IL-9 and IL-13 induce mucous cell metaplasia that is reduced by IFN-gamma in a Bax-mediated pathway

Cytokine Storm and Mucus Hypersecretion in COVID-19: Review of Mechanisms

Mucus is an integral part of the respiratory physiology. It protects the respiratory tract by acting as a physical barrier against inhaled particles and microbes. Excessive inflammation in conditions such as COVID-19 can result in over-production of mucus which obstructs the airway. Build-up of mucus can also contribute to recurrent airway infection, causing further obstruction. This article summarizes the current understanding and knowledge of respiratory mucus production and proposes the role of cytokine storm in inducing sudden mucus hypersecretion in COVID-19. Based on these cascades, the active constituents that inhibit or activate several potential targets are outlined for further research. These may be explored for the discovery and design of drugs to combat cytokine storm and its ensuing complications.

A review on the effect of COVID-19 in type 2 asthma and its management

Background

COVID-19 is considered the most critical health pandemic of 21st century. Due to extremely high transmission rate, people are more susceptible to viral infection. COVID-19 patients having chronic type-2 asthma prevails a major risk as it may aggravate the disease and morbidities.

Objective

The present review mainly focuses on correlating the influence of COVID-19 in type-2 asthmatic patients. Besides, it delineates the treatment measures and drugs that can be used to manage mild, moderate, and severe symptoms of COVID-19 in asthmatic patients, thus preventing any exacerbation.

Methods

An in-depth research was carried out from different peer-reviewed articles till September 2020 from several renowned databases like PubMed, Frontier, MEDLINE, and related websites like WHO, CDC, MOHFW, and the information was analysed and written in a simplified manner.

Results

The progressive results were quite conflicting as severe cases of COVID-19 shows an increase in the level of several cytokines that can augment inflammation to the bronchial tracts, worsening the asthma attacks. Contradicting to this, certain findings reveal the decrease in the severity of COVID-19 due to the elevation of T-cells in type-2 asthmatic patients, as prominent reduction of T-cell is seen in most of the COVID-19 positive patients. This helps to counteract the balance of immune responses and hence ameliorate the disease progression.

Conclusion

Asthmatic patients must remain cautious during the COVID-19 pandemic by maintaining all the precautions to stay safe due to limited research data. Future strategies should include a better understanding of asthmatic exacerbation and its relation to COVID-19.

IL-13 in LPS-Induced Inflammation Causes Bcl-2 Expression to Sustain Hyperplastic Mucous cells

Exposure to lipopolysaccharides (LPS) causes extensive neutrophilic inflammation in the airways followed by mucous cell hyperplasia (MCH) that is sustained by the anti-apoptotic protein, Bcl-2. To identify inflammatory factor(s) that are responsible for Bcl-2 expression, we established an organ culture system consisting of airway epithelial tissue from the rat nasal midseptum. The highest Muc5AC and Bcl-2 expression was observed when organ cultures were treated with brochoalveolar lavage (BAL) fluid harvested from rats 10 h post LPS instillation. Further, because BAL harvested from rats depleted of polymorphonuclear cells compared to controls showed increased Bcl-2 expression, analyses of cytokine levels in lavages identified IL-13 as an inducer of Bcl-2 expression. Ectopic IL-13 treatment of differentiated airway epithelial cells increased Bcl-2 and MUC5AC expression in the basal and apical regions of the cells, respectively. When Bcl-2 was blocked using shRNA or a small molecule inhibitor, ABT-263, mucous cell numbers were reduced due to increased apoptosis that disrupted the interaction of Bcl-2 with the pro-apoptotic protein, Bik. Furthermore, intranasal instillation of ABT-263 reduced the LPS-induced MCH in bik +/+ but not bik -/- mice, suggesting that Bik mediated apoptosis in hyperplastic mucous cells. Therefore, blocking Bcl-2 function could be useful in reducing IL-13 induced mucous hypersecretion.

Effect of TH2 cytokines and interferon gamma on beat frequency of human respiratory cilia

BACKGROUND

In asthmatic airways secondary ciliary dyskinesia contributes to impaired mucociliary clearance. To investigate underlying mechanisms, we studied the effects of cytokines associated with asthma phenotype on the ciliary beat frequency (CBF) in a cell culture model of ciliated human respiratory epithelial cells.

