RESUMEN
BACKGROUND: During inhalation, airborne particles such as particulate matter ≤ 2.5 µm (PM2.5), can deposit and accumulate on the alveolar epithelial tissue. In vivo studies have shown that fractions of PM2.5 can cross the alveolar epithelium to blood circulation, reaching secondary organs beyond the lungs. However, approaches to quantify the translocation of particles across the alveolar epithelium in vivo and in vitro are still not well established. In this study, methods to assess the translocation of standard diesel exhaust particles (DEPs) across permeable polyethylene terephthalate (PET) inserts at 0.4, 1, and 3 µm pore sizes were first optimized with transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-VIS), and lock-in thermography (LIT), which were then applied to study the translocation of DEPs across human alveolar epithelial type II (A549) cells. A549 cells that grew on the membrane (pore size: 3 µm) in inserts were exposed to DEPs at different concentrations from 0 to 80 µg.mL- 1 ( 0 to 44 µg.cm- 2) for 24 h. After exposure, the basal fraction was collected and then analyzed by combining qualitative (TEM) and quantitative (UV-VIS and LIT) techniques to assess the translocated fraction of the DEPs across the alveolar epithelium in vitro. RESULTS: We could detect the translocated fraction of DEPs across the PET membranes with 3 µm pore sizes and without cells by TEM analysis, and determine the percentage of translocation at approximatively 37% by UV-VIS (LOD: 1.92 µg.mL- 1) and 75% by LIT (LOD: 0.20 µg.cm- 2). In the presence of cells, the percentage of DEPs translocation across the alveolar tissue was determined around 1% at 20 and 40 µg.mL- 1 (11 and 22 µg.cm- 2), and no particles were detected at higher and lower concentrations. Interestingly, simultaneous exposure of A549 cells to DEPs and EDTA can increase the translocation of DEPs in the basal fraction. CONCLUSION: We propose a combination of analytical techniques to assess the translocation of DEPs across lung tissues. Our results reveal a low percentage of translocation of DEPs across alveolar epithelial tissue in vitro and they correspond to in vivo findings. The combination approach can be applied to any traffic-generated particles, thus enabling us to understand their involvement in public health.
Asunto(s)
Material Particulado , Alveolos Pulmonares , Emisiones de Vehículos , Humanos , Emisiones de Vehículos/toxicidad , Emisiones de Vehículos/análisis , Células A549 , Material Particulado/toxicidad , Material Particulado/análisis , Alveolos Pulmonares/efectos de los fármacos , Alveolos Pulmonares/metabolismo , Tamaño de la Partícula , Microscopía Electrónica de Transmisión , Tereftalatos Polietilenos/química , Tereftalatos Polietilenos/toxicidad , Células Epiteliales Alveolares/efectos de los fármacos , Células Epiteliales Alveolares/metabolismo , Contaminantes Atmosféricos/toxicidad , Contaminantes Atmosféricos/análisisRESUMEN
The mechanisms of particle-induced pathogenesis in the lung remain poorly understood. Neutrophilic inflammation and oxidative stress in the lung are hallmarks of toxicity. Some investigators have postulated that oxidative stress from particle surface reactive oxygen species (psROS) on the dust produces the toxicopathology in the lungs of dust-exposed animals. This postulate was tested concurrently with the studies to elucidate the toxicity of lunar dust (LD), which is believed to contain psROS due to high-speed micrometeoroid bombardment that fractured and pulverized lunar surface regolith. Results from studies of rats intratracheally instilled (ITI) with three LDs (prepared from an Apollo-14 lunar regolith), which differed 14-fold in levels of psROS, and two toxicity reference dusts (TiO2 and quartz) indicated that psROS had no significant contribution to the dusts' toxicity in the lung. Reported here are results of further investigations by the LD toxicity study team on the toxicological role of oxidants in alveolar neutrophils that were harvested from rats in the 5-dust ITI