The impact of detoxifying and repair gene polymorphisms on oxidative stress in ischemic stroke

Modulation of gene expression and influence of gene polymorphisms related to genotoxicity and redox status on occupational exposure to inhaled anesthetics

The extensive use of inhalational anesthetics contributes to both indoor and outdoor (environmental) pollution. The influence of genetic susceptibility on DNA damage and oxidative stress and the possible modulation of gene expression have not yet been investigated upon occupational exposure to waste anesthetic gases (WAGs). This study assessed 8-oxoguanine DNA glycosylase 1 (OGG1) and superoxide dismutase 2 (SOD2) gene expression, which are related to oxidized DNA repair and antioxidant capacity, respectively, and the influence of their polymorphisms (OGG1 rs1052133 and SOD2 rs4880) in 100 professionals highly exposed to WAGs and 93 unexposed volunteers (control group). Additionally, X-ray repair cross complementing 1 (XRCC1 rs25487 and rs1799782) and ataxia telangiectasia mutated (ATM rs600931) gene polymorphisms as well as genetic instability (micronucleus-MN and nuclear bud-NBUD) and oxidative stress (malondialdehyde-MDA and ferric reducing antioxidant power-FRAP) biomarkers were assessed in the groups (control and exposed) and in the subgroups of the exposed group according to job occupation (anesthesiologists versus surgeons/technicians). Except for the ATM TT controls (associated with increased FRAP), there were no influences of OGG1, XRCC1, ATM, and SOD2 polymorphisms on MN, NBUD, MDA, and FRAP values in exposed or control subjects. No significant difference in the expression of either gene evaluated (OGG1 and SOD2) was found between the exposed and control groups. Increased OGG1 expression was observed among OGG1 -/Cys individuals only in the control group. Among the exposed group, anesthesiologists had a greater duration of WAG exposure (both h/week and years) than surgeons/technicians, which was associated with increased MDA and decreased antioxidant capacity (FRAP) and SOD2 expression (redox status). Higher expression of OGG1 was found in -/Cys surgeons/technicians than in anesthesiologists with the same genotype. Increased antioxidant capacity was noted in the surgeons/technicians carrying the ATM T allele and in those carrying XRCC1 -/Gln. Increased MN was influenced by OGG1 -/Cys in surgeons/technicians. Anesthesiologists with ATM CC exhibited increased MN, and those carrying the C allele (CC/CT genotype) exhibited increased NBUD. SOD2 polymorphism did not seem to be relevant for WAG exposure. These findings contribute to advancing the knowledge on genetic susceptibility/gene expression/genetic instability/oxidative stress, including differences in job occupation considering the workload, in response to occupational exposure to WAGs.

Catalytic activity of OGG1 is impaired by Zinc deficiency

Oxidative stress-induced DNA base modifications, if unrepaired, can increase mutagenesis and genomic instability, ultimately leading to cell death. Cells predominantly use the base excision repair (BER) pathway to repair oxidatively-induced non-helix distorting lesions. BER is initiated by DNA glycosylases, such as 8-oxoguanine DNA glycosylase (OGG1), which repairs oxidatively modified guanine bases, including 7,8-dihydro-8-oxoguanine (8-oxoG) and ring-opened formamidopyrimidine lesions, 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyG). The OGG1 protein contains a C2H2 zinc (Zn) finger DNA binding domain. However, the impact of dietary Zn deficiency on OGG1 catalytic activity has not been extensively studied. Zn is a common nutrient of concern with increasing age, and the prevalence of oxidative DNA damage is also concurrently increased during aging. Thus, understanding the potential regulation of OGG1 activity by Zn is clinically relevant. The present study investigates the impact of a range of Zn statuses, varying from severe Zn deficiency to exogenous Zn-supplementation, in the context of young and aged animals to determine the impact of dietary Zn-status on OGG1 activity and oxidative DNA damage in mice. Our findings suggest that nutritional Zn deficiency impairs OGG1 activity and function, without altering gene expression, and that aging further exacerbates these effects. These results have important implications for nutritional management of Zn during aging to mitigate age-associated DNA damage.

DNA damage response, a double-edged sword for vascular aging

Vascular aging is a major risk factor for age-related cardiovascular diseases, which have high rates of morbidity and mortality. It is characterized by changes in the blood vessels, such as macroscopically increased vascular diameter and intima-medial thickness, chronic inflammation, vascular calcification, arterial stiffening, and atherosclerosis. DNA damage and the subsequent various DNA damage response (DDR) pathways are important causative factors of vascular aging. Deficient DDR, which may result in the accumulation of unrepaired damaged DNA or mutations, can lead to vascular aging. On the other hand, over-activation of some DDR proteins, such as poly (ADP ribose) polymerase (PARP) and ataxia telangiectasia mutated (ATM), also can enhance the process of vascular aging, suggesting that DDR can have both positive and negative effects on vascular aging. Despite the evidence reviewed in this paper, the role of DDR in vascular aging and potential therapeutic targets remain poorly understood and require further investigation.

