hOGG1 Expression Research Articles

HOGG1: A novel mediator in nitrosamine-induced esophageal tumorigenesis

BackgroundThe effect of human 8-Oxoguanine DNA Glycosylase (hOGG1) on exogenous chemicals in esophageal squamous cell carcinoma (ESCC) remain unclear. The study plans to determine hOGG1 expression levels in ESCC and possible interactions with known environmental risk factors in ESCC. Material and methodsWe analyzed levels of exposure to urinary nitrosamines in volunteers from high and low prevalence areas by GC-MS. And we performed the interaction between hOGG1 gene and nitrosamine disinfection by-products by analyzing hOGG1 gene expression in esophageal tissues. ResultsIn ESCC, nitrosamine levels were significantly increased and hOGG1 mRNA expression levels were significantly decreased. There was a statistically significant interaction between reduced hOGG1 mRNA levels and non-tap drinking water sources in ESCC. The apparent indirect association between ESCC and NMEA indicated that 33.4% of the association between ESCC and NMEA was mediated by hOGG1. ConclusionIn populations which exposed to high levels of environmental pollutants NDMA, low expression of hOGG1 may promote the high incidence of esophageal cancer in Huai'an. hOGG1 may be a novel mediator in nitrosamine-induced esophageal tumorigenesis.

Modulation of gene expression and inflammation but not DNA damage after sevoflurane anesthesia.

This study assessed, for the first time, the expression of the genes hOGG1, TP53, and IL-6 in leukocytes by real-time quantitative polymerase chain reaction in surgical patients before (baseline), during (2 h of anesthesia) and 1 day after sevoflurane anesthesia. Additionally, DNA damage was detected by the comet assay, serum interleukin (IL)-6 was detected by flow cytometry, and differential leukocyte counting was also performed. TP53 and hOGG1 expression was downregulated on the day after anesthesia compared to before anesthesia. However, IL-6 expression did not change, and no DNA damage induction was observed during or after anesthesia. At the systemic level, mild neutrophilia and an increase in IL-6 levels occurred after anesthesia. Our findings suggest that sevoflurane anesthesia downregulates gene expression (hOGG1 and TP53) and contributes to an inflammatory status (increased systemic IL-6 and mild neutrophilia) but is not associated with DNA damage in patients without comorbidities who undergo minor elective surgery.

STUDY THE EFFECTS OF (8-OXO-GUANINE DNA GLYCOSYLASE 1 RS1052133) POLYMORPHISM ON GENE EXPRESSION AS A PREDISPOSING FACTOR FOR DNA MUTATION IN MIDLAND REFINERIES COMPANY-DURA REFINERY WORKERS

Background: Refineries are exposed to different types of air pollutants, among them, polycyclic aromatic hydrocarbons (PAHs), they are a group of over hundred different kinds of hazardous organic chemicals (pollutants), which are formed primarily during the incomplete burning of oil, gas and coal. PAHs are metabolized in different organs of human body especially in the liver leading to generation of mutagenic metabolites, of them, the reactive oxygen species, which damage DNA by binding with guanine base leading to formation of 8-hydroxyguanine. The 8-oxo-guanine DNA glycosylase (hOGG1 rs1052133) gene, is a regulatory gene binds with 8-oxo-DG in the DNA to initiate base excision repair (BER) pathway. Objective: To investigate the role of (hOGG1 rs1052133) gene polymorphism in single nucleotide polymorphism repair. Methods: One hundred sixty-eight (168) subjects were participated in this study. They were they divided into three groups (country side, office workers and field workers). PAHs were analyzed in all participant by Gas Chromatography Coupled with a Mass Spectrophotometry GC/MS. SNP for hOGG1 and gene expression were detecting by real time polymerase chain reaction and quantitative polymerase chain reaction for each subject respectively. Results: PAH were detected in blood serum of refineries workers and not detected in country side participants. The level of hOGG1 gene expression was higher in GG genotype than GC and CC genotype. Conclusion: Refineries worker are at high risk of developing malignant transformation and serious disease due to high level of PAH compared to other population. hOGG1 plays an important role in DNA repair following DNA mutation. Keywords: Poly cyclic aromatic hydrocarbons, HOGGI, gene expression Citation: Al-Ani RH, Al-Wasiti EA, Shukur AS. Study the Effects of (8-oxo-Guanine DNA Glycosylase 1 rs1052133) Polymorphism on Gene Expression as a Predisposing Factor for DNA Mutation in Midland Refineries Company-Dura Refinery Workers. Iraqi JMS. 2022; 20(1): 90-97. doi: 10.22578/IJMS.20.1.12

Oxidative Damage in Sporadic Colorectal Cancer: Molecular Mapping of Base Excision Repair Glycosylases MUTYH and hOGG1 in Colorectal Cancer Patients.

