8-Hydroxy-2’-deoxyguanosine as a biomarker of oxidative stress in acute exacerbation of chronic obstructive pulmonary disease

Diurnal Variation of 8-hydroxy-2'-deoxyguanosine in Continuous Time Series of Two Breast Cancer Survivors

8-hydroxy-2'deoxyguanosine (8-OHdG) is an oxidative product removed from DNA following radical oxygen species-induced damage. As a water-soluble molecule, it can be measured non-invasively in urine and is commonly used as a marker for 'whole-body' oxidative stress. However, its validity and reliability in assessing oxidative stress across various chronic diseases and in early carcinogenesis screening in clinical diagnosis and research remain subjects of debate. To determine optimal measurement timing and duration, it is essential to establish the circadian profile of 8-OHdG under everyday life conditions. Here, applying the integrative single-case design, we show the presence of day-night differences for 8-OHdG in continuous time series of two breast cancer survivors while considering different correction approaches. The participants sampled their urine in 12-h-pooled collections over one month. In both subjects, 8-OHdG levels were significantly higher during the day than at night regardless of whether they were corrected by creatinine or urine volume (creatinine corrected: t = -6.43, p < 0.01 [subject 1], t = -2.69, p = 0.01 [subject 2]; volume corrected: t = -7.30, p < 0.01 [subject 1], t = -3.69, p < 0.01 [subject 2]). Notably, urinary 8-OHdG levels show higher variability in night samples compared to day samples. These findings underscore the importance of considering daily fluctuations in 8-OHdG levels in both clinical and research studies, as well as the need to account for the dynamic characteristics of stress markers to minimize the risk of inconsistent or misleading results in clinical diagnostics.

Identification of Oxidative Stress-Associated Biomarkers in Chronic Obstructive Pulmonary Disease: An Integrated Bioinformatics Analysis

Purpose

Chronic obstructive pulmonary disease (COPD) is among the three leading causes of death worldwide, with its prevalence, morbidity, and mortality rates increasing annually. Oxidative stress (OS) is a key mechanism in COPD development, making the identification of OS-related biomarkers beneficial for improving its diagnosis and treatment.

Methods

The genetic data from patients with COPD and controls were obtained from the Gene Expression Omnibus database to identify OS-related genes (OSRGs). Functional enrichment analysis was conducted using the Kyoto encyclopedia of genes and genomes signaling pathway and gene ontology (GO). Protein-protein interaction networks were constructed to identify the core genes, which were further evaluated using receiver operating characteristic (ROC) curves. Diagnostic models were developed based on the core genes. Besides, the correlation between the expression of the core genes and the immune cells was analyzed using single-sample gene set enrichment analysis. Drug-gene interactions were explored to predict target drugs, and related microribonucleic acid (miRNA) and transcription factors (TFs) were identified using miRNet.

Results

In this study, we identified 299 differential genes, including 16 OSRGs. Among these, five core genes-heat shock protein family A (Hsp70) member 1A (HSPA1A), glutamate-cysteine ligase modifier subunit, interleukin-1 beta (IL-1β), intercellular adhesion molecule 1 (ICAM1), and glutamate-cysteine ligase catalytic subunit (GCLC)-were screened and validated using ROC curve analysis. The results of GO enrichment analysis were mainly focused on the OS response, the negative regulation of the exogenous apoptosis signaling pathway, and the regulation of the apoptosis signaling pathway. Additionally, 33 target drugs were predicted, including ofloxacin, cisplatin, and pegolimumab, among others. Meanwhile, the regulatory networks comprising 33 miRNAs related to the core genes and 38 TFs associated with HSPA1A, IL-1β, ICAM1, and GCLC were constructed. A diagnostic model based on the five genes was constructed and validated with an area under the curve of 0.981 (95% confidence interval: 0.941-1.000).

Conclusion

This study identifies potential biomarkers for diagnosing COPD, new potential targets, and new directions for drug development and treatment.

