Hepatocytes in liver injury: Victim, bystander, or accomplice in progressive fibrosis?

Role of mitogens in normal and pathological liver regeneration

The liver has a unique ability to regenerate to meet the body's metabolic needs, even following acute or chronic injuries. The cellular and molecular mechanisms underlying normal liver regeneration have been well investigated to improve organ transplantation outcomes. Once liver regeneration is impaired, pathological regeneration occurs, and the underlying cellular and molecular mechanisms require further investigations. Nevertheless, a plethora of cytokines and growth factor-mediated pathways have been reported to modulate physiological and pathological liver regeneration. Regenerative mitogens play an essential role in hepatocyte proliferation. Accelerator mitogens in synergism with regenerative ones promote liver regeneration following hepatectomy. Finally, terminator mitogens restore the proliferating status of hepatocytes to a differentiated and quiescent state upon completion of regeneration. Chronic loss of hepatocytes, which can manifest in chronic liver disorders of any etiology, often has undesired structural consequences, including fibrosis, cirrhosis, and liver neoplasia due to the unregulated proliferation of remaining hepatocytes. In fact, any impairment in the physiological function of the terminator mitogens results in the progression of pathological liver regeneration. In the current review, we intend to highlight the updated cellular and molecular mechanisms involved in liver regeneration and discuss the impairments in central regulating mechanisms responsible for pathological liver regeneration.

Human umbilical cord-derived mesenchymal stem cells attenuate liver fibrosis by inhibiting hepatocyte ferroptosis through mitochondrial transfer

Liver fibrosis is a reversible dynamic pathological process induced by chronic liver injury. Without intervention, liver fibrosis can progress to become cirrhosis, liver failure, or hepatocellular carcinoma, thus posing a high global health burden. Therefore, effective therapies for liver fibrosis are urgently required. Although transplantation of mesenchymal stem cells (MSCs) has significant value as a treatment strategy for liver damage, the underlying mechanisms remain unclear. Chronic liver injury progression is significantly influenced by hepatocyte ferroptosis, and targeting ferroptosis is emerging as a potential treatment strategy for liver fibrosis. Here, we showed that the infusion of human umbilical cord-derived MSCs (hUC-MSCs) alleviated TAA-induced liver fibrosis, improved liver functionality, and decreased ferroptosis in mice. hUC-MSCs inhibit ferroptosis-related mitochondrial damage and lipid peroxidation in AML12 cells in vitro. Mechanistically, under oxidative stress, hUC-MSCs transfer healthy mitochondria to damaged hepatocytes through tunneling nanotubes (TNTs). Cytochalasin D (CytoD), an inhibitor of TNT formation, abrogated the protective effects of hUC-MSCs against ferroptosis. This research emphasizes the ability of hUC-MSCs to serve as a promising treatment for liver fibrosis via mitochondrial transfer through TNTs.

Miniaturized Liver Disease Mimics to Gain Insights into MMP Expression during Disease Progression

Nonalcoholic fatty liver disease (NAFLD) encompasses a spectrum of liver conditions, ranging from hepatic steatosis to steatohepatitis, fibrosis, and severe outcomes such as cirrhosis or cancer. The progression from hepatic steatosis to fibrosis involves significant extracellular matrix (ECM) remodeling, characterized by increased collagen deposition and cross-linking of ECM proteins, causing increased tissue stiffness and altered MMP expression patterns. Dysregulated MMP expression and extracellular acidosis are key contributors to NAFLD progression. Unlike other MMPs, which may be relevant only at specific disease stages, MMP-9 serves as a universal marker, allowing for monitoring of its expression in relation to disease states and ECM parameters. Understanding dysregulated MMP-9 expression across different NAFLD stages can provide crucial insights into disease progression and serve as both a diagnostic and a prognostic biomarker, identifying potential therapeutic targets. This study introduces a three-dimensional (3D) collagen/alginate-based liver disease model designed to investigate how matrix collagen content, elasticity, and diseased cell conditions influence MMP expression and pH levels in situ using nanoprobes. The platform offered an understanding of the relationships between these factors and their role in NAFLD progression, offering valuable insights into disease progression and potential resolution. To examine how various physicochemical and biological factors, particularly MMP expression and collagen deposition, drive NAFLD progression, three 3D NAFLD models were developed, simulating healthy (HL), steatotic (SL), and fibrotic (FL) liver matrices. Additionally, the role of collagenase treatment in the FL matrix in enhancing MMP expression and potentially mitigating fibrosis was also explored. By employing dual-sensitive fluorescent nanoprobes to monitor real-time in situ changes in MMP-9 expression and pH levels, this platform offers a novel approach to understanding the in vitro roles of matrix stiffness, collagen deposition, and diseased cell conditions in NAFLD pathogenesis.

Unveiling the interplay between hepatocyte SATB1 and innate immunity in autoimmune hepatitis

BACKGROUND

Investigating the function of SATB1 in hepatocytes is essential for developing therapeutic strategies for autoimmune hepatitis (AIH). Although SATB1 has been extensively studied in immune cells, its specific activity in hepatocytes within the context of AIH remains unclear.

METHODS

SATB1 expression in AIH hepatocytes was assessed by qRT-PCR, Western blotting, flow cytometry, and immunohistochemistry. In vivo modulation used RNA interference viruses and overexpression plasmids. SATB1's proinflammatory effects were analyzed with protein microarray, immunohistochemistry, and flow cytometry. Chemotactic effects on RAW264.7 macrophages were tested in vitro, with mechanisms explored by dual-luciferase assays and CUT&RUN qPCR. Liver injury was evaluated by histopathology and serum biochemistry.

RESULTS

SATB1 was significantly upregulated in hepatocytes of AIH patients and models, showing a stronger increase in hepatocytes than in CD45+ cells, and positively correlated with liver injury severity. In vivo RNAi-mediated SATB1 inhibition reduced liver inflammation, while SATB1 overexpression aggravated AIH progression. Both interference and overexpression experiments confirmed that SATB1 promotes liver injury by facilitating the infiltration of proinflammatory (Ly6Chigh) macrophage. In vitro, supernatant from SATB1-overexpressing hepatocytes enriched chemokine signaling pathways, leading to increased CCL2 expression and release, which attracted macrophages and drove their proinflammatory polarization. Mechanistically, SATB1 promoted CCL2 transcription by binding to its DNA and recruiting p300/CBP.

CONCLUSIONS

This study reveals that SATB1 is upregulated in hepatocytes in AIH. Elevated SATB1 levels in liver cells contribute to autoimmune hepatitis by increasing CCL2 expression, promoting the recruitment of inflammatory monocyte-derived macrophage, and reshaping the composition of the liver immune microenvironment.

The paradigm of stem cell secretome in tissue repair and regeneration: Present and future perspectives

As the number of patients requiring organ transplants continues to rise exponentially, there is a dire need for therapeutics, with repair and regenerative properties, to assist in alleviating this medical crisis. Over the past decade, there has been a shift from conventional stem cell treatments towards the use of the secretome, the protein and factor secretions from cells. These components may possess novel druggable targets and hold the key to profoundly altering the field of regenerative medicine. Despite the progress in this field, clinical translation of secretome-containing products is limited by several challenges including but not limited to ensuring batch-to-batch consistency, the prevention of further heterogeneity, production of sufficient secretome quantities, product registration, good manufacturing practice protocols and the pharmacokinetic/pharmacodynamic profiles of all the components. Despite this, the secretome may hold the key to unlocking the regenerative blockage scientists have encountered for years. This review critically analyses the secretome derived from different cell sources and used in several tissues for tissue regeneration. Furthermore, it provides an overview of the current delivery strategies and the future perspectives for the secretome as a potential therapeutic. The success and possible shortcomings of the secretome are evaluated.

