Lipid peroxidation-derived etheno-DNA adducts in human atherosclerotic lesions

Molecular Study on Twin Cohort with Discordant Birth Weight

The increased rate of twinning has pointed out newer challenges in clinical practices related to gestational complications, intrauterine growth restriction, perinatal mortality, and comorbidities. As a twin pregnancy progresses, the increased demand for oxygen supply can easily disrupt the redox homeostasis balance and further impose a greater challenge for the developing fetuses. A substantial birth-weight difference acts as an indicator of a deficit in oxygenation or blood flow to one of the fetuses, which might be related to a low bioavailable nitric oxide level. Therefore, in this study, we focused on networks involved in the adjustment of oxygen supply, like the activation of inducible and endothelial nitric oxide synthase (NOS3) along with free radical and lipid peroxide formation in mature twin pairs with high birth-weight differences. The selected parameters were followed by immunofluorescence staining, fluorescence-activated cell sorting analysis, and biochemical measurements in the umbilical cord vessels and fetal red blood cells. Based on our data set, it is clear that the lower-weight siblings are markedly exposed to persistent intrauterine hypoxic conditions, which are connected to a decreased level in NOS3 activation. Furthermore, the increased level of peroxynitrite aggravates lipid peroxidation and induces morphological and functional damage and loss in redox homeostasis.

Lipoxidation in cardiovascular diseases

Lipids can go through lipid peroxidation, an endogenous chain reaction that consists in the oxidative degradation of lipids leading to the generation of a wide variety of highly reactive carbonyl species (RCS), such as short-chain carbonyl derivatives and oxidized truncated phospholipids. RCS exert a wide range of biological effects due to their ability to interact and covalently bind to nucleophilic groups on other macromolecules, such as nucleic acids, phospholipids, and proteins, forming reversible and/or irreversible modifications and generating the so-called advanced lipoxidation end-products (ALEs). Lipoxidation plays a relevant role in the onset of cardiovascular diseases (CVD), mainly in the atherosclerosis-based diseases in which oxidized lipids and their adducts have been extensively characterized and associated with several processes responsible for the onset and development of atherosclerosis, such as endothelial dysfunction and inflammation. Herein we will review the current knowledge on the sources of lipids that undergo oxidation in the context of cardiovascular diseases, both from the bloodstream and tissues, and the methods for detection, characterization, and quantitation of their oxidative products and protein adducts. Moreover, lipoxidation and ALEs have been associated with many oxidative-based diseases, including CVD, not only as potential biomarkers but also as therapeutic targets. Indeed, several therapeutic strategies, acting at different levels of the ALEs cascade, have been proposed, essentially blocking ALEs formation, but also their catabolism or the resulting biological responses they induce. However, a deeper understanding of the mechanisms of formation and targets of ALEs could expand the available therapeutic strategies.

Stress Echocardiography Positivity Predicts Cancer Death

BACKGROUND

Stress echocardiography (SE) predicts cardiac death, but an increasing share of cardiac patients eventually die of cancer. The aim of the study was to assess whether SE positivity predicts cancer death.

METHODS AND RESULTS

In a retrospective analysis of prospectively acquired single-center, observational data, we evaluated 4673 consecutive patients who underwent SE from 1983 to 2009. All patients were cancer-free at index SE and were followed up for a median of 131 months (interquartile range 134). We separately analyzed predetermined end points: cardiovascular, cancer, and noncardiovascular, noncancer death, with and without competing risk. SE was positive in 1757 and negative in 2916 patients; 869 cardiovascular, 418 cancer, and 625 noncardiovascular, noncancer deaths were registered. The 25-year mortality was higher in SE-positive than in SE-negative patients, considering cardiovascular (40% versus 31%; P<0.001) and cancer mortality (26% versus 17%; P<0.01). SE positivity was a strong predictor of cancer (cause-specific hazard ratio 1.19; 95% confidence interval, 1.16-1.73; P=0.05) and cardiovascular mortality (1.18; 95% confidence interval, 1.03-1.35; P=0.02). Fine-Gray analysis to account for competing risk gave similar results. Cancer risk diverged after 15 years, whereas differences were already significant at 5 years for cardiovascular risk.

CONCLUSIONS

SE results predict cardiovascular and cancer mortality. SE may act as a proxy of the shared risk factor milieu for cancer or cardiovascular death.

Oxidative status and reduced glutathione levels in premature coronary artery disease and coronary artery disease

Identifying patients at risk of developing premature coronary artery disease (PCAD) which occurs at age below 45 years old and constitutes approximately 7-10% of coronary artery disease (CAD) worldwide remains a problem. Oxidative stress has been proposed as a crucial step in the early development of PCAD. This study was conducted to determine the oxidative status of PCAD in comparison to CAD patients. PCAD (<45 years old) and CAD (>60 years old) patients were recruited with age-matched controls (n = 30, each group). DNA damage score, plasma malondialdehyde (MDA) and protein carbonyl content were measured for oxidative damage markers. Antioxidants such as erythrocyte glutathione (GSH), oxidised glutathione (GSSG), and glutathione peroxidase activity (GPx), superoxide dismutase (SOD) and catalase (CAT) were also determined. DNA damage score and protein carbonyl content were significantly higher in both PCAD and CAD when compared to age-matched controls while MDA level was increased only in PCAD (p<.05). In contrast, GSH, GSH/GSSG ratio, α-tocotrienol isomer, and GPx activity were significantly decreased, but only in PCAD when compared to age-matched controls. The decrease in GSH was associated with PCAD (OR = 0.569 95%CI [0.375 - 0.864], p = .008) and cut-off values of 6.69 μM with areas under the ROC curves (AUROC) 95%CI: 0.88 [0.80-0.96] (sensitivity of 83.3%; specificity of 80%). However, there were no significant differences in SOD and CAT activities in all groups. A higher level of oxidative stress indicated by elevated MDA levels and low levels of GSH, α-tocotrienol and GPx activity in patients below 45 years old may play a role in the development of PCAD and has potential as biomarkers for PCAD.

Oxysterols and 4-hydroxy-2-nonenal contribute to atherosclerotic plaque destabilization

A growing bulk of evidence suggests that cholesterol oxidation products, known as oxysterols, and 4-hydroxy-2-nonenal (HNE), the major proatherogenic components of oxidized low density lipoproteins (oxLDLs), significantly contribute to atherosclerotic plaque progression and destabilization, with eventual plaque rupture. These oxidized lipids are involved in various key steps of this complex process, mainly thanks to their ability to induce inflammation, oxidative stress, and apoptosis. This review summarizes the current knowledge of the effects induced by these compounds on vascular cells, after their accumulation in the arterial wall and in the atherosclerotic plaque.

