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

"Micronuclei and Disease" special issue: Aims, scope, and synthesis of outcomes

The purpose of the "Micronuclei and Disease" special issue (SI) is to: (i) Determine the level of evidence for association of micronuclei (MN), a biomarker of numerical and structural chromosomal aberrations, with risk of specific diseases in humans; (ii) Define plausible mechanisms that explain association of MN with each disease; (iii) Identify knowledge gaps and research needed to translate MN assays into clinical practice. The "MN and Disease" SI includes 14 papers. The first is a review of mechanisms of MN formation and their consequences in humans. 11 papers are systematic reviews and/or meta-analyses of the association of MN with reproduction, child health, inflammation, auto-immune disease, glycation, metabolic diseases, chronic kidney disease, cardiovascular disease, eleven common cancers, ageing and frailty. The penultimate paper focuses on effect of interventions on MN frequency in the elderly. A road map for translation of MN data into clinical practice is the topic of the final paper. The majority of reviewed studies were case-control studies in which the ratio of mean MN frequency in disease cases relative to controls, i.e. the mean ratio (MR), was calculated. The mean of these MR values, estimated by meta-analyses, for lymphocyte and buccal cell MN in non-cancer diseases were 2.3 and 3.6 respectively, and for cancers they were 1.7 and 2.6 respectively. The highest MR values were observed in studies of cancer cases in which MN were measured in the same tissue as the tumour (MR = 4.9-10.8). This special issue is an important milestone in the evidence supporting MN as a reliable genomic biomarker of developmental and degenerative disease risk. These advances, together with results from prospective cohort studies, are helping to identify diseases in which MN assays can be practically employed in the clinical setting to better identify high risk patients and to prioritise them for preventive therapy.

Molecular Epidemiology of Mitochondrial Cardiomyopathy: A Search Among Mitochondrial and Nuclear Genes

Mitochondrial Cardiomyopathy (MCM) is a common manifestation of multi-organ Mitochondrial Diseases (MDs), occasionally present in non-syndromic cases. Diagnosis of MCM is complex because of wide clinical and genetic heterogeneity and requires medical, laboratory, and neuroimaging investigations. Currently, the molecular screening for MCM is fundamental part of MDs management and allows achieving the definitive diagnosis. In this article, we review the current genetic knowledge associated with MDs, focusing on diagnosis of MCM and MDs showing cardiac involvement. We searched for publications on mitochondrial and nuclear genes involved in MCM, mainly focusing on genetic screening based on targeted gene panels for the molecular diagnosis of the MCM, by using Next Generation Sequencing. Here we report twelve case reports, four case-control studies, eleven retrospective studies, and two prospective studies, for a total of twenty-nine papers concerning the evaluation of cardiac manifestations in mitochondrial diseases. From the analysis of published causal mutations, we identified 130 genes to be associated with mitochondrial heart diseases. A large proportion of these genes (34.3%) encode for key proteins involved in the oxidative phosphorylation system (OXPHOS), either as directly OXPHOS subunits (22.8%), and as OXPHOS assembly factors (11.5%). Mutations in several mitochondrial tRNA genes have been also reported in multi-organ or isolated MCM (15.3%). This review highlights the main disease-genes, identified by extensive genetic analysis, which could be included as target genes in next generation panels for the molecular diagnosis of patients with clinical suspect of mitochondrial cardiomyopathies.

Do Mitochondrial DNA Mutations Play a Key Role in the Chronification of Sterile Inflammation? Special Focus on Atherosclerosis

BACKGROUND

The aim of the elucidation of mechanisms implicated in the chronification of inflammation is to shed light on the pathogenesis of disorders that are responsible for the majority of the incidences of diseases and deaths, and also causes of ageing. Atherosclerosis is an example of the most significant inflammatory pathology. The inflammatory response of innate immunity is implicated in the development of atherosclerosis arising locally or focally. Modified low-density lipoprotein (LDL) was regarded as the trigger for this response. No atherosclerotic changes in the arterial wall occur due to the quick decrease in inflammation rate. Nonetheless, the atherosclerotic lesion formation can be a result of the chronification of local inflammation, which, in turn, is caused by alteration of the response of innate immunity.

OBJECTIVE

In this review, we discussed potential mechanisms of the altered response of the immunity in atherosclerosis with a particular emphasis on mitochondrial dysfunctions.

CONCLUSION

A few mitochondrial dysfunctions can be caused by the mitochondrial DNA (mtDNA) mutations. Moreover, mtDNA mutations were found to affect the development of defective mitophagy. Modern investigations have demonstrated the controlling mitophagy function in response to the immune system. Therefore, we hypothesized that impaired mitophagy, as a consequence of mutations in mtDNA, can raise a disturbed innate immunity response, resulting in the chronification of inflammation in atherosclerosis.

Pathogenic Mechanisms of Somatic Mutation and Genome Mosaicism in Aging

Age-related accumulation of postzygotic DNA mutations results in tissue genetic heterogeneity known as somatic mosaicism. Although implicated in aging as early as the 1950s, somatic mutations in normal tissue have been difficult to study because of their low allele fractions. With the recent emergence of cost-effective high-throughput sequencing down to the single-cell level, enormous progress has been made in our capability to quantitatively analyze somatic mutations in human tissue in relation to aging and disease. Here we first review how recent technological progress has opened up this field, providing the first broad sets of quantitative information on somatic mutations in vivo necessary to gain insight into their possible causal role in human aging and disease. We then propose three major mechanisms that can lead from accumulated de novo mutations across tissues to cell functional loss and human disease.

Micronucleus assay for predicting coronary artery disease: A systematic review and meta-analysis

Coronary artery disease (CAD) is the leading cause of morbidity and mortality worldwide. Coronary angiography allows an accurate assessment of the extent and severity of atherosclerotic coronary narrowing, but it provides little characterization of early detection of potentially asymptomatic vulnerable plaque. The identification of the coronary "vulnerable patient" or high-risk plaques remains a major challenge in the treatment of CAD. Recently, growing evidence shows that DNA damage plays a role in the initiation and progression of atherosclerotic plaque. Cytokinesis-block micronucleus (CBMN) assay is one of the most frequently used and validated method for assessing chromosomal damage and genetic instability. Accordingly, the purpose of this systematic review was to retrieve and discuss existing literature on the studies assessing the association between MN and angiographically-proven CAD. A total of 8 studies published between 2001 and 2017 were included in the meta-analysis. Despite a large heterogeneity between studies (I²= 99.7 %, p < 0.0001), an overall increase of MN frequencies was found in patients with CAD compared with control group (meta-MR = 1.96; 95 % CI, 1.5-3.2, p = 0.009). A subgroup analysis showed an increase in the frequency of MN formation for both two- vessel (MR = 2.13, 95 % CI: 0.9-6.9, p = 0.08) and three-vessel disease (MR = 2.89, 95 % CI: 1.84-4.55, P = 0.06). Overall, the results of this meta-analysis provide evidence of an association between CBMN and presence, extent and severity of angiographically-assessed CAD. However, the small number of papers analyzed requires further large and more rigorously designed studies, carefully considering a series of clinical confounding factors, such as the quality of the metabolic control, the influence of drugs and radiation imaging treatments.

