Effects of multiday exposure to ozone on airway inflammation as determined using sputum induction

The role of non-invasive biomarkers in detecting acute respiratory effects of traffic-related air pollution

The role of non-invasive methods in the investigation of acute effects of traffic-related air pollution is not clearly established. We evaluated the usefulness of non-invasive biomarkers in detecting acute air pollution effects according to the age of participants, the disease status, their sensitivity compared with lung function tests and their specificity for a type of pollutant. Search terms lead to 535 titles, among them 128 had potentially relevant abstracts. Sixtynine full papers were reviewed, while 59 articles were excluded as they did not meet the selection criteria. Methods used to assess short-term effects of air pollution included analysis of nasal lavage (NAL) for the upper airways, and induced sputum (IS), exhaled breath condensate (EBC) and exhaled nitric oxide (FeNO) for central and lower airways. There is strong evidence that FeNO evaluation is useful independently from subject age, while IS analysis is suitable almost for adults. Biomarker changes are generally observed upon pollutant exposure irrespective of the disease status of the participants. None of the biomarkers identified are specific for a type of pollutant exposure. Based on experimental exposure studies, there is moderate evidence that IS analysis is more sensitive than lung function tests, whereas this is not the case for biomarkers obtained by NAL or EBC. Cells and some cytokines (IL-6, IL-8 and myeloperoxidase) have been measured both in the upper respiratory tract (NAL) and in the lower airways (IS). Overall, the response to traffic exposure seems different in the two compartments. In conclusion, this survey of current literature displays the complexity of this research field, highlights the significance of short-term studies on traffic pollution and gives important tips when planning studies to detect acute respiratory effects of air pollution in a non-invasive way.

Peripheral blood neutrophilia as a biomarker of ozone-induced pulmonary inflammation

BACKGROUND

Ozone concentrations are predicted to increase over the next 50 years due to global warming and the increased release of precursor chemicals. It is therefore urgent that good, reliable biomarkers are available to quantify the toxicity of this pollutant gas at the population level. Such a biomarker would need to be easily performed, reproducible, economically viable, and reflective of ongoing pathological processes occurring within the lung.

METHODOLOGY

We examined whether blood neutrophilia occurred following a controlled ozone challenge and addressed whether this could serve as a biomarker for ozone-induced airway inflammation. Three separate groups of healthy subjects were exposed to ozone (0.2 ppm, 2h) and filtered air (FA) on two separate occasions. Peripheral blood samples were collected and bronchoscopy with biopsy sampling and lavages was performed at 1.5h post exposures in group 1 (n=13), at 6h in group 2 (n=15) and at 18h in group 3 (n=15). Total and differential cell counts were assessed in blood, bronchial tissue and airway lavages.

RESULTS

In peripheral blood, we observed fewer neutrophils 1.5h after ozone compared with the parallel air exposure (-1.1±1.0x10(9) cells/L, p<0.01), at 6h neutrophil numbers were increased compared to FA (+1.2±1.3x10(9) cells/L, p<0.01), and at 18h this response had fully attenuated. Ozone induced a peak in neutrophil numbers at 6h post exposure in all compartments examined, with a positive correlation between the response in blood and bronchial biopsies.

CONCLUSIONS

These data demonstrate a systemic neutrophilia in healthy subjects following an acute ozone exposure, which mirrors the inflammatory response in the lung mucosa and lumen. This relationship suggests that blood neutrophilia could be used as a relatively simple functional biomarker for the effect of ozone on the lung.

Environmental and non-infectious factors in the aetiology of pharyngitis (sore throat)

OBJECTIVES

The aim of this review is to examine the causes, pathophysiology and experimental models of non-infectious pharyngitis (sore throat).

INTRODUCTION

The causes of sore throat can be infectious (viruses, bacteria, and fungi) or non-infectious, although the relative proportion of each is not well documented.

METHODS

A PubMed database search was performed for studies of non-infectious sore throat.

