TGF-β1 induces Fstl1 via the Smad3-c-Jun pathway in lung fibroblasts

FSTL1: A double-edged sword in cancer development

Flolistatin-related protein 1 (FSTL1), a secreted glycoprotein that is involved in many physiological functions, has attracted much interest and has been implicated in a wide range of diseases, including heart diseases and inflammatory diseases. In recent years, the involvement of FSTL1 in cancer progression has been implicated and researched. FSTL1 plays a contradictory role in cancer, depending on the cancer type as well as the contents of the tumor microenvironment. As reviewed here, the structure and distribution of FSTL1 are first introduced. Subsequently, the expression and clinical significance of FSTL1 in various types of cancer as a tumor enhancer or inhibitor are addressed. Furthermore, we discuss the functional role of FSTL1 in various processes that involve tumor cell proliferation, metastasis, immune responses, stemness, cell apoptosis, and resistance to chemotherapy. FSTL1 expression is tightly controlled in cancer, and a multitude of cancer-related signaling cascades like TGF-β/BMP/Smad signaling, AKT, NF-κB, and Wnt-β-catenin signaling pathways are modulated by FSTL1. Finally, FSTL1 as a therapeutic target using monoclonal antibodies is stated. Herein, we review recent findings showing the double-edged characteristics and mechanisms of FSTL1 in cancer and elaborate on the current understanding of therapeutic approaches targeting FSTL1.

A genomic perspective of the aging human and mouse lung with a focus on immune response and cellular senescence

BACKGROUND

The aging lung is a complex process and influenced by various stressors, especially airborne pathogens and xenobiotics. Additionally, a lifetime exposure to antigens results in structural and functional changes of the lung; yet an understanding of the cell type specific responses remains elusive. To gain insight into age-related changes in lung function and inflammaging, we evaluated 89 mouse and 414 individual human lung genomic data sets with a focus on genes mechanistically linked to extracellular matrix (ECM), cellular senescence, immune response and pulmonary surfactant, and we interrogated single cell RNAseq data to fingerprint cell type specific changes.

RESULTS

We identified 117 and 68 mouse and human genes linked to ECM remodeling which accounted for 46% and 27%, respectively of all ECM coding genes. Furthermore, we identified 73 and 31 mouse and human genes linked to cellular senescence, and the majority code for the senescence associated secretory phenotype. These cytokines, chemokines and growth factors are primarily secreted by macrophages and fibroblasts. Single-cell RNAseq data confirmed age-related induced expression of marker genes of macrophages, neutrophil, eosinophil, dendritic, NK-, CD4+, CD8+-T and B cells in the lung of aged mice. This included the highly significant regulation of 20 genes coding for the CD3-T-cell receptor complex. Conversely, for the human lung we primarily observed macrophage and CD4+ and CD8+ marker genes as changed with age. Additionally, we noted an age-related induced expression of marker genes for mouse basal, ciliated, club and goblet cells, while for the human lung, fibroblasts and myofibroblasts marker genes increased with age. Therefore, we infer a change in cellular activity of these cell types with age. Furthermore, we identified predominantly repressed expression of surfactant coding genes, especially the surfactant transporter Abca3, thus highlighting remodeling of surfactant lipids with implications for the production of inflammatory lipids and immune response.

CONCLUSION

We report the genomic landscape of the aging lung and provide a rationale for its growing stiffness and age-related inflammation. By comparing the mouse and human pulmonary genome, we identified important differences between the two species and highlight the complex interplay of inflammaging, senescence and the link to ECM remodeling in healthy but aged individuals.

FSTL1 promotes alveolar epithelial cell aging and worsens pulmonary fibrosis by affecting SENP1-mediated DeSUMOylation

Alveolar epithelial cell (AEC) senescence-induced changes of lung mesenchymal cells are key to starting the progress of pulmonary fibrosis. Follistatin-like 1 (FSTL1) plays a central regulatory role in the complex process of senescence and pulmonary fibrosis by enhancing transforming growth factor-β1 (TGF-β1) signal pathway activity. Activation of Smad4 and Ras relies on SUMO-specific peptidase 1 (SENP1)-mediated deSUMOylation during TGF-β signaling pathway activation. We hypothesized that SENP1-mediated deSUMOylation may be a potential therapeutic target by modulating FSTL1-regulated cellular senescence in pulmonary fibrosis. In verifying this hypothesis, we found that FSTL1 expression was upregulated in the lung tissues of patients with idiopathic pulmonary fibrosis and that SENP1 was overexpressed in senescent AECs. TGF-β1-induced FSTL1 not only promoted AEC senescence but also upregulated SENP1 expression. Interfering with SENP1 expression inhibited FSTL1-dependent promotion of AEC senescence and improved pulmonary fibrosis in mouse lungs. FSTL1 enhancement of TGF-β1 signaling pathway activation was dependent on SENP1 in senescent AEC. Our work identifies a novel mechanism by which FSTL1 is involved in AEC senescence. Inhibition of SENP1 in epithelial cells alleviated pulmonary fibrosis by blocking FSTL1-enhanced TGF signaling.

A key driver to promote HCC: Cellular crosstalk in tumor microenvironment

Liver cancer is the third greatest cause of cancer-related mortality, which of the major pathological type is hepatocellular carcinoma (HCC) accounting for more than 90%. HCC is characterized by high mortality and is predisposed to metastasis and relapse, leading to a low five-year survival rate and poor clinical prognosis. Numerous crosstalk among tumor parenchymal cells, anti-tumor cells, stroma cells, and immunosuppressive cells contributes to the immunosuppressive tumor microenvironment (TME), in which the function and frequency of anti-tumor cells are reduced with that of associated pro-tumor cells increasing, accordingly resulting in tumor malignant progression. Indeed, sorting out and understanding the signaling pathways and molecular mechanisms of cellular crosstalk in TME is crucial to discover more key targets and specific biomarkers, so that develop more efficient methods for early diagnosis and individualized treatment of liver cancer. This piece of writing offers insight into the recent advances in HCC-TME and reviews various mechanisms that promote HCC malignant progression from the perspective of mutual crosstalk among different types of cells in TME, aiming to assist in identifying the possible research directions and methods in the future for discovering new targets that could prevent HCC malignant progression.

