Silicosis is one of the most common occupational pulmonary fibrosis caused by respirable silica-based particle exposure, with no ideal drugs at present. Metformin, a commonly used biguanide antidiabetic agent, could activate AMP-activated protein kinase (AMPK) to exert its pharmacological action. Therefore, we sought to investigate the role of metformin in silica-induced lung fibrosis.

Pulmonary fibrosis is a chronic progressive fibrotic interstitial lung disease characterized by excessive extracellular matrix (ECM) deposition caused by activated fibroblasts. Increasing evidence shows that matrix stiffness is essential in promoting fibroblast activation and profibrotic changes. Here, we investigated the expression and function of matrix stiffness-regulated ZNF416 in pulmonary fibrotic lung fibroblasts.

Expression of β2-microglobulin (β2M) is involved in fibrosis progression in kidney, liver, and heart. In this case-controlled retrospective study, we investigated the role of β2M in the development of pulmonary fibrosis in patients with chronic obstructive pulmonary disease (COPD). Analysis of 450 COPD patients revealed that patients with decreased pulmonary diffusing capacity (DLCO) had increased β2M serum levels. Compared to patients with lower β2M serum levels, patients with increased β2M levels exhibited increased alveolar wall/septal thickening and lung tissue β2M expression. In addition, patients with increased β2M levels had increased lung expression of TGF-β1, Smad4, and a-SMA. Animal experiments showed that increased β2M expression resulted in epithelial-mesenchymal transition (EMT), alveolar wall/septal thickening, and pulmonary fibrosis in a rat COPD model. Together, these results indicate that β2M serum levels may serve as a new indicator for assessment of pulmonary diffusion function and pulmonary fibrosis severity in clinical practice and may provide a potential target for treatment of pulmonary fibrosis in the future.

The transmembrane chemokine (C-X-C motif) ligand 16 (CXCL16) plays a vital role in the pathogenesis of organ fibrosis, including the liver and kidney. However, the detailed biological function of CXCL16 is still not fully understood in the progression of pulmonary fibrosis (PF). The aim of present study is to examine the function of CXCL16 in PF.

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.

Pulmonary fibrosis (PF), as an end-stage clinical phenotype of interstitial lung diseases (ILDs), is frequently initiated after alveolar injury, in which ferroptosis has been identified as a critical event aggravating the pathophysiological progression of this disease. Here in, a comprehensive analysis of two mouse models of pulmonary fibrosis developed in our lab demonstrated that lung damage-induced ferroptosis of alveolar epithelial Type2 cells (AEC2) significantly accumulates during the development of pulmonary fibrosis while ferroptosis suppressor genes GPX4 and FSP1 are dramatically inactivated. Mechanistically, upregulation of de novo methylation regulator Uhrf1 sensitively elevates CpG site methylation levels in promoters of both GPX4 and FSP1 genes and induces the epigenetic repression of both genes, subsequently leading to ferroptosis in chemically interfered AEC2 cells. Meanwhile, specific inhibition of UHRF1 highly arrests the ferroptosis formation and blocks the progression of pulmonary fibrosis in both of our research models. This study first, to our knowledge, identified the involvement of Uhrf1 in mediating the ferroptosis of chemically injured AEC2s via de novo promoter-specific methylation of both GPX4 and FSP1 genes, which consequently accelerates the process of pulmonary fibrosis. The above findings also strongly suggested Uhrf1 as a novel potential target in the treatment of pulmonary fibrosis.

Pulmonary fibrosis develops when myofibroblasts and extracellular matrix excessively accumulate in the injured lung, but what drives fibrosis is not fully understood. Glycolysis has been linked to cell growth and proliferation, and several studies have shown enhanced glycolysis promotes pulmonary fibrosis. However, detailed studies describing this switch remain limited. Here, we identified that TGF-β1 effectively increased the expression of circHIPK3 in lung fibroblasts, and circHIPK3 inhibition attenuated the activation, proliferation, and glycolysis of fibroblasts in vitro. Dual-luciferase reporter gene assays, RNA immunoprecipitation (RIP), and RNA pull-down assays showed that circHIPK3 could function as a sponge of miR-30a-3p and inhibit its expression. Furthermore, FOXK2, a driver transcription factor of glycolysis, was identified to be a direct target of miR-30a-3p. Mechanistically, circHIPK3 could enhance the expression of FOXK2 via sponging miR-30a-3p, thereby facilitating fibroblast glycolysis and activation. Besides, miR-30a-3p overexpression or FOXK2 knockdown blocked fibroblast activation induced by TGF-β1 and abrogated the profibrotic effects of circHIPK3. Moreover, circHIPK3 and miR-30a-3p were also dysregulated in fibrotic murine lung tissues induced by silica. Adeno-associated virus (AAV)-mediated circHIPK3 silence or miR-30a-3p overexpression alleviated silica-induced pulmonary fibrosis in vivo. In conclusion, our results identified circHIPK3/miR-30a-3p/FOXK2 regulatory pathway as an important glycolysis cascade in pulmonary fibrosis.

