Functional role of intrahepatic monocyte subsets for the progression of liver inflammation and liver fibrosis in vivo

From Inflammation to Oncogenesis: Tracing Serum DCLK1 and miRNA Signatures in Chronic Liver Diseases

Chronic liver diseases, fibrosis, cirrhosis, and HCC are often a consequence of persistent inflammation. However, the transition mechanisms from a normal liver to fibrosis, then cirrhosis, and further to HCC are not well understood. This study focused on the role of the tumor stem cell protein doublecortin-like kinase 1 (DCLK1) in the modulation of molecular factors in fibrosis, cirrhosis, or HCC. Serum samples from patients with hepatic fibrosis, cirrhosis, and HCC were analyzed via ELISA or NextGen sequencing and were compared with control samples. Differentially expressed (DE) microRNAs (miRNA) identified from these patient sera were correlated with DCLK1 expression. We observed elevated serum DCLK1 levels in fibrosis, cirrhosis, and HCC patients; however, TGF-β levels were only elevated in fibrosis and cirrhosis. While DE miRNAs were identified for all three disease states, miR-12136 was elevated in fibrosis but was significantly increased further in cirrhosis. Additionally, miR-1246 and miR-184 were upregulated when DCLK1 was high, while miR-206 was downregulated. This work distinguishes DCLK1 and miRNAs' potential role in different axes promoting inflammation to tumor progression and may serve to identify biomarkers for tracking the progression from pre-neoplastic states to HCC in chronic liver disease patients as well as provide targets for treatment.

Chronic liver diseases: From development to novel pharmacological therapies: IUPHAR Review 37

Chronic liver diseases comprise a broad spectrum of burdensome diseases that still lack effective pharmacological therapies. Our research group focuses on fibrosis, which is a major precursor of liver cirrhosis. Fibrosis consists in a progressive disturbance of liver sinusoidal architecture characterised by connective tissue deposition as a reparative response to tissue injury. Multifactorial events and several types of cells participate in fibrosis initiation and progression, and the process still needs to be completely understood. The development of experimental models of liver fibrosis alongside the identification of critical factors progressing fibrosis to cirrhosis will facilitate the development of more effective therapeutic approaches for such condition. This review provides an overlook of the main process leading to hepatic fibrosis and therapeutic approaches that have emerged from a deep knowledge of the molecular regulation of fibrogenesis in the liver. LINKED ARTICLES: This article is part of a themed issue on Translational Advances in Fibrosis as a Therapeutic Target. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.22/issuetoc.

The Role of Mesenchymal Stem Cells and Imatinib in the Process of Liver Fibrosis Healing Through CCL2-CCR2 and CX3CL1-CX3CR1 Axes

Background

Persistent liver damage contributes to the development of liver fibrosis, marked by an accumulation of extracellular matrix. Macrophages play a pivotal role in this process, with the CCL2-CCR2 and CX3CR1-CX3CL1 axes serving as key regulators of macrophage recruitment, liver infiltration, and differentiation. In this study, utilizing a rat model of carbon tetrachloride (CCL4)-induced liver fibrosis, we aimed to investigate the impact of imatinib and bone marrow-derived mesenchymal stem cells (BM-MSCs) on the expression of these axis.

Methods

Sixteen Sprague-Dawley rats were divided into four groups: healthy, liver fibrosis, imatinib-recipient, and BM-MSC-recipient. Treatment effects were evaluated using histopathology and Sirus-red staining. Quantitative real-time PCR was employed to analyze changes in the expression of the genes CCL2, CCR2, CX3CL1, and CX3CR1.

Results

Histopathological assessments revealed the efficacy of imatinib and BM-MSCs in mitigating liver fibrosis. Our findings demonstrated a significant reduction in CCL2 and CCR2 expression in both imatinib and BM-MSCs treatment groups compared to the liver fibrosis group. Conversely, the gene expression of CX3CL1 and CX3CR1 increased in both therapeutic groups compared to the liver fibrosis groups.

Conclusions

The notable decrease in CCL2-CCR2 genes in both therapeutic groups suggests that BM-MSCs and imatinib may contribute to a decline in inflammatory macrophages within the liver. The lower CCL2-CCR2 expression in imatinib-recipient rats indicates better efficacy in modulating the recruitment of inflammatory macrophages. The elevated expression of CX3CL1 in BM-MSC-recipient rats suggests a greater impact on the polarization of LY6Chigh (inflammatory) to LY6Clow (anti-inflammatory) macrophages, warranting further investigation.

Heterogeneous population of macrophages in the development of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is characterized by a spectrum of hepatic diseases, including fatty liver, non-alcoholic steatohepatitis, cirrhosis, and hepatocellular carcinoma. NAFLD is a hepatic manifestation of metabolic syndrome and has become the leading cause of liver transplantation, necessitating an in-depth understanding of its underlying pathogenic mechanisms and the identification of viable drug targets. Although fatty liver is benign and does not exert marked liver damage or inflammation, NAFLD progression involves inflammatory processes facilitated by immune cells. Macrophages and monocytes constitute the pool of innate immune cells that contribute to NAFLD development in association with other cell types, such as neutrophils, T cells, and natural killer cells. The concept that macrophages contribute to the inflammatory processes in NAFLD development has long been debated; however, the remarkable advances in experimental techniques have rapidly uncovered new subpopulations of macrophages and monocytes, whose functions need to be comprehensively elucidated. The current review focuses on the recent expansion of our knowledge of the heterogeneous population of macrophages crucially involved in NAFLD development. In addition, the present paper discusses ongoing efforts to target macrophages and inflammatory processes to develop optimal therapeutic agents against non-alcoholic steatohepatitis.

Thymosin Beta 4 Inhibits LPS and ATP-Induced Hepatic Stellate Cells via the Regulation of Multiple Signaling Pathways

Risk signals are characteristic of many common inflammatory diseases and can function to activate nucleotide-binding oligomerization (NLR) family pyrin domain-containing 3 (NLRP3), the innate immune signal receptor in cytoplasm. The NLRP3 inflammasome plays an important role in the development of liver fibrosis. Activated NLRP3 nucleates the assembly of inflammasomes, leading to the secretion of interleukin (IL)-1β and IL-18, the activation of caspase-1, and the initiation of the inflammatory process. Therefore, it is essential to inhibit the activation of the NLRP3 inflammasome, which plays a vital role in the immune response and in initiating inflammation. RAW 264.7 and LX-2 cells were primed with lipopolysaccharide (LPS) for 4 h and subsequently stimulated for 30 min with 5 mM of adenosine 5'-triphosphate (ATP) to activate the NLRP3 inflammasome. Thymosin beta 4 (Tβ4) was supplemented to RAW264.7 and LX-2 cells 30 min before ATP was added. As a result, we investigated the effects of Tβ4 on the NLRP3 inflammasome. Tβ4 prevented LPS-induced NLRP3 priming by inhibiting NF-kB and JNK/p38 MAPK expression and the LPS and ATP-induced production of reactive oxygen species. Moreover, Tβ4 induced autophagy by controlling autophagy markers (LC3A/B and p62) through the inhibition of the PI3K/AKT/mTOR pathway. LPS combined with ATP significantly increased thee protein expression of inflammatory mediators and NLRP3 inflammasome markers. These events were remarkably suppressed by Tβ4. In conclusion, Tβ4 attenuated NLRP3 inflammasomes by inhibiting NLRP3 inflammasome-related proteins (NLRP3, ASC, IL-1β, and caspase-1). Our results indicate that Tβ4 attenuated the NLRP3 inflammasome through multiple signaling pathway regulations in macrophage and hepatic stellate cells. Therefore, based on the above findings, it is hypothesized that Tβ4 could be a potential inflammatory therapeutic agent targeting the NLRP3 inflammasome in hepatic fibrosis regulation.

Macrophage: Key player in the pathogenesis of autoimmune diseases

The macrophage is an essential part of the innate immune system and also serves as the bridge between innate immunity and adaptive immune response. As the initiator and executor of the adaptive immune response, macrophage plays an important role in various physiological processes such as immune tolerance, fibrosis, inflammatory response, angiogenesis and phagocytosis of apoptotic cells. Consequently, macrophage dysfunction is a vital cause of the occurrence and development of autoimmune diseases. In this review, we mainly discuss the functions of macrophages in autoimmune diseases, especially in systemic lupus erythematosus (SLE), rheumatic arthritis (RA), systemic sclerosis (SSc) and type 1 diabetes (T1D), providing references for the treatment and prevention of autoimmune diseases.

Circulating soluble CD36 as a novel biomarker for progression and prognosis of HBV-related liver diseases

BACKGROUND

Our previous study suggested CD36 may be a positive regulator of hepatitis B virus (HBV) replication in vitro. Therefore, the present study aimed to investigate whether circulating soluble CD36 (sCD36) could serve as a diagnostic and prognostic biomarker for HBV-related liver diseases based on the clinic collected data.