Developing an RNA Signature for Radiation Injury Using a Human Liver-on-a-Chip Model

Radiation exposure in a therapeutic setting or during a mass casualty event requires improved medical triaging, where the time to delivery and quantity of medical countermeasures are critical to survival. Radiation-induced liver injury (RILI) and fibrosis can lead to death, but clinical symptoms manifest late in disease pathogenesis and there is no simple diagnostic test to determine RILI. Because animal models do not completely recapitulate clinical symptoms, we used a human liver-on-a-chip model to identify biomarkers of RILI. The goals of this study were: 1. to establish a microfluidic liver-on-a-chip device as a physiologically relevant model for studying radiation-induced tissue damage; and 2. to determine acute changes in RNA expression and biological pathway regulation that identify potential biomarkers and mechanisms of RILI. To model functional human liver tissue, we used the Emulate organ-on-a-chip system to establish a co-culture of human liver sinusoidal endothelial cells (LSECs) and hepatocytes. The chips were subject to 0 Gy (sham), 1 Gy, 4 Gy, or 10 Gy irradiation and cells were collected at 6 h, 24 h, or 7 days postirradiation for RNA isolation. To identify significant expression changes in messenger RNA (mRNA) and long non-coding RNA (lncRNA), we performed RNA sequencing (RNASeq) to conduct whole transcriptome analysis. We found distinct differences in expression patterns by time, dose, and cell type, with higher doses of radiation resulting in the most pronounced expression changes, as anticipated. Ingenuity Pathway Analysis indicated significant inhibition of the cell viability pathway 24 h after 10 Gy exposure in LSECs but activation of this pathway in hepatocytes, highlighting differences between cell types despite receiving the same radiation dose. Overall, hepatocytes showed fewer gene expression changes in response to radiation, with only 3 statistically significant differentially expressed genes at 7 days: APOBEC3H, PTCHD4, and GDNF. We further highlight lncRNA of interest including DINO and PURPL in hepatocytes and TMPO-AS1 and PRC-AS1 in LSECs, identifying potential biomarkers of RILI. We demonstrated the potential utility of a human liver-on-a-chip model with primary cells to model organ-specific radiation injury, establishing a model for radiation medical countermeasure development and further biomarker validation. Furthermore, we identified biomarkers that differentiate radiation dose and defined cell-specific targets for potential radiation mitigation therapies.

Targeting chronic liver diseases: Molecular markers, drug delivery strategies and future perspectives

Chronic liver inflammation, a pervasive global health issue, results in millions of annual deaths due to its progression from fibrosis to the more severe forms of cirrhosis and hepatocellular carcinoma (HCC). This insidious condition stems from diverse factors such as obesity, genetic conditions, alcohol abuse, viral infections, autoimmune diseases, and toxic accumulation, manifesting as chronic liver diseases (CLDs) such as metabolic dysfunction-associated steatotic liver disease (MASLD), metabolic dysfunction-associated steatohepatitis (MASH), alcoholic liver disease (ALD), viral hepatitis, drug-induced liver injury, and autoimmune hepatitis. Late detection of CLDs necessitates effective treatments to inhibit and potentially reverse disease progression. However, current therapies exhibit limitations in consistency and safety. A potential breakthrough lies in nanoparticle-based drug delivery strategies, offering targeted delivery to specific liver cell types, such as hepatocytes, Kupffer cells, and hepatic stellate cells. This review explores molecular targets for CLD treatment, ongoing clinical trials, recent advances in nanoparticle-based drug delivery, and the future outlook of this research field. Early intervention is crucial for chronic liver disease. Having a comprehensive understanding of current treatments, molecular biomarkers and novel nanoparticle-based drug delivery strategies can have enormous impact in guiding future strategies for the prevention and treatment of CLDs.

3D microscaffolds with triple-marker sensitive nanoprobes for studying fatty liver disease in vitro

Non-alcoholic fatty liver disease (NAFLD) is a heterogeneous condition that encompasses a wide range of liver diseases that progresses from simple hepatic steatosis to the life-threatening state of cirrhosis. However, due to the heterogeneity of this disease, comprehensive analysis of several physicochemical and biological factors that drive its progression is necessary. Therefore, an in vitro platform is required that would enable real-time monitoring of these changes to better understand the progression of these diseases. The earliest stage of NAFLD, i.e. hepatic steatosis, is characterised by triglyceride accumulation in the form of lipid vacuoles in the cytosol of hepatocytes. This fatty acid accumulation is usually accompanied by hepatic inflammation, leading to tissue acidification and dysregulated expression of certain proteases such as matrix metalloproteinases (MMPs). Taking cues from the biological parameters of the disease, we report here a 3D in vitro GelMA/alginate microscaffold platform encapsulating a triple-marker (pH, MMP-3 and MMP-9) sensitive fluorescent nanoprobe for monitoring, and hence, distinguishing the fatty liver disease (hepatic steatosis) from healthy livers on the basis of pH change and MMP expression. The nanoprobe consists of a carbon nanoparticle (CNP) core, which exhibits intrinsic pH-dependent fluorescence properties, decorated either with an MMP-3 (NpMMP3) or MMP-9 (NpMMP9) sensitive peptide substrate. These peptide substrates are flanked with a fluorophore-quencher pair that separates on enzymatic cleavage, resulting in fluorescence emission. The cocktail of these nanoprobes generated multiple fluorescence signals corresponding to slightly acidic pH (blue) and overexpression of MMP-3 (green) and MMP-9 (red) enzymes in a 3D in vitro fatty liver model, whereas no/negligible fluorescence signals were observed in a healthy liver model. Moreover, this platform enabled us to mimic fatty liver disease in a more realistic manner. Therefore, this 3D in vitro platform encapsulating triple-marker sensitive fluorescent nanoprobes would facilitate the monitoring of the changes in pH and MMP expression, thereby enabling us to distinguish a healthy liver from a diseased liver and to study liver disease stages on the basis of these markers.

Dibutyl phthalate (DBP) promotes Epithelial-Mesenchymal Transition (EMT) to aggravate liver fibrosis into cirrhosis and portal hypertension (PHT) via ROS/TGF-β1/Snail-1 signalling pathway in adult rats

OBJECTIVE

The primary objective of this study was to investigate the toxicological impact of Dibutyl phthalate (DBP) on the process of liver fibrosis transitioning into cirrhosis and the subsequent development of portal hypertension (PHT) through the mechanism of epithelial-mesenchymal transition (EMT) mediated by the ROS/TGF-β/Snail-1 signaling pathway.

METHOD

Carbon tetrachloride (CCl4) (1 mg/kg) was introduced in adult rats by oral feeding in CCl4 and CCl4+DBP groups twice a week for 8 weeks, and twice for another 8 week in CCl4 group. DBP was introduced by oral feeding in the CCl4+DBP group twice over the following 8 weeks. We subsequently analyzed hemodynamics measurements and liver cirrhosis degree, hepatic inflammation and liver function in the different groups. EMT related genes expression in rats in the groups of Control, DBP, CCl4 and CCl4+DBP were measured by immunohistochemistry (IHC). Enzyme-linked immunosorbent Assay (ELISA), qRT-PCR, western blot were used to detect the EMT related proteins and mRNA gene expression levels in rats and primary hepatocytes (PHCs). Reactive oxygen species (ROS) were examined with a ROS detection kit.

RESULTS

The results showed that the CCl4+DBP group had higher portal pressure (PP) and lower mean arterial pressure (MAP) than the other groups. Elevated collagen deposition, profibrotic factor, inflammation, EMT levels were detected in DBP and CCl4+DBP groups. ROS, TGF-β1 and Snail-1 were highly expressed after DBP exposure in vitro. TGF-β1 had the potential to regulate Snail-1, and both of them were subject to regulation by ROS.

CONCLUSION

DBP could influence the progression of EMT through its toxicological effect by ROS/TGF-β1/Snail-1 signalling pathway, causing cirrhosis and PHT in final. The findings of this research might contribute to a novel comprehension of the underlying toxicological mechanisms and animal model involved in the progression of cirrhosis and PHT, and potentially offered a promising therapeutic target for the treatment of the disease.

The egg ribonuclease SjCP1412 accelerates liver fibrosis caused by Schistosoma japonicum infection involving damage-associated molecular patterns (DAMPs)

Schistosomiasis, a parasite infectious disease caused by Schistosoma japonicum, often leads to egg granuloma and fibrosis due to the inflammatory reaction triggered by egg antigens released in the host liver. This study focuses on the role of the egg antigens CP1412 protein of S. japonicum (SjCP1412) with RNase activity in promoting liver fibrosis. In this study, the recombinant egg ribonuclease SjCP1412, which had RNase activity, was successfully prepared. By analysing the serum of the population, it has been proven that the anti-SjCP1412 IgG in the serum of patients with advanced schistosomiasis was moderately correlated with liver fibrosis, and SjCP1412 may be an important antigen associated with liver fibrosis in schistosomiasis. In vitro, the rSjCP1412 protein induced the human liver cancer cell line Hep G2 and liver sinusoidal endothelial cells apoptosis and necrosis and the release of proinflammatory damage-associated molecular patterns (DAMPs). In mice infected with schistosomes, rSjCP1412 immunization or antibody neutralization of SjCP1412 activity significantly reduced cell apoptosis and necroptosis in liver tissue, thereby reducing inflammation and liver fibrosis. In summary, the SjCP1412 protein plays a crucial role in promoting liver fibrosis during schistosomiasis through mediating the liver cells apoptosis and necroptosis to release DAMPs inducing an inflammatory reaction. Blocking SjCP1412 activity could inhibit its proapoptotic and necrotic effects and alleviate hepatic fibrosis. These findings suggest that SjCP1412 may be served as a promising drug target for managing liver fibrosis in schistosomiasis japonica.

