Modeling pulmonary fibrosis with bleomycin. Curr Opin Pulm Med. 2011;17:355-361. [PMID: 21832918 DOI: 10.1097/mcp.0b013e328349ac2b]

Deregulated immune cell recruitment orchestrated by c-MET impairs pulmonary inflammation and fibrosis

BACKGROUND

Pulmonary fibrosis (PF) represents the pathologic end stage of several interstitial lung diseases (ILDs) associated with high morbidity and mortality rates. However, current treatments can only delay disease progression rather than provide a cure. The role of inflammation in PF progression is well-established, but new insights into immune regulation are fundamental for developing more efficient therapies. c-MET signaling has been implicated in the migratory capacity and effector functions of immune cells. Nevertheless, the role of this signaling pathway in the context of PF-associated lung diseases remains unexplored.

METHODS

To determine the influence of c-MET in immune cells in the progression of pulmonary fibrosis, we used a conditional deletion of c-Met in immune cells. To induce pulmonary fibrosis mice were administered with bleomycin (BLM) intratracheally. Over the course of 21 days, mice were assessed for weight change, and after euthanasia at different timepoints, bronchoalveolar lavage fluid cells and lung tissue were assessed for inflammation and fibrosis. Furthermore, c-MET expression was assessed in cryobiopsy sections, bronchoalveolar lavage fluid cells samples and single cell RNA-sequencing dataset from human patients with distinct interstitial lung diseases.

RESULTS

c-MET expression was induced in lung immune cells, specifically in T cells, interstitial macrophages, and neutrophils, during the inflammatory phase of BLM-induced PF mouse model. Deletion of c-Met in immune cells correlated with earlier weight recovery and improved survival of BLM-treated mice. Moreover, the deletion of c-Met in immune cells was associated with early recruitment of the immune cell populations, normally found to express c-MET, leading to a subsequent attenuation of the cytotoxic and proinflammatory environment. Consequently, the less extensive inflammatory response, possibly coupled with tissue repair, culminated in less exacerbated fibrotic lesions. Furthermore, c-MET expression was up-regulated in lung T cells from patients with fibrosing ILD, suggesting a potential involvement of c-MET in the development of fibrosing disease.

CONCLUSIONS

These results highlight the critical contribution of c-MET signaling in immune cells to their enhanced uncontrolled recruitment and activation toward a proinflammatory and profibrotic phenotype, leading to the exacerbation of lung injury and consequent development of fibrosis.

Sumatriptan mitigates bleomycin-induced lung fibrosis in male rats: Involvement of inflammation, oxidative stress and α-SMA

INTRODUCTION

Idiopathic pulmonary fibrosis (IPF) is a fibrotic lung condition that produces symptoms including coughing which may cause by excessive accumulation of scar tissue inflammatory and oxidative stress exacerbation. Sumatriptan, utilized for migraine treatment as a selective 5-HT1B/1D receptor agonist, has demonstrated significant anti-inflammatory and antioxidant properties in multiple preclinical investigations. Operating primarily on serotonin receptors, sumatriptan leverages the diverse physiological functions of serotonin, playing a pivotal role in regulating both inflammation and oxidative stress which is particularly relevant in the context of IPF.

MATERIALS & METHODS

Thirty-five male Wistar rats were divided to five group, including: Sham (without IPF induction), control (BLM 5 mg/kg, intraperitoneally), and three fibrosis group with sumatriptan (0.5, 1, and 3 mg/kg, i.p. for 2 weeks) administration. IPF was induced by injection of BLM (single dose, 5 mg/kg intratracheally). Lung tissues were separated for measurement of myeloperoxidase (MPO) as an oxidative stress hallmark, and tumor necrosis factor-α (TNF-α), interleukin-1β (IL-β), and transforming growth factor-β (TGF-β) as inflammatory markers as well as alpha smooth muscle actin (α-SMA). Also, for histological investigations, tissue damages were assessed by Hematoxylin-eosin (H&E) and Masson's trichrome staining method.

RESULTS

BLM-induced fibrosis could increase α-SMA, MPO, TNF-α, IL-1β, and TGF-β, while treatment with sumatriptan has reversed the α-SMA, MPO, and IL-1β levels. Moreover, the results of H&E and Masson's trichrome staining indicated that sumatriptan (1 and 3 mg/kg) reduced tissue damages, alveolar wall thickness, collagen accumulation, and pulmonary fibrosis induced by BLM.

CONCLUSION

According to the data achieved from this study, Sumatriptan appears to have therapeutic benefits in IPF, possibly via reducing α-SMA as well as inflammation and the toxicity caused by oxidative stress.

Elucidating the crosstalk between endothelial-to-mesenchymal transition (EndoMT) and endothelial autophagy in the pathogenesis of atherosclerosis

Atherosclerosis, a chronic systemic inflammatory condition, is implicated in most cardiovascular ischemic events. The pathophysiology of atherosclerosis involves various cell types and associated processes, including endothelial cell activation, monocyte recruitment, smooth muscle cell migration, involvement of macrophages and foam cells, and instability of the extracellular matrix. The process of endothelial-to-mesenchymal transition (EndoMT) has recently emerged as a pivotal process in mediating vascular inflammation associated with atherosclerosis. This transition occurs gradually, with a significant portion of endothelial cells adopting an intermediate state, characterized by a partial loss of endothelial-specific gene expression and the acquisition of "mesenchymal" traits. Consequently, this shift disrupts endothelial cell junctions, increases vascular permeability, and exacerbates inflammation, creating a self-perpetuating cycle that drives atherosclerotic progression. While endothelial cell dysfunction initiates the development of atherosclerosis, autophagy, a cellular catabolic process designed to safeguard cells by recycling intracellular molecules, is believed to exert a significant role in plaque development. Identifying the pathological mechanisms and molecular mediators of EndoMT underpinning endothelial autophagy, may be of clinical relevance. Here, we offer new insights into the underlying biology of atherosclerosis and present potential molecular mechanisms of atherosclerotic resistance and highlight potential therapeutic targets.

IQGAP1 Regulates Actin Polymerization and Contributes to Bleomycin-Induced Lung Fibrosis

We previously found IQ motif containing GTPase activating protein (IQGAP1) to be consistently elevated in lung fibroblasts (LF) isolated from patients with scleroderma (systemic sclerosis, SSc)-associated interstitial lung disease (ILD) and reported that IQGAP1 contributed to SSc by regulating expression and organization of α-smooth muscle actin (SMA) in LF. The aim of this study was to compare the development of ILD in the presence and absence of IQGAP1. Pulmonary fibrosis was induced in IQGAP1 knockout (KO) and wild-type (WT) mice by a single-intratracheal instillation of bleomycin. Two and three weeks later, mice were euthanized and investigated. We observed that the IQGAP1 KO mouse was characterized by a reduced rate of actin polymerization with reduced accumulation of actin in the lung compared to the WT mouse. After exposure to bleomycin, the IQGAP1 KO mouse demonstrated decreased contractile activity of LF, reduced expression of SMA, TGFβ, and collagen, and lowered overall fibrosis scores compared to the WT mouse. The numbers of inflammatory cells and expression of pro-inflammatory cytokines in lung tissue were not significantly different between IQGAP1 KO and WT mice. We conclude that IQGAP1 plays an important role in the development of lung fibrosis induced by bleomycin, and the absence of IQGAP1 reduces the contractile activity of lung fibroblast and bleomycin-induced pulmonary fibrosis. Thus, IQGAP1 may be a potential target for novel anti-fibrotic therapies for lung fibrosis.

Ivermectin ameliorates bleomycin-induced lung fibrosis in male rats by inhibiting the inflammation and oxidative stress

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a pulmonary fibrotic disease characterized by a poor prognosis, which its pathogenesis involves the accumulation of abnormal fibrous tissue, inflammation, and oxidative stress. Ivermectin, a positive allosteric modulator of GABAA receptor, exerts anti-inflammatory and antioxidant properties in preclinical studies. The present study investigates the potential protective effects of ivermectin treatment in rats against bleomycin-induced IPF.

MATERIALS AND METHODS

The present study involved 42 male Wistar rats, which were divided into five groups: control (without induction of IPF), bleomycin (IPF-induced by bleomycin 2.5 mg/kg, by intratracheal administration), and three fibrosis groups receiving ivermectin (0.5, 1, and 3 mg/kg). lung tissues were harvested for measurement of oxidative stress [via myeloperoxidase (MPO), superoxide dismutase (SOD), glutathione (GSH)] and inflammatory markers (tumor necrosis factor-α [TNF-α], interleukin-1β [IL-1β], and transforming growth factor-β [TGF-β]). Histological assessments of tissue damage were performed using hematoxylin-eosin (H&E) and Masson's trichrome staining methods.