METHODS

A total of 282 subjects were divided into healthy controls (HC, n = 47), chronic hepatitis B (CHB, n = 68), HBV-related liver cirrhosis (HBV-LC, n = 167). Soluble CD36 in plasma was measured by ELISA, and monocyte or platelet CD36 expression was determined by flow cytometry.

RESULTS

There was a step-wise increase of sCD36 with the progression of chronic HBV infection, and it was the highest in the HBV- LC group with liver failure (1.50, IQR:1.04-2.00) as compared with HC (0.38, IQR:0.27-0.38), CHB (0.75, IQR:0.40-1.13), and HBV-LC without liver failure (1.02, IQR,0.61-1.35) group. Circulating sCD36 was not correlated with serum HBV DNA levels, but correlated with liver function parameters. Additionally, ROC analysis confirmed sCD36 could be used to predict liver failure for HBV-LC patients, which yielded an AUC of 0.775 with 71.0% sensitivity and 72.2% specificity. Multivariate logistic regression analysis revealed sCD36 is an independent risk factor in predicting liver failure. Moreover, plasma sCD36 in HBV-LC patients was significantly correlated with prognostic indices, including MELD, MELD-Na and CHILD-PUGH scores. On the other hand, CD36 expression on monocytes or platelets was positively correlated with plasma sCD36 levels, whereas they were not strongly associated with the disease severity.

CONCLUSION

Circulating sCD36 could be used as a novel noninvasive biomarker for predicting liver failure and prognosis in chronic HBV infected patients.

Bioluminescence imaging of mouse monocyte chemoattractant protein-1 expression in inflammatory processes

Monocyte chemoattractant protein-1 (MCP-1) plays a crucial role in various inflammatory diseases. To reveal the impact of MCP-1 during diseases and to develop anti-inflammatory agents, we establish a transgenic mouse line. The firefly luciferase gene is incorporated into the mouse genome and driven by the endogenous MCP-1 promoter. A bioluminescence photographing system is applied to monitor luciferase levels in live mice during inflammation, including lipopolysaccharide-induced sepsis, concanavalin A-induced T cell-dependent liver injury, CCl ₄-induced acute hepatitis, and liver fibrosis. The results demonstrate that the luciferase signal induced in inflammatory processes is correlated with endogenous MCP-1 expression in mice. Furthermore, the expressions of MCP-1 and the luciferase gene are dramatically inhibited by administration of the anti-inflammatory drug dexamethasone in a septicemia model. Our results suggest that the transgenic MCP-1-Luc mouse is a useful model to study MCP-1 expression in inflammation and disease and to evaluate the efficiency of anti-inflammatory drugs in vivo.

miR204 potentially promotes non-alcoholic fatty liver disease by inhibition of cpt1a in mouse hepatocytes

Non-alcoholic fatty liver disease (NAFLD) is associated with hepatic metabolism dysfunction. However, the mechanistic role of miR204 in the development of NAFLD is unknown. We investigate the functional significance of miR204 in the evolution of NAFLD. IDH2 KO mice feed a normal diet (ND) or HFD increased body weight, epididymal fat-pad weight, lipid droplet in liver, blood parameter and inflammation compared to WT mice fed a ND or HFD. Moreover, the expression of miR204 is increased in mice with IDH2 deficiency. Increased miR204 by IDH2 deficiency regulates carnitine palmitoyltransferase 1a (cpt1a) synthesis, which inhibits fatty acid β-oxidation. Inhibition of miR204 prevents the disassembly of two fatty acid-related genes by activating CPT1a expression, which decreases lipid droplet in liver, inflammatory cytokines, epididymal fat pad weight, blood parameters. Increased miR204 by IDH2 deficiency promotes the pathogenesis of HFD-induced NAFLD by regulating hepatic fatty acid metabolism and inflammation.

Chemokines in Primary Liver Cancer

The liver is responsible for extremely important functions in the human body. In the liver’s structure, we distinguish between connective tissue (stroma) and parenchyma, the latter of which is formed from the basic structural and functional units of the liver—hepatocytes. There are many factors, that negatively affect the liver cells, contributing to their damage. This may lead to fibrosis, liver failure and, in consequence, primary liver cancer, which is the sixth most commonly diagnosed malignancy and the fourth leading cause of cancer death worldwide. Chemokines are a large family of secreted proteins. Their main role is to direct the recruitment and migration of cells to sites of inflammation or injury. Some authors suggest that these proteins might play a potential role in the development of many malignancies, including primary liver cancer. The aim of this study was to evaluate and summarize the knowledge regarding liver diseases, especially primary liver cancer (HCC) and the participation of chemokines in the development of this malignancy. Chemokines involved in the initiation of this type of tumor belong mainly to the CC and CXC chemokines. Their significant role in the course of hepatocellular carcinoma proves their usefulness in detecting and monitoring the course and treatment in patients with this disease.

The Translational Potential of Microglia and Monocyte-Derived Macrophages in Ischemic Stroke

The immune response to ischemic stroke is an area of study that is at the forefront of stroke research and presents promising new avenues for treatment development. Upon cerebral vessel occlusion, the innate immune system is activated by danger-associated molecular signals from stressed and dying neurons. Microglia, an immune cell population within the central nervous system which phagocytose cell debris and modulate the immune response via cytokine signaling, are the first cell population to become activated. Soon after, monocytes arrive from the peripheral immune system, differentiate into macrophages, and further aid in the immune response. Upon activation, both microglia and monocyte-derived macrophages are capable of polarizing into phenotypes which can either promote or attenuate the inflammatory response. Phenotypes which promote the inflammatory response are hypothesized to increase neuronal damage and impair recovery of neuronal function during the later phases of ischemic stroke. Therefore, modulating neuroimmune cells to adopt an anti-inflammatory response post ischemic stroke is an area of current research interest and potential treatment development. In this review, we outline the biology of microglia and monocyte-derived macrophages, further explain their roles in the acute, subacute, and chronic stages of ischemic stroke, and highlight current treatment development efforts which target these cells in the context of ischemic stroke.

Macrophages as key regulators of liver health and disease

Macrophages are a heterogeneous population of innate immune cells and key cellular components of the liver. Hepatic macrophages consist of embryologically-derived resident Kupffer cells (KC), recruited monocyte-derived macrophages (MDM) and capsular macrophages. Both the diversity and plasticity of hepatic macrophage subsets explain their different functions in the maintenance of hepatic homeostasis and in injury processes in acute and chronic liver diseases. In this review, we assess the evidence for macrophage involvement in regulating both liver health and injury responses in liver diseases including acute liver injury (ALI), chronic liver disease (CLD) (including liver fibrosis) and hepatocellular carcinoma (HCC). In healthy livers, KC display critical functions such as phagocytosis, danger signal recognition, cytokine release, antigen processing and the ability to orchestrate immune responses and maintain immunological tolerance. However, in most liver diseases there is a striking hepatic MDM expansion, which orchestrate both disease progression and regression. Single-cell approaches have transformed our understanding of liver macrophage heterogeneity, dynamics, and functions in both human samples and preclinical models. We will further discuss the new insights provided by these approaches and how they are enabling high-fidelity work to specifically identify pathogenic macrophage subpopulations. Given the important role of macrophages in regulating injury responses in a broad range of settings, there is now a huge interest in developing new therapeutic strategies aimed at targeting macrophages. Therefore, we also review the current approaches being used to modulate macrophage function in liver diseases and discuss the therapeutic potential of targeting macrophage subpopulations as a novel treatment strategy for patients with liver disorders.

Study protocol: a multicentre, open-label, parallel-group, phase 2, randomised controlled trial of autologous macrophage therapy for liver cirrhosis (MATCH)

INTRODUCTION

Liver cirrhosis is a growing global healthcare challenge. Cirrhosis is characterised by severe liver fibrosis, organ dysfunction and complications related to portal hypertension. There are no licensed antifibrotic or proregenerative medicines and liver transplantation is a scarce resource. Hepatic macrophages can promote both liver fibrogenesis and fibrosis regression. The safety and feasibility of peripheral infusion of ex vivo matured autologous monocyte-derived macrophages in patients with compensated cirrhosis has been demonstrated.

METHODS AND ANALYSIS

The efficacy of autologous macrophage therapy, compared with standard medical care, will be investigated in a cohort of adult patients with compensated cirrhosis in a multicentre, open-label, parallel-group, phase 2, randomised controlled trial. The primary outcome is the change in Model for End-Stage Liver Disease score at 90 days. The trial will provide the first high-quality examination of the efficacy of autologous macrophage therapy in improving liver function, non-invasive fibrosis markers and other clinical outcomes in patients with compensated cirrhosis.

ETHICS AND DISSEMINATION

The trial will be conducted according to the ethical principles of the Declaration of Helsinki 2013 and has been approved by Scotland A Research Ethics Committee (reference 15/SS/0121), National Health Service Lothian Research and Development department and the Medicine and Health Care Regulatory Agency-UK. Final results will be presented in peer-reviewed journals and at relevant conferences.

TRIAL REGISTRATION NUMBERS

ISRCTN10368050 and EudraCT; reference 2015-000963-15.

