Glutathione-related antioxidant defence, DNA damage, and DNA repair in patients suffering from post-COVID conditions.

Post-COVID conditions are defined as the continuation of the symptoms of Coronavirus Disease 2019 (COVID-19) 3 months after the initial Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection, with no other explanation. Post-COVID conditions are seen among 30%-60% of patients with asymptomatic or mild forms of COVID-19. The underlying pathophysiological mechanisms of post-COVID conditions are not known. In SARS-CoV-2 infection, activation of the immune system leads to increased production of reactive oxygen molecules, depleted antioxidant reserve, and finally occurrence of oxidative stress. In oxidative stress conditions, DNA damage increases and DNA repair systems impair. In this study, glutathione (GSH) level, glutathione peroxidase (GPx) activity, 8-hydroxydeoxyguanosine (8-OHdG) level, basal, induced, and post-repair DNA damage were investigated in individuals suffering from post-COVID conditions. In the red blood cells, GSH levels and GPx activities were measured with a spectrophotometric assay and a commercial kit. Basal, in vitro H2O2 (hydrogen peroxide)-induced, and post-repair DNA damage (DNA damage after a repair incubation following H2O2-treatment, in vitro) were determined in lymphocytes by the comet assay. The urinary 8-OHdG levels were measured by using a commercial ELISA kit. No significant difference was found between the patient and control groups for GSH level, GPx activity, and basal and H2O2-induced DNA damage. Post-repair DNA damage was found to be higher in the patient group than those in the control group. Urinary 8-OHdG level was lower in the patient group compared to the control group. In the control group, GSH level and post-repair DNA damage were higher in the vaccinated individuals. In conclusion, oxidative stress formed due to the immune response against SARS-COV-2 may impair DNA repair mechanisms. Defective DNA repair may be an underlying pathological mechanism of post-COVID conditions.

Antiobesity effects of phytochemicals from an epigenetic perspective.

Obesity is an important cause of morbidity and mortality due to its close association with metabolic disorders including diabetes, cardiovascular diseases, and certain types of cancer. According to the Developmental Origins of Adult Health and Disease hypothesis, obesity is likely caused by epigenetic changes. Recent studies have shown an association between epigenetic dysregulation of certain genes and obesity. Due to their reversible characteristic, epigenetic dysregulations can be restored. Restoration of epigenetic dysregulation in obesity-related genes by epigenetic modifiers may be a new treatment option for obesity. Certain phytochemicals such as tea polyphenols, curcumin, genistein, isothiocyanates, and citrus isoflavonoids were shown to prevent weight gain. These phytochemicals are known for their antioxidant effects but they also modify epigenetic mechanisms. These phytochemicals may have a therapeutic potential in the management of obesity. The aim of this study was to review the epigenetic effects of certain phytochemicals on the expression of obesity-related genes.

DNA repair gene OGG1 polymorphism and its relation with oxidative DNA damage in patients with Alzheimer's disease.

There is considerable evidence that oxidative DNA damage is increased, DNA repair capacity is decreased in patients with Alzheimer's disease. Base excision repair is the major pathway in removal of oxidative DNA damage. 8-oxo-deoxyguanosine DNA glycosylase 1 (OGG1) is the enzyme which is involved in the first step of this repair process. Alterations in DNA repair capacity may be related with polymorphisms in DNA repair genes. In order to investigate the effect of OGG1 Ser326Cys polymorphism on oxidative DNA damage level, OGG1 genotyping was performed, basal and oxidative DNA damage in lymphocytes and 8-OHdG level in plasma were examined in patients with Alzheimer's disease. Basal and oxidative DNA damage and 8-OHdG level were measured by OGG1-modified comet assay and enzyme-linked immunoassay, respectively. OGG1 genotyping was performed by polymerase chain reaction- restriction fragment length polymorphism assay. Basal and oxidative DNA damage and plasma 8-OHdG levels were found to be higher in the Alzheimer's disease group than those in the control group (P < 0.001). In the Alzheimer's disease group, the levels of oxidative DNA damage was higher in the patients having OGG1 (Ser326Cys + Cys326Cys) genotype than those in the patients having OGG1 Ser326Ser genotype. It was concluded that oxidative DNA damage is increased in patients with Alzheimer's disease and OGG1 Ser326Cys polymorphism may be responsible for this increase.

