Coronary atherosclerosis and somatic mutations: an overview of the contributive factors for oxidative DNA damage

A urinary marker of oxidative stress covaries positively with hostility among midlife community volunteers

OBJECTIVE

Although not all findings are consistent, growing evidence suggests that individuals high in dispositional hostility are at elevated risk for cardiovascular disease and all-cause mortality; however, the mechanisms of these associations remain unclear. One possibility is that hostility is associated with oxidative stress. Here, we explore relationships between hostility and a measure of systemic oxidative stress among a mid-life sample.

METHODS

In a community sample of 223 adults aged 30 to 54 years (86% white, 50% female), oxidative stress was measured as the 24-hour urinary excretion of 8-hydroxy-2'-deoxyguanosine (8-OHdG). An abbreviated Cook Medley Hostility Scale was used to measure dimensions of hostility.

RESULTS

Regression analyses controlling for demographic characteristics and cardiovascular risk factors showed a positive relationship of 8-OHdG with total hostility (beta = 0.003, p = .03) and hostile affect (beta = 0.018, p < .001).

CONCLUSIONS

These findings provide evidence that dispositional hostility, and in particular, hostile affect, covary positively with systemic oxidative stress, raising the possibility that oxidative stress contributes to the pathogenicity of hostile attributes.

Non-cancer diseases and non-targeted effects

It is well established that moderate to high doses of radiation can increase the occurrence also of a variety of non-cancer effects in exposed individuals, but for radiation protection purposes it has generally been assumed that there is a threshold of dose below which no significant non-cancer effects (apart from hereditary disease) arise. In recent years, there is growing epidemiological evidence of excess risk of late occurring cardiovascular disease at much lower radiation doses and occurring over much longer intervals after radiation exposure without a clear cut threshold. However, the epidemiological evidence available so far for non-cancer health effects after exposure to moderate or low radiation doses is suggestive rather than persuasive. The mechanisms of radiation-induced vascular disease induction are far away from being understood. However, it seems to be very likely that inflammatory responses are involved. Recent experimental studies by Stewart et al. [25] could demonstrate that high dose exposure to the cardiovascular system is associated with an earlier onset and accelerated development of macrophage-rich, inflammatory atherosclerotic lesions prone to intra-plaque hemorrhage and may also cause a decrease in myocardial perfusion. Both, macro-vascular and micro-vascular radiation effects involve the endothelium and pro-inflammatory signalling cascades. If modulation of inflammatory response is arguably also the most likely cause of radiation-induced cardiovascular disease after low dose exposure, this also implies a role for non-targeted radiation effects. In the absence of a convincing mechanistic explanation of the currently available epidemiological evidence for radiation-induced cardiovascular risk at low radiation doses, caution is required in the interpretation of the statistical associations. On the other hand, the possibility of such a causal explanation cannot be reliably excluded. Further epidemiological and biological evidence from currently ongoing research projects will allow a firmer conclusion to be drawn.

DNA repair gene polymorphism is associated with the genetic basis of atherosclerotic coronary artery disease

BACKGROUND

Atherosclerotic coronary artery disease (CAD) is a multifactorial process that appears to be caused by the interaction of environmental risk factors with multiple predisposing genes. It is nowadays accepted that increased levels of DNA damage induced by xenobiotics play an important role in the early phases of atherogenesis. Therefore, in this study, we focus on determining whether genetic variations in xenobiotic-metabolizing [glutathione-S-transferase theta 1 (GSTT1), glutathione-S-transferase mu 1 (GSTM1), cytochrome P450 IIEI (CYP2E1)] and DNA repair [X-ray cross-complementing group 1 (XRCC1)] genes might be associated with increased risk for CAD.

METHODS

A case-control study was conducted with 400 individuals who underwent subjected to coronary angiography. A total of 299 were patients diagnosed with effective coronary atherosclerosis (case group; >20% obstructive lesion), and 101 (control group) were individuals diagnosed as negative for CAD (<20% obstructive lesions). The polymorphism identifications for GSTM1 and GSTT1, and for CYP2E1 and XRCC1 genes were performed by polymerase chain reaction (PCR) amplification and by PCR-RFLP, respectively.

RESULTS AND CONCLUSIONS

The XRCC1 homozygous wild-type genotype Arg/Arg for codon 399 was statistically less pronounced in the case subjects (21.4%) than in controls (38.5%); individuals with the variant XRCC1 genotype had a 2.3-fold increased risk for coronary atherosclerosis than individuals with the wild-type genotype (OR=2.3, 95% CI=1.13-4.69). Conversely, no association between GSTM1, GSTT1, and CYP2E1gene polymorphisms and coronary atherosclerosis was detected. The results provide evidence of the role of DNA damage and repair in cardiovascular disease.

Ionizing radiation and aging: rejuvenating an old idea

This paper reviews the contemporary evidence that radiation can accelerate aging, degenerative health effects and mortality. Around the 1960s, the idea that ionizing radiation caused premature aging was dismissed as the radiation-induced health effects appeared to be virtually confined to neoplasms. More recently, radiation has become associated with a much wider spectrum of age-related diseases, including cardiovascular disease; although some diseases of old age, such as diabetes, are notably absent as a radiation risk. On the basis of recent research, is there a stronger case today to be made linking radiation and aging? Comparison is made between the now-known biological mechanisms of aging and those of radiation, including oxidative stress, chromosomal damage, apoptosis, stem cell exhaustion and inflammation. The association between radiation effects and the free-radical theory of aging as the causative hypothesis seems to be more compelling than that between radiation and the nutrient-sensing TOR pathway. Premature aging has been assessed by biomarkers in calorie restriction studies; yet, biomarkers such as telomere erosion and p16(INK4a) are ambiguous for radiation-induced aging. Some animal studies suggest low dose radiation may even demonstrate hormesis health benefits. Regardless, there is virtually no support for a life span extending hypothesis for A-bomb survivors and other exposed subjects.

Susceptibility to Oxidative Stress is Greater in Korean Patients with Coronary Artery Disease than Healthy Subjects

There are some evidences that the increased oxidative stress and thus increased oxidizability of lipoproteins and DNA can contribute to the development of certain human diseases, such as cardiovascular disease. To confirm the association of DNA damage with cardiovascular disease, we investigated susceptibility of DNA to oxidation in lymphocytes and oxidative stress related parameters in blood of patients with coronary artery disease (CAD). Subjects were consisted of 42 patients (27 men, 15 women) with documented CAD and 49 apparently healthy subjects (33 men, 16 women) as controls. Cellular DNA damage induced by 100 microM H(2)O(2) was measured using Comet assay and quantified by TL. There were no differences in age (61.4 +/- 1.7 years vs 62.0 +/- 2.2 years) between the two groups. All the findings were shown to be independent of either sex or smoking habit. The patients showed significantly higher TL (87.3 +/- 1.6 microm) compared to the control (79.3 +/- 1.7 microm, p<0.01). Plasma TRAP, vitamin C, gamma-tocopherol, and alpha-carotene levels in patients group were lower than those of control groups, while erythrocytic catalase activity increased in patients group. In conclusion, we observed that reduced overall antioxidant status was closely connected to higher susceptibility of DNA damage in CAD patients.

Alcohol consumption is associated with high concentrations of urinary hydroxytyrosol

BACKGROUND

Previously, we reported the presence of hydroxytyrosol in red wine and higher human urinary recovery of total hydroxytyrosol than that expected after a single red wine intake. We hypothesized that the alcohol present in wine could promote endogenous hydroxytyrosol generation.

OBJECTIVE

The objective was to assess the relation between alcohol consumption and urinary hydroxytyrosol concentrations.

DESIGN

This was a cross-sectional study with baseline data from a subsample of the PREvención con DIeta MEDiterránea (PREDIMED) trial, an intervention study directed at testing the efficacy of the Mediterranean diet on the primary prevention of cardiovascular disease. Participants included 1045 subjects, aged 55-80 y, who were at high cardiovascular risk. Alcohol consumption was estimated through a validated food-frequency questionnaire. Urinary hydroxytyrosol and ethyl glucuronide, a biomarker of alcohol consumption, were measured.

