Mechanisms of pulmonary fibrosis

The mitigating effect of para-hydroxycinnamic acid in bleomycin-induced pulmonary fibrosis in mice through targeting oxidative, inflammatory and fibrotic pathways

This study investigated the therapeutic benefits of para-hydroxycinnamic acid in mice with bleomycin-induced lung fibrosis. Forty male BALB/c mice were randomly assigned to four groups: normal, which received 0.9% normal saline; induced, which received a single dose of bleomycin (5 mg/kg) by oropharyngeal challenge; pirfenidone-treated; and para-hydroxycinnamic acid-treated, which challenged with bleomycin and received a daily oral dose of 300 and 50 mg/kg, respectively, from day 7 to day 21. Tissue pro-fibrotic and inflammatory cytokines, oxidative indicators, pulmonary histopathology, immunohistochemistry of fibrotic proteins and the assessment of gene expression by RT-qPCR were evaluated on day 22 after euthanizing animals. Pirfenidone and para-hydroxycinnamic acid managed to alleviate the fibrotic endpoints by statistically improving the weight index, histopathological score and reduced expression of fibrotic-related proteins in immune-stained lung sections, as well as fibrotic markers measured in serum samples. They also managed to alleviate tissue levels of oxidative stress and inflammatory and pro-fibrotic mediators. para-Hydroxycinnamic acid enhanced the expression of crucial genes associated with oxidative stress, inflammation and fibrosis in vivo. para-Hydroxycinnamic acid has demonstrated similar effectiveness to pirfenidone, suggesting it could be a promising treatment for fibrotic lung conditions by inhibiting the TGF-β1/Smad3 pathway or through its anti-inflammatory and antioxidant properties.

Harmine inhibits pulmonary fibrosis through regulating DNA damage repair-related genes and activation of TP53-Gadd45α pathway

BACKGROUND

Harmine has many pharmacological activities and has been found to significantly inhibit the fibrosis of keloid fibroblasts. DNA damage repair (DDR) is essential to prevent fibrosis. This study aimed to investigate the effects of harmine on pulmonary fibrosis and its underlying mechanisms.

METHODS

Bleomycin and TGF-β1 were used to construct pulmonary fibrosis models in vivo and in vitro, then treated with harmine to explore harmine's effects in treating experimental pulmonary fibrosis and its related mechanisms. Then, RNA sequencing was applied to investigate further the crucial DDR-related genes and drug targets of harmine against pulmonary fibrosis. Finally, the expression levels of DDR-related genes were verified by real-time quantitative PCR (RT-qPCR) and western blot.

RESULTS

Our in vivo experiments showed that harmine treatment could improve weight loss and lung function and reduce tissue fibrosis in mice with pulmonary fibrosis. The results confirmed that harmine could inhibit the viability and migration of TGF-β1-induced MRC-5 cells, induce their apoptosis, and suppress the F-actin expression, suggesting that harmine could suppress the phenotypic transition from lung fibroblasts to lung myoblasts. In addition, RNA sequencing identified 1692 differential expressed genes (DEGs), and 10 DDR-related genes were screened as critical DDR-related genes. RT-qPCR and western blotting showed that harmine could down-regulate the expression of CHEK1, ERCC1, ERCC4, POLD1, RAD51, RPA1, TOP1, and TP53, while up-regulate FEN1, H2AX and GADD45α expression.

CONCLUSIONS

Harmine may inhibit pulmonary fibrosis by regulating DDR-related genes and activating the TP53-Gadd45α pathway.

Enhanced Detection of Early Pulmonary Fibrosis Disease Using 68Ga-FAPI-LM3 PET

Early detection of pulmonary fibrosis is a critical yet insufficiently met clinical necessity. This study evaluated the effectiveness of FAPI-LM3, a 68Ga-radiolabeled heterobivalent molecular probe that targets fibroblast activating protein (FAP) and somatostatin receptor 2 (SSTR2), in the early detection of pulmonary fibrosis, leveraging its potential for early disease identification. A bleomycin-induced early pulmonary fibrosis model was established in C57BL/6 mice for 7 days. FAP and SSTR2 expression levels were quantitatively assessed in human idiopathic pulmonary fibrosis lung tissue samples and bleomycin-treated mouse lung tissues by using western blotting, real-time quantitative PCR (RT-qPCR), and immunofluorescence techniques. The diagnostic performance of FAPI-LM3 was investigated by synthesizing monomeric radiotracers 68Ga-FAPI-46 and 68Ga-DOTA-LM3 alongside the heterobivalent probe 68Ga-FAPI-LM3. These imaging radiopharmaceuticals were used in small-animal PET to compare their uptake in fibrotic and normal lung tissues. Results indicated significant upregulation of FAP and SSTR2 at both RNA and protein levels in fibrotic lung tissues compared with that in normal controls. PET imaging demonstrated significantly enhanced uptake of the 68Ga-FAPI-LM3 probe in fibrotic lung tissues, with superior visual effects compared to monomeric tracers. At 60 min postinjection, early stage fibrotic tissues (day 7) demonstrated low-to-medium uptake of monomeric probes, including 68Ga-DOTA-LM3 (0.45 ± 0.04% ID/g) and 68Ga-FAPI-46 (0.78 ± 0.09% ID/g), whereas the uptake of the heterobivalent probe 68Ga-FAPI-LM3 (1.90 ± 0.10% ID/g) was significantly higher in fibrotic lesions than in normal lung tissue. Blockade experiments confirmed the specificity of 68Ga-FAPI-LM3 uptake, which was attributed to synergistic targeting of FAP and SSTR2. This study demonstrates the potential of 68Ga-FAPI-LM3 for early pulmonary fibrosis detection via molecular imaging, offering significant benefits over monomeric tracers 68Ga-FAPI-46 and 68Ga-DOTA-LM3. This strategy offers new possibilities for noninvasive and precise early detection of pulmonary fibrosis.

Zerumbone alleviated bleomycin-induced pulmonary fibrosis in mice via SIRT1/Nrf2 pathway

Pulmonary fibrosis (PF) is a persistent interstitial lung condition for which effective treatment options are currently lacking. Zerumbone (zerum), a humulane sesquiterpenoid extracted from Zingiber zerumbet Smith, has been documented in previous studies to possess various pharmacological benefits. The aim of this study was to observe and investigate the therapeutic effects and mechanisms of zerum on pulmonary fibrosis. We utilized a transforming growth factor (TGF)-β1-induced human lung fibroblast (MRC-5) activation model and a bleomycin-induced pulmonary fibrosis mouse model. Cell counting kit 8 (CCK8) and cell migration assays were performed to assess the effects of zerum on MRC-5 cells. Masson's trichrome, Hematoxylin and Eosin (HE), and Sirius Red staining were conducted for pathological evaluation of lung tissue. Western blot experiments were conducted to measure the protein expression levels of Collagen I, α-SMA, Nrf2, and SIRT1. Immunofluorescence and immunohistochemistry assays were used to detect the expression of reactive oxygen species (ROS), Nrf2, and α-SMA. ELISA was employed to measure the levels of MDA, SOD, and GSH-Px. Our findings from in vitro and in vivo studies demonstrated that zerum significantly inhibited the migration ability of TGF-β1-induced MRC-5 cells, reduced ROS production in TGF-β1-induced MRC-5 cells and pulmonary fibrosis mice, and decreased the expression of Collagen I and α-SMA proteins. Additionally, zerum activated the SIRT1/Nrf2 signaling pathway in TGF-β1-induced MRC-5 cells and pulmonary fibrosis mice. Knockdown of SIRT1 abolished the anti-fibrotic effects of zerum. These results suggest that zerum inhibits TGF-β1 and BLM-induced cell and mouse pulmonary fibrosis by activating the SIRT1/Nrf2 pathway.

Diazepam inhibits LPS-induced pyroptosis and inflammation and alleviates pulmonary fibrosis in mice by regulating the let-7a-5p/MYD88 axis

BACKGROUND AND OBJECTIVE

Pulmonary fibrosis caused by lung injury is accompanied by varying degrees of inflammation, and diazepam can reduce the levels of inflammatory factors. Therefore, the purpose of this study was to determine whether diazepam can inhibit inflammation and ameliorate pulmonary fibrosis by regulating the let-7a-5p/myeloid differentiation factor 88 (MYD88) axis.

METHODS

Lipopolysaccharide (LPS) was used to induce cell pyroptosis in an animal model of pulmonary fibrosis. After treatment with diazepam, changes in cell proliferation and apoptosis were observed, and the occurrence of inflammation and pulmonary fibrosis in the mice was detected.

RESULTS

The results showed that LPS can successfully induce cell pyroptosis and inflammatory responses and cause lung fibrosis in mice. Diazepam inhibits the expression of pyroptosis-related factors and inflammatory factors; moreover, it attenuates the occurrence of pulmonary fibrosis in mice. Mechanistically, diazepam can upregulate the expression of let-7a-5p, inhibit the expression of MYD88, and reduce inflammation and inhibit pulmonary fibrosis by regulating the let-7a-5p/MYD88 axis.

