GP130-STAT3 regulates epithelial cell migration and is required for repair of the bronchiolar epithelium

Dysregulated Airway Host Defense in Hyper IgE Syndrome due to STAT3 Mutations

Rationale

Hyper IgE syndrome (STAT3-HIES), also known as Job's syndrome, is a rare immunodeficiency disease typically caused by dominant-negative STAT3 mutations. STAT3-HIES syndrome is characterized by chronic pulmonary infection and inflammation, suggesting impairment of pulmonary innate host defense.

Objectives

To identify airway epithelial host defense defects consequent to STAT3 mutations that, in addition to reported mutant STAT3 immunologic abnormalities, produce pulmonary infection.

Methods

STAT3-HIES sputum was evaluated for biochemical/biophysical properties. STAT3-HIES excised lungs were harvested for histology; bronchial brush samples were collected for RNA sequencing and in vitro culture. A STAT3-HIES-specific mutation (R382W), expressed by lentiviruses, and a STAT3 knockout, generated by CRISPR/Cas9, were maintained in normal human bronchial epithelia under basal or inflammatory (IL1β) conditions. Effects of STAT3 deficiency on transcriptomics, and epithelial ion channel, secretory, antimicrobial, and ciliary functions were assessed.

Measurements and Main Results

Mucus concentrations and viscoelasticity were increased in STAT3-HIES sputum. STAT3-HIES excised lungs exhibited mucus obstruction and elevated IL1β expression. STAT3 deficiency impaired CFTR-dependent fluid and mucin secretion, inhibited expression of antimicrobial peptides, cytokines, and chemokines, and acidified airway surface liquid at baseline and post-IL1β exposure in vitro. Notably, mutant STAT3 suppressed IL1R1 expression. STAT3 mutations also inhibited ciliogenesis in vivo and impaired mucociliary transport in vitro, a process mediated via HES6 suppression. Administration of a γ-secretase inhibitor increased HES6 expression and improved ciliogenesis in STAT3 R382W mutant cells.

Conclusions

STAT3 dysfunction leads to multi-component defects in airway epithelial innate defense, which, in conjunction with STAT3-HIES immune deficiency, contributes to chronic pulmonary infection.

STAT3 mutation-associated airway epithelial defects in Job syndrome

BACKGROUND

Job syndrome is a disease of autosomal dominant hyper-IgE syndrome (AD-HIES). Patients harboring STAT3 mutation are particularly prone to airway remodeling and airway infections.

OBJECTIVES

Airway epithelial cells play a central role as the first line of defense against pathogenic infection and express high levels of STAT3. This study thus interrogates how AD-HIES STAT3 mutations impact the physiological functions of airway epithelial cells.

METHODS

This study created human airway basal cells expressing 4 common AD-HIES STAT3 mutants (R382W, V463del, V637M, and Y657S). In addition, primary airway epithelial cells were isolated from a patient with Job syndrome who was harboring a STAT3-S560del mutation and from mice harboring a STAT3-V463del mutation. Cell proliferation, differentiation, barrier function, bacterial elimination, and innate immune responses to pathogenic infection were quantitatively analyzed.

RESULTS

STAT3 mutations reduce STAT3 protein phosphorylation, nuclear translocation, transcription activity, and protein stability in airway basal cells. As a consequence, STAT3-mutated airway basal cells give rise to airway epithelial cells with abnormal cellular composition and loss of coordinated mucociliary clearance. Notably, AD-HIES STAT3 airway epithelial cells are defective in bacterial killing and fail to initiate vigorous proinflammatory responses and neutrophil transepithelial migration in response to an experimental model of Pseudomonas aeruginosa infection.

CONCLUSIONS

AD-HIES STAT3 mutations confer numerous abnormalities to airway epithelial cells in cell differentiation and host innate immunity, emphasizing their involvement in the pathogenesis of lung complications in Job syndrome. Therefore, therapies must address the epithelial defects as well as the previously noted immune cell defects to alleviate chronic infections in patients with Job syndrome.

Inhibition of gp130 alleviates LPS-induced lung injury by attenuating apoptosis and inflammation through JAK1/STAT3 signaling pathway

BACKGROUND AND OBJECTIVE

Acute lung injury or acute respiratory distress syndrome (ALI/ARDS) is a life-threatening respiratory disease. Gp130 is a signal transduction receptor that participates in a variety of essential biological processes. The biological function of gp130 in ALI/ARDS is unclear. This study aims to investigate the roles and potential mechanisms of gp130 in lung injury induced by lipopolysaccharide (LPS).

METHODS

The ALI/ARDS mouse model was established using intratracheal LPS administration. Hematoxylin and eosin staining and bronchoalveolar lavage fluid analysis were used to evaluate the degree of lung injury. Cell apoptosis was assessed by TUNEL staining, flow cytometry, and western blot. Then the expression of gp130, IL-6, IL-10, TNF-α, and the JAK1/STAT3 signaling pathway-related proteins was assessed by RT-PCR, western blot, and immunohistochemistry.

RESULTS

The expression of gp130 increased after 24 h of LPS treatment. Inhibiting gp130 improved inflammatory infiltration and alveolar collapsed, decreased IL-6 and TNF-α levels, raised IL-10 levels, and decreased cell apoptosis in LPS-induced mice. Meanwhile, suppressing gp130 reduced the inflammatory response and cell apoptosis in LPS-induced Beas-2B cells. Furthermore, p-JAK1 and p-STAT3 expressions were elevated after LPS stimulation and decreased following gp130 inhibition, suggesting that gp130 may regulate the JAK1/STAT3 signaling pathway in LPS-induced mice and Beas-2B cells.

CONCLUSION

The findings suggest that gp130 regulates the inflammatory response and cell apoptosis through the JAK1/STAT3 signaling pathway, thereby mitigating LPS-induced lung injury. Gp130 may be a potential therapeutic target for ALI/ARDS.

IL-6 family cytokines in respiratory health and disease

Chronic lung diseases including asthma, chronic obstructive pulmonary disease (COPD) and lung fibrosis represent a major burden on healthcare systems with limited effective therapeutic options. Developing effective treatments for these debilitating diseases requires an understanding of how alterations at the molecular level affect lung macroscopic architecture. A common theme among these lung disorders is the presence of an underlying dysregulated immune system which can lead to sustained chronic inflammation. In this respect, several inflammatory cytokines have been implicated in the pathogenesis of lung diseases, thus leading to the notion that cytokines are attractive therapeutic targets for these disorders. In this review, we discuss and highlight the recent breakthroughs that have enhanced our understanding of the role of the interleukin (IL)-6 family of cytokines in lung homeostasis and chronic diseases including asthma, COPD, lung fibrosis and lung cancer.

Evaluation of the Toxicity on Lung Cells of By-Products Present in Naphthalene Secondary Organic Aerosols

In 2018, seven million people died prematurely due to exposure to pollution. Polycyclic aromatic hydrocarbons (PAHs) are a significant source of secondary organic aerosol (SOA) in urban areas. We investigated the toxic effects of by-products of naphthalene SOA on lung cells. These by-products were 1,4-naphthoquinone (1,4-NQ), 2-hydroxy-1,4-naphthoquinone (2-OH-NQ), phthalic acid (PA) and phthaldialdehyde (OPA). Two different assessment methodologies were used to monitor the toxic effects: real-time cell analysis (RTCA) and the Holomonitor, a quantitative phase contrast microscope. The chemicals were tested in concentrations of 12.5 to 100 µM for 1,4-NQ and 1 to 10 mM for 2-OH-NQ, PA and OPA. We found that 1,4-NQ is toxic to cells from 25 to 100 µM (EC50: 38.7 µM ± 5.2); 2-OH-NQ is toxic from 1 to 10mM (EC50: 5.3 mM ± 0.6); PA is toxic from 5 to 10 mM (EC50: 5.2 mM ± 0.3) and OPA is toxic from 2.5 to 10 mM (EC50: 4.2 mM ± 0.5). Only 1,4-NQ and OPA affected cell parameters (migration, motility, motility speed and optical volume). Furthermore, 1,4-NQ is the most toxic by-product of naphthalene, with an EC50 value that was one hundred times higher than those of the other compounds. RTCA and Holomonitor analysis showed a complementarity when studying the toxicity induced by chemicals.