The Relationship between Serum Vitamin C and Uric Acid Levels, Antioxidant Status and Coronary Artery Disease: a Case-Control Study

Coronary artery disease (CAD) is among the main causes of death in adults. Increase of oxidative stress and defects in antioxidant defense play a major role in endothelium performance and are affecting factors in the progress of atherosclerosis. The aim of this study was to measure serum levels of uric acid (UA) and vitamin C as well as the antioxidant status in patients with CAD, and compared them with those in healthy individuals. The present case-control study was performed on 44 cases and 44 controls. Demographic data and anthropometric indices were measured. The Food Frequency Questionnaire (FFQ) and International Physical Activity Questionnaire (IPAQ) were completed. After 12 hours of fasting,10 mL blood was sampled from the participants. Serum levels of UA, vitamin C, Total Antioxidant Capacity (TAC) and Malondialdehyde (MDA) were also measured. The data were finally analyzed by SPSS v22. A significant difference was observed between the groups in terms of UA and vitamin C. However, mean levels of MDA and TAC were not significantly different between groups. The differences between groups in terms of vitamin A, vitamin E, beta-carotene, zinc and selenium intakes were not significant either. A significant difference was detected between the groups in terms of vitamin C intake. Our results suggest that increase in UA and decrease in vitamin C in serum levels can be considered as risk factors for CAD patients. Due to a lack of any significant correlation between TAC and CAD risk in this study, further study with bigger sample size is needed.

Possible Role of Mitochondrial DNA Mutations in Chronification of Inflammation: Focus on Atherosclerosis

Chronification of inflammation is the process that lies at the basis of several human diseases that make up to 80% of morbidity and mortality worldwide. It can also explain a great deal of processes related to aging. Atherosclerosis is an example of the most important chronic inflammatory pathology in terms of public health impact. Atherogenesis is based on the inflammatory response of the innate immunity arising locally or focally. The main trigger for this response appears to be modified low-density lipoprotein (LDL), although other factors may also play a role. With the quick resolution of inflammation, atherosclerotic changes in the arterial wall do not occur. However, a violation of the innate immunity response can lead to chronification of local inflammation and, as a result, to atherosclerotic lesion formation. In this review, we discuss possible mechanisms of the impaired immune response with a special focus on mitochondrial dysfunction. Some mitochondrial dysfunctions may be due to mutations in mitochondrial DNA. Several mitochondrial DNA mutations leading to defective mitophagy have been identified. The regulatory role of mitophagy in the immune response has been shown in recent studies. We suggest that defective mitophagy promoted by mutations in mitochondrial DNA can cause innate immunity disorders leading to chronification of inflammation.

The alterations of mitochondrial DNA in coronary heart disease

Coronary heart disease (CHD) is the major cause of death in modern society. CHD is characterized by atherosclerosis, which could lead to vascular cavity stenosis or obstruction, resulting in ischemic cardiac conditions such as angina and myocardial infarction. In terms of the mitochondrion, the main function is to produce adenosine triphosphate (ATP) for cells. And the alterations (including mutations, altered copy number and haplogroups) of mitochondrial DNA (mtDNA) are associated with the abnormal expression of oxidative phosphorylation (OXPHOS) system, resulting in mitochondrial dysfunction, then leading to perturbation on the electron transport chain and increased ROS generation and reduction in ATP level, contributing to ATP-producing disorders and oxidative stress, which may further accelerate development or vulnerability of atherosclerosis and myocardial ischemic injury. Therefore, the mtDNA defects may play an important role in making an early diagnosis, identifying disease-specific biomarkers and therapeutic targets, and predicting outcomes for patients with atherosclerosis and CHD. In this review, we aim to summarize the contribution of mtDNA mutations, altered mtDNA copy number and mtDNA haplogroups on the occurrence and development of CHD.

Obesity and cancer: A mechanistic overview of metabolic changes in obesity that impact genetic instability

Obesity, defined as a state of positive energy balance with a body mass index exceeding 30 kg/m2 in adults and 95th percentile in children, is an increasing global concern. Approximately one-third of the world's population is overweight or obese, and in the United States alone, obesity affects one in six children. Meta-analysis studies suggest that obesity increases the likelihood of developing several types of cancer, and with poorer outcomes, especially in children. The contribution of obesity to cancer risk requires a better understanding of the association between obesity-induced metabolic changes and its impact on genomic instability, which is a major driving force of tumorigenesis. In this review, we discuss how molecular changes during adipose tissue dysregulation can result in oxidative stress and subsequent DNA damage. This represents one of the many critical steps connecting obesity and cancer since oxidative DNA lesions can result in cancer-associated genetic instability. In addition, the by-products of the oxidative degradation of lipids (e.g., malondialdehyde, 4-hydroxynonenal, and acrolein), and gut microbiota-mediated secondary bile acid metabolites (e.g., deoxycholic acid and lithocholic acid), can function as genotoxic agents and tumor promoters. We also discuss how obesity can impact DNA repair efficiency, potentially contributing to cancer initiation and progression. Finally, we outline obesity-related epigenetic changes and identify the gaps in knowledge to be addressed for the development of better therapeutic strategies for the prevention and treatment of obesity-related cancers.