The novel mechanism facilitating chronic hepatitis B infection: immunometabolism and epigenetic modification reprogramming

Hepatitis B Virus (HBV) infections pose a global public health challenge. Despite extensive research on this disease, the intricate mechanisms underlying persistent HBV infection require further in-depth elucidation. Recent studies have revealed the pivotal roles of immunometabolism and epigenetic reprogramming in chronic HBV infection. Immunometabolism have identified as the process, which link cell metabolic status with innate immunity functions in response to HBV infection, ultimately contributing to the immune system's inability to resolve Chronic Hepatitis B (CHB). Within hepatocytes, HBV replication leads to a stable viral covalently closed circular DNA (cccDNA) minichromosome located in the nucleus, and epigenetic modifications in cccDNA enable persistence of infection. Additionally, the accumulation or depletion of metabolites not only directly affects the function and homeostasis of immune cells but also serves as a substrate for regulating epigenetic modifications, subsequently influencing the expression of antiviral immune genes and facilitating the occurrence of sustained HBV infection. The interaction between immunometabolism and epigenetic modifications has led to a new research field, known as metabolic epigenomics, which may form a mutually reinforcing relationship with CHB. Herein, we review the recent studies on immunometabolism and epigenetic reprogramming in CHB infection and discuss the potential mechanisms of persistent HBV infection. A deeper understanding of these mechanisms will offer novel insights and targets for intervention strategies against chronic HBV infection, thereby providing new hope for the treatment of related diseases.

Citral-Enriched Fraction of Lemon Essential Oil Mitigates LPS-Induced Hepatocyte Injuries

Lemon essential oil (LEO) is known for its aromatic and healthy properties; however, less consideration is given to the biological properties of the fractions obtained from LEO. This study aims to evaluate the ability of a citral-enriched fraction obtained from LEO (Cfr-LEO) to counteract lipopolysaccharide (LPS)-mediated inflammation, oxidative stress, and epithelial-mesenchymal transition (EMT) in healthy human hepatocytes. Human immortalized hepatocytes (THLE-2 cell line) were pretreated with Cfr-LEO and subsequently exposed to LPS at various time points. We report that the pretreatment with Cfr-LEO counteracts LPS-mediated effects by inhibiting inflammation, oxidative stress, and epithelial-mesenchymal transition in THLE-2. In particular, we found that pretreatment with Cfr-LEO reduced NF-κB activation and the subsequent proinflammatory cytokines release, ROS production, and NRF2 and p53 expression. Furthermore, the pretreatment with Cfr-LEO showed its beneficial effect in counteracting LPS-induced EMT. Taken together, these results support Cfr-LEO application in the nutraceutical research field not only for its organoleptic properties, conferred by citral enrichment, but also for its biological activity. Our study could lay the basis for the development of foods/drinks enriched with Cfr-LEO, aimed at preventing or alleviating chronic conditions associated with liver dysfunction.

S-nitrosylation of EMMPRIN influences the migration of HSCs and MMP activity in liver fibrosis

The mechanism of extracellular matrix metalloproteinase inducer (EMMPRIN) in the regulation of liver fibrosis has not been clarified. This study aims to investigate the role of EMMPRIN S-nitrosylation (SNO) in the regulation of hepatic stellate cell (HSC) migration and matrix metalloproteinase (MMP) activities in liver fibrosis. The results from the tissue microarrays and rat/mouse liver tissues suggest that EMMPRIN mRNA and protein levels in the fibrotic livers are lower than those in the corresponding normal control livers, but higher SNO level of EMMPRIN in fibrotic liver area was shown by immunohistochemistry, immunofluorescence staining, and biotin-switch assay conversely in vivo. Primary EMMPRIN comes from hepatocytes and liver sinus epithelial cells (LSECs) rather than quiescent HSCs. To mimic the uptake of extrinsic EMMPRIN, supernatants from mouse primary hepatocytes/293 cells transfected with EMMPRIN wild-type plasmids (WT) and EMMPRIN SNO site (cysteine 87) mutation plasmids (MUT) were collected and added to JS-1/LX2 cell medium. The MUT EMMPRIN diminishes SNO successfully, enhances the activities of MMP2 and MMP9, and subsequently increases HSC migration. In conclusion, SNO of EMMPRIN influences HSC migration and MMP activities in liver fibrosis. This finding may shed light on the possible regulatory mechanism of MMPs in ECM accumulation in liver fibrosis.

Interleukin-1 family cytokines in liver cell death: a new therapeutic target for liver diseases

INTRODUCTION

Liver cell death represents a basic biological process regulating the progression of liver diseases via distinct mechanisms. Accumulating evidence has uncovered participation of interleukin (IL)-1 family cytokines in liver cell death. Upon activation of cell death induced by hepatotoxic stimuli, IL1 family cytokines released by hepatic dead cells stimulate recruitment of immune cells, which in turn influence inflammation and subsequent liver injury, thus highlighting their potential as therapeutic targets in liver diseases. Enhancing our comprehension of mechanisms underlying IL1 family cytokine signaling in cell death responses could pave the way for novel therapeutic interventions aimed at addressing liver cell death-related liver pathologies.

AREAS COVERED

This review summarizes the recent findings reported in preclinical and clinical studies on mechanisms of liver cell death, alongside participation of IL1 family members consisting of IL1α, ILβ, IL18, and IL33 in liver cell death and their significant implications in liver diseases.

EXPERT OPINION

Discovery of new and innovative therapeutic approaches for liver diseases will need close cooperation between fundamental and clinical scientists to better understand the multi-step processes behind IL1 family cytokines' contributions to liver cell death.

AGER1 deficiency-triggered ferroptosis drives fibrosis progression in nonalcoholic steatohepatitis with type 2 diabetes mellitus

Hyperglycemia is an independent risk factor for the rapid progression of nonalcoholic steatohepatitis (NASH) to liver fibrosis with an incompletely defined mechanism. Ferroptosis is a novel form of programmed cell death that has been identified as a pathogenic mechanism in various diseases. However, the role of ferroptosis in the development of liver fibrosis in NASH with type 2 diabetes mellitus (T2DM) is unclear. Here, we observed the histopathological features of the progression of NASH to liver fibrosis as well as hepatocyte epithelial-mesenchymal transition (EMT) in a mouse model of NASH with T2DM and high-glucose-cultured steatotic human normal liver (LO2) cells. The distinctive features of ferroptosis, including iron overload, decreased antioxidant capacity, the accumulation of reactive oxygen species, and elevated lipid peroxidation products, were confirmed in vivo and in vitro. Liver fibrosis and hepatocyte EMT were markedly alleviated after treatment with the ferroptosis inhibitor ferrostatin-1. Furthermore, a decrease in the gene and protein levels of AGE receptor 1 (AGER1) was detected in the transition from NASH to liver fibrosis. Overexpression of AGER1 dramatically reversed hepatocyte EMT in high-glucose-cultured steatotic LO2 cells, whereas the knockdown of AGER1 had the opposite effect. The mechanisms underlying the phenotype appear to be associated with the inhibitory effects of AGER1 on ferroptosis, which is dependent on the regulation of sirtuin 4. Finally, in vivo adeno-associated virus-mediated AGER1 overexpression effectively relieved liver fibrosis in a murine model. Collectively, these findings suggest that ferroptosis participates in the pathogenesis of liver fibrosis in NASH with T2DM by promoting hepatocyte EMT. AGER1 could reverse hepatocyte EMT to ameliorate liver fibrosis by inhibiting ferroptosis. The results also suggest that AGER1 may be a potential therapeutic target for the treatment of liver fibrosis in patients with NASH with T2DM. Chronic hyperglycemia is associated with increased advanced glycation end products, resulting in the downregulation of AGER1. AGER1 deficiency downregulates Sirt4, which disturbs key regulators of ferroptosis (TFR-1, FTH, GPX4, and SLC7A11). These lead to increased iron uptake, decreasing the antioxidative capacity and enhanced lipid ROS production, ultimately leading to ferroptosis, which further promotes hepatocyte epithelial-mesenchymal transition and fibrosis progression in NASH with T2DM.

Effect of zearalenone on aflatoxin B1-induced intestinal and ovarian toxicity in pregnant and lactating rats

Aflatoxin B1 (AFB1) and zearalenone (ZEN) cause serious damage to mammals, but few studies have investigated the impacts of these toxins on pregnant and lactating mammals. This study investigated the effects of ZEN on AFB1-induced intestinal and ovarian toxicity in pregnant and lactating rats. Based on the results, AFB1 reduces the digestion, absorption, and antioxidant capacity in the intestine, increases intestinal mucosal permeability, destroys intestinal mechanical barriers, and increases pathogenic bacteria' relative abundances. Simultaneously, ZEN can exacerbate the intestinal injury caused by AFB1. The intestines of the offspring were also damaged, but the damage was less severe than that observed for the dams. While AFB1 activates various signalling pathways in the ovary and affects genes related to endoplasmic reticulum stress, apoptosis, and inflammation, ZEN may exacerbate or antagonize the AFB1 toxicity on gene expression in the ovary through key node genes and abnormally expressed genes. Our study found that mycotoxins can not only directly damage the ovaries and affect gene expression in the ovaries but can also impact ovarian health by disrupting intestinal microbes. Mycotoxins are an important environmental pathogenic factor for intestinal and ovarian disease in pregnancy and lactation mammals.