Interleukin 22 mitigates endothelial glycocalyx shedding after lipopolysaccharide injury

BACKGROUND

The endothelial glycocalyx (EG) on the luminal surface of endothelial cells contributes to the permeability barrier of vessels and prevents activation of the coagulation cascade. Endothelial glycocalyx damage, which occurs in the shock state, results in endotheliopathy. Interleukin (IL)-22 is a cytokine with both proinflammatory and anti-inflammatory properties, and how IL-22 affects the EG has not been studied. We hypothesized that IL-22:Fc, a recombinant fusion protein with human IL-22 and the Fc portion of human immunoglobulin G1 (which extends the protein half-life), would not affect EG shedding in endothelium after injury.

METHODS

Human umbilical vein endothelial cells (HUVECs) were exposed to 1 μg/mL lipopolysaccharide (LPS). Lipopolysaccharide-injured cells (n = 284) were compared with HUVECs with LPS injury plus 0.375 μg/mL of IL-22:Fc treatment (n = 293) for 12 hours. These two cohorts were compared with control HUVECs (n = 286) and HUVECs exposed to IL-22:Fc alone (n = 269). Cells were fixed and stained with fluorescein isothiocyanate-labeled wheat germ agglutinin to quantify EG. Total RNA was collected, and select messenger RNAs were quantified by real time - quantitative polymerase chain reaction (RT-qPCR) using SYBR green fluorescence.

RESULTS

Exposure of HUVECs to LPS resulted in degradation of the EG compared with control (5.86 vs. 6.09 arbitrary unit [AU], p = 0.01). Interleukin-22:Fc alone also resulted in degradation of EG (5.08 vs. 6.09 AU, p = 0.01). Treatment with IL-22:Fc after LPS injury resulted in less degradation of EG compared with LPS injury alone (5.86 vs. 5.08 AU, p = 0.002). Expression of the IL-22Ra1 receptor was not different for IL-22:Fc treated compared with LPS injury only (0.69 vs. 0.86 relative expression, p = 0.10). Treatment with IL-22:Fc after LPS injury resulted in less matrix metalloproteinase 2 (0.79 vs. 1.70 relative expression, p = 0.005) and matrix metalloproteinase 14 (0.94 vs. 2.04 relative expression, p = 0.02).

CONCLUSIONS

Interleukin-22:Fc alone induces EG degradation. However, IL-22:Fc treatment after LPS injury appears to mitigate EG degradation. This protective effect appears to be mediated via reduced expression of metalloproteinases.

Ceramide induces MMP-9 expression through JAK2/STAT3 pathway in airway epithelium

BACKGROUND

Ceramide, a bioactive lipid, plays an essential role in the development of several pulmonary inflammatory diseases. Matrix metallopeptidase 9 (MMP-9) regulates the synthesis and degradation of extracellular matrix, and is associated with airway remodeling and tissue injury. This study was conducted to investigate the effects and underlying mechanisms of ceramide on MMP-9 expression in airway epithelium.

METHODS

BEAS-2B cells, normal human bronchial epithelium cell lines, were pretreated with AG490, a selective janus tyrosine kinase 2 (JAK2) inhibitor, or Stattic, a selective signal transducer and activator of transcription 3 (STAT3) inhibitor. The cells were then stimulated with C6-ceramide. The levels of MMP-9 were determined by ELISA and real-time quantitative PCR (RT-qPCR). JAK2, phosphorylated JAK2 (p-JAK2), STAT3, and phosphorylated STAT3 (p-STAT3) expression was examined by Western blotting. BALB/c mice were pretreated with AG490 or Stattic before intratracheally instillated with C6-ceramide. Pathological changes in lung tissues were examined by Hematoxylin and Eosin staining, Periodic-acid Schiff staining, and Masson's trichrome staining. MMP-9, JAK2, p-JAK2, STAT3, and p-STAT3 expression in the lung tissues was examined by Western blotting.

RESULTS

The expression of MMP-9, p-JAK2 and p-STAT3 in BEAS-2B cells was significantly increased after the treatment of C6-ceramide. Furthermore, the increased expression of MMP-9 induced by C6-ceramide was inhibited by AG490 and Stattic. Similar results were obtained in the lung tissues of C6-ceramide-exposed mice which were treated with AG490 or Stattic.

CONCLUSIONS

Ceramide could up-regulate MMP-9 expression through the activation of the JAK2/STAT3 pathway in airway epithelium. Targeted modulation of the ceramide signaling pathway may offer a potential therapeutic approach for inhibiting MMP-9 expression. This study points to a potentially novel approach to alleviating airway remodeling in inflammatory airway diseases.

Emergence of azole resistant-Aspergillus fumigatus infections during STAT3-deficiency

Introduction. Signal transducer and activator of transcription 3 (STAT3) deficiency is a rare primary immunodeficiency associated with increased susceptibility to bacterial and fungal infections, notably pulmonary aspergillosis.Aim. We describe the emergence of azole-resistant Aspergillus fumigatus infections in STAT3-deficient patients.Methodology. During a retrospective study of 13 pulmonary aspergillosis cases in STAT3-deficient patients conducted in France, we identified patients infected with azole-resistant A. fumigatus isolates.Results. Two out of the 13 STAT3-deficient patients with aspergillosis had azole-resistant A. fumigatus infection, indicating an unexpectedly high prevalence of resistance. The first patient with STAT3 deficiency presented several flares of allergic bronchopulmonary aspergillosis-like episodes. He was chronically infected with two azole-resistant A. fumigatus isolates (TR₃₄/L98). Despite prolonged antifungal treatment, including caspofungin and amphotericin B, the patient was not able to clear the azole-resistant A. fumigatus. The second patient had chronic cavitary pulmonary aspergillosis (CCPA). The A. fumigatus isolate was initially azole susceptible but harboured three F46Y, M172V and E427K point mutations. Despite prolonged antifungal therapies, lesions worsened and the isolate became resistant to all azoles. Surgery and caspofungin treatments were then required to cure CCPA. Resistance was probably acquired from the environment (TR₃₄/L98) in the first case whereas resistance developed under antifungal treatments in the second case. These infections required long-term antifungal treatments and surgery.Conclusions. The emergence of azole-resistant A. fumigatus infections in STAT3-deficiency dramatically impacts both curative and prophylactic antifungal strategies. Physicians following patients with primary immune-deficiencies should be aware of this emerging problem as it complicates management of the patient.

Effects of cannabis oil extract on immune response gene expression in human small airway epithelial cells (HSAEpC): implications for chronic obstructive pulmonary disease (COPD)

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is commonly associated with both a pro-inflammatory and a T-helper 1 (Th1) immune response. It was hypothesized that cannabis oil extract can alleviate COPD symptoms by eliciting an anti-inflammatory Th2 immune response. Accordingly, the effects of cannabis oil extract on the expression of 84 Th2 and related immune response genes in human small airways epithelial cells (HSAEpC) were investigated.

METHODS

HSAEpC from a single donor were treated with three dilutions of a standardized cannabis oil extract (1:400, 1:800 and 1:1600) along with a solvent control (0.25% [2.5 ul/ml] ethanol) for 24 h. There were four replicates per treatment dilution, and six for the control. RNA isolated from cells were employed in pathway-focused quantitative polymerase chain reaction (qPCR) microarray assays.

RESULTS

The extract induced significant (P < 0.05) changes in expression of 37 tested genes. Six genes (CSF2, IL1RL1, IL4, IL13RA2, IL17A and PPARG) were up-regulated at all three dilutions. Another two (CCL22 and TSLP) were up-regulated while six (CLCA1, CMA1, EPX, LTB4R, MAF and PMCH) were down-regulated at the 1:400 and 1:800 dilutions. The relationship of differentially-expressed genes of interest to biologic pathways was explored using the Database for Annotation, Visualization and Integrated Discovery (DAVID).

CONCLUSIONS

This exploratory investigation indicates that cannabis oil extract may affect expression of specific airway epithelial cell genes that could modulate pro-inflammatory or Th1 processes in COPD. These results provide a basis for further investigations and have prompted in vivo studies of the effects of cannabis oil extract on pulmonary function.

TRIAL REGISTRATION

NONE (all in vitro experiments).

Building and Regenerating the Lung Cell by Cell

The unique architecture of the mammalian lung is required for adaptation to air breathing at birth and thereafter. Understanding the cellular and molecular mechanisms controlling its morphogenesis provides the framework for understanding the pathogenesis of acute and chronic lung diseases. Recent single-cell RNA sequencing data and high-resolution imaging identify the remarkable heterogeneity of pulmonary cell types and provides cell selective gene expression underlying lung development. We will address fundamental issues related to the diversity of pulmonary cells, to the formation and function of the mammalian lung, and will review recent advances regarding the cellular and molecular pathways involved in lung organogenesis. What cells form the lung in the early embryo? How are cell proliferation, migration, and differentiation regulated during lung morphogenesis? How do cells interact during lung formation and repair? How do signaling and transcriptional programs determine cell-cell interactions necessary for lung morphogenesis and function?

