Epithelial-mesenchymal interactions in pulmonary fibrosis

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.

Targeting CEBPA to restore cellular identity and tissue homeostasis in pulmonary fibrosis

Fibrosis in the lung is thought to be driven by epithelial cell dysfunction and aberrant cell-cell interactions. Unveiling the molecular mechanisms of cellular plasticity and cell-cell interactions is imperative to elucidating lung regenerative capacity and aberrant repair in pulmonary fibrosis. By mining publicly available RNA-Seq data sets, we identified loss of CCAAT enhancer-binding protein alpha (CEBPA) as a candidate contributor to idiopathic pulmonary fibrosis (IPF). We used conditional KO mice, scRNA-Seq, lung organoids, small-molecule inhibition, and potentially novel gene manipulation methods to investigate the role of CEBPA in lung fibrosis and repair. Long-term (6 months or more) of Cebpa loss in AT2 cells caused spontaneous fibrosis and increased susceptibility to bleomycin-induced fibrosis. Cebpa knockout (KO) in these mice significantly decreased AT2 cell numbers in the lung and reduced expression of surfactant homeostasis genes, while increasing inflammatory cell recruitment as well as upregulating S100a8/a9 in AT2 cells. In vivo treatment with an S100A8/A9 inhibitor alleviated experimental lung fibrosis. Restoring CEBPA expression in lung organoids ex vivo and during experimental lung fibrosis in vivo rescued CEBPA deficiency-mediated phenotypes. Our study establishes a direct mechanistic link between CEBPA repression, impaired AT2 cell identity, disrupted tissue homeostasis, and lung fibrosis.

Lipid-Laden Macrophages in Pulmonary Diseases

Pulmonary surfactants play a crucial role in managing lung lipid metabolism, and dysregulation of this process is evident in various lung diseases. Alternations in lipid metabolism lead to pulmonary surfactant damage, resulting in hyperlipidemia in response to lung injury. Lung macrophages are responsible for recycling damaged lipid droplets to maintain lipid homeostasis. The inflammatory response triggered by external stimuli such as cigarette smoke, bleomycin, and bacteria can interfere with this process, resulting in the formation of lipid-laden macrophages (LLMs), also known as foamy macrophages. Recent studies have highlighted the potential significance of LLM formation in a range of pulmonary diseases. Furthermore, growing evidence suggests that LLMs are present in patients suffering from various pulmonary conditions. In this review, we summarize the essential metabolic and signaling pathways driving the LLM formation in chronic obstructive pulmonary disease, pulmonary fibrosis, tuberculosis, and acute lung injury.

Integrated analysis of ceRNA-miRNA changes in paraquat-induced pulmonary epithelial-mesenchymal transition via high-throughput sequencing

Recent studies have shown that epithelial-mesenchymal transition (EMT) plays an important role in paraquat (PQ)-induced tissue fibrosis, which is the main cause of death in patients with PQ poisoning. However, no effective treatment for pulmonary interstitial fibrosis caused by PQ poisoning exists. It is of great significance for us to find new therapeutic targets through bioinformatics in PQ-induced EMT. We conducted transcriptome sequencing to determine the expression profiles of 1210 messenger RNAs (mRNAs), 558 long noncoding RNAs, 28 microRNAs (miRNAs), including 18 known-miRNAs, 10 novel-miRNAs and 154 circular RNAs in the PQ-exposed EMT group mice. Using gene ontology and Kyoto Encyclopaedia of Genes and Genomes analyses, we identified the pathways associated with signal transduction, cancers, endocrine systems and immune systems were involved in PQ-induced EMT. Furthermore, we constructed long noncoding RNA-miRNA-mRNA interrelated networks and found that upregulated genes included Il22ra2, Mdm4, Slc35e2 and Angptl4, and downregulated genes included RGS2, Gabpb2, Acvr1, Prkd3, Sp100, Tlr12, Syt15 and Camk2d. Thirteen new potential competitive endogenous RNA targets were also identified for further treatment of PQ-induced pulmonary tissue fibrosis. Through further study of the pathway and networks, we may identify new molecular targets in PQ-induced pulmonary EMT.

The Plastic Interplay between Lung Regeneration Phenomena and Fibrotic Evolution: Current Challenges and Novel Therapeutic Perspectives

Interstitial lung diseases (ILDs) are a heterogeneous group of pulmonary disorders characterized by variable degrees of inflammation, interstitial thickening, and fibrosis leading to distortion of the pulmonary architecture and gas exchange impairment. Among them, idiopathic pulmonary fibrosis (IPF) displays the worst prognosis. The only therapeutic options consist of the two antifibrotic drugs, pirfenidone and nintedanib, which limit fibrosis progression but do not reverse the lung damage. The shift of the pathogenetic paradigm from inflammatory disease to epithelium-derived disease has definitively established the primary role of type II alveolar cells, which lose their epithelial phenotype and acquire a mesenchymal phenotype with production of collagen and extracellular matrix (EMC) deposition. Some predisposing environmental and genetic factors (e.g., smoke, pollution, gastroesophageal reflux, variants of telomere and surfactant genes) leading to accelerated senescence set a pro-fibrogentic microenvironment and contribute to the loss of regenerative properties of type II epithelial cells in response to pathogenic noxae. This review provides a complete overview of the different pathogenetic mechanisms leading to the development of IPF. Then, we summarize the currently approved therapies and the main clinical trials ongoing. Finally, we explore the potentialities offered by agents not only interfering with the processes of fibrosis but also restoring the physiological properties of alveolar regeneration, with a particular focus on potentialities and concerns about cell therapies based on mesenchymal stem cells (MSCs), whose anti-inflammatory and immunomodulant properties have been exploited in other fibrotic diseases, such as graft versus host disease (GVHD) and COVID-19-related ARDS.

Nocturnal Hypoxemia Associates With Symptom Progression and Mortality in Patients With Progressive Fibrotic Interstitial Lung Disease

BACKGROUND

OSA and nocturnal hypoxemia (NH) are common in patients with fibrotic interstitial lung disease (F-ILD), but their relationship with disease outcomes remains unclear.

RESEARCH QUESTION

What is the relationship between NH and OSA and clinical outcomes in patients with F-ILD?

STUDY DESIGN AND METHODS

This was a prospective observational cohort study of patients with F-ILD and without daytime hypoxemia. Patients underwent home sleep study at baseline and were followed up for at least 1 year or until death. NH was defined as ≥ 10% of sleep with oxygen saturation of < 90%. OSA was defined as an apnea-hypopnea index of ≥ 15 events/h.

RESULTS

Among 102 participants (male, 74.5%; age, 73.0 ± 8.7 years; FVC, 2.74 ± 0.78 L; 91.1% idiopathic pulmonary fibrosis), 20 patients (19.6%) demonstrated prolonged NH and 32 patients (31.4%) showed OSA. No significant differences were found between those with and without NH or OSA at baseline. Despite this, NH was associated with a more rapid decline in both quality of life as measured by the King's Brief Interstitial Lung Disease questionnaire (change, -11.3 ± 5.3 points in the NH group vs -6.7 ± 6.5 in those without NH; P = .005) and higher all-cause mortality at 1 year (hazard ratio, 8.21; 95% CI, 2.40-28.1; P < .001). No statistically significant difference was seen between the groups in annualized change in measures of pulmonary function testing.

INTERPRETATION

Prolonged NH, but not OSA, is associated with worsening disease-related quality of life and increased mortality in patients with F-ILD.

Taste papilla cell differentiation requires the regulation of secretory protein production by ALK3-BMP signaling in the tongue mesenchyme

Taste papillae are specialized organs, each of which comprises an epithelial wall hosting taste buds and a core of mesenchymal tissue. In the present study, we report that during early taste papilla development in mouse embryos, bone morphogenetic protein (BMP) signaling mediated by type 1 receptor ALK3 in the tongue mesenchyme is required for epithelial Wnt/β-catenin activity and taste papilla differentiation. Mesenchyme-specific knockout (cKO) of Alk3 using Wnt1-Cre and Sox10-Cre resulted in an absence of taste papillae at E12.0. Biochemical and cell differentiation analyses demonstrated that mesenchymal ALK3-BMP signaling governed the production of previously unappreciated secretory proteins, i.e. it suppressed those that inhibit and facilitated those that promote taste papilla differentiation. Bulk RNA-sequencing analysis revealed many more differentially expressed genes (DEGs) in the tongue epithelium than in the mesenchyme in Alk3 cKO versus control. Moreover, we detected downregulated epithelial Wnt/β-catenin signaling and found that taste papilla development in the Alk3 cKO was rescued by the GSK3β inhibitor LiCl, but not by Wnt3a. Our findings demonstrate for the first time the requirement of tongue mesenchyme in taste papilla cell differentiation.