Implications of DNA damage in chronic lung disease

DNA plays an indispensable role in ensuring the perpetuation of life and safeguarding the genetic stability of living organisms. The emergence of diseases linked to a wide spectrum of responses to DNA damage has garnered increasing attention within the scientific community. There is growing evidence that patterns of DNA damage response in the lungs are associated with the onset, progression, and treatment of chronic lung diseases such as chronic obstructive pulmonary disease (COPD), asthma, and bronchopulmonary dysplasia (BPD). Currently, some studies have analyzed the mechanisms by which environmental factors induce lung DNA damage. In this article, we summarize inducible factors of lung DNA damage, current indicators, and methods for diagnosing DNA damage in chronic lung diseases and explore repair mechanisms after DNA damage including nonhomologous end-joining and homology-directed repair end joining pathways. Additionally, drug treatments that may reduce DNA damage or promote repair after it occurs in the lungs are briefly described. In general, more accurate assessment of the degree of lung DNA damage caused by various factors is needed to further elucidate the mechanism of lung DNA damage and repair after damage, so as to search for potential therapeutic targets.

Evaluation of inflammatory biomarkers and vitamins in hospitalized patients with SARS-CoV-2 infection and post-COVID syndrome

OBJECTIVES

Concentrations of neopterin, kynurenine and kynurenine/tryptophan ratios predict prognosis and the need for oxygen therapy in patients hospitalized for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. The aims of the present study were to evaluate the changes of these biomarkers early in the course of infection, the association with the prior coronavirus disease (COVID-19) vaccination and therapeutic administration of Anti-SARS-CoV-2 monoclonal antibodies, investigation of other potential biomarkers including neuropilin, 8-hydroxy-2-deoxyguanosine and 8-hydroxyguanosine in patients hospitalized with SARS-CoV-2 infection and an assessment of these biomarkers and vitamins A, E and D in patients with post-COVID syndrome.

METHODS

Urine and blood samples were obtained on the 1st to the 4th day and 4th to 7th day from 108 patients hospitalized with COVID-19. Chromatography tandem mass spectrometry methods were used to analyse neopterin, kynurenine, tryptophan, liposoluble vitamins, and DNA damage biomarkers.

RESULTS

A statistically significant decrease of neopterin, kynurenine and kynurenine/tryptophan ratios was observed on after 4th to 7th day of hospitalization, and concentrations of these biomarkers were increased in patients with poor prognosis and subsequent post-COVID syndrome. The concentrations of remaining biomarker and vitamins were not associated with outcomes, although markedly decreased concentrations of vitamin A, E and D were noted.

CONCLUSIONS

The concentrations of neopterin, kynurenine and kynurenine/tryptophan ratios decrease during the course of infection SARS-CoV-2 and are associated with the post-COVID syndrome. No other prognostic biomarkers were identified.

Impact of Particulate Matter Exposure and Aerobic Exercise on Circulating Biomarkers of Oxidative Stress, Antioxidant Status, and Inflammation in Young and Aged Mice

Exposure to particulate matter (PM) and exercise training can have antagonistic effects on inflammatory responses and the balance between pro-oxidants and antioxidants in the body. However, the underlying mechanisms of these effects remain unclear. This study aimed to investigate the effects of PM exposure and aerobic exercise training on oxidative stress, antioxidant status, and inflammation in mice of different ages. Two groups of male C57BL/6 mice, comprising forty 1-month-old and forty 12-month-old mice, were exposed to either PM or exercise training or both for 8 weeks. PM exposure led to significantly higher 8-hydroxydeoxyguanosine (8-OHdG), malondialdehyde (MDA), interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor α (TNF-α) levels (p < 0.05) and significantly lower superoxide dismutase (SOD) and catalase (CAT) activities (p < 0.05) in both age groups exposed to PM compared to the control groups. Conversely, aerobic exercise training led to significantly lower 8-OHdG, MDA, IL-1β, IL-6, and TNF-α levels (p < 0.05) and significantly higher SOD and CAT activities (p < 0.05) in both age groups receiving exercise training, compared to those exposed to PM. Moreover, young mice in the exercise training and PM group showed significantly lower 8-OHdG, MDA, and IL-1β levels (p < 0.05) and significantly higher SOD and CAT activities (p < 0.05) than young mice in the PM exposure group. However, these levels did not vary significantly between the group of old mice that either received exercise training or exposure to PM. Our results suggest that while PM exposure could cause pro-oxidant/antioxidant imbalances and inflammatory responses, regular aerobic exercise could ameliorate these negative effects, although these vary with age. Nevertheless, the antioxidant and anti-inflammatory effects of exercise were countered by PM exposure, especially in older mice.