METHODS

Nasal respiratory epithelial cells of 21 patients were used to prepare multicellular cells (spheroids) in the presence of the T helper (TH) 2 cytokines interleukin (IL)-4, IL-5, IL-9 and IL-13, and the TH1 cytokine interferon gamma (IFN-γ). CBF was determined by high-speed video microscopy.

RESULTS

Addition of IL-4 and IL-13 and IL-4 + IL-13 decreased the mean CBF by 17, 21, and 22%, respectively, compared with untreated controls. Addition of IL-5 and IL-9 lead to an increase in mean CBF (20 and 10%, respectively). Lower concentrations of IFN-γ (0.1 and 1 ng/ml) decreased mean CBF and higher concentrations (10 ng/ml) increased CBF by 6%. Addition of IFN-γ to IL-13 reversed the effect of IL-13 on the CBF of spheroids.

CONCLUSION

Cytokines directly influence the ciliary function of respiratory epithelium and contribute to the impaired mucociliary clearance in asthmatic disease. Our study encourages further research to investigate IFN-γ as a treatment option in diseases with impaired mucociliary clearance like asthma.

The potential for genetically altered microglia to influence glioma treatment

Diffuse and unstoppable infiltration of brain and spinal cord tissue by neoplastic glial cells is the single most important therapeutic problem posed by the common glioma group of tumors: astrocytoma, oligoastrocytoma, oligodendroglioma, their malignant variants and glioblastoma. These neoplasms account for more than two thirds of all malignant central nervous system tumors. However, most glioma research focuses on an examination of the tumor cells rather than on host-specific, tumor micro-environmental cells and factors. This can explain why existing diffuse glioma therapies fail and why these tumors have remained incurable. Thus, there is a great need for innovation. We describe a novel strategy for the development of a more effective treatment of diffuse glioma. Our approach centers on gaining control over the behavior of the microglia, the defense cells of the CNS, which are manipulated by malignant glioma and support its growth. Armoring microglia against the influences from glioma is one of our research goals. We further discuss how microglia precursors may be genetically enhanced to track down infiltrating glioma cells.

hCLCA1 DNA vaccine suppresses cell hyperplasia and mucin expression of goblet cells in vitro

BACKGROUND

Excessive airway mucus secretion is a remarkable trait of asthma. Mucus overproduction mainly resulted from an increase in goblet cell numbers, which causes considerable damage to health. However, effective therapeutic treatments are still lacking for mucus hypersecretion. Human calcium-activated chloride channel 1 (hCLCA1) has been identified to be predominantly responsible for mucus hypersecretion.

OBJECTIVES

In this study, we investigated the effects of an hCLCA1 DNA vaccine on the control of mucus production and goblet cell proliferation using an in vitro model goblet cell line (NCI-H292).

METHODS

The effect of the hCLCA1 DNA vaccine on cell viability and proliferative activity of NCI-H292/hCLCA1 was analyzed by electron microscopy, MTT assay, and flow cytometry. Expression of mucins and MUC5AC, a major member of the mucin gene family in airway goblet cells, was assessed under hCLCA1 DNA vaccine challenges by periodic acid-Schiff staining, quantitative real-time PCR and Western blot, respectively, and the expression profile of granulocyte-macrophage colony-stimulating factor (GM-CSF), a critical cytokine in airway inflammation, was also examined by real-time PCR and immunocytochemistry.

RESULTS

Results showed that hCLCA1 overexpression caused high cell proliferation and mucin expression, whereas the hCLCA1 DNA vaccine could effectively reverse these abnormal effects. In addition, GM-CSF expression was highly induced by hCLCA1 overexpression and efficiently suppressed by hCLCA1 DNA vaccine.

CONCLUSIONS

These results illustrate that the hCLCA1 DNA vaccine effectively inhibits cell hyperplasia and mucin gene expression of goblet cells, suggesting that the hCLCA1 DNA vaccine has potential value in the treatment of human asthma.

