Comparative study of the formation of oxidative damage marker 8-hydroxy-2′-deoxyguanosine (8-OHdG) adduct from the nucleoside 2′-deoxyguanosine by transition metals and suspensions of particulate matter in relation to metal content and redox reactivity

Impact of Airborne Exposure to PM10 Increases Susceptibility to P. aeruginosa Infection

The effects of exposure to airborne particulate matter with a size of 10 μm or less (PM10) on C57BL/6 mouse corneas, their response to Pseudomonas aeruginosa (PA) infection, and the protective effects of SKQ1 were determined. C57BL/6 mouse corneas receiving PBS or SKQ1 were exposed to control (air) or PM10 for 2 weeks, infected, and the disease was documented by clinical score, PMN quantitation, bacterial plate count, RT-PCR and Western blot. PBS-treated, PM10-exposed corneas did not differ at 1 day postinfection (dpi), but exhibited earlier (3 dpi) corneal thinning compared to controls. By 3 dpi, PM10 significantly increased corneal mRNA levels of several pro-inflammatory cytokines, but decreased IL-10, NQO1, GR1, GPX4, and Nrf2 over control. SKQ1 reversed these effects and Western blot selectively confirmed the RT-PCR results. PM10 resulted in higher viable bacterial plate counts at 1 and 3 dpi, but SKQ1 reduced them at 3 dpi. PM10 significantly increased MPO in the cornea at 3 dpi and was reduced by SKQ1. SKQ1, used as an adjunctive treatment to moxifloxacin, was not significantly different from moxifloxacin alone. Exposure to PM10 increased the susceptibility of C57BL/6 to PA infection; SKQ1 significantly reversed these effects, but was not effective as an adjunctive treatment.

Differential Pattern of Cell Death and ROS Production in Human Airway Epithelial Cells Exposed to Quinones Combined with Heated-PM2.5 and/or Asian Sand Dust

The combined toxicological effects of airborne particulate matter (PM), such as PM2.5, and Asian sand dust (ASD), with surrounding chemicals, particularly quinones, on human airway epithelial cells remain underexplored. In this study, we established an in vitro combination exposure model using 1,2-naphthoquinones (NQ) and 9,10-phenanthroquinones (PQ) along with heated PM (h-PM2.5 and h-ASD) to investigate their potential synergistic effects. The impacts of quinones and heated PM on tetrazolium dye (WST-1) reduction, cell death, and cytokine and reactive oxygen species (ROS) production were examined. Results revealed that exposure to 9,10-PQ with h-PM2.5 and/or h-ASD dose-dependently increased WST-1 reduction at 1 μM compared to the corresponding control while markedly decreasing it at 10 μM. Higher early apoptotic, late apoptotic, or necrotic cell numbers were detected in 9,10-PQ + h-PM2.5 exposure than in 9,10-PQ + h-ASD or 9,10-PQ + h-PM2.5 + h-ASD. Additionally, 1,2-NQ + h-PM2.5 exposure also resulted in an increase in cell death compared to 1,2-NQ + h-ASD and 1,2-NQ + h-PM2.5 + h-ASD. Quinones with or without h-PM2.5, h-ASD, or h-PM2.5 + h-ASD significantly increased ROS production, especially with h-PM2.5. Our findings suggest that quinones, at relatively low concentrations, induce cell death synergistically in the presence of h-PM2.5 rather than h-ASD and h-PM2.5 + h-ASD, partially through the induction of apoptosis with increased ROS generation.

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.

Rapid Assessment of Oxidative Damage Potential: A Comparative Study of Engineered Stone Dusts Using a Deoxyguanosine Assay

The popularity of engineered stone (ES) has been associated with a global increase in occupational lung disease in workers exposed to respirable dust during the fabrication of benchtops and other ES products. In this study, the reactivity and subsequent oxidative reduction potential of freshly generated ES dusts were evaluated by (i) comparing different engineered and natural stones, (ii) comparing settled and respirable stone dust fractions and (iii) assessing the effect of ageing on the reactivity of freshly generated stone dust. An established cell-free deoxyguanosine hydroxylation assay was used to assess the potential for oxidative DNA damage. ES dust exhibited a higher relative reactivity than two of the three natural stones tested. Respirable dust fractions were found to be significantly more reactive than their corresponding settled fraction (ANOVA, p < 0.05) across all stone types and samples. However, settled dust still displayed high relative reactivity. The lower reactivity of the settled dust was not due to decay in reactivity of the respirable dust when it settled but rather a result of the admixture of larger nonrespirable particles. No significant change in respirable dust reactivity was observed for three ES samples over a 21-day time period, whereas a significant decrease in reactivity was observed in the natural stone studied. This study has practical implications for dust control and housekeeping in industry, risk assessment and hazard management.

Nucleotide Excision Repair Pathway Activity Is Inhibited by Airborne Particulate Matter (PM10) through XPA Deregulation in Lung Epithelial Cells

Airborne particulate matter with a diameter size of ≤10 µm (PM₁₀) is a carcinogen that contains polycyclic aromatic hydrocarbons (PAH), which form PAH–DNA adducts. However, the way in which these adducts are managed by DNA repair pathways in cells exposed to PM₁₀ has been partially described. We evaluated the effect of PM₁₀ on nucleotide excision repair (NER) activity and on the levels of different proteins of this pathway that eliminate bulky DNA adducts. Our results showed that human lung epithelial cells (A549) exposed to 10 µg/cm² of PM₁₀ exhibited PAH–DNA adducts as well as an increase in RAD23 and XPD protein levels (first responders in NER). In addition, PM₁₀ increased the levels of H4K20me2, a recruitment signal for XPA. However, we observed a decrease in total and phosphorylated XPA (Ser196) and an increase in phosphatase WIP1, aside from the absence of XPA–RPA complex, which participates in DNA-damage removal. Additionally, an NER activity assay demonstrated inhibition of the NER functionality in cells exposed to PM₁₀, indicating that XPA alterations led to deficiencies in DNA repair. These results demonstrate that PM₁₀ exposure induces an accumulation of DNA damage that is associated with NER inhibition, highlighting the role of PM₁₀ as an important contributor to lung cancer.

Printer center nanoparticles alter the DNA repair capacity of human bronchial airway epithelial cells

Nano-enabled, toner-based printing equipment emit nanoparticles during operation. The bioactivity of these nanoparticles as documented in a plethora of published toxicological studies raises concerns about their potential health effects. These include pro-inflammatory effects that can lead to adverse epigenetic alterations and cardiovascular disorders in rats. At the same time, their potential to alter DNA repair pathways at realistic doses remains unclear. In this study, size-fractionated, airborne particles from a printer center in Singapore were sampled and characterized. The PM_0.1 size fraction (particles with an aerodynamic diameter less than 100 nm) of printer center particles (PCP) were then administered to human lung adenocarcinoma (Calu-3) or lymphoblastoid (TK6) cells. We evaluated plasma membrane integrity, mitochondrial activity, and intracellular reactive oxygen species (ROS) generation. Moreover, we quantified DNA damage and alterations in the cells' capacity to repair 6 distinct types of DNA lesions. Results show that PCP altered the ability of Calu-3 cells to repair 8oxoG:C lesions and perform nucleotide excision repair, in the absence of acute cytotoxicity or DNA damage. Alterations in DNA repair capacity have been correlated with the risk of various diseases, including cancer, therefore further genotoxicity studies are needed to assess the potential risks of PCP exposure, at both occupational settings and at the end-consumer level.