Hepatocytes: A key role in liver inflammation

Hepatocytes, the major parenchymal cells in the liver, are responsible for a variety of cellular functions including carbohydrate, lipid and protein metabolism, detoxification and immune cell activation to maintain liver homeotasis. Recent studies show hepatocytes play a pivotal role in liver inflammation. After receiving liver insults and inflammatory signals, hepatocytes may undergo organelle damage, and further respond by releasing mediators and expressing molecules that can act in the microenvironment as well as initiate a robust inflammatory response. In this review, we summarize how the hepatic organelle damage link to liver inflammation and introduce numerous hepatocyte-derived pro-inflammatory factors in response to chronic liver injury.

microRNAs-based diagnostic and therapeutic applications in liver fibrosis

Liver fibrosis is a process of over-extracellular matrix (ECM) aggregation and angiogenesis, which develops into cirrhosis and hepatocellular carcinoma (HCC). With the increasing pressure of liver fibrosis, new therapeutics to cure this disease requires much attention. Exosome-cargoed microRNAs (miRNAs) are emerging approaches in the precision of the liver fibrotic paradigm. In this review, we outlined the different types of hepatic cells derived miRNAs that drive intra-/extra-cellular interactive communication in liver fibrosis with different physiological and pathological processes. Specifically, we highlighted the possible mechanism of liver fibrosis pathogenesis associated with immune response and angiogenesis. In addition, potential clinical biomarkers and different stem cell transplant-derived miRNAs-based therapeutic strategies in liver fibrosis were summarized in this review. miRNAs-based approaches might help researchers devise new candidates for the cell-free treatment of liver fibrosis. This article is categorized under: RNA in Disease and Development > RNA in Disease.

TM4SF5-Mediated Regulation of Hepatocyte Transporters during Metabolic Liver Diseases

Nonalcoholic fatty liver disease (NAFLD) is found in up to 30% of the world’s population and can lead to hepatocellular carcinoma (HCC), which has a poor 5-year relative survival rate of less than 40%. Clinical therapeutic strategies are not very successful. The co-occurrence of metabolic disorders and inflammatory environments during the development of steatohepatitis thus needs to be more specifically diagnosed and treated to prevent fatal HCC development. To improve diagnostic and therapeutic strategies, the identification of molecules and/or pathways responsible for the initiation and progression of chronic liver disease has been explored in many studies, but further study is still required. Transmembrane 4 L six family member 5 (TM4SF5) has been observed to play roles in the regulation of metabolic functions and activities in hepatocytes using in vitro cell and in vivo animal models without or with TM4SF5 expression in addition to clinical liver tissue samples. TM4SF5 is present on the membranes of different organelles or vesicles and cooperates with transporters for fatty acids, amino acids, and monocarbohydrates, thus regulating nutrient uptake into hepatocytes and metabolism and leading to phenotypes of chronic liver diseases. In addition, TM4SF5 can remodel the immune environment by interacting with immune cells during TM4SF5-mediated chronic liver diseases. Because TM4SF5 may act as an NAFLD biomarker, this review summarizes crosstalk between TM4SF5 and nutrient transporters in hepatocytes, which is related to chronic liver diseases.

Mangiferin prevents hepatocyte epithelial-mesenchymal transition in liver fibrosis via targeting HSP27-mediated JAK2/STAT3 and TGF-β1/Smad pathway

Hepatocytes has been confirmed to undergo EMT and can be converted into myofibroblasts during hepatic fibrogenesis. However, the mechanism of hepatocyte EMT regulation in hepatic fibrosis, particularly through HSP27 (human homologue of rodent HSP25), remains unclear. Mangiferin (MAN), a compound extracted from Mangifera indica L, has been reported to attenuate liver injury. This study aimed to investigate the mechanisms underlying HSP27 inhibition and the anti-fibrotic effect of MAN in liver fibrosis. Our results revealed that the expression of HSP27 was remarkably increased in the liver tissues of patients with liver cirrhosis and CCl₄ -induced fibrotic rats. However, HSP27 shRNA treatment significantly alleviated fibrosis. Furthermore, MAN was found to inhibit CCl₄ - and TGF-β1-induced liver fibrosis and reduced hepatocyte EMT. More importantly, MAN decreased HSP27 expression to suppress the JAK2/STAT3 pathway, and subsequently blocked TGF-β1/Smad signaling, which were consistent with its protection against CCl₄ -induced EMT and liver fibrosis. Together, these results suggest that HSP27 may play a crucial role in hepatocyte EMT and liver fibrosis by activating JAK2/STAT3 signaling and TGF-β1/Smad pathway. The suppression of HSP27 expression by MAN may be a novel strategy for attenuating the hepatocyte EMT in liver fibrosis.

Crosstalk between TM4SF5 and GLUT8 regulates fructose metabolism in hepatic steatosis

OBJECTIVE

Transmembrane 4 L six family member 5 (TM4SF5) is likely involved in non-alcoholic steatohepatitis, although its roles and cross-talks with glucose/fructose transporters in phenotypes derived from high-carbohydrate diets remain unexplored. Here, we investigated the modulation of hepatic fructose metabolism by TM4SF5.

METHODS

Wild-type or Tm4sf5-/- knockout mice were evaluated via different diets, including normal chow, high-sucrose diet, or high-fat diet without or with fructose in drinking water (30% w/v). Using liver tissues and blood samples from the mice or hepatocytes, the roles of TM4SF5 in fructose-mediated de novo lipogenesis (DNL) and steatosis via a crosstalk with glucose transporter 8 (GLUT8) were assessed.

RESULTS

Tm4sf5 suppression or knockout in both in vitro and in vivo models reduced fructose uptake, DNL, and steatosis. Extracellular fructose treatment of hepatocytes resulted in an inverse relationship between fructose-uptake activity and TM4SF5-mediated translocalization of GLUT8 through dynamic binding at the cell surface. Following fructose treatment, TM4SF5 binding to GLUT8 transiently decreased with translocation to the plasma membrane (PM), where GLUT8 separated and became active for fructose uptake and DNL.

CONCLUSIONS

Overall, hepatic TM4SF5 modulated GLUT8 localization and activity through transient binding, leading to steatosis-related fructose uptake and lipogenesis. Thus, TM4SF5 and/or GLUT8 may be promising treatment targets against liver steatosis resulting from excessive fructose consumption.

Oleanolic acid-loaded nanoparticles attenuate activation of hepatic stellate cells via suppressing TGF-β1 and oxidative stress in PM2.5-exposed hepatocytes

Liver fibrosis has the potential to progress into liver cirrhosis, liver failure, and even death. Hepatic stellate cells (HSCs) activation play a central role in liver fibrosis, and persistently damaged hepatocytes secrete soluble factors that activate transdifferentiation of HSCs into myofibroblasts. Our previous studies indicated that fine particulate matter (PM2.5) can activate HSCs by stimulating hepatocytes to secrete TGF-β1. However, whether PM2.5 activates HSCs by regulating oxidative stress in hepatocytes remains uncertain. Oleanolic acid (OA) has been widely used in the clinic for hepatoprotection in Chinese medicine. In the present study, OA-loaded nanoparticles (OA-NP) with high solubility were used to attenuate the activation of HSCs induced by PM2.5-treated hepatocytes, and further studies were performed to explore the mechanism in which OA-NP plays a vital part. Our results showed that consistently PM2.5 treatment induced oxidative stress in hepatocytes. Moreover, the activation of HSCs induced by PM2.5-treated hepatocytes was reversed by antioxidant N-acetylcysteine treatment. Hence, PM2.5 may participate in the activation of HSCs by regulating oxidative stress in hepatocytes. Using a co-cultivation system, our results proved pretreatment with OA-NP significantly attenuates the activation of HSCs induced by PM2.5-exposed hepatocytes. In addition, the TGF-β1 expression and oxidative stress in hepatocytes with PM2.5 treated were reduced by the incubation with OA-NP. These observations demonstrated that OA-NP protects against the activation of HSCs by decreasing the TGF-β1 level and oxidative stress in PM2.5-exposed hepatocytes.

Multi-omics analyses of early liver injury reveals cell-type-specific transcriptional and epigenomic shift

Background

Liver fibrosis is a wound-healing response to tissue injury and inflammation hallmarked by the extracellular matrix (ECM) protein deposition in the liver parenchyma and tissue remodelling. Different cell types of the liver are known to play distinct roles in liver injury response. Hepatocytes and liver endothelial cells receive molecular signals indicating tissue injury and activate hepatic stellate cells which produce ECM proteins upon their activation. Despite the growing knowledge on the molecular mechanism underlying hepatic fibrosis in general, the cell-type-specific gene regulatory network associated with the initial response to hepatotoxic injury is still poorly characterized.

