Emerging therapies for idiopathic pulmonary fibrosis, a progressive age-related disease

Dupuytren's disease: a localised and accessible human fibrotic disorder

We review the biology of Dupuytren's disease (DD), a common localised fibrotic disorder of the hand. The disease develops through a complex interplay of genetic and environmental factors, and epigenetic signalling. The early-stage disease nodules comprise a complex milieu of stromal and immune cells which interact to promote disease development. Recently, inhibition of tumour necrosis factor (TNF) locally resulted in softening and a decrease in nodule size, potentially controlling disease progression. Unlike fibrotic disorders of the visceral organs, the easy access to tissue in DD patients enables dissection of the cellular landscape and molecular signalling pathways. In addition, the study of DD may have wider benefits in enhancing our understanding of less-accessible fibrotic tissues.

Deciphering the role of lipoproteins and lipid metabolic alterations in ageing and ageing-associated renal fibrosis

Fibrosis is the ultimate pathological feature of many chronic diseases, and ageing a major risk factor for fibrotic diseases. Current therapies are limited to those that reduce the rate of functional decline in patients with mild to moderate disease, but few interventions are available to specifically target the pathogenesis of fibrosis. In this context, new treatments that can significantly improve survival time and quality of life for these patients are urgently needed. In this review, we outline both the synthesis and metabolism of lipids and lipoproteins associated with ageing-associated renal fibrosis and the prominent contribution of lipids and lipidomics in the discovery of biomarkers that can be used for the prevention, diagnosis, and treatment of renal ageing and fibrosis. Next, we describe the effect of dyslipidaemia on ageing-related renal fibrosis and the pathophysiological changes in the kidney caused by dyslipidaemia. We then summarize the enzymes, transporters, transcription factors, and RNAs that contribute to dysregulated lipid metabolism in renal fibrosis and discuss their role in renal fibrosis in detail. We conclude by discussing the progress in research on small molecule therapeutic agents that prevent and treat ageing and ageing-associated renal fibrosis by modulating lipid metabolism. A growing number of studies suggest that restoring aberrant lipid metabolism may be a novel and promising therapeutic strategy to combat ageing and ageing-associated renal fibrosis.

Targeting galectin-driven regulatory circuits in cancer and fibrosis

Galectins are a family of endogenous glycan-binding proteins that have crucial roles in a broad range of physiological and pathological processes. As a group, these proteins use both extracellular and intracellular mechanisms as well as glycan-dependent and independent pathways to reprogramme the fate and function of numerous cell types. Given their multifunctional roles in both tissue fibrosis and cancer, galectins have been identified as potential therapeutic targets for these disorders. Here, we focus on the therapeutic relevance of galectins, particularly galectin 1 (GAL1), GAL3 and GAL9 to tumour progression and fibrotic diseases. We consider an array of galectin-targeted strategies, including small-molecule carbohydrate inhibitors, natural polysaccharides and their derivatives, peptides, peptidomimetics and biological agents (notably, neutralizing monoclonal antibodies and truncated galectins) and discuss their mechanisms of action, selectivity and therapeutic potential in preclinical models of fibrosis and cancer. We also review the results of clinical trials that aim to evaluate the efficacy of galectin inhibitors in patients with idiopathic pulmonary fibrosis, nonalcoholic steatohepatitis and cancer. The rapid pace of glycobiology research, combined with the acute need for drugs to alleviate fibrotic inflammation and overcome resistance to anticancer therapies, will accelerate the translation of anti-galectin therapeutics into clinical practice.

Small-molecule-mediated OGG1 inhibition attenuates pulmonary inflammation and lung fibrosis in a murine lung fibrosis model

Interstitial lung diseases such as idiopathic pulmonary fibrosis (IPF) are caused by persistent micro-injuries to alveolar epithelial tissues accompanied by aberrant repair processes. IPF is currently treated with pirfenidone and nintedanib, compounds which slow the rate of disease progression but fail to target underlying pathophysiological mechanisms. The DNA repair protein 8-oxoguanine DNA glycosylase-1 (OGG1) has significant roles in the modulation of inflammation and metabolic syndromes. Currently, no pharmaceutical solutions targeting OGG1 have been utilized in the treatment of IPF. In this study we show Ogg1-targeting siRNA mitigates bleomycin-induced pulmonary fibrosis in male mice, highlighting OGG1 as a tractable target in lung fibrosis. The small molecule OGG1 inhibitor, TH5487, decreases myofibroblast transition and associated pro-fibrotic gene expressions in fibroblast cells. In addition, TH5487 decreases levels of pro-inflammatory mediators, inflammatory cell infiltration, and lung remodeling in a murine model of bleomycin-induced pulmonary fibrosis conducted in male C57BL6/J mice. OGG1 and SMAD7 interact to induce fibroblast proliferation and differentiation and display roles in fibrotic murine and IPF patient lung tissue. Taken together, these data suggest that TH5487 is a potentially clinically relevant treatment for IPF but further study in human trials is required.

Integrating Network Pharmacology and Experimental Validation to Explore the Pharmacological Mechanism of Astragaloside IV in Treating Bleomycin-Induced Pulmonary Fibrosis

Purpose

Our study aims to reveal the pharmacological mechanism of Astragaloside IV in the treatment of pulmonary fibrosis(PF) through network pharmacology and experimental validation.

Methods

We first determined the in vivo anti-pulmonary fibrosis effect of Astragaloside IV by HE, MASSON staining, and lung coefficients, then used network pharmacology to predict the signaling pathways and molecularly docked key pathway proteins, and finally validated the results by in vivo and in vitro experiments.

Results

In in vivo experiments, we found that Astragaloside IV improved body weight (P < 0.05), increased lung coefficients (P < 0.05), and reduced lung inflammation and collagen deposition in mice with pulmonary fibrosis. The network pharmacology results showed that Astragaloside IV had 104 cross-targets with idiopathic pulmonary fibrosis, and the results of KEGG enrichment analysis indicated that cellular senescence could be an important pathway for Astragaloside IV in the treatment of pulmonary fibrosis. Astragaloside IV also bound well to senescence-associated proteins, according to molecular docking results. The results of both in vivo and in vitro experiments showed that Astragaloside IV significantly inhibited senescence protein markers such as P53, P21, and P16 and delayed cellular senescence (P < 0.05). In in vivo experiments, we also found that Astragaloside IV reduced the production of SASPs (P < 0.05), and in in vitro experiments, Astragaloside IV also reduced the production of ROS. In addition, by detecting epithelial-mesenchymal transition(EMT)-related marker protein expression, we also found that Astragaloside IV significantly inhibited the development of EMT in both in vivo and in vitro experiments (P < 0.05).

Conclusion

Our research found that Astragaloside IV could alleviate bleomycin-induced PF by preventing cellular senescence and EMT.

TRIB3 Mediates Fibroblast Activation and Fibrosis though Interaction with ATF4 in IPF

Idiopathic pulmonary fibrosis (IPF) is a fatal interstitial lung disease characterized by fibroblast activation, excessive deposition of extracellular matrix, and progressive scarring; the pathogenesis remains elusive. The present study explored the role of Tribbles pseudokinase 3 (TRIB3), a well-known stress and metabolic sensor, in IPF. TRIB3 is down-regulated in the lungs of IPF patients in comparison to control subjects. Deficiency of TRIB3 markedly inhibited A549 epithelial cells' proliferation and migration, significantly reducing wound healing. Conversely, overexpression of TRIB3 promoted A549 cell proliferation and transmigration while it inhibited its apoptosis. Meanwhile, overexpressed TRIB3 inhibited fibroblast activation and decreased ECM synthesis and deposition in MRC5 cells. TRIB3 attenuated pulmonary fibrosis by negative regulation of ATF4, while TRIB3 expression markedly inhibited ATF4 promoter-driven transcription activity and down-regulated ATF4 expression. A co-culture system showed that TRIB3 is important to maintain the normal epithelial-mesenchymal crosstalk and regulate fibroblast activation. Taken together, our data suggested that an axis of TRIB3-ATF4 is a key mediator in IPF which might be a potential target for fibroproliferative lung disease treatment.