Metabolomics mapping changed after olanzapine therapy in drug-naive schizophrenia patients—the significant impact of gene polymorphisms

Oxidative stress may contribute to the development of schizophrenia and antipsychotics used in schizophrenia treatment may also cause oxidative stress. Gene polymorphisms on antioxidant and repair enzymes are responsible for individual variations and may change the efficacy of olanzapine treatment among schizophrenia patients. In our study, we assessed oxidative stress-related metabolite changes due to genetic polymorphisms on first diagnosed-schizophrenia patients treated with olanzapine. Blood samples (n = 30 patients) were taken before treatment (T1), after 10 ± 1 days (T2), and after 3 ± 1 months (T3). T1 served as control for T2 and T3, since it is advantageous to perform on same patient to evaluate the impact of olanzapine only. GSTs (GSTM1, GSTT1, and GSTP1) and OGG1 gene polymorphisms were analyzed by polymerase chain reaction. Changes in metabolites were detected with metabolomics profiling by gas chromatography–mass spectrometry according to each genotype before and after treatment. Multivariate analysis showed that metabolomics profiles differed after olanzapine treatment regardless gene polymorphisms. Tryptophan could be a biomarker in response to olanzapine treatment since its levels were increased after treatment. GSTM1 gene polymorphism caused significant changes in some metabolites after treatment. Urea, palmitic acid, and caprylic acid levels increased and alanine levels decreased in patients with GSTM1 null genotypes after olanzapine. In future, targeted metabolomics with these prominent metabolites and assessing gene expressions of GSTs will be beneficial to understand the mechanism of action.

Serum levels of vitamin A, selenium and better dietary total antioxidant capacity are related to lower oxidative DNA damage: a cross-sectional study of individuals at cardiovascular risk

The risk for cardiovascular diseases (CVR) has been associated with oxidative DNA damage, but the genetic and environmental factors involved in the antioxidant and DNA repair system contributing to this damage are unknown. The aim was to evaluate the levels of oxidative DNA damage in CVR subjects and how it is related with some genetic and nutritional factors. The cross-sectional study evaluated 136 individuals of both sexes, aged 20-59 years, with at least one cardiovascular risk factor. The global risk score was used to classify individuals at low, intermediate and high cardiovascular risk. The dietary total antioxidant capacity (DTAC) was calculated using table with FRAP values. The oxidative DNA damage was verified by the comet assay. The variants null of Glutathione-S-transferases Mu1 and Theta 1(GSTM1 and GSTT1) and rs25487 of X-Ray Repair Cross Complementing Protein 1 (XRCC1) were analyzed by real-time PCR and PCR-RFLP, respectively. The oxidative DNA damage was higher in patients with intermediate/high CVR than in patients with low CVR (p=0.01). Individuals with GSTT1/GSTM1 null genotypes or arg/gln + gln/gln genotypes of the XRCC1 (rs25487) gene showed similar levels of oxidative DNA damage compared wild genotype. Multivariate regression analysis demonstrated that oxidative DNA damage in individuals with CVR depends on serum levels of vitamin A, selenium and DTAC independently of the other factors [F(6.110)=8.213; p<0.001; R2=0.330]. These findings suggest that nutritional factors such as DTAC, vitamin A and selenium may have a protective effect against oxidative DNA damage in these individuals.

Impact of Oxidative DNA Damage and the Role of DNA Glycosylases in Neurological Dysfunction

The human brain requires a high rate of oxygen consumption to perform intense metabolic activities, accounting for 20% of total body oxygen consumption. This high oxygen uptake results in the generation of free radicals, including reactive oxygen species (ROS), which, at physiological levels, are beneficial to the proper functioning of fundamental cellular processes. At supraphysiological levels, however, ROS and associated lesions cause detrimental effects in brain cells, commonly observed in several neurodegenerative disorders. In this review, we focus on the impact of oxidative DNA base lesions and the role of DNA glycosylase enzymes repairing these lesions on brain function and disease. Furthermore, we discuss the role of DNA base oxidation as an epigenetic mechanism involved in brain diseases, as well as potential roles of DNA glycosylases in different epigenetic contexts. We provide a detailed overview of the impact of DNA glycosylases on brain metabolism, cognition, inflammation, tissue loss and regeneration, and age-related neurodegenerative diseases based on evidence collected from animal and human models lacking these enzymes, as well as post-mortem studies on patients with neurological disorders.

