II. Alcoholic liver injury involves activation of Kupffer cells by endotoxin

The effect of liver disease on hepatic microenvironment and implications for immune therapy

Hepatocellular carcinoma (HCC) is the most common primary liver cancer and the fourth leading cause of cancer-related death worldwide. HCC often occurs in the setting of chronic liver disease or cirrhosis. Recent evidence has highlighted the importance of the immune microenvironment in the development and progression of HCC, as well as its role in the potential response to therapy. Liver disease such as viral hepatitis, alcohol induced liver disease, and non-alcoholic fatty liver disease is a major risk factor for the development of HCC and has been demonstrated to alter the immune microenvironment. Alterations in the immune microenvironment may markedly influence the response to different therapeutic strategies. As such, research has focused on understanding the complex relationship among tumor cells, immune cells, and the surrounding liver parenchyma to treat HCC more effectively. We herein review the immune microenvironment, as well as the relative effect of liver disease on the immune microenvironment. In addition, we review how changes in the immune microenvironment can lead to therapeutic resistance, as well as highlight future strategies aimed at developing the next-generation of therapies for HCC.

The Role of Sex in Acute and Chronic Liver Damage

Acute and chronic hepatic damages are caused by xenobiotics or different diseases affecting the liver, characterized by different etiologies and pathological features. It has been demonstrated extensively that liver damage progresses differently in men and women, and some chronic liver diseases show a more favorable prognosis in women than in men. This review aims to update the most recent advances in the comprehension of the molecular basis of the sex difference observed in both acute and chronic liver damage. With this purpose, we report experimental studies on animal models and clinical observations investigating both acute liver failure, e.g., drug-induced liver injury (DILI), and chronic liver diseases, e.g., viral hepatitis, alcoholic liver disease (ALD), non-alcoholic fatty liver disease (NAFLD), autoimmune liver diseases, and hepatocellular carcinoma (HCC).

Microbiome-Based Metabolic Therapeutic Approaches in Alcoholic Liver Disease

Alcohol consumption is a global healthcare problem. Chronic alcohol consumption generates a wide spectrum of hepatic lesions, the most characteristic of which are steatosis, hepatitis, fibrosis, and cirrhosis. Alcoholic liver diseases (ALD) refer to liver damage and metabolomic changes caused by excessive alcohol intake. ALD present several clinical stages of severity found in liver metabolisms. With increased alcohol consumption, the gut microbiome promotes a leaky gut, metabolic dysfunction, oxidative stress, liver inflammation, and hepatocellular injury. Much attention has focused on ALD, such as alcoholic fatty liver (AFL), alcoholic steatohepatitis (ASH), alcoholic cirrhosis (AC), hepatocellular carcinoma (HCC), a partnership that reflects the metabolomic significance. Here, we report on the global function of inflammation, inhibition, oxidative stress, and reactive oxygen species (ROS) mechanisms in the liver biology framework. In this tutorial review, we hypothetically revisit therapeutic gut microbiota-derived alcoholic oxidative stress, liver inflammation, inflammatory cytokines, and metabolic regulation. We summarize the perspective of microbial therapy of genes, gut microbes, and metabolic role in ALD. The end stage is liver transplantation or death. This review may inspire a summary of the gut microbial genes, critical inflammatory molecules, oxidative stress, and metabolic routes, which will offer future promising therapeutic compounds in ALD.

Novel insights into alcoholic liver disease: Iron overload, iron sensing and hemolysis

The liver is the major target organ of continued alcohol consumption at risk and resulting alcoholic liver disease (ALD) is the most common liver disease worldwide. The underlying molecular mechanisms are still poorly understood despite decades of scientific effort limiting our abilities to identify those individuals who are at risk to develop the disease, to develop appropriate screening strategies and, in addition, to develop targeted therapeutic approaches. ALD is predestined for the newly evolving translational medicine, as conventional clinical and health care structures seem to be constrained to fully appreciate this disease. This concept paper aims at summarizing the 15 years translational experience at the Center of Alcohol Research in Heidelberg, namely based on the long-term prospective and detailed characterization of heavy drinkers with mortality data. In addition, novel experimental findings will be presented. A special focus will be the long-known hepatic iron accumulation, the somewhat overlooked role of the hematopoietic system and novel insights into iron sensing and the role of hepcidin. Our preliminary work indicates that enhanced red blood cell (RBC) turnover is critical for survival in ALD patients. RBC turnover is not primarily due to vitamin deficiency but rather to ethanol toxicity directly targeted to erythrocytes but also to the bone marrow stem cell compartment. These novel insights also help to explain long-known aspects of ALD such as mean corpuscular volume of erythrocytes (MCV) and elevated aspartate transaminase (GOT/AST) levels. This work also aims at identifying future projects, naming unresolved observations, and presenting novel hypothetical concepts still requiring future validation.

Effect of alcohol on clinical complications of hepatitis virus-induced liver cirrhosis: a consecutive ten-year study

Background and aims

Although coexisting alcohol-induced liver disease and hepatitis B or C virus-induced liver cirrhosis (ALD + HBV or ALD + HCV) has been the center of recent hepatology researches, numerous controversies still persist. This study aimed to showcase the influence of alcohol on the laboratory values and on the clinical outcomes of patients with hepatitis B and C virus-induced liver cirrhosis.

Methods

Patients diagnosed with liver cirrhosis (n = 22,287) from January 2010 to December 2019 were enrolled, and divided into five groups according to the etiology: alcohol-induced liver disease (ALD, 1652 cases), hepatitis B virus (HBV, 18,079 cases), hepatitis C virus (HCV, 682 cases), ALD + HBV (1594 cases) and ALD + HCV (280 cases). Laboratory results and proportion of different liver cirrhosis complications were contrasted between groups.

Results

The proportions of patients with Child Pugh grade C (28.0% vs 18.8%, P < 0.001) or MELD greater than 18 (24.1% vs 18.5%, P < 0.001) in the ALD + HBV group exceeded significantly those in the HBV group. Multivariate logistic regression revealed that the risk of hepatocellular carcinoma (HCC) and that of esophageal gastric variceal bleeding (EGVB) in the ALD + HBV group was respectively 2.01-fold and 1.74-fold that in the HBV group (HCC: OR = 2.01, 95% CI [1.58–2.55]; EGVB: OR = 1.74, 95% CI [1.30–2.33]) after adjusting for potential confounders. Furthermore, a linear-by-linear analysis test showed a decrease in the risk of HCC and EGVB with the duration of alcohol abstinence. Moreover, patients with both antiviral treatment and alcohol abstinence had the lowest risk of HCC and EGVB (HCC: OR = 0.10, 95% CI [0.05–0.20], P < 0.001; EGVB: OR = 0.17, 95% CI [0.06–0.45], P < 0.001) compared to those without any treatment, those with abstinence alone and those with antiviral therapy alone. Similar pattern was noticed while comparing the ALD + HCV group to the HCV group.

Conclusion

Heavy alcohol use increased the severity of liver function impairment and the prevalence of HCC and EGVB in hepatitis virus-induced liver cirrhosis patients. Remarkably, long-term alcohol abstinence coupled with antiviral treatment effectively decreased the risk of HCC and EGVB in these populations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-022-02198-w.

Alcohol-Related Elevation of Liver Transaminase Is Associated With Gut Microbiota in Male

Alcoholic liver damage has become a widespread health problem as alcohol consumption increases and is usually identified by elevated liver transaminase. We conducted this study to investigate the role of the gut microbiome in the individual susceptibility to alcoholic liver injury. We divided the participants into four groups based on alcohol consumption and liver transaminase elevation, which were drinking case group, drinking control group, non-drinking case group, and non-drinking control group. The drinking case group meant participants who were alcohol consumers with elevated liver transaminase. We found that alpha and beta diversities of the drinking case group differed from the other three groups. Species Faecalibacterium prausnitzii and Roseburia hominis were significantly in lower abundance in the drinking case group and were proved the protective effect against inflammatory liver damage in the former study. Ruminococcus gnavus exhibited the most positive association to alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and contributed to liver inflammation.

Targeting the Intestinal Barrier to Prevent Gut-Derived Inflammation and Disease: A Role for Intestinal Alkaline Phosphatase

Background

Intestinal alkaline phosphatase (IAP) as a tissue-specific isozyme of alkaline phosphatases is predominantly produced by enterocytes in the proximal small intestine. In recent years, an increasing number of pathologies have been identified to be associated with an IAP deficiency, making it very worthwhile to review the various roles, biological functions, and potential therapeutic aspects of IAP.

