Human bronchial and parenchymal fibroblasts display differences in basal inflammatory phenotype and response to IL-17A

PM2.5 activates IL-17 signaling pathway in human nasal mucosa-derived fibroblasts

Fine particulate matter (PM2.5) represents a prevalent environmental pollutant in the atmosphere, capable of exerting deleterious effects on human health. Numerous studies have indicated a correlation between PM2.5 exposure and the development of chronic upper airway inflammatory diseases. The objective of this study was to investigate the impact of PM2.5 on the transcriptome of fibroblasts derived from nasal mucosa. Initially, nasal mucosa-derived fibroblasts were isolated, cultured, and subsequently stimulated with PM2.5 (100 μg/mL) or an equivalent volume of normal culture medium for a duration of 24 h. Following this, total RNA from these cells was extracted, purified, and subjected to sequencing using next-generation RNA sequencing technology. Differentially expressed genes (DEGs) were then identified and utilized for functional enrichment analysis. A protein-protein interaction (PPI) network of DEGs was constructed, and validation of key genes and proteins was carried out using quantitative real-time PCR and ELISA methods. Results revealed 426 DEGs, comprising 276 up-regulated genes and 150 down-regulated genes in nasal mucosa-derived fibroblasts treated with PM2.5 compared to control cells. Functional enrichment analysis indicated that DEGs were predominantly associated with inflammation-related pathways, including the IL-17 signaling pathway. In alignment with this, PPI analysis highlighted that hub genes were primarily involved in the regulation of the IL-17 signaling pathway. Subsequent validation through quantitative real-time PCR and ELISA confirmed significant alterations in the relative expressions of IL-17 signaling pathway-related genes and concentrations of IL-17 signaling pathway related proteins in nasal mucosa-derived fibroblasts treated with PM2.5 compared to control cells. In conclusion, PM2.5 intervention substantially altered the transcriptome of nasal mucosa-derived fibroblasts. Furthermore, PM2.5 has the potential to exacerbate the inflammatory responses of these fibroblasts by modulating the expression of key genes in the IL-17 signaling pathway.

Pharmacological Rationale for Targeting IL-17 in Asthma

Asthma is a respiratory disease that currently affects around 300 million people worldwide and is defined by coughing, shortness of breath, wheezing, mucus overproduction, chest tightness, and expiratory airflow limitation. Increased levels of interleukin 17 (IL-17) have been observed in sputum, nasal and bronchial biopsies, and serum of patients with asthma compared to healthy controls. Patients with higher levels of IL-17 have a more severe asthma phenotype. Biologics are available for T helper 2 (Th2)-high asthmatics, but the Th17-high subpopulation has a relatively low response to these treatments, rendering it a rather severe asthma phenotype to treat. Several experimental models suggest that targeting the IL-17 pathway may be beneficial in asthma. Moreover, as increased activation of the Th17/IL-17 axis is correlated with reduced inhaled corticosteroids (ICS) sensitivity, targeting the IL-17 pathway might reverse ICS unresponsiveness. In this review, we present and discuss the current knowledge on the role of IL-17 in asthma and its interaction with the Th2 pathway, focusing on the rationale for therapeutic targeting of the IL-17 pathway.

DNA Methylation of Fibroblast Phenotypes and Contributions to Lung Fibrosis

Fibroblasts are an integral part of connective tissue and play a crucial role in developing and modulating the structural framework of tissues by acting as the primary source of extracellular matrix (ECM). A precise definition of the fibroblast remains elusive. Lung fibroblasts orchestrate the assembly and turnover of ECM to facilitate gas exchange alongside performing immune functions including the secretion of bioactive molecules and antigen presentation. DNA methylation is the covalent attachment of a methyl group to primarily cytosines within DNA. DNA methylation contributes to diverse cellular phenotypes from the same underlying genetic sequence, with DNA methylation profiles providing a memory of cellular origin. The lung fibroblast population is increasingly viewed as heterogeneous with between 6 and 11 mesenchymal populations identified across health and lung disease to date. DNA methylation has been associated with different lung fibroblast populations in health and with alterations in lung disease, but to varying extents. In this review, we will discuss lung fibroblast heterogeneity and the evidence for a contribution from DNA methylation to defining cell populations and alterations in disease.

