The tumor suppressor protein PTEN inhibits rat hepatic stellate cell activation

The interactive role of microRNA and other non-coding RNA in hepatitis B (HBV) associated fibrogenesis

One of the outstanding features of chronic hepatitis B infection (CHB) is its strong association with liver fibrosis. CHB induced inflammation and injury trigger multiple biochemical and physical changes that include the promotion of a wide range of cytokines, chemokines and growth factors that activate hepatic stellate cells (HSCs) CHB induced activation of hepatic stellate cells (HSCs) is regarded as a central event in fibrogenesis to directly promote the synthesis of myofibroblasts and the expression of a range of materials to repair injured liver tissue. Fibrogenesis is modulated by the mainstream epigenetic machinery, as well as by non-coding RNA (ncRNA) that are often referred to as an ancillary epigenetic response to fine tune gene expression. Although extensive research has explained the regulatory role of ncRNA in liver fibrogenesis, most of this research relates to non-CHB etiologies. This review paper outlines the complex interactive regulatory role of microRNA (miRNA) and their interaction with long non-coding RNA (lncRNA), circular RNA (circRNA) and the mainstream epigenetic machinery in CHB induced liver fibrosis. The paper also illustrates some of the difficulties involved in translating candidate ncRNA into approved drugs or diagnostic tools. In conclusion, the important regulatory role of ncRNA in CHB induced liver fibrosis warrants further investigation to exploit their undoubted potential as diagnostic and therapeutic agents.

Signaling pathways that activate hepatic stellate cells during liver fibrosis

Liver fibrosis is a complex process driven by various factors and is a key feature of chronic liver diseases. Its essence is liver tissue remodeling caused by excessive accumulation of collagen and other extracellular matrix. Activation of hepatic stellate cells (HSCs), which are responsible for collagen production, plays a crucial role in promoting the progression of liver fibrosis. Abnormal expression of signaling pathways, such as the TGF-β/Smads pathway, contributes to HSCs activation. Recent studies have shed light on these pathways, providing valuable insights into the development of liver fibrosis. Here, we will review six signaling pathways such as TGF-β/Smads that have been studied more in recent years.

Interplays of liver fibrosis-associated microRNAs: Molecular mechanisms and implications in diagnosis and therapy

microRNAs (miRNAs) are a class of non-coding functional small RNA composed of 21-23 nucleotides, having multiple associations with liver fibrosis. Fibrosis-associated miRNAs are roughly classified into pro-fibrosis or anti-fibrosis types. The former is capable of activating hepatic stellate cells (HSCs) by modulating pro-fibrotic signaling pathways, mainly including TGF-β/SMAD, WNT/β-catenin, and Hedgehog; the latter is responsible for maintenance of the quiescent phenotype of normal HSCs, phenotypic reversion of activated HSCs (aHSCs), inhibition of HSCs proliferation and suppression of the extracellular matrix-associated gene expression. Moreover, several miRNAs are involved in regulation of liver fibrosis via alternative mechanisms, such as interacting between hepatocytes and other liver cells via exosomes and increasing autophagy of aHSCs. Thus, understanding the role of these miRNAs may provide new avenues for the development of novel interventions against hepatic fibrosis.

Regulatory Functions and Mechanisms of Circular RNAs in Hepatic Stellate Cell Activation and Liver Fibrosis

Chronic liver injury induces the activation of hepatic stellate cells (HSCs) into myofibroblasts, which produce excessive amounts of extracellular matrix (ECM), resulting in tissue fibrosis. If the injury persists, these fibrous scars could be permanent and disrupt liver architecture and function. Currently, effective anti-fibrotic therapies are lacking; hence, understanding molecular mechanisms that control HSC activation could hold a key to the development of new treatments. Recently, emerging studies have revealed roles of circular RNAs (circRNAs), a class of non-coding RNAs that was initially assumed to be the result of splicing errors, as new regulators in HSC activation. These circRNAs can modulate the activity of microRNAs (miRNAs) and their interacting protein partners involved in regulating fibrogenic signaling cascades. In this review, we will summarize the current knowledge of this class of non-coding RNAs for their molecular function in HSC activation and liver fibrosis progression.

RNA sequencing of LX-2 cells treated with TGF-β1 identifies genes associated with hepatic stellate cell activation

Background

Hepatic stellate cells (HSCs) are liver-resident myofibroblast precursors responsible for the production of collagen and maintenance of the hepatic extracellular matrix (ECM). As such, they are generally associated with fibrotic liver diseases. HSCs become “activated” in response to tissue damage or pathogen invasion, a process most commonly driven by transforming growth factor-β1 (TGF-β1). Despite this, the full extent of TGF-β1 signalling in these cells is poorly understood. Clarifying the range and diversity of this signalling will further improve our understanding of the process of HSC activation.

Methods and results

RNA sequencing was used to quantitate the transcriptomic changes induced in LX-2 cells, an activated human HSC line, following TGF-b1 treatment. In total, 5,258 genes were found to be significantly differentially expressed with a false discovery rate cut-off of < 0.1. The topmost deregulated of these genes included those with no currently characterised role in either HSC activation or fibrotic processes, including CIITA and SERPINB2. In silico analysis revealed the prominent signalling pathways downstream of TGF-β1 in LX-2 cells.

Conclusions

In this study, we describe the genes and signalling pathways significantly deregulated in LX-2 cells following TGF-β1 treatment. We identified several highly deregulated genes with no currently characterised role in HSC activation, which may represent novel mediators of fibrotic responses in HSCs or the liver macroenvironment. This work may be of use in the identification of new markers of liver fibrosis and could provide insight into prospective genes or pathways that might be targeted for the amelioration of fibrotic liver disease in the future.

Hepatic Stellate Cells and Hepatocarcinogenesis

Hepatic stellate cells (HSCs) are a significant component of the hepatocellular carcinoma (HCC) tumor microenvironment (TME). Activated HSCs transform into myofibroblast-like cells to promote fibrosis in response to liver injury or chronic inflammation, leading to cirrhosis and HCC. The hepatic TME is comprised of cellular components, including activated HSCs, tumor-associated macrophages, endothelial cells, immune cells, and non-cellular components, such as growth factors, proteolytic enzymes and their inhibitors, and other extracellular matrix (ECM) proteins. Interactions between HCC cells and their microenvironment have become topics under active investigation. These interactions within the hepatic TME have the potential to drive carcinogenesis and create challenges in generating effective therapies. Current studies reveal potential mechanisms through which activated HSCs drive hepatocarcinogenesis utilizing matricellular proteins and paracrine crosstalk within the TME. Since activated HSCs are primary secretors of ECM proteins during liver injury and inflammation, they help promote fibrogenesis, infiltrate the HCC stroma, and contribute to HCC development. In this review, we examine several recent studies revealing the roles of HSCs and their clinical implications in the development of fibrosis and cirrhosis within the hepatic TME.

