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.     

Accumulation of 8-nitroguanine in human gastric epithelium induced by Helicobacter pylori infection

Helicobacter pylori infection causes chronic inflammation, which can lead to gastric carcinoma. A double immunofluorescence labeling study demonstrated that the level of 8-nitroguanine and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) apparent in gastric gland epithelium was significantly higher in gastritis patients with H. pylori infection than in those without infection. A significant accumulation of proliferating cell nuclear antigen, a prognostic factor for gastric cancer, was observed in gastric gland epithelial cells in patients with H. pylori infection as compared to those without infection, and its accumulation was closely correlated with the formation of 8-nitroguanine and 8-oxodG. These results suggest that nitrosative and oxidative DNA damage in gastric epithelial cells and their proliferation by H. pylori infection may lead to gastric carcinoma. 8-Nitroguanine could be not only a promising biomarker for inflammation but also a useful indicator of the risk of gastric cancer development in response to chronic H. pylori infection.     

Oxidative and nitrative DNA damage in animals and patients with inflammatory diseases in relation to inflammation-related carcinogenesis

Infection and chronic inflammation are proposed to contribute to carcinogenesis through inflammation-related mechanisms. Infection with hepatitis C virus, Helicobacter pylori and the liver fluke, Opisthorchis viverrini (OV), are important risk factors for hepatocellular carcinoma (HCC), gastric cancer and cholangiocarcinoma, respectively. Inflammatory bowel diseases (IBDs) and oral diseases, such as oral lichen planus (OLP) and leukoplakia, are associated with colon carcinogenesis and oral squamous cell carcinoma (OSCC), respectively. We performed a double immunofluorescence labeling study and found that nitrative and oxidative DNA lesion products, 8-nitroguanine and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), were formed and inducible nitric oxide synthase (iNOS) was expressed in epithelial cells and inflammatory cells at the site of carcinogenesis in humans and animal models. Antibacterial, antiviral and antiparasitic drugs dramatically diminished the formation of these DNA lesion markers and iNOS expression. These results suggest that oxidative and nitrative DNA damage occurs at the sites of carcinogenesis, regardless of etiology. Therefore, it is considered that excessive amounts of reactive nitrogen species produced via iNOS during chronic inflammation may play a key role in carcinogenesis by causing DNA damage. On the basis of our results, we propose that 8-nitroguanine is a promising biomarker to evaluate the potential risk of inflammation-mediated carcinogenesis.     

Nonylphenol exposure is associated with oxidative and nitrative stress in pregnant women

ABSTRACT

Animal studies have shown that exposure to nonylphenol (NP) increases oxidative/nitrative stress, but whether it does so in humans is unknown. This study examines prenatal exposure to NP and its effects on oxidatively/nitratively damaged DNA, lipid peroxidation, and the activities of antioxidants. A total of 146 urine and blood specimens were collected during gestational weeks 27–38 and hospital admission for delivery, respectively. Urinary NP was analyzed by high-performance liquid chromatography (HPLC). Urinary biomarkers of oxidatively/nitratively damaged DNA and lipid peroxidation, including 8-oxo-7,8-dihydro-2’-deoxyguanosine (8-oxodG), 8-nitroguanine (8-NO₂Gua), 8-iso-prostaglandin F_2α (8-isoPF_2α) and 4-hydroxy-2-nonenal-mercapturic acid (HNE-MA), were simultaneously analyzed using isotope-dilution liquid-chromatography/electron spray ionization tandem mass spectrometry. The activities of maternal plasma superoxide dismutase and glutathione peroxidase were analyzed by enzyme-linked immunosorbent assay. Urinary NP level was significantly associated with 8-oxodG and 8-NO₂Gua levels in late pregnancy, suggesting that NP may enhance oxidatively and nitratively damaged DNA. The adjusted odds ratios for high 8-oxodG level exhibited a significantly dose–response relationship with NP levels, stratified into four quartiles. 8-oxodG appears to be a more sensitive and effective biomarker of NP exposure than 8-NO₂Gua. These relationships suggest NP may play a role in the pregnancy complications.     

The B-cell lymphoma 2 (BCL2)-inhibitors, ABT-737 and ABT-263, are substrates for P-glycoprotein

To investigate whether mutant stem cells participate in inflammation-related carcinogenesis, we performed immunohistochemical analysis to examine nitrative and oxidative DNA lesions (8-nitroguanine and 8-oxodG) and a stem cell marker Oct3/4 in bladder tissues obtained from cystitis and bladder cancer patients infected with Schistosomahaematobium (S. haematobium). We also detected the expression of nuclear factor-κB (NF-κB) and inducible nitric oxide synthase (iNOS), which lead to 8-nitroguanine formation. The staining intensity of 8-nitroguanine and 8-oxodG was significantly higher in bladder cancer and cystitis tissues than in normal tissues. iNOS expression was colocalized with NF-κB in 8-nitroguanine-positive tumor cells from bladder cancer patients. Oct3/4 expression was significantly increased in cells from S. haematobium-associated bladder cancer tissues in comparison to normal bladder and cancer tissues without infection. Oct3/4 was also expressed in epithelial cells of cystitis patients. Moreover, 8-nitroguanine was formed in Oct3/4-positive stem cells in S. haematobium-associated cystitis and cancer tissues. In conclusion, inflammation by S.haematobium infection may increase the number of mutant stem cells, in which iNOS-dependent DNA damage occurs via NF-κB activation, leading to tumor development.     

