Reactive oxygen species in pulmonary inflammation by ambient particulates

Effect of particles of ashes produced from sugarcane burning on the respiratory system of rats

The practice of burning sugarcane obtained by non-mechanized harvesting exposes workers and the people of neighboring towns to high concentrations of particulate matter (PM) that is harmful to health, and may trigger a series of cardiorespiratory diseases. The aim of this study was to analyze the chemical composition of the micro-particles coming from sugarcane burning residues and to verify the effects of this micro-particulate matter on lung and tracheal tissues. Micro-particulate matter (PM10) was obtained by dissolving filter paper containing burnt residues in NaCl solution. This material was instilled into the Wistar rats' nostrils. Histological analyses (hematoxylin and eosin - HE) of cardiac, lung and tracheal tissues were performed. Inflammatory mediators were measured in lung tissues by using ELISA. The chemical composition of the particulate material revealed a large quantity of the phthalic acid ester, high concentrations of phenolic compounds, anthracene and polycyclic aromatic hydrocarbons (PAH). Histological analysis showed a reduction in subjacent conjunctive tissue in the trachea, lung inflammation with inflammatory infiltrate formation and reduction of alveolar spaces and a significant increase (p<0.05) in the release of IL-1α, IL-1β, IL-6, and INF-γ in the group treated with PM10 when compared to the control group. We concluded that the burning sugarcane residues release many particles, which have toxic chemical compounds. The micro-particulate matter can induce alterations in the respiratory system.

Decreasing effect and mechanism of FeSO4 seed particles on secondary organic aerosol in α-pinene photooxidation

α-Pinene/NOx and α-pinene/HONO photooxidation experiments at varying humidity were conducted in smog chambers in the presence or absence of FeSO4 seed particles. FeSO4 seed particles decrease SOA mass as long as water was present on the seed particle surface, but FeSO4 seed particles have no decreasing effect on SOA under dryer conditions at 12% relative humidity (RH). The decreasing effect of FeSO4 seed particles on the SOA mass is proposed to be related to oxidation processes in the surface layer of water on the seed particles. Free radicals, including OH, can be formed from catalytic cycling of Fe(2+) and Fe(3+) in the aqueous phase. These radicals can react further with the organic products of α-pinene oxidation on the seed particles. The oxidation may lead to formation of smaller molecules which have higher saturation vapor pressures and favor repartitioning to the gas phase, and therefore, reduces SOA mass.

Time course of pulmonary burden in mice exposed to residual oil fly ash

Residual oil fly ash (ROFA) is a common pollutant in areas where oil is burned. This particulate matter (PM) with a broad distribution of particle diameters can be inhaled by human beings and putatively damage their respiratory system. Although some studies deal with cultured cells, animals, and even epidemiological issues, so far a comprehensive analysis of respiratory outcomes as a function of the time elapsed after exposure to a low dose of ROFA is wanted. Thus, we aimed to investigate the time course of mechanical, histological, and inflammatory lung changes, as well as neutrophils in the blood, in mice exposed to ROFA until 5 days after exposure. BALB/c mice (25 ± 5 g) were randomly divided into 7 groups and intranasally instilled with either 10 μL of sterile saline solution (0.9% NaCl, CTRL) or ROFA (0.2 μg in 10 μL of saline solution). Pulmonary mechanics, histology (normal and collapsed alveoli, mononuclear and polymorphonuclear cells, and ultrastructure), neutrophils (in blood and bronchoalveolar lavage fluid) were determined at 6 h in CTRL and at 6, 24, 48, 72, 96, and 120 h after ROFA exposure. ROFA contained metal elements, especially iron, polycyclic aromatic hydrocarbons (PAHs), and organochlorines. Lung resistive pressure augmented early (6 h) in the course of lung injury and other mechanical, histological and inflammatory parameters increased at 24 h, returning to control values at 120 h. Blood neutrophilia was present only at 24 and 48 h after exposure. Swelling of endothelial cells with adherent neutrophils was detected after ROFA instillation. No neutrophils were present in the lavage fluid. In conclusion, the exposure to ROFA, even in low doses, induced early changes in pulmonary mechanics, lung histology and accumulation of neutrophils in blood of mice that lasted for 4 days and disappeared spontaneously.

Global perspective on the oxidative potential of airborne particulate matter: a synthesis of research findings

An emerging hypothesis in the field of air pollution is that oxidative stress is one of the important pathways leading to adverse health effects of airborne particulate matter (PM). To advance our understanding of sources and chemical elements contributing to aerosol oxidative potential and provide global comparative data, we report here on the biological oxidative potential associated with size-segregated airborne PM in different urban areas of the world, measured by a biological (cell-based) reactive oxygen species (ROS) assay. Our synthesis indicates a generally greater intrinsic PM oxidative potential as well as higher levels of exposure to redox-active PM in developing areas of the world. Moreover, on the basis of our observations, smaller size fractions are generally associated with higher intrinsic ROS activity compared with larger PM size fractions. Another important outcome of our study is the identification of major species and sources that are associated with ROS activity. Water-soluble transition metals (e.g., Fe, Ni, Cu, Cr, Mn, Zn and V) and water-soluble organic carbon (WSOC) showed consistent correlations with the oxidative potential of airborne PM across different urban areas and size ranges. The major PM sources associated with these chemical species include residual/fuel oil combustion, traffic emissions, and secondary organic aerosol formation, indicating that these sources are major drivers of PM-induced oxidative potential. Moreover, comparison of ROS activity levels across different seasons indicated that photochemical aging increases the intrinsic oxidative potential of airborne PM.

Pulmonary inflammation and cell death in mice after acute exposure to air particulate matter from an industrial region of Buenos Aires

Epidemiological studies have shown that air particulate matter (PM) can increase respiratory morbidity and mortality being the lungs the main target organ to PM body entrance. Even more, several in vivo and in vitro studies have shown that air PM has a wide toxicity spectra depending among other parameters, on its size, morphology, and chemical composition. The Reconquista River is the second most polluted river from Buenos Aires, and people living around its basin are constantly exposed to its contaminated water, soil and air. However, the air PM from the Reconquista River (RR-PMa) has not been characterized, and its biological impact on lung has yet not been assessed. Therefore, the present investigation was undertaken to study (1) RR-PMa morphochemical characteristic and (2) RR-PMa lung acute effects after intranasal instillation exposure through the analysis of three end points: oxidative stress, inflammation, and apoptosis. A single acute exposure of RR-PMa (1 mg/kg body weight) after 24 h caused significant (p < 0.05) enrichment in bronchoalveolar total cell number and polymorphonuclear (PNM) fraction, superoxide anion generation, production of pro-inflammatory cytokines TNF-α and IL-6, and induction of apoptosis. It was also observed that in lung homogenates, none of the antioxidant enzymes assayed showed differences between exposed RR-PMa and control mice. These data demonstrate that air PM from the Reconquista River induce lung oxidative stress, inflammation, and cell death therefore represents a potential hazard to human health.

