8-hydroxy-2' -deoxyguanosine (8-OHdG): A critical biomarker of oxidative stress and carcinogenesis

A system consisting of cation-exchange chromatography, combined surface-activated chemical and electrospray ionization, and ion-trap analysis for the analysis of 8-oxo-7,8-dihydro-2'-deoxyguanosine in urine

RATIONALE

8-Hydroxy-2'-deoxyguanosine has served as a biomarker for oxidative damage to DNA from different types of biological samples, and various techniques have been used to analyze it. In particular, liquid chromatography coupled to mass spectrometry has been used to identify 8-hydroxy-2'-deoxyguanosine in urine samples. Usually, a triple quadrupole analyzer and multiple reaction monitoring have been employed for its detection. Only a few studies have used a less expensive ion-trap analyzer instead.

METHODS

We have developed a new liquid chromatography/mass spectrometry procedure that incorporates cation-exchange chromatography in conjunction with surface-activated and electrospray ionization with an ion trap analyzer for the mass spectral step.

RESULTS

The combination of two ionization sources reduced the matrix effect arising from in-source reactions, thus increasing the sensitivity to levels comparable with those obtained by triple quadrupole analyzers.

CONCLUSIONS

This new method for 8-hydroxy-2'-deoxyguanosine detection provided increased sensitivity and reduced chemical noise, using a less expensive, stable and accurate mass spectrometric technology.

Neuroglobin protection in retinal ischemia

PURPOSE

Neuroglobin (Ngb) is a vertebrate globin that is predominantly expressed in the retina and brain. To explore the role of Ngb in retinal neuroprotection during ischemia reperfusion (IR), the authors examined the effect of Ngb overexpression in the retina in vivo by using Ngb-transgenic (Ngb-Tg) mice.

METHODS

Retinal IR was induced in Ngb overexpressing Ngb-Tg mice and wild type (WT) mice by cannulating the anterior chamber and transiently elevating the IOP for 60 minutes. After Day 7 of reperfusion, the authors evaluated Ngb mRNA and protein expression in nonischemic control as well as ischemic mice and its effect on retinal histology, mitochondrial oxidative stress, and apoptosis, using morphometry and immunohistochemistry, quantitative PCR analysis and Western blot techniques.

RESULTS

Ngb-Tg mice without ischemia overexpress Ngb mRNA 11.3-fold (SE ± 0.457, P < 0.05) higher than WT control mice, and this overexpression of Ngb protein was localized to the mitochondria of the ganglion cells, outer and inner plexiform layers, and photoreceptor inner segments. This overexpression of Ngb is associated with decreased mitochondrial DNA damage in Ngb-Tg mice with IR in comparison with WT. Ngb-Tg mice with IR also revealed significant preservation of retinal thickness, significantly less activated caspase 3 protein expression, and apoptosis in comparison with WT mice.

CONCLUSIONS

Neuroglobin overexpression plays a neuroprotective role against retinal ischemia reperfusion injury due to decreasing of mitochondrial oxidative stress-mediated apoptosis.

8-Oxo-7, 8-dihydro-2′-deoxyguanosine as a biomarker of DNA damage by mobile phone radiation

We examined the effect of exposure to mobile phone 1800 MHz radio frequency radiation (RFR) upon the urinary excretion of 8-oxo-7, 8-dihydro-2′-deoxyguanosine (8-oxodG), one major form of oxidative DNA damage, in adult male Sprague-Dawley rats. Twenty-four rats were used in three independent experiments (RFR exposed and control, 12 rats, each). The animals were exposed to RFR for 2 h from Global System for Mobile Communications (GSM) signal generator with whole-body-specific absorption rate of 1.0 W/kg. Urine samples were collected from the rat while housed in a metabolic cage during the exposure period over a 4-h period at 0.5, 1.0, 2.0 and 4.0 h from the beginning of exposure. In the control group, the signal generator was left in the turn-off position. The creatinine-standardized concentrations of 8-oxodG were measured. With the exception of the urine collected in the last half an hour of exposure, significant elevations were noticed in the levels of 8-oxodG in urine samples from rats exposed to RFR when compared to control animals. Significant differences were seen overall across time points of urine collection with a maximum at 1 h after exposure, suggesting repair of the DNA lesions leading to 8-oxodG formation.

Phototoxicity and environmental transformation of polycyclic aromatic hydrocarbons (PAHs)-light-induced reactive oxygen species, lipid peroxidation, and DNA damage

Polycyclic aromatic hydrocarbons (PAHs) are a class of mutagenic and tumorigenic environmental contaminants. Although the mechanisms by which PAHs induce cancer in experimental animals have been extensively studied and the metabolic activation pathways have been determined, the environmental fate of PAHs and the phototoxicity exerted by PAHs, as well as their photoreaction products formed in the environment, have received much less attention. In this review, the formation of oxygenated PAHs, PAH quinones, nitro-PAHs, and halogenated PAHs from photoreaction of environmental PAHs are addressed. Upon light irradiation, PAHs and all PAH photoreaction products can absorb light energy to reach photo-excited states, which react with molecular oxygen, medium, and coexisting chemicals to produce reactive oxygen species (ROS) and other reactive intermediates, such as oxygenated PAHs and free radicals. These intermediates, including ROS, induce lipid peroxidation, and DNA damage including DNA strand breakage, oxidation to 8-oxo-2'-deoxyguanosine, and DNA-adducts. Since these toxicological endpoints are associated with age-related diseases, including cancer, environmental PAHs concomitantly exposed to sunlight may potentially promote human skin damage, leading to ageing and skin cancers. Thus, we suggest that (i) in addition to the widely recognized metabolic pathways, more attention must be paid to photoreaction as an important activation pathway for PAHs, (ii) risk assessment of environmental PAHs should take into consideration the complex photochemical reactions leading to mixtures of products that are also phototoxic; and (iii) the study of structure-toxicity relationships should be expanded to cover the complex photoreactions and extrinsic factors that affect phototoxicity endpoints.

In vivo genotoxicity assessment in rats exposed to Prestige-like oil by inhalation

One of the largest oil spill disasters in recent times was the accident of the oil tanker Prestige in front of the Galician coast in 2002. Thousands of people participated in the cleanup of the contaminated areas, being exposed to a complex mixture of toxic substances. Acute and prolonged respiratory symptoms and genotoxic effects were reported, although environmental exposure measurements were restricted to current determinations, such that attribution of effects observed to oil exposure is difficult to establish. The aim of this study was to analyze peripheral blood leukocytes (PBL) harvested from a rat model of subchronic exposure to a fuel oil with similar characteristics to that spilled by the Prestige tanker, in order to determine potential genotoxic effects under strictly controlled, in vivo exposure. Wistar Han and Brown Norway rats were exposed to the oil for 3 wk, and micronucleus test (MN) and comet assay, standard and modified with 8-oxoguanine DNA glycosylase (OGG1) enzyme, were employed to assess genotoxicity 72 h and 15 d after the last exposure. In addition, the potential effects of oil exposure on DNA repair capacity were determined by means of mutagen sensitivity assay. Results obtained from this study showed that inhalation oil exposure induced DNA damage in both Brown Norway and Wistar Han rats, especially in those animals evaluated 15 d after exposure. Although alterations in the DNA repair responses were noted, the sensitivity to oil substances varied depending on rat strain. Data support previous positive genotoxicity results reported in humans exposed to Prestige oil during cleanup tasks.

Mitochondria in neurodegeneration

Many neurodegenerative diseases demonstrate abnormal mitochondrial morphology and biochemical dysfunction. Alterations are often systemic rather than brain-limited. Mitochondrial dysfunction may arise as a consequence of abnormal mitochondrial DNA, mutated nuclear proteins that interact directly or indirectly with mitochondria, or through unknown causes. In most cases it is unclear where mitochondria sit in relation to the overall disease cascades that ultimately causes neuronal dysfunction and death, and there is still controversy regarding the question of whether mitochondrial dysfunction is a necessary step in neurodegeneration. In this chapter we highlight and catalogue mitochondrial perturbations in some of the major neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD). We consider data that suggest mitochondria may be critically involved in neurodegenerative disease neurodegeneration cascades.

