New therapeutic targets in alcoholic hepatitis

Hepatic β-arrestins: potential roles in liver health and disease

Β-arrestins are intracellular scaffolding proteins that have multifaceted roles in different types of disorders. In this review article, we gave a summary about the discovery, characterization and classification of these proteins and their intracellular functions. Moreover, this review article focused on the hepatic expression of β-arrestins and their hepatocellular distribution and function in each liver cell type. Also, we showed that β-arrestins are key regulators of distinct types of hepatic disorders. On the other hand, we addressed some important points that have never been studied before regarding the role of β-arrestins in certain types of hepatic disorders which needs more research efforts to cover.

Role of targeting TLR4 signaling axis in liver-related diseases

Toll-like receptor 4 (TLR4) plays an important role as a key signal-receiving transmembrane protein molecule in the liver, and substances that target the liver exert therapeutic effects via TLR4-related signaling pathways. This article provides a comprehensive review of targeting the TLR4 signaling axis to play an important role in the liver based on endogenous substances. Articles were divided into 5 major types of liver disease, acute liver injury, viral hepatitis, alcoholic and non-alcoholic liver disease, cirrhosis, and liver cancer, to elucidate how various endogenous substances affect the liver via the TLR4 pathway and the important role of the pathway itself in liver-related diseases to discover the potential therapeutic implications of the TLR4-related pathway in the liver. The results indicate that activation of the TLR4-related signaling axis primarily plays a role in promoting disease progression in liver-related diseases, and the TLR4/MyD88/NF-κB axis plays the most dominant role. Therefore, exploring the full effects of drugs targeting the TLR4-related signaling axis in the liver and the new use of old drugs may be a new research direction.

CD73 Attenuates Alcohol-Induced Liver Injury and Inflammation via Blocking TLR4/MyD88/NF-κB Signaling Pathway

Background

Alcoholic liver disease (ALD) is liver damage caused by long-term drinking. Inflammation plays a central role in the progression of ALD. CD73 is a ubiquitously expressed glycosylphosphatidylinositol-anchored glycoprotein that is a key enzyme that converts ATP into adenosine. Evidence has shown that CD73 plays an important role in many diseases, but the role and mechanism of CD73 in alcohol-induced liver injury and inflammation is still unclear.

Methods

The alcohol-induced liver injury and inflammation mouse model was established. The rAAV9-CD73 was used to overexpress CD73. Isolation of primary macrophages (MΦ) from the liver was conducted. The effects of CD73 on alcohol-induced liver injury and inflammation were evaluated by quantitative real‑time PCR, Western blotting, ELISA, and immunohistochemical assay. Flow cytometry was used to detect the cell cycle and apoptosis.

Results

Our results showed that overexpression of CD73 can reduce alcohol-induced liver damage, lipid accumulation, and the secretion of inflammatory cytokines. pEX3-CD73 can promote RAW264.7 cells proliferation and inhibit apoptosis via suppressing the activation of TLR4/MyD88/NF-κB signaling pathway. Inhibition of TLR4 further enhanced the anti-inflammatory effect of overexpression of CD73.

Conclusion

Overexpression of CD73 can reduce alcohol-induced liver injury and inflammation. CD73 may serve as a potential therapeutic target for ALD.

NIK links inflammation to hepatic steatosis by suppressing PPARα in alcoholic liver disease

Background: Inflammation and steatosis are the main pathological features of alcoholic liver disease (ALD), in which, inflammation is one of the critical drivers for the initiation and development of alcoholic steatosis. NIK, an inflammatory pathway component activated by inflammatory cytokines, was suspected to link inflammation to hepatic steatosis during ALD. However, the underlying pathogenesis is not well-elucidated. Methods: Alcoholic steatosis was induced in mice by chronic-plus-binge ethanol feeding. Both the loss- and gain-of-function experiments by the hepatocyte-specific deletion, pharmacological inhibition and adenoviral transfection of NIK were utilized to elucidate the role of NIK in alcoholic steatosis. Rate of fatty acid oxidation was assessed in vivo and in vitro. PPARα agonists or antagonists of MEK1/2 and ERK1/2 were used to identify the NIK-induced regulation of PPARα, MEK1/2, and ERK1/2. The potential interactions between NIK, MEK1/2, ERK1/2 and PPARα and the phosphorylation of PPARα were clarified by immunoprecipitation, immunoblotting and far-western blotting analysis. Results: Hepatocyte-specific deletion of NIK protected mice from alcoholic steatosis by sustaining hepatic fatty acid oxidation. Moreover, overexpression of NIK contributed to hepatic lipid accumulation with disrupted fatty acid oxidation. The pathological effect of NIK in ALD may be attributed to the suppression of PPARα, the main controller of fatty acid oxidation in the liver, because PPARα agonists reversed NIK-mediated hepatic steatosis and malfunction of fatty acid oxidation. Mechanistically, NIK recruited MEK1/2 and ERK1/2 to form a complex that catalyzed the inhibitory phosphorylation of PPARα. Importantly, pharmacological intervention against NIK significantly attenuated alcoholic steatosis in ethanol-fed mice. Conclusions: NIK targeting PPARα via MEK1/2 and ERK1/2 disrupts hepatic fatty acid oxidation and exhibits high value in ALD therapy.

