Molecular mechanism of hepatic stellate cell activation and antifibrotic therapeutic strategies

Increased expression of phosphodiesterase 4 in activated hepatic stellate cells promotes cytoskeleton remodeling and cell migration

Activation and transdifferentiation of hepatic stellate cells (HSC) into migratory myofibroblasts is a key process in liver fibrogenesis. Cell migration requires an active remodeling of the cytoskeleton, which is a tightly regulated process coordinated by Rho-specific guanine nucleotide exchange factors (GEFs) and the Rho family of small GTPases. Rho-associated kinase (ROCK) promotes assembly of focal adhesions and actin stress fibers by regulating cytoskeleton organization. GEF exchange protein directly activated by cAMP 1 (EPAC1) has been implicated in modulating TGFβ1 and Rho signaling; however, its role in HSC migration has never been examined. The aim of this study was to evaluate the role of cAMP-degrading phosphodiesterase 4 (PDE4) enzymes in regulating EPAC1 signaling, HSC migration, and fibrogenesis. We show that PDE4 protein expression is increased in activated HSCs expressing alpha smooth muscle actin and active myosin light chain (MLC) in fibrotic tissues of human nonalcoholic steatohepatitis cirrhosis livers and mouse livers exposed to carbon tetrachloride. In human livers, TGFβ1 levels were highly correlated with PDE4 expression. TGFβ1 treatment of LX2 HSCs decreased levels of cAMP and EPAC1 and increased PDE4D expression. PDE4 specific inhibitor, rolipram, and an EPAC-specific agonist decreased TGFβ1-mediated cell migration in vitro. In vivo, targeted delivery of rolipram to the liver prevented fibrogenesis and collagen deposition and decreased the expression of several fibrosis-related genes, and HSC activation. Proteomic analysis of mouse liver tissues identified the regulation of actin cytoskeleton by the kinase effectors of Rho GTPases as a major pathway impacted by rolipram. Western blot analyses confirmed that PDE4 inhibition decreased active MLC and endothelin 1 levels, key proteins involved in cytoskeleton remodeling and contractility. The current study, for the first time, demonstrates that PDE4 enzymes are expressed in hepatic myofibroblasts and promote cytoskeleton remodeling and HSC migration. © 2023 The Pathological Society of Great Britain and Ireland.

Hepatocellular Carcinoma Prevention in the Era of Hepatitis C Elimination

The hepatitis C virus (HCV), a single-stranded RNA virus belonging to the Flaviviridae family, is a major cause of hepatocellular carcinoma (HCC) worldwide. Tumors caused by HCC have an increased mortality rate globally, which is more accentuated in Western countries. The carcinogenic potential of this virus is mediated through a wide range of mechanisms, spanning from the induction of chronic inflammation to oxidative stress and deregulation of cellular pathways by viral proteins. As the number of new infections continues unabated, HCC-related mortality should be prioritized through early detection, continued prevention of HCV transmission, and treatment of HCV with safe and efficacious direct antiviral agents (DAAs). People who inject drugs (PWID) are a significant reservoir of new HCV infections globally, and in order to eliminate hepatitis C as a global health threat, as set out by the World Health Organization, an integrated approach based on the optimization of care delivery and increased access to harm reduction and treatment for PWID is needed. Thanks to the development of safe and effective antiviral agents, eradication of the infection is now possible in almost all treated patients, leading to a significant reduction but not the elimination of the risk for HCC in cured patients. This is particularly relevant among aged populations who have cofactors of morbidity known to accelerate HCC progression, such as diabetes, obesity, and excessive alcohol consumption. Given the restless accumulation of individuals with cured HCV infection, the implementation of risk-stratified surveillance programs becomes impellent from a cost-effectiveness perspective, whereas the availability of a performant biomarker to predict HCC in cured patients remains an unmet clinical need.

Identification of Liver Fibrosis-Related MicroRNAs in Human Primary Hepatic Stellate Cells Using High-Throughput Sequencing

MicroRNAs (miRNAs) participate in hepatic stellate cell (HSC) activation, which drives liver fibrosis initiation and progression. We aimed to identify novel hepatic fibrosis targets using miRNA sequencing (miRNA-seq) of human primary HSCs. Surgically resected liver tissues were used to extract HSCs. Based on next-generation sequencing, miRNA-seq was performed on four pairs of HSCs before and after in vitro culture. Additionally, we compared our data with open access miRNA-seq data derived from fourteen cirrhotic and nine healthy liver tissues. Selected miRNAs associated with fibrosis were verified by quantitative real-time PCR. Target mRNAs of differentially expressed (DE) miRNAs were predicted to construct co-expression networks. We identified 230 DEmiRNAs (118 upregulated and 112 downregulated) upon HSC activation. Of the 17 miRNAs with the most significant differences in expression, liver disease-related miRNAs included miR-758-3p, miR-493-5p, miR-409-3p, miR-31-5p, miR-1268a, and miR-381-3p, which might play roles in hepatic fibrosis. Moreover, let-7g-5p, miR-107, miR-122-5p, miR-127-3p, miR-139-5p, miR-148a-3p, miR-194-5p, miR-215-5p, miR-26a-5p, miR-340-5p, miR-451a, and miR-99a-5p were common between our data and the publicly available sequencing data. A co-expression network comprising 1891 matched miRNA-mRNA pairs representing 138 DEmiRNAs and 1414 DEmRNAs was constructed. MiR-1268a and miR-665, possessing the richest target DEmRNAs, may be vital in HSC activation. The targeted genes were involved in collagen metabolism, extracellular matrix structural constituent, cytoskeletal protein binding, and cell adhesion. The miRNAs we identified may provide a basis and reference for the selection of diagnostic and therapeutic targets for hepatic fibrosis.

Targeting A-kinase anchoring protein 12 phosphorylation in hepatic stellate cells regulates liver injury and fibrosis in mouse models

Trans-differentiation of hepatic stellate cells (HSCs) to activated state potentiates liver fibrosis through release of extracellular matrix (ECM) components, distorting the liver architecture. Since limited antifibrotics are available, pharmacological intervention targeting activated HSCs may be considered for therapy. A-kinase anchoring protein 12 (AKAP12) is a scaffolding protein that directs protein kinases A/C (PKA/PKC) and cyclins to specific locations spatiotemporally controlling their biological effects. It has been shown that AKAP12's scaffolding functions are altered by phosphorylation. In previously published work, observed an association between AKAP12 phosphorylation and HSC activation. In this work, we demonstrate that AKAP12's scaffolding activity toward the endoplasmic reticulum (ER)-resident collagen chaperone, heat-shock protein 47 (HSP47) is strongly inhibited by AKAP12's site-specific phosphorylation in activated HSCs. CRISPR-directed gene editing of AKAP12's phospho-sites restores its scaffolding toward HSP47, inhibiting HSP47's collagen maturation functions, and HSC activation. AKAP12 phospho-editing dramatically inhibits fibrosis, ER stress response, HSC inflammatory signaling, and liver injury in mice. Our overall findings suggest a pro-fibrogenic role of AKAP12 phosphorylation that may be targeted for therapeutic intervention in liver fibrosis.

Protective Effects of Wine Polyphenols on Oxidative Stress and Hepatotoxicity Induced by Acrylamide in Rats

In recent years, it has been increasingly suggested that the consumption of natural polyphenols, in moderate amounts, is beneficial for health. The aim of this study was to investigate the efficacy of a red wine (the administered dose of 7 mL/kg/day being equivalent to ~16.5 mg/kg/day total polyphenols) compared to a white wine (the administered dose of 7 mL/kg/day being equivalent to ~1.7 mg/kg/day total polyphenols), on the prevention of acrylamide-induced subacute hepatic injury and oxidative stress in Wistar rats. Hepatic damage due to acrylamide intoxication (the administered dose being 250 µg/kg body weight, for 28 days, by intragastric gavage) was assessed by employing biochemical parameters (aspartate aminotransferase (AST) and alanine aminotransferase (ALT)) and by histopathological studies. Markers of oxidative damage were measured in terms of plasma malondialdehyde (MDA), hepatic Thiobarbituric Acid Reactive Substances (TBARS) and glutathione (GSH) levels, and liver antioxidant enzyme (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx)) activities. Regarding hepatic enzyme activities, treatment with red wine significantly decreased the AST values (p < 0.05), while for the ALT values only a normalization tendency was observed. Treatment with red wine and white wine, respectively, significantly prevented the increase in MDA and TBARS levels (p < 0.05), as well as the depletion of GSH (p < 0.05). Red wine treatment normalized the activities of the antioxidant enzymes CAT and SOD in rats intoxicated with acrylamide, while supplementing the diet with white wine did not produce significant differences in the antioxidant enzyme activities. Histopathological findings revealed a moderate protective effect of red wine after four weeks of daily consumption. Our findings provide evidence that red wine, having a higher phenolic content than white wine, has a significant protective effect on oxidative stress and liver injury induced by acrylamide in rats, through its antioxidative activity.

