Stat3 signaling activation crosslinking of TGF-β1 in hepatic stellate cell exacerbates liver injury and fibrosis

Inhibition of STAT3 by S3I-201 suppress peritoneal fibroblast phenotype conversion and alleviate peritoneal fibrosis

Peritoneal fibrosis is a common pathological response to long-term peritoneal dialysis (PD) and a major cause for PD discontinuation. Understanding the cellular and molecular mechanisms underlying the induction and progression of peritoneal fibrosis is of great interest. In our study, in vitro study revealed that signal transducer and activator of transcription 3 (STAT3) is a key factor in fibroblast activation and extracellular matrix (ECM) synthesis. Furthermore, STAT3 induced by IL-6 trans-signalling pathway mediate the fibroblasts of the peritoneal stroma contributed to peritoneal fibrosis. Inhibition of STAT3 exerts an antifibrotic effect by attenuating fibroblast activation and ECM production with an in vitro co-culture model. Moreover, STAT3 plays an important role in the peritoneal fibrosis in an animal model of peritoneal fibrosis developed in mice. Blocking STAT3 can reduce the peritoneal morphological changes induced by chlorhexidine gluconate. In conclusion, our findings suggested STAT3 signalling played an important role in peritoneal fibrosis. Therefore, blocking STAT3 might become a potential treatment strategy in peritoneal fibrosis.

Effect of curcumin nanoparticles on proliferation and migration of mouse airway smooth muscle cells and airway inflammatory infiltration

Curcumin (CUR) possesses the capability to inhibit various inflammatory factors, exert anti-inflammatory effects, and alleviate asthma attacks; however, its hydrophobicity and instability significantly impede its clinical application. In this study, we synthesized CUR-loaded nanoparticles (CUR-NPs) and evaluated their impact on the proliferation, migration, and inflammatory infiltration of mouse airway smooth muscle cells (ASMCs), while investigating their underlying mechanisms. To achieve this objective, ASMCs were isolated from BALB/c mice and subjected to TGF-β1-induced cell proliferation and migration. Our findings demonstrate that CUR-NPs effectively regulate the release of CUR within cells with superior intracellular uptake compared to free CUR. The CCK-8 assay results indicate that the blank carrier does not exhibit any cytotoxic effects on cells, thus rendering the impact of the carrier itself negligible. The TGF-β1 group exhibited a significant increase in cell proliferation, whereas treatment with CUR-NPs significantly suppressed TGF-β1-induced cell proliferation. The findings from both the cell scratch assay and transwell assay demonstrated that TGF-β1 substantially enhanced cell migration, while CUR-NPs treatment effectively attenuated TGF-β1-induced cell migration. The Western blot analysis demonstrated a substantial increase in the expression levels of TGF-β1, p-STAT3, and CTGF in ASMCs following treatment with TGF-β1 when compared to the control group. Nevertheless, this effect was effectively counteracted upon administration of CUR-NPs. Furthermore, an asthma mouse model was successfully established and CUR-NPs were administered through tail vein injection. The serum levels of TGF-β1 and the expression levels of TGF-β1, p-STAT3, and CTGF proteins in the lung tissue of mice in the model group exhibited significant increases compared to those in the control group. However, CUR-NPs treatment effectively attenuated this change. Our research findings suggest that CUR-NPs possess inhibitory effects on ASMC proliferation, migration, and inflammatory infiltration by suppressing activation of the TGF-β1/p-STAT3/CTGF signaling pathway, thereby facilitating inhibition of airway remodeling.

STAT3 Decoy Oligodeoxynucleotides Suppress Liver Inflammation and Fibrosis in Liver Cancer Cells and a DDC-Induced Liver Injury Mouse Model

Liver damage caused by various factors results in fibrosis and inflammation, leading to cirrhosis and cancer. Fibrosis results in the accumulation of extracellular matrix components. The role of STAT proteins in mediating liver inflammation and fibrosis has been well documented; however, approved therapies targeting STAT3 inhibition against liver disease are lacking. This study investigated the anti-fibrotic and anti-inflammatory effects of STAT3 decoy oligodeoxynucleotides (ODN) in hepatocytes and liver fibrosis mouse models. STAT3 decoy ODN were delivered into cells using liposomes and hydrodynamic tail vein injection into 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-fed mice in which liver injury was induced. STAT3 target gene expression changes were verified using qPCR and Western blotting. Liver tissue fibrosis and bile duct proliferation were assessed in animal experiments using staining techniques, and macrophage and inflammatory cytokine distribution was verified using immunohistochemistry. STAT3 decoy ODN reduced fibrosis and inflammatory factors in liver cancer cell lines and DDC-induced liver injury mouse model. These results suggest that STAT3 decoy ODN may effectively treat liver fibrosis and must be clinically investigated.

Bromodomain protein 4 mediates the roles of TGFβ1-induced Stat3 signaling in mouse liver fibrogenesis

Epigenetic reader Bromodomain protein 4 (BrD4) functions as a global genomic regulator to direct hepatic stellate cell (HSC) activation (a key step in liver fibrogenesis) and liver fibrosis. The pivotal pro-fibrotic cytokine transforming growth factor-β1 (TGFβ1) signals through both Smad and Stat3 to elicit a wide array of biological effects. Stat3 is widely acknowledged as a regulator of gene transcription and is involved in fibrosis of multiple tissues. The present study focused on BrD4 function implication in the roles of TGFβ1-induced Stat3 signaling in HSC activation and liver fibrosis by using heterozygous TGFβ1 knockout mice and HSC culture. Results showed that Stat3 was required for TGFβ1-induced BrD4 expression in HSCs. BrD4 expression paralleled Stat3 activation in activated HSCs in human cirrhotic livers. BrD4 was involved in the roles of TGFβ1-induced Stat3 in HSC activation and liver fibrogenesis. Smad3 bound to phosphorylated-Stat3 and contributed to TGFβ1-induced Stat3 signaling. BrD4 expression induced by Stat3 signaling required the early-immediate gene Egr1. Egr1 had a positive feedback on Stat3 activation. In conclusion, a network consisting of Stat3 signaling, Smad3 signaling, Egr1, and BrD4 was involved in the effects of TGFβ1 on liver fibrosis, providing new toxicological mechanisms for TGFβ1 in liver fibrogenesis.

Human Wharton's jelly mesenchymal stem cells derived-exosomes enriched by miR-124 promote an anti-fibrotic response in an experimental model of liver fibrosis

BACKGROUND

Liver fibrosis is a significant challenge to global health that results in organ failure through inflammation and the release of fibrotic biomarkers. Due to the lack of effective treatments for liver fibrosis, anti-fibrotic and anti-inflammatory therapies are being developed. Since there has been an association between aberrant expression of miR-124 and liver disease progression, we investigated whether delivery of miR-124 through human Wharton's jelly mesenchymal stem cells derived-exosomes (hWJMSC-Exo) can improve liver fibrosis.

METHODS

We established a 6-week carbon tetrachloride (CCl4)-induced mouse model of liver fibrosis, then we administered hWJMSC-Exo and miR-124-3p-enriched exosomes (ExomiR-124) for three weeks. The extent of fibrosis and inflammation was assessed by histology, biochemistry, Real-time PCR, immunohistochemistry, and Enzyme-linked immunoassays (ELISA). The inflammatory status of the spleen was also investigated using flow cytometry.

RESULTS

Based on the gene and protein expression measurement of IL-6, IL-17, TGF-β, STAT3, α-SMA, and COL1, In vivo administration of Exo and ExomiR-124 effectively reduce collagen accumulation and inhibition of inflammation. Regarding histopathology findings, the therapeutic effect of ExomiR-124 against liver fibrosis was significantly greater than hWJMSC-Exo. In addition, we found that Exo and ExomiR-124 was capable of phenotype switching of splenic monocytes from inflammatory Ly6C^hi to restorative Ly6C^lo.

CONCLUSIONS

MSC-derived exosomes demonstrated anti-inflammatory effect via different aspects. Aside from the therapeutic approach, enrichment of exosomes as a nanocarrier by miR-124 revealed the down-regulation of STAT3, which plays a crucial role in liver fibrosis. The anti-inflammatory and anti-fibrotic properties of ExomiR-124 could be a promising option in liver fibrosis combination therapies.

Discovery and development of benzene sulfonamide derivatives as anti-hepatic fibrosis agents

A novel benzene sulfonamide compound named IMB16-4 exhibits excellent anti-hepatic fibrosis activity in a recent study. To develop potential anti-hepatic fibrosis agents, a series of benzene sulfonamide derivatives were designed and synthesized based on the scaffold of the lead compound IMB16-4. As it turned out, most of the derivatives displayed potential anti-hepatic fibrosis activity, among which, compounds 11a, 11b, 11d, 13a, 36b, and 47b exhibited inhibition rates of 42.3%, 48.7%, 42.4%, 40.0%, 39.4%, and 49.3%, respectively, which were equivalent to the control IMB16-4 with an inhibition rate of 35.9%, Costunolide with an inhibition rate of 45.4%, and much more potent than that of Epigallocatechin gallate (EGCG) with an inhibition rate of 25.3%. Especially, compounds 46a, 46b, and 46c exhibited excellent anti-hepatic fibrosis activity with inhibition rates of 61.7%, 54.8%, and 60.7%, which were almost 1.5-fold inhibition rates of IMB16-4. In addition, compounds 46a, 46b, and 46c exhibited remarkable inhibitory activity in the gene expression of COL1A1, MMP-2, and the protein expression of COL1A1, FN, α-SMA, and TIMP-1 by inhibiting the JAK1-STAT1/3 pathway. These findings furnished valuable inspiration for the further development of anti-hepatic fibrosis agents.