RESULTS

The induction of fibrosis via bleomycin was found to increase levels of MPO as well as TNF-α, IL-1β, and TGF-β while decrease SOD activity and GSH level. Treatment with ivermectin at a dosage of 3 mg/kg was able to reverse the effects of bleomycin-induced fibrosis on these markers. In addition, results from H&E and Masson's trichrome staining showed that ivermectin treatment at this same dose reduced tissue damage and pulmonary fibrosis.

CONCLUSION

The data obtained from this study indicate that ivermectin may have therapeutic benefits for IPF, likely due to its ability to reduce inflammation and mitigate oxidative stress-induced toxicity.

Mechanosensing regulates tissue repair program in macrophages

Tissue-resident macrophages play important roles in tissue homeostasis and repair. However, how macrophages monitor and maintain tissue integrity is not well understood. The extracellular matrix (ECM) is a key structural and organizational component of all tissues. Here, we find that macrophages sense the mechanical properties of the ECM to regulate a specific tissue repair program. We show that macrophage mechanosensing is mediated by cytoskeletal remodeling and can be performed in three-dimensional environments through a noncanonical, integrin-independent mechanism analogous to amoeboid migration. We find that these cytoskeletal dynamics also integrate biochemical signaling by colony-stimulating factor 1 and ultimately regulate chromatin accessibility to control the mechanosensitive gene expression program. This study identifies an "amoeboid" mode of ECM mechanosensing through which macrophages may regulate tissue repair and fibrosis.

Trigonelline mitigates bleomycin-induced pulmonary inflammation and fibrosis: Insight into NLRP3 inflammasome and SPHK1/S1P/Hippo signaling modulation

AIMS

Pulmonary fibrosis (PF) is a chronic interstitial lung disease with an increasing incidence following the COVID-19 outbreak. Pirfenidone (Pirf), an FDA-approved pulmonary anti-fibrotic drug, is poorly tolerated and exhibits limited efficacy. Trigonelline (Trig) is a natural plant alkaloid with diverse pharmacological actions. We investigated the underlying prophylactic and therapeutic mechanisms of Trig in ameliorating bleomycin (BLM)-induced PF and the possible synergistic antifibrotic activity of Pirf via its combination with Trig.

MATERIALS AND METHODS

A single dose of BLM was administered intratracheally to male Sprague-Dawley rats for PF induction. In the prophylactic study, Trig was given orally 3 days before BLM and then for 28 days. In the therapeutic study, Trig and/or Pirf were given orally from day 8 after BLM until the 28th day. Biochemical assay, histopathology, qRT-PCR, ELISA, and immunohistochemistry were performed on lung tissues.

KEY FINDINGS

Trig prophylactically and therapeutically mitigated the inflammatory process via targeting NF-κB/NLRP3/IL-1β signaling. Trig activated the autophagy process which in turn attenuated alveolar epithelial cells apoptosis and senescence. Remarkably, Trig attenuated lung SPHK1/S1P axis and its downstream Hippo targets, YAP-1, and TAZ, with a parallel decrease in YAP/TAZ profibrotic genes. Interestingly, Trig upregulated lung miR-375 and miR-27a expression. Consequently, epithelial-mesenchymal transition in lung tissues was reversed upon Trig administration. These results were simultaneously associated with profound improvement in lung histological alterations.

SIGNIFICANCE

The current study verifies Trig's prophylactic and antifibrotic effects against BLM-induced PF via targeting multiple signaling. Trig and Pirf combination may be a promising approach to synergize Pirf antifibrotic effect.

Functional Pdgfra fibroblast heterogeneity in normal and fibrotic mouse lung

Aberrant fibroblast function plays a key role in the pathogenesis of idiopathic pulmonary fibrosis, a devastating disease of unrelenting extracellular matrix deposition in response to lung injury. Platelet-derived growth factor α-positive (Pdgfra+) lipofibroblasts (LipoFBs) are essential for lung injury response and maintenance of a functional alveolar stem cell niche. Little is known about the effects of lung injury on LipoFB function. Here, we used single-cell RNA-Seq (scRNA-Seq) technology and PdgfraGFP lineage tracing to generate a transcriptomic profile of Pdgfra+ fibroblasts in normal and injured mouse lungs 14 days after bleomycin exposure, generating 11 unique transcriptomic clusters that segregated according to treatment. While normal and injured LipoFBs shared a common gene signature, injured LipoFBs acquired fibrogenic pathway activity with an attenuation of lipogenic pathways. In a 3D organoid model, injured Pdgfra+ fibroblast-supported organoids were morphologically distinct from those cultured with normal fibroblasts, and scRNA-Seq analysis suggested distinct transcriptomic changes in alveolar epithelia supported by injured Pdgfra+ fibroblasts. In summary, while LipoFBs in injured lung have not migrated from their niche and retain their lipogenic identity, they acquire a potentially reversible fibrogenic profile, which may alter the kinetics of epithelial regeneration and potentially contribute to dysregulated repair, leading to fibrosis.

N-(2-Aminophenyl)-benzamide Inhibitors of Class I HDAC Enzymes with Antiproliferative and Antifibrotic Activity

Inhibitors of histone deacetylases (HDACs) have received special attention as novel anticancer agents. Among various types of synthetic inhibitors, benzamides constitute an important class, and one is an approved drug (chidamide). Here, we present a novel class of HDAC inhibitors containing the N-(2-aminophenyl)-benzamide functionality as the zinc-binding group linked to various cap groups, including the amino acids pyroglutamic acid and proline. We have identified benzamides that inhibit HADC1 and HDAC2 at nanomolar concentrations, with antiproliferative activity at micromolar concentrations against A549 and SF268 cancer cell lines. Docking studies shed light on the mode of binding of benzamide inhibitors to HDAC1, whereas cellular analysis revealed downregulated expression of EGFR mRNA and protein. Two benzamides were investigated in a mouse model of bleomycin-induced pulmonary fibrosis, and both showed efficacy on a preventative dosing schedule. N-(2-Aminophenyl)-benzamide inhibitors of class I HDACs might lead to new approaches for treating fibrotic disorders.

Macrophages and fibrosis: how resident and infiltrating mononuclear phagocytes account for organ injury, regeneration or atrophy

Mononuclear phagocytes (MP), i.e., monocytes, macrophages, and dendritic cells (DCs), are essential for immune homeostasis via their capacities to clear pathogens, pathogen components, and non-infectious particles. However, tissue injury-related changes in local microenvironments activate resident and infiltrating MP towards pro-inflammatory phenotypes that contribute to inflammation by secreting additional inflammatory mediators. Efficient control of injurious factors leads to a switch of MP phenotype, which changes the microenvironment towards the resolution of inflammation. In the same way, MP endorses adaptive structural responses leading to either compensatory hypertrophy of surviving cells, tissue regeneration from local tissue progenitor cells, or tissue fibrosis and atrophy. Under certain circumstances, MP contribute to the reversal of tissue fibrosis by clearance of the extracellular matrix. Here we give an update on the tissue microenvironment-related factors that, upon tissue injury, instruct resident and infiltrating MP how to support host defense and recover tissue function and integrity. We propose that MP are not intrinsically active drivers of organ injury and dysfunction but dynamic amplifiers (and biomarkers) of specific tissue microenvironments that vary across spatial and temporal contexts. Therefore, MP receptors are frequently redundant and suboptimal targets for specific therapeutic interventions compared to molecular targets upstream in adaptive humoral or cellular stress response pathways that influence tissue milieus at a contextual level.

SRC and TKS5 mediated podosome formation in fibroblasts promotes extracellular matrix invasion and pulmonary fibrosis

The activation and accumulation of lung fibroblasts resulting in aberrant deposition of extracellular matrix components, is a pathogenic hallmark of Idiopathic Pulmonary Fibrosis, a lethal and incurable disease. In this report, increased expression of TKS5, a scaffold protein essential for the formation of podosomes, was detected in the lung tissue of Idiopathic Pulmonary Fibrosis patients and bleomycin-treated mice. Τhe profibrotic milieu is found to induce TKS5 expression and the formation of prominent podosome rosettes in lung fibroblasts, that are retained ex vivo, culminating in increased extracellular matrix invasion. Tks5+/- mice are found resistant to bleomycin-induced pulmonary fibrosis, largely attributed to diminished podosome formation in fibroblasts and decreased extracellular matrix invasion. As computationally predicted, inhibition of src kinase is shown to potently attenuate podosome formation in lung fibroblasts and extracellular matrix invasion, and bleomycin-induced pulmonary fibrosis, suggesting pharmacological targeting of podosomes as a very promising therapeutic option in pulmonary fibrosis.

