Pathogenesis of idiopathic pulmonary fibrosis: review of recent findings

Metabolomic insights into pulmonary fibrosis: a mendelian randomization study

BACKGROUND

This study leverages a two-sample Mendelian Randomization (MR) approach to explore the causal relationships between 1,400 metabolites and pulmonary fibrosis, using genetic variation as instrumental variables. By adhering to stringent criteria for instrumental variable selection, the research aims to uncover metabolic pathways that may influence the risk and progression of pulmonary fibrosis, providing insights into potential therapeutic targets.

METHODS

Utilizing data from the OpenGWAS project, which includes a significant European cohort, and metabolite GWAS data from the Canadian Longitudinal Aging Study (CLSA), the study employs advanced statistical methods. These include inverse variance weighting (IVW), weighted median estimations, and comprehensive sensitivity analyses conducted using the R software environment to ensure the robustness of the causal inferences.

RESULTS

The study identified 62 metabolites with significant causal relationships with pulmonary fibrosis, highlighting both risk-enhancing and protective metabolic factors. This extensive list of metabolites presents a broad spectrum of potential therapeutic targets and biomarkers for early detection, underscoring the metabolic complexity underlying pulmonary fibrosis.

CONCLUSIONS

The findings from this MR study significantly advance our understanding of the metabolic underpinnings of pulmonary fibrosis, suggesting that alterations in specific metabolites could influence the risk and progression of the disease. These insights pave the way for the development of novel diagnostic and therapeutic strategies, emphasizing the potential of metabolic modulation in managing pulmonary fibrosis.

Antrodia cinnamomea extract alleviates bleomycin-induced pulmonary fibrosis in mice by inhibiting the mTOR pathway

BACKGROUND

Pulmonary fibrosis is a progressive diffuse parenchymal lung disorder with a high mortality rate. Studies have indicated that injured lung tissues release various pro-inflammatory factors, and produce a large amount of nitric oxide. There is also accumulation of collagen and oxidative stress-induced injury, collectively leading to pulmonary fibrosis. Antrodia cinnamomea is an endemic fungal growth in Taiwan, and its fermented extracts exert anti-inflammatory effects to alleviate liver damages. Hence, we hypothesized and tested the feasibility of using A. cinnamomea extracts for treatment of pulmonary fibrosis.

METHODS

The TGF-β1-induced human lung fibroblast cells (MRC-5) in vitro cell assay were used to evaluate the effects of A. cinnamomea extracts on the collagen production in MRC-5. Eight-week-old ICR mice were intratracheally administered bleomycin and then fed with an A. cinnamomea extract on day 3 post-administration of bleomycin. At day 21 post-bleomycin administration, the pulmonary functional test, the expression level of inflammation- and fibrosis-related genes in the lung tissue, and the histopathological change were examined.

RESULTS

The A. cinnamomea extract significantly attenuated the expression level of collagen in the TGF-β1-induced MRC-5 cells. In the A. cinnamome-treated bleomycin-induced lung fibrotic mice, the bodyweight increased, pulmonary functions improved, the lung tissues expression level of inflammatory factor and the fibrotic indicator were decreased, and the histopathological results showed the reduction of thickening of the inter-alveolar septa.

CONCLUSIONS

The Antrodia cinnamomea extract significant protects mice against bleomycin-induced lung injuries through improvement of body weight gain and lung functions, and attenuation of expression of inflammatory and fibrotic indicators.

Machine learning-based metabolism-related genes signature, single-cell RNA sequencing, and experimental validation in hypersensitivity pneumonitis

Metabolism is involved in the pathogenesis of hypersensitivity pneumonitis. To identify diagnostic feature biomarkers based on metabolism-related genes (MRGs) and determine the correlation between MRGs and M2 macrophages in patients with hypersensitivity pneumonitis (HP). We retrieved the gene expression matrix from the Gene Expression Omnibus database. The differentially expressed MRGs (DE-MRGs) between healthy control (HC) and patients with HP were identified using the "DESeq2" R package. The "clusterProfiler" R package was used to perform "Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses" on DE-MRGs. We used machine learning algorithms for screening diagnostic feature biomarkers for HP. The "receiver operating characteristic curve" was used to evaluate diagnostic feature biomarkers' discriminating ability. Next, we used the "Cell-type Identification by Estimating Relative Subsets of RNA Transcripts" algorithm to determine the infiltration status of 22 types of immune cells in the HC and HP groups. Single-cell sequencing and qRT-PCR were used to validate the diagnostic feature biomarkers. Furthermore, the status of macrophage polarization in the peripheral blood of patients with HP was determined using flow cytometry. Finally, the correlation between the proportion of M2 macrophages in peripheral blood and the diagnostic biomarker expression profile in HP patients was determined using Spearman analysis. We identified a total of 311 DE-MRGs. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis showed that DE-MRGs were primarily enriched in processes like steroid hormone biosynthesis, drug metabolism, retinol metabolism, etc. Finally, we identified NPR3, GPX3, and SULF1 as diagnostic feature biomarkers for HP using machine learning algorithms. The bioinformatic results were validated using the experimental results. The CIERSORT algorithm and flow cytometry showed a significant difference in the proportion of M2 macrophages in the HC and HP groups. The expression of SULF1 was positively correlated with the proportion of M2-type macrophages. In addition, a positive correlation was observed between SULF1 expression and M2 macrophage proportion. Finally, we identified NPR3, GPX3, and SULF1 as diagnostic feature biomarkers for HP. Further, a correlation between SULF1 and M2 macrophages was observed, providing a novel perspective for treating patients with HP and future studies.

