Superoxide produced by Kupffer cells is an essential effector in concanavalin A-induced hepatitis in mice

Cucurbitacin IIb mitigates concanavalin A-induced acute liver injury by suppressing M1 macrophage polarization

Cucurbitacins are a class of triterpenoid compounds extracted from plants and possess various pharmacological applications. Cucurbitacin IIb (CuIIb), extracted from the medicinal plant Hemsleya amabilis (Cucurbitaceae), has served as a traditional Chinese medicine for the treatment of bacterial dysentery and intestinal inflammation. CuIIb has been shown to exhibit anti-inflammatory activity; however, the protective effect of CuIIb against concanavalin A (Con A)-induced acute liver injury (ALI) and the fundamental mechanism remain unelucidated. In this study, we established an acute liver injury mouse model using Con A to investigate the effects of CuIIb on ALI. The results revealed that CuIIb significantly reduced serum aminotransferase levels and increased the survival rate of mice. Additionally, CuIIb effectively attenuated hepatocyte apoptosis, hepatic histopathological damage, and oxidative stress. Notably, CuIIb inhibited the polarization of M1 macrophages in vivo and in vitro. Moreover, the expression levels of pro-inflammatory cytokines related to M1 macrophages, such as interleukin (IL)-12, IL-1β, IL-6 and tumor necrosis factor-α (TNF-α), were reduced. CuIIb regulated M1 macrophage activation by modulating the nuclear factor (NF)-κB and mitogen-activated protein kinase (MAPK) signaling pathways. Conclusively, these results demonstrated that CuIIb significantly prevented Con A-induced ALI by suppressing M1 macrophage polarization via the MAPK and NF-κB signaling pathways, demonstrating the potential use of CuIIb for ALI treatment.

Zingerone attenuates concanavalin A-induced acute liver injury by restricting inflammatory responses

Autoimmune hepatitis (AIH), an immune-mediated liver injury, plays an important role in the development and pathogenesis of several liver diseases. However, therapeutic alternatives for the treatment of AIH remain limited. Zingerone (ZIN) is a natural non-toxic phenolic compound extracted from ginger that possesses various pharmacological activities. Thus, this study aimed to investigate the effect of ZIN on AIH using a mouse model of acute liver injury induced by concanavalin A (Con A). To establish liver injury, C57BL/6J mice were intraperitoneally administered ZIN, followed by 20 mg/kg Con A after 3 h. Thereafter, the liver and serum were collected for analysis. The results revealed that ZIN pretreatment significantly suppressed the elevation of liver injury markers induced by Con A exposure and improved the survival of mice. Additionally, ZIN significantly ameliorated liver histopathological injury, hepatocyte apoptosis, and oxidative stress. Notably, ZIN inhibited hepatic M1 macrophage polarization and decreased the expression of M1 macrophage-associated pro-inflammatory genes and cytokines, including interleukin-1β (IL-1β), IL-12, IL-6, and tumor necrosis factor-α (TNF-α). Western blotting analysis indicated that ZIN inhibited the phosphorylation of extracellular receptor kin, c-Jun N-terminal kinase, and p65 in vitro. Taken together, these results suggest that ZIN exerts a protective effect in the Con A-induced acute liver injury model by inhibiting M1 macrophage polarization and suppressing NF-κB, mitogen-activated protein kinase, and interferon regulatory factor signaling pathways. This highlights the possibility of using ZIN as a safe drug for the treatment of liver injury and provides a novel therapeutic direction for clinical studies on liver diseases.

Sappanone A Ameliorates Concanavalin A-induced Immune-Mediated Liver Injury by Regulating M1 Macrophage Polarization

Sappanone A (SAP), a high-isoflavone compound derived from the traditional Chinese medicine Sumu, exhibits various pharmacological activities, including anti-inflammatory and anti-oxidant effects. However, its protective effects on the liver have rarely been reported. The aim of this study was to investigate the effects of SAP on immune-mediated liver injury induced by concanavalin A (Con A) in mice and to explore the underlying molecular mechanisms. Mice were administered SAP intraperitoneally (50 mg/kg body weight). Three hours later, Con A (18 mg/kg) was injected via the tail vein to induce liver damage. Livers and blood were collected 12 h after Con A challenge. Liver cell apoptosis, oxidative stress, and M1 macrophage activation in vivo were investigated. Bone marrow-derived macrophages were used to confirm the effects of SAP on M1 polarization in vitro. The results indicated that SAP decreased transaminase levels, inhibited apoptosis, and improved oxidative stress in mouse livers. Furthermore, SAP significantly reduced the proportion of macrophages, inhibited the expression of CD86, and downregulated the expression of M1 macrophage-related inflammatory cytokines. Moreover, SAP-treated macrophages alleviated liver damage caused by Con A compared to non-SAP-treated macrophages. Mechanistically, SAP inhibited the phosphorylation of key molecules in the MAPK and NF-κB signaling pathways in macrophages, resulting in an inhibitory effect on M1 macrophage activation. Taken together, SAP alleviates immune-mediated liver injury induced by Con A by suppressing M1 macrophage polarization, which is partially associated with NF-κB and MAPK signaling pathways.