Effect of green tea catechins on oxidative DNA damage of hamster pancreas and liver induced by N-Nitrosobis(2-oxopropyl)amine and/or oxidized soybean oil

It has been indicated that high fat diet is a risk factor of the pancreatic cancer by epidemiological studies. We examined whether the oxidized soybean oil (ox-oil) express the synergistic effect on the formation of 8-oxo-2'-deoxyguanosine (8-oxodG) in nuclear DNA of hamster pancreas induced by N-Nitrosobis(2-oxopropyl)amine (BOP) and whether the green tea catechins (GTC) suppressed it. Ox-oil was prepared by air oxidation, and the content of lipid hydroperoxide was 6.22 mg/ml. Hamsters were administered 0.3 ml of ox-oil/day orally for 4 weeks before BOP treatment. GTC was given ad libitum as a 0.1% aqueous solution. Four hours after subcutaneous administration of BOP, hamsters were sacrificed, and the contents of 8-oxodG were measured in nuclear DNA of pancreas and liver. The 8-oxodG content in the pancreas was increased by BOP and/or ox-oil administration. However, it was not suppressed by an intake of GTC. In the liver, though the content of 8-oxodG was increased by ox-oil, it tended to suppress the rise of 8-oxodG by a GTC intake. These results suggested that the long term intake of ox-oil might have the possibility to induce carcinogenesis in hamster pancreas and liver, and an intake of GTC might have the beneficial effect on liver.     

Reactive Nitrogen Species Mediate DNA Damage in Helicobacter pylori-Infected Gastric Mucosa

Background:  Reactive oxygen species (ROS) and reactive nitrogen species (RNS) can play an important role in cellular injury and carcinogenesis of gastric epithelial cells infected with Helicobacter pylori . 8-OH-deoxy guanosine (8-OHdG) and 8-nitroguanine (8-NG) are markers for ROS- and RNS-mediated DNA oxidation, respectively. In this study, RNS-mediated DNA damage in gastric mucosa was observed directly using a newly developed antibody to 8-NG to clarify how H. pylori infection causes nitrative DNA damage to gastric epithelial cells.
Methods:  Immunohistochemistry with anti-8-OHdG and anti-8-NG antibodies was performed on gastric tissue samples from 45 patients (25 men and 20 women) with H. pylori -positive gastritis and 19 patients (11 men and 8 women) exhibiting successful H. pylori eradication. Histologic factors for gastric mucosal inflammation were graded according to the guidelines of the Updated Sydney system.
Results:  In corpus mucosa, 8-OHdG and 8-NG production were significantly associated with the degree of glandular atrophy, infiltration of chronic inflammatory cells and intestinal metaplasia in the glandular epithelial cells. Successful H. pylori eradication resulted in a significant reduction of chronic inflammatory cell infiltration and neutrophilic activity. Mean 8-OHdG production was lower after H. pylori eradication in both corpus and antral mucosa ( p  = .022 and .049, respectively). However, the reduction in 8-NG exhibited was more pronounced than the reduction of 8-OhdG ( p  = .004 and .007, respectively).
Conclusions:  Helicobacter pylori infection can induce inflammatory cells infiltration, which evokes DNA damage of gastric epithelial cells through ROS and RNS production. 8-NG might be a more sensitive biomarker than 8-OHdG for H. pylori -induced DNA damage in gastric mucosa.     

Biological and dietary antioxidants protect against DNA nitration induced by reaction of hypochlorous acid with nitrite

Nitryl chloride, formed by reaction of hypochlorous acid with nitrite, might contribute to nitrative damage of biomolecules in addition to peroxynitrite. Damage of DNA by these reactive nitrogen oxide species is implicated in carcinogenesis associated with chronic infections and inflammation. Nitrated DNA adducts, such as 8-nitroguanine and 8-nitroxanthine, are not stable in DNA since they undergo spontaneous depurination, leading to apurinic site formation. In this report, we investigate the protective effect of biological and dietary antioxidants in inhibiting DNA nitration induced by nitryl chloride. The effect of inhibition was evaluated by decrease of 8-nitroxanthine and 8-nitroguanine formation. Among the 21 compounds examined, dihydrolipoic acid is the most effective in preventing DNA nitration, followed by N-acetyl-L-cysteine and folic acid. For sulfur-containing compounds, the more highly reduced compounds are stronger inhibitors of DNA nitration. The major product of N-acetyl-L-cysteine reaction with nitryl chloride is characterized as the (R)-2-acetylamino-3-sulfopropionic acid, a physiologically irreversible product, suggesting that nitryl chloride is a strong oxidizing agent.     

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

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