Time-dependent changes of markers associated with inflammation in the lungs of humans exposed to ambient levels of ozone

Inhalation Pharmacodynamics

Pharmacodynamics (PD) is discussed in relation to inhalation exposure to inhaled pharmaceutical and toxic agents. Clearly PD is closely related to pharmacokinetics, and this relation is illustrated with reference to inhaled insulin. PD can be related to pharmacologic responses, and some examples are cited. However, PD can also be thought of as the improvement or deterioration in lung disease state. Some of the major PD endpoints, including histopathology, pulmonary function, and bronchoalveolar lavage are reviewed. Brief reference is also given to other specialty biomarkers of PD response.

Effects of Ozone on Sickness and Depressive-like Behavioral and Biochemical Phenotypes and Their Regulation by Serum Amyloid A in Mice

Ozone (O₃) is an air pollutant that primarily damages the lungs, but growing evidence supports the idea that O₃ also harms the brain; acute exposure to O₃ has been linked to central nervous system (CNS) symptoms such as depressed mood and sickness behaviors. However, the mechanisms by which O₃ inhalation causes neurobehavioral changes are limited. One hypothesis is that factors in the circulation bridge communication between the lungs and brain following O₃ exposure. In this study, our goals were to characterize neurobehavioral endpoints of O₃ exposure as they relate to markers of systemic and pulmonary inflammation, with a particular focus on serum amyloid A (SAA) and kynurenine as candidate mediators of O₃ behavioral effects. We evaluated O₃-induced dose-, time- and sex-dependent changes in pulmonary inflammation, circulating SAA and kynurenine and its metabolic enzymes, and sickness and depressive-like behaviors in Balb/c and CD-1 mice. We found that 3 parts per million (ppm) O₃, but not 2 or 1 ppm O₃, increased circulating SAA and lung inflammation, which were resolved by 48 h and was worse in females. We also found that indoleamine 2,3-dioxygenase (Ido1) mRNA expression was increased in the brain and spleen 24 h after 3 ppm O₃ and that kynurenine was increased in blood. Sickness and depressive-like behaviors were observed at all O₃ doses (1-3 ppm), suggesting that behavioral responses to O₃ can occur independently of increased SAA or neutrophils in the lungs. Using SAA knockout mice, we found that SAA did not contribute to O₃-induced pulmonary damage or inflammation, systemic increases in kynurenine post-O₃, or depressive-like behavior but did contribute to weight loss. Together, these findings indicate that acute O₃ exposure induces transient symptoms of sickness and depressive-like behaviors that may occur in the presence or absence of overt pulmonary neutrophilia and systemic increases of SAA. SAA does not appear to contribute to pulmonary inflammation induced by O₃, although it may contribute to other aspects of sickness behavior, as reflected by a modest effect on weight loss.

Ozone-Induced Models of Airway Hyperreactivity and Epithelial Injury

Ozone (O₃), a criterion air pollutant produced as a product of internal combustion, generates increased inflammation, lung permeability, and airway hyperreactivity when exposed to rodents in laboratory settings. Airway hyperreactivity is defined as an exaggerated acute obstructive response of the airways to one or more nonspecific stimuli. Lung permeability is a measure of barrier functions that separate internal and external environments to limit access of pathogens and other noxious material. By modeling in vivo O₃ exposure in rodents, this allows investigators to explore pulmonary and nonpulmonary O₃ effects as a means of understanding its impact on human health and lung function. Furthermore, direct effects of O₃ on epithelial permeability can be defined using in vitro exposures to airway epithelial cells. This chapter will focus on methods of generating O₃ and then exposing rodents and cultured epithelial cells in laboratory settings.

The Acute Effects of Exercising in Air Pollution: A Systematic Review of Randomized Controlled Trials

BACKGROUND

The acute effects of air pollution (AP) exposure during physical activity have been studied. However, comprehensive systematic reviews are lacking, particularly regarding moderate-to-vigorous physical activity (MVPA).

OBJECTIVE

Our objective was to determine the acute health- and exercise-related effects of AP exposure during a bout of MVPA in healthy individuals.

METHODS

We searched for randomized controlled trials in MEDLINE, Embase, Cochrane CENTRAL, SPORTDiscus, Agricultural and Environmental Science Database, ClinicalTrials.gov, International Standard Randomised Controlled Trial Number Registry, and the World Health Organization (WHO) International Clinical Trials Registry Platform up to July 2020 without language or date restrictions. Studies including healthy subjects engaging in a bout of MVPA while exposed to one or more of the following air pollutants were eligible: particulate matter, black carbon, carbon monoxide, nitrogen dioxide, ozone, diesel exhaust, and traffic-related air pollution (TRAP). Main outcome measures were markers of pulmonary function, symptoms, cardiovascular function, cognitive function, systemic inflammation, and exercise response. The evidence was synthesized by vote counting based on direction of effect.