FSTL1 promotes liver fibrosis by reprogramming macrophage function through modulating the intracellular function of PKM2

OBJECTIVE

Follistatin-like protein 1 (FSTL1) is widely recognised as a secreted glycoprotein, but its role in modulating macrophage-related inflammation during liver fibrosis has not been documented. Herein, we aimed to characterise the roles of macrophage FSTL1 in the development of liver fibrosis.

DESIGN

Expression analysis was conducted with human liver samples obtained from 33 patients with liver fibrosis and 18 individuals without fibrosis serving as controls. Myeloid-specific FSTL1-knockout (FSTL1^M-KO) mice were constructed to explore the function and mechanism of macrophage FSTL1 in 3 murine models of liver fibrosis induced by carbon tetrachloride injection, bile duct ligation or a methionine-deficient and choline-deficient diet.

RESULTS

FSTL1 expression was significantly elevated in macrophages from fibrotic livers of both humans and mice. Myeloid-specific FSTL1 deficiency effectively attenuated the progression of liver fibrosis. In FSTL1^M-KO mice, the microenvironment that developed during liver fibrosis showed relatively less inflammation, as demonstrated by attenuated infiltration of monocytes/macrophages and neutrophils and decreased expression of proinflammatory factors. FSTL1^M-KO macrophages exhibited suppressed proinflammatory M1 polarisation and nuclear factor kappa B pathway activation in vivo and in vitro. Furthermore, this study showed that, through its FK domain, FSTL1 bound directly to the pyruvate kinase M2 (PKM2). Interestingly, FSTL1 promoted PKM2 phosphorylation and nuclear translocation, reduced PKM2 ubiquitination to enhance PKM2-dependent glycolysis and increased M1 polarisation. Pharmacological activation of PKM2 (DASA-58) partially countered FSTL1-mediated glycolysis and inflammation.

CONCLUSION

Macrophage FSTL1 promotes the progression of liver fibrosis by inducing M1 polarisation and inflammation based on the intracellular PKM2 reprogramming function of macrophages.

Molecular Mechanisms Linking Inflammation to Autoimmunity in Sjögren's Syndrome: Identification of New Targets

Sjögren's syndrome (SS) is a systemic autoimmune rheumatic disorder characterized by the lymphocytic infiltration of exocrine glands and the production of autoantibodies to self-antigens. The involvement of the exocrine glands drives the pathognomonic manifestations of dry eyes (keratoconjunctivitis sicca) and dry mouth (xerostomia) that define sicca syndrome. To date, the molecular mechanisms mediating pathological salivary gland dysfunction in SS remain to be elucidated, despite extensive studies investigating the underlying cause of this disease, hampering the development of novel therapeutic strategies. Many researchers have identified a multifactorial pathogenesis of SS, including environmental, genetic, neuroendocrine, and immune factors. In this review, we explore the latest developments in understanding the molecular mechanisms involved in the pathogenesis of SS, which have attracted increasing interest in recent years.

The Expression of Follistatin-like 1 Protein Is Associated with the Activation of the EMT Program in Sjögren’s Syndrome

Background: The activation of the epithelial to mesenchymal transition (EMT) program is a pathological response of the Sjögren’s syndrome (SS) salivary glands epithelial cells (SGEC) to chronic inflammation. Follistatin-like 1 protein (FSTL1) is a secreted glycoprotein induced by transforming growth factor-β1 (TGF-β1), actively involved in the modulation of EMT. However, the role of FSTL1 in the EMT program activation in SS has not yet been investigated. Methods: TGF-β1-stimulated healthy human SGEC, SS SGEC, and SS salivary glands (SGs) biopsies were used to assess the effect of FSTL1 on the activation of the EMT program. FSTL1 gene activity was inhibited by the siRNA gene knockdown technique. Results: Here we reported that FSTL1 is up-regulated in SS SGs tissue in a correlated manner with the inflammatory grade. Blockage of FSTL1 gene expression by siRNA negatively modulates the TGF-β1-induced EMT program in vitro. We discovered that these actions were mediated through the modulation of the SMAD2/3-dependent EMT signaling pathway. Conclusions: Our data suggest that the TGF-β1-FSTL1-SMAD2/3 regulatory circuit plays a key role in the regulation of EMT in SS and targeting FSTL1 may be a strategy for the treatment of SGs EMT-dependent fibrosis.

Endogenous Follistatin-like 1 guarantees the immunomodulatory properties of mesenchymal stem cells during liver fibrotic therapy

Background

Mesenchymal stem cell (MSC) therapy has been shown to be a promising option for liver fibrosis treatment. However, critical factors affecting the efficacy of MSC therapy for liver fibrosis remain unknown. Follistatin-like 1 (FSTL1), a TGF-β-induced matricellular protein, is documented as an intrinsic regulator of proliferation and differentiation in MSCs. In the present study, we characterized the potential role of FSTL1 in MSC-based anti-fibrotic therapy and further elucidated the mechanisms underlying its action.

Methods

Human umbilical cord-derived MSCs were characterized by flow cytometry. FSTL1^low MSCs were achieved by FSTL1 siRNA. Migration capacity was evaluated by wound-healing and transwell assay. A murine liver fibrotic model was created by carbon tetrachloride (CCl₄) injection, while control MSCs or FSTL1^low MSC were transplanted via intravenous injection 12 weeks post CCl₄ injection. Histopathology, liver function, fibrosis degree, and inflammation were analysed thereafter. Inflammatory cell infiltration was evaluated by flow cytometry after hepatic nonparenchymal cell isolation. An MSC-macrophage co-culture system was constructed to further confirm the role of FSTL1 in the immunosuppressive capacity of MSCs. RNA sequencing was used to screen target genes of FSTL1.