Purple sweet potato polysaccharide ameliorates concanavalin A-induced hepatic injury by inhibiting inflammation and oxidative stress

BACKGROUND

Autoimmune hepatitis (AIH) is a prevalent liver disease that can potentially lead to hepatic fibrosis and cirrhosis. The prolonged administration of immunosuppressive medications carries significant risks for patients. Purple sweet potato polysaccharide (PSPP), a macromolecule stored in root tubers, exhibits anti-inflammatory, antioxidant, immune-enhancing, and intestinal flora-regulating properties. Nevertheless, investigation into the role and potential mechanisms of PSPP in AIH remains notably scarce.

PURPOSE

Our aim was to explore the possible protective impacts of PSPP against concanavalin A (Con A)-induced liver injury in mice.

METHODS

Polysaccharide was isolated from purple sweet potato tubers using water extraction and alcohol precipitation, followed by purification through DEAE-52 cellulose column chromatography and Sephadex G-100 column chromatography. A highly purified component was obtained, and its monosaccharide composition was characterized by high performance liquid chromatography (HPLC). Mouse and cellular models induced by Con A were set up to investigate the impacts of PSPP on hepatic histopathology, apoptosis, as well as inflammation- and oxidative stress-related proteins in response to PSPP treatment.

RESULTS

The administration of PSPP significantly reduced hepatic pathological damage, suppressed elevation of ALT and AST levels, and attenuated hepatic apoptosis in Con A-exposed mice. PSPP was found to mitigate Con A-induced inflammation by suppressing the TLR4-P2X7R/NLRP3 signaling pathway in mice. Furthermore, PSPP alleviated Con A-induced oxidative stress by activating the PI3K/AKT/mTOR signaling pathway in mice. Additionally, PSPP demonstrated the ability to reduce inflammation and oxidative stress in RAW264.7 cells induced by Con A in vitro.

CONCLUSION

PSPP has the potential to ameliorate hepatic inflammation via the TLR4-P2X7R/NLRP3 pathway and inhibit hepatic oxidative stress through the PI3K/AKT/mTOR pathway during the progression of Con A-induced hepatic injury. The results of this study have unveiled the potential hepatoprotective properties of purple sweet potato and its medicinal value for humans. Moreover, this study serves as a valuable reference, highlighting the potential of PSPP-1 as a drug candidate for the treatment of immune liver injury.

Hepatocytes-derived Prdx1 regulates macrophage phenotypes via TLR4 activation in acute liver injury

Acute liver injury (ALI) is a significant causative factor for multiple hepatic diseases. The excessive inflammatory response triggers proinflammatory immune cells recruitment, infiltration and differentiation, further contributing to inflammatory injuries in liver. As a proinflammatory factor, circulating Peroxiredoxin 1 (Prdx1) is elevated in ALI patients and mice. In this study, through carbon tetrachloride (CCl4) and cecal puncture and ligation (CLP)-induced liver injury mice model, we found hepatocytes-derived Prdx1 expression was increased in ALI. After AAV8-Prdx1-mediated Prdx1 knockdown, CCl4 and CLP-induced ALI was alleviated, along with the reduced proinflammatory cytokines, suppressed myeloid cells recruitment, decreased proportions of hepatic macrophages and neutrophils, restrained proinflammatory macrophage differentiation and infiltration. Mechanistically, hepatocyte-derived Prdx1 regulated macrophages through paracrine activation of the TLR4 signal. Our data support the immune and inflammatory regulatory role of Prdx1 in ALI pathological process to suggest its potential therapeutic application and clinical value.

DNAM-1 Immunoreceptor Protects Mice from Concanavalin A-Induced Acute Liver Injury by Reducing Neutrophil Infiltration

DNAX accessory molecule-1 (DNAM-1; CD226) is an activating immunoreceptor on T cells and NK cells. The interaction of DNAM-1 with its ligand CD155 expressed on hematopoietic and nonhematopoietic cells plays an important role in innate and adaptive immune responses. In this study, we investigated the role of the DNAM-1-CD155 axis in the pathogenesis of T cell-mediated Con A-induced acute liver injury. Unexpectedly, DNAM-1-deficient (Cd226-/-) mice exhibited more severe acute liver injury and higher concentrations of IL-6 and TNF-α than did wild-type (WT) mice after Con A injection. We found that a larger number of neutrophils infiltrated into the liver of Cd226-/- mice compared with WT mice after Con A injection. Depletion of neutrophils ameliorated liver injury and decreased IL-6 and TNF-α in Cd226-/- mice after Con A injection, suggesting that neutrophils exacerbate the liver injury in Cd226-/- mice. Hepatocytes produced more significant amounts of CXCL1, a chemoattractant for neutrophils, in Cd226-/- mice than in WT mice after Con A injection. In the coculture of hepatocytes with liver lymphocytes, either DNAM-1 deficiency in liver lymphocytes or CD155 deficiency in hepatocytes promoted CXCL1 production by hepatocytes. These results suggest that the interaction of DNAM-1 with CD155 inhibits CXCL1 production by hepatocytes, leading to ameliorating acute liver injury.