RESULTS

In total, 53 studies were included in the systematic review. Studies employed a heterogeneous mix of exercise protocols, AP interventions, and measured outcomes. Pooled results suggest ozone exposure during MVPA has an adverse effect on pulmonary function (100% [95% confidence interval (CI) 88-100], p < 0.001; high-certainty evidence) and reported symptoms (88% [95% CI 69-96], p < 0.001; low-certainty evidence). The effect of exposure to carbon monoxide, nitrogen dioxide, small engine exhaust, or diesel exhaust during MVPA on health- and exercise-related outcomes is uncertain because of insufficient evidence and the low to very low certainty of available evidence.

DISCUSSION

The evidence is strongest for ozone, exposure to which generally induced a reduction in pulmonary function and increased symptoms during MVPA. The research related to other outcome domains remains inconclusive. Although long-term exposure to AP is proven to be hazardous, the evidence for healthy individuals to forgo MVPA during periods of high (non-ozone) pollution remains weak.

TRIAL REGISTRATION

Retrospectively registered in PROSPERO (CRD42020188280) on 10 July 2020.

Differential expression of pro-inflammatory and oxidative stress mediators induced by nitrogen dioxide and ozone in primary human bronchial epithelial cells

CONTEXT

NO2 and O3 are ubiquitous air toxicants capable of inducing lung damage to the respiratory epithelium. Due to their oxidizing capabilities, these pollutants have been proposed to target specific biological pathways, but few publications have compared the pathways activated.

OBJECTIVE

This work will test the premise that NO2 and O3 induce toxicity by activating similar cellular pathways.

METHODS

Primary human bronchial epithelial cells (HBECs, n = 3 donors) were exposed for 2 h at an air-liquid interface to 3 ppm NO2, 0.75 ppm O3, or filtered air and harvested 1 h post-exposure. To give an overview of pathways that may be influenced by each exposure, gene expression was measured using PCR arrays for toxicity and oxidative stress. Based on the results, genes were selected to quantify whether expression changes were changed in a dose- and time-response manner using NO2 (1, 2, 3, or 5 ppm), O3 (0.25, 0.50, 0.75, or 1.00 ppm), or filtered air and harvesting 0, 1, 4 and 24 h post-exposure.

RESULTS

Using the arrays, genes related to oxidative stress were highly induced with NO2 while expression of pro-inflammatory and vascular function genes was found subsequent to O3. NO2 elicited the greatest HMOX1 response, whereas O3 more greatly induced IL-6, IL-8 and PTGS2 expression. Additionally, O3 elicited a greater response 1 h post-exposure and NO2 produced a maximal response after 4 h.

CONCLUSION

We have demonstrated that these two oxidant gases stimulate differing mechanistic responses in vitro and these responses occur at dissimilar times.

Ozone exposure effect on systemic prostaglandin F2α in rat plasma and urine may not reveal pulmonary damage through inflammation

The acute ozone induced lung injury model has been widely used to explore injury and repair processes induced by oxidant overload. The current study evaluated acute ozone exposure effects on prostaglandin F_2α (PGF_2α) in male Fischer rat plasma and urine with the hypothesis that ozone may induce an inflammatory response in the body that can be measured by the induction of PGF_2α. That might then lead to the identification of potential marker for acute lung injury through systemic inflammation. The time and dose-dependent effects of ozone exposure on the plasma and urinary levels of a major PGF_2α metabolite15-keto-dihydro-PGF_2α were determined using a radioimmunoassay. No statistically significant differences in the PGF_2α metabolite were found between the control and the experimental groups at either ozone exposure dose (2ppm and 5ppm) or any time point (2h, 7h and 16h) post exposure for plasma and at 7 different post exposure time points (between 2 and 80h) for urine. It is concluded that acute ozone exposure does not cause changes in plasma and urinary PGF_2α, and therefore their measurement in plasma and urine may not be used to reveal pulmonary inflammation and damage by ozone.

Inflammatory markers in bronchoalveolar lavage fluid from human volunteers 2 hours after hydrogen fluoride exposure

Fluoride has been in focus as a possible causal agent for respiratory symptoms amongst aluminium potroom workers for several decades. Previously, using bronchoalveolar lavage (BAL), we demonstrated airway inflammation in healthy volunteers 24 hours after exposure to hydrogen fluoride (HF). The objective of the present study was to examine early lung responses to HF exposure. Bronchoscopy with BAL was performed 2 hours after the end of 1-hour exposure to HF. Significant reductions in the total cell number and the number of neutrophils and lymphocytes were observed in bronchoalveolar portion (BAP), whereas there were no significant changes in the bronchial portion (BP). Significantly decreased concentrations of b2-MG, IL-6 and total protein were found in both BAP and BP. Additionally, IL-8 was significantly reduced in BP, and ICAM-1 and albumin were present in lower concentrations in BAP. Lung function measurements were not affected by HF exposure. These reported effects are presumably transitory, as many were not present in the airways 24 hours after a similar HF exposure.

Parameters of lung inflammation in asthmatic as compared to healthy children in a contaminated city

Background

The impact of air pollution on the respiratory system has been estimated on the basis of respiratory symptoms and lung function. However; few studies have compared lung inflammation in healthy and asthmatics children exposed to high levels of air pollution. The aim of the study was to elucidate the modulatory effect of air pollution on Cysteinyl-leukotrienes (Cys-LTs) levels in exhaled breath condensate (EBC) among healthy and asthmatic children.