DNA damage, DNA susceptibility to oxidation and glutathione redox status in patients with Alzheimer's disease treated with and without memantine.

The aim of the current study was to compare oxidative DNA damage, DNA susceptibility to oxidation, and ratio of GSH/GSSG in patients with Alzheimer's disease (AD) treated with acetylcholinesterase inhibitor (AChEI) and combined AChEI+memantine. The study included 67 patients with AD and 42 volunteers as control. DNA damage parameters (strand breaks, oxidized purines, H2O2-induced DNA damage) in lymphocyte DNA and GSH/GSSG ratio in erythrocytes were determined by the comet assay and spectrophotometric assay, respectively. DNA damage was found to be higher, GSH/GSSG ratio was found to be lower in the AD group than those in the control group. DNA strand breaks and H2O2-induced DNA damage were lower in the patients taking AChEI+memantine than those in the patients taking AChEI but no significant difference was determined between the groups for oxidized purines and GSH/GSSG ratio. In conclusion, increased systemic oxidative DNA damage and DNA susceptibility to oxidation may be resulted from diminished GSH/GSSG ratio in AD patients. Although DNA strand breaks and H2O2-induced DNA damage are lower in the AD patients treated with combined AChEI and memantine, this may not indicate protective effect of memantine against DNA oxidation due to similar levels of oxidized purines in the patients treated with AChEI and AChEI+memantine.

DNA Repair Gene Polymorphisms and Their Relation With DNA Damage, DNA Repair, and Total Antioxidant Capacity in Childhood Acute Lymphoblastic Leukemia Survivors.

Oxidative stress and defective DNA repair are major contributory factors in the initiation and progression of carcinogenesis. Chemotherapy and radiotherapy cause oxidative DNA damage, consume antioxidant capacity, and impair DNA repair activity. These effects of chemotherapy and radiotherapy may be contributory factors in the development of secondary malignancy in cancer survivors. Basal, H2O2-induced, and postrepair DNA damage; urinary 8-hydroxydeoxyguanosine level as a marker of oxidatively damaged DNA; and serum total antioxidant capacity were measured; XPD Lys751Gln, XRCC1 Arg399Gln, and XRCC1 Arg194Trp polymorphisms were analyzed in childhood acute lymphoblastic leukemia (ALL) survivors. Basal and H2O2-induced DNA damage were found to be higher in the ALL survivor group versus the control group, however, there was no significant difference between the other parameters. No association was found between the examined parameters and polymorphisms of XPD 751 and XRCC1 399 and both the groups. XRCC1 194Trp allele was found to be associated with a low level of postrepair DNA damage in the ALL survivors. In conclusion, basal DNA damage and susceptibility to oxidation are high in childhood ALL survivors. This situation which may easily lead to occurrence of a secondary cancer does not seem to be a result of deficient DNA repair.

Alzheimer's disease and epigenetic diet.

Alzheimer's disease (AD) is the most common neurodegenerative disease. Many efforts have been directed to prevent AD due to its rising prevalence and the lack of an effective curative treatment. Various epigenetic mechanisms are linked to pathogenesis of AD. Epigenetic alterations may occur through external factors and are known for their reversibility. Dietary factors can influence epigenetic mechanisms. Several neuroprotective nutrients have been shown to enhance cognition, memory and other impaired functions seen in AD. Within recent years neuroprotective nutrients have gained more attention in the field of epigenetic. A growing body of evidence suggest that epigenetic changes triggered by dietary nutrients have an important role in health and in prevention of some diseases, especially neurodegenerative disorders. Several studies have shown that folic acid, vitamin B12, choline, zinc, selenium, dietary polyphenols are capable of interacting with epigenetic mechanisms and ultimately gene expression. Epigenetic mechanisms resulting in neuronal dysfunction may be modified by diet. Therefore manipulation of epigenetic mechanisms via dietary nutrients may affect influence the vulnerability of neurons to degeneration which is seen in AD. The aim of this article is to provide a brief overview about the recent findings related to epigenetic alterations that are linked to AD pathogenesis, and to discuss the bioactive nutrients which can affect these epigenetic mechanisms.