Integration of miRNA-regulatory networks in hepatic stellate cells identifies TIMP3 as a key factor in chronic liver disease

BACKGROUND & AIMS

Activation of hepatic stellate cells (HSC) is a critical process involved in liver fibrosis. Several miRNAs are implicated in gene regulation during this process but their exact and respective contribution is still incompletely understood. Here we propose an integrative approach of miRNA-regulatory networks to predict new targets.

METHODS

miRNA regulatory networks in activated HSCs were built using lists of validated miRNAs and the CyTargetLinker tool. The resulting graphs were filtered according to public transcriptomic data and the reduced graphs were analysed through GO annotation. A miRNA network regulating the expression of TIMP3 was further studied in human liver samples, isolated hepatic cells and mouse model of liver fibrosis.

RESULTS

Within the up-regulated miRNAs, we identified a subnetwork of five miRNAs (miR-21-5p, miR-222-3p, miR-221-3p miR-181b-5p and miR-17-5p) that target TIMP3. We demonstrated that TIMP3 expression is inversely associated with inflammatory activity and IL1-ß expression in vivo. We further showed that IL1-ß inhibits TIMP3 expression in HSC-derived LX-2 cells. Using data from The Cancer Genome Atlas (TCGA), we showed that, in hepatocellular carcinoma (HCC), TIMP3 expression is associated with survival (P < .001), while miR-221 (P < .05), miR-222 (P < .01) and miR-181b (P < .01) are markers for a poor prognosis.

CONCLUSIONS

Several miRNAs targeting TIMP3 are up-regulated in activated HSCs and down-regulation of TIMP3 expression is associated with inflammatory activity in liver fibrosis and poor prognosis in HCC. The regulatory network including specific miRNAs and TIMP3 is therefore central for the evolution of chronic liver disease.

Molecular hydrogen regulates PTEN-AKT-mTOR signaling via ROS to alleviate peritoneal dialysis-related peritoneal fibrosis

As a convenient, effective and economical kidney replacement therapy for end-stage renal disease (ESRD), peritoneal dialysis is available in approximately 11% of ESRD patients worldwide. However, long-term peritoneal dialysis treatment causes peritoneal fibrosis. In recent years, the application potential of molecular hydrogen in the biomedicine has been well recognized. Molecular hydrogen selectively scavenges cytotoxic reactive oxygen species (ROS) and acts as an antioxidant. In this experiment, a high glucose-induced peritoneal fibrosis mouse model was successfully established by intraperitoneal injection of high glucose peritoneal dialysate, and peritoneal fibrosis mice were treated with hydrogen-rich peritoneal dialysate. In addition, in vitro studies of high glucose-induced peritoneal fibrosis were performed using MeT-5A cells. In vitro and in vivo experiments show that molecular hydrogen could inhibit peritoneal fibrosis progress induced by high glucose effectively. Furthermore, it has been found that molecular hydrogen alleviate fibrosis by eliminating intracellular ROS and inhibiting the activation of the PTEN/AKT/mTOR pathway. The present data proposes that molecular hydrogen exerts the capacity of anti-peritoneal fibrosis through the ROS/PTEN/AKT/mTOR pathway. Therefore, molecule hydrogen is a potential, safe, and effective treatment agent, with peritoneal protective property and great clinical significance.

Liquiritigenin suppresses the activation of hepatic stellate cells via targeting miR-181b/PTEN axis

BACKGROUND

Liquiritigenin (LQ), an aglycone of liquiritin in licorice, has demonstrated antioxidant, anti-inflammatory and anti-tumor activities. Previously, LQ was found to inhibit liver fibrosis progression.

PURPOSE

Phosphatase and tensin homolog (PTEN) has been reported to act as a negative regulator of hepatic stellate cell (HSC) activation. However, the roles of PTEN in the effects of LQ on liver fibrosis have not been identified to date.

METHODS

The effects of LQ on liver fibrosis in carbon tetrachloride (CCl₄) mice as well as primary HSCs were examined. Moreover, the roles of PTEN and microRNA-181b (miR-181b) in the effects of LQ on liver fibrosis were examined.

RESULTS

LQ markedly ameliorated CCl₄-induced liver fibrosis, with a reduction in collagen deposition as well as α-SMA level. Moreover, LQ induced an increase in PTEN and effectively inhibited HSC activation including cell proliferation, α-SMA and collagen expression, which was similar with curcumin (a positive control). Notably, loss of PTEN blocked down the effects of LQ on HSC activation. PTEN was confirmed as a target of miR-181b and miR-181b-mediated PTEN was involved in the effects of LQ on liver fibrosis. LQ led to a significant reduction in miR-181b expression. LQ-inhibited HSC activation could be restored by over-expression of miR-181b. Further studies demonstrated that LQ down-regulated miR-181b level via Sp1. Collectively, we demonstrate that LQ inhibits liver fibrosis, at least in part, via regulation of miR-181b and PTEN.

CONCLUSION

LQ down-regulates miR-181b level, leading to the restoration of PTEN expression, which contributes to the suppression of HSC activation. LQ may be a potential candidate drug against liver fibrosis.

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Botulinum toxin type A prevents the phenotypic transformation of fibroblasts induced by TGF‑β1 via the PTEN/PI3K/Akt signaling pathway

Hypertrophic scar (HS) is a common type of dermatosis. Botulinum toxin type A (BTXA) can exert an anti-HS effect; however, the regulatory mechanisms underlying this effect remain unclear. Thus, the aim of this study was to examine the effects of BTXA on phosphatase and tensin homolog deleted on chromosome ten (PTEN) expression and the fibroblast phenotypic transformation induced by transforming growth factor (TGF)-β1, which is an important regulatory factor involved in the process of HS. For this purpose, fibroblasts were treated with various concentrations of BTXA and then treated with 10 ng/ml of TGF-β1 with gradient concentrations of BTXA. The proliferation and apoptosis of fibroblasts were measured by cell counting kit-8 assay (CCK-8) and flow cytometry, respectively. PTEN methylation was analyzed by methylation-specific PCR (MSP) and DNA methyltransferase (DNMT) activity was determined using a corresponding kit. RT-qPCR and western blot analysis were performed to detect the transcription and translation levels. The results revealed that BTXA suppressed the proliferation and increased the apoptosis of fibroblasts treated with TGF-β1 in a dose-dependent manner. BTXA in combination with TGF-β1 suppressed the expression of molecules related to the extracellular matrix (ECM), epithelial-mesenchymal transition (EMT) and apoptosis. BTXA reduced the PTEN methylation level and downregulated the expression levels of methylation-associated genes. BTXA also inhibited the phosphorylation of phosphoinositide 3-kinase (PI3K) and Akt. On the whole, the findings of this study indicate that BTXA may inhibit fibroblast phenotypic transformation by regulating PTEN methylation and the phosphorylation of related pathways. The findings of this study can provide a theoretical basis for HS treatment.