DNA damage caused by inorganic particulate matter on Raji and HepG2 cell lines exposed to ultraviolet radiation

Epidemiological studies have correlated exposure to ultraviolet-irradiated particulate matter with cardiovascular, respiratory, and lung diseases. This study investigated the DNA damage induced by two major inorganic particulate matter compounds found in diesel exhaust, ammonium nitrate and ammonium sulfate, on Burkitt's lymphoma (Raji) and hepatocellular carcinoma (HepG2) cell lines. We found a dose-dependent positive correlation of accumulated DNA damage at concentrations of ammonium nitrate (25 μg/ml, 50 μg/ml, 100 μg/ml, 200 μg/ml, 400 μg/ml) with ultraviolet exposure (250 J/m(2), 400 J/m(2), 600 J/m(2), 850 J/m(2)), as measured by the comet assay in both cell lines. There was a significant difference between the treated ammonium nitrate samples and negative control samples in Raji and HepG2 cells (p<0.001). Apoptosis was shown in Raji and HepG2 cells when exposed to high concentrations of ammonium nitrate (200 μg/ml and 400 μg/ml) for 1h in samples without ultraviolet exposure, as assessed by the comet assay. However, the level of apoptosis greatly diminished after ultraviolet exposure at these concentrations. Over a 24h period, at intervals of 1, 4, 8, 12, 18, and 24h, we also observed that ammonium nitrate decreased viability in Raji and HepG2 cell lines and inhibited cell growth. Ammonium sulfate-induced DNA damage was minimal in both cell lines, but there remained a significant difference (p<0.05) between the ultraviolet radiation treated and negative control samples. These results indicate that the inorganic particulate compound, ammonium nitrate, induced DNA strand breaks at all concentrations, and indications of apoptosis at high concentrations in Raji and HepG2 cells, with ultraviolet radiation preventing apoptosis at high concentrations. We hypothesize that ultraviolet radiation may inhibit an essential cellular mechanism, possibly involving p53, thereby explaining this phenomenon. Further studies are necessary to characterize the roles of apoptosis inhibition induced by DNA damage caused by inorganic particulate matter.

Early postnatal, but not late, exposure to chemical ambient pollutant 1,2-naphthoquinone increases susceptibility to pulmonary allergic inflammation at adulthood

High diesel exhaust particle levels are associated with increased health effects; however, knowledge on the impact of its chemical contaminant 1,2-naphthoquinone (1,2-NQ) is limited. We investigated whether postnatal and adult exposures to 1,2-NQ influence allergic reaction and the roles of innate and adaptive immunity. Male neonate (6 days) and adult (56 days) C57Bl/6 mice were exposed to 1,2-NQ (100 nM; 15 min) for 3 days, and on day 59, they were sensitized and later challenged with ovalbumin (OVA). Airway hyper-responsiveness (AHR) and production of cytokines, immunoglobulin E (IgE) and leukotriene B4 (LTB4) were measured in the airways. Postnatal exposure to 1,2-NQ activated dendritic cells in splenocytes by increasing expressing cell surface molecules (e.g., CD11c). Co-exposure to OVA effectively polarized T helper (Th) type 2 (Th2) by secreting Th2-mediated cytokines. Re-stimulation with unspecific stimuli (PMA and ionomycin) generated a mixed Th1 (CD4(+)/IFN-γ(+)) and Th17 (CD4(+)/IL-17(+)) phenotype in comparison with the vehicle-matched group. Postnatal exposure to 1,2-NQ did not induce eosinophilia in the airways at adulthood, although it evoked neutrophilia and exacerbated OVA-induced eosinophilia, Th2 cytokines, IgE and LTB4 production without affecting AHR and mast cell degranulation. At adulthood, 1,2-NQ exposure evoked neutrophilia and increased Th1/Th2 cytokine levels, but failed to affect OVA-induced eosinophilia. In conclusion, postnatal exposure to 1,2-NQ increases the susceptibility to antigen-induced asthma. The mechanism appears to be dependent on increased expression of co-stimulatory molecules, which leads to cell presentation amplification, Th2 polarization and enhanced LTB4, humoral response and Th1/Th2 cytokines. These findings may be useful for future investigations on treatments focused on pulmonary illnesses observed in children living in heavy polluted areas.

Antioxidant therapeutics: Pandora's box

Evolution has favored the utilization of dioxygen (O2) in the development of complex multicellular organisms. O2 is actually a toxic mutagenic gas that is highly oxidizing and combustible. It is thought that plants are largely to blame for polluting the earth's atmosphere with O2 owing to the development of photosynthesis by blue-green algae over 2 billion years ago. The rise of the plants and atmospheric O2 levels placed evolutionary stress on organisms to adapt or become extinct. This implies that all the surviving creatures on our planet are mutants that have adapted to the "abnormal biology" of O2. Much of the adaptation to the presence of O2 in biological systems comes from well-coordinated antioxidant and repair systems that focus on converting O2 to its most reduced form, water (H2O), and the repair and replacement of damaged cellular macromolecules. Biological systems have also harnessed O2's reactive properties for energy production, xenobiotic metabolism, and host defense and as a signaling messenger and redox modulator of a number of cell signaling pathways. Many of these systems involve electron transport systems and offer many different mechanisms by which antioxidant therapeutics can alternatively produce an antioxidant effect without directly scavenging oxygen-derived reactive species. It is likely that each agent will have a different set of mechanisms that may change depending on the model of oxidative stress, organ system, or disease state. An important point is that all biological processes of aerobes have coevolved with O2 and this creates a Pandora's box for trying to understand the mechanism(s) of action of antioxidants being developed as therapeutic agents.

A chemical free, nanotechnology-based method for airborne bacterial inactivation using engineered water nanostructures

Airborne pathogens are associated with the spread of infectious diseases and increased morbidity and mortality. Herein we present an emerging chemical free, nanotechnology-based method for airborne pathogen inactivation. This technique is based on transforming atmospheric water vapor into Engineered Water Nano-Structures (EWNS) via electrospray. The generated EWNS possess a unique set of physical, chemical, morphological and biological properties. Their average size is 25 nm and they contain reactive oxygen species (ROS) such as hydroxyl and superoxide radicals. In addition, EWNS are highly electrically charged (10 electrons per particle on average). A link between their electric charge and the reduction of their evaporation rate was illustrated resulting in an extended lifetime (over an hour) at room conditions. Furthermore, it was clearly demonstrated that the EWNS have the ability to interact with and inactivate airborne bacteria. Finally, inhaled EWNS were found to have minimal toxicological effects, as illustrated in an acute in-vivo inhalation study using a mouse model. In conclusion, this novel, chemical free, nanotechnology-based method has the potential to be used in the battle against airborne infectious diseases.