Oxidative stress, oxidative DNA damage and resulting mutations play a role in colorectal carcinogenesis. Impaired equilibrium between DNA damage formation, antioxidant status, and DNA repair capacity is responsible for the accumulation of genetic mutations and genomic instability. The lesion-specific DNA glycosylases, e.g., hOGG1 and MUTYH, initiate the repair of oxidative DNA damage. Hereditary syndromes (MUTYH-associated polyposis, NTHL1-associated tumor syndrome) with germline mutations causing a loss-of-function in base excision repair glycosylases, serve as straight forward evidence on the role of oxidative DNA damage and its repair. Altered or inhibited function of above glycosylases result in an accumulation of oxidative DNA damage and contribute to the adenoma-adenocarcinoma transition. Oxidative DNA damage, unless repaired, often gives rise G:C > T:A mutations in tumor suppressor genes and proto-oncogenes with subsequent occurrence of chromosomal copy-neutral loss of heterozygosity. For instance, G>T transversions in position c.34 of a KRAS gene serves as a pre-screening tool for MUTYH-associated polyposis diagnosis. Since sporadic colorectal cancer represents more complex and heterogenous disease, the situation is more complicated. In the present study we focused on the roles of base excision repair glycosylases (hOGG1, MUTYH) in colorectal cancer patients by investigating tumor and adjacent mucosa tissues. Although we found downregulation of both glycosylases and significantly lower expression of hOGG1 in tumor tissues, accompanied with G>T mutations in KRAS gene, oxidative DNA damage and its repair cannot solely explain the onset of sporadic colorectal cancer. In this respect, other factors (especially microenvironment) per se or in combination with oxidative DNA damage warrant further attention. Base excision repair characteristics determined in colorectal cancer tissues and their association with disease prognosis have been discussed as well.

Maternal Transmission of Human OGG1 Protects Mice Against Genetically- and Diet-Induced Obesity Through Increased Tissue Mitochondrial Content

Obesity and related metabolic disorders are pressing public health concerns, raising the risk for a multitude of chronic diseases. Obesity is multi-factorial disease, with both diet and lifestyle, as well as genetic and developmental factors leading to alterations in energy balance. In this regard, a novel role for DNA repair glycosylases in modulating risk for obesity has been previously established. Global deletion of either of two different glycosylases with varying substrate specificities, Nei-like endonuclease 1 (NEIL1) or 8-oxoguanine DNA glycosylase-1 (OGG1), both predispose mice to diet-induced obesity (DIO). Conversely, enhanced expression of the human OGG1 gene renders mice resistant to obesity and adiposity. This resistance to DIO is mediated through increases in whole body energy expenditure and increased respiration in adipose tissue. Here, we report that hOGG1 expression also confers resistance to genetically-induced obesity. While Agouti obese (Ay/a) mice are hyperphagic and consequently develop obesity on a chow diet, hOGG1 expression in Ay/a mice (Ay/aTg) prevents increased body weight, without reducing food intake. Instead, obesity resistance in Ay/aTg mice is accompanied by increased whole body energy expenditure and tissue mitochondrial content. We also report for the first time that OGG1-mediated obesity resistance in both the Ay/a model and DIO model requires maternal transmission of the hOGG1 transgene. Maternal, but not paternal, transmission of the hOGG1 transgene is associated with obesity resistance and increased mitochondrial content in adipose tissue. These data demonstrate a critical role for OGG1 in modulating energy balance through changes in adipose tissue function. They also demonstrate the importance of OGG1 in modulating developmental programming of mitochondrial content and quality, thereby determining metabolic outcomes in offspring.