Methods

We performed a cross-sectional comparative study. Children between 7–12 years of age, asthmatics and non-asthmatics, residents of a city with high levels of PM₁₀ were included. In all cases, forced spirometry, Cys-LTs levels in EBC, and the International Study of Asthma and Allergies in Childhood questionnaire were evaluated. We also obtained average of PM₁₀, CO, SO₂ and O₃ levels during the period of the study by the State Institute of Ecology.

Results

We studied 103 children (51 asthmatics and 52 non-asthmatics). Cys-LTs levels were higher in asthmatics than in non-asthmatics (77.3 ± 21.6 versus 60.3 ± 26.8 pg/ml; p = 0.0005). Also, Cys-LTs levels in children with intermittent asthma were lower than in children with persistent asthma (60.4 ± 20.4 versus 84.7 ± 19.2 pg/ml; p = 0.0001). In the multiple regression model, factors associated with levels of Cys-LTs were passive smoking (β = 13.1, p 0.04) and to be asthmatic (β = 11.5, p 0.03).

Conclusions

Cys-LTs levels are higher in asthmatic children than in healthy children in a contaminated city and its levels are also associated with passive smoking.

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.

Ozone enhances diesel exhaust particles (DEP)-induced interleukin-8 (IL-8) gene expression in human airway epithelial cells through activation of nuclear factors- kappaB (NF-kappaB) and IL-6 (NF-IL6)

Ozone, a highly reactive oxidant gas is a major component of photochemical smog. As an inhaled toxicant, ozone induces its adverse effects mainly on the lung. Inhalation of particulate matter has been reported to cause airway inflammation in humans and animals. Furthermore, epidemiological evidence has indicated that exposure to particulate matter (PM[2.5-10]), including diesel exhaust particles (DEP) has been correlated with increased acute and chronic respiratory morbidity and exacerbation of asthma. Previously, exposure to ozone or particulate matter and their effect on the lung have been addressed as separate environmental problems. Ozone and particulate matter may be chemically coupled in the ambient air. In the present study we determined whether ozone exposure enhances DEP effect on interleukin-8 (IL-8) gene expression in human airway epithelial cells. We report that ozone exposure (0.5 ppm x 1 hr) significantly increased DEP-induced IL-8 gene expression in A549 cells (117 +/- 19 pg/ml, n = 6, p < 0.05) as compared to cultures treated with DEP (100 microg/ml x 4 hr) alone (31 +/- 3 pg/ml, n = 6), or cultures exposed to purified air (24 +/- 6 pg/ml, n = 6). The increased DEP-induced IL-8 gene expression following ozone exposure was attributed to ozone-induced increase in the activity of the transcription factors NF-kappaB and NF-IL6. The results of the present study indicate that ozone exposure enhances the toxicity of DEP in human airway epithelial cells by augmenting IL-8 gene expression, a potent chemoattractant of neutrophils in the lung.

Breath condensate levels of 8-isoprostane and leukotriene B4 after ozone inhalation are greater in sensitive versus nonsensitive subjects

Ozone (O3) inhalation induces pulmonary function decrements and inflammation. The present study was designed to determine if a relationship exists between O3 induced pulmonary function changes and the presence of inflammatory markers as measured in exhaled breath condensates (EBCs) obtained from O3-sensitive and nonsensitive human subjects. Eight healthy adult volunteers (4 males/4 females, age 18 to 30 years) were studied, characterized as to their ozone sensitivity and placed into 2 groups (sensitive and nonsensitive) with each group having 2 males and 2 females. Subjects completed a 20-minute EBC collection and pulmonary function test (PFT) prior to a single 60-minute bout of cycle ergometer exercise (V(E) = 50-55 L/min) while breathing filtered air (FA) or 0.35 ppm O3. Subjective symptom scores (SSSs) were collected at 6, 20, 40, and 60 minutes during exposure. An immediate postexposure PFT was performed followed by an EBC collection. Subjective symptom scores, EBCs, and PFTs were collected at 1, 4 and 8 hours post exposure. EBCs were analyzed for prostaglandin E2 (PGE2), leukotriene B4 (LTB4), 8-isoprostane, and total nitric oxide (NO) metabolites (nitrate + nitrite content). Sensitive subjects, breathing O3, had significantly greater functional decrements in PFTs, increased SSSs, and increased rapid shallow breathing as well as elevated levels of 8-isoprostane and LTB4 in EBCs compared to those breathing FA. In addition, there were significant increases in nitrate + nitrite content in both sensitive and nonsensitive subjects breathing O3 compared to FA. These results indicate that sensitive subjects have elevated arachidonic acid metabolites in EBCs compared to nonsensitive subjects after O3 inhalation.