Analysis of the safety and efficacy of different plasma concentrations of pirfenidone in patients with idiopathic pulmonary fibrosis

The high incidence and mortality of idiopathic pulmonary fibrosis (IPF) have led to the widespread use of antifibrotic drugs such as pirfenidone; however, the associated adverse reactions greatly vary among individuals and the dose is not fixed. To date, no reliable blood concentration range of pirfenidone is available to monitor adverse reactions and clinical efficacy. This real study assessed the efficacy and safety of different plasma concentrations of pirfenidone in patients with IPF. The study included 99 patients with IPF orally treated with pirfenidone capsules for at least 52 weeks. Ultra-performance liquid chromatography–mass spectrometry was used to analyze drug plasma concentrations. The annual rate of forced vital capacity (FVC) decline, assessed at week 52, was set as the primary end point. Secondary end points were the change from the baseline in the 6-min walk distance (6 MWD) and the time to the first acute exacerbation of IPF, both of which evaluated over 52 weeks. In the total population, the annual FVC decline in the high-concentration group was −90.0 ml per year versus −260.0 ml per year in the low-concentration group, for a between-group difference of 190.3 ml per year. The proportion of patients treated with high plasma concentrations of pirfenidone who showed an absolute decline of ≥10% in FVC% predicted, with a 6 MWD reduction of ≥50 m, or died, was lower than that of patients treated with low plasma concentrations of pirfenidone. High concentrations of pirfenidone reduced the risk of acute exacerbation in patients with IPF. Considerable differences were not observed for the total St. George’s Respiratory Questionnaire score or the rates of death between the high- and low-concentration groups. Mild to moderate adverse events, mainly involving the gastrointestinal system and the skin, were more common in the high-concentration group than in the low-concentration group but did not lead to termination of treatment in most cases. Our results suggest that treatment of IPF with high blood concentration of pirfenidone is both safe and effective. In the case of tolerable adverse reactions, patients with IPF may benefit from high concentrations of pirfenidone.

Senescent AECⅡ and the implication for idiopathic pulmonary fibrosis treatment

Idiopathic pulmonary fibrosis (IPF) is a chronic and lethal lung disease with limited treatment options. The onset of IPF increases with age, indicating that aging is a major risk factor for IPF. Among the hallmarks of aging, cellular senescence is the primordial driver and primary etiological factor for tissue and organ aging, and an independent risk factor for the progression of IPF. In this review, we focus on the senescence of alveolar type II epithelial cells (AECIIs) and systematically summarize abnormal changes in signal pathways and biological process and implications of senescent AECIIs during IPF progression. Meanwhile, we objectively analyze current medications targeting the elimination of senescent cells or restoration of vitality such as senolytics, senomorphics, autophagy regulators, and stem cell therapy. Finally, we dialectically discuss the feasibility and limitation of targeting senescent AECIIs for IPF treatment. We hope that the understanding will provide new insights to the development of senescent AECII-based approaches for the prevention and mitigation of IPF.

Managing Apoptosis in Lung Diseases using Nano-assisted Drug Delivery System

Several factors exist that limit the efficacy of lung cancer treatment. These may be tumor-specific delivery of therapeutics, airway geometry, humidity, clearance mechanisms, presence of lung diseases, and therapy against tumor cell resistance. Advancements in drug delivery using nanotechnology based multifunctional nanocarriers, have emerged as a viable method for treating lung cancer with more efficacy and fewer adverse effects. This review does a thorough and critical examination of effective nano-enabled approaches for lung cancer treatment, such as nano-assisted drug delivery systems. In addition, to therapeutic effectiveness, researchers have been working to determine several strategies to produce nanotherapeutics by adjusting the size, drug loading, transport, and retention. Personalized lung tumor therapies using sophisticated nano modalities have the potential to provide great therapeutic advantages based on individual unique genetic markers and disease profiles. Overall, this review provides comprehensive information on newer nanotechnological prospects for improving the management of apoptosis in lung cancer.

Stem cell-based therapy for pulmonary fibrosis

Pulmonary fibrosis (PF) is a chronic and relentlessly progressive interstitial lung disease in which the accumulation of fibroblasts and extracellular matrix (ECM) induces the destruction of normal alveolar structures, ultimately leading to respiratory failure. Patients with advanced PF are unable to perform physical labor and often have concomitant cough and dyspnea, which markedly impair their quality of life. However, there is a paucity of available pharmacological therapies, and to date, lung transplantation remains the only possible treatment for patients suffering from end-stage PF; moreover, the complexity of transplantation surgery and the paucity of donors greatly restrict the application of this treatment. Therefore, there is a pressing need for alternative therapeutic strategies for this complex disease. Due to their capacity for pluripotency and paracrine actions, stem cells are promising therapeutic agents for the treatment of interstitial lung disease, and an extensive body of literature supports the therapeutic efficacy of stem cells in lung fibrosis. Although stem cell transplantation may play an important role in the treatment of PF, some key issues, such as safety and therapeutic efficacy, remain to be resolved. In this review, we summarize recent preclinical and clinical studies on the stem cell-mediated regeneration of fibrotic lungs and present an analysis of concerning issues related to stem cell therapy to guide therapeutic development for this complex disease.

Regeneration or Repair? The Role of Alveolar Epithelial Cells in the Pathogenesis of Idiopathic Pulmonary Fibrosis (IPF)

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive interstitial lung disease (ILD) with unknown etiology in which gradual fibrotic scarring of the lungs leads to usual interstitial pneumonia (UIP) and, ultimately, to death. IPF affects three million people worldwide, and the only currently available treatments include the antifibrotic drugs nintedanib and pirfenidone, which effectively reduce fibrosis progression are, unfortunately, not effective in curing the disease. In recent years, the paradigm of IPF pathogenesis has shifted from a fibroblast-driven disease to an epithelium-driven disease, wherein, upon recurrent microinjuries, dysfunctional alveolar type II epithelial cells (ATII) are not only unable to sustain physiological lung regeneration but also promote aberrant epithelial–mesenchymal crosstalk. This creates a drift towards fibrosis rather than regeneration. In the context of this review article, we discuss the most relevant mechanisms involved in IPF pathogenesis with a specific focus on the role of dysfunctional ATII cells in promoting disease progression. In particular, we summarize the main causes of ATII cell dysfunction, such as aging, environmental factors, and genetic determinants. Next, we describe the known mechanisms of physiological lung regeneration by drawing a parallel between embryonic lung development and the known pathways involved in ATII-driven alveolar re-epithelization after injury. Finally, we review the most relevant interventional clinical trials performed in the last 20 years with the aim of underlining the urgency of developing new therapies against IPF that are not only aimed at reducing disease progression by hampering ECM deposition but also boost the physiological processes of ATII-driven alveolar regeneration.

Matrix Metalloproteinases and Their Inhibitors in Pulmonary Fibrosis: EMMPRIN/CD147 Comes into Play

Pulmonary fibrosis (PF) is characterized by aberrant extracellular matrix (ECM) deposition, activation of fibroblasts to myofibroblasts and parenchymal disorganization, which have an impact on the biomechanical traits of the lung. In this context, the balance between matrix metalloproteinases (MMPs) and their tissue inhibitors of metalloproteinases (TIMPs) is lost. Interestingly, several MMPs are overexpressed during PF and exhibit a clear profibrotic role (MMP-2, -3, -8, -11, -12 and -28), but a few are antifibrotic (MMP-19), have both profibrotic and antifibrotic capacity (MMP7), or execute an unclear (MMP-1, -9, -10, -13, -14) or unknown function. TIMPs are also overexpressed in PF; hence, the modulation and function of MMPs and TIMP are more complex than expected. EMMPRIN/CD147 (also known as basigin) is a transmembrane glycoprotein from the immunoglobulin superfamily (IgSF) that was first described to induce MMP activity in fibroblasts. It also interacts with other molecules to execute non-related MMP aactions well-described in cancer progression, migration, and invasion. Emerging evidence strongly suggests that CD147 plays a key role in PF not only by MMP induction but also by stimulating fibroblast myofibroblast transition. In this review, we study the structure and function of MMPs, TIMPs and CD147 in PF and their complex crosstalk between them.

