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Idiopathic pulmonary fibrosis bronchoalveolar lavage cells RNA-seq indicates macrophage expression of pro-inflammatory M1/M2 activation concomitant with radical species metabolism inhibition

ABSTRACT: Current concepts of idiopathic pulmonary fibrosis (IPF) are that microscopic injury drives alveolar epithelial cell dysregulated activation and epithelial mesenchymal transition, ensuing fibrocyte recruitment, fibroblast proliferation and ECM deposition. With the background that IPF is also characterized by chronic accumulation of activated alveolar macrophages (aMAC) in the lower respiratory tract, we assessed IPFaMAC gene expression to identify patterns of activation, by RNA-seq using Illumina platform. To this we evaluated a population of 7 normal smoking controls and 16 IPF smoking patients. All IPFs had abnormal lung function and bronchoalveolar lavage (BAL) showing >80% macrophage counts and augmented spontaneous O2 radical release. RNA was extracted from whole BAL cells. Reads were mapped onto the UCSC mRNA database (GRCh37/hg19 version), and transcripts were aggregated by gene symbol, obtaining a final 19,723 unique protein-coding gene ID list, used for further analysis.

ORGANISM(S): Homo sapiens

PROVIDER: GSE79544 | GEO | 2018/04/16

REPOSITORIES: GEO

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Project description:Background While smoking is known to associate with development of multiple diseases, the underlying mechanisms are still poorly understood. Tobacco smoking can modify the chemical integrity of DNA leading to changes in transcriptional activity, partly through an altered epigenetic state. We aimed to investigate the impact of smoking on lung cells collected from bronchoalveolar lavage (BAL). Methods We profiled changes in DNA methylation (5mC) and its oxidized form hydroxymethylation (5hmC) using conventional bisulfite (BS) treatment and oxidative bisulfite treatment with Illumina Infinium MethylationEPIC BeadChip, and examined gene expression by RNA-seq in healthy smokers. Findings We identified 1,667 BS methyl (5mC+5hmC), 1,756 5mC and 67 5hmC differentially methylated positions (DMPs) between smokers and nonsmokers (FDR <0.05, absolute Δβ >0.15). Both 5mC DMPs and to a lesser extent BS methyl (5mC+5hmC) were predominantly hypomethylated. In contrast, almost all 5hmC DMPs were hypermethylated, supporting the hypothesis that smoking-associated oxidative stress can lead to DNA demethylation, via the established sequential oxidation of which 5hmC is the first step. While we confirmed differential methylation of previously reported smoking-associated BS methyl CpGs using former generations of BeadChips in alveolar macrophages, the large majority of identified DMPs, BS methyl (1,639/1,667), 5mC (1,738/1,756), and 5hmC (67/67), have not been previously reported. Most of these novel smoking-associating sites are specific to the EPIC BeadChip and, interestingly, many of them are associated to FANTOM5 enhancers. Transcriptional changes affecting 633 transcripts were consistent with DNA methylation profiles and converged to alteration of genes involved in migration, signaling and inflammatory response of immune cells. Interpretation Collectively, these findings suggest that tobacco smoke exposure epigenetically modifies BAL cells, possibly involving a continuous active demethylation and subsequent increased activity of inflammatory processes in the lungs. -

Project description:Segmental instillation of lipopolysaccharide (LPS) by bronchoscopy can be used as a model to safely induce transient airway inflammation in the human lung. The LPS challenge model enables investigation of cellular mechanisms involved in pulmonary inflammatory processes as well as pharmacodynamic analysis of investigational drugs for the treatment of respiratory diseases. Aim of this work was to describe the transcriptomic profile of the human segmental LPS challenge model with contextualization to major respiratory diseases. Pre-challenge bronchoalveolar lavage fluid (BAL) and biopsies were sampled from twenty-eight smoking, healthy subjects, followed by segmental LPS challenge and saline control challenge. Twenty-four hours post instillation, BAL and biopsies were collected from the challenged lung segments. Total RNA of cells from BAL and biopsy samples were sequenced for subsequent data analysis. Differential gene expression analysis resulted in 6316 upregulated differentially expressed genes (DEGs) and 241 downregulated DEG in BAL, but only one downregulated DEG in biopsy samples after LPS challenge compared to saline challenge. Upregulated DEG in BAL were related to molecular functions such as “Inflammatory response” or “antimicrobial humoral immune response mediated by antimicrobial peptide”, enriched biological processes such as “chemokine receptor activity”, and upregulated pro-inflammatory pathways such as “Wnt signaling pathway”, “Ras signaling pathway” or “JAK-STAT signaling pathway”. Furthermore, the segmental LPS challenge model resembled aspects of the five most prevalent respiratory diseases chronic obstructive pulmonary disease (COPD), asthma, pneumonia, tuberculosis and lung cancer and featured similarities with acute exacerbations in COPD (AECOPD) and community-acquired pneumonia (CAP). Overall, our study provides extensive information about the transcriptomic profile from BAL cells and mucosal biopsies following LPS challenge in healthy smokers. It expands the knowledge about the LPS challenge model providing potential overlap with respiratory diseases in general and infection-triggered respiratory insults such as AECOPD in particular.

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Idiopathic pulmonary fibrosis bronchoalveolar lavage cells RNA-seq indicates macrophage expression of pro-inflammatory M1/M2 activation concomitant with radical species metabolism inhibition

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