Tangeretin attenuates bleomycin-induced pulmonary fibrosis by inhibiting epithelial-mesenchymal transition via the PI3K/Akt pathway

Background: Pulmonary fibrosis (PF) is a terminal pathological change in a variety of lung diseases characterized by excessive deposition of extracellular matrix, for which effective treatment is lacking. Tangeretin (Tan), a flavonoid derived from citrus, has been shown to have a wide range of pharmacological effects. This study aimed to investigate the role and potential mechanisms of Tan on pulmonary fibrosis. Methods: A model of pulmonary fibrosis was established by administering bleomycin through tracheal drip, followed by administering Tan or pirfenidone through gavage. HE and Masson staining were employed to assess the extent of pulmonary fibrosis. Subsequently, Western blot, enzyme-linked immunosorbent assay (ELISA), RNA sequencing, and immunohistochemistry techniques were employed to uncover the protective mechanism of Tan in PF mice. Furthermore, A549 cells were stimulated with TGF-β1 to induce epithelial-mesenchymal transition (EMT) and demonstrate the effectiveness of Tan in mitigating PF. Results: Tan significantly ameliorated bleomycin-induced pulmonary fibrosis, improved fibrotic pathological changes, and collagen deposition in the lungs, and reduced lung inflammation and oxidative stress. The KEGG pathway enrichment analysis revealed a higher number of enriched genes in the PI3K/Akt pathway. Additionally, Tan can inhibit the EMT process related to pulmonary fibrosis. Conclusion: Taken together, the above research results indicate that Tan suppresses inflammation, oxidative stress, and EMT in BLM-induced pulmonary fibrosis via the PI3K/Akt pathway and is a potential agent for the treatment of pulmonary fibrosis.

Increased lipocalin-2 expression in pulmonary inflammation and fibrosis

Introduction

Idiopathic Pulmonary Fibrosis (IPF) is a chronic, progressive interstitial lung disease with dismal prognosis. The underlying pathogenic mechanisms are poorly understood, resulting in a lack of effective treatments. However, recurrent epithelial damage is considered critical for disease initiation and perpetuation, via the secretion of soluble factors that amplify inflammation and lead to fibroblast activation and exuberant deposition of ECM components. Lipocalin-2 (LCN2) is a neutrophil gelatinase-associated lipocalin (NGAL) that has been suggested as a biomarker of kidney damage. LCN2 has been reported to modulate innate immunity, including the recruitment of neutrophils, and to protect against bacterial infections by sequestering iron.

Methods

In silico analysis of publicly available transcriptomic datasets; ELISAs on human IPF patients' bronchoalveolar lavage fluids (BALFs); bleomycin (BLM)-induced pulmonary inflammation and fibrosis and LPS-induced acute lung injury (ALI) in mice: pulmonary function tests, histology, Q-RT-PCR, western blot, and FACS analysis.

Results and discussion

Increased LCN2 mRNA expression was detected in the lung tissue of IPF patients negatively correlating with respiratory functions, as also shown for BALF LCN2 protein levels in a cohort of IPF patients. Increased Lcn2 expression was also detected upon BLM-induced pulmonary inflammation and fibrosis, especially at the acute phase correlating with neutrophilic infiltration, as well as upon LPS-induced ALI, an animal model characterized by neutrophilic infiltration. Surprisingly, and non withstanding the limitations of the study and the observed trends, Lcn2-/- mice were found to still develop BLM- or LPS-induced pulmonary inflammation and fibrosis, thus questioning a major pathogenic role for Lcn2 in mice. However, LCN2 qualifies as a surrogate biomarker of pulmonary inflammation and a possible indicator of compromised pulmonary functions, urging for larger studies.

Advances in the Use of N-Acetylcysteine in Chronic Respiratory Diseases

N-acetylcysteine (NAC) is widely used because of its mucolytic effects, taking part in the therapeutic protocols of cystic fibrosis. NAC is also administered as an antidote in acetaminophen (paracetamol) overdosing. Thanks to its wide antioxidative and anti-inflammatory effects, NAC may also be of benefit in other chronic inflammatory and fibrotizing respiratory diseases, such as chronic obstructive pulmonary disease, bronchial asthma, idiopathic lung fibrosis, or lung silicosis. In addition, NAC exerts low toxicity and rare adverse effects even in combination with other treatments, and it is cheap and easily accessible. This article brings a review of information on the mechanisms of inflammation and oxidative stress in selected chronic respiratory diseases and discusses the use of NAC in these disorders.

Alcohol-mediated susceptibility to lung fibrosis is associated with group 2 innate lymphoid cells in mice

Chronic alcohol ingestion promotes acute lung injury and impairs immune function. However, the mechanisms involved are incompletely understood. Here, we show that alcohol feeding enhances bleomycin-induced lung fibrosis and inflammation via the regulation of type 2 innate immune responses, especially by group 2 innate lymphoid cells (ILC2s). Neuroimmune interactions have emerged as critical modulators of lung inflammation. We found alcohol consumption induced the accumulation of ILC2 and reduced the production of the neuropeptide calcitonin gene-related peptide (CGRP), primarily released from sensory nerves and pulmonary neuroendocrine cells (PNECs). CGRP potently suppressed alcohol-driven type 2 cytokine signals in vivo. Vagal ganglia TRPV1+ afferents mediated immunosuppression occurs through the release of CGRP. Inactivation of the TRPV1 receptor enhanced bleomycin-induced fibrosis. In addition, mice lacking the CGRP receptor had the increased lung inflammation and fibrosis and type 2 cytokine production as well as exaggerated responses to alcohol feeding. Together, these data indicate that alcohol consumption regulates the interaction of CGRP and ILC2, which is a critical contributor of lung inflammation and fibrosis.

NO-sensitive guanylyl cyclase discriminates pericyte-derived interstitial from intra-alveolar myofibroblasts in murine pulmonary fibrosis

BACKGROUND

The origin of αSMA-positive myofibroblasts, key players within organ fibrosis, is still not fully elucidated. Pericytes have been discussed as myofibroblast progenitors in several organs including the lung.

METHODS

Using tamoxifen-inducible PDGFRβ-tdTomato mice (PDGFRβ-CreER^T2; R26tdTomato) lineage of lung pericytes was traced. To induce lung fibrosis, a single orotracheal dose of bleomycin was given. Lung tissue was investigated by immunofluorescence analyses, hydroxyproline collagen assay and RT-qPCR.

RESULTS

Lineage tracing combined with immunofluorescence for nitric oxide-sensitive guanylyl cyclase (NO-GC) as marker for PDGFRβ-positive pericytes allows differentiating two types of αSMA-expressing myofibroblasts in murine pulmonary fibrosis: (1) interstitial myofibroblasts that localize in the alveolar wall, derive from PDGFRβ⁺ pericytes, express NO-GC and produce collagen 1. (2) intra-alveolar myofibroblasts which do not derive from pericytes (but express PDGFRβ de novo after injury), are negative for NO-GC, have a large multipolar shape and appear to spread over several alveoli within the injured areas. Moreover, NO-GC expression is reduced during fibrosis, i.e., after pericyte-to-myofibroblast transition.

CONCLUSION

In summary, αSMA/PDGFRβ-positive myofibroblasts should not be addressed as a homogeneous target cell type within pulmonary 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.

Radiolabeled GPVI-Fc for PET Imaging of Multiple Extracellular Matrix Fibers: A New Look into Pulmonary Fibrosis Progression

Invariably fatal and with a particularly fast progression, pulmonary fibrosis (PF) is currently devoid of curative treatment options. Routine clinical diagnosis relies on breathing tests and visualizing the changes in lung structure by CT, but anatomic information is often not sufficient to identify early signs of progressive PF. For more efficient diagnosis, additional imaging techniques were investigated in combination with CT, such as 18F-FDG PET, although with limited success because of lack of disease specificity. Therefore, novel molecular targets enabling specific diagnosis are investigated, in particular for molecular imaging techniques. Methods: In this study, we used a 64Cu-radiolabeled platelet glycoprotein VI fusion protein (64Cu-GPVI-Fc) targeting extracellular matrix (ECM) fibers as a PET tracer to observe longitudinal ECM remodeling in a bleomycin-induced PF mouse model. Results: 64Cu-GPVI-Fc showed significant uptake in fibrotic lungs, matching histology results. Contrary to 18F-FDG PET measurements, 64Cu-GPVI-Fc uptake was linked entirely to the fibrotic activity of tissue and not was susceptible to inflammation. Conclusion: Our study highlights 64Cu-GPVI-Fc as a specific tracer for ECM remodeling in PF, with clear therapy-monitoring and clinical translation potential.