Carbon disulfide exposure induced lung function reduction partly through oxidative protein damage: A cross-sectional and longitudinal analysis

Carbon disulfide (CS₂) exposure has been associated with lung function reduction in occupational population. However, evidence on the general population with relatively low CS₂ exposure is lacking and the mechanism involved remains largely unknown. Urinary CS₂ metabolite (2-mercaptothiazolidine-4-carboxylic acid, TTCA) and lung function were determined in the urban adults from the Wuhan-Zhuhai cohort at baseline in 2011-2012 and were repeated every 3 years. Cross-sectional and longitudinal associations between TTCA and lung function were estimated using linear mixed models. Inflammation and oxidative damage biomarkers in blood/urine were measured to evaluate their potential mediating roles involved. Cross-sectionally, participants in the highest quartile of TTCA level showed a 0.64% reduction in FEV₁/FVC and a -308.22 mL/s reduction in PEF, compared to those in the lowest quartile. Longitudinally, participants with consistently high TTCA level had annually -90.27 mL/s decline in PEF, compared to those with consistently low TTCA level. Mediation analysis revealed that plasma protein carbonyl mediated 49.89% and 22.10% of TTCA-associated FEV₁/FVC and PEF reductions, respectively. Conclusively, there was a cross-sectional and longitudinal association between CS₂ exposure and lung function reduction in the general urban adults, and protein carbonylation (oxidative protein damage) partly mediated lung function reduction from CS₂ exposure.

A biochemical and histology experimental approach to investigate the adverse effect of chronic lead acetate and dietary furan on rat lungs

Despite lead widespread environmental pollution, its effect on humans and livestock's respiratory systems remains inadequately investigated. Similarly, furan is industrially relevant with enormous environmental presence. Lead and furan can be ingested -via lead pipes contaminated water and heat-treated food respectively. Thus, humans are inadvertently exposed continuously. Lead toxicity is well studied, and furan have earned a position on the IARC's list of carcinogens. Here, we evaluate the effect of co-exposure to lead and furan on rat lungs. Thirty Wistar rats were grouped randomly into six cohorts (n = 6) consisting of a control group, furan alone group, lead acetate (PbAc) alone group and three other groups co-exposure to graded PbAc (1, 10 & 100 µg/L) alongside a constant furan (8 mg/kg) dose. After twenty-eight days, enzymatic and non-enzymatic antioxidant, oxidative stress and inflammatory biomarkers were biochemically evaluated. The ELISA-based technique was used to measure oxidative-DNA damage (8-OHG), tumour protein 53 (TP53) expressed and tumour necrotic factor-alpha (TNF-α) level. Dose-dependent increases (p < 0.05) in reactive oxygen and nitrogen species, malondialdehyde, nitric oxide, myeloperoxidase, TNF-α and TP53 level, with an associated decrease (p < 0.05) in enzymatic and non-enzymatic antioxidants were observed in the furan, PbAc and the co-treated rats relative to the control. In addition, PbAc and furan treatment impaired the histoarchitectural structures of rat lungs, exemplified by pro-inflammatory cell infiltration and trafficking into the bronchioles and alveolar spaces. Co-exposure to furan and PbAc may contribute to lung dysfunction via loss of redox balance, genomic damage/instability, inflammation and disrupted histoarchitectural features.

