Oxidative interactions of synthetic lung epithelial lining fluid with metal-containing particulate matter

Zn2+ loading as a critical contributor to the circ_0008553-mediated oxidative stress and inflammation in response to PM2.5 exposures

Inflammation is a major adverse outcome induced by inhaled particulate matter with a diameter of ≤ 2.5 µm (PM_2.5), and a critical trigger of most PM_2.5 exposure-associated diseases. However, the key molecular events regulating the PM_2.5-induced airway inflammation are yet to be elucidated. Considering the critical role of circular RNAs (circRNAs) in regulating inflammation, we predicted 11 circRNAs that may be involved in the PM_2.5-induced airway inflammation using three previously reported miRNAs through the starBase website. A novel circRNA circ_0008553 was identified to be responsible for the PM_2.5-activated inflammatory response in human bronchial epithelial cells (16HBE) via inducing oxidative stress. Using a combinatorial model PM_2.5 library, we found that the synergistic effect of the insoluble core and loaded Zn²⁺ ions at environmentally relevant concentrations was the major contributor to the upregulation of circ_0008553 and subsequent induction of oxidative stress and inflammation in response to PM_2.5 exposures. Our findings provided new insight into the intervention of PM_2.5-induced adverse outcomes.

Upregulation of circ_0035266 contributes to the malignant progression of inflammation-associated malignant transformed cells induced by tobacco-specific carcinogen NNK

Cigarette smoking-induced chronic inflammation has been considered a vital driver of lung tumorigenesis. The compounds 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a tobacco-specific carcinogen, and lipopolysaccharide (LPS), an inflammatory inducer, are important components of tobacco smoke which have been implicated in inflammation-driven carcinogenesis. However, the biological effects and underlying mechanisms of LPS-mediated inflammation on NNK-induced tumorigenesis are still unclear. In this study, BEAS-2B human bronchial epithelial cells were exposed to NNK, LPS or both, for short- or long-term periods. We found that acute LPS exposure promoted the secretion of granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin (IL)-6 in NNK-treated BEAS-2B cells. In addition, chronic LPS exposure facilitated the NNK-induced malignant transformation process by promoting cell proliferation, cell cycle alteration, migration and clonal formation. Previously, we determined that circular RNA circ_0035266 enhanced cellular inflammation in response to NNK+LPS by sponging miR-181d-5p and regulating expression of its downstream target DEAD-Box Helicase 3 X-Linked (DDX3X). Here, we found that knockdown of circ_0035266 or DDX3X led to a remarkable inhibition of the proliferation, cell cycle progression and migration of NNK+LPS-transformed BEAS-2B cells, while overexpression of these genes produced the opposite effects, indicating the oncogenic roles of circ_0035266 and DDX3X in the malignant progression of chronic inflammation-driven malignant transformed cells. Moreover, the regulatory relationships among circ_0035266, miR-181d-5p and DDX3X were further confirmed using a group of lung cancer tissues. Conclusively, our findings provide novel insights into our understanding of inflammation-driven tumorigenesis using a cellular malignant transformation model, and indicate a novel tumor-promoting role for circ_0035266 in chemical carcinogenesis.

Effects of albumin, transferrin and humic-like substances on iron-mediated OH radical formation in human lung fluids

Inhalation of particulate matter is hypothesized to contribute to health effects by overproducing reactive oxygen species (ROS) and inducing oxidative stress. Fe(II) has been shown to contribute to ROS generation in acellular simulated lung fluids. Atmospheric humic-like substances (HULIS) have been shown to chelate Fe(II) and significantly enhance this ROS generation. Here, we investigate Fe(II)-mediated ^.OH generation from the iron active proteins in lung fluid, albumin and transferrin, and fulvic acid, a surrogate for HULIS, in human bronchoalveolar lavage fluid (BALF). We find that albumin enhances ^.OH generation from inorganic Fe(II) and that transferrin attenuates this enhancement. We estimate the rate constants for albumin-Fe(II) and fulvic acid-Fe(II) mediated O₂^.- reduction (1.9 ± 0.3) M^-1 s^-1 and (2.7 ± 0.3) M^-1s^-1 (pH = 5.5, T = 37 °C), 17-25 times the rate for free iron, which we measured to be (110 ± 20) × 10^-3 M^-1s^-1, in agreement with the literature. ^.OH generation measured from fulvic acid-Fe(II) in BALF from 8 individuals with added fulvic acid is successfully predicted rates of ^.OH generation by mixtures of Fe(II), albumin, transferrin, fulvic acid, and ascorbate in saline solution. This indicates that fulvic acid enhances ^.OH formation in BALF, and that albumin and transferrin in BALF moderate the effect. We propose that fulvic acid, and thereby HULIS, is capable of mobilizing Fe(II) away from albumin and transferrin and this increases the formation rate of O₂^.- and ultimately of ^.OH. Furthermore, we find that albumin and transferrin have significantly different impacts on Fe(II)-mediated ^.OH than citrate, a common component of simulated lung fluids, a factor that should be considered carefully in the interpretation of results obtained from solutions containing citrate.