study and from rats that were exposed to airborne LD for 4 weeks. The oxidants per neutrophils and all neutrophils increased with dose, exposure time and dust's cytotoxicity. The results suggest that alveolar neutrophils play a critical role in particle-induced injury and toxicity in the lung of dust-exposed animals. Based on these results, we propose an adverse outcome pathway (AOP) for particle-associated lung disease that centers on the crucial role of alveolar neutrophil-derived oxidant species. A critical review of the toxicology literature on particle exposure and lung disease further supports a neutrophil-centric mechanism in the pathogenesis of lung disease and may explain previously reported animal species differences in responses to poorly soluble particles. Key findings from the toxicology literature indicate that (1) after exposures to the same dust at the same amount, rats have more alveolar neutrophils than hamsters; hamsters clear more particles from their lungs, consequently contributing to fewer neutrophils and less severe lung lesions; (2) rats exposed to nano-sized TiO2 have more neutrophils and more severe lesions in their lungs than rats exposed to the same mass-concentration of micron-sized TiO2; nano-sized dust has a greater number of particles and a larger total particle-cell contact surface area than the same mass of micron-sized dust, which triggers more alveolar epithelial cells (AECs) to synthesize and release more cytokines that recruit a greater number of neutrophils leading to more severe lesions. Thus, we postulate that, during chronic dust exposure, particle-inflicted AECs persistently release cytokines, which recruit neutrophils and activate them to produce oxidants resulting in a prolonged continuous source of endogenous oxidative stress that leads to lung toxicity. This neutrophil-driven lung pathogenesis explains why dust exposure induces more severe lesions in rats than hamsters; why, on a mass-dose basis, nano-sized dusts are more toxic than the micron-sized dusts; why lung lesions progress with time; and why dose-response curves of particle toxicity exhibit a hockey stick like shape with a threshold. The neutrophil centric AOP for particle-induced lung disease has implications for risk assessment of human exposures to dust particles and environmental particulate matter.
Asunto(s)
Polvo , Enfermedades Pulmonares , Cricetinae , Ratas , Humanos , Animales , Neutrófilos/patología , Pulmón , Citocinas/toxicidad , Oxidantes/toxicidad , Tamaño de la PartículaRESUMEN
A wide literature has demonstrated that internal combustion engines are the main responsible for the emission of fine particles in urban areas. Within this scope, ultrafine particles within diesel exhausted gas have been widely proven to exert a significantly harmful impact on human health and environment. This scenario has led the research community to turn the attention from particle mass to diameter and surface area. In this paper, non-thermal plasma (NTP) technology was applied to a heavy duty diesel engine. Chemical reactions of diesel particles in plasma zone were analyzed. Additionally, variation in diesel particles' number and surface area distributions, engendered by above reactions, were thoroughly investigated. The results showed that diesel exhausted particles experienced oxidation, aggregation, and crush because of enhanced plasma transports and active species in plasma zone. NTP presents excellent reduction effectiveness of diesel particles covering different sizes. Being more than 50%, the most considerable surface area concentration drop was found in correspondence of 1800 RPM. Differently, the lowest drop of surface area concentration was seen at 1200 RPM. As a result of the NTP actions, surface area concentration distributions were almost the same for diameters being larger than 0.5 µm at different engine modes, except at 900 RPM. This research made a foundation of dropping particle emissions and evaluating the effectiveness of NTP dropping particle harms to human health.