A systematic review of air pollution as a risk factor for cardiovascular disease in South Asia: limited evidence from India and Pakistan

Cardiovascular diseases (CVD) are major contributors to mortality and morbidity in South Asia. Chronic exposure to air pollution is an important risk factor for cardiovascular diseases, although the majority of studies to date have been conducted in developed countries. Both indoor and outdoor air pollution are growing problems in developing countries in South Asia yet the impact on rising rates of CVD in these regions has largely been ignored. We aimed to assess the evidence available regarding air pollution effects on CVD and CVD risk factors in lower income countries in South Asia. A literature search was conducted in PubMed and Web of Science. Our inclusion criteria included peer-reviewed, original, empirical articles published in English between the years 1990 and 2012, conducted in the World Bank South Asia region (Afghanistan, Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan and Sri Lanka). This resulted in 30 articles. Nine articles met our inclusion criteria and were assessed for this systematic review. Most of the studies were cross-sectional and examined measured particulate matter effects on CVD outcomes and indicators. We observed a bias as nearly all of the studies were from India. Hypertension and CVD deaths were positively associated with higher particulate matter levels. Biomarkers of oxidative stress such as increased levels of P-selection expressing platelets, depleted superoxide dismutase and reactive oxygen species generation as well as elevated levels of inflammatory-related C-reactive protein, interleukin-6 and interleukin-8 were also positively associated with biomass use or elevated particulate matter levels. An important outcome of this investigation was the evidence suggesting important air pollution effects regarding CVD risk in South Asia. However, too few studies have been conducted. There is as an urgent need for longer term investigations using robust measures of air pollution with different population groups that include a wider range of air pollutants and outcomes, including early indicators of CVD. These regions are facing burdens from increasing urbanization, air pollution and populations, generally weaker health infrastructure, aging populations and increased incidence of non-communicable diseases, included CVD. The extent to which the problem of air pollution and CVD will impact these countries will depend largely on the information available to inform policy and programs, which are still lacking, political will as well as social and economic development.

Induction of apoptosis associated with chromosomal DNA fragmentation and caspase-3 activation in leukemia L1210 cells by TiO2 nanoparticles

We investigated the effects of nanosized TiO2 particles on the death of mouse leukemia L1210 cells. TiO2 particles suppressed proliferation and induced cell death, as measured by lactate dehydrogenase (LDH) release into the culture medium. Chromatin condensation, which is typical of the initiation of cell death, was observed in approximately 14% cells cultured with titanium dioxide (TiO2) particles for 12 h. Furthermore, giant DNA fragments of approximately 2 Mbp and high-molecular-weight DNA fragments between 100 kbp and 1 Mbp were observed in cells cultured for 18 h with TiO2 particles. These giant and high-molecular-weight DNA fragments were further degraded into smaller DNA fragments, appearing as DNA ladders. Corresponding to the generation of DNA fragments, caspase-3 activity increased in cells treated with TiO2 particles. TiO2 particle-induced LDH release was not inhibited by cytochalasin D, an inhibitor of endocytosis. These results suggest that nanosized TiO2 particles can induce apoptosis associated with DNA fragmentation and caspase-3 activation and that TiO2 particle-induced apoptosis is not caused by endocytosis but is associated with contact of the particles with the cell surface.

Tight junction proteins and oxidative stress in heavy metals-induced nephrotoxicity

Kidney is a target organ for heavy metals. They accumulate in several segments of the nephron and cause profound alterations in morphology and function. Acute intoxication frequently causes acute renal failure. The effects of chronic exposure have not been fully disclosed. In recent years increasing awareness of the consequences of their presence in the kidney has evolved. In this review we focus on the alterations induced by heavy metals on the intercellular junctions of the kidney. We describe that in addition to the proximal tubule, which has been recognized as the main site of accumulation and injury, other segments of the nephron, such as glomeruli, vessels, and distal nephron, show also deleterious effects. We also emphasize the participation of oxidative stress as a relevant component of the renal damage induced by heavy metals and the beneficial effect that some antioxidant drugs, such as vitamin A (all-trans-retinoic acid) and vitamin E (α-tocopherol), depict on the morphological and functional alterations induced by heavy metals.

Biological effects of polycyclic aromatic hydrocarbon derivatives

Polycyclic aromatic hydrocarbons (PAHs) are included in various environmental pollutants such as airborne particles and have been reported to induce a variety of toxic effects. On the other hand, PAH derivatives are generated from PAHs both through chemical reaction in the atmosphere and metabolism in the body.PAH derivatives have become known for their specific toxicities such as estrogenic/antiestrogenic activities and oxidative stress, and correlations between the toxicities and structures of PAH derivatives have been shown in recent studies. These studies are indispensable for demonstrating the health effects of PAH derivatives, since they would contribute to the comprehensive toxicity prediction of many kinds of PAH derivatives.

Indoor air pollution and risk of lung cancer among Chinese female non-smokers

PURPOSE

To investigate indoor particulate matter (PM) level and various indoor air pollution exposure, and to examine their relationships with risk of lung cancer in an urban Chinese population, with a focus on non-smoking women.

METHODS

We conducted a case-control study in Taiyuan, China, consisting of 399 lung cancer cases and 466 controls, of which 164 cases and 218 controls were female non-smokers. Indoor PM concentrations, including PM(1), PM(2.5), PM(7), PM(10), and TSP, were measured using a particle mass monitor. Unconditional logistic regression models were used to calculate odds ratios (ORs) and 95 % confidence intervals after adjusting for age, education, annual income, and smoking.

RESULTS

Among non-smoking women, lung cancer was strongly associated with multiple sources of indoor air pollution 10 years ago, including heavy exposure to environmental tobacco smoke at work (aOR = 3.65), high frequency of cooking (aOR = 3.30), and solid fuel usage for cooking (aOR = 4.08) and heating (aOR(coal stove) = 2.00). Housing characteristics related to poor ventilation, including single-story, less window area, no separate kitchen, no ventilator, and rarely having windows open, are associated with lung cancer. Indoor medium PM(2.5) concentration was 68 μg/m(3), and PM(10) was 230 μg/m(3). PM levels in winter are strongly correlated with solid fuel usage for cooking, heating, and ventilators. PM(1) levels in cases are more than 3 times higher than that in controls. Every 10 μg/m(3) increase in PM(1) is associated with 45 % increased risk of lung cancer.

CONCLUSIONS

Indoor air pollution plays an important role in the development of lung cancer among non-smoking Chinese women.

Teduglutide, a glucagon-like peptide 2 analogue: a novel protective agent with anti-apoptotic and anti-oxidant properties in mice with lung injury

Teduglutide is a long-acting synthetic analogue of human glucagon-like peptide-2 (GLP-2). GLP-2 regulates cell proliferation and apoptosis as well as normal physiology in the gastrointestinal tract. In the present study, possible cytoprotective and reparative effects of teduglutide were analyzed on a mouse model with lung injury induced by tumor necrosis factor-alpha (TNF-α) and actinomycin D (Act D). BALB/c mice were divided into six groups: control mice (I), mice injected intraperitoneally with 15 μg/kg TNF-α (II), 800 μg/kg Act D (III), Act D 2 min prior to TNF-α administration with the same doses (IV), mice injected subcutaneously with 200 μg/kg teduglutide every 12h for 10 consecutive days (V), and mice given Act D 2 min prior to TNF-α administration on day 11 after receiving teduglutide for 10 days (VI). The TNF-α/Act D administration made the lung a sensitive organ to damage. Mice lung subjected to TNF-α/Act D were characterized by the disruption of alveolar wall, induced pulmonary endothelial/epithelial cell apoptosis and expression of active caspase-3. These mice exhibited an increase in lipid peroxidation, glutathione levels, and activities of myeloperoxidase, superoxide dismutase, catalase, glutathione peroxidase and xanthine oxidase, as well as reduced tissue factor and sodium-potassium/ATPase activities. Teduglutide pretreatment regressed the structural damage, cell apoptosis and oxidative stress by reducing lipid peroxidation in mice received TNF-α/Act D. GLP-2 receptors were present on the cell membrane of type II pneumocytes and interstitial cells. Thus, teduglutide can be suggested as a novel protective agent, which possesses anti-apoptotic and anti-oxidant properties, against lung injury.

