The role of autophagy in idiopathic pulmonary fibrosis: from mechanisms to therapies

Supramolecular Nanofibers Ameliorate Bleomycin-Induced Pulmonary Fibrosis by Restoring Autophagy

Idiopathic pulmonary fibrosis (IPF) is a progressive and ultimately fatal interstitial lung disease, with limited therapeutic options available. Impaired autophagy resulting from aberrant TRB3/p62 protein-protein interactions (PPIs) contributes to the progression of IPF. Restoration of autophagy by modulating the TRB3/p62 PPIs has rarely been reported for the treatment of IPF. Herein, peptide nanofibers are developed that specifically bind to TRB3 protein and explored their potential as a therapeutic approach for IPF. By conjugating with the self-assembling fragment (Ac-GFFY), a TRB3-binding peptide motif A2 allows for the formation of nanofibers with a stable α-helix secondary structure. The resulting peptide (Ac-GFFY-A2) nanofibers exhibit specific high-affinity binding to TRB3 protein in saline buffer and better capacity of cellular uptake to A2 peptide. Furthermore, the TRB3-targeting peptide nanofibers efficiently interfere with the aberrant TRB3/p62 PPIs in activated fibroblasts and fibrotic lung tissue of mice, thereby restoring autophagy dysfunction. The TRB3-targeting peptide nanofibers inhibit myofibroblast differentiation, collagen production, and fibroblast migration in vitro is demonstrated, as well as bleomycin-induced pulmonary fibrosis in vivo. This study provides a supramolecular method to modulate PPIs and highlights a promising strategy for treating IPF diseases by restoring autophagy.

Dynamic changes in autophagy activity in different degrees of pulmonary fibrosis in mice

The aim of this study is to observe the changes in autophagy activities in lung tissues of mice with different degrees of pulmonary fibrosis (PF), and explore the association between PF and autophagy activity. The PF model was established by bleomycin (BLM, 25 and 35 mg/kg) atomization inhalation in C57BL/6 mice, samples were collected on the 7, 14, and 28 days after BLM administration. Hematoxylin-eosin staining was used to observe the pathological changes in lung tissues. Masson staining was utilized to assess areas of blue collagen fiber deposition in lung tissues. Quantitative real time polymerase chain reaction was used to detect the mRNA expressions of autophagy-related genes, including Atg5, Atg7, and Atg10 in lung tissues. Western blot was used to detect the protein expressions of autophagy-related genes, including p62 and LC3II/LC3I in lung tissues. Compared with control group, BLM dose-dependently decreased PaO2, mRNA expressions of Atg5, Atg7, Atg10, and LC3II/LC3I, while increased lung wet weight, lung coefficient, PF score, the blue area of collagen fibers, and p62 protein on the 7th, 14th, and 28th days. In conclusion, the more severe the PF induced by BLM, the lower the autophagy activity.

Lactate facilitated mitochondrial fission-derived ROS to promote pulmonary fibrosis via ERK/DRP-1 signaling

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, fibrotic interstitial lung diseases, which mainly existed in middle-aged and elderly people. The accumulation of reactive oxygen species (ROS) is a common characteristic of IPF. Previous research also shown that lactate levels can be abnormally elevated in IPF patients. Emerging evidence suggested a relationship between lactate and ROS in IPF which needs further elucidation. In this article, we utilized a mouse model of BLM-induced pulmonary fibrosis to detect alterations in ROS levels and other indicators associated with fibrosis. Lactate could induce mitochondrial fragmentation by modulating expression and activity of DRP1 and ERK. Moreover, Increased ROS promoted P65 translocation into nucleus, leading to expression of lung fibrotic markers. Finally, Ulixertinib, Mdivi-1 and Mito-TEMPO, which were inhibitor activity of ERK, DRP1 and mtROS, respectively, could effectively prevented mitochondrial damage and production of ROS and eventually alleviate pulmonary fibrosis. Taken together, these findings suggested that lactate could promote lung fibrosis by increasing mitochondrial fission-derived ROS via ERK/DRP1 signaling, which may provide novel therapeutic solutions for IPF.

Pazopanib attenuated bleomycin-induced pulmonary fibrosis via suppressing TGF-β1 signaling pathway

Background

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive interstitial lung disease with a high mortality rate and limited treatment efficacy. Nintedanib, a tyrosine kinase inhibitor, is clinically used to treat pulmonary fibrosis. At present, only nintedanib is on the market for the treatment of pulmonary fibrosis. Pazopanib is a drug for the treatment of renal cell carcinoma and advanced soft tissue sarcoma.

