miR-34a-5p Attenuates EMT through targeting SMAD4 in silica-induced pulmonary fibrosis

SMAD4 promotes EMT in COPD airway remodeling induced by cigarette smoke through interaction with O-GlcNAc transferase

Cigarette smoke (CS) is a prevalent chemical indoor air contaminant known to be the primary cause of EMT during airway remodeling in COPD. While some evidence indicates the involvement of SMAD4 in EMT across certain diseases, its specific role in CS-induced EMT in airway remodeling associated with COPD is not established. In our research, we observed a substantial upregulation in SMAD4 expression, O-GlcNAcylation and EMT in patients with COPD, as well as in vitro and in vivo COPD models induced by CS, than those of the controls. Downregulation of SMAD4 resulted in a reduction in CS-induced EMT in vitro and in vivo. As a post-translational modification of proteins, O-GlcNAcylation is dynamically controlled by the duo of enzymes: O-linked N-acetylglucosamine (O-GlcNAc) transferase (OGT) and O-GlcNAcase (OGA). We further discovered the enhancement of O-GlcNAcylation levels induced by CS was due to an elevated OGT expression, as the expression of OGA remained unchanged. Using an OGT inhibitor (OSMI-1) counteracted the effects of SMAD4 on EMT. Whereas, overexpressing OGT increased SMAD4 expression and promoted EMT. OGT-mediated SMAD4 O-GlcNAcylation shielded SMAD4 from proteasomal degradation by reducing its ubiquitination, thereby aiding in SMAD4 stabilization in response to EMT induced by CS. Overall, this research uncovers a fresh pathway for CS-induced EMT in the airway remodeling of COPD and offers valuable insights.

Bicyclol attenuates pulmonary fibrosis with silicosis via both canonical and non-canonical TGF-β1 signaling pathways

BACKGROUND

Silicosis is an irreversible fibrotic disease of the lung caused by chronic exposure to silica dust, which manifests as infiltration of inflammatory cells, excessive secretion of pro-inflammatory cytokines, and pulmonary diffuse fibrosis. As the disease progresses, lung function further deteriorates, leading to poorer quality of life of patients. Currently, few effective drugs are available for the treatment of silicosis. Bicyclol (BIC) is a compound widely employed to treat chronic viral hepatitis and drug-induced liver injury. While recent studies have demonstrated anti-fibrosis effects of BIC on multiple organs, including liver, lung, and kidney, its therapeutic benefit against silicosis remains unclear. In this study, we established a rat model of silicosis, with the aim of evaluating the potential therapeutic effects of BIC.

METHODS

We constructed a silicotic rat model and administered BIC after injury. The FlexiVent instrument with a forced oscillation system was used to detect the pulmonary function of rats. HE and Masson staining were used to assess the effect of BIC on silica-induced rats. Macrophages-inflammatory model of RAW264.7 cells, fibroblast-myofibroblast transition (FMT) model of NIH-3T3 cells, and epithelial-mesenchymal transition (EMT) model of TC-1 cells were established in vitro. And the levels of inflammatory mediators and fibrosis-related proteins were evaluated in vivo and in vitro after BIC treatment by Western Blot analysis, RT-PCR, ELISA, and flow cytometry experiments.

RESULTS

BIC significantly improved static compliance of lung and expiratory and inspiratory capacity of silica-induced rats. Moreover, BIC reduced number of inflammatory cells and cytokines as well as collagen deposition in lungs, leading to delayed fibrosis progression in the silicosis rat model. Further exploration of the underlying molecular mechanisms revealed that BIC suppressed the activation, polarization, and apoptosis of RAW264.7 macrophages induced by SiO2. Additionally, BIC inhibited SiO2-mediated secretion of the inflammatory cytokines IL-1β, IL-6, TNF-α, and TGF-β1 in macrophages. BIC inhibited FMT of NIH-3T3 as well as EMT of TC-1 in the in vitro silicosis model, resulting in reduced proliferation and migration capability of NIH-3T3 cells. Further investigation of the cytokines secreted by macrophages revealed suppression of both FMT and EMT by BIC through targeting of TGF-β1. Notably, BIC blocked the activation of JAK2/STAT3 in NIH-3T3 cells required for FMT while preventing both phosphorylation and nuclear translocation of SMAD2/3 in TC-1 cells necessary for the EMT process.