Summary

IAP primarily originates and acts in the intestinal tract but affects other organs through specific biological axes related to its fundamental roles such as promoting gut barrier function, dephosphorylation/detoxification of lipopolysaccharides (LPS), and regulation of gut microbiota.

Key Messages

Numerous studies reporting on the different roles and the potential therapeutic value of IAP across species have been published during the last decade. While IAP deficiency is linked to varying degrees of physiological dysfunctions across multiple organ systems, the supplementation of IAP has been proven to be beneficial in several translational and clinical studies. The increasing evidence of the salutary functions of IAP underlines the significance of the naturally occurring brush border enzyme.

Modeling alcohol-associated liver disease in a human Liver-Chip

Alcohol-associated liver disease (ALD) is a global health issue and leads to progressive liver injury, comorbidities, and increased mortality. Human-relevant preclinical models of ALD are urgently needed. Here, we leverage a triculture human Liver-Chip with biomimetic hepatic sinusoids and bile canaliculi to model ALD employing human-relevant blood alcohol concentrations (BACs) and multimodal profiling of clinically relevant endpoints. Our Liver-Chip recapitulates established ALD markers in response to 48 h of exposure to ethanol, including lipid accumulation and oxidative stress, in a concentration-dependent manner and supports the study of secondary insults, such as high blood endotoxin levels. We show that remodeling of the bile canalicular network can provide an in vitro quantitative readout of alcoholic liver toxicity. In summary, we report the development of a human ALD Liver-Chip as a powerful platform for modeling alcohol-induced liver injury with the potential for direct translation to clinical research and evaluation of patient-specific responses.

The History of Alcoholic Liver Disease: From an Unrecognized Disease to One of the Most Frequent Diseases in Hepatology

This review describes the history of alcoholic liver disease from the beginning of the 1950s until now. It details how the hepatotoxicity of alcohol was discovered by epidemiology and basic research primarily by using new feeding techniques in rodents and primates. The article also recognizes the pioneering work of scientists who contributed to the understanding of the pathophysiology of alcoholic liver disease. In addition, clinical aspects, such as the development of diagnostics and treatment options for alcoholic liver disease, are discussed. Up-to-date knowledge of the mechanism of the disease in 2020 is presented.

Therapeutic efficiency of bone marrow-derived mesenchymal stem cells for liver fibrosis: A systematic review of in vivo studies

Although multiple drugs are accessible for recovering liver function in patients, none are considered efficient. Liver transplantation is the mainstay therapy for end-stage liver fibrosis. However, the worldwide shortage of healthy liver donors, organ rejection, complex surgery, and high costs are prompting researchers to develop novel approaches to deal with the overwhelming liver fibrosis cases. Mesenchymal stem cell (MSC) therapy is an emerging alternative method for treating patients with liver fibrosis. However, many aspects of this therapy remain unclear, such as the efficiency compared to conventional treatment, the ideal MSC sources, and the most effective way to use it. Because bone marrow (BM) is the largest source for MSCs, this paper used a systematic review approach to study the therapeutic efficiency of MSCs against liver fibrosis and related factors. We systematically searched multiple published articles to identify studies involving liver fibrosis and BM-MSC-based therapy. Analyzing the selected studies showed that compared with conventional treatment BM-MSC therapy may be more efficient for liver fibrosis in some cases. In contrast, the cotreatment presented a more efficient way. Nevertheless, BM-MSCs are lacking as a therapy for liver fibrosis; thus, this paper also reviews factors that affect BM-MSC efficiency, such as the implementation routes and strategies employed to enhance the potential in alleviating liver fibrosis. Ultimately, our review summarizes the recent advances in the BM-MSC therapy for liver fibrosis. It is grounded in recent developments underlying the efficiency of BM-MSCs as therapy, focusing on the preclinical in vivo experiments, and comparing to other treatments or sources and the strategies used to enhance its potential while mentioning the research gaps.

cAMP Signaling in Pathobiology of Alcohol Associated Liver Disease

The importance of cyclic adenosine monophosphate (cAMP) in cellular responses to extracellular signals is well established. Many years after discovery, our understanding of the intricacy of cAMP signaling has improved dramatically. Multiple layers of regulation exist to ensure the specificity of cellular cAMP signaling. Hence, disturbances in cAMP homeostasis could arise at multiple levels, from changes in G protein coupled receptors and production of cAMP to the rate of degradation by phosphodiesterases. cAMP signaling plays critical roles in metabolism, inflammation and development of fibrosis in several tissues. Alcohol-associated liver disease (ALD) is a multifactorial condition ranging from a simple steatosis to steatohepatitis and fibrosis and ultimately cirrhosis, which might lead to hepatocellular cancer. To date, there is no FDA-approved therapy for ALD. Hence, identifying the targets for the treatment of ALD is an important undertaking. Several human studies have reported the changes in cAMP homeostasis in relation to alcohol use disorders. cAMP signaling has also been extensively studied in in vitro and in vivo models of ALD. This review focuses on the role of cAMP in the pathobiology of ALD with emphasis on the therapeutic potential of targeting cAMP signaling for the treatment of various stages of ALD.

Role of B Cell Lymphoma 2 in the Regulation of Liver Fibrosis in miR-122 Knockout Mice

MicroRNA-122 (miR-122) has been identified as a marker of various liver injuries, including hepatitis- virus-infection-, alcoholic-, and non-alcoholic steatohepatitis (NASH)-induced liver fibrosis. Here, we report that the extracellular miR-122 from hepatic cells can be delivered to hepatic stellate cells (HSCs) to modulate their proliferation and gene expression. Our published Argonaute crosslinking immunoprecipitation (Ago-CLIP) data identified several pro-fibrotic genes, including Ctgf, as miR-122 targets in mice livers. However, treating Ctgf as a therapeutic target failed to rescue the fibrosis developed in the miR-122 knockout livers. Alternatively, we compared the published datasets of human cirrhotic livers and miR-122 KO livers, which revealed upregulation of BCL2, suggesting its potential role in regulating fibrosis. Notably, ectopic miR-122 expression inhibited BCL2 expression in human HSC (LX-2) cells). Publicly available ChIP-seq data in human hepatocellular cancer (HepG2) cells and mice livers suggested miR-122 could regulate BCL2 expression indirectly through c-MYC, which was confirmed by siRNA-mediated depletion of c-MYC in Hepatocellular Carcinoma (HCC) cell lines. Importantly, Venetoclax, a potent BCL2 inhibitor approved for the treatment of leukemia, showed promising anti-fibrotic effects in miR-122 knockout mice. Collectively, our data demonstrate that miR-122 suppresses liver fibrosis and implicates anti-fibrotic potential of Venetoclax.

Alcohol and Liver Function in Women

Alcohol-related liver disease generally has been ascribed to men because men reportedly consume alcohol at an increased rate and quantity as compared to women. Recent literature has reported, however, that rates of liver disease attributed to alcohol use by women have increased, largely due, in part, to the increased number of women who consume alcohol regularly. This increase is a paramount concern, as women are more susceptible than men to the effects of alcohol-related liver injury. Health care providers should make efforts to counsel women on the risks of excess alcohol consumption to prevent further increase in alcohol-related liver disease and its associated complications.

Are Probiotics Effective in Targeting Alcoholic Liver Diseases?

Alcoholic liver disease (ALD) encompasses a broad spectrum of disorders including steatosis, steatohepatitis, fibrosis, and cirrhosis. Despite intensive research in the last two decades, there is currently no Food and Drug Administration-approved therapy for treating ALD. Several studies have demonstrated the importance of the gut-liver axis and gut microbiome on the pathogenesis of ALD. Alcohol may induce intestinal dysbiosis and increased intestinal permeability, which in turn result in increased levels of pathogen-associated molecular patterns such as lipopolysaccharide (LPS) and translocation of microbial products from the gut to the liver (bacterial translocation). LPS is an inflammatory signal that activates toll-like receptor 4 on Kupffer cells, contributing to the inflammation observed in ALD. Recently, probiotics have been shown to be effective in reducing or preventing the progression of ALD. A potential mechanism is that the probiotics transforms the composition of intestinal microbiota, which leads to reductions in alcohol-induced dysbiosis, intestinal permeability, bacterial translocation, endotoxemia, and consequently, the development of ALD. While transformation of intestinal microbiota by probiotics appears to be a promising therapeutic strategy for the treatment of intestinal barrier dysfunction, there is a scarcity of research that studies probiotics in the context of ALD. In this review, we discuss the potential therapeutic applications of probiotics in the treatment of ALD.

