Pharmacological Inhibition of CCR2/5 Signaling Prevents and Reverses Alcohol-Induced Liver Damage, Steatosis, and Inflammation in Mice

Cellular Mechanisms of Liver Fibrosis

The liver is a central organ in the human body, coordinating several key metabolic roles. The structure of the liver which consists of the distinctive arrangement of hepatocytes, hepatic sinusoids, the hepatic artery, portal vein and the central vein, is critical for its function. Due to its unique position in the human body, the liver interacts with components of circulation targeted for the rest of the body and in the process, it is exposed to a vast array of external agents such as dietary metabolites and compounds absorbed through the intestine, including alcohol and drugs, as well as pathogens. Some of these agents may result in injury to the cellular components of liver leading to the activation of the natural wound healing response of the body or fibrogenesis. Long-term injury to liver cells and consistent activation of the fibrogenic response can lead to liver fibrosis such as that seen in chronic alcoholics or clinically obese individuals. Unidentified fibrosis can evolve into more severe consequences over a period of time such as cirrhosis and hepatocellular carcinoma. It is well recognized now that in addition to external agents, genetic predisposition also plays a role in the development of liver fibrosis. An improved understanding of the cellular pathways of fibrosis can illuminate our understanding of this process, and uncover potential therapeutic targets. Here we summarized recent aspects in the understanding of relevant pathways, cellular and molecular drivers of hepatic fibrosis and discuss how this knowledge impact the therapy of respective disease.

Macrophages in Chronic Liver Failure: Diversity, Plasticity and Therapeutic Targeting

Chronic liver injury results in immune-driven progressive fibrosis, with risk of cirrhosis development and impact on morbidity and mortality. Persistent liver cell damage and death causes immune cell activation and inflammation. Patients with advanced cirrhosis additionally experience pathological bacterial translocation, exposure to microbial products and chronic engagement of the immune system. Bacterial infections have a high incidence in cirrhosis, with spontaneous bacterial peritonitis being the most common, while the subsequent systemic inflammation, organ failure and immune dysregulation increase the mortality risk. Tissue-resident and recruited macrophages play a central part in the development of inflammation and fibrosis progression. In the liver, adipose tissue, peritoneum and intestines, diverse macrophage populations exhibit great phenotypic and functional plasticity determined by their ontogeny, epigenetic programming and local microenvironment. These changes can, at different times, promote or ameliorate disease states and therefore represent potential targets for macrophage-directed therapies. In this review, we discuss the evidence for macrophage phenotypic and functional alterations in tissue compartments during the development and progression of chronic liver failure in different aetiologies and highlight the potential of macrophage modulation as a therapeutic strategy for liver disease.

Kadsura heteroclita stem ethanol extract protects against carbon tetrachloride-induced liver injury in mice via suppression of oxidative stress, inflammation, and apoptosis

ETHNOPHARMACOLOGICAL RELEVANCE

Kadsura heteroclita stem (KHS) is a well-known hepatoprotective Tujia ethnomedicine (folk named Xuetong), has long been used for the prevention and treatment of hepatitis and liver diseases.

AIM OF THE STUDY

To explore the protective effects of KHS against carbon tetrachloride (CCl4)-induced liver injury and the underlying mechanism, particularly antioxidative, anti-inflammatory, and anti-apoptotic potentials.

MATERIALS AND METHODS

The acute toxicity of KHS was measured by the method of maximum tolerated dose (MTD). Liver injury in mice was induced by intraperitoneal injection of 25% carbon tetrachloride (olive oil solubilization) 2 times every week. After modeling, mice in KHS groups were treated with KHS at 100, 200, 400 mg/kg/d, mice in positive control group were treated with bifendate (30 mg/kg/d), and mice in normal and model groups were given ultrapure water. After 4 weeks of treatment, blood of mice was taken from the orbital venous plexus before mice euthanized, the liver, spleen, and thymus of mice were weighed by dissecting the abdominal cavity after mice euthanized. Moreover, the liver of mice was selected for histological examination. The alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities in mice serum were measured using the automatic biochemical analyzer. The levels of superoxide dismutase (SOD), myeloperoxidase (MPO), malondialdehyde (MDA), glutathione peroxidase (GPX-2), tumor necrosis factor (TNF-α), interleukin-6 (IL-6), interleukin-10 (IL-10), Bcl-2-associated X (Bax), B-cell lymphoma-2 (Bcl-2), Caspase-3, and Caspase-8 in mice liver were measured by Elisa kits. Furthermore, the protein expression of Bcl-2 and Bax in mice liver tissue was detected by Western blot.

RESULTS

The MTD of KHS was determined to be 26 g/kg in both sexes of mice. Treatment with KHS dose-dependently protected the liver and other main organs against CCl4-induced liver injury in mice. The ALT and AST levels in mice liver were significantly reduced after treatment with KHS at the dose of 100, 200, and 400 mg/kg. In addition, the liver histopathological analyses revealed that KHS markedly alleviated inflammatory cell infiltration, hepatic fibrosis, hepatocyte ballooning, necrosis and severe apoptosis of hepatocytes induced by CCl4. Further assay indicated that KHS significantly suppressed the production of MDA and MPO, while markedly increased the level of SOD and GPx-2. The TNF-α and IL-6 level in mice liver tissue were decreased by KHS, whereas the IL-10 level was increased. KHS also inhibited hepatocyte apoptosis by significantly reducing the expression of Bax, Caspase-3, Caspase-8, as well as increasing the expression of Bcl-2. Besides, the Western blot results strongly demonstrated that KHS inhibited hepatocyte apoptosis, as evidenced by reducing the expression of Bax protein and increasing the expression of Bcl-2 protein in liver injury tissues.

CONCLUSIONS

This research firstly clarified that KHS has a significant protective effect against CCl4-induced liver injury, which might be closely related to alleviating oxidative stress, reducing inflammatory response, and inhibiting hepatocyte apoptosis.