FGF1 Signaling Modulates Biliary Injury and Liver Fibrosis in the Mdr2-/- Mouse Model of Primary Sclerosing Cholangitis

Fibroblast growth factor 1 (FGF1) belongs to a family of growth factors involved in cellular growth and division. MicroRNA 16 (miR-16) is a regulator of gene expression, which is dysregulated during liver injury and insult. However, the role of FGF1 in the progression of biliary proliferation, senescence, fibrosis, inflammation, angiogenesis, and its potential interaction with miR-16, are unknown. In vivo studies were performed in male bile duct-ligated (BDL, 12-week-old) mice, multidrug resistance 2 knockout (Mdr2-/-) mice (10-week-old), and their corresponding controls, treated with recombinant human FGF1 (rhFGF1), fibroblast growth factor receptor (FGFR) antagonist (AZD4547), or anti-FGF1 monoclonal antibody (mAb). In vitro, the human cholangiocyte cell line (H69) and human hepatic stellate cells (HSCs) were used to determine the expression of proliferation, fibrosis, angiogenesis, and inflammatory genes following rhFGF1 treatment. PSC patient and control livers were used to evaluate FGF1 and miR-16 expression. Intrahepatic bile duct mass (IBDM), along with hepatic fibrosis and inflammation, increased in BDL mice treated with rhFGF1, with a corresponding decrease in miR-16, while treatment with AZD4547 or anti-FGF1 mAb decreased hepatic fibrosis, IBDM, and inflammation in BDL and Mdr2-/- mice. In vitro, H69 and HSCs treated with rhFGF1 had increased expression of proliferation, fibrosis, and inflammatory markers. PSC samples also showed increased FGF1 and FGFRs with corresponding decreases in miR-16 compared with healthy controls. Conclusion: Our study demonstrates that suppression of FGF1 and miR-16 signaling decreases the presence of hepatic fibrosis, biliary proliferation, inflammation, senescence, and angiogenesis. Targeting the FGF1 and miR-16 axis may provide therapeutic options in treating cholangiopathies such as PSC.

Autophagy and Exosomes: Cross-Regulated Pathways Playing Major Roles in Hepatic Stellate Cells Activation and Liver Fibrosis

Chronic liver injury, regardless of the underlying disease, results in gradual alteration of the physiological hepatic architecture and in excessive production of extracellular matrix, eventually leading to cirrhosis Liver cellular architecture consists of different cell populations, among which hepatic stellate cells (HSCs) have been found to play a major role in the fibrotic process. Under normal conditions, HSCs serve as the main storage site for vitamin A, however, pathological stimuli lead to their transdifferentiation into myofibroblast cells, with autophagy being the key regulator of their activation, through lipophagy of their lipid droplets. Nevertheless, the role of autophagy in liver fibrosis is multifaceted, as increased autophagic levels have been associated with alleviation of the fibrotic process. In addition, it has been found that HSCs receive paracrine stimuli from neighboring cells, such as injured hepatocytes, Kupffer cells, sinusoidal endothelial cells, which promote liver fibrosis. These stimuli have been found to be transmitted via exosomes, which are incorporated by HSCs and can either be degraded through lysosomes or be secreted back into the extracellular space via fusion with the plasma membrane. Furthermore, it has been demonstrated that autophagy and exosomes may be concomitantly or reciprocally regulated, depending on the cellular conditions. Given that increased levels of autophagy are required to activate HSCs, it is important to investigate whether autophagy levels decrease at later stages of hepatic stellate cell activation, leading to increased release of exosomes and further propagation of hepatic fibrosis.

Old wine in new bottles: Kaempferol is a promising agent for treating the trilogy of liver diseases

As a source of various compounds, natural products have long been important and valuable for drug development. Kaempferol (KP) is the most common flavonol with bioactive activity and has been extracted from many edible plants and traditional Chinese medicines. It has a wide range of pharmacological effects on inflammation, oxidation, and tumour and virus regulation. The liver is an important organ and is involved in metabolism and activity. Because the pathological process of liver diseases is extremely complicated, liver diseases involving ALD, NASH, liver fibrosis, and HCC are often complicated and difficult to treat. Fortunately, there have been many reports that KP has a good pharmacological effect on a series of complex liver diseases. To fully understand the mechanism of KP and provide new ideas for its clinical application in the treatment of liver diseases, this article reviews the pharmacological mechanism and potential value of KP in different studies involving various liver diseases. In the trilogy of liver disease, high concentrations of ROS stimulate peroxidation and activate the inflammatory signal cascade, which involves signalling pathways such as MAPK/JAK-STAT/PERK/Wnt/Hipp, leading to varying degrees of cell degradation and liver damage. The development of liver disease is promoted in an inflammatory environment, which is conducive to the activation of TGF-β1, leading to increased expression of pro-fibrosis and pro-inflammatory genes. Inflammation and oxidative stress promote the formation of tumour microenvironments, and uncontrolled autophagy of cancer cells further leads to the development of liver cancer. The main pathway in this process is AMPK/PTEN/PI3K-Akt/TOR. KP can not only protect liver parenchymal cells through a variety of antioxidant and anti-apoptotic mechanisms but also reduces the immune inflammatory response in the liver microenvironment, thereby preventing cell apoptosis; it can also inhibit the ER stress response, prevent inflammation and inhibit tumour growth. KP exerts multiple therapeutic effects on liver disease by regulating precise signalling targets and is expected to become an emerging therapeutic opportunity to treat liver disease in the future.

Treatment for Viral Hepatitis as Secondary Prevention for Hepatocellular Carcinoma

Chronic infections with either hepatitis B or C virus (HBV or HCV) are among the most common risk factors for developing hepatocellular carcinoma (HCC). The hepatocarcinogenic potential of these viruses is mediated through a wide range of mechanisms, including the induction of chronic inflammation and oxidative stress and the deregulation of cellular pathways by viral proteins. Over the last decade, effective anti-viral agents have made sustained viral suppression or cure a feasible treatment objective for most chronic HBV/HCV patients. Given the tumorigenic potential of HBV/HCV, it is no surprise that obtaining sustained viral suppression or eradication proves to be effective in preventing HCC. This review summarizes the mechanisms by which HCV and HBV exert their hepatocarcinogenic activity and describes in detail the efficacy of anti-HBV and anti-HCV therapies in terms of HCC prevention. Although these treatments significantly reduce the risk for HCC in patients with chronic viral hepatitis, this risk is not eliminated. Therefore, we evaluate potential strategies to improve these outcomes further and address some of the remaining controversies.

Effect of Hepatocyte Growth Factor-Transfected Human Umbilical Cord Mesenchymal Stem Cells on Hepatic Stellate Cells by Regulating Transforming Growth Factor-β1/Smads Signaling Pathway

Studies have shown that human umbilical cord mesenchymal stem cells (hUCMSCs) could ameliorate liver fibrosis (LF) through inhibiting the activation of hepatic stellate cells (HSCs). However, the specific mechanisms have not been studied clearly. The purpose of this study was to explore the possible mechanism of hepatocyte growth factor (HGF)-transfected hUCMSCs in inhibiting the proliferation and activation of HSCs-T6. The upper and lower double-cell coculture system was established among HGF-hUCMSCs, LV5-NC-hUCMSCs, hUCMSCs, and HSCs-T6 in experimental groups; HSCs-T6 were cultured alone as control group. After coculturing for 1, 2, and 3 days, results showed that HGF-transfected hUCMSCs could decrease cell viability of HSCs-T6 and promote apoptosis; inhibit their activation and reduce the expression of Collagen I, Collagen III, TGF-β1, Smad2 and Smad3, which may be related to inhibiting the activation of TGF-β1/Smads signaling pathway. These findings suggested that HGF-transfected hUCMSCs may be used as an alternative and novel therapeutic approach for the treatment of LF.

Caffeine-induced inversion of prostaglandin E2 effects on hepatic stellate cell activation

BACKGROUND AND AIMS

Liver inflammation leads to the activation of hepatic stellate cells (HSCs), resulting in the development of liver fibrosis. The present study aimed to investigate the effects of prostaglandin E₂ (PGE₂), which is biosynthesized by Kupffer cells, hepatocytes, and HSCs during inflammation, on HSC activation, including its combinatory effect with caffeine.

METHODS

HSCs isolated from mice were activated by culturing in a medium supplemented with 10% fetal bovine serum for 7 days on plastic plates. The activation of HSCs was evaluated by immunofluorescence of α-smooth muscle actin in HSCs. Comprehensive gene expression analysis was performed using mRNA-sequencing to compare HSCs cultured for 1 or 7 days, with or without PGE₂, caffeine, or both.