Alcohol-related liver disease. Clinical practice guidelines. Consensus document sponsored by AEEH

Alcohol-related liver disease (ARLD) is the most prevalent cause of advanced liver disease and liver cirrhosis in Europe, including Spain. According to the World Health Organization the fraction of liver cirrhosis attributable to alcohol use in Spain is 73.8% among men and 56.3% among women. ARLD includes various stages such as steatohepatitis, cirrhosis and hepatocellular cancer. In addition, patients with underlying ARLD and heavy alcohol intake may develop alcoholic hepatitis, which is associated with high mortality. To date, the only effective treatment to treat ARLD is prolonged withdrawal. There are no specific treatments, and the only treatment that increases life expectancy in alcoholic hepatitis is prednisolone. For patients with alcoholic hepatitis who do not respond to treatment, some centres offer the possibility of an early transplant. These clinical practice guidelines aim to propose recommendations on ARLD taking into account their relevance as a cause of advanced chronic liver disease and liver cirrhosis in our setting. This paper aims to answer the key questions for the clinical practice of Gastroenterology, Hepatology, as well as Internal Medicine and Primary Health Centres, making the most up-to-date information regarding the management and treatment of ARLD available to health professionals. These guidelines provide evidence-based recommendations for the clinical management of this disease.

Cilostazol protects hepatocytes against alcohol-induced apoptosis via activation of AMPK pathway

Alcoholic liver disease (ALD) is a worldwide health problem and hepatocyte apoptosis has been associated with the development/progression of ALD. However, no definite effective pharmacotherapy for ALD is currently available. Cilostazol, a selective type III phosphodiesterase inhibitor has been shown to protect hepatocytes from ethanol-induced apoptosis. In the present study, the underlying mechanisms for the protective effects of cilostazol were examined. Primary rat hepatocytes were treated with ethanol in the presence or absence of cilostazol. Cell viability and intracellular cAMP were measured. Apoptosis was detected by Hoechst staining, TUNEL assay, and caspase-3 activity assay. The roles of cAMP and AMP-activated protein kinase (AMPK) pathways in the action of CTZ were explored using pharmacological inhibitors and siRNAs. Liver from mice received ethanol (5 g/kg body weight) by oral gavage following cilostazol treatment intraperitoneally was obtained for measurement of apoptosis and activation of AMPK pathway. Cilostazol inhibited ethanol-induced hepatocyte apoptosis and potentiated the increases in cAMP level induced by forskolin. However, the anti-apoptotic effect of cilostazol was not reversed by an inhibitor of adenylyl cyclase. Interestingly, cilostazol activated AMPK and increased the level of LC3-II, a marker of autophagy. The inhibition of AMPK abolished the effects of cilostazol on LC3-II expression and apoptosis. Moreover, the inhibition of LKB1 and CaMKK2, upstream kinases of AMPK, dampened cilostazol-inhibited apoptosis as well as AMPK activation. In conclusion, cilostazol protected hepatocytes from apoptosis induced by ethanol mainly via AMPK pathway which is regulated by both LKB1 and CaMKK2. Our results suggest that cilostazol may have potential as a promising therapeutic drug for treatment of ALD.

Meta-analysis of patient survival and rate of alcohol relapse in liver-transplanted patients for acute alcoholic hepatitis

PURPOSE

This review investigated survival and alcoholic relapse following liver transplantation (LT) in patients with severe acute alcoholic hepatitis (AH) without 6 months of alcohol abstinence.

METHODS

All studies comparing acute AH patients undergoing LT with a control group were included. CENTRAL, MEDLINE, and Web of Science databases were searched. Survival benefits or odds ratios (OR) and 95% confidence intervals (CI) were assessed by meta-analyses using a random effects model. The study was registered in PROSPERO (CRD42017057971). According to the search results, two separate meta-analyses were performed: meta-analysis A compared early LT with medical therapy alone in patients with severe AH that were not responding to medical therapy and meta-analysis B compared LT outcome in patients with AH and chronic alcoholic cirrhosis (AC).