SIRT1 ubiquitination is regulated by opposing activities of APC/C-Cdh1 and AROS during stress-induced premature senescence

SIRT1, a member of the mammalian sirtuin family, is a nicotinamide adenosine dinucleotide (NAD)-dependent deacetylase with key roles in aging-related diseases and cellular senescence. However, the mechanism by which SIRT1 protein homeostasis is controlled under senescent conditions remains elusive. Here, we revealed that SIRT1 protein is significantly downregulated due to ubiquitin-mediated proteasomal degradation during stress-induced premature senescence (SIPS) and that SIRT1 physically associates with anaphase-promoting complex/cyclosome (APC/C), a multisubunit E3 ubiquitin ligase. Ubiquitin-dependent SIRT1 degradation is stimulated by the APC/C coactivator Cdh1 and not by the coactivator Cdc20. We found that Cdh1 depletion impaired the SIPS-promoted downregulation of SIRT1 expression and reduced cellular senescence, likely through SIRT1-driven p53 inactivation. In contrast, AROS, a SIRT1 activator, reversed the SIRT1 degradation induced by diverse stressors and antagonized Cdh1 function through competitive interactions with SIRT1. Furthermore, our data indicate opposite roles for Cdh1 and AROS in the epigenetic regulation of the senescence-associated secretory phenotype genes IL-6 and IL-8. Finally, we demonstrated that pinosylvin restores downregulated AROS (and SIRT1) expression levels in bleomycin-induced mouse pulmonary senescent tissue while repressing bleomycin-promoted Cdh1 expression. Overall, our study provides the first evidence of the reciprocal regulation of SIRT1 stability by APC/C-Cdh1 and AROS during stress-induced premature senescence, and our findings suggest pinosylvin as a potential senolytic agent for pulmonary fibrosis.

Comparing species-different responses in pulmonary fibrosis research: Current understanding of in vitro lung cell models and nanomaterials

Pulmonary fibrosis (PF) is a chronic, irreversible lung disease that is typically fatal and characterized by an abnormal fibrotic response. As a result, vast areas of the lungs are gradually affected, and gas exchange is impaired, making it one of the world's leading causes of death. This can be attributed to a lack of understanding of the onset and progression of the disease, as well as a poor understanding of the mechanism of adverse responses to various factors, such as exposure to allergens, nanomaterials, environmental pollutants, etc. So far, the most frequently used preclinical evaluation paradigm for PF is still animal testing. Nonetheless, there is an urgent need to understand the factors that induce PF and find novel therapeutic targets for PF in humans. In this regard, robust and realistic in vitro fibrosis models are required to understand the mechanism of adverse responses. Over the years, several in vitro and ex vivo models have been developed with the goal of mimicking the biological barriers of the lung as closely as possible. This review summarizes recent progress towards the development of experimental models suitable for predicting fibrotic responses, with an emphasis on cell culture methods, nanomaterials, and a comparison of results from studies using cells from various species.

Inhibitory Effects of 3-Cyclopropylmethoxy-4-(difluoromethoxy) Benzoic Acid on TGF-β1-Induced Epithelial-Mesenchymal Transformation of In Vitro and Bleomycin-Induced Pulmonary Fibrosis In Vivo

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease characterized by lung inflammation and excessive deposition of extracellular matrix components. Transforming growth factor-β1 (TGF-β1) induced epithelial-mesenchymal transformation of type 2 lung epithelial cells leads to excessive extracellular matrix deposition, which plays an important role in fibrosis. Our objective was to evaluate the effects of 3-cyclopropylmethoxy-4-(difluoromethoxy) benzoic acid (DGM) on pulmonary fibrosis and aimed to determine whether EMT plays a key role in the pathogenesis of pulmonary fibrosis and whether EMT can be used as a therapeutic target for DGM therapy to reduce IPF. Firstly, stimulation of in vitro cultured A549 cells to construct EMTs with TGF-β1. DGM treatment inhibited the expression of proteins such as α-SMA, vimentin, and collagen Ⅰ and increased the expression of E-cadherin. Accordingly, Smad2/3 phosphorylation levels were significantly reduced by DGM treatment. Secondly, models of tracheal instillation of bleomycin and DGM were used to treat rats to demonstrate their therapeutic effects, such as improving lung function, reducing lung inflammation and fibrosis, reducing collagen deposition, and reducing the expression of E-cadherin. In conclusion, DGM attenuates TGF-β1-induced EMT in A549 cells and bleomycin-induced pulmonary fibrosis in rats.

Bu-Fei-Huo-Xue capsule alleviates bleomycin-induced pulmonary fibrosis in mice through modulating gut microbiota

Introduction: Bu-Fei-Huo-Xue capsule (BFHX) has been used to treat pulmonary fibrosis (PF) in clinic. However, the mechanism of Bu-Fei-Huo-Xue capsule on pulmonary fibrosis remains unclear. Recent studies have shown that the changes in gut microbiota were closely related to the progression of pulmonary fibrosis. Modulating gut microbiota provides new thoughts in the treatment of pulmonary fibrosis. Methods: In this study,a mouse model of pulmonary fibrosis was induced using bleomycin (BLM) and treated with Bu-Fei-Huo-Xue capsule. We firstly evaluated the therapeutic effects of Bu-Fei-Huo-Xue capsule on pulmonary fibrosis model mice. Besides,the anti-inflammatory and anti- oxidative effects of Bu-Fei-Huo-Xue capsule were evaluated. Furthermore, 16S rRNA sequencing was used to observe the changes in gut microbiota in pulmonary fibrosis model mice after Bu-Fei-Huo-Xue capsule treatment. Results: Our results showed that Bu-Fei-Huo-Xue capsule significantly reduced the collagen deposition in pulmonary fibrosis model mice. Bu-Fei-Huo-Xue capsule treatment also reduced the levels and mRNA expression of pro-inflammatory cytokines and inhibited the oxidative stress in lung. 16S rRNA sequencing showed that Bu-Fei-Huo-Xue capsule affected the diversity of gut microbiota and the relative abundances of gut microbiota such as Lactobacillus, Lachnospiraceae_NK4A136_group, and Romboutsia. Conclusion: Our study demonstrated the therapeutic effects of Bu-Fei-Huo-Xue capsule on pulmonary fibrosis. The mechanisms of Bu-Fei-Huo-Xue capsule on pulmonary fibrosis may be associated with regulating gut microbiota.

Immune Mechanisms of Pulmonary Fibrosis with Bleomycin

Fibrosis and structural remodeling of the lung tissue can significantly impair lung function, often with fatal consequences. The etiology of pulmonary fibrosis (PF) is diverse and includes different triggers such as allergens, chemicals, radiation, and environmental particles. However, the cause of idiopathic PF (IPF), one of the most common forms of PF, remains unknown. Experimental models have been developed to study the mechanisms of PF, and the murine bleomycin (BLM) model has received the most attention. Epithelial injury, inflammation, epithelial-mesenchymal transition (EMT), myofibroblast activation, and repeated tissue injury are important initiators of fibrosis. In this review, we examined the common mechanisms of lung wound-healing responses after BLM-induced lung injury as well as the pathogenesis of the most common PF. A three-stage model of wound repair involving injury, inflammation, and repair is outlined. Dysregulation of one or more of these three phases has been reported in many cases of PF. We reviewed the literature investigating PF pathogenesis, and the role of cytokines, chemokines, growth factors, and matrix feeding in an animal model of BLM-induced PF.

Berberine regulates pulmonary inflammatory microenvironment and decreases collagen deposition in response to bleomycin-induced pulmonary fibrosis in mice

The purpose of this study was to explore the protective effect and potential mechanism of berberine on bleomycin (BLM)-induced fibrosis after lung injury in conjunction with network pharmacology. Berberine and pulmonary fibrosis prediction targets were collected for Gene Ontology (GO) functional analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis and so forth. A single intranasal dose of BLM (2.5 mg/kg) was administered to establish a model of fibrosis after lung injury, and berberine (50 mg/kg) was administered intraperitoneally daily for treatment. Network pharmacology results suggested that the mitogen-activated protein kinase (MAPK) signalling pathway may be a potential mechanism of berberine in delaying pulmonary fibrosis. The results of animal experiments showed that compared with the BLM group, after 14 days of berberine treatment, lung inflammatory cell aggregation was reduced and the expression levels of tumour necrosis factor-α (TNF-α), interleukin (IL)-8 and IL-6 were down-regulated in mice (p < 0.05); after 42 days of berberine treatment, the expression levels of transforming growth factor (TGF)-β1, platelet-derived growth factor-AB (PDGF-AB), hydroxyproline (HYP) and α-smooth muscle actin (α-SMA) were significantly down-regulated (p < 0.05), and the expression levels of total p38 MAPKα and p38 MAPKα (pT180/Y182) were down-regulated also (p < 0.05), inhibited collagen production and deposition, and increased the survival rate of mice to 70%. In conclusion, berberine attenuated inflammation mice, inhibited collagen production and showed some anti-pulmonary fibrosis potential in the MAPK signalling pathway.

TLR4/ MyD88/NF-κB signaling pathway involved in the protective effect of diacerein against lung fibrosis in rats

PURPOSE

Pulmonary fibrosis (PF) is an inescapable problem. Diacerein, a chondro-protective drug, has antioxidant and anti-inflammatory effects. Its effect on PF injury has not yet been fully clarified. Therefore, the current study aimed to detect its protective effect on lung tissue with the explanation of possible underlying mechanisms.