Medical radiation exposure and human carcinogenesis-genetic and epigenetic mechanisms.

Ionizing radiation (IR) is a potential carcinogen. Evidence for the carcinogenic effect of IR radiation has been shown after long-term animal investigations and observations on survivors of the atom bombs in Hiroshima and Nagasaki. However, IR has been widely used in a controlled manner in the medical imaging for diagnosis and monitoring of various diseases and also in cancer therapy. The collective radiation dose from medical imagings has increased six times in the last two decades, and grow continuously day to day. A large number of evidence has revealed the increased cancer risk in the people who had frequently exposed to x-rays, especially in childhood. It has also been shown that secondary malignancy may develop within the five years in cancer survivors who have received radiotherapy, because of IR-mediated damage to healthy cells. In this article, we review the current knowledge about the role of medical x-ray exposure in cancer development in humans, and recently recognized epigenetic mechanisms in IR-induced carcinogenesis.

Leukocyte DNA damage in children with iron deficiency anemia: effect of iron supplementation.

Iron deficiency is frequently associated with anemia. Iron is a transition-metal ion, and it can induce free radical formation, which leads to formation of various lesions in DNA, proteins, and lipids. The aim of this study was to investigate baseline oxidative DNA damage and to clarify the role of the administration of a therapeutic dose of iron on DNA oxidation in children with iron deficiency anemia (IDA). Twenty-seven children with IDA and 20 healthy children were enrolled in the study. Leukocyte DNA damage (strand breaks and Fpg-sensitive sites) was assessed using comet assay before and after 12 weeks of daily iron administration. Before the iron administration, the frequency of DNA strand breaks in the children with IDA was found to be lower than those in the control group (P < 0.05), but there was not a significant difference for frequency of Fpg-sensitive sites. After 12 weeks of iron administration, the frequency of both DNA strand breaks and Fpg-sensitive sites were found to be increased (P < 0.01). No significant association was determined between DNA damage parameters and hemoglobin, hematocrit, serum iron, total iron binding capacity, and ferritin. In conclusion, basal level of DNA strand breaks is at a low level in children with IDA. After iron administration, DNA strand breaks and Fpg-sensitive sites, which represent oxidatively damaged DNA, increased. However, this increase was unrelated to serum level of iron and ferritin.

Assessment of DNA nucleo base oxidation and antioxidant defense in postmenopausal women under hormone replacement therapy.

BACKGROUND AND OBJECTIVE: The aim of the present study was to evaluate oxidative stress by investing oxidatively damaged DNA AS Formamidopyrimidine DNA glycosylase (Fpg) -sensitive sites, glutathione peroxidase (GPx), superoxide dismutase (SOD) activities reduced glutathione (GSH) level and nitrite level as satble end product of in women receiving hormone replacement therapy (HRT). MATERIALS AND METHODS: 127 healthy postmenopausal women receiving HRT and 25 healthy control postmenopausal women were included in this study. Women receiving HRT, comprised surgical menopausal women who underwent surgery for benign conditions and received conjugated equine estrogen, 0.625 mg/day for 1 year (group 1), 5 years (group 2) and more than 10 years (group 3), spontaneous postmenopausal women received conjugated equine estrogen, 0.625 (Premarin) mg/day and medroxyprogesterone acetate, 2.5 mg/day (Premelle) for 1 year (group 4), 5 years (group 5) and more than 5 years (group 6).We investigated in the present study the effects of HRT on nitrite level and GSH level, activities of SOD and GPx and oxidative damage to DNA by comet assays by measuring levels of Fpg-sensitive sites. RESULTS: Although no significant differences were found in the SOD activities, in total group receiving HRT, increased DNA oxidation (P<0.001) together with an increased GPx activity (P<0.001) and nitrite level (P<0.001) as well as a decreased GSH level (P < 0.05) as compared with controls were observed. CONCLUSION: Estrogen alone or oestrogen in combination with progesterone and duration of use did not significantly alter the results. We evaluated that caused oxidative stress by investigating oxidative DNA damage as Fp-sensitive sites and GSH.NO levels in women receiving HRT.

