Determination of 8-oxoguanine and 8-hydroxy-2'-deoxyguanosine in the rat cerebral cortex using microdialysis sampling and capillary electrophoresis with electrochemical detection

Changes in antioxidant status and DNA repair capacity are corroborated with molecular alterations in malignant thyroid tissue of patients with papillary thyroid cancer

Introduction: Papillary thyroid cancer (PTC) accounts for approximately 80% of all thyroid cancer cases. The mechanism of PTC tumourigenesis is not fully understood, but oxidative imbalance is thought to play a role. To gain further insight, this study evaluated antioxidant status, DNA repair capacity and genetic alterations in individuals diagnosed with benign thyroid lesion in one lobe (BTG) and PTC lesion in another. Methods: Individuals with coexisting BTG and PTC lesions in their thyroid lobes were included in this study. Reactive oxygen species (ROS) level, ABTS radical scavenging activity, ferric reducing antioxidant capacity, glutathione peroxidase and superoxide dismutase activities were measured in the thyroid tissue lysate. The expression of selected genes and proteins associated with oxidative stress defence and DNA repair were analysed through quantitative real-time PCR and Western blotting. Molecular alterations in genomic DNA were analysed through whole-exome sequencing and the potentially pathogenic driver genes filtered through Cancer-Related Analysis of Variants Toolkit (CRAVAT) analysis were subjected to pathway enrichment analysis using Metascape. Results: Significantly higher ROS level was detected in the PTC compared to the BTG lesions. The PTC lesions had significantly higher expression of GPX1, SOD2 and OGG1 but significantly lower expression of CAT and PRDX1 genes than the BTG lesions. Pathway enrichment analysis identified "regulation of MAPK cascade," "positive regulation of ERK1 and ERK2 cascade" and "negative regulation of reactive oxygen species metabolic process" to be significantly enriched in the PTC lesions only. Four pathogenic genetic variants were identified in the PTC lesions; BRAF V600E, MAP2K7-rs2145142862, BCR-rs372013175 and CD24 NM_001291737.1:p.Gln23fs while MAP3K9 and G6PD were among 11 genes that were mutated in both BTG and PTC lesions. Conclusion: Our findings provided further insight into the connection between oxidative stress, DNA damage, and genetic changes associated with BTG-to-PTC transformation. The increased oxidative DNA damage due to the heightened ROS levels could have heralded the BTG-to-PTC transformation, potentially through mutations in the genes involved in the MAPK signalling pathway and stress-activated MAPK/JNK cascade. Further in-vitro functional analyses and studies involving a larger sample size would need to be carried out to validate the findings from this pilot study.

Challenges in Quantifying 8-OHdG and 8-Isoprostane in Exhaled Breath Condensate

Exhaled breath condensate (EBC) has attracted substantial interest in the last few years, enabling the assessment of airway inflammation with a non-invasive method. Concentrations of 8-Hydroxydesoxyguanosine (8-OHdG) and 8-isoprostane in EBC have been suggested as candidate biomarkers for lung diseases associated with inflammation and oxidative stress. EBC is a diluted biological matrix and consequently, requires highly sensitive chemical analytic methods (picomolar range) for biomarker quantification. We developed a new liquid chromatography coupled to tandem mass spectrometry method to quantify 8-OHdG and 8-isoprostane in EBC simultaneously. We applied this novel biomarker method in EBC obtained from 10 healthy subjects, 7 asthmatic subjects, and 9 subjects with chronic obstructive pulmonary disease. Both biomarkers were below the limit of detection (LOD) despite the good sensitivity of the chemical analytical method (LOD = 0.5 pg/mL for 8-OHdG; 1 pg/mL for 8-isoprostane). This lack of detection might result from factors affecting EBC collections. These findings are in line with methodological concerns already raised regarding the reliability of EBC collection for quantification of 8-OHdG and 8-isoprostane. Precaution is therefore needed when comparing literature results without considering methodological issues relative to EBC collection and analysis. Loss of analyte during EBC collection procedures still needs to be resolved before using these oxidative stress biomarkers in EBC.