Polymorphism in ERCC1 confers susceptibility of coronary artery disease and severity of coronary artery atherosclerosis in a Chinese Han population

Excision repair cross-complementing 1 (ERCC1) gene encodes ERCC1 protein, which is mainly responsible for the repair of DNA damage in different diseases including coronary artery atherosclerosis by acting as a rate-limiting element in nucleotide excision repair (NER). Using a three-stage case-control study with 3037 coronary artery disease (CAD) patients and 3002 controls, we investigated associations of three single nucleotide polymorphisms (SNPs) with CAD risk and severity of coronary artery atherosclerosis in Chinese Han population. In the discovery set, the variant allele T of rs11615 was significantly associated with higher CAD risk (adjusted OR = 1.27, P = 0.006) and severity of coronary artery atherosclerosis (adjusted OR = 1.54, P = 0.003). These associations were more remarkable in the merged set (adjusted OR = 1.23, P = 8 × 10^-6 for CAD risk; adjusted OR = 1.36, P = 4.3 × 10^-5 for severity of coronary artery atherosclerosis). And the expression level of ERCC1 was significantly higher in CAD cases than controls. Multiplicative interactions among SNP rs11615, alcohol drinking, history of T2DM, and history of hyperlipidemia could increase 5.06-fold risk of CAD (P = 1.59 × 10^-9). No significant association of rs2298881 and rs3212986 with CAD risk was identified. Taken together, SNP rs11615 in ERCC1 gene might confer susceptibility to CAD and severity of coronary atherosclerosis in a Chinese Han population.

Imbalanced adaptive responses associated with microsatellite instability in cholangiocarcinoma

The adaptive response of the genome protection mechanism occurs in cells when exposed to genotoxic stress due to the overproduction of free radicals via inflammation and infection. In such circumstances, cells attempt to maintain health via several genome protection mechanisms. However, evidence is increasing that this adaptive response may have deleterious effect; a reduction of antioxidant enzymes and/or imbalance in the DNA repair system generates microsatellite instability (MSI), which has procarcinogenic implications. Therefore, the present study hypothesized that MSI caused by imbalanced responses of antioxidant enzymes and/or DNA repair enzymes as a result of oxidative/nitrative stress arising from the inflammatory response is involved in liver fluke-associated cholangiocarcinogenesis. The present study investigated this hypothesis by identifying the expression patterns of antioxidant enzymes, including superoxide dismutase 2 (SOD2) and catalase (CAT), and DNA repair enzymes, including alkyladenine DNA glycosylase (AAG), apurinic endonuclease (APE) and DNA polymerase β (DNA pol β). In addition, the activities of the antioxidant enzymes, SOD2 and CAT, were examined in human cholangiocarcinoma (CCA) tissues using immunohistochemical staining. MSI was also analyzed in human CCA tissues. The resulting data demonstrated that the expression levels of the SOD2 and CAT enzymes decreased. The activities of SOD2 and CAT decreased significantly in the CCA tissues, compared with the hepatic tissue of cadaveric donors. In the DNA repairing enzymes, it was found that the expression levels of AAG and DNA pol β enzymes increased, whereas the expression of APE decreased. In addition, it was found that MSI-high was present in 69% of patients, whereas MSI-low was present in 31% of patients, with no patients classified as having microsatellite stability. In the patients, a MSI-high was correlated with poor prognosis, indicated by a shorter survival rate. These results indicated that the reduction of antioxidant enzymes and adaptive imbalance of base excision repair enzymes in human CCA caused MSI, and may be associated with the progression of cancer.

Increased levels of urinary biomarkers of lipid peroxidation products among workers occupationally exposed to diesel engine exhaust

Diesel engine exhaust (DEE) was found to induce lipid peroxidation (LPO) in animal exposure studies. LPO is a class of oxidative stress and can be reflected by detecting the levels of its production, such as malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE), and etheno-DNA adducts including 1,N(6)-etheno-2'-deoxyadenosine (ɛdA) and 3,N(4)-etheno-2'-deoxycytidine (ɛdC). However, the impact of DEE exposure on LPO has not been explored in humans. In this study, we evaluated urinary MDA, 4-HNE, ɛdA, and ɛdC levels as biomarkers of LPO among 108 workers with exclusive exposure to DEE and 109 non-DEE-exposed workers. Results showed that increased levels of urinary MDA and ɛdA were observed in subjects occupationally exposed to DEE before and after age, body mass index (BMI), smoking status, and alcohol use were adjusted (all p < 0.001). There was a statistically significant relationship between the internal exposure dose (urinary ΣOH-PAHs) and MDA, 4-HNE, and ɛdA (all p < 0.001). Furthermore, significant increased relations between urinary etheno-DNA adduct and MDA, 4-HNE were observed (all p < 0.05). The findings of this study suggested that the level of LPO products (MDA and ɛdA) was increased in DEE-exposed workers, and urinary MDA and ɛdA might be feasible biomarkers for DEE exposure. LPO induced DNA damage might be involved and further motivated the genomic instability could be one of the pathogeneses of cancer induced by DEE-exposure. However, additional investigations should be performed to understand these observations.

Flavonoid Fraction of Orange and Bergamot Juices Protect Human Lung Epithelial Cells from Hydrogen Peroxide-Induced Oxidative Stress

It has been reported that oxidant/antioxidant imbalance triggers cell damage that in turn causes a number of lung diseases. Flavonoids are known for their health benefits, and Citrus fruits juices are one of the main food sources of these secondary plant metabolites. The present study was designed to evaluate the effect of the flavonoid fraction of bergamot and orange juices, on H2O2-induced oxidative stress in human lung epithelial A549 cells. First we tested the antioxidant properties of both extracts in cell-free experimental models and then we assayed their capability to prevent the cytotoxic effects induced by H2O2. Our results demonstrated that both Citrus juice extracts reduce the generation of reactive oxygen species and membrane lipid peroxidation, improve mitochondrial functionality, and prevent DNA-oxidative damage in A549 cells incubated with H2O2. Our data indicate that the mix of flavonoids present in both bergamot and orange juices may be of use in preventing oxidative cell injury and pave the way for further research into a novel healthy approach to avoid lung disorders.

Covalent modification of DNA by α, β-unsaturated aldehydes derived from lipid peroxidation: Recent progress and challenges

Oxidative stress-induced lipid peroxidation (LPO) has been associated with human physiology and pathophysiology. LPO generates an array of oxidation products and among them reactive lipid aldehydes have received intensive research attentions due to their roles in modulating functions of biomolecules through covalent modification. Thus, covalent modification of DNA by these reactive lipid electrophiles has been postulated to be partially responsible for the biological roles of LPO. In this review, we summarized recent progress and challenges in studying the roles of covalent modification of DNA including nuclear and mitochondrial DNA by reactive lipid metabolites from LPO. We focused on the novel mechanistic insights into generation of lipid aldehydes from cellular membranes especially mitochondria through LPO. Recent advances in the technological front using mass spectrometry have also been highlighted in the settings of studying DNA damage caused by LPO and its biological relevance.

