The miR-3074/BMP7 axis regulates TGF-β-caused activation of hepatic stellate cells in vitro and CCl4-caused murine liver fibrosis in vivo

Continuously progressive hepatic fibrosis might cause chronic liver diseases, resulting in hepatic failure. The activation of hepatic stellate cells (HSCs) residing in the liver might induce and influence hepatic fibrosis. In the present study, microRNA 3074 (miR-3074) was found increased within transforming growth factor-β (TGF-β)-activated HSCs and enriched within the TGF-β signaling. In activated HSCs by TGF-β, miR-3074 overexpression aggravated TGF-β-induced fibrotic changes, whereas miR-3074 inhibition exerted opposite effects. miR-3074 directly targeted bone morphogenetic protein 7 (BMP7) and inhibited BMP7 expression. Under TGF-β induction, overexpressed BMP7 notably attenuated the promotive roles of miR-3074 overexpression in TGF-β-activated HSCs. Within carbon tetrachloride (CCl4)-caused liver fibrosis murine model, miR-3074 agomir administration promoted, while LV-BMP7 administration alleviated CCl4-induced fibrotic changes; LV-BMP7 significantly attenuated the effects of miR-3074 agomir. Lastly, mmu-miR-3074 also targeted mouse BMP7 and inhibited mouse BMP7 expression. In conclusion, the miR-3074/BMP7 axis regulates TGF-β-caused activation of HSCs in vitro and CCl4-caused murine liver fibrosis in vivo. BMP7-mediated Smad1/5/8 activation might be involved.

Metformin induces mitochondrial fission and reduces energy metabolism by targeting respiratory chain complex I in hepatic stellate cells to reverse liver fibrosis

The activation and proliferation of hepatic stellate cells (HSCs) are critical processes for the treatment of liver fibrosis. It is necessary to identify effective drugs for the treatment of liver fibrosis and elucidate their mechanisms of action. Metformin can inhibit HSCs; however, no systematic studies demonstrating the effects of metformin on mitochondria in HSCs have been reported. This study demonstrated that metformin induces mitochondrial fission by phosphorylating AMPK/DRP1 (S616) in HSCs to decrease the expression of α-SMA and collagen. Additionally, metformin repressed the total ATP production rate, especially the production rate of ATP produced through mitochondrial oxidative phosphorylation, by inhibiting the enzymatic activity of complex I. Further analysis revealed that metformin strongly constrained the transcription of mitochondrial genes (ND1-ND6 and ND4L) that encode the core subunits of respiratory chain I. Upregulation of the mRNA expression of HK2 and GLUT1 slightly enhanced glycolysis. Additionally, metformin increased mitochondrial DNA (mtDNA) copy number to suppress the proliferation and activation of HSCs, indicating that mtDNA copy number can alter the fate of HSCs. In conclusion, metformin can induce mitochondrial fragmentation and low-level energy metabolism in HSCs, thereby suppressing HSCs activation and proliferation to reverse liver fibrosis.

Ganoderma lucidum polysaccharide inhibits HSC activation and liver fibrosis via targeting inflammation, apoptosis, cell cycle, and ECM-receptor interaction mediated by TGF-β/Smad signaling

BACKGROUND

Ganoderma lucidum polysaccharide (GLP) has many biological properties, however, the anti-fibrosis effect of GLP is unknown at present.

PURPOSE

This study aimed to examine the anti-fibrogenic effect of GLP and its underlying molecular mechanisms in vivo and in vitro.

STUDY DESIGN

Both CCl₄-induced mouse and TGF-β1-induced HSC-T6 cellular models of fibrosis were established to examine the anti-fibrogenic effect of a water-soluble GLP (25 kDa) extracted from the sporoderm-removed spores of G. lucidum..

METHOD

Serum markers of liver injury, histology and fibrosis of liver tissues, and collagen formation were examined using an automatic biochemical analyzer, H&E staining, Sirius red staining, immunohistochemistry, immunofluorescence, ELISA, Western blotting, and qRT-PCR. RNA-sequencing, enrichment pathway analysis, Western blotting, qRT-PCR, and flow cytometry were employed to identify the potential molecular targets and signaling pathways that are responsible for the anti-fibrotic effect of GLP.

