SENP2 alleviates CCl4-induced liver fibrosis by promoting activated hepatic stellate cell apoptosis and reversion

Knockdown of circ_0044226 promotes endoplasmic reticulum stress-mediated autophagy and apoptosis in hepatic stellate cells via miR-4677-3p/SEC61G axis

Downregulation of circ_0044226 has been demonstrated to reduce pulmonary fibrosis, but the role of circ_0044226 in liver fibrosis remains to be explored. In this work, we found that circ_0044226 expression was upregulated during liver fibrosis. Knockdown of circ_0044226 inhibited proliferation, promoted autophagy and apoptosis of hepatic stellate cell LX-2. Bioinformatic analysis and dual luciferase reporter assays confirmed the interaction between circ_0044226, miR-4677-3p and SEC61G. Mechanistically, knockdown of circ_0044226 suppressed SEC61G expression by releasing miR-4677-3p, thereby enhancing endoplasmic reticulum stress. Overexpression of SEC61G or endoplasmic reticulum stress inhibitor 4-phenylbutiric acid partially reversed the effect of knockdown circ_0044226 on LX-2 cell function. In vivo experiments showed that inhibition of circ_0044226 attenuated CCL4-induced liver fibrosis in mice. These imply that circ_0044226 may be a potential target for the treatment of liver fibrosis.

Knockdown of TXNDC5 alleviates CCL4-induced hepatic fibrosis in mice by enhancing endoplasmic reticulum stress

BACKGROUND

Hepatic fibrosis is a common pathological process in many chronic liver diseases. TXNDC5 has been shown to be involved in the progression of renal and pulmonary fibrosis. However, the role of TXNDC5 in hepatic fibrosis is unknown. The purpose of this study is to explore the role and mechanism of TXNDC5 in hepatic fibrosis.

METHODS

We used TGF-β1 to activate LX-2 cells and reduced TXNDC5 expression by short hairpin RNA. Cell viability was assessed by CCK-8 assay. Cell apoptosis was analyzed by flow cytometry or Tunel assay. The fibrosis-related proteins and endoplasmic reticulum stress (ERs)-related proteins were measured by western blot. ELISA was performed to detect COL1AL levels and MMP2/9 activities in cell medium. A mouse model of hepatic fibrosis was constructed by intraperitoneal injection of CCL4. HE and Masson staining were performed to assess fibrosis in mouse liver tissue.

RESULTS

The results show that TXNDC5 was up-regulated in activated LX-2 cells and CCL4-induced hepatic fibrosis mice. Knockdown of TXNDC5 inhibited the viability of activated LX-2 cells and the production of collagen COL1A1. Knockdown of TXNDC5 promoted apoptosis of activated LX-2 cells. Mechanically, inhibition of TXNDC5 enhanced ERs, and the ERs inhibitor 4-Phenylbutyric acid (4-PBA) reversed the effect of TXNDC5 on activated LX-2 cells. More importantly, knockdown of TXNDC5 alleviated CCl4-induced hepatic fibrosis in mice.

CONCLUSIONS

Knockdown of TXNDC5 may reduce hepatic fibrosis by regulating ERs, and targeting TXNDC5 seems to be a candidate treatment for hepatic fibrosis.

Lymphocyte-Specific Protein Tyrosine Kinase Contributes to Spontaneous Regression of Liver Fibrosis may by Interacting with Suppressor of Cytokine Signaling 1

Quiescent hepatic stellate cells (qHSCs), converted to myofibroblasts, produce fibrous scars, which is an essential event during liver fibrogenesis. Clinical and experimental fibrosis undergo remarkable regression when the underlying etiological agent is removed. Some myofibroblasts revert to an inactive phenotype (iHSCs) during the regression of fibrosis. However, the mechanisms underlying HSC activation and reversal remain unclear. The present study demonstrated that the expression of lymphocyte-specific protein tyrosine kinase (LCK) was increased in fibrotic livers but decreased after spontaneous recovery in vivo and in vitro, which was correlated with the expression of α-smooth muscle actin (α-SMA) and type I collagen (COL-1). Further investigation indicated that specific knockdown of LCK by a recombination adeno-associated virus 9 (rAAV9) in C57BL/6 mice ameliorated liver fibrosis. Co-incubation of TGF-β1-induced HSC-T6 cells with LCK-siRNA inhibited cell proliferation and activation. Overexpression of LCK inhibited activated HSCs going to inactivated phenotype. Interestingly, we found that LCK may interact with suppressor of cytokine signaling 1 (SOCS1) and may influence the expression of p-JAK1 and p-STAT1/3. These data suggest that LCK may play a regulatory role in liver fibrosis by inhibiting SOCS1, indicating that LCK is a potential therapeutic target for liver fibrosis treatment.