Pancreatogenic Diabetes: Triggering Effects of Alcohol and HIV

Multiorgan failure may not be completely resolved among people living with HIV despite HAART use. Although the chances of organ dysfunction may be relatively low, alcohol may potentiate HIV-induced toxic effects in the organs of alcohol-abusing, HIV-infected individuals. The pancreas is one of the most implicated organs, which is manifested as diabetes mellitus or pancreatic cancer. Both alcohol and HIV may trigger pancreatitis, but the combined effects have not been explored. The aim of this review is to explore the literature for understanding the mechanisms of HIV and alcohol-induced pancreatotoxicity. We found that while premature alcohol-inducing zymogen activation is a known trigger of alcoholic pancreatitis, HIV entry through C-C chemokine receptor type 5(CCR5)into pancreatic acinar cells may also contribute to pancreatitis in people living with HIV (PLWH). HIV proteins induce oxidative and ER stresses, causing necrosis. Furthermore, infiltrative immune cells induce necrosis on HIV-containing acinar cells. When necrotic products interact with pancreatic stellate cells, they become activated, leading to the release of both inflammatory and profibrotic cytokines and resulting in pancreatitis. Effective therapeutic strategies should block CCR5 and ameliorate alcohol's effects on acinar cells.

α-Ketoglutarate Modulates Macrophage Polarization Through Regulation of PPARγ Transcription and mTORC1/p70S6K Pathway to Ameliorate ALI/ARDS

As tissue-resident cells in the lung, alveolar macrophages display remarkable heterogeneity and play a crucial role in the development and control of septic acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Recent evidence suggests that α-ketoglutarate (α-KG) plays an important role in alternative activation of macrophage (M2) through metabolic and epigenetic reprogramming, and thus possesses anti-inflammatory properties. However, the underlying mechanisms of α-KG's effect on alveolar macrophage polarization and the potential effects of α-KG in ALI/ARDS remain unclear. Here, we examined the effects and mechanisms of α-KG on alveolar macrophage polarization, and investigated the possible effects of α-KG on lipopolysaccharide (LPS)-induced ALI/ARDS in a mouse model. We found that α-KG inhibited M1 macrophage polarization and promoted IL-4-induced M2 macrophage polarization in MH-S cells (a murine alveolar macrophage cell line). Further experiments showed that α-KG down-regulated the expression of M1-polarized marker genes and inhibited the activities of mammalian target of rapamycin complex 1 (mTORC1)/p70 ribosomal protein S6 kinase (p70S6K) signaling pathway in M1-polarized MH-S cells. Moreover, our results showed that α-KG promoted IL-4-induced M2 polarization of MH-S cells by augmenting nuclear translocation of peroxisome proliferator-activated receptor γ (PPARγ) and increasing expression of relevant fatty acid metabolic genes. Finally, using an LPS-induced ALI/ARDS mouse model, we found that α-KG ameliorated the LPS-induced inflammation and lung pathological damage, as well as α-KG pretreated mice had better clinical scores compared with the LPS group. These findings reveal new mechanisms of α-KG in regulating macrophage polarization which may provide novel strategies for the prevention and treatment of inflammatory diseases, including sepsis and septic ALI/ARDS.

Control of human toxoplasmosis

Toxoplasmosis is caused by Toxoplasma gondii, an apicomplexan parasite that is able to infect any nucleated cell in any warm-blooded animal. Toxoplasma gondii infects around 2 billion people and, whilst only a small percentage of infected people will suffer serious disease, the prevalence of the parasite makes it one of the most damaging zoonotic diseases in the world. Toxoplasmosis is a disease with multiple manifestations: it can cause a fatal encephalitis in immunosuppressed people; if first contracted during pregnancy, it can cause miscarriage or congenital defects in the neonate; and it can cause serious ocular disease, even in immunocompetent people. The disease has a complex epidemiology, being transmitted by ingestion of oocysts that are shed in the faeces of definitive feline hosts and contaminate water, soil and crops, or by consumption of intracellular cysts in undercooked meat from intermediate hosts. In this review we examine current and future approaches to control toxoplasmosis, which encompass a variety of measures that target different components of the life cycle of T. gondii. These include: education programs about the parasite and avoidance of contact with infectious stages; biosecurity and sanitation to ensure food and water safety; chemo- and immunotherapeutics to control active infections and disease; prophylactic options to prevent acquisition of infection by livestock and cyst formation in meat; and vaccines to prevent shedding of oocysts by definitive feline hosts.

Immunological mechanisms and therapeutic targets of fatty liver diseases

Alcoholic liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD) are the two major types of chronic liver disease worldwide. Inflammatory processes play key roles in the pathogeneses of fatty liver diseases, and continuous inflammation promotes the progression of alcoholic steatohepatitis (ASH) and nonalcoholic steatohepatitis (NASH). Although both ALD and NAFLD are closely related to inflammation, their respective developmental mechanisms differ to some extent. Here, we review the roles of multiple immunological mechanisms and therapeutic targets related to the inflammation associated with fatty liver diseases and the differences in the progression of ASH and NASH. Multiple cell types in the liver, including macrophages, neutrophils, other immune cell types and hepatocytes, are involved in fatty liver disease inflammation. In addition, microRNAs (miRNAs), extracellular vesicles (EVs), and complement also contribute to the inflammatory process, as does intertissue crosstalk between the liver and the intestine, adipose tissue, and the nervous system. We point out that inflammation also plays important roles in promoting liver repair and controlling bacterial infections. Understanding the complex regulatory process of disrupted homeostasis during the development of fatty liver diseases may lead to the development of improved targeted therapeutic intervention strategies.

Targeted treatment of alcoholic liver disease based on inflammatory signalling pathways

Targeted therapy is an emerging treatment strategy for alcoholic liver disease (ALD). Inflammation plays an important role in the occurrence and development of ALD, and is a key choice for its targeted treatment, and anti-inflammatory treatment has been considered beneficial for liver disease. Surprisingly, immune checkpoint inhibitors have become important therapeutic agents for hepatocellular carcinoma (HCC). Moreover, studies have shown that the combination of inflammatory molecule inhibitors and immune checkpoint inhibitors can exert better effects than either alone in mouse models of HCC. This review discusses the mechanism of hepatic ethanol metabolism and the conditions under which inflammation occurs. In addition, we focus on the potential molecular targets in inflammatory signalling pathways and summarize the potential targeted inhibitors and immune checkpoint inhibitors, providing a theoretical basis for the targeted treatment of ALD and the development of new combination therapy strategies for HCC.