DEHP-elicited small extracellular vesicles miR-26a-5p promoted metastasis in nearby normal A549 cells

Small extracellular vesicles (sEV) are small lipid bilayer particles released by cells. sEV have been shown to play critical roles in intercellular communication. Di (2-ethylhexyl) phthalate (DEHP), widely used as plasticizers, has been detected in the environment and human beings. DEHP was found to exist in the air particles and showed pulmonary toxicity. However, there's little knowledge about the role of sEV in mediating the toxicity of DEHP-induced lung toxicity. We hypothesized that sEV mediated the toxicity of DEHP through their cargo. To validate this, lung epithelial cells (A549) were exposed to various concentrations (0, 0.2, 2 and 20 μM) of DEHP for 48 h. sEV extracted from DEHP-exposed A549 cells were cultured with unexposed A549 cells. Results showed that DEHP induced the epithelial-mesenchymal transition (EMT) and promoted the migration and invasion ability of A549 cells. The number of released sEV significantly increased in the culture media in DEHP-exposed groups compared to unexposed groups. The sEV can enter the unexposed A549 cells and enhance its EMT and the ability of migration and invasion. Treatment with GW4869 in DEHP-exposed A549 cells almost blocked the effects of DEHP-elicited sEV in normal A549 cells. Sequencing and functional analysis showed that the enrichment of significantly differentially expressed sEV miRNAs were related to tumor etiology. MiR-26a-5p was significantly enriched in DEHP-elicited sEV. Inhibition of miR-26a-5p in DEHP-exposed cells led to the downregulation of miR-26a-5p in sEV, and thus abolished the effects of DEHP-elicited sEV in normal A549 cells, whereas overexpression of miR-26a-5p restored the effects. The transcription factors twist is one of the downstream targets in the effects of sEV-miR-26a-5p on EMT process. In all, our results showed that DEHP exposure promoted the secretion of miR-26a-5p in sEV, which subsequently enhanced the EMT, migration and invasion ability in neighboring normal cells via the twist.

Tobacco-Related Exposure Upregulates Circ_0035266 to Exacerbate Inflammatory Responses in Human Bronchial Epithelial Cells

One of the most carcinogenic chemicals found in cigarette tobacco smoke is 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), which has been confirmed to be associated with the etiology of diverse cancers. Lipopolysaccharide (LPS), another biologically active component of cigarette smoke, is a risk factor which enhances NNK-induced lung tumorigenesis due to chronic lung inflammation. Although inflammatory responses play critical roles in the initiation of many tumors, our knowledge about the mechanisms of NNK+LPS on inflammation is currently limited. Here, we investigated the inflammatory effects of NNK+LPS in human bronchial epithelial cells (BEAS-2B) and explored the underlying mechanisms mediated by circular RNAs (circRNAs). We identified a novel circRNA, circ_0035266, which was strongly upregulated in NNK+LPS-induced BEAS-2B cells and enhanced the inflammatory responses to NNK+LPS by regulating the secretion of pro-inflammatory cytokines interleukin (IL)-6 and IL-8. Specifically, circ_0035266 knockdown alleviated NNK+LPS-induced inflammatory responses, whereas overexpression of circ_0035266 had the opposite effect. Moreover, dual-luciferase reporter and fluorescence in situ hybridization (FISH) assays verified that circ_0035266 bound to miR-181d-5p directly in the cytoplasm. qRT-PCR, dual-luciferase reporter assays, and Western blot analyses showed that DDX3X (DDX3) was the downstream target of miR-181d-5p and that DDX3X expression levels were modulated by circ_0035266. These results suggested that circ_0035266 served as a competitive endogenous RNA for miR-181d-5p to regulate DDX3X expression, which is involved in the modulation of NNK+LPS-induced inflammatory responses in BEAS-2B cells.