Oxidized LDL stimulates lipid peroxidation-derived DNA and protein adducts in human vascular endothelial and smooth muscle cells

Oxidized low density lipoprotein (oxLDL) can trigger intracellular production of reactive oxygen species and lipid peroxidation (LPO), and is thought to contribute to initiation and progression of atherosclerosis. In order to understand the correlation between oxLDL and macromolecular damage, we measured levels of LPO-derived miscoding etheno-DNA adducts and LPO-modified proteins in cultured human vascular endothelial and smooth muscle cells after incubation with oxLDL for up to 48 h. A semi-quantative analysis method for 1, N6-ethenodeoxyadenosine (ɛdA) by immunohistochemistry was applied. After oxLDL stimulation, ɛdA-stained nuclei were significantly increased in both endothelial and smooth muscle cells. Similarly, 4-hydroxy-2-nonenal (4-HNE)-modified proteins, as analyzed by immunohistochemistry and Western blotting, were also 3-5 fold increased. It was concluded LPO-derived etheno-DNA adducts and LPO-modified proteins are strongly induced by oxLDL in human vascular endothelial and smooth muscle cells. This macromolecular damage may contribute to the dysfunction of arterial endothelium and the onset of atherosclerosis.

Genetic variants in the DNA repair gene NEIL3 and the risk of myocardial infarction in a nested case-control study. The HUNT Study

BACKGROUND

Enhanced generation of reactive oxygen species and increased oxidative-induced DNA damage have been identified as possible contributors to atherosclerosis. The base excision repair (BER) pathway is the principal mechanism by which mammalian cells repair oxidative DNA damage. BER deficiency can potentially accelerate atherogenesis.

METHODS

We evaluated the association of Single Nucleotide Polymorphisms (SNPs) in genes encoding four different BER proteins (NEIL3, OGG1, APEX1 and XRCC1) with the incidence of myocardial infarction in a nested case-control study among participants of the second survey of the HUNT Study. The study population included 1624 cases and 4087 age- and sex-matched controls.

RESULTS

For the NEIL3 SNP rs12645561, the TT genotype was associated with increased risk of MI (OR 1.47, 95% CI 1.02-2.12, p uncorrected for multiple comparisons = 0.04) both in the genotypic test (compared to the CC genotype) and in the recessive genetic model (compared to the CC and CT genotypes combined). For the other two NEIL3 SNPs (rs10013040 and rs1395479) and for the SNPs of OGG1 (rs1052133), APEX1 (rs1878703) and XRCC1 (rs25489) we observed no association with risk of myocardial infarction.

CONCLUSION

We found that the NEIL3 rs12645561 SNP TT genotype was associated with increased risk of myocardial infarction. If confirmed in other studies, this association may suggest a possible role of attenuated DNA repair, and NEIL3 in particular, in atherogenesis.

The endogenous exposome

The concept of the Exposome is a compilation of diseases and one's lifetime exposure to chemicals, whether the exposure comes from environmental, dietary, or occupational exposures; or endogenous chemicals that are formed from normal metabolism, inflammation, oxidative stress, lipid peroxidation, infections, and other natural metabolic processes such as alteration of the gut microbiome. In this review, we have focused on the endogenous exposome, the DNA damage that arises from the production of endogenous electrophilic molecules in our cells. It provides quantitative data on endogenous DNA damage and its relationship to mutagenesis, with emphasis on when exogenous chemical exposures that produce identical DNA adducts to those arising from normal metabolism cause significant increases in total identical DNA adducts. We have utilized stable isotope labeled chemical exposures of animals and cells, so that accurate relationships between endogenous and exogenous exposures can be determined. Advances in mass spectrometry have vastly increased both the sensitivity and accuracy of such studies. Furthermore, we have clear evidence of which sources of exposure drive low dose biology that results in mutations and disease. These data provide much needed information to impact quantitative risk assessments, in the hope of moving towards the use of science, rather than default assumptions.

Effects of 4-hydroxynonenal on vascular endothelial and smooth muscle cell redox signaling and function in health and disease

4-hydroxynonenal (HNE) is a lipid hydroperoxide end product formed from the oxidation of n-6 polyunsaturated fatty acids. The relative abundance of HNE within the vasculature is dependent not only on the rate of lipid peroxidation and HNE synthesis but also on the removal of HNE adducts by phase II metabolic pathways such as glutathione-S-transferases. Depending on its relative concentration, HNE can induce a range of hormetic effects in vascular endothelial and smooth muscle cells, including kinase activation, proliferation, induction of phase II enzymes and in high doses inactivation of enzymatic processes and apoptosis. HNE also plays an important role in the pathogenesis of vascular diseases such as atherosclerosis, diabetes, neurodegenerative disorders and in utero diseases such as pre-eclampsia. This review examines the known production, metabolism and consequences of HNE synthesis within vascular endothelial and smooth muscle cells, highlighting alterations in mitochondrial and endoplasmic reticulum function and their association with various vascular pathologies.

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HNE is a lipid peroxidation endproduct regulating vascular redox signaling.

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HNE detoxification is tightly regulated in vascular and other cell types.

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Elevated HNE levels are associated with various vascular diseases.

Noni juice reduces lipid peroxidation-derived DNA adducts in heavy smokers

Food plants provide important phytochemicals which help improve or maintain health through various biological activities, including antioxidant effects. Cigarette smoke–induced oxidative stress leads to the formation of lipid hydroperoxides (LOOHs) and their decomposition product malondialdehyde (MDA), both of which cause oxidative damage to DNA. Two hundred forty-five heavy cigarette smokers completed a randomized, double-blind, placebo-controlled clinical trial designed to investigate the effect of noni juice on LOOH- and MDA-DNA adducts in peripheral blood lymphocytes (PBLs). Volunteers drank noni juice or a fruit juice placebo every day for 1 month. DNA adducts were measured by ³²P postlabeling analysis. Drinking 29.5–118 mL of noni juice significantly reduced adducts by 44.6–57.4%. The placebo, which was devoid of iridoid glycosides, did not significantly influence LOOH- and MDA-DNA adduct levels in current smokers. Noni juice was able to mitigate oxidative damage of DNA in current heavy smokers, an activity associated with the presence of iridoids.

DNA and protein adducts in human tissues resulting from exposure to tobacco smoke

Tobacco smoke contains a variety of genotoxic carcinogens that form adducts with DNA and protein in the tissues of smokers. Not only are these biochemical events relevant to the carcinogenic process, but the detection of adducts provides a means of monitoring exposure to tobacco smoke. Characterization of smoking-related adducts has shed light on the mechanisms of smoking-related diseases and many different types of smoking-derived DNA and protein adducts have been identified. Such approaches also reveal the potential harm of environmental tobacco smoke (ETS) to nonsmokers, infants and children. Because the majority of tobacco-smoke carcinogens are not exclusive to this source of exposure, studies comparing smokers and nonsmokers may be confounded by other environmental sources. Nevertheless, certain DNA and protein adducts have been validated as biomarkers of exposure to tobacco smoke, with continuing applications in the study of ETS exposures, cancer prevention and tobacco product legislation. Our article is a review of the literature on smoking-related adducts in human tissues published since 2002.