CONCLUSION

The collective data suggest that BIC prevents both FMT and EMT processes, in turn, reducing aberrant collagen deposition. Our findings demonstrate for the first time that BIC ameliorates inflammatory cytokine secretion, in particular, TGF-β1, and consequently inhibits FMT and EMT via TGF-β1 canonical and non-canonical pathways, ultimately resulting in reduction of aberrant collagen deposition and slower progression of silicosis, supporting its potential as a novel therapeutic agent.

MicroRNA-452-5p regulates fibrogenesis via targeting TGF-β/SMAD4 axis in SCN5A-knockdown human cardiac fibroblasts

The mutated SCN5A gene encoding defective Nav1.5 protein causes arrhythmic ailments and is associated with enhanced cardiac fibrosis. This study investigated whether SCN5A mutation directly affects cardiac fibroblasts and explored how defective SCN5A relates to cardiac fibrosis. SCN5A knockdown (SCN5AKD) human cardiac fibroblasts (HCF) had higher collagen, α-SMA, and fibronectin expressions. Micro-RNA deep sequencing and qPCR analysis revealed the downregulation of miR-452-5p and bioinformatic analysis divulged maladaptive upregulation of transforming growth factor β (TGF-β) signaling in SCN5AKD HCF. Luciferase reporter assays validated miR-452-5p targets SMAD4 in SCN5AKD HCF. Moreover, miR-452-5p mimic transfection in SCN5AKD HCF or AAV9-mediated miR-452-5p delivery in isoproterenol-induced heart failure (HF) rats, resulted in the attenuation of TGF-β signaling and fibrogenesis. The exogenous miR-452-5p significantly improved the poor cardiac function in HF rats. In conclusion, miR-452-5p regulates cardiac fibrosis progression by targeting the TGF-β/SMAD4 axis under the loss of the SCN5A gene.

LncRNA MRAK052509 competitively adsorbs miR-204-3p to regulate silica dust-induced EMT process

Silicosis is a systemic disease caused by long-term inhalation of free SiO2 and retention in the lungs. At present, it is still the most important occupational health hazard disease in the world. Existing studies have shown that non-coding RNA can also participate in complex fibrosis regulatory networks. However, its role in regulating silicotic fibrosis is still unclear. In this study, we constructed a NR8383/RLE-6TN co-culture system to simulate the pathogenesis of silicosis in vitro. Design of miR-204-3p mimics and inhibitors to overexpress or downregulate miR-204-3p in RLE-6TN cells. Design of short hairpin RNA (sh-RNA) to downregulate MRAK052509 in RLE-6TN cells. The regulatory mechanism of miR-204-3p and LncRNA MRAK052509 on EMT process was studied by Quantitative real-time PCR, Western blotting, Immunofluorescence and Cell scratch test. The results revealed that miR-204-3p affects the occurrence of silica dust-induced cellular EMT process mainly through regulating TGF-βRΙ, a key molecule of TGF-β signaling pathway. In contrast, Lnc MRAK052509 promotes the EMT process in epithelial cells by competitively adsorbing miR-204-3p and reducing its inhibitory effect on the target gene TGF-βRΙ, which may influence the development of silicosis fibrosis. This study perfects the targeted regulation relationship between LncRNA MRAK052509, miR-204-3p and TGF-βRΙ, and may provide a new strategy for the study of the pathogenesis and treatment of silicosis.

Advances in the Study of Non-Coding RNA in the Signaling Pathway of Pulmonary Fibrosis

Pulmonary fibrosis is a group of chronic, progressive, and irreversible interstitial lung diseases, which are common to most end-stage lung diseases and are one of the most difficult diseases of the respiratory system. In recent years, due to the frequent occurrence of air pollution and smog, the incidence of pulmonary fibrosis in China has increased year by year, the morbidity and mortality rates of pulmonary fibrosis have gradually increased and the age of the disease tends to be younger. However, the pathogenesis of pulmonary fibrosis is not yet fully understood and is needed to further explore new drug targets. Studies have shown that non-coding RNAs play an important role in regulating the process of pulmonary fibrosis, non-coding RNAs and their specifically expressed can promote or inhibit the process. Here, we review the role of some in the regulation of pulmonary fibrosis signaling pathways and provide new ideas for the clinical diagnosis and treatment of pulmonary fibrosis.