Results

FSTL1^low MSCs had comparable gene expression for surface markers to wildtype but limited differentiation and migration capacity. FSTL1^low MSCs failed to alleviate CCl₄-induced hepatic fibrosis in a mouse model. Our data indicated that FSTL1 is essential for the immunosuppressive action of MSCs on inflammatory macrophages during liver fibrotic therapy. FSTL1 silencing attenuated this capacity by inhibiting the downstream JAK/STAT1/IDO pathway.

Conclusions

Our data suggest that FSTL1 facilitates the immunosuppression of MSCs on macrophages and that guarantee the anti-fibrotic effect of MSCs in liver fibrosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03042-4.

Aerobic exercise training-induced follistatin-like 1 secretion in the skeletal muscle is related to arterial stiffness via arterial NO production in obese rats

Follistatin‐like 1 (FSTL1), which is mainly secreted from skeletal muscle and myocardium, upregulates protein kinase B (Akt) and endothelial nitric oxide synthase (eNOS) phosphorylation in vascular endothelial cells. It is unclear whether skeletal muscle‐ and myocardium‐derived FSTL1 secretion induced by aerobic exercise training is involved in the reduction of arterial stiffness via arterial NO production in obese rats. This study aimed to clarify whether aerobic exercise training‐induced FSTL1 secretion in myocardium and skeletal muscle is associated with a reduction in arterial stiffness via arterial Akt‐eNOS signaling pathway in obese rats. Sixteen Otsuka Long‐Evans Tokushima Fatty (OLETF) obese rats were randomly divided into two groups: sedentary control (OLETF‐CON) and eight‐week aerobic exercise training (treadmill for 60min at 25m/min, 5days/week, OLETF‐AT). Eight Long‐Evans Tokushima Otsuka (LETO) rats were used as a healthy sedentary control group. In OLETF‐CON, serum FSTL1, arterial Akt and eNOS phosphorylation, and arterial nitrite/nitrate (NOx) levels were significantly lower, and carotid‐femoral pulse wave velocity (cfPWV) was significantly greater than those in LETO. These parameters were improved in the OLETF‐AT compared to the OLETF‐CON. In the OLETF‐AT, FSTL1 levels in slow‐twitch fiber‐rich soleus muscle were significantly greater than those in the OLETF‐CON, but not in myocardium, fast‐twitch fiber‐rich tibialis anterior muscle, and adipose tissue. Serum FSTL1 levels were positively correlated with soleus FSTL1, arterial eNOS phosphorylation, and NOx levels and negatively correlated with cfPWV. Thus, aerobic exercise training‐induced FSTL1 secretion in slow‐twitch fiber‐rich muscles may be associated with a reduction in arterial stiffness via arterial NO production in obese rats.

Molecular Mechanisms of Alveolar Epithelial Stem Cell Senescence and Senescence-Associated Differentiation Disorders in Pulmonary Fibrosis

Pulmonary senescence is accelerated by unresolved DNA damage response, underpinning susceptibility to pulmonary fibrosis. Recently it was reported that the SARS-Cov-2 viral infection induces acute pulmonary epithelial senescence followed by fibrosis, although the mechanism remains unclear. Here, we examine roles of alveolar epithelial stem cell senescence and senescence-associated differentiation disorders in pulmonary fibrosis, exploring the mechanisms mediating and preventing pulmonary fibrogenic crisis. Notably, the TGF-β signalling pathway mediates alveolar epithelial stem cell senescence by mechanisms involving suppression of the telomerase reverse transcriptase gene in pulmonary fibrosis. Alternatively, telomere uncapping caused by stress-induced telomeric shelterin protein TPP1 degradation mediates DNA damage response, pulmonary senescence and fibrosis. However, targeted intervention of cellular senescence disrupts pulmonary remodelling and fibrosis by clearing senescent cells using senolytics or preventing senescence using telomere dysfunction inhibitor (TELODIN). Studies indicate that the development of senescence-associated differentiation disorders is reprogrammable and reversible by inhibiting stem cell replicative senescence in pulmonary fibrosis, providing a framework for targeted intervention of the molecular mechanisms of alveolar stem cell senescence and pulmonary fibrosis. Abbreviations: DPS, developmental programmed senescence; IPF, idiopathic pulmonary fibrosis; OIS, oncogene-induced replicative senescence; SADD, senescence-associated differentiation disorder; SALI, senescence-associated low-grade inflammation; SIPS, stress-induced premature senescence; TERC, telomerase RNA component; TERT, telomerase reverse transcriptase; TIFs, telomere dysfunction-induced foci; TIS, therapy-induced senescence; VIS, virus-induced senescence.

GANE can Improve Lung Fibrosis by Reducing Inflammation via Promoting p38MAPK/TGF-β1/NF-κB Signaling Pathway Downregulation

There is a trend to use nanoparticles as distinct treatments for cancer treatment because they have overcome many of the limitations of traditional drug delivery systems. Gallic acid (GA) is an effective polyphenol in the treatment of tissue injuries. In this study, GA was loaded onto niosomes to produce gallic acid nanoemulsion (GANE) using a green synthesis technique. GANE's efficiency, morphology, UV absorption, release, and Fourier-transform infrared spectroscopy (FTIR) analysis were evaluated. An in vitro study was conducted on the A549 lung carcinoma cell line to determine the GANE cytotoxicity. Also, our study was extended to evaluate the protective effect of GANE against lipopolysaccharide (LPS)-induced pulmonary fibrosis in rats. GANE showed higher encapsulation efficiency and strong absorption at 280 nm. Transmission electron microscopy presented a spherical shape of the prepared nanoparticles, and FTIR demonstrated different spectra for the free gallic acid sample compared to GANE. GANE showed cytotoxicity for the A549 carcinoma lung cell line with a low IC₅₀ value. It was found that oral administration of GANE at 32.8 and 82 mg/kg.b.w. and dexamethasone (0.5 mg/kg) provided significant protection against LPS-induced pulmonary fibrosis. GANE enhanced production of superoxide dismutase, GPx, and GSH. It simultaneously reduced the MDA level. The GANE and dexamethasone, induced the production of IL-4, but suppressed TNF-α and IL-6. On the other hand, the lung p38MAPK, TGF-β1, and NF-κB gene expression was downregulated in rats administrated with GANE when compared with the LPS-treated rats. Histological studies confirmed the effective effect of GANE as it had a lung-protective effect against LPS-induced lung fibrosis. It was noticed that GANE can inhibit oxidative stress, lipid peroxidation, and cytokines and downregulate p38MAPK, TGF-β1, and NF-κB gene expression to suppress the proliferation and migration of lung fibrotic cells.

