Effect of RhoA on transforming growth factor β1-induced rat hepatic stellate cell migration

From Quiescence to Activation: The Reciprocal Regulation of Ras and Rho Signaling in Hepatic Stellate Cells

Chronic liver diseases are marked by persistent inflammation and can evolve into liver fibrosis, cirrhosis, and hepatocellular carcinoma. In an affected liver, hepatic stellate cells (HSCs) transition from a quiescent to an activated state and adopt a myofibroblast-like cell phenotype. While these activated cells play a role in supporting liver regeneration, they can also have detrimental effects on liver function as the disease progresses to fibrosis and cirrhosis. These findings highlight the dynamic switching between different signaling pathways involving Ras, Rho GTPases, and Notch signaling. Notably, two specific members of the Ras and Rho GTPases, Eras and Rnd3, are predominantly expressed in quiescent HSCs, while Mras and Rhoc are more abundant in their activated forms. In addition, this study highlights the critical role of cytosolic Notch1 in quiescent HSCs and Rock in activated HSCs. We hypothesize that distinct yet interdependent intracellular signaling networks regulate HSC fate decisions in two key ways: by maintaining HSC quiescence and homeostasis and by facilitating HSC activation, thereby influencing processes such as proliferation, transdifferentiation, and mesenchymal transition. The proposed signaling model, combined with specific methodological tools for maintaining HSCs in a quiescent state, will deepen our understanding of the mechanisms underlying chronic liver disease and may also pave the way for innovative therapies. These therapies could include small molecule drugs targeting Ras- and Rho-dependent pathways.

Radiation-sensitive circRNA hsa_circ_0096498 inhibits radiation-induced liver fibrosis by suppressing EIF4A3 nuclear translocation to decrease CDC42 expression in hepatic stellate cells

BACKGROUND

Radiation-induced liver fibrosis (RILF) is a common manifestation of radiation-induced liver injury (RILI) and is caused primarily by activated hepatic stellate cells (HSCs). Circular RNAs (circRNAs) play critical roles in various diseases, but little is known about the function and mechanism of circRNAs in RILF.

METHODS

RNA pull-down and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to screen binding proteins of hsa_circ_0096498 (circ96498). RNA-binding protein immunoprecipitation, RNA pull-down and nuclear and cytoplasmic protein extraction were conducted to confirm the interaction between circ96498 and eukaryotic initiation factor 4A3 (EIF4A3). RNA sequencing was performed to screen target genes regulated by EIF4A3. HSCs with altered circ96498 and cell division cycle 42 (CDC42) expression were used to assess irradiated HSC activation. Circ96498 inhibition and CDC42 blockade were evaluated in RILF mouse models.

RESULTS

In this study, we identified a radiation-sensitive circ96498, which was highly expressed in the irradiated HSCs of paracancerous tissues from RILI patients. Circ96498 inhibited the proliferation but promoted the apoptosis of irradiated HSCs, suppressed the secretion of proinflammatory cytokines IL-1β, IL-6 and TNF-α, and decreased the expression of profibrotic markers (α-SMA and collagen 1) in irradiated HSCs. Mechanistically, irradiation induced the transport of EIF4A3 into the nucleus, and nuclear EIF4A3 increased the stability of CDC42 mRNA and increased CDC42 expression, thereby promoting HSC activation through the NF-κB and JNK/Smad2 pathways. However, the binding of circ96498 to EIF4A3 impeded the translocation of EIF4A3 into the nucleus, resulting in the inhibition of CDC42 expression and subsequent HSC activation. Furthermore, circ96498 knockdown promoted the development of the early and late stages of RILF in a mouse model, which was mitigated by CDC42 blockade.

CONCLUSIONS

Collectively, our findings elucidate the involvement of the circ96498/EIF4A3/CDC42 axis in inhibiting irradiated HSC activation, which offers a novel approach for RILF prevention and treatment.

Stellate cell-specific adhesion molecule protocadherin 7 regulates sinusoidal contraction

BACKGROUND AND AIMS

Sustained inflammation and hepatocyte injury in chronic liver disease activate HSCs to transdifferentiate into fibrogenic, contractile myofibroblasts. We investigated the role of protocadherin 7 (PCDH7), a cadherin family member not previously characterized in the liver, whose expression is restricted to HSCs.