Activation of transcription factor IL-6 (NF-IL-6) and nuclear factor-kappaB (NF-kappaB) by lipid ozonation products is crucial to interleukin-8 gene expression in human airway epithelial cells

Ozone (O(3)) is a major component of smog and an inhaled toxicant to the lung. O(3) rapidly reacts with the airway epithelial cell membrane phospholipids to generate lipid ozonation products (LOP). 1-Hydroxy-1-hydroperoxynonane (HHP-C9) is an important LOP, produced from the ozonation of 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphatidylcholine. This LOP, at a biologically relevant concentration (100 microM), increases the activity of phospholipase C, nuclear factors-kappaB (NF-kappaB), and interleukin-6 (NF-IL-6) and the expression of the inflammatory gene, interleukin-8 (IL-8) in a cultured human bronchial epithelial cell line (BEAS-2B). The signaling pathways of ozone and its biologically-active products are as yet undefined. In the present study, we report that the HHP LOP, HHP-C9 (100 microM x 4 h), activated the expression of IL-8 (218 +/- 26% increase over control, n = 4, P < 0.01) through an apparent interaction between the two transcription factors, NF-kappaB and NF-IL-6. Transfection studies using luciferase reporter assays demonstrated that HHP-C9 induced a significant increase in NF-kappaB-DNA binding activity (37 +/- 7% increase over control, n = 6, P < 0.05). Inhibition of NF-kappaB showed a statistically significant but modest decrease in IL-8 release, which suggested a role for another transcription factor, NF-IL-6. Exposure of BEAS-2B cells to HHP-C9 induced a significant increase in the DNA binding activity of NF-IL-6 (45 +/- 11% increase over control, n = 6, P < 0.05). The results of the present study indicate that NF-IL-6 interacts with NF-kappaB in regulating the expression of IL-8 in cultured human airway epithelial cells exposed to LOP, the biological products of ozone in the lung.

Acute ozone-induced differential gene expression profiles in rat lung

Ozone is an oxidant gas that can directly induce lung injury. Knowledge of the initial molecular events of the acute O3 response would be useful in developing biomarkers of exposure or response. Toward this goal, we exposed rats to toxic concentrations of O3 (2 and 5 ppm) for 2 hr and the molecular changes were assessed in lung tissue 2 hr postexposure using a rat cDNA expression array containing 588 characterized genes. Gene array analysis indicated differential expression in almost equal numbers of genes for the two exposure groups: 62 at 2 ppm and 57 at 5 ppm. Most of these genes were common to both exposure groups, suggesting common roles in the initial toxicity response. However, we also identified the induction of nine genes specific to 2-ppm (thyroid hormone-beta receptor c-erb-A-beta; and glutathione reductase) or 5-ppm exposure groups (c-jun, induced nitric oxide synthase, macrophage inflammatory protein-2, and heat shock protein 27). Injury markers in bronchoalveolar lavage fluid (BALF) were used to assess immediate toxicity and inflammation in rats similarly exposed. At 2 ppm, injury was marked by significant increases in BALF total protein, N-acetylglucosaminidase, and lavageable ciliated cells. Because infiltration of neutrophils was observed only at the higher 5 ppm concentration, the distinctive genes suggested a potential amplification role for inflammation in the gene profile. Although the specific gene interactions remain unclear, this is the first report indicating a dose-dependent direct and immediate induction of gene expression that may be separate from those genes involved in inflammation after acute O3 exposure.

Application of quantitative structure activity relationship (QSAR) models to predict ozone toxicity in the lung

The sequence of events leading to ozone-induced airway inflammation is not well known. To elucidate the molecular and cellular events underlying ozone toxicity in the lung, we hypothesized that lipid ozonation products (LOPs) generated by the reaction of ozone with unsaturated fatty acids in the epithelial lining fluid and cell membranes play a key role in mediating ozone-induced airway inflammation. To test our hypothesis, we ozonized 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) and generated LOPs. Confluent human bronchial epithelial cells were exposed to the derivatives of ozonized POPC-9-oxononanoyl, 9-hydroxy-9-hydroperoxynonanoyl, and 8-(5-octyl-1,2,4-trioxolan-3-yl-)octanoyl-at a concentration of 10 muM, and the activity of phospholipases A2 (PLA2), C (PLC), and D (PLD) was measured (1, 0.5, and 1 h, respectively). Quantitative structure-activity relationship (QSAR) models were utilized to predict the biological activity of LOPs in airway epithelial cells. The QSAR results showed a strong correlation between experimental and computed activity (r = 0.97, 0.98, 0.99, for PLA2, PLC, and PLD, respectively). The results indicate that QSAR models can be utilized to predict the biological activity of the various ozone-derived LOP species in the lung.

Effect of ozone on bronchial mucosal inflammation in asthmatic and healthy subjects

Epidemiological studies suggestthat asthmatics are more affected by ozone than healthy people. This study tested three hypotheses (1) that short-term exposure to ozone induces inflammatory cell increases and up-regulation of vascular adhesion molecules in airway lavages and bronchial tissue 6 h after ozone exposure in healthy subjects; (2) these responses are exaggerated in subjects with mild allergic asthma; (3) ozone exacerbates pre-existent allergic airways inflammation. We exposed 15 mild asthmatic and 15 healthy subjects to 0.2 ppm of ozone or filtered air for 2 h on two separate occasions. Airway lavages and bronchial biopsies were obtained 6 h post-challenge. We found that ozone induced similar increases in bronchial wash neutrophils in both groups, although the neutrophil increase in the asthmatic group was on top of an elevated baseline. In healthy subjects, ozone exposure increased the expression of the vascular endothelial adhesion molecules P-selectin and ICAM- 1, as well as increasing tissue neutrophil and mast cell numbers. The asthmatics showed allergic airways inflammation at baseline but ozone did not aggravate this at the investigated time point. At 6 h post-ozone-exposure, we found no evidence that mild asthmatics were more responsive than healthy to ozone in terms of exaggerated neutrophil recruitment or exacerbation of pre-existing allergic inflammation. Further work is needed to assess the possibility of a difference in time kinetics between healthy and asthmatic subjects in their response to ozone.