DNA damage and glutathione level in children with asthma bronchiale: effect of antiasthmatic therapy.

When the production of reactive oxygen species (ROS) exceeds the capacity of antioxidant defences, a condition known as oxidative stress occurs and it has been implicated in many pathological conditions including asthma. Interaction of ROS with DNA may result in mutagenic oxidative base modifications such as 8-hydroxydeoxyguanosine (8-oxo-dGuo) and DNA strand breaks. Reduced glutathione (GSH) serves as a powerful antioxidant against harmful effects of ROS. The aim of this study was to describe DNA damage as level of DNA strand breaks and formamidopyrimidine DNA glycosylase (Fpg)-sensitive sites, which reflects oxidative DNA damage and GSH level in children with mild-to-moderate persistent asthma; and to examine the effect of antiasthmatic therapy on these DNA damage parameters and GSH level. Before and after 8 wk of antiasthmatic therapy blood samples were taken, DNA strand breaks and Fpg-sensitive sites in peripheral leukocytes were determined by comet assay, GSH level of whole blood was measured by spectrophotometric method. DNA strand breaks and Fpg-sensitive sites in the asthma group were found to be increased as compared with control group. GSH level in the asthma group was not significantly different from those in the control group. Levels of strand breaks, Fpg-sensitive sites and GSH were found to be decreased in the asthma group after the treatment. In conclusion, oxidative DNA damage (strand breaks and Fpg-sensitive sites) is at a high level in children with asthma. DNA damage parameters and GSH level were found to be decreased after therapy. Our findings imply that antiasthmatic therapy including glucocorticosteroids not only controls asthma but also decreases mutation risk in children with asthma bronchiale.

Circulating p53 and cytochrome c levels in acute myocardial infarction patients.

BACKGROUND: Apoptosis causes myocardiocyte loss during and after myocardial infarction. Therapeutic approaches designed to arrest apoptosis would be a significant new development in the recovery of acute myocardial infarction (AMI). In order to examine apoptotic markers in the circulation, serum levels of p53 and cytochrome c were assessed in patients with AMI. METHODS: Blood samples were taken on admission (before initiation of therapy) and on the 3rd and 7th days of hospitalization. Serum levels of p53 and cytochrome c were measured by enzyme-linked immunassay. RESULTS: The serum level of p53 was higher in AMI patients on admission compared to the control group. A time-dependent decrease was observed in the serum level of p53, but there was no significant change in the serum level of cytochrome c during therapy. CONCLUSIONS: p53, but not cytochrome c, appears to have potential as a biomarker for reporting on apoptosis following myocardial infarction.

Serum levels of p53 and cytochrome c in subjects with type 2 diabetes and impaired glucose tolerance.

PURPOSE: To examine apoptotic markers in serum of subjects with diabetes and impaired glucose tolerance (IGT). Serum levels of p53 and cytochrome c, regulator molecules for apoptosis, were measured in subjects with type 2 diabetes, subjects with IGT and healthy controls. METHODS: Forty one subjects with type 2 diabetes, 27 with IGT and 27 healthy volunteers were included in the study. Serum level of cytochrome c and p53 were measured with competitive ELISA. RESULTS: Serum levels of p53 were lower in the group of subjects with type 2 diabetes (085+/-0.39 U/ml) than in controls (1.09+/-0.49 U/ml) (P < 0.05) and in the subjects with IGT (0.98+/-0.37 U/ml) (P < 0.05). There was no significant difference between the group with IGT and controls. Also, there was no difference for serum level of cytochrome c among the groups. In the group of subjects with type 2 diabetes, serum level of cytochrome c was mildly correlated with HbA1c (r:0.39, P < 0.05). CONCLUSION: The present study shows that the serum level of p53 is lower in the patients with type 2 diabetes than in controls or in subjects with IGT. No difference was seen among the the groups for the serum level of cytochrome c.

Oxidative DNA damage and antioxidant defense after reperfusion in acute myocardial infarction.

