A method for exposing rodents to resuspended particles using whole-body plethysmography

Aeroparticles, Composition, and Lung Diseases

Urban air pollution is a serious worldwide problem due to its impact on human health. In the past 60 years, growing evidence established a correlation between exposure to air pollutants and the developing of severe respiratory diseases. Recently particulate matter (PM) is drawing more public attention to various aspects including historical backgrounds, physicochemical characteristics, and its pathological role. Therefore, this review is focused on these aspects. The most famous air pollution disaster happened in London on December 1952; it has been calculated that more than 4,000 deaths occurred during this event. Air pollution is a complex mix of gases and particles. Gaseous pollutants disseminate deeply into the alveoli, allowing its diffusion through the blood–air barrier to several organs. Meanwhile, PM is a mix of solid or liquid particles suspended in the air. PM is deposited at different levels of the respiratory tract, depending on its size: coarse particles (PM₁₀) in upper airways and fine particles (PM_2.5) can be accumulated in the lung parenchyma, inducing several respiratory diseases. Additionally to size, the composition of PM has been associated with different toxicological outcomes on clinical and epidemiological, as well as in vivo and in vitro animal and human studies. PM can be constituted by organic, inorganic, and biological compounds. All these compounds are capable of modifying several biological activities, including alterations in cytokine production, coagulation factors balance, pulmonary function, respiratory symptoms, and cardiac function. It can also generate different modifications during its passage through the airways, like inflammatory cells recruitment, with the release of cytokines and reactive oxygen species (ROS). These inflammatory mediators can activate different pathways, such as MAP kinases, NF-κB, and Stat-1, or induce DNA adducts. All these alterations can mediate obstructive or restrictive respiratory diseases like asthma, COPD, pulmonary fibrosis, and even cancer. In 2013, outdoor air pollution was classified as Group 1 by IARC based on all research studies data about air pollution effects. Therefore, it is important to understand how PM composition can generate several pulmonary pathologies.

Measuring respiratory function in mice using unrestrained whole-body plethysmography

Respiratory dysfunction is one of the leading causes of morbidity and mortality in the world and the rates of mortality continue to rise. Quantitative assessment of lung function in rodent models is an important tool in the development of future therapies. Commonly used techniques for assessing respiratory function including invasive plethysmography and forced oscillation. While these techniques provide valuable information, data collection can be fraught with artefacts and experimental variability due to the need for anesthesia and/or invasive instrumentation of the animal. In contrast, unrestrained whole-body plethysmography (UWBP) offers a precise, non-invasive, quantitative way by which to analyze respiratory parameters. This technique avoids the use of anesthesia and restraints, which is common to traditional plethysmography techniques. This video will demonstrate the UWBP procedure including the equipment set up, calibration and lung function recording. It will explain how to analyze the collected data, as well as identify experimental outliers and artefacts that results from animal movement. The respiratory parameters obtained using this technique include tidal volume, minute volume, inspiratory duty cycle, inspiratory flow rate and the ratio of inspiration time to expiration time. UWBP does not rely on specialized skills and is inexpensive to perform. A key feature of UWBP, and most appealing to potential users, is the ability to perform repeated measures of lung function on the same animal.

Comparative toxicity of size-fractionated airborne particulate matter collected at different distances from an urban highway

BACKGROUND

Epidemiologic studies have reported an association between proximity to highway traffic and increased cardiopulmonary illnesses.

OBJECTIVES

We investigated the effect of size-fractionated particulate matter (PM), obtained at different distances from a highway, on acute cardiopulmonary toxicity in mice.

METHODS

We collected PM for 2 weeks in July-August 2006 using a three-stage (ultrafine, < 0.1 microm; fine, 0.1-2.5 microm; coarse, 2.5-10 microm) high-volume impactor at distances of 20 m [near road (NR)] and 275 m [far road (FR)] from an interstate highway in Raleigh, North Carolina. Samples were extracted in methanol, dried, diluted in saline, and then analyzed for chemical constituents. Female CD-1 mice received either 25 or 100 microg of each size fraction via oropharyngeal aspiration. At 4 and 18 hr postexposure, mice were assessed for pulmonary responsiveness to inhaled methacholine, biomarkers of lung injury and inflammation; ex vivo cardiac pathophysiology was assessed at 18 hr only.

RESULTS

Overall chemical composition between NR and FR PM was similar, although NR samples comprised larger amounts of PM, endotoxin, and certain metals than did the FR samples. Each PM size fraction showed differences in ratios of major chemical classes. Both NR and FR coarse PM produced significant pulmonary inflammation irrespective of distance, whereas both NR and FR ultrafine PM induced cardiac ischemia-reperfusion injury.

CONCLUSIONS

On a comparative mass basis, the coarse and ultrafine PM affected the lung and heart, respectively. We observed no significant differences in the overall toxicity end points and chemical makeup between the NR and FR PM. The results suggest that PM of different size-specific chemistry might be associated with different toxicologic mechanisms in cardiac and pulmonary tissues.

Cardiopulmonary responses of Wistar Kyoto, spontaneously hypertensive, and stroke-prone spontaneously hypertensive rats to particulate matter (PM) exposure

Humans with underlying cardiovascular disease, including stroke, are more susceptible to ambient particulate matter (PM)-induced morbidity and mortality. We hypothesized that stroke-prone spontaneously hypertensive rats (SHRSP) would be more susceptible than healthy Wistar Kyoto (WKY) rats to PM-induced cardiac oxidative stress and pulmonary injury. We further postulated that PM-induced injury would be greater in SHRSP than in spontaneously hypertensive rats (SHR) based on the greater disease severity in SHRSP than SHR. First, male WKY and SHRSP were intratracheally (IT) instilled with saline or 1.11, 3.33, or 8.33 mg/kg of oil combustion PM and responses were analyzed 4 or 24 h later. Second, SHR and SHRSP were IT instilled with saline or 3.33 or 8.33 mg/kg of the same PM and responses were analyzed 24 h later. Pulmonary injury and inflammation were assessed in bronchoalveolar lavage fluid (BALF) and cardiac markers in cytosolic and mitochondrial fractions. BALF neutrophilic inflammatory response was induced similarly in all strains following PM exposure. BALF protein leakage, gamma-glutamyl transferase, and N-acetylglucosaminidase activities, but not lactate dehydrogenase activity, were exacerbated in SHRSP compared to WKY or SHR. Pulmonary cytosolic and cardiac mitochondrial ferritin levels decreased, and cardiac cytosolic superoxide dismutase (SOD) activity increased in SHRSP only. Pulmonary SOD activity decreased in WKY and SHRSP. Cardiac mitochondrial isocitrate dehydrogenase (ICDH) activity decreased in PM-exposed WKY and SHR; control levels were lower in SHRSP than SHR or WKY. In summary, strain-related differences exist in pulmonary protein leakage and oxidative stress markers. PM-induced changes in cardiac oxidative stress sensitive enzymes are small, and appear only slightly exacerbated in SHRSP compared to WKY or SHR. Multiple biological markers may be differentially affected by PM in genetic models of cardiovascular diseases. Preexisting cardiovascular disease may influence susceptibility to PM pulmonary and cardiac health effects in a disease-specific manner.