RESULTS

The search yielded 2232 articles. Eight studies were included in the two meta-analyses-two studies in meta-analysis A and six studies in meta-analysis B. The two studies (n = 70) included in meta-analysis A revealed that 1-year patient survival was significantly higher in the LT group compared with the medical therapy-alone group (survival benefit, 15.88; 95% CI, 3.98-63.35; p < 0.0001). The six studies in meta-analysis B (including 1091 patients) showed that 1-year (survival benefit, 1.65; 95% CI, 0.95-2.89; p = 0.08), 3-year (survival benefit, 1.31; 95% CI, 0.79-2.18; p = 0.30), and 5-year survival (survival benefit, 1.54; 95% CI, 0.92-2.56; p = 0.10) were not significantly different between AH and AC groups. There was no significant difference in the rate of alcohol relapse between the groups (OR, 1.26; 95% CI, 0.53-2.96; p = 0.60).

CONCLUSIONS

Early LT is a life-saving treatment for AH patients that do not respond to medical therapy. The chance of alcohol relapse after LT is not increased in selected patients.

Gut Microbiota's Relationship with Liver Disease and Role in Hepatoprotection by Dietary Natural Products and Probiotics

A variety of dietary natural products have shown hepatoprotective effects. Increasing evidence has also demonstrated that gut microorganisms play an important role in the hepatoprotection contributed by natural products. Gut dysbiosis could increase permeability of the gut barrier, resulting in translocated bacteria and leaked gut-derived products, which can reach the liver through the portal vein and might lead to increased oxidative stress and inflammation, thereby threatening liver health. Targeting gut microbiota modulation represents a promising strategy for hepatoprotection. Many natural products could protect the liver from various injuries or mitigate hepatic disorders by reverting gut dysbiosis, improving intestinal permeability, altering the primary bile acid, and inhibiting hepatic fatty acid accumulation. The mechanisms underlying their beneficial effects also include reducing oxidative stress, suppressing inflammation, attenuating fibrosis, and decreasing apoptosis. This review discusses the hepatoprotective effects of dietary natural products via modulating the gut microbiota, mainly focusing on the mechanisms of action.

β-Arrestin 2 Promotes Hepatocyte Apoptosis by Inhibiting Akt Pathway in Alcoholic Liver Disease

Alcoholic liver disease (ALD) is a complex process that includes a wide range of hepatic lesions, from steatosis to cirrhosis, and even hepatocellular carcinoma (HCC). Accumulating evidence shows that the cytotoxic effects of ethanol metabolism lead to cell apoptosis and necrosis in ALD. Recently, several studies revealed that multifunctional protein β-arrestin 2 (Arrb2) modulated cell apoptosis in liver fibrosis and HCC, but its role in ALD has not been fully understood. The aim of this study is to explore the function and underlying mechanism of Arrb2 in hepatocyte survival and apoptosis in ALD. In our study, the primary hepatocytes were isolated from the livers of C57BL/6 mice fed EtOH-containing diet, it showed an increased level of Arrb2. EtOH also significantly up-regulated Arrb2 production in AML-12 cells in vitro. Furthermore, TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) and FCM results demonstrated that knockdown of Arrb2 could inhibit hepatocyte apoptosis induced by EtOH in vivo and vitro while over-expression of Arrb2 induced apoptosis in ALD. In addition, western blot results revealed that Arrb2 remarkably suppressed the Akt signaling. Taken together, our data suggested that Arrb2 may serve as a potential therapeutic target for ALD by promoting hepatocyte apoptosis via Akt suppression.

Triiodothyronine alleviates alcoholic liver disease injury through the negative regulation of the NLRP3 signaling pathway