METHODS

Adult male albino rats were assigned to four groups: control group, diacerein control group, PF non-treated group, and PF diacerein pretreated group. Lung tissue oxidative stress parameters, inflammatory biomarkers mainly Toll-like receptors-4 (TLR4), and myeloid differentiation factor 88 (MyD88) levels were determined. Histopathological examination of lung tissue and immunohistochemical studies of nuclear factor-kappa B (NF-κB), and transforming growth factor- β (TGF-β) were also done.

RESULTS

Diacerein pretreatment has the ability to restore the PF damaging effect, proved by the reduction of the oxidative stress and lung tissue inflammation via downregulation of TLR4/NF-κB signaling pathway together with the restoration of TGF-β level and improvement of the histopathological and immunohistochemical study findings in the lung tissue.

CONCLUSION

These results suggested the protective effect of diacerein on PF relies on its antioxidant and anti-inflammatory effects reducing TLR4/NF-κB signaling pathway.

Atorvastatin and ezetimibe protect against hypercholesterolemia-induced lung oxidative stress, inflammation, and fibrosis in rats

Background

Hypercholesterolemia is a major risk factor for interstitial lung disease (ILD). Atorvastatin and ezetimibe are antilipemic drugs that have pleiotropic effects. However, their effects on pulmonary fibrosis prevention and the mechanisms underlying hypercholesterolemia have not been fully investigated. This study aimed to evaluate the individual effects of atorvastatin and ezetimibe on lung inflammation and fibrosis in high-cholesterol diet (HCD)-fed rats.

Materials and methods

Male Sprague-Dawley rats were divided into four groups — standard diet (S), standard diet + 1% cholesterol (SC), standard diet + 1% cholesterol with 30 mg/kg/day atorvastatin (SCA), and standard diet + 1% cholesterol with 10 mg/kg/day ezetimibe (SCE). At the end of an 8-week dietary schedule, serum lipid parameters and the levels of lung oxidative stress, inflammatory cytokines, and fibrotic mediators were determined.

Results

Atorvastatin and ezetimibe treatment remarkably reduced serum lipid profiles with reversed pulmonary histological alterations, in addition to reducing the levels of lung oxidative stress, inflammation, and fibrosis in hypercholesterolemic rats.

Conclusion

Atorvastatin and ezetimibe treatment showed a protective effect against hypercholesterolemia-induced pulmonary fibrosis in rats. This information appears potentially useful in the prevention of PF in a hypercholesterolemia model; however, further rigorous investigations are needed to prove their clinical utility on antifibrosis.

Allies or enemies? The effect of regulatory T cells and related T lymphocytes on the profibrotic environment in bleomycin-injured lung mouse models

Idiopathic pulmonary fibrosis (IPF) is characterized by permanent scarring of lung tissue and declining lung function, and is an incurable disease with increase in prevalence over the past decade. The current consensus is that aberrant wound healing following repeated injuries to the pulmonary epithelium is the most probable cause of IPF, with various immune inflammatory pathways having been reported to impact disease pathogenesis. While the role of immune cells, specifically T lymphocytes and regulatory T cells (Treg), in IPF pathogenesis has been reported and discussed recently, the pathogenic or beneficial roles of these cells in inducing or preventing lung fibrosis is still debated. This lack of understanding could be due in part to the difficulty in obtaining diseased human lung tissue for research purposes. For this reason, many animal models have been developed over the years to attempt to mimic the main clinical hallmarks of IPF: among these, inducing lung injury in rodents with the anti-cancer agent bleomycin has now become the most commonly studied animal model of IPF. Pulmonary fibrosis is the major side effect when bleomycin is administered for cancer treatment in human patients, and a similar effect can be observed after intra-tracheal administration of bleomycin to rodents. Despite many pathophysiological pathways of lung fibrosis having been investigated in bleomycin-injured animal models, one central facet still remains controversial, namely the involvement of specific T lymphocyte subsets, and in particular Treg, in disease pathogenesis. This review aims to summarize the major findings and conclusions regarding the involvement of immune cells and their receptors in the pathogenesis of IPF, and to elaborate on important parallels between animal models and the human disease. A more detailed understanding of the role of Treg and other immune cell subsets in lung injury and fibrosis derived from animal models is a critical basis for translating this knowledge to the development of new immune-based therapies for the treatment of human IPF.

Pathophysiological Changes in Rhesus Monkeys with Paraquat-Induced Pulmonary Fibrosis

Purpose

Pulmonary fibrosis is a life-threatening lung disorder. A comprehensive understanding of the pathophysiological changes in the development of pulmonary fibrosis will lead to new insights into its treatment.

Methods

We used a paraquat (PQ)-induced rhesus monkey model of pulmonary fibrosis to comprehensively investigate the process of pulmonary fibrosis development. Rhesus monkeys were orally administered PQ at concentrations of 25 mg/kg, 40 mg/kg, and 80 mg/kg. The dose was given once. Behavior and clinical data, such as PQ concentration, arterial oxygen saturation, biochemical evaluation, lung histopathology, and medical imaging, were continuously observed.

Results

Paraquat-exposed monkeys developed pulmonary fibrosis following an expected time course, especially at 25 mg/kg. CT images showed ground-glass lesions in the lung after 4 weeks, and pulmonary fibrosis persisted until the end of follow-up. Using pathological examination, the lung sustained collagen deposition and slight inflammatory cell infiltration. All rhesus monkeys had obvious inflammatory infiltration within 1 week according to the immunohistochemical results and the number of leukocytes in the blood. The CT results showed that pulmonary fibrosis had not formed, indicating that drugs with powerful anti-inflammatory ability are potential candidates for early pulmonary fibrosis treatment.

Conclusion

Our study describes the dynamic process of paraquat-induced pulmonary fibrosis in rhesus monkeys and provided a pathophysiological basis for the treatment of pulmonary fibrosis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00408-022-00572-9.

Integrated RNA-sequencing and network pharmacology approach reveals the protection of Yiqi Huoxue formula against idiopathic pulmonary fibrosis by interfering with core transcription factors

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a refractory disease. Therefore, developing effective therapies for IPF is the need of the hour.

PURPOSE

Yiqi Huoxue Formula (YQHX) is an herbal formula comprising three herbal medicines: Ligusticum chuanxiong Hort. (Chuanxiong Rhizoma, CR), Panax notoginseng (Burk.) F. H. Chen (Notoginseng Radix Et Rhizoma, NR) and Panax ginseng C. A. Mey. (Ginseng Radix Et Rhizoma, GR). This study aims to determine the anti-pulmonary fibrosis effect of YQHX and explore its mechanism of action.

STUDY

Design and Methods: The chemical components in the GR, CR and NR extracts were identified by High Performance Liquid Chromatography. A TGF-β1-induced myofibroblast cell model was used to test the anti-fibrosis effect of GR, CR, NR and YQHX. RNA-sequencing was used to identify the differentially expressed genes (DEGs) after YQHX treatment. Subsequently, gene enrichment analysis and key transcription factors (TFs) prediction for YQHX-regulated DEGs was performed. The active constituents of GR, CR and NR were obtained from the Traditional Chinese Medicine Database and Analysis Platform. Targets of the active constituents were predicted using the similarity ensemble approach search server and Swiss Target Prediction tool. YQHX-targeted key TFs that transcribed the DEGs were screened out. Then, the effect of YQHX on the bleomycin-induced pulmonary fibrosis mouse model was studied. Finally, one of the predicted TFs, STAT3, was selected to validate the prediction accuracy.

RESULTS

Seven, two, and five compounds were identified in the GR, CR, and NR extracts, respectively. YQHX and its constituents-GR, CR and NR-inhibited the expression of fibrotic markers, including α -SMA and fibronectin, indicating that YQHX inhibited TGF-β1-induced myofibroblast activation. RNA-sequencing identified 291 genes that were up-regulated in the TGF-β1 group but down-regulated after YQHX treatment. In total, 55 key TFs that transcribed YQHX-regulated targets were predicted. A regulatory network of 24 active ingredients and 232 corresponding targets for YQHX was established. Among YQHX's predicted targets, 20 were TFs. On overlapping YQHX-targeted TFs and DEGs' key TFs, six key TFs, including HIF1A, STAT6, STAT3, PPARA, DDIT3 and AR, were identified as the targets of YQHX. Additionally, YQHX alleviated bleomycin-induced pulmonary fibrosis in a mouse model by inhibiting the phosphorylation of STAT3 in the lungs of pulmonary fibrosis mice.

CONCLUSIONS

This study provides pharmacological support for the use of YQHX in the treatment of IPF. The potential mechanism of action of YQHX is speculated to involve the modulation of core TFs and inhibition of pathogenetic gene expressions in IPF.

