Effects of Particulate Matter on Cytokine Production In Vitro: A Comparative Analysis of Published Studies

Characterizing the neuroimmune environment of offspring in a novel model of maternal allergic asthma and particulate matter exposure

Inflammation during pregnancy is associated with an increased risk for neurodevelopmental disorders (NDD). Increased gestational inflammation can be a result of an immune condition/disease, exposure to infection, and/or environmental factors. Epidemiology studies suggest that cases of NDD are on the rise. Similarly, rates of asthma are increasing, and the presence of maternal asthma during pregnancy increases the likelihood of a child being later diagnosed with NDD such as autism spectrum disorders (ASD). Particulate matter (PM), via air pollution, is an environmental factor known to worsen the symptoms of asthma, but also, PM has been associated with increased risk of neuropsychiatric disorders. Despite the links between asthma and PM with neuropsychiatric disorders, there is a lack of laboratory models investigating combined prenatal exposure to asthma and PM on offspring neurodevelopment. Thus, we developed a novel mouse model that combines exposure to maternal allergic asthma (MAA) and ultrafine iron-soot (UIS), a common component of PM. In the current study, female BALB/c mice were sensitized for allergic asthma with ovalbumin (OVA) prior to pregnancy. Following mating and beginning on gestational day 2 (GD2), dams were exposed to either aerosolized OVA to induce allergic asthma or phosphate buffered saline (PBS) for 1 h. Following the 1-h exposure, pregnant females were then exposed to UIS with a size distribution of 55 to 169 nm at an average concentration of 176 ± 45 μg/m3) (SD), or clean air for 4 h, over 8 exposure sessions. Offspring brains were collected at postnatal days (P)15 and (P)35. Cortices and hippocampal regions were then isolated and assessed for changes in cytokines using a Luminex bead-based multiplex assay. Analyses identified changes in many cytokines across treatment groups at both timepoints in the cortex, including interleukin-1 beta (IL-1β), and IL-17, which remained elevated from P15 to P35 in all treatment conditions compared to controls. There was a suppressive effect of the combined MAA plus UIS on the anti-inflammatory cytokine IL-10. Potentially shifting the cytokine balance towards more neuroinflammation. In the hippocampus at P15, elevations in cytokines were also identified across the treatment groups, namely IL-7. The combination of MAA and UIS exposure (MAA-UIS) during pregnancy resulted in an increase in microglia density in the hippocampus of offspring, as identified by IBA-1 staining. Together, these data indicate that exposure to MAA, UIS, and MAA-UIS result in changes in the neuroimmune environment of offspring that persist into adulthood.

Characterizing the Neuroimmune Environment of Offspring in a Novel Model of Maternal Allergic Asthma and Particulate Matter Exposure

Autism spectrum disorders (ASD) are neurodevelopmental disorders characterized by the presence of decreased social interactions and an increase in stereotyped and repetitive behaviors. Epidemiology studies suggest that cases of ASD are on the rise. Similarly, rates of asthma are increasing, and the presence of maternal asthma during pregnancy increases the likelihood of a child being later diagnosed with ASD. Particulate matter (PM), via air pollution, is an environmental factor known to worsen the symptoms of asthma, but also, PM has been associated with increased risk of neuropsychiatric disorders including ASD. Despite the links between asthma and PM with neuropsychiatric disorders, there is a lack of laboratory models investigating combined prenatal exposure to asthma and PM on offspring neurodevelopment. Thus, we developed a novel mouse model that combines exposure to maternal allergic asthma (MAA) and ultrafine iron-soot (UIS), a common component of PM. In the current study, female BALB/c mice were primed for allergic asthma with ovalbumin (OVA) prior to pregnancy. Following mating and beginning on gestational day 2 (GD2), dams were exposed to either aerosolized OVA or phosphate buffered saline (PBS) for 1 hour. Following the 1-hour exposure, pregnant females were then exposed to UIS or clean air for 4 hours. Offspring brains were collected at postnatal days (P)15 and (P)35. Cortices and hippocampal regions were then isolated and assessed for changes in cytokines using a Luminex bead-based multiplex assay. Analyses identified changes in many cytokines across treatment groups at both timepoints in the cortex, including interleukin-1 beta (IL-1β), IL-2, IL-13, and IL-17, which remained elevated from P15 to P35 in all treatment conditions compared to controls. In the hippocampus at P15, elevations in cytokines were also identified across the treatment groups, namely interferon gamma (IFNγ) and IL-7. The combination of MAA and UIS exposure (MAA-UIS) during pregnancy resulted in an increase in microglia density in the hippocampus of offspring, as identified by IBA-1 staining. Together, these data indicate that exposure to MAA, UIS, and MAA-UIS result in changes in the neuroimmune environment of offspring that persist into adulthood.

Climate change and public health: The effects of global warming on the risk of allergies and autoimmune diseases: The effects of global warming on the risk of allergies and autoimmune diseases

Global climate change and extreme weather events are associated with epigenetic modifications in immune cells, leading to the possible increased risk and prevalence of allergies and autoimmune diseases.

Health and Clinical Impacts of Air Pollution and Linkages with Climate Change

Air Pollution Impacts and Climate Change LinksAs part of the NEJM Group series on climate change, Keswani and colleagues review the linkages between climate change and air pollution and suggest strategies that clinicians may use to mitigate the adverse health impacts of air pollution.

In-vitro oxidative potential and inflammatory response of ambient PM2.5 in a rural region of Northwest China: Association with chemical compositions and source contribution

Overproduction of reactive oxygen species (ROS) induced by atmospheric particles and subsequent inflammatory responses are considered as one of the most important pathological mechanisms with regard to the adverse effects of air pollution exposure. In this study, fine particulate matter (PM_2.5) samples were collected at a rural site in Guanzhong Basin, Northwest China, in both summer (August 3-23, 2016) and winter (January 5-February 1, 2017). Then, human bronchial epithelial BEAS-2B cells were exposed to the PM_2.5, cultured for 24 h, and then assayed for particle-induced ROS and three inflammatory factors (tumor necrosis-α (TNF-α), interleukin-6 (IL-6), and interferon-γ (IFN-γ)) in vitro. The oxidative potential (OP) induced by winter PM_2.5 samples was higher than that induced by summertime samples, whereas inflammatory values showed contrasting seasonal variations. Both OP and inflammatory factors were significantly correlated with most chemical compounds in winter, but not in summer, which was thought to be related mainly to the higher contribution from secondary aerosols formed during the warm season. Source apportionment results showed secondary aerosols formation have significant contribution to OP of PM_2.5 in both seasons, but the dominant oxidation processes is different. Secondary nitrates-related process was the major contributors regulating the OP in winter; however, secondary sulfates formation were mainly responsible for the ROS responses in summer. For primary emission, biomass burning, rather than coal emission or vehicle exhaust, was the significant source for OP of PM_2.5 in winter. In most cases, the source contribution of each inflammatory factor was similar to that of the ROS. Our results highlighted the significant health risk of atmospheric aerosols from biomass burning in the rural regions of Guanzhong Basin, Northwest China.