FSTL1 Secreted by Activated Fibroblasts Promotes Hepatocellular Carcinoma Metastasis and Stemness

The tumor microenvironment plays a critical role in maintaining the immature phenotype of tumor-initiating cells (TIC) to promote cancer. Hepatocellular carcinoma (HCC) is a unique disease in that it develops in the setting of fibrosis and cirrhosis. This pathologic state commonly shows an enrichment of stromal myofibroblasts, which constitute the bulk of the tumor microenvironment and contribute to disease progression. Follistatin-like 1 (FSTL1) has been widely reported as a proinflammatory mediator in different fibrosis-related and inflammatory diseases. Here we show FSTL1 expression to be closely correlated with activated fibroblasts and to be elevated in regenerative, fibrotic, and disease liver states in various mouse models. Consistently, FSTL1 lineage cells gave rise to myofibroblasts in a CCL₄-induced hepatic fibrosis mouse model. Clinically, high FSTL1 in fibroblast activation protein-positive (FAP⁺) fibroblasts were significantly correlated with more advanced tumors in patients with HCC. Although FSTL1 was expressed in primary fibroblasts derived from patients with HCC, it was barely detectable in HCC cell lines. Functional investigations revealed that treatment of HCC cells and patient-derived 3D organoids with recombinant FSTL1 or with conditioned medium collected from hepatic stellate cells or from cells overexpressing FSTL1 could promote HCC growth and metastasis. FSTL1 bound to TLR4 receptor, resulting in activation of AKT/mTOR/4EBP1 signaling. In a preclinical mouse model, blockade of FSTL1 mitigated HCC malignancy and metastasis, sensitized HCC tumors to sorafenib, prolonged survival, and eradicated the TIC subset. Collectively, these data suggest that FSTL1 may serve as an important novel diagnostic/prognostic biomarker and therapeutic target in HCC. SIGNIFICANCE: This study shows that FSTL1 secreted by activated fibroblasts in the liver microenvironment augments hepatocellular carcinoma malignancy, providing a potential new strategy to improve treatment of this aggressive disease.

Targeting USP11 may alleviate radiation-induced pulmonary fibrosis by regulating endothelium tight junction

PURPOSE

Radiation-induced pulmonary fibrosis (RIPF) is a major side effect after radiotherapy for thoracic malignancies. However, rare anti-RIPF therapeutics show definitive effects for treating this disease. Ubiquitin-specific peptidase 11 (USP11) has been reported to promote transforming growth factor β (TGFβ) signaling which plays an essential role underlying RIPF. Herein, we explored the role of USP11 on RIPF.

MATERIALS AND METHODS

In the present study, USP11-knockout (Usp11^-/-) mice were used to explore the effects of USP11 on RIPF. The lung tissue was obtained after receiving 30 Gy X-ray irradiation. The expression of USP11, TGF-β1, and a-SMA was determined by immunohistochemical and Western Blot, respectively. γ-H₂AX foci and TUNEL positive cells were detected by fluorescent technique to assess DNA damage and apoptosis. High-throughput proteomic analysis was applied to further explore the related mechanisms. The transwell co-culture method was used to investigate bystander effects in HELF cells induced by irradiated HMEC-1 cells in vitro.

RESULTS

Here we found that radiation activated USP11 in vivo and in vitro. Our results showed that USP11 deficiency effectively decreased serum TGF-β1 level, suppressed α-SMA expression, and mitigated pulmonary fibrosis. In addition, fewer γ-H₂AX foci and decreased apoptotic cells were identified after irradiation in the primary cells isolated from the lungs of Usp11^-/- mice. High-throughput proteomics analysis results showed that 22-upregulated and 158-downregulated proteins were identified in the lung tissues of Usp11^-/- mice after irradiation. Furthermore, gene set enrichment analysis (GSEA) revealed that USP11 deficiency affects the tight junction signaling pathway.

CONCLUSIONS

We verified that USP11 deficiency remarkably reinforced tight junction in the endothelial cells and alleviated TGF-β1 to inhibit fibrosis of fibroblast cells. The present study preliminarily showed that USP11-knockout mitigated RIPF via reinforcement endothelial barrier function.

Maiwei Yangfei decoction prevents bleomycin-induced pulmonary fibrosis in mice

Maiwei Yangfei (MWYF) is a compound Chinese herb that is safe and effective in the clinical setting in patients with pulmonary fibrosis (PF). The aim of the present study was to assess the role of a (MWYF) decoction in a bleomycin (BLM)-induced PF mouse model and to investigate the underlying functional mechanism. Chemical components within the MWYF decoction were analysed using liquid chromatography-mass spectrometry. A total of 50 C57BL/6 mice were randomly assigned to one of the following five groups with 10 mice per group: Control, model, low dose MWYF (20 g/kg), medium dose MWYF (40 g/kg) and high dose MWYF (60 g/kg). A mouse PF model was established by the tracheal instillation of BLM (5 mg/kg) prior to MWYF treatment, except for mice in the control group. After 21 days of treatment with MWYF, the mice were sacrificed and the body weights were recorded. In addition, pulmonary tissues and bronchial alveolar lavage fluid were collected. TNF-α, IL-6, IL-17, hydroxyproline, pyridinoline and collagen I levels were determined using ELISA. Vimentin, α-smooth muscle actin (α-SMA), fibronectin, TGF-β1, Smad3, TNF-α, IL-6, IL-17, collagen I and collagen III were determined using western blotting. Vimentin and α-SMA levels were also determined using immunofluorescence analysis. Collagens I and III were detected using immunohistochemical analysis and TGF-β1 and Smad3 levels were determined using reverse transcription-quantitative PCR. Following treatment with MWYF decoction, the body weight of the mice in the PF group increased, the degree of pulmonary alveolitis and PF was reduced, collagen levels were reduced and the expression levels of α-SMA, vimentin and fibronectin were decreased. Although both protein and mRNA expression levels of TGF-β1 and Smad3 were reduced, they remained higher than those observed in the control group. To conclude, MWYF decoction delayed the development of BLM-induced PF in mice, where the functional mechanism was likely associated with the TGF-β1/Smad3 signalling pathway.