lncRNA GAS5 restrains CCl4-induced hepatic fibrosis by targeting miR-23a through the PTEN/PI3K/Akt signaling pathway

Hepatic fibrosis is chronic liver damage with many causes that has a relatively high death rate. The current study showed that long noncoding RNA (lncRNA) growth arrest-specific transcript 5 (GAS5), microRNA-23a (miR-23a), and phosphatase and tensin homolog (PTEN) play important roles in the pathological process of hepatic fibrosis but have a relatively unclear regulatory mechanism. This study aimed to investigate the roles of lncRNA GAS5, miR-23a, and PTEN in the pathological process of hepatic fibrosis and hepatic stellate cell (HSC) activation. We used carbon tetrachloride (CCl₄) intraperitoneal injections to establish a rat hepatic fibrosis model and exogenous transforming growth factor-β1 to establish an HSC activation model. Quantitative RT-PCR, Western blot, dual-luciferase reporter system, and RNA pull-down assays were used to investigate which microRNAs and lncRNAs participate in the process of hepatic fibrosis and HSC activation. miR-23a expression increased significantly in hepatic fibrosis tissues and activated HSCs. miR-23a interaction with and degradation of PTEN further influenced the downstream signaling pathway phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin/Snail (PI3K/Akt/mTOR/Snail), causing E-cadherin expression levels to decrease and α-smooth muscle actin and collagen I expression levels to increase. lncRNA GAS5 can be used as a sponge platform for miR-23a to decrease miR-23a expression levels competitively. We revealed the role of the lncRNA GAS5/miR-23a/PTEN/PI3K/Akt/mTOR/Snail signaling pathway in hepatic fibrosis, providing molecular targets for the treatment of hepatic fibrosis. NEW & NOTEWORTHY This is the first study revealing that microRNA-23a (miR-23a) promotes hepatic fibrosis through the phosphatase and tensin homolog/phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin/Snail signaling pathway, and long noncoding RNA (lncRNA) growth arrest-specific transcript 5 (GAS5) can act as a sponge platform for miR-23a. Therefore, lncRNA GAS5/miR-23a may bring molecular targets for hepatic fibrosis therapy.

Effects of the tumor suppressor PTEN on biological behaviors of activated pancreatic stellate cells in pancreatic fibrosis

Pancreatic stellate cells (PSCs), when activated, are characterized by proliferation and collagen synthesis, and contribute to extracellular matrix deposition in pancreatic fibrosis. Concomitantly, fibrosis is linked with the loss of PTEN (phosphatase and tensin homolog) protein in several organs. This study investigated the association between PTEN protein levels and the activated or apoptotic status of PSCs in a rat model of chronic pancreatitis. In addition, the activation status and biological behaviors of culture-activated PSCs were analyzed after lentiviral transfection with wildtype or mutant (G129E) PTEN for upregulation, or PTEN short hairpin RNA for downregulation, of PTEN. In vivo, PTEN levels gradually decreased during pancreatic fibrosis, which positively correlated with apoptosis of activated PSCs, but negatively with PSC activation. In vitro, activated PSCs with wildtype PTEN showed less proliferation, migration, and collagen synthesis compared with control PSCs, and greater numbers were apoptotic; activated PSCs with mutant PTEN showed similar, but weaker, effects. Furthermore, AKT and FAK/ERK signaling was involved in this process. In summary, activated PSCs during pancreatic fibrosis in vivo have lower levels of PTEN. In vitro, PTEN appears to prevent PSCs from further activation and promotes apoptosis through regulation of the AKT and FAK/ERK pathways.

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.

Effects and mechanism of adenovirus-mediated phosphatase and tension homologue deleted on chromosome ten gene on collagen deposition in rat liver fibrosis

AIM

To evaluate the effects of phosphatase and tension homologue deleted on chromosome ten (PTEN) gene on collagen metabolism in hepatic fibrosis and the underlying mechanisms.

METHODS

Rat primary hepatic stellate cells (HSCs) and human LX-2 cells were transfected with adenovirus containing cDNA constructs encoding wild-type PTEN (Ad-PTEN), PTEN mutant G129E gene (Ad-G129E), and RNA interference constructs targeting the PTEN sequence PTEN short hairpin RNA to up-regulate and down-regulate the expression of PTEN. HSCs were assayed using fluorescent microscopy, real-time polymerase chain reaction, and western blotting. Moreover, a CCl4-induced rat hepatic fibrosis model was established to investigate the in vivo effects. Hematoxylin and eosin, and Masson's trichrome were used to assess the histological changes. The expression of collagen I and III was assessed using immunohistochemistry and western blot analysis.

RESULTS

Elevated expression of PTEN gene reduced serum levels of alanine transaminase and aspartate transaminase, decreased collagen deposition in the liver, and reduced hepatocyte necrosis. In contrast, knockdown of PTEN expression had an opposite effect, such as increased collagen deposition in the liver, and was molecularly characterized by the increased expression of matrix metalloproteinase (MMP)-13 (P < 0.01) and MMP-2 (P < 0.01), as well as decreased expression of the tissue inhibitor of metalloproteinase (TIMP)-1 (P < 0.01) and TIMP-2 (P < 0.01).

CONCLUSION

These data indicated that gene therapy using recombinant adenovirus encoding PTEN might be a novel way of treating hepatic fibrosis.