The Adverse Effect of Air Pollution with Polycyclic Aromatic hydrocarbon (PAH) on 8-OXO-DG and gene expression (HOGG1) in Midland Refineries Company-Daura Refinery Workers

Introduction: Polycyclic aromatic hydrocarbons (PAHs) are a group of different kind of hazardous organic chemicals which are considered to be the top of pollutants that released by petroleum industries exploration activities to the environment. PAH Metabolites that affect initiation of cancer by reaction with DNA are practically modified chemically by enzymes. PAH Mutagenic metabolites include radical PAH cations, diol epoxides, and quinones. Reactive oxygen species (ROS) mostly produce by routine oxidation processes in mitochondria is responsible for many types of DNA damage. The aim of study identify the DNA alteration due to air pollution by modulation of gene expression and regulatory gene Human 8-oxoguanine DNA Glycosylase (HOOG1) and association with 7,8-dihydro-8-oxoguanine (8-oxo-dg). Methods: there were 168 participants included in this study divided in three groups (control, office workers and in field workers) .PAH, 8-OXO-DG and gene expression (HOGG1) detected for each participant by GC/MS, competitive ELISA and quantitative-competitive reverse transcription-PCR respectively. Results: PAH were not detected in the blood of control group, and there was significant difference in the concentration of PAH between office and field workers. The concentration of (8-oxo DG) and (hOGG1) was significantly higher in field worker than in office worker and control group, significant difference was found between office workers and control. Discussion: It is observed that increased levels of PAH and its metabolites when exposed to polluted air. PAHs metabolism is associated with production of ROS as well as oxidative damaged. Among this damage, the most common lesion is (8-OHdG) .Increase in (8-OHdG) levels associated with increase oxidative stress and (HOGG1) gene. Conclusion: (a) increased PAH and its metabolites levels in serum causing high 8-OHdG and (HOGG1) expression levels in refineries workers (b) there is a correlation between 8-OHdG and hOGG1 expression with PAH.

Correlation analysis of mRNA expression and prognosis of hOGG1 gene polymorphism in patients with non-small cell lung cancer.

Level of mRNA expression and gene polymorphism of human 8-hydroxyguanine glycosidase 1 (hOGG1) in patients with non-small cell lung cancer (NSCLC) were investigated. A polymorphism analysis of hOGG1 gene rs1052133 locus in 182 NSCLC patients (NSCLC group) surgically treated in Xiang Yang No. 1 People's Hospital, Hubei University of Medicine from January 2008 to January 2012 and 200 healthy individuals (control group) was performed. The expression level of hOGG1 was compared between cancer tissues and adjacent tissues of NSCLC patients, and the survival rate was analyzed. The expression level of hOGG1 was significantly higher in cancer tissues than that in adjacent tissues (P<0.001). Taqman probe method was used to detect the genotypes of hOGG1 polymorphism locus rs1052133, with the genotype distribution frequencies of NSCLC group (P=0.411) and control group (P=0.354) consistent with the Hardy-Weinberg equilibrium. The proportion of C/C gene was significantly higher in NSCLC group than that in control group (P=0.008, OR=2.2, 95%, CI=1.27–4.52). The median value of the hOGG1 expression level in detection results as the boundary, NSCLC patients were divided into hOGG1 high expression group (≥3.61) with 91 cases and hOGG1 low expression group (<3.61) with 91 cases. The 1-, 2- and 3-year survival rates of patients in hOGG1 low expression group were significantly higher than those in hOGG1 high expression group (P=0.007). The 3-year survival rate in hOGG1 low expression group is significantly higher than that in hOGG1 high expression group (P=0.007). The sensitivity, specificity and AUC of hOGG1 to patient survival prediction were 83.33%, 64.29%, and 0.816, respectively. In conclusion, hOGG1 is highly expressed in NSCLC tissues. Compared to S/S and S/C genotypes, the C/C gene was found to be more common in NSCLC group than in control group. Thus, hOGG1 has a high predictive value for patient survival.

Oxidative stress and deregulations in base excision repair pathway as contributors to gallbladder anomalies and carcinoma – a study involving North-East Indian population

