Histopathological and Molecular Signatures of a Mouse Model of Acute-on-Chronic Alcoholic Liver Injury Demonstrate Concordance With Human Alcoholic Hepatitis

Alcohol-Associated Liver Disease Outcomes: Critical Mechanisms of Liver Injury Progression

Alcohol-associated liver disease (ALD) is a substantial cause of morbidity and mortality worldwide and represents a spectrum of liver injury beginning with hepatic steatosis (fatty liver) progressing to inflammation and culminating in cirrhosis. Multiple factors contribute to ALD progression and disease severity. Here, we overview several crucial mechanisms related to ALD end-stage outcome development, such as epigenetic changes, cell death, hemolysis, hepatic stellate cells activation, and hepatic fatty acid binding protein 4. Additionally, in this review, we also present two clinically relevant models using human precision-cut liver slices and hepatic organoids to examine ALD pathogenesis and progression.

LPS-TLR4 pathway exaggerates alcoholic hepatitis via provoking NETs formation

BACKGROUND

Intrahepatic infiltration of neutrophils is a character of alcoholic hepatitis (AH) and neutrophil extracellular traps (NETs) are an important strategy for neutrophils to fix and kill invading microorganisms. The gut-liver axis has been thought to play a critical role in many liver diseases also including AH. However, whether NETs appear in AH and play role in AH is still unsure.

METHODS

Serum samples from AH patients were collected and LPS and MPO-DNA were detected. WT, NE KO, and TLR4 KO mice were used to build the AH model, and the intestinal bacteria were eliminated at the same time and LPS was given. Then the formation of NETs and AH-related markers were detected.

RESULTS

The serum MPO-DNA and LPS concentration was increased in AH patients and a correlation was revealed between these two indexes. More intrahepatic NETs formed in AH mice. NETs formation decreased with antibiotic intervention and restored with antibiotic intervention plus LPS supplement. While NETs formation failed to change with gut microbiome or combine LPS supplement in TLR4 KO mice. As we tested AH-related characters, liver injury, intrahepatic fat deposition, inflammation, and fibrosis alleviated with depletion of NE. These related marks were also attenuated with gut sterilization by antibiotics and recovered with a combined treatment with antibiotics plus LPS. But the AH-related markers did show a difference in TLR4 KO mice when they received the same treatment.

CONCLUSION

Intestinal-derived LPS promotes NETs formation in AH through the TLR4 pathway and further accelerates the AH process by NETs.

Unveiling the hidden players: exploring the role of gut mycobiome in cancer development and treatment dynamics

The role of gut fungal species in tumor-related processes remains largely unexplored, with most studies still focusing on fungal infections. This review examines the accumulating evidence suggesting the involvement of commensal and pathogenic fungi in cancer biological process, including oncogenesis, progression, and treatment response. Mechanisms explored include fungal influence on host immunity, secretion of bioactive toxins/metabolites, interaction with bacterial commensals, and migration to other tissues in certain types of cancers. Attempts to utilize fungal molecular signatures for cancer diagnosis and fungal-derived products for treatment are discussed. A few studies highlight fungi's impact on the responsiveness and sensitivity to chemotherapy, radiotherapy, immunotherapy, and fecal microbiota transplant. Given the limited understanding and techniques in fungal research, the studies on gut fungi are still facing great challenges, despite having great potentials.

The Elk-3 target Abhd10 ameliorates hepatotoxic injury and fibrosis in alcoholic liver disease

