Modulation of hepatic fibrosis by c-Jun-N-terminal kinase inhibition

Inhibitory Effect of a Human MicroRNA, miR-6133-5p, on the Fibrotic Activity of Hepatic Stellate Cells in Culture

BACKGROUND

We recently identified 39 human microRNAs, which effectively suppress hepatitis B virus (HBV) replication in hepatocytes. Chronic HBV infection often results in active, hepatitis-related liver fibrosis; hence, we assessed whether any of these microRNAs have anti-fibrotic potential and predicted that miR-6133-5p may target several fibrosis-related genes.

METHODS

The hepatic stellate cell line LX-2 was transfected with an miR-6133-5p mimic and subsequently treated with Transforming growth factor (TGF)-β. The mRNA and protein products of the COL1A1 gene, encoding collagen, and the ACTA2 gene, an activation marker of hepatic stellate cells, were quantified.

RESULTS

The expression of COL1A1 and ACTA2 was markedly reduced in LX-2 cells treated with miR-6133-5p. Interestingly, phosphorylation of c-Jun N-terminal kinase (JNK) was also significantly decreased by miR-6133-5p treatment. The expression of several predicted target genes of miR-6133-5p, including TGFBR2 (which encodes Transforming Growth Factor Beta Receptor 2) and FGFR1 (which encodes Fibroblast Growth Factor Receptor 1), was also reduced in miR-6133-5p-treated cells. The knockdown of TGFBR2 by the corresponding small interfering RNA greatly suppressed the expression of COL1A1 and ACTA2. Treatment with the JNK inhibitor, SP600125, also suppressed COL1A1 and ACTA2 expression, indicating that TGFBR2 and JNK mediate the anti-fibrotic effect of miR-6133-5p. The downregulation of FGFR1 may result in a decrease of phosphorylated Akt, ERK (extracellular signal-regulated kinase), and JNK.

CONCLUSION

miR-6133-5p has a strong anti-fibrotic effect, mediated by inactivation of TGFBR2, Akt, and JNK.

Pulmonary fibrosis and COVID-19: the potential role for antifibrotic therapy

In December, 2019, reports emerged from Wuhan, China, of a severe acute respiratory disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). By the end of April, 2020, over 3 million people had been confirmed infected, with over 1 million in the USA alone, and over 215 000 deaths. The symptoms associated with COVID-19 are diverse, ranging from mild upper respiratory tract symptoms to severe acute respiratory distress syndrome. The major risk factors for severe COVID-19 are shared with idiopathic pulmonary fibrosis (IPF), namely increasing age, male sex, and comorbidities such as hypertension and diabetes. However, the role of antifibrotic therapy in patients with IPF who contract SARS-CoV-2 infection, and the scientific rationale for their continuation or cessation, is poorly defined. Furthermore, several licensed and potential antifibrotic compounds have been assessed in models of acute lung injury and viral pneumonia. Data from previous coronavirus infections such as severe acute respiratory syndrome and Middle East respiratory syndrome, as well as emerging data from the COVID-19 pandemic, suggest there could be substantial fibrotic consequences following SARS-CoV-2 infection. Antifibrotic therapies that are available or in development could have value in preventing severe COVID-19 in patients with IPF, have the potential to treat severe COVID-19 in patients without IPF, and might have a role in preventing fibrosis after SARS-CoV-2 infection.

Liver fibrogenesis: un update on established and emerging basic concepts

Liver fibrogenesis is defined as a dynamic and highly integrated process occurring during chronic injury to liver parenchyma that can result in excess deposition of extracellular matrix (ECM) components (i.e., liver fibrosis). Liver fibrogenesis, together with chronic inflammatory response, is then primarily involved in the progression of chronic liver diseases (CLD) irrespective of the specific etiology. In the present review we will first offer a synthetic and updated overview of major basic concepts in relation to the role of myofibroblasts (MFs), macrophages and other hepatic cell populations involved in CLD to then offer an overview of established and emerging issues and mechanisms that have been proposed to favor and/or promote CLD progression. A special focus will be dedicated to selected issues that include emerging features in the field of cholangiopathies, the emerging role of genetic and epigenetic factors as well as of hypoxia, hypoxia-inducible factors (HIFs) and related mediators.

Possible Pathways of Hepatotoxicity Caused by Chemical Agents

BACKGROUND

Liver injury induced by drugs has become a primary reason for acute liver disease and therefore posed a potential regulatory and clinical challenge over the past few decades and has gained much attention. It also remains the most common cause of failure of drugs during clinical trials. In 50% of all acute liver failure cases, drug-induced hepatoxicity is the primary factor and 5% of all hospital admissions.

METHODS

The various hepatotoxins used to induce hepatotoxicity in experimental animals include paracetamol, CCl4, isoniazid, thioacetamide, erythromycin, diclofenac, alcohol, etc. Among the various models used to induce hepatotoxicity in rats, every hepatotoxin causes toxicity by different mechanisms.

RESULTS

The drug-induced hepatotoxicity caused by paracetamol accounts for 39% of the cases and 13% hepatotoxicity is triggered by other hepatotoxic inducing agents.

CONCLUSION

Research carried out and the published papers revealed that hepatotoxins such as paracetamol and carbon- tetrachloride are widely used for experimental induction of hepatotoxicity in rats.

Liver, Tumor and Viral Hepatitis: Key Players in the Complex Balance Between Tolerance and Immune Activation

Liver cancer is the third most common cause of cancer related death in the World. From an epidemiological point of view the risk factors associated to primary liver cancer are mainly viral hepatitis infection and alcohol consumption. Even though there is a clear correlation between liver inflammation, cirrhosis and cancer, other emerging liver diseases (like fatty liver) could also lead to liver cancer. Moreover, the liver is the major site of metastasis from colon, breast, ovarian and other cancers. In this review we will address the peculiar status of the liver as organ that has to balance between tolerance and immune activation. We will focus on macrophages and other key cellular components of the liver microenvironment that play a central role during tumor progression. We will also discuss how current and future therapies may affect the balance toward immune activation.

CDKN2a/p16 Antagonizes Hepatic Stellate Cell Activation and Liver Fibrosis by Modulating ROS Levels

The lipid-storage hepatic stellate cells (HSC) play as pivotal role in liver fibrosis being able to trans-differentiate into myofibroblasts in response to various pro-fibrogenic stimuli. In the present study we investigated the role of CDKN2a/p16, a negative regulator of cell cycling, in HSC activation and the underlying mechanism. Levels of p16 were significantly down-regulated in activated HSCs isolated from mice induced to develop liver fibrosis compared to quiescent HSCs isolated from the control mice ex vivo. There was a similar decrease in p16 expression in cultured HSCs undergoing spontaneous activation or exposed to TGF-β treatment in vitro. More important, p16 down-regulation was observed to correlate with cirrhosis in humans. In a classic model of carbon tetrachloride (CCl₄) induced liver fibrosis, fibrogenesis was far more extensive in mice with p16 deficiency (KO) than the wild type (WT) littermates. Depletion of p16 in cultured HSCs promoted the synthesis of extracellular matrix (ECM) proteins. Mechanistically, p16 deficiency accelerated reactive oxygen species (ROS) generation in HSCs likely through the p38 MAPK signaling. P38 inhibition or ROS cleansing attenuated ECM production in p16 deficient HSCs. Taken together, our data unveil a previously unappreciated role for p16 in the regulation of HSC activation. Screening for small-molecule compounds that can boost p16 activity may yield novel therapeutic strategies against liver fibrosis.

