Glucocorticoids enhance airway epithelial barrier integrity

Olfactory Loss in Rhinosinusitis: Mechanisms of Loss and Recovery

Chronic rhinosinusitis (CRS) is a highly prevalent disease and up to 83% of CRS patients suffer from olfactory dysfunction (OD). Because OD is specifically seen in those CRS patients that present with a type 2 eosinophilic inflammation, it is believed that type 2 inflammatory mediators at the level of the olfactory epithelium are involved in the development of this olfactory loss. However, due to the difficulties in obtaining tissue from the olfactory epithelium, little is known about the true mechanisms of inflammatory OD. Thanks to the COVID-19 pandemic, interest in olfaction has been growing rapidly and several studies have been focusing on disease mechanisms of OD in inflammatory conditions. In this paper, we summarize the most recent data exploring the pathophysiological mechanisms underlying OD in CRS. We also review what is known about the potential capacity of olfactory recovery of the currently available treatments in those patients.

Airway remodelling in asthma and the epithelium: on the edge of a new era

Asthma is a chronic, heterogeneous disease of the airways, often characterised by structural changes known collectively as airway remodelling. In response to environmental insults, including pathogens, allergens and pollutants, the epithelium can initiate remodelling via an inflammatory cascade involving a variety of mediators that have downstream effects on both structural and immune cells. These mediators include the epithelial cytokines thymic stromal lymphopoietin, interleukin (IL)-33 and IL-25, which facilitate airway remodelling through cross-talk between epithelial cells and fibroblasts, and between mast cells and airway smooth muscle cells, as well as through signalling with immune cells such as macrophages. The epithelium can also initiate airway remodelling independently of inflammation in response to the mechanical stress present during bronchoconstriction. Furthermore, genetic and epigenetic alterations to epithelial components are believed to influence remodelling. Here, we review recent advances in our understanding of the roles of the epithelium and epithelial cytokines in driving airway remodelling, facilitated by developments in genetic sequencing and imaging techniques. We also explore how new and existing therapeutics that target the epithelium and epithelial cytokines could modify airway remodelling.

Tezepelumab: patient selection and place in therapy in severe asthma

Asthma is a disease characterised by heterogeneous and multifaceted airway inflammation. Despite the availability of effective treatments, a substantial percentage of patients with the type 2 (T2)-high, but mainly the T2-low, phenotype complain of persistent symptoms, airflow limitation, and poor response to treatments. Currently available biologicals target T2 cytokines, but no monoclonal antibodies or other specific therapeutic options are available for non-T2 asthma. However, targeted therapy against alarmins is radically changing this perspective. The development of alarmin-targeted therapies, of which tezepelumab (TZP) is the first example, may offer broad action on inflammatory pathways as well as an enhanced therapeutic effect on epithelial dysfunction. In this regard, TZP demonstrated positive results not only in patients with severe T2 asthma but also those with non-allergic, non-eosinophilic disease. Therefore, it is necessary to identify clinical features of patients who can benefit from an upstream targeted therapy such as anti-thymic stromal lymphopoietin. The aims of this narrative review are to understand the role of alarmins in asthma pathogenesis and epithelial dysfunction, examine the rationale underlying the indication of TZP treatment in severe asthma, summarise the results of clinical studies, and recognise the specific characteristics of patients potentially eligible for TZP treatment.

The effect of combining an inhaled corticosteroid and a long-acting muscarinic antagonist on human airway epithelial cells in vitro

BACKGROUND

Airway epithelial cells (AECs) are a major component of local airway immune responses. Direct effects of type 2 cytokines on AECs are implicated in type 2 asthma, which is driven by epithelial-derived cytokines and leads to airway obstruction. However, evidence suggests that restoring epithelial health may attenuate asthmatic features.

METHODS

We investigated the effects of passive sensitisation on IL-5, NF-κB, HDAC-2, ACh, and ChAT in human bronchial epithelial cells (HBEpCs) and the effects of fluticasone furoate (FF) and umeclidinium (UME) alone and in combination on these responses.

RESULTS

IL-5 and NF-κB levels were increased, and that of HDAC-2 reduced in sensitised HEBpCs. Pretreatment with FF reversed the effects of passive sensitisation by concentration-dependent reduction of IL-5, resulting in decreased NF-κB levels and restored HDAC-2 activity. Addition of UME enhanced these effects. Sensitized HEBpCs also exhibited higher ACh and ChAT levels. Pretreatment with UME significantly reduced ACh levels, and addition of FF caused a further small reduction.

CONCLUSION

This study confirmed that passive sensitisation of AECs results in an inflammatory response with increased levels of IL-5 and NF-κB, reduced levels of HDAC-2, and higher levels of ACh and ChAT compared to normal cells. Combining FF and UME was found to be more effective in reducing IL-5, NF-κB, and ACh and restoring HDAC-2 compared to the individual components. This finding supports adding a LAMA to established ICS/LABA treatment in asthma and suggests the possibility of using an ICS/LAMA combination when needed.

8-Bromo-cAMP attenuates human airway epithelial barrier disruption caused by titanium dioxide fine and nanoparticles

Titanium dioxide fine particles (TiO2-FPs) and nanoparticles (TiO2-NPs) are the most widely used whitening pigments worldwide. Inhalation of TiO2-FPs and TiO2-NPs can be harmful as it triggers toxicity in the airway epithelial cells. The airway epithelium serves as the respiratory system's first line of defense in which airway epithelial cells are significant targets of inhaled pathogens and environmental particles. Our group previously found that TiO2-NPs lead to a disrupted barrier in the polarized airway epithelial cells. However, the effect of TiO2-FPs on the respiratory epithelial barrier has not been examined closely. In this study, we aimed to compare the effects of TiO2-FPs and TiO2-NPs on the structure and function of the airway epithelial barrier. Additionally, we hypothesized that 8-Bromo-cAMP, a cyclic adenosine monophosphate (cAMP) derivative, would alleviate the disruptive effects of both TiO2-FPs and TiO2-NPs. We observed increased epithelial membrane permeability in both TiO2-FPs and TiO2-NPs after exposure to 16HBE cells. Immunofluorescent labeling showed that both particle sizes disrupted the structural integrity of airway epithelial tight junctions and adherens junctions. TiO2-FPs had a slightly more, but insignificant impact on the epithelial barrier disruption than TiO2-NPs. Treatment with 8-Bromo-cAMP significantly attenuated the barrier-disrupting impact of both TiO2-FPs and TiO2-NPs on cell monolayers. Our study demonstrates that both TiO2-FPs and TiO2-NPs cause comparable barrier disruption and suggests a protective role for cAMP signaling. The observed effects of TiO2-FPs and TiO2-NPs provide a necessary understanding for characterizing the pathways involved in the defensive role of the cAMP pathway on TiO2-induced airway barrier disruption.

Exercise-induced bronchoconstriction in elite athletes: a narrative review

Exercise-induced bronchoconstriction (EIB) is the most common chronic disease among elite athletes and when left untreated, can impact both respiratory health and sports performance. In recent years, there has been an increase in the awareness and detection of EIB in elite athletes. This narrative review aims to evaluate the risk, prevention, diagnosis, medication, and anti-doping policies of EIB in elite athletes, and to provide more references for athletes with EIB. The results showed that athletes of endurance, winter, and water sports generally have a higher prevalence of EIB than athletes of other sports. Adaptive warm-up before formal exercise and using heat exchange masks at low temperatures are effective ways for athletes to prevent EIB. For physicians, the exercise challenge test and eucapnic voluntary hyperpnea are the recommended diagnostic methods for EIB in athletes. The treatment of athletes with EIB is medication-based, such as inhaled corticosteroids and beta-2 agonists, but current anti-doping policies should be considered when used.