Lactobacillus rhamnosus Granules Dose-Dependently Balance Intestinal Microbiome Disorders and Ameliorate Chronic Alcohol-Induced Liver Injury

As the functions of Lactobacilli become better understood, there are increasing numbers of applications for Lactobacillus products. Previously, we have demonstrated that Lactobacillus rhamnosus GG (LGG) can prevent alcoholic liver injury. LGG granules were produced by fluid bed granulation with a media composed of starch, skimmed milk powder, whey powder, microcrystalline cellulose and maltose, and LGG fermented liquid that comprised 30-50% of the total weight. We found LGG granules dose-dependently protected against chronic alcoholic liver disease. When alcohol was consumed for 8 weeks with LGG treatment during the last 2 weeks, we demonstrated that the dose dependence of LGG granules can improve alcohol-induced liver injury through decreasing the levels of lipopolysaccharide and tumor necrosis factor-α in serum and prevent liver steatosis by suppressing triglyceride, free fatty acid, and malondialdehyde production in liver. Alcohol feeding caused a decline in the number of both Lactobacillus and Bifidobacterium, with a proportional increase in the number of Clostridium perfringens in ileum, and expansion of the Gram-negative bacteria Proteobacteria, Campylobacterales, and Helicobacter in cecum. However, LGG granule treatment restored the content of these microorganisms. In conclusion, LGG granule supplementation can improve the intestinal microbiota, reduce the number of gram-negative bacteria, and ameliorate alcoholic liver injury.

Magnesium and liver disease

Magnesium is a vital cation that takes part in many cellular processes. Magnesium balance can be disturbed in multiple conditions, and differences in magnesium concentration can be responsible for numerous physiological and pathological processes. Magnesium deficiency is commonly associated with liver diseases, and may result from low nutrient uptake, greater urinary secretion, low serum albumin concentration, or hormone inactivation. In turn, low magnesium content in serum and liver tissue can lead to the progression of these diseases, due to a disruption in mitochondrial function, defective protein kinase C (PKC) translocation, inflammatory responses, oxidative stress, or metabolic disorders. Furthermore, magnesium supplementation can improve liver function in certain liver diseases. This paper comprehensively reviews the changes in magnesium concentrations associated with liver cirrhosis, alcoholic liver disease (ALD), liver cancer, and viral hepatitis, and explains how such changes may in turn impact these disease processes.

Recent Insights Into the Role of Immune Cells in Alcoholic Liver Disease

Accumulating clinical and experimental evidences have demonstrated that both innate and adaptive immunity are involved in the pathogenesis of alcoholic liver disease (ALD), in which the role of immunity is to fuel the inflammation and to drive the progression of ALD. Various immune cells are implicated in the pathogenesis of ALD. The activation of innate immune cells induced by alcohol and adaptive immune response triggered by oxidative modification of hepatic constituents facilitate the persistent hepatic inflammation. Meanwhile, the suppressed antigen-presenting capability of various innate immune cells and impaired function of T cells may consequently lead to an increased risk of infection in the patients with advanced ALD. In this review, we summarized the significant recent findings of immune cells participating in ALD. The pathways and molecules involved in the regulation of specific immune cells, and novel mediators protecting the liver from alcoholic injury via affecting these cells are particularly highlighted. This review aims to update the knowledge about immunity in the pathogenesis of ALD, which may facilitate to enhancement of currently available interventions for ALD treatment.

Alcohol and hepatocellular carcinoma

BACKGROUND

Alcohol is classified as a Group 1 carcinogen by the International Agency for Research on Cancer because it induces hepatocellular carcinoma (among other cancers) in humans. An excessive alcohol intake may result in fatty liver, acute/chronic hepatitis, and cirrhosis and eventually lead to hepatocellular carcinoma. It has been reported that alcohol abuse increases the relative risk of hepatocellular carcinoma by 3- to 10-fold.

AIM AND METHODS

To clarify the known mechanisms of alcohol-related carcinogenesis, we searched Pubmed using the terms alcohol and immune mechanism, alcohol and cancer, and immune mechanism and cancer and summarized the articles as a qualitative review.

RESULTS

From a clinical perspective, it is well known that alcohol interacts with other factors, such as smoking, viral hepatitis, and diabetes, leading to an increased risk of hepatocellular carcinoma. There are several possible mechanisms through which alcohol may induce liver carcinogenicity, including the mutagenic effects of acetaldehyde and the production of ROS due to the excessive hepatic deposition of iron. Furthermore, it has been reported that alcohol accelerates hepatitis C virus-induced liver tumorigenesis through TLR4 signaling. Despite intense investigations to elucidate the mechanisms, they remain poorly understood.

CONCLUSION

This review summarizes the recent findings of clinical and pathological studies that have investigated the carcinogenic effects of alcohol in the liver.

Medium-Chain Triglycerides Attenuate Liver Injury in Lipopolysaccharide-Challenged Pigs by Inhibiting Necroptotic and Inflammatory Signaling Pathways

This study was conducted to investigate whether medium-chain triglycerides (MCTs) attenuated lipopolysaccharide (LPS)-induced liver injury by down-regulating necroptotic and inflammatory signaling pathways. A total of 24 pigs were randomly allotted to four treatments in a 2 × 2 factorial design including diet (0 and 4% MCTs) and immunological challenge (saline and LPS). After three weeks of feeding with or without 4% MCTs, pigs were challenged with saline or LPS. MCTs led to a significant increase in eicosapentaenoic acid, docosahexaenoic acid and total (n-3) polyunsaturated fatty acid concentrations. MCTs attenuated LPS-induced liver injury as indicated by an improvement in liver histomorphology and ultrastructural morphology of hepatocytes, a reduction in serum alanine aminotransferase and alkaline phosphatase activities as well as an increase in claudin-1 protein expression. In addition, MCTs also reduced serum tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6 concentrations, liver TNF-α and IL-1β mRNA expression and protein concentrations and enhanced liver heat shock protein 70 protein expression in LPS-challenged pigs. Moreover, MCTs decreased mRNA expression of receptor-interacting serine/threonine-protein kinase (RIP) 3, mixed-lineage kinase domain-like protein (MLKL) and phosphoglycerate mutase 5 and inhibited MLKL phosphorylation in the liver. Finally, MCTs decreased liver mRNA expression of toll-like receptor (TLR) 4, nucleotide-binding oligomerization domain protein (NOD) 1 and multiple downstream signaling molecules. MCTs also suppressed LPS-induced p38 mitogen-activated protein kinase (MAPK) phosphorylation and increased extracellular signal-related kinase 1/2 phosphorylation in the liver. These results indicated that MCTs are capable of attenuating LPS-induced liver damage by suppressing hepatic necroptotic (RIP1/RIP3/MLKL) and inflammatory (TLR4/NOD1/p38 MAPK) signaling pathways.

Lipid peroxidation derived reactive aldehydes in alcoholic liver disease

Lipid peroxidation is a known consequence of oxidative stress and is thought to play a key role in numerous disease pathologies, including alcoholic liver disease (ALD). The overaccumulation of lipid peroxidation products during chronic alcohol consumption results in pathogenic lesions on protein, DNA, and lipids throughout the cell. Molecular adducts due to secondary end products of lipid peroxidation impact a host of biochemical processes, including inflammation, antioxidant defense, and metabolism. The aggregate burden of lipid peroxidation which occurs due to chronic alcohol metabolism, including downstream signaling events, contributes to the development and progression of ALD. In this current opinion we highlight recent studies and approaches relating cellular mechanisms of lipid peroxidation to the pathogenesis of alcoholic liver disease.

NLRP3 Inflammasome and IL-33: Novel Players in Sterile Liver Inflammation

In sterile liver inflammation, danger signals are released in response to tissue injury to alert the immune system; e.g., by activation of the NLRP3 inflammasome. Recently, IL-33 has been identified as a novel type of danger signal or “alarmin”, which is released from damaged and necrotic cells. IL-33 is a pleiotropic cytokine that targets a broad range of immune cells and exhibits pro- and anti-inflammatory properties dependent on the disease. This review summarizes the immunomodulatory roles of the NLRP3 inflammasome and IL-33 in sterile liver inflammation and highlights potential therapeutic strategies targeting these pathways in liver disease.