Phototoxicity of kava - formation of reactive oxygen species leading to lipid peroxidation and DNA damage

Kava is one of the most widely sold herbal dietary supplements in the United States. It has been reported that, besides exhibiting hepatotoxicity, kava also possesses photosensitivity and induces dermopathy in humans. In this study, we determined that UVA irradiation of kava in the presence of a lipid, methyl linoleate, generated lipid peroxidation which was mediated by singlet oxygen generated during photoirradiation. The six major kavalactones(yangonin, 7,8-dihydrokawa in, kawain, 7,8-dihydromethysticin, methysticin, and 5,6-dehydrokawain) were also studied in parallel; only 5,6-dehydrokawain and yangonin-induced a low level of lipid peroxidation. UVA irradiation of kava in human HaCaT skin keratinocytes induced cytotoxicity which was mediated by oxidative stress, led to DNA strand cleavage, and produced 8-hydroxy-2'-deoxyguanosine (8-OHdG) adduct. Study by the electron spin resonance (ESR) method revealed that UVA irradiation of kava produced singlet oxygen and carbon-centered radicals. The overall results suggest that kava is photocytotoxic and photogenotoxic, both mediated by free radicals generated during photoirradiation.

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone is correlated with 8-hydroxy-2'-deoxyguanosine in humans after exposure to environmental tobacco smoke

Cigarette smoking and exposure to environmental tobacco smoke (ETS) are important risk factors for many cancers. However, exposure doses have usually not been quantitatively assessed in human studies. In humans 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol and its glucuronate conjugate (defined as total NNAL) are the major metabolites of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, a cigarette-specific carcinogen. Although animal studies have shown that exposure to cigarette smoke increases tissue oxidative DNA damage, the relationship between cigarette smoke and 8-hydroxydeoxyguanosine (8-OHdG) is not consistent in human studies. In the present study, we have developed a simple, sensitive, and robust LC-MS/MS method for quantifying total NNAL and 8-OHdG concentrations in human plasma. We quantified total NNAL and 8-OHdG in plasma as well as 8-OHdG in urine of 121 healthy male subjects. Total NNAL levels were significantly higher in ever-smokers than in never-smokers. Furthermore, total NNAL levels in plasma were increased with numbers of cigarettes smoked per day in ever-smokers. It suggests that total NNAL in plasma is a good biomarker for cigarette smoke exposure. After stratifying by smoking status and adjusting for age, ETS exposure and occupation category, total NNAL was associated with plasma and urinary 8-OHdG in never-smokers, but not in ever-smokers. Since total NNAL levels in nonsmokers represented the ETS exposure, it appears that 8-OHdG levels are dose-dependently correlated with their ETS exposure dose. Furthermore, this correlation supports the hypothesis that oxidative DNA damage is one of major adverse effects induced by ETS exposure in humans.

[DNA damage in human pleural mesothelial cells induced by exposure to carbon nanotubes]

OBJECTIVES

Nanomaterials are currently used in electronics, industrial materials, cosmetics, and medicine because they have useful physicochemical properties, such as strength, conductivity, durability, and chemical stability. As these materials have become widespread, many questions have arisen regarding their effects on health and the environment. In particular, recent studies have demonstrated that carbon nanotubes (CNTs) cause significant inflammation and mesothelioma in vivo. In this study, we investigated the potential risk posed by singlewalled carbon nanotube (SWCNT) and multiwalled carbon nanotube (MWCNT) exposure in human pleural mesothelial cells.

METHODS

CNT cytotoxicity was determined by a trypan blue exclusion assay, and DNA damage was detected by an alkaline comet assay. The concentration of 8-oxodeoxyguanosine (8-OHdG) in DNA was measured by high perhormance liquid chromatography with electrochemical detection. The expression of base excision repair enzymes in the cell was estimated by immunoblot analysis.

RESULTS

We observed inhibitory effects on cell proliferation and the induction of DNA damage following exposure of cells to purified CNTs that were suspended in dispersion medium. However, accumulation of 8-OHdG in DNA was not found. In addition, the expression levels of base excision enzymes that are involved in hOGG1, hMTH1, and MYH in MeT-5A cells remained unchanged for 24 h after carbon nanotube exposure.

CONCLUSIONS

CNTs significantly inhibit cell proliferation and decrease DNA damage in human pleural mesothelial cells. Our results indicate that the mechanism of CNT-induced genotoxicity is different from that following exposure to reactive oxygen species, which causes oxidative DNA modifications and 8-OHdG production. Further investigation is required to characterize the specific DNA mutations that occur following CNT exposure.

Biomarkers of exposure to polycyclic aromatic hydrocarbons (PAHs) and DNA damage: a cross-sectional pilot study among roofers in South Florida

OBJECTIVE

The main goal of this pilot study was to assess the technical and logistic feasibility of a future study. The research hypothesis is that occupational exposures to polycyclic aromatic hydrocarbons (PAHs) are associated with increased risk of DNA damage among roofers who work with hot asphalt.

DESIGN

This is a cross-sectional pilot study.

SETTING

The study included roofers from four different construction sites in Miami-Dade County, Florida.

PARTICIPANTS

19 roofers were recruited (six Hispanics and 13 African-Americans, all male), all of whom were eligible (no history of cancer and no history of chronic diseases of kidneys or liver). All participants provided pre-shift samples and 18 provided post-shift samples. Samples of one participant were excluded from the final analyses as they were considered unreliable.

RESULTS

Levels of urinary PAH metabolites increased during 6 h of work. Linear regression models of post-shift metabolites included their pre-shift levels, post-shift urinary creatinine levels (for models of 1-OHPyr and 9-OHPhe), and skin burn due to contact with hot asphalt (for models of 1-OHPyr and 1-OHNap). Pre-shift levels of urinary 8-OHdG were not associated with any of the variables considered. For post-shift levels of 8-OHdG, however, post-shift 1-OHPyr (95% CI 0.091 to 0.788) and use of protective gloves (95% CI -1.57 to -0.61) during work explained 86.8% of its variation. Overall, highest levels of urinary PAH metabolites and of 8-OHdG were observed among workers who reported having skin burn and who did not use gloves during work.

CONCLUSIONS

Urinary 1-OHPyr is a promising predictor of oxidative DNA damage among roofers. Work-related skin burn and use of protective gloves appear to influence PAH exposure and DNA damage levels in this group, suggesting the importance of dermal absorption.

The HIV-1 transactivator factor (Tat) induces enterocyte apoptosis through a redox-mediated mechanism

The intestinal mucosa is an important target of human immunodeficiency virus (HIV) infection. HIV virus induces CD4+ T cell loss and epithelial damage which results in increased intestinal permeability. The mechanisms involved in nutrient malabsorption and alterations of intestinal mucosal architecture are unknown. We previously demonstrated that HIV-1 transactivator factor (Tat) induces an enterotoxic effect on intestinal epithelial cells that could be responsible for HIV-associated diarrhea. Since oxidative stress is implicated in the pathogenesis and morbidity of HIV infection, we evaluated whether Tat induces apoptosis of human enterocytes through oxidative stress, and whether the antioxidant N-acetylcysteine (NAC) could prevent it. Caco-2 and HT29 cells or human intestinal mucosa specimens were exposed to Tat alone or combined with NAC. In an in-vitro cell model, Tat increased the generation of reactive oxygen species and decreased antioxidant defenses as judged by a reduction in catalase activity and a reduced (GSH)/oxidized (GSSG) glutathione ratio. Tat also induced cytochrome c release from mitochondria to cytosol, and caspase-3 activation. Rectal dialysis samples from HIV-infected patients were positive for the oxidative stress marker 8-hydroxy-2'-deoxyguanosine. GSH/GSSG imbalance and apoptosis occurred in jejunal specimens from HIV-positive patients at baseline and from HIV-negative specimens exposed to Tat. Experiments with neutralizing anti-Tat antibodies showed that these effects were direct and specific. Pre-treatment with NAC prevented Tat-induced apoptosis and restored the glutathione balance in both the in-vitro and the ex-vivo model. These findings indicate that oxidative stress is one of the mechanism involved in HIV-intestinal disease.

