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

Comparison of Cell-based and Nanoparticle-based Therapeutics in Treating Atherosclerosis

Today, cardiovascular diseases are among the biggest public health threats worldwide. Atherosclerosis, a chronic inflammatory disease with complex aetiology and pathogenesis, predispose many of these conditions, including the high mortality rate-causing ischaemic heart disease and stroke. Nevertheless, despite the alarming prevalence and absolute death rate, established treatments for atherosclerosis are unsatisfactory in terms of efficacy, safety, and patient acceptance. The rapid advancement of technologies in healthcare research has paved new treatment approaches, namely cell-based and nanoparticle-based therapies, to overcome the limitations of conventional therapeutics. This paper examines the different facets of each approach, discusses their principles, strengths, and weaknesses, analyses the main targeted pathways and their contradictions, provides insights on current trends as well as highlights any unique mechanisms taken in recent years to combat the progression of atherosclerosis.

Transfer of microRNA-221 from mesenchymal stem cell-derived extracellular vesicles inhibits atherosclerotic plaque formation

Mesenchymal stem cells (MSCs) have emerged as a cell-based therapy in many diseases including atherosclerosis (AS) due to their capability of immunomodulation and tissue regeneration. However, the pathway for MSCs' antiatherosclerotic activity remains to be elucidated. Here, we test the hypothesis that microRNA-221 (miR-221) from MSC-derived extracellular vesicles (EVs) alleviates AS. Male ApoE-/- mice were fed a high-fat diet for 12 weeks to induce AS, and were then treated with human bone marrow mesenchymal stem cell-derived EVs by tail vein injection. The expression pattern of miR-221 and N-acetyltransferase-1 (NAT1) in AS mice was characterized by quantitative RNA analysis and their interaction was identified by dual-luciferase reporter gene assay. In other studies, human arterial smooth muscle cells treated with oxidized low-density lipoprotein-were co-cultured with MSC-released EVs to evaluate the EV-mediated transfer of miR-221. NAT1 was highly expressed in atherosclerotic lesions. Adenovirus-mediated NAT1 knockdown resulted in a reduced lipid deposition in AS mice. Human bone marrow mesenchymal stem cell -derived EVs carrying miR-221 were internalized by human arterial smooth muscle cells and transferred their miR-221 contents to downregulate the target gene NAT1. Injection of miR-221-containing EVs inhibited lipid deposition in AS mice, in part by downregulating NAT1. The present study provides evidence that miR-221 shuttled by MSC-derived EVs can inhibit atherosclerotic plaque formation in AS model mice, suggesting that miR-221 may serve as a target for improving MSC-based therapeutic strategy against AS.

The molecular biomarkers of vascular aging and atherosclerosis: telomere length and mitochondrial DNA4977 common deletion

Age is the dominant risk factor for the most prevalent atherosclerotic vascular diseases, including coronary artery disease, myocardial infarction, cerebrovascular disease and stroke. In human, telomere erosion and mitochondrial DNA (mtDNA) damage play a central role in the mechanisms leading to cellular aging decline. This review summarizes the most relevant findings on the role of telomere shortening and the common mtDNA⁴⁹⁷⁷ deletion in the progression and evolution of atherosclerosis by combining insight from experimental models and human clinical studies. The current evidence shows a link between telomere erosion and compromised mitochondrial function and provides a new perspective regarding their potential role as clinical biomarkers and therapeutic targets.

Human primary endothelial cells are impaired in nucleotide excision repair and sensitive to benzo[a]pyrene compared with smooth muscle cells and pericytes