RESULTS

Urinary ethyl glucuronide concentrations were directly related to alcohol and wine consumption (P < 0.001) as well as to urinary hydroxytyrosol in both sexes (P < 0.001). The degree of alcohol consumption was directly associated with urinary hydroxytyrosol in male alcohol consumers (P < 0.001). Multivariate logistic regression analyses showed a significant linear trend (P < 0.05) for elevated hydroxytyrosol concentrations with an increase in alcohol consumption. Intakes of >20 g (2 drinks)/d and >10 g (1 drink)/d alcohol in men and women, respectively, were associated (P < 0.05) with elevated concentrations of hydroxytyrosol.

CONCLUSIONS

We report for the first time a direct association between urinary hydroxytyrosol and alcohol consumption at a population level. These findings reinforce previous work in human and animal models that examines wine as a source of hydroxytyrosol and alcohol as an indirect promoter of endogenous hydroxytyrosol generation. This trial was registered at controlled-trials.com/isrctn/ as ISRCTN 35739639.

Wine and oxidative stress: up-to-date evidence of the effects of moderate wine consumption on oxidative damage in humans

Wine and alcohol consumption has been considered to be protective against coronary heart disease development, an oxidative stress associated disease. Wine contains polyphenols displaying antioxidant properties tested in in vitro and in vivo studies. Due to this, a general consensus exists, both among the general public and the scientific community, that wine, particularly red wine, is an antioxidant beverage. Alcohol consumption, however, is associated with oxidative damage. Several studies have been carried out on the antioxidant health benefits of wine and wine polyphenols. However, adequate scientific evidence (Level I or II) is required to be provided before recommendations or statements which can reach the general public can be formulated. Here, we summarize the state of the art of the up-to-date body of knowledge, and the extent to which there exists evidence of the benefits of moderate wine consumption on oxidative damage in humans. From the available data, there is no evidence, at present, that sustained wine consumption provides antioxidant benefits in healthy volunteers other than to counteract a possible pro-oxidative effect of the alcohol. On the contrary, data on the antioxidant protective effect of red wine in oxidative stress situations are promising. In this way, the postprandial oxidative stress after a meal, despite the diversity of biomarkers used for its evaluation, is counteracted by the ingestion of wine. Further studies are warranted.

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.

Ectodermal-neural cortex 1 down-regulates Nrf2 at the translational level

The transcription factor Nrf2 is the master regulator of a cellular defense mechanism against environmental insults. The Nrf2-mediated antioxidant response is accomplished by the transcription of a battery of genes that encode phase II detoxifying enzymes, xenobiotic transporters, and antioxidants. Coordinated expression of these genes is critical in protecting cells from toxic and carcinogenic insults and in maintaining cellular redox homeostasis. Activation of the Nrf2 pathway is primarily controlled by Kelch-like ECH-associated protein 1 (Keap1), which is a molecular switch that turns on or off the Nrf2 signaling pathway according to intracellular redox conditions. Here we report our finding of a novel Nrf2 suppressor ectodermal-neural cortex 1 (ENC1), which is a BTB-Kelch protein and belongs to the same family as Keap1. Transient expression of ENC1 reduced steady-state levels of Nrf2 and its downstream gene expression. Although ENC1 interacted with Keap1 indirectly, the ENC1-mediated down-regulation of Nrf2 was independent of Keap1. The negative effect of ENC1 on Nrf2 was not due to a change in the stability of Nrf2 because neither proteasomal nor lysosomal inhibitors had any effects. Overexpression of ENC1 did not result in a change in the level of Nrf2 mRNA, rather, it caused a decrease in the rate of Nrf2 protein synthesis. These results demonstrate that ENC1 functions as a negative regulator of Nrf2 through suppressing Nrf2 protein translation, which adds another level of complexity in controlling the Nrf2 signaling pathway.

5-Lipoxygenase-mediated endogenous DNA damage

Lipoxygenases (LOs) convert polyunsaturated fatty acids into lipid hydroperoxides. Homolytic decomposition of lipid hydroperoxides gives rise to endogenous genotoxins such as 4-oxo-2(E)-nonenal, which cause the formation of mutagenic DNA adducts. Chiral lipidomics analysis was employed to show that a 5-LO-derived lipid hydroperoxide was responsible for endogenous DNA-adduct formation. The study employed human lymphoblastoid CESS cells, which expressed both 5-LO and the required 5-LO-activating protein (FLAP). The major lipid peroxidation product was 5(S)-hydroperoxy-6,8,11,14-(E,Z,Z,Z)-eicosatetraenoic acid, which was analyzed as its reduction product, 5(S)-hydroxy-6,8,11,14-(E,Z,Z,Z)-eicosatetraenoic acid (5(S)-HETE)). Concentrations of 5(S)-HETE increased from 0.07 +/- 0.01 to 45.50 +/- 4.05 pmol/10(7) cells upon stimulation of the CESS cells with calcium ionophore A23187. There was a concomitant increase in the 4-oxo-2(E)-nonenal-derived DNA-adduct, heptanone-etheno-2'-deoxyguanosine (HepsilondGuo) from 2.41 +/- 0.35 to 6.31 +/- 0.73 adducts/10(7) normal bases. Biosynthesis of prostaglandins, 11(R)-hydroxy-5,8,12,14-(Z,Z,E,Z)-eicosatetraenoic acid, and 15(R,S)-hydroxy-5,8,11,13-(Z,Z,Z,E)-eicosatetraenoic acid revealed that there was cyclooxygenase (COX) activity in the CESS cells. Western blot analysis revealed that COX-1 was expressed by the cells, but there was no COX-2 or 15-LO-1. FLAP inhibitor reduced HepsilondGuo-adducts and 5(S)-HETE to basal levels. In contrast, aspirin, which had no effect on 5(S)-HETE, blocked the formation of prostaglandins, 15-HETE, and 11-HETE but did not inhibit HepsilondGuo-adduct formation. These data showed that 5-LO was the enzyme responsible for the generation of the HepsilondGuo DNA-adduct in CESS cells.

Three job stress models/concepts and oxidative DNA damage in a sample of workers in Japan

OBJECTIVE

Three job stress models/concepts (the job demands-control [DC] model, the effort-reward imbalance [ERI] model, and organizational justice) have been linked to coronary heart disease (CHD) at work. In recent years, oxidative DNA damage has been identified as a new risk factor for CHD. However, evidence for the association between these job stressors and oxidative DNA damage is limited. The present cross-sectional study investigated the association between these job stress models/concepts and oxidative DNA damage as a possible mediator of the adverse health effects of job stress.

METHODS

A total of 166 male and 51 female workers of a manufacturing factory in Japan were surveyed using a mailed questionnaire regarding job stressors and demographic, occupational, and lifestyle variables. Urinary concentrations of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a biomarker of oxidative DNA damage, were also measured.

RESULTS

In male subjects, the urinary concentrations of 8-OHdG were significantly higher among the group with lower interactional justice, one of the two components of organizational justice; however, no association was observed with the DC model or the ERI model. In female subjects, high job demands/control ratio was significantly and positively associated with the urinary concentrations of 8-OHdG.

CONCLUSION

Interactional justice among male workers and the DC model-based strain among female workers may be associated with increased urinary concentrations of 8-OHdG which possibly reflects oxidative DNA damage.