Recent advances targeting C-C chemokine receptor type 2 for liver diseases in monocyte/macrophage

Liver plays a critical role in metabolism, nutrient storage and detoxification. Emergency signals or appropriate immune response leads to pathological inflammation and breaks the steady state when liver dysfunction appears, which makes body more susceptible to chronic liver infection, autoimmune diseases and tumour. Compelling proof has illustrated the non-redundant importance of C-C chemokine receptor type 2 (CCR2), one of G-protein-coupled receptors, in different diseases. Selectively expressed on the surface of cells, CCR2 is involved in various signalling pathways and regulates the migration of cells. Especially, a peculiar role of CCR2 has been identified within decades in the onset and progression of hepatic diseases, which led to particular focusing on CCR2 as a new therapeutic and diagnostic target for non-alcoholic fatty liver disease and hepatocellular carcinoma. In this review, we discuss the effect of CCR2 in monocytes/macrophages on liver diseases. The application and translation of the decades of discoveries into therapies promise novel approaches in the treatment of liver disease.

Sex specific effect of alcohol on hepatic plasmacytoid dendritic cells

Alcoholic liver disease includes a spectrum of clinical and histological entities. They result from the combined direct effect of alcohol and its metabolites on immune cells and resident tissue cells. In humans and mice, females are more susceptible to alcoholic liver injury than males. Despite being involved in sex specific differences of immune mediated tissue injury, plasmacytoid dendritic cells (pDCs) have not been thoroughly assessed as a cellular target of alcohol in humans or mice. Therefore, Meadows-Cook diet was used to study alcohol effect on hepatic dendritic cells. Alcohol consumption for 12 weeks increased hepatic pDCs in female mice. The expression of the C-C chemokine receptor type 2 (CCR2) increased in hepatic pDC of alcohol-fed female mice. Bone marrow transplant chimera showed CCR2 dependent bone marrow egress of pDCs. Chronic alcohol exposure has a sex specific effect on hepatic pDCs population that may explain sex differences to alcoholic liver disease.

Metabolic Functions of G Protein-Coupled Receptors in Hepatocytes-Potential Applications for Diabetes and NAFLD

G protein-coupled receptors (GPCRs) are cell surface receptors that mediate the function of extracellular ligands. Understanding how GPCRs work at the molecular level has important therapeutic implications, as 30–40% of the drugs currently in clinical use mediate therapeutic effects by acting on GPCRs. Like many other cell types, liver function is regulated by GPCRs. More than 50 different GPCRs are predicted to be expressed in the mouse liver. However, knowledge of how GPCRs regulate liver metabolism is limited. A better understanding of the metabolic role of GPCRs in hepatocytes, the dominant constituent cells of the liver, could lead to the development of novel drugs that are clinically useful for the treatment of various metabolic diseases, including type 2 diabetes, nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). In this review, we describe the functions of multiple GPCRs expressed in hepatocytes and their role in metabolic processes.

Hepatic macrophages in liver homeostasis and diseases-diversity, plasticity and therapeutic opportunities

Macrophages, which are key cellular components of the liver, have emerged as essential players in the maintenance of hepatic homeostasis and in injury and repair processes in acute and chronic liver diseases. Upon liver injury, resident Kupffer cells (KCs) sense disturbances in homeostasis, interact with hepatic cell populations and release chemokines to recruit circulating leukocytes, including monocytes, which subsequently differentiate into monocyte-derived macrophages (MoMϕs) in the liver. Both KCs and MoMϕs contribute to both the progression and resolution of tissue inflammation and injury in various liver diseases. The diversity of hepatic macrophage subsets and their plasticity explain their different functional responses in distinct liver diseases. In this review, we highlight novel findings regarding the origins and functions of hepatic macrophages and discuss the potential of targeting macrophages as a therapeutic strategy for liver disease.

Chronic alcohol-induced neuroinflammation involves CCR2/5-dependent peripheral macrophage infiltration and microglia alterations

Background

Chronic alcohol consumption is associated with neuroinflammation, neuronal damage, and behavioral alterations including addiction. Alcohol-induced neuroinflammation is characterized by increased expression of proinflammatory cytokines (including TNFα, IL-1β, and CCL2) and microglial activation. We hypothesized chronic alcohol consumption results in peripheral immune cell infiltration to the CNS. Since chemotaxis through the CCL2-CCR2 signaling axis is critical for macrophage recruitment peripherally and centrally, we further hypothesized that blockade of CCL2 signaling using the dual CCR2/5 inhibitor cenicriviroc (CVC) would prevent alcohol-induced CNS infiltration of peripheral macrophages and alter the neuroinflammatory state in the brain after chronic alcohol consumption.

Methods

C57BL/6J female mice were fed an isocaloric or 5% (v/v) ethanol Lieber DeCarli diet for 6 weeks. Some mice received daily injections of CVC. Microglia and infiltrating macrophages were characterized and quantified by flow cytometry and visualized using CX3CR1^eGFP/+ CCR2^RFP/+ reporter mice. The effect of ethanol and CVC treatment on the expression of inflammatory genes was evaluated in various regions of the brain, using a Nanostring nCounter inflammation panel. Microglia activation was analyzed by immunofluorescence. CVC-treated and untreated mice were presented with the two-bottle choice test.

Results

Chronic alcohol consumption induced microglia activation and peripheral macrophage infiltration in the CNS, particularly in the hippocampus. Treatment with CVC abrogated ethanol-induced recruitment of peripheral macrophages and partially reversed microglia activation. Furthermore, the expression of proinflammatory markers was upregulated by chronic alcohol consumption in various regions of the brain, including the cortex, hippocampus, and cerebellum. Inhibition of CCR2/5 decreased alcohol-mediated expression of inflammatory markers. Finally, microglia function was impaired by chronic alcohol consumption and restored by CVC treatment. CVC treatment did not change the ethanol consumption or preference of mice in the two-bottle choice test.

Conclusions

Together, our data establish that chronic alcohol consumption promotes the recruitment of peripheral macrophages into the CNS and microglia alterations through the CCR2/5 axis. Therefore, further exploration of the CCR2/5 axis as a modulator of neuroinflammation may offer a potential therapeutic approach for the treatment of alcohol-associated neuroinflammation.