Systematic review of preclinical studies on the neutrophil-mediated immune response to air pollutants, 1980-2020

Preclinical evidence about the neutrophil-mediated response in exposure to air pollutants is scattered and heterogeneous. This has prevented the consolidation of this research field around relevant models that could advance towards clinical research. The purpose of this study was to systematic review the studies of the neutrophils response to air pollutants, following the recommendations of the Cochrane Collaboration and the PRISMA guide, through 54 search strategies in nine databases. We include 234 studies (in vitro, and in vivo), being more frequent using primary neutrophils, Balb/C and C57BL6/J mice, and Sprague-Dawley and Wistar rats. The most frequent readouts were cell counts, cytokines and histopathology. The temporal analysis showed that in the last decade, the use of mice with histopathological and cytokine measurement have predominated. This systematic review has shown that study of the neutrophils response to air pollutants started 40 years ago, and composed of 100 different preclinical models, 10 pollutants, and 11 immunological outcomes. Mechanisms of neutrophils-mediated immunopathology include cellular activation, ROS production, and proinflammatory effects, leading to cell-death, oxidative stress, and inflammatory infiltrates in lungs. This research will allow consolidating the research efforts in this field, optimizing the study of causal processes, and facilitating the advance to clinical studies.

Air pollution and its effects on the immune system

A well-functioning immune system is vital for a healthy body. Inadequate and excessive immune responses underlie diverse pathologies such as serious infections, metastatic malignancies and auto-immune conditions. Therefore, understanding the effects of ambient pollutants on the immune system is vital to understanding how pollution causes disease, and how that pathology could be abrogated. The immune system itself consists of multiple types of immune cell that act together to generate (or fail to generate) immune responses and in this article we review evidence of how air pollutants can affect different immune cell types such as particle-clearing macrophages, inflammatory neutrophils, dendritic cells that orchestrate adaptive immune responses and lymphocytes that enact those responses. Common themes that emerge are of the capacity of air pollutants to stimulate pro-inflammatory immune responses across multiple classes of immune cell. Air pollution can enhance T helper lymphocyte type 2 (Th2) and T helper lymphocyte type 17 (Th17) adaptive immune responses, as seen in allergy and asthma, and dysregulate anti-viral immune responses. The clinical effects of air pollution, in particular the known association between elevated ambient pollution and exacerbations of asthma and chronic obstructive pulmonary disease (COPD), are consistent with these identified immunological mechanisms. Further to this, as inhaled air pollution deposits primarily on the respiratory mucosa this review focuses on mechanisms of respiratory disease. However, as discussed in the article, air pollution also affects the wider immune system for example in the neonate and gastrointestinal tract. Whilst the many identified actions of air pollution on the immune system are notably diverse, immunological research does suggest potential strategies to ameliorate such effects, for example with vitamin D supplementation. An in-depth understanding of the immunological effects of ambient pollutants should hopefully yield new ideas on how to reduce the adverse health effects of air pollution.

Investigation and Comparison of In Vitro Genotoxic Potency of PM10 Collected in Rural and Urban Sites at Tehran in Different Metrological Conditions and Different Seasons

The particulate matter has become a serious health problem in some large cities in the world. These particles are a complex mixture of chemical compounds which change based on location and time and, consequently, can cause different health-related effects. The exact mechanism of the effect of these particles is not yet known for certain. However, it seems that numerous mechanisms through the production of ROS and, eventually, DNA destruction, which are related to a wide range of diseases, are among the causes of particles' health-related effects. The present study is aimed to evaluate and compare the genotoxicity potential of particles collected in Tehran, Iran, in urban and rural regions during spring and autumn as well as dusty and inversion conditions. These effects were examined using the comet assay on human pulmonary epithelial cells (A549). Results showed that all the particles had the potential for genotoxicity at the concentration used in this study (75,150 and 300 μg/ml). Moreover, DNA destruction changed with season, site, and even dusty and inversion atmospheric conditions. These changes mostly belonged to urban particles. In general, urban particles in autumn and, specifically, on days with inversion had higher genotoxicity (p < 0.01). Difference was observed between dusty and regular days so that regular days were more potent (p < 0.05). A strong correlation was observed between the effects of most PAH compounds and other metals such as Cr, Co, Cd, Mn, As, and also SO₄, which were mostly the result of combustion in vehicle engines in urban regions. No difference was observed for rural particles at different conditions and seasons.

Ambient particulate matter activates the aryl hydrocarbon receptor in dendritic cells and enhances Th17 polarization

The objective of this study was to explore the role of the aryl hydrocarbon receptor (AhR) in ambient particulate matter (PM)-mediated activation of dendritic cells (DCs) and Th17-immune responses in vitro. To assess the potential role of the AhR in PM-mediated activation of DCs, co-stimulation, and cytokine expression, bone marrow (BM)-derived macrophages and DCs from C57BL/6 wildtype or AhR knockout (AhR-/-) mice were treated with PM. Th17 differentiation was assessed via co-cultures of wildtype or AhR-/- BMDCs with autologous naive T cells. PM2.5 significantly induced AhR DNA binding activity to dioxin responsive elements (DRE) and expression of the AhR repressor (AhRR), cytochrome P450 (CYP) 1A1, and CYP1B1, indicating activation of the AhR. In activated (OVA sensitized) BMDCs, PM2.5 induced interleukin (IL)-1β, CD80, CD86, and MHC class II, suggesting enhanced DC activation, co-stimulation, and antigen presentation; responses that were abolished in AhR deficient DCs. DC-T cell co-cultures treated with PM and lipopolysaccharide (LPS) led to elevated IL-17A and IL-22 expression at the mRNA level, which is mediated by the AhR. PM-treated DCs were essential in endowing T cells with a Th17-phenotype, which was associated with enhanced expression of MHC class II and cyclooxygenase (COX)-2. In conclusion, PM enhances DC activation that primes naive T cell differentiation towards a Th17-like phenotype in an AhR-dependent manner.

Ozone augments interleukin-8 production induced by ambient particulate matter

Background

Experimental and controlled human exposure studies have demonstrated additive effects of ambient particulate matter and ozone on health. A few epidemiological studies have suggested that ambient particulate matter components are important for the combined effects of ambient particulate matter and ozone on health. However, few studies have examined whether ozone changes the effects of ambient particulate matter on pro-inflammatory cytokine production. In this study, the influence of ozone on pro-inflammatory cytokine production in response to ambient particulate matter was evaluated.

Results

Ambient particulate matter smaller than 1 μm was collected and the suspension of this particulate matter was bubbled through 0.12 ppm and 0.24 ppm ozone. THP1 cells were stimulated by the solution containing the particulate matter with and without bubbling through ozone at 1 μg/mL. The interleukin-8 concentrations in the supernatants of THP1 cells stimulated by collected particulate matter dissolved in solution were 108.3 ± 24.7 pg/mL without ozone exposure, 165.0 ± 26.1 pg/mL for 0.12 ppm ozone bubbling for 1 min, 175.1 ± 33.1 pg/mL for 0.12 ppm for 5 min, 183.3 ± 17.8 pg/mL for 0.12 ppm for 15 min, 167.8 ± 35.9 pg/mL for 0.24 ppm for 1 min, 209.2 ± 8.4 pg/mL for 0.24 ppm for 5 min, and 209.3 ± 14.3 pg/mL for 0.24 ppm for 15 min. Ozone significantly increased interleukin-8 concentrations compared to those for particulate matter dissolved in solution without ozone exposure and the solvent only (8.2 ± 0.9 pg/mL) in an ozone concentration-dependent manner. Collected particulate matter in solutions with or without bubbling through ozone had no effect on interleukin-6 production. The antioxidant N-acetyl-_L-cysteine significantly inhibited the increases in interleukin-8 induced by solutions with particulate matter, regardless of ozone exposure. The reactive oxygen species concentration in solutions with collected particulate matter was not associated with ozone bubbling.