MRE11A Polymorphisms Are Associated With Subclinical Atherosclerosis and Cardiovascular Risk Factors. A Case-Control Study of the GEA Mexican Project

DNA damage and subsequent repair pathways have been involved in the initiation and progression of atherosclerosis. Meiotic recombination 11 homolog A (MRE11A) gene polymorphisms have been associated with the presence of myocardial infarction. We analyzed five MRE11A gene polymorphisms in 386 individuals with subclinical atherosclerosis and 1093 healthy controls. Under different models, the rs13447720 (Odds ratio = 0.646, P_additive = 0.009; Odds ratio = 0.636, P_dominant = 0.012; Odds ratio = 0.664, P_{over–dominant} = 0.025; Odds ratio = 0.655, P_codominant1 = 0.021) and rs499952 (Odds ratio = 0.807, P_additive = 0.032; Odds ratio = 0.643, P_codominant2 = 0.034) polymorphisms were associated with a lower risk of subclinical atherosclerosis. On the other hand, the rs2155209 polymorphism was associated with a reduced risk of having a coronary artery calcification score ≥ 100 Agatston units. The rs13447720, rs499952, and rs2155209 polymorphisms, as well as the haplotypes that included the five studied polymorphisms were associated with some clinical and metabolic parameters in both subclinical atherosclerosis and healthy individuals. Our results suggest that the rs13447720 and rs499952 polymorphisms are associated with a decreased risk of developing subclinical atherosclerosis, whereas the rs2155209 is associated with a lower subclinical atherosclerosis severity (coronary artery calcification < 100 Agatston units). MRE11A polymorphisms and haplotypes were associated with clinical and metabolic parameters.

Mechanisms of vascular dysfunction evoked by ionizing radiation and possible targets for its pharmacological correction

Ionizing radiation (IR) leads to a variety of the cardiovascular diseases, including the arterial hypertension. A number of studies have demonstrated that blood vessels represent important target for IR, and the endothelium is one of the most vulnerable components of the vascular wall. IR causes an inhibition of nitric oxide (NO)-mediated endothelium-dependent vasodilatation and generation of reactive oxygen (ROS) and nitrogen (RNS) species trigger this process. Inhibition of NO-mediated vasodilatation could be due to endothelial NO synthase (eNOS) down-regulation, inactivation of endothelium-derived NO, and abnormalities in diffusion of NO from the endothelial cells (ECs) leading to a decrease in NO bioavailability. Beside this, IR suppresses endothelial large conductance Ca²⁺-activated K⁺ channels (BK_Ca) activity, which control NO synthesis. IR also leads to inhibition of the BK_Ca current in vascular smooth muscle cells (SMCs) which is mediated by protein kinase C (PKC). On the other hand, IR-evoked enhanced vascular contractility may result from PKC-mediated increase in SMCs myofilament Ca²⁺ sensitivity. Also, IR evokes vascular wall inflammation and atherosclerosis development. Vascular function damaged by IR can be effectively restored by quercetin-filled phosphatidylcholine liposomes and mesenchymal stem cells injection. Using RNA-interference technique targeted to different PKC isoforms can also be a perspective approach for pharmacological treatment of IR-induced vascular dysfunction.

Prognostic value of mitochondrial DNA4977 deletion and mitochondrial DNA copy number in patients with stable coronary artery disease

BACKGROUND AND AIMS

Mitochondrial DNA copy number (mtDNA-CN) depletion has been recently associated with an increased cardiovascular risk. However, the integrity of mtDNA is another key aspect of the energy metabolism and mitochondrial function. We investigated the prognostic role of peripheral blood common mitochondrial deletion (mtDNA⁴⁹⁷⁷) and mtDNA-CN on long-term major adverse cardiac events (MACEs) and all-cause mortality in a cohort of patients with coronary artery disease (CAD).

METHODS

Within the Italian GENOCOR (Genetic Mapping for Assessment of Cardiovascular Risk) cohort, we studied 515 patients (450 males, 65 ± 8 years) with known or suspected stable CAD. mtDNA⁴⁹⁷⁷ deletion and mtDNA-CN were assessed in peripheral blood using qRT-PCR.

RESULTS

During a mean follow-up of 4.5 ± 1.1 years, 78 (15%) patients had MACEs (15 cardiac deaths, 17 nonfatal myocardial infarction and 46 coronary revascularizations) and 28 patients died for non-cardiac causes. Patients with high levels of mtDNA⁴⁹⁷⁷ deletion (>75th) had increased risk of MACEs (log rank = 7.2, p=0.007) and all-cause mortality (log rank = 5.7, p=0.01) compared with patients with low mtDNA⁴⁹⁷⁷ deletion (≤75th). Multivariate Cox regression analysis showed that log mtDNA⁴⁹⁷⁷ was a significant predictor of MACEs (HR = 2.17; 95% CI, 1.31-3.59; p=0.003) and all-cause mortality (HR = 2.03; 95% CI: 1.13-3.65, p=0.02). Log mtDNA-CN was not significantly associated with MACEs or all-cause mortality. However, patients with high mtDNA⁴⁹⁷⁷ deletion (>75th) and low mtDNA-CN (<25th) had significantly increased risk for MACEs (HR: 3.73; 95% CI: 1.79-7.79; p=0.0005).

CONCLUSIONS

Mitochondria DNA damage was associated with an increased risk of MACEs and all-cause mortality in patients with stable CAD, confirming the critical role of mitochondrial dysfunction in atherosclerosis.

A high-fidelity method for genomic sequencing of single somatic cells reveals a very high mutational burden

Postzygotic mutations in somatic cells lead to genome mosaicism and can be the cause of cancer, possibly other human diseases and aging. Somatic mutations are difficult to detect in bulk tissue samples. Here, we review the available assays for measuring somatic mutations, with a focus on recent single-cell, whole genome sequencing methods. Impact statement Somatic mutations cause cancer, possibly other diseases and aging. Yet, very little is known about the frequency of such mutations in vivo, their distribution across the genome, and their possible functional consequences other than cancer. Even in cancer, we do not know the heterogeneity of mutations within a tumor and if seemingly normal cells in its surroundings already have elevated mutation frequencies. Here, we review a new, whole genome amplification system that allows accurate quantification and characterization of single-cell mutational landscapes in human cells and tissues in relation to disease.

The relationship of micronucleus frequency and nuclear division index with coronary artery disease SYNTAX and Gensini scores

Objective:

We aimed to evaluate the relationship of micronucleus (MN) frequency and nuclear division index (NDI) with SYNTAX and Gensini scores and thrombolysis in myocardial infarction (TIMI) frame counts of coronary arteries in patients undergoing coronary angiography.

