In vitro toxicity evaluation in A549 cells of diesel particulate matter from two different particle sampling systems and several resuspension media

In urban areas, inhalation of fine particles from combustion sources such as diesel engines causes adverse health effects. For toxicity testing, a substantial amount of particulate matter (PM) is needed. Conventional sampling involves collection of PM onto substrates by filtration or inertial impaction. A major drawback to those methodologies is that the extraction process can modify the collected particles and alter their chemical composition. Moreover, prior to toxicity testing, PM samples need to be resuspended, which can alter the PM sample even further. Lastly, the choice of the resuspension medium may also impact the detected toxicological responses. In this study, we compared the toxicity profile of PM obtained from two alternative sampling systems, using in vitro toxicity assays. One system makes use of condensational growth before collection in water in an impinger - BioSampler (CG-BioSampler), and the other, a Dekati® Gravimetric Impactor (DGI), is based on inertial impaction. In addition, various methods for resuspension of DGI collected PM were compared. Tested endpoints included cytotoxicity, formation of cellular reactive oxygen species, and genotoxicity. The alternative collection and suspension methods affected different toxicological endpoints. The water/dimethyl sulfoxide mixture and cell culture medium resuspended particles, along with the CG-BioSampler sample, produced the strongest responses. The water resuspended sample from the DGI appeared least toxic. CG-BioSampler collected PM caused a clear increased response in apoptotic cell death. We conclude that the CG-BioSampler PM sampler is a promising alternative to inertial impaction sampling.

The toxic potential of a fourth-generation E-cigarette on human lung cell lines and tissue explants

The use of electronic cigarettes (E-cigs) is rapidly increasing. The latest generation of E-cigs is highly customizable, allowing for high heating coil temperatures. The aim of this study was to assess the toxic potential of a fourth-generation E-cig. Aerosols generated from E-liquid with (24 mg/mL) and without nicotine, using a fourth-generation E-cig, were chemically analysed and compared with cigarette smoke (K3R4F). Human lung epithelial cell lines and distal lung tissue explants were exposed to E-cig vapour extract (EVE) and cigarette smoke extract for 24 hours and assessed for viability, inflammation, oxidative stress and genotoxicity. E-cig aerosols contained measurable levels of volatile organic compounds, aldehydes and polycyclic aromatic hydrocarbons, in general, to a much lesser extent than cigarette smoke. Higher levels of certain carbonyls, e.g. formaldehyde, were detected in the E-cig aerosols. EVEs decreased cell viability of BEAS-2B cells, whereas little effect was seen in A549 cells and distal lung tissue. The nicotine-containing EVE caused a greater decrease in cell viability and significant increase in DNA damage than the nicotine-free EVE. Increased cytotoxicity, reactive oxygen species production and genotoxicity were seen with cells and tissue exposed to cigarette smoke extract compared with EVEs. Although E-cig aerosols were less toxic than cigarette smoke, it was not benign. Moreover, the EVE containing nicotine was more toxic than the nicotine-free EVE. More research is needed on the short- and long-term health effects of vaping and the usage of newly emerging E-cig devices to evaluate better the potential negative effects of E-cigs on human health.

Brief exposure to Swedish snus causes divergent vascular responses in healthy male and female volunteers

Introduction

The use of Swedish oral moist snuff, known as snus, has for a long time been limited to the Scandinavian countries. With declining cigarette sales in the western world, tobacco companies have looked to the development of alternative tobacco products. In 2006 snus products were launched in the US. Even though several studies have demonstrated negative health effects, snus is often depicted as harmless.

The aim of the present study was to investigate acute vascular effects of snus as measured by arterial stiffness as well as blood pressure and heart rate.

Methods

Two separate randomized double-blind crossover studies with the same study design were pooled for analysis. Twenty-nine healthy snus-users (17 females, 12 males) were included. Snus (Göteborgs Rapé) and tobacco free snus (Onico) were administered in a randomized order at two separate visits. Arterial stiffness, blood pressure and heart rate were measured at baseline as well as every five minutes for 40 minutes during exposure. Following snus removal, measurements continued for 30 minutes post exposure. Arterial stiffness was measured using pulse wave velocity (Vicorder) and pulse wave analysis (Sphygmocor).

Results

Compared to placebo, snus significantly increased systolic and diastolic blood pressure as well as heart rate, however, only in females (p = 0.004, p = 0.006 and p<0.001 respectively). No changes were seen in arterial stiffness measurements in either gender.

Conclusion

We observed an increase in blood pressure and heart rate only in females, but not in males due to snus usage as compared to placebo. This novel finding was surprising and needs to be further investigated considering most of the earlier studies have mainly focused on male snus users and the increasing usage of snus among females.