Versatile workflow for cell type-resolved transcriptional and epigenetic profiles from cryopreserved human lung

Complexity of lung microenvironment and changes in cellular composition during disease make it exceptionally hard to understand molecular mechanisms driving development of chronic lung diseases. Although recent advances in cell type-resolved approaches hold great promise for studying complex diseases, their implementation relies on local access to fresh tissue, as traditional tissue storage methods do not allow viable cell isolation. To overcome these hurdles, we developed a versatile workflow that allows storage of lung tissue with high viability, permits thorough sample quality check before cell isolation, and befits sequencing-based profiling. We demonstrate that cryopreservation enables isolation of multiple cell types from both healthy and diseased lungs. Basal cells from cryopreserved airways retain their differentiation ability, indicating that cellular identity is not altered by cryopreservation. Importantly, using RNA sequencing and EPIC Array, we show that gene expression and DNA methylation signatures are preserved upon cryopreservation, emphasizing the suitability of our workflow for omics profiling of lung cells. Moreover, we obtained high-quality single-cell RNA-sequencing data of cells from cryopreserved human lungs, demonstrating that cryopreservation empowers single-cell approaches. Overall, thanks to its simplicity, our workflow is well suited for prospective tissue collection by academic collaborators and biobanks, opening worldwide access to viable human tissue.

TWIST1 DNA methylation is a cell marker of airway and parenchymal lung fibroblasts that are differentially methylated in asthma

Background

Mesenchymal fibroblasts are ubiquitous cells that maintain the extracellular matrix of organs. Within the lung, airway and parenchymal fibroblasts are crucial for lung development and are altered with disease, but it has been difficult to understand their roles due to the lack of distinct molecular markers. We studied genome-wide DNA methylation and gene expression in airway and parenchymal lung fibroblasts from healthy and asthmatic donors, to identify a robust cell marker and to determine if these cells are molecularly distinct in asthma.

Results

Airway (N = 8) and parenchymal (N = 15) lung fibroblasts from healthy individuals differed in the expression of 158 genes, and DNA methylation of 3936 CpGs (Bonferroni adjusted p value < 0.05). Differential DNA methylation between cell types was associated with differential expression of 42 genes, but no single DNA methylation CpG feature (location, effect size, number) defined the interaction. Replication of gene expression and DNA methylation in a second cohort identified TWIST1 gene expression, DNA methylation and protein expression as a cell marker of airway and parenchymal lung fibroblasts, with DNA methylation having 100% predictive discriminatory power. DNA methylation was differentially altered in parenchymal (112 regions) and airway fibroblasts (17 regions) with asthmatic status, with no overlap between regions.

Conclusions

Differential methylation of TWIST1 is a robust cell marker of airway and parenchymal lung fibroblasts. Airway and parenchymal fibroblast DNA methylation are differentially altered in individuals with asthma, and the role of both cell types should be considered in the pathogenesis of asthma.

IL-17A Neutralization Improves the Neurological Outcome of Mice With Ischemic Stroke and Inhibits Caspase-12-Dependent Apoptosis

We previously reported that the levels of astrocyte-derived interleukin-17A (IL-17A) increased both in the peri-infarct region and cerebrospinal fluid (CSF) of mice with 1-h middle cerebral artery (MCA) occlusion/12-h reperfusion (1-h MCAO/R 12 h)-induced ischemic stroke. However, the effects of IL-17A neutralization on the neurological outcome of mice with ischemic stroke and its underlying molecular mechanism are unclear. In this study, we found that the intracerebroventricular injection of IL-17A-neutralizing monoclonal antibody (mAb; 2.0 μg) could reduce the infarct volume, alleviate neuron loss, and improve the neurological outcomes of mice with 1-h MCAO/R 24-h- or 3-day-induced ischemic-stroke mice. The IL-17A neutralization could also significantly inhibit the increase of pro-caspase-3 cleavage through caspase-12-dependent cell apoptosis, as well as preventing the decrease of antiapoptotic factor B-cell lymphoma 2 (Bcl-2) and the increase of proapoptotic Bcl-2-associated X protein (Bax) in the peri-infarct region of mice following ischemic stroke. In addition, we confirmed that the recombinant mouse (rm) IL-17A could significantly aggravate 1-h oxygen–glucose deprivation/24-h reoxygenation (1-h OGD/R 24 h)-induced ischemic injuries in cortical neurons in a dose-dependent manner, and the rmIL-17A could also exacerbate neuronal apoptosis through caspase-12 (not caspase-8 or caspase-9)-dependent pathway. These results suggest that IL-17A neutralization could improve the neurological outcome of mice with ischemic stroke through inhibiting caspase-12-dependent neuronal apoptosis.