Mesenchymal stem cell transplantation improves chronic colitis-associated complications through inhibiting the activity of toll-like receptor-4 in mice

Background

A variety of extra-intestinal manifestations (EIMs), including hepatobiliary complications, are associated with inflammatory bowel disease (IBD). Mesenchymal stem cells (MSCs) have been shown to play a potential role in the therapy of IBD. This study was designed to investigate the effect and mechanism of MSCs on chronic colitis-associated hepatobiliary complications using mouse chronic colitis models induced by dextran sulfate sodium (DSS).

Methods

DSS-induced mouse chronic colitis models were established and treated with MSCs. Severity of colitis was evaluated by disease activity index (DAI), body weight (BW), colon length and histopathology. Serum lipopolysaccharide (LPS) levels were detected by limulus amebocyte lysate test (LAL-test). Histology and liver function of the mice were checked correspondingly. Serum LPS levels and bacterial translocation of mesenteric lymph nodes (MLN) were detected. Pro-inflammatory cytokines including tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-1β (IL-1β), interleukin-17A (IL-17A), Toll receptor 4 (TLR4), TNF receptor-associated factor 6 (TRAF6) and nuclear factor kappa B (NF-κB) were detected by immunohistochemical staining, western blot analysis and real-time PCR, respectively.

Results

The DSS-induced chronic colitis model was characterized by reduced BW, high DAI, worsened histologic inflammation, and high levels of LPS and E. coli. Liver histopathological lesions, impaired liver function, enhanced proteins and mRNA levels of TNF-α, IFN-γ, IL-1β, IL-17A, TLR4, TRAF6 and NF-κB were observed after DSS administration. MSCs transplantation markedly ameliorated the pathology of colon and liver by reduction of LPS levels and proteins and mRNA expressions of TNF-α, IFN-γ, IL-1β, IL-17A, TLR4, TRAF6 and NF-κB.

Conclusions

MSCs can improve chronic colitis-associated hepatobiliary complications, probably by inhibition of enterogenous endotoxemia and hepatic inflammation through LPS/TLR4 pathway. MSCs may represent a novel therapeutic approach for chronic colitis-associated hepatobiliary complications.

Inhibition of Hepatotoxicity by a LXR Inverse Agonist in a Model of Alcoholic Liver Disease

Alcohol abuse is a major cause of liver disease and mortality worldwide and is a significant public health issue. Patients with alcoholic liver disease (ALD) have severe hepatic lipid accumulation, inflammation, and fibrosis. Therapies for ALD are very limited and even abstinence from alcohol consumption does not necessarily protect patients from progression of the disease. We sought to evaluate the efficacy of a liver X receptor (LXR) inverse agonist, SR9238, in an animal model of ALD. SR9238 suppresses hepatic lipogenesis, a pathological hallmark of ALD, and we hypothesized that targeting suppression of hepatic metabolic pathways that are activated in ALD may be an effective treatment for the disease. A chronic ethanol diet with or without a final ethanol binge treatment was used to induce ALD in mice. Mice were administered the liver specific LXR inverse agonist SR9238 for 4 weeks after the mice had been maintained on the ethanol diet for 14 days. Mice developed all the hallmarks of advanced ALD demonstrating significant pathophysiology and hepatotoxicity. SR9238 significantly attenuated liver injury and hepatic steatosis and fibrosis was nearly eliminated in SR9238 treated mice. SR9238 treatment reversed the damage associated with chronic ethanol use returning the liver to near normal morphology. These results indicate that inhibiting LXR activity using the inverse agonist has a hepatoprotective effect in rodent models of ALD; thus, this pharmacological approach may be efficacious for treatment of ALD in humans.

Relevance of the NLRP3 Inflammasome in the Pathogenesis of Chronic Liver Disease

Inflammation is a common characteristic of chronic liver disease (CLD). Inflammasomes are multiprotein complexes that can sense and recognize various exogenous and endogenous danger signals, eventually activating interleukin (IL)-1β and IL-18. The sensor component of the inflammasome system is a nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs). The NLRs family pyrin domain containing 3 (NLRP3) inflammasome has been involved in the initiation and progression of CLD. However, the molecular mechanisms by which it triggers liver inflammation and damage remain unclear. Here, we focus on recent advances on the potential role of NLRP3 inflammasome activation in the progression of CLD, including viral hepatitis, non-alcoholic steatohepatitis and alcoholic liver disease, and in particular, its ability to alleviate liver inflammation in animal models. Additionally, we also discuss various pharmacological inhibitors identifying the NLRP3 inflammasome signaling cascade as novel therapeutic targets in the treatment of CLD. In summary, this review summarizes the relevance of the NLRP3 inflammasome in the initiation and progression of CLD, and provides critical targets to suppress the development of CLD in clinical management.

Intestinal Alkaline Phosphatase Attenuates Alcohol-Induced Hepatosteatosis in Mice

BACKGROUND AND AIMS

Bacterially derived factors from the gut play a major role in the activation of inflammatory pathways in the liver and in the pathogenesis of alcoholic liver disease. The intestinal brush-border enzyme intestinal alkaline phosphatase (IAP) detoxifies a variety of bacterial pro-inflammatory factors and also functions to preserve gut barrier function. The aim of this study was to investigate whether oral IAP supplementation could protect against alcohol-induced liver disease.

METHODS

Mice underwent acute binge or chronic ethanol exposure to induce alcoholic liver injury and steatosis ± IAP supplementation. Liver tissue was assessed for biochemical, inflammatory, and histopathological changes. An ex vivo co-culture system was used to examine the effects of alcohol and IAP treatment in regard to the activation of hepatic stellate cells and their role in the development of alcoholic liver disease.

RESULTS

Pretreatment with IAP resulted in significantly lower serum alanine aminotransferase compared to the ethanol alone group in the acute binge model. IAP treatment attenuated the development of alcohol-induced fatty liver, lowered hepatic pro-inflammatory cytokine and serum LPS levels, and prevented alcohol-induced gut barrier dysfunction. Finally, IAP ameliorated the activation of hepatic stellate cells and prevented their lipogenic effect on hepatocytes.

CONCLUSIONS

IAP treatment protected mice from alcohol-induced hepatotoxicity and steatosis. Oral IAP supplementation could represent a novel therapy to prevent alcoholic-related liver disease in humans.

Gut-liver axis and sterile signals in the development of alcoholic liver disease

BACKGROUND

Innate immunity plays a critical role in the development of alcohol-induced liver inflammation. Understanding the inter-relationship of signals from within and outside of the liver that trigger liver inflammation is pivotal for development of novel therapeutic targets of alcoholic liver disease (ALD).

AIM

The aim of this paper is to review recent advances in the field of alcohol-induced liver inflammation.

METHODS

A detailed literature review was performed using the PubMed database published between January 1980 and December 2016.

RESULTS

We provide an update on the role of intestinal microbiome, metabolome and the gut-liver axis in ALD, discuss the growing body of evidence on the diversity of liver macrophages and their differential contribution to alcohol-induced liver inflammation, and highlight the crucial role of inflammasomes in integration of inflammatory signals in ALD. Studies to date have identified a multitude of new therapeutic targets, some of which are currently being tested in patients with severe alcoholic hepatitis. These treatments aim to strengthen the intestinal barrier, ameliorate liver inflammation and augment hepatocyte regeneration.

CONCLUSION

Given the complexity of inflammation in ALD, multiple pathobiological mechanisms may need to be targeted at the same time as it seems unlikely that there is a single dominant pathogenic pathway in ALD that would be easily targeted using a single target drug approach.

SHORT SUMMARY

Here, we focus on recent advances in immunopathogenesis of alcoholic liver disease (ALD), including gut-liver axis, hepatic macrophage activation, sterile inflammation and synergy between bacterial and sterile signals. We propose a multiple parallel hit model of inflammation in ALD and discuss its implications for clinical trials in alcoholic hepatitis.

