The Bleomycin Model of Pulmonary Fibrosis

Geniposide ameliorates bleomycin-induced pulmonary fibrosis in mice by inhibiting TGF-β/Smad and p38MAPK signaling pathways

Pulmonary fibrosis (PF) is an interstitial lung disease characterized by inflammation and fibrotic changes, with an unknown cause. In the early stages of PF, severe inflammation leads to the destruction of lung tissue, followed by upregulation of fibrotic factors like Transforming growth factor-β (TGF-β) and connective tissue growth factor (CTGF), which disrupt normal tissue repair. Geniposide, a natural iridoid glycoside primarily derived from the fruits of Gardenia jasminoides Ellis, possesses various pharmacological activities, including liver protection, choleretic effects, and anti-inflammatory properties. In this study, we investigated the effects of Geniposide on chronic inflammation and fibrosis induced by bleomycin (BLM) in mice with pulmonary fibrosis (PF). PF was induced by intratracheal instillation of bleomycin, and Geniposide(100/50/25mg•kg-1) was orally administered to the mice once a day until euthanasia(14 day/28 day). The Raw264.7 cell inflammation induced by LPS was used to evaluate the effect of Geniposide on the activation of macrophage. Our results demonstrated that Geniposide reduced lung coefficients, decreased the content of Hydroxyproline, and improved pathological changes in lung tissue. It also reduced the number of inflammatory cells and levels of pro-inflammatory cytokines in bronchoalveolar lavage fluid (BALF) of bleomycin-induced PF mice. At the molecular level, Geniposide significantly down-regulated the expression of TGF-β1, Smad2/3, p38, and CTGF in lung tissues of PF mice induced by bleomycin. Molecular docking results revealed that Geniposide exhibited good binding activity with TGF-β1, Smad2, Smad3, and p38. In vitro study showed Geniposide directly inhibited the activation of macrophage induced by LPS. In conclusion, our findings suggest that Geniposide can ameliorate bleomycin-induced pulmonary fibrosis in mice by inhibiting the TGF-β/Smad and p38MAPK signaling pathways.

Metabolic profiling of idiopathic pulmonary fibrosis in a mouse model: implications for pathogenesis and biomarker discovery

Background

Alterations in metabolites and metabolic pathways are thought to be important triggers of idiopathic pulmonary fibrosis (IPF), but our lack of a comprehensive understanding of this process has hampered the development of IPF-targeted drugs.

Methods

To fully understand the metabolic profile of IPF, C57BL/6 J male mice were injected intratracheally with bleomycin so that it could be used to construct a mouse model of IPF, and lung tissues from 28-day and control IPF mice were analyzed by pathology and immunohistochemistry. In addition, serum metabolites from IPF mice were examined using LC-ESI-MS/MS, and the differential metabolites were analyzed for KEGG metabolic pathways and screened for biomarkers using machine learning algorithms.

Results

In total, the levels of 1465 metabolites were detected, of which 104 metabolites were significantly altered after IPF formation. In IPF mouse serum, 52% of metabolite expression was downregulated, with lipids (e.g., GP, FA) and organic acids and their derivatives together accounting for more than 70% of the downregulated differentially expressed metabolites. In contrast, FA and oxidised lipids together accounted for 60% of the up-regulated differentially expressed metabolites. KEGG pathway enrichment analyses of differential metabolites were mainly enriched in the biosynthesis of unsaturated fatty acids, pentose phosphate pathway, and alanine, aspartate, and glutamate metabolism. Seven metabolites were screened by machine learning LASSO models and evaluated as ideal diagnostic tools by receiver operating characteristic curves (ROCs).

Discussion

In conclusion, the serum metabolic disorders found to be associated with pulmonary fibrosis formation will help to deepen our understanding of the pathogenesis of pulmonary fibrosis.

Interstitial Lung Diseases and Non-Small Cell Lung Cancer: Particularities in Pathogenesis and Expression of Driver Mutations

INTRODUCTION

Interstitial lung diseases are a varied group of diseases associated with chronic inflammation and fibrosis. With the emerging and current treatment options, survival rates have vastly improved. Having in mind that the most common type is idiopathic pulmonary fibrosis and that a significant proportion of these patients will develop lung cancer as the disease progresses, prompt diagnosis and personalized treatment of these patients are fundamental.

SCOPE AND METHODS

The scope of this review is to identify and characterize molecular and pathogenetic pathways that can interconnect Interstitial Lung Diseases and lung cancer, especially driver mutations in patients with NSCLC, and to highlight new and emerging treatment options in that view.

RESULTS

Common pathogenetic pathways have been identified in sites of chronic inflammation in patients with interstitial lung diseases and lung cancer. Of note, the expression of driver mutations in EGFR, BRAF, and KRAS G12C in patients with NSCLC with concurrent interstitial lung disease is vastly different compared to those patients with NSCLC without Interstitial Lung Disease.

CONCLUSIONS

NSCLC in patients with Interstitial Lung Disease is a challenging diagnostic and clinical entity, and a personalized medicine approach is fundamental to improving survival and quality of life. Newer anti-fibrotic medications have improved survival in IPF/ILD patients; thus, the incidence of lung cancer is going to vastly increase in the next 5-10 years.

Shengxian decoction improves lung function in rats with bleomycin-induced idiopathic pulmonary fibrosis through the inhibition of PANoptosis

ETHNOPHARMACOLOGICAL RELEVANCE

Shengxian decoction (SXD) is a classic Chinese medicinal formula that can effectively improve clinical symptoms and quality of life and delay disease progression in idiopathic pulmonary fibrosis (IPF) patients; however, the underlying mechanisms remain unclear.

AIM OF THE STUDY

This study aimed to observe PANoptosis in bleomycin-induced IPF and to assess the efficacy and mechanism of action of SXD in the treatment of IPF.

MATERIALS AND METHODS

Fifty SD rats were randomly divided into the sham, IPF, IPF + pirfenidone (PFD), IPF + SXD-medium dose (SXD-M), and IPF + SXD-low dose (SXD-L) groups. Lung function analysis and microcomputed tomography imaging of the rats with IPF treated with oral pirfenidone or oral SXD for 28 days were performed. Hematoxylin and eosin (HE) staining and Masson's trichrome staining were used to observe pathological lung damage. Enzyme-linked immunosorbent assays (ELISAs) were used to determine the serum levels of IL-1β, IL-18, TNF-α, and IFN-γ. Pyroptosis, apoptosis, and necroptosis were assessed using TUNEL, TUNEL/caspase-1, and PI fluorescence staining, respectively. GSDMD, caspase-3, and MLKL were examined by immunohistochemistry. The expression of fibrin-, ZBP1-, pyroptosis-, apoptosis-, and necroptosis-related proteins in the lung tissue was determined by western blotting.

RESULTS

SXD normalized lung function in rats with bleomycin-induced IPF and reduced serum inflammatory factor levels and lung tissue fibrosis. The underlying mechanism of action involves the inhibition of pyroptosis pathway proteins, such as NLRP3, caspase-1, cleaved caspase-1, and GSDMD; apoptotic pathway proteins, such as Bax, Bcl-2, cleaved caspase-3, and caspase-3; and necroptosis pathway proteins, such as RIPK1, RIPK3, p-MLKL and MLKL. These pathways are modulated by the PANoptosis initiator ZBP1. Notably, the efficacy of SXD is concentration dependent, with a medium dose exhibiting superior effectiveness compared to a low dose.

CONCLUSION

Bleomycin induced PANoptosis in the lung tissue of rats with IPF. Additionally, SXD effectively delayed or reversed the early pathological changes in bleomycin-induced pulmonary fibrosis by inhibiting PANoptosis.

Carvacrol protects rats against bleomycin-induced lung oxidative stress, inflammation, and fibrosis

The main objective of this study was to investigate the potential efficacy of carvacrol (CAR) in mitigating bleomycin (BLM)-induced pulmonary fibrosis (PF). Sixty-six male Wistar rats were assigned into two main groups of 7 and 21 days. They were divided into the subgroups of control, BLM, CAR 80 (only for the 21-day group), and CAR treatment groups. The CAR treatment groups received CAR (20, 40, and 80 mg/kg, orally) for 7 or 21 days after an instillation of BLM (5 mg/kg, intratracheally). Results indicated that BLM significantly increased total cell count in bronchoalveolar lavage fluid and the percentages of neutrophils and lymphocytes, and reduced the percentage of macrophages. CAR dose-dependently decreased total cell count and the percentage of neutrophils and lymphocytes. CAR significantly reduced thiobarbituric acid reactive substances and hydroxyproline levels and elevated the total thiol level and catalase, superoxide dismutase, and glutathione peroxidase activities in BLM-exposed rats. Furthermore, CAR decreased the transforming growth factor-β1, connective transforming growth factor, and tumor necrosis factor-α on days 7 and 21. BLM increased interferon-γ on day 7 but decreased its level on day 21. However, CAR reversed interferon-γ levels on days 7 and 21. Based on histopathological findings, BLM induced inflammation on days 7 and 21, but for induction of fibrosis, 21-day study showed more fibrotic injuries than the 7-day group. CAR showed the improvement of fibrotic injuries. The effect of CAR against BLM-induced pulmonary fibrosis is possibly due to its antioxidant, anti-inflammatory, and antifibrotic activity.

