Chronic Expression of a Clinical SFTPC Mutation Causes Murine Lung Fibrosis with Idiopathic Pulmonary Fibrosis Features

Alveolar type 2 cells marker gene SFTPC inhibits epithelial-to-mesenchymal transition by upregulating SOX7 and suppressing WNT/β-catenin pathway in non-small cell lung cancer

Introduction

Surfactant Protein C gene (SFTPC) is a marker gene of alveolar type 2 cells (AT2), which are the key structures of alveoli. Mutations or deletions in SFTPC cause idiopathic pulmonary fibrosis (IPF). Importantly, IPF is an independent risk factor for non-small cell lung cancer (NSCLC). It suggests that abnormal expression of SFTPC may be relevant to development of NSCLC. However, the function and mechanism of SFTPC in NSCLC are still poor understood until now.

Methods

The expression of SFTPC and the relationship between SFTPC and prognosis of NSCLC were analyzed in TCGA database and our collected clinical NSCLC tissues. Subsequently, the function and mechanism of SFTPC in NSCLC were explored by RNA-sequence, qRT-PCR, Western blot, Immunohistochemical, Wound-healing, Millicell, Transwell assays and mouse tumor xenograft model.

Results

SFTPC was dramatically downregulated in NSCLC tissues from TCGA database and 40 out of 46 collected clinical LUAD tissues compared with adjacent non-tumor tissues. Low expression of SFTPC was associated with poor prognosis of LUAD by TCGA database. Importantly, we confirmed that overexpression of SFTPC significantly inhibited Epithelial-to-Mesenchymal Transition (EMT) process of NSCLC cells by upregulating SOX7 and then inactivating WNT/β-catenin pathway in vitro and in vivo. Particularly, we discovered that low expression of SFTPC was associated with EMT process and low expression of SOX7 in NSCLC tissues.

Conclusion

Our study revealed a novel mechanism of SFTPC in NSCLC development. Meanwhile, it also might provide a new clue for exploring the molecular mechanism about NSCLC development in patients with IPF in the future.

Cellular therapies for idiopathic pulmonary fibrosis: current progress and future prospects

Idiopathic pulmonary fibrosis (IPF) is an interstitial, fibrotic lung disease characterized by progressive damage. Lung tissues with IPF are replaced by fibrotic tissues with increased collagen deposition, modified extracellular matrix, all which overall damages the alveoli. These changes eventually impede the gas exchange function of the alveoli, and eventually leads to fatal respiratory failure of the lung. Investigations have been conducted to further understand IPF's pathogenesis, and significant progress in understanding its development has been made. Additionally, two therapeutic treatments, Nintedanib and Pirfenidone, have been approved and are currently used in medical applications. Moreover, cell-based treatments have recently come to the forefront of developing disease therapeutics and are the focus of many current studies. Furthermore, a sizable body of research encompassing basic, pre-clinical, and even clinical trials have all been amassed in recent years and hold a great potential for more widespread applications in patient care. Herein, this article reviews the progress in understanding the pathogenesis and pathophysiology of IPF. Additionally, different cell types used in IPF therapy were reviewed, including alveolar epithelial cells (AECs), circulating endothelial progenitors (EPCs), mixed lung epithelial cells, different types of stem cells, and endogenous lung tissue-specific stem cells. Finally, we discussed the contemporary trials that employ or explore cell-based therapy for IPF.

Activation of alveolar epithelial ER stress by β-coronavirus infection disrupts surfactant homeostasis in mice: implications for COVID-19 respiratory failure