Gallbladder cancer (GBC) is a fatal condition with dismal prognosis and aggressive local invasiveness; and with uncharacterised molecular pathology relating to non-specific therapeutic modalities. Given the importance of oxidative stress in chronic diseases and carcinogenesis, and the lacunae in literature regarding its role in gallbladder diseases, this study aimed to study the involvement of oxidative stress and deregulation in the base excision repair (BER) pathway in the pathogenesis of gallbladder diseases including GBC. This study involved patients from the North-East Indian population, where the numbers of reported cases are increasing rapidly and alarmingly. Oxidative stress, based on 8-OH-dG levels, was found to be significantly higher in gallbladder anomalies (cholelithiasis [CL] and cholecystitis [CS]) and GBC at the plasma and DNA level, and was associated with GBC severity. The expressions of key BER pathway genes were downregulated in gallbladder anomalies and GBC compared to controls, and in GBC compared to both non-neoplastic controls and gallbladder anomalies. Expression of XRCC1 and hOGG1 was significantly associated with both susceptibility and severity of GBC. The XRCC1 codon280 polymorphism was associated with disease susceptibility; and significantly higher oxidative stress was observed in hOGG1 genotypic variants. The genomes of GBC patients were found to be more hypermethylated compared to controls, with the promoters of XRCC1 and hOGG1 being hypermethylated and, therefore, being silenced. This study underlined the prognostic significance of the oxidative stress marker 8-OH-dG and BER pathway genes, especially hOGG1 and XRCC1, in gallbladder anomalies and GBC, as well as stated their potential for therapeutic targeting.

Decreased 8-oxoguanine DNA glycosylase 1 (hOGG1) expression and DNA oxidation damage induced by Cr (VI)

Occupational exposure to Cr (VI) can cause DNA damage, genetic instability and elevate the risk of cancer. Here we investigated Cr (VI)-induced DNA damage and 8-oxoguanine DNA glycosylase 1 (hOGG1) gene expression in electroplating workers. The hOGG1 gene encodes a DNA repair enzyme that is crucial in DNA oxidation damage repair. Deficiency in hOGG1 DNA repair capacity contributes to the accumulation of DNA damage and genetic instability. To address the issues, we collected peripheral blood samples and urine samples from 162 electroplating workers and 84 control subjects. We measured blood chromium levels, urine chromium levels, DNA damage, and hOGG1 mRNA expression. We found significantly higher levels of blood chromium, urine chromium, and DNA damage in electroplating workers compared with controls, whereas mRNA levels of the hOGG1 gene were significantly lower in the exposed workers. Furthermore, in electroplating workers we found that blood Cr had a positive association with DNA damage as measured with the tail DNA%. Meanwhile, tail DNA% was positively associated with hOGG1 mRNA expression. Finally, the effect of potassium dichromate treatment was investigated in a human B lymphoblastoid cell line (LCL). We observed that potassium dichromate induced a concentration-dependent decrease in hOGG1 mRNA. After removing the K2Cr2O7-containing medium for 3 days and 7 days, the abundance of hOGG1 mRNA expression recovered to a similar level as the controls. Collectively, our findings suggest that decreased hOGG1 mRNA expression in occupationally exposed populations partially contribute to Cr (VI) induced DNA damage.

Expression and promoter methylation status of two DNA repair genes in leukocytes from patients undergoing propofol or isoflurane anaesthesia.

Despite the widespread use of the anaesthetics propofol (PROP) and isoflurane (ISO), data about their toxicogenomic potential and interference in epigenetic events are unknown. This study evaluated the expression and methylation profile of two important DNA-repair genes (XRCC1 and hOGG1) in 40 patients undergoing elective and minimally invasive surgery (tympanoplasty and septoplasty) under ISO or PROP anaesthesia. The endpoints were examined at three sampling times: before anaesthesia (T0), 2 h after the beginning of anaesthesia (T2) and 24 h after the beginning of surgery (T24). Both gene expressions were assessed by quantitative real-time polymerase chain reaction (qRT-PCR), whereas methylation specific-PCR (MS-PCR) evaluated the DNA methylation patterns. Increased expression of XRCC1 was observed at T2 only in the PROP group. On the other hand, hOGG1 and XRCC1 expressions were decreased at T24 in both groups. There were no statistical significant differences between the two anaesthetics at the respective sampling times. The methylation status of XRCC1 (methylated at T0) and hOGG1 (unmethylated at T0) remained unchanged in the three sampling times. In conclusion, this study showed modulations of hOGG1 and XRCC1 expression especially 1 day after elective surgery in patients undergoing PROP and ISO anaesthesia. However, the data indicated that methylation was not the mechanism by which the genes were regulated. More studies are warranted to further investigate the possible epigenetic mechanisms involved after exposure to anaesthetics.