Chronic IL9 and IL-13 exposure leads to an altered differentiation of ciliated cells in a well-differentiated paediatric bronchial epithelial cell model

Asthma is a chronic inflammatory disease characterised by airways remodelling. In mouse models IL-9 and IL-13 have been implicated in airways remodelling including mucus hypersecretion and goblet cell hyperplasia. Their role, especially that of IL-9, has been much less studied in authentic human ex vivo models of the bronchial epithelium from normal and asthmatic children. We assessed the effects of IL-9, IL-13 and an IL-9/IL-13 combination, during differentiation of bronchial epithelial cells from normal (n = 6) and asthmatic (n = 8) children. Cultures were analysed for morphological markers and factors associated with altered differentiation (MUC5AC, SPDEF and MMP-7). IL-9, IL-9/IL-13 combination and IL-13 stimulated bronchial epithelial cells from normal children had fewer ciliated cells [14.8% (SD 8.9), p = 0.048, 12.4 (SD 6.1), p = 0.016 and 7.3% (SD 6.6), p = 0.031] respectively compared with unstimulated [(21.4% (SD 9.6)]. IL-9 stimulation had no effect on goblet cell number in either group whereas IL-9/IL-13 combination and IL-13 significantly increased goblet cell number [24.8% (SD 8.8), p = 0.02), 32.9% (SD 8.6), p = 0.007] compared with unstimulated normal bronchial cells [(18.6% (SD 6.2)]. All stimulations increased MUC5AC mRNA in bronchial epithelial cells from normal children and increased MUC5AC mucin secretion. MMP-7 localisation was dysregulated in normal bronchial epithelium stimulated with Th2 cytokines which resembled the unstimulated bronchial epithelium of asthmatic children. All stimulations resulted in a significant reduction in transepithelial electrical resistance values over time suggesting a role in altered tight junction formation. We conclude that IL-9 does not increase goblet cell numbers in bronchial epithelial cell cultures from normal or asthmatic children. IL-9 and IL-13 alone and in combination, reduce ciliated cell numbers and transepithelial electrical resistance during differentiation of normal epithelium, which clinically could inhibit mucociliary clearance and drive an altered repair mechanism. This suggests an alternative role for IL-9 in airways remodelling and reaffirms IL-9 as a potential therapeutic target.

Serum interleukin-9 levels are associated with clinical severity in children with atopic dermatitis

Atopic dermatitis (AD) is an inflammatory disorder of the skin characterized by impaired immune response. Th9 cells are a sub-population of T cells that release interleukin (IL)-9. No study has investigated the role of IL-9 in AD. This study compared 64 children with AD with 45 healthy children. Serum IL-9 levels were measured and clinical symptoms were assessed. Children with AD had higher serum IL-9 levels than controls (p = 0.01). Clinical severity was significantly related to IL-9 level, indicating that IL-9 might exert a pathogenic role in symptom occurrence in individuals with AD. Children with AD may have higher serum IL-9 levels than healthy children, and IL-9 levels are significantly related to symptom severity.

Histopathologic and morphometric evaluation of the nasal and pulmonary airways of cats with experimentally induced asthma

BACKGROUND

Allergic rhinitis frequently occurs as a comorbid condition in asthmatic people, suggesting that the upper and lower airways may be immunologically linked. Our research group has developed an experimental aeroallergen model of asthma in cats. We hypothesized that aeroallergen sensitization and challenge would induce morphologic changes in the nasal airways of cats that mimic those observed in the bronchial airways.

METHODS

Five mixed breed cats were sensitized to Bermuda grass allergen and then serially challenged with aerosolized Bermuda grass allergen to induce an asthmatic phenotype. Four control cats were similarly treated with saline vehicle. Nasal tissues and lungs were processed for histopathological and morphometric analyses.

RESULTS

Eosinophilic inflammation, epithelial hypertrophy and mucous cell metaplasia were observed along the pulmonary axial airway mucosa of allergen-sensitized (asthmatic) cats. Mild eosinophilic inflammation was observed in the nasal airways of asthmatic cats. This alteration was confined primarily to the anterior nasal cavity, resulting in an increase in tissue eosinophils at this site compared to controls (p < 0.05). A marked increase in tissue mast cells was observed throughout all regions of the nasal airways of asthmatic cats compared to control cats (p < 0.05). There was no difference in intraepithelial mucosubstances between the nasal airways of controls and asthmatic cats. There was no correlation between upper and lower airway eosinophils or mast cells.