APPROACH AND RESULTS

We created a PCDH7 fl/fl mouse line, which was crossed to lecithin retinol acyltransferase-Cre mice to generate HSC-specific PCDH7 knockout animals. HSC contraction in vivo was tested in response to the HSC-selective vasoconstrictor endothelin-1 using intravital multiphoton microscopy. To establish a PCDH7 null HSC line, cells were isolated from PCDH7 fl/fl mice and infected with adenovirus-expressing Cre. Hepatic expression of PCDH7 was strictly restricted to HSCs. Knockout of PCDH7 in vivo abrogated HSC-mediated sinusoidal contraction in response to endothelin-1. In cultured HSCs, loss of PCDH7 markedly attenuated contractility within collagen gels and led to altered gene expression in pathways governing adhesion and vasoregulation. Loss of contractility in PCDH7 knockout cells was impaired Rho-GTPase signaling, as demonstrated by altered gene expression, reduced assembly of F-actin fibers, and loss of focal adhesions.

CONCLUSIONS

The stellate cell-specific cadherin, PCDH7, is a novel regulator of HSC contractility whose loss leads to cytoskeletal remodeling and sinusoidal relaxation.

Therapeutic potential of exosome derived from hepatocyte growth factor-overexpressing adipose mesenchymal stem cells in TGFβ1-stimulated hepatic stellate cells

Cirrhosis is a familiar end-stage of multiple chronic liver diseases. The gene-modified mesenchymal stem cells (MSCs) have become one of the most promising schemes for the treatment of cirrhosis. MSCs exhibit their therapeutic role mainly by secreting hepatocyte growth factor (HGF). The aim of this research was to probe the anti-fibrosis role of exosomes secreted by HGF modified-mouse adipose MSCs (ADMSCs) on activated hepatic stellate cells (HSCs) and to preliminarily explore the possible mechanism. Firstly, mouse ADMSCs were isolated and identified. Quantitative real-time polymerase chain reaction verified the transfection efficiency of ADMSC transfected with HGF lentivirus. Exosomes derived from ADMSC transfecting negative control/HGF (ADMSCNC-Exo/ADMSCHGF-Exo) were extracted by density gradient centrifugation. HSCs were allocated to the control, TGF-β, TGF-β + ADMSC-Exo, TGF-β + ADMSCNC-Exo, and TGF-β + ADMSCHGF-Exo groups. Moreover, all mice were distributed to the control, CCl4 (40% CCl4 in olive oil), CCl4+ADMSC-Exo, CCl4+ADMSCNC-Exo, and CCl4+ADMSCHGF-Exo groups. Exosomes derived from ADMSCs with or without HGF transfection suppressed HSC activation, as evidenced by attenuating cell viability and cell cycle arrest at S phase but inducing apoptosis. Moreover, ADMSC-Exo, ADMSCNC-Exo, and ADMSCHGF-Exo effectively repressed the gene and protein levels of α-SMA, Col-I, Rho A, Cdc42, and Rac1 in TGF-β-treated HSCs, and ADMSCHGF-Exo had the best effect. ADMSCHGF-Exo had a stronger regulatory effect on serum liver index than ADMSCNC-Exo in CCl4-induced mice. In conclusion, ADMSCHGF-Exo alleviated liver fibrosis by weakening the Rho pathway, thus reducing collagen production.

Pathophysiological communication between hepatocytes and non-parenchymal cells in liver injury from NAFLD to liver fibrosis

Non-alcoholic fatty liver disease (NAFLD) is a multifactorial disease that encompasses a spectrum of pathological conditions, ranging from simple steatosis (NAFL), nonalcoholic steatohepatitis (NASH), fibrosis/cirrhosis which can further progress to hepatocellular carcinoma and liver failure. The progression of NAFL to NASH and liver fibrosis is closely associated with a series of liver injury resulting from lipotoxicity, oxidative stress, redox imbalance (excessive nitric oxide), ER stress, inflammation and apoptosis that occur sequentially in different liver cells which ultimately leads to the activation of liver regeneration and fibrogenesis, augmenting collagen and extracellular matrix deposition and promoting liver fibrosis and cirrhosis. Type 2 diabetes is a significant risk factor in NAFLD development by accelerating liver damage. Here, we overview recent findings from human study and animal models on the pathophysiological communication among hepatocytes (HCs), Kupffer cells (KCs), hepatic stellate cells (HSCs) and liver sinusoidal endothelial cells (LSECs) during the disease development. The mechanisms of crucial signaling pathways, including Toll-like receptor, TGFβ and hedgehog mediated hepatic injury are also discussed. We further highlight the potentials of precisely targeting hepatic individual cell-type using nanotechnology as therapeutic strategy for the treatment of NASH and liver fibrosis.