MicroRNA-195-3p promotes hepatic stellate cell activation and liver fibrosis by suppressing PTEN expression

Liver fibrosis is a reversible wound healing reaction characterized by abnormal accumulation of extracellular matrix (ECM) in response to liver injury. Recent studies have shown that it can be epigenetically regulated, especially by microRNAs (miRNAs). It has been acknowledged that activation of hepatic stellate cells (HSCs) is a pivotal step in the initiation and progression of liver fibrosis. Notably, our results showed that miR-195-3p was increased in HSCs isolated from CCl₄-treated mice and that the increase was more pronounced as the degree of liver fibrosis increased. Moreover, treatment of LX-2 cells, a human immortalized hepatic stellate cell line, with TGF-β1 resulted remarkable upregulation of miR-195-3p. Gain-of-function and loss-of-function experiments have suggested that the increased levels of miR-195-3p inhibit the expression of phosphatase and tension homolog deleted on chromosome 10 (PTEN), a negative regulator of the PI3K/Akt/mTOR signaling pathway in liver fibrosis, thereby contributing to HSC activation and proliferation and promoting the expression of profibrotic genes, such as α-SMA and collagen I, in LX-2 cells, which accelerates the accumulation of fibrous extracellular matrix deposition in the liver, while knockdown of miR-195-3p induced the opposite effect. Taken together, these results provide evidence for the harmful role of miR-195-3p in CCl₄-treated mouse liver fibrosis.

Hesperetin derivative-16 attenuates CCl4-induced inflammation and liver fibrosis by activating AMPK/SIRT3 pathway

Liver fibrosis, a chronic inflammatory healing reaction, progresses to hepatocirrhosis without effective intervention. Hesperetin derivative (HD-16), a monomer compound derived from hesperitin, exerts anti-inflammatory and hepatoprotective effects against a spectrum of liver diseases. However, the anti-fibrotic potential of HD-16 in liver fibrosis and its underlying mechanism have not yet been elucidated. In this study, we investigated the anti-fibrotic effect of HD-16 on mouse liver fibrosis induced by CCl₄ and on LX-2 cells (human immortalized HSCs) stimulated by TGF-β1, in vivo and in vitro. HD-16 exerted an anti-fibrotic effect via regulation of the AMPK/SIRT3 pathway. Pharmacodynamic results showed that HD-16 alleviated the degree of injury and inflammation in CCl₄-induced mouse liver fibrosis. Consistently, HD-16 also effectively inhibited the expression of α-SMA, Col1α1, Col3α1, and TIMP-1 in TGF-β1-activated LX-2 cells. Mechanistically, HD-16 promoted SIRT3 expression and activity in fibrotic liver and activated LX-2 cells. Furthermore, SIRT3 depletion attenuated the anti-fibrotic effects of HD-16. Intriguingly, HD-16 increased AMPK phosphorylation, whereas inhibition of SIRT3 expression did not affect AMPK phosphorylation. In contrast, AMPK silencing suppressed SIRT3 expression, suggesting that SIRT3 is a downstream target of AMPK in liver fibrosis. Overall, HD-16 attenuated CCl₄-induced liver inflammation and fibrosis by activating the AMPK/SIRT3 pathway, and HD-16 may be a potential anti-fibrotic compound in the treatment of liver fibrosis.

Circular RNA circPSD3 alleviates hepatic fibrogenesis by regulating the miR-92b-3p/Smad7 axis

Recently, circular RNAs (circRNAs) have been frequently reported to be involved in hepatocellular carcinoma (HCC) development and progression. However, the role of circRNAs in hepatic fibrosis (HF) is still unclear. Our previous high-throughput screen revealed changes in many circRNAs in mice with carbon tetrachloride (CCl₄)-induced HF. For instance, the expression of circPSD3, a circRNA derived from the Pleckstrin and Sec7 domain-containing 3 (PSD3) gene, was considerably downregulated in primary hepatic stellate cells (HSCs) and liver tissues of mice with CCl₄-induced HF compared to those in the vehicle group. In vivo overexpression of circPSD3 using AAV8-circPSD3 arrested the deterioration of CCl₄-induced HF as indicated by reduced serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) content, liver hydroxyproline level, collagen deposition, and pro-fibrogenic gene and pro-inflammatory cytokine levels. Moreover, in vitro loss-of-function and gain-of-function analyses suggested that circPSD3 inhibited the activation and proliferation of HSCs. Mechanistically, circPSD3 served as a sponge for miR-92b-3p, subsequently promoting the expression of Smad7. In conclusion, our present findings reveal a novel mechanism by which circPSD3 alleviates hepatic fibrogenesis by targeting the miR-92b-3p/Smad7 axis, and they also indicate that circPSD3 may serve as a potential biomarker for HF.

