Modelling the asthma phenotype: impact of cigarette smoke exposure

Neutrophils and Asthma

Although eosinophilic inflammation is characteristic of asthma pathogenesis, neutrophilic inflammation is also marked, and eosinophils and neutrophils can coexist in some cases. Based on the proportion of sputum cell differentiation, asthma is classified into eosinophilic asthma, neutrophilic asthma, neutrophilic and eosinophilic asthma, and paucigranulocytic asthma. Classification by bronchoalveolar lavage is also performed. Eosinophilic asthma accounts for most severe asthma cases, but neutrophilic asthma or a mixture of the two types can also present a severe phenotype. Biomarkers for the diagnosis of neutrophilic asthma include sputum neutrophils, blood neutrophils, chitinase-3-like protein, and hydrogen sulfide in sputum and serum. Thymic stromal lymphoprotein (TSLP)/T-helper 17 pathways, bacterial colonization/microbiome, neutrophil extracellular traps, and activation of nucleotide-binding oligomerization domain-like receptor family, pyrin domain-containing 3 pathways are involved in the pathophysiology of neutrophilic asthma and coexistence of obesity, gastroesophageal reflux disease, and habitual cigarette smoking have been associated with its pathogenesis. Thus, targeting neutrophilic asthma is important. Smoking cessation, neutrophil-targeting treatments, and biologics have been tested as treatments for severe asthma, but most clinical studies have not focused on neutrophilic asthma. Phosphodiesterase inhibitors, anti-TSLP antibodies, azithromycin, and anti-cholinergic agents are promising drugs for neutrophilic asthma. However, clinical research targeting neutrophilic inflammation is required to elucidate the optimal treatment.

Differential effects of dexamethasone and roflumilast on asthma in mice with or without short cigarette smoke exposure

Appropriate drug treatment for smoking asthmatics is uncertain because most smokers with asthma are less sensitive to treatment with glucocorticoids compared with non-smokers with asthma. We hypothesized that roflumilast (Rof), a selective phosphodiesterases-4 inhibitor regarded as an add-on therapy for chronic obstructive pulmonary disease, might be more effective than glucocorticoids for improving asthma in smokers. To investigate this hypothesis, we compared the therapeutic effects of dexamethasone (Dex) and Rof in a mouse model of ovalbumin-induced asthma with or without concurrent cigarette smoke (CS) exposure for 2 weeks. We found that recurrent asthma attacks increased lung tissue resistance. CS exposure in asthmatic mice decreased the central airway resistance, increased lung compliance, and attenuated airway hyper-responsiveness (AHR). CS exposure in asthmatic mice also increased the number of neutrophils and macrophages in the bronchoalveolar fluid. Treatment with Dex in asthmatic mice without CS exposure reduced airway resistance, AHR and airway eosinophilia. In asthmatic mice with CS exposure, however, Dex treatment unexpectedly increased lung tissue resistance and restored AHR that had been otherwise suppressed. Dex treatment in asthmatic mice with CS exposure inhibited eosinophilic inflammation but conversely exacerbated neutrophilic inflammation. On the other hand, treatment with Rof in asthmatic mice without CS exposure reduced airway resistance and airway eosinophilia, although the inhibitory effect of Rof on AHR was unremarkable. In asthmatic mice with CS exposure, Rof treatment did not exacerbate lung tissue resistance but modestly restored AHR, without any significant effects on airway inflammation. These results suggest that CS exposure mitigates sensitivity to both Dex and Rof. In asthmatic mice with CS exposure, Dex is still effective in reducing eosinophilic inflammation but increases lung tissue resistance, AHR and neutrophilic inflammation. Rof is ineffective in improving lung function and inflammation in asthmatic mice with CS exposure. This study did not support our initial hypothesis that Rof might be more effective than glucocorticoids for improving asthma in smokers. However, glucocorticoids may have a detrimental effect on smoking asthmatics.

Different Phenotypes in Asthma: Clinical Findings and Experimental Animal Models

Asthma is a respiratory allergic disease presenting a high prevalence worldwide, and it is responsible for several complications throughout life, including death. Fortunately, asthma is no longer recognized as a unique manifestation but as a very heterogenic manifestation. Its phenotypes and endotypes are known, respectively, as pathologic and molecular features that might not be directly associated with each other. The increasing number of studies covering this issue has brought significant insights and knowledge that are constantly expanding. In this review, we intended to summarize this new information obtained from clinical studies, which not only allowed for the creation of patient clusters by means of personalized medicine and a deeper molecular evaluation, but also created a connection with data obtained from experimental models, especially murine models. We gathered information regarding sensitization and trigger and emphasizing the most relevant phenotypes and endotypes, such as Th2-^high asthma and Th2-^low asthma, which included smoking and obesity-related asthma and mixed and paucigranulocytic asthma, not only in physiopathology and the clinic but also in how these phenotypes can be determined with relative similarity using murine models. We also further investigated how clinical studies have been treating patients using newly developed drugs focusing on specific biomarkers that are more relevant according to the patient's clinical manifestation of the disease.