Airborne particulate matter induces oxidative damage, DNA adduct formation and alterations in DNA repair pathways

Air pollution, which includes particulate matter (PM), is classified in group 1 as a carcinogen to humans by the International Agency for Research in Cancer. Specifically, PM exposure has been associated with lung cancer in patients living in highly polluted cities. The precise mechanism by which PM is linked to cancer has not been completely described, and the genotoxicity induced by PM exposure plays a relevant role in cell damage. In this review, we aimed to analyze the types of DNA damage and alterations in DNA repair pathways induced by PM exposure, from both epidemiological and toxicological studies, to comprehend the contribution of PM exposure to carcinogenesis. Scientific evidence supports that PM exposure mainly causes oxidative stress by reactive oxygen species (ROS) and the formation of DNA adducts, specifically by polycyclic aromatic hydrocarbons (PAH). PM exposure also induces double-strand breaks (DSBs) and deregulates the expression of some proteins in DNA repair pathways, precisely, base and nucleotide excision repairs and homologous repair. Furthermore, specific polymorphisms of DNA repair genes could lead to an adverse response in subjects exposed to PM. Nevertheless, information about the effects of PM on DNA repair pathways is still limited, and it has not been possible to conclude which pathways are the most affected by exposure to PM or if DNA damage is repaired properly. Therefore, deepening the study of genotoxic damage and alterations of DNA repair pathways is needed for a more precise understanding of the carcinogenic mechanism of PM.

A novel LaFeO3 catalyst synthesized from sodium diethylenetriamine pentamethylene phosphonate for degradation of diclofenac through peroxymonosulfate activation: degradation pathways and mechanism study

A series of LaFeO3 catalysts were prepared using the sol–gel method with sodium diethylenetriamine pentamethylene phosphonate as the complexing agent and were applied to activate PMS to produce active oxides to degrade DCF.

Effect of Air Pollution on Glutathione S-Transferase Activity and Total Antioxidant Capacity: Cross Sectional Study in Kuwait

BACKGROUND

Air pollution poses a significant threat to human health worldwide. Investigating potential health impacts is essential to the development of regulations and legislation to minimize health risks.

OBJECTIVES

The aim of the present study was to investigate the potentially hazardous effect of air pollution on the Ali Sabah Al Salem residential area in Kuwait by comparing the pollution level to a control area (Al-Qirawan) by assessing two biomarkers: erythrocyte glutathione S-transferases (e-GST) and total blood antioxidant, and then correlating the activity to pollution-related oxidative stress.

METHODS

The average concentrations of several airborne gases were measured at Ali Sabah Al Salem and Al-Qirawan, including ozone, carbon monoxide, nitrogen dioxide, nitrogen oxides, particulate matter less than 10 μm (PM₁₀), sulfur dioxide, ammonia, carbon dioxide, hydrogen sulfide, methane, and non-methane hydrocarbon. A total of fifty-eight participants were sampled from two different areas and divided into two groups. The study group was composed of 40 residents exposed to polluted ambient air in the Ali Sabah Al Salem residential area. A reference group composed of 18 residents in the Al-Qairawan area living far from major pollution sources was also tested.

RESULTS

All measured gases were higher in concentration at Ali Sabah Al Salem compared to the Al-Qirawan area. Furthermore, PM₁₀ and sulfur dioxide were higher than World Health Organization (WHO) guidelines. The e-GST activity was lower among participants of the Ali Sabah Al Salem residential area compared to participants living in the Al-Qairawan area. The total antioxidant capacity in whole blood of Ali Sabah Al Salem residents was significantly (p<0.0001) higher than in control subjects.

CONCLUSIONS

Residents in Ali Sabah Al Salem are exposed to a high level of air pollution that has a serious impact on glutathione S-transferases levels. Subsequently, regulations on pollution sources are needed to lower current health risks. Furthermore, the present study provides evidence that finger-prick blood sampling is a quick, non-invasive method suitable for screening e-GST activity and total antioxidants which may be applied for surveillance purposes.

PARTICIPANT CONSENT

Obtained.

ETHICS APPROVAL

The study was approved by the Scientific Research Committee of the Public Authority for Applied Education and Training, Kuwait.

COMPETING INTERESTS

The authors declare no competing financial interests.

Suitability of MDA, 8-OHdG and wild-type p53 as genotoxic biomarkers in metal (Co, Ni and Cr) exposed dental technicians: a cross-sectional study

BACKGROUND

High concentrations of Co, Ni, and Cr in the blood serum of dental technicians are strongly associated with free radical formation. It has highly reactive properties that can cause further oxidation of molecule in the vicinity.

PURPOSE

This study intended to investigate whether the Dental Technician occupational exposure of Co, Ni and Cr, could contribute to the high incidence of cancer.

METHODS

This was a cross-sectional study to dental technicians, performed after acccepting ethical clearance. Blood was sampled in 3 examinations for Co, Ni, Cr using Atomic Absorbance Spectrophotometry (AAS), MDA was examined with TBARS test, also 8 OHdG and wildtype p53 proteins determined by ELISA method.

RESULTS

Comparative statistical analysis, showing a significant difference (p < 0.05) between levels of Co, Ni, and Cr in exposed groups to the control group. But, not all variables was proven to be positively correlated, only with Cr, and Co, and negatively correlated with wild-type p53.

CONCLUSION

MDA,8-OHdG and wildtype p53 can be used as genotoxic biomarkers in the metal exposed group, since they can accurately reflect the degree of Oxidative damage.

Effects of selenium supplementation on lung oxidative stress after exposure to exhaust emissions from pyrolysis oil, biodiesel and diesel

The exposure to exhaust emissions from fuels as diesel and pyrolysis oil may result in adverse effects on human lungs. This study investigated the effects of exposing mice to the exhaust emissions from diesel, biodiesel or pyrolysis oil, for 1 hour/day for 3 days, on lung oxidative stress and whether selenium administration into these mice affects the oxidative stress. The levels of lung malondialdehyde and nitric oxide were increased after exposure to pyrolysis oil exhaust. The intraperitoneal injection of 1.78 μg selenium/kg body weight 15 minutes before the exposure to the pyrolysis oil exhaust (pyrolysis oil + selenium group) restored the normal levels of malondialdehyde and nitric oxide. The catalase and SOD activities were decreased in the groups of the mice exposed to the exhaust emissions from pyrolysis oil, biodiesel or diesel. Selenium pretreatment of these groups showed no significant change in the activities of both enzymes. In conclusion, the increased lung levels of malondialdehyde and nitric oxide after the exposure to the exhaust emission from pyrolysis oil were restored to normal by selenium administration.

The etiologic origins for chronic obstructive pulmonary disease

COPD, characterized by long-term poorly irreversible airway limitation and persistent respiratory symptoms, has resulted in enormous challenges to human health worldwide, with increasing rates of prevalence, death, and disability. Although its origin was thought to be in the interactions of genetic with environmental factors, the effects of environmental factors on the disease during different life stages remain little known. Without clear mechanisms and radical cure for it, early screening and prevention of COPD seem to be important. In this review, we will discuss the etiologic origins for poor lung function and COPD caused by specific adverse effects during corresponding life stages, as well as try to find new insights and potential prevention strategies for this disease.