Electronic cigarette exposure disrupts airway epithelial barrier function and exacerbates viral infection

The use of electronic cigarettes (e-cigs), especially among teenagers, has reached alarming and epidemic levels, posing a significant threat to public health. However, the short- and long-term effects of vaping on the airway epithelial barrier are unclear. Airway epithelial cells are the forefront protectors from viruses and pathogens. They contain apical junctional complexes (AJCs), which include tight junctions (TJs) and adherens junctions (AJs) formed between adjacent cells. Previously, we reported respiratory syncytial virus (RSV) infection, the leading cause of acute lower respiratory infection-related hospitalization in children and high-risk adults, induces a "leaky airway" by disrupting the epithelial AJC structure and function. We hypothesized chemical components of e-cigs disrupt airway epithelial barrier and exacerbate RSV-induced airway barrier dysfunction. Using confluent human bronchial epithelial (16HBE) cells and well-differentiated normal human bronchial epithelial (NHBE) cells, we found that exposure to extract and aerosol e-cig nicotine caused a significant decrease in transepithelial electrical resistance (TEER) and the structure of the AJC even at noncytotoxic concentrations. Western blot analysis of 16HBE cells exposed to e-cig nicotine extract did not reveal significant changes in AJC proteins. Exposure to aerosolized e-cig cinnamon or menthol flavors also induced barrier disruption and aggravated nicotine-induced airway barrier dysfunction. Moreover, preexposure to nicotine aerosol increased RSV infection and the severity of RSV-induced airway barrier disruption. Our findings demonstrate that e-cig exposure disrupts the airway epithelial barrier and exacerbates RSV-induced damage. Knowledge gained from this study will provide awareness of adverse e-cig respiratory effects and positively impact the mitigation of e-cig epidemic.NEW & NOTEWORTHY Electronic cigarette (e-cig) use, especially in teens, is alarming and at epidemic proportions, threatening public health. Our study shows that e-cig nicotine exposure disrupts airway epithelial tight junctions and increases RSV-induced barrier dysfunction. Furthermore, exposure to aerosolized flavors exaggerates e-cig nicotine-induced airway barrier dysfunction. Our study confirms that individual and combined components of e-cigs deleteriously impact the airway barrier and that e-cig exposure increases susceptibility to viral infection.

Treatment Strategy of Uncontrolled Chronic Rhinosinusitis with Nasal Polyps: A Review of Recent Evidence

Chronic rhinosinusitis (CRS) is recognized as a heterogeneous disease with a wide range of clinical features, resulting in significant morbidity and cost to the healthcare system. While the phenotypic classification is determined by the presence or absence of nasal polyps and comorbidities, the endotype classification has been established based on molecular biomarkers or specific mechanisms. Research on CRS has now developed based on information based on three major endotypes: types 1, 2, and 3. Recently, biological therapies targeting type 2 inflammation have been clinically expanded and may be applied to other inflammatory endotypes in the future. The purpose of this review is to discuss the treatment options according to the type of CRS and summarize recent studies on new therapeutic approaches for patients with uncontrolled CRS with nasal polyps.

Epidermal growth factor receptor in asthma: A promising therapeutic target?

Activation of the epidermal growth factor receptor (EGFR) pathway is involved in the pathogenesis of asthma. Although decades of intensive research have focused on the role of EGFR in asthma, the specific mechanisms and pathways of EGFR signaling remain unclear. Various reports have indicated that inhibition of EGFR improves the pathological features in asthma models. However, extending these experimental findings to clinical applications is difficult. Several measures can be adopted to promote clinical application of EGFR inhibitors. This review focuses on the role of EGFR in the pathogenesis of asthma and the development of a potentially novel therapeutic target for asthma.

The Role of Defective Epithelial Barriers in Allergic Lung Disease and Asthma Development

The respiratory epithelium constitutes the physical barrier between the human body and the environment, thus providing functional and immunological protection. It is often exposed to allergens, microbial substances, pathogens, pollutants, and environmental toxins, which lead to dysregulation of the epithelial barrier and result in the chronic inflammation seen in allergic diseases and asthma. This epithelial barrier dysfunction results from the disturbed tight junction formation, which are multi-protein subunits that promote cell–cell adhesion and barrier integrity. The increasing interest and evidence of the role of impaired epithelial barrier function in allergy and asthma highlight the need for innovative approaches that can provide new knowledge in this area. Here, we review and discuss the current role and mechanism of epithelial barrier dysfunction in developing allergic diseases and the effect of current allergy therapies on epithelial barrier restoration.

Endotypes of chronic rhinosinusitis: Relationships to disease phenotypes, pathogenesis, clinical findings, and treatment approaches

Chronic rhinosinusitis (CRS) is a common clinical syndrome that produces significant morbidity and costs to our health system. The study of CRS has progressed from an era focused on phenotype to include endotype-based information. Phenotypic classification has identified clinical heterogeneity in CRS based on endoscopically observed features such as presence of nasal polyps, presence of comorbid or systemic diseases, and timing of disease onset. More recently, laboratory-based findings have established CRS endotype based upon specific mechanisms or molecular biomarkers. Understanding the basis of widespread heterogeneity in the manifestations of CRS is advanced by findings that the three main endotypes, Type 1, 2, and 3, orchestrate the expression of three distinct large sets of genes. The development and use of improved methods of endotyping disease in the clinic are ushering in an expansion of the use of biological therapies targeting Type 2 inflammation now and perhaps other inflammatory endotypes in the near future. The purpose of this review is to discuss the phenotypic and endotypic heterogeneity of CRS from the perspective of advancing the understanding of the pathogenesis and improvement of treatment approaches and outcomes.

Mometasone furoate and fluticasone furoate are equally effective in restoring nasal epithelial barrier dysfunction in allergic rhinitis

Tight junction defects (TJ) have been associated with a defective epithelial barrier function in allergic rhinitis (AR). Intranasal corticosteroids are potent drugs frequently used to treat AR and are shown to restore epithelial integrity by acting on TJs and by reducing type 2 cytokine production. However, the effect of different classes of intranasal corticosteroids on the epithelial barrier has not been studied. Therefore, we compared the effect of 2 intranasal corticosteroids, ie, fluticasone furoate (FF) and mometasone furoate (MF) on epithelial barrier function. Both FF and MF similarly increased trans-epithelial electrical resistance of primary nasal epithelial cell cultures from AR patients. In a house dust mite-induced allergic asthma mouse model, FF and MF had similar beneficial effects on fluorescein isothiocyanate-dextran 4 kDa mucosal permeability, eosinophilic infiltration and IL-13 levels. Both molecules increased mRNA expression of the TJ proteins occludin and zonula occludens-1, thereby restoring epithelial barrier function. Lastly, we showed that long-term FF treatment also increased expression of occludin in AR patients compared to controls. In conclusion, both FF and MF effectively restore epithelial barrier function by increasing expression of TJ proteins in AR patients.

Oxidative Stress Promotes Corticosteroid Insensitivity in Asthma and COPD

Corticosteroid insensitivity is a key characteristic of patients with severe asthma and COPD. These individuals experience greater pulmonary oxidative stress and inflammation, which contribute to diminished lung function and frequent exacerbations despite the often and prolonged use of systemic, high dose corticosteroids. Reactive oxygen and nitrogen species (RONS) promote corticosteroid insensitivity by disrupting glucocorticoid receptor (GR) signaling, leading to the sustained activation of pro-inflammatory pathways in immune and airway structural cells. Studies in asthma and COPD models suggest that corticosteroids need a balanced redox environment to be effective and to reduce airway inflammation. In this review, we discuss how oxidative stress contributes to corticosteroid insensitivity and the importance of optimizing endogenous antioxidant responses to enhance corticosteroid sensitivity. Future studies should aim to identify how antioxidant-based therapies can complement corticosteroids to reduce the need for prolonged high dose regimens in patients with severe asthma and COPD.

Budesonide repairs decreased barrier integrity of eosinophilic nasal polyp epithelial cells caused by PM2.5

BACKGROUND

Eosinophilic chronic rhinitis with nasal polyps (eos-CRSwNP) is a subtype of nasal polyps (NPs) characterized by severe type-2 inflammation and defective epithelial barrier function. The epithelial barrier plays important roles in the pathogenesis of NPs and type-2 inflammation. Particular matter 2.5 (PM2.5) are fine particles with a diameter less than 2.5 μm, containing a mixture of different components. Here, we investigated the impact of PM2.5 on the barrier function of the eos-CRSwNP epithelium and explored the reparative function of budesonide.

METHODS

Samples from noninflammatory nasal mucosa and eos-CRSwNP were collected to establish an in vitro air-liquid interface cultured model. The cells were exposed to PM2.5 at 50 or 100 µg/ml intermittently for 72 h, with or without budesonide pretreatment. Barrier function and tight junction (TJ) expression were reflected by measuring transepithelial resistance (TER), paracellular flux permeability of fluorescein isothiocyanate-labeled 4-kDa dextran, quantitative real-time polymerase chain reaction (qPCR), and immunofluorescence staining of TJ proteins. Cytokine expression was measured by qPCR and enzyme-linked immunosorbent assay or Luminex.