CONCLUSION

Our findings indicated that diazepam can inhibit LPS-induced pyroptosis and inflammatory responses and alleviate pulmonary fibrosis in mice by regulating the let-7a-5p/MYD88 axis.

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

BACKGROUND

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Dual-color FISH analyses of xenogeneic human fibroblast sheets transplanted to repair lung pleural defects in an immunocompromised rat model

BACKGROUND

Pulmonary air leaks (PALs) due to visceral pleura injury during surgery is frequently observed after pulmonary resections and the complication is difficult to avoid in thoracic surgery. The development of postoperative PALs is the most common cause of prolonged hospitalization. Previously, we reported that PALs sealants using autologous dermal fibroblast sheets (DFSs) harvested from temperature-responsive culture dishes successfully closed intraoperative PALs during lung resection.

OBJECTIVE

In this study, we investigated the fate of human DFSs xenogenetically transplanted onto lung surfaces to seal PALs of immunocompromised rat. Dual-color FISH analyses of human fibroblast was employed to detect transplantation human cells on the lung surface.

RESULTS

One month after transplantation, FISH analyses revealed that transplanted human fibroblasts still composed a sheet-structure, and histology also showed that beneath the sheet's angiogenesis migrating into the sheets was observed from the recipient tissues. FISH analyses revealed that even at 3 months after transplantation, the transplanted human fibroblasts still remained in the sheet. Dual-color FISH analyses of the transplanted human fibroblasts were sparsely present as a result of the cells reaching the end of their lifespan, the cells producing extracellular matrix, and remained inside the cell sheet and did not invade the lungs of the host.

CONCLUSIONS

DFS-transplanted human fibroblasts showed that they are retained within cell sheets and do not invade the lungs of the host.

Circular RNA MKLN1 promotes epithelial-mesenchymal transition in pulmonary fibrosis by regulating the miR-26a/b-5p/CDK8 axis in human alveolar epithelial cells and mice models

Pulmonary fibrosis involves destruction of the lung parenchyma and extracellular matrix deposition. Effective treatments for pulmonary fibrosis are lacking and its pathogenesis is still unclear. Studies have found that epithelial-mesenchymal transition (EMT) of alveolar epithelial cells (AECs) plays an important role in progression of pulmonary fibrosis. Thus, an in-depth exploration of its mechanism might identify new therapeutic targets. In this study, we revealed that a novel circular RNA, MKLN1 (circMKLN1), was significantly elevated in two pulmonary fibrosis models (intraperitoneally with PQ, 50 mg/kg for 7 days, and intratracheally with BLM, 5 mg/kg for 28 days). Additionally, circMKLN1 was positively correlated with the severity of pulmonary fibrosis. Inhibition of circMKLN1 expression significantly reduced collagen deposition and inhibited EMT in AECs. EMT was aggravated after circMKLN1 overexpression in AECs. MiR-26a-5p/miR-26b-5p (miR-26a/b), the targets of circMKLN1, were confirmed by luciferase reporter assays. CircMKLN1 inhibition elevated miR-26a/b expression. Significantly decreased expression of CDK8 (one of the miR-26a/b targets) was observed after inhibition of circMKLN1. EMT was exacerbated again, and CDK8 expression was significantly increased after circMKLN1 inhibition and cotransfection of miR-26a/b inhibitors in AECs. Our research indicated that circMKLN1 promoted CDK8 expression through sponge adsorption of miR-26a/b, which regulates EMT and pulmonary fibrosis. This study provides a theoretical basis for finding new targets or biomarkers in pulmonary fibrosis.

Atmospheric fine particulate matter (PM2.5) induces pulmonary fibrosis by regulating different cell fates via autophagy

The presence of respiratory diseases demonstrates a positive correlation with atmospheric fine particulate matter (PM2.5) exposure. The respiratory system is the main target organ affected by PM2.5, and exposure to PM2.5 elevates the likelihood of developing pulmonary fibrosis (PF). In this study, lung epithelial cell (BEAS-2B) and fibroblast (NIH-3T3) were used as in vitro exposure models to explore the mechanisms of PF. PM2.5 exposure caused mitochondrial damage in BEAS-2B cells and increased a fibrotic phenotype in NIH-3T3 cells. Epithelial cells and fibroblasts have different fates after PM2.5 exposure due to their different sensitivities to trigger autophagy. Exposure to PM2.5 inhibits mitophagy in BEAS-2B cells, which hinders the removal of damaged mitochondria and triggers cell death. In this process, the nuclear retention of the mitophagy-related protein Parkin prevents it from being recruited to mitochondria, resulting in mitophagy inhibition. In contrast, fibroblasts exhibit increased levels of autophagy, which may isolate PM2.5 and cause abnormal fibroblast proliferation and migration. Fibrotic phenotypes such as collagen deposition and increased α-actin also appear in fibroblasts. Our results identify PM2.5 as a trigger of PF and delineate the molecular mechanism of autophagy in PM2.5 induced PF, which provides new insights into the pulmonary injury.

Fibrotic lung diseases in children

In children, pulmonary fibrosis (PF) is an extremely unusual entity that can be observed in some types of interstitial lung disease (ILD). Defining whether ILD is accompanied by PF is important for targeted therapy. Algorithm for the diagnosis of PF in children is not clearly established. Besides, the clinical, radiological, and histological definitions commonly used to diagnose particularly the cases of idiopathic PF in adult patients, is not applicable to pediatric cases. However, a few studies conducted in children offer good exemplary diagnostic approach to fibrosing ILD. Thorax high resonance computed tomography and/or lung biopsy scanning can provide valuable information about PF. Another issue that has not been clearly established is when to start antifibrotic treatment in pediatric patients with PF. The objective of this current review is to provide a comprehensive overview of pediatric PF by drawing upon adult research, particularly focusing on the areas of uncertainty.

Paclitaxel Aggravating Radiation-Induced Pulmonary Fibrosis Is Associated with the Down-Regulation of the Negative Regulatory Function of Spry2

Paclitaxel (PTX) is capable of aggravating radiation-induced pulmonary fibrosis (RIPF), but the mechanism is unknown. Spry2 is a negative regulator of receptor tyrosine kinase-related Ras/Raf/extracellular signal regulated kinase (ERK) pathway. This experiment was aimed at exploring whether the aggravation of RIPF by PTX is related to Spry2. The RIPF model was established with C57BL/6 mice by thoracic irradiation, and PTX was administered concurrently. Western blot was used to detect the expression level of ERK signaling molecules and the distribution of Spry2 in the plasma membrane/cytoplasm. Co-immunoprecipitation (co-IP) and immunofluorescence were used to observe the colocalization of Spry2 with the plasma membrane and tubulin. The results showed that PTX-concurrent radiotherapy could aggravate fibrotic lesions in RIPF, downregulate the content of membrane Spry2, and upregulate the levels of p-c-Raf and p-ERK in lung tissue. It was found that knockdown of Spry2 in fibroblast abolished the upregulation of p-c-Raf and p-ERK by PTX. Both co-IP results and immunofluorescence staining showed that PTX increased the binding of Spry2 to tubulin, and microtubule depolymerizing agents could abolish PTX's inhibition of Spry2 membrane distribution and inhibit PTX's upregulation of Raf/ERK signaling. Both nintedanib and ERK inhibitor were effective in relieving PTX-exacerbated RIPF. Taken together, the mechanism of PTX's aggravating RIPF was related to its ability to enhance Spry2's binding to tubulin, thus attenuating Spry2's negative regulation on Raf/ERK pathway. SIGNIFICANCE STATEMENT: This study revealed that paclitaxel (PTX) concurrent radiation therapy exacerbates radiation-induced pulmonary fibrosis during the treatment of thoracic tumors, which is associated with PTX restraining Spry2 and upregulating the Raf/extracellular signal regulated kinase signaling pathway, and provided drug targets for mitigating this complication.

Machine learning-based approach for automated classification of cell and extracellular matrix using nanomechanical properties

Fibrosis characterized by excess accumulation of extracellular matrix (ECM) due to complex cell-ECM interactions plays a pivotal role in pathogenesis. Herein, we employ the pancreatic ductal adenocarcinoma (PDAC) model to investigate dynamic alterations in nanomechanical attributes arising from the cell-ECM interactions to study the fibrosis paradigm. Several segregated studies performed on cellular and ECM components fail to recapitulate their complex collaboration. We utilized collagen and fibronectin, the two most abundant PDAC ECM components, and studied their nanomechanical attributes. We demonstrate alteration in morphology and nanomechanical attributes of collagen with varying thicknesses of collagen gel. Furthermore, by mixing collagen and fibronectin in various stoichiometry, their nanomechanical attributes were observed to vary. To demonstrate the dynamicity and complexity of cell-ECM, we utilized Panc-1 and AsPC-1 cells with or without collagen. We observed that Panc-1 and AsPC-1 cells interact differently with collagen and vice versa, evident from their alteration in nanomechanical properties. Further, using nanomechanics data, we demonstrate that ML-based techniques were able to classify between ECM as well as cell, and cell subtypes in the presence/absence of collagen with higher accuracy. This work demonstrates a promising avenue to explore other ECM components facilitating deeper insights into tumor microenvironment and fibrosis paradigm.