The role of epithelial cells in fibrosis: Mechanisms and treatment

Fibrosis is a pathological process that affects multiple organs and is considered one of the major causes of morbidity and mortality in multiple diseases, resulting in an enormous disease burden. Current studies have focused on fibroblasts and myofibroblasts, which directly lead to imbalance in generation and degradation of extracellular matrix (ECM). In recent years, an increasing number of studies have focused on the role of epithelial cells in fibrosis. In some cases, epithelial cells are first exposed to external physicochemical stimuli that may directly drive collagen accumulation in the mesenchyme. In other cases, the source of stimulation is mainly immune cells and some cytokines, and epithelial cells are similarly altered in the process. In this review, we will focus on the multiple dynamic alterations involved in epithelial cells after injury and during fibrogenesis, discuss the association among them, and summarize some therapies targeting changed epithelial cells. Especially, epithelial mesenchymal transition (EMT) is the key central step, which is closely linked to other biological behaviors. Meanwhile, we think studies on disruption of epithelial barrier, epithelial cell death and altered basal stem cell populations and stemness in fibrosis are not appreciated. We believe that therapies targeted epithelial cells can prevent the progress of fibrosis, but not reverse it. The epithelial cell targeting therapies will provide a wonderful preventive and delaying action.

MiR-26a-5p from HucMSC-derived extracellular vesicles inhibits epithelial mesenchymal transition by targeting Adam17 in silica-induced lung fibrosis

Silicosis is one of several potentially fatal occupational pathologies caused by the prolonged inhalation of respirable crystalline silica. Previous studies have shown that lung epithelial-mesenchymal transition (EMT) plays a significant role in the fibrosis effect of silicosis. Human umbilical cord mesenchymal stem cells-derived Extracellular vesicles (hucMSC-EVs) have attracted great interest as a potential therapy of EMT and fibrosis-related diseases. However, the potential effects of hucMSC-EVs in inhibiting EMT in silica-induced fibrosis, as well as its underlying mechanisms, remain largely unknown. In this study, we used the EMT model in MLE-12 cells and observed the effects and mechanism of hucMSC-EVs inhibition of EMT. The results revealed that hucMSC-EVs can indeed inhibit EMT. MiR-26a-5p was highly enriched in hucMSC-EVs but was down-regulated in silicosis mice. We found that miR-26a-5p in hucMSC-EVs was over-expressed after transfecting miR-26a-5p expressing lentivirus vectors into hucMSCs. Subsequently, we explored if miR-26a-5p, attained from hucMSC-EVs, was involved in inhibiting EMT in silica-induced lung fibrosis. Our findings suggested that hucMSC-EVs could deliver miR-26a-5p into MLE-12 cells and cause the inhibition of the Adam17/Notch signalling pathway to ameliorate EMT in silica-induced pulmonary fibrosis. These findings might represent a novel insight into treating silicosis fibrosis.

Total flavonoid extract from Dracocephalum moldavica L. improves pulmonary fibrosis by reducing inflammation and inhibiting the hedgehog signaling pathway

Dracocephalum Moldavica L. is a traditional herb for improving pharynx and relieving cough. However, the effect on pulmonary fibrosis is not clear. In this study, we explored the impact and molecular mechanism of total flavonoid extract from Dracocephalum moldavica L. (TFDM) on bleomycin-induced pulmonary fibrosis mouse model. Lung function testing, lung inflammation and fibrosis, and the related factors were detected by the lung function analysis system, HE and Masson staining, ELISA, respectively. The expression of proteins was studied through Western Blot, immunohistochemistry, and immunofluorescence while the expression of genes was analyzed by RT-PCR. The results showed that TFDM significantly improved lung function in mice, reduced the content of inflammatory factors, thereby reducing the inflammation. It was found that expression of collagen type I, fibronectin, and α-smooth muscle actin was significantly decreased by TFDM. The results further showed that TFDM interferes with hedgehog signaling pathway by decreasing the expression of Shh, Ptch1, and SMO proteins and thereby inhibiting the generation of downstream target gene Gli1 and thus improving pulmonary fibrosis. Conclusively, these findings suggest that TFDM improve pulmonary fibrosis by reducing inflammation and inhibition of the hedgehog signaling pathway.