Encapsulation of an Antioxidant in Redox-Sensitive Self-Assembled Albumin Nanoparticles for the Treatment of Hepatitis

Hepatitis is an inflammation of the liver caused by the inadequate elimination of reactive oxygen species (ROS) derived from Kupffer cells. Edaravone is clinically used as an antioxidant but shows poor liver distribution. Herein, we report on the design of a Kupffer cell-oriented nanoantioxidant based on a disulfide cross-linked albumin nanoparticle containing encapsulated edaravone (EeNA) as a therapeutic for the treatment of hepatitis. Since the edaravone is bound to albumin, this results in a soluble and stable form of edaravone in water. Exchanging the intramolecular disulfide bonds to intermolecular disulfide bridges of albumin molecules allowed the preparation of a redox responsive albumin nanoparticle that is stable in the blood circulation but can release drugs into cells. Consequently, EeNA was fabricated by the nanoscale self-assembly of edaravone and albumin nanoparticles without the additives that are contained in commercially available edaravone preparations. EeNA retained its nanostructure under serum conditions, but the encapsulated edaravone was released efficiently under intracellular reducing conditions in macrophages. The EeNA was largely distributed in the liver and subsequently internalized into Kupffer cells within 60 min after injection in a concanavalin-A-induced hepatitis mouse. The survival rate of the hepatitis mice was significantly improved by EeNA due to the suppression of liver necrosis and oxidative stress by scavenging excessive ROS. Moreover, even through the postadministration, EeNA showed an excellent hepatoprotective action as well. In conclusion, EeNA has the potential for use as a nanotherapeutic against various types of hepatitis because of its Kupffer cell targeting ability and redox characteristics.

M1 macrophage-derived exosomes promote autoimmune liver injury by transferring long noncoding RNA H19 to hepatocytes

Exosomes mediate intercellular communication by transmitting active molecules. The function of long noncoding RNA (lncRNA) H19 in autoimmune liver injury is unclear. Concanavalin A (ConA)-induced liver injury is well-characterized immune-mediated hepatitis. Here, we showed that lncRNA H19 expression was increased in the liver after ConA treatment, accompanied by increased exosome secretion. Moreover, injection of AAV-H19 aggravated ConA-induced hepatitis, with an increase in hepatocyte apoptosis. However, GW4869, an exosome inhibitor, alleviated ConA-induced liver injury and inhibited the upregulation of lncRNA H19. Intriguingly, lncRNA H19 expression in the liver was significantly downregulated, after macrophage depletion. Importantly, the lncRNA H19 was primarily expressed in type I macrophage (M1) and encapsulated in M1-derived exosomes. Furthermore, H19 was transported from M1 to hepatocytes via exosomes, and exosomal H19 dramatically induced hepatocytes apoptosis both in vitro and vivo. Mechanistically, H19 upregulated the transcription of hypoxia-inducible factor-1 alpha (HIF-1α), which accumulated in the cytoplasm and mediated hepatocyte apoptosis by upregulating p53. M1-derived exosomal lncRNA H19 plays a pivotal role in ConA-induced hepatitis through the HIF-1α-p53 signaling pathway. These findings identify M1 macrophage-derived exosomal H19 as a novel target for the treatment of autoimmune liver diseases.

Stellate cell in hepatic inflammation and acute injury

The perisinusoidal hepatic stellate cells (HSCs) have been investigated extensively for their role as the major fibrogenic cells during chronic liver injury. HSCs also produce numerous cytokines, chemokines, and growth mediators, and express cell adhesion molecules constitutively and in response to stimulants such as endotoxin (lipopolysaccharide). With this property and by interacting with resident and recruited immune and inflammatory cells, HSCs regulate hepatic immune homeostasis, inflammation, and acute injury. Indeed, experiments with HSC-depleted animal models and cocultures have provided evidence for the prominent role of HSCs in the initiation and progression of inflammation and acute liver damage due to various toxic agents. Thus HSCs and/or mediators derived thereof during acute liver damage may be considered as potential therapeutic targets.

Liver-Targeted Near-Infrared Fluorescence/Photoacoustic Dual-Modal Probe for Real-Time Imaging of In Situ Hepatic Inflammation

Early diagnosis of hepatic inflammation is the key to timely treatment and avoid the worsening of liver inflammation. Near-infrared fluorescence (NIRF) probes have high sensitivity but low spatial resolution in lesion imaging, while photoacoustic (PA) imaging has good spatial location information. Therefore, the development of a NIRF/PA dual-modal probe integrated with high sensitivity and spatial location feedback can achieve an accurate early diagnosis of hepatic inflammation. Here, we report an activatable NIRF/PA dual-modal probe (hCy-Tf-CA) for the detection of the superoxide anion (O₂^·-) in early hepatic inflammation. hCy-Tf-CA showed high selectivity and sensitivity for detecting O₂^·- fluctuation in vitro. More importantly, by introducing hepatocyte-targeting cholic acid (CA), the probe successfully achieved accurate in situ imaging of acute inflammatory liver injury (AILI) and autoimmune hepatitis (AIH) in vivo. The introduced CA not only promotes the hepatic targeting accumulation of probes but also improves the performance of low background dual-modal imaging in vivo. Therefore, hCy-Tf-CA provides an effective strategy for significantly improving in situ imaging performance and holds great potential for early, sensitive, and accurate diagnosis of hepatic inflammation.