Discoidin domain receptor 2 signaling through PIK3C2α in fibroblasts promotes lung fibrosis

Pulmonary fibrosis, especially idiopathic pulmonary fibrosis (IPF), portends significant morbidity and mortality, and current therapeutic options are suboptimal. We have previously shown that type I collagen signaling through discoidin domain receptor 2 (DDR2), a receptor tyrosine kinase expressed by fibroblasts, is critical for the regulation of fibroblast apoptosis and progressive fibrosis. However, the downstream signaling pathways for DDR2 remain poorly defined and could also be attractive potential targets for therapy. A recent phosphoproteomic approach indicated that PIK3C2α, a poorly studied member of the PI3 kinase family, could be a downstream mediator of DDR2 signaling. We hypothesized that collagen I/DDR2 signaling through PIK3C2α regulates fibroblast activity during progressive fibrosis. To test this hypothesis, we found that primary murine fibroblasts and IPF-derived fibroblasts stimulated with endogenous or exogenous type I collagen led to the formation of a DDR2/PIK3C2α complex, resulting in phosphorylation of PIK3C2α. Fibroblasts treated with an inhibitor of PIK3C2α or with deletion of PIK3C2α had fewer markers of activation after stimulation with TGFβ and more apoptosis after stimulation with a Fas-activating antibody. Finally, mice with fibroblast-specific deletion of PIK3C2α had less fibrosis after bleomycin treatment than did littermate control mice with intact expression of PIK3Cα. Collectively, these data support the notion that collagen/DDR2/PIK3C2α signaling is critical for fibroblast function during progressive fibrosis, making this pathway a potential target for antifibrotic therapy. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Pterostilbene: a potential therapeutic agent for fibrotic diseases

Fibrosis is a prevailing pathology in chronic diseases and accounts for 45% of deaths in developed countries. This condition is primarily identified by the transformation of fibroblasts into myofibroblasts and the overproduction of extracellular matrix (ECM) by myofibroblasts. Pterostilbene (PTS) is a natural analogue of resveratrol and is most commonly found in blueberries. Research has shown that PTS exerts a wide range of pharmacological effects, such as antioxidant, anti-inflammatory, and anticancer effects. As a result, PTS has the potential to prevent and cure numerous diseases. Emerging evidence has indicated that PTS can alleviate myocardial fibrosis, renal fibrosis, pulmonary fibrosis, hepatic fibrosis, and colon fibrosis via the inhibition of inflammation, oxidative stress, and fibrogenesis effects in vivo and in vitro, and the potential mechanisms are linked to various pathways, including transforming growth factor-β1 (TGF-β1)/small mother against decapentaplegic proteins (Smads) signalling, the reactive oxygen species (ROS)-driven Pitx2c/mir-15b pathway, nuclear factor kappa B (NF-κB) signalling, Kelch-like epichlorohydrin-associated protein-1 (Keap-1)/NF-E2-related factor-2 (Nrf2) cascade, the NLR family pyridine structure domain 3 (NLRP3) pathway, the Janus kinase-2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway, and the Src/STAT3 pathway. In this review, we comprehensively summarize the antifibrotic effects of PTS both in vivo and in vitro and the pharmacological mechanisms, pharmacokinetics, and toxicology of PTS and provide insights into and strategies for exploring promising agents for the treatment of fibrosis.

Fibrosis-on-Chip: A Guide to Recapitulate the Essential Features of Fibrotic Disease

Fibrosis, which is primarily marked by excessive extracellular matrix (ECM) deposition, is a pathophysiological process associated with many disorders, which ultimately leads to organ dysfunction and poor patient outcomes. Despite the high prevalence of fibrosis, currently there exist few therapeutic options, and importantly, there is a paucity of in vitro models to accurately study fibrosis. This review discusses the multifaceted nature of fibrosis from the viewpoint of developing organ-on-chip (OoC) disease models, focusing on five key features: the ECM component, inflammation, mechanical cues, hypoxia, and vascularization. The potential of OoC technology is explored for better modeling these features in the context of studying fibrotic diseases and the interplay between various key features is emphasized. This paper reviews how organ-specific fibrotic diseases are modeled in OoC platforms, which elements are included in these existing models, and the avenues for novel research directions are highlighted. Finally, this review concludes with a perspective on how to address the current gap with respect to the inclusion of multiple features to yield more sophisticated and relevant models of fibrotic diseases in an OoC format.

Role of platelet factor 4 in arteriovenous fistula maturation failure: What do we know so far?

The rate of arteriovenous fistula (AVF) maturation failure remains unacceptably high despite continuous efforts on technique improvement and careful pre-surgery planning. In fact, half of all newly created AVFs are unable to be used for hemodialysis (HD) without a salvage procedure. While vascular stenosis in the venous limb of the access is the culprit, the underlying factors leading to vascular narrowing and AVF maturation failure are yet to be determined. We have recently demonstrated that AVF non-maturation is associated with post-operative medial fibrosis and fibrotic stenosis, and post-operative intimal hyperplasia (IH) exacerbates the situation. Multiple pathological processes and signaling pathways are underlying the stenotic remodeling of the AVF. Our group has recently indicated that a pro-inflammatory cytokine platelet factor 4 (PF4/CXCL4) is upregulated in veins that fail to mature after AVF creation. Platelet factor 4 is a fibrosis marker and can be detected in vascular stenosis tissue, suggesting that it may contribute to AVF maturation failure through stimulation of fibrosis and development of fibrotic stenosis. Here, we present an overview of the how PF4-mediated fibrosis determines AVF maturation failure.

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

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

YuPingFeng (YPF) upregulates caveolin-1 (CAV1) to alleviate pulmonary fibrosis through the TGF-β1/Smad2 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese medicine (TCM) is considered a valuable asset in China's medical tradition. YPF is a classic prescription that has been derived from the "Jiu Yuan Fang" formula and consists of three herbs: Huangqi (Astragalus membranaceus Bunge), Baizhu (Atractylodes rubra Dekker), and Fangfeng (Saposhnikovia divaricata (Turcz.) Schischk). This prescription is widely acclaimed for its exceptional pharmacological properties, including potent antioxidant effects, hormone regulation, and immune modulation effects.

AIM OF THE STUDY

Previous research provides evidence suggesting that YPF may have therapeutic effects on pulmonary fibrosis. Further exploration is essential to confirm its effectiveness and elucidate the fundamental processes.

MATERIALS AND METHODS

First, the active components and target genes of YPF were extracted from the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database. Next, the GSE53845 dataset, which contains information on pulmonary fibrosis, was downloaded from the GEO database. Network informatics methods was then be utilized to identify target genes associated with pulmonary fibrosis. A YPF-based network of protein-protein interactions was constructed to pinpoint possible target genes for pulmonary fibrosis treatment. Additionally, an in vitro model of pulmonary fibrosis induced by bleomycin (BLM) was established to further investigate and validate the possible mechanisms underlying the effectiveness of YPF.

RESULTS

In this study, a total of 24 active ingredients of YPF, along with 178 target genes associated with the treatment, were identified. Additionally, 615 target genes related to pulmonary fibrosis were identified. Functional enrichment analysis revealed that 18 candidate genes (CGs) exhibited significant responses to tumor necrosis factor, NF-kB survival signaling, and positive regulation of apoptosis processes. Among these CGs, CAV1, VCAM1, and TP63 were identified as key target genes. Furthermore, cell experiments confirmed that the expression of CAV1 protein and RNA expression was increased in pulmonary fibrosis, but significantly decreased after treatment with YPF. Additionally, the expression of pSmad2, α-SMA, TGF-β1, and TNF-α was also decreased following YPF treatment.

CONCLUSIONS

Network pharmacology analysis revealed that YPF exhibits significant potential as a therapeutic intervention for pulmonary fibrosis by targeting various compounds and pathways. This study emphasizes that the efficacy of YPF in treating pulmonary fibrosis may be attributed to its ability to up-regulate CAV1 expression and inhibiting pulmonary fibrosis via modulation of the TGF-β1/Smad2 signaling pathway. These findings underscore the promising role of YPF and its ability to potentially alleviate pulmonary fibrosis.