Therapeutic targets, novel drugs, and delivery systems for diabetes associated NAFLD and liver fibrosis

Type 2 diabetes mellitus (T2DM) associated non-alcoholic fatty liver disease (NAFLD) is the fourth-leading cause of death. Hyperglycemia induces various complications, including nephropathy, cirrhosis and eventually hepatocellular carcinoma (HCC). There are several etiological factors leading to liver disease development, which involve insulin resistance and oxidative stress. Free fatty acid (FFA) accumulation in the liver exerts oxidative and endoplasmic reticulum (ER) stresses. Hepatocyte injury induces release of inflammatory cytokines from Kupffer cells (KCs), which are responsible for activating hepatic stellate cells (HSCs). In this review, we will discuss various molecular targets for treating chronic liver diseases, including homeostasis of FFA, lipid metabolism, and decrease in hepatocyte apoptosis, role of growth factors, and regulation of epithelial-to-mesenchymal transition (EMT) and HSC activation. This review will also critically assess different strategies to enhance drug delivery to different cell types. Targeting nanocarriers to specific liver cell types have the potential to increase efficacy and suppress off-target effects.

The Role of Innate Immune Cells in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a very common hepatic pathology featuring steatosis and is linked to obesity and related conditions, such as the metabolic syndrome. When hepatic steatosis is accompanied by inflammation, the disorder is defined as nonalcoholic steatohepatitis (NASH), which in turn can progress toward fibrosis development that can ultimately result in cirrhosis. Cells of innate immunity, such as neutrophils or macrophages, are central regulators of NASH-related inflammation. Recent studies utilizing new experimental technologies, such as single-cell RNA sequencing, have revealed substantial heterogeneity within the macrophage populations of the liver, suggesting distinct functions of liver-resident Kupffer cells and recruited monocyte-derived macrophages with regards to regulation of liver inflammation and progression of NASH pathogenesis. Herein, we discuss recent developments concerning the function of innate immune cell subsets in NAFLD and NASH.

miR-21-regulated M2 polarization of macrophage is involved in arsenicosis-induced hepatic fibrosis through the activation of hepatic stellate cells

Arsenicosis induced by chronic exposure to arsenic is recognized as one of the main damaging effects on public health. Exposure to arsenic can cause hepatic fibrosis, but the molecular mechanisms by which this occurs are complex and elusive. It is not known if miRNAs are involved in arsenic-induced liver fibrosis. We found that in the livers of mice exposed to arsenite, there were elevated levels of microRNA-21 (miR-21), phosphorylated mammalian target of rapamycin (p-mTOR), and arginase 1 (Arg1); low levels of phosphatase and tensin homolog (PTEN); and more extensive liver fibrosis. For cultured cells, arsenite-induced miR-21, p-mTOR, and Arg1; decreased PTEN; and promoted M2 polarization of macrophages derived from THP-1 monocytes (THP-M), which caused secretion of fibrogenic cytokines, including transforming growth factor-β1. Coculture of arsenite-treated, THP-M with LX-2 cells induced α-SMA and collagen I in the LX-2 cells and resulted in the activation of these cells. Downregulation of miR-21 in THP-M inhibited arsenite-induced M2 polarization and activation of LX-2 cells, but cotransfection with PTEN siRNA or a miR-21 inhibitor reversed this inhibition. Moreover, knockout of miR-21 in mice attenuated liver fibrosis and M2 polarization compared with WT mice exposed to arsenite. Additionally, LN, PCIII, and HA levels were higher in patients with higher hair arsenic levels, and levels of miR-21 were higher than controls and positively correlated with PCIII, LN, and HA levels. Thus, arsenite induces the M2 polarization of macrophages via miR-21 regulation of PTEN, which is involved in the activation of hepatic stellate cells and hepatic fibrosis. The results establish a previously unknown mechanism for arsenicosis-induced fibrosis.

Fuzheng Huayu Recipe Prevented and Treated CCl4-Induced Mice Liver Fibrosis through Regulating Polarization and Chemotaxis of Intrahepatic Macrophages via CCL2 and CX3CL1

Background

Fuzheng Huayu recipe (FZHY) is an original Chinese patent medicine which was developed and marketed by our institute. It could markedly improve liver tissue inflammation and ameliorate hepatic fibrosis in the clinical study. The intrahepatic macrophages recruitment and polarization play an important role in the progress of liver inflammation and fibrosis. Whether FZHY exerted its antiliver fibrosis effects through regulating intrahepatic macrophages phenotypic ratios is still unknown. This study aims to explore the antifibrosis mechanism of FZHY on regulating the recruitment and polarization of intrahepatic macrophages.

Methods

C57/B6 mice were used for the establishment of the CCl4-induced mice liver fibrosis model. Liver inflammation and fibrosis were evaluated by HE and Sirius red staining, hydroxyproline assays, and biochemical tests. The levels of chemokines and inflammatory cytokines in liver tissue were measured by RNA-Seq transcriptome analysis, western blot assay, RT-qPCR, and immunofluorescence assay. The macrophages recruitment and phenotypic polarization were observed by flow cytometry.

Results

FZHY significantly improved liver inflammation and reduced liver fibrosis degree. TNF signaling pathway, involved in macrophages recruitment and phenotypic polarization, was discovered by RNA-Seq transcriptome analysis. In TNF signaling pathway, CCL2 expression was significantly decreased and CX3CL1 expression was significantly upregulated by FZHY in liver tissue and primary intrahepatic macrophages. The ratio of proinflammatory hepatic resident macrophage-Kupffer cells (F4/80⁺CD11b⁻CD86⁺) was downregulated by FZHY, while the proportion of anti-inflammatory Kupffer cells (F4/80⁺CD11b⁻CD206⁺) was upregulated. Meanwhile, the ratio of proinflammatory Ly6C^high macrophages (F4/80⁺CD11b⁺Ly6C^high) which were recruited from blood circulation by CCL2 was reduced by FZHY, while the ratio of restorative Ly6C^low macrophages (F4/80⁺CD11b⁺Ly6C^low) which were recruited from blood circulation or induced from Ly6C^high macrophages polarization by CX3CL1 was significantly increased.

Conclusions

FZHY could regulate the recruitment and polarization of intrahepatic macrophages via CCL2 and CX3CL1, so as to play its anti-inflammation and antifibrosis pharmacological effects in the liver.

Role of Chemokines in the Biology of Cholangiocarcinoma

Cholangiocarcinoma (CCA), a heterogeneous tumor with poor prognosis, can arise at any level in the biliary tree. It may derive from epithelial cells in the biliary tracts and peribiliary glands and possibly from progenitor cells or even hepatocytes. Several risk factors are responsible for CCA onset, however an inflammatory milieu nearby the biliary tree represents the most common condition favoring CCA development. Chemokines play a key role in driving the immunological response upon liver injury and may sustain tumor initiation and development. Chemokine receptor-dependent pathways influence the interplay among various cellular components, resulting in remodeling of the hepatic microenvironment towards a pro-inflammatory, pro-fibrogenic, pro-angiogenic and pre-neoplastic setting. Moreover, once tumor develops, chemokine signaling may influence its progression. Here we review the role of chemokines in the regulation of CCA development and progression, and the modulation of angiogenesis, metastasis and immune control. The potential role of chemokines and their receptors as possible biomarkers and/or therapeutic targets for hepatobiliary cancer is also discussed.

Elucidating Potential Profibrotic Mechanisms of Emerging Biomarkers for Early Prognosis of Hepatic Fibrosis

Hepatic fibrosis has been associated with a series of pathophysiological processes causing excessive accumulation of extracellular matrix proteins. Several cellular processes and molecular mechanisms have been implicated in the diseased liver that augments fibrogenesis, fibrogenic cytokines and associated liver complications. Liver biopsy remains an essential diagnostic tool for histological evaluation of hepatic fibrosis to establish a prognosis. In addition to being invasive, this methodology presents with several limitations including poor cost-effectiveness, prolonged hospitalizations, and risks of peritoneal bleeding, while the clinical use of this method does not reveal underlying pathogenic mechanisms. Several alternate noninvasive diagnostic strategies have been developed, to determine the extent of hepatic fibrosis, including the use of direct and indirect biomarkers. Immediate diagnosis of hepatic fibrosis by noninvasive means would be more palatable than a biopsy and could assist clinicians in taking early interventions timely, avoiding fatal complications, and improving prognosis. Therefore, we sought to review some common biomarkers of liver fibrosis along with some emerging candidates, including the oxidative stress-mediated biomarkers, epigenetic and genetic markers, exosomes, and miRNAs that needs further evaluation and would have better sensitivity and specificity. We also aim to elucidate the potential role of cardiotonic steroids (CTS) and evaluate the pro-inflammatory and profibrotic effects of CTS in exacerbating hepatic fibrosis. By understanding the underlying pathogenic processes, the efficacy of these biomarkers could allow for early diagnosis and treatment of hepatic fibrosis in chronic liver diseases, once validated.