Study on the Mechanism of Astragalus Polysaccharide in Treating Pulmonary Fibrosis Based on "Drug-Target-Pathway" Network

Pulmonary fibrosis is a chronic, progressive and irreversible heterogeneous disease of pulmonary interstitial tissue. Its incidence is increasing year by year in the world, and it will be further increased due to the pandemic of COVID-19. However, at present, there is no safe and effective treatment for this disease, so it is very meaningful to find drugs with high efficiency and less adverse reactions. The natural astragalus polysaccharide has the pharmacological effect of anti-pulmonary fibrosis with little toxic and side effects. At present, the mechanism of anti-pulmonary fibrosis of astragalus polysaccharide is not clear. Based on the network pharmacology and molecular docking method, this study analyzes the mechanism of Astragalus polysaccharides in treating pulmonary fibrosis, which provides a theoretical basis for its further clinical application. The active components of Astragalus polysaccharides were screened out by Swisstarget database, and the related targets of pulmonary fibrosis were screened out by GeneCards database. Protein-protein interaction network analysis and molecular docking were carried out to verify the docking affinity of active ingredients. At present, through screening, we have obtained 92 potential targets of Astragalus polysaccharides for treating pulmonary fibrosis, including 11 core targets. Astragalus polysaccharides has the characteristics of multi-targets and multi-pathways, and its mechanism of action may be through regulating the expression of VCAM1, RELA, CDK2, JUN, CDK1, HSP90AA1, NOS2, SOD1, CASP3, AHSA1, PTGER3 and other genes during the development of pulmonary fibrosis.

Collagen Biosynthesis, Processing, and Maturation in Lung Ageing

In addition to providing a macromolecular scaffold, the extracellular matrix (ECM) is a critical regulator of cell function by virtue of specific physical, biochemical, and mechanical properties. Collagen is the main ECM component and hence plays an essential role in the pathogenesis and progression of chronic lung disease. It is well-established that many chronic lung diseases, e.g., chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF) primarily manifest in the elderly, suggesting increased susceptibility of the aged lung or accumulated alterations in lung structure over time that favour disease. Here, we review the main steps of collagen biosynthesis, processing, and turnover and summarise what is currently known about alterations upon lung ageing, including changes in collagen composition, modification, and crosslinking. Recent proteomic data on mouse lung ageing indicates that, while the ER-resident machinery of collagen biosynthesis, modification and triple helix formation appears largely unchanged, there are specific changes in levels of type IV and type VI as well as the two fibril-associated collagens with interrupted triple helices (FACIT), namely type XIV and type XVI collagens. In addition, levels of the extracellular collagen crosslinking enzyme lysyl oxidase are decreased, indicating less enzymatically mediated collagen crosslinking upon ageing. The latter contrasts with the ageing-associated increase in collagen crosslinking by advanced glycation endproducts (AGEs), a result of spontaneous reactions of protein amino groups with reactive carbonyls, e.g., from monosaccharides or reactive dicarbonyls like methylglyoxal. Given the slow turnover of extracellular collagen such modifications accumulate even more in ageing tissues. In summary, the collective evidence points mainly toward age-induced alterations in collagen composition and drastic changes in the molecular nature of collagen crosslinks. Future work addressing the consequences of these changes may provide important clues for prevention of lung disease and for lung bioengineering and ultimately pave the way to novel targeted approaches in lung regenerative medicine.