Radical-containing ultrafine particulate matter initiates epithelial-to-mesenchymal transitions in airway epithelial cells

Environmentally persistent free radicals (EPFRs) in combustion-generated particulate matter (PM) are capable of inducing pulmonary pathologies and contributing to the development of environmental asthma. In vivo exposure of infant rats to EPFRs demonstrates their ability to induce airway hyperresponsiveness to methacholine, a hallmark of asthma. However, the mechanisms by which combustion-derived EPFRs elicit in vivo responses remain elusive. In this study, we used a chemically defined EPFR consisting of approximately 0.2 μm amorphrous silica containing 3% cupric oxide with the organic pollutant 1,2-dichlorobenzene (DCB-230). DCB-230 possesses similar radical content to urban-collected EPFRs but offers several advantages, including lack of contaminants and chemical uniformity. DCB-230 was readily taken up by BEAS-2B and at high doses (200 μg/cm(2)) caused substantial necrosis. At low doses (20 μg/cm(2)), DCB-230 particles caused lysosomal membrane permeabilization, oxidative stress, and lipid peroxidation within 24 hours of exposure. During this period, BEAS-2B underwent epithelial-to-mesenchymal transition (EMT), including loss of epithelial cell morphology, decreased E-cadherin expression, and increased α-smooth muscle actin (α-SMA) and collagen I production. Similar results were observed in neonatal air-liquid interface culture (i.e., disruption of epithelial integrity and EMT). Acute exposure of infant mice to DCB-230 resulted in EMT, as confirmed by lineage tracing studies and evidenced by coexpression of epithelial E-cadherin and mesenchymal α-SMA proteins in airway cells and increased SNAI1 expression in the lungs. EMT in neonatal mouse lungs after EPFR exposure may provide an explanation for epidemiological evidence supporting PM exposure and increased risk of asthma.

Thiol-redox antioxidants protect against lung vascular endothelial cytoskeletal alterations caused by pulmonary fibrosis inducer, bleomycin: comparison between classical thiol-protectant, N-acetyl-L-cysteine, and novel thiol antioxidant, N,N'-bis-2-mercaptoethyl isophthalamide

Lung vascular alterations and pulmonary hypertension associated with oxidative stress have been reported to be involved in idiopathic lung fibrosis (ILF). Therefore, here, we hypothesize that the widely used lung fibrosis inducer, bleomycin, would cause cytoskeletal rearrangement through thiol-redox alterations in the cultured lung vascular endothelial cell (EC) monolayers. We exposed the monolayers of primary bovine pulmonary artery ECs to bleomycin (10 µg) and studied the cytotoxicity, cytoskeletal rearrangements, and the macromolecule (fluorescein isothiocyanate-dextran, 70,000 mol. wt.) paracellular transport in the absence and presence of two thiol-redox protectants, the classic water-soluble N-acetyl-L-cysteine (NAC) and the novel hydrophobic N,N'-bis-2-mercaptoethyl isophthalamide (NBMI). Our results revealed that bleomycin induced cytotoxicity (lactate dehydrogenase leak), morphological alterations (rounding of cells and filipodia formation), and cytoskeletal rearrangement (actin stress fiber formation and alterations of tight junction proteins, ZO-1 and occludin) in a dose-dependent fashion. Furthermore, our study demonstrated the formation of reactive oxygen species, loss of thiols (glutathione, GSH), EC barrier dysfunction (decrease of transendothelial electrical resistance), and enhanced paracellular transport (leak) of macromolecules. The observed bleomycin-induced EC alterations were attenuated by both NAC and NBMI, revealing that the novel hydrophobic thiol-protectant, NBMI, was more effective at µM concentrations as compared to the water-soluble NAC that was effective at mM concentrations in offering protection against the bleomycin-induced EC alterations. Overall, the results of the current study suggested the central role of thiol-redox in vascular EC dysfunction associated with ILF.

Particulate matter air pollution disrupts endothelial cell barrier via calpain-mediated tight junction protein degradation

Background

Exposure to particulate matter (PM) is a significant risk factor for increased cardiopulmonary morbidity and mortality. The mechanism of PM-mediated pathophysiology remains unknown. However, PM is proinflammatory to the endothelium and increases vascular permeability in vitro and in vivo via ROS generation.

Objectives

We explored the role of tight junction proteins as targets for PM-induced loss of lung endothelial cell (EC) barrier integrity and enhanced cardiopulmonary dysfunction.

Methods

Changes in human lung EC monolayer permeability were assessed by Transendothelial Electrical Resistance (TER) in response to PM challenge (collected from Ft. McHenry Tunnel, Baltimore, MD, particle size >0.1 μm). Biochemical assessment of ROS generation and Ca²⁺ mobilization were also measured.

Results

PM exposure induced tight junction protein Zona occludens-1 (ZO-1) relocation from the cell periphery, which was accompanied by significant reductions in ZO-1 protein levels but not in adherens junction proteins (VE-cadherin and β-catenin). N-acetyl-cysteine (NAC, 5 mM) reduced PM-induced ROS generation in ECs, which further prevented TER decreases and atteneuated ZO-1 degradation. PM also mediated intracellular calcium mobilization via the transient receptor potential cation channel M2 (TRPM2), in a ROS-dependent manner with subsequent activation of the Ca²⁺-dependent protease calpain. PM-activated calpain is responsible for ZO-1 degradation and EC barrier disruption. Overexpression of ZO-1 attenuated PM-induced endothelial barrier disruption and vascular hyperpermeability in vivo and in vitro.

Conclusions

These results demonstrate that PM induces marked increases in vascular permeability via ROS-mediated calcium leakage via activated TRPM2, and via ZO-1 degradation by activated calpain. These findings support a novel mechanism for PM-induced lung damage and adverse cardiovascular outcomes.

Iron solubility related to particle sulfur content in source emission and ambient fine particles

The chemical factors influencing iron solubility (soluble iron/total iron) were investigated in source emission (e.g., biomass burning, coal fly ash, mineral dust, and mobile exhaust) and ambient (Atlanta, GA) fine particles (PM2.5). Chemical properties (speciation and mixing state) of iron-containing particles were characterized using X-ray absorption near edge structure (XANES) spectroscopy and micro-X-ray fluorescence measurements. Bulk iron solubility (soluble iron/total iron) of the samples was quantified by leaching experiments. Major differences were observed in iron solubility in source emission samples, ranging from low solubility (<1%, mineral dust and coal fly ash) up to 75% (mobile exhaust and biomass burning emissions). Differences in iron solubility did not correspond to silicon content or Fe(II) content. However, source emission and ambient samples with high iron solubility corresponded to the sulfur content observed in single particles. A similar correspondence between bulk iron solubility and bulk sulfate content in a series of Atlanta PM2.5 fine particle samples (N = 358) further supported this trend. In addition, results of linear combination fitting experiments show the presence of iron sulfates in several high iron solubility source emission and ambient PM2.5 samples. These results suggest that the sulfate content (related to the presence of iron sulfates and/or acid-processing mechanisms by H(2)SO(4)) of iron-containing particles is an important proxy for iron solubility.