Metabolic and Epigenetic Regulation of SMAD7 by Stanniocalcin-1 (STC1) Ameliorates Lung Fibrosis

As shown in our previous studies, the intratracheal-administration of stanniocalcin-1 (STC1) ameliorates pulmonary fibrosis by reducing oxidative and endoplasmic reticulum stress through the uncoupling of respiration in a bleomycin (BLM)-treated mouse model. However, the overall effect of STC1 on metabolism was not examined. Therefore, we first conducted a comprehensive metabolomics analysis to screen the overall metabolic changes induced by STC1 in an alveolar epithelial cell line using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS). The results were subsequently validated in multiple alveolar epithelial and fibroblast cell lines by performing precise analyses of each substance. STC1 stimulated glycolysis, acetyl-CoA synthesis, and the methionine and cysteine-glutathione pathways, which are closely related to the uncoupling of respiration, modulation of epigenetics and reduction in oxidative stress. These results are consistent with our previous study. Subsequently, we focused on the inhibitory factor SMAD7, which exerts an antifibrotic effect and is susceptible to epigenetic regulation. STC1 upregulates SMAD7 in an uncoupling protein 2-dependent manner, induces demethylation of the SMAD7 promoter region and acetylation of the SMAD7 protein in human alveolar epithelial and fibroblast cell lines and a BLM-treated mouse model, and subsequently attenuates fibrosis. The antifibrotic effects of STC1 may partially depend on the regulation of SMAD7. In the evaluation using lung tissue from idiopathic pulmonary fibrosis patients, SMAD7 expression and acetylation were high in the alveolar structure-preserving region and low in the fibrotic region. The intratracheal-administration of STC1 may prevent the development of pulmonary fibrosis by regulating the metabolism-mediated epigenetic modification of SMAD7 in patients.

Ongoing Clinical Trials in Aging-Related Tissue Fibrosis and New Findings Related to AhR Pathways

Fibrosis is a pathological manifestation of wound healing that replaces dead/damaged tissue with collagen-rich scar tissue to maintain homeostasis, and complications from fibrosis contribute to nearly half of all deaths in the industrialized world. Ageing is closely associated with a progressive decline in organ function, and the prevalence of tissue fibrosis dramatically increases with age. Despite the heavy clinical and economic burden of organ fibrosis as the population ages, to date, there is a paucity of therapeutic strategies that are specifically designed to slow fibrosis. Aryl hydrocarbon receptor (AhR) is an environment-sensing transcription factor that exacerbates aging phenotypes in different tissues that has been brought back into the spotlight again with economic development since AhR could interact with persistent organic pollutants derived from incomplete waste combustion. In addition, gut microbiota dysbiosis plays a pivotal role in the pathogenesis of numerous diseases, and microbiota-associated tryptophan metabolites are dedicated contributors to fibrogenesis by acting as AhR ligands. Therefore, a better understanding of the effects of tryptophan metabolites on fibrosis modulation through AhR may facilitate the exploitation of new therapeutic avenues for patients with organ fibrosis. In this review, we primarily focus on how tryptophan-derived metabolites are involved in renal fibrosis, idiopathic pulmonary fibrosis, hepatic fibrosis and cardiac fibrosis. Moreover, a series of ongoing clinical trials are highlighted.

COX-2/sEH Dual Inhibitor PTUPB Attenuates Epithelial-Mesenchymal Transformation of Alveolar Epithelial Cells via Nrf2-Mediated Inhibition of TGF-β1/Smad Signaling

Background

Arachidonic acid (ARA) metabolites are involved in the pathogenesis of epithelial-mesenchymal transformation (EMT). However, the role of ARA metabolism in the progression of EMT during pulmonary fibrosis (PF) has not been fully elucidated. The purpose of this study was to investigate the role of cytochrome P450 oxidase (CYP)/soluble epoxide hydrolase (sEH) and cyclooxygenase-2 (COX-2) metabolic disorders of ARA in EMT during PF.

Methods

A signal intratracheal injection of bleomycin (BLM) was given to induce PF in C57BL/6 J mice. A COX-2/sEH dual inhibitor PTUPB was used to establish the function of CYPs/COX-2 dysregulation to EMT in PF mice. In vitro experiments, murine alveolar epithelial cells (MLE12) and human alveolar epithelial cells (A549) were used to explore the roles and mechanisms of PTUPB on transforming growth factor (TGF)-β1-induced EMT.

Results

PTUPB treatment reversed the increase of mesenchymal marker molecule α-smooth muscle actin (α-SMA) and the loss of epithelial marker molecule E-cadherin in lung tissue of PF mice. In vitro, COX-2 and sEH protein levels were increased in TGF-β1-treated alveolar epithelial cells (AECs). PTUPB decreased the expression of α-SMA and restored the expression of E-cadherin in TGF-β1-treated AECs, accompanied by reduced migration and collagen synthesis. Moreover, PTUPB attenuated TGF-β1-Smad2/3 pathway activation in AECs via Nrf2 antioxidant cascade.

Conclusion

PTUPB inhibits EMT in AECs via Nrf2-mediated inhibition of the TGF-β1-Smad2/3 pathway, which holds great promise for the clinical treatment of PF.

Fibroblasts From Idiopathic Pulmonary Fibrosis Induce Apoptosis and Reduce the Migration Capacity of T Lymphocytes

Idiopathic pulmonary fibrosis (IPF) is a progressive and irreversible lung disease of unknown etiology. Myofibroblasts are organized in peculiar subepithelial fibroblasts foci (FF), where they abnormally persist and exclude lymphocytes by unclear mechanisms. FF are the source of an excessive extracellular matrix, which results in progressive stiffening and destruction of the lung architecture. We hypothesized that the absence of T cells inside the FF could be related, at least partially, to an inefficient function of lymphocytes induced by IPF fibroblasts. Here, we evaluated the effect of a supernatant from IPF fibroblasts on T-cell apoptosis and migration capacity. Data showed that IPF fibroblasts secrete pro-apoptotic molecules (both from extrinsic and intrinsic pathways), generating a microenvironment that induces apoptosis of T cells at 3 h of culture, despite a weak anti-apoptotic profile exhibited by these T cells. At 24 h of culture, the supernatants from both IPF and control fibroblasts provoked T-cell death. However, at this time of culture, IPF fibroblasts caused a marked decrease in T-cell migration; in contrast, control lung fibroblasts induced an increase of T-cell migration. The reduction of T-cell migratory capacity provoked by IPF fibroblasts was associated with a negative regulation of RHOA and ROCK, two essential GTPases for migration, and was independent of the expression of chemokine receptors. In conclusion, our findings demonstrate that IPF fibroblasts/myofibroblasts induce apoptosis and affect T-cell migration, revealing a mechanism involved in the virtual absence of T lymphocytes inside the FF.

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.