Ursolic acid reverses liver fibrosis by inhibiting interactive NOX4/ROS and RhoA/ROCK1 signalling pathways

Liver fibrosis is the reversible deposition of extracellular matrix (ECM) and scar formation after liver damage by various stimuli. The interaction between NOX4/ROS and RhoA/ROCK1 in liver fibrosis is not yet clear. Ursolic acid (UA) is a traditional Chinese medicine with anti-fibrotic effects, but the molecular mechanism underlying these effects is still unclear. We investigated the interaction between NOX4/ROS and RhoA/ROCK1 during liver fibrosis and whether these molecules are targets for the anti-fibrotic effects of UA. First, we confirmed that UA reversed CCl4-induced liver fibrosis. In the NOX4 intervention and RhoA intervention groups, related experimental analyses confirmed the decrease in CCl4-induced liver fibrosis. Next, we determined that the expression of NOX4 and RhoA/ROCK1 was decreased in UA-treated liver fibrotic mice. Furthermore, RhoA/ROCK1 expression was decreased in the NOX4 intervention group, but there was no significant change in the expression of NOX4 in the RhoA intervention group. Finally, we found that liver fibrotic mice showed a decline in their microbiota diversity and abundance, a change in their microbiota composition, and a reduction in the number of potential beneficial bacteria. However, in UA-treated liver fibrotic mice, the microbiota dysbiosis was ameliorated. In conclusion, the NOX4/ROS and RhoA/ROCK1 signalling pathways are closely linked to the development of liver fibrosis. UA can reverse liver fibrosis by inhibiting the NOX4/ROS and RhoA/ROCK1 signalling pathways, which may interact with each other.

Gut Microbial Dysbiosis Is Associated With Profibrotic Factors in Liver Fibrosis Mice

Background and Aims: Continuous development will evolve into end-stage liver disease. Profibrotic factors NOX4 and RhoA participate in the activation of HSC and accelerate the development of liver fibrosis. Abnormal intrahepatic metabolism during liver fibrosis interferes with intestinal homeostasis through the liver—gut axis.

Methods: Wild-type (WT), NOX4 knockout, RhoA expression inhibition C57BL/6 mice were randomly divided into 6 groups as follows: control group, CCl₄ group, NOX4^−/− group, AP group, RhoAi group, and FA group.

Results: The results of alpha-diversity suggest that the diversity and abundance of intestinal flora in liver fibrosis mice is lower than that in normal mice, but there is some recovery in liver fibrosis mice with NOX4 or RhoA intervention. The flora structure showed that the intestinal flora of the control group, NOX4^−/− group, AP group, RhoAi group, and FA group belonged to one type, while the intestinal flora of the CCl₄ group belonged to another type. In addition, analysis of the composition of the flora at the level of the phylum and genus also suggested the decline in Firmicutes and Lactobacillus caused by liver fibrosis has partially restore in the liver fibrosis mice with NOX4 or RhoA intervention. In terms of functional prediction, the “Secondary metabolites biosynthesis, transport and catabolism,” “Infectious diseases,” and “Xenobiotics biodegradation and metabolism” signaling pathways are mainly enriched in liver fibrosis mice, and the “Energy production and conversion,” “Defense mechanisms,” and “Carbohydrate metabolism” signaling pathways are mainly enriched in the NOX4 and RhoA intervention groups.

Conclusion: In the case of liver fibrosis, the intestinal flora is disordered, and the disorder is related to NOX4 and RhoA. This study provides theoretical support for a better understanding of the underlying mechanisms of liver fibrosis development.

Mechanisms of liver fibrosis and its role in liver cancer

Hepatic fibrogenesis is a pathophysiological outcome of chronic liver injury hallmarked by excessive accumulation of extracellular matrix proteins. Fibrosis is a dynamic process that involves cross-talk between parenchymal cells (hepatocytes), hepatic stellate cells, sinusoidal endothelial cells and both resident and infiltrating immune cells. In this review, we focus on key cell-types that contribute to liver fibrosis, cytokines, and chemokines influencing this process and what it takes for fibrosis to regress. We discuss how mitochondria and metabolic changes in hepatic stellate cells modulate the fibrogenic process. We also briefly review how the presence of fibrosis affects development of hepatocellular carcinoma.

siRNA- and miRNA-based therapeutics for liver fibrosis

Liver fibrosis is a wound-healing process induced by chronic liver injuries, such as nonalcoholic steatohepatitis, hepatitis, alcohol abuse, and metal poisoning. The accumulation of excessive extracellular matrix (ECM) in the liver is a key characteristic of liver fibrosis. Activated hepatic stellate cells (HSCs) are the major producers of ECM and therefore play irreplaceably important roles during the progression of liver fibrosis. Liver fibrogenesis is highly correlated with the activation of HSCs, which is regulated by numerous profibrotic cytokines. Using RNA interference to downregulate these cytokines in activated HSCs is a promising strategy to reverse liver fibrosis. Meanwhile, microRNAs (miRNAs) have also been exploited for the treatment of liver fibrosis. This review focuses on the current siRNA- and miRNA-based liver fibrosis treatment strategies by targeting activated HSCs in the liver.