Glutathione S-transferase T1- and M1-null genotypes and coronary artery disease risk in patients with Type 2 diabetes mellitus Cardiovasc

Introduction: Since long-term exposure to oxidative stress is strongly implicated in the pathogenesis of diabetic complications, polymorphic genes of detoxifying enzymes must be involved in the development of coronary artery disease (CAD). We assessed the potential glutathione S-transferase (GST) gene–gene (GSTM1null–GSTT1null) and gene–smoking interactions on the development of CAD in patients with Type 2 diabetes. Materials & methods: In a case-only design, we enrolled 231 patients with Type 2 diabetes (147 male, 66.1 ± 9.7 years) referred to our institute for coronary angiography investigation. CAD was diagnosed if there was over 50% obstruction of one or more major vessels. Results: Coronary angiography revealed significant CAD in 184 patients (80%). Male gender (p < 0.001), smoking habits (p = 0.003) and GSTT1null genotype (p = 0.003) were significantly correlated with the increasing extent of the coronary atherosclerosis. Case-only analysis revealed that patients with both Mnull–Tnull genotypes had the highest risk for 3-vessel CAD compared with patients who express both GST genes (odds ratio: 3.1; 95% confidence interval: 1.0–10.3, p = 0.04). A nearly threefold interaction existed between cigarette smoking and Mnull–Tnull genotypes (odds ratio: 2.9, 95% confidence interval: 1.7–7.8, p = 0.03). A significant interaction between Mnull–Tnull genotypes and smoking was also observed on the increasing number of coronary vessels that were diseased (χ2 = 14.0; p = 0.03). Conclusion: These data suggest that polymorphisms in GSTM1 and GSTT1 genes are risk factors for CAD in Type 2 diabetic patients, especially among smokers. These genetic markers may permit the targeting of preventive and early intervention on high-risk patients to reduce their cardiovascular risk.

Relation of increased chromosomal damage to future adverse cardiac events in patients with known coronary artery disease

Somatic deoxyribonucleic acid (DNA) damage has been associated with early-phase and/or acute complications of atherosclerosis. However, it remains unclear whether circulating levels of DNA damage have prognostic value in patients with coronary artery disease (CAD). The aim of this study was to assess the prognostic significance of chromosomal DNA damage in human lymphocytes on the rate of major adverse cardiovascular events in patients with CAD. A follow-up prospective cohort study was carried out of 178 patients (153 men, mean age 61.9 +/- 9.7 years) with angiographically proved CAD who underwent micronucleus assay, a sensitive biomarker of chromosomal damage and genetic instability, from March 1999 and June 2001. During a mean follow-up period of 51.4 +/- 23.8 months, 58 patients had major adverse cardiovascular events (cardiac death, myocardial infarction, stroke, congestive heart failure, unstable angina, or coronary and peripheral revascularization). The overall event-free survival rates were 77.5%, 70.4%, and 49.0% in patients in the lower, middle, and upper tertiles of micronucleus level, respectively (log rank = 11.5, p = 0.003). In a multivariate Cox regression model, only the upper tertiles were significantly associated with a higher risk for major adverse cardiovascular events (hazard ratio 2.2, 95% confidence interval 1.1 to 4.7, p = 0.03). In conclusion, levels of peripheral chromosomal DNA damage may be a new sensitive biomarker of prognostic stratification in patients with known CAD.

NRP/B mutations impair Nrf2-dependent NQO1 induction in human primary brain tumors

Brain tumors are associated with genetic alterations of oncogenes and tumor suppressor genes. Accumulation of reactive oxygen species (ROS) in cells leads to oxidative stress-induced damage, resulting in tumorigenesis. Here, we showed that the nuclear matrix protein nuclear restricted protein in brain (NRP/B) was colocalized and interacted with NF-E2-related factor 2 (Nrf2). During oxidative stress response, NRP/B expression and its interaction with Nrf2 were upregulated in SH-SY5Y cells. Association of NRP/B with Nrf2 was crucial for NAD(P)H:quinone oxidoreductase 1 (NQO1) expression. NRP/B was localized predominantly in the nucleus of normal brain cells, whereas in primary brain tumors NRP/B was almost exclusively contained in the cytoplasm. In addition, unlike wild-type NRP/B, the expression of NRP/B mutants isolated from primary brain tumors was found in the cytoplasm, and these mutants failed to induce Nrf2-dependent NQO1 transcription. Thus, NRP/B mutations and their altered localization resulted in changes in NRP/B function and deregulation of Nrf2-dependent NQO1 activation in brain tumors. This study provides insights into the mechanism by which the NRP/B modulates Nrf2-dependent NQO1 induction in cellular protection against ROS in brain tumors.

Statins Use a Novel Nijmegen Breakage Syndrome-1–Dependent Pathway to Accelerate DNA Repair in Vascular Smooth Muscle Cells

Although the hydroxymethylglutaryl-coenzyme A reductase inhibitors (statins) are widely used in atherosclerosis to reduce serum cholesterol, statins have multiple other effects, including direct effects on cells of the vessel wall. Recently, DNA damage, including telomere shortening, has been identified in vascular smooth muscle cells (VSMCs) in human atherosclerosis. Although statins reduce DNA damage in vitro, the mechanisms by which they might protect DNA integrity in VSMCs are unknown. We show that human atherosclerotic plaque VSMCs exhibit increased levels of double-stranded DNA breaks and basal activation of DNA repair pathways involving ataxia telangiectasia–mutated (ATM) and the histone H2AX in vivo and in vitro. Oxidant stress induced DNA damage and activated DNA repair pathways in VSMCs. Statin treatment did not reduce oxidant stress or DNA damage but markedly accelerated DNA repair. Accelerated DNA repair required both the Nijmegen breakage syndrome (NBS)-1 protein and the human double minute protein Hdm2, accompanied by phosphorylation of Hdm2, dissociation of NBS-1 and Hdm2, inhibition of NBS-1 degradation, and accelerated phosphorylation of ATM. Statin treatment reduced VSMC senescence and telomere attrition in culture, accelerated DNA repair and reduced apoptosis in vivo after irradiation, and reduced ATM/ATR (ATM and Rad3-related) activity in atherosclerosis. We conclude that statins activate a novel mechanism of accelerating DNA repair, dependent on NBS-1 stabilization and Hdm2. Statin treatment may delay cell senescence and promote DNA repair in atherosclerosis.

A systematic review of epidemiological associations between low and moderate doses of ionizing radiation and late cardiovascular effects, and their possible mechanisms

Little, M. P., Tawn, E. J., Tzoulaki, I., Wakeford, R., Hildebrandt, G., Paris, F., Tapio, S. and Elliott, P. A Systematic Review of Epidemiological Associations Between Low and Moderate Doses of Ionizing Radiation and Late Cardiovascular Effects, and Their Possible Mechanisms. Radiat. Res. 169, 99-109 (2008). The link between high doses of ionizing radiation and damage to the heart and coronary arteries is established. In this paper, we systematically review the epidemiological evidence for associations between low and moderate doses (<5 Gy) of ionizing radiation and late-occurring cardiovascular disease. Risks per unit dose in epidemiological studies vary over at least two orders of magnitude, possibly a result of confounding factors. An examination of possible biological mechanisms indicates that the most likely causative effect of radiation exposure is damage to endothelial cells and subsequent induction of an inflammatory response, although it seems unlikely that this would extend to low-dose and low-dose-rate exposure. However, a role for somatic mutation has been proposed that would indicate a stochastic effect. In the absence of a convincing mechanistic explanation of epidemiological evidence that is less than persuasive at present, a cause-and-effect interpretation of the reported statistical associations cannot be reliably inferred, although neither can it be reliably excluded. Further epidemiological and biological evidence will allow a firmer conclusion to be drawn.

The Nuclear Matrix Protein, NRP/B, Enhances Nrf2-Mediated Oxidative Stress Responses in Breast Cancer Cells

The transcription factor NF-E2-related factor 2 (Nrf2) translocates into the nucleus and activates phase II genes encoding detoxification enzymes and antioxidant proteins, resulting in the protection of cells from oxidative insults. However, the involvement of Nrf2-mediated oxidative stress responses in breast cancer cells is largely unknown. Notably, during our study of the Nrf2 pathway in breast cancer cells, we observed that the nuclear matrix protein NRP/B was expressed and colocalized with Nrf2 in these cells, suggesting that NRP/B is involved in Nrf2-mediated oxidative stress responses. The expression level of NRP/B was variable in different breast cancer cells and breast cancer tissues, and was found to be localized in the nucleus. NRP/B expression was increased after exposure to the oxidative stress agent, hydrogen peroxide (H(2)O(2)), particularly in the highly aggressive MDA-MB-231 breast cancer cells. Association of NRP/B with Nrf2 in vitro and in vivo was observed in MDA-MB-231 breast cancer cells, and this association was up-regulated upon exposure to H(2)O(2), but not to sodium nitroprusside, SIN-1, and DETA-NO. NRP/B also enhanced Nrf2-mediated NAD(P)H:quinine oxidoreductase 1 promoter activity. Thus, this study reveals that NRP/B enhances oxidative stress responses in breast cancer cells via the Nrf2 pathway, identifying a novel role of nuclear matrix protein(s) in oxidative stress responses.