Spatial molecular and cellular determinants of STAT3 activation in liver fibrosis progression in non-alcoholic fatty liver disease

Background & Aims

The prevalence of non-alcoholic fatty liver disease (NAFLD) and its severe form, non-alcoholic steatohepatitis (NASH), is increasing. Individuals with NASH often develop liver fibrosis and advanced liver fibrosis is the main determinant of mortality in individuals with NASH. We and others have reported that STAT3 contributes to liver fibrosis and hepatocellular carcinoma in mice.

Methods

Here, we explored whether STAT3 activation in hepatocyte and non-hepatocyte areas, measured by phospho-STAT3 (pSTAT3), is associated with liver fibrosis progression in 133 patients with NAFLD. We further characterized the molecular and cellular determinants of STAT3 activation by integrating spatial distribution and transcriptomic changes in fibrotic NAFLD livers.Results: pSTAT3 scores in non-hepatocyte areas progressively increased with fibrosis severity (r = 0.53, p <0.001). Correlation analyses between pSTAT3 scores and expression of 1,540 immune- and cancer-associated genes revealed a large effect of STAT3 activation on gene expression changes in non-hepatocyte areas and confirmed a major role for STAT3 activation in fibrogenesis. Digital spatial transcriptomic profiling was also performed on 13 regions selected in hepatocyte and non-hepatocyte areas from four NAFLD liver biopsies with advanced fibrosis, using a customized panel of markers including pSTAT3, PanCK+CK8/18, and CD45. The regions were further segmented based on positive or negative pSTAT3 staining. Cell deconvolution analysis revealed that activated STAT3 was enriched in hepatic progenitor cells (HPCs) and sinusoidal endothelial cells. Regression of liver fibrosis upon STAT3 inhibition in mice with NASH resulted in a reduction of HPCs, demonstrating a direct role for STAT3 in HPC expansion.

Conclusion

Increased understanding of the spatial dependence of STAT3 signaling in NASH and liver fibrosis progression could lead to novel targeted treatment approaches.

Impact and implications

Advanced liver fibrosis is the main determinant of mortality in patients with NASH. This study showed using liver biopsies from 133 patients with NAFLD, that STAT3 activation in non-hepatocyte areas is strongly associated with fibrosis severity, inflammation, and progression to NASH. STAT3 activation was enriched in hepatic progenitor cells (HPCs) and sinusoidal endothelial cells (SECs), as determined by innovative technologies interrogating the spatial distribution of pSTAT3. Finally, STAT3 inhibition in mice resulted in reduced liver fibrosis and depletion of HPCs, suggesting that STAT3 activation in HPCs contributes to their expansion and fibrogenesis in NAFLD.

Yao medicine Amydrium hainanense suppresses hepatic fibrosis by repressing hepatic stellate cell activation via STAT3 signaling

Ethnopharmacological relevance: Hepatic fibrosis (HF) occurs in response to chronic liver injury and may easily develop into irreversible liver cirrhosis or even liver cancer. Amydrium hainanense water extract (AHWE) is a water-soluble component extracted from the Yao medicine Amydrium hainanense (H.Li, Y.Shiao & S.L.Tseng) H.Li, which is commonly used for treating inflammatory diseases in folk. Previous evidence suggested that AHWE significantly inhibited hepatic stellate cell activation. However, little is known regarding the therapeutic effect of AHWE in HF and its underlying action mechanism. Objective: Investigation of the therapeutic effect of AHWE in HF and its underlying mechanism. Methods: The therapeutic effect of AHWE was tested in vivo using an HF mouse model via an intraperitoneal injection of carbon tetrachloride (CCl₄). Histological evaluation of liver injury and fibrosis were tested by H&E staining and Masson's trichrome staining. Serum levels of ALT, AST, collagen type I (Col I), and hydroxyproline (HYP) were measured. The mRNA expression of liver fibrotic and inflammatory genes were tested, and the protein levels of alpha smooth muscle actin (α-SMA) and signal transducers and activators of transcription 3 (STAT3) were analyzed. The in vitro experiments were conducted using HSC-T6 and RAW264.7 cell lines. Results: Treatment with AHWE significantly reversed histopathological liver damage and liver function abnormalities in CCl₄ mouse model. Also, the serum levels of ALT, AST, Col I, and HYP in CCl₄-induced HF mice were improved in AHWE treatment. Further, AHWE showed a remarkable inhibitory effect on the expression of fibrosis markers (Acta2, Col1a1, and Col3a1) and inflammatory factors (Stat3, Tnfa, Il6, and Il1b) induced by CCl₄. The results of in vitro experiments were consistent with those obtained in vivo. In addition, it is shown that STAT3 signaling was involved in the anti-fibrotic effects of AHWE as evidenced by STAT3 overexpression. Conclusion: The present study proposed a novel ethnomedicine for HF and suggested the underlying role of STAT3 signaling pathway regulation in this anti-fibrotic effect of the proposed medicine. These findings would serve as solid scientific evidence in support of the development of AHWE as a novel alternative or complementary therapy for HF prevention and treatment.

Systematic review of Lonicerae Japonicae Flos: A significant food and traditional Chinese medicine

Lonicerae Japonicae Flos has been used as a tea and medicine for more than 1,500 years. It has the functions of clearing heat, detoxification, and is often used to treat carbuncle, furuncle, throat arthralgia, erysipelas, heat-toxic blood dysentery, febrile fever. This paper summarizes the botany, ethnopharmacology, chemical composition and pharmacological action of Lonicerae Japonicae Flos from 1986 to 2022, and looks forward to the future research direction of Lonicerae Japonicae Flos. At present, the components isolated from Lonicerae Japonicae Flos include essential oils, organic acids, flavonoids, iridoids, saponins and other compounds. It has the effects of anti-inflammation, anti-virus, anti-bacteria, anti-oxidation, anti-tumor, protect liver and galltesticles, hypotensive, hypolipidemic, anti-thrombosis, anti-allergy, immune regulation and so on. It is often used in clinical treatment of diarrhea, hematochezia, febrile disease, exogenous wind-heat, and cold, swelling and toxin of carbuncle, sore throat and so on. The comprehensive evaluation of the quality of Lonicerae Japonicae Flos and the understanding of multi-target network pharmacology also need to be studied. As a kind of health food with high value, LJF is worthy of further promotion and development.

Bicyclol ameliorates advanced liver diseases in murine models via inhibiting the IL-6/STAT3 signaling pathway

Bicyclol, a synthetic hepatoprotective and anti-inflammatory agent approved in China, was widely used to treat various hepatitis accompanied by elevated serum aminotransferases. However, the pharmacological effects and mechanisms of bicyclol on advanced liver diseases, such as fibrosis/cirrhosis and hepatocellular carcinoma (HCC), remain to be explored. Here, we revealed that bicyclol prevents from formatting severe fibrosis, slows the progression of moderate liver fibrosis, accelerates the regression of moderate liver fibrosis, decreases the malignancy of HCC in rat models induced by diethylnitrosamine (DEN), and also blocks steatohepatitis to HCC in mice induced by western diet plus carbon tetrachloride and DEN. The detailed pharmacological mechanism showed that bicyclol alleviates chronic progressive liver diseases by inhibiting the levels of IL-6 and subsequent phosphorylated STAT3. Conclusion: Bicyclol plays significant protective roles in multiply stages of fibrosis/cirrhosis-HCC and nonalcoholic fatty liver disease-related HCC via inhibiting IL-6/STAT3 signaling pathway. Therefore, bicyclol might be a promising therapeutic strategy for treating advanced liver diseases.

Lycorine Ameliorates Thioacetamide-Induced Hepatic Fibrosis in Rats: Emphasis on Antioxidant, Anti-Inflammatory, and STAT3 Inhibition Effects

Liver fibrosis is a foremost medical concern worldwide. In Saudi Arabia, numerous risk factors contribute to its high rates. Lycorine—a natural alkaloid—has antioxidant, anti-inflammatory, and antitumor activates. It has been reported to inhibit STAT3 in cancer. Therefore, this study aimed at investigating the possible antifibrotic effect of lycorine against thioacetamide (TAA)-induced liver fibrosis in rats and at elucidating the possible mechanisms. Liver fibrosis was induced by TAA (200 mg/kg i.p.), three per week for four weeks. Treatment with lycorine (0.5 and 1 mg/kg/d) amended TAA-induced rise of serum transaminases that was confirmed histopathologically. Moreover, it ameliorated liver fibrosis in a dose-dependent manner, as indicated by hindering the TAA-induced increase of hepatic hydroxyproline content, α-smooth muscle actin (α-SMA) and transforming growth factor (TGF-β1) expressions. TAA-induced oxidative stress was amended by lycorine treatment via restoring reduced glutathione and diminishing lipid peroxidation. Moreover, lycorine ameliorated hepatic inflammation by preventing the rise of inflammatory cytokines. Notably, lycorine inhibited STAT3 activity, as evidenced by the decreased phospho-STAT3 expression, accompanied by the elevation of the hepatic Bax/Bcl-2 ratio. In conclusion, lycorine hinders TAA-induced liver fibrosis in rats, due to—at least partly—its antioxidative and anti-inflammatory properties, along with its ability to inhibit STAT3 signaling.

Stevioside inhibits lipopolysaccharide-induced epithelial-to-mesenchymal transition of NRK-52E cells by PPARγ activation

BACKGROUND

Stevioside is a natural diterpenoid compound that possesses anti-inflammatory, immunomodulatory, anti-diabetic, anti-hypertensive, and renal protective effects, but its effect on lipopolysaccharide (LPS)-induced epithelial-to-mesenchymal transition (EMT) of renal tubular epithelial cells, an important immune pathological mechanism of renal fibrosis, remains unknown. This study employed the renal proximal tubular cells NRK-52E to investigate the effect of stevioside.