DNA damage and repair in atherosclerosis: current insights and future perspectives

Atherosclerosis is the leading cause of morbidity and mortality among Western populations. Over the past two decades, considerable evidence has supported a crucial role for DNA damage in the development and progression of atherosclerosis. These findings support the concept that the prolonged exposure to risk factors (e.g., dyslipidemia, smoking and diabetes mellitus) leading to reactive oxygen species are major stimuli for DNA damage within the plaque. Genomic instability at the cellular level can directly affect vascular function, leading to cell cycle arrest, apoptosis and premature vascular senescence. The purpose of this paper is to review current knowledge on the role of DNA damage and DNA repair systems in atherosclerosis, as well as to discuss the cellular response to DNA damage in order to shed light on possible strategies for prevention and treatment.

Oxidative damage and genotoxicity biomarkers in transfused and untransfused thalassemic subjects

Chronic anemia and tissue hypoxia increase intestinal iron absorption and mitochondrial impairment in thalassemic patients. Regular blood transfusions improve hemoglobin levels but determine an iron overload that induces reactive oxygen species (ROS) overproduction. The aim of this study was to assess cellular oxidative damage by detection of ROS, lipid peroxidation, 8-oxo-dG, and mitochondrial transmembrane potential (Δψ(m)) in transfused and untransfused thalassemic patients. We have also evaluated genotoxicity by CBMN and comet assay. Our data show that ROS and lipid hydroperoxides are significantly higher in thalassemic patients than in controls, especially in untransfused thalassemia intermedia patients. Moreover, the latter have a significant decrease in Δψ(m) that highlights the energetic failure in hypoxic state and the ROS overproduction in the respiratory chain. 8-OHdG levels are higher in thalassemics than in controls, but do not differ significantly between the two patient groups. Both genotoxicity biomarkers highlight the mutagenic potential of hydroxyl radicals released by iron in the Fenton reaction. Values for percentage of DNA in the comet tail and micronuclei frequency, significantly higher in transfused patients, could also be due to active hepatitis C virus infection and to the many drug treatments. Our biomonitoring study confirms the oxidative damage in patients with thalassemia major and shows an unexpected cellular oxidative damage in untransfused thalassemic patients. In addition to iron overload, the results highlight the important role played by hypoxia-driven mitochondrial ROS overproduction in determining oxidative damage in β-thalassemias.

Infection-induced colitis in mice causes dynamic and tissue-specific changes in stress response and DNA damage leading to colon cancer

Helicobacter hepaticus-infected Rag2(-/-) mice emulate many aspects of human inflammatory bowel disease, including the development of colitis and colon cancer. To elucidate mechanisms of inflammation-induced carcinogenesis, we undertook a comprehensive analysis of histopathology, molecular damage, and gene expression changes during disease progression in these mice. Infected mice developed severe colitis and hepatitis by 10 wk post-infection, progressing into colon carcinoma by 20 wk post-infection, with pronounced pathology in the cecum and proximal colon marked by infiltration of neutrophils and macrophages. Transcriptional profiling revealed decreased expression of DNA repair and oxidative stress response genes in colon, but not in liver. Mass spectrometric analysis revealed higher levels of DNA and RNA damage products in liver compared to colon and infection-induced increases in 5-chlorocytosine in DNA and RNA and hypoxanthine in DNA. Paradoxically, infection was associated with decreased levels of DNA etheno adducts. Levels of nucleic acid damage from the same chemical class were strongly correlated in both liver and colon. The results support a model of inflammation-mediated carcinogenesis involving infiltration of phagocytes and generation of reactive species that cause local molecular damage leading to cell dysfunction, mutation, and cell death. There are strong correlations among histopathology, phagocyte infiltration, and damage chemistry that suggest a major role for neutrophils in inflammation-associated cancer progression. Further, paradoxical changes in nucleic acid damage were observed in tissue- and chemistry-specific patterns. The results also reveal features of cell stress response that point to microbial pathophysiology and mechanisms of cell senescence as important mechanistic links to cancer.

Oxidative and non-oxidative DNA damage and cardiovascular disease

Evidence for the association of DNA damage with cardiovascular disease has been obtained from in vitro cell culture models, experimental cardiovascular disease and analysis of samples obtained from humans with disease. There is general acceptance that several factors associated with the risk of developing cardiovascular disease cause oxidative damage to DNA in cell culture models with both nuclear and mitochondrial DNA as targets. Moreover, evidence obtained over the past 10 years points to a possible mechanistic role for DNA damage in experimental atherosclerosis culminating in recent studies challenging the assumption that DNA damage is merely a biomarker of the disease process. This kind of mechanistic insight provides a renewed impetus for further studies in this area.

Identification of 3,N(4)-etheno-5-methyl-2'-deoxycytidine in human DNA: a new modified nucleoside which may perturb genome methylation

Methylation of cytidine at dCpdG sequences regulates gene expression and is altered in many chronic inflammatory diseases. Inflammation generates lipid peroxidation (LPO) products which can react with deoxycytidine, deoxyadenosine, and deoxyguanosine in DNA to form pro-mutagenic exocyclic etheno-nucleoside residues. Since 5-methyl-2'-deoxycytidine (5mdC) residues exhibit increased nucleophilicity at N3, they should be even better targets for LPO products. We synthesized and characterized 3,N(4)-etheno-5-methyl-2'-deoxycytidine-3'-phosphate and showed that LPO products can indeed form the corresponding etheno-5mdC (ε5mdC) lesion in DNA in vitro. Our newly developed (32)P-postlabeling method was subsequently used to detect ε5mdC lesions in DNA from human white blood cells, lung, and liver at concentrations 4-10 times higher than that observed for etheno adducts on nonmethylated cytidine. Our new detection method can now be used to explore the hypothesis that this DNA lesion perturbs the DNA methylation status.

Quantitative analysis of multiple exocyclic DNA adducts in human salivary DNA by stable isotope dilution nanoflow liquid chromatography-nanospray ionization tandem mass spectrometry

Exocyclic DNA adducts, including 1,N(2)-propano-2'-deoxyguanosine derived from acrolein (AdG) and crotonaldehyde (CdG) and the three lipid peroxidation-related etheno adducts 1,N(6)-etheno-2'-deoxyadenosine (εdAdo), 3,N(4)-etheno-2'-deoxycytidine (εdCyt), and 1,N(2)-etheno-2'-deoxyguanosine (1,N(2)-εdGuo), play an important role in cancer formation and they are associated with oxidative-stress-induced DNA damage. Saliva is an easily accessible and available biological fluid and a potential target of noninvasive biomarkers. In this study, a highly sensitive and specific assay based on isotope dilution nanoflow LC-nanospray ionization tandem mass spectrometry (nanoLC-NSI/MS/MS) is developed for simultaneous detection and quantification of these five adducts in human salivary DNA. The levels of AdG, CdG, εdAdo, εdCyd, and 1,N(2)-εdGuo, measured in 27 human salivary DNA samples from healthy volunteers, were determined as 104 ± 50, 7.6 ± 12, 99 ± 50, 72 ± 49, 391 ± 198 (mean ± SD) in 10(8) normal nucleotides, respectively, starting with 25 μg of DNA isolated from an average of 3 mL of saliva. Statistically significant correlations were found between levels of εdAdo and εdCyd (γ = 0.8007, p < 0.0001), between levels of εdAdo and 1,N(2)-εdGuo (γ = 0.6778, p = 0.0001), between levels of εdCyd and 1,N(2)-εdGuo (γ = 0.5643, p = 0.0022), between levels of AdG and 1,N(2)-εdGuo (γ = 0.5756, p = 0.0017), and between levels of AdG and εdAdo (γ = 0.3969, p = 0.0404). Only 5 μg of DNA sample was analyzed for simultaneous quantification of these adducts. The easy accessibility and availability of saliva and the requirement for the small amount of DNA samples make this nanoLC-NSI/MS/MS assay clinically feasible in assessing the possibility of measuring 1,N(2)-propano-2'-deoxyguanosine and etheno adducts levels in human salivary DNA as noninvasive biomarkers for DNA damage resulting from oxidative stress and for evaluating their roles in cancer formation and prevention.