Cross-sectional and longitudinal relationships between urinary 1-bromopropane metabolite and pulmonary function and underlying role of oxidative damage among urban adults in the Wuhan-Zhuhai cohort in China

1-bromopropane is a US Environmental Protection Agency-identified significant hazardous air pollutant with concerned adverse respiratory effect. We aimed to investigate the relationship between 1-bromopropane exposure and pulmonary function and the underlying role of oxidative damage, which all remain unknown. Pulmonary function and urinary biomarkers of 1-bromopropane exposure (N-Acetyl-S-(n-propyl)-L-cysteine, BPMA) and oxidative damage to DNA (8-hydroxy-deoxyguanosine, 8-OHdG) and lipid (8-iso-prostaglandin-F2α, 8-iso-PGF2α) were measured for 3259 Chinese urban adults from the Wuhan-Zhuhai cohort. The cross-sectional relationship of BPMA with pulmonary function and the joint relationship of BPMA and 8-OHdG or 8-iso-PGF2α with pulmonary function were investigated by linear mixed models. The mediating roles of 8-OHdG and 8-iso-PGF2α were evaluated by mediation analysis. Additionally, a panel of 138 subjects was randomly convened from the same cohort to evaluate the stability of BPMA repeatedly measured in urine samples collected over consecutive three days and intervals of one, two, and three years, and to estimate the longitudinal relationship of BPMA with pulmonary function change in three years. We found each 3-fold increase in BPMA was cross-sectionally related to FVC and FEV₁ reductions by 29.88-mL and 25.67-mL, respectively (all P < 0.05). Joint relationship of BPMA and 8-OHdG rather than 8-iso-PGF2α with reduced pulmonary function was observed. Moreover, 8-OHdG significantly mediated 9.44% of the BPMA-related FVC reduction. Findings from the panel revealed a fair to excellent stability (intraclass correlation coefficient: 0.43-0.79) of BPMA in repeated urines collected over a period of three years. Besides, BPMA was longitudinally related to pulmonary function reduction in three years: compared with subjects with persistently low BPMA level, those with persistently high BPMA level had 79.08-mL/year and 49.80-mL/year declines in FVC and FEV₁, respectively (all P < 0.05). Conclusively, 1-bromopropane exposure might impair pulmonary function of urban adult population, and oxidative DNA damage might be a potential mechanism underlying 1-bromopropane impairing pulmonary function especially FVC.

Graphene-Based Biosensors for Molecular Chronic Inflammatory Disease Biomarker Detection

Chronic inflammatory diseases, such as cancer, diabetes mellitus, stroke, ischemic heart diseases, neurodegenerative conditions, and COVID-19 have had a high number of deaths worldwide in recent years. The accurate detection of the biomarkers for chronic inflammatory diseases can significantly improve diagnosis, as well as therapy and clinical care in patients. Graphene derivative materials (GDMs), such as pristine graphene (G), graphene oxide (GO), and reduced graphene oxide (rGO), have shown tremendous benefits for biosensing and in the development of novel biosensor devices. GDMs exhibit excellent chemical, electrical and mechanical properties, good biocompatibility, and the facility of surface modification for biomolecular recognition, opening new opportunities for simple, accurate, and sensitive detection of biomarkers. This review shows the recent advances, properties, and potentialities of GDMs for developing robust biosensors. We show the main electrochemical and optical-sensing methods based on GDMs, as well as their design and manufacture in order to integrate them into robust, wearable, remote, and smart biosensors devices. We also describe the current application of such methods and technologies for the biosensing of chronic disease biomarkers. We also describe the current application of such methods and technologies for the biosensing of chronic disease biomarkers with improved sensitivity, reaching limits of detection from the nano to atto range concentration.

Aconitine induces autophagy via activating oxidative DNA damage-mediated AMPK/ULK1 signaling pathway in H9c2 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Aconitum species, with a medicinal history of 2000 years, was traditionally used in the treatment of rheumatism, arthritis, bruises, and pains. However, many studies have reported that Aconitum species can cause arrhythmia in experimental animals, resulting in myocardial fibrosis and cardiomyocyte damage. Cardiotoxicity is the main toxic effect of aconitine, but the detailed mechanism remains unclear.