Methods

In this study, we explored whether pazopanib can attenuate bleomycin (BLM)-induced pulmonary fibrosis and explored its antifibrotic mechanism. In vivo and in vitro investigations were carried out to investigate the efficacy and mechanism of action of pazopanib in pulmonary fibrosis.

Results

In vivo experiments showed that pazopanib can alleviate pulmonary fibrosis caused by BLM, reduce the degree of collagen deposition and improve lung function. In vitro experiments showed that pazopanib suppressed transforming growth factor-β1 (TGF-β1)-induced myofibroblast activation and promoted apoptosis and autophagy in myofibroblasts. Further mechanistic studies demonstrated that pazopanib inhibited the TGF-β1/Smad and non-Smad signaling pathways during fibroblast activation.

Conclusions

In conclusion, pazopanib attenuated BLM-induced pulmonary fibrosis by suppressing the TGF-β1 signaling pathway. Pazopanib inhibits myofibroblast activation, migration, autophagy, apoptosis, and extracellular matrix (ECM) buildup by downregulating the TGF-β1/Smad signal route and the TGF-β1/non-Smad signal pathway. It has the same target as nintedanib and is a tyrosine kinase inhibitor.

Unraveling the interplay between vital organelle stress and oxidative stress in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive lung disease characterized by excessive accumulation of extracellular matrix, leading to irreversible fibrosis. Emerging evidence suggests that endoplasmic reticulum (ER) stress, mitochondrial stress, and oxidative stress pathways play crucial roles in the pathogenesis of IPF. ER stress occurs when the protein folding capacity of the ER is overwhelmed, triggering the unfolded protein response (UPR) and contributing to protein misfolding and cellular stress in IPF. Concurrently, mitochondrial dysfunction involving dysregulation of key regulators, including PTEN-induced putative kinase 1 (PINK1), Parkin, peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), and sirtuin 3 (SIRT3), disrupts mitochondrial homeostasis and impairs cellular energy metabolism. This leads to increased reactive oxygen species (ROS) production, release of pro-fibrotic mediators, and activation of fibrotic pathways, exacerbating IPF progression. The UPR-induced ER stress further disrupts mitochondrial metabolism, resulting in altered mitochondrial mechanisms that increase the generation of ROS, resulting in further ER stress, creating a feedback loop that contributes to the progression of IPF. Oxidative stress also plays a pivotal role in IPF, as ROS-mediated activation of TGF-β, NF-κB, and MAPK pathways promotes inflammation and fibrotic responses. This review mainly focuses on the links between ER stress, mitochondrial dysfunctions, and oxidative stress with different signaling pathways involved in IPF. Understanding these mechanisms and targeting key molecules within these pathways may offer promising avenues for intervention.

AMPK signaling inhibits the differentiation of myofibroblasts: impact on age-related tissue fibrosis and degeneration

Disruption of the extracellular matrix (ECM) and an accumulation of fibrotic lesions within tissues are two of the distinctive hallmarks of the aging process. Tissue fibroblasts are mesenchymal cells which display an impressive plasticity in the regulation of ECM integrity and thus on tissue homeostasis. Single-cell transcriptome studies have revealed that tissue fibroblasts exhibit a remarkable heterogeneity with aging and in age-related diseases. Excessive stress and inflammatory insults induce the differentiation of fibroblasts into myofibroblasts which are fusiform contractile cells and abundantly secrete the components of the ECM and proteolytic enzymes as well as many inflammatory mediators. Detrimental stresses can also induce the transdifferentiation of certain mesenchymal and myeloid cells into myofibroblasts. Interestingly, many age-related stresses, such as oxidative and endoplasmic reticulum stresses, ECM stiffness, inflammatory mediators, telomere shortening, and several alarmins from damaged cells are potent inducers of myofibroblast differentiation. Intriguingly, there is convincing evidence that the signaling pathways stimulated by the AMP-activated protein kinase (AMPK) are potent inhibitors of myofibroblast differentiation and accordingly AMPK signaling reduces fibrotic lesions within tissues, e.g., in age-related cardiac and pulmonary fibrosis. AMPK signaling is not only an important regulator of energy metabolism but it is also able to control cell fate determination and many functions of the immune system. It is known that AMPK signaling can delay the aging process via an integrated signaling network. AMPK signaling inhibits myofibroblast differentiation, e.g., by suppressing signaling through the TGF-β, NF-κB, STAT3, and YAP/TAZ pathways. It seems that AMPK signaling can alleviate age-related tissue fibrosis and degeneration by inhibiting the differentiation of myofibroblasts.

