Low dose of chlorine exposure exacerbates nasal and pulmonary allergic inflammation in mice

Effect of VAChT reduction on lung alterations induced by exposure to iron particles in an asthma model

INTRODUCTION

Pollution harms the health of people with asthma. The effect of the anti-inflammatory cholinergic pathway in chronic allergic inflammation associated to pollution is poorly understood.

METHODS

One hundred eight animals were divided into 18 groups (6 animals). Groups included: wild type mice (WT), genetically modified with reduced VAChT (VAChTKD), and those sensitized with ovalbumin (VAChTKDA), exposed to metal powder due to iron pelletizing in mining company (Local1) or 3.21 miles away from a mining company (Local2) in their locations for 2 weeks during summer and winter seasons. It was analyzed for hyperresponsivity, inflammation, remodeling, oxidative stress responses and the cholinergic system.

RESULTS

During summer, animals without changes in the cholinergic system revealed that Local1 exposure increased the hyperresponsiveness (%Rrs, %Raw), and inflammation (IL-17) relative to vivarium animals, while animals exposed to Local2 also exhibited elevated IL-17. During winter, animals without changes in the cholinergic system revealed that Local2 exposure increased the hyperresponsiveness (%Rrs) relative to vivarium animals. Comparing the exposure local of these animals during summer, animals exposed to Local1 showed elevated %Rrs, Raw, and IL-5 compared to Local 2, while in winter, Local2 exposure led to more IL-17 than Local1. Animals with VAChT attenuation displayed increased %Rrs, NFkappaB, IL-5, and IL-13 but reduced alpha-7 compared to animals without changes in the cholinergic system WT. Animals with VAChT attenuation and asthma showed increased the hyperresponsiveness, all inflammatory markers, remodeling and oxidative stress compared to animals without chronic lung inflammation. Exposure to Local1 exacerbated the hyperresponsiveness, oxidative stressand inflammation in animals with VAChT attenuation associated asthma, while Local2 exposure led to increased inflammation, remodeling and oxidative stress.

CONCLUSIONS

Reduced cholinergic signaling amplifies lung inflammation in a model of chronic allergic lung inflammation. Furthermore, when associated with pollution, it can aggravate specific responses related to inflammation, oxidative stress, and remodeling.

Dose and gender dependence of chlorine inhalation in a conscious ovine model

Characterization of the pathophysiology of ARDS following chlorine gas inhalation in clinically relevant translational large animal models is essential, as the opportunity for clinical trials in this type of trauma is extremely limited. To investigate Cl2 concentration and gender-dependent ARDS severity. Sheep (n = 54) were exposed to air or Cl2 premixed in air at a concentration of 50, 100, 200, and 300 ppm for 30 min under anesthesia/analgesia and monitored for an additional 48 h in a conscious state. Cardiopulmonary variables and survival endpoints were compared between male and female sheep. Overall there were no significant differences in the responses of female and male sheep except pulmonary oxygenation tended to be better in the male sheep (300 ppm group), and the pulmonary arterial pressure was lower (200 ppm group). The onset of mild ARDS (200 < PaO2/FiO2 ≤ 300) was observed at 36 h post exposure in the 50 ppm group, whereas the 100 ppm group developed mild and moderate (100 ≤ PaO2/FiO2 ≤ 200) ARDS by 12 and 36 h after injury, respectively. The 200 ppm and 300 ppm groups developed moderate ARDS within 6 and 3 h after injury, respectively. The 300 ppm group progressed to severe (PaO2/FiO2 ≤ 100) ARDS at 18 h after injury. Increases in pPeak and pPlateau were noted in all injured animals. Compared to sham, inhalation of 200 ppm and 300 ppm Cl2 significantly increased lung extravascular water content. The thoracic cavity fluid accumulation dose-dependently increased with the severity of trauma as compared to sham. At necropsy, the lungs were red, heavy, solidified, and fluid filled; the injury severity grew with increasing Cl2 concentration. The severity of ARDS and mortality rate directly correlated to inhaled Cl2 concentrations. No significant sex-dependent differences were found in measured endpoint variables.

Exposure to Sodium Hypochlorite or Cigarette Smoke Induces Lung Injury and Mechanical Impairment in Wistar Rats

Pulmonary irritants, such as cigarette smoke (CS) and sodium hypochlorite (NaClO), are associated to pulmonary diseases in cleaning workers. We examined whether their association affects lung mechanics and inflammation in Wistar rats. Exposure to these irritants alone induced alterations in the lung mechanics, inflammation, and remodeling. The CS increased airway cell infiltration, acid mucus production, MMP-12 expression, and alveolar enlargement. NaClO increased the number of eosinophils and macrophages in the bronchoalveolar lavage fluid, with cells expressing IL-13, MMP-12, MMP-9, TIMP-1, and iNOS in addition to increased IL-1β and TNF-α levels. Co-exposure to both irritants increased epithelial and smooth muscle cell area, acid mucus production, and IL-13 expression in the airways, while it reduced the lung inflammation. In conclusion, the co-exposure of CS with NaClO reduced the pulmonary inflammation, but increased the acidity of mucus, which may protect lungs from more injury. A cross-resistance in people exposed to multiple lung irritants should also be considered.