Carboxylate microsphere-induced cellular toxicity in human lung fibroblasts

Carboxylate microspheres (CMs) are mainly used in industrial, biomedical and various household products. In this study, we assessed the cytotoxic effects of CMs on human MRC-5 lung fibroblasts by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Oxidative stress was determined by measurements of reactive oxygen species and antioxidant (superoxide dismutase and catalase) levels and proinflammatory cytokines quantified by enzyme-linked immunosorbent assay. Morphological changes were examined by light microscopy, confocal microscopy and transmission electron microscopy. The lung fibroblasts were exposed to increasing concentrations of CMs (0.1–1000 μmol/L) for 24 h. The results showed significant changes in cell morphology with induction of cytotoxicity and oxidative stress observed in 10–1000 μmol/L concentrations of CM-treated fibroblasts. Ultrastructural examination revealed the presence of CMs inside the cytoplasm of treated lung fibroblasts. CMs also induced elevated interleukin (IL)-1, IL-6, IL-8, IL-10 and tumor necrosis factor α levels at higher concentrations. We have demonstrated that CMs significantly reduce cell viability in a dose-dependant manner in lung fibroblasts at 0.1–1000 μmol/L doses. The findings suggest that high doses of CMs have the potential to induce cellular toxicity to the lung in vitro.

Diurnal trends in oxidative potential of coarse particulate matter in the Los Angeles Basin and their relation to sources and chemical composition

To investigate the relationship among sources, chemical composition, and redox activity of coarse particulate matter (CPM), three sampling sites were set up up in the Los Angeles Basin to collect ambient coarse particles at four time periods (morning, midday, afternoon, and overnight) in summer 2009 and winter 2010. The generation of reactive oxygen species (ROS) was used to assess the redox activity of these particles. Our results present distinct diurnal profiles of CPM-induced ROS formation in the two seasons, with much higher levels in summer than winter. Higher ROS activity was observed in the midday/afternoon during summertime, while the peak activity occurred in the overnight period in winter. Crustal materials, the major component of CPM, demonstrated very low water-solubility, in contrast with the modestly water-soluble anthropogenic metals, including Ba and Cu. The water-soluble fraction of four elements (V, Pd, Cu, and Rh) with primary anthropogenic origins displayed the highest associations with ROS activity (R(2) > 0.60). Our results show that coarse particles generated by anthropogenic activities, despite their low contribution to CPM mass, are important to the biological activity of CPM, and that a more targeted control strategy may be needed to protect the public health from these toxic CPM sources.

Siderite (FeCO₃) and magnetite (Fe₃O₄) overload-dependent pulmonary toxicity is determined by the poorly soluble particle not the iron content

The two poorly soluble iron containing solid aerosols of siderite (FeCO₃) and magnetite (Fe₃O₄) were compared in a 4-week inhalation study on rats at similar particle mass concentrations of approximately 30 or 100 mg/m³. The particle size distributions were essentially identical (MMAD ≈1.4 μm). The iron-based concentrations were 12 or 38 and 22 or 66 mg Fe/m³ for FeCO₃ and Fe₃O₄, respectively. Modeled and empirically determined iron lung burdens were compared with endpoints suggestive of pulmonary inflammation by determinations in bronchoalveolar lavage (BAL) and oxidative stress in lung tissue during a postexposure period of 3 months. The objective of study was to identify the most germane exposure metrics, that are the concentration of elemental iron (mg Fe/m³), total particle mass (mg PM/m³) or particle volume (μl PM/m³) and their associations with the effects observed. From this analysis it was apparent that the intensity of pulmonary inflammation was clearly dependent on the concentration of particle-mass or -volume and not of iron. Despite its lower iron content, the exposure to FeCO₃ caused a more pronounced and sustained inflammation as compared to Fe₃O₄. Similarly, borderline evidence of increased oxidative stress and inflammation occurred especially following exposure to FeCO₃ at moderate lung overload levels. The in situ analysis of 8-oxoguanine in epithelial cells of alveolar and bronchiolar regions supports the conclusion that both FeCO₃ and Fe₃O₄ particles are effectively endocytosed by macrophages as opposed to epithelial cells. Evidence of intracellular or nuclear sources of redox-active iron did not exist. In summary, this mechanistic study supports previous conclusions, namely that the repeated inhalation exposure of rats to highly respirable pigment-type iron oxides cause nonspecific pulmonary inflammation which shows a clear dependence on the particle volume-dependent lung overload rather than any increased dissolution and/or bioavailability of redox-active iron.

Generation of reactive oxygen species mediated by humic-like substances in atmospheric aerosols

Particulate matter (PM)-mediated reactive oxygen species (ROS) generation has been implicated in health effects posed by PM. Humic-like substances (HULIS) are an unresolved mixture of water-extracted organic compounds from atmospheric aerosol particles or isolated from fog/cloudwater samples. In this study, we use a cell-free dithiothreitol (DTT) assay to measure ROS production mediated by HULIS. The HULIS samples are isolated from aerosols collected at a rural location and a suburban location in the Pearl River Delta, China. In our experiments, ROS activities by residue metal ions in the HULIS fraction are suppressed by including a strong chelating agent in the DTT assay. Under conditions of DTT consumption not exceeding 90%, the HULIS-catalyzed oxidation of DTT follows the zero-order kinetics with respect to DTT concentration, and the rate of DTT oxidation is proportional to the dose of HULIS. The ROS activity of the aerosol HULIS, on a per unit mass basis is 2% of the ROS activity by a reference quinone compound, 1,4-naphthoquinone and exceeds that of two aquatic fulvic acids. The HULIS fraction in the ambient samples tested exhibits comparable ROS activities to the organic solvent extractable fraction, which would contain compounds such as quinones, a known organic compound class capable of catalyzing generation of ROS in cells. HULIS was found to be the major redox active constituent of the water-extractable organic fraction in PM. It is plausible that HULIS contains reversible redox sites, thereby serving as electron carriers to catalyze the formation of ROS. Our work suggests that HULIS could be an active PM component in generating ROS and further work is warranted to characterize its redox properties.

The effect of air pollution on haemostasis

Ambient environmental air pollutants include gaseous and particulate components. In polluted air, especially particulate matter seems responsible for cardiovascular complications: It consists of a heterogeneous mixture of solid and liquid particles with different diameters ranging from large thoracic to ultrafine particles, with a diameter <100 nm. Ultrafines can penetrate deeply into the lung to deposit in the alveoli. Cardiovascular manifestations result both from short-term and long-term exposure and have been linked to interference with the autonomic nervous system, direct translocation into the systemic circulation, pulmonary inflammation and oxidative stress. Thrombotic complications associated with air pollution comprise arterial and probably venous thrombogenicity. This review describes the existing epidemiological and experimental evidence to explain the rapid induction of myocardial infarction within 1-2 hours after exposure to polluted air and advances several explanations as to why more chronic exposure will lead to enhanced venous thrombogenicity. Mechanisms such as platelet activation, endothelial dysfunction, coagulation factor changes and microvesicle production are discussed.

