The integrated stress response in lung disease.

Lungs are repeatedly exposed to inhaled toxic insults, such as smoke, diesel exhaust, and microbes, which elicit cellular stress responses. The phosphorylation of eukaryotic translation initiation factor 2α by one of four stress-sensing kinases triggers a pathway called the integrated stress response that helps protect cellular reserves of nutrients and prevents the accumulation of toxic proteins. In this review, we discuss how activation of the integrated stress response has been shown to play an important role in pulmonary pathology, and how its study may help in the development of novel therapies for diverse conditions, from hypoxia to cancer

Repairing damaged lungs using regenerative therapy

There is an urgent need for better treatment of lung diseases that are a major cause of morbidity and mortality worldwide. This urgency is illustrated by the current COVID-19 health crisis. Moderate-to-extensive lung injury characterizes several lung diseases, and not only therapies that reduce such lung injury are needed but also those that regenerate lung tissue and repair existing lung injury. At present, such therapies are not available, but as a result of a rapid increase in our understanding of lung development and repair, lung regenerative therapies are on the horizon. Here, we discuss existing targets for treatment, as well as novel strategies for development of pharmacological and cell therapy-based regenerative treatment for a variety of lung diseases and clinical studies. We discuss how both patient-relevant in vitro disease models using innovative culture techniques and other advanced new technologies aid in the development of pulmonary regenerative medicine

The lower airways microbiome and antimicrobial peptides in idiopathic pulmonary fibrosis differ from chronic obstructive pulmonary disease

Background The lower airways microbiome and host immune response in chronic pulmonary diseases are incompletely understood. We aimed to investigate possible microbiome characteristics and key antimicrobial peptides and proteins in idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD). Methods 12 IPF patients, 12 COPD patients and 12 healthy controls were sampled with oral wash (OW), protected bronchoalveolar lavage (PBAL) and right lung protected sterile brushings (rPSB). The antimicrobial peptides and proteins (AMPs), secretory leucocyte protease inhibitor (SLPI) and human beta defensins 1 and 2 (hBD-1 & hBD-2), were measured in PBAL by enzyme linked immunosorbent assay (ELISA). The V3V4 region of the bacterial 16S rDNA gene was sequenced. Bioinformatic analyses were performed with QIIME 2. Results hBD-1 levels in PBAL for IPF were lower compared with COPD. The predominant phyla in IPF were Firmicutes, Bacteroides and Actinobacteria; Proteobacteria were among top three in COPD. Differential abundance analysis at genus level showed significant differences between study groups for less abundant, mostly oropharyngeal, microbes. Alpha diversity was lower in IPF in PBAL compared to COPD (p = 0.03) and controls (p = 0.01), as well as in rPSB compared to COPD (p = 0.02) and controls (p = 0.04). Phylogenetic beta diversity showed significantly more similarity for IPF compared with COPD and controls. There were no significant correlations between alpha diversity and AMPs. Conclusions IPF differed in microbial diversity from COPD and controls, accompanied by differences in antimicrobial peptides. Beta diversity similarity between OW and PBAL in IPF may indicate that microaspiration contributes to changes in its microbiome.publishedVersio

Function of monocytes and monocyte-derived macrophages in α1-antitrypsin deficiency.

α1-antitrypsin deficiency is the most widely recognised genetic disorder causing chronic obstructive pulmonary disease (COPD). Mutant Z α1-antitrypsin expression has previously been linked to intracellular accumulation and polymerisation of this proteinase inhibitor. Subsequently, this has been described to underlie an exaggerated endoplasmic reticulum stress response and enhanced nuclear factor-κB signalling. However, whether monocyte-derived macrophages display the same features remains unknown. Monocytes from homozygous PiZZ α1-antitrypsin deficiency patients and PiMM controls were cultured for 6 days in the presence of granulocyte-macrophage or macrophage colony-stimulating factor to obtain pro- and anti-inflammatory macrophages (mφ-1 and mφ-2, respectively). We first showed that, in contrast to monocytes, pre-stressed mφ-1 and mφ-2 from healthy blood donors display an enhanced endoplasmic reticulum stress response upon a lipopolysaccharide trigger (XBP1 splicing, CHOP, GADD34 and GRP78 mRNA). However, this endoplasmic reticulum stress response did not differ between monocyte-derived macrophages and monocytes from ZZ patients compared to MM controls. Furthermore, these ZZ cells do not secrete higher cytokine levels, and α1-antitrypsin polymers were not detectable by ELISA. These data suggest that monocyte-derived macrophages are not the local source of Z α1-antitrypsin polymers found in the lung and that endoplasmic reticulum stress and pro-inflammatory cytokine release is not altered.This study was supported by a grant from the Netherlands Asthma Foundation (grant no. 3.2.08.0032). E.F.A. van't Wout is an European Alpha-1-Antitrypsin Laurell’s Training Awardee (sponsored by Grifols, Barcelona, Spain). D.A. Lomas is supported by the Medical Research Council (London, UK) and the NIHR UCLH Biomedical Research Centre (London). S.J. Marciniak is a Medical Research Council Senior Clinical Research Fellow (grant no. G1002610)

