EZH2-mediated repression of Dkk1 promotes hepatic stellate cell activation and hepatic fibrosis

The landscape of histone modification in organ fibrosis

An increase in fibrous connective tissue and a decrease in parenchymal cells in organ tissues are the primary pathological alterations linked to organ fibrosis. If fibrosis is not treated, organ structure is destroyed, function can decline, or even fail, posing a serious risk to human life and health. Numerous organs develop fibrosis, and organ fibroproliferative illnesses account for almost 45% of patient deaths from various diseases in the industrialized world, as well as a major cause of disability and mortality in many other diseases. Recently, it has become evident that histone modification is an important way to regulate gene expression in organ fibrosis. Histone modifications alter the structure of chromatin, thereby affecting gene accessibility. Histone acetylation modifications relax chromatin, making it easier for gene transcription factors to access DNA, thereby promoting gene transcription. In addition, histone modifications recruit other proteins to interact with chromatin to form complexes that further regulate gene expression. Histone methylation modifications recruit methylation-reading proteins that recognize methylation marks and alter gene expression status. It not only affects the normal physiological function of cells, but also plays an important role in organ fibrosis. This article reviews the important role played by histone modifications in organ fibrosis and potential therapeutic approaches.

Targeting histone methylation and demethylation for non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the leading chronic liver disease worldwide, facing increasing challenges in terms of prevention and treatment. The methylation of lysine and arginine residues on histone proteins is dynamically controlled by histone methyltransferases (HMTs) and histone demethylases (HDMs), regulating chromatin structure and gene transcription. Mutations, genetic translocations, and altered gene expression involving HMTs and HDMs are frequently observed in NAFLD. HMTs and HDMs are receiving increasing attention in regulating NALFD. Targeting specific HMTs and HDMs for drug development is becoming a new strategy for treating NAFLD. This review provides a comprehensive summary of the regulatory mechanism of histone methylation/demethylation in NAFLD. Additionally, we discuss the potential applications of HMTs and HDMs inhibitors in preventing NAFLD, which may provide a scientific basis for the treatment of NAFLD.

EZH2-H3K27me3-Mediated Epigenetic Silencing of DKK1 Induces Nucleus Pulposus Cell Pyroptosis in Intervertebral Disc Degeneration by Activating NLRP3 and NAIP/NLRC4

Nucleus pulposus (NP) cell pyroptosis is crucial for intervertebral disc degeneration (IDD). However, the precise mechanisms underlying pyroptosis in IDD remain elusive. Therefore, this study aimed to investigate how dickkopf-1 (DKK1) influences NP cell pyroptosis and delineate the regulatory mechanisms of IDD. Behavioral tests and histological examinations were conducted in rat IDD models to assess the effect of DKK1 on the structure and function of intervertebral discs. Detected pyroptosis levels using Hoechst 33,342/propidium iodide (PI) double staining, and determined pyroptosis-related protein expression via western blotting. The cellular mechanisms of DKK1 in pyroptosis were explored in interleukin (IL)-1β-induced NP cells transfected with or without DKK1 overexpression plasmids (oe-DKK1). In addition, IL-1β-treated NP cells transfected with sh-EZH2 and/or sh-DKK1 were utilized to clarify the interplay between the enhancer of zeste homologue 2 (EZH2) and DKK1 in pyroptosis. Additionally, the epigenetic regulation of DKK1 by EZH2 was explored in NP cells treated with the EZH2 inhibitors GSK126/DZNep. DKK1 expression decreased in IDD rats. Transfection with oe-DKK1 reduced pro-inflammatory factors and extracellular matrix markers in IDD rats. In IL-1β-induced NP cells, DKK1 overexpression suppressed pyroptosis and inhibited the NLRP3 and NAIP/NLRC4 inflammasome activation. EZH2 knockdown increased DKK1 expression and reduced pyroptosis-related proteins. Conversely, DKK1 downregulation reversed the inhibitory effects of EZH2 knockdown on pyroptosis. Furthermore, EZH2 suppressed DKK1 expression via H3K27 methylation at the DKK1 promoter. EZH2 negatively regulates DKK1 expression via H3K27me3 methylation, promoting NP cell pyroptosis in IDD patients. This regulatory effect involves the activation of NLRP3 and NAIP/NLRC4 inflammasomes.

Liver Fibrosis: From Basic Science towards Clinical Progress, Focusing on the Central Role of Hepatic Stellate Cells

The burden of chronic liver disease is globally increasing at an alarming rate. Chronic liver injury leads to liver inflammation and fibrosis (LF) as critical determinants of long-term outcomes such as cirrhosis, liver cancer, and mortality. LF is a wound-healing process characterized by excessive deposition of extracellular matrix (ECM) proteins due to the activation of hepatic stellate cells (HSCs). In the healthy liver, quiescent HSCs metabolize and store retinoids. Upon fibrogenic activation, quiescent HSCs transdifferentiate into myofibroblasts; lose their vitamin A; upregulate α-smooth muscle actin; and produce proinflammatory soluble mediators, collagens, and inhibitors of ECM degradation. Activated HSCs are the main effector cells during hepatic fibrogenesis. In addition, the accumulation and activation of profibrogenic macrophages in response to hepatocyte death play a critical role in the initiation of HSC activation and survival. The main source of myofibroblasts is resident HSCs. Activated HSCs migrate to the site of active fibrogenesis to initiate the formation of a fibrous scar. Single-cell technologies revealed that quiescent HSCs are highly homogenous, while activated HSCs/myofibroblasts are much more heterogeneous. The complex process of inflammation results from the response of various hepatic cells to hepatocellular death and inflammatory signals related to intrahepatic injury pathways or extrahepatic mediators. Inflammatory processes modulate fibrogenesis by activating HSCs and, in turn, drive immune mechanisms via cytokines and chemokines. Increasing evidence also suggests that cellular stress responses contribute to fibrogenesis. Recent data demonstrated that LF can revert even at advanced stages of cirrhosis if the underlying cause is eliminated, which inhibits the inflammatory and profibrogenic cells. However, despite numerous clinical studies on plausible drug candidates, an approved antifibrotic therapy still remains elusive. This state-of-the-art review presents cellular and molecular mechanisms involved in hepatic fibrogenesis and its resolution, as well as comprehensively discusses the drivers linking liver injury to chronic liver inflammation and LF.

Paeoniflorin promotes PPARγ expression to suppress HSCs activation by inhibiting EZH2-mediated histone H3K27 trimethylation

BACKGROUND

The alleviating effect of paeoniflorin (Pae) on liver fibrosis has been established; however, the molecular mechanism and specific target(s) underlying this effect remain elusive.

PURPOSE

This study was to investigate the molecular mechanism underlying the regulatory effect of Pae on hepatic stellate cells (HSCs) activation in liver fibrosis, with a specific focus on the role of Pae in modulating histone methylation modifications.

METHODS

The therapeutic effect of Pae was evaluated by establishing in vivo and in vitro models of carbon tetrachloride (CCl4)-induced mice and transforming growth factor β1 (TGF-β1)-induced LX-2 cells, respectively. Molecular docking, surface plasmon resonance (SPR), chromatin immunoprecipitation-quantitative real time PCR (ChIP-qPCR) and other molecular biological methods were used to clarify the molecular mechanism of Pae regulating HSCs activation.

RESULTS

Our study found that Pae inhibited HSCs activation and histone trimethylation modification in liver of CCl4-induced mice and LX-2 cells. We demonstrated that the inhibitory effect of Pae on the activation of HSCs was dependent on peroxisome proliferator-activated receptor γ (PPARγ) expression and enhancer of zeste homolog 2 (EZH2). Mechanistically, Pae directly binded to EZH2 to effectively suppress its enzymatic activity. This attenuation leaded to the suppression of histone H3K27 trimethylation in the PPARγ promoter region, which induced upregulation of PPARγ expression.

CONCLUSION

This investigative not only sheds new light on the precise targets that underlie the remission of hepatic fibrogenesis induced by Pae but also emphasizes the critical significance of EZH2-mediated H3K27 trimethylation in driving the pathogenesis of liver fibrosis.