The endothelium represents the inner cell layer of blood vessels and is supported by smooth muscle cells and pericytes, which form the vessel structure. The endothelium is involved in the pathogenesis of many diseases, including the development of atherosclerosis. Due to direct blood contact, the blood vessel endothelium is inevitably exposed to genotoxic substances that are systemically taken up by the body, including benzo[a]pyrene, which is a major genotoxic component in cigarette smoke and a common environmental mutagen and human carcinogen. Here, we evaluated the impact of benzo[a]pyrene diol epoxide (BPDE), which is the reactive metabolite of benzo[a]pyrene, on the three innermost vessel cell types. Primary human endothelial cells (HUVEC), primary human smooth muscle cells (HUASMC) and primary human pericytes (HPC) were treated with BPDE, and analyses of cytotoxicity, cellular senescence and genotoxic effects were then performed. The results showed that HUVEC were more sensitive to the cytotoxic activity of BPDE than HUASMC and HPC. We further show that HUVEC display a detraction in the repair of BPDE-induced adducts, as determined through the comet assay and the quantification of BPDE adducts in post-labelling experiments. A screening for DNA repair factors revealed that the nucleotide excision repair (NER) proteins ERCC1, XPF and ligase I were expressed at lower levels in HUVEC compared with HUASMC and HPC, which corresponds with the impaired NER-mediated removal of BPDE adducts from DNA. Taken together, the data revealed that HUVEC exhibit an unexpected DNA repair-impaired phenotype, which has implications on the response of the endothelium to genotoxicants that induce bulky DNA lesions, including the development of vascular diseases resulting from smoking and environmental pollution.

Literature-Based Enrichment Insights into Redox Control of Vascular Biology

In cellular physiology and signaling, reactive oxygen species (ROS) play one of the most critical roles. ROS overproduction leads to cellular oxidative stress. This may lead to an irrecoverable imbalance of redox (oxidation-reduction reaction) function that deregulates redox homeostasis, which itself could lead to several diseases including neurodegenerative disease, cardiovascular disease, and cancers. In this study, we focus on the redox effects related to vascular systems in mammals. To support research in this domain, we developed an online knowledge base, DES-RedoxVasc, which enables exploration of information contained in the biomedical scientific literature. The DES-RedoxVasc system analyzed 233399 documents consisting of PubMed abstracts and PubMed Central full-text articles related to different aspects of redox biology in vascular systems. It allows researchers to explore enriched concepts from 28 curated thematic dictionaries, as well as literature-derived potential associations of pairs of such enriched concepts, where associations themselves are statistically enriched. For example, the system allows exploration of associations of pathways, diseases, mutations, genes/proteins, miRNAs, long ncRNAs, toxins, drugs, biological processes, molecular functions, etc. that allow for insights about different aspects of redox effects and control of processes related to the vascular system. Moreover, we deliver case studies about some existing or possibly novel knowledge regarding redox of vascular biology demonstrating the usefulness of DES-RedoxVasc. DES-RedoxVasc is the first compiled knowledge base using text mining for the exploration of this topic.

Effects of the Ser326Cys Polymorphism in the DNA Repair OGG1 Gene on Cancer, Cardiovascular, and All-Cause Mortality in the PREDIMED Study: Modulation by Diet

BACKGROUND

Oxidatively induced DNA damage, an important factor in cancer etiology, is repaired by oxyguanine glycosylase 1 (OGG1). The lower repair capacity genotype (homozygote Cys326Cys) in the OGG1-rs1052133 (Ser326Cys) polymorphism has been associated with cancer risk. However, no information is available in relation to cancer mortality, other causes of death, and modulation by diet.

OBJECTIVE

Our aim was to evaluate the association of the OGG1-rs1052133 with total, cancer, and cardiovascular disease (CVD) mortality and to analyze its modulation by the Mediterranean diet, focusing especially on total vegetable intake as one of the main characteristics of this diet.

DESIGN

Secondary analysis in the PREDIMED (Prevención con Dieta Mediterránea) trial is a randomized, controlled trial conducted in Spain from 2003 to 2010.

PARTICIPANTS/SETTING

Study participants (n=7,170) were at high risk for CVD and were aged 55 to 80 years.

INTERVENTION

Participants were randomly allocated to two groups with a Mediterranean diet intervention or a control diet. Vegetable intake was measured at baseline.

MAIN OUTCOME MEASURES

Main outcomes were all-cause, cancer, and CVD mortality after a median follow-up of 4.8 years.

STATISTICAL ANALYSES

Multivariable-adjusted Cox regression models were fitted.