RESULTS

PGE₂ (1 μM) facilitated the activation of HSCs but inhibited the HSC activation in the presence of caffeine (3 mM). Comprehensive gene expression analysis revealed that HSCs treated with PGE₂ in the presence of caffeine were classified in the same class as HSCs cultured for 1 day, i.e., quiescent HSCs. In contrast, PGE₂ did not exhibit an inhibitory effect on HSC activation when co-treated with any isoform-specific phosphodiesterase inhibitors. Although the adenylate cyclase inhibitor 2',5'-dideoxyadenosine suppressed the elevation of intracellular cAMP level induced by PGE₂ in the presence of caffeine, it had no effect on the inhibition of HSC activation by PGE₂ plus caffeine.

CONCLUSION

The effect of PGE₂ on HSC activation is changed from facilitatory to inhibitory when combined with caffeine, suggesting that caffeine may effectively suppress liver fibrosis during inflammation.

Hepatic stellate cells role in the course of metabolic disorders development - A molecular overview

Fibrosis is characterized by an abnormal accumulation of extracellular matrix (ECM) constituents in the liver parenchyma that lead to hepatic cirrhosis. After liver injury, the hepatic stellate cells (HSCs) undergo a response called "activation", transforming the cells into proliferative, fibrogenic and contractile myofibroblasts, representing the main collagen-producing cells in the injured tissue. Activated HSCs are considered as pro-inflammatory cells producing cytokines and several hepatomatogens; they are additionally involved in the recruitment of Kupffer cells, circulating monocytes and macrophages through the production of chemokines. Moreover, HSC have been proposed as being involved in the development of insulin resistance mainly mediated by their inflammatory properties, which undeniably links their activation to the development of diabetes and Non-alcoholic fatty liver disease. In addition, when the liver is injured, a complex interaction between hepatocytes and HSCs occurs, inducing mitochondrial dysfunction, which contributes to the accumulation of fats in hepatocytes that trigger to liver lipotoxicity. These mechanisms underlying the activation of HSC suggest their major role in the development of metabolic disorders. It turns out that several molecules including MicroRNAs and proteins have the ability to inhibit the activation and the proliferation of HSCs, which makes them interesting therapeutic targets for the subsequent management of metabolic conditions. This review focuses on the mechanisms and molecular pathways underlying the initiation and onset of metabolic disorders following HSCs activation, as well as on molecular therapeutic targets, which could limit their fibrogenic transdifferentiation and therefore improve the liver condition in the course of metabolic imbalance.

Hepatic stellate cells - from past till present: morphology, human markers, human cell lines, behavior in normal and liver pathology

Hepatic stellate cell (HSC), initially analyzed by von Kupffer, in 1876, revealed to be an extraordinary mesenchymal cell, essential for both hepatocellular function and lesions, being the hallmark of hepatic fibrogenesis and carcinogenesis. Apart from their implications in hepatic injury, HSCs play a vital role in liver development and regeneration, xenobiotic response, intermediate metabolism, and regulation of immune response. In this review, we discuss the current state of knowledge regarding HSCs morphology, human HSCs markers and human HSC cell lines. We also summarize the latest findings concerning their roles in normal and liver pathology, focusing on their impact in fibrogenesis, chronic viral hepatitis and liver tumors.

Albumin inhibits the nuclear translocation of Smad3 via interleukin-1beta signaling in hepatic stellate cells

Activation of quiescent hepatic stellate cells (HSCs) to myofibroblasts plays a key role in liver fibrosis. We had previously shown that albumin and its derivative, R-III (a retinol-binding protein—albumin domain III fusion protein), inhibited HSC activation by sequestering retinoic acid (RA) and that R-III administration reduced carbon tetrachloride (CCl₄)-induced liver fibrosis. In this study, we aimed to elucidate the mechanism of action of albumin downstream of RA sequestration. Nuclear factor-κB p65 was evenly distributed in the cytoplasm in activated mouse HSCs, whereas albumin expression or R-III treatment (albumin/R-III) caused the nuclear translocation of p65, probably via RA sequestration, resulting in a dramatic increase in interleukin-1beta (IL-1β) expression. Albumin/R-III in turn induced the phosphorylation of Smad3 at the linker region, inhibiting its nuclear import in an IL-1β-dependent manner. Consistent with the in vitro results, the level of IL-1β mRNA expression was higher in CCl₄/R-III-treated livers than in CCl₄-treated livers. These findings reveal that albumin/R-III inhibits the transforming growth factor-β-Smad3 signaling as well as the retinoic acid receptor-mediated pathway, which probably contributes to the inhibition of HSC activation, and suggest that R-III may be an anti-fibrotic drug candidate.

Hepatic stellate cells specific liposomes with the Toll-like receptor 4 shRNA attenuates liver fibrosis

The hepatic stellate cells (HSCs) play a significant role in the onset of liver fibrosis, which can be treated by the inhibition and reversal of HSC activation. The RNA interference-mediated TLR4 gene silencing might be a potential therapeutic approach for liver fibrosis. The crucial challenge in this method is the absence of an efficient delivery system for the RNAi introduction in the target cells. HSCs have an enhanced capacity of vitamin A intake as they contain retinoic acid receptors (RARs). In the current study, we developed cationic liposomes modified with vitamin A to improve the specificity of delivery vehicles for HSCs. The outcome of this study revealed that the VitA-coupled cationic liposomes delivered the TLR4 shRNA to aHSCs more efficiently, as compared to the uncoupled cationic liposomes, both in the in vitro and in vivo conditions. Besides, as evident from the outcome of this study, the TLR4 gene silencing inhibited the HSCs activation and attenuated the liver fibrosis via the NF-κB transcriptional inactivation, pro-inflammatory cytokines secretion and reactive oxygen species (ROS) synthesis. Thus, the VitA-coupled liposomes encapsulated with the TLR4-shRNA might prove as an efficient therapeutic agent for liver fibrosis.

In vitro analysis of hepatic stellate cell activation influenced by transmembrane 6 superfamily 2 polymorphism

Non‑alcoholic steatohepatitis (NASH) may progress via liver fibrosis along with hepatic stellate cell (HSC) activation. A single nucleotide polymorphism (SNP; rs58542926) located in transmembrane 6 superfamily 2 (TM6SF2) has been reported to be significantly associated with fibrosis in patients with NASH, but the precise mechanism is still unknown. The present study aimed to explore the role of TM6SF2 in HSC activation in vitro. Plasmids producing TM6SF2 wild-type (WT) and mutant type (MT) containing E167K amino acid substitution were constructed, and the activation of LX‑2 cells was analyzed by overexpressing or knocking down TM6SF2 under transforming growth factor β1 (TGFβ) treatment. Intracellular α‑smooth muscle actin (αSMA) expression in LX‑2 cells was significantly repressed by TM6SF2‑WT overexpression and increased by TM6SF2 knockdown. Following treatment with TGFβ, αSMA expression was restored in TM6SF2‑WT overexpressed LX‑2 cells and was enhanced in TM6SF2 knocked‑down LX‑2 cells. Comparing αSMA expression under TM6SF2‑WT or ‑MT overexpression, expression of αSMA in TM6SF2‑MT overexpressed cells was higher than that in TM6SF2‑WT cells and was further enhanced by TGFβ treatment. The present study demonstrated that intracellular αSMA expression in HCS was negatively regulated by TM6SF2 while the E167K substitution released this negative regulation and led to enhanced HSC activation by TGFβ. These results suggest that the SNP in TM6SF2 may relate to sensitivity of HSC activation.

Cyclin-like proteins tip regenerative balance in the liver to favour cancer formation

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide. A variety of factors can contribute to the onset of this disease, including viral infection, obesity, alcohol abuse and non-alcoholic fatty liver disease (NAFLD). These stressors predominantly introduce chronic inflammation leading to liver cirrhosis and finally the onset of HCC; however, approximately 20% of HCC cases arise in the absence of cirrhosis via a poorly defined mechanism. The atypical cyclin-like protein Spy1 is capable of overriding cell cycle checkpoints, promoting proliferation and has been implicated in HCC. We hypothesize that Spy1 promotes sustained proliferation making the liver more susceptible to accumulation of deleterious mutations, leading to the development of non-cirrhotic HCC. We report for the first time that elevation of Spy1 within the liver of a transgenic mouse model leads to enhanced spontaneous liver tumourigenesis. We show that the abundance of Spy1 enhanced fat deposition within the liver and decreased the inflammatory response. Interestingly, Spy1 transgenic mice have a significant reduction in fibrosis and sustained rates of hepatocyte proliferation, and endogenous levels of Spy1 are downregulated during the normal fibrotic response. Our results provide support that abnormal regulation of Spy1 protein drives liver tumorigenesis in the absence of elevated fibrosis and, hence, may represent a potential mechanism behind non-cirrhotic HCC. This work may implicate Spy1 as a prognostic indicator and/or potential target in the treatment of diseases of the liver, such as HCC. The cyclin-like protein Spy1 enhances lipid deposition and reduces fibrosis in the liver. Spy1 also promotes increased hepatocyte proliferation and onset of non-cirrhotic hepatocellular carcinoma (HCC). Thus, Spy1 may be used as a potential target in the treatment of HCC.