RESULTS

PM2.5 increased paracellular flux and downregulated TJ protein expression (zona occuldens-1, occludin, and claudin-1), but did not change TER. These changes could be partially restored by budesonide treatment. Interleukin (IL)-8, IL-10, IL-1α, and tissue inhibitor of metalloproteinase (TIMP)-1 concentrations were significantly increased in the culture medium of cells exposed to PM2.5, and budesonide significantly reduced the changes in IL-8, IL-1α, and TIMP-1.

CONCLUSION

PM2.5 impaired the barrier function of eos-CRSwNP epithelial cells and increased the permeability of large molecules. PM2.5 also increased the secretion of pro-inflammatory cytokines by nasal epithelial cells. Budesonide could partially repair the damage, suggesting potential applications in clinical practice.

Epithelial Barrier Dysfunction in Chronic Respiratory Diseases

Mucosal surfaces are lined by epithelial cells, which provide a complex and adaptive module that ensures first-line defense against external toxics, irritants, antigens, and pathogens. The underlying mechanisms of host protection encompass multiple physical, chemical, and immune pathways. In the lung, inhaled agents continually challenge the airway epithelial barrier, which is altered in chronic diseases such as chronic obstructive pulmonary disease, asthma, cystic fibrosis, or pulmonary fibrosis. In this review, we describe the epithelial barrier abnormalities that are observed in such disorders and summarize current knowledge on the mechanisms driving impaired barrier function, which could represent targets of future therapeutic approaches.

Anti-VEGF treatment suppresses remodeling factors and restores epithelial barrier function through the E-cadherin/β-catenin signaling axis in experimental asthma models

Besides maintaining a physical barrier with adherens junctional (AJ) and tight junctional proteins, airway epithelial cells have important roles in modulating the inflammatory processes of allergic asthma. E-cadherin and β-catenin are the key AJ proteins that are involved in airway remodeling. Various mediators such as transforming growth factor-β (TGF-β), epidermal growth factor (EGF), fibroblast growth factor (FGF), platelet derived growth factor (PDGF), insulin-like growth factor (IGF), tumor necrosis factor-α (TNF-α) and angiogenic factors, such as vascular endothelial growth factor (VEGF), are released by the airway epithelium in allergic asthma. The signaling pathways activated by these growth factors trigger epithelial-mesenchymal transition (EMT), which contributes to fibrosis and subsequent downregulation of E-cadherin. The present study used a mouse asthma model to investigate the effects of anti-VEGF, anti-TNF and corticosteroid therapies on growth factor and E-cadherin/β-catenin expression. The study used 38 male BALB/c mice, divided into 5 groups. A chronic mouse asthma model was created by treating 4 of the groups with inhaled and intraperitoneal ovalbumin (n= 8 per group). Saline, anti-TNF-α (etanercept), anti-VEGF (bevacizumab) or a corticosteroid (dexamethasone) were applied to each group by intraperitoneal injection. No medication was administered to the control group (n=6). Immunohistochemistry for E-cadherin, β-catenin and growth factors was performed on lung tissues and protein expression levels assessed using H-scores. Statistically significant differences were observed in E-cadherin, β-catenin, EGF, FG, and PFGF (P<0.001 for all) as well as the IGF H-scores between the five groups (P<0.005). Only anti-VEGF treatment caused E-cadherin and β-catenin levels to increase to the level of non-asthmatic control groups (P>0.005). All treatment groups had reduced TGF-β, PDGF and FGF H-scores in comparison with the untreated asthma group (P=0.001). The EGF and IGF levels were not significantly different between the untreated asthmatic and non-asthmatic controls. The results suggested that anti-VEGF and TNF-α inhibition treatments are effective in decreasing growth factors, in a similar manner to conventional corticosteroid treatments. Anti-VEGF and TNF inhibition therapy may be an effective treatment for remodeling in asthma while offering an alternative therapeutic option to steroid protective agents. The data suggested that anti-VEGF treatment offered greater restoration of the epithelial barrier than both anti-TNF-α and corticosteroid treatment.

Epithelial barrier function properties of the 16HBE14o- human bronchial epithelial cell culture model

The human bronchial epithelial cell line, 16HBE14o- (16HBE), is widely used as a model for respiratory epithelial diseases and barrier function. During differentiation, transepithelial electrical resistance (TER) increased to approximately 800 Ohms × cm², while ¹⁴C-d-mannitol flux rates (J_m) simultaneously decreased. Tight junctions (TJs) were shown by diffusion potential studies to be anion-selective with P_C1/P_Na = 1.9. Transepithelial leakiness could be induced by the phorbol ester, protein kinase C (PKC) activator, 12-O-tetradecanoylphorbol-13-acetate (TPA), and the proinflammatory cytokine, tumor necrosis factor-α (TNF-α). Basal barrier function could not be improved by the micronutrients, zinc, or quercetin. Of methodological significance, TER was observed to be more variable and to spontaneously, significantly decrease after initial barrier formation, whereas J_m did not significantly fluctuate or increase. Unlike the strong inverse relationship between TER and J_m during differentiation, differentiated cell layers manifested no relationship between TER and J_m. There was also much greater variability for TER values compared with J_m. Investigating the dependence of 16HBE TER on transcellular ion conductance, inhibition of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) chloride channel with GlyH-101 produced a large decrease in short-circuit current (I_sc) and a slight increase in TER, but no significant change in J_m. A strong temperature dependence was observed not only for I_sc, but also for TER. In summary, research utilizing 16HBE as a model in airway barrier function studies needs to be aware of the complexity of TER as a parameter of barrier function given the influence of CFTR-dependent transcellular conductance on TER.

Incense smoke-induced oxidative stress disrupts tight junctions and bronchial epithelial barrier integrity and induces airway hyperresponsiveness in mouse lungs

Recent clinical studies have suggested that inhalation of incense smoke (IS) may result in impaired lung function and asthma. However, there is little experimental evidence to link IS with airway hyperresponsiveness (AHR) and bronchial epithelial barrier function. Using mouse and cell culture models, we evaluated the effects of IS exposure on AHR, expression of multiple epithelial tight junction (TJ)- and adherens junction-associated mRNAs and proteins in the lungs, and the barrier function of bronchial epithelial cells assessed by transepithelial electronic resistance (TEER). Exposure of BALB/c mice to IS increased AHR and inflammatory macrophage recruitment to BALF; reduced claudin-1, -2, -3, -7, -10b, -12, -15, and -18, occludin, zonula occludens-1 [ZO-1], and E-cadherin mRNA expression; and caused discontinuity of claudin-2 and ZO-1 protein immunostaining in lung tissue. IS extract dose-dependently decreased TEER and increased reactive oxygen species production in bronchial epithelial cell cultures. Treatment with N-acetyl-l-cysteine, but not glucocorticosteroids or long-acting β₂-agonists, prevented the detrimental effects of IS. IS exposure can be problematic for respiratory health, as evidenced by AHR, increased recruitment of inflammatory macrophages and disruption of TJ proteins in the lung, and damage to epithelial barrier function. However, antioxidants may be useful for the treatment of IS-induced airway dysfunction.

Dexamethasone Conjugates: Synthetic Approaches and Medical Prospects

Dexamethasone (DEX) is the most commonly prescribed glucocorticoid (GC) and has a wide spectrum of pharmacological activity. However, steroid drugs like DEX can have severe side effects on non-target organs. One strategy to reduce these side effects is to develop targeted systems with the controlled release by conjugation to polymeric carriers. This review describes the methods available for the synthesis of DEX conjugates (carbodiimide chemistry, solid-phase synthesis, reversible addition fragmentation-chain transfer [RAFT] polymerization, click reactions, and 2-iminothiolane chemistry) and perspectives for their medical application as GC drug or gene delivery systems for anti-tumor therapy. Additionally, the review focuses on the development of DEX conjugates with different physical-chemical properties as successful delivery systems in the target organs such as eye, joint, kidney, and others. Finally, polymer conjugates with improved transfection activity in which DEX is used as a vector for gene delivery in the cell nucleus have been described.

Epithelial dysfunction in chronic respiratory diseases, a shared endotype?

PURPOSE OF REVIEW

Epithelial barrier defects are being appreciated in various inflammatory disorders; however, causal underlying mechanisms are lacking. In this review, we describe the disruption of the airway epithelium with regard to upper and lower airway diseases, the role of epigenetic alterations underlying this process, and potential novel ways of interfering with dysfunctional epithelial barriers as a novel therapeutic approach.