ACPA Alleviates Bleomycin-Induced Pulmonary Fibrosis by Inhibiting TGF-β-Smad2/3 Signaling-Mediated Lung Fibroblast Activation

Pulmonary fibrosis is a group of life-threatening diseases with limited therapeutic options. The involvement of cannabinoid type 1 receptors (CB₁R) has been indicated in fibrotic diseases, but whether or not the activation of CB₁R can be a benefit for fibrosis treatment is controversial. In this study, we investigated the effects of arachidonoylcyclopropylamide (ACPA), as a selective CB₁R agonist, on bleomycin (BLM)-induced pulmonary fibrosis. We showed that ACPA treatment significantly improved the survival rate of BLM-treated mice, alleviated BLM-induced pulmonary fibrosis, and inhibited the expressions of extracellular matrix (ECM) markers, such as collagen, fibronectin, and α-SMA. The enhanced expressions of ECM markers in transforming growth factor-beta (TGF-β)-challenged primary lung fibroblasts isolated from mouse lung tissues were inhibited by ACPA treatment in a dose-dependent manner, and the fibroblast migration triggered by TGF-β was dose-dependently diminished after ACPA administration. Moreover, the increased mRNA levels of CB₁R were observed in both lung fibroblasts of BLM-induced fibrotic mice in vivo and TGF-β-challenged primary lung fibroblasts in vitro. CB₁R-specific agonist ACPA significantly diminished the activation of TGF-β–Smad2/3 signaling, i.e., the levels of p-Smad2 and p-Smad3, and decreased the expressions of downstream effector proteins including slug and snail, which regulate ECM production, in TGF-β-challenged primary lung fibroblasts. Collectively, these findings demonstrated that CB₁R-specific agonist ACPA exhibited antifibrotic efficacy in both in vitro and in vivo models of pulmonary fibrosis, revealing a novel anti-fibrosis approach to fibroblast-selective inhibition of TGF-β-Smad2/3 signaling by targeting CB₁R.

Inhaled mRNA Nanoformulation with Biogenic Ribosomal Protein Reverses Established Pulmonary Fibrosis in a Bleomycin-Induced Murine Model

Idiopathic pulmonary fibrosis (IPF), a lethal respiratory disease with few treatment options, occurs due to repetitive microinjuries to alveolar epithelial cells (AECs) and progresses with an overwhelming deposition of extracellular matrix (ECM), ultimately resulting in fibrotic scars and destroyed the alveolar architecture. Here, an inhaled ribosomal protein-based mRNA nanoformulation is reported for clearing the intrapulmonary ECM and re-epithelializing the disrupted alveolar epithelium, thereby reversing established fibrotic foci in IPF. The nanoformulation is sequentially assembled by a ribosomal protein-condensed mRNA core, a bifunctional peptide-modified corona and keratinocyte growth factor (KGF) with a PEGylated shielding shell. When inhaled via a nebulizer, the nanoformulations carried by microdrops are deposited in the alveoli, and penetrate into fibrotic foci, where the outer KGFs are detached after matrix metalloproteinase 2 (MMP2) triggering. The RGD motif-grafted cores then expose and specifically target the integrin-elevated cells for the intracellular delivery of mRNA. Notably, repeated inhalation of the nanoformulations accelerates the clearance of locoregional collagen by boosting the intralesional expression of MMP13 and alveolar re-epithelialization mediated by KGFs, which synergistically ameliorates the lung function of a bleomycin-induced murine model. Therefore, this work provides an alternative mRNA-inhalation delivery strategy, which shows great potential for the treatment of IPF.

A vasculature niche orchestrates stromal cell phenotype through PDGF signaling: Importance in human fibrotic disease

Tissue fibrotic diseases, for example of the liver and lung, represent a huge unmet medical need. In this study, using single-cell RNA sequencing, cytometry by time of flight (CyTOF), tissue imaging, and functional assays, we identify a complex vascular niche in Dupuytren’s disease (DD), a common localized fibrotic condition of the palm, where early-disease-stage tissue can be accessed readily. We uncover a population of myofibroblast precursors within the pericyte compartment and demonstrate that the endothelium instructs the differentiation of functionally distinct stromal cells, thereby orchestrating discrete microenvironments in the fibrotic milieu. Together, these findings provide a basis for the concept of targeting blood vessel signaling to control the progression of human fibrosis.

Fibrosis is characterized by excessive matrix protein accumulation and contributes to significant morbidity and mortality in the Western world. The relative lack of effective antifibrotic therapeutics for the majority of these conditions reflects the difficulty in identifying targets for human fibrosis. Animal models fail to recapitulate all of the facets of human disease, and the limited clinical samples from patients with fibrosis of visceral organs are usually of late-stage disease [J. Nanchahal, B. Hinz, Proc. Natl. Acad. Sci. U.S.A. 113, 7291–7293 (2016)]. Here, we use Dupuytren’s disease (DD), a localized fibrotic condition of the hand, as a model to profile the vasculature niche of human fibrosis at single-cell resolution. Our spatially resolved molecular taxonomy of fibrotic blood vessels identifies distinct endothelial and pericyte populations and demonstrates a complex topological organization in the fibrotic microenvironment. In developing fibrosis, we show that the endothelium acts to promote immune regulatory fibroblast phenotype through platelet-derived growth factor (PDGF) signaling, thereby sustaining an immune cell–enriched perivascular niche. Moreover, we highlight pericytes as “housing” a putative myofibroblast precursor in DD. Overall, our results elucidate a tightly coupled vasculature niche in fibrosis that instructs the differentiation of functionally distinct stromal cells. These findings provide an important translational resource and highlight the therapeutic potential of targeting blood vessel signaling in human fibrosis.

Hsp90 in Human Diseases: Molecular Mechanisms to Therapeutic Approaches

The maturation of hemeprotein dictates that they incorporate heme and become active, but knowledge of this essential cellular process remains incomplete. Studies on chaperon Hsp90 has revealed that it drives functional heme maturation of inducible nitric oxide synthase (iNOS), soluble guanylate cyclase (sGC) hemoglobin (Hb) and myoglobin (Mb) along with other proteins including GAPDH, while globin heme maturations also need an active sGC. In all these cases, Hsp90 interacts with the heme-free or apo-protein and then drives the heme maturation by an ATP dependent process before dissociating from the heme-replete proteins, suggesting that it is a key player in such heme-insertion processes. As the studies on globin maturation also need an active sGC, it connects the globin maturation to the NO-sGC (Nitric oxide-sGC) signal pathway, thereby constituting a novel NO-sGC-Globin axis. Since many aggressive cancer cells make Hbβ/Mb to survive, the dependence of the globin maturation of cancer cells places the NO-sGC signal pathway in a new light for therapeutic intervention. Given the ATPase function of Hsp90 in heme-maturation of client hemeproteins, Hsp90 inhibitors often cause serious side effects and this can encourage the alternate use of sGC activators/stimulators in combination with specific Hsp90 inhibitors for better therapeutic intervention.

Biomechanical Force and Cellular Stiffness in Lung Fibrosis

Lung fibrosis is characterized by the continuous accumulation of extracellular matrix (ECM) proteins produced by apoptosis-resistant (myo)fibroblasts. Lung epithelial injury promotes the recruitment and activation of fibroblasts, which are necessary for tissue repair and restoration of homeostasis. However, under pathologic conditions, a vicious cycle generated by profibrotic growth factors/cytokines, multicellular interactions, and matrix-associated signaling propagates the wound repair response and promotes lung fibrosis characterized not only by increased quantities of ECM proteins but also by changes in the biomechanical properties of the matrix. Importantly, changes in the biochemical and biomechanical properties of the matrix itself can serve to perpetuate fibroblast activity and propagate fibrosis, even in the absence of the initial stimulus of injury. The development of novel experimental models and methods increasingly facilitates our ability to interrogate fibrotic processes at the cellular and molecular levels. The goal of this review is to discuss the impact of ECM conditions in the development of lung fibrosis and to introduce new approaches to more accurately model the in vivo fibrotic microenvironment. This article highlights the pathologic roles of ECM in terms of mechanical force and the cellular interactions while reviewing in vitro and ex vivo models of lung fibrosis. The improved understanding of the fundamental mechanisms that contribute to lung fibrosis holds promise for identification of new therapeutic targets and improved outcomes.