Dynamic resistance exercise increases skeletal muscle-derived FSTL1 inducing cardiac angiogenesis via DIP2A-Smad2/3 in rats following myocardial infarction

PURPOSE

The aim of this study was to investigate the potential of dynamic resistance exercise to generate skeletal muscle-derived follistatin like-1 (FSTL1), which may induce cardioprotection in rats following myocardial infarction (MI) by inducing angiogenesis.

METHODS

Male, adult Sprague-Dawley rats were randomly divided into 5 groups (n = 12 in each group): sham group (S), sedentary MI group (MI), MI + resistance exercise group (MR), MI + adeno-associated virus (AAV)-FSTL1 injection group (MA), and MI + AAV-FSTL1 injection + resistance exercise group (MAR). The AAV-FSTL1 vector was prepared by molecular biology methods and injected into the anterior tibialis muscle. The MI model was established by ligation of the left anterior descending coronary artery. Rats in the MR and MAR groups underwent 4 weeks of dynamic resistance exercise training using a weighted climbing-up ladder. Heart function was evaluated by hemodynamic measures. Collagen volume fraction of myocardium was observed and analyzed by Masson's staining. Human umbilical vein vessel endothelial cells culture and recombinant human FSTL1 protein or transforming growth factor-β receptor 1 (TGFβR1) inhibitor treatment were used to elucidate the molecular signaling mechanism of FSTL1. Angiogenesis, cell proliferation, and disco interacting protein 2 homolog A (DIP2A) location were observed by immunofluorescence staining. The expression of FSTL1, DIP2A, and the activation of signaling pathways were detected by Western blotting. Angiogenesis of endothelial cells was observed by tubule experiment. One-way analysis of variance and Student's t test were used for statistical analysis.

RESULTS

Resistance exercise stimulated the secretion of skeletal muscle FSTL1, which promoted myocardial angiogenesis, inhibited pathological remodeling, and protected cardiac function in MI rats. Exercise facilitated skeletal muscle FSTL1 to play a role in protecting the heart. Exogenous FSTL1 promoted the human umbilical vein vessel endothelial cells proliferation and up-regulated the expression of DIP2A, while TGFβR1 inhibitor intervention down-regulated the phosphorylation level of Smad2/3 and the expression of vascular endothelial growth factor-A, which was not conducive to angiogenesis. FSTL1 bound to the receptor, DIP2A, to regulate angiogenesis mainly through the Smad2/3 signaling pathway. FSTL1-DIP2A directly activated Smad2/3 and was not affected by TGFβR1.

CONCLUSION

Dynamic resistance exercise stimulates the expression of skeletal muscle-derived FSTL1, which could supplement the insufficiency of cardiac FSTL1 and promote cardiac rehabilitation through the DIP2A-Smad2/3 signaling pathway in MI rats.

Gremlin2 Activates Fibroblasts to Promote Pulmonary Fibrosis Through the Bone Morphogenic Protein Pathway

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease causing unremitting extracellular matrix deposition. Transforming growth factor-β (TGF-β) superfamily involves bone morphogenetic proteins (BMPs) and TGF-β, and the balance between the activation of TGF-β-dependent SMADs (Smad2/3) and BMP-dependent SMADs (Smad1/5/8) is essential for fibrosis process. GREM2, initially identified as a TGF-β-inducible gene, encodes a small secreted glycoprotein belonging to a group of matricellular proteins, its role in lung fibrosis is not clear. Here, we identified Gremlin2 as a key regulator of fibroblast activation. Gremlin2 was highly expressed in the serum and lung tissues in IPF patients. Bleomycin-induced lung fibrosis model exhibited high expression of Gremlin2 in the bronchoalveolar lavage fluid (BALF) and lung tissue. Isolation of primary cells from bleomycin-induced fibrosis lung showed a good correlation of Gremlin2 and Acta2 (α-SMA) expressions. Overexpression of Gremlin2 in human fetal lung fibroblast 1 (HFL-1) cells increased its invasion and migration. Furthermore, Gremlin2 regulates fibrosis functions through mediating TGF-β/BMP signaling, in which Gremlin2 may activate TGF-β signaling and inhibit BMP signaling. Therefore, we provided in vivo and in vitro evidence to demonstrate that Gremlin2 may be a potential therapeutic target for the treatment of IPF.

TGF‑β1: Gentlemanly orchestrator in idiopathic pulmonary fibrosis (Review)

Idiopathic pulmonary fibrosis (IPF) is a worldwide disease characterized by the chronic and irreversible decline of lung function. Currently, there is no drug to successfully treat the disease except for lung transplantation. Numerous studies have been devoted to the study of the fibrotic process of IPF and findings showed that transforming growth factor‑β1 (TGF‑β1) plays a central role in the development of IPF. TGF‑β1 promotes the fibrotic process of IPF through various signaling pathways, including the Smad, MAPK, and ERK signaling pathways. There are intersections between these signaling pathways, which provide new targets for researchers to study new drugs. In addition, TGF‑β1 can affect the fibrosis process of IPF by affecting oxidative stress, epigenetics and other aspects. Most of the processes involved in TGF‑β1 promote IPF, but TGF‑β1 can also inhibit it. This review discusses the role of TGF‑β1 in IPF.

FSTL1 aggravates OVA-induced inflammatory responses by activating the NLRP3/IL-1β signaling pathway in mice and macrophages

OBJECTIVE

Asthma, a well-known disease with high morbidity, is characterized by chronic airway inflammation. However, the allergic inflammation mechanisms of follistatin-like protein 1 (FSTL1) have not been elucidated. This study aims to investigate the effects of FSTL1 in ovalbumin (OVA)-induced mice and macrophages on nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3)/interleukin-1β (IL-1β) signaling pathway.