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.

Comprehensive immune cell analysis of human menstrual-blood-derived stem cells therapy to concanavalin A hepatitis

Autoimmune hepatitis is an autoimmune disease with increasing occurrence worldwide. The most common and convenient mouse model is the concanavalin A (ConA) mouse model. Human menstrual-blood-derived stem cells (MenSCs) have shown great potential as a type of mesenchymal stem cell for treating various diseases. Time-of-flight mass cytometry was performed in phosphate-buffered saline control (NC) group and ConA injection with or without MenSCs treatment groups, and conventional flow cytometry was used for further validation. The serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels and H&E staining depicted that MenSCs treatment could significantly alleviate ConA-induced hepatitis. The t-distributed stochastic neighbor embedding (t-SNE) analysis of nine liver samples displayed favorable cell clustering, and the NC group was significantly different from the other two groups. The proportions of CD69⁺ T cells, NKT cells, and PD-L1⁺ macrophages were notably increased by ConA injection, while MenSCs could decrease ConA-induced macrophage percentage and M1 polarization in the liver tissue. The analysis of proinflammatory factors carried out by cytometric bead array demonstrated that tumor necrosis factor alpha (TNF-α), interleukin (IL)-17A, IL-12p70, IL-6, IL-2, IL-1b, and interferon gamma (IFN-γ) were upregulated after ConA injection and then rapidly decreased at 12 h. MenSCs also played an important role in downregulating these cytokines. Here, we described the comprehensive changes in leukocytes in the liver tissue of ConA-induced hepatitis at 12 h after ConA injection and found that MenSCs rescued ConA-induced hepatitis mostly by inhibiting macrophages and M1 polarization in mouse liver.

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.

Infections, Reactions of Natural Killer T Cells and Natural Killer Cells, and Kidney Injury

Natural killer T (NKT) cells and NK cells are representative innate immune cells that perform antitumor and antimicrobial functions. The involvement of these cells in various renal diseases, including acute kidney injury (AKI), has recently become evident. Murine NKT cells are activated and cause AKI in response to various stimuli, such as their specific ligand, cytokines, and bacterial components. Both renal vascular endothelial cell injury (via the perforin-mediated pathway) and tubular epithelial cell injury (via the tumor necrosis factor-alpha/Fas ligand pathway) are independently involved in the pathogenesis of AKI. NK cells complement the functions of NKT cells, thereby contributing to the development of infection-associated AKI. Human CD56⁺ T cells, which are a functional counterpart of murine NKT cells, as well as a subpopulation of CD56⁺ NK cells, strongly damage intrinsic renal cells in vitro upon their activation, possibly through mechanisms similar to those in mice. These cells are also thought to be involved in the acute exacerbation of pre-existing glomerulonephritis triggered by infection in humans, and their roles in sepsis-associated AKI are currently under investigation. In this review, we will provide an overview of the recent advances in the understanding of the association among infections, NKT and NK cells, and kidney injury, which is much more profound than previously considered. The important role of liver macrophages in the activation of NKT cells will also be introduced.

Effects of a CCR2 antagonist on macrophages and Toll-like receptor 9 expression in a mouse model of diabetic nephropathy

The pathogenesis of diabetic nephropathy (DN) is related to macrophage (Mφ) recruitment to the kidneys, tumor necrosis factor-α (TNF-α) production, and oxidative stress. Toll-like receptor 9 (TLR9) activation is reportedly involved in systemic inflammation, and it exacerbates this condition in metabolic syndrome. Therefore, we hypothesized that TLR9 plays a role in the pathogenesis of DN. Two subsets of kidney Mφs in DN model (db/db) mice were analyzed using flow cytometry to evaluate their distribution and TLR9 expression and function. Mice were administered the CCR2 antagonist INCB3344 for 8 wk; changes in Mφ distribution and function and its therapeutic effects on DN pathology were examined. Bone marrow-derived CD11bhigh (BM-Mφ) and tissue-resident CD11blow Mφs (Res-Mφ) were identified in the mouse kidneys. As DN progressed, the BM-Mφ number, TLR9 expression, and TNF-α production increased significantly. In Res-Mφs, reactive oxygen species (ROS) production and phagocytic activity were enhanced. INCB3344 decreased albuminuria, serum creatinine level, BM-Mφ abundance, TLR9 expression, and TNF-α production by BM-Mφs and ROS production by Res-Mφs. Both increased activation of BM-Mφ via TLR9 and TNF-α production and increased ROS production by Res-Mφs were involved in DN progression. Thus, inactivating Mφs and their TLR9 expression by INCB3344 is a potential therapeutic strategy for DN.NEW & NOTEWORTHY We classified kidney macrophages (Mφs) into bone marrow-derived Mφs (BM-Mφs) expressing high CD11b and tissue-specific resident Mφ (Res-Mφs) expressing low CD11b. In diabetic nephropathy (DN) model mice, Toll-like receptor 9 (TLR9) expression and TNF-α production via TLR9 activation in BM-Mφs and ROS production in Res-Mφs were enhanced. Furthermore, CCR2 antagonist suppressed the kidney infiltration of BM-Mφs and their function and the ROS production by Res-Mφs, with concomitant TLR9 suppression. Our study presents a new therapeutic strategy for DN.