Results

In this study, we used thioacetamide (TAA) to induce hepatic injury in adult zebrafish. We isolated three major liver cell types - hepatocytes, endothelial cells and hepatic stellate cells - and identified cell-type-specific chromatin accessibility and transcriptional changes in an early stage of liver injury. We found that TAA induced transcriptional shifts in all three cell types hallmarked by significant alterations in the expression of genes related to fatty acid and carbohydrate metabolism, as well as immune response-associated and vascular-specific genes. Interestingly, liver endothelial cells exhibit the most pronounced response to liver injury at the transcriptome and chromatin level, hallmarked by the loss of their angiogenic phenotype.

Conclusion

Our results uncovered cell-type-specific transcriptome and epigenome responses to early stage liver injury, which provide valuable insights into understanding the molecular mechanism implicated in the early response of the liver to pro-fibrotic signals.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08173-1.

TM4SF5-mediated liver malignancy involves NK cell exhaustion-like phenotypes

Aberrant extracellular matrix and immune cell alterations within the tumor microenvironment promote the pathological progression of liver carcinogenesis. Although transmembrane 4 L six family member 5 (TM4SF5) is involved in liver fibrosis and cancer, its mechanism avoiding immune surveillance during carcinogenesis remains unknown. We investigated how TM4SF5-mediated signaling caused immune evasion using in vitro primary cells and in vivo liver tissues from genetic or chemically induced mouse models. TM4SF5-transgenic and diethylnitrosamine (DEN)-induced liver cancer mouse models exhibited fibrotic and cancerous livers, respectively, with enhanced TM4SF5, pY⁷⁰⁵STAT3, collagen I, and laminin γ2 levels. These TM4SF5-mediated effects were abolished by TM4SF5 inhibitor, 4'-(p-toluenesulfonylamido)-4-hydroxychalcone (TSAHC). TM4SF5-dependent tumorigenesis involved natural killer (NK) cell exhaustion-like phenotypes including the reduction of NK cell number or function, which were blocked with TSAHC treatment. TM4SF5 expression in cancer cells downregulated stimulatory ligands and receptors for NK cell cytotoxicity, including SLAMF6, SLAMF7, MICA/B, and others. TM4SF5 suppression or inhibition reduced STAT3 signaling activity and recovered the receptor levels and NK cell surveillance, leading to reduced fibrotic and cancerous phenotypes, and longer survival. Altogether, these findings suggest that TM4SF5-mediated STAT3 activity for extracellular matrix modulation is involved in the progression of liver disease to HCC and that TM4SF5 appears to suppress NK cells during liver carcinogenesis.

Imaging of the chemotherapy-induced hepatic damage: Yellow liver, blue liver, and pseudocirrhosis

The liver is the major drug-metabolizing and drug-detoxifying organ. Many drugs can cause liver damage through various mechanisms; however, the liver response to injury includes a relatively narrow spectrum of alterations that, regardless of the cause, are represented by phlogosis, oxidative stress and necrosis. The combination of these alterations mainly results in three radiological findings: vascular alterations, structural changes and metabolic function reduction. Chemotherapy has changed in recent decades in terms of the drugs, protocols and duration, allowing patients a longer life expectancy. As a consequence, we are currently observing an increase in chemotherapy-associated liver injury patterns once considered unusual. Recognizing this form of damage in an early stage is crucial for reconsidering the therapy regimen and thus avoiding severe complications. In this frontier article, we analyze the role of imaging in detecting some of these pathological patterns, such as pseudocirrhosis, "yellow liver" due to chemotherapy-associated steatosis-steatohepatitis, and "blue liver", including sinusoidal obstruction syndrome, veno-occlusive disease and peliosis.

TM4SF5-dependent crosstalk between hepatocytes and macrophages to reprogram the inflammatory environment

Chronic injury to hepatocytes results in inflammation, steatohepatitis, fibrosis, and nonalcoholic fatty liver disease (NAFLD). The tetraspanin TM4SF5 is implicated in fibrosis and cancer. We investigate the role of TM4SF5 in communication between hepatocytes and macrophages (MΦs) and its possible influence on the inflammatory microenvironment that may lead to NAFLD. TM4SF5 induction in differentiated MΦs promotes glucose uptake, glycolysis, and glucose sensitivity, leading to M1-type MΦ activation. Activated M1-type MΦs secrete pro-inflammatory interleukin-6 (IL-6), which induces the secretion of CCL20 and CXCL10 from TM4SF5-positive hepatocytes. Although TM4SF5-dependent secretion of these chemokines enhances glycolysis in M0 MΦs, further chronic exposure reprograms MΦs for an increase in the proportion of M2-type MΦs in the population, which may support diet- and chemical-induced NAFLD progression. We suggest that TM4SF5 expression in MΦs and hepatocytes is critically involved in modulating the inflammatory environment during NAFLD progression.

Mesenchymal Stem Cells Influence Activation of Hepatic Stellate Cells, and Constitute a Promising Therapy for Liver Fibrosis

Liver fibrosis is a common feature of chronic liver disease. Activated hepatic stellate cells (HSCs) are the main drivers of extracellular matrix accumulation in liver fibrosis. Hence, a strategy for regulating HSC activation is crucial in treating liver fibrosis. Mesenchymal stem cells (MSCs) are multipotent stem cells derived from various post-natal organs. Therapeutic approaches involving MSCs have been studied extensively in various diseases, including liver disease. MSCs modulate hepatic inflammation and fibrosis and/or differentiate into hepatocytes by interacting directly with immune cells, HSCs, and hepatocytes and secreting modulators, thereby contributing to reduced liver fibrosis. Cell-free therapy including MSC-released secretomes and extracellular vesicles has elicited extensive attention because they could overcome MSC transplantation limitations. Herein, we provide basic information on hepatic fibrogenesis and the therapeutic potential of MSCs. We also review findings presenting the effects of MSC itself and MSC-based cell-free treatments in liver fibrosis, focusing on HSC activation. Growing evidence supports the anti-fibrotic function of either MSC itself or MSC modulators, although the mechanism underpinning their effects on liver fibrosis has not been established. Further studies are required to investigate the detailed mechanism explaining their functions to expand MSC therapies using the cell itself and cell-free treatments for liver fibrosis.

Resveratrol suppresses cholestasis-induced liver injury and fibrosis in rats associated with the inhibition of TGFβ1-Smad3-miR21 axis and profibrogenic and hepatic injury biomarkers

Cholestasis caused by slowing or blockage of bile flow is a serious liver disease that can lead to liver fibrosis and cirrhosis. The link between transforming growth factor beta 1 (TGFβ1), Smad family member 3 (Smad3), and microRNA 21 (miR21) in bile duct ligation (BDL)-induced liver fibrosis in the presence and absence of the anti-inflammatory and antioxidant compound, resveratrol (RSV), has not been previously studied. Therefore, we tested whether RSV can protect against BDL-induced liver fibrosis associated with the inhibition of the TGFβ1-Smad3-miR21 axis and profibrogenic and hepatic injury biomarkers. The model group of rats had their bile duct ligated (BDL) for 3 weeks before being killed, whereas, the BDL-treated rats were separated into three groups that received 10, 20, and 30 mg/kg RSV daily until the end of the experiment. Using light microscopy and ultrasound examinations, we documented in the BDL group, the development of hepatic injury and fibrosis as demonstrated by hepatocytes necrosis, bile duct hyperplasia, collagen deposition, enlarged liver with increased echogenicity, irregular nodular border and dilated common bile duct, which were more effectively inhibited by the highest used RSV dosage. In addition, RSV significantly (p ≤ 0.0027) inhibited BDL-induced hepatic TGFβ1, Smad3, miR21, the profibrogenic biomarker tissue inhibitor of metalloproteinases-1 (TIMP-1), malondialdehyde (MDA), interleukin-17a (IL-17a), and blood levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and bilirubin. These findings show that RSV at 30 mg/kg substantially protects against BDL-induced liver injuries, which is associated with the inhibition of TGFβ1-Smad3-miR21 axis, and biomarkers of profibrogenesis, oxidative stress, and inflammation.