Exosomal miR-17-5p from human embryonic stem cells prevents pulmonary fibrosis by targeting thrombospondin-2

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and irreversible lung disease characterized by pulmonary fibrosis and lung dysfunction, ultimately leading to respiratory failure. Many preclinical studies have investigated the therapeutic potential of stem cell-derived exosomes in this disease, particularly mesenchymal stem cell-derived exosomes. However, the effects of embryonic stem cell-derived exosomes in IPF remain unclear.

METHODS

We established a bleomycin (BLM)-induced pulmonary fibrosis mice model and administered human embryonic stem cell exosomes (hESC-exo) from the first day after BLM treatment. The effects of hESC-exo were assessed by pulmonary function tests, biochemical analysis, histochemistry, quantitative real-time polymerase chain reaction (qPCR), and western blot (WB). RNA-seq was used to screen for the potential therapeutic targets of hESC-exo in fibrotic lungs; the identified signaling axis was characterized using a luciferase assay, qPCR, and WB.

RESULTS

Results indicated hESC-exo administration notably alleviated inflammation, removed deposited collagen, and rescued alveolar architecture in the lungs of BLM-induced mice. In vivo and in vitro tests revealed that hESC-exo-derived miR-17-5p directly bound thrombospondin-2 (Thbs2) to regulate inflammation and fibrosis; thus, hESC-exo protected against BLM toxicity in the lungs via the miR-17-5p/Thbs2 axis.

CONCLUSION

These results suggest a promising new treatment for fibrosis-associated diseases.

The aged extracellular matrix and the profibrotic role of senescence-associated secretory phenotype

Idiopathic pulmonary fibrosis (IPF) is an irreversible and fatal lung disease that is primarily found in the elderly population, and several studies have demonstrated that aging is the major risk factor for IPF. IPF is characterized by the presence of apoptosis-resistant, senescent fibroblasts that generate an excessively stiff extracellular matrix (ECM). The ECM profoundly affects cellular functions and tissue homeostasis, and an aberrant ECM is closely associated with the development of lung fibrosis. Aging progressively alters ECM components and is associated with the accumulation of senescent cells that promote age-related tissue dysfunction through the expression of factors linked to a senescence-associated secretary phenotype (SASP). There is growing evidence that SASP factors affect various cell behaviors and influence ECM turnover in lung tissue through autocrine and/or paracrine signaling mechanisms. Since life expectancy is increasing worldwide, it is important to elucidate how aging affects ECM dynamics and turnover via SASP and thereby promotes lung fibrosis. In this review, we will focus on the molecular properties of SASP and its regulatory mechanisms. Furthermore, the pathophysiological process of ECM remodeling by SASP factors and the influence of an altered ECM from aged lungs on the development of lung fibrosis will be highlighted. Finally, recent attempts to target ECM alteration and senescent cells to modulate fibrosis will be introduced.NEW & NOTEWORTHY Aging is the most prominent nonmodifiable risk factor for various human diseases including Idiopathic pulmonary fibrosis. Aging progressively alters extracellular matrix components and is associated with the accumulation of senescent cells that promote age-related tissue dysfunction. In this review, we will discuss the pathological impact of aging and senescence on lung fibrosis via senescence-associated secretary phenotype factors and potential therapeutic approaches to limit the progression of lung fibrosis.

Geranylgeranylacetone, an inducer of heat shock protein 70, attenuates pulmonary fibrosis via inhibiting NF-κB/NOX4/ROS signalling pathway in vitro and in vivo

Idiopathic pulmonary fibrosis (IPF) is a devastating and progressive pulmonary disease which is characterized by epithelial cell damage and extracellular collagen deposition. To date, the therapeutic options for IPF are still very limited, so the relevant mechanisms need to be explored. Heat shock protein 70 (HSP70), which has protective versus antitumor effects on cells under stress, is a member of the heat shock protein family. In the current study, qRT-PCR, western blotting, immunofluorescence staining, and migration assays were used to explore the Epithelial-mesenchymal transition (EMT) process in BEAS-2B cells. Moreover, the role of GGA in the process of pulmonary fibrosis was detected by HE, Masson staining, pulmonary function test and immunohistochemistry in C57BL/6 mice. Our results indicated that GGA, as an inducer of HSP70, enhanced the transformation of BEAS-2B cells from epithelial to mesenchymal cells through the NF-κB/NOX4/ROS (reactive oxygen species) signalling pathway and could significantly reduce apoptosis of BEAS-2B cells induced by TGF-β1(Transforming growth factor β1) in vitro. In vivo studies demonstrated that HSP70-inducing drugs, such as GGA, attenuated pulmonary fibrosis progression induced by bleomycin (BLM). Collectively, these results suggested that overexpression of HSP70 attenuated pulmonary fibrosis induced by BLM in C57BL/6 mice and EMT process induced by TGF-β1 through NF-κB/NOX4/ROS pathway in vitro. Thus, HSP70 might be a potential therapeutic strategy for human lung fibrosis.

Nanotherapeutic Approaches to Treat COVID-19-Induced Pulmonary Fibrosis

There have been significant collaborative efforts over the past three years to develop therapies against COVID-19. During this journey, there has also been a lot of focus on understanding at-risk groups of patients who either have pre-existing conditions or have developed concomitant health conditions due to the impact of COVID-19 on the immune system. There was a high incidence of COVID-19-induced pulmonary fibrosis (PF) observed in patients. PF can cause significant morbidity and long-term disability and lead to death in the long run. Additionally, being a progressive disease, PF can also impact the patient for a long time after COVID infection and affect the overall quality of life. Although current therapies are being used as the mainstay for treating PF, there is no therapy specifically for COVID-induced PF. As observed in the treatment of other diseases, nanomedicine can show significant promise in overcoming the limitations of current anti-PF therapies. In this review, we summarize the efforts reported by various groups to develop nanomedicine therapeutics to treat COVID-induced PF. These therapies can potentially offer benefits in terms of targeted drug delivery to lungs, reduced toxicity, and ease of administration. Some of the nanotherapeutic approaches may provide benefits in terms of reduced immunogenicity owing to the tailored biological composition of the carrier as per the patient needs. In this review, we discuss cellular membrane-based nanodecoys, extracellular vesicles such as exosomes, and other nanoparticle-based approaches for potential treatment of COVID-induced PF.

Taste papilla cell differentiation requires tongue mesenchyme via ALK3-BMP signaling to regulate the production of secretory proteins

Taste papillae are specialized organs each of which is comprised of an epithelial wall hosting taste buds and a core of mesenchymal tissue. In the present study, we report that during the early stages of embryonic development, bone morphogenetic protein (BMP) signaling mediated by type 1 receptor ALK3 in the tongue mesenchyme is required for the epithelial Wnt/β-catenin activity and taste papilla cell differentiation. Mesenchyme-specific knockout ( cKO ) of Alk3 using Wnt1-Cre and Sox10-Cre resulted in an absence of taste papillae at E12.0. Biochemical and cell differentiation analyses demonstrated that mesenchymal ALK3-BMP signaling governs the production of previously unappreciated secretory proteins, i.e., suppresses those that inhibiting and facilitates those promoting taste cell differentiation. Bulk RNA-Sequencing analysis revealed many more differentially expressed genes (DEGs) in the tongue epithelium than in the mesenchyme in Alk3 cKO vs control. Moreover, we detected a down-regulated epithelial Wnt/β-catenin signaling, and taste papilla development in the Alk3 cKO was rescued by GSK3β inhibitor LiCl, but not Wnt3a. Our findings demonstrate for the first time the requirement of tongue mesenchyme in taste papilla cell differentiation.

Summary statement

This is the first set of data to implicate the requirement of tongue mesenchyme in taste papilla cell differentiation.