METHODS

The LPS-stimulated renal NRK-52E cells were treated with 50, 100, or 200 μM stevioside in the presence or absence of peroxisome proliferator-activated receptor γ (PPARγ) antagonist GW9662, the expression levels of intracellular E-cadherin, vimentin, α-smooth muscle actin (α-SMA), PPARγ, nuclear factor kappa B (NF-κB) p65, transforming growth factor-β1 (TGF-β1), signal transducer and activator of transcription 3 (STAT3), p-STAT3, Smad2/3, and p-Smad2/3 proteins were detected by Western blot analysis.

RESULTS

In LPS-stimulated NRK-52E cells, stevioside treatment could reverse the expressions of EMT-related E-cadherin, vimentin, and α-SMA proteins, increase the expression of PPARγ protein, and decrease the expressions of NF-κB p65, TGF-β1, p-STAT3, Smad2/3, and p-Smad2/3 proteins, especially in the 200 μM stevioside-treated group. However, these beneficial effects of stevioside were attenuated or canceled by pretreatment with PPARγ antagonist GW9662.

CONCLUSIONS

Stevioside can inhibit the LPS-induced EMT via the reductions of NF-κB, TGF-β1, Smad2/3, p-Smad2/3, and p-STAT3 protein expressions by PPARγ activation in NRK-52E cells, which may provide a pharmacological basis for the potential application of stevioside in the prevention and treatment of renal fibrosis.

Perilipin 5 Ameliorates Hepatic Stellate Cell Activation via SMAD2/3 and SNAIL Signaling Pathways and Suppresses STAT3 Activation

Comprehending the molecular mechanisms underlying hepatic fibrogenesis is essential to the development of treatment. The hallmark of hepatic fibrosis is the development and deposition of excess fibrous connective tissue forcing tissue remodeling. Hepatic stellate cells (HSC) play a major role in the pathogenesis of liver fibrosis. Their activation via the transforming growth factor-β1 (TGF-β1) as a key mediator is considered the crucial event in the pathophysiology of hepatic fibrogenesis. It has been shown that Perilipin 5 (PLIN5), known as a lipid droplet structural protein that is highly expressed in oxidative tissue, can inhibit such activation through various mechanisms associated with lipid metabolism. This study aimed to investigate the possible influence of PLIN5 on TGF-β1 signaling. Our findings confirm the importance of PLIN5 in maintaining HSC quiescence in vivo and in vitro. PLIN5 overexpression suppresses the TGF-β1-SMAD2/3 and SNAIL signaling pathways as well as the activation of the signal transducers and activators of transcription 3 (STAT3). These findings derived from experiments in hepatic cell lines LX-2 and Col-GFP, in which overexpression of PLIN5 was able to downregulate the signaling pathways SMAD2/3 and SNAIL activated previously by TGF-β1 treatment. Furthermore, TGF-β1-mediatedinduction of extracellular matrix proteins, such as collagen type I (COL1), Fibronectin, and α-smooth muscle actin (α-SMA), was suppressed by PLIN5. Moreover, STAT3, which is interrelated with TGF-β1 was already basally activated in the cell lines and inhibited by PLIN5 overexpression, leading to a further reduction in HSC activity shown by lowered α-SMA expression. This extension of the intervening mechanisms presents PLIN5 as a potent and pleiotropic target in HSC activation.

Study on the effect of Mongolian medicine Qiwei Qinggan Powder on hepatic fibrosis through JAK2/STAT3 pathway

This research aimed to evaluate the antihepatic fibrosis effect and explore the mechanism of Qiwei Qinggan Powder (QGS-7) in vivo and in vitro. Carbon tetrachloride (CCl4)-treated rats and hepatic stellate cells (HSCs) were used. QGS-7 treatment significantly improved the liver function of rats as indicated by decreased serum enzymatic activities of alanine aminotransferase, aspartate transaminase, and alkaline phosphatase. Meanwhile, the hydroxyproline of liver was significantly decreased. Histopathological results indicated that QGS-7 alleviated liver damage and reduced the formation of fibrosis septa. Moreover, QGS-7 significantly attenuated expressions of Alpha smooth muscle actin, Collagen I, Janus kinase 2 (JAK2), phosphorylation-JAK2, signal transducer and activator of transcription 3 (STAT3), phosphorylation-STAT3 in the rat hepatic fibrosis model. QGS-7 inhibited HSC proliferation and promoted it apoptosis. QGS-7 may affect hepatic fibrosis through JAK2/STAT3 signaling pathway so as to play an antihepatic fibrosis role.

Exosomal miRNAs as Potential Biomarkers to Monitor Phosphodiesterase 5 Inhibitor Induced Anti-Fibrotic Effects on CCl4 Treated Rats

MicroRNAs (miRNAs) are short, non-coding RNA species that are important post-transcriptional regulators of gene expression and play an important role in the pathogenesis of non-alcoholic fatty liver disease. Here, we investigated the phosphodiesterase 5 (PDE5) inhibitor induced effects on hepatic and plasma exosomal miRNA expression in CCl₄-treated rats. In the present study, hepatic miRNA profiling was conducted using the Nanostring nCounter technology and mRNA profiling using RNA sequencing from PDE5 treated rats in the model of CCl₄-induced liver fibrosis. To evaluate if the PDE5 inhibitor affected differentially expressed miRNAs in the liver can be detected in plasma exosomes, qRT-PCR specific assays were used. In livers from CCl₄-treated rats, the expression of 22 miRNAs was significantly increased (>1.5-fold, adj. p < 0.05), whereas the expression of 16 miRNAs was significantly decreased (>1.5-fold, adj. p < 0.05). The majority of the deregulated miRNA species are implicated in fibrotic and inflammatory processes. The PDE5 inhibitor suppressed the induction of pro-fibrotic miRNAs, such as miR-99b miR-100 and miR-199a-5p, and restored levels of anti-fibrotic miR-122 and miR-192 in the liver. In plasma exosomes, we observed elevated levels of miR-99b, miR-100 and miR-142-3p after treatment with the PDE5-inhibitor compared to CCl₄/Vehicle-treated. Our study demonstrated for the first time that during the development of hepatic fibrosis in the preclinical model of CCl₄-induced liver fibrosis, defined aspects of miRNA regulated liver pathogenesis are influenced by PDE5 treatment. In conclusion, miRNA profiling of plasma exosomes might be used as a biomarker for NASH progression and monitoring of treatment effects.

Diabetic fibrosis

Diabetes-associated morbidity and mortality is predominantly due to complications of the disease that may cause debilitating conditions, such as heart and renal failure, hepatic insufficiency, retinopathy or peripheral neuropathy. Fibrosis, the excessive and inappropriate deposition of extracellular matrix in various tissues, is commonly found in patients with advanced type 1 or type 2 diabetes, and may contribute to organ dysfunction. Hyperglycemia, lipotoxic injury and insulin resistance activate a fibrotic response, not only through direct stimulation of matrix synthesis by fibroblasts, but also by promoting a fibrogenic phenotype in immune and vascular cells, and possibly also by triggering epithelial and endothelial cell conversion to a fibroblast-like phenotype. High glucose stimulates several fibrogenic pathways, triggering reactive oxygen species generation, stimulating neurohumoral responses, activating growth factor cascades (such as TGF-β/Smad3 and PDGFs), inducing pro-inflammatory cytokines and chemokines, generating advanced glycation end-products (AGEs) and stimulating the AGE-RAGE axis, and upregulating fibrogenic matricellular proteins. Although diabetes-activated fibrogenic signaling has common characteristics in various tissues, some organs, such as the heart, kidney and liver develop more pronounced and clinically significant fibrosis. This review manuscript summarizes current knowledge on the cellular and molecular pathways involved in diabetic fibrosis, discussing the fundamental links between metabolic perturbations and fibrogenic activation, the basis for organ-specific differences, and the promises and challenges of anti-fibrotic therapies for diabetic patients.

Hepatoprotective Potency of Chrysophanol 8-O-Glucoside from Rheum palmatum L. against Hepatic Fibrosis via Regulation of the STAT3 Signaling Pathway

Rhubarb is a well-known herb worldwide and includes approximately 60 species of the Rheum genus. One of the representative plants is Rheum palmatum, which is prescribed as official rhubarb due to its pharmacological potential in the Korean and Chinese pharmacopoeia. In our bioactive screening, we found out that the EtOH extract of R. palmatum inhibited hepatic stellate cell (HSC) activation by transforming growth factor β1 (TGF-β1). Chemical investigation of the EtOH extract led to the isolation of chrysophanol 8-O-glucoside, which was determined by structural analysis using NMR spectroscopic techniques and electrospray ionization mass spectrometry (ESIMS). To elucidate the effects of chrysophanol 8-O-glucoside on HSC activation, activated LX-2 cells were treated for 48 h with chrysophanol 8-O-glucoside, and α-SMA and collagen, HSC activation markers, were measured by comparative quantitative real-time PCR (qPCR) and western blotting analysis. Chrysophanol 8-O-glucoside significantly inhibited the protein and mRNA expression of α-SMA and collagen compared with that in TGF-β1-treated LX-2 cells. Next, the expression of phosphorylated SMAD2 (p-SMAD2) and p-STAT3 was measured and the translocation of p-STAT3 to the nucleus was analyzed by western blotting analysis. The expression of p-SMAD2 and p-STAT3 showed that chrysophanol 8-O-glucoside strongly downregulated STAT3 phosphorylation by inhibiting the nuclear translocation of p-STAT3, which is an important mechanism in HSC activation. Moreover, chrysophanol 8-O-glucoside suppressed the expression of p-p38, not that of p-JNK or p-Erk, which can activate STAT3 phosphorylation and inhibit MMP2 expression, the downstream target of STAT3 signaling. These findings provided experimental evidence concerning the hepatoprotective effects of chrysophanol 8-O-glucoside against liver damage and revealed the molecular basis underlying its anti-fibrotic effects through the blocking of HSC activation.

