Oxidative and non-oxidative DNA damage and cardiovascular disease

Abstract

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.     

Oxidative stress-induced DNA damage by particulate air pollution

Exposure to ambient air particulate matter (PM) is associated with pulmonary and cardiovascular diseases and cancer. The mechanisms of PM-induced health effects are believed to involve inflammation and oxidative stress. The oxidative stress mediated by PM may arise from direct generation of reactive oxygen species from the surface of particles, soluble compounds such as transition metals or organic compounds, altered function of mitochondria or NADPH-oxidase, and activation of inflammatory cells capable of generating ROS and reactive nitrogen species. Resulting oxidative DNA damage may be implicated in cancer risk and may serve as marker for oxidative stress relevant for other ailments caused by particulate air pollution. There is overwhelming evidence from animal experimental models, cell culture experiments, and cell free systems that exposure to diesel exhaust and diesel exhaust particles causes oxidative DNA damage. Similarly, various preparations of ambient air PM induce oxidative DNA damage in in vitro systems, whereas in vivo studies are scarce. Studies with various model/surrogate particle preparations, such as carbon black, suggest that the surface area is the most important determinant of effect for ultrafine particles (diameter less than 100 nm), whereas chemical composition may be more important for larger particles. The knowledge concerning mechanisms of action of PM has prompted the use of markers of oxidative stress and DNA damage for human biomonitoring in relation to ambient air. By means of personal monitoring and biomarkers a few studies have attempted to characterize individual exposure, explore mechanisms and identify significant sources to size fractions of ambient air PM with respect to relevant biological effects. In these studies guanine oxidation in DNA has been correlated with exposure to PM(2.5) and ultrafine particles outdoor and indoor. Oxidative stress-induced DNA damage appears to an important mechanism of action of urban particulate air pollution. Related biomarkers and personal monitoring may be useful tools for risk characterization.     

ReviewPart of the Series: From Dietary Antioxidants to Regulators in Cellular Signalling and Gene ExpressionReview: When is an antioxidant not an antioxidant? A review of novel actions and reactions of vitamin C

Vitamin C (or ascorbic acid) is regarded as the most important water-soluble antioxidant in human plasma and mammalian cells which have mechanisms to recycle and accumulate it against a concentration gradient, suggesting that the vitamin might also have important intracellular functions. In this review we summarize evidence from human trials that have attempted an association between vitamin C supplementation and an effect on biomarkers of oxidative DNA damage. Most studies reviewed herein showed either a vitamin C-mediated reduction in oxidative DNA damage or a null effect, whereas only a few studies showed an increase in specific base lesions. We also address the possible beneficial effects of vitamin C supplementation for the prevention of cancer and cardiovascular disease. Finally, we discuss the contribution of cell culture studies to our understanding of the mode of action of vitamin C and we review recent evidence that vitamin C is able to modulate gene expression and cellular function, with a particular interest in cell differentiation.     

Review: When is an antioxidant not an antioxidant? A review of novel actions and reactions of vitamin C

Vitamin C (or ascorbic acid) is regarded as the most important water-soluble antioxidant in human plasma and mammalian cells which have mechanisms to recycle and accumulate it against a concentration gradient, suggesting that the vitamin might also have important intracellular functions. In this review we summarize evidence from human trials that have attempted an association between vitamin C supplementation and an effect on biomarkers of oxidative DNA damage. Most studies reviewed herein showed either a vitamin C-mediated reduction in oxidative DNA damage or a null effect, whereas only a few studies showed an increase in specific base lesions. We also address the possible beneficial effects of vitamin C supplementation for the prevention of cancer and cardiovascular disease. Finally, we discuss the contribution of cell culture studies to our understanding of the mode of action of vitamin C and we review recent evidence that vitamin C is able to modulate gene expression and cellular function, with a particular interest in cell differentiation.     