Methylated +322-327 CpG site decreases hOGG1 mRNA expression in non-small cell lung cancer.

hOGG1 plays a role in several disease pathways, including various cancers. Despite such functional importance, how hOGG1 is regulated at the transcriptional level in human non-small cell lung cancer (NSCLC) remains unknown, particularly via DNA methylation changes. We obtained NSCLC tissues and adjacent non-cancerous tissues and examined hOGG1 mRNA expression levels. NSCLC cells were treated with 5-Aza to test whether DNA methylation can influence the expression of hOGG1. The MassARRAY EpiTYPER and luciferase reporter gene assays were used to define the functional region of the hOGG1 gene (including CpG sites). Finally, ChIP assay was utilized to verify transcription factor binding to the hOGG1 5'-UTR region. Our previous studies supported the idea that the methylation of the hOGG1 gene promoter region occurs frequently in NSCLC. Treatment with 5-Aza, a demethylating agent, led to a significant restoration of hOGG1 expression in NSCLC cell lines. Quantitative PCR and MassARRAY EpiTYPER assays demonstrated that methylation of the +322-327 CpG site in the 5'-UTR region of hOGG1 was higher in NSCLC tissues compared with adjacent non-cancerous tissues. Notably, the methylation level of +322-327 site (T/N) was inversely correlated with that of hOGG1 mRNA level (T/N) in 25 NSCLC tissues. ChIP assay and insilico prediction showed an association between the +322-327 CpG site and Sp1, which has been reported to be an activator of transcription. Importantly, luciferase reporter gene and ChIP assays showed that +322-327 CpG site methylation particularly reduced the recruitment of Sp1 to the 5'-UTR sequence in hOGG1 and reduced transcriptional activity ~50%. In summary, we have demonstrated that hOGG1 mRNA is downregulated in NSCLC tissues. Moreover, we identified that the methylated +322-327 CpG site in the hOGG1 5'-UTR is associated with reduced expression of hOGG1 by decreasing the recruitment of Sp1 to the 5'-UTR of hOGG1.

Aberrant promoter methylation of hOGG1 may be associated with increased risk of non-small cell lung cancer.

DNA methylation may epigenetically inactivate tumor suppressor genes in NSCLC. As the human 8-oxoguanine DNA glycosylase (hOGG1) gene promoter is frequently methylated in NSCLC, we evaluated whether genetic or epigenetic alterations of hOGG1 are associated with increased risk of non-small cell lung cancer. Three hOGG1 haplotype-tagging SNPs (htSNP) were genotyped in PCR-restriction fragment length polymorphism assays, and one htSNP was genotyped in a PCR-single-strand conformation polymorphism assay in case-control studies of 217 NSCLC patients and 226 healthy controls. The methylation profiles of peripheral blood mononuclear cell specimens from 121 NSCLC patients and 121 controls were determined through methylation-specific PCR of hOGG1. No differences in allele or genotype frequencies between NSCLC patients and controls were observed at any of the four polymorphic sites (rs159153, rs125701, rs1052133, and rs293795). However, hOGG1 methylation-positive carriers had a 2.25-fold greater risk of developing NSCLC (adjusted odds ratio: 2.247; 95% confidence interval: 1.067-4.734; P = 0.03) than methylation-free subjects. Furthermore, the demethylating agent 5-aza-2’-deoxycytidine restored hOGG1 expression in NSCLC cell lines. These data provide strong evidence of an association between peripheral blood mononuclear cell hOGG1 methylation and the risk of NSCLC in a Chinese population.

Enforced DNA repair enzymes rescue neurons from apoptosis induced by target deprivation and axotomy in mouse models of neurodegeneration

It is unknown whether DNA damage accumulation is an upstream instigator or secondary effect of the cell death process in different populations of adult postmitotic neurons in the central nervous system. In two different mouse models of injury-induced neurodegeneration characterized by relatively synchronous accumulation of mitochondria, oxidative stress, and DNA damage prior to neuronal apoptosis, we enforced the expression of human 8-oxoguanine DNA glycosylase (hOGG1) and human apurinic-apyrimidinic endonuclease-1/Ref1 (hAPE) using recombinant adenoviruses (Ad). Thalamic lateral geniculate neurons and lumbar spinal cord motor neurons were transduced by Ad-hOGG1 and Ad-hAPE injections into the occipital cortex and skeletal muscle, respectively, prior to their target deprivation- and axotomy-induced retrograde apoptosis. Enforced expression of hOGG1 and hAPE in thalamus and spinal cord was confirmed by western blotting and immunohistochemistry. In injured populations of neurons in thalamus and spinal cord, a DNA damage response (DDR) was registered, as shown by localization of phospho-activated p53, Rad17, and replication protein A-32 immunoreactivities, and this DDR was attenuated more effectively by enforced hAPE expression than by hOGG1 expression. Enforced expression of hOGG1 and hAPE significantly protected thalamic neurons and motor neurons from retrograde apoptosis induced by target deprivation and axotomy. We conclude that a DDR response is engaged pre-apoptotically in different types of injured mature CNS neurons and that DNA repair enzymes can regulate the survival of retrogradely dying neurons, suggesting that DNA damage and activation of DDR are upstream mechanisms for this form of adult neurodegeneration in vivo, thus identifying DNA repair as a therapeutic target for neuroprotection.