Temporal analysis of lung injury induced by real-ambient PM2 .5 exposure in mice

Fine particulate matter (PM2.5 ) has been shown to induce lung injury. However, the pathophysiological mechanisms of PM2.5 -induced pulmonary injury after different exposure times are poorly understood. In this study, we exposed male ICR mice to a whole-body PM2.5 inhalation system at daily mean concentration range from 92.00 to 862.00 μg/m3 for 30, 60, and 90 days. We found that following prolonged exposure to PM2.5 , pulmonary injury was increasingly evident with significant histopathological alterations. Notably, the pulmonary inflammatory response and fibrosis caused by PM2.5 after different exposure times were closely associated with histopathological changes. In addition, PM2.5 exposure caused oxidative stress, DNA damage and impairment of DNA repair in a time-dependent manner in the lung. Importantly, exposure to PM2.5 eventually caused apoptosis in the lung through upregulation of cleaved-caspase-3 and downregulation of Bcl-2. Overall, our data demonstrated that PM2.5 led to pulmonary injury in a time-dependent manner via upregulation of proinflammatory and fibrosis-related genes, and activation of the DNA damage response. Our findings provided a novel perspective on the pathophysiology of respiratory diseases caused by airborne pollution.

Anoctamin-1 is induced by TGF-β and contributes to lung myofibroblast differentiation

Idiopathic pulmonary fibrosis (IPF) is a devastating disease characterized by progressive scarring of the lungs and resulting in deterioration in lung function. Transforming growth factor-β (TGF-β) is one of the most established drivers of fibrotic processes. TGF-β promotes the transformation of tissue fibroblasts to myofibroblasts, a key finding in the pathogenesis of pulmonary fibrosis. We report here that TGF-β robustly upregulates the expression of the calcium-activated chloride channel anoctamin-1 (ANO1) in human lung fibroblasts (HLFs) at mRNA and protein levels. ANO1 is readily detected in fibrotic areas of IPF lungs in the same area with smooth muscle α-actin (SMA)-positive myofibroblasts. TGF-β-induced myofibroblast differentiation (determined by the expression of SMA, collagen-1, and fibronectin) is significantly inhibited by a specific ANO1 inhibitor, T16Ainh-A01, or by siRNA-mediated ANO1 knockdown. T16Ainh-A01 and ANO1 siRNA attenuate profibrotic TGF-β signaling, including activation of RhoA pathway and AKT, without affecting initial Smad2 phosphorylation. Mechanistically, TGF-β treatment of HLFs results in a significant increase in intracellular chloride levels, which is prevented by T16Ainh-A01 or by ANO1 knockdown. The downstream mechanism involves the chloride-sensing "with-no-lysine (K)" kinase (WNK1). WNK1 siRNA significantly attenuates TGF-β-induced myofibroblast differentiation and signaling (RhoA pathway and AKT), whereas the WNK1 kinase inhibitor WNK463 is largely ineffective. Together, these data demonstrate that 1) ANO1 is a TGF-β-inducible chloride channel that contributes to increased intracellular chloride concentration in response to TGF-β; and 2) ANO1 mediates TGF-β-induced myofibroblast differentiation and fibrotic signaling in a manner dependent on WNK1 protein but independent of WNK1 kinase activity.NEW & NOTEWORTHY This study describes a novel mechanism of differentiation of human lung fibroblasts (HLFs) to myofibroblasts: the key process in the pathogenesis of pulmonary fibrosis. Transforming growth factor-β (TGF-β) drives the expression of calcium-activated chloride channel anoctmin-1 (ANO1) leading to an increase in intracellular levels of chloride. The latter recruits chloride-sensitive with-no-lysine (K) kinase (WNK1) to activate profibrotic RhoA and AKT signaling pathways, possibly through activation of mammalian target of rapamycin complex-2 (mTORC2), altogether promoting myofibroblast differentiation.

Immune factors have a complex causal regulation on pulmonary fibrosis: Insights from a two-sample Mendelian randomization analysis

Pulmonary fibrosis is a chronic, progressive lung disease characterized by excessive scarring of lung tissue, and its pathophysiological mechanisms have not been fully elucidated. Immune cells play a key role in many diseases, and this study aims to explore the causal link between immune cell characteristics and pulmonary fibrosis using Mendelian randomization. Utilizing the public GWAS database Open GWAS, this study collected whole-genome association study datasets of peripheral blood immune phenotypes and summary data of GWAS related to pulmonary fibrosis. Through Mendelian randomization (MR) analysis, we identified single nucleotide polymorphisms (SNPs) significantly associated with immune traits as instrumental variables. After pleiotropy and heterogeneity tests, causal effects were assessed using methods such as inverse-variance weighted (IVW), weighted median, and MR-Egger. Comprehensive MR analysis indicated a significant causal relationship between various immune cell types, including regulatory T cells (Tregs), natural killer (NK) cells, and specific monocyte subgroups, with the risk of pulmonary fibrosis. Specifically, phenotypes such as Activated & resting Treg %CD4+, CCR2-positive monocytes, and CD16-CD56 positive NK cells were associated with a reduced risk of pulmonary fibrosis. In contrast, CD8 + T cell subgroups were associated with an increased risk. This study provides evidence of a causal relationship between immune cell characteristics and pulmonary fibrosis, highlighting the protective role of regulatory T cells and specific NK cell subgroups, as well as the potential harm of CD8 + T cell subgroups. These findings offer new insights into the immunoregulatory mechanisms of pulmonary fibrosis and the development of novel therapeutic strategies.

The lncRNA H19/miR-29a-3p/SNIP1/c-myc regulatory axis is involved in pulmonary fibrosis induced by Nd2O3

Some rare earth elements are occupational and environmental toxicants and can cause organ and systemic damage; therefore, they have attracted global attention. Neodymium oxide (Nd2O3) is a rare earth element that is refined and significantly utilized in China. The long noncoding RNA (lncRNA) H19 is encoded by the H19/IGF2 imprinted gene cluster located on human chromosome 11p15.5. H19 has become a research focus due to its ectopic expression leading to the promotion of fibrosis. However, the mechanisms by which it causes pulmonary fibrosis are elusive. This investigation indicates that biologically active Nd2O3 increases H19, SNIP1, and c-myc, decreases miR-29a-3p, accelerates macrophage M2 polarization, and causes pulmonary fibrosis in mice lung tissues. In macrophage-differentiated THP-1 cells, Nd2O3 (25 μg/ml) enhanced H19, SNIP1, and c-myc, reduced miR-29a-3p, accelerated macrophages M2 polarization, and stimulated fibrogenic cytokine (TGF-β1) secretion. Furthermore, the coculturing of Nd2O3-treated macrophage-differentiated THP-1 cells. And human embryonic lung fibroblast cells activated lung fibroblast, which increases the levels of collagen I, α-SMA, p-Smad2/3, and Smad4, whereas H19 knockdown or miR-29a-3p upregulation in macrophages had opposite effects. Moreover, it was revealed that H19/miR-29a-3p/SNIP1/c-myc regulatory axis is involved in pulmonary fibrosis induced by Nd2O3. Therefore, this study provides new molecular insights into the mechanism of pulmonary fibrosis by Nd2O3.

CircZNF609 regulates pulmonary fibrosis via miR-145-5p/KLF4 axis and its translation function

BACKGROUND

Pulmonary fibrosis is a growing clinical problem that develops as a result of abnormal wound healing, leading to breathlessness, pulmonary dysfunction and ultimately death. However, therapeutic options for pulmonary fibrosis are limited because the underlying pathogenesis remains incompletely understood. Circular RNAs, as key regulators in various diseases, remain poorly understood in pulmonary fibrosis induced by silica.

METHODS

We performed studies with fibroblast cell lines and silica-induced mouse pulmonary fibrosis models. The expression of circZNF609, miR-145-5p, and KLF4 was determined by quantitative real-time polymerase chain reaction (qRT-PCR) analysis. RNA immunoprecipitation (RIP) assays and m6A RNA immunoprecipitation assays (MeRIP), Western blotting, immunofluorescence assays, and CCK8 were performed to investigate the role of the circZNF609/miR-145-5p/KLF4 axis and circZNF609-encoded peptides in fibroblast activation.

RESULTS

Our data showed that circZNF609 was downregulated in activated fibroblasts and silica-induced fibrotic mouse lung tissues. Overexpression of circZNF609 could inhibit fibroblast activation induced by transforming growth factor-β1 (TGF-β1). Mechanically, we revealed that circZNF609 regulates pulmonary fibrosis via miR-145-5p/KLF4 axis and circZNF609-encoded peptides. Furthermore, circZNF609 was highly methylated and its expression was controlled by N6-methyladenosine (m6A) modification. Lastly, in vivo studies revealed that overexpression of circZNF609 attenuates silica-induced lung fibrosis in mice.

CONCLUSIONS

Our data indicate that circZNF609 is a critical regulator of fibroblast activation and silica-induced lung fibrosis. The circZNF609 and its derived peptides may represent novel promising targets for the treatment of pulmonary fibrosis.