COVID-19 syndrome is characterized by acute lung injury, hypoxemic respiratory failure, and high mortality. Alveolar type 2 (AT2) cells are essential for gas exchange, repair, and regeneration of distal lung epithelium. We have shown that the causative agent, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and other members of the β-coronavirus genus induce an endoplasmic reticulum (ER) stress response in vitro; however, the consequences for host AT2 cell function in vivo are less understood. To study this, two murine models of coronavirus infection were used-mouse hepatitis virus-1 (MHV-1) in A/J mice and a mouse-adapted SARS-CoV-2 strain. MHV-1-infected mice exhibited dose-dependent weight loss with histological evidence of distal lung injury accompanied by elevated bronchoalveolar lavage fluid (BALF) cell counts and total protein. AT2 cells showed evidence of both viral infection and increased BIP/GRP78 expression, consistent with activation of the unfolded protein response (UPR). The AT2 UPR included increased inositol-requiring enzyme 1α (IRE1α) signaling and a biphasic response in PKR-like ER kinase (PERK) signaling accompanied by marked reductions in AT2 and BALF surfactant protein (SP-B and SP-C) content, increases in surfactant surface tension, and emergence of a reprogrammed epithelial cell population (Krt8+ and Cldn4+). The loss of a homeostatic AT2 cell state was attenuated by treatment with the IRE1α inhibitor OPK-711. As a proof-of-concept, C57BL6 mice infected with mouse-adapted SARS-CoV-2 demonstrated similar lung injury and evidence of disrupted surfactant homeostasis. We conclude that lung injury from β-coronavirus infection results from an aberrant host response, activating multiple AT2 UPR stress pathways, altering surfactant metabolism/function, and changing AT2 cell state, offering a mechanistic link between SARS-CoV-2 infection, AT2 cell biology, and acute respiratory failure.NEW & NOTEWORTHY COVID-19 syndrome is characterized by hypoxemic respiratory failure and high mortality. In this report, we use two murine models to show that β-coronavirus infection produces acute lung injury, which results from an aberrant host response, activating multiple epithelial endoplasmic reticular stress pathways, disrupting pulmonary surfactant metabolism and function, and forcing emergence of an aberrant epithelial transition state. Our results offer a mechanistic link between SARS-CoV-2 infection, AT2 cell biology, and respiratory failure.

Learning from cystic fibrosis: How can we start to personalise treatment of Children's Interstitial Lung Disease (chILD)?

Cystic fibrosis (CF) is a monogenic disorder cause by mutations in the CF Transmembrane Regulator (CFTR) gene. The prognosis of cystic fibrosis has been transformed by the discovery of highly effective modulator therapies (HEMT). Treatment has changed from reactive therapy dealing with complications of the disease to pro-active correction of the underlying molecular functional abnormality. This has come about by discovering the detailed biology of the different CF molecular sub-endotypes; the development of biomarkers to assess response even in mild disease or young children; the performance of definitive large randomised controlled trials in patients with a common mutation and the development of in vitro testing systems to test efficacy in those patients with rare CFTR mutations. As a result, CF is now an umbrella term, rather than a specific diagnostic label; we have moved from clinical phenotypes to molecular subendotypes. Children's Interstitial Lung Diseases (chILDs) comprise more than 200 entities, and are a diverse group of diseases, for an increasing number of which an underlying gene mutation has been discovered. Many of these entities are umbrella terms, such as pulmonary alveolar proteinosis or hypersensitivity pneumonitis, for each of which there are multiple and very different endotypes. Even those chILDs for which a specific gene mutation has been discovered comprise, as with CF, different molecular subendotypes likely mandating different therapies. For most chILDs, current treatment is non-specific (corticosteroids, azithromycin, hydroxychloroquine). The variability of the different entities means that there is little evidence for the efficacy of any treatment. This review considers how some of the lessons of the success story of CF are being applied to chILD, thus opening the opportunities for truly personalised medicine in these conditions. Advances in knowledge in the molecular biology of surfactant protein C and Adenosine triphosphate binding cassette subfamily A member 3 (ABCA3), and the possibilities of discovering novel therapies by in vitro studies will especially be highlighted.

A roadmap to precision treatments for familial pulmonary fibrosis

Interstitial lung diseases (ILDs) in adults and children (chILD) are a heterogeneous group of lung disorders leading to inflammation, abnormal tissue repair and scarring of the lung parenchyma often resulting in respiratory failure and death. Inherited factors directly cause, or contribute significantly to the risk of developing ILD, so called familial pulmonary fibrosis (FPF), and monogenic forms may have a poor prognosis and respond poorly to current treatments. Specific, variant-targeted or precision treatments are lacking. Clinical trials of repurposed drugs, anti-fibrotic medications and specific treatments are emerging but for many patients no interventions exist. We convened an expert working group to develop an overarching framework to address the existing research gaps in basic, translational, and clinical research and identified areas for future development of preclinical models, candidate medications and innovative clinical trials. In this Position Paper, we summarise working group discussions, recommendations, and unresolved questions concerning precision treatments for FPF.

Effects of Natural Products through Inhibiting Endoplasmic Reticulum Stress on Attenuation of Idiopathic Pulmonary Fibrosis

With ever-increasing intensive studies of idiopathic pulmonary fibrosis (IPF), significant progresses have been made. Endoplasmic reticulum stress (ERS)/unfolded protein reaction (UPR) is associated with the development and progression of IPF, and targeting ERS/UPR may be beneficial in the treatment of IPF. Natural product is a tremendous source of new drug discovery, and accumulating studies have reported that many natural products show potential therapeutic effects for IPF via modulating one or more branches of the ERS signaling pathway. Therefore, this review focuses on critical roles of ERS in IPF development, and summarizes herbal preparations and bioactive compounds which protect against IPF through regulating ERS.

