Arginine Methylation of Integrin Alpha-4 Prevents Fibrosis Development in Alcohol-Associated Liver Disease

Discovery of novel ancestry specific genes for androgens and hypogonadism in Million Veteran Program Men

Given the various roles of testosterone in men's health, we conducted a multi-ancestral genetic analysis of total testosterone, free testosterone, SHBG, and hypogonadism in men within the Million Veteran Program (MVP). Here we identified 157 significant testosterone genetic variants, of which 8 have significant ancestry-specific associations. These variants implicate several genes, including SERPINF2, PRPF8, BAIAP2L1, SHBG, PRMT6, and PPIF, related to liver function. Genetic regulators of testosterone have cell type-specific effects in the testes, liver, and adrenal gland and are associated with disease risk. We conducted a meta-analysis amongst ancestry groups to identify 188 variants significantly associated with testosterone, of which 22 are novel associations. We constructed genetic scores for total testosterone, SHBG levels, and hypogonadism and find that men with higher testosterone genetic scores have lower odds of diabetes, hyperlipidemia, gout, and cardiac disorders. These findings provide insight into androgen regulation and identify novel variants for disease risk stratification.

Continuous Activation of C/EBPβ Transcription Factor Prevents Fibrosis Resolution After Alcohol Cessation

BACKGROUND & AIMS

Abstinence is an important therapeutic intervention for patients with alcohol-associated liver disease (ALD). However, fibrosis improvement after cessation is not uniform and some patients do not improve.

METHODS

Mice were fed high-fat diet with 20% alcohol in the drinking water for 20 weeks (ALD) followed by 4 weeks of chow diet with plain water (resolution). scATAC-seq dataset was analyzed using Signac R package. Cebpb floxed mice received AAV-TBG-Cre or AAV-control at the time of alcohol cessation. Hepatocyte-macrophage and endothelial cell-hepatocytes crosstalk was investigated using a Transwell coculture system. To test the role of angiopoietin mice were treated with recombinant angiopoietin-1, 1 week after alcohol cessation.

RESULTS

We analyzed differentially accessible regions in hepatocytes from control, ALD, or 4 weeks post alcohol cessation mice and identified transcription factors activated in ALD that remained activated after alcohol withdrawal. The top hit was CCAAT enhancer binding protein beta (C/EBPβ). We found that hepatocyte-specific Cebpb knockout at the time of alcohol cessation promoted fibrosis resolution. The resolution was mediated by altered hepatocyte-macrophage crosstalk. C/EBPβ suppressed the expression of CYP3A family of enzymes in hepatocytes and downstream macrophage collagen degradation ability. Cebpb knockout in hepatocytes promoted a proresolving phenotype in liver macrophages. We further identified upstream events leading to persistent C/EBPβ activation. C/EBPβ was induced by alcohol-mediated endothelial changes during ALD development and resolution. Restoring endothelial cell function with angiopoietin-1 supplementation reduced C/EBPβ and promoted fibrosis resolution.

CONCLUSIONS

Taken together, alcohol-induced C/EBPβ activation is a key driver of poor disease resolution in ALD and a promising target for patients who fail to recover after alcohol abstinence.

Role of integrin α4 in the inhibition of fibrosis in activated hepatic stellate cells by Periplaneta americana extract

This study aims to investigate the role of integrin α4 (ITGA4) in the inhibition of hepatic stellate cells (HSCs) fibrosis by Periplaneta americana extract (PAE), as well as to explore its molecular mechanisms. In vitro experiments utilized TGFβ-induced LX2 and HSC-T6 cells to examine the anti-fibrotic effects of PAE, particularly through ITGA4 overexpression, to elucidate its involvement in PAE-mediated inhibition via the PI3K-AKT signaling pathway. Cell viability was assessed using the CCK-8 method, and the IC50 for PAE was determined through statistical analysis. We evaluated cell proliferation using scratch and EDU assays, and migration capabilities using Transwell assays. Molecular mechanisms were investigated through western blot (WB), quantitative PCR (QPCR), and transcriptome analysis. Results indicate that PAE reduces hepatic fibrosis by curbing hepatic stellate cells (HSCs) proliferation, migration, collagen synthesis, inflammatory cytokine production, and epithelial-mesenchymal transition (EMT). Additionally, while PAE suppressed ITGA4's high expression in activated HSCs, ITGA4 overexpression counteracted PAE's effects on HSC proliferation, migration, and collagen synthesis. These findings demonstrate that PAE primarily mitigates fibrosis in activated HSCs by inhibiting ITGA4, thus delivering anti-fibrotic effects in the liver.