CONCLUSION

Cats with experimentally induced asthma exhibit morphologic changes in the nasal airways that are distinct from the alterations observed in the lungs. These results are similar to those observed in people with comorbid asthma and allergic rhinitis.

IL-13 dampens human airway epithelial innate immunity through induction of IL-1 receptor-associated kinase M

BACKGROUND

Impaired airway mucosal immunity can contribute to increased respiratory tract infections in asthmatic patients, but the involved molecular mechanisms have not been fully clarified. Airway epithelial cells serve as the first line of respiratory mucosal defense to eliminate inhaled pathogens through various mechanisms, including Toll-like receptor (TLR) pathways. Our previous studies suggest that impaired TLR2 function in T(H)2 cytokine-exposed airways might decrease immune responses to pathogens and subsequently exacerbate allergic inflammation. IL-1 receptor-associated kinase M (IRAK-M) negatively regulates TLR signaling. However, IRAK-M expression in airway epithelium from asthmatic patients and its functions under a T(H)2 cytokine milieu remain unclear.

OBJECTIVES

We sought to evaluate the role of IRAK-M in IL-13-inhibited TLR2 signaling in human airway epithelial cells.

METHODS

We examined IRAK-M protein expression in epithelia from asthmatic patients versus that in normal airway epithelia. Moreover, IRAK-M regulation and function in modulating innate immunity (eg, TLR2 signaling) were investigated in cultured human airway epithelial cells with or without IL-13 stimulation.

RESULTS

IRAK-M protein levels were increased in asthmatic airway epithelium. Furthermore, in primary human airway epithelial cells, IL-13 consistently upregulated IRAK-M expression, largely through activation of phosphoinositide 3-kinase pathway. Specifically, phosphoinositide 3-kinase activation led to c-Jun binding to human IRAK-M gene promoter and IRAK-M upregulation. Functionally, IL-13-induced IRAK-M suppressed airway epithelial TLR2 signaling activation (eg, TLR2 and human β-defensin 2), partly through inhibiting activation of nuclear factor κB.

CONCLUSIONS

Our data indicate that epithelial IRAK-M overexpression in T(H)2 cytokine-exposed airways inhibits TLR2 signaling, providing a novel mechanism for the increased susceptibility of infections in asthmatic patients.

Up-regulation of MUC18 in airway epithelial cells by IL-13: implications in bacterial adherence

Airway bacterial infections are a major problem in lung diseases, including asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis. Increased Th2 cytokines, such as IL-13, are observed in lung diseases and may contribute to bacterial infections. How Th2 cytokines affect bacterial infection remains unknown. MUC18, an adhesion molecule shown to be involved in the pathogenesis of malignant melanoma, has been recently identified in airway epithelial cells of patients with COPD. We investigated MUC18 regulation by IL-13 and the role of MUC18 in bacterial adherence to epithelial cells. Human airway tissues, brushed bronchial epithelial cells from normal subjects and subjects with asthma, and epithelial cell lines (e.g., HEK293 cells) were used to study the regulation of MUC18 by IL-13 and the involvement of MUC18 in bacterial (e.g., Mycoplasma pneumoniae [Mp] and nontypeable Haemophilus influenzae [NTHi]) adherence to epithelial cells. Asthmatic bronchial epithelium expressed higher levels of MUC18 than normal bronchial epithelium. IL-13 increased MUC18 in cultured bronchial epithelial cells from normal subjects and particularly from subjects with asthma. IL-13-induced MUC18 expression may be modulated in part through transcription factor specificity protein 1. Overexpression of human MUC18 in HEK293 cells increased cell-associated Mp and NTHi levels. Moreover, MUC18 was shown to directly interact with Mp and NTHi. These results for the first time show that an allergic airway milieu (e.g., IL-13) increases MUC18 expression, which may contribute to increased bacterial infection/colonization in asthma and other lung diseases.