Ziziphus spina-christi L. extract attenuates bleomycin-induced lung fibrosis in mice via regulating TGF-β1/SMAD pathway: LC-MS/MS Metabolic profiling, chemical composition, and histology studies

Ancient Egyptians (including Bedouins and Nubians) have long utilized Ziziphus spina-christi (L.), a traditional Arabian medicinal herb, to alleviate swellings and inflammatory disorders. It is also mentioned in Christian and Muslim traditions. Ziziphus spina-christi L. (Family: Rhamnaceae) is a plentiful source of polyphenols, revealing free radical scavenging, antioxidant, metal chelating, cytotoxic, and anti-inflammatory activities. Herein, different classes of the existing bioactive metabolites in Z. spina-christi L. were detected using liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the first time. The study also aimed to assess the anti-inflammatory and antifibrotic properties of Z. spina-christi L. extract against bleomycin-induced lung fibrosis in an experimental mouse model. 32 male Swiss Albino mice were assigned into 4 groups; the first and second were the normal control group and the bleomycin positive control (single 2.5 U/kg bleomycin intratracheal dose). The third and fourth groups received 100 and 200 mg/kg/day Z. spina-christi L. extract orally for 3 weeks, 2 weeks before bleomycin, and 1 week after. The bioactive metabolites in Z. spina-christi L. extract were identified as phenolic acids, catechins, flavonoids, chalcones, stilbenes, triterpenoid acids, saponins, and sterols. The contents of total phenolic compounds and flavonoids were found to be 196.62 mg GAE/gm and 33.29 mg QE/gm, respectively. In the experimental study, histopathological examination revealed that lung fibrosis was attenuated in both Z. spina-christi L.- treated groups. Z. spina-christi L. extract downregulated the expression of nuclear factor kappa B (NF-κB) p65 and decreased levels of the inflammatory markers tumor necrosis factor-alpha (TNF-α), monocyte chemoattractant protein-1 (MCP-1), and c-Jun N-terminal kinase (JNK) in lung tissue. Z. spina-christi L. also downregulated the expression of the fibrotic parameters collagen-1, alpha-smooth muscle actin (α-SMA), transforming growth factor-beta 1 (TGF-β1), matrix metalloproteinase-9 (MMP-9) and SMAD3, with upregulation of the antifibrotic SMAD7 in lung tissue. Overall, the present study suggests a potential protective effect of Z. spina-christi L. extract against bleomycin-induced lung fibrosis through regulation of the TGF-β1/SMAD pathway.

RNA-sequencing reveals differential fibroblast responses to bleomycin and pneumonectomy

Pulmonary fibrosis is characterized by pathological accumulation of scar tissue in the lung parenchyma. Many of the processes that are implicated in fibrosis, including increased extracellular matrix synthesis, also occur following pneumonectomy (PNX), but PNX instead results in regenerative compensatory growth of the lung. As fibroblasts are the major cell type responsible for extracellular matrix production, we hypothesized that comparing fibroblast responses to PNX and bleomycin (BLM) would unveil key differences in the role they play during regenerative versus fibrotic lung responses. RNA-sequencing was performed on flow-sorted fibroblasts freshly isolated from mouse lungs 14 days after BLM, PNX, or sham controls. RNA-sequencing analysis revealed highly similar biological processes to be involved in fibroblast responses to both BLM and PNX, including TGF-β1 and TNF-α. Interestingly, we observed smaller changes in gene expression after PNX than BLM at Day 14, suggesting that the fibroblast response to PNX may be muted by expression of transcripts that moderate pro-fibrotic pathways. Itpkc, encoding inositol triphosphate kinase C, was a gene uniquely up-regulated by PNX and not BLM. ITPKC overexpression in lung fibroblasts antagonized the pro-fibrotic effect of TGF-β1. RNA-sequencing analysis has identified considerable overlap in transcriptional changes between fibroblasts following PNX and those overexpressing ITPKC.

PGC1-Alpha/Sirt3 Signaling Pathway Mediates the Anti-Pulmonary Fibrosis Effect of Hirudin by Inhibiting Fibroblast Senescence

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive fibrotic lung disease for which there is a lack of effective pharmacological treatments. Hirudin, a natural peptide extracted from leeches, has been used for broad pharmacological purposes. In this study, we investigated the therapeutic effects of hirudin on IPF and its related mechanism of action. By constructing a mouse model of pulmonary fibrosis and treating it with hirudin in vivo, we found that hirudin exerted anti-fibrotic, anti-oxidative, and anti-fibroblast senescence effects. Moreover, using an in vitro model of stress-induced premature senescence in primary mouse lung fibroblasts and treating with hirudin, we observed inhibition of fibroblast senescence and upregulation of PGC1-alpha and Sirt3 expression. However, specific silencing of PGC1-alpha or Sirt3 suppressed the anti-fibroblast senescence effect of hirudin. Thus, the PGC1-alpha/Sirt3 pathway mediates the anti-fibroblast senescence effect of hirudin, potentially serving as a molecular mechanism underlying its anti-fibrosis and anti-oxidative stress effects exerted on the lungs.

Noninvasive assessment of the lung inflammation-fibrosis axis by targeted imaging of CMKLR1

Precision management of fibrotic lung diseases is challenging due to their diverse clinical trajectories and lack of reliable biomarkers for risk stratification and therapeutic monitoring. Here, we validated the accuracy of CMKLR1 as an imaging biomarker of the lung inflammation-fibrosis axis. By analyzing single-cell RNA sequencing datasets, we demonstrated CMKLR1 expression as a transient signature of monocyte-derived macrophages (MDMφ) enriched in patients with idiopathic pulmonary fibrosis (IPF). Consistently, we identified MDMφ as the major driver of the uptake of CMKLR1-targeting peptides in a murine model of bleomycin-induced lung fibrosis. Furthermore, CMKLR1-targeted positron emission tomography in the murine model enabled quantification and spatial mapping of inflamed lung regions infiltrated by CMKLR1-expressing macrophages and emerged as a robust predictor of subsequent lung fibrosis. Last, high CMKLR1 expression by bronchoalveolar lavage cells identified an inflammatory endotype of IPF with poor survival. Our investigation supports the potential of CMKLR1 as an imaging biomarker for endotyping and risk stratification of fibrotic lung diseases.

Assessing Lung Fibrosis with ML-Assisted Minimally Invasive OCT Imaging

This paper presents a combined optical coherence tomography (OCT) imaging/machine learning (ML) technique for real-time analysis of lung tissue morphology to determine the presence and level of invasiveness of idiopathic lung fibrosis (ILF). This is an important clinical problem as misdiagnosis is common, resulting in patient exposure to costly and invasive procedures and substantial use of healthcare resources. Therefore, biopsy is needed to confirm or rule out radiological findings. Videoscopic-assisted thoracoscopic wedge biopsy (VATS) under general anesthesia is typically necessary to obtain enough tissue to make an accurate diagnosis. This kind of biopsy involves the placement of several tubes through the chest wall, one of which is used to cut off a piece of lung to send for evaluation. The removed tissue is examined histopathologically by microscopy to confirm the presence and the pattern of fibrosis. However, VATS pulmonary biopsy can have multiple side effects, including inflammation, tissue morbidity, and severe bleeding, which further degrade the quality of life for the patient. Furthermore, the results are not immediately available, requiring tissue processing and analysis. Here, we report an initial attempt of using ML-assisted polarization sensitive OCT (PS-OCT) imaging for lung fibrosis assessment. This approach has been preliminarily tested on a rat model of lung fibrosis. Our preliminary results show that ML-assisted PS-OCT imaging can detect the presence of ILF with an average of 77% accuracy and 89% specificity.

Diallyl disulfide, the bioactive component of Allium species, ameliorates pulmonary fibrosis by mediating the crosstalk of farnesoid X receptor and yes-associated protein 1 signaling pathway

Environmental pollution, virus infection, allergens, and other factors may cause respiratory disease, which could be improved by dietary therapy. Allium species are common daily food seasoning and have high nutritional and medical value. Diallyl disulfide (DADS) is the major volatile oil compound of Allium species. The present study aims to explore the preventive effect and potential mechanism of DADS on pulmonary fibrosis. C57BL/6J mice were intratracheally injected with bleomycin (BLM) to establish pulmonary fibrosis and then administrated with DADS. Primary lung fibroblasts or A549 were stimulated with BLM, followed by DADS, farnesoid X receptor (FXR) agonist (GW4064), yes-associated protein 1 (YAP1) inhibitor (verteporfin), or silencing of FXR and YAP1. In BLM-stimulated mice, DADS significantly ameliorated histopathological changes and interleukin-1β levels in bronchoalveolar lavage fluid. DADS decreased fibrosis markers, HIF-1α, inflammatory cytokines, and epithelial-mesenchymal transition in pulmonary mice and activated fibroblasts. DADS significantly enhanced FXR expression and inhibited YAP1 activation, which functions as GW4064 and verteporfin. A deficiency of FXR or YAP1 could result in the increase of these two protein expressions, respectively. DADS ameliorated extracellular matrix deposition, hypoxia, epithelial-mesenchymal transition, and inflammation in FXR or YAP1 knockdown A549. Taken together, targeting the crosstalk of FXR and YAP1 might be the potential mechanism for DADS against pulmonary fibrosis. DADS can serve as a potential candidate or dietary nutraceutical supplement for the treatment of pulmonary fibrosis.

A mouse model of TB-associated lung fibrosis reveals persistent inflammatory macrophage populations during treatment

Post-TB lung disease (PTLD) causes a significant burden of global disease. Fibrosis is a central component of many clinical features of PTLD. To date, we have a limited understanding of the mechanisms of TB-associated fibrosis and how these mechanisms are similar to or dissimilar from other fibrotic lung pathologies. We have adapted a mouse model of TB infection to facilitate the mechanistic study of TB-associated lung fibrosis. We find that the morphologies of fibrosis that develop in the mouse model are similar to the morphologies of fibrosis observed in human tissue samples. Using Second Harmonic Generation (SHG) microscopy, we are able to quantify a major component of fibrosis, fibrillar collagen, over time and with treatment. Inflammatory macrophage subpopulations persist during treatment; matrix remodeling enzymes and inflammatory gene signatures remain elevated. Our mouse model suggests that there is a therapeutic window during which adjunctive therapies could change matrix remodeling or inflammatory drivers of tissue pathology to improve functional outcomes after treatment for TB infection.