ASK1 inhibition reduces cell death and hepatic fibrosis in an Nlrp3 mutant liver injury model

Hepatic inflammasome activation is considered a major contributor to liver fibrosis in NASH. Apoptosis signal-regulating kinase 1 (ASK1) is an apical mitogen-activated protein kinase that activates hepatic JNK and p38 to promote apoptosis, inflammation, and fibrosis. The aim of the current study was to investigate whether pharmacologic inhibition of ASK1 could attenuate hepatic fibrosis driven by inflammasome activation using gain-of-function NOD-like receptor protein 3 (Nlrp3) mutant mice. Tamoxifen-inducible Nlrp3 knock-in (Nlrp3A350V/+CreT-KI) mice and WT mice were administered either control chow diet or diet containing the selective ASK1 inhibitor GS-444217 for 6 weeks. Livers of Nlrp3-KI mice had increased inflammation, cell death, and fibrosis and increased phosphorylation of ASK1, p38, and c-Jun. GS-444217 reduced ASK1 pathway activation, liver cell death, and liver fibrosis. ASK1 inhibition resulted in a significant downregulation of genes involved in collagen production and extracellular matrix deposition, as well as in a reduced hepatic TNF-α expression. ASK1 inhibition also directly reduced LPS-induced gene expression of Collagen 1A1 (Col1a1) in hepatic stellate cells isolated from Nlrp3-KI mice. In conclusion, ASK1 inhibition reduced liver cell death and fibrosis downstream of inflammatory signaling induced by NLRP3. These data provide mechanistic insight into the antifibrotic mechanisms of ASK1 inhibition.

Induction of E6AP by microRNA-302c dysregulation inhibits TGF-β-dependent fibrogenesis in hepatic stellate cells

Hepatic stellate cells (HSCs) are essential for liver fibrosis. E6 associated protein (E6AP) is one of the E3-ubiquitin-protein ligase and has been studied in proliferation and cellular stress. Currently, no information is available on the role of E6AP on transforming growth factor-β (TGF-β) signaling and hepatic fibrogenesis. This study examined whether E6AP is overexpressed in activated HSCs, and if so, its effect on hepatic fibrogenesis and the molecular mechanism. E6AP was expressed higher in HSCs than hepatocytes, and was up-regulated in activated HSCs, HSCs from the livers of carbon tetrachloride-injected mice, or TGF-β-treated LX-2 cells. The TGF-β-mediated E6AP up-regulation was not due to altered mRNA level nor protein stability. Thus, we performed microRNA (miRNA, miR) analysis and found that miR-302c was dysregulated in TGF-β-treated LX-2 cells or activated primary HSCs. We revealed that miR-302c was a modulator of E6AP. E6AP overexpression inhibited TGF-β-induced expression of plasminogen activator inhibitor-1 in LX-2 cells, albeit it was independent of Smad pathway. Additionally, E6AP inhibited TGF-β-mediated phosphorylation of mitogen-activated protein kinases. To conclude, E6AP overexpression due to decreased miR-302c in HSCs attenuated hepatic fibrogenesis through inhibition of the TGF-β-induced mitogen-activated protein kinase signaling pathway, implying that E6AP and other molecules may contribute to protection against liver fibrosis.

Induction of E6AP by microRNA-302c dysregulation inhibits TGF-β-dependent fibrogenesis in hepatic stellate cells

Hepatic stellate cells (HSCs) are essential for liver fibrosis. E6 associated protein (E6AP) is one of the E3-ubiquitin-protein ligase and has been studied in proliferation and cellular stress. Currently, no information is available on the role of E6AP on transforming growth factor-β (TGF-β) signaling and hepatic fibrogenesis. This study examined whether E6AP is overexpressed in activated HSCs, and if so, its effect on hepatic fibrogenesis and the molecular mechanism. E6AP was expressed higher in HSCs than hepatocytes, and was up-regulated in activated HSCs, HSCs from the livers of carbon tetrachloride-injected mice, or TGF-β-treated LX-2 cells. The TGF-β-mediated E6AP up-regulation was not due to altered mRNA level nor protein stability. Thus, we performed microRNA (miRNA, miR) analysis and found that miR-302c was dysregulated in TGF-β-treated LX-2 cells or activated primary HSCs. We revealed that miR-302c was a modulator of E6AP. E6AP overexpression inhibited TGF-β-induced expression of plasminogen activator inhibitor-1 in LX-2 cells, albeit it was independent of Smad pathway. Additionally, E6AP inhibited TGF-β-mediated phosphorylation of mitogen-activated protein kinases. To conclude, E6AP overexpression due to decreased miR-302c in HSCs attenuated hepatic fibrogenesis through inhibition of the TGF-β-induced mitogen-activated protein kinase signaling pathway, implying that E6AP and other molecules may contribute to protection against liver fibrosis.

New drugs for NAFLD: lessons from basic models to the clinic

The term nonalcoholic fatty liver disease (NAFLD) comprises a spectrum of increasingly harmful conditions ranging from nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH) to liver fibrosis and end-stage cirrhosis. NAFLD is the currently most common form of chronic liver disease in both adults and children worldwide. As NAFLD evolves as a global pandemic alongside the still growing prevalence of metabolic syndrome, obesity, and diabetes, it is inevitable to develop effective counterstrategies. Over the last decades, great effort has been dedicated to the understanding of the pathogenesis of NAFLD. This includes the development of an array of models for NAFLD, ranging from advanced in vitro (primary cells, 3D cultures, biochip, spheroids, organoids) to in vivo rodent models (particularly in mice). Based on these approaches novel therapies have been proposed and subsequently evaluated for patients with advanced forms of NAFLD, in particular those with NASH and liver fibrosis or cirrhosis. In this review, we delineate the current understanding of disease pathophysiology and depict how novel therapeutic strategies aim to exploit these different mechanisms to ameliorate, treat, or stop progression of NASH. We also discuss obstacles and chances along the way from basic models to promising clinical treatment options.

Mechanistic aspects of antifibrotic effects of honokiol in Con A-induced liver fibrosis in rats: Emphasis on TGF-β/SMAD/MAPK signaling pathways

Aim Liver fibrosis represents a massive global health burden with limited therapeutic options. Thus, the need for curative options is evident. Thus, this study aimed to assess the potential antifibrotic effect of honokiol in Concanavalin A (Con A) induced immunological model of liver fibrosis as well the possible underlying molecular mechanisms.

METHODS

Male Sprague-Dawley rats were treated with either Con A (20 mg/kg, IV) and/or honokiol (10 mg/kg, orally) for 4 weeks. Hepatotoxicity indices were as well as histopathological evaluation was done. Hepatic fibrosis was assessed by measuring alpha smooth muscle actin (α-SMA) expression and collagen fibers deposition by Masson's trichrome stain and hydroxyproline content. To elucidate the underlying molecular mechanisms, the effect of honokiol on oxidative stress, inflammatory markers as well as transforming growth factor beta (TGF-β)/SMAD and mitogen-activated protein kinase (MAPK) pathways was assessed.

KEY FINDINGS

Honokiol effectively reversed the hepatotoxicity indices elevations and abnormal histopathological changes induced by Con A. Besides, honokiol attenuated Con A-induced liver fibrosis by down-regulation of hydroxyproline levels, α-SMA expression together with a marked decrease in collagen fibers deposition. Mechanistically Con A induced oxidative stress, provocation of inflammatory responses and activation of TGF-β/SMAD/MAPK pathways. Contrariwise, honokiol co-treatment significantly restored antioxidant defence mechanisms, down-regulated inflammatory cascades and inhibited TGF-β/SMAD/MAPK signaling pathways.

CONCLUSION

The results provide an evidence for the promising antifibrotic effect of honokiol that could be partially due to suppressing oxidative stress and inflammatory processes as well as inhibition of TGF-β/SMAD/MAPK signaling pathways.

The Bile Acid-Phospholipid Conjugate Ursodeoxycholyl-Lysophosphatidylethanolamide (UDCA-LPE) Disintegrates the Lipid Backbone of Raft Plasma Membrane Domains by the Removal of the Membrane Phospholipase A2

The bile acid-phospholipid conjugate ursodeoxycholyl-lysophosphatidylethanolamide (UDCA-LPE) was shown to have anti-inflammatory, antisteatotic, and antifibrotic properties, rendering it as a drug targeting non-alcoholic steatohepatitis (NASH). On a molecular level, it disrupted the heterotetrameric fatty acid uptake complex localized in detergent-resistant membrane domains of the plasma membrane (DRM-PM). However, its mode of action was unclear. Methodologically, UDCA-LPE was incubated with the liver tumor cell line HepG2 as well as their isolated DRM-PM and all other cellular membranes (non-DRM). The membrane cholesterol and phospholipids were quantified as well as the DRM-PM protein composition by Western blotting. The results show a loss of DRM-PM by UDCA-LPE (50 µM) with a 63.13 ± 7.14% reduction of phospholipids and an 81.94 ± 8.30% reduction of cholesterol in relation to mg total protein. The ratio of phospholipids to cholesterol changed from 2:1 to 4:1, resembling those of non-DRM fractions. Among the members of the fatty acid uptake complex, the calcium-independent membrane phospholipase A2 (iPLA₂β) abandoned DRM-PM most rapidly. As a consequence, the other members of this transport system disappeared as well as the DRM-PM anchored fibrosis regulating proteins integrin β-1 and lysophospholipid receptor 1 (LPAR-1). It is concluded that UDCA-LPE executes its action by iPLA₂β removal from DRM-PM and consequent dissolution of the raft lipid platform.