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

Atherosclerosis and cancer are characterized by uncontrolled cell proliferation and share common risk factors, such as cigarette smoking, dietary habits and ageing. Growth of smooth muscle cells (SMCs) in atherosclerotic plaques may result from DNA damage, caused either by exogenous mutagens or by agents endogenously generated due to oxidative stress and lipid peroxidation (LPO). Hydroxy-2-nonenal (HNE), a major LPO product, binds covalently to cellular DNA to form the exocyclic etheno-DNA-base adducts, 1,N(6)-ethenodeoxyadenine (varepsilondA) and 3,N(4)-ethenodeoxycytosine (varepsilondC). By applying an ultrasensitive (32)P-postlabeling-immunoaffinity method, varepsilondA and varepsilondC were quantified in abdominal aorta SMCs from 13 atherosclerotic patients and 3 non-smoking subjects without atherosclerotic lesions. The levels of etheno-adducts ranged for varepsilondA from 2.3 to 39.6/10(8)dA and for varepsilondC from 10.7 to 157.7/10(8)dC, with a high correlation between varepsilondA and varepsilondC (r=0.84, P=0.0001). Etheno-adduct levels were higher in atherosclerotic smokers than in ex-smokers for both varepsilondA (means 15.2 versus 7.3, P=0.06) and varepsilondC (71.9 versus 51.6, not significant). varepsilondC levels were higher in either ex-smokers (P=0.03) or smokers (P=0.07) than in non-smokers. There was a poor correlation between either varepsilondA or varepsilondC and 8-hydroxy-2'-deoxyguanosine, whereas significant positive correlations were detected with the levels of several postlabeled bulky aromatic DNA adducts. In conclusion, two different types of DNA damage may be involved in atherosclerotic plaque formation and progression: (i) bulky aromatic compounds, to which aorta SMCs are chronically exposed in smokers, can either covalently bind to DNA, induce redox-cycling via quinone intermediates and/or activate local chronic inflammatory processes in the arterial wall; ii) this in turn leads to a self perpetuating generation of reactive oxygen species, LPO-products and increasing DNA-damage, as documented by the presence of high levels of miscoding etheno-DNA adducts in human aorta SMCs.

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.

GSTM1, GSTT1 and CYP1A1 detoxification gene polymorphisms and susceptibility to smoking-related coronary artery disease: a case-only study

Cigarette smoking is a powerful risk factor for coronary artery disease (CAD), leading to the formation of DNA alterations within blood vessels and heart. However, the degree of smoking-related atherosclerosis varies from individual to individual. Genetic polymorphisms of relevant xenobiotic metabolising enzymes may determine the susceptibility of an individual response to environmental toxicants. The purpose of this study was to test the hypothesis that the inheritance of polymorphic genes encoding cytochrome P450 1A1 (CYP1A1 MspI) and glutathione S-transferases (GSTM1(null) and GSTT1(null)) may be causally associated with the presence and severity of smoking-induced CAD. In a case-only design, 222 (179 male, 57.8+/-10.3 years) consecutive smoker patients who had undergone elective and diagnostic coronary angiography were recruited. We found a group (n=169) of smoker patients with significant CAD, defined as>50% reduction in diameter of at least one major vessel, and a group without obstructive CAD (n=53). No significant differences were observed in CYP1A1 genotypes frequencies between CAD and non-CAD smokers (p=0.1). Homozygous deletion of GSTM1 had a frequency of 58.6% among patients with CAD and 45.3% among those without CAD (p=0.08). The frequency of the GSTT1(null) genotype was 43.8% among the patients with CAD and 24.5% among CAD-free subjects (p=0.01). After adjustment for traditional risk factors, the presence of combined GSTM1(null)GSTT1(null) genotypes was significantly associated with an increased risk of CAD (OR=3.9; 95% CI: 1.3-11.4, p=0.01). Moreover, smokers with combined GSTM1(null)GSTT1(null) genotypes had significantly higher number of stenosed vessels than those with the positive genotype (2.3+/-0.9 versus 1.7+/-0.8, p=0.03). Our findings showed that smokers carrying GST deleted genotypes have an increased susceptibility to the smoking related coronary artery disease. Exploring gene-smoking effect provides an excellent model in order to understand gene-environment toxicants interaction and its implications to cardiovascular disease.

Effect of coronary angiography on oxidative DNA damage observed in circulating lymphocytes

Endogenous oxidative DNA damage is caused by multiple endogenous and exogenous factors. It is not completely known whether coronary angiography has an effect on DNA damage. The aim of this study was to investigate whether coronary angiography causes oxidative DNA damage. Fifty-four patients who underwent elective coronary angiography for diagnostic purpose were enrolled to the study. For each subject, the frequency of oxidative DNA damage was analyzed by using the comet assay, which is a sensitive biomarker of DNA damage, before and after diagnostic procedures. A highly significant increase of DNA damage mean score was observed in all patients after the coronary angiography procedure (p < 0.001). No significant associations were found between the change in oxidative DNA damage and dose of contrast media and radiation exposure time. A significant correlation was observed between the change of DNA damage and age, hyperlipidemia, hypertension, smoking, Gensini score index, and vitamin B(12) (r = 0.496, p< 0.001 ; r = 0.416, p = 0.002; r = 0.284, p = 0.038; r = 0.275, p = 0.044; r = 0.742, p < 0.001; r = -0.347, p = 0.048, respectively). The change of oxidative DNA damage was higher in patients with 3-vessel disease compared with 2-vessel disease, 1-vessel disease, and normal coronary arteries (99.6 +/-8.4, 62.0 +/-2.0, 43.2 +/-8.4, 21.6 +/-11.6 respectively; ANOVA p < 0.001). Multiple linear regression analysis showed that age and Gensini score index were independent predictors of the change of DNA damage (beta = 0.425, p = 0.003, beta = 0.684, p = 0.001 respectively). Our findings demonstrate that increased oxidative DNA damage in undergoing coronary angiography might be dependent on the severity of coronary artery disease and age, rather than on contrast media and radiation exposure time.

Increased lymphocyte deoxyribonucleic acid damage in patients with cardiac syndrome X

OBJECTIVES

To investigate whether there is lymphocyte deoxyribonucleic acid (DNA) damage in patients with cardiac syndrome X (CSX), and its relation with total antioxidant status (TAS), inflammation and ischemia.

METHODS

Twenty-three patients with CSX, 21 patients with non-CSX (NCSX) and 20 healthy volunteers were included in the study. Lymphocyte DNA damage (Arbitrary Unit) was assessed by alkaline single cell electrophoresis (comet) assay in peripheral lymphocyte, and plasma levels of TAS (mmol Trolox equiv./l) were determined using a novel automated measurement method. High sensitive C-reactive protein (hsCRP) and other biochemical parameters were measured from all subjects. Treadmill exercise test and coronary angiography were performed to CSX and NCSX groups.

RESULTS

Lymphocyte DNA damage was increased in patients with CSX compared with NCSX and control group (p<0.001, for both). Also, TAS was decreased, and hsCRP was increased in CSX compared with NCSX and control group (p<0.001, for all). Lymphocyte DNA damage was correlated with magnitude of ST depression (p=0.034), hsCRP (p=0.001), TAS (p<0.001) and presence of diabetes (p=0.022) in bivariate analysis. In multiple linear regression analysis, lymphocyte DNA damage was correlated with only TAS (beta=-0.413, p=0.017) and hsCRP (beta=0.414, p=0.006).

CONCLUSION

Lymphocyte DNA damage was increased in patients with CSX. The increase in lymphocyte DNA damage may be related with increased oxidative stress and inflammation in patients with CSX.

Lymphocyte DNA damage is associated with increased aortic intima-media thickness

OBJECTIVES

To investigate whether there is an association between lymphocyte DNA damage and aortic intima-media thickness (IMT).