MALAT1-miR-30c-5p-CTGF/ATG5 axis regulates silica-induced experimental silicosis by mediating EMT in alveolar epithelial cells

Epithelial-mesenchymal transdifferentiation of alveolar type Ⅱ epithelial cells is a vital source of pulmonary myofibroblasts, and myofibroblasts formation is recognized as an important phase in the pathological process of silicosis. miR-30c-5p has been determined to be relevant in the activation of the epithelial-mesenchymal transition (EMT) in numerous disease processes. However, elucidating the role played by miR-30c-5p in the silicosis-associated EMT process remains a great challenge. In this work, based on the establishment of mouse silicosis and A549 cells EMT models, miR-30c-5p was interfered with in vivo and in vitro models to reveal its effects on EMT and autophagy. Moreover, metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), connective tissue growth factor (CTGF), autophagy-related gene 5 (ATG5), and autophagy were further interfered with in the A549 cells models to uncover the possible molecular mechanism through which miR-30c-5p inhibits silicosis associated EMT. The results demonstrated the targeted binding of miR-30c-5p to CTGF, ATG5, and MALAT1, and showed that miR-30c-5p could prevent EMT in lung epithelial cells by acting on CTGF and ATG5-associated autophagy, thereby inhibiting the silicosis fibrosis process. Furthermore, we also found that lncRNA MALAT1 might competitively absorb miR-30c-5p and affect the EMT of lung epithelial cells. In a word, interfering with miR-30c-5p and its related molecules (MALAT1, CTGF, and ATG5-associated autophagy) may provide a reference point for the application of silicosis intervention-related targets.

NLRP3 Inflammasome Mediates Silica-induced Lung Epithelial Injury and Aberrant Regeneration in Lung Stem/Progenitor Cell-derived Organotypic Models

Silica-induced lung epithelial injury and fibrosis are vital pathogeneses of silicosis. Although the NOD-like receptor protein 3 (NLRP3) inflammasome contributes to silica-induced chronic lung inflammation, its role in epithelial injury and regeneration remains unclear. Here, using mouse lung stem/progenitor cell-derived organotypic systems, including 2D air-liquid interface and 3D organoid cultures, we investigated the effects of the NLRP3 inflammasome on airway epithelial phenotype and function, cellular injury and regeneration, and the potential mechanisms. Our data showed that silica-induced NLRP3 inflammasome activation disrupted the epithelial architecture, impaired mucociliary clearance, induced cellular hyperplasia and the epithelial-mesenchymal transition in 2D culture, and inhibited organoid development in 3D system. Moreover, abnormal expression of the stem/progenitor cell markers SOX2 and SOX9 was observed in the 2D and 3D organotypic models after sustained silica stimulation. Notably, these silica-induced structural and functional abnormalities were ameliorated by MCC950, a selective NLRP3 inflammasome inhibitor. Further studies indicated that the NF-κB, Shh-Gli and Wnt/β-catenin pathways were involved in NLRP3 inflammasome-mediated abnormal differentiation and dysfunction of the airway epithelium. Thus, prolonged NLRP3 inflammasome activation caused injury and aberrant lung epithelial regeneration, suggesting that the NLRP3 inflammasome is a pivotal target for regulating tissue repair in chronic inflammatory lung diseases.

A2aR inhibits fibrosis and the EMT process in silicosis by regulating Wnt/β-catenin pathway

Silicosis, a disease characterized by diffuse fibrosis of the lung tissue, is caused by long-term inhalation of free silica (SiO2) dust in the occupational environment and is currently the most serious occupational diseases of pneumoconiosis. Several studies have suggested that alveolar type Ⅱ epithelial cells (AEC Ⅱ) undergo epithelial-mesenchymal transition (EMT) as one of the crucial components of silicosis in lung fibroblasts. A2aR can play a critical regulatory role in fibrosis-related diseases by modulating the Wnt/β-catenin pathway, but its function in the EMT process of silicosis has not been explained. In this study, an EMT model of A549 cells was established. The results revealed that A2aR expression is reduced in the EMT model. Furthermore, activation of A2aR or suppression of the Wnt/β-catenin pathway reversed the EMT process, while the opposite result was obtained by inhibiting A2aR. In addition, activation of A2aR in a mouse silicosis model inhibited the Wnt/β-catenin pathway and ameliorated the extent of silica-induced lung fibrosis in mice. To sum up, we uncovered that A2aR inhibits fibrosis and the EMT process in silicosis by regulating the Wnt/β-catenin pathway. Our study can provide an experimental basis for elucidating the role of A2aR in the development of silicosis and offer new ideas for further exploration of interventions for silicosis.

