Epithelial LIF signaling limits apoptosis and lung injury during bacterial pneumonia
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ABSTRACT: During bacterial pneumonia, alveolar epithelial cells are critical for maintaining gas exchange and providing antimicrobial as well as pro-immune properties. We previously demonstrated that leukemia inhibitory factor (LIF), an IL-6 family cytokine, is produced by type II alveolar epithelial cells (ATII) and is critical for tissue protection during bacterial pneumonia. However, the target cells and mechanisms of LIF-mediated protection remain unknown. Here, we demonstrate that antibody-induced LIF blockade remodels the lung epithelial transcriptome in association with increased apoptosis. Based on these data, we performed pneumonia studies using a novel mouse model in which LIFR (the unique receptor for LIF) is absent in lung epithelium. While LIFR was detected on the surface of epithelial cells, its absence only minimally contributed to tissue protection during pneumonia. Single-cell RNA-sequencing (scRNAseq) was conducted to identify adult murine lung cell types most prominently expressing LIFR, revealing endothelial cells, mesenchymal cells, and ATIIs as major sources of LIFR. Sequencing data indicated that ATII cells were significantly impacted as a result of pneumonia, with additional differences observed in response to LIF neutralization, including but not limited to gene programs related to cell death, injury, and inflammation. Overall, our data suggest that LIF signaling on epithelial cells alters responses in this cell type during pneumonia. However, our results also suggest separate and perhaps more prominent roles of LIFR in other cell types, such as endothelial cells or mesenchymal cells, which provide grounds for future investigation.
Project description:Resident stem/progenitor cells in lungs are important for tissue homeostasis and repair. We isolated human lung progenitor cells and named alveolar epithelial progenitor cells (AEPCs)(Fujino N, et al. 2011. Lab Invest. 91:363). AEPCs have phenotypes of both alveolar epithelial type II (ATII) cells and mesenchymal stem cells. AEPCs had the potential to generate ATII-like cells in vitro. ATII-like cells derived from AEPCs expressed protein and mRNA of pulmonary surfactant, and displayed lamellar bodies containing the surfactants. However, it has not been evaluated whether global gene expression of the ATII-like cells from AEPCs was similar to that of mature ATII cells isolated from human lung tissues. This study demonstrated gene expression profiles of ATII-like cells from AEPCs. In addition, transcriptomes in AEPCs and mature ATII cells were deposited in the GEO website (GSE21095 and GSE29133, respectively). We isolated AEPCs from tissue samples obtained from patients who underwent lung resection at Department of Thoracic Surgery, Tohoku University Hospital. We induced differentiation of AEPCs to ATII-like cells on extracellular matrix with medium containing KGF, cAMP and IBMX, as previously described (Fujino N, et al. 2011. Lab Invest. 91:363). We profiled the gene expression in three different batches of the ATII-like cells. We extracted total RNA from the differentiated cells. This study was approved by the Ethics Committee at Tohoku University School of Medicine. All subjects gave informed consent.
Project description:Idiopathic pulmonary fibrosis (IPF) is the prototypic progressive fibrotic lung disease with a median survival of 2-4 years. Injury to and/or dysfunction of alveolar epithelium are strongly implicated in IPF disease initiation, but what factors determine why fibrosis progresses rather than normal tissue repair occurs remain poorly understood. We previously demonstrated that ZEB1-mediated epithelial-mesenchymal transition (EMT) in human alveolar epithelial type II (ATII) cells augments TGF-β-induced profibrogenic responses in underlying lung fibroblasts by paracrine signalling. Here we investigated bi-directional epithelial-mesenchymal crosstalk and its potential to drive fibrosis progression. RNA sequencing (RNA-seq) of lung fibroblasts exposed to conditioned media from ATII cells undergoing RAS-induced EMT identified many differentially expressed genes including those involved in cell migration and extracellular matrix (ECM) regulation. We confirmed that paracrine signalling between AS-activated ATII cells and fibroblasts augmented fibroblast recruitment and demonstrated that this involved a ZEB1-tissue plasminogen activator (tPA) axis. In a reciprocal fashion, paracrine signalling from TGF-β-activated lung fibroblasts or IPF fibroblasts induced RAS activation in ATII cells, at least partially via the secreted protein, SPARC. Together these data identify that aberrant bi-directional epithelial-mesenchymal crosstalk in IPF drives a chronic feedback loop that maintains a wound-healing phenotype and provides self-sustaining pro-fibrotic signals.
Project description:Leukemia inhibitory factor (LIF) is a cytoprotective cytokine that reduces lung injury during pneumonia. The purpose of this study was to determine the influence of LIF on pneumonia-induced gene changes in lung epithelium. Mice received intratracheal instillations of vehicle (PBS) or Escherichia coli (10^6 CFU). Control IgG or anti-LIF specific IgG was included in the instillate. 6 hours after the challenge, lung epithelial cells (EpCAM+/CD45-) were sorted from enzymatic lung digests and used for RNA isolation and microarray analysis.
Project description:Leukemia inhibitory factor (LIF) is a cytoprotective cytokine that reduces lung injury during pneumonia. The purpose of this study was to determine the influence of LIF on pneumonia-induced gene changes in lung epithelium. Mice received intratracheal instillations of vehicle (PBS) or Escherichia coli (10^6 CFU). Control IgG or anti-LIF specific IgG was included in the instillate. 24 hours after the challenge, lung epithelial cells (EpCAM+/CD45-) were sorted from enzymatic lung digests and used for RNA isolation and microarray analysis.