Construction of a damage site-specific fluorescent biosensor for single-molecule detection of DNA damage

The 8-oxoguanine (8-oxoG) represents the most common DNA damage type, and it has been regarded as the oxidative stress biomarker, but the reported 8-oxoguanine assays are limited by poor specificity and low sensitivity. Herein, we demonstrate the construction of damage site-specific fluorescent biosensor for 8-oxoG assay by integrating single-molecule detection with hyperbranched signal amplification. In this assay, the 8-oxoG damages in DNA can generate free 3' OH with the assistance of formamidopyrimidine DNA glycosylase (Fpg) and polynucleotide kinase (PNK), which subsequently triggers the incorporation of abundant Cy5-labeled dUTPs via terminal deoxynucleotidyl transferase (TDT)-mediated site-specific hyperbranched nucleic acid amplification. After digestion of amplification products with nuclease treatment, abundant mononucleotide Cy5-dUTPs are produced, which will be easily monitored via single-molecule imaging and detection. The introduction of hyperbranched nucleic acid amplification and single-molecule detection can greatly improve the sensitivity to achieve a detection limit of 7.62 × 10^-18 M. This biosensor is highly specific with the capability of discriminating 0.001% 8-oxoG target from the DNA mixture. Moreover, it can be applied for quantitative detection of 8-oxoG damage in genomic DNAs with a detection limit of 0.0017 ng, and even accurately quantifies the absolute number (7025 - 8506) of 8-oxoG damage base in single HeLa cell treated with 150 μM H₂O₂. Importantly, this biosensor can measure the 8-oxoG damage level in different cancer cell lines, facilitating the oxidative damage-associated biomedical researches and clinical diagnosis.

Lycopene Protects against Smoking-Induced Lung Cancer by Inducing Base Excision Repair

Background: Oxidative stress plays a critical role in lung cancer progression. Carotenoids are efficient antioxidants. The objective of this study was to explore the efficacy of all-trans retinoic acid (ATRA) and carotenoids in cigarette smoke-induced oxidative stress within A549 human lung cancer epithelial cells. Methods: A549 cells were pretreated with 1-nM, 10-nM, 100-nM, 1-μM and 10-μM ATRA, β-carotene (BC) and lycopene for 24 h, followed by exposure to cigarette smoke using a smoking chamber. Results: The OxyBlot analysis showed that smoking significantly increased oxidative stress, which was inhibited by lycopene at 1 nM and 10 nM (p < 0.05). In the cells exposed to smoke, lycopene increased 8-oxoguanine DNA glycosylase (OGG1) expression at 1 nM, 10 nM, 100 nM, and 1 μM (p < 0.05), but not at 10 μM. Lycopene at lower doses also improved Nei like DNA glycosylases (NEIL1, NEIL2, NEIL3), and connexin-43 (Cx43) protein levels (p < 0.05). Interestingly, lycopene at lower concentrations promoted OGG1 expression within the cells exposed to smoke to an even greater extent than the cells not exposed to smoke (p < 0.01). This may be attributed to the increased SR-B1 mRNA levels with cigarette smoke exposure (p < 0.05). Conclusions: Lycopene treatment at a lower dosage could inhibit smoke-induced oxidative stress and promote genome stability. These novel findings will shed light on the molecular mechanism of lycopene action against lung cancer.

Lipid peroxidation mediated the association of urinary 1-bromopropane metabolites with plasma glucose and the risk of diabetes: A cross-sectional study of urban adults in China

Exposure to 1-bromopropane (1-BP) has been reported to cause glutathione depletion and increase the level of oxidative damage, which play critical roles in diabetes. However, the possible associations or mechanisms of the exposure of 1-BP with the plasma glucose level and the risk of diabetes are unclear. In this study, we explored the relationships of the urinary 1-BP metabolite N-Acetyl-S-(n-propyl)-l-cysteine (BPMA) with fasting plasma glucose (FPG) levels and the risk of diabetes, and the mediating role of oxidative damage in the above relationships in 3678 urban adults from the Wuhan-Zhuhai cohort in China. We found a significant dose-response relationship between BPMA and FPG levels with a β of 0.09 (95 % CI: 0.04, 0.14). In addition, mediating effect of urinary BPMA on FPG levels was observed depending on elevated 8-isoprostane level, with a median proportion of 32.06 %. Furthermore, we observed a significant association between urinary BPMA and the risk of diabetes, with an adjusted odds ratio of 1.34 (1.18, 1.52) for all participants. These results indicated that urinary 1-BP metabolites were positively associated with FPG levels and the risk of diabetes among urban adults in this cross-sectional study. Lipid peroxidation partially mediated the association between urinary 1-BP metabolites and FPG levels.