Individual susceptibility has a major impact on strong association between oxidative stress, defence systems and Parkinson's disease

Oxidative stress plays an important role in the degeneration of dopaminergic neurons, which causes Parkinson's disease (PD). Oxidative stress products, antioxidant and their balance have important roles in the development of oxidative stress-based PD. The impact of reactive oxygen species (ROS) and defence systems can be altered by genetic polymorphisms, and thus the risk of PD may also be affected. We aimed to investigate the possible association of individual susceptibility with the development of oxidative stress-based PD. For this purpose, we measured serum levels of folic acid, homocysteine, Vitamin B6 and B12 that play roles in folate-dependent one-carbon pathway, oxidant or antioxidant enzymes (NADPH oxidase, MnSOD, GPX), 8-OHdG and repair enzymes (OGG1, XRCC1 and MTH1) by ELISA, and analysed related gene polymorphisms by PCR-RFLP. XRCC1, ROS, NADPH and folic acid levels were found to be statistically higher in patients than controls. XRCC1, MnSOD and GPX activities were increased. We observed higher levels of 8-OHdG in patients with MnSOD and XRCC1 mutant genotypes and higher XRCC1 levels in patients with NOX p22 fox mutant genotypes rather than controls. We suggest that routinely clinical validation of major oxidative stress-related biomarkers will be a good approach to manage detrimental effects of PD.

DNA Hypomethylation of the MPO Gene in Peripheral Blood Leukocytes Is Associated with Cerebral Stroke in the Acute Phase

Dysregulation of the oxidant-antioxidant system contributes to the pathogenesis of cerebral stroke (CS). Epigenetic changes of redox homeostasis genes, such as glutamate-cysteine ligase (GCLM), glutathione-S-transferase-P1 (GSTP1), thioredoxin reductase 1 (TXNRD1), and myeloperoxidase (MPO), may be biomarkers of CS. In this study, we assessed the association of DNA methylation levels of these genes with CS and clinical features of CS. We quantitatively analyzed DNA methylation patterns in the promoter or regulatory regions of 4 genes (GCLM, GSTP1, TXNRD1, and MPO) in peripheral blood leukocytes of 59 patients with CS in the acute phase and in 83 relatively healthy individuals (controls) without cardiovascular and cerebrovascular diseases. We found that in both groups, the methylation level of CpG sites in genes TXNRD1 and GSTP1 was ≤ 5%. Lower methylation levels were registered at a CpG site (chr1:94,374,293, GRCh37 [hg19]) in GCLM in patients with ischemic stroke compared with the control group (9% [7%; 11.6%] (median and interquartile range) versus 14.7% [10.4%; 23%], respectively, p < 0.05). In the leukocytes of patients with CS, the methylation level of CpG sites in the analyzed region of MPO (chr17:56,356,470, GRCh3 [hg19]) on average was significantly lower (23.5% [19.3%; 26.7%]) than that in the control group (35.6% [30.4%; 42.6%], p < 0.05). We also found increased methylation of MPO in smokers with CS (27.2% [23.5%; 31.1%]) compared with nonsmokers with CS (21.7% [18.1%; 24.8%]). Thus, hypomethylation of CpG sites in GCLM and MPO in blood leukocytes is associated with CS in the acute phase.

MPG and NPRL3 Polymorphisms are Associated with Ischemic Stroke Susceptibility and Post-Stroke Mortality

Ischemic stroke is a complicated disease which is affected by environmental factors and genetic factors. In this field, various studies using whole-exome sequencing (WES) have focused on novel and linkage variants in diverse diseases. Thus, we have investigated the various novel variants, which focused on their linkages to each other, in ischemic stroke. Specifically, we analyzed the N-methylpurine DNA glycosylase (MPG) gene, which plays an initiating role in DNA repair, and the nitrogen permease regulator-like 3 (NPRL3) gene, which is involved in regulating the mammalian target of rapamycin pathway. We took blood samples of 519 ischemic stroke patients and 417 controls. Genetic polymorphisms were detected by polymerase chain reaction (PCR), real-time PCR, and restriction fragment length polymorphism (RFLP) analysis. We found that two NPRL3 polymorphisms (rs2541618 C>T and rs75187722 G>A), as well as the MPG rs2562162 C>T polymorphism, were significantly associated with ischemic stroke. In Cox proportional hazard regression models, the MPG rs2562162 was associated with the survival of small-vessel disease patients in ischemic stroke. Our study showed that NPRL3 and MPG polymorphisms are associated with ischemic stroke prevalence and ischemic stroke survival. Taken together, these findings suggest that NPRL3 and MPG genotypes may be useful clinical biomarkers for ischemic stroke development and prognosis.