O-GlcNAcylation Regulates Centrosome Behavior and Cell Polarity to Reduce Pulmonary Fibrosis and Maintain the Epithelial Phenotype

O-GlcNAcylation functions as a cellular nutrient and stress sensor and participates in almost all cellular processes. However, it remains unclear whether O-GlcNAcylation plays a role in the establishment and maintenance of cell polarity, because mice lacking O-GlcNAc transferase (OGT) are embryonically lethal. Here, a mild Ogt knockout mouse model is constructed and the important role of O-GlcNAcylation in establishing and maintaining cell polarity is demonstrated. Ogt knockout leads to severe pulmonary fibrosis and dramatically promotes epithelial-to-mesenchymal transition. Mechanistic studies reveal that OGT interacts with pericentriolar material 1 (PCM1) and centrosomal protein 131 (CEP131), components of centriolar satellites required for anchoring microtubules to the centrosome. These data further show that O-GlcNAcylation of PCM1 and CEP131 promotes their centrosomal localization through phase separation. Decrease in O-GlcNAcylation prevents PCM1 and CEP131 from localizing to the centrosome, instead dispersing these proteins throughout the cell and impairing the microtubule-centrosome interaction to disrupt centrosome positioning and cell polarity. These findings identify a previously unrecognized role for protein O-GlcNAcylation in establishing and maintaining cell polarity with important implications for the pathogenesis of pulmonary fibrosis.

The critical role of osteopontin (OPN) in fibrotic diseases

Fibrosis is a pathological condition characterized by the excessive deposition of extracellular matrix components in tissues and organs, leading to progressive architectural remodelling and contributing to the development of various diseases. Osteopontin (OPN), a highly phosphorylated glycoprotein, has been increasingly recognized for its involvement in the progression of tissue fibrosis. This review provides a comprehensive overview of the genetic and protein structure of OPN and focuses on our current understanding of the role of OPN in the development of fibrosis in the lungs and other tissues. Additionally, special attention is given to the potential of OPN as a biomarker and a novel therapeutic target in the treatment of fibrosis.

Regulation of alveolar macrophage death in pulmonary fibrosis: a review

Pulmonary fibrosis (PF) is a disease in which excessive extracellular matrix (ECM) accumulation occurs in pulmonary mesenchyme, which induces the destruction of alveolar structures and poor prognosis. Macrophage death is responsible for ECM accumulation after alveolar epithelial injury in PF. Depending on the local micro-environments, macrophages can be polarized to either classically activated (M1) or alternatively activated (M2) macrophage phenotypes. In general, M1 macrophages can promote inflammation and sterilization, stop the continuous damage process and prevent excessive repair, while M2 macrophages are anti-inflammatory and promote tissue repair, and excessive M2 macrophage activity may inhibit the absorption and degradation of ECM. Emerging evidence has revealed that death forms such as pyroptosis mediated by inflammasome affect polarization direction and ultimately lead to the development of PF. Pharmacological manipulation of macrophages death signals may serve as a logical therapeutic strategy for PF. This review will focus on the current state of knowledge regarding the regulation and underlying mechanisms of macrophages and their mediators in the influence of macrophage death on the development of PF. We expect to provide help in developing effective therapeutic strategies in clinical settings.

Pulmonary fibrosis: from pathogenesis to clinical decision-making

Pulmonary fibrosis (PF) encompasses a spectrum of chronic lung diseases that progressively impact the interstitium, resulting in compromised gas exchange, breathlessness, diminished quality of life (QoL), and ultimately respiratory failure and mortality. Various diseases can cause PF, with their underlying causes primarily affecting the lung interstitium, leading to their referral as interstitial lung diseases (ILDs). The current understanding is that PF arises from abnormal wound healing processes triggered by various factors specific to each disease, leading to excessive inflammation and fibrosis. While significant progress has been made in understanding the molecular mechanisms of PF, its pathogenesis remains elusive. This review provides an in-depth exploration of the latest insights into PF pathophysiology, diagnosis, treatment, and future perspectives.

Silicon dioxide-induced endoplasmic reticulum stress of alveolar macrophages and its role on the formation of silicosis fibrosis: a review article

Silicosis is a chronic lung inflammatory disease induced by long-term inhalation of high concentrations of silicon dioxide (SiO2), characterized by pulmonary fibrosis. Inhalation of silica invades alveolar macrophages (AMs) and changes the micro-environment of the cell, resulting in abnormal morphology and dysfunction of the endoplasmic reticulum (ER). Once beyond the range of cell regulation, the endoplasmic reticulum stress (ERS) will occur, which will lead to cell damage, necrosis, and apoptosis, eventually causing silicosis fibrosis through various mechanisms. This is a complex and delicate process accompanied by various macrophage-derived cytokines. Unfortunately, the details have not been systematically summarized yet. In this review, we systematically introduce the basic two processes: the process of inducing ERS by inhaling SiO2 and the process of inducing pulmonary fibrosis by ERS. Moreover, the underlying mechanism of the above two sequential events is also be discussed. We conclude that the ERS of alveolar macrophages caused by silica dust are involved deeply in the pathogenesis of silicosis. Therefore, changing the states of SiO2-induced ERS of macrophage may be an attractive therapeutic target for silicosis fibrosis.

Progress in Understanding the Role and Therapeutic Targets of Polarized Subtypes of Macrophages in Pulmonary Fibrosis

Pulmonary fibrosis represents the advanced phase of diverse pulmonary ailments, and at present, a definitive cure for these ailments is lacking. Furthermore, underlying mechanisms causative of these ailments remain elusive. Macrophages are immune cells that resist external stimuli in the early stages after birth. These cells can polarize into the classically (M1) and alternatively (M2) activated macrophages. When stimulated owing to the presence of toxic factors, M1 macrophages produce several pro-inflammatory factors, which mediate the inflammatory injury response of the alveolar tissue. The secretion of diverse growth factors by M2 macrophages contributes to the pathogenesis of aberrant alveolar structural fibrosis and remodeling. The abnormal activity of M2 macrophages is considered a critical factor in the formation of pulmonary fibrosis. In this mini-review, to highlight the clinical implications of research studies, we summarize the role and therapeutic targets of polarized subtypes of macrophages in pulmonary fibrosis and the role of targeting macrophages for the treatment of pulmonary fibrosis.

Vanadium Carbide Nanosheets with Broad-Spectrum Antioxidant Activity for Pulmonary Fibrosis Therapy

Idiopathic pulmonary fibrosis is a chronic and highly lethal lung disease that largely results from oxidative stress; however, effective antioxidant therapy by targeting oxidative stress pathogenesis is still lacking. The big challenge is to develop an ideal antioxidant material with superior antifibrotic effects. Herein, we report that V4C3 nanosheets (NSs) can serve as a potential antioxidant for treatment of pulmonary fibrosis by scavenging reactive oxygen and nitrogen species. Interestingly, subtle autoxidation can adjust the valence composition of V4C3 NSs and significantly improve their antioxidant behavior. Valence engineering triggers multiple antioxidant mechanisms including electron transfer, H atom transfer, and enzyme-like catalysis, thus endowing V4C3 NSs with broad-spectrum, high-efficiency, and persistent antioxidant capacity. Benefiting from antioxidant properties and good biocompatibility, V4C3 NSs can significantly prevent myofibroblast proliferation and extracellular matrix abnormality, thus alleviating the progression of bleomycin-induced pulmonary fibrosis in vivo by scavenging ROS, anti-inflammation, and rebuilding antioxidant defenses. This study not only provides an important strategy for designing excellent antioxidant nanomaterials, but also proposes a proof-of-concept demonstration for the treatment of pulmonary fibrosis and other oxidative stress-related diseases.

Emerging opportunities to treat idiopathic pulmonary fibrosis: Design, discovery, and optimizations of small-molecule drugs targeting fibrogenic pathways

Idiopathic pulmonary fibrosis (IPF) is the most common fibrotic form of idiopathic diffuse lung disease. Due to limited treatment options, IPF patients suffer from poor survival. About ten years ago, Pirfenidone (Shionogi, 2008; InterMune, 2011) and Nintedanib (Boehringer Ingelheim, 2014) were approved, greatly changing the direction of IPF drug design. However, limited efficacy and side effects indicate that neither can reverse the process of IPF. With insights into the occurrence of IPF, novel targets and agents have been proposed, which have fundamentally changed the treatment of IPF. With the next-generation agents, targeting pro-fibrotic pathways in the epithelial-injury model offers a promising approach. Besides, several next-generation IPF drugs have entered phase II/III clinical trials with encouraging results. Due to the rising IPF treatment requirements, there is an urgent need to completely summarize the mechanisms, targets, problems, and drug design strategies over the past ten years. In this review, we summarize known mechanisms, target types, drug design, and novel technologies of IPF drug discovery, aiming to provide insights into the future development and clinical application of next-generation IPF drugs.