Methods:

In a single-center prospective observational study, a total of 63 individuals, 48 consecutive patients with coronary artery disease (CAD) and 15 healthy people were included. Before coronary angiography (exposure to X-ray), blood samples were collected for lymphocyte cultures, MN and NDI measurements. According to the SYNTAX and Gensini scores, patients were allocated into two groups. Group 1 and 2 included the patients with SYNTAX scores <22 and ≥22 points, respectively. Similarly, groups according to Gensini scores included the ones <23 and ≥23 points. MN test was used for in vitro studies in human peripheral lymphocytes. Binucleated lymphocytes were calculated for each patient.

Results:

MN frequency was significantly higher in group 2 than group 1 and in group 1 than control group (p<0.001). NDI was significantly higher in control group than group 1 and in group 1 than group 2 (p=0.003). MN frequency had positive but moderate correlation with SYNTAX and Gensini scores and TFCs of left anterior descending (LAD), circumflex and right coronary arteries (r=0.394, p=0.003; r=0.458, p<0.001; r=0.425, p<0.001; r=0.469, p<0.001; and r=0.475, p<0.001, respectively).

Conclusion:

We can conclude that as the degree of atherosclerosis increases and coronary flow worsens, MN frequency increases and NDI decreases. Our results may help to elucidate the relationship of DNA damage in pathophysiology of atherosclerosis and endothelial dysfunction in patients with stable CAD.

Up-regulation of MSH2, XRCC1 and ATM genes in patients with type 2 diabetes and coronary artery disease

AIMS

Coronary artery disease (CAD) is a major problem in some patients with type 2 diabetes mellitus (T2DM). CAD has been suggested to be the main result of reduced efficacy of DNA repair systems. Analysis of the DNA repair system in patients with diabetes can potentially uncover the molecular basis of their susceptibility to the CAD. The aim of the present study was to compare the expression levels of some important DNA repair genes, including ATM, XRCC1 and MSH2, in CAD+ versus CAD- patients with T2DM. Furthermore, the relevance of putative single nucleotide polymorphisms (SNPs) in the promoter regions of these genes with mRNA expression was evaluated.

METHODS

Expression analysis was performed by RT-qPCR on 76 patients with T2DM (41 CAD+ and 35 CAD- individuals confirmed by angiography). The genotypes of the patients were examined by polymerase chain reaction-restriction fragment length polymorphism analysis.

RESULTS

Significant up-regulation of the MSH2 (2.49-fold, P=0.001), XRCC1 (2.11-fold, P=0.001) and ATM (2.15-fold, P=0.003) genes was observed in patients with T2DM and CAD. We could not detect any function for SNPs by comparing gene expression. In a receiver operating characteristic (ROC) curve analysis, the area under the ROC curve for sum of relative expressions of all genes reached 0.81 (95% CI: 0.690-0.936, P=0.003), which indicates a potential biomarker for identifying patients with T2DM and CAD.

CONCLUSION

These results suggest that expression levels of DNA repair genes may serve as informative biomarkers for identifying patients with T2DM and CAD.

Circulating cell-free mitochondrial deoxyribonucleic acid is increased in coronary heart disease patients with diabetes mellitus

Aims/Introduction

Circulating cell‐free mitochondrial deoxyribonucleic acid (ccf‐mtDNA) is presumably derived from injured tissues or cells in the body and has been suggested to be potential biomarker in several diseases. The present study explored whether mtDNA could be used as a biomarker to evaluate disease in coronary heart disease (CHD) patients with or without diabetes mellitus (DM).

Materials and Methods

A total of 50 CHD patients with type 2 diabetes, 50 CHD patients without type 2 diabetes, and 50 age‐ and sex‐matched patients without CHD and DM (non‐CHD‐DM) were recruited. Ccf‐mtDNA levels were assessed by measuring the nicotinamide adenine dinucleotide dehydrogenase 1 gene using quantitative real‐time polymerase chain reaction. Receiver operating characteristic curve analysis of plasma mtDNA in CHD with or without DM was also determined. Multivariate logistic regression analyses were carried out to determine the correlation between the mtDNA levels and traditional CHD risk factors.

Results

The plasma ccf‐mtDNA levels were significantly elevated in CHD patients with DM compared with those without and non‐CHD‐DM. The area under the receiver operating characteristic curves of mtDNA in CHD patients with DM vs non‐CHD‐DM was 0.907%. Correlation analyses of the mtDNA levels and traditional CHD risk factors showed that the mtDNA levels were significantly correlated with fasting blood glucose in CHD patients with DM.

Conclusions

Ccf‐mtDNA levels can be used as a biomarker in CHD patients with DM.

Association of mutations in the mitochondrial genome with the subclinical carotid atherosclerosis in women

The importance of the study of an association of mitochondrial DNA mutations with asymptomatic atherosclerosis in women is undeniable. In the present study, a series of PCR with primers for mutation region and further amplificate pyrosequencing were carried out to identify point substitutions or microdeletions of the mitochondrial genome. The results obtained were processed using the original method of estimating the level of heteroplasmy. Five mutations in the mitochondrial genome, namely C3256T, G14709A, G12315A, G13513A and G14846A, in which the heteroplasmy level was associated with the degree of preclinical atherosclerosis in women, were identified. The data obtained in the study showed that C3256T, G14709A and G12315A mutations have a positive correlation with atherosclerosis while G13513A and G14846A mutations have a negative correlation with atherosclerotic lesions. Total mutational load of the mitochondrial genome for C3256T, G14709A, G12315A, G13513A and G14846A mutations explains 68% of the variability of thickness of the carotid intima-medial layer, while the complex of traditional risk factors for cardiovascular diseases explains only 8% of the IMT variability. Data on the correlation between heteroplasmy levels of C3256T, G14709A, G12315A, G13513A and G14846A mutations prompt a suggestion that these mutations may be present on the same haplotypes of mitochondrial genome, associated with atherosclerosis.

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

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

Somatic mutations, genome mosaicism, cancer and aging

Genomes are inherently unstable due to the need for DNA sequence variation in the germ line to fuel evolution through natural selection. In somatic tissues mutations accumulate during development and aging, generating genome mosaics. There is little information about the possible causal role of increased somatic mutation loads in late-life disease and aging, with the exception of cancer. Characterizing somatic mutations and their functional consequences in normal tissues remains a formidable challenge due to their low, individual abundance. Here, I will briefly review our current knowledge of somatic mutations in animals and humans in relation to aging, how they arise and lead to genome mosaicism, the technology to study somatic mutations and how they possibly could cause non-clonal disease.