TGF-β induces phosphorylation of phosphatase and tensin homolog: implications for fibrosis of the trabecular meshwork tissue in glaucoma

Fundamental cell signaling mechanisms that regulate dynamic remodeling of the extracellular matrix (ECM) in mechanically loaded tissues are not yet clearly understood. Trabecular meshwork (TM) tissue in the eye is under constant mechanical stress and continuous remodeling of ECM is crucial to maintain normal aqueous humor drainage and intraocular pressure (IOP). However, excessive ECM remodeling can cause fibrosis of the TM as in primary open-angle glaucoma (POAG) patients, and is characterized by increased resistance to aqueous humor drainage, elevated IOP, optic nerve degeneration and blindness. Increased levels of active transforming growth factor-β2 (TGF-β2) in the aqueous humor is the main cause of fibrosis of TM in POAG patients. Herein, we report a novel finding that, in TM cells, TGF-β-induced increase in collagen expression is associated with phosphorylation of phosphatase and tensin homolog (PTEN) at residues Ser380/Thr382/383. Exogenous overexpression of a mutated form of PTEN with enhanced phosphatase activity prevented the TGF-β-induced collagen expression by TM cells. We propose that rapid alteration of PTEN activity through changes in its phosphorylation status could uniquely regulate the continuous remodeling of ECM in the normal TM. Modulating PTEN activity may have high therapeutic potential to alleviating the fibrosis of TM in POAG patients.

HOTAIR Epigenetically Modulates PTEN Expression via MicroRNA-29b: A Novel Mechanism in Regulation of Liver Fibrosis

Homeobox transcript antisense RNA (HOTAIR), as a long intergenic non-coding RNA (lincRNA), is upregulated in various cancers and involved in diverse cellular functions. However, its role in liver fibrosis is unclear. In this study, HOTAIR expression was upregulated in hepatic stellate cells (HSCs) in vivo and in vitro during liver fibrosis. HOTAIR knockdown suppressed HSC activation including α-smooth muscle actin (α-SMA) and typeIcollagen in vitro and in vivo. Both HSC proliferation and cell cycle were inhibited by HOTAIR knockdown. Notably, inhibition of HOTAIR led to an increase in PTEN, associated with the loss of DNA methylation. miR-29b-mediated control of PTEN methylation was involved in the effects of HOTAIR knockdown. HOTAIR was confirmed a target of miR-29b and lack of the miR-29b binding site in HOTAIR prevented the suppression of miR-29b, suggesting HOTAIR contributes to PTEN expression downregulation via sponging miR-29b. Interestingly, increased HOTAIR was also observed in hepatocytes during liver fibrosis. Loss of HOTAIR additionally led to the increase in PTEN and the reduction in typeIcollagen in hepatocytes. Collectively, we demonstrate that HOTAIR downregulates miR-29b expression and attenuates its control on epigenetic regulation, leading to enhanced PTEN methylation, which contributes to the progression of liver fibrosis.

MicroRNAs in hepatic pathophysiology

MicroRNAs (miRNAs) are a group of small non-coding RNAs that range in length from 20 to 25 nucleotides. MicroRNAs are specific for multiple cellular functions, including cell generation, differentiation, multiplication, carcinogenesis, and apoptosis. Many researchers have recently reported that the aberrant expression of miRNAs in hepatic tissue was related to the pathogenesis of liver disease, including viral hepatitis, hepatocellular carcinoma, and fatty liver disease. Multiple studies have proposed that an analysis of circulating miRNAs may be useful for diagnosing etiologies or staging the progression of liver disease, as well as for therapeutic purposes, for example, nucleic acid therapy. This review summarizes and discusses recent advances in the knowledge of miRNAs for chronic liver diseases, with special interest in viral hepatitis, liver fibrosis, and biomarkers.

Effect of Phosphatase and Tensin Homologue on Chromosome 10 on Angiotensin II-Mediated Proliferation, Collagen Synthesis, and Akt/P27 Signaling in Neonatal Rat Cardiac Fibroblasts

Cardiac fibroblasts (CFs) play a key role in cardiac fibrosis by regulating the balance between extracellular matrix synthesis and breakdown. Although phosphatase and tensin homologue on chromosome 10 (PTEN) has been found to play an important role in cardiovascular disease, it is not clear whether PTEN is involved in functional regulation of CFs. In the present study, PTEN was overexpressed in neonatal rat CFs via recombinant adenovirus-mediated gene transfer. The effects of PTEN overexpression on cell-cycle progression and angiotensin II- (Ang II-) mediated regulation of collagen metabolism, synthesis of matrix metalloproteinases, and Akt/P27 signaling were investigated. Compared with uninfected cells and cells infected with green fluorescent protein-expressing adenovirus (Ad-GFP), cells infected with PTEN-expressing adenovirus (Ad-PTEN) significantly increased PTEN protein and mRNA levels in CFs (P < 0.05). The proportion of CFs in the G1/S cell-cycle phase was significantly higher for PTEN-overexpressing cells. In addition, Ad-PTEN decreased mRNA expression and the protein synthesis rate of collagen types I and III and antagonized Ang II-induced collagen synthesis. Overexpression of PTEN also decreased Ang II-induced matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-1 (TIMP-1) production as well as gelatinase activity. Moreover, Ad-PTEN decreased Akt expression and increased P27 expression independent of Ang II stimulation. These results suggest that PTEN could regulate its functional effects in neonatal rat CFs partially via the Akt/P27 signaling pathway.

Identification of a Novel lincRNA-p21-miR-181b-PTEN Signaling Cascade in Liver Fibrosis

Previously, we found that long intergenic noncoding RNA-p21 (lincRNA-p21) inhibits hepatic stellate cell (HSC) activation and liver fibrosis via p21. However, the underlying mechanism of the antifibrotic role of lincRNA-p21 in liver fibrosis remains largely unknown. Here, we found that lincRNA-p21 expression was significantly downregulated during liver fibrosis. In LX-2 cells, the reduction of lincRNA-p21 induced by TGF-β1 was in a dose- and time-dependent manner. lincRNA-p21 expression was reduced in liver tissues from patients with liver cirrhosis when compared with that of healthy controls. Notably, lincRNA-p21 overexpression contributed to the suppression of HSC activation. lincRNA-p21 suppressed HSC proliferation and induced a significant reduction in α-SMA and type I collagen. All these effects induced by lincRNA-p21 were blocked down by the loss of PTEN, suggesting that lincRNA-p21 suppressed HSC activation via PTEN. Further study demonstrated that microRNA-181b (miR-181b) was involved in the effects of lincRNA-p21 on HSC activation. The effects of lincRNA-p21 on PTEN expression and HSC activation were inhibited by miR-181b mimics. We demonstrated that lincRNA-p21 enhanced PTEN expression by competitively binding miR-181b. In conclusion, our results disclose a novel lincRNA-p21-miR-181b-PTEN signaling cascade in liver fibrosis and suggest lincRNA-p21 as a promising molecular target for antifibrosis therapy.

miR-1273g-3p modulates activation and apoptosis of hepatic stellate cells by directly targeting PTEN in HCV-related liver fibrosis

MicroRNA (miRNA) play a pivotal role in the development of liver fibrosis. However, the functions of miRNA in hepatitis C virus (HCV)-related liver fibrosis remain unclear. In this study, we systematically analyzed the microarray data of the serum miRNA in patients with HCV-induced hepatic fibrosis. Among 41 dysregulated miRNA, miR-1273g-3p was the most significantly upregulated miRNA and correlated with the stage of liver fibrosis. Overexpression of miR-1273g-3p could inhibit translation of PTEN, increase the expression of α-SMA, Col1A1, and reduce apoptosis in HSCs. Hence, we conclude that miR-1273g-3p might affect the activation and apoptosis of HSCs by directly targeting PTEN in HCV-related liver fibrosis.