Effect of fluticasone propionate on human nasal fibroblasts exposed to urban particulate matter

OBJECTIVE

Particulate matter (PM), which contains organic compounds and toxic metals, is the major cause of air pollution. PM enters the body, causing various health problems. Although the effects of PM on the lower respiratory tract have been extensively investigated, the effects on the upper respiratory tract (including the nasal cavity) require further evaluation. To investigate the effect of fluticasone propionate (FP) on nasal fibroblasts exposed to UPM.

METHODS

Samples of inferior turbinate tissue were obtained from six patients. The fibroblasts isolated from these samples were exposed to UPM and/or FP. The expression of interleukin (IL)-6, CXC chemokine ligand (CXCL) 1, IL-1β, and tumour necrosis factor-alpha (TNF-α) in nasal fibroblasts was analysed using real-time PCR and enzyme-linked immunosorbent assays. The protein levels of nuclear factor kappa B (NF-κB) and signal transducer and activator of transcription 3 (STAT3) were analysed by western blotting.

RESULTS

FP reversed the UPM-induced reduction in cell viability. The mRNA and protein levels of IL-6, CXCL1, IL-1β, and TNF-α were significantly increased by UPM. FP reversed the UPM-induced increases in the protein levels of NF-κB and phosphorylated-STAT3 in a dose-dependent manner. In addition, TNF-α, an inducer of NF-κB, reversed the FP-induced reduction in the levels of signalling molecules.

CONCLUSION

UPM induces the expression of IL-6, CXCL1, IL-1β, and TNF-α in nasal fibroblasts and this effect is reversed by FP via the STAT3 and NF-κB signalling pathways. These results suggest that FP has therapeutic potential for nasal diseases related to UPM, such as allergic and chronic rhinitis.

IL-17 Induced Autophagy Regulates Mitochondrial Dysfunction and Fibrosis in Severe Asthmatic Bronchial Fibroblasts

The accumulation of fibroblasts, their synthesis of extracellular matrix (ECM) proteins and their innate resistance to apoptosis are characteristics of subepithelial fibrosis observed in severe asthma. Interleukin-17 (IL-17) is an important regulator of airway remodeling in asthma. However, the contribution of IL-17 to the pro-fibrotic phenotype of bronchial fibroblasts is not well-characterized. In this study, we investigated whether IL-17 induced autophagy regulates mitochondrial and pro-fibrotic function in bronchial fibroblasts. The primary cultured bronchial fibroblasts isolated from non-asthmatic (NHBF) and severe asthmatic (DHBF) subjects were treated with IL-17 in order to ascertain its effect on mitochondrial function, mitochondrial quality control, and apoptosis using immunoblotting and flow cytometric analyses. At baseline, DHBF exhibited higher levels of mitophagy and mitochondrial biogenesis compared to NHBF. Immunohistochemical evaluation of bronchial biopsies showed intense PINK1 immunoreactivity in severe asthma than in control. IL-17 intensified the mitochondrial dysfunction and impaired the mitochondrial quality control machinery in NHBF and DHBF. Moreover, IL-17 augmented a pro-fibrotic and anti-apoptotic response in both group of fibroblasts. Inhibition of autophagy using bafilomycin-A1 reduced PINK1 expression in NHBF and restored the IL-17 mediated changes in PINK1 to their basal levels in DHBF. Bafilomycin-A1 also reversed the IL-17 associated fibrotic response in these fibroblasts, suggesting a role for IL-17 induced autophagy in the induction of fibrosis in bronchial fibroblasts. Taken together, our findings suggest that IL-17 induced autophagy promotes mitochondrial dysfunction and fibrosis in bronchial fibroblasts from both non-asthmatic and severe asthmatic subjects. Our study provides insights into the therapeutic potential of targeting autophagy in ameliorating fibrosis, particularly in severe asthmatic individuals.