Altered nitric oxide bioavailability contributes to diesel exhaust inhalation-induced cardiovascular dysfunction in man

Background

Diesel exhaust inhalation causes cardiovascular dysfunction including impaired vascular reactivity, increased blood pressure, and arterial stiffness. We investigated the role of nitric oxide (NO) bioavailability in mediating these effects.

Methods and Results

In 2 randomized double‐blind crossover studies, healthy nonsmokers were exposed to diesel exhaust or filtered air. Study 1: Bilateral forearm blood flow was measured during intrabrachial infusions of acetylcholine (ACh; 5 to 20 μg/min) and sodium nitroprusside (SNP; 2 to 8 μg/min) in the presence of the NO clamp (NO synthase inhibitor N^G‐monomethyl‐l‐arginine (l‐NMMA) 8 μg/min coinfused with the NO donor SNP at 90 to 540 ng/min to restore basal blood flow). Study 2: Blood pressure, arterial stiffness, and cardiac output were measured during systemic NO synthase inhibition with intravenous l‐NMMA (3 mg/kg). Following diesel exhaust inhalation, plasma nitrite concentrations were increased (68±48 versus 41±32 nmol/L; P=0.006) despite similar l‐NMMA–induced reductions in basal blood flow (−20.6±14.7% versus −21.1±14.6%; P=0.559) compared to air. In the presence of the NO clamp, ACh and SNP caused dose‐dependent vasodilatation that was not affected by diesel exhaust inhalation (P>0.05 for both). Following exposure to diesel exhaust, l‐NMMA caused a greater increase in blood pressure (P=0.048) and central arterial stiffness (P=0.007), but reductions in cardiac output and increases in systemic vascular resistance (P>0.05 for both) were similar to those seen with filtered air.

Conclusions

Diesel exhaust inhalation disturbs normal vascular homeostasis with enhanced NO generation unable to compensate for excess consumption. We suggest the adverse cardiovascular effects of air pollution are, in part, mediated through reduced NO bioavailability.

Clinical Trial Registration

URL: http://www.ClinicalTrials.gov. Unique identifiers: NCT00845767 and NCT01060930.

Cardiovascular effects of particulate air pollution exposure: time course and underlying mechanisms

Air pollution is now recognized as an important independent risk factor for cardiovascular morbidity and mortality and may be responsible for up to 3 million premature deaths each year worldwide. The mechanisms underlying the observed effects are poorly understood but are likely to be multifactorial. Here, we review the acute and chronic effects of air pollution exposure on the cardiovascular system and discuss how these effects may explain the observed increases in cardiovascular morbidity and mortality.

Antioxidant airway responses following experimental exposure to wood smoke in man

Background

Biomass combustion contributes to the production of ambient particulate matter (PM) in rural environments as well as urban settings, but relatively little is known about the health effects of these emissions. The aim of this study was therefore to characterize airway responses in humans exposed to wood smoke PM under controlled conditions. Nineteen healthy volunteers were exposed to both wood smoke, at a particulate matter (PM_2.5) concentration of 224 ± 22 μg/m³, and filtered air for three hours with intermittent exercise. The wood smoke was generated employing an experimental set-up with an adjustable wood pellet boiler system under incomplete combustion. Symptoms, lung function, and exhaled NO were measured over exposures, with bronchoscopy performed 24 h post-exposure for characterisation of airway inflammatory and antioxidant responses in airway lavages.

Results

Glutathione (GSH) concentrations were enhanced in bronchoalveolar lavage (BAL) after wood smoke exposure vs. air (p = 0.025), together with an increase in upper airway symptoms. Neither lung function, exhaled NO nor systemic nor airway inflammatory parameters in BAL and bronchial mucosal biopsies were significantly affected.

Conclusions

Exposure of healthy subjects to wood smoke, derived from an experimental wood pellet boiler operating under incomplete combustion conditions with PM emissions dominated by organic matter, caused an increase in mucosal symptoms and GSH in the alveolar respiratory tract lining fluids but no acute airway inflammatory responses. We contend that this response reflects a mobilisation of GSH to the air-lung interface, consistent with a protective adaptation to the investigated wood smoke exposure.

Ozone exposure enhances mast-cell inflammation in asthmatic airways despite inhaled corticosteroid therapy

Asthmatics are recognised to be more susceptible than healthy individuals to adverse health effects caused by exposure to the common air pollutant ozone. Ozone has been reported to induce airway neutrophilia in mild asthmatics, but little is known about how it affects the airways of asthmatic subjects on inhaled corticosteroids. We hypothesised that ozone exposure would exacerbate the pre-existent asthmatic airway inflammation despite regular inhaled corticosteroid treatment. Therefore, we exposed subjects with persistent asthma on inhaled corticosteroid therapy to 0.2 ppm ozone or filtered air for 2 h, on 2 separate occasions. Lung function was evaluated before and immediately after exposure, while bronchoscopy was performed 18 h post exposure. Compared to filtered air, ozone exposure increased airway resistance. Ozone significantly enhanced neutrophil numbers and myeloperoxidase levels in airway lavages, and induced a fourfold increase in bronchial mucosal mast cell numbers. The present findings indicate that ozone worsened asthmatic airway inflammation and offer a possible biological explanation for the epidemiological findings of increased need for rescue medication and hospitalisation in asthmatic people following exposure to ambient ozone.