Characterization of the Roles of Vimentin in Regulating the Proliferation and Migration of HSCs during Hepatic Fibrogenesis

The activation of hepatic stellate cells (HSCs) manifested as proliferation and migration is the pivotal event involved in liver fibrogenesis. The vimentin network, an intermediate filament (IF) system, is one of the critical cascades by which the cell morphology, growth, and motility are modulated. However, the vimentin-mediated cytoskeletal cross talk, as well as the signaling transduction, which further coordinates the cellular responses during hepatic fibrogenesis, is poorly understood. In the current study, both messenger RNA (mRNA) and the vimentin protein were significantly increased in a time-dependent manner in the dimethylnitrosamine (DMN)-exposed liver. In particular, vimentin was highly expressed in the activated HSCs. Again, the overexpressed vimentin was observed in the plasma samples derived from patients with hepatic fibrosis/cirrhosis, suggesting that vimentin may be a key factor in regulating the progression of liver fibrosis. Meanwhile, vimentin knockdown suppressed the migratory propensity, provoked morphological changes, and disturbed the focal adhesions in the HSCs due to the breakdown of associated cytoskeletal proteins. Western blotting showed that vimentin deletion inhibited proliferating cell nuclear antigen (PCNA) and arrested the Rho GTPase family, thereby impairing the HSCs’ growth as well as motility. The phosphorylated extracellular-signal regulated kinase (ERK) and AKT signals were also notably reduced in response to the silence of vimentin. Inhibitors of selected signaling pathways suppressed the migration and differentiation of activated HSCs by regulating specific serine phosphorylated sites on vimentin. Taken together, these findings revealed a novel mechanism of vimentin through which various signaling pathways controlled the proliferation, differentiation, and movement of the HSCs via the ERK/AKT and Rho cascades.

Rap1 regulates hepatic stellate cell migration through the modulation of RhoA activity in response to TGF‑β1

Although the migration of hepatic stellate cells (HSCs) is important for hepatic fibrosis, the regulation of this migration is poorly understood. Notably, transforming growth factor (TGF)‑β1 induces monocyte migration to sites of injury or inflammation during the early phase, but inhibits cell migration during the late phase. In the present study, the role of transforming protein RhoA signaling in TGF‑β1‑induced HSC migration was investigated. TGF‑β1 was found to increase the protein and mRNA levels of smooth muscle actin and collagen type I in HSC‑T6 cells. The level of RhoA‑GTP in TGF‑β1‑stimulated cells was significantly higher than that in control cells. Furthermore, the phosphorylation of cofilin and formation of filamentous actin (F‑actin) were more marked in TGF‑β1‑stimulated cells than in control cells. Additionally, TGF‑β1 induced the activation of nuclear factor‑κB, and the expression of extracellular matrix proteins and several cytokines in HSC‑T6 cells. The active form of Rap1 (Rap1 V12) suppressed RhoA‑GTP levels, whereas the dominant‑negative form of Rap1 (Rap1 N17) augmented RhoA‑GTP levels. Therefore, the data confirmed that Rap1 regulated the activation of RhoA in TGF‑β1‑stimulated HSC‑T6 cells. These findings suggest that TGF‑β1 regulates Rap1, resulting in the suppression of RhoA, activation of and formation of F‑actin during the migration of HSCs.

Interaction Mechanisms Between the NOX4/ROS and RhoA/ROCK1 Signaling Pathways as New Anti- fibrosis Targets of Ursolic Acid in Hepatic Stellate Cells

Background

Studies have shown that both NOX4 and RhoA play essential roles in fibrosis and that they regulate each other. In lung fibrosis, NOX4/ROS is located upstream of the RhoA/ROCK1 signaling pathway, and the two molecules are oppositely located in renal fibrosis. Currently, no reports have indicated whether the above mechanisms or other regulatory mechanisms exist in liver fibrosis.

Objectives

To investigate the effects of the NOX4/ROS and RhoA/ROCK1 signaling pathways on hepatic stellate cell (HSC)-T6 cells, the interaction mechanisms of the two pathways, and the impact of UA on the two pathways to elucidate the role of UA in the reduction of hepatic fibrosis and potential mechanisms of HSC-T6 cell proliferation, migration, and activation.