The aim of the present study was to investigate the effect and mechanism of triiodothyronine (T3) on alcoholic liver disease (ALD)-induced injuries in mice. A total of 40 male C57/BL6 mice were randomly divided into the Control, ALD, ALD+T3 and ALD+T3+AMP-activated protein kinase inhibitor (CC) groups. Mice were administered alcohol (4 g/kg/day) intragastrically for 4 weeks except for Control group. Mice in the ALD+T3 group were given T3 (0.1 mg/kg/day) while mice in ALD+T3+CC group were given T3 (0.1 mg/kg/day) and CC (10 mg/kg/day) for 1 week. Control and ALD groups were treated with saline. Liver tissue and blood samples were obtained for testing. Alanine aminotransferase (ALT), aspartate aminotransferase (AST) and total bilirubin (TBIL) levels were determined and morphological changes in the liver tissues were observed under the optical microscope. Inflammatory factors, including IL-1β and transforming growth factor (TGF)-β/1, α-smooth muscle actin (SMA) and protein levels of nucleotide-binding oligomerization domain, leucine rich repeat containing family, pyrin domain containing 3 (NLRP3), caspase-1 and pro-IL-1β were measured. Serum ALT, AST and TBIL levels in the ALD+T3 group were significantly reduced compared with the ALD group, while they were significantly increased in the ALD+T3+CC group (P<0.05). The number of hepatic lobules in the ALD+T3 group was significantly reduced compared with the ALD group, whereas the number in the ALD+T3+CC group was significantly increased (P<0.05). IL-1β and TGF-β1 levels in the ALD+T3 group were significantly decreased compared with the ALD group; however, levels in the ALD+T3+CC group were significantly increased compared with the ALD+T3 group (P<0.05). In addition, it was revealed that the expression of α-SMA mRNA and protein in the ALD+T3 group was significantly decreased compared with the ALD group, whereas it was significantly increased in the ALD+T3+CC group compared with the ALD+T3 group. Expression of NLRP3, caspase-1, IL-1β and TGF-β1 in the ALD+T3 group was significantly decreased compared with the ALD group, while expression was significantly increased in the ALD+T3+CC group. Conversely, compared with the ALD group, expression of pro-IL-1β was significantly increased in the ALD+T3 group and decreased in the ALD+T3+CC group. In conclusion, T3 may reduce the inflammatory response and severity of liver cirrhosis in mice with ALD by negatively regulating the NLRP3 signaling pathway.

Controversies in clinical trials for alcoholic hepatitis

Alcoholic hepatitis (AH) is the most severe form of alcoholic liver disease, contributing to significant morbidity and mortality. Yet, the only available therapies that improve survival are corticosteroids and liver transplantation, with no new drugs successfully developed for decades. This article briefly describes the current state of affairs in AH therapy and examines the practical and ethical challenges of conducting controlled trials in patients with severe AH. While prednisolone is considered standard of care in severe AH, this recommendation remains controversial given the marginal benefits and questionable long-term safety of steroids. Placebo-controlled trials without steroids may be necessary and ethically justified in certain populations with AH who have not been adequately investigated. Ultimately, we suggest that the field will advance with the development of a plausible animal model of true AH, a consensus on a composite clinical endpoint that does not rely solely on mortality, as well as the adoption of the NIAAA Alcoholic Hepatitis Consortia recommendations regarding standard definitions and when to request a liver biopsy prior to study entry.

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.

Emerging concepts in alcoholic hepatitis

Severe alcoholic hepatitis is implicated as a costly, worldwide public health issue with high morbidity and mortality. The one-month survival for severe alcoholic hepatitis is low with mortality rates high as 30%-50%. Abstinence from alcohol is the recommended first-line treatment. Although corticosteroids remain as the current evidence based option for selected patients with discriminant function > 32, improvement of short-term survival rate may be the only benefit. Identification of individuals with risk factors for the development of severe alcoholic hepatitis may provide insight to the diverse clinical spectrum and prognosis of the disease. The understanding of the complex pathophysiologic processes of alcoholic hepatitis is the key to elucidating new therapeutic treatments. Newer research describes the use of gut microbiota modification, immune modulation, stimulation of liver regeneration, caspase inhibitors, farnesoid X receptors, and the extracorporeal liver assist device to aid in hepatocellular recovery. Liver transplantation can be considered as the last medical option for patients failing conventional medical interventions. Although the preliminary data is promising in patients with low risk of recividism, controversy remains due to organ scarcity. This review article comprehensively summarizes the epidemiology, pathophysiology, risk factors, and prognostic indicators of severe alcoholic hepatitis with a focus on the current and emerging therapeutics.

Using Big Data to Discover Diagnostics and Therapeutics for Gastrointestinal and Liver Diseases

Technologies such as genome sequencing, gene expression profiling, proteomic and metabolomic analyses, electronic medical records, and patient-reported health information have produced large amounts of data from various populations, cell types, and disorders (big data). However, these data must be integrated and analyzed if they are to produce models or concepts about physiological function or mechanisms of pathogenesis. Many of these data are available to the public, allowing researchers anywhere to search for markers of specific biological processes or therapeutic targets for specific diseases or patient types. We review recent advances in the fields of computational and systems biology and highlight opportunities for researchers to use big data sets in the fields of gastroenterology and hepatology to complement traditional means of diagnostic and therapeutic discovery.