The concanavalin A model of acute hepatitis in mice

Gastrointestinal pharmacology activins in liver health and disease

Activins are a subgroup of the TGFβ superfamily of growth and differentiation factors, dimeric in nature and consisting of two inhibin beta subunits linked via a disulfide bridge. Canonical activin signaling occurs through Smad2/3, with negative feedback initiated by Smad6/7 following signal transduction, which binds activin type I receptor preventing phosphorylation of Smad2/3 and activation of downstream signaling. In addition to Smad6/7, other inhibitors of activin signaling have been identified as well, including inhibins (dimers of an inhibin alpha and beta subunit), BAMBI, Cripto, follistatin, and follistatin-like 3 (fstl3). To date, activins A, B, AB, C, and E have been identified and isolated in mammals, with activin A and B having the most characterization of biological activity. Activin A has been implicated as a regulator of several important functions of liver biology, including hepatocyte proliferation and apoptosis, ECM production, and liver regeneration; the role of other subunits of activin in liver physiology are less understood. There is mounting data to suggest a link between dysregulation of activins contributing to various hepatic diseases such as inflammation, fibrosis, and hepatocellular carcinoma, and emerging studies demonstrating the protective and regenerative effects of inhibiting activins in mouse models of liver disease. Due to their importance in liver biology, activins demonstrate utility as a therapeutic target for the treatment of hepatic diseases such as cirrhosis, NASH, NAFLD, and HCC; further research regarding activins may provide diagnostic or therapeutic opportunity for those suffering from various liver diseases.

Tripterygium wilfordii protects against an animal model of autoimmune hepatitis

ETHNOPHARMACOLOGICAL RELEVANCE

Tripterygium wilfordii tablets (TWT) is widely used to treat autoimmune diseases such as rheumatoid arthritis. Celastrol, one main active ingredient in TWT, has been shown to produce a variety of beneficial effects, including anti-inflammatory, anti-obesity, anti-cancer, and immunomodulatory. However, whether TWT could protect against Concanavalin A (Con A)-induced hepatitis remains unclear.

THE AIM OF THE STUDY

This study aims to investigate the protective effect of TWT against Con A-induced hepatitis and elucidate the underlying mechanism.

MATERIALS AND METHODS

Metabolomic analysis, pathological analysis, biochemical analysis, qPCR and Western blot analysis and the Pxr-null mice were used in this study.

RESULTS

The results indicated that TWT and its active ingredient celastrol could protect against Con A-induced acute hepatitis. Plasma metabolomics analysis revealed that metabolic perturbations related to bile acid and fatty acid metabolism induced by Con A were reversed by celastrol. The level of itaconate in the liver was increased by celastrol and speculated as an active endogenous compound mediating the protective effect of celastrol. Administration of 4-octanyl itaconate (4-OI) as a cell-permeable itaconate mimicker was found to attenuate Con A-induced liver injury through activation of the pregnane X receptor (PXR) and enhancement of the transcription factor EB (TFEB)-mediated autophagy.

CONCLUSIONS

Celastrol increased itaconate and 4-OI promoted activation of TFEB-mediated lysosomal autophagy to protect against Con A-induced liver injury in a PXR-dependent manner. Our study reported a protective effect of celastrol against Con A-induced AIH via an increased production of itaconate and upregulation of TFEB. The results highlighted that PXR and TFEB-mediated lysosomal autophagic pathway may offer promising therapeutic target for the treatment of autoimmune hepatitis.

The Effects of Programmed Cell Death of Mesenchymal Stem Cells on the Development of Liver Fibrosis

Mesenchymal stem cells have shown noticeable potential for unlimited self-renewal. They can differentiate into specific somatic cells, integrate into target tissues via cell-cell contact, paracrine effects, exosomes, and other processes and then regulate the target cells and tissues. Studies have demonstrated that transplantation of MSCs could decrease the expression and concentration of collagen in the liver, thereby reducing liver fibrosis. A growing body of evidence indicates that apoptotic MSCs could inhibit harmful immune responses and reduce inflammatory responses more effectively than viable MSCs. Accumulating evidence suggests that mitochondrial transfer from MSCs is a novel strategy for the regeneration of various damaged cells via the rescue of their respiratory activities. This study is aimed at reviewing the functions of MSCs and the related roles of the programmed cell death of MSCs, including autophagy, apoptosis, pyroptosis, and ferroptosis, as well as the regulatory pathogenic mechanisms of MSCs in liver fibrosis. Research has demonstrated that the miR-200B-3p gene is differentially expressed gene between LF and normal liver samples, and that the miR-200B-3p gene expression is positively correlated with the degree of liver fibrosis, suggesting that MSCs could inhibit liver fibrosis through pyroptosis. It was confirmed that circulating monocytes could deliver MSC-derived immunomodulatory molecules to different sites by phagocytosis of apoptotic MSCs, thereby achieving systemic immunosuppression. Accordingly, it was suggested that characterization of the programmed cell death-mediated immunomodulatory signaling pathways in MSCs should be a focus of research.

Celastrol pretreatment attenuates concanavalin A-induced hepatitis in mice by suppressing interleukin-6/STAT3-interleukin-17 signaling

BACKGROUND AND AIM

Celastrol is extracted from Tripterygium wilfordii Hook F. It has been reported to have protective effects against various liver diseases and immune regulation of autoimmune diseases. However, little is known about whether celastrol protects against immune-mediated hepatitis. This study aimed to investigate the effect of celastrol on liver injury induced by concanavalin A (ConA) and the potential mechanisms.

METHODS

Intravenous administration of ConA was applied to induce acute liver injury in mice with or without pretreatment of celastrol. The effects of celastrol on ConA-induced liver injury were further demonstrated by biochemical and histopathological assessments, immunoblotting, and flow cytometry analysis.

RESULTS

Both biochemical and histopathological observations showed that pretreatment of celastrol significantly ameliorated liver injury induced by ConA. Moreover, the hepatocyte apoptosis and inflammatory responses induced by ConA were also improved in celastrol-pretreated mice. Further studies revealed that these improvements were characterized as the celastrol-mediated suppression of total interleukin (IL)-17 from liver mononuclear cells in ConA-treated mice. Flow cytometry analysis suggested that celastrol specifically decreased IL-17 production by CD4⁺ T cells but not by CD8⁺ T cells. Fundamentally, pretreatment with celastrol inhibited both the IL-6 produced by F4/80⁺ macrophages and the IL-6 receptor on Th17 cells in the liver, which further led to the downregulated activation of STAT3, thus accounting for blocked Th17 signaling.

CONCLUSIONS

Celastrol may exhibit immune regulatory effects by regulating IL-6/STAT3-IL-17 signaling in ConA-induced hepatitis, which suggested new potentials for celastrol to be applied in treating immune-mediated liver diseases.

Toll-like receptor-7 signaling in Kupffer cells exacerbates concanavalin A-induced liver injury in mice

Concanavalin A (ConA) is a plant lectin that can induce immune-mediated liver damage. ConA induced liver damage animal model is a widely accepted model that can mimic clinical acute hepatitis and immune-mediated liver injury in humans. Toll-like receptor-7 (TLR7), a member of the TLR family, plays a key role in pathogen recognition and innate immune activation. The aim of this study was to examine the role of TLR7 in the pathogenesis of ConA-induced liver injury. Acute liver injury was induced by intravenous injection with ConA in WT (wild-type) and TLR7 knockout (KO) mice. Results showed that attenuated liver injury in TLR7-deficient mice, as indicated by increased survival rate, decreased aminotransferase levels, and reduced pathological lesions, was associated with decreased release of pro-inflammatory cytokines in livers. Consistently, significantly decreased proliferation of CD4⁺ T cell was detected in ConA-stimulated TLR7-deficient splenocytes, but not in CD3/CD28 stimulated TLR7-deficient CD4⁺ T cells. Moreover, TLR7 deficiency in KCs specifically suppressed the expression of TNF-α (tumor necrosis factor-α). Depletion of KCs abolished the detrimental role of TLR7 in ConA-induced liver injury. Taken together, these results demonstrate that TLR7 can regulate the expression of TNF-α in KCs, which is necessary for the full progression of ConA-induced liver injury.

Deletion of Cyclic GMP-AMP Synthase Aggravates Concanavalin A-Induced Acute Hepatic Injury by Facilitating Leukocyte Chemotaxis

Growing evidence demonstrates that cyclic GMP-AMP synthase (cGAS), as a cytosolic DNA sensor, is essential for activating innate immunity and regulating inflammatory response against cellular damage. However, its role in immune-mediated hepatitis remains unclear. Here by challenging the cGAS knockout (KO) and their littermate wide-type (WT) mice with intravenous ConA injection to induce acute immune-mediated liver injury, we found that lack of cGAS drastically aggravated liver damage post ConA treatment for 24 h, reflected by increased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels and amplified hepatic necrosis. The number of apoptotic hepatocytes was also significantly increased in the KO mice. RNA-sequencing analysis revealed that leukocyte chemotaxis and migration-related genes were remarkably upregulated in the KO livers. Consistently, immunofluorescence assays illustrated that the infiltrating F4/80-positive macrophages, Ly6G-positive neutrophils, and CD3-positive T cells were all significantly increased in the KO liver sections. The hepatic expression of the pro-inflammatory genes was elevated as well. Supporting the in vivo findings, the knockdown of cGAS in cultured macrophages showed promoted migration potential and enhanced pro-inflammatory gene expression. These results collectively demonstrated that deletion of cGAS could aggravate ConA-induced acute liver injury, at least at the 24-h time point, and its mechanism might be related to facilitating leukocyte chemotaxis and promoting liver inflammatory response.

TPN10466 ameliorates Concanavalin A-induced autoimmune hepatitis in mice via inhibiting ERK/JNK/p38 signaling pathway

Autoimmune hepatitis (AIH) eventually progresses to liver fibrosis, cirrhosis, and even hepatocellular carcinoma, causing irreversible damage to the liver. Concanavalin A-induced hepatitis in mice is a well-established model with pathophysiology similar to that of immune-mediated liver injury in human viral and autoimmune hepatitis, and it has been widely used to explore the pathogenesis and clinical treatment of human immune hepatitis. Artemisinin has been shown to exhibit anti-inflammatory effects through unclear mechanisms. In this study, we aimed to assess the effect of the artemisinin derivative TPN10466 on AIH. In vitro studies showed that TPN10466 dose dependently inhibited the percentage of IFN-γ-producing T cells. Further studies showed that TPN10466 attenuated the disease severity of AIH by downregulating the ability of lymphocytes to secrete IFN-γ and by reducing lymphocyte number in the liver. In addition, we found that TPN10466 treatment reduced T-cell responses by inhibiting JNK, ERK, and p38 pathways. In conclusion, our work suggests that TPN10466 provides protection against the autoimmune disease AIH by suppressing the inflammatory response of T cells, suggesting that TPN10466 may be a promising potential agent for the treatment of AIH.

Administration of spermidine attenuates concanavalin A-induced liver injury

A previous study revealed that treatment with the anticoagulant heparin attenuated concanavalin A (ConA)-induced liver injury. The administration of spermidine (SPD) increased urokinase-type plasminogen activator (uPA) levels in the serum. uPA is clinically used for the treatment of some thrombotic diseases such as cerebral infarction. Therefore, SPD may attenuate ConA-induced liver injury that is exacerbated by blood coagulation. The present study investigated the effect of SPD on liver injury in mice with autoimmune hepatopathy induced by ConA. A model of liver injury was created by intravenous injection of ConA into mice. SPD was administered in free drinking water and was biochemically and pathologically examined over time. The administration of SPD to ConA-treated mice significantly reduced liver injury. However, SPD treatment upregulated the mRNA expression of TNF-α and IFN-ϒ in the livers of ConA-treated mice. In contrast, the mRNA expression of tissue factor in the livers of SPD-treated mice was decreased after ConA injection. The frequency of lymphocytes and lymphocyte activation were not affected by SPD administration in ConA-treated mice. SPD treatment increased uPA levels in the serum and decreased the level of D-dimer in ConA-treated mice. Moreover, SPD decreased fibrin in the livers of ConA-treated mice. These results indicated that SPD treatment increased anticoagulant ability by increasing of uPA and attenuated ConA-induced liver injury.

Hepatocyte estrogen sulfotransferase inhibition protects female mice from concanavalin A-induced T cell-mediated hepatitis independent of estrogens

Autoimmune hepatitis (AIH) is a typical T cell-mediated chronic liver disease with a higher incidence in females. However, the molecular mechanism for the female predisposition is poorly understood. Estrogen sulfotransferase (Est) is a conjugating enzyme best known for its function in sulfonating and deactivating estrogens. The goal of this study is to investigate whether and how Est plays a role in the higher incidence of AIH in females. Concanavalin A (ConA) was used to induce T cell-mediated hepatitis in female mice. We first showed that Est was highly induced in the liver of ConA-treated mice. Systemic or hepatocyte-specific ablation of Est, or pharmacological inhibition of Est, protected female mice from ConA-induced hepatitis regardless of ovariectomy, suggesting the effect of Est inhibition was estrogen independent. In contrast, we found that hepatocyte-specific transgenic reconstitution of Est in the whole-body Est knockout (EstKO) mice abolished the protective phenotype. Upon the ConA challenge, EstKO mice exhibited a more robust inflammatory response with elevated production of proinflammatory cytokines and changed liver infiltration of immune cells. Mechanistically, we determined that ablation of Est led to the hepatic induction of lipocalin 2 (Lcn2), whereas ablation of Lcn2 abolished the protective phenotype of EstKO females. Our findings demonstrate that hepatocyte Est is required for the sensitivity of female mice to ConA-induced and T cell-mediated hepatitis in an estrogen-independent manner. Est ablation may have protected female mice from ConA-induced hepatitis by upregulating Lcn2. Pharmacological inhibition of Est might be a potential strategy for the treatment of AIH.

New Insight into the Concanavalin A-Induced Apoptosis in Hepatocyte of an Animal Model: Possible Involvement of Caspase-Independent Pathway

Concanavalin A (Con A) is known to be a T-cell mitogen and has been shown to induce hepatitis in mice through the triggering of conventional T cells and NKT cells. However, it remains unknown whether Con A itself can directly induce rapid hepatocyte death in the absence of a functional immune system. Here, by using an immunodeficient mouse model, we found Con A rapidly induced liver injury in vivo despite a lack of immunocyte involvement. We further observed in vitro that hepatocytes underwent a dose-dependent but caspase-independent apoptosis in response to Con A stimulation in vitro. Moreover, transcriptome RNA-sequencing analysis revealed that apoptosis pathways were activated in both our in vivo and in vitro models. We conclude that Con A can directly induce rapid but non-classical apoptosis in hepatocytes without the participation of immunocytes. These findings provide new insights into the mechanism of Con A-induced hepatitis.

CX3CR1 deficiency exacerbates immune-mediated hepatitis by increasing NF-κB-mediated cytokine production in macrophage and T cell

Immune-mediated hepatitis is marked by liver inflammation characterized by immune cell infiltration, chemokine/cytokine production, and hepatocyte injury. C-X3C motif receptor 1 (CX3CR1), as the receptor of chemokine C-X3C motif ligand 1 (CX3CL1)/fractalkine, is mainly expressed on immune cells including monocytes and T cells. Previous studies have shown that CX3CR1 protects against liver fibrosis, but the exact role of CX3CL1/CX3CR1 in acute immune-mediated hepatitis remains unknown. Here, we investigate the role of the CX3CL1/CX3CR1 axis in immune-mediated hepatitis using concanavalin A (ConA)-induced liver injury model in CX3CR1-deficient (Cx3cr1^-/-) mice. We observed that Cx3cr1^-/- mice had severe liver injury and increased pro-inflammatory cytokines (tumor necrosis factor-alpha [TNF-α], interferon-gamma [IFN-γ], interleukin-1 beta [IL-1β], and IL-6) in serum and liver compared to wild-type (Cx3cr1^+/+) mice after ConA injection. The deficiency of CX3CR1 did not affect ConA-induced immune cell infiltration in liver but led to elevated production of TNF-α in macrophages as well as IFN-γ in T cells after ConA treatment. On the contrary, exogenous CX3CL1 attenuated ConA-induced cytokine production in wild type, but not CX3CR1-deficient macrophages and T cells. Furthermore, in vitro results showed that CX3CR1 deficiency promoted the pro-inflammatory cytokine expression by increasing the phosphorylation of nuclear factor kappa B (NF-κB) p65 (p-NF-κB p65). Finally, pre-treatment of p-NF-κB p65 inhibitor, resveratrol, attenuated ConA-induced liver injury and inflammatory responses, especially in Cx3cr1^-/- mice. In conclusion, our data show that the deficiency of CX3CR1 promotes pro-inflammatory cytokine production in macrophages and T cells by enhancing the phosphorylation of NF-κB p65, which exacerbates liver injury in ConA-induced hepatitis.

An update on animal models of liver fibrosis

The development of liver fibrosis primarily determines quality of life as well as prognosis. Animal models are often used to model and understand the underlying mechanisms of human disease. Although organoids can be used to simulate organ development and disease, the technology still faces significant challenges. Therefore animal models are still irreplaceable at this stage. Currently, in vivo models of liver fibrosis can be classified into five categories based on etiology: chemical, dietary, surgical, transgenic, and immune. There is a wide variety of animal models of liver fibrosis with varying efficacy, which have different implications for proper understanding of the disease and effective screening of therapeutic agents. There is no high-quality literature recommending the most appropriate animal models. In this paper, we will describe the progress of commonly used animal models of liver fibrosis in terms of their development mechanisms, applications, advantages and disadvantages, and recommend appropriate animal models for different research purposes.

Koumine ameliorates concanavalin A-induced autoimmune hepatitis in mice: involvement of the Nrf2, NF-κB pathways, and gut microbiota

Gelsemiumelegans(Gardner. & Chapm.) Benth. has long been considered a traditional Chinese medicine effective against rheumatoid pain, cancer, cirrhosis, and skin diseases. Koumine (KM), the most abundant alkaloid in G.elegans Benth., demonstrates a variety of biological effects, including antitumor, analgesic, anxiolytic, anti-inflammatory, antidepressant, antioxidant, immunoregulatory, and hepatoprotective effects. Furthermore, the relatively low toxicity of KM makes it a promising drug candidate. This study aimed to investigate the protective effects of KM and its possible mechanisms using a concanavalin A (Con A)-induced autoimmune hepatitis (AIH) model in mice. Mice were orally administered different doses of KM for 14 d before Con A tail vein injections. The effects of KM on serum biochemical markers and liver histopathology were then evaluated 12 h after Con A exposure. The Nrf2 and NF-κB signaling pathways and alterations in gut microbiota were determined using western blotting, immunohistochemistry, and 16S rRNA sequencing to explore the underlying mechanisms of KM exposure. KM pretreatment dose-dependently decreased serum liver injury markers (Alanine aminotransferase, and aspartate aminotransferase) and cytokine levels (Tumor necrosis factor-α and interleukin-6), as well as the liver pathological damage triggered by Con A. Furthermore, the results of the multi-technique analysis indicated that KM activated the Nrf2 pathway, upregulated the expression of anti-oxidation factors HO-1 and Nrf2, and downregulated the expression of Keap1. Moreover, the NF-κB signaling pathway was inhibited. Interestingly, pre-treatment with KM also significantly improved the composition of the gut microbiota probably because it increases the richness of probiotics. Our findings suggest that KM pretreatment could attenuate Con A-induced AIH, the Nrf2 and NF-κB signaling pathways, and that gut microbiota are involved in the process of the hepatoprotective effect. This study provides a theoretical basis for the development of KM as an effective agent against AIH.

Garcinone E Mitigates Oxidative Inflammatory Response and Protects against Experimental Autoimmune Hepatitis via Modulation of Nrf2/HO-1, NF-κB and TNF-α/JNK Axis

Garcinia mangostana L. (Clusiaceae), a popular tropical fruit for its juiciness and sweetness, is an opulent fountain of prenylated and oxygenated xanthones with a vast array of bio-activities. Garcinone E (GE), a xanthone derivative reported from G. mangostana, possesses cytotoxic and aromatase inhibitory activities. The present research endeavors to investigate the hepato-protection efficaciousness of GE on concanavalin-A (Con-A)-instigated hepatitis. Results showed that GE pretreating noticeably diminishes both the serum indices (transaminases, ALP, LDH, and γ-GT) and histopathological lesions of the liver. It counteracted neutrophil and CD4+ infiltration into the liver. GE furthered the Nrf2 genetic expression and its antioxidants' cascade, which resulted in amelioration of Con-A-caused oxidative stress (OS), lipid per-oxidative markers (4-HNE, MDA, PC) reduction, and intensified antioxidants (TAC, SOD, GSH) in the hepatic tissue. Additionally, GE prohibited NF-ĸB (nuclear factor kappa-B) activation and lessened the genetics and levels of downstream cytokines (IL1β and IL6). Moreover, the TNF-α/JNK axis was repressed in GE-treated mice, which was accompanied by attenuation of Con-A-induced apoptosis. These findings demonstrated the protective potential of GE in Con-A-induced hepatitis which may be associated with Nrf2/HO-1 signaling activation and OS suppression, as well as modulation of the NF-κB and TNF-α/JNK/apoptosis signaling pathway. These results suggest the potential use of GE as a novel hepato-protective agent against autoimmune hepatitis.

Narciclasine ameliorated T cell mediated acute liver injury through activating AMPK pathway

Hepatitis is closely related to cirrhosis and liver cancer, and it is vital that we develop new drugs and identify new drug targets. Traditional Chinese medicine has demonstrated excellent curative effects on liver diseases. The ingredients from Chinese herbals are important source for drug development in the treatment of hepatitis. Here, we found that narciclasine (NCS), a major component extracted from narcissus bulbs, showed hepatoprotective effect against concanavalin A (Con A) induced hepatitis. NCS treatment significantly reduced hepatocyte death, hepatic inflammatory cells infiltration, and serum cytokine levels in Con A challenged mice. We further observed that NCS directly inhibited Con A induced splenocytes proliferation and cytokine production in vitro. RNA-seq results showed that genes related to immune response were upregulated in Con A treated CD4+ T cells, which were down-regulated in the presence of NCS. Moreover, the AMPK pathway had been found activated in response to NCS treatment, suggesting a potential target for NCS targets. In conclusion, our results reveal that NCS is a powerful immunosuppressor against T cell activation, thus leading to protection against Con A induced liver injury in mice. These findings provide new insights into the use of natural products in the treatment of autoimmune hepatitis.

Salidroside in the Treatment of NAFLD/NASH

Non-alcoholic fatty liver disease (NAFLD) is the commonest reason for chronic liver diseases in the world and is commonly related to the hepatic manifestation of the metabolic syndrome. Non-alcoholic steatohepatitis (NASH) is a deteriorating form of NAFLD, which can eventually develop into fibrosis, cirrhosis, and liver cancer. The reason for NAFLD/NASH development is complicated, such as liver lipid metabolism, oxidative stress, inflammatory response, apoptosis and autophagy, liver fibrosis and gut microbiota. Apart from bariatric surgery and lifestyle changes, officially approved drug therapy for NAFLD/NASH treatment is lacking. Salidroside (SDS) is a phenolic compound extensively distributed in the tubers of Rhodiola plants, which possesses many significant biological activities. This review summarized the related targets regulated by SDS in treating NAFLD/NASH. It is indicated that SDS could improve the status of NAFLD/NASH by ameliorating abnormal lipid metabolism, inhibiting oxidative stress, regulating apoptosis and autophagy, reducing inflammatory response, alleviating fibrosis and regulating gut microbiota. In conclusion, although the multiple bioactivities of SDS have been confirmed, the clinical data are inadequate and need to become the focus of attention in the later study.

Resolving the conflicts around Par2 opposing roles in regeneration by comparing immune-mediated and toxic-induced injuries

BACKGROUND

Different factors may lead to hepatitis. Among which are liver inflammation and poisoning. We chose two hepatitis models, typical for these two underlying causes. Thus, we aimed to characterize the role of protease-activated receptor 2 (Par2) in liver regeneration and inflammation to reconcile Par2 conflicting role in many damage models, which sometimes aggravates the induced damage and sometimes alleviates it.

METHODS

WT and knockout (Par2KO) mice were injected with concanavalin A (ConA) to induce immune-mediated hepatitis or with carbon tetrachloride (CCl₄) to elicit direct hepatic damage. To distinguish the immune component from the liver regenerative response, we conducted bone marrow (BM) replacements of WT and Par2KO mice and repeated the damage models.

RESULTS

ConA injection caused limited damage in Par2KO mice livers, while in the WT mice severe damage followed by leukocyte infiltration was evident. Reciprocal BM replacement of WT and Par2KO showed that WT BM-reconstituted Par2KO mice displayed marked liver damage, while in Par2KO BM-reconstituted WT mice, the tissue was generally protected. In the CCl₄ direct damage model, hepatocytes regenerated in WT mice, whereas Par2KO mice failed to recover. Reciprocal BM replacement did not show significant differences in hepatic regeneration. In Par2KO mice, hepatitis was more apparent, while WT recovered regardless of the BM origin.

CONCLUSIONS

We conclude that Par2 activation in the immune system aggravates hepatitis and that Par2 activation in the damaged tissue promotes liver regeneration. When we incorporate this finding and revisit the literature reports, we reconciled the conflicts surrounding Par2's role in injury, recovery, and inflammation.

Hepatocyte DAX1 Deletion Exacerbates Inflammatory Liver Injury by Inducing the Recruitment of CD4+ and CD8+ T Cells through NF-κB p65 Signaling Pathway in Mice

Fulminant hepatitis is characterized by rapid and massive immune-mediated liver injury. Dosage-sensitive sex reversal-adrenal hypoplasia congenita critical region on the X chromosome, gene 1 (DAX1; NR0B1) represses the transcription of various genes. Here, we determine whether DAX1 serves as a regulator of inflammatory liver injury induced by concanavalin A (ConA). C57BL/6J (WT), myeloid cell-specific Dax1 knockout (MKO), and hepatocyte-specific Dax1 knockout (LKO) mice received single intravenous administration of ConA. Histopathological changes in liver and plasma alanine aminotransferase and aspartate aminotransferase levels in Dax1 MKO mice were comparable with those in WT mice following ConA administration. Unlike Dax1 MKO mice, Dax1 LKO mice were greatly susceptible to ConA-induced liver injury, which was accompanied by enhanced infiltration of immune cells, particularly CD4⁺ and CD8⁺ T cells, in the liver. Factors related to T-cell recruitment, including chemokines and adhesion molecules, significantly increased following enhanced and prolonged phosphorylation of NF-κB p65 in the liver of ConA-administered Dax1 LKO mice. This is the first study to demonstrate that hepatocyte-specific DAX1 deficiency exacerbates inflammatory liver injury via NF-κB p65 activation, thereby causing T-cell infiltration by modulating inflammatory chemokines and adhesion molecules. Our results suggest DAX1 as a therapeutic target for fulminant hepatitis treatment.

Multi-Omics Analysis Reveals the Protection of Gasdermin D in Concanavalin A-Induced Autoimmune Hepatitis

Autoimmune hepatitis (AIH) is a progressive inflammation-associated liver injury. Pyroptosis is a novel inflammatory programmed cell death wherein gasdermin D (GSDMD) serves as the executioner. Our work challenged Gsdmd^-/- mice with concanavalin A (ConA) to try to unveil the actual role of GSDMD in AIH. After ConA injection, Gsdmd^-/- mice exhibited more severe liver damage characterized by a lower survival rate, more extensive hepatocyte necrosis and apoptosis, and higher serum transaminase levels, indicating the protection of GSDMD in ConA-induced AIH. Furthermore, the Gsdmd^-/- mice exhibited higher hepatic expression and serum levels of inflammatory cytokines (gamma interferon [IFN-γ], tumor necrosis factor alpha [TNF-α], and interleukin-17A [IL-17A]) and more infiltration of macrophages and neutrophils after ConA treatment than did wild-type (WT) mice. Gsdmd^-/- mice with AIH showed increased hepatic l-glutamine levels but decreased glycerophospholipid metabolites levels. L-glutamine levels showed positive correlations while glycerophospholipid metabolites showed negative associations with liver injury indexes and inflammation markers. We further observed a destroyed intestinal barrier in Gsdmd^-/- mice after ConA injection as indicated by decreased transcriptional expressions of Tjp1, Ocln, Reg3g, and Muc2. ConA-treated Gsdmd^-/- mice also exhibited higher serum LPS binding protein (LBP) concentrations and hepatic Tlr4 and Cd14 mRNA levels. Further fecal 16S rRNA gene sequencing demonstrated decreased relative abundances of Lactobacillus and Roseburia but increased relative abundances of Allobaculum and Dubosiella in Gsdmd^-/- mice with AIH. Lactobacillus was negatively correlated with liver injury and inflammation indexes and positively associated with Ocln, Muc2, and Reg3g levels. Allobaculum was positively related to liver injury and inflammatory cytokines and negatively correlated with gut barrier indexes. IMPORTANCE Our study provides the first direct clues to the protective role of gasdermin D (GSDMD) in autoimmune hepatitis (AIH). We demonstrated that Gsdmd knockout exacerbated concanavalin A (ConA)-induced AIH in mice. It may be due to the destroyed intestinal barrier and changes in certain intestinal microbes and hepatic metabolites resulting in increased liver injury and inflammation in ConA-treated Gsdmd^-/- mice. This finding suggested a nonnegligible role of GSDMD in AIH and also confirmed its physiological nonpyroptosis effects on the host. The role of GSDMD in autoimmune liver diseases or other liver diseases is complex and intriguing, deserving deep investigation.

Alpha-Mangostin as a New Therapeutic Candidate for Concanavalin A-Induced Autoimmune Hepatitis: Impact on the SIRT1/Nrf2 and NF-κB Crosstalk

Alpha-mangostin (α-MN) is a xanthone obtained from Garcinia mangostana that has diverse anti-oxidative and anti-inflammatory potentials. However, its pharmacological activity against autoimmune hepatitis (AIH) has not been investigated before. Concanavalin A (Con A) was injected into mice to induce AIH and two doses of α-MN were tested for their protective effects against Con A-induced AIH. The results demonstrated the potent hepatoprotective activity of α-MN evidenced by a remarkable decrease of serum indices of the hepatic injury and amendment of the histological lesions. α-MN significantly attenuated the level and immuno-expression of myeloperoxidase (MPO) indicating a decrease in the neutrophil infiltration into the liver. Additionally, the recruitment of the CD4+ T cell was suppressed in the α-MN pre-treated animals. α-MN showed a potent ability to repress the Con A-induced oxidative stress evident by the reduced levels of malondialdehyde (MDA), 4-hydroxynonenal (4-HNE), and protein carbonyl (PC), as well as the enhanced levels of antioxidants as the reduced glutathione (GSH), superoxide dismutase (SOD), and total antioxidant capacity (TAC). The ELISA, RT-PCR, and IHC analyses revealed that α-MN enhanced the sirtuin1/nuclear factor erythroid 2 related factor-2 (SIRT1/Nrf2) signaling and its downstream cascade genes concurrently with the inhibition of the nuclear factor kappa B (NF-κB) and the inflammatory cytokines (tumor necrosis factor-alpha and interleukine-6) signaling. Taken together, these results inferred that the hepatoprotective activity of α-MN could prevent Con A-induced AIH through the modulation of the SIRT1/Nrf2/NF-κB signaling. Hence, α-MN may be considered as a promising candidate for AIH therapy.

Escin suppresses immune cell infiltration and selectively modulates Nrf2/HO-1, TNF-α/JNK, and IL-22/STAT3 signaling pathways in concanavalin A-induced autoimmune hepatitis in mice

The current study aims to investigate the possible protective effect of escin, the active constituent of a natural mixture of triterpene saponin glycoside, against immune-mediated hepatitis driven by concanavalin A (Con A) and to elucidate its possible underlying mechanisms. Adult male mice were administered Con A (15 mg/kg, intravenously) for 8 h. In the treated groups, mice were pretreated with escin daily (10 mg/kg in CMC, orally) for 4 days before Con A intoxication. In addition, escin was administered in a group to examine its effect on normal mice. Our results showed that escin inhibited Con A-induced elevation in liver enzymes (ALT, AST, and LDH) and curbed the Con A-induced hepatocyte necrosis and apoptosis together with abrogating the death pathway, JNK. Coincidentally, escin has shown a reduction in neutrophil, CD4+ T cell, and monocyte infiltration into the liver. In addition, escin modulated the cellular oxidant status by compensating for the Con A-depleted expression of the transcription factor Nrf2 and the stress protein hemeoxygenase-1. These effects were in good agreement with the restraining effect of escin on Con A-instigated overexpression of NF-κB and the pro-inflammatory cytokines TNF-α and IL-17A. Interestingly, Con A provoked the cellular protective pathway IL-22/STAT3, which was revoked by the escin pretreatment. In conclusion, escin shows extended antioxidant, anti-inflammatory, antinecrotic, and anti-apoptotic effects against Con A-induced immune-mediated hepatitis. These effects may collectively be via suppressing immune cell infiltration into the liver and selective modulation of Nrf2/HO-1, TNF-α/NF-κB, TNF-α/JNK, and IL-22/STAT3 signaling pathways.

Berbamine and thymoquinone exert protective effects against immune-mediated liver injury via NF-κB dependent pathway

Background

Immune-mediated hepatitis is a severe impendence to human health, and no effective treatment is currently available. Therefore, new, safe, low-cost therapies are desperately required. Berbamine (BE), a natural substance obtained primarily from Berberis vulgaris L, is a traditional herbal medicine with several bioactivities, such as antimicrobial and anticancer activities. Thymoquinone (TQ), a phytochemical molecule derived from the Nigella sativa plant's black cumin seeds, has attracted interest owing to itsanti-inflammatory, antioxidant, and anticancer properties.

Aim

This current study's aims was to examine the protective impacts of BE and TQ in Concanavalin A (ConA)- induced acute liver injury and the action's underlying mechanism.

Methods

sixty mice of both sexes were used and divided into four groups (each group with six mice) as follows: Group I obtained distilled water (negative control group). Group II received distilled water with a single dose of 0.1 ml ConA (20 mg/kg) on day 4 by retro-orbital route (model group). Groups III and IV received BE (30 mg/kg/day) and TQ (25 mg/kg/day), respectively, by oral gavage for four successive days, with a single dose of ConA (20 mg/kg) on day 4, then all animals were sacrificed after 8 h and prepared for liver and blood collection.

Results

ConA administration increased the ALT, AST, TNF-α, INFγ, and NF-κB significantly (p < 0.001) in the model group. Both BE and TQ could reduce these parameters significantly (p < 0.001) in groups III and IV, respectively, compared to the model group.

Conclusion

Both BE and TQ prominently attenuated ConA immune-mediated liver injury. These findings give a remarkable insight into developing a new therapeutic agent for treating hepatitis and other autoimmune diseases.

Inducible nitric oxide synthase regulates macrophage polarization via the MAPK signals in concanavalin A-induced hepatitis

INTRODUCTION

Acute liver inflammatory reactions contribute to many health problems; thus, it is critical to understand the underlying pathogenic mechanisms of acute hepatitis. In this study, an experimental in vivo model of concanavalin A (ConA)-induced hepatitis was used.

MATERIALS AND METHODS

C57BL/6 (wild-type, WT) or inducible nitric oxide synthase-deficient (iNOS-/- ) mice were injected with PBS or 15 mg/kg ConA via tail vein. Detection of liver injury by histological examination and apoptosis, and flow cytometry to detect the effect of immune cells on liver injury.

RESULTS

iNOS-/-  mice had lower levels of the liver enzymes aspartate aminotransferase and alanine aminotransferase, suggesting that they were protected against ConA-induced pathological liver injury and that iNOS participated in the regulation of hepatitis. Furthermore, iNOS deficiency was found to lower CD86 expression and suppressed the messenger RNA levels of inflammatory factors in the liver. In vitro experiments also demonstrated that iNOS deficiency suppressed the sequential phosphorylation of the mitogen-activated protein kinase pathway cascade, thereby inhibiting the M1 polarization of macrophages and consequently suppressing the transcription of inflammation factors.

CONCLUSION

iNOS may contribute to ConA-induced inflammation by promoting the activation of proinflammatory macrophages.

Mannose-targeting Concanavalin A-Epirubicin Conjugate for Targeted Intravesical Chemotherapy of Bladder Cancer

Intravesical instillation of chemotherapeutic drugs such as epirubicin (EPI) is routinely used to prevent tumor recurrence and progression after transurethral resection of bladder tumor. However, the lack of tumor selectivity often causes severe damage to normal bladder urothelium leading to intolerable side effects. Here, we analyzed abnormal changes in glycosylation in bladder cancer and identified mannose as the most aberrantly expressed glycan on the surface of bladder cancer cell lines and human bladder tumor tissues. We then constructed a lectin-drug conjugate by linking concanavalin A (ConA) - a lectin that specifically binds to mannose, with EPI through a pH-sensitive linker. This ConA-EPI conjugate conferred EPI with mannose-targeting ability and selectively internalized cancer cells in vitro. This conjugate showed selective cytotoxicity to cancer cells in vitro and better antitumor activity in an orthotopic mouse model of bladder cancer. Our lectin-drug conjugation strategy makes targeted intravesical chemotherapy of bladder cancer possible.

Targeting Glutamine Metabolism Ameliorates Autoimmune Hepatitis via Inhibiting T Cell Activation and Differentiation

Background

Autoimmune hepatitis (AIH) is mediated by a cascade of T cell-mediated events directed at liver cells and persistent inflammation within the liver can eventually result in liver cirrhosis. Targeting glutamine metabolism has an impact on T cell activation and differentiation. However, the effect of glutamine metabolism blocking upon AIH remains unknown. We use glutaminase antagonist 6-diazo-5-oxo-L-norleucine (DON) for in vitro assays and its prodrug 2-(2-amino-4-methylpentanamido)-DON (JHU083) for in vivo assays to investigate the potential therapeutic effect and molecular mechanism of glutamine metabolism blocking in an AIH murine model.

Methods

AIH mice were treated with JHU083 or vehicle before concanavalin A (ConA) administration, and disease severity was examined. Then activation and differentiation [including Th1/Th17 cells and cytotoxic T lymphocytes (CTL)] of T cells from Vehicle-WT, JHU083-AIH and Vehicle-AIH mice were tested. Furthermore, in vitro T cell activation and differentiation were measured using separated splenocytes stimulated with ConA with or without DON. The activation and differentiation of T cells were tested using flow cytometry, qRT-PCR and ELISA. Phosphorylation level of mammalian target of rapamycin (mTOR) and 70 kDa ribosomal protein S6 kinase (P70S6K) were examined by western blotting.

Results

JHU083 and DON significantly suppressed the activation of T cells and inhibited the differentiation of Th1/Th17 cells and CTL in vivo and in vitro. Besides, we demonstrated that glutamine metabolism blocking inhibited T cells activation and differentiation through decreasing the mRNA expression of amino acid transporter solute carrier family 7 member 5 (SLC7A5) and mitigating the activation of mTOR signaling.

Conclusions

We proved that targeting glutamine metabolism represents a potential new treatment strategy for patients with AIH and other T cell-mediated disease. Mechanistically, we demonstrated that glutamine metabolism blocking inhibits T cells activation and suppresses the differentiation of Th1/Th17 cells and CTL.

AhR Activation Leads to Attenuation of Murine Autoimmune Hepatitis: Single-Cell RNA-Seq Analysis Reveals Unique Immune Cell Phenotypes and Gene Expression Changes in the Liver

The aryl hydrocarbon receptor (AhR) is a ubiquitously expressed ligand-activated transcription factor. While initially identified as an environmental sensor, this receptor has been shown more recently to regulate a variety of immune functions. AhR ligands vary in structure and source from environmental chemicals such as 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and indoles found in cruciferous vegetables to endogenous ligands derived from tryptophan metabolism. In the current study, we used TCDD, a high affinity AhR ligand to study the impact of AhR activation in the murine model of autoimmune hepatitis (AIH). Primarily, we used single-cell RNA-sequencing (scRNA-seq) technology to study the nature of changes occurring in the immune cells in the liver at the cellular and molecular level. We found that AhR activation attenuated concanavalin A (ConA)-induced AIH by limiting chemotaxis of pro-inflammatory immune cell subsets, promoting anti-inflammatory cytokine production, and suppressing pro-inflammatory cytokine production. scRNA-seq analysis showed some unusual events upon ConA injection such as increased presence of mature B cells, natural killer (NK) T cells, CD4+ or CD8+ T cells, Kupffer cells, memory CD8+ T cells, and activated T cells while TCDD treatment led to the reversal of most of these events. Additionally, the immune cells showed significant alterations in the gene expression profiles. Specifically, we observed downregulation of inflammation-associated genes including Ptma, Hspe1, and CD52 in TCDD-treated AIH mice as well as alterations in the expression of migratory markers such as CXCR2. Together, the current study characterizes the nature of inflammatory changes occurring in the liver during AIH, and sheds light on how AhR activation during AIH attenuates liver inflammation by inducing phenotypic and genotypic changes in immune cells found in the liver.

Bcl-3 promotes TNF-induced hepatocyte apoptosis by regulating the deubiquitination of RIP1

Tumor necrosis factor-α (TNF) is described as a main regulator of cell survival and apoptosis in multiple types of cells, including hepatocytes. Dysregulation in TNF-induced apoptosis is associated with many autoimmune diseases and various liver diseases. Here, we demonstrated a crucial role of Bcl-3, an IκB family member, in regulating TNF-induced hepatic cell death. Specifically, we found that the presence of Bcl-3 promoted TNF-induced cell death in the liver, while Bcl-3 deficiency protected mice against TNF/D-GalN induced hepatoxicity and lethality. Consistently, Bcl-3-depleted hepatic cells exhibited decreased sensitivity to TNF-induced apoptosis when stimulated with TNF/CHX. Mechanistically, the in vitro results showed that Bcl-3 interacted with the deubiquitinase CYLD to synergistically switch the ubiquitination status of RIP1 and facilitate the formation of death-inducing Complex II. This complex further resulted in activation of the caspase cascade to induce apoptosis. By revealing this novel role of Bcl-3 in regulating TNF-induced hepatic cell death, this study provides a potential therapeutic target for liver diseases caused by TNF-related apoptosis.

Personalized-Inherent Variability in a Time-Dependent Immune Response: A Look into the Fifth Dimension in Biology

Introduction

Individualized response to the immune triggers influences the course of immune-mediated diseases and the response to immunotherapies. Both inter- and intra-subject variations occur in time-dependent dynamics of biological systems. The present study aimed to establish a model for inherent personalized-time-dependent variability in response to immune triggers.

Methods

Male C57BL/6 mice were administered concanavalin A (ConA) and followed every 2 h for 10 h and at 24 h for serum alanine aminotransferase (ALT) levels.

Results

A marked intragroup variability was noted for both the timing of the effect of ConA, the magnitude of the increase in ALT levels, and the time to peak. While in some mice, a peak level was achieved, whereas a continuous increase in liver damage was noted in others. Four mice died at different time points during the study irrespective of their liver damage, further supporting the individualized-based response to the trigger.

Conclusions

This feasibility study established a model for determining the personalized-inherent variability in a time-dependent response to the immune triggers. These results highlight the importance of considering both the time and the wide range of individualized variability in immune responses while designing personalized-based immunotherapies.

Mesenchymal Stromal/Stem Cells and Their Extracellular Vesicles Application in Acute and Chronic Inflammatory Liver Diseases: Emphasizing on the Anti-Fibrotic and Immunomodulatory Mechanisms

Various factors, including viral and bacterial infections, autoimmune responses, diabetes, drugs, alcohol abuse, and fat deposition, can damage liver tissue and impair its function. These factors affect the liver tissue and lead to acute and chronic liver damage, and if left untreated, can eventually lead to cirrhosis, fibrosis, and liver carcinoma. The main treatment for these disorders is liver transplantation. Still, given the few tissue donors, problems with tissue rejection, immunosuppression caused by medications taken while receiving tissue, and the high cost of transplantation, liver transplantation have been limited. Therefore, finding alternative treatments that do not have the mentioned problems is significant. Cell therapy is one of the treatments that has received a lot of attention today. Hepatocytes and mesenchymal stromal/stem cells (MSCs) are used in many patients to treat liver-related diseases. In the meantime, the use of mesenchymal stem cells has been studied more than other cells due to their favourable characteristics and has reduced the need for liver transplantation. These cells increase the regeneration and repair of liver tissue through various mechanisms, including migration to the site of liver injury, differentiation into liver cells, production of extracellular vesicles (EVs), secretion of various growth factors, and regulation of the immune system. Notably, cell therapy is not entirely excellent and has problems such as cell rejection, undesirable differentiation, accumulation in unwanted locations, and potential tumorigenesis. Therefore, the application of MSCs derived EVs, including exosomes, can help treat liver disease and prevent its progression. Exosomes can prevent apoptosis and induce proliferation by transferring different cargos to the target cell. In addition, these vesicles have been shown to transport hepatocyte growth factor (HGF) and can promote the hepatocytes'(one of the most important cells in the liver parenchyma) growths.

Hepatoprotective Role of 4-Octyl Itaconate in Concanavalin A-Induced Autoimmune Hepatitis

4-Octyl itaconate (OI) is a novel anti-inflammatory metabolite that exerts protective effects in many various disease models. However, its function in autoimmune hepatitis- (AIH-) associated hepatic injury has not been investigated. In this study, we successfully used concanavalin A (Con A) to establish an AIH-associated liver injury model. Furthermore, we investigated the effect of OI in Con A-induced liver injury and found that OI mitigated Con A-induced histopathological damage. OI administration reduced serum levels of alanine transaminase and aspartate transaminase in Con A-treated mice and attenuated the infiltration of macrophages induced by Con A. Moreover, OI effectively inhibited the expression of proinflammatory cytokines including interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), and IL-1β induced by Con A. Furthermore, OI decreased hepatocyte apoptosis and malondialdehyde levels and increased the reduced glutathione/oxidized glutathione ratio in the Con A-induced liver injury model. In addition, we found that OI inhibited Con A-induced hepatocyte apoptosis in vitro, while Nrf2 deletion eliminated this effect. Furthermore, we administrated the Nrf2 inhibitor ML385 in OI+Con A-treated mice and found that ML385 eliminated the protective effect of OI in vivo. In addition, OI inhibited Con A-induced activation of nuclear factor-kappa B (NF-𝜅B) and the expression of proinflammatory cytokines in macrophages. Therefore, OI protected mice from Con A-induced liver damage and may be associated with Nrf2 activation and NF-𝜅B inhibition. Finally, our study revealed that OI inhibited TNF-α, or supernatants from Con A-treated RAW264.7 cells induced hepatocyte apoptosis. In conclusion, our study indicated that OI alleviated Con A-induced hepatic damage by reducing inflammatory response, oxidative stress, and apoptosis.

Concanavalin A-induced autoimmune hepatitis model in mice: Mechanisms and future outlook

The concanavalin A (Con A)-induced liver injury mouse model is a typical animal model focusing on T cell-dependent hepatic damage in the field of autoimmune hepatitis (AIH). However, the underlying mechanism of hepatic dysfunction due to cell activation or signaling pathways triggered by Con A has not been fully clarified. Therefore, the controversy on this model remains in the academic community. In this article, we first summarized the merit and demerit of this contentious model from the perspectives of cell dysfunction, microcirculation disturbance, involved signaling pathways, as well as the properties of Con A. Then, we summed up the scientific implications of the model in elucidating the pathogenesis of AIH, and the shortcomings of this model were also summarized to elucidate the pathogenesis and application prospect of this classical liver injury mouse model in the study of AIH.

Corilagin Ameliorates Con A-Induced Hepatic Injury by Restricting M1 Macrophage Polarization

Immune-mediated hepatic injury plays a key role in the initiation and pathogenesis of diverse liver diseases. However, treatment choice for immune-mediated hepatic injury remains limited. Corilagin, a natural ellagitannin extracted from various traditional Chinese medicines, has been demonstrated to exhibit multiple pharmacological activities, such as anti-inflammatory, anti-tumor, and hepatoprotective properties. The present study aimed to investigate the effects of corilagin on immune-mediated hepatic injury using a murine model of concanavalin A (Con A)-induced hepatitis, which is well-characterized to study acute immune-mediated hepatitis. Herein, mice were administered corilagin (25 mg/kg) intraperitoneally twice at 12 h intervals, and 1 h later, the mice were challenged with Con A (20 mg/kg body weight); serum and liver samples were collected after 12 h. The results showed that corilagin significantly increased the survival of mice and reduced serum alanine transaminase (ALT) and aspartate aminotransferase (AST) levels. In addition, corilagin markedly improved histopathological damage, hepatocyte apoptosis, and oxidative stress in the liver. The activation of M1 macrophages in the hepatic mononuclear cells was also significantly reduced compared with that in the control group. The expression of M1 macrophage-associated proinflammatory cytokines and genes, including interleukin (IL)-6, IL-12, and inducible nitric oxide synthase (iNOS), was also decreased after corilagin treatment. Finally, the results demonstrated that corilagin regulated macrophage polarization by modulating the mitogen-activated protein kinases (MAPK), nuclear factor (NF)-κB, and interferon regulatory factor (IRF) signaling pathways. Thus, the findings indicate that corilagin protects mice from Con A-induced immune-mediated hepatic injury by limiting M1 macrophage activation via the MAPK, NF-κB, and IRF signaling pathways, suggesting corilagin as a possible treatment choice for immune-mediated hepatic injury.

The Protective Role of IL-36/IL-36R Signal in Con A-Induced Acute Hepatitis

The IL-36 family, including IL-36α, IL-36β, IL-36γ, and IL-36R antagonist, belong to the IL-1 superfamily. It was reported that IL-36 plays a role in immune diseases. However, it remains unclear how IL-36 regulates inflammation. To determine the role of IL-36/IL-36R signaling pathways, we established an acute hepatitis mouse model (C57BL/6) by i.v. injection of the plant lectin Con A. We found that the levels of IL-36 were increased in the liver after Con A injection. Our results demonstrated the infiltrated neutrophils, but not the hepatocytes, were the main source of IL-36 in the liver. Using the IL-36R-/- mouse model (H-2b), we surprisingly found that the absence of IL-36 signals led to aggravated liver injury, as evidenced by increased mortality, elevated serum alanine aminotransferase and aspartate aminotransferase levels, and severe liver pathological changes. Further investigations demonstrated that a lack of IL-36 signaling induced intrahepatic activation of CD4+ and CD8+ T lymphocytes and increased the production of inflammatory cytokines. In addition, IL-36R-/- mice had reduced T regulatory cell numbers and chemokines in the liver. Together, our results from the mouse model suggested a vital role of IL-36 in regulating T cell function and homeostasis during liver inflammation.

Taraxasterol mitigates Con A-induced hepatitis in mice by suppressing interleukin-2 expression and its signaling in T lymphocytes

Discovery of anti-inflammatory drugs that can suppress T lymphocyte activation and proliferation by inhibiting TCR/CD3 and IL-2/IL-2R signaling is still needed in clinic, though rapamycin and other related reagents have made great success. Taraxasterol (TAS) is an active ingredient of dandelion, an anti-inflammatory medicinal herb with low in vivo toxicity that has long been used in China. Yet the action mechanism of TAS on lymphocytes remains elusive. The anti-inflammatory effects of TAS were evaluated in C57BL/6 mouse primary lymphocytes stimulated with concanavalin A (Con A) in vitro and in mouse model of Con A-induced acute hepatitis in vivo. Our results showed that TAS significantly suppressed Con A-induced acute hepatitis in a mouse model, reducing the hepatic necrosis areas, the release of aminotransferases, and the production of IL-2 and other inflammatory cytokines. Supporting this, in vitro study also showed that TAS reduced the production of IL-2 and the expression of IL-2 receptor subunit α (CD25) upon the stimulation of Con A, which was likely mediated by suppressing NF-κB activation. The downstream pathways of IL-2/IL-2R signaling, including the activation of PI3K/PDK1/mTOR, STAT3 and STAT5, were also suppressed by TAS. Consistently, Con A-induced T cell proliferation was also inhibited by TAS in vitro. Our data indicate that TAS can suppress both T lymphocyte activation and cell proliferation by down-regulating IL-2 expression and its signaling pathway thereby ameliorating Con A-induced acute hepatitis, highlighting TAS as a potential drug candidate for treating inflammatory diseases including autoimmune hepatitis.

Preclinical models of acute liver failure: a comprehensive review

Acute liver failure is marked by the rapid deterioration of liver function in a previously well patient over period of days to weeks. Though relatively rare, it is associated with high morbidity and mortality. This makes it a challenging disease to study clinically, necessitating reliance on preclinical models as means to explore pathophysiology and novel therapies. Preclinical models of acute liver failure are artificial by nature, and generally fall into one of three categories: surgical, pharmacologic or immunogenic. This article reviews preclinical models of acute liver failure and considers their relevance in modeling clinical disease.

The JAK inhibitor ruxolitinib abrogates immune hepatitis instigated by concanavalin A in mice

Therapeutics that impair the innate immune responses of the liver during the inflammatory cytokine storm like that occurring in COVID-19 are greatly needed. Much interest is currently directed toward Janus kinase (JAK) inhibitors as potential candidates to mitigate this life-threatening complication. Accordingly, this study investigated the influence of the novel JAK inhibitor ruxolitinib (RXB) on concanavalin A (Con A)-induced hepatitis and systemic hyperinflammation in mice to simulate the context occurring in COVID-19 patients. Mice were orally treated with RXB (75 and 150 mg/kg) 2 h prior to the intravenous administration of Con A (20 mg/kg) for a period of 12 h. The results showed that RXB pretreatments were efficient in abrogating Con A-instigated hepatocellular injury (ALT, AST, LDH), necrosis (histopathology), apoptosis (cleaved caspase-3) and nuclear proliferation due to damage (PCNA). The protective mechanism of RXB were attributed to i) prevention of Con A-enhanced hepatic production and systemic release of the proinflammatory cytokines TNF-α, IFN-γ and IL-17A, which coincided with decreasing infiltration of immune cells (monocytes, neutrophils), ii) reducing Con A-induced hepatic overexpression of IL-1β and CD98 alongside NF-κB activation, and iii) lessening Con A-induced consumption of GSH and GSH peroxidase and generation of oxidative stress products (MDA, 4-HNE, NOx) in the liver. In summary, JAK inhibition by RXB led to eminent protection of the liver against Con A-deleterious manifestations primarily via curbing the inflammatory cytokine storm driven by TNF-α, IFN-γ and IL-17A.

Pathogenesis of Concanavalin A induced autoimmune hepatitis in mice

Autoimmune hepatitis (AIH) is an autoimmune disease characterized by liver parenchymal destruction and chronic fibrosis. Its exact etiology and pathogenesis are not yet fully understood.(Please connect with the following, do not leave a line) Concanavalin A (Con A)-induced mice hepatitis model is a liver injury mediated by T cell and macrophage activation, and its pathogenesis and pathological changes are similar to human AIH. The establishment of this model has greatly promoted the research progress of AIH pathogenesis. However, the exact mechanism of Con A induced liver injury in mice, and its possible defects or deficiencies, has not yet been described in a clear and detailed manner. Therefore, the model has some limitations when applied to the study of the pathogenesis and treatment mechanism of AIH. This article reveals the pathogenesis of Con A induced liver injury in mice from the aspects of immune disorder and coagulation mechanism, expounds the significance of non-coding RNA in this model, summarizes the signal transduction pathways involved in this model, and summarizes the advantages and disadvantages of the model, which provides a theoretical basis and research target for the application of Con A induced liver injury model in AIH in the future.

CQMUH-011 mitigates autoimmune hepatitis via inhibiting the function of T lymphocytes

CQMUH-011 is a modified adamantane sulfonamide compound, that inhibits macrophage proliferation and possesses anti-inflammatory properties. Here, fresh mouse splenocytes were obtained and stimulated with concanavalin A (ConA, 5 μg/ml) in vitro; and experimental autoimmune hepatitis (AIH) was induced by ConA (20 mg/kg, iv) in vivo, to clarify the protective effects of CQMUH-011 against AIH and its possible mechanisms. Our results demonstrated that CQMUH-011 pretreatment can dose-dependently inhibit the proliferation of splenocytes in vitro. In vivo, CQMUH-011 administration reduced the hepatic histopathological score and the infiltration of lymphocytes in the liver parenchyma; additionally, it downregulated the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and pro-inflammatory cytokines interferon (IFN)-γ, tumor necrosis factor (TNF)-α, and interleukin (IL)-6 in serum, as well as those of methane dicarboxylic aldehyde and myeloperoxidase in the liver tissues. It also down-regulated the expression of p-NF-κB and related proteins in the liver tissues. Furthermore, CQMUH-011 could maintain the balance of CD3+ CD4+ /CD3+ CD8+ and decrease the percentages of CD8+ CD69+ and CD4+ CD25+/- CD69+ T-cells in the splenocytes of ConA-challenged mice. Moreover, we found thatCD4+ CD25+/- CD69+ T-cells were significantly correlated with ALT levels, especially CD4+ CD25- CD69+ T-cells. In conclusion, CQMUH-011 exerts potential protective effects against ConA-induced hepatitis, which may be partially attributed to its inhibition of T cells, especially the suppression of the proliferation of CD4+ CD25- CD69+ and CD8+ CD69+ subsets in the spleen. CQMUH-011 also reduced the early apoptosis of lymphocytes in the thymus.

Emerging Roles on Immunological Effect of Indoleamine 2,3-Dioxygenase in Liver Injuries

Indoleamine 2,3-dioxygenase (IDO) is one of the initial rate-limiting enzymes of the kynurenine pathway (KP), which causes immune suppression and induction of T cell anergy. It is associated with the imbalance of immune homeostasis in numerous diseases including cancer, chronic viral infection, allergy, and autoimmune diseases. Recently, IDO has extended its role to liver field. In this review, we summarize the dysregulation and potentials of IDO in the emerging field of liver injuries, as well as current challenges for IDO targets. In particular, we discuss unexpected conclusions against previous work published. IDO is induced by pro-inflammatory cytokines in liver dysfunction and exerts an immunosuppressive effect, whereas the improvement of liver injury may require consideration of multiple factors besides IDO.

SRSF1 plays a critical role in invariant natural killer T cell development and function

Invariant natural killer T (iNKT) cells are highly conserved innate-like T lymphocytes that originate from CD4⁺CD8⁺ double-positive (DP) thymocytes. Here, we report that serine/arginine splicing factor 1 (SRSF1) intrinsically regulates iNKT cell development by directly targeting Myb and balancing the abundance of short and long isoforms. Conditional ablation of SRSF1 in DP cells led to a substantially diminished iNKT cell pool due to defects in proliferation, survival, and TCRα rearrangement. The transition from stage 0 to stage 1 of iNKT cells was substantially blocked, and the iNKT2 subset was notably diminished in SRSF1-deficient mice. SRSF1 deficiency resulted in aberrant expression of a series of regulators that are tightly correlated with iNKT cell development and iNKT2 differentiation, including Myb, PLZF, Gata3, ICOS, and CD5. In particular, we found that SRSF1 directly binds and regulates pre-mRNA alternative splicing of Myb and that the expression of the short isoform of Myb is substantially reduced in SRSF1-deficient DP and iNKT cells. Strikingly, ectopic expression of the Myb short isoform partially rectified the defects caused by ablation of SRSF1. Furthermore, we confirmed that the SRSF1-deficient mice exhibited resistance to acute liver injury upon α-GalCer and Con A induction. Our findings thus uncovered a previously unknown role of SRSF1 as an essential post-transcriptional regulator in iNKT cell development and functional differentiation, providing new clinical insights into iNKT-correlated disease.

Ferroptosis as a new therapeutic opportunity for nonviral liver disease

Nonviral liver disease is a global public health problem due to its high mortality and morbidity. However, its underlying mechanism is unclear. Ferroptosis is a novel form of cell death that is involved in a variety of disease processes. Both abnormal iron metabolism (e.g., iron overload) and lipid peroxidation, which is induced by deletion of glutathione (GSH) or glutathione peroxidase 4 (GPX4), and the accumulation of polyunsaturated fatty acid-containing phospholipids (PUFA-PLs) trigger ferroptosis. Recently, ferroptosis has been involved in the pathological process of nonviral liver diseases [including alcohol-related liver disease (ALD); nonalcoholic fatty liver disease (NAFLD); hereditary hemochromatosis (HH); drug-, ischemia/reperfusion- or immune-induced liver injury; liver fibrosis; and liver cancer]. Hepatocyte ferroptosis is activated in ALD; NAFLD; HH; drug-, ischemia/reperfusion- or immune-induced liver injury; and liver fibrosis, whereas hepatic stellate cell and liver cancer cell ferroptosis are inhibited in liver fibrosis and liver cancer, respectively. Thus, ferroptosis is an ideal target for nonviral liver diseases. In the present review, we discuss the latest findings on ferroptosis and potential drugs targeting ferroptosis for nonviral liver diseases. This review will highlight further directions for the treatment and prevention of nonviral liver diseases.

OX40-targeted immune agonist antibodies induce potent antitumor immune responses without inducing liver damage in mice

Despite promising preclinical and clinical data demonstrating that immune agonist antibody immunotherapies (IAAs) such as αOX40 induce strong antitumor immune responses, clinical translation has been significantly hampered by the propensity of some IAAs to induce dose-limiting and sometimes life-threatening immunotoxicities such as cytokine release syndrome and hepatotoxicity. For example, in a recent study αOX40 was shown to induce significant liver damage in mice by inducing the pyroptosis of liver natural killer T cells (NKT) cells. Surprisingly; however, given these previous reports, αOX40 treatment in our hands did not induce NKT cell pyroptosis or liver damage. We investigated numerous potential confounding factors including age, sex, tumor burden, dosing strategy, and the gut microbiota, which could have explained this discrepancy with the previous study. In none of these experiments did we find that αOX40 induced any more than very mild inflammation in the liver. Our study therefore suggests that, preclinically, αOX40 is a safe and effective immunotherapy and further studies into the clinical benefit of αOX40 are warranted.

Glucosylceramide synthase regulates hepatocyte repair after concanavalin A-induced immune-mediated liver injury

BACKGROUND

Sphingolipids produce pleiotropic signaling pathways, and participate in the pathological mechanism of hepatocyte apoptosis and necrosis during liver injury. However, the role of glucosylceramide synthase (GCS)-key enzyme that catalyzes the first glycosylation step, in liver injury is still vague.

METHODS

All experiments were conducted using 7-9-week-old pathogen-free male C57BL/6 mice. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were detected in murine models of liver disease, in addition to histological characterization of liver injuries. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the relative expression of the GCS, matrix metallopeptidase-1 (MMP-1), and tissue inhibitor of metalloproteinase-1 (TIMP-1) genes. The GCS was observed through a fluorescence microscope, and the flow cytometry was used to detect hepatocyte apoptosis. The concentrations of serum IL-4, IL-6, and IL-10 were measured using enzyme-linked immune-sorbent assay (ELISA) kit. MMP-1 and TIMP-1 protein expression was measured via western blot (WB) analysis.

RESULTS

Con A is often used as a mitogen to activate T lymphocytes and promote mitosis. A single dose of Con A injected intravenously will cause a rapid increase of ALT and AST, which is accompanied by the release of cytokines that cause injury and necrosis of hepatocytes. In this study, we successfully induced acute immune hepatitis in mice by Con A. Con A administration resulted in GCS upregulation in liver tissues. Moreover, the mice in the Con A group had significantly higher levels of ALT, AST, IL-4, IL-6, IL-10 and increased hepatocyte apoptosis than the control group. In contrast, all of the aforementioned genes were significantly downregulated after the administration of a GCS siRNA or Genz-123346 (i.e., a glucosylceramide synthase inhibitor) to inhibit the GCS gene. Additionally, the histopathological changes observed herein were consistent with our ALT, AST, IL-4, IL-6, and IL-10 expression results. However, unlike this, hepatocyte apoptosis has been further increased on the basis of the Con A group. Moreover, our qRT-PCR and WB results indicated that the expression of MMP-1 in the Con A group was significantly lower than that in the control group, whereas TIMP-1 exhibited the opposite trend. Conversely, MMP-1 expression in the GCS siRNA and Genz-123346 groups was higher than that in the Con A group, whereas TIMP-1 expression was lower.

CONCLUSIONS

GCS inhibition reduces Con A-induced immune-mediated liver injury in mice, which may be due to the involvement of GCS in the hepatocyte repair process after injury.

Human Wharton's jelly-derived mesenchymal stem cells alleviate concanavalin A-induced fulminant hepatitis by repressing NF-κB signaling and glycolysis

Background

Fulminant hepatitis is a severe life-threatening clinical condition with rapid progressive loss of liver function. It is characterized by massive activation and infiltration of immune cells into the liver and disturbance of inflammatory cytokine production. Mesenchymal stem cells (MSCs) showed potent immunomodulatory properties. Transplantation of MSCs is suggested as a promising therapeutic approach for a host of inflammatory conditions.

Methods

In the current study, a well-established concanavalin A (Con A)-induced fulminant hepatitis mouse model was used to investigate the effects of transplanting human umbilical cord Wharton's jelly-derived MSCs (hWJ-MSCs) on fulminant hepatitis.

Results

We showed that hWJ-MSCs effectively alleviate fulminant hepatitis in mouse models, primarily through inhibiting T cell immunity. RNA sequencing of liver tissues and human T cells co-cultured with hWJ-MSCs showed that NF-κB signaling and glycolysis are two main pathways mediating the protective role of hWJ-MSCs on both Con A-induced hepatitis in vivo and T cell activation in vitro.

Conclusion

In summary, our data confirmed the potent therapeutic role of MSCs-derived from Wharton's jelly of human umbilical cord on Con A-induced fulminant hepatitis, and uncovered new mechanisms that glycolysis metabolic shift mediates suppression of T cell immunity by hWJ-MSCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02560-x.

Irf5 siRNA-loaded biodegradable lipid nanoparticles ameliorate concanavalin A-induced liver injury

RNA interference-based gene silencing drugs are attracting attention for treating various diseases. Lipid nanoparticles (LNPs) are carriers that efficiently deliver small interfering RNA (siRNA) to the cytoplasm of target cells. Recently, we developed potent and well-tolerated biodegradable LNPs with asymmetric ionizable lipids. Here, we evaluated the effect of LNPs on immune cells in mice. After intravenous administration, LNPs were efficiently incorporated into several tissue-resident macrophages, including liver macrophages, through an apolipoprotein E (ApoE)-independent mechanism. Administration of LNP-encapsulated siRNA against Irf5, encoding the transcription factor critical for inflammatory responses, sharply reduced its expression in macrophages in vivo, and persisted for as long as 7 days. The therapeutic potential of Irf5 siRNA-loaded LNPs in inflammatory diseases was tested in a concanavalin A (Con A)-induced hepatitis model, whose pathogenic mechanisms are dependent on cytokine secretion from macrophages. We found that Con A-induced liver injury was significantly attenuated after LNP injection. Serum aspartate transaminase, alanine aminotransferase, and inflammatory cytokine levels were significantly reduced in mice injected with Irf5 siRNA-loaded LNPs compared to those injected with control siRNA-loaded LNPs. Our results suggest that administering biodegradable LNPs to deliver siRNA is a promising strategy for treating inflammatory disorders.

Animal and Human Models of Tissue Repair and Fibrosis: An Introduction

Reductionist cell culture systems are not only convenient but essential to understand molecular mechanisms of myofibroblast activation and action in carefully controlled conditions. However, tissue myofibroblasts do not act in isolation and the complexity of tissue repair and fibrosis in humans cannot be captured even by the most elaborate culture models. Over the past five decades, numerous animal models have been developed to study different aspects of myofibroblast biology and interactions with other cells and extracellular matrix. The underlying principles can be broadly classified into: (1) organ injury by trauma such as prototypical full thickness skin wounds or burns; (2) mechanical challenges, such as pressure overload of the heart by ligature of the aorta or the pulmonary vein; (3) toxic injury, such as administration of bleomycin to lungs and carbon tetrachloride to the liver; (4) organ infection with viruses, bacteria, and parasites, such as nematode infections of liver; (5) cytokine and inflammatory models, including local delivery or viral overexpression of active transforming growth factor beta; (6) "lifestyle" and metabolic models such as high-fat diet; and (7) various genetic models. We will briefly summarize the most widely used mouse models used to study myofibroblasts in tissue repair and fibrosis as well as genetic tools for manipulating myofibroblast repair functions in vivo.

The molecular mechanism of acute liver injury and inflammatory response induced by Concanavalin A

Acute liver injury is a common but urgent clinical condition, and its underlying mechanism remains to be further elucidated. Concanavalin A (ConA)-induced liver injury was investigated in the study. Different from the caspase-dependent cell apoptosis in lipopolysaccharide/D-aminogalactose (LPS/D-GalN) induced liver injury, ConA-induced hepatocyte death was independent on caspase. Increased hepatocytic expressions of mixed lineage kinase domain like (MLKL) and receptor-interacting protein kinase 1 (RIPK1), and higher serum concentration of tumor necrosis factor-α (TNF-α) were noticed in mice with ConA-induced liver injury. Inhibition of RIPK1 protein or deletion of MLKL gene could significantly attenuate the acute liver injury and improve mice survival. Besides, the ConA treatment induced severe hepatic inflammation in wide type (WT) mice in comparison with Mlkl-/- mice, suggesting the RIPK1-MLKL-mediated hepatocellular necroptosis might participate in the process of liver injury. Moreover, mitochondrial damage associated molecular patterns (DAMPs) were subsequently released after the hepatocyte death, and further activated the p38 mitogen-activated protein kinase (MAPK) pathway, which could be reduced by deletion or inhibition of Toll-like receptor 9 (TLR9). Taken together, our research revealed that ConA-induced acute liver injury was closely related to TNF-α-mediated cell necroptosis, and inhibiting RIPK1 or deleting MLKL gene could alleviate liver injury in mice. The mitochondrial DNA released by dead hepatocytes further activated neutrophils through TLR9, thus resulting in the exacerbation of liver injury.

Co-exposures of TiO2 nanoparticles and cadmium ions at non-lethal doses aggravates liver injury in mice with ConA-induced hepatitis

The wide applications of titanium dioxide nanoparticles (TNP) and ubiquitous cadmium (Cd) pollution increase the chances of their co-existence in the environment and also pose potential health risks to humans. However, toxicological understanding of effects of co-exposures of TNP and Cd to mammals is still lacking. In this study, non-lethal doses of TNP and CdCl2 were intravenously co-administered to healthy or Concanavalin A (ConA)-induced acute hepatitis mice. Co-exposures of TNP and CdCl2 increased the accumulation of Cd2+ in the liver of hepatitis mice, which was 1.42-fold higher than that of healthy mice. Co-exposures also caused liver damage only in hepatitis mice on the basis of histopathological and biochemical evidence. Further study showed that co-exposure upregulated hepatic oxidative stress, which further induced autophagy and apoptosis only in the liver of hepatitis mice. This finding underlines the potential toxicological consequences of co-exposures of TNP and CdCl2 in hepatitis sufferers.