Controlling parameters and characteristics of electrochemical biosensors for enhanced detection of 8-hydroxy-2'-deoxyguanosine

This work discusses the parameters and characteristics required on the development of a scalable and reliable electrochemical sensor board for detecting 8-hydroxy-2′-deoxyguanosine (8-OHdG), an oxidative stress biomarker for diabetic nephropathy, cancer and Parkinson’s disease. We used Printed Circuit Board (PCB) technology to make a precise, low-cost bare sensor board. ZnO nanorods (NRs) and ZnO NRs: reduced graphene oxide (RGO) composites were used as a pathway for antibody immobilization on the working electrode (WE). The parameters and characteristics of the WE were controlled for enhancing the quality of the electrochemical sensor board. Thickness of the gold and the presence of ZnO NRs or their composite on the WE have influence on charge transference process and reproducibility of the sensor board. The amount of the antibody, and its incubation period are crucial to avoid saturation of the sites during immobilization step and reduce the cost of the sensor. Our ZnO NRs-based electrochemical sensor board showed high sensitivity and selectivity to 8-OHdG with detection capacity in the range of 0.001–5.00 ng.mL⁻¹. The successful application of our immunosensor to detect 8-OHdG in urine was evidenced.

Study on the interaction between active components from traditional Chinese medicine and plasma proteins

Traditional Chinese medicine (TCM), as a unique form of natural medicine, has been used in Chinese traditional therapeutic systems over two thousand years. Active components in Chinese herbal medicine are the material basis for the prevention and treatment of diseases. Research on drug-protein binding is one of the important contents in the study of early stage clinical pharmacokinetics of drugs. Plasma protein binding study has far-reaching influence on the pharmacokinetics and pharmacodynamics of drugs and helps to understand the basic rule of drug effects. It is important to study the binding characteristics of the active components in Chinese herbal medicine with plasma proteins for the medical science and modernization of TCM. This review summarizes the common analytical methods which are used to study the active herbal components-protein binding and gives the examples to illustrate their application. Rules and influence factors of the binding between different types of active herbal components and plasma proteins are summarized in the end. Finally, a suggestion on choosing the suitable technique for different types of active herbal components is provided, and the prospect of the drug-protein binding used in the area of TCM research is also discussed.

Luminescent Device for the Detection of Oxidative Stress Biomarkers in Artificial Urine

A luminescent paper-based device for the visual detection of oxidative stress biomarkers is reported. The device consists of a polyvinylidene fluoride membrane impregnated with poly(3-alkoxy-4-methylthiophene) (PT) for colorimetric detection. 8-hydroxy-2'-deoxyguanosine (8-OHdG), a biomarker associated with oxidative stress, is used as a model system for validating the proposed methodology. The detection strategy is based on monitoring the changes in optical properties of PT associated with its conformational changes upon interaction with an aptamer in the presence and in the absence of 8-OHdG. Fluorometric and colorimetric monitoring revealed linear responses for 8-OHdG concentrations between 50 pM and 500 nM (∼14 pg/mL to 140 ng/mL), with limits of detection of ∼300 pM and  ∼350 pM, respectively for ( n = 3). Colorimetric responses in artificial urine ascertained rapid, sensitive, and selective detection of 8-OHdG at clinically relevant (pM to nM) concentration levels. Furthermore, the proposed methodology enables point-of-care diagnostics for oxidative stress without requiring sophisticated instrumentation.

8-hydroxy-2'-deoxyguanosine (8-OHdG) biomarker detection down to picoMolar level on a plastic antibody film

An innovative biosensor assembly relying on a simple and straightforward in-situ construction is presented to monitor urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) down to the pmol/L level. The sensing film of the biosensor consisted of a molecularly imprinted polymer (MIP) layer for 8-OHdG assembled on a gold electrode through electropolymerization of monomer combined with the template. The analytical features of the resulting biosensor were assessed by Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). Some experimental parameters such as the initial concentration of the monomer and the ratio template-monomer were investigated and optimized in order to finely tune the performance of the MIP-based sensor. Under optimal conditions, the developed biosensor was able to rebind 8-OHdG with a linear response against EIS from 0.1 to 100pg/ml 3.5-3500 pM. The interference of coexisting species was tested, also with calibrations on urine samples, and good selectivity towards 8-OHdG was obtained. RAMAN spectroscopy, FTIR and SEM evaluations of the prepared films confirmed the formation of a polyphenol thin-film on the electrode surface. The presence and distribution of the imprinted cavities on the MIP layer was confirmed by confocal microscopy imaging of the film, after a post-treatment with Fluorescein Isothiocyanate (FITC) labeled 8-OHdG antibody. Overall, this label-free biosensor for urinary 8-OHdG detection constitutes a promising low-cost alternative to the conventional immunoassay approaches, due to its simplicity, stability, high sensitivity and selectivity for biological sample assays, opening new doors for other applications.