Activation of hepatic stellate cell in Pten null liver injury model

BACKGROUND

Hepatic fibrosis is a prominent pathological feature associated with chronic liver disease including non-alcoholic hepatosteatosis (NASH), and a precursor for liver cancer development. We previously reported that PTEN loss in the liver, which leads to hyperactivated liver insulin signaling results in NASH development. Here we used the same mouse model to study the progression from steatosis to fibrosis.

RESULTS

The Pten null livers develop progressive liver fibrosis as indicated by Sirius Red staining and increased expression of collagen I, Timp 1, SMAα, and p75NTR. Consistently, hepatic stellate cells (HSCs) isolated from Pten null livers are readily activated when compared with that from mice with intact PTEN. Deletion of AKT2, the downstream target of PTEN signal, blocked NASH development, and alleviated fibrosis. HSCs from the Pten/Akt2 double null mice are quiescent like those isolated from the control livers. Our analysis shows that the activation of HSCs does not depend on the intrinsic signals regulated by PI3K/AKT, the target of PTEN, but does depend on steatosis and injury to the liver. During the progression of liver fibrosis in the Pten null model, Wnt ligands and signaling receptor are induced, concurrent with the reduction of sFRP5, a Wnt antagonist. We showed that treatment of HSCs with Wnt receptor antagonist blocks the observed morphological changes when HSCs undergo activation in culture. This signal appears to be mediated by β-catenin, as manipulating β-catenin signaling alters marker gene expressions of HSC activation.

CONCLUSIONS

Wnt/β-catenin activation serves as an important mediator for fibrosis development resulting from NASH using a mouse model where NASH is mimicked by PTEN loss.

Regulatory Effects and Mechanism of Adenovirus-Mediated PTEN Gene on Hepatic Stellate Cells

BACKGROUND

Tension homology deleted on chromosome ten (PTEN) is important in liver fibrosis.

AIMS

The purpose of this study was to evaluate the PTEN gene effects and mechanism of action on hepatic stellate cells (HSCs).

METHODS

The rat primary HSCs and human LX-2 cells were transfected by an adenovirus containing cDNA constructs encoding the wild-type PTEN (Ad-PTEN), the PTEN mutant G129E gene (Ad-G129E) and RNA interference targeting the PTEN sequence PTEN short hairpin RNA (PTEN shRNA), to up-regulate and down-regulate PTEN expression, respectively. The HSCs were assayed with a fluorescent microscope, real time PCR, Western blot, MTT, flow cytometry and Terminal-deoxynucleoitidyl transferase mediated nick end labeling. In addition, the CCl4 induced rat hepatic fibrosis model was also established to check the in vivo effects of the recombinant adenovirus with various levels of PTEN expression.

RESULTS

The data have shown that the over-expressed PTEN gene led to reduced HSCs activation and viability, caspase-3 activity and cell cycle arrest in the G0/G1 and G2/M phases, as well as negative regulation of the PI3K/Akt and FAK/ERK signaling pathways in vitro. The over-expressed PTEN gene improved liver function, inhibited proliferation and promoted apoptosis of HSCs both in vitro and in vivo.

CONCLUSIONS

These data have shown that gene therapy using the recombinant adenovirus encoding wild-type PTEN inhibits proliferation and induces apoptosis of HSCs, which is a potential treatment option for hepatic fibrosis.

Up-regulated expression of PTEN after splenetomy may prevent the progression of liver fibrosis in rats

BACKGROUND/PURPOSE

To investigate the mechanisms of delaying progression of liver fibrosis by splenectomy.

METHODS

Liver fibrosis was induced by common bile duct ligation. Rats were divided into 3 groups randomly: group A with common bile duct ligation and splenectomy (n = 45), group B with common bile duct ligation and spleen sham operation (n = 45), group C with sham common bile duct ligation and spleen sham operation (n = 45). Liver samples were collected at the 1st, 3rd and 5th week. H&E staining and Sirius staining were used to evaluate the degree of liver fibrosis, immunohistochemical staining was used to measure the expression of α-SMA and PTEN. PTEN mRNA and protein expression was measured by real-time PCR and Western-blot.

RESULTS

Over time, liver fibrosis developed gradually in group A and B. The expression of PTEN mRNA and protein in group A was higher than that in group B (P < 0.05), while the expression of α-SMA was higher in group B (P < 0.05). The expression of PTEN was negatively correlated with α-SMA (r = -0.86, P < 0.05).

CONCLUSIONS

In this study, splenectomy can up-regulate the expression of PTEN and reduce the secretion of α-SMA, thereby deterring the progression of liver fibrosis.

Hepatic stellate cell is activated by microRNA-181b via PTEN/Akt pathway

Activation of hepatic stellate cells (HSCs) is an essential event in the initiation and progression of liver fibrosis. MicroRNAs have been shown to play a pivotal role in regulating HSC functions such as cell proliferation, differentiation, and apoptosis. Recently, miR-181b has been reported to promote HSCs proliferation by targeting p27. But whether alpha-smooth muscle actin (α-SMA) or collagens could be promoted by miR-181b in activated HSCs is still not clear. Therefore, the understanding of the role of miR-181b in liver fibrosis remains limited. Our results showed that miR-181b expression was increased much higher than miR-181a expression in vitro in transforming growth factor-β1-induced HSC activation as well as in vivo in carbon tetrachloride-induced rat liver fibrosis. Of note, overexpression of miR-181b significantly increased the expressions level of α-SMA and type I collagen, and further promoted HSCs proliferation. Furthermore, phosphatase and tensin homologs deleted on chromosome 10 (PTEN), a negative regulator of PI3K/Akt pathway, were confirmed as a direct target of miR-181b. We demonstrated that miR-181b could suppress PTEN expression and increase Akt phosphorylation in HSCs. Interestingly, the effects of miR-181b on the activation of HSCs were blocked down by Akt inhibitor LY294002. Our results revealed a profibrotic role of miR-181b in HSC activation and demonstrated that miR-181b could activate HSCs, at least in part, via PTEN/Akt pathway.

