Persistent rhinitis and epithelial remodeling induced by cyclic ozone exposure in the nasal airways of infant monkeys

Association of Air Pollutant Exposure and Sinonasal Histopathology Findings in Chronic Rhinosinusitis

BACKGROUND

Ambient air pollution is well known to cause inflammatory change in respiratory epithelium and is associated with exacerbations of inflammatory conditions such as asthma and chronic obstructive pulmonary disease. However, limited work has been done on the impact of air pollution on pathogenesis of chronic rhinosinusitis and there are no reports in the literature of how pollutant exposure may impact sinonasal histopathology in patients with chronic rhinosinusitis.

OBJECTIVE

This study aims to identify associations between certain histopathologic characteristics seen in sinus tissue of patients with chronic rhinosinusitis (CRS) and levels of particulate air pollution (PM_2.5) and ground-level ozone in their place of residence.

METHODS

A structured histopathology report was created to characterize the tissues of CRS patients undergoing sinus surgery. An estimate for each patient's exposure to air pollutants including small particulate matter (PM_2.5) and ground-level ozone was obtained using the Environmental Protection Agency's (EPA) Environmental Justice Screening and Mapping Tool (EJSCREEN). Mean pollutant exposures for patients whose tissues exhibited varying histopathologic features were compared using logistic regression models.

RESULTS

Data from 291 CRS patients were analyzed. Higher degree of inflammation was significantly associated with increased ozone exposure (p = 0.031). Amongst the patients with CRSwNP (n=131), presence of eosinophilic aggregates (p = 0.018) and Charcot-Leyden crystals (p = 0.036) was associated with increased ozone exposure.

CONCLUSION

Exposure to ambient air pollutants may contribute to pathogenesis of CRS. Increasing ozone exposure was linked to both higher tissue inflammation and presence of eosinophilic aggregates and Charcot-Leyden crystals in CRSwNP patients.

Monkeys fight more in polluted air

Air pollution is a global environmental problem, and its effects on human behavior, psychology, and health have been well studied. However, very few studies were done on if and how air pollution affects animal behavior, for example, social conflict. Many physiological and psychological evidences suggest a possible positive relationship between air pollution and animal social conflict, thus we established a multiple linear regression model using a captive monkey group to explore if monkeys behave more aggressively in polluted air. Our results confirmed that daily social fighting behaviors occurred more when air is polluted. Temperature has a nonlinear effect on monkey social conflict, with a fighting peak at 25-29 °C. To our knowledge, this is the first report that animal social conflict, like humans, is also affected by air pollution and temperature.

An acute exposure to ozone impairs human olfactory functioning

INTRODUCTION

Ozone is a ubiquitous and irritant gas. We questioned whether an acute exposure to 0.2 ppm ozone impaired olfactory functioning.

METHODS

Healthy, normosmic subjects were exposed according to a parallel group design either to 0.2 ppm ozone (n = 15) or to sham (n = 13) in an exposure chamber for two hours. Possible irritating effects were assessed by questionnaire (range 0-5). The detection threshold of n-butanol was measured with the Sniffin' Sticks test before and after exposure. Olfactory thresholds were logarithmized and a two-way analysis of variance (ANOVA) with repeated measurements was carried out to test the effects of exposure (ozone vs. sham) and time (before vs. after exposure). Additionally, nasal secretions were taken at a preliminary examination and after exposure to determine interleukins 1ß and 8.

RESULTS

No irritating effects to the upper airways were observed. In the ozone group, the median score for cough increased from 0 to 2 at the end of exposure (sham group 0 and 0, respectively, p < 0.001). The ANOVA showed a main effect for ozone exposure (F (1, 26) = 27.6, p = 0.0002), indicating higher olfactory thresholds in the ozone group. Concentrations of interleukins in nasal secretions did not increase following ozone exposure.

CONCLUSIONS

This study shows a clear impairment of olfactory functioning following an acute exposure to 0.2 ppm ozone.