Intercellular Communication by Vascular Endothelial Cell-Derived Extracellular Vesicles and Their MicroRNAs in Respiratory Diseases

Respiratory diseases and their comorbidities, such as cardiovascular disease and muscle atrophy, have been increasing in the world. Extracellular vesicles (EVs), which include exosomes and microvesicles, are released from almost all cell types and play crucial roles in intercellular communication, both in the regulation of homeostasis and the pathogenesis of various diseases. Exosomes are of endosomal origin and range in size from 50 to 150 nm in diameter, while microvesicles are generated by the direct outward budding of the plasma membrane in size ranges of 100-2,000 nm in diameter. EVs can contain various proteins, metabolites, and nucleic acids, such as mRNA, non-coding RNA species, and DNA fragments. In addition, these nucleic acids in EVs can be functional in recipient cells through EV cargo. The endothelium is a distributed organ of considerable biological importance, and disrupted endothelial function is involved in the pathogenesis of respiratory diseases such as chronic obstructive pulmonary disease, pulmonary hypertension, and acute respiratory distress syndrome. Endothelial cell-derived EVs (EC-EVs) play crucial roles in both physiological and pathological conditions by traveling to distant sites through systemic circulation. This review summarizes the pathological roles of vascular microRNAs contained in EC-EVs in respiratory diseases, mainly focusing on chronic obstructive pulmonary disease, pulmonary hypertension, and acute respiratory distress syndrome. Furthermore, this review discusses the potential clinical usefulness of EC-EVs as therapeutic agents in respiratory diseases.

Proteomics in idiopathic pulmonary fibrosis: the quest for biomarkers

Idiopathic pulmonary fibrosis (IPF) is a debilitating chronic progressive and fibrosing lung disease that culminates in the destruction of alveolar integrity and dismal prognosis. Its etiology is unknown and pathophysiology remains unclear. While great advances have been made in elucidating the pathogenesis mechanism, considerable gaps related to information on pathogenetic pathways and key protein targets involved in the clinical course of the disease exist. These issues need to be addressed for better clinical management of this highly challenging disease. Omics approach has revolutionized the entire area of disease understanding and holds promise in its translation to clinical biomarker discovery. This review outlines the contribution of proteomics towards identification of important biomarkers in IPF in terms of their clinical utility, i.e. prognosis, differential diagnosis, disease progression and treatment monitoring. The major dysregulated pathways associated with IPF are also discussed. Based on numerous proteomics studies on human and animal models, it is proposed that IPF pathogenesis involves complex interactions of several pathways such as oxidative stress, endoplasmic reticulum stress, unfolded protein response, coagulation system, inflammation, abnormal wounding, fibroblast proliferation, fibrogenesis and deposition of extracellular matrix. These pathways and their key path-changing mediators need further validation in large well-planned multi-centric trials at various geographical locations for successful development of clinical biomarkers of this confounding disease.

Caveolin-1-derived peptide limits development of pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal fibrotic lung disease with a median 5-year survival of ~20%. Current U.S. Food and Drug Administration-approved pharmacotherapies slow progression of IPF, providing hope that even more effective treatments can be developed. Alveolar epithelial progenitor type II cell (AEC) apoptosis and proliferation, and accumulation of activated myofibroblasts or fibrotic lung fibroblasts (fLfs) contribute to the progression of IPF. Full-length caveolin-1 scaffolding domain peptide (CSP; amino acids 82 to 101 of Cav1: DGIWKASFTTFTVTKYWFYR) inhibits AEC apoptosis and fLf activation and expansion and attenuates PF in bleomycin (BLM)-induced lung injury in mice. Like full-length CSP, a seven-amino acid deletion fragment of CSP, CSP7 (FTTFTVT), demonstrated antifibrotic effects in murine models of lung fibrosis. When CSP7 was administered during the fibrotic phase in three preclinical models [single-dose BLM, repeated-dose BLM, and adenovirus expressing constitutively active transforming growth factor-β1 (Ad-TGF-β1)-induced established PF], CSP7 reduced extracellular matrix (ECM) markers characteristic of PF, increased AEC survival, and improved lung function. CSP7 is amenable to both systemic (intraperitoneal) or direct lung delivery in a nebulized or dry powder form. Furthermore, CSP7 treatment of end-stage human IPF lung tissue explants attenuated ECM production and promoted AEC survival. Ames testing for mutagenicity and in vitro human peripheral blood lymphocyte and in vivo mouse micronucleus transformation assays indicated that CSP7 is not carcinogenic. Together, these findings support the further development of CSP7 as an antifibrotic treatment for patients with IPF or other interstitial lung diseases.

