The memory of airway epithelium damage in smokers and COPD patients.

Chronic obstructive pulmonary disease (COPD), a devastating and irreversible lung disease, causes structural and functional defects in the bronchial epithelium, the (ir)reversibility of which remains unexplored in vitro. This study aimed to investigate the persistence of COPD-related epithelial defects in long-term airway epithelial cultures derived from non-smokers, smokers, and COPD patients. Barrier function, polarity, cell commitment, epithelial-to-mesenchymal transition, and inflammation were evaluated and compared with native epithelium characteristics. The role of inflammation was explored using cytokines. We show that barrier dysfunction, compromised polarity, and lineage abnormalities observed in smokers and COPD persisted for up to 10 wk. Goblet cell hyperplasia was associated with recent cigarette smoke exposure. Conversely, increased IL-8/CXCL-8 release and abnormal epithelial-to-mesenchymal transition diminished over time. These ex vivo observations matched surgical samples' abnormalities. Cytokine treatment induced COPD-like changes in control cultures and reactivated epithelial-to-mesenchymal transition in COPD cells. In conclusion, these findings suggest that the airway epithelium of smokers and COPD patients retains a multidimensional memory of its original state and previous cigarette smoke-induced injuries, maintaining these abnormalities for extended periods.

Restin protein expression in non-small cell lung cancer.

BACKGROUND: Restin is a member of the melanoma-associated antigen (MAGE) superfamily. Its expression has been reported to be up- or downregulated in cancer. Preclinical data suggest it is a tumor suppressor. In this study, we aimed to evaluate restin expression and prognostic value in non-small cell lung cancer (NSCLC). METHODS: Restin expression was analyzed by immunohistochemistry in three tissue microarrays consisting of formalin-fixed/paraffin-embedded NSCLC specimens from 113 patients, represented in triplicate. Restin staining H-score was the result of the staining intensity (0-no, 1-weak, 2-moderate, and 3-strong) multiplied by the percentage of stained tumor cells; it was defined as low if 1-100, moderate if 101-200, and strong if 201-300. Haverage-score was the average H-score in the triplicate. Restin Haverage-scores were tested for correlations with clinical and pathological characteristics and patient outcome. RESULTS: Restin expression was localized to the cytoplasm, with nuclear enhancement, of 112/113 (99.1%) NSCLCs. Restin Haverage-scores were 0 in 1/113 (0.88%), low in 15/113 (13.3%), moderate in 48/113 (42.5%), and strong in 49/113 (43.4%) NSCLCs. Restin Haverage-scores did not correlate with NSCLC histological subtype, disease stage, recurrence/progression-free, or overall survival. CONCLUSION: Restin is moderately to strongly expressed in the majority of NSCLC tumors but its expression has no prognostic value in patients with NSCLC.

Bleomycin-induced lung injury: Revisiting an old tool to model group III PH associated with pulmonary fibrosis.

Pulmonary hypertension (PH) is a chronic disorder of the pulmonary circulation that often associates with other respiratory diseases (i.e., group III PH), leading to worsened symptoms and prognosis, notably when combined with interstitial lung diseases such as pulmonary fibrosis (PF). PH may lead to right ventricular (RV) failure, which accounts for a substantial part of the mortality in chronic lung disease patients. The disappointing results of pulmonary arterial hypertension (PAH)-related therapies in patients with PF emphasize the need to better understand the pathophysiologic mechanisms that drive PH development and progression in this specific setting. In this work, we validated an animal model of group III PH associated with PF (PH-PF), by using bleomycin (BM) intratracheal instillation and characterizing the nature of induced lung and vascular remodeling, including the influence on RV structure and function. To our knowledge, this is the first work describing this dose of BM in Sprague Dawley rats and the effects upon the heart and lungs, using different techniques such as echocardiography, heart catheterization, and histology. Our data shows the successful implementation of a rat model that mimics combined PF-PH, with most features seen in the equivalent human disease, such as lung and arterial remodeling, increased mPAP and RV dysfunction.

Disruption of GCN2 Pathway Aggravates Vascular and Parenchymal Remodeling during Pulmonary Fibrosis.