Effects of ozone stimulation of bronchial epithelial cells on proliferation and collagen synthesis of co-cultured lung fibroblasts

Ozone (O₃) as a major air pollutant is widely recognized for causing pathological changes of the airway system. However, it is not clear whether O₃ exposure of bronchial epithelial cells (BECs) influences the proliferation and collagen synthesis of submucosal fibroblasts and contributes to the pathogenesis of airway remodeling in diseases, including asthma. In the present study, a co-culture method was applied to culture human lung fibroblasts (HLFs) with human bronchial epithelial cells (HBECs) that were pre-stimulated with O₃. Following co-culture for up to 24 h, the proliferation of HLFs was measured using MTT colorimetry. Furthermore, the collagen synthesis capacity of HLFs was determined by the level of hydroxyproline. In addition, the protein expression levels of cytokines, including transforming growth factor (TGF)-β1, tumor necrosis factor (TNF)-α and prostaglandin E2 (PGE2) were assessed. Results indicated that the proliferation of HLFs co-cultured with HBECs was significantly inhibited when compared with HLFs cultured alone (P<0.05). By contrast, co-culture with O₃-stimulated HBECs significantly promoted the proliferation of HLFs compared with the HLFs cultured alone or those cultured with HBECs but no O₃ stimulation, respectively (P<0.05 and P<0.01). Furthermore, similar effects were observed regarding the collagen synthesis capacity of HLFs co-cultured with HBECs for 24. In the supernatant, TGF-β1 concentration was continuously increased over 24 h, whereas the concentration of PGE2 increased and plateaued between 12 to 24 h and TNF-α concentration was not significantly altered during the assessed time period. To conclude, the present results suggest that O₃ pre-exposure of HBECs may promote the transformation of HLFs from the typical inhibitory state into a promoting state with respect to proliferation and collagen synthesis, which may likely occur through a mechanism that influences the balance between pro- and anti-inflammatory factors, including TGF-β1 and PGE2. The present findings may improve the understanding of the mechanism involved in O₃-induced airway remodeling from a novel perspective of maintenance/loss of steady-state function of the airway epithelium.

Targeting acetylcholine receptor M3 prevents the progression of airway hyperreactivity in a mouse model of childhood asthma

Asthma often progresses into adulthood from early-life episodes of adverse environmental exposures. However, how the injury to developing lungs contributes to the pathophysiology of persistent asthma remains poorly understood. In this study, we identified an age-related mechanism along the cholinergic nerve-airway smooth muscle (ASM) axis that underlies prolonged airway hyperreactivity (AHR) in mice. We showed that ASM continued to mature until ∼3 wk after birth. Coinciding with postnatal ASM maturation, there was a critical time window for the development of ASM hypercontractility after cholinergic stimulation. We found that allergen exposure in neonatal mice, but not in adult mice, elevated the level and activity of cholinergic nerves (termed neuroplasticity). We demonstrated that cholinergic neuroplasticity is necessary for the induction of persistent AHR after neonatal exposure during rescue assays in mice deficient in neuroplasticity. In addition, early intervention with cholinergic receptor muscarinic (ChRM)-3 blocker reversed the progression of AHR in the neonatal exposure model, whereas β2-adrenoceptor agonists had no such effect. Together, our findings demonstrate a functional relationship between cholinergic neuroplasticity and ASM contractile phenotypes that operates uniquely in early life to induce persistent AHR after allergen exposure. Targeting ChRM3 may have disease-modifying benefits in childhood asthma.-Patel, K. R., Bai, Y., Trieu, K. G., Barrios, J., Ai, X. Targeting acetylcholine receptor M3 prevents the progression of airway hyperreactivity in a mouse model of childhood asthma.

Effects of air pollutants on upper airway disease

PURPOSE OF REVIEW

We discuss the effects of air pollutants on upper airway disease; the topic has hitherto received little attention.

RECENT FINDINGS

Several epidemiological studies have shown that air pollutants aggravate airway diseases including asthma, bronchitis, and chronic obstructive pulmonary disorder. Pollutants also have negative effects on other upper airway diseases such as allergic and nonallergic rhinitis, sinusitis, and otitis media. Traffic-related air pollutants (diesel exhaust particles and nitrogen dioxide and tobacco smoke) have been widely studied in this context. Increasing evidence suggests that particulate matter, photochemical pollutants, and ozone are associated with such conditions. Young children and the obese are more vulnerable. Work in vivo and in vitro has explored the relationships between pollutants and disease, and possible pathophysiological mechanisms. Reactive oxygen species, apoptosis, and inflammation are all in play.

SUMMARY

Traffic-derived materials and tobacco smoke are major air pollutants that aggravate upper airway disease. Novel mechanisms of action have been suggested and risk factors have been defined. However, the data are conflicting, and controlled prospective studies are required.

