Male-Specific Activation of Lysine Demethylases 5B and 5C Mediates Alcohol-Induced Liver Injury and Hepatocyte Dedifferentiation

Protective role of 17β-estradiol in alcohol-associated liver fibrosis is mediated by suppression of integrin signaling

BACKGROUND

Alcohol-associated liver disease is a complex disease regulated by genetic and environmental factors such as diet and sex. The combination of high-fat diet and alcohol consumption has synergistic effects on liver disease progression. Female sex hormones are known to protect females from liver disease induced by high-fat diet. In contrast, they promote alcohol-mediated liver injury. We aimed to define the role of female sex hormones on liver disease induced by a combination of high-fat diet and alcohol.

METHODS

Wild-type and protein arginine methyltransferase (Prmt)6 knockout female mice were subjected to gonadectomy (ovariectomy, OVX) or sham surgeries and then fed western diet and alcohol in the drinking water.

RESULTS

We found that female sex hormones protected mice from western diet/alcohol-induced weight gain, liver steatosis, injury, and fibrosis. Our data suggest that these changes are, in part, mediated by estrogen-mediated induction of arginine methyltransferase PRMT6. Liver proteome changes induced by OVX strongly correlated with changes induced by Prmt6 knockout. Using Prmt6 knockout mice, we confirmed that OVX-mediated weight gain, steatosis, and injury are PRMT6 dependent, while OVX-induced liver fibrosis is PRMT6 independent. Proteomic and gene expression analyses revealed that estrogen signaling suppressed the expression of several components of the integrin pathway, thus reducing integrin-mediated proinflammatory (Tnf, Il6) and profibrotic (Tgfb1, Col1a1) gene expression independent of PRMT6 levels. Integrin signaling inhibition using Arg-Gly-Asp peptides reduced proinflammatory and profibrotic gene expression in mice, suggesting that integrin suppression by estrogen is protective against fibrosis development.

CONCLUSIONS

Taken together, estrogen signaling protects mice from liver disease induced by a combination of alcohol and high-fat diet through upregulation of Prmt6 and suppression of integrin signaling.

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.

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.

MYC in liver cancer: mechanisms and targeted therapy opportunities

MYC, a major oncogenic transcription factor, regulates target genes involved in various pathways such as cell proliferation, metabolism and immune evasion, playing a critical role in the tumor initiation and development in multiple types of cancer. In liver cancer, MYC and its signaling pathways undergo significant changes, exerting a profound impact on liver cancer progression, including tumor proliferation, metastasis, dedifferentiation, metabolism, immune microenvironment, and resistance to comprehensive therapies. This makes MYC an appealing target, despite it being previously considered an undruggable protein. In this review, we discuss the role and mechanisms of MYC in liver physiology, chronic liver diseases, hepatocarcinogenesis, and liver cancer progression, providing a theoretical basis for targeting MYC as an ideal therapeutic target for liver cancer. We also summarize and prospect the strategies for targeting MYC, including direct and indirect approaches to abolish the oncogenic function of MYC in liver cancer.

Single ethanol binge causes severe liver injury in mice fed Western diet

BACKGROUND AND AIMS

Alcohol-associated liver disease (ALD) and NAFLD often coexist in Western societies that consume energy-rich and cholesterol-containing Western diets. Increased rates of ALD mortality in young people in these societies are likely attributable to binge drinking. It is largely unknown how alcohol binge causes liver damage in the setting of Western diets.

APPROACH AND RESULTS

In this study, we showed that a single ethanol binge (5 g/kg body weight) induced severe liver injury as shown by marked increases in serum activities of the 2 aminotransferases AST and ALT in C57BL/6J mice that have been fed a Western diet for 3 weeks. The Western diet plus binge ethanol-fed mice also displayed severe lipid droplet deposition and high contents of triglycerides and cholesterol in the liver, which were associated with increased lipogenic and reduced fatty acid oxidative gene expression. These animals had the highest Cxcl1 mRNA expression and myeloperoxidase (MPO)-positive neutrophils in the liver. Their hepatic ROS and lipid peroxidation were the highest, but their hepatic levels of mitochondrial oxidative phosphorylation proteins remained largely unaltered. Hepatic levels of several ER stress markers, including mRNAs for CHOP, ERO1A, ERO1B, BIM, and BIP, as well as Xbp1 splicing and proteins for BIP/GRP78 and IRE-α were also the highest in these animals. Interestingly, Western diet feeding for 3 weeks or ethanol binge dramatically increased hepatic caspase 3 cleavage, and the combination of the 2 did not further increase it. Thus, we successfully established a murine model of acute liver injury by mimicking human diets and binge drinking.