3′5-Dimaleamylbenzoic Acid Attenuates Bleomycin-Induced Pulmonary Fibrosis in Mice

Idiopathic pulmonary fibrosis (IPF) is a chronic lung disease characterized by parenchymal scarring, leading progressively to alveolar architecture distortion, respiratory failure, and eventually death. Currently, there is no effective treatment for IPF. Previously, 3′5-dimaleamylbenzoic acid (3′5-DMBA), a maleimide, demonstrated pro-apoptotic, anti-inflammatory, and anti-cancer properties; however, its potential therapeutic effects on IPF have not been addressed. Bleomycin (BLM) 100 U/kg was administered to CD1 mice through an osmotic minipump. After fourteen days of BLM administration, 3′5-DMBA (6 mg/kg or 10 mg/kg) and its vehicle carboxymethylcellulose (CMC) were administered intragastrically every two days until day 26. On day 28, all mice were euthanized. The 3′5-DMBA effect was assessed by histological and immunohistochemical staining, as well as by RT-qPCR. The redox status on lung tissue was evaluated by determining the glutathione content and the GSH/GSSG ratio. 3′5-DMBA treatment re-established typical lung histological features and decreased the expression of BLM-induced fibrotic markers: collagen, α-SMA, and TGF-β1. Furthermore, 3′5-DMBA significantly reduced the expression of genes involved in fibrogenesis. In addition, it decreased reduced glutathione and increased oxidized glutathione content without promoting oxidative damage to lipids, as evidenced by the decrease in the lipid peroxidation marker 4-HNE. Therefore, 3′5-DMBA may be a promising candidate for IPF treatment.

Mechanisms exploration of Terrestrosin D on pulmonary fibrosis based on plasma metabolomics and network pharmacology

Terrestrosin D (TED) is the active ingredient of Tribulus terrestris L., which is used in traditional Chinese medicine (TCM) formulations and has a wide range of pharmacological activities. A previous study showed that TED alleviated bleomycin (BLM)-induced pulmonary fibrosis (PF) in mice. However, the mechanisms underlying the therapeutic effect of TED are still unclear and need further investigation. In this study, we evaluated the effect of TED in a mice of BLM-induced PF in terms of histopathological and biochemical indices. UHPLC-MS-based plasma metabolomics combined with network pharmacology was used to explore the pathological basis of PF and the mechanism of action of TED. Histological and biochemical analyses showed that TED mitigated inflammatory injury in the lungs, especially at the dosage of 20 mg/kg. Furthermore, BLM changed the plasma metabolite profile in the mice, which was reversed by TED via regulation of amino acid and lipid metabolism. Subsequently, a biomarkers-targets-disease network was constructed, tumor necrosis factor (TNF)-α and transforming growth factor (TGF)-β1 were identified as the putative therapeutic targets of TED. Both factors were quantitatively analyzed by enzyme-linked immunosorbent assay (ELISA). Taken together, the combination of UHPLC-MS-based metabolomics and network pharmacology can unveil the mechanisms of diseases and drug action.

Catalpol Attenuates Pulmonary Fibrosis by Inhibiting Ang II/AT1 and TGF-β/Smad-Mediated Epithelial Mesenchymal Transition

Background

Idiopathic pulmonary fibrosis (IPF) is a progressive and devastating chronic lung condition affecting over 3 million people worldwide with a high mortality rate and there are no effective drugs. Angiotensin II (Ang II), as a major effector peptide of the renin angiotensin aldosterone system, has been shown to act in tandem with the transforming growth factor-β (TGF-β) signaling pathway to promote the infiltration of inflammatory cells, production of reactive oxygen species (ROS) and profibrotic factors after lung injury, and to participate in the process of epithelial mesenchymal transition (EMT). Catalpol (CAT) has been shown to have anti-inflammatory and antifibrotic effects. However, the effects and mechanisms of CAT on pulmonary fibrosis are not clear.

Purpose

To assess the effects and mechanisms of catalpol on bleomycin-induced pulmonary fibrosis in mice.

Methods

We used bleomycin-induced mouse model of pulmonary fibrosis to evaluate the alleviation effect of CAT at 7, 14, 28d, respectively. Next, enzyme-linked immunosorbent assay, hematoxylin-eosin staining, immunofluorescence, Masson trichrome staining and western blotting were used to study the underlying mechanism of CAT on bleomycin-induced pulmonary fibrosis.

Results

It's demonstrated that CAT exerted a potent anti-fibrotic function in BLM-induced mice pulmonary fibrosis via alleviating inflammatory, ameliorating collagen deposition, reducing the level of Ang II and HYP and alleviating the degree of EMT. Moreover, CAT attenuate BLM-induced fibrosis by targeting Ang II/AT₁ and TGF-β/Smad signaling in vivo.

Conclusion

CAT may serve as a novel therapeutic candidate for the simultaneous blockade of Ang II and TGF-β pathway to attenuate pulmonary 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.

Inhibition of CHIT1 as a novel therapeutic approach in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and eventually fatal lung disease with a complex etiology. Approved drugs, nintedanib and pirfenidone, modify disease progression, but IPF remains incurable and there is an urgent need for new therapies. We identified chitotriosidase (CHIT1) as new driver of fibrosis in IPF and a novel therapeutic target. We demonstrate that CHIT1 activity and expression are significantly increased in serum (3-fold) and induced sputum (4-fold) from IPF patients. In the lungs CHIT1 is expressed in a distinct subpopulation of profibrotic, disease-specific macrophages, which are only present in patients with ILDs and CHIT1 is one of the defining markers of this fibrosis-associated gene cluster. To define CHIT1 role in fibrosis, we used the therapeutic protocol of the bleomycin-induced pulmonary fibrosis mouse model. We demonstrate that in the context of chitinase induction and the macrophage-specific expression of CHIT1, this model recapitulates lung fibrosis in ILDs. Genetic inactivation of Chit1 attenuated bleomycin-induced fibrosis (decreasing the Ashcroft scoring by 28%) and decreased expression of profibrotic factors in lung tissues. Pharmacological inhibition of chitinases by OATD-01 reduced fibrosis and soluble collagen concentration. OATD-01 exhibited anti-fibrotic activity comparable to pirfenidone resulting in the reduction of the Ashcroft score by 32% and 31%, respectively. These studies provide a preclinical proof-of-concept for the antifibrotic effects of OATD-01 and establish CHIT1 as a potential new therapeutic target for IPF.

Reciprocal regulation of IL-33 receptor-mediated inflammatory response and pulmonary fibrosis by TRAF6 and USP38

Significance IL-33R mediates local inflammatory responses and plays crucial roles in the pathogenesis of immune diseases. In this study, we identified USP38, which negatively regulates IL-33-triggered signaling by mediating K27-linked deubiquitination of IL-33R at K511 and its autophagic degradation. USP38 deficiency aggravates IL-33-induced lung inflammatory response and bleomycin-induced pulmonary fibrosis. We further show that the E3 ubiquitin ligase TRAF6 catalyzes K27-linked polyubiquitination of IL-33R at K511, and that deficiency of TRAF6 inhibits IL-33-mediated signaling. Our findings reveal an important mechanism regarding how IL-33R is precisely regulated to ensure its inactivation in rest cells and proper activation following IL-33 stimulation.

Irreversibility of Pulmonary Fibrosis

Pulmonary fibrosis, a kind of terminal pathological changes in the lung, is caused by aberrant wound healing, deposition of extracellular matrix (ECM), and eventually replacement of lung parenchyma by ECM. Pulmonary fibrosis induced by acute lung injury and some diseases is reversible under treatment. While idiopathic pulmonary fibrosis is persistent and irreversible even after treatment. Currently, the pathogenesis of irreversible pulmonary fibrosis is not fully elucidated. The known factors associated with the development of irreversible fibrosis include apoptosis resistance of (myo)fibroblasts, dysfunction of pulmonary vessel, cell mitochondria and autophagy, aberrant epithelia hyperplasia and lipid metabolism disorder. In this review, other than a brief introduction of reversible pulmonary fibrosis, we focus on the underlying pathogenesis of irreversible pulmonary fibrosis from the above aspects as well as preclinical disease models, and also suggest directions for future studies.

Inhibition of nuclear factor κB in the lungs protect bleomycin-induced lung fibrosis in mice

BACKGROUND

Pulmonary fibrosis is a debilitating condition with limited therapeutic avenues. The pathogenicity of pulmonary fibrosis constitutes involvement of cellular proliferation, activation, and transformational changes of fibroblast to myofibroblasts. It is a progressive lung disease and is primarily characterized by aberrant accumulation of extracellular matrix proteins in the lungs with poor prognosis. The inflammatory response in the pathogenesis of lung fibrosis is suggested because of release of several cytokines; however, the underlying mechanism remains undefined. A genetic model is the appropriate way to delineate the underlying mechanism of pulmonary fibrosis.

METHODS AND RESULTS

In this report, we have used cc-10 promoter based IκBα mutant mice (IKBM, an inhibitor of NF-κB) which were challenged with bleomycin (BLM). Compared to wild-type (WT) mice, the IKBM mice showed significant reduction in several fibrotic, vascular, and inflammatory genes. Moreover, we have identified a new set of dysregulated microRNAs (miRNAs) by miRNA array analysis in BLM-induced WT mice. Among these miRNAs, let-7a-5p and miR-503-5p were further analyzed. Our data showed that these two miRNAs were upregulated in WT-BLM and were reduced in IKBM-BLM mice. Bioinformatic analyses showed that let-7a-5p and miR-503-5p target for endothelin1 and bone morphogenic receptor 1A (BMPR1A), respectively, and were downregulated in WT-BLM mice indicating a link in pulmonary fibrosis.