Chemical characterization and redox potential of coarse and fine particulate matter (PM) in underground and ground-level rail systems of the Los Angeles Metro

A campaign was conducted to assess personal exposure of coarse (2.5 μm < d(p) < 10 μm) and fine (d(p) < 2.5 μm) PM for two lines of the L.A. Metro-a subway (red) and light-rail (gold) line. Concurrent measurements were taken at University of Southern California (USC) to represent ambient conditions. A comprehensive chemical analysis was performed including total and water-soluble metals, inorganic ions, elemental and organic carbon, and organic compounds. Mass balance showed that in coarse PM, iron makes up 27%, 6%, and 2% of gravimetric mass for the red line, the gold line, and USC, respectively; in fine PM, iron makes up 32%, 3%, and 1%. Ambient air is the primary source of inorganic ions and organic compounds for both lines. Noncrustal metals, particularly Cr, Mn, Co, Ni, Mo, Cd, and Eu, were elevated for the red line and, to a lesser degree, the gold line. Mo exhibited the greatest crustal enrichment factors. The enriched species were less water-soluble on the red line than corresponding species on the gold line. Bivariate analysis showed that reactive oxygen species (ROS) activity is strongly correlated with water-soluble Fe (R(2) = 0.77), Ni (R(2 )= 0.95), and OC (R(2 )= 0.92). A multiple linear regression model (R(2) = 0.94, p < 0.001) using water-soluble Fe and OC as predictor variables was developed to explain the variance in ROS. In addition, PM from the red line generates 65% and 55% more ROS activity per m(3) of air than PM from USC and the gold line, respectively; however, one unit of PM mass from the gold line may be as intrinsically toxic as one unit of PM from the red line.

Urban particulate matter activates Akt in human lung cells

The normally picturesque Cache Valley in northern Utah is frequently reported to have the worst particulate (PM) air pollution in the United States. Numerous epidemiological studies conducted elsewhere have associated PM exposure to a variety of cardiovascular diseases and early mortality. We have previously shown that Cache Valley PM (CVPM) is pro-inflammatory, through a variety of mechanisms involving the release of inflammatory cytokines, unfolded protein response, ER stress, and C-reactive protein (CRP). This study was undertaken to determine whether Cache Valley PM (CVPM) would activate Akt, an upstream mechanism common to these events. Human lung (BEAS-2B) cells were treated with either fine (PM(2.5)) or coarse (PM(10)) particles (12.5 and 25 μg/ml) for periods up to 24 h. PM-exposed cells exhibited Akt activation as evidenced by phosphorylation at Thr(308) and Ser(473). Events downstream of Akt activation such as NF-κB activation were observed at 1 and 24 h, but IκB phosphorylation occurred only at 24 h, indicating that mechanisms of PM-mediated NF-κB activation are time dependent. Akt and NF-κB related inflammatory cytokine IL-1α, and IL-6 and the chemokine IL-8 were upregulated in treated cells at 6 and 24 h. The calpain inhibitor leupeptin limited Akt phosphorylation to Ser(473) and reduced release of IL-1α, IL-6, and IL-8, indicating that calpain or similar protease(s) are involved in PM-induced activation of Akt and subsequent release of inflammatory cytokines. Our data indicate that PM activates Akt, which may play a role in the pro-inflammatory response to PM exposure.

Nrf2 regulates hyperoxia-induced Nox4 expression in human lung endothelium: identification of functional antioxidant response elements on the Nox4 promoter

Reactive oxygen species (ROS) generated by vascular endothelial and smooth muscle cells contribute to the development and progression of vascular diseases. We have recently shown that hyperoxia enhances NADPH oxidase 4 (Nox4) expression, which regulates lung endothelial cell migration and angiogenesis. Regulation of Nox4 in the vasculature is poorly understood. The objective of this study was to identify the transcriptional factor(s) involved in regulation of endothelial Nox4. We found that hyperoxia-induced Nox4 expression was markedly reduced in Nrf2(-/-) mice, compared to Nrf2(+/+) mice. Exposure of human lung microvascular endothelial cells (HLMVECs) to hyperoxia stimulated Nrf2 translocation from the cytoplasm to the nucleus and increased Nox4 expression. Knockdown of Nrf2 expression using an siRNA approach attenuated basal Nox4 expression; however, it enhanced superoxide/ROS generation under both normoxia and hyperoxia. In silico analysis revealed the presence of at least three consensus sequences for the antioxidant response element (ARE) in the promoter region of Nox4. In transient transfections, hyperoxia stimulated Nox4 promoter activity in HLMVECs, and deletion of the -438 to -458 and -619 to -636 sequences markedly reduced hyperoxia-stimulated Nox4 promoter activation. ChIP analysis revealed an enhanced recruitment of Nrf2 to the endogenous Nox4 promoter spanning these two AREs after hyperoxic insult. Collectively, these results demonstrate, for the first time, a novel role for Nrf2 in regulating hyperoxia-induced Nox4 transcription via AREs in lung endothelium.

Asian dust and titanium dioxide particles-induced inflammation and oxidative DNA damage in C57BL/6 mice

Inhaled particulate matter (PM) might influence many adverse health effects in human body, including increased exacerbations of pulmonary and cardiovascular diseases. In this study, we examined the associations between PM and pulmonary adverse effects. Two types of particles, Asian dust (AD) and titanium dioxide (TiO(2)), were administered intratracheally to C57BL/6 mice. The mice were exposed to saline and saline suspensions of 20 mg/kg of AD, TiO(2) particles twice a week for 12 weeks. Following exposure with these particles, the lungs were analyzed histopathologically by hematoxylin and eosin (H&E) and Masson's trichrome (MT) staining. Oxidative injuries were determined by immunohistochemistry (IHC) for 8-oxoguanine in the lungs and Comet assays in peripheral blood mononuclear cells (PBMCs) of C57BL/6 mice. Mice exposed to AD and TiO(2) showed significant inflammatory changes and oxidative damages in the lungs as compared with the control group. DNA damage in PBMCs was also increased significantly in AD and TiO(2)-exposed mice. However, lung fibrosis was minimal and there was no significant difference between PM exposed and control mice. Exposure to AD and TiO(2) particles-induced similar inflammatory damages in the lungs and elicited oxidative DNA damage in the PBMCs.

Anti-oxidative and inflammatory responses induced by fly ash particles and carbon black in lung epithelial cells

Combustion-derived nanoparticles as constituents of ambient particulate matter have been shown to induce adverse health effects due to inhalation. However, the components inducing these effects as well as the biological mechanisms are still not fully understood. The fine fraction of fly ash particles collected from the electrostatic precipitator of a municipal solid waste incinerator was taken as an example for real particles with complex composition released into the atmosphere to study the mechanism of early biological responses of BEAS-2B human lung epithelial cells. The studies include the effects of the water-soluble and -insoluble fractions of the fly ash and the well-studied carbon black nanoparticles were used as a reference. Fly ash induced reactive oxygen species (ROS) and increased the total cellular glutathione (tGSH) content. Carbon black also induced ROS generation; however, in contrast to the fly ash, it decreased the intracellular tGSH. The fly ash-induced oxidative stress was correlated with induction of the anti-oxidant enzyme heme oxygenase-1 and increase of the redox-sensitive transcription factor Nrf2. Carbon black was not able to induce HO-1. ROS generation, tGSH increase and HO-1 induction were only induced by the insoluble fraction of the fly ash, not by the water-soluble fraction. ROS generation and HO-1 induction were markedly inhibited by pre-incubation of the cells with the anti-oxidant N-acetyl cysteine which confirmed the involvement of oxidative stress. Both effects were also reduced by the metal chelator deferoxamine indicating a contribution of bioavailable transition metals. In summary, both fly ash and carbon black induce ROS but only fly ash induced an increase of intracellular tGSH and HO-1 production. Bioavailable transition metals in the solid water-insoluble matrix of the fly ash mostly contribute to the effects.

