Inflammatory cytokine response to ambient particles varies due to field collection procedures

Chemical and Biological Characterization of Particulate Matter (PM 2.5) and Volatile Organic Compounds Collected at Different Sites in the Los Angeles Basin

Background: Most studies on air pollution (AP) exposure have focused on adverse health effects of particulate matter (PM). Less well-studied are the actions of volatile organic compounds (VOCs) not retained in PM collections. These studies quantified chemical and biological properties of both PM2.5 and VOCs. Methods: Samples were collected near the Port of Los Angeles (Long Beach, LB), railroads (Commerce, CM), and a pollution-trapping topography-site (San Bernardino, SB). Quantitative assays were conducted: (1) chemical—prooxidant and electrophile content, (2) biological—tumor necrosis factor-α (TNF-α) and heme oxygenase-1 (HO-1) expression (3), VOC modulation of PM effects and (4), activation of the antioxidant response element (ARE) using murine RAW 264.7 macrophages. Results: SB site samples were the most potent in the chemical and biological assays, followed by a CM railroad site. Only PM2.5 exhibited significant proinflammatory responses. VOCs were more potent than PM2.5 in generating anti-inflammatory responses; further, VOC pretreatment reduced PM-associated TNF-α expression. VOCs significantly increased ARE activation compared to their corresponding PM2.5 which remained at background levels. Conclusion: Ambient VOCs are major contributors to adaptive responses that can modulate PM effects, in vitro, and, as such, need to be included in comprehensive assessments of AP.

The protective effects of selenium supplementation on ambient PM2.5-induced cardiovascular injury in rats

Substantial epidemiological and experimental studies have shown that ambient fine particulate matter (PM_2.5) exposure can lead to myocardial damage in human and animal through the mechanism of inflammation and oxidative stress. The purpose of the current study was to investigate whether selenium yeast (SeY) supplementation could prevent cardiovascular injury caused by PM_2.5 in rats. Fifty-six Sprague-Dawley rats were randomly divided into seven groups: saline control group; solvent control group, low-, middle-, and high-dose Se pretreatment groups, PM_2.5 exposure group, and high-dose Se control group. The rats were pretreated with different concentration of dietary SeY for 28 days, then were exposed to PM₂.₅ by intratracheal instillation every other day, a total of three times. The levels of inflammatory markers (tumor necrosis factor-alpha (TNF-α), interleukin-1beta (IL-1β), soluble intercellular adhesion molecule-1 (sICAM-1), and oxidative responses-related indicators total antioxidant capacity (T-AOC), total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px), and malondialdehyde (MDA) were measured in blood and myocardium of the left ventricle. The results showed that although PM_2.5 caused a decrease of T-AOC, T-AOD, and GSH-Px and increase of MDA and sICM-1, pretreatment with SeY induced a dose-dependent increase in these anti-oxidative indicators and a decrease in oxidative indicators. In addition, the levels of TNF-α and IL-1β in Se pretreatment groups were significantly lower than that in PM_2.5 exposure group. The results indicated that Se supplementation could effectively prevent cardiovascular inflammation and oxidative stress induced by PM_2.5. The results also indicated that the nutritional supplementation might be an effective way to protecting people's health from air pollution.

Combined effects of vitamin E and omega-3 fatty acids on protecting ambient PM2.5-induced cardiovascular injury in rats

OBJECTIVE

This study aims to observe whether the combined treatment with vitamin E (vit E) and omega-3 polyunsaturated fatty acids (Ω-3 FA) could prevent the fine particulate matter (PM_2.5)-induced cardiovascular injury through alleviating inflammation and oxidative stress. At the same time, the appropriate combination dosage of vit E and Ω-3 FA was explored to find an optimized protective dose to protect the injury induced by PM_2.5.

METHODS

The SD rats were pretreated with different concentration of vit E and Ω-3 FA separately or jointly. Then the rats were exposed to ambient PM_2.5 by intratracheal instillation for three times. The expression of tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6) in serum and supernatant of cardiac tissue were detected by ELISA kits. The levels of malondialdehyde (MDA), superoxide Dismutase (SOD) and glutathione-peroxidase (GSH-Px) in myocardium and the level of MDA in serum were measured. Meanwhile, the cardiac injury was evaluated by histopathological examination.