Steroid-resistant nephrotic syndrome: pharmacogenetics and epigenetic points and views

Introduction: Glucocorticoids (GCs) are the first-line therapy for patients with nephrotic syndrome (NS), a common glomerular disease, that cause complete remission in most of the cases. In response to the treatment, NS patients are divided into glucocorticoid-sensitive and -resistant. This variation is due to the differences in pharmacokinetics and pharmacodynamics of GCs in each patient that affect the response to the treatment modality. Since the genetic variations in drug-metabolizing enzymes and transporter proteins significantly impact the pharmacokinetics, efficacy and safety of the applied medications, this review highlights the basic mechanisms of genetic variations involved in GCs metabolism in drug-resistant NS patients.Areas covered: This review explains the pharmacogenetic variations that influence the profile of GCs responses and their pharmacokinetics in NS patients. Moreover, the epigenetic variations including histone modifications and miRNA gene regulation that have an influence on GCs responses will review. A comprehensive literature search was performed using different keywords to the reviewed topics.Expert opinion: The accumulative data suggest the importance of pharmacogenetic studies to develop personalized therapies and increase the GCs responsiveness in these patients. It is imperative to know that genetic testing does not give absolute answers to all existing questions in steroid resistance.

Increased DNA damage is not associated to polymorphisms in OGGI DNA repair gene, CYP2E1 detoxification gene, and biochemical and hematological findings in soybeans farmers from Central Brazil

Our study evaluated 163 individuals, being 74 soybean farmers, occupationally exposed to pesticides, and 89 individuals from Goias municipalities, Central Brazil, with similar conditions to the exposed group, comprising the control group. Of the 74 soybean farmers, 43 exposed directly to pesticides and 31 exposed indirectly. The exposed group consisted of individuals aged 19 to 63 years, 21 women and 53 men, and the control group had ages ranging from 18 to 64 years, being 36 women and 53 men. 18.9% of the exposed group were poisoned by pesticides, and the most common symptoms were headache and gastrointestinal problems. The genotype frequencies of the rs2031920 (T>C) polymorphism in the CYP2E1 gene present significant differences between the exposed and control groups (p = 0.02), showing that 24.3% of the exposed group were heterozygotes against 6.7% in the control group. For the OGG1 gene, two SNPs, rs1052133 (G>C) and rs293795 (T>C), were evaluated and the genotype frequencies were not statistically different between the exposed and control groups. The DNA damage was distinct (p < 0.05) in the three analyzed comet parameters (tail length, Olive tail moment, %DNA) between groups. However, there was no influence of age and alcohol consumption between the groups associated with the polymorphisms in the CYP2E1 and OGG1 genes and DNA damage. We also did not find altered hematological and biochemical parameters in the exposed group. Thus, this pioneering study at Goias State carried out an overview of the health of soybean farmers. We evaluated classic laboratory exams, associated with exposure markers (comet assay) and susceptibility markers (genetic polymorphisms), emphasizing the need to expand the Brazilian health assessment protocol. We found, in soybean farmers, increased DNA damage and a higher number of heterozygotes in CYP2E1 gene, compared with the control group, despite the lack of association with age, educational level, smoking, drinking habits, and genetic polymorphisms.

Antineuroinflammation of Minocycline in Stroke

Accumulating research substantiates the statement that inflammation plays an important role in the development of stroke. Both proinflammatory and anti-inflammatory mediators are involved in the pathogenesis of stroke, an imbalance of which leads to inflammation. Anti-inflammation is a kind of hopeful strategy for the prevention and treatment of stroke. Substantial studies have demonstrated that minocycline, a second-generation semisynthetic antibiotic belonging to the tetracycline family, can inhibit neuroinflammation, inflammatory mediators and microglia activation, and improve neurological outcome. Experimental and clinical data have found the preclinical and clinical potential of minocycline in the treatment of stroke due to its anti-inflammation properties and anti-inflammation-induced pathogeneses, including antioxidative stress, antiapoptosis, inhibiting leukocyte migration and microglial activation, and decreasing matrix metalloproteinases activity. Hence, it suggests a great future for minocycline in the therapeutics of stroke that diminish the inflammatory progress of stroke.

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.