Recapitulating pancreatic tumor microenvironment through synergistic use of patient organoids and organ-on-a-chip vasculature

Tumor progression relies heavily on the interaction between the neoplastic epithelial cells and their surrounding stromal partners. This cell cross-talk affects stromal development, and ultimately the heterogeneity impacts drug efflux and efficacy. To mimic this evolving paradigm, we have micro-engineered a three-dimensional (3D) vascularized pancreatic adenocarcinoma tissue in a tri-culture system composed of patient derived pancreatic organoids, primary human fibroblasts and endothelial cells on a perfusable InVADE platform situated in a 96-well plate. Uniquely, through synergistic engineering we combined the benefits of cellular fidelity of patient tumor derived organoids with the addressability of a plastic organ-on-a-chip platform. Validation of this platform included demonstrating the growth of pancreatic tumor organoids by monitoring the change in metabolic activity of the tissue. Investigation of tumor microenvironmental behavior highlighted the role of fibroblasts in symbiosis with patient organoid cells, resulting in a six-fold increase of collagen deposition and a corresponding increase in tissue stiffness in comparison to fibroblast free controls. The value of a perfusable vascular network was evident in drug screening, as perfusion of gemcitabine into a stiffened matrix did not show the dose-dependent effects on tumor viability as those under static conditions. These findings demonstrate the importance of studying the dynamic synergistic relationship between patient cells with stromal fibroblasts, in a 3D perfused vascular network, to accurately understand and recapitulate the tumor microenvironment.

Stevioside inhibits unilateral ureteral obstruction-induced kidney fibrosis and upregulates renal PPARγ expression in mice

This study aimed to examine the inhibitory effect of stevioside on unilateral ureteral obstruction (UUO)-induced kidney fibrosis. The UUO mice were daily given 50-100 mg/kg stevioside by gavage for 14 days after the operation. The results showed that stevioside decreased the levels of blood urea nitrogen and renal hydroxyproline, severity of kidney fibrosis, and expressions of renal collagen I/III and α-smooth muscle actin proteins. Importantly, stevioside increased the expressions of renal peroxisome proliferator-activated receptor γ (PPARγ) and Smad7 proteins and level of renal glutathione peroxidase, decreased the expressions of renal nuclear factor kappa B (NF-κB), signal transducer and activator of transcription 3 (STAT3), p-STAT3, transforming growth factor-β1 (TGF-β1), Smad2/3, and p-Smad2/3 proteins, suggesting that the antifibrotic mechanisms are related to the activation of PPARγ and subsequent downregulations of NF-κB-mediated STAT3 and TGF-β1 expressions and inhibition of Smad-mediated signaling pathway. These findings provide an applied perspective of stevioside for kidney fibrosis. PRACTICAL APPLICATIONS: Stevioside is widely used in food products as a sweetener, and it has many beneficial biological effects, including antidiabetes, antihypertension, and renal protective action. Here, we provide a novel potential application of stevioside in the prevention and treatment of kidney fibrosis.

Targeting Janus Kinases and Signal Transducer and Activator of Transcription 3 to Treat Inflammation, Fibrosis, and Cancer: Rationale, Progress, and Caution

Before it was molecularly cloned in 1994, acute-phase response factor or signal transducer and activator of transcription (STAT)3 was the focus of intense research into understanding the mammalian response to injury, particularly the acute-phase response. Although known to be essential for liver production of acute-phase reactant proteins, many of which augment innate immune responses, molecular cloning of acute-phase response factor or STAT3 and the research this enabled helped establish the central function of Janus kinase (JAK) family members in cytokine signaling and identified a multitude of cytokines and peptide hormones, beyond interleukin-6 and its family members, that activate JAKs and STAT3, as well as numerous new programs that their activation drives. Many, like the acute-phase response, are adaptive, whereas several are maladaptive and lead to chronic inflammation and adverse consequences, such as cachexia, fibrosis, organ dysfunction, and cancer. Molecular cloning of STAT3 also enabled the identification of other noncanonical roles for STAT3 in normal physiology, including its contribution to the function of the electron transport chain and oxidative phosphorylation, its basal and stress-related adaptive functions in mitochondria, its function as a scaffold in inflammation-enhanced platelet activation, and its contributions to endothelial permeability and calcium efflux from endoplasmic reticulum. In this review, we will summarize the molecular and cellular biology of JAK/STAT3 signaling and its functions under basal and stress conditions, which are adaptive, and then review maladaptive JAK/STAT3 signaling in animals and humans that lead to disease, as well as recent attempts to modulate them to treat these diseases. In addition, we will discuss how consideration of the noncanonical and stress-related functions of STAT3 cannot be ignored in efforts to target the canonical functions of STAT3, if the goal is to develop drugs that are not only effective but safe. SIGNIFICANCE STATEMENT: Key biological functions of Janus kinase (JAK)/signal transducer and activator of transcription (STAT)3 signaling can be delineated into two broad categories: those essential for normal cell and organ development and those activated in response to stress that are adaptive. Persistent or dysregulated JAK/STAT3 signaling, however, is maladaptive and contributes to many diseases, including diseases characterized by chronic inflammation and fibrosis, and cancer. A comprehensive understanding of JAK/STAT3 signaling in normal development, and in adaptive and maladaptive responses to stress, is essential for the continued development of safe and effective therapies that target this signaling pathway.

DTNA promotes HBV-induced hepatocellular carcinoma progression by activating STAT3 and regulating TGFβ1 and P53 signaling

OBJECTIVE

Hepatitis B virus (HBV) infection causes liver fibrosis, cirrhosis and hepatocellular carcinoma (HCC) development, but the underlying mechanism remains poorly understood. This study aimed to investigate the roles and molecular mechanisms of Dystrobrevin-α (DTNA) in HBV-induced liver cirrhosis and HCC pathogenesis.

METHODS

DTNA expression was bioinformatically analyzed using the GEO database. DTNA expression was silenced by transfection with shRNAs. Cell proliferation and apoptosis were evaluated by MTT and flow cytometry respectively. The expression of genes in mRNA or protein levels was assessed by quantitative RT-PCR and western blotting. The interaction between proteins was predicted with the String and GCBI online softwares, and then confirmed by co-immunoprecipitation. Animal models were established by injecting nude mice with AVV8-HBV1.3 vector.

RESULTS

Bioinformatics analysis showed a significantly increase in DTNA expression in HBV-positive liver cirrhosis and HCC patients. HBV infection caused a significantly increase in DTNA expression in HCC cell lines HepAD38 and HepG2.2.15. DTNA knockdown suppressed proliferation and promoted apoptosis of HBV-infected HepAD38 and HepG2.2.15 cells. HBV induced elevated expression of fibrosis-related genes Collagen II and TGFβ1 in LO-2 cells, which were suppressed by DTNA knockdown. DTNA directly binded with STAT3 protein to promote STAT3 phosphorylation and TGFβ1 expression and repress P53 expression in HBV-infected HepAD38 and LO-2 cells. The DTNA/STAT3 axis was activated during HBV-induced fibrosis, cirrhosis and HCC development in mouse model.

CONCLUSION

DTNA binds with and further activates STAT3 to induce TGFβ1 expression and repress P53 expression, thus promoting HBV-induced liver fibrosis, cirrhosis and hepatocellular carcinoma progression.

Targeting Activated Hepatic Stellate Cells Using Collagen-Binding Chitosan Nanoparticles for siRNA Delivery to Fibrotic Livers

Activated hepatic stellate cells (aHSCs) are the main orchestrators of the fibrotic cascade in inflamed livers, with transforming growth factor-beta (TGF-β) being the most potent pro-fibrotic cytokine. Hence, aHSCs serve as interesting therapeutic targets. However, drug delivery to aHSCs is hindered by excessive collagen deposition in the extracellular matrix (ECM) and capillarization of liver sinusoids. Chitosan-nanoparticles (CS-NPs) show intrinsic affinity for collagen, holding potential for drug delivery to fibrotic livers. Here, we employed CS-NPs for anti-TGF-β siRNA delivery, promoting delivery into aHSCs via modification with platelet-derived growth factor receptor-beta binding peptides. In-vitro experiments using aHSCs demonstrated the association of unmodified CS-NPs to the collagen-rich ECM, with reduced intracellular accumulation. Peptide-modified CS-NPs showed a higher propensity to localize intracellularly; however, this was only the case upon ECM-collagen reduction via collagenase treatment. Peptide-modified CS-NPs were more potent than unmodified CS-NPs in reducing TGF-β expression, implying that while collagen binding promotes liver accumulation, it hinders cell-specific siRNA delivery. In-vivo, CS-NPs successfully accumulated in fibrotic livers via collagen binding. Similar to in-vitro findings, when mice were pretreated with collagenase-loaded CS-NPs, the accumulation of peptide-modified NPs increased. Our findings demonstrate the usefulness of NPs modification with targeting ligands and collagenase treatment for aHSCs targeting and highlight the importance of chitosan-collagen binding in drug delivery to fibrotic diseases.

