Monocyte chemotactic protein-1 as a chemoattractant for human hepatic stellate cells

Ductular reaction in non-alcoholic fatty liver disease: When Macbeth is perverted

Non-alcoholic fatty liver disease (NAFLD) or metabolic (dysfunction)-associated fatty liver disease is the leading cause of chronic liver diseases defined as a disease spectrum comprising hepatic steatosis, non-alcoholic steatohepatitis (NASH), liver fibrosis, cirrhosis, and hepatic carcinoma. NASH, characterized by hepatocyte injury, steatosis, inflammation, and fibrosis, is associated with NAFLD prognosis. Ductular reaction (DR) is a common compensatory reaction associated with liver injury, which involves the hepatic progenitor cells (HPCs), hepatic stellate cells, myofibroblasts, inflammatory cells (such as macrophages), and their secreted substances. Recently, several studies have shown that the extent of DR parallels the stage of NASH and fibrosis. This review summarizes previous research on the correlation between DR and NASH, the potential interplay mechanism driving HPC differentiation, and NASH progression.

Protein phosphatases regulate the liver microenvironment in the development of hepatocellular carcinoma

The liver is a complicated heterogeneous organ composed of different cells. Parenchymal cells called hepatocytes and various nonparenchymal cells, including immune cells and stromal cells, are distributed in liver lobules with hepatic architecture. They interact with each other to compose the liver microenvironment and determine its characteristics. Although the liver microenvironment maintains liver homeostasis and function under healthy conditions, it also shows proinflammatory and profibrogenic characteristics that can induce the progression of hepatitis and hepatic fibrosis, eventually changing to a protumoral microenvironment that contributes to the development of hepatocellular carcinoma (HCC). According to recent studies, phosphatases are involved in liver diseases and HCC development by regulating protein phosphorylation in intracellular signaling pathways and changing the activities and characteristics of liver cells. Therefore, this review aims to highlight the importance of protein phosphatases in HCC development and in the regulation of the cellular components in the liver microenvironment and to show their significance as therapeutic targets.

Regulation and functional roles of chemokines in liver diseases

Inflammation is a major contributor to the pathogenesis of almost all liver diseases. Low-molecular-weight proteins called chemokines are the main drivers of liver infiltration by immune cells such as macrophages, neutrophils and others during an inflammatory response. During the past 25 years, tremendous progress has been made in understanding the regulation and functions of chemokines in the liver. This Review summarizes three main aspects of the latest advances in the study of chemokine function in liver diseases. First, we provide an overview of chemokine biology, with a particular focus on the genetic and epigenetic regulation of chemokine transcription as well as on the cell type-specific production of chemokines by liver cells and liver-associated immune cells. Second, we highlight the functional roles of chemokines in liver homeostasis and their involvement in progression to disease in both human and animal models. Third, we discuss the therapeutic opportunities targeting chemokine production and signalling in the treatment of liver diseases, such as alcohol-associated liver disease and nonalcoholic steatohepatitis, including the relevant preclinical studies and ongoing clinical trials.

Multidimensional Biomarker Analysis Including Mitochondrial Stress Indicators for Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is accompanied by a complex and multifactorial pathogenesis with sequential progressions from inflammation to fibrosis and then to cancer. This heterogeneity interferes with the development of precise diagnostic and prognostic strategies for NAFLD. The current approach for the diagnosis of simple steatosis, steatohepatitis, and cirrhosis mainly consists of ultrasonography, magnetic resonance imaging, elastography, and various serological analyses. However, individual dry and wet biomarkers have limitations demanding an integrative approach for the assessment of disease progression. Here, we review diagnostic strategies for simple steatosis, steatohepatitis and hepatic fibrosis, followed by potential biomarkers associated with fat accumulation and mitochondrial stress. For mitochondrial stress indicators, we focused on fibroblast growth factor 21 (FGF21), growth differentiation factor 15 (GDF15), angiopoietin-related growth factor and mitochondrial-derived peptides. Each biomarker may not strongly indicate the severity of steatosis or steatohepatitis. Instead, multidimensional analysis of different groups of biomarkers based on pathogenic mechanisms may provide decisive diagnostic/prognostic information to develop a therapeutic plan for patients with NAFLD. For this purpose, mitochondrial stress indicators, such as FGF21 or GDF15, could be an important component in the multiplexed and contextual interpretation of NAFLD. Further validation of the integrative evaluation of mitochondrial stress indicators combined with other biomarkers is needed in the diagnosis/prognosis of NAFLD.

SAA1/TLR2 axis directs chemotactic migration of hepatic stellate cells responding to injury

Hepatic stellate cells (HSCs) are crucial for liver injury repair and cirrhosis. However, the mechanism of chemotactic recruitment of HSCs into injury loci is still largely unknown. Here, we demonstrate that serum amyloid A1 (SAA1) acts as a chemokine recruiting HSCs toward injury loci signaling via TLR2, a finding proven by gene manipulation studies in cell and mice models. The mechanistic investigations revealed that SAA1/TLR2 axis stimulates the Rac GTPases through PI3K-dependent pathways and induces phosphorylation of MLC (pSer19). Genetic deletion of TLR2 and pharmacological inhibition of PI3K diminished the phosphorylation of MLCpSer19 and migration of HSCs. In brief, SAA1 serves as a hepatic endogenous chemokine for the TLR2 receptor on HSCs, thereby initiating PI3K-dependent signaling and its effector, Rac GTPases, which consequently regulates actin filament remodeling and cell directional migration. Our findings provide novel targets for anti-fibrosis drug development.

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SAA1 serves as a chemokine to guide migration of HSCs toward injury locus

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TLR2 acts as a functional receptor for SAA1 in HSCs

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SAA1/TLR2 axis-mediated migration of HSCs operates through PI3K/Rac1 signaling

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SAA1/TLR2 axis provides a link for the cross talk between hepatocytes and HSCs

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.

ACE2: from protection of liver disease to propagation of COVID-19

Twenty years ago, the discovery of angiotensin-converting enzyme 2 (ACE2) was an important breakthrough dramatically enhancing our understanding of the renin-angiotensin system (RAS). The classical RAS is driven by its key enzyme ACE and is pivotal in the regulation of blood pressure and fluid homeostasis. More recently, it has been recognised that the protective RAS regulated by ACE2 counterbalances many of the deleterious effects of the classical RAS. Studies in murine models demonstrated that manipulating the protective RAS can dramatically alter many diseases including liver disease. Liver-specific overexpression of ACE2 in mice with liver fibrosis has proved to be highly effective in antagonising liver injury and fibrosis progression. Importantly, despite its highly protective role in disease pathogenesis, ACE2 is hijacked by SARS-CoV-2 as a cellular receptor to gain entry to alveolar epithelial cells, causing COVID-19, a severe respiratory disease in humans. COVID-19 is frequently life-threatening especially in elderly or people with other medical conditions. As an unprecedented number of COVID-19 patients have been affected globally, there is an urgent need to discover novel therapeutics targeting the interaction between the SARS-CoV-2 spike protein and ACE2. Understanding the role of ACE2 in physiology, pathobiology and as a cellular receptor for SARS-CoV-2 infection provides insight into potential new therapeutic strategies aiming to prevent SARS-CoV-2 infection related tissue injury. This review outlines the role of the RAS with a strong focus on ACE2-driven protective RAS in liver disease and provides therapeutic approaches to develop strategies to prevent SARS-CoV-2 infection in humans.