Alcoholic liver disease (ALD) and other forms of chronic hepatotoxic injury can lead to transforming growth factor β1 (TGFβ1)-induced hepatic fibrosis and compromised liver function, underscoring the need to develop novel treatments for these conditions. Herein, our analyses of liver tissue samples from severe alcoholic hepatitis (SAH) patients and two murine models of ALD reveals that the ALD phenotype was associated with upregulation of the transcription factor ETS domain-containing protein (ELK-3) and ELK-3 signaling activity coupled with downregulation of α/β hydrolase domain containing 10 (ABHD10) and upregulation of deactivating S-palmitoylation of the antioxidant protein Peroxiredoxin 5 (PRDX5). In vitro, we further demonstrate that ELK-3 can directly bind to the ABHD10 promoter to inhibit its transactivation. TGFβ1 and epidermal growth factor (EGF) signaling induce ABHD10 downregulation and PRDX5 S-palmitoylation via ELK-3. This ELK-3-mediated ABHD10 downregulation drives oxidative stress and disrupts mature hepatocyte function via enhancing S-palmitoylation of PRDX5's Cys100 residue. In vivo, ectopic Abhd10 overexpression ameliorates liver damage in ALD model mice. Overall, these data suggest that the therapeutic targeting of the ABHD10-PRDX5 axis may represent a viable approach to treating ALD and other forms of hepatotoxicity.

Is Candida albicans a contributor to cancer? A critical review based on the current evidence

The association between Candida albicans (C. albicans) and cancer has been noticed for decades. Whether C. albicans infection is a complication of cancer status or as a contributor to cancer development remains to be discussed. This review systematically summarized the up-to-date knowledge about associations between C. albicans and various types of cancer, and discussed the role of C. albicans in cancer development. Most of the current clinical and animal evidence support the relationship between C. albicans and oral cancer development. However, there is insufficient evidence to demonstrate the role of C. albicans in other types of cancer. Moreover, this review explored the underlying mechanisms for C. albicans promoting cancer. It was hypothesized that C. albicans may promote cancer progression by producing carcinogenic metabolites, inducing chronic inflammation, remodeling immune microenvironment, activating pro-cancer signals, and synergizing with bacteria.

An update on animal models of liver fibrosis

The development of liver fibrosis primarily determines quality of life as well as prognosis. Animal models are often used to model and understand the underlying mechanisms of human disease. Although organoids can be used to simulate organ development and disease, the technology still faces significant challenges. Therefore animal models are still irreplaceable at this stage. Currently, in vivo models of liver fibrosis can be classified into five categories based on etiology: chemical, dietary, surgical, transgenic, and immune. There is a wide variety of animal models of liver fibrosis with varying efficacy, which have different implications for proper understanding of the disease and effective screening of therapeutic agents. There is no high-quality literature recommending the most appropriate animal models. In this paper, we will describe the progress of commonly used animal models of liver fibrosis in terms of their development mechanisms, applications, advantages and disadvantages, and recommend appropriate animal models for different research purposes.

Prospect of Animal Models for Acute-on-chronic Liver Failure: A Mini-review

Acute-on-chronic liver failure (ACLF) is a clinical syndrome that develops in patients with chronic liver diseases following a precipitating event and associated with a high mortality rate due to systemic multiorgan failure. Establishing a suitable and stable animal model to precisely elucidate the molecular basis of ACLF pathogenesis is essential for the development of effective early diagnostic and treatment strategies. In this context, this article provides a concise and inclusive review of breakthroughs in ACLF animal model development.

Animal models applied to acute-on-chronic liver failure: Are new models required to understand the human condition?

The liver is a multifaceted organ; its location and detoxifying function expose this organ to countless injuries. Acute-on-chronic failure liver (ACLF) is a severe syndrome that affects the liver due to acute decompensation in patients with chronic liver disease. An infection environment, ascites, increased liver enzymes and prothrombin time, encephalopathy and fast-evolving multiorgan failure, leading to death, usually accompany this. The pathophysiology remains poorly understand. In this context, animal models become a very useful tool in this regard, as understanding; the disease may be helpful in developing novel therapeutic methodologies for ACLF. However, although animal models display several similarities to the human condition, they do not represent all ACLF manifestations, resulting in significant challenges. An initial liver cirrhosis framework followed by the induction of an acute decompensation by administering lipopolysaccharide and D-GaIN, potentiating liver damage supports the methodologies applied to induce experimental ACLF. The entire methodology has been described mostly for rats. Nevertheless, a quick PubMed database search indicates about 30 studies concerning ACFL models and over 1000 regarding acute liver failure models. These findings demonstrate the clear need to establish easily reproducible ACFL models to elucidate questions about this quickly established and often fatal syndrome.