RESULTS

We showed that GLP (150 and 300 mg/kg) significantly inhibited hepatic fibrogenesis and inflammation in CCl₄-treated mice as mediated by the TLR4/NF-κB/MyD88 signaling pathway. We further demonstrated that GLP significantly inhibited hepatic stellate cell (HSCs) activation in mice and in TGF-β1-induced HSC-T6 cells as manifested by reduced collagen I and a-SMA expressions. RNA-sequencing uncovered inflammation, apoptosis, cell cycle, ECM-receptor interaction, TLR4/NF-κB, and TGF-β/Smad signalings as major pathways suppressed by GLP administration. Further studies demonstrated that GLP elicits anti-fibrotic actions that are associated with a novel dual effect on apoptosis in vivo (inhibit) or in vitro (promote), suppression of cell cycle in vivo, induction of S phase arrest in vitro, and attenuation of ECM-receptor interaction-associated molecule expressions including integrins ITGA6 and ITGA8. Furthermore, GLP significantly inhibited the TGF-β/Smad signaling in mice, and reduced TGF-β1 or its agonist SRI-011381-induced Smad2 and Smad3 phosphorylations, but increased Samd7 expression in HSC-T6 cells.

CONCLUSION

This study provides the first evidence that GLP could be a promising dietary strategy for treating liver fibrosis, which protects against liver fibrosis and HSC activation through targeting inflammation, apoptosis, cell cycle, and ECM-receptor interactions that are mediated by TGF-β/Smad signaling.

The phenolic compounds tyrosol and hydroxytyrosol counteract liver fibrogenesis via the transcriptional modulation of NADPH oxidases and oxidative stress-related miRNAs

Liver fibrosis is the result of a chronic pathological condition caused by the activation of hepatic stellate cells (HSCs), which induces the excessive deposition of extracellular matrix. Fibrogenesis is sustained by an exaggerated production of reactive oxidative species (ROS) by NADPH oxidases (NOXs), which are overactivated in hepatic inflammation. In this study, we investigated the antifibrotic properties of two phenolic compounds of natural origin, tyrosol (Tyr) and hydroxytyrosol (HTyr), known for their antioxidant and anti-inflammatory effects. We assessed Tyr and HTyr antifibrotic and antioxidant activity both in vitro, by a co-culture of LX2, HepG2 and THP1-derived Mϕ macrophages, set up to simulate the hepatic microenvironment, and in vivo, in a mouse model of liver fibrosis obtained by carbon tetrachloride treatment. We evaluated the mRNA and protein expression of profibrotic and oxidative markers (α-SMA, COL1A1, NOX1/4) by qPCR and/or immunocytochemistry or immunohistochemistry. The expression of selected miRNAs in mouse livers were measured by qPCR. Tyr and HTyr reduces fibrogenesis in vitro and in vivo, by downregulating all fibrotic markers. Notably, they also modulated oxidative stress by restoring the physiological levels of NOX1 and NOX4. In vivo, this effect was accompanied by a transcriptional regulation of inflammatory genes and of 2 miRNAs involved in the control of oxidative stress damage (miR-181-5p and miR-29b-3p). In conclusion, Tyr and HTyr exert antifibrotic and anti-inflammatory effects in preclinical in vitro and in vivo models of liver fibrosis, by modulating hepatic oxidative stress, representing promising candidates for further development.

Mitigation of liver fibrosis via hepatic stellate cells mitochondrial apoptosis induced by metformin

Liver fibrosis, a disease characterized by the excessive accumulation of extracellular matrix originating from activated hepatic stellate cells (HSCs), is a common pathological response to chronic liver injury resulting from a variety of insults. However, drugs that effectively block the activation of HSCs have still not been adequately investigated. This study demonstrates that metformin decreased the number of activated-HSCs through induction of apoptosis, but did not impact numbers of hepatocytes. Metformin upregulated BAX activation with facilitation of BIM, BAD and PUMA; downregulated Bcl-2 and Bcl-xl, but did not affect Mcl-1. Additionally, metformin induced cytochrome c release from mitochondria into the cytoplasm, directly triggering caspase-9-mediated mitochondrial apoptosis. The decline in mitochondrial membrane potential (ΔΨm) and deposition of superoxide in mitochondria accelerated the destruction of the integrity of mitochondrial membrane. Moreover, we verified the therapeutic effect of metformin in our mouse model of liver fibrosis associated with nonalcoholic steatohepatitis (NASH) in which hepatic function, NASH lesions and fibrosis were improved by metformin. In conclusion, this study indicated that metformin has significant therapeutic value in NASH-derived liver fibrosis by inducing apoptosis in HSCs, but does not affect the proliferation of hepatocytes.