RESULTS

Three hundred eighteen deaths were detected (cancer, n=127; CVD, n=81; and other, n=110). Cys326Cys individuals (prevalence 4.2%) presented higher total mortality rates than Ser326-carriers (P=0.009). The multivariable-adjusted hazard ratio for Cys326Cys vs Ser326-carriers was 1.69 (95% CI 1.09 to 2.62; P=0.018). This association was greater for CVD mortality (P=0.001). No relationship was detected for cancer mortality in the whole population (hazard ratio 1.07; 95% CI 0.47 to 2.45; P=0.867), but a significant age interaction (P=0.048) was observed, as Cys326Cys was associated with cancer mortality in participants <66.5 years (P=0.029). Recessive effects limited our ability to investigate Cys326Cys×diet interactions for cancer mortality. No statistically significant interactions for total or CVD mortality were found for the Mediterranean diet intervention. However, significant protective interactions for CVD mortality were found for vegetable intake (hazard ratio interaction per standard deviation 0.42; 95% CI 0.18 to 0.98; P=0.046).

CONCLUSIONS

In this population, the Cys326Cys-OGG1 genotype was associated with all-cause mortality, mainly CVD instead of cancer mortality. Additional studies are needed to provide further evidence on its dietary modulation.

The role of oxidative DNA damage and GSTM1, GSTT1, and hOGG1 gene polymorphisms in coronary artery disease risk

Objective:

Atherosclerotic coronary artery disease (CAD) appears to be a multifactorial process caused by the interaction of environmental risk factors with multiple predisposing genes. Therefore, in this study we aimed to determine the role of oxidative DNA damage and some variations in glutathione S-transferase (GSTM1 and GSTT1) and DNA repair (hOGG1) genes in CAD risk.

Methods:

A case-control study was conducted on 59 individuals who had undergone coronary angiographic evaluation. Of these, 29 were patients diagnosed with CAD (mean age =61.5±10.3) and 30 were controls examined for reasons other than suspected CAD and who had angiographically documented normal coronary arteries (mean age =60.4±11.6). Basal DNA damage as well as pyrimidine and purine base damage were evaluated in peripheral blood lymphocytes using the modified comet assay. Polymerase chain reaction-restriction length polymorphism (PCR-RFLP)-based assay was used for genotyping.

Results:

Basal DNA damage levels in patients [9.16 (3.26)] were significantly higher than those in controls [7.59 (3.23); p=0.017], and basal DNA and pyrimidine base damage levels were significantly correlated with disease severity based on Gensini scoring (r=0.352, p=0.006; r=0.318, p=0.014, respectively). However, no significant differences were observed in terms of oxidized DNA bases between patients and controls. The frequencies of studied genotypes (GSTM1, GSTT1, and hOGG1) were similar between groups.

Conclusion:

The results of this study pointed out the role of DNA damage in CAD and its severity. However, GSTM1, GSTT1, and hOGG1 gene polymorphisms seemed to have no effect on individual susceptibility for disease progression. (Anatol J Cardiol 2016; 16: 931-8)

Molecular damage and lung tumors in cigarette smoke-exposed mice

Cigarette smoke (CS) induces lung cancer through a multistep process that is now being depicted by molecular analyses. During the early phase (weeks), DNA damage occurs in nuclear and mitochondrial DNA, triggering adaptive responses activated by transient microRNA downregulation in the expression of defensive genes and proteins. During the intermediate phase (months), damaged cells are removed by apoptosis and the resulting cell loss is counteracted by a recruitment of stem cells that are highly sensitive to genotoxic damage. In parallel, microRNA downregulation becomes irreversible because of an accumulation of molecular damage in DICER. During the late phase (years), apoptosis efficacy is decreased by fragile histidine triad loss, while irreversible microRNA downregulation triggers the expression of mutated oncogenes, resulting in adenoma appearance. Furthermore, deletions occur in microRNA-encoding genes, causing carcinoma formation and uncontrolled growth. All reported pathogenic steps are required to obtain a fully developed lung cancer. This complex pathogenesis develops over a long period of time; therefore, it is difficult to induce cancer in short-living animals exposed to CS, whereas in humans there is a long latency from the start of smoke exposure to the onset of cancer.

