Increased peripheral mononuclear cells expression of adhesion molecules in alcoholic cirrhosis: its relation to immune activation

Alcohol Consumption Accumulation of Monocyte Derived Macrophages in Female Mice Liver Is Interferon Alpha Receptor Dependent

Monocytes develop in the bone marrow from the hematopoietic stem cells and represent heterogeneous phagocyte cells in the circulation. In homeostatic and inflammatory conditions, after recruitment into tissues, monocytes differentiate into macrophages and dendritic cells. Alcohol use causes about 3.3 million worldwide deaths per year, which is about 5.9% of all deaths. In the United States and Europe, alcohol use disorders represent the fifth leading cause of death. Females are more susceptible to alcoholic liver injury in both humans and mice. Strikingly, we still do not know how much of this difference in tissue injury is due to the differential effect of alcohol and its toxic metabolites on a) parenchymal or resident cells and/or b) immune response to alcohol. Therefore, we used a model of chronic alcohol exposure in mice to investigate the dynamics of monocytes, an innate immune cell type showed to be critical in alcoholic liver injury, by using immunophenotypic characterization. Our data reveal a sex-dimorphism of alcohol response of hepatic monocytes in female mice that is interferon receptor alpha dependent. This dimorphism could shed light on potential cellular mechanism(s) to explain the susceptibility of females to alcoholic immunopathogenesis and suggests an additional targetable pathway for alcoholic liver injury in females.

The Role of Myeloid-Derived Cells in the Progression of Liver Disease

Control of homeostasis and rapid response to tissue damage in the liver is orchestrated by crosstalk between resident and infiltrating inflammatory cells. A crucial role for myeloid cells during hepatic injury and repair has emerged where resident Kupffer cells, circulating monocytes, macrophages, dendritic cells and neutrophils control local tissue inflammation and regenerative function to maintain tissue architecture. Studies in humans and rodents have revealed a heterogeneous population of myeloid cells that respond to the local environment by either promoting regeneration or driving the inflammatory processes that can lead to hepatitis, fibrogenesis, and the development of cirrhosis and malignancy. Such plasticity of myeloid cell responses presents unique challenges for therapeutic intervention strategies and a greater understanding of the underlying mechanisms is needed. Here we review the role of myeloid cells in the establishment and progression of liver disease and highlight key pathways that have become the focus for current and future therapeutic strategies.

Plasma levels of soluble ST2, but not IL-33, correlate with the severity of alcoholic liver disease

Alcoholic liver disease (ALD) is a complication that is a burden on global health and economy. Interleukin‐33 (IL‐33) is a newly identified member of the IL‐1 cytokine family and is released as an “alarmin” during inflammation. Soluble suppression of tumourigenicity 2 (sST2), an IL‐33 decoy receptor, has been reported as a new biomarker for the severity of systemic and highly inflammatory diseases. Here, we found the levels of plasma sST2, increased with the disease severity from mild to severe ALD. Importantly, the plasma sST2 levels in ALD patients not only correlated with scores for prognostic models (Maddrey's discriminant function, model for end‐stage liver disease and Child‐Pugh scores) and indexes for liver function (total bilirubin, international normalized ratio, albumin, and cholinesterase) but also correlated with neutrophil‐associated factors as well as some proinflammatory cytokines. In vitro, lipopolysaccharide‐activated monocytes down‐regulated transmembrane ST2 receptor but up‐regulated sST2 mRNA and protein expression and produced higher levels of tumour necrosis factor‐α (TNF‐α). By contrast, monocytes pretreated with recombinant sST2 showed decreased TNF‐α production. In addition, although plasma IL‐33 levels were comparable between healthy controls and ALD patients, we found the IL‐33 expression in liver tissues from ALD patients was down‐regulated at both RNA and protein levels. Immunohistochemical staining further showed that the decreased of IL‐33‐positive cells were mainly located in liver lobule area. These results suggested that sST2, but not IL‐33, is closely related to the severity of ALD. Consequently, sST2 could be used as a potential biomarker for predicting the prognosis of ALD.

Decreased monocyte shedding of the migration inhibitor soluble CD18 in alcoholic hepatitis

OBJECTIVES

During alcoholic hepatitis (AH) monocytes traverse the vascular boundaries and massively invade the liver. In principle, tissue extravasation can be limited through shedding of CD18 integrins from leukocytes, including monocytes. The soluble (s) product sCD18 conceals adhesion receptors on the endothelium, which reduces monocyte extravasation. In AH, monocytes are dysfunctional, but whether this involves their self-generated anti-migration is unknown. Our aim was, therefore, to investigate monocyte CD18 dynamics in AH.