Conclusion

Ozone may augment the production of interleukin-8 in response to ambient particulate matter by a mechanism unrelated to reactive oxygen species. These results support the epidemiological evidence for combined effects of ambient particulate matter and ozone on human health.

Mechanisms and treatments for severe, steroid-resistant allergic airway disease and asthma

Severe, steroid-resistant asthma is clinically and economically important since affected individuals do not respond to mainstay corticosteroid treatments for asthma. Patients with this disease experience more frequent exacerbations of asthma, are more likely to be hospitalized, and have a poorer quality of life. Effective therapies are urgently required, however, their development has been hampered by a lack of understanding of the pathological processes that underpin disease. A major obstacle to understanding the processes that drive severe, steroid-resistant asthma is that the several endotypes of the disease have been described that are characterized by different inflammatory and immunological phenotypes. This heterogeneity makes pinpointing processes that drive disease difficult in humans. Clinical studies strongly associate specific respiratory infections with severe, steroid-resistant asthma. In this review, we discuss key findings from our studies where we describe the development of representative experimental models to improve our understanding of the links between infection and severe, steroid-resistant forms of this disease. We also discuss their use in elucidating the mechanisms, and their potential for developing effective therapeutic strategies, for severe, steroid-resistant asthma. Finally, we highlight how the immune mechanisms and therapeutic targets we have identified may be applicable to obesity-or pollution-associated asthma.

Toxicity of Urban PM10 and Relation with Tracers of Biomass Burning

The chemical composition of particles varies with space and time and depends on emission sources, atmospheric chemistry and weather conditions. Evidence suggesting that particles differ in toxicity depending on their chemical composition is growing. This in vitro study investigated the biological effects of PM₁₀ in relation to PM-associated chemicals. PM₁₀ was sampled in ambient air at an urban traffic site (Borgerhout) and a rural background location (Houtem) in Flanders (Belgium). To characterize the toxic potential of PM₁₀, airway epithelial cells (Beas-2B cells) were exposed to particles in vitro. Different endpoints were studied including cell damage and death (cell viability) and the induction of interleukin-8 (IL-8). The mutagenic capacity was assessed using the Ames II Mutagenicity Test. The endotoxin levels in the collected samples were analyzed and the oxidative potential (OP) of PM₁₀ particles was evaluated by electron paramagnetic resonance (EPR) spectroscopy. Chemical characteristics of PM₁₀ included tracers for biomass burning (levoglucosan, mannosan and galactosan), elemental and organic carbon (EC/OC) and polycyclic aromatic hydrocarbons (PAHs). Most samples displayed dose-dependent cytotoxicity and IL-8 induction. Spatial and temporal differences in PM₁₀ toxicity were seen. PM₁₀ collected at the urban site was characterized by increased pro-inflammatory and mutagenic activity as well as higher OP and elevated endotoxin levels compared to the background area. Reduced cell viability (−0.46 < r_s < −0.35, p < 0.01) and IL-8 induction (−0.62 < r_s < −0.67, p < 0.01) were associated with all markers for biomass burning, levoglucosan, mannosan and galactosan. Furthermore, direct and indirect mutagenicity were associated with tracers for biomass burning, OC, EC and PAHs. Multiple regression analyses showed levoglucosan to explain 16% and 28% of the variance in direct and indirect mutagenicity, respectively. Markers for biomass burning were associated with altered cellular responses and increased mutagenic activity. These findings may indicate a role of biomass burning in the observed adverse health effect of particulate matter.

Evaluating Cytokines in Immunotoxicity Testing

One of the most powerful tools in immunotoxicology is the assessment of cytokines, the proteins/peptides responsible for regulating a variety of processes including immunity, inflammation, apoptosis, and hematopoiesis. Cytokine production measurements offer outstanding information and may eventually substitute for other more laborious procedures in the assessment of immunotoxicity. The particular profile of cytokine production provides indeed important information regarding the nature of many immunotoxic responses.Recent expansion in the knowledge of cytokine biology and the realization that cytokines play a role in human diseases have created a need for the precise assessment and accurate interpretation of their presence and activity in body fluids, tissues, and cells. Proper evaluation of cytokines requires attention to several technical details. Multi-cytokine analysis still needs to be standardized in terms of optimum source for analysis, protocols, and quality control issues, such as the use of reference standards and the expression of results.Important practical details and considerations will be discussed in this chapter, including the source of the sample to be tested (circulating fluids or ex vivo/in vitro isolated cells); the potential effects of collection, processing, and storage of the results of the assays, as well as potential variables associated with the source material (matrix effects, relevance, inhibitory substances); and factors influencing the choice of assay used (bioassay, immunoassay, molecular biology technique, flow cytometry).

Association between transported Asian dust and outdoor fungal concentration during winter in a rural area of western Japan

Background

Recently, Asian dust (AD) has become a serious health problem and several studies have clearly proven that AD can aggravate asthma. However, it remains unclear as to which components of AD have a strong effect on the asthma exacerbation caused by AD exposure. Outdoor fungi can increase emergency department visits and hospitalization for asthma exacerbation and can aggravate asthma symptoms. Therefore, this study was aimed at investigating the relationship between AD and outdoor fungi and determining the potential of fungi to cause airborne particulate matter (PM)-related inflammatory responses.

Methods

Airborne PM was collected each day from January 26, 2015 to February 27, 2015. Daily levels of outdoor fungi-associated PM were calculated using a culture-based method. Production of cytokines such as interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-α was assessed in THP1 cells stimulated by the collected airborne PM each day.

Results

Daily levels of AD particles were assessed using Light Detection and Ranging and did not correlate with outdoor fungi (r = −0.17, P = 0.94). There was also no association between outdoor fungi and the daily production of IL-6 (r = 0.16, P = 0.37), IL-8 (r = 0.19, P = 0.30), or TNF-α induced by collected PM (r = 0.07, P = 0.70). However, the daily levels of AD particles were significantly associated with IL-6 (r = 0.91, P < 0.0001), IL-8 (r = 0.64, P = 0.0004), and TNF-α (r = 0.72, P < 0.0001) production.

Conclusion

AD did not increase the acute levels of outdoor fungi and outdoor fungi did not affect the cytokine production induced by airborne PM. These results suggest that outdoor fungi do not have any detectable effect on the asthma exacerbation caused by AD exposure.