Fatty acid metabolism-related genes in bronchoalveolar lavage fluid unveil prognostic and immune infiltration in idiopathic pulmonary fibrosis

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive condition with an unfavorable prognosis. A recent study has demonstrated that IPF patients exhibit characteristic alterations in the fatty acid metabolism in their lungs, suggesting an association with IPF pathogenesis. Therefore, in this study, we have explored whether the gene signature associated with fatty acid metabolism could be used as a reliable biological marker for predicting the survival of IPF patients.

METHODS

Data on the fatty acid metabolism-related genes (FAMRGs) were extracted from databases like Kyoto Encyclopedia of Genes and Genomes (KEGG), Hallmark, and Reactome pathway. The GSE70866 dataset with information on IPF patients was retrieved from the Gene Expression Omnibus (GEO). Next, the consensus clustering method was used to identify novel molecular subgroups. Gene Set Enrichment Analysis (GSEA) was performed to understand the mechanisms involved. The Cell-type Identification by Estimating Relative Subsets of RNA Transcripts (CIBERSORT) algorithm was used to evaluate the level of immune cell infiltration in the identified subgroups based on gene expression signatures of immune cells. Finally, the Least Absolute Shrinkage and Selection Operator (LASSO) regression and multivariate Cox regression analysis were performed to develop a prognostic risk model.

RESULTS

The gene expression signature associated with fatty acid metabolism was used to create two subgroups with significantly different prognoses. GSEA reveals that immune-related pathways were significantly altered between the two subgroups, and the two subgroups had different metabolic characteristics. High infiltration of immune cells, mainly activated NK cells, monocytes, and activated mast cells, was observed in the subgroup with a poor prognosis. A risk model based on FAMRGs had an excellent ability to predict the prognosis of IPF. The nomogram constructed using the clinical features and the risk model could accurately predict the prognosis of IPF patients.

CONCLUSION

The fatty acid metabolism-related gene expression signature could be used as a potential biological marker for predicting clinical outcomes and the level of infiltration of immune cells. This could eventually enhance the accuracy of the treatment of IPF patients.

Inhibition of aberrant tissue remodelling by mesenchymal stromal cells singly coated with soft gels presenting defined chemomechanical cues

The precise understanding and control of microenvironmental cues could be used to optimize the efficacy of cell therapeutics. Here, we show that mesenchymal stromal cells (MSCs) singly coated with a soft conformal gel presenting defined chemomechanical cues promote matrix remodelling by secreting soluble interstitial collagenases in response to the presence of tumour necrosis factor alpha (TNF-α). In mice with fibrotic lung injury, treatment with the coated MSCs maintained normal collagen levels, fibre density and microelasticity in lung tissue, and the continuous presentation of recombinant TNF-α in the gel facilitated the reversal of aberrant tissue remodelling by the cells when inflammation subsided in the host. Gel coatings with predefined chemomechanical cues could be used to tailor cells with specific mechanisms of action for desired therapeutic outcomes.

Novel imidazo[1,2-a]pyridine derivatives as potent ATX allosteric inhibitors: Design, synthesis and promising in vivo anti-fibrotic efficacy in mice lung model

Aiming to develop novel allosteric autotaxin (ATX) inhibitors, hybrid strategy was utilized by assembling the benzyl carbamate fragment in PF-8380 onto the imidazo[1,2-a]pyridine skeleton of GLPG-1690. The piperazine moiety in GLPG-1690 was replaced with phenyl ring to enhance the π-π interactions with adjacent residues. In the light of FS-3 based ATX enzymatic assay, further structure-guided optimizations were implemented by exploring the substituents within the carbamate aromatic moiety and examining the effect of the 2-ethyl. Eventually, 13c bearing 1,3-benzodioxole and 2-hydroxyethyl piperazine group was identified as a powerful ATX inhibitor with an IC₅₀ value of 2.7 nM. Subsequently, 13c was forwarded into an in vivo bleomycin-induced mice lung fibrosis model. In histopathological and immunohistochemical assays, 13c could typically alleviate the severity of fibrosis tissues and effectively reduce the deposition of fibrotic biomarker α-SMA. At a dose of 60 mg/kg, 13c was observed equivalent or even better potency than GLPG-1690 with a significant inhibition of the in vivo ATX activity. Except for the fundamental H-bond and π-π interactions, an extra H-bond between the 1,3-benzodioxole (O atom) and Phe306 offered great rationale in constraining the binding conformation of 13c. Finally, binding free energy calculation was conducted to assist in the efficient identification of allosteric ATX inhibitors.

Roxithromycin attenuates bleomycin-induced pulmonary fibrosis by targeting senescent cells

Idiopathic pulmonary fibrosis (IPF) is an aging-associated disease with a poor prognosis. Emerging evidence has revealed that targeting senescent cells may be a potential treatment for IPF. In this study, we aimed to explore whether roxithromycin (RXM) can improve lung fibrosis by targeting senescent cells. First, we confirmed the ability of RXM to selectively kill senescent cells by inducing apoptosis and inhibiting the expression of senescence-associated secretory phenotype (SASP) factors, suggesting the potential role of RXM as a "senolytic" and "senomorphic" drug. Next, we observed that TGF-β- and senescent cell-induced lung fibroblast activation was inhibited by RXM treatment, which prompted us to further investigate its effect in vivo. In a mouse model of bleomycin (BLM)-induced pulmonary fibrosis, RXM was shown to attenuate lung injury, inflammation, and fibrosis. Furthermore, the senescent phenotype of lung tissues induced by BLM was significantly diminished after RXM administration, indicating the potential of RXM as an antifibrotic and antisenescent agent. Interestingly, NADPH oxidase 4 (NOX4), implicated in lung fibrosis and cell senescence, was shown to be inhibited by RXM treatments. The antifibroblast activation and antisenescent effects of RXM were abolished in NOX4 knockdown cells, demonstrating that RXM may ameliorate BLM-induced pulmonary fibrosis by targeting senescent cells mediated by the NOX4 pathway. Collectively, these data demonstrated that RXM may be a potential clinical agent for IPF and further supported the notion that targeting cellular senescence is a promising treatment for progressive age-related disease.

Role of Non-Coding RNAs in Post-Transcriptional Regulation of Lung Diseases

Non-coding RNAs (ncRNAs), notably microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), have recently gained increasing consideration because of their versatile role as key regulators of gene expression. They adopt diverse mechanisms to regulate transcription and translation, and thereby, the function of the protein, which is associated with several major biological processes. For example, proliferation, differentiation, apoptosis, and metabolic pathways demand fine-tuning for the precise development of a specific tissue or organ. The deregulation of ncRNA expression is concomitant with multiple diseases, including lung diseases. This review highlights recent advances in the post-transcriptional regulation of miRNAs and lncRNAs in lung diseases such as asthma, chronic obstructive pulmonary disease, cystic fibrosis, and idiopathic pulmonary fibrosis. Further, we also discuss the emerging role of ncRNAs as biomarkers as well as therapeutic targets for lung diseases. However, more investigations are required to explore miRNAs and lncRNAs interaction, and their function in the regulation of mRNA expression. Understanding these mechanisms might lead to early diagnosis and the development of novel therapeutics for lung diseases.

miR-26a-5p protects against drug-induced liver injury via targeting bid

BACKGROUNDS

miR-26a-5p is a short noncoding RNA that is abnormally expressed in drug-induced liver injury (DILI), but its pathophysiologic role in the mechanism of disease in DILI is still vague.

METHODS

The expression of miR-26a-5p, viability of hepatic stellate cells (HSCs) proliferation, and apoptosis were explored via real-time PCR, CCK-8 assay, Tunel fluorescence, and flow cytometry. The expression of Bid was detected via Western blot assays, real-time PCR, and immunofluorescence. The apoptosis-associated proteins were determined through Western blot. The interaction between miR-26a-5p and Bid was measured via Dual luciferase reporter assay.