METHODS

Mice were randomly divided into control-WT, OVA-WT, control-Fstl1±, OVA-Fstl1±. Histological changes were assessed by HE and PAS staining. The protein levels of Muc-5AC, FSTL1, NLRP3, and IL-1β in lung tissue were detected by immunohistochemistry and ELISA. The bronchoalveolar lavage fluid (BALF) in mice and human serum samples were detected by ELISA. Then, mice were grouped into control, FSTL1, MCC950 + FSTL1 to further investigate the relationship between FSTL1 and NLRP3/IL-1β. Alveolar macrophage cells (MH-S cells) were separated into control, OVA, FSTL1, OVA + FSTL1, OVA + siNC, OVA + siFSTL1, MCC950, and FSTL1 + MCC950 groups to explore the effect of FSTL1 on the NLRP3/IL-1β signaling. The protein expression of NLRP3 and IL-1β in MH-S cells was detected by Western blot analysis.

RESULTS

The present results uncovered that Fstl1± significantly ameliorated OVA-induced Muc-5AC production and mucus hypersecretion. Fstl1± was also found to decrease the production of inflammatory cytokines and inflammatory cell infiltration in OVA-induced asthmatic mice. Meanwhile, the serum concentrations of FSTL1 and IL-1β were higher in  asthma subjects than the health subjects, and Fstl1± ameliorated the production of NLRP3 and IL-1β in OVA-induced asthmatic mice. Furthermore, mice by injected FSTL1 substantially stimulated the expression of NLRP3 and IL-1β, while pretreatment with MCC950 in mice significantly weakened the production of NLRP3 and IL-1β induced by injection FSTL1. Pretreatment with siFSTL1 or MCC950 significantly reduced the production of NLRP3 and IL-1β induced by OVA or FSTL1 in MH-S cells.

CONCLUSIONS

The study results showed that FSTL1 played an important role in allergic airway inflammation by activating NLRP3/IL-1β. Hence, inhibition FSTL1 could be applied as a therapeutic agent against asthma.

Association between follistatin-related protein 1 and the functional status of patients with anti-neutrophil cytoplasmic antibody-associated vasculitis

BACKGROUND

Follistatin-like 1 (FSTL1) plays both pro-inflammatory and anti-inflammatory roles in the inflammatory processes. We investigated whether serum FSTL1 could predict the current anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV)-specific indices.

METHODS

We randomly selected 74 patients with AAV from a prospective and observational cohort of Korean patients with AAV. Clinical and laboratory data and AAV-specific indices were recorded. FSTL1 concentration was determined using the stored sera. The lowest tertile of the short-form 36-item health survey (SF-36) was defined as the current low SF-36. The cutoffs of serum FSTL1 for the current low SF-36 physical component summary (PCS) and SF-36 mental component summary (MCS) were extrapolated by the receiver operator characteristic curve.

RESULTS

The median age was 62.5 years (55.4% were women). Serum FSTL1 was significantly correlated with SF-36 PCS (r =  - 0.374), SF-36 MCS (r = -0.377), and C-reactive protein (CRP) (r = 0.307), but not with Birmingham vasculitis activity score (BVAS). In the multivariable linear regression analyses, BVAS, CRP, and serum FSTL1 were independently associated with the current SF-36 PCS (β = -0.255, β = -0.430, and β = -0.266, respectively) and the current SF-36 MCS (β = -0.234, β =-0.229, and β = -0.296, respectively). Patients with serum FSTL1 ≥779.8 pg/mL and those with serum FSTL1 ≥841.6 pg/mL exhibited a significantly higher risk of having the current low SF-36 PCS and SF-36 MCS than those without (relative risk 7.583 and 6.200, respectively).

CONCLUSION

Serum FSTL1 could predict the current functional status in AAV patients.

Follistatin-like protein 1 functions as a potential target of gene therapy in proliferative diabetic retinopathy

The degree of retinal fibrosis increased in proliferative diabetic retinopathy (PDR) patients after administration of anti-Vascular endothelial growth factor (VEGF) injections. Previous studies showed that the balance between connective tissue growth factor (CTGF) and VEGF plays an important role. Therefore, in a high-glucose state, an anti-VEGF and CTGFshRNA dual-target model was used to simulate clinical dual-target treatment in PDR patients, and RNA sequencing (RNA-Seq) technology was used for whole transcriptome sequencing. A hypoxia model was constructed to verify the sequencing results at the cellular level, and the vitreous humor and proliferative membranes were collected from patients for verification. All sequencing results included Follistatin-like protein 1 (FSTL1) and extracellular matrix (ECM) receptor pathway, indicated that anti-VEGF therapy may upregulate FSTL1 expression, while dual-target treatment downregulated FSTL1. Thus, we further studied the function of FSTL1 on the expression of VEGF and ECM factors by both overexpressing and silencing FSTL1. In conclusion, our results suggested that FSTL1 may be involved in the pathogenesis of PDR and is related to fibrosis caused by the anti-VEGF treatment, thus providing a potential target for gene therapy in PDR.

Emerging Roles of Matricellular Proteins in Systemic Sclerosis

Systemic sclerosis is a rare chronic heterogenous disease that involves inflammation and vasculopathy, and converges in end-stage development of multisystem tissue fibrosis. The loss of tight spatial distribution and temporal expression of proteins in the extracellular matrix (ECM) leads to progressive organ stiffening, which is a hallmark of fibrotic disease. A group of nonstructural matrix proteins, known as matricellular proteins (MCPs) are implicated in dysregulated processes that drive fibrosis such as ECM remodeling and various cellular behaviors. Accordingly, MCPs have been described in the context of fibrosis in sclerosis (SSc) as predictive disease biomarkers and regulators of ECM synthesis, with promising therapeutic potential. In this present review, an informative summary of major MCPs is presented highlighting their clear correlations to SSc- fibrosis.