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

Background/aim

8-Hydroxy-2’-deoxyguanosine (8-OHdG) is a biomarker of oxidative stress and has been implicated in many diseases. The aim of this study was to investigate the clinical value of plasma 8-OHdG level in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD).

Materials and methods

A total of 154 subjects were enrolled in this study, including 20 healthy volunteers, 24 COPD patients in the stable phase, and 110 AECOPD patients. Peripheral blood samples, demographic information, and clinical characteristics were collected from all subjects at the time of being recruited into the study. Plasma 8-OHdG level was detected by enzyme-linked immunosorbent a ss ay.

Results

8-OHdG was increased in patients with AECOPD compared to healthy subjects and patients with stable COPD, especially in smokers. It also increased with the GOLD stage, mMRC grade, CAT score, and group level of combined COPD assessment. Additionally, further analysis revealed that 8-OHdG was negatively correlated with FEV1, FEV1% predicted, and FEV1/FVC and positively correlated with C-reactive protein, procalcitonin, and neutrophil CD64.

Conclusion

8-OHdG is associated with spirometric severity, symptomatic severity, exacerbation risk, and inflammatory biomarkers in AECOPD patients, suggesting it as a promising biomarker for reflecting disease severity and guiding the choice of optimal therapeutic decision.

Human inflammatory response of endotoxin affected by particulate matter-bound transition metals

Bacterial endotoxins are a component of particulate matter (PM) with anticipated health implications, yet we know little about how host reception of endotoxin through toll-like receptor 4 (TLR4) is affected by its association with other PM components. Subsequently, we investigated the relationship between endotoxin concentration (recombinant Factor C (rFC) assay) and host recognition (HEK Blue-TLR4 NF-kB reporter cell line based assay) in various compositions of urban PM, including road traffic, industrial and urban green land use classes. While the assays did not correlate strongly between each other, the TLR4 reporter cell line was found to be better correlated to the IL-8 response of PM. Furthermore, the ability of the quantified endotoxin (rFC assay) to stimulate the TLR4/MD-2 complex was significantly affected by the urban land use class, where traffic locations were found to be significantly higher in bioactive endotoxin than the industrial and green locations. We subsequently turned our attention to PM composition and characterized the samples based on transition metal content (through ICP-MS). The effect of nickel and cobalt - previously reported to activate the hTLR4/MD-2 complex - was found to be negligible in comparison to that of iron. Here, the addition of iron as a factor significantly improved the regression model between the two endotoxin assays, explaining 77% of the variation of the TLR4 stimulation and excluding the significant effect of land use class. Moreover, the effect of iron proved to be more than a correlation, since dosing LPS with Fe²⁺ led to an increase up to 64% in TLR4 stimulation, while Fe²⁺ without LPS was unable to stimulate a response. This study shows that endotoxin quantification assays (such as the rFC assay) may not always correspond to human biological recognition of endotoxin in urban PM, while its toxicity can be synergistically influenced by the associated PM composition.

Ibandronate metal complexes: solution behavior and antiparasitic activity

To face the high costs of developing new drugs, researchers in both industry and academy are looking for ways to repurpose old drugs for new uses. In this sense, bisphosphonates that are clinically used for bone diseases have been studied as agents against Trypanosoma cruzi, causative parasite of Chagas disease. In this work, the development of first row transition metal complexes (M = Co²⁺, Mn²⁺, Ni²⁺) with the bisphosphonate ibandronate (iba, H₄iba representing the neutral form) is presented. The in-solution behavior of the systems containing iba and the selected 3d metal ions was studied by potentiometry. Mononuclear complexes [M(H_xiba)]^(2-x)- (x = 0-3) and [M(Hiba)₂]^4- together with the formation of the neutral polynuclear species [M₂iba] and [M₃(Hiba)₂] were detected for all studied systems. In the solid state, complexes of the formula [M₃(Hiba)₂(H₂O)₄]·6H₂O were obtained and characterized. All obtained complexes, forming [M(Hiba)]^- species under the conditions of the biological studies, were more active against the amastigote form of T. cruzi than the free iba, showing no toxicity in mammalian Vero cells. In addition, the same complexes were selective inhibitors of the parasitic farnesyl diphosphate synthase (FPPS) enzyme showing poor inhibition of the human one. However, the increase of the anti-T. cruzi activity upon coordination could not be explained neither through the inhibition of TcFPPS nor through the inhibition of TcSPPS (T. cruzi solanesyl-diphosphate synthase). The ability of the obtained metal complexes of catalyzing the generation of free radical species in the parasite could explain the observed anti-T. cruzi activity.

Unraveling mechanisms of toxicant-induced oxidative stress in cardiovascular disease

To date, numerous clinical studies examining correlations between oxidative stress biomarkers and cardiovascular diseases (CVD) have repeatedly suggested a role for oxidant injury in the pathogenesis of diseases such as atherosclerosis. Despite this, antioxidant supplementation trials have not demonstrated a reduction in disease progression. Nevertheless, small animal and epidemiological studies have linked exposures to certain toxicants with increased CVD risk involving putative oxidative stress mechanisms. A few prototypical vascular toxicants will be discussed as examples of toxicants that likely act via oxidative stress mechanisms. For discussion, we will classify these toxicants as those that induce direct (e.g., arsenic, nucleoside reverse transcriptase inhibitors) versus indirect (particulate matter, ozone) oxidative stress mechanisms, and those that likely induce CVD through both direct and indirect mechanisms (cigarette smoke). Finally, new findings in oxidative stress research, including the emerging importance of reactive sulfur species, hydrogen peroxide as a presumed endothelium-derived hyperpolarizing factors, etc., will be discussed, as well as the need to determine the role of toxicants in modulating these newly identified pathways. Moreover, given the lack of success in conclusively demonstrating the roles of oxidative stress in CVD risk stratification, research probing the roles of toxicant exposures in propagating CVD pathogenesis may be a novel approach for more conclusively delineating the causal role of oxidative stress in CVD initiation and progression.

PM2.5 in the Yangtze River Delta, China: Chemical compositions, seasonal variations, and regional pollution events

Fine particle (PM_2.5) samples were collected simultaneously at three urban sites (Shanghai, Nanjing, and Hangzhou) and one rural site near Ningbo in the Yangtze River Delta (YRD) region, China, on a weekly basis from September 2013 to August 2014. In addition, high-frequency daily sampling was conducted in Shanghai and Nanjing for one month during each season. Severe regional PM_2.5 pollution episodes were frequently observed in the YRD, with annual mean concentrations of 94.6 ± 55.9, 97.8 ± 40.5, 134 ± 54.3, and 94.0 ± 57.6 μg m^-3 in Shanghai, Nanjing, Hangzhou, and Ningbo, respectively. The concentrations of PM_2.5 and ambient trace metals at the four sites showed clear seasonal trends, with higher concentrations in winter and lower concentrations in summer. In Shanghai, similar seasonal patterns were found for organic carbon (OC), elemental carbon (EC), and water-soluble inorganic ions (K⁺, NH₄⁺, Cl^-, NO₃^-, and SO₄^2-). Air mass backward trajectory and potential source contribution function (PSCF) analyses implied that areas of central and northern China contributed significantly to the concentration and chemical compositions of PM_2.5 in Shanghai during winter. Three heavy pollution events in Shanghai were observed during autumn and winter. The modelling results of the Nested Air Quality Prediction Modeling System (NAQPMS) showed the sources and transport of PM_2.5 in the YRD during the three pollution processes. The contribution of secondary species (SOC, NH₄⁺, NO₃^-, and SO₄^2-) in pollution event (PE) periods was much higher than in BPE (before pollution event) and APE (after pollution event) periods, suggesting the importance of secondary aerosol formation during the three pollution events. Furthermore, the bioavailability of Cu, and Zn in the wintertime PM_2.5 samples from Shanghai was much higher during the pollution days than during the non-pollution days.