METHODS

We studied 70 patients (mean age: 41.6+/-10 years) who underwent transesophageal echocardiography for various indications. Four different grades were determined according to intima-media thickness (IMT) of thoracic aorta measured by transesophageal echocardiography. DNA damage was assessed by alkaline single cell electrophoresis (comet) assay in peripheral lymphocytes. Plasma level of total antioxidant status (TAS) was determined by using automated measurement method. High sensitive C-reactive protein and other biochemical markers were studied in all subjects.

RESULTS

The major increase in lymphocyte DNA damage was observed in patients with grade 4 IMT when compared with other groups (p<0.001, for all). Lymphocyte DNA damage of patients with grade 1 IMT was also lower than patients with grade 2 IMT (p=0.013) and patients with grade 3 IMT (p<0.001). Lymphocyte DNA damage of patients with grade 2 IMT was found at low level compared with patients with grade 3 IMT (p=0.012) as well. In multiple linear regression analysis, IMT was independently correlated with lymphocyte DNA damage (beta=0.515, p<0.001), TAS level (beta=-420, p<0.001), total cholesterol (beta=0.407, p<0.001) and LDL cholesterol level (beta=287, p=0.020).

CONCLUSION

Lymphocyte DNA damage may be an independent predictor for the grade of thoracic IMT, and may play a role in pathogenesis of thoracic atherosclerosis besides TAS and cholesterol levels.

Mitochondrial dysfunction in atherosclerosis

Increased production of reactive oxygen species in mitochondria, accumulation of mitochondrial DNA damage, and progressive respiratory chain dysfunction are associated with atherosclerosis or cardiomyopathy in human investigations and animal models of oxidative stress. Moreover, major precursors of atherosclerosis-hypercholesterolemia, hyperglycemia, hypertriglyceridemia, and even the process of aging-all induce mitochondrial dysfunction. Chronic overproduction of mitochondrial reactive oxygen species leads to destruction of pancreatic beta-cells, increased oxidation of low-density lipoprotein and dysfunction of endothelial cells-factors that promote atherosclerosis. An additional mechanism by which impaired mitochondrial integrity predisposes to clinical manifestations of vascular diseases relates to vascular cell growth. Mitochondrial function is required for normal vascular cell growth and function. Mitochondrial dysfunction can result in apoptosis, favoring plaque rupture. Subclinical episodes of plaque rupture accelerate the progression of hemodynamically significant atherosclerotic lesions. Flow-limiting plaque rupture can result in myocardial infarction, stroke, and ischemic/reperfusion damage. Much of what is known on reactive oxygen species generation and modulation comes from studies in cultured cells and animal models. In this review, we have focused on linking this large body of literature to the clinical syndromes that predispose humans to atherosclerosis and its complications.

DNA damage, p53, apoptosis and vascular disease

Atherosclerosis is the commonest cause of death in the Western world. The atherosclerotic plaque shows evidence of DNA damage, activation of damage repair pathways, p53 expression and apoptosis, involving a variety of different cell types. This review summarises the evidence for DNA damage in atherosclerosis, the likely stimuli inducing damage, and the increasing role of p53 in mediating apoptosis and its consequences in atherosclerosis.

PGAM5, a Bcl-XL-interacting Protein, Is a Novel Substrate for the Redox-regulated Keap1-dependent Ubiquitin Ligase Complex

Keap1 is a BTB-Kelch substrate adaptor protein for a Cul3-dependent ubiquitin ligase complex that functions as a sensor for thiol-reactive chemopreventive compounds and oxidative stress. Inhibition of Keap1-dependent ubiquitination of the bZIP transcription factor Nrf2 enables Nrf2 to activate a cyto-protective transcriptional program that counters the damaging effects of oxidative stress. In this report we have identified a member of the phosphoglycerate mutase family, PGAM5, as a novel substrate for Keap1. The N terminus of the PGAM5 protein contains a conserved NXESGE motif that binds to the substrate binding pocket in the Kelch domain of Keap1, whereas the C-terminal PGAM domain binds Bcl-X(L). Keap1-dependent ubiquitination of PGAM5 results in proteasome-dependent degradation of PGAM5. Quinone-induced oxidative stress and the chemopreventive agent sulforaphane inhibit Keap1-dependent ubiquitination of PGAM5. The identification of PGAM5 as a novel substrate of Keap1 suggests that Keap1 regulates both transcriptional and post-transcriptional responses of mammalian cells to oxidative stress.

DNA damage in metabolic syndrome and its association with antioxidative and oxidative measurements

The purpose of this study was to assess DNA damage levels in subjects with metabolic syndrome (MetS). Sixty-five subjects with MetS and 65 controls were enrolled in this study. Levels of DNA damage, total antioxidant capacity (TAC), total peroxide and oxidative stress index (OSI) were measured. We found that DNA damage levels were significantly increased [155.5 (60-264) vs. 93.2 (0-208) arbitrary units; p < 0.001] and TAC levels were significantly decreased in MetS than in control (1.34 +/- 0.27 vs. 55 +/- 0.33 mmol Trolox equivalent/l; p < 0.001). A significant falling trend in TAC levels and a significant rising trend in DNA damage values with the increase in the number of metabolic disturbances (anova p < 0.001 for both) were observed. Total peroxide (30.9 +/- 4.9 vs. 21.3 +/- 2.5 micromol H2O2/l; p < 0.001) and OSI levels [2.4 (1.3-3.8) vs. 1.4 (0.7-2.3) arbitrary units; p < 0.001] were significantly higher in the subjects with MetS than in controls. We found significant negative correlation between DNA damage and TAC levels in MetS (r = -0.656, p < 0.001) and in control (r = -0.546, p < 0.001). In multiple linear regression analysis, age, body mass index, presence of MetS and number of the components of MetS were independent predictors of log-transformed DNA damage (p < 0.05, for all). DNA damage is increased in patients with MetS. The increase in DNA damage might be occur because of the increase in the imbalance between the production of oxidants and antioxidant defences in subjects with MetS.

Chromosomal damage and atherosclerosis. A protective effect from simvastatin

In uremic patients, the frequency of sister chromatid exchanges appears markedly higher than in the general population. Statins are well known for their pleiotropic effects, which are independent of any reduction in cholesterol circulating levels. The aim of the present study was to determine the effects of exposure to escalating doses of simvastatin on the sister chromatid exchange rate in cultured lymphocytes in order to identify the influence of statin on genomic damage. Peripheral lymphocytic samples for culture were obtained from 25 healthy volunteers, 20 patients with documented carotid atherosclerosis and 30 atherosclerotic patients on maintenance regular acetate-free biofiltration. Hemodialyzed patients had a greater percentage of high frequency cells (50%) than healthy controls (3%) and a significantly higher average number of sister chromatid (9.82+/-2.1 vs. 4.65+/-2.18). The subgroup of hemodialyzed patients with high plaque score values was characterized by significantly greater values for both sister chromatid exchanges rate and high frequency cells percentage. Our findings demonstrate that there is an association between sister chromatid exchanges and high frequency cells rate and atherosclerosis in acetate-free biofiltration patients. In cultures with added simvastatin, high frequency cells percentages and mean sister chromatid exchanges levels were significantly lower than in cultures with an added vehicle alone, the reduction occurring in a dose-dependent fashion, above all in cultures from end stage renal disease patients. The findings, moreover, demonstrate new effects of simvastatin, which appeared to mitigate the expression of genomic damage in our model. However, it is not yet clear whether this effect is due to the prevention of genomic damage or to the potentiation of the DNA repair capacity. Statins may therefore have an anti-atherogenic action partly ascribable to their ability to provide protection against the development of atherosclerotic plaque.

Increased serum levels of 8-hydroxy-2'-deoxyguanosine in clinical depression

OBJECTIVE

We sought to understand the pathophysiological effects of depression by examining group differences in serum levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a biomarker of oxidative damage.

METHODS

Our sample consisted of 169 participants. Eight-four of these participants met diagnostic criteria for clinical depression. The 85 participants in our comparison group were matched on age, gender, and ethnicity to the depressed group. 8-OHdG was measured by enzyme-linked immunosorbent assay.