Mitochondrial DNA damage and repair in neurodegenerative disorders

By producing ATP and regulating intracellular calcium levels, mitochondria are vital for the function and survival of neurons. Oxidative stress and damage to mitochondrial DNA during the aging process can impair mitochondrial energy metabolism and ion homeostasis in neurons, thereby rendering them vulnerable to degeneration. Mitochondrial abnormalities have been documented in all of the major neurodegenerative disorders-Alzheimer's, Parkinson's and Huntington's diseases, and amyotrophic lateral sclerosis. Mitochondrial DNA damage and dysfunction may be downstream of primary disease processes such as accumulation of pathogenic proteins. However, recent experimental evidence demonstrates that mitochondrial DNA damage responses play important roles in aging and in the pathogenesis of neurodegenerative diseases. Therapeutic interventions that target mitochondrial regulatory systems have been shown effective in cell culture and animal models, but their efficacy in humans remains to be established.     

Epigenetics in hyperhomocysteinemic states. A special focus on uremia

Aim of this article is to review the topic of epigenetic control of gene expression, especially regarding DNA methylation, in chronic kidney disease and uremia. Hyperhomocysteinemia is considered an independent cardiovascular risk factor, although the most recent intervention studies utilizing folic acid are negative. The accumulation of homocysteine in blood leads to an intracellular increase of S-adenosylhomocysteine (AdoHcy), a powerful competitive methyltransferase inhibitor, which is itself considered a predictor of cardiovascular events. The extent of methylation inhibition of each individual methyltransferase depends on the methyl donor S-adenosylmethionine (AdoMet) availability, on the [AdoMet]/[AdoHcy] ratio, and on the individual Km value for AdoMet and Ki for AdoHcy. DNA methyltransferases are among the principal targets of hyperhomocysteinemia, as studies in several cell culture and animal models, as well as in humans, almost unequivocally show. In vivo, DNA methylation may be also influenced by various factors in different tissues, for example by rate of cell growth, folate status, etc. and importantly inflammation.     

The role of tobacco smoke induced mitochondrial damage in vascular dysfunction and atherosclerosis

The majority of individuals chronically exposed to tobacco smoke will eventually succumb to cardiovascular disease (CVD). However, despite the major cardiovascular health implications of tobacco smoke exposure, concepts of how such exposure specifically results in cardiovascular cell dysfunction that leads to CVD development are still being explored. Moreover, surprisingly little is known about the effects of prenatal and childhood tobacco smoke exposure on adult CVD development. Herein, it is proposed that the mitochondrion is a central target for environmental oxidants, including tobacco smoke. By virtue of its multiple, essential roles in cell function including energy production, oxidant signaling, apoptosis, immune response, and thermogenesis, damage to the mitochondrion will likely play an important role in the development of multiple common forms of human disease, including CVD. Specifically, this review will discuss the potential role of tobacco smoke and environmental oxidant exposure in the induction of mitochondrial damage which is related to CVD development. Furthermore, mechanisms of how mitochondrial damage can initiate and/or contribute to CVD are discussed, as are experimental results that are consistent with the hypothesis that mitochondrial damage and dysfunction will increase CVD susceptibility. Aspects of both adult and developmental (fetal and childhood) exposure to tobacco smoke on mitochondrial damage, function and disease development are also discussed, including the future implications and direction of studies involving the role of the mitochondrion in influencing disease susceptibility mediated by environmental factors.     

Mitochondrial dysfunction in cardiovascular disease

Whereas the pathogenesis of atherosclerosis has been intensively studied and described, the underlying events that initiate cardiovascular disease are not yet fully understood. A substantial number of studies suggest that altered levels of oxidative and nitrosoxidative stress within the cardiovascular environment are essential in the development of cardiovascular disease; however, the impact of such changes on the subcellular or organellar components and their functions that are relevant to cardiovascular disease inception are less understood. In this regard, studies are beginning to show that mitochondria not only appear susceptible to damage mediated by increased oxidative and nitrosoxidative stress, but also play significant roles in the regulation of cardiovascular cell function. In addition, accumulating evidence suggests that a common theme among cardiovascular disease development and cardiovascular disease risk factors is increased mitochondrial damage and dysfunction. This review discusses aspects relating mitochondrial damage and function to cardiovascular disease risk factors and disease development.     