RESULTS

miR-26a-5p expression was greatly decreased in HSCs and serum treated with azithromycin, simvastatin and diclofenac sodium, respectively. Hepatocyte viability was largely suppressed while hepatocyte apoptosis was markedly increased in DILI. Correspondingly, the apoptosis-associated proteins including Bid, caspase-8 and cytochrome C in HSCs were significantly upregulated when treated with either of these drugs. Moreover, miR-26a-5p interacted with Bid, and hepatocyte proliferation and apoptosis influenced by miR-26a-5p mimics were obviously reversed when co-treated with overexpressed Bid plasmids.

CONCLUSIONS

miR-26a-5p played a protective role against DILI via targeting Bid.

Di-Tyrosine Crosslinking and NOX4 Expression as Oxidative Pathological Markers in the Lungs of Patients with Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a noninflammatory progressive lung disease. Oxidative damage is a hallmark of IPF, but the sources and consequences of oxidant generation in the lungs are unclear. In this study, we addressed the link between the H₂O₂-generating enzyme NADPH oxidase 4 (NOX4) and di-tyrosine (DT), an oxidative post-translational modification in IPF lungs. We performed immunohistochemical staining for DT and NOX4 in pulmonary tissue from patients with IPF and controls using validated antibodies. In the healthy lung, DT showed little or no staining and NOX4 was mostly present in normal vascular endothelium. On the other hand, both markers were detected in several cell types in the IPF patients, including vascular smooth muscle cells and epithelium (bronchial cells and epithelial cells type II). The link between NOX4 and DT was addressed in human fibroblasts deficient for NOX4 activity (mutation in the CYBA gene). Induction of NOX4 by Transforming growth factor beta 1 (TGFβ1) in fibroblasts led to moderate DT staining after the addition of a heme-containing peroxidase in control cells but not in the fibroblasts deficient for NOX4 activity. Our data indicate that DT is a histological marker of IPF and that NOX4 can generate a sufficient amount of H₂O₂ for DT formation in vitro.

Deleterious Role of Th9 Cells in Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disease of unknown etiology. Immune disorders play an important role in IPF pathogenesis. Here, we show that Th9 cells differentiate and activate in the lung tissue of patients with IPF and bleomycin (BLM)-induced lung fibrosis mice. Moreover, we found that Th9 cells promote pulmonary fibrosis in two ways. On the one hand, Th9 cells promote fibroblast differentiation, activation, and collagen secretion by secreting IL-9. On the other hand, they promote differentiation of Th0 cells into Th2 cells by secreting IL-4. Th9 cells and Th2 cells can promote each other, accelerating the Th1/Th2 imbalance and eventually forming a positive feedback of pulmonary fibrosis. In addition, we found that neutralizing IL-9 in both preventive and therapeutic settings ameliorates bleomycin-induced pulmonary fibrosis. Furthermore, we identified several critical signaling pathways involved in the effect of neutralizing IL-9 on pulmonary fibrosis by proteomics study. From an immunological perspective, we elucidated the novel role and underlying mechanism of Th9 cells in pulmonary fibrosis. Our study suggested that Th9-based immunotherapy may be employed as a treatment strategy for IPF.

Ionizing irradiation-induced Fgr in senescent cells mediates fibrosis

The role of cellular senescence in radiation-induced pulmonary fibrosis (RIPF) and the underlying mechanisms are unknown. We isolated radiation-induced senescent tdTOMp16 positive mesenchymal stem cells, established their absence of cell division, then measured levels of irradiation-induced expression of biomarkers of senescence by RNA-seq analysis. We identified a Log2 6.17-fold upregulation of tyrosine kinase Fgr, which was a potent inducer of biomarkers of fibrosis in target cells in non-contact co-cultures. Inhibition of Fgr by shRNA knockdown did not block radiation-induced senescence in vitro; however, both shRNA knockdown, or addition of a specific small-molecule inhibitor of Fgr, TL02-59, abrogated senescent cell induction of profibrotic genes in transwell-separated target cells. Single-cell RNA-seq (scRNAseq) analysis of mouse lungs at day 150 after 20 Gy thoracic irradiation revealed upregulation of Fgr in senescent neutrophils, and macrophages before detection of lung fibrosis. Thus, upregulated Fgr in radiation-induced senescent cells mediates RIPF and is a potential therapeutic target for the prevention of this radiation late effect.

Bioinformatic analysis of differentially expressed genes and pathways in idiopathic pulmonary fibrosis

Background

Using bioinformatic methods to explore the differentially expressed genes (DEGs) of human idiopathic pulmonary fibrosis (IPF) and to elucidate the pathogenesis of IPF from the genetic level.

Methods

The GSE110147 gene expression profile was downloaded from the GEO database. The data of lung adenocarcinoma (LUAD) samples, lung squamous cell carcinoma (LUSC) samples and normal samples were downloaded from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) databases. DEGs between IPF patients and healthy donors were analyzed using the GEO2R tool. Use the "clusterprofiler" package in R software to perform gene ontology (GO) and KEGG pathway enrichment analysis, and then perform function annotation and protein-protein interaction (PPI) network construction in the STRING online tool. The Genome Browser tool of the university of california santa cruz (UCSC) online website was used to predict transcription factors (TFs) of genes. In the final, the results were analyzed synthetically.

Results

A total of 9,183 DEGs were identified, of which 4,545 genes were down-regulated, and 4638 were up-regulated. MMP1, SPP1, and BPIFB1 were the top three DEGs with the highest significant up-regulation. These DEGs played an important role in the occurrence of IPF through the MAPK (mitogen-activated protein kinase) signaling pathway. Furthermore, 50 DEGs were enriched in the expression of PD-L1 and the PD-1 checkpoint pathway in cancer, of which 11 genes were re-enriched in the pathway of non-small cell lung cancer. The expression of the 11 genes were extensively regulated by CTCFL, SP2 and ZNF341. Most of them were differentially expressed between lung cancers and normal lung tissues. The overall survival (OS) curve of LUAD were significantly stratified by AKT2, KRAS, PIK3R1, meanwhile the OS curve of LUAC was significantly stratified by MAPK3.

Conclusions

Bioinformatics analysis revealed that DEGs including MPP1 might be potential targets and biomarkers of IPF, and the MAPK signaling pathway is related to the occurrence and development of IPF. The development of IPF lung cancer complications may be related to the activation of genes enriched in PD-L1 expression and PD-1 checkpoint pathway, which provides clues to the pathogenesis of IPF combined with lung cancer.

ADEIP: an integrated platform of age-dependent expression and immune profiles across human tissues

Gene expression and immune status in human tissues are changed with aging. There is a need to develop a comprehensive platform to explore the dynamics of age-related gene expression and immune profiles across tissues in genome-wide studies. Here, we collected RNA-Seq datasets from GTEx project, containing 16 704 samples from 30 major tissues in six age groups ranging from 20 to 79 years old. Dynamic gene expression along with aging were depicted and gene set enrichment analysis was performed among those age groups. Genes from 34 known immune function categories and immune cell compositions were investigated and compared among different age groups. Finally, we integrated all the results and developed a platform named ADEIP (http://gb.whu.edu.cn/ADEIP or http://geneyun.net/ADEIP), integrating the age-dependent gene expression and immune profiles across tissues. To demonstrate the usage of ADEIP, we applied two datasets: severe acute respiratory syndrome coronavirus 2 and human mesenchymal stem cells-assoicated genes. We also included the expression and immune dynamics of these genes in the platform. Collectively, ADEIP is a powerful platform for studying age-related immune regulation in organogenesis and other infectious or genetic diseases.

Autophagy in major human diseases

Autophagy is a core molecular pathway for the preservation of cellular and organismal homeostasis. Pharmacological and genetic interventions impairing autophagy responses promote or aggravate disease in a plethora of experimental models. Consistently, mutations in autophagy-related processes cause severe human pathologies. Here, we review and discuss preclinical data linking autophagy dysfunction to the pathogenesis of major human disorders including cancer as well as cardiovascular, neurodegenerative, metabolic, pulmonary, renal, infectious, musculoskeletal, and ocular disorders.