Animal models applied to acute-on-chronic liver failure: Are new models required to understand the human condition?

The liver is a multifaceted organ; its location and detoxifying function expose this organ to countless injuries. Acute-on-chronic failure liver (ACLF) is a severe syndrome that affects the liver due to acute decompensation in patients with chronic liver disease. An infection environment, ascites, increased liver enzymes and prothrombin time, encephalopathy and fast-evolving multiorgan failure, leading to death, usually accompany this. The pathophysiology remains poorly understand. In this context, animal models become a very useful tool in this regard, as understanding; the disease may be helpful in developing novel therapeutic methodologies for ACLF. However, although animal models display several similarities to the human condition, they do not represent all ACLF manifestations, resulting in significant challenges. An initial liver cirrhosis framework followed by the induction of an acute decompensation by administering lipopolysaccharide and D-GaIN, potentiating liver damage supports the methodologies applied to induce experimental ACLF. The entire methodology has been described mostly for rats. Nevertheless, a quick PubMed database search indicates about 30 studies concerning ACFL models and over 1000 regarding acute liver failure models. These findings demonstrate the clear need to establish easily reproducible ACFL models to elucidate questions about this quickly established and often fatal syndrome.

Dual therapy with zinc acetate and rifaximin prevents from ethanol-induced liver fibrosis by maintaining intestinal barrier integrity

BACKGROUND

Hepatic overload of gut-derived lipopolysaccharide dictates the progression of alcoholic liver disease (ALD) by inducing oxidative stress and activating Kupffer cells and hepatic stellate cells through toll-like receptor 4 signaling. Therefore, targeting the maintenance of intestinal barrier integrity has attracted attention for the treatment of ALD. Zinc acetate and rifaximin, which is a nonabsorbable antibiotic, had been clinically used for patients with cirrhosis, particularly those with hepatic encephalopathy, and had been known to improve intestinal barrier dysfunction. However, only few studies focused on their efficacies in preventing the ALD-related fibrosis development.

AIM

To investigate the effects of a combined zinc acetate with rifaximin on liver fibrosis in a mouse ALD model.

METHODS

To induce ALD-related liver fibrosis, female C57BL/6J mice were fed a 2.5% (v/v) ethanol-containing Lieber-DeCarli liquid diet and received intraperitoneal carbon tetrachloride (CCl₄) injection twice weekly (1 mL/kg) for 8 wk. Zinc acetate (100 mg/L) and/or rifaximin (100 mg/L) were orally administered during experimental period. Hepatic steatosis, inflammation and fibrosis as well as intestinal barrier function were evaluated by histological and molecular analyses. Moreover, the direct effects of both agents on Caco-2 barrier function were assessed by in vitro assays.

RESULTS

In the ethanol plus CCl₄-treated mice, combination of zinc acetate and rifaximin attenuated oxidative lipid peroxidation with downregulation of Nox2 and Nox4. This combination significantly inhibited the Kupffer cells expansion and the proinflammatory response with blunted hepatic exposure of lipopolysaccharide and the toll-like receptor 4/nuclear factor kB pathway. Consequently, liver fibrosis and hepatic stellate cells activation were efficiently suppressed with downregulation of Mmp-2, -9, -13, and Timp1. Both agents improved the atrophic changes and permeability in the ileum, with restoration of tight junction proteins (TJPs) by decreasing the expressions of tumor necrosis factor α and myosin light chain kinase. In the in vitro assay, both agents directly reinforced ethanol or lipopolysaccharide-stimulated paracellular permeability and upregulated TJPs in Caco-2 cells.

CONCLUSION

Dual therapy with zinc acetate and rifaximin may serve as a strategy to prevent ALD-related fibrosis by maintaining intestinal barrier integrity.