Polymorphisms of genes involved in polycyclic aromatic hydrocarbons' biotransformation and atherosclerosis

Polycyclic aromatic hydrocarbons (PAHs) are among the most prevalent environmental pollutants and result from the incomplete combustion of hydrocarbons (coal and gasoline, fossil fuel combustion, byproducts of industrial processing, natural emission, cigarette smoking, etc.). The first phase of xenobiotic biotransformation in the PAH metabolism includes activities of cytochrome P450 from the CYP1 family and microsomal epoxide hydrolase. The products of this biotransformation are reactive oxygen species that are transformed in the second phase through the formation of conjugates with glutathione, glucuronate or sulphates. PAH exposure may lead to PAH-DNA adduct formation or induce an inflammatory atherosclerotic plaque phenotype. Several genetic polymorphisms of genes encoded for enzymes involved in PAH biotransformation have been proven to lead to the development of diseases. Enzyme CYP P450 1A1, which is encoded by the CYP1A1 gene, is vital in the monooxygenation of lipofilic substrates, while GSTM1 and GSTT1 are the most abundant isophorms that conjugate and neutralize oxygen products. Some single nucleotide polymorphisms of the CYP1A1 gene as well as the deletion polymorphisms of GSTT1 and GSTM1 may alter the final specific cellular inflammatory respond. Occupational exposure or conditions from the living environment can contribute to the production of PAH metabolites with adverse effects on human health. The aim of this study was to obtain data on biotransformation and atherosclerosis, as well as data on the gene polymorphisms involved in biotransformation, in order to better study gene expression and further elucidate the interaction between genes and the environment.

Development of a new multiplex quantitative real-time PCR assay for the detection of the mtDNA(4977) deletion in coronary artery disease patients: a link with telomere shortening

Mitochondrial DNA (mtDNA) and telomere shortening have been proposed as important contributors to vascular disease and atherogenesis. The role of mitochondrial and telomere alterations has been examined frequently, but usually separately. Recently, an integrated model in which DNA damage and metabolic pathways intersect in age-associated cardiovascular disease has been proposed. In this study we developed a fast and reliable real-time PCR-based procedure to investigate relative quantification of the 4,977 bp mitochondrial DNA deletion (also indicated as "mtDNA(4977) deletion"), employing TaqMan probes with a multiplex approach. As a validation of the assay, a nested PCR coamplification was performed. Telomere shortening was evaluated by a real-time monochrome multiplex PCR technique employing a SybrGreen-based analysis. The study of mtDNA(4977) deletion and telomere shortening was carried out in atrial biopsies from 11 patients undergoing coronary artery (n = 5) and valve surgery (n = 6). The relative quantifications showed that the amount of mtDNA(4977) deletion was greater in tissue of patients with coronary artery disease (CAD) (P = 0.01) and that telomere length (expressed as telomere length relative to a single copy reference gene) was significantly shorter in tissue of CAD patients, compared to patients without CAD (P = 0.03). Moreover, most conventional risk factors were significantly more frequent in CAD patients, smoking and dyslipidemia having the strongest association with the degree of mtDNA(4977) deletion and a significant correlation with telomere attrition (P = 0.02 and P = 0.006, respectively). In conclusion, the present study suggests that mtDNA(4977) deletion and telomere shortening may represent additional and synergic major risk factors for the pathogenesis of CAD and its complications.

Does morphology of carotid plaque depend on patient's oxidative stress?

OBJECTIVES

This study explored the relationship between oxidative stress biomarkers and stability of carotid plaque. We decided to analyze the broad range of parameters describing oxidative stress in patients with carotid stenosis.

DESIGN AND METHODS

124 consecutive patients undergoing carotid endarterectomy were enrolled in the study group. The control group consisted of 49 patients without symptoms of atherosclerosis. The stability of carotid plaques was assessed using GSM (gray-scale median) scoring system and the study group was divided into three subgroups according to echogenicity of the plaque. The following parameters of oxidative stress/DNA damage were analyzed: i) urinary excretion of the products of oxidative DNA damage repair; ii) the background level of 8-oxo-7,8-dihydro-2'-deoxyguanosine in leukocytes' DNA and in atherosclerotic plaques; and iii) the concentrations of antioxidant vitamins, uric acid and C-reactive protein in plasma.