Biomarkers and their potential functions in idiopathic pulmonary fibrosis

Introduction: Idiopathic pulmonary fibrosis (IPF) is a chronic, devastating, and progressive lung disease that is characterized by fibrosis and respiratory failure. IPF holds high morbidity and poor prognosis and still faces considerable problems of reliable diagnosis and valid prognosis. A growing body of literature have reported changes in the level of various biomarkers in IPF patients, which means that they are expected to become a new tool for the clinical practice of IPF.Areas covered: We reviewed the recent literature about biomarkers and focus on the role they play in IPF. We systematically searched Medline/PubMed through February 2020. Many works of literature have shown that a variety of biomolecules and genomics played multiple roles in the diagnosis or differential diagnosis, prognosis, and indication of acute deterioration of IPF and so on.Expert opinion: Significant advances have been made in the role of biomarkers for IPF these years; however, current data indicate that a single biomarker is unlikely to have a transformative effect on clinical practice; therefore, the combined effect of various biomarkers can be considered to improve the accuracy of diagnosis and prognosis. Further research of biomarkers may provide new insights for the diagnosis, prognosis, and even therapy of IPF.

Korean Guidelines for Diagnosis and Management of Interstitial Lung Diseases: Part 2. Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive fibrosing interstitial pneumonia, which presents with a progressive worsening dyspnea, and thus a poor outcome. The members of the Korean Academy of Tuberculosis and Respiratory Diseases as well as the participating members of the Korea Interstitial Lung Disease Study Group drafted this clinical practice guideline for IPF management. This guideline includes a wide range of topics, including the epidemiology, pathogenesis, risk factors, clinical features, diagnosis, treatment, prognosis, and acute exacerbation of IPF in Korea. Additionally, we suggested the PICO for the use of pirfenidone and nintendanib and for lung transplantation for the treatment of patients with IPF through a systemic literature review using experts' help in conducting a meta-analysis. We recommend this guideline to physicians, other health care professionals, and government personnel in Korea, to facilitate the treatment of patients with IPF.

Stem cell-based Lung-on-Chips: The best of both worlds?

Pathologies of the respiratory system such as lung infections, chronic inflammatory lung diseases, and lung cancer are among the leading causes of morbidity and mortality, killing one in six people worldwide. Development of more effective treatments is hindered by the lack of preclinical models of the human lung that can capture the disease complexity, highly heterogeneous disease phenotypes, and pharmacokinetics and pharmacodynamics observed in patients. The merger of two novel technologies, Organs-on-Chips and human stem cell engineering, has the potential to deliver such urgently needed models. Organs-on-Chips, which are microengineered bioinspired tissue systems, recapitulate the mechanochemical environment and physiological functions of human organs while concurrent advances in generating and differentiating human stem cells promise a renewable supply of patient-specific cells for personalized and precision medicine. Here, we discuss the challenges of modeling human lung pathophysiology in vitro, evaluate past and current models including Organs-on-Chips, review the current status of lung tissue modeling using human pluripotent stem cells, explore in depth how stem-cell based Lung-on-Chips may advance disease modeling and drug testing, and summarize practical consideration for the design of Lung-on-Chips for academic and industry applications.

Heterozygous TERT gene mutation associated with familial idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic interstitial lung disease of unknown cause that occurs sporadically, but it can also occur in families and so named as Familial Pulmonary Fibrosis (FPF). Some forms of FPF overlaps IPF features, namely the radiological and histological pattern of usual interstitial pneumonia (UIP). Genetic and environmental factors commonly play an important role in the pathogenesis of FPF and the most commonly identified mutations involve the telomerase complex. Here, we report a rare case of FPF in a male at the age of 44, in whom genetic testing showed heterozygous variants for the telomerase reverse transcriptase gene (TERT). Our report highlights the importance of compiling a thorough family history in younger patients identified with UIP serving as a resource for identifying the current and future genetic links to disease. Families with UIP hold a great promise in defining UIP pathogenesis, potentially suggesting targets for the development of future therapies.

Application of Isobaric Tags for Relative and Absolute Quantification (iTRAQ) Coupled with Two-Dimensional Liquid Chromatography/Tandem Mass Spectrometry in Quantitative Proteomic Analysis for Discovery of Serum Biomarkers for Idiopathic Pulmonary Fibrosis

Background

The present study was performed to explore the presence of informative protein biomarkers of human serum proteome in idiopathic pulmonary fibrosis (IPF).

Material/Methods

Serum samples were profiled using iTRAQ coupled with two-dimensional liquid chromatography/tandem mass spectrometry (2D-LC-MS/MS) technique, and ELISA was used to validate candidate biomarkers.