Nitric oxide facilitates the targeting Kupffer cells of a nano-antioxidant for the treatment of NASH

Kupffer cells are a key source of reactive oxygen species (ROS) and are implicated in the development of steatohepatitis and fibrosis in nonalcoholic steatohepatitis (NASH). We recently developed a polythiolated and mannosylated human serum albumin (SH-Man-HSA), a nano-antioxidant that targets Kupffer cells, in which the mannosyl units on albumin allows their specific uptake by Kupffer cells via the mannose receptor C type 1 (MRC1), and in which the polythiolation confers antioxidant activity. The aim of this study was to investigate the therapeutic potential of SH-Man-HSA in NASH model mice. In livers from mice and/or patients with NASH, we observed a reduced blood flow in the liver lobes and the down-regulation in MRC1 expression in Kupffer cells, and SH-Man-HSA alone failed to improve the pathological phenotype in NASH. However, the administration of a nitric oxide (NO) donor restored hepatic blood flow and increased the expression of the mannose receptor C type 2 (MRC2) instead of MRC1. Consequently, treatment with a combination of SH-Man-HSA and an NO donor improved oxidative stress-associated pathology. Finally, we developed a hybrid type of nano-antioxidant (SNO-Man-HSA) via the S-nitrosation of SH-Man-HSA. This nanomedicine efficiently delivered both NO and thiol groups to the liver, with a hepatoprotective effect that was comparable to the combination therapy of SH-Man-HSA and an NO donor. These findings suggest that SNO-Man-HSA has the potential for functioning as a novel nano-therapy for the treatment of NASH.

Liver X receptors regulate natural killer T cell population and antitumor activity in the liver of mice

The nuclear receptors liver X receptor α (LXRα) and LXRβ are lipid sensors that regulate lipid metabolism and immunity. Natural killer T (NKT) cells, a T cell subset expressing surface markers of both natural killer cells and T lymphocytes and involved in antitumor immunity, are another abundant immune cell type in the liver. The potential function of the metabolic regulators LXRα/β in hepatic NKT cells remains unknown. In this study, we examined the role of LXRα and LXRβ in NKT cells using mice deficient for LXRα and/or LXRβ, and found that hepatic invariant NKT (iNKT) cells are drastically decreased in LXRα/β-KO mice. Cytokine production stimulated by the iNKT cell activator α-galactosylceramide was impaired in LXRα/β-KO hepatic mononuclear cells and in LXRα/β-KO mice. iNKT cell-mediated antitumor effect was also disturbed in LXRα/β-KO mice. LXRα/β-KO mice transplanted with wild-type bone marrow showed decreased iNKT cells in the liver and spleen. The thymus of LXRα/β-KO mice showed a decreased population of iNKT cells. In conclusion, LXRα and LXRβ are essential for NKT cell-mediated immunity, such as cytokine production and hepatic antitumor activity, and are involved in NKT cell development in immune tissues, such as the thymus.

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.

Contrasting functional responses of resident Kupffer cells and recruited liver macrophages to irradiation and liver X receptor stimulation

In the murine liver, there are two major macrophage populations, namely resident Kupffer cells (resKCs) with phagocytic activity and recruited macrophages (recMφs) with cytokine-producing capacity. This study was performed to clarify the functional differences between these two populations, focusing on their susceptibility to radiation and response to stimulation via liver X receptors (LXRs), which are implicated in cholesterol metabolism and immune regulation. Liver mononuclear cells (MNCs) were obtained from C57BL/6 (WT) mice with or without 2 Gy irradiation, and the phagocytic activity against Escherichia coli (E. coli) as well as TNF-α production were compared between the two macrophage populations. To assess LXR functions, phagocytosis, TNF-α production, and endocytosis of acetylated low-density lipoprotein (LDL) were compared after synthetic LXR ligand stimulation. Furthermore, LXRα/β knockout (KO) mice and LXRα KO mice were compared with WT mice. Irradiation decreased intracellular TNF-α production by recMφs but did not affect the phagocytic activity of resKCs. In vitro LXR stimulation enhanced E. coli phagocytosis by resKCs but decreased E. coli-stimulated TNF-α production by recMφs. Phagocytic activity and acetylated LDL endocytosis were decreased in both LXRα/β KO mice and LXRα KO mice, with serum TNF-α levels after E. coli injection in the former being higher than those in WT mice. In conclusion, resKCs and recMφs exhibited different functional features in response to radiation and LXR stimulation, highlighting their distinct roles liver immunity and lipid metabolism.

Diallyl trisulfide protects against concanavalin A-induced acute liver injury in mice by inhibiting inflammation, oxidative stress and apoptosis

AIMS

To investigate the protective effects and underlying mechanisms of diallyl trisulfide (DATS) against acute liver injury induced by concanavalin A (Con A).