Effect of Chest Physiotherapy on Quality of Life, Exercise Capacity and Pulmonary Function in Patients with Idiopathic Pulmonary Fibrosis: A Systematic Review and Meta-Analysis

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is one of the most deleterious diseases of the pulmonary fibrosis spectrum. Its clinical presentation includes irreversible loss of lung function, and increasing cough, dyspnea and impaired quality of life. Chest physiotherapy can improve ventilation capacity, gas exchange, dyspnea, exercise capacity and quality of life. The aim of this study was to review the evidence about chest physiotherapy in IPF, specifically meta-analyzing quality of life, exercise capacity and pulmonary function.

METHODS

A wide search was conducted in PubMed, Embase, Cochrane and Web of Science for articles included until October 2023. PROSPERO Identifier: CRD42022333496. The Downs and Black scale and the Cochrane tool were employed to evaluate quality assessments and to assess the risk of bias. Data were pooled, and a meta-analysis was conducted.

RESULTS

We selected 10 studies in which a chest physiotherapy program was performed with a total of 340 patients; of these, three articles were meta-analyzed. Significant effects in favor of chest physiotherapy were found for quality of life (MD = -8.60, 95% CI = -11.30, -5.90; p < 0.00001; I2 = 24%), exercise capacity (MD = 37.62, 95% CI = 15.10, 60.13; p = 0.001; I2 = 65%) and pulmonary function (MD = 7.86, 95% CI = 2.54, 13.17; p = 0.004; I2 = 80%).

CONCLUSIONS

The systematic review showed significant results for the application of chest physiotherapy regarding pulmonary capacity, diffusion of gases and quality of life in IPF patients. The meta-analysis showed a significant improvement associated with applying chest physiotherapy in pulmonary function, exercise capacity and quality of life.

Identification and Validation of Genes Exhibiting Dynamic Alterations in Response to Bleomycin-Induced Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) carries a high mortality rate and has a poor prognosis. The pathogenesis of pulmonary fibrosis (PF) is highly related to dysregulation of multiple RNAs. This study aims to identify and validate dysregulated RNAs that exhibited dynamic alterations in response to bleomycin (BLM)-induced PF. The results will provide therapeutic targets for patients suffering from IPF. Whole transcriptomic profiles of BLM-induced PF were obtained through high-throughput RNA sequencing. miRNA profiling was downloaded from GSE45789 database in the Gene Expression Omnibus (GEO). We identified the differentially expressed RNAs (DERNAs) that exhibited dynamic alterations in response to BLM-induced PF. Subsequently, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genome (KEGG) pathway enrichment analysis were conducted to discovery regulatory processes of PF. Weighted gene co-expression network analysis (WGCNA), protein-protein interaction (PPI) analysis, and co-expression analysis were performed to identify key genes and pathogenic pattern during the progression of PF. MiRanda, miRcode, and TargetScan were utilized to predict target relationships in the potential competing endogenous RNA (ceRNA) network. The results were verified by qRT-PCR analysis. In the context of BLM-induced PF, this study identified a total of 167 differentially expressed messenger RNAs (DEmRNAs), 115 differentially expressed long non-coding RNAs (DElncRNAs), 45 differentially expressed circular RNAs (DEcircRNAs), and 87 differentially expressed microRNAs (DEmiRNAs). These RNA molecules showed dynamic alterations in response to BLM-induced PF. These DEmRNAs exhibited a predominant association with the biological processes pertaining to the organization of extracellular matrix. A regulatory network was built in PF, encompassing 31 DEmRNAs, 18 DE lncRNAs, 13 DEcircRNAs, and 13 DEmiRNAs. Several DERNA molecules were subjected to validate using additional BLM-induced PF model. The outcomes of this validation process shown a strong correlation with the results obtained from RNA sequencing analysis. The GSE213001 dataset was utilized to validate the expression levels and diagnostic efficacy of four specific hub mRNAs (CCDC80, CLU, COL5A1, and COL6A3) in individuals diagnosed with PF. In this study, we identified and validated several RNA molecules that exhibited dynamic alternations in response to BLM-induced PF. These dysregulated RNAs participated in the pathogenesis of PF and can be used as therapeutic targets for early-stage IPF. Although more work must be done to confirm the results, our study may provide directions for future studies.

PM2.5 triggers autophagic degradation of Caveolin-1 via endoplasmic reticulum stress (ERS) to enhance the TGF-β1/Smad3 axis promoting pulmonary fibrosis

Air pollution is highly associated with respiratory diseases. However, the influence and mechanism of particulate matter with aerodynamic equal to or less than 2.5 μm (PM2.5) in lung homeostasis remain unclear. Herein, we demonstrated the induction of pulmonary fibrosis (PF) by PM2.5 exposure. The animal model showed that PM2.5 exposure could activate the oxidative stress and inflammation response, promoting epithelial-mesenchymal transition and accumulation of collagen, high expression of pro-fibrotic factors, and pathological characteristics of fibrosis. The proteomic analysis indicated that PM2.5 exposure decreased the expression of caveolin-1 (Cav-1), and many differential proteins were enriched in the TGF-β1/Smad, endoplasmic reticulum stress (ERS) and autophagy pathways. Combining in vivo and in vitro experiments, it was found that PM2.5 exposure could reduce Cav-1 protein levels and activate TGF-β1/Smad3 signaling pathways through ERS and autophagy pathways, thereby inducing cell apoptosis and promoting pulmonary fibrosis. However, inhibiting ERS could alleviate the occurrence of autophagy, and blocking the autophagy system could increase the level of Cav-1 protein and inhibit TGF- β 1/Smad3 signaling pathway to improve pulmonary fibrosis. Therefore, we demonstrated that the exposure of PM2.5 could enhance the ERS induced-autophagy-mediated Cav-1 degradation, thus activating the TGF-β1/Smad3 axis to promote pneumonocytes apoptosis and overproduction of extracellular matrix (ECM), finally aggravating PF. Moreover, our findings revealed that intermittent exposure to high doses of PM2.5 was more toxic than continuous exposure to low dose.

Astragaloside IV protects against lung injury and pulmonary fibrosis in COPD by targeting GTP-GDP domain of RAS and downregulating the RAS/RAF/FoxO signaling pathway

BACKGROUND

Pulmonary fibrosis is a chronic progressive interstitial lung disease characterized by the replacement of lung parenchyma with fibrous scar tissue, usually as the final stage of lung injury like COPD. Astragaloside IV (AST), a bioactive compound found in the Astragalus membranaceus (Fisch.) used in traditional Chinese medicine, has been shown to improve pulmonary function and exhibit anti-pulmonary fibrosis effects. However, the exact molecular mechanisms through which it combats pulmonary fibrosis, especially in COPD, remain unclear.

PURPOSE

This study aimed to identify the potential therapeutic target and molecular mechanisms for AST in improving lung injury especially treating COPD type pulmonary fibrosis both in vivo and in vitro.

METHODS

Multi lung injury models were established in mice using lipopolysaccharide (LPS), cigarette smoke (CS), or LPS plus CS to simulate the processes of pulmonary fibrosis in COPD. The effect of AST on lung function protection was evaluated, and proteomic and metabolomic analysis were applied to identify the signaling pathway affected by AST and to find potential targets of AST. The interaction between AST and wild-type and mutant RAS proteins was studied. The RAS/RAF/FoxO signaling pathway was stimulated in BEAS-2B cells and in mice lung tissues by LPS plus CS to investigate the anti-pulmonary fibrosis mechanism of AST analyzed by western blotting. The regulatory effects of AST on the RAS/RAF/FoxO pathway dependent on RAS were further confirmed using RAS siRNA.

RESULTS

RAS was predicted and identified as the target protein of AST in anti-pulmonary fibrosis in COPD and improving lung function. The administration of AST was observed to impede the conversion of fibroblasts into myofibroblasts, reduce the manifestation of inflammatory factors and extracellular matrix, and hinder the activation of epithelial mesenchymal transition (EMT). Furthermore, AST significantly suppressed the RAS/RAF/FoxO signaling pathway in both in vitro and in vivo settings.

CONCLUSION

AST exhibited lung function protection and anti-pulmonary fibrosis effect by inhibiting the GTP-GDP domain of RAS, which downregulated the RAS/RAF/FoxO signaling pathway. This study revealed AST as a natural candidate molecule for the protection of pulmonary fibrosis in COPD.

PANoptosis: Mechanism and Role in Pulmonary Diseases

PANoptosis is a newly defined programmed cell death (PCD) triggered by a series of stimuli, and it engages three well-learned PCD forms (pyroptosis, apoptosis, necroptosis) concomitantly. Normally, cell death is recognized as a strategy to eliminate unnecessary cells, inhibit the proliferation of invaded pathogens and maintain homeostasis; however, vigorous cell death can cause excessive inflammation and tissue damage. Acute lung injury (ALI) and chronic obstructive pulmonary syndrome (COPD) exacerbation is related to several pathogens (e.g., influenza A virus, SARS-CoV-2) known to cause PANoptosis. An understanding of the mechanism and specific regulators may help to address the pathological systems of these diseases. This review presents our understanding of the potential mechanism of PANoptosis and the role of PANoptosis in different pulmonary diseases.