Asunto(s)
Contaminantes Atmosféricos , Gases em Plasma , Contaminantes Atmosféricos/análisis , Gasolina/análisis , Humanos , Tamaño de la Partícula , Material Particulado/análisis , Emisiones de Vehículos/análisisRESUMEN
BACKGROUND: Emissions from diesel vehicles and biomass burning are the principal sources of primary ultrafine particles (UFP). The exposure to UFP has been associated to cardiovascular and pulmonary diseases, including lung cancer. Although many aspects of the toxicology of ambient particulate matter (PM) have been unraveled, the molecular mechanisms activated in human cells by the exposure to UFP are still poorly understood. Here, we present an RNA-seq time-course experiment (five time point after single dose exposure) used to investigate the differential and temporal changes induced in the gene expression of human bronchial epithelial cells (BEAS-2B) by the exposure to UFP generated from diesel and biomass combustion. A combination of different bioinformatics tools (EdgeR, next-maSigPro and reactome FI app-Cytoscape and prioritization strategies) facilitated the analyses the temporal transcriptional pattern, functional gene set enrichment and gene networks related to cellular response to UFP particles. RESULTS: The bioinformatics analysis of transcriptional data reveals that the two different UFP induce, since the earliest time points, different transcriptional dynamics resulting in the activation of specific genes. The functional enrichment of differentially expressed genes indicates that the exposure to diesel UFP induces the activation of genes involved in TNFα signaling via NF-kB and inflammatory response, and hypoxia. Conversely, the exposure to ultrafine particles from biomass determines less distinct modifications of the gene expression profiles. Diesel UFP exposure induces the secretion of biomarkers associated to inflammation (CCXL2, EPGN, GREM1, IL1A, IL1B, IL6, IL24, EREG, VEGF) and transcription factors (as NFE2L2, MAFF, HES1, FOSL1, TGIF1) relevant for cardiovascular and lung disease. By means of network reconstruction, four genes (STAT3, HIF1a, NFKB1, KRAS) have emerged as major regulators of transcriptional response of bronchial epithelial cells exposed to diesel exhaust. CONCLUSIONS: Overall, this work highlights modifications of the transcriptional landscape in human bronchial cells exposed to UFP and sheds new lights on possible mechanisms by means of which UFP acts as a carcinogen and harmful factor for human health.
Asunto(s)
Biomasa , Bronquios/metabolismo , Células Epiteliales/metabolismo , Perfilación de la Expresión Génica , Regulación de la Expresión Génica/efectos de los fármacos , Material Particulado/efectos adversos , Emisiones de Vehículos/envenenamiento , Bronquios/citología , Bronquios/efectos de los fármacos , Células Cultivadas , Células Epiteliales/citología , Células Epiteliales/efectos de los fármacos , Humanos , TranscriptomaRESUMEN
In addition to the well-established effects of air pollution on the cardiovascular and respiratory systems, emerging evidence has implicated it in inducing negative effects on the central nervous system. Diesel exhaust particulate matter (DEP), a major component of air pollution, is a complex mixture of numerous toxicants. Limited studies have shown that DEP-induced dopaminergic neuron dysfunction is mediated by microglia, the resident immune cells of the brain. Here we show that mouse microglia similarly mediate primary cerebellar granule neuron (CGN) death in vitro. While DEP (0, 25, 50, 100µg/2cm2) had no effect on CGN viability after 24h of treatment, in the presence of primary cortical microglia neuronal cell death increased by 2-3-fold after co-treatment with DEP, suggesting that microglia are important contributors to DEP-induced CGN neurotoxicity. DEP (50µg/2cm2) treatment of primary microglia for 24h resulted in morphological changes indicative of microglia activation, suggesting that DEP may induce the release of cytotoxic factors. Microglia-conditioned medium after 24h treatment with DEP, was also toxic to CGNs. DEP caused a significant increase in reactive oxygen species in microglia, however, antioxidants failed to protect neurons from DEP/microglia-induced toxicity. DEP increased mRNA levels of the pro-inflammatory cytokines IL-6 and IL1-ß, and the release of IL-6. The antibiotic minocycline (50µM) and the peroxisome proliferator-activated receptor-γ agonist pioglitazone (50µM) attenuated DEP-induced CGN death in the co-culture system. Microglia and CGNs from male mice appeared to be somewhat more susceptible to DEP neurotoxicity than cells from female mice possibly because of lower paraoxonase-2 expression. Together, these results suggest that microglia-induced neuroinflammation may play a critical role in modulating the effect of DEP on neuronal viability. .