Regulation of Mesenchymal Cell Fate by Transfer of Active Gasdermin-D via Monocyte-Derived Extracellular Vesicles

Fibrosis is characterized by inappropriately persistent myofibroblast accumulation and excessive extracellular matrix deposition with the disruption of tissue architecture and organ dysfunction. Regulated death of reparative mesenchymal cells is critical for normal wound repair, but profibrotic signaling promotes myofibroblast resistance to apoptotic stimuli. A complex interplay between immune cells and structural cells underlies lung fibrogenesis. However, there is a paucity of knowledge on how these cell populations interact to orchestrate physiologic and pathologic repair of the injured lung. In this context, gasdermin-D (GsdmD) is a cytoplasmic protein that is activated following cleavage by inflammatory caspases and induces regulated cell death by forming pores in cell membranes. This study was undertaken to evaluate the impact of human (Thp-1) monocyte-derived extracellular vesicles and GsdmD on human lung fibroblast death. Our data show that active GsdmD delivered by monocyte-derived extracellular vesicles induces caspase-independent fibroblast and myofibroblast death. This cell death was partly mediated by GsdmD-independent induction of cellular inhibitor of apoptosis 2 (cIAP-2) in the recipient fibroblast population. Our findings, to our knowledge, define a novel paradigm by which inflammatory monocytes may orchestrate the death of mesenchymal cells in physiologic wound healing, illustrating the potential to leverage this mechanism to eliminate mesenchymal cells and facilitate the resolution of fibrotic repair.

miRNA Expression in Fibroblastic Foci within Idiopathic Pulmonary Fibrosis Lungs Reveals Novel Disease-Relevant Pathways

miRNAs are a class of noncoding RNAs of approximately 22 nucleotides long that play an important role in regulating gene expression at a post-transcriptional level. Aberrant levels of miRNAs have been associated with profibrotic processes in idiopathic pulmonary fibrosis (IPF). However, most of these studies used whole IPF tissue or in vitro monocultures in which fibrosis has been artificially induced. In this study, we used laser microdissection to collect fibroblastic foci (FF), the key pathologic lesion in IPF, then isolate miRNAs and compare their expression levels with those found in whole IPF lung tissue and/or in vitro cultured fibroblast from IPF or normal lungs. Sequencing libraries were generated, and data generated were bioinformatically analyzed. A total of 18 miRNAs were significantly overexpressed in FF tissue when compared with whole IPF tissue; of these molecules, 15 were unique to FF. Comparison of FF with cultured IPF fibroblasts also revealed differences in miRNA composition that impact on several signaling pathways. The miRNA composition of FF is both overlapping and distinct from that of whole IPF tissue or cultured IPF fibroblasts and highlights the importance of characterizing FF biology as a phenotypically and functionally discrete tissue microenvironment.

The Role of IL-6 in Fibrotic Diseases: Molecular and Cellular Mechanisms

Fibrosis is a detrimental outcome of most chronic inflammatory disorders and is defined by the buildup of excess extracellular matrix (ECM) components, which eventually leads to organ failure and death. Interleukin 6 (IL-6) is promptly produced by immune cells in response to tissue injuries and has a wide range of effects on cellular processes such as acute responses, hematopoiesis, and immune reactions. Furthermore, high levels of IL-6 have been found in a variety of chronic inflammatory disorders characterized by fibrosis, and this factor plays a significant role in fibrosis in various organs via Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) activation. Here, we review what is known about the role of IL-6 in fibrosis and why targeting IL-6 for fibrotic disease treatment makes sense.

Roles of NRF2 in Fibrotic Diseases: From Mechanisms to Therapeutic Approaches

Fibrosis is a persistent inflammatory response that causes scarring and tissue sclerosis by stimulating myofibroblasts to create significant quantities of extracellular matrix protein deposits in the tissue. Oxidative stress has also been linked to the development of fibrosis in several studies. The nuclear erythroid 2-related factor 2 (NRF2) transcription factor controls the expression of several detoxification and antioxidant genes. By binding to antioxidant response elements, NRF2 is activated by oxidative or electrophilic stress and promotes its target genes, resulting in a protective effect on cells. NRF2 is essential for cell survival under oxidative stress conditions. This review describes Kelch-like epichlorohydrin-associated protein 1 (KEAP1)/NRF2 signaling mechanisms and presents recent research advances regarding NRF2 and its involvement in primary fibrotic lesions such as pulmonary fibrosis, hepatic fibrosis, myocardial fibrosis, and renal fibrosis. The related antioxidant substances and drugs are described, along with the mechanisms by which KEAP1/NRF2 regulation positively affects the therapeutic response. Finally, the therapeutic prospects and potential value of NRF2 in fibrosis are summarized. Further studies on NRF2 may provide novel therapeutic approaches for fibrosis.

Blueberry Juice Attenuates Pulmonary Fibrosis via Blocking the TGF-β1/Smad Signaling Pathway

Idiopathic pulmonary fibrosis (IPF) is a progressive, fatal, and chronic lung disease, lacking a validated and effective therapy. Blueberry has demonstrated multiple pharmacological activities including anti-inflammatory, antioxidant, and anticancer. Therefore, the objective of this study was to investigate whether blueberry juice (BBJ) could ameliorate IPF. Experiments in vitro revealed that BBJ could significantly reduce the expressions of TGF-β1 modulated fibrotic protein, which were involved in the cascade of fibrosis in NIH/3T3 cells and human pulmonary fibroblasts. In addition, for rat primary lung fibroblasts (RPLFs), BBJ promoted the cell apoptosis along with reducing the expressions of α-SMA, vimentin, and collagen I, while increasing the E-cadherin level. Furthermore, BBJ could reverse epithelial–mesenchymal transition (EMT) phenotypic changes and inhibit cell migration, along with inducing the upregulation of E-cadherin in A549 cells. Compared with the vehicle group, BBJ treatment alleviated fibrotic pathological changes and collagen deposition in both bleomycin-induced prevention and treatment pulmonary fibrosis models. In fibrotic lung tissues, BBJ remarkably suppressed the expressions of collagen I, α-SMA, and vimentin and improved E-cadherin, which may be related to its inhibition of the TGF-β1/Smad pathway and anti-inflammation efficacy. Taken together, these findings comprehensively proved that BBJ could effectively prevent and attenuate idiopathic pulmonary fibrosis via suppressing EMT and the TGF-β1/Smad signaling pathway.

C/EBP homologous protein promotes Sonic Hedgehog secretion from type II alveolar epithelial cells and activates Hedgehog signaling pathway of fibroblast in pulmonary fibrosis

Background

Endoplasmic reticulum (ER) stress is involved in the pathological process of pulmonary fibrosis, including IPF. It affects a broad scope of cellular types during pulmonary fibrosis but the role in epithelial-mesenchymal crosstalk has not been fully defined. The present study aimed to investigate the effects of Shh secretion by ER  stress-challenged type II alveolar epithelial cells (AECII) on fibroblast and pulmonary fibrosis.

Methods

Conditioned medium (CM) from tunicamycin (TM)-treated AECII was collected and incubated with fibroblast. Short hairpin RNA (shRNA) was used for RNA interference of C/EBP homologous protein (CHOP). The effects of CHOP and HH signaling were evaluated by TM administration under the background of bleomycin-induced pulmonary fibrosis in mice.

Results

Both expression of CHOP and Shh in AECII, and HH signaling in mesenchyme were upregulated in IPF lung. TM-induced Shh secretion from AECII activates HH signaling and promotes pro-fibrotic effects of fibroblast. Interfering CHOP expression reduced ER stress-induced Shh secretion and alleviated pulmonary fibrosis in mice.

Conclusions

Our work identified a novel mechanism by which ER stress is involved in pulmonary fibrosis. Inhibition of ER stress or CHOP in epithelial cells alleviated pulmonary fibrosis by suppressing Shh/HH signaling pathway of fibroblasts.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02012-x.

Exploring the Potential Effects and Mechanisms of Asarum sieboldii Radix Essential Oil for Treatment of Asthma

Asthma, a common chronic pulmonary disorder characterized by airway remodeling, hyperresponsiveness and obstruction, can be aggravated by repeated exposure to particulate matter (PM). The potential effect and mechanisms of Asarum sieboldii Radix essential oil (AEO) against asthma were explored based on network pharmacology. AEO was pre-treated using a nebulizer for 3 weeks and the mice were sensitized to ovalbumin (OVA) and PM10 with the co-treatment of AEO for 4 weeks. In addition, A549 lung epithelial cells were sensitized with PM10 to investigate the underlying mechanisms of AEO regarding the lung-fibrosis-related mediators. The target genes of methyl eugenol, a main compound of AEO, were highly matched by 48% with the gene set of asthma. AEO markedly inhibited the increase in epithelial thickness through the accumulation of goblet cells in the airways. Collagen deposition in the lung tissues of OVA+PM10-challenged asthmatic mice was significantly decreased by AEO. AEO also inhibited the influx of inflammatory cells in the bronchoalveolar lavage fluid, as well as the increases in serum IgE and IgG2a and cytokines in the lung tissues. Furthermore, AEO regulated the expressions of fibrotic mediators, especially POSTN and TGF-β. In conclusion, we expect that AEO can be one of the effective alternative therapeutics to relieve asthma.

Inflammogenic effect of polyacrylic acid in rat lung following intratracheal instillation

Background

Some organic chemicals are known to cause allergic disorders such as bronchial asthma and hypersensitivity pneumonitis, and it has been considered that they do not cause irreversible pulmonary fibrosis. It has recently been reported, however, that cross-linked acrylic acid-based polymer, an organic chemical, might cause serious interstitial lung diseases, including pulmonary fibrosis. We investigated whether or not intratracheal instillation exposure to cross-linked polyacrylic acid (CL-PAA) can cause lung disorder in rats.