Ozone-Induced Type 2 Immunity in Nasal Airways. Development and Lymphoid Cell Dependence in Mice

Inhalation exposures to ozone commonly encountered in photochemical smog cause airway injury and inflammation. Elevated ambient ozone concentrations have been epidemiologically associated with nasal airway activation of neutrophils and eosinophils. In the present study, we elucidated the temporal onset and lymphoid cell dependency of eosinophilic rhinitis and associated epithelial changes in mice repeatedly exposed to ozone. Lymphoid cell-sufficient C57BL/6 mice were exposed to 0 or 0.5 parts per million (ppm) ozone for 1, 2, 4, or 9 consecutive weekdays (4 h/d). Lymphoid cell-deficient, Rag2(-/-)Il2rg(-/-) mice were similarly exposed for 9 weekdays. Nasal tissues were taken at 2 or 24 hours after exposure for morphometric and gene expression analyses. C57BL/6 mice exposed to ozone for 1 day had acute neutrophilic rhinitis, with airway epithelial necrosis and overexpression of mucosal Ccl2 (MCP-1), Ccl11 (eotaxin), Cxcl1 (KC), Cxcl2 (MIP-2), Hmox1, Il1b, Il5, Il6, Il13, and Tnf mRNA. In contrast, 9-day ozone exposure elicited type 2 immune responses in C57BL/6 mice, with mucosal mRNA overexpression of Arg1, Ccl8 (MCP-2), Ccl11, Chil4 (Ym2), Clca1 (Gob5), Il5, Il10, and Il13; increased density of mucosal eosinophils; and nasal epithelial remodeling (e.g., hyperplasia/hypertrophy, mucous cell metaplasia, hyalinosis, and increased YM1/YM2 proteins). Rag2(-/-)Il2rg(-/-) mice exposed to ozone for 9 days, however, had no nasal pathology or overexpression of transcripts related to type 2 immunity. These results provide a plausible paradigm for the activation of eosinophilic inflammation and type 2 immunity found in the nasal airways of nonatopic individuals subjected to episodic exposures to high ambient ozone.

Neural Abnormalities in Nonallergic Rhinitis

Sensory nerve endings within the airway epithelial cells and the solitary chemoreceptor cells, synapsing with sensory nerves, respond to airborne irritants. Transient receptor potential (TRP) channels (A1 and V1 subtypes, specifically) on these nerve endings initiate local antidromic reflexes resulting in the release of neuropeptides such as substance P and calcitonin G-related peptides. These neuropeptides dilate epithelial submucosal blood vessels and may therefore increase transudation across these vessels resulting in submucosal edema, congestion, and rhinitis. Altered expression or activity of these TRP channels can therefore influence responsiveness to irritants. Besides these pathogenic mechanisms, additional mechanisms such as dysautonomia resulting in diminished sympathetic activity and comparative parasympathetic overactivity have also been suggested as a probable mechanism. Therapeutic effectiveness for this condition has been demonstrated through desensitization of TRPV1 channels with typical agonists such as capsaicin. Other agents effective in treating nonallergic rhinitis (NAR) such as azelastine have been demonstrated to exhibit TRPV1 channel activity through the modulation of Ca(2+) signaling on sensory neurons and in nasal epithelial cells. Roles of antimuscarinic agents such as tiotropium in NAR have been suggested by associations of muscarinic cholinergic receptors with TRPV1. The associations between these channels have also been suggested as mechanisms of airway hyperreactivity in asthma. The concept of the united airway disease hypothesis suggests a significant association between rhinitis and asthma. This concept is supported by the development of late-onset asthma in about 10-40 % of NAR patients who also exhibit a greater severity in their asthma. The factors and mechanisms associating NAR with nonallergic asthma are currently unknown. Nonetheless, free immunoglobulin light chains and microRNA alteration as mediators of these inflammatory conditions may play key roles in this association.

Ambient ozone and emergency department visits due to lower respiratory condition

OBJECTIVES

Ambient ozone (O3) exposure is associated with a variety of health conditions. The objective of this study was to examine the effect of increased daily concentrations of ozone on emergency department (ED) visits due to lower respiratory diseases (LRD), such as acute or chronic bronchitis, in Edmonton, Canada.

MATERIALS AND METHODS

Data concerning 10 years (1992-2002) were obtained from 5 Edmonton hospital Emergency Departments. Odds ratios (ORs) for ED visits associated with the increased ozone levels were calculated employing a case-crossover technique with a time-stratified strategy to define controls. In the constructed conditional logistic regression models, adjustments were made for daily number of influenza ED visits and weather variables using natural splines. ORs and their 95% confidence intervals (95% CI) were reported in relation to an increase in the interquartile range (IQR = 17.9 ppb) of the ground-level ozone.