Inhibition of Renal Stellate Cell Activation Reduces Renal Fibrosis

Interstitial fibrosis is a common feature of chronic kidney disease, and platelet-derived growth factor receptor-β (PDGFR-β)-positive mesenchymal cells are reportedly the major source of scar-producing myofibroblasts. We had previously demonstrated that albumin and its derivative R-III (a retinol-binding protein-albumin domain III fusion protein) inhibited the transdifferentiation/activation of hepatic stellate cells (HSCs) to myofibroblasts and that R-III administration reduced liver fibrosis. In this study, we isolated cells (referred to as renal stellate cells, RSCs) from rat kidney tissues using the HSC isolation protocol and compared their morphological and biochemical characteristics with those of HSCs. RSCs shared many characteristics with HSCs, such as storage of vitamin A-containing lipid droplets and expression of HSC markers as well as pericyte markers. RSCs underwent spontaneous transdifferentiation into myofibroblasts in in vitro culture, which was inhibited by albumin expression or R-III treatment. We also evaluated the therapeutic effects of R-III in unilateral ureteral obstruction (UUO)-induced renal fibrosis in mice. Injected R-III localized predominantly in cytoglobin/stellate cell activation-associated protein (Cygb/STAP)-positive cells in the kidney and reduced renal fibrosis. These findings suggest that RSCs can be recognized as the renal counterparts of HSCs and that RSCs represent an attractive therapeutic target for anti-fibrotic therapy.

Molecular mechanisms of viral hepatitis induced hepatocellular carcinoma

Chronic infection with viral hepatitis affects half a billion individuals worldwide and can lead to cirrhosis, cancer, and liver failure. Liver cancer is the third leading cause of cancer-associated mortality, of which hepatocellular carcinoma (HCC) represents 90% of all primary liver cancers. Solid tumors like HCC are complex and have heterogeneous tumor genomic profiles contributing to complexity in diagnosis and management. Chronic infection with hepatitis B virus (HBV), hepatitis delta virus (HDV), and hepatitis C virus (HCV) are the greatest etiological risk factors for HCC. Due to the significant role of chronic viral infection in HCC development, it is important to investigate direct (viral associated) and indirect (immune-associated) mechanisms involved in the pathogenesis of HCC. Common mechanisms used by HBV, HCV, and HDV that drive hepatocarcinogenesis include persistent liver inflammation with an impaired antiviral immune response, immune and viral protein-mediated oxidative stress, and deregulation of cellular signaling pathways by viral proteins. DNA integration to promote genome instability is a feature of HBV infection, and metabolic reprogramming leading to steatosis is driven by HCV infection. The current review aims to provide a brief overview of HBV, HCV and HDV molecular biology, and highlight specific viral-associated oncogenic mechanisms and common molecular pathways deregulated in HCC, and current as well as emerging treatments for HCC.

The Differential and Dynamic Progression of Hepatic Inflammation and Immune Responses During Liver Fibrosis Induced by Schistosoma japonicum or Carbon Tetrachloride in Mice

Liver fibrosis can result from various causes and could progress to cirrhosis and cancer; however, there are no effective treatments due to that its molecular mechanism is unclear. liver fibrosis model made by Schistosoma japonicum (S. japonicum) infection or Carbon tetrachloride (CCl₄) intraperitoneal injection is a conventional model used in liver fibrosis-related studies for mechanism or pharmaceutical research purposes. But the differences in the pathological progression, immune responses and the underlying mechanism between the two liver fibrosis model have not been carefully compared and characterized, which hinders us from correctly understanding and making better use of the two models. In the present study, the pathological changes to the liver, and the cytokines, inflammatory factors, macrophages, and lymphocytes subsets involved were analyzed in the liver fibrosis model of S. japonicum infection or CCl₄ intraperitoneal injection. Additionally, the pathological progression, immune responses and the underlying injury mechanism in these two models were compared and characterized. The results showed that the changing trend of interleukin-13 (IL-13), transforming growth factor beta (TGF-β), inflammatory factors, and M1, M2 macrophages, were consistent with the development trend of fibrosis regardless of whether liver fibrosis was caused by S. japonicum or CCl₄. For lymphocyte subsets, the proportions of CD3⁺ T cells and CD4⁺ T cells decreased gradually, while proportion of CD8⁺ T cells peaked at 6 weeks in mice infected with S. japonicum and at 12 weeks in mice injected with CCl₄. With prolonged S. japonicum infection time, Th1 (CD4⁺IFN-γ⁺) immunity converted to Th2 (CD4⁺IL-4⁺)/Th17 (CD4⁺IL-17⁺) with weaker regulatory T cell (Treg) (CD4⁺CD25⁺FOXP3⁺) immunity. However, in liver fibrosis caused by CCl₄, Th1 cells occupied the dominant position, while proportions of Th2, Th17, and Treg cells decreased gradually. In conclusion, liver fibrosis was a complex pathological process that was regulated by a series of cytokines and immune cells. The pathological progressions and immune responses to S. japonicum or CCl₄ induced liver fibrosis were different, possibly because of their different injury mechanisms. The appropriate animal model should be selected according to the needs of different experiments and the pathogenic factors of liver fibrosis in the study.

Relevance of SIRT1-NF-κB Axis as Therapeutic Target to Ameliorate Inflammation in Liver Disease

Inflammation is an adaptive response in pursuit of homeostasis reestablishment triggered by harmful conditions or stimuli, such as an infection or tissue damage. Liver diseases cause approximately 2 million deaths per year worldwide and hepatic inflammation is a common factor to all of them, being the main driver of hepatic tissue damage and causing progression from non-alcoholic fatty liver disease (NAFLD) to non-alcoholic steatohepatitis (NASH), cirrhosis and, ultimately, hepatocellular carcinoma (HCC). The metabolic sensor SIRT1, a class III histone deacetylase with strong expression in metabolic tissues such as the liver, and transcription factor NF-κB, a master regulator of inflammatory response, show an antagonistic relationship in controlling inflammation. For this reason, SIRT1 targeting is emerging as a potential strategy to improve different metabolic and/or inflammatory pathologies. In this review, we explore diverse upstream regulators and some natural/synthetic activators of SIRT1 as possible therapeutic treatment for liver diseases.

Fucoxanthin inhibits hepatic oxidative stress, inflammation, and fibrosis in diet-induced nonalcoholic steatohepatitis model mice

Nonalcoholic steatohepatitis (NASH) is associated with hepatocyte injury, excessive oxidative stress, and chronic inflammation in fatty liver, and can progress to more severe liver diseases, such as cirrhosis and hepatocellular carcinoma. However, currently there are no effective therapies for NASH. Marine carotenoid, fucoxanthin (Fx), abundant in brown seaweeds, has variable biological properties, such as anti-cancer, anti-inflammatory, anti-oxidative and anti-obesity. However, the effect of Fx on the development of NASH has not been explored. We investigated the protective effects of Fx in diet-induced NASH model mice fed choline-deficient L-amino acid-defined high fat diet (CDAHFD). Fx administration significantly attenuated liver weight gain and hepatic fat accumulation, resulting in the alleviation of hepatic injury. Furthermore, the Fx-fed mice, not only exhibited reduced hepatic lipid oxidation, but also decreased mRNA expression levels of inflammation and infiltration-related genes compared to that of the CDAHFD-fed mice. Moreover, fucoxanthinol and amarouciaxanthin A, two Fx metabolites exerted anti-inflammatory effects in the liver via inhibiting the chemokine production in hepatocytes. In case of fibrosis, one of the features of advanced NASH, the expression of fibrogenic factors including activated-hepatic stellate cell marker was significantly decreased in the liver of Fx-fed mice. Thus, the present study elucidated that dietary Fx not only inhibited hepatic oxidative stress and inflammation but also prevented early phase of fibrosis in the diet-induced NASH model mice.

YAP1 is an independent prognostic marker in pancreatic cancer and associated with extracellular matrix remodeling

Background

Pancreatic cancer is a major cause of cancer-related mortality. The identification of effective biomarkers is essential in order to improve management of the disease. Yes-associated protein 1 (YAP1) is a downstream effector of the Hippo pathway, a signal transduction system implicated in tissue repair and regeneration, as well as tumorigenesis. Here we evaluate the biomarker potential of YAP1 in pancreatic cancer tissue.