Methods

Male F344 rats were intratracheally instilled with dispersed CL-PAA at low (0.2 mg/rat) and high (1.0 mg/rat) doses, and were sacrificed at 3 days, 1 week, 1 month, 3 months and 6 months after exposure to examine inflammatory and fibrotic responses and related gene expressions in the lungs. Rat lungs exposed to crystalline silica, asbestos (chrysotile), and NiO and CeO2 nanoparticles were used as comparators.

Results

Persistent increases in total cell count, neutrophil count and neutrophil percentage, and in the concentration of the cytokine-induced neutrophil chemoattractant (CINC)-1, CINC-2 and C-X-C motif chemokine 5 (CXCL5), which correlated with lung tissue gene expression, were observed in bronchoalveolar lavage fluid (BALF) from 3 days until at least 1 month following CL-PAA intratracheal instillation. Persistent increases in heme oxygenase-1 (HO-1) in the lung tissue were also observed from 3 days to 6 months after exposure. Histopathological findings of the lungs demonstrated that extensive inflammation at 3 days was greater than that in exposure to silica, NiO nanoparticles and CeO2 nanoparticles, and equal to or greater than that in asbestos (chrysotile) exposure, and the inflammation continued until 1 month. Fibrotic changes also progressed after 1 month postexposure.

Conclusion

Our results suggested that CL-PAA potentially causes strong neutrophil inflammation in the rat and human lung.

Lung fibrosis is induced in ADAR2 overexpressing mice via HuR-induced CTGF signaling

Adenosine deaminase acting on RNA 2 (ADAR2), an RNA editing enzyme is involved in a site-selective modification of adenosine (A) to inosine (I) in double-stranded RNA (dsRNA). Its role in the lungs is unknown. The phenotypic characterization of Adarb1 mice that lacked ADAR2 auto-regulation due to the deletion of editing complementary sequence (ΔECS mice) determined the functional role of ADAR2 in the lungs. ADAR2 protein expression increased in the ΔECS mice. These mice display immune cell infiltration and alveolar disorganization. The lung wet by dry ratio indicates there is no lung edema in ΔECS mice. Bronchoalveolar lavage (BAL) analysis of ΔECS mice reveals a significant increase in neutrophils. Interestingly, ΔECS mice spontaneously develop lung fibrosis as indicated by Sirius red staining of collagen fibers in the lung sections and a significant increase in hydroxyproline level in their lungs. ADAR2 expression increased significantly in a bleomycin mouse model, implicating a role of ADAR2 in lung fibrosis. Furthermore, there is a likely possibility that the genetically modified ΔECS mice does not model the physiological or pathophysiological process of lung fibrosis. Nevertheless, this model is useful in interrogating the role of ADAR2 in the lungs. The Ctgf mRNA and connective tissue growth factor (CTGF) protein significantly increased in ΔECS lungs and occurs in bronchial epithelial cells. There is a significant increase in Human antigen R (ELAVL1; HuR) protein levels in ΔECS lungs and suggests a role in stabilizing Ctgf mRNA. Lung mechanics such as total respiratory resistance, Newtonian resistance and tissue damping were increased, whereas inspiratory capacity was decreased in the ΔECS mice. Taken together, these data indicate that overexpression of ADAR2 causes spontaneous lung fibrosis via HuR-mediated CTGF signaling and implicate a role for ADAR2 auto-regulation in lung homeostasis. The identification of ADAR2 target genes in ΔECS mice would facilitate a mechanistic understanding of the role of ADAR2 in the lungs and provide a therapeutic strategy for lung fibrosis.

A phycocyanin derived eicosapeptide attenuates lung fibrosis development

Pulmonary fibrosis (PF) is a progressive respiratory disease. Phycocyanin derived eicosapeptide (PP20) is a novel peptide derived from active protein C-phycocyanin in Cyanobacteria. The aim of our study was to explore the anti-fibrotic activity of the PP20 and its underlying mechanism. Characteristic features of pulmonary fibrosis in oleic acid (OA)-induced mice and epithelial-mesenchymal transition (EMT) in TGF-β1-exposed A549 and HFL-1 cells with or without PP20 and the change of TGF-β/Smad and MAPK signaling pathways were examined. Smad and MAPK agonists were used to explore the role of TGF-β/Smad and MAPK signaling in TGF-β1- induced collagen I expression in A549 cells and α-SMA expression in HFL-1 cells when treated with PP20. Our results showed that PP20 significantly alleviated the inflammatory response and tissue destruction, inhibited EMT, restored the imbalance of TIMP-1/MMP-9 and reduced collagen fiber deposition. Moreover, PP20 inhibited TGF-β1-induced EMT and collagen I expression in A549 cells. PP20 could also inhibit the proliferation, and decrease TGF-β1-induced the expression of collagen I and transformation of fibroblasts into myofibroblasts in HFL-1 cells. Additionally, animal experiments and cell experiments combined with pathway agonists have shown that PP20 can negatively regulate TGF-β/Smad and MAPK pathways and show anti-fibrotic properties. PP20 may be a promising drug candidate for protection against pulmonary fibrosis.

Modulation of Oxidative Phosphorylation with IM156 Attenuates Mitochondrial Metabolic Reprogramming and Inhibits Pulmonary Fibrosis

Metabolic reprogramming of the myofibroblast plays a fundamental role in the pathogenesis of fibrosing interstitial lung diseases. Here, we characterized the in vitro and in vivo metabolic and anti-fibrotic effects of IM156, an oxidative phosphorylation (OXPHOS) modulator that acts by inhibiting Protein Complex 1 (PC1). In vitro, IM156 inhibited TGFβ-dependent increases in mitochondrial oxygen consumption rate and expression of myofibroblast markers in human pulmonary fibroblasts without altering cell viability or adding to TGF-β induced increases in the extracellular acidification rate (ECAR). IM156 significantly increased cellular AMPK phosphorylation and was 60-fold more potent than metformin. In vivo, chronic oral administration of IM156 was highly distributed to major peripheral organs (i.e. lung, liver, kidney, heart) and had significant dose-related effects on the plasma metabolome consistent with OXPHOS modulation and AMPK activation. IM156 increased glycolysis, lipolysis, β-oxidation and amino acids, and decreased free fatty acids, TCA cycle activity and protein synthesis. In the murine bleomycin model of pulmonary fibrosis, daily oral administration of IM156 administered 7 days after lung injury, attenuated body/lung weight changes, and reduced lung fibrosis and inflammatory cell infiltration. The plasma exposures of IM156 were comparable to well-tolerated doses in human studies. In conclusion, the metabolic and anti-fibrotic effects of IM156 suggest that OXPHOS modulation can attenuate myofibroblast metabolic reprogramming and support testing IM156 as a therapy for IPF and other fibrotic diseases. Significance Statement Fibrosing Interstitial Lung Diseases (FILD) have a poor prognosis and current anti-fibrotic treatments have significant limitations. This study demonstrates that attenuation of fibrogenic metabolic remodeling, by modulation of OXPHOS with IM156, prevents the myofibroblast phenotype/collagen deposition and is a potentially effective and translational anti-fibrotic strategy.

Exosomes derived from bone marrow mesenchymal stem cells reverse epithelial-mesenchymal transition potentially via attenuating Wnt/β-catenin signaling to alleviate silica-induced pulmonary fibrosis

Pulmonary fibrosis induced by silica dust is an irreversible, chronic, and fibroproliferative lung disease with no effective treatment at present. BMSCs-derived exosomes (BMSCs-Exo) possess similar functions to their parent cells. In this study, we investigated the therapeutic potential and underlying molecular mechanism for BMSCs-Exo in the treatment of silica-induced pulmonary fibrosis. The rat model of experimental silicosis pulmonary fibrosis was induced with 1.0 mL of one-off infusing silica suspension using the non-exposed intratracheal instillation (50 mg/mL/rat). In vivo transplantation of BMSCs-Exo effectively alleviated silica-induced pulmonary fibrosis, including a reduction in collagen accumulation, inhibition of TGF-β1, and decreased HYP content. Treatment of BMSCs-Exo increased the expression of epithelial marker proteins including E-cadherin (E-cad) and cytokeratin19 (CK19) and reduced the expression of fibrosis marker proteins including α-Smooth muscle actin (α-SMA) after exposure to silica suspension. Furthermore, we found that BMSCs-Exo inhibited the expression of Wnt/β-catenin pathway components (P-GSK3β, β-catenin, Cyclin D1) in pulmonary fibrosis tissue. BMSCs-Exo is involved in the alleviation of silica-induced pulmonary fibrosis by reducing the level of profibrotic factor TGF-β1 and inhibiting the progression of epithelial-mesenchymal transition (EMT). Additionally, attenuation of the Wnt/β-catenin signaling pathway closely related to EMT may be one of the mechanisms involved in anti-fibrotic effects of exosomes.