New advances of DNA/RNA methylation modification in liver fibrosis

Liver fibrosis is a complex pathological process caused by multiple pathogenic factors，such as ethanol, viruses, toxins, drugs or cholestasis, and it can eventually develop into liver cirrhosis without effective treatment. Activation of hepatic stellate cells (HSCs) is a pivotal cellular event in the pathogenesis of liver fibrosis. However, the pathogenesis of liver fibrosis has not been fully elucidated. DNA/RNA methylation can regulate gene expression without alteration in its sequence, and numerous studies have shown the involvement of DNA methylation in the activation of HSCs and then promote the progression of liver fibrosis. In addition, RNA methylation has recently been reported to play a regulatory role in this process. In this review, we focus on the aberrant DNA/RNA methylation of selected genes and explore their functional mechanism in regulating HSCs activation and liver fibrogenesis. All of these findings will enhance our understanding of DNA/RNA methylation and their roles in liver fibrosis and provide the basis to identify effective therapeutic targets.

Foresight regarding drug candidates acting on the succinate-GPR91 signalling pathway for non-alcoholic steatohepatitis (NASH) treatment

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease, and it is a liver manifestation of metabolic syndrome, with a histological spectrum from simple steatosis to non-alcoholic steatohepatitis (NASH). NASH can evolve into progressive liver fibrosis and eventually lead to liver cirrhosis. The pathological mechanism of NASH is multifactorial, involving a series of metabolic disorders and changes that trigger low-level inflammation in the liver and other organs. In the pathogenesis of NASH, the signal transduction pathway involving succinate and the succinate receptor (G-protein-coupled receptor 91, GPR91) regulates inflammatory cell activation and liver fibrosis. This review describes the mechanism of the succinate-GPR91 signalling pathway in NASH and summarizes the drugs that act on this pathway, with the aim of providing a new approach to NASH treatment.

MicroRNA-503 Targets Mothers Against Decapentaplegic Homolog 7 Enhancing Hepatic Stellate Cell Activation and Hepatic Fibrosis

BACKGROUND

The hyper-accumulation of extracellular matrix (ECM) is the leading cause of hepatic fibrosis, and TGF-β-induced activation of hepatic stellate cells (HSCs) is the central event of hepatic fibrosis pathogenesis. The deregulation and dysfunction of miRNAs in hepatic fibrosis have been reported previously.

AIMS

To identify miRNA(s) playing a role in HSC activation and the underlying mechanism.

METHODS

We analyzed online microarray expression datasets from Gene Expression Omnibus (GEO) for differentially expressed miRNAs in hepatic fibrosis-related disease liver tissues, examined the specific effects of the candidate miRNA on TGF-β-induced HSC activation, and screened for the targets of the candidate miRNA in the TGF-β/SMAD signaling. Then, the predicted miRNA-mRNA binding, the specific effects of the target mRNA, and the dynamic effects of miRNA and mRNA on TGF-β-induced HSC activation were investigated.

RESULTS

The miR-503 expression was upregulated in TGF-β-activated HSCs. miR-503 overexpression enhanced, while miR-503 inhibition attenuated TGF-β-induced HSC proliferation and ECM accumulation in HSCs. miR-503 targeted SMAD7 to inhibit SMAD7 expression. SMAD7 knockdown also aggravated TGF-β-induced HSC proliferation and ECM accumulation in HSCs. The effects of miR-503 overexpression on TGF-β-induced HSC activation were partially reversed by SMAD7 overexpression. In CCl₄-induced hepatic fibrosis model in rats, miR-503 overexpression aggravated, whereas SMAD7 overexpression improved CCl₄-induced fibrotic changes in rats' liver tissues. The effects of miR-503 overexpression on CCl₄-induced fibrotic changes were partially reversed by SMAD7 overexpression.