Glycyrrhizin mediated liver-targeted alginate nanogels delivers quercetin to relieve acute liver failure

Acute liver failure is an uncommon and dramatic clinical syndrome with a high risk of mortality. Previous treatments existed some limitations of poor bioavailability and targeting the efficiency of drugs. In this study, a novel glycyrrhizin mediated liver-targeted alginate nanogels, which can deliver the antioxidant quercetin to the liver for the treatment of acute liver injury. In vitro radical scavenging results showed that the antioxidant activity of quercetin was increased 81-fold. The tissue distribution results indicated that glycyrrhizin-mediated nanogels showed stronger fluorescence intensity in the liver, which improved liver targeting and therapeutic efficacy. Quercetin-glycyrrhizin nanogels were more effective at restoring liver injury as indicated on serum markers, including alanine transaminase, aspartate aminotransferase, and total bilirubin. The histopathology result showed that quercetin-glycyrrhizin nanogels reversed liver damage. Oxidative parameters of malondialdehyde and glutathione s-transferase were decreased, which provided supporting evidence of antioxidation. Moreover, quercetin-glycyrrhizin nanogels were more effective in down-regulating the inflammation-related gene expression of tumor necrosis factor-α, interleukin-6, inducible nitric oxide synthase and monocyte chemotactic protein-1. In conclusion, the novel glycyrrhizin mediated liver-targeted alginate nanogels might be a promising treatment for acute liver failure.

Pericytes in the Liver

Liver pericytes, commonly named hepatic stellate cells (HSCs), reside in the space between liver sinusoidal endothelial cells (LSECs) and hepatocytes. They display important roles in health and disease. HSCs ensure the storage of the majority of vitamin A in a healthy body, and they represent the major source of fibrotic tissue in liver disease. Surrounding cells, such as LSECs, hepatocytes, and Kupffer cells, present a significant role in modulating HSC behavior. Therapeutic strategies against liver disease are being currently developed, where HSCs represent an ideal target. In this chapter, we will discuss HSC quiescence and activation in the context of healthy liver and diseases, such as fibrosis, steatohepatitis, and hepatocellular carcinoma.

Molecular pathways of nonalcoholic fatty liver disease development and progression

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

Chemokines and Chemokine Receptors in the Development of NAFLD

Chemokines are chemo-attractants for leukocyte trafficking, growth, and activation in injured and inflammatory tissues. The chemokine system is comprised of 50 chemokine ligands and 20 cognate chemokine receptors. In the context of liver diseases, leukocytes, hepatocytes, hepatic stellate cells, endothelial cells, and vascular smooth muscle cells are capable of producing chemokines. Chemokine receptors are typically expressed in various leukocyte subsets. Given that inflammation is a critical factor for the transition from simple steatosis to non-alcoholic steatohepatitis (NASH), and fibrosis, the chemokine system may play a prominent role in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Indeed, accumulating evidence shows elevated expression of chemokines and their receptors in the livers of obese patients with advanced steatosis and NASH. This chapter will discuss the underlying molecular mechanisms and the therapeutic potential of the chemokine systems in the pathogenesis of NAFLD. Among chemokines, we will highlight CCL2, CCL5, CXCL8-10, CX3CL1, and CXCL16 as pivotal mediators in the development of steatosis, NASH, and fibrosis.

CCR5, MCP-1 and VDR Gene Polymorphisms Are Associated with the Susceptibility to HBV Infection

Genetic variants of chemokine and regulatory cytokines play functional roles in chronic HBV infection. The objective of the study, was to evaluate the association between the CCR5D32, CCR5-2459A/G, MCP-1-2518A/G, VDR-APa1A/C, VDR-Taq1T/C SNPs and HBV susceptibility, in samples of Iranian populations. The CCR5D32, CCR5-2459A/G, MCP1-2518A/G, VDR-APa1A/C, VDR-Taq1T/C polymorphisms were analyzed by polymerase chain reaction and PCR-RFLP using 100 chronic HBV infected (HBV) patients, 40 spontaneously recovered HBV (SR) subjects and 100 healthy controls (C). Also, serum levels of protein were monitored. The study showed that the existence of CCR5-2459A, MCP1-2518G and VDR-CC alleles significantly increased risk of chronic HBV infection. In addition, WtAGCC haplotype had a higher frequency in HBV patients than C and SR groups and might relate to the natural history of the infection. Statistical analysis indicated positive correlations between CCR5-2459A/G, MCP1-2518A/G, VDR-APa1A/C, VDR-Taq1T/C genotypes and serum levels of the CCR5, MCP-1 and VDR in HBV patients. According to the statistical analysis, significant associations with susceptibility to chronic HBV infection was observed with CCR5-2459A/G, MCP1-2518A/G, VDR-APa1A/C, VDR-Taq1T/C polymorphisms. In addition, no association of the CCR5D32 SNP with the disease was found.

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.

The multifaceted roles of perlecan in fibrosis

Perlecan, or heparan sulfate proteoglycan 2 (HSPG2), is a ubiquitous heparan sulfate proteoglycan that has major roles in tissue and organ development and wound healing by orchestrating the binding and signaling of mitogens and morphogens to cells in a temporal and dynamic fashion. In this review, its roles in fibrosis are reviewed by drawing upon evidence from tissue and organ systems that undergo fibrosis as a result of an uncontrolled response to either inflammation or traumatic cellular injury leading to an over production of a collagen-rich extracellular matrix. This review focuses on examples of fibrosis that occurs in lung, liver, kidney, skin, kidney, neural tissues and blood vessels and its link to the expression of perlecan in that particular organ system.

The Intestinal Microbiome in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease is the most common cause of chronic liver disease in North America and is growing as a cause of chronic liver disease in many other parts of the world as well. It has 2 principal clinical-pathologic phenotypes: (1) nonalcoholic fatty liver and (2) nonalcoholic steatohepatitis. The development of both phenotypes is tightly linked to excess body weight and insulin resistance. This review discusses the emerging tools for the analysis of the microbiome, their limitations, and the existing literature with respect to the intestinal microbiome and their role in nonalcoholic fatty liver.

Relationship between hepatic progenitor cells and stellate cells in chronic hepatitis C genotype 4

Hepatitis C virus (HCV) infection represents a major health problem in many areas of the world, especially Egypt. Hepatic progenitor cells (HPCs) and hepatic stellate cells (HSCs) have been implicated in fibrosis progression in chronic HCV. The aim of this study was to investigate the role of HPCs and HSCs in chronic HCV infection and the relationship between both cell types. This retrospective study was conducted on 100 chronic HCV patients. Immunohistochemistry was performed on liver tissue sections for cytokeratin 19 (progenitor cell markers), smooth muscle actin (stellate cell markers), matrix metalloproteinase-9 (MMP-9), and transforming growth factor beta (TGF-ß). The necroinflammatory activity was significantly related to the number of isolated HPCs and TGF-ß expression (p = 0.003 and p = 0.001 respectively). Advanced stages of fibrosis showed significantly increase number of HPCs (p = 0.001), higher ratio of HSCs (p = 0.004), more expression of TGF-ß (p = 0.001) and MMP-9 (p = 0.001). There was a significant direct correlation between immunoexpression of HPCs and HSCs for isolated cells (r = 0.569, p = 0.001) and ductular reaction (r = 0.519, p = 0.001). Hepatic progenitor cells and stellate cells play a significant role in the development and progression of fibrosis in chronic HCV. More interestingly, the significant direct correlation between HPCs and HSCs suggests a synergistic interrelation.