Enhanced colorectal cancer metastases in the alcohol-injured liver

Metastatic liver disease is a major cause of mortality in colorectal cancer (CRC) patients. Alcohol consumption is a noted risk factor for secondary cancers yet the role of alcoholic liver disease (ALD) in colorectal liver metastases (CRLM) is not defined. This work evaluated tumor cell colonization in the alcoholic host liver using a novel preclinical model of human CRC liver metastases. Immunocompromised Rag1-deficient mice were fed either ethanol (E) or isocaloric control (C) diets for 4 weeks prior to intrasplenic injection of LS174T human CRC cells. ALD and CRLM were evaluated 3 or 5 weeks post-LS174T cell injection with continued C/E diet administration. ALD was confirmed by increased serum transaminases, hepatic steatosis and expression of cytochrome P4502E1, a major ethanol-metabolizing enzyme. Alcohol-mediated liver dysfunction was validated by impaired endocytosis of asialoorosomucoid and carcinoembryonic antigen (CEA), indicators of hepatocellular injury and progressive CRC disease, respectively. Strikingly, the rate and burden of CRLM was distinctly enhanced in alcoholic livers with metastases observed earlier and more severely in E-fed mice. Further, alcohol-related increases (1.5-3.0 fold) were observed in the expression of hepatic cytokines (TNF-α, IL-1 beta, IL-6, IL-10) and other factors noted to be involved in the colonization of CRC cells including ICAM-1, CCL-2, CCL-7, MMP-2, and MMP-9. Also, alcoholic liver injury was associated with altered hepatic localization as well as increased circulating levels of CEA released from CRC cells. Altogether, these findings indicate that the alcoholic liver provides a permissive environment for the establishment of CRLM, possibly through CEA-related inflammatory mechanisms.

Protective effects of recombinant human cytoglobin against chronic alcohol-induced liver disease in vivo and in vitro

Alcoholic liver disease (ALD) is an important worldwide public health issue with no satisfying treatment available since now. Here we explore the effects of recombinant human cytoglobin (rhCygb) on chronic alcohol-induced liver injury and the underlying mechanisms. In vivo studies showed that rhCygb was able to ameliorate alcohol-induced liver injury, significantly reversed increased serum index (ALT, AST, TG, TC and LDL-C) and decreased serum HDL-C. Histopathology observation of the liver of rats treated with rhCygb confirmed the biochemical data. Furthermore, rhCygb significantly inhibited Kupffer cells (KCs) proliferation and TNF-α expression in LPS-induced KCs. rhCygb also inhibited LPS-induced NADPH oxidase activity and ROS, NO and O₂•^- generation. These results collectively indicate that rhCygb exert the protective effect on chronic alcohol-induced liver injury through suppression of KC activation and oxidative stress. In view of its anti-oxidative stress and anti-inflammatory features, rhCygb might be a promising candidate for development as a therapeutic agent against ALD.

Glycine prevents metabolic steatohepatitis in diabetic KK-Ay mice through modulation of hepatic innate immunity

Strategies for prevention and treatment of nonalcoholic steatohepatitis remain to be established. We evaluated the effect of glycine on metabolic steatohepatitis in genetically obese, diabetic KK-A^y mice. Male KK-A^y mice were fed a diet containing 5% glycine for 4 wk, and liver pathology was evaluated. Hepatic mRNA levels for lipid-regulating molecules, cytokines/chemokines, and macrophage M1/M2 markers were determined by real-time RT-PCR. Hepatic expression of natural killer (NK) T cells was analyzed by flow cytometry. Body weight gain was significantly blunted and development of hepatic steatosis and inflammatory infiltration were remarkably prevented in mice fed the glycine-containing diet compared with controls. Indeed, hepatic induction levels of molecules related to lipogenesis were largely blunted in the glycine diet-fed mice. Elevations of hepatic mRNA levels for TNFα and chemokine (C-C motif) ligand 2 were also remarkably blunted in the glycine diet-fed mice. Furthermore, suppression of hepatic NK T cells was reversed in glycine diet-fed KK-A^y mice, and basal hepatic expression levels of NK T cell-derived cytokines, such as IL-4 and IL-13, were increased. Moreover, hepatic mRNA levels of arginase-1, a marker of macrophage M2 transformation, were significantly increased in glycine diet-fed mice. In addition, dietary glycine improved glucose tolerance and hyperinsulinemia in KK-A^y mice. These observations clearly indicate that glycine prevents maturity-onset obesity and metabolic steatohepatitis in genetically diabetic KK-A^y mice. The underlying mechanisms most likely include normalization of hepatic innate immune responses involving NK T cells and M2 transformation of Kupffer cells. It is proposed that glycine is a promising immunonutrient for prevention and treatment of metabolic syndrome-related nonalcoholic steatohepatitis.

Critical Roles of Kupffer Cells in the Pathogenesis of Alcoholic Liver Disease: From Basic Science to Clinical Trials

Alcoholic liver disease (ALD) encompasses a spectrum of liver injury ranging from steatosis to steatohepatitis, fibrosis, and finally cirrhosis. Accumulating evidences have demonstrated that Kupffer cells (KCs) play critical roles in the pathogenesis of both chronic and acute ALD. It has become clear that alcohol exposure can result in increased hepatic translocation of gut-sourced endotoxin/lipopolysaccharide, which is a strong M1 polarization inducer of KCs. The activated KCs then produce a large amount of reactive oxygen species (ROS), pro-inflammatory cytokines, and chemokines, which finally lead to liver injury. The critical roles of KCs and related inflammatory cascade in the pathogenesis of ALD make it a promising target in pharmaceutical drug developments for ALD treatment. Several drugs (such as rifaximin, pentoxifylline, and infliximab) have been evaluated or are under evaluation for ALD treatment in randomized clinical trials. Furthermore, screening pharmacological regulators for KCs toward M2 polarization may provide additional therapeutic agents. The combination of these potentially therapeutic drugs with hepatoprotective agents (such as zinc, melatonin, and silymarin) may bring encouraging results.

Alcohol Use and Human Immunodeficiency Virus (HIV) Infection: Current Knowledge, Implications, and Future Directions

Alcohol use is common among people living with human immunodeficiency virus (HIV). In this narrative review, we describe literature regarding alcohol's impact on transmission, care, coinfections, and comorbidities that are common among people living with HIV (PLWH), as well as literature regarding interventions to address alcohol use and its influences among PLWH. This narrative review identifies alcohol use as a risk factor for HIV transmission, as well as a factor impacting the clinical manifestations and management of HIV. Alcohol use appears to have additive and potentially synergistic effects on common HIV-related comorbidities. We find that interventions to modify drinking and improve HIV-related risks and outcomes have had limited success to date, and we recommend research in several areas. Consistent with Office of AIDS Research/National Institutes of Health priorities, we suggest research to better understand how and at what levels alcohol influences comorbid conditions among PLWH, to elucidate the mechanisms by which alcohol use is impacting comorbidities, and to understand whether decreases in alcohol use improve HIV-relevant outcomes. This should include studies regarding whether state-of-the-art medications used to treat common coinfections are safe for PLWH who drink alcohol. We recommend that future research among PLWH include validated self-report measures of alcohol use and/or biological measurements, ideally both. Additionally, subgroup variation in associations should be identified to ensure that the risks of particularly vulnerable populations are understood. This body of research should serve as a foundation for a next generation of intervention studies to address alcohol use from transmission to treatment of HIV. Intervention studies should inform implementation efforts to improve provision of alcohol-related interventions and treatments for PLWH in healthcare settings. By making further progress on understanding how alcohol use affects PLWH in the era of HIV as a chronic condition, this research should inform how we can mitigate transmission, achieve viral suppression, and avoid exacerbating common comorbidities of HIV and alcohol use and make progress toward the 90-90-90 goals for engagement in the HIV treatment cascade.

Identifying Novel Targets for Treatment of Liver Fibrosis: What Can We Learn from Injured Tissues which Heal Without a Scar?

The liver is unique in that it is able to regenerate. This regeneration occurs without formation of a scar in the case of non-iterative hepatic injury. However, when the liver is exposed to chronic liver injury, the purely regenerative process fails and excessive extracellular matrix proteins are deposited in place of normal liver parenchyma. While much has been discovered in the past three decades, insights into fibrotic mechanisms have not yet lead to effective therapies; liver transplant remains the only cure for advanced liver disease. In an effort to broaden the collection of possible therapeutic targets, this review will compare and contrast the liver wound healing response to that found in two types of wound healing: scarless wound healing of fetal skin and oral mucosa and scar-forming wound healing found in adult skin. This review will examine wound healing in the liver and the skin in relation to the role of humoral and cellular factors, as well as the extracellular matrix, in this process. While several therapeutic targets are similar between fibrotic liver and adult skin wound healing, others are unique and represent novel areas for hepatic anti-fibrotic research. In particular, investigations into the role of hyaluronan in liver fibrosis and fibrosis resolution are warranted.