Interpreting Immunoregulation in Lung Fibrosis: A New Branch of the Immune Model

Immunostimulation is recognized as an important contribution in lung fibrosis in some animal models and patient subsets. With this review, we illustrate an additional scenario covering the possible implication of immunoregulation during fibrogenesis. Available animal and human data indicate that pulmonary fibrosis also includes diverse and discrete immunoregulating populations comprising regulatory lymphocytes (T and B regs) and myeloid cells (immunosuppressive macrophages and myeloid-derived suppressive cells; MDSC). They are initially recruited to limit the establishment of deleterious inflammation but participate in the development of lung fibrosis by producing immunoregulatory mediators (mainly TGF-β1 and IL-10) that directly or indirectly stimulate fibroblasts and matrix protein deposition. The existence of this silent immunoregulatory environment sustains an alternative mechanism of fibrosis that explains why in some conditions neither pro-inflammatory cytokine deficiency nor steroid and immunosuppressive therapies limit lung fibrosis. Therefore, the persistent presence of immunoregulation is an important parameter to consider for refining therapeutical strategies in lung fibrotic disorders under non-immunostimulatory conditions.

Vitamin D suppresses bleomycin-induced pulmonary fibrosis by targeting the local renin-angiotensin system in the lung

Idiopathic pulmonary fibrosis (IPF) is a severe disorder leading to progressive and irreversible loss of pulmonary function. In this study we investigated the anti-fibrotic effect of vitamin D using a mouse model of IPF. Lung fibrosis was induced with bleomycin in vitamin D-sufficient and vitamin D-deficient C57BL/6 mice. We found that treatment with active vitamin D analog paricalcitol prevented mouse body weight loss and alleviated lung fibrosis, whereas vitamin D deficiency severely aggravated lung injury. At the molecular level, paricalcitol treatment suppressed the induction of fibrotic inducer TGF-β and extracellular matrix proteins α-SMA, collagen type I and fibronectin in the lung, whereas vitamin D deficiency exacerbated the induction of these proteins. Interestingly, bleomycin treatment activated the local renin–angiotensin system (RAS) in the lung, manifested by the induction of renin, angiotensinogen, angiotensin II and angiotensin receptor type 1 (AT1R). Paricalcitol treatment suppressed the induction of these RAS components, whereas vitamin D deficiency enhanced the activation of the lung RAS. We also showed that treatment of bleomycin-induced vitamin D-deficient mice with AT1R antagonist losartan relieved weight loss, substantially ameliorated lung fibrosis and markedly blocked TGF-β induction in the lung. Moreover, we demonstrated that in lung fibroblast cultures, TGF-β and angiotensin II synergistically induced TGF-β, AT1R, α-SMA, collagen type I and fibronectin, whereas 1,25-dihydroxyvitamin D markedly suppressed the induction of these fibrotic markers. Collectively, these observations strongly suggest that vitamin D mitigates lung fibrosis by blocking the activation of the lung RAS in this mouse model of IPF.

Long Noncoding RNA FENDRR Inhibits Lung Fibroblast Proliferation via a Reduction of β-Catenin

Idiopathic Pulmonary Fibrosis (IPF) is a chronic, progressive, and usually lethal lung disease and it has been widely accepted that fibroblast proliferation is one of the key characteristics of IPF. Long noncoding RNAs (lncRNAs) play vital roles in the pathogenesis of many diseases. In this study, we investigated the role of lncRNA FENDRR on fibroblast proliferation. Human lung fibroblasts stably overexpressing FENDRR showed a reduced cell proliferation compared to those expressing the control vector. On the other hand, FENDRR silencing increased fibroblast proliferation. FENDRR bound serine-arginine rich splicing factor 9 (SRSF9) and inhibited the phosphorylation of p70 ribosomal S6 kinase 1 (PS6K), a downstream protein of the mammalian target of rapamycin (mTOR) signaling. Silencing SRSF9 reduced fibroblast proliferation. FENDRR reduced β-catenin protein, but not mRNA levels. The reduction of β-catenin protein levels in lung fibroblasts by gene silencing or chemical inhibitor decreased fibroblast proliferation. Adenovirus-mediated FENDRR transfer to the lungs of mice reduced asbestos-induced fibrotic lesions and collagen deposition. RNA sequencing of lung tissues identified 7 cell proliferation-related genes that were up-regulated by asbestos but reversed by FENDRR. In conclusion, FENDRR inhibits fibroblast proliferation and functions as an anti-fibrotic lncRNA.

Dynamic Observation of Autophagy and Transcriptome Profiles in a Mouse Model of Bleomycin-Induced Pulmonary Fibrosis

Pulmonary fibrosis is a group of progressive, fibrotic, and fatal lung diseases, and the role of autophagy in pulmonary fibrosis is controversial. In the current research, we dynamically observed a bleomycin-induced pulmonary fibrosis mouse model after 3, 7, 14, 21, and 28 days and investigated the expression of autophagy markers. We found that autophagy markers were not significantly changed on the indicated days in the mouse lung tissue. Then, RNA-Seq was used to analyze the gene expression and associated functions and pathways in fibrotic lung tissue on different days post-bleomycin. In addition, short time series expression miner (STEM) analysis was performed to explore the temporal post-bleomycin gene expression. Through STEM, continually up- or downregulated profiles did not demonstrate the critical role of autophagy in the development of fibrosis. Furthermore, gene ontology (GO) annotations showed that continually upregulated profiles were mainly related to fibrosis synthesis, extracellular space, and inflammation, while enriched pathways were mainly related to the PI3K-Akt signaling pathway, ECM-receptor interactions, and focal adhesion signaling pathway. For continually downregulated profiles, GO annotations mainly involved sarcomere organization, muscle contraction, and muscle fiber development. The enriched KEGG signaling pathways were the cAMP signaling pathway, cGMP-PKG signaling pathway, calcium signaling pathway, and cardiac muscle contraction. Moreover, we analyzed autophagy-related genes' expression in specific cells from a publicly available database of three human and one animal study of pulmonary fibrosis using single-cell sequencing technology. All results consistently demonstrated no critical role of autophagy in the pathogenesis of pulmonary fibrosis. In summary, autophagy may not critically and consistently change during the development of pulmonary fibrosis at different stages post-bleomycin in a mouse model. These continually up- or downregulated profiles, including gene profiles, and the corresponding functions and pathways may provide mechanistic insights into IPF therapy.

Switching antifibrotics in patients with idiopathic pulmonary fibrosis: a multi-center retrospective cohort study

BACKGROUND

Currently, there are two antifibrotics used to treat idiopathic pulmonary fibrosis (IPF): pirfenidone and nintedanib. Antifibrotics slow disease progression by reducing the annual decline of forced vital capacity (FVC), which possibly improves outcomes in IPF patients. During treatment, patients occasionally switch antifibrotic treatments. However, prognostic implication of changing antifibrotics has not yet been evaluated.

METHODS

This multi-center retrospective cohort study examined 262 consecutive IPF patients who received antifibrotic therapy. Antifibrotic agents were switched in 37 patients (14.1%). The prognoses were compared between the patient cohort that switched antifibrotics (Switch-IPF) and those without (Non-Switch-IPF) using propensity-score matched analyses.

RESULTS

The median period between the initiation of antifibrotic therapy and the drug switch was 25.8 (12.7-35.3) months. The most common reasons for the switch were disease progression (n = 17) followed by gastrointestinal disorders (n = 12). Of the 37 patients that switched antifibrotics, only eight patients disrupted switched antifibrotics by their adverse reactions. The overall prognosis of the Switch-IPF cohort was significantly better than the Non-Switch-IPF cohort (median periods: 67.2 vs. 27.1 months, p < 0.0001). In propensity-score matched analyses that were adjusted to age, sex, FVC (%), history of acute exacerbation, and usage of long-term oxygen therapy, the Switch-IPF cohort had significantly longer survival times than the Non-Switch-IPF group (median 67.2 vs. 41.3 months, p = 0.0219). The second-line antifibrotic therapy showed similar survival probabilities than those in first-line antifibrotic therapy in multistate model analyses.