Epithelial Barrier Dysfunction in Chronic Respiratory Diseases

Mucosal surfaces are lined by epithelial cells, which provide a complex and adaptive module that ensures first-line defense against external toxics, irritants, antigens, and pathogens. The underlying mechanisms of host protection encompass multiple physical, chemical, and immune pathways. In the lung, inhaled agents continually challenge the airway epithelial barrier, which is altered in chronic diseases such as chronic obstructive pulmonary disease, asthma, cystic fibrosis, or pulmonary fibrosis. In this review, we describe the epithelial barrier abnormalities that are observed in such disorders and summarize current knowledge on the mechanisms driving impaired barrier function, which could represent targets of future therapeutic approaches.

Tauroursodeoxycholic acid alleviates pulmonary endoplasmic reticulum stress and epithelial-mesenchymal transition in bleomycin-induced lung fibrosis

Background

Several studies demonstrate that endoplasmic reticulum (ER) stress-mediated epithelial-mesenchymal transition (EMT) is involved in the process of bleomycin (BLM)-induced pulmonary fibrosis. Tauroursodeoxycholic acid (TUDCA), a bile acid with chaperone properties, is an inhibitor of ER stress. This study aimed to investigate the preventive effects of TUDCA on BLM-induced EMT and lung fibrosis.

Methods

The model of lung fibrosis was established by intratracheal injection with a single dose of BLM (3.0 mg/kg). In TUDCA + BLM group, mice were intraperitoneally injected with TUDCA (250 mg/kg) daily.

Results

BLM-induced alveolar septal destruction and inflammatory cell infiltration were alleviated by TUDCA. BLM-induced interstitial collagen deposition, as determined by Sirius Red staining, was attenuated by TUDCA. BLM-induced elevation of pulmonary α-smooth muscle actin (α-SMA) and reduction of pulmonary E-cadherin were attenuated by TUDCA. BLM-induced pulmonary Smad2/3 phosphorylation was suppressed by TUDCA. BLM-induced elevation of Ki67 and PCNA was inhibited by TUDCA in mice lungs. In addition, BLM-induced elevation of HO-1 (heme oxygenase-1) and 3-NT (3-nitrotyrosine) was alleviated by TUDCA. Finally, BLM-induced upregulation of pulmonary GRP78 and CHOP was attenuated by TUDCA.

Conclusions

These results provide evidence that TUDCA pretreatment inhibits Smad2/3-medited EMT and subsequent lung fibrosis partially through suppressing BLM-induced ER stress and oxidative stress.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01514-6.

CREB-dependent LPA-induced signaling initiates a pro-fibrotic feedback loop between small airway basal cells and fibroblasts

Background

Lysophosphatidic acid (LPA), generated extracellularly by the action of autotaxin and phospholipase A2, functions through LPA receptors (LPARs) or sphingosine-1-phosphate receptors (S1PRs) to induce pro-fibrotic signaling in the lower respiratory tract of patients with idiopathic pulmonary fibrosis (IPF). We hypothesized that LPA induces changes in small airway epithelial (SAE) basal cells (BC) that create cross-talk between the BC and normal human lung fibroblasts (NHLF), enhancing myofibroblast formation.

Methods

To assess LPA-induced signaling, BC were treated with LPA for 2.5 min and cell lysates were analyzed by phosphokinase array and Western blot. To assess transcriptional changes, BC were treated with LPA for 3 h and harvested for collection and analysis of RNA by quantitative polymerase chain reaction (qPCR). To assess signaling protein production and function, BC were washed thoroughly after LPA treatment and incubated for 24 h before collection for protein analysis by ELISA or functional analysis by transfer of conditioned medium to NHLF cultures. Transcription, protein production, and proliferation of NHLF were assessed.

Results

LPA treatment induced signaling by cAMP response element-binding protein (CREB), extracellular signal-related kinases 1 and 2 (Erk1/2), and epithelial growth factor receptor (EGFR) resulting in elevated expression of connective tissue growth factor (CTGF), endothelin-1 (EDN1/ET-1 protein), and platelet derived growth factor B (PDGFB) at the mRNA and protein levels. The conditioned medium from LPA-treated BC induced NHLF proliferation and increased NHLF expression of collagen I (COL1A1), smooth muscle actin (ACTA2), and autotaxin (ENPP2) at the mRNA and protein levels. Increased autotaxin secretion from NHLF correlated with increased LPA in the NHLF culture medium. Inhibition of CREB signaling blocked LPA-induced changes in BC transcription and translation as well as the pro-fibrotic effects of the conditioned medium on NHLF.

Conclusion

Inhibition of CREB signaling may represent a novel target for alleviating the LPA-induced pro-fibrotic feedback loop between SAE BC and NHLF.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01677-0.

The PAR-1 antagonist vorapaxar ameliorates kidney injury and tubulointerstitial fibrosis

Protease-activated receptor (PAR)-1 has emerged as a key profibrotic player in various organs including kidney. PAR-1 activation leads to deposition of extracellular matrix (ECM) proteins in the tubulointerstitium and induction of epithelial-mesenchymal transition (EMT) during renal fibrosis. We tested the anti-fibrotic potential of vorapaxar, a clinically approved PAR-1 antagonist for cardiovascular protection, in an experimental kidney fibrosis model of unilateral ureteral obstruction (UUO) and an AKI-to-chronic kidney disease (CKD) transition model of unilateral ischemia-reperfusion injury (UIRI), and dissected the underlying renoprotective mechanisms using rat tubular epithelial cells. PAR-1 is activated mostly in the renal tubules in both the UUO and UIRI models of renal fibrosis. Vorapaxar significantly reduced kidney injury and ameliorated morphologic changes in both models. Amelioration of kidney fibrosis was evident from down-regulation of fibronectin (Fn), collagen and α-smooth muscle actin (αSMA) in the injured kidney. Mechanistically, inhibition of PAR-1 inhibited MAPK ERK1/2 and transforming growth factor-β (TGF-β)-mediated Smad signaling, and suppressed oxidative stress, overexpression of pro-inflammatory cytokines and macrophage infiltration into the kidney. These beneficial effects were recapitulated in cultured tubular epithelial cells in which vorapaxar ameliorated thrombin- and hypoxia-induced TGF-β expression and ECM accumulation. In addition, vorapaxar mitigated capillary loss and the expression of adhesion molecules on the vascular endothelium during AKI-to-CKD transition. The PAR-1 antagonist vorapaxar protects against kidney fibrosis during UUO and UIRI. Its efficacy in human CKD in addition to CV protection warrants further investigation.

Snail-mediated partial epithelial mesenchymal transition augments the differentiation of local lung myofibroblast

The pathogenesis of pulmonary fibrosis diseases is considered to be related with environmental exposures, but the exact mechanism is unclear and there are no effective treatments. The contribution of epithelial-mesenchymal transition (EMT) to lung fibrosis has been controversial. It was found that partial EMT might play a vital role in renal fibrosis. We also found that partial EMT might be involved in fibrosis diseases. In this study, we used a silicosis animal model of pulmonary fibrosis to observe whether partial EMT existed in pulmonary fibrosis disease and a co-culture system culturing fibroblasts and alveolar epithelial cells stimulated by TGF-β1 to evaluate the probable effects of partial EMT, thus determined the probable role of partial EMT in pulmonary fibrosis diseases. In vivo, the results revealed that partial EMT might exist in silica-induced lung fibrosis model and Snail which is a potent EMT inducer was involved during the process. In vitro, a co-culture system was used to evaluate the effects of EMT in murine alveolar epithelial type II (ATII) cells on the activation of underlying murine lung fibroblasts into myofibroblasts. The results showed that epithelial cells undergoing EMT promoted the differentiation of lung myofibroblast and this epithelial-mesenchymal crosstalk was mainly controlled by Snail. Following Snail silencing the EMT and the activation of NIH-3T3 into myofibroblast were obviously inhibited. It indicated that targeting this novel Snail might be a viable strategy for the treatment of lung fibrosis diseases.