The alveolus: Our current knowledge of how the gas exchange unit of the lung is constructed and repaired

The mammalian lung completes its last step of development, alveologenesis, to generate sufficient surface area for gas exchange. In this process, multiple cell types that include alveolar epithelial cells, endothelial cells, and fibroblasts undergo coordinated cell proliferation, cell migration and/or contraction, cell shape changes, and cell-cell and cell-matrix interactions to produce the gas exchange unit: the alveolus. Full functioning of alveoli also involves immune cells and the lymphatic and autonomic nervous system. With the advent of lineage tracing, conditional gene inactivation, transcriptome analysis, live imaging, and lung organoids, our molecular understanding of alveologenesis has advanced significantly. In this review, we summarize the current knowledge of the constituents of the alveolus and the molecular pathways that control alveolar formation. We also discuss how insight into alveolar formation may inform us of alveolar repair/regeneration mechanisms following lung injury and the pathogenic processes that lead to loss of alveoli or tissue fibrosis.

Lung regeneration: diverse cell types and the therapeutic potential

Lung tissue has a certain regenerative ability and triggers repair procedures after injury. Under controllable conditions, lung tissue can restore normal structure and function. Disruptions in this process can lead to respiratory system failure and even death, causing substantial medical burden. The main types of respiratory diseases are chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and acute respiratory distress syndrome (ARDS). Multiple cells, such as lung epithelial cells, endothelial cells, fibroblasts, and immune cells, are involved in regulating the repair process after lung injury. Although the mechanism that regulates the process of lung repair has not been fully elucidated, clinical trials targeting different cells and signaling pathways have achieved some therapeutic effects in different respiratory diseases. In this review, we provide an overview of the cell type involved in the process of lung regeneration and repair, research models, and summarize molecular mechanisms involved in the regulation of lung regeneration and fibrosis. Moreover, we discuss the current clinical trials of stem cell therapy and pharmacological strategies for COPD, IPF, and ARDS treatment. This review provides a reference for further research on the molecular and cellular mechanisms of lung regeneration, drug development, and clinical trials.

PGF2α signaling drives fibrotic remodeling and fibroblast population dynamics in mice

Idiopathic pulmonary fibrosis (IPF) is a chronic parenchymal lung disease characterized by repetitive alveolar cell injury, myofibroblast proliferation, and excessive extracellular matrix deposition for which unmet need persists for effective therapeutics. The bioactive eicosanoid, prostaglandin F2α, and its cognate receptor FPr (Ptgfr) are implicated as a TGF-β1-independent signaling hub for IPF. To assess this, we leveraged our published murine PF model (IER-SftpcI73T) expressing a disease-associated missense mutation in the surfactant protein C (Sftpc) gene. Tamoxifen-treated IER-SftpcI73T mice developed an early multiphasic alveolitis and transition to spontaneous fibrotic remodeling by 28 days. IER-SftpcI73T mice crossed to a Ptgfr-null (FPr-/-) line showed attenuated weight loss and gene dosage-dependent rescue of mortality compared with FPr+/+ cohorts. IER-SftpcI73T/FPr-/- mice also showed reductions in multiple fibrotic endpoints for which administration of nintedanib was not additive. Single-cell RNA-Seq, pseudotime analysis, and in vitro assays demonstrated Ptgfr expression predominantly within adventitial fibroblasts, which were reprogrammed to an "inflammatory/transitional" cell state in a PGF2α /FPr-dependent manner. Collectively, the findings provide evidence for a role for PGF2α signaling in IPF, mechanistically identify a susceptible fibroblast subpopulation, and establish a benchmark effect size for disruption of this pathway in mitigating fibrotic lung remodeling.

Emerging opportunities to treat idiopathic pulmonary fibrosis: Design, discovery, and optimizations of small-molecule drugs targeting fibrogenic pathways

Idiopathic pulmonary fibrosis (IPF) is the most common fibrotic form of idiopathic diffuse lung disease. Due to limited treatment options, IPF patients suffer from poor survival. About ten years ago, Pirfenidone (Shionogi, 2008; InterMune, 2011) and Nintedanib (Boehringer Ingelheim, 2014) were approved, greatly changing the direction of IPF drug design. However, limited efficacy and side effects indicate that neither can reverse the process of IPF. With insights into the occurrence of IPF, novel targets and agents have been proposed, which have fundamentally changed the treatment of IPF. With the next-generation agents, targeting pro-fibrotic pathways in the epithelial-injury model offers a promising approach. Besides, several next-generation IPF drugs have entered phase II/III clinical trials with encouraging results. Due to the rising IPF treatment requirements, there is an urgent need to completely summarize the mechanisms, targets, problems, and drug design strategies over the past ten years. In this review, we summarize known mechanisms, target types, drug design, and novel technologies of IPF drug discovery, aiming to provide insights into the future development and clinical application of next-generation IPF drugs.