MATERIALS AND METHODS

DATS (20, 40, 80 mg/kg) were gavaged to ICR mice 1 h before Con A (20 mg/kg) tail vein injection. The survival rate of mice, alterations of serum biochemical markers and liver histopathology were measured to evaluate the protective effects of DATS at 24 h after Con A exposure. The indexes of inflammation, oxidative stress and apoptosis were determined to explore the possible mechanisms.

KEY FINDINGS

DATS pretreatment increased survival rate of mice in a dose-dependent manner, inhibited the increase of liver-to-spleen ratio and serum liver injury markers, and attenuated liver pathological damage induced by Con A. Further study showed that DATS pretreatment inhibited the activation of Kupffer cells/macrophages, release of tumor necrosis factor-α (TNF-α) and Caspase-1-dependent inflammation induced by Con A. Moreover, DATS pretreatment alleviated the oxidative stress induced by Con A, which was evidenced by increased superoxide dismutase (SOD) and catalase (CAT) activities and decreased malondialdehyde (MDA) content in DATS and Con A co-treated mice compared with Con A alone group. Finally, DATS pretreatment reduced eosinophilic body formation, TUNEL positive staining and increased Bcl-2/Bax ratio in liver of Con A-injected mice, indicating attenuated apoptosis.

SIGNIFICANCE

Collectively, the results suggest that DATS displays potent protective effects against Con A-induced acute liver injury in mice possibly through inhibition of inflammation, oxidative stress and apoptosis.

Hepatoprotective Effect of Mixture of Dipropyl Polysulfides in Concanavalin A-Induced Hepatitis

The main biologically active components of plants belonging to the genus Allium, responsible for their biological activities, including anti-inflammatory, antioxidant and immunomodulatory, are organosulfur compounds. The aim of this study was to synthetize the mixture of dipropyl polysulfides (DPPS) and to test their biological activity in acute hepatitis. C57BL/6 mice were administered orally with DPPS 6 h before intravenous injection of Concanavalin A (ConA). Liver inflammation, necrosis and hepatocytes apoptosis were determined by histological analyses. Cytokines in liver tissue were determined by ELISA, expression of adhesive molecules and enzymes by RT PCR, while liver mononuclear cells were analyzed by flow cytometry. DPPS pretreatment significantly attenuated liver inflammation and injury, as evidenced by biochemical and histopathological observations. In DPPS-pretreated mice, messenger RNA levels of adhesion molecules and NADPH oxidase complex were significantly reduced, while the expression of SOD enzymes was enhanced. DPPS pretreatment decreased protein level of inflammatory cytokines and increased percentage of T regulatory cells in the livers of ConA mice. DPPS showed hepatoprotective effects in ConA-induced hepatitis, characterized by attenuation of inflammation and affection of Th17/Treg balance in favor of T regulatory cells and implicating potential therapeutic usage of DPPS mixture in inflammatory liver diseases.

Activation of Liver X Receptor α Sensitizes Mice to T-Cell Mediated Hepatitis

Autoimmune hepatitis (AIH) is an inflammatory disease of the liver. Liver X receptors (LXRs), including the α and β isoforms, are previously known for their anti-inflammatory activities. The goal of this study is to determine whether and how LXR plays a role in AIH. LXRα gain-of-function and loss-of-function mouse models were used, in conjunction with the concanavalin A (ConA) model of T-cell mediated hepatitis. We first showed that the hepatic expression of LXRα was decreased in the ConA model of hepatitis and in human patients with AIH. In the ConA model, we were surprised to find that activation of LXRα in the constitutively activated VP-LXRα whole-body knock-in (LXRα-KI) mice exacerbated ConA-induced AIH, whereas the LXRα-/- mice showed attenuated ConA-induced AIH. Interestingly, hepatocyte-specific activation of LXRα in the fatty acid binding protein-VP-LXRα transgenic mice did not exacerbate ConA-induced hepatitis. Mechanistically, the sensitizing effect of the LXRα-KI allele was invariant natural killer T (iNKT)-cell dependent, because the sensitizing effect was abolished when the LXRα-KI allele was bred into the NKT-deficient CD1d-/- background. In addition, LXRα-enhanced ConA-induced hepatitis was dependent on interferon gamma. In contrast, adoptive transfer of hepatic iNKT cells isolated from LXRα-KI mice was sufficient to sensitize CD1d-/- mice to ConA-induced AIH. Conclusion: Activation of LXRα sensitizes mice to ConA-induced AIH in iNKT and interferon gamma-dependent manner. Our results suggest that LXRα plays an important role in the development of AIH.