Deoxyribonucleic acid repair gene X-ray repair cross-complementing group 1 polymorphisms and non-carcinogenic disease risk in different populations: A meta-analysis

PURPOSE

This study aims to assess a meta-analysis of the association of X-ray repair cross-complementing group 1 (XRCC1) polymorphisms with the risk of various non-carcinogenic diseases in different population.

MATERIALS AND METHODS

This meta-analysis was performed by critically reviewing reveals 38 studies involving 10043 cases and 11037 controls. Among all the eligible studies, 14 focused on Arg194Trp polymorphism, 33 described the Arg399Gln and three articles investigated on Arg280His. Populations were divided into three different ethnic subgroups include Caucasians, Asians and other (Turkish and Iranian).

RESULTS

Pooled results showed no correlation between Arg194Trp and non-carcinogenic disease. There was only weak relation in the recessive (odds ratio [OR] =1.11, 95% confidence interval [CI]: 0.86-1.44) model in Asian population and dominant (OR = 1.04, 95% CI: 0.66-1.63) model of other populations. In Arg399Gln polymorphism, there was no relation with diseases of interest generally. In the pooled analysis, there were weak relation in the dominant (OR = 1.08, 95% CI: 0.86-1.35) model of Asian population and quite well-correlation with recessive (OR = 1.49, 95% CI: 1.19-1.88), dominant (OR = 1.23, 95% CI: 0.94-1.62), and additive (OR = 1.23, 95% CI: 0.94-1.62) models of other subgroup. For Arg280His, there was a weak relation only in the dominant model (OR = 1.06, 95% CI: 0.74-1.51).

CONCLUSION

The present meta-analysis correspondingly shows that Arg399Gln variant to be associated with increased non-carcinogenic diseases risk through dominant and recessive modes among Iranian and Turkish population. It also suggests a trend of dominant and recessive effect of Arg280His variant in all population and its possible protective effect on non-carcinogenic diseases.

Meta-analysis of genetic polymorphisms and ophthalmologic disease risk in Asian populations: a case of DNA repair XRCC1 gene

This study aimed to assess a meta-analysis of the association of XRCC1 polymorphisms with the risk of various ophthalmologic diseases in Asian population. This meta-analysis was performed by critically reviewing reveals 38 studies involving 1373 cases and 1745 controls. Among all the eligible studies, one focused on Arg194Trp polymorphism, nine described the Arg399Gln and no article investigated on Arg280His. There was a large between-study heterogeneity in ORs of individual studies of the dominant model (chi2 = 74.18, I2 = 58.9%, p = 0.013) and the additive (chi2 = 56.18, I2 = 41.4%, p = 0.091) models, but a moderate heterogeneity in the recessive model (chi2 = 72.27, I2 = 78.8%, p = 0.000) was observed. So, we pooled the results using the random-effect analysis and found that Arg399Gln has a weak relation with ophthalmologic disease in the recessive (OR = 0.96, 95% CI: 0.64-1.44), the dominant (OR = 1.05, 95% CI: 0.82-1.33) and the additive (OR = 1.15, 95% CI: 0.77-1.70) and models. The present meta-analysis correspondingly shows that comprising diverse population is very important since susceptibility loci might vary indifferent ethnic groups. To ratify our findings, widespread studies with enlarged sample size and various populations are essential to explain the role of all polymorphism of XRCC1 genes in the pathogenesis of ophthalmologic diseases. Finally, our meta-analysis showed Arg399Gln variant was not associated with increased ophthalmologic diseases risk via dominant and recessive modes among Asian population.

Sildenafil ameliorates biomarkers of genotoxicity in an experimental model of spontaneous atherosclerosis

BACKGROUND

It is well known that enhanced production of reactive oxygen species (ROS) leads to oxidative stress observed in atherosclerosis and that ROS can also cause damage in cellular macromolecules, including DNA. Considering previous report that sildenafil, an inhibitor of phosphodiesterase 5 (PDE5), has antioxidant effects, in the present study we evaluated the effect of this drug on genotoxicity of blood mononuclear cells (MNC) and liver cells from atherosclerotic apolipoprotein E knockout mice (apoE(-/-)).

METHODS

ROS production in MNC was evaluated by flow cytometry with the fluorescent dye dihydroethidium (DHE), a method that has been used to quantify the production of superoxide anion, and DNA damage was evaluated in both MNC and liver cells using the alkaline comet assay. Sildenafil-administered apoE(-/-) mice were compared with strain-matched mice administered with vehicle and with C57BL/6 wild-type (WT) mice.

RESULTS

MNC from apoE(-/-) vehicle exhibited a 2-fold increase in production of superoxide anion in comparison with WT. In contrast, sildenafil-administered apoE(-/-) mice showed superoxide anion levels similar to those observed in WT mice. Similarly, MNC and liver cells from apoE(-/-) vehicle mice showed a 4-fold and 2-fold augmented DNA fragmentation compared with WT, respectively, and sildenafil-administered apoE(-/-) mice exhibited minimal DNA damage in those cells similar to WT mice.

CONCLUSIONS

ApoE(-/-) mice chronically administered with sildenafil exhibited reduced levels of superoxide anion in MNC and less DNA fragmentation in MNC and liver cells, which are biomarkers of genotoxicity. Therefore, sildenafil may offer a new perspective to the use of PDE5 inhibitors to protect against DNA damage, in cells involved in the inflammatory and dyslipidemic processes that accompany atherosclerosis.

Molecular studies on coronary artery disease-a review

Coronary artery disease (CAD) remains the major cause of mortality and morbidity in the entire world population. The conventional risk factors of CAD include hypertension, hyperlipidemia, diabetes mellitus, family history, smoking etc. These factors contribute only 50 % of the total risk of CAD. For providing a complete risk assessment in CAD, it is mandatory to have well-planned clinical, biochemical and genetic studies in patients with CAD and subjects who are at risk of developing CAD. In this review an attempt is made to critically evaluate the conventional and emerging risk factors which predispose the individual to CAD. Specifically, the molecular basis of CAD including high oxidative stress, low antioxidant status and increased DNA damage are covered. A comprehensive and multifactorial approach to the problem is the better way to reduce the morbidity and mortality of the disease.