Specneuzhenide improves bleomycin-induced pulmonary fibrosis in mice via AMPK-dependent reduction of PD-L1

BACKGROUND

Pulmonary fibrosis (PF) is an escalating global health issue, characterized by rising rates of morbidity and mortality annually. Consequently, further investigation of potential damage mechanisms and potential preventive strategies for PF are warranted. Specnuezhenide (SPN), a prominent secoiridoid compound derived from Ligustrum lucidum Ait, exhibits anti-inflammatory and anti-oxidative capacities, indicating the potential therapeutic actions on PF. However, the underlying mechanisms of SPN on PF remain unclear.

PURPOSE

This work was aimed at investigating the protective actions of SPN on PF and the potential mechanism.

METHODS

In vivo, mice were administrated with bleomycin (BLM) to establish PF model. PF mice were treated with SPN (45/90 mg/kg) by gavage. In vitro, we employed TGF-β1 (10 ng/mL)-induced MLE-12 and PLFs cells, which then were treated with SPN (5, 10, 20 µM). DARTS assay, biofilm interference experiment and molecular docking were performed to investigate the molecular target of SPN.

RESULTS

In vivo, we found SPN treatment improved survival rate, alleviated pathological changes through reducing BLM-induced extracellular matrix (ECM) deposition, as well as BLM-induced epithelial-mesenchymal transition (EMT). In vitro, SPN inhibited EMT and lung fibroblast transdifferentiation. Mechanistically, SPN activated the AMPK protein to decrease the abnormally high level of PD-L1. Furthermore, the compound C, known as an AMPK inhibitor, exhibited a significant hindrance to the inhibition of SPN on TGF-β1-caused fibroblast transdifferentiation and proliferation. This outcome could be attributed to the fact that compound C could eliminate the inhibitory effects of SPN on PD-L1 expression. Interestingly, DARTS assay, biofilm interference experiment and molecular docking results all indicated that SPN could bind to AMPK, which suggested that SPN might be a potential agonist targeting AMPK protein.

CONCLUSION

Altogether, the results in our work illustrated that SPN promoted AMPK-dependent reduction of PD-L1 protein, contributing to the inhibition of fibrosis progression. Thus, SPN may represent a potential AMPK agonist for PF treatment.

Bortezomib restrains M2 polarization and reduces CXCL16-associated CXCR6+CD4 T cell chemotaxis in bleomycin-induced pulmonary fibrosis

BACKGROUND

The development of pulmonary fibrosis involves a cascade of events, in which inflammation mediated by immune cells plays a pivotal role. Chemotherapeutic drugs have been shown to have dual effects on fibrosis, with bleomycin exacerbating pulmonary fibrosis and bortezomib alleviating tissue fibrotic processes. Understanding the intricate interplay between chemotherapeutic drugs, immune responses, and pulmonary fibrosis is likely to serve as the foundation for crafting tailored therapeutic strategies.

METHODS

A model of bleomycin-induced pulmonary fibrosis was established, followed by treatment with bortezomib. Tissue samples were collected for analysis of immune cell subsets and functional assessment by flow cytometry and in vitro cell experiments. Additionally, multi-omics analysis was conducted to further elucidate the expression of chemokines and chemokine receptors, as well as the characteristics of cell populations.

RESULTS

Here, we observed that the expression of CXCL16 and CXCR6 was elevated in the lung tissue of a pulmonary fibrosis model. In the context of pulmonary fibrosis or TGF-β1 stimulation in vitro, macrophages exhibited an M2-polarized phenotype and secreted more CXCL16 than those of the control group. Moreover, flow cytometry revealed increased expression levels of CD69 and CXCR6 in pulmonary CD4 T cells during fibrosis progression. The administration of bortezomib alleviated bleomycin-induced pulmonary fibrosis, accompanied by reduced ratio of M2-polarized macrophages and decreased accumulation of CD4 T cells expressing CXCR6.

CONCLUSIONS

Our findings provide insights into the key immune players involved in bleomycin-induced pulmonary fibrosis and offer preclinical evidence supporting the repurposing strategy and combination approaches to reduce lung fibrosis.

The impact of formaldehyde exposure on lung inflammatory disorders: Insights into asthma, bronchitis, and pulmonary fibrosis

Lung inflammatory disorders are a major global health burden, impacting millions of people and raising rates of morbidity and death across many demographic groups. An industrial chemical and common environmental contaminant, formaldehyde (FA) presents serious health concerns to the respiratory system, including the onset and aggravation of lung inflammatory disorders. Epidemiological studies have shown significant associations between FA exposure levels and the incidence and severity of several respiratory diseases. FA causes inflammation in the respiratory tract via immunological activation, oxidative stress, and airway remodelling, aggravating pre-existing pulmonary inflammation and compromising lung function. Additionally, FA functions as a respiratory sensitizer, causing allergic responses and hypersensitivity pneumonitis in sensitive people. Understanding the complicated processes behind formaldehyde-induced lung inflammation is critical for directing targeted strategies aimed at minimizing environmental exposures and alleviating the burden of formaldehyde-related lung illnesses on global respiratory health. This abstract explores the intricate relationship between FA exposure and lung inflammatory diseases, including asthma, bronchitis, allergic inflammation, lung injury and pulmonary fibrosis.

[Idiopathic pulmonary fibrosis: Desperately seeking a model]

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive and fatal lung disease of which the origin and development mechanisms remain unknown. The few available pharmacological treatments can only slow the progression of the disease. The development of curative treatments is hampered by the absence of experimental models that can mimic the specific pathophysiological mechanisms of IPF. The aim of this mini-review is to provide an overview of the most commonly used experimental animal models in the study of IPF and to underline the urgent need to seek out new, more satisfactory models.

Exploring therapeutic targets for molecular therapy of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis is a chronic and progressive interstitial lung disease with a poor prognosis. Idiopathic pulmonary fibrosis is characterized by repeated alveolar epithelial damage leading to abnormal repair. The intercellular microenvironment is disturbed, leading to continuous activation of fibroblasts and myofibroblasts, deposition of extracellular matrix, and ultimately fibrosis. Moreover, pulmonary fibrosis was also found as a COVID-19 complication. Currently, two drugs, pirfenidone and nintedanib, are approved for clinical therapy worldwide. However, they can merely slow the disease's progression rather than rescue it. These two drugs have other limitations, such as lack of efficacy, adverse effects, and poor pharmacokinetics. Consequently, a growing number of molecular therapies have been actively developed. Treatment options for IPF are becoming increasingly available. This article reviews the research platform, including cell and animal models involved in molecular therapy studies of idiopathic pulmonary fibrosis as well as the promising therapeutic targets and their development progress during clinical trials. The former includes patient case/control studies, cell models, and animal models. The latter includes transforming growth factor-beta, vascular endothelial growth factor, platelet-derived growth factor, fibroblast growth factor, lysophosphatidic acid, interleukin-13, Rho-associated coiled-coil forming protein kinase family, and Janus kinases/signal transducers and activators of transcription pathway. We mainly focused on the therapeutic targets that have not only entered clinical trials but were publicly published with their clinical outcomes. Moreover, this work provides an outlook on some promising targets for further validation of their possibilities to cure the disease.

Dedifferentiated early postnatal lung myofibroblasts redifferentiate in adult disease

Alveolarization ensures sufficient lung surface area for gas exchange, and during bulk alveolarization in mice (postnatal day [P] 4.5-14.5), alpha-smooth muscle actin (SMA)+ myofibroblasts accumulate, secrete elastin, and lay down alveolar septum. Herein, we delineate the dynamics of the lineage of early postnatal SMA+ myofibroblasts during and after bulk alveolarization and in response to lung injury. SMA+ lung myofibroblasts first appear at ∼ P2.5 and proliferate robustly. Lineage tracing shows that, at P14.5 and over the next few days, the vast majority of SMA+ myofibroblasts downregulate smooth muscle cell markers and undergo apoptosis. Of note, ∼8% of these dedifferentiated cells and another ∼1% of SMA+ myofibroblasts persist to adulthood. Single cell RNA sequencing analysis of the persistent SMA- cells and SMA+ myofibroblasts in the adult lung reveals distinct gene expression profiles. For instance, dedifferentiated SMA- cells exhibit higher levels of tissue remodeling genes. Most interestingly, these dedifferentiated early postnatal myofibroblasts re-express SMA upon exposure of the adult lung to hypoxia or the pro-fibrotic drug bleomycin. However, unlike during alveolarization, these cells that re-express SMA do not proliferate with hypoxia. In sum, dedifferentiated early postnatal myofibroblasts are a previously undescribed cell type in the adult lung and redifferentiate in response to injury.

Multiphase micro-computed tomography reconstructions provide dynamic respiratory function in a mouse lung fibrosis model

Micro-computed tomography derived functional biomarkers used in lung disease research can significantly complement end-stage histomorphometric measures while also allowing for longitudinal studies. However, no approach for visualizing lung dynamics across a full respiratory cycle has yet been described. Using bleomycin-induced lung fibrosis and the antifibrotic drug nintedanib as a test model, we implemented a four-dimensional (4D) micro-CT imaging approach consisting of 30 reconstructed volumes per respiratory cycle, coupled with deep-learning-assisted segmentation of lung volumes. 4D micro-CT provided an accurate description of inhalatory and exhalatory lung dynamics under resting conditions and revealed an inflammation-related obstructive pattern at day 7, followed by a restrictive pattern associated with fibrosis development at day 21. A milder restriction and fibrotic pathology resulted from nintedanib treatment. The similarity of 4D micro-CT data with those produced by diagnostic measurements, also points to its great potential as an exploratory tool for the discovery of clinically relevant therapeutic compounds.