miR-106b-25/miR-17-92 clusters: Polycistrons with oncogenic roles in hepatocellular carcinoma

MicroRNAs are small endogenously expressed RNA molecules which are involved in the process of silencing gene expression through translational regulation. The polycistronic miR-17-92 cluster is the first microRNA cluster shown to play a role in tumorigenesis. It has two other paralogs in the human genome, the miR-106b-25 cluster and the miR-106a-363 cluster. Collectively, the microRNAs encoded by these clusters can be further grouped based on the seed sequences into four families, namely the miR-17, the miR-92, the miR-18 and the miR-19 families. Over-expression of the miR-106b-25 and miR-17-92 clusters has been reported not only during the development of cirrhosis but also subsequently during the development of hepatocellular carcinoma. Members of these clusters have also been shown to affect the replication of hepatitis B and hepatitis C viruses. Various targets of these microRNAs have been identified, and these targets are involved in tumor growth, cell survival and metastasis. In this review, we first describe the regulation of these clusters by c-Myc and E2F1, and how the members of these clusters in turn regulate E2F1 expression forming an auto-regulatory loop. In addition, the roles of the various members of the clusters in affecting relevant target gene expression in the pathogenesis of hepatocellular carcinoma will also be discussed.

Suppression of collagen synthesis by Dicer gene silencing in hepatic stellate cells

MicroRNAs (miRNAs) have emerged as important mediators of hepatic stellate cells (HSCs) and are pivotal in the pathogenesis of liver fibrosis. Dicer, the key enzyme in the RNA interference (RNAi) pathway, is involved in cutting precursor miRNAs to functionally mature forms. Emerging evidence has demonstrated that Dicer expression is dysregulated in embryo development and tumors. In the present study, we aimed to address whether Dicer expression was correlated with the activity of HSCs. We used a recombinant lentivirus to generate short hairpin RNAs (shRNAs) targeting Dicer. The mRNA and protein expression of Dicer was effectively inhibited by three pairs of Dicer shRNA vectors, of which the shRNA1 vector exhibited the strongest inhibitory effect. The shRNA1 vector demonstrated a marked inhibitory effect on the activity of HSCs, resulting in the reduction of cell proliferation and the decrease of fibrosis-related genes, including type Ⅰ collagen (Col1A1), α-smooth muscle actin (α-SMA) and tissue inhibitor of metalloproteinases (TIMP). The mRNA expression of Col1A1, α-SMA and TIMP were decreased by 60, 56 and 49%, respectively. The protein expression was reduced by 56, 52 and 42%, respectively. Additionally, the inhibition of Dicer resulted in a decrease of miR-138, -143, -140 and -122 levels, of which miR-138 exhibited the strongest decline. The firefly luciferase reporter experiments and RT-PCR indicated that phosphatase and tension homolog deleted on chromosome 10 (PTEN), Ras GTPase activating-like protein 1 (RASAL1), acyl-CoA synthetase long-chain family member 1 (ACSL1) and p27 3' untranslated region sequences were targeted by miR-138, -143, -140 and -122, respectively. Taken together, the present study contributes important new findings for the role of Dicer-mediated miRNA processing in collagen synthesis of HSCs, which may serve as a foundation for RNAi study of liver fibrosis in vivo.

Guggulsterone attenuates activation and survival of hepatic stellate cell by inhibiting nuclear factor kappa B activation and inducing apoptosis

BACKGROUND AND AIM

Liver fibrosis is associated with the deposition of the extracellular matrix, and hepatic stellate cells (HSCs) are the major source of these matrix proteins. Guggulsterone has recently been shown to induce apoptosis in several cell lines. Thus, the aim of this study was to evaluate whether guggulsterone has antifibrotic activities by reducing the activation and survival of HSCs.

METHODS

Apoptotic and fibrosis-related signaling pathways and nuclear factor kappa B (NF-κB) activity were explored in LX-2 cells, an immortalized human HSC line, and in a mice model of liver fibrosis.

RESULTS

Guggulsterone suppressed LX-2 cell growth in a dose- and activation-dependent manner. This growth suppression was due to the induction of HSC apoptosis, which was mediated by the activation of c-Jun N-terminal kinase and mitochondrial apoptotic signaling. Additionally, guggulsterone regulated phosphorylation of Akt and adenosine monophosphate-activated protein kinase, which were subsequently proven responsible for the guggulsterone-induced HSC growth suppression. Guggulsterone inhibited NF-κB activation in LX-2 cells, which is one of the major mediators in HSC activation. Indeed, guggulsterone decreased collagen α1 synthesis and α-smooth muscle actin expression in these cells. Compared with the control mice or mice treated with a low dose of guggulsterone, high dose of guggulsterone significantly decreased the extent of collagen deposition and the percentage of activated HSCs undergoing apoptosis.

CONCLUSIONS

These results demonstrate that guggulsterone suppressed HSC activation and survival by inhibiting NF-κB activation and inducing apoptosis. Therefore, guggulsterone may be useful as an antifibrotic agent in chronic liver diseases.

MicroRNA-21 activates hepatic stellate cells via PTEN/Akt signaling

Activation of hepatic stellate cells is the key event in the liver fibrosis. miRs have been shown to play fundamental role in diverse biological and pathological processes. In the present study, we investigated the fibrogenic role of miR-21 in human hepatic stellate LX-2 cells and explored underlying mechanisms. The results showed that treatment of LX-2 cells with platelet-derived growth factor (PDGF)-BB significantly stimulated α1(I) collagen mRNA synthesis and the protein expression of α-SMA, which are characteristics of activation of hepatic stellate cells and simultaneously increased miR-21 expression. Downregulation of miR-21 expression by transfection of anti-miR-21 into LX-2 cells prevented PDGF-BB-induced LX-2 cell activation. Overexpression of miR-21 expression alone also stimulated LX-2 cell activation, while downregulation of miR-21 expression suppressed LX-2 cell activation. miR-21 also played a role in mRNA expression and activity of matrix metalloproteinase 2 (MMP2) in LX-2 cells. Moreover, overexpression of miR-21 decreased protein expression of PTEN in LX-2 cells, resulting in activation of the Akt. Inhibition of Akt signaling by specific inhibitor LY 294002 blocked miR-21-induced fibrogenic effects in LX-2 cells. In summary, miR-21 is an important mediator in LX-2 cell activation. The fibrogenic effects of miR-21 on LX-2 cell activation are mediated through PTEN/Akt pathway. miR-21 may be a potential novel molecular target for the liver fibrosis.