Methods

Stable cell lines were constructed using the lentiviral transduction technique. Cell proliferation, apoptosis, migration, and invasion were examined using the MTS, TdT-mediated dUTP nick-end labeling, cell scratch, and Transwell invasion assays, respectively. The DCFH-DA method was used to investigate the ROS levels in each group. RT-qPCR and western blotting techniques were utilized to assess the mRNA and protein expression in each group. CoIP and the Biacore protein interaction analysis systems were used to evaluate protein interactions.

Results

The NOX4/ROS and RhoA/ROCK1 signaling pathways promoted the proliferation, migration, and activation of HSCs. UA inhibited cell proliferation, migration, and activation by inhibiting the activation of the two signaling pathways, but the mechanism of apoptosis was independent of these two pathways. The NOX4/ROS pathway was upstream of and positively regulated the RhoA/ROCK1 pathway in HSCs. No direct interaction between the NOX4 and RhoA proteins was detected.

Conclusion

The NOX4/ROS and RhoA/ROCK1 signaling pathways are two critical signaling pathways in a series of behavioral processes in HSCs, and NOX4/ROS regulates RhoA/ROCK1 through an indirect pathway to control the activation of HSCs. Additionally, NOX4/ROS and RhoA/ROCK1 constitute a new target for UA antifibrosis treatment.

Molecular pathways of nonalcoholic fatty liver disease development and progression

Nonalcoholic fatty liver disease (NAFLD) is a main hepatic manifestation of metabolic syndrome. It represents a wide spectrum of histopathological abnormalities ranging from simple steatosis to nonalcoholic steatohepatitis (NASH) with or without fibrosis and, eventually, cirrhosis and hepatocellular carcinoma. While hepatic simple steatosis seems to be a rather benign manifestation of hepatic triglyceride accumulation, the buildup of highly toxic free fatty acids associated with insulin resistance-induced massive free fatty acid mobilization from adipose tissue and the increased de novo hepatic fatty acid synthesis from glucose acts as the "first hit" for NAFLD development. NAFLD progression seems to involve the occurrence of "parallel, multiple-hit" injuries, such as oxidative stress-induced mitochondrial dysfunction, endoplasmic reticulum stress, endotoxin-induced, TLR4-dependent release of inflammatory cytokines, and iron overload, among many others. These deleterious factors are responsible for the triggering of a number of signaling cascades leading to inflammation, cell death, and fibrosis, the hallmarks of NASH. This review is aimed at integrating the overwhelming progress made in the characterization of the physiopathological mechanisms of NAFLD at a molecular level, to better understand the factor influencing the initiation and progression of the disease.

High Mobility Group Box-1 Drives Fibrosis Progression Signaling via the Receptor for Advanced Glycation End Products in Mice

High-mobility group box-1 (HMGB1) is a damage-associated molecular pattern (DAMP) increased in response to liver injury. Because HMGB1 is a ligand for the receptor for advanced glycation endproducts (RAGE), we hypothesized that induction of HMGB1 could participate in the pathogenesis of liver fibrosis though RAGE cell-specific signaling mechanisms. Liver HMGB1 protein expression correlated with fibrosis stage in patients with chronic hepatitis C virus (HCV) infection, primary biliary cirrhosis (PBC), or alcoholic steatohepatitis (ASH). Hepatic HMGB1 protein expression and secretion increased in five mouse models of liver fibrosis attributed to drug-induced liver injury (DILI), cholestasis, ASH, or nonalcoholic steatohepatitis (NASH). HMGB1 was up-regulated and secreted mostly by hepatocytes and Kupffer cells (KCs) following CCl₄ treatment. Neutralization of HMGB1 protected, whereas injection of recombinant HMGB1 promoted liver fibrosis. Hmgb1 ablation in hepatocytes (Hmgb1^ΔHep ) or in myeloid cells (Hmgb1^ΔMye ) partially protected, whereas ablation in both (Hmgb1^ΔHepΔMye ) prevented liver fibrosis in vivo. Coculture with hepatocytes or KCs from CCl₄ -injected wild-type (WT) mice up-regulated Collagen type I production by hepatic stellate cells (HSCs); yet, coculture with hepatocytes from CCl₄ -injected Hmgb1^ΔHep or with KCs from CCl₄ -injected Hmgb1^ΔMye mice partially blunted this effect. Rage ablation in HSCs (Rage^ΔHSC ) and RAGE neutralization prevented liver fibrosis. Last, we identified that HMGB1 stimulated HSC migration and signaled through RAGE to up-regulate Collagen type I expression by activating the phosphorylated mitogen-activated protein kinase kinase (pMEK)1/2, phosphorylated extracellular signal-regulated kinase (pERK)1/2 and pcJun signaling pathway. Conclusion: Hepatocyte and KC-derived HMGB1 participates in the pathogenesis of liver fibrosis by signaling through RAGE in HSCs to activate the pMEK1/2, pERK1/2 and pcJun pathway and increase Collagen type I deposition.

