Lung epithelial permeability and bronchial responsiveness in subjects with stable asthma

Proteomic and metabolomic proof of concept for unified airways in chronic rhinosinusitis and asthma

BACKGROUND

The pathogenesis of chronic rhinosinusitis with nasal polyps (CRSwNP) with comorbid asthma remains unclear.

OBJECTIVE

To assess upper and lower airway unity and identify a possible common pathogenesis in CRSwNP with asthma.

METHODS

This study analyzed the expression of proteins and metabolites in nasal lavage fluid cells (NLFCs) and induced sputum cells (ISCs). Differentially expressed proteins and their function-related metabolites in the upper and lower airways of patients having CRSwNP with or without asthma were identified; relevant signaling pathways were analyzed, and key pathway-related proteins were identified. Parallel reaction monitoring was used to verify these target proteins.

RESULTS

Protein or metabolite expression between NLFCs and ISCs was highly correlated and conservative on the basis of expression profiles and weighted gene coexpression network analysis. There were 17 differentially coexpressed proteins and their function-related 13 metabolites that were identified in the NLFCs and ISCs of CRSwNP, whereas 11 proteins and 11 metabolites were identified in CRSwNP with asthma. An asthma pathway was involved in the copathogenesis of upper and lower airways in whether CRSwNP or CRSwNP with asthma. The asthma pathway-related proteins proteoglycan 2 and eosinophil peroxidase, as the core of the protein-metabolism interaction networks between the upper and lower airways, were both highly coexpressed in NLFCs and ISCs in patients having either CRSwNP or CRSwNP with asthma by parallel reaction monitoring validation.

CONCLUSION

Proteomics and metabolomics reveal upper and lower airway unity. Asthma pathway-related proteins proteoglycan 2 and eosinophil peroxidase from the upper airway could be used to assess the potential risk of lower airway dysfunction in CRSwNP.

Effects of Oxidative Stress on Airway Epithelium Permeability in Asthma and Potential Implications for Patients with Comorbid Obesity

20 million adults and 4.2 million children in the United States have asthma, a disease resulting in inflammation and airway obstruction in response to various factors, including allergens and pollutants and nonallergic triggers. Obesity, another highly prevalent disease in the US, is a major risk factor for asthma and a significant cause of oxidative stress throughout the body. People with asthma and comorbid obesity are susceptible to developing severe asthma that cannot be sufficiently controlled with current treatments. More research is needed to understand how asthma pathobiology is affected when the patient has comorbid obesity. Because the airway epithelium directly interacts with the outside environment and interacts closely with the immune system, understanding how the airway epithelium of patients with asthma and comorbid obesity is altered compared to that of lean asthma patients will be crucial for developing more effective treatments. In this review, we discuss how oxidative stress plays a role in two chronic inflammatory diseases, obesity and asthma, and propose a mechanism for how these conditions may compromise the airway epithelium.

Epithelial barriers in allergy and asthma

The respiratory epithelium provides a physical, functional, and immunologic barrier to protect the host from the potential harming effects of inhaled environmental particles and to guarantee maintenance of a healthy state of the host. When compromised, activation of immune/inflammatory responses against exogenous allergens, microbial substances, and pollutants might occur, rendering individuals prone to develop chronic inflammation as seen in allergic rhinitis, chronic rhinosinusitis, and asthma. The airway epithelium in asthma and upper airway diseases is dysfunctional due to disturbed tight junction formation. By putting the epithelial barrier to the forefront of the pathophysiology of airway inflammation, different approaches to diagnose and target epithelial barrier defects are currently being developed. Using single-cell transcriptomics, novel epithelial cell types are being unraveled that might play a role in chronicity of respiratory diseases. We here review and discuss the current understandings of epithelial barrier defects in type 2-driven chronic inflammation of the upper and lower airways, the estimated contribution of these novel identified epithelial cells to disease, and the current clinical challenges in relation to diagnosis and treatment of allergic rhinitis, chronic rhinosinusitis, and asthma.

Airways exudation of plasma macromolecules: Innate defense, epithelial regeneration, and asthma

This review discusses in vivo airway aspects of plasma exudation in relation to current views on epithelial permeability and epithelial regeneration in health and disease. Microvascular-epithelial exudation of bulk plasma proteins characteristically occurs in asthmatic patients, being especially pronounced in those with severe and exacerbating asthma. Healthy human and guinea pig airways challenged by noninjurious histamine-leukotriene–type autacoids also respond through prompt mucosal exudation of nonsieved plasma macromolecules. Contrary to current beliefs, epithelial permeability in the opposite direction (ie, absorption of inhaled molecules) has not been increased in patients with asthma and allergic rhinitis or in acutely exuding healthy airways. A slightly increased subepithelial hydrostatic pressure produces such unidirectional outward perviousness to macromolecules. Lack of increased absorption permeability in asthmatic patients can further be reconciled with occurrence of epithelial shedding, leaving small patches of denuded basement membrane. Counteracting escalating barrier breaks, plasma exudation promptly covers the denuded patches. Here it creates and sustains a biologically active barrier involving a neutrophil-rich, fibrin-fibronectin net. Furthermore, in the plasma-derived milieu, all epithelial cell types bordering the denuded patch dedifferentiate and migrate from all sides to cover the denuded basement membrane. However, this speedy epithelial regeneration can come at a cost. Guinea pig in vivo studies demonstrate that patches of epithelial denudation regeneration are exudation hot spots evoking asthma-like features, including recruitment/activation of granulocytes, proliferation of fibrocytes/smooth muscle cells, and basement membrane thickening. In conclusion, nonsieved plasma macromolecules can operate on the intact airway mucosa as potent components of first-line innate immunity responses. Exuded plasma also takes center stage in epithelial regeneration. When exaggerated, epithelial regeneration can contribute to the inception and development of asthma.