CpG oligodeoxynucleotides attenuate RORγt-mediated Th17 response by restoring histone deacetylase-2 in cigarette smoke-exposure asthma

BACKGROUND

Cigarette smoke (CS) exposure increases corticosteroid insensitive asthma related to increased Th17 phenotype, and new treatment strategies are needed for CS-associated asthma. Histone deacetylase 2 (HDAC2), found in the airway epithelium, is critical for ameliorating glucocorticoids insensitivity. We recently demonstrated the anti-inflammatory effects of CpG oligodeoxynucleotides (CpG-ODNs) on CS-exposure asthma. However, the effects of CpG-ODNs on HDAC2 expression and enzymatic activity remain unclear. This study aimed to assess whether CpG-ODNs protect against excessive Th17 immune responses in CS-induced asthma through HDAC2-dependent mechanisms and compared their effects with those of corticosteroids.

METHODS

The effects of CpG-ODNs alone and in combination with budesonide (BUD) on airway inflammation and Th2/Th17-related airway immune responses were determined using an in vivo model of CS-induced asthma and in cultured bronchial epithelial (HBE) cells administered ovalbumin (OVA) and/or cigarette smoke extract (CSE). HDAC2 and retinoid-related orphan nuclear receptor γt (RORγt) expression were also assessed in mouse lung specimens and HBE cells.

RESULTS

CpG-ODNs and BUD synergistically attenuated CS exposure asthmatic responses in vivo by modulating the influx of eosinophils and neutrophils, airway remodeling, Th2/Th17 associated cytokine and chemokine production, and airway hyperresponsiveness and blocking RORγt-mediated Th17 inflammation through induced HDAC2 expression/activity. In vitro, CpG-ODNs synergized with BUD to inhibit Th17 cytokine production in OVA- and CSE-challenged HBE cells while suppressing RORγt and increasing epithelial HDAC2 expression/activity.

CONCLUSIONS

CpG-ODNs reversed CS-induced HDAC2 downregulation and enhanced the sensitivity of CS-exposed asthmatic mice and CSE-induced HBE cells to glucocorticoid treatment. This effect may be associated with HDAC2 restoration via RORγt/IL-17 pathway regulation, suggesting that CpG-ODNs are potential corticosteroid-sparing agents for use in CS-induced asthma with Th17-biased immune conditions.

Suppressive effect of environmental tobacco smoke on murine Th2 cell-mediated nasal eosinophilic inflammation

Background

Environmental tobacco smoke (ETS) exposure is recognized as a risk factor for the development of various respiratory diseases.

Objective

In this study, the effect of ETS on allergen-immunized and allergen-specific Th2 cell-transferred murine eosinophilic inflammation models and that of cigarette smoke extract (CSE) and nicotine on allergen-induced Th2 cell proliferation and interleukin (IL)-4 production were investigated.

Methods

Ovalbumin (OVA)-immunized and OVA-specific Th2 cell-transferred BALB/c mice were exposed to ETS and were challenged with OVA. Then, the number of inflammatory cells in the nasal mucosa and nasal hyperresponsiveness (NHR) were assessed. The effects of CSE and nicotine on the allergen-induced proliferative response of and IL-4 production by Th2 cells were determined in vitro.

Results

In OVA-immunized and Th2 cell-transferred mice, allergen-induced NHR and nasal eosinophil infiltration were significantly suppressed by ETS exposure, whereas the accumulation of neutrophils was rather enhanced. Allergen-specific Th2 cell proliferation and IL-4 production were inhibited by coculture with CSE. The same effects were induced by nicotine, though the effect on proliferation was relatively weak.

Conclusion

Regardless of its harmful effect, ETS suppresses NHR, probably through the inhibition of Th2 cell responses.

Tobacco smoking aggravates airway inflammation by upregulating endothelin-2 and activating the c-Jun amino terminal kinase pathway in asthma

BACKGROUND

Asthma is closely associated with tobacco smoking (TS) and is more difficult to effectively treat after exposure to TS.

OBJECTIVE

To observe the effects of TS on the expression of endothelin-2 (ET-2) and airway inflammation in asthmatic rats and to explore the related mechanisms.

METHODS

We established an animal model of asthma with ovalbumin (OVA)/Al(OH)₃ and subjected different animal groups to TS and/or dexamethasone/bosentan. The differences in the inflammatory cell infiltration, the pathological changes to the bronchial wall and the bronchial smooth muscle thickness, and the expression of ET-2, c-Jun amino terminal kinase (JNK1/2), malondialdehyde (MDA), and glutathione peroxidase (GSH) in the lung tissue and of interleukin (IL)-7 in bronchoalveolar lavage fluid (BALF) were assessed.