Predictive and Prognostic Biomarkers of Respiratory Diseases due to Particulate Matter Exposure

Air pollution is getting severe and concerns about its toxicity effects on airway and lung disease are also increasing. Particulate matter (PM) is major component of air pollutant. It causes respiratory diseases, such as asthma, chronic obstructive pulmonary disease, lung cancer, and so on. PM particles enter the airway and lung by inhalation, causing damages to them. Especially, PM_2.5 can penetrate into the alveolus and pass to the systemic circulation. It can affect the cardiopulmonary system and cause cardiopulmonary disorders. In this review, we focused on PM-inducing toxicity mechanisms in the framework of oxidative stress, inflammation, and epigenetic changes. We also reviewed its correlation with respiratory diseases. In addition, we reviewed biomarkers related to PM-induced respiratory diseases. These biomarkers might be used for disease prediction and early diagnosis. With recent trend of using genomic analysis tools in the field of toxicogenomics, respiratory disease biomarkers associated with PM will be continuously investigated. Effective biomarkers derived from earlier studies and further studies might be utilized to reduce respiratory diseases.

Development of an assay to assess genotoxicity by particulate matter extract

The current study describes a method for assessing the oxidative potential of common environmental stressors (ambient air particulate matter), using a plasmid relaxation assay where the extract caused single-strand breaks, easily visualised through electrophoresis. This assay utilises a miniscule amount (11 µg) of particulate matter (PM) extract compared to other, cell-based methods (~3,000 µg). The negative impact of air pollution on human health has been extensively recognised. Among the air pollutants, PM plays an eminent role, as reflected in the broad scientific interest. PM toxicity highly depends on its composition (metals and organic compounds), which in turn has been linked to multiple health effects (such as cardiorespiratory diseases and cancer) through multiple toxicity mechanisms; the induction of oxidative stress is considered a major mechanism among these. In this study, the PM levels, oxidative potential, cytotoxicity and genotoxicity of PM in the region of Larissa, Greece were examined using the plasmid relaxation assay. Finally, coffee extracts from different varieties, derived from both green and roasted seeds, were examined for their ability to inhibit PM-induced DNA damage. These extracts also exerted an inhibitory effect on xanthine oxidase and catalase, but had no effect against superoxide dismutase. Overall, this study highlights the importance of assays for assessing the oxidative potential of widespread environmental stressors (PM), as well as the antioxidant capacity of beverages and food items, with the highlight being the development of a plasmid relaxation assay to assess the genotoxicity caused by PM using only a miniscule amount.

Association of IL-6 with PM2.5 Components: Importance of Characterizing Filter-Based PM2.5 Following Extraction

Filter-based toxicology studies are conducted to establish the biological plausibility of the well-established health impacts associated with fine particulate matter (PM_2.5) exposure. Ambient PM_2.5 collected on filters is extracted into solution for toxicology applications, but frequently, characterization is nonexistent or only performed on filter-based PM_2.5, without consideration of compositional differences that occur during the extraction processes. To date, the impact of making associations to measured components in ambient instead of extracted PM_2.5 has not been investigated. Filter-based PM_2.5 was collected at locations (n = 5) and detailed characterization of both ambient and extracted PM_2.5 was performed. Alveolar macrophages (AMJ2-C11) were exposed (3, 24, and 48 h) to PM_2.5 and the pro-inflammatory cytokine interleukin (IL)-6 was measured. IL-6 release differed significantly between PM_2.5 collected from different locations; surprisingly, IL-6 release was highest following treatment with PM_2.5 from the lowest ambient concentration location. IL-6 was negatively correlated with the sum of ambient metals analyzed, as well as with concentrations of specific constituents which have been previously associated with respiratory health effects. However, positive correlations of IL-6 with extracted concentrations indicated that the negative associations between IL-6 and ambient concentrations do not accurately represent the relationship between inflammation and PM_2.5 exposure. Additionally, seven organic compounds had significant associations with IL-6 release when considering ambient concentrations, but they were not detected in the extracted solution. Basing inflammatory associations on ambient concentrations that are not necessarily representative of in vitro exposures creates misleading results; this study highlights the importance of characterizing extraction solutions to conduct accurate health impact research.

Nickel Release, ROS Generation and Toxicity of Ni and NiO Micro- and Nanoparticles

Occupational exposure to airborne nickel is associated with an elevated risk for respiratory tract diseases including lung cancer. Therefore, the increased production of Ni-containing nanoparticles necessitates a thorough assessment of their physical, chemical, as well as toxicological properties. The aim of this study was to investigate and compare the characteristics of nickel metal (Ni) and nickel oxide (NiO) particles with a focus on Ni release, reactive oxygen species (ROS) generation, cellular uptake, cytotoxicity and genotoxicity. Four Ni-containing particles of both nano-size (Ni-n and NiO-n) and micron-size (Ni-m1 and Ni-m2) were tested. The released amount of Ni in solution was notably higher in artificial lysosomal fluid (e.g. 80–100 wt% for metallic Ni) than in cell medium after 24h (ca. 1–3 wt% for all particles). Each of the particles was taken up by the cells within 4 h and they remained in the cells to a high extent after 24 h post-incubation. Thus, the high dissolution in ALF appeared not to reflect the particle dissolution in the cells. Ni-m1 showed the most pronounced effect on cell viability after 48 h (alamar blue assay) whereas all particles showed increased cytotoxicity in the highest doses (20–40 μg cm²) when assessed by colony forming efficiency (CFE). Interestingly an increased CFE, suggesting higher proliferation, was observed for all particles in low doses (0.1 or 1 μg cm^-2). Ni-m1 and NiO-n were the most potent in causing acellular ROS and DNA damage. However, no intracellular ROS was detected for any of the particles. Taken together, micron-sized Ni (Ni-m1) was more reactive and toxic compared to the nano-sized Ni. Furthermore, this study underlines that the low dose effect in terms of increased proliferation observed for all particles should be further investigated in future studies.

Addressing Emerging Risks: Scientific and Regulatory Challenges Associated with Environmentally Persistent Free Radicals

Airborne fine and ultrafine particulate matter (PM) are often generated through widely-used thermal processes such as the combustion of fuels or the thermal decomposition of waste. Residents near Superfund sites are exposed to PM through the inhalation of windblown dust, ingestion of soil and sediments, and inhalation of emissions from the on-site thermal treatment of contaminated soils. Epidemiological evidence supports a link between exposure to airborne PM and an increased risk of cardiovascular and pulmonary diseases. It is well-known that during combustion processes, incomplete combustion can lead to the production of organic pollutants that can adsorb to the surface of PM. Recent studies have demonstrated that their interaction with metal centers can lead to the generation of a surface stabilized metal-radical complex capable of redox cycling to produce ROS. Moreover, these free radicals can persist in the environment, hence their designation as Environmentally Persistent Free Radicals (EPFR). EPFR has been demonstrated in both ambient air PM_2.5 (diameter < 2.5 µm) and in PM from a variety of combustion sources. Thus, low-temperature, thermal treatment of soils can potentially increase the concentration of EPFR in areas in and around Superfund sites. In this review, we will outline the evidence to date supporting EPFR formation and its environmental significance. Furthermore, we will address the lack of methodologies for specifically addressing its risk assessment and challenges associated with regulating this new, emerging contaminant.