eRF3b-37 inhibits the TGF-β1-induced activation of hepatic stellate cells by regulating cell proliferation, G0/G1 arrest, apoptosis and migration

The therapeutic management of liver fibrosis remains an unresolved clinical problem. The activation of hepatic stellate cells (HSCs) serves a pivotal role in the formation of liver fibrosis. In our previous study, matrix‑assisted laser desorption/ionization time‑of‑flight mass spectrometry (MALDI‑TOF MS) was employed to identify potential serum markers for liver cirrhosis, such as eukaryotic peptide chain releasing factor 3b polypeptide (eRF3b‑37), which was initially confirmed by our group to serve a protective role in liver tissues in a C‑C motif chemokine ligand 4‑induced liver cirrhosis mouse model. Therefore, eRF3b‑37 was hypothesized to affect the activation state of HSCs, which was determined by the expression of pro‑fibrogenic associated factors in HSCs. In the present study, peptide synthesis technology was employed to elucidate the role of eRF3b‑37 in the expression of pro‑fibrogenic factors induced by transforming growth factor‑β1 (TGF‑β1) in LX‑2 cells that were treated with either control, TGF‑β1 and TGF‑β1+eRF3b‑37. 3‑(4,5‑Dimethyl‑2‑thiazolyl)‑2,5‑diphenyltetrazolium bromide and flow cytometric assays, and fluorescent microscope examinations were performed to evaluate the effects of eRF3b‑37 on proliferation viability, G0/G1 arrest, apoptosis and cell migration. The results of the present study indicated that eRF3b‑37 inhibited the activation of HSCs. The increased mRNA and protein expression of the pro‑fibrogenic factors collagen I, connective tissue growth factor and α‑smooth muscle actin (SMA) stimulated by TGF‑β1 were reduced by eRF3b‑37 via the following mechanisms: i) Inhibiting LX‑2 cell proliferation, leading to G0/G1 cell cycle arrest and inhibition of DNA synthesis by downregulating the mRNA expressions of Cyclin D1 and cyclin dependent kinase‑4, and upregulating the levels of P21; ii) increasing cell apoptosis by upregulating the mRNA level of B‑cell lymphoma-2 (Bcl‑2)‑associated X protein (Bax) and Fas, and downregulating the expression of Bcl‑2; and iii) reducing cell migration by downregulating the mRNA and protein expression of α‑SMA. In addition, eRF3b‑37 is thought to serve a role in HSCs by inhibiting TGF‑β signaling. Therefore, eRF3b‑37 may be a novel therapeutic agent for targeting HSCs for hepatic fibrosis.

Transforming Growth Factor-β-Induced Cell Plasticity in Liver Fibrosis and Hepatocarcinogenesis

The Transforming Growth Factor-beta (TGF-β) family plays relevant roles in the regulation of different cellular processes that are essential for tissue and organ homeostasis. In the case of the liver, TGF-β signaling participates in different stages of disease progression, from initial liver injury toward fibrosis, cirrhosis and cancer. When a chronic injury takes place, mobilization of lymphocytes and other inflammatory cells occur, thus setting the stage for persistence of an inflammatory response. Macrophages produce profibrotic mediators, among them, TGF-β, which is responsible for activation -transdifferentiation- of quiescent hepatic stellate cells (HSC) to a myofibroblast (MFB) phenotype. MFBs are the principal source of extracellular matrix protein (ECM) accumulation and prominent mediators of fibrogenesis. TGF-β also mediates an epithelial-mesenchymal transition (EMT) process in hepatocytes that may contribute, directly or indirectly, to increase the MFB population. In hepatocarcinogenesis, TGF-β plays a dual role, behaving as a suppressor factor at early stages, but contributing to later tumor progression, once cells escape from its cytostatic effects. As part of its potential pro-tumorigenic actions, TGF-β induces EMT in liver tumor cells, which increases its pro-migratory and invasive potential. In parallel, TGF-β also induces changes in tumor cell plasticity, conferring properties of a migratory tumor initiating cell (TIC). The main aim of this review is to shed light about the pleiotropic actions of TGF-β that explain its effects on the different liver cell populations. The cross-talk with other signaling pathways that contribute to TGF-β effects, in particular the Epidermal Growth Factor Receptor (EGFR), will be presented. Finally, we will discuss the rationale for targeting the TGF-β pathway in liver pathologies.