Results

A total of 394 proteins were identified and 97 proteins were associated with IPF. Four biomarker candidates generated from iTRAQ experiments – CRP, fibrinogen-α chain, haptoglobin, and kininogen-1 – were successfully verified using ELISA.

Conclusions

The present study demonstrates that levels of CRP and fibrinogen-α are higher and levels of haptoglobin and kininogen-1 are lower in patients with IPF compared to levels in healthy controls. We found they are useful candidate biomarkers for IPF.

Type 2 macrophages and Th2 CD4+ cells in interstitial lung diseases (ILDs): an overview

Interstitial lung diseases (ILDs) are a heterogeneous group characterized mainly by damage to pulmonary parenchyma, through histopathological processes such as granulomatous pneumopathy, inflammation and fibrosis. Factors that generate susceptibility to ILDs include age, exposure to occupational and environmental compounds, genetic, family history, radiation and chemotherapy/immunomodulatory and cigarette smoke. IFN-γ, IL-1β, and LPS are necessary to induce a classical activation of macrophages, whereas cytokines as IL-4 and IL-13 can induce an alternative activation in macrophages, through the JAK-STAT mediated signal transduction. M2 macrophages are identified based on the gene transcription or protein expression of a set of M2 markers. These markers include transmembrane glycoproteins, scavenger receptors, enzymes, growth factors, hormones, cytokines, and cytokine receptors with diverse and often yet unexplored functions. Fibrotic lung disorders may have a M2 polarization background. The Th2 pathway with an elevated CCL-18 (marker of M2) concentration in the bronchoalveolar lavage fluid (BALF) is linked to fibrosis in ILDs. Besides the role of M2 in tissue repair and ECM remodeling, activated fibroblasts summon and stimulate macrophages by producing MCP-1, M-CSF and other chemokines, as well as activated macrophages secrete cytokines that attract and stimulate proliferation, survival and migration of fibroblast mediated by platelet-derived growth factor (PDGF). (Sarcoidosis Vasc Diffuse Lung Dis 2018; 35: 98-108).

lncRNAPCAT29 inhibits pulmonary fibrosis via the TGF‑β1‑regulated RASAL1/ERK1/2 signal pathway

Pulmonary fibrosis is a severe respiratory disease characterized by the aggregation of extracellular matrix components and inflammation‑associated injury. Studies have suggested that long non‑coding RNAs (lncRNA) may serve a role in the pathophysiological processes of pulmonary fibrosis. However, the potential molecular mechanisms involving the lncRNA, prostate cancer‑associated transcript 29 (lncRNAPCAT29) in the progression of pulmonary fibrosis are yet to be determined. In the present study, the role of lncRNAPCAT29 and the potential signaling mechanism in pulmonary fibrosis progression was investigated. Reverse transcription‑quantitative polymerase chain reaction and immunohistochemistry revealed that the expression levels of lncRNAPCAT29 were downregulated within interstitial lung cells from mice with silica‑induced pulmonary fibrosis. Transfection with lncRNAPCAT29 was associated with upregulated expression of microRNA (miRNA)‑221 and downregulated expression of transforming growth factor‑β1 (TGF‑β1); reduced inflammation and fibrotic progression was also associated with lncRNAPCAT29 transfection. TGF‑β1 expression levels were inhibited within pulmonary fibroblasts due to lncRNAPCAT29 expression; NEDD4 binding protein 2 and Plexin‑A4 expression levels were also suppressed. Analysis of the potential mechanism underlying silica‑induced pulmonary fibrosis revealed that the expression levels of RAS protein activator like 1 (RASAL1) and extracellular signal‑regulated kinases 1/2 (ERK1/2) were suppressed due to lncRNAPCAT29 expression. The results of the present study demonstrated that lncRNAPCAT29 induced miRNA‑221 upregulation and TGF‑β1 downregulation. These observations were associated with reduced inflammation and progression of silica‑induced pulmonary fibrosis via the TGF‑β1‑regulated RASAL1/ERK1/2 signaling pathway, which may serve as a potential target for the treatment of pulmonary fibrosis.