RESULTS

Exposure to TS or OVA caused an obvious increase in the inflammatory cells in the BALF over what was observed in the control group. In asthma models, the expression of ET-1, JNK1/2, MDA, and GSH in the lung tissues, as well as that of IL-17 in the BALF, was increased. After treatment with dexamethasone/bosentan, the expression of IL-17, JNK1/2, MDA, and GSH decreased compared to the smoking group; airway inflammation and the staining intensity in the lung tissue were also reduced.

CONCLUSION

TS exposure can clearly exacerbate airway inflammation in asthmatic rats, while bosentan can alleviate airway inflammation through regulation of the ET-2/JNK1/2 signalling pathway.

Danger in the vapor? ECMO for adolescents with status asthmaticus after vaping

Introduction: Electronic nicotine delivery systems (ENDS) use is on the rise in the adolescent and young adult populations, especially in the wake of sweet flavored ENDS solutions and youth-targeted marketing. While the extent of effect of ENDS use and aerosolized flavorings on airway epithelium is not known, there remains significant concern that use of ENDS adversely affects airway epithelial function, particularly in populations with asthma.Case Study: In this case series, we review two cases of adolescents with history of recent and past ENDS use and asthma who required veno-venous extracorporeal membrane oxygenation (VV-ECMO) for status asthmaticus in the year 2018.Results: Both patients experienced hypercarbic respiratory failure requiring VV-ECMO secondary to their status asthmaticus, with slow recovery on extensive bronchodilator and steroid regimens. They both recovered back to respiratory baseline and were counseled extensively on cessation of ENDS use.Conclusion: While direct causation by exposure to ENDS cannot be determined, exposure likely contributed to symptoms. Based on the severity of these cases and their potential relationship with ENDS use, we advocate for increased physician screening of adolescents for ENDS use, patient and parent education on the risks of use, and family cessation counseling.

The increase of asthma prevalence has levelled off and symptoms decreased in adults during 20 years from 1996 to 2016 in Helsinki, Finland

BACKGROUND

Mortality and hospitalization due to asthma have decreased in many European countries, but asthma symptoms still cause a lot of morbidity and costs.

OBJECTIVES

We evaluated prevalence trends of asthma, asthma symptoms and allergic rhinoconjunctivitis in adults aged 20-69 years during a 20-year period from 1996 to 2016 in the city of Helsinki, the capital of Finland.

METHODS

Three cross-sectional postal surveys were conducted in random population samples 10 years apart. In 1996, 2006 and 2016, a total of 6062 (response rate 75.9%), 2449 (61.9%) and 4026 subjects (50.3%) took part, respectively.

RESULTS

In all responders, the prevalence of physician-diagnosed asthma was 6.6% in 1996, 10% in 2006 and 10.9% in 2016. The prevalence increased from 1996 to 2006, but stabilized from 2006 to 2016, both in men and women and in smokers and non-smokers. The prevalence of current asthma (8.5% in 2006 and 8.8% in 2016) and of asthma with rhinoconjunctivitis (7.6% in 2006 and 7.5% in 2016) remained also at the same level. Allergic rhinoconjunctivitis decreased significantly from 2006 (42.7%) to 2016 (39.0%, p = 0.004). Those with physician diagnosed asthma reported significantly less symptoms in 2016 compared to 2006 and 1996, although there was no change in smoking habits or medication use. Young asthmatics (20-29 years) without rhinoconjunctivitis reported least symptoms.

CONCLUSION

Previously observed increase of physician-diagnosed asthma prevalence in adults seems to be levelling off in Helsinki, and patients have fewer symptoms than 20 years ago. In addition, allergic rhinoconjunctivitis is less frequent than 10 years earlier. (247 words).

Passive smoking induces pediatric asthma by affecting the balance of Treg/Th17 cells

BACKGROUND

We aimed to explore the effects of passive smoking on the severity of pediatric asthma and associated molecular mechanisms.

METHODS

A total of 378 children with asthma were assigned into four groups according to asthma severity (from grades I to IV). Univariate and multivariate regression analyses were used to analyze possible factors associated with asthma severity in children. Environmental tobacco smoke (ETS) exposure was measured via cotinine concentration in urine. Serum levels of immunoglobulin E (IgE) and cytokines were measured using allergen diagnostic and ELISA (enzyme-linked immunosorbent assay) kits. The percentage of T-regulatory (Treg) and T-helper type 17 (Th17) cells in peripheral blood mononuclear cells (PMBCs) were measured by flow cytometry. Treg- and Th17-associated transcription factors from PMBCs were measured by using ELISA kits.

RESULTS

The levels of ETS and serum IgE, and the duration and amounts of passive smoking were closely associated with asthma severity. Passive smoking significantly reduced the levels of FoxP3 (Forkhead/winged helix transcription factor) and tumor growth factor-β, which were associated with Treg cells, and increased the levels of interleukin-17A and interleukin-23, which were associated with Th17 cells. Meanwhile, passive smoking significantly reduced the ratio of Treg/Th17 cells (P < 0.05).

CONCLUSIONS

Passive smoking was closely associated with the severity of childhood asthma by affecting the balance of Treg/Th17 cells.