Invigorating human MSCs for transplantation therapy via Nrf2/DKK1 co-stimulation in an acute-on-chronic liver failure mouse model

Background

Since boosting stem cell resilience in stressful environments is critical for the therapeutic efficacy of stem cell-based transplantations in liver disease, this study aimed to establish the efficacy of a transient plasmid-based preconditioning strategy for boosting the capability of mesenchymal stromal cells (MSCs) for anti-inflammation/antioxidant defenses and paracrine actions in recipient hepatocytes.

Methods

Human adipose mesenchymal stem cells (hADMSCs) were subjected to transfer, either with or without the nuclear factor erythroid 2-related factor 2 (Nrf2)/Dickkopf1 (DKK1) genes, followed by exposure to TNF-α/H2O2. Mouse models were subjected to acute chronic liver failure (ACLF) and subsequently injected with either transfected or untransfected MSCs. These hADMSCs and ACLF mouse models were used to investigate the interaction between Nrf2/DKK1 and the hepatocyte receptor cytoskeleton-associated protein 4 (CKAP4).

Results

Activation of Nrf2 and DKK1 enhanced the anti-stress capacity of MSCs in vitro. In a murine model of ACLF, transient co-overexpression of Nrf2 and DKK1 via plasmid transfection improved MSC resilience against inflammatory and oxidative assaults, boosted MSC transplantation efficacy, and promoted recipient liver regeneration due to a shift from the activation of the anti-regenerative IFN-γ/STAT1 pathway to the pro-regenerative IL-6/STAT3 pathway in the liver. Importantly, the therapeutic benefits of MSC transplantation were nullified when the receptor CKAP4, which interacts with DKK1, was specifically removed from recipient hepatocytes. However, the removal of the another receptor low-density lipoprotein receptor-related protein 6 (LRP6) had no impact on the effectiveness of MSC transplantation. Moreover, in long-term observations, no tumorigenicity was detected in mice following transplantation of transiently preconditioned MSCs.

Conclusions

Co-stimulation with Nrf2/DKK1 safely improved the efficacy of human MSC-based therapies in murine models of ACLF through CKAP4-dependent paracrine mechanisms.

27-Hydroxycholesterol induces liver fibrosis via down-regulation of trimethylation of histone H3 at lysine 27 by activating oxidative stress; effect of nutrient interventions

BACKGROUND

Chronic liver injury caused by activation of hepatic stellate cells (HSCs) is a key event in the development of liver fibrosis (LF). A high-cholesterol diet can prompt accumulation of free cholesterol in HSCs, which promotes HSC activation and progression of LF.

OBJECTIVE

27-Hydroxycholesterol (27HC) is the most abundant cholesterol metabolite. Here, we investigated whether the HSC activation and LF induced by high cholesterol is caused by its metabolite 27HC, and whether TGFβ classical signaling were involved in these processes.

METHODS

In vitro, LX2 and HSC-T6 cells were used to explore the effects of 27HC on activation of HSCs, while LSECs were used to observe the effects of 27HC on capillarization. In vivo, zebrafish were used to assess the effect of 27HC on LF.

RESULTS

The cholesterol metabolite 27HC promoted the proliferation of HSCs and up-regulated expression of COL-1 and α-SMA as well as CTGF and TIMP1. Also, 27HC up-regulated expression of Smad2/3 and phosphorylated Smad2/3 in HSCs. Furthermore, 27HC-induced up-regulation of COL-1, α-SMA, CTGF, and TIMP1 protein levels was inhibited by Smad2/3 knockout. In addition, 27HC down-regulated H3K27me3 by inhibition of EZH2 and promotion of UTX and JMJD3 expression via the TGFβ signaling, thereby inducing activation of HSCs. Notably, 27HC significantly aggravated the pathological damage induced by DEN, and induced deposition of collagen fibers in zebrafish liver. Folic acid (FA) and resveratrol (RES) both reduced 27HC-induced production of reactive oxygen species (ROS) and inhibited the effects of TGFβ signaling on EZH2, UTX, and JMJD3, thereby increasing H3K27me3, and finally jointly inhibiting LF.

CONCLUSION

Cholesterol is metabolized to 27HC, which mediates activation of HSCs and onset of LF. Reduced expression of H3k27me3 by TGFβ signaling is crucial to 27HC-induced LF. FA and RES ameliorated activation of HSCs and LF by reducing 27HC-induced production of ROS and regulating of H3K27me3.

N6-methyladenosine-modified circIRF2, identified by YTHDF2, suppresses liver fibrosis via facilitating FOXO3 nuclear translocation

Circular RNA (circRNA) has been implicated in liver fibrosis and modulated by multiple elusive molecular mechanisms, while the effects of N6-methyladenosine (m6A) modification on circRNA are still elusive. Herein, we identify circIRF2 from our circRNA sequencing data, which decreased in liver fibrogenesis stage and restored in resolution stage, indicating that dysregulated circIRF2 may be closely associated with liver fibrosis. Gain/loss-of-function analysis was performed to evaluate the effects of circIRF2 on liver fibrosis at both the fibrogenesis and resolution in vivo. Ectopic expression of circIRF2 attenuated liver fibrogenesis and HSCs activation at the fibrogenesis stage, whereas downregulation of circIRF2 impaired mouse liver injury repair and inflammation resolution. Mechanistically, YTHDF2 recognized m6A-modified circIRF2 and diminished circIRF2 stability, partly accounting for the decreased circIRF2 in liver fibrosis. Microarray was applied to investigate miRNAs regulated by circIRF2, our data elucidate cytoplasmic circIRF2 may directly harbor miR-29b-1-5p and competitively relieve its inhibitory effect on FOXO3, inducing FOXO3 nuclear translocation and accumulation. Clinically, circIRF2 downregulation was prevalent in liver fibrosis patients compared with healthy individuals. In summary, our findings offer a novel insight into m6A modification-mediated regulation of circRNA and suggest that circIRF2 may be an exploitable prognostic marker and/or therapeutic target for liver fibrosis.

Fibrosis-the tale of H3K27 histone methyltransferases and demethylases

Fibrosis, or excessive scarring, is characterized by the emergence of alpha-smooth muscle actin (αSMA)-expressing myofibroblasts and the excessive accumulation of fibrotic extracellular matrix (ECM). Currently, there is a lack of effective treatment options for fibrosis, highlighting an unmet need to identify new therapeutic targets. The acquisition of a fibrotic phenotype is associated with changes in chromatin structure, a key determinant of gene transcription activation and repression. The major repressive histone mark, H3K27me3, has been linked to dynamic changes in gene expression in fibrosis through alterations in chromatin structure. H3K27-specific homologous histone methylase (HMT) enzymes, Enhancer of zeste 1 and 2 (EZH1, EZH2), which are the alternative subunits of the Polycomb Repressive Complex 2 (PRC2) and demethylase (KDM) enzymes, Ubiquitously transcribed tetratricopeptide repeat, X chromosome (UTX), and Lysine demethylase 6B (KDM6B), are responsible for regulating methylation status of H3K27me3. In this review, we explore how these key enzymes regulate chromatin structure to alter gene expression in fibrosis, highlighting them as attractive targets for the treatment of fibrosis.

EZH2 serves as a promising therapeutic target for fibrosis

Fibrosis affects the function of many organs and tissues, and its persistent development can lead to tissue sclerosis and cancer, even leading to death further. Recent studies suggested that enhancer of zeste homolog 2 (EZH2), a major regulator of epigenetic repression, played an important role in the occurrence and development of fibrosis through gene silencing or transcriptional activation. As the most studied and powerful pro-fibrotic cytokine closely related to EZH2, TGF-β1 was primarily involved in the regulation of fibrosis along with the typical Smads and non-Smads signaling pathways. In addition, EZH2 inhibitors demonstrated inhibitory effects in several types of fibrosis. This review summarized the relationship underlying the action of EZH2, TGF-β1/Smads, and TGF-β1/non-Smads with fibrosis and described the research progress of EZH2 inhibitors in the treatment of fibrosis.