CONCLUSIONS

This simple Western diet plus single ethanol binge model recapitulates major hepatic phenotypes of ALD, including steatosis and steatohepatitis characterized by neutrophil infiltration, oxidative stress, and ER stress.

Loss of Mettl3 enhances liver tumorigenesis by inducing hepatocyte dedifferentiation and hyperproliferation

While a few works have shown that Mettl3 plays oncogenic roles in hepatocellular carcinoma (HCC), its function in early HCC tumorigenesis remains unclear. In Mettl3^flox/flox; Alb-Cre knockout mice, Mettl3 loss leads to aberrant hepatocyte homeostasis and liver damage. Importantly, Mettl3 deletion dramatically accelerates liver tumorigenesis in various HCC mouse models. Depletion of Mettl3 in adult Mettl3^flox/flox mice through TBG-Cre administration also enhances liver tumor development, while overexpression of Mettl3 inhibits hepatocarcinogenesis. Mechanistically, aggravated tumorigenesis upon Mettl3 deletion is a consequence of hepatocyte dedifferentiation and hyperproliferation via m⁶A-mediated modulation on Hnf4α and cell cycle genes. In contrast, by using Mettl3^flox/flox; Ubc-Cre mice, depletion of Mettl3 in established HCC ameliorates tumor progression. Additionally, Mettl3 is overexpressed in HCC tumors compared with adjacent non-tumor tissues. The present findings define a tumor-suppressive role of Mettl3 in liver tumorigenesis, indicating its potentially opposite stage-dependent functions in HCC initiation versus progression.

KDM5 Family Demethylase Inhibitor KDOAM-25 Reduces Entry of SARS-CoV-2 Pseudotyped Viral Particles into Cells

We studied the effect of KDM5 family demethylase inhibitors (JIB-04, PBIT, and KDOAM-25) on the penetration of SARS-CoV-2 pseudotyped viruses into differentiated Caco-2 cells and HEK293T cells with ACE2 hyperexpression. The above drugs were not cytotoxic. Only KDOAM-25 significantly reduced virus entry into the cells. The expression of ACE2 mRNA in Caco-2 significantly increased, while TMPRSS2 expression did not significantly change under these conditions. In differentiated Caco-2 cells, KDOAM-25 did not affect the expression of BRCA1, CDH1, TP53, SNAI1, VIM, and UGCG genes, for which an association with knockdown or overexpression of KDM5 demethylases or with the action of demethylase inhibitors had previously been shown. In undifferentiated Caco-2 cells, the expression of BRCA1, SNAI1, VIM, and CDH1 was significantly increased under the action of KDOAM-25.

Histone Demethylation Profiles in Nonalcoholic Fatty Liver Disease and Prognostic Values in Hepatocellular Carcinoma: A Bioinformatic Analysis

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease with multifactorial pathogenesis; histone demethylases (HDMs) are emerging as attractive targets. We identified HDM genes (including KDM5C, KDM6B, KDM8, KDM4A, and JMJD7) that were differentially expressed in NAFLD and normal samples by exploring gene expression profiling datasets. There was no significant difference in the expression of genes related to histone demethylation between mild and advanced NAFLD. In vitro and in vivo studies indicated that KDM6B and JMJD7 were upregulated at the mRNA level in NAFLD. We explored the expression levels and prognostic values of the identified HDM genes in hepatocellular carcinoma (HCC). KDM5C and KDM4A were upregulated in HCC compared to normal tissue, while KDM8 showed downregulation. The abnormal expression levels of these HDMs could provide prognostic values. Furthermore, KDM5C and KDM4A were associated with immune cell infiltration in HCC. HDMs were associated with cellular and metabolic processes and may be involved in the regulation of gene expression. Differentially expressed HDM genes identified in NAFLD may provide value to understanding pathogenesis and in the development of epigenetic therapeutic targets. However, on the basis of the inconsistent results of in vitro studies, future in vivo experiments combined with transcriptomic analysis are needed for further validation.