The Genetic Heterogeneity among Different Mouse Strains Impacts the Lung Injury Potential of Multiwalled Carbon Nanotubes

Genetic variation constitutes an important variable impacting the susceptibility to inhalable toxic substances and air pollutants, as reflected by epidemiological studies in humans and differences among animal strains. While multiwalled carbon nanotubes (MWCNTs) are capable of causing lung fibrosis in rodents, it is unclear to what extent the genetic variation in different mouse strains influence the outcome. Four inbred mouse strains, including C57Bl/6, Balb/c, NOD/ShiLtJ, and A/J, to test the pro-fibrogenic effects of a library of MWCNTs in vitro and in vivo are chosen. Ex vivo analysis of IL-1β production in bone marrow-derived macrophages (BMDMs) as molecular initiating event (MIE) is performed. The order of cytokine production (Balb/c > A/J > C57Bl/6 > NOD/ShiLtJ) in BMDMs is also duplicated during assessment of IL-1β production in the bronchoalveolar lavage fluid of the same mouse strains 40 h after oropharyngeal instillation of a representative MWCNT. Animal test after 21 d also confirms a similar hierarchy in TGF-β1 production and collagen deposition in the lung. Statistical analysis confirms a correlation between IL-1β production in BMDM and the lung fibrosis. All considered, these data demonstrate that genetic background indeed plays a major role in determining the pro-fibrogenic response to MWCNTs in the lung.

Human Lung Tissue Transcriptome: Influence of Sex and Age

Background

Sex and age strongly influence the pathophysiology of human lungs, but scarce information is available about their effects on pulmonary gene expression.

Methods

We followed a discovery-validation strategy to identify sex- and age-related transcriptional differences in lung.

Results

We identified transcriptional profiles significantly associated with sex (215 genes; FDR < 0.05) and age at surgery (217 genes) in non-involved lung tissue resected from 284 lung adenocarcinoma patients. When these profiles were tested in three independent series of non-tumor lung tissue from an additional 1,111 patients, we validated the association with sex and age for 25 and 22 genes, respectively. Among the 17 sex-biased genes mapping on chromosome X, 16 have been reported to escape X-chromosome inactivation in other tissues or cells, suggesting that this mechanism influences lung transcription too. Our 22 age-related genes partially overlap with genes modulated by age in other tissues, suggesting that the aging process has similar consequences on gene expression in different organs. Finally, seven genes whose expression was modulated by sex in non-tumor lung tissue, but no age-related gene, were also validated using publicly available data from 990 lung adenocarcinoma samples, suggesting that the physiological regulatory mechanisms are only partially active in neoplastic tissue.

Conclusions

Gene expression in non-tumor lung tissue is modulated by both sex and age. These findings represent a validated starting point for research on the molecular mechanisms underlying the observed differences in the course of lung diseases among men and women of different ages.

Melatonin attenuates TGFβ1-induced epithelial-mesenchymal transition in lung alveolar epithelial cells

Idiopathic pulmonary fibrosis (IPF) is the most common interstitial lung disease. However, the pathogenesis remains to be fully elucidated. Melatonin is secreted by the pineal gland, it has a strong antioxidant effect, and exerts an anti-fibrosis effect. Whether melatonin attenuates pulm -onary fibrosis by inhibiting epithelial‑mesenchymal transition (EMT) requires further research. The present study aimed to investigate whether melatonin prevents transforming growth factor‑β1 (TGF‑β1)‑induced EMT and underlying signaling pathways using reverse transcription‑quantitative polymerase chain reaction, western blot analysis and immunofluorescence. The results demonstrated that melatonin inhibits EMT in A549 cells, and the Wnt/β‑catenin and Smad2/3 signaling pathways are involved in the EMT of the A549 cell line as they were suppressed by melatonin. The present study indicates that melatonin inhibited TGFβ1‑induced epithelial‑mesenchymal transition in the A549 cell line and may potentially be useful in the treatment of IPF.

Lung Pericytes and Resident Fibroblasts: Busy Multitaskers

Pericytes, resident fibroblasts, and mesenchymal stem cells are poorly described cell populations. They have recently been characterized in much greater detail in rodent lungs and have been shown to play important roles in development, homeostasis, response to injury and pathogens, as well as recovery from damage. These closely related mesenchymal cell populations form extensive connections to the lung's internal structure, as well as its internal and external surfaces. They generate and remodel extracellular matrix, coregulate the vasculature, help maintain and restore the epithelium, and act as sentries for the immune system. In this review, we revisit these functions in light of significant advances in characterizing and tracking lung fibroblast populations in rodents. Lineage tracing experiments have mapped the heritage, identified functions that discriminate lung pericytes from resident fibroblasts, identified a subset of mesenchymal stem cells, and shown these populations to be the predominant progenitors of pathological fibroblasts and myofibroblasts in lung diseases. These findings point to the importance of resident lung mesenchymal populations as therapeutic targets in acute lung injury as well as fibrotic and degenerative diseases. Far from being passive and quiescent, pericytes and resident fibroblasts are busily sensing and responding, through diverse mechanisms, to changes in lung health and function.