Particulate metal bioaccessibility in physiological fluids and cell culture media: Toxicological perspectives

According to the literature, tiny amounts of transition metals in airborne fine particles (PM_2.5) may induce proinflammatory cell response through reactive oxygen species production. The solubility of particle-bound metals in physiological fluids, i.e. the metal bioaccessibility is driven by factors such as the solution chemical composition, the contact time with the particles, and the solid-to-liquid phase ratio (S/L). In this work, PM_2.5-bound metal bioaccessibility was assessed in various physiological-like solutions including cell culture media in order to evidence the potential impact on normal human bronchial epithelial cells (NHBE) when studying the cytotoxicity and inflammatory responses of PM_2.5 towards the target bronchial compartment. Different fluids (H₂O, PBS, LHC-9 culture medium, Gamble and human respiratory mucus collected from COPD patients), various S/L conditions (from 1/6000 to 1/100,000) and exposure times (6, 24 and 72h) were tested on urban PM_2.5 samples. In addition, metals' total, soluble and insoluble fractions from PM_2.5 in LHC-9 were deposited on NHBE cells (BEAS-2B) to measure their cytotoxicity and inflammatory potential (i.e., G6PDH activity, secretion of IL-6 and IL-8). The bioaccessibility is solution-dependent. A higher salinity or organic content may increase or inhibit the bioaccessibiliy according to the element, as observed in the complex mucus matrix. Decreasing the S/L ratio also affect the bioaccessibility depending on the solution tested while the exposure time appears less critical. The LHC-9 culture medium appears to be a good physiological proxy as it induces metal bioaccessibilities close to the mucus values and is little affected by S/L ratios or exposure time. Only the insoluble fraction can be linked to the PM_2.5-induced cytotoxicity. By contrast, both soluble and insoluble fractions can be related to the secretion of cytokines. The metal bioaccessibility in LHC-9 of the total, soluble, and insoluble fractions of the PM_2.5 under study did not explain alone, the cytotoxicity nor the inflammatory response observed in BEAS-2B cells. These findings confirm the urgent need to perform further toxicological studies to better evaluate the synergistic effect of both bioaccessible particle-bound metals and organic species.

Whole Blood Cytokine Response to Local Traffic-Related Particulate Matter in Peruvian Children With and Without Asthma

This study sought to investigate if acute phase immune responses of whole blood from Peruvian children with controlled and uncontrolled asthma differed from children without asthma, following exposure to traffic-related particulate matter (TRPM). TRPM, including particulate matter from diesel combustion, has been shown to stimulate acute airway inflammation in individuals with and without asthma. For this study, a whole blood assay (WBA) was used to test peripheral whole blood samples from 27 children with asthma, and 12 without asthma. Participant blood samples were stimulated, ex vivo, for 24-h with an aqueous extract of TRPM that was collected near study area highways in Lima, Peru. All participant blood samples were tested against the same TRPM extract, in addition to purified bacterial endotoxin and pyrogen-free water, which served as positive and negative WBA controls, respectively. The innate and adaptive cytokine responses were evaluated in cell-free supernatants of the whole blood incubations. Comparatively similar levels were recorded for nine out of the 10 cytokines measured [e.g., – Interleukin (IL)-1β, IL-6, IL-10], regardless of study participant asthma status. However, IL-8 levels in TRPM-stimulated blood from children with uncontrolled asthma were diminished, compared to subjects without asthma (633 pg/ml vs. 1,023 pg/ml, respectively; p < 0.01); IL-8 responses for subjects with controlled asthma were also reduced, but to a lesser degree (799 pg/ml vs. 1,023 pg/ml, respectively; p = 0.10). These relationships were present before, and after, adjusting for age, sex, obesity/overweight status, C-reactive protein levels, and residential proximity to the study area’s major roadway. For tests conducted with endotoxin, there were no discernible differences in cytokine response between groups, for all cytokines measured. The WBA testing conducted for this study highlighted the capacity of the TRPM extract to potently elicit the release of IL-8 from the human whole blood system. Although the small sample size of the study limits the capacity to draw definitive conclusions, the IL-8 responses suggest that that asthma control may be associated with the regulation of a key mediator in neutrophil chemotaxis, at a systemic level, following exposure to PM derived from traffic-related sources.

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

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

A panel study of airborne particulate matter composition versus concentration: Potential for inflammatory response and impaired pulmonary function in children

BACKGROUND

The relationship between airborne particulate matter (PM) and pulmonary function in children has not been consistent among studies, potentially owing to differences in the inflammatory response to PM, based on PM types and sources. The objective of this study was to investigate the effect of airborne PM on pulmonary function in schoolchildren and its potential for an inflammatory response.

METHODS

Daily morning peak expiratory flow (PEF) was measured in 339 schoolchildren in February 2015. Interleukin (IL)-8 production was assessed in THP1 cells stimulated by airborne PM collected every day during the study period, and these IL-8 concentrations are described as the daily IL-8 levels. A linear mixed model was used to estimate the association between PEF values and the daily levels of suspended PM (SPM), PM diameters smaller than 2.5 μm (PM_2.5), and IL-8.

RESULTS

The daily IL-8 levels were significantly associated with those of SPM and PM_2.5. A 0.83 μg/mL increase in IL-8 levels was significantly associated with a -1.07 L/min (95% confidence interval, -2.05 to -0.08) decrease in PEF. A 12.0 μg/m³ increase in SPM and a 10.0 μg/m³ increase in PM_2.5 were associated with a -1.36 L/min (-2.93 to 0.22) and -1.72 L/min (-3.82 to 0.36) decreases in PEF, respectively. There were no significant relationships between PEF, SPM, and PM_2.5.

CONCLUSIONS

These findings suggest that the effects of airborne PM on pulmonary function in schoolchildren might depend more on the pro-inflammatory response than the mass concentration of the PM.

Fine particulate matter (PM2.5) enhances allergic sensitization in BALB/c mice

Ambient particulate matter (PM), a component of air pollution, exacerbates airway inflammation and hyperreactivity in asthmatic patients. Studies showed that PM possesses adjuvant-like properties that enhance the allergic inflammatory response; however, the mechanism (or mechanisms) by which PM enhances the allergic response remains to be determined. The aim of this study was to assess how exposure to fine PM collected from Sacramento, CA, shapes the allergic airway immune response in BALB/c mice undergoing sensitization and challenge with ovalbumin (OVA). Eight-week-old BALB/c male mice were sensitized/challenged with phosphate-buffered saline (PBS/PBS; n = 6), PM/PBS (n = 6), OVA/OVA (n = 6), or OVA + PM/OVA (n = 6). Lung tissue, bronchoalveolar lavage fluid (BALF), and plasma were analyzed for cellular inflammation, cytokines, immunoglobulin E, and heme oxygenase-1 (HO-1) expression. Mice in the OVA + PM/OVA group displayed significantly increased airway inflammation compared to OVA/OVA animals. Total cells, macrophages, and eosinophils recovered in BALF were significantly elevated in the OVA + PM/OVA compared to OVA/OVA group. Histopathological grading indicated that OVA + PM/OVA treatment induced significant inflammation compared to OVA/OVA. Both immunoglobulin (Ig) E and tumor necrosis factor (TNF) α levels were significantly increased in OVA/OVA and OVA + PM /OVA groups compared to PBS/PBS control. The number of HO-1 positive alveolar macrophages was significantly elevated in lungs of mice treated with OVA + PM /OVA compared to OVA/OVA. Our findings suggest that fine PM enhances allergic inflammatory response in pulmonary tissue through mechanisms involving increased oxidative stress.

Effects of Short-Term Exposure to Particulate Air Pollutants on the Inflammatory Response and Respiratory Symptoms: A Panel Study in Schoolchildren from Rural Areas of Japan

The relationship between particulate air pollutants and respiratory symptoms in children has not been consistent among studies, potentially owing to differences in the inflammatory response to different particulate air pollutants. This study aimed to investigate the effect of particulate air pollutants on respiratory symptoms and the inflammatory response in schoolchildren. Three hundred-and-sixty children were included in the study. The children recorded daily respiratory symptom scores for October 2015. In addition, the daily amount of interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-α production was assessed in THP1 cells stimulated with suspended particulate matter (SPM), which was collected every day during the study period. Generalized estimating equation logistic regression analyses were used to estimate the associations among respiratory symptoms and the daily levels of SPM, IL-6, IL-8, and TNF-α. Daily SPM levels were not associated with respiratory symptoms or the daily IL-6, IL-8, and TNF-α levels. Conversely, there was a significant association between respiratory symptoms and the daily IL-6, IL-8, and TNF-α levels. These results suggested that the effects of particulate air pollutants on respiratory symptoms in schoolchildren might depend more on the pro-inflammatory response to them than on their mass concentration.