AIM OF THE STUDY

This study aimed to explore the effects and underlying mechanism of autophagy in H9c2 cardiomyocytes induced by aconitine.

MATERIALS AND METHODS

H9c2 cells were incubated with different concentrations of aconitine for 24 h, and the intervention sections were pretreated with various inhibitors for 1 h. The effects of aconitine on the oxidative DNA damage, autophagy and viability of H9c2 cells were evaluated by flow cytometry, confocal microscopy, enzyme-linked immunosorbent assay and Western blot.

RESULTS

In H9c2 cells, the cell viability declined, LDH release rate, the number of autophagosomes, protein expression levels of LC3 and Beclin-1 increased significantly after 24 h of aconitine incubation. The pretreatment of autophagy inhibitor 3-MA decreased markedly autophagosomes and protein expression levels of LC3 and Beclin-1, which suggested that aconitine could induce cell autophagy. The significant increase of ROS and 8-OHdG showed that aconitine could cause oxidative DNA damage through ROS accumulation. Meanwhile, treatment of aconitine dramatically increased AMPK^Thr172 and ULK1^Ser317 phosphorylation, and Compound C inhibited AMPK^Thr172 and ULK1^Ser317 phosphorylation, which proved that aconitine induced autophagy via AMPK activation mediated ULK1 phosphorylation. Antioxidant NAC significantly reduced LDH, ROS and 8-OHdG, inhibited the phosphorylation of AMPK^Thr172 and ULK1^Ser317, and down-regulated autophagosomes and proteins expression levels of LC3 and Beclin-1. Consequently, the inhibition of oxidative DNA damage and AMPK/ULK1 signaling pathway alleviated the aconitine-induced autophagic death of H9c2 cells.

CONCLUSIONS

These results showed that aconitine induces autophagy of H9c2 cardiomyocytes by activating AMPK/ULK1 signaling pathway mediated by oxidative DNA damage. The autophagy induced by aconitine in cardiomyocytes is dependent on the activation of the AMPK pathway, which may provide novel insights into the prevention of aconitine-related toxicity.

Novel pharmacological strategies to treat cognitive dysfunction in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a major incurable global health burden and currently the 3rd largest cause of death in the world, with approximately 3.23 million deaths per year. Globally, the financial burden of COPD is approximately €82 billion per year and causes substantial morbidity and mortality. Importantly, much of the disease burden and health care utilisation in COPD is associated with the management of its comorbidities and viral and bacterial-induced acute exacerbations (AECOPD). Recent clinical studies have shown that cognitive dysfunction is present in up to 60% of people with COPD, with impairments in executive function, memory, and attention, impacting on important outcomes such as quality of life, hospitalisation and survival. The high prevalence of cognitive dysfunction in COPD may also help explain the insufficient adherence to therapeutic plans and strategies, thus worsening disease progression in people with COPD. However, the mechanisms underlying the impaired neuropathology and cognition in COPD remain largely unknown. In this review, we propose that the observed pulmonary oxidative burden and inflammatory response of people with COPD 'spills over' into the systemic circulation, resulting in damage to the brain and leading to cognitive dysfunction. As such, drugs targeting the lungs and comorbidities concurrently represent an exciting and unique therapeutic opportunity to treat COPD and cognitive impairments, which may lead to the production of novel targets to prevent and reverse the debilitating and life-threatening effects of cognitive dysfunction in COPD.

Investigation the levels of endotoxin and 8-hydroxy-2'-deoxyguanosine in sera of patients with Helicobacter pylori-positive peptic ulcer

BACKGROUND

Peptic ulcer is considered an important public health problem and generally associated with complicated conditions such as bleeding and perforation. The aim of this study is to reflect the rate of oxidative damage in the body among dyspeptic patients with Helicobacter pylori-positive peptic ulcer by measuring 8-hydroxy-2'-deoxyguanosine (8-OHdG) level in serum samples and its association with the level of bacterial endotoxin.