Mechanotransductive receptor Piezo1 as a promising target in the treatment of fibrosis diseases

Fibrosis could happen in every organ, leading to organic malfunction and even organ failure, which poses a serious threat to global health. Early treatment of fibrosis has been reported to be the turning point, therefore, exploring potential correlates in the pathogenesis of fibrosis and how to reverse fibrosis has become a pressing issue. As a mechanism-sensitive cationic calcium channel, Piezo1 turns on in response to changes in the lipid bilayer of the plasma membrane. Piezo1 exerts multiple biological roles, including inhibition of inflammation, cytoskeletal stabilization, epithelial-mesenchymal transition, stromal stiffness, and immune cell mechanotransduction, interestingly enough. These processes are closely associated with the development of fibrotic diseases. Recent studies have shown that deletion or knockdown of Piezo1 attenuates the onset of fibrosis. Therefore, in this paper we comprehensively describe the biology of this gene, focusing on its potential relevance in pulmonary fibrosis, renal fibrosis, pancreatic fibrosis, and cardiac fibrosis diseases, except for the role of drugs (agonists), increased intracellular calcium and mechanical stress using this gene in alleviating fibrosis.

Pulmonary fibrosis and COVID-19

The COVID-19 pandemic has caused the death of millions and many more have been infected worldwide. The causative virus, SARS-CoV-2, affects the lung where it elicits an aggressive inflammatory response leading to respiratory failure in severe cases. This infection has been linked to pulmonary fibrosis, a process characterized by fibroproliferation and the exaggerated deposition of collagen and other extracellular matrices. These events damage the lung architecture, especially its gas-exchanging units, leading to hypoxemic respiratory failure. The mechanisms by which the virus affects the lung remain incompletely understood, but it is postulated that after entering the airways, the virus binds to Angiotensin Converting Enzyme (ACE) receptors on the surface of epithelial cells, not only stimulating oxidative stress and inflammation, but also promoting the expression of soluble pro-fibrotic factors responsible for the accumulation of fibroblasts, their activation into myofibroblasts, and their unregulated expression of extracellular matrices. These events may trigger the rapid progression or exacerbation of underlying interstitial lung disorders or promote fibrosis in a previously healthy lung. Although the natural progression of such conditions cannot always be predicted, fibrosis may progress even after the virus has been eliminated or, in cases where it does not progress, may become irreversible, leading to long-standing symptoms like shortness of breath and exercise intolerance resulting from loss of lung function. Although COVID-19 related pulmonary fibrosis is not common, preventive measures like vaccination are encouraged, as they are expected to reduce infection or its severity, thereby decreasing the possibility of life-changing respiratory conditions such as pulmonary fibrosis.

Targeting Mitochondrial Sirtuins in Age-Related Neurodegenerative Diseases and Fibrosis

Aging is a natural and complex biological process that is associated with widespread functional declines in numerous physiological processes, terminally affecting multiple organs and tissues. Fibrosis and neurodegenerative diseases (NDs) often occur with aging, imposing large burdens on public health worldwide, and there are currently no effective treatment strategies for these diseases. Mitochondrial sirtuins (SIRT3-5), which are members of the sirtuin family of NAD+-dependent deacylases and ADP-ribosyltransferases, are capable of regulating mitochondrial function by modifying mitochondrial proteins that participate in the regulation of cell survival under various physiological and pathological conditions. A growing body of evidence has revealed that SIRT3-5 exert protective effects against fibrosis in multiple organs and tissues, including the heart, liver, and kidney. SIRT3-5 are also involved in multiple age-related NDs, including Alzheimer's disease, Parkinson's disease, and Huntington's disease. Furthermore, SIRT3-5 have been noted as promising targets for antifibrotic therapies and the treatment of NDs. This review systematically highlights recent advances in knowledge regarding the role of SIRT3-5 in fibrosis and NDs and discusses SIRT3-5 as therapeutic targets for NDs and fibrosis.

MiR-30a inhibits silica dust-induced epithelial-mesenchymal transition by targeting Snail

The mechanism of action of MicroRNA-30a(miR-30a) and Snail, a transcription factor, in silica(SiO2) dust-induced pulmonary EMT and secondary pulmonary fibrosis remains elusive. In this study, the cellular EMT model induced by the stimulation of A549 cells with SiO2 was established. A549 cells were transfected with miR-30a mimic and miR-30a inhibitor and the SNAIL gene was silenced to examine the mechanism of miR-30a targeting Snail to regulate silica dust-induced EMT. The results showed that 50 μg/mL SiO2 stained A549 cells for 24 h could induce EMT in A549 cells. Exposure of A549 cells to SiO2 dust decreased miR-30a expression, as well as mRNA and protein expression levels of E-cad. Conversely, SiO2 exposure increased mRNA and protein expression levels of α-SMA, vimentin, and Snail. The miR-30a mimic upregulated mRNA and protein expression levels of E-cadherin in SiO2-induced A549 cells, while downregulating mRNA and protein expression levels of α-SMA, vimentin and Snail. MiR-30a inhibitors have the opposite effect. Silencing the SNAIL gene, followed by SiO2 dust-induced stimulation of A549 cells, could enhance mRNA and protein expression levels of E-cad, whereas those of α-SMA and vimentin were reduced. Altogether, we found that miR-30a directly targeted Snail and inhibited its expression, thereby delaying silica induced pulmonary EMT.

FOXO4-D-Retro-Inverso targets extracellular matrix production in fibroblasts and ameliorates bleomycin-induced pulmonary fibrosis in mice

Pulmonary fibrosis (PF) occurs in various end stages of lung disease, and it is characterized by persistent scarring of the lung parenchyma with excessive deposition of extracellular matrix (ECM), leading to degressive quality of life and earlier mortality. FOXO4-D-Retro-Inverso (FOXO4-DRI), a synthesis peptide as a specific FOXO4 blocker, selectively induced dissociation of the FOXO4-p53 complex and nuclear exclusion of p53. Simultaneously, the p53 signaling pathway has been reported to activate in fibroblasts isolated from IPF fibrotic lung tissues and the p53 mutants cooperate with other factors that have the ability to disturb the synthesis of ECM. Yet, whether FOXO4-DRI influences the nuclear exclusion of p53 and then obstructs PF progress is still unknown. In this research, we explored the effect of FOXO4-DRI on bleomycin (BLM)-induced PF mouse model and activated fibroblasts model. The animal group of FOXO4-DRI therapeutic administration shows a milder pathologic change and less collagen deposition compared with the BLM-induced group. We also found the FOXO4-DRI resets the distribution of intranuclear p53 and concurrently decreased the total ECM proteins content. After further validation, FOXO4-DRI may well be a promising therapeutic approach to treating pulmonary fibrosis.

Nestin and Notch3 collaboratively regulate angiogenesis, collagen production, and endothelial-mesenchymal transition in lung endothelial cells

BACKGROUND

Nestin, an intermediate filament protein, participates in various pathophysiological processes, including wound healing, angiogenesis, endothelial-mesenchymal transition (EndoMT), and fibrosis. However, the pathophysiological roles of lung nestin-expressing cells remain unclear due to conflicting reports. The objective of this study is to elucidate the characteristics and functions of lung nestin-expressing cells.

METHODS

We conducted a series of in vitro and in vivo experiments using endothelial cell line MS1 and nestin-GFP mice. This animal model allows for nestin-expressing cell detection without the use of anti-nestin antibodies.

RESULTS

Lung nestin-expressing cells occurred in approximately 0.2% of CD45- cells and was co-expressed with epithelial, endothelial, and mesenchymal cell-surface markers. Importantly, virtually all nestin-expressing cells co-expressed CD31. When compared to lung nestin-nonexpressing endothelial cells, nestin-expressing endothelial cells showed robust angiogenesis with frequent co-expression of PDGFRβ and VEGFR2. During TGFβ-mediated EndoMT, the elevation of Nes mRNA expression preceded that of Col1a1 mRNA, and nestin gene silencing using nestin siRNA resulted in further upregulation of Col1a1 mRNA expression. Furthermore, Notch3 expression was regulated by nestin in vitro and in vivo; nestin siRNA resulted in reduced Notch3 expression accompanied with enhanced EndoMT. Contrary to previous reports, neither Nes mRNA expression nor nestin-expressing cells were increased during pulmonary fibrosis.