Methods

YAP1 was selected as a possible biomarker for pancreatic cancer from global protein sequencing of fresh frozen pancreatic cancer tissue samples and normal pancreas controls. The prognostic utility of YAP1 was evaluated using mRNA expression data from 176 pancreatic cancer patients in The Cancer Genome Atlas (TCGA), as well as protein expression data from immunohistochemistry analysis of a local tissue microarray (TMA) cohort comprising 140 pancreatic cancer patients. Ingenuity Pathway Analysis was applied to outline the interaction network for YAP1 in connection to the pancreatic tumor microenvironment. The expression of YAP1 target gene products was evaluated after treatment of the pancreatic cancer cell line Panc-1 with three substances interrupting YAP–TEAD interaction, including Super-TDU, Verteporfin and CA3.

Results

Mass spectrometry based proteomics showed that YAP1 is the top upregulated protein in pancreatic cancer tissue when compared to normal controls (log2 fold change 6.4; p = 5E−06). Prognostic analysis of YAP1 demonstrated a significant correlation between mRNA expression level data and reduced overall survival (p = 0.001). In addition, TMA and immunohistochemistry analysis suggested that YAP1 protein expression is an independent predictor of poor overall survival [hazard ratio (HR) 1.870, 95% confidence interval (CI) 1.224–2.855, p = 0.004], as well as reduced disease-free survival (HR 1.950, 95% CI 1.299–2.927, p = 0.001). Bioinformatic analyses coupled with in vitro assays indicated that YAP1 is involved in the transcriptional control of target genes, associated with extracellular matrix remodeling, which could be modified by selected substances disrupting the YAP1-TEAD interaction.

Conclusions

Our findings indicate that YAP1 is an important prognostic biomarker for pancreatic cancer and may play a regulatory role in the remodeling of the extracellular matrix.

CD8+ T cells regulate liver injury in obesity-related nonalcoholic fatty liver disease

Nonalcoholic steatohepatitis (NASH) has increased in Western countries due to the prevalence of obesity. Current interests are aimed at identifying the type and function of immune cells that infiltrate the liver and key factors responsible for mediating their recruitment and activation in NASH. We investigated the function and phenotype of CD8⁺ T cells under obese and nonobese NASH conditions. We found an elevation in CD8 staining in livers from obese human subjects with NASH and cirrhosis that positively correlated with α-smooth muscle actin, a marker of hepatic stellate cell (HSC) activation. CD8⁺ T cells were elevated 3.5-fold in the livers of obese and hyperlipidemic NASH mice compared with obese hepatic steatosis mice. Isolated hepatic CD8⁺ T cells from these mice expressed a cytotoxic IL-10-expressing phenotype, and depletion of CD8⁺ T cells led to significant reductions in hepatic inflammation, HSC activation, and macrophage accumulation. Furthermore, hepatic CD8⁺ T cells from obese and hyperlipidemic NASH mice activated HSCs in vitro and in vivo. Interestingly, in the lean NASH mouse model, depletion and knockdown of CD8⁺ T cells did not impact liver inflammation or HSC activation. We demonstrated that under obese/hyperlipidemia conditions, CD8⁺ T cell are key regulators of the progression of NASH, while under nonobese conditions they play a minimal role in driving the disease. Thus, therapies targeting CD8⁺ T cells may be a novel approach for treatment of obesity-associated NASH.NEW & NOTEWORTHY Our study demonstrates that CD8⁺ T cells are the primary hepatic T cell population, are elevated in obese models of NASH, and directly activate hepatic stellate cells. In contrast, we find CD8⁺ T cells from lean NASH models do not regulate NASH-associated inflammation or stellate cell activation. Thus, for the first time to our knowledge, we demonstrate that hepatic CD8⁺ T cells are key players in obesity-associated NASH.

Immunotherapy in hepatocellular carcinoma: the complex interface between inflammation, fibrosis, and the immune response

Hepatocellular carcinoma (HCC) is the third leading cause of cancer deaths worldwide and confers a poor prognosis. Beyond standard systemic therapy with multikinase inhibitors, recent studies demonstrate the potential for robust and durable responses from immune checkpoint inhibition in subsets of HCC patients across disease etiologies. The majority of HCC arises in the context of chronic inflammation and from within a fibrotic liver, with many cases associated with hepatitis virus infections, toxins, and fatty liver disease. Many patients also have concomitant cirrhosis which is associated with both local and systemic immune deficiency. Furthermore, the liver is an immunologic organ in itself, which may enhance or suppress the immune response to cancer arising within it. Here, we explore the immunobiology of the liver from its native state to chronic inflammation, fibrosis, cirrhosis and then to cancer, and summarize how this unique microenvironment may affect the response to immunotherapy.

Sulforaphane inhibits the activation of hepatic stellate cell by miRNA-423-5p targeting suppressor of fused

Liver fibrosis, a common pathological process in chronic liver diseases, is characterized by excessive accumulation of extracellular matrix proteins and considered as a wound healing response to chronic liver injury. Hepatic stellate cell (HSC) activation plays a key role in liver fibrosis development. Previous studies showed that sulforaphane (SFN) has wide protective effects against tissue injury and inflammation. Accumulating evidence has shown that microRNAs play important roles in the development of hepatic fibrosis, some of which have been identified as potential therapeutic targets. This study was conducted to explore the role of SFN in the suppression of HSC activation. Quantitative real-time PCR showed that HSC miR-423-5p levels were up-regulated during HSC activation and down-regulated after SFN administration. Further, transfection of a miR-423-5p mimic demonstrated that inhibition of HSC activation by SFN required down-regulation of miR-423-5p. We showed that suppressor of fused is the direct target of miR-423-5p. SFN may play a role in inhibiting hepatic fibrosis by downregulating miRNA-423-5p. MiRNA-423-5p may be useful as a therapeutic target for treating hepatic fibrosis.

Health Benefits of Carotenoids: A Role of Carotenoids in the Prevention of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases with a prevalence of ~25% worldwide. NAFLD includes simple hepatic steatosis, non-alcoholic steatohepatitis, fibrosis, and cirrhosis, which can further progress to hepatocellular carcinoma. Therefore, effective strategies for the prevention of NAFLD are needed. The pathogenesis of NAFLD is complicated due to diverse injury insults, such as fat accumulation, oxidative stress, inflammation, lipotoxicity, and apoptosis, which may act synergistically. Studies have shown that carotenoids, a natural group of isoprenoid pigments, prevent the development of NAFLD by exerting antioxidant, lipid-lowering, anti-inflammatory, anti-fibrotic, and insulin-sensitizing properties. This review summarizes the protective action of carotenoids, with primary focuses on astaxanthin, lycopene, β-carotene, β-cryptoxanthin, lutein, fucoxanthin, and crocetin, against the development and progression of NAFLD.

A novel STAT3 inhibitor, STX-0119, attenuates liver fibrosis by inactivating hepatic stellate cells in mice

Liver fibrosis is characterized by formation of scar tissue in the liver. The role of STAT3 signaling has been implicated on activating hepatic stellate cells (HSC) to myofibroblast-like cells in liver fibrosis. Major factors that activate STAT3 signaling are TGF-β1 and IL-6, which are upregulated in the liver in patients afflicted with liver fibrosis. Recent reports indicate that not only IL-6, but also the non-canonical signaling pathway of TGF-β1 is associated with STAT3 signaling. In this study, we demonstrate a new function of the STAT3 inhibitor, STX-0119, in liver fibrosis. STX-0119 is an inhibitor of STAT3 dimerization, which is required for nuclear localization of STAT3. We first investigated the anti-fibrotic effect of STX-0119 in in vitro experiments. Exposure to STX-0119 inhibited the nuclear localization of STAT3 in HSCs, resulting in decreased expression of its target genes, such as col1a1 and αSMA. In addition, STX-0119 also inhibited the TGF-β1/IL-6-induced activation of HSCs. Next, we examined the in vivo effect of STX-0119 in the liver fibrosis mouse model using thioacetamide (TAA) and carbon tetrachloride (CCl₄). STX-0119 attenuated the TAA-induced liver fibrosis by inhibiting activation of HSCs to myofibroblast-like cells. Consistent with the in vivo results using TAA-induced liver fibrosis model, treatment of STX-0119 similarly attenuated CCl₄-induced liver fibrosis. In conclusion, we believe that STX-0119 inhibits the development of liver fibrosis by blocking the activation of hepatic stellate cells. These results indicate that STX-0119 is a potential new therapeutic strategy to prevent disease progression to cirrhosis.

