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Aims. Acute-on-chronic liver failure (ACLF) and acute liver failure (ALF) are similar in many respects during their acute exacerbation; however, ACLF generally has a poorer prognosis. We aimed to investigate the role and dynamic changes of regulatory T cell (Treg) and T helper 17 (Th17) cell proportions during ACLF progress. Methods. All rats were classified into two groups randomly: ACLF group and ALF group (control group). The rat model of ACLF was preestablished by intraperitoneal injection of carbon tetrachloride for 2 months. Then acute liver injury was induced by combined D-galactosamine and lipopolysaccharide. Six time points were examined before or after acute induction. Liver samples were performed with hematoxylin-eosin and Masson staining; circulatory Treg and Th17 cell frequencies were determined using flow cytometry assays; serum levels of alanine aminotransferase, aspartate aminotransferase, interleukin-10 (IL-10), and interferon-γ (IFN-γ) were examined. Results. In group ACLF, both Th17 cell proportion and IFN-γ level presented upgrade firstly and then descend latter tendency; the trends of Treg cell proportion and IL-10 level were observed to gradually decrease and became stable. Conclusion. The Treg cells played an important role in the immunologic mechanism during the process of ACLF. And the function of Treg cells in ACLF was defective.

Acetaminophen (APAP) overdose is a common cause of drug-induced acute liver failure. Although hepatocyte cell death is considered to be the critical event in APAP-induced hepatotoxicity, the underlying mechanism remains unclear. Ferroptosis is a newly discovered type of cell death that is caused by a loss of cellular redox homeostasis. As glutathione (GSH) depletion triggers APAP-induced hepatotoxicity, we investigated the role of ferroptosis in a murine model of APAP-induced acute liver failure. APAP-induced hepatotoxicity (evaluated in terms of ALT, AST, and the histopathological score), lipid peroxidation (4-HNE and MDA), and upregulation of the ferroptosis maker PTGS2 mRNA were markedly prevented by the ferroptosis-specific inhibitor ferrostatin-1 (Fer-1). Fer-1 treatment also completely prevented mortality induced by high-dose APAP. Similarly, APAP-induced hepatotoxicity and lipid peroxidation were prevented by the iron chelator deferoxamine. Using mass spectrometry, we found that lipid peroxides derived from n-6 fatty acids, mainly arachidonic acid, were elevated by APAP, and that auto-oxidation is the predominant mechanism of APAP-derived lipid oxidation. APAP-induced hepatotoxicity was also prevented by genetic inhibition of acyl-CoA synthetase long-chain family member 4 or α-tocopherol supplementation. We found that ferroptosis is responsible for APAP-induced hepatocyte cell death. Our findings provide new insights into the mechanism of APAP-induced hepatotoxicity and suggest that ferroptosis is a potential therapeutic target for APAP-induced acute liver failure.

ObjectiveAcute liver failure (ALF) is characterised by overwhelming hepatocyte death and liver inflammation with massive infiltration of myeloid cells in necrotic areas. The mechanisms underlying resolution of acute hepatic inflammation are largely unknown. Here, we aimed to investigate the impact of Mer tyrosine kinase (MerTK) during ALF and also examine how the microenvironmental mediator, secretory leucocyte protease inhibitor (SLPI), governs this response.DesignFlow cytometry, immunohistochemistry, confocal imaging and gene expression analyses determined the phenotype, functional/transcriptomic profile and tissue topography of MerTK+ monocytes/macrophages in ALF, healthy and disease controls. The temporal evolution of macrophage MerTK expression and its impact on resolution was examined in APAP-induced acute liver injury using wild-type (WT) and Mer-deficient (Mer−/−) mice. SLPI effects on hepatic myeloid cells were determined in vitro and in vivo using APAP-treated WT mice.ResultsWe demonstrate a significant expansion of resolution-like MerTK+HLA-DRhigh cells in circulatory and tissue compartments of patients with ALF. Compared with WT mice which show an increase of MerTK+MHCIIhigh macrophages during the resolution phase in ALF, APAP-treated Mer−/− mice exhibit persistent liver injury and inflammation, characterised by a decreased proportion of resident Kupffer cells and increased number of neutrophils. Both in vitro and in APAP-treated mice, SLPI reprogrammes myeloid cells towards resolution responses through induction of a MerTK+HLA-DRhigh phenotype which promotes neutrophil apoptosis and their subsequent clearance.ConclusionsWe identify a hepatoprotective, MerTK+, macrophage phenotype that evolves during the resolution phase following ALF and represents a novel immunotherapeutic target to promote resolution responses following acute liver injury.