Contextualization of causal regulatory networks from toxicogenomics data applied to drug-induced liver injury

In recent years, network-based methods have become an attractive analytical approach for toxicogenomics studies. They can capture not only the global changes of regulatory gene networks but also the relationships between their components. Among them, a causal reasoning approach depicts the mechanisms of regulation that connect upstream regulators in signaling networks to their downstream gene targets. In this work, we applied CARNIVAL, a causal network contextualisation tool, to infer upstream signaling networks deregulated in drug-induced liver injury (DILI) from gene expression microarray data from the TG-GATEs database. We focussed on six compounds that induce observable histopathologies linked to DILI from repeated dosing experiments in rats. We compared responses in vitro and in vivo to identify potential cross-platform concordances in rats as well as network preservations between rat and human. Our results showed similarities of enriched pathways and network motifs between compounds. These pathways and motifs induced the same pathology in rats but not in humans. In particular, the causal interactions "LCK activates SOCS3, which in turn inhibits TFDP1" was commonly identified as a regulatory path among the fibrosis-inducing compounds. This potential pathology-inducing regulation illustrates the value of our approach to generate hypotheses that can be further validated experimentally.

BIR repeat-containing ubiquitin conjugating enzyme (BRUCE) regulation of β-catenin signaling in the progression of drug-induced hepatic fibrosis and carcinogenesis

BACKGROUND

BIR repeat-containing ubiquitin conjugating enzyme (BRUCE) is a liver tumor suppressor, which is downregulated in a large number of patients with liver diseases. BRUCE facilitates DNA damage repair to protect the mouse liver against the hepatocarcinogen diethylnitrosamine (DEN)-dependent acute liver injury and carcinogenesis. While there exists an established pathologic connection between fibrosis and hepatocellular carcinoma (HCC), DEN exposure alone does not induce robust hepatic fibrosis. Further studies are warranted to identify new suppressive mechanisms contributing to DEN-induced fibrosis and HCC.

AIM

To investigate the suppressive mechanisms of BRUCE in hepatic fibrosis and HCC development.

METHODS

Male C57/BL6/J control mice [loxp/Loxp; albumin-cre (Alb-cre)^-] and BRUCE Alb-Cre KO mice (loxp/Loxp; Alb-Cre⁺) were injected with a single dose of DEN at postnatal day 15 and sacrificed at different time points to examine liver disease progression.

RESULTS

By using a liver-specific BRUCE knockout (LKO) mouse model, we found that BRUCE deficiency, in conjunction with DEN exposure, induced hepatic fibrosis in both premalignant as well as malignant stages, thus recapitulating the chronic fibrosis background often observed in HCC patients. Activated in fibrosis and HCC, β-catenin activity depends on its stabilization and subsequent translocation to the nucleus. Interestingly, we observed that livers from BRUCE KO mice demonstrated an increased nuclear accumulation and elevated activity of β-catenin in the three stages of carcinogenesis: Pre-malignancy, tumor initiation, and HCC. This suggests that BRUCE negatively regulates β-catenin activity during liver disease progression. β-catenin can be activated by phosphorylation by protein kinases, such as protein kinase A (PKA), which phosphorylates it at Ser-675 (pSer-675-β-catenin). Mechanistically, BRUCE and PKA were colocalized in the cytoplasm of hepatocytes where PKA activity is maintained at the basal level. However, in BRUCE deficient mouse livers or a human liver cancer cell line, both PKA activity and pSer-675-β-catenin levels were observed to be elevated.

CONCLUSION

Our data support a “BRUCE-PKA-β-catenin” signaling axis in the mouse liver. The BRUCE interaction with PKA in hepatocytes suppresses PKA-dependent phosphorylation and activation of β-catenin. This study implicates BRUCE as a novel negative regulator of both PKA and β-catenin in chronic liver disease progression. Furthermore, BRUCE-liver specific KO mice serve as a promising model for understanding hepatic fibrosis and HCC in patients with aberrant activation of PKA and β-catenin.

Targeting Certain Interleukins as Novel Treatment Options for Liver Fibrosis

The liver is a major metabolic organ and an immunologically complex organ. It produces and uses many substances such as acute phase proteins, cytokines, chemokines, and complementary components to maintain the balance between immunity and tolerance. Interleukins are important immune control cytokines, that are produced by many body cells. In liver injury, interleukins are produced in large amount by various cell types, and act as pro-inflammatory (e.g. interleukin (IL)-6, IL-13, IL-17, and IL-33) as well as anti-inflammatory (e.g. IL-10) functions in hepatic cells. Recently, interleukins are regarded as interesting therapeutic targets for the treatment of liver fibrosis patients. Hepatic cells such as hepatocytes, hepatic stellate cells, and hepatic macrophages are involved to the initiation, perpetuation, and resolution of fibrosis. The understanding of the role of interleukins in such cells provides opportunity for the development of therapeutic target drugs. This paper aims to understand the functional roles of interleukins in hepatic and immune cells when the liver is damaged, and suggests the possibility of interleukins as a new treatment target in liver fibrosis.

Palmitate and Fructose Interact to Induce Human Hepatocytes to Produce Pro-Fibrotic Transcriptional Responses in Hepatic Stellate Cells Exposed to Conditioned Media

BACKGROUND/AIMS

Excessive consumption of dietary fat and sugar is associated with an elevated risk of nonalcoholic fatty liver disease (NAFLD). Hepatocytes exposed to saturated fat or sugar exert effects on nearby hepatic stellate cells (HSCs); however, the mechanisms by which this occurs are poorly understood. We sought to determine whether paracrine effects of hepatocytes exposed to palmitate and fructose produced profibrotic transcriptional responses in HSCs.

METHODS

We performed expression profiling of mRNA and lncRNA from HSCs treated with conditioned media (CM) from human hepatocytes treated with palmitate (P), fructose (F), or both (PF).

RESULTS

In HSCs exposed to CM from palmitate-treated hepatocytes, we identified 374 mRNAs and 607 lncRNAs showing significant differential expression (log₂ foldchange ≥ |1|; FDR ≤0.05) compared to control cells. In HSCs exposed to CM from PF-treated hepatocytes, the number of differentially expressed genes was much higher (1198 mRNAs and 3348 lncRNAs); however, CM from fructose-treated hepatocytes elicited no significant changes in gene expression. Pathway analysis of differentially expressed genes showed enrichment for hepatic fibrosis and hepatic stellate cell activation in P- (FDR =1.30E-04) and PF-(FDR =9.24E-06)
groups. We observed 71 lncRNA/nearby mRNA pairs showing differential expression under PF conditions. There were 90 mRNAs and 264 lncRNAs strongly correlated between the PF group and differentially expressed transcripts from a comparison of activated and quiescent HSCs, suggesting that some of the transcriptomic changes occurring in response to PF overlap with HSC activation.

CONCLUSION

The results reported here have implications for dietary modifications in the prevention and treatment of NAFLD.

Differential TM4SF5-mediated SIRT1 modulation and metabolic signaling in nonalcoholic steatohepatitis progression

Nonalcoholic fatty liver disease is a chronic condition involving steatosis, steatohepatitis and fibrosis, and its progression remains unclear. Although the tetraspanin transmembrane 4 L six family member 5 (TM4SF5) is involved in hepatic fibrosis and cancer, its role in nonalcoholic steatohepatitis (NASH) progression is unknown. We investigated the contribution of TM4SF5 to liver pathology using transgenic and KO mice, diet- or drug-treated mice, in vitro primary cells, and in human tissue. TM4SF5-overexpressing mice exhibited nonalcoholic steatosis and NASH in an age-dependent manner. Initially, TM4SF5-positive hepatocytes and liver tissue exhibited lipid accumulation, decreased Sirtuin 1 (SIRT1), increased sterol regulatory-element binding proteins (SREBPs) and inactive STAT3 via suppressor of cytokine signaling (SOCS)1/3 upregulation. In older mice, TM4SF5 promoted inflammatory factor induction, SIRT1 expression and STAT3 activity, but did not change SOCS or SREBP levels, leading to active STAT3-mediated ECM production for NASH progression. A TM4SF5-associated increase in chemokines promoted SIRT1 expression and progression to NASH with fibrosis. Suppression of the chemokine CCL20 reduced immune cell infiltration and ECM production. Liver tissue from high-fat diet- or CCl4 -treated mice and human patients exhibited TM4SF5-dependent steatotic or steatohepatitic livers with links between TM4SF5-mediated SIRT1 modulation and SREBP or SOCS/STAT3 signaling axes. TM4SF5-mediated STAT3 activation in fibrotic NASH livers increased collagen I and laminin γ2. Both collagen I α1 and laminin γ2 suppression resulted in reduced SIRT1 and active STAT3, but no change in SREBP1 or SOCS, and abolished CCl4 -mediated mouse liver damage. TM4SF5-mediated signaling pathways that involve SIRT1, SREBPs and SOCS/STAT3 promoted progression to NASH. Therefore, TM4SF5 and its downstream effectors may be promising therapeutic targets to treat nonalcoholic fatty liver disease. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Curcumin blunts epithelial-mesenchymal transition of hepatocytes to alleviate hepatic fibrosis through regulating oxidative stress and autophagy