Antioxidant and inflammatory response after acute nitrogen dioxide and ozone exposures in C57Bl/6 mice

Ozone (O(3)) and nitrogen dioxide (NO(2)) are highly reactive and toxic oxidant pollutants. The objective of this study is to compare chemokine, cytokine, and antioxidant changes elicited by acute exposures of O(3) and NO(2) in a genetically sensitive mouse. Eight-week-old C57Bl/6J mice were exposed to 1 or 2.5 ppm ozone or 15 or 30 ppm NO(2) for 4 or 24 h. Changes in mRNA abundance in lung were assayed by slot blot and ribonuclease protection assay (RPA). Messages encoding metallothionein (Mt), heme oxygenase I (HO-I), and inducible nitric oxide synthase (iNOS) demonstrated increased message abundance after 4 and 24 h of exposure to either O(3) or NO(2). Furthermore, increases in message abundance were of a similar magnitude for O(3) and NO(2). Messages encoding eotaxin, macrophage inflammatory protein (MIP)-1alpha, and MIP-2 were elevated after 4 and 24 h of exposure to 1 ppm ozone. Interleukin-6 was elevated after 4 h of exposure to ozone. After 4 h of 2.5 ppm ozone exposure, increased mRNAs of eotaxin, MIP-1alpha, MIP-2, Mt, HO-I, and iNOS were elevated to a higher magnitude than were detected after 1 ppm ozone. Monocyte chemoattractant protein (MCP-1) was elevated following 15 ppm NO(2) exposure. After 4 h of 30 ppm NO(2) exposure, messages encoding eotaxin, MIP-1alpha, MIP-2, and MCP-1 were elevated to levels similar to those detected after ozone exposure. Our results demonstrate a similar antioxidant and chemokine response during both O(3) and NO(2) exposure. Induction of these messages is associated with the duration and concentration of exposure. These studies suggest that these gases exert toxic action through a similar mechanism.

Induction of inflammatory mediators in human airway epithelial cells by lipid ozonation products

We have proposed that exposure of epithelial cell membrane lipids in the lung (mainly phospholipids) to ozone will generate lipid ozonation products (LOP), which could be responsible for the proinflammatory effects of ozone. The ozonation of phosphocholine, the principal membrane phospholipid, produces a limited number of LOP, including hydroxyhydroperoxides and aldehydes. We now report that exposure of cultured human bronchial epithelial cells to the ozonized 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) product, 1-palmitoyl-2-(9-oxononanoyl)-sn-glycero-3-phosphocholine (PC-ALD), a phospholipase A(2) (PLA(2))-stimulatory LOP, resulted in a 113 +/- 11% increase in the amounts of tritiated platelet-activating factor ((3)H-PAF) released apically. (3)H-PAF release was also induced by 1-hydroxy-1-hydroperoxynonane of ozonized POPC (HHP-C9), a phospholipase C (PLC)- stimulatory LOP (134 +/- 40% increase in (3)H-PAF). PC-ALD at 10 microM, but not HHP-C9, induced a 127 +/- 24% increase in prostaglandin E(2) (PGE(2)) release (n = 6, p < 0.05). In contrast, HHP-C9, but not PC-ALD, induced interleukin (IL)-6 release (178 +/- 23% increase, n = 6, p < 0.05) and IL-8 release (101 +/- 23% increase, n = 8, p < 0. 05). These results suggest that LOP-dependent release of proinflammatory mediators may play an important role in the early inflammatory response seen during exposure to ozone.

Air pollution and respiratory illness of children in São Paulo, Brazil

This investigation reports the association between air pollution and paediatric respiratory emergency visits in São Paulo, Brazil, the largest city in South America. Daily records of emergency visits were obtained from the Children's Institute of the University of São Paulo for the period from May 1991 to April 1993. Visits were classified as respiratory and non-respiratory causes. Respiratory visits were further divided into three categories: upper respiratory illness, lower respiratory illness and wheezing. Daily records of SO2, CO, particulate matter (PM10), O3 and NO2 concentrations were obtained from the State Air Pollution Controlling Agency of São Paulo. Associations between respiratory emergency visits and air pollution were assessed by simple comparative statistics, simple correlation analysis and by estimating a variety of regression models. Significant associations between the increase of respiratory emergency visits and air pollution were observed. The most robust associations were observed with PM10, and to a lesser extent with O3. These associations were stable across different model specifications and several controlling variables. A significant increase in the counts of respiratory emergency visits--more than 20%--was observed on the most polluted days, indicating that air pollution is a substantial paediatric health concern in São Paulo.