METHODS

Patients referred to Harran University Gastroenterology Outpatient Clinic with dyspeptic complaints were enrolled in this study. According to gastrointestinal endoscopy findings, 43 dyspeptic patients with H pylori-positive peptic ulcer patients and 43 healthy volunteers were included in this study. Infection with H pylori was diagnosed by H pylori urea breath and stool antigen tests. Serum 8-OHdG and endotoxins were measured by ELISA.

RESULTS

A total of 43 dyspeptic patients with peptic ulcer (13 women and 30 men) and 43 healthy individuals (16 women and 27 men) were enrolled in the study. In biopsies taken endoscopically, H pylori severity was mild in 19 patients (43.9%), moderate in 21 patients (48.5%) and severe in 3 patients (7.6%). 8-OHdG was compared with the healthy and patient group. It was observed that there was a statistically significant difference (P < .01). In addition, a weak correlation was found between OHdG and bacterial endotoxin.

CONCLUSION

Serum 8-OHdG and endotoxin levels are only weakly associated implying that they reflect specific aspects of oxidative damage. Helicobacter pylori and its endotoxin have a significant role in peptic ulcer pathogenesis. The detection of serum 8-OHdG in dyspeptic patients may be used as a biomarker for the presence of peptic ulcers.

Effect of tiger milk mushroom (Lignosus rhinocerus) supplementation on respiratory health, immunity and antioxidant status: an open-label prospective study

Tiger milk mushroom (TMM; Lignosus rhinocerus) have been used for a long time by indigenous communities in South East Asia regions as traditional medicine for different ailments, including respiratory disorders. The beneficial effects of TMM have been proven through in vivo and in vitro models, but these effects have yet to be validated in a clinical study. In this study, the beneficial effects of TMM supplementation were investigated in 50 voluntary participants. Participants were required to take 300 mg of TMM twice daily for three months. Level of interleukin 1β (IL-1β), interleukin 8 (IL-8), immunoglobulin A (IgA), total antioxidant capacity, malondialdehyde (MDA), 3-nitrotyrosine (3-NT), 8-hydroxydeoxyguanosine (8-OHdG), pulmonary function and respiratory symptoms were assessed during baseline and monthly follow-up visits. Results demonstrated that supplementation of TMM significantly (p < 0.05) suppressed the level of IL-1β, IL-8, MDA, as well as respiratory symptoms. In additional to that, TMM also significantly (p < 0.05) induced the level of IgA, total antioxidant capacity, as well as pulmonary function. Analyses of data indicated that gender and BMI were factors influencing the outcomes of antioxidant status. Collectively, our findings suggested that TMM supplementation effectively improves respiratory health, immunity and antioxidant status.

Oxidative Stress Biomarkers in Chronic Obstructive Pulmonary Disease Exacerbations: A Systematic Review

Background: Chronic Obstructive Pulmonary Disease (COPD) is a progressive disease characterized by a not fully reversible airflow limitation associated with an abnormal inflammatory response. Exacerbations of COPD are of major importance in the acceleration of disease progression, in healthcare costs, and negatively affect the patient’s quality of life. Exacerbations are characterized by a further increase in the airway inflammation likely driven by oxidative stress. In order to deepen the knowledge about this topic, several studies have focused on oxidative stress biomarkers levels. This review summarizes the literature findings about oxidative stress biomarkers in exacerbated COPD patients compared to ones in the stable state. Methods: a systematic search in electronic databases Pubmed, Web of Science, Scopus and Google Scholar from inception to January 2021, was conducted using the terms: “oxidative stress”, “chronic obstructive pulmonary disease” or “COPD”, “exacerbation”. Results: 23 studies were selected for the systematic review. They showed the presence of an imbalance between oxidant and antioxidant molecules in favor of the former in exacerbation of COPD. Conclusions: future studies using standardized methods in better characterized population are needed. However, this review suggests that targeting oxidative stress could be useful in monitoring the disease progression in COPD patients and especially in those more susceptible to exacerbations.