CONCLUSION

miR-503 acts on HSC activation and hepatic fibrosis through SMAD7. The miR-503/SMAD7 axis enhances HSC activation and hepatic fibrosis through the TGF-β/SMAD pathway.

Carvacrol alleviates liver fibrosis by inhibiting TRPM7 and modulating the MAPK signaling pathway

Liver fibrosis is a compensatory response to the tissue repair process. The activation and proliferation of hepatic stellate cells (HSCs) are thought to be related to the occurrence of hepatic fibrosis. Therefore, inhibiting the activation and proliferation of HSCs is a key step in alleviating liver fibrosis. As a non-specific inhibitor of transient receptor potential melastatin 7 (TRPM7), carvacrol has anti-tumor, anti-inflammatory and anti-hepatic fibrosis activities. This study aimed to explore the protective effect of carvacrol on liver fibrosis and related molecular mechanisms. A CCl4-induced liver fibrosis mouse model and platelet-derived growth factor (PDGF-BB)-activated HSC-T6 cells (a rat hepatic stellate cell line) were employed for in vivo and in vitro experiments. C57BL/6J mice were orally administered different concentrations of carvacrol every day for 6 weeks during the development of CCl4-induced liver fibrosis. The results show that carvacrol could effectively reduce liver damage and the progression of liver fibrosis in mice, which are expressed as fibrotic markers levels were reduced and histopathological characteristics were improved. Moreover, carvacrol inhibited the proliferation and activation of HSC-T6 cells induced by PDGF-BB. In addition, it was found that carvacrol inhibits the expression of TRPM7 and mediated through mitogen-activated protein kinases (MAPK). Collectively, our study shows that carvacrol can reduce liver fibrosis by inhibiting the activation and proliferation of hepatic stellate cells, and the MAPK signaling pathway might be involved in this process.

A lncRNA Gpr137b-ps/miR-200a-3p/CXCL14 axis modulates hepatic stellate cell (HSC) activation

Hepatic fibrosis is the wound healing response upon the liver tissue damage caused by multiple stimuli. Targeting activated hepatic stellate cells (HSCs), the major extracellular matrix (ECM)-producing cells within the damaged liver, has been regarded as one of the main treatments for hepatic fibrosis. In the present study, we performed preliminary bioinformatics analysis attempting to identify possible factors related to hepatic fibrosis and found that lncRNA G protein-coupled receptor 137B (Gpr137b-ps) and C-X-C motif chemokine ligand 14 (CXCL14) showed to be markedly upregulated within carbon tetrachloride (CCl4)-caused hepatic fibrotic mice tissue samples and activated HSCs. CXCL14 The silencing of lncRNA Gpr137b-ps or CXCL14 alone could significantly improve CCl4-induced fibrotic changes in mice liver in vivo and collagen I and III release by HSCs and HSC proliferation in vitro. miR-200a-3p directly targeted lncRNA Gpr137b-ps and CXCL14, respectively. LncRNA Gpr137b-ps relieved miR-200a-3p-induced inhibition on CXCL14 expression via acting as a ceRNA. In HSCs, the effects of lncRNA Gpr137b-ps silencing on collagen I and III release by HSCs and HSC proliferation were significantly reversed by miR-200a-3p inhibition, and the effects of miR-200a-3p inhibition were reversed by CXCL14 silencing. In conclusion, we demonstrated a lncRNA Gpr137b-ps/miR-200a-3p/CXCL14 axis that modulates HSC activation and might exert an effect on the pathogenesis of liver fibrosis.