Reactive species and DNA damage in chronic inflammation: reconciling chemical mechanisms and biological fates

Chronic inflammation has long been recognized as a risk factor for many human cancers. One mechanistic link between inflammation and cancer involves the generation of nitric oxide, superoxide and other reactive oxygen and nitrogen species by macrophages and neutrophils that infiltrate sites of inflammation. Although pathologically high levels of these reactive species cause damage to biological molecules, including DNA, nitric oxide at lower levels plays important physiological roles in cell signaling and apoptosis. This raises the question of inflammation-induced imbalances in physiological and pathological pathways mediated by chemical mediators of inflammation. At pathological levels, the damage sustained by nucleic acids represents the full spectrum of chemistries and likely plays an important role in carcinogenesis. This suggests that DNA damage products could serve as biomarkers of inflammation and oxidative stress in clinically accessible compartments such as blood and urine. However, recent studies of the biotransformation of DNA damage products before excretion point to a weakness in our understanding of the biological fates of the DNA lesions and thus to a limitation in the use of DNA lesions as biomarkers. This review will address these and other issues surrounding inflammation-mediated DNA damage on the road to cancer.

DNA damage induced by endogenous aldehydes: current state of knowledge

DNA damage plays a major role in various pathophysiological conditions including carcinogenesis, aging, inflammation, diabetes and neurodegenerative diseases. Oxidative stress and cell processes such as lipid peroxidation and glycation induce the formation of highly reactive endogenous aldehydes that react directly with DNA, form aldehyde-derived DNA adducts and lead to DNA damage. In occasion of persistent conditions that influence the formation and accumulation of aldehyde-derived DNA adducts the resulting unrepaired DNA damage causes deregulation of cell homeostasis and thus significantly contributes to disease phenotype. Some of the most highly reactive aldehydes produced endogenously are 4-hydroxy-2-nonenal, malondialdehyde, acrolein, crotonaldehyde and methylglyoxal. The mutagenic and carcinogenic effects associated with the elevated levels of these reactive aldehydes, especially, under conditions of stress, are attributed to their capability of causing directly modification of DNA bases or yielding promutagenic exocyclic adducts. In this review, we discuss the current knowledge on DNA damage induced by endogenously produced reactive aldehydes in relation to the pathophysiology of human diseases.

Quantifying etheno-DNA adducts in human tissues, white blood cells, and urine by ultrasensitive (32)P-postlabeling and immunohistochemistry

Exocyclic etheno-DNA adducts are formed by the reaction of lipid peroxidation products, such as 4-hydroxy-2-nonenal (HNE) with DNA bases to yield 1,N (6)-etheno-2'-deoxyadenosine (εdA), 3,-N (4)-etheno-2'-deoxycytidine (εdC), and etheno-2'-deoxyguanosine. These adducts act as a driving force for many human malignancies and are elevated in the organs of cancer-prone patients suffering from chronic inflammation and infections. Here, we describe the ultrasensitive and specific techniques for the detection of εdA and εdC in tissue and white blood cell (WBC) DNA. This approach is based on -combined immunopurification by monoclonal antibodies and (32)P-postlabeling analysis. The detection limit is about five adducts per 10(10) parent nucleotides, requiring 5-10 μg of DNA. In addition, we describe techniques for immunohistochemical detection of εdA and εdC in tissue biopsies, and the approaches for the -analysis of εdA and εdC excreted in urine. The utility of these detection methods for human studies is based on: (1) high sensitivity and specificity, (2) low amounts of DNA required, (3) capability to detect "background" levels of etheno-DNA adducts in biopsies, WBC, and urine samples of healthy subjects, and (4) reliable monitoring of the disease-related increase of these substances in patients.The described methods are useful in diagnosis and monitoring of chronic degenerative diseases, including cancer, atherosclerosis, and neurodegenerative disorders.

Detection of lipid peroxidation-induced DNA adducts caused by 4-oxo-2(E)-nonenal and 4-oxo-2(E)-hexenal in human autopsy tissues

DNA adducts are produced both exogenously and endogenously via exposure to various DNA-damaging agents. Two lipid peroxidation (LPO) products, 4-oxo-2(E)-nonenal (4-ONE) and 4-oxo-2(E)-hexenal (4-OHE), induce substituted etheno-DNA adducts in cells and chemically treated animals, but the adduct levels in humans have never been reported. It is important to investigate the occurrence of 4-ONE- and 4-OHE-derived DNA adducts in humans to further understand their potential impact on human health. In this study, we conducted DNA adductome analysis of several human specimens of pulmonary DNA as well as various LPO-induced DNA adducts in 68 human autopsy tissues, including colon, heart, kidney, liver, lung, pancreas, small intestine, and spleen, by liquid chromatography tandem mass spectrometry. In the adductome analysis, DNA adducts derived from 4-ONE and 4-OHE, namely, heptanone-etheno-2'-deoxycytidine (HεdC), heptanone-etheno-2'-deoxyadenosine (HεdA), and butanone-etheno-2'-deoxycytidine (BεdC), were identified as major adducts in one human pulmonary DNA. Quantitative analysis revealed 4-ONE-derived HεdC, HεdA, and heptanone-etheno-2'-deoxyguanosine (HεdG) to be ubiquitous in various human tissues at median values of 10, 15, and 8.6 adducts per 10(8) bases, respectively. More importantly, an extremely high level (more than 100 per 10(8) bases) of these DNA adducts was observed in several cases. The level of 4-OHE-derived BεdC was highly correlated with that of HεdC (R(2) = 0.94), although BεdC was present at about a 7-fold lower concentration than HεdC. These results suggest that 4-ONE- and 4-OHE-derived DNA adducts are likely to be significant DNA adducts in human tissues, with potential for deleterious effects on human health.