METHODS

We studied 50 AH patients and 20 healthy controls. We measured monocyte expression and conformational activation of CD18, plasma (P)-sCD18, stimulated in vitro CD18 shedding and P-sCD18 in a short-term chronic-binge mouse model.

RESULTS

AH-derived monocytes had a 30-60% higher expression of active CD18 receptors (p < 0.01), but the sCD18 concentration per monocyte was reduced in vivo by 30% and in vitro by 120% (p < 0.01). Ethanol reduced the in vitro shedding of CD18 in the patients only. TNFα increased sCD18 concentration per monocyte, but less so in the patients (p < 0.04). P-sCD18 per monocyte was inversely related to disease severity. In early alcoholic liver disease, P-sCD18 was decreased in the mouse model.

CONCLUSIONS

The monocyte CD18 integrins are highly activated in AH and the single monocyte shedding of CD18 was decreased favoring tissue extravasation. Alcohol in itself and altered monocyte responsiveness to TNFα may explain this lowered shedding.

TRANSLATIONAL IMPACT

The contribution of this mechanism to the excessive monocyte liver infiltration in AH should be further explored as it may serve as a potential therapeutic target to limit liver inflammation.

Summary of the 2016 Alcohol and Immunology Research Interest Group (AIRIG) meeting

On November 18, 2016 the 21st annual Alcohol and Immunology Research Interest Group (AIRIG) meeting was held at the Center for Translational Research and Education at Loyola University Chicago's Health Sciences Campus in Maywood, IL. The 2016 meeting focused broadly on alcohol and inflammation, epigenetics, and the microbiome. The four plenary sessions of the meeting were Alcohol, Inflammation, and Immunity; Alcohol and Epigenetics; Alcohol, Transcriptional Regulation, and Epigenetics; and Alcohol, Intestinal Mucosa, and the Gut Microbiome. Presentations in all sessions of the meeting explored putative underlying causes for chronic diseases and mortality associated with alcohol consumption, shedding light on future work and potential therapeutic targets to alleviate the negative effects of alcohol misuse.

Evaluating the effect of diallyl sulfide on regulation of inflammatory mRNA expression in 3T3L1 adipocytes and RAW 264.7 macrophages during ethanol treatment

Diallyl sulfide (DAS) has been studied extensively for its alleged role as an anticancer and protective agent. Alcohol influences and effects on human health have been extensively studied. However, investigations toward developing and testing therapeutic agents that can reduce the tissue injury caused by ethanol are scarce. In this backdrop, this study was designed to explore the potential effect of DAS in reducing alcohol induced damage of 3T3L1 adipocytes and RAW 264.7 macrophages. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay was performed to determine the DAS effect on cell viability. Reactive oxygen species (ROS) production was assessed by flow cytometer. Expression of inflammatory genes was studied by the qRT-PCR method. Our study results showed that DAS at concentrations less than 200 μM was not toxic to the cells and the viability of ethanol-exposed 3T3L1 adipocyte cells was found to be significantly increased when ethanol-exposed cells were treated with DAS. Further, treatment of ethanol-exposed 3T3L1 cells with 100 μM DAS for 24 h was found to reduce ethanol induced ROS production, expression of pro-inflammatory cytokines, and enhance anti-inflammatory cytokine production in the cells. Also, 100 μM DAS was found to increase the expression of M2 phenotype-specific genes in ethanol-exposed RAW 264.7 macrophage cells. Further, 100 μM DAS also improved the levels of lipid accumulation in 3T3L1 adipocytes that was down-regulated by ethanol exposure. Taken together, our study results imply that DAS may be effective in reducing ethanol induced injury of cells thereby suggesting its potential to be used in drug formulations.