Proteomics reveals different pathological processes of adipose tissue, liver, and skeletal muscle under insulin resistance

Type 2 diabetes mellitus is the most common type of diabetes, and insulin resistance (IR) is its core pathological mechanism. Proteomics is an ingenious and promising Omics technology that can comprehensively describe the global protein expression profiling of body or specific tissue, and is widely applied to the study of molecular mechanisms of diseases. In this paper, we focused on insulin target organs: adipose tissue, liver, and skeletal muscle, and analyzed the different pathological processes of IR in these three tissues based on proteomics research. By literature studies, we proposed that the main pathological processes of IR among target organs were diverse, which showed unique characteristics and focuses. We further summarized the differential proteins in target organs which were verified to be related to IR, and discussed the proteins that may play key roles in the emphasized pathological processes, aiming at discovering potentially specific differential proteins of IR, and providing new ideas for pathological mechanism research of IR.

Follistatin-like 1: A dual regulator that promotes cardiomyocyte proliferation and fibrosis

Follistatin-like 1 (FSTL1) is a key factor in maintaining cardiac growth and development. It can be activated by exercise training and has a dual role in promoting cardiomyocyte proliferation and fibrosis, but its underlying mechanism is not fully understood. To elucidate the dual mechanism and target of FSTL1 regulating of cardiomyocyte proliferation and myocardial fibrosis, and the mechanism by which exercise-regulated FSTL1 improves cardiovascular disease, we explored the signal transduction pathway of FSTL1 promoting cardiomyocyte proliferation and fibrosis, and compared the effects of different modes of exercise on the dual role of FSTL1. We believe that the dual role of promoting cardiomyocyte proliferation and fibrosis may be related to the ratio of cardiomyocyte and myocardial interstitial cell proliferation, different stages of the disease, different degrees of fibrosis, immune repair process, and transforming growth factor-β activation. Compared with long-term excessive endurance exercise, moderate resistance exercise can activate cardiomyocyte proliferation pathway through FSTL1, which is one of the effective ways to prevent cardiovascular disease.

TGF-β- and lipopolysaccharide-induced upregulation of circular RNA PWWP2A promotes hepatic fibrosis via sponging miR-203 and miR-223

Both transforming growth factor-beta (TGF-β) and lipopolysaccharide (LPS) can activate hepatic stellate cells (HSCs), thus increasing expressions of alpha smooth muscle actin (α-SMA) and type I collagen alpha 1 (Col1α1) and promoting liver fibrosis. However, whether TGF-β and LPS have a common downstream reactor remains unclear. Recently, a strong relationship of circular RNAs (circRNAs) and fibrogenesis has been elucidated. In this study, we compared the expressions of several circRNAs in TGF-β- and LPS-activated HSCs, and found that circ-PWWP2A was upregulated in both TGF-β- and LPS-activated HSCs and in mouse fibrotic liver tissues. Meanwhile, circ-PWWP2A was positively correlated with HSC activation and proliferation. Two microRNAs, miR-203 and miR-223, were identified to be the downstream targets of circ-PWWP2A using luciferase reporter assay and pull-down interaction assay. Circ-PWWP2A was suggested to promote HSC activation and proliferation via sponging miR-203 and miR-223, and subsequently increasing Fstl1 and TLR4, respectively. Furthermore, downregulating circ-PWWP2A was indicated to alleviate hepatic fibrosis in vivo. In conclusion, our findings indicated that circ-PWWP2A is the common downstream reactor of TGF-β and LPS in HSC activation, and that circ-PWWP2A plays a critical role in hepatic fibrogenesis via sponging miR-203 and miR-223.

Tanshinone IIA attenuates silica-induced pulmonary fibrosis via inhibition of TGF-β1-Smad signaling pathway

Transforming growth factor-β 1 (TGF-β1) is a key mediator in fibrogenesis, and is upregulated and activated in fibrotic diseases. The exact role of TGF-β1-Smad signaling in the progression of silicosis fibrosis is yet to be conclusively determined. Using a Wistar rat silicosis model, we examined whether tanshinone IIA (Tan IIA) could meliorate silicosis fibrosis. The pulmonary fibroblasts of rats from the normal control group and silicosis-induced model group were extracted and examined so as to further explore the disruption of TGF-β1-Smad signaling pathway in silicosis pathogenesis and the intervention of Tan IIA in this pathway. Using RT-PCR, immunohistochemical staining, and immunofluorescence analysis, we determined that Tan IIA could ameliorate silicosis fibrosis, downregulate collagen I, collagen III, and α-SMA expression both, in vivo and in vitro. In silicosis fibroblasts, TGF-β1 induced phosphorylation of Smad2, Smad3, and negative feedback Smad7 inhibition in a dose dependent manner, and the phosphorylation of Smad3 persisted when the upstream signal was blocked. Tan IIA treatment effectively inhibited the TGF-β1-induced phosphorylation of Smads, especially the persistent phosphorylation of Smad3 in the nucleus, and upregulated the expression of Smad7 in silicosis fibroblasts, leading to a reduction in ECM deposition. Our findings indicate that dysregulation of the TGF-β1-Smad signaling pathway may play an important role in the pathological process of silicosis. Tan IIA thus ameliorates silicosis fibrosis partially by suppressing activation of TGF-β1-Smad signaling pathway, which may turn out to be a potential therapeutic approach to prevent silicosis fibrosis.