Alveolar Epithelial Denudation Is a Major Factor in the Pathogenesis of Pleuroparenchymal Fibroelastosis

The pathogenesis of pleuroparenchymal fibroelastosis (PPFE), a rare interstitial lung disease, remains unclear. Based on previous reports and our experience, we hypothesized that alveolar epithelial denudation (AED) was involved in the pathogenesis of PPFE. This multicenter retrospective study investigated the percentage of AED and the features of the denudated areas in 26 PPFE cases, 30 idiopathic pulmonary fibrosis (IPF) cases, and 29 controls. PPFE patients had lower forced vital capacities and higher residual volume/total lung capacities in pulmonary function tests compared to IPF and control patients. Histopathologically, subpleural fibroelastosis was observed in PPFE, and AED was observed in 12.01% of cases in the subpleural or interlobular septa regardless of fibroelastosis. The percentage of AED in the PPFE group was significantly higher than that in the IPF group (6.84%; p = 0.03) and the normal group (1.19%; p < 0.001). In the IPF group, the percentage of AED and the presence of PPFE-like lesions in the upper lobes were examined radiologically, but no correlation was found. We showed that AED frequently occurred in PPFE. AED was less frequent in IPF, which, in combination with imaging data, suggests that PPFE may have a different pathogenesis from IPF.

Rho-Kinase 1/2 Inhibition Prevents Transforming Growth Factor-β-Induced Effects on Pulmonary Remodeling and Repair

Transforming growth factor (TGF)-β-induced myofibroblast transformation and alterations in mesenchymal-epithelial interactions contribute to chronic lung diseases such as chronic obstructive pulmonary disease (COPD), asthma and pulmonary fibrosis. Rho-associated coiled-coil-forming protein kinase (ROCK) consists as two isoforms, ROCK1 and ROCK2, and both are playing critical roles in many cellular responses to injury. In this study, we aimed to elucidate the differential role of ROCK isoforms on TGF-β signaling in lung fibrosis and repair. For this purpose, we tested the effect of a non-selective ROCK 1 and 2 inhibitor (compound 31) and a selective ROCK2 inhibitor (compound A11) in inhibiting TGF-β-induced remodeling in lung fibroblasts and slices; and dysfunctional epithelial-progenitor interactions in lung organoids. Here, we demonstrated that the inhibition of ROCK1/2 with compound 31 represses TGF-β-driven actin remodeling as well as extracellular matrix deposition in lung fibroblasts and PCLS, whereas selective ROCK2 inhibition with compound A11 did not. Furthermore, the TGF-β induced inhibition of organoid formation was functionally restored in a concentration-dependent manner by both dual ROCK 1 and 2 inhibition and selective ROCK2 inhibition. We conclude that dual pharmacological inhibition of ROCK 1 and 2 counteracts TGF-β induced effects on remodeling and alveolar epithelial progenitor function, suggesting this to be a promising therapeutic approach for respiratory diseases associated with fibrosis and defective lung repair.

Extracellular Vesicles from Airway Secretions: New Insights in Lung Diseases

Lung diseases (LD) are one of the most common causes of death worldwide. Although it is known that chronic airway inflammation and excessive tissue repair are processes associated with LD such as asthma, chronic obstructive pulmonary disease (COPD) or idiopathic pulmonary fibrosis (IPF), their specific pathways remain unclear. Extracellular vesicles (EVs) are heterogeneous nanoscale membrane vesicles with an important role in cell-to-cell communication. EVs are present in general biofluids as plasma or urine but also in secretions of the airway as bronchoalveolar lavage fluid (BALF), induced sputum (IS), nasal lavage (NL) or pharyngeal lavage. Alterations of airway EV cargo could be crucial for understanding LD. Airway EVs have shown a role in the pathogenesis of some LD such as eosinophil increase in asthma, the promotion of lung cancer in vitro models in COPD and as biomarkers to distinguishing IPF in patients with diffuse lung diseases. In addition, they also have a promising future as therapeutics for LD. In this review, we focus on the importance of airway secretions in LD, the pivotal role of EVs from those secretions on their pathophysiology and their potential for biomarker discovery.

Melatonin prevents LPS-induced epithelial-mesenchymal transition in human alveolar epithelial cells via the GSK-3β/Nrf2 pathway

BACKGROUND

Oxidative stress plays a critical role in pulmonary fibrosis after acute lung injury (ALI), and epithelial-mesenchymal transition (EMT) events are involved in this process. The purpose of this study was to investigate the protective effects of melatonin, a natural antioxidant, on lipopolysaccharide (LPS)-induced EMT in human alveolar epithelial cells.

METHODS

Human type II alveolar epithelial cell-derived A549 cells were incubated with LPS and melatonin alone or in combination for up to 24 h. The morphological changes of the treated cells were evaluated as well as indexes of oxidative stress. EMT-related proteins and the Nrf2 signaling pathway were detected by western blot analysis and immunofluorescence staining, respectively. To further investigate the underlying mechanisms, the effects of melatonin on cells transfected Nrf2 short hairpin RNA (shRNA) and the PI3K / GSK-3β signaling pathway were evaluated.

RESULTS

Treatment with melatonin upregulated Nrf2 expression, inhibited LPS-induced cell morphological change, reversed the expressions of EMT-related proteins, and reduced reactive oxygen species (ROS) production in A549 cells, as well as the levels of malondialdehyde (MDA) and anti-oxidative enzymes. Yet, the effects of melatonin were almost completely abolished in cells transfected Nrf2 shRNA. Furthermore, the data demonstrated that melatonin could activate the PI3K/AKT signaling pathway, resulting in phosphorylation of GSK-3β (Ser9) and upregulation of the Nrf2 protein in A549 cells, which ultimately attenuated LPS-induced EMT.

CONCLUSION

The present study is the first to demonstrate that melatonin can protect human alveolar epithelial cells against oxidative stress by effectively inhibiting LPS-induced EMT, which was mostly dependent on upregulation of the Nrf2 pathway via the PI3K/GSK-3β axis. Further studies are warranted to investigate the role of melatonin for the treatment of oxidative stress-associated diseases, as well as pulmonary fibrosis after ALI.

A Novel Fibroblast Reporter Cell Line for in vitro Studies of Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal disease of the lower respiratory tract with restricted therapeutic options. Repetitive injury of the bronchoalveolar epithelium leads to activation of pulmonary fibroblasts, differentiation into myofibroblasts and excessive extracellular matrix (ECM) deposition resulting in aberrant wound repair. However, detailed molecular and cellular mechanisms underlying initiation and progression of fibrotic changes are still elusive. Here, we report the generation of a representative fibroblast reporter cell line (10-4A BFP ) to study pathophysiological mechanisms of IPF in high throughput or high resolution in vitro live cell assays. To this end, we immortalized primary fibroblasts isolated from the distal lung of Sprague-Dawley rats. Molecular and transcriptomic characterization identified clone 10-4A as a matrix fibroblast subpopulation. Mechanical or chemical stimulation induced a reversible fibrotic state comparable to effects observed in primary isolated fibroblasts. Finally, we generated a reporter cell line (10-4A BFP ) to express nuclear blue fluorescent protein (BFP) under the promotor of the myofibroblast marker alpha smooth muscle actin (Acta2) using CRISPR/Cas9 technology. We evaluated the suitability of 10-4A BFP as reporter tool in plate reader assays. In summary, the 10-4A BFP cell line provides a novel tool to study fibrotic processes in vitro to gain new insights into the cellular and molecular processes involved in fibrosis formation and propagation.

Signaling pathways promoting epithelial mesenchymal transition in oral submucous fibrosis and oral squamous cell carcinoma

Epithelial-mesenchymal transition (EMT) is a critical process that occurs during the embryonic development, wound healing, organ fibrosis and the onset of malignancy. Emerging evidence suggests that the EMT is involved in the invasion and metastasis of cancers. The inflammatory reaction antecedent to fibrosis in the onset of oral submucous fibrosis (OSF) and the role of EMT in its malignant transformation indicates a hitherto unexplored involvement of EMT. This review focuses on the role of EMT markers which are regulators of the EMT mediated complex network of molecular mechanisms involved in the pathogenesis of OSF and OSCC. Further the gene enrichment analysis and pathway analysis supports the association of the upregulated and downregulated genes in various EMT regulating pathways.

Brd4-p300 inhibition downregulates Nox4 and accelerates lung fibrosis resolution in aged mice

Tissue regeneration capacity declines with aging in association with heightened oxidative stress. Expression of the oxidant-generating enzyme, NADPH oxidase 4 (Nox4), is elevated in aged mice with diminished capacity for fibrosis resolution. Bromodomain-containing protein 4 (Brd4) is a member of the bromodomain and extraterminal (BET) family of proteins that function as epigenetic "readers" of acetylated lysine groups on histones. In this study, we explored the role of Brd4 and its interaction with the p300 acetyltransferase in the regulation of Nox4 and the in vivo efficacy of a BET inhibitor to reverse established age-associated lung fibrosis. BET inhibition interferes with the association of Brd4, p300, and acetylated histone H4K16 with the Nox4 promoter in lung fibroblasts stimulated with the profibrotic cytokine, TGF-β1. A number of BET inhibitors, including I-BET-762, JQ1, and OTX015, downregulate Nox4 gene expression and activity. Aged mice with established and persistent lung fibrosis recover capacity for fibrosis resolution with OTX015 treatment. This study implicates epigenetic regulation of Nox4 by Brd4 and p300 and supports BET/Brd4 inhibition as an effective strategy for the treatment of age-related fibrotic lung disease.