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Citocinas/metabolismo , Microglía/fisiología , Neuronas/efectos de los fármacos , Emisiones de Vehículos/toxicidad , Análisis de Varianza , Animales , Animales Recién Nacidos , Arildialquilfosfatasa/metabolismo , Muerte Celular/efectos de los fármacos , Células Cultivadas , Cerebelo/citología , Técnicas de Cocultivo , Medios de Cultivo Condicionados/farmacología , Citocinas/genética , Relación Dosis-Respuesta a Droga , L-Lactato Deshidrogenasa/metabolismo , Ratones , Ratones Endogámicos C57BL , Microglía/química , Neuronas/metabolismo , ARN Mensajero/metabolismo , Caracteres SexualesRESUMEN
Diesel engine emissions are among the most prevalent anthropogenic pollutants worldwide, and with the growing popularity of diesel-fueled engines in the private transportation sector, they are becoming increasingly widespread in densely populated urban regions. However, a large number of toxicological studies clearly show that diesel engine emissions profoundly affect human health. Thus the interest in the molecular and cellular mechanisms underlying these effects is large, especially concerning the nature of the components of diesel exhaust responsible for the effects and how they could be eliminated from the exhaust. This review describes the fundamental properties of diesel exhaust as well as the human respiratory tract and concludes that adverse health effects of diesel exhaust not only emerge from its chemical composition, but also from the interplay between its physical properties, the physiological and cellular properties, and function of the human respiratory tract. Furthermore, the primary molecular and cellular mechanisms triggered by diesel exhaust exposure, as well as the fundamentals of the methods for toxicological testing of diesel exhaust toxicity, are described. The key aspects of adverse effects induced by diesel exhaust exposure described herein will be important for regulators to support or ban certain technologies or to legitimate incentives for the development of promising new technologies such as catalytic diesel particle filters.
Asunto(s)
Contaminantes Atmosféricos/toxicidad , Material Particulado/toxicidad , Mucosa Respiratoria/efectos de los fármacos , Enfermedades Respiratorias/inducido químicamente , Emisiones de Vehículos/toxicidad , Contaminantes Atmosféricos/química , Animales , Daño del ADN , Humanos , Estrés Oxidativo/efectos de los fármacos , Material Particulado/química , Neumonía/inducido químicamente , Neumonía/metabolismo , Neumonía/patología , Mucosa Respiratoria/metabolismo , Mucosa Respiratoria/patología , Enfermedades Respiratorias/metabolismo , Enfermedades Respiratorias/patología , Propiedades de Superficie , Emisiones de Vehículos/análisisRESUMEN
Combustion experiments were conducted to evaluate the effects of using blends of ultralow sulfur diesel (ULSD) with biodiesel or n-butanol on physicochemical and toxicological characteristics of particulate emissions from a non-road diesel engine. The results indicated that compared to ULSD, both the blended fuels could effectively reduce the particulate mass and elemental carbon emissions, with butanol being more effective than biodiesel. The proportion of organic carbon and volatile organic compounds in particles increased for both blended fuels. However, biodiesel blended fuels showed lower total particle-phase polycyclic aromatic hydrocarbons (PAHs) emissions. The total number emissions of particles ≤560nm in diameter decreased gradually for the butanol blended fuels, but increased significantly for the biodiesel blended fuels. Both the blended fuels indicated lower soot ignition temperature and activation energy. All the particle extracts showed a decline in cell viability with the increased dose. However, the change in cell viability among test fuels is not statistically significant different with the exception of DB-4 (biodiesel-diesel blend containing 4% oxygen) used at 75% engine load.