Biophysical, Biochemical, and Cell Based Approaches Used to Decipher the Role of Carbonic Anhydrases in Cancer and to Evaluate the Potency of Targeted Inhibitors

Carbonic anhydrases (CAs) are thought to be important for regulating pH in the tumor microenvironment. A few of the CA isoforms are upregulated in cancer cells, with only limited expression in normal cells. For these reasons, there is interest in developing inhibitors that target these tumor-associated CA isoforms, with increased efficacy but limited nonspecific cytotoxicity. Here we present some of the biophysical, biochemical, and cell based techniques and approaches that can be used to evaluate the potency of CA targeted inhibitors and decipher the role of CAs in tumorigenesis, cancer progression, and metastatic processes. These techniques include esterase activity assays, stop flow kinetics, and mass inlet mass spectroscopy (MIMS), all of which measure enzymatic activity of purified protein, in the presence or absence of inhibitors. Also discussed is the application of X-ray crystallography and Cryo-EM as well as other structure-based techniques and thermal shift assays to the studies of CA structure and function. Further, large-scale genomic and proteomic analytical methods, as well as cell based techniques like those that measure cell growth, apoptosis, clonogenicity, and cell migration and invasion, are discussed. We conclude by reviewing approaches that test the metastatic potential of CAs and how the aforementioned techniques have contributed to the field of CA cancer research.

Curcumin protects against hepatic stellate cells activation and migration by inhibiting the CXCL12/CXCR4 biological axis in liver fibrosis：A study in vitro and in vivo

The C-X-C motif chemokine 12/C-X-C chemokine receptor type 4 (CXCL12/ CXCR4) biological axis plays an important role in the pathogenesis of liver fibrosis. Curcumin is known to have an anti-fibrosis effect, but the specific mechanism needs to be elucidated. There is currently no evidence illustrating a connection between curcumin and the CXCL12/CXCR4 axis in liver fibrosis. Here, we investigated the contribution of curcumin on CXCL12/ CXCR4 biological axis in liver fibrosis. Our results showed that curcumin remarkably improved hepatic function and liver fibrosis, and the effects are similar as silymarin. The alleviation of liver fibrosis with curcumin treatment was associated with a reduction of CXCL12, CXCR4, α-SMA and RhoA. In addition, curcumin markedly inhibited the proliferation and migration of HSC-T6 cells. This study indicates that curcumin could protect against hepatic stellate cells activation and migration by inhibiting the CXCL12/CXCR4 biological axis in liver fibrosis.

Silencing of α-complex protein-2 reverses alcohol- and cytokine-induced fibrogenesis in hepatic stellate cells

BACKGROUND AND AIM

α-complex protein-2 (αCP2) encoded by the poly (rC) binding protein 2(PCBP2) gene is responsible for the accumulation of type I collagen in fibrotic livers. In this study, we silenced the PCBP2 gene using a small interfering RNA (siRNA) to reverse alcohol-and cytokine-induced profibrogenic effects on hepatic stellate cells (HSCs).

METHODS

Primary rat HSCs and the HSC-T6 cell line were used as fibrogenic models to mimic the initiation and perpetuation stages of fibrogenesis, respectively. We previously found that a PCBP2 siRNA, which efficiently silences expression of αCP2, reduces the stability of type I collagen mRNA. We investigated the effects of the PCBP2 siRNA on cell proliferation and migration. Expression of type I collagen in HSCs was analyzed by quantitative real-time PCR and western blotting. In addition, we evaluated the effects of the PCBP2 siRNA on apoptosis and the cell cycle.

RESULTS

PCBP2 siRNA reversed multiple alcohol- and cytokine-induced profibrogenic effects on primary rat HSCs and HSC-T6 cells. The PCBP2 siRNA also reversed alcohol- and cytokine-induced accumulation of type I collagen as well as cell proliferation and migration. Moreover, the combination of LY2109761, a transforming growth factor-β1 inhibitor, and the PCBP2 siRNA exerted a synergistic inhibitive effect on the accumulation of type I collagen in HSCs.

CONCLUSIONS

Silencing of PCBP2 using siRNA could be a potential therapeutic strategy for alcoholic liver fibrosis.