Characterization of different DNA repair pathways in hepatic cells of Zebrafish (Danio rerio)

The concern about DNA damage has directed efforts toward evaluating the genotoxic potential of physical and chemical agents. Since the extent of DNA damage is also related to the capacity of the organism in repairing the DNA, the advance of toxicological studies on this area depends on the characterization of the DNA repair mechanisms in the available models. The cellular zebrafish models, for example, replace mammalian cells to answer ecologically relevant questions on aquatic toxicology. So, the aim of the present study was to characterize the nucleotide excision repair (NER) and photoreactivation (PER) in two cellular models of Danio rerio liver, primary hepatocytes and ZF-L (Zebrafish Liver) cell line. We performed kinetic studies of the DNA damage levels after exposure to 6.8 J/m² UVC using the T4-PDG modified Comet Assay, and determined the expression levels of important genes involved in NER, PER and base excision repair using RT-qPCR. It was observed that both ZF-L cell line and primary hepatocytes exhibit similar NER and PER activity. Primary hepatocytes showed similarities in the gene expression of most of the evaluated repair genes with the original tissue. These results indicate that both primary hepatocytes and ZF-L cells are useful models for toxicological studies aiming to evaluate NER and PER in hepatic cells. Moreover, the similarities in gene expression between the cellular models suggest that the ZF-L cells retain the DNA repair characteristics of the primary hepatocytes and, thus, could serve as replacement to this primary culture, reducing the use of animals in research.     

Long Term Culture of Human Kidney Proximal Tubule Epithelial Cells Maintains Lineage Functions and Serves as an Ex vivo Model for Coronavirus Associated Kidney Injury

The mechanism of how SARS-CoV-2 causes severe multi-organ failure is largely unknown. Acute kidney injury(AKI) is one of the frequent organ damage in severe COVID-19 patients. Previous studies have shown that human renal tubule cells could be the potential host cells targeted by SARS-CoV-2. Traditional cancer cell lines or immortalized cell lines are genetically and phenotypically different from host cells. Animal models are widely used, but often fail to reflect a physiological and pathogenic status because of species tropisms. There is an unmet need for normal human epithelial cells for disease modeling. In this study, we successfully established long term cultures of normal human kidney proximal tubule epithelial cells(KPTECs) in 2 D and 3 D culture systems using conditional reprogramming(CR) and organoids techniques.These cells had the ability to differentiate and repair DNA damage, and showed no transforming property. Importantly, the CR KPTECs maintained lineage function with expression of specific transporters(SLC34 A3 and cubilin). They also expressed angiotensin-converting enzyme 2(ACE2), a receptor for SARS-CoV and SARS-CoV-2. In contrast, cancer cell line did not express endogenous SLC34 A3, cubilin and ACE2. Very interestingly, ACE2 expression was around twofold higher in 3 D organoids culture compared to that in 2 D CR culture condition. Pseudovirion assays demonstrated that SARS-CoV spike(S) protein was able to enter CR cells with luciferase reporter. This integrated 2 D CR and 3 D organoid cultures provide a physiological ex vivo model to study kidney functions, innate immune response of kidney cells to viruses, and a novel platform for drug discovery and safety evaluation.     

红细胞分布宽度与高血压靶器官损害研究进展

高血压是最常见的心血管疾病,血压持续升高可导致左室肥厚、心力衰竭、脑卒中以及慢性肾病等相关靶器官损害。红细胞分布宽度(RDW)是一项测量红细胞变量宽度的指标,近年来研究证实RDW与心脑血管疾病存在一定相关性,RDW升高提示高血压患者预后不良,说明RDW可作为高血压患者预后风险评估的潜在指标。本文对近年来RDW与高血压引起的心脏损害、脑卒中、肾损害及血管损害等相关研究进行综述,进一步探讨RDW对相关疾病预防及治疗的预测价值。     

Integrated Stochastic Model of DNA Damage Repair by Non-homologous End Joining and p53/p21- Mediated Early Senescence Signalling