Improvement of derivatized amino acid detection sensitivity in micellar electrokinetic capillary chromatography by means of acid-induced pH-mediated stacking technique

Derivatization is a frequently used sample preparation procedure applicable to the enhancement of analyte detection sensitivity. Amino acids mostly require derivatization prior to electrophoretic or chromatographic analysis, especially if spectrophotometric detection is used. This study presents an on-line preconcentration technique for derivatized amino acids. The sensitivity of the method was improved by the utilization of the proposed acid-induced pH-mediated stacking mechanism. The method is demonstrated by preconcentration of amino acids labeled with 2,4-dinitrofluorobenzene. Use of optimized conditions for a large sample volume injection (40 s, 13.8 kPa) followed by electrokinetic injection of 0.1 M HCl (20 s, 10 kV) gave a 20- to 30-fold enhancement of sensitivity. The significance of the sweeping mechanism and pseudo-isotachophoresis for the on-line sample focusing and the influence of parameters on the preconcentration process were discussed. The applicability of the elaborated method was demonstrated using human urine samples.

Concentrations of urinary 8-hydroxy-2'-deoxyguanosine and 8-isoprostane in women exposed to woodsmoke in a cookstove intervention study in San Marcos, Peru

Nearly half of the world's population is exposed to household air pollution (HAP) due to long hours spent in close proximity to unvented cooking fires. The effect of woodsmoke exposure on oxidative stress was examined by investigating the association between woodsmoke exposure and biomarkers of DNA oxidation (8-hydroxy-2'-deoxyguanosine [8-OHdG]) and lipid peroxidation (8-isoprostane) among control and intervention stove users. HAP exposure assessment was conducted within the framework of a community-randomized controlled trial of 51 communities in San Marcos Province, Cajamarca Region, Peru. The first morning urine voids after 48h HAP exposure assessment from a subset of 45 control and 39 intervention stove users were analyzed for 8-OHdG and 8-isoprostane. General linear models and correlation analyses were performed. Urinary oxidative stress biomarkers ranged from 11.2 to 2270.0μg/g creatinine (median: 132.6μg/g creatinine) for 8-OHdG and from 0.1 to 4.5μg/g creatinine (median: 0.8μg/g creatinine) for 8-isoprostane among all study subjects (n=84). After controlling for the effects of traffic in the community and eating food exposed to fire among all subjects, cooking time was weakly, but positively associated with urinary 8-OHdG (r=0.29, p=0.01, n=80). Subjects' real-time personal CO exposures were negatively associated with 8-OHdG, particularly the maximum 30-second CO exposure during the sampling period (r=-0.32, p=0.001, n=73). 48h time integrated personal PM2.5 was negatively, but marginally associated with urinary 8-isoprostane (r=-0.21, p=0.09, n=69) after controlling for the effect of distance of homes to the road. Urinary 8-isoprostane levels reported in the available literature are comparable to results found in the current study. However there were relatively high levels of urinary 8-OHdG compared to data in the available literature for 8-OHdG excretion. Results suggest a sustained systemic oxidative stress among these Peruvian women chronically exposed to wood smoke.

Structural context effects in the oxidation of 8-oxo-7,8-dihydro-2'-deoxyguanosine to hydantoin products: electrostatics, base stacking, and base pairing

8-Oxo-7,8-dihydroguanine (OG) is the most common base damage found in cells, where it resides in many structural contexts, including the nucleotide pool, single-stranded DNA at transcription forks and replication bubbles, and duplex DNA base-paired with either adenine (A) or cytosine (C). OG is prone to further oxidation to the highly mutagenic hydantoin products spiroiminodihydantoin (Sp) and 5-guanidinohydantoin (Gh) in a sharply pH-dependent fashion within nucleosides. In the present work, studies were conducted to determine how the structural context affects OG oxidation to the hydantoins. These studies revealed a trend in which the Sp yield was greatest in unencumbered contexts, such as nucleosides, while the Gh yield increased in oligodeoxynucleotide (ODN) contexts or at reduced pH. Oxidation of oligomers containing hydrogen-bond modulators (2,6-diaminopurine, N(4)-ethylcytidine) or alteration of the reaction conditions (pH, temperature, and salt) identify base stacking, electrostatics, and base pairing as the drivers of the key intermediate 5-hydroxy-8-oxo-7,8-dihydroguanine (5-HO-OG) partitioning along the two hydantoin pathways, allowing us to propose a mechanism for the observed base-pairing effects. Moreover, these structural effects cause an increase in the effective pK(a) of 5-HO-OG, following an increasing trend from 5.7 in nucleosides to 7.7 in a duplex bearing an OG·C base pair, which supports the context-dependent product yields. The high yield of Gh in ODNs underscores the importance of further study on this lesion. The structural context of OG also determined its relative reactivity toward oxidation, for which the OG·A base pair is ~2.5-fold more reactive than an OG·C base pair, and with the weak one-electron oxidant ferricyanide, the OG nucleoside reactivity is >6000-fold greater than that of OG·C in a duplex, leading to the conclusion that OG in the nucleoside pool should act as a protective agent for OG in the genome.