The lymphatic system in alcohol-associated liver disease

The lymphatic system plays vital roles in interstitial fluid balance and immune cell surveillance. The effect of alcohol on the lymphatic system is poorly understood. This review article explores the role of the lymphatic system in the pathogenesis of alcohol-related disease including alcoholic liver disease (ALD) and the therapeutic potential of targeting hepatic lymphatics for the treatment of ALD.

Emerging medical therapies for severe alcoholic hepatitis

Severe alcoholic hepatitis (AH) is an acute and often devastating form of alcohol-associated liver disease. Clinically, AH is characterized by elevated bilirubin, model for end stage liver disease scores >20, and nonspecific symptoms that are caused by underlying inflammation, hepatocyte injury, and impaired intestinal barrier function. Compromised immune defense in AH contributes to infections, sepsis and organ failure. To date, corticosteroids are the only recommended treatment for severe AH, however it does not provide survival benefits beyond 1 month. Recent preclinical and early clinical studies in AH aided understanding of the disease and presented opportunities for new therapeutic options targeting inflammation, oxidative stress, liver regeneration and modification of intestinal microbiota. In this comprehensive review, we discuss promising preclinical results and ongoing clinical trials evaluating novel therapeutic agents for the treatment of severe AH.

Evaluating the Therapeutic Potential of Cenicriviroc in the Treatment of Nonalcoholic Steatohepatitis with Fibrosis: A Brief Report on Emerging Data

Non-alcoholic steatohepatitis (NASH) is associated with significant morbidity and mortality due to liver cirrhosis, liver failure, and hepatocellular carcinoma, and represents a leading indication for liver transplantation in the United States (U.S.). A growing spectrum of novel therapies are currently in clinical development and target several mechanisms of action which address hepatic steatosis, steatohepatitis, and hepatic fibrosis. Cenicriviroc (Allergan, Dublin, Ireland) is a novel oral antagonist of CC-motif chemokine receptors 2 and 5 (CCR2/5) which have demonstrated expression on circulating monocytes and Kupffer cells. Preclinical models have confirmed that CCR2/5 antagonism may block fat accumulation and Kupffer cell activation and disrupt monocyte/macrophage recruitment and hepatic stellate cell activation responsible for fibrogenesis. Herein we review results from the phase 2b CENTAUR trial and study designs for the phase 2b TANDEM and phase 3 AURORA trials and discuss the potential role of cenicriviroc in future pharmacotherapy for NASH fibrosis.

A modular framework for the development of targeted Covid-19 blood transcript profiling panels

BACKGROUND

Covid-19 morbidity and mortality are associated with a dysregulated immune response. Tools are needed to enhance existing immune profiling capabilities in affected patients. Here we aimed to develop an approach to support the design of targeted blood transcriptome panels for profiling the immune response to SARS-CoV-2 infection.

METHODS

We designed a pool of candidates based on a pre-existing and well-characterized repertoire of blood transcriptional modules. Available Covid-19 blood transcriptome data was also used to guide this process. Further selection steps relied on expert curation. Additionally, we developed several custom web applications to support the evaluation of candidates.

RESULTS

As a proof of principle, we designed three targeted blood transcript panels, each with a different translational connotation: immunological relevance, therapeutic development relevance and SARS biology relevance.

CONCLUSION

Altogether the work presented here may contribute to the future expansion of immune profiling capabilities via targeted profiling of blood transcript abundance in Covid-19 patients.

Triterpenoids Extracted From Antrodia cinnamomea Mycelia Attenuate Acute Alcohol-Induced Liver Injury in C57BL/6 Mice via Suppression Inflammatory Response

Excessive alcohol consumption causes liver injury–induced mortality. Here we systematically analyzed the structure of triterpenoids extracted from Antrodia cinnamomea mycelia (ACT) and investigated their protective effects against acute alcohol-induced liver injury in mice. Liquid chromatography–mass spectrometry and liquid chromatography with tandem mass spectrometry were performed to determine the structures of ACT constituents. Alcohol-induced liver injury was generated in C57BL/6 mice by oral gavage of 13 g/kg white spirit (a wine at 56% ABV). Mice were treated with either silibinin or ACT for 2 weeks. Liver injury markers and pathological signaling were then quantified with enzyme-linked immunosorbent assays, antibody array assays, and Western blots, and pathological examinations were performed using hematoxylin-eosin staining and periodic acid–Schiff staining. Triterpenoids extracted from A. cinnamomea mycelia contain 25 types of triterpenoid compounds. A 2-weeks alcohol consumption treatment caused significant weight loss, liver dyslipidemia, and elevation of alanine aminotransferase, aspartate aminotransferase, γ-glutamyl transferase, and alkaline phosphatase activities in the serum and/or liver. These effects were markedly reversed after 2-weeks ACT administration. Triterpenoids extracted from A. cinnamomea mycelia alleviated the organ structural changes and inflammatory infiltration of alcohol-damaged tissues. Triterpenoids extracted from A. cinnamomea mycelia inhibited proinflammatory cytokine levels and enhanced anti-inflammatory cytokine levels. Acute alcohol treatment promoted inflammation with significant correlations to hypoxia-inducible factor 1α (HIF-1α), which was reduced by ACT and was partially related to modulation of the protein kinase B (Akt)/70-kDa ribosomal protein S6 kinase phosphorylation (p70S6K) and Wnt/β-catenin signaling pathways. In conclusion, ACT protected against acute alcohol-induced liver damage in mice mainly through its suppression of the inflammatory response, which may be related to HIF-1α signaling.

The Roles of Immune Cells in the Pathogenesis of Fibrosis

Tissue injury and inflammatory response trigger the development of fibrosis in various diseases. It has been recognized that both innate and adaptive immune cells are important players with multifaceted functions in fibrogenesis. The activated immune cells produce various cytokines, modulate the differentiation and functions of myofibroblasts via diverse molecular mechanisms, and regulate fibrotic development. The immune cells exhibit differential functions during different stages of fibrotic diseases. In this review, we summarized recent advances in understanding the roles of immune cells in regulating fibrotic development and immune-based therapies in different disorders and discuss the underlying molecular mechanisms with a focus on mTOR and JAK-STAT signaling pathways.