Pulmonary fibrosis (PF) and pulmonary hypertension (PH) are chronic diseases of the pulmonary parenchyma and circulation, respectively, which may coexist, but underlying mechanisms remain elusive. Mutations in the GCN2 (general control nonderepressible 2) gene (EIF2AK4 [eukaryotic translation initiation factor 2 alpha kinase 4]) were recently associated with pulmonary veno-occlusive disease. The aim of this study is to explore the involvement of the GCN2/eIF2α (eukaryotic initiation factor 2α) pathway in the development of PH during PF, in both human disease and in a laboratory animal model. Lung tissue from patients with PF with or without PH was collected at the time of lung transplantation, and control tissue was obtained from tumor resection surgery. Experimental lung disease was induced in either male wild-type or EIF2AK4-mutated Sprague-Dawley rats, randomly receiving a single intratracheal instillation of bleomycin or saline. Hemodynamic studies and organ collection were performed 3 weeks after instillation. Only significant results (P < 0.05) are presented. In PF lung tissue, GCN2 protein expression was decreased compared with control tissue. GCN2 expression was reduced in CD31+ endothelial cells. In line with human data, GCN2 protein expression was decreased in the lung of bleomycin rats compared with saline. EIF2AK4-mutated rats treated with bleomycin showed increased parenchymal fibrosis (hydroxyproline concentrations) and vascular remodeling (media wall thickness) as well as increased right ventricular systolic pressure compared with wild-type animals. Our data show that GCN2 is dysregulated in both humans and in an animal model of combined PF and PH. The possibility of a causative implication of GCN2 dysregulation in PF and/or PH development should be further studied.

Salvia miltiorrhiza Bunge as a Potential Natural Compound against COVID-19.

Salvia miltiorrhiza Bunge, commonly called danshen, is widely used in traditional Chinese medicine for its cardiovascular and neuroprotective effects, which include antioxidative, anti-inflammatory, and antifibrotic properties. The purpose of this study was to evaluate the preclinical potential of S. miltiorrhiza extracts for the treatment of COVID-19. First, the impact of the extract on the binding between SARS-CoV-2 and the cellular ACE2 receptors was assessed using atomic force microscopy (AFM), showing a significant reduction in binding by the extract at concentrations in the µg/mL range. Second, the interference of this extract with the inflammatory response of blood mononuclear cells (PBMCs) was determined, demonstrating potent inhibitory properties in the same concentration range on pro-inflammatory cytokine release and interference with the activation of NFκB signaling. Together, these in vitro data demonstrate the potential of S. miltiorrhiza against COVID-19, consisting first of the blockade of the binding of SARS-CoV-2 to the ACE2 receptor and the mitigation of the inflammatory response from leukocytes by interfering with NFκB signaling. This dataset prompts the launch of a clinical trial to address in vivo the clinical benefits of this promising agent.

Loss of ciliated cells and altered airway epithelial integrity in cystic fibrosis.

BACKGROUND: In cystic fibrosis, the respiratory epithelium is the target tissue of both the genetic abnormality of the disease and of external aggressions, notably by pathogens (Pseudomonas aeruginosa). A detailed characterisation of the cystic fibrosis bronchial epithelium is however lacking, as most previous studies focused on the nasal epithelium or on cell lines. This study aimed to characterise the abnormal phenotype and epithelial-to-mesenchymal transition in cystic fibrosis bronchial epithelium and to evaluate in cell cultures whether abnormalities persist ex vivo. METHODS: Explant lung tissues (n = 44) were assessed for bronchial epithelial cell phenotyping by immunostaining. Human bronchial epithelial cells were derived from basal cells isolated from cystic fibrosis patients or control donors and cultured in air-liquid interface for 2, 4 or 6 weeks. RESULTS: Enhanced mucin 5AC and decreased ß-tubulin expression were observed in cystic fibrosis airways reflecting a decreased ciliated/goblet cell ratio, associated with increased number of vimentin-positive cells, indicating epithelial-to-mesenchymal transition process. These features were recapitulated in vitro, in cystic fibrosis-derived reconstituted epithelium. However, they were not induced by CFTR inhibition or Pseudomonas infection, and most abnormalities tended to disappear in long-term culture (6 weeks) except for increased fibronectin release, an epithelial-to-mesenchymal transition marker. CONCLUSIONS: This study provides new insights into airway epithelial changes in cystic fibrosis, which are imprinted through an acquired mechanism that we could not relate to CFTR function.