Context-Dependent Role of NF-κB Signaling in Primary Liver Cancer-from Tumor Development to Therapeutic Implications

Chronic inflammatory cell death is a major risk factor for the development of diverse cancers including liver cancer. Herein, disruption of the hepatic microenvironment as well as the immune cell composition are major determinants of malignant transformation and progression in hepatocellular carcinomas (HCC). Considerable research efforts have focused on the identification of predisposing factors that promote induction of an oncogenic field effect within the inflammatory liver microenvironment. Among the most prominent factors involved in this so-called inflammation-fibrosis-cancer axis is the NF-κB pathway. The dominant role of this pathway for malignant transformation and progression in HCC is well documented. Pathway activation is significantly linked to poor prognostic traits as well as stemness characteristics, which places modulation of NF-κB signaling in the focus of therapeutic interventions. However, it is well recognized that the mechanistic importance of the pathway for HCC is highly context and cell type dependent. While constitutive pathway activation in an inflammatory etiological background can significantly promote HCC development and progression, absence of NF-κB signaling in differentiated liver cells also significantly enhances liver cancer development. Thus, therapeutic targeting of NF-κB as well as associated family members may not only exert beneficial effects but also negatively impact viability of healthy hepatocytes and/or cholangiocytes, respectively. The review presented here aims to decipher the complexity and paradoxical functions of NF-κB signaling in primary liver and non-parenchymal cells, as well as the induced molecular alterations that drive HCC development and progression with a particular focus on (immune-) therapeutic interventions.

Smooth muscle-specific TMEM16A expression protects against angiotensin II-induced cerebrovascular remodeling via suppressing extracellular matrix deposition

Cerebrovascular remodeling is the leading factor for stroke and characterized by increased extracellular matrix deposition, migration and proliferation of vascular smooth muscle cells, and inhibition of their apoptosis. TMEM16A is an important component of Ca²⁺-activated Cl^- channels. Previously, we showed that downregulation of TMEM16A in the basilar artery was negatively correlated with cerebrovascular remodeling during hypertension. However, it is unclear whether TMEM16A participates in angiotensin II (Ang II)-induced vascular remodeling in mice that have TMEM16A gene modification. In this study, we generated a transgenic mouse that overexpresses TMEM16A specifically in vascular smooth muscle cells. We observed that vascular remodeling in the basilar artery during Ang II-induced hypertension was significantly suppressed upon vascular smooth muscle-specific overexpression of TMEM16A relative to control mice. Specifically, we observed a large reduction in the deposition of fibronectin and collagen I. The expression of matrix metalloproteinases (MMP-2, MMP-9, and MMP-14), and tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) were upregulated in the basilar artery during Ang II-induced hypertension, but this was suppressed upon overexpression of TMEM16A in blood vessels. Furthermore, TMEM16A overexpression alleviated the overactivity of the canonical TGF-β1/Smad3, and non-canonical TGF-β1/ERK and JNK pathways in the basilar artery during Ang II-induced hypertension. These in vivo results were similar to the results derived in vitro with basilar artery smooth muscle cells stimulated by Ang II. Moreover, we observed that the inhibitory effect of TMEM16A on MMPs was mediated by decreasing the activation of WNK1, which is a Cl^--sensitive serine/threonine kinase. In conclusion, this study demonstrates that TMEM16A protects against cerebrovascular remodeling during hypertension by suppressing extracellular matrix deposition. We also showed that TMEM16A exerts this effect by reducing the expression of MMPs via inhibiting WNK1, and decreasing the subsequent activities of TGF-β1/Smad3, ERK, and JNK. Accordingly, our results suggest that TMEM16A may serve as a novel therapeutic target for vascular remodeling.

Metabolic disorder induces fatty liver in Japanese seabass, Lateolabrax japonicas fed a full plant protein diet and regulated by cAMP-JNK/NF-kB-caspase signal pathway

A 10-week growth trial was conducted to investigate the effects of replacing dietary fishmeal with plant proteins on nutrition metabolism, immunity, inflammation and apoptosis responses in liver tissues of Japanese seabass, Lateolabrax japonicas (initial body weight = 10.42 ± 0.01 g). Two isonitrogenous and isoenergetic diets were formulated. A basal diet containing 54% fishmeal (FM), whereas another diet was prepared by totally replacing FM with a plant protein blend (PP) composed with soybean protein concentrate and cottonseed protein concentrate. Although essential amino acids, fatty acids, and available phosphorus had been balanced according to the FM diet profile, the significantly lower growth performance, metabolic disorder, and fatty liver symptom were observed in the PP group. Compared with the FM group, fish in the PP group showed significantly lower plasma free EAA level and PPV. Glucose metabolism disorder was expressed as the uncontrollable fasting glycolysis and pyruvate aerobic oxidation at postprandial 24 h with significantly up-regulated GK, PK and PDH genes expression, which potentially over-produced acetyl-CoA as the substrate for protein and lipid synthesis. Significantly reduced plasma GLU, but increased GC level, along with very significantly reduced liver GLY storage could be observed in the PP group. Plasma TG and hepatic NEFA contents were significantly decreased, but the hepatic TC content was very significantly increased in the PP group, in addition, hepatocyte vacuolation appeared. The significantly up-regulated cholesterol synthesis gene (HMGCR) expression but down-regulated bile acid synthesis gene (CYP7A1) expression could be the main reason for the fatty liver induced by cholesterol accumulation. The reduced plasma IgM content accompanied by the up-regulated mRNA levels of pro-inflammatory cytokines (TNFα and IL1β) and activated apoptosis signals of liver tissues were found in the PP group. The hyperthyroidism (higher plasma T3 and T4) and the accelerated energy metabolism rate decreased the growth performance in the PP group. The activated p65NF-kB may promote the hepatocytes apoptosis via the extrinsic pathway (caspase8/caspase3). Simultaneously, a "self-saving" response could be observed that activated cAMP promoted the lipolysis/β-oxidation process and up-regulated gene expression of anti-inflammatory cytokine IL10 via promoting CREB expression, further inhibited the over-phosphorylation of JNK protein, which might impede the intrinsic apoptosis pathway (caspase9/caspase3). In conclusion, the nutrient and energy metabolic disorder induced fatty liver related to the cholesterol accumulation in Japanese seabass fed full PP diet, which was under the regulation by cAMP-JNK/NF-kB-caspase signaling pathway. The hemostasis phosphorylation of JNK protein protected the liver tissues from more serious damage.

Signaling pathways involved in p38-ERK and inflammatory factors mediated the anti-fibrosis effect of AD-2 on thioacetamide-induced liver injury in mice

Ginseng is a type of medicinal and edible homologous plant that is very common in medicine, food and even cosmetics.