RECENT FINDINGS

A defective epithelial barrier, impaired innate defence mechanisms or hampered epithelial cell renewal are found in upper and lower airway diseases. Barrier dysfunction might facilitate the entrance of foreign substances, initiating and facilitating the onset of disease. Latest data provided novel insights for possible involvement of epigenetic alterations induced by inflammation or other unknown mechanisms as a potential mechanism responsible for epithelial defects. Additionally, these mechanisms might precede disease development, and represent a novel therapeutic approach for restoring epithelial defects.

SUMMARY

A better understanding of the role of epigenetics in driving and maintaining epithelial defects in various inflammatory diseases, using state-of-the-art biology tools will be crucial in designing novel therapies to protect or reconstitute a defective airway epithelial barrier.

Retinoic acid improves baseline barrier function and attenuates TNF-α-induced barrier leak in human bronchial epithelial cell culture model, 16HBE 14o

Retinoic acid (RA) has been shown to improve epithelial and endothelial barrier function and development and even suppress damage inflicted by inflammation on these barriers through regulating immune cell activity. This paper thus sought to determine whether RA could improve baseline barrier function and attenuate TNF-α-induced barrier leak in the human bronchial epithelial cell culture model, 16HBE14o- (16HBE). We show for the first time that RA increases baseline barrier function of these cell layers indicated by an 89% increase in transepithelial electrical resistance (TER) and 22% decrease in ¹⁴C-mannitol flux. A simultaneous, RA-induced 70% increase in claudin-4 attests to RA affecting the tight junctional (TJ) complex itself. RA was also effective in alleviating TNF-α-induced 16HBE barrier leak, attenuating 60% of the TNF-α-induced leak to ¹⁴C-mannitol and 80% of the leak to ¹⁴C-inulin. Interleukin-6-induced barrier leak was also reduced by RA. Treatment of 16HBE cell layers with TNF-α resulted in dramatic decrease in immunostaining for occludin and claudin-4, as well as a downward “band-shift” in occludin Western immunoblots. The presence of RA partially reversed TNF-α’s effects on these select TJ proteins. Lastly, RA completely abrogated the TNF-α-induced increase in ERK-1,2 phosphorylation without significantly decreasing the TNF-driven increase in total ERK-1,2. This study suggests RA could be effective as a prophylactic agent in minimizing airway barrier leak and as a therapeutic in preventing leak triggered by inflammatory cascades. Given the growing literature suggesting a “cytokine storm” may be related to COVID-19 morbidity, RA may be a useful adjuvant for use with anti-viral therapies.

DsRNA induction of microRNA-155 disrupt tight junction barrier by modulating claudins

Background

The impaired barrier function of the airway epithelium due to RNA virus infection is closely related to the development and exacerbation of allergic airway inflammation.

Objective

In this study, we investigated the roles of microRNAs on the mechanisms of double-stranded RNA (dsRNA)-induced epithelial barrier dysfunction.

Methods

16HBE14o- human bronchial epithelial cells were grown to confluence on Transwell inserts and exposed to poly-I:C. We studied epithelial barrier function by measuring transepithelial electrical resistance and paracellular flux of fluorescent markers and structure of tight junctions by immunofluorescence microscopy.

Results

Poly-I:C treated 16HBE14o- cells increased paracellular permeability. Knockdown of Toll-like receptor 3 and TRIF abrogated these effects. The expression of microRNA-155 (miR-155) was increased by poly-I:C in dose-dependent manner. Transfection of mir155 mimics into 16HBE14o- cells increased permeability and inhibited tight junction formation. Transfection of miR-155 inhibitor suppressed poly-I:C-induced barrier disruption. Poly-I:C treatment significantly decreased the expression of claudin members—claudin-1, -3, -4, -5, -9, -11, -16, -18 and -19. Transfection of miR-155 mimics showed similar changing expression pattern of claudin members with those of poly-I:C treatment.

Conclusion

These results suggest that RNA virus infection can impair the epithelial barrier disruption mechanism by down-regulation of claudin members through the induction of miR-155.

Establishment of an in vitro culture model to study milk production and the blood–milk barrier with bovine mammary epithelial cells

This study attempted to establish a culture model to recreate the milk production pathway in bovine mammary epithelial cells (BMECs). BMECs were isolated from Holstein cows (nonlactating, nonpregnant, and parous) and were stored by cryopreservation. To separate the apical and basolateral compartments, BMECs were cultured on a cell culture insert with a collagen gel in the presence of bovine pituitary extract and dexamethasone to induce milk production and tight junction (TJ) formation. The culture model showed the secretion of the major milk components, such as β-casein, lactose, and triglyceride, and formed less-permeable TJs in BMECs. Moreover, the TJs were distinctly separated from the apical and basolateral membranes. Glucose transporter-1, which transports glucose into the cytoplasm through the basolateral membrane, localized in the lateral membrane of BMECs. Toll-like receptor-4, which binds to lipopolysaccharide in the alveolar lumen in mastitis, localized in the apical membrane. Beta-casein was mainly localized near the Golgi apparatus and the apical membrane. Moreover, milk components were almost secreted into the upper chamber of the cell culture insert. These findings indicate that this model has clear cell polarity as well as in vivo and is effective to study of milk production and the blood-milk barrier in lactating BMECs.

Dexamethasone loaded bilayered 3D tubular scaffold reduces restenosis at the anastomotic site of tracheal replacement: in vitro and in vivo assessments

Despite recent developments in the tracheal tissue engineering field, the creation of a patient specific substitute possessing both appropriate mechanical and biointerfacial properties remains challenging. Most tracheal replacement therapies fail due to restenosis at the anastomosis site. In this study, we designed a robust, biodegradable, 3D tubular scaffold by combining electrospinning (ELSP) and 3D (three-dimensional) printing techniques for use in transplantation therapy. After that, we loaded dexamethasone (DEX) onto the 3D tubular scaffold using mild surface modification reactions by using polydopamine (PDA), polyethyleneimine (PEI), and carboxymethyl-β-cyclodextrin (βCD). As a result, the fabricated 3D tubular scaffold had robust mechanical properties and the chemical modifications were confirmed to have proceeded successfully by physico-chemical analysis. The surface treatments allowed for a larger amount of DEX to be loaded onto the βCD modified scaffold as compared to the bare group. In vitro and in vivo studies demonstrated that the DEX loaded 3D tubular scaffold exhibited significantly enhanced anti-inflammation activity, enhanced tracheal mucosal regeneration, and formation of a patent airway. From our results, we believe that our system may represent an innovative paradigm in tracheal tissue engineering by providing proper mechanical properties and successful formation of tracheal tissue as a means of remodeling and healing tracheal defects for use in transplantation therapy.

Particulate Matter 2.5 Causes Deficiency in Barrier Integrity in Human Nasal Epithelial Cells

Purpose

The effect of air pollution-related particulate matter (PM) on epithelial barrier function and tight junction (TJ) expression in human nasal mucosa has not been studied to date. This study therefore aimed to assess the direct impact of PM with an aerodynamic diameter less than 2.5 μm (PM2.5) on the barrier function and TJ molecular expression of human nasal epithelial cells.

Methods

Air-liquid interface cultures were established with epithelial cells derived from noninflammatory nasal mucosal tissue collected from patients undergoing paranasal sinus surgery. Confluent cultures were exposed to 50 or 100 µg/mL PM2.5 for up to 72 hours, and assessed for 1) epithelial barrier integrity as measured by transepithelial resistance (TER) and permeability of fluorescein isothiocyanate (FITC) 4 kDa; 2) expression of TJs using real-time quantitative polymerase chain reaction and immunofluorescence staining, and 3) proinflammatory cytokines by luminometric bead array or enzyme-linked immunosorbent assay.

Results

Compared to control medium, 50 and/or 100 µg/mL PM2.5-treatment 1) significantly decreased TER and increased FITC permeability, which could not be restored by budesonide pretreatment; 2) significantly decreased the expression of claudin-1 messenger RNA, claudin-1, occludin and ZO-1 protein; and 3) significantly increased production of the cytokines interleukin-8, TIMP metallopeptidase inhibitor 1 and thymic stromal lymphopoietin.

Conclusions

Exposure to PM2.5 may lead to loss of barrier function in human nasal epithelium through decreased expression of TJ proteins and increased release of proinflammatory cytokines. These results suggest an important mechanism of susceptibility to rhinitis and rhinosinusitis in highly PM2.5-polluted areas.