A comparison of biomarkers of ozone exposure in human plasma, nasal lavage, and sputum

We examined ozone-induced upper and lower airway inflammatory responses and the concentrations of hydroxylated salicylate metabolites using nasal lavage fluid and induced sputum, in order to identify noninvasive and sensitive biomarkers for ozone exposure and effects. A time course for plasma concentration of 2, 3-dihydroxybenzoic acid (2,3-DHBA, a salicylate metabolite and an indicator for hydroxyl radical) in response to 0.12 ppm ozone was also studied. Healthy, young, nonsmoking volunteers were given acetylsalicylic acid (ASA, 975 mg) or placebo orally. Subjects were exposed to ozone (0.12 or 0.4 ppm) or filtered air in an environmental chamber for 2 h, while performing intermittent exercise. Blood was collected hourly over a 4-h period. After exposure, nasal lavage fluid was collected, and sputum was induced using hypertonic saline. Results show that in sputum the percentage of neutrophils was significantly higher after the subjects were exposed to 0.4 ppm ozone (p<.05) than after they were exposed to filtered air or 0.12 ppm ozone. The absolute number and the percentage of macrophages were significantly lower at 0.4 ppm ozone than for filtered air control or 0.12 ppm ozone. The percentage of lymphocytes in sputum was also significantly lower at 0.4 ppm ozone than for filtered air control or 0.12 ppm ozone. The sputum cellular responses to ozone were not significantly altered by ASA treatment. In nasal lavage, cell counts and differentials did not change significantly after exposure to ozone in comparison to filtered air control. The cellular data indicate an acute inflammation developed during ozone exposure in the lower respiratory tract. The concentrations of total protein and interleukin-8 and the activity of N-acetyl-beta-D-glucosaminidase (a lysosomal enzyme) in nasal lavage and sputum did not change significantly following exposure to ozone in comparison to filtered air control. Plasma 2,3-DHBA concentration increased significantly following exposure to 0.12 ppm ozone in an exposure-dependent temporal pattern. Salicylate metabolites in nasal lavage fluid and sputum did not increase significantly following exposure to ozone. There was a marked variation of 2,3-DHBA concentrations in airway fluids. Data suggest that plasma 2,3-DHBA is a sensitive marker indicating acute ozone exposure, even at an ozone concentration that causes minimal observable airway effects in healthy subjects.

Antioxidant supplementation and respiratory functions among workers exposed to high levels of ozone

Ozone exposure has been related to adverse respiratory effects, in particular to lung function decrements. Antioxidant vitamins are free-radical scavengers and could have a protective effect against photo-oxidant exposure. To evaluate whether acute effects of ozone on lung functions could be attenuated by antioxidant vitamin supplementation, we conducted a randomized trial using a double-blind crossover design. Street workers (n = 47) of Mexico City were randomly assigned to take daily a supplement (75 mg vitamin E, 650 mg vitamin C, 15 mg beta carotene) or a placebo and were followed from March to August 1996. Pulmonary function tests were done twice a week at the end of the workday. During the follow-up, the mean 1-h maximum ozone level was 123 ppb (SD = 40). During the first phase, ozone levels were inversely associated with FVC (beta = -1.60 ml/ppb), FEV1 (beta = -2.11 ml/ppb), and FEF25-75 (beta = -4.92 ml/ppb) (p < 0.05) in the placebo group but not in the supplement group. The difference between the two groups was significant for FVC, FEV1, and FEF25-75 (p < 0.01). During the second phase, similar results were observed, but the lung function decrements in the placebo group were smaller, suggesting that the supplementation may have had a residual protective effect on the lung. These results need to be confirmed in larger supplementation studies.

In vivo salicylate hydroxylation: a potential biomarker for assessing acute ozone exposure and effects in humans

Ozone is known to yield hydroxyl radical, which may contribute to ozone-mediated lung injury. In the presence of hydroxyl radical, salicylate is hydroxylated to form 2,3-dihydroxybenzoic acid (2,3-DHBA). There is no evidence of enzymatic formation of 2,3-DHBA. We hypothesized that salicylate hydroxylation might be used as a biomarker indicating human exposure to ozone. Healthy, nonsmoking volunteers, 18 to 34 yr of age, were given acetylsalicylic acid (975 mg) or placebo orally 0.5 h before an exposure. Subjects were exposed to ozone (0.12 or 0.4 ppm) or filtered air in an environmental chamber for 2 h, while performing intermittent exercise. Results indicate significant decrements in FVC, FEV1.0, forced expiratory flows at 50% and 75% of FVC, and peak expiratory flow rate, and an increase in airway resistance, after exposure to 0.4 ppm ozone in comparison with air control (p < 0.05). Exposure to 0.4 ppm ozone also resulted in increased symptom numbers and severity (p < 0.05). When subjects were exposed to 0.12 ppm ozone, changes of pulmonary function and symptoms reported were minimal. Plasma concentration of 2,3-DHBA was significantly increased after exposure to 0.12 and 0.4 ppm ozone in comparison with air control (p < 0.05). There was a significant correlation between ozone-induced changes of pulmonary function and normalized salicylate hydroxylation (p < 0.05). The results indicate that exposure to ozone can initiate in vivo production of hydroxyl radical, a potent reactive agent. Salicylate hydroxylation may then serve as a sensitive dosimetric biomarker for ozone exposure, even at subclinical ozone exposure levels.