Effect of SEPT6 on the biological behavior of hepatic stellate cells and liver fibrosis in rats and its mechanism

Hepatic stellate cells (HSCs) are key effectors during the development of liver fibrosis. Septin 6 (SEPT6) is a highly evolutionarily conserved GTP-binding protein that regulates various cell biological behaviors. The expression and function of SEPT6 in HSCs remain unknown. Here we demonstrate that SEPT6 expression is significantly elevated following the activation of primary rat HSCs, the human hepatic stellate cell line LX-2 and the rat hepatic stellate cell line HSC-T6, as well as in both human and rat fibrotic liver tissue. In vitro, the overexpression of SEPT6 promoted HSCs activation, proliferation, cell cycle progression and migration and inhibited HSCs apoptosis. In contrast, knockdown of SEPT6 exerted the opposite effects on HSCs. Mechanistically, SEPT6 exerted its pro-fibrogenic effect by promoting the expression of TGF-β1 and the phosphorylation of Smad2, Smad3, extracellular-signal-regulated kinase, c-Jun NH2-terminal kinase, stress-activated protein kinase-2, and protein kinase B. However, in HSC-T6 cells, blockade of the TGF-β1/Smad signaling pathway by SB431542 significantly decreased the expression of α-smooth muscle actin, cyclin D1, BCL2, and matrix metalloproteinase-2 and -9, which had been enhanced by SEPT6 overexpression. In vivo, adenovirus-mediated SEPT6 inhibition attenuated thioacetamide (TAA)-induced liver fibrosis in rats by decreasing the deposition of the extracellular matrix (ECM). SEPT6 inhibition decreased the proliferation capacity of HSCs and induced apoptosis of HSCs. Collectively, our results reveal that SEPT6 regulates various biological behaviors in HSCs through TGF-β1/Smad, mitogen-activated protein kinases and phosphatidylinositol-3-kinase/protein kinase B signaling pathways, thus promoting liver fibrosis.

Protective role of c-Jun N-terminal kinase-2 (JNK2) in ibuprofen-induced acute liver injury

Ibuprofen is a worldwide used non-steroidal anti-inflammatory drug which may cause acute liver injury (ALI) requiring liver transplantation. We aimed to unveil the molecular pathways involved in triggering ibuprofen-induced ALI, which, at present, remain elusive. First, we investigated activation of essential pathways in human liver sections of ibuprofen-induced ALI. Next, we assessed the cytotoxicity of ibuprofen in vitro and developed a novel murine model of ibuprofen intoxication. To assess the role of JNK, we used animals carrying constitutive deletion of c-Jun N-terminal kinase 1 (Jnk1^-/- ) or Jnk2 (Jnk2^-/- ) expression and included investigations using animals with hepatocyte-specific Jnk deletion either genetically (Jnk1^Δhepa ) or by siRNA (siJnk2^Δhepa ). We found in human and murine samples of ibuprofen-induced acute liver failure that JNK phosphorylation was increased in the cytoplasm of hepatocytes and other non-liver parenchymal cells (non-LPCs) compared with healthy tissue. In mice, ibuprofen intoxication resulted in a significantly stronger degree of liver injury compared with vehicle-treated controls as evidenced by serum transaminases, and hepatic histopathology. Next, we investigated molecular pathways. PKCα, AKT, JNK and RIPK1 were significantly increased 8 h after ibuprofen intoxication. Constitutive Jnk1^-/- and Jnk2^-/- deficient mice exhibited increased liver dysfunction compared to wild-type (WT) animals. Furthermore, siJnk2^Δhepa animals showed a dramatic increase in biochemical markers of liver function, which correlated with significantly higher serum liver enzymes and worsened liver histology, and MAPK activation compared to Jnk1^Δhepa or WT animals. In our study, cytoplasmic JNK activation in hepatocytes and other non-LPCs is a hallmark of human and murine ibuprofen-induced ALI. Functional in vivo analysis demonstrated a protective role of hepatocyte-specific Jnk2 during ibuprofen ALI. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Inactivation of caspase 8 in liver parenchymal cells confers protection against murine obstructive cholestasis

BACKGROUND & AIMS

Caspase 8 (CASP8) is the apical initiator caspase in death receptor-mediated apoptosis. Strong evidence for a link between death receptor signaling pathways and cholestasis has recently emerged. Herein, we investigated the role of CASP8-dependent and independent pathways during experimental cholestasis.

METHODS

Liver injury was characterized in a cohort of human sera (n = 28) and biopsies from patients with stage IV primary biliary cholangitis. In parallel, mice with either specific deletion of Casp8 in liver parenchymal cells (Casp8^Δhepa) or hepatocytes (Casp8^Δhep), and mice with constitutive Ripk3 (Ripk3^-/-) deletion, were subjected to surgical ligation of the common bile duct (BDL) from 2 to 28 days. Floxed (Casp8^fl/fl) and Ripk3^+/+ mice were used as controls. Moreover, the pan-caspase inhibitor IDN-7314 was used, and cell death mechanisms were studied in primary isolated hepatocytes.

RESULTS

Overexpression of activated caspase 3, CASP8 and RIPK3 was characteristic of liver explants from patients with primary biliary cholangitis. Twenty-eight days after BDL, Casp8^Δhepamice showed decreased necrotic foci, serum aminotransferase levels and apoptosis along with diminished compensatory proliferation and ductular reaction. These results correlated with a decreased inflammatory profile and ameliorated liver fibrogenesis. A similar phenotype was observed in Ripk3^-/- mice. IDN-7314 treatment decreased CASP8 levels but failed to prevent BDL-induced cholestasis, independently of CASP8 in hepatocytes.

CONCLUSION

These findings show that intervention against CASP8 in liver parenchymal cells - specifically in cholangiocytes - might be a beneficial option for treating obstructive cholestasis, while broad pan-caspase inhibition might trigger undesirable side effects.

LAY SUMMARY

Loss of caspase 8 - a protein involved in programmed cell death - in liver parenchymal cells protects against experimental cholestasis. Therefore, specific pharmacological intervention against caspase 8 might be a valid alternative for the treatment of obstructive cholestasis in the clinic, whereas broad pan-caspase inhibiting drugs might trigger undesirable side effects.

Cytokines in adipose-derived mesenchymal stem cells promote the healing of liver disease

Adipose-derived mesenchymal stem cells (ADSCs) are a treatment cell source for patients with chronic liver injury. ADSCs are characterized by being harvested from the patient's own subcutaneous adipose tissue, a high cell yield (i.e., reduced immune rejection response), accumulation at a disease nidus, suppression of excessive immune response, production of various growth factors and cytokines, angiogenic effects, anti-apoptotic effects, and control of immune cells via cell-cell interaction. We previously showed that conditioned medium of ADSCs promoted hepatocyte proliferation and improved the liver function in a mouse model of acute liver failure. Furthermore, as found by many other groups, the administration of ADSCs improved liver tissue fibrosis in a mouse model of liver cirrhosis. A comprehensive protein expression analysis by liquid chromatography with tandem mass spectrometry showed that the various cytokines and chemokines produced by ADSCs promote the healing of liver disease. In this review, we examine the ability of expressed protein components of ADSCs to promote healing in cell therapy for liver disease. Previous studies demonstrated that ADSCs are a treatment cell source for patients with chronic liver injury. This review describes the various cytokines and chemokines produced by ADSCs that promote the healing of liver disease.

Sasa veitchii extract protects against carbon tetrachloride-induced hepatic fibrosis in mice

BACKGROUND

The current study aimed to investigate the hepatoprotective effects of Sasa veitchii extract (SE) on carbon tetrachloride (CCl₄)-induced liver fibrosis in mice.

METHODS

Male C57BL/6J mice were intraperitoneally injected with CCl₄ dissolved in olive oil (1 g/kg) twice per week for 8 weeks. SE (0.1 mL) was administered orally once per day throughout the study, and body weight was measured weekly. Seventy-two hours after the final CCl₄ injection, mice were euthanized and plasma samples were collected. The liver and kidneys were collected and weighed.

RESULTS

CCl₄ administration increased liver weight, decreased body weight, elevated plasma alanine aminotransferase, and aspartate aminotransferase and increased liver oxidative stress (malondialdehyde and glutathione). These increases were attenuated by SE treatment. Overexpression of tumor necrosis factor-α was also reversed following SE treatment. Furthermore, CCl₄-induced increases in α-smooth muscle actin, a marker for hepatic fibrosis, were attenuated in mice treated with SE. Moreover, SE inhibited CCl₄-induced nuclear translocation of hepatic nuclear factor kappa B (NF-κB) p65 and phosphorylation of mitogen-activated protein kinase (MAPK).

CONCLUSION

These results suggested that SE prevented CCl₄-induced hepatic fibrosis by inhibiting the MAPK and NF-κB signaling pathways.