Sirtuin 6 ameliorates bleomycin-induced pulmonary fibrosis via activation of lipid catabolism

Pulmonary fibrosis is a chronic and serious interstitial lung disease with little effective therapies currently. Our incomplete understanding of its pathogenesis remains obstacles in therapeutic developments. Sirtuin 6 (SIRT6) has been shown to mitigate multiple organic fibrosis. However, the involvement of SIRT6-mediated metabolic regulation in pulmonary fibrosis remains unclear. Here, we demonstrated that SIRT6 was predominantly expressed in alveolar epithelial cells in human lung tissues by using a single-cell sequencing database. We showed that SIRT6 protected against bleomycin-induced injury of alveolar epithelial cells in vitro and pulmonary fibrosis of mice in vivo. High-throughput sequencing revealed enriched lipid catabolism in Sirt6 overexpressed lung tissues. Mechanismly, SIRT6 ameliorates bleomycin-induced ectopic lipotoxicity by enhancing lipid degradation, thereby increasing the energy supply and reducing the levels of lipid peroxides. Furthermore, we found that peroxisome proliferator-activated receptor α (PPARα) was essential for SIRT6-mediated lipid catabolism, anti-inflammatory responses, and antifibrotic signaling. Our data suggest that targeting SIRT6-PPARα-mediated lipid catabolism could be a potential therapeutic strategy for diseases complicated with pulmonary fibrosis.

Modeling Molecular Pathogenesis of Idiopathic Pulmonary Fibrosis-Associated Lung Cancer in Mice

Idiopathic pulmonary fibrosis (IPF) is characterized by progressive, often fatal loss of lung function due to overactive collagen production and tissue scarring. Patients with IPF have a sevenfold-increased risk of developing lung cancer. The COVID-19 pandemic has increased the number of patients with lung diseases, and infection can worsen prognoses for those with chronic lung diseases and disease-associated cancer. Understanding the molecular pathogenesis of IPF-associated lung cancer is imperative for identifying diagnostic biomarkers and targeted therapies that will facilitate prevention of IPF and progression to lung cancer. To understand how IPF-associated fibroblast activation, matrix remodeling, epithelial-to-mesenchymal transition (EMT), and immune modulation influences lung cancer predisposition, we developed a mouse model to recapitulate the molecular pathogenesis of pulmonary fibrosis-associated lung cancer using the bleomycin and Lewis lung carcinoma models. We demonstrate that development of pulmonary fibrosis-associated lung cancer is likely linked to increased abundance of tumor-associated macrophages and a unique gene signature that supports an immune-suppressive microenvironment through secreted factors. Not surprisingly, preexisting fibrosis provides a pre-metastatic niche and results in augmented tumor growth, and tumors associated with bleomycin-induced fibrosis are characterized by a dramatic loss of cytokeratin expression, indicative of EMT.

IMPLICATIONS

This characterization of tumors associated with lung diseases provides new therapeutic targets that may aid in the development of treatment paradigms for lung cancer patients with preexisting pulmonary diseases.

8-Oxoguanine DNA glycosylase protects cells from senescence via the p53-p21 pathway

Cellular senescence is an important factor leading to pulmonary fibrosis. Deficiency of 8-oxoguanine DNA glycosylase (OGG1) in mice leads to alleviation of bleomycin (BLM)-induced mouse pulmonary fibrosis, and inhibition of the OGG1 enzyme reduces the epithelial mesenchymal transition (EMT) in lung cells. In the present study, we find decreased expression of OGG1 in aged mice and BLM-induced cell senescence. In addition, a decrease in OGG1 expression results in cell senescence, such as increases in the percentage of SA-β-gal-positive cells, and in the p21 and p-H2AX protein levels in response to BLM in lung cells. Furthermore, OGG1 promotes cell transformation in A549 cells in the presence of BLM. We also find that OGG1 siRNA impedes cell cycle progression and inhibits the levels of telomerase reverse transcriptase (TERT) and LaminB1 in BLM-treated lung cells. The increase in OGG1 expression results in the opposite phenomenon. The mRNA levels of senescence-associated secretory phenotype (SASP) components, including IL-1α, IL-1β, IL-6, IL-8, CXCL1/CXCL2, and MMP-3, in the absence of OGG1 are obviously increased in A549 cells treated with BLM. Interestingly, we demonstrate that OGG1 binds to p53 to inhibit the activation of p53 and that silencing of p53 reverses the inhibition of OGG1 on senescence in lung cells. Additionally, the augmented cell senescence is shown in vivo in OGG1-deficient mice. Overall, we provide direct evidence in vivo and in vitro that OGG1 plays an important role in protecting tissue cells against aging associated with the p53 pathway.

Advocating for Generalizability: Accepting Inherent Variability in Translation of Animal Research Outcomes

Advancing scientific discovery requires investigators to embrace research practices that increase transparency and disclosure about materials, methods, and outcomes. Several research advocacy and funding organizations have produced guidelines and recommended practices to enhance reproducibility through detailed and rigorous research approaches; however, confusion around vocabulary terms and a lack of adoption of suggested practices have stymied successful implementation. Although reproducibility of research findings cannot be guaranteed due to extensive inherent variables in attempts at experimental repetition, the scientific community can advocate for generalizability in the application of data outcomes to ensure a broad and effective impact on the comparison of animals to translation within human research. This report reviews suggestions, based upon work with National Institutes of Health advisory groups, for improving rigor and transparency in animal research through aspects of experimental design, statistical assessment, and reporting factors to advocate for generalizability in the application of comparative outcomes between animals and humans.

Bufotalin attenuates pulmonary fibrosis via inhibiting Akt/GSK-3β/β-catenin signaling pathway

Idiopathic pulmonary fibrosis (IPF) is a chronic interstitial lung disease with no cure. Bufotalin (BT), an active component extracted from Venenum Bufonis, has been prescribed as a treatment for chronic inflammatory diseases. However, whether BT has antifibrotic properties has never been investigated. In this study, we report on the potential therapeutic effect and mechanism of BT on IPF. BT was shown to attenuate lung injury, inflammation, and fibrosis as well as preserve pulmonary function in bleomycin (BLM)-induced pulmonary fibrosis model. We next confirmed BT's ability to inhibit TGF-β1-induced epithelial-mesenchymal transition (EMT) and myofibroblast activation (including differentiation, proliferation, migration, and extracellular matrix production) in vitro. Furthermore, transcriptional profile analysis indicated the Wnt signaling pathway as a potential target of BT. Mechanistically, BT effectively prevented β-catenin from translocating into the nucleus to activate transcription of profibrotic genes. This was achieved by blunting TGF-β1-induced increases in phosphorylated Akt Ser437 (p-Akt S437) and phosphorylated glycogen synthase kinase (GSK)-3β Ser9 (p-GSK-3β S9), thereby reactivating GSK-3β. Additionally, the antifibrotic effects of BT were further validated in another in vivo model of radiation-induced pulmonary fibrosis. Collectively, these data demonstrated the potent antifibrotic actions of BT through inhibition of Akt/GSK-3β/β-catenin axis downstream of TGF-β1. Thus, BT could be a potential option to be further explored in IPF treatment.

Buyang Huanwu Decoction alleviates blood stasis, platelet activation, and inflammation and regulates the HMGB1/NF-κB pathway in rats with pulmonary fibrosis

ETHNOPHARMACOLOGICAL RELEVANCE

Qi deficiency and blood stasis are identified to be pathological factors of pulmonary fibrosis (PF) in traditional Chinese medicine (TCM) theory. Buyang Huanwu Decoction (BYHWD) is a traditional Chinese prescription ameliorating Qi deficiency and blood stasis.

AIM OF THE STUDY

The objective of this study was to investigate the anti-fibrosis effect of BYHWD and the potential molecular mechanism in rats.

MATERIALS AND METHODS

Bleomycin was used to construct PF rat models. 27 PF rats were randomly divided into three groups based on treatments: model group (saline solution, n = 9), low-dose BYHWD group (3.5 g/kg, n = 9), and high-dose BYHWD group (14.0 g/kg, n = 9). Moreover, 9 normal rats were used as the blank group. The blood viscosity, coagulation indexes (APTT, TT, PT, and FIB), platelet-related parameters (PLT, PDW, MPV, PCT, and PLCR), platelet microparticles (PMPs), and inflammatory factors (IL-2, IL-10, IL-1β, IL-6, IL-8, IL-17, IFN-γ, TNF-α, PAC-1, HMGB1, NF-κB, and TF) were determined. The lung tissue samples of rats were observed after hematoxylin-eosin (HE) staining. The full component analysis of the BYHWD extract was performed using the ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method. The signaling pathway included into the study was selected on the basis of bioinformatics analysis and the results of the phytochemical analysis. The expression levels of genes and proteins involved in the selected signaling pathway were detected.

RESULTS

Compared to the blank group, the whole blood viscosity, PLR, PDW, MPV, PCT, PLCR, PMPs, and the levels of IL-1β, IL-6, IL-8, IL-17, TNF-α, PAC-1, HMGB1, NF-κB, and TF were increased, while the levels of IL-2 and IL-10 were decreased in the model group. Both low-dose BYHWD and high-dose BYHWD reversed these PF-induced effects in spite of the fact that low-dose BYHWD had no significant effect on the level of NF-κB. In addition, BYHWD ameliorated PF-induced inflammation in the rat lung tissue. The phytochemical analysis of the BYHWD extract combined with the bioinformatics analysis suggested that the therapeutical effect of BYHWD on PF was related to the HMGB1/NF-κB pathway, which consisted of NF-κB, IKBKB, ICAM1, VCAM1, HMGB1, and TLR4. Both RT-qPCR and western blot analyses showed that PF induced increases in the expression levels of NF-κB, ICAM1, VCAM1, HMGB1, and TLR4, but a decrease in the expression level of IKBKB. Moreover, both low-dose BYHWD and high-dose BYHWD exerted the opposite effects, and recovered the expression levels of NF-κB, ICAM1, VCAM1, HMGB1, TLR4, and IKBKB, despite the fact that low-dose BYHWD had no effects on the mRNA expression levels of NF-κB or TLR4.

CONCLUSIONS

In summary, BYHWD alleviated PF-induced blood stasis, platelet activation, and inflammation in the rats. Our study suggested BYHWD had a therapeutic effect on PF and was a good alternative for the complementary therapy of PF, and the potential molecular mechanism was modulation of HMGB1/NF-κB signaling pathway, and it needs further study.