Simultaneous analysis of the local and systemic immune responses in mice to study the occupational asthma mechanisms induced by chromium and platinum

As a result of industrial development, increased exposure to platinum and chromium compounds and the subsequent development of occupational asthma (OA) has been reported. Although specific IgE antibodies, an indicator of allergic asthma, against chromium and platinum have been detected in workers with OA, the immunopathological mechanisms involved in this disease are not fully understood. To better understand these complex mechanisms, the local and systemic immune responses were simultaneously analyzed in mice sensitized and challenged three, four, or five times with sodium hexachloroplatinate (Pt salt) and with potassium dichromate (Cr salt) via the respiratory route. Dinitrochlorobenzene (DNCB) and anhydride trimellitic (TMA) were included in this study as reference compounds that induce Th1 and Th2 responses respectively. All the compounds studied may provoke pulmonary sensitization. In the Pt salt-treated mice with a significant increase in local Th2 cytokine production, the increase in IgE and mucus production and in eosinophil number had a positive correlation with the number of challenges (r=0.942, 0.976, and 0.978 respectively), whereas in the Cr salt-treated mice with no local increase in Th2 cytokines, the increase in IgE production and eosinophil numbers had an inverse correlation with the number of challenges (r=-0.895 and -0.999 respectively). The Th2-dominated response induced by Pt salt was very close to that induced by TMA and may thrive after the fifth challenge, probably due to the constancy of the significant decrease in IFN-γ level in the spleens. The results of the present work may increase our understanding of the immunopathological mechanisms of OA induced by platinum and chromium, and emphasize the advantage of simultaneously analyzing local and systemic immune response when studying respiratory allergy.

beta2-agonists promote host defense against bacterial infection in primary human bronchial epithelial cells

Background

Airway epithelial cells are critical in host defense against bacteria including Mycoplasma pneumoniae (Mp) in chronic obstructive pulmonary disease (COPD) and asthma. β2-agonists are mainstay of COPD and asthma therapy, but whether β2-agonists directly affect airway epithelial host defense functions is unclear.

Methods

Epithelial cells from bronchial brushings of normal (n = 8), asthma (n = 8) and COPD (n = 8) subjects were grown in air-liquid interface cultures, and treated with cigarette smoke extract (CSE) and/or Th2 cytokine IL-13, followed by Mp infection and treatment with β2-agonists albuterol and formoterol for up to seven days. Mp and host defense proteins short palate, lung, and nasal epithelial clone 1 (SPLUNC1) and β-defensin-2 were quantified. Expression of β2-adrenergic receptors was also measured by real-time quantitative RT-PCR.

Results

(R)- or racemic albuterol and (R,R)- or racemic formoterol significantly decreased Mp levels in normal and asthma epithelial cells. Normal cells treated with Mp and (R)- or racemic albuterol showed an increase in SPLUNC1, but not in β-defensin-2. COPD cells did not respond to drug treatment with a significant decrease in Mp or an increase in SPLUNC1. IL-13 attenuated drug effects on Mp, and markedly decreased SPLUNC1 and β2-adrenergic receptors.

Conclusions

These results for the first time show that β2-agonists enhance host defense functions of primary bronchial epithelial cells from normal and asthma subjects, which is attenuated by IL-13.

How ERK1/2 activation controls cell proliferation and cell death: Is subcellular localization the answer?

Extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) are members of the mitogen-activated protein kinase super family that can mediate cell proliferation and apoptosis. The Ras-Raf-MEK-ERK signaling cascade controlling cell proliferation has been well studied but the mechanisms involved in ERK1/2-mediated cell death are largely unknown. This review focuses on recent papers that define ERK1/2 translocation to the nucleus and the proteins involved in the cytosolic retention of activated ERK1/2. Cytosolic retention of ERK1/2 denies access to the transcription factor substrates that are responsible for the mitogenic response. In addition, cytosolic ERK1/2, besides inhibiting survival and proliferative signals in the nucleus, potentiates the catalytic activity of some proapoptotic proteins such as DAP kinase in the cytoplasm. Studies that further define the function of cytosolic ERK1/2 and its cytosolic substrates that enhance cell death will be essential to harness this pathway for developing effective treatments for cancer and chronic inflammatory diseases.