Asunto(s)
Material Particulado/toxicidad , Emisiones de Vehículos/toxicidad , Biocombustibles , Butanoles , Línea Celular , Supervivencia Celular , Gasolina , Humanos , Oxidación-Reducción , Material Particulado/química , Termogravimetría , Compuestos Orgánicos Volátiles/análisisRESUMEN
BACKGROUND: Diesel exhaust particles (DEPs) are globally relevant air pollutants that exert a detrimental human health impact. However, mechanisms of damage by DEP exposure to human respiratory health and human susceptibility factors are only partially known. Matrix metalloproteinase-1 (MMP-1) has been implied as an (etio)pathogenic factor in human lung and airway diseases such as emphysema, chronic obstructive pulmonary disease, chronic asthma, tuberculosis, and bronchial carcinoma and has been reported to be regulated by DEPs. OBJECTIVE: We elucidated the molecular mechanisms of DEPs' up-regulation of MMP-1. METHODS/RESULTS: Using permanent and primary human bronchial epithelial (HBE) cells at air-liquid interface, we show that DEPs activate the human MMP-1 gene via RAS and subsequent activation of RAF-MEK-ERK1/2 mitogen-activated protein kinase signaling, which can be scaffolded by beta-arrestins. Short interfering RNA mediated beta-arrestin1/2 knockout eliminated formation, subsequent nuclear trafficking of phosphorylated ERK1/2, and resulting MMP-1 transcriptional activation. Transcriptional regulation of the human MMP-1 promoter was strongly influenced by the presence of the -1607GG polymorphism, present in 60-80% of humans, which led to striking up-regulation of MMP-1 transcriptional activation. CONCLUSION: Our results confirm up-regulation of MMP-1 in response to DEPs in HBE and provide new mechanistic insight into how these epithelia, the first line of protection against environmental insults, up-regulate MMP-1 in response to DEP inhalation. These mechanisms include a role for the human -1607GG polymorphism as a susceptibility factor for an accentuated response, which critically depends on the ability of beta-arrestin1/2 to generate scaffolding and nuclear trafficking of phosphorylated ERK1/2.
Asunto(s)
Arrestinas/metabolismo , Bronquios/citología , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Metaloproteinasa 1 de la Matriz/metabolismo , Mucosa Respiratoria/efectos de los fármacos , Emisiones de Vehículos/toxicidad , Análisis de Varianza , Arrestinas/genética , Western Blotting , Bronquios/efectos de los fármacos , Línea Celular , Cartilla de ADN/genética , Ensayo de Inmunoadsorción Enzimática , Humanos , Inmunohistoquímica , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , beta-Arrestinas , Proteínas ras/metabolismoRESUMEN
BACKGROUND: Airborne emissions from numerous point, area, and mobile sources, along with stagnant meteorologic conditions, contribute to frequent episodes of elevated air pollution in Houston, Texas. To address this problem, decision makers must set priorities among thousands of individual air pollutants as they formulate effective and efficient mitigation strategies. OBJECTIVES: Our aim was to compare and rank relative health risks of 179 air pollutants in Houston using an evidence-based approach supplemented by the expert judgment of a panel of academic scientists. METHODS: Annual-average ambient concentrations by census tract were estimated from the U.S. Environmental Protection Agency's National-scale Air Toxics Assessment and augmented with measured levels from the Houston monitoring network. Each substance was assigned to one of five risk categories (definite, probable, possible, unlikely, uncertain) based on how measured or monitored concentrations translated into comparative risk estimates. We used established unit risk estimates for carcinogens and/or chronic reference values for noncarcinogens to set thresholds for each category. Assignment to an initial risk category was adjusted, as necessary, based on expert judgment about the quality and quantity of information available. RESULTS: Of the 179 substances examined, 12 (6.7%) were deemed definite risks, 9 (5.0%) probable risks, 24 (13.4%) possible risks, 16 (8.9%) unlikely risks, and 118 (65.9%) uncertain risks. CONCLUSIONS: Risk-based priority setting is an important step in the development of cost-effective solutions to Houston's air pollution problem.