Unrepaired or inaccurately repaired DNA damage can lead to a range of cell fates, such as apoptosis, cellular senescence or cancer, depending on the efficiency and accuracy of DNA damage repair and on the downstream DNA damage signalling. DNA damage repair and signalling have been studied and modelled in detail separately, but it is not yet clear how they integrate with one another to control cell fate. In this study, we have created an integrated stochastic model of DNA damage repair by non-homologous end joining and of gamma irradiation-induced cellular senescence in human cells that are not apoptosis-prone. The integrated model successfully explains the changes that occur in the dynamics of DNA damage repair after irradiation. Simulations of p53/p21 dynamics after irradiation agree well with previously published experimental studies, further validating the model. Additionally, the model predicts, and we offer some experimental support, that low-dose fractionated irradiation of cells leads to temporal patterns in p53/p21 that lead to significant cellular senescence. The integrated model is valuable for studying the processes of DNA damage induced cell fate and predicting the effectiveness of DNA damage related medical interventions at the cellular level.     

Acetylation pharmacogenetics: experimental models for human toxicity

Hereditary acetylation polymorphisms well-suited to experimental pharmacogenetic investigation are now known in three laboratory animal species (rabbit, mouse, and hamster). These animal models provide new evidence for the profound influence of this trait on the metabolic fate of arylamines and hydrazines, and on their pharmacological and toxicological profiles. The rabbit polymorphism most closely resembles that in humans. For the rabbit model, studies have shown that 1) monoacetylhydrazine is a polymorphic substrate for liver N-acetyltransferase in rapid and slow acetylators. This observation, in conjunction with human epidemiological data of others, opposes the commonly held view that rapid acetylators are predisposed to isoniazid (INH)-induced hepatotoxicity. 2) Slow acetylators are much more sensitive than rapid acetylators to the lethal central nervous system toxicity of INH. 3) In hepatocytes in short-term culture and exposed to arylamines and hydrazines, DNA damage is produced by hydralazine in slow acetylator hepatocytes but not in rapid acetylator hepatocytes, whereas hepatocytes from rapid acetylators are more sensitive to toxicity and DNA damage from 2-aminofluorene and benzidine. These investigations in animal models of the acetylation polymorphism provide new insights into human toxicity resulting from environmental arylamines and hydrazines.     

Studies on BrdU labeling of hematopoietic cells: stem cells and cell lines

Studies using chronic in vivo BrdU exposure, isolating primitive stem cells, and determining BrdU labeling, indicate that stem cells cycle. BrdU is also incorporated into DNA during damage/repair. DNA, which has incorporated BrdU due to cycle transit is heavier than normal, while the density of DNA with damage/repair incorporation is intermediate. DNA density of purified lineage-rhodamine low (rho(low)) Hoechst low (Ho(low)) stem cells or FDC-P1 cell line cells-was assessed in vitro, after exposure to cytokines and BrdU (cycling model) or cytokines and BrdU with bleomycin to induce strand breaks and hydroxyurea to halt cycle progression (damage/repair model). We determined DNA density using cesium chloride (CsCl) gradients and either fluorometry or dot blot chemiluminesence. DNA from BrdU labeled cycling Lin-rho(lo)Ho(lo) or FDC-P1 cells was heavier than normal DNA, while damage repair DNA had an intermediate density. We then assessed BrdU labeling of Lin-rho(lo)Ho(lo) cells in vivo. We found that 70.9% of lin-rho(lo)Ho(lo) cells labeled at 5 weeks. DNA density of these cells was low, in the damage/repair range, but similar results were obtained with stem cells, which had proliferated in vivo. Dilution of BrdU in in vitro culture of proliferating FDC-P1 cells also resulted in damage/repair density. We conclude that in vitro BrdU labeling models can distinguish between proliferation and damage/repair, but that we cannot obtain high enough in vivo levels to address this issue. All together, while we cannot absolutely exclude damage/repair as contributing to stem cell BrdU labeling, the data indicate that primitive bone marrow stem cells are probably a cycling population.     