Mitochondria:at the crossroads of regulating lung epithelial cell function in chronic obstructive pulmonary disease

Disturbances in mitochondrial structure and function in lung epithelial cells have been implicated in the pathogenesis of various lung diseases, including chronic obstructive pulmonary disease (COPD). Such disturbances affect not only cellular energy metabolism but also alter a range of indispensable cellular homeostatic functions in which mitochondria are known to be involved. These range from cellular differentiation, cell death pathways, and cellular remodeling to physical barrier function and innate immunity. all of which are known to be impacted by exposure to cigarette smoke and have been linked to COPD pathogenesis. Next to their well-established role as the first physical frontline against external insults, lung epithelial cells are immunologically active. Malfunctioning epithelial cells with defective mitochondria are unable to maintain homeostasis and respond adequately to further stress or injury, which may ultimately shape the phenotype of lung diseases. In this review, we provide a comprehensive overview of the impact of cigarette smoke on the development of mitochondrial dysfunction in the lung epithelium and highlight the consequences for cell function, innate immune responses, epithelial remodeling, and epithelial barrier function in COPD. We also discuss the applicability and potential therapeutic value of recently proposed strategies for the restoration of mitochondrial function in the treatment of COPD

Reproducibility of exhaled nitric oxide measurements in overweight and obese adults

Exhaled nitric oxide is a noninvasive measure of airway inflammation that can be detected by a handheld device. Obesity may influence the reproducibility of exhaled nitric oxide measurements, by - for instance - decreased expiratory reserve volume. We analyzed triple exhaled nitric oxide measurements from 553 participants (aged 45 to 65 years with a body mass index ≥27 kg/m2) of the Netherlands Epidemiology of Obesity Study. The interclass correlation coefficient (single measurement reliability) was 0.965 (95% CI: 0.960, 0.970). We conclude that for assessment of exhaled nitric oxide in large cohorts of overweight and obese adults a single measurement suffice

High miR203a-3p and miR-375 expression in the airways of smokers with and without COPD

Smoking is a leading cause of chronic obstructive pulmonary disease (COPD). It is known to have a significant impact on gene expression and (inflammatory) cell populations in the airways involved in COPD pathogenesis. In this study, we investigated the impact of smoking on the expression of miRNAs in healthy and COPD individuals. We aimed to elucidate the overall smoking-induced miRNA changes and those specific to COPD. In addition, we investigated the downstream effects on regulatory gene expression and the correlation to cellular composition. We performed a genome-wide miRNA expression analysis on a dataset of 40 current- and 22 ex-smoking COPD patients and a dataset of 35 current- and 38 non-smoking respiratory healthy controls and validated the results in an independent dataset. miRNA expression was then correlated with mRNA expression in the same patients to assess potential regulatory effects of the miRNAs. Finally, cellular deconvolution analysis was used to relate miRNAs changes to specific cell populations. Current smoking was associated with increased expression of three miRNAs in the COPD patients and 18 miRNAs in the asymptomatic smokers compared to respiratory healthy controls. In comparison, four miRNAs were lower expressed with current smoking in asymptomatic controls. Two of the three smoking-related miRNAs in COPD, miR-203a-3p and miR-375, were also higher expressed with current smoking in COPD patients and the asymptomatic controls. The other smoking-related miRNA in COPD patients, i.e. miR-31-3p, was not present in the respiratory healthy control dataset. miRNA-mRNA correlations demonstrated that miR-203a-3p, miR-375 and also miR-31-3p expression were negatively associated with genes involved in pro-inflammatory pathways and positively associated with genes involved in the xenobiotic pathway. Cellular deconvolution showed that higher levels of miR-203a-3p were associated with higher proportions of proliferating-basal cells and secretory (club and goblet) cells and lower levels of fibroblasts, luminal macrophages, endothelial cells, B-cells, amongst other cell types. MiR-375 expression was associated with lower levels of secretory cells, ionocytes and submucosal cells, but higher levels of endothelial cells, smooth muscle cells, and mast cells, amongst other cell types. In conclusion, we identified two smoking-induced miRNAs (miR-375 and miR-203a-3p) that play a role in regulating inflammation and detoxification pathways, regardless of the presence or absence of COPD. Additionally, in patients with COPD, we identified miR-31-3p as a miRNA induced by smoking. Our identified miRNAs should be studied further to unravel which smoking-induced inflammatory mechanisms are reactive and which are involved in COPD pathogenesis