Neonatal therapy with PF543, a sphingosine kinase 1 inhibitor, ameliorates hyperoxia-induced airway remodeling in a murine model of bronchopulmonary dysplasia

Hyperoxia (HO)-induced lung injury contributes to bronchopulmonary dysplasia (BPD) in preterm newborns. Intractable wheezing seen in BPD survivors is associated with airway remodeling (AWRM). Sphingosine kinase 1 (SPHK1)/sphingosine-1-phosphate (S1P) signaling promotes HO-mediated neonatal BPD; however, its role in the sequela of AWRM is not known. We noted an increased concentration of S1P in tracheal aspirates of neonatal infants with severe BPD, and earlier, demonstrated that Sphk1^-/- mice showed protection against HO-induced BPD. The role of SPHK1/S1P in promoting AWRM following exposure of neonates to HO was investigated in a murine model. Therapy using PF543, the specific SPHK1 inhibitor, during neonatal HO reduced alveolar simplification followed by reduced AWRM in adult mice. This was associated with reduced airway hyperreactivity to intravenous methacholine. Neonatal HO exposure was associated with increased expression of SPHK1 in lung tissue of adult mice, which was reduced with PF543 therapy in the neonatal stage. This was accompanied by amelioration of HO-induced reduction of E-cadherin in airway epithelium. This may be suggestive of arrested partial epithelial mesenchymal transition (EMT) induced by HO. In vitro studies using human primary airway epithelial cells (HAEpCs) showed that SPHK1 inhibition or deletion restored HO-induced reduction in E-cadherin and reduced formation of mitochondrial reactive oxygen species (mtROS). Blocking mtROS with MitoTempo attenuated HO-induced partial EMT of HAEpCs. These results collectively support a therapeutic role for PF543 in preventing HO-induced BPD in neonates and the long-term sequela of AWRM, thus conferring a long-term protection resulting in improved lung development and function.

Paracrine SPARC signaling dysregulates alveolar epithelial barrier integrity and function in lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic scarring disease in which aging, environmental exposure(s) and genetic susceptibility have been implicated in disease pathogenesis, however, the causes and mechanisms of the progressive fibrotic cascade are still poorly understood. As epithelial-mesenchymal interactions are essential for normal wound healing, through human 2D and 3D in vitro studies, we tested the hypothesis that IPF fibroblasts (IPFFs) dysregulate alveolar epithelial homeostasis. Conditioned media from IPFFs exaggerated the wound-healing response of primary human Type II alveolar epithelial cells (AECs). Furthermore, AECs co-cultured with IPFFs exhibited irregular epithelialization compared with those co-cultured with control fibroblasts (NHLFs) or AECs alone, suggesting that epithelial homeostasis is dysregulated in IPF as a consequence of the abnormal secretory phenotype of IPFFs. Secretome analysis of IPFF conditioned media and functional studies identified the matricellular protein, SPARC, as a key mediator in the epithelial-mesenchymal paracrine signaling, with increased secretion of SPARC by IPFFs promoting persistent activation of alveolar epithelium via an integrin/focal adhesion/cellular-junction axis resulting in disruption of epithelial barrier integrity and increased macromolecular permeability. These findings suggest that in IPF fibroblast paracrine signaling promotes persistent alveolar epithelial activation, so preventing normal epithelial repair responses and restoration of tissue homeostasis. Furthermore, they identify SPARC-mediated paracrine signaling as a potential therapeutic target to promote the restoration of lung epithelial homoestasis in IPF patients.

Increased serum calpain activity is associated with HMGB1 levels in systemic sclerosis

Background

Systemic sclerosis (SSc) or scleroderma is an intractable autoimmune disorder that affects multiple organs. The objectives were to investigate clinical correlations of serum calpain activity and high mobility group box 1 (HMGB1) levels with immunological and clinical traits.

Methods

A total of 31 patients with SSc, 20 age- and gender-matched healthy control subjects (HC), and 10 patients with other connective tissue diseases (CTD) were recruited in the study. We measured serum calpain activity and HMGB1 levels and analyzed the datasets (GSE40839, GSE48149, GSE76808, GSE81292, GSE33463, and GSE58095) from Gene Expression Omnibus (GEO) database to explore the potential mechanism by which calpain exerts its function through bioinformatics methods.

Results

Serum calpain activity was significantly increased in patients with SSc compared with those in HC and in patients with CTD and was correlated with serum HMGB1 levels, modified Rodnan skin score, erythrocyte sedimentation rate, mean platelet volume, and plateletcrit. Notably, serum calpain activity and HMGB1 levels in SSc patients with interstitial lung disease (ILD) were significantly higher than those in SSc patients without ILD. Serum calpain activity and HMGB1 levels could be the independent risk factors for SSc-ILD and novel biomarkers in patients with SSc.

Conclusion

This is the first study that reports increased serum calpain activity and the correlation between calpain and HMGB1 in patients with SSc or SSc-ILD. The serum calpain activity and HMGB1 levels may serve as measures of ILD in patients with SSc. Also, calpain and HMGB1 could be potential therapeutic targets for patients with SSc or SSc-ILD in the future.

Nascent Lung Organoids Reveal Epithelium- and Bone Morphogenetic Protein-mediated Suppression of Fibroblast Activation

Reciprocal epithelial-mesenchymal interactions are pivotal in lung development, homeostasis, injury, and repair. Organoids have been used to investigate such interactions, but with a major focus on epithelial responses to mesenchyme and less attention to epithelial effects on mesenchyme. In the present study, we used nascent organoids composed of human and mouse lung epithelial and mesenchymal cells to demonstrate that healthy lung epithelium dramatically represses transcriptional, contractile, and matrix synthetic functions of lung fibroblasts. Repression of fibroblast activation requires signaling via the bone morphogenetic protein (BMP) pathway. BMP signaling is diminished after epithelial injury in vitro and in vivo, and exogenous BMP4 restores fibroblast repression in injured organoids. In contrast, inhibition of BMP signaling in healthy organoids is sufficient to derepress fibroblast matrix synthetic function. Our results reveal potent repression of fibroblast activation by healthy lung epithelium and a novel mechanism by which epithelial loss or injury is intrinsically coupled to mesenchymal activation via loss of repressive BMP signaling.

The role and mechanism of lncRNA NEAT1 in the fibrosis of pulmonary epithelial cell

Background

Pulmonary fibrosis is a serious clinical fatal disease. Epithelial–mesenchymal transition (EMT) and lncRNA NEAT1 have been implied in its development and progression.

Objective

To study the role of lncRNA NEAT1 in the progression of fibrosis in human pulmonary epithelial cells (BEAS-2B). Specifically, BEAS-2B was transfected with NEAT1 and miR-29c, EMT and cell proliferation were measured and the expression level of relevant genes was determined by Western blot.

Result

Results showed that NEAT1 promotes fibrosis and proliferation of BEAS-2B cells via the up-regulation of α-SMA, Vimentin, Snail and proliferation-related genes including Cyclin D1 and Cyclin E; miR-29c is a target gene of NEAT1 and through which NEAT1 regulates EMT and expression of proliferation-related genes.

Conclusion

This study investigated the mechanism of pulmonary fibrosis progression by elucidating the role of NEAT1/miR-29c in the fibrosis and proliferation of BEAS-2B cells, thus providing a basis for the new therapeutic targets of pulmonary fibrosis.

Synthesis and biological activity of thieno[3,2-d]pyrimidines as potent JAK3 inhibitors for the treatment of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a serious and fatal lung disease, with a median survival of only 3-5 years from diagnosis. Janus kinase 3 (JAK3) has a well-established role in the pathogenesis of various autoimmune diseases, including rheumatoid arthritis (RA) and autoimmune-related pulmonary fibrosis. In this study, through the use of a conformationally-constrained design strategy, a series of thieno[3,2-d]pyrimidines were synthesized as potent JAK3 inhibitors for the treatment of IPF. Among them, the most potent JAK3 inhibitor, namely 8e (IC₅₀ = 1.38 nM), significantly reduced the degree of airsacculitis and fibrosis according to hematoxylin-eosin (HE) staining assay for the lung tissue in the bleomycin (BLM)-induced pulmonary fibrosis mouse model. The clear reduction of the lung collagen deposition by the determination of Masson and hydroxyproline (HYP) content also demonstrated its efficacy in the treatment of fibrosis. In addition, 8e also reduced the expression of the inflammatory markers IL-6, IL-17A, TNF-α and malondialdehyde (MDA) in lung tissue, which indicated its higher anti-inflammatory activity compared with that of the reference agents (nintedanib and gefitinib). Furthermore, it possessed low cytotoxicity against normal human bronchial epithelia (HBE) cells (IC₅₀ > 39.0 μM) and C57BL mice. All these evaluated biological properties suggest that 8e may be a potential JAK3 inhibitor for the treatment of IPF.