Effects of cigarette smoke on barrier function and tight junction proteins in the bronchial epithelium: protective role of cathelicidin LL-37

Background

Airway epithelial barrier function is maintained by the formation of tight junctions (TJs) and adherens junctions (AJs). Inhalation of cigarette smoke causes airway epithelial barrier dysfunction and may contribute to the pathogenesis of chronic lung diseases such as asthma and chronic obstructive pulmonary disease (COPD). We assessed the effects of cigarette smoke on barrier function and expression of multiple TJ and AJ proteins in the bronchial epithelium. We also examined whether treatment with glucocorticosteroids (GCSs), long-acting β₂-agonists (LABAs), and human cathelicidin LL-37 can protect against cigarette smoke extract (CSE)-induced barrier dysfunction.

Methods

Calu-3 cells cultured at the air-liquid interface were pretreated with or without GCSs, LABAs, GCSs plus LABAs, or LL-37, and subsequently exposed to CSE. Barrier function was assessed by transepithelial electronic resistance (TEER) measurements. Gene and protein expression levels of TJ and AJ proteins were analyzed by quantitative PCR and western blotting, respectively. Immunofluorescence staining of TJ and AJ proteins was performed.

Results

CSE decreased TEER and increased permeability in a concentration-dependent manner. CSE suppressed gene expression of claudin-1, claudin-3, claudin-4, claudin-7, claudin-15, occludin, E-cadherin, junctional adhesion molecule-A (JAM-A) and zonula occludens-1 (ZO-1) within 12 h post-CSE exposure, while suppressed protein expression levels of occludin at 12 h. CSE-treated cells exhibited discontinuous or attenuated immunostaining for claudin-1, claudin-3, claudin-4, occludin, ZO-1, and E-cadherin compared with untreated cells. GCS treatment partially restored CSE-induced TEER reduction, while LABA treatment had no effect. GCS and LABA combination treatment had no additive effect on CSE-induced TEER reduction and gene suppression of TJ and AJ proteins. Human cathelicidin LL-37 counteracted CSE-induced TEER reduction and prevented disruption of occludin and ZO-1. LL-37 also attenuated CSE-induced decreases in gene and protein expression levels of occludin.

Conclusions

CSE caused airway epithelial barrier dysfunction and simultaneously downregulated multiple TJ and AJ proteins. GCS and LABA combination treatment had no additive effect on CSE-induced TEER reduction. LL-37 counteracted CSE-induced TEER reduction and prevented disruption of occludin and ZO-1. Use of LL-37 to counteract airway epithelial barrier dysfunction may have significant benefits for respiratory diseases such as asthma and COPD.

Role of Nrf2 in the pathogenesis of respiratory diseases

Nuclear factor erythroid 2-related factor (Nrf)2 is a transcription factor that integrates cellular stress signals by directing various transcriptional programs. As an evolutionarily conserved intracellular defense mechanism, Nrf2 and its endogenous inhibitor Kelch-like ECH-associated protein (Keap)1 inhibit oxidative stress in the lung, which is the internal organ that is continuously exposed to the environment. Oxidative stress is implicated in the pathogenesis of various lung diseases including asthma, acute lung injury, chronic obstructive pulmonary disease (COPD), and interstitial lung disease (ILD). Thus, Nrf2 is considered as a potential therapeutic target in lung diseases owing to its antioxidant effect. Nrf2 also plays a complex role in lung cancer, acting as a tumor suppressor and promoter; recent studies have revealed the tumor-promoting effects of Nrf2 in tumors that have undergone malignant transformation. Lung cancer-associated mutations in Keap1 disrupt Keap1-Nrf2 complex formation, resulting in the ubiquitination and degradation of Keap1, and the constitutive activation of Nrf2. In lung cancer cells, persistently high nuclear Nrf2 levels induce the expression of genes that contribute to metabolic reprogramming, and stimulate cell proliferation. In this review, we outlined the major functions of Nrf2, and discussed its importance in pulmonary diseases such as asthma, acute respiratory distress syndrome, and lung cancer. Elucidating the mechanisms through which Nrf2 modulates the initiation and progression of pulmonary diseases can lead to the development of therapeutics specifically targeting this pathway.

Inhaled budesonide for the prevention of acute mountain sickness: A meta-analysis of randomized controlled trials

BACKGROUND

Altitude induces acute mountain sickness (AMS), which can affect the health or limit the activities of 15 -80% of climbers and workers. Budesonide has been applied to prevent AMS. However, its prophylactic efficacy is controversial. Our purpose was to conduct a meta-analysis to assess whether budesonide qualifies as a prophylaxis for AMS.

METHODS

A literature search was performed in PubMed, EMBASE, Web of Science, and the Cochrane Library in February 2019. Only randomized controlled trials (RCTs) were selected. The main outcome, AMS, was estimated with the relative risk (RR), weighted mean difference (WMD), and 95% confidence intervals (95% CI). The statistical analysis was performed using Rev. Man 5.3.

RESULTS

Five groups in six articles met the eligibility criteria with 304 participants, including two articles with the same participants but different measurements. Inhaled budesonide showed a potential trend towards preventing AMS, but it was not statistically significant (RR = 0.68, 95% CI: 0.41-1.13, p = 0.14). The subgroup analysis based on dosage (200 µg) did not have significant results. A similar trend was observed for severe AMS and in subgroups stratified by the Lake Louise Score (LLC). However, there was a significant improvement in heart rate (HR) (WMD = -5.41, 95% CI: -8.26 to -2.55, p = 0.0002) and pulse oxygen saturation (SPO2) (WMD = 2.36, 95% CI: 1.62-3.1, p < 0.00001) in the group with inhaled budesonide. Additionally, no side effects were reported in any included study.

CONCLUSION

The current meta-analysis indicates that inhaled budesonide does not protect against AMS or severe AMS. However, it is successful at reducing HR and increasing SPO₂ without any side effects.

Stress axis variability is associated with differential ozone-induced lung inflammatory signaling and injury biomarker response

Ozone (O₃), a ubiquitous urban air pollutant, causes adverse pulmonary and extrapulmonary effects. A large variability in acute O₃-induced effects has been observed; however, the basis for interindividual differences in susceptibility is unclear. We previously demonstrated a role for the hypothalamic-pituitary-adrenal (HPA) stress axis and glucocorticoid response in acute O₃ toxicity. Glucocorticoids have important anti-inflammatory actions, and have been shown to regulate lung inflammatory responses. We hypothesised that a hyporesponsive HPA axis would be associated with greater O₃-dependent lung inflammatory signaling. Two genetically-related rat strains with known differences in stress axis reactivity, highly-stress responsive Fischer (F344) and less responsive Lewis (LEW), were exposed for 4 h by nose-only inhalation to clean air or 0.8 ppm O₃, and euthanized immediately after exposure. As expected, baseline (air-exposed) plasma corticosterone was significantly lower in the hypo-stress responsive LEW. Although O₃ exposure increased plasma corticosterone in both strains, corticosterone remained significantly lower in LEW when compared to F334. LEW exhibited greater O₃-induced inflammatory cytokine/chemokine signaling compared to F344, consistent with the lower corticosterone levels. Since we observed strain-specific differences in inflammatory signaling, we further investigated injury biomarkers (total protein, albumin and lactate dehydrogenase). Although the hyper-responsive F344 exhibited lower inflammatory signaling in response to O₃ compared with LEW, they had greater levels of lung injury biomarkers. Our results indicate that stress axis variability is associated with differential O₃-induced lung toxicity. Given the large variability in stress axis reactivity among humans, stress axis regulation could potentially be a determining factor underlying O₃ sensitivity.

The effects of respiratory inhaled drugs on the prevention of acute mountain sickness

BACKGROUND

Acute mountain sickness (AMS) is common in high-altitude travelers, and may lead to life-threatening high-altitude cerebral edema (HACE) or high-altitude pulmonary edema (HAPE). The inhaled drugs have a much lower peak serum concentrations and a shorter half-life period than oral drugs, which give them a special character, greater local effects in the lung. Meanwhile, short-term administration of inhaled drugs results in almost no adverse reactions.

METHODS

We chose inhaled ipratropium bromide/salbutamol sulfate (combivent, COM), budesonide (pulmicortrespules, BUD), and salbutamol sulfate (ventolin, VEN) in our study to investigate their prophylactic efficacy against AMS. Since COM is a compound drug of ipratropium bromide and salbutamol sulfate, to verify which part of COM plays a role in the prevention of AMS, we also tested VEN in our experiment.

RESULTS

In our study, Lake Louise scores (LLS) in the COM (1.14 ± 0.89 vs 1.91 ± 1.23, P < .05) and BUD (1.35 ± 0.94 vs 1.91 ± 1.23, P < .05) groups were both significantly lower than the placebo group at 72 hours. There were no significant differences in LLS scores among the 4 groups at 120 hours. The incidence of AMS in the COM group was significantly reduced at 72 hours (16.7% in COM group vs 43.4% in placebo group, P < .05) after exposure to high-altitude. There were no significant differences in AMS incidences at 120 hours among the 4 groups.