Endothelial Erg Regulates Expression of Pulmonary Lymphatic Junctional and Inflammation Genes in Mouse Lungs Impacting Lymphatic Transport

The ETS transcription factor ERG is a master regulator of endothelial gene specificity and highly enriched in the capillary, vein, and arterial endothelial cells. ERG expression is critical for endothelial barrier function, permeability, and vascular inflammation. A dysfunctional vascular endothelial ERG has been shown to impair lung capillary homeostasis, contributing to pulmonary fibrosis as previously observed in IPF lungs. Our preliminary observations indicate that lymphatic endothelial cells (LEC) in the human IPF lung also lack ERG. To understand the role of ERG in pulmonary LECs, we developed LEC-specific inducible Erg-CKO and Erg-GFP-CKO conditional knockout (CKO) mice under Prox1 promoter. Whole lung microarray analysis, flow cytometry, and qPCR confirmed an inflammatory and pro-lymphvasculogenic predisposition in Erg-CKO lung. FITC-Dextran tracing analysis showed an increased pulmonary interstitial lymphatic fluid transport from the lung to the axial lymph node. Single-cell transcriptomics confirmed that genes associated with cell junction integrity were downregulated in Erg-CKO pre-collector and collector LECs. Integrating Single-cell transcriptomics and CellChatDB helped identify LEC specific communication pathways contributing to pulmonary inflammation, trans-endothelial migration, inflammation, and Endo-MT in Erg-CKO lung. Our findings suggest that downregulation of lymphatic Erg crucially affects LEC function, LEC permeability, pulmonary LEC communication pathways and lymphatic transcriptomics.

Amentoflavone Mitigates Cyclophosphamide-Induced Pulmonary Toxicity: Involvement of -SIRT-1/Nrf2/Keap1 Axis, JAK-2/STAT-3 Signaling, and Apoptosis

Background and objectives: Cyclophosphamide (CPA) is an alkylating agent that is used for the management of various types of malignancies and as an immunosuppressive agent for the treatment of immunological disorders. However, its use is limited by its potential to cause a wide range of pulmonary toxicities. Amentoflavone (AMV) is a flavonoid that had proven efficacy in the treatment of disease states in which oxidative stress, inflammation, and apoptosis may play a pathophysiologic role. This study investigated the potential ameliorative effects of the different doses of AMV on CPA-induced pulmonary toxicity, with special emphasis on its antioxidant, anti-inflammatory, and apoptosis-modulating effects. Materials and methods: In a rat model of CPA-induced pulmonary toxicity, the effect of AMV at two dose levels (50 mg/kg/day and 100 mg/kg/day) was investigated. The total and differential leucocytic counts, lactate dehydrogenase activity, and levels of pro-inflammatory cytokines in the bronchoalveolar lavage fluid were estimated. Also, the levels of oxidative stress parameters, sirtuin-1, Keap1, Nrf2, JAK2, STAT3, hydroxyproline, matrix metalloproteinases 3 and 9, autophagy markers, and the cleaved caspase 3 were assessed in the pulmonary tissues. In addition, the histopathological and electron microscopic changes in the pulmonary tissues were evaluated. Results: AMV dose-dependently ameliorated the pulmonary toxicities induced by CPA via modulation of the SIRT-1/Nrf2/Keap1 axis, mitigation of the inflammatory and fibrotic events, impaction of JAK-2/STAT-3 axis, and modulation of the autophagic and apoptotic signals. Conclusions: AMV may open new horizons towards the mitigation of the pulmonary toxicities induced by CPA.

Eupatilin inhibits pulmonary fibrosis by activating Sestrin2/PI3K/Akt/mTOR dependent autophagy pathway

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a progressive chronic inflammatory disease with poor clinical outcomes and ineffective drug treatment options. Eupatilin is a major component extracted from the traditional herbal medicine Artemisia asiatica Nakai. Notably, it was demonstrated to have an anti-fibrosis effect in endometrial fibrosis, vocal fold, and hepatic fibrosis. Its role and mechanism in IPF remain unclear.

METHODS

This study used the TGF-β1-induced human embryonic lung fibroblasts (MRC-5) activation, IPF lung fibroblasts, and bleomycin-induced lung fibrosis mice model. Western blot, immunofluorescence staining, quantitative real time-PCR, hematoxylin and eosin staining, Masson's trichrome staining, and immunohistochemistry were used to evaluate the effects of eupatilin on fibroblast activation, pulmonary fibrosis, and autophagy. The autophagosomes were observed with a transmission electron microscope (TEM). RNA sequencing was used to determine the signaling pathway and key regulator related to autophagy.