Large global variations in measured airborne metal concentrations driven by anthropogenic sources

Globally consistent measurements of airborne metal concentrations in fine particulate matter (PM_2.5) are important for understanding potential health impacts, prioritizing air pollution mitigation strategies, and enabling global chemical transport model development. PM_2.5 filter samples (N ~ 800 from 19 locations) collected from a globally distributed surface particulate matter sampling network (SPARTAN) between January 2013 and April 2019 were analyzed for particulate mass and trace metals content. Metal concentrations exhibited pronounced spatial variation, primarily driven by anthropogenic activities. PM_2.5 levels of lead, arsenic, chromium, and zinc were significantly enriched at some locations by factors of 100–3000 compared to crustal concentrations. Levels of metals in PM_2.5 and PM₁₀ exceeded health guidelines at multiple sites. For example, Dhaka and Kanpur sites exceeded the US National Ambient Air 3-month Quality Standard for lead (150 ng m⁻³). Kanpur, Hanoi, Beijing and Dhaka sites had annual mean arsenic concentrations that approached or exceeded the World Health Organization’s risk level for arsenic (6.6 ng m⁻³). The high concentrations of several potentially harmful metals in densely populated cites worldwide motivates expanded measurements and analyses.

Human airway construct model is suitable for studying transcriptome changes associated with indoor air particulate matter toxicity

In vitro models mimicking the human respiratory system are essential when investigating the toxicological effects of inhaled indoor air particulate matter (PM). We present a pulmonary cell culture model for studying indoor air PM toxicity. We exposed normal human bronchial epithelial cells, grown on semi-permeable cell culture membranes, to four doses of indoor air PM in the air-liquid interface. We analyzed the chemokine interleukin-8 concentration from the cell culture medium, protein concentration from the apical wash, measured tissue electrical resistance, and imaged airway constructs using light and transmission electron microscopy. We sequenced RNA using a targeted RNA toxicology panel for 386 genes associated with toxicological responses. PM was collected from a non-complaint residential environment over 1 week. Sample collection was concomitant with monitoring size-segregated PM counts and determination of microbial levels and diversity. PM exposure was not acutely toxic for the cells, and we observed up-regulation of 34 genes and down-regulation of 17 genes when compared to blank sampler control exposure. The five most up-regulated genes were related to immunotoxicity. Despite indications of incomplete cell differentiation, this model enabled the comparison of a toxicological transcriptome associated with indoor air PM exposure.

Simulation of airborne trace metals in fine particulate matter over North America

Trace metal distributions are of relevance to understand sources of fine particulate matter (PM2.5), PM2.5-related health effects, and atmospheric chemistry. However, knowledge of trace metal distributions is lacking due to limited ground-based measurements and model simulations. This study develops a simulation of 12 trace metal concentrations (Si, Ca, Al, Fe, Ti, Mn, K, Mg, As, Cd, Ni and Pb) over continental North America for 2013 using the GEOS-Chem chemical transport model. Evaluation of modeled trace metal concentrations with observations indicates a spatial consistency within a factor of 2, an improvement over previous studies that were within a factor of 3-6. The spatial distribution of trace metal concentrations reflects their primary emission sources. Crustal element (Si, Ca, Al, Fe, Ti, Mn, K) concentrations are enhanced over the central US from anthropogenic fugitive dust and over the southwestern U.S. due to natural mineral dust. Heavy metal (As, Cd, Ni and Pb) concentrations are high over the eastern U.S. from industry. K is abundance in the southeast from biomass burning and high concentrations of Mg is observed along the coast from sea spray. The spatial pattern of PM2.5 mass is most strongly correlated with Pb, Ni, As and K due to their signature emission sources. Challenges remain in accurately simulating observed trace metal concentrations. Halving anthropogenic fugitive dust emissions in the 2011 National Air Toxic Assessment (NATA) inventory and doubling natural dust emissions in the default GEOS-Chem simulation was necessary to reduce biases in crustal element concentrations. A fivefold increase of anthropogenic emissions of As and Pb was necessary in the NATA inventory to reduce the national-scale bias versus observations by more than 80 %, potentially reflecting missing sources.

Urban particulate matter (PM) suppresses airway antibacterial defence

Background

Epidemiological studies have shown that urban particulate matter (PM) increases the risk of respiratory infection. However, the underlying mechanisms are poorly understood. PM has been postulated to suppress the activation of airway epithelial innate defence in response to infection.