Amygdalin inhibits TGFβ1-induced activation of hepatic stellate cells (HSCs) in vitro and CCl4-induced hepatic fibrosis in rats in vivo

The activation of hepatic stellate cells (HSCs) has been considered one of the major events in hepatic fibrosis. Amygdalin has been used to treat cancers and alleviate pain; however, its role and mechanism in HSC activation and hepatic fibrosis remain unclear. In the present study, transforming growth factor-beta 1 (TGF-β1) stimulated the activation of HSCs, as indicated by significantly increased alpha-smooth muscle actin (α-SMA), desmin, collagen I, and tissue inhibitor of metalloproteinase-1 (TIMP-1) protein levels. Amygdalin treatment dramatically suppressed TGF-β1-induced HSC proliferation and activation. Moreover, amygdalin treatment also reduced the TGF-β1-induced secretion of cytokines, including tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), platelet-derived growth factor (PDGF), and chemokine (C-C motif) ligand 2 (CCL2), as well as the phosphorylation of Smad2, Smad3, and p65. In the CCl4-stimulated liver fibrosis rat model, amygdalin treatment improved liver fibrosis and liver damage by reducing focal necrosis, collagen fiber accumulation, and the protein levels of α-SMA, desmin, collagen I, and TIMP-1 in hepatic tissue samples and reducing serum alanine transaminase (ALT) and aspartate transaminase (AST) levels. In conclusion, we demonstrated the suppressive effects of amygdalin in TGF-β1-induced HSC activation through modulating proliferation, fibrogenesis, and inflammation signaling in vitro and the antifibrotic effects of amygdalin in CCl4-stimulated hepatic fibrosis in rats in vivo.

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.

Matrix metalloproteinase-8 (MMP-8) regulates the activation of hepatic stellate cells (HSCs) through the ERK-mediated pathway

Hepatic stellate cells (HSCs) are known to play a key role in the progression of liver fibrosis by producing excessive extracellular matrix (ECM). Matrix metalloproteinases (MMPs) belong to a family of endopeptidases, which have a well-established role in the degradation of ECM. Our study suggests that, besides the degradation of the extracellular matrix, matrix metalloproteinase-8 (MMP-8) has a non-canonical role in activating the quiescent HSCs to myofibroblasts by regulating the expression of Col1A1 and αSMA. We have identified that MMP-8 secreted from macrophages as a response to LPS stimulation activates HSCs via ERK1/2-dependent pathway. In addition to this, we determined that MMP-8 may regulate the homodimerization of c-Jun in LX-2 cells, during the trans-differentiation process from quiescent HSC to activate myofibroblasts. Macrophage-released MMP-8 plays a master role in activating the dormant HSCs to activate myofibroblasts through the Erk-mediated pathway and Jun cellular translocation leading to liver fibrosis. Significance MMP-8 can be used as a therapeutic target against liver fibrosis.

Pirfenidone alleviates concanavalin A-induced liver fibrosis in mice

AIMS

Liver fibrosis (LF) is a life-threatening complication of most chronic liver diseases resulting from a variety of injurious agents and hepatotoxic insults. To date, there are no specific therapies for LF, and all the currently available drugs have been developed for other indications. Thus, there is a pressing need to develop new drugs for treatment of LF. Therefore, the current study aimed to elucidate the potential antifibrotic effect of Pirfenidone (PFD) against concanavalin A (ConA)-induced immunological model of liver fibrosis in mice.

MAIN METHODS

Hepatic fibrosis was induced in mice by injecting ConA (10 mg/kg/wk./i.v) for 4 weeks. Then, the mice were treated with or without PFD (125 mg/kg/ip/day) for 2 weeks. Hepatic fibrosis was determined by Masson Trichrome staining; Haematoxylin & eosin (H&E) staining, immunohistochemistry staining of type II and IV collagens, and colorimetric assessment of hydroxyprolline (HP) content in the liver tissues. In addition, the expression of α-SMA mRNA was determined by real time RT-PCR. The serum levels of TGF-β, TNF-α, TIMP-1 and MMP-2 were measured by ELISA.

KEY FINDINGS

Treatment with PFD significantly reduced ConA-induced expression of type II and IV collagens, α-SMA mRNA expression, and HP content and decreased inflammatory cells infiltration in hepatic tissues. Furthermore, serum levels of TGF-β, TNF-α, and TIMP-1 were significantly reduced with concomitant increase in MMP-2 expression.