Personal PM2.5 exposure and lung function: Potential mediating role of systematic inflammation and oxidative damage in urban adults from the general population

BACKGROUND

Short-term effects of fine particulate matter (PM_2.5) exposure on lung function have been reported. However, few studies have assessed PM_2.5 exposure on the personal level, and the mechanism underlying the effects of PM_2.5 exposure on lung function remains less clear.

OBJECTIVES

To evaluate the association between personal PM_2.5 exposure and lung function alteration in general population and to explore the roles of systematic inflammation and oxidative damage in this association.

METHODS

A total of 7685 lung function tests were completed among 4697 urban adults in Wuhan, China. Plasma C-reactive protein (CRP), urinary 8-iso-prostaglandin-F_2α (8-iso-PGF_2α) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels were measured. Personal PM_2.5 exposure levels were estimated using an estimation model from the actual measurements of individual PM_2.5 levels in 191 participants. Mixed linear models were used to evaluate the association between personal PM_2.5 exposure and lung function. Mediation analyses were conducted to investigate the roles of CRP, 8-iso-PGF_2α and 8-OHdG in above associations.

RESULTS

After adjusting for confounders, each 10 μg/m³ increase in the previous-day personal PM_2.5 exposure was associated with 2.94 mL, 2.02 mL and 16.14 mL/s decreases in forced vital capacity (FVC), forced expiration volume in 1 s (FEV₁) and peak expiratory flow, respectively. The associations were more obvious among never smokers compared with current smokers. Cumulative 7-day exposure to PM_2.5 led to the strongest adverse effects on lung function. Among never smokers with high PM_2.5 exposure levels, a positive relationship was observed between personal PM_2.5 level and urinary 8-iso-PGF_2α, and 8-iso-PGF_2α meditated 4.69% and 12.30% of the association between the 7-day moving PM_2.5 concentration and FVC and FEV₁, respectively. We did not observe a significant positive association between PM_2.5 exposure and plasma CRP or urinary 8-OHdG.

CONCLUSION

Short-term personal exposure to PM_2.5 is associated with reduced pulmonary ventilation function. Urinary 8-iso-PGF_2α partly mediates these associations.

Oxidative and Nitrosative Stress in the Pathogenesis of Obstructive Lung Diseases of Increasing Severity

The imbalance between increased oxidative agents and antioxidant defence mechanisms is central in the pathogenesis of obstructive lung diseases such as asthma and COPD. In these patients, there are increased levels of reactive oxygen species. Superoxide anions (O₂ -), Hydrogen Peroxide (H₂O₂) and hydroxyl radicals (•OH) are critical for the formation of further cytotoxic radicals in the bronchi and lung parenchyma. Chronic inflammation, partly induced by oxidative stress, can further increase the oxidant burden through activated phagocytic cells (neutrophils, eosinophils, macrophages), particularly in severer disease states. Antioxidants and anti-inflammatory genes are, in fact, frequently downregulated in diseased patients. Nrf2, which activates the Antioxidant Response Element (ARE) leading to upregulation of GPx, thiol metabolism-associated detoxifying enzymes (GSTs) and stressresponse genes (HO-1) are all downregulated in animal models and patients with asthma and COPD. An exaggerated production of Nitric Oxide (NO) in the presence of oxidative stress can promote the formation of oxidizing reactive nitrogen species, such as peroxynitrite (ONO₂ -), leading to nitration and DNA damage, inhibition of mitochondrial respiration, protein dysfunction, and cell damage in the biological systems. Protein nitration also occurs by activation of myeloperoxidase and H₂O₂, promoting oxidation of nitrite (NO₂ -). There is increased nitrotyrosine and myeloperoxidase in the bronchi of COPD patients, particularly in severe disease. The decreased peroxynitrite inhibitory activity found in induced sputum of COPD patients correlates with pulmonary function. Markers of protein nitration - 3- nitrotyrosine, 3-bromotyrosine, and 3-chlorotyrosine - are increased in the bronchoalveolar lavage of severe asthmatics. Targeting the oxidative, nitrosative stress and associated lung inflammation through the use of either denitration mechanisms or new drug delivery strategies for antioxidant administration could improve the treatment of these chronic disabling obstructive lung diseases.