Oxidative products from alcohol metabolism differentially modulate pro-inflammatory cytokine expression in Kupffer cells and hepatocytes

Pro-inflammatory cytokines play a vital role in the pathogenesis of alcoholic steatohepatitis. The present study was to determine the role of alcohol-induced oxidative stress in modulating cytokine production. A rat model of alcohol consumption was used to determine alcohol-induced hepatic cytokine expression. Chronic alcohol exposure caused lipid accumulation, oxidative stress, and inflammation in the livers of Wistar rats. The role of oxidative stress in regulating cell type-specific cytokine production was further dissected in vitro. Lipopolysaccharide (LPS) dose-dependently upregulated TNF-α, MIP-1α, MCP-1, and CINC-1 in Kupffer cells-SV40, whereas TNF-α dose-dependently induced CINC-1, IP-10, and MIP-2 expression in H4IIEC3 hepatoma cells. An additive effect on cytokine production was observed in both Kupffer cells-SV40 and hepatocytes when combined hydrogen peroxide with LPS or TNF-α, respectively, which was associated with NF-κB activation and histone H3 hyper-acetylation. Unexpectedly, an inhibitory effect of 4-hydroxynonenal on cytokine production was revealed in LPS-treated Kupffer cells-SV40. Mechanistic study showed that 4-hydroxynonenal significantly enhanced mRNA degradation of TNF-α, MCP-1, and MIP-1α, and decreased the protein levels of MCP-1 in LPS-stimulated Kupffer cells-SV40 through reducing the phosphorylation of mRNA binding proteins. This study suggests that Kupffer cells and hepatocytes express distinct pro-inflammatory cytokines/chemokines in response to alcohol intoxication, and oxidative products (4-hydroxynonenal) differentially modulate pro-inflammatory cytokine/chemokine production via NF-κB signaling, histone acetylation, and mRNA stability.

Effects of Linderae radix extracts on a rat model of alcoholic liver injury

Traditional treatments have a poor effect on alcoholic liver diseases. Linderae radix (LR), the dried root of Lindera aggregata (Sims) Kosterm., has been frequently used in traditional Chinese medicine for treating various diseases, and has been shown to exhibit a protective effect on liver injury. In the present study, LR extracts were made using various solvents, and then administrated to rats to establish a model of ethanol-induced liver injury. The study aimed to investigate the therapeutic effects and potential mechanism of LR extracts on acute alcoholic liver injury. The serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), triglycercide (TG), cholesterol (TC), methane dicarboxylic aldehyde (MDA) and superoxide dismutase (SOD) were determined using an automatic biochemistry analyzer. In addition, pathological examination was performed by hematoxylin-eosin staining. The levels of MDA and SOD, and the expression levels of nuclear factor (NF)-κB, tumor necrosis factor (TNF)-α and interleukin (IL)-1β in liver tissue were investigated immunohistochemically. The expression of cytochrome P450 2E1 (CYP2E1) mRNA was quantified by reverse transcription-quantitative polymerase chain reaction. The results indicated that LR extracts improved the histopathological status and decreased the serum levels of ALT, AST, TG, TC and MDA. Furthermore, the levels of MDA and inflammatory mediators (NF-κB, TNF-α and IL-1β) were decreased in liver tissues, and the overexpression of CYP2E1 mRNA induced by ethanol treatment. LR extracts exhibited a protective effect on alcoholic liver injury and the mechanism may be associated with the anti-inflammatory and anti-oxidative action.

Hepatoprotective Effects of Chinese Medicinal Herbs: A Focus on Anti-Inflammatory and Anti-Oxidative Activities

The liver is intimately connected to inflammation, which is the innate defense system of the body for removing harmful stimuli and participates in the hepatic wound-healing response. Sustained inflammation and the corresponding regenerative wound-healing response can induce the development of fibrosis, cirrhosis and eventually hepatocellular carcinoma. Oxidative stress is associated with the activation of inflammatory pathways, while chronic inflammation is found associated with some human cancers. Inflammation and cancer may be connected by the effect of the inflammation-fibrosis-cancer (IFC) axis. Chinese medicinal herbs display abilities in protecting the liver compared to conventional therapies, as many herbal medicines have been shown as effective anti-inflammatory and anti-oxidative agents. We review the relationship between oxidative stress and inflammation, the development of hepatic diseases, and the hepatoprotective effects of Chinese medicinal herbs via anti-inflammatory and anti-oxidative mechanisms. Moreover, several Chinese medicinal herbs and composite formulae, which have been commonly used for preventing and treating hepatic diseases, including Andrographis Herba, Glycyrrhizae Radix et Rhizoma, Ginseng Radix et Rhizoma, Lycii Fructus, Coptidis Rhizoma, curcumin, xiao-cha-hu-tang and shi-quan-da-bu-tang, were selected for reviewing their hepatoprotective effects with focus on their anti-oxidative and ant-inflammatory activities. This review aims to provide new insight into how Chinese medicinal herbs work in therapeutic strategies for liver diseases.

Chronic Alcohol Consumption Causes Liver Injury in High-Fructose-Fed Male Mice Through Enhanced Hepatic Inflammatory Response

BACKGROUND

Obesity and the metabolic syndrome occur in approximately one-third of patients with alcoholic liver disease (ALD). The increased consumption of fructose parallels the increased prevalence of obesity and the metabolic syndrome in the United States and worldwide. In this study, we investigated whether dietary high fructose potentiates chronic alcohol-induced liver injury, and explored potential mechanism(s).

METHODS

Six-week-old male C57BL/6J mice were assigned to 4 groups: control, high fructose, chronic ethanol (EtOH), and high fructose plus chronic alcohol. The mice were fed either control diet or high-fructose diet (60%, w/w) for 18 weeks. Chronic alcohol-fed mice were given 20% (v/v) ethanol (Meadows-Cook model) ad libitum as the only available liquid from the 9th week through the 18th week. Liver injury, steatosis, hepatic inflammatory gene expression, and copper status were assessed.

RESULTS

High-fructose diet and chronic alcohol consumption alone each induce hepatic fat accumulation and impair copper status. However, the combination of dietary high fructose plus chronic alcohol synergistically induced liver injury as evidenced by robustly increased plasma alanine aminotransferase and aspartate aminotransferase, but the combination did not exacerbate hepatic fat accumulation nor worsen copper status. Moreover, FE-fed mice were characterized by prominent microvesicular steatosis. High-fructose diet and chronic alcohol ingestion together led to a significant up-regulation of Kupffer cell (KC) M1 phenotype gene expression (e.g., tumor necrosis factor-α and monocyte chemoattractant protein-1), as well as Toll-like receptor 4 (TLR4) signaling gene expression, which is also associated with the up-regulation of KCs and activation marker gene expression, including Emr1, CD68, and CD163.

CONCLUSIONS

Our data suggest that dietary high fructose may potentiate chronic alcohol consumption-induced liver injury. The underlying mechanism might be due to the synergistic effect of dietary high fructose and alcohol on the activation of the TLR4 signaling pathway, which in turn leads to KC activation and phenotype switch toward M1 polarization. This study suggests that alcohol-fructose combination contributes to ALD progression.

Regulation of matrix metalloproteinase-1 and alpha-smooth muscle actin expression by interleukin-1 alpha and tumour necrosis factor alpha in hepatic stellate cells

Hepatic stellate cells (HSCs) are key players in liver fibrosis and regeneration via collagen degradation and synthesis. These phenomena involve inflammatory cytokines released from non-parenchymal liver cells such as Kupffer cells. Although the effects of individual cytokines on many cell types have been investigated in various conditions, such as inflammation and tissue fibrosis, investigating the effect of combined cytokines would further our understanding of the regulatory mechanisms in tissue fibrosis. Here, we report the effect of multiple cytokine combinations on primary HSCs. We first examined the effect of individual cytokines and then the simultaneous exposure of different cytokines, including interleukin-6 (IL-6), IL-1 alpha (IL-1α), platelet-derived growth factor (PDGF), tumour necrosis factor-alpha (TNF-α) and transforming growth factor-beta (TGF-β), on matrix metalloproteinase-1 (MMP1) gene expression in primary HSCs. We observed that the combination of all five cytokines induced higher levels of MMP1 gene expression. Of these cytokines, TNF-α and IL-1α were found to be the key cytokines for not only inducing MMP1 expression, but also increasing α-smooth muscle actin gene expression. In conclusion, the combined treatment of TNF-α and IL-1α on HSCs had an enhanced effect on the expression of the fibrotic genes, MMP1 and α-smooth muscle actin, so appears to be an important regulator for tissue regeneration. This finding suggests that stimulation with combined anti-fibrotic cytokines is a potential approach in the development of a novel therapy for the recovery of liver fibrosis.