Organic synthesis of 1,2-dipalmitoyl-rac-glycero-3-phosphatidylethanolamine and its effect on the induction of apoptosis in normal human lung fibroblasts

BACKGROUND /OBJECTIVE

The phospholipid 1,2-dipalmitoyl-rac-glycero-3-phosphatidylethanolamine (PE) comprises two fatty acid chains: glycerol, phosphate, and ethanolamine. PE participates in critical cellular processes such as apoptosis and autophagy, which places it as a target for designing new therapeutic alternatives in diseases such as pulmonary fibrosis. Therefore, this study aimed obtain PE through a six-step organic synthesis pathway and determine its biological effect on apoptosis induction in normal human lung fibroblasts (NHLF).

METHODOLOGY

The first step of the organic synthesis route began with protected glycerol that was benzylated at sn-3; later, it was deprotected to react with palmitic acid at sn-1, sn-2. To remove the benzyl group, hydrogenation was performed with palladium on carbon (Pd/C); subsequently, the molecule was phosphorylated in sn-3 with phosphorus oxychloride and triethylamine, and the intermediate was hydrolyzed in an acid medium to obtain the final compound. After PE synthesis, apoptosis assessment was performed: apoptosis was induced using exposure to annexin V-FITC/propidium iodide-ECD (PI) and quantified using flow cytometry. The experiments were performed in three NHLF cell lines with different concentrations of PE 10, 100 and 1000 µg/mL for 24 and 48 h.

RESULTS

The PE obtained by organic synthesis presented a melting point of 190-192 °C, a purity of 95%, and a global yield of 8%. The evaluation of apoptosis with flow cytometry showed that at 24 h, exposure to PE 10, 100, and 1000 µg/mL induces early apoptosis in 19.42%- 25.54%, while late apoptosis was only significant P < 0.05 in cells challenged with 100 µg/mL PE. At 48 h, NHLF exposed to PE 10, 100, and 1000 µg/mL showed decreasing early apoptosis: 28.69-32.16%, 12.59-18.84%, and 10.91-12.61%, respectively. The rest of the NHLF exposed to PE showed late apoptosis: 12.03-16-42%, 11.04-15.94%, and 49.23-51.28%. Statistical analysis showed a significance P < 0.05 compared to the control.

CONCLUSION

The organic synthesis route of PE allows obtaining rac-1,2-O-Dipalmitoyl-glycero-3-phosphoethanolamine (1), which showed an apoptotic effect on NHLF.

Disruption of Prostaglandin F2α Receptor Signaling Attenuates Fibrotic Remodeling and Alters Fibroblast Population Dynamics in A Preclinical Murine Model of Idiopathic Pulmonary Fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is a chronic parenchymal lung disease characterized by repetitive alveolar cell injury, myofibroblast proliferation, and excessive extracellular matrix deposition for which unmet need persists for effective therapeutics. The bioactive eicosanoid, prostaglandin F2α, and its cognate receptor FPr (Ptfgr) are implicated as a TGFβ1 independent signaling hub for IPF. To assess this, we leveraged our published murine PF model (IER - SftpcI73T) expressing a disease-associated missense mutation in the surfactant protein C (Sftpc) gene. Tamoxifen treated IER-SftpcI73T mice develop an early multiphasic alveolitis and transition to spontaneous fibrotic remodeling by 28 days. IER-SftpcI73T mice crossed to a Ptgfr null (FPr-/-) line showed attenuated weight loss and gene dosage dependent rescue of mortality compared to FPr+/+ cohorts. IER-SftpcI73T/FPr-/- mice also showed reductions in multiple fibrotic endpoints for which administration of nintedanib was not additive. Single cell RNA sequencing, pseudotime analysis, and in vitro assays demonstrated Ptgfr expression predominantly within adventitial fibroblasts which were reprogrammed to an "inflammatory/transitional" cell state in a PGF2α/FPr dependent manner. Collectively, the findings provide evidence for a role for PGF2α signaling in IPF, mechanistically identify a susceptible fibroblast subpopulation, and establish a benchmark effect size for disruption of this pathway in mitigating fibrotic lung remodeling.