Methods

The effects of PM on antibacterial defence were studied using an in vitro infection model. The levels of antimicrobial peptides were measured using RT-PCR and ELISA. In addition to performing colony-forming unit counts and flow cytometry, confocal microscopy was performed to directly observe bacterial invasion upon PM exposure.

Results

We found that PM PM increased bacterial invasion by impairing the induction of β-defensin-2 (hBD-2), but not the other antimicrobial peptides (APMs) secreted by airway epithelium. PM further increases bacteria-induced ROS production, which is accompanied by an accelerated cell senescence and a decrease in bacteria-induced hBD-2 production, and the antioxidant NAC treatment attenuates these effects. The PM exposure further upregulated the expression of IL-8 but downregulated the expression of IL-13 upon infection.

Conclusions

PM promotes bacterial invasion of airway epithelial cells by attenuating the induction of hBD-2 via an oxidative burst. These findings associate PM with an increased susceptibility to infection. These findings provide insight into the underlying mechanisms regarding the pathogenesis of particulate matter.

Health Outcomes of Exposure to Biological and Chemical Components of Inhalable and Respirable Particulate Matter

Particulate matter (PM) is a key indicator of air pollution and a significant risk factor for adverse health outcomes in humans. PM is not a self-contained pollutant but a mixture of different compounds including chemical and biological fractions. While several reviews have focused on the chemical components of PM and associated health effects, there is a dearth of review studies that holistically examine the role of biological and chemical components of inhalable and respirable PM in disease causation. A literature search using various search engines and (or) keywords was done. Articles selected for review were chosen following predefined criteria, to extract and analyze data. The results show that the biological and chemical components of inhalable and respirable PM play a significant role in the burden of health effects attributed to PM. These health outcomes include low birth weight, emergency room visit, hospital admission, respiratory and pulmonary diseases, cardiovascular disease, cancer, non-communicable diseases, and premature death, among others. This review justifies the importance of each or synergistic effects of the biological and chemical constituents of PM on health. It also provides information that informs policy on the establishment of exposure limits for PM composition metrics rather than the existing exposure limits of the total mass of PM. This will allow for more effective management strategies for improving outdoor air quality.

A Novel High-Throughput Approach to Measure Hydroxyl Radicals Induced by Airborne Particulate Matter

Oxidative stress is one of the key mechanisms linking ambient particulate matter (PM) exposure with various adverse health effects. The oxidative potential of PM has been used to characterize the ability of PM induced oxidative stress. Hydroxyl radical (•OH) is the most destructive radical produced by PM. However, there is currently no high-throughput approach which can rapidly measure PM-induced •OH for a large number of samples with an automated system. This study evaluated four existing molecular probes (disodium terephthalate, 3′-p-(aminophenyl)fluorescein, coumarin-3-carboxylic acid, and sodium benzoate) for their applicability to measure •OH induced by PM in a high-throughput cell-free system using fluorescence techniques, based on both our experiments and on an assessment of the physicochemical properties of the probes reported in the literature. Disodium terephthalate (TPT) was the most applicable molecular probe to measure •OH induced by PM, due to its high solubility, high stability of the corresponding fluorescent product (i.e., 2-hydroxyterephthalic acid), high yield compared with the other molecular probes, and stable fluorescence intensity in a wide range of pH environments. TPT was applied in a high-throughput format to measure PM (NIST 1648a)-induced •OH, in phosphate buffered saline. The formed fluorescent product was measured at designated time points up to 2 h. The fluorescent product of TPT had a detection limit of 17.59 nM. The soluble fraction of PM contributed approximately 76.9% of the •OH induced by total PM, and the soluble metal ions of PM contributed 57.4% of the overall •OH formation. This study provides a promising cost-effective high-throughput method to measure •OH induced by PM on a routine basis.

Macrophages treated with particulate matter PM2.5 induce selective neurotoxicity through glutaminase-mediated glutamate generation