Comparison of the beneficial effects of RS504393, maraviroc and cenicriviroc on neuropathic pain-related symptoms in rodents: behavioral and biochemical analyses

The latest research highlights the role of chemokine signaling pathways in the development of nerve injury-induced pain. Recent studies have provided evidence for the involvement of CCR2 and CCR5 in the pathomechanism underlying neuropathy. Thus, the aim of our study was to compare the effects of a selective CCR2 antagonist (RS504393), selective CCR5 antagonist (maraviroc) and dual CCR2/CCR5 antagonist (cenicriviroc) and determine whether the simultaneous blockade of both receptors is better than blocking only one of them selectively. All experiments were performed using Wistar rats/Swiss albino mice subjected to chronic constriction injury (CCI) of the sciatic nerve. To assess pain-related reactions, the von Frey and cold plate tests were used. The mRNA analysis was performed using RT-qPCR. We demonstrated that repeated intrathecal administration of the examined antagonists attenuated neuropathic pain in rats 7 days post-CCI. mRNA analysis showed that RS504393 did not modulate the spinal expression of the examined chemokines, whereas maraviroc reduced the CCI-induced elevation of CCL4 level. Cenicriviroc significantly lowered the spinal levels of CCL2-4 and CCL7. At the dorsal root ganglia, strong impacts of RS504393 and cenicriviroc on chemokine expression were observed; both reduced the CCI-induced elevation of CCL2-5 and CCL7 levels, whereas maraviroc decreased only the CCL5 level. Importantly, we demonstrated that a single intrathecal/intraperitoneal injection of cenicriviroc had greater analgesic properties than RS504393 or maraviroc in neuropathic mice. Additionally, we demonstrated that cenicriviroc enhanced opioid-induced analgesia. Based on our results, we suggest that targeting CCR2 and CCR5 simultaneously, is an interesting alternative for neuropathic pain pharmacotherapy.

Intestinal and hepatic microbiota changes associated with chronic ethanol administration in mice

Alcohol-induced liver disease is closely related to translocation of bacterial products and bacteria from the intestine to the liver. However, it is not known whether bacterial translocation to the liver depends on certain intestinal microbiota changes that would predispose bacteria to translocate to the liver. In this study, we investigated the microbiota in the jejunum, ileum, cecum, feces and liver of mice subjected to chronic ethanol feeding using a Lieber DeCarli diet model of chronic ethanol feeding for 8 weeks. We demonstrate that chronic ethanol administration changes alpha diversity in the ileum and the liver and leads to compositional changes especially in the ileum. This is largely driven by an increase in gram-negative phyla - the source of endotoxins. Moreover, gram-negative Prevotella not only increased in the mucus layer of the ileum but also in liver samples. These results suggest that bacterial translocation to the liver might be associated with microbiota changes in the distal gastrointestinal tract.

The Medium-Chain Fatty Acid Receptor GPR84 Mediates Myeloid Cell Infiltration Promoting Steatohepatitis and Fibrosis

Medium-chain fatty acids (MCFAs) have been associated with anti-steatotic effects in hepatocytes. Expression of the MCFA receptor GPR84 (G protein-coupled receptor 84) is induced in immune cells under inflammatory conditions and can promote fibrogenesis. We aimed at deciphering the role of GPR84 in the pathogenesis of non-alcoholic steatohepatitis (NASH), exploring its potential as a therapeutic target. GPR84 expression is upregulated in liver from patients with non-alcoholic fatty liver disease (NAFLD), correlating with the histological degree of inflammation and fibrosis. In mouse and human, activated monocytes and neutrophils upregulate GPR84 expression. Chemotaxis of these myeloid cells by GPR84 stimulation is inhibited by two novel, small molecule GPR84 antagonists. Upon acute liver injury in mice, treatment with GPR84 antagonists significantly reduced the hepatic recruitment of neutrophils, monocytes, and monocyte-derived macrophages (MoMF). We, therefore, evaluated the therapeutic inhibition of GPR84 by these two novel antagonists in comparison to selonsertib, an apoptosis signal-regulating kinase 1 (ASK1) inhibitor, in three NASH mouse models. Pharmacological inhibition of GPR84 significantly reduced macrophage accumulation and ameliorated inflammation and fibrosis, to an extent similar to selonsertib. In conclusion, our findings support that GPR84 mediates myeloid cell infiltration in liver injury and is a promising therapeutic target in steatohepatitis and fibrosis.

Recent advances in alcohol-related liver disease (ALD): summary of a Gut round table meeting

Alcohol-related liver disease (ALD), which includes a range of disorders of different severity and is one of the most prevalent types of liver disease worldwide, has recently regained increased attention. Among other reasons, the realisation that any alcohol intake, regardless of type of beverage represents a health risk, and the new therapeutic strategies tested in recently published or undergoing clinical trials spur scientific interest in this area.In April 2019, Gut convened a round table panel of experts during the European Association for the Study of the Liver International Liver Congress in Vienna to discuss critical and up-to-date issues and clinical trial data regarding ALD, its epidemiology, diagnosis, management, pathomechanisms, possible future treatments and prevention. This paper summarises the discussion and its conclusions.

Systemic MCP-1 Levels Derive Mainly From Injured Liver and Are Associated With Complications in Cirrhosis

Background and Aims: Monocyte chemotactic protein-1 (MCP-1) is a potent chemoattractant for monocytes. It is involved in pathogenesis of several inflammatory diseases. Hepatic MCP-1 is a readout of macrophage activation. While inflammation is a major driver of liver disease progression, the origin and role of circulating MCP-1 as a biomarker remains unclear.

Methods: Hepatic CC-chemokine ligand 2 (CCL2) expression and F4/80 staining for Kupffer cells were measured and correlated in a mouse model of chronic liver disease (inhalative CCl₄ for 7 weeks). Next, hepatic RNA levels of CCL2 were measured in explanted livers of 39 patients after transplantation and correlated with severity of disease. Changes in MCP-1 were further evaluated in a rat model of experimental cirrhosis and acute-on-chronic liver failure (ACLF). Finally, we analyzed portal and hepatic vein levels of MCP-1 in patients receiving transjugular intrahepatic portosystemic shunt insertion for complications of portal hypertension.