Preventive and therapeutic effects of MG132 by activating Nrf2-ARE signaling pathway on oxidative stress-induced cardiovascular and renal injury

So far, cardiovascular and renal diseases have brought us not only huge economic burden but also serious society problems. Since effective therapeutic strategies are still limited, to find new methods for the prevention or therapy of these diseases is important. Oxidative stress has been found to play a critical role in the initiation and progression of cardiovascular and renal diseases. In addition, activation of nuclear-factor-E2-related-factor-2- (Nrf2-) antioxidant-responsive element (ARE) signaling pathway protects cells and tissues from oxidative damage. As a proteasomal inhibitor, MG132 was reported to activate Nrf2 expression and function, which was accompanied with significant preventive and/or therapeutic effect on cardiovascular and renal diseases under most conditions; therefore, MG132 seems to be a potentially effective drug to be used in the prevention of oxidative damage. In this paper, we will summarize the information available regarding the effect of MG132 on oxidative stress-induced cardiovascular and renal damage, especially through Nrf2-ARE signaling pathway.

Non-homologous end-joining pathway associated with occurrence of myocardial infarction: gene set analysis of genome-wide association study data

PURPOSE

DNA repair deficiencies have been postulated to play a role in the development and progression of cardiovascular disease (CVD). The hypothesis is that DNA damage accumulating with age may induce cell death, which promotes formation of unstable plaques. Defects in DNA repair mechanisms may therefore increase the risk of CVD events. We examined whether the joints effect of common genetic variants in 5 DNA repair pathways may influence the risk of CVD events.

METHODS

The PLINK set-based test was used to examine the association to myocardial infarction (MI) of the DNA repair pathway in GWAS data of 866 subjects of the GENetic DEterminants of Restenosis (GENDER) study and 5,244 subjects of the PROspective Study of Pravastatin in the Elderly at Risk (PROSPER) study. We included the main DNA repair pathways (base excision repair, nucleotide excision repair, mismatch repair, homologous recombination and non-homologous end-joining (NHEJ)) in the analysis.

RESULTS

The NHEJ pathway was associated with the occurrence of MI in both GENDER (P = 0.0083) and PROSPER (P = 0.014). This association was mainly driven by genetic variation in the MRE11A gene (PGENDER = 0.0001 and PPROSPER = 0.002). The homologous recombination pathway was associated with MI in GENDER only (P = 0.011), for the other pathways no associations were observed.

CONCLUSION

This is the first study analyzing the joint effect of common genetic variation in DNA repair pathways and the risk of CVD events, demonstrating an association between the NHEJ pathway and MI in 2 different cohorts.

Association of oxidative DNA damage and C-reactive protein in women at risk for cardiovascular disease

OBJECTIVE

The aim of the current study was to examine the relationship between clinical markers of inflammation and 8-oxo-7,8-dihydro-2'deoxyguanosine (8-oxodG), an oxidative stress marker, in middle-aged women drawn from the HANDLS study, a longitudinal epidemiological study.

METHODS AND RESULTS

We examined commonly assayed markers of inflammation, the DNA base adduct 8-oxodG, a marker of oxidative stress, and cardiovascular risk factors in a cohort of women matched on age and race in 3 groups (n=39 per group) who had low (<3 mg/L) high-sensitivity C-reactive protein (hsCRP), mid (>3-20 mg/L), and high (>20 mg/L) hsCRP. We found a significant relationship between hsCRP level and the oxidative stress marker, 8-oxodG. 8-oxodG was positively correlated with systolic blood pressure, pulse pressure, and interleukin-23. hsCRP was associated with obesity variables, high-density lipoprotein, serum insulin levels, interleukin-12p70 and intracellular adhesion molecule-1. Incubation of primary human endothelial cells with hsCRP generated reactive oxygen species in vitro. Furthermore, hsCRP specifically induced DNA base lesions, but not other forms of DNA damage, including single and double strand breaks.

CONCLUSIONS

These data suggest that in women 8-oxodG is associated with hsCRP and is independently related to select cardiovascular risk factors. Our data in women suggest that hsCRP may contribute to cardiovascular disease by increasing oxidative stress.

The Mediterranean diet improves the systemic lipid and DNA oxidative damage in metabolic syndrome individuals. A randomized, controlled, trial

BACKGROUND & AIMS

Metabolic syndrome (MetS), in which a non-classic feature is an increase in systemic oxidative biomarkers, presents a high risk of diabetes and cardiovascular disease (CVD). Adherence to the Mediterranean Diet (MedDiet) is associated with a reduced risk of MetS. However, the effect of the MedDiet on biomarkers for oxidative damage has not been assessed in MetS individuals. We have investigated the effect of the MedDiet on systemic oxidative biomarkers in MetS individuals.

METHODS

Randomized, controlled, parallel clinical trial in which 110 female with MetS, aged 55-80, were recruited into a large trial (PREDIMED Study) to test the efficacy of the traditional MedDiet on the primary prevention of CVD. Participants were assigned to a low-fat diet or two traditional MedDiets (MedDiet + virgin olive oil or MedDiet + nuts). Both MedDiet group participants received nutritional education and either free extra virgin olive oil for all the family (1 L/week), or free nuts (30 g/day). Diets were ad libitum. Changes in urine levels of F2-Isoprostane (F2-IP) and the DNA damage base 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) were evaluated at 1-year trial.

RESULTS

After 1-year urinary F2-IP decreased in all groups, the decrease in MedDiet groups reaching a borderline significance versus that of the Control group. Urinary 8-oxo-dG was also reduced in all groups, with a higher decrease in both MedDiet groups versus the Control one (P < 0.001).

CONCLUSIONS

MedDiet reduces oxidative damage to lipids and DNA in MetS individuals. Data from this study provide evidence to recommend the traditional MedDiet as a useful tool in the MetS management.

Short-term magnesium deficiency upregulates ceramide synthase in cardiovascular tissues and cells: cross-talk among cytokines, Mg2+, NF-κB, and de novo ceramide

The present study tested the hypotheses that 1) short-term dietary deficiency (MgD) of magnesium (21 days) would result in the upregulation of ceramide synthase (CS) in left ventricular (LV), right ventricular, atrial, and aortic smooth muscle, as well as induce a synthesis/release of select cytokines and chemokines into the LV and aortic smooth muscle and serum; 2) exposure of primary cultured vascular smooth muscle cells (VSMCs) to low extracellular Mg concentration would lead to the synthesis/release of select cytokines/chemokines, activation of N-SMase, and the de novo synthesis of ceramide; and 3) inhibition of CS by fumonisin B1 (FB1) or inhibition of neutral sphingomyelinase (N-SMase) by scyphostatin (SCY) in VSMCs exposed to low Mg would result in reductions in the levels of the cytokines/chemokines and lowered levels of ceramide concomitant with inhibition of NF-κB activation. The data indicated that short-term MgD (10% normal dietary intake) resulted in the upregulation of CS in ventricular, atrial, and aortic smooth muscles coupled to the synthesis/release of 12 different cytokines/chemokines, as well as activation of NF-κB in the LV and aortic smooth muscle and sera; even very low levels of water-borne Mg (e.g., 15 mg·l−1·day−1) either prevented or ameliorated the upregulation and synthesis of the cytokines/chemokines. Our experiments also showed that VSMCs exposed to low extracellular Mg resulted in the synthesis of 5 different cytokines and chemokines concomitant with synthesis/release of ceramide. However, inhibition of the synthesis and release of ceramide by either FB1 or SCY attenuated, markedly , the generation of ceramide, release of the cytokines/chemokines, and activation of NF-κB (as measured by activated p65 and cRel).