Metabolic reprogramming is implicated in macrophage activation, but the underlying mechanisms are poorly understood. Here, we demonstrate that the NOTCH1 pathway dictates activation of M1 phenotypes in isolated mouse hepatic macrophages (HMacs) and in a murine macrophage cell line by coupling transcriptional upregulation of M1 genes with metabolic upregulation of mitochondrial oxidative phosphorylation and ROS (mtROS) to augment induction of M1 genes. Enhanced mitochondrial glucose oxidation was achieved by increased recruitment of the NOTCH1 intracellular domain (NICD1) to nuclear and mitochondrial genes that encode respiratory chain components and by NOTCH-dependent induction of pyruvate dehydrogenase phosphatase 1 (Pdp1) expression, pyruvate dehydrogenase activity, and glucose flux to the TCA cycle. As such, inhibition of the NOTCH pathway or Pdp1 knockdown abrogated glucose oxidation, mtROS, and M1 gene expression. Conditional NOTCH1 deficiency in the myeloid lineage attenuated HMac M1 activation and inflammation in a murine model of alcoholic steatohepatitis and markedly reduced lethality following endotoxin-mediated fulminant hepatitis in mice. In vivo monocyte tracking further demonstrated the requirement of NOTCH1 for the migration of blood monocytes into the liver and subsequent M1 differentiation. Together, these results reveal that NOTCH1 promotes reprogramming of mitochondrial metabolism for M1 macrophage activation.

Hepatic stellate cells are liver-specific mesenchymal cells that play vital roles in liver physiology and fibrogenesis. They are located in the space of Disse and maintain close interactions with sinusoidal endothelial cells and hepatic epithelial cells. It is becoming increasingly clear that hepatic stellate cells have a profound impact on the differentiation, proliferation, and morphogenesis of other hepatic cell types during liver development and regeneration. In this Review, we summarize and evaluate the recent advances in our understanding of the formation and characteristics of hepatic stellate cells, as well as their function in liver development, regeneration, and cancer. We also discuss how improved knowledge of these processes offers new perspectives for the treatment of patients with liver diseases.

Protein delivery with cell-penetrating peptide is opening up the possibility of using targets inside cells for therapeutic or biological applications; however, cell-penetrating peptide-mediated protein delivery commonly suffers from ineffective endosomal escape and low tolerance in serum, thereby limiting in vivo efficacy. Here, we present an intracellular protein delivery system consisting of four modules in series: cell-penetrating peptide, pH-dependent membrane active peptide, endosome-specific protease sites and a leucine zipper. This system exhibits enhanced delivery efficiency and serum tolerance, depending on proteolytic cleavage-facilitated endosomal escape and leucine zipper-based dimerisation. Intravenous injection of protein phosphatase 1B fused with this system successfully suppresses the tumour necrosis factor-α-induced systemic inflammatory response and acetaminophen-induced acute liver failure in a mouse model. We believe that the strategy of using multifunctional chimaeric peptides is valuable for the development of cell-penetrating peptide-based protein delivery systems, and facilitate the development of biological macromolecular drugs for use against intracellular targets. Protein delivery with cell-penetrating peptides suffers from ineffective endosomal escape and low tolerance in serum, thereby limiting treatment success. Here the authors present an intracellular protein delivery system and demonstrate efficient delivery in vitro and therapeutic efficacy in a liver failure model in vivo.

Acute liver failure (ALF) is a life-threatening condition caused by rapid hepatocyte death and impaired liver regeneration. Here we show that extracellular vesicles engineered to express Signal Regulatory Protein Alpha (SIRP-EVs), produced via a scalable 3D bioreactor process with high yield and purity, exhibit significant therapeutic potential by targeting damaged cells and promoting tissue repair. SIRP-EVs block CD47, a crucial inhibitory signal on necroptotic cells, to enhance macrophage-mediated clearance of dying hepatocytes. They also deliver regenerative cargo from mesenchymal stem cells, reprogramming macrophages to support liver regeneration. In male animal models, SIRP-EVs significantly reduce liver injury markers and improve survival, demonstrating their dual-function therapeutic efficacy. By integrating the resolution of necroptosis with regenerative macrophage reprogramming, SIRP-EVs represent a promising platform for restoring liver function. These findings support the development of EV-based in vivo macrophage reprogramming therapies for ALF and other inflammation-driven diseases, paving the way for the clinical application of engineered EV therapeutics. Acute liver failure arises from rapid cell death and impaired liver regeneration. Here, the authors show that scalable, high-purity engineered extracellular vesicles derived from stem cells promote the clearance of dying hepatocytes and drive liver repair through in vivo macrophage reprogramming.