SIGNIFICANCE

Treatment with PFD ameliorates concanavalin A-induced hepatic inflammation and fibrosis in mice. Thus, PFD may represent a promising therapeutic option for hepatic fibrosis and its related complications.

miR-21 promotes proliferation and inhibits apoptosis of hepatic stellate cells through targeting PTEN/PI3K/AKT pathway

To investigate the effect of microRNA 21 (miR-21) on hepatic stellate cells (HSCs) proliferation and apoptosis, and further to study its potential mechanisms. LX-2 cells were divided into miR-21 mimic group (Mimic), miR-21 mimic negative control group (NM), miR-21 inhibitor group (Inhibitor), miR-21 inhibitor negative control group (NC), and blank control group (Control). The cell proliferation was detected by CCK-8 assay and the cell migration and invasion were detected by scratch and transwell assay. Cell cycle and apoptosis were detected by flow cytometry. The levels of interleukin (IL)-6, tumor necrosis factor (TNF)-α, and transforming growth factor (TGF)-β1 were detected by enzyme-linked immunosorbent assay (ELISA). Proliferation, apoptosis, and phosphatase and tensin homolog (PTEN)/phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway related genes and proteins were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot, respectively. The cells proliferation, migration, and invasion were promoted in Mimic group. The levels of IL-6, TNF-α, and TGF-β1 were increased after miR-21 administration. The expression of α-smooth muscle actin (SMA) and collagen 1 (Colla1) were increased, while Bax/B-cell lymphoma (Bcl)-2 ratio and programed cell death 4 (PDCD4) were reduced after miR‑21 treatment. Meanwhile, the mRNA and protein expression of PTEN were reduced and PI3K/AKT pathway been promoted. Our study demonstrated that miR-21 could promote proliferation and inhibit apoptosis of HSCs, and its mechanism may be related to PTEN/PI3K/AKT pathway.

miR-374a/Myc axis modulates iron overload-induced production of ROS and the activation of hepatic stellate cells via TGF-β1 and IL-6

The transformation of hepatic stellate cells (HSCs) to activated myofibroblasts plays a critical role in the progression of hepatic fibrosis, while iron-catalyzed production of free radical, including reaction and active oxygen (ROS), and activation and transformation of HSC into a myofibroblasts has been regarded as a major mechanism. In the present study, we attempted to investigate the mechanism of iron overload in hepatic fibrosis from the perspective of regulating HSC activation via oxidative stress and miR-374a/Myc axis. FAC stimulation significantly increased ROS production and TGF-β1 and IL-6 release dose-dependently in hepatocytes. miR-374a could target Myc, a co-transcription factor of both TGF-β1 and IL-6, to negatively regulate Myc expression; FAC stimulation significantly suppressed miR-374a expression, whereas the suppressive effect of FAC stimulation on miR-374a expression could be reversed by ROS inhibitor NAC, indicating that miR-374a could be modulated by iron overload-induced ROS. Via targeting Myc, miR-374a overexpression significantly reduced FAC-induced increases in TGF-β1 and IL-6 levels within L02 cells, whereas the effects of miR-374a overexpression were significantly attenuated via Myc overexpression. Finally, miR-374a overexpression attenuated FAC-induced activity of HSCs by decreasing α-SMA and Collagen I levels whereas Myc overexpression enhanced FAC-induced activity of HSCs by increasing α-SMA and Collagen I levels; the effects of miR-374a overexpression could also be significantly reversed by Myc overexpression, indicating that miR-374a suppresses the activation of HSCs by inhibiting Myc to reduce FAC-induced increases in TGF-β1 and IL-6 release. In conclusion, we demonstrate a novel mechanism of miR-374a/Myc axis modulating iron overload-induced production of ROS and the activation of HSCs via TGF-β1 and IL-6.

CREB family: A significant role in liver fibrosis

Liver fibrosis (LF) is known as a result of the progressive accumulation of extracellular matrix (ECM), and always ascribed to chronic liver diseases. Advanced liver fibrosis results in cirrhosis, liver failure, portal hypertension, and even multi-organ dysfunction and will bring up a health care burden worldwide. Cyclic AMP response-element binding protein (CREB), as a critical transcriptional factor, binds with conserved cAMP response-element (CRE), which is located in the promoter of targeted genes, to regulate the transcription. In the past decades, numerous studies have contributed to improved understanding of the links between CREB and liver fibrosis. In this review, we will summarize molecular mechanisms of CREB pathways and discuss contributions of CREB to liver fibrosis, focusing on activation and proliferation of hepatic stellate cells (HSCs), proliferation of cholangiocytes, deposition of extracellular matrix (ECM) and inflammation, for the development of antifibrotic therapies.