Silicosis is associated with fibroblast proliferation and extracellular matrix deposition in lung tissues. The dysregulation of miR-1224-5p has been implicated in several human cancers; however, the expression and function of miR-1224-5p in silicosis is unknown. The mitochondrial dysfunctions play critical roles in some diseases, but how these processes are regulated in silicosis remains limited. Here, we explored the role of miR-1224-5p in a mouse model of silicosis. We showed that the expression of miR-1224-5p is increased both in lung tissues of silica-induced pulmonary fibrosis and fibroblasts exposed to TGF-β1. Repression of miR-1224-5p expression attenuated silica-induced fibrotic progression in vivo and TGF-β1-induced myofibroblast differentiation in vitro. Additionally, we demonstrated that miR-1224-5p facilitated silica-induced pulmonary fibrosis primarily by repressing one of target genes, BECN1, thereby blocking PARK2 translocation to mitochondria and inducing the accumulation of damaged mitochondria. Furthermore, the activation of PDGFR signal mediated by mitochondrial damage and insufficient mitophagy resulted in myofibroblast differentiation. Collectively, these data indicated that miR-1224-5p exerts key functions in silica-induced pulmonary fibrosis and may represent a potential therapeutic target for silicosis.

Silicosis is a universal occupational disease, which is caused by long-term crystalline silica exposure. Recent studies have shown that noncoding RNAs participate in diverse pathological cellular pathways. However, the precise regulation mechanism remains limited in silicosis. Here, we established a silica-induced mouse fibrosis model (all mice received a one-time intratracheal instillation with 50 mg/kg of silica in 0.05 mL sterile saline). MiR-490-3p was significantly downregulated in silica-induced fibrotic mouse lung tissues and TGF-β1 treated fibroblasts. Moreover, overexpressed miR-490-3p could relieve silica-induced lung fibrosis in vivo, and prevent the process of fibroblast-to-myofibroblast transition(FMT)in vitro. Mechanistically, TGFBR1 was one of the major target genes of miR-490-3p, and tightly associated with the process of fibroblasts activation. SNHG20, as opposed to miR-490-3p expression, was elevated in TGF-β1-treated fibroblast cell lines and contributed to decreased levels of miR-490-3p. Taken together, these data indicated that miR-490-3p plays a key role in silica-induced pulmonary fibrosis. Our results suggested that SNHG20/miR-490-3p/TGFBR1 axis may provide a new treatment target of pulmonary fibrosis.

Silicosis is a very serious occupational disease and it features pathological manifestations of inflammatory infiltration, excessive proliferation of fibroblasts and massive depositions of the extracellular matrix in the lungs. Recent studies described the roles of a variety of microRNAs (miRNAs) in fibrotic diseases. Here, we aimed to explore the potential mechanism of miR-542-5p in the activation of lung fibroblasts. To induce a pulmonary fibrosis mouse model, silica suspension and the miR-542-5p agomir were administered to mice by intratracheal instillation and tail vein injection. We found that miR-542-5p was significantly decreased in mouse fibrotic lung tissues and up-regulation of miR-542-5p visually attenuated a series of fibrotic lesions, including alveolar structural damage, alveolar interstitial thickening and silica-induced nodule formation. The down-regulation of miR-542-5p was also observed in mouse fibroblast (NIH-3T3) treated with transforming growth factor β1 (TGF-β1). The proliferation and migration ability of NIH-3T3 cells were also inhibited by the transfection of miR-542-5p mimic. Integrin α6 (Itga6), reported as a cell surface protein associated with fibroblast proliferation, was confirmed to be a direct target of miR-542-5p. The knockdown of Itga6 significantly inhibited the phosphorylation of FAK/PI3K/AKT. In conclusion, miR-542-5p has a potential function for reducing the proliferation of fibroblasts and inhibiting silica-induced pulmonary fibrosis, which might be partially realized by directly binding to Itga6. Our data suggested that miR-542-5p might be a new therapeutic target for silicosis or other pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease for which diagnosis and management remain challenging. Defining the circulating proteome in IPF may identify targets for biomarker development. We sought to quantify the circulating proteome in IPF, determine differential protein expression between subjects with IPF and controls, and examine relationships between protein expression and markers of disease severity.