Effects of epigallocatechin gallate, L-ascorbic acid, alpha-tocopherol, and dihydrolipoic acid on the formation of deoxyguanosine adducts derived from lipid peroxidation

Oxidation of polyunsaturated fatty acids (PUFAs) releases alpha,beta-unsaturated aldehydes that modify deoxyguanosine (dG) to form cyclic 1,N(2)-propanodeoxyguanosine adducts. One of the major adducts detected in vivo is acrolein (Acr)-derived 1,N(2)-propanodeoxyguanosine (Acr-dG). We used a chemical model system to examine the effects of 4 antioxidants known to inhibit fatty acid oxidation on the formation of Acr-dG and 8-oxodeoxyguaonsine (8-oxodG) from the PUFA docosahexaenoic acid (DHA) under oxidative conditions. We found that epigallocatechin gallate (EGCG) and dihydrolipoic acid (DHLA) inhibit both Acr-dG and 8-oxodG formation. In contrast, ascorbic acid and alpha-tocopherol actually increase Acr-dG at high concentrations and do not show a concentration-dependant inhibition of 8-oxodG. We also studied their effects on blocking Acr-dG formation directly from Acr. EGCG and DHLA can both effectively block Acr-dG formation, but ascorbic acid and alpha-tocopherol show weak or little effect. These results highlight the complexity of antioxidant mechanisms and also reveal that EGCG and DHLA are effective at suppressing lipid peroxidation-induced Acr-dG and 8-oxodG formation as well as blocking the reaction of dG with Acr.

Role of somatic mutations in vascular disease formation

Coronary artery disease, cerebrovascular disease, pulmonary artery hypertension and Alzheimer's disease all lead to substantial morbidity and mortality, and we currently lack effective treatments for these vascular diseases. Since the discovery, decades ago, that atherosclerotic lesions display clonal growth, atherosclerosis and other vascular diseases have been postulated to be neoplastic processes, arising through a series of critical somatic mutations. There is conflicting evidence supporting this but studies of DNA damage and mutagenesis, both genomic and mitochondrial, in atherosclerotic and vascular lesions, have yielded evidence that somatic mutations are involved in atherogenesis and vascular disease development. The roles of mitochondrial DNA damage, oxidative stress and signaling by members of the TGF-beta receptor family are implicated. With the increasing convenience and cost-effectiveness of genome sequencing, it is feasible to continue to seek specific genetic targets in the pathogenesis of these devastating diseases, with the hope of developing personalized genomic medicine in the future.

Chronic inflammation and mutagenesis

Inflammation is a necessary part of the immune response. However, when inflammation persists, the resultant state of chronic inflammation may have a number of secondary consequences associated with increased risk of chronic disease. Among these is an increased rate of mutation. There is evidence to suggest that the accumulation of reactive oxygen and nitrogen species may be a causal factor in chronic inflammation. These reactive species are also produced through the oxidative burst associated with the inflammatory process, and may interact with various cellular components including proteins, lipids and, most important for mutagenesis, nucleic acids. DNA strand breaks are commonly produced, leading to chromosomal mutation. Oxidized bases, abasic sites, DNA-DNA intrastrand adducts, and DNA-protein cross-links also occur. Not only do the nucleic acid products act directly as pro-mutagenic lesions, lipid peroxidation products may also lead to secondary DNA damage, including pro-mutagenic exocyclic DNA adducts. While frameshift and chromosomal mutations have been associated with chronic inflammation, much of the evidence reveals base pair substitution mutations associated with polymerase stalling near the lesions, and base pair mis-incorporation. There are also indirect effects of ROS/RNS through inhibition of DNA repair enzymes and/or effects on metabolic activation of known carcinogens. Certain disease states, including the Inflammatory bowel diseases, Crohn's disease and ulcerative colitis are associated with enhanced levels of chronic inflammation, and show evidence of enhanced levels of genetic damage in the colonic mucosa. Mutations may provide at least part of the cause of enhanced susceptibility to chronic diseases associated with chronic inflammation.

Lipid peroxidation and etheno DNA adducts in white blood cells of liver fluke-infected patients: protection by plasma alpha-tocopherol and praziquantel

Chronic infection by the liver fluke Opisthorchis viverrini is a strong risk factor for cholangiocarcinoma. To clarify the involvement of oxidative stress and lipid peroxidation-derived DNA damage, etheno (epsilon)-DNA adducts (epsilondA, epsilondC) in WBC and plasma alpha-tocopherol were measured in samples collected from O. viverrini-infected Thai patients (n = 50) and healthy noninfected volunteers (n = 20). epsilondA and epsilondC levels were three to five times higher (P < 0.001) in infected patients than in controls; O. viverrini infection also increased two to three times in the plasma inflammatory indicators, 8-isoprostane, malondialdehyde, and nitrate/nitrite. Mean plasma alpha-tocopherol levels were two times lower in patients than in healthy controls (P < 0.001). Two months after a single dose to infected patients of the antiparasitic drug praziquantel, epsilondA and epsilondC levels in WBC were decreased to control level (P < 0.03); plasma 8-isoprostane, malondialdehyde, nitrate/nitrite, and alkaline phosphatase (ALP) were concomitantly lowered. epsilondA and epsilondC levels in WBC were positively correlated with plasma 8-isoprostane, malondialdehyde, and nitrate/nitrite levels and ALP activity, whereas plasma alpha-tocopherol levels showed inverse correlations. We conclude that chronic O.viverrini infection induces an accumulation of lipid peroxidation-derived DNA damage through oxidative/nitrative stress, which is lowered by the plasma alpha-tocopherol and by antiparasitic drug therapy. Etheno adducts in WBC and urine should be explored as a risk marker for opisthorchiasis-related cholangiocarcinoma, and to assess the efficacy of preventive and therapeutic interventions.

Structural, chemical and biological aspects of antioxidants for strategies against metal and metalloid exposure

Oxidative stress contributes to the pathophysiology of exposure to heavy metals/metalloid. Beneficial renal effects of some medications, such as chelation therapy depend at least partially on the ability to alleviate oxidative stress. The administration of various natural or synthetic antioxidants has been shown to be of benefit in the prevention and attenuation of metal induced biochemical alterations. These include vitamins, N-acetylcysteine, alpha-lipoic acid, melatonin, dietary flavonoids and many others. Human studies are limited in this regard. Under certain conditions, surprisingly, the antioxidant supplements may exhibit pro-oxidant properties and even worsen metal induced toxic damage. To date, the evidence is insufficient to recommend antioxidant supplements in subject with exposure to metals. Prospective, controlled clinical trials on safety and effectiveness of different therapeutic antioxidant strategies either individually or in combination with chelating agent are indispensable. The present review focuses on structural, chemical and biological aspects of antioxidants particularly related to their chelating properties.

Role of dietary mutagens in cancer and atherosclerosis

PURPOSE OF REVIEW

To provide an updated summary of dietary mutagens and their potential role in the etiology of cancer and atherosclerosis.

RECENT FINDINGS

Compelling evidence supports an accumulation of somatic mutations during carcinogenesis, leading to the activation of oncogenes or inactivation of tumor suppressor genes or both. There is also suggestive evidence that mutation provides an early event in atherosclerosis. Genome-wide association studies (GWAS) identify genes associated with familial cancers and atherosclerosis, but genes involved in sporadic events are less well characterized. Many dietary components are mutagenic, including natural dietary components, mutagens generated during cooking and processing of food or through contamination. Molecular epidemiology associates specific mutagens with specific types of cancer. Although chromosome mutations may provide a risk biomarker for atherosclerosis, they are not necessarily causal.