Liver fibrosis: Pathophysiology, pathogenetic targets and clinical issues

The progression of chronic liver diseases (CLD), irrespective of etiology, involves chronic parenchymal injury, persistent activation of inflammatory response as well as sustained activation of liver fibrogenesis and wound healing response. Liver fibrogenesis, is a dynamic, highly integrated molecular, cellular and tissue process responsible for driving the excess accumulation of extracellular matrix (ECM) components (i.e., liver fibrosis) sustained by an eterogeneous population of hepatic myofibroblasts (MFs). The process of liver fibrogenesis recognizes a number of common and etiology-independent mechanisms and events but it is also significantly influenced by the specific etiology, as also reflected by peculiar morphological patterns of liver fibrosis development. In this review we will analyze the most relevant established and/or emerging pathophysiological issues underlying CLD progression with a focus on the role of critical hepatic cell populations, mechanisms and signaling pathways involved, as they represent potential therapeutic targets, to finally analyze selected and relevant clinical issues.

JNK1 induces hedgehog signaling from stellate cells to accelerate liver regeneration in mice

BACKGROUND & AIMS

To improve outcomes of two-staged hepatectomies for large/multiple liver tumors, portal vein ligation (PVL) has been combined with parenchymal transection (associating liver partition and portal vein ligation for staged hepatectomy [coined ALPPS]) to greatly accelerate liver regeneration. In a novel ALPPS mouse model, we have reported paracrine Indian hedgehog (IHH) signaling from stellate cells as an early contributor to augmented regeneration. Here, we sought to identify upstream regulators of IHH.

METHODS

ALPPS in mice was compared against PVL and additional control surgeries. Potential IHH regulators were identified through in silico mining of transcriptomic data. c-Jun N-terminal kinase (JNK1 [Mapk8]) activity was reduced through SP600125 to evaluate its effects on IHH signaling. Recombinant IHH was injected after JNK1 diminution to substantiate their relationship during accelerated liver regeneration.

RESULTS

Transcriptomic analysis linked Ihh to Mapk8. JNK1 upregulation after ALPPS was validated and preceded the IHH peak. On immunofluorescence, JNK1 and IHH co-localized in alpha-smooth muscle actin-positive non-parenchymal cells. Inhibition of JNK1 prior to ALPPS surgery reduced liver weight gain to PVL levels and was accompanied by downregulation of hepatocellular proliferation and the IHH-GLI1-CCND1 axis. In JNK1-inhibited mice, recombinant IHH restored ALPPS-like acceleration of regeneration and re-elevated JNK1 activity, suggesting the presence of a positive IHH-JNK1 feedback loop.

CONCLUSIONS

JNK1-mediated induction of IHH paracrine signaling from hepatic stellate cells is essential for accelerated regeneration of parenchymal mass. The JNK1-IHH axis is a mechanism unique to ALPPS surgery and may point to therapeutic alternatives for patients with insufficient regenerative capacity.

LAY SUMMARY

Associating liver partition and portal vein ligation for staged hepatectomy (so called ALPPS), is a new two-staged approach to hepatectomy, which induces an unprecedented acceleration of liver regeneration, enabling treatment of patients with liver tumors that would otherwise be considered unresectable. Herein, we demonstrate that JNK1-IHH signaling from stellate cells is a key mechanism underlying the regenerative acceleration that is induced by ALPPS.

Clinico-Pathological Importance of TGF-β/Phospho-Smad Signaling during Human Hepatic Fibrocarcinogenesis

Chronic viral hepatitis is a global public health problem, with approximately 570 million persons chronically infected. Hepatitis B and C viruses increase the risk of morbidity and mortality from liver cirrhosis, hepatocellular carcinoma (HCC), and extrahepatic complications that develop. Hepatitis virus infection induces transforming growth factor (TGF)-β, which influences microenvironments within the infected liver. TGF-β promotes liver fibrosis by up-regulating extracellular matrix production by hepatic stellate cells. TGF-β is also up-regulated in patients with HCC, in whom it contributes importantly to bringing about a favorable microenvironment for tumor growth. Thus, TGF-β is thought to be a major factor regulating liver fibrosis and carcinogenesis. Since TGF-β carries out regulatory signaling by influencing the phosphorylation of Smads, we have generated several kinds of phospho-specific antibodies to Smad2/3. Using these, we have identified three types of phospohorylated forms: COOH-terminally phosphorylated Smad2/3 (pSmad2C and pSmad3C), linker phosphorylated Smad2/3 (pSmad2L and pSmad3L), and dually phosphorylated Smad3 (pSmad2L/C and pSmad3L/C). TGF-β-mediated pSmad2/3C signaling terminates cell proliferation; on the other hand, cytokine-induced pSmad3L signaling accelerates cell proliferation and promotes fibrogenesis. This review addresses TGF-β/Smad signal transduction in chronic liver injuries and carcinogenic processes. We also discuss the reversibility of Smad signaling after antiviral therapy.

A humanized mouse model of liver fibrosis following expansion of transplanted hepatic stellate cells

Hepatic stellate cells (HSCs) are major contributors to liver fibrosis, as hepatic injuries may cause their transdifferentiation into myofibroblast-like cells capable of producing excessive extracellular matrix proteins. Also, HSCs can modulate engraftment of transplanted hepatocytes and contribute to liver regeneration. Therefore, understanding the biology of human HSCs (hHSCs) is important, but effective methods have not been available to address their fate in vivo. To investigate whether HSCs could engraft and repopulate the liver, we transplanted GFP-transduced immortalized hHSCs into immunodeficient NOD/SCID mice. Biodistribution analysis with radiolabeled hHSCs showed that after intrasplenic injection, the majority of transplanted cells rapidly translocated to the liver. GFP-immunohistochemistry demonstrated that transplanted hHSCs engrafted alongside hepatic sinusoids. Prior permeabilization of the sinusoidal endothelial layer with monocrotaline enhanced engraftment of hHSCs. Transplanted hHSCs remained engrafted without relevant proliferation in the healthy liver. However, after CCl₄ or bile duct ligation-induced liver damage, transplanted hHSCs expanded and contributed to extracellular matrix production, formation of bridging cell-septae and cirrhosis-like hepatic pseudolobules. CCl₄-induced injury recruited hHSCs mainly to zone 3, whereas after bile duct ligation, hHSCs were mainly in zone 1 of the liver lobule. Transplanted hHSCs neither transdifferentiated into other cell types nor formed tumors in these settings. In conclusion, a humanized mouse model was generated by transplanting hHSCs, which proliferated during hepatic injury and inflammation, and contributed to liver fibrosis. The ability to repopulate the liver with transplanted hHSCs will be particularly significant for mechanistic studies of cell-cell interactions and fibrogenesis within the liver.

Gα12 overexpression induced by miR-16 dysregulation contributes to liver fibrosis by promoting autophagy in hepatic stellate cells

BACKGROUND & AIMS

Hepatic stellate cells (HSCs) have a role in liver fibrosis. Guanine nucleotide-binding α-subunit 12 (Gα₁₂) converges signals from G-protein-coupled receptors whose ligand levels are elevated in the environment during liver fibrosis; however, information is lacking on the effect of Gα₁₂ on HSC trans-differentiation. This study investigated the expression of Gα₁₂ in HSCs and the molecular basis of the effects of its expression on liver fibrosis.

METHODS

Gα₁₂ expression was assessed by immunostaining, and immunoblot analyses of mouse fibrotic liver tissues and primary HSCs. The role of Gα₁₂ in liver fibrosis was estimated using a toxicant injury mouse model with Gα₁₂ gene knockout and/or HSC-specific Gα₁₂ delivery using lentiviral vectors, in addition to primary HSCs and LX-2 cells using microRNA (miR) inhibitors, overexpression vectors, or adenoviruses. miR-16, Gα₁₂, and LC3 were also examined in samples from patients with fibrosis.

RESULTS

Gα₁₂ was overexpressed in activated HSCs and fibrotic liver, and was colocalised with desmin. In a carbon tetrachloride-induced fibrosis mouse model, Gα₁₂ ablation prevented increases in fibrosis and liver injury. This effect was attenuated by HSC-specific lentiviral delivery of Gα₁₂. Moreover, Gα₁₂ activation promoted autophagy accompanying c-Jun N-terminal kinase-dependent ATG12-5 conjugation. In addition, miR-16 was found to be a direct inhibitor of the de novo synthesis of Gα₁₂. Modulations of miR-16 altered autophagy in HSCs. In a fibrosis animal model or patients with severe fibrosis, miR-16 levels were lower than in their corresponding controls. Consistently, cirrhotic patient liver tissues showed Gα₁₂ and LC3 upregulation in desmin-positive areas.