Identification and Analysis of the Blood lncRNA Signature for Liver Cirrhosis and Hepatocellular Carcinoma

As one of the most common malignant tumors, hepatocellular carcinoma (HCC) is the fifth major cause of cancer-associated mortality worldwide. In 90% of cases, HCC develops in the context of liver cirrhosis and chronic hepatitis B virus (HBV) infection is an important etiology for cirrhosis and HCC, accounting for 53% of all HCC cases. To understand the underlying mechanisms of the dynamic chain reactions from normal to HBV infection, from HBV infection to liver cirrhosis, from liver cirrhosis to HCC, we analyzed the blood lncRNA expression profiles from 38 healthy control samples, 45 chronic hepatitis B patients, 46 liver cirrhosis patients, and 46 HCC patients. Advanced machine-learning methods including Monte Carlo feature selection, incremental feature selection (IFS), and support vector machine (SVM) were applied to discover the signature associated with HCC progression and construct the prediction model. One hundred seventy-one key HCC progression-associated lncRNAs were identified and their overall accuracy was 0.823 as evaluated with leave-one-out cross validation (LOOCV). The accuracies of the lncRNA signature for healthy control, chronic hepatitis B, liver cirrhosis, and HCC were 0.895, 0.711, 0.870, and 0.826, respectively. The 171-lncRNA signature is not only useful for early detection and intervention of HCC, but also helpful for understanding the multistage tumorigenic processes of HCC.

miR-200b regulates cellular senescence and inflammatory responses by targeting ZEB2 in pulmonary emphysema

Smoking is an important factor in the pathogenesis of chronic obstructive pulmonary disease (COPD), which is commonly characterised by cellular senescence and inflammation. Recently, miR-200b has emerged as an important target to cure lung disease; however, the function of miR-200b in reducing cellular senescence and inflammatory responses has not been reported. In this study, we found that miR-200b was downregulated in the lungs of COPD model mice, and its expression is correlated with cellular senescence and inflammatory responses. We hypothesised that miR-200b may be a potential novel therapy for treating COPD. We performed senescence-Associated-β-galactosidase (SA-β-GAL) staining, western blot, qRT-PCR and ELISA; our data suggested that miR-200b is an anti-aging factor in the lungs that is involved in inflammatory responses. We also confirmed that ZEB2 (Zinc finger E-box binding homeobox 2) is a target gene of miR-200b using luciferase reporter assay. In addition, we verified the function of ZEB2 in cellular senescence and inflammatory responses through transfection experiments. Moreover, we found that the protective effects of miR-200b are inhibited when cells overexpress the ZEB2 protein. In conclusion, our results suggest that miR-200b may attenuate cellular senescence and inflammatory responses by targeting ZEB2 in pulmonary emphysema.

CD73 regulates hepatic stellate cells activation and proliferation through Wnt/β-catenin signaling pathway

Alcoholic liver fibrosis (ALF) is commonly associated with long-term alcohol consumption and the activation of hepatic stellate cells (HSCs). Inhibiting the activation and proliferation of HSCs is a critical step to alleviate liver fibrosis. Increasing evidence indicates that ecto-5'-nucleotidase (CD73) plays a vital role in liver disease as a critical component of extracellular adenosine pathway. However, the regulatory role of CD73 in ALF has not been elucidated. In this study, both ethanol plus CCl₄-induced liver fibrosis mice model and acetaldehyde-activated HSC-T6 cell model were employed and the expression of CD73 was consistently elevated in vivo and in vitro. C57BL/6 J mice were intraperitoneally injected with CD73 inhibitor Adenosine 5'-(α, β-methylene) diphosphate sodium salt (APCP) from 5th week to the 8th week in the development of ALF. The results showed APCP could inhibit the activation of HSCs, reduce fibrogenesis marker expression and thus alleviate ALF. Silencing of CD73 inhibited the activation of HSC-T6 cells and promoted apoptosis of activated HSC-T6 cells. What's more, the proliferation of HSC-T6 cells was inhibited, which was characterized by decreased cell viability and cycle arrest. Mechanistically, Wnt/β-catenin pathway was activated in acetaldehyde-activated HSC-T6 cells and CD73 silencing or overexpression could regulate Wnt/β-catenin signaling pathway. Collectively, our study unveils the role of CD73 in HSCs activation, and Wnt/β-catenin signaling pathway might be involved in this progression.