Panax notoginseng saponin alleviates pulmonary fibrosis in rats by modulating the renin-angiotensin system

ETHNOPHARMACOLOGICAL RELEVANCE

Pulmonary fibrosis (PF) is a chronic, progressive, and often fatal interstitial lung disease. Traditional Chinese medicine formulations and their active ingredients have shown potential in the treatment of PF. Panax notoginseng saponin (PNS) is extracted from the widely used traditional Chinese medicinal herb Panax notoginseng (Burkill) F. H. Chen, exhibiting therapeutic effects in pulmonary diseases treatment.

AIM OF THE STUDY

This study aimed to investigate the effects and elucidate possible potential mechanisms of PNS on bleomycin (BLM)-induced PF in rats.

MATERIALS AND METHODS

PF was induced in rats by intratracheal administration of bleomycin (BLM, 5 mg/kg). After disease model induction, the rats were treated with PNS (50, 100, or 200 mg/kg per day) or pirfenidone (PFD, 50 mg/kg per day) for 28 days. Lung function, histopathological changes, collagen deposition, and E- and N-cadherin levels in lung tissue were evaluated. The mechanism of action of PNS was investigated using tandem mass tag-based quantitative proteomics analysis. Immunohistochemistry, enzyme-linked immunosorbent assay (ELISA), and Western blot analysis were performed to verify the proteomic results.

RESULTS

PNS treatment improved lung function, ameliorated the BLM-induced increase in the lung coefficient, attenuated the degree of alveolar inflammation and fibrosis, and reduced the elevated collagen level in PF rats. PNS treatment also down-regulated the expression of N-cadherin while up-regulating the expression of E-cadherin. Proteomic and bioinformatic analyses revealed that the renin-angiotensin system (RAS) was closely related to the therapeutic effect of PNS. Immunohistochemistry, Western blot, and ELISA results indicated that PNS exerted its anti-fibrotic effect via regulation of the balance between the angiotensin-converting enzyme (ACE)-angiotensin (Ang)II-AngII receptor type 1 (AT1R) and ACE2-Ang(1-7)-MasR axes.

CONCLUSIONS

PNS ameliorates BLM-induced PF in rats by modulating the RAS homeostasis, and is a new potential therapeutic agent for PF.

YTHDC1 delays cellular senescence and pulmonary fibrosis by activating ATR in an m6A-independent manner

Accumulation of DNA damage in the lung induces cellular senescence and promotes age-related diseases such as idiopathic pulmonary fibrosis (IPF). Hence, understanding the mechanistic regulation of DNA damage repair is important for anti-aging therapies and disease control. Here, we identified an m6A-independent role of the RNA-binding protein YTHDC1 in counteracting stress-induced pulmonary senescence and fibrosis. YTHDC1 is primarily expressed in pulmonary alveolar epithelial type 2 (AECII) cells and its AECII expression is significantly decreased in AECIIs during fibrosis. Exogenous overexpression of YTHDC1 alleviates pulmonary senescence and fibrosis independent of its m6A-binding ability, while YTHDC1 deletion enhances disease progression in mice. Mechanistically, YTHDC1 promotes the interaction between TopBP1 and MRE11, thereby activating ATR and facilitating DNA damage repair. These findings reveal a noncanonical function of YTHDC1 in delaying cellular senescence, and suggest that enhancing YTHDC1 expression in the lung could be an effective treatment strategy for pulmonary fibrosis.

Icariside Ⅱ attenuates bleomycin-induced pulmonary fibrosis by modulating macrophage polarization

ETHNOPHARMACOLOGICAL RELEVANCE

Numerous studies have provided evidence supporting the significant roles of icariin, in the prevention of multiple chronic diseases like diabetes, liver fibrosis, cardiac fibrosis, renal fibrosis, and pulmonary fibrosis. In particular, Icariside II (ISE II), a prominent flavonoid glycoside derived from Epimedium brevicornum Maxim, the principal metabolite of icariin, has demonstrated noteworthy anti-inflammatory and anti-oxidant properties, along with its ability to protect against lung remodeling. However, the research exploring ISE Ⅱ's application in treating pulmonary fibrosis remains limited.

AIM OF THE STUDY

The aim of this study was to assess the therapeutic efficacy of ISE II in models of pulmonary fibrosis, while also investigating its potential mechanisms of action in cell signaling pathways.

MATERIALS AND METHODS

An in vitro model of pulmonary fibrosis was established by treating NIH-3T3 cells with transforming growth factor-β1 (TGF-β1). Western blot, RT-qPCR, and scratch test were performed to assess the effect of ISE Ⅱ. In addition, a murine model of pulmonary fibrosis was induced by intratracheal instillation of bleomycin, and the therapeutic effect of ISE Ⅱ was tested by orally administering ISE Ⅱ at a dose of 10 mg/kg. Three weeks later, lung function, micro-CT, hydroxyproline content, pathological staining, and cytokines detection of BALF or serum were used to assess the anti-fibrosis effects of ISE Ⅱ. Next, immunofluorescence staining, flow cytometry, and in vivo transcriptomics were used to investigate the underlying mechanisms of action.

RESULTS

Our data revealed a significant inhibitory effect of ISE Ⅱ on the upregulation of α-smooth muscle actin (α-SMA) and collagen production induced by TGF-β1 in fibroblasts. Meanwhile, ISE Ⅱ exerted a therapeutic effect against bleomycin-induced pulmonary fibrosis in mice by improving lung function, decreasing collagen deposition, and reducing the expression of interleukin (IL)-1β, tumor necrosis factor α (TNF-α), TGF-β1 and platelet-derived growth factor (PDGF) in serum and bronchoalveolar lavage fluid (BALF). Additionally, ISE Ⅱ treatment effectively attenuated the infiltration of M2 macrophages, concurrently downregulating the expression level of M2 marker genes, such as CD206, arginase-1(Arg-1), and Chitinase-Like Protein 3 (YM-1). Importantly, we observed a statistically significant reduction in the M2 phenotype of interstitial macrophages (IMs). However, the impact of ISE Ⅱ on the M2 polarization of alveolar macrophages (AMs) did not reach statistical significance. Lastly, transcriptome sequencing results suggested that the anti-pulmonary fibrosis effects of ISE Ⅱ may be mediated by the suppression of the WNT/β-catenin signaling pathway, which modulated M2 polarization in macrophages and contributed to the amelioration of pulmonary fibrosis. By immunohistochemical analysis, it was verified that ISE Ⅱ treatment dramatically inhibited the activation of β-catenin in fibrosis murine.

CONCLUSION

Our findings indicated that ISE Ⅱ exerted anti-fibrotic effects by inhibiting pro-fibrotic macrophage polarization. The underlying mechanism of action might be mediated by modulating the WNT/β-catenin signaling pathway to inhibit the M2 program in IMs.

Anthelmintic nitazoxanide protects against experimental pulmonary fibrosis

BACKGROUND AND PURPOSE

Nitazoxanide is a therapeutic anthelmintic drug. Our previous studies found that nitazoxanide and its metabolite tizoxanide activated adenosine 5'-monophosphate-activated protein kinase (AMPK) and inhibited signal transducer and activator of transcription 3 (STAT3) signals. As AMPK activation and/or STAT3 inhibition are targets for treating pulmonary fibrosis, we hypothesized that nitazoxanide would be effective in experimental pulmonary fibrosis.

EXPERIMENTAL APPROACH

The mitochondrial oxygen consumption rate of cells was measured by using the high-resolution respirometry system Oxygraph-2K. The mitochondrial membrane potential of cells was evaluated by tetramethyl rhodamine methyl ester (TMRM) staining. The target protein levels were measured by using western blotting. The mice pulmonary fibrosis model was established through intratracheal instillation of bleomycin. The examination of the lung tissues changes were carried out using haematoxylin and eosin (H&E), and Masson staining.

KEY RESULTS

Nitazoxanide and tizoxanide activated AMPK and inhibited STAT3 signalling in human lung fibroblast cells (MRC-5 cells). Nitazoxanide and tizoxanide inhibited transforming growth factor-β1 (TGF-β1)-induced proliferation and migration of MRC-5 cells, collagen-I and α-smooth muscle cell actin (α-SMA) expression, and collagen-I secretion from MRC-5 cells. Nitazoxanide and tizoxanide inhibited epithelial-mesenchymal transition (EMT) and inhibited TGF-β1-induced Smad2/3 activation in mouse lung epithelial cells (MLE-12 cells). Oral administration of nitazoxanide reduced the bleomycin-induced mice pulmonary fibrosis and, in the established bleomycin-induced mice, pulmonary fibrosis. Delayed nitazoxanide treatment attenuated the fibrosis progression.

CONCLUSIONS AND IMPLICATIONS

Nitazoxanide improves the bleomycin-induced pulmonary fibrosis in mice, suggesting a potential application of nitazoxanide for pulmonary fibrosis treatment in the clinic.

Heterogenous Intrapulmonary Distribution of Aerosolized Model Compounds in Mice with Bleomycin-Induced Pulmonary Fibrosis

Background: A distinctive pathological feature of idiopathic pulmonary fibrosis (IPF) is the aberrant accumulation of extracellular matrix components in the alveoli in abnormal remodeling and reconstruction following scarring of the alveolar structure. The current antifibrotic agents used for IPF therapy frequently result in systemic side effects because these agents are distributed, through the blood, to many different tissues after oral administration. In contrast to oral administration, the intrapulmonary administration of aerosolized drugs is believed to be an efficient method for their direct delivery to the focus sites in the lungs. However, how fibrotic lesions alter the distribution of aerosolized drugs following intrapulmonary administration remains largely unknown. In this study, we evaluate the intrapulmonary distribution characteristics of aerosolized model compounds in mice with bleomycin-induced pulmonary fibrosis through imaging the organs and alveoli. Methods: Aerosolized model compounds were administered to mice with bleomycin-induced pulmonary fibrosis using a Liquid MicroSprayer®. The intrapulmonary distribution characteristics of aerosolized model compounds were evaluated through several imaging techniques, including noninvasive lung imaging using X-ray computed tomography, ex vivo imaging using zoom fluorescence microscopy, frozen tissue section observation, and three-dimensional imaging with tissue-clearing treatment using confocal laser microscopy. Results: In fibrotic lungs, the aerosolized model compounds were heterogeneously distributed. In observations of frozen tissue sections, model compounds were observed only in the fibrotic foci near airless spaces called honeycombs. In three-dimensional imaging of cleared tissue from fibrotic lungs, the area of the model compound in the alveolar space was smaller than in healthy lungs. Conclusion: The intrapulmonary deposition of extracellular matrix associated with pulmonary fibrosis limits the intrapulmonary distribution of aerosolized drugs. The development of delivery systems for antifibrotic agents to improve the distribution characteristics in fibrotic foci is necessary for effective IPF therapy.