[Study of the Changes on Tree Shrew Bronchial Epithelium Induced by Xuanwei Bituminous Coal Dust]

BACKGROUND AND OBJECTIVE

Lung cancer is the type of cancer with the highest incidence and mortality in numerous countries and regions. Establishing an appropriate animal model that can be used to simulate lung cancer etiology, pathogenesis, and similar processes, is urgent. We explore the feasibility of establishing a lung cancer model induced by Xuanwei bituminous coal dust PM10 (particulate matter with diameters of 10 μm or less), which affects bronchial epithelium of tree shrews.

METHODS

The neck skin of adult tree shrews is dissected, and the thyroid cartilage is fully exposed. Subsequently, the weak part at the top of the thyroid cartilage is treated with intratracheal agents by perfusion via a special infusion needle puncture method. Regular X-ray examination and lung tissue biopsy were performed on the sacrificed animals to observe changes in pulmonary imaging and bronchial epithelial cells after perfusion of Xuanwei bituminous coal dust PM 10.

RESULTS

The tree shrews of the experimental group (exposed to bituminous coal dust) died in a week after perfusion with PM10, whereas no animal died until the end of the experiment in the blank control and the solvent control groups. Sections of lung tissue biopsy of the regularly killed tree shrews were stained with hematoxylin and eosin. The lung tissues of tree shrews in the experimental group showed a serial changes caused by bronchial epithelial hyperplasia, such as squamous metaplasia, dysplasia, and early invasive carcinoma, whereas no significant pathological changes were observed in the blank control and solvent control groups.

CONCLUSIONS

Endotracheal infusion of Xuanwei bituminous coal dust PM10 induces lung cancer in tree shrews. Thus, the lung cancer model was established.
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Spatial Variation and Land Use Regression Modeling of the Oxidative Potential of Fine Particles

BACKGROUND

Oxidative potential (OP) has been suggested to be a more health-relevant metric than particulate matter (PM) mass. Land use regression (LUR) models can estimate long-term exposure to air pollution in epidemiological studies, but few have been developed for OP.

OBJECTIVES

We aimed to characterize the spatial contrasts of two OP methods and to develop and evaluate LUR models to assess long-term exposure to the OP of PM2.5.

METHODS

Three 2-week PM2.5 samples were collected at 10 regional background, 12 urban background, and 18 street sites spread over the Netherlands/Belgium in 1 year and analyzed for OP using electron spin resonance (OP(ESR)) and dithiothreitol (OP(DTT)). LUR models were developed using temporally adjusted annual averages and a range of land-use and traffic-related GIS variables.

RESULTS

Street/urban background site ratio was 1.2 for OP(DTT) and 1.4 for OP(ESR), whereas regional/urban background ratio was 0.8 for both. OP(ESR) correlated moderately with OP(DTT) (R2 = 0.35). The LUR models included estimated regional background OP, local traffic, and large-scale urbanity with explained variance (R2) of 0.60 for OP(DTT) and 0.67 for OP(ESR). OP(DTT) and OP(ESR) model predictions were moderately correlated (R2 = 0.44). OP model predictions were moderately to highly correlated with predictions from a previously published PM2.5 model (R2 = 0.37-0.52), and highly correlated with predictions from previously published models of traffic components (R2 > 0.50).

CONCLUSION

LUR models explained a large fraction of the spatial variation of the two OP metrics. The moderate correlations among the predictions of OP(DTT), OP(ESR), and PM2.5 models offer the potential to investigate which metric is the strongest predictor of health effects.

CITATION

Yang A, Wang M, Eeftens M, Beelen R, Dons E, Leseman DL, Brunekreef B, Cassee FR, Janssen NA, Hoek G. 2015. Spatial variation and land use regression modeling of the oxidative potential of fine particles. Environ Health Perspect 123:1187-1192; http://dx.doi.org/10.1289/ehp.1408916.

Characterization of ambient and extracted PM2.5 collected on filters for toxicology applications

Research on the health effects of fine particulate matter (PM2.5) frequently disregards the differences in particle composition between that measured on an ambient filter versus that measured in the corresponding extraction solution used for toxicological testing. This study presents a novel method for characterizing the differences, in metallic and organic species, between the ambient samples and the corresponding extracted solutions through characterization of extracted PM2.5 suspended on filters. Removal efficiency was found to be 98.0 ± 1.4% when measured using pre- and post-removal filter weights, however, this efficiency was significantly reduced to 80.2 ± 0.8% when measured based on particle mass in the extraction solution. Furthermore, only 47.2 ± 22.3% of metals and 24.8 ± 14.5% of organics measured on the ambient filter were found in the extraction solution. Individual metallic and organic components were extracted with varying efficiency, with many organics being lost entirely during extraction. Finally, extraction efficiencies of specific PM2.5 components were inversely correlated with total mass. This study details a method to assess compositional alterations resulting from extraction of PM2.5 from filters, emphasizing the need for standardized procedures that maintain compositional integrity of ambient samples for use in toxicology studies of PM2.5.

Rates of Hydroxyl Radical Production from Transition Metals and Quinones in a Surrogate Lung Fluid

Hydroxyl radical ((•)OH) is the most reactive, and perhaps most detrimental to health, of the reactive oxygen species. (•)OH production in lungs following inhalation of particulate matter (PM) can result from redox-active chemicals, including iron and copper, but the relative importance of these species is unknown. This work investigates (•)OH production from iron, copper, and quinones, both individually and in mixtures at atmospherically relevant concentrations. Iron, copper, and three of the four quinones (1,2-naphthoquinone, phenanthrenequinone and 1,4-naphthoquinone) produce (•)OH. Mixtures of copper or quinones with iron synergistically produce (•)OH at a rate 20-130% higher than the sum of the rates of the individual redox-active species. We developed a regression equation from 20 mixtures to predict the rate of (•)OH production from the particle composition. For typical PM compositions, iron and copper account for most (•)OH production, whereas quinones are a minor source, although they can contribute if present at very high concentrations. This work shows that Cu contributes significantly to (•)OH production in ambient PM; other work has shown that Cu appears to be the primary driver of HOOH production and dithiothreitol (DTT) loss in ambient PM extracts. Taken together, these results indicate that copper appears to be the most important individual contributor to direct oxidant production from inhaled PM.

Spatial and seasonal heterogeneity of atmospheric particles induced reactive oxygen species in urban areas and the role of water-soluble metals

Adverse health effects are associated with exposure to atmospheric particulate matter (PM), which carry various chemical constituents and induce both exogenous and endogenous oxidative stress. This study investigated the spatial and seasonal variability of PM-induced ROS at four sites with different characteristics in Hong Kong. Cytotoxicity, exogenous and endogenous ROS was determined on a dose and time dependent analysis. Large spatial variation of ROS was observed with fine PM at urban site showing highest ROS levels while coarse PM at traffic site ranks the top. No consistent seasonal difference was observed for ROS levels among all sites. The highly heterogeneous distribution of PM-induced ROS demonstrates the differential capability of PM to produce oxidative stress, and the need to use appropriate metrics as surrogates of exposure instead of PM mass in epidemiologic studies. Several transition metals were found associated with ROS by different degree illustrating the complexity of mechanisms involved.