Prevention of DNA damage in renal transplantation by losartan and enalapril: the role of renin-angiotensin system polymorphisms

BACKGROUND

In this study the effect of losartan and enalapril on the reduction of DNA damage was evaluated in regard to renin-angiotensin system (RAS) polymorphisms.

METHODS

After determination of genotypes of RAS polymorphism by PCR, 64 renal transplant recipients were randomly allocated to one of four groups: the first and second groups were treated with E (E+: 10 mg/day) and L (L+: 50 mg/day) alone, respectively. The third group received E+L (E+L+: 10 + 50 mg/day), and the forth group received no medication (E-L-). The subjects were followed for 8 weeks. After a 2-week washout period, the E group changed to L and vice versa as a cross-over design. They were followed for another 8 weeks. Before and after treatment, we checked 8-OHdG and malondialdehyde (MDA) as biomarkers of DNA damage and lipid peroxidation, respectively.

RESULTS

8-OHdG levels were significantly decreased after treatment in the E+L+ and L+ groups (P < 0.001, P = 0.001, respectively). Only the TT genotype of AGT had the most antioxidative role regarding the treatment (P = 0.01). We found a remarkable correlation between MDA and DNA damage levels before and after intervention (r = 0.48, P < 0.001; r = 0.35, P = 0.006).

CONCLUSION

The protective effects of L+ and E+L+ on DNA breaks are surprising regarding the RAS polymorphisms.

Time-resolved microdialysis for in vivo neurochemical measurements and other applications

Monitoring changes in chemical concentrations over time in complex environments is typically performed using sensors and spectroscopic techniques. Another approach is to couple sampling methods, such as microdialysis, with chromatographic, electrophoretic, or enzymatic assays. Recent advances of such coupling have enabled improvements in temporal resolution, multianalyte capability, and automation. In a sampling and analysis method, the temporal resolution is set by the mass sensitivity of the analytical method, analysis time, and zone dispersion during sampling. Coupling methods with high speed and mass sensitivity to microdialysis sampling help to reduce some of these contributions to yield methods with temporal resolution of seconds. These advances have been primarily used in monitoring neurotransmitters in vivo. This review covers the problems associated with chemical monitoring in the brain, recent advances in using microdialysis for time-resolved in vivo measurements, sample applications, and other potential applications of the technology such as determining reaction kinetics and process monitoring.

Chromatographic and electrophoretic methods for the analysis of biomarkers of oxidative damage to macromolecules (DNA, lipids, and proteins)

Free radicals and other reactive species can cause oxidative damage to biomolecules when oxidant species exceed the antioxidant defences in the body, resulting in oxidative stress. Oxidatively damaged products have been associated with aging as well as with the development of pathologies like cancer, cardiovascular disease, neurodegenerative disorders, diabetes, inflammation, etc. Reliable measurements of biomarkers of oxidative damage to macromolecules would afford information on the pre-disposition and prognosis of certain pathologies, being of utmost importance in evaluation of the effect of intervention with antioxidants on the incidence of diseases associated to oxidative stress. This review will present and compare different analytical methods, especially those involving chromatographic and electrophoretic techniques, commonly used for the analysis of biomarkers of oxidative damage to the three main macromolecules, namely oxidised DNA, lipid peroxidation products, and protein carbonyls.

Contemporary sample stacking in CE: A sophisticated tool based on simple principles

Sample stacking is a general term for methods in CE which are used for on-line concentration of diluted analytes. During the stacking process, analytes present at low concentrations in a long injected sample zone are concentrated into a short zone (stack). The stacked analytes are then separated and individual zones are detected. Thus stacking provides better separation efficiency and detection sensitivity. Many papers have been published on stacking till now, various procedures have been described, and, many names have been proposed for stacking procedures utilizing the same principles. This contribution brings an easy and unified view on stacking, describes the basic principles utilized, makes a list of recognized operational principles and brings an overview of principal current procedures. Further, it surveys selected recent practical applications ordered according to their operational principles and includes the terms, nicknames, and acronyms used for these actual stacking procedures. This contribution may help both newcomers and experts in the field of CE to orient themselves in the already quite complex topic of sample stacking.