Differential toxicity of an organic PM2.5 extract to human lung cells cultured in three dimensions (3D) and monolayers

Several epidemiological studies have associated PM2.5 (particulate matter, aerodynamic diameter 2.5 µm) exposure with an increase in morbidity and mortality attributed to cardiopulmonary diseases. Based upon these observations and the growing effort to replace the use of animals in research, in vitro A549 cells cultured in three dimensions (3D), an alternative method to the use of animals, as well as monolayers were investigated to examine whether organic PM2.5 extract induced equivalent cytotoxic changes in vitro as compared to in vivo. PM2.5 was collected on Brazil Avenue, Rio de Janeiro, Brazil, from November 2010 to May 2011, except March, and analyzed for the ability to induce cytotoxicity in A549 cells using various established assays. Samples collected in all months significantly decreased viability of A549 cells using both types of cell death assays, and those collected in November showed lower cytotoxicity. It is worthwhile noting that for samples collected in all months except for April, PM2.5 induced greater toxicity in cells grown in monolayers than in 3D. Data demonstrated that cell behavior varied based upon type of culture system employed. Since the 3D cell culture mimics the architecture of in vivo tissue to a greater extent than monolayers, it is suggested that data from 3D studies resemble more closely human exposure conditions and thus may provide more reliable findings to be utilized in risk assessment following PM exposure than results obtained in traditional culture system.

Association of Sand Dust Particles with Pulmonary Function and Respiratory Symptoms in Adult Patients with Asthma in Western Japan Using Light Detection and Ranging: A Panel Study

Light detection and ranging (LIDAR) can estimate daily volumes of sand dust particles from the East Asian desert to Japan. The objective of this study was to investigate the relationship between sand dust particles and pulmonary function, and respiratory symptoms in adult patients with asthma. One hundred thirty-seven patients were included in the study. From March 2013 to May 2013, the patients measured their morning peak expiratory flow (PEF) and kept daily lower respiratory symptom diaries. A linear mixed model was used to estimate the correlation of the median daily levels of sand dust particles, symptoms scores, and PEF. A heavy sand dust day was defined as an hourly concentration of sand dust particles of >0.1 km(-1). By this criterion, there were 8 heavy sand dust days during the study period. Elevated sand dust particles levels were significantly associated with the symptom score (0.04; 95% confidence interval (CI); 0.03, 0.05), and this increase persisted for 5 days. There was no significant association between PEF and heavy dust exposure (0.01 L/min; 95% CI, -0.62, 0.11). The present study found that sand dust particles were significantly associated with worsened lower respiratory tract symptoms in adult patients with asthma, but not with pulmonary function.

Difference in interleukin-8 transcriptional activity induced in THP-G8 cells by particulate matter collected in winter and summer in western Japan

BACKGROUND

Airborne particulate matter (PM) may stimulate production of pro-inflammatory cytokines, and thus exposure to PM affects pulmonary diseases. However, the effects of PM on pulmonary diseases have differed among studies.

METHODS

PM was collected from February 2 to 28 (winter) and June 1 to 17 (summer) in 2013 in Yurihama, Japan, using filters to separate particles with different aerodynamic diameters (1.1 to <2.2 μm, 2.2 to <3.3 μm, 3.3 to <7.0 μm, and 7.0 to <10 μm). Interleukin (IL)-8 transcriptional activity in THP-G8 cells was examined in response to winter and summer PM with different diameters.

RESULTS

IL-8 transcriptional activity induced by winter PM was significantly higher than that with summer PM for each diameter. For winter PM, IL-8 activity increased with an increased diameter, whereas this activity did not differ between a solvent control and each summer PM diameter. This indicates that summer PM does not stimulate production of IL-8 in THP-G8 cells.

CONCLUSION

The effects of PM on production of pro-inflammatory cytokines differ with the season and PM diameter. This suggests that the compositions of PM differ on season, and the evaluation of compositions of PM is important in understanding the association of health with short-term exposure to PM.

Difference in Pro-Inflammatory Cytokine Responses Induced in THP1 Cells by Particulate Matter Collected on Days with and without ASIAN Dust Storms

The associations between particulate matter from Asian dust storms (ADS) and health disorders differ among studies, and the underlying mechanisms remain unclear. In this study, ADS and non-ADS particles were tested for their potential to induce pro-inflammatory cytokines associated with adverse respiratory effects. Particulate matter was collected in Japan during four periods in 2013 (2 × ADS periods; 2 × non-ADS). THP1 cells were exposed to this particulate matter, and the levels of various interleukins (ILs), and tumor necrosis factor (TNF)-α were measured. Levels of IL-2 increased significantly following exposure to all particulate matter samples (compared to levels in a solvent control). Increased levels of IL-10 and TNF-α were also observed following exposure to particles collected during three (one ADS and two non-ADS) and two (one ADS and one non-ADS) collection periods, respectively. Thus, the effects of particulate matter on cytokine responses differed according to collection period, and the effects of ADS particles differed for each ADS event. Additionally, the levels of pro-inflammatory cytokines induced by ADS particles were not always higher than those induced by non-ADS particles.

An in vitro alveolar macrophage assay for the assessment of inflammatory cytokine expression induced by atmospheric particulate matter

Exposures to air pollution in the form of particulate matter (PM) can result in excess production of reactive oxygen species (ROS) in the respiratory system, potentially causing both localized cellular injury and triggering a systemic inflammatory response. PM-induced inflammation in the lung is modulated in large part by alveolar macrophages and their biochemical signaling, including production of inflammatory cytokines, the primary mechanism via which inflammation is initiated and sustained. We developed a robust, relevant, and flexible method employing a rat alveolar macrophage cell line (NR8383) which can be applied to routine samples of PM from air quality monitoring sites to gain insight into the drivers of PM toxicity that lead to oxidative stress and inflammation. Method performance was characterized using extracts of ambient and vehicular engine exhaust PM samples. Our results indicate that the reproducibility and the sensitivity of the method are satisfactory and comparisons between PM samples can be made with good precision. The average relative percent difference for all genes detected during 10 different exposures was 17.1%. Our analysis demonstrated that 71% of genes had an average signal to noise ratio (SNR) ≥ 3. Our time course study suggests that 4 h may be an optimal in vitro exposure time for observing short-term effects of PM and capturing the initial steps of inflammatory signaling. The 4 h exposure resulted in the detection of 57 genes (out of 84 total), of which 86% had altered expression. Similarities and conserved gene signaling regulation among the PM samples were demonstrated through hierarchical clustering and other analyses. Overlying the core congruent patterns were differentially regulated genes that resulted in distinct sample-specific gene expression "fingerprints." Consistent upregulation of Il1f5 and downregulation of Ccr7 was observed across all samples, while TNFα was upregulated in half of the samples and downregulated in the other half. Overall, this PM-induced cytokine expression assay could be effectively integrated into health studies and air quality monitoring programs to better understand relationships between specific PM components, oxidative stress activity and inflammatory signaling potential.