Analytical methods for assessing metal bioaccessibility in airborne particulate matter: A scoping review

In contrast to the existence of standardized methods to assess metal bioaccessibility via the gastrointestinal route, there are no widely-accepted, established in vitro testing protocols to measure elemental solubility in the human lung. This may be attributed, in part, to the difficulty associated with simulating the lung's complex in vivo conditions. The purpose of this review is two-fold: (1) to determine how the bioaccessibility of metals associated with ambient particulate matter (PM) in the human lung has been assessed in the literature, and (2) examine the suitability and biological relevance of applied methods for the measurement of metal bioaccessibility employed to date. The review revealed that limited attention has been paid to the development and application of biologically-relevant in vitro methods to measure elemental solubility in ambient PM as a proxy for bioaccessibility in the human lung. Few studies (n=14) used synthetic lung fluids to simulate in vivo conditions, with only half extracting samples at a biologically-relevant temperature of 37°C. There was limited evidence suggesting that the use of water is less effective as a leaching agent compared to simulated lung fluids. In sum, this scoping review highlights a critical need to develop standardized methods for the systematic assessment of elemental bioaccessibility via the respiratory route. Priority should be placed on the validation of biologically-relevant methods, including the use of leaching agents and extraction parameters used, which allow for testing to be conducted in a reliable, yet cost efficient, manner.

Genotoxic and epigenotoxic effects of fine particulate matter from rural and urban sites in Lebanon on human bronchial epithelial cells

Assessment of air pollution by particulate matter (PM) is strongly required in Lebanon in the absence of an air quality law including updated air quality standards. Using two different PM2.5-0.3 samples collected at an urban and a rural site, we examined genotoxic/epigenotoxic effects of PM exposure within a human bronchial epithelial cell line (BEAS-2B). Inorganic and organic contents evidence the major contribution of traffic and generating sets in the PM2.5-0.3 composition. Urban PM2.5-0.3 sample increased the phosphorylation of H2AX, the telomerase activity and the miR-21 up-regulation in BEAS-2B cells in a dose-dependent manner. Furthermore, urban PM2.5-0.3 induced a significant increase in CYP1A1, CYP1B1 and AhRR genes expression. The variable concentrations of transition metals and organic compounds detected in the collected PM2.5-0.3 samples might be the active agents leading to a cumulative DNA damage, critical for carcinogenesis.

Iron-mediated redox modulation in neural plasticity

The role of iron in brain physiology has focused on the neuropathological, effects due to iron-induced oxidative stress. However, our recent work has established a physiological relationship between the iron-mediated oxidative modification and normal neuronal function. Our results obtained from hippocampal neurons, suggest that iron-generated reactive species oxygen (ROS) are involved in calcium signaling initiated by stimulation of NMDA receptors. This signal is amplified by ryanodine receptors (RyR), a redox- sensitive calcium channel, allowing the phosphorylation and nuclear translocation of ERK1/2. Furthermore, using electrophysiological approaches, we showed that iron is required for basal synaptic transmission and full expression of long-term potentiation, a type of synaptic plasticity. Our data combined suggest that the oxidative effect of iron is critical to activate processes that are downstream of NMDAR activation. Finally, due to the high reactivity of DNA with iron-generated ROS, we hypothesize an additional function of iron in gene regulation.

Iron deficiency on neuronal function

Because of the intrinsic ability of iron to catalyze the formation of reactive oxygen species, it has been associated with oxidative stress and neurodegenerative diseases. However, iron deficiency (ID) also negatively impacts various functions of the brain, suggesting that iron plays an important physiological role in neuronal processes such as myelination, synaptogenesis, behavior and synaptic plasticity (SP). ID not only produces changes in the hippocampus, striatum, amygdale or prefrontal cortex, it also affects the interaction among these systems. In both humans and rodents, the perturbations of these structures are associated to cognitive deficits. These cognitive alterations have been well correlated with changes in neural plasticity, the possible cellular substrate of memory and learning. Given that SP is strongly affected by early ID and the lasting-neurological consequences remain even after ID has been corrected, it is important to prevent ID as well as to seek effective therapeutic interventions that reduce or reverse the long-term effects of the ID in the nervous system. This review will give an overview of the literature on the effects of iron deficit in neuronal functions such as behavior, neurotransmission and SP. We also discuss our recent data about the possible oxidative effect of iron on the mechanisms involved in neural plasticity.

Impacts of Antioxidants on Hydroxyl Radical Production from Individual and Mixed Transition Metals in a Surrogate Lung Fluid

Inhalation of ambient particulate matter causes morbidity and mortality in humans. One hypothesized mechanism of toxicity is the particle-induced formation of reactive oxygen species (ROS) - including the highly damaging hydroxyl radical ((·)OH) - followed by inflammation and a variety of diseases. While past studies have found correlations between ROS formation and a variety of metals, there are no quantitative measurements of (·)OH formation from transition metals at concentrations relevant to 24-hour ambient particulate exposure. This research reports specific and quantitative measurements of (·)OH formation from 10 individual transition metals (and several mixtures) in a cell-free surrogate lung fluid (SLF) with four antioxidants: ascorbate, citrate, glutathione, and uric acid. We find that Fe and Cu can produce (·)OH under all antioxidant conditions as long as ascorbate is present and that mixtures of the two metals synergistically increase (·)OH production. Manganese and vanadium can also produce (·)OH under some conditions, but given that their ambient levels are typically very low, these metals are not likely to chemically produce significant levels of (·)OH in the lung fluid. Cobalt, chromium, nickel, zinc, lead, and cadmium do not produce (·)OH under any of our experimental conditions. The antioxidant composition of our SLF significantly affects (·)OH production from Fe and Cu: ascorbate is required for (·)OH formation, citrate increases (·)OH production from Fe, and both citrate and glutathione suppress (·)OH production from Cu. MINTEQ ligand speciation modeling indicates that citrate and glutathione affect (·)OH production by changing metal speciation, altering the reactivity of the metals. In the most realistic SLF (i.e., with all four antioxidants), Fe generates approximately six times more (·)OH than does the equivalent amount of Cu. Since levels of soluble Fe in PM are typically higher than those of Cu, our results suggest that Fe dominates the chemical generation of (·)OH from deposited particles in the lungs.