Taurocholate Induces Biliary Differentiation of Liver Progenitor Cells Causing Hepatic Stellate Cell Chemotaxis in the Ductular Reaction: Role in Pediatric Cystic Fibrosis Liver Disease

Cystic fibrosis liver disease (CFLD) in children causes progressive fibrosis leading to biliary cirrhosis; however, its cause(s) and early pathogenesis are unclear. We hypothesized that a bile acid-induced ductular reaction (DR) drives fibrogenesis. The DR was evaluated by cytokeratin-7 immunohistochemistry in liver biopsies, staged for fibrosis, from 60 children with CFLD, and it demonstrated that the DR was significantly correlated with hepatic fibrosis stage and biliary taurocholate levels. To examine the mechanisms involved in DR induction, liver progenitor cells (LPCs) were treated with taurocholate, and key events in DR evolution were assessed: LPC proliferation, LPC biliary differentiation, and hepatic stellate cell (HSC) chemotaxis. Taurocholate induced a time-dependent increase in LPC proliferation and expression of genes associated with cholangiocyte differentiation (cytokeratin 19, connexin 43, integrin β4, and γ-glutamyltranspeptidase), whereas the hepatocyte specification marker HNF4α was suppressed. Functional cholangiocyte differentiation was demonstrated via increased acetylated α-tubulin and SOX9 proteins, the number of primary cilia⁺ LPCs, and increased active γ-glutamyltranspeptidase enzyme secretion. Taurocholate induced LPCs to release MCP-1, MIP1α, and RANTES into conditioned medium causing HSC chemotaxis, which was inhibited by anti-MIP1α. Immunofluorescence confirmed chemokine expression localized to CK7⁺ DR and LPCs in CFLD liver biopsies. This study suggests that taurocholate is involved in initiating functional LPC biliary differentiation and the development of the DR, with subsequent induction of chemokines that drive HSC recruitment in CFLD.

Ultrastructural Characteristics of Rat Hepatic Oval Cells and Their Intercellular Contacts in the Model of Biliary Fibrosis: New Insights into Experimental Liver Fibrogenesis

PURPOSE

Recently, it has been emphasized that hepatic progenitor/oval cells (HPCs) are significantly involved in liver fibrogenesis. We evaluated the multipotential population of HPCs by transmission electron microscope (TEM), including relations with adherent hepatic nonparenchymal cells (NPCs) in rats with biliary fibrosis induced by bile duct ligation (BDL).

METHODS

The study used 6-week-old Wistar Crl: WI(Han) rats after BDL for 1, 6, and 8 weeks.

RESULTS

Current ultrastructural analysis showed considerable proliferation of HPCs in experimental intensive biliary fibrosis. HPCs formed proliferating bile ductules and were scattered in periportal connective tissue. We distinguished 4 main types of HPCs: 0, I, II (bile duct-like cells; most common), and III (hepatocyte-like cells). We observed, very seldom presented in literature, cellular interactions between HPCs and adjacent NPCs, especially commonly found transitional hepatic stellate cells (T-HSCs) and Kupffer cells/macrophages. We showed the phenomenon of penetration of the basement membrane of proliferating bile ductules by cytoplasmic processes sent by T-HSCs and the formation of direct cell-cell contact with ductular epithelial cells related to HPCs.

CONCLUSIONS

HPC proliferation induced by BDL evidently promotes portal fibrogenesis. Better understanding of the complex cellular interactions between HPCs and adjacent NPCs, especially T-HSCs, may help develop antifibrotic therapies in the future.

Hepatic Stellate Cells in Liver Fibrosis and siRNA-Based Therapy

Hepatic fibrosis is a reversible wound-healing response to either acute or chronic liver injury caused by hepatitis B or C, alcohol, and toxic agents. Hepatic fibrosis is characterized by excessive accumulation and reduced degradation of extracellular matrix (ECM). Excessive accumulation of ECM alters the hepatic architecture leading to liver fibrosis and cirrhosis. Cirrhosis results in failure of common functions of the liver. Hepatic stellate cells (HSC) play a major role in the development of liver fibrosis as HSC are the main source of the excessive production of ECM in an injured liver. RNA interference (RNAi) is a recently discovered therapeutic tool that may provide a solution to manage multiple diseases including liver fibrosis through silencing of specific gene expression in diseased cells. However, gene silencing using small interfering RNA (siRNA) is encountering many challenges in the body after systemic administration. Efficient and stable siRNA delivery to the target cells is a key issue for the development of siRNA therapeutic. For that reason, various viral and non-viral carriers for liver-targeted siRNA delivery have been developed. This review will cover the current strategies for the treatment of liver fibrosis as well as discussing non-viral approaches such as cationic polymers and lipid-based nanoparticles for targeted delivery of siRNA to the liver.

Protective effect of human serum amyloid P on CCl4-induced acute liver injury in mice

Human serum amyloid P (hSAP), a member of the pentraxin family, inhibits the activation of fibrocytes in culture and inhibits experimental renal, lung, skin and cardiac fibrosis. As hepatic inflammation is one of the causes of liver fibrosis, in the present study, we investigated the hepatoprotective effects of hSAP against carbon tetrachloride (CCl₄)-induced liver injury. Our data indicated that hSAP attenuated hepatic histopathological abnormalities and significantly decreased inflammatory cell infiltration and pro-inflammatory factor expression. Moreover, CCl₄-induced apoptosis in the mouse liver was inhibited by hSAP, as measured by terminal-deoxynucleotidyl transferase mediated nick-end labeling (TUNEL) assay and cleaved caspase-3 expression. hSAP significantly restored the expression of B cell lymphoma/leukemia (Bcl)-2 and suppressed the expression of Bcl-2-associated X protein (Bax) in vivo. The number of hepatocytes in early apoptosis stained with Annexin V was significantly reduced by 28–30% in the hSAP treatment group compared with the CCl₄ group, and the expression of Bcl-2 was increased, whereas the expression of Bax and cleaved caspase-3 were significantly inhibited in the hSAP pre-treatment group compared with the CCl₄ group. hSAP administration also inhibited the migration and activation of hepatic stellate cells (HSCs) in CCl₄-injured liver and suppressed the activation of isolated primary HSCs induced by transforming growth factor (TGF)-β1 in vitro. Collectively, these findings suggest that hSAP exerts a protective effect againts CCl₄-induced hepatic injury by suppressing the inflammatory response and hepatocyte apoptosis, potentially by inhibiting HSC activation.

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).

Functional Immune Anatomy of the Liver-As an Allograft

The liver is an immunoregulatory organ in which a tolerogenic microenvironment mitigates the relative "strength" of local immune responses. Paradoxically, necro-inflammatory diseases create the need for most liver transplants. Treatment of hepatitis B virus, hepatitis C virus, and acute T cell-mediated rejection have redirected focus on long-term allograft structural integrity. Understanding of insults should enable decades of morbidity-free survival after liver replacement because of these tolerogenic properties. Studies of long-term survivors show low-grade chronic inflammatory, fibrotic, and microvascular lesions, likely related to some combination of environment insults (i.e. abnormal physiology), donor-specific antibodies, and T cell-mediated immunity. The resultant conundrum is familiar in transplantation: adequate immunosuppression produces chronic toxicities, while lightened immunosuppression leads to sensitization, immunological injury, and structural deterioration. The "balance" is more favorable for liver than other solid organ allografts. This occurs because of unique hepatic immune physiology and provides unintended benefits for allografts by modulating various afferent and efferent limbs of allogenic immune responses. This review is intended to provide a better understanding of liver immune microanatomy and physiology and thereby (a) the potential structural consequences of low-level, including allo-antibody-mediated injury; and (b) how liver allografts modulate immune reactions. Special attention is given to the microvasculature and hepatic mononuclear phagocytic system.