Differential expression of PTEN in hepatic tissue and hepatic stellate cells during rat liver fibrosis and its reversal

To evaluate the change in phosphatase and tensin homology deleted on chromosome ten (PTEN) expression in liver fibrogenesis, particularly the reversal of fibrogenic liver tissues, and to investigate the relation with the proliferation and apoptosis of hepatic stellate cells (HSCs) in vivo, a rat model of hepatic fibrosis was established by hypodermic injection of carbon tetrachloride (CCl4) mixed with olive oil at the concentration of 40% for 5 weeks (2 ml/kg, twice a week). Reversal of fibrosis was achieved with normal feedings for 4 weeks after CCl4 injection for 5 weeks. The expression of PTEN was measured by immunofluorescence, western blot analysis and real-time PCR. Co-expression of α-smooth muscle actin (α-SMA) with PTEN and α-SMA with terminal deoxynucleotidyltransferase-mediated dUTP nick end labelling (TUNEL) were assessed by confocal laser scanning microscopy. The results displayed that the expression of PTEN was reduced with fibrosis in both rat liver tissues and activated HSCs. By contrast, PTEN expression was increased with the reversal of liver fibrosis. Compared to the fibrogenic state, there were increased numbers of apoptotic activated HSCs during reversal of fibrosis. These data suggest that the dynamic expression of PTEN in rat liver tissues is negatively correlated with liver fibrosis and activated HSCs and is positively correlated with reversal of fibrosis and apoptotic activated HSCs. Modulation of PTEN expression may be an effective and novel method for the treatment of liver fibrosis.

DNMT1-mediated PTEN hypermethylation confers hepatic stellate cell activation and liver fibrogenesis in rats

Hepatic stellate cell (HSC) activation is an essential event during liver fibrogenesis. Phosphatase and tension homolog deleted on chromosome 10 (PTEN), a tumor suppressor, is a negative regulator of this process. PTEN promoter hypermethylation is a major epigenetic silencing mechanism in tumors. The present study aimed to investigate whether PTEN promoter methylation was involved in HSC activation and liver fibrosis. Treatment of activated HSCs with the DNA methylation inhibitor 5-aza-2'-deoxycytidine (5-azadC) decreased aberrant hypermethylation of the PTEN gene promoter and prevented the loss of PTEN expression that occurred during HSC activation. Silencing DNA methyltransferase 1 (DNMT1) gene also decreased the PTEN gene promoter methylation and upregulated the PTEN gene expression in activated HSC-T6 cells. In addition, knockdown of DNMT1 inhibited the activation of both ERK and AKT pathways in HSC-T6 cells. These results suggest that DNMT1-mediated PTEN hypermethylation caused the loss of PTEN expression, followed by the activation of the PI3K/AKT and ERK pathways, resulting in HSC activation.

Cell signals influencing hepatic fibrosis

Liver fibrosis is the result of the entire organism responding to a chronic injury. Every cell type in the liver contributes to the fibrosis. This paper first discusses key intracellular signaling pathways that are induced during liver fibrosis. The paper then examines the effects of these signaling pathways on the major cell types in the liver. This will provide insights into the molecular pathophysiology of liver fibrosis and should identify therapeutic targets.

PTEN inhibits proliferation and functions of hypertrophic scar fibroblasts

Hypertrophic scar (HS) remains a major problem in plastic surgery. In order to explore the regulative effect of phosphatase and tensin homolog (PTEN) on HS, PTEN and AKT expression was detected by reverse transcription PCR, immunohistochemistry and western blot. Adenovirus-mediated PTEN overexpression in cultured hypertrophic scar fibroblasts (HSFBs) and normal skin fibroblasts was also introduced to evaluate its biological function. Our results showed that PTEN expression was significantly decreased in HS whereas p-Akt level was significantly higher in HS compared with normal skin (P < 0.01). Furthermore, we found that adenovirus-mediated PTEN overexpression led to decreased AKT activation, and significantly reduced cell proliferation and collagen synthesis of HSFBs, while increased the apoptosis. Taken together, these data suggest that PTEN inhibits proliferation and function of HSFBs through AKT pathway. Our results reveal a novel biological role for PTEN/AKT pathway in HS and suggest PTEN as a potential therapeutic target for HS treatment.

miRNA studies in in vitro and in vivo activated hepatic stellate cells

AIM

To understand which and how different miRNAs are implicated in the process of hepatic stellate cell (HSC) activation.

METHODS

We used microarrays to examine the differential expression of miRNAs during in vitro activation of primary HSCs (pHSCs). The transcriptome changes upon stable transfection of rno-miR-146a into an HSC cell line were studied using cDNA microarrays. Selected differentially regulated miRNAs were investigated by quantitative real-time polymerase chain reaction during in vivo HSC activation. The effect of miRNA mimics and inhibitor on the in vitro activation of pHSCs was also evaluated.

RESULTS

We found that 16 miRNAs were upregulated and 26 were downregulated significantly in 10-d in vitro activated pHSCs in comparison to quiescent pHSCs. Overexpression of rno-miR-146a was characterized by marked upregulation of tissue inhibitor of metalloproteinase-3, which is implicated in the regulation of tumor necrosis factor-α activity. Differences in the regulation of selected miRNAs were observed comparing in vitro and in vivo HSC activation. Treatment with miR-26a and 29a mimics, and miR-214 inhibitor during in vitro activation of pHSCs induced significant downregulation of collagen type I transcription.

CONCLUSION

Our results emphasize the different regulation of miRNAs in in vitro and in vivo activated pHSCs. We also showed that miR-26a, 29a and 214 are involved in the regulation of collagen type I mRNA.

miRNA studies in in vitro and in vivo activated hepatic stellate cells

AIM

To understand which and how different miRNAs are implicated in the process of hepatic stellate cell (HSC) activation.

METHODS

We used microarrays to examine the differential expression of miRNAs during in vitro activation of primary HSCs (pHSCs). The transcriptome changes upon stable transfection of rno-miR-146a into an HSC cell line were studied using cDNA microarrays. Selected differentially regulated miRNAs were investigated by quantitative real-time polymerase chain reaction during in vivo HSC activation. The effect of miRNA mimics and inhibitor on the in vitro activation of pHSCs was also evaluated.

RESULTS

We found that 16 miRNAs were upregulated and 26 were downregulated significantly in 10-d in vitro activated pHSCs in comparison to quiescent pHSCs. Overexpression of rno-miR-146a was characterized by marked upregulation of tissue inhibitor of metalloproteinase-3, which is implicated in the regulation of tumor necrosis factor-α activity. Differences in the regulation of selected miRNAs were observed comparing in vitro and in vivo HSC activation. Treatment with miR-26a and 29a mimics, and miR-214 inhibitor during in vitro activation of pHSCs induced significant downregulation of collagen type I transcription.