Integrative Physiology of Pneumonia

Pneumonia is a type of acute lower respiratory infection that is common and severe. The outcome of lower respiratory infection is determined by the degrees to which immunity is protective and inflammation is damaging. Intercellular and interorgan signaling networks coordinate these actions to fight infection and protect the tissue. Cells residing in the lung initiate and steer these responses, with additional immunity effectors recruited from the bloodstream. Responses of extrapulmonary tissues, including the liver, bone marrow, and others, are essential to resistance and resilience. Responses in the lung and extrapulmonary organs can also be counterproductive and drive acute and chronic comorbidities after respiratory infection. This review discusses cell-specific and organ-specific roles in the integrated physiological response to acute lung infection, and the mechanisms by which intercellular and interorgan signaling contribute to host defense and healthy respiratory physiology or to acute lung injury, chronic pulmonary disease, and adverse extrapulmonary sequelae. Pneumonia should no longer be perceived as simply an acute infection of the lung. Pneumonia susceptibility reflects ongoing and poorly understood chronic conditions, and pneumonia results in diverse and often persistent deleterious consequences for multiple physiological systems.

TSLP promotes asthmatic airway remodeling via p38-STAT3 signaling pathway in human lung fibroblast

PURPOSE

Thymic stromal lymphopoietin (TSLP) acts as a critical cytokine involved in asthmatic airway remodeling. Our study aimed to characterize the crosstalk between airway epithelial cells and fibroblasts regulated by TSLP through the signaling pathways of Mitogen-activated protein kinase (MAPK) and signal transducer and activator of transcription 3 (STAT3).

MATERIALS AND METHODS

Human biopsy specimens and lung tissues from mice were stained with hematoxylin and eosin (H&E) and immunohistochemistry. Human lung fibroblasts were stimulated with human recombinant TSLP. The protein expression of phosphorylation of STAT3 (p-STAT3) and phosphorylation of MAPK as well as the expression of collagen I and alpha-smooth muscle actin (α-SMA) were detected by Western blotting and immunofluorescence. Co-culture was performed to detect the influence of TSLP secreted by airway epithelial cells on fibroblasts. An ovalbumin (OVA)-induced asthmatic murine model was established with or without intraperitoneal injection of SB203580 (inhibitor of p-38). Protein expression in lung tissue was detected by immunohistochemistry and western blotting.

RESULT

TSLP could activate MAPK in HLF-1. SB203580 could inhibit the activation of p38, attenuate phosphorylation of STAT3, and decrease the expression of collagen I and α-SMA consequently in human fibroblasts. Co-culture demonstrated that TSLP secreted by epithelial cells could promote the expression of collagen I and α-SMA and aggravates airway remodeling in fibroblasts. In vivo, expression of TSLP, collagen I, α-SMA, p-p38 and p-STAT3 was upregulated in airway tissue of OVA-challenged mice and downregulated in mice which were treated by SB203580. The tissue staining showed that airway structure change was attenuated by SB203580 compared with OVA challenged mice as well.

CONCLUSIONS

TSLP might promote asthmatic airway remodeling via p38 MAPK-STAT3 axis activation and the crosstalk between airway epithelial cells and fibroblasts could aggravate remodeling. Blockade of p38 could alleviate airway remodeling which might provide a new therapeutic target for asthma.

Updates on T helper type 17 immunity in respiratory disease

Interleukin-17 (IL-17)-producing cells play a critical role in mucosal immunity including the respiratory tract. This review will highlight recent advances in our understanding of these cells in mucosal immunity in the lung as well as their potential pathogenic roles in respiratory diseases. The IL-17-producing cells include γδ T cells, natural killer cells, group 3 innate lymphoid cells, and T helper type 17 (Th17) cells. There have been recent advances in our understanding of these cell populations in the lung as well as emerging data on how these cells are regulated in the lung. Moreover, Th17 cells may be a key component of tissue-resident memory cells that may be acquired over time or elicited by mucosal immunization that provides the host with enhanced immunity against certain pathogens.

Notch signaling regulates cell density-dependent apoptosis of NIH 3T3 through an IL-6/STAT3 dependent mechanism

Apoptosis is a physiological process that plays a critical maintenance role in cellular homeostasis. Previous reports have demonstrated that cells undergo apoptosis in a cell density-dependent manner, which is regulated, in part, by signal transducers and activators of transcription (STAT) 3. The molecular mechanisms regulating cell density-dependent apoptosis, however, has not been thoroughly investigated to date. Since Notch signaling is activated via direct cell-to-cell contact and plays a pivotal role in cell fate decisions, we examined the role of Notch signaling in cell density-dependent apoptosis of mouse embryonic fibroblasts NIH 3T3 cells. With the increase in cell density, IL-6 expression was induced, which was necessary for STAT3 activation as well as apoptosis regulation. Notch signaling was also activated in a cell-density dependent manner. Blocking Notch signaling either through siRNA-mediated targeting of Jagged1 expression or γ-secretase inhibitor treatment demonstrated that Notch signaling activation was necessary for IL-6 induction. Constitutive activation of Notch signaling via the overexpression of Notch1 intracellular domain was sufficient for the induction of IL-6, which was mediated via direct transcriptional activation. Taken together, our study indicates that Notch signaling regulates cell density-dependent apoptosis through IL-6/STAT3-dependent mechanism. Consequently, Notch signaling might represent a novel therapeutic target in diseases characterized by dysregulated apoptosis.

MEG3 is increased in idiopathic pulmonary fibrosis and regulates epithelial cell differentiation

Idiopathic pulmonary fibrosis (IPF) is a chronic interstitial lung disease causing fibrotic remodeling of the peripheral lung, leading to respiratory failure. Peripheral pulmonary epithelial cells lose normal alveolar epithelial gene expression patterns and variably express genes associated with diverse conducting airway epithelial cells, including basal cells. Single-cell RNA sequencing of pulmonary epithelial cells isolated from IPF lung tissue demonstrated altered expression of LncRNAs, including increased MEG3. MEG3 RNA was highly expressed in subsets of the atypical IPF epithelial cells and correlated with conducting airway epithelial gene expression patterns. Expression of MEG3 in human pulmonary epithelial cell lines increased basal cell-associated RNAs, including TP63, KRT14, STAT3, and YAP1, and enhanced cell migration, consistent with a role for MEG3 in regulating basal cell identity. MEG3 reduced expression of TP73, SOX2, and Notch-associated RNAs HES1 and HEY1, in primary human bronchial epithelial cells, demonstrating a role for MEG3 in the inhibition of genes influencing basal cell differentiation into club, ciliated, or goblet cells. MEG3 induced basal cell genes and suppressed genes associated with terminal differentiation of airway cells, supporting a role for MEG3 in regulation of basal progenitor cell functions, which may contribute to tissue remodeling in IPF.

spd1672, a novel in vivo-induced gene, affects inflammatory response in a murine model of Streptococcus pneumoniae infection

spd1672, a novel Streptococcus pneumoniae (hereinafter S. pn) gene induced in vivo, has been identified to contribute to the virulence of S. pn; however, the role of spd1672 during host innate immune reaction against S. pn infection is unknown. In the present study, mice were infected with wild-type D39 and mutant D39Δspd1672 strains. Compared with the D39-infected mice, reduced bacterial load and attenuated inflammatory response were observed in the D39Δspd1672-treated mice. The levels of proinflammatory cytokines, including IFN-γ, TNF-α, and IL-1β, in the blood of D39Δspd1672-infected mice were lower than that in the D39-infected group. Additionally, attenuated activation of STAT3 and AKT was observed in the D39Δspd1672-infected mice. In conclusion, our data indicated that spd1672 expression modulates the release of proinflammatory cytokines, and AKT–STAT3 signaling appears to participate in the process. In conclusion, the present study extends our understanding of the role of an in vivo-induced gene in S. pn–host interaction.