Increased Angiotensin-Converting Enzyme 2 and Loss of Alveolar Type II Cells in COVID-19-related Acute Respiratory Distress Syndrome.

Rationale: ACE2 (angiotensin-converting enzyme 2), the entry receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is expressed in type 2 alveolar epithelial cells (AT2) that may play key roles in postinjury repair. An imbalance between ACE2 and ACE has also been hypothesized to contribute to lung injury. Objectives: To characterize the expression and distribution of ACE2 and ACE and to compare AT2 with endothelial cell expression in coronavirus disease (COVID-19)-related or -unrelated acute respiratory distress syndrome (ARDS) and controls. Methods: Lung tissue stainings (using multiplex immunofluorescence) and serum concentrations of ACEs were determined retrospectively in two different cohorts of patients. AT2 and endothelial cells were stained in lung tissue for ProSPC (pro-surfactant protein C) and CD31, respectively. Measurements and Main Results: Pulmonary ACE2 expression was increased in patients with COVID-19-related and -unrelated ARDS (0.06% of tissue area and 0.12% vs. 0.006% for control subjects; P = 0.013 and P < 0.0001, respectively). ACE2 was upregulated in endothelial cells (0.32% and 0.53% vs. 0.01%; P = 0.009 and P < 0.0001) but not in AT2 cells (0.13% and 0.08% vs. 0.03%; P = 0.94 and P = 0.44). Pulmonary expression of ACE was decreased in both COVID-19-related and -unrelated ARDS (P = 0.057 and P = 0.032). Similar increases in ACE2 and decreases in ACE were observed in sera of COVID-19 (P = 0.0054 and P < 0.0001) and non-COVID-19 ARDS (P < 0.0001 and P = 0.016). In addition, AT2 cells were decreased in patients with COVID-19-related ARDS compared with COVID-19-unrelated ARDS (1.395% vs. 2.94%, P = 0.0033). Conclusions: ACE2 is upregulated in lung tissue and serum of both COVID-19-related and -unrelated ARDS, whereas a loss of AT2 cells is selectively observed in COVID-19-related ARDS.

Canonical WNT pathway is activated in the airway epithelium in chronic obstructive pulmonary disease.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a devastating lung disease, mainly due to cigarette smoking, which represents the third cause of mortality worldwide. The mechanisms driving its epithelial salient features remain largely elusive. We aimed to evaluate the activation and the role of the canonical, ß-catenin-dependant WNT pathway in the airway epithelium from COPD patients. METHODS: The WNT/ß-catenin pathway was first assessed by WNT-targeted RNA sequencing of the air/liquid interface-reconstituted bronchial epithelium from COPD and control patients. Airway expression of total and active ß-catenin was assessed in lung sections, as well as WNT components in laser-microdissected airway epithelium. Finally, we evaluated the role of WNT at the bronchial epithelial level by modulating the pathway in the reconstituted COPD epithelium. FINDINGS: We show that the WNT/ß-catenin pathway is upregulated in the COPD airway epithelium as compared with that of non-smokers and control smokers, in targeted RNA-sequencing of in vitro reconstituted airway epithelium, and in situ in lung tissue and laser-microdissected epithelium. Extrinsic activation of this pathway in COPD-derived airway epithelium inhibited epithelial differentiation, polarity and barrier function, and induced TGF-ß-related epithelial-to-mesenchymal transition (EMT). Conversely, canonical WNT inhibition increased ciliated cell numbers, epithelial polarity and barrier function, whilst inhibiting EMT, thus reversing COPD features. INTERPRETATION: In conclusion, the aberrant reactivation of the canonical WNT pathway in the adult airway epithelium recapitulates the diseased phenotype observed in COPD patients, suggesting that this pathway or its downstream effectors could represent a future therapeutic target. FUNDING: This study was supported by the Fondation Mont-Godinne, the FNRS and the WELBIO.

Lung immunoglobulin A immunity dysregulation in cystic fibrosis.