CONCLUSIONS

Our study showed that (1) lung nestin-expressing cells are an endothelial lineage but are distinct from nestin-nonexpressing endothelial cells; (2) nestin regulates Notch3 and they act collaboratively to regulate angiogenesis, collagen production, and EndoMT; and (3) nestin plays novel roles in lung angiogenesis and fibrosis. Video Abstract.

AT2 cell-derived IgA trapped by the extracellular matrix in silica-induced pulmonary fibrosis

Pulmonary fibrosis is an interstitial lung disease caused by various factors such as exposure to workplace environmental contaminants, drugs, or X-rays. Epithelial cells are among the driving factors of pulmonary fibrosis. Immunoglobulin A (IgA), traditionally thought to be secreted by B cells, is an important immune factor involved in respiratory mucosal immunity. In the current study, we found that lung epithelial cells are involved in IgA secretion, which, in turn, promotes pulmonary fibrosis. Spatial transcriptomics and single-cell sequencing suggest that Igha transcripts were highly expressed in the fibrotic lesion areas of lungs from silica-treated mice. Reconstruction of B-cell receptor (BCR) sequences revealed a new cluster of AT2-like epithelial cells with a shared BCR and high expression of genes related to IgA production. Furthermore, the secretion of IgA by AT2-like cells was trapped by the extracellular matrix and aggravated pulmonary fibrosis by activating fibroblasts. Targeted blockade of IgA secretion by pulmonary epithelial cells may be a potential strategy for treating pulmonary fibrosis.

Hydrolysable tannins as a potential therapeutic drug for the human fibrosis-associated disease

Fibrosis is a pathological change with abnormal tissue regeneration due to a response to persistent injury, which is extensively related to organ damage and failure, leading to high morbidity and mortality worldwide. Although the pathogenesis of fibrosis has been comprehensively elucidated, there are few effective therapies for treating fibrotic diseases. Natural products are increasingly regarded as an effective strategy for fibrosis with numerous favorable functions. Hydrolysable tannins (HT) are a type of natural products that have the potential to treat the fibrotic disease. In this review, we describe some biological activities and the therapeutic prospects of HT in organ fibrosis. Furthermore, the underlying mechanisms of inhibition of HT on fibrotic organs in relation to inflammation, oxidative stress, epithelial-mesenchymal transition, fibroblast activation and proliferation, and extracellular matrix accumulation are discussed. Understanding the mechanism of HT against fibrotic diseases will provide a new strategy for the prevention and attenuation of fibrosis progression.

NETosis promotes chronic inflammation and fibrosis in systemic lupus erythematosus and COVID-19

Pulmonary fibrosis, a serious complication of systemic lupus erythematosus (SLE) and coronavirus disease 2019 (COVID-19), leads to irreversible lung damage. However, the underlying mechanism of this condition remains unclear. In this study, we revealed the landscape of transcriptional changes in lung biopsies from individuals with SLE, COVID-19-induced pulmonary fibrosis, and idiopathic pulmonary fibrosis (IPF) using histopathology and RNA sequencing, respectively. Despite the diverse etiologies of these diseases, lung expression of matrix metalloproteinase genes in these diseases showed similar patterns. Particularly, the differentially expressed genes were significantly enriched in the pathway of neutrophil extracellular trap formation, showing similar enrichment signature between SLE and COVID-19. The abundance of Neutrophil extracellular traps (NETs) was much higher in the lungs of individuals with SLE and COVID-19 compared to those with IPF. In-depth transcriptome analyses revealed that NETs formation pathway promotes epithelial-mesenchymal transition (EMT). Furthermore, stimulation with NETs significantly up-regulated α-SMA, Twist, Snail protein expression, while decreasing the expression of E-cadherin protein in vitro. This indicates that NETosis promotes EMT in lung epithelial cells. Given drugs that are efficacious in degrading damaged NETs or inhibiting NETs production, we identified a few drug targets that were aberrantly expressed in both SLE and COVID-19. Among these targets, the JAK2 inhibitor Tofacitinib could effectively disrupted the process of NETs and reversed NET-induced EMT in lung epithelial cells. These findings support that the NETs/EMT axis, activated by SLE and COVID-19, contributes to the progression of pulmonary fibrosis. Our study also highlights that JAK2 as a potential target for the treatment of fibrosis in these diseases.

Idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive devastating lung disease with substantial morbidity. It is associated with cough, dyspnea and impaired quality of life. If left untreated, IPF has a median survival of 3 years. IPF affects ∼3 million people worldwide, with increasing incidence in older patients. The current concept of pathogenesis is that pulmonary fibrosis results from repetitive injury to the lung epithelium, with fibroblast accumulation, myofibroblast activation, and deposition of matrix. These injuries, in combination with innate and adaptive immune responses, dysregulated wound repair and fibroblast dysfunction, lead to recurring tissue remodeling and self-perpetuating fibrosis as seen in IPF. The diagnostic approach includes the exclusion of other interstitial lung diseases or underlying conditions and depends on a multidisciplinary team-based discussion combining radiological and clinical features and well as in some cases histology. In the last decade, considerable progress has been made in the understanding of IPF clinical management, with the availability of two drugs, pirfenidone and nintedanib, that decrease pulmonary lung function decline. However, current IPF therapies only slow disease progression and prognosis remains poor. Fortunately, there are multiple clinical trials ongoing with potential new therapies targeting different disease pathways. This review provides an overview of IPF epidemiology, current insights in pathophysiology, diagnostic and therapeutic management approaches. Finally, a detailed description of current and evolving therapeutic approaches is also provided.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Nicotinamide N-methyltransferase mediates lipofibroblast-myofibroblast transition and apoptosis resistance

Metabolism controls cellular phenotype and fate. In this report, we demonstrate that nicotinamide N-methyltransferase (NNMT), a metabolic enzyme that regulates developmental stem cell transitions and tumor progression, is highly expressed in human idiopathic pulmonary fibrosis (IPF) lungs, and is induced by the pro-fibrotic cytokine, transforming growth factor-β1 (TGF-β1) in lung fibroblasts. NNMT silencing reduces the expression of extracellular matrix proteins, both constitutively and in response to TGF-β1. Furthermore, NNMT controls the phenotypic transition from homeostatic, pro-regenerative lipofibroblasts to pro-fibrotic myofibroblasts. This effect of NNMT is mediated, in part, by the downregulation of lipogenic transcription factors, TCF21 and PPARγ, and the induction of a less proliferative but more differentiated myofibroblast phenotype. NNMT confers an apoptosis-resistant phenotype to myofibroblasts that is associated with the downregulation of pro-apoptotic members of the Bcl-2 family, including Bim and PUMA. Together, these studies indicate a critical role for NNMT in the metabolic reprogramming of fibroblasts to a pro-fibrotic and apoptosis-resistant phenotype and support the concept that targeting this enzyme may promote regenerative responses in chronic fibrotic disorders such as IPF.

Natural plant resource flavonoids as potential therapeutic drugs for pulmonary fibrosis

Pulmonary fibrosis is an enduring and advancing pulmonary interstitial disease caused by multiple factors that ultimately lead to structural changes in normal lung tissue. Currently, pulmonary fibrosis is a global disease with a high degree of heterogeneity and mortality rate. Nitidine and pirfenidone have been approved for treating pulmonary fibrosis, and the quest for effective therapeutic drugs remains unabated. In recent years, the anti-pulmonary fibrosis properties of natural flavonoids have garnered heightened attention, although further research is needed. In this paper, the resources, structural characteristics, anti-pulmonary fibrosis properties and mechanisms of natural flavonoids were reviewed. We hope to provide potential opportunities for the application of flavonoids in the fight against pulmonary fibrosis.

Cellular mechanotransduction in health and diseases: from molecular mechanism to therapeutic targets

Cellular mechanotransduction, a critical regulator of numerous biological processes, is the conversion from mechanical signals to biochemical signals regarding cell activities and metabolism. Typical mechanical cues in organisms include hydrostatic pressure, fluid shear stress, tensile force, extracellular matrix stiffness or tissue elasticity, and extracellular fluid viscosity. Mechanotransduction has been expected to trigger multiple biological processes, such as embryonic development, tissue repair and regeneration. However, prolonged excessive mechanical stimulation can result in pathological processes, such as multi-organ fibrosis, tumorigenesis, and cancer immunotherapy resistance. Although the associations between mechanical cues and normal tissue homeostasis or diseases have been identified, the regulatory mechanisms among different mechanical cues are not yet comprehensively illustrated, and no effective therapies are currently available targeting mechanical cue-related signaling. This review systematically summarizes the characteristics and regulatory mechanisms of typical mechanical cues in normal conditions and diseases with the updated evidence. The key effectors responding to mechanical stimulations are listed, such as Piezo channels, integrins, Yes-associated protein (YAP) /transcriptional coactivator with PDZ-binding motif (TAZ), and transient receptor potential vanilloid 4 (TRPV4). We also reviewed the key signaling pathways, therapeutic targets and cutting-edge clinical applications of diseases related to mechanical cues.