RESULTS AND CONCLUSIONS

Non-infectious causes of sore throat include: physico-chemical factors, such as smoking, snoring, shouting, tracheal intubation, medications, or concomitant illness; and environmental factors including indoor and outdoor air pollutants, temperature and humidity, and hazardous or occupational irritants. The pathophysiology underlying non-infectious sore throat is largely uncharacterised, although neurogenic inflammation looks to be a promising candidate. It is likely that there will be individual disposition factors or the coincidence of more than one irritant with possible--up to now unknown--interactions between them. Therefore, experimental models with defined conditions and objective endpoints are needed. A new model using cold dry air to directly induce pharyngeal irritation in humans, with pharyngeal lavage to measure biomarkers, may provide a useful tool for the study of mechanisms and treatment of non-infectious sore throat.

Investigating performance and lung function in a hot, humid and ozone-polluted environment

Large urbanized areas, where sports events take place, have a polluted environment and can also reach high temperatures and humidity levels. The aim of this study was to investigate the impact of a hot, humid and ozone-polluted (O(3)) environment on (1) performance of an 8 km time trial run, (2) pulmonary function, and (3) subjective respiratory symptoms in endurance-trained runners. Using crossover randomized design, 10 male participants (mean V(O)₂(max)= 64.4 mlO(2) kg(-1) min(-1), SD = 4.4) took part in a time trial run under four different conditions: 20 degrees C + 50% relative humidity (rh) (Control), 20 degrees C + 50% rh + 0.10 ppm O(3) (Control + O(3)), 31 degrees C + 70% rh (Heat), 31 degrees C + 70% rh + 0.10 ppm O(3) (Heat + O(3)). Heart rate, ratings of perceived exertion and minute ventilation were collected during the run. Lung function was measured pre and post-exercise. The runners completed a respiratory symptoms questionnaire after each trial. The completion time of both the Heat (32 min 35 s) and Heat + O(3) (33 min 09 s) trials were significantly higher (P < 0.0001) when compared to the Control + O(3) (30 min 27 s) and Control (30 min 15 s) trials. There were no significant changes between pre/post lung function measures or between trials. The effective dose of ozone simulated in the present study did not affect the performance and therefore, ozone-pollution, at an environmentally relevant concentration, did not compound the impairment in performance beyond that induced by a hot, humid environment.

20-HETE mediates ozone-induced, neutrophil-independent airway hyper-responsiveness in mice

Background

Ozone, a pollutant known to induce airway hyper-responsiveness (AHR), increases morbidity and mortality in patients with obstructive airway diseases and asthma. We postulate oxidized lipids mediate in vivo ozone-induced AHR in murine airways.

Methodology/Principal Findings

Male BALB/c mice were exposed to ozone (3 or 6 ppm) or filtered air (controls) for 2 h. Precision cut lung slices (PCLS; 250 µm thickness) containing an intrapulmonary airway (∼0.01 mm² lumen area) were prepared immediately after exposure or 16 h later. After 24 h, airways were contracted to carbachol (CCh). Log EC₅₀ and E_max values were then calculated by measuring the airway lumen area with respect to baseline. In parallel studies, dexamethasone (2.5 mg/kg), or 1-aminobenzotriazol (ABT) (50 mg/kg) were given intraperitoneal injection to naïve mice 18 h prior to ozone exposure. Indomethacin (10 mg/kg) was administered 2 h prior. Cell counts, cytokine levels and liquid chromatography-mass spectrometry (LC-MS) for lipid analysis were assessed in bronchoalveolar lavage (BAL) fluid from ozone exposed and control mice. Ozone acutely induced AHR to CCh. Dexamethasone or indomethacin had little effect on the ozone-induced AHR; while, ABT, a cytochrome P450 inhibitor, markedly attenuated airway sensitivity. BAL fluid from ozone exposed animals, which did not contain an increase in neutrophils or interleukin (IL)-6 levels, increased airway sensitivity following in vitro incubation with a naïve PCLS. In parallel, significant increases in oxidized lipids were also identified using LC-MS with increases of 20-HETE that were decreased following ABT treatment.