Cigarette Smoke Induces Human Epidermal Receptor 2-Dependent Changes in Epithelial Permeability

The airway epithelium constitutes a protective barrier against inhaled insults, such as viruses, bacteria, and toxic fumes, including cigarette smoke (CS). Maintenance of bronchial epithelial integrity is central for airway health, and defective epithelial barrier function contributes to the pathogenesis of CS-mediated diseases, such as chronic obstructive pulmonary disease. Although CS has been shown to increase epithelial permeability, current understanding of the mechanisms involved in CS-induced epithelial barrier disruption remains incomplete. We have previously identified that the receptor tyrosine kinase human epidermal receptor (HER) 2 growth factor is activated by the ligand neuregulin-1 and increases epithelial permeability in models of inflammatory acute lung injury. We hypothesized that CS activates HER2 and that CS-mediated changes in barrier function would be HER2 dependent in airway epithelial cells. We determined that HER2 was activated in whole lung, as well as isolated epithelial cells, from smokers, and that acute CS exposure resulted in HER2 activation in cultured bronchial epithelial cells. Mechanistic studies determined that CS-mediated HER2 activation is independent of neuregulin-1 but required upstream activation of the epidermal growth factor receptor. HER2 was required for CS-induced epithelial permeability as knockdown of HER2 blocked increases in permeability after CS. CS caused an increase in IL-6 production by epithelial cells that was dependent on HER2-mediated extracellular signal-regulated kinases (Erk) activation. Finally, blockade of IL-6 attenuated CS-induced epithelial permeability. Our data indicate that CS activates pulmonary epithelial HER2 and that HER2 is a central mediator of CS-induced epithelial barrier dysfunction.

Significance of Stat3 Signaling in Epithelial Cell Differentiation of Fetal Mouse Lungs

To study the significance of signal transducer and activator of transcription (Stat) 3 in lung epithelial development of fetal mice, we examined fetal mouse lungs, focusing on the expression of Clara cell secretory protein (CCSP), Forkhead box protein J1 (Foxj1), calcitonin gene-related peptide (CGRP), phosphorylated Stat3 (Tyr705), and hairy/enhancer of split (Hes) 1, and observed cultured fetal lungs upon treatment with IL-6, a Stat3 activator, or cucurbitacin I, a Stat3 inhibitor. Moreover, the interaction of Stat3 signaling and Hes1 was studied using Hes1 gene-deficient mice. Phosphorylated Stat3 was detected in fetal lungs and, immunohistochemically, phosphorylated Stat3 was found to be co-localized in developing Clara cells, but not in ciliated cells. In the organ culture studies, upon treatment with IL-6, quantitative RT-PCR revealed that CCSP mRNA increased with increasing Stat3 phosphorylation, while cucurbitacin I decreased Hes1, CCSP, Foxj1 and CGRP mRNAs with decreasing Stat3 phosphorylation. In the lungs of Hes1 gene-deficient mice, Stat3 phosphorylation was not markedly different from wild-type mice, the expression of CCSP and CGRP was enhanced, and the treatment of IL-6 or cucurbitacin I induced similar effects on mouse lung epithelial differentiation regardless of Hes1 expression status. Stat3 signaling acts in fetal mouse lung development, and seems to regulate Clara cell differentiation positively. Hes1 could regulate Clara cell differentiation in a manner independent from Stat3 signaling.

XB130 promotes bronchioalveolar stem cell and Club cell proliferation in airway epithelial repair and regeneration

Proliferation of bronchioalveolar stem cells (BASCs) is essential for epithelial repair. XB130 is a novel adaptor protein involved in the regulation of epithelial cell survival, proliferation and migration through the PI3K/Akt pathway. To determine the role of XB130 in airway epithelial injury repair and regeneration, a naphthalene-induced airway epithelial injury model was used with XB130 knockout (KO) mice and their wild type (WT) littermates. In XB130 KO mice, at days 7 and 14, small airway epithelium repair was significantly delayed with fewer number of Club cells (previously called Clara cells). CCSP (Club cell secreted protein) mRNA expression was also significantly lower in KO mice at day 7. At day 5, there were significantly fewer proliferative epithelial cells in the KO group, and the number of BASCs significantly increased in WT mice but not in KO mice. At day 7, phosphorylation of Akt, GSK-3β, and the p85α subunit of PI3K was observed in airway epithelial cells in WT mice, but to a much lesser extent in KO mice. Microarray data also suggest that PI3K/Akt-related signals were regulated differently in KO and WT mice. An inhibitory mechanism for cell proliferation and cell cycle progression was suggested in KO mice. XB130 is involved in bronchioalveolar stem cell and Club cell proliferation, likely through the PI3K/Akt/GSK-3β pathway.

STAT3 accelerates uterine epithelial regeneration in a mouse model of decellularized uterine matrix transplantation

Although a close connection between uterine regeneration and successful pregnancy in both humans and mice has been consistently observed, its molecular basis remains unclear. We here established a mouse model of decellularized uterine matrix (DUM) transplantation. Resected mouse uteri were processed with SDS to make DUMs without any intact cells. DUMs were transplanted into the mouse uteri with artificially induced defects, and all the uterine layers were recovered at the DUM transplantation sites within a month. In the regenerated uteri, normal hormone responsiveness in early pregnancy was observed, suggesting the regeneration of functional uteri. Uterine epithelial cells rapidly migrated and formed a normal uterine epithelial layer within a week, indicating a robust epithelial-regenerating capacity. Stromal and myometrial regeneration occurred following epithelial regeneration. In ovariectomized mice, uterine regeneration of the DUM transplantation was similarly observed, suggesting that ovarian hormones are not essential for this regeneration process. Importantly, the regenerating epithelium around the DUM demonstrated heightened STAT3 phosphorylation and cell proliferation, which was suppressed in uteri of Stat3 conditional knockout mice. These data suggest a key role of STAT3 in the initial step of the uterine regeneration process. The DUM transplantation model is a powerful tool for uterine regeneration research.

Cell adhesion and polarity in squamous cell carcinoma of the lung

Lung cancer is a deadly disease that can roughly be classified into three histopathological groups: lung adenocarcinomas, lung squamous cell carcinomas (LSCCs), and small cell carcinomas. These types of lung cancer are molecularly, phenotypically, and regionally diverse neoplasms, reflecting differences in their cells of origin. LSCCs commonly arise in the airway epithelium of a main or lobar bronchus, which is an important line of defence against the external environment. Furthermore, most LSCCs are characterized histopathologically by the presence of keratinization and/or intercellular bridges, consistent with the molecular features of these tumours, characterized by high levels of transcripts encoding keratins and proteins relevant to intercellular junctions and cell polarity. In this review, the relationships between the molecular features of LSCCs and the types of cell and epithelia of origin are discussed. Recurrent alterations in genes involved in intercellular adhesion and cell polarity in LSCCs are also reviewed, emphasizing the importance of the disruption of PAR3 and the PAR complex. Finally, the possible functional effects of these alterations on epithelial homeostasis, and how they contribute to the development of LSCC, are discussed.

The 1918 Influenza Virus PB2 Protein Enhances Virulence through the Disruption of Inflammatory and Wnt-Mediated Signaling in Mice

The 1918-1919 influenza pandemic remains the single greatest infectious disease outbreak in the past century. Mouse and nonhuman primate infection models have shown that the 1918 virus induces overly aggressive innate and proinflammatory responses. To understand the response to viral infection and the role of individual 1918 genes on the host response to the 1918 virus, we examined reassortant avian viruses nearly identical to the pandemic 1918 virus (1918-like avian virus) carrying either the 1918 hemagglutinin (HA) or PB2 gene. In mice, both genes enhanced 1918-like avian virus replication, but only the mammalian host adaptation of the 1918-like avian virus through reassortment of the 1918 PB2 led to increased lethality. Through the combination of viral genetics and host transcriptional profiling, we provide a multidimensional view of the molecular mechanisms by which the 1918 PB2 gene drives viral pathogenicity. We demonstrate that 1918 PB2 enhances immune and inflammatory responses concomitant with increased cellular infiltration in the lung. We also show for the first time, that 1918 PB2 expression results in the repression of both canonical and noncanonical Wnt signaling pathways, which are crucial for inflammation-mediated lung regeneration and repair. Finally, we utilize regulatory enrichment and network analysis to define the molecular regulators of inflammation, epithelial regeneration, and lung immunopathology that are dysregulated during influenza virus infection. Taken together, our data suggest that while both HA and PB2 are important for viral replication, only 1918 PB2 exacerbates lung damage in mice infected with a reassortant 1918-like avian virus.

IMPORTANCE

As viral pathogenesis is determined in part by the host response, understanding the key host molecular driver(s) of virus-mediated disease, in relation to individual viral genes, is a promising approach to host-oriented drug efforts in preventing disease. Previous studies have demonstrated the importance of host adaptive genes, HA and PB2, in mediating disease although the mechanisms by which they do so are still poorly understood. Here, we combine viral genetics and host transcriptional profiling to show that although both 1918 HA and 1918 PB2 are important mediators of efficient viral replication, only 1918 PB2 impacts the pathogenicity of an avian influenza virus sharing high homology to the 1918 pandemic influenza virus. We demonstrate that 1918 PB2 enhances deleterious inflammatory responses and the inhibition of regeneration and repair functions coordinated by Wnt signaling in the lungs of infected mice, thereby promoting virus-associated disease.