Oxidative damage mediates the association between polycyclic aromatic hydrocarbon exposure and lung function

BACKGROUND

Exposure to polycyclic aromatic hydrocarbons (PAHs) is related to decreased lung function. However, whether oxidative damage is involved in this relationship remains unclear. This study was aimed to explore the potential mediating role of oxidative DNA or lipid damage in the association between PAH exposure and lung function.

METHODS

The urinary levels of monohydroxy polycyclic aromatic hydrocarbon metabolites (OH-PAHs) and lung function parameters were measured among 3367 participants from the baseline of the Wuhan-Zhuhai cohort. Urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 8-isoprostane (8-iso-PGF2α) were determined to evaluate the individuals' oxidative DNA and lipid damage degrees, respectively. Linear mixed models were used to investigate the associations of urinary OH-PAHs, 8-OHdG and 8-iso-PGF2α with lung function parameters. Mediation analysis was further conducted to assess the potential role of oxidative damage in the association between urinary OH-PAHs and lung function.

RESULTS

Each one-percentage increase in the sum of urinary OH-PAHs, high-molecular-weight or low-molecular-weight OH-PAHs (ƩOH-PAHs, ƩHMW OH-PAH or ƩLMW OH-PAHs, respectively) was associated with a 0.2152-, 0.2076- or 0.1985- ml decrease in FEV₁, and a 0.1891-, 0.2195- or 0.1634- ml decrease in FVC, respectively. Additionally, significantly positive dose-response relationships of ƩOH-PAHs, ƩHMW OH-PAH and ƩLMW OH-PAHs with urinary 8-OHdG or 8-iso-PGF2α, as well as an inverse dose-response relationship between urinary 8-OHdG and FVC, were observed (all P for trend < 0.05). Mediation analysis indicated that urinary 8-OHdG mediated 14.22% of the association between ƩHMW OH-PAH and FVC.

CONCLUSION

Higher levels of oxidative DNA damage might be involved in the decreased levels of FVC caused by high-molecular-weight PAH exposure.

Polychlorinated dibenzo-dioxins and polychlorinated dibenzo-furans exposure and altered lung function: The mediating role of oxidative stress

The lung has been reported to be one of the target organs of polychlorinated dibenzo-dioxins and polychlorinated dibenzo-furans (PCDD/Fs) in many toxicological studies. While the associations between PCDD/Fs exposure and lung function levels have not been investigated thoroughly. This study aimed to explore these associations and the potential mediating role of oxidative stress. In this study, 201 foundry workers and 222 non-exposed general residents were recruited from central China, and their lung function parameters were measured. Air and food samples were collected to determine the PCDD/Fs levels for individual PCDD/Fs exposure estimation. Serum PCDD/Fs levels were determined in a subgroup of individuals randomly selected from the study population to reflect the body burden. It was found that each 1-unit increase in ln-transformed concentration of PCDD/Fs exposure (fg TEQ/bw/day) was associated with a 0.47 L decrease in FVC and a 0.25 L decrease in FEV₁. Each 1-unit increase in ln-transformed concentration of serum PCDD/Fs (fg TEQ/g lipid) was associated with a 0.36 L decrease in FVC and a 0.24 L decrease in FEV₁. Urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) was not only positively related to PCDD/Fs exposure, but also inversely associated with FVC and FEV₁ are FVC (β = -0.15, 95% CI: -0.22 to -0.08) and FEV₁ (β = -0.07, 95% CI: -0.13 to -0.02). Mediation analysis revealed that urinary 8-OHdG mediated 12.22% of the associations of external PCDD/Fs exposure with FVC levels, 28.61% and 27.87% of the associations of serum PCDD/Fs with FVC and FEV₁ levels respectively. Our findings suggested that PCDD/Fs exposure was associated with decreased lung function levels by a mechanism partly involving oxidatively generated damage to DNA.