NLR Family Pyrin Domain-Containing 3 Inflammasome Activation in Hepatic Stellate Cells Induces Liver Fibrosis in Mice

The NLR family pyrin domain-containing 3 (NLRP3) inflammasome plays an important role in liver fibrosis (LF) development. However, the mechanisms involved in NLRP3-induced fibrosis are unclear. Our aim was to test the hypothesis that the NLRP3 inflammasome in hepatic stellate cells (HSCs) can directly regulate their activation and contribute to LF. Primary HSCs isolated from wild-type (WT), Nlrp3^-/- , or Nlrp3^L351PneoR knock-in crossed to inducible (estrogen receptor Cre-CreT) mice were incubated with lipopolysaccharide (LPS) and adenosine triphosphate (ATP), or 4OH-tamoxifen, respectively. HSC-specific Nlrp3^L351P knock-in mice were generated by crossing transgenic mice expressing lecithin retinol acyltransferase (Lrat)-driven Cre and maintained on standard rodent chow for 6 months. Mice were then sacrificed; liver tissue and serum were harvested. Nlrp3 inflammasome activation along with HSC phenotype and fibrosis were assessed by RT-PCR, western blotting, fluorescence-activated cell sorting (FACS), enzyme-linked immunosorbent assay, immunofluorescence (IF), and immunohistochemistry (IHC). Stimulated WT HSCs displayed increased levels of NLRP3 inflammasome-induced reactive oxygen species (ROS) production and cathepsin B activity, accompanied by an up-regulation of mRNA and protein levels of fibrotic makers, an effect abrogated in Nlrp3^-/- HSCs. Nlrp3^L351P CreT HSCs also showed elevated mRNA and protein expression of fibrotic markers 24 hours after inflammasome activation induced with 4-hydroxytamoxifen (4OHT). Protein and mRNA expression levels of fibrotic markers were also found to be increased in isolated HSCs and whole liver tissue from Nlrp3^L351P Lrat Cre mice compared to WT. Liver sections from 24-week-old Nlrp^L351P Lrat Cre mice showed fibrotic changes with increased alpha smooth muscle actin (αSMA) and desmin-positive cells and collagen deposition, independent of inflammatory infiltrates; these changes were also observed after LPS challenge in 8-week-old Nlrp^L351P Lrat Cre mice. Conclusion: Our results highlight a direct role for the NLRP3 inflammasome in the activation of HSCs directly triggering LF.

Alpha Mangostin Inhibits the Proliferation and Activation of Acetaldehyde Induced Hepatic Stellate Cells through TGF-β and ERK 1/2 Pathways

Liver fibrosis is characterized by excessive accumulation of extracellular matrix in chronic liver injury. Alcohol-induced fibrosis may develop into cirrhosis, one of the major causes of liver disease mortality. Previous studies have shown that alpha mangostin can decrease ratio of pSmad/Smad and pAkt/Akt in TGF-β-induced liver fibrosis model in vitro. Further investigation of the mechanism of action of alpha mangostin in liver fibrosis model still needs to be done. The present study aimed to analyze the mechanism of action of alpha mangostin on acetaldehyde induced liver fibrosis model on TGF-β and ERK 1/2 pathways. Immortalized HSCs, LX-2 cells, were incubated with acetaldehyde, acetaldehyde with alpha mangostin (10 and 20 μM), or alpha mangostin only (10 μM). Sorafenib 10 μM was used as positive control. LX-2 viability was counted using trypan blue exclusion method. The effect of alpha mangostin on hepatic stellate cells proliferation and activation markers and its possible mechanism of action via TGF-β and ERK1/2 were studied. Acetaldehyde was shown to increase proliferation and expression of profibrogenic and migration markers on HSC, while alpha mangostin treatment resulted in a reduced proliferation and migration of HSC and decreased Ki-67 and pERK 1/2 expressions. These findings were followed with decreased expressions and concentrations of TGF-β; decreased expression of Col1A1, TIMP1, and TIMP3; increased expression of MnSOD and GPx; and reduction in intracellular reactive oxygen species. These effects were shown to be dose dependent. Therefore, we conclude that alpha mangostin inhibits hepatic stellate cells proliferation and activation through TGF-β and ERK 1/2 pathways.

Hepatic stellate cells retain retinoid-laden lipid droplets after cellular transdifferentiation into activated myofibroblasts

Loss of retinyl ester (RE)-rich lipid droplets (LDs) from hepatic stellate cells (HSCs) is cited as a key event in their cellular transdifferentiation to activated, pro-fibrotic myofibroblasts; however, it remains unclear if changes in LD morphology or RE content are causal for transdifferentiation. To better understand LD dynamics in vitro within a common model of HSC activation, we used novel approaches preserving LD morphology and allowing for quantitation of RE. The size and quantity of LDs within in vitro and in vivo bile duct ligation (BDL)-activated HSCs were quantitated using adipocyte differentiation-related protein (ADRP) labeling and oil red o (ORO) staining (gold standard), and RE content was determined using fluorescence microscopy. We found during HSC activation in vitro that LD number differed significantly when measured by ADRP and ORO, respectively ( day 1: 56 vs. 5, P = 0.03; day 4: 101 vs. 39, P = 0.03; day 14: 241 vs. 12, P = 0.02). Ex vivo HSCs activated in vivo contained the same number of LDs as day 4 in vitro activated HSCs (118 vs. 101, P = 0.54). Decline in LD RE occurred beyond day 4 in vitro and day 1 ex vivo , after HSC transdifferentiation was underway. Lastly, in situ HSCs examined using electron microscopy show LDs tend to be smaller but are ultimately retained in BDL injured livers. Therefore, we conclude that during HSC transdifferentiation, LDs are not lost but are retained, decreasing in size. Additionally, RE content declines after transdifferentiation is underway. These data suggest that these LD changes are not causal for HSC transdifferentiation. NEW & NOTEWORTHY Loss of retinoid-laden lipid droplets from hepatic stellate cells has long been held as a hallmark of their transdifferentiation into activated myofibroblasts, the dominant cells that drive hepatic fibrosis. This study demonstrates that stellate cells activated in culture and after liver injury in vivo retain their lipid droplets and that these droplets become smaller and more numerous, with decreases in droplet retinoid concentration occurring only after cellular transdifferentiation is underway.

Carcinogenesis on the background of liver fibrosis: Implications for the management of hepatocellular cancer

Hepatocellular carcinoma (HCC) is now the second leading cause of cancer-related deaths globally and many patients have incurable disease. HCC predominantly occurs in the setting of liver cirrhosis and is a paradigm for inflammation-induced cancer. The causes of chronic liver disease promote the development of transformed or premalignant hepatocytes and predisposes to the development of HCC. For HCC to grow and progress it is now clear that it requires an immunosuppressive niche within the fibrogenic microenvironment of cirrhosis. The rationale for targeting this immunosuppression is supported by responses seen in recent trials with checkpoint inhibitors. With the impact of immunotherapy, HCC progression may be delayed and long term durable responses may be seen. This makes the management of the underlying liver cirrhosis in HCC even more crucial as studies demonstrate that measures of liver function are a major prognostic factor in HCC. In this review, we discuss the development of cancer in the setting of liver inflammation and fibrosis, reviewing the microenvironment that leads to this tumourigenic climate and the implications this has for patient management.

Role of hepatic stellate cell (HSC)-derived cytokines in hepatic inflammation and immunity

In their quiescent state, Hepatic stellate cells (HSCs), are present in the sub-endothelial space of Disse and have minimal interaction with immune cells. However, upon activation following injury, HSCs directly or indirectly interact with various immune cells that enter the space of Disse and thereby regulate diverse hepatic function and immune physiology. Other than the normal physiological functions of HSCs such as hepatic homeostasis, maturation and differentiation, they also participate in hepatic inflammation by releasing a battery of inflammatory cytokines and chemokines and interacting with other liver cells. Here, we have reviewed the role of HSC in the pathogenesis of liver inflammation and some infectious diseases in order to understand how the interplay between immune cells and HSCs regulates the overall outcome and disease pathology.

Role of cAMP and phosphodiesterase signaling in liver health and disease

Liver disease is a significant health problem worldwide with mortality reaching around 2 million deaths a year. Non-alcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD) are the major causes of chronic liver disease. Pathologically, NAFLD and ALD share similar patterns of hepatic disorders ranging from simple steatosis to steatohepatitis, fibrosis and cirrhosis. It is becoming increasingly important to identify new pharmacological targets, given that there is no FDA-approved therapy yet for either NAFLD or ALD. Since the evolution of liver diseases is a multifactorial process, several mechanisms involving parenchymal and non-parenchymal hepatic cells contribute to the initiation and progression of liver pathologies. Moreover, certain protective molecular pathways become repressed during liver injury including signaling pathways such as the cyclic adenosine monophosphate (cAMP) pathway. cAMP, a key second messenger molecule, regulates various cellular functions including lipid metabolism, inflammation, cell differentiation and injury by affecting gene/protein expression and function. This review addresses the current understanding of the role of cAMP metabolism and consequent cAMP signaling pathway(s) in the context of liver health and disease. The cAMP pathway is extremely sophisticated and complex with specific cellular functions dictated by numerous factors such abundance, localization and degradation by phosphodiesterases (PDEs). Furthermore, because of the distinct yet divergent roles of both of its effector molecules, the cAMP pathway is extensively targeted in liver injury to modify its role from physiological to therapeutic, depending on the hepatic condition. This review also examines the behavior of the cAMP-dependent pathway in NAFLD, ALD and in other liver diseases and focuses on PDE inhibition as an excellent therapeutic target in these conditions.