Epigenetics as a versatile regulator of fibrosis

Fibrosis, a process caused by excessive deposition of extracellular matrix (ECM), is a common cause and outcome of organ failure and even death. Researchers have made many efforts to understand the mechanism of fibrogenesis and to develop therapeutic strategies; yet, the outcome remains unsatisfactory. In recent years, advances in epigenetics, including chromatin remodeling, histone modification, DNA methylation, and noncoding RNA (ncRNA), have provided more insights into the fibrotic process and have suggested the possibility of novel therapy for organ fibrosis. In this review, we summarize the current research on the epigenetic mechanisms involved in organ fibrosis and their possible clinical applications.

Long non-coding RNA telomerase RNA elements improve glucocorticoid-induced osteoporosis by EZH2 to regulate DKK1

BACKGROUND

Glucocorticoid-induced osteoporosis is the most common secondary cause of osteoporosis, which increases the risk of fracture. Long non-coding RNA telomerase RNA elements (TERC) has been proven to be closely related to osteoporosis. However, the role of TERC in glucocorticoid-induced osteoporosis and its underlying molecular mechanism remains unclear.

METHODS

The in vitro model of osteoporosis was established after bone marrow mesenchymal stem cells (BMSCs) were exposed to dexamethasone (DEX). The cell viability, alkaline phosphatase (ALP) activity and mineralized nodules of BMSCs were evaluated. The messenger RNA and protein levels were detected by quantitative real-time polymerase chain reaction and Western blot. The interaction between TERC, enhancer of zeste homolog 2 (EZH2) and dickkopf-1 (DKK1) was confirmed by chromatin immunoprecipitation and RNA immunoprecipitation assays.

RESULTS

Bone marrow mesenchymal stem cells were isolated, identified and induced osteogenic differentiation. The findings showed that the levels of osteogenic marker genes, including ALP, Runt-related transcription factor 2 (RUNX2) and osteocalcin (OCN) in BMSCs were increased dependent on the osteogenic induction time. Similarly, TERC was significantly increased, but DKK1 was significantly decreased during BMSC osteogenic differentiation. Functional research showed that TERC overexpression promoted cell viability, ALP activity and mineralized nodules of BMSCs and increased the levels of osteogenic differentiation-related genes (ALP, RUNX2 and OCN), and TERC overexpression increased EZH2 protein level. Moreover, the decrease of cell viability, ALP activity and mineralized nodules induced by DEX was reversed by TERC overexpression. Furthermore, TERC inhibited DKK1 expression by promoting the histone modification of DKK1, and TERC overexpression alleviated DEX suppressed osteogenic differentiation of BMSCs by interaction with EZH2 to regulate DKK1.

CONCLUSION

Our findings illustrated that TERC overexpression alleviated DEX-induced osteoporosis by recruiting EZH2 to regulate DKK1. Our research provided a novel direction for the treatment of glucocorticoid-induced osteoporosis.

TGF-β1/Smad3 upregulates UCA1 to promote liver fibrosis through DKK1 and miR18a

TGF-β1 is the strongest cytokine known to promote liver fibrosis. It has been previously demonstrated that the activation of TGF-β1 initiates a temporary collagen accumulation program, which is important for wound repair in several organs. Furthermore, temporary extracellular matrix enhancement often leads to progressive fibrosis, which is accountable for cases of severe morbidity and mortality worldwide. However, its action mechanism has not been fully explored. It was previously reported that UCA1 could promote its occurrence and development in various tumors. Importantly, it was reported that TGF-β1 could activate the expression of UCA1 in liver cancer, gastric cancer, and breast cancer. However, the role of UCA1 in organ fibrosis, including liver fibrosis, remains unreported. The present study reported for the first time that TGF-β1/Smad3 could promote liver fibrosis by upregulating UCA1, which further affected DKK1 and collagen, such as COL1A1, COL1A2, and COL3A1. Meanwhile, UCA1 could competitively bind with miR18a to stabilize Smad3 to constitute a positive feedback pathway, which played a significant role in the promotion of liver fibrosis. Altogether, the present study provides a theoretical basis for devising promising treatment strategies for liver fibrosis. KEY MESSAGES : UCA1 was found to promote the progression of liver fibrosis in vitro. UCA1 is regulated by TGF-β1 and promotes liver fibrosis through the canonical Smad pathway. UCA1 can competitively bind with miR18a, promote liver fibrosis by stabilizing Smad3, and form a UCA1-miR18a/Smad3 positive feedback. UCA1 binds EZH2 to inhibit the DKK1 expression and promote liver fibrosis.

Human amniotic mesenchymal stem cells-derived IGFBP-3, DKK-3, and DKK-1 attenuate liver fibrosis through inhibiting hepatic stellate cell activation by blocking Wnt/β-catenin signaling pathway in mice

Background

Liver fibrosis is an outcome of restoring process in chronic liver injury. Human amniotic mesenchymal stem cells (hAMSCs) derived from amniotic membrane have multilineage differentiation, immunosuppressive, and anti-inflammatory potential which makes them suitable for treating liver fibrosis. This study aimed to explore the effect and mechanism of hAMSCs on liver fibrosis.

Methods

hAMSCs were transplanted into carbon tetrachloride (CCl₄)-induced liver fibrosis mice via tail vein, and the effects of hAMSCs on hepatic fibrosis were assessed. The effects of hAMSCs and hAMSCs conditional medium (CM) on the activation of hepatic stellate cells (HSCs) were investigated in vivo and in vitro. Antibody array assay was used to identify the cytokines secreted by hAMSCs that may inhibit the activation of HSCs. Finally, the underlying mechanisms were explored by assessing IGF-1R/PI3K/AKT and GSK3β/β-catenin signaling pathways in the activated HSCs (LX-2) with hAMSCs and hAMSCs transfected with corresponding siRNAs.

Results

Our results showed that hAMSCs possessed the characterizations of mesenchymal stem cells. hAMSCs significantly reduced liver fibrosis and improved liver function in mice by inhibiting HSCs activation in vivo. Both hAMSCs and hAMSC-CM remarkably inhibited the collagen deposition and activation of LX-2 cells in vitro. Antibody array assay showed that insulin-like growth factor binding protein-3 (IGFBP-3), Dickkopf-3 (DKK-3), and Dickkopf-1 (DKK-1) were highly expressed in the co-culture group and hAMSC-CM group compared with LX-2 group. Western blot assay demonstrated that IGFBP-3, DKK-3, and DKK-1 derived from hAMSCs inhibit LX-2 cell activation through blocking canonical Wnt signaling pathway.

Conclusions

Our results demonstrated that IGFBP-3, Dkk3, and DKK-1 secreted by hAMSCs attenuated liver fibrosis in mice through inhibiting HSCs activation via depression of Wnt/β-catenin signaling pathway, suggesting that hAMSCs or hAMSC-CM provides an alternative therapeutic approach for the treatment of liver fibrosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02906-z.

lncRNAs UC.145 and PRKG1-AS1 Determine the Functional Output of DKK1 in Regulating the Wnt Signaling Pathway in Gastric Cancer

DKK1 inhibits the canonical Wnt signaling pathway that is known to be involved in various cancers. However, whether DKK1 acts as an oncogene or tumor suppressor gene remains controversial. Furthermore, the DKK1-regulating mechanism in gastric cancer has not yet been defined. The aim of this study was to explore whether the ultraconserved region UC.145 regulates epigenetic changes in DKK1 expression in gastric cancer. Microarray analysis revealed that UC.145 exhibited the highest binding affinity to EZH2, a histone methyltransferase. The effects of UC.145 inactivation were assessed in gastric cancer cell lines using siRNA. The results indicated that UC.145 triggers DKK1 methylation via interaction with EZH2 and is involved in the canonical Wnt signaling pathway. Additionally, interaction between UC.145 and another long non-coding RNA adjacent to DKK1, PRKG1-AS1, induced a synergistic effect on Wnt signaling. The regulation of these three genes was closely associated with patient overall survival. Inactivation of UC.145 induced apoptosis and inhibited the growth and migratory, invasive, and colony-forming abilities of gastric cancer cells. The study findings provide insights into Wnt signaling in gastric cancer and support UC.145 as a potential novel predictive biomarker for the disease.