CTNNAL1 participates in the regulation of mucus overproduction in HDM‐induced asthma mouse model through the YAP‐ROCK2 pathway

Our previous study indicated that adhesion molecule catenin alpha‐like 1(CTNNAL1) is downregulated in airway epithelial cells of asthma patients and asthma animal model but little is known about how the CTNNAL1 affects asthma pathogenesis. To reveal the direct relationship between asthma and CTNNAL1, CTNNAL1‐deficient mouse model in bronchopulmonary tissue was constructed by introducing CTNNAL1‐siRNA sequence using adeno‐associated virus (AAV) as vector. The mouse model of asthma was established by stimulation of house dust mite (HDM). After HDM‐challenged, there was marked airway inflammation, especially mucus hypersecretion in the CTNNAL1‐deficient mice. In addition, the CTNNAL1‐deficient mice exhibited an increase of lung IL‐4 and IL‐13 levels, as well as a significant increase of goblet cell hyperplasia and MUC5AC after HDM exposure. The expression of Yes‐associated protein (YAP), protein that interacted with α‐catenin, was downregulated after CTNNAL1 silencing and was upregulated due to its overexpression. In addition, the interaction between CTNNAL1 and YAP was confirmed by CO‐IP. Besides, inhibition of YAP could decrease the secretion of MUC5AC, IL‐4 and IL‐13 in CTNNAL1‐deficient 16HBE14o‐cells. Above results indicated us that CTNNAL1 regulated mucus hypersecretion through YAP pathway. In addition, the expression of ROCK2 increased when CTNNAL1 was silenced and decreased after YAP silencing, and inhibition of YAP decreased the expression of ROCK2 in CTNNAL1‐deficient HBE cells. Inhibition of ROCK2 decreased MUC5AC expression and IL‐13 secretion. In all, our study demonstrates that CTNNAL1 plays an important role in HDM‐induced asthma, mediating mucus secretion through the YAP‐ROCK2 pathway.

Differential Regulation of the Asthmatic Phenotype by the Aryl Hydrocarbon Receptor

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that regulates the metabolism of xenobiotics. There is growing evidence that the AhR is implicated in physiological processes such proliferation, differentiation, and immune responses. Recently, a role of the AhR in regulating allergic asthma has been suggested, but whether the AhR also regulates other type of asthma, particularly occupational/irritant-induced asthma, remains unknown. Using AhR-deficient (Ahr^−/−) mice, we compared the function of the AhR in the response to ovalbumin (OVA; allergic asthma) vs. chlorine (Cl₂; irritant-induced asthma) exposure. Lung inflammation and airway hyperresponsiveness were assessed 24h after exposure to Cl₂ or OVA challenge in Ahr^−/− and heterozygous (Ahr^+/−) mice. After OVA challenge, absence of AhR was associated with significantly enhanced eosinophilia and lymphocyte influx into the airways of Ahr^−/− mice. There were also increased levels of interleukin-4 (IL-4) and IL-5 in the airways. However, OVA-induced airway hyperresponsiveness was not affected. In the irritant-induced asthma model caused by exposure to Cl₂, the AhR did not regulate the inflammatory response. However, absence of AhR reduced Cl₂-induced airway hyperresponsiveness. Collectively, these results support a differential role for the AhR in regulating asthma outcomes in response to diverse etiological agents.

Respiratory symptoms of exposure to substances in the workplace among Bulgarian dentists

OBJECTIVES

Dentists are exposed to a variety of airborne chemicals that can act as irritants and sensitizers and may give rise to work-related respiratory symptoms. The aim of this study was to estimate the prevalence of respiratory symptoms of exposure to substances in the workplace and associated risk factors in Bulgarian dentists.

METHODS

A cross-sectional study was performed among Bulgarian dentists by using a self-report questionnaire. A direct acyclic graph (DAG) was elaborated to illustrate the direct and indirect causal pathways between exposure to irritants and/or allergens from dental environment and work-related respiratory symptoms among dentists. Multiple logistic regression analysis was conducted in order to investigate the relationship between sex, work experience, daily exposure to chemicals from dental environment, history of atopic disorder and work-related respiratory symptoms.