BACKGROUND: In cystic fibrosis (CF), recurrent infections suggest impaired mucosal immunity but whether production of secretory immunoglobulin A (S-IgA) is impaired remains elusive. S-IgA is generated following polymeric immunoglobulin receptor (pIgR)-mediated transepithelial transport of dimeric (d-)IgA and represents a major defence through neutralisation of inhaled pathogens like Pseudomonas aeruginosa (Pa). METHODS: Human lung tissue (n = 74), human sputum (n = 118), primary human bronchial epithelial cells (HBEC) (cultured in air-liquid interface) (n = 19) and mouse lung tissue and bronchoalveolar lavage were studied for pIgR expression, IgA secretion and regulation. FINDINGS: Increased epithelial pIgR immunostaining was observed in CF lung explants, associated with more IgA-producing plasma cells, sputum and serum IgA, especially Pa-specific IgA. In contrast, pIgR and IgA transport were downregulated in F508del mice, CFTR-inhibited HBEC, and CF HBEC. Moreover, the unfolded protein response (UPR) due to F508del mutation, inhibited IgA transport in Calu-3 cells. Conversely, pIgR expression and IgA secretion were strongly upregulated following Pa lung infection in control and F508del mice, through an inflammatory host response involving interleukin-17. INTERPRETATION: A complex regulation of IgA secretion occurs in the CF lung, UPR induced by CFTR mutation/dysfunction inhibiting d-IgA transcytosis, and Pa infection unexpectedly unleashing this secretory defence mechanism. FUNDING: This work was supported by the Forton's grant of the King Baudouin's Foundation, Belgium, the Fondazione Ricerca Fibrosi Cistica, Italy, and the Fonds National de la Recherche Scientifique, Belgium.

Altered generation of ciliated cells in chronic obstructive pulmonary disease.

In COPD, epithelial changes are prominent features in the airways, such as goblet cell hyperplasia and squamous metaplasia. In contrast, it remains unclear whether ciliated cells are reduced and which pathways dysregulate epithelial differentiation. We hypothesized that bronchial epithelial cell lineage specification is dysregulated in COPD because of an aberrant reprogramming through transforming growth factor (TGF)-ß1. Surgical lung tissue from 81 COPD and 61 control (smokers and non-smokers) patients was assessed for bronchial epithelial cell phenotyping by immunohistochemistry, both in situ and in vitro in reconstituted air-liquid interface (ALI) cultures. The role of TGF-ß1 was studied in vitro. COPD epithelium in large airways, when compared to controls, showed decreased ß-tubulin IV + ciliated cells (4.4%, 2.5-8.8% versus 8.5%, 6.3-11.8% of surface staining, median and IQR, p = 0.0009) and increased MUC5AC + goblet cells (34.8%, 24.4-41.9% versus 10.3%, 5.1-17.6%, p < 0.0001). Both features were recapitulated in the ALI-cultured epithelium from COPD patients. Exogenous TGF-ß1 reduced mucociliary differentiation while neutralizing TGF-ß1 during ALI increased both specialized cell types. The COPD airway epithelium displays altered differentiation for ciliated cells, which recapitulates in vitro, at least in part through TGF-ß1.

Increased Expression and Activation of FAK in Small-Cell Lung Cancer Compared to Non-Small-Cell Lung Cancer.

INTRODUCTION: Focal adhesion kinase (FAK) plays a crucial role in cancer development and progression. FAK is overexpressed and/or activated and associated with poor prognosis in various malignancies. However, in lung cancer, activated FAK expression and its prognostic value are unknown. METHODS: FAK and activated FAK (phospho-FAK Y397) expressions were analyzed by multiplex immunofluorescence staining in formalin-fixed paraffin-embedded tissues from 95 non-small-cell lung cancer (NSCLC) and 105 small-cell lung cancer (SCLC) patients, and 37 healthy donors. The FAK staining score was defined as the percentage (%) of FAK-stained tumor area multiplied by (×) FAK mean intensity and phospho-FAK staining score as the (% of phospho-FAK-stained area of low intensity × 1) + (% of phospho-FAK-stained area of medium intensity × 2) + (% of the phospho-FAK-stained area of high intensity × 3). FAK and phospho-FAK staining scores were compared between normal, NSCLC, and SCLC tissues. They were also tested for correlations with patient characteristics and clinical outcomes. RESULTS: The median follow-up time after the first treatment was 42.5 months and 6.4 months for NSCLC and SCLC patients, respectively. FAK and phospho-FAK staining scores were significantly higher in lung cancer than in normal lung and significantly higher in SCLC compared to NSCLC tissues (p < 0.01). Moreover, the ratio between phospho-FAK and FAK staining scores was significantly higher in SCLC than in NSCLC tissues (p < 0.01). However, FAK and activated FAK expression in lung cancer did not correlate with recurrence-free and overall survival in NSCLC and SCLC patients. CONCLUSIONS: Total FAK and activated FAK expressions are significantly higher in lung cancer than in normal lung, and significantly higher in SCLC compared to NSCLC, but are not prognostic biomarkers in this study.