Single-Cell RNA Transcriptome Profiling of Liver Cells of Short-Term Alcoholic Liver Injury in Mice

Alcoholic liver disease (ALD) is currently considered a global healthcare problem with limited pharmacological treatment options. There are abundant cell types in the liver, such as hepatocytes, endothelial cells, Kupffer cells and so on, but little is known about which kind of liver cells play the most important role in the process of ALD. To obtain a cellular resolution of alcoholic liver injury pathogenesis, 51,619 liver single-cell transcriptomes (scRNA-seq) with different alcohol consumption durations were investigated, 12 liver cell types were identified, and the cellular and molecular mechanisms of the alcoholic liver injury were revealed. We found that more aberrantly differential expressed genes (DEGs) were present in hepatocytes, endothelial cells, and Kupffer cells than in other cell types in alcoholic treatment mice. Alcohol promoted the pathological processes of liver injury; the specific mechanisms involved: lipid metabolism, oxidative stress, hypoxia, complementation and anticoagulation, and hepatocyte energy metabolism on hepatocytes; NO production, immune regulation, epithelial and cell migration on endothelial cells; antigen presentation and energy metabolism on Kupffer cells, based on the GO analysis. In addition, our results showed that some transcription factors (TFs) are activated in alcohol-treated mice. In conclusion, our study improves the understanding of liver cell heterogeneity in alcohol-fed mice at the single-cell level. It has potential value for understanding key molecular mechanisms and improving current prevention and treatment strategies for short-term alcoholic liver injury.

A Pathogenic Role of Non-Parenchymal Liver Cells in Alcohol-Associated Liver Disease of Infectious and Non-Infectious Origin

Now, much is known regarding the impact of chronic and heavy alcohol consumption on the disruption of physiological liver functions and the induction of structural distortions in the hepatic tissues in alcohol-associated liver disease (ALD). This review deliberates the effects of alcohol on the activity and properties of liver non-parenchymal cells (NPCs), which are either residential or infiltrated into the liver from the general circulation. NPCs play a pivotal role in the regulation of organ inflammation and fibrosis, both in the context of hepatotropic infections and in non-infectious settings. Here, we overview how NPC functions in ALD are regulated by second hits, such as gender and the exposure to bacterial or viral infections. As an example of the virus-mediated trigger of liver injury, we focused on HIV infections potentiated by alcohol exposure, since this combination was only limitedly studied in relation to the role of hepatic stellate cells (HSCs) in the development of liver fibrosis. The review specifically focusses on liver macrophages, HSC, and T-lymphocytes and their regulation of ALD pathogenesis and outcomes. It also illustrates the activation of NPCs by the engulfment of apoptotic bodies, a frequent event observed when hepatocytes are exposed to ethanol metabolites and infections. As an example of such a double-hit-induced apoptotic hepatocyte death, we deliberate on the hepatotoxic accumulation of HIV proteins, which in combination with ethanol metabolites, causes intensive hepatic cell death and pro-fibrotic activation of HSCs engulfing these HIV- and malondialdehyde-expressing apoptotic hepatocytes.

Alcohol-associated fibrosis in females is mediated by female-specific activation of lysine demethylases KDM5B and KDM5C

Alcohol-associated liver disease is a major cause of alcohol-related mortality. However, the mechanisms underlying disease progression are not fully understood. Recently we found that liver molecular pathways are altered by alcohol consumption differently in males and females. We were able to associate these sex-specific pathways with two upstream regulators: H3K4-specific demethylase enzymes KDM5B and KDM5C. Mice were fed the Lieber-DeCarli alcohol liquid diet for 3 weeks or a combination of a high-fat diet with alcohol in water for 16 weeks (western diet alcohol model [WDA] model). To assess the role of histone demethylases, mice were treated with AAV-shControl, AAV-shKdm5b, and/or AAV-shKdm5c and/or AAV-shAhR vectors. Gene expression and epigenetic changes after Kdm5b/5c knockdown were assessed by RNA-sequencing and H3K4me3 chromatin immunoprecipitation analysis. We found that less than 5% of genes affected by Kdm5b/Kdm5c knockdown were common between males and females. In females, Kdm5b/Kdm5c knockdown prevented fibrosis development in mice fed the WDA alcohol diet for 16 weeks and decreased fibrosis-associated gene expression in mice fed the Lieber-DeCarli alcohol liquid diet. In contrast, fibrosis was not affected by Kdm5b/Kdm5c knockdown in males. We found that KDM5B and KDM5C promote fibrosis in females through down-regulation of the aryl hydrocarbon receptor (AhR) pathway components in hepatic stellate cells. Kdm5b/Kdm5c knockdown resulted in an up-regulation of Ahr, Arnt, and Aip in female but not in male mice, thus preventing fibrosis development. Ahr knockdown in combination with Kdm5b/Kdm5c knockdown restored profibrotic gene expression. Conclusion: KDM5 demethylases contribute to differences between males and females in the alcohol response in the liver. The KDM5/AhR axis is a female-specific mechanism of fibrosis development in alcohol-fed mice.