CONCLUSION

The prophylactic use of COM could prevent AMS in young Chinese male at 72 hours after high-altitude exposure. BUD also could reduce LLS but not prevent AMS at 72 hours. Ipratropium bromide maybe the effective drug in COM work on the prevention of AMS alone.

Role of airway epithelial barrier dysfunction in pathogenesis of asthma

Bronchial asthma is characterized by persistent cough, increased sputum, and repeated wheezing. The pathophysiology underlying these symptoms is the hyper-responsiveness of the airway along with chronic airway inflammation. Repeated injury, repair, and regeneration of the airway epithelium following exposure to environmental factors and inflammation results in histological changes and functional abnormalities in the airway mucosal epithelium; such changes are believed to have a significant association with the pathophysiology of asthma. Damage to the barrier functions of the airway epithelium enhances mucosal permeability of foreign substances in the airway epithelium of patients with asthma. Thus, epithelial barrier fragility is closely involved in releasing epithelial cytokines (e.g., TSLP, IL-25, and IL-33) because of the activation of airway epithelial cells, dendritic cells, and innate group 2 innate lymphoid cells (ILC2). Functional abnormalities of the airway epithelial cells along with the activation of dendritic cells, Th2 cells, and ILC2 form a single immunopathological unit that is considered to cause allergic airway inflammation. Here we use the latest published literature to discuss the potential pathological mechanisms regarding the onset and progressive severity of asthma with regard to the disruption of the airway epithelial function.

Vitamin A maintains the airway epithelium in a murine model of asthma by suppressing glucocorticoid-induced leucine zipper

BACKGROUND

The effects of glucocorticoids (GCs) on the repair of the airway epithelium in asthma are controversial, and we previously reported that the GC dexamethasone (Dex) inhibits the repair of human airway epithelial cells and that this process is mediated by glucocorticoid-induced leucine zipper (GILZ) through MAPK-ERK signaling in vitro. Vitamin A (VA) is involved in the regulation of the MAPK-ERK pathway but has not been widely supplied during asthma treatment. It is unclear whether VA attenuates the negative regulation of GILZ on the MAPK-ERK pathway and maintains airway epithelium integrity during asthma treatment.

METHODS

Female BALB/c mice were sensitized and challenged with ovalbumin (OVA) and subsequently treated with Dex, VA or intranasal inhalation of adenovirus sh-GILZ vectors. Indexes of airway epithelium integrity, including pathological alterations, pulmonary EGFR expression and airway hyperresponsiveness (AHR), were then measured. The expression of GILZ and key components of activated MAPK-ERK signals (p-Raf-1, p-MEK, and p-Erk1/2) were also detected.

RESULTS

Dex failed to relieve OVA-induced asthma airway epithelium injury, as assessed through H&E staining, EGFR expression and AHR. Moreover, in the OVA-challenged mice treated with Dex, GLIZ expression was increased, whereas the ratios of p-Raf-1/Raf-1, p-MEK/MEK and p-Erk1/2/Erk1/2 were significantly decreased. Further study indicated that GILZ expression was decreased and that the ratios of p-Raf-1/Raf-1, p-MEK/MEK and p-Erk1/2/Erk1/2 were up-regulated in the GILZ-silenced OVA-challenged mice and VA-fed OVA-challenged mice, independent of Dex treatment. The airway epithelium integrity of the OVA-challenged mice was maintained by treatment with both VA and Dex.

CONCLUSIONS

Vitamin A maintained the Dex-treated asthma airway epithelium via the down-regulation of GILZ expression and the activation MAPK-ERK signaling, and these effects might contribute to improving the effects of GC therapeutics on asthma.

Effect of matrix metalloproteinase inhibitor on disrupted E-cadherin after acid exposure in the human nasal epithelium

OBJECTIVE

Laryngopharyngeal reflux disease (LPRD) is one of potential factors in recalcitrant chronic rhinosinusitis with or without polyps. An increase in junctional permeability in the nasal mucosa in LPRD may be due to disrupted protein bridge formation with cell-to-cell adhesion molecules such as E-cadherin. Despite the relationship between nasal mucosal inflammation and LPRD, the clear mechanism by which acid reflux affects the nasal epithelium remains unclear.

METHODS

The expression levels and distribution patterns of E-cadherin in primary culture of nasal epithelial cells after acid exposure with or without dexamethasone and matrix metalloproteinase (MMP) inhibitor were determined using Western blot and immunocytochemistry. The functional roles of MMP inhibitor in maintaining junctional permeability in the nasal epithelium were elucidated by transepithelial permeability test.

RESULTS

By acid exposure to nasal epithelial cells, mature E-cadherin was decreased and cleaved E-cadherin was increased. This was thought to be caused by cleavage of mature E-cadherin between cells and was confirmed by the increment of E-cadherin inside a cell in immunocytochemical evaluation. Whereas disruption of E-cadherin was not recovered by steroid medication with various treatments of dexamethasone, disrupted E-cadherin was restored to normal by inhibition of MMPs with actinonin, a broad MMP inhibitor. This recovery was functionally demonstrated by transepithelial permeability test.

CONCLUSION

Our results suggest that altered expression of E-cadherin in the nasal epithelium by acid exposure may be a possible mechanism for nasal tissue injury in chronic nasal inflammation with LPRD, and that MMP inhibition is a potential treatment.

LEVEL OF EVIDENCE

NA. Laryngoscope, 128:E1-E7, 2018.

Nanoencapsulation of a glucocorticoid improves barrier function and anti-inflammatory effect on monolayers of pulmonary epithelial cell lines

The anti-inflammatory effect of polymeric deflazacort nanocapsules (NC-DFZ) was investigated, and possible improvement of epithelial barrier function using filter grown monolayers of Calu-3 cells was assessed. NC prepared from poly(ε-caprolactone) (PCL) had a mean size around 200nm, slightly negative zeta potential (∼-8mV), and low polydispersity index (<0.10). Encapsulation of DFZ had an efficiency of 85%. No cytotoxic effects were observed at particle concentration of 9.85×10¹¹NC/ml, which was therefore chosen to evaluate the effect of NC-DFZ at 1% (w/v) of PCL and 0.5% (w/v) of DFZ on the epithelial barrier function of Calu-3 monolayers. Nanoencapsulated drug at 0.5% (w/v) increased transepithelial electrical resistance and decreased permeability of the paracellular marker sodium fluorescein, while non-encapsulated DFZ failed to improve these parameters. Moreover, NC-DFZ reduced the lipopolysaccharide (LPS) mediated secretion of the inflammatory marker IL-8. In vitro dissolution testing revealed controlled release of DFZ from nanocapsules, which may explain the improved effect of DFZ on the cells. These data suggest that nanoencapsulation of pulmonary delivered corticosteroids could be advantageous for the treatment of inflammatory conditions, such as asthma and chronic obstructive pulmonary diseases.

Magnetofection Enhances Lentiviral-Mediated Transduction of Airway Epithelial Cells through Extracellular and Cellular Barriers

Gene transfer to airway epithelial cells is hampered by extracellular (mainly mucus) and cellular (tight junctions) barriers. Magnetofection has been used to increase retention time of lentiviral vectors (LV) on the cellular surface. In this study, magnetofection was investigated in airway epithelial cell models mimicking extracellular and cellular barriers. Bronchiolar epithelial cells (H441 line) were evaluated for LV-mediated transduction after polarization onto filters and dexamethasone (dex) treatment, which induced hemicyst formation, with or without magnetofection. Sputum from cystic fibrosis (CF) patients was overlaid onto cells, and LV-mediated transduction was evaluated in the absence or presence of magnetofection. Magnetofection of unpolarized H441 cells increased the transduction with 50 MOI (multiplicity of infection, i.e., transducing units/cell) up to the transduction obtained with 500 MOI in the absence of magnetofection. Magnetofection well-enhanced LV-mediated transduction in mucus-layered cells by 20.3-fold. LV-mediated transduction efficiency decreased in dex-induced hemicysts in a time-dependent fashion. In dome-forming cells, zonula occludens-1 (ZO-1) localization at the cell borders was increased by dex treatment. Under these experimental conditions, magnetofection significantly increased LV transduction by 5.3-fold. In conclusion, these results show that magnetofection can enhance LV-mediated gene transfer into airway epithelial cells in the presence of extracellular (sputum) and cellular (tight junctions) barriers, representing CF-like conditions.