Quercetin suppresses cytochrome P450 mediated ROS generation and NFκB activation to inhibit the development of 7,12-dimethylbenz[a]anthracene (DMBA) induced hamster buccal pouch carcinomas

Increased production of reactive oxygen species (ROS) has long been recognized to play a pivotal role in carcinogenesis. Quercetin, a naturally occurring dietary flavonoid is known for its ROS scavenging properties. The present study was designed to investigate the chemopreventive and chemotherapeutic effects of quercetin based on cytochrome P450 (CYP) mediated ROS generation, ROS-induced cellular damage and activation of the NFκB signalling circuit during 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. Administration of quercetin inhibited the development of DMBA-induced HBP carcinomas by impairing CYP-mediated ROS production via downregulation of the expression of CYP1A1 and CYP1B1, and upregulation of antioxidant defences. Attenuation of ROS generation by quercetin in turn abrogated NFκB signalling by preventing the phosphorylation and degradation of IκB, nuclear translocation of NFκB and transactivation of its target genes associated with cell proliferation and apoptosis evasion. Thus dietary flavonoids such as quercetin that can block ROS generation and inhibit the redox regulated transcription factor NFκB, by virtue of their antioxidant potential are promising candidates for future antioxidant-based anticancer regimens.

Immunochemical detection of oxidatively damaged DNA

Oxidatively damaged DNA is implicated in various diseases, including neurodegenerative disorders, cancer, diabetes, cardiovascular and inflammatory diseases as well as aging. Several methods have been developed to detect oxidatively damaged DNA. They include chromatographic techniques, the Comet assay, (32)P-postlabelling and immunochemical methods that use antibodies to detect oxidized lesions. In this review, we discuss the detection of 8-oxo-7,8-dihydro-29-deoxyguanosine (8-oxodG), the most abundant oxidized nucleoside. This lesion is frequently used as a marker of exposure to oxidants, including environmental pollutants, as well as a potential marker of disease progression. We concentrate on studies published between the years 2000 and 2011 that used enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry to detect 8-oxodG in humans, laboratory animals and in cell lines. Oxidative damage observed in these organisms resulted from disease, exposure to environmental pollutants or from in vitro treatment with various chemical and physical factors.

Poly(ADP-ribose) polymerase-1 is a key mediator of cisplatin-induced kidney inflammation and injury

Cisplatin is a commonly used chemotherapeutic drug, the clinical use of which is limited by the development of dose-dependent nephrotoxicity. Enhanced inflammatory response, oxidative stress, and cell death have been implicated in the development of cisplatin-induced nephropathy; however, the precise mechanisms are elusive. Overactivation of the nuclear enzyme poly(ADP-ribose) polymerase-1 (PARP-1) by oxidative DNA damage under various pathological conditions promotes cell death and up-regulation of key proinflammatory pathways. In this study, using a well-established model of nephropathy, we have explored the role of PARP-1 in cisplatin-induced kidney injury. Genetic deletion or pharmacological inhibition of PARP-1 markedly attenuated the cisplatin-induced histopathological damage, impaired renal function (elevated serum BUN and creatinine levels), and enhanced inflammatory response (leukocyte infiltration; TNF-α, IL-1β, F4/80, adhesion molecules ICAM-1/VCAM-1 expression) and consequent oxidative/nitrative stress (4-HNE, 8-OHdG, and nitrotyrosine content; NOX2/NOX4 expression). PARP inhibition also facilitated the cisplatin-induced death of cancer cells. Thus, PARP activation plays an important role in cisplatin-induced kidney injury, and its pharmacological inhibition may represent a promising approach to preventing the cisplatin-induced nephropathy. This is particularly exciting because several PARP inhibitors alone or in combination with DNA-damaging anticancer agents show considerable promise in clinical trials for treatment of various malignancies (e.g., triple-negative breast cancer).

Telomere length is a biomarker of cumulative oxidative stress, biologic age, and an independent predictor of survival and therapeutic treatment requirement associated with smoking behavior

Globally, tobacco use is associated with 5 million deaths per annum and is regarded as one of the leading causes of premature death. Major chronic disorders associated with smoking include cardiovascular diseases, several types of cancer, and chronic obstructive pulmonary disease (lung problems). Cigarette smoking (CS) generates a cumulative oxidative stress, which may contribute to the pathogenesis of chronic diseases. Mainstream and side stream gas-phase smoke each have about the same concentration of reactive free radical species, about 1 × 10(16) radicals per cigarette (or 5 × 10(14) per puff). This effect is critical in understanding the biologic effects of smoke. Several lines of evidence suggest that cigarette smoke constituents can directly activate vascular reactive oxygen species production. In this work we present multiple evidence that CS provide the important risk factors in many age-related diseases, and is associated with increased cumulative and systemic oxidative stress and inflammation. The cited processes are marked by increased white blood cell (leucocytes, WBCs) turnover. The data suggest an alteration of the circulating WBCs by CS, resulting in increased adherence to endothelial cells. Telomeres are complex DNA-protein structures located at the end of eukaryotic chromosomes. Telomere length shortens with biologic age in all replicating somatic cells. It has been shown that tobacco smoking enhances telomere shortening in circulating human WBCs. Telomere attrition (expressed in WBCs) can serve as a biomarker of the cumulative oxidative stress and inflammation induced by smoking and, consequently, show the pace of biologic aging. We originally propose that patented specific oral formulations of nonhydrolized carnosine and carcinine provide a powerful tool for targeted therapeutic inhibition of cumulative oxidative stress and inflammation and protection of telomere attrition associated with smoking. The longitudinal studies of the clinical population groups described in this study including elderly support the hypothesis that telomere length is a predictor of survival and therapeutic treatment requirement associated with smoking behavior.

Microfluidic tool based on the antibody-modified paramagnetic particles for detection of 8-hydroxy-2'-deoxyguanosine in urine of prostate cancer patients

Guanosine derivatives are important for diagnosis of oxidative DNA damage including 8-hydroxy-2'-deoxyguanosine (8-OHdG) as one of the most abundant products of DNA oxidation. This compound is commonly determined in urine, which makes 8-OHdG a good non-invasive marker of oxidation stress. In this study, we optimized and tested the isolation of 8-OHdG from biological matrix by using paramagnetic particles with an antibody-modified surface. 8-OHdG was determined using 1-naphthol generated by alkaline phosphatase conjugated with the secondary antibody. 1-Naphthol was determined by stopped flow injection analysis (SFIA) with electrochemical detector using a glassy carbon working electrode and by stationary electrochemical detection using linear sweep voltammetry. A special modular electrochemical SFIA system which needs only 10  μL of sample including working buffer for one analysis was completely designed and successfully verified. The recoveries in different matrices and analyte concentration were estimated. Detection limit (3 S/N) was estimated as 5  pg/mL of 8-OHdG. This method promises to be very easily modified to microfluidic systems as "lab on valve". The optimized method had sufficient selectivity and thus could be used for determination of 8-OHDG in human urine and therefore for estimation of oxidative DNA damage as a result of oxidation stress in prostate cancer patients.

Lyophilized plasma reconstituted with ascorbic acid suppresses inflammation and oxidative DNA damage

BACKGROUND

Lyophilized plasma (LP) has been shown to be as effective as fresh frozen plasma (FFP) for resuscitation in polytrauma and hemorrhagic shock. LP reconstituted with ascorbic acid is associated with suppression of cytokines when compared with fresh frozen plasma. We aimed to determine the effect of using alternate LP reconstitution acids on physiologic parameters, blood loss, coagulation, oxidative DNA damage, and proinflammatory cytokines in a polytrauma and hemorrhagic shock model.

METHODS

Thirty swine were anesthetized, subjected to polytrauma, hemorrhagic shock, and randomized to resuscitation with LP-ascorbic acid (AA), LP-citric acid (CA), or LP-hydrochloric acid (HCL). Physiologic data were continuously monitored, blood loss measured, and serum collected at baseline, 2 hours, and 4 hours for enzyme-linked immunosorbent assays. Measured 8-OH-2'-deoxyguanosine (8-OHdG) was a biomarker of oxidative DNA damage.