Airway inflammation in smokers and nonsmokers with varying responsiveness to ozone

Exposure to ozone causes symptoms, changes in lung function, and airway inflammation. We studied whether individuals who differ in lung-function responsiveness to ozone, or in smoking status, also differ in susceptibility to airway inflammation. Healthy subjects were selected on the basis of responsiveness to a classifying exposure to 0.22 ppm ozone for 4 h with exercise (responders, with a decrease in FEV1 > 15%; and non-responders, with a decrease in FEV1 < 5%). Three groups were studied: nonsmoker-nonresponders (n = 12), nonsmoker-responders (n = 13), and smokers (n = 13, 11 nonresponders and two responders). Each subject underwent two exposures to ozone and one to air, separated by at least 3 wk; bronchoalveolar and nasal lavages were performed on three occasions: immediately (early) and 18 h (late) after ozone exposure, and either early or late after air exposure. Recovery of polymorphonuclear leukocytes (PMN) increased progressively in all groups, and by up to 6-fold late after ozone exposure. Interleukin-6 (IL-6) and IL-8 increased early (by up to 10-fold and up to 2-fold, respectively), and correlated with the late increase in PMN. Lymphocytes, mast cells, and eosinophils also increased late after exposure. We conclude that ozone-induced airway inflammation is independent of smoking status or airway responsiveness to ozone.

Mechanisms of pollution-induced airway disease: in vivo studies

Several studies have investigated the effects of ozone, sulphur dioxide (SO2), and nitrogen dioxide (NO2) on lung function in normal and asthmatic subjects. Decreased lung function has been observed with ozone levels as low as 0.15 ppm-this effect is concentration dependent and is exacerbated by exercise. A number of lines of evidence suggest that the effect on lung function is mediated, at least in part, by neural mechanisms. In both normals and asthmatics, ozone has been shown to induce neutrophilic inflammation, with increased levels of several inflammatory mediators, including prostaglandin E2. However, in normal subjects, none of the markers of inflammation correlate with changes in lung function. The lung function changes in asthmatics may be associated with inflammatory effects; alternatively, ozone may prime the airways for an increased response to subsequently inhaled allergen. Indeed, an influx of both polymorphonucleocytes and eosinophils has been observed in asthmatic patients after ozone exposure. It has been suggested that the effect of ozone on classic allergen-induced bronchoconstriction may be more significant than any direct effect of this pollutant in asthmatics. SO2 does not appear to affect lung function in normal subjects, but may induce bronchoconstriction in asthmatics. Nasal breathing, which is often impaired in asthmatics, reduces the pulmonary effects of SO2, since this water-soluble gas is absorbed by the nasal mucosa. NO2 may also influence lung function in asthmatics, but further research is warranted. SO2 and NO2 alone do not seem to have a priming effect in asthmatics, but a combination of these two gases has resulted in a heightened sensitivity to subsequently inhaled allergen.

Effects of cyclo-oxygenase inhibition on ozone-induced respiratory inflammation and lung function changes

Inhalation of O3 causes airways neutrophilic inflammation accompanied by other changes including increased levels of cyclo-oxygenase products of arachidonic acid in bronchoalveolar lavage fluid (BALF). Ozone O3 exposure also causes decreased forced vital capacity (FVC) and forced expiratory volume after 1 s (FEV(1)), associated with cough and substernal pain on inspiration, and small increases in specific airway resistance (SRAW). The spirometric decrements are substantially blunted by pretreatment with indomethacin. Since the O3-induced decrement in FVC is due to involuntary inhibition of inspiration, a role for stimulation of nociceptive respiratory tract afferents has been suggested and cyclo-oxygenase products have been hypothesized to mediate this stimulation. However, the relation (if any) between the O3-induced neutrophilic airways inflammation and decreased inspiratory capacity remains unclear. We studied the effects of pharmacologic inhibition of O3-induced spirometric changes on the inflammatory changes. Each of ten healthy men was exposed twice (5-week interval) to 0.4 ppm O3 for 2 h, including 1 h of intermittent exercise (ventilation 601*min(-1)). One-and-a-half hours prior to and midway during each exposure the subject ingested 800 mg and 200 mg, respectively, of the non-steroidal anti-inflammatory drug ibuprofen (IBU), or placebo [PLA (sucrose)], in randomized, double-blind fashion. Spirometry and body plethysmography were performed prior to drug administration, and before and after O3 exposure. Immediately following postexposure testing, fiberoptic bronchoscopy with bronchoalveolar lavage (BAL) was performed. Neither IBU nor PLA administration changed pre-exposure lung function. O3 exposure (with PLA) caused a significant 17 percent mean decrement in FEV(1) (P <0.01) and a 56 percent increase in mean SRAW. Following IBU pretreatment, O3 exposure induced a significantly lesser mean decrement in FEV(1) (7 percent) but still a 50 percent increase in mean SRAW. IBU pretreatment significantly decreased post-O3 BAL levels of prostaglandin E2 (PGE2) by 60.4 percent (P <0.05) and thromboxane B(2) (TxB(2)) by 25.5 percent (P <0.05). Of the proteins, only interleukin-6 was significantly reduced (45 percent, P <0.05) by IBU as compared to PLA pretreatment. As expected, O3 exposure produced neutrophilia in BALF. There was, however, no effect of IBU on this finding. None of the major cell types in the BALF differed significantly between pretreatments. We found no association between post-exposure changes of BALF components and pulmonary function decrements. We conclude that IBU causes significant inhibition of O3-induced increases in respiratory tract PGE(2) and TxB(2) levels concomitant with a blunting of the spirometric response. This is consistent with the hypothesis that the products of AA metabolism mediate inhibition of inspiration. However, IBU did not alter the modest SRAW response to O3.