Project description:Resident stem/progenitor cells in lungs are important for tissue homeostasis and repair. We isolated human lung progenitor cells and named alveolar epithelial progenitor cells (AEPCs)(Fujino N, et al. 2011. Lab Invest. 91:363). AEPCs have phenotypes of both alveolar epithelial type II (ATII) cells and mesenchymal stem cells. AEPCs had the potential to generate ATII-like cells in vitro. ATII-like cells derived from AEPCs expressed protein and mRNA of pulmonary surfactant, and displayed lamellar bodies containing the surfactants. However, it has not been evaluated whether global gene expression of the ATII-like cells from AEPCs was similar to that of mature ATII cells isolated from human lung tissues. This study demonstrated gene expression profiles of ATII-like cells from AEPCs. In addition, transcriptomes in AEPCs and mature ATII cells were deposited in the GEO website (GSE21095 and GSE29133, respectively).
Project description:Resident stem/progenitor cells in the lung are important for tissue homeostasis and repair. However, a progenitor population for alveolar type II (ATII) cells in adult human lungs have not been identified. Here we isolated alveolar epithelial progenitor cells (AEPCs) from adult human lungs. AEPCs showed mesenchymal stem cell (MSC)-like characteristics combined with ATII cell-phenotypes. AEPCs had the capability for self-renewal and the potential to generate ATII cells in vitro. Furthermore, cells expressing similar markers were present within alveolar walls in normal lungs and these cells were significantly increased in ATII cell hyperplasias. These results suggest that adult human lungs contain a progenitor population for ATII cells.
Project description:Community-acquired pneumonia is a widespread disease with significant morbidity and mortality. Alveolar macrophages are tissue-resident lung cells that play a crucial role in innate immunity against bacteria causing pneumonia. We hypothesized that alveolar macrophages display adaptive characteristics after resolution of bacterial pneumonia. We studied mice one to six months after self-limiting lung infection due to Streptococcus pneumoniae, the most common cause of bacterial pneumonia. Among the myeloid cells recovered from the lung, only alveolar macrophages showed long-term modifications of their surface marker phenotype. The remodeling of alveolar macrophages was: (i) long-lasting (still observed 6 months post infection), (ii) regionally localized (only observed in the affected lobe after lobar pneumonia), and (iii) associated with a macrophage-dependent enhanced lung protection to another pneumococcal serotype. Metabolomic and transcriptomic profiling revealed that alveolar macrophages of mice which recovered from pneumonia had new baseline activities and altered responses to infection. Thus, the enhanced lung protection after mild and self-limiting respiratory infection includes a profound remodeling of alveolar macrophages that is long-lasting, compartmentalized, and manifest across surface receptors, metabolites, and both resting and stimulated transcriptomes. We used microarrays to detail the global program of gene expression for mouse alveolar macrophages sorted from lungs that were naïve or infected more than a month previously, at rest and during an acute (4-hour) infection.
Project description:Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, irreversible, and lethal lung disease. The initiation of IPF involves microinjuries to and/or dysfunction of the alveolar epithelium, but factors that determine fibrosis progression or normal tissue repair are largely unknown. We previously demonstrated that autophagy inhibition-mediated epithelial-mesenchymal transition (EMT) in human alveolar epithelial type II (ATII) cells augments local myofibroblast differentiation in pulmonary fibrosis by paracrine signalling. Here, we report that liver kinase B1 (LKB1) inactivation in ATII cells induces autophagy inhibition and EMT as a consequence. In IPF lungs, this is caused by a downregulation of CAB39L, a key subunit within the LKB1 complex. 3D co-cultures of ATII cells and lung fibroblast MRC5 coupled with RNA sequencing (RNA-seq) confirmed that paracrine signalling between LKB1-depleted ATII cells and fibroblasts augmented myofibroblast differentiation. Together these data suggest that reduced autophagy caused by LKB1 inhibition can induce EMT in ATII cells and contribute to fibrosis via aberrant epithelial–fibroblast crosstalk.
Project description:Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, irreversible, and lethal lung disease. The initiation of IPF involves microinjuries to and/or dysfunction of the alveolar epithelium, but factors that determine fibrosis progression or normal tissue repair are largely unknown. We previously demonstrated that autophagy inhibition-mediated epithelial-mesenchymal transition (EMT) in human alveolar epithelial type II (ATII) cells augments local myofibroblast differentiation in pulmonary fibrosis by paracrine signalling. Here, we report that liver kinase B1 (LKB1) inactivation in ATII cells induces autophagy inhibition and EMT as a consequence. In IPF lungs, this is caused by a downregulation of CAB39L, a key subunit within the LKB1 complex. 3D co-cultures of ATII cells and lung fibroblast MRC5 coupled with RNA sequencing (RNA-seq) confirmed that paracrine signalling between LKB1-depleted ATII cells and fibroblasts augmented myofibroblast differentiation. Together these data suggest that reduced autophagy caused by LKB1 inhibition can induce EMT in ATII cells and contribute to fibrosis via aberrant epithelial–fibroblast crosstalk.
Project description:Alveolar epithelial type II (ATII) cells play a critical role in homeostasis and repair process of the lungs. In lung diseases such as chronic obstructive pulmonary disease (COPD), ATII cells are damaged and fall into apoptosis or senescence. Until to date, global gene expression of ATII cells in COPD lungs has not been analyzed. We isolated ATII cells from three non-COPD and three COPD patients using a FACS method. Then, we performed microarray analysis to compare gene expression profiles of ATII cells between non-COPD and COPD patients.