Inhibition of Oncogenic Src Ameliorates Silica-Induced Pulmonary Fibrosis via PI3K/AKT Pathway

Silicosis is a refractory disease. Previous studies indicate that damaged alveolar epithelial cells act as a driver in pulmonary fibrosis. Our results show that epithelial cells that acquire the mesenchymal phenotype are associated with the pathogenesis of silicosis. c-Src kinase, a non-receptor tyrosine kinase, has been shown to be a positive regulator of organ fibrosis, but specific mechanisms remain unclear and rarely researched in silicosis. The activated Phosphatidylinositol-3 kinases/AKT(PI3K/AKT) pathway promotes fibrosis. We aimed to determine whether c-Src regulates fibrosis via the PI3K/AKT signaling pathway in the development of silicosis. C57/BL mice were intratracheally perfused with 10 mg silica suspension to establish a model of silicosis. In vivo, silica particles induced lung fibrosis. The profibrotic cytokine transforming growth factor-β1 (TGF-β1) exhibited a high expression in pulmonary fibrosis. The phosphorylated c-Src protein was increased and the PI3K/AKT pathway was activated in model lung tissue. In vitro, silica increased the expression of TGF-β1- and TGF-β1-induced mesenchymal phenotype and fibrosis in a mouse epithelial cells line. siRNA-Src inhibited the c-Src, the phosphorylation of the PI3K/AKT pathway, and the mesenchymal phenotype induced by TGF-β1. LY294002, a specific inhibitor of PI3K, suppressed the phosphorylation of PI3K/AKT but did not affect Src activation. SU6656, a selective Src inhibitor, attenuated fibrosis in silicosis model. In summary, c-Src promotes fibrosis via the PI3K/AKT pathway in silica-induced lung fibrosis, and Src kinase inhibitors are potentially effective for silicosis treatment.

The emerging role of epigenetic regulation in the progression of silicosis

Silicosis is one of the most severe occupational diseases worldwide and is characterized by silicon nodules and diffuse pulmonary fibrosis. However, specific treatments for silicosis are still lacking at present. Therefore, elucidating the pathogenesis of silicosis plays a significant guiding role for its treatment and prevention. The occurrence and development of silicosis are accompanied by many regulatory mechanisms, including epigenetic regulation. The main epigenetic regulatory mechanisms of silicosis include DNA methylation, non-coding RNA (ncRNA), and histone modifications. In recent years, the expression and regulation of genes related to silicosis have been explored at epigenetic level to reveal its pathogenesis further, and the identification of aberrant epigenetic markers provides new biomarkers for prediction and diagnosis of silicosis. Here, we summarize the studies on the role of epigenetic changes in the pathogenesis of silicosis to give some clues for finding specific therapeutic targets for silicosis.

MicroRNA-34a: A Novel Therapeutic Target in Fibrosis

Fibrosis can occur in many organs, and severe cases leading to organ failure and death. No specific treatment for fibrosis so far. In recent years, microRNA-34a (miR-34a) has been found to play a role in fibrotic diseases. MiR-34a is involved in the apoptosis, autophagy and cellular senescence, also regulates TGF-β1/Smad signal pathway, and negatively regulates the expression of multiple target genes to affect the deposition of extracellular matrix and regulate the process of fibrosis. Some studies have explored the efficacy of miR-34a-targeted therapies for fibrotic diseases. Therefore, miR-34a has specific potential for the treatment of fibrosis. This article reviews the important roles of miR-34a in fibrosis and provides the possibility for miR-34a as a novel therapeutic target in fibrosis.

Current and prospective applications of exosomal microRNAs in pulmonary fibrosis (Review)

Pulmonary fibrosis (PF) is a chronic, progressive, irreversible and life‑threatening lung disease. However, the pathogenesis and molecular mechanisms of this condition remain unclear. Extracellular vesicles (EVs) are structures derived from the plasma membrane, with a diameter ranging from 30 nm to 5 µm, that play an important role in cell‑to‑cell communications in lung disease, particularly between epithelial cells and the pulmonary microenvironment. In particular, exosomes are a type of EV that can deliver cargo molecules, including endogenous proteins, lipids and nucleic acids, such as microRNAs (miRNAs/miRs). These cargo molecules are encapsulated in lipid bilayers through target cell internalization, receptor‑ligand interactions or lipid membrane fusion. miRNAs are single‑stranded RNA molecules that regulate cell differentiation, proliferation and apoptosis by degrading target mRNAs or inhibiting translation to modulate gene expression. The aim of the present review was to discuss the current knowledge available on exosome biogenesis, composition and isolation methods. The role of miRNAs in the pathogenesis of PF was also reviewed. In addition, emerging diagnostic and therapeutic properties of exosomes and exosomal miRNAs in PF were described, in order to highlight the potential applications of exosomal miRNAs in PF.