Ozone-induced human respiratory dysfunction and disease

Exercising volunteers exposed in chambers to as little as 80 ppb O3 for several hours exhibit impaired lung function and irritative lower airway symptoms. Comparable changes occur among children and young adults exposed to summer smog containing O3. Intensity of the response is reproducible but varies widely among individuals. The (reversible) decrements in vital capacity are due to involuntary inhibition of deep inspiration probably mediated by nociceptive bronchial C-fibers that may be stimulated by local prostaglandin release, and can be modulated by appropriate pharmacologic agents. A second characteristic response to low O3 levels is mucosal neutrophilic inflammation probably mediated by phospholipid-derived products and by epithelial cell-derived chemokines and cytokines, but poorly correlated with lung function changes. Fluctuations in ambient O3 levels are associated with acute respiratory health effects in exposed populations but concomitant acid aerosol pollution is an important confounder. Whether irreversible impairment of lung function occurs among residents of chronically high ozone-pollution areas is debated.

Attenuation of acute lung injury by ozone inhalation--the effect of low level pre-exposure

The attenuating influence of a pre-exposure of rats to a low concentration of ozone (O3) for 7 days on a subsequent O3 challenge was investigated. Effects of O3 were quantified by measuring indicators of lung permeability and inflammation in bronchoalveolar lavage fluid. The results suggest that pre-exposure to relatively low levels of O3 produces a diminished permeability response in lower airways of rats upon a following challenge with a higher level of O3. Extrapolated to human exposure situations, these data suggest that health effect evaluation of repeated exposure periods of enhanced O3 levels is rather complex and needs further investigation.

Ambient ozone causes upper airways inflammation in children

Ozone constitutes a major air pollutant in Western Europe. During the summer national air quality standards are frequently exceeded, which justifies concern about the health effects of ozone at ambient concentrations. We studied upper airways inflammation after ozone exposure in 44 children by repeated nasal lavages from May to October 1991. During this time period five to eight lavages were performed for each child. On 14 days following high ozone exposure (daily maximum > or = 180 micrograms/m3) 148 nasal lavages were performed, and on 10 days following low ozone exposure (daily maximum < or = 140 micrograms/m3) 106 nasal lavages were performed. A significant increase of intra-individual mean polymorphonuclear leukocytes (PMN) counts from low ozone days (median, 20.27 x 10(3)) to high ozone days (median, 27.38 x 10(3); p < 0.01) was observed. Concomitant with a decrease of ozone concentrations in the fall mean PMN counts showed a downward trend. Linear regression analysis of log-PMN counts yielded a significant effect for ozone (p = 0.017). In a subsample humoral markers of inflammation were measured for each child's highest and lowest exposure. A significant increase was observed for eosinophilic cationic protein (median, 77.39 micrograms/L on low ozone days versus 138.6 micrograms/L on high ozone days; p < 0.05). Thus we conclude that ozone at ambient concentrations initiates a reversible inflammatory response of the upper airways in normal children.

Toxicologic testing of inhaled pharmaceutical aerosols

This paper reviews technical issues related to the toxicologic testing of inhaled pharmaceuticals. Although there are commonalities between approaches to general and inhalation toxicity testing, there also are specific challenges in the toxicity testing of inhaled pharmaceuticals. A major issue is that of dose; inhaled dose is more difficult to determine than intravenous or oral doses. Also, it is harder to relate dose in laboratory animals to that in man for inhalation exposure than for other routes of administration. Additionally, in the case of inhaled pharmaceuticals, people generally inhale through the mouth, whereas most laboratory animals inhale primarily through the nose. This presents significant challenges in exposure methodology and technology that often need innovative approaches involving alteration to particle size of the agent or dosing procedure. Because the respiratory tract is the site of deposition, local respiratory toxicity and possible damage to lung cells need to be assessed. Systemic toxicity also needs to be evaluated and may be an issue in some cases. Special studies on pulmonary function, mucociliary clearance, or immune response may be needed, depending on the nature of the inhaled pharmaceutical. This review explores the main issues involved in toxicity testing of inhaled pharmaceuticals, the approaches that have been used, and the current and future challenges.