The BH3-only protein Bik/Blk/Nbk inhibits nuclear translocation of activated ERK1/2 to mediate IFNgamma-induced cell death

IFNγ induces cell death in epithelial cells, but the mediator for this death pathway has not been identified. In this study, we find that expression of Bik/Blk/Nbk is increased in human airway epithelial cells (AECs [HAECs]) in response to IFNγ. Expression of Bik but not mutant BikL61G induces and loss of Bik suppresses IFNγ-induced cell death in HAECs. IFNγ treatment and Bik expression increase cathepsin B and D messenger RNA levels and reduce levels of phospho–extracellular regulated kinase 1/2 (ERK1/2) in the nuclei of bik^+/+ compared with bik^−/− murine AECs. Bik but not BikL61G interacts with and suppresses nuclear translocation of phospho-ERK1/2, and suppression of ERK1/2 activation inhibits IFNγ- and Bik-induced cell death. Furthermore, after prolonged exposure to allergen, hyperplastic epithelial cells persist longer, and nuclear phospho-ERK is more prevalent in airways of IFNγ^−/− or bik^−/− compared with wild-type mice. These results demonstrate that IFNγ requires Bik to suppress nuclear localization of phospho-ERK1/2 to channel cell death in AECs.

Expression of the proapoptotic protein Bax is reduced in bronchial mucous cells of asthmatic subjects

The present studies were designed to determine whether our findings in mice showing that the Bcl-2-associated protein X (Bax), which plays a role in the resolution of allergen-induced mucous cell metaplasia, can be applied to asthma in humans. Immunostaining of autopsy tissues from mild and severe asthmatic subjects showed a significant reduction in the percentage of Bax-positive mucous cells compared with those from nonasthmatic controls. To exclude the possibility that postmortem changes may have affected Bax expression, Bax mRNA levels in airway epithelial cells obtained from nonsmoking asthmatic subjects were compared with those from nonasthmatic controls. Because the number of cells obtained by bronchial brushings is limited, we developed a robust preamplification procedure of cDNA before quantitative real-time PCR to allow detection of 100 gene targets from limited sample size, even when it was prepared from partially degraded RNA. cDNA was prepared by reverse transcription from RNA isolated from bronchial epithelial cells obtained by bronchial brushings from well-characterized subjects without lung disease and from subjects with mild asthma. Quantitative analysis showed that Bax mRNA levels were significantly reduced in samples obtained from asthma patients compared with nonasthma controls. Furthermore, Bax mRNA levels were reduced when primary airway epithelial cells from 10 individuals were treated in culture with the T helper 2 cytokine IL-13. These studies show that Bax expression is reduced in airway epithelial cells of even mild asthmatic subjects and suggest that restoring Bax expression may provide a clinical approach for restoring the normal numbers of epithelial cells and reduced mucous hypersecretion in asthma.

Increased mucus accumulation in horses chronically affected with recurrent airway obstruction is not associated with up-regulation of CLCA1, EGFR, MUC5AC, Bcl-2, IL-13 and INF-gamma expression

The mechanisms leading to mucus accumulation in equine inflammatory airway disease (IAD) and recurrent airway obstruction (RAO) are unclear. In airways of human patients with asthma and/or chronic obstructive pulmonary disease as well as in animal models of these diseases, associations of mucus hyperproduction with increased calcium-activated chloride channel 1 (CLCA1), epidermal growth factor receptor (EGFR), mucin 5AC (MUC5AC), B-cell lymphoma 2 (Bcl-2), interleukin (IL)-13 and interferon (IFN)-gamma expression have been reported. We hypothesized that increased mucus accumulation in RAO and IAD are associated with alterations in inflammatory cytokine (IL-13 and IFN-gamma) and epithelial gene (CLCA1, EGFR, Bcl-2 and MUC5AC) profiles. Therefore, mRNA expression of these genes in cell pellets extracted from bronchoalveolar lavage fluid (BALF) and bronchial epithelial brushing (BEB) was compared between 11 clinically healthy (Control group), 7 IAD- and 12 RAO-affected horses by reverse transcription polymerase chain reaction. We also performed arterial blood gas analysis, endoscopic scoring of mucus accumulation in the trachea and cytology of tracheo-bronchial secretions (TBS) and of BALF. Tracheal mucus accumulation, along with TBS and BALF neutrophils were significantly increased and arterial pO(2) was decreased in RAO-affected horses compared to the Control group. IL-13 in BALF samples was significantly lower in the RAO group. None of the other genes' relative mRNA levels displayed significant differences between groups. Our findings suggest that mucus production in equine RAO is induced by pathways independent of IL-13, CLCA1, EGFR, MUC5AC and Bcl-2 up-regulation.