Anti-IL-20 antibody improved motor function and reduced glial scar formation after traumatic spinal cord injury in rats

BACKGROUND

Spinal cord injury (SCI) causes devastating neurological consequences, which can result in partial or total paralysis. Irreversible neurological deficits and glial scar formation are characteristic of SCI. Inflammatory responses are a major component of secondary injury and play a central role in regulating the pathogenesis of SCI. IL-20 is a proinflammatory cytokine involved in renal fibrosis and liver cirrhosis through its role in upregulating TGF-β1 production. However, the role of IL-20 in SCI remains unclear. We hypothesize that IL-20 is upregulated after SCI and is involved in regulating the neuroinflammatory response.

METHODS

The expression of IL-20 and its receptors was examined in SCI rats. The regulatory roles of IL-20 in astrocytes and neuron cells were examined. The therapeutic effects of anti-IL-20 monoclonal antibody (mAb) 7E in SCI rats were evaluated.

RESULTS

Immunofluorescence staining showed that IL-20 and its receptors were expressed in astrocytes, oligodendrocytes, and microglia in the spinal cord after SCI in rats. In vitro, IL-20 enhanced astrocyte reactivation and cell migration in human astrocyte (HA) cells by upregulating glial fibrillary acidic protein (GFAP), TGF-β1, TNF-α, MCP-1, and IL-6 expression. IL-20 inhibited cell proliferation and nerve growth factor (NGF)-derived neurite outgrowth in PC-12 cells through Sema3A/NRP-1 upregulation. In vivo, treating SCI rats with anti-IL-20 mAb 7E remarkably inhibited the inflammatory responses. 7E treatment not only improved motor and sensory functions but also improved spinal cord tissue preservation and reduced glial scar formation in SCI rats.

CONCLUSIONS

IL-20 might regulate astrocyte reactivation and axonal regeneration and result in the secondary injury in SCI. These findings demonstrated that IL-20 may be a promising target for SCI treatment.

The JAK2/STAT3 pathway inhibitor, AG490, suppresses the abnormal behavior of keloid fibroblasts in vitro

AG490 is a selective inhibitor of the Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway. The present study examined its effects on the abnormal behavior of human keloid fibroblasts (HKFs) and evaluated its potential use in the treatment of keloids. Human normal fibroblasts (HNFs) and HKFs were treated with increasing concentrations of AG490. The proliferation of HNFs and HKFs was inhibited by AG490 in both a time‑ and concentration‑dependent manner by increasing apoptosis and inducing G1 cell cycle arrest. The downregulation of cyclin D1 and connective tissue growth factor (CTGF) expression was associated with a decrease in STAT3 expression in response to AG490. The effects of AG490 on TGF‑β‑stimulated fibroblasts, including HNFs, HKFs and hypertrophic scar fibroblasts (HSFs) were also evaluated. The TGF‑β1‑stimulated excessive proliferation and CTGF production were markedly inhibited by the application of AG490 in the HNFs, HSFs and HKFs. In addition, the STAT3‑specific decoy oligodeoxynucleotides (SODNs) were transfected into HKFs. The invasive ability of the SODN‑transfected HKFs was determined and the expression of extracellular matrix components was quantified. Similarly, SODNs blocked the constitutive activation of STAT3. SODNs inhibited the invasion and progression of HKFs, possibly via the upregulation of the expression of tissue inhibitor of metalloproteinase‑2 (TIMP‑2), and the downregulation of the expression of matrix metalloproteinase‑2 (MMP‑2) and vascular endothelial growth factor (VEGF). On the whole, the findings of the present study demonstrate that STAT3‑specific elimination, such as the application of AG490 and decoy ODNs, may serve as promising therapeutic strategies for the treatment of keloids.

Dual TBK1/IKKɛ inhibitor amlexanox attenuates the severity of hepatotoxin-induced liver fibrosis and biliary fibrosis in mice

Although numerous studies have suggested that canonical IκB kinases (IKK) play a key role in the progression of liver fibrosis, the role of non-canonical IKKε and TANK-binding kinase 1 (TBK1) on the development and progression of liver fibrosis remains unclear. To demonstrate such issue, repeated injection of CCl4 was used to induce hepatotoxin-mediated chronic liver injury and biliary fibrosis was induced by 0.1% diethoxycarbonyl-1, 4-dihydrocollidine diet feeding for 4 weeks. Mice were orally administered with amlexanox (25, 50, and 100 mg/kg) during experimental period. Significantly increased levels of TBK1 and IKKε were observed in fibrotic livers or hepatic stellate cells (HSCs) isolated from fibrotic livers. Interestingly, amlexanox treatment significantly inhibited the phosphorylation of TBK1 and IKKε accompanied by reduced liver injury as confirmed by histopathologic analysis, decreased serum biochemical levels and fibro-inflammatory responses. Additionally, treatment of amlexanox promoted the fibrosis resolution. In accordance with these findings, amlexanox treatment suppressed HSC activation and its related fibrogenic responses by partially inhibiting signal transducer and activator of transcription 3. Furthermore, amlexanox decreased the activation and inflammatory responses in Kupffer cells. Collectively, we found that inhibition of the TBK1 and IKKε by amlexanox is a promising therapeutic strategy to cure liver fibrosis.

(-)-Catechin-7-O-β-d-Apiofuranoside Inhibits Hepatic Stellate Cell Activation by Suppressing the STAT3 Signaling Pathway

Hepatic fibrosis is characterized by the abnormal deposition of extracellular matrix (ECM) proteins. During hepatic fibrogenesis, hepatic stellate cell (HSC) activation followed by chronic injuries is considered a key event in fibrogenesis, and activated HSCs are known to comprise approximately 90% of ECM-producing myofibroblasts. Here, we demonstrated that (–)-catechin-7-O-β-d-apiofuranoside (C7A) significantly inhibited HSC activation via blocking the signal transducer and activator of transcription 3 (STAT3) signaling pathway. This is the first study to show the hepatic protective effects of C7A with possible mechanisms in vitro and in vivo. In our bioactivity screening, we figured out that the EtOH extract of Ulmus davidiana var. japonica root barks, which have been used as a Korean traditional medicine, inhibited collagen synthesis in HSCs. Four catechins isolated from the EtOAc fraction of the EtOH extract were compared with each other in terms of reduction in collagen, which is considered as a marker of hepatic protective effects, and C7A showed the strongest inhibitory effects on HSC activation in protein and qPCR analyses. As a possible mechanism, we investigated the effects of C7A on the STAT3 signaling pathway, which is known to activate HSCs. We found that C7A inhibited phosphorylation of STAT3 and translocation of STAT3 to nucleus. C7A also inhibited expressions of MMP-2 and MMP-9, which are downstream genes of STAT3 signaling. Anti-fibrotic effects of C7A were evaluated in a thioacetamide (TAA)-induced liver fibrosis model, which indicated that C7A significantly inhibited ECM deposition through inhibiting STAT3 signaling. C7A decreased serum levels of aspartate amino transferase and alanine transaminase, which were markedly increased by TAA injection. Moreover, ECM-associated proteins and mRNA expression were strongly suppressed by C7A. Our study provides the experimental evidence that C7A has inhibitory effects on HSC activation after live injury and has preventive and therapeutic potentials for the management of hepatic fibrosis.

Pin1 Plays Essential Roles in NASH Development by Modulating Multiple Target Proteins

Pin1 is one of the three known prolyl-isomerase types and its hepatic expression level is markedly enhanced in the obese state. Pin1 plays critical roles in favoring the exacerbation of both lipid accumulation and fibrotic change accompanying inflammation. Indeed, Pin1-deficient mice are highly resistant to non-alcoholic steatohepatitis (NASH) development by either a high-fat diet or methionine-choline-deficient diet feeding. The processes of NASH development can basically be separated into lipid accumulation and subsequent fibrotic change with inflammation. In this review, we outline the molecular mechanisms by which increased Pin1 promotes both of these phases of NASH. The target proteins of Pin1 involved in lipid accumulation include insulin receptor substrate 1 (IRS-1), AMP-activated protein kinase (AMPK) and acetyl CoA carboxylase 1 (ACC1), while the p60 of the NF-kB complex and transforming growth factor β (TGF-β) pathway appear to be involved in the fibrotic process accelerated by Pin1. Interestingly, Pin1 deficiency does not cause abnormalities in liver size, appearance or function. Therefore, we consider the inhibition of increased Pin1 to be a promising approach to treating NASH and preventing hepatic fibrosis.

miR-140-3p Knockdown Suppresses Cell Proliferation and Fibrogenesis in Hepatic Stellate Cells via PTEN-Mediated AKT/mTOR Signaling

PURPOSE

Liver fibrosis is a major cause of morbidity and mortality and the outcome of various chronic liver diseases. Activation of hepatic stellate cells (HSCs) is the key event in liver fibrosis. Studies have confirmed that miR-140-3p plays a potential regulatory effect on HSC activation. However, whether miR-140-3p mediates the liver fibrosis remains unknown.

MATERIALS AND METHODS

Expression of miR-140-3p was detected by real-time quantitative PCR (qPCR). Cell proliferation was measured by MTT, while cell apoptosis rate was determined via flow cytometry. Western blot assay was used to detect the expression of cleaved PARP. The fibrogenic effect was evaluated by expression of α-smooth muscle actin and desmin. Functional experiments were performed in transforming growth factor β1 (TGF-β1)-induced HSC-T6 cells with transfection of anti-miR-140-3p and/or siPTEN. Target binding between miR-140-3p and PTEN was predicted by the TargetScan database and identified using luciferase reporter assay and RNA immunoprecipitation.