Arsenic projects in SE Asia.

Early life exposure to inorganic arsenic is associated with a wide range of malignant and chronic disease outcomes in humans. Prenatal arsenic exposure may give rise to adverse effects on child health and development as arsenic readily passes through the placenta in human beings. The impact of maternal arsenic exposure on fetal gene expression was conducted in pregnant women living in Southern Thailand. Arsenic exposed newborns had significantly higher levels of arsenic in cord blood, and a set of genes associated with numerous biological pathways, including cell signaling, apoptosis, inflammatory and stress response. A slight increase in promoter methylation of p53 in cord blood lymphocytes which correlated with arsenic accumulation in nails was observed in these exposed newborns. A follow-up study on these exposed children showed a significant increase in oxidative DNA damage, measured as 8-hydroxydeoxyguanosine (8-OHdG) in saliva. In addition, levels of urinary 8-OHdG excretion and salivary hOGG1 expression were significantly decreased in exposed children suggesting a defect in repair of 8-OHdG in arsenic-exposed children. Our study indicates that prenatal arsenic and continued exposure through early childhood can trigger various genetic and epigenetic alterations that may lead to disease development later in life.

Effects of Turkish propolis on expression of hOGG-1 and NEIL-1.

Propolis is a bee product with antioxidative, antimutagenic, and other beneficial properties, and it is used as a natural drug. It is rich in polyphenolic compounds. Its composition varies depending on the particular geographical region. Oxidative stress is caused by an imbalanced free radical production and antioxidant system. The effects of flavonoids on the expression of DNA repair enzymes have been examined previously; however, no study has investigated the effects of propolis. This study investigated the effects of ethanolic extracts of Turkish propolis (EEP) on the expression of DNA repair enzymes. The effects of EEP and tertiary-butyl-hydroperoxide (t-BHP) on cell viability were determined using MTT DNA damage was determined using comet assay. mRNA expression of target enzymes was detected using RT-PCR. According to the cytotoxicity analysis, after a recovery time of 4 h, appropriate damage agent t-BHP and optimum EEP concentrations were 300 µM and 200 µg/mL, respectively. 8-Oxoguanine-glycosylase (hOGG-1) and endonuclease-VIII-like-1 (NEIL-1) expressions increased in the positive control group (t-BHP alone) and the study group (t-BHP+EEP). Maximum increase in NEIL-I expression was at hour 12 in the positive control group and at hour 8 in the study group. EEP can be considered as a potential source of functional food and pharmaceutical agents.

Redox-linked effects of green tea on DNA damage and repair, and influence of microsatellite polymorphism in HMOX-1: results of a human intervention trial.