Impact of acute exposure to WTC dust on ciliated and goblet cells in lungs of rats

Clinical studies and the World Trade Center (WTC) Health Registry have revealed increases in the incidence of chronic (non-cancer) lung disorders among first responders (FR) who were at Ground Zero during the initial 72 h after the collapse. Our previous analyses of rats exposed to building-derived WTC dusts using exposure scenarios/levels that mimicked FR mouth-breathing showed that a single WTC dust exposure led to changes in expression of genes whose products could be involved in the lung ailments, but few other significant pathologies. We concluded that rather than acting as direct inducers of many of the FR health effects, it was more likely inhaled WTC dusts instead may have impacted on toxicities induced by other rescue-related co-pollutants present in Ground Zero air. To allow for such effects to occur, we hypothesized that the alkaline WTC dusts induced damage to the normal ability of the lungs to clear inhaled particles. To validate this, rats were exposed on two consecutive days (2 h/d, by intratracheal inhalation) to WTC dust (collected 12-13 September 2001) and examined over a 1-yr period thereafter for changes in the presence of ciliated cells in the airways and hyperplastic goblet cells in the lungs. WTC dust levels in the lungs were assessed in parallel to verify that any changes in levels of these cells corresponded with decreases in host ability to clear the particles themselves. Image analyses of the rat lungs revealed a significant decrease in ciliated cells and increase in hyperplastic goblet cells due to the single series of WTC dust exposures. The study also showed there was only a nominal non-significant decrease (6-11%) in WTC dust burden over a 1-yr period after the final exposure. These results provide support for our current hypothesis that exposure to WTC dusts caused changes in airway morphology/cell composition; such changes could, in turn, have led to potential alterations in the clearance/toxicities of other pollutants inhaled at Ground Zero in the critical initial 72-h period.

Primary Immunodeficiencies with Elevated IgE

In recent years a number of primary immunodeficiencies (PIDs) characterized by elevated Immunoglobulin E (IgE) levels have been uncovered and termed as Hyper-IgE syndrome (HIES). In addition to the elevated levels of IgE, patients with these PIDs display a spectrum of infections by staphylococci and fungi, and in some cases viruses, particularly affecting skin and lungs. Most of these PIDs also have a non-infectious phenotype, comprising musculoskeletal, vascular, and neurological abnormalities. The genetic basis for the majority of conditions with elevated IgE has now been established and includes mutations in STAT3, DOCK8, TYK2, and most recently PGM3 molecules. However, in some patients with the relevant phenotype, mutations in these molecules are not identified, suggesting additional genetic etiologies of HIES not yet discovered. As the immunological and molecular basis of HIES is being unraveled, important insights are emerging that may have implications for our understanding of basic principles of immunology and protective immunity as well as for the pathogenesis and clinical management of patients with these complex and challenging PIDs. In this review, are presented the current knowledge on the clinical presentation, infectious phenotype, and the genetic and immunological pathogenesis of hyper-IgE syndromes as well as some other PIDs with elevated levels of IgE.

XB130 deficiency affects tracheal epithelial differentiation during airway repair

The repair and regeneration of airway epithelium is important for maintaining homeostasis of the respiratory system. XB130 is an adaptor protein involved in the regulation of cell proliferation, survival and migration. In the human trachea, XB130 is expressed on the apical site of ciliated epithelial cells. We hypothesize that XB130 may play a role in epithelial repair and regeneration after injury. Xb130 knockout (KO) mice were generated, and a mouse isogenic tracheal transplantation model was used. Adult Xb130 KO mice did not show any significant anatomical and physiological phenotypes in comparison with their wild type (WT) littermates. The tracheal epithelium in Xb130 KO mice, however, was significantly thicker than that in WT mice. Severe ischemic epithelial injury was observed immediately after the tracheal transplantation, which was followed by epithelial cell flattening, proliferation and differentiation. No significant differences were observed in terms of initial airway injury and apoptosis. However, at Day 10 after transplantation, the epithelial layer was significantly thicker in Xb130 KO mice, and associated with greater proliferative (Ki67+) and basal (CK5+) cells, as well as thickening of the connective tissue and fibroblast layer between the epithelium and tracheal cartilages. These results suggest that XB130 is involved in the regulation of airway epithelial differentiation, especially during airway repair after injury.

Oncostatin M overexpression induces matrix deposition, STAT3 activation, and SMAD1 Dysregulation in lungs of fibrosis-resistant BALB/c mice

Adverse health outcomes in pulmonary fibrosis are associated with extracellular matrix (ECM) accumulation. Although transforming growth factor-β (TGF-β) has been reported to be an important regulator of fibrosis pathogenesis, TGF-β-independent pathways may also be involved. Here, we investigated responses of putative relatively fibrosis-resistant BALB/c mice to transient pulmonary overexpression of oncostatin M (OSM) using an adenovirus vector encoding OSM (AdOSM) and compared responses with the relatively fibrosis-prone C57Bl/6 strain. Interestingly, BALB/c mice showed similar ECM accumulation and collagen 1A1 and 3A1 mRNA elevation to C57Bl/6 mice 7 days after endotracheal administration of AdOSM. TGF-β1 mRNA levels and pSMAD2 signal were not regulated in either strain in total lung extracts. In contrast to C57Bl/6 mice, BALB/c mice lacked eosinophil, Th2 cytokine, and pro-inflammatory cytokine elevation in the broncholveolar space. OSM overexpression induced STAT3 activation and SMAD1/5/8 signaling suppression in lung from both mice strains, which was associated with a downregulation of BMPR2 and BMP ligands, and increased expression of the BMP antagonist gremlin. Although we also observed STAT3 activation and SMAD1/5/8 signaling suppression in mouse lung fibroblast cultures in vitro upon OSM stimulation, immunohistochemistry analyses indicated that the AdOSM-induced pSMAD1/5/8 signal suppression was primarily localized to the airway epithelium. Other gp130 cytokines including IL-6, LIF, CT-1, but not IL-31, also induced STAT3 activation and SMAD1/5/8 signaling suppression in C10 mouse lung epithelial cells and BEAS 2B bronchial epithelial cells, and we found that pharmacological inhibition of STAT3 activation reversed OSM-induced SMAD1/5/8 signaling suppression in vitro. The results demonstrate that OSM induces ECM accumulation in fibrosis-resistant BALB/c mouse lung in the absence of Th2 inflammation or TGF-β signaling, and highlight a dichotomy of STAT3 activation versus SMAD1 suppression in this process.

IL-6/STAT3 promotes regeneration of airway ciliated cells from basal stem cells

The pseudostratified airway epithelium of the lung contains a balanced proportion of multiciliated and secretory luminal cells that are maintained and regenerated by a population of basal stem cells. However, little is known about how these processes are modulated in vivo, and about the potential role of cytokine signaling between stem and progenitor cells and their niche. Using a clonal 3D organoid assay, we found that IL-6 stimulated, and Stat3 inhibitors reduced, the generation of ciliated vs. secretory cells from basal cells. Gain-of-function and loss-of-function studies with cultured mouse and human basal cells suggest that IL-6/Stat3 signaling promotes ciliogenesis at multiple levels, including increases in multicilin gene and forkhead box protein J1 expression and inhibition of the Notch pathway. To test the role of IL-6 in vivo genetically, we followed the regeneration of mouse tracheal epithelium after ablation of luminal cells by inhaled SO2. Stat3 is activated in basal cells and their daughters early in the repair process, correlating with an increase in Il-6 expression in platelet-derived growth factor receptor alpha(+) mesenchymal cells in the stroma. Conditional deletion in basal cells of suppressor of cytokine signaling 3, encoding a negative regulator of the Stat3 pathway, results in an increase in multiciliated cells at the expense of secretory and basal cells. By contrast, Il-6 null mice regenerate fewer ciliated cells and an increased number of secretory cells after injury. The results support a model in which IL-6, produced in the reparative niche, functions to enhance the differentiation of basal cells, and thereby acts as a "friend" to promote airway repair rather than a "foe."

Dynamics of lung defense in pneumonia: resistance, resilience, and remodeling

Pneumonia is initiated by microbes in the lung, but physiological processes integrating responses across diverse cell types and organ systems dictate the outcome of respiratory infection. Resistance, or actions of the host to eradicate living microbes, in the lungs involves a combination of innate and adaptive immune responses triggered by air-space infection. Resilience, or the ability of the host tissues to withstand the physiologically damaging effects of microbial and immune activities, is equally complex, precisely regulated, and determinative. Both immune resistance and tissue resilience are dynamic and change throughout the lifetime, but we are only beginning to understand such remodeling and how it contributes to the incidence of severe pneumonias, which diminishes as childhood progresses and then increases again among the elderly. Here, we review the concepts of resistance, resilience, and remodeling as they apply to pneumonia, highlighting recent advances and current significant knowledge gaps.