RESULTS

TGF-β1 induced the activation of HSC-T6 cells, and miR-140-3p expression varied according to HSC-T6 cell activation status. Knockdown of miR-140-3p reduced cell proliferation and the expressions of α-SMA and desmin, as well as increased apoptosis, in TGF-β1-induced HSC-T6 cells, which could be blocked by PTEN silencing. Additionally, inactivation of the AKT/mTOR signaling pathway stimulated by miR-140-3p knockdown was abolished when silencing PTEN expression. PTEN was negatively regulated by miR-140-3p via direct binding in HSC-T6 cells.

CONCLUSION

miR-140-3p is an important mediator in HSC-T6 cell activation, and miR-140-3p knockdown suppresses cell proliferation and fibrogenesis in TGF-β1-induced HSC-T6 cells, indicating that miR-140-3p may be a potential novel molecular target for liver fibrosis.

miR-455-3p Alleviates Hepatic Stellate Cell Activation and Liver Fibrosis by Suppressing HSF1 Expression

Liver fibrosis is a common pathological process of end-stage liver diseases. However, the role of microRNA (miRNA) in liver fibrosis is poorly understood. The activated hepatic stellate cells (HSCs) are the major source of fibrogenic cells and play a central role in liver fibrosis. In this study, we investigated the differential expression of miRNAs in resting and transforming growth factor β1 (TGF-β1) activated HSCs by microarray analysis and found that miR-455-3p was significantly downregulated during HSCs activation. In addition, the reduction of miR-455-3p was correlated with liver fibrosis in mice with carbon tetrachloride (CCl₄), bile duct ligation (BDL), and high-fat diet (HFD)-induced liver fibrosis. Our functional analyses demonstrated that miR-455-3p inhibited expression of profibrotic markers and cell proliferation in HSCs in vitro. Moreover, miR-455-3p regulated heat shock factor 1 (HSF1) expression by binding to the 3′ UTR of its mRNA directly. Overexpression of HSF1 facilitated HSCs activation and proliferation by promoting heat shock protein 47 (Hsp47) expression, leading to activation of the TGF-β/Smad4 signaling pathway. To explore the clinical potential of miR-455-3p, we injected ago-miR-455-3p into mice with CCl₄-, BDL-, and HFD-induced hepatic fibrosis in vivo. The overexpression of miR-455-3p suppressed HSF1 expression and reduced fibrosis marker expression, which resulted in alleviated liver fibrosis in mice. In conclusion, our present study suggests that miR-455-3p inhibits the activation of HSCs through targeting HSF1 involved in the Hsp47/TGF-β/Smad4 signaling pathway. Therefore, miR-455-3p might be a promising therapeutic target for liver fibrosis.

A novel STAT3 inhibitor, STX-0119, attenuates liver fibrosis by inactivating hepatic stellate cells in mice

Liver fibrosis is characterized by formation of scar tissue in the liver. The role of STAT3 signaling has been implicated on activating hepatic stellate cells (HSC) to myofibroblast-like cells in liver fibrosis. Major factors that activate STAT3 signaling are TGF-β1 and IL-6, which are upregulated in the liver in patients afflicted with liver fibrosis. Recent reports indicate that not only IL-6, but also the non-canonical signaling pathway of TGF-β1 is associated with STAT3 signaling. In this study, we demonstrate a new function of the STAT3 inhibitor, STX-0119, in liver fibrosis. STX-0119 is an inhibitor of STAT3 dimerization, which is required for nuclear localization of STAT3. We first investigated the anti-fibrotic effect of STX-0119 in in vitro experiments. Exposure to STX-0119 inhibited the nuclear localization of STAT3 in HSCs, resulting in decreased expression of its target genes, such as col1a1 and αSMA. In addition, STX-0119 also inhibited the TGF-β1/IL-6-induced activation of HSCs. Next, we examined the in vivo effect of STX-0119 in the liver fibrosis mouse model using thioacetamide (TAA) and carbon tetrachloride (CCl₄). STX-0119 attenuated the TAA-induced liver fibrosis by inhibiting activation of HSCs to myofibroblast-like cells. Consistent with the in vivo results using TAA-induced liver fibrosis model, treatment of STX-0119 similarly attenuated CCl₄-induced liver fibrosis. In conclusion, we believe that STX-0119 inhibits the development of liver fibrosis by blocking the activation of hepatic stellate cells. These results indicate that STX-0119 is a potential new therapeutic strategy to prevent disease progression to cirrhosis.

Aberrant expression of miR-125a-3p promotes fibroblast activation via Fyn/STAT3 pathway during silica-induced pulmonary fibrosis

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.

Sparstolonin B (SsnB) attenuates liver fibrosis via a parallel conjugate pathway involving P53-P21 axis, TGF-beta signaling and focal adhesion that is TLR4 dependent

SsnB previously showed a promising role to lessen liver inflammation observed in a mouse model of NAFLD. Since NAFLD can progress to fibrosis, studies were designed to unravel its role in attenuating NAFLD associated fibrosis. Using both in vivo and in vitro approaches, the study probed the possible mechanisms that underlined the role of SsnB in mitigating fibrosis. Mechanistically, SsnB, a TLR4 antagonist, decreased TLR4-PI3k akt signaling by upregulating PTEN protein expression. It also decreased MDM2 protein activation and increased p53 and p21 gene and protein expression. SsnB also downregulated pro-fibrogenic hedgehog signaling pathway, inhibited hepatic stellate cell proliferation and induced apoptosis in hepatic stellate cells, a mechanism that was LPS dependent. Further, SsnB decreased fibrosis by antagonizing TLR4 induced TGFβ signaling pathway. Alternatively, SsnB augmented BAMBI (a TGFβ pseudo-receptor) expression in mice liver by inhibiting TLR4 signaling pathway and thus reduced TGFβ signaling, resulting in decreased hepatic stellate cell activation and extracellular matrix deposition. In vitro experiments on human hepatic stellate cell line showed that SsnB increased gene and protein expression of BAMBI. It also decreased nuclear co-localization of phospho SMAD2/3 and SMAD4 protein and thus attenuated TGFβ signaling in vitro. We also observed a significant decrease in phosphorylation of SMAD2/3 protein, decreased STAT3 activation, alteration of focal adhesion protein and stress fiber disassembly upon SsnB administration in hepatic stellate cells which further confirmed the antagonistic effect of SsnB on TLR4-induced fibrogenesis.

The STAT3 inhibitor S3I-201 suppresses fibrogenesis and angiogenesis in liver fibrosis

Liver fibrosis is a common pathological response to chronic hepatic injury. STAT3 is actively involved in the fibrogenesis and angiogenesis seen in liver fibrosis. S3I-201 (NSC 74859) is a chemical inhibitor of STAT3 activity, which blocks the dimerization of STAT3, STAT3-DNA binding and transcription activity. This study evaluated the effects of S3I-201 against liver fibrosis. S3I-201 inhibited the proliferation, migration, and actin filament formation in primary human hepatic stellate cells (HSCs), as well as the expression of α-SMA, collagen I and TIMP1 in both primary HSC and in a CCl₄-induced fibrosis mouse model. S3I-201 induced both apoptosis and cell cycle arrest in the HSC cell line (LX-2). S3I-201 inhibited the expression of fibrogenesis factors TGFβ1 and TGFβRII, as well as the downstream phosphorylation of Smad2, Smad3, Akt and ERK induced by TGFβ1. In addition to fibrogenesis, both in vitro and in vivo assays showed that S3I-201 inhibited angiogenesis through expression suppression of VEGF and VEGFR2. Moreover, S3I-201 also had a synergistic effect with sorafenib, an FDA approved liver cancer drug, in the proliferation, apoptosis, angiogenesis and fibrogenesis of HSC. S3I-201 suppressed liver fibrosis through multiple mechanisms, and combined with sorafenib, S3I-201 could be a potentially effective antifibrotic agent.

Bone marrow derived-mesenchymal stem cells downregulate IL17A dependent IL6/STAT3 signaling pathway in CCl4-induced rat liver fibrosis

Therapeutic potential of bone marrow–derived mesenchymal stem cells (BM-MSCs) has been reported in several animal models of liver fibrosis. Interleukin (IL) 17A, IL6 and Stat3 have been described to play crucial roles in chronic liver injury. However, the modulatory effect of MSCs on these markers was controversial in different diseases. BM-MSCs might activate the IL6/STAT3 signaling pathway and promote cell invasion in hepatocellular carcinoma, but the immunomodulatory role of BM-MSCs on IL17A/IL6/STAT3 was not fully elucidated in liver fibrosis. In the present study, we evaluated the capacity of the BM-MSCs in the modulation of cytokines milieu and signal transducers, based on unique inflammatory genes Il17a and Il17f and their receptors Il17rc and their effect on the IL6/STAT3 pathway in CCl₄-induced liver fibrosis in rats. A single dose of BM-MSCs was administered to the group with induced liver fibrosis, and the genes and proteins of interest were evaluated along six weeks after treatment. Our results showed a significant downregulation of Il17a, Il17ra, il17f and Il17rc genes. In accordance, BM-MSCs administration declined IL17, IL2 and IL6 serum proteins and downregulated IL17A and IL17RA proteins in liver tissue. Interestingly, BM-MSCs downregulated both Stat3 mRNA expression and p-STAT3, while Stat5a gene was downregulated and p-STAT5 protein was elevated. Also P-SMAD3 and TGFβR2 proteins were downregulated in response to BM-MSCs treatment. Collectively, we suggest that BM-MSCs might play an immunomodulatory role in the treatment of liver fibrosis through downregulation of IL17A affecting IL6/STAT3 signaling pathway.