Sputum microbiota and inflammation at stable state and during exacerbations in a cohort of chronic obstructive pulmonary disease (COPD) patients

Background: Exacerbations of chronic obstructive pulmonary disease (COPD) are debilitating events and spur disease progression. Infectious causes are frequent; however, it is unknown to what extent exacerbations are caused by larger shifts in the airways’ microbiota. The aim of the current study was to analyse the changes in microbial composition between stable state and during exacerbations, and the corresponding immune response. Methods: The study sample included 36 COPD patients examined at stable state and exacerbation from the Bergen COPD Cohort and Exacerbations studies, and one patient who delivered sputum on 13 different occasions during the three-year study period. A physician examined the patients at all time points, and sputum induction was performed by stringent protocol. Only induced sputum samples were used in the current study, not spontaneously expectorated sputum. Sputum inflammatory markers (IL-6, IL-8, IL-18, IP-10, MIG, TNF-α) and antimicrobial peptides (AMPs, i.e. LL-37/hCAP-18, SLPI) were measured in supernatants, whereas target gene sequencing (16S rRNA) was performed on corresponding cell pellets. The microbiome bioinformatics platform QIIME2TM and the statistics environment R were applied for bioinformatics analyses. Results: Levels of IP-10, MIG, TNF-α and AMPs were significantly different between the two disease states. Of 36 sample pairs, 24 had significant differences in the 12 most abundant genera between disease states. The diversity was significantly different in several individuals, but not when data was analysed on a group level. The one patient case study showed longitudinal dynamics in microbiota unrelated to disease state. Conclusion: Changes in the sputum microbiota with changing COPD disease states are common, and are accompanied by changes in inflammatory markers. However, the changes are highly individual and heterogeneous events.publishedVersio

Wnt/β-catenin signaling is critical for regenerative potential of distal lung epithelial progenitor cells in homeostasis and emphysema

Wnt/β-catenin signaling regulates progenitor cell fate decisions during lung development and in various adult tissues. Ectopic activation of Wnt/β-catenin signaling promotes tissue repair in emphysema, a devastating lung disease with progressive loss of parenchymal lung tissue. The identity of Wnt/β-catenin responsive progenitor cells and the potential impact of Wnt/β-catenin signaling on adult distal lung epithelial progenitor cell function in emphysema are poorly understood. Here, we used a TCF/Lef:H2B/GFP reporter mice to investigate the role of Wnt/β-catenin signaling in lung organoid formation. We identified an organoid-forming adult distal lung epithelial progenitor cell population characterized by a low Wnt/β-catenin activity, which was enriched in club and alveolar epithelial type (AT)II cells. Endogenous Wnt/β-catenin activity was required for the initiation of multiple subtypes of distal lung organoids derived from the Wntlow epithelial progenitors. Further ectopic Wnt/β-catenin activation specifically led to an increase in alveolar organoid number; however, the subsequent proliferation of alveolar epithelial cells in the organoids did not require constitutive Wnt/β-catenin signaling. Distal lung epithelial progenitor cells derived from the mouse model of elastase-induced emphysema exhibited reduced organoid forming capacity. This was rescued by Wnt/β-catenin signal activation, which largely increased the number of alveolar organoids. Together, our study reveals a novel mechanism of lung epithelial progenitor cell activation in homeostasis and emphysema