Antioxidant Capacity and Hepatoprotective Role of Chitosan-Stabilized Selenium Nanoparticles in Concanavalin A-Induced Liver Injury in Mice

Selenium nanoparticles (SeNPs) have attracted wide attention for their use in nutritional supplements and nanomedicine applications. However, their potential to protect against autoimmune hepatitis has not been fully investigated, and the role of their antioxidant capacity in hepatoprotection is uncertain. In this study, chitosan-stabilized SeNPs (CS-SeNPs) were prepared by means of rapid ultra-filtration, and then their antioxidant ability and free-radical scavenging capacity were evaluated. The hepatoprotective potential of a spray-dried CS-SeNPs powder against autoimmune liver disease was also studied in the concanavalin A (Con A)-induced liver injury mouse model. CS-SeNPs with size of around 60 nm exhibited acceptable oxygen radical absorbance capacity and were able to scavenge DPPH, superoxide anion, and hydroxyl radicals. The CS-SeNPs powder alleviated Con A-caused hepatocyte necrosis and reduced the elevated levels of serum alanine transaminase, aspartate transaminase, and lactic dehydrogenase in Con A-treated mice. These results suggest that the CS-SeNPs powder protected the mice from Con-A-induced oxidative stress in the liver by retarding lipid oxidation and by boosting the activities of superoxide dismutase, glutathione peroxidase, and catalase, partly because of its ability to improve Se retention. In conclusion, SeNPs present potent hepatoprotective potential against Con A-induced liver damage by enhancing the redox state in the liver; therefore, they deserve further development.

Caveolin-1 dictates ferroptosis in the execution of acute immune-mediated hepatic damage by attenuating nitrogen stress

Ferroptosis is a new regulated cells death manner defined as results of iron-dependent accumulation of lipid peroxidation. However, the specific mechanisms of regulating ferroptosis remain unclear. In our present study, we demonstrated that Caveolin-1 (Cav-1) played a central role in protecting hepatocytes against ferroptosis in autoimmunity-mediated hepatitis (AIH). The down-regulated Cav-1 in liver tissues, accompanied by ferroptotic events and RNS production, were contributed to the outcome of ConA-induced hepatic damage, which were rescued by ferrostatin-1 (an inhibitor of ferroptosis) in vivo and in vitro. Additionally, Cav-1 deficiency aggravated ConA-induced hepatocellular death and ferroptosis associated with excessive nitrogen stress response. Short hairpin RNA of Cav-1 in hepatocytes promoted ferroptosis and nitrative stress in response to erastin in vitro, which was ameliorated by Cav-1 over-expression. Meanwhile, administration of the iNOS inhibitor (1400W) or ONOO^- scavenger (Fe-TMPyP), diminished reactive nitrogen species (RNS), remarkably reduced hepatocytes ferroptosis and attenuated ConA-induced liver damage. Furthermore, immune inhibition by gadolinium chloride (GdCl₃), a well-known Kupffer cell depletor, elevated hepatic Cav-1 but inhibited ferroptosis and nitrative stress under ConA exposure. In conclusion, these data revealed a novel molecular mechanism of ferroptosis with the Cav-1 regulation was essential for pathogenesis of ConA-induced hepatitis. Downstream of Cav-1, RNS-mediated ferroptosis was a pivotal step that drives the execution of acute immune-mediated hepatic damage.

Repeated Administration of Kupffer Cells-Targeting Nanoantioxidant Ameliorates Liver Fibrosis in an Experimental Mouse Model

Kupffer cells are a major producer of reactive oxygen species and have been implicated in the development of liver fibrosis during chronic hepatitis in non-alcoholic steatohepatitis (NASH) and alcoholic steatohepatitis (ASH). We recently reported on the development of a polythiolated and mannosylated human serum albumin (SH-Man-HSA) that functions as a Kupffer cell-targeting nanoantioxidant. In this material, the albumin is mannosylated, which permits it to be taken up by mannose receptor C type 1 expressed on Kupffer cells, and is also polythiolated to have antioxidant activity. To clarify the anti-fibrotic property of this nanoantioxidant, we repeatedly administered SH-Man-HSA to a liver fibrosis mouse model that was induced by the repeated treatment of the concanavalin-A, which mimics the liver fibrosis observed in NASH and ASH. SH-Man-HSA dramatically improved the survival rate and suppressed liver fibrosis in the experimental model. In addition, SH-Man-HSA suppressed hepatic oxidative stress levels, thereby decreasing the numbers of apoptotic cells. In contrast, N-acetylcysteine, which contains the same thiol content as the SH-Man-HSA, failed to show a substantial therapeutic effect in these mice. The expression levels of inflammatory genes including epidermal growth factor module-containing mucin-like receptor (Emr-1/F4/80), Toll-like receptor-4 (TLR-4), high mobility group box-1 (HMGB-1), CC chemokine ligand-5 (CCL-5), tumor necrosis factor-α (TNF-α), CCL-2, interleukin-6 (IL-6), and IL-1β, as well as fibrotic (α-smooth muscle actin (α-SMA), transforming growth factor-β (TGF-β), and Snail) and extracellular matrix genes (collagen, type Iα2 (Col1α2), matrix metalloproteinase-9 (MMP-9), and tissue inhibitor of metalloproteinase 1 (TIMP-1)), showed some decreasing trends by the SH-Man-HSA administration. These findings suggest that the repeated administration of the Kupffer cell-targeting nanoantioxidant, SH-Man-HSA, ameliorates liver fibrosis in mice by suppressing the level of oxidative stress and a portion of the inflammation, and has a potential therapeutic effect against NASH and ASH.