Therapeutic Potential of Focal Adhesion Kinase Inhibition in Small Cell Lung Cancer.

Small cell lung cancer (SCLC) has a poor prognosis. Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase regulating cell proliferation, survival, migration, and invasion, which is overexpressed and/or activated in several cancers, including SCLC. We wanted to determine whether FAK contributes to SCLC aggressive behavior. We first evaluated the effect of FAK small-molecule inhibitor PF-573,228 in NCI-H82, NCI-H146, NCI-H196, and NCI-H446 SCLC cell lines. PF-573,228 (0.1-5 µmol/L) inhibited FAK activity by decreasing phospho-FAK (Tyr397), without modifying total FAK expression. PF-573,228 decreased proliferation, decreased DNA synthesis, induced cell-cycle arrest in G2-M phases, and increased apoptosis in all cell lines. PF-573,228 also decreased motility in adherent cell lines. To make sure that these effects were not off-target, we then used a genetic method to inhibit FAK in NCI-H82 and NCI-H446, namely stable transduction with FAK shRNA and/or FAK-related nonkinase (FRNK), a splice variant lacking the N-terminal and kinase domains. Although FAK shRNA transduction decreased total and phospho-FAK (Tyr397) expression, it did not affect proliferation, DNA synthesis, or progression through cell cycle. However, restoration of FAK-targeting (FAT) domain (attached to focal adhesion complex where it inhibits pro-proliferative proteins such as Rac-1) by FRNK transduction inhibited proliferation, DNA synthesis, and induced apoptosis. Moreover, although FAK shRNA transduction increased active Rac1 level, FRNK reexpression in cells previously transduced with FAK shRNA decreased it. Therefore, FAK appears important in SCLC biology and targeting its kinase domain may have a therapeutic potential, while targeting its FAT domain should be avoided to prevent Rac1-mediated protumoral activity.

Increased IgA Expression in Lung Lymphoid Follicles in Severe Chronic Obstructive Pulmonary Disease.

RATIONALE: Accumulation of B cells and lymphoid follicles (LFs) has been described in chronic obstructive pulmonary disease (COPD) airways, but the functional status of lung B cells remains poorly known. OBJECTIVES: To characterize LFs for expression of IgA, the main mucosal antibody. METHODS: The presence of B cells and LFs, including intrafollicular IgA expression, were determined in the lung from patients with COPD (n = 37) versus control subjects (n = 34) by immunohistochemistry. We also evaluated follicular IgA responses in the lungs from mice infected with Pseudomonas aeruginosa (PAO1) (n = 10 per group) and in smoking mice. MEASUREMENTS AND MAIN RESULTS: Whereas in smokers B-cell numbers slightly increased, robust increases in B-cell and LF numbers (mainly in distal airways) were only observed in severe COPD. Most follicular B cells were IgM+ (70-80%), but IgA+ (and not IgG+) B-cell numbers were increased in LFs from severe COPD compared with control subjects (twofold, 44.7% vs. 25.2%), and this was significant in distal but not proximal airways. Follicular IgA response was also observed in PAO1-infected mouse lungs, but not after smoke exposure. Moreover, follicular IgA expression associated with expression of IL-21, which was very potent to activate immunoglobulin production in vitro. CONCLUSIONS: This study shows that IgA production occurs in peribronchiolar LFs from severe COPD, where IL-21-producing T cells are present, and presumably represents a feature of exacerbated mucosal adaptive immune responses against microbial and/or self-antigens.

Bronchial Epithelial IgA Secretion Is Impaired in Asthma. Role of IL-4/IL-13.