Switch regulation of interleukin-1 beta in downstream of inflammatory cytokines induced by two micro-sized silica particles on differentiated THP-1 macrophages

To investigate the regulated role of IL-1β in initiating and maintaining inflammation, PMA-differentiated THP-1 macrophages were exposed to two micro-sized crystalline silica particles (Si3-5μm and Si1μm) from 3h to 24h, respectively. Cytotoxicity and inflammatory cytokines (IL-1β, TNF-α and IL-6) expressions measured showed that they were induced by both silica particles in positive dose-dependent manners. The levels of inflammatory cytokines induced by Si1μm were higher than those induced by Si3-5μm at low concentration. When pretreated with anti-human IL-1β, not only the high levels of IL-1β but also elevated TNF-α and IL-6 induced by both silica particles were remarkably blocked, especially Si1μm particle. In addition, recombinant human IL-1β protein could induce macrophages to strikingly augment TNF-α and IL-6 expressions. Our data suggest that IL-1β could play a critical role of switching regulation in the downstream inflammation induced by micro-sized silica particles.

Physico-chemical characterization of African urban aerosols (Bamako in Mali and Dakar in Senegal) and their toxic effects in human bronchial epithelial cells: description of a worrying situation

Background

The involvement of particulate matter (PM) in cardiorespiratory diseases is now established in developed countries whereas in developing areas such as Africa with a high level of specific pollution, PM pollution and its effects are poorly studied. Our objective was to characterize the biological reactivity of urban African aerosols on human bronchial epithelial cells in relation to PM physico-chemical properties to identify toxic sources.

Methods

Size-speciated aerosol chemical composition was analyzed in Bamako (BK, Mali, 2 samples with one having desert dust event BK1) and Dakar (DK; Senegal) for Ultrafine UF, Fine F and Coarse C PM. PM reactivity was studied in human bronchial epithelial cells investigating six biomarkers (oxidative stress responsive genes and pro-inflammatory cytokines).

Results

PM mass concentrations were mainly distributed in coarse mode (60%) and were impressive in BK1 due to the desert dust event. BK2 and DK samples showed a high content of total carbon characteristic of urban areas. The DK sample had huge PAH quantities in bulk aerosol compared with BK that had more water soluble organic carbon and metals. Whatever the site, UF and F PM triggered the mRNA expression of the different biomarkers whereas coarse PM had little or no effect. The GM-CSF biomarker was the most discriminating and showed the strongest pro-inflammatory effect of BK2 PM. The analysis of gene expression signature and of their correlation with main PM compounds revealed that PM-induced responses are mainly related to organic compounds. The toxicity of African aerosols is carried by the finest PM as with Parisian aerosols, but when considering PM mass concentrations, the African population is more highly exposed to toxic particulate pollution than French population. Regarding the prevailing sources in each site, aerosol biological impacts are higher for incomplete combustion sources resulting from two-wheel vehicles and domestic fires than from diesel vehicles (Dakar). Desert dust events seem to produce fewer biological impacts than anthropogenic sources.

Discussion

Our study shows that combustion sources contribute to the high toxicity of F and UF PM of African urban aerosols, and underlines the importance of emission mitigation and the imperative need to evaluate and to regulate particulate pollution in Africa.

Tumor necrosis factor-α mediates interactions between macrophages and epithelial cells underlying proinflammatory gene expression induced by particulate matter

Ambient particulate matter (PM) exposure is known to have adverse effects on respiratory health, but the underlying mechanisms remain obscure. We tested the hypothesis that macrophages and epithelial cells synergize to produce maximal cytokine release in response to PM exposure, thereby promoting inflammatory responses. We developed a co-culture model using MLE-12 (mouse lung epithelial) cells and RAW 264.7 (mouse monocyte/macrophage) cells. MLE-12 cells produced KC (Cxcl1) but not tumor necrosis factor-α (TNF), and KC was upregulated only at high levels of urban particulate matter (UPM; NIST 1648a). RAW 264.7 cells produced TNF but not KC, and TNF production was increased by treatment with UPM. In contrast, KC production was upregulated by co-culture of MLE-12 and RAW 264.7 cells, and it was further increased by treatment with a concentration of UPM that had no effect on MLE-12 cells alone. Multiplex cytokine assay revealed a similar pattern of synergistic production of MIG (Cxcl9) and IP-10 (Cxcl10) in co-cultures in response to UPM. TNF was implicated as mediating the synergistic increase in KC production because TNF upregulated KC production in MLE-12 cells, and UPM-induced KC production in co-cultures could be inhibited by a TNF blocking antibody. Intratracheal instillation of UPM into both wild-type and TNF receptor knockout mice resulted in increased TNF production in lavage fluid and increased TNF mRNA expression in cells recovered from lavage fluid. Additionally, UPM instillation into wild-type mice resulted in increased neutrophils and KC in lavage fluid, and these were inhibited in UPM-exposed TNF receptor knockout mice. These results are consistent with a model in which PM activates TNF production in macrophages which in turn stimulates epithelial cells to produce proinflammatory cytokines such as KC. The findings suggest a potential mechanism by which inhaled PM induces inflammation in the lung.

Low levels of residual oil fly ash (ROFA) impair innate immune response against environmental mycobacteria infection in vitro

Epidemiological studies have shown that pollution derived from industrial and vehicular transportation provokes adverse health effects causing broad spectrum of ambient respiratory diseases. Therefore, air pollution should be taken into account when microbial diseases are evaluated. Environmental mycobacteria (EM) are opportunist pathogens in a variety of immunocompromised patients eliciting significant impact on human morbidity and mortality. The aim of this study was to evaluate the in vitro effects of residual oil fly ash (ROFA) on the alveolar macrophages (AMs) response to opportunistic bacteria. AMs from young Wistar rats were obtained by bronchoalveolar lavage and co-cultured with Mycobacterium phlei (MOI 10). We exposed AM cultures to ROFA to characterize the effect of low ROFA concentrations (0, 2.5, and 5μg/ml) and evaluated the response of pre-exposed AM against the bacilli. Low ROFA concentrations induced superoxide anion and nitrites production (p<0.001). Pre-exposure to ROFA (2.5 and 5μg/ml) caused a significant reduction on TNFα (p<0.001) and superoxide anion (p<0.001) production but, did not modify the nitrite production when AM were co-cultured with M. phlei. In addition, ROFA significantly diminished AM killing ability in culture (p<0.001). Hence, our results indicate that pre-exposure to low levels of ROFA modifies the innate pulmonary defence mechanisms against environmental mycobacteria.

Markers of inflammation in alveolar cells exposed to fine particulate matter from prescribed fires and urban air

OBJECTIVE

To assess the effect of fine particulate matter (PM(2.5)) from different particle sources on tumor necrosis factor- (TNF-) α, we measured TNF production from rat alveolar macrophages (AM) and human dendritic cells (DC) exposed to PM(2.5) from different sources.

METHODS

Fire-related PM(2.5) samples, rural ambient, and urban indoor and outdoor samples were collected in the Southeast United States. Tumor necrosis factor release was measured from rat AM and human DC following incubation with PM(2.5).

RESULTS

Tumor necrosis factor release in AMs was greatest for fire-related PM(2.5) compared with other samples (TNF: P value = 0.005; mortality: P value = 0.005). Tumor necrosis factor releases from the DCs and AMs exposed to fire-associated PM(2.5) were strongly correlated (r = 0.87, P value < 0.0001).