Oxidative DNA damage: antioxidant response in postprandial hyperglycaemia in type 2 diabetes mellitus

The mechanism by which postprandial glucose load and sudden cardiac death are linked is not fully understood. This study compares the postprandial response of 8-hydroxy-deoxy-guanosine (8-OHdG)and erythrocyte glutathione (GSH) in control and type 2 diabetes groups. 8-OHdG was significantly elevated in type 2 diabetic patients (824.1±331.2 and 1087±273.1 pg/ml at the first and second hours respectively, p<0.05, versus 600.4±214.4 pg/ml at baseline) following a glucose load. This was associated with a significant reduction in the level of erythrocyte GSH after the first hour (59.1±9 mg/100ml; p<0.001) compared with the basal level (72.1±9 mg/100ml), followed by a significant elevation in the second hour (71.5±11.1 mg/100ml; p<0.001) compared with the first hour, bringing the GSH level only back to base level. The increase in 8-OHdG in people with type 2 diabetes during the postprandial period further supports previous evidence of a defective antioxidant response and greater risk of heart attack due to blood vessel endothelial cell damage and smooth muscle proliferation.

The association of micronucleus frequency with obesity, diabetes and cardiovascular disease

Obesity and metabolic syndrome (MetS) are serious and growing health care problems worldwide, leading an increased risk for type 2 diabetes (T2D) and cardiovascular disease (CVD). Over the past decade, emerging evidence has shown that an increased chromosomal damage, as determined by the cytokinesis-block micronucleus (CBMN) assay, is correlated to the pathogenesis of metabolic and CVD. An increased micronuclei (MN) frequency has been demonstrated in peripheral blood lymphocytes of patients with polycystic ovary syndrome, a common condition in reproductive-aged women associated with impaired glucose tolerance, T2D mellitus and the MetS. High levels of MN have been detected to be significantly correlated with T2D as well as with the occurrence and the severity of coronary artery disease (CAD). Long-term follow-up studies have shown that an increased MN frequency is a predictive biomarker of cardiovascular mortality within a population of healthy subjects as well as of major adverse cardiovascular events in patients with known CAD. Overall, these findings support the hypothesis that CBMN assay may provide an useful tool for screening of the MetS and its progression to diabetes and CVD in adults as well in children. Large population-based cohorts are needed in order to compare the MN frequencies as well as to better define whether MN is a biomarker or a mediator of cardiometabolic diseases.

Carcinoembryonic antigen concentrations in patients with acute coronary syndrome

BACKGROUND

Carcinoembryonic antigen (CEA), one of the most widely used tumor markers, has been recently associated with carotid atherosclerosis. The aim of our study was to evaluate whether CEA concentrations have a role in coronary artery disease (CAD).

METHODS

Serum CEA concentrations were evaluated in 89 patients, including 50 patients with acute coronary syndrome (ACS) (Group I, 44 with acute myocardial infarction, six with unstable angina, 38 males, 65 ± 2 years) and 39 patients with stable CAD (Group II, 33 males, 66 ± 3 years). In addition, 33 subjects (16 males, 62 ± 2 years) were also included as a control group (Group III).

RESULTS

ACS was significantly associated with increased mean CEA concentrations (3.1 ± 0.3 vs. 1.75 ± 0.1 and 1.7 ± 0.2 ng/mL in Groups I, II and III, respectively, p < 0.001). Increased CEA concentrations remained an independent determinant for ACS (OR=3.1, 95% CI=1.2-7.9, p < 0.05) after correcting for other significant risk factors.

CONCLUSIONS

CEA might represent a potential new candidate biomarker for the prediction of risk associated with ACS.

Somatic DNA damages in cardiovascular autonomic neuropathy

Cardiovascular autonomic neuropathy (CAN) is one of the most clinically significant complications of diabetes mellitus. Even though many ethological factors have been attributed for the pathogenesis of this disease no attempts were made to correlate DNA damage as a causative factor. Hence the present study was undertaken to asses the extent of somatic DNA damages by cytokinesis-block micronuclei assay (CBMN). An attempt is also being made to correlate the habits and/or risk factors and socioeconomic status with CAN. The CBMN frequency of 46 patients suffering from autonomic neuropathy was compared with that of 25 healthy age and sex matched controls. All the subjects were suffering from type 2 diabetes for at least 8 years and have varying degrees of coronary artery diseases. The mean CBMN frequency of the patients was statistically higher than that of the healthy control subjects (P < 0.05). The CBMN frequency was found to be significantly altered in CAN patients who where physical inactivity and smoking. A significant correlation could also be observed between CAN and smoking, diabetes mellitus, hypertension, dyslipidemia, abdominal obesity, and physical activity.

Short-term magnesium deficiency upregulates sphingomyelin synthase and p53 in cardiovascular tissues and cells: relevance to the de novo synthesis of ceramide

The present study tested the hypotheses that 1) short-term dietary deficiency of magnesium (21 days) in rats would result in the upregulation of sphingomyelin synthase (SMS) and p53 in cardiac and vascular (aortic) smooth muscles, 2) low levels of Mg(2+) added to drinking water would either prevent or greatly reduce the upregulation of both SMS and p53, 3) exposure of primary cultured vascular smooth muscle cells (VSMCs) to low extracellular Mg(2+) concentration ([Mg(2)](o)) would lead to the de novo synthesis of ceramide, 4) inhibition of either SMS or p53 in primary culture VSMCs exposed to low [Mg(2+)](o) would lead to reductions in the levels of de novo ceramide synthesis, and 5) inhibition of sphingomyelin palmitoyl-CoA transferase (SPT) or ceramide synthase (CS) in primary cultured VSMCs exposed to low [Mg(2+)](o) would lead to a reduction in the levels of de novo ceramide synthesis. The data indicated that short-term magnesium deficiency (10% normal dietary intake) resulted in the upregulation of SMS and p53 in both ventricular and aortic smooth muscles; even very low levels of water-borne Mg(2+) (e.g., 15 mg·l(-1)·day(-1)) either prevented or ameliorated the upregulation in SMS and p53. Our experiments also showed that VSMCs exposed to low [Mg(2+)](o) resulted in the de novo synthesis of ceramide; the lower the [Mg(2+)](o), the greater the synthesis of ceramide. In addition, the data indicated that inhibition of either SMS, p53, SPT, or CS in VSMCs exposed to low [Mg(2+)](o) resulted in marked reductions in the de novo synthesis of ceramide.