CONCLUSIONS

miR-16 dysregulation in HSCs results in Gα₁₂ overexpression, which activates HSCs by facilitating autophagy through ATG12-5 formation. This suggests that Gα₁₂ and its regulatory molecules could serve as targets for the amelioration of liver fibrosis.

LAY SUMMARY

Guanine nucleotide-binding α-subunit 12 (Gα₁₂) is upregulated in activated hepatic stellate cells (HSCs) as a consequence of the dysregulation of a specific microRNA that is abundant in HSCs, facilitating the progression of liver fibrosis. This event is mediated by c-Jun N-terminal kinase-dependent ATG12-5 formation and the promotion of autophagy. We suggest that Gα₁₂ and its associated regulators could serve as new targets in HSCs for the treatment of liver fibrosis.

Geranylgeranylacetone attenuates fibrogenic activity and induces apoptosis in cultured human hepatic stellate cells and reduces liver fibrosis in carbon tetrachloride-treated mice

Background

Geranylgeranylacetone (GGA), an anti-ulcer drug widely used in Japan, has attracted interest because of its various therapeutic effects. Therefore, we investigated the effects of GGA on human hepatic stellate cells (HSCs) in vitro and in a mouse model of liver fibrosis.

Methods

LX2, an immortalized human HSC line, was cultured and treated with GGA at concentrations up to 0.5 mM. After GGA treatment, changes in cellular morphology, apoptosis, and fibrosis-related gene expression were assessed. Male C57BL/6 J mouse model of carbon tetrachloride (CCl₄)-induced liver fibrosis was treated with GGA. Liver fibrosis was evaluated using Sirius red staining and immunohistochemistry for α-smooth muscle actin (SMA).

Results

GGA decreased the density of LX2 and primary human hepatic stellate cells but not that of HepG2 cells (a human hepatoma cell line), which was employed as control. In addition, GGA decreased the expression of fibrogenic genes and increased that of C/EBP homologous protein (CHOP). It also induced endoplasmic reticulum (ER) stress and increased apoptosis. CHOP knockdown, however, failed to suppress the GGA-induced decrease in LX2 cell density, suggesting the involvement of additional molecules in ER stress–associated apoptosis. Expression of death receptor 5, mitogen-activated protein kinase, heat shock protein 70, and Akt, all of which affect the activity of stellate cells, was unchanged in relation to LX2 cell fibrogenic activity. In the mouse model of liver fibrosis, GGA decreased the extent of Sirius red staining and SMA expression.

Conclusions

GGA attenuated fibrogenic activity and induced apoptosis in cultured human HSCs, and suppressed liver fibrosis in mice, suggesting its potential as an agent for treating liver fibrosis.

Electronic supplementary material

The online version of this article (10.1186/s12876-018-0761-7) contains supplementary material, which is available to authorized users.

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.

MicroRNA-221/222 Family Counteracts Myocardial Fibrosis in Pressure Overload-Induced Heart Failure

Pressure overload causes cardiac fibroblast activation and transdifferentiation, leading to increased interstitial fibrosis formation and subsequently myocardial stiffness, diastolic and systolic dysfunction, and eventually heart failure. A better understanding of the molecular mechanisms underlying pressure overload-induced cardiac remodeling and fibrosis will have implications for heart failure treatment strategies. The microRNA (miRNA)-221/222 family, consisting of miR-221-3p and miR-222-3p, is differentially regulated in mouse and human cardiac pathology and inversely associated with kidney and liver fibrosis. We investigated the role of this miRNA family during pressure overload-induced cardiac remodeling. In myocardial biopsies of patients with severe fibrosis and dilated cardiomyopathy or aortic stenosis, we found significantly lower miRNA-221/222 levels as compared to matched patients with nonsevere fibrosis. In addition, miRNA-221/222 levels in aortic stenosis patients correlated negatively with the extent of myocardial fibrosis and with left ventricular stiffness. Inhibition of both miRNAs during AngII (angiotensin II)-mediated pressure overload in mice led to increased fibrosis and aggravated left ventricular dilation and dysfunction. In rat cardiac fibroblasts, inhibition of miRNA-221/222 derepressed TGF-β (transforming growth factor-β)-mediated profibrotic SMAD2 (mothers against decapentaplegic homolog 2) signaling and downstream gene expression, whereas overexpression of both miRNAs blunted TGF-β-induced profibrotic signaling. We found that the miRNA-221/222 family may target several genes involved in TGF-β signaling, including JNK1 (c-Jun N-terminal kinase 1), TGF-β receptor 1 and TGF-β receptor 2, and ETS-1 (ETS proto-oncogene 1). Our findings show that heart failure-associated downregulation of the miRNA-221/222 family enables profibrotic signaling in the pressure-overloaded heart.

miRNA-21 ablation protects against liver injury and necroptosis in cholestasis

Inhibition of microRNA-21 (miR-21) prevents necroptosis in the mouse pancreas. Necroptosis contributes to hepatic necro-inflammation in the common bile duct ligation (BDL) murine model. We aimed to evaluate the role of miR-21 in mediating deleterious processes associated with cholestasis. Mechanistic studies established a functional link between miR-21 and necroptosis through cyclin-dependent kinase 2-associated protein 1 (CDK2AP1). miR-21 expression increased in the liver of primary biliary cholangitis (PBC) patients and BDL wild-type (WT) mice at both 3 and 14 days. Notably, under BDL, miR-21 ^-/- mice displayed decreased liver injury markers in serum compared with WT mice, accompanied by reduced hepatocellular degeneration, oxidative stress and fibrosis. Hallmarks of necroptosis were decreased in the liver of BDL miR-21 ^-/- mice, via relieved repression of CDK2AP1. Further, miR-21 ^-/- mice displayed improved adaptive response of bile acid homeostasis. In conclusion, miR-21 ablation ameliorates liver damage and necroptosis in BDL mice. Inhibition of miR-21 should arise as a promising approach to treat cholestasis.

Components of the Hepatocellular Carcinoma Microenvironment and Their Role in Tumor Progression

This review summarizes recently published data on the mechanisms of tumor cell interaction with the tumor microenvironment. Tumor stroma influences the processes of hepatocarcinogenesis, epithelial-to-mesenchymal transition, invasion, and metastasis. The tumor microenvironment includes both cellular and noncellular components. Main cellular components of hepatocellular carcinoma (HCC) stroma are tumor-associated fibroblasts, hepatic stellate cells, immune cells, and endothelial cells that produce extracellular components of tumor microenvironment such as extracellular matrix, various proteins, proteolytic enzymes, growth factors, and cytokines. The noncellular components of the stroma modulate signaling pathways in tumor cells and stimulate invasion and metastasis. The tumor microenvironment composition and organization can serve as prognostic factors in HCC pathogenesis. Current approaches in HCC targeted therapy are aimed at creating efficient strategies for interrupting tumor interactions with the stroma. Recent data on the composition and role of the microenvironment in HCC pathogenesis, as well as new developments in antitumor drug design are discussed.

Interdependent and independent multidimensional role of tumor microenvironment on hepatocellular carcinoma

The novelty of an effective therapeutic targeting for hepatocellular carcinoma (HCC) is based on improved understanding of each component of tumor microenvironment (TME) and its correspondent interactions at biological and molecular levels. In this context, new expansions for the treatment against TME and its communication with HCC are under exploration. Despite of the fact that blockage of growth factor receptors has become a treatment of choice in late phases of HCC in clinical practice, still a precise targeted treatment should address all the components of TME. Targeting one specific element out of cellular (cancer associated fibroblasts, endothelial cells, hepatic stellate cells, Kupffer cells and lymphocytes) or non-cellular (extracellular matrix, growth factors, inflammatory cytokines, proteolytic enzymes) parts of TME may not be a successful remedy for the disease because of well-designed hindrances of each component and their functional alternativeness. Meanwhile there are some elements of TME like epithelial-mesenchymal transition and CAF, which are considerably important and need thorough investigations. Ascertaining the potential role of these elements, and a single or combinational drug therapy targeting these elements of TME simultaneously, may provide the appreciable considerations to eventually improve in clinical practices and may also minimize the chances of reoccurrence of HCC.