PURPOSE: Myocardial damage mediated by oxidative stress during acute myocardial infarction (MI) has been suggested as an obstructive factor on recovery after an MI. 8-Hydroxydeoxyguanosine (8-OHdG) is a marker for oxidative DNA damage; superoxide dismutase (SOD) and glutathione peroxidase (G-Px) are major antioxidant enzymes. We determined changes in the plasma level of 8-OHdG and activities of SOD and G-Px in patients with MI and examined the relations between those changes and other cardiac markers. METHODS: Blood samples were taken at the beginning of the therapy, on the third day of hospitalization, and on the day patients were discharged home. Plasma level of 8-OHdG and SOD and G-Px activities were measured by enzyme-linked immunosorbent assay and spectrophotometric kits, respectively. RESULTS: 8-Hydroxydeoxyguanosine level at the beginning of the therapy was found to be decreased on the third day of therapy and on the day patients were discharged home. With respect to the treatment way, 8-OHdG level was found to be slightly decreased on the third day of therapy and then remained stable in the group treated with thrombolytic agents. However, 8-OHdG level was found to be sharply decreased on the third day of therapy in the group that underwent primary percutaneous transluminal coronary angioplasty. No significant relations were determined between those measured parameters and serum levels of cardiac markers. CONCLUSION: Although not correlated with other cardiac markers, plasma level of 8-OHdG shows a decrease after reperfusion therapy in patients with MI, and primary percutaneous transluminal coronary angioplasty seems much more effective than thrombolytic therapy for providing a low level of 8-OHdG.

Assessment of DNA oxidation and antioxidant activity in hypertensive patients with chronic kidney disease.

The aim of this study was to evaluate the oxidative DNA damage, antioxidant activity, and effects of antihypertensive drugs on oxidative stress in hypertensive patients with different stages of chronic kidney disease (CKD). Fifty-three non-dialyzed hypertensive CKD patients were included by the study. Serum and urinary 8-hydroxydeoxy guanosine (8-OHdG) levels (as a marker of oxidative DNA damage), serum superoxide dismutase (SOD), and glutathione peroxidase (G-Px) activities (as antioxidant enzymes) were measured. SOD activity was higher and G-Px activity was lower in the patient group as compared to control group. Serum and urinary 8-OHdG levels were found to be higher in the patients with proteinuria greater than 3 g/day than those in the patients with proteinuria less than 3 g/day. It has been determined that G-Px activity and urinary 8-OHdG level were lower in the patients treated with angiotensin-converting enzyme (ACE) inhibitor compared to patients treated with calcium channel blocker. The present data show oxidative DNA damage at a higher level in the patients with proteinuria greater than 3 g/day. In comparison to a calcium channel blocker, an ACE inhibitor seems much more protective against oxidative DNA damage in hypertensive patients with different stages of CKD.

Oxidative DNA damage and antioxidant activity in patients with inflammatory bowel disease.

Chronic inflammation may contribute to cancer risk through the accumulation of specific products as a result of DNA damage. Endogenous antioxidant enzymes prevent the formation of these harmful products. Oxidative DNA damage and endogenous antioxidant defense were determined in patients with inflammatory bowel disease (IBD). Plasma levels of 8-hydroxydeoxyguanosine (8-OHdG) and nitric oxide (NO) and plasma activities of glutathione peroxidase (G-Px) and superoxide dismutase (SOD) were determined in patients with IBD by ELISA and spectrophotometric assay, respectively. Plasma levels of 8-OHdG, SOD, and G-Px activity were found to be increased in the patient group compared to the control group (P < 0.02, P < 0.001, and P < 0.001, respectively), whereas NO was unchanged. 8-OHdG level was found to be weakly correlated with age, NO, and SOD. The results show increased DNA damage in patients with IBD. This may explain the increased risk of developing colon cancer in these patients.

Nitric oxide and antioxidant defense in patients with gastric cancer.

In the present study, total nitrate and nitrite level (as end product of nitric oxide), superoxide dismutase activity, and glutathione peroxidase activity in leukocytes were determined in patients with gastric cancer, and the relationship between measured parameters and tumor grade were evaluated. Leukocyte nitrate and nitrite level was found to be increased and superoxide dismutase activity was found to be decreased in patients compared to controls. When the patient group was categorized, nitrate and nitrite level was found to be higher in patients with a high-grade tumor than in patients with a grade I tumor. We concluded that an increased level of leukocyte nitrate and nitrite is related to tumor grade in patients with gastric cancer; antioxidant activity is also impaired in these patients but it does not seem to be related to grade of tumor.