Liver-Targeted siRNA Lipid Nanoparticles Treat Hepatic Cirrhosis by Dual Antifibrotic and Anti-inflammatory Activities

Previous studies on the treatment of hepatic cirrhosis have been focusing on how to inhibit liver fibrosis, while ignoring liver inflammation, a key and underlying factor that promotes cirrhosis. High mobility group box-1 (HMGB1) protein, a pro-inflammatory factor and fibroblast chemokine, can promote the proliferation of hepatic stellate cells (HSCs) and the development of hepatic inflammation and fibrosis, playing a key role in cirrhosis formation. In this study, we prepared pPB peptide (C*SRNLIDC*)-modified and HMGB1-siRNA-loaded stable nucleic acid lipid nanoparticles (HMGB1-siRNA@SNALP-pPB) to effectively treat hepatic cirrhosis by their dual antifibrotic and anti-inflammatory activities. The pPB peptide-modified and heat shock protein 47 (HSP47)-siRNA-loaded stable nucleic acid lipid nanoparticles (HSP47-siRNA@SNALP-pPB), which have only an antifibrotic effect without an anti-inflammatory effect, was used as control. The results demonstrated that HMGB1-siRNA@SNALP-pPB were actively targeted to HSCs by the mediation of pPB peptide, effectively silenced the HMGB1 gene, inhibited the activation and proliferation of HSCs, reduced the release of HMGB1 protein, inhibited collagen deposition and fibrosis formation in the liver, and significantly prolonged the survival time of cirrhotic mice models. HMGB1-siRNA@SNALP-pPB showed a stronger therapeutic effect on liver cirrhosis than HSP47-siRNA@SNALP-pPB. This study provides an actively targeted siRNA delivery system for cirrhosis treatment based on the dual antifibrotic and anti-inflammatory effects. In addition, this study clarified the role of inflammatory problems in cirrhosis treatment in addition to liver fibrosis, providing a useful idea and scientific basis for the development of cirrhosis treatment strategies in the future.

Hic-5 deficiency attenuates hepatic ischemia reperfusion injury through TLR4/NF-κB signaling pathways

AIM

To explore the role and mechanism of Hydrogen peroxide-inducible clone-5 (Hic-5) in hepatic ischemia reperfusion injury.

METHODS

Hic-5 KO and WT mice were used to establish the liver ischemia reperfusion model (HI/R). Primary hepatocytes were isolated to establish hypoxic reoxygenation model (H/R). AST and ALT were measured by automatic biochemical analyzer. Liver tissue sections were stained with HE and Tunnel. RNA and proteins were extracted from liver tissues, and expressions of Il-6, Il-10, CCL-2, CXCL-10, P65, Caspase-3, TLR4 and FADD were detected at gene and protein levels. Liver cell apoptosis was detected by flow cytometry and immunofluorescence. Primary hepatocytes were stimulated by LPS to establish a model of hepatocyte apoptosis, and cell inflammation and apoptosis-related proteins were detected.

RESULTS

After HI/R, ALT and AST in serum were up-regulated, some hepatocyte apoptosis were observed in pathological sections. Hic-5 expression was increased in WT mice after HI/R, and liver damage were severer than KO mice. The expression of IL-6, CCL-2 and CXCL-10 in the liver of KO mice was low, and the expression of IL-10 was high. Further studies showed that KO mice showed lower expression of P65, Caspase3 and TLR4. In H/R model, hepatocytes also showed the same trend. Finally, after LPS stimulation, the results showed that the inflammation and apoptosis induced by LPS were significantly reduced in Hic-5 knocked hepatocytes.

CONCLUSION

Hic-5 was found to promote inflammation through NF-kb signaling pathway and apoptosis through TLR4-FADD signaling pathway in mice with HI/R, thus aggravating liver injury in mice.

CD47 Deficiency in Mice Exacerbates Chronic Fatty Diet-Induced Steatohepatitis Through Its Role in Regulating Hepatic Inflammation and Lipid Metabolism

Inflammation is one of the hallmarks of non-alcoholic steatohepatitis. CD47 is a widely expressed transmembrane protein that signals through inhibitory receptor signal regulatory protein α (SIRPα) to inhibit macrophage activation and phagocytosis. In this study, we sought to investigate the role of CD47 in hepatosteatosis and fibrosis induced by a chronic high-fat diet (HFD), by comparing disease development in wild-type (WT) and CD47KO mice fed HFD for 40 weeks. The HFD induced remarkably more severe hepatic steatosis and fibrosis but less body weight gain and less subcutaneous fat accumulation in CD47KO mice compared to WT mice. Liver tissues from HFD-fed CD47KO mice exhibited enhanced inflammation characterized by increased proinflammatory cytokine production and increased nuclear factor-κB (NF-κB) activation compared to similarly fed WT mice. Although higher expression of apolipoproteins was observed in CD47KO mice compared to WT mice under a low-fat diet (LFD), HFD-fed WT and CD47KO mice showed comparably prominent downregulation of these apolipoprotein genes, suggesting that the marked difference observed in lipid accumulation and hepatosteatosis between these mice cannot be explained by changes in apolipoproteins. Like apolipoproteins, sirtuin 1 (SIRT1) and peroxisome proliferator activated receptor alpha (PPARα), which are involved in regulation of both lipid metabolism and inflammation, were more highly expressed in CD47KO than WT mice under LFD but more severely suppressed in CD47KO than in WT mice under HFD. Taken together, our results indicate that CD47 plays a significant role in the pathogenesis of HFD-induced hepatosteatosis and fibrosis through its role in regulation of inflammation and lipid metabolism.

Therapeutic Targeting of Hepatic Macrophages for the Treatment of Liver Diseases

Hepatic macrophages play a central role in maintaining homeostasis in the liver, as well as in the initiation and progression of liver diseases. Hepatic macrophages are mainly derived from resident hepatic macrophages called Kupffer cells or circulating bone marrow-derived monocytes. Kupffer cells are self-renewing and typically non-migrating macrophages in the liver and are stationed in the liver sinusoids in contrast to macrophages originating from circulating monocytes. Kupffer cells regulate liver homeostasis by mediating immunity against non-pathogenic blood-borne molecules, while participating in coordinated immune responses leading to pathogen clearance, leukocyte recruitment and antigen presentation to lymphocytes present in the vasculature. Monocyte-derived macrophages infiltrate into the liver tissue when metabolic or toxic damage instigates and are likely dispensable for replenishing the macrophage population in homeostasis. In recent years, different populations of hepatic macrophages have been identified with distinct phenotypes with discrete functions, far beyond the central dogma of M1 and M2 macrophages. Hepatic macrophages play a central role in the pathogenesis of acute and chronic liver failure, liver fibrosis, non-alcoholic fatty liver disease, alcoholic liver disease, viral hepatitis, and hepatocellular carcinoma, as well as in disease resolution. The understanding of the role of hepatic macrophages in liver diseases provides opportunities for the development of targeted therapeutics for respective malignancies. This review will summarize the current knowledge of the hepatic macrophages, their origin, functions, their critical role in maintaining homeostasis and in the progression or resolution of liver diseases. Furthermore, we will provide a comprehensive overview of the therapeutic targeting strategies against hepatic macrophages developed for the treatment of liver diseases.

Effects of a blend of green tea and curcuma extract supplementation on lipopolysaccharide-induced inflammation in horses and ponies

Background

In horses and ponies numerous medical conditions are known to be linked with inflammation in different tissues, especially in the liver. Besides affecting other metabolic pathways such as the expression of certain interleukins (IL), inflammation is associated with stress of the endoplasmic reticulum (ER). In particular, ER stress leads to adaptive stress response and can be measured by several markers of inflammatory and stress signalling pathways, like nuclear factor κB (NF-kB).

Objectives

To investigate lipopolysaccharide (LPS)-induced inflammatory reactions and their modulation in horses and ponies by feeding a polyphenol-rich supplement consisting of green tea and curcuma.

Methods

In a cross-over study, 11 animals were allocated to either a placebo or a supplement group and supplemented with 10 g of a blend of green tea and curcuma extract (GCE) or a placebo (calcium carbonate) once daily. After 21 days of supplementation, all animals underwent a LPS challenge to induce moderate systemic inflammation. Blood samples and liver biopsies were taken at standardized time points: 24 hours before and 12 hours after LPS challenge. Inflammatory blood parameters such as serum amyloid A (SAA), haptoglobin and retinol binding protein 4 (RBP4) were measured in serum. Hepatic mRNA levels of selected markers of inflammation such as haptoglobin, tumor necrosis factor α (TNF-α), IL-1β, IL-6, cluster of differentiation 68 (CD68), fibroblast growth factor 21 (FGF-21), NF-κB, activating transcription factor 4 (ATF4) were quantified by RT-qPCR. In addition, liver biopsies were examined histologically for inflammatory alterations.