Mouse models of nonalcoholic steatohepatitis in preclinical drug development

Nonalcoholic fatty liver disease (NAFLD) has become the most common cause of chronic liver disease in the Western world. NAFLD is a complex spectrum of liver diseases ranging from benign hepatic steatosis to its more aggressive necroinflammatory manifestation, nonalcoholic steatohepatitis (NASH). NASH pathogenesis is multifactorial and risk factors are almost identical to those of the metabolic syndrome. This has prompted substantial efforts to identify novel drug therapies for correcting underlying metabolic deficits, and to prevent or alleviate hepatic fibrosis in NASH. Available mouse models of NASH address different aspects of the disease, have varying clinical translatability, and, therefore, also show different utility in drug discovery.

Mechanisms of hepatic stellate cell activation

Hepatic fibrosis is a dynamic process characterized by the net accumulation of extracellular matrix resulting from chronic liver injury of any aetiology, including viral infection, alcoholic liver disease and NASH. Activation of hepatic stellate cells (HSCs) - transdifferentiation of quiescent, vitamin-A-storing cells into proliferative, fibrogenic myofibroblasts - is now well established as a central driver of fibrosis in experimental and human liver injury. Yet, the continued discovery of novel pathways and mediators, including autophagy, endoplasmic reticulum stress, oxidative stress, retinol and cholesterol metabolism, epigenetics and receptor-mediated signals, reveals the complexity of HSC activation. Extracellular signals from resident and inflammatory cells including macrophages, hepatocytes, liver sinusoidal endothelial cells, natural killer cells, natural killer T cells, platelets and B cells further modulate HSC activation. Finally, pathways of HSC clearance have been greatly clarified, and include apoptosis, senescence and reversion to an inactivated state. Collectively, these findings reinforce the remarkable complexity and plasticity of HSC activation, and underscore the value of clarifying its regulation in hopes of advancing the development of novel diagnostics and therapies for liver disease.

Activation of hepatic stellate cells by the ubiquitin C-terminal hydrolase 1 protein secreted from hepatitis C virus-infected hepatocytes

Hepatitis C virus (HCV) infection of hepatocytes promotes liver fibrosis by activation of hepatic stellate cells (HSCs) and excessive deposition of extracellular matrix in liver tissue. Whether or not host factors released from the HCV-infected hepatocytes play role in HSCs activation is unclear. In this study, HSCs were activated by the conditioned medium derived from HCV replicon cells. Secretomic profiling of HCV replicon cells and the parental Huh7 cells revealed ubiquitin carboxy-terminal hydrolase L1 (UCHL1) as a novel secreted protein from HCV-infected hepatocytes. UCHL1 expression in hepatocytes was induced by HCV infection. UCHL1 was expressed in the liver and found in the plasma of patients with chronic hepatitis C. Molecular analysis by use of the anti-UCHL1 neutralization antibody and purified UCHL1 protein showed that secreted UCHL1 protein was bound to the cell surface of HSCs and activated JNK signaling leading to overexpression of alpha-smooth muscle actin and the activation of HSCs. These results provide further for understanding the underlying mechanism in HCV-mediated hepatic fibrogenesis.

p21 maintains senescent cell viability under persistent DNA damage response by restraining JNK and caspase signaling

Cellular senescence is a permanent state of cell cycle arrest that protects the organism from tumorigenesis and regulates tissue integrity upon damage and during tissue remodeling. However, accumulation of senescent cells in tissues during aging contributes to age‐related pathologies. A deeper understanding of the mechanisms regulating the viability of senescent cells is therefore required. Here, we show that the CDK inhibitor p21 (CDKN1A) maintains the viability of DNA damage‐induced senescent cells. Upon p21 knockdown, senescent cells acquired multiple DNA lesions that activated ataxia telangiectasia mutated (ATM) and nuclear factor (NF)‐κB kinase, leading to decreased cell survival. NF‐κB activation induced TNF‐α secretion and JNK activation to mediate death of senescent cells in a caspase‐ and JNK‐dependent manner. Notably, p21 knockout in mice eliminated liver senescent stellate cells and alleviated liver fibrosis and collagen production. These findings define a novel pathway that regulates senescent cell viability and fibrosis.

The PNPLA3 I148M variant modulates the fibrogenic phenotype of human hepatic stellate cells

The genetic polymorphism I148M of patatin-like phospholipase domain-containing 3 (PNPLA3) is robustly associated with hepatic steatosis and its progression to steatohepatitis, fibrosis, and cancer. Hepatic stellate cells (HSCs) are key players in the development of liver fibrosis, but the role of PNPLA3 and its variant I148M in this process is poorly understood. Here we analyzed the expression of PNPLA3 during human HSC activation and thereby explored how a PNPLA3 variant impacts hepatic fibrogenesis. We show that expression of PNPLA3 gene and protein increases during the early phases of activation and remains elevated in fully activated HSCs (P < 0.01). Knockdown of PNPLA3 significantly decreases the profibrogenic protein alpha-smooth muscle actin (P < 0.05). Primary human I148M HSCs displayed significantly higher expression and release of proinflammatory cytokines, such as chemokine (C-C motif) ligand 5 (P < 0.01) and granulocyte-macrophage colony-stimulating factor (P < 0.001), thus contributing to migration of immune cells (P < 0.05). Primary I148M HSCs showed reduced retinol (P < 0.001) but higher lipid droplet content (P < 0.001). In line with this, LX-2 cells stably overexpressing I148M showed augmented proliferation and migration, lower retinol, and abolished retinoid X receptor/retinoid A receptor transcriptional activities but more lipid droplets. Knockdown of I148M PNPLA3 (P < 0.001) also reduces chemokine (C-C motif) ligand 5 and collagen1α1 expression (P < 0.05). Notably, I148M cells display reduced peroxisome proliferator-activated receptor gamma transcriptional activity, and this effect was attributed to increased c-Jun N-terminal kinase, thereby inhibiting peroxisome proliferator-activated receptor gamma through serine 84 phosphorylation and promoting activator protein 1 transcription. Conversely, the c-Jun N-terminal kinase inhibitor SP600125 and the peroxisome proliferator-activated receptor gamma agonist rosiglitazone decreased activator protein 1 promoter activity.

CONCLUSIONS

These data indicate that PNPLA3 is required for HSC activation and that its genetic variant I148M potentiates the profibrogenic features of HSCs, providing a molecular mechanism for the higher risk of progression and severity of liver diseases conferred to patients carrying the I148M variant. (Hepatology 2017;65:1875-1890).

Genome-wide DNA methylation analysis in lung fibroblasts co-cultured with silica-exposed alveolar macrophages

Background

Exposure to crystalline silica is considered to increase the risk of lung fibrosis. The primary effector cell, the myofibroblast, plays an important role in the deposition of extracellular matrix (ECM). DNA methylation change is considered to have a potential effect on myofibroblast differentiation. Therefore, the present study was designed to investigate the genome-wide DNA methylation profiles of lung fibroblasts co-cultured with alveolar macrophages exposed to crystalline silica in vitro.

Methods

AM/fibroblast co-culture system was established. CCK8 was used to assess the toxicity of AMs. mRNA and protein expression of collagen I, α-SMA, MAPK9 and TGF-β1 of fibroblasts after AMs exposed to 100 μg /ml SiO₂ for 0–, 24–, or 48 h were determined by means of quantitative real-time PCR, immunoblotting and immunohistochemistry. Genomic DNA of fibroblasts was isolated using MeDIP-Seq to sequence. R software, GO, KEGG and Cytoscape were used to analyze the data.

Results

SiO₂ exposure increased the expression of collagen I and α-SMA in fibroblasts in co-culture system. Analysis of fibroblast methylome identified extensive methylation changes involved in several signaling pathways, such as the MAPK signaling pathway and metabolic pathways. Several candidates, including Tgfb1 and Mapk9, are hubs who can connect the gene clusters. MAPK9 mRNA expression was significantly higher in fibroblast exposed to SiO₂ in co-culture system for 48 h. MAPK9 protein expression was increased at both 24-h and 48-h treatment groups. TGF-β1 mRNA expression of fibroblast has a time-dependent manner, but we didn’t observe the TGF-β1 protein expression.