A 3-dimensional in vitro model of epithelioid granulomas induced by high aspect ratio nanomaterials

Background

The most common causes of granulomatous inflammation are persistent pathogens and poorly-degradable irritating materials. A characteristic pathological reaction to intratracheal instillation, pharyngeal aspiration, or inhalation of carbon nanotubes is formation of epithelioid granulomas accompanied by interstitial fibrosis in the lungs. In the mesothelium, a similar response is induced by high aspect ratio nanomaterials, including asbestos fibers, following intraperitoneal injection. This asbestos-like behaviour of some engineered nanomaterials is a concern for their potential adverse health effects in the lungs and mesothelium. We hypothesize that high aspect ratio nanomaterials will induce epithelioid granulomas in nonadherent macrophages in 3D cultures.

Results

Carbon black particles (Printex 90) and crocidolite asbestos fibers were used as well-characterized reference materials and compared with three commercial samples of multiwalled carbon nanotubes (MWCNTs). Doses were identified in 2D and 3D cultures in order to minimize acute toxicity and to reflect realistic occupational exposures in humans and in previous inhalation studies in rodents. Under serum-free conditions, exposure of nonadherent primary murine bone marrow-derived macrophages to 0.5 μg/ml (0.38 μg/cm²) of crocidolite asbestos fibers or MWCNTs, but not carbon black, induced macrophage differentiation into epithelioid cells and formation of stable aggregates with the characteristic morphology of granulomas. Formation of multinucleated giant cells was also induced by asbestos fibers or MWCNTs in this 3D in vitro model. After 7-14 days, macrophages exposed to high aspect ratio nanomaterials co-expressed proinflammatory (M1) as well as profibrotic (M2) phenotypic markers.

Conclusions

Induction of epithelioid granulomas appears to correlate with high aspect ratio and complex 3D structure of carbon nanotubes, not with their iron content or surface area. This model offers a time- and cost-effective platform to evaluate the potential of engineered high aspect ratio nanomaterials, including carbon nanotubes, nanofibers, nanorods and metallic nanowires, to induce granulomas following inhalation.

Subchronic inhalation toxicity of iron oxide (magnetite, Fe(3) O(4) ) in rats: pulmonary toxicity is determined by the particle kinetics typical of poorly soluble particles

Wistar rats were nose-only exposed to pigment-sized iron oxide dust (Fe(3) O(4) , magnetite) in a subchronic 13-week inhalation study according to the OECD testing guidelines TG#413 and GD#39. A 4 week pilot study with a 6 month post exposure period served as basis for validating the kinetic modeling approaches utilized to design the subchronic study. Kinetic analyses made during this post exposure period demonstrated that a diminution in particle clearance and lung inflammation occurred at cumulative exposure levels exceeding the lung overload threshold. Animals were exposed 6 h per day, five days per week for 13 consecutive weeks at actual concentrations of 0, 4.7, 16.6 and 52.1 mg m(-3) (mass median aerodynamic diameter ≈1.3 μm, geometric standard deviation = 2). The exposure to iron oxide dust was tolerated without mortality, consistent changes in body weights, food and water consumption or systemic toxicity. While general clinical pathology and urinalysis were unobtrusive, hematology revealed changes of unclear toxicological significance (minimally increased differential neutrophil counts in peripheral blood). Elevations of neutrophils in bronchoalveolar lavage (BAL) appeared to be the most sensitive endpoint of study. Histopathology demonstrated responses to particle deposition in the upper respiratory tract (goblet cell hyper- and/or metaplasia, intraepithelial eosinophilic globules in the nasal passages) and the lower respiratory tract (inflammatory changes in the bronchiolo-alveolar region). Consistent changes suggestive of pulmonary inflammation were evidenced by BAL, histopathology, increased lung and lung-associated-lymph node (LALN) weights at 16.6 and 52.1 mg m(-3) . Increased septal collagenous fibers were observed at 52.1 mg m(-3) . Particle translocation into LALN occurred at exposure levels causing pulmonary inflammation. In summary, the retention kinetics iron oxide reflected that of poorly soluble particles. The empirical no-observed-adverse-effect level (NOAEL) and the lower bound 95% confidence limit on the benchmark concentration (BMCL) obtained by benchmark analysis was 4.7 and 4.4 mg m(-3) , respectively, and supports an OEL (time-adjusted chronic occupational exposure level) of 2 mg m(-3) (alveolar fraction).

Lung injury after cigarette smoking is particle related

The specific component responsible and the mechanistic pathway for increased human morbidity and mortality after cigarette smoking are yet to be delineated. We propose that 1) injury and disease following cigarette smoking are associated with exposure to and retention of particles produced during smoking and 2) the biological effects of particles associated with cigarette smoking share a single mechanism of injury with all particles. Smoking one cigarette exposes the human respiratory tract to between 15,000 and 40,000 μg particulate matter; this is a carbonaceous product of an incomplete combustion. There are numerous human exposures to other particles, and these vary widely in composition, absolute magnitude, and size of the particle. Individuals exposed to all these particles share a common clinical presentation with a loss of pulmonary function, increased bronchial hyperresponsiveness, pathologic changes of emphysema and fibrosis, and comorbidities, including cardiovascular disease, cerebrovascular disease, peripheral vascular disease, and cancers. Mechanistically, all particle exposures produce an oxidative stress, which is associated with a series of reactions, including an activation of kinase cascades and transcription factors, release of inflammatory mediators, and apoptosis. If disease associated with cigarette smoking is recognized to be particle related, then certain aspects of the clinical presentation can be predicted; this would include worsening of pulmonary function and progression of pathological changes and comorbidity (eg, emphysema and carcinogenesis) after smoking cessation since the particle is retained in the lung and the exposure continues.

Augmentation of arginase 1 expression by exposure to air pollution exacerbates the airways hyperresponsiveness in murine models of asthma

Background

Arginase overexpression contributes to airways hyperresponsiveness (AHR) in asthma. Arginase expression is further augmented in cigarette smoking asthmatics, suggesting that it may be upregulated by environmental pollution. Thus, we hypothesize that arginase contributes to the exacerbation of respiratory symptoms following exposure to air pollution, and that pharmacologic inhibition of arginase would abrogate the pollution-induced AHR.