RESULTS

No differences were observed in physiologic measures, blood loss, or coagulation parameters. Interleukin-6 increased over time for all groups, but at 2 hours, the concentration in AA (median [minimum, maximum]: 113 ng/mL [0, 244]) was lower compared with CA (181 ng/mL [69, 314], p = 0.01) and HCL (192 ng/mL [41, 310], p = 0.03). Comparing 4 hours to baseline, a significant increase in oxidative DNA damage was observed in CA (22.9 ng/mL [16.3, 34.3] vs. 15.6 ng/mL [13.6, 26.7], p = 0.03) and HCL (19.6 ng/mL [15.7, 56.7] vs. 15.8 ng/mL [11.6, 21.4], p = 0.01) but not in AA (17.9 ng/mL [12.6, 26.9] vs. 17.1 ng/mL [11.8, 18.4], p = 0.24).

CONCLUSIONS

Resuscitation with AA results in decreased interleukin-6 expression and oxidative DNA damage compared with CA and HCL.

Alkaline, Endo III and FPG modified comet assay as biomarkers for the detection of oxidative DNA damage in rats with experimentally induced diabetes

Increased production of reactive oxygen species under diabetic condition underlines the higher oxidatively damaged DNA in different tissues. However, it is practically difficult to assess the oxidatively damaged DNA in different internal organs. Therefore, the present study was aimed to evaluate the extent of oxidative stress-induced DNA damage in different organs with the progression of diabetes. Diabetic and control Sprague Dawley rats were sacrificed in time-dependent manner and the lung, liver, heart, aorta, kidney, pancreas and peripheral blood lymphocytes (PBL) were analyzed for both alkaline and modified comet assay with endonuclease-III (Endo III) and formamidopyrimidine-DNA glycosylase (FPG) (hereafter called modified comet assay) for the detection of oxidative DNA damage. The statistically significant increase in olive tail moment (OTM) was found in all the tested tissues. The extent of DNA damage was increased with the progression of diabetes as revealed by the parameter of OTM in alkaline and modified comet assay. Further, the positive correlations were observed between OTM of the lung, liver, heart, aorta, kidney and pancreas with PBL of diabetic rat in the alkaline and modified comet assay. Moreover, significant increase in the 8-oxodG positive nuclei in the lung, liver, heart, aorta, kidney and pancreas was observed in 4th and 8th week diabetic rat as compared to control. Results of the present study clearly indicated the suitability of alkaline and modified comet assay for the detection of multi-organ oxidative DNA damage in streptozotocin (STZ)-induced diabetic rat and showed that damaged DNA of PBL can be used as a suitable biomarker to assess the internal organs response to DNA damage in diabetes.

6-gingerol prevents patulin-induced genotoxicity in HepG2 cells

Patulin (PAT) is a mycotoxin produced by several Penicillium, Aspergillus and Byssochlamys species. Since PAT is a potent genotoxic compound, and PAT contamination is common in fruits and fruit products, the search for newer, better agents for protection against genotoxicity of PAT is required. In this study, the chemoprotective effect of 6-gingerol against PAT-induced genotoxicity in HepG2 cells was investigated. The comet assay and micronucleus test (MNT) were used to monitor genotoxic effects. To further elucidate the underlying mechanisms, the intracellular generation of reactive oxygen species (ROS) and level of reduced glutathione (GSH) were tested. In addition, the level of oxidative DNA damage was evaluated by immunocytochemical analysis of 8-hydroxydeoxyguanosine (8-OHdG). The results showed that 6-gingerol significantly reduced the DNA strand breaks and micronuclei formation caused by PAT. Moreover, 6-gingerol effectively suppressed PAT-induced intracellular ROS formation and 8-OHdG level. The GSH depletion induced by PAT in HepG2 cells was also attenuated by 6-gingerol pretreatment. These findings suggest that 6-gingerol has a strong protective ability against the genotoxicity caused by PAT, and the antioxidant activity of 6-gingerol may play an important part in attenuating the genotoxicity of PAT.

Effects of alcohol consumption on biomarkers of oxidative damage to DNA and lipids in ethanol-fed pigs

Chronic alcohol consumption is known to result in tissue injury, particularly in the liver, and is considered a major risk factor for cancers of the upper respiratory tract. Here we assessed the oxidative effects of subchronic ethanol consumption on DNA and lipids by measuring biomarkers 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and malondialdehyde (MDA), respectively. Physiological responses of pigs (n = 4) administered ethanol in drinking water for 39 days were compared with those of water-fed pigs (n = 4). Alcoholisation resulted in serum ethanol concentration of 1.90 g L(-1) and in a moderate but significant increase in alanine aminotransferase activity, an index of liver injury. However, between the alcoholised and control groups there were no significant differences in the levels of 8-oxodG (8-oxodG per 10(6) 2'deoxyguanosine) from leucocytes (2.52 ± 0.42 Vs 2.39 ± 0.34) or from target organs, liver, cardia and oesophagus. Serum MDA levels were also similar in ethanol-fed pigs (0.33 ± 0.04 μM) and controls (0.28 ± 0.03 μM). Interestingly, levels of 8-oxodG in cardia were positively correlated with those in oesophagus (Spearman correlation coefficient R = 1, P < 0.0001). Our results suggest that alcohol consumption may not cause oxidative damage to DNA and lipids as measured by 8-oxodG and MDA, respectively. The duration of alcoholisation and the potential alcohol-induced nutritional deficiency may be critical determinants of ethanol toxicity. Relevant biomarkers, such as factors involved in sensitization to ethanol-induced oxidative stress are required to better elucidate the relationship between alcohol consumption, oxidative stress and carcinogenesis.

Nitrative DNA damage and Oct3/4 expression in urinary bladder cancer with Schistosoma haematobium infection

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.

Oxidative stress, inflammation, and muscle soreness in an 894-km relay trail run

We describe the effects of multi-day relay trail running on muscle soreness and damage, and systemic immune, inflammatory, and oxidative responses. 16 male and 4 female athletes ran 894 km in 47 stages over 95 h, with mean (SD) 6.4 (1.0) stages per athlete and 19.0 (1.7) km per stage. We observed post-pre run increases in serum creatine kinase (qualified effect size extremely large, p = 0.002), IL-6 (extremely large, p < 0.001), urinary 8-isoprostane/creatinine (extremely large, p = 0.04), TNF-α (large, p = 0.002), leukocyte count (very large, p < 0.0001) and neutrophil fraction (very large, p < 0.001); and reductions in hemoglobin (moderate, p < 0.001), hematocrit (moderate, p < 0.001), and lymphocyte fraction (trivial, p < 0.001). An increase in ORAC total antioxidant capacity (TAC, small, p = 0.3) and decrease in urinary 8-OHdG/creatinine (small, p = 0.1) were not statistically significant. During the run, muscle soreness was most frequent in the quadriceps. The threshold for muscle pain (pain-pressure algometry) in the vastus lateralis and gastrocnemius was lower post-run (small, p = 0.04 and 0.03). Average running speed was correlated with algometer pain and leukocyte count (large, r = 0.52), and TAC was correlated with IL-6 (very large, r = 0.76) and 8-isoprostane/creatinine (very large, r = -0.72). Multi-day stage-racing increases inflammation, lipid peroxidation, muscle damage and soreness without oxidative DNA damage. High TAC is associated with reduced exercise-induced lipid peroxidation, but is not related to immune response or muscle damage.

Chronic resveratrol intake reverses pro-inflammatory cytokine profile and oxidative DNA damage in ageing hybrid mice

Thymic involution and shrinkage of secondary lymphoid organs are leading causes of the deterioration of the T-cell compartment with age. Inflamm-aging, a sustained inflammatory status, has been associated with chronic diseases and shortened longevity. This is the first study to investigate the effect of treating aging hybrid mice with long-term, low-dose resveratrol (RSV) in drinking water by assessing multiple immunological markers and profiles in the immune system. We found that hybrid mice exhibited marked age-related changes in the CD3+CD4+, C3+CD8+, CD4+CD25+, CD4M and CD8M surface markers. RSV reversed surface phenotypes of old mice to that of young mice by maintaining the CD4+ and CD8+ population in splenocytes as well as reducing CD8+CD44+ (CD8M) cells in the aged. RSV also enhanced the CD4+CD25+ population in old mice. Interestingly, pro-inflammatory status in young mice was transiently elevated by RSV but it consequently mitigated the age-dependent increased pro-inflammatory cytokine profile while preserving the anti-inflammatory cytokine condition in the old mice. Age-dependent increase in 8OHdG, an oxidative DNA damage marker was ameliorated by RSV. Immunological-focused microarray gene expression analysis showed that only the CD72 gene was significantly downregulated in the 12-month RSV-treated mice compared to age-matched controls. Our study indicates that RSV even at low physiological relevant levels is able to affect the immune system without causing marked gene expression changes.