Chronic Hyperglycaemia Induced Alterations of Hepatic Stellate Cells Differ from the Effect of TGFB1, and Point toward Metabolic Stress

The deleterious effect of hyperglycemia on the biology of the liver is supported by clinical evidence. It can promote the development of fatty liver, liver fibrosis, even liver cancer as complication of diabetes mellitus. As liver fibrosis is the consequence of hepatic stellate cell (HSC) activation, the questions were addressed whether alterations induced by high glucose concentration are directly related to TGFB1 effect, or other mechanisms are activated. In order to obtain information on the response of HSC for high glucose, LX-2 cells (an immortalized human HSC cell lineage) were cultured in 15.3 mM glucose containing medium for 21 days. The effect of glucose was compared to that of TGFB1. Our data revealed that chronic exposure of high glucose concentration initiated profound alteration of LX-2 cells and the effect is different from those observed upon interaction with TGFB1. Whereas TGFB1 induced the production of extracellular matrix proteins, high glucose exposure resulted in decreased MMP2 activity, retardation of type I collagen in the endoplasmic reticulum, with decreased pS6 expression, pointing to development of endoplasmic stress and sequestration of p21^CIP1/WAF1 in the cytoplasm which can promote the proliferation of LX2 cells.

Antifibrotic effects of gallic acid on hepatic stellate cells: In vitro and in vivo mechanistic study

Few studies reported the antifibrotic effects of gallic acid (GA) despite its known hepatoprotective and antioxidant activities. Accordingly, this study investigated the antifibrotic effects of GA through clarifying its mechanisms on hepatic stellate cells' (HSCs) activation, proliferation and/or apoptosis. In vitro effects of GA on HSC-T6 activation/proliferation, morphology and safety on hepatocytes were assessed. In vivo, hepatic fibrosis was induced via chronic thioacetamide (TAA)-intoxication. TAA-intoxicated rats were treated with silyamrin or GA. At end of experiment, liver functions, hepatic MDA, GSH, PDGF-BB, TGF-β1, TIMP-1 and hydroxyproline were determined. Histological analysis and Sirius red staining of hepatic sections, expressions of alpha-smooth muscle actin (α-SMA), proliferating cellular nuclear antigen (PCNA) and caspase-3 were examined. In vitro, GA resulted in a concentration and time-dependent inhibition in HSCs activation, proliferation (IC₅₀= 45 and 19 μg/mL at 24 and 48 h respectively); restored the quiescent morphology of some activated HSCs plus its safety on hepatocytes. In vivo, GA reduced ALT, AST, MDA, PDGF-BB levels, collagen deposition and fibrosis score (S1 vs S4); increased caspase-3 expression and restored GSH stores, TGF-β1 level, α-SMA and PCNA expressions. In conclusion, GA counteracted the progression of hepatic fibrosis through reduction of HSCs proliferation/activation mutually with their apoptosis induction.

Platelet-derived growth factor receptor α in hepatocellular carcinoma is a prognostic marker independent of underlying liver cirrhosis

Background and Aims

Platelet-derived growth factor receptor alpha (PDGFRα) is suggested as a prognosis marker for hepatocellular carcinoma (HCC). Since PDGFRα is also known as a marker for activated hepatic stellate cells (HSCs), this study aimed to investigate whether PDGFRα expression in HCC was dependent on the background liver fibrous condition.

Results

Strong PDGFRα expression in the tumor lesions was associated with decreased survival after curative HCC resection. Expression of PDGFRα in the tumor correlated with increased collagen α1(I), lecithin retinol acyltransferase, and smooth muscle α-actin suggesting increased HSCs in tumor sites. The expression of PDGFRα in the tumor sites was associated neither with underlying liver fibrosis/cirrhosis nor with the expression of PDGFRα in adjacent non-tumor sites of the liver.

Materials and Methods

Patients with HCC who underwent liver resection as curative treatment were included in this study. Using liver samples of 95 patients, tissue microarray was constructed and immunohistochemical study of PDGFRα was conducted in both tumor and non-tumor sites. PDGFRα expression in tumor and matching non-tumor sites was compared. Freshly frozen liver tissue specimens of 16 HCC patients were used for gene expression analysis of PDGFRα and fibrosis related genes.

Conclusions

Our results suggest that PDGFRα overexpression in HCC is a prognostic marker independent of adjacent non-tumor site liver fibrosis status.

Caffeine Suppresses the Activation of Hepatic Stellate Cells cAMP-Independently by Antagonizing Adenosine Receptors

During liver injury, hepatic stellate cells (HSCs) are activated by various cytokines and transdifferentiated into myofibroblast-like activated HSCs, which produce collagen, a major source of liver fibrosis. Therefore, the suppression of HSC activation is regarded as a therapeutic target for liver fibrosis. Several epidemiological reports have revealed that caffeine intake decreases the risk of liver disease. In this study, therefore, we investigated the effect of caffeine on the activation of primary HSCs isolated from mice. Caffeine suppressed the activation of HSC in a concentration-dependent manner. BAPTA-AM, an intracellular Ca²⁺ chelator, had no effect on the caffeine-induced suppression of HSC activation. None of the isoform-selective inhibitors of phosphodiesterase1 to 5 affected changes in the morphology of HSC during activation, whereas CGS-15943, an adenosine receptor antagonist, inhibited them. Caffeine had no effect on intracellular cAMP level or on the phosphorylation of extracellular signal-regulated kinase (ERK)1/2. In contrast, caffeine significantly decreased the phosphorylation of Akt1. These results suggest that caffeine inhibits HSC activation by antagonizing adenosine receptors, leading to Akt1 signaling activation.

Current Perspectives Regarding Stem Cell-Based Therapy for Liver Cirrhosis

Liver cirrhosis is a major cause of mortality and a common end of various progressive liver diseases. Since the effective treatment is currently limited to liver transplantation, stem cell-based therapy as an alternative has attracted interest due to promising results from preclinical and clinical studies. However, there is still much to be understood regarding the precise mechanisms of action. A number of stem cells from different origins have been employed for hepatic regeneration with different degrees of success. The present review presents a synopsis of stem cell research for the treatment of patients with liver cirrhosis according to the stem cell type. Clinical trials to date are summarized briefly. Finally, issues to be resolved and future perspectives are discussed with regard to clinical applications.

β-Actin-dependent global chromatin organization and gene expression programs control cellular identity

During differentiation and development, cell fate and identity are established by waves of genetic reprogramming. Although the mechanisms are largely unknown, during these events, dynamic chromatin reorganization is likely to ensure that multiple genes involved in the same cellular functions are coregulated, depending on the nuclear environment. In this study, using high-content screening of embryonic fibroblasts from a β-actin knockout (KO) mouse, we found major chromatin rearrangements and changes in histone modifications, such as methylated histone (H)3-lysine-(K)9. Genome-wide H3K9 trimethylation-(Me)3 landscape changes correlate with gene up- and down-regulation in β-actin KO cells. Mechanistically, we found loss of chromatin association by the Brahma-related gene ( Brg)/Brahma-associated factor (BAF) chromatin remodeling complex subunit Brg1 in the absence of β-actin. This actin-dependent chromatin reorganization was concomitant with the up-regulation of sets of genes involved in angiogenesis, cytoskeletal organization, and myofibroblast features in β-actin KO cells. Some of these genes and phenotypes were gained in a β-actin dose-dependent manner. Moreover, reintroducing a nuclear localization signal-containing β-actin in the knockout cells affected nuclear features and gene expression. Our results suggest that, by affecting the genome-wide organization of heterochromatin through the chromatin-binding activity of the BAF complex, β-actin plays an essential role in the determination of gene expression programs and cellular identity.-Xie, X., Almuzzaini, B., Drou, N., Kremb, S., Yousif, A., Östlund Farrants, A.-K., Gunsalus, K., Percipalle, P. β-Actin-dependent global chromatin organization and gene expression programs control cellular identity.

The Role of Signal Transducer and Activator of Transcription 5 and Transforming Growth Factor-β1 in Hepatic Fibrosis Induced by Chronic Hepatitis C Virus Infection in Egyptian Patients

OBJECTIVE

To investigate the possible role of signal transducer and activator of transcription 5 (STAT5) in the pathogenesis of liver fibrosis in Egyptian patients with chronic hepatitis C (CHC) virus infection and its relation to hepatic stellate cells (HSC).