Oxidative stress and DNA damage after cerebral ischemia: Potential therapeutic targets to repair the genome and improve stroke recovery

The past two decades have witnessed remarkable advances in oxidative stress research, particularly in the context of ischemic brain injury. Oxidative stress in ischemic tissues compromises the integrity of the genome, resulting in DNA lesions, cell death in neurons, glial cells, and vascular cells, and impairments in neurological recovery after stroke. As DNA is particularly vulnerable to oxidative attack, cells have evolved the ability to induce multiple DNA repair mechanisms, including base excision repair (BER), nucleotide excision repair (NER) and non-homogenous endpoint jointing (NHEJ). Defective DNA repair is tightly correlated with worse neurological outcomes after stroke, whereas upregulation of DNA repair enzymes, such as APE1, OGG1, and XRCC1, improves long-term functional recovery following stroke. Indeed, DNA damage and repair are now known to play critical roles in fundamental aspects of stroke recovery, such as neurogenesis, white matter recovery, and neurovascular unit remodeling. Several DNA repair enzymes are essential for comprehensive neural repair mechanisms after stroke, including Polβ and NEIL3 for neurogenesis, APE1 for white matter repair, Gadd45b for axonal regeneration, and DNA-PKs for neurovascular remodeling. This review discusses the emerging role of DNA damage and repair in functional recovery after stroke and highlights the contribution of DNA repair to regenerative elements after stroke. This article is part of the Special Issue entitled 'Cerebral Ischemia'.

Can crosstalk between DOR and PARP reduce oxidative stress mediated neurodegeneration?

The progressive loss of structure and function of neurons leads to neurodegenerative processes which become the causative reason for various neurodegenerative diseases such as Parkinson's disease (PD), Alzheimer's disease (AD) etc. These diseases are multifactorial in nature but they have been seen to possess similar causative agents to a certain extent. Oxidative Stress (OS) has been identified as a major stressor and a mediator in most of these diseases. OS not only leads to the generation of free radical species but if persistent, can possibly lead to lipid peroxidation, protein damage, DNA damage, and cell death. Anti-oxidants are endogenously present in our body to tackle oxygen metabolites but their levels reduce greatly under continuous OS conditions. In such a case, dietary supplements to replenish the anti-oxidant levels in our body is a good way of treatment but it is very slow and may not be as effective in chronic stress conditions. Thus, there is a need for more effective mechanisms to attenuate OS. Two such mechanisms which can be considered are the activation of Delta opioid receptor (DOR) and Inhibition of Poly (ADP-ribose)-polymerase1 (PARP1), which have been suggested to protect neurons and increase neuronal cell survivability in both in-vitro and in-vivo disease models. Various signaling pathways have been highlighted to probably play a significant role in attenuating OS by the activation of DOR. It would be an interesting topic of investigation to see if one of the probable mechanisms by which DOR attenuates OS could be by modulation of PARP through a cascade of intracellular signaling reactions.

Oxidative stress gene polymorphisms may have an impact in the development of ischemic stroke

BACKGROUND

Antioxidants are responsible for detoxification of harmful effects of reactive oxygen species. Genetic factors may influence antioxidant activity as a result of polymorphisms on antioxidant enzymes. These polymorphisms can be risk in ischemic stroke (IS) risk. IS is a disorder with genetic and environmental factors contributing to overall risk. Although a few studies have been conducted, there have been no reports on catalase (CAT C262T), manganese superoxide dismutase (MnSOD Ala16Val) and glutathione peroxidase 1 (GPX1 Pro198Leu) gene polymorphisms and IS risk.

METHODS

We aimed to perform a case-control study to increase the awareness of the impact of oxidative stress (OS) gene polymorphism in the development of IS. A restriction fragment length polymorphism-polymerase chain reaction was used to determine genotypes. The interactions between genes and smoking and possible risk factors were evaluated.

RESULTS

An approximately four-fold higher IS risk was found in patients with the Val allele compared to the Ala allele. Smoking was a risk factor in the development of IS for CAT TT and MnSOD Ala/Val genotypes; we found a 3.5- to 5.5-fold higher IS risk in CAT TT and MnSOD Ala/Val genotypes. Different logistic regression models were performed for possible risk factors (smoking, body mass index, low-density lipoprotein and diabetes mellitus). The IS risk increases statistically significant only with age by multiple logistic regression analysis. CAT gene polymorphisms in IS patients were not different from controls.

CONCLUSIONS

It is unlikely that CAT and GPX1 single nucleotide polymorphisms are risk factors for IS. The results of the present study show that smoking may be a risk factor for IS risk in patients with MnSOD mutant genotypes.