Engineering in vitro models of hepatofibrogenesis

Chronic liver disease is a major cause of morbidity and mortality worldwide marked by chronic inflammation and fibrosis/scarring, resulting in end-stage liver disease and its complications. Hepatic stellate cells (HSCs) are a dominant contributor to liver fibrosis by producing excessive extracellular matrix (ECM), irrespective of the underlying disease aetiologies, and for many decades research has focused on the development of a number of anti-fibrotic strategies targeting this cell. Despite major improvements in two-dimensional systems (2D) by using a variety of cell culture models of different complexity, an efficient anti-fibrogenic therapy has yet to be developed. The development of well-defined three-dimensional (3D) in vitro models, which mimic ECM structures as found in vivo, have demonstrated the importance of cell-matrix bio-mechanics, the complex interactions between HSCs and hepatocytes and other non-parenchymal cells, and this to improve and promote liver cell-specific functions. Henceforth, refinement of these 3D in vitro models, which reproduce the liver microenvironment, will lead to new objectives and to a possible new era in the search for antifibrogenic compounds.

Activated hepatic stellate cells directly induce pathogenic Th17 cells in chronic hepatitis B virus infection

Th17 cells are involved in liver fibrosis by activating hepatic stellate cells (HSCs). We aimed to investigate whether HSCs are able to regulate the function of Th17 cells and to determine the relevant mechanism. Sixty-five patients diagnosed with chronic hepatitis B (CHB) were enrolled in this study. To determine the effect of HSCs on T cells, naïve CD4⁺T cells and Th17 cells were sorted from CHB patients and cultured with or without activated-HSCs, and cytokine expression and gene transcription were analyzed. In addition, the regulatory mechanism of HSCs was investigated. ELISA and qRT-PCR showed that Th17 cells from CHB patients were more pathogenic, on the basis of the expression of IL-17A, IL-23R, RORC, CCL20 and CCR6, and meanwhile, they could activate the primary HSCs. Co-culture experiments indicated that activated HSCs dramatically promoted proliferation of CD4⁺T cells in a time- and dose-dependent manner. In addition, they could induce naïve CD4⁺T cells to become Th17 cells which had a more pathogenic phenotype. Moreover, activated HSCs-mediated induction of Th17 cells might depend on the release of IL-1β and IL-6 as well as on the COX-PGE2 pathway. Th17 cells cooperated with HSCs in a proinflammatory feedback loop might provide a better understanding of the pathogenic role of Th17 cells in the chronicity of HBV infection.

Aging aggravates alcoholic liver injury and fibrosis in mice by downregulating sirtuin 1 expression

BACKGROUND & AIMS

Aging is known to exacerbate the progression of alcoholic liver disease (ALD), but the underlying mechanisms remain obscure. The aim of this study was to use a chronic plus binge ethanol feeding model in mice to evaluate the effects of aging on alcohol-induced liver injury.

METHODS

C57BL/6 mice were subjected to short-term (10days) ethanol plus one binge or long-term (8weeks) ethanol plus multiple binges of ethanol. Liver injury and fibrosis were determined. Hepatic stellate cells (HSCs) were isolated and used in in vitro studies.

RESULTS

Middle-aged (12-14months) and old-aged (>16months) mice were more susceptible to liver injury, inflammation, and oxidative stress induced by short-term plus one binge or long-term plus multiple binges of ethanol feeding when compared to young (8-12weeks) mice. Long-term plus multiple binges of ethanol feeding induced greater liver fibrosis in middle-aged mice than that in young mice. Hepatic expression of sirtuin 1 (SIRT1) protein was downregulated in the middle-aged mice compared to young mice. Restoration of SIRT1 expression via the administration of adenovirus-SIRT1 vector ameliorated short-term plus binge ethanol-induced liver injury and fibrosis in middle-aged mice. HSCs isolated from middle-aged mice expressed lower levels of SIRT1 protein and were more susceptible to spontaneous activation in in vitro culture than those from young mice. Overexpression of SIRT1 reduced activation of HSCs from middle-aged mice in vitro with downregulation of PDGFR-α and c-Myc, while deletion of SIRT1 activated HSCs isolated from young mice in vitro. Finally, HSC-specific SIRT1 knockout mice were more susceptible to long-term chronic-plus-multiple binges of ethanol-induced liver fibrosis with upregulation of PDGFR-α expression.