Identification of differentially expressed genes and preliminary validations in cardiac pathological remodeling induced by transverse aortic constriction

Cardiac remodeling predisposes to heart failure if the burden is unresolved, and heart failure is an important cause of mortality in humans. The aim of the present study was to identify the key genes involved in cardiac pathological remodeling induced by pressure overload. Gene expression profiles of the GSE5500, GSE18224, GSE36074 and GSE56348 datasets were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs), defined as |log2FC|>1 (FC, fold change) and an adjusted P‑value of <0.05, were screened using the R software with the limma package. Gene ontology enrichment analysis was performed and a protein‑protein interaction (PPI) network of the DEGs was constructed. A cardiac remodeling model induced by transverse aortic constriction (TAC) was established. Furthermore, consistent DEGs were further validated using reverse transcription‑quantitative polymerase chain reaction (RT‑PCR) analysis, western blotting and immunohistochemistry in the ventricular tissue samples after TAC or sham operation. A total of 24 common DEGs were identified (23 significantly upregulated and 1 downregulated), of which 9 genes had been previously confirmed to be directly involved in cardiac remodeling. Hence, the level of expression of the other 15 genes was detected in subsequent studies via RT‑PCR. Based on the results of the PPI network analysis and RT‑PCR, we further detected the protein levels of Itgbl1 and Asporin, which were consistent with the results of bioinformatics analysis and RT‑PCR. The expression of Itgbl1, Aspn, Fstl1, Mfap5, Col8a1, Ltbp2, Mfap4, Pamr1, Cnksr1, Aqp8, Meox1, Gdf15 and Srpx was found to be upregulated in a mouse model of cardiac remodeling, while that of Retnla was downregulated. Therefore, the present study identified the key genes implicated in cardiac remodeling, aiming to provide new insight into the underlying mechanism.

Role of A2B adenosine receptor-dependent adenosine signaling in multi-walled carbon nanotube-triggered lung fibrosis in mice

Background

Multi-walled carbon nanotube (MWCNT)-induced lung fibrosis leads to health concerns in human. However, the mechanisms underlying fibrosis pathogenesis remains unclear. The adenosine (ADO) is produced in response to injury and serves a detrimental role in lung fibrosis. In this study, we aimed to explore the ADO signaling in the progression of lung fibrosis induced by MWCNT.

Results

MWCNT exposure markedly increased A_2B adenosine receptor (A_2BAR) expression in the lungs and ADO level in bronchoalveolar lavage fluid, combined with elevation of blood neutrophils, collagen fiber deposition, and activation of myeloperoxidase (MPO) activity in the lungs. Furthermore, MWCNT exposure elicited an activation of transforming growth factor (TGF)-β1 and follistatin-like 1 (Fstl1), leading to fibroblasts recruitment and differentiation into myofibroblasts in the lungs in an A_2BAR-dependent manner. Conversely, treatment of the selective A_2BAR antagonist CVT-6883 exhibited a significant reduction in levels of fibrosis mediators and efficiently decreased cytotoxicity and inflammatory in MWCNT treated mice.

Conclusion

Our results reveal that accumulation of extracellular ADO promotes the process of the fibroblast-to-myofibroblast transition via A_2BAR/TGF-β1/Fstl1 signaling in MWCNT-induced lung fibrosis.

Expression of TGF-beta receptor 1 and Smads in the tissues of primary spontaneous pneumothorax

BACKGROUND

Primary spontaneous pneumothorax (PSP) is a common disease which is often caused by the rupture of bullae in the lungs. The underlying pathogenesis of PSP remains unclear. Some molecules may be involved in the development of PSP potentially. The aim of this study was to investigate the expression of TGF-beta receptor 1 (TβR1), Smad2, Smad3 and Smad4 in the resected bullae of patients with PSP.

METHODS

From May 2015 to May 2016, 34 patients with PSP underwent video-assisted thoracoscopic surgery (VATS) bullectomy. Immunohistochemistry was performed to identify the expression of TβR1, Smad2, Smad3 and Smad4 in the resected pulmonary bullae tissues. The levels of these cytokines were calculated by immunoreactivity scoring system (IRS). Ten patients without pneumothorax associated disease were selected as the control group.

RESULTS

The analysis showed that the expression levels of TβR1, Smad2 and Smad4 were significantly higher in bullae tissues of patients with PSP than that in normal lung tissues (P=0.012, 0.031, 0.000 respectively). There was no significant difference between the expression level of Smad3 in bullae tissue of PSP patients and that in normal lung tissues of the control group (P=0.140). However, the absolute quantity of Smad3 expression in PSP bullae tissues was (4.2529±1.7193), scored by the IRS, which is higher than that in the control lung tissues (3.2600±2.2132). Also, the expression of TβR1, Smad2, Smad3 and Smad4 were not showed correlation with the clinical characteristics of PSP patients, such as age, sex, body mass index (BMI), recurrence and side of pneumothorax.

CONCLUSIONS

TβR1, Smad2 and Smad4 highly expressed in bullae tissues of PSP patients. Our findings suggested that TβR1, Smad2 and Smad4 may be related to the development of PSP bullae.

Shikonin suppresses pulmonary fibroblasts proliferation and activation by regulating Akt and p38 MAPK signaling pathways

Fibroblast is believed to be the primary effector in idiopathic pulmonary fibrosis (IPF), a progressive lung disorder characterized by aberrant tissue remodeling and the formation of fibroblastic foci. Due to the complicated etiology and mechanism, there are few effective drugs for this fatal disease. Shikonin (SHI), which is the major ingredient isolated from the plant Lithospermum Erythrorhizon, has long been used as traditional medicine for many diseases including inflammation and cancer. The roles of SHI in attenuating skin scar and renal fibrosis by reducing TGFβ1-stimulated fibroblast activation are also reported. But whether SHI works on IPF which exhibits both inflammatory and carcinoma-like features remains unknown. In this study, using isolated pulmonary fibroblasts, we demonstrated that SHI inhibited the proliferation, migration of fibroblasts, enhanced cell apoptosis and led to cell cycle arrest at G1 and G2/M phase. Moreover, SHI reduced the production of α-SMA, fibronectin, collagen I and III in response to TGF-β induction in pulmonary fibroblasts, and all of these gene production is the key component of extracellular matrix for tissue remodeling for IPF. The phosphorylation of Akt was down-regulated, p53 increased, the mRNA levels of p21 and p27 enhanced after SHI treatments. The phosphorylation of both p38 MAPK and Akt stimulated by TGF-β was reduced after SHI treatments. Collectively, these data indicate that SHI has a strong cytotoxicity in pulmonary fibroblast via inhibiting Akt activation signaling pathway, and attenuates TGF-β induced extracellular matrix genes production in pulmonary fibroblasts via modulating the activities of p38 MAPK and Akt. SHI might serve as a therapeutically candidate for IPF patients.