RESULTS

A total of 4675 dentists completed the questionnaire (response rate 48.1%). The prevalence of self-reported work-related respiratory symptoms was 20.7%. The most common repeated causes of respiratory reactions were disinfectants (65.7%) and materials based on acrylic resins (29.7%). Factors associated with work-related respiratory symptoms are personal history of asthma (odds ratio (OR) 2.50, 95% confidence interval [CI]: 1.71-3.64), work experience >20 years (OR 2.17, 95% CI: 1.74-2.70) and female gender (OR 2.14, 95% CI: 1.81-2.56).

CONCLUSION

Work-related respiratory symptoms are frequent among dentists and indicate a need for efforts to establish effective programmes and techniques of reducing or eliminating direct exposure to airborne chemicals in the dental environment.

Are asthmatics more sensitive to irritants?

Asthma is a heterogeneous inflammatory disease characterized by increased airway hyper-responsiveness to external stimuli such as irritants. One may speculate that asthmatics are more sensitive to irritants in the air than healthy subjects, i.e. react at lower concentrations. We reviewed the scientific support for this speculation and investigated to what extent asthma is considered when setting exposure limits and guidance values. We found that the experimental studies comparing healthy and asthmatic subjects are often inconclusive. Still, the available studies are underused, by expert committees and industry alike. Data for a few irritants suggest that asthmatics are up to three-fold more sensitive than the healthy. The most abundant data were found for sulfur dioxide. Here, a benchmark concentration analysis suggests a nine-fold difference in sensitivity. Based on these data a default assessment factor of 10 is suggested when setting exposure limits and guidance values for irritants.

Chronic exposure to diesel particles worsened emphysema and increased M2-like phenotype macrophages in a PPE-induced model

Chronic exposure to ambient levels of air pollution induces respiratory illness exacerbation by increasing inflammatory responses and apoptotic cells in pulmonary tissues. The ineffective phagocytosis of these apoptotic cells (efferocytosis) by macrophages has been considered an important factor in these pathological mechanisms. Depending on microenvironmental stimuli, macrophages can assume different phenotypes with different functional actions. M1 macrophages are recognized by their proinflammatory activity, whereas M2 macrophages play pivotal roles in responding to microorganisms and in efferocytosis to avoid the progression of inflammatory conditions. To verify how exposure to air pollutants interferes with macrophage polarization in emphysema development, we evaluated the different macrophage phenotypes in a PPE- induced model with the exposure to diesel exhaust particles. C57BL/6 mice received intranasal instillation of porcine pancreatic elastase (PPE) to induce emphysema, and the control groups received saline. Both groups were exposed to diesel exhaust particles or filtered air for 60 days according to the groups. We observed that both the diesel and PPE groups had an increase in alveolar enlargement, collagen and elastic fibers in the parenchyma and the number of macrophages, lymphocytes and epithelial cells in BAL, and these responses were exacerbated in animals that received PPE instillation prior to exposure to diesel exhaust particles. The same response pattern was found inCaspase-3 positive cell analysis, attesting to an increase in cell apoptosis, which is in agreement with the increase in M2 phenotype markers, measured by RT-PCR and flow cytometry analysis. We did not verify differences among the groups for the M1 phenotype. In conclusion, our results showed that both chronic exposure to diesel exhaust particles and PPE instillation induced inflammatory conditions, cell apoptosis and emphysema development, as well as an increase in M2 phenotype macrophages, and the combination of these two factors exacerbated these responses. The predominance of the M2-like phenotype likely occurred due to the increased demand for efferocytosis. However, M2 macrophage activity was ineffective, resulting in emphysema development and worsening of symptoms.

Toxic effects of chlorine gas and potential treatments: a literature review

Chlorine gas is one of the highly produced chemicals in the USA and around the world. Chlorine gas has several uses in water purification, sanitation, and industrial applications; however, it is a toxic inhalation hazard agent. Inhalation of chlorine gas, based on the concentration and duration of the exposure, causes a spectrum of symptoms, including but not limited to lacrimation, rhinorrhea, bronchospasm, cough, dyspnea, acute lung injury, death, and survivors develop signs of pulmonary fibrosis and reactive airway disease. Despite the use of chlorine gas as a chemical warfare agent since World War I and its known potential as an industrial hazard, there is no specific antidote. The resurgence of the use of chlorine gas as a chemical warfare agent in recent years has brought speculation of its use as weapons of mass destruction. Therefore, developing antidotes for chlorine gas-induced lung injuries remains the need of the hour. While some of the pre-clinical studies have made substantial progress in the understanding of chlorine gas-induced pulmonary pathophysiology and identifying potential medical countermeasure(s), yet none of the drug candidates are approved by the U.S. Food and Drug Administration (FDA). In this review, we summarized pathophysiology of chlorine gas-induced pulmonary injuries, pre-clinical animal models, development of a pipeline of potential medical countermeasures under FDA animal rule, and future directions for the development of antidotes for chlorine gas-induced lung injuries.