Lung transplantation remains the only curative treatment for end-stage lung disease, conferring a better survival for some IPF patients, but whether they should receive double lung transplantation (DLT) or single lung transplantation (SLT) is still controversial. The aim of this study was to determine which type of lung transplantation was more effective and relatively safe in IPF patients by meta-analysis.

N6-methyladenosine (m6A) is the most common and abundant internal modification of RNA. Its critical functions in multiple physiological and pathological processes have been reported. However, the role of m6A in silica-induced pulmonary fibrosis has not been fully elucidated. AlkB homolog 5 (ALKBH5), a well-known m6A demethylase, is upregulated in the silica-induced mouse pulmonary fibrosis model. Here, we sought to investigate the function of ALKBH5 in pulmonary fibrosis triggered by silica inhalation.

Long non-coding RNAs (lncRNAs) are important signal transduction regulators that act by various patterns. However, little is known about the molecular mechanisms of lncRNA related pathways in occupational lung fibrosis. Our previous study found that epithelial-mesenchymal transition (EMT) was one of the key events in silica-induced pulmonary fibrosis. This study showed that the lncRNA-ATB promoted EMT by acting as a miR-200c sponge. miR-200c was identified by miRNA array as a potential target of lncRNA-ATB and verified by dual luciferase reporter gene together with RNA pull-down assays. Moreover, our findings demonstrated that lncRNA-ATB is abundantly expressed during EMT of lung epithelial cells, which contributes to decreased levels of miR-200c. miR-200c targeted ZEB1 to relief silicosis by blocking EMT in vivo and in vitro. The results also suggested M2 macrophages secreted transforming growth factor-β1 (TGF-β1) to induce EMT process by activating lncRNA-ATB in epithelial cells. Collectively, silica-stimulated macrophages secreted TGF-β1 to induce lncRNA-ATB in epithelia cells, promoting EMT by binding with miR-200c and releasing ZEB1. These observations provide further understanding of the regulatory network of silica-induced pulmonary fibrosis and identify new therapeutic targets hopefully.

Various miRNAs are dysregulated during initiation and progression of pulmonary fibrosis. However, their function remains limited in silicosis. Here, we observed that miR-125a-3p was downregulated in silica-induced fibrotic murine lung tissues. Ectopic miR-125a-3p expression with chemotherapy attenuated silica-induced pulmonary fibrosis. Further in vitro experiments revealed that TGF-β1 effectively decreased miR-125a-3p expression in fibroblast lines (NIH/3T3 and MRC-5). Overexpression of miR-125a-3p blocked fibroblast activation stimulated by TGF-β1. Mechanistically, miR-125a-3p could bind to the 3'-untranslated region of Fyn and inhibit its expression in both mRNA and protein levels, thus causing inactivation of Fyn downstream effector STAT3. Fyn and p-STAT3, as opposed to miR-125a-3p expression, were elevated in silica-induced fibrotic murine lung tissues and TGF-β1-treated fibroblast lines. Furthermore, Fyn knockdown or p-STAT3 suppression effectively attenuated fibroblast activation and ECM production. Taken together, miR-125a-3p is involved in fibrosis pathogenesis by fibroblast activation, suggesting that targeting miR-125a-3p/Fyn/STAT3 signaling pathway could be a potential therapeutic approach for pulmonary fibrosis.

Dysregulation of non-coding RNAs (ncRNAs) has been proved to play pivotal roles in epithelial-mesenchymal transition (EMT) and fibrosis. We have previously demonstrated the crucial function of long non-coding RNA (lncRNA) ATB in silica-induced pulmonary fibrosis-related EMT progression. However, the underlying molecular mechanism has not been fully elucidated. Here, we verified miR-29b-2-5p and miR-34c-3p as two vital downstream targets of lncRNA-ATB. As opposed to lncRNA-ATB, a significant reduction of both miR-29b-2-5p and miR-34c-3p was observed in lung epithelial cells treated with TGF-β1 and a murine silicosis model. Overexpression miR-29b-2-5p or miR-34c-3p inhibited EMT process and abrogated the pro-fibrotic effects of lncRNA-ATB in vitro. Further, the ectopic expression of miR-29b-2-5p and miR-34c-3p with chemotherapy attenuated silica-induced pulmonary fibrosis in vivo. Mechanistically, TGF-β1-induced lncRNA-ATB accelerated EMT as a sponge of miR-29b-2-5p and miR-34c-3p and shared miRNA response elements with MEKK2 and NOTCH2, thus relieving these two molecules from miRNA-mediated translational repression. Interestingly, the co-transfection of miR-29b-2-5p and miR-34c-3p showed a synergistic suppression effect on EMT in vitro. Furthermore, the co-expression of these two miRNAs by using adeno-associated virus (AAV) better alleviated silica-induced fibrogenesis than single miRNA. Approaches aiming at lncRNA-ATB and its downstream effectors may represent new effective therapeutic strategies in pulmonary fibrosis.