Update on implications and mechanisms of angiogenesis in liver fibrosis

Liver fibrosis occurs as a compensatory response to the process of tissue repair in a wide range of chronic liver injures. It is characterized by excessive deposition of extracellular matrix in liver tissues. As the pathogenesis progresses without effective management, it will lead to formation of liver fiber nodules and disruption of normal liver structure and function, finally culminating in cirrhosis and hepatocellular carcinoma. A new discovery shows that liver angiogenesis is strictly associated with, and may even favor fibrogenic progression of chronic liver diseases. Recent basic and clinical investigations also demonstrate that liver fibrogenesis is accompanied by pathological angiogenesis and sinusoidal remodeling, which critically determine the pathogenesis and prognosis of liver fibrosis. Inhibition of pathological angiogenesis is considered to be a new strategy for the treatment of liver fibrosis. This review summarizes current knowledge on the process of angiogenesis, the relationships between angiogenesis and liver fibrosis, and on the molecular mechanisms of liver angiogenesis. On the other hand, it also presents the different strategies that have been used in experimental models to counteract excessive angiogenesis and the role of angiogenesis in the prevention and treatment of liver fibrosis.

Systems level analysis and identification of pathways and networks associated with liver fibrosis

Toxic liver injury causes necrosis and fibrosis, which may lead to cirrhosis and liver failure. Despite recent progress in understanding the mechanism of liver fibrosis, our knowledge of the molecular-level details of this disease is still incomplete. The elucidation of networks and pathways associated with liver fibrosis can provide insight into the underlying molecular mechanisms of the disease, as well as identify potential diagnostic or prognostic biomarkers. Towards this end, we analyzed rat gene expression data from a range of chemical exposures that produced observable periportal liver fibrosis as documented in DrugMatrix, a publicly available toxicogenomics database. We identified genes relevant to liver fibrosis using standard differential expression and co-expression analyses, and then used these genes in pathway enrichment and protein-protein interaction (PPI) network analyses. We identified a PPI network module associated with liver fibrosis that includes known liver fibrosis-relevant genes, such as tissue inhibitor of metalloproteinase-1, galectin-3, connective tissue growth factor, and lipocalin-2. We also identified several new genes, such as perilipin-3, legumain, and myocilin, which were associated with liver fibrosis. We further analyzed the expression pattern of the genes in the PPI network module across a wide range of 640 chemical exposure conditions in DrugMatrix and identified early indications of liver fibrosis for carbon tetrachloride and lipopolysaccharide exposures. Although it is well known that carbon tetrachloride and lipopolysaccharide can cause liver fibrosis, our network analysis was able to link these compounds to potential fibrotic damage before histopathological changes associated with liver fibrosis appeared. These results demonstrated that our approach is capable of identifying early-stage indicators of liver fibrosis and underscore its potential to aid in predictive toxicity, biomarker identification, and to generally identify disease-relevant pathways.

High mobility group box-1 promotes the proliferation and migration of hepatic stellate cells via TLR4-dependent signal pathways of PI3K/Akt and JNK

BACKGROUND

The migration of hepatic stellate cells (HSCs) is essential to the hepatic fibrotic response, and recently High-mobility group box 1 (HMGB1) has been shown up-regulated during liver fibrosis. Nevertheless, whether HMGB1 can modulate the proliferation and migration of HSCs is poorly understood, as well as the involved intracellular signaling. In this study, we examined the effect of HMGB1 on proliferation, migration, pro-fibrotic function of HSCs and investigated whether toll-like family of receptor 4 (TLR4) dependent signal pathway is involved in the intracellular signaling regulation.

METHODOLOGY/PRINCIPAL FINDINGS

Modified transwell chamber system to mimic the space of Disse was used to evaluate the migration of human primary HSCs, and the protein expressions of related signal factors were evaluated by western blot. Cell proliferation was analyzed by MTT assay, the pro-fibrotic functions of HSCs by qRT-PCR and ELISA respectively. Recombinant human HMGB1 could significantly promote migration of HSCs under both haptotactic and chemotactic stimulation, especially the latter. Human TLR4 neutralizing antibody could markedly inhibit HMGB1-induced migration of HSCs. HMGB1 could enhance the phosphorylation of JNK and PI3K/Akt, and TLR4 neutralizing antibody inhibited HMGB1-enhanced phosphorylation of JNK and PI3K/Akt and activation of NF-κB. JNK inhibitor (SP600125) and PI3K inhibitor (LY 294002) significantly inhibited HMGB1-induced proliferation and migration of HSCs, and also reduced HMGB1-enhanced related collagen expressions and pro-fibrotic cytokines production.

CONCLUSIONS/SIGNIFICANCE

HMGB1 could significantly enhance migration of HSCs in vitro, and TLR4-dependent JNK and PI3K/Akt signal pathways are involved in the HMGB1-induced proliferation, migration and pro-fibrotic effects of HSCs, which indicates HMGB1 might be an effective target to treat liver fibrosis.