Neddylation: A Versatile Pathway Takes on Chronic Liver Diseases

Neddylation is a ubiquitin-like posttranslational modification that conjugates neural precursor cell expressed developmentally downregulated-8 (Nedd8) to specific substrates for regulation of protein activity. In light of current researches, the neddylation pathway is aberrant in the pathogenesis of many diseases. In our review, we summarize the versatile roles of neddylation in chronic liver diseases (CLDs). CLDs are one of the leading causes of chronic disease-associated deaths worldwide. There are diverse etiologic agents causing CLDs, mainly including hepatitis B virus (HBV) infection, nonalcoholic fatty liver disease (NAFLD), chronic exposure to alcohol or drugs, and autoimmune causes. So far, however, there remains a paucity of effective therapeutic approach to CLDs. In this review, we summarized the role of the neddylation pathway which runs through the chronic hepatitis B/NAFLD-liver fibrosis-cirrhosis-hepatocellular carcinoma (HCC) axis, a canonical pattern in the process of CLD development and progression. The dysregulation of neddylation may provide a better understanding of CLD pathology and even a novel therapeutic strategy. Correspondingly, inhibiting neddylation via MLN4924, a small molecule compound targeting NEDD8-activating enzyme (NAE), can potently alleviate CLD progression and improve the outcome. On this basis, profiling and characterization of the neddylation pathway can provide new insights into the CLD pathology as well as novel therapeutic strategies, independently of the etiology of CLD.

Scoparone alleviates hepatic fibrosis by inhibiting the TLR-4/NF-κB pathway

The aim of this study was to investigate the role of scoparone (SCO) in hepatic fibrosis. For this, we conducted in vivo and in vitro experiments. In vivo rats that were divided into six groups, control, carbon tetrachloride, and colchicine, as well as SCO groups, SCO50, SCO100, and SCO200 treated with 50, 100, and 200 mg/kg SCO doses, respectively. Furthermore, SCO was shown to inhibit Toll-like receptor-4 (TLR-4)/nuclear factor kappa-B (NF-κB; TLR-4/NF-κB) signals by inhibiting TLR-4, which in turn downregulates the expression of MyD88, promotes NF-κB inhibitor-α, NF-κB inhibitor-β, and NF-κB inhibitor-ε activation, while inhibiting NF-κB inhibitor-ζ. Subsequently, the decrease of phosphorylation of nuclear factor-κB levels leads to the downregulation of the downstream inflammatory factors' tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and IL-1 beta, thus weakening hepatic fibrosis. Notably, the SCO200 treated group presented the most significant improvement. Hence, we conclude that SCO alleviates hepatic fibrosis by inhibiting TLR-4/NF-κB signals.

Oleanolic Acid Derived from Plants: Synthesis and Pharmacological Properties of A-ring Modified Derivatives

Background:

Oleanolic Acid (OA) is a ubiquitous product of triterpenoid compounds. Due to its inexpensive availability, unique bioactivities, pharmacological effects and non-toxic properties, OA has attracted tremendous interest in the field of drug design and synthesis. Furthermore, many OA derivatives have been developed for ameliorating the poor water solubility and bioavailability.

Objective:

Over the past few decades, various modifications of the OA framework structure have led to the observation of enhancement in bioactivity. Herein, we focused on the synthesis and medicinal performance of OA derivatives modified on A-ring. Moreover, we clarified the relationship between structures and activities of OA derivatives with different functional groups in A-ring. The future application of OA in the field of drug design and development also was discussed and inferred.

Conclusion:

This review concluded the novel achievements that could add paramount information to the further study of OA-based drugs.