Silicosis is a kind of chronic, progressive and incurable lung fibrotic diseases with largely unknown and complex pathogenesis and molecular mechanisms. Mounting evidence suggests that microRNAs (miRNAs, miRs) are involved in the pathogenesis of silicosis. Our previous study based on miRNA microarray had shown that the expression levels of miR-503 were down-regulated in mouse lung tissues of silica-induced pulmonary fibrosis. Here, we validated the decreased expression of miR-503 in the fibrotic mouse lung tissues, human bronchial epithelial cells (HBE) and human lung adenocarcinoma A549 cells which were exposed to silica. In addition, overexpressed miR-503 inhibited silica-induced pulmonary fibrosis by attenuating the severity and the distribution of lesions in vivo and limiting the process of epithelial-mesenchymal transition (EMT) in vitro. Our molecular study further demonstrated that PI3K p85 is one of the target genes of miR-503 and the downstream molecules (Akt, mTOR and Snail) are tightly associated with EMT. Furthermore, the up-regulated lncRNA Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), acted as a competing endogenous RNA (ceRNA), can directly bound to miR-503, which indicated that lncRNA MALAT1 may modulate the expression of miR-503 thus triggering the activation of downstream fibrotic signaling pathways. Taken together, our data suggested that MALAT1-miR-503-PI3K/Akt/mTOR/Snail pathway plays critical roles in silica-induced pulmonary fibrosis.

IntroductionThere is an unmet need for new treatments for idiopathic pulmonary fibrosis (IPF). The oral preferential phosphodiesterase 4B inhibitor, BI 1015550, prevented a decline in forced vital capacity (FVC) in a phase II study in patients with IPF. This study design describes the subsequent pivotal phase III study of BI 1015550 in patients with IPF (FIBRONEER-IPF).

Pulmonary fibrosis is a chronic and progressive interstitial lung disease associated with the decay of pulmonary function, which leads to a fatal outcome. As an essential epigenetic regulator of DNA methylation, the involvement of ubiquitin-like containing PHD and RING finger domains 1 (UHRF1) in fibroblast activation remains largely undefined in pulmonary fibrosis. In the present study, we found that TGF-β1-mediated upregulation of UHRF1 repressed beclin 1 via methylated induction of its promoter, which finally resulted in fibroblast activation and lung fibrosis both in vitro and in vivo. Moreover, knockdown of UHRF1 significantly arrested fibroblast proliferation and reactivated beclin 1 in lung fibroblasts. Thus, intravenous administration of UHRF1 siRNA-loaded liposomes significantly protected mice against experimental pulmonary fibrosis. Accordingly, our data suggest that UHRF1 might be a novel potential therapeutic target in the pathogenesis of pulmonary fibrosis.

Myocardial fibrosis is a major complication of diabetic cardiomyopathy (DCM) that is primarily caused by cardiac fibroblasts that are highly activated by persistent hyperglycemic stimulation, resulting in excessive collagen deposition. Calcium sensing receptor (CaSR) is a member of the G protein‑coupled receptor superfamily and regulates intracellular calcium concentrations, which are associated with numerous diseases, including myocardial infarction, tumors and pulmonary hypertension. However, whether CaSR participates in the pathological process of myocardial fibrosis in DCM remains unknown. The present study aimed to investigate the mechanism via which CaSR regulates high glucose (HG)‑induced cardiac fibrosis in vitro. HG treated‑cardiac fibroblast (CFs) were used and western blotting, immunoprecipitation, Cell Counting Kit‑8 assay, ELISA and transfection technology were performed to examine the role of CaSR. In the HG group, treatment with HG increased CaSR, α‑smooth muscle actin, collagen I/III and matrix metalloproteinase 2/9 expression and enhanced autophagosome generation and CF proliferation. Furthermore, CaSR activation upregulated the expression of Smad ubiquitin regulatory factor 2 (Smurf2), which led to increased intracellular Ca2+ concentrations, increased ubiquitination levels of SKI like proto‑oncogene and Smad7 and autophagy activation. Furthermore, the CaSR agonist (R568) or the CaSR inhibitor (Calhex231) and Smurf2‑small interfering RNA promoted or inhibited HG‑induced alterations, including the enhanced and weakened effects, respectively. Taken together, the results from the present study suggested that increased CaSR expression in CFs activated the Smurf2‑ubiquitin proteasome and autophagy, causing excessive CF proliferation and extensive collagen deposition, which resulted in HG‑induced myocardial fibrosis. These findings indicated a novel pathogenesis of DCM and may provide a novel strategy for the diagnosis and treatment of DCM.