive substances (TBARS) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) at basal and after experimental conditions. Cell capacity to form colonies and resistance to doxorubicin were also studied. P5 cells, treated with alpha-TS, became resistant to ADP-Fe3+ and to ionizing radiation-induced lipid peroxidation as P1(0.5) cells. Exposure to ADP-Fe3+ or ionizing radiation increased TBARS and the 8-OHdG content in the P5 cells, while vitamin E enrichment abolished these effects. Irradiation doses at 5 cGy increased TBARS and 8-OHdG. They also inhibited cell capacity to form colonies in the untreated P5 cells. Incubation with alpha-TS fully reverted this effect and significantly (p < 0.01) reduced the inhibitory effect of cell proliferation induced by irradiation doses at >500 cGy. Resistance to doxorubicin was not affected by alpha-TS. These observations demonstrate the role of vitamin E in conferring protection from lipid peroxidation, ionizing radiation and oxidative DNA damage on the human HCC cell line. They also rule out any role of P-gp over-expression as being responsible for these observations in cells with MDR phenotype expression.

Structural and stereoisomer effects of model estrogen quinone-derived DNA adducts: N6-(2-hydroxyestron-6(alpha,beta)-yl)-2'-deoxyadenosine and N2-(2-hydroxyestron-6(alpha,beta)-yl)-2'-deoxyguanosine

An extensive conformational analysis has been carried out for two diastereoisomeric pairs of model estrogen quinone-derived DNA adducts, N6-(2-hydroxyestron-6(alpha,beta)-yl)-2'-deoxyadenosine (2-OHE1-6(alpha,beta)-N6-dA) and N2-(2-hydroxyestron-6(alpha,beta)-yl)-2'-deoxyguanosine (2-OHE1-6(alpha,beta)-N2-dG), in a B-DNA duplex and at a primer-template junction in a pol alpha family DNA polymerase. In vitro primer extension studies in pol alpha [Terashima, I., et al. (1998) Biochemistry 37, 13807-13815] have shown that the adenine adducts can incorporate dT, together with a small proportion of the incorrect base dC opposite the lesion, and they block less strongly than the guanine adducts. We have carried out conformational searches with energy minimization for four DNA duplexes containing 2-OHE1-6alpha-N6-dA, 2-OHE1-6beta-N6-dA, 2-OHE1-6alpha-N2-dG, or 2-OHE1-6beta-N2-dG. Our searches revealed that the four-ring nonplanar 2-hydroxyestrone (2-OHE1) moiety strongly prefers to reside in the major groove of the adenine adducts or the minor groove of the guanine adducts in a B-DNA duplex, with stereochemistry-dependent orientational differences in each case. No low energy conformations involving intercalation of the 2-OHE1 moiety were located in the searches. This stems from the largely nonplanar, nonaromatic nature of the 2-OHE1 ring system and implies that the proclivity for such bulky, nonplanar adducts to reside at the DNA helix exterior is a plausible conformational feature of other structurally similar estrogen quinone-derived DNA adducts, independent of base sequence context. In addition, the adenine adduct isomers, located in the major groove, manifest serious disturbance to the Watson-Crick base pairs at and near the lesion site, suggesting repair susceptibility. Possible structures of these adducts in a pol alpha family polymerase were also investigated through molecular modeling. The results rationalized the experimental in vitro primer extension studies. In addition, poor accommodation of the beta-stereoisomers within the polymerase was noted, suggesting that these stereoisomers would be more prone to cause blockage. Stereochemistry-dependent differences in adduct orientation could be expected to produce different biochemical effects, as has been observed in adducts derived from polycyclic aromatic hydrocarbons.

Oxidative DNA damage induced by a hydroperoxide derivative of cyclophosphamide

Interstrand DNA cross-linking has been considered to be the primary action mechanism of cyclophosphamide (CP) and its hydroperoxide derivative, 4-hydroperoxycyclophosphamide (4-HC). To clarify the mechanism of anti-tumor effects by 4-HC, we investigated DNA damage in a human leukemia cell line, HL-60, and its H(2)O(2)-resistant clone HP100. Apoptosis DNA ladder formation was detected in HL-60 cells treated with 4-HC, whereas it was not observed in HP100 cells. 4-HC significantly increased 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) formation, a marker of oxidative DNA damage, in HL-60 cells. On the other hand, CP did not significantly induce 8-oxodG formation and apoptosis in HL-60 cells under the same conditions as did 4-HC. Using (32)P-labeled DNA fragments from the human p53 tumor suppressor gene, 4-HC was found to cause Cu(II)-mediated oxidative DNA damage, but CP did not. Catalase inhibited 4-HC-induced DNA damage, including 8-oxodG formation, suggesting the involvement of H(2)O(2). The generation of H(2)O(2) during 4-HC degradation was ascertained by procedures using scopoletin and potassium iodide. We conclude that, in addition to DNA cross-linking, oxidative DNA damage through H(2)O(2) generation may participate in the anti-tumor effects of 4-HC.

Mechanism of NO-mediated oxidative and nitrative DNA damage in hamsters infected with Opisthorchis viverrini: a model of inflammation-mediated carcinogenesis

Inflammation mediated by infection is an important factor causing carcinogenesis. Opisthorchis viverrini (OV) infection is a risk factor of cholangiocarcinoma (CHCA), probably through chronic inflammation. Formation of 8-nitroguanine and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), and expression of inducible nitric oxide synthase (iNOS) and heme oxygenase-1 (HO-1) were assessed in the liver of hamsters infected with OV. We newly produced specific anti-8-nitroguanine antibody without cross-reaction. Double immunofluorescence staining revealed that 8-oxodG and 8-nitroguanine were formed mainly in the same inflammatory cells and epithelium of bile ducts from day 7 and showed the strongest immunoreactivity on days 21 and 30, respectively. It is noteworthy that 8-oxodG and 8-nitroguanine still remained in epithelium of bile ducts on day 180, although amount of alanine aminotransferase activity returned to normal level. A time course of 8-nitroguanine was associated with iNOS expression. Furthermore, this study demonstrated that HO-1 expression and subsequent iron accumulation may be involved in enhancement of oxidative DNA damage in epithelium of small bile ducts. In conclusion, nitrative and oxidative DNA damage via iNOS expression in hamsters infected with OV may participate in CHCA carcinogenesis.