Chronic rhinosinusitis: the rationale for current treatments

INTRODUCTION

Chronic rhinosinusitis (CRS) is a broad clinical syndrome linked by mucosal inflammation. Primary treatment modalities are corticosteroids and antibiotics with surgery an option for failures, but the level of supporting evidence is generally low. The primary reason is that CRS is a symptom complex and not a specific disease. Areas covered: The primary treatment modalities for CRS are corticosteroids, antibiotics and surgery. Corticosteroids, which have very broad anti-inflammatory properties, also have the strongest evidence for efficacy. Antibiotics are likely effective in a subpopulation of patients but the various phenotypes and endotypes that make up CRS have thus far been poorly defined. Early surgery as well as biologics may also be more efficacious and cost effective in some phenotypes as well. Expert commentary: A better understanding of the inflammatory pathways that drive CRS will permit investigators to separate patient groups. This will allow for clinical trials that target specific subpopulations and more personalized therapy for CRS patients in the future.

Modulation of Human Airway Barrier Functions during Burkholderia thailandensis and Francisella tularensis Infection Running Title: Airway Barrier Functions during Bacterial Infections

The bronchial epithelium provides protection against pathogens from the inhaled environment through the formation of a highly-regulated barrier. In order to understand the pulmonary diseases melioidosis and tularemia caused by Burkholderia thailandensis and Fransicella tularensis, respectively, the barrier function of the human bronchial epithelium were analysed. Polarised 16HBE14o- or differentiated primary human bronchial epithelial cells (BECs) were exposed to increasing multiplicities of infection (MOI) of B. thailandensis or F. tularensis Live Vaccine Strain and barrier responses monitored over 24-72 h. Challenge of polarized BECs with either bacterial species caused an MOI- and time-dependent increase in ionic permeability, disruption of tight junctions, and bacterial passage from the apical to the basolateral compartment. B. thailandensis was found to be more invasive than F. tularensis. Both bacterial species induced an MOI-dependent increase in TNF-α release. An increase in ionic permeability and TNF-α release was induced by B. thailandensis in differentiated BECs. Pretreatment of polarised BECs with the corticosteroid fluticasone propionate reduced bacterial-dependent increases in ionic permeability, bacterial passage, and TNF-α release. TNF blocking antibody Enbrel(®) reduced bacterial passage only. BEC barrier properties are disrupted during respiratory bacterial infections and targeting with corticosteroids or anti-TNF compounds may represent a therapeutic option.

Budesonide, but not dexamethasone, blunted the response of aldosterone to renin elevation by suppressing angiotensin converting enzyme upon high-altitude exposure

INTRODUCTION

Inhaled budesonide is a novel approach to prevent acute mountain sickness (AMS). However, its mechanism is not completely understood. We aimed to investigate the effects of budesonide and dexamethasone on renin-angiotensin-aldosterone system in AMS prevention.

MATERIALS AND METHODS

Data were obtained from a randomised controlled trial including 138 participants. The participants were randomly assigned to receive budesonide, dexamethasone or placebo as prophylaxis before they travelled to 3450 m altitude from 400 m by car. Their plasma concentrations of renin, angiotensin-converting enzyme (ACE) and aldosterone were measured at both altitudes.

RESULTS

All parameters were comparable among the three groups at 400 m. After high-altitude exposure of 3450, renin in all groups increased significantly; the ACE, aldosterone concentrations, as well as the aldosterone/renin ratio, rose markedly in the dexamethasone and placebo groups but not in the budesonide group. Moreover, the aldosterone/renin ratio correlated closely with ACE concentration.

CONCLUSIONS

Upon acute high-altitude exposure, budesonide, but not dexamethasone, blunted the response of aldosterone to renin elevation by suppressing angiotensin converting enzyme.

Impaired barrier function in patients with house dust mite-induced allergic rhinitis is accompanied by decreased occludin and zonula occludens-1 expression

BACKGROUND

Tight junction (TJ) defects have recently been associated with asthma and chronic rhinosinusitis. The expression, function, and regulation of nasal epithelial TJs remain unknown in patients with allergic rhinitis (AR).

OBJECTIVE

We investigated the expression, function, and regulation of TJs in the nasal epithelium of patients with house dust mite (HDM)-induced AR and in an HDM-induced murine model of allergic airway disease.

METHODS

Air-liquid interface cultures of primary nasal epithelial cells of control subjects and patients with HDM-induced AR were used for measuring transepithelial resistance and passage to fluorescein isothiocyanate-dextran 4 kDa (FD4). Ex vivo transtissue resistance and FD4 permeability of nasal mucosal explants were measured. TJ expression was evaluated by using real-time quantitative PCR and immunofluorescence. In addition, the effects of IL-4, IFN-γ, and fluticasone propionate (FP) on nasal epithelial cells were investigated in vitro. An HDM murine model was used to study the effects of allergic inflammation and FP treatment on transmucosal passage of FD4 in vivo.

RESULTS

A decreased resistance in vitro and ex vivo was found in patients with HDM-induced AR, with increased FD4 permeability and reduced occludin and zonula occludens-1 expression. AR symptoms correlated inversely with resistance in patients with HDM-induced AR. In vitro IL-4 decreased transepithelial resistance and increased FD4 permeability, whereas IFN-γ had no effect. FP prevented IL-4-induced barrier dysfunction in vitro. In an HDM murine model FP prevented the allergen-induced increased mucosal permeability.

CONCLUSION

We found impaired nasal epithelial barrier function in patients with HDM-induced AR, with lower occludin and zonula occludens-1 expression. IL-4 disrupted epithelial integrity in vitro, and FP restored barrier function. Better understanding of nasal barrier regulation might lead to a better understanding and treatment of AR.

The footprint of TGF-β in airway remodeling of the mustard lung

Mustard lung is a major pulmonary complication in individuals exposed to sulfur mustard (SM) gas during the Iran-Iraq war. It shares common pathological and clinical features with some chronic inflammatory lung disorders, particularly chronic obstructive pulmonary disease (COPD). Airway remodeling, which is one of the main causes of lung dysfunction and the dominant phenomenon of chronic pulmonary diseases, is seen in the mustard lung. Among all mediators involved in the remodeling process, the transforming growth factor (TGF)-β plays a pivotal role in lung fibrosis and consequently in the airway remodeling. Regarding the high levels of this mediator detected in mustard lung patients, in the present study, we have discussed the possible roles of TGF-β in airway remodeling (including epithelial layer damage, subepithelial fibrosis and angiogenesis). Finally, based on TGF-β targeting, we have reviewed new airway remodeling therapeutic approaches.

Nuclear factor erythroid 2-related factor 2 (Nrf2) regulates airway epithelial barrier integrity

BACKGROUND

Inhaled corticosteroids enhance airway epithelial barrier integrity. However, the mechanism by which they accomplish this is unclear. Therefore, we investigated steroid-inducible genes and signaling pathways that were involved in enhancing airway epithelial barrier integrity.

METHODS

A human bronchial epithelial cell line (16HBE cells) was cultured with 10(-6) M dexamethasone (DEX) for 3 days to enhance epithelial barrier integrity. After measuring transepithelial electrical resistance (TER) and paracellular permeability, we extracted total RNA from 16HBE cells and performed microarray and pathway analysis. After we identified candidate genes and a canonical pathway, we measured TER and immunostained for tight junction (TJ) and adherent junction (AJ) proteins in cells that had been transfected with specific small interfering RNAs (siRNAs) for these genes.

RESULTS

We identified a nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated oxidative stress response pathway which was primarily involved in the steroid-induced enhancement of airway epithelial barrier integrity. Transfecting cells with Nrf2 specific siRNA reduced the steroid-induced enhancement of airway epithelial barrier integrity and the accumulation of TJ and AJ proteins at sites of cell-cell contact. Moreover, based on pathway analysis, aldehyde oxidase 1 (AOX1) was identified as a downstream enzyme of Nrf2. Transfecting cells with AOX1-specific siRNA also reduced the steroid-induced enhancement of airway epithelial barrier integrity.

CONCLUSIONS

Our results indicated that the Nrf2/AOX1 pathway was important for enhancing airway epithelial barrier integrity. Because the airway epithelium of asthmatics is susceptible to reduced barrier integrity, this pathway might be a new therapeutic target for asthma.