LncRNA MEG3 up-regulates SIRT6 by ubiquitinating EZH2 and alleviates nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a global health threat. Here, we presented the significant role of a novel signaling axis comprising long non-coding RNA maternally expressed gene 3 (MEG3), enhancer of zeste homolog 2 (EZH2), and sirtuin 6 (SIRT6) in controlling lipid accumulation, inflammation, and the progression of NAFLD. Mice fed with high-fat diet (HFD) were established as in vitro and in vivo NAFLD models, respectively. Lipid accumulation was measured by oil red O staining and assays for triglycerides or cholesterol. Inflammation was examined by ELISA for pro-inflammatory cytokines. Gene expressions were examined by RT-qPCR or Western blot. Interactions between key signaling molecules were examined by combining expressional analysis, RNA immunoprecipitation, cycloheximide stability assay, co-immunoprecipitation, and chromatin immunoprecipitation. MEG3 level was reduced in FFA-challenged hepatocytes or liver from HFD-fed mice, and the reduction paralleled the severity of NAFLD in clinic. Overexpressing MEG3 suppressed FFA-induced lipid accumulation or inflammation in hepatocytes. By promoting the ubiquitination and degradation of EZH2, MEG3 upregulated SIRT6, an EZH2 target. SIRT6 essentially mediated the protective effects of MEG3 in hepatocytes. Consistently, overexpressing MEG3 alleviated HFD-induced NAFLD in vivo. By controlling the expressions of genes involved in lipid metabolism and inflammation, the MEG3/EZH2/SIRT6 axis significantly suppressed lipid accumulation and inflammation in vitro, and NAFLD development in vivo. Therefore, boosting MEG3 level may benefit the treatment of NAFLD.

Adenoviral Transduction of Dickkopf-1 Alleviates Silica-Induced Silicosis Development in Lungs of Mice

Silicosis is an occupational disease caused by inhalation of silica dust, which is hallmarked by progressive pulmonary fibrosis associated with poor prognosis. Wnt/β-catenin signaling is implicated in the development of fibrosis and is a therapeutic target for fibrotic diseases. Previous clinical studies of patients with pneumoconiosis, including silicosis, revealed an increased concentration of circulating WNT3A and DKK1 proteins and inflammatory cells in bronchoalveolar lavage compared with healthy subjects. The present study evaluated the effects of adenovirus-mediated transduction of Dickkopf-1 (Dkk1), a Wnt/β-catenin signaling inhibitor, on the development of pulmonary silicosis in mice. Consistent with previous human clinical studies, our experimental studies in mice demonstrated an aberrant Wnt/β-catenin signaling activity coinciding with increased Wnt3a and Dkk1 proteins and inflammation in lungs of silica-induced silicosis mice compared with controls. Intratracheal delivery of adenovirus expressing murine Dkk1 (AdDkk1) inhibited Wnt/β-catenin activity in mouse lungs. The adenovirus-mediated Dkk1 gene transduction demonstrated the potential to prevent silicosis development and ameliorate silica-induced lung fibrogenesis in mice, accompanied by the reduced expression of epithelia--mesenchymal transition markers and deposition of extracellular matrix proteins compared with mice treated with "null" adenoviral vector. Mechanistically, AdDkk1 is able to attenuate the lung silicosis by inhibiting a silica-induced spike in TGF-β/Smad signaling. In addition, the forced expression of Dkk1 suppressed silica-induced epithelial cell proliferation in polarized human bronchial epithelial cells. This study provides insight into the underlying role of Wnt/β-catenin signaling in promoting the pathogenesis of silicosis and is proof-of-concept that targeting Wnt/β-catenin signaling by Dkk1 gene transduction may be an alternative approach in the prevention and treatment of silicosis lung disease.

Epigenetic regulation in fibrosis progress

Fibrosis, a common process of chronic inflammatory diseases, is defined as a repair response disorder when organs undergo continuous damage, ultimately leading to scar formation and functional failure. Around the world, fibrotic diseases cause high mortality, unfortunately, with limited treatment means in clinical practice. With the development and application of deep sequencing technology, comprehensively exploring the epigenetic mechanism in fibrosis has been allowed. Extensive remodeling of epigenetics controlling various cells phenotype and molecular mechanisms involved in fibrogenesis was subsequently verified. In this review, we summarize the regulatory mechanisms of DNA methylation, histone modification, noncoding RNAs (ncRNAs) and N6-methyladenosine (m6A) modification in organ fibrosis, focusing on heart, liver, lung and kidney. Additionally, we emphasize the diversity of epigenetics in the cellular and molecular mechanisms related to fibrosis. Finally, the potential and prospect of targeted therapy for fibrosis based on epigenetic is discussed.

Exosomes secreted by palmitic acid-treated hepatocytes promote LX-2 cell activation by transferring miRNA-107

Activation of hepatic stellate cells (HSCs) is a key inducer of liver fibrogenesis in nonalcoholic fatty liver disease (NAFLD). Exosomes play an important role between hepatocytes and HSCs. This study aims to explore the role of exosomes derived from palmitic acid (PA)-treated hepatocytes in regulating HSCs (LX-2 cell) proliferation and activation and the underlying mechanisms. Exosomes were isolated from PA-treated human normal hepatocytes and incubated with LX-2 cells. Cell Counting Kit-8 (CCK-8) was performed to determine LX-2 cell proliferation, and the expression of fibrosis markers α-smooth muscle actin (α-SMA) and collagen type 1 α1 (CoL1A1) were examined to evaluateLX-2 cell activation. PA induced hepatocytes to release more exosomes enriched in miR-107. Mechanically, on the one hand, exosomes from PA-treated hepatocytes shuttled miR-107 to LX-2 cells, where miR-107 activated Wnt signaling by targeting DKK1 and thereby induced LX-2 cell activation; on the other hand, PA-treated hepatocytes derived exosomes also delivered miR-107 to CD4 + T lymphocytes, where miR-107 elevated IL-9 expression by targeting Foxp1, which bound to the IL-9 promoter in CD4 + T cells and suppressed Th9 cell differentiation and reduced IL-9 expression, and thus promoted LX-2 cell activation by activating Raf/MEK/ERK signaling pathway.

DZNep, an inhibitor of the histone methyltransferase EZH2, suppresses hepatic fibrosis through regulating miR-199a-5p/SOCS7 pathway

Background

Hepatic fibrosis is a common response to chronic liver injury. Recently, the role of DZNep (a histone methyltransferase EZH2 inhibitor) in repressing pulmonary and renal fibrosis was verified. However, the potential effect of DZNep on hepatic fibrosis has not been elucidated.

Methods

The hepatic fibrosis model was established in rats treated with CCl4 and in hepatic stellate cells (HSCs) treated with TGF-β1. The liver tissues were stained with H&E and Masson’s trichrome. The expression of EZH2, SOCS7, collagen I, αSMA mRNA and miR-199-5p was assessed using qPCR, immunohistochemical or western blot analysis. A dual-luciferase reporter assay was carried out to validate the regulatory relationship of miR-199a-5p with SOCS7.

Results

The EZH2 level was increased in CCl4-treated rats and in TGF-β1-treated HSCs, whereas DZNep treatment significantly inhibited EZH2 expression. DZNep repressed hepatic fibrosis in vivo and in vitro, as evidenced by the decrease of hepatic fibrosis markers (α-SMA and Collagen I). Moreover, miR-199a-5p expression was repressed by DZNep in TGF-β1-activated HSCs. Notably, downregulation of miR-199a-5p decreased TGF-β1-induced expression of fibrosis markers. SOCS7 was identified as a direct target of miR-199a-5p. The expression of SOCS7 was decreased in TGF-β1-activated HSCs, but DZNep treatment restore d SOCS7 expression. More importantly, SOCS7 knockdown decreased the effect of DZNep on collagen I and α SMA expression in TGF-β1-activated HSCs.

Conclusions

DZNep suppresses hepatic fibrosis through regulating miR-199a-5p/SOCS7 axis, suggesting that DZNep may represent a novel treatment for fibrosis.