Results

Blood markers of acute inflammatory response increased after LPS challenge. In the liver, the proinflammatory cytokine IL-1β showed significantly lower mRNA levels after LPS challenge in the supplemented group (P = 0.04) compared to the placebo group. Levels of the hepatic CD68 mRNA increased significantly in the placebo group (P = 0.04). There were no significant differences between supplemented and placebo groups concerning other markers of inflammation and markers of ER stress within the liver. The number of hepatic macrophages were not different after LPS challenge in both feeding groups.

Conclusion

LPS was able to induce inflammation but seemed less suitable to induce ER stress in the horses and ponies. The polyphenol-rich supplement showed some potential to reduce inflammatory responses. Nevertheless, the supplementation did not exert an overall anti-inflammatory effect in horses and ponies.

Sphingosine 1-Phosphate Receptor Blockade Affects Pro-Inflammatory Bone Marrow-Derived Macrophages and Relieves Mouse Fatty Liver Injury

Fatty liver injury is characterized by liver fat accumulation and results in serious health problems worldwide. There is no effective treatment that reverses fatty liver injury besides etiological therapy. Inflammation is an important macrophage-involving pathological process of liver injury. Here, we investigated the role of sphingosine 1-phosphate receptors (S1PRs) in fatty liver injury and explored whether S1PR_2/3 blockade could cure fatty liver injury. A methionine-choline-deficient and a high-fat (MCDHF) diet was used to induce fatty liver injury, and the number of macrophages was evaluated by flow cytometry. Gene expressions were detected using RT-qPCR and cytometric bead array. In MCDHF-diet-fed mice, pro-inflammatory factor expressions were upregulated by fatty liver injury. The S1P level and S1PR_2/3 expressions were significantly elevated. Moreover, increased S1P level and S1PR_2/3 mRNA expressions were positively correlated with pro-inflammatory factor expressions in the liver. Furthermore, the number of pro-inflammatory macrophages (iMφ) increased in injured liver, and they were mainly bone-marrow-derived macrophages. In vivo, S1PR_2/3 blockade decreased the amount of iMφ and inflammation and attenuated liver injury and fibrosis, although liver fat accumulation was unchanged. These data strongly suggest that anti-inflammatory treatment by blocking the S1P/S1PR_2/3 axis attenuates fatty liver injury, which might serve as a potential target for fatty liver injury.

Role of macrophages in experimental liver injury and repair in mice

Liver macrophages make up the largest proportion of tissue macrophages in the host and consist of two dissimilar groups: Kupffer cells (KCs) and monocyte-derived macrophages (MoMø). As the liver is injured, KCs sense the injury and initiate inflammatory cascades mediated by the release of inflammatory cytokines and chemokines. Subsequently, inflammatory monocytes accumulate in the liver via chemokine-chemokine receptor interactions, resulting in massive inflammatory MoMø infiltration. When live r injury ceases, restorative macrophages, derived from recruited inflammatory monocytes (lymphocyte antigen 6 complex, locus Chi monocytes), promote the resolution of hepatic damage and fibrosis. Consequently, a large number of studies have assessed the mechanisms by which liver macrophages exert their opposing functions at different time-points during liver injury. The present review primarily focuses on the diverse functions of macrophages in experimental liver injury, fibrosis and repair in mice and illustrates how macrophages may be targeted to treat liver disease.

The immunoregulatory effects of CD8 T-cell-derived perforin on diet-induced nonalcoholic steatohepatitis

The liver is a central immunologic organ with a high density of myeloid and lymphoid immune cells that play important roles in the development and progression of nonalcoholic steatohepatitis (NASH). However, the immune-cell-mediated regulation of NASH and its underlying mechanisms remain obscure. In this study, Prf1^null mice showed significantly higher plasma alanine transaminase levels, with increased liver fat accumulation, lobular inflammation, and focal necrosis compared with wild-type (WT) mice after 4 wk of feeding on a methionine- and choline-deficient diet (MCD) or 16 wk of feeding on a high-fat diet. Perforin deficiency promoted the M1 polarization of infiltrated monocytes. Moreover, MCD-fed Prf1^null mice exhibited increased accumulation, survival, activation, and proinflammatory cytokine production of CD8 T cells but not NK cells or CD4 T cells. Adoptive transfer of CD8 T cells or NK cells from WT or Prf1^null mice, together with non-CD8 cells or non-NK cells from WT mice, indicated that CD8 T-cell-derived perforin participates in the mechanism regulating liver inflammation and thus plays a protective role in the development of NASH. Perforin-deficient CD8 T cells exhibited decreased cytotoxicity toward bone marrow-derived M1 monocytes and macrophages. According to the RNA sequencing data, the perforin deficiency inhibited cell apoptosis and enhanced the activation, migration, and proinflammatory cytokine production of CD8 T cells in mice with NASH. Furthermore, we found higher plasma soluble perforin levels and hepatic perforin expression in NASH patients, suggesting clinical relevance of the findings. We have elucidated an important role for the cytotoxic immune effector molecule perforin from CD8 T cells in restricting hepatic inflammation in mice with NASH and suggest that therapies designed to maximize the function of endogenous perforin in CD8 T cells might have potential benefits as NASH treatments.-Wang, T., Sun, G., Wang, Y., Li, S., Zhao, X., Zhang, C., Jin, H., Tian, D., Liu, K., Shi, W., Tian, Y., Zhang, D. The immunoregulatory effects of CD8 T-cell-derived perforin on diet-induced nonalcoholic steatohepatitis.

Serum interleukin-34 level can be an indicator of liver fibrosis in patients with chronic hepatitis B virus infection

AIM

To investigate whether serum interleukin (IL)-34 levels are correlated with hepatic inflammation and fibrosis in patients with chronic hepatitis B virus (HBV) infection.

METHODS

In this study, serum IL-34 levels were assessed by enzyme-linked immunosorbent assay in 19 healthy controls and 175 patients with chronic HBV infection undergoing biopsy. The frequently used serological markers of liver fibrosis were based on laboratory indexes measured at the Clinical Laboratory of the Second Affiliated Hospital of Anhui Medical University. Liver stiffness was detected by transient elastography with FibroTouch. The relationships of non-invasive makers of liver fibrosis and IL-34 levels with inflammation and fibrosis were analyzed. The diagnostic value of IL-34 and other liver fibrosis makers were evaluated using areas under the receiver operating characteristic curves, sensitivity and specificity.

RESULTS

Serum IL-34 levels were associated with inflammatory activity in the liver, and IL-34 levels differed among phases of chronic HBV infection (P = 0.001). By comparing serum IL-34 levels among patients with various stages of liver fibrosis determined by liver biopsy, we found that IL-34 levels ≥ 15.83 pg/mL had a high sensitivity of 86.6% and a specificity of 78.7% for identifying severe fibrosis (S3-S4). Furthermore, we showed that IL-34 is superior to the fibrosis-4 score, one of the serum makers of liver fibrosis, in identifying severe liver fibrosis and early cirrhosis in patients with HBV-related liver fibrosis in China.

CONCLUSION

Our results indicate that IL-34, a cytokine involved in the induction of activation of profibrogenic macrophages, can be an indicator of liver inflammation and fibrosis in patients with chronic HBV infection.

Dietary butylated hydroxytoluene improves lipid metabolism, antioxidant and anti-apoptotic response of largemouth bass (Micropterus salmoides)

A 10-week growth trail was conducted to investigate the efficacy and tolerance of dietary butylated hydroxytoluene (BHT) by evaluating inflammation, apoptosis and hepatic disease related to oxidative stress in largemouth bass (Micropterus salmoides). Four experimental diets were prepared with BHT supplement levels of 0 (B0), 150 (B150), 300 (B300) and 1500 (B1500) mg/kg, in which B150 was at the maximum recommended level established by European Union Regulation, and the B300 and B1500 levels were 2 and 10-fold of B150, respectively. Each diet was fed to 6 replicates with 30 largemouth bass (initial body weight, IBW = 6.20 ± 0.01 g) in each tank. The BHT inclusion level did not affect the specific growth rate, but fish in the B150 group showed the lowest feed conversion rate (P < 0.05). BHT inclusion significantly decreased the levels of plasma TC, TG, LDL, ALT and AKP, and increased the (HDL-C)/TC ratio (P < 0.05). Plasma MDA was significantly decreased in the B150 group and GSH-Px was extremely enhanced in each BHT inclusion group (P < 0.05). Hepatic T-AOC was significantly enhanced and O₂^- was significantly decreased in each BHT inclusion group compared to the B0 group (P < 0.05), as well as hepatic MDA was significantly decreased in B1500 group (P < 0.05). Dietary BHT inclusion down-regulated the hepatic mRNA levels of inflammation, apoptosis and fibrosis related genes, including TNFα, TGF-β1, α-SMA, IL8, IL11β and caspase-9. Moreover, BHT could improve hepatic lipid metabolism via up-regulating the mRNA levels of APOA1, CYP7A1, CYP8B1, and down-regulating the mRNA levels of PPAR-γ and APOB. Histological examination of the liver morphology with H&E and Sirius Red staining showed that BHT inclusion decreased necrotic degenerative changes and collagen deposition in largemouth bass. An immunofluorescence examination revealed significantly decreased cleaved caspase-3 signals in the BHT groups. In conclusion, the results demonstrated that ROS induces hepatic cell apoptosis and fibrosis via the intrinsic pathway of apoptosis by activating caspase-9 in the mitochondria and then initiates apoptosis by activating caspase-3. Consuming 2.32-23.80 mg/kg·bw/d (150-1500 mg/kg in diet) of BHT effectively improved the plasma and hepatic lipid metabolism, antioxidant response as well as reduced ROS production, protecting hepatic cells from injury. It is implied that even a 10-fold increase of the maximum level of BHT (150 mg/kg) is safe for the largemouth bass.