RATIONALE: Asthma is associated with increased lung IgE production, but whether the secretory IgA system is affected in this disease remains unknown. OBJECTIVES: We explored mucosal IgA transport in human asthma and its potential regulation by T-helper cell type 2 inflammation. METHODS: Bronchial biopsies from asthma and control subjects were assayed for bronchial epithelial polymeric immunoglobulin receptor (pIgR) expression and correlated to T-helper cell type 2 biomarkers. Bronchial epithelium reconstituted in vitro from these subjects, on culture in air-liquid interface, was assayed for pIgR expression and regulation by IL-4/IL-13. MEASUREMENTS AND MAIN RESULTS: Downregulation of pIgR protein was observed in the bronchial epithelium from patients with asthma (P = 0.0002 vs. control subjects). This epithelial defect was not observed ex vivo in the cultured epithelium from patients with asthma. Exogenous IL-13 and IL-4 could inhibit pIgR expression and IgA transcytosis. Mechanistic experiments showed that autocrine transforming growth factor-ß mediates the IL-4/IL-13 effect on the pIgR, with a partial contribution of upregulated transforming growth factor-α/epidermal growth factor receptor. CONCLUSIONS: This study shows impaired bronchial epithelial pIgR expression in asthma, presumably affecting secretory IgA-mediated frontline defense as a result of type 2 immune activation of the transforming growth factor pathway.

Imprinting of the COPD airway epithelium for dedifferentiation and mesenchymal transition.

In chronic obstructive pulmonary disease (COPD), epithelial changes and subepithelial fibrosis are salient features in conducting airways. Epithelial-to-mesenchymal transition (EMT) has been recently suggested in COPD, but the mechanisms and relationship to peribronchial fibrosis remain unclear. We hypothesised that de-differentiation of the COPD respiratory epithelium through EMT could participate in airway fibrosis and thereby, in airway obstruction. Surgical lung tissue and primary broncho-epithelial cultures (in air-liquid interface (ALI)) from 104 patients were assessed for EMT markers. Cell cultures were also assayed for mesenchymal features and for the role of transforming growth factor (TGF)-ß1. The bronchial epithelium from COPD patients showed increased vimentin and decreased ZO-1 and E-cadherin expression. Increased vimentin expression correlated with basement membrane thickening and airflow limitation. ALI broncho-epithelial cells from COPD patients also displayed EMT phenotype in up to 2 weeks of culture, were more spindle shaped and released more fibronectin. Targeting TGF-ß1 during ALI differentiation prevented vimentin induction and fibronectin release. In COPD, the airway epithelium displays features of de-differentiation towards mesenchymal cells, which correlate with peribronchial fibrosis and airflow limitation, and which are partly due to a TGF-ß1-driven epithelial reprogramming.

Increased IgA production by B-cells in COPD via lung epithelial interleukin-6 and TACI pathways.

Despite their relevance to mucosal defense, production of IgA and the function of lung B-cells remain unknown in chronic obstructive pulmonary disease (COPD). We assessed IgA synthesis in the lungs of COPD (n=28) and control (n=21) patients, and regulation of B-cells co-cultured with in vitro-reconstituted airway epithelium. In COPD lung tissue, synthesis of IgA1 was increased, which led to its accumulation in subepithelial areas. In vitro, the COPD bronchial epithelium imprinted normal human B-cells for increased production of IgA (mainly IgA1) and maturation into CD38(+) plasma cells. These effects were associated with upregulation of TACI (transmembrane activator and CAML interactor) and were observed under resting conditions, while being partly inhibited upon stimulation with cigarette smoke extract. Interleukin (IL)-6 and BAFF (B-cell activating factor)/APRIL (a proliferation-inducing ligand) were upregulated in the COPD epithelium and lung tissue, respectively; the IgA-promoting effect of the COPD bronchial epithelium was inhibited by targeting IL-6 and, to a lower extent, by blocking TACI. These data show that in COPD, the bronchial epithelium imprints B-cells with signals promoting maturation into IgA-producing plasma cells through the action of two epithelial/B-cell axes, namely the IL-6/IL-6 receptor and BAFF-APRIL/TACI pathways, while cigarette smoke partly counteracts this IgA-promoting effect.

Polymeric immunoglobulin receptor down-regulation in chronic obstructive pulmonary disease. Persistence in the cultured epithelium and role of transforming growth factor-ß.