Serum Amyloid A Induces Inflammation, Proliferation and Cell Death in Activated Hepatic Stellate Cells

Serum amyloid A (SAA) is an evolutionary highly conserved acute phase protein that is predominantly secreted by hepatocytes. However, its role in liver injury and fibrogenesis has not been elucidated so far. In this study, we determined the effects of SAA on hepatic stellate cells (HSCs), the main fibrogenic cell type of the liver. Serum amyloid A potently activated IκB kinase, c-Jun N-terminal kinase (JNK), Erk and Akt and enhanced NF-κB-dependent luciferase activity in primary human and rat HSCs. Serum amyloid A induced the transcription of MCP-1, RANTES and MMP9 in an NF-κB- and JNK-dependent manner. Blockade of NF-κB revealed cytotoxic effects of SAA in primary HSCs with signs of apoptosis such as caspase 3 and PARP cleavage and Annexin V staining. Serum amyloid A induced HSC proliferation, which depended on JNK, Erk and Akt activity. In primary hepatocytes, SAA also activated MAP kinases, but did not induce relevant cell death after NF-κB inhibition. In two models of hepatic fibrogenesis, CCl₄ treatment and bile duct ligation, hepatic mRNA levels of SAA1 and SAA3 were strongly increased. In conclusion, SAA may modulate fibrogenic responses in the liver in a positive and negative fashion by inducing inflammation, proliferation and cell death in HSCs.

Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) increases human hepatic stellate cell activation

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a halogenated aromatic hydrocarbon that elicits toxicity through the aryl hydrocarbon receptor (AhR). In the liver, gross markers of TCDD toxicity are attributed to AhR activation in parenchymal hepatocytes. However, less is known regarding the consequences of TCDD treatment on non-parenchymal cells in the liver. Hepatic stellate cells (HSCs) are non-parenchymal cells that store vitamin A when quiescent. Upon liver injury, activated HSCs lose this storage ability and instead function in the development and maintenance of inflammation and fibrosis through the production of pro-inflammatory mediators and collagen type I. Reports that TCDD exposure disrupts hepatic retinoid homeostasis and dysregulates extracellular matrix remodeling in the liver led us to speculate that TCDD treatment may disrupt HSC activity. The human HSC line LX-2 was used to test the hypothesis that TCDD treatment directly activates HSCs. Results indicate that exposure to 10nM TCDD almost completely inhibited lipid droplet storage in LX-2 cells cultured with retinol and palmitic acid. TCDD treatment also increased LX-2 cell proliferation, expression of α-smooth muscle actin, and production of monocyte chemoattractant protein-1 (MCP-1), all of which are characteristics of activated HSCs. However, TCDD treatment had no effect on Col1a1 mRNA levels in LX-2 cells stimulated with the potent profibrogenic mediator, transforming growth factor-β. The TCDD-mediated increase in LX-2 cell proliferation, but not MCP-1 production, was abolished when phosphoinositide 3-kinase was inhibited. These results indicate that HSCs are susceptible to direct modulation by TCDD and that TCDD likely increases HSC activation through a multi-faceted mechanism.

Non-Canonical Wnt Predominates in Activated Rat Hepatic Stellate Cells, Influencing HSC Survival and Paracrine Stimulation of Kupffer Cells

The Wnt system is highly complex and is comprised of canonical and non-canonical pathways leading to the activation of gene expression. Our aim was to examine changes in the expression of Wnt ligands and regulators during hepatic stellate cell (HSC) transdifferentiation and assess the relative contributions of the canonical and non-canonical Wnt pathways in fibrogenic activated HSC. The expression profile of Wnt ligands and regulators in HSC was not supportive for a major role for β-catenin-dependent canonical Wnt signalling, this verified by inability to induce Topflash reporter activity in HSC even when expressing a constitutive active β-catenin. We detected expression of Wnt5a in activated HSC which can signal via non-canonical mechanisms and showed evidence for non-canonical signalling in these cells involving phosphorylation of Dvl2 and pJNK. Stimulation of HSC or Kupffer cells with Wnt5a regulated HSC apoptosis and expression of TGF-β1 and MCP1 respectively. We were unable to confirm a role for β-catenin-dependent canonical Wnt in HSC and instead propose autocrine and paracrine functions for Wnts expressed by activated HSC via non-canonical pathways. The data warrant detailed investigation of Wnt5a in liver fibrosis.

Hepatic progenitor cells in children with chronic hepatitis C: correlation with histopathology, viremia, and treatment response

OBJECTIVE

Hepatic progenitor cells (HPCs) are bipotential stem cells that can differentiate towards the hepatocytic and cholangiocytic lineages. Many studies have investigated HPCs in adults with hepatitis C virus infection; however, none has been carried out in the pediatric population. Therefore, this work aimed to investigate HPCs expansion in children with chronic hepatitis C (CHC) and its correlation with histopathology, viremia, and treatment response.

PATIENTS AND METHODS

Eighty children with CHC, 73 of whom received interferon-based therapy, were recruited. Sections of their liver biopsies were prepared for immunostaining of HPCs using cytokeratin-7 antibody.

RESULTS

HPCs were expanded in most children (81.3%) with CHC. Expansion occurred in two forms: intraparenchymal isolated hepatic progenitor cell form and periportal ductular reaction form. There was a significant increase in HPCs expansion in higher stages of fibrosis (50, 81.8, and 100% in no, mild, and moderate fibrosis, respectively, with P=0.029). Also, HPCs expansion increased with increased grade of necroinflammatory activity (0, 77.8, 81.8, and 100%, in no, minimal, mild, and moderate activity, respectively), although this was statistically insignificant. Moreover, a significant positive correlation was found between the isolated hepatic progenitor cell number and ductular reaction grade (r=0.755, P<0.0001), and both were significantly correlated with the level of viremia and the grade of necroinflammatory activity. Finally, HPCs expansion was not related to the treatment response.

CONCLUSION

The relationship of HPCs with both the severity of hepatitis and the stage of fibrosis may be because of a role of HPCs in their pathogenesis.

P311 modulates hepatic stellate cells migration

BACKGROUND & AIMS

Liver fibrosis is induced by the accumulation of extracellular matrix, deposited mainly by activated hepatic stellate cells (HSCs). One key characteristic of stellate cell activation is the directional migration to the site of injury during the wound-healing process. P311 is a protein that has been shown to play a role in migration and we aimed to study a possible role for this protein during stellate cell migration.

METHODS

Mouse stellate cells were isolated and cultured in vitro to investigate P311 protein and gene expression during HSC activation by immunocytochemistry and RT-qPCR respectively. Expression of P311 during in vivo activation was evaluated in CCl4 and bile duct ligation-induced liver fibrosis. Production of reactive oxygen species was determined using the fluorescent probe DCFH-DA. By siRNA-mediated knockdown of P311, we investigated a possible effect on proliferation by incorporation of EdU and on migration by Boyden chamber assays.

RESULTS

P311 gene expression was increased during both in vitro and in vivo activation of HSCs. siRNA-mediated knockdown led to a decrease in reactive oxygen production and cell proliferation. Migration induced by different chemokines, such as PDGF-bb and MCP-1 was inhibited by knockdown of P311.

CONCLUSIONS

P311 is central to reactive oxygen species-mediated HSC migration induced by different chemokines.

Antifibrotic effects of luteolin on hepatic stellate cells and liver fibrosis by targeting AKT/mTOR/p70S6K and TGFβ/Smad signalling pathways

BACKGROUND & AIMS

Luteolin has been reported to exert antifibrogenic effects in CCl4 -induced hepatic fibrosis in mice. However, limited information is available on the cellular and molecular events responsible for this effect. This study focused on the action of luteolin on hepatic stellate cells (HSCs) and the relevant signalling molecules and pathways as well as the antifibrotic efficacy in multiple models of fibrosis.

METHODS

The in vitro effect of luteolin on rat HSCs and HSC-T6 cells was assessed using proliferation assays, invasion chamber, quantitative real-time PCR analysis and Western blotting. The in vivo effect of luteolin on progression of fibrosis was assessed in three experimental rat models induced by CCl4 , dimethylnitrosamine (DMN) and bile duct ligation (BDL).

RESULTS

Luteolin inhibited proliferation, migration, collagen synthesis as well as expression of fibrosis-related genes in the activated HSCs and HSC-T6 cells stimulated with or without transforming growth factor-β1(TGFβ1) or platelet-derived growth factor (PDGF). Luteolin induced HSC apoptosis associated with the increased caspase 3 activity and p53 expression, and induced G1 arrest with the decreased expression of bcl-2, Cyclin E and p-Cdk-2. Moreover, luteolin significantly inhibited PDGF and TGFβ1-simulated phosphorylation of AKT and Smad pathway. In vivo study showed that luteolin administration markedly alleviated hepatic fibrosis along with reduced elevations of alanine aminotransferase and aspartate aminotransferase. HSCs were found to undergo apoptosis and decreased expression of p-Smad2 and p-AKT in luteolin-treated animals.

CONCLUSIONS

This study demonstrates that luteolin prevents the progression of liver fibrosis through multiple mechanisms and indicates that luteolin has potential for effective treatment of liver fibrosis.

Role of C-C motif ligand 2 and C-C motif receptor 2 in murine pulmonary graft-versus-host disease after lipopolysaccharide inhalations

Environmental exposures are a potential trigger of chronic pulmonary graft-versus-host disease (pGVHD) after successful recovery from hematopoietic cell transplant (HCT). We hypothesized that inhalations of LPS, a prototypic environmental stimulus, trigger pGVHD via increased pulmonary recruitment of donor-derived antigen-presenting cells (APCs) through the C-C motif ligand 2 (CCL2)-C-C motif receptor 2 (CCR2) chemokine axis. B10.BR(H2(k)) and C57BL/6(H2(b)) mice underwent allogeneic (Allo) or syngeneic (Syn) HCT with wild-type (WT) C57BL/6, CCL2(-/-), or CCR2(-/-) donors. After 4 weeks, recipient mice received daily inhaled LPS for 5 days and were killed at multiple time points. Allo mice exposed to repeated inhaled LPS developed prominent lymphocytic bronchiolitis, similar to human pGVHD. The increase in pulmonary T cells in Allo mice after LPS exposures was accompanied by increased CCL2, CCR2, and Type-1 T-helper cytokines as well as by monocytes and monocyte-derived dendritic cells (moDCs) compared with Syn and nontransplanted controls. Using CCL2(-/-) donors leads to a significant decrease in lung DCs but to only mildly reduced CD4 T cells. Using CCR2(-/-) donors significantly reduces lung DCs and moDCs but does not change T cells. CCL2 or CCR2 deficiency does not alter pGVHD pathology but increases airway hyperreactivity and IL-5 or IL-13 cytokines. Our results show that hematopoietic donor-derived CCL2 and CCR2 regulate recruitment of APCs to the Allo lung after LPS exposure. Although they do not alter pathologic pGVHD, their absence is associated with increased airway hyperreactivity and IL-5 and IL-13 cytokines. These results suggest that the APC changes that result from CCL2-CCR2 blockade may have unexpected effects on T cell differentiation and physiologic outcomes in HCT.

Analysis of the intrahepatic ductular reaction and progenitor cell responses in hepatitis C virus recurrence after liver transplantation

Fibrosis in livers with hepatitis C virus (HCV) recurrence after liver transplantation (LT) can be rapidly progressive, and the mechanisms underlying this process are poorly understood. In livers with HCV infections in the non-LT setting, there is a significant relationship between the development of structures known as the ductular reaction (DR), hepatic progenitor cells (HPCs), and fibrosis. This study characterizes the DR, HPCs, and fibrosis associated with HCV recurrence after LT. Immunohistochemistry and confocal microscopy were used to characterize the DR, HPC, and fibrosis in liver biopsy specimens. Key findings were confirmed in a separate, independent cohort. The initial characterization cohort had 194 biopsy samples from 105 individuals with HCV recurrence after LT. The immunophenotype, morphology, and location of the DR were consistent with an HPC origin. The DR correlated with intrahepatic fibrosis (rs  = 0.529, P < 0.001) and the number of activated hepatic stellate cells (HSCs; rs  = 0.446, P < 0.001). There was an early occurrence of hepatocyte replicative arrest as well as increased hepatocyte proliferation that correlated with the DR (rs  = 0.295, P < 0.001). Replicative arrest preceded hepatocyte proliferation in early-stage injury. Hepatocyte proliferation decreased with advanced fibrosis; in contrast, the extent of the DR and the number of activated HSCs continued to increase. In the second cohort of 37 individuals, the DR and the number of HPCs similarly correlated with fibrosis and inflammation after LT. In conclusion, this is the first characterization of the DR in HCV-associated liver injury after LT. There was a significant correlation between the DR and the development of progressive fibrosis in HCV recurrence. These results suggest a pivotal role for both the DR and the HPC responses in the aggressive fibrosis seen with HCV recurrence after LT.

Hepatic stellate cells and liver fibrosis

Hepatic stellate cells are resident perisinusoidal cells distributed throughout the liver, with a remarkable range of functions in normal and injured liver. Derived embryologically from septum transversum mesenchyme, their precursors include submesothelial cells that invade the liver parenchyma from the hepatic capsule. In normal adult liver, their most characteristic feature is the presence of cytoplasmic perinuclear droplets that are laden with retinyl (vitamin A) esters. Normal stellate cells display several patterns of intermediate filaments expression (e.g., desmin, vimentin, and/or glial fibrillary acidic protein) suggesting that there are subpopulations within this parental cell type. In the normal liver, stellate cells participate in retinoid storage, vasoregulation through endothelial cell interactions, extracellular matrix homeostasis, drug detoxification, immunotolerance, and possibly the preservation of hepatocyte mass through secretion of mitogens including hepatocyte growth factor. During liver injury, stellate cells activate into alpha smooth muscle actin-expressing contractile myofibroblasts, which contribute to vascular distortion and increased vascular resistance, thereby promoting portal hypertension. Other features of stellate cell activation include mitogen-mediated proliferation, increased fibrogenesis driven by connective tissue growth factor, and transforming growth factor beta 1, amplified inflammation and immunoregulation, and altered matrix degradation. Evolving areas of interest in stellate cell biology seek to understand mechanisms of their clearance during fibrosis resolution by either apoptosis, senescence, or reversion, and their contribution to hepatic stem cell amplification, regeneration, and hepatocellular cancer.

Selective α1B- and α1D-adrenoceptor antagonists suppress noradrenaline-induced activation, proliferation and ECM secretion of rat hepatic stellate cells in vitro

AIM

To explore the effects of noradrenaline (NA) on hepatic stellate cells (HSCs) in vitro and to determine the adrenoceptor (AR) subtypes and underlying mechanisms.

METHODS

The distribution and expressions of α1A-, α1B-, and α1D-ARs in HSC-T6 cells were analyzed using immunocytochemistry and RT-PCR. Cell proliferation was evaluated with MTT assay. The expression of HSC activation factors [transforming factor-β1 (TGF-β1) and α-smooth muscle actin (α-SMA)], extracellular matrix (ECM) secretion factors [tissue inhibitor of metalloproteinase-1 (TIMP-1) and collagen-Ι (ColΙ)] and PKC-PI3K-AKT signaling components (PKC, PI3K, and AKT) in the cells were detected by Western blotting and RT-PCR.

RESULTS

Both α1B- and α1D-AR were expressed in the membrane of HSC-T6 cells, whereas α1A-AR was not detected. Treatment of the cells with NA concentration-dependently increased cell proliferation (EC50=277 nmol/L), which was suppressed by the α1B-AR antagonist CEC or by the α1D-AR antagonist BMY7378. Furthermore, NA (0.001, 0.1, and 10 μmol/L) concentration-dependently increased the expression of TGF-β1, α-SMA, TIMP-1 and ColΙ, PKC and PI3K, and phosphorylation of AKT in HSC-T6 cells, which were suppressed by CEC or BMY7378, or by pertussis toxin (PT), RO-32-0432 (PKC antagonist), LY294002 (PI3K antagonist) or GSK690693 (AKT antagonist).

CONCLUSION

NA promotes HSC-T6 cell activation, proliferation and secretion of ECM in vitro via activation of Gα-coupled α1B-AR and α1D-AR and the PKC-PI3K-AKT signaling pathway.

Roles for chemokines in liver disease

Sustained hepatic inflammation is an important factor in progression of chronic liver diseases, including hepatitis C or non-alcoholic steatohepatitis. Liver inflammation is regulated by chemokines, which regulate the migration and activities of hepatocytes, Kupffer cells, hepatic stellate cells, endothelial cells, and circulating immune cells. However, the effects of the different chemokines and their receptors vary during pathogenesis of different liver diseases. During development of chronic viral hepatitis, CCL5 and CXCL10 regulate the cytopathic versus antiviral immune responses of T cells and natural killer cells. During development of nonalcoholic steatohepatitis, CCL2 and its receptor are up-regulated in the liver, where they promote macrophage accumulation, inflammation, fibrosis, and steatosis, as well as in adipose tissue. CCL2 signaling thereby links hepatic and systemic inflammation related to metabolic disorders and insulin resistance. Several chemokine signaling pathways also promote hepatic fibrosis. Recent studies have shown that other chemokines and immune cells have anti-inflammatory and antifibrotic activities. Chemokines and their receptors can also contribute to the pathogenesis of hepatocellular carcinoma, promoting proliferation of cancer cells, the inflammatory microenvironment of the tumor, evasion of the immune response, and angiogenesis. We review the roles of different chemokines in the pathogenesis of liver diseases and their potential use as biomarkers or therapeutic targets.

Chronic permanent hypoxemia predisposes to mild elevation of liver stiffness

AIM: To evaluate the impact of long term permanent hypoxemia noticed in patients with non operated congenital cyanogenic cyanotic cardiopathy on liver stiffness.

METHODS: We included ten adult patients with non operated inoperate cyanotic cardiopathy and ten matched patients for age and gender admitted to the gastroenterology department for proctologic diseases; Clinical and laboratory data were collected [age, gender, body mass index, oxygen saturation, glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT), glycemia and cholesterol]. Measurement of hepatic stiffness by transient elastography was carried out in all patients using the Fibroscan device. All patients underwent an echocardiography to eliminate congestive heart failure.

RESULTS: Among the patients with cyanotic cardiopathy, median liver stiffness 5.9 ± 1.3 kPa was greater than control group (4.7 ± 0.4 kPa) (P = 0.008). Median levels of GOT, GPT, gamma-glutamyltransferase, glycemia and cholesterol were comparable in cardiopathy and control group. In regression analysis including age, gender, body mass index, oxygen saturation, GOT, GPT, glycemia, cholesterol showed that only oxygen saturation was related to liver stiffness (r = -0.63 P = 0.002).

CONCLUSION: Chronic permanent hypoxemia can induce mild increase of liver stiffness, but further studies are needed to explore the histological aspects of liver injury induced by chronic permanent hypoxemia.

Strain dependence of diet-induced NASH and liver fibrosis in obese mice is linked to diabetes and inflammatory phenotype

BACKGROUND & AIMS

Obese Alms1 mutant (foz/foz) NOD.B10 mice develop diabetes and fibrotic NASH when fed high-fat(HF) diet. To establish whether diabetes or obesity is more closely associated with NASH fibrosis, we compared diabetic foz/foz C57BL6/J with non-diabetic foz/foz BALB/c mice. We also determined hepatic cytokines, growth factors and related profibrotic pathways.

METHODS

Male and female foz/foz BALB/c and C57BL6/J mice were fed HF or chow for 24 weeks before determining metabolic indices, liver injury, cytokines, growth factors, pathology/fibrosis and matrix deposition pathways.

RESULTS

All foz/foz mice were obese. Hepatomegaly, hyperinsulinemia, hyperglycaemia and hypoadiponectinaemia occurred only in foz/foz C57BL6/J mice, whereas foz/foz BALB/c formed more adipose. Serum ALT, steatosis, ballooning, liver inflammation and NAFLD activity score were worse in C57BL6/J mice. In HF-fed mice, fibrosis was severe in foz/foz C57BL6/J, appreciable in WT C57BL6/J, but absent in foz/foz BALB/c mice. Hepatic mRNA expression of TNF-α, IL-12, IL-4, IL-10 was increased (but not IFN-γ, IL-1β, IL-17A), and IL-4:IFN-γ ratio (indicating Th-2 predominance) was higher in HF-fed foz/foz C57BL6/J than BALB/c mice. In livers of HF-fed foz/foz C57BL6/J mice, TGF-β was unaltered but PDGFα and CTGF were increased in association with enhanced α-SMA, CD147and MMP activity.

CONCLUSIONS

In mice with equivalent genetic/dietary obesity, NASH development is linked to strain differences in hyperinsulinaemia and hyperglycaemia inversely related to lipid partitioning between adipose and liver. Diabetes-mediated CTGF-regulation of MMPs as well as cytokines/growth factors (Th-2 cytokine predominant, PDGFα, not TGF-β) mobilized in the resultant hepatic necroinflammatory change may contribute to strain differences in NASH fibrosis.

CCL2 mediates anti-fibrotic effects in human fibroblasts independently of CCR2

CCL2 is known for its major role as a chemoattractant of monocytes for immunological surveillance and to site of inflammation. CCL2 acts mainly through the G-protein-coupled receptor CCR2 but has also been described to mediate its effects independently of this receptor in vitro and in vivo. Emerging pieces of evidence indicate that the CCL2/CCR2 axis is involved in fibrotic diseases, such as increased plasma levels of CCL2 and the presence of CCL2-hyperresponsive fibroblasts explanted from patients with systemic sclerosis and idiopathic pulmonary fibrosis. One of the profibrotic key mediators is the myofibroblast characterized by overexpression of α-smooth muscle actin and collagen I. However, the correlation between the CCL2/CCR2 axis and the activation of fibroblasts is not yet fully understood. We have screened human fibroblasts of various origins, human pulmonary fibroblasts (HPF), human fetal lung fibroblasts (HFL-1) and primary preadipocytes (SPF-1) in regard to CCL2 stimulated fibrotic responses. Surprisingly we found that CCL2 mediates anti-fibrotic effects independently of CCR2 in human fibroblasts of different origins.

Hepatic stellate cells promote tumor progression by enhancement of immunosuppressive cells in an orthotopic liver tumor mouse model

The immunosuppressive properties of hepatic stellate cells (HSCs) contribute to the occurrence and development of hepatocellular carcinoma (HCC). The accumulation of cells with immune suppressive activities, such as myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs) is a key mechanism for tumor immune evasion. However, the impact of HSCs on immune cell populations in tumor-bearing hosts is unclear. In this study, we established an orthotopic liver tumor mouse model for studying the complex tumor-host interactions in HCC. The activated HSCs promoted HCC growth not only induced tumor angiogenesis and lymphangiogenesis, but also significantly increased the suppressive immune cell population of Tregs and MDSCs in the spleen, bone marrow, and tumor tissues of the tumor-bearing mice. Murine HCC cell line H22-activated HSCs also expanded the expression of Tregs and MDSCs in vitro. In conclusion, our study suggests a novel role for HSCs in the HCC microenvironment. HSCs can promote HCC progression by enhancement of the immunosuppressive cell population. Targeting HSCs, which is a new concept in adjuvant immunotherapy, may be introduced in the near future to improve the outcome of patients with HCC.

Hepatic stellate cells that coexpress LRAT and CRBP-1 partially contribute to portal fibrogenesis in patients with human viral hepatitis

BACKGROUND & AIMS

Precisely what type of cells mainly contributes to portal fibrosis, especially in chronic viral hepatitis, such as hepatic stellate cells (HSCs) in the parenchyma or myofibroblasts in the portal area, still remains unclear. It is necessary to clarify the characteristics of cells that contribute to portal fibrosis in order to determine the mechanism of portal fibrogenesis and to develop a therapeutic target for portal fibrosis. This study was undertaken to examine whether LRAT+/CRBP-1+ HSCs contribute to portal fibrosis on viral hepatitis.

METHODS

Antibodies to lecithin:retinol acyltransferase (LRAT), cellular retinol-binding protein-1 (CRBP-1) and widely ascertained antibodies to HSCs (alpha-smooth muscle actin, neurotrophin-3) and endothelial cells (CD31) were used for immunohistochemical studies to assess the distribution of cells that contribute to the development of portal fibrosis with the aid of fluorescence microscopy. A quantitative analysis of LRAT+/CRBP-1+ HSCs was performed.

RESULTS

The number of LRAT+/CRBP-1+ HSCs was increased in fibrotic liver in comparison with normal liver in the portal area and fibrous septa. The number of double positive cells was less than 20% of all cells/field in maximum.

CONCLUSION

This study provides evidence that functional HSCs coexpressing both LRAT and CRBP-1 that continue to maintain the ability to store vitamin A contribute in part to the development of portal fibrogenesis in addition to parenchymal fibrogenesis in patients with viral hepatitis.

Hepatitis C virus-induced changes in microRNA 107 (miRNA-107) and miRNA-449a modulate CCL2 by targeting the interleukin-6 receptor complex in hepatitis

Hepatitis C virus (HCV)-mediated liver diseases are one of the major health issues in the United States and worldwide. HCV infection has been reported to modulate microRNAs (miRNAs) that control various cell surface receptors and gene-regulatory complexes involved in hepatic inflammation and liver diseases. We report here that specific downregulation of miRNA-107 and miRNA-449a following HCV infection in patients with HCV-mediated liver diseases modulates expression of CCL2, an inflammatory chemokine upregulated in patients with chronic liver diseases, by targeting components of the interleukin-6 receptor (IL-6R) complex. Computational analysis for DNA-bound transcription factors in the CCL2 promoter identified adjacent binding sites for CCAAT/CEBPα, spleen focus-forming virus, proviral integration oncogene (SPI1/PU.1), and STAT3. We demonstrate that CEBPα, PU.1, and STAT3 interacted with each other physically to cooperatively bind to the promoter and activate CCL2 expression. Analysis of IL-6R and JAK1 expression in HCV patients by quantitative PCR showed significant upregulation when there was impaired miRNA-107 and miRNA-449a expression, along with upregulation of PU.1 and STAT3, but not CEBPα. miRNA-449a and miRNA-107 target expression of IL-6R and JAK1, respectively, in vitro and also inhibit IL-6 signaling and impair STAT3 activation in human hepatocytes. Taken together, our results demonstrate a novel gene-regulatory mechanism in which HCV-induced changes in miRNAs (miRNA-449a and miRNA-107) regulate CCL2 expression by activation of the IL-6-mediated signaling cascade, which we propose will result in HCV-mediated induction of inflammatory responses and fibrosis.

IMPORTANCE

Hepatitis C virus (HCV)-induced hepatitis is a major health concern worldwide. HCV infection results in modulation of noncoding microRNAs affecting major cellular pathways, including inflammatory responses. In this study, we have identified a microRNA-regulated pathway for the chemokine CCL2 in HCV-induced hepatitis. Understanding microRNA-mediated transcriptional-regulatory pathways will result in development of noninvasive biomarkers for better disease prediction and development of effective therapeutics.

Kupffer Cells in Health and Disease

Kupffer cells (KC), the resident macrophages of the liver, represent the largest population of mononuclear phagocytes in the body. Phenotypic, developmental, and functional aspects of these cells in steady state and in different diseases are the focus of this review. Recently it has become evident that KC precursors seed the liver already early in fetal development, and the population can be maintained independently from circulating monocytes. However, inflammatory conditions allow rapid differentiation of monocytes into mature cells that are indistinguishable from genuine KC. KC are located in the lumen of sinusoids that receive blood both from the portal vein, carrying nutrients and microbial products from the gut, and from the hepatic artery. This positions KC ideally for their prime function, namely surveillance and clearance of the circulation. As such, they are important in iron recycling by phagocytosing effete erythrocytes, for instance. The immunophenotype of KC, characterized by a wide variety of endocytic receptors, is indicative of this scavenger function. In maintaining homeostasis, KC have an ambivalent response to exogenous triggers. On the one hand, their surveillance function requires alert responses to potentially hazardous substances. On the other hand, continuous exposure of the cells to the trigger-rich content of blood originating from the gut dampens their responsiveness to further stimuli. This ambivalence is also reflected in their diverse roles in disease pathogenesis. For the latter, we sketch the contribution of KC by giving examples of their role in metabolic disease, infections, and liver injury.

Transforming growth factor-β and toll-like receptor-4 polymorphisms are not associated with fibrosis in haemochromatosis

AIM: To investigate the role of genetic polymorphisms in the progression of hepatic fibrosis in hereditary haemochromatosis.

METHODS: A cohort of 245 well-characterised C282Y homozygous patients with haemochromatosis was studied, with all subjects having liver biopsy data and DNA available for testing. This study assessed the association of eight single nucleotide polymorphisms (SNPs) in a total of six genes including toll-like receptor 4 (TLR4), transforming growth factor-beta (TGF-β), oxoguanine DNA glycosylase, monocyte chemoattractant protein 1, chemokine C-C motif receptor 2 and interleukin-10 with liver disease severity. Genotyping was performed using high resolution melt analysis and sequencing. The results were analysed in relation to the stage of hepatic fibrosis in multivariate analysis incorporating other cofactors including alcohol consumption and hepatic iron concentration.

RESULTS: There were significant associations between the cofactors of male gender (P = 0.0001), increasing age (P = 0.006), alcohol consumption (P = 0.0001), steatosis (P = 0.03), hepatic iron concentration (P < 0.0001) and the presence of hepatic fibrosis. Of the candidate gene polymorphisms studied, none showed a significant association with hepatic fibrosis in univariate or multivariate analysis incorporating cofactors. We also specifically studied patients with hepatic iron loading above threshold levels for cirrhosis and compared the genetic polymorphisms between those with no fibrosis vs cirrhosis however there was no significant effect from any of the candidate genes studied. Importantly, in this large, well characterised cohort of patients there was no association between SNPs for TGF-β or TLR4 and the presence of fibrosis, cirrhosis or increasing fibrosis stage in multivariate analysis.

CONCLUSION: In our large, well characterised group of haemochromatosis subjects we did not demonstrate any relationship between candidate gene polymorphisms and hepatic fibrosis or cirrhosis.

Gene expression profiling of early hepatic stellate cell activation reveals a role for Igfbp3 in cell migration

Background

Scarring of the liver is the result of prolonged exposure to exogenous or endogenous stimuli. At the onset of fibrosis, quiescent hepatic stellate cells (HSCs) activate and transdifferentiate into matrix producing, myofibroblast-like cells.

Aim and methods

To identify key players during early HSC activation, gene expression profiling was performed on primary mouse HSCs cultured for 4, 16 and 64 hours. Since valproic acid (VPA) can partly inhibit HSC activation, we included VPA-treated cells in the profiling experiments to facilitate this search.

Results

Gene expression profiling confirmed early changes for known genes related to HSC activation such as alphasmoothmuscleactin (Acta2), lysyloxidase (Lox) and collagen, type I, alpha 1 (Col1a1). In addition we noticed that, although genes which are related to fibrosis change between 4 and 16 hours in culture, most gene expression changes occur between 16 and 64 hours. Insulin-likegrowthfactorbinding protein 3 (Igfbp3) was identified as a gene strongly affected by VPA treatment. During normal HSC activation Igfbp3 is up regulated and this can thus be prevented by VPA treatment invitro and invivo. siRNA-mediated silencing of Igfbp3 in primary mouse HSCs induced matrix metalloproteinase (Mmp) 9 mRNA expression and strongly reduced cell migration. The reduced cell migration after Igfbp3 knock-down could be overcome by tissue inhibitor of metalloproteinase (TIMP) 1 treatment.

Conclusion

Igfbp3 is a marker for culture-activated HSCs and plays a role in HSC migration. VPA treatment prevents Igfbp3 transcription during activation of HSCs invitro and invivo.

Scutellariae radix suppresses LPS-induced liver endothelial cell activation and inhibits hepatic stellate cell migration

ETHNOPHARMACOLOGICAL RELEVANCE

Liver fibrosis is the result of long-term liver damage and the wound-healing process, in which the hepatic stellate cell (HSC) plays a crucial role during fibrogenesis. The liver sinusoidal endothelial cell (LSEC) is a liver-resident scavenger, contributing to sinusoidal remodeling, HSC activation and liver fibrosis. Lipopolysaccharide (LPS) causes an inflammatory reaction associated with portal circulation and LSECs signaling. Scutellariae radix, the root of Scutellaria baicalensis Georgi, is a Chinese herb widely used for liver diseases. However, its effect on LSEC activation and HSC migration in liver fibrosis has not been investigated yet.

AIM OF THIS STUDY

LPS-induced rat LSEC (rLSEC) activation was used as a model to screen and explore the active components of Scutellariae radix. The anti-fibrotic effect of Scutellariae radix on rLSEC activation and rHSC migration was further investigated.

MATERIALS AND METHODS

LPS-induced rLSEC mRNA expression, including VEGF, VEGFR, MCP-1, and TGF-β1, were examined by real-time PCR analyses. MCP-1 protein levels were measured by an ELISA kit. rLSEC conditioned medium on rHSC migration was measured by wound-healing assay and transwell chemoattraction assay.

RESULTS

Results showed LPS-induced rLSEC activation with upregulated MCP-1 mRNA and protein expressions, and that rLSEC-condition medium enhanced rHSC migration. Both baicalein and wogonin from the active subfraction significantly reduced MCP-1 expression, but only baicalein markedly inhibited rHSC migration in rLSEC conditioned medium.

CONCLUSION

This study demonstrated that Scutellariae radix attenuates LPS-induced rLSEC activation and HSC migration with downregulation of MCP-1 expression. The results provide supporting evidence that Scutellariae radix may be beneficial for the amelioration of liver fibrosis.

Octreotide modulates the effects on fibrosis of TNF-α, TGF-β and PDGF in activated rat hepatic stellate cells

BACKGROUND AND AIMS

Somatostatin and its analogs may influence hepatic fibrosis interfering through several mechanisms. The aim of this study was to investigate the effect of octreotide on cytokine activated hepatic stellate cells (HSC).

METHODS

Primary HSCs were isolated from rats and were cultured on plastic for activation. Expression of somatostatin receptors (SSTR) was investigated in cultured HSCs by immunofluorescence and western blot. The effect of octreotide on cellular proliferation was studied with the MTT assay and western blot for α1-procollagen (α1-PROC) production in TNFα, TGF-β1 or PDGF treated HSCs. Phosphotyrosine (PTP) and phosphoserine-phosphothreonine (STP) phosphatases inhibition was performed with sodium orthovanadate and okadaic acid respectively.

RESULTS

Activated HSC express SSTR subtypes 1, 2A, 2B, 3 and 4 and their expression is enhanced by further HSC activation. Octreotide did not have an effect on HSC proliferation but inhibited plastic induced α1-PROC production. Interestingly, it enhanced PDGF-induced HSC proliferation but inhibited PDGF and TGFβ1 dependent expression of α1-PROC, while an opposite effect was observed in TNFα-induced cell proliferation and collagen production. PTP inhibition reversed the inhibitory effect of octreotide on α1-PROC, but potentiated its effect on PDGF and TGFβ1 dependent α1-PROC production. Finally, STP inhibition profoundly inhibited α1-PROC expression in all cases suggesting that both STP and PTP phosphatases are important regulators of pro-fibrotic mechanisms.

CONCLUSIONS

The net effect of octreotide on HSCs and therefore liver fibrosis is subject to the cytokine microenvironment of these cells. This effect is modulated by PTPs and STPs inhibition. Especially in the case of STPs their profibrotic effects could be an interesting new therapeutic target in liver fibrosis.

Posttranslational regulation of tissue inhibitor of metalloproteinase-1 by calcium-dependent vesicular exocytosis

Liver myofibroblasts derived from hepatic stellate cells (HSC) are critical mediators of liver fibrosis. Release of tissue inhibitor of metalloproteinase-1 (TIMP-1) advances liver fibrosis by blocking fibrinolysis. The mechanisms responsible for the posttranslational regulation of TIMP-1 by myofibroblastic HSC are unknown. Here, we demonstrate that TIMP-1 release by HSC is regulated in a posttranslational fashion via calcium-sensitive vesicular exocytosis. To our knowledge, this is the first article to directly examine vesicular trafficking in myofibroblastic HSC, potentially providing a new target to treat and or prevent liver fibrosis.