Exposure to atmospheric particulate matter PM2.5 (aerodynamic diameter ≤ 2.5 μm) has been epidemiologically associated with respiratory illnesses. However, recent data have suggested that PM2.5 is able to infiltrate into circulation and elicit a systemic inflammatory response. Potential adverse effects of air pollutants to the central nervous system (CNS) have raised concerns, but whether PM2.5 causes neurotoxicity remains unclear. In this study, we have demonstrated that PM2.5 impairs the tight junction of endothelial cells and increases permeability and monocyte transmigration across endothelial monolayer in vitro, indicating that PM2.5 is able to disrupt blood-brain barrier integrity and gain access to the CNS. Exposure of primary neuronal cultures to PM2.5 resulted in decrease in cell viability and loss of neuronal antigens. Furthermore, supernatants collected from PM2.5 -treated macrophages and microglia were also neurotoxic. These macrophages and microglia significantly increased extracellular levels of glutamate following PM2.5 exposure, which were negatively correlated with neuronal viability. Pre-treatment with NMDA receptor antagonist MK801 alleviated neuron loss, suggesting that PM2.5 neurotoxicity is mediated by glutamate. To determine the potential source of excess glutamate production, we investigated glutaminase, the main enzyme for glutamate generation. Glutaminase was reduced in PM2.5 -treated macrophages and increased in extracellular vesicles, suggesting that PM2.5 induces glutaminase release through extracellular vesicles. In conclusion, these findings indicate PM2.5 as a potential neurotoxic factor, crucial to understanding the effects of air pollution on the CNS.

Water-insoluble fraction of airborne particulate matter (PM10 ) induces oxidative stress in human lung epithelial A549 cells

Exposure to ambient airborne particulate matter (PM) with an aerodynamic diameter less than 10 μm (PM10 ) links with public health hazards and increases risk for lung cancer and other diseases. Recent studies have suggested that oxidative stress is a key mechanism underlying the toxic effects of exposure to PM10 . Several components of water-soluble fraction of PM10 (sPM10 ) have been known to be capable of inducing oxidative stress in in vitro studies. In this study, we investigated if water-insoluble fraction of PM10 (iPM10 ) could be also capable of inducing oxidative stress and oxidative damage. Human lung epithelial A549 cells were exposed to 10 μg/mL of sPM10 , iPM10 or total PM10 (tPM10 ) preparation for 24 h. Here, we observed that all three PM10 preparations reduced cell viability and induced apoptotic cell death in A549 cells. We further found that, similar to the exposure to sPM10 and tPM10 , the intracellular level of hydrogen peroxide (H2 O2 ) in the iPM10 -exposed cells was increased significantly; meanwhile the activity of catalase was decreased significantly as compared with the unexposed control cells, resulting in significant DNA damage. Our data obtained from inductively coupled plasma-mass spectrometry (ICP-MS) assays showed that iron is the most abundant metal in all three PM10 preparations. Thus, we have demonstrated that, similar to sPM10 , iPM10 is also capable of inducing oxidative stress by probably inducing generation of H2 O2 and impairing enzymatic antioxidant defense, resulting in oxidative DNA damage and even apoptotic cell death through the iron-catalyzed Fenton reaction.

Cardiopulmonary toxicity of pulmonary exposure to occupationally relevant zinc oxide nanoparticles

Exposure to zinc oxide (ZnO) metal fumes is linked to adverse human health effects; however, the hazards of ZnO nanoparticles (ZnONPs) remain unclear. To determine pulmonary exposure to occupationally relevant ZnONPs cause cardiopulmonary injury, Sprague-Dawley rats were exposed to ZnONPs via intratracheal (IT) instillation and inhalation. The relationship between intrapulmonary zinc levels and pulmonary oxidative-inflammatory responses 72 h after ZnONP instillation was determined in bronchoalveolar lavage fluid (BALF). Instilled ZnONPs altered zinc balance and increased the levels of total cells, neutrophils, lactate dehydrogenase (LDH) and total protein in BALF and 8-hydroxy-2'-deoxyguanosine (8-OHdG) in blood after 72 h. The ZnONPs accumulated predominantly in the lungs over 24 h, and trivial amounts of zinc were determined in the heart, liver, kidneys and blood. Furthermore, the inflammatory-oxidative responses induced by occupationally relevant levels of 1.1 and 4.9 mg/m(3) of ZnONP inhalation for 2 weeks were determined in BALF and blood at 1, 7 and 30 days post-exposure. Histopathological examinations of the rat lungs and hearts were performed. Inhalation of ZnONP caused an inflammatory cytological profile. The total cell, neutrophil, LDH and total protein levels were acutely increased in the BALF, and there was an inflammatory pathology in the lungs. There were subchronic levels of white blood cells, granulocytes and 8-OHdG in the blood. Cardiac inflammation and the development of fibrosis were detected 7 days after exposure. Degeneration and necrosis of the myocardium were detected 30 days after exposure. The results demonstrate that ZnONPs cause cardiopulmonary impairments. These findings highlight the occupational health effects for ZnONP-exposed workers.