LEFTY2 alleviates hepatic stellate cell activation and liver fibrosis by regulating the TGF-β1/Smad3 pathway

Activated hepatic stellate cells (HSCs) are the major cell type involved in the deposition of extracellular matrix (ECM) during the development of hepatic fibrosis. In this study, we revealed that left-right determination factor 2 (LEFTY2), one of the proteins belonging to the transforming growth factor-β (TGF-β) protein superfamily, was remarkedly decreased in human hepatic fibrosis tissues and in a carbon tetrachloride (CCl₄)-induced liver fibrosis mouse model. In addition, TGF-β1 treatment markedly reduced the level of LEFTY2 in HSCs. Importantly, overexpression of LEFTY2 suppressed the activation and proliferation of HSCs. LEFTY2 inhibited the expression of TGF-β1-induced fibrosis-associated genes (α-SMA and COL1a1) in human (LX-2) and rat (HSC-T6) HSC cell lines in vitro. Mechanistically, we demonstrated, for the first time, the role of LEFTY2 in inhibiting TGF-β1/Smad3 signaling, suggesting that there is a mutual antagonism between LEFTY2 and TGF-β1/Smad3 signaling during liver fibrosis. Similarly, we observed that LEFTY2 has a negative effect on its downstream genes, including c-MYC, CDK4, and cyclin D1, in liver fibrosis. Collectively, our data strongly indicated that LEFTY2 plays an important role in controlling the proliferation and activation of HSCs in the progression of liver fibrosis and this could be a potential therapeutic target for its treatment.

PLK1 regulates hepatic stellate cell activation and liver fibrosis through Wnt/β-catenin signalling pathway

As an outcome of chronic liver disease, liver fibrosis involves the activation of hepatic stellate cells (HSCs) caused by a variety of chronic liver injuries. It is important to explore approaches to inhibit the activation and proliferation of HSCs for the treatment of liver fibrosis. PLK1 is overexpressed in many human tumour cells and has become a popular drug target in tumour therapy. Therefore, further study of the function of PLK1 in the cell cycle is valid. In the present study, we found that PLK1 expression was elevated in primary HSCs isolated from CCl4 -induced liver fibrosis mice and LX-2 cells stimulated with TGF-β1. Knockdown of PLK1 inhibited α-SMA and Col1α1 expression and reduced the activation of HSCs in CCl4 -induced liver fibrosis mice and LX-2 cells stimulated with TGF-β1. We further showed that inhibiting the expression of PLK1 reduced the proliferation of HSCs and promoted HSCs apoptosis in vivo and in vitro. Furthermore, we found that the Wnt/β-catenin signalling pathway may be essential for PLK1-mediated HSCs activation. Together, blocking PLK1 effectively suppressed liver fibrosis by inhibiting HSC activation, which may provide a new treatment strategy for liver fibrosis.

PRC1 promotes GLI1-dependent osteopontin expression in association with the Wnt/β-catenin signaling pathway and aggravates liver fibrosis

Background

PRC1 (Protein regulator of cytokinesis 1) regulates microtubules organization and functions as a novel regulator in Wnt/β-catenin signaling pathway. Wnt/β-catenin is involved in development of liver fibrosis (LF). We aim to investigate effect and mechanism of PRC1 on liver fibrosis.

Methods

Carbon tetrachloride (CCl₄)-induced mice LF model was established and in vitro cell model for LF was induced by mice primary hepatic stellate cell (HSC) under glucose treatment. The expression of PRC1 in mice and cell LF models was examined by qRT-PCR (quantitative real-time polymerase chain reaction), western blot and immunohistochemistry. MTT assay was used to detect cell viability, and western blot to determine the underlying mechanism. The effect of PRC1 on liver pathology was examined via measurement of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and hydroxyproline, as well as histopathological analysis.

Results

PRC1 was up-regulated in CCl₄-induced mice LF model and activated HSC. Knockdown of PRC1 inhibited cell viability and promoted cell apoptosis of activated HSC. PRC1 expression was regulated by Wnt3a signaling, and PRC1 could regulate downstream β-catenin activation. Moreover, PRC1 could activate glioma-associated oncogene homolog 1 (GLI1)-dependent osteopontin expression to participate in LF. Adenovirus-mediated knockdown of PRC1 in liver attenuated LF and reduced collagen deposition.

Conclusions

PRC1 aggravated LF through regulating Wnt/β-catenin mediated GLI1-dependent osteopontin expression, providing a new potential therapeutic target for LF treatment.