CISH is a negative regulator of IL-13-induced CCL26 production in lung fibroblasts

BACKGROUND

Bronchial asthma is a chronic airway disease characterized by eosinophilic airway inflammation. Lung fibroblasts activated by IL-13 serve as important sources of chemokines, such as eotaxins, contributing to persistent eosinophilic inflammation. Src-homology 2-containing protein (CISH), belonging to the suppressor of cytokine signaling (SOCS) family, acts as a negative regulator of cytokine induction. The aim of this study was to elucidate the role of CISH in the production of eosinophil chemotactic chemokines in human lung fibroblasts.

METHODS

Normal human lung fibroblasts were stimulated by IL-13, and global gene expression profile was assessed by cDNA microarray. Expression changes and downstream of IL-13 signaling were evaluated by quantitative RT-PCR, ELISA or western blotting. Loss- and gain-of-function analyses of CISH were performed by small interfering RNA and vector overexpression, respectively.

RESULTS

Ingenuity pathway analysis revealed that IL-13 induced chemokine signaling, including the eotaxin family, while significantly suppressing IFN-α/β signaling. Among eight SOCS family members, CISH was most strongly induced by IL-13 via phosphorylation of signal transducer and activator of transcription 6 (STAT6). Loss- and gain-of-function studies demonstrated that CISH negatively regulated the expression of CCL26.

CONCLUSIONS

These findings suggest that CISH plays a key role in the eosinophilic inflammation associated with bronchial asthma by regulating IL-13-induced CCL26 production. Augmentation of CISH function could be a novel approach for treating eosinophilic inflammation in severe asthma.

Altered DNA methylation is associated with aberrant gene expression in parenchymal but not airway fibroblasts isolated from individuals with COPD

Background

Chronic obstructive pulmonary disease (COPD) is a heterogeneous disease of the lungs that is currently the fourth leading cause of death worldwide. Genetic factors account for only a small amount of COPD risk, but epigenetic mechanisms, including DNA methylation, have the potential to mediate the interactions between an individual's genetics and environmental exposure. DNA methylation is highly cell type-specific, and individual cell type studies of DNA methylation in COPD are sparse. Fibroblasts are present within the airway and parenchyma of the lung and contribute to the aberrant deposition of extracellular matrix in COPD. No assessment or comparison of genome-wide DNA methylation profiles in the airway and parenchymal fibroblasts from individuals with and without COPD has been undertaken. These data provide valuable insight into the molecular mechanisms contributing to COPD and the differing pathologies of small airways disease and emphysema in COPD.

Methods

Genome-wide DNA methylation was evaluated at over 485,000 CpG sites using the Illumina Infinium HumanMethylation450 BeadChip array in the airway (non-COPD n = 8, COPD n = 7) and parenchymal fibroblasts (non-COPD n = 17, COPD n = 29) isolated from individuals with and without COPD. Targeted gene expression was assessed by qPCR in matched RNA samples.

Results

Differentially methylated DNA regions were identified between cells isolated from individuals with and without COPD in both airway and parenchymal fibroblasts. Only in parenchymal fibroblasts was differential DNA methylation associated with differential gene expression. A second analysis of differential DNA methylation variability identified 359 individual differentially variable CpG sites in parenchymal fibroblasts. No differentially variable CpG sites were identified in the airway fibroblasts. Five differentially variable-methylated CpG sites, associated with three genes, were subsequently assessed for gene expression differences. Two genes (OAT and GRIK2) displayed significantly increased gene expression in cells isolated from individuals with COPD.

Conclusions

Differential and variable DNA methylation was associated with COPD status in the parenchymal fibroblasts but not airway fibroblasts. Aberrant DNA methylation was associated with altered gene expression imparting biological function to DNA methylation changes. Changes in DNA methylation are therefore implicated in the molecular mechanisms underlying COPD pathogenesis and may represent novel therapeutic targets.