Transcriptomic Cross-Species Analysis of Chronic Liver Disease Reveals Consistent Regulation Between Humans and Mice

Mouse models are frequently used to study chronic liver diseases (CLDs). To assess their translational relevance, we quantified the similarity of commonly used mouse models to human CLDs based on transcriptome data. Gene‐expression data from 372 patients were compared with data from acute and chronic mouse models consisting of 227 mice, and additionally to nine published gene sets of chronic mouse models. Genes consistently altered in humans and mice were mapped to liver cell types based on single‐cell RNA‐sequencing data and validated by immunostaining. Considering the top differentially expressed genes, the similarity between humans and mice varied among the mouse models and depended on the period of damage induction. The highest recall (0.4) and precision (0.33) were observed for the model with 12‐months damage induction by CCl₄ and by a Western diet, respectively. Genes consistently up‐regulated between the chronic CCl₄ model and human CLDs were enriched in inflammatory and developmental processes, and mostly mapped to cholangiocytes, macrophages, and endothelial and mesenchymal cells. Down‐regulated genes were enriched in metabolic processes and mapped to hepatocytes. Immunostaining confirmed the regulation of selected genes and their cell type specificity. Genes that were up‐regulated in both acute and chronic models showed higher recall and precision with respect to human CLDs than exclusively acute or chronic genes. Conclusion: Similarly regulated genes in human and mouse CLDs were identified. Despite major interspecies differences, mouse models detected 40% of the genes significantly altered in human CLD. The translational relevance of individual genes can be assessed at https://saezlab.shinyapps.io/liverdiseaseatlas/.

A Novel Mouse Model of Acute-on-Chronic Cholestatic Alcoholic Liver Disease: A Systems Biology Comparison With Human Alcoholic Hepatitis

BACKGROUND

Alcohol-related liver disease is the main cause of liver-related mortality worldwide. The development of novel targeted therapies for patients with advanced forms (i.e., alcoholic hepatitis, AH) is hampered by the lack of suitable animal models. Here, we developed a novel mouse model of acute-on-chronic alcohol liver injury with cholestasis and fibrosis and performed an extensive molecular comparative analysis with human AH.

METHODS

For the mouse model of acute-on-chronic liver injury, we used 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC, 0.05% w/w) diet for 8 weeks to establish cholestatic liver fibrosis. After 1-week washout period, male mice were fed intragastrically for 4 weeks with up to 24 g/kg of ethyl alcohol in a high-fat diet. This animal model was phenotyped using histopathology, clinical chemistry, microbiome, and gene expression approaches. Data were compared to the phenotypes of human alcohol-related liver disease, including AH.

RESULTS

Mice with cholestatic liver fibrosis and subsequent alcohol exposure (DDC + EtOH) exhibited exacerbated liver fibrosis with a pericellular pattern, increased neutrophil infiltration, and ductular proliferation, all characteristics of human AH. DDC administration had no effect on urine alcohol concentration or liver steatosis. Importantly, DDC- and alcohol-treated mice showed a transcriptomic signature that resembled that of patients with AH. Finally, we show that mice in the DDC + EtOH group had an increased gut barrier dysfunction, mimicking an important pathophysiological mechanism of human AH.

CONCLUSIONS

We developed a novel mouse model of acute-on-chronic cholestatic alcoholic liver injury that has considerable translational potential and can be used to test novel therapeutic modalities for AH.

Defective HNF4alpha-dependent gene expression as a driver of hepatocellular failure in alcoholic hepatitis

Alcoholic hepatitis (AH) is a life-threatening condition characterized by profound hepatocellular dysfunction for which targeted treatments are urgently needed. Identification of molecular drivers is hampered by the lack of suitable animal models. By performing RNA sequencing in livers from patients with different phenotypes of alcohol-related liver disease (ALD), we show that development of AH is characterized by defective activity of liver-enriched transcription factors (LETFs). TGFβ1 is a key upstream transcriptome regulator in AH and induces the use of HNF4α P2 promoter in hepatocytes, which results in defective metabolic and synthetic functions. Gene polymorphisms in LETFs including HNF4α are not associated with the development of AH. In contrast, epigenetic studies show that AH livers have profound changes in DNA methylation state and chromatin remodeling, affecting HNF4α-dependent gene expression. We conclude that targeting TGFβ1 and epigenetic drivers that modulate HNF4α-dependent gene expression could be beneficial to improve hepatocellular function in patients with AH.