Dynamics study on the role of curcumin on TGF-β1 expression and pathological changes in acute paraquat poisoned rats

Role of curcumin on TGF-β1 expression and pathological changes in acute paraquat (PQ) poisoned rats were investigated. Forty-eight SD rats were divided into three groups: control group, PQ group, and PQ + curcumin group, with 16 rats in each group. PQ group rats received the lavagation of PQ every day, PQ + curcumin group was given the lavagation of curcumin treatment on the basis of the PQ group. Control group received the lavagation of physiological saline. The body weight of rats was recorded every day. Six rats were randomly selected on the 1st, 3rd and 7th day after treatment from each group and sacrificed by cervical dislocation. The blood and liver tissues of each rat were collected. The morphology change of the liver tissue was observed by hematoxylin and eosin (H&E) staining. The expression level of TGF-β1 in the liver tissue was detected by western blot analysis and RT-qPCR. The blood samples were sent to the inspection section of the hospital for the detection of reactive oxygen species (ROS), alanine aminotransferase (ALT), aspartate aminotransferase (AST), malondialdehyde (MDA) and superoxide dismutase (SOD). On the 1st day after poisoning, the liver cells of PQ rats had obvious edema; obvious fatty degeneration was observed on the 3rd day; and large number of cavities appeared on the 7th day due to necrosis. For the PQ + curcumin group, liver cell edema appeared on the 3rd day, and mild swelling of liver cells was observed on the 7th day. Compared with the control group, the expression of TGF-β1 was increased in the PQ group. The TGF-β1 level in PQ + curcumin group rats reached the peak on the 3rd day, then decreased, and it was lower than those in PQ group. The level of ROS, ALT, AST, MDA of the rats in PQ + curcumin group reached the highest value on the 3rd day, while the level of SOD reached the lowest value; furthermore, the level of ROS, ALT, AST, MDA was lower than that in PQ group, while the level of SOD was higher than that of the PQ group. The results showed that curcumin can effectively inhibit the expression of TGF-β1, prevent PQ-induced liver cell oxidative damage and play an important role in the protection of liver function.

Contribution of STAT3 to Inflammatory and Fibrotic Diseases and Prospects for its Targeting for Treatment

Signal transducer and activator of transcription (STAT) 3 plays a central role in the host response to injury. It is activated rapidly within cells by many cytokines, most notably those in the IL-6 family, leading to pro-proliferative and pro-survival programs that assist the host in regaining homeostasis. With persistent activation, however, chronic inflammation and fibrosis ensue, leading to a number of debilitating diseases. This review summarizes advances in our understanding of the role of STAT3 and its targeting in diseases marked by chronic inflammation and/or fibrosis with a focus on those with the largest unmet medical need.

Aldehyde dehydrogenase 2 activation ameliorates CCl4 -induced chronic liver fibrosis in mice by up-regulating Nrf2/HO-1 antioxidant pathway

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is critical in the pathogenesis of alcoholic liver cirrhosis. However, the effect of ALHD2 on liver fibrosis remains to be further elucidated. This study aimed to demonstrate whether ALDH2 regulates carbon tetrachloride (CCl₄)‐induced liver fibrosis and to investigate the efficacy of Alda‐1, a specific activator of ALDH2, on attenuating liver fibrosis. ALDH2 expression was increased after chronic CCl₄ exposure. ALDH2 deficiency accentuated CCl₄‐induced liver fibrosis in mice, accompanied by increased expression of collagen 1α1, α‐SMA and TIMP‐1. Moreover, ALDH2 knockout triggered more ROS generation, hepatocyte apoptosis and impaired mitophagy after CCl₄ treatment. In cultured HSC‐T6 cells, ALDH2 knockdown by transfecting with lentivirus vector increased ROS generation and α‐SMA expression in an in vitro hepatocyte fibrosis model using TGF‐β1. ALDH2 overexpression by lentivirus or activation by Alda‐1 administration partly reversed the effect of TGF‐β1, whereas ALDH2 knockdown totally blocked the protective effect of Alda‐1. Furthermore, Alda‐1 administration protected against liver fibrosis in vivo, which might be mediated through up‐regulation of Nrf2/HO‐1 cascade and activation of Parkin‐related mitophagy. These findings indicate that ALDH2 deficiency aggravated CCl₄‐induced hepatic fibrosis through ROS overproduction, increased apoptosis and mitochondrial damage, whereas ALDH2 activation through Alda‐1 administration alleviated hepatic fibrosis partly through activation of the Nrf2/HO‐1 antioxidant pathway and Parkin‐related mitophagy, which indicate ALDH2 as a promising anti‐fibrotic target and Alda‐1 as a potential therapeutic agent in treating CCl₄‐induced liver fibrosis.

Luteolin-Mediated Inhibition of Hepatic Stellate Cell Activation via Suppression of the STAT3 Pathway

Hepatic stellate cell (HSC) activation is responsible for hepatic fibrogenesis and is associated with an overexpression of transcription 3 (STAT3). Luteolin, a common dietary flavonoid with potent anti-inflammatory properties, has previously demonstrated antifibrogenic properties in HSCs but the mechanism has not been fully elucidated. Activated human and rat hepatic stellate cell lines LX-2 and HSC-T6 were used to study the effects of luteolin on HSCs. Cellular proteins were determined by western blot and immunofluorescence. Cell proliferation was assessed with Alamar Blue assay. Luteolin significantly decreased LX-2 and HSC-T6 cell viability in a time-and-dose-dependent manner, as well as decreased HSC end-products α-smooth muscle actin (α-SMA), collagen I, and fibronectin. Luteolin decreased levels of total and phosphorylated STAT3, suppressed STAT3 nuclear translocation and transcriptional activity, and attenuated expression of STAT3-regulated proteins c-myc and cyclin D1. STAT3 specific inhibitors stattic and SH-4-54 demonstrated similar effects on HSC viability and α-SMA production. In LX-2 and HSC-T6 cells, luteolin demonstrates a potent ability to inhibit hepatic fibrogenesis via suppression of the STAT3 pathway. These results further elucidate the mechanism of luteolin as well as the effect of the STAT3 pathway on HSC activation.

RNAi screening identifies a mechanosensitive ROCK-JAK2-STAT3 network central to myofibroblast activation

Myofibroblasts play key roles in wound healing and pathological fibrosis. Here, we used an RNAi screen to characterize myofibroblast regulatory genes, using a high-content imaging approach to quantify α-smooth muscle actin stress fibers in cultured human fibroblasts. Screen hits were validated on physiological compliance hydrogels, and selected hits tested in primary fibroblasts from patients with idiopathic pulmonary fibrosis. Our RNAi screen led to the identification of STAT3 as an essential mediator of myofibroblast activation and function. Strikingly, we found that STAT3 phosphorylation, while responsive to exogenous ligands on both soft and stiff matrices, is innately active on a stiff matrix in a ligand/receptor-independent, but ROCK- and JAK2-dependent fashion. These results demonstrate how a cytokine-inducible signal can become persistently activated by pathological matrix stiffening. Consistent with a pivotal role for this pathway in driving persistent fibrosis, a STAT3 inhibitor attenuated murine pulmonary fibrosis when administered in a therapeutic fashion after bleomycin injury. Our results identify novel genes essential for the myofibroblast phenotype, and point to STAT3 as an important target in pulmonary fibrosis and other fibrotic diseases.

Global microRNA expression profiling in the liver biopsies of hepatitis B virus-infected patients suggests specific microRNA signatures for viral persistence and hepatocellular injury

Hepatitis B virus (HBV) can manipulate the microRNA (miRNA) regulatory networks in infected cells to create a permissive environment for viral replication, cellular injury, disease onset, and its progression. The aim of the present study was to understand the miRNA networks and their target genes in the liver of hepatitis B patients involved in HBV replication, liver injury, and liver fibrosis. We investigated differentially expressed miRNAs by microarray in liver biopsy samples from different stages of HBV infection and liver disease (immune-tolerant [n = 8], acute viral hepatitis [n = 8], no fibrosis [n = 16], early [F1+F2, n = 19] or late [F3+F4, n = 14] fibrosis, and healthy controls [n = 7]). miRNA expression levels were analyzed by unsupervised principal component analysis and hierarchical clustering. Analysis of miRNA-mRNA regulatory networks identified 17 miRNAs and 18 target gene interactions with four distinct nodes, each representing a stage-specific gene regulation during disease progression. The immune-tolerant group showed elevated miR-199a-5p, miR-221-3p, and Let-7a-3p levels, which could target genes involved in innate immune response and viral replication. In the acute viral hepatitis group, miR-125b-5p and miR-3613-3p were up, whereas miR-940 was down, which might affect cell proliferation through the signal transducer and activator of transcription 3 pathway. In early fibrosis, miR-34b-3p, miR-1224-3p, and miR-1227-3p were up, while miR-499a-5p was down, which together possibly mediate chronic inflammation. In advanced fibrosis, miR-1, miR-10b-5p, miR-96-5p, miR-133b, and miR-671-5p were up, while miR-20b-5p and miR-455-3p were down, possibly allowing chronic disease progression. Interestingly, only 8 of 17 liver-specific miRNAs exhibited a similar expression pattern in patient sera.

CONCLUSION

miRNA signatures identified in this study corroborate previous findings and provide fresh insight into the understanding of HBV-associated liver diseases which may be helpful in developing early-stage disease diagnostics and targeted therapeutics. (Hepatology 2018;67:1695-1709).