Stevioside attenuates bleomycin-induced pulmonary fibrosis by activating the Nrf2 pathway and inhibiting the NF-κB and TGF-β1/Smad2/3 pathways

Objective: This study aimed to investigate the effects of stevioside (STE) on pulmonary fibrosis (PF) and the potential mechanisms. Methods: In this study, a mouse model of PF was established by a single intratracheal injection of bleomycin (BLM, 3 mg/kg). The experiment consisted of four groups: control group, BLM group, and STE treatment groups (STE 50 and 100 mg/kg). ELISA and biochemical tests were conducted to determine the levels of TNF-α, IL-1β, IL-6, NO, hydroxyproline (HYP), SOD, GSH, and MDA. Histopathological changes and collagen deposition in lung tissues were observed by HE and Masson staining. Immunohistochemistry was performed to determine the levels of collagen I-, collagen III-, TGF-β1- and p-Smad2/3-positive cells. Western blot analysis was used to measure the expression of epithelial-mesenchymal transition (EMT) markers, including α-SMA, vimentin, E-cadherin, and ZO-1, as well as proteins related to the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, nuclear transcription factor-κB (NF-κB) pathway, and TGF-β1/Smad2/3 pathway in lung tissues. Results: STE significantly alleviated BLM-induced body weight loss and lung injury in mice, decreased HYP levels, and reduced the levels of collagen I- and collagen III-positive cells, thereby decreasing extracellular matrix (ECM) deposition. Moreover, STE markedly improved oxidative stress (MDA levels were decreased, while SOD and GSH activity were enhanced), the inflammatory response (the levels of TNF-α, IL-1β, IL-6, and NO were reduced), and EMT (the expression of α-SMA and vimentin was downregulated, and the expression of E-cadherin and ZO-1 was upregulated). Further mechanistic analysis revealed that STE could activate the Nrf2 pathway and inhibit the NF-κB and TGF-β1/Smad2/3 pathways. Conclusion: STE may alleviate oxidative stress by activating the Nrf2 pathway, suppress the inflammatory response by downregulating the NF-κB pathway, and inhibit EMT progression by blocking the TGF-β1/Smad2/3 pathway, thereby improving BLM-induced PF.

Ginkgo biloba Extract 50 (GBE50) Exerts Antifibrotic and Antioxidant Effects on Pulmonary Fibrosis in Mice by Regulating Nrf2 and TGF-β1/Smad Pathways

BACKGROUND

Pulmonary fibrosis (PF) is a progressive lung disorder with a poor prognosis. GBE50 is a new standardized Ginkgo biloba extract that has been widely used in cardiovascular diseases. However, the protective mechanism of GBE50 against PF remains to be elucidated.

METHODS

C57BL/6J mice were treated with bleomycin (Bleo) to induce PF in the presence or absence of GBE50. Protein content in bronchoalveolar lavage fluid (BALF) and wet weight/dry weight ratio were examined for analysis of pulmonary edema. Hematoxylin-eosin staining and Masson trichrome staining were used for histopathological observation of murine lung tissues. Ashcroft score was used for semi-quantitation of lung fibrosis degree. RT-qPCR was utilized for assessing mRNA levels of pro-fibrotic mediators in lung tissues. TUNEL staining was implemented for cell apoptosis assessment. The levels of oxidative stress- and inflammation-related markers were evaluated by corresponding commercial assay kits. Western blotting was used to evaluate levels of nuclear factor erythroid 2-related factor 2 (Nrf2) signaling- and transforming growth factor (TGF)-β1/SMAD signaling-related proteins.

RESULTS

GBE50 alleviated lung injury and severity of fibrosis, reduced collagen deposition and cell apoptosis in lung tissues, and suppressed inflammatory response and oxidative stress injury in Bleo-stimulated PF mice. GBE50 activated Nrf2 signaling pathway and inactivated TGF-β1/SMAD signaling pathway in the lungs of Bleo-induced PF mice. Inhibition of Nrf2 signaling reversed GBE50-mediated inactivation of TGF-β1/SMAD signaling and attenuation of inflammation and oxidative stress in Bleo-induced PF mice.

CONCLUSION

GBE50 protects against Bleo-induced PF in mice by mitigating fibrosis, inflammation and oxidative stress via Nrf2 and TGF-β1/SMAD signaling pathways.

Catch your breath: The protective role of the angiotensin AT2 receptor for the treatment of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease whereby excessive deposition of extracellular matrix proteins (ECM) ultimately leads to respiratory failure. While there have been advances in pharmacotherapies for pulmonary fibrosis, IPF remains an incurable and irreversible disease. There remains an unmet clinical need for treatments that reverse fibrosis, or at the very least have a more tolerable side effect profile than currently available treatments. Transforming growth factor β1(TGFβ1) is considered the main driver of fibrosis in IPF. However, as our understanding of the role of the pulmonary renin-angiotensin system (PRAS) in the pathogenesis of IPF increases, it is becoming clear that targeting angiotensin receptors represents a potential novel treatment strategy for IPF - in particular, via activation of the anti-fibrotic angiotensin type 2 receptor (AT2R). This review describes the current understanding of the pathophysiology of IPF and the mediators implicated in its pathogenesis; focusing on TGFβ1, angiotensin II and related peptides in the PRAS and their contribution to fibrotic processes in the lung. Preclinical and clinical assessment of currently available AT2R agonists and the development of novel, highly selective ligands for this receptor will also be described, with a focus on compound 21, currently in clinical trials for IPF. Collectively, this review provides evidence of the potential of AT2R as a novel therapeutic target for IPF.

MARCH8 downregulation modulates profibrotic responses including myofibroblast differentiation

Interstitial lung diseases can result in poor patient outcomes, especially in idiopathic pulmonary fibrosis (IPF), a severe interstitial lung disease with unknown causes. The lack of treatment options requires further understanding of the pathological process/mediators. Membrane-associated RING-CH 8 (MARCH8) has been implicated in immune function regulation and inflammation, however, its role in the development of pulmonary fibrosis and particularly the fibroblast to myofibroblast transition (FMT) remains a gap in existing knowledge. In this study, we demonstrated decreased MARCH8 expression in patients with IPF compared with non-PF controls and in bleomycin-induced PF. TGF-β dose- and time-dependently decreased MARCH8 expression in normal and IPF human lung fibroblast (HLFs), along with induction of FMT markers α-SMA, collagen type I (Col-1), and fibronectin (FN). Interestingly, overexpression of MARCH8 significantly suppressed TGF-β-induced expression of α-SMA, Col-1, and FN. By contrast, the knockdown of MARCH8 using siRNA upregulated basal expression of α-SMA/Col-1/FN. Moreover, MARCH8 knockdown enhanced TGF-β-induced FMT marker expression. These data clearly show that MARCH8 is a critical "brake" for FMT and potentially affects PF. We further found that TGF-β suppressed MARCH8 mRNA expression and the proteasome inhibitor MG132 failed to block MARCH8 decrease induced by TGF-β. Conversely, TGF-β decreases mRNA levels of MARCH8 in a dose- and time-dependent manner, suggesting the transcriptional regulation of MARCH8 by TGF-β. Mechanistically, MARCH8 overexpression suppressed TGF-β-induced Smad2/3 phosphorylation, which may account for the observed effects. Taken together, this study demonstrated an unrecognized role of MARCH8 in negatively regulating FMT and profibrogenic responses relevant to interstitial lung diseases.NEW & NOTEWORTHY MARCH8 is an important modulator of inflammation, immunity, and other cellular processes. We found that MARCH8 expression is downregulated in the lungs of patients with idiopathic pulmonary fibrosis (IPF) and experimental models of pulmonary fibrosis. Furthermore, TGF-β1 decreases MARCH8 transcriptionally in human lung fibroblasts (HLFs). MARCH8 overexpression blunts TGF-β1-induced fibroblast to myofibroblast transition while knockdown of MARCH8 drives this profibrotic change in HLFs. The findings support further exploration of MARCH8 as a novel target in IPF.

Efficient intervention for pulmonary fibrosis via mitochondrial transfer promoted by mitochondrial biogenesis

The use of exogenous mitochondria to replenish damaged mitochondria has been proposed as a strategy for the treatment of pulmonary fibrosis. However, the success of this strategy is partially restricted by the difficulty of supplying sufficient mitochondria to diseased cells. Herein, we report the generation of high-powered mesenchymal stem cells with promoted mitochondrial biogenesis and facilitated mitochondrial transfer to injured lung cells by the sequential treatment of pioglitazone and iron oxide nanoparticles. This highly efficient mitochondrial transfer is shown to not only restore mitochondrial homeostasis but also reactivate inhibited mitophagy, consequently recovering impaired cellular functions. We perform studies in mouse to show that these high-powered mesenchymal stem cells successfully mitigate fibrotic progression in a progressive fibrosis model, which was further verified in a humanized multicellular lung spheroid model. The present findings provide a potential strategy to overcome the current limitations in mitochondrial replenishment therapy, thereby promoting therapeutic applications for fibrotic intervention.