Kupffer cell diversity maintains liver function in alcohol-associated liver disease

BACKGROUND AND AIMS

Liver macrophages are heterogeneous and play an important role in alcohol-associated liver disease (ALD) but there is limited understanding of the functions of specific macrophage subsets in the disease. We used a Western diet alcohol (WDA) mouse model of ALD to examine the hepatic myeloid cell compartment by single cell RNAseq and targeted KC ablation to understand the diversity and function of liver macrophages in ALD.

APPROACH AND RESULTS

In the WDA liver, KCs and infiltrating monocytes/macrophages each represented about 50% of the myeloid pool. Five major KC clusters all expressed genes associated with receptor-mediated endocytosis and lipid metabolism, but most were predicted to be noninflammatory and antifibrotic with 1 minor KC cluster having a proinflammatory and extracellular matrix degradation gene signature. Infiltrating monocyte/macrophage clusters, in contrast, were predicted to be proinflammatory and profibrotic. In vivo, diphtheria toxin-based selective KC ablation during alcohol exposure resulted in a liver failure phenotype with increases in PT/INR and bilirubin, loss of differentiated hepatocyte gene expression, and an increase in expression of hepatocyte progenitor markers such as EpCAM, CK7, and Igf2bp3. Gene set enrichment analysis of whole-liver RNAseq from the KC-ablated WDA mice showed a similar pattern as seen in human alcoholic hepatitis.

CONCLUSIONS

In this ALD model, KCs are anti-inflammatory and are critical for the maintenance of hepatocyte differentiation. Infiltrating monocytes/macrophages are largely proinflammatory and contribute more to liver fibrosis. Future targeting of specific macrophage subsets may provide new approaches to the treatment of liver failure and fibrosis in ALD.

Alcohol-related liver disease (ALD): current perspectives on pathogenesis, therapeutic strategies, and animal models

Alcohol-related liver disease (ALD) is a major cause of morbidity and mortality worldwide. It encompasses conditions such as fatty liver, alcoholic hepatitis, chronic hepatitis with liver fibrosis or cirrhosis, and hepatocellular carcinoma. Numerous recent studies have demonstrated the critical role of oxidative stress, abnormal lipid metabolism, endoplasmic reticulum stress, various forms of cell death (including apoptosis, necroptosis, and ferroptosis), intestinal microbiota dysbiosis, liver immune response, cell autophagy, and epigenetic abnormalities in the pathogenesis of ALD. Currently, abstinence, corticosteroids, and nutritional therapy are the traditional therapeutic interventions for ALD. Emerging therapies for ALD mainly include the blockade of inflammatory pathways, the promotion of liver regeneration, and the restoration of normal microbiota. Summarizing the advances in animal models of ALD will facilitate a more systematic investigation of the pathogenesis of ALD and the exploration of therapeutic targets. This review summarizes the latest insight into the pathogenesis and molecular mechanisms of ALD, as well as the pros and cons of ALD rodent models, providing a basis for further research on therapeutic strategies for ALD.

Anoikis in cell fate, physiopathology, and therapeutic interventions

The extracellular matrix (ECM) governs a wide spectrum of cellular fate processes, with a particular emphasis on anoikis, an integrin-dependent form of cell death. Currently, anoikis is defined as an intrinsic apoptosis. In contrast to traditional apoptosis and necroptosis, integrin correlates ECM signaling with intracellular signaling cascades, describing the full process of anoikis. However, anoikis is frequently overlooked in physiological and pathological processes as well as traditional in vitro research models. In this review, we summarized the role of anoikis in physiological and pathological processes, spanning embryonic development, organ development, tissue repair, inflammatory responses, cardiovascular diseases, tumor metastasis, and so on. Similarly, in the realm of stem cell research focused on the functional evolution of cells, anoikis offers a potential solution to various challenges, including in vitro cell culture models, stem cell therapy, cell transplantation, and engineering applications, which are largely based on the regulation of cell fate by anoikis. More importantly, the regulatory mechanisms of anoikis based on molecular processes and ECM signaling will provide new strategies for therapeutic interventions (drug therapy and cell-based therapy) in disease. In summary, this review provides a systematic elaboration of anoikis, thus shedding light on its future research.