The endogenous cannabinoid anandamide increases human airway epithelial cell permeability through an arachidonic acid metabolite

Injury to the bronchial epithelium in respiratory diseases such as asthma and COPD results in the loss of barrier function and an elevated sensitivity to environmental insults. An increased release of the endogenous cannabinoid, anandamide in response to inhalation of allergen in asthmatic patients has been reported. The aim of this study was, therefore, to determine the effects of endocannabinoids on bronchial epithelial cell permeability and to investigate the mechanisms involved. Calu-3 human bronchial epithelial cells were cultured at air-liquid interface to allow development of tight junctions. Changes in Transepithelial Electrical Resistance (TEER), a reflection of epithelial permeability, were measured at various time points post-treatment, and expression of the tight junction proteins, occludin and ZO-1, were determined using Western immunoblotting. Anandamide produced a significant reduction in TEER, which was unaffected by cannabinoid receptor antagonists, but attenuated by URB597, an inhibitor of fatty acid amide hydrolase, and by a combination of cyclooxygenase (COX) and lipoxygenase (LOX) blockade. The anandamide metabolite, arachidonic acid, showed similar TEER decrease that was also prevented in the presence of COX and LOX inhibitor. Expression of occludin and ZO-1 were also reduced by anandamide. These findings indicate a pro-inflammatory-like effect of anandamide on bronchial epithelial permeability, mediated by cyclooxygenase and lipoxygenase metabolites, and suggest that inhibition of anandamide degradation might provide a novel approach to treat airway inflammation.

The role of Tc-99m DTPA aerosol scintigraphy in the differential diagnosis of COPD and asthma

OBJECTIVE

Chronic obstructive lung disease (COPD) and asthma are characterized as similar to each other in causing airway obstruction and being an inflammatory process. The purpose of this study was to investigate whether technetium-99m diethylenetriaminepentaacetic acid ((99m) Tc-DTPA) aerosol scintigraphy could be used in the differential diagnosis of asthma and COPD.

METHODS

Eighty-four patients (male/female: 32/52; mean age 50.2 ± 12.7 years) with obstructive lung disease and 30 healthy volunteers as the control group were enrolled in the study. The patients were divided into two groups as COPD and asthma and also smoking subgroups. Alveolar clearance study was performed using a radiolabeled aerosol of (99m) Tc-DTPA. Mucociliary clearance was evaluated with T½ , cap value and penetration index parameters. All patient underwent pulmonary function tests and Forced expiratory volume (FEV1 ), forced vital capacity (FVC) and FEV1 /FVC parameters were obtained.

RESULTS

The mean of T½ values of (99m) Tc-DTPA aerosol and FEV1 /FVC value among spirometric tests of the nonsmoking COPD patients were significantly lower than nonsmoking asthma patients (46.1 ± 14.3, 62.3 ± 18.7, P = 0.02; 65.2 ± 10.8, 81.4 ± 16.5, P = 0.04, respectively). The cap value was significantly higher in nonsmoking COPD patients (1.21 ± 0.49, 0.76 ± 0.22, P = 0.03). While there were no statistically and significantly different between control and asthmatic groups at the scintigraphic parameters and spirometric parameters, the mean of T½ values, cap value and spirometric parameters were statistically different between control and COPD groups (P < 0.05).

CONCLUSION

We showed that assessment of mucociliary permeability with (99m) Tc-DTPA aerosol scintigraphy was a useful, easy to apply and a noninvasive technique to use in the differential diagnosis of nonsmoker COPD and asthma.

Fluticasone Induces Epithelial Injury and Alters Barrier Function in Normal Subjects

Objective

The airway epithelium has a number of roles pivotal to the pathogenesis of asthma, including provision of a physical and immune barrier to the inhaled environment. Dysregulated injury and repair responses in asthma result in loss of airway epithelial integrity. Inhaled corticosteroids are a corner stone of asthma treatment. While effective in controlling asthma symptoms, they fail to prevent airway remodeling. Direct cytopathic effects on the airway epithelium may contribute to this.