SUBJECTS AND METHODS

Sixty-five patients (46 males and 19 females) were divided into 4 groups based on the severity of fibrosis as detected by Fibroscan as follows: F1, n = 15; F2, n = 21; F3, n = 13; and F4, n = 16. Twenty age- and gender-matched healthy persons volunteered as controls. The serum levels of STAT5, TGF-β1, α-smooth muscle actin (α-SMA), fasting blood sugar, and fasting insulin, as well as homeostasis model assessment of insulin resistance (HOMA-IR), were determined and compared for all groups. The usefulness of the studied serum biomarkers for predicting liver fibrosis was evaluated using a receiver operating characteristic curve.

RESULTS

Serum levels of STAT5 were significantly lower in patients compared to controls (9.69 ± 5.62 vs. 14.73 ± 6.52, p ≤ 0.001); on the contrary, TGF-β1, α-SMA, and HOMA-IR were significantly higher in patients compared to controls (mean: 1,796.04 vs. 1,636.94; 14.94 vs. 8.1; and 7.91 vs. 4.18; p ≤ 0.01 and 0.001, respectively). TGF-β1 and α-SMA showed a progressive increase with advancing severity of hepatic fibrosis (mean TGF-β1: 2,058.4 in F1-F2 and 1,583.8 in F3-F4, p ≤ 0.04; mean α-SMA: 13.59 in F1-F2 and 16.62 in F3-F4, p ≤ 0.05). STAT5 had a significant negative correlation with TGF-β1 (p ≤ 0.001), while no correlation was detected with α-SMA (p ≤ 0.8).

CONCLUSIONS

STAT5 may play a significant role in hepatic fibrogenesis through the induction of TGF-β1 but not through the activation of hepatic stellate cells.

Environmental peer pressure: CD4+ T cell help in tolerance and transplantation

The liver participates in a multitude of metabolic functions that are critical for sustaining human life. Despite constant encounters with antigenic-rich intestinal blood, oxidative stress, and metabolic intermediates, there is no appreciable immune response. Interestingly, patients undergoing orthotopic liver transplantation benefit from a high rate of graft acceptance in comparison to other solid organ transplant recipients. In fact, cotransplantation of a donor liver in tandem with a rejection-prone graft increases the likelihood of graft acceptance. A variety of players may account for this phenomenon including the interaction of intrahepatic antigen-presenting cells with CD4⁺ T cells and the preferential induction of forkhead box P3 (Foxp3) expression on CD4⁺ T cells following injurious stimuli. Ineffective insult management can cause chronic liver disease, which manifests systemically as the following: antibody-mediated disorders, ineffective antiviral and antibacterial immunity, and gastrointestinal disorders. These sequelae sharing the requirement of CD4⁺ T cell help to coordinate aberrant immune responses. In this review, we will focus on CD4⁺ T cell help due to the shared requirements in hepatic tolerance and coordination of extrahepatic immune responses. Overall, intrahepatic deviations from steady state can have deleterious systemic immune outcomes and highlight the liver's remarkable capacity to maintain a balance between tolerance and inflammatory response while simultaneously being inundated with a panoply of antigenic stimuli. Liver Transplantation 24 89-97 2018 AASLD.

CCN1/Cyr61 enhances the function of hepatic stellate cells in promoting the progression of hepatocellular carcinoma

Hepatic stellate cells (HSCs) are the main extracellular matrix (ECM)-producing cells in liver fibrosis. Activated HSCs stimulate the proliferation and migration of hepatocellular carcinoma (HCC) cells. Cysteine-rich 61 (CCN1/Cyr61) is an ECM protein. Our previous studies demonstrated that the expression of CCN1 was significantly higher in benign hepatic cirrhosis tissue and cancer-adjacent hepatic cirrhosis tissues. CCN1 is a target gene of β-catenin in HCC and promotes the proliferation of HCC cells. The present study aimed to examine whether CCN1 can activate HSCs and affect the function of activated HSCs in promoting the progression of HCC. CCN1 expression was determined during the progression of liver fibrosis in a mouse model. LX-2 cells, which were infected with adenoviruses AdCCN1 or AdRFP, and HepG2 cells were co-cultured or subcutaneously co-implanted into in nude mice. MTT assay, Crystal Violet staining, Boyden chamber, matrigel invasion and monolayer scratch assays were used to analyze the proliferation, migration and invasion capability of HepG2 cells. Xenograft sizes were measured and histological analyses were performed by hematoxylin and eosin, immunohistochemical, immunefluorescence and Sirius Red staining. It was demonstrated that the expression of CCN1 was continually increased in liver fibrosis and the that expression may be correlated with the progression of liver fibrosis. CCN1 affected the function of LX-2 and enhanced the effect of LX-2 on promoting the viability, migration and invasion of HepG2 cells in vitro. CCN1 enhanced the effect of LX-2 on promoting the growth of HepG2 xenografts in vivo. CCN1 also affected the function of activated HSCs and regulated the formation of the xenograft microenvironment, including fibrogenesis and angiogenesis, which are beneficial for the progression of HCC. These findings demonstrated that CCN1 may be involved in the progression of the hepatic cirrhosis-HCC axis through regulating HSCs.

Estrogen receptor‑β‑dependent effects of saikosaponin‑d on the suppression of oxidative stress‑induced rat hepatic stellate cell activation

Saikosaponin-d (SSd) is one of the major triterpenoid saponins derived from Bupleurum falcatum L., which has been reported to possess antifibrotic activity. At present, there is little information regarding the potential target of SSd in hepatic stellate cells (HSCs), which serve an important role in excessive extracellular matrix (ECM) deposition during the pathogenesis of hepatic fibrosis. Our recent study indicated that SSd may be considered a novel type of phytoestrogen with estrogen-like actions. Therefore, the present study aimed to investigate the effects of SSd on the proliferation and activation of HSCs, and the underlying mechanisms associated with estrogen receptors. In the present study, a rat HSC line (HSC-T6) was used and cultured with dimethyl sulfoxide, SSd, or estradiol (E₂; positive control), in the presence or absence of three estrogen receptor (ER) antagonists [ICI-182780, methylpiperidinopyrazole (MPP) or (R,R)-tetrahydrochrysene (THC)], for 24 h as pretreatment. Oxidative stress was induced by exposure to hydrogen peroxide for 4 h. Cell proliferation was assessed by MTT growth assay. Malondialdehyde (MDA), CuZn-superoxide dismutase (CuZn-SOD), tissue inhibitor of metalloproteinases-1 (TIMP- 1), matrix metalloproteinase-1 (MMP-1), transforming growth factor-β1 (TGF-β1), hydroxyproline (Hyp) and collagen-1 (COL1) levels in cell culture supernatants were determined by ELISA. Reactive oxygen species (ROS) was detected by flow cytometry. Total and phosphorylated mitogen-activated protein kinases (MAPKs) and α-smooth muscle actin (α-SMA) were examined by western blot analysis. TGF-β1 mRNA expression was determined by RT-quantitative (q)PCR. SSd and E₂ were able to significantly suppress oxidative stress-induced proliferation and activation of HSC-T6 cells. Furthermore, SSd and E₂ were able to reduce ECM deposition, as demonstrated by the decrease in transforming growth factor-β1, hydroxyproline, collagen-1 and tissue inhibitor of metalloproteinases-1, and by the increase in matrix metalloproteinase-1. These results suggested that the possible molecular mechanism could involve downregulation of the reactive oxygen species/mitogen-activated protein kinases signaling pathway. Finally, the effects of SSd and E₂ could be blocked by co-incubation with ICI-182780 or THC, but not MPP, thus indicating that ERβ may be the potential target of SSd in HSC-T6 cells. In conclusion, these findings suggested that SSd may suppress oxidative stress-induced activation of HSCs, which relied on modulation of ERβ.

Therapeutic effects of hepatocyte growth factor-overexpressing dental pulp stem cells on liver cirrhosis in a rat model

Cirrhosis is the terminal stage of hepatic diseases and is prone to develop into hepatocyte carcinoma. Increasing evidence suggests that the transplantation of dental pulp stem cells (DPSCs) may promote recovery from cirrhosis, but the key regulatory mechanisms involved remain to be determined. In this study, we overexpressed human hepatocyte growth factor (hHGF) in primary rat DPSCs and evaluated the effects of HGF overexpression on the biological behaviors and therapeutic efficacy of grafted DPSCs in cirrhosis. Liver cirrhosis was induced via the intraperitoneal injection of CCl₄ twice weekly for 12 weeks and was verified through histopathological and serological assays. HGF was overexpressed in DPSCs via transduction with a hHGF-lentiviral vector and confirmed based on the elevated expression and secretion of HGF. The HGF-overexpressing DPSCs were transplanted into rats intravenously. The HGF-overexpressing DPSCs showed increased survival and hepatogenic differentiation in host liver tissue at 6 weeks after grafting. They also exhibited a significantly greater repair potential in relation to cirrhosis pathology and impaired liver function than did DPSCs expressing HGF at physiological levels. Our study may provide an experimental basis for the development of novel methods for the treatment of liver cirrhosis in clinical practice.