The long life of birds: the rat-pigeon comparison revisited

The most studied comparison of aging and maximum lifespan potential (MLSP) among endotherms involves the 7-fold longevity difference between rats (MLSP 5y) and pigeons (MLSP 35y). A widely accepted theory explaining MLSP differences between species is the oxidative stress theory, which purports that reactive oxygen species (ROS) produced during mitochondrial respiration damage bio-molecules and eventually lead to the breakdown of regulatory systems and consequent death. Previous rat-pigeon studies compared only aspects of the oxidative stress theory and most concluded that the lower mitochondrial superoxide production of pigeons compared to rats was responsible for their much greater longevity. This conclusion is based mainly on data from one tissue (the heart) using one mitochondrial substrate (succinate). Studies on heart mitochondria using pyruvate as a mitochondrial substrate gave contradictory results. We believe the conclusion that birds produce less mitochondrial superoxide than mammals is unwarranted. We have revisited the rat-pigeon comparison in the most comprehensive manner to date. We have measured superoxide production (by heart, skeletal muscle and liver mitochondria), five different antioxidants in plasma, three tissues and mitochondria, membrane fatty acid composition (in seven tissues and three mitochondria), and biomarkers of oxidative damage. The only substantial and consistent difference that we have observed between rats and pigeons is their membrane fatty acid composition, with rats having membranes that are more susceptible to damage. This suggests that, although there was no difference in superoxide production, there is likely a much greater production of lipid-based ROS in the rat. We conclude that the differences in superoxide production reported previously were due to the arbitrary selection of heart muscle to source mitochondria and the provision of succinate. Had mitochondria been harvested from other tissues or other relevant mitochondrial metabolic substrates been used, then very different conclusions regarding differences in oxidative stress would have been reached.

Venlafaxine protects against stress-induced oxidative DNA damage in hippocampus during antidepressant testing in mice

Venlafaxine (VLF) is an approved antidepressant that is claimed to have superior clinical efficacy to comparable drugs. Recently, many studies showed the relationship between depression and increased oxidative stress. This study investigated the relationship between the antidepressant effect of VLF and its ability to protect animals against stress-induced oxidative lipid peroxidation and DNA damage induced during antidepressant testing.

METHODS

The antidepressant effect of long-term treatment (21 days) of VLF in doses 5, 10 and 20mg/kg/day, i.p. was tested using forced swimming test (FST) and tail suspension test (TST). The effects of VLF on hippocampal lipid peroxidation (MDA), nitric oxide (NO), glutathione (GSH), total antioxidant (TAC) levels and glutathione-S-transferase (GST) activity were tested. Furthermore, the corresponding changes in serum and hippocampal 8-hydroxy-2'-deoxyguanosine (8-OHdG) were measured.

RESULTS

Long-term VLF treatment showed a significant, antidepressant effect in both FST and TST. VLF could decrease the hippocampal MDA and NO and to increase hippocampal GSH and TAC levels and GST activity in the tested animals. Only GSH and TAC levels were increased by VLF in the non-tested animals. In addition, both serum and hippocampal 8-OHdG levels were significantly reduced by VLF in animals exposed to antidepressant tests.

CONCLUSION

Long-term VLF treatment in the effective antidepressant doses can protect against stress-induced oxidative cellular and DNA damage. This action may be through antagonizing the oxidative stress and enhancing the antioxidant defense mechanisms. Consequently, pharmacological modulation of stress-induced oxidative DNA damage as a possible stress-management approach should be an important avenue of further research.

Lung injury caused by high tidal volume mechanical ventilation and hyperoxia is dependent on oxidant-mediated c-Jun NH2-terminal kinase activation

Both prolonged exposure to hyperoxia and large tidal volume mechanical ventilation can each independently cause lung injury. However, the combined impact of these insults is poorly understood. We recently reported that preexposure to hyperoxia for 12 h, followed by ventilation with large tidal volumes, induced significant lung injury and epithelial cell apoptosis compared with either stimulus alone (Makena et al. Am J Physiol Lung Cell Mol Physiol 299: L711-L719, 2010). The upstream mechanisms of this lung injury and apoptosis have not been clearly elucidated. We hypothesized that lung injury in this model was dependent on oxidative signaling via the c-Jun NH(2)-terminal kinases (JNK). We, therefore, evaluated lung injury and apoptosis in the presence of N-acetyl-cysteine (NAC) in both mouse and cell culture models, and we provide evidence that NAC significantly inhibited lung injury and apoptosis by reducing the production of ROS, activation of JNK, and apoptosis. To confirm JNK involvement in apoptosis, cells treated with a specific JNK inhibitor, SP600125, and subjected to preexposure to hyperoxia, followed by mechanical stretch, exhibited significantly reduced evidence of apoptosis. In conclusion, lung injury and apoptosis caused by preexposure to hyperoxia, followed by high tidal volume mechanical ventilation, induces ROS-mediated activation of JNK and mitochondrial-mediated apoptosis. NAC protects lung injury and apoptosis by inhibiting ROS-mediated activation of JNK and downstream proapoptotic signaling.

Quercetin protects human-derived liver cells against mercury-induced DNA-damage and alterations of the redox status

Aim of this study was to investigate the cytotoxic and genotoxic properties of inorganic and organic mercury compounds, i.e., HgCl(2) and methylmercury (MeHg). In addition, the DNA-protective and antioxidant effects of the flavonoid quercetin (QC) were studied. All experiments were conducted with human-derived liver cells (HepG2), which possess antioxidant and drug-metabolizing enzymes in an inducible form. 8-Hydroxydeoxyguanosine (8-OHdG) and comet formation were monitored as endpoints of DNA damage. The impact of the metal compounds on the redox status was also investigated, since it is assumed that their toxic effects are due to oxidative damage. A number of biochemical parameters related to oxidative stress, namely glutathione, malondialdehyde, protein carbonyl and formation of reactive oxygen species (ROS) were measured after treatment of the cells with the mercury compounds in the presence and absence of quercetin. To elucidate the mechanisms that underlie the effects of QC, three protocols (pre-, simultaneous and post-treatment) were used. Both mercury compounds (range 0.1-5.0μM) caused induction of DNA migration and formation of 8-OHdG. In combination with the flavonoid (range 0.1-5.0μM), DNA-protective effects of QC were observed after pre- and simultaneous treatment but not when the flavonoid was added after treatment with the metal compounds. Exposure to the metal compounds led also to substantial changes of all parameters of the redox status and co-treatment experiments with QC showed that these alterations are reversed by the flavonoid. Taken together, the results of our experiments indicate that these two mercury compounds cause DNA damage and oxidative stress in human-derived liver cells and that the flavonoid reduces these effects. Since the concentrations of the metals and of the flavonoids used in the present work reflect human exposure, our findings can be taken as an indication that QC may protect humans against the adverse effects caused by the metal.