CONCLUSION

Our results emphasize the different regulation of miRNAs in in vitro and in vivo activated pHSCs. We also showed that miR-26a, 29a and 214 are involved in the regulation of collagen type I mRNA.

Therapeutics Based on microRNA: A New Approach for Liver Cancer

Hepatocellular carcinoma (HCC) is a serious public health hazard. Polygenes involvement, accumulation of genetic and epigenetic changes and immune response of viral vector during gene therapy have resulted in the high mortality rate without marked change. To provide a safeguard for gene therapy and the feasibility for a clinical application, efforts have been focused predominantly upon constructing liver-targeted vector recently. MicroRNAs (miRNAs), a class of short endogenous RNAs, regulate the gene expression at the post-transcriptional level through imperfect base pairing with the 3′-untranslated region of target mRNAs. miRNAs, especially the liver-specific miRNA: miR-122, have multiple functions in liver development and abnormal expression of miRNAs could lead to liver diseases. Altered miRNA expressions have been observed in HCCs, viral hepatitis and hepatic fibrosis. The different expression profiles of miRNAs in HCC suggest that miRNAs may serve as either novel potential targets acting directly as oncogenes or therapeutic molecules working as tumor suppressor genes. Moreover, the abundance in general and liver specificity in particular, all together make them attractive to be considered as elements for hepatic specific targeting viral vector. This review describes recent progress in miRNA investigation on liver associated for better understanding the relationship between miRNA and liver cancer in order to raise prospects for therapy.

Snail1 transcription factor is a critical mediator of hepatic stellate cell activation following hepatic injury

Following liver injury, the wound-healing process is characterized by hepatic stellate cell (HSC) activation from the quiescent fat-storing phenotype to a highly proliferative myofibroblast-like phenotype. Snail1 is a transcription factor best known for its ability to trigger epithelial-mesenchymal transition, to influence mesoderm formation during embryonic development, and to favor cell survival. In this study, we evaluated the expression of Snail1 in experimental and human liver fibrosis and analyzed its role in the HSC transdifferentiation process. Liver samples from patients with liver fibrosis and from mice treated by either carbon tetrachloride (CCl(4)) or thioacetamide (TAA) were evaluated for mRNA expression of Snail1. The transcription factor expression was investigated by immunostaining and real-time quantitative RT-PCR (qRT-PCR) on in vitro and in vivo activated murine HSC. Snail1 knockdown studies on cultured HSC and on CCl(4)-treated mice were performed by adenoviral delivery of short-hairpin RNA; activation-related genes were quantitated by real-time qRT-PCR and Western blotting. Snail1 mRNA expression resulted upregulated in murine experimental models of liver injury and in human hepatic fibrosis. In vitro studies showed that Snail1 is expressed by HSC and that its transcription is augmented in in vitro and in vivo activated HSC compared with quiescent HSC. At the protein level, we could observe the nuclear translocation of Snail1 in activated HSC. Snail1 knockdown resulted in the downregulation of activation-related genes both in vitro and in vivo. Our data support a role for Snail1 transcription factor in the hepatic wound-healing response and its involvement in the HSC transdifferentiation process.

Dihydrosphingosine 1-phosphate has a potent antifibrotic effect in scleroderma fibroblasts via normalization of phosphatase and tensin homolog levels

OBJECTIVE

Previous studies have revealed a phosphatase and tensin homolog (PTEN)-dependent interaction between the sphingolipid agonist dihydrosphingosine 1-phosphate (dhS1P) and the transforming growth factor beta/Smad3 signaling pathway. This study was undertaken to examine responses of systemic sclerosis (SSc) fibroblasts to sphingosine 1-phosphate (S1P) and dhS1P and to gain further insight into the regulation of the S1P/dhS1P/PTEN pathway in SSc fibrosis.

METHODS

Fibroblast cultures were established from skin biopsy samples obtained from patients with SSc and matched healthy controls. Western blotting and quantitative polymerase chain reaction were used to measure protein and messenger RNA levels, respectively. PTEN protein was examined in skin biopsy samples by immunohistochemistry.

RESULTS

PTEN protein levels were low in SSc fibroblasts and correlated with elevated levels of collagen and phospho-Smad3 and reduced levels of matrix metalloproteinase 1 (MMP-1). Treatment with dhS1P restored PTEN levels and normalized collagen and MMP-1 expression, as well as Smad3 phosphorylation status in SSc fibroblasts. S1P was strongly profibrotic in SSc and control fibroblasts. Distribution of S1P receptor isoforms was altered in SSc fibroblasts, which had reduced levels of S1P receptor 1 and S1P receptor 2 and elevated levels of S1P receptor 3. Only depletion of S1P receptor 1 abrogated the effects of dhS1P and S1P in control dermal fibroblasts. In contrast, depletion of either S1P receptor 1 or S1P receptor 2 prevented the effects of S1P and dhS1P in SSc fibroblasts.

CONCLUSION

Our findings demonstrate that PTEN deficiency is a critical determinant of the profibrotic phenotype of SSc fibroblasts. The antifibrotic effect of dhS1P is mediated through normalization of PTEN expression, suggesting that dhS1P or its derivatives may be effective as therapeutic antifibrotic agents. The distribution and function of S1P receptors differ in SSc and healthy fibroblasts, suggesting that alteration in the sphingolipid signaling pathway may contribute to SSc fibrosis.

Emerging role of microRNAs in liver diseases

MicroRNAs are a class of small non-coding RNAs that are found in plants, animals, and some viruses. They modulate the gene function at the post-transcriptional level and act as a fine tuner of various processes, such as development, proliferation, cell signaling, and apoptosis. They are associated with different types and stages of cancer. Recent studies have shown the involvement of microRNAs in liver diseases caused by various factors, such as Hepatitis C, Hepatitis B, metabolic disorders, and by drug abuse. This review highlights the role of microRNAs in liver diseases and their potential use as therapeutic molecules.

Emerging role of microRNAs in liver diseases

MicroRNAs are a class of small non-coding RNAs that are found in plants, animals, and some viruses. They modulate the gene function at the post-transcriptional level and act as a fine tuner of various processes, such as development, proliferation, cell signaling, and apoptosis. They are associated with different types and stages of cancer. Recent studies have shown the involvement of microRNAs in liver diseases caused by various factors, such as Hepatitis C, Hepatitis B, metabolic disorders, and by drug abuse. This review highlights the role of microRNAs in liver diseases and their potential use as therapeutic molecules.