Transcriptional regionalization of the fruit fly's airway epithelium

Although airway epithelia are primarily devoted to gas exchange, they have to fulfil a number of different tasks including organ maintenance and the epithelial immune response to fight airborne pathogens. These different tasks are at least partially accomplished by specialized cell types in the epithelium. In addition, a proximal to distal gradient mirroring the transition from airflow conduction to real gas exchange, is also operative. We analysed the airway system of larval Drosophila melanogaster with respect to region-specific expression in the proximal to distal axis. The larval airway system is made of epithelial cells only. We found differential expression between major trunks of the airways and more distal ones comprising primary, secondary and terminal ones. A more detailed analysis was performed using DNA-microarray analysis to identify cohorts of genes that are either predominantly expressed in the dorsal trunks or in the primary/secondary/terminal branches of the airways. Among these differentially expressed genes are especially those involved in signal transduction. Wnt-signalling associated genes for example are predominantly found in secondary/terminal airways. In addition, some G-protein coupled receptors are differentially expressed between both regions of the airways, exemplified by those activated by octopamine or tyramine, the invertebrate counterparts of epinephrine and norepinephrine. Whereas the OAMB is predominantly found in terminal airway regions, the oct3βR has higher expression levels in dorsal trunks. In addition, we observed a significant association of both, genes predominantly expressed in dorsal trunks or in primary to terminal branches branches with those regulated by hypoxia. Taken together, this observed differential expression is indicative for a proximal to distal transcriptional regionalization presumably reflecting functional differences in these parts of the fly’s airway system.

STAT3 and the Hyper-IgE syndrome: Clinical presentation, genetic origin, pathogenesis, novel findings and remaining uncertainties

During recent years a number of primary immunodeficiencies resulting from impaired function of JAK-STAT molecules have been described. One of these is the Hyper-IgE syndrome (HIES) characterized by elevated IgE levels, eczema, recurrent staphylococcal skin and pulmonary infections and pleiotropic somatic manifestations. In 2007 the genetic basis of HIES was revealed by identification of dominant negative STAT3 mutations in HIES patients. Subsequently impaired function of Tyk2 and DOCK8 have been implicated in milder forms of HIES. Since STAT3 acts as a central transcription factor downstream of multiple cytokine and growth factor receptors and thus regulates antimicrobial responses and cell survival, impaired STAT3 function results in immunodeficiency and in some cases tumorigenesis. However, as the immunological and molecular basis of HIES is being unraveled, important biological and immunological insight into JAK-STAT signaling is emerging that may have implications for our understanding of the pathogenesis and clinical management of patients with HIES.

Clinical features, STAT3 gene mutations and Th17 cell analysis in nine children with hyper-IgE syndrome in mainland China

Hyper-IgE syndrome (HIES) is a rare primary immunodeficiency disease characterized by eczema, recurrent staphylococcal aureus skin abscesses, pneumonia with pneumatocele formation, remarkably high serum IgE levels, eosinophilia and involvement of skeleton and connective tissues. Heterozygous signal transducer and activator of transcription 3 (STAT3) mutations were shown to be the cause of autosomal dominant HIES (AD-HIES). In this study, we diagnosed nine patients with HIES from 9 unrelated families on the basis of a National Institutes of Health (NIH) score of ≥40 points, sequenced the STAT3 gene of all nine patients, and quantified Th17 cells in peripheral blood of seven patients by flow cytometry in mainland China. All nine patients had characteristic manifestation of HIES with the range of NIH scores 45-77 points. STAT3 hot mutations V637M or R382W/Q were identified in five patients. We identified two novel heterozygous missense mutations (T620S and R609G) located in Src homology 2 (SH2) domain in two patients, respectively. In two other patients, no STAT3 mutations were found. Quantified Th17 cell numbers were markedly decreased or absent (0-0.28% of CD4(+) T cells) in six patients with STAT3 mutations and almost normal (0.53% of CD4(+) T cells) in one wild-type STAT3 patient compared with healthy controls (0.40-2.25% of CD4(+) T cells). These results suggest that not all patients with HIES who had NIH scores over 40 points carry STAT3 mutations, those whose Th17 cell numbers strikingly decreased probably had AD-HIES with STAT3 mutations.

The cup runneth over: lessons from the ever-expanding pool of primary immunodeficiency diseases

A recent surge in newly described primary immunodeficiencies (PIDs) has highlighted new physiological and pathophysiological pathways that affect the immune system. Furthermore, the study of individuals with PIDs has substantially improved our understanding of basic cellular and signalling pathways in host defence and immune regulation. Single-gene defects can lead to disease manifestations that range from extremely narrow infectious phenotypes to remarkably broad multisystem effects. Hypomorphic or hypermorphic gene mutations often occur in human diseases; when coupled with the fact that humans are exposed to naturally encountered antigens and pathogens, this helps to make the case that the study of immunological diseases in humans should be at the forefront of basic immunological research.

Safety of major abdominal surgical procedures in patients with hyperimmunoglobulinemia E (Job's syndrome): a changing paradigm?

INTRODUCTION

Autosomal dominant hyperimmunoglobulinemia E syndrome (HIES), also called Job's syndrome, is a primary immunodeficiency characterized by the triad of elevated immunoglobulin E levels, eczema, and infections. Its clinical course manifests as recurrent skin and pulmonary infections, and variable skeletal, connective tissue, and vascular abnormalities. There is evidence of abnormal tissue remodeling with pneumatocoeles frequently complicating pyogenic pneumonias and leading to secondary infections that cause the majority of morbidity and mortality. Complications are known to occur after lung surgery with a high frequency of bronchopleural fistulae, but little has been reported concerning abdominal surgeries.

DISCUSSION

Here, we report on the outcome and safety of two separate complex cases (hepatectomy and subtotal gastrectomy) and document our entire experience with abdominal surgical procedures performed on patients with HIES. Despite initial complications, all patients eventually made a full recovery.

CONCLUSION

As HIES patients now frequently live beyond the third and fourth decade, surgical issues similar to those in the general population may increase. Complex surgical procedures can be performed safely and benefit select patients with HIES, but benefit strongly from multidisciplinary teams and awareness of complications related to abnormal healing. We discuss current treatment and potential complications post-operatively in patients with HIES.

Dual oxidase-1 is required for airway epithelial cell migration and bronchiolar reepithelialization after injury

The respiratory epithelium plays a critical role in innate defenses against airborne pathogens and pollutants, and alterations in epithelial homeostasis and repair mechanisms are thought to contribute to chronic lung diseases associated with airway remodeling. Previous studies implicated the nicotinamide adenine dinucleotide phosphate-reduced oxidase dual oxidase-1 (DUOX1) in redox signaling pathways involved in in vitro epithelial wound responses to infection and injury. However, the importance of epithelial DUOX1 in in vivo epithelial repair pathways has not been established. Using small interfering (si)RNA silencing of DUOX1 expression, we show the critical importance of DUOX1 in wound responses in murine tracheal epithelial (MTE) cells in vitro, as well as its contribution to epithelial regeneration in vivo in a murine model of epithelial injury induced by naphthalene, a selective toxicant of nonciliated respiratory epithelial cells (club cells [Clara]). Whereas naphthalene-induced club-cell injury is normally followed by epithelial regeneration after 7 and 14 days, such airway reepithelialization was significantly delayed after the silencing of airway DUOX1 by oropharyngeal administration of DUOX1-targeted siRNA. Wound closure in MTE cells was related to DUOX1-dependent activation of the epidermal growth factor receptor (EGFR) and the transcription factor signal transducer and activator of transcription-3 (STAT3), known mediators of epithelial cell migration and wound responses. Moreover, in vivo DUOX1 silencing significantly suppressed naphthalene-induced activation of STAT3 and EGFR during early stages of epithelial repair. In conclusion, these experiments demonstrate for the first time an important function for epithelial DUOX1 in lung epithelial regeneration in vivo, by promoting EGFR-STAT3 signaling and cell migration as critical events in initial repair.