Hepatic macrophages in homeostasis and liver diseases: from pathogenesis to novel therapeutic strategies

Macrophages represent a major cell type of innate immunity and have emerged as a critical player and therapeutic target in many chronic inflammatory diseases. Hepatic macrophages consist of Kupffer cells, which are originated from the fetal yolk-sack, and infiltrated bone marrow-derived monocytes/macrophages. Hepatic macrophages play a central role in maintaining homeostasis of the liver and in the pathogenesis of liver injury, making them an attractive therapeutic target for liver diseases. However, the various populations of hepatic macrophages display different phenotypes and exert distinct functions. Thus, more research is required to better understand these cells to guide the development of macrophage-based therapeutic interventions. This review article will summarize the current knowledge on the origins and composition of hepatic macrophages, their functions in maintaining hepatic homeostasis, and their involvement in both promoting and resolving liver inflammation, injury, and fibrosis. Finally, the current strategies being developed to target hepatic macrophages for the treatment of liver diseases will be reviewed.

Expression of β2-integrin on leukocytes in liver cirrhosis

AIM: To analyze β2-integrin expression on blood leukocytes in liver cirrhosis.

METHODS: In 40 patients with liver cirrhosis and 20 healthy individuals, the evaluation of expression of CD11a (LFA-1α), CD11b (Mac-1α), CD11c (αX) and CD49d (VLA-4α) on peripheral blood leukocytes was performed using flow cytometry. The analysis was carried out in groups of patients divided into B and C according to Child-Pugh’s classification.

RESULTS: An increased CD11a, CD11b, CD11c and CD49d integrin expression was observed on peripheral blood leukocytes in liver cirrhosis. The integrin levels were elevated as the advancement of liver failure progressed. The highest expression of integrins occurred predominantly on monocytes. A slight expression of VLA-4 was found on lymphocytes and granulocytes and it increased together with liver failure. A positive correlation was noted between median intensity of fluorescence (MIF) expression on polymorphonuclear cells of CD11a and CD11c and CD49d (r = 0.42, P < 0.01; r = 053, P < 0.01, respectively) in liver cirrhosis stage C. However, no correlation was observed between integrin expression on leukocytes. The concentrations of sICAM-1, sVCAM-1, and TNFα, were significantly elevated in liver cirrhosis.

CONCLUSION: β2-integrin expression on leukocytes increases in liver cirrhosis decompensated as the stage of liver failure increases, which is a result of permanent activation of leukocytes circulating through the inflamed liver environment. β2-integrin expression on circulating leukocytes can intensify liver cirrhosis.

Patients with acute on chronic liver failure display "sepsis-like" immune paralysis

BACKGROUND/AIMS

Cellular immune depression is linked to high mortality in sepsis, but has yet to be systematically analysed in liver cirrhosis. The aim of the present study was to directly compare functional immune parameters in patients with acute on chronic liver failure (ACLF), severe sepsis, and non-decompensated cirrhosis.

METHODS

Patients with ACLF (n=27) were investigated at admission to a medical ICU. Patients with stable liver cirrhosis (n=24) and severe sepsis (n=31) served as control groups. In all subjects, serum levels of IL-6 and IL-10, ex vivo production of TNF-alpha in a whole blood assay, and monocyte surface HLA-DR expression were determined.

RESULTS

In patients with ACLF or sepsis, ex vivo TNF-alpha production and HLA-DR expression were severely decreased compared to subjects with stable cirrhosis (both P<0.001). Contrary, IL-6 levels were highest in septic patients, followed by subjects with ACLF and cirrhotic patients (both P<0.05). Immune dysfunction in ACLF was independent of aetiology of liver cirrhosis and associated with high mortality.

CONCLUSIONS

Patients with ACLF and severe sepsis show a similar degree of cellular immune depression. The reduced cellular immune function in subjects with ACLF might contribute to the increased infectious morbidity of these patients and provide a rational basis for prevention strategies.

Role of cell adhesion molecules in leukocyte recruitment in the liver and gut

This article reviews the evidence that adhesion molecules are critical in leukocyte recirculation and pathogenesis of diseases affecting the closely related tissues of the liver and gut, which offer novel opportunities for treatment.