Serine 574 phosphorylation alters transcriptional programming of FOXO3 by selectively enhancing apoptotic gene expression

Forkhead box O3 (FOXO3) is a multispecific transcription factor that is responsible for multiple and conflicting transcriptional programs such as cell survival and apoptosis. The protein is heavily post-translationally modified and there is considerable evidence that post-transcriptional modifications (PTMs) regulate protein stability and nuclear-cytosolic translocation. Much less is known about how FOXO3 PTMs determine the specificity of its transcriptional program. In this study we demonstrate that exposure of hepatocytes to ethanol or exposure of macrophages to lipopolysaccharide (LPS) induces the c-Jun N-terminal kinase (JNK)-dependent phosphorylation of FOXO3 at serine-574. Chromatin immunoprecipitation (ChIP), mRNA and protein measurements demonstrate that p-574-FOXO3 selectively binds to promoters of pro-apoptotic genes but not to other well-described FOXO3 targets. Both unphosphorylated and p-574-FOXO3 bound to the B-cell lymphoma 2 (Bcl-2) promoter, but the unphosphorylated form was a transcriptional activator, whereas p-574-FOXO3 was a transcriptional repressor. The combination of increased TRAIL (TNF-related apoptosis-inducing ligand) and decreased Bcl-2 was both necessary and sufficient to induce apoptosis. LPS treatment of a human monocyte cell line (THP-1) induced FOXO3 S-574 phosphorylation and apoptosis. LPS-induced apoptosis was prevented by knockdown of FOXO3. It was restored by overexpressing wild-type FOXO3 but not by overexpressing a nonphosphorylatable S-574A FOXO3. Expression of an S-574D phosphomimetic form of FOXO3 induced apoptosis even in the absence of LPS. A similar result was obtained with mouse peritoneal macrophages where LPS treatment increased TRAIL, decreased Bcl-2 and induced apoptosis in wild-type but not FOXO3(-/-) cells. This work thus demonstrates that S-574 phosphorylation generates a specifically apoptotic form of FOXO3 with decreased transcriptional activity for other well-described FOXO3 functions.

TLR4 Expression by Liver Resident Cells Mediates the Development of Glucose Intolerance and Insulin Resistance in Experimental Periodontitis

BACKGROUND

Results from epidemiological studies indicate a close association between periodontitis and type 2 diabetes mellitus. However, the mechanism linking periodontitis to glucose intolerance (GI) and insulin resistance (IR) is unknown. We therefore tested the hypothesis that periodontitis induces the development of GI/IR through a liver Toll-like receptor 4 (TLR4) dependent mechanism.

METHODS

TLR4 chimeric mice were developed by bone marrow transplantation using green fluorescent protein expressing TLR4WT mouse (GFPWT) as donor and TLR4 WT or TLR4-/- as recipient mice (GFPWT:WT and GFPWT:KO chimeras respectively). These chimeras were subjected to experimental chronic periodontitis induced by repeated applications of LPS to the gingival sulci for 18 weeks. The levels of GI/IR were monitored and plasma cytokines and LPS were determined at 18 weeks when differences in glucose tolerance were most apparent. Cytokine gene expression was measured in liver tissue by qPCR.

RESULTS

Alveolar bone loss was significantly greater in GFPWT:WT chimeras treated with LPS compared with chimeras treated with PBS or GFPWT:KO chimeras. However, the degree of gingival inflammation was similar between GFPWT:WT and GFPWT:KO mice with LPS application. Severe GI/IR occurred in GFPWT:WT chimeras but not in the GFPWT:KO chimeras that were subjected to 18 weeks of LPS. Serum LPS was detected only in animals to which LPS was applied and the level was similar in GFPWT:WT and GFPWT:KO mice at the 18 week time point. Surprisingly, there was no significant difference in the plasma levels of IL1β, IL6 and TNFα at 18 weeks in spite of the severe GI/IR in the GFPWT:WT chimeras with LPS application. Also, no difference in the expression of TNFα or IL6 mRNA was detected in the liver of GFPWT:WT vs GFPWT:KO mice. In contrast, liver IL1β expression was significantly greater in GFPWT:WT chimeras compared to GFPWT:KO chimeras treated with LPS.

CONCLUSION

We observed that GFPWT:WT, but not GFPWT:KO chimeras, treated with LPS developed GI/IR despite similar degrees of gingival inflammation, circulating cytokine levels, and LPS concentrations. We conclude that LPS from periodontitis sites has a pivotal role in triggering the development of GI/IR through a mechanism that involves TLR4 expression by resident macrophages/Kupffer cells in the liver.

Delayed liver fibrosis in HTLV-2-infected patients co-infected with HIV-1 and hepatitis C virus with suppressive antiretroviral therapy

OBJECTIVES

The absence of direct clinical symptoms clearly associated to HTLV-2 infection may partially explain an underestimate of the real HTLV-2 prevalence rate and its effects in patients concurrently infected with HIV-1 and hepatitis C virus (HCV). Hence, to date, the influence of HTLV-2 on hepatic fibrosis has been poorly studied.

DESIGN

Retrospective study to clarify the influence of HTLV-2 infection in HCV infection and hepatic fibrosis among patients co-infected with HIV-1.

METHODS

This is a comparative cohort study including 39 HTLV-2-HIV-1-HCV co-infected patients and 42 HIV-1-HCV co-infected patients conducted in a tertiary care hospital. They were evaluated for transaminase levels, hepatic fibrosis stage, interleukin (IL)-28B genotype, Th1/Th2/Th17 cytokine levels, immune activation, inflammation, and microbial translocation.

RESULTS

HTLV-2-HIV-1-HCV co-infected patients had lower alanine aminotransferase levels (P = 0.023) and hepatic fibrosis (P = 0.012), compared to HIV-1-HCV co-infected patients. Moreover, Kaplan-Meier survival analysis showed a delay in hepatic fibrosis development for up to 5 years (P = 0.032). HTLV-2-HIV-1-HCV co-infected patients also had higher Th1/Th2 ratio (interferon γ/IL-4 ratio, P = 0.043; tumor necrosis factor α/IL-4 ratio, P = 0.010) and Th17 response (P = 0.015), whereas lower CD8 T-cell activation (P = 0.017) and lipopolysaccharide level (P = 0.001).

CONCLUSION

Findings strongly support that HTLV-2 co-infection might delay fibrosis development in HCV-HIV-1 co-infected patients.

Is there a role for probiotics in liver disease?

Intestinal microbiota plays an important role in health and disease. Alteration in its healthy homeostasis may result in the development of numerous liver disorders including complications of liver cirrhosis. On the other hand, restoration and modulation of intestinal flora through the use of probiotics is potentially an emerging therapeutic strategy. There is mounting evidence that probiotics are effective in the treatment of covert and overt hepatic encephalopathy, as well as in the prevention of recurrence of encephalopathy. The beneficial effect of probiotics also extends to liver function in cirrhosis, nonalcoholic fatty liver disease, and alcoholic liver disease. On the other hand, data associating probiotics and portal hypertension is scanty and conflicting. Probiotic therapy has also not been shown to prevent primary or secondary spontaneous bacterial peritonitis. Larger clinical studies are required before probiotics can be recommended as a treatment modality in liver diseases.