RESULTS

Overall, 48 252 ED visits due to LRD were identified, of which 53% were made by males. The presentations peaked in December (12%) and February (11.7%) and were the lowest in August (5.6%). Positive and statistically significant results were obtained for acute bronchitis: for same day (OR = 1.09, 95% CI: 1.05-1.13, lag 0) and for lag 2, lag 3-7 and 9 days; for chronic bronchitis: for lag 6, 7, and lag 9 days (OR = 1.11, 95% CI: 1.05-1.18, lag 9). For all ED visits for LRD, lag 0, lag 1, and lag 3-9 days showed positive and statistically significant associations (OR = 1.06, 95% CI: 1.03-1.09, lag 0).

CONCLUSIONS

These findings support the hypothesis concerning positive associations between ozone and the ED visits due to LRD.

Effects of prenatal community violence and ambient air pollution on childhood wheeze in an urban population

BACKGROUND

Prenatal exposures to stress and physical toxins influence children's respiratory health, although few studies consider these factors together.

OBJECTIVES

We sought to concurrently examine the effects of prenatal community-level psychosocial (exposure to community violence [ECV]) and physical (air pollution) stressors on repeated wheeze in 708 urban children followed to age 2 years.

METHODS

Multi-item ECV reported by mothers in pregnancy was summarized into a continuous score by using Rasch modeling. Prenatal black carbon exposure was estimated by using land-use regression (LUR) modeling; particulate matter with a diameter of less than 2.5 μm (PM2.5) was estimated by using LUR modeling incorporating satellite data. Mothers reported child's wheeze every 3 months. The effects of ECV and air pollutants on repeated wheeze (≥ 2 episodes) were examined by using logistic regression. Interactions between ECV and pollutants were examined.

RESULTS

Mothers were primarily black (29%) and Hispanic (55%), with lower education (62% with ≤ 12 years); 87 (12%) children wheezed repeatedly. In models examining concurrent exposures, ECV (odds ratio [OR], 1.95; 95% CI, 1.13-3.36; highest vs lowest tertile) and black carbon (OR, 1.84; 95% CI, 1.08-3.12; median or greater vs less than median) were independently associated with wheeze adjusting for sex, birth season, maternal atopy, education, race, and cockroach antigen. Associations were similar for PM2.5 (adjusted OR, 2.02; 95% CI, 1.20-3.40). An interaction between ECV with air pollution levels was suggested.

CONCLUSIONS

These findings suggest that both prenatal community violence and air pollution can contribute to respiratory health in these urban children. Moreover, place-based psychosocial stressors might affect host resistance such that physical pollutants can have adverse effects, even at relatively lower levels.

Programming of respiratory health in childhood: influence of outdoor air pollution

PURPOSE OF REVIEW

This overview highlights recent experimental and epidemiological evidence for the programming effects of outdoor air pollution exposures during early development on lung function and chronic respiratory disorders, such as asthma and related allergic disorders.

RECENT FINDINGS

Air pollutants may impact anatomy and/or physiological functioning of the lung and interrelated systems. Programming effects may result from pollutant-induced shifts in a number of molecular, cellular, and physiological states and their interacting systems. Specific key regulatory systems susceptible to programming may influence lung development and vulnerability to respiratory diseases, including both central and peripheral components of neuroendocrine pathways and autonomic nervous system (ANS) functioning which, in turn, influence the immune system. Starting in utero, environmental factors, including air pollutants, may permanently organize these systems toward trajectories of enhanced pediatric (e.g., asthma, allergy) as well as adult disease risk (e.g., chronic obstructive pulmonary disease). Evidence supports a central role of oxidative stress in the toxic effects of air pollution. Additional research suggests xenobiotic metabolism and subcellular components, such as mitochondria are targets of ambient air pollution and play a role in asthma and allergy programming. Mechanisms operating at the level of the placenta are being elucidated. Epigenetic mechanisms may be at the roots of adaptive developmental programming.

SUMMARY

Optimal coordinated functioning of many complex processes and their networks of interaction are necessary for normal lung development and the maintenance of respiratory health. Outdoor air pollution may play an important role in early programming of respiratory health and is potentially amenable to intervention.