Knowledge translation: airway epithelial cell migration and respiratory diseases

Airway epithelial cell migration is essential for lung development and growth, as well as the maintenance of respiratory tissue integrity. This vital cellular process is also important for the repair and regeneration of damaged airway epithelium. More importantly, several lung diseases characterized by aberrant tissue remodeling result from the improper repair of damaged respiratory tissue. Epithelial cell migration relies upon extracellular matrix molecules and is further regulated by numerous local, neuronal, and hormonal factors. Under inflammatory conditions, cell migration can also be stimulated by certain cytokines and chemokines. Many well-known environmental factors involved in the pathogenesis of chronic lung diseases (e.g., cigarette smoking, air pollution, alcohol intake, inflammation, viral and bacterial infections) can inhibit airway epithelial cell migration. Further investigation of cellular and molecular mechanisms of cell migration with advanced techniques may provide knowledge that is relevant to physiological and pathological conditions. These studies may eventually lead to the development of therapeutic interventions to improve lung repair and regeneration and to prevent aberrant remodeling in the lung.

Foxm1 transcription factor is critical for proliferation and differentiation of Clara cells during development of conducting airways

Respiratory epithelial cells are derived from cell progenitors in the foregut endoderm that subsequently differentiate into the distinct cell types lining the conducting and alveolar regions of the lung. To identify transcriptional mechanisms regulating differentiation and maintenance of respiratory epithelial cells, we conditionally deleted Foxm1 transcription factor from the conducting airways of the developing mouse lung. Conditional deletion of Foxm1 from Clara cells, controlled by the Scgb1a1 promoter, dramatically altered airway structure and caused peribronchial fibrosis, resulting in airway hyperreactivity in adult mice. Deletion of Foxm1 inhibited proliferation of Clara cells and disrupted the normal patterning of epithelial cell differentiation in the bronchioles, causing squamous and goblet cell metaplasia, and the loss of Clara and ciliated cells. Surprisingly, conducting airways of Foxm1-deficient mice contained highly differentiated cuboidal type II epithelial cells that are normally restricted to the alveoli. Lineage tracing studies showed that the ectopic alveolar type II cells in Foxm1-deficient airways were derived from Clara cells. Deletion of Foxm1 inhibited Sox2 and Scgb1a1, both of which are critical for differentiation and function of Clara cells. In co-transfection experiments, Foxm1 directly bound to and induced transcriptional activity of Scgb1a1 and Sox2 promoters. Foxm1 is required for differentiation and maintenance of epithelial cells lining conducting airways.

CCAAT/enhancer binding protein-α regulates the protease/antiprotease balance required for bronchiolar epithelium regeneration

Many transcription factors that regulate lung morphogenesis during development are reactivated to mediate repairs of the injured adult lung. We hypothesized that CCAAT/enhancer binding protein-α (C/EBPα), a transcription factor critical for perinatal lung maturation, regulates genes required for the normal repair of the bronchiolar epithelium after injury. Transgenic Cebpα(Δ/Δ) mice, in which Cebpa was conditionally deleted from Clara cells and Type II cells after birth, were used in this study. Airway injury was induced in mice by the intraperitoneal administration of naphthalene to ablate bronchiolar epithelial cells. Although the deletion of C/EBPα did not influence lung structure and function under unstressed conditions, C/EBPα was required for the normal repair of terminal bronchiolar epithelium after naphthalene injury. To identify cellular processes that are influenced by C/EBPα during repair, mRNA microarray was performed on terminal bronchiolar epithelial cells isolated by laser-capture microdissection. Normal repair of the terminal bronchiolar epithelium was highly associated with the mRNAs regulating antiprotease activities, and their induction required C/EBPα. The defective deposition of fibronectin in Cebpα(Δ/Δ) mice was associated with increased protease activity and delayed differentiation of FoxJ1-expressing ciliated cells. The fibronectin and ciliated cells were restored by the intratracheal treatment of Cebpα(Δ/Δ) mice with the serine protease inhibitor. In conclusion, C/EBPα regulates the expression of serine protease inhibitors that are required for the normal increase of fibronectin and the restoration of ciliated cells after injury. Treatment with serine protease inhibitor may aid in the recovery of injured bronchiolar epithelial cells, and prevent common chronic lung diseases.

Leukemia inhibitory factor signaling is required for lung protection during pneumonia

Lung infections represent a tremendous disease burden and a leading cause of acute lung injury. STAT3 signaling is essential for controlling lung injury during pneumonia. We previously identified LIF as a prominent STAT3-activating cytokine expressed in the airspaces of pneumonic lungs, but its physiological significance in this setting has never been explored. To do so, Escherichia coli was intratracheally instilled into C57BL/6 mice in the presence of neutralizing anti-LIF IgG or control IgG. Anti-LIF completely eliminated lung LIF detection and markedly exacerbated lung injury compared with control mice as evidenced by airspace albumin content, lung liquid accumulation, and histological analysis. Although lung bacteriology was equivalent between groups, bacteremia was more prevalent with anti-LIF treatment, suggestive of compromised barrier function rather than impaired antibacterial defense as the cause of dissemination. Inflammatory cytokine expression was also exaggerated in anti-LIF-treated lungs, albeit after injury had ensued. Interestingly, alveolar neutrophil recruitment was modestly but significantly reduced compared with control mice despite elevated cytokine levels, indicating that inflammatory injury was not a consequence of excessive neutrophilic alveolitis. Lastly, the lung transcriptome was dramatically remodeled during pneumonia, but far more so following LIF neutralization, with gene changes implicating cell death and epithelial homeostasis among other processes relevant to tissue injury. From these findings, we conclude that endogenous LIF facilitates tissue protection during pneumonia. The LIF-STAT3 axis is identified in this study as a critical determinant of lung injury with clinical implications for pneumonia patients.

Inborn errors of human JAKs and STATs

Inborn errors of the genes encoding two of the four human JAKs (JAK3 and TYK2) and three of the six human STATs (STAT1, STAT3, and STAT5B) have been described. We review the disorders arising from mutations in these five genes, highlighting the way in which the molecular and cellular pathogenesis of these conditions has been clarified by the discovery of inborn errors of cytokines, hormones, and their receptors, including those interacting with JAKs and STATs. The phenotypic similarities between mice and humans lacking individual JAK-STAT components suggest that the functions of JAKs and STATs are largely conserved in mammals. However, a wide array of phenotypic differences has emerged between mice and humans carrying biallelic null alleles of JAK3, TYK2, STAT1, or STAT5B. Moreover, the high degree of allelic heterogeneity at the human JAK3, TYK2, STAT1, and STAT3 loci has revealed highly diverse immunological and clinical phenotypes, which had not been anticipated.

Deregulated Stat3 signaling dissociates pulmonary inflammation from emphysema in gp130 mutant mice

Interleukin (IL)-6 is a potent immunomodulatory cytokine that is associated with emphysema, a major component of chronic obstructive pulmonary disease (COPD). IL-6 signaling via the gp130 coreceptor is coupled to multiple signaling pathways, especially the latent transcription factor signal transducer and activator of transcription (Stat)3. However, the pathological role of endogenous gp130-dependent Stat3 activation in emphysema is ill defined. To elucidate the role of the IL-6/gp130/Stat3 signaling axis in the cellular and molecular pathogenesis of emphysema, we employed a genetic complementation strategy using emphysematous gp130F/F mice displaying hyperactivation of endogenous Stat3 that were interbred with mice to impede Stat3 activity. Resected human lung tissue from patients with COPD and COPD-free individuals was also evaluated by immunohistochemistry. Genetic reduction of Stat3 hyperactivity in gp130F/F: Stat3 −/+ mice prevented lung inflammation and excessive protease activity; however, emphysema still developed. In support of these findings, Stat3 activation levels in human lung tissue correlated with the extent of pulmonary inflammation but not airflow obstruction in COPD. Furthermore, COPD lung tissue displayed increased levels of IL-6 and apoptotic alveolar cells, supporting our previous observation that increased endogenous IL-6 expression in the lungs of gp130F/F mice contributes to emphysema by promoting alveolar cell apoptosis. Collectively, our data suggest that IL-6 promotes emphysema via upregulation of Stat3-independent apoptosis, whereas IL-6 induction of lung inflammation occurs via Stat3. We propose that while discrete targeting of Stat3 may alleviate pulmonary inflammation, global targeting of IL-6 potentially represents a therapeutically advantageous approach to combat COPD phenotypes where emphysema predominates.