RESULTS

After adjusting for age, gender, race/ethnicity, years of education, daily smoking, average number of alcoholic drinks per week, average amount of physical activity per week, and body mass index, participants in the depressed group had significantly higher levels of oxidative DNA damage compared with participants in the control group. Pairwise comparisons showed that participants with major depression had significantly higher levels of 8-OHdG than control subjects and marginally higher levels of 8-OHdG compared with those with minor depression. Furthermore, participants with recurrent episodes of depression had more oxidative damage than participants with single episodes, who in turn had more damage than healthy control subjects. Finally, participants with recurrent episodes of major depression had more DNA damage than other depressed participants, who in turn had more damage than healthy control subjects.

CONCLUSIONS

Our findings suggest that increased oxidative damage may represent a common pathophysiological mechanism, whereby depressed individuals become vulnerable to comorbid medical illness.

Myeloperoxidase generates 5-chlorouracil in human atherosclerotic tissue: a potential pathway for somatic mutagenesis by macrophages

Somatic mutations induced by oxidative damage of DNA might play important roles in atherogenesis. However, the underlying mechanisms remain poorly understood. Myeloperoxidase, a heme protein expressed by select populations of artery wall macrophages, initiates one potentially mutagenic pathway by generating hypochlorous acid. This potent chlorinating agent reacts rapidly with primary amines to yield long-lived, selectively reactive N-chloramines. In the current studies, we demonstrate that myeloperoxidase produced by human macrophages differentiated in the presence of granulocyte macrophage colony-stimulating factor generates 5-chlorouracil, a mutagenic thymine analog. The primary amine taurine fails to block the reaction, suggesting that N-haloamines produced by macrophages might oxidize uracil. Model system studies demonstrated that N-chloramines convert uracil to 5-chlorouracil. Interestingly, the tertiary amine nicotine dramatically enhances uracil chlorination, suggesting that cigarette smoke might promote nucleobase oxidation by N-chloramines. To look for evidence that myeloperoxidase promotes uracil oxidation in vivo, we measured 5-chlorouracil levels in human aortic tissue, using isotope dilution gas chromatography-mass spectrometry. The level of 5-chlorouracil was 10-fold higher in atherosclerotic aortic tissue obtained during vascular surgery than in normal aortic tissue, suggesting that halogenated nucleobases produced by macrophages might contribute to atherogenesis. Because 5-chlorouracil can be incorporated into nuclear DNA, our observations raise the possibility that halogenation reactions initiated by phagocytes provide one pathway for mutagenesis, phenotypic modulation, and cytotoxicity during atherogenesis.

Does measurement of oxidative damage to DNA have clinical significance?

Oxidative damage to DNA is the seemingly inevitable consequence of cellular metabolism. Furthermore, despite protective mechanisms, cellular levels of damage may increase under conditions of oxidative stress, arising from exposure to a variety of physical or chemical insults. Elevated levels of oxidatively damaged DNA have been measured in numerous diseases, and as a result, it has been hypothesised that such damage plays an integral role in the aetiology of that disease. This review examines the validity of this hypothesis, exploring the mechanisms by which oxidative DNA damage may lead to disease. We conclude that further validation of biomarkers of oxidative DNA damage, along with further elucidation of the role of damage in disease, may allow these biomarkers to become potentially useful clinical tools.

Ubiquitination of Keap1, a BTB-Kelch substrate adaptor protein for Cul3, targets Keap1 for degradation by a proteasome-independent pathway

Keap1 is a BTB-Kelch protein that functions as a substrate adaptor protein for a Cul3-dependent E3 ubiquitin ligase complex. Keap1 targets its substrate, the Nrf2 transcription factor, for ubiquitination and subsequent degradation by the 26 S proteasome. Inhibition of Keap1-dependent ubiquitination of Nrf2 increases steady-state levels of Nrf2 and enables activation of cytoprotective Nrf2-dependent genes. In this report, we demonstrate that Keap1 and three other BTB-Kelch proteins, including GAN1, ENC1, and Sarcosin, are ubiquitinated by a Cul3-dependent complex. Ubiquitination of Keap1 is markedly increased in cells exposed to quinone-induced oxidative stress, occurs in parallel with inhibition of Keap1-dependent ubiquitination of Nrf2, and results in decreased steady-state levels of Keap1, particularly in cells that are unable to synthesize glutathione. Degradation of Keap1 is independent of the 26 S proteasome, because inhibitors of the 26 S proteasome do not prevent loss of Keap1 following exposure of cells to quinone-induced oxidative stress. Our results suggest that a switch from substrate to substrate adaptor ubiquitination is a critical regulatory step that controls steady-state levels of both BTB-Kelch substrate adaptor proteins and their cognate substrates.

Genomic rearrangements on VCAM1, SELE, APEG1and AIF1 loci in atherosclerosis

The inflammatory nature of atherosclerosis has been well established. However, the initial steps that trigger this response in the arterial intima remain obscure. Previous studies reported a significant rate of genomic alterations in human atheromas. The accumulation of genomic rearrangements in vascular endothelium and smooth muscle cells may be important for disease development. To address this issue, 78 post-mortem obtained aortic atheromas were screened for microsatellite DNA alterations versus correspondent venous blood. To evaluate the significance of these observations, 33 additional histologically normal aortic specimens from age and sex-matched cases were examined. Loss of heterozygosity (LOH) was found in 47,4% of the cases and in 18,2% of controls in at least one locus. The LOH occurrence in aortic tissue is associated to atherosclerosis risk (OR 4,06, 95% CI 1,50 to 10,93). Significant genomic alterations were found on 1p32-p31, 1q22-q25, 2q35 and 6p21.3 where VCAM1, SELE, APEG1 and AIF1 genes have been mapped respectively. Our data implicate somatic DNA rearrangements, on loci associated to leukocyte adhesion, vascular smooth muscle cells growth, differentiation and migration, to atherosclerosis development as an inflammatory condition.

Relationship between DNA damage, total antioxidant capacity and coronary artery disease

OBJECTIVE

It has been known that there was a relation between the levels of DNA damage and the severity of the coronary artery disease (CAD). However, little is known about association of DNA damage with total antioxidant capacity (TAC) and CAD. The aim of this study is to evaluate the relationship between DNA damage, TAC and CAD.

METHODS

We used the comet assay to measure DNA damage from 53 patients with angiographically documented CAD and 42 patients with angiographically documented normal coronary vessel. The extent and severity of CAD was calculated to Gensini score index. TAC of plasma was determined using a novel automated measurement method.

RESULTS

Mean values of DNA damage were significantly higher in CAD patients than in the control group (p<0.001). There was a positive correlation between Gensini score index and DNA damage (r=0.590, p<0.001). Additionally, significantly positive correlations between score of DNA damage, and diabetes, smoking, obesity and hyperlipidemia were found (p<0.05). There was also a negative correlation between TAC and DNA damage (r=-0.711, p<0.001). The DNA damage was significantly higher in diabetic, smoker, hyperlipidemic and obese individuals than those without these conditions (p=0.001, p=0.006, p=0.001, p=0.004, respectively).

CONCLUSIONS

These data indicate that the level of DNA damage is increased and TAC level is decreased in CAD. DNA damage is correlated with the severity of the CAD, and levels of TAC.