Chronic alcohol ingestion modulates hepatic macrophage populations and functions in mice

Hepatic Macs, consisting of resident KCs and infiltrating monocytes/IMs, are thought to play an important role in the pathogenesis of ALD. Previous work has focused on KCs or studied hepatic Macs as one cell population. The aim of the current study is to distinguish IMs from KCs and to compare their phenotypes and functions. We show here that a 4-week ethanol feeding of C57BL/6J mice causes recruitment of IMs into the liver. KCs and IMs can be distinguished based on their differential expression of F4/80 and CD11b. IMs can be divided further into two subsets based on their differential expression of Ly6C. KCs and two subsets of IMs were separately purified by FACS. The phagocytosis abilities and the expression profiles of genes related to various functions were compared among different populations of hepatic Macs. Ly6C(low) IMs exhibit an anti-inflammatory and tissue-protective phenotype; in contrast, Ly6C(hi) IMs exhibit a proinflammatory, tissue-damaging phenotype. The ratio of Ly6C(hi)/Ly6C(low) increases when mice chronically fed ethanol were binged, which significantly enhanced liver injury. Moreover, upon phagocytosis of apoptotic hepatocytes, Ly6C(hi) IMs switch to Ly6C(low) IMs. Taken together, chronic ethanol feeding induces the recruitment of two subsets of hepatic IMs, which play different or even opposite roles in regulating liver inflammation and repair. These findings may not only increase our understanding of the complex functions of Macs in the pathogenesis of ALD but also help us to identify novel therapeutic targets for the treatment of this disease.

NADPH oxidases: an overview from structure to innate immunity-associated pathologies

Oxygen-derived free radicals, collectively termed reactive oxygen species (ROS), play important roles in immunity, cell growth, and cell signaling. In excess, however, ROS are lethal to cells, and the overproduction of these molecules leads to a myriad of devastating diseases. The key producers of ROS in many cells are the NOX family of NADPH oxidases, of which there are seven members, with various tissue distributions and activation mechanisms. NADPH oxidase is a multisubunit enzyme comprising membrane and cytosolic components, which actively communicate during the host responses to a wide variety of stimuli, including viral and bacterial infections. This enzymatic complex has been implicated in many functions ranging from host defense to cellular signaling and the regulation of gene expression. NOX deficiency might lead to immunosuppression, while the intracellular accumulation of ROS results in the inhibition of viral propagation and apoptosis. However, excess ROS production causes cellular stress, leading to various lethal diseases, including autoimmune diseases and cancer. During the later stages of injury, NOX promotes tissue repair through the induction of angiogenesis and cell proliferation. Therefore, a complete understanding of the function of NOX is important to direct the role of this enzyme towards host defense and tissue repair or increase resistance to stress in a timely and disease-specific manner.

Chinese medicinal formula, Qinggan Huoxue Recipe protects rats from alcoholic liver disease via the lipopolysaccharide-Kupffer cell signal conduction pathway

The Chinese medicinal formula, Qinggan (QG) Huoxue (HX) Recipe (R) exerts a range of pharmacological effects, including reversible steatosis, decreased levels of inflammatory cytokines and lipid peroxidation resistance. The aim of the present study was to determine the specific mechanisms of QGHXR hepatoprotection through the lipopolysaccharide-Kupffer cell (LPS-KC) signal conduction pathway in rats with alcoholic liver disease (ALD). ALD rats were exposed to the compound factors, QGR and HXR. Hematoxylin and eosin staining was conducted to evaluate the pathological changes in the liver following QGHXR treatment and an enzyme-linked immunosorbent assay was performed to measure the content of tumor necrosis factor (TNF)-α in the plasma. Immunohistochemical staining was conducted to examine the expression of cell differentiation antigen (CD) 68 and 14. In addition, western blot analysis and reverse transcription-polymerase chain reaction were used to measure the expression of Toll-like receptor 4 (TLR₄), phosphorylated-extracellular regulated protein kinases (p-ERK), nuclear factor (NF)-κB, CD14 and TNF-α. Following stimulation with the compound factors, the rats exhibited increased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, as well as marked pathological changes. Furthermore, the related molecules in the LPS-KC pathway were upregulated and QGHXR was identified to be effective in the LPS-KC signal conduction pathway in the ALD rats. QGHXR was superior to QGR and HXR in reducing the serum ALT and AST levels, regulating CD14, TLR₄, NF-κB, ERK and TNF-α as well as improving the pathological changes. The results indicated that QGHXR therapy may provide a novel strategy for treating ALD via regulation of the related molecules in the LPS-KC signaling pathway.

Chronic ethanol feeding modulates inflammatory mediators, activation of nuclear factor-κB, and responsiveness to endotoxin in murine Kupffer cells and circulating leukocytes

Chronic ethanol abuse is known to increase susceptibility to infections after injury, in part, by modification of macrophage function. Several intracellular signalling mechanisms are involved in the initiation of inflammatory responses, including the nuclear factor-κB (NF-κB) pathway. In this study, we investigated the systemic and hepatic effect of chronic ethanol feeding on in vivo activation of NF-κB in NF-κB^EGFP reporter gene mice. Specifically, the study focused on Kupffer cell proinflammatory cytokines IL-6 and TNF-α and activation of NF-κB after chronic ethanol feeding followed by in vitro stimulation with lipopolysaccharide (LPS). We found that chronic ethanol upregulated NF-κB activation and increased hepatic and systemic proinflammatory cytokine levels. Similarly, LPS-stimulated IL-1β release from whole blood was significantly enhanced in ethanol-fed mice. However, LPS significantly increased IL-6 and TNF-α levels. These results demonstrate that chronic ethanol feeding can improve the responsiveness of macrophage LPS-stimulated IL-6 and TNF-α production and indicate that this effect may result from ethanol-induced alterations in intracellular signalling through NF-κB. Furthermore, LPS and TNF-α stimulated the gene expression of different inflammatory mediators, in part, in a NF-κB-dependent manner.

The functional role of microRNAs in alcoholic liver injury

The function of microRNAs (miRNAs) during alcoholic liver disease (ALD) has recently become of great interest in biological research. Studies have shown that ALD associated miRNAs play a crucial role in the regulation of liver-inflammatory agents such as tumour necrosis factor-alpha (TNF-α), one of the key inflammatory agents responsible for liver fibrosis (liver scarring) and the critical contributor of alcoholic liver disease. Lipopolysaccharide (LPS), a component of the cell wall of gram-negative bacteria, is responsible for TNF-α release by Kupffer cells. miRNAs are the critical mediators of LPS signalling in Kupffer cells, hepatocytes and hepatic stellate cells. Certain miRNAs, in particular miR-155 and miR-21, show a positive correlation in up-regulation of LPS signalling when they are exposed to ethanol. ALD is related to enhanced gut permeability that allows the levels of LPS to increase, leads to increased secretion of TNF-α by the Kupffer cells and subsequently promotes alcoholic liver injury through specific miRNAs. Meanwhile, two of the most frequently dysregulated miRNAs in steatohepatitis, miR-122 and miR-34a are the critical mediators in ethanol/LPS activated survival signalling during ALD. In this review, we summarize recent findings regarding the experimental and clinical aspects of functions of specific microRNAs, focusing mainly on inflammation and cell survival after ethanol/LPS treatment, and advances on the role of circulating miRNAs in human alcoholic disorders.

Alcohol-induced liver injury is modulated by Nlrp3 and Nlrc4 inflammasomes in mice

Alcoholic liver disease (ALD) is characterized by increased hepatic lipid accumulation (steatosis) and inflammation with increased expression of proinflammatory cytokines. Two of these cytokines, interleukin-1β (IL-1β) and IL-18, require activation of caspase-1 via members of the NOD-like receptor (NLR) family. These NLRs form an inflammasome that is activated by pathogens and signals released through local tissue injury or death. NLR family pyrin domain containing 3 (Nlrp3) and NLR family CARD domain containing protein 4 (Nlrc4) have been studied minimally for their role in the development of ALD. Using mice with gene targeted deletions for Nlrp3 (Nlrp3^−/−) and Nlrc4 (Nlrc4^−/−), we analyzed the response to chronic alcohol consumption. We found that Nlrp3^−/− mice have more severe liver injury with higher plasma alanine aminotransferase (ALT) levels, increased activation of IL-18, and reduced activation of IL-1B. In contrast, the Nlrc4^−/− mice had similar alcohol-induced liver injury compared to C57BL/6J (B6) mice but had greatly reduced activation of IL-1β. This suggests that Nlrp3 and Nlrc4 inflammasomes activate IL-1β and IL-18 via caspase-1 in a differential manner. We conclude that the Nlrp3 inflammasome is protective during alcohol-induced liver injury.