SUMMARY

Association studies, supported by molecular epidemiology, provide evidence that certain dietary mutagens, including aflatoxin B1, aristolochic acid and benzo[a]pyrene, are causal in some human cancers. Similar studies have correlated the level of oxidative DNA damage, DNA adducts and clastogenesis in arterial smooth muscle cells with atherogenic risk factors described through traditional epidemiology. However, establishing whether or not dietary mutagens lead to mutations that are causal in atherosclerosis remains a challenge for the newer genomic technologies.

Urinary 8-oxodeoxyguanosine levels in children exposed to air pollutants

Oxidative stress is believed to be one of the mechanisms of effects of air pollution to human health. We investigated levels of 8-oxodeoxyguanosine (8-oxodG), a marker of oxidative damage to DNA, in urine samples of 894 children from two districts in the Czech Republic: Teplice and Prachatice. We assessed the association between 8-oxodG levels and exposure to particulate matter of different size: <or=10 microm (PM10), <or=2.5 microm (PM2.5) and carcinogenic polycyclic aromatic hydrocarbons (c-PAHs); as well as between 8-oxodG levels and individual lifestyle, health and pregnancy outcomes. An ELISA technique was used for analysis of 8-oxodG levels. Median levels (range) of 8-oxodG in children from Teplice vs. Prachatice were as follows: 14.6 (3.1-326.5) nmol/mmol vs. 15.2 (3.0-180.8) nmol/mmol creatinine (p=0.34). Levels of 8-oxodG were elevated in children exposed to environmental tobacco smoke (ETS) (p<0.05) and among the Gypsy population (p<0.01). Levels of 8-oxodG decreased with the child's age (p<0.001) and increasing level of the mother's education (p<0.01). Multivariate statistical analyses confirmed the effect of the child's age and ETS exposure on 8-oxodG levels. The exposure to PM10 and PM2.5 measured by stationary monitors during a 7-day period before urine collection, as well as the exposure to c-PAHs measured during 3-day periods 1-3 and 7-9 days before urine collection were identified as factors affecting 8-oxodG levels in multivariate models. The obtained results indicate that 8-oxodG is a sensitive biomarker for measuring the exposure of children to air pollution.

Typical signature of DNA damage in white blood cells: a pilot study on etheno adducts in Danish mother-newborn child pairs

The impact of DNA damage commonly thought to be involved in chronic degenerative disease causation is particularly detrimental during fetal development. Within a multicenter study, we analyzed 77 white blood cell (WBC) samples from mother-newborn child pairs to see if imprinting of DNA damage in mother and newborn shows a similar pattern. Two adducts 1,N(6)-ethenodeoxyadenosine (epsilondA) and 3,N(4)-ethenodeoxycytidine (epsilondC) were measured by our ultrasensitive immunoaffinity (32)P-post-labeling method. These miscoding etheno-DNA adducts are generated by the reaction of lipid peroxidation (LPO) end products such as 4-hydroxy-2-nonenal with DNA bases. Mean epsilondA and epsilondC levels when expressed per 10(9) parent nucleotides in WBC-DNA from cord blood were 138 and 354, respectively; in maternal WBC-DNA, the respective values were 317 and 916. Thus, the DNA-etheno adduct levels were reliably detectable and about two times lower in child cord blood, the difference being significant at P < 0.0004. Analysis of epsilondA and epsilondC levels in cord versus maternal blood WBC showed strong positive correlations (R(2) approximately 0.9, P < 0.00001). In conclusion, LPO-induced DNA damage arising from endogenous reactive aldehydes in WBC of both mother and newborn can be reliably assessed by epsilondA and epsilondC as biomarkers. The high correlation of etheno adduct levels in mother and child WBC suggests that a typical signature of DNA damage is induced similarly in fetus and mother. Prospective cohort studies have to reveal whether these two WBC-DNA adducts could serve as risk indicator for developing hematopoietic cancers and other disorders later in life.

Nutrition and Mutagenesis

Diet-related mutagenesis plays an etiologic role in chronic diseases, including cardiovascular disease and cancer. Many dietary mutagens are DNA reactive, leading to distinct spectra of base-pair substitution mutations and structural chromosome changes. Examples include aflatoxin B1, ochratoxin A, ptaquiloside, various pyrrolizidine alkaloids, heterocyclic amines including 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, and polycyclic aromatic hydrocarbons such as benzo[a]pyrene. However, endogenously or exogenously formed reactive species, inhibitors of topoisomerase II enzymes (e.g., flavonoids), of DNA repair (e.g., caffeine), or of the mitotic spindle (possibly acrylamide), also cause mutations, including structural chromosome changes and copy number variants. Genomic instability also results from inadequate nutrient intake (e.g., folate and selenium). Antimutagens include vitamin C, carotenoids, chlorophyllin, dietary fibers, and plant polyphenols acting through various mechanisms. Polymorphisms in genes for nutrient uptake, metabolism, and excretion will affect dietary intake in determining individual risk of disease development. Human studies utilizing nutrigenomic/nutrigenetic technologies will be essential to quantifying and overcoming diet-related mutagenesis.

Exposure of mice to cigarette smoke and/or light causes DNA alterations in heart and aorta

Cigarette smoke (CS) is a major risk factor for cardiovascular diseases, cancer, and other chronic degenerative diseases. UV-containing light is the most ubiquitous DNA-damaging agent existing in nature, but its possible role in cardiovascular diseases had never been suspected before, although it is known that mortality for cardiovascular diseases is increased during periods with high temperature and solar irradiation. We evaluated whether exposure of Swiss CD-1 mice to environmental CS (ECS) and UV-C-covered halogen quartz lamps, either individually or in combination, can cause DNA damage in heart and aorta cells. Nucleotide alterations were evaluated by (32)P postlabeling methods and by HPLC-electrochemical detection. The whole-body exposure of mice to ECS considerably increased the levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) and of bulky DNA adducts in both heart and aorta. Surprisingly, even exposure to a light that simulated solar irradiation induced oxidatively generated damage in both tissues. The genotoxic effects of UV light in internal organs is tentatively amenable to formation of unidentified long-lived mutagenic products in the skin of irradiated mice. Nucleotide alterations were even more pronounced when the mice were exposed to smoke and/or light during the first 5 weeks of life rather than during adulthood for an equivalent period of time. Although the pathogenetic meaning is uncertain, DNA damage in heart and aorta may tentatively be related to cardiomyopathies and to the atherogenesis process, respectively.