Cav-1 deficiency promotes liver fibrosis in carbon tetrachloride (CCl4)-induced mice by regulation of oxidative stress and inflammation responses

Caveolin-1 (Cav-1), as a membrane protein involved in the formation of caveolae, binds steroid receptors and endothelial nitric oxide synthase, limiting its translocation and activation. In the present study, we investigated the role of Cav-1 in the progression of hepatic fibrosis induced by carbon tetrachloride (CCl₄) in murine animals. Therefore, the wild type (WT) and Cav-1-knockout (Cav-1^-/-) mice were used in our study and subjected to CCl₄. The results indicated that CCl₄ induced the decrease of Cav-1 expression in liver tissue samples. And Cav-1^-/- intensified CCl₄-triggered hepatic injury, evidenced by the stronger hepatic histological alterations, serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels and liver terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells. CCl₄ led to oxidative stress, supported by the reduced superoxide dismutase (SOD) activity and glutathione (GSH) levels, as well as enhanced malondialdehyde (MDA) and O₂^- levels in liver samples. And the process was intensified by Cav-1^-/-. Additionally, CCl₄-caused hepatic inflammation was aggregated by Cav-1^-/- via further increasing the secretion of pro-inflammatory cytokines. Moreover, CCl₄-caused fibrosis was strengthened by Cav-1^-/-, which was evidenced by the up-regulation of α-smooth muscle actin (α-SMA), collagen alpha 1 type 1 (Col1A1), lysyl oxidase (Lox) and transforming growth factor-β1 (TGF-β1) in liver tissues. Similar results were observed in TGF-β1-stimulated hepatic stellate cells (HSCs) and LX-2 cells without Cav-1 expressions that in vitro, suppressing Cav-1 further accelerated TGF-β1-induced oxidative stress, inflammation and fibrosis development. In conclusion, our results indicated that Cav-1 played an important role in CCl₄-induced hepatic injury, which may be used as potential therapeutic target for hepatic fibrosis treatment.

Involvement of NF-κBIZ and related cytokines in age-associated renal fibrosis

Chronic inflammation is a major contributor to age-related nephropathic changes, including renal fibrosis. In this study, various experimental paradigms were designed to delineate the role played by NF-κBIZ (also known as IκBζ) in age-associated renal fibrosis. Analyses based on RNA-sequencing findings obtained by next generation sequencing (NGS) revealed the upregulations of NF-κBIZ and of IL-6 and MCP-1 (both known to be regulated by NF-κBIZ) during aging. The up-regulation of NF-κBIZ in aged rat kidneys coincided with increased macrophage infiltration. In LPS-treated macrophages, oxidative stress was found to play a pivotal role in NF-κBIZ expression, suggesting age-related oxidative stress is associated with NF-κBIZ activation. Furthermore, these in vitro findings were confirmed in LPS-treated old rats, which showed higher levels of oxidative stress and NF-κBIZ in kidneys than LPS-treated young rats. Additional in vitro experiments using macrophages and kidney fibroblasts demonstrated NF-κBIZ and related cytokines participate in fibrosis. In particular, increased levels of NF-κBIZ-associated cytokines in macrophages significantly up-regulated TGF-β induced kidney fibroblast activation. Moreover, experiments with NF-κBIZ knocked down macrophages showed reduced TGF-β-induced kidney fibroblast activation. The findings of the present study provide evidence regarding an involvement of NF-κBIZ in age-associated progressive renal fibrosis and provides potential targets for its prevention.

Cucurbitacin-B attenuates CCl4 -induced hepatic fibrosis in mice through inhibition of STAT-3

Liver fibrosis is a major health concern worldwide. Inhibitors of Signal Transducer and Activator of Transcription 3 (STAT3) have been reported to attenuate experimental liver fibrosis. Therefore, the aim of this study was to investigate the potential ameliorative effect of cucurbitacin-B (Cucu-B) against CCl₄ -induced liver fibrosis in mice. Treatment with Cucu-B (5 mg/kg) preserved hepatocellular membrane integrity and amended the metabolic function as indicated by preventing the rise of serum liver function markers. This was confirmed histologically. CCl₄ -induced oxidative stress was improved by Cucu-B treatment (1 and 5 mg/kg). Furthermore, Cucu-B treatment ameliorated the fibrotic state as evidenced by inhibiting the rise of hydroxyproline liver content and mitigating the overexpressions of collagen-1α, α-smooth muscle actin (α-SMA) and transforming growth factor beta (TGF-β) as well as the downexpression of matrix metalloproteinase-2 (MMP-2) mRNA. Importantly, STAT3 activity was inhibited by Cucu-B as confirmed by decreased phosphorylation of STAT3 without changing total STAT3 expression. This was substantiated by the reduced Bcl-2 together with increased Bax mRNA expressions with subsequent elevation of Bax/Bcl-2 ratio. In conclusion, Cucu-B hampers CCl₄ -induced liver fibrosis in mice. This can be attributed-at least partly-to inhibition of oxidative stress, inflammation and STAT3 signalling.

Inhibition of canonical WNT signaling pathway by β-catenin/CBP inhibitor ICG-001 ameliorates liver fibrosis in vivo through suppression of stromal CXCL12

Quiescent hepatic stellate cells (HSCs), in response to liver injury, undergo characteristic morphological transformation into proliferative, contractile and ECM-producing myofibroblasts. In this study, we investigated the implication of canonical Wnt signaling pathway in HSCs and liver fibrogenesis. Canonical Wnt signaling pathway activation and inhibition using β-catenin/CBP inhibitor ICG001 was examined in-vitro in TGFβ-activated 3T3, LX2, primary human HSCs, and in-vivo in CCl₄-induced acute liver injury mouse model. Fibroblasts-conditioned medium studies were performed to assess the Wnt-regulated paracrine factors involved in crosstalk between HSCs-macrophages and HSCs-endothelial cells. Canonical Wnt signaling pathway components were significantly up-regulated in-vitro and in-vivo. In-vitro, ICG-001 significantly inhibited fibrotic parameters, 3D-collagen contractility and wound healing. Conditioned medium induced fibroblasts-mediated macrophage and endothelial cells activation was significantly inhibited by ICG-001. In-vivo, ICG-001 significantly attenuated collagen accumulation and HSC activation. Interestingly, ICG-001 drastically inhibited macrophage infiltration, intrahepatic inflammation and angiogenesis. We further analyzed the paracrine factors involved in Wnt-mediated effects and found CXCL12 was significantly suppressed both in-vitro and in-vivo following Wnt inhibition. Wnt-regulated CXCL12 secretion from activated HSCs potentiated macrophage infiltration and activation, and angiogenesis. Pharmacological inhibition of canonical Wnt signaling pathway via suppression of stromal CXCL12 suggests a potential therapeutic approach targeting activated HSCs in liver fibrosis.

Activation of STAT3 integrates common profibrotic pathways to promote fibroblast activation and tissue fibrosis

Signal transducer and activator of transcription 3 (STAT3) is phosphorylated by various kinases, several of which have been implicated in aberrant fibroblast activation in fibrotic diseases including systemic sclerosis (SSc). Here we show that profibrotic signals converge on STAT3 and that STAT3 may be an important molecular checkpoint for tissue fibrosis. STAT3 signaling is hyperactivated in SSc in a TGFβ-dependent manner. Expression profiling and functional studies in vitro and in vivo demonstrate that STAT3 activation is mediated by the combined action of JAK, SRC, c-ABL, and JNK kinases. STAT3-deficient fibroblasts are less sensitive to the pro-fibrotic effects of TGFβ. Fibroblast-specific knockout of STAT3, or its pharmacological inhibition, ameliorate skin fibrosis in experimental mouse models. STAT3 thus integrates several profibrotic signals and might be a core mediator of fibrosis. Considering that several STAT3 inhibitors are currently tested in clinical trials, STAT3 might be a candidate for molecular targeted therapies of SSc.

STAT3 is a transcription factor that is activated in fibrotic diseases such as systemic sclerosis. Here the authors show that STAT3 is the converging point for multiple pro-fibrotic signalling pathways, and that its genetic ablation or inhibition ameliorate skin fibrosis in mouse models.

Endothelial fibrosis induced by suppressed STAT3 expression mediated by signaling involving the TGF-β1/ALK5/Smad pathway

During systemic inflammatory pathologies, mediators of inflammation circulate in the bloodstream and interact with endothelial cells (ECs), resulting in endothelial dysfunction that maintains and enhances the pathological condition. Inflammatory mediators change the protein expression profile of ECs, which become activated fibroblasts via endothelial-to-mesenchymal transition. This process is characterized by downregulated endothelial proteins and strongly upregulated fibrotic-specific genes and extracellular matrix-forming proteins. The main inductor of endothelial fibrosis is transforming growth factor-β1 (TGF-β1), which acts through the TGF-β1/activin receptor-like kinase 5 (ALK5)/Smads intracellular signaling pathway. The signal transducer and activator of transcription 3 (STAT3) is also involved in fibrosis in several tissues (e.g. heart and vascular system), where STAT3 signaling decreases TGF-β1-induced responses by directly interacting with Smad proteins, suggesting that decreased STAT3 could induce TGF-β1-mediated fibrosis. However, it is unknown if suppressed STAT3 expression induces EC fibrosis through a mechanism involving the TGF-β signaling pathway. The present study evaluated the fibrotic actions of STAT3 suppression in ECs and investigated TGF-β1/ALK5/Smad4 signaling pathway participation. Suppressed STAT3 expression stimulated fibrotic conversion in ECs, as mediated by protein expression reprograming that decreased endothelial marker expression and increased fibrotic and extracellular matrix protein levels. The potential mechanism underlying these changes was dependent on TGF-β1 secretion, the ALK5 activation pathway, and Smad4 translocation into the nucleus. We conclude that suppressed STAT3 expression converts ECs into activated fibroblasts via TGF-β1/ALK5/Smad4 signaling pathway involvement.