Exposure to polycyclic aromatic hydrocarbons, arsenic and environmental tobacco smoke, nutrient intake, and oxidative stress in Japanese preschool children

The association between oxidative stress and exposure to environmental chemicals was assessed in a group of Japanese preschool children. The concentrations of 8-hydroxy-2'-deoxyguanosine (8-OHdG), 1-hydroxypyrene (1-OHP), inorganic arsenic (iAs) and monomethylarsonic acid (MMA), and cotinine in spot urine samples, collected from 134 children (3-6 yrs) from a kindergarten in Kanagawa, Japan, were measured as biomarkers of oxidative stress or exposure to environmental chemicals. For 76 subjects of the 134, intakes of anti-oxidant nutrients (vitamins A, C, and E, manganese, copper, zinc and selenium (Se)) were estimated from a food consumption survey carried out 2-4 weeks after urine sampling and by urine analysis (Se). The median (min-max) creatinine-corrected concentrations of urinary biomarkers were 4.45 (1.98-12.3), 0.127 (0.04-2.41), 4.78 (1.18-12.7), and 0.62 (<0.6-19.0) μg/g cre for 8-OHdG, 1-OHP, iAs+MMA, and cotinine, respectively. Multiple regression analysis was carried out using 8-OHdG concentration as a dependent variable and urinary biomarkers of exposure and Se intake, intakes of vitamins and biological attributes of the subjects as independent variables. To explain 8-OHdG concentrations, intake of vitamin A and age were significant variables with negative coefficients, while 1-OHP concentration had a positive coefficient. These results indicated that oxidative stress of children is affected by chemical exposure at environmental levels, by nutrient intake and by physiological factors in a complex manner. On the other hand, unstable statistical results due to sub-grouping of subject, based on the availability of food consumption data, were found: the present results should further be validated by future studies with suitable research design.

Freshwater shrimp (Palaemonetes australis) as a potential bioindicator of crustacean health

Palaemonetes australis is a euryhaline shrimp found in southwestern Australian estuaries. To determine if P. australis is a suitable bioindicator species for monitoring the health of estuarine biota, they were exposed to measured concentrations of the polycyclic aromatic hydrocarbon, benzo[a]pyrene (B[a]P) at 0.01, 0.1, or 1 ppm for 14 days under laboratory conditions. At the end of exposure the shrimp were sacrificed for biomarker [ethoxycoumarin O-deethylase (ECOD), 8-oxo-dG concentration, and sorbitol dehydrogenase (SDH) activity] analyses. Gender did not appear to influence biomarker responses of the shrimp in this study. ECOD activity was induced in the treatment groups in a linear fashion from three (0.01 ppm) times to 12 (1 ppm) times the negative controls. 8-oxo-dG concentration was reduced three times in treatment groups below the controls suggesting impaired DNA repair pathways. There was no increase in SDH, signifying hepatopancreatic cell damage had not occurred in any treatment group. The response of P. australis to B[a]P exposure indicates that this crustacean is suitable bioindicator species for both laboratory studies and field monitoring. A combination of ECOD and SDH activities and 8-oxo-dG concentration represent a suitable suite of biomarkers for environmental monitoring of the sublethal effects of organic pollution to crustaceans from an estuarine environment.

δ-tocopherol is more active than α - or γ -tocopherol in inhibiting lung tumorigenesis in vivo

In contrast to strong epidemiologic, preclinical, and secondary clinical evidence for vitamin E (tocopherols) in reducing cancer risk, large-scale clinical cancer-prevention trials of α-tocopherol have been negative. This vexing contrast helped spur substantial preclinical efforts to better understand and improve the antineoplastic activity of tocopherol through, for example, the study of different tocopherol forms. We previously showed that the γ-tocopherol-rich mixture (γ-TmT) effectively inhibited colon and lung carcinogenesis and the growth of transplanted lung-cancer cells in mice. We designed this study to determine the relative activities of different forms of tocopherol in a xenograft model, comparing the anticancer activities of δ-tocopherol with those of α- and γ-tocopherols. We subcutaneously injected human lung cancer H1299 cells into NCr nu/nu mice, which then received α-, γ-, or δ-tocopherol or γ-TmT in the diet (each at 0.17% and 0.3%) for 49 days. δ-Tocopherol inhibited tumor growth most strongly. γ-Tocopherol and γ-TmT (at 0.3%) also inhibited growth significantly, but α-tocopherol did not. δ-Tocopherol also effectively decreased oxidative DNA damage and nitrotyrosine formation and enhanced apoptosis in tumor cells; again, γ-tocopherol also was active in these regards but less so, and α-tocopherol was not. Each supplemented diet increased serum levels of its tocopherol - up to 45 μmol/L for α-tocopherol, 9.7 μmol/L for γ-tocopherol, and 1.2 μmol/L for δ-tocopherol; dietary γ- or δ-tocopherol, however, decreased serum α-tocopherol levels, and dietary α-tocopherol decreased serum levels of γ-tocopherol. Each dietary tocopherol also increased its corresponding side-chain-degradation metabolites, with concentrations of δ-tocopherol metabolites greater than γ-tocopherol and far greater than α-tocopherol metabolites in serum and tumors. This study is the first in vivo assessment of δ-tocopherol in tumorigenesis and shows that δ-tocopherol is more active than α- or γ-tocopherol in inhibiting tumor growth, possibly through trapping reactive oxygen and nitrogen species and inducing apoptosis; δ-tocopherol metabolites could contribute significantly to these results.

Increase of urinary concentrations of 8-hydroxy-2'-deoxyguanosine in diesel exhaust emission inspector exposed to polycyclic aromatic hydrocarbons

PURPOSE

The objectives of this study were to explore the factors influencing urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels in diesel engine exhaust emission inspectors (inspectors), the association between polycyclic aromatic hydrocarbons (PAHs) exposure and fine particulate matter (PM(2.5)) levels in diesel exhaust particles (DEPs), and the PAHs exposure levels in diesel vehicle emission inspection stations (inspection stations).

METHODS

Twenty-eight inspectors and a control group of thirty-eight individuals matched by age and gender were recruited for this study. Fifteen ambient air samples and eighty-four personal air samples were monitored during 3-day work periods using a repeated-measures study design in each inspection station. Airborne samples were analyzed with a fluorescence detector and by high-performance liquid chromatography. Urinary 8-OHdG was measured in 168 pre- and post-work urine samples from inspectors, and in 38 urine samples from controls.

RESULTS

The concentrations of PAHs in DEP(2.5) (PM(2.5) in DEPs) were significantly and positively related to urinary log(10) 8-OHdG levels after adjusting for smoking status and BMI. Statistically, there was a significant correlation between air log(10) PAHs and air log(10) PM(2.5) concentrations in inspectors. Fifteen PAHs compounds within DEP(2.5) revealed the concentrations ranged from 5.18 to 22.93 ng/m(3) in ambient air monitoring and 1.03 to 12.60 ng/m(3) in personal air monitoring.

CONCLUSIONS

This study is the first to indicate an association between occupational PAHs exposure from DEP(2.5) at an inspection station and an increased excretion of urinary 8-OHdG in inspectors. In addition, this study also found smoking is not a confounder in inspectors exposed to PAHs in DEP(2.5).

Pathogenesis and biomarkers of carcinogenesis in ulcerative colitis

One of the most serious complications of ulcerative colitis is the development of colorectal cancer. Screening patients with ulcerative colitis by standard histological examination of random intestinal biopsy samples might be inefficient as a method of cancer surveillance. This Review focuses on the current understanding of the pathogenesis of ulcerative colitis-associated colorectal cancer and how this knowledge can be transferred into patient management to assist clinicians and pathologists in identifying patients with ulcerative colitis who have an increased risk of colorectal cancer. Inflammation-driven mechanisms of DNA damage, including the generation and effects of reactive oxygen species, microsatellite instability, telomere shortening and chromosomal instability, are reviewed, as are the molecular responses to genomic stress. We also discuss how these mechanisms can be translated into usable biomarkers. Although progress has been made in the understanding of inflammation-driven carcinogenesis, markers based on these findings possess insufficient sensitivity or specificity to be usable as reliable biomarkers for risk of colorectal cancer development in patients with ulcerative colitis. However, screening for mutations in p53 could be relevant in the surveillance of patients with ulcerative colitis. Several other new biomarkers, including senescence markers and α-methylacyl-CoA-racemase, might be future candidates for preneoplastic markers in ulcerative colitis.