RESULTS

Eupatilin significantly decreased the expression of Col1A1, fibronectin, α-SMA, and SQSTM1/p62. In contrast, it increased the expression of LC3B II/I and the number of autophagosomes in TGF-β1 treated MRC-5, IPF lung fibroblasts, and bleomycin-induced lung fibrosis mice model; it also alleviated bleomycin-induced lung fibrosis. The KEGG pathway mapping displayed that PI3K/Akt and Sestrin2 were associated with the enhanced fibrogenic process. Eupatilin suppressed the phosphorylation of PI3K/Akt/mTOR. Autophagy inhibitor 3-methyladenine (3-MA) and Akt activator SC-79 abrogated the anti-fibrotic effect of eupatilin. Sestrin2 expression was also downregulated in TGF-β1 treated lung fibroblasts and lung tissues of the bleomycin-induced pulmonary fibrosis mice model. Furthermore, eupatilin promoted Sestrin2 expression, and the knockdown of Sestrin2 significantly aggravated the degree of fibrosis, increased the phosphorylation of PI3K/Akt/mTOR, and decreased autophagy.

CONCLUSION

These findings indicate that eupatilin ameliorates pulmonary fibrosis through Sestrin2/PI3K/Akt/mTOR-dependent autophagy pathway.

Current and Future Treatment Landscape for Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) remains a disease with poor survival. The pathogenesis is complex and encompasses multiple molecular pathways. The first-generation antifibrotics pirfenidone and nintedanib, approved more than 10 years ago, have been shown to reduce the rate of progression, increase the length of life for patients with IPF, and work for other fibrotic lung diseases. In the last two decades, most clinical trials on IPF have failed to meet the primary endpoint and an urgent unmet need remains to identify agents or treatment strategies that can stop disease progression. The pharmacotherapeutic landscape for IPF is moving forward with a number of new drugs currently in clinical development, mostly in phase I and II trials, while only a few phase III trials are running. Since our understanding of IPF pathogenesis is still limited, we should keep focusing our efforts to deeper understand the mechanisms underlying this complex disease and their reflection on clinical phenotypes. This review discusses the key pathogenetic concepts for the development of new antifibrotic agents, presents the newest data on approved therapies, and summarizes new compounds currently in clinical development. Finally, future directions in antifibrotics development are discussed.

Role of the epithelial barrier in intestinal fibrosis associated with inflammatory bowel disease: relevance of the epithelial-to mesenchymal transition

In inflammatory bowel disease (IBD), chronic inflammation in the gastrointestinal tract can lead to tissue damage and remodelling, which can ultimately result in fibrosis. Prolonged injury and inflammation can trigger the activation of fibroblasts and extracellular matrix (ECM) components. As fibrosis progresses, the tissue becomes increasingly stiff and less functional, which can lead to complications such as intestinal strictures, obstructive symptoms, and eventually, organ dysfunction. Epithelial cells play a key role in fibrosis, as they secrete cytokines and growth factors that promote fibroblast activation and ECM deposition. Additionally, epithelial cells can undergo a process called epithelial-mesenchymal transition, in which they acquire a more mesenchymal-like phenotype and contribute directly to fibroblast activation and ECM deposition. Overall, the interactions between epithelial cells, immune cells, and fibroblasts play a critical role in the development and progression of fibrosis in IBD. Understanding these complex interactions may provide new targets for therapeutic interventions to prevent or treat fibrosis in IBD. In this review, we have collected and discussed the recent literature highlighting the contribution of epithelial cells to the pathogenesis of the fibrotic complications of IBD, including evidence of EMT, the epigenetic control of the EMT, the potential influence of the intestinal microbiome in EMT, and the possible therapeutic strategies to target EMT. Finally we discuss the pro-fibrotic interactions epithelial-immune cells and epithelial-fibroblasts cells.