Airborne urban particles (Milan winter-PM2.5) cause mitotic arrest and cell death: Effects on DNA, mitochondria, AhR binding and spindle organization

Airborne particulate matter (PM) is considered to be an important contributor to lung diseases. In the present study we report that Milan winter-PM2.5 inhibited proliferation in human bronchial epithelial cells (BEAS-2B) by inducing mitotic arrest. The cell cycle arrest was followed by an increase in mitotic-apoptotic cells, mitotic slippage and finally an increase in "classical" apoptotic cells. Exposure to winter-PM10 induced only a slight effect which may be due to the presence of PM2.5 in this fraction while pure combustion particles failed to disturb mitosis. Fewer cells expressing the mitosis marker phospho-histone H3 compared to cells with condensed chromosomes, suggest that PM2.5 induced premature mitosis. PM2.5 was internalized into the cells and often localized in laminar organelles, although particles without apparent plasma membrane covering were also seen. In PM-containing cells mitochondria and lysosomes were often damaged, and in mitotic cells fragmented chromosomes often appeared. PM2.5 induced DNA strands breaks and triggered a DNA-damage response characterized by increased phosphorylation of ATM, Chk2 and H2AX; as well as induced a marked increase in expression of the aryl hydrocarbon receptor (AhR)-regulated genes, CYP1A1, CYP1B1 and AhRR. Furthermore, some disturbance of the organization of microtubules was indicated. It is hypothesized that the induced mitotic arrest and following cell death was due to a premature chromosome condensation caused by a combination of DNA, mitochondrial and spindle damage.

Acute decrease in HDL cholesterol associated with exposure to welding fumes

OBJECTIVE

To investigate acute changes in circulating lipids after exposure to relatively high levels of particulate matter through welding.

METHODS

Using a repeated measures panel study, lipid levels before and after welding and personal exposures to fine particulate matter (PM2.5) were measured in 36 male welders over 63 exposure and/or control days.

RESULTS

There was a trend toward decrease in HDL (-2.3 mg/dL, P = 0.08) 18 hours after welding. This effect became significant (-2.6 mg/dL, P = 0.05) after adjustment for possible confounders. The effect was strongest (-4.3 mg/dL, P = 0.02) among welders who did not weld the day before the study. There were no significant changes in other lipids associated with welding or PM2.5 exposure.

CONCLUSION

Welding exposure was associated with an acute decrease in circulating HDL, which may relate to the inflammatory and proatherosclerotic effects of fine particle exposure.

Oxidative stress, DNA damage, and inflammation induced by ambient air and wood smoke particulate matter in human A549 and THP-1 cell lines

Combustion of biomass and wood for residential heating and/or cooking contributes substantially to both ambient air and indoor levels of particulate matter (PM). Toxicological characterization of ambient air PM, especially related to traffic, is well advanced, whereas the toxicology of wood smoke PM (WSPM) is poorly assessed. We assessed a wide spectrum of toxicity end points in human A549 lung epithelial and THP-1 monocytic cell lines comparing WSPM from high or low oxygen combustion and ambient PM collected in a village with many operating wood stoves and from a rural background area. In both cell types, all extensively characterized PM samples (1.25-100 μg/mL) induced dose-dependent formation of reactive oxygen species and DNA damage in terms of strand breaks and formamidopyrimidine DNA glycosylase sites assessed by the comet assay with WSPM being most potent. The WSPM contained more polycyclic aromatic hydrocarbons (PAH), less soluble metals, and expectedly also had a smaller particle size than PM collected from ambient air. All four types of PM combined increased the levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine dose-dependently in A549 cells, whereas there was no change in the levels of etheno-adducts or bulky DNA adducts. Furthermore, mRNA expression of the proinflammatory genes monocyte chemoattractant protein-1, interleukin-8, and tumor necrosis factor-α as well as the oxidative stress gene heme oxygenase-1 was upregulated in the THP-1 cells especially by WSPM and ambient PM sampled from the wood stove area. Expression of oxoguanine glycosylase 1, lymphocyte function-associated antigen-1, and interleukin-6 did not change. We conclude that WSPM has small particle size, high level of PAH, low level of water-soluble metals, and produces high levels of free radicals, DNA damage as well as inflammatory and oxidative stress response gene expression in cultured human cells.

Towards a unifying, systems biology understanding of large-scale cellular death and destruction caused by poorly liganded iron: Parkinson's, Huntington's, Alzheimer's, prions, bactericides, chemical toxicology and others as examples

Exposure to a variety of toxins and/or infectious agents leads to disease, degeneration and death, often characterised by circumstances in which cells or tissues do not merely die and cease to function but may be more or less entirely obliterated. It is then legitimate to ask the question as to whether, despite the many kinds of agent involved, there may be at least some unifying mechanisms of such cell death and destruction. I summarise the evidence that in a great many cases, one underlying mechanism, providing major stresses of this type, entails continuing and autocatalytic production (based on positive feedback mechanisms) of hydroxyl radicals via Fenton chemistry involving poorly liganded iron, leading to cell death via apoptosis (probably including via pathways induced by changes in the NF-κB system). While every pathway is in some sense connected to every other one, I highlight the literature evidence suggesting that the degenerative effects of many diseases and toxicological insults converge on iron dysregulation. This highlights specifically the role of iron metabolism, and the detailed speciation of iron, in chemical and other toxicology, and has significant implications for the use of iron chelating substances (probably in partnership with appropriate anti-oxidants) as nutritional or therapeutic agents in inhibiting both the progression of these mainly degenerative diseases and the sequelae of both chronic and acute toxin exposure. The complexity of biochemical networks, especially those involving autocatalytic behaviour and positive feedbacks, means that multiple interventions (e.g. of iron chelators plus antioxidants) are likely to prove most effective. A variety of systems biology approaches, that I summarise, can predict both the mechanisms involved in these cell death pathways and the optimal sites of action for nutritional or pharmacological interventions.

Evidence of oxidative stress in the pathogenesis of fuchs endothelial corneal dystrophy

Fuchs endothelial corneal dystrophy (FECD) is a progressive, blinding disease characterized by corneal endothelial (CE) cell apoptosis. Corneal transplantation is the only measure currently available to restore vision in these patients. Despite the identification of some genetic factors, the pathophysiology of FECD remains unclear. In this study, we observed a decrease in the antioxidant response element-driven antioxidants in FECD corneal endothelium. We further demonstrated that nuclear factor erythroid 2-related factor 2, a transcription factor known to bind the antioxidant response element and activate antioxidant defense, is down-regulated in FECD endothelium. Importantly, we detected significantly higher levels of oxidative DNA damage and apoptosis in FECD endothelium compared with normal controls and pseudophakic bullous keratopathy (iatrogenic CE cell loss) specimens. A marker of oxidative DNA damage, 8-hydroxy-2'-deoxyguanosine, colocalized to mitochondria, indicating that the mitochondrial genome is the specific target of oxidative stress in FECD. Oxidative DNA damage was not detected in pseudophakic bullous keratopathy corneas, whereas it colocalized with terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive cells in FECD samples. Ex vivo, oxidative stress caused characteristic morphological changes and apoptosis of CE, suggestive of findings that characterize FECD in vivo. Together, these data suggest that suboptimal nuclear factor erythroid 2-related factor 2-regulated defenses may account for oxidant-antioxidant imbalance in FECD, which in turn leads to oxidative DNA damage and apoptosis. This study provides evidence that oxidative stress plays a key role in FECD pathogenesis.