CONCLUSION

We concluded that inhibition of NF-κB and modulation of let-7a-5p and miR-503-5p contribute a pivotal role in pulmonary fibrosis and may be considered as possible therapeutic target for the clinical management of lung fibrosis.

Bioinformatics Analysis Identifies Potential Ferroptosis Key Genes in the Pathogenesis of Pulmonary Fibrosis

Objective: Ferroptosis has an important role in developing pulmonary fibrosis. The present project aimed to identify and validate the potential ferroptosis-related genes in pulmonary fibrosis by bioinformatics analyses and experiments.

Methods: First, the pulmonary fibrosis tissue sequencing data were obtained from Gene Expression Omnibus (GEO) and FerrDb databases. Bioinformatics methods were used to analyze the differentially expressed genes (DEGs) between the normal control group and the pulmonary fibrosis group and extract ferroptosis-related DEGs. Hub genes were screened by enrichment analysis, protein-protein interaction (PPI) analysis, and random forest algorithm. Finally, mouse pulmonary fibrosis model was made for performing an exercise intervention and the hub genes’ expression was verified through qRT-PCR.

Results: 13 up-regulated genes and 7 down-regulated genes were identified as ferroptosis-related DEGs by comparing 103 lung tissues with idiopathic pulmonary fibrosis (IPF) and 103 normal lung tissues. PPI results indicated the interactions among these ferroptosis-related genes. Kyoto Encyclopedia of Genes and Genomes (KEGG) Pathway enrichment and Genome-Ontology (GO) enrichment analyses showed that these ferroptosis-related genes involved in the organic anion transport, response to hypoxia, response to decrease oxygen level, HIF-1 signaling pathway, renal cell carcinoma, and arachidonic acid metabolism signaling pathway. The confirmed genes using PPI analysis and random forest algorithm included CAV1, NOS2, GDF15, HNF4A, and CDKN2A. qRT-PCR of the fibrotic lung tissues from the mouse model showed that the mRNA levels of NOS2 and GDF15 were up-regulated, while CAV1 and CDKN2A were down-regulated. Also, treadmill training led to an increased expression of CAV1 and CDKN2A and a decrease in the expression of NOS2 and GDF15.

Conclusion: Using bioinformatics analysis, 20 potential genes were identified to be associated with ferroptosis in pulmonary fibrosis. CAV1, NOS2, GDF15, and CDKN2A were demonstrated to be influencing the development of pulmonary fibrosis by regulating ferroptosis. These findings suggested that, as an aerobic exercise treatment, treadmill training reduced ferroptosis in the pulmonary fibrosis tissues, and thus, reduces inflammation in the lungs. Aerobic exercise training initiate concomitantly with induction of pulmonary fibrosis reduces ferroptosis in lung. These results may develop our knowledge about pulmonary fibrosis and may contribute to its treatment.

Bimodal fibrosis in a novel mouse model of bleomycin-induced usual interstitial pneumonia

Idiopathic pulmonary fibrosis is pathologically represented by usual interstitial pneumonia (UIP). Conventional bleomycin models used to study pathogenic mechanisms of pulmonary fibrosis display transient inflammation and fibrosis, so their relevance to UIP is limited. We developed a novel chronic induced-UIP (iUIP) model, inducing fibrosis in D1CC×D1BC transgenic mice by intra-tracheal instillation of bleomycin mixed with microbubbles followed by sonoporation (BMS). A bimodal fibrotic lung disease was observed over 14 wk, with an acute phase similar to nonspecific interstitial pneumonia (NSIP), followed by partial remission and a chronic fibrotic phase with honeycombing similar to UIP. In this secondary phase, we observed poor vascularization despite elevated PDGFRβ expression. γ2PF- and MMP7-positive epithelial cells, consistent with an invasive phenotype, were predominantly adjacent to fibrotic areas. Most invasive cells were Scgb1a1 and/or Krt5 positive. This iUIP mouse model displays key features of idiopathic pulmonary fibrosis and has identified potential mechanisms contributing to the onset of NSIP and progression to UIP. The model will provide a useful tool for the assessment of therapeutic interventions to oppose acute and chronic fibrosis.

Effective-compound combination inhibits the M2-like polarization of macrophages and attenuates the development of pulmonary fibrosis by increasing autophagy through mTOR signaling

BACKGROUND AND PURPOSE

The M2 polarization of macrophages substantially contributes to the progression of pulmonary fibrosis (PF). Effective-compound combination (ECC), which is composed of isoliquiritigenin, icariin, nobiletin, peimine, and paeoniflorin, ameliorated bleomycin-induced PF in rats. Hence, we investigated the anti-PF mechanism of ECC with a focus on the suppression of M2 polarization in macrophages in vivo and in vitro.

METHODS

The PF rat model was generated via the intratracheal instillation of bleomycin. Histological changes, M2 macrophages, and profibrotic mediators were detected. The M2 polarization model was generated by incubating macrophages with IL-4. Quantitative PCR and Western blotting were used to measure mRNA and protein levels, respectively.

RESULTS

ECC attenuated bleomycin-induced PF in rats, which might be associated with reduced macrophage infiltration, M2 polarization, and profibrotic mediator expression. Furthermore, ECC significantly suppressed M2 polarization in IL-4-treated macrophages, which was accompanied by the upregulation of autophagy. An autophagy inhibitor abrogated the inhibitory effect of ECC on M2 polarization. In addition, ECC decreased the levels of p-p70S6K/p-4EBP and p-AKT473/p-GSK3β, which are critical regulators of autophagy.

CONCLUSION

ECC can ameliorate PF, which might be associated with the inhibition of M2 polarization through the promotion of autophagy via mTOR signaling suppression.

Animal models of drug-induced pulmonary fibrosis: an overview of molecular mechanisms and characteristics

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease characterized by progressive loss of pulmonary function. Drug-induced interstitial lung disease has been reported as a severe adverse effect of some drugs, such as bleomycin, amiodarone, and methotrexate. Based on good characteristics, drug-induced pulmonary fibrosis (PF) animal model has played a key role in our understanding of the molecular mechanisms of PF pathogenesis and recapitulates the specific pathology in patients and helps develop therapeutic strategies. Here, we summarize the mechanisms and characteristics of given fibrotic drug-induced animal models for PFs. Together with the key publications describing these models, this brief but detailed overview would be helpful for the pharmacological research with animal models of PFs. Potential mechanisms underlying drug induced lung toxicity.

Evaluating the protective role of Deglycyrrhizinated licorice root supplement on bleomycin induced pulmonary oxidative damage

The goal of this study was to investigate the protective effect of licorice supplements in a rat model of Bleomycin-induced lung oxidative damage over a duration of one month. The rats were randomly divided into six groups (n = 10 per group). Control group; Bleomycin group (B): rats were IP injected with bleomycin 5 mg/kg twice weekly. Licorice group (L): rats received orally 300 mg/kg licorice extract. Bleomycin and a low dose of Licorice group (BLLG): rats received orally 75 mg/kg licorice daily and injected as the B group. Bleomycin and a middle dose of Licorice group (BMLG): rats received orally 150 mg/kg licorice daily and injected as the Bleomycin group. Bleomycin and a high dose of Licorice group (BHLG): rats received orally 300 mg/kg licorice daily and injected as the Bleomycin group. Treatment with Bleomycin induced inflammation and oxidative damage to the lungs expressed in the disturbance of the measured parameters in the blood serum, the lung tissue, and the broncholavage fluid. In addition to the decreased expression of superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), and catalase (CAT) in the lung tissues. Bleomycin caused deformative changes in the histopathological and cellular examination of the lungs especially in the alveolar cells and the interstitial space. On the other hand, treated the bleomycin group with different doses of licorice supplement activates the antioxidant defense mechanism and attenuates the oxidative damage and damage induced to the lung. In conclusion, Deglycyrrhizinated licorice root supplement provided strong antioxidant and protective effects on Bleomycin-induced lung damage.