Conclusion

Tgfb1 and Mapk9 are helpful to explore the mechanism of myofibroblast differentiation. The genome-wide DNA methylation profiles of fibroblasts in this experimental silicosis model will be useful for future studies on epigenetic gene regulation during myofibroblast differentiation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-017-0576-z) contains supplementary material, which is available to authorized users.

TIMP-1 is upregulated, but not essential in hepatic fibrogenesis and carcinogenesis in mice

Tissue inhibitor of metalloproteinases-1 (TIMP-1) is upregulated during hepatic fibrogenesis and considered to promote fibrosis in the injured liver by inhibition of matrix metalloproteases (MMP) and degradation of extracellular matrix. Moreover, TIMP-1 displays anti-apoptotic properties, in patients with hepatocellular carcinoma (HCC) TIMP-1 serum levels are elevated and high TIMP-1 expression levels in HCC are associated with a poor prognosis. Therefore, TIMP-1 could functionally link fibrogenesis and carcinogenesis in the liver. The aim of our study was to characterize the role of TIMP-1 in hepatic fibrogenesis and carcinogenesis. Experimental hepatic fibrogenesis as well as diethylnitrosamine (DEN) -induced hepatocarcinogenesis were studied in TIMP-1-deficient mice and wild type littermates. Hepatic TIMP-1 expression was upregulated following induction of liver fibrosis by bile duct ligation (BDL) or by carbon tetrachloride (CCl₄). Unexpectedly, in comparison to wild type littermates, TIMP-1-deficient mice were not protected from liver fibrosis induced by BDL or CCl₄. TIMP-1 expression was significantly higher in HCC nodules than in surrounding liver tissue. However, experimental hepatic carcinogenesis was similar in TIMP-1-deficient mice and wild type littermates following DEN-treatment or combined treatment with DEN and CCl₄. Therefore we concluded that TIMP-1 is not essential for hepatic fibrogenesis and carcinogenesis in mice.

A small-molecule inhibitor of NF-κB-inducing kinase (NIK) protects liver from toxin-induced inflammation, oxidative stress, and injury

Potent and selective chemical probes are valuable tools for discovery of novel treatments for human diseases. NF-κB-inducing kinase (NIK) is a key trigger in the development of liver injury and fibrosis. Whether inhibition of NIK activity by chemical probes ameliorates liver inflammation and injury is largely unknown. In this study, a small-molecule inhibitor of NIK, B022, was found to be a potent and selective chemical probe for liver inflammation and injury. B022 inhibited the NIK signaling pathway, including NIK-induced p100-to-p52 processing and inflammatory gene expression, both in vitro and in vivo Furthermore, in vivo administration of B022 protected against not only NIK but also CCl4-induced liver inflammation and injury. Our data suggest that inhibition of NIK is a novel strategy for treatment of liver inflammation, oxidative stress, and injury.-Ren, X., Li, X., Jia, L., Chen, D., Hou, H., Rui, L., Zhao, Y., Chen, Z. A small-molecule inhibitor of NF-κB-inducing kinase (NIK) protects liver from toxin-induced inflammation, oxidative stress, and injury.

Management strategies for liver fibrosis

Liver fibrosis resulting from chronic liver injury are major causes of morbidity and mortality worldwide. Among causes of hepatic fibrosis, viral infection is most common (hepatitis B and C). In addition, obesity rates worldwide have accelerated the risk of liver injury due to nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). Also liver fibrosis is associated with the consumption of alcohol, or autoimmune hepatitis and chronic cholangiophaties. The response of hepatocytes to inflammation plays a decisive role in the physiopathology of hepatic fibrosis, which involves the recruitment of both pro- and anti-inflammatory cells such as monocytes and macrophages. As well as the production of other cytokines and chemokines, which increase the stimulus of hepatic stellate cells by activating proinflammatory cells. The aim of this review is to identify the therapeutic options available for the treatment of the liver fibrosis, enabling the prevention of progression when is detected in time.

Proteomics-Based Identification of the Molecular Signatures of Liver Tissues from Aged Rats following Eight Weeks of Medium-Intensity Exercise

Physical activity has emerged as a powerful intervention that promotes healthy aging by maintaining the functional capacity of critical organ systems. Here, by combining functional and proteomics analyses, we examined how hepatic phenotypes might respond to exercise treatment in aged rats. 16 male aged (20 months old) SD rats were divided into exercise and parallel control groups at random; the exercise group had 8 weeks of treadmill training with medium intensity. Whole protein samples of the liver were extracted from both groups and separated by two-dimensional gel electrophoresis. Alternatively objective protein spots with >2-fold difference in expression were selected for enzymological extraction and MS/MS identification. Results show increased activity of the manganese superoxide dismutase and elevated glutathione levels in the livers of exercise-treated animals, but malondialdehyde contents obviously decreased in the liver of the exercise group. Proteomics-based identification of differentially expressed proteins provided an integrated view of the metabolic adaptations occurring in the liver proteome during exercise, which significantly altered the expression of several proteins involved in key liver metabolic pathways including mitochondrial sulfur, glycolysis, methionine, and protein metabolism. These findings indicate that exercise may be beneficial to aged rats through modulation of hepatic protein expression profiles.

Hydroxylase inhibition regulates inflammation-induced intestinal fibrosis through the suppression of ERK-mediated TGF-β1 signaling. [corrected]

Fibrosis is a complication of chronic inflammatory disorders such as inflammatory bowel disease, a condition which has limited therapeutic options and often requires surgical intervention. Pharmacologic inhibition of oxygen-sensing prolyl hydroxylases, which confer oxygen sensitivity upon the hypoxia-inducible factor pathway, has recently been shown to have therapeutic potential in colitis, although the mechanisms involved remain unclear. Here, we investigated the impact of hydroxylase inhibition on inflammation-driven fibrosis in a murine colitis model. Mice exposed to dextran sodium sulfate, followed by a period of recovery, developed intestinal fibrosis characterized by alterations in the pattern of collagen deposition and infiltration of activated fibroblasts. Treatment with the hydroxylase inhibitor dimethyloxalylglycine ameliorated fibrosis. TGF-β1 is a key regulator of fibrosis that acts through the activation of fibroblasts. Hydroxylase inhibition reduced TGF-β1-induced expression of fibrotic markers in cultured fibroblasts, suggesting a direct role for hydroxylases in TGF-β1 signaling. This was at least in part due to inhibition of noncanonical activation of extracellular signal-regulated kinase (ERK) signaling. In summary, pharmacologic hydroxylase inhibition ameliorates intestinal fibrosis through suppression of TGF-β1-dependent ERK activation in fibroblasts. We hypothesize that in addition to previously reported immunosupressive effects, hydroxylase inhibitors independently suppress profibrotic pathways.

Inhibition of JNK suppresses autophagy and attenuates insulin resistance in a rat model of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a common chronic liver disease, the pathological process of which is complex. Activation of the c‑Jun N‑terminal kinase (JNK) signaling pathway is associated with the mechanism underlying obesity-induced insulin resistance. Furthermore, the JNK signaling pathway and dysfunctional autophagy serve important roles in hepatic lipid metabolism. However, the exact role of JNK in autophagy and obesity‑induced insulin resistance is not fully understood. Therefore, the present study aimed to investigate the underlying mechanisms by which the JNK signaling pathway regulates autophagy and insulin resistance in fatty liver. A rat model of NAFLD was established using a high‑fat diet (HFD), and insulin resistance in the livers of HFD rats was determined by peritoneal glucose tolerance testing. The results indicated that a HFD induced impaired glucose tolerance, liver function injury, insulin resistance and increased autophagy in rats. Treatment with SP600125, an inhibitor of JNK, relieved NAFLD in rats. Furthermore, SP600125 decreased the expression levels of autophagy-associated genes, including Beclin-1, microtubule-associated protein 1A/1B light chain 3, autophagy related gene (Atg)3 and Atg5, and the phosphorylation of insulin receptor (IR) β-subunit, IR substrate-1 and protein kinase B in vivo. In conclusion, JNK inhibition may suppress autophagy and attenuate insulin resistance. Therefore, JNK inhibition may provide a novel therapeutic strategy for the treatment of NAFLD.