Detection of mtDNA with 4977 bp deletion in blood cells and atherosclerotic lesions of patients with coronary artery disease

Recent evidence suggests that somatic mutations in nuclear and mitochondrial DNA accumulated during aging, may significantly contribute to the pathogenesis of chronic-degenerative illness such as coronary artery disease (CAD). Mitochondrial DNA with 4977 bp deletion mutation (mtDNA4977) is a common type of mtDNA alteration in humans. However, little attempt has been made to detect the presence of mtDNA4977 deletion in cells and tissues of cardiovascular patients. This study investigated the presence of mtDNA4977 in blood samples of 65 cardiovascular patients and 23 atherosclerotic plaques of human coronaries with severe atherosclerosis. Moreover, the presence of the deletion has been investigated in blood cells from 22 healthy age-matched subjects. The detection of mtDNA4977 has been performed by using a nested polymerase chain reaction (PCR) protocol and normalized to wild-type mtDNA. A significant higher incidence of mtDNA4977 was observed in CAD patients with respect to healthy subjects (26.2% versus 4.5%; P=0.03). Furthermore, the relative amount of the deletion was significantly higher in the patients compared to the control group (P=0.02). The mtDNA4977 was detected in 17 of the 65 patients blood samples (26.2%) and deletion levels ranged from 0.18 to 0.46% of the total mtDNA (mean: 0.34+/-0.02%). For what concerns atherosclerotic lesions, 5 patients (21.7%) showed the deletion ranging from 0.13 to 0.45% of the total mtDNA (mean: 0.35+/-0.06%). In both samples from patients, the incidence and the relative amount of mtDNA4977 was not significantly influenced by atherogenic risk factors and clinical parameters. The obtained results may suggest that the increase of oxidative stress in cardiovascular disease may be responsible for the accumulation of mtDNA damage in coronary artery disease patients.

Diabetes and chronic nitrate therapy as co-determinants of somatic DNA damage in patients with coronary artery disease

Somatic DNA damage has been linked to coronary artery disease (CAD). However, whether genetic instability is linked to CAD per se or to concomitant potentially genotoxic metabolic and pharmacological factors remains still unclear. The aim of this study was to evaluate the determinants of somatic DNA damage in a large population of patients undergoing coronary angiography. A total of 278 in-hospital patients (215 men, age 61.8+/-0.7 years) were studied by using micronucleus assay (MN) in human lymphocytes, which is one of the most commonly used biomarker for somatic DNA damage. Significant CAD (>50% diameter stenosis) was present in 210 patients (179 men, age 62.3+/-0.7 years). Normal coronary arteries were observed in 68 patients (35 men, age 60.2+/-1.7 years). There were no significant differences between patients with and without CAD, but patients with multivessel disease had the highest MN levels (P=0.01). MN frequency was also found significantly higher in presence of type 2 diabetes (P<0.0001), dyslipidemia (P=0.048) and nitrate therapy (P=0.0002). A significant additive effect was also observed between diabetes and nitrate therapy (P=0.02). On multivariate logistic regression analysis, diabetes [odds ratio=6.8 (95% confidence interval, 3.2-14.5), P<0.0001] and nitrate therapy [odds ratio=2.4 (95% confidence interval, 1.3-4.7), P=0.01] remained the only significant determinants for the 50th percentile of MN (>12 per thousand). These results indicated that diabetes and, to a lesser extent, chronic nitrate therapy are major determinants of somatic DNA instability in patients with CAD. DNA damage might represent an additional pathogenetic dimension and a possible therapeutic target in the still challenging management of coronary artery disease concerning diabetics.

Keap1 is a redox-regulated substrate adaptor protein for a Cul3-dependent ubiquitin ligase complex

The bZIP transcription factor Nrf2 controls a genetic program that protects cells from oxidative damage and maintains cellular redox homeostasis. Keap1, a BTB-Kelch protein, is the major upstream regulator of Nrf2 and controls both the subcellular localization and steady-state levels of Nrf2. In this report, we demonstrate that Keap1 functions as a substrate adaptor protein for a Cul3-dependent E3 ubiquitin ligase complex. Keap1 assembles into a functional E3 ubiquitin ligase complex with Cul3 and Rbx1 that targets multiple lysine residues located in the N-terminal Neh2 domain of Nrf2 for ubiquitin conjugation both in vivo and in vitro. Keap1-dependent ubiquitination of Nrf2 is inhibited following exposure of cells to quinone-induced oxidative stress and sulforaphane, a cancer-preventive isothiocyanate. A mutant Keap1 protein containing a single cysteine-to-serine substitution at residue 151 within the BTB domain of Keap1 is markedly resistant to inhibition by either quinone-induced oxidative stress or sulforaphane. Inhibition of Keap1-dependent ubiquitination of Nrf2 correlates with decreased association of Keap1 with Cul3. Neither quinone-induced oxidative stress nor sulforaphane disrupts association between Keap1 and Nrf2. Our results suggest that the ability of Keap1 to assemble into a functional E3 ubiquitin ligase complex is the critical determinant that controls steady-state levels of Nrf2 in response to cancer-preventive compounds and oxidative stress.

The role of hyperosmolal food in the development of atherosclerosis

Hyperosmolality of ingested food causes excessive thermogenesis in humans. And when this heat does not find a way to dissipate or expelled from body it causes the blood circulatory system to build an insulator wall by depositing fat in aorta resulting in atherosclerosis. The mechanism of excessive thermogenesis is presently unknown. It seems that the hyperosmolal food stimulates intestinal osmoreceptors and raises plasma osmolality. However, the dissipation of this heat is less likely to occur in obese people than skinny people because there is an extra layer of fat in obese people. In addition, the climatic conditions do not affect the development of atherosclerosis. Therefore, hyperosmolality of ingested food is the primary factor in the development of atherosclerosis and obesity is only secondary. In addition, the ingestion of fat has practically no effect on the development of atherosclerosis because it does not cause thermogenesis like amino acids, sugars, and NaCl do. Thus, both skinny as well as obese people are at risk of developing atherosclerosis if they habitually consume hyperosmolal foods irrespective of what part of the world they live in.

Crystal Structure of the Kelch Domain of Human Keap1

Keap1 is a substrate adaptor protein for an ubiquitin ligase complex that targets the Nrf2 transcription factor for degradation. Keap1 binds Nrf2 through its C-terminal Kelch domain, which contains six copies of the evolutionarily conserved kelch repeat sequence motif. The structure of the Kelch domain from human Keap1 has been determined by x-ray crystallography to a resolution of 1.85 A. The Kelch domain forms a 6-bladed beta-propeller structure, with residues at the C terminus forming the first strand in the first blade. Key structural roles have been identified for the highly conserved glycine, tyrosine, and tryptophan residues that define the kelch repeat sequence motif. In addition, we show that substitution of a single amino acid located within a loop that extends out from the bottom of the beta-propeller structure abolishes binding of Nrf2. The structure of the Kelch domain of Keap1 represents a high quality model for the superfamily of eukaryotic kelch repeat proteins and provides insight into how disease-causing mutations perturb the structural integrity of the Kelch domain.

Oxidative stress and its association with coronary artery disease and different atherogenic risk factors

OBJECTIVE

It is well known that free radicals contribute to endothelial dysfunction and are involved in the pathogenesis and development of cardiovascular diseases, such as atherosclerosis. The aim of this study was to provide evidence for enhanced oxidative stress in coronary artery disease (CAD).

METHODS

Plasma levels of 8-isoprostane (8-epiPGF(2alpha)), marker of lipid peroxidation, were measured in 68 subjects (age: 60 +/- 2 years, mean +/- SEM). Subjects included 30 healthy control subjects and 38 patients with angiographically proven CAD. In addition, the total antioxidant power (PAO) was evaluated in a subgroup (40 subjects, 12 healthy and 28 CAD).

RESULTS

Levels of 8-epiPGF(2alpha) increased with the number of affected vessels (one- and multi-vessel disease versus control subjects, P < 0.001) and considering different risk determinants for atherosclerosis (i.e. hypertension, gender, hypercholesterolaemia, P < 0.01). In multivariate regression models the number of affected vessels was independently correlated with 8-epiPGF(2alpha) (P < 0.05). PAO values significantly decreased with increased number of affected vessels (P < 0.05) and in hypertensive patients when compared with those without hypertension (P < 0.05). In multivariate regression models the number of affected vessels resulted an independent determinant for PAO (P < 0.05). Concentration of 8-epiPGF(2alpha) and PAO also correlated with the number of cardiovascular risk factors (P < 0.01 and P = 0.07, respectively).

CONCLUSION

These findings indicate that elevated levels of plasma 8-epiPGF(2alpha) and reduced antioxidant capacity are associated with the extent and the severity of CAD and with the occurrence and number of different atherogenic risk factors. This observation may assist in providing more information as to how oxidative stress may predispose to atherogenesis and suggest attractive therapeutic strategies in the prevention and treatment of cardiovascular disease.