Green tea has many reported health benefits, including genoprotective and antioxidant effects, but green tea has pro-oxidant activity in vitro. A tea-induced pro-oxidant shift that triggers cytoprotective adaptations has been postulated, but human data are lacking. We investigated effects on oxidation-induced DNA damage and redox-linked cytoprotective factors, including 8-oxoguanine glycosylase (hOGG1) and heme oxygenase 1 (HMOX-1) in lymphocytes in a randomised, placebo-controlled, cross-over supplementation trial. hOGG1 catalyses the first step in base excision repair; increased HMOX-1 is a sign of cytoprotective response to pro-oxidant change. The influence of microsatellite polymorphisms in the HMOX-1 promoter region was also explored. Higher numbers of GT repeats [GT(n)] in this region reportedly diminish response to pro-oxidant change. Green tea [2 × 150 ml of 1% w/v tea/day (or water as control)] was taken for 12 weeks by 43 Type 2 diabetes subjects {20 with short [S/S; GT(n) < 25] and 23 with long [L/L; GT(n) ≥ 25]}. Fasting venous blood was collected before and after each treatment. The formamidopyrimidine DNA glycosylase-assisted comet assay was used to measure DNA damage in lymphocytes. For measuring hOGG1 activity, we used photo-damaged HeLa cells incubated with lymphocyte extracts from test subjects, in combination with the comet assay. Lymphocyte HMOX-1 and hOGG1 protein concentrations and expression (mRNA) of redox-sensitive genes, including HMOX-1 and hOGG1, were also investigated. Results showed significantly (P < 0.01) lower (~15%) DNA damage, higher (~50%) hOGG1 activity and higher (~40%) HMOX-1 protein concentration after tea. No changes in mRNA expression were seen. Baseline HMOX-1 protein and hOGG1 activity were higher (P < 0.05) in the S/S group, but tea-associated responses were similar in both GT(n) groups. Green tea is clearly associated with lowered DNA damage, increased hOGG1 activity and higher HMOX-1 protein levels. Further study is needed to confirm a cause and effect relationship and to establish if these effects are mediated by post-translational changes in proteins or by increased gene expression.

Feasibility of 8-OHdG formation and hOGG1 induction in PBMCs for assessing oxidative DNA damage in the lung of COPD patients.

Oxidative stress has long been recognized to play a role in chronic obstructive pulmonary disease (COPD); however, approaches for assessing oxidative stress are lacking. The objective of this study was to address the feasibility of measuring 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-OHdG) formation and human 8-oxoguanine DNA glycosylase (hOGG1) induction in peripheral blood mononuclear cell (PBMC) to assess oxidative deoxyribonucleic acid (DNA) damage in the lung of smoking COPD patients. PBMC were obtained from 412 participants including 129 smokers with COPD, 143 healthy smokers and 140 healthy non-smokers. Lung tissue specimens and PBMC were obtained from smoker COPD (n = 12), healthy smokers (n = 12) and healthy non-smokers (n = 10). 8-OHdG and hOGG1 were detected, and correlation analysis was conducted for assessing the feasibility. Oxidative DNA damage (8-OHdG formation) along with impaired induction of hOGG1 expression in the lung was a prominent feature for smokers COPD patients. PBMC originated from smokers COPD patients also displayed similar features to that of lung tissues. Correlation analysis suggests that PBMC could be used as a surrogate for oxidative DNA damage in lung of smokers COPD patients. Indeed, 8-OHdG levels in PBMC DNA were negatively correlated with lung function, while hOGG1 induction in PBMC was associated with improved lung function in smokers COPD patients. COPD patients manifest oxidative DNA damage of 8-OHdG along with impaired hOGG1 expression in the lung, whereas 8-OHdG formation and hOGG1 induction in PBMC could be a biomarker of oxidative DNA damage in the lung.

Ferulic acid prevents ultraviolet-B radiation induced oxidative DNA damage in human dermal fibroblasts

Aim: Protective effects of ferulic acid (FA) against ultraviolet-B (290-320 nm) radiation induced cellular changes were investigated in human dermal fibroblasts (HDFa). Materials and Methods: HDFa cells pretreated with increasing concentrations of FA (0, 10, 20, 40 μg/ml) for 30 min, were UVB irradiated and different cellular and oxidative end points were analyzed. Results: The percentage of cytotoxicity, intracellular reactive oxygen species (ROS) levels, mitochondrial membrane potential, thiobarbituric acid reactive substances (TBARS) and DNA damage, were significantly increased in 19.8 mJ/cm 2 ultraviolet-B (UVB)-exposed HDFa. Further, exposure to UVB causes significantly decreased antioxidants status in HDFa cells. Treatment of HDFa cells with FA before 30 min of UVB-irradiation significantly restored mitochondrial membrane potential, ROS levels and antioxidant status in HDFa. Further, FA treatment reverted UVB-induced mutagenesis in Ames tester strains and DNA damage in HDFa. Moreover, we noticed increased expression of GADD 45α, XRCC1 and HOGG1 in UVB exposed HDFa. Conversely, FA pretreatment significantly attenuated UVB-induced expression of DNA repair genes in HDFa. Conclusion: The present findings indicate that FA act as a sunscreen rather than working at molecular level to offer photoprotection.