Results: In this mouse model of fibrotic hepatitis, hepatic expression of CCL2 (P = 0.009) and the amount of F4/80 positive cells in the liver (P < 0.001) significantly increased after induction of hepatitis by CCl₄ compared to control animals. Moreover, strong correlation of hepatic CCL2 expression and F4/80 positive cells were seen (P = 0.023). Furthermore, in human liver explants, hepatic transcription levels of CCL2 correlated with the MELD score of the patients, and thus disease severity (P = 0.007). The experimental model of ACLF in rats revealed significantly higher levels of MCP-1 plasma (P = 0.028) and correlation of hepatic CCL2 expression (R = 0.69, P = 0.003). Particularly, plasma MCP-1 levels did not correlate with peripheral blood monocyte CCL2 expression. Finally, higher levels of MCP-1 were observed in the hepatic compared to the portal vein (P = 0.01) in patients receiving TIPS. Similarly, a positive correlation of MCP-1 with Child-Pugh score was observed (P = 0.018). Further, in the presence of ACLF, portal and hepatic vein levels of MCP-1 were significantly higher compared to patients without ACLF (both P = 0.039).

Conclusion: Circulating levels of MCP-1 mainly derive from the injured liver and are associated with severity of liver disease. Therefore, liver macrophages contribute significantly to disease progression. Circulating MCP-1 may reflect the extent of hepatic macrophage activation.

PSMP/MSMP promotes hepatic fibrosis through CCR2 and represents a novel therapeutic target

BACKGROUND & AIMS

C-C motif chemokine receptor 2 (CCR2) has been recognized as a promising target for the treatment of liver fibrosis. PC3-secreted microprotein (PSMP)/microseminoprotein (MSMP) is a novel chemotactic cytokine and its receptor is CCR2. In the present study we investigated the expression and role of PSMP in liver fibrosis/cirrhosis.

METHODS

PSMP expression was studied in patients with fibrosis/cirrhosis and in 3 murine models of liver fibrosis, including mice treated with carbon tetrachloride (CCl₄), bile-duct ligation, or a 5-diethoxycarbonyl-1,4-dihydrocollidine diet. The role of PSMP was evaluated in Psmp^-/- mice and after treatment with a PSMP antibody in wild-type mice. The direct effects of PSMP on macrophages and hepatic stellate cells were studied in vitro.

RESULTS

In this study, we found that PSMP was highly expressed in fibrotic/cirrhotic tissues from patients with different etiologies of liver disease and in the 3 experimental mouse models of fibrosis. Damage-associated molecular pattern molecules HMGB-1 and IL-33 induced hepatocytes to produce PSMP. PSMP deficiency resulted in a marked amelioration of hepatic injury and fibrosis. In CCl₄-induced hepatic injury, the infiltration of macrophages and CCR2⁺ monocytes into the liver was significantly decreased in Psmp^-/- mice. Consistent with the decreased levels of intrahepatic macrophages, proinflammatory cytokines were significantly reduced. Moreover, adeno-associated virus-8 vectors successfully overexpressing human PSMP in Psmp^-/- mouse livers could reverse the attenuation of liver injury and fibrosis induced by CCl₄ in a CCR2-dependent manner. Treatment with a specific PSMP-neutralizing antibody, 3D5, prevented liver injury and fibrosis induced by CCl₄ in mice. At the cellular level, PSMP directly promoted M1 polarization of macrophages and activation of LX-2 cells.

CONCLUSION

PSMP enhances liver fibrosis through its receptor, CCR2. PSMP is a potentially attractive therapeutic target for the treatment of patients with liver fibrosis.

LAY SUMMARY

Our present study identifies the essential role of the protein PSMP for the development and progression of liver fibrosis in humans and mice. PSMP promotes liver fibrosis through inflammatory macrophage infiltration, polarization and production of proinflammatory cytokines, as well as direct activation of hepatic stellate cells via its receptor CCR2. A PSMP antibody can significantly reduce liver fibrosis development in vivo. These findings indicate that PSMP is a potential therapeutic target and its antibody is a potential therapeutic agent for the treatment of liver fibrosis.

Pyroptosis: The missing puzzle among innate and adaptive immunity crosstalk

Pyroptosis is a newly discovered programmed cell death with inflammasome formation. Pattern recognition receptors that identify repetitive motifs of prospective pathogens such as LPS of gram-negative bacteria are crucial to pyroptosis. Upon stimulation by pathogen-associated molecular patterns or damage-associated molecular patterns, proinflammatory cytokines, mainly IL-1 family members IL-1β and IL-18, are released through pyroptosis specific pore-forming protein, gasdermin D. Even though IL-1 family members are mainly involved in innate immunity, they can be factors in adaptive immunity. Given the importance of IL-1 family members in health and diseases, deciphering the role of pyroptosis in the regulation of innate and adaptive immunity is of great importance, especially with the recent progress in identifying the exact mechanism of such a pathway. In this review, we will focus on how the innate inflammatory mediators can regulate the adaptive immune system and vice versa via pyroptosis.

Silencing lncRNA Lfar1 alleviates the classical activation and pyoptosis of macrophage in hepatic fibrosis

Hepatic fibrosis is a common pathological consequence of a sustained wound healing response to continuous liver injury, characterized by increased production and accumulation of extracellular matrix. If unresolved, the fibrotic process results in organ failure, and eventually death after the development of cirrhosis. It has been suggested that macrophages play central role in the progression of hepatic fibrosis, which is related to inflammation and pyroptosis, a novel programmed and proinflammatory cell death. However, it remains far less clear if, or how, lncRNAs regulates the activation and pyroptosis of macrophage in hepatic fibrosis. In the present study, we demonstrated that the liver-enriched lncRNA Lfar1, which has been reported to promote hepatic fibrosis through inducing hepatic stellate cells activation and hepatocytes apoptosis, was dysregulated during proinflammatory M1 activation and pyroptosis of macrophage. Our study revealed that silencing lnc-Lfar1 by a lentivirus-shRNA alleviated CCl₄- and BDL-induced proinflammatory M1 macrophage activation and NLRP3 inflammasome-mediated pyroptosis. Furthermore, the in vitro experiments demonstrated that lnc-Lfar1 knockdown significantly suppressed LPS- and IFN-γ-induced proinflammatory activation of macrophages, and inhibited LPS/ATP- and LPS/Nigericin-induced NLRP3 inflammasome-mediated pyroptosis. Mechanistically, lnc-Lfar1 regulated LPS- and IFN-γ-induced proinflammatory activation of macrophages through the NF-ĸB pathway. All these data supported our conclusion that lnc-Lfar1 plays a vital role in controlling the activation and pyroptosis of macrophage, thus providing a possible therapeutic target against inflammation-related disorders including hepatic fibrosis.