Methods

This study examined the effects of a 4-week treatment regimen of inhaled fluticasone 500 μg twice daily in healthy human subjects. Induced sputum was collected for cell counts and markers of inflammation. Barrier function was examined by diethylenetriaminepentacetic acid (DTPA) clearance measured by nuclear scintillation scan, and albumin concentration in induced sputum.

Results

Steroid exposure resulted in epithelial injury as measured by a significant increase in the number of airway epithelial cells in induced sputum. There was no change in airway inflammation by induced sputum inflammatory cell counts or cytokine levels. Epithelial shedding was associated with an increase in barrier function, as measured by both a decrease in DTPA clearance and decreased albumin in induced sputum. This likely reflects the normal repair response.

Conclusion

Inhaled corticosteroids cause injury to normal airway epithelium. These effects warrant further evaluation in asthma, where the dysregulated repair response may contribute to airway remodeling.

AIR inhaled insulin versus subcutaneous insulin: pharmacokinetics, glucodynamics, and pulmonary function in asthma

OBJECTIVE

This study evaluated pharmacokinetic and glucodynamic responses to AIR inhaled insulin relative to subcutaneous insulin lispro, safety, pulmonary function, and effects of salbutamol coadministration.

RESEARCH DESIGN AND METHODS

Healthy, mildly asthmatic, and moderately asthmatic subjects (n = 13/group, aged 19-58 years, nonsmoking, and nondiabetic) completed this phase I, open-label, randomized, crossover euglycemic clamp study. Subjects received 12 units equivalent AIR insulin or 12 units subcutaneous insulin lispro or salbutamol plus AIR insulin (moderate asthma group only) before the clamp.

RESULTS

AIR insulin exposure was reduced 34 and 41% (both P < 0.01) in asthmatic subjects (area under the curve(0-t'), 24.0 and 21.1 nmol x min x l(-1) in mild and moderate asthma subjects, respectively) compared with healthy subjects (35.2 nmol x min x l(-1)), respectively. Glucodynamic (G) effects were similar in healthy and mildly asthmatic subjects (G(tot) = 38.7 and 23.4 g, respectively; P = 0.16) and were reduced in moderately asthmatic subjects (G(tot) = 10.7 g). Salbutamol pretreatment (moderately asthmatic subjects) improved bioavailability. AIR insulin had no discernable effect on pulmonary function. AIR insulin adverse events (cough, headache, and dizziness) were mild to moderate in intensity and have been previously reported or are typical of studies involving glucose clamp procedures.

CONCLUSIONS

This study suggests that pulmonary disease severity and asthma treatment status influence the metabolic effect of AIR insulin in individuals with asthma but do not affect AIR insulin pulmonary safety or tolerability. In view of the potential interactions between diabetes treatment and pulmonary status, it is prudent to await the results of ongoing clinical trials in diabetic patients with comorbid lung disease before considering the use of inhaled insulin in such patients.

Effect of ozone and nitrogen dioxide on the permeability of bronchial epithelial cell cultures of non-asthmatic and asthmatic subjects

BACKGROUND

Although epidemiological as well as in vivo exposure studies suggest that ozone (O3) and nitrogen dioxide (NO2) may play a role in airway diseases such as asthma, the underlying mechanisms are not clear.

OBJECTIVE

Our aim was to investigate the effect of O3 and NO2 on the permeability of human bronchial epithelial cell (HBEC) cultures obtained from non-atopic non-asthmatic (non-asthmatics) and atopic mild asthmatic (asthmatics) individuals.

METHODS

We cultured HBECs from bronchial biopsies of non-asthmatics and asthmatics, and exposed these for 6 h to air, 10 to 100 parts per billion (p.p.b.) O3, or to 100 to 400 p.p.b. NO2, and assessed changes in electrical resistance (ER) and movement of 14C-BSA across the cell cultures.

RESULTS

Although exposure to either O3 or NO2 did not alter the permeability of HBEC cultures of non-asthmatics, 10 to 100 p.p.b. O3 and 400 p.p.b. NO2 significantly decreased the ER of HBEC cultures of asthmatics, when compared with exposure to air. Additionally, 10, 50 and 100 p.p.b. O3 led to a significant increase in the movement of 14C-BSA across asthmatic HBEC cultures, after 6 h of exposure (medians = 1.73%; P < 0.01, 1.50%; P < 0.05 and 1.53%, P < 0.05, respectively), compared with air exposed cultures (median = 0.89%). Similarly, exposure for 6 h to both 200 and 400 p.p.b. NO2 significantly increased the movement of 14C-BSA across asthmatic HBEC cultures, when compared with air exposure. A comparison of data obtained from the two study groups demonstrated that 10 to 100 p.p.b. O3- and 200 to 400 p.p.b. NO2-induced epithelial permeability was greater in cultures of asthmatics compared with non-asthmatics.

CONCLUSION

These results suggest that HBECs of asthmatics may be more susceptible to the deleterious effects of these pollutants. Whether in patients with asthma the greater susceptibility of bronchial epithelial cells to O3 and NO2 contributes to the development of the disease, or is a secondary characteristic of this condition, remains to be determined.