Monocyte activation in alcoholic liver disease

Activated monocytes and macrophages have been postulated to play an important role in the pathogenesis of alcoholic liver disease (ALD). Monocyte activation can be documented by measurement of neopterin, adhesion cell molecules, and certain proinflammatory cytokines and chemokines. We first became interested in the role of monocytes and monocyte-derived cytokines in ALD in relation to altered zinc metabolism that occurs regularly in ALD. Patients with ALD have hypozincemia, which responds poorly to oral zinc supplementation. We have shown that in ALD monocytes make a low-molecular-weight substance that, when injected into rabbits, causes prominent hypozincemia. Subsequently, multiple cytokines [especially tumor necrosis factor (TNF) and interleukin (IL)-8] have been shown to be overproduced by monocytes in ALD. We initially showed that monocytes in ALD spontaneously produce TNF and overproduce TNF in response to a lipopolysaccharide (LPS) stimulus, and this could be attenuated by antioxidants in vitro and in vivo. Alterations in the endotoxin-binding protein LPS-binding protein, in CD14, and in the endotoxin receptor Toll-like receptor 4 all may play roles in enhanced proinflammatory cytokine signaling in ALD. Moreover, several groups have documented increased TNF receptor density in monocytes in ALD. Inadequate negative regulation of TNF occurs at multiple levels in ALD. This includes decreased monocyte production of the important antiinflammatory cytokine IL-10 and blunted response to the antiinflammatory properties of adenosine. Finally, generation of reactive oxygen species (which occurs during alcohol metabolism) and products of lipid peroxidation induce production of cytokines, such as TNF and IL-8. In conclusion, there are multiple overlapping potential mechanisms for enhanced proinflammatory cytokine production by monocytes in ALD. We postulate that activation of monocytes and macrophages with subsequent proinflammatory cytokine production plays an important role in certain metabolic complications of ALD and is a component of the liver injury of ALD.

Attenuation of CCl(4)-induced hepatic fibrosis by GdCl(3) treatment or dietary glycine

The role of Kupffer cells in CCl(4)-induced fibrosis was investigated in vivo. Male Wistar rats were treated with phenobarbital and CCl(4) for 9 wk, and a group of rats were injected with the Kupffer cell toxicant gadolinium chloride (GdCl(3)) or were fed glycine, which inactivates Kupffer cells. After CCl(4) alone, the fibrosis score was 3.0 +/- 0.1 and collagen protein and mRNA expression were elevated, but GdCl(3) or glycine blunted these parameters. Glycine did not alter cytochrome P-450 2E1, making it unlikely that glycine affects CCl(4) metabolism. Treatment with GdCl(3) or glycine prevented CCl(4)-induced increases in transforming growth factor (TGF)-beta 1 protein levels and expression. CCl(4) treatment increased alpha-smooth muscle actin staining (score 3.0 +/- 0.2), whereas treatment with GdCl(3) and glycine during CCl(4) exposure blocked this effect (1.2 +/- 0.5); there was no staining with glycine treatment. These results support previous in vitro data and demonstrate that treatment of rats with the selective Kupffer cell toxicant GdCl(3) prevents stellate cell activation and the development of fibrosis.

Serial analysis of serum and ascitic fluid levels of soluble adhesion molecules and chemokines in patients with spontaneous bacterial peritonitis

The aim of this work was the evaluation of serum and ascitic fluid levels of chemokines (IL-8, growth-regulated oncogene (Gro-alpha), and monocyte chemotactic protein-1 (MCP-1)), and of soluble adhesion molecules (P-selectin, E-selectin, L-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1)) in patients with spontaneous bacterial peritonitis (SBP). These compounds were serially analysed in serum and ascitic fluid by ELISA in patients with SBP (n = 20), non-infected cirrhotic controls (n = 12), and healthy controls (n = 15). Infected and non-infected cirrhotic patients showed significantly higher serum levels of adhesion molecules. SBP was associated with significantly higher serum and ascitic fluid levels of IL-8, Gro-alpha and ICAM-1 and with ascitic fluid concentrations of MCP-1. Significantly elevated serum levels of both ICAM-1 and VCAM-1 were detected in patient non-survivors after SBP. Thus, higher ascitic fluid levels of chemokines could be implicated in the peritoneal infiltrate in patients with SBP. Prognostic significance can be attributed to serum levels of ICAM-1 and VCAM-1 in these patients.

sICAM-1, sCD95 and sCD95L levels in chronic liver diseases of different etiology

The release of soluble circulating molecules represents a prominent feature during the course of immune-mediated clinical conditions. To further assess the relationship between serum concentrations of adhesion or apoptotic-related soluble structures and liver diseases, we evaluated the levels of intercellular adhesion molecule-1 (sICAM-1), Fas receptor (CD95) and Fas ligand (sCD95L) in a group of patients affected by Hepatitis C Virus (HCV)-induced chronic hepatitis (CH-C), HCV-positive liver cirrhosis with superimposed hepatocellular carcinoma (HCC), autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC) and alcoholic liver cirrhosis (ALC). Results show that sICAM-1 values were in all instances significantly elevated when compared to those seen in healthy donors. Similar findings were noted in subjects with liver diseases in terms of sCD95 concentrations, even if to a different degree of statistical significance. Finally, sCD95L amounts were augmented in AIH, PBC, ALC and CH-C in comparison to controls, while in the HCC counterpart sCD95L levels fell within normal range. All together, these findings emphasize the occurrence of circulating soluble molecules in patients with various chronic liver diseases, likely reflecting the involvement of several pathogenetic mechanisms.