Adipose-derived mesenchymal stem cell therapy for reverse bleomycin-induced experimental pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive respiratory disease. Arguably, the complex interplay between immune cell subsets, coupled with an incomplete understanding of disease pathophysiology, has hindered the development of successful therapies. Despite efforts to understand its pathophysiology and develop effective treatments, IPF remains a fatal disease, necessitating the exploration of new treatment options. Mesenchymal stromal/stem cell (MSC) therapy has shown promise in experimental models of IPF, but further investigation is needed to understand its therapeutic effect. This study aimed to assess the therapeutic effect of adipose-derived mesenchymal stem cells in a bleomycin-induced pulmonary fibrosis model. First, MSC cells were obtained from mice and characterized using flow cytometry and cell differentiation culture methods. Then adult C57BL/6 mice were exposed to endotracheal instillation of bleomycin and concurrently treated with MSCs for reversal models on day 14. Experimental groups were evaluated on days 14, 21, or 28. Additionally, lung fibroblasts challenged with TGF-β1 were treated with MSCs supernatant or MSCs to explore the mechanisms underlying of pulmonary fibrosis reversal. Mesenchymal stem cells were successfully isolated from mouse adipose tissue and characterized based on their differentiation ability and cell phenotype. The presence of MSCs or their supernatant stimulated the proliferation and migration of lung fibrotic cells. MSCs supernatant reduced lung collagen deposition, improved the Ashcroft score and reduced the gene and protein expression of lung fibrosis-related substances. Bleomycin-challenged mice exhibited severe septal thickening and prominent fibrosis, which was effectively reversed by MSCs treatment. MSC supernatant could suppress the TGF-β1/Smad signaling pathway and supernatant promotes fibroblast autophagy. In summary, this study demonstrates that MSCs supernatant treatment is as effective as MSCs in revert the core features of bleomycin-induced pulmonary fibrosis. The current study has demonstrated that MSCs supernatant alleviates the BLM-induced pulmonary fibrosis in vivo. In vitro experiments further reveal that MSC supernatant could suppress the TGF-β1/Smad signaling pathway to inhibit the TGF-β1-induced fibroblast activation, and promotes fibroblast autophagy by Regulating p62 expression. These findings contribute to the growing body of evidence supporting the therapeutic application of MSCs in cell therapy medicine for IPF.

Autophagy in intestinal fibrosis: relevance in inflammatory bowel disease

Chronic inflammation is often associated with fibrotic disorders in which an excessive deposition of extracellular matrix is a hallmark. Long-term fibrosis starts with tissue hypofunction and finally ends in organ failure. Intestinal fibrosis is not an exception, and it is a frequent complication of inflammatory bowel disease (IBD). Several studies have confirmed the link between deregulated autophagy and fibrosis and the presence of common prognostic markers; indeed, both up- and downregulation of autophagy are presumed to be implicated in the progression of fibrosis. A better knowledge of the role of autophagy in fibrosis may lead to it becoming a potential target of antifibrotic therapy. In this review we explore novel advances in the field that highlight the relevance of autophagy in fibrosis, and give special focus to fibrosis in IBD patients.

Identification and validation of chemokine system-related genes in idiopathic pulmonary fibrosis

Background

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive interstitial lung disease with limited therapeutic options. Recent studies have demonstrated that chemokines play a vital role in IPF pathogenesis. In the present study, we explored whether the gene signature associated with chemokines could be used as a reliable biological marker for patients with IPF.

Methods

Chemokine-related differentially expressed genes (CR-DEGs) in IPF and control lung tissue samples were identified using data from the Gene Expression Omnibus database. A chemokine-related signature of the diagnostic model was established using the LASSO-Cox regression. In addition, unsupervised cluster analysis was conducted using consensus-clustering algorithms. The CIBERSORT algorithm was used to calculate immune cell infiltration across patient subgroups. Finally, we established a mouse model of bleomycin-induced pulmonary fibrosis and a model of fibroblasts treated with TGFβ1. Expression levels of chemokine-related signature genes were determined using real-time quantitative polymerase chain reaction (RT-qPCR).

Results

We established a chemokine-related eleven-gene signature of a diagnostic model consisting of CXCL2, CCRL2, ARRB1, XCL1, GRK5, PPBP, CCL19, CCL13, CCL11, CXCL6, and CXCL13, which could easily distinguish between IPF patients and controls. Additionally, we identified two subtypes of IPF samples based on chemokine-related gene expression. Pulmonary function parameters and stromal scores were significantly higher in subtype 1 than in subtype 2. Several immune cell types, especially plasma cells and macrophages, differ significantly between the two subtypes. RT-qPCR results showed that the expression levels of Cxcl2 and Ccl2 increased considerably in bleomycin-induced mice. Meanwhile, Arrb1, Ccrl2, Grk5, and Ppbp expression was significantly reduced. Furthermore, multiple chemokine-related genes were altered in TGFβ1 or TNFα-induced fibroblast cells.

Conclusions

A novel chemokine-related eleven-signature of diagnostic model was developed. These genes are potential biomarkers of IPF and may play essential roles in its pathogenesis.