Clinical significance of chemokine receptor antagonists

Introduction: Chemokine receptors are important therapeutic targets for the treatment of many human diseases. This study will provide an overview of approved chemokine receptor antagonists and promising candidates in advanced clinical trials.Areas covered: We will describe clinical aspects of chemokine receptor antagonists regarding their clinical efficacy, mechanisms of action, and re-purposed applications.Expert opinion: Three chemokine antagonists have been approved: (i) plerixafor is a small-molecule CXCR4 antagonist that mobilizes hematopoietic stem cells; (ii) maraviroc is a small-molecule CCR5 antagonist for anti-HIV treatment; and (iii) mogamulizumab is a monoclonal-antibody CCR4 antagonist for the treatment of mycosis fungoides or Sézary syndrome. Moreover, phase 3 trials are ongoing to evaluate many potent candidates, including CCR5 antagonists (e.g. leronlimab), dual CCR2/CCR5 antagonists (e.g. cenicriviroc), and CXCR4 antagonists (e.g. balixafortide, mavorixafor, motixafortide). The success of chemokine receptor antagonists depends on the selective blockage of disease-relevant chemokine receptors which are indispensable for disease progression. Although clinical translation has been slow, antagonists targeting chemokine receptors with multifaced functions offer the potential to treat a broad spectrum of human diseases.

Inhibition of the Inflammasome Signaling Cascade Reduces Alcohol Consumption in Female But Not Male Mice

BACKGROUND

Alcohol use disorder is a significant societal and medical burden that is associated with both organ pathology and addiction. Excessive alcohol use results in neuroinflammation characterized by activation of the inflammasome, a multiprotein complex, and IL-1β increase in the brain. Recent studies suggest that inflammation could contribute to alcohol addiction. Here, we targeted components of the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome cascade, which senses and responds to immunologic stimuli, to determine whether NLRP3 inhibition modulates alcohol consumption.

METHODS

C57BL/6J male and female mice were provided a 2-bottle choice of alcohol at increasing concentrations (3, 6, 9, and 12%, 4 days each) or water, and some were treated with daily injections of an NLRP3 inhibitor (MCC950), a caspase-1 inhibitor (VX765), IL-1 receptor antagonist (IL-1ra; anakinra), or vehicle injection.

RESULTS

Treatment with VX765, MCC950, and IL-1ra significantly reduced alcohol consumption and preference in female mice (p < 0.05). Treatment with MCC950 and IL-1ra reduced alcohol consumption, while IL-1ra reduced alcohol preference in male mice (p < 0.05). VX765 did not affect alcohol consumption or preference in male mice.

CONCLUSIONS

These findings highlight gender differences in alcohol preference and demonstrate that inhibition of different steps in inflammasome signaling can reduce alcohol consumption in females. Inhibition of NLRP3 inflammasome activation and the inflammasome-IL-1β cascade opens novel insights into the development of new therapies to address alcohol use disorder in an era of targeted and precision medicine.

Dual CCR5/CCR2 targeting: opportunities for the cure of complex disorders

The chemokine system mediates acute inflammation by driving leukocyte migration to damaged or infected tissues. However, elevated expression of chemokines and their receptors can contribute to chronic inflammation and malignancy. Thus, great effort has been taken to target these molecules. The first hint of the druggability of the chemokine system was derived from the role of chemokine receptors in HIV infection. CCR5 and CXCR4 function as essential co-receptors for HIV entry, with the former accounting for most new HIV infections worldwide. Not by chance, an anti-CCR5 compound, maraviroc, was the first FDA-approved chemokine receptor-targeting drug. CCR5, by directing leukocytes to sites of inflammation and regulating their activation, also represents an important player in the inflammatory response. This function is shared with CCR2 and its selective ligand CCL2, which constitute the primary chemokine axis driving the recruitment of monocytes/macrophages to inflammatory sites. Both receptors are indeed involved in the pathogenesis of several immune-mediated diseases, and dual CCR5/CCR2 targeting is emerging as a more efficacious strategy than targeting either receptor alone in the treatment of complex human disorders. In this review, we focus on the distinctive and complementary contributions of CCR5 and CCR2/CCL2 in HIV infection, multiple sclerosis, liver fibrosis and associated hepatocellular carcinoma. The emerging therapeutic approaches based on the inhibition of these chemokine axes are highlighted.

Crosstalk network among multiple inflammatory mediators in liver fibrosis

Liver fibrosis is the common pathological basis of all chronic liver diseases, and is the necessary stage for the progression of chronic liver disease to cirrhosis. As one of pathogenic factors, inflammation plays a predominant role in liver fibrosis via communication and interaction between inflammatory cells, cytokines, and the related signaling pathways. Damaged hepatocytes induce an increase in pro-inflammatory factors, thereby inducing the development of inflammation. In addition, it has been reported that inflammatory response related signaling pathway is the main signal transduction pathway for the development of liver fibrosis. The crosstalk regulatory network leads to hepatic stellate cell activation and proinflammatory cytokine production, which in turn initiate the fibrotic response. Compared with the past, the research on the pathogenesis of liver fibrosis has been greatly developed. However, the liver fibrosis mechanism is complex and many pathways involved need to be further studied. This review mainly focuses on the crosstalk regulatory network among inflammatory cells, cytokines, and the related signaling pathways in the pathogenesis of chronic inflammatory liver diseases. Moreover, we also summarize the recent studies on the mechanisms underlying liver fibrosis and clinical efforts on the targeted therapies against the fibrotic response.