Quantitative comparison between in vivo DNA adduct formation from exposure to selected DNA-reactive carcinogens, natural background levels of DNA adduct formation and tumour incidence in rodent bioassays

This study aimed at quantitatively comparing the occurrence/formation of DNA adducts with the carcinogenicity induced by a selection of DNA-reactive genotoxic carcinogens. Contrary to previous efforts, we used a very uniform set of data, limited to in vivo rat liver studies in order to investigate whether a correlation can be obtained, using a benchmark dose (BMD) approach. Dose-response data on both carcinogenicity and in vivo DNA adduct formation were available for six compounds, i.e. 2-acetylaminofluorene, aflatoxin B1, methyleugenol, safrole, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline and tamoxifen. BMD(10) values for liver carcinogenicity were calculated using the US Environmental Protection Agency BMD software. DNA adduct levels at this dose were extrapolated assuming linearity of the DNA adduct dose response. In addition, the levels of DNA adducts at the BMD(10) were compared to available data on endogenous background DNA damage in the target organ. Although for an individual carcinogen the tumour response increases when adduct levels increase, our results demonstrate that when comparing different carcinogens, no quantitative correlation exists between the level of DNA adduct formation and carcinogenicity. These data confirm that the quantity of DNA adducts formed by a DNA-reactive compound is not a carcinogenicity predictor but that other factors such as type of adduct and mutagenic potential may be equally relevant. Moreover, comparison to background DNA damage supports the notion that the mere occurrence of DNA adducts above or below the level of endogenous DNA damage is neither correlated to development of cancer. These data strongly emphasise the need to apply the mode of action framework to understand the contribution of other biological effect markers playing a role in carcinogenicity.

NAD(P)H: quinone oxidoreductase 1 deficiency conjoint with marginal vitamin C deficiency causes cigarette smoke induced myelodysplastic syndromes

Background

The etiology of myelodysplastic syndromes (MDS) is largely unknown. Exposure to cigarette smoke (CS) is reported to be associated with MDS risk. There is inconsistent evidence that deficiency of NAD(P)H-quinone: oxidoreductase 1 (NQO1) increases the risk of MDS. Earlier we had shown that CS induces toxicity only in marginal vitamin C-deficient guinea pigs but not in vitamin C-sufficient ones. We therefore considered that NQO1 deficiency along with marginal vitamin C deficiency might produce MDS in CS-exposed guinea pigs.

Methodology and Principal Findings

Here we show that CS exposure for 21 days produces MDS in guinea pigs having deficiency of NQO1 (fed 3 mg dicoumarol/day) conjoint with marginal vitamin C deficiency (fed 0.5 mg vitamin C/day). As evidenced by morphology, histology and cytogenetics, MDS produced in the guinea pigs falls in the category of refractory cytopenia with unilineage dysplasia (RCUD): refractory anemia; refractory thrombocytopenia that is associated with ring sideroblasts, micromegakaryocytes, myeloid hyperplasia and aneuploidy. MDS is accompanied by increased CD34(+) cells and oxidative stress as shown by the formation of protein carbonyls and 8-oxodeoxyguanosine. Apoptosis precedes MDS but disappears later with marked decrease in the p53 protein. MDS produced in the guinea pigs are irreversible. MDS and all the aforesaid pathophysiological events do not occur in vitamin C-sufficient guinea pigs. However, after the onset of MDS vitamin C becomes ineffective.

Conclusions and Significance

CS exposure causes MDS in guinea pigs having deficiency of NQO1 conjoint with marginal vitamin C deficiency. The syndromes are not produced in singular deficiency of NQO1 or marginal vitamin C deficiency. Our results suggest that human smokers having NQO1 deficiency combined with marginal vitamin C deficiency are likely to be at high risk for developing MDS and that intake of a moderately large dose of vitamin C would prevent MDS.

A review on the oxidative and nitrosative stress (O&NS) pathways in major depression and their possible contribution to the (neuro)degenerative processes in that illness

This paper reviews the body of evidence that major depression is accompanied by a decreased antioxidant status and by induction of oxidative and nitrosative (IO&NS) pathways. Major depression is characterized by significantly lower plasma concentrations of a number of key antioxidants, such as vitamin E, zinc and coenzyme Q10, and a lowered total antioxidant status. Lowered antioxidant enzyme activity, e.g. glutathione peroxidase (GPX), is another hallmark of depression. The abovementioned lowered antioxidant capacity may impair protection against reactive oxygen species (ROS), causing damage to fatty acids, proteins and DNA by oxidative and nitrosative stress (O&NS). Increased ROS in depression is demonstrated by increased levels of plasma peroxides and xanthine oxidase. Damage caused by O&NS is shown by increased levels of malondialdehyde (MDA), a by-product of polyunsaturated fatty acid peroxidation and arachidonic acid; and increased 8-hydroxy-2-deoxyguanosine, indicating oxidative DNA damage. There is also evidence in major depression, that O&NS may have changed inactive autoepitopes to neoantigens, which have acquired immunogenicity and serve as triggers to bypass immunological tolerance, causing (auto)immune responses. Thus, depression is accompanied by increased levels of plasma IgG antibodies against oxidized LDL; and increased IgM-mediated immune responses against membrane fatty acids, like phosphatidyl inositol (Pi); oleic, palmitic, and myristic acid; and NO modified amino-acids, e.g. NO-tyrosine, NO-tryptophan and NO-arginine; and NO-albumin. There is a significant association between depression and polymorphisms in O&NS genes, like manganese superoxide dismutase, catalase, and myeloperoxidase. Animal models of depression very consistently show lowered antioxidant defences and activated O&NS pathways in the peripheral blood and the brain. In animal models of depression, antidepressants consistently increase lowered antioxidant levels and normalize the damage caused by O&NS processes. Antioxidants, such as N-acetyl-cysteine, compounds that mimic GPX activity, and zinc exhibit antidepressive effects. This paper reviews the pathways by which lowered antioxidants and O&NS may contribute to depression, and the (neuro)degenerative processes that accompany that illness. It is concluded that aberrations in O&NS pathways are--together with the inflammatory processes--key components of depression. All in all, the results suggest that depression belongs to the spectrum of (neuro)degenerative disorders.

Urinary 8-OHdG elevations in a partial lesion rat model of Parkinson's disease correlate with behavioral symptoms and nigrostriatal dopaminergic depletion

Increased oxidative stress contributes to pathogenesis of Parkinson's disease (PD). 8-hydroxy-2'-deoxyguanosine (8-OHdG) is the oxidation product most frequently measured as an indicator of oxidative DNA damage. Several studies have shown increased 8-OHdG in PD patients. There are few basic laboratory data examining 8-OHdG levels in animal models of PD. In this study, we utilized hemiparkinsonian model of rats induced by intrastriatal injection of 6-hydroxydopamine (6-OHDA). The urinary 8-OHdG level was measured in relation to behavioral and pathological deficits arising from 6-OHDA-induced neurotoxic effects on the nigrostriatal dopaminergic pathway. All rats were subjected to a series of behavioral tests for 42 days after 6-OHDA injection. We collected urine samples with subsequent measurement of 8-OHdG level using ELISA kits. For immunohistochemical evaluation, tyrosine hydroxylase (TH) staining was performed. Significant increments in urinary 8-OHdG level were observed continuously from day 7 until day 35 compared to control group, which showed a trend of elevation as early as day 3. Such elevated urinary 8-OHdG level significantly correlated with all of the behavioral deficits measured here, suggesting that urinary 8-OHdG level provides a good index of severity of parkinsonism. Urinary 8-OHdG level also had a significant positive correlation with the survival rate of dopaminergic fibers or neurons, advancing the concept that oxidative stress during the early phase of 6-OHDA neurotoxicity may correspond to disease progression closely approximating neuronal degeneration in the nigrostriatal dopaminergic system. The present results demonstrate that alterations in urinary 8-OHdG level closely approximate onset and disease progression in PD.

Urine markers and prostate cancer

Prostate cancer (PCa) is globally the most common cancer in men, with an estimated prevalence of more than two million cases. Given the poor success rate in treating advanced PCa, intervention in early stages may reduce the progression of a small, localized carcinoma to a large metastatic lesion, thereby reducing disease-related deaths. Urine is readily available and can be used to detect either exfoliated cancer cells or secreted products. The major advantages of urine-based assays are their noninvasive character and ability to monitor PCa with heterogeneous foci. The aim of this review was to summarize the current evidence regarding performance characteristics of tests proposed for urine-based prostate cancer detection.