Diesel exhaust exposure enhances the ozone-induced airway inflammation in healthy humans

Exposure to particulate matter and ozone cause adverse airway reactions. Individual pollutant effects are often addressed separately, despite coexisting in ambient air. The present investigation was performed to study the effects of sequential exposures to diesel exhaust (DE) and ozone on airway inflammation in human subjects. Healthy subjects underwent bronchoscopy with bronchoalveolar lavage (BAL) and bronchial wash (BW) sampling on two occasions. Once following a DE exposure (with 300 mug.m(-3) particles with a 50% cut-off aerodynamic diameter of 10 mum) with subsequent exposure to O(3) (0.2 ppm) 5 h later. The other bronchoscopy was performed after a filtered air exposure followed by an ozone exposure, using an identical protocol. Bronchoscopy was performed 24 h after the start of the initial exposure. Significant increases in neutrophil and macrophage numbers were found in BW after DE followed by ozone exposure versus air followed by ozone exposure. DE pre-exposure also raised eosinophil protein X levels in BAL compared with air. The present study indicates additive effects of diesel exhaust on the ozone-induced airway inflammation. Together with similar results from a recent study with sequential diesel exhaust and ozone exposures, the present data stress a need to consider the interaction and cumulative effects of different air pollutants.

Ozone enhances the airway inflammation initiated by diesel exhaust

Exposure to air pollution is associated with adverse health effects, with particulate matter (PM) and ozone (O(3)) both indicated to be of considerable importance. Diesel engine exhaust (DE) and O(3) generate substantial inflammatory effects in the airways. However, as yet it has not been determined whether a subsequent O(3) exposure would add to the diesel-induced airway inflammatory effects. Healthy subjects underwent two separate exposure series: A 1-h DE exposure at a PM-concentration of 300 microg/m(3), followed after 5h by a 2-h exposure to filtered air and 0.2 ppm O(3), respectively. Induced sputum was collected 18 h after the second exposure. A significant increase in the percentage of neutrophils (PMN) and concentration of myeloperoxidase (MPO) was seen in sputum post DE+O(3) vs. DE+air (p<0.05 and <0.05, respectively). Significant associations were observed between the responses in MPO concentration and total PMN cells (p=0.001), and also between MPO and matrix metalloproteinase-9 (MMP-9) (p<0.001). The significant increase of PMN and MPO after the DE+O(3) exposures, compared to DE+air, denotes an O(3)-induced magnification of the DE-induced inflammation. Furthermore, the correlation between responses in MPO and number of PMNs and MMP-9 illustrate that the PMNs are activated, resulting in a more potent inflammatory response. The present study indicates that O(3) exposure adds significantly to the inflammatory response that is established by diesel exhaust. This interaction between exposure to particulate pollution and O(3) in sequence should be taken into consideration when health effects of air pollution are considered.

Ozone-induced bronchial epithelial cytokine expression differs between healthy and asthmatic subjects

BACKGROUND

Ozone (O3) is a common air pollutant associated with adverse health effects. Asthmatics have been suggested to be a particularly sensitive group.

OBJECTIVE

This study evaluated whether bronchial epithelial cytokine expression would differ between healthy and allergic asthmatics after ozone exposure, representing an explanatory model for differences in susceptibility.

METHODS

Healthy and mild allergic asthmatic subjects (using only inhaled beta2-agonists prn) were exposed for 2 h in blinded and randomized sequence to 0.2 ppm of O3 and filtered air. Bronchoscopy with bronchial mucosal biopsies was performed 6 h after exposure. Biopsies were embedded in GMA and stained with mAbs for epithelial expression of IL-4, IL-5, IL-6, IL-8, IL-10, TNF-alpha, GRO-alpha, granulocyte-macrophage colony-stimulating factor (GM-CSF), fractalkine and ENA-78.

RESULTS

When comparing the two groups at baseline, the asthmatic subjects showed a significantly higher expression of IL-4 and IL-5. After O3 exposure the epithelial expression of IL-5, GM-CSF, ENA-78 and IL-8 increased significantly in asthmatics, as compared to healthy subjects.

CONCLUSION

The present study confirms a difference in epithelial cytokine expression between mild atopic asthmatics and healthy controls, as well as a differential epithelial cytokine response to O3. This O3-induced upregulation of T helper type 2 (Th2)-related cytokines and neutrophil chemoattractants shown in the asthmatic group may contribute to a subsequent worsening of the airway inflammation, and help to explain their differential sensitivity to O3 pollution episodes.