CONCLUSIONS

Aging exacerbates ALD in mice through the downregulation of SIRT1 in hepatocytes and HSCs. Activation of SIRT1 may serve as a novel target for the treatment of ALD.

LAY SUMMARY

Aged mice are more susceptible to alcohol-induced liver injury and fibrosis, which is, at least in part, due to lower levels of sirtuin 1 protein in hepatocytes and hepatic stellate cells. Our findings suggest that sirtuin 1 activators may have beneficial effects for the treatment of alcoholic liver disease in aged patients.

Knockdown of HIPK2 attenuates the pro-fibrogenic response of hepatic stellate cells induced by TGF-β1

Homeodomain-interacting protein kinase 2 (HIPK2), a member of HIPKs family, is considered as a key regulator in fibrosis. However, the roles of HIPK2 in hepatic stellate cells (HSCs) activation and liver fibrosis are still unclear. Therefore, in this study, we investigated the roles of HIPK2 in HSCs activation and liver fibrosis. Our results showed that HIPK2 expression was significantly up-regulated in liver fibrotic tissues and TGF-β1-treated HSCs. Knockdown of HIPK2 significantly inhibited TGF-β1-induced HSCs proliferation, as well as decreased the expression levels of α-SMA and collagen I. Furthermore, knockdown of HIPK2 attenuated the phosphorylation of Smad3 in the presence of TGF-β1. In conclusion, these results demonstrated that HIPK2 may function as a novel regulator to modulate HSC activation, potentially by inhibiting the TGF-β1/Smad3 signaling pathway. The results provide supporting evidence that HIPK2 may be a potential target for the treatment of liver fibrosis.

Cellular and molecular functions of hepatic stellate cells in inflammatory responses and liver immunology

The liver is a central immunological organ. Liver resident macrophages, Kupffer cells (KC), but also sinusoidal endothelial cells, dendritic cells (DC) and other immune cells are involved in balancing immunity and tolerance against pathogens, commensals or food antigens. Hepatic stellate cells (HSCs) have been primarily characterized as the main effector cells in liver fibrosis, due to their capacity to transdifferentiate into collagen-producing myofibroblasts (MFB). More recent studies elucidated the fundamental role of HSC in liver immunology. HSC are not only the major storage site for dietary vitamin A (Vit A) (retinol, retinoic acid), which is essential for proper function of the immune system. This pericyte further represents a versatile source of many soluble immunological active factors including cytokines [e.g., interleukin 17 (IL-17)] and chemokines [C-C motif chemokine (ligand) 2 (CCL2)], may act as an antigen presenting cell (APC), and has autophagy activity. Additionally, it responds to many immunological triggers via toll-like receptors (TLR) (e.g., TLR4, TLR9) and transduces signals through pathways and mediators traditionally found in immune cells, including the Hedgehog (Hh) pathway or inflammasome activation. Overall, HSC promote rather immune-suppressive responses in homeostasis, like induction of regulatory T cells (Treg), T cell apoptosis (via B7-H1, PDL-1) or inhibition of cytotoxic CD8 T cells. In conditions of liver injury, HSC are important sensors of altered tissue integrity and initiators of innate immune cell activation. Vice versa, several immune cell subtypes interact directly or via soluble mediators with HSC. Such interactions include the mutual activation of HSC (towards MFB) and macrophages or pro-apoptotic signals from natural killer (NK), natural killer T (NKT) and gamma-delta T cells (γδ T-cells) on activated HSC. Current directions of research investigate the immune-modulating functions of HSC in the environment of liver tumors, cellular heterogeneity or interactions promoting HSC deactivation during resolution of liver fibrosis. Understanding the role of HSC as central regulators of liver immunology may lead to novel therapeutic strategies for chronic liver diseases.