Induction of Connective Tissue Growth Factor Expression by Hypoxia in Human Lung Fibroblasts via the MEKK1/MEK1/ERK1/GLI-1/GLI-2 and AP-1 Pathways

Several reports have indicated that hypoxia, GLI, and connective tissue growth factor (CTGF) contribute to pulmonary fibrosis in idiopathic pulmonary fibrosis. We investigated the participation of mitogen-activated protein kinase kinase (MEK) kinase 1 (MEKK1)/MEK1/ERK1/GLI-1/2 and activator protein-1 (AP-1) signaling in hypoxia-induced CTGF expression in human lung fibroblasts. Hypoxia time-dependently increased CTGF expression, which was attenuated by the small interfering RNA (siRNA) of GLI-1 (GLI-1 siRNA) and GLI-2 (GLI-2 siRNA) in both human lung fibroblast cell line (WI-38) and primary human lung fibroblasts (NHLFs). Moreover, GLI-1 siRNA and GLI-2 siRNA attenuated hypoxia-induced CTGF-luciferase activity, and the treatment of cells with hypoxia induced GLI-1 and GLI-2 translocation. Furthermore, hypoxia-induced CTGF expression was reduced by an MEK inhibitor (PD98059), MEK1 siRNA, ERK inhibitor (U0126), ERK1 siRNA, and MEKK1 siRNA. Both PD98059 and U0126 significantly attenuated hypoxia-induced CTGF-luciferase activity. Hypoxia time-dependently increased MEKK1, ERK, and p38 MAPK phosphorylation. Moreover, SB203580 (a p38 MAPK inhibitor) also apparently inhibited hypoxia-induced CTGF expression. The treatment of cells with hypoxia induced ERK, GLI-1, or GLI-2 complex formation. Hypoxia-induced GLI-1 and GLI-2 translocation into the nucleus was significantly attenuated by U0126. In addition, hypoxia-induced ERK Tyr204 phosphorylation was impeded by MEKK1 siRNA. Moreover, hypoxia-induced CTGF-luciferase activity was attenuated by cells transfected with AP-1 site mutation in a CTGF construct. Exposure to hypoxia caused a time-dependent phosphorylation of c-Jun, but not of c-Fos. Chromatin immunoprecipitation (ChIP) revealed that hypoxia induced the recruitment of c-Jun, GLI-1, and GLI-2 to the AP-1 promoter region of CTGF. Hypoxia-treated cells exhibited an increase in α-smooth muscle actin (α-SMA) and collagen production, which was blocked by GLI-1 siRNA and GLI-2 siRNA. Overall, these data implied that the MEKK1/MEK1/ERK1/GLI-1/GLI-2, and AP-1 pathways mediated hypoxia-induced CTGF expression in human lung fibroblasts. Furthermore, GLI-1 and GLI-2 found to be involved in hypoxia-induced α-SMA and collagen expression.

Macrophage polarization in interstitial lung diseases

The role of bronchoalveolar lavage fluid (BALf) examination in differential diagnosis of interstitial lung diseases (ILD) was established. Currently, functional polarization into M1 (pro-inflammatory) and M2 (anti-inflammatory) subpopulations is emphasized. The aim of our study was to compare the proportion of M1 and M2 in BALf of patients with different ILD. BALf samples were collected from 75 ILD patients: sarcoidosis (SA, 36), hypersensitivity pneumonitis (HP, 10), non-specific interstitial pneumonia (NSIP, 8), idiopathic pulmonary fibrosis (IPF, 6) and other ILD (15). Phenotyping was performed by immunocytochemistry with anti-CD40 and CD163 antibodies (for M1 and M2, respectively). For both, CD40 and CD163, three populations of cells have been specified: small cells with strong (+++), large cells with weak (+) and cells with no (-) reaction. Due to lack of statistically significant differences between patients with HP, NSIP and IPF, they were classified into a common group and compared to the group of patients with sarcoidosis. The median proportion of macrophage population was as follows: for CD40: 61%, 35%, 2% in patients with SA and 49%, 47%, 3% in patients with other ILD and for CD163: 55%, 35%, 5% in SA and 53%, 43%, 1% in ILD patients, respectively. We found a significantly higher proportion of M1 in SA when compared with other ILD. Our study showed no evidence of defined polarization of alveolar macrophages in different types of interstitial lung diseases. However, we emphasized the role of CD40 positive cells in sarcoidosis and the role of CD163 positive cells in fibrotic diffuse lung diseases.