Dynamic plasticity of macrophage functions in diseased liver

Liver macrophages attract increasing interest due to their crucial roles in homeostasis and hepatic diseases. Recent findings in mice and man suggest a remarkable phenotypic and functional diversity of liver macrophages. Kupffer cells, the subset of tissue resident macrophages with sentinel functions in liver, mainly arise from embryogenic precursors, whereas in injury, liver tissue is engrafted by monocyte-derived macrophages. Both principal macrophage populations respond to local or systemic signals and have substantial effects on reduction as well as aggravation of hepatic diseases. Despite contrasting functions of heterogeneous macrophage subsets in disease progression and regression, they may provide promising targets for novel therapeutic interventions in hepatology. Areas of intense research include their multifaceted roles in metabolic diseases (non-alcoholic steatohepatitis, NASH), fibrosis or liver cancer (hepatocellular or cholangiocellular carcinoma, HCC or CCA). We discuss recent findings on the origin, diversity and functional plasticity of liver macrophages in homeostasis and hepatic disease conditions.

Hepatic recruitment of CD11b+Ly6C+ inflammatory monocytes promotes hepatic ischemia/reperfusion injury

Monocytes infiltrate damaged liver tissue during noninfectious liver injury and often have dual roles, perpetuating inflammation and promoting resolution of inflammation and fibrosis. However, how monocyte subsets distribute and are differentially recruited in the liver remain unclear. In the current study, the subpopulations of infiltrating monocytes were examined following liver ischemia/reperfusion (I/R) injury in mice using flow cytometry. CD11b⁺Ly6C high (Ly6C^hi) cells (inflammatory monocytes) and CD11b⁺Ly6C low cells (reparative monocytes) were recruited into the liver following I/R injury. Treatment with clodronate-loaded liposomes, which transiently deplete systemic macrophages, alleviated hepatic damage. Mice genetically deficient in C-C motif chemokine ligand 2 (CCL2), or its receptor C-C chemokine receptor 2 (CCR2), exhibited diminished hepatic damage compared with wild-type mice following I/R, by controlling intrahepatic inflammatory Ly6C^hi monocyte accumulation. In addition, the CCR2 specific inhibitor RS504393 alleviated hepatic I/R injury. The results suggest that the CCR2/ CCL2 axis an important role in monocyte infiltration and may represent a novel target for the treatment of liver I/R injury.

Non-alcoholic steatohepatitis induces transient changes within the liver macrophage pool

Kupffer cells (KCs) and monocyte-derived macrophages are implicated in non-alcoholic steatohepatitis (NASH) pathogenesis but their functions remain unclear due to the lack of specific markers to distinguish between the different cell types. Additionally, it is unclear if multiple subsets of KCs are present during NASH. Here, we characterized the liver macrophage subsets during methionine/choline deficient (MCD) diet-induced NASH and recovery. We observed a significant reduced contribution of Ly6C^loClec4F⁺Tim4⁺KCs to the hepatic macrophage pool in MCD fed mice, which normalized during recovery. Ly6C^loClec4F^-Tim4^- monocyte-derived macrophages increased during MCD feeding and returned to baseline during recovery. Ly6C^loClec4F⁺Tim4^- monocyte-derived KCs developed during initial recovery but did not self-renew as their numbers were reduced after full recovery. Initial recovery from MCD diet feeding was further characterized by increased proportions of Ki-67⁺ proliferating KCs. In conclusion, the hepatic macrophage pool undergoes substantial albeit transient changes during NASH and recovery, with the KC pool being maintained by proliferation and differentiation of short-lived monocyte-derived KCs.

Steroid-Mediated Decrease in Blood Mesenchymal Stem Cells in Liver Transplant could Impact Long-Term Recovery

Orthotopic liver transplant (OLT) remains the standard of care for end stage liver disease. To circumvent allo-rejection, OLT subjects receive gluococorticoids (GC). We investigated the effects of GC on endogenous mesenchymal stem (stromal) cells (MSCs) in OLT. This question is relevant because MSCs have regenerative potential and immune suppressor function. Phenotypic analyses of blood samples from 12 OLT recipients, at pre-anhepatic, anhepatic and post-transplant (2 h, Days 1 and 5) indicated a significant decrease in MSCs after GC injection. The MSCs showed better recovery in the blood from subjects who started with relatively low MSCs as compared to those with high levels at the prehepatic phase. This drop in MSCs appeared to be linked to GC since similar change was not observed in liver resection subjects. In order to understand the effects of GC on decrease MSC migration, in vitro studies were performed in transwell cultures. Untreated MSCs could not migrate towards the GC-exposed liver tissue, despite CXCR4 expression and the production of inflammatory cytokines from the liver cells. GC-treated MSCs were inefficient with respect to migration towards CXCL12, and this correlated with retracted cytoskeleton and motility. These dysfunctions were partly explained by decreases in the CXCL12/receptor axis. GC-associated decrease in MSCs in OLT recipients recovered post-transplant, despite poor migratory ability towards GC-exposed liver. In total, the study indicated that GC usage in transplant needs to be examined to determine if this could be reduced or avoided with adjuvant cell therapy.

Erythropoietin enhances Kupffer cell number and activity in the challenged liver

Erythropoietin (EPO) is the main hormone driving mammalian erythropoiesis, with activity mediated via the surface receptor, EPO-R, on erythroid progenitor cells. Recombinant human EPO is currently used clinically for the treatment of anemia in patients with end-stage renal disease, and in certain cancer patients suffering from anemia induced either by the tumor itself or by chemotherapy. EPO-R expression is also detected in non-erythroid cells, including macrophages present in the peritoneum, spleen, and bone marrow (BM). Here we demonstrate that Kupffer cells (KCs) - the liver-resident macrophages - are EPO targets. We show that, in vitro, EPO initiated intracellular signalling and enhanced phagocytosis in a rat KC line (RKC-2) and in sorted KCs. Moreover, continuous EPO administration in mice, resulted in an increased number of KCs, up-regulation of liver EPO-R expression and elevated production of the monocyte chemoattractant CCL2, with corresponding egress of Ly6C^hi monocytes from the BM. In a model of acute acetaminophen-induced liver injury, EPO administration increased the recruitment of Ly6C^hi monocytes and neutrophils to the liver. Taken together, our results reveal a new role for EPO in stimulating KC proliferation and phagocytosis, and in recruiting Ly6C^hi monocytes in response to liver injury.

Macrophage Phenotype in Liver Injury and Repair

Macrophages hold a critical position in the pathogenesis of liver injury and repair, in which their infiltrations is regarded as a main feature for both acute and chronic liver diseases. It is noted that, based on the distinct phenotypes and origins, hepatic macrophages are capable of clearing pathogens, promoting/or inhibiting liver inflammation, while regulating liver fibrosis and fibrolysis through interplaying with hepatocytes and hepatic stellate cells (HSC) via releasing different types of pro- or anti-inflammatory cytokines and growth factors. Macrophages are typically categorized into M1 or M2 phenotypes by adapting to local microenvironment during the progression of liver injury. In most occasions, M1 macrophages play a pro-inflammatory role in liver injury, while M2 macrophages exert an anti-inflammatory or pro-fibrotic role during liver repair and fibrosis. In this review, we focused on the up-to-date information about the phenotypic and functional plasticity of the macrophages and discussed the detailed mechanisms through which the phenotypes and functions of macrophages are regulated in different stages of liver injury and repair. Moreover, their roles in determining the fate of liver diseases were also summarized. Finally, the macrophage-targeted therapies against liver diseases were also be evaluated.

Effects of dyslipidaemia on monocyte production and function in cardiovascular disease

Monocytes are heterogeneous effector cells involved in the maintenance and restoration of tissue integrity. Monocytes and macrophages are involved in cardiovascular disease progression, and are associated with the development of unstable atherosclerotic plaques. Hyperlipidaemia can accelerate cardiovascular disease progression. However, monocyte responses to hyperlipidaemia are poorly understood. In the past decade, accumulating data describe the relationship between the dynamic blood lipid environment and the heterogeneous circulating monocyte pool, which might have profound consequences for cardiovascular disease. In this Review, we explore the updated view of monocytes in cardiovascular disease and their relationship with macrophages in promoting the homeostatic and inflammatory responses related to atherosclerosis. We describe the different definitions of dyslipidaemia, highlight current theories on the ontogeny of monocyte heterogeneity, discuss how dyslipidaemia might alter monocyte production, and explore the mechanistic interface linking dyslipidaemia with monocyte effector functions, such as migration and the inflammatory response. Finally, we discuss the role of dietary and endogenous lipid species in mediating dyslipidaemic responses, and the role of these lipids in promoting the risk of cardiovascular disease through modulation of monocyte behaviour.