CONCLUSIONS

Particulate matter exposure produces TNF release consistent with pulmonary inflammation in rat AMs and human DCs, with the response in rat AMs differing by particle source.

PM10-biogenic fraction drives the seasonal variation of proinflammatory response in A549 cells

PM10 was collected in a Milan urban site, representative of the city air quality, during winter and summer 2006. Mean daily PM10 concentration was 48 μg m(-3) during summer and 148 μg m(-3) during winter. Particles collected on Teflon filters were chemically characterized and the endotoxin content determined by the LAL test. PM10-induced cell toxicity, assessed with MTT and LDH methods, and proinflammatory potential, monitored by IL-6 and IL-8 cytokines release, were investigated on the human alveolar epithelial cell line A549 exposed to increasing doses of PM. Besides untreated cells, exposure to inert carbon particles (2-12 μm) was also used as additional control. Both cell toxicity and proinflammatory potency resulted to be higher for summer PM10 with respect of winter PM10, with IL-6 showing the highest dose-dependent release. The relevance of biogenic components adsorbed onto PM10 in eliciting the proinflammatory mediators release was investigated by inhibition experiments. Polymixin B (Poly) was used to inhibit particle-bind LPS while Toll-like receptor-2 antibody (a-TLR2) to specifically block the activation of this receptor. While cell viability was not modulated in cells coexposed to PM10 and Poly or a-TLR2 or both, inflammatory response did it, with IL-6 release being the most inhibited. In conclusion, Milan PM10-induced seasonal-dependent biological effects, with summer particles showing higher cytotoxic and proinflammatory potential. Cytotoxicity seemed to be unaffected by the PM biogenic components, while inflammation was significantly reduced after the inhibition of some biogenic activated pathways. Besides, the PM-associated biogenic activity does not entirely justify the PM-induced inflammatory effects. © 2010 Wiley Periodicals, Inc. Environ Toxicol 2012.

Ultrafine and nanoparticles-induced oxidative stress: the role of heme oxygenase-1 and carbon monoxide as anti-inflammatory pathways

INTRODUCTION

Particulate matter (PM) is an environmental factor that has been associated with increased respiratory morbidity and mortality. The major effect of ambient PM on the pulmonary system is that it promotes inflammation in susceptible people. One of the mechanisms by which ambient PM exerts its proinflammatory effects is by generating increased oxidative stress induced by chemical compounds and metal constituents. Cellular responses to PM-induced oxidative stress include activation of antioxidant defense. OBJECTIVE. To investigate the anti-inflammatory and anti-apoptotic roles of heme oxygenase-1 (HO-1) and carbon monoxide (CO) in the PM-induced oxidative stress arm, inflammation, and toxicity. Methods. Particle size analyses were performed according to a laser technique based on the time of transition theory using an Eyetech Analyzer (Donner Technologies Ltd., Israel). HO-1 was analyzed by quantitative reverse transcriptase polymerase chain reaction (RT-PCR) in induced sputum (IS) samples.

RESULTS

We demonstrate the feasibility of measuring micro- and nanoparticles in IS samples of exposed individuals in and out of the workplace to determine the protective role of HO-1 and CO.

CONCLUSIONS

Ongoing studies will further elucidate the protective role of HO-1 and CO in the PM-induced oxidative stress model.

In vitro toxicity of particulate matter (PM) collected at different sites in the Netherlands is associated with PM composition, size fraction and oxidative potential--the RAPTES project

Background

Ambient particulate matter (PM) exposure is associated with respiratory and cardiovascular morbidity and mortality. To what extent such effects are different for PM obtained from different sources or locations is still unclear. This study investigated the in vitro toxicity of ambient PM collected at different sites in the Netherlands in relation to PM composition and oxidative potential.

Method

PM was sampled at eight sites: three traffic sites, an underground train station, as well as a harbor, farm, steelworks, and urban background location. Coarse (2.5-10 μm), fine (< 2.5 μm) and quasi ultrafine PM (qUF; < 0.18 μm) were sampled at each site. Murine macrophages (RAW 264.7 cells) were exposed to increasing concentrations of PM from these sites (6.25-12.5-25-50-100 μg/ml; corresponding to 3.68-58.8 μg/cm²). Following overnight incubation, MTT-reduction activity (a measure of metabolic activity) and the release of pro-inflammatory markers (Tumor Necrosis Factor-alpha, TNF-α; Interleukin-6, IL-6; Macrophage Inflammatory Protein-2, MIP-2) were measured. The oxidative potential and the endotoxin content of each PM sample were determined in a DTT- and LAL-assay respectively. Multiple linear regression was used to assess the relationship between the cellular responses and PM characteristics: concentration, site, size fraction, oxidative potential and endotoxin content.

Results

Most PM samples induced a concentration-dependent decrease in MTT-reduction activity and an increase in pro-inflammatory markers with the exception of the urban background and stop & go traffic samples. Fine and qUF samples of traffic locations, characterized by a high concentration of elemental and organic carbon, induced the highest pro-inflammatory activity. The pro-inflammatory response to coarse samples was associated with the endotoxin level, which was found to increase dramatically during a three-day sample concentration procedure in the laboratory. The underground samples, characterized by a high content of transition metals, showed the largest decrease in MTT-reduction activity. PM size fraction was not related to MTT-reduction activity, whereas there was a statistically significant difference in pro-inflammatory activity between Fine and qUF PM. Furthermore, there was a statistically significant negative association between PM oxidative potential and MTT-reduction activity.

Conclusion

The response of RAW264.7 cells to ambient PM was markedly different using samples collected at various sites in the Netherlands that differed in their local PM emission sources. Our results are in support of other investigations showing that the chemical composition as well as oxidative potential are determinants of PM induced toxicity in vitro.

Transcriptional modulation of a human monocytic cell line exposed to PM(10) from an urban area

Insight into the mechanisms by which ambient air particulate matter mediates adverse health effects is needed to provide biological plausibility to epidemiological studies demonstrating an association between PM(10) exposure and increased morbidity and mortality. In vitro studies of the effects of air pollution on human cells help to establish conditions for the analysis of cause-effect relationships. One of the major challenges is to test native atmosphere in its complexity, rather than the various components individually. We have developed an in vitro system in which human monocyte-macrophage U937 cells are directly exposed to filters containing different amounts of PM(10) collected in the city of Rome. Transcriptional profiling obtained after short exposure (1h) of cells to a filter containing 1666μg PM(10) (77.6μg/cm(2)) using a macroarray panel of 1176 genes reveals a significant change in the mRNA level (>2 fold) for 87 genes relative to cells exposed to a control filter. Overall, 9 out of 87 modulated genes were annotated as "lung cancer". qRT-PCR confirmed the induction of relevant genes involved in DNA repair and apoptosis, specifically: ERCC1, TDG, DAD1 and MCL1. In cells exposed for 10min, 1h and 3h to different amounts of PM(10), transcription of TNFα and TRAP1, which code for a key pro-inflammatory cytokine and a mitochondrial protein involved in cell protection from oxidative stress, respectively, was shown to be modulated in a time-dependent, but not a dose-dependent manner. Taken together, these data indicate that it is possible to analyze the effects of untreated particulate matter on human cells by the direct-exposure approach we have developed, possibly providing new clues to traffic-related health hazard.

