A two-hit model of alcoholic liver disease that exhibits rapid, severe fibrosis

Ethanol extracts of Isochrysis zhanjiangensis alleviate acute alcoholic liver injury and modulate intestinal bacteria dysbiosis in mice

BACKGROUND

Alcoholic liver disease (ALD) is responsible for 3.3 million deaths per annum. Efficacious therapeutic modalities or drug treatments for ALD have not yet been found, so it is urgent to seek new agents for preventing ALD and its related disease. Many experiments have indicated that modulating the gut microbiota and regulating the toll-like receptor 4 (TLR4)/nuclear transcription factor-κB (NF-κB) inflammatory pathway can provide a new target for prevention and treatment of ALD. Marine microalgae have their natural metabolic pathways to synthesize various of bioactive compounds as promising candidates for hepatoprotection. In this study, we investigated ethanol extracts from Isochrysis zhanjiangensis (EEIZ) to evaluate their ability to alleviate acute alcoholic liver injury, regulate TLR4/NF-κB inflammatory pathway and modulate intestinal bacteria dysbiosis in mice for ALD treatment.

RESULTS

In the acute ALD mouse model, EEIZ reduced levels of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, triacylglyceride, total cholesterol and low-density lipoprotein, while increasing the level of high-density lipoprotein. Besides, TLR4, myeloid differentiation factor 88, NF-κB and tumor necrosis factor-α expression levels in liver tissue were effectively downregulated by EEIZ. Furthermore, treatment with EEIZ enhanced intestinal homeostasis and significantly alleviated the damage caused by alcohol.

CONCLUSION

EEIZ showed effective hepatoprotective activity against alcohol-induced acute liver injury in mice as it could alleviate hepatocyte damage, suppress the TLR4/NF-κB inflammatory pathway and regulate the intestinal flora structure. EEIZ could be a good candidate for preventing acute alcoholic liver injury. © 2024 Society of Chemical Industry.

Alcohol-induced epigenetic changes prevent fibrosis resolution after alcohol cessation in miceresolution

BACKGROUND AND AIMS

Alcohol-associated liver disease is a major cause of alcohol-associated mortality. Recently, we identified hepatic demethylases lysine demethylase (KDM)5B and KDM5C as important epigenetic regulators of alcohol response in the liver. In this study, we aimed to investigate the role of KDM5 demethylases in alcohol-associated liver disease resolution.

APPROACH AND RESULTS

We showed that alcohol-induced liver steatosis rapidly resolved after alcohol cessation. In contrast, fibrosis persisted in the liver for up to 8 weeks after the end of alcohol exposure. Defects in fibrosis resolution were in part due to alcohol-induced KDM5B and KDM5C-dependent epigenetic changes in hepatocytes. Using cell-type-specific knockout mice, we found that adeno-associated virus-mediated knockout of KDM5B and KDM5C demethylases in hepatocytes at the time of alcohol withdrawal promoted fibrosis resolution. Single-cell ATAC sequencing analysis showed that during alcohol-associated liver disease resolution epigenetic cell states largely reverted to control conditions. In addition, we found unique epigenetic cell states distinct from both control and alcohol states and identified associated transcriptional regulators, including liver X receptor (LXR) alpha (α). In vitro and in vivo analysis confirmed that knockout of KDM5B and KDM5C demethylases promoted LXRα activity, likely through regulation of oxysterol biosynthesis, and this activity was critical for the fibrosis resolution process. Reduced LXR activity by small molecule inhibitors prevented fibrosis resolution in KDM5-deficient mice.

CONCLUSIONS

In summary, KDM5B and KDM5C demethylases prevent liver fibrosis resolution after alcohol cessation in part through suppression of LXR activity.

Development of LXR inverse agonists to treat MAFLD, NASH, and other metabolic diseases

Activation of LXR activity by synthetic agonists has been the focus of many drug discovery efforts with a focus on treatment of dyslipidemia and atherosclerosis. Many agonists have been developed, but all have been hindered due to their ability to efficaciously stimulate de novo lipogenesis. Here, we review the development of LXR inverse agonists that were originally optimized for their ability to enable recruitment of corepressors leading to silencing of genes that drive de novo lipogenesis. Such compounds have efficacy in animal models of MAFLD, dyslipidemia, and cancer. Several classes of LXR inverse agonists have been identified and one is now in clinical trials for treatment of severe dyslipidemia.

Pathogenesis of Alcohol-Associated Liver Disease

Excessive alcohol consumption is a global healthcare problem with enormous social, economic, and clinical consequences. While chronic, heavy alcohol consumption causes structural damage and/or disrupts normal organ function in virtually every tissue of the body, the liver sustains the greatest damage. This is primarily because the liver is the first to see alcohol absorbed from the gastrointestinal tract via the portal circulation and second, because the liver is the principal site of ethanol metabolism. Alcohol-induced damage remains one of the most prevalent disorders of the liver and a leading cause of death or transplantation from liver disease. Despite extensive research on the pathophysiology of this disease, there are still no targeted therapies available. Given the multifactorial mechanisms for alcohol-associated liver disease pathogenesis, it is conceivable that a multitherapeutic regimen is needed to treat different stages in the spectrum of this disease.

A Western diet with alcohol in drinking water recapitulates features of alcohol-associated liver disease in mice

BACKGROUND

Mouse models of alcohol-associated liver disease vary greatly in their ease of implementation and the pathology they produce. Effects range from steatosis and mild inflammation with the Lieber-DeCarli liquid diet to severe inflammation, fibrosis, and pyroptosis seen with the Tsukamoto-French intragastric feeding model. Implementation of all of these models is limited by the labor-intensive nature of the protocols and the specialized skills necessary for successful intragastric feeding. We thus sought to develop a new model to reproduce features of alcohol-induced inflammation and fibrosis with minimal operational requirements.

METHODS

Over a 16-week period, mice were fed ad libitum with a pelleted high-fat Western diet (WD; 40% calories from fat) and alcohol added to the drinking water. We found the optimal alcohol consumption to be that at which the alcohol concentration was 20% for 4 days and 10% for 3 days per week. Control mice received WD pellets with water alone.

RESULTS

Alcohol consumption was 18 to 20 g/kg/day in males and 20 to 22 g/kg/day in females. Mice in the alcohol groups developed elevated serum transaminase levels after 12 weeks in males and 10 weeks in females. At 16 weeks, both males and females developed liver inflammation, steatosis, and pericellular fibrosis. Control mice on WD without alcohol had mild steatosis only. Alcohol-fed mice showed reduced HNF4α mRNA and protein expression. HNF4α is a master regulator of hepatocyte differentiation, down-regulation of which is a known driver of hepatocellular failure in alcoholic hepatitis.

CONCLUSION

A simple-to-administer, 16-week WD alcohol model recapitulates the inflammatory, fibrotic, and gene expression aspects of human alcohol-associated steatohepatitis.