The Role of Mitochondrial Dysfunction in Idiopathic Pulmonary Fibrosis: New Perspectives for a Challenging Disease

Mitochondrial biology has always been a relevant field in chronic diseases such as fibrosis or cancer in different organs of the human body, not to mention the strong association between mitochondrial dysfunction and aging. With the development of new technologies and the emergence of new methodologies in the last few years, the role of mitochondria in pulmonary chronic diseases such as idiopathic pulmonary fibrosis (IPF) has taken an important position in the field. With this review, we will highlight the latest advances in mitochondrial research on pulmonary fibrosis, focusing on the role of the mitochondria in the aging lung, new proposals for mechanisms that support mitochondrial dysfunction as an important cause for IPF, mitochondrial dysfunction in different cell populations of the lung, and new proposals for treatment of the disease.

Asarinin attenuates bleomycin-induced pulmonary fibrosis by activating PPARγ

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive interstitial lung disease that lacks effective treatment modalities. Once patients are diagnosed with IPF, their median survival is approximately 3-5 years. PPARγ is an important target for the prevention and treatment of pulmonary fibrosis. Asarinin is a lignan compound that can be extracted from food plant Asarum heterotropoides. In this study, we investigated the therapeutic effects of asarinin in a pulmonary fibrosis model constructed using bleomycin in mice and explored the underlying mechanisms. Intraperitoneal administration of asarinin to mice with pulmonary fibrosis showed that asarinin effectively attenuated pulmonary fibrosis, and this effect was significantly inhibited by the PPARγ inhibitor GW9662. Asarinin inhibited TGF-β1-induced fibroblast-to-myofibroblast transition in vitro, while GW9662 and PPARγ gene silencing significantly inhibited this effect. In addition, asarinin inhibited not only the canonical Smad pathway of TGF-β but also the non-canonical AKT and MAPK pathways by activating PPARγ. Our study demonstrates that asarinin can be used as a therapeutic agent for pulmonary fibrosis, and that PPARγ is its key target.

Therapy-related Myeloid Neoplasms: Considerations for Patients' Clinical Evaluation

Therapy-related myeloid neoplasms (t-MNs) encompass a specific sub-group of myeloid malignancies arising after exposure to radio/cytotoxic agents for the treatment of unrelated diseases. Such malignancies present unique features, including advanced age, high comorbidities burden, and unfavorable genetic profiles. All these features justify the need for a specific diagnostic work-up and dedicated treatment algorithms. However, as new classification systems recognize the unique clinical characteristics exhibited by t-MN patients, how to assess fitness status in this clinical setting is largely unexplored. Optimizing fitness assessment would be crucial in the management of t-MN patients, considering that factors usually contributing to a worse or better outcome (like age, comorbidities, and treatment history) are patient-specific. In the absence of specific tools for fitness assessment in this peculiar category of AML, the aim of this review is to describe all those factors related to patient, treatment, and disease that allow planning treatments with an optimal risk/benefit ratio.

Preparation and evaluation of sustained release pirfenidone-loaded microsphere dry powder inhalation for treatment of idiopathic pulmonary fibrosis

Pirfenidone (PFND) is a recommended oral drug used to treat idiopathic pulmonary fibrosis, but have low bioavailability and high hepatotoxicity. The study, therefore, seeks to improve the therapeutic activities of the drug via increased bioavailability and reduced associated side effects by developing a novel drug delivery system. The electrostatic spray technology was used to prepare a sustained release pirfenidone-loaded microsphere dry powder inhalation with PEG-modified chitosan (PFND-mPEG-CS-MS). The entrapment efficiency, drug loading, and in vitro cumulative drug release rate (at 24 h and with a sustained release effect) of PFND-mPEG-CS-MS were 77.35±3.01%, 11.45±0.64%, and 90.4%, respectively. The Carr's index of PFND-mPEG-CS-MS powder was 17.074±2.163% with a theoretical mass median aerodynamic diameter (MMADt) of 0.99±0.07 μm, and a moisture absorption weight gain rate (Rw) of 4.61±0.72%. The emptying rate, pulmonary deposition rate (fine particle fraction) and actual mass median aerodynamic diameter (MMADa) were 90%∼95%, 48.72±7.04% and 3.10±0.16 μm, respectively. MTT bioassay showed that mPEG-CS-MS (200 μg/mL) had good biocompatibility (RGR = 90.25%) and PFND-mPEG-CS-MS (200 μg/mL) had significant inhibitory activity (RGR = 49.82%) on fibroblast growth. The pharmacokinetic data revealed that the t1/2 (5.02 h) and MRT (10.66 h) of PFND-mPEG-CS-MS were prolonged compared with the free PFND (t1/2, 1.67 h; MRT, 2.71 h). The pharmacodynamic results also showed that the formulated-drug group had slight pathological changes, lower lung hydroxyproline content, and reduced hepatotoxicity compared with the free-drug group. The PFND-mPEG-CS-MS further significantly down-regulated TGF-β cytokines, Collagen I, and α-SMA protein expression levels compared with the free drug. The findings indicated that the PFND-mPEG-CS-MS had a good sustained release effect, enhanced bioavailability, decreased toxicity, and increased anti-fibrotic activities.

Macrophage Implication in IPF: Updates on Immune, Epigenetic, and Metabolic Pathways

Idiopathic pulmonary fibrosis (IPF) is a lethal interstitial lung disease of unknown etiology with a poor prognosis. It is a chronic and progressive disease that has a distinct radiological and pathological pattern from common interstitial pneumonia. The use of immunosuppressive medication was shown to be completely ineffective in clinical trials, resulting in years of neglect of the immune component. However, recent developments in fundamental and translational science demonstrate that immune cells play a significant regulatory role in IPF, and macrophages appear to be among the most crucial. These highly plastic cells generate multiple growth factors and mediators that highly affect the initiation and progression of IPF. In this review, we will provide an update on the role of macrophages in IPF through a systemic discussion of various regulatory mechanisms involving immune receptors, cytokines, metabolism, and epigenetics.

Prolyl oligopeptidase inhibition ameliorates experimental pulmonary fibrosis both in vivo and in vitro

BACKGROUND

Pulmonary fibrosis is a progressive disease characterized by lung remodeling due to excessive deposition of extracellular matrix. Although the etiology remains unknown, aberrant angiogenesis and inflammation play an important role in the development of this pathology. In this context, recent scientific research has identified new molecules involved in angiogenesis and inflammation, such as the prolyl oligopeptidase (PREP), a proteolytic enzyme belonging to the serine protease family, linked to the pathology of many lung diseases such as pulmonary fibrosis. Therefore, the aim of this study was to investigate the effect of a selective inhibitor of PREP, known as KYP-2047, in an in vitro and in an in vivo model of pulmonary fibrosis.

METHODS

The in vitro model was performed using human alveolar A549 cells. Cells were exposed to lipopolysaccharide (LPS) 10 μg/ml and then, cells were treated with KYP-2047 at the concentrations of 1 μM, 10 μM and 50 μM. Cell viability was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) bromide colorimetric assay, while inflammatory protein expression was assessed by western blots analysis. The in vivo model was induced in mice by intra-tracheal administration of bleomycin (1 mg/kg) and then treated intraperitoneally with KYP-2047 at doses of 1, 2.5 and 5 mg/kg once daily for 12 days and then mice were sacrificed, and lung tissues were collected for analyses.

RESULTS

The in vitro results demonstrated that KYP-2047 preserved cell viability, reduced inflammatory process by decreasing IL-18 and TNF-α, and modulated lipid peroxidation as well as nitrosative stress. The in vivo pulmonary fibrosis has demonstrated that KYP-2047 was able to restore histological alterations reducing lung injury. Our data demonstrated that KYP-2047 significantly reduced angiogenesis process and the fibrotic damage modulating the expression of fibrotic markers. Furthermore, KYP-2047 treatment modulated the IκBα/NF-κB pathway and reduced the expression of related pro-inflammatory enzymes and cytokines. Moreover, KYP-2047 was able to modulate the JAK2/STAT3 pathway, highly involved in pulmonary fibrosis.

CONCLUSION

In conclusion, this study demonstrated the involvement of PREP in the pathogenesis of pulmonary fibrosis and that its inhibition by KYP-2047 has a protective role in lung injury induced by BLM, suggesting PREP as a potential target therapy for pulmonary fibrosis. These results speculate the potential protective mechanism of KYP-2047 through the modulation of JAK2/STAT3 and NF-κB pathways.

Crosstalk between Interleukin-1 Receptor-Like 1 and Transforming Growth Factor-β Receptor Signaling Promotes Renal Fibrosis

IL-33, a member of the IL-1 family, acts as an alarmin in immune response. Epithelial-mesenchymal transition and transforming growth factor-β (TGF-β)–induced fibroblast activation are key events in the development of renal interstitial fibrosis. The current study found increased expression of IL-33 and interleukin-1 receptor-like 1 (IL1RL1, alias ST2), the receptor for IL-33, in human fibrotic renal tissues. In addition, IL-33– or ST2-deficient mice showed significantly reduced levels of fibronectin, α-smooth muscle actin, and vimentin, and increased E-cadherin levels. In HK-2 cells, IL-33 promotes the phosphorylation of the TGF-β receptor (TGF-βR), Smad2, and Smad3, and the production of extracellular matrix (ECM), with reduced expression of E-cadherin. Blocking TGF-βR signaling or suppressing ST2 expression impeded Smad2 and Smad3 phosphorylation, thereby reducing ECM production, suggesting that IL-33–induced ECM synthesis requires cooperation between the two pathways. Mechanistically, IL-33 treatment induced a proximate interaction between ST2 and TGF-βRs, activating downstream Smad2 and Smad3 for ECM production in renal epithelial cells. Collectively, this study identified a novel and essential role for IL-33 in promoting TGF-β signaling and ECM production in the development of renal fibrosis. Therefore, targeting IL-33/ST2 signaling may be an effective therapeutic strategy for renal fibrosis.