An acellular assay to assess the genotoxicity of complex mixtures of organic pollutants bound on size segregated aerosol. Part II: oxidative damage to DNA

Ambient air particulate matter (atmospheric aerosol; PM) is an important factor in the development of various diseases. Oxidative stress is believed to be one of the mechanisms of action of PM on the human organism. The aim of our study was to investigate the ability of organic extracts of size segregated aerosol particles (EOM; three fractions of aerodynamic diameter 1-10μm, 0.5-1μm and 0.17-0.5μm) to induce oxidative damage to DNA in an in vitro acellular system of calf thymus (CT) DNA with and without S9 metabolic activation. PM was collected in the Czech Republic at four places with different levels of air pollution. Levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) tended to increase with decreasing sizes of PM. S9 metabolic activation increased the oxidative capacity of PM; mean levels of 8-oxodG/10(5) dG per 1000m(3) of air for samples with and without metabolic activation were 0.093 and 0.067, respectively (p<0.05). When results of oxidative damage to DNA were normalized per microgram of aerosol mass, mean levels of 8-oxodG/10(5) dG were 0.265 and 0.191, for incubation with and without S9 fraction, respectively (p<0.05). We observed a significant positive association between concentrations of polycyclic aromatic hydrocarbons (c-PAHs) bound to PM and levels of 8-oxodG/10(5) dG per 1000m(3) of air after metabolic activation of EOM samples (R=0.695, p<0.05). The correlation was weaker and non-significant for samples without metabolic activation (R=0.523, p=0.08). In conclusion, we showed that organic extracts of PM were able to induce oxidative damage to DNA in vitro; this ability was increased after S9 metabolic activation of EOM and with decreasing sizes of PM.

Electron Paramagnetic Resonance - A Powerful Tool of Medical Biochemistry in Discovering Mechanisms of Disease and Treatment Prospects

In pathophysiological conditions related to oxidative stress, the application of selected antioxidants could have beneficial effects on human health. Electron paramagnetic resonance (EPR) spectroscopy is a technique that provides unique insight into the redox biochemistry, due to its ability to: (i) distinguish and quantify different reactive species, such as hydroxyl radical, superoxide, carbon centered radicals, hydrogen atom, nitric oxide, ascorbyl radical, melanin, and others; (ii) evaluate the antioxidative capacity of various compounds, extracts and foods; (iii) provide information on other important parameters of biological systems. A combination of EPR spectroscopy and traditional biochemical methods represents an efficient tool in the studies of disease mechanisms and antioxidative therapy prospects, providing a more complete view into the redox processes in the human organism.

Probing the source of hydrogen peroxide associated with coarse mode aerosol particles in southern California

Coarse mode aerosols were collected at three sites in the Los Angeles area, two in Riverside, CA, one upwind and the other downwind of a major freeway, and also on the campus of the University of California, Los Angeles (UCLA). Coarse mode aerosol mass, H(2)O(2), and H(2)O(2) normalized to aerosol mass averaged 46 +/- 22 microg/m(3), 17 +/- 8 ng/m(3), and 0.48 +/- 0.32 ng/microg at the upwind Riverside site and 97 +/- 27 microg/m(3), 34 +/- 14 ng/m(3), and 0.37 +/- 0.18 ng/microg at the downwind Riverside site, respectively. H(2)O(2), which appears to be generated by the particles (Arellanes, C.; Paulson, S. E.; Fine, P. M.; Sioutas, C. Environ. Sci. Technol. 2006, 40, 4859-4866), was uncorrelated with particle mass, but was strongly correlated with soluble iron, zinc, and copper (r = 0.47-0.67, p = 0.00-0.01). H(2)O(2) levels were not affected by the addition of dithiothreitol, a marker for quinone redox activity. H(2)O(2) levels were sensitive to the pH of the particle extraction solutions, increasing as the pH was decreased. The initial rate of H(2)O(2) generation by coarse mode aerosols was 7.8 (+/-5.7) x 10(-8) M min(-1), similar to initial rates of hydroxyl radical generation from dissolved Fe(2+), Cu(2+), and Zn(2+) solutions. The results support the notion that the majority of coarse mode H(2)O(2) generation is mediated by a small set of transition metals.

Acute effects of diesel emission from the urea selective catalytic reduction engine system on male rats

Short-term inhalation experiments were performed using Fischer 344 rats exposed to emission from the urea selective catalytic reduction (SCR) diesel engine system to identify health effects and compare them to those of the conventional diesel engine system. Rats were exposed to high-, middle-, or low-concentration emission (dilution ratio 1:29, 1:290, or 1:580) or clean air (control) for 1, 3, or 7 days (6 h/day), under driving conditions at a speed of 1320 rpm and a torque of 840 Nm. For the high-concentration group, the major components of the urea SCR emission were 0.04 mg/m(3) particulate matter (PM) and 0.78 ppm nitrogen dioxide (NO(2)); those of the conventional emission were 0.95 mg/m(3) PM and 0.31 ppm NO(2). The authors evaluated the respiratory effects of each emission on rats. Lymphocytes for 3-day exposure of both emissions significantly increased in bronchoalveolar lavage fluid, but there were slight differences. With an increase in potential antioxidant (PAO), 8-hydroxy-2'-deoxyguanosine for the urea SCR emission was significantly decreased, but that of the conventional emission was highest among all groups and did not show a response to PAO. In lungs, heme oxygenase (HO)-1 and tumor necrosis factor (TNF)-alpha mRNA expressions for the urea SCR emission showed a tendency to increase compared to those of the conventional emission. Thus, gene analysis results suggested that NO(2) from the urea SCR emission affected the expressions of mRNAs in lungs. However, as a whole, the results suggested that the health effects of the urea SCR emission might be less than the conventional emission on rats.

Role of oxidative damage in toxicity of particulates

Particulates are small particles of solid or liquid suspended in liquid or air. In vitro studies show that particles generate reactive oxygen species, deplete endogenous antioxidants, alter mitochondrial function and produce oxidative damage to lipids and DNA. Surface area, reactivity and chemical composition play important roles in the oxidative potential of particulates. Studies in animal models indicate that particles from combustion processes (generated by combustion of wood or diesel oil), silicate, titanium dioxide and nanoparticles (C60 fullerenes and carbon nanotubes) produce elevated levels of lipid peroxidation products and oxidatively damaged DNA. Biomonitoring studies in humans have shown associations between exposure to air pollution and wood smoke particulates and oxidative damage to DNA, deoxynucleotides and lipids measured in leukocytes, plasma, urine and/or exhaled breath. The results indicate that oxidative stress and elevated levels of oxidatively altered biomolecules are important intermediate endpoints that may be useful markers in hazard characterization of particulates.

PM(10) impairs the antioxidant defense system and exacerbates oxidative stress driven cell death

The aim of this study was to investigate the effect of airborne particulate matter with a mean aerodynamic diameter of < or =10microm (PM(10)) on oxidative stress markers and antioxidant enzymatic activity and its relevance in the face of acute oxidative challenge in a human lung epithelial cell line (A549). PM(10)-induced reactive oxygen species (ROS) generation and oxidative damage with no changes in cellular viability. In addition, PM(10) decreased glutathione (GSH) levels (54.9%) and the activity of the antioxidant enzymes superoxide dismutase (65%), catalase (31.2%), glutathione reductase (61.5%) and glutathione-S-transferase (42.39%). Trolox, a scavenger of reactive species, prevented the increase of ROS generation and the decrease in GSH levels but partially prevented PM(10)-induced oxidative damage. Interestingly, it was unable to avoid the decrease in the activity of antioxidant enzymes. Finally, the survival of the cells previously exposed to PM(10) and challenged with hydrogen peroxide was significantly lower. We conclude that the impairment in the antioxidant defense system induced by PM(10) weaken ROS detoxification which exacerbates cell death when these cells are exposed to an acute oxidative challenge.