PM2.5 induces Nrf2-mediated defense mechanisms against oxidative stress by activating PIK3/AKT signaling pathway in human lung alveolar epithelial A549 cells

It has been well documented in in vitro studies that ambient airborne particulate matter (PM) with an aerodynamic diameter less than 2.5 μm (PM(2.5)) is capable of inducing oxidative stress, which plays a key role in PM(2.5)-mediated cytotoxicity. Although nuclear factor erythroid-2-related factor 2 (Nrf2) has been shown to regulate the intracellular defense mechanisms against oxidative stress, a potential of the Nrf2-mediated cellular defense against oxidative stress induced by PM(2.5) remains to be determined. This study was aimed to explore the potential signaling pathway of Nrf2-mediated defense mechanisms against PM(2.5)-induced oxidative stress in human type II alveolar epithelial A549 cells. We exposed A549 cells to PM(2.5) particles collected from Beijing at a concentration of 16 μg/cm(2). We observed that PM(2.5) triggered an increase of intracellular reactive oxygen species (ROS) in a time-dependent manner during a period of 2 h exposure. We also found that Nrf2 overexpression suppressed and Nrf2 knockdown increased PM(2.5)-induced ROS generation. Using Western blot and confocal microscopy, we found that PM(2.5) exposure triggered significant translocation of Nrf2 into nucleus, resulting in AKT phosphorylation and significant transcription of ARE-driven phases II enzyme genes, such as NAD(P)H:quinone oxidoreductase (NQO-1), heme oxygenase-1 (HO-1), and glutamate-cysteine ligase catalytic subunit (GCLC) in A549 cells. Evaluation of signaling pathways showed that a phosphatidylinositol 3-kinase (PI3K) inhibitor (LY294002), but not an ERK 1/2 inhibitor (PD98059) or a p38 MAPK (SB203580), significantly down-regulated PM(2.5)-induced Nrf2 nuclear translocation and HO-1 mRNA expression, indicating PI3K/AKT is involved in the signaling pathway leads to the PM(2.5)-induced nuclear translocation of Nrf2 and subsequent Nrf2-mediated HO-1 transcription. Taken together, our results suggest that PM(2.5)-induced ROS may function as signaling molecules to activate Nrf2-mediated defenses, such as HO-1 expression, against oxidative stress induced by PM(2.5) through the PI3K/AKT signaling pathway.

PM(2.5) in the central part of Upper Silesia, Poland: concentrations, elemental composition, and mobility of components

The paper discusses ambient concentrations of PM(2.5) (ambient fine particles) and of 29 PM(2.5)-related elements in Zabrze and Katowice, Poland, in 2007. The elemental composition of PM(2.5) was determined using energy dispersive X-ray fluorescence (EDXRF). The mobility (cumulative percentage of the water-soluble and exchangeable fractions of an element in its total concentration) of 18 PM(2.5)-related elements in Zabrze and Katowice was computed by using sequential extraction and EDXRF combined into a simple method. The samples were extracted twice: in deionized water and in ammonium acetate. In general, the mobility and the concentrations of the majority of the elements were the same in both cities. S, Cl, K, Ca, Zn, Br, Ba, and Pb in both cities, Ti and Se in Katowice, and Sr in Zabrze had the mobility greater than 70%. Mobility of typical crustal elements, Al, Si, and Ti, because of high proportion of their exchangeable fractions in PM, was from 40 to 66%. Mobility of Fe and Cu was lower than 30%. Probable sources of PM(2.5) were determined by applying principal component analysis and multiple regression analysis and computing enrichment factors. Great part of PM(2.5) (78% in Katowice and 36% in Zabrze) originated from combustion of fuels in domestic furnaces (fossil fuels, biomass and wastes, etc.) and liquid fuels in car engines. Other identified sources were: power plants, soil, and roads in Zabrze and in Katowice an industrial source, probably a non-ferrous smelter or/and a steelwork, and power plants.