CONCLUSION

Switching antifibrotics is feasible and may improve prognosis in patients with IPF. A further prospective study will be required to confirm clinical implication of switching the antifibrotics.

Dissecting the Role of Mesenchymal Stem Cells in Idiopathic Pulmonary Fibrosis: Cause or Solution

Idiopathic pulmonary fibrosis (IPF) is one of the most aggressive forms of idiopathic interstitial pneumonias, characterized by chronic and progressive fibrosis subverting the lung's architecture, pulmonary functional decline, progressive respiratory failure, and high mortality (median survival 3 years after diagnosis). Among the mechanisms associated with disease onset and progression, it has been hypothesized that IPF lungs might be affected either by a regenerative deficit of the alveolar epithelium or by a dysregulation of repair mechanisms in response to alveolar and vascular damage. This latter might be related to the progressive dysfunction and exhaustion of the resident stem cells together with a process of cellular and tissue senescence. The role of endogenous mesenchymal stromal/stem cells (MSCs) resident in the lung in the homeostasis of these mechanisms is still a matter of debate. Although endogenous MSCs may play a critical role in lung repair, they are also involved in cellular senescence and tissue ageing processes with loss of lung regenerative potential. In addition, MSCs have immunomodulatory properties and can secrete anti-fibrotic factors. Thus, MSCs obtained from other sources administered systemically or directly into the lung have been investigated for lung epithelial repair and have been explored as a potential therapy for the treatment of lung diseases including IPF. Given these multiple potential roles of MSCs, this review aims both at elucidating the role of resident lung MSCs in IPF pathogenesis and the role of administered MSCs from other sources for potential IPF therapies.

Long non‑coding RNA HOTTIP enhances the fibrosis of lung tissues by regulating the miR‑744‑5p/PTBP1 signaling axis

Fibrosis of lung tissue can induce the occurrence and development of numerous types of lung disease. The expression levels of the long non-coding RNA (lncRNA) HOXA distal transcript antisense RNA (HOTTIP) have been reported to be upregulated during the development of fibrosis in liver tissues, which subsequently activated hepatic stellate cells. However, whether the lncRNA HOTTIP participates in the occurrence and development of lung fibrosis remains unknown. The present study aimed to investigate the role of lncRNA HOTTIP in lung fibrosis and its potential mechanism. In the present study, A549 cells were stimulated with TGF-β1 to induce lung fibrosis in vitro. A549 was transfected with short hairpin RNA-HOTTP, overexpression-polypyrimidine tract binding protein 1 (PTBP1), microRNA (miR)-744-5p mimic or miR-744-5p to regulate gene expression. Cell proliferation and migration were determined using 5′-ethynl-2′-deoxyuridine and wound healing assays, respectively. The expression levels of α-smooth muscle actin, collagen I, collagen III and fibronectin 1 were analyzed using western blotting. starBase was used to identify molecules that may interact with the lncRNA HOTTIP and dual luciferase reporter assays were used to validate the findings. Moreover, an in vivo lung fibrosis model was established by bleomycin induction in mice. Histological injury was observed using hematoxylin and eosin and masson staining. The results of the present study revealed that the proliferation and migration of A549 cells were both suppressed following the knockdown of HOTTIP. The lncRNA HOTTIP was found to target and downregulate the expression levels of miR-744-5p. The overexpression of miR-744-5p inhibited the proliferation and migration of A549 cells. Furthermore, miR-744-5p targeted and downregulated the expression levels of PTBP1. It was subsequently demonstrated that the overexpression of PTBP1 rescued miR-744-5p-induced suppression of the proliferation and migration of A549 cells. The knockdown of lncRNA HOTTIP expression also relieved the fibrosis of the lung tissues of mice. In conclusion, the results of the present study suggested that the lncRNA HOTTIP may promote the fibrosis of lung tissues by downregulating the expression levels of miR-744-5p and upregulating the expression levels of PTBP1.

Cellular Senescence in Lung Fibrosis

Fibrosing interstitial lung diseases (ILDs) are chronic and ultimately fatal age-related lung diseases characterized by the progressive and irreversible accumulation of scar tissue in the lung parenchyma. Over the past years, significant progress has been made in our incomplete understanding of the pathobiology underlying fibrosing ILDs, in particular in relation to diverse age-related processes and cell perturbations that seem to lead to maladaptation to stress and susceptibility to lung fibrosis. Growing evidence suggests that a specific biological phenomenon known as cellular senescence plays an important role in the initiation and progression of pulmonary fibrosis. Cellular senescence is defined as a cell fate decision caused by the accumulation of unrepairable cellular damage and is characterized by an abundant pro-inflammatory and pro-fibrotic secretome. The senescence response has been widely recognized as a beneficial physiological mechanism during development and in tumour suppression. However, recent evidence strengthens the idea that it also drives degenerative processes such as lung fibrosis, most likely by promoting molecular and cellular changes in chronic fibrosing processes. Here, we review how cellular senescence may contribute to lung fibrosis pathobiology, and we highlight current and emerging therapeutic approaches to treat fibrosing ILDs by targeting cellular senescence.

Targeting Alveolar Repair in Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis is a fatal interstitial lung disease with limited therapeutic options. Current evidence suggests that IPF may be initiated by repeated epithelial injury in the distal lung followed by abnormal wound healing responses which occur due to intrinsic and extrinsic factors. Mechanisms contributing to chronic damage of the alveolar epithelium in IPF include dysregulated cellular processes such as apoptosis, senescence, abnormal activation of developmental pathways, aging, as well as genetic mutations. Therefore, targeting the regenerative capacity of the lung epithelium is an attractive approach in the development of novel therapies for IPF. Endogenous lung regeneration is a complex process involving coordinated cross-talk between multiple cell types and re-establishment of a normal extracellular matrix environment. This review will describe the current knowledge of reparative epithelial progenitor cells in the alveolar region of the lung and discuss potential novel therapeutic approaches for IPF focusing on endogenous alveolar repair. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Fibroblasts positive for meflin have anti-fibrotic property in pulmonary fibrosis

The prognosis of elderly individuals with idiopathic pulmonary fibrosis (IPF) remains poor. Fibroblastic foci, in which aggregates of proliferating fibroblasts and myofibroblasts are involved, are the pathological hallmark lesions in IPF to represent focal areas of active fibrogenesis. Fibroblast heterogeneity in fibrotic lesions hampers the discovery of the pathogenesis of pulmonary fibrosis. Therefore, to determine of the pathogenesis of IPF, identification of functional fibroblasts is warranted. This study was aimed to determine the role of fibroblasts positive for meflin, identified as a potential marker for mesenchymal stromal cells, during the development of pulmonary fibrosis. We characterised meflin-positive cells in a single cell atlas established by single-cell RNA sequencing (scRNA-seq)-based profiling of 243 472 cells from 32 IPF lungs and 29 normal lung samples. scRNA-seq combined with in situ RNA hybridisation identified proliferating fibroblasts positive for meflin in fibroblastic foci, not dense fibrosis, of fibrotic lungs in IPF patients. We determined the role of fibroblasts positive for meflin using bleomycin (BLM)-induced pulmonary fibrosis. A BLM-induced lung fibrosis model for meflin-deficient mice showed that fibroblasts positive for meflin had anti-fibrotic property to prevent pulmonary fibrosis. Although transforming growth factor-β-induced fibrogenesis and cell senescence with senescence-associated secretory phenotype were exacerbated in fibroblasts via the repression or lack of meflin, these were inhibited in meflin-deficient fibroblasts with meflin reconstitution. These findings provide evidence to show the biological importance of meflin expression on fibroblasts and myofibroblasts in the active fibrotic region of pulmonary fibrosis.