A novel role for interleukin-27 (IL-27) as mediator of intestinal epithelial barrier protection mediated via differential signal transducer and activator of transcription (STAT) protein signaling and induction of antibacterial and anti-inflammatory proteins

The role of the Th17 cell inhibiting cytokine IL-27 in the pathogenesis of inflammatory bowel disease is contradictory. Its effects on the intestinal barrier have so far not been investigated, which was the aim of this study. We show that intestinal epithelial cells (IEC) express both IL-27 receptor subunits IL-27RA and gp130. The IL-27 receptor expression is up-regulated in intestinal inflammation and during bacterial infection. IL-27 activates ERK and p38 MAPKs as well as Akt, STAT1, STAT3, and STAT6 in IEC. IL-27 significantly enhances cell proliferation and IEC restitution. These functions of IL-27 are dependent on the activation of STAT3 and STAT6 signaling pathways. As analyzed by microarray, IL-27 modulates the expression of 428 target genes in IEC (316 up and 112 down; p<0.05). IL-27 as well as its main target genes are up-regulated in colonic tissue and IEC isolated from mice with dextran sulfate sodium (DSS)-induced colitis. The IL-27-induced expression of the anti-bacterial gene deleted in malignant brain tumor 1 (DMBT1) is mediated by p38 and STAT3 signaling, whereas the activation of the anti-inflammatory and anti-bacterial gene indoleamine 2,3-dioxygenase (IDO1) is dependent on STAT1 signal transduction. IL-27-induced indoleamine 2,3-dioxygenase enzymatic activity leads to growth inhibition of intestinal bacteria by causing local tryptophan depletion. For the first time, we characterize IL-27 as a mediator of intestinal epithelial barrier protection mediated via transcriptional activation of anti-inflammatory and antibacterial target genes.

Ruptured thoracoabdominal aneurysm in a 27-year-old with hyper IgE syndrome

Hyperimmunoglobulin E syndrome is a rare primary immunodeficiency disorder defined by high serum immunoglobulin E titers and associated with characteristic infectious, dermatologic, skeletal, and dental abnormalities. We present the case of a 27-year-old man presenting acutely with a ruptured type IV thoracoabdominal aortic aneurysm. He was successfully treated by open operative repair and discharged with long-term prophylactic antibiotics. To our knowledge, this is the first such case reported in the English literature.

Elf3 plays a role in regulating bronchiolar epithelial repair kinetics following Clara cell-specific injury

E74-like transcription factor-3 (Elf3), a member of the E26 transformation-specific transcription factor family, is strongly expressed in epithelial-rich tissues, such as small intestine, fetal lung, and various lung cancers. Although previous studies have shown a defect in terminal differentiation of the small intestinal epithelium of Elf3-deficient (Elf3-/-) mice during embryonic development, very little is known about the role Elf3 may play in repair of the airway epithelium after injury. In order to investigate whether Elf3 is involved in regeneration of the bronchiolar epithelium after Clara cell-specific injury, we administered naphthalene to both wild-type (Elf3+/+) and Elf3-/- mice. Histopathological analysis revealed no significant difference in the extent of naphthalene-induced Clara cell necrosis between Elf3+/+ mice and Elf3-/- mice. In the bronchiolar epithelium of Elf3-/- mice, there was a substantial delay in the kinetics of cell proliferation and mitosis along with Clara cell renewal, whereas in the peribronchiolar interstitium, there was a significantly greater level of cell proliferation and mitosis in Elf3-/- mice than in Elf3+/+ mice. Last, the intensity of immunopositive signal for transforming growth factor-β type II receptor, which is a well-known transcriptional target gene of Elf3 and involved in the induction of epithelial cell differentiation, was significantly lower in the bronchiolar epithelium of Elf3-/- mice when compared with Elf3+/+ mice. Taken together, our results suggest that Elf3 plays an important role in the regulation of lung cell proliferation and differentiation during repair of the injured bronchiolar airway epithelium.

Clinical review: gene-based therapies for ALI/ARDS: where are we now?

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) confer substantial morbidity and mortality, and have no specific therapy. The accessibility of the distal lung epithelium via the airway route, and the relatively transient nature of ALI/ARDS, suggest that the disease may be amenable to gene-based therapies. Ongoing advances in our understanding of the pathophysiology of ALI/ARDS have revealed multiple therapeutic targets for gene-based approaches. Strategies to enhance or restore lung epithelial and/or endothelial cell function, to strengthen lung defense mechanisms against injury, to speed clearance of infection and to enhance the repair process following ALI/ARDS have all demonstrated promise in preclinical models. Despite three decades of gene therapy research, however, the clinical potential for gene-based approaches to lung diseases including ALI/ARDS remains to be realized. Multiple barriers to effective pulmonary gene therapy exist, including the pulmonary architecture, pulmonary defense mechanisms against inhaled particles, the immunogenicity of viral vectors and the poor transfection efficiency of nonviral delivery methods. Deficits remain in our knowledge regarding the optimal molecular targets for gene-based approaches. Encouragingly, recent progress in overcoming these barriers offers hope for the successful translation of gene-based approaches for ALI/ARDS to the clinical setting.

Conditional deletion of Nrf2 in airway epithelium exacerbates acute lung injury and impairs the resolution of inflammation

Oxidant stress, resulting from an excess of reactive electrophiles produced in the lung by both resident (epithelial and endothelial) and infiltrated leukocytes, is thought to play an obligatory role in tissue injury and abnormal repair. Previously, using a conventional (whole-body) knockout model, we showed that antioxidative gene induction regulated by the transcription factor Nrf2 is critical for mitigating oxidant-induced (hyperoxic) stress, as well as for preventing and resolving tissue injury and inflammation in vivo. However, the contribution to pathogenic acute lung injury (ALI) of the cellular stress produced by resident versus infiltrated leukocytes remains largely undefined in vivo. To address this critical gap in our knowledge, we generated mice with a conditional deletion of Nrf2 specifically in Clara cells, subjected these mice to hyperoxic insult, and allowed them to recover. We report that a deficiency of Nrf2 in airway epithelia alone is sufficient to contribute to the development and progression of ALI. When exposed to hyperoxia, mice lacking Nrf2 in Clara cells showed exacerbated lung injury, accompanied by greater levels of cell death and epithelial sloughing than in their wild-type littermates. In addition, we found that an Nrf2 deficiency in Clara cells is associated with a persistent inflammatory response and epithelial sloughing in the lungs during recovery from sublethal hyperoxic insult. Our results demonstrate (for the first time, to the best of our knowledge) that Nrf2 signaling in Clara cells is critical for conferring protection from hyperoxic lung injury and for resolving inflammation during the repair process.

Recurrent allergic bronchopulmonary aspergillosis in a patient with rheumatoid arthritis treated with etanercept and tocilizumab

We report the case of a 68-year-old woman with Stage III and Class II rheumatoid arthritis (RA) that was resistant to prednisolone, methotrexate, and infliximab. After treatment with etanercept or tocilizumab, suspicious allergic bronchopulmonary aspergillosis (ABPA) repeatedly occurred and then rapidly improved after the withdrawal of each drug. We suspect that administration of etanercept and tocilizumab caused suspicious ABPA in this patient. The relevance to the pathogenesis of ABPA under these biological drugs is also discussed.

Interleukin-6 promotes pulmonary emphysema associated with apoptosis in mice

The IL-6 cytokine family, which signals via the shared gp130 coreceptor, is linked with the pathogenesis of emphysema. However, the definitive mechanisms by which these cytokines cause emphysema remain ill-defined. We took an in vivo genetic complementation approach to identify the specific IL-6 cytokine family members and gp130-regulated cellular processes that cause emphysema. We used gp130(F/F) mice homozygous for a subtle knock-in mutation in gp130 that deregulates intracellular signaling by the IL-6 cytokine family. The gp130(F/F) mice spontaneously develop emphysema by age 6 months. Within the IL-6 cytokine family, only IL-6 was significantly up-regulated in the lungs of gp130(F/F) mice, and the genetic targeting of IL-6 in gp130(F/F) mice (gp130(F/F):IL-6(-/-)) prevented emphysema. By contrast, the genetic ablation of receptor signaling via IL-11, which like IL-6 signals via a gp130 homodimer and uses the same signaling machinery, failed to ameliorate emphysema in gp130(F/F) mice. Among the disease-associated processes examined, emphysema strongly correlated with elevated alveolar cell apoptosis. Acute (4-day) exposure to cigarette smoke (CS) further augmented the expression of IL-6 in lungs of gp130(F/F) mice, and subchronic (6-week) exposure to CS exacerbated emphysematous and apoptotic changes in the lungs of gp130(F/F) but not gp130(F/F): IL-6(-/-) mice. IL-6 is the main causative agent of IL-6 cytokine family-induced emphysema, and operates to induce apoptosis in the lung. We propose that the discrete targeting of IL-6 signaling may provide an effective therapeutic strategy against human lung disease.