RATIONALE: The generation of protective secretory IgA relies on the epithelial polymeric immunoglobulin receptor (pIgR). pIgR expression is reduced in chronic obstructive pulmonary disease (COPD), but correlation to disease severity and underlying mechanisms remains unknown. OBJECTIVES: To address the hypothesis that pIgR down-regulation in COPD concerns severe disease in relation to aberrant programming of the bronchial epithelium. METHODS: Surgical lung tissue and primary bronchial epithelium (cultured in air-liquid interface, ALI) obtained from a large series of patients (n = 116) were studied for pIgR expression and regulation. MEASUREMENTS AND MAIN RESULTS: pIgR immunostaining in the bronchial epithelium is decreased in severe COPD. In contrast, pIgR transcription was up-regulated in smokers with or without COPD. In ALI (vs. submerged) cultures, pIgR expression was strongly induced, whereas pIgR expression and IgA-transcytosis capacity were decreased in cultures from subjects with severe COPD as compared with control subjects. In addition, COPD cultures released more transforming growth factor-ß1 (TGF-ß1), reflecting increased epithelial TGF-ß1 immunostaining in COPD lung tissue. Finally, besides inducing epithelial dedifferentiation, exogenous TGF-ß1 dose-dependently inhibited pIgR production, whereas pIgR increased on blockade of TGF-ß1 activity during ALI differentiation. CONCLUSIONS: pIgR down-regulation in COPD correlates with disease severity, and the bronchial epithelium reconstituted in vitro from these patients retains its aberrant imprinting for pIgR expression. This study also links pIgR down-regulation to TGF-ß-driven reprogramming of the bronchial epithelium, which results in impaired lung IgA immunity in patients with COPD.

FcαRI-mediated inhibition of IL-12 production and priming by IFN-γ of human monocytes and dendritic cells.

We showed that IgA induces IL-10 in monocytes and dendritic cells. Because reciprocal inhibition exists between IL-10 and IL-12, we explored whether IgA could regulate this other immunoregulatory cytokine. In human monocytes and monocyte-derived dendritic cells preincubated with IFN-γ before stimulation by LPS, suppression of p40 and IL-12p70 production was observed upon IgA treatment during IFN-γ priming. Washout experiments and inhibition of IFN-γ-induced CXCL10 (IP-10) and FcγRI (CD64) indicated that inhibition by IgA occurred at both the LPS and IFN-γ levels. Inhibition was not affected by blockade of IL-10 or MAPK but involved FcαRI/CD89-mediated suppression of STAT1 phosphorylation. These data indicate that FcαRI ligation on human monocytes and dendritic cells inhibits IL-12 expression and type 1 activation by interfering with STAT1 activation.

Platelet-derived growth factor-producing CD4+ Foxp3+ regulatory T lymphocytes promote lung fibrosis.

RATIONALE: There is evidence that CD4(+) effector T lymphocytes (T eff) participate in the development of lung fibrosis, but the role of their CD4(+) regulatory T-cell (T reg) counterparts remains to be determined. OBJECTIVES: To elucidate the contribution of T reg cells in a mouse model of lung fibrosis induced by silica (SiO(2)) particles. METHODS: Lung T reg and T eff cells purified from SiO(2)-treated Foxp3-GFP transgenic mice were cocultured with naive lung fibroblasts or transferred to the lungs of healthy mice. DEREG mice, which express the diphtheria toxin receptor under the control of the foxp3 gene, were used to deplete T reg cells during fibrogenesis. MEASUREMENTS AND MAIN RESULTS: CD4(+) Foxp3(+) T reg cells were persistently recruited in the lungs in response to SiO(2). T reg accumulation paralleled the establishment of pulmonary immunosuppression and fibrosis. T reg cells highly expressed platelet-derived growth factor (PDGF)-B via a TGF-ß autocrine signaling pathway, directly stimulated fibroblast proliferation in vitro, and increased lung collagen deposition upon transfer in the lung of naive mice. The direct profibrotic effects of T reg cells were abolished by the inhibitor of the PDGF-B/TGF-ß signaling pathway, imatinib mesylate. Neutralization of T reg-immunosuppressive activity resulted in enhanced accumulation of T eff cells and IL-4-driven pulmonary fibrogenesis, further demonstrating that T reg cells control T eff cell functions during inflammatory fibrosis. CONCLUSIONS: Our study indicates that T reg cells contribute to lung fibrosis by stimulating fibroblasts through the secretion of PDGF-B in noninflammatory conditions and regulate detrimental T eff cell activities during inflammation-related fibrosis.