Protective effects of pulmonary epithelial lining fluid on oxidative stress and DNA single-strand breaks caused by ultrafine carbon black, ferrous sulphate and organic extract of diesel exhaust particles

Pulmonary epithelial lining fluid (ELF) is the first substance to make contact with inhaled particulate matter (PM) and interacts chemically with PM components. The objective of this study was to determine the role of ELF in oxidative stress, DNA damage and the production of proinflammatory cytokines following physicochemical exposure to PM. Ultrafine carbon black (ufCB, 15 nm; a model carbonaceous core), ferrous sulphate (FeSO(4); a model transition metal) and a diesel exhaust particle (DEP) extract (a model organic compound) were used to examine the acellular oxidative potential of synthetic ELF and non-ELF systems. We compared the effects of exposure to ufCB, FeSO(4) and DEP extract on human alveolar epithelial Type II (A549) cells to determine the levels of oxidative stress, DNA single-strand breaks and interleukin-8 (IL-8) production in ELF and non-ELF systems. The effects of ufCB and FeSO(4) on the acellular oxidative potential, cellular oxidative stress and DNA single-strand breakage were mitigated significantly by the addition of ELF, whereas there was no decrease following treatment with the DEP extract. There was no significant effect on IL-8 production following exposure to samples that were suspended in ELF/non-ELF systems. The results of the present study indicate that ELF plays an important role in the initial defence against PM in the pulmonary environment. Experimental components, such as ufCB and FeSO(4), induced the production of oxidative stress and led to DNA single-strand breaks, which were moderately prevented by the addition of ELF. These findings suggest that ELF plays a protective role against PM-driven oxidative stress and DNA damage.

Interactive enhancements of ascorbic acid and iron in hydroxyl radical generation in quinone redox cycling

Quinones are toxicological substances in inhalable particulate matter (PM). The mechanisms by which quinones cause hazardous effects can be complex. Quinones are highly active redox molecules that can go through a redox cycle with their semiquinone radicals, leading to formation of reactive oxygen species. Electron spin resonance spectra have been reported for semiquinone radicals in PM, indicating the importance of ascorbic acid and iron in quinone redox cycling. However, these findings are insufficient for understanding the toxicity associated with quinone exposure. Herein, we investigated the interactions among anthraquinone (AQ), ascorbic acid, and iron in hydroxyl radical (·OH) generation through the AQ redox cycling process in a physiological buffer. We measured ·OH concentration and analyzed the free radical process. Our results showed that AQ, ascorbic acid, and iron have synergistic effects on ·OH generation in quinone redox cycling; i.e., ascorbyl radical oxidized AQ to semiquinone radical and started the redox cycling, iron accelerated this oxidation and enhanced ·OH generation through Fenton reactions, while ascorbic acid and AQ could help iron to release from quartz surface and enhance its bioavailability. Our findings provide direct evidence for the redox cycling hypothesis about airborne particle surface quinone in lung fluid.

Determination of metal-based hydroxyl radical generating capacity of ambient and diesel exhaust particles

Numerous studies have suggested the association of reactive oxygen species (ROS) with adverse health effects derived from exposure to airborne particulate matter (PM) and diesel exhaust particles (DEP). This redox activity has been attributed to both inorganic and organic species present in these particles, but a clear distinction has not been established between the contribution of each. This article describes an application of an analytical procedure, based on the reaction of salicylic acid with hydroxyl radical to form dihydroxybenzoate (DHBA) isomers, to measure transition metal-based redox activity associated with ambient and diesel exhaust particles. In the procedure, ascorbic acid (AA) is used as electron source for reduction of metal ions and oxygen to generate superoxide, which is further reduced to hydroxyl radical in the presence of transition metal ions. Hydroxyl radical reacts with salicylate to generate DHBA isomers, which are measured by high-performance liquid chromatography (HPLC) with electrochemical detector. Both copper (Cu) and iron (Fe) ions generated DHBA isomers in a concentration-dependent manner but at different rates. The procedure was applied to DEP and ambient particles and the results showed Cu ion to be the major contributor to DHBA formation. The procedure provides a quantitative measure of transition metal-based redox activity associated with ambient samples with different physicochemical properties.

Oxidative stress induced by zero-valent iron nanoparticles and Fe(II) in human bronchial epithelial cells

To identify the mechanism through which nanoparticulate zero-valent iron (nZVI; Fe0(s)) damages cells, a series of experiments were conducted in which nZVI in phosphate-buffered saline (PBS) was exposed to oxygen in the presence and absence of human bronchial epithelial cells. When nZVI is added to PBS, a burst of oxidants is produced as Fe0 and ferrous iron (Fe[II]) are converted to ferric iron (Fe[II]). Cytotoxicity and internal reactive oxygen species (ROS) production in cells exposed to nZVI is equivalent to the response observed when cells are exposed to the same concentration of dissolved Fe(II). Experiments conducted in the absence of cells indicate that the oxidant produced during Fe(II) oxidation reacts with methanol and dimethyl sulfoxide, but not with compounds such as tert-butanol and benzoate that react exclusively with hydroxyl radical. The role of reactive oxidants produced during Fe(II) oxidation in cytotoxicity and internal ROS production is further supported by experiments in which cell damage was limited by the addition of ligands that prevented Fe(II) oxidation and by the absence of cell damage when the nanoparticles were oxidized prior to exposure. The behavior of the oxidant produced by nZVI is consistent with an oxidant such as the ferryl ion, rather than hydroxyl radical.