Effects of silver nanoparticles on oxidative DNA damage–repair as a function of p38 MAPK status: A comparative approach using human Jurkat T cells and the nematode Caenorhabditis elegans

The large-scale use of silver nanoparticles (AgNPs) has raised concerns over potential impacts on the environment and human health. We previously reported that AgNP exposure causes an increase in reactive oxygen species, DNA damage, and induction of p38 MAPK and PMK-1 in Jurkat T cells and in Caenorhabditis elegans. To elucidate the underlying mechanisms of AgNP toxicity, here we evaluate the effects of AgNPs on oxidative DNA damage-repair (in human and C. elegans DNA glycosylases hOGG1, hNTH1, NTH-1, and 8-oxo-GTPases-hMTH1, NDX-4) and explore the role of p38 MAPK and PMK-1 in this process. Our comparative approach examined viability, gene expression, and enzyme activities in wild type (WT) and p38 MAPK knock-down (KD) Jurkat T cells (in vitro) and in WT and pmk-1 loss-of-function mutant strains of C. elegans (in vivo). The results suggest that p38 MAPK/PMK-1 plays protective role against AgNP-mediated toxicity, reduced viability and greater accumulation of 8OHdG was observed in AgNP-treated KD cells, and in pmk-1 mutant worms compared with their WT counterparts, respectively. Furthermore, dose-dependent alterations in hOGG1, hMTH1, and NDX-4 expression and enzyme activity, and survival in ndx-4 mutant worms occurred following AgNP exposure. Interestingly, the absence or depletion of p38 MAPK/PMK-1 caused impaired and additive effects in AgNP-induced ndx-4(ok1003); pmk-1(RNAi) mutant survival, and hOGG1 and NDX-4 expression and enzyme activity, which may lead to higher accumulation of 8OHdG. Together, the results indicate that p38 MAPK/PMK-1 plays an important protective role in AgNP-induced oxidative DNA damage-repair which is conserved from C. elegans to humans.

The significance of the alteration of 8-OHdG in serous ovarian carcinoma

BackgroundOxidative damage and DNA repair dysfunction are associated with carcinogenesis. 8-OHdG is one of the major oxidative DNA adducts. Present work aims to investigate whether the expression of 8-OHdG and its key repair gene hOGG1 play distinctive role in two types of serous ovarian cancer.Materials and methods8-OHdG level in DNA from tumor and matched tumor-adjacent normal tissue in 48 high-grade papillary serous carcinomas (HG-SOC), 24 low-grade papillary serous carcinomas (LG-SOC), 20 serous cystadenomas, and 16 non-tumor control ovaries was tested. The Cox proportional hazards model and the log-rank test were used to assess the associations between the 8-OHdG level in two types of serous cancer and patients’ survival. Real-time polymerase chain reaction and protein immunoblot were employed to detect hOGG1 mRNA and protein levels in tumor and adjacent normal tissues. Immunohistochemistry was used to determine the expression of hOGG1 and p53.ResultsThere was no difference of average 8-OHdG/106dG DNA level either between HG-SOC (27.8 ± 8.9), LG-SOC (25.2 ± 7.4) and benign serous cystadenoma (26.5 ± 7.7, p = 0.35); or between the tumor-adjacent normal tissue of HG-SOC (18.8 ± 5.2), LG-SOC (21.4 ± 6.5), benign serous cystadenoma (20.5 ± 9.1) and non-tumor ovary (21.6 ± 4.9, p = 0.62). The 8-OHdG/106dG level was significantly higher in tumor comparing to that in matched normal tissue adjacent to carcinoma in HG-SOC (1.52 ± 0.52, p = 0.02), but not in LG-SOC or benign serous cystadenoma. Increased level of 8-OHdG in tumor DNA was an independent factor of overall survival in serous ovarian carcinoma upon multivariate analysis (p < 0.01). Increased level of 8-OHdG in tumor DNA indicates poorer overall and progression-free survival durations than counterparts (47.3 vs 105.7 months and 13.5 vs 45.3 months, respectively). Protein levels of hOGG1 were remarkably decreased in HG-SOC (p < 0.01), but not in LG-SOC and serous cystadenoma compared with the tissue adjacent to carcinoma. A positive result on p53 immunostaining was associated with lower hOGG1 expression in HG-SOC (p = 0.04).ConclusionIncreased 8-OHdG level and decreased expression of hOGG1 in tumor were found in HG-SOC but not LG-SOC. Increased 8-OHdG level in tumor DNA was significantly associated with poorer overall survival and progression-free survival in serous ovarian carcinoma.