Multiple roles of mothers against decapentaplegic homolog 4 in tumorigenesis, stem cells, drug resistance, and cancer therapy

The transforming growth factor (TGF)-β signaling pathway controls many cellular processes, including proliferation, differentiation, and apoptosis. Abnormalities in the TGF-β signaling pathway and its components are closely related to the occurrence of many human diseases, including cancer. Mothers against decapentaplegic homolog 4 (Smad4), also known as deleted in pancreatic cancer locus 4, is a typical tumor suppressor candidate gene locating at q21.1 of human chromosome 18 and the common mediator of the TGF-β/Smad and bone morphogenetic protein/Smad signaling pathways. It is believed that Smad4 inactivation correlates with the development of tumors and stem cell fate decisions. Smad4 also interacts with cytokines, miRNAs, and other signaling pathways, jointly regulating cell behavior. However, the regulatory function of Smad4 in tumorigenesis, stem cells, and drug resistance is currently controversial. In addition, Smad4 represents an attractive therapeutic target for cancer. Elucidating the specific role of Smad4 is important for understanding the mechanism of tumorigenesis and cancer treatment. Here, we review the identification and characterization of Smad4, the canonical TGF-β/Smad pathway, as well as the multiple roles of Smad4 in tumorigenesis, stem cells, and drug resistance. Furthermore, we provide novel insights into the prospects of Smad4-targeted cancer therapy and the challenges that it will face in the future.

Epigenetic Changes and Functions in Pneumoconiosis

Pneumoconiosis is one of the most common occupational diseases in the world, and specific treatment methods of pneumoconiosis are lacking at present, so it carries great social and economic burdens. Pneumoconiosis, coronavirus disease 2019, and idiopathic pulmonary fibrosis all have similar typical pathological changes-pulmonary fibrosis. Pulmonary fibrosis is a chronic lung disease characterized by excessive deposition of the extracellular matrix and remodeling of the lung tissue structure. Clarifying the pathogenesis of pneumoconiosis plays an important guiding role in its treatment. The occurrence and development of pneumoconiosis are accompanied by epigenetic factors (e.g., DNA methylation and noncoding RNA) changes, which in turn can promote or inhibit the process of pneumoconiosis. Here, we summarize epigenetic changes and functions in the several kinds of evidence classification (epidemiological investigation, in vivo, and in vitro experiments) and main types of cells (macrophages, fibroblasts, and alveolar epithelial cells) to provide some clues for finding specific therapeutic targets for pneumoconiosis and even for pulmonary fibrosis.

Herbal compounds in the treatment of pulmonary silicosis

Herbal compounds including those already well-established in traditional Chinese medicine have been increasingly tested in the treatment of various diseases. Recent studies have shown that herbal compounds can be of benefit also for pulmonary silicosis as they can diminish changes associated with silica-induced inflammation, fibrosis, and oxidative stress. Due to a lack of effective therapeutic strategies, development of novel approaches which may be introduced particularly in the early stage of the disease, is urgently needed. This review summarizes positive effects of several alternative plant-based drugs in the models of experimental silicosis with a potential for subsequent clinical investigation and use in future.

Herbal Compounds in the Treatment of Pulmonary Silicosis

Herbal compounds including those already well-established in traditional Chinese medicine have been increasingly tested in the treatment of various diseases. Recent studies have shown that herbal compounds can be of benefit also for pulmonary silicosis as they can diminish changes associated with silica-induced inflammation, fibrosis, and oxidative stress. Due to a lack of effective therapeutic strategies, development of novel approaches which may be introduced particularly in the early stage of the disease, is urgently needed. This review summarizes positive effects of several alternative plant-based drugs in the models of experimental silicosis with a potential for subsequent clinical investigation and use in future.