Mutagenesis and repair induced by the DNA advanced glycation end product N2-1-(carboxyethyl)-2'-deoxyguanosine in human cells

Glycation of biopolymers by glucose-derived α-oxo-aldehydes such as methylglyoxal (MG) is believed to play a major role in the complex pathologies associated with diabetes and metabolic disease. In contrast to the extensive literature detailing the formation and physiological consequences of protein glycation, there is little information about the corresponding phenomenon for DNA. To assess the potential contribution of DNA glycation to genetic instability, we prepared shuttle vectors containing defined levels of the DNA glycation adduct N(2)-(1-carboxyethyl)-2'-deoxyguanosine (CEdG) and transfected them into isogenic human fibroblasts that differed solely in the capacity to conduct nucleotide excision repair (NER). In the NER-compromised fibroblasts, the induced mutation frequencies increased up to 18-fold relative to background over a range of ∼10-1400 CEdG adducts/10(5) dG, whereas the same substrates transfected into NER-competent cells induced a response that was 5-fold over background at the highest adduct density. The positive linear correlation (R(2) = 0.998) of mutation frequency with increasing CEdG level in NER-defective cells suggested that NER was the primary if not exclusive mechanism for repair of this adduct in human fibroblasts. Consistent with predictions from biochemical studies using CEdG-substituted oligonucleotides, guanine transversions were the predominant mutation resulting from replication of MG-modified plasmids. At high CEdG levels, significant increases in the number of AT → GC transitions were observed exclusively in NER-competent cells (P < 0.0001). This suggested the involvement of an NER-dependent mutagenic process in response to critical levels of DNA damage, possibly mediated by error-prone Y-family polymerases.

Oxidative stress and oxidative damage in chemical carcinogenesis

Reactive oxygen species (ROS) are induced through a variety of endogenous and exogenous sources. Overwhelming of antioxidant and DNA repair mechanisms in the cell by ROS may result in oxidative stress and oxidative damage to the cell. This resulting oxidative stress can damage critical cellular macromolecules and/or modulate gene expression pathways. Cancer induction by chemical and physical agents involves a multi-step process. This process includes multiple molecular and cellular events to transform a normal cell to a malignant neoplastic cell. Oxidative damage resulting from ROS generation can participate in all stages of the cancer process. An association of ROS generation and human cancer induction has been shown. It appears that oxidative stress may both cause as well as modify the cancer process. Recently association between polymorphisms in oxidative DNA repair genes and antioxidant genes (single nucleotide polymorphisms) and human cancer susceptibility has been shown.

Saturated hydrogen saline protects rats from acute lung injury induced by paraquat

BACKGROUND

Paraquat (PQ) intoxication causes lung oxidative stress damage. Saturated hydrogen saline, a newly explored antioxidant, has been documented to play a powerful antioxidant role in preventing oxidative stress damage. This study aimed to investigate the protective effects and the possible mechanisms of intoxication on rats with acute lung injury (ALI) caused by paraquat poisoning.

METHODS

Thirty PQ poisoned rats were randomly divided into a PQ intoxication group (intoxication group), a saturated hydrogen saline intervention group (intervention group), and a control group, with 10 rats in each group. The first two groups accepted an intragastric administration of PQ at a dose of 50 mg/kg for every single rat, and the control group was fed with a same volume of normal saline. Five mL/kg of saturated hydrogen saline was given to the intervention group three times a day by peritoneal injection for three days after intoxication. Arterial blood gas was detected on the third day. The rats were executed and their lungs were taken for measurement of wet dry weight ratio, homogenate malondialdehyde (MDA), and 8-hydroxy-2'-deoxyguanosine (8-OhdG). Histological changes of the lungs were also observed.

RESULTS

Compared with the control group, the intoxication group had more serious hypoxemia, greater wet/dry weight ratio, higher MDA level, higher expression of 8-OhdG and more severe lung damage (P<0.01 or P<0.05). However, after intervention with saturated hydrogen saline, poisoned animals turned to have lighter hypoxemia, smaller wet/dry weight ratio, lower MDA level, lower expression of 8-OhdG, and milder lung damage (P<0.01 or P<0.05).

CONCLUSIONS

Saturated hydrogen saline is effective in preventing acute lung injury caused by PQ. Possibly, it can neutralize toxic oxygen radicals selectively and alleviate the oxidative stress injury induced by PQ.

The relationship between urinary 8-hydroxydeoxyguanosine and metabolic risk factors in asymptomatic subjects

OBJECTIVE

The aim of this study was to investigate the relationship between metabolic risk factors and oxidative stress using urinary 8-hydroxydeoxyguanosine (8-OHdG), a recently utilized biological marker, in asymptomatic subjects.

METHODS

Ninety subjects (males/females = 30/60; mean age = 52 years), who were nonsmoking, nondiabetic and not on any medicine, were enrolled in the study. The body mass index, blood pressure, total cholesterol, triglyceride (TG), high-density lipoprotein cholesterol (HDL-C) and glucose as well as urinary 8-OHdG and creatinine were measured.

RESULTS

The median level of 8-OHdG was 9.3 ng/mg creatinine (interquartile range: 5.8-23.2). TG (Pearson's correlation: r = 0.262, p = 0.013) and HDL-C (r = -0.259, p = 0.014) showed a significant correlation with 8-OHdG. A multiple linear regression analysis adjusted for all the variables revealed that only TG had an independently significant and positive correlation with 8-OHdG (β = 0.231, p = 0.046).

CONCLUSION

The data in this population suggest that, among metabolic risk factors, hypertriglyceridemia may be weakly but significantly associated with hyperoxidative stress as assessed by 8-OHdG.

Furazolidone induced oxidative DNA damage via up-regulating ROS that caused cell cycle arrest in human hepatoma G2 cells

Furazolidone (FZD) is an antimicrobial agent that has been shown to have mutagenic, genotoxic and potentially carcinogenic properties when tested in a variety of systems in vitro and in vivo. In this study, we investigated FZD's DNA damaging effect in human hepatoma cells aiming at further defining the molecular mechanism of FZD's cytotoxicity. Addition of FZD resulted in cell growth suppression and cell cycle arrest in S phase accompanied by remarkable DNA strand breaks with increased levels of intracellular reactive oxygen species (ROS) and 8-hydroxydeoxyguanosine. Activities of antioxidases were down-regulated following FZD treatment and antioxidant agent catalase and superoxide dismutase ameliorated FZD's DNA damaging effects. Moreover, FZD caused much more extensive damage to mitochondrial DNA (mtDNA) than to nuclear DNA for which the decrease in mtDNA content correlated with FZD usage in a dose-dependent manner. However, there was no evidence of FZD induced mtDNA mutation in the mitochondrial DNA displacement loop. These results demonstrate that FZD up-regulates the production of intracellular ROS to cause oxidative DNA damage with mtDNA being the most vulnerable targets. Oxidative stress and the injury of mtDNA could be early indicators of FZD-induced cytotoxicity, with the resulting abnormal progression of the cell cycle.

Redox regulation in cancer: a double-edged sword with therapeutic potential

Oxidative stress, implicated in the etiology of cancer, results from an imbalance in the production of reactive oxygen species (ROS) and cell’s own antioxidant defenses. ROS deregulate the redox homeostasis and promote tumor formation by initiating an aberrant induction of signaling networks that cause tumorigenesis. Ultraviolet (UV) exposures, γ-radiation and other environmental carcinogens generate ROS in the cells, which can exert apoptosis in the tumors, thereby killing the malignant cells or induce the progression of the cancer growth by blocking cellular defense system. Cancer stem cells take the advantage of the aberrant redox system and spontaneously proliferate. Oxidative stress and gene-environment interactions play a significant role in the development of breast, prostate, pancreatic and colon cancer. Prolonged lifetime exposure to estrogen is associated with several kinds of DNA damage. Oxidative stress and estrogen receptor-associated proliferative changes are suggested to play important roles in estrogen-induced breast carcinogenesis. BRCA1, a tumor suppressor against hormone responsive cancers such as breast and prostate cancer, plays a significant role in inhibiting ROS and estrogen mediated DNA damage; thereby regulate the redox homeostasis of the cells. Several transcription factors and tumor suppressors are involved during stress response such as Nrf2, NFκB and BRCA1. A promising strategy for targeting redox status of the cells is to use readily available natural substances from vegetables, fruits, herbs and spices. Many of the phytochemicals have already been identified to have chemopreventive potential, capable of intervening in carcinogenesis.