Oxidative DNA damage and disease: induction, repair and significance

The generation of reactive oxygen species may be both beneficial to cells, performing a function in inter- and intracellular signalling, and detrimental, modifying cellular biomolecules, accumulation of which has been associated with numerous diseases. Of the molecules subject to oxidative modification, DNA has received the greatest attention, with biomarkers of exposure and effect closest to validation. Despite nearly a quarter of a century of study, and a large number of base- and sugar-derived DNA lesions having been identified, the majority of studies have focussed upon the guanine modification, 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-OH-dG). For the most part, the biological significance of other lesions has not, as yet, been investigated. In contrast, the description and characterisation of enzyme systems responsible for repairing oxidative DNA base damage is growing rapidly, being the subject of intense study. However, there remain notable gaps in our knowledge of which repair proteins remove which lesions, plus, as more lesions identified, new processes/substrates need to be determined. There are many reports describing elevated levels of oxidatively modified DNA lesions, in various biological matrices, in a plethora of diseases; however, for the majority of these the association could merely be coincidental, and more detailed studies are required. Nevertheless, even based simply upon reports of studies investigating the potential role of 8-OH-dG in disease, the weight of evidence strongly suggests a link between such damage and the pathogenesis of disease. However, exact roles remain to be elucidated.

C677T polymorphism of the methylenetetrahydrofolate reductase gene is a risk factor of adverse events after coronary revascularization

BACKGROUND

A common point mutation (C677T) in the gene for 5,10-methylenetetrahydrofolate reductase (MTHFR) is associated with hyperhomocysteinemia, an independent risk factor and a strong predictor of mortality in patients with coronary artery disease (CAD). The aim of this study was to investigate whether C677T polymorphism can be a predictor of major adverse cardiac events after myocardial revascularization.

METHODS

We determined MTHFR genotype in 159 patients with CAD undergoing myocardial revascularization [72 percutaneous transluminal coronary angioplasty (PTCA) and 87 coronary artery bypass graft (CABG)]. Recurrent angina, nonfatal myocardial infarction (MI), target vessel revascularization, heart failure and cardiac death were considered major adverse cardiac events that occurred after discharge from index hospitalization.

RESULTS

During the follow-up (6.9+/-0.3 months, mean+/-S.E.M.), the composite endpoint accounted for 25.9%, 11.4% and 4.3% for TT, CT and CC genotype (log-rank statistic 5.2, p=0.02), respectively. Subjects with mutant TT genotype had a threefold increase of any cardiac event (hazard ratio [HR]=3.0; 95% [CI], 1.1-8.1). In multiple-variable regression Cox, predictors of events were TT genotype (HR=2.8; 95% CI, 1.01-7.62, p=0.047), low-ejection fraction<40% (HR=4.5; 95% CI, 1.62-12.6, p=0.004) and revascularization procedure (HR=6.1; 95% CI, 1.86-20.34, p=0.003).

CONCLUSIONS

These data indicate that the TT genotype seems to be significantly associated with major adverse cardiac events after myocardial revascularization in CAD patients, suggesting a potential pathological influence of homocysteine in the clinical outcome.

Atherosclerotic Plaque Smooth Muscle Cells Have a Distinct Phenotype

Objective— The present study addresses the question, “Are plaque smooth muscles cells (SMCs) genetically distinct from medial SMCs as reflected by the ability to maintain a distinctive expression phenotype in vitro?”

Methods and Results— Multiple cell strains were developed from carotid endarcterectomy specimens, and quadruplicate array hybridizations were completed for each sample. A new normalization protocol was developed and used to analyze the data. Permutation analysis suggests that most of the significant differences in expression could not have occurred by chance. A broad pattern of significant expression differences, consisting of almost 5% of the genes probed, was detected. Quantitative polymerase chain reaction (QPCR) confirmation was found in 70% of a subset of genes selected for validation.

Conclusions— The SMC cultures were nearly indistinguishable by morphological features, population doubling time, and sensitivity to cell death induced by Fas cross-linking. Surprisingly, array expression analysis identified differences so extensive that we conclude that plaque and medial SMCs are distinctly different SMC cell types.

Genetic polymorphisms in folate and homocysteine metabolism as risk factors for DNA damage

Epidemiological studies indicated a role for polymorphisms in genes of folate and homocysteine (Hcy) metabolism in the etiology of neurodegenerative disease, congenital defects and coronary artery disease (CAD). This study investigated the effect of several polymorphisms [C677 T, A1298C of methylenetetrahydrofolate reductase (MTHFR) and A66G of methionine synthase reductase (MTRR) genes] on Hcy levels and DNA damage in 68 patients who underwent coronary angiography. Plasma Hcy concentrations were higher in patients with multivessel disease with respect to monovessel disease and no-CAD patients (19.4+/-2.6 vs 11.6+/-1.2 and 13.7+/-1.4 micromol/l, respectively; P=0.03). 677TT patients had higher Hcy levels than those with 677CC or 677CT genotypes (26.2+/-4.3 vs 13.1+/-1.4 and 13.0+/-1.4 micromol/l, respectively; P=0.0006). No significant associations were found between A1298C and A66G polymorphisms and plasma Hcy levels. Among patients with 677CC genotype, 66GG individuals tended to have higher levels of Hcy than 66AA homozygotes (14.5+/-1.9 vs 8.9+/-0.7 micromol/l, P=0.06). Multivessel disease patients showed an increased frequency of DNA damage, measured by the micronucleus (MN) frequency, as compared to monovessel disease and no-CAD subjects (12.5+/-1.1 vs 8.5+/-0.8 and 8.2+/-0.9, respectively; P=0.006). The MN were positively correlated with Hcy levels (r=0.33, P=0.006) and were significantly higher in subjects with the 677TT genotype compared with the 677CC or 677CT genotypes (14.4+/-2.0 vs 8.8+/-1.2 and 9.5+/-0.7, respectively; P=0.006). A1298C and A66G polymorphisms had no effect on MN frequency. However, among 677TT patients, 66GG subjects tended to have higher levels of MN than those 66AG and 66AA (18.2+/-3.6 vs 13.8+/-4.0 and 10.3+/-1.7, respectively; P=NS). Our results indicate that genetic instability may be associated with increased risk for multiple Hcy-related diseases.

Interactive effect of the glutathione S-transferase genes and cigarette smoking on occurrence and severity of coronary artery risk

Cardiovascular diseases and cancer are the main causes of death in developed countries. Mortality trends for these diseases suggest that they share common pathogenetic mechanisms. Glutathione S-transferase (GST) is a family of enzymes that detoxify reactive electrophiles, particularly present in tobacco smoke. Glutathione S-transferase null M1 and T1 (GSTM1 and GSTT1) genotypes have often been associated with increased risk of developing cancer. Our hypothesis was that the polymorphic GSTM1 and GSTT1 genes modulate the risk of smoking-coronary artery disease (CAD). We evaluated the distribution of GST genotypes in 430 angiographically defined patients (308 CAD and 122 non-CAD). The frequencies of GST null genotypes did not differ significantly between patients with CAD and without CAD. However, smokers with GSTM1 and GSTT1 null genotypes had a significantly higher risk of CAD than never-smokers with these genotypes present (OR 2.2 and 3.4 for smokers with null GSTM1 and GSTT1 genes, respectively). There was also evidence of multiple interaction between GSTM1 and GSTT1 deleted genotypes and smoking. In nonsmokers carrying both null genotypes the risk of CAD was 0.66. In smokers with both present genotypes the OR was 1.5 and was significantly increased in smokers with concurrent lack for GSTM1 and GSTT1 genes (OR=4.0). Moreover, smokers lacking GST genes had both more stenosed vessels and a higher Duke score than smokers expressing the genes. We also examined the levels of DNA damage in 66 men patients using the micronucleus test, a sensitive assay for evaluating chromosome damage. Micronucleus levels were higher in smokers with null genes than in smokers with present genes. These observations suggest that GST-null genotypes strengthen the effect of smoking on CAD risk by modulating the detoxification of genotoxic atherogens.