Conclusions/Significance

These data show that ozone acutely induces AHR to CCh independent of inflammation and is insensitive to steroid treatment or cyclooxygenase (COX) inhibition. BAL fluid from ozone exposed mice mimicked the effects of in vivo ozone exposure that were associated with marked increases in oxidized lipids. 20-HETE plays a pivotal role in mediating acute ozone-induced AHR.

Age, strain, and gender as factors for increased sensitivity of the mouse lung to inhaled ozone

Ozone (O(3)) is a respiratory irritant that leads to airway inflammation and pulmonary dysfunction. Animal studies show that neonates are more sensitive to O(3) inhalation than adults, and children represent a potentially susceptible population. This latter notion is not well established, and biological mechanisms underlying a predisposition to pollution-induced pulmonary effects are unknown. We examined age and strain as interactive factors affecting differential pulmonary responses to inhaled O(3). Male and female adult mice (15 weeks old) and neonates (15-16 days old) from eight genetically diverse inbred strains were exposed to 0.8 ppm O(3) for 5 h. Pulmonary injury and lung inflammation were quantified as total protein concentration and total polymorphonuclear neutrophil (PMN) number in lavage fluid recovered 24-h postexposure. Dose-response and time-course curves were generated using SJL/J pups, and (18)O lung burden dose was assessed in additional mice. Interstrain differences in response to O(3) were seen in neonatal mice: Balb/cJ and SJL/J being most sensitive and A/J and 129x1/SvJ most resistant. The PMN response to O(3) was greater in neonates than in adults, specifically for SJL/J and C3H/HeJ strains, independent of dose. Small gender differences were also observed in adult mice. Variation in protein concentrations and PMN counts between adults and pups were strain dependent, suggesting that genetic determinants do play a role in age-related sensitivity to O(3). Further research will help to determine what genetic factors contribute to these heightened responses, and to quantify the relative contribution of genes vs. environment in O(3)-induced health effects.

Induced sputum and exhaled nitric oxide as noninvasive markers of airway inflammation from work exposures

PURPOSE OF REVIEW

Noninvasive measures of airway inflammation are increasingly used in the investigation and management of asthma. Their role in the investigation of occupational lung diseases, however, is not as clearly established. The present article reviews the use of noninvasive methods - induced sputum and exhaled nitric oxide - in the assessment of airway inflammation during the investigation of occupational asthma and eosinophilic bronchitis, and reviews studies investigating the effect of exposure to various occupational agents on airway inflammation in healthy individuals.

RECENT FINDINGS

A number of studies have confirmed the association between exposure to occupational agents and the presence of eosinophilic airway inflammation after that exposure in individuals with occupational asthma. Individuals with positive specific inhalation challenges to occupational agents seem to show a greater increase in exhaled nitric oxide than those with negative specific inhalation challenges. Exposure to various agents associated with an increase in exhaled nitric oxide mainly induced a neutrophilic inflammation.

SUMMARY

Increasing evidence supports the use of induced sputum as an additional tool in the investigation of occupational asthma. The role of exhaled nitric oxide in the investigation of occupational asthma needs to be clarified due to conflicting evidence reported in the literature.

Intentional exposure studies of environmental agents on human subjects: assessing benefits and risks

In this article, I assess the benefits and risks of studies that intentionally expose research subjects to environmental agents. I describe these types of studies, identify their benefits and risks, compare them to other research methods that can be used to investigate the relationship between environmental exposures and disease, and discuss some issues related to research design and risk minimization. I argue that the benefits of intentional environmental exposure studies outweigh the risks when 1) the knowledge gained is likely to improve our understanding of the relationship between environmental exposure and disease, 2) this knowledge cannot be obtained by other methods, 3) the experiments are well designed, 4) the subjects will receive some benefits, such as medical evaluations, 5) risks are minimized, and 6) the risks to human subjects are less than those encountered in a typical Phase I drug study. Only in rare circumstances (i.e., when an intentional environmental exposure study is needed to implement an important environmental or public health intervention or regulation) may such studies expose research subjects to risks as high as those encountered in a typical Phase I drug trail.