Effect and Mechanism of Qingfei Paidu Decoction in the Management of Pulmonary Fibrosis and COVID-19

Qingfei Paidu decoction (QFPD) has been repeatedly recommended for the clinical treatment of novel coronavirus disease 2019 (COVID-19) in multiple provinces throughout China. A possible complication of COVID-19 lung involvement is pulmonary fibrosis, which causes chronic breathing difficulties and affects the patient's quality of life. Therefore, there is an important question regarding whether QFPD can alleviate the process of pulmonary fibrosis and its potential mechanisms. To explore this issue, this study demonstrated the anti-pulmonary fibrosis activity and mode of action of QFPD in vivo and in vitro pulmonary fibrosis models and network pharmacology. The results showed that QFPD effectively ameliorated the bleomycin-induced inflammation and collagen deposition in mice and significantly improved the epithelial-mesenchymal transition in pulmonary fibrosis in mice. In addition, QFPD inhibited bleomycin-induced M2 polarization of macrophages in pulmonary tissues. An in-depth study of the mechanism of QFPD in the treatment of pulmonary fibrosis based on network pharmacology and molecular simulation revealed that SRC was the main target of QFPD and sitosterol (a key compound in QFPD). QFPD and sitosterol regulate the EMT process and M2 polarization of macrophages by inhibiting the activation of SRC, thereby alleviating pulmonary fibrosis in mice. COVID-19 infection might produce severe fibrosis, and antifibrotic therapy with QFPD may be valuable in preventing severe neocoronavirus disease in patients with IPF, which could be a key factor explaining the role of QFPD in the treatment of COVID-19.

Pulmonary fibrosis from molecular mechanisms to therapeutic interventions: lessons from post-COVID-19 patients

Pulmonary fibrosis (PF) is characterised by several grades of chronic inflammation and collagen deposition in the interalveolar space and is a hallmark of interstitial lung diseases (ILDs). Recently, infectious agents have emerged as driving causes for PF development; however, the role of viral/bacterial infections in the initiation and propagation of PF is still debated. In this context, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for the current coronavirus disease 2019 (COVID-19) pandemic, has been associated with acute respiratory distress syndrome (ARDS) and PF development. Although the infection by SARS-CoV-2 can be eradicated in most cases, the development of fibrotic lesions cannot be precluded; furthermore, whether these lesions are stable or progressive fibrotic events is still unknown. Herein, an overview of the main molecular mechanisms driving the fibrotic process together with the currently approved and newly proposed therapeutic solutions was given. Then, the most recent data that emerged from post-COVID-19 patients was discussed, in order to compare PF and COVID-19-dependent PF, highlighting shared and specific mechanisms. A better understanding of PF aetiology is certainly needed, also to develop effective therapeutic strategies and COVID-19 pathology is offering one more chance to do it. Overall, the work reported here could help to define new approaches for therapeutic intervention in the diversity of the ILD spectrum.

Evaluation on epithelial-mesenchymal state and microRNAs focusing on isolated alveolar epithelial cells from bleomycin injured rat lung

Several studies using bleomycin (BLM)-induced lung injury rat model revealed that epithelial-mesenchymal transition (EMT) contributes to pulmonary fibrosis. Conversely, microRNAs (miRNAs) are considered as useful markers of various diseases. In the present study, we aimed to characterize the EMT state through focusing on alveolar epithelial cells and identify the miRNAs that can be used as markers to predict pulmonary fibrosis using a BLM-induced lung injury rat model. Intratracheal administration of BLM increased hydroxyproline, a component of collagen, in lung tissues at day 14, but not at day 7. However, BLM induced EMT at day 7, which was accompanied with increased mRNA expression of α-smooth muscle actin, a representative EMT marker, in alveolar epithelium, thereby suggesting that EMT occurs prior to pulmonary fibrosis in alveolar epithelial cells. Using this rat model, the expression levels of several EMT-associated miRNAs were examined, and miR-222 was found to be upregulated in alveolar epithelial cells as well as bronchoalveolar lavage fluid from day 3. Our findings indicate that EMT in alveolar epithelial cells may occur before pulmonary fibrosis, and miR-222 may be used as a potential marker for early prediction of pulmonary fibrosis.