Investigation on inhibitory effect of folic acid on methotrexate-induced epithelial-mesenchymal transition focusing on dihydrofolate reductase

Use of methotrexate (MTX) can induce serious adverse lung reactions, such as pulmonary fibrosis. Recently, we demonstrated that the epithelial-mesenchymal transition (EMT), which triggers pulmonary fibrosis, was induced by MTX, and folic acid (FA) suppressed MTX-induced EMT in A549 cells. In this study, the role of dihydrofolate reductase (DHFR), a target of MTX, in FA-mediated inhibition of MTX-induced EMT was evaluated. The inhibitory effects of FA and tetrahydrofolate (THF), a metabolite of FA produced by DHFR, on MTX-induced increases in mRNA expression of α-SMA, an EMT marker, were compared. The IC₅₀ values of FA and THF for DHFR were 103.3 and 19.4 μM, respectively. In contrast, DHFR knockdown did not alter the mRNA expression of α-SMA. Notably, the inhibitory effect of FA, but not THF, on MTX-induced EMT was blunted in DHFR knockdown cells. These results suggested that DHFR may not directly contribute to MTX-induced EMT, but may contribute to suppression of MTX-induced EMT via production of THF in A549 cells.

TRB3 regulates pulmonary interstitial fibrosis through the MAPK signaling pathway

This study aims to investigate the effects of TRB3 on the EMT and MAPK signaling pathways in a bleomycin (BLM)-induced pulmonary fibrosis mouse model. TRB3 adenovirus vector with green fluorescent protein (GFP) and TRB3-siRNA adenovirus vector were constructed for overexpression and down-regulation of TRB3, respectively. The pulmonary fibrosis mouse model was induced by bleomycin, and then treated with adenovirus on the next day. The mice were randomly killed at the 7^th (D7), 14^th (D14) and 28^th (D28) day, respectively. The lung tissues were collected for histopathologic observations, hydroxyproline determination, Immunohistochemistry, western blot and RT-qPCR to detect the expression of TRB3 and EMT-related proteins. Overexpression of TRB3 caused more severe pulmonary fibrosis (P<0.05), while downregulation of TRB3 significantly reduced pulmonary fibrosis (P<0.05). The expression of MAPK pathway-related and EMT-related genes and proteins was markedly upregulated by TRB3 overexpression (P<0.05), but prominently downregulated by TRB3-shRNA (P<0.05). In conclusion, exogenous regulation of TRB3 may have effects on bleomycin-induced pulmonary fibrosis in mice.

Biofabrication of phenotypic pulmonary fibrosis assays

Biofabrication techniques have enabled the formation of complex models of many biological tissues. We present a framework to contextualize biofabrication techniques within a disease modeling application. Fibrosis is a progressive disease interfering with tissue structure and function, which stems from an aberrant wound healing response. Epithelial injury and clot formation lead to fibroblast invasion and activation, followed by contraction and remodeling of the extracellular matrix. These stages have healthy wound healing variants in addition to the pathogenic analogs that are seen in fibrosis. This review evaluates biofabrication of a variety of phenotypic cell-based fibrosis assays. By recapitulating different contributors to fibrosis, these assays are able to evaluate biochemical pathways and therapeutic candidates for specific stages of fibrosis pathogenesis. Biofabrication of these culture models may enable phenotypic screening for improved understanding of fibrosis biology as well as improved screening of anti-fibrotic therapeutics.

Mechanisms for the Resolution of Organ Fibrosis

Fibrosis is a dynamic process with the potential for reversibility and restoration of near-normal tissue architecture and organ function. Herein, we review mechanisms for resolution of organ fibrosis, in particular that involving the lung, with an emphasis on the critical roles of myofibroblast apoptosis and clearance of deposited matrix.

Bone marrow mesenchymal stromal cells attenuate silica-induced pulmonary fibrosis potentially by attenuating Wnt/β-catenin signaling in rats

BACKGROUND

Pulmonary fibrosis induced by silica dust is an irreversible, chronic, and fibroproliferative lung disease with no effective treatment at present. Previous studies have shown that early intervention with bone marrow mesenchymal stem/stromal cells (BMSCs) has positive effect on anti-pulmonary fibrosis caused by silica dust. However, early intervention using BMSCs is not practical, and the therapeutic effects of BMSCs advanced intervention on pulmonary fibrosis have rarely been reported. In this study, we investigated the effects of advanced transplantation (on the 28th day after exposure to silica suspension) of BMSCs on an established rat model of pulmonary fibrosis.

METHODS

Sprague Dawley (SD) rats were randomly divided into four groups including (1) control group (n = 6) which were normally fed, (2) silica model group (n = 6) which were exposed to silica suspension (1 mL of 50 mg/mL/rat), (3) BMSC transplantation group (n = 6) which received 1 mL BMSC suspension (2 × 10⁶ cells/mL) by tail vein injection on the 28th day after exposure to silica suspension, and (4) BMSC-CM (conditioned medium) transplantation group (n = 6) which received CM from the same cell number by tail vein injection on the 28th day after exposure to silica suspension. On the 56th day after exposure to silica suspension, we used computed tomography (CT), hematoxylin and eosin (H&E), and Masson's trichrome staining to evaluate the changes in lung tissue. We examined the expression of epithelial-mesenchymal transition (EMT) and Wnt/β-catenin pathway-related proteins in lung tissue using immunohistochemistry and western blotting.

RESULTS

Successful construction of a pulmonary fibrosis model was confirmed by H&E and Masson's trichrome staining on the 28th day after exposure to silica suspension. On the 56th day after exposure, pulmonary CT examination showed a relieving effect of BMSCs on silica-induced pulmonary fibrosis which was confirmed by H&E and Masson's trichrome staining. Treatment of BMSCs increased the expression of epithelial marker proteins including E-cadherin (E-cad) and cytokeratin19 (CK19) and reduced the expression of fibrosis marker proteins including Vimentin (Vim) and α-Smooth actin (α-SMA) after exposure to silica suspension. Furthermore, we found that Wnt/β-catenin signaling pathway is abnormally activated in silica-induced pulmonary fibrosis, and exogenous transplantation of BMSCs may attenuate their expression.

CONCLUSIONS

BMSC transplantation inhibits the EMT to alleviate silica-induced pulmonary fibrosis in rats and the anti-fibrotic effect potentially by attenuating Wnt/β-catenin signaling. ᅟ: ᅟ.

BCL2 Regulates Differentiation of Intestinal Fibroblasts

BACKGROUND

Fibrosis in patients with Crohn's disease (CD) results from an imbalance toward excessive fibrous tissue formation driven by fibroblasts. Activation of fibroblasts is linked to the B-cell lymphoma 2 (BCL2) family, which is involved in the induction of apoptosis. We investigated the impact of BCL2 repression on fibrogenesis.

METHODS

The model of dextran sodium sulfate (DSS)-induced chronic colitis and the heterotopic transplantation model of fibrosis were used. Following the administration of the BCL2 antagonist (ABT-737, 50 mg/kg/d), collagen layer thickness and hydroxyproline (HYP) content were determined. Fibroblasts were stimulated with the BCL2 antagonist (0.01-100 µM). BCL2, alpha smooth muscle actin (αSMA), and collagen I (COL1A1) were determined by quantitative polymerase chain reaction (qPCR), immunofluorescence microscopy (IF), and western blot (WB). mRNA expression pattern was determined by next-generation sequencing (NGS).

RESULTS

Collagen layer thickness was significantly decreased in both DSS-induced chronic colitis and the transplantation model of fibrosis upon BCL2 antagonist administration compared with vehicle. Decreased HYP content confirmed the preventive effects of the BCL2 antagonist on fibrosis. In vitro, a significant increase in PI+/annexin V+ human colonic fibroblasts was determined by fluorescence-activated cell sorting upon treatment with high-dose BCL2 antagonist; at a lower dose, αSMA, COL1A1, and TGF were decreased. NGS, IF, and qPCR revealed decreased expression and nuclear translocation of GATA6 and SOX9, known for reprogramming fibroblasts.

CONCLUSION

BCL2 antagonist administration partially prevented fibrogenesis in both fibrosis models. The BCL2 antagonist reduced the expression of TGFβ-induced factors involved in differentiation of myofibroblasts, and therefore might represent a potential treatment option against CD-associated fibrosis.