Methods

To investigate the role of arginase in the air pollution-induced exacerbation of airways responsiveness, we employed two murine models of allergic airways inflammation. Mice were sensitized to ovalbumin (OVA) and challenged with nebulized PBS (OVA/PBS) or OVA (OVA/OVA) for three consecutive days (sub-acute model) or 12 weeks (chronic model), which exhibit inflammatory cell influx and remodeling/AHR, respectively. Twenty-four hours after the final challenge, mice were exposed to concentrated ambient fine particles plus ozone (CAP+O₃), or HEPA-filtered air (FA), for 4 hours. After the CAP+O₃ exposures, mice underwent tracheal cannulation and were treated with an aerosolized arginase inhibitor (S-boronoethyl-L-cysteine; BEC) or vehicle, immediately before determination of respiratory function and methacholine-responsiveness using the flexiVent^®. Lungs were then collected for comparison of arginase activity, protein expression, and immunohistochemical localization.

Results

Compared to FA, arginase activity was significantly augmented in the lungs of CAP+O₃-exposed OVA/OVA mice in both the sub-acute and chronic models. Western blotting and immunohistochemical staining revealed that the increased activity was due to arginase 1 expression in the area surrounding the airways in both models. Arginase inhibition significantly reduced the CAP+O₃-induced increase in AHR in both models.

Conclusions

This study demonstrates that arginase is upregulated following environmental exposures in murine models of asthma, and contributes to the pollution-induced exacerbation of airways responsiveness. Thus arginase may be a therapeutic target to protect susceptible populations against the adverse health effects of air pollution, such as fine particles and ozone, which are two of the major contributors to smog.

Variation in echocardiographic and cardiac hemodynamic effects of PM and ozone inhalation exposure in strains related to Nppa and Npr1 gene knock-out mice

Elevated levels of ambient co-pollutants are associated with adverse cardiovascular outcomes shown by epidemiology studies. The role of particulate matter (PM) and ozone (O3) as co-pollutants in this association is unclear. We hypothesize that cardiac function following PM and O3 exposure is variably affected by genetic determinants (Nppa and Npr1 genes) and age. Heart function was measured before and after 2 days each of the following exposure sequence; (1) 2-h filtered air (FA) and 3-h carbon black (CB; 0.5 microg/m(3)); (2) 2-h O3 (0.6 ppm) and 3-h FA; (3) 5-h FA; and, (4) 2-h O3 and 3-h CB. Two age groups (5 and 18 months old (mo)) were tested in C57Bl/6J (B6) and 129S1/SvImJ (129) mice using echocardiographic (echo) and in vivo hemodynamic (IVH) measurements. With echo, posterior wall thickness was significantly (P < 0.01) greater in 129 relative to B6 mice at baseline. With CB exposure, young B6 and older 129 mice show significant (P < 0.01) reductions in fractional shortening (FS) compared to FA. With O3 exposure, FS was significantly (P < 0.01) diminished in young 129, which was attributable to significant increases in end-systolic left ventricular diameter. With O3 and CB combined, notable (P < 0.01) declines in heart rate and end-systolic posterior wall thickness occurred in young 129 mice. The IVH measurements showed striking (P < 0.05) compromises in cardiac function after CB and O3 exposure; however, strain differences were undetectable. These results suggest that PM and O3 exposures, alone and combined, lead to different cardiac functional changes, and these unique changes are age-specific and dependent on Nppa and Npr1 genes.

Chemical composition of ambient particulate matter and redox activity

Exposure to ambient particulate matter (PM) has been associated with a number of adverse health effects. Increasing studies have suggested that such adverse health effects may derive from oxidative stress, initiated by the formation of reactive oxygen species (ROS) within affected cells. The study aimed to assess physical characteristics and chemical compositions of PM and to correlate the results to their redox activity. PM(2.5) (mass aerodynamic diameter < or =2.5 microm) and ultrafine particles (UFPs, mass media aerodynamic diameter <0.1 microm) were collected in an urban area, which had heavy traffic and represented ambient air pollution associated with vehicle exhaust. Background samples were collected in a rural area, with low traffic flow. Organic carbon (OC), elemental carbon (EC), polycyclic aromatic hydrocarbons (PAHs), and metals were analyzed. The dithiothreitol activity assay was used to measure the redox activity of PM. Results showed that UFPs have higher concentrations of OC, EC, and PAHs than those of PM(2.5). Several metals, including Fe, Cu, Zn, Ti, Pb, and Mn, were detected. Among them, Cu had the highest concentrations, followed by Fe and Zn. Organic carbon constituted 22.8% to 59.7% of the content on the surface of PM(2.5) and UFPs. Our results showed higher redox activity on a per PM mass basis for UFPs as compared to PM(2.5). Linear multivariable regression analyses showed that redox activity highly correlated with PAH concentrations and organic compounds, and insignificantly correlated with EC and metals, except soluble Fe, which increased redox activity in particle suspension due to the presence of ROS.

Antioxidant intervention compensates oxidative stress in blood of subjects exposed to emissions from a coal electric-power plant in South Brazil

In the process of energy generation, particulate matter (PM) emissions derived from coal combustion expose humans to serious occupational diseases, which are associated with overgeneration of reactive oxygen species (ROS). The purpose of the present study is to better understand the relations between PM exposure derived from a coal electric-power plant and the oxidative damage in subjects (n=20 each group) directly (working at the burning area) or indirectly (working at the office or living in the vicinity of the electric-power plant=group of residents) exposed to airborne contamination, before and after daily supplementation with vitamins C (500mg) and E (800mg) during six months, which were compared to non-exposed subjects (control group). Several biomarkers of oxidative stress were examined such as levels of thiobarbituric acid reactive substances (TBARS), protein carbonyls (PC), protein thiols (PT) and vitamin E in plasma, levels of reduced glutathione (GSH) in whole blood, and of activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione S-transferase (GST) in red cells. Before supplementation, TBARS and PC levels were significantly increased, levels of GSH and vitamin E were decreased, while the activities of SOD and CAT were increased in workers groups and GST were increased in all groups in compared to controls. After the antioxidant supplementation essentially all these biomarkers were normalized to control levels. The antioxidant intervention was able to confer a protective effect of vitamins C and E against the oxidative insult associated with airborne contamination derived from coal burning of an electric-power plant.

Oxidative potential of logwood and pellet burning particles assessed by a novel profluorescent nitroxide probe

This study reports the potential toxicological impact of particles produced during biomass combustion by an automatic pellet boiler and a traditional logwood stove under various combustion conditions using a novel profluorescent nitroxide probe, BPEAnit. This probe is weakly fluorescent but yields strong fluorescence emission upon radical trapping or redox activity. Samples were collected by bubbling aerosol through an impinger containing BPEAnit solution, followed by fluorescence measurement. The fluorescence of BPEAnit was measured for particles produced during various combustion phases: at the beginning of burning (cold start), stable combustion after refilling with the fuel (warm start), and poor burning conditions. For particles produced by the logwood stove under cold-start conditions, significantly higher amounts of reactive species per unit of particulate mass were observed compared to emissions produced during a warm start. In addition, sampling of logwood burning emissions after passing through a thermodenuder at 250 degrees C resulted in an 80-100% reduction of the fluorescence signal of the BPEAnit probe, indicating that the majority of reactive species were semivolatile. Moreover, the amount of reactive species showed a strong correlation with the amount of particulate organic material. This indicates the importance of semivolatile organics in particle-related toxicity. Particle emissions from the pellet boiler, although of similar mass concentration, were not observed to lead to an increase in fluorescence signal during any of the combustion phases.