Mesenchymal stem cells ameliorate silica-induced pulmonary fibrosis by inhibition of inflammation and epithelial-mesenchymal transition

Silicosis is a devastating occupational disease caused by long-term inhalation of silica particles, inducing irreversible lung damage and affecting lung function, without effective treatment. Mesenchymal stem cells (MSCs) are a heterogeneous subset of adult stem cells that exhibit excellent self-renewal capacity, multi-lineage differentiation potential and immunomodulatory properties. The aim of this study was to explore the effect of bone marrow-derived mesenchymal stem cells (BMSCs) in a silica-induced rat model of pulmonary fibrosis. The rats were treated with BMSCs on days 14, 28 and 42 after perfusion with silica. Histological examination and hydroxyproline assays showed that BMSCs alleviated silica-induced pulmonary fibrosis in rats. Results from ELISA and qRT-PCR indicated that BMSCs inhibited the expression of inflammatory cytokines TNF-α, IL-1β and IL-6 in lung tissues and bronchoalveolar lavage fluid of rats exposed to silica particles. We also performed qRT-PCR, Western blot and immunohistochemistry to examine epithelial-mesenchymal transition (EMT)-related indicators and demonstrated that BMSCs up-regulate E-cadherin and down-regulate vimentin and extracellular matrix (ECM) components such as fibronectin and collagen Ⅰ. Additionally, BMSCs inhibited the silica-induced increase in TGF-β1, p-Smad2 and p-Smad3 and decrease in Smad7. These results suggested that BMSCs can inhibit inflammation and reverse EMT through the inhibition of the TGF-β/Smad signalling pathway to exhibit an anti-fibrotic effect in the rat silicosis model. Our study provides a new and meaningful perspective for silicosis treatment strategies.

New Insights into Pathomechanisms and Treatment Possibilities for Lung Silicosis

Inhalation of silica particles is an environmental and occupational cause of silicosis, a type of pneumoconiosis. Development of the lung silicosis is a unique process in which the vicious cycle of ingestion of inhaled silica particles by alveolar macrophages and their release triggers inflammation, generation of nodular lesions, and irreversible fibrosis. The pathophysiology of silicosis is complex, and interactions between the pathomechanisms have not been completely understood. However, elucidation of silica-induced inflammation cascades and inflammation-fibrosis relations has uncovered several novel possibilities of therapeutic targeting. This article reviews new information on the pathophysiology of silicosis and points out several promising treatment approaches targeting silicosis-related pathways.

miR34a: a novel small molecule regulator with a big role in bronchopulmonary dysplasia

Preterm infants with bronchopulmonary dysplasia (BPD), characterized by pulmonary inflammation leading to impaired alveolarization and vascular dysregulation, have an increased risk of abnormal lung function in infancy, childhood, and adulthood. These include a heightened risk of pulmonary hypertension, and respiratory illnesses. MicroRNAs (miRNAs) are known to disrupt normal lung development and function by interrupting alveolarization and vascularization resulting in the development of BPD. Among the various miRs involved in BPD, miR34a has been shown to have a significant role in BPD pathogenesis. Targeting miR34a or its downstream targets may be a promising therapeutic intervention for BPD. In this review, we summarize the data on cellular arrest, proliferation, differentiation, epithelial-mesenchymal transition, mitochondrial dysfunction, and apoptosis impacted by miR34a in the development of BPD pulmonary phenotypes while predicting the future perspective of miR34a in BPD.

miR-34a-5p Attenuates EMT through targeting SMAD4 in silica-induced pulmonary fibrosis

Silicosis is an incurable occupational disease, and its pathological feature is diffuse pulmonary fibrosis. Pulmonary epithelial-mesenchymal transition (EMT) is one of the important events in the pathogenesis of silicosis. Previous studies found that abnormal expression of various microRNAs (miRNAs) involved in the development of lung fibrosis. However, their roles in silicosis have not been elucidated. To research the biological effects of miR-34a in EMT process in silica-induced lung fibrosis, we established the silicosis model in mouse and miR-34a intervention in a cell model of TGF-β1 stimulated lung epithelial cells (A549). The results showed that miR-34a expression was down-regulated in the fibrotic lung tissue after silica treatment, and it was similarly expressed in A549 cells stimulated by TGF-β1. Meanwhile, silica-induced EMT process can increase expression of two mesenchymal markers, α-SMA and vimentin. Furthermore, overexpression miR-34a markedly inhibited EMT stimulated by TGF-β1. Mechanistically, SMAD4 was identified as the target of miR-34a. SMAD4 levels decreased in mRNA and protein levels in A549 cells upon miR-34a overexpression. In addition, the knockdown of SMAD4 blocked the EMT process. Taken together, miR-34a regulated EMT, which might be partially realized by targeting SMAD4. Our data might provide new insight into treatment targets for silica-induced pulmonary fibrosis.