TINF2 Gene Mutation in a Patient with Pulmonary Fibrosis

Pulmonary fibrosis is a frequent manifestation of telomere syndromes. Telomere gene mutations are found in up to 25% and 3% of patients with familial disease and sporadic disease, respectively. The telomere gene TINF2 encodes an eponymous protein that is part of the shelterin complex, a complex involved in telomere protection and maintenance. A TINF2 gene mutation was recently reported in a family with pulmonary fibrosis. We identified a heterozygous Ser245Tyr mutation in the TINF2 gene of previously healthy female patient that presented with progressive cough due to pulmonary fibrosis as well as panhypogammaglobulinemia at age 52. Retrospective multidisciplinary evaluation classified her as a case of possible idiopathic pulmonary fibrosis. Telomere length-measurement indicated normal telomere length in the peripheral blood compartment. This is the first report of a TINF2 mutation in a patient with sporadic pulmonary fibrosis, which represents another association between TINF2 mutations and this disease. Furthermore, this case underlines the importance of telomere dysfunction and not telomere length alone in telomere syndromes and draws attention to hypogammaglobulinemia as a manifestation of telomere syndromes.

A proteomics approach to identifying key protein targets involved in VEGF inhibitor mediated attenuation of bleomycin-induced pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with a life expectancy of less than 5 years post diagnosis for most patients. Poor molecular characterization of IPF has led to insufficient understanding of the pathogenesis of the disease, resulting in lack of effective therapies. In this study, we have integrated a label-free LC-MS based approach with systems biology to identify signaling pathways and regulatory nodes within protein interaction networks that govern phenotypic changes that may lead to IPF. Ingenuity Pathway Analysis of proteins modulated in response to bleomycin treatment identified PI3K/Akt and Wnt signaling as the most significant profibrotic pathways. Similar analysis of proteins modulated in response to vascular endothelial growth factor (VEGF) inhibitor (CBO-P11) treatment identified natural killer cell signaling and PTEN signaling as the most significant antifibrotic pathways. Mechanistic/mammalian target of rapamycin (mTOR) and extracellular signal-regulated kinase (ERK) were identified to be key mediators of pro- and antifibrotic response, where bleomycin (BLM) treatment resulted in increased expression and VEGF inhibitor treatment attenuated expression of mTOR and ERK. Using a BLM mouse model of pulmonary fibrosis and VEGF inhibitor CBO-P11 as a therapeutic measure, we identified a comprehensive set of signaling pathways and proteins that contribute to the pathogenesis of pulmonary fibrosis that can be targeted for therapy against this fatal disease.

FK506-Binding Protein 10, a Potential Novel Drug Target for Idiopathic Pulmonary Fibrosis

RATIONALE

Increased abundance and stiffness of the extracellular matrix, in particular collagens, is a hallmark of idiopathic pulmonary fibrosis (IPF). FK506-binding protein 10 (FKBP10) is a collagen chaperone, mutations of which have been indicated in the reduction of extracellular matrix stiffness (e.g., in osteogenesis imperfecta).

OBJECTIVES

To assess the expression and function of FKBP10 in IPF.

METHODS

We assessed FKBP10 expression in bleomycin-induced lung fibrosis (using quantitative reverse transcriptase-polymerase chain reaction, Western blot, and immunofluorescence), analyzed microarray data from 99 patients with IPF and 43 control subjects from a U.S. cohort, and performed Western blot analysis from 6 patients with IPF and 5 control subjects from a German cohort. Subcellular localization of FKBP10 was assessed by immunofluorescent stainings. The expression and function of FKBP10, as well as its regulation by endoplasmic reticulum stress or transforming growth factor-β1, was analyzed by small interfering RNA-mediated loss-of-function experiments, quantitative reverse transcriptase-polymerase chain reaction, Western blot, and quantification of secreted collagens in the lung and in primary human lung fibroblasts (phLF). Effects on collagen secretion were compared with those of the drugs nintedanib and pirfenidone, recently approved for IPF.

MEASUREMENTS AND MAIN RESULTS

FKBP10 expression was up-regulated in bleomycin-induced lung fibrosis and IPF. Immunofluorescent stainings demonstrated localization to interstitial (myo)fibroblasts and CD68(+) macrophages. Transforming growth factor-β1, but not endoplasmic reticulum stress, induced FKBP10 expression in phLF. The small interfering RNA-mediated knockdown of FKBP10 attenuated expression of profibrotic mediators and effectors, including collagens I and V and α-smooth muscle actin, on the transcript and protein level. Importantly, loss of FKBP10 expression significantly suppressed collagen secretion by phLF.

CONCLUSIONS

FKBP10 might be a novel drug target for IPF.