Heme oxygenase-1 and cardiovascular disease

Heme oxygenase (HO)-1 is the inducible isoform of the first and rate-controlling enzyme of heme degradation. HO-1 is up-regulated by a host of oxidative stress stimuli and has potent cytoprotective and anti-inflammatory functions via decreasing tissue levels of the prooxidant heme along with production of bilirubin and the signaling gas carbon monoxide. This review deals with recent findings that highlight the emerging significance of HO-1 in cardiovascular disease. Evidence is presented on how heme and various oxidative stress stimuli may cause endothelial cell dysfunction and how HO-1 may counteract the detrimental effects of oxidative stress in the endothelium. Recent advances in the understanding of the role of endothelial HO-1 for the regulation of the inflammatory response are summarized, including the modulation of leukocyte recruitment and transmigration through the endothelial barrier. Furthermore, experimental evidence from various cell culture and animal models is discussed which suggests an association of HO-1 with the complex sequence of events that cause atherosclerosis. In the second part of the review we present potential strategies that apply HO-1 as a therapeutic target in the treatment of cardiovascular disease. Specific inducers of HO-activity which may ultimately lead to the development of clinically relevant pharmacological applications are introduced.     

A mathematical model of proliferation and aging of cells in culture

A mathematical model is presented which describes the proliferative senescence of cells in culture. The model is based on the DNA damage hypothesis of cellular aging and is able to account for both the limited and unlimited in vitro proliferative potential of normal and transformed cells. It is predicted that the destiny of a cell population is determined by two counteracting factors: the proliferation rate of the dividable cells and the gene damage accumulation rate. The formation of an immortal cell line requires high rate of proliferation and/or low rate of gene damage accumulation. The related computer simulations on a number of proliferative properties of cell culture produces results in agreement, in the general properties, with experimental observations.     

Variation in DNA repair is a factor in cancer susceptibility: a paradigm for the promises and perils of individual and population risk estimation?

The repair of DNA damage protects the genome of the cell from the insults of cancer causing agents. This was originally demonstrated in individuals with the rare genetic disease, xeroderma pigmentosum, the prototype of cancer genes, and subsequently in the relationship of mismatch repair to colon cancer. Recent studies suggests that individuals with less dramatic reductions in the capacity to repair DNA damage are observed at polymorphic frequency and these individuals have an increased susceptibility to several types of cancer. Screening of individuals for DNA sequence variation in the exons of 9 DNA repair genes has resulted in identification of 15 different polymorphic amino acid substitution variants. Although the studies to relate these variants to reduced DNA repair capacity and cancer status have not been completed, the available information is sufficient to suggest that DNA repair genes should be incorporated into molecular epidemiology and cancer susceptibility studies. The availability of molecular epidemiology data presents exciting opportunities for refinement of risk estimation models and identification of individuals at increased risk of disease, with resultant opportunities for effective surveillance and early intervention and treatment. The opportunities to acquire susceptibility data are associated with possible perils for establishment of regulations for permissible exposures to carcinogenic agents and also stigmatization of ‘at risk’ individuals that may result in decreased access to employment opportunities and health care.     

Aging and amyloid beta-induced oxidative DNA damage and mitochondrial dysfunction in Alzheimer's disease: implications for early intervention and therapeutics

Alzheimer's disease (AD) is an age-related progressive neurodegenerative disease affecting thousands of people in the world and effective treatment is still not available. Over two decades of intense research using AD postmortem brains, transgenic mouse and cell models of amyloid precursor protein and tau revealed that amyloid beta (Aβ) and hyperphosphorylated tau are synergistically involved in triggering disease progression. Accumulating evidence also revealed that aging and amyloid beta-induced oxidative DNA damage and mitochondrial dysfunction initiate and contributes to the development and progression of the disease. The purpose of this article is to summarize the latest progress in aging and AD, with a special emphasis on the mitochondria, oxidative DNA damage including methods of its measurement. It also discusses the therapeutic approaches against oxidative DNA damage and treatment strategies in AD.