Metallic species in atmospheric particulate matter in Las Palmas de Gran Canaria

In this work, we quantified the total, water-soluble and insoluble fractions of 12 metallic species (Na, Ca, K, Mg, Fe, Zn, Cr, Ni, Cu, Cd, Pb and Mn) present in total suspended particulates (TSP) in an urban area with heavy traffic (about 80 000 vehicles/day) of Las Palmas de Gran Canaria (Canary Islands). Experimental measurements were made from July to December 2003 on a total of 42 samples (7 per month). Particulate matter (TSP) was collected in fiber filters and high volume samplers. PM10 levels were estimated assuming the PM10 fraction is about 70% of all TSP. Total fractions was determined gravimetrically. Water-soluble fraction was extracted by sonication. Concentrations of metallic elements were analyzed by flame atomic absorption spectrophotometer. Temporal changes in the concentrations of the target elements were examined and a multivariate approach used to identify the primary sources for each species. Mean value for TSP is 71.92microg/m3. The water-soluble fraction consisted mainly of Na, Ca, Mg, and K. The insoluble fraction contained higher concentrations of all elements than the soluble except Na. In the water-soluble fraction, Na, K, Ca and Mg were found to come mainly from natural sources; Cr, Pb, Cd, Ni, Zn and Cu from anthropogenic sources.

Towards a multidisciplinary and integrated strategy in the assessment of adverse health effects related to air pollution: the case study of Cracow (Poland) and asthma

Complex interaction between anthropogenic activities, air quality and human health in urban areas, such as in Cracow sustains the need for the development of an interdisciplinary and integrated risk-assessment methodology. In such purpose, we propose a pilot study performed on asthmatics and based on a combined use of a biomarker, such as metallothionein 2A (MT-2A) in the characterization of human exposure to one or a mixture of pollutants and of Geographical Information Systems (G.I.S.) which integrates climatic and urban anthropogenic parameters in the assessment of spatio-temporal dispersion of air pollutants. Considering global incidence of air pollution on asthma and on peripheral blood lymphocytes MT-2A expression should provide a complementary information on biological risks linked to urban anthropogenic activities. Such study would help for the establishment of a sustainable development in urban areas that can maintain the integrity of air quality and preserve human health.

Alveolar epithelial cells secrete chemokines in response to IL-1beta and lipopolysaccharide but not to ozone

Ozone exposure produces acute inflammation and neutrophil influx in the distal lung. Alveolar epithelial cells cover a large surface area, secrete chemokines, and may initiate or modify the inflammatory response. The effect of ozone on chemokine production by these cells has not been defined. Isolated rat type II cells were cultured in different conditions to express the morphologic appearance and biochemical markers for the type I and the type II cell phenotypes. These cells were exposed to ozone at an air/liquid interface. The type I-like cells were more susceptible to injury than the type II cells and showed signs of injury at exposure levels of 100 ppb ozone for 60 min. Both phenotypes showed evidence of lipid peroxidation after ozone exposure as measured by 8-isoprostane production, but neither phenotype secreted increased amounts of MIP-2 (CXCL3), CINC-1 (CXCL1), or MCP-1 (CCL2) in response to ozone. Both cell phenotypes secreted MIP-2 and MCP-1 in response to IL-1beta or lipopolysaccharide, but there was no priming or synergy with ozone. It is likely that the inflammatory response to ozone in the alveolar compartment is not due to the direct effect of ozone on epithelial cells.

Air pollution and health

The health effects of air pollution have been subject to intense study in recent years. Exposure to pollutants such as airborne particulate matter and ozone has been associated with increases in mortality and hospital admissions due to respiratory and cardiovascular disease. These effects have been found in short-term studies, which relate day-to-day variations in air pollution and health, and long-term studies, which have followed cohorts of exposed individuals over time. Effects have been seen at very low levels of exposure, and it is unclear whether a threshold concentration exists for particulate matter and ozone below which no effects on health are likely. In this review, we discuss the evidence for adverse effects on health of selected air pollutants.