Alcohol-induced IL-17A production in Paneth cells amplifies endoplasmic reticulum stress, apoptosis, and inflammasome-IL-18 activation in the proximal small intestine in mice

Gut microbial translocation contributes to alcoholic hepatitis. Using a mouse model of alcoholic hepatitis, we investigated the effects of chronic alcohol plus binge and found increased abundance of Paneth cells and IL-17A in the proximal small intestine (PSI). Alcohol increased IL-17A production and pro-apoptotic signaling evidenced by Bax, Bim, caspase-3, and caspase-8 increases via endoplasmic reticulum (ER) stress indicated by C/EBP homologous protein (CHOP) upregulation; this was prevented by the ER stress inhibitor, 4-PBA, in isolated crypts in vitro and in vivo. Mechanistically, IL-17 augmented alcohol-induced ER stress in isolated crypts. In vivo IL-17A blocking antibody administration in alcohol-treated mice attenuated ER stress-mediated apoptosis and IL-18 induction and prevented alcohol-induced impairment of tight junctions in the PSI and LPS translocation to the liver. Acute-on-chronic alcohol resulted in inflammasome activation, caspase-1 cleavage, and IL-18 production in the PSI. In vivo treatment with antibiotics or 4-PBA prevented CHOP upregulation and inflammasome activation. Our data suggest that alcohol upregulates innate immune mechanisms by increasing Paneth cell numbers and IL-17A release contributing to apoptosis amplification, inflammasome activation, and gut leakiness in the PSI. Binge alcohol-induced Paneth cell expansion, ER stress, and inflammasome activation in the PSI are modulated by the gut microbiome.

Cenicriviroc ameliorates the severity of graft-versus-host disease through inhibition of CCR5 in a rat model of liver transplantation

Acute graft-versus-host disease (aGVHD) is one of the major complications after liver transplantation (LTx), which is induced by over-activation of T helper lymphocytes. Cenicriviroc (CVC) exerts its anti-inflammatory effect through inhibition of C-C chemokine receptor 5 (CCR5). However, whether CVC ameliorates aGVHD after liver transplantation remains unknown. In the present study, a rat aGVHD liver transplantation model (LTx-aGVHD) was constructed. CVC was intravenously injected from day 7 to day 14 after LTx. Liver and intestine samples were harvested to evaluate GVHD severity. Peripheral blood mononuclear cells (PBMCs) were collected and CCR5 antibodies were prepared to further explore the molecular mechanism in vitro. CVC significantly decreased the severity of GVHD associated skin and intestine injury. Quality of life of the LTx-GVHD rats was improved after CVC treatment. Flow cytometry further confirmed diminished peripheral donor-derived Th cells after CVC treatment. Molecularly, CVC treatment showed similar anti-inflammatory effects to CCR5 antibody injection. The level of CCR5, C-C motif chemokine ligand 5 (CCL5), and pro-inflammatory cytokines in the liver and intestines were inhibited after CVC treatment. Thus, CVC deactivated Th lymphocytes and decreased the severity of LTx-aGVHD through inhibition of CCR5.

Pathogenesis, Early Diagnosis, and Therapeutic Management of Alcoholic Liver Disease

Alcoholic liver disease (ALD) refers to the damages to the liver and its functions due to alcohol overconsumption. It consists of fatty liver/steatosis, alcoholic hepatitis, steatohepatitis, chronic hepatitis with liver fibrosis or cirrhosis, and hepatocellular carcinoma. However, the mechanisms behind the pathogenesis of alcoholic liver disease are extremely complicated due to the involvement of immune cells, adipose tissues, and genetic diversity. Clinically, the diagnosis of ALD is not yet well developed. Therefore, the number of patients in advanced stages has increased due to the failure of proper early detection and treatment. At present, abstinence and nutritional therapy remain the conventional therapeutic interventions for ALD. Moreover, the therapies which target the TNF receptor superfamily, hormones, antioxidant signals, and MicroRNAs are used as treatments for ALD. In particular, mesenchymal stem cells (MSCs) are gaining attention as a potential therapeutic target of ALD. Therefore, in this review, we have summarized the current understandings of the pathogenesis and diagnosis of ALD. Moreover, we also discuss the various existing treatment strategies while focusing on promising therapeutic approaches for ALD.

Adipocyte Death Preferentially Induces Liver Injury and Inflammation Through the Activation of Chemokine (C-C Motif) Receptor 2-Positive Macrophages and Lipolysis

Adipocyte death occurs under various physiopathological conditions, including obesity and alcohol drinking, and can trigger organ damage particularly in the liver, but the underlying mechanisms remain obscure. To explore these mechanisms, we developed a mouse model of inducible adipocyte death by overexpressing the human CD59 (hCD59) on adipocytes (adipocyte-specific hCD59 transgenic mice). Injection of these mice with intermedilysin (ILY), which rapidly lyses hCD59 expressing cells exclusively by binding to the hCD59 but not mouse CD59, resulted in the acute selective death of adipocytes, adipose macrophage infiltration, and elevation of serum free fatty acid (FFA) levels. ILY injection also resulted in the secondary damage to multiple organs with the strongest injury observed in the liver, with inflammation and hepatic macrophage activation. Mechanistically, acute adipocyte death elevated epinephrine and norepinephrine levels and activated lipolysis pathways in adipose tissue in a chemokine (C-C motif) receptor 2-positive (CCR2⁺ ) macrophage-dependent manner, which was followed by FFA release and lipotoxicity in the liver. Additionally, acute adipocyte death caused hepatic CCR2⁺ macrophage activation and infiltration, further exacerbating liver injury. Conclusion: Adipocyte death predominantly induces liver injury and inflammation, which is probably due to the superior sensitivity of hepatocytes to lipotoxicity and the abundance of macrophages in the liver.

Role of the Gut-Liver Axis in Liver Inflammation, Fibrosis, and Cancer: A Special Focus on the Gut Microbiota Relationship

The gut and the liver are anatomically and physiologically connected, and this “gut–liver axis” exerts various influences on liver pathology. The gut microbiota consists of various microorganisms that normally coexist in the human gut and have a role of maintaining the homeostasis of the host. However, once homeostasis is disturbed, metabolites and components derived from the gut microbiota translocate to the liver and induce pathologic effects in the liver. In this review, we introduce and discuss the mechanisms of liver inflammation, fibrosis, and cancer that are influenced by gut microbial components and metabolites; we include recent advances in molecular‐based therapeutics and novel mechanistic findings associated with the gut–liver axis and gut microbiota.