Methylguanine DNA methyl transferase activities, glutathione s transferase and nitric oxide in bladder cancer patients.

Tumor formation is a multistep process that can be divided in to the stages of tumor initiation, promotion, and progression. DNA repair protein; MGMT is a key suicide enzyme that repairs the mispairing base methylguanine, which is induced in DNA as a minor lesion. The glutathione S transferases (GSTs) are a family of enzymes that are important to protect against alkylating agents. Nitric oxide, contributes to the regulation of tumor angiogenesis. A substantial body of experimental evidence supports the hypothesis that tumor angiogenesis is fundamental for the growth and metastasis of solid tumors. We measured the activities of GST, MGMT, and levels of NO3-/NO2- in the leukocytes from patients with bladder carcinoma and healthy controls and activities of MGMT in the tissue from patients with bladder carcinoma and adjacent normal tissue in bladder. Both GST and tissue MGMT activites were significantly increased in the patient group. There was no significant difference between controls and patients for MGMT activity in peripheral blood leukocytes (PBL). Nitrate/nitrite levels in PBL, there was no significant difference between controls and patients. Nitrate/nitrite levels were increased in G2-G3 tumors. In conclusion, we determined high concentrations of nitrite in leukocytes are suspected alkylation damage by induction nitrosamine. Increased DNA alkylation damage may lead the stimulation of MGMT and GST.

Significance of the O6-methylguanine-DNA methyltransferase and glutathione S-transferase activity in the sera of patients with malignant and benign ovarian tumors.

OBJECTIVE: To demonstrate O6-methylguanine-DNA methyltransferase (MGMT) and glutathione S-transferase (GST) activities by analyzing the sera separately obtained from patients with malignant ovarian tumors, benign ovarian tumors, and healthy individuals. STUDY DESIGN: Fourty-nine patients with ovarian cancer, nine patients with benign tumors, and 22 healthy women were included in this study. Blood samples were obtained from all the subjects in the malignant-tumor, benign-tumor, and control groups. Patients with malignant tumors underwent second and third phlebotomies one week following the surgery and after the chemotherapy regimen, respectively. MGMT, GST, and protein levels were measured for each serum sample. GST activity of the samples was measured by the method of Habig et al. using l-chloro-2-4 dinitrobenzene (CDNB) as substrate. MGMT activity was measured by the transfer of radio labelled methyl groups from a prepared MG-DNA substrate to the enzyme fraction of serum. Protein concentration was measured by biuret method. RESULTS: Our work demonstrated that untreated patients with malignant ovarian tumors revealed significantly greater MGMT and GST activities in their sera than did both healthy individuals and patients with benign ovarian tumors, while no significant difference was found between the healthy group and the patients with benign ovarian tumors with respect to their sera MGMT and GST activities. GST activity following chemotherapy was significantly lower than the postoperative values preceding chemotherapy. A relationship between sera MGMT and GST activities, tumor histology and pathology was not found in this study. CONCLUSION: Our work suggests the fact that detection of sera MGMT and GST activities is important in diagnostic and therapeutic approaches during the course of ovarian cancer.

O(6)-methylguanine DNA methyltransferase activity in diabetic patients.

In the present study, we evaluated O(6)-methylguanine-DNA methyltransferase (MGMT) activity in diabetic patients. The study was performed on 27 patients with Type 1 diabetes, and 42 with Type 2 diabetes. Patients with complications were excluded from the study. 36 non-diabetic volunteers, non-smokers who do not consume alcoholic beverage, were chosen from the medical staff as control subjects. MGMT activity was measured by the transfer of radiolabeled methyl groups from a prepared methylguanine-DNA substrate to the enzyme fraction of leukocyte extract. Leukocyte MGMT activity was significantly reduced in both Type 1 and Type 2 diabetes patients as compared with control subjects (P<0.001). The present study demonstrates decreased MGMT activity in leukocytes from patients with Type 1 and Type 2 diabetes.