Protocadherin-1 is a glucocorticoid-responsive critical regulator of airway epithelial barrier function

Background

Impaired epithelial barrier function renders the airway vulnerable to environmental triggers associated with the pathogenesis of bronchial asthma. We investigated the influence of protocadherin-1 (PCDH1), a susceptibility gene for bronchial hyperresponsiveness, on airway epithelial barrier function.

Methods

We applied transepithelial electric resistance and dextran permeability testing to evaluate the barrier function of cultured airway epithelial cells. We studied PCDH1 function by siRNA-mediated knockdown and analyzed nasal or bronchial tissues from 16 patients with chronic rhinosinusitis (CRS) and nine patients with bronchial asthma for PCDH1 expression.

Results

PCDH1 was upregulated with the development of epithelial barrier function in cultured airway epithelial cells. Immunocytochemical analysis revealed that PCDH localized to cell-cell contact sites and colocalized with E-cadherin at the apical site of airway epithelial cells. PCDH1 gene knockdown disrupted both tight and adhesion junctions. Immunohistochemical analysis revealed strong PCDH1 expression in nasal and bronchial epithelial cells; however, expression decreased in inflamed tissues sampled from patients with CRS or bronchial asthma. Dexamethasone (Dex) increased the barrier function of airway epithelial cells and increased PCDH1 expression. PCDH1 gene knockdown eradicated the effect of Dex on barrier function.

Conclusion

These results suggest that PCDH1 is important for airway function as a physical barrier, and its dysfunction is involved in the pathogenesis of allergic airway inflammation. We also suggest that glucocorticoids promotes epithelial barrier integrity by inducing PCDH1.

1,25-Dihydroxyvitamin D3 prevents toluene diisocyanate-induced airway epithelial barrier disruption

The loss of airway epithelial integrity contributes significantly to asthma pathogenesis. Evidence suggests that vitamin D plays an important role in the prevention and treatment of asthma. However, its role in airway epithelial barrier function remains uncertain. We have previously demonstrated impaired epithelial junctions in a model of toluene diisocyanate (TDI)-induced asthma. In the present study, we hypothesized that 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] may prevent TDI-induced epithelial barrier disruption. Male BALB/c mice were dermally sensitized and then challenged with TDI. The mice were then administered 1,25(OH)2D3 intraperitoneally prior to challenge with TDI. For in vitro experiments, 16HBE bronchial epithelial cells were cultured and stimulated with TDI-human serum albumin (HSA). The results revealed that the mice treated with 1,25(OH)2D3 displayed decreased airway hyperresponsiveness (AHR), suppressed neutrophil and eosinophil infiltration into the airways, as well as an increased E-cadherin and zonula occludens-1 (ZO-1) expression at the cell-cell contact sites. In vitro, exposure of the cells to TDI-HSA induced a rapid decline in transepithelial electrical resistance (TER) and an increase in cell permeability, followed by a decrease in occludin expression and the redistribution of E-cadherin, accompanied by a significant upregulation in the levels of phosphorylated extracellular signal-regulated kinase (ERK)1/2. These effects were all partly reversed by treatment with either 1,25(OH)2D3 or an ERK1/2 inhibitor. In conclusion, the findings of our study demonstrate that 1,25(OH)2D3 prevents TDI-induced epithelial barrier disruption, and that the ERK1/2 pathway may play a role in this process.

Vascular endothelial growth factor antagonism restores epithelial barrier dysfunction via affecting zonula occludens proteins

Epithelial barrier dysfunction is important in the pathogenesis of asthma and allergic responses, and is therefore a therapeutic target. The aim of the present study was to investigate the effects of dexamethasone, a classic therapeutic agent, an anti-tumor necrosis factor agent (etanercept), which is used to treat difficult cases of asthma, and an anti-vascular endothelial growth factor (VEGF) agent (bevacizumab), which is an angiogenesis inhibitor, on zonula occludens (ZO) proteins in an experimental asthma model. The experimental model of asthma was developed using intraperitoneal (IP) and inhaled administration of ovalbumin in 38 BALB/c mice, which were divided into four groups. The control group (n=6) did not receive any treatment, while the four remaining groups (n=8 per group) received an IP injection of saline, etanercept, bevacizumab or dexamethasone, respectively. Occludin, claudin and junctional adhesion molecule (JAM) were immunohistochemically stained in the left middle lobe samples using an indirect avidin-peroxidase method, after which the staining was semiquantified with H-scores. Statistically significant differences were observed in the occludin, claudin and JAM H-scores among the four groups (P<0.001). In the untreated asthma, etanercept, bevacizumab and dexamethasone groups, the median H-scores for occludin were 93, 177, 280 and 198, respectively, while the H-scores for claudin were 82, 193.5, 274 and 202.5, respectively, and the median H-scores for JAM were 130, 210, 288 and 210, respectively. Pairwise comparisons revealed that all three ZO protein H-scores were significantly lower in the saline group when compared with each treatment group. However, the H-scores of the ZO proteins were not significantly different between the etanercept and dexamethasone groups. Furthermore, the bevacizumab group exhibited higher H-scores for all the proteins compared with the dexamethasone group. Therefore, antagonism of VEGF with bevacizumab restores the epithelial barrier to a greater extent when compared with dexamethasone treatment. This result may be promising for the development of novel therapeutic agents.

Inhaled budesonide and oral dexamethasone prevent acute mountain sickness

BACKGROUND

This double-blind, randomized controlled trial aimed to investigate inhaled budesonide and oral dexamethasone compared with placebo for their prophylactic efficacy against acute mountain sickness after acute high-altitude exposure.

METHODS

There were 138 healthy young male lowland residents recruited and randomly assigned to receive inhaled budesonide (200 μg, twice a day [bid]), oral dexamethasone (4 mg, bid), or placebo (46 in each group). They traveled to 3900 m altitude from 400 m by car. Medication started 1 day before high-altitude exposure and continued until the third day of exposure. Primary outcome measure was the incidence of acute mountain sickness after exposure.

RESULTS

One hundred twenty-four subjects completed the study (42, 39, and 43 in the budesonide, dexamethasone, and placebo groups, respectively). Demographic characteristics were comparable among the 3 groups. After high-altitude exposure, significantly fewer participants in the budesonide (23.81%) and dexamethasone (30.77%) groups developed acute mountain sickness compared with participants receiving placebo (60.46%) (P = .0006 and P = .0071, respectively). Both the budesonide and dexamethasone groups had lower heart rate and higher pulse oxygen saturation (SpO2) than the placebo group at altitude. Only the budesonide group demonstrated less deterioration in forced vital capacity and sleep quality than the placebo group. Four subjects in the dexamethasone group reported adverse reactions.

CONCLUSIONS

Both inhaled budesonide (200 μg, bid) and oral dexamethasone (4 mg, bid) were effective for the prevention of acute mountain sickness, especially its severe form, compared with placebo. Budesonide caused fewer adverse reactions than dexamethasone.

Effect of intramammary administration of prednisolone on the blood-milk barrier during the immune response of the mammary gland to lipopolysaccharide

OBJECTIVE

To investigate effects of intramammary administration of prednisolone on the immune response of mammary glands in cows.

ANIMALS

5 lactating Red Holsteins.

PROCEDURES

Cows received a different intramammary infusion in each mammary gland (10 mg of prednisolone, 100 μg of lipopolysaccharide [LPS], 100 μg of LPS and 10 mg of prednisolone, or saline [0.9% NaCl] solution). Milk samples were collected before (time 0) and 3, 6, 9, 12, 24, and 36 hours after treatment. Somatic cell count (SCC), lactate dehydrogenase (LDH) activity, and concentrations of serum albumin (SA) and tumor necrosis factor (TNF)-α in milk and mRNA expression of TNF-α, interleukin (IL)-8, and IL-1β in milk somatic cells were analyzed.

RESULTS

Saline solution or prednisolone did not change SCC, LDH activity, and SA and TNF-α concentrations in milk and mRNA expression of TNF-α, IL-1β, and IL-8 in milk somatic cells. The SCC and TNF-α concentration in milk increased similarly in glands infused with LPS, independent of prednisolone administration. However, the increase of LDH activity and SA concentration in milk after LPS infusion was diminished by prednisolone administration. The mRNA expression of TNF-α, IL-8, and IL-1β in milk somatic cells increased after LPS infusion and was unaffected by prednisolone.

CONCLUSIONS AND CLINICAL RELEVANCE

Intramammary administration of prednisolone did not induce an immune response and did not change mRNA expression of TNF-α, IL-8, and L-1β during the response to intramammary administration of LPS. However, prednisolone reduced disruption of the blood-milk barrier. This could influence the severity and cure rate of mastitis.