Potentiation of hepatic stellate cell activation by extracellular ATP is dependent on P2X7R-mediated NLRP3 inflammasome activation

Purinergic receptor P2x7 (P2x7R) is a key modulator of liver inflammation and fibrosis. The present study aimed to investigate the role of P2x7R in hepatic stellate cells activation. Lipopolysaccharide (LPS) or the conditioned medium (CM) from LPS-stimulated RAW 264.7 mouse macrophages was supplemented to human hepatic stellate cells, LX-2 for 24h and P2x7R selective antagonist A438079 (10μM) was supplemented to LX-2 cells 1h before LPS or CM stimulation. In addition LX-2 cells were primed with LPS for 4h and subsequently stimulated for 30min with 3mM of adenosine 5'-triphosphate (ATP). A438079 was supplemented to LX-2 cells 10min prior to ATP. Directly treated with LPS on LX-2 cells, mRNA expressions of interleukin (IL)-1β, IL-18 and IL-6 were increased, as well as mRNA expressions of P2x7R, caspase-1, apoptosis-associated speck-like protein containing CARD (ASC) and NOD-like receptor family, pyrin domain containing 3 (NLRP3) mRNA. LPS also increased α-smooth muscle actin (α-SMA) and type I collagen mRNA expressions, as well as collagen deposition. Interestingly treatment of LX-2 cells with LPS-activated CM exhibited the greater increase of above factors than those in LX-2 cells directly treated with LPS. Pretreatment of A438079 on LX-2 cells stimulated by LPS or LPS-activated CM both suppressed IL-1β mRNA expression. LPS combined with ATP dramatically increased protein synthesis and cleavage of IL-1β and its mRNA level than those in HSC treated with LPS or ATP alone. Additionally LX-2 cells primed with LPS and subsequently stimulated for 30min with ATP greatly increased mRNA and protein expression of caspase-1, NLRP3 and P2x7R, as well as liver fibrosis markers, α-SMA and type I collagen. These events were remarkably suppressed by A438079 pretreatment. siRNA against P2x7R reduced protein expression of NLRP3 and α-SMA, and suppressed deposition and secretion of type I collagen. The involvement of P2X7R-mediated NLRP3 inflammasome activation in IL-1β production of HSC might contribute to ECM deposition and suggests that blockade of the P2x7R-NLRP3 inflammasome axis represents a potential therapeutic target to liver fibrosis.

Bone marrow-derived macrophages distinct from tissue-resident macrophages play a pivotal role in Concanavalin A-induced murine liver injury via CCR9 axis

The fundamental mechanism how heterogeneous hepatic macrophage (Mφ) subsets fulfill diverse functions in health and disease has not been elucidated. We recently reported that CCR9⁺ inflammatory Mφs play a critical role in the course of acute liver injury. To clarify the origin and differentiation of CCR9⁺Mφs, we used a unique partial bone marrow (BM) chimera model with liver shielding for maintaining hepatic resident Mφs. First, irradiated mice developed less liver injury with less Mφs accumulation by Concanavalin A (Con A) regardless of liver shielding. In mice receiving further BM transplantation, CD11b^lowF4/80^high hepatic-resident Mφs were not replaced by transplanted donors under steady state, while under inflammatory state by Con A, CCR9⁺Mφs were firmly replaced by donors, indicating that CCR9⁺Mφs originate from BM, but not from hepatic-resident cells. Regarding the mechanism of differentiation and proliferation, EdU⁺CCR9⁺Mφs with a proliferative potential were detected specifically in the inflamed liver, and in vitro study revealed that BM-derived CD11b⁺ cells co-cultured with hepatic stellate cells (HSCs) or stimulated with retinoic acids could acquire CCR9 with antigen-presenting ability. Collectively, our study demonstrates that inflammatory Mφs originate from BM and became locally differentiated and proliferated by interaction with HSCs via CCR9 axis during acute liver injury.

An Agent-Based Model of a Hepatic Inflammatory Response to Salmonella: A Computational Study under a Large Set of Experimental Data

We present an agent-based model (ABM) to simulate a hepatic inflammatory response (HIR) in a mouse infected by Salmonella that sometimes progressed to problematic proportions, known as "sepsis". Based on over 200 published studies, this ABM describes interactions among 21 cells or cytokines and incorporates 226 experimental data sets and/or data estimates from those reports to simulate a mouse HIR in silico. Our simulated results reproduced dynamic patterns of HIR reported in the literature. As shown in vivo, our model also demonstrated that sepsis was highly related to the initial Salmonella dose and the presence of components of the adaptive immune system. We determined that high mobility group box-1, C-reactive protein, and the interleukin-10: tumor necrosis factor-α ratio, and CD4+ T cell: CD8+ T cell ratio, all recognized as biomarkers during HIR, significantly correlated with outcomes of HIR. During therapy-directed silico simulations, our results demonstrated that anti-agent intervention impacted the survival rates of septic individuals in a time-dependent manner. By specifying the infected species, source of infection, and site of infection, this ABM enabled us to reproduce the kinetics of several essential indicators during a HIR, observe distinct dynamic patterns that are manifested during HIR, and allowed us to test proposed therapy-directed treatments. Although limitation still exists, this ABM is a step forward because it links underlying biological processes to computational simulation and was validated through a series of comparisons between the simulated results and experimental studies.

Monocyte Heterogeneity: Consequences for Monocyte-Derived Immune Cells

Blood monocytes are precursors of dendritic cells, macrophages, and osteoclasts. They are a heterogeneous cell population with differences in size, phenotype, and function. Although monocytes maintain several tissue-specific populations of immune cells in homeostasis, their contribution to populations of dendritic cells, macrophages, and osteoclasts is significantly increased in inflammation. Identification of a growing number of functionally different subsets of cells within populations of monocyte-derived immune cells has recently put monocyte heterogeneity into sharp focus. Here, we summarize recent findings in monocyte heterogeneity and their differentiation into dendritic cells, macrophages, and osteoclasts. We also discuss these advances in the context of the formation of functionally different monocyte-derived subsets of dendritic cells, macrophages, and osteoclasts.

HIV infection is associated with higher levels of monocyte chemoattractant protein-1 and eotaxin among people with recent hepatitis C virus infection

Background

Human immunodeficiency virus (HIV) infection leads to more rapid progression of hepatitis C virus (HCV)-related liver fibrosis, which could be linked to differences in the severity of liver inflammation among HIV/HCV co-infected individuals compared to HCV mono-infected individuals.

This study assessed the association of HIV co-infection with pro-inflammatory and pro-fibrogenic cytokines and chemokines during recent HCV infection.

Methods

Participants from the ATAHC study, a prospective cohort of recent HCV infection, with detectable HCV RNA at the time of acute HCV detection were included. Concentrations of 27 plasma cytokines and chemokines were measured by multiplex immunoassays and compared between those with, and without, HIV co-infection.

Results

Out of 117 individuals with recent HCV infection included in analysis, 73 had HCV mono-infection and 44 had HIV/HCV co-infection. Individuals with HIV/HCV co-infection had significantly higher mean levels of eotaxin (1.79 vs. 1.62 log pg/mL; P < 0.001), monocyte chemotactic protein 1 (MCP-1; 2.10 vs. 1.98 log pg/mL; P < 0.001), and interferon-gamma inducible protein-10 (IP-10; 3.11 vs. 2.98 log pg/mL; P = 0.013). Linear regression analyses adjusting for age, alanine transaminase (ALT), HCV RNA levels, and assay run, higher eotaxin levels were independently associated with HIV/HCV co-infection (adjusted β: 0.12; 95%CI: 0.01, 0.24; P = 0.039). Higher MCP-1 levels were also independently associated with HIV/HCV co-infection in adjusted analysis (adjusted β: 0.11; 95%CI: 0.03, 0.18; P = 0.009).

Conclusions

During recent HCV, those with HIV/HCV co-infection had a stronger pro-fibrogenic mediator profile compared to those with HCV mono-infection. These findings may provide a potential explanation for accelerated liver fibrosis in HIV/HCV co-infection.

Trial registration

Australian Trial in Acute Hepatitis C (ATAHC) study was registered with ClinicalTrials.gov registry on September 11, 2005. NCT00192569.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1567-2) contains supplementary material, which is available to authorized users.