The massive production and activation of myofibroblasts (MFB) is key to the development of liver fibrosis. In many studies, it has been proven that hepatocytes are an important part of MFB, and can be transformed into MFB through epithelial-mesenchymal transition (EMT) during hepatic fibrogenesis. In our previous study, we confirmed that curcumin inhibited EMT procession and differentiation of hepatocytes into MFB. In addition, in previous studies, it has been shown that autophagy plays an important role in the regulation of cellular EMT procession. In the current study, we showed that curcumin inhibited TGF-β/Smad signaling transmission by activating autophagy, thereby inhibiting EMT. The mechanism of degradative polyubiquitylation of Smad2 and Smad3 is likely through inhibiting tetratricopeptide repeat domain 3 (TTC3) and by inducing ubiquitylation and proteasomal degradation of Smad ubiquitination regulatory factor 2 (SMURF2), which on account of the increase of autophagy in hepatocytes. Curcumin inhibits levels of reactive oxygen species (ROS) and oxidative stress in hepatocytes by activating PPAR-α, and regulates upstream signaling pathways of autophagy AMPK and PI3K/AKT/mTOR, leading to an increase of the autophagic flow in hepatocytes. In this study, we confirm that curcumin effectively reduced the occurrence of EMT in hepatocytes and inhibited production of the extracellular matrix (ECM) by activating autophagy, which provides a potential novel therapeutic strategy for hepatic fibrosis.

Exosomal MALAT1 derived from hepatic cells is involved in the activation of hepatic stellate cells via miRNA-26b in fibrosis induced by arsenite

In the liver microenvironment, interactions among diverse types of hepatic cells are involved in liver fibrosis. In fibrotic tissues, exosomes act as transporters in intercellular communication. Long non-coding RNAs (lncRNAs) are involved in the activation of hepatic stellate cells (HSCs), which are participants in liver fibrosis. However, the functions of exosomal lncRNAs in liver fibrosis induced by arsenite are undefined. The purposes of the present study were (a) to determine if lncRNAs secreted from human hepatic (L-02) cells exposed to arsenite are shuttled to hepatic stellate LX-2 cells and (b) to establish their effects on LX-2 cells. In mice, MALAT1 was overexpressed in the progression of liver fibrosis induced by arsenite as well as in L-02 cells exposed to arsenite. Co-cultures with arsenite-treated L-02 cells induced the activation of LX-2 cells and overexpression of MALAT1. Arsenite-treated L-02 cells transported MALAT1 into LX-2 cells. Downregulation of MALAT1, which reduced the MALAT1 levels in exosomes derived from arsenite-treated L-02 cells, inhibited the activation of LX-2 cells. Additionally, exosomal MALAT1 derived from arsenite-treated L-02 cells promoted the activation of LX-2 cells via microRNA-26b regulation of COL1A2. Furthermore, circulating exosomal MALAT1 was up-regulated in people exposed to arsenite. In sum, exosomes derived from arsenite-treated hepatic cells transferred MALAT1 to HSCs, which induced their activation. These findings support the concept that, during liver fibrosis induced by arsenite, exosomal lncRNAs are involved in cell-cell communication.

Current therapies and novel approaches for biliary diseases

Chronic liver diseases that inevitably lead to hepatic fibrosis, cirrhosis and/or hepatocellular carcinoma have become a major cause of illness and death worldwide. Among them, cholangiopathies or cholestatic liver diseases comprise a large group of conditions in which injury is primarily focused on the biliary system. These include congenital diseases (such as biliary atresia and cystic fibrosis), acquired diseases (such as primary sclerosing cholangitis and primary biliary cirrhosis), and those that arise from secondary damage to the biliary tree from obstruction, cholangitis or ischaemia. These conditions are associated with a specific pattern of chronic liver injury centered on damaged bile ducts that drive the development of peribiliary fibrosis and, ultimately, biliary cirrhosis and liver failure. For most, there is no established medical therapy and, hence, these diseases remain one of the most important indications for liver transplantation. As a result, there is a major need to develop new therapies that can prevent the development of chronic biliary injury and fibrosis. This mini-review briefly discusses the pathophysiology of liver fibrosis and its progression to cirrhosis. We make a special emphasis on biliary fibrosis and current therapeutic options, such as angiotensin converting enzyme-2 (known as ACE2) over-expression in the diseased liver as a novel potential therapy to treat this condition.

Regulation of gasdermin D by miR-379-5p is involved in arsenite-induced activation of hepatic stellate cells and in fibrosis via secretion of IL-1β from human hepatic cells

Arsenic is an environmental toxicant and human carcinogen.

The Role of Long Non-Coding RNAs (lncRNAs) in the Development and Progression of Fibrosis Associated with Nonalcoholic Fatty Liver Disease (NAFLD)

Nonalcoholic fatty liver disease (NAFLD) encompasses a spectrum of conditions ranging from hepatic steatosis to inflammation (nonalcoholic steatohepatitis or NASH) with or without fibrosis, in the absence of significant alcohol consumption. The presence of fibrosis in NASH patients is associated with greater liver-related morbidity and mortality; however, the molecular mechanisms underlying the development of fibrosis and cirrhosis in NAFLD patients remain poorly understood. Long non-coding RNAs (lncRNAs) are emerging as key contributors to biological processes that are underpinning the initiation and progression of NAFLD fibrosis. This review summarizes the experimental findings that have been obtained to date in animal models of liver fibrosis and NAFLD patients with fibrosis. We also discuss the potential applicability of circulating lncRNAs to serve as biomarkers for the diagnosis and prognosis of NAFLD fibrosis. A better understanding of the role played by lncRNAs in NAFLD fibrosis is critical for the identification of novel therapeutic targets for drug development and improved, noninvasive methods for disease diagnosis.

Interleukin (IL)-13, Prostaglandin E2 (PGE2), and Prostacyclin 2 (PGI2) Activate Hepatic Stellate Cells via Protein kinase C (PKC) Pathway in Hepatic Fibrosis

BACKGROUND Protein kinase C (PKC), interleukin (IL)-13, prostaglandin E2 (PGE2), and prostacyclin 2 (PGI2) can all play crucial roles in pulmonary fibrosis. However, their functions remain unclear in hepatic fibrosis mediated by hepatic stellate cells (HSCs), which has been demonstrated to be related to transforming growth factor-β (TGF-β) and platelet-derived growth factor (PDGF). MATERIAL AND METHODS All the experiments were based on LX-2 Hepatic stellate cells. The expression of TGF-β1 and PDGF were assessed by ELISA, RT-PCR, and Western blotting in human HSCs treated by IL-13, PGE2, and PGI2, respectively. At the same time, bridge assay and CCK8 assay were used to detect the cell proliferation and activity, PKC activity assay was used to test the activity of PKC, and PKC agonist and antagonist were used to verify the results obtained previously. RESULTS We found that IL-13, PGE2, and PGI2 significantly enhanced the expression of TGF-β1 and PDGF in human HSCs, which also clearly improved the proliferation and cell activity of HSCs. Moreover, PKC activity was significantly increased following IL-13, PGE2, and PGI2 treatments. We also found that the expression of TGF-β1 and PDGF, as well as the proliferation and cell activity of HSCs, were significantly enhanced by the PKC agonist phorbol 12-myristate 13-acetate (PMA), but suppressed by the PKC antagonist calphostin C. CONCLUSIONS We found that IL-13, PGE2, and PGI2 stimulated HSCs proliferation and secretion of TGF-β1 and PDGF by activating PKC, which predicted their potential roles in hepatic fibrosis.

Gene expression profiling of human hepatocytes grown on differing substrate stiffness

OBJECTIVE

To study the effects of different substrate stiffness on human hepatocytes using RNA sequencing (RNA-Seq) technology. The stiffness was corresponding to physiology and pathology stiffness of liver tissues.

RESULTS

With the aid of RNA-Seq technology, our study characterizes the transcriptome of hepatocytes cultured on soft, moderate, stiff and plastic substrates. Compared to soft substrate, our RNA-Seq results revealed 1131 genes that were up-regulated and 2534 that were down-regulated on moderate substrate, 1370 genes that were up-regulated and 2677 down-regulated genes on stiff substrate. Functional enrichment analysis indicated that differentially expressed genes were associated with the regulation of actin cytoskeleton, focal adhesion, tight junction, adherens junction as well as antigen processing and presentation. RNA-Seq results were further verified by a quantitative real-time reverse transcriptase polymerase chain reaction.

CONCLUSION

Our study provides a comprehensive picture of the gene expression landscape in hepatocytes grown on different substrate stiffness, offering insights into the role of substrate stiffness in hepatic pathology.

A novel flow cytometry tool for fibrosis scoring through hepatic stellate cell differentiation

Hepatic stellate cells (HSCs) are a central fibrogenic cell type that contributes to collagen accumulation during chronic liver disease. Peripheral blood lymphocytes from HCV patients are phagocytized by HSCs and induce their differentiation. This study aimed to characterize HSCs differentiation using a flow cytometry tool for fibrosis scoring. NK cells from healthy donors and from patients with chronic HCV with various severities of fibrosis were co-cultured with a human HSC line (LX2). LX2 phagocytosis of NK cells were stained for NK cells (CD45/CD56/CD3) and NK activation marker (CD107a) as well as INF-γ, apoptosis (Annexin-V) and α-smooth-muscle-actin (αSMA, as a marker of LX2 activation). In addition, reactive oxygen species (ROS) and the senescence marker P15 were analyzed prior to flow cytometry analysis. LX2 mono-cultures demonstrated a homogenous cell-population according to size (forward-scattered; FSC), granularity and αSMA expressions. However, on their co-culture with NK cells, the HSCs formed four subpopulations, which were stratified by αSMA intensities and cell size. NK cells isolated from heathy donors did not activate LX2-cells. In contrast, HCV exposed to NK cells from both F1 and F4 fibrosis grade patients, showed elevated CD107a and INF-γ levels and increased αSMA intensities in two of the four cell populations, with fibrosis scoring showing a linear correlation with αSMA intensities and NK phagocytosis. The αSMA^intermediate /Size^Low HSCs sub-population showed higher proliferation following F4-NK cells with higher phagocytosis ability, suggesting an active/regulatory population. The αSMA^high /Size^high subpopulations showed low proliferation and phagocytosis capacity, and were correlated with higher apoptosis, increased ROS and P15 intensities, suggesting senescing cells. Taken together, NK cells lead to heterogeneous differentiation of HSCs. Flow-cytometry may provide a novel means of characterizing HSCs in relation to the severity of liver fibrosis. © 2017 International Society for Advancement of Cytometry.

Fate tracing of hepatocytes in mouse liver

Hepatocytes perform most of the functions of the liver and are considered terminally differentiated cells. Recently, it has been suggested that hepatocytes might have the potential to transdifferentiate or dedifferentiate under physiological or pathological conditions in vivo. Epithelial-mesenchymal transition of hepatocytes in liver fibrosis has also been proposed. However, these findings have not been fully confirmed. In this study, hepatocytes were genetically labelled for cell fate tracing using lacZ via the tamoxifen-induced CreERT/loxP system. After induction with tamoxifen, alb + cells were permanently marked by lacZ expression, and all progeny lacZ + cells were derived from a single source with no interference. We did not observe transdifferentiation or dedifferentiation of hepatocytes into cholangiocytes or hepatic progenitor cells under conditions of liver homeostasis or following a 2/3 partial hepatectomy. Meanwhile, lacZ/OPN-positive cells were observed in livers of 3,5-diethoxycarbonyl-1,4-dihydrocollidine-fed mice, and lacZ/alpha-smooth muscle actin-positive cells were detected in carbon tetrachloride-induced chronic liver injury models. These results suggested that some existing differentiated alb + cells might have the potential of transdifferentiation/dedifferentiation or epithelial-to-mesenchymal transition in vivo in some liver injury models, but the proportion of these alb + cells in liver was very low, and their significance and actual function during the pathological process remains to be elucidated.

Comparative transcriptomics of hepatic differentiation of human pluripotent stem cells and adult human liver tissue

Hepatocytes derived from human pluripotent stem cells (hPSC-HEP) have the potential to replace presently used hepatocyte sources applied in liver disease treatment and models of drug discovery and development. Established hepatocyte differentiation protocols are effective and generate hepatocytes, which recapitulate some key features of their in vivo counterparts. However, generating mature hPSC-HEP remains a challenge. In this study, we applied transcriptomics to investigate the progress of in vitro hepatic differentiation of hPSCs at the developmental stages, definitive endoderm, hepatoblasts, early hPSC-HEP, and mature hPSC-HEP, to identify functional targets that enhance efficient hepatocyte differentiation. Using functional annotation, pathway and protein interaction network analyses, we observed the grouping of differentially expressed genes in specific clusters representing typical developmental stages of hepatic differentiation. In addition, we identified hub proteins and modules that were involved in the cell cycle process at early differentiation stages. We also identified hub proteins that differed in expression levels between hPSC-HEP and the liver tissue controls. Moreover, we identified a module of genes that were expressed at higher levels in the liver tissue samples than in the hPSC-HEP. Considering that hub proteins and modules generally are essential and have important roles in the protein-protein interactions, further investigation of these genes and their regulators may contribute to a better understanding of the differentiation process. This may suggest novel target pathways and molecules for improvement of hPSC-HEP functionality, having the potential to finally bring this technology to a wider use.

Schisandrin B attenuates CCl4-induced liver fibrosis in rats by regulation of Nrf2-ARE and TGF-β/Smad signaling pathways

Liver fibrosis is a major pathological feature of chronic liver diseases and there is no effective therapy program at present. Schisandrin B (Sch B) is the major bioactive ingredient of Schisandra chinensis, with antioxidative, anti-inflammatory, antitumor, and hepatoprotective properties. This study aimed to investigate the protective effect and related molecular mechanism of Sch B against carbon tetrachloride (CCl₄)-induced liver fibrosis in rats. The in vivo therapeutic effect of Sch B on liver fibrosis induced by CCl₄ was examined in rats. In vitro, rat hepatic stellate cells (HSC-T6) were used to assess the effect of Sch B on the activation of HSCs. Sch B effectively attenuated liver damage and progression of liver fibrosis in rats, as evidenced by improved liver function and decreased collagen deposition. The effects of Sch B were associated with attenuating oxidative stress by activating nuclear factor-erythroid 2-related factor 2 (Nrf2)-mediated antioxidant signaling and suppressing HSC activation by inhibiting the transforming growth factor-β (TGF-β)/Smad signaling pathway. In an in vitro study, it was shown that Sch B inhibited TGF-β-induced HSC activation. Finally, Sch B significantly inhibited TGF-β1-stimulated phosphorylation of Smad and signaling of mitogen-activated protein kinases. This study demonstrates that Sch B prevents the progression of liver fibrosis by the regulation of Nrf2-ARE and TGF-β/Smad signaling pathways, and indicates that Sch B can be used for the treatment of liver fibrosis.

Enhanced Wnt Signalling in Hepatocytes is Associated with Schistosoma japonicum Infection and Contributes to Liver Fibrosis

Liver fibrosis is the most serious pathology caused by Schistosoma japonicum infection, which arises when schistosome eggs are deposited in the liver. Eosinophils, macrophages and hepatic stellate cells (HSCs) have been identified as major cellular contributors to the development of granulomas and fibrosis, but little is known about the effects of hepatocytes on granuloma formation. Here, we found that the levels of Wnt signalling-related molecules, transforming growth factor β (TGF-β) and connective tissue growth factor (CTGF) in hepatocytes were markedly elevated after S. japonicum infection. Liver fibrosis was exacerbated when exogenous Wnt3a was introduced, but was alleviated when Wnt signalling was suppressed by DKK1, accompanied by the reduced expression of TGF-β and CTGF in hepatocytes. These results indicate that the hepatocytic expression of TGF-β and CTGF is mediated by Wnt signalling. Additionally, the hepatocytes isolated from infected mice promoted the activation of primary HSCs in vitro, however, this effect was not observed when hepatocytes from DKK1 treated S. japonicum-infected mice was employed in the co-culture system. Our findings identify a novel pro-fibrogenic role of hepatocytes in schistosomiasis-induced liver fibrosis that is dependent on Wnt signalling, which may serve as a potential target for ameliorating hepatic fibrosis caused by helminths.

HBV Viral Load and Liver Enzyme Levels May Be Associated with the Wild MBL2 AA Genotype

The present study investigated the frequencies of rs1800450 (MBL ^⁎B, G>A), rs1800451 (MBL ^⁎C, G>A), and rs5030737 (MBL ^⁎D, C>T) polymorphisms in exon 1 of the MBL2 gene among patients with chronic viral hepatitis. Blood samples from patients infected with hepatitis B virus (HBV; n = 65), hepatitis C virus (HCV; n = 92), and a noninfected control group (n = 300) were investigated. The presence of polymorphisms was detected using a real-time polymerase chain reaction to correlate with liver disease pathogenesis and fibrosis staging according to the Metavir classification. The genotypic and allelic frequencies showed no significant differences between the groups, but patients with active HBV and the wild AA genotype presented a positive correlation between increased transaminase and HBV DNA levels and the presence of mild to moderate fibrosis. Patients with HCV and the wild AA genotype presented mild inflammation and higher HCV RNA levels, although the same association was not observed for the fibrosis scores. The results suggest that the mutations in exon 1 of the MBL2 gene do not contribute directly to the clinical and laboratory features of HCV and HBV infections, but further studies should be performed to confirm whether the wild AA genotype has indirect effect on disease progression.