Effects of Satureja khuzestanica on Serum Glucose, Lipids and Markers of Oxidative Stress in Patients with Type 2 Diabetes Mellitus: A Double-Blind Randomized Controlled Trial

Satureja khuzestanica is an endemic plant of Iran that is widely distributed in the Southern part of the country. It has antioxidant properties and thus it seems to be useful in diseases related to oxidative stress such as diabetes and hyperlipidemia. The present study investigates the effect of S. khuzestanica supplement in metabolic parameters of hyperlipidemic patients with type 2 diabetes mellitus. Twenty-one hyperlipidemic patients with type 2 diabetes mellitus were randomized in a double blind, placebo controlled clinical trial to receive either S. khuzestanica (tablets contain 250 mg dried leaves) or placebo once a day for 60 days. Blood samples were obtained at baseline and at the end of the study. Samples were analyzed for levels of glucose, total cholesterol, LDL-cholesterol, HDL-cholesterol, triglyceride, creatinine, thiobarbituric acid reactive substances (TBARS) as marker of lipid peroxidation and ferric reducing ability (total antioxidant power, TAP). Treatment of patients by S. khuzestanica for 60 days induced significant decrease in total cholesterol (P = 0.008) and LDL-cholesterol (P = 0.03) while increased HDL-cholesterol (P = 0.02) and TAP (P = 0.007) in comparison with the baseline values. S. khuzestanica did not alter blood glucose, triglyceride, creatinin and TBARS levels. In comparison with baseline values, no significant change was observed in blood glucose, total cholesterol, LDL-cholesterol, HDL-cholesterol, triglyceride, creatinine, TBARS and TAP in placebo-treated group. Usage of S. khuzestanica as a supplement to drug regimen of diabetic type 2 patients with hyperlipidemia is recommended.

Genetic damage in chronic renal failure patients is associated with the glomerular filtration rate index

Chronic renal failure (CRF) patients are considered to present genomic instability and, as a consequence, elevated levels of genetic damage. An open question is whether this damage is related to the stage of the pathology. To determine the background levels of genetic damage, a large population of 258 Caucasian adults (201 CRF patients and 57 controls) was analysed using the micronucleus (MN) assay. The frequency of MN in CRF patients was significantly higher than in controls and correlated with the progression of the disease, according to the glomerular filtration rate. In addition, a significant association was observed between genetic damage and serum creatinine levels. Genetic damage, measured as frequency of MN, increases when renal function decreases. The fact that an increased level of MN is already observed in patients' Stage 2 seems to indicate a genetic predisposition on these patients. Nevertheless, part of the observed damage can be attributed to the uraemic state itself.

Biochemical and genetic studies on cardiometabolic syndrome

Cardiometabolic syndrome is one of the major public health issues of this century which describes a cluster of clinical characteristics. Seventy two patients with coronary artery disease (CAD) and cardiometabolic syndrome and forty healthy age and sex matched normal controls were selected for this study. Detailed clinical epidemiological and anthropometric characteristics were noted. Lipid profile and Cytokinesis-block micronuclei (CBMN) assay using cytochalasin B were carried out in all the subjects. Serum total cholesterol, triglyceride and LDL-cholesterol was significantly higher and HDL cholesterol was significantly lower in patients compared to their normal counter-parts (P<0.05). CBMN frequency of the patients was significantly higher at all ages compared to their normal counter parts (P<0.05). Various risk factors like diabetes, hypertension, dyslipidemia, abdominal obesity, smoking and alcoholism were found influenced the CBMN frequency; but the changes were not significant. From this study it can be concluded that DNA damage was found to be higher in patients with cardiometabolic syndrome which may be attributed to the generation of free radicals associated with alcohol consumption, tobacco use, dyslipidemia and glucose intolerance and the accumulation of free radicals with increase in age.

Do non-targeted effects increase or decrease low dose risk in relation to the linear-non-threshold (LNT) model?

In this paper we review the evidence for departure from linearity for malignant and non-malignant disease and in the light of this assess likely mechanisms, and in particular the potential role for non-targeted effects. Excess cancer risks observed in the Japanese atomic bomb survivors and in many medically and occupationally exposed groups exposed at low or moderate doses are generally statistically compatible. For most cancer sites the dose-response in these groups is compatible with linearity over the range observed. The available data on biological mechanisms do not provide general support for the idea of a low dose threshold or hormesis. This large body of evidence does not suggest, indeed is not statistically compatible with, any very large threshold in dose for cancer, or with possible hormetic effects, and there is little evidence of the sorts of non-linearity in response implied by non-DNA-targeted effects. There are also excess risks of various types of non-malignant disease in the Japanese atomic bomb survivors and in other groups. In particular, elevated risks of cardiovascular disease, respiratory disease and digestive disease are observed in the A-bomb data. In contrast with cancer, there is much less consistency in the patterns of risk between the various exposed groups; for example, radiation-associated respiratory and digestive diseases have not been seen in these other (non-A-bomb) groups. Cardiovascular risks have been seen in many exposed populations, particularly in medically exposed groups, but in contrast with cancer there is much less consistency in risk between studies: risks per unit dose in epidemiological studies vary over at least two orders of magnitude, possibly a result of confounding and effect modification by well known (but unobserved) risk factors. In the absence of a convincing mechanistic explanation of epidemiological evidence that is, at present, less than persuasive, a cause-and-effect interpretation of the reported statistical associations for cardiovascular disease is unreliable but cannot be excluded. Inflammatory processes are the most likely mechanism by which radiation could modify the atherosclerotic disease process. If there is to be modification by low doses of ionizing radiation of cardiovascular disease through this mechanism, a role for non-DNA-targeted effects cannot be excluded.