UBQLN1 deficiency mediates telomere shortening and IPF through interacting with RPA1

Premature telomere shortening is a known factor correlated to idiopathic pulmonary fibrosis (IPF) occurrence, which is a chronic, progressive, age-related disease with high mortality. The etiology of IPF is still unknown. Here, we found that UBQLN1 plays a key role in telomere length maintenance and is potentially relevant to IPF. UBQLN1 involves in DNA replication by interacting with RPA1 and shuttling it off from the replication fork. The deficiency of UBQLN1 retains RPA1 at replication fork, hinders replication and thus causes cell cycle arrest and genome instability. Especially at telomere regions of the genome, where more endogenous replication stress exists because of G rich sequences, UBQLN1 depletion leads to rapid telomere shortening in HeLa cells. It revealed that UBQLN1 depletion also shortens telomere length at mouse lung and accelerates mouse lung fibrosis. In addition, the UBQLN1 expression level in IPF patients is downregulated and correlated to poor prognosis. Altogether, these results uncover a new role of UBQLN1 in ensuring DNA replication and maintaining telomere stability, which may shed light on IPF pathogenesis and prevention.

Mesenchymal stromal cells facilitate resolution of pulmonary fibrosis by miR-29c and miR-129 intercellular transfer

To date, pulmonary fibrosis remains an unmet medical need. In this study, we evaluated the potency of mesenchymal stromal cell (MSC) secretome components to prevent pulmonary fibrosis development and facilitate fibrosis resolution. Surprisingly, the intratracheal application of extracellular vesicles (MSC-EVs) or the vesicle-depleted secretome fraction (MSC-SF) was not able to prevent lung fibrosis when applied immediately after the injury caused by bleomycin instillation in mice. However, MSC-EV administration induced the resolution of established pulmonary fibrosis, whereas the vesicle-depleted fraction did not. The application of MSC-EVs caused a decrease in the numbers of myofibroblasts and FAPa⁺ progenitors without affecting their apoptosis. Such a decrease likely occurred due to their dedifferentiation caused by microRNA (miR) transfer by MSC-EVs. Using a murine model of bleomycin-induced pulmonary fibrosis, we confirmed the contribution of specific miRs (miR-29c and miR-129) to the antifibrotic effect of MSC-EVs. Our study provides novel insights into possible antifibrotic therapy based on the use of the vesicle-enriched fraction of the MSC secretome.

Is there a role for specialized pro-resolving mediators in pulmonary fibrosis?

Pulmonary fibrotic diseases are characterized by proliferation of lung fibroblasts and myofibroblasts and excessive deposition of extracellular matrix proteins. Depending on the specific form of lung fibrosis, there can be progressive scarring of the lung, leading in some cases to respiratory failure and/or death. Recent and ongoing research has demonstrated that resolution of inflammation is an active process regulated by families of small bioactive lipid mediators termed "specialized pro-resolving mediators." While there are many reports of beneficial effects of SPMs in animal and cell culture models of acute and chronic inflammatory and immune diseases, there have been fewer reports investigating SPMs and fibrosis, especially pulmonary fibrosis. Here, we will review evidence that resolution pathways are impaired in interstitial lung disease, and that SPMs and other similar bioactive lipid mediators can inhibit fibroblast proliferation, myofibroblast differentiation, and accumulation of excess extracellular matrix in cell culture and animal models of pulmonary fibrosis, and we will consider future therapeutic implications of SPMs in fibrosis.

Insights on the mechanism of bleomycin to induce lung injury and associated in vivo models: A review

Acute lung injury leads to the development of chronic conditions such as idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD), asthma as well as alveolar sarcoma. Various investigations are being performed worldwide to understand the pathophysiology of these diseases, develop novel bioactive compounds and inhibitors to target the ailment. Generally, in vivo models are used to understand the disease outcome and therapeutic suppressing effects for which the animals are chemically or physically induced to mimic the onset of definite disease conditions. Amongst the chemical inducing agents, Bleomycin (BLM) is the most successful inducer. It is reported to target various receptors and activate inflammatory pathways, cellular apoptosis, epithelial mesenchymal transition leading to the release of inflammatory cytokines, and proteases. Mice is one of the most widely used animal model for BLM induced pulmonary associated studies apart from rat, rabbit, sheep, pig, and monkey. Although, there is considerable variation amongst in vivo studies for BLM induction which suggests a detailed study on the same to understand the mechanism of action of BLM at molecular level. Hence, herein we have reviewed various chemical inducers, mechanism of action of BLM in inducing lung injury in vivo, its advantages and disadvantages. Further, we have also discussed the rationale behind various in vivo models and recent development in BLM induction for various animals.

ATRA ameliorates fibrosis by suppressing the pro-fibrotic molecule Fra2/AP-1 in systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune connective tissue disease that leads to irreversible fibrosis of the skin and the internal organs. The etiology of SSc is complex, its pathophysiology is poorly understood, and clinical therapeutic options are restricted. Thus, research into medications and targets for treating fibrosis is essential and urgent. Fos-related antigen 2 (Fra2) is a transcription factor that is a member of the activator protein-1 family. Fra2 transgenic mice were shown to have spontaneous fibrosis. All-trans retinoic acid (ATRA) is a vitamin A intermediate metabolite and ligand for the retinoic acid receptor (RAR), which possesses anti-inflammatory and anti-proliferative properties. Recent research has demonstrated that ATRA also has an anti-fibrotic effect. However, the exact mechanism is not fully understood. Interestingly, we identified potential binding sites for the transcription factor RARα to the promoter region of the FRA2 gene through JASPAR and PROMO databases. In this study, the pro-fibrotic effect of Fra2 in SSc is confirmed. SSc dermal fibroblasts and bleomycin-induced fibrotic tissues of SSc animals exhibit increased levels of Fra2. Inhibition of Fra2 expression in SSc dermal fibroblasts with Fra2 siRNA markedly decreased collagen I expression. ATRA reduced the expressions of Fra2, collagen I, and α-smooth muscle actin(α-SMA) in SSc dermal fibroblasts and bleomycin-induced fibrotic tissues of SSc mice. In addition, chromatin immunoprecipitation and dual-luciferase assays demonstrated that retinoic acid receptor RARα binds to the FRA2 promoter and modulates its transcriptional activity. ATRA decreases collagen I expression both in vivo and in vitro via the reduction of Fra2 expression. This work establishes the rationale for expanding the use of ATRA in the treatment of SSc and indicates that Fra2 can be used as an anti-fibrotic target.

Cigarette Smoke-Induced Respiratory Response: Insights into Cellular Processes and Biomarkers

Cigarette smoke (CS) poses a significant risk factor for respiratory, vascular, and organ diseases owing to its high content of harmful chemicals and reactive oxygen species (ROS). These substances are known to induce oxidative stress, inflammation, apoptosis, and senescence due to their exposure to environmental pollutants and the presence of oxidative enzymes. The lung is particularly susceptible to oxidative stress. Persistent oxidative stress caused by chronic exposure to CS can lead to respiratory diseases such as chronic obstructive pulmonary disease (COPD), pulmonary fibrosis (PF), and lung cancer. Avoiding exposure to environmental pollutants, like cigarette smoke and air pollution, can help mitigate oxidative stress. A comprehensive understanding of oxidative stress and its impact on the lungs requires future research. This includes identifying strategies for preventing and treating lung diseases as well as investigating the underlying mechanisms behind oxidative stress. Thus, this review aims to investigate the cellular processes induced by CS, specifically inflammation, apoptosis, senescence, and their associated biomarkers. Furthermore, this review will delve into the alveolar response provoked by CS, emphasizing the roles of potential therapeutic target markers and strategies in inflammation and oxidative stress.

PRDX1 negatively regulates bleomycin-induced pulmonary fibrosis via inhibiting the epithelial-mesenchymal transition and lung fibroblast proliferation in vitro and in vivo

BACKGROUND

Pulmonary fibrosis is a major category of end-stage changes in lung diseases, characterized by lung epithelial cell damage, proliferation of fibroblasts, and accumulation of extracellular matrix. Peroxiredoxin 1 (PRDX1), a member of the peroxiredoxin protein family, participates in the regulation of the levels of reactive oxygen species in cells and various other physiological activities, as well as the occurrence and development of diseases by functioning as a chaperonin.

METHODS

Experimental methods including MTT assay, morphological observation of fibrosis, wound healing assay, fluorescence microscopy, flow cytometry, ELISA, western blot, transcriptome sequencing, and histopathological analysis were used in this study.

RESULTS

PRDX1 knockdown increased ROS levels in lung epithelial cells and promoted epithelial-mesenchymal transition (EMT) through the PI3K/Akt and JNK/Smad signalling pathways. PRDX1 knockout significantly increased TGF-β secretion, ROS production, and cell migration in primary lung fibroblasts. PRDX1 deficiency also increased cell proliferation, cell cycle circulation, and fibrosis progression through the PI3K/Akt and JNK/Smad signalling pathways. BLM treatment induced more severe pulmonary fibrosis in PRDX1-knockout mice, mainly through the PI3K/Akt and JNK/Smad signalling pathways.

CONCLUSIONS

Our findings strongly suggest that PRDX1 is a key molecule in BLM-induced lung fibrosis progression and acts through modulating EMT and lung fibroblast proliferation; therefore, it may be a therapeutic target for the treatment of BLM-induced lung fibrosis.

TIMP-1 and its potential diagnostic and prognostic value in pulmonary diseases

Tissue inhibitors of metalloproteases (TIMPs) have caught the attention of many scientists due to their role in various physiological and pathological processes. TIMP-1, 2, 3, and 4 are known members of the TIMPs family. TIMPs exert their biological effects by, but are not limited to, inhibiting the activity of metalloproteases (MMPs). The balance between MMPs and TIMPs is critical for maintaining homeostasis of the extracellular matrix (ECM), while the imbalance between MMPs and TIMPs can lead to pathological changes, such as cancer. In this review, we summarized the current knowledge of TIMP-1 in several pulmonary diseases namely, acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), pneumonia, asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis, and pulmonary fibrosis. Considering the potential of TIMP-1 serving as a non-invasive diagnostic and/or prognostic biomarker, we also reviewed the circulating TIMP-1 levels in translational and clinical studies.