GED-0507 attenuates lung fibrosis by counteracting myofibroblast transdifferentiation in vivo and in vitro

The development of more effective, better tolerated drug treatments for progressive pulmonary fibrosis (of which idiopathic pulmonary fibrosis is the most common and severe form) is a research priority. The peroxisome proliferator-activated receptor gamma (PPAR-γ) is a key regulator of inflammation and fibrosis and therefore represents a potential therapeutic target. However, the use of synthetic PPAR-γ agonists may be limited by their potentially severe adverse effects. In a mouse model of bleomycin (BLM)-induced pulmonary fibrosis, we have demonstrated that the non-racemic selective PPAR-γ modulator GED-0507 is able to reduce body weight loss, ameliorate clinical and histological features of pulmonary fibrosis, and increase survival rate without any safety concerns. Here, we focused on the biomolecular effects of GED-0507 on various inflammatory/fibrotic pathways. We demonstrated that preventive and therapeutic administration of GED-0507 reduced the BLM-induced mRNA expression of several markers of fibrosis, including transforming growth factor (TGF)-β, alpha-smooth muscle actin, collagen and fibronectin as well as epithelial-to-mesenchymal transition (EMT) and expression of mucin 5B. The beneficial effect of GED-0507 on pulmonary fibrosis was confirmed in vitro by its ability to control TGFβ-induced myofibroblast activation in the A549 human alveolar epithelial cell line, the MRC-5 lung fibroblast line, and primary human lung fibroblasts. Compared with the US Food and Drug Administration-approved antifibrotic drugs pirfenidone and nintedanib, GED-0507 displayed greater antifibrotic activity by controlling alveolar epithelial cell dysfunction, EMT, and extracellular matrix remodeling. In conclusion, GED-0507 demonstrated potent antifibrotic properties and might be a promising drug candidate for the treatment of pulmonary fibrosis.

SSC-ILD mouse model induced by osmotic minipump delivered bleomycin: effect of Nintedanib

Systemic sclerosis (SSc) is an autoimmune disease characterized by an excessive production and accumulation of collagen in the skin and internal organs often associated with interstitial lung disease (ILD). Its pathogenetic mechanisms are unknown and the lack of animal models mimicking the features of the human disease is creating a gap between the selection of anti-fibrotic drug candidates and effective therapies. In this work, we intended to pharmacologically validate a SSc-ILD model based on 1 week infusion of bleomycin (BLM) by osmotic minipumps in C57/BL6 mice, since it will serve as a tool for secondary drug screening. Nintedanib (NINT) has been used as a reference compound to investigate antifibrotic activity either for lung or skin fibrosis. Longitudinal Micro-CT analysis highlighted a significant slowdown in lung fibrosis progression after NINT treatment, which was confirmed by histology. However, no significant effect was observed on lung hydroxyproline content, inflammatory infiltrate and skin lipoatrophy. The modest pharmacological effect reported here could reflect the clinical outcome, highlighting the reliability of this model to better profile potential clinical drug candidates. The integrative approach presented herein, which combines longitudinal assessments with endpoint analyses, could be harnessed in drug discovery to generate more reliable, reproducible and robust readouts.

Cell tracing reveals the transdifferentiation fate of mouse lung epithelial cells during pulmonary fibrosis in vivo

Idiopathic pulmonary fibrosis (IPF) is a progressive and devastating interstitial lung disease. The origin of myofibroblasts is still to be elucidated and the existence of epithelial-mesenchymal transition (EMT) in IPF remains controversial. Hence, it is important to clarify the origin of fibroblasts by improving modeling and labeling methods and analyzing the differentiation pathway of alveolar epithelial cells (AEC) in pulmonary fibrosis with cell tracking technology. In the present study, adult transgenic mice with SPC-rtTA^+/-/tetO₇-CMV-Cre^+/-/mTmG^+/- were induced with doxycycline for 15 days. The gene knockout phenomenon occurred in type II AECs in the lung and the reporter gene cell membrane-localized enhanced green fluorescence protein (mEGFP) was expressed in the cell membrane. The expression of Cre recombinase and SPC was analyzed using immunohistochemical (IHC) staining to detect the labeling efficiency. A repetitive intraperitoneal bleomycin-induced pulmonary fibrosis model was established, and the mice were sacrificed on day 28. The co-localization of mEGFP and mesenchymal markers α-smooth muscle actin (α-SMA) and S100 calcium binding protein A4 (S100A4) were detected by multiple IHC staining. The results revealed that Cre was expressed in the airway and AECs in the lung tissue of adult transgenic mice with SPC-rtTA^+/-/tetO₇-CMV-Cre^+/-/mTmG^+/- induced by doxycycline; the labeling efficiency in the peripheral lung tissue was 63.27±7.51%. mEGFP was expressed on the membrane of type II AECs and their differentiated form of type I AECs. Expression of mEGFP was mainly observed in the fibrotic region in bleomycin-induced pulmonary fibrosis; 1.94±0.08% of α-SMA-positive cells were mEGFP-positive and 9.68±2.06% of S100A4-positive cells were mEGFP-positive in bleomycin-induced pulmonary fibrosis. In conclusion, the present results suggested that while EMT contributes to the pathogenesis of pulmonary fibrosis, it is not the major causative factor of this condition.

TGFβ2 and TGFβ3 isoforms drive fibrotic disease pathogenesis

Transforming growth factor-β (TGFβ) is a key driver of fibrogenesis. Three TGFβ isoforms (TGFβ1, TGFβ2, and TGFβ3) in mammals have distinct functions in embryonic development; however, the postnatal pathological roles and activation mechanisms of TGFβ2 and TGFβ3 have not been well characterized. Here, we show that the latent forms of TGFβ2 and TGFβ3 can be activated by integrin-independent mechanisms and have lower activation thresholds compared to TGFβ1. Unlike TGFB1, TGFB2 and TGFB3 expression is increased in human lung and liver fibrotic tissues compared to healthy control tissues. Thus, TGFβ2 and TGFβ3 may play a pathological role in fibrosis. Inducible conditional knockout mice and anti-TGFβ isoform-selective antibodies demonstrated that TGFβ2 and TGFβ3 are independently involved in mouse fibrosis models in vivo, and selective TGFβ2 and TGFβ3 inhibition does not lead to the increased inflammation observed with pan-TGFβ isoform inhibition. A cocrystal structure of a TGFβ2-anti-TGFβ2/3 antibody complex reveals an allosteric isoform-selective inhibitory mechanism. Therefore, inhibiting TGFβ2 and/or TGFβ3 while sparing TGFβ1 may alleviate fibrosis without toxicity concerns associated with pan-TGFβ blockade.

GSE4-loaded nanoparticles a potential therapy for lung fibrosis that enhances pneumocyte growth, reduces apoptosis and DNA damage

Idiopathic pulmonary fibrosis is a lethal lung fibrotic disease, associated with aging with a mean survival of 2-5 years and no curative treatment. The GSE4 peptide is able to rescue cells from senescence, DNA and oxidative damage, inflammation, and induces telomerase activity. Here, we investigated the protective effect of GSE4 expression in vitro in rat alveolar epithelial cells (AECs), and in vivo in a bleomycin model of lung fibrosis. Bleomycin-injured rat AECs, expressing GSE4 or treated with GSE4-PLGA/PEI nanoparticles showed an increase of telomerase activity, decreased DNA damage, and decreased expression of IL6 and cleaved-caspase 3. In addition, these cells showed an inhibition in expression of fibrotic markers induced by TGF-β such as collagen-I and III among others. Furthermore, treatment with GSE4-PLGA/PEI nanoparticles in a rat model of bleomycin-induced fibrosis, increased telomerase activity and decreased DNA damage in proSP-C cells. Both in preventive and therapeutic protocols GSE4-PLGA/PEI nanoparticles prevented and attenuated lung damage monitored by SPECT-CT and inhibited collagen deposition. Lungs of rats treated with bleomycin and GSE4-PLGA/PEI nanoparticles showed reduced expression of α-SMA and pro-inflammatory cytokines, increased number of pro-SPC-multicellular structures and increased DNA synthesis in proSP-C cells, indicating therapeutic efficacy of GSE4-nanoparticles in experimental lung fibrosis and a possible curative treatment for lung fibrotic patients.

Pleural mesothelial cell migration into lung parenchyma by calpain contributes to idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is defined as a specific form of chronic, progressive fibrosing interstitial pneumonia. It is unknown why fibrosis in IPF distributes in the peripheral or named sub-pleural area. Migration of pleural mesothelial cells (PMC) should contribute to sub-pleural fibrosis. Calpain is known to be involved in cell migration, but the role of calpain in PMC migration has not been investigated. In this study, we found that PMCs migrated into lung parenchyma in patients with IPF. Then using Wt1^{tm1(EGFP/Cre)Wtp} /J knock-in mice, we observed PMC migration into lung parenchyma in bleomycin-induced pleural fibrosis models, and calpain inhibitor attenuated pulmonary fibrosis with prevention of PMC migration. In vitro studies revealed that bleomycin and transforming growth factor-β1 increased calpain activity in PMCs, and activated calpain-mediated focal adhesion (FA) turnover as well as cell migration, cell proliferation, and collagen-I synthesis. Furthermore, we determined that calpain cleaved FA kinase in both C-terminal and N-terminal regions, which mediated FA turnover. Lastly, the data revealed that activated calpain was also involved in phosphorylation of cofilin-1, and p-cofilin-1 induced PMC migration. Taken together, this study provides evidence that calpain mediates PMC migration into lung parenchyma to promote sub-pleural fibrosis in IPF.