Critical role of IL-1β in the pathogenesis of Agrocybe aegerita galectin-induced liver injury through recruiting T cell to liver

Acute liver failure (ALF) can be the consequence of various etiologies, which immune response plays a pivotal role in the pathogenesis. For the diversity of etiologies, more animal models are still needed in this field. Here, we developed a new acute liver injury mouse model induced by a fungal lectin AAGL (Agrocybe aegerita galectin). Intravenous injection of AAGL could induce the infiltration and activation of T, NKT and NK cells in liver and T cell played an important role in the pathogenesis. However, compared with the widely used concanavalin A model, AAGL model showed different immune mechanism. Transcriptome analysis of live tissue suggested that inflammation mediated by chemokine and cytokine signaling pathway was different between AAGL and Con A model. Fluorescent quantitative PCR verification assay showed that IL-1β was expressed much higher in AAGL-treated mice and anti-IL-1β could ameliorate AAGL-induced liver injury by inhibiting NF-κB and p38 signaling pathway. The expression of CXCL9 which was responsible for T cell infiltration in liver was also inhibited in AAGL model. We found a critical role of IL-1β in the pathogenesis of AAGL model through recruiting T cells to liver, which highlighted that IL-1β antibody might be a candidate therapy for ALF.

CXCL9 regulates acetaminophen-induced liver injury via CXCR3

Drug-induced liver injury has become a serious public health problem. Although the mechanism of acetaminophen (APAP)-induced liver injury has been studied for decades it has not been fully elucidated. In-depth study into the mechanisms underlying APAP-induced liver injury may provide useful information for more effective prevention and treatment. In the present study, the role of C-X-C motif chemokine ligand-9 (CXCL9) in APAP-induced liver injury was investigated thus providing a novel direction for the prevention and treatment of drug hepatitis. A total of 20 fasting male patients ingested APAP tablets at Nanjing First Hospital. In addition, wild type (WT) mice were treated with 250 mg/kg APAP or isodose PBS for 1, 3, 6 and 12 h, respectively. Results from reverse-transcription-quantitative polymerase chain reaction analyses demonstrated that CXCL9 mRNA levels were increased in the blood of patients who took APAP in a fasting state and in the livers of APAP-treated WT mice, compared with their respective controls. Hepatocyte apoptosis in the liver tissue of APAP-treated mice decreased following administration of a CXCL9 neutralizing antibody. Caspase-3, caspase-8 and phosphorylated-AKT (S437) were activated in primary hepatocytes isolated from WT mice following CXCL9 treatment. However, no significant differences in expression of caspase-3, caspase-8 and p-AKT (S437) were detected in hepatocytes isolated from C-X-C motif chemokine receptor 3 (CXCR3)^−/− mice following CXCL9 treatment. After CXCL9 administration, WT mice exhibited higher serum levels of aspartate transaminase and increased caspase-3 and caspase-8 activity in liver tissue compared with controls. The same trends were not observed in CXCR3^−/− mice. In conclusion, CXCL9 regulated APAP-induced liver injury through stimulation of hepatocyte apoptosis via binding to CXCR3. These findings provide a novel prevention and treatment strategy for DILI.

Frontline Science: Concanavalin A-induced acute hepatitis is attenuated in vitamin D receptor knockout mice with decreased immune cell function

The vitamin D receptor (VDR) is a nuclear receptor for the active form of vitamin D, 1α,25-dihydroxyvitamin D₃ , and regulates various physiologic processes, such as bone and calcium metabolism, cellular proliferation and differentiation, and immunity. VDR is highly expressed in the intestine, kidney, bone, and macrophages, but is expressed at a low level in the liver. The liver is a major metabolic organ and also acts as an immune gateway for dietary nutrients and xenobiotics. In this study, we investigated the function of VDR in hepatic immune cells, such as Kupffer cells/macrophages, utilizing VDR knockout (KO) mice. We showed that VDR is functionally expressed in hepatic mononuclear cells, specifically resident Kupffer cells. We examined the role of VDR in acute hepatitis induced by concanavalin A (Con-A) and found that Con-A-induced hepatitis is attenuated in VDR-KO mice compared to wild-type (WT) mice. Con-A-induced hepatitis is known to be mediated by NKT cell activation, cytokine production, and reactive oxygen species (ROS) production in Kupffer cells/macrophages. However, the proportions of Kupffer cells/macrophages and the NKT cell activation were similar in the liver of WT and VDR-KO mice and inflammatory cytokine gene expression was increased in VDR-KO mice. On the other hand, plasma and hepatic ROS levels were decreased in the liver of VDR-KO mice compared to WT mice. The phagocytic activity of resident Kupffer cells and hepatic neutrophils were also decreased in VDR-KO mice. Therefore, VDR is necessary for Con-A-induced acute hepatitis and plays an important role in hepatic immune cell functions.

Modulation of Chemokine- and Adhesion-Molecule Gene Expression and Recruitment of Neutrophil Granulocytes in Rat and Mouse Liver after a Single Gadolinium Chