Modulation of monocyte/macrophage function: a therapeutic strategy in the treatment of acute liver failure

FTY720 alleviates D-GalN/LPS-induced acute liver failure by regulating the JNK/MAPK pathway

Acute liver failure (ALF) poses a considerable health and economic burden worldwide and has limited treatment options. Sphingosine-1-phosphate (S1P) is a pleiotropic bioactive phospholipid that participates in various cellular processes by through S1P receptors (S1PRs). Previous studies have showed that the hepatic S1P levels were increased. Notably, deletion or inhibition of sphingosine kinase 1 (SphK1), the key enzyme responsible for S1P biosynthesis, could alleviate D-galactosamine (D-GalN)/lipopolysaccharide (LPS)-induced ALF in mice. However, the role of the S1P receptor modulator FTY720 in ALF remains unclear. In this study, we investigated the effects of FTY720 on D-GalN/LPS-induced ALF model. Our results demonstrated that FTY720 pretreatment significantly alleviated liver injury, decreased the serum levels of alanine aminotransferase and aspartate aminotransferase, and mitigated histopathological damage in ALF model mice. Mechanistically, FTY720 could inhibit the inflammatory response and reduced apoptosis. The protective effect of FTY720 was mediated by c-Jun N-terminal kinase (JNK)/mitogen-activated protein kinase (MAPK) signalling. A pharmacological JNK activator (anisomycin) partially counteracted these protective effects. FTY720, targeting S1PRs, is expected to be an effective therapeutic strategy for ALF.

MSCs Suppress Macrophage Necroptosis and Foster Liver Regeneration by Modulating SP1/SK1 Axis in Treating Acute Severe Autoimmune Hepatitis

Acute severe autoimmune hepatitis (AS-AIH) is characterized by rapid progression and poor prognosis, with a current lack of effective targeted treatments. Stem cell therapy has demonstrated significant therapeutic promise across various autoimmune diseases. However, the intricate pathogenesis of AS-AIH has hindered the widespread utilization of mesenchymal stem cells (MSCs) in this domain. Herein, it is demonstrated that necroptosis, as the primary mode of cell death in AIH, is crucial in causing AS-AIH. Inflammatory macrophages are the primary cell population involved in necroptosis. Inhibition of the specificity protein 1/sphingosine kinase 1/sphingosine-1-phosphate (SP1/SK1/S1P) axis is responsible for this phenomenon, leading to excessive activation of the intrahepatic immune system and aggravating liver damage. Furthermore, the S1P/S1PR2/YAP axis is the key pathway in initiating liver regeneration during AS-AIH. S1P synthesized by hepatocytes is the primary source, and this process is also regulated by the SP1/SK1 axis. MSCs promote S1P synthesis by macrophages through the delivery of SP1, which inhibits necroptosis and synergistically enhances liver regeneration. In addition, MSCs also promote S1P synthesis in hepatocytes through the same mechanism, further aiding liver regeneration. These findings unveil the core pathogenesis of AS-AIH and provide a theoretical foundation for using MSCs as a potential targeted therapeutic modality.

Ameliorating macrophage pyroptosis via ANXA1/NLRP3/Caspase-1/GSDMD pathway: Ac2-26/OGP-loaded intelligent hydrogel enhances bone healing in diabetic periodontitis

Craniofacial bone defect healing in periodontitis patients with diabetes background has long been difficult due to increased blood glucose levels which cause overproduction of reactive oxygen species (ROS) and a low pH environment. These conditions negatively affect the function of macrophages, worsen inflammation and oxidative stress, and ultimately, hinder osteoblasts' bone repair potential. In this study, we for the first time found that annexin A1 (ANXA1) expression in macrophages was reduced in a diabetic periodontitis (DP) environment, with the activation of the NLRP3/Caspase-1/GSDMD signaling pathway, and, eventually, increased macrophage pyroptosis. Next, we have developed a new GPPG intelligent hydrogel system which was ROS and pH responsive, and loaded with Ac2-26, an ANXA1 bioactive peptide, and osteogenic peptide OGP as well. We found that Ac2-26/OGP/GPPG can effectively reduce ROS, mitigates macrophage pyroptosis via the ANXA1/NLRP3/Caspase-1/GSDMD pathway and enhanced osteogenic differentiation. The effect of Ac2-26/OGP/GPPG in regulation of pyroptosis and bone defect repair was also further validated by animal experiments on periodontitis-induced tooth loss model in diabetic rats. To conclude, our study unveils the effect of ANXA1 on macrophage pyroptosis in periodontitis patients with diabetes, based on which we introduced a promising innovative hydrogel system for improvement of bone defects repair in DP patients via targeting macrophage pyroptosis and enhancing osteogenic potential.

PKM2-mediated STAT3 phosphorylation promotes acute liver failure via regulating NLRP3-dependent pyroptosis

Acute liver failure (ALF) is a life-threatening clinical syndrome characterized by high-grade inflammation and multi-organ failure. Our previous study shows that targeting the M2 isoform of pyruvate kinase (PKM2) to inhibit macrophage inflammation may be a promising strategy for ALF treatment. however, the mechanism by which PKM2 regulates the inflammatory response is unclear. Here we demonstrate that PKM2 contributes to ALF by modulating NLRP3-mediated pyroptosis activation in liver macrophages. The specific knockout of PKM2 in myeloid cells reduces mortality and alleviates hepatic injury in D-galactosamine/LPS-induced ALF mice. Single-cell transcriptome analysis suggests that NLRP3 inflammasome activation of macrophages involves in ALF, knockout of PKM2 in macrophages reduces the expression of NLRP3, and activation of pyroptosis. Pharmacological inhibition of the PKM2 nuclear translocation, but not glycolytic activity, protects mice from ALF. Pharmacological and genetic inhibition of PKM2 attenuates NLRP3-mediated pyroptosis activation and consequently reduces the release of IL-1β and IL-18 by macrophages. Mechanistically, PKM2 translocates into the nucleus and combines with STAT3, enhancing its phosphorylation and recruitment to the NLRP3 promoter region, thereby increasing NLRP3 expression. This work defines PKM2 acts as an important nonmetabolic regulator of NLRP3 that modulates pyroptosis activation in macrophages and guides future therapeutic strategies development for ALF.

Metabolic Reprograming of Macrophages: A New Direction in Traditional Chinese Medicine for Treating Liver Failure

Acute liver failure (ALF) is a fulminant clinical syndrome that usually leads to multiple organ failure and high mortality. Macrophages play a crucial role in the initiation, development, and recovery of ALF. Targeting macrophages through immunotherapy holds significant promise as a therapeutic strategy. These cells exhibit remarkable plasticity, enabling them to differentiate into various subtypes based on changes in their surrounding microenvironment. M1-type macrophages are associated with a pro-inflammatory phenotype and primarily rely predominantly on glycolysis. In contrast, M2-type macrophages, which are characterized by anti-inflammatory phenotype, predominantly obtain their energy from oxidative phosphorylation (OXPHOS) and fatty acid oxidation (FAO). Shifting macrophage metabolism from glycolysis to OXPHOS inhibits M1 macrophage activation and promotes M2 macrophage activation, thereby exerting anti-inflammatory and reparative effects. This study elucidates the relationship between macrophage activation and glucose metabolism reprograming from an immunometabolism perspective. A comprehensive literature review revealed that several signaling pathways may regulate macrophage polarization through energy metabolism, including phosphatidyl-inositol 3-kinase/protein kinase B (PI3K/AKT), mammalian target of rapamycin (mTOR)/hypoxia-inducible factor 1α (HIF-1α), nuclear factor-κB (NF-κB), and AMP-activated protein kinase (AMPK), which exhibit crosstalk with one another. Additionally, we systematically reviewed several traditional Chinese medicine (TCM) monomers that can modulate glucose metabolism reprograming and influence the polarization states of M1 and M2 macrophages. This review aimed to provide valuable insights that could contribute to the development of new therapies or drugs for ALF.

Sappanone A enhances hepatocyte proliferation in lipopolysaccharide-induced acute liver injury in mice by promoting injured hepatocyte apoptosis and regulating macrophage polarization

OBJECTIVES

Lipopolysaccharide (LPS), also known as endotoxin, is the main toxic component of the cell wall of gram negative bacteria, which is released after bacterial death and widely exists in the living environment. Human exposure to endotoxin may cause sepsis. The occurrence of septic liver injury is a prominent factor contributing to mortality in patients with sepsis. The purpose of this study is to explore the role of Sappanone A (SA), a homoisoflavonoid isolated from the heartwood of Caesalpinia sappan Linn., in LPS-induced acute liver injury (ALI).

METHODS

An LPS-induced ALI mouse model was used to evaluate the effects of SA on septic ALI, and murine cells were treated with LPS to explore the mechanisms underlying SA-provided effects.

RESULTS

Treating SA substantially improved LPS-induced ALI. We also performed in silico prediction and RNA-seq analysis to elucidate SA's potential mechanisms of action. The terms generated by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment of predicted target proteins of SA include inflammation, oxidative stress, and apoptosis; protein-protein interaction network (PPI) analysis indicated that fas binding protein 1 (Fbf1) has the strongest correlation with SA. Consistently, RNA-seq analysis displayed that SA administration regulates cell apoptosis and inflammatory responses, which was further confirmed by checking related markers in livers of mice and murine cells challenged with LPS. Of note, SA significantly decreased the expression of Fbf1 in mouse livers, and promoted apoptosis of injured hepatocytes and hepatocyte proliferation, which were substantially abolished by Fbf1 knockdown in AML12 cells. Besides, SA could increase M2 phenotype polarization but inhibit M1 macrophage polarization in LPS-induced ALI in mice.

CONCLUSION

SA enhances hepatocyte proliferation and liver repair in LPS-induced ALI in mcie by promoting injured hepatocyte apoptosis through Fbf1 inhibition and regulating macrophage polarization.

CCL25 contributes to the pathogenesis of D-Gal/LPS-induced acute liver failure

BACKGROUND AND AIM

Acute liver failure (ALF) is a fatal clinical syndrome of severe hepatic dysfunction. Chemokines promote liver diseases by recruiting and activating immune cells. We aimed to investigate the role of C-C chemokine ligand 25 (CCL25) in ALF.

METHODS

An ALF mouse model induced by D-galactosamine/lipopolysaccharide was evaluated through liver hematoxylin and eosin staining and serum transaminase and cytokine measurement. CCL25 expression in serum was analyzed by ELISA and in liver by immunohistochemical staining and western blot. C-C chemokine receptor 9 (CCR9)-expressing cells in the liver were identified by immunofluorescence staining. The effects of anti-CCL25 on ALF were evaluated in vivo. Cytokine expression and migration of CCL25-stimulated RAW264.7 macrophages were studied. We also investigated the role of anti-CCL25 and BMS-345541, an NF-κB signaling inhibitor, in vitro. NF-κB activation was assessed via western blot, and p65 nuclear translocation was detected using cellular immunofluorescence.

RESULTS

ALF mice showed severe histological damage and high serum levels of aminotransferase and inflammatory cytokines. Elevated CCL25 and NF-κB activation was observed in vivo. CCR9 was expressed on macrophages in ALF mouse liver. ALF was suppressed after anti-CCL25 treatment, with significant NF-κB inhibition. In vitro, CCL25 induced strong migration and cytokine release in RAW264.7 macrophages, which were eliminated by anti-CCL25 and BMS-345541. Furthermore, the NF-κB activation and p65 nuclear translocation induced by CCL25 were also inhibited by anti-CCL25 and BMS-345541.

CONCLUSION

CCL25 contributes to ALF development by inducing macrophage-mediated inflammation via activation of the NF-κB signaling.

CD24 regulates liver immune response and ameliorates acute hepatic injury through controlling hepatic macrophages

Liver injury releases danger-associated molecular patterns, which trigger the immune response. CD24 negatively regulates the immune response by binding with danger-associated molecular patterns, but the specific role of CD24 in modulating macrophage-related inflammation during liver injury remains largely unexplored. Here, we aimed to investigate the mechanisms of macrophage CD24 in the development of liver injury. Our results show that CD24 expression is upregulated primarily in hepatic macrophages (HMs) during acute liver injury. CD24-deficient mice exhibited more severe liver injury and showed a significantly higher frequency and number of HMs, particularly Ly6Chi monocyte-derived macrophages. Mechanistically, the CD24-Siglec-G interaction plays a vital role in mitigating acute liver injury. CD24-mediated inhibitory signaling in HMs primarily limits downstream NF-κB and p38 MAPK activation through the recruitment of SHP1. Our work unveils the critical role of macrophage CD24 in negatively regulating innate immune responses and protecting against acute liver injury, thus providing potential therapeutic targets for liver-associated diseases.

Continuous renal replacement therapy and therapeutic plasma exchange in pediatric liver failure

Patients with acute liver failure (ALF) and acute on chronic liver failure (ACLF) have significant morbidity and mortality. They require extracorporeal blood purification modalities like continuous renal replacement therapy (CRRT) and therapeutic plasma exchange (TPE) as a bridge to recovery or liver transplantation. Limited data are available on the outcomes of patients treated with these therapies. This is a retrospective single-center study of 23 patients from 2015 to 2022 with ALF/ACLF who underwent CRRT and TPE. We aimed to describe the clinical characteristics and outcomes of these patients. Median (IQR) age was 0.93 years (0.57, 9.88), range 16 days to 20 years. Ten (43%) had ALF and 13 (57%) ACLF. Most (n = 19, 82%) started CRRT for hyperammonemia and/or hepatic encephalopathy and all received TPE for refractory coagulopathy. CRRT was started at a median of 2 days from ICU admission, and TPE started on the same day in most. The liver transplant was done in 17 (74%), and 2 recovered native liver function. Four patients, all with ACLF, died prior to ICU discharge without a liver transplant. The median peak ammonia pre-CRRT was 131 µmol/L for the whole cohort. The mean (SD) drop in ammonia after 48 h of CRRT was 95.45 (43.72) µmol/L in those who survived and 69.50 (21.70) µmol/L in those who did not (p 0.26). Those who survived had 0 median co-morbidities compared to 2.5 in non-survivors (aOR (95% CI) for mortality risk of 2.5 (1.1-5.7), p 0.028).  Conclusion: In this cohort of 23 pediatric patients with ALF or ACLF who received CRRT and TPE, 83% survived with a liver transplant or recovered with their native liver. Survival was worse in those who had ACLF and those with co-morbid conditions. What is Known: •  Pediatric acute liver failure is associated with high mortality. •  Patients may require extracorporeal liver assist therapies (like CRRT, TPE, MARS, SPAD) to bridge them over to a transplant or recovery of native liver function. What is New: • Standard volume plasma exhange has not been evaluated against high volume plasma exchange for ALF. • The role, dose, and duration of therapeutic plasma exchange in patients with acute on chronic liver failure is not well described.

Good Cells Go Bad: Immune Dysregulation in the Transition from Acute Liver Injury to Liver Failure After Acetaminophen Overdose

The role of inflammatory cells and other components of the immune system in acetaminophen (APAP)-induced liver injury and repair has been extensively investigated. Although this has resulted in a wealth of information regarding the function and regulation of immune cells in the liver after injury, apparent contradictions have fueled controversy around the central question of whether the immune system is beneficial or detrimental after APAP overdose. Ultimately, this may not be a simple assignment of "good" or "bad." Clinical studies have clearly demonstrated an association between immune dysregulation and a poor outcome in patients with severe liver damage/liver failure induced by APAP overdose. To date, studies in mice have not uniformly replicated this connection. The apparent disconnect between clinical and experimental studies has perhaps stymied progress and further complicated investigation of the immune system in APAP-induced liver injury. Mouse models are often dismissed as not recapitulating the clinical scenario. Moreover, clinical investigation is most often focused on the most severe APAP overdose patients, those with liver failure. Notably, recent studies have made it apparent that the functional role of the immune system in the pathogenesis of APAP-induced liver injury is highly context dependent and greatly influenced by the experimental conditions. In this review, we highlight some of these recent findings and suggest strategies seeking to resolve and build on existing disconnects in the literature. SIGNIFICANCE STATEMENT: Acetaminophen overdose is the most frequent cause of acute liver failure in the United States. Studies indicate that dysregulated innate immunity contributes to the transition from acute liver injury to acute liver failure. In this review, we discuss the evidence for this and the potential underlying causes.

Peripheral Injection of hUC-MSCs in the Treatment of Acute Liver Failure: A Pre-Clinical Cohort Study in Rhesus Monkeys

BACKGROUND

Using a toxin-induced lethal acute liver failure (ALF) monkey model, we have recently shown that early peripheral infusion of human umbilical cord mesenchymal stem cells (hUC-MSCs) can alleviate liver damage and improve animal survival by suppressing the activation of circulating monocytes and the subsequent cytokine storm. Here, we explored whether the administration of hUC-MSCs could still improve ALF when the cytokine storm is fully developed.

METHOD

We treated ALF monkeys with peripheral delivery of hUC-MSCs at 48 hr after toxin challenge. Liver indices, histology, imaging, and animal survival were recorded and analyzed.

RESULTS

In our cohort study, we conducted and demonstrated that the infusion of hUC-MSCs significantly improved liver histology, effectively controlled inflammatory cytokine storms, and increased survival rates. Additionally, the administration of a higher dose of hUC-MSCs (2 × 107/monkey) yielded superior outcomes compared to a lower dose (1 × 107/monkey).

CONCLUSION

Treatment of hUC-MSCs can significantly improve the pathological and survival outcomes of ALF even when the cytokine storm has been fully developed, indicating a promising clinical solution for ALF.

Mesenchymal Stem Cells Alleviate Acute Liver Failure through Regulating Hepatocyte Apoptosis and Macrophage Polarization

BACKGROUND AND AIMS

Acute liver failure (ALF) is a life-threatening clinical problem with limited treatment options. Administration of human umbilical cord mesenchymal stem cells (hUC-MSCs) may be a promising approach for ALF. This study aimed to explore the role of hUC-MSCs in the treatment of ALF and the underlying mechanisms.

METHODS

A mouse model of ALF was induced by lipopolysaccharide and d-galactosamine administration. The therapeutic effects of hUC-MSCs were evaluated by assessing serum enzyme activity, histological appearance, and cell apoptosis in liver tissues. The apoptosis rate was analyzed in AML12 cells. The levels of inflammatory cytokines and the phenotype of RAW264.7 cells co-cultured with hUC-MSCs were detected. The C-Jun N-terminal kinase/nuclear factor-kappa B signaling pathway was studied.

RESULTS

The hUC-MSCs treatment decreased the levels of serum alanine aminotransferase and aspartate aminotransferase, reduced pathological damage, alleviated hepatocyte apoptosis, and reduced mortality in vivo. The hUC-MSCs co-culture reduced the apoptosis rate of AML12 cells in vitro. Moreover, lipopolysaccharide-stimulated RAW264.7 cells had higher levels of tumor necrosis factor-α, interleukin-6, and interleukin-1β and showed more CD86-positive cells, whereas the hUC-MSCs co-culture reduced the levels of the three inflammatory cytokines and increased the ratio of CD206-positive cells. The hUC-MSCs treatment inhibited the activation of phosphorylated (p)-C-Jun N-terminal kinase and p-nuclear factor-kappa B not only in liver tissues but also in AML12 and RAW264.7 cells co-cultured with hUC-MSCs.

CONCLUSIONS

hUC-MSCs could alleviate ALF by regulating hepatocyte apoptosis and macrophage polarization, thus hUC-MSC-based cell therapy may be an alternative option for patients with ALF.

Siglec-H-/- Plasmacytoid Dendritic Cells Protect Against Acute Liver Injury by Suppressing IFN-γ/Th1 Response and Promoting IL-21+ CD4 T Cells

BACKGROUND & AIMS

Siglec-H is a receptor specifically expressed in mouse plasmacytoid dendritic cells (pDCs), which functions as a negative regulator of interferon-α production and plays a critical role in pDC maturation to become antigen-presenting cells. The function of pDCs in autoimmune and inflammatory diseases has been reported. However, the effect of Siglec-H expression in pDCs in liver inflammation and diseases remains unclear.

METHODS

Using the model of concanavalin A-induced acute liver injury (ALI), we investigated the Siglec-H/pDCs axis during ALI in BDCA2 transgenic mice and Siglec-H-/- mice. Anti-BDCA2 antibody, anti-interleukin (IL)-21R antibody, and Stat3 inhibitor were used to specifically deplete pDCs, block IL21 receptor, and inhibit Stat3 signaling, respectively. Splenocytes and purified naive CD4 T cells and bone marrow FLT3L-derived pDCs were cocultured and stimulated with phorbol myristate acetate/ionomycin and CD3/CD28 beads, respectively.

RESULTS

Data showed that specific depletion of pDCs aggravated concanavalin A-induced ALI. Remarkably, alanine aminotransferase, hyaluronic acid, and proinflammatory cytokines IL6 and tumor necrosis factor-α levels were lower in the blood and liver of Siglec-H knockout mice. This was associated with attenuation of both interferon-γ/Th1 response and Stat1 signaling in the liver of Siglec-H knockout mice while intrahepatic IL21 and Stat3 signaling pathways were upregulated. Blocking IL21R or Stat3 signaling in Siglec-H knockout mice restored concanavalin A-induced ALI. Finally, we observed that the Siglec-H-null pDCs exhibited immature and immunosuppressive phenotypes (CCR9LowCD40Low), resulting in reduction of CD4 T-cell activation and promotion of IL21+CD4 T cells in the liver.

CONCLUSIONS

During T-cell-mediated ALI, Siglec-H-null pDCs enhance immune tolerance and promote IL21+CD4 T cells in the liver. Targeting Siglec-H/pDC axis may provide a novel approach to modulate liver inflammation and disease.

A novel role for the ROS-ATM-Chk2 axis mediated metabolic and cell cycle reprogramming in the M1 macrophage polarization

Reactive oxygen species (ROS) play a pivotal role in macrophage-mediated acute inflammation. However, the precise molecular mechanism by which ROS regulate macrophage polarization remains unclear. Here, we show that ROS function as signaling molecules that regulate M1 macrophage polarization through ataxia-telangiectasia mutated (ATM) and cell cycle checkpoint kinase 2 (Chk2), vital effector kinases in the DNA damage response (DDR) signaling pathway. We further demonstrate that Chk2 phosphorylates PKM2 at the T95 and T195 sites, promoting glycolysis and facilitating macrophage M1 polarization. In addition, Chk2 activation increases the Chk2-dependent expression of p21, inducing cell cycle arrest for subsequent macrophage M1 polarization. Finally, Chk2-deficient mice infected with lipopolysaccharides (LPS) display a significant decrease in lung inflammation and M1 macrophage counts. Taken together, these results suggest that inhibiting the ROS-Chk2 axis can prevent the excessive inflammatory activation of macrophages, and this pathway can be targeted to develop a novel therapy for inflammation-associated diseases and expand our understanding of the pathophysiological functions of DDR in innate immunity.

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.

Albiflorin Alleviates Sepsis-induced Acute Liver Injury through mTOR/p70S6K Pathway

BACKGROUND

Sepsis often induces hepatic dysfunction and inflammation, accounting for a significant increase in the incidence and mortality rates. To this end, albiflorin (AF) has garnered enormous interest due to its potent anti-inflammatory activity. However, the substantial effect of AF on sepsis-mediated acute liver injury (ALI), along with its potential mechanism of action, remains to be explored.

METHODS

An LPS-mediated primary hepatocyte injury cell model in vitro and a mouse model of CLP-mediated sepsis in vivo were initially built to explore the effect of AF on sepsis. Furthermore, the hepatocyte proliferation by CCK-8 assay in vitro and animal survival analyses in vivo for the survival time of mice were carried out to determine an appropriate concentration of AF. Then, flow cytometry, Western blot (WB), and TUNEL staining analyses were performed to investigate the effect of AF on the apoptosis of hepatocytes. Moreover, the expressions of various inflammatory factors by ELISA and RT-qPCR analyses and oxidative stress by ROS, MDA, and SOD assays were determined. Finally, the potential mechanism of AF alleviating the sepsis-mediated ALI via the mTOR/p70S6K pathway was explored through WB analysis.

RESULTS

AF treatment showed a significant increase in the viability of LPS-inhibited mouse primary hepatocytes cells. Moreover, the animal survival analyses of the CLP model mice group indicated a shorter survival time than the CLP+AF group. AF-treated groups showed significantly decreased hepatocyte apoptosis, inflammatory factors, and oxidative stress. Finally, AF exerted an effect by suppressing the mTOR/p70S6K pathway.

CONCLUSION

In summary, these findings demonstrated that AF could effectively alleviate sepsis-mediated ALI via the mTOR/p70S6K signaling pathway.

The role and mechanisms of macrophage polarization and hepatocyte pyroptosis in acute liver failure

Acute liver failure (ALF) is a severe liver disease caused by disruptions in the body's immune microenvironment. In the early stages of ALF, Kupffer cells (KCs) become depleted and recruit monocytes derived from the bone marrow or abdomen to replace the depleted macrophages entering the liver. These monocytes differentiate into mature macrophages, which are activated in the immune microenvironment of the liver and polarized to perform various functions. Macrophage polarization can occur in two directions: pro-inflammatory M1 macrophages and anti-inflammatory M2 macrophages. Controlling the ratio and direction of M1 and M2 in ALF can help reduce liver injury. However, the liver damage caused by pyroptosis should not be underestimated, as it is a caspase-dependent form of cell death. Inhibiting pyroptosis has been shown to effectively reduce liver damage induced by ALF. Furthermore, macrophage polarization and pyroptosis share common binding sites, signaling pathways, and outcomes. In the review, we describe the role of macrophage polarization and pyroptosis in the pathogenesis of ALF. Additionally, we preliminarily explore the relationship between macrophage polarization and pyroptosis, as well as their effects on ALF.

Prevalence, Risk Factors, and Impact of Bacterial or Fungal Infections in Acute Liver Failure Patients from India

BACKGROUND

We evaluated the prevalence, risk factors, and impact of bacterial/fungal infections in acute liver failure (ALF) patients.

METHODS

We analyzed clinical, biochemical, and microbiological data of ALF patients with and without bacterial/fungal infections admitted at an institute over the last 5 years.

RESULTS

We enrolled 143 patients, 50% males, median age 25 years, with acute viral hepatitis (32.2%), drug-induced injury (18.2%), and tropical illness (14%) as aetiologies of ALF. 110 patients (76.9%) developed bacterial/fungal infections [Bacterial infection: MDR: 70%, PDR: 7%, ESBL: 40%, CRE: 30%, CRAB: 26.6%, MDR-EF: 13.3% and fungal infection: 19 (17.3%)]. On univariable analysis, SIRS (33.6% vs.3%), ICU admission (78.2% vs. 45.5%), mechanical ventilation (88.2% vs. 51.5%), inotropes (39.1% vs. 6.1%), invasive catheters (91.8% vs. 39.4%), and prolonged catheterization (6 days vs. 0 days) were significant risk factors for infections (p < 0.05, each). In contrast, SIRS and catheterization independently predicted infection on multivariable regression. Organ failures [3 (2-4) vs. 1 (0-2)], grade-III-IV HE (67.3% vs. 33.3%), circulatory failure (39.1% vs. 6.1%), coagulopathy (INR > 2.5: 58.2% vs. 33.3%), renal injury (28.2% vs. 6.1%) (p < 0.05), MELD (32.9 ± 8.2 vs. 26.7 ± 8.3) and CPIS [3(2-4) vs. 2(0-2)] were higher in infected vs. non-infected patients (p < 0.001). 30-day survival was significantly lower in infected vs. non-infected patients (17.3% vs. 75.8%, p < 0.001), while no patient survived with fungal infections. Refractory septic shock was the commonest cause of mortality in patients.

CONCLUSIONS

Infections due to MDR organisms are high, fungal infections are fatal, and refractory septic shock is the dominant reason for mortality, implying bacterial and fungal infections as the major killer in ALF patients.

HIF-1α inhibition in macrophages preserves acute liver failure by reducing IL-1β production

The development of acute liver failure (ALF) is dependent on its local inducer. Inflammation is a high-frequency and critical factor that accelerates hepatocyte death and liver failure. In response to injury stress, the expression of the transcription factor hypoxia-inducible factor-1α (HIF-1α) in macrophages is promoted by both oxygen-dependent and oxygen-independent mechanisms, thus promoting the expression and secretion of the cytokine interleukin-1β (IL-1β). IL-1β further induces hepatocyte apoptosis or necrosis by signaling through the receptor (IL-1R) on hepatocyte. HIF-1α knockout in macrophages or IL-1R knockout in hepatocytes protects against liver failure. However, whether HIF-1α inhibition in macrophages has a protective role in ALF is unclear. In this study, we revealed that the small molecule HIF-1α inhibitor PX-478 inhibits the expression and secretion of IL-1β, but not tumor necrosis factor α (TNFα), in bone marrow-derived macrophages (BMDMs). PX-478 pretreatment alleviates liver injury in LPS/D-GalN-induced ALF mice by decreasing the hepatic inflammatory response. In addition, preventive or therapeutic administration of PX-478 combined with TNFα neutralizing antibody markedly improved LPS/D-GalN-induced ALF. Taken together, our data suggest that PX-478 administration leads to HIF-1α inhibition and decreased IL-1β secretion in macrophages, which represents a promising therapeutic strategy for inflammation-induced ALF.

Artificial cells delivering itaconic acid induce anti-inflammatory memory-like macrophages to reverse acute liver failure and prevent reinjury

Hepatic macrophages represent a key cellular component of the liver and are essential for the progression of acute liver failure (ALF). We construct artificial apoptotic cells loaded with itaconic acid (AI-Cells), wherein the compositions of the synthetic plasma membrane and surface topology are rationally engineered. AI-Cells are predominantly localized to the liver and further transport to hepatic macrophages. Intravenous administration of AI-Cells modulates macrophage inflammation to protect the liver from acetaminophen-induced ALF. Mechanistically, AI-Cells act on caspase-1 to suppress NLRP3 inflammasome-mediated cleavage of pro-IL-1β into its active form in macrophages. Notably, AI-Cells specifically induce anti-inflammatory memory-like hepatic macrophages in ALF mice, which prevent constitutive overproduction of IL-1β when liver reinjury occurs. In light of AI-Cells' precise delivery and training of memory-like hepatic macrophages, they offer promising therapeutic potential in reversing ALF by finely controlling inflammatory responses and orchestrating liver homeostasis, which potentially affect the treatment of various types of liver failure.

Liver Regeneration in Acute on Chronic Liver Failure

Liver regeneration is a multifaceted process by which the organ regains its original size and histologic organization. In recent decades, substantial advances have been made in our understanding of the mechanisms underlying regeneration following loss of hepatic mass. Liver regeneration in acute liver failure possesses several classic pathways, while also exhibiting unique differences in key processes such as the roles of differentiated cells and stem cell analogs. Here we summarize these unique differences and new molecular mechanisms involving the gut-liver axis, immunomodulation, and microRNAs with an emphasis on applications to the patient population through stem cell therapies and prognostication.

Repurposing Niclosamide as a Therapeutic Drug against Acute Liver Failure by Suppressing Ferroptosis

Acute liver failure (ALF) is a severe liver disease with a high mortality rate without effective therapeutic drugs. Ferroptosis is a form of programmed cell death that plays an important role in ALF. In this study, we aimed to identify ferroptosis-related genes in ALF, thereby predicting promising compounds to treat ALF. First, mRNA microarray data were utilized to identify the ferroptosis-related differentially expressed genes (DEGs). Hub genes were screened in the protein-protein interaction network and validated. Subsequently, potential drugs to treat ALF were predicted. One of the predicted drugs was tested in an ALF model of mice. Ferroptosis examination and molecular docking were analyzed to explore the mechanism. A total of 37 DEGs were identified, ten hub genes were extracted, and their expression in ALF was validated. The predicted drug niclosamide mitigated lipopolysaccharide/D-galactosamine-induced hepatotoxicity, and decreased mortality of mice in the ALF model. Mechanically, niclosamide may combine with signal transducer and activator of transcription 3 to inhibit ALF progression by suppressing ferroptosis. This study may help advance our understanding of the role of ferroptosis in ALF, and niclosamide may be promising for therapeutic efficacy in patients with ALF.

LncRNA 220: A Novel Long Non-Coding RNA Regulates Autophagy and Apoptosis in Kupffer Cells via the miR-5101/PI3K/AKT/mTOR Axis in LPS-Induced Endotoxemic Liver Injury in Mice

Sepsis is a severe medical condition distinguished by immune systematic dysfunction and multiple organic injury, or even failure, resulting from an acute systemic inflammatory response. Acute liver injury (ALI) could be considered as a notable inflammatory outcome of sepsis. Studies have demonstrated the essential roles played by long non-coding RNAs (lncRNAs) in mediating the processes of various diseases, including their ability to engage in interactions with microRNAs (miRNAs) as complexes of competing endogenous RNA (ceRNA) to modulate signaling pathways. In this study, a newly discovered lncRNA, named 220, was identified to function in regulating autophagy and apoptosis in Kupffer cells treated with lipopolysaccharide (LPS). This was achieved through sponging miR-5101 as a ceRNA complex, as identified via high-throughput sequencing. The expression of 220 was found to be significantly different in the hepatic tissues of endotoxemic mice that were treated with LPS for 8 h, ultimately modulating the ALI process. Our studies have collectively demonstrated that 220 is a novel regulator that acts on LPS-induced autophagy and apoptosis in Kupffer cells, thereby mediating the ALI process induced by LPS. Furthermore, the validation of our findings using clinical databases suggests that 220 could potentially serve as a molecular target of clinical, diagnostic, and therapeutic significance in septic liver injury.

Orchestrated regulation of immune inflammation with cell therapy in pediatric acute liver injury

Acute liver injury (ALI) in children, which commonly leads to acute liver failure (ALF) with the need for liver transplantation, is a devastating life-threatening condition. As the orchestrated regulation of immune hemostasis in the liver is essential for resolving excess inflammation and promoting liver repair in a timely manner, in this study we focused on the immune inflammation and regulation with the functional involvement of both innate and adaptive immune cells in acute liver injury progression. In the context of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic, it was also important to incorporate insights from the immunological perspective for the hepatic involvement with SARS-CoV-2 infection, as well as the acute severe hepatitis of unknown origin in children since it was first reported in March 2022. Furthermore, molecular crosstalk between immune cells concerning the roles of damage-associated molecular patterns (DAMPs) in triggering immune responses through different signaling pathways plays an essential role in the process of liver injury. In addition, we also focused on DAMPs such as high mobility group box 1 (HMGB1) and cold-inducible RNA-binding protein (CIRP), as well as on macrophage mitochondrial DNA-cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway in liver injury. Our review also highlighted novel therapeutic approaches targeting molecular and cellular crosstalk and cell-based therapy, providing a future outlook for the treatment of acute liver injury.

Oral Delivery of siRNA Using Fluorinated, Small-Sized Nanocapsules toward Anti-Inflammation Treatment

Oral delivery of small interfering RNA (siRNA) provides a promising paradigm for treating diseases that require regular injections. However, the multiple gastrointestinal (GI) and systemic barriers often lead to inefficient oral absorption and low bioavailability of siRNA. Technologies that can overcome these barriers are still lacking, which hinders the clinical potential of orally delivered siRNA. Herein, small-sized, fluorinated nanocapsules (F-NCs) are developed to mediate efficient oral delivery of tumor necrosis factor α (TNF-α) siRNA for anti-inflammation treatment. The NCs possess a disulfide-cross-linked shell structure, thus featuring robust stability in the GI tract. Because of their small size (≈30 nm) and fluorocarbon-assisted repelling of mucin adsorption, the best-performing F₃ -NCs show excellent mucus penetration and intestinal transport capabilities without impairing the intestinal tight junction, conferring the oral bioavailability of 20.4% in relative to intravenous injection. The disulfide cross-linker can be cleaved inside target cells, causing NCs dissociation and siRNA release to potentiate the TNF-α silencing efficiency. In murine models of acute and chronic inflammation, orally delivered F₃ -NCs provoke efficient TNF-α silencing and pronounced anti-inflammatory efficacies. This study therefore provides a transformative strategy for oral siRNA delivery, and will render promising utilities for anti-inflammation treatment.

Targeting Notch1-YAP Circuit Reprograms Macrophage Polarization and Alleviates Acute Liver Injury in Mice

BACKGROUND & AIMS

Hepatic immune system disorder plays a critical role in the pathogenesis of acute liver injury. The intrinsic signaling mechanisms responsible for dampening excessive activation of liver macrophages are not completely understood. The Notch and Hippo-YAP signaling pathways have been implicated in immune homeostasis. In this study, we investigated the interactive cell signaling networks of Notch1/YAP pathway during acute liver injury.

METHODS

Myeloid-specific Notch1 knockout (Notch1^M-KO) mice and the floxed Notch1 (Notch1^FL/FL) mice were subjected to lipopolysaccharide/D-galactosamine toxicity. Some mice were injected via the tail vein with bone marrow-derived macrophages transfected with lentivirus-expressing YAP. Some mice were injected with YAP siRNA using an in vivo mannose-mediated delivery system.

RESULTS

We found that the activated Notch1 and YAP signaling in liver macrophages were closely related to lipopolysaccharide/D-galactosamine-induced acute liver injury. Macrophage/neutrophil infiltration, proinflammatory mediators, and hepatocellular apoptosis were markedly ameliorated in Notch1^M-KO mice. Importantly, myeloid Notch1 deficiency depressed YAP signaling and facilitated M2 macrophage polarization in the injured liver. Furthermore, YAP overexpression in Notch1^M-KO livers exacerbated liver damage and shifted macrophage polarization toward the M1 phenotype. Mechanistically, macrophage Notch1 signaling could transcriptionally activate YAP gene expression. Reciprocally, YAP transcriptionally upregulated the Notch ligand Jagged1 gene expression and was essential for Notch1-mediated macrophage polarization. Finally, dual inhibition of Notch1 and YAP in macrophages further promoted M2 polarization and alleviated liver damage.

CONCLUSIONS

Our findings underscore a novel molecular insight into the Notch1-YAP circuit for controlling macrophage polarization in acute liver injury, raising the possibility of targeting macrophage Notch1-YAP circuit as an effective strategy for liver inflammation-related diseases.

FABP5 Deficiency Impaired Macrophage Inflammation by Regulating AMPK/NF-κB Signaling Pathway

Fatty acid binding protein 5 (FABP5) is mainly involved in the uptake, transport, and metabolism of fatty acid in the cytoplasm, and its role in immune cells has been recognized in recent years. However, the role of FABP5 in macrophage inflammation and its underlying mechanisms were not fully addressed. In our study, the acute liver injury and sepsis mouse models were induced by i.p. injection of LPS and cecal contents, respectively. Oleic acid (0.6 g/kg) was injected four times by intragastric administration every week, and this lasted for 1 wk before the LPS or cecal content challenge. We found that myeloid-specific deletion of FABP5 mitigated LPS-induced acute liver injury with reduced mortality of mice, histological liver damage, alanine aminotransferase, and proinflammatory factor levels. Metabolic analysis showed that FABP5 deletion increased the intracellular unsaturated fatty acids, especially oleic acid, in LPS-induced macrophages. The addition of oleic acid also decreased LPS-stimulated macrophage inflammation in vitro and reduced acute liver injury in LPS-induced or cecal content-induced sepsis mice. RNA-sequencing and molecular mechanism studies showed that FABP5 deletion or oleic acid supplementation increased the AMP/ATP ratio and AMP-activated protein kinase (AMPK) activation and inhibited the NF-κB pathway during the inflammatory response to LPS stimulation of macrophages. Inhibiting AMPK activation or expression by chemical or genetic approaches significantly rescued the decreased NF-κB signaling pathway and inflammatory response in LPS-treated FABP5-knockout macrophages. Our present study indicated that inhibiting FABP5 or supplementation of oleic acid might be used for the treatment of sepsis-caused acute liver injury.

Edaravone protects against liver fibrosis progression via decreasing the IL-1β secretion of macrophages

Edaravone (EDA), a strong novel free radical scavenger, have been demonstrated to exert neurovascular protective effects clinically. Furthermore, EDA can suppress the lung injury, pulmonary fibrosis and skin fibrosis, while the precise effects and mechanisms of EDA on liver injury and fibrosis remain unclear. The effects of EDA on the Thioacetamide (TAA)-induced liver fibrosis were evaluated by sirius red staining, α-SMA immunohistochemistry. The percentages of immune cell subsets were analyzed by flow cytometry. Immunofluorescence assay was performed to identify the fibrotic properties of hepatic stellate cells (HSCs). Western blot and qPCR were used to detect the levels of liver fibrosis-related molecules and IL-1β. EDA displayed a hepatic protective role in TAA-induced chronic liver fibrosis via inhibiting monocyte/macrophages recruitment and IL-1β production of macrophages. Mechanically, EDA inhibited of NF-κB signal pathway and reactive oxygen species (ROS) production in macrophages. Moreover, EDA treatment indirectly suppressed the activation of HSCs by decreasing the IL-1β secretion of macrophages. Together, EDA protects against TAA-induced liver fibrosis via decreasing the IL-1β production of macrophages, thereby providing a feasible solution for clinical treatment of liver fibrosis.

The role of macrophage TAM receptor family in the acute-to-chronic progression of liver disease: From friend to foe?

Hepatic macrophages, the key cellular components of the liver, emerge as essential players in liver inflammation, tissue repair and subsequent fibrosis, as well as tumorigenesis. Recently, the TAM receptor tyrosine kinase family, consisting of Tyro3, Axl and MerTK, was found to be a pivotal modulator of macrophages. Activation of macrophage TAM receptor signalling promotes the efferocytosis of apoptotic cells and skews the polarization of macrophages. After briefly reviewing the mechanisms of TAM receptor signalling in macrophage polarization, we focus on their role in liver diseases from acute injury to chronic inflammation, fibrosis and then to tumorigenesis. Notably, macrophage TAM receptor signalling seems to be a two-edged sword for liver diseases. On one hand, the activation of TAM receptor signalling inhibits inflammation and facilitates tissue repair during acute liver injury. On the other hand, continuous activation of the signalling contributes to the process of chronic inflammation into fibrosis and tumorigenesis by evoking hepatic stellate cells and inhibiting anti-tumour immunity. Therefore, targeting macrophage TAM receptors and clarifying its downstream pathways will be exciting prospects for the precaution and treatment of liver diseases, particularly at different stages or statuses.

The Mechanisms of Systemic Inflammatory and Immunosuppressive Acute-on-Chronic Liver Failure and Application Prospect of Single-Cell Sequencing

Acute-on-chronic liver failure (ACLF) is a complex clinical syndrome, and patients often have high short-term mortality. It occurs with intense systemic inflammation, often accompanied by a proinflammatory event (such as infection or alcoholic hepatitis), and is closely related to single or multiple organ failure. Liver inflammation begins when innate immune cells (such as Kupffer cells (KCs)) are activated by binding of pathogen-associated molecular patterns (PAMPs) from pathogenic microorganisms or damage-associated molecular patterns (DAMPs) of host origin to their pattern recognition receptors (PRRs). Activated KCs can secrete inflammatory factors as well as chemokines and recruit bone marrow-derived cells such as neutrophils and monocytes to the liver to enhance the inflammatory process. Bacterial translocation may contribute to ACLF when there are no obvious precipitating events. Immunometabolism plays an important role in the process (including mitochondrial dysfunction, amino acid metabolism, and lipid metabolism). The late stage of ACLF is mainly characterized by immunosuppression. In this process, the dysfunction of monocyte and macrophage is reflected in the downregulation of HLA-DR and upregulation of MER tyrosine kinase (MERTK), which weakens the antigen presentation function and reduces the secretion of inflammatory cytokines. We also describe the specific function of bacterial translocation and the gut-liver axis in the process of ACLF. Finally, we also describe the transcriptomics in HBV-ACLF and the recent progress of single-cell RNA sequencing as well as its potential application in the study of ACLF in the future, in order to gain a deeper understanding of ACLF in terms of single-cell gene expression.

Effectiveness of High-Volume Therapeutic Plasma Exchange for Acute and Acute-on-Chronic Liver Failure in Korean Pediatric Patients

PURPOSE

Liver transplantation (LT) is the only curative treatment for acute liver failure (ALF) and acute-on-chronic liver failure (ACLF). In high-volume therapeutic plasma exchange (HV-TPE), extracorporeal liver support filters accumulate toxins and improve the coagulation factor by replacing them. In this study, we aimed to evaluate the effectiveness of HV-TPE in pediatric patients with ALF and ACLF.

METHODS

We reviewed the records of children waiting for LT at Severance Hospital who underwent HV-TPE between 2017 and 2021. Aspartate aminotransferase (AST), alanine aminotransferase (ALT), total and direct bilirubin (TB and DB), gamma-glutamyl transferase (GGT), ammonia, and coagulation parameter-international normalized ratio (INR) were all measured before and after HV-TPE to analyze the liver function. The statistical analysis was performed using IBM SPSS Statistics for Windows, version 26.0 (IBM Co., Armonk, NY, USA).

RESULTS

Nine patients underwent HV-TPE with standard medical therapy while waiting for LT. One had neonatal hemochromatosis, four had biliary atresia, and the other four had ALF of unknown etiology. Significant decreases in AST, ALT, TB, DB, GGT, and INR were noted after performing HV-TPE (930.38-331.75 IU/L, 282.62-63.00 IU/L, 11.75-5.59 mg/dL, 8.10-3.66 mg/dL, 205.62-51.75 IU/L, and 3.57-1.50, respectively, p<0.05). All patients underwent LT, and two expired due to acute complications.

CONCLUSION

HV-TPE could remove accumulated toxins and improve coagulation. Therefore, we conclude that HV-TPE can be regarded as a representative bridging therapy before LT.

Spotlight on liver macrophages for halting liver disease progression and injury

INTRODUCTION

Over the past two decades, understanding of hepatic macrophage biology has provided astounding details of their role in the progression and regression of liver diseases. The hepatic macrophages constitute resident macrophages, Kupffer cells, and circulating bone marrow monocyte-derived macrophages, which play a diverse role in liver injury and repair. Imbalance in the macrophage population leads to pathological consequences and is responsible for the initiation and progression of acute and chronic liver injuries. Further, distinct populations of hepatic macrophages and their high heterogeneity make their complex role enigmatic. The unique features of distinct phenotypes of macrophages have provided novel biomarkers for defining the stages of liver diseases. The distinct mechanisms of hepatic macrophages polarization and recruitment have been at the fore front of research. In addition, the secretome of hepatic macrophages and their immune regulation has provided clinically relevant therapeutic targets.

AREAS COVERED

Herein we have highlighted the current understanding in the area of hepatic macrophages, and their role in the progression of liver injury.

EXPERT OPINION

It is essential to ascertain the physiological and pathological role of evolutionarily conserved distinct macrophage phenotypes in different liver diseases before viable approaches may see a clinical translation.

Advances in medical management of acute liver failure in children: promoting native liver survival

Paediatric acute liver failure (PALF) is defined as a biochemical evidence of acute liver injury in a child with no previous history of chronic liver disease characterised by an international normalised ratio (INR) of 1·5 or more unresponsive to vitamin K with encephalopathy, or INR of 2·0 or more with or without encephalopathy. PALF can rapidly progress to multiorgan dysfunction or failure. Although the transplant era has substantially changed the outlook for these patients, transplantation itself is not without risks, including those associated with life-long immunosuppression. Consequently, there has been an increased focus on improving medical management to prioritise bridging of patients to native liver survival, which is possible due to improved understanding of the underlying pathophysiology of multiorgan involvement in PALF. In this Review, we discuss recent advances in the medical management of PALF with an aim of reducing the need for liver transplantation. The Review will focus on the non-specific immune-mediated inflammatory response, extracorporeal support devices, neuromonitoring and neuroprotection, and emerging cellular and novel future therapeutic options.

Identification of effective diagnostic biomarker and immune cell infiltration characteristics in acute liver failure by integrating bioinformatics analysis and machine-learning strategies

Background: To determine effective biomarkers for the diagnosis of acute liver failure (ALF) and explore the characteristics of the immune cell infiltration of ALF.

Methods: We analyzed the differentially expressed genes (DEGs) between ALF and control samples in GSE38941, GSE62029, GSE96851, GSE120652, and merged datasets. Co-expressed DEGs (co-DEGs) identified from the five datasets were analyzed for enrichment analysis. We further constructed a PPI network of co-DEGs using the STRING database. Then, we integrated the two kinds of machine-learning strategies to identify diagnostic biomarkers of top hub genes screened based on MCC and Degree methods. And the potential diagnostic performance of the biomarkers for ALF was estimated using the AUC values. Data from GSE14668, GSE74000, and GSE96851 databases was performed as external verification sets to validate the expression level of potential diagnostic biomarkers. Furthermore, we analyzed the difference in the protein level of diagnostic biomarkers between normal and ALF mice models. Finally, we used CIBERSORT to estimate relative infiltration levels of 22 immune cell subsets in ALF samples and further analyzed the relationships between the diagnostic biomarkers and infiltrated immune cells.

Results: A total of 200 co-DEGs were screened. Enrichment analyses depicted that they are highly enriched in metabolism and matrix collagen production-associated processes. The top 28 hub genes were obtained by integrating MCC and Degree methods. Then, the collagen type IV alpha 2 chain (COL4A2) was regarded as the diagnostic biomarker and showed excellent specificity and sensitivity. COL4A2 also showed a statistically significant difference and excellent diagnostic effectiveness in the verification set. In addition, there was a significant upregulation in the COL4A2 protein level in ALF mice models compared with the normal group. CIBERSORT analysis showed that activated CD4 T cells, plasma cells, macrophages, and monocytes may be implicated in the progress of ALF. In addition, COL4A2 showed different degrees of correlation with immune cells.

Conclusion: In conclusion, COL4A2 may be a diagnostic biomarker for ALF, and immune cell infiltration may have important implications for the occurrence and progression of ALF.

The Inhibition of Bruton Tyrosine Kinase Alleviates Acute Liver Failure via Downregulation of NLRP3 Inflammasome

There is no effective treatment for acute liver failure (ALF) except for an artificial liver support system (ALSS) and liver transplant. Bruton tyrosine kinase (Btk) plays important immunoregulatory roles in the inflammatory diseases, but its possible function in ALF remains to be characterized. In this study, we detected the phosphorylation level of Btk in ALF mouse liver and analyzed the protective effects of Btk inhibitor on survival rate and liver damage in ALF mouse models. We measured the expression levels of various inflammatory cytokines in the ALF mouse liver and primary human monocytes. In addition, we examined the expression of the NLRP3 inflammasome in mouse models with or without Btk inhibition. Clinically, we observed the dynamic changes of Btk expression in PBMCs of ALSS-treated patients. Our results showed that Btk was upregulated significantly in the experimental ALF mouse models and that Btk inhibition alleviated liver injury and reduced the mortality in these models. The protective effect of Btk inhibitors on ALF mice partially depended on the suppression of NLRP3 inflammasome signaling. Clinical investigations revealed that the dynamic changes of Btk expression in PBMCs could predict the effect of ALSS treatment. Our work shows that Btk inhibition is an effective therapeutic strategy for ALF. Moreover, Btk is a useful indicator to predict the therapeutic effect of ALSS on liver failure, which might have great value in clinical practice.

Pluripotent Stem Cell-derived Strategies to Treat Acute Liver Failure: Current Status and Future Directions

Liver disease has long been a heavy health and economic burden worldwide. Once the disease is out of control and progresses to end-stage or acute organ failure, orthotopic liver transplantation (OLT) is the only therapeutic alternative, and it requires appropriate donors and aggressive administration of immunosuppressive drugs. Therefore, hepatocyte transplantation (HT) and bioartificial livers (BALs) have been proposed as effective treatments for acute liver failure (ALF) in clinics. Although human primary hepatocytes (PHs) are an ideal cell source to support these methods, the large demand and superior viability of PH is needed, which restrains its wide usage. Thus, a finding alternative to meet the quantity and quality of hepatocytes is urgent. In this context, human pluripotent stem cells (PSC), which have unlimited proliferative and differential potential, derived hepatocytes are a promising renewable cell source. Recent studies of the differentiation of PSC into hepatocytes has provided evidence that supports their clinical application. In this review, we discuss the recent status and future directions of the potential use of PSC-derived hepatocytes in treating ALF. We also discuss opportunities and challenges of how to promote such strategies in the common applications in clinical treatments.

Therapeutic plasma exchange in children with acute liver failure (ALF): is it time for incorporation into the ALF armamentarium?

Paediatric acute liver failure (PALF) is a rare but devastating condition with high mortality. An exaggerated inflammatory response is now recognised as pivotal in the pathogenesis and prognosis of ALF, with cytokine spill from the liver to systemic circulation implicated in development of multi-organ failure associated with ALF. With advances in medical management, especially critical care, there is an increasing trend towards spontaneous liver regeneration, averting the need for emergency liver transplantation or providing stability to the patient awaiting a graft. Hence, research is ongoing for therapies, including extracorporeal liver support devices, that can bridge patients to transplant or spontaneous liver recovery. Considering the immune-related pathogenesis and inflammatory phenotype of ALF, plasma exchange serves as an ideal liver assist device as it performs both the excretory and synthetic functions of the liver and, in addition, works as an immunomodulatory therapy by suppressing the early innate immune response in ALF. After a recent randomised controlled trial in adults demonstrated a beneficial effect of high-volume plasma exchange on clinical outcomes, this therapy was incorporated in European Association for the Study of Liver (EASL) recommendations for managing adult patients with ALF, but no guidelines exist for PALF. In this review, we discuss rationale, timing, practicalities, and existing evidence regarding the use of plasma exchange as an immunomodulatory treatment in PALF. We discuss controversies in delivery of this therapy as an extracorporeal device, and practicalities of use of plasma exchange as a 'hybrid' therapy alongside other extracorporeal liver assist devices, before finally reviewing outstanding research questions for the future.

Noncanonical Wnt5a/JNK Signaling Contributes to the Development of D-Gal/LPS-Induced Acute Liver Failure

Acute liver failure (ALF) is a deadly clinical disorder with few effective treatments and unclear pathogenesis. In our previous study, we demonstrated that aberrant Wnt5a expression was involved in acute-on-chronic liver failure. However, the role of Wnt5a in ALF is unknown. We investigated the expression of Wnt5a and its downstream c-Jun N-terminal kinase (JNK) signaling in a mouse model of ALF established by coinjection of D-galactosamine (D-Gal) and lipopolysaccharide (LPS) in C57BL/6 mice. We also investigated the role of Box5, a Wnt5a antagonist, in vivo. Moreover, the effect of Wnt5a/JNK signaling on downstream inflammatory cytokine expression, phagocytosis, and migration in THP-1 macrophages was studied in vitro. Aberrant Wnt5a expression and JNK activation were detected in D-Gal/LPS-induced ALF mice. Box5 pretreatment reversed JNK activation and eventually decreased the mortality rate of D-Gal/LPS-treated mice, with reduced hepatic necrosis and apoptosis, serum ALT and AST levels, and liver inflammatory cytokine expression, although the latter was not significant. We further demonstrated that recombinant Wnt5a (rWnt5a)-induced tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) mRNA expression and increased THP-1 macrophage phagocytosis in a JNK-dependent manner, which could be restored by Box5. In addition, rWnt5a-induced migration of THP-1 macrophages was also reversed by Box5. Our findings suggested that Wnt5a/JNK signaling plays an important role in the development of ALF and that Box5 could have particular hepatoprotective effects in ALF.

Blockade of mIL‐6R alleviated lipopolysaccharide‐induced systemic inflammatory response syndrome by suppressing NF‐κB‐mediated Ccl2 expression and inflammasome activation

Systemic inflammatory response syndrome (SIRS) is characterized by dysregulated cytokine release, immune responses and is associated with organ dysfunction. IL‐6R blockade indicates promising therapeutic effects in cytokine release storm but still remains unknown in SIRS. To address the issue, we generated the human il‐6r knock‐in mice and a defined epitope murine anti‐human membrane‐bound IL‐6R (mIL‐6R) mAb named h‐mIL‐6R mAb. We found that the h‐mIL‐6R and the commercial IL‐6R mAb Tocilizumab significantly improved the survival rate, reduced the levels of TNF‐α, IL‐6, IL‐1β, IFN‐γ, transaminases and blood urea nitrogen of LPS‐induced SIRS mice. Besides, the h‐mIL‐6R mAb could also dramatically reduce the levels of inflammatory cytokines in LPS‐treated THP‐1 cells in vitro. RNA‐seq analysis indicated that the h‐mIL‐6R mAb could regulate LPS‐induced activation of NF‐κB/Ccl2 and NOD‐like receptor signaling pathways. Furthermore, we found that the h‐mIL‐6R mAb could forwardly inhibit Ccl2 expression and NLRP3‐mediated pyroptosis by suppressing NF‐κB in combination with the NF‐κB inhibitor. Collectively, mIL‐6R mAbs suppressed NF‐κB/Ccl2 signaling and inflammasome activation. IL‐6R mAbs are potential alternative therapeutics for suppressing excessive cytokine release, over‐activated inflammatory responses and alleviating organ injuries in SIRS.

Clinical Implication of Plasma CD163 in Patients With Acute-on-Chronic Liver Failure

BACKGROUND

It was postulated that CD163 plasma level should be incorporated into existing predictive systems to improve prognostic performance in patients with acute-on-chronic liver failure (ACLF).

PATIENTS AND METHODS

Plasma CD163 was assessed in 24 consecutive patients with ACLF (17 male, 7 female; mean age 54.9 years; 50% with alcohol-related liver disease) and compered with the existing scoring tools to predict the availability of transplantation or survival without liver transplant (LT).

RESULTS

There were no differences in plasma CD163 levels between graft recipients and deceased patients on the waiting list or transplant survivors vs nonsurvivors. CD163 did not correlate with CLIF-ACLF, CLIF Consortium organ failure score (CLIF-OF), and ACLF grades (all P < .05). However, sequential organ failure assessment (SOFA), CLIF Consortium acute-on-chronic liver failure score (CLIF-C) ACLF, and CLIF-C OF scores correlated significantly with mortality (P < .01) in contrast to Child-Pugh scale and Model for End-Stage Liver Disease score (all P > .05). Transplanted survivors and deceased individuals differed robustly with respect to the SOFA and CLIF-SOFA scores and the CLIF-C OF, CLIF-C Grade, and CLIF-C ACLF scales (all P < .05). CLIF-C performed well in ACLF prognostication with an area under receiver operating characteristic curve (AUROC) 0.893 (95% CI, 0.766-1), surpassing in that respect CD163 with AUROC of 0.664 (95% CI, 0417-0.911).

CONCLUSIONS

Our preliminary results showed that the plasma CD163 level in patients with ACLF played only a minor role in predicting LT futility/benefit, with no impact on the narrow transplant window. Moreover, to optimize LT outcomes, newly developed CLIF-C scales showed superior predictive value.

SIRT6 Activator UBCS039 Inhibits Thioacetamide-Induced Hepatic Injury In Vitro and In Vivo

SIRT6 has been reported to have multiple functions in inflammation and metabolism. In the present study, we explored the regulatory effects and mechanisms of SIRT6 in thioacetamide (TAA)-induced mice acute liver failure (ALF) models. The SIRT6 activator UBCS039 was used in this animal and cell experiments. We observed that UBCS039 ameliorated liver damage, including inflammatory responses and oxidative stress. Further study of mechanisms showed that the upregulation of SIRT6 inhibited the inflammation reaction by suppressing the nuclear factor-κB (NF-κB) pathway in the TAA-induced ALF mice model and lipopolysaccharide-stimulated macrophages. In addition, the upregulation of SIRT6 alleviated oxidative stress damage in hepatocytes by regulating the Nrf2/HO-1 pathway. These findings demonstrate that pharmacologic activator of SIRT6 could be a promising target for ALF.

Standard-Volume Plasma Exchange Improves Outcomes in Patients With Acute Liver Failure: A Randomized Controlled Trial

BACKGROUND

High volume plasma-exchange (HVPE) improves survival in patients with acute liver failure (ALF), but apprehension regarding volume overload and worsening of cerebral edema remain.

METHODS

In an open-label randomized controlled trial, 40 consecutive patients of ALF were randomized 1:1 to either standard medical treatment (SMT) or SMT with standard-volume plasma-exchange (SVPE). SVPE was performed using centrifugal apheresis [target volume of 1.5 to 2.0 plasma volumes per session] until desired response was achieved. Cerebral edema was assessed by brain imaging. Results were analyzed in an intention-to-treat analysis. Primary outcome was 21-day transplant-free survival. The levels of cytokines, damage-associated molecular patterns (DAMPs) and endotoxins were analyzed at baseline and day 5.

RESULTS

ALF patients [aged 31.5 ± 12.2 years, 60% male, 78% viral, 83% hyperacute, 70% with SIRS were included. At day 5, SVPE [mean sessions 2.15 ± 1.42, median plasma volume replaced 5.049 L] compared to SMT alone, resulted in higher lactate clearance (p = .02), amelioration of SIRS (84% vs. 26%; P = .02), reduction in ammonia levels [(221.5 ± 96.9) vs.(439 ± 385.6) μg/dl, P = .02) and SOFA scores [9.9(±3.3) vs. 14.6(±4.8); P = .001]. There were no treatment related deaths. SVPE was associated with a higher 21-day transplant free-survival [75% vs. 45%; P = .04, HR 0.30, 95%CI 0.01-0.88]. A significant decrease in levels of pro-inflammatory cytokines and an increase in anti-inflammatory cytokines along with a decrease in endotoxin and DAMPs was seen with SVPE.

CONCLUSION

In ALF patients with cerebral edema, SVPE is safe and effective and improves survival possibly by a reduction in cytokine storm and ammonia.

CLINICALTRIAL

gov (identifier: NCT02718079).

Immunomodulatory Activity of Granulocyte Colony-Stimulating Factor and its Therapeutic Effect on Liver Failure

Abstract

Liver failure is characterized by the rapid deterioration of liver function, often accompanied by ascites, coagulation dysfunction, hepatic encephalopathy, and other critical complications. Owing to the complex multifaceted pathogenesis and consequential clinical manifestations of the disease, liver failure displays poor prognosis and warrants comprehensive clinical treatment and management. Liver transplantation remains the only well-established treatment for liver failure. However, several factors including transplantation cost and low organ donation rates limit the rate of liver transplantation. The development of a suitable therapy for liver failure is a significant challenge and remains a cause of concern for the medical world. Granulocyte colony-stimulating factor (G-CSF), a member of the cytokine family of hematopoietic growth factors, is involved in the migration of hematopoietic stem cells into the damaged liver, and effectuates their dedifferentiation into hepatocytes. Liver regeneration involves a complex crosstalk of multiple cell types, including hepatocytes, endothelial cells, and inflammatory cells. Neutrophils and monocytes/macrophages that present different types of innate immune cells were found to play a crucial role in the progression of inflammation and restoration of the liver tissue. G-CSF, known as the most common used cytokine, may also affect these immune cells by combining G-CSF receptors on their surface. The immunomodulatory activity of G-CSF should be studied and described in order to ascertain its therapeutic effect on liver failure.

MCC950 Ameliorates Acute Liver Injury Through Modulating Macrophage Polarization and Myeloid-Derived Suppressor Cells Function

Acute liver injury (ALI) raises high mortality rates due to a rapid pathological process. MCC950, a highly selective nod-like receptor family pyrin domain containing 3 (NLRP3) inhibitor, has already been reported to show strong hepatoprotective effects in many different liver diseases. In this study, we unveiled the role of MCC950 in carbon tetrachloride (CCl₄)-induced ALI and its underlying molecular mechanisms on days 1, 2, and 3. MCC950 could significantly inhibit liver injury, evidenced by decreased serum alamine aminotransferase (ALT) and aspartate aminotransferase (AST) levels on days 1 and 2, increased Albumin (ALB) level on day 3, and decreased histological score during the whole period. Moreover, lower M1 macrophage related to pro-inflammatory genes expression was observed in MCC950-treated ALI mice on day 1, while MCC950 pretreatment also polarized macrophage to M2 phenotype indicating anti-inflammatory response on days 2 and 3. Additionally, MDSC was significantly increased in blood, liver, and spleen in ALI mice at different time courses. Specifically, upregulated myeloid-derived suppressor cell (MDSC) proportions were found in blood and spleen on days 1 and 2, but showed decreased trend on day 3. However, liver MDSC numbers were increased on days 2 and 3, but no significance on day 1. In conclusion, MCC950 pretreatment alleviates CCl₄-induced ALI through enhanced M2 macrophage and MDSC function at different time points of ALI. Further understanding of MCC950 in ALI may be a new potential therapeutic strategy.

Plasma Exchange in Acute and Acute on Chronic Liver Failure

Liver failure in the context of acute (ALF) and acute on chronic liver failure (ACLF) is associated with high mortality in the absence of a liver transplant. For decades, therapeutic plasma exchange (TPE) is performed for the management of immune-mediated diseases. TPE has emerged as an attractive extracorporeal blood purification technique in patients with ALF and ACLF. The basic premise of using TPE is to remove the toxic substances which would allow recovery of native liver functions by facilitating liver regeneration. In recent years, encouraging data have emerged, suggesting the benefits of TPE in patients with liver failure. TPE has emerged as an attractive liver support device for the failing liver until liver transplantation or clinical recovery. The data in patients with ALF suggest routine use of high-volume TPE, while the data for such a strategy are less robust for patients with ACLF.

Hemodynamic Alteration in the Liver in Acute Hepatitis: A Quantitative Evaluation Using Computed Tomographic Perfusion

BACKGROUND/AIM

We aimed to elucidate the hemodynamic alterations in the liver of patients with acute hepatitis (AH) using computed tomography perfusion imaging.

PATIENTS AND METHODS

For 14 patients with AH and nine patients with no disease (ND group), we compared the mean arterial blood flow (AF), portal blood flow (PF) and perfusion index (%) [PI=AF/(AF+PF) ×100] of the right and left liver lobes and investigated their relationship with clinical factors.

RESULTS

The mean PI of the right lobe in the AH group (30.5±10.0%) was significantly higher than that in the ND group (20.8±9.7%) (p=0.031). For all patients of the AH and ND groups, the PI of the right lobe was increased as the prothrombin time decreased (R=-0.56, p=0.006) and as the prothrombin time-international normalized ratio increased (R=0.48, p=0.02).

CONCLUSION

The PI of the right liver lobe may increase in AH and may be a predictive parameter for the severity of hepatic failure.