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.

Sepsis-induced endothelial dysfunction drives acute-on-chronic liver failure through Angiopoietin-2-HGF-C/EBPβ pathway

BACKGROUND AND AIMS

Acute-on-chronic liver failure (ACLF) is an acute liver and multisystem failure in patients with previously stable cirrhosis. A common cause of ACLF is sepsis secondary to bacterial infection. Sepsis-associated ACLF involves a loss of differentiated liver function in the absence of direct liver injury, and its mechanism is unknown. We aimed to study the mechanism of sepsis-associated ACLF using a novel mouse model.

APPROACH AND RESULTS

Sepsis-associated ACLF was induced by cecal ligation and puncture procedure (CLP) in mice treated with thioacetamide (TAA). The combination of TAA and CLP resulted in a significant decrease in liver synthetic function and high mortality. These changes were associated with reduced metabolic gene expression and increased CCAAT enhancer binding protein beta (C/EBPβ) transcriptional activity. We found that C/EBPβ binding to its target gene promoters was increased. In humans, C/EBPβ chromatin binding was similarly increased in the ACLF group compared with control cirrhosis. Hepatocyte-specific Cebpb knockout mice had reduced mortality and increased gene expression of hepatocyte differentiation markers in TAA/CLP mice, suggesting that C/EBPβ promotes liver failure in these mice. C/EBPβ activation was associated with endothelial dysfunction, characterized by reduced Angiopoietin-1/Angiopoietin-2 ratio and increased endothelial production of HGF. Angiopoietin-1 supplementation or Hgf knockdown reduced hepatocyte C/EBPβ accumulation, restored liver function, and reduced mortality, suggesting that endothelial dysfunction induced by sepsis drives ACLF through HGF-C/EBPβ pathway.

CONCLUSIONS

The transcription factor C/EBPβ is activated in both mouse and human ACLF and is a potential therapeutic target to prevent liver failure in patients with sepsis and cirrhosis.

Integrative Evaluation of the Clinical Significance Underlying Protein Arginine Methyltransferases in Hepatocellular Carcinoma

HCC is a major contributor to cancer-related mortality worldwide. Curative treatments are available for a minority of patients diagnosed at early stages; however, only a few multikinase inhibitors are available and are marginally effective in advanced cases, highlighting the need for novel therapeutic targets. One potential target is the protein arginine methyltransferase, which catalyzes various forms of arginine methylation and is often overexpressed in various cancers. However, the diverse expression patterns and clinical values of PRMTs in HCC remain unclear. In the present study, we evaluated the transcriptional expression of PRMTs in HCC cohorts using publicly available datasets. Our results revealed a significant association between PRMTs and prognosis in HCC patients with diverse clinical characteristics and backgrounds. This highlights the promising potential of PRMTs as prognostic biomarkers in patients with HCC. In particular, single-cell RNA (scRNA) sequencing analysis coupled with another human cohort study highlighted the pivotal role of PRMT1 in HCC progression, particularly in the context of Tex. Translating these findings into specific therapeutic decisions may address the unmet therapeutic needs of patients with HCC.

Establishment of repeated liver biopsy technique in experimental mice

Biopsy is a commonly used method for determining pathological diagnoses by directly using human tissues and cells. Biopsies are widely used to determine disease progression and treatment efficacy. Although organs and tissues are usually obtained by sacrifice during animal experiments, it is theoretically possible to use the same biopsy techniques in humans. In the present study, we examined the feasibility of performing four repeated liver biopsies in a spontaneous metabolic syndrome mouse model. Even though a small number of mice died accidently, most mice were able to undergo four liver biopsies without significant adverse events. We also performed three liver biopsies in mouse liver tumor carcinogen models at 4, 8, and 12 weeks of age. In addition to the sample collected at 16 weeks of age during sacrifice, we successfully collected four liver samples from the same mice at different stages of disease progression. The application of this liver biopsy technique might make it possible for direct evaluation of pathological conditions in the same individual over time, thereby reducing the number of experimental animals.