The levels of several cytokines and chemokines are elevated in various liver diseases, especially in fulminant hepatic failure (FHF). Activated macrophages may have a role in the production of these immune modulators. CD163 is a member of a scavenger receptor family and is expressed mainly on activated macrophages, and a soluble form of CD163 (sCD163) is released from activated macrophages. The aim of this study was to assess sCD163 levels in patients with FHF and to evaluate their clinical significance. The levels of sCD163 in the sera were measured in 21 patients with FHF, 17 patients with acute hepatitis (AH), 22 patients with chronic hepatitis (CH), and 14 normal healthy controls (NC), by an enzyme-linked immunosorbent assay. The levels of sCD163 were observed serially in patients with FHF and AH. The levels of sCD163 in the sera from patients with FHF were significantly higher than those in patients with AH and CH and the NC group (P < 0.0001). There was a good correlation between serum levels of sCD163 and prothrombin time (r = -0.677; P < 0.0001). A kinetic study revealed that the levels of sCD163 decreased in patients with AH and in survivors of FHF, whereas the levels of sCD163 progressively increased in nonsurvivors of FHF. This study shows that the products of activated macrophages may be involved in the pathogenesis of FHF. This study also inspires optimism that sCD163 may possess prognostic importance in FHF.

To evaluate liver function using dynamic hepatobiliary single-photon emission computed tomography (SPECT) in different rat models of acute liver failure. Twenty-four 6-8-week-old male Sprague-Dawley rats (weight 190-200 g) were evenly divided into four groups. Acute liver failure was induced by intraperitoneal injection of D-galactosamine (D-GalN, 600 mg/kg) and lipopolysaccharide (LPS, 10 µg/kg), common bile duct ligation surgery, and removing 70% of the liver mass. The fourth group served as the control without intervention. The time-activity curves for the liver and heart were generated from dynamic SPECT scans with 99mTc-ethylene hepatobiliary iminodiacetic acid (EHIDA). Image-derived functional parameters (5-minute heart/liver index [HLI5] and 15-minute receptor index [LHL15]) were calculated. Furthermore, correlations of image-derived parameters with serum interleukin-6 (IL-6) levels, liver aspartate aminotransferase (AST) and alanine transaminase (ALT) levels, and liver mRNA expression levels of tumor necrosis factor-α (TNF-α) and chemokine ligand-10 (CXCL-10) were analyzed. All animals in the experimental groups exhibited varying degrees of liver damage. The SPECT images and indexes (HLI5 and LHL15) of the experimental groups significantly differed from those of the control group (P < 0.05). In the experimental groups, serum IL-6 levels and liver mRNA levels of TNF-α and CXCL-10 were significantly higher, while liver AST and ALT levels were significantly lower than those in the control group (P < 0.05). Using SPECT with 99mTc-EHIDA, along with the calculated indexes and levels of various cytokines, presents a dependable method for assessing liver function.

The present study aimed to investigate the anti-ferroptosis effects of the HMGB1 inhibitor glycyrrhizin (GLY). The present study used a cell and animal model of acute liver failure (ALF), induced using tumor necrosis factor-α, lipopolysaccharide and D-galactosamine, to investigate the effects of GLY. The expression of glutathione peroxidase 4 (GPX4) and high mobility group protein B1 (HMGB1), heme oxygenase-1 (HO-1) and nuclear factor erythroid 2-related factor 2 (Nrf2) were detected were detected by western blotting in L02 hepatocytes and mouse liver. The expression of GPX4 and HMGB1 in L02 hepatocytes and mouse liver was detected by immunofluorescence. The pathological changes to liver tissues were determined by hematoxylin and eosin staining. The levels of lactate dehydrogenase (LDH), Fe2+, reactive oxygen species (ROS) and glutathione (GSH) were tested using kits. Compared with the normal group, the degree of liver damage and liver function in the model animal group was severe. The protein levels of HMGB1 in L02 cells and liver tissues were significantly increased. The expression of NRF2, HO-1 and GPX4 was significantly decreased. The levels of LDH, Fe2+, malondialdehyde (MDA) and ROS were increased, whereas the level of GSH was decreased. Treatment with GLY reduced the degree of liver damage, the expression of HMGB1 was decreased, and the levels of Nrf2, HO-1 and GPX4 were increased. The levels of LDH, Fe2+, MDA, ROS were decreased, while the level of GSH was increased by GLY treatment. The results of the present study indicated that HMGB1 is involved in the process of ferroptosis. The HMGB1 inhibitor GLY significantly reduced the degree of ferroptosis during ALF by inhibiting oxidative stress.