Ubiquitin-Like Post-Translational Modifications (Ubl-PTMs): Small Peptides with Huge Impact in Liver Fibrosis

Liver fibrosis is characterized by the excessive deposition of extracellular matrix proteins including collagen that occurs in most types of chronic liver disease. Even though our knowledge of the cellular and molecular mechanisms of liver fibrosis has deeply improved in the last years, therapeutic approaches for liver fibrosis remain limited. Profiling and characterization of the post-translational modifications (PTMs) of proteins, and more specifically NEDDylation and SUMOylation ubiquitin-like (Ubls) modifications, can provide a better understanding of the liver fibrosis pathology as well as novel and more effective therapeutic approaches. On this basis, in the last years, several studies have described how changes in the intermediates of the Ubl cascades are altered during liver fibrosis and how specific targeting of particular enzymes mediating these ubiquitin-like modifications can improve liver fibrosis, mainly in in vitro models of hepatic stellate cells, the main fibrogenic cell type, and in pre-clinical mouse models of liver fibrosis. The development of novel inhibitors of the Ubl modifications as well as novel strategies to assess the modified proteome can provide new insights into the overall role of Ubl modifications in liver fibrosis.

Circ_1639 induces cells inflammation responses by sponging miR-122 and regulating TNFRSF13C expression in alcoholic liver disease

Ethanol is a key factor in the pathogenesis of alcoholic liver disease (ALD), commonly characterized as liver inflammation. Recently, circular (circ)RNAs have emerged as important targets to cure liver diseases. However, there are no studies investigating the role of circ_1639 in reducing inflammatory responses in ALD. In this study, we found that circ_1639 was upregulated in Kupffer cells from the livers of alcohol fed mice. We hypothesized that circ_1639 inhibition is a potential novel therapy for treating ALD. To test this hypothesis, RAW 264.7 cells were treated with ethanol and transfected with circ_1639 overexpression or knockdown plasmids. We present western blotting, qRT-PCR, and ELISA data that suggest that circ_1639 is a proinflammatory factor in the liver and is involved in the activation of the NF-κB signaling pathway. Using luciferase reporter assay, we confirmed that microRNA (miR)-122 is a target gene of circ_1639. We also show that TNFRSF13C is a key regulator of RAW 264.7 cell activation, and acts as a downstream target for miR-122. In summary, our results suggest that inhibition of circ_1639 expression may reduce inflammatory responses in ALD.

DNMT1 controls LncRNA H19/ERK signal pathway in hepatic stellate cell activation and fibrosis

Hepatic stellate cells (HSCs) activation is considered as a pivotal event in liver fibrosis. In HSCs activation and fibrosis, epigenetic events are important. Although HSCs activation alters DNA methylation, it is unknown, whether it also affects other epigenetic processes, including LncRNA and its recognition. The aim of this study was to identify the mechanism of DNA methyltransferase 1 (DNMT1) expression and its role in regulating LncRNA H19 during HSCs activation and fibrosis. Expression of DNMT1 and LncRNA H19 were determined in activated HSCs and CCl₄-induced rat liver fibrosis tissue. The relationship between the LncRNA H19 and DNMT1 expression was examined in vitro. LncRNA H19 expression was reduced in activated HSCs and rat liver fibrosis tissue, whereas DNMT1 expression and methylation of the LncRNA H19 promoter were increased. Treatment of HSCs of DNMT1-siRNA blocked cell proliferation. Knockdown of DNMT1 elevated H19 expression in activated HSCs, and over-expression of DNMT1 inhibited H19 expression in activated HSCs. Moreover, we investigated the effect of H19 on ERK signal pathway. Treatment HSCs with H19-siRNA increased the expression of p-ERK1/2 in HSCs. Treatment with 5'-aza-2'-deoxycytidine in activated HSCs model reduced fibrosis gene and DNMT1 expression, enhanced H19 expression, and attenuated HSCs activation. These data connect HSCs activation with a DNMT1-LncRNA H19 epigenetic pathway that is important for liver fibrosis.

Circular RNA in Liver: Health and Diseases

Circular RNA (circRNA) is an important class of noncoding RNA characterized by covalently closed continuous loop structures. In recent years, the various functions of circRNAs have been continuously documented, including effects on cell proliferation and apoptosis and nutrient metabolism. The liver is the largest solid organ in mammals, and it also performs many functions in the body, which is considered to be the busiest organ in the body. At the same time, the liver is vulnerable to multiple pathogenic factors, causing various acute and chronic liver diseases. The pathogenesis of liver disease is still not fully understood. As a rising star for the past few years, circRNAs have been proven involved in the regulation of liver homeostasis and disease. This chapter will explain the role of circRNAs in liver health and diseases and sort out the confusion in the present study.