RESULTS

Compared with the severe injury of rats in PM_2.5 exposure group, the rats in vit E or Ω-3 FA-pretreated groups had a slighter injury in heart. Meanwhile, pretreatment with vit E or Ω-3 FA induced a significantly alleviation of the inflammatory cytokines (TNF-α, IL-1β, IL-6) and the elevation of the anti-oxidative activity especially in the rats pretreated with combined vit E and Ω-3 FA. In addition, the combined protecting effects of vit E and Ω-3 FA showed a dose-dependent manner.

CONCLUSION

Supplementation with vit E and Ω-3 FA could protect the PM_2.5-induced injury, and the combination of vit E and Ω-3 FA might produce more effective effects than the separate nutrient did.

Inflammatory response of monocytes to ambient particles varies by highway proximity

Epidemiological studies have demonstrated associations of chronic respiratory disease with near-roadway pollutant exposure, effects that were independent of those of regional air pollutants. However, there has been limited study of the potential mechanisms for near-roadway effects. Therefore, we examined the in vitro effect of respirable particulate matter (PM) collected adjacent to a major Los Angeles freeway and at an urban background location. PM was collected on filters during two consecutive 15-day periods. Oxidative stress and inflammatory response (intracellular reactive oxygen species [ROS], IL-1β, IL-6, IL-8, and TNF-α) to PM aqueous extract was assessed in THP-1 cells, a model for evaluating monocyte/macrophage lineage cell responses. The near-roadway PM induced statistically significantly higher levels of IL-6, IL-8, and TNF-α (P < 0.01) and a near significant increase in IL-1β (P = 0.06) but did not induce ROS activity (P = 0.17). The contrast between urban background and near-roadway PM-induced inflammatory cytokines was similar in magnitude to that corresponding to temporal differences between the two collection periods. PM-induced proinflammatory protein expression was attenuated by antioxidant pretreatment, and PM stimulation enhanced the activity of protein kinases, including extracellular signal-regulated kinase and c-Jun N-terminal kinase. Pretreatment of THP-1 cells with kinase inhibitors reduced PM-induced proinflammatory mediator expression. The proinflammatory response was also reduced by pretreatment with polymyxin B, suggesting a role for endotoxin. However, the patterns of PM-induced protein kinase response and the attenuation of inflammatory responses by antioxidant or polymyxin B pretreatment did not vary between near-roadway and urban background locations. We conclude that near-roadway PM produced greater inflammatory response than urban background PM, a finding consistent with emerging epidemiologic findings, but these differences were not explained by PM endotoxin content or by MAPK pathways. Nevertheless, THP-1 cells may be a model for the development of biologically relevant metrics of long-term spatial variation in exposure for study of chronic disease.

Petrodiesel and Waste Grease Biodiesel (B20) Emission Particles at a Rural Recycling Center: Characterization and Effects on Lung Epithelial Cells and Macrophages

Diesel engine emissions are an important source of ultrafine particulate matter (PM) in both ambient air and many occupational settings. Biodiesel is a popular, 'green' alternative to petroleum diesel fuel, but little is known about the impact of 'real world' biodiesel combustion on workplace PM concentrations and particle characteristics including size, morphology, and composition; or on biological responses. The objectives of the present work were to characterize PM workplace concentrations and tailpipe emissions produced by the combustion of commercially purchased low sulfur petrodiesel and a waste grease B20 blend (20% biodiesel/80% petrodiesel by volume) in heavy duty diesel (HDD) nonroad equipment operating in a 'real world' rural recycling center. Furthermore, we assessed the in vitro responses of cell lines representing human lung epithelial cells (BEAS-2B) and macrophages (THP-1) after 24 h of exposure to these real-world particles. Compared to petroleum diesel, use of B20 in HDD equipment resulted in lower mass concentrations of PM2.5, PM<0.25 (particle diameter less than 2.5 and 0.25 micrometer, respectively), and elemental carbon. Transmission electron analysis of PM showed that primary particle size and morphology were similar between fuel types. Metals composition analysis revealed differences between fuels, with higher Fe, Al, V, and Se measured during B20 use, and higher As, Cd, Cu, Mn, Ni and Pb concentrations measured during petrodiesel use. In vitro responses varied between fuels but data supported that waste grease B20 particles elicited inflammatory responses in human macrophages and lung epithelial cells comparable to petrodiesel particles. However, the effects were more pronounced with B20 than petrodiesel at the same mass concentration. Since the primary particle size and morphology were similar between fuels, it is likely that the differential results seen in the in vitro assays points to differences in the composition of the PM. Future research should focus on the organic carbon and metals speciation and potential impact of real world particles on reactive oxygen species generation and mechanisms for differences in the cellular inflammatory responses.