Lipid peroxidation-induced DNA damage in cancer-prone inflammatory diseases: a review of published adduct types and levels in humans

Persistent oxidative stress and excess lipid peroxidation (LPO), induced by inflammatory processes, impaired metal storage, and/or dietary imbalance, cause accumulations and massive DNA damage. This massive DNA damage, along with deregulation of cell homeostasis, leads to malignant diseases. Reactive aldehydes produced by LPO, such as 4-hydroxy-2-nonenal, malondialdehyde, acrolein, and crotonaldehyde, react directly with DNA bases or generate bifunctional intermediates which form exocyclic DNA adducts. Modification of DNA bases by these electrophiles, yielding promutagenic exocyclic adducts, is thought to contribute to the mutagenic and carcinogenic effects associated with oxidative stress-induced LPO. Ultrasensitive detection methods have facilitated studies of the concentrations of promutagenic DNA adducts in human tissues, white blood cells, and urine, where they are excreted as modified nucleosides and bases. Thus, immunoaffinity-(32)P-postlabeling, high-performance liquid chromatography-electrochemical detection, gas chromatography-mass spectrometry, liquid chromatography-tandem mass spectrometry, immunoslotblot assay, and immunohistochemistry have made it possible to detect background concentrations of adducts arising from endogenous LPO products in vivo and studies of their role in carcinogenesis. These background adduct levels in asymptomatic human tissues occur in the order of 1 adduct/10(8) and in organs affected by cancer-prone inflammatory diseases these can be 1 or 2 orders of magnitude higher. In this review, we critically discuss the accuracy of the available methods and their validation and summarize studies in which measurement of exocyclic adducts suggested new mechanisms of cancer causation, providing potential biomarkers for cancer risk assessment in humans with cancer-prone diseases.

Past and future applications of CYP450-genetic polymorphisms for biomonitoring of environmental toxicants

Cytochrome P450s (CYPs) are a huge gene superfamily of heme enzymes involved in xenobioitc as well as endobiotic metabolism. They play a critical role in adaptation to environmental changes for survival of living organisms. In addition, the huge environmental loads of human-made chemicals are biotransformed into bioactive or detoxified forms by CYPs. Thus, CYPs have been used for biomonitoring of environmental pollutants, screening of their metabolisms and exploring remedy. In particular, the induction or inhibition of CYPs has been applied to exposure monitoring of environmental toxicants, which are biotransformed by CYPs. This review considers past and future applications of CYP-genetic polymorphisms as susceptibility biomarkers for biomonitoring. Furthermore, we suggest the needs for further understanding of the characteristics of each CYP isozyme, consideration of real-life exposures such as mixed contamination with various chemicals, and incorporation of the presence of other phase I and phase II enzymes, for proper applications of CYP polymorphisms on biomonitoring.

Mutagenesis and cardiovascular diseases Molecular mechanisms, risk factors, and protective factors

Although no generalization can be made, it is of interest that cancer, cardiovascular diseases, and other chronic conditions often share common risk factors and common protective factors as well as common pathogenetic determinants, such as DNA damage, oxidative stress, and chronic inflammation. Atherosclerosis is the most important cause of vascular forms representing the major cause of death in the population of many geographical areas. A great deal of studies support the "response-to-injury" theory. A variety of experimental and epidemiological findings are also in favor of the somatic mutation theory, which maintains that the earliest event in the atherogenic process is represented by mutations in arterial smooth muscle cells, akin to formation of a benign tumor. These two theories can be harmonized, also taking into account the highly diversified nature of atherosclerotic lesions. Molecular epidemiology studies performed in our laboratory and other laboratories have shown that DNA adducts are systematically present in arterial smooth muscle cells, and their levels are correlated with atherogenic risk factors known from traditional epidemiology. Oxidative DNA damage was also consistently detected in these cells. The role of glutathione S-transferase polymorphisms on the frequency of the above molecular alterations and of arterial diseases is rather controversial. Prevention of both cancer and atherosclerosis is based on avoidance of exposure to risk factors and on fortification of the host defense mechanisms by means of dietary principles and chemopreventive drugs.

Survival of atherosclerotic patients as related to oxidative stress and gene polymorphisms

A prospective molecular epidemiology study was implemented in a cohort of 98 subjects suffering from severe atherosclerotic lesions requiring removal of an abdominal aorta fragment. We previously published the results relative to detection, in the aorta medium layer, of bulky DNA adducts and fluorescent polycyclic aromatic hydrocarbon-related DNA adducts, oxidative DNA damage, and mitochondrial DNA 4977 common deletion, as well as GSTM1 and GSTT1 gene polymorphisms. We report herein new data, relative to oxidative stress biomarkers, including oxidative DNA damage in both inner and medium aorta layers, malondialdehyde in the medium layer, homocysteine and reduced glutathione in plasma, and those relative to additional gene polymorphisms, including NAT1, NAT2, OGG1, MTHFR, Leiden factor V, and prothrombin. The results of biochemical and molecular analyses were related to survival of the patients, whose average age was 70 at the start of the follow up. During the following 14 years, 71.4% of them died. The results obtained provide evidence for the crucial impact of oxidative stress and certain gene polymorphisms on clinical and biochemical patterns as well as on survival of patients. Survival was significantly affected not only by traditional risk factors for atherosclerosis but also by molecular end-points and adverse gene polymorphisms, and by their combinations.

Decreased levels of lipid peroxidation-induced DNA damage in the onset of atherogenesis in apolipoprotein E deficient mice

Increased oxidative stress and subsequent lipid peroxidation (LPO) are thought to be critical events in the formation of atherosclerotic lesions in apolipoprotein E deficient mice (ApoE-KO). LPO derived reactive aldehydes react with DNA to form exocyclic etheno-DNA adducts. These pro-mutagenic DNA lesions are known to be involved in the initiation of carcinogenesis, but their role in the development of atherosclerosis is unknown. In the present study we show that levels of the LPO derived 1,N(6)-ethenodeoxyadenosine (varepsilondA) and 3,N(4)-ethenodeoxycytidine (varepsilondC) were both significantly lower in aorta of 12 weeks old ApoE-KO mice as compared to their wild type controls (1.6+/-0.3 versus 3.2+/-0.8 varepsilondA per 10(8) parent nucleotides, P=0.04 and 4.8+/-0.8 versus 9.2+/-2.1 for varepsilondC, P=0.02). Moreover, levels of both DNA adduct types were inversely related with total plasma cholesterol levels. Consequently, lowest etheno-DNA adduct levels were observed in ApoE-KO mice on a high fat diet. Hypercholesterolemia has previously been associated with increased expression of base excision repair (BER) enzymes, which could explain the lower levels of etheno-DNA adducts in ApoE-KO mice as compared to wild type controls. Indeed, increased staining for the BER-specific DNA repair enzyme apurinic/apyrimidinic endonuclease (Ape1/Ref1) was observed by immunohistochemistry in the endothelium and the first layers of arterial smooth muscle cells of ApoE-KO mice as compared to their wild type counterparts. A high fat diet further increased overall Ape1/Ref1 protein expression in ApoE-KO mice. Although these data suggest no role for increased LPO derived DNA damage in the onset of atherogenesis in ApoE-KO mice, the potentially modulating role of Ape1/Ref1 in the arterial wall deserves further attention.