Triterpenoid saponins from Ilex cornuta protect H9c2 cardiomyocytes against H2O2-induced apoptosis by modulating Ezh2 phosphorylation

ETHNOPHARMACOLOGICAL RELEVANCE

Ilex cornuta Lindl. et Paxt. (Aquifoliaceae family) belongs to the Ilex genus. The leaves of this plant are used for the popular herbal tea "Ku-Ding-Cha" in China due to their health benefits for sore throat, obesity and hypertension. Our previous studies have shown that the extract of Ilex cornuta root exerts cardioprotective effects in rat models of myocardial ischaemic injury, and several new kinds of triterpenoid saponins from Ilex cornuta (TSIC) have protective effects against hydrogen peroxide (H2O2)-induced cardiomyocyte injury.

AIM OF THE STUDY

The aim of this study was to clarify the underlying mechanisms by which TSIC protect against H2O2-induced cardiomyocyte injury.

MATERIALS AND METHODS

An H2O2-treated H9c2 cardiomyocyte line was used as an in vitro model of oxidation-damaged cardiomyocytes to evaluate the effects of TSIC. Apoptosis was detected with CCK-8 and annexin V assays and via analysis of the levels of apoptosis-associated proteins or genes. The underlying mechanisms related to Akt signalling, Ezh2 expression and activity, and ROS were clarified by Western blotting, quantitative PCR, flow cytometry and rescue experiments.

RESULTS

TSIC protected H9c2 cells from H2O2-induced apoptosis. This effect of TSIC was attributable to inhibition of Ezh2 activity, as exhibited by attenuation of H2O2-induced Akt signalling-dependent phosphorylation of Ezh2 at serine 21 (pEzh2_S21) upon TSIC pretreatment. In addition, feedback pathway between Akt-dependent Ezh2 phosphorylation and ROS was involved in TSIC-mediated protection of H9c2 cells from apoptosis.

CONCLUSIONS

Our findings indicate a pivotal role of the pEzh2_S21 network in TSIC-mediated protection against cardiomyocyte apoptosis, potentially providing evidence of the mechanism of TSIC in the treatment and prevention of cardiovascular diseases.

Astilbin Protects Against Carbon Tetrachloride-Induced Liver Fibrosis in Rats

BACKGROUND

Hepatic fibrosis is an inflammatory liver disease, and there is no effective therapy at present. Astilbin is a bioactive ingredient found in many medicinal and food plants, with antioxidative, anti-inflammatory, and antitumor properties.

OBJECTIVES

This study aimed to investigate the protective effect and related molecular mechanism of astilbin against carbon tetrachloride (CCl4)-induced liver fibrosis in rats.

METHODS

Liver fibrosis was induced by injection of CCl4 in male Sprague-Dawley rats, and those rats were then treated with astilbin at different concentrations. Pathological changes, collagen production, inflammatory cytokine, and oxidative stress were evaluated to evaluate the effects of astilbin on CCl4-induced hepatic fibrosis. Real-time PCR and western blot were performed to detect the mRNA and protein expression of indicated genes.

RESULTS

We discovered that CCl4 caused significant fibrosis damage in rat liver, and astilbin dose-dependently improved the liver functions and fibrosis degree. Astilbin treatment significantly decreased collagen production, inflammatory response, and oxidative stress in vivo. Mechanically, administration of astilbin obviously elevated the hepatic levels of Nrf2 and its downstream components, including NAD(P)H:quinone oxidoreductase 1 (Nqo1), heme oxygenase (HO-1), glutamate-cysteine ligase catalytic subunit, and glutamate cysteine ligase modifier.

CONCLUSIONS

Taken together, these findings demonstrate that astilbin could protect against CCL4 induced-liver fibrosis in rats.

IOX1 protects from TGF-β induced fibrosis in LX-2 cells via the regulation of extracellular matrix protein expression

The aim of the present study was to investigate the effect of the histone H3K9 demethylase inhibitor, IOX1, on the mechanism of hepatic fibrosis in TGF-β-induced human hepatic stellate LX-2 cells. Cellular proliferation, apoptosis, histone H3K9 dimethylation (H3K9me2), protein expression of extracellular matrix (ECM)-related proteins α-smooth muscle actin (SMA), type I collagen (Col I), MMP-1 and TIMP-1 were measured. H3K9me2 levels in the promoter region of ECM-related genes were detected by real-time cell analysis (RTCA), flow cytometry, western blotting and chromatin immunoprecipitation (ChIP) in LX-2 cells. IOX1 significantly inhibited cell proliferation and the IC₅₀ of IOX1 was 100 µM in cells treated with IOX1 for 48 h. IOX1 significantly induced apoptosis in LX-2 cells in a concentration-dependent manner. In addition, different concentration of IOX1 increased the level of H3K9me2 and downregulated the expression of α-SMA, Col I, MMP-1 and TIMP-1 in TGF-β-induced LX-2 cells. ChIP measurements indicated that H3K9me2 levels in the promotor region of the corresponding genes were increased in TGF-β-induced LX-2 cells. IOX1 may elevate H3K9me2 in the promotor region of Col I, MMP-1, and TIMP-1 genes to regulate α-SMA, Col I, MMP-1 and TIMP-1 protein expression to induce cell apoptosis, inhibit LX-2 cell proliferation and oppose hepatic fibrotic activity.

Dual Pharmacological Targeting of HDACs and PDE5 Inhibits Liver Disease Progression in a Mouse Model of Biliary Inflammation and Fibrosis

Simple Summary

Chronic liver injury and inflammation leads to excessive deposition of extracellular matrix, known as liver fibrosis, and the distortion of the hepatic parenchyma. Liver fibrosis may progress to cirrhosis, a condition in which hepatic function is impaired and most cases of liver tumors occur. Currently, there are no effective therapies to inhibit and reverse the progression of liver fibrosis, and therefore, chronic liver disease remains a global health problem. In this study we have tested the efficacy of a new class of molecules that simultaneously target two molecular pathways known to be involved in the pathogenesis of hepatic fibrosis. In a clinically relevant mouse model of liver injury and inflammation we show that the combined inhibition of histones deacetylases and the cyclic guanosine monophosphate (cGMP) phosphodiesterase phosphodiesterase 5 (PDE5) results in potent anti-inflammatory and anti-fibrotic effects. Our findings open new avenues for the treatment of liver fibrosis and therefore, the prevention of hepatic carcinogenesis.

Abstract

Liver fibrosis, a common hallmark of chronic liver disease (CLD), is characterized by the accumulation of extracellular matrix secreted by activated hepatic fibroblasts and stellate cells (HSC). Fibrogenesis involves multiple cellular and molecular processes and is intimately linked to chronic hepatic inflammation. Importantly, it has been shown to promote the loss of liver function and liver carcinogenesis. No effective therapies for liver fibrosis are currently available. We examined the anti-fibrogenic potential of a new drug (CM414) that simultaneously inhibits histone deacetylases (HDACs), more precisely HDAC1, 2, and 3 (Class I) and HDAC6 (Class II) and stimulates the cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG) pathway activity through phosphodiesterase 5 (PDE5) inhibition, two mechanisms independently involved in liver fibrosis. To this end, we treated Mdr2-KO mice, a clinically relevant model of liver inflammation and fibrosis, with our dual HDAC/PDE5 inhibitor CM414. We observed a decrease in the expression of fibrogenic markers and collagen deposition, together with a marked reduction in inflammation. No signs of hepatic or systemic toxicity were recorded. Mechanistic studies in cultured human HSC and cholangiocytes (LX2 and H69 cell lines, respectively) demonstrated that CM414 inhibited pro-fibrogenic and inflammatory responses, including those triggered by transforming growth factor β (TGFβ). Our study supports the notion that simultaneous targeting of pro-inflammatory and fibrogenic mechanisms controlled by HDACs and PDE5 with a single molecule, such as CM414, can be a new disease-modifying strategy.

EZH2 as a Potential Target for NAFLD Therapy

Non-alcoholic fatty liver disease (NAFLD) is a complex disease that is affected by genetic predisposition and epigenetic modification. Deregulation of epigenetic pathways is now recognized as a frequent event in NAFLD, and understanding the mechanistic roles of these epigenetic factors may lead to new strategies for NAFLD treatment. Enhancer of zeste homolog 2 (EZH2) catalyzes methylation on Lys 27 of histone H3, which leads to chromatin compaction and gene silencing. EZH2 regulates embryonic development and cell lineage determination and is related to many human diseases. Recent studies show that EZH2 has critical roles in liver development, homeostasis, and regeneration. Moreover, aberrant activation of EZH2 promotes NAFLD progression. Several EZH2 inhibitors have been developed and studied both in vitro and in clinical trials. In this review, we summarize our current understanding of the role of EZH2 in NAFLD and highlight its potential as a novel therapeutic target for NAFLD treatment.

Epigenetics in Liver Fibrosis: Could HDACs be a Therapeutic Target?

Chronic liver diseases (CLD) represent a worldwide health problem. While CLDs may have diverse etiologies, a common pathogenic denominator is the presence of liver fibrosis. Cirrhosis, the end-stage of CLD, is characterized by extensive fibrosis and is markedly associated with the development of hepatocellular carcinoma. The most important event in hepatic fibrogenesis is the activation of hepatic stellate cells (HSC) following liver injury. Activated HSCs acquire a myofibroblast-like phenotype becoming proliferative, fibrogenic, and contractile cells. While transient activation of HSCs is part of the physiological mechanisms of tissue repair, protracted activation of a wound healing reaction leads to organ fibrosis. The phenotypic changes of activated HSCs involve epigenetic mechanisms mediated by non-coding RNAs (ncRNA) as well as by changes in DNA methylation and histone modifications. During CLD these epigenetic mechanisms become deregulated, with alterations in the expression and activity of epigenetic modulators. Here we provide an overview of the epigenetic alterations involved in fibrogenic HSCs transdifferentiation with particular focus on histones acetylation changes. We also discuss recent studies supporting the promising therapeutic potential of histone deacetylase inhibitors in liver fibrosis.

Wnt signaling pathway in aging-related tissue fibrosis and therapies

Fibrosis is the final hallmark of pathological remodeling, which is a major contributor to the pathogenesis of various chronic diseases and aging-related organ failure to fully control chronic wound-healing and restoring tissue function. The process of fibrosis is involved in the pathogenesis of the kidney, lung, liver, heart and other tissue disorders. Wnt is a highly conserved signaling in the aberrant wound repair and fibrogenesis, and sustained Wnt activation is correlated with the pathogenesis of fibrosis. In particular, mounting evidence has revealed that Wnt signaling played important roles in cell fate determination, proliferation and cell polarity establishment. The expression and distribution of Wnt signaling in different tissues vary with age, and these changes have key effects on maintaining tissue homeostasis. In this review, we first describe the major constituents of the Wnt signaling and their regulation functions. Subsequently, we summarize the dysregulation of Wnt signaling in aging-related fibrotic tissues such as kidney, liver, lung and cardiac fibrosis, followed by a detailed discussion of its involvement in organ fibrosis. In addition, the crosstalk between Wnt signaling and other pathways has the potential to profoundly add to the complexity of organ fibrosis. Increasing studies have demonstrated that a number of Wnt inhibitors had the potential role against tissue fibrosis, specifically in kidney fibrosis and the implications of Wnt signaling in aging-related diseases. Therefore, targeting Wnt signaling might be a novel and promising therapeutic strategy against aging-related tissue fibrosis.

Regulatory T cells are a double-edged sword in pulmonary fibrosis

Pulmonary fibrosis (PF) is a chronic progressive interstitial lung disease. The pathogenesis of PF has not been clearly elucidated, and there is no obvious effective treatment to arrest the progression of PF to date. A long-term chronic inflammatory response and inappropriate repair process after lung injury are important causes and pathological processes of PF. As an influential type of the body's immune cells, regulatory T cells (Tregs) play an irreplaceable role in inhibiting the inflammatory response and promoting the repair of lung tissue. However, the exact roles of Tregs in the process of PF have not been clearly established, and the available literature concerning the roles of Tregs in PF are contradictory. First, Tregs can advance the progression of pulmonary fibrosis by secreting platelet-derived growth factor (PDGF), transforming growth factor-β (TGF-β) and other related factors, promoting epithelial-mesenchymal transition (EMT) and affecting the Th1 and Th2 balance, etc. Second, Tregs can inhibit PF by promoting the repair of epithelial cell damage, inhibiting the accumulation of fibroblasts, and strongly inhibiting the production and function of other related pro-inflammatory factors and pro-inflammatory cells. Accordingly, in this review, we focus on the multiple roles of Tregs in different models and different pulmonary fibrosis phases, thereby providing theoretical support for a better understanding of the multiple roles of these cells in PF and a theoretical basis for identifying targets for PF therapy.

Epigenetic modulation as a therapy in systemic sclerosis

SSc is an autoimmune idiopathic disease in which there is an inflammatory component driving fibrosis. The chief cell involved is the myofibroblast, which when activated secretes copious amounts of extracellular matrix that forms deposits, leading to stiffness and fibrosis. The fibrosis is most prevalent in the skin and lungs. In recent years epigenetic modifications have been uncovered that positively and negatively regulate the genesis of the myofibroblasts and that can be activated and regulated by a variety of cytokines and hormones. The epigenetic contribution to these cells and to SSc is only now really coming to light, and this opens up a new therapeutic target for the disease for which many epigenetic drugs, such as miRNA replacements, are beginning to be developed. This review will examine the epigenetic regulators in the disease and possible targeting of these.

Proteasomal Degradation of Enhancer of Zeste Homologue 2 in Cholangiocytes Promotes Biliary Fibrosis

During biliary disease, cholangiocytes become activated by various pathological stimuli, including transforming growth factor β (TGF-β). The result is an epigenetically regulated transcriptional program leading to a pro-fibrogenic microenvironment, activation of hepatic stellate cells (HSCs), and progression of biliary fibrosis. This study evaluated how TGF-β signaling intersects with epigenetic machinery in cholangiocytes to support fibrogenic gene transcription. We performed RNA sequencing in cholangiocytes with or without TGF-β. Ingenuity pathway analysis identified "HSC Activation" as the highly up-regulated pathway, including overexpression of fibronectin 1 (FN), connective tissue growth factor, and other genes. Bioinformatics identified enhancer of zeste homologue 2 (EZH2) as an epigenetic regulator of the cholangiocyte TGF-β response. EZH2 overexpression suppressed TGF-β-induced FN protein in vitro, suggesting FN as a direct target of EZH2-based repression. Chromatin immunoprecipitation assays identified an FN promoter element in which EZH2-mediated tri-methylation of lysine 27 on histone 3 is diminished by TGF-β. TGF-β also caused a 50% reduction in EZH2 protein levels. Proteasome inhibition rescued EZH2 protein and led to reduced FN production. Immunoprecipitation followed by mass spectrometry identified ubiquitin protein ligase E3 component N-recognin 4 in complex with EZH2, which was validated by western blotting in vitro. Ubiquitin mutation studies suggested K63-based ubiquitin linkage and chain elongation on EZH2 in response to TGF-β. A deletion mutant of EZH2, lacking its N-terminal domain, abrogates both TGF-β-stimulated EZH2 degradation and FN release. In vivo, cholangiocyte-selective knockout of EZH2 exacerbates bile duct ligation-induced fibrosis whereas MDR2^-/- mice are protected from fibrosis by the proteasome inhibitor bortezomib. Conclusion: TGF-β regulates proteasomal degradation of EZH2 through N-terminal, K63-linked ubiquitination in cholangiocytes and activates transcription of a fibrogenic gene program that supports biliary fibrosis.

Increased Levels of DKK1 in Vitreous Fluid of Patients with Pathological Myopia and the Correlation between DKK1 Levels and Axial Length

Purpose: Dickkopf 1 (DKK1) functions as a natural antagonist of the canonical Wnt/β-catenin pathway. The purpose of this study was to examine the expression of DKK1 in vitreous samples of patients with pathological myopia, in order to search for possible correlations between DKK1 and axial length.Materials and Methods: The expression of DKK1 and other cytokines in vitreous samples of 44 non-myopic eyes, 42 eyes with low-to-moderate myopia, and 51 eyes with pathological myopia were examined using multiplex cytokine detection technology. Ophthalmologic characteristics, including axial length and subfoveal choroidal thickness, were clinically measured for further analysis.Results: The intravitreous levels of DKK1 (P < .0001) were markedly higher in the pathological myopia group than in the control group. There were no differences of DKK1 levels in different vitreoretinal conditions. Additionally, we found that the DKK1 levels were positively correlated with HGF (β = 0.268, P = .032), and TIMP-3 (β = 0.209, P = .047) levels, as well as with axial length (β = 0.714, P < .0001) in the pathological myopia group.Conclusions: Elevated levels of DKK1 were found in the eyes with elongated axial length.

EZH2 as a novel therapeutic target for atrial fibrosis and atrial fibrillation

Angiotensin II (Ang-II)-induced fibroblast differentiation plays an important role in the development of atrial fibrosis and atrial fibrillation (AF). Here, we show that the expression of the histone methyltransferase enhancer of zeste homolog 2 (EZH2) is increased in atrial muscle and atrial fibroblasts in patients with AF, accompanied by significant atrial fibrosis and atrial fibroblast differentiation. In addition, EZH2 is induced in murine models of atrial fibrosis. Furthermore, either pharmacological GSK126 inhibition or molecular silencing of EZH2 can inhibit the differentiation of atrial fibroblasts and the ability to produce ECM induced by Ang-II. Simultaneously, inhibition of EZH2 can block the Ang-II-induced migration of atrial fibroblasts. We found that EZH2 promotes fibroblast differentiation mainly through the Smad signaling pathway and can form a transcription complex with Smad2 to bind to the promoter region of the ACTA2 gene. Finally, our in vivo experiments demonstrated that the EZH2 inhibitor GSK126 significantly inhibited Ang-II-induced atrial enlargement and fibrosis and reduced AF vulnerability. Our results demonstrate that targeting EZH2 or EZH2-regulated genes might present therapeutic potential in AF.

Plantamajoside exerts antifibrosis effects in the liver by inhibiting hepatic stellate cell activation

The pathogenesis of liver fibrosis involves the activation of hepatic stellate cells (HSCs) into muscle fiber cells and fibroblasts. The aim of the current study was to investigate whether plantamajoside (PMS) exerted antifibrosis effects by affecting HSCs activation and survival during liver fibrosis, and to investigate the underlying mechanism. HSC-T6 cells were activated by exposure to platelet-derived growth factor BB (PDGF-BB), and were subsequently treated with increasing concentrations of PMS (0, 20, 40, 80 and 160 µg/ml). Cell viability, apoptosis, migration and invasion were determined using the Cell Counting Kit-8 (CCK-8) assay, flow cytometry and the Transwell assay, respectively. Results indicated that PDGF-BB significantly activated HSC-T6 cells, demonstrated by increased cell proliferation, enhanced cell migration and invasion as well as increased expression of α-smooth muscle actin (α-SMA) and collagen type 1 α 1 (Col1α1). PMS inhibited proliferation, induced cell apoptosis and prevented cell migration and invasion in PDGF-BB-treated HSC-T6 cells in what appeared to be a dose-dependent manner. PMS appeared to dose-dependently reduce the protein and mRNA levels of α-SMA and Col1α1 in PDGF-BB-treated HSC-T6 cells. Furthermore, the results of the present study suggested that PMS administration inhibited the protein expression of phosphorylated-protein kinase B in what appeared to be a dose-dependent manner. In conclusion, the data indicated that PMS exhibited an antifibrotic effect in the liver by inhibiting hepatic stellate cell activation and survival.

Research progress on the anti-hepatic fibrosis action and mechanism of natural products

Hepatic fibrosis is the most common pathological feature of most chronic liver diseases, and its continuous deterioration gradually develops into liver cirrhosis and eventually leads to liver cancer. At present, there are many kinds of drugs used to treat liver fibrosis. However, Western drugs tend to only target single genes/proteins and induce many adverse reactions. Most of the mechanisms and active ingredients of traditional Chinese medicine (TCM) are not clear, and there is a lack of unified diagnosis and treatment standards. Natural products, which are characterized by structural diversity, low toxicity, and origination from a wide range of sources, have unique advantages and great potential in anti-liver fibrosis. This article summarizes the work done over the previous decade, on the active ingredients in natural products that are reported to have anti-hepatic fibrosis effects. The effective anti-hepatic fibrosis ingredients identified can be generally divided into flavonoids, saponins, polysaccharides and alkaloids. Mechanisms of anti-liver fibrosis include inhibition of liver inflammation, anti-lipid peroxidation injury, inhibition of the activation and proliferation of hepatic stellate cells (HSCs), modulation of the synthesis and secretion of pro-fibrosis factors, and regulation of the synthesis and degradation of the extracellular matrix (ECM). This review provides suggestions for the development of anti-hepatic fibrosis drugs.

DLX3 regulates osteogenic differentiation of bone marrow mesenchymal stem cells via Wnt/β-catenin pathway mediated histone methylation of DKK4

OBJECTIVE

Distal-less homeobox 3 (DLX3) is an important transcription factor involved in the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). However, the underlying mechanism is not clear. This study investigated the underlying mechanism of DLX3 in osteogenic differentiation.

METHODS

DLX3 overexpression and knockdown in cells were achieved using lentiviruses. The osteogenic differentiation of BMSCs was detected using alkaline phosphatase expression, alizarin red staining, real-time quantitative polymerase chain reaction (RT-qPCR), Western blotting, and chromatin immunoprecipitation (ChIP) assays.

RESULTS

DLX3 overexpression promoted the osteogenic differentiation of BMSCs, whereas DLX3 knockdown reduced the osteogenic differentiation of BMSCs. RT-qPCR and Western blotting assays showed that DLX3 modulated osteogenic differentiation via the Wnt/β-catenin pathway. ChIP-qPCR showed that DLX3 knockdown promoted DKK4 expression by decreasing the enrichment of histone H3 lysine 27 trimethylation (H3K27me3) in the promotor region of DKK4.

CONCLUSION

Our data implied that DLX3 regulated Wnt/β-catenin pathway through histone modification of DKK4 during the osteogenic differentiation of BMSCs.

EGR1-induced upregulation of lncRNA FOXD2-AS1 promotes the progression of hepatocellular carcinoma via epigenetically silencing DKK1 and activating Wnt/β-catenin signaling pathway

Long non-coding RNAs (lncRNAs) are regarded as a group of biomarkers in the initiation and development of various cancers, including hepatocellular carcinoma (HCC). LncRNA FOXD2-AS1 has been studied in human colorectal cancer and glioma as an oncogene. However, the function and mechanism of lncRNA FOXD2-AS1 in hepatocellular carcinoma are marked. In this study, we found that high expression of FOXD2-AS1 predicted poor prognosis of HCC patients in the TCGA database. The dysregulation of FOXD2-AS1 was determined in HCC tissues and cell lines by qRT-PCR. Functionally, silenced FOXD2-AS1 efficiently suppressed HCC progression by regulating cell proliferation, apoptosis, migration and epithelial-mesenchymal transition (EMT). Mechanistically, FOXD2-AS1 was found to be activated by the transcription factor EGR1. Furthermore, FOXD2-AS1 could activate the Wnt/β-catenin signaling pathway. The mechanism contributed to the interaction between FOXD2-AS1 and Wnt/β-catenin signaling pathway was analyzed. It was uncovered that FOXD2-AS1 enhanced the activity of Wnt/β-catenin signaling pathway by epigenetically silencing the inhibitor of Wnt/β-catenin signaling pathway (DKK1). Rescue assays demonstrated that DKK1 and Wnt/β-catenin signaling pathway involved in FOXD2-AS1-mediated HCC progression. In conclusion, our study demonstrated that EGR1-induced upregulation of lncRNA FOXD2-AS1 promotes the progression of hepatocellular carcinoma via epigenetically silencing DKK1 and activating Wnt/β-catenin signaling pathway.

The Role of Epigenetic Modifications in Systemic Sclerosis: A Druggable Target

Systemic sclerosis (SSc) is a rare autoimmune disorder characterised by skin fibrosis that often also affects internal organs, eventually resulting in mortality. Although management of the symptoms has extended lifespan, patients still suffer from poor quality of life, hence the need for improved therapies. Development of efficacious treatments has been stymied by the unknown aetiology, although recent advancements suggest a potentially key role for epigenetics - the regulation of gene expression by noncoding RNAs and chemical modifications to DNA or DNA-associated proteins. Herein, the evidence implicating epigenetics in the pathogenesis of SSc is discussed with an emphasis on the therapeutic potential this introduces to the field - particularly the repurposing of epigenetic targeting cancer therapeutics and newly emerging miRNA-based strategies.

Reactive Oxygen Species Drive Epigenetic Changes in Radiation-Induced Fibrosis

Radiation-induced fibrosis (RIF) develops months to years after initial radiation exposure. RIF occurs when normal fibroblasts differentiate into myofibroblasts and lay down aberrant amounts of extracellular matrix proteins. One of the main drivers for developing RIF is reactive oxygen species (ROS) generated immediately after radiation exposure. Generation of ROS is known to induce epigenetic changes and cause differentiation of fibroblasts to myofibroblasts. Several antioxidant compounds have been shown to prevent radiation-induced epigenetic changes and the development of RIF. Therefore, reviewing the ROS-linked epigenetic changes in irradiated fibroblast cells is essential to understand the development and prevention of RIF.

Cancer driver mutations in endometriosis: Variations on the major theme of fibrogenesis

BACKGROUND

One recent study reports cancer driver mutations in deep endometriosis, but its biological/clinical significance remains unclear. Since the natural history of endometriosis is essentially gradual progression toward fibrosis, it is thus hypothesized that the six driver genes reported to be mutated in endometriosis (the RP set) may play important roles in fibrogenesis but not necessarily malignant transformation.

METHODS

Extensive PubMed search to see whether RP and another set of driver genes not yet reported (NR) to be mutated in endometriosis have any roles in fibrogenesis. All studies reporting on the role of fibrogenesis of the genes in both RP and NR sets were retrieved and evaluated in this review.

RESULTS

All six RP genes were involved in various aspects of fibrogenesis as compared with only three NR genes. These nine genes can be anchored in networks linking with their upstream and downstream genes that are known to be aberrantly expressed in endometriosis, piecing together seemingly unrelated findings.

CONCLUSIONS

Given that somatic driver mutations can and do occur frequently in physiologically normal tissues, it is argued that these mutations in endometriosis are not necessarily synonymous with malignancy or premalignancy, but the result of enormous pressure for fibrogenesis.

Enhancer of Zeste Homologue 2 Inhibition Attenuates TGF-β Dependent Hepatic Stellate Cell Activation and Liver Fibrosis

BACKGROUND & AIMS

Transdifferentiation of hepatic stellate cells (HSCs) into myofibroblasts is a key event in the pathogenesis of liver fibrosis. Transforming growth factor β (TGF-β) and platelet-derived growth factor (PDGF) are canonical HSC activators after liver injury. The aim of this study was to analyze the epigenetic modulators that differentially control TGF-β and PDGF signaling pathways.

METHODS

We performed a transcriptomic comparison of HSCs treated with TGF-β or PDGF-BB using RNA sequencing. Among the targets that distinguish these 2 pathways, we focused on the histone methyltransferase class of epigenetic modulators.

RESULTS

Enhancer of zeste homolog 2 (EZH2) was expressed differentially, showing significant up-regulation in HSCs activated with TGF-β but not with PDGF-BB. Indeed, EZH2 inhibition using either a pharmacologic (GSK-503) or a genetic (small interfering RNA) approach caused a significant attenuation of TGF-β-induced fibronectin, collagen 1α1, and α-smooth muscle actin, both at messenger RNA and protein levels. Conversely, adenoviral overexpression of EZH2 in HSCs resulted in a significant stimulation of fibronectin protein and messenger RNA levels in TGF-β-treated cells. Finally, we conducted in vivo experiments with mice chronically treated with carbon tetrachloride or bile duct ligation. Administration of GSK-503 to mice receiving either carbon tetrachloride or bile duct ligation led to attenuated fibrosis as assessed by Trichrome and Sirius red stains, hydroxyproline, and α-smooth muscle actin/collagen protein assays.

CONCLUSIONS

TGF-β and PDGF share redundant and distinct transcriptomic targets, with the former predominating in HSC activation. The EZH2 histone methyltransferase is preferentially involved in the TGF-β as opposed to the PDGF signaling pathway. Inhibition of EZH2 attenuates fibrogenic gene transcription in TGF-β-treated HSCs and reduces liver fibrosis in vivo. The data discussed in this publication have been deposited in NCBI's Gene Expression Omnibus and are accessible through GEO Series accession number GSE119606 (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE119606).

Role of EZH2 in liver disease

Overexpression of enhancer of zeste homolog 2 (EZH2) protein has been found in several malignant tumor tissues and is closely related to the degree of tumor differentiation, clinical stage, tumor size, and prognosis. The latest research shows that overexpression of EZH2 is related not only with immunoregulation but also with the replication of hepatitis B virus, the occurrence of non-alcoholic fatty liver disease, and the progress of liver fibrosis, which may become an important subject in the field of liver disease research. This paper reviews the role of EZH2 in some liver diseases and its potential application in treatment of these diseases in recent ten years.

Epigenetic Contribution of High-Mobility Group A Proteins to Stem Cell Properties

High-mobility group A (HMGA) proteins have been examined to understand their participation as structural epigenetic chromatin factors that confer stem-like properties to embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and cancer stem cells (CSCs). The function of HMGA was evaluated in conjunction with that of other epigenetic factors such as histones and microRNAs (miRs), taking into consideration the posttranscriptional modifications (PTMs) of histones (acetylation and methylation) and DNA methylation. HMGA proteins were coordinated or associated with histone and DNA modification and the expression of the factors related to pluripotency. CSCs showed remarkable differences compared with ESCs and iPSCs.

The WNT signaling pathways in wound healing and fibrosis

The WNT signaling pathways are major regulators of organ development. Ample research over the past few decades revealed that these pathways are critically involved in adult tissue homeostasis and stem cell function as well as the development of chronic diseases, such as cancer and fibrosis. In this review, we will describe the different WNT signal pathways, summarize the current evidence of WNT signal involvement in wound healing and fibrosis, and highlight potential novel therapeutic options for fibrotic disorders targeting WNT signaling pathways.

Carnosol-mediated Sirtuin 1 activation inhibits Enhancer of Zeste Homolog 2 to attenuate liver fibrosis

Quiescent hepatic stellate cell (HSC) activation and subsequent conversion into myofibroblasts is the central event in hepatic fibrosis pathogenesis. Epithelial-mesenchymal transition (EMT), another vital participant in liver fibrosis, has the potential to initiate HSC activation, which promotes abundant myofibroblast production. Previous studies suggest that Enhancer of Zeste Homolog 2 (EZH2) plays a significant role in myofibroblast transdifferentiation; however, the underlying mechanisms remain largely unaddressed. Carnosol (CS), a compound extracted from rosemary, displays multiple pharmacological activities. This study aimed to investigate the signaling mechanisms underlying EZH2 inhibition and the anti-fibrotic effect of CS in liver fibrosis. We found that CS significantly inhibited CCl₄- and TGFβ1-induced liver fibrosis and reduced both HSC activation and EMT. EZH2 knockdown also prevented these processes induced by TGFβ1 in HSCs and AML-12 cells. Interestingly, the protective effect of CS was positively associated with Sirtuin 1 (SIRT1) activation and accompanied by EZH2 inhibition. SIRT1 knockdown attenuated the EZH2 inhibition induced by CS and increased EZH2 acetylation, which enhanced its stability. Conversely, upon TGFβ1 exposure, SIRT1 activation significantly reduced the level of EZH2 acetylation; however, EZH2 overexpression prevented the SIRT1 activation that primed myofibroblast inhibition, indicating that EZH2 is a target of SIRT1. Thus, SIRT1/EZH2 regulation could be used as a new therapeutic strategy for fibrogenesis. Together, this study provides evidence of activation of the SIRT1/EZH2 pathway by CS that inhibits myofibroblast generation, and thus, CS may represent an attractive candidate for anti-fibrotic clinical therapy.