Respiratory epithelial cytotoxicity and membrane damage (holes) caused by amine-modified nanoparticles

The respiratory epithelium is a significant target of inhaled, nano-sized particles, the biological reactivity of which will depend on its physicochemical properties. Surface-modified, 50 and 100 nm, polystyrene latex nanoparticles (NPs) were used as model particles to examine the effect of particle size and surface chemistry on transformed human alveolar epithelial type 1-like cells (TT1). Live images of TT1 exposed to amine-modified NPs taken by hopping probe ion conductance microscopy revealed severe damage and holes on cell membranes that were not observed with other types of NPs. This paralleled induction of cell detachment, cytotoxicity and apoptotic (caspase-3/7 and caspase-9) cell death, and increased release of CXCL8 (IL-8). In contrast, unmodified, carboxyl-modified 50 nm NPs and the 100 nm NPs did not cause membrane damage, and were less reactive. Thus, the susceptibility and membrane damage to respiratory epithelium following inhalation of NPs will depend on both surface chemistry (e.g., cationic) and nano-size.

Integrated risk assessment of a hydroxyapatite-protein-composite for use in oral care products: a weight-of-evidence case study

Risk assessment of cosmetic ingredients represents a regulatory standard requirement in Europe and other regions. An integrated approach was designed to assess the safety of HPC, a particulate composite of hydroxyapatite and protein (gelatin) for use in oral care products, employing a weight-of-evidence assessment and considering specific physico-chemical properties and exposure conditions. An initial evaluation of the constituents suggested that their chemical nature does not represent a particular health hazard per se. Hydroxyapatite is the main component of teeth and bones in mammals; gelatin is used in food and assumed to be safe once a BSE/TSE risk has been excluded. In vitro screening tests were chosen to further evaluate the biocompatibility: Hen's egg test-chorioallantoic membrane (HET-CAM) to assess irritating effects towards mucous membranes; MTT cytotoxicity test with 3T3 fibroblasts; human corneal epithelial models to investigate inflammatory mediators and cytotoxicity; macrophage assays to measure cytotoxicity, inflammatory mediators and oxidative stress. Together with results from clinical studies, exposure estimates and analyses of kinetic properties, the presented information provides sound evidence to support the safe use of HPC. This is an example of a risk assessment for cosmetic use of small particles without the need for additional animal studies.

Evaluating cytokines in immunotoxicity testing

One of the most potentially useful tools in immunotoxicology is the assessment of cytokines, the proteins/peptides that are responsible for regulating a variety of processes including immunity, inflammation, apoptosis, and hematopoiesis. Cytokine production measurements offer an outstanding promise and may eventually substitute for other more laborious procedures. The particular profile of cytokine production may provide an important information regarding the nature of many immunotoxic responses.Recent expansion in the knowledge of cytokine biology and the realization that cytokines play a role in human diseases have created a need for the precise assessment and accurate interpretation of their presence and activity in the body fluids, tissues and cells. Proper evaluation of cytokines requires attention to several technical details. Multi-cytokine analysis still needs to be standardized in terms of optimum source for analysis, protocols and quality control issues, such as the use of reference standards and the expression of results.Important practical details and considerations will be discussed in this chapter, including the source of the sample to be tested (circulating fluids, or ex vivo/in vitro isolated cells), the potential effects of collection, processing, and storage of the results of the assays, as well as potential variables associated with the source material (matrix effects, relevance, inhibitory substances), and factors influencing the choice of assay used (bioassay, immunoassay, molecular biology technique, flow cytometry).

Exploratory investigation of the chemical characteristics and relative toxicity of ambient air particulates from two New Zealand cities

We examined the chemical composition and biological response associated with particulate emissions from the two largest cities in New Zealand, Auckland and Christchurch. The organic and water-soluble fractions were isolated from the particulate matter (PM). The organic fraction was examined for PAH content, direct mutagenicity, CYP1A1 induction, and cytotoxicity and TNF-alpha release in RAW264.7 macrophages. The water-soluble fraction was examined for metal content, and cytotoxicity and TNF-alpha release in RAW264.7 macrophages. Particulate, PAH and water-soluble metal concentrations were all higher in PM collected from Christchurch, being highest in May-July when woodburners for home heating are widely in use. In contrast, PM from Auckland showed the highest concentrations in March, but PAH and metal concentrations were highest in July. We found marked differences in the biological response elicited by ambient air PM: the organic extracts of Christchurch PM(2.5) and PM(10) showed higher mutagenicity and CYP1A1 induction compared with PM(10) from Auckland. In contrast, water-soluble extracts of Auckland PM were more cytotoxic and resulted in greater TNF-alpha release than those from Christchurch PM, although they had a lower metal content. The organic fraction of PM from both cities did not induce any cytokine release, and the organic extract from Auckland samples showed no cytotoxicity; smaller PM mass was available for testing for these samples. Biological responses typically occurred at lower doses of the organic extract, indicating that organic components may be more important in eliciting effects than water-soluble components. Preliminary apportionment of the biological responses to the dominant sources of PM in both cities-woodburners and vehicles-was undertaken. This indicated that for both cities, vehicles have a greater contribution to the direct mutagenic activity of ambient PM than woodsmoke, despite a lower contribution to ambient PM. In contrast, woodsmoke is estimated to have a greater contribution to CYP1A1 induction of ambient PM. The calculated activity forms only a small proportion of the activity observed in extracts of ambient PM from Christchurch, particularly for mutagenicity, and may indicate a significant influence of atmospheric transformation processes on biological response. Only data for mutagenicity and CYP1A1 activity could be used for apportionment as low and/or variable cytotoxicity or TNF-alpha release response were obtained for either the individual source or ambient PM at the doses tested. Further, in the case of the water-soluble extracts from Auckland, additional components are suggested to have a role in the observed activity.

Oxidative stress and inflammation response after nanoparticle exposure: differences between human lung cell monocultures and an advanced three-dimensional model of the human epithelial airways

Combustion-derived and manufactured nanoparticles (NPs) are known to provoke oxidative stress and inflammatory responses in human lung cells; therefore, they play an important role during the development of adverse health effects. As the lungs are composed of more than 40 different cell types, it is of particular interest to perform toxicological studies with co-cultures systems, rather than with monocultures of only one cell type, to gain a better understanding of complex cellular reactions upon exposure to toxic substances. Monocultures of A549 human epithelial lung cells, human monocyte-derived macrophages and monocyte-derived dendritic cells (MDDCs) as well as triple cell co-cultures consisting of all three cell types were exposed to combustion-derived NPs (diesel exhaust particles) and to manufactured NPs (titanium dioxide and single-walled carbon nanotubes). The penetration of particles into cells was analysed by transmission electron microscopy. The amount of intracellular reactive oxygen species (ROS), the total antioxidant capacity (TAC) and the production of tumour necrosis factor (TNF)-alpha and interleukin (IL)-8 were quantified. The results of the monocultures were summed with an adjustment for the number of each single cell type in the triple cell co-culture. All three particle types were found in all cell and culture types. The production of ROS was induced by all particle types in all cell cultures except in monocultures of MDDCs. The TAC and the (pro-)inflammatory reactions were not statistically significantly increased by particle exposure in any of the cell cultures. Interestingly, in the triple cell co-cultures, the TAC and IL-8 concentrations were lower and the TNF-alpha concentrations were higher than the expected values calculated from the monocultures. The interplay of different lung cell types seems to substantially modulate the oxidative stress and the inflammatory responses after NP exposure.