Gene expression of TNF-receptors in peripheral blood mononuclear cells of patients with alcoholic cirrhosis

BACKGROUND/AIMS

Elevated concentrations of tumor necrosis factor receptors have been detected in alcoholic cirrhosis, but it remains unknown whether or not peripheral blood mononuclear cells are a source of tumor necrosis factor receptors and reflect the clinical disease activity of patients with advanced alcoholic liver disease.

METHODS

Twenty-two abstinent patients in different stages of alcohol-induced cirrhosis according to the criteria of the Child-Pugh classification (Child-Pugh stage A: 4, Child-Pugh stage B: 10, Child-Pugh stage C: 8) were compared with four healthy individuals. Semi-quantitative reverse transcriptase-polymerase chain reaction was used for the measurement of the expression of tumor necrosis factor-alpha, soluble tumor necrosis factor receptors-p55, -p75, interleukin-10 and inducible nitric oxide synthase in unstimulated peripheral blood mononuclear cells.

RESULTS

Unstimulated peripheral blood mononuclear cells of patients with alcoholic cirrhosis demonstrate a stage-dependent enhanced RNA expression of tumor necrosis factor-alpha (healthy controls 0/4, Child-Pugh stage A 2/4, stage B 10/10, stage C 8/8; p<0.01). The mRNA expression of TNF-receptors-p55/-p75 is significantly higher in patients with severe alcoholic cirrhosis (Child-Pugh stage B or C patients) than healthy controls (p<0.05), while peripheral blood mononuclear cells from patients with Child-Pugh stage A show a similiar pattern of gene expression to healthy controls. No significant up-regulation of interleukin-10 was found. Inducible nitric oxide synthase was detectable in Child-Pugh stage C (p<0.05).

CONCLUSIONS

Unstimulated peripheral blood mononuclear cells of patients with severe alcoholic cirrhosis (Child-Pugh stage B and C) demonstrate a systemic leukocyte activation and gene expression of tumor necrosis factor-alpha and tumor necrosis factor receptors-p55/-p75, which is correlated with the activity of the disease. Our data confirm previous studies that reported a correlation between plasma levels of pro-inflammatory cytokines and the severity of alcoholic cirrhosis. The role of interleukin-10 and inducible nitric oxide synthase in the pathogenesis of alcoholic cirrhosis remains to be fully elucidated.

Neopterin-induced expression of intercellular adhesion molecule-1 (ICAM-1) in type II-like alveolar epithelial cells

Production and release of proinflammatory mediators such as tumour necrosis factor-alpha and neopterin are common events following the activation of the cellular immune system. Concerning inflammatory disorders of the lung, e.g. sepsis or sarcoidosis, high serum neopterin levels have been reported to correlate well with the severity of the disease. These situations are often associated with an increased expression of ICAM-1 reported to be induced in type II alveolar epithelial cells. In our study we investigated the potential effects of neopterin on ICAM-1 synthesis in the type II-like pneumocyte cell line L2. Detection of ICAM-1 gene expression by reverse transcriptase-polymerase chain reaction revealed a dose-dependent effect of neopterin, with maximum impact following 12-h incubations. Comparable results were obtained when ICAM-1 protein synthesis was measured via a cell-based ELISA. In a second set of experiments we were able to show that coincubation of L2 cells with pyrrolidine dithiocarbamate (PDTC) significantly suppressed neopterin-induced ICAM-1 synthesis. Since PDTC is known to be a potent inhibitor of NF-kappaB, the stimulating effects of neopterin on ICAM-1 gene expression and protein generation may be mediated by activation of this transcription factor. From these data we conclude that neopterin stimulates ICAM-1 production in L2 cells. In vivo, these effects may contribute to the prolongation of the inflammatory response, including cytotoxic cell host defence mechanisms that impair the functions of the airway epithelium.