RESULTS

Oxidative stress (described by redox status) was higher in the patient group than in the control group. There is a correlation between oxidative stress of the patients and stability of the plaque, echolucent plaques (GSM<25) being associated with the highest antioxidant level and lowest excretion of DNA repair markers.

CONCLUSIONS

The plaque formation/morphology may depend on local environment and is independent of oxidative stress/inflammation observed on the level of the whole body.

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 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.

Genomic biomarkers and clinical outcomes of physical activity

Clinical and experimental studies in humans provide evidence that moderate physical activity significantly decreases artery oxidative damage to nuclear DNA, DNA-adducts related to age and dyslipedemia, and mitochondrial DNA damage. Maintenance of adequate mitochondrial function is crucial for preventing lipid accumulation and peroxidation occurring in atherosclerosis. Studies performed on human muscle biopsies analyzing gene expression in living humans reveal that physically active subjects improve the expression of genes involved in mitochondrial function and of related microRNAs. The attenuation of oxidative damage to nuclear and mitochondrial DNA by physical activity resulted in beneficial effects due to polymorphisms of glutathione S-transferases genes. Subjects bearing null GSTM1/T1 polymorphisms have poor life expectancy in the case of being sedentary, which was increased 2.6-fold in case they performed physical activity. These findings indicate that the preventive effect of physical activity undergoes interindividual variation affected by genetic polymorphisms.

Polymorphisms in NAT2 gene and atherosclerosis in an Algerian population

BACKGROUND AND AIMS

The etiology of atherosclerosis is multifactorial. Genetic and environmental factors are involved in the development of atherosclerosis. Human arylamine N-acetyltransferase 2 (NAT2) is an important metabolizing enzyme that exhibits genetic polymorphisms and modifies individual response and/or toxicity to many xenobiotics. We undertook this study to investigate the NAT2 polymorphisms in patients with atherosclerosis.

METHODS

Genotyping for NAT2 alleles was performed using polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP) in 285 Algerian patients with atherosclerosis and 286 controls.

RESULTS

There was no association between NAT2 polymorphisms and atherosclerosis risk. However, the haplotype NAT2(*)5F decreased susceptibility to the disease (p = 0.005, OR = 0.55, 95% CI = 0.37-0.84). The frequency of the slow acetylator phenotype was approximately 50% in both cases and controls.

CONCLUSIONS

These results suggest that NAT2 polymorphisms may not be involved in the pathogenesis of atherosclerosis.

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.

Can we predict top-level sports performance in power vs endurance events? A genetic approach

The goal of our study was to discriminate potential genetic differences between humans who are in both endpoints of the sports performance continuum (i.e. world-class endurance vs power athletes). We used DNA-microarray technology that included 36 genetic variants (within 20 different genes) to compare the genetic profile obtained in two cohorts of world-class endurance (N=100) and power male athletes (N=53) of the same ethnic origin. Stepwise multivariate logistic regression showed that the rs1800795 (IL6-174 G/C), rs1208 (NAT2 K268R) and rs2070744 (NOS3-786 T/C) polymorphisms significantly predicted sport performance (model χ(2) =25.3, df=3, P-value <0.001). Receiver-operating characteristic (ROC) curve analysis showed a significant discriminating accuracy of the model, with an area under the ROC curve of 0.72 (95% confidence interval: 0.66-0.81). The contribution of the studied genetic factors to sports performance was 21.4%. In summary, although an individual's potential for excelling in endurance or power sports can be partly predicted based on specific genetic variants (many of which remain to be identified), the contribution of complex gene-gene interactions, environmental factors and epigenetic mechanisms are also important contributors to the "complex trait" of being an athletic champion. Such trait is likely not reducible to defined genetic polymorphisms.

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.

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.