Differential Roles of Angiogenesis in the Induction of Fibrogenesis and the Resolution of Fibrosis in Liver

Liver fibrosis is a wound healing process that includes inflammation, deposition of extracellular matrix molecules, and pathological neovascularization. Angiogenesis, which is defined by the formation of new blood vessels from pre-existing vessels, is a complex and dynamic process under both physiological and pathological conditions. Although whether angiogenesis can induce or occur in parallel with the progression of hepatic fibrosis has not yet been determined, intrahepatic sinusoidal formation and remodeling are key features of liver fibrosis. Some recent evidence has suggested that experimental inhibition of angiogenesis ameliorates the development of liver fibrosis, while other recent studies indicate that neutralization or genetic ablation of vascular endothelial growth factor (VEGF) in myeloid cells can delay tissue repair and fibrosis resolution in damaged liver. In this review, we briefly summarize the current knowledge about the differential roles of angiogenesis in the induction of fibrogenesis and the resolution of fibrosis in damaged livers. Possible strategies for the prevention and treatment of liver fibrosis are also discussed.

The role of immune cells in metabolism-related liver inflammation and development of non-alcoholic steatohepatitis (NASH)

The low grade inflammatory state present in obesity promotes the progression of Non-Alcoholic Fatty Liver Disease (NAFLD). In Non-Alcoholic Steatohepatitis (NASH), augmented hepatic steatosis is accompanied by aberrant intrahepatic inflammation and exacerbated hepatocellular injury. NASH is an important disorder and can lead to fibrosis, cirrhosis and even neoplasia. The pathology of NASH involves a complex network of mechanisms, including increased infiltration of different subsets of immune cells, such as monocytes, T-lymphocytes and neutrophils, to the liver, as well as activation and in situ expansion of liver resident cells such as Kupffer cells or stellate cells. In this review, we summarize recent advances regarding understanding the role of the various cells of the innate and adaptive immunity in NASH development and progression, and discuss possible future therapeutic options and tools to interfere with disease progression.

Propofol Attenuates Lipopolysaccharide-Induced Monocyte Chemoattractant Protein-1 Production Through Enhancing apoM and foxa2 Expression in HepG2 Cells

Monocyte chemoattractant protein-1 (MCP-1) is a cytokine that mediates the influx of cells to sites of inflammation. Our group recently reported that propofol exerted an anti-inflammatory effect and could inhibit lipopolysaccharide (LPS)-induced production of pro-inflammatory cytokines. However, the effect and possible mechanisms of propofol on MCP-1 expression remain unclear. LPS-stimulated HepG2 cells were treated with 50 μM propofol for 0, 6, 12, and 24 h, respectively. The transcript and protein levels were measured by real-time quantitative PCR and Western blot analyses, respectively. We found that propofol markedly decreased both MCP-1 messenger RNA (mRNA) and protein levels in LPS-stimulated HepG2 cells in a time-dependent manner. Expression of apolipoprotein M (apoM) and forkhead box protein A2 (foxa2) was increased by propofol treatment in HepG2 cells. In addition, the inhibitory effect of propofol on MCP-1 expression was significantly abolished by small interfering RNA against apoM and foxa2 in LPS-stimulated HepG2 cells. Propofol attenuates LPS-induced MCP-1 production through enhancing apoM and foxa2 expression in HepG2 cells.

Emerging therapeutic targets for the treatment of hepatic fibrosis

Fibrosis represents a response to chronic injury, aimed at maintaining organ integrity. Hepatic fibrosis is mainly related to chronic viral hepatitis B or C (HBV or HCV), alcoholic and nonalcoholic steatohepatitis (NASH), and biliary diseases. A deep understanding of the cellular and molecular mechanisms underlying liver fibrosis has enabled the development of 'pathogenetic tailored' therapeutic interventions. However, effective drugs to prevent or revert hepatic fibrosis are still lacking. In this review, we discuss the cellular populations and the molecular pathways involved in liver fibrogenesis as well as the novel approaches currently being tested in clinical trials.

Phenotypic and functional characterization of macrophages with therapeutic potential generated from human cirrhotic monocytes in a cohort study

BACKGROUND AIMS

Macrophages have complex roles in the liver. The aim of this study was to compare profiles of human monocyte-derived macrophages between controls and cirrhotic patients, to determine whether chronic inflammation affects precursor number or the phenotype, with the eventual aim to develop a cell therapy for cirrhosis.

METHODS

Infusion of human macrophages in a murine liver fibrosis model demonstrated a decrease in markers of liver injury (alanine transaminase, bilirubin, aspartate transaminase) and fibrosis (transforming growth factor-β, α-smooth muscle actin, phosphatidylserine receptor) and an increase in markers of liver regeneration (matrix metalloproteinases [MMP]-9, MMP-12 and TNF-related weak inducer of apoptosis). CD14+ monocytes were then isolated from controls. Monocytes were matured into macrophages for 7 days using a Good Manufacturing Practice-compatible technique.

RESULTS

There was no significant difference between the mean number of CD14+ monocytes isolated from cirrhotic patients (n = 9) and controls (n = 10); 2.8 ± SEM 0.54 × 10(8) and 2.5 ± 0.56 × 10(8), respectively. The mean yield of mature macrophages cultured was also not significantly different between cirrhotic patients and controls (0.9 × 10(8) ± 0.38 × 10(8), with more than 90% viability and 0.65 × 10(8) ± 0.16 × 10(8), respectively. Maturation to macrophages resulted in up-regulation of a number of genes (MMP-9, CCL2, interleukin [IL]-10 and TNF-related weak inducer of apoptosis). A cytokine and chemokine polymerase chain reaction array, comparing the control and cirrhotic macrophages, revealed no statistically significant differences.

CONCLUSIONS

Macrophages can be differentiated from cirrhotic patients' apheresis-derived CD14 monocytes and develop the same pro-resolution phenotype as control macrophages, indicating their suitability for clinical therapy.

Mathematical Model of Innate and Adaptive Immunity of Sepsis: A Modeling and Simulation Study of Infectious Disease

Sepsis is a systemic inflammatory response (SIR) to infection. In this work, a system dynamics mathematical model (SDMM) is examined to describe the basic components of SIR and sepsis progression. Both innate and adaptive immunities are included, and simulated results in silico have shown that adaptive immunity has significant impacts on the outcomes of sepsis progression. Further investigation has found that the intervention timing, intensity of anti-inflammatory cytokines, and initial pathogen load are highly predictive of outcomes of a sepsis episode. Sensitivity and stability analysis were carried out using bifurcation analysis to explore system stability with various initial and boundary conditions. The stability analysis suggested that the system could diverge at an unstable equilibrium after perturbations if r_t2max (maximum release rate of Tumor Necrosis Factor- (TNF-) α by neutrophil) falls below a certain level. This finding conforms to clinical findings and existing literature regarding the lack of efficacy of anti-TNF antibody therapy.

Angiogenesis and Fibrogenesis in Chronic Liver Diseases

Pathologic angiogenesis appears to be intrinsically associated with the fibrogenic progression of chronic liver diseases, which eventually leads to the development of cirrhosis and related complications, including hepatocellular carcinoma. Several laboratories have suggested that this association is relevant for chronic liver disease progression, with angiogenesis proposed to sustain fibrogenesis. This minireview offers a synthesis of relevant findings and opinions that have emerged in the last few years relating liver angiogenesis to fibrogenesis. We discuss liver angiogenesis in normal and pathophysiologic conditions with a focus on the role of hypoxia and hypoxia-inducible factors and assess the evidence supporting a clear relationship between angiogenesis and fibrogenesis. A section is dedicated to the critical interactions between liver sinusoidal endothelial cells and either quiescent hepatic stellate cells or myofibroblast-like stellate cells. Finally, we introduce the unusual, dual (profibrogenic and proangiogenic) role of hepatic myofibroblasts and emerging evidence supporting a role for specific mediators like vasohibin and microparticles and microvesicles.

Role of chemokine pathways in hepatobiliary cancer

Persistent hepatic inflammation resulting from hepatitis B or C virus infections (HBV or HCV, respectively), obesity-associated non-alcoholic steatohepatitis (NASH) or alcohol abuse is a hallmark feature of chronic liver diseases and appears to be an essential prerequisite of hepatocarcinogenesis. The inflammatory processes in the liver are regulated by various chemokines, which orchestrate the interaction between parenchymal liver cells, Kupffer cells (resident macrophages), hepatic stellate cells (HSC), endothelial cells, and infiltrating immune cells. In consequence, these cellular interactions result in the re-modeling of the hepatic microenvironment toward a pro-inflammatory, pro-fibrotic, pro-angiogenic and thus pre-neoplastic milieu. Once developed, liver neoplasms provoke pro- and anti-tumor immune responses that are also critically regulated through differential activation of chemokine pathways. With respect to hepatobiliary cancers, including hepatocellular carcinoma (HCC), gallbladder cancer and cholangiocellular carcinoma (cholangiocarcinoma), together belonging to the highest causes of cancer-related deaths worldwide, this review article will give an overview of chemokine pathways involved in both the establishment of a pro-tumorigenic microenvironment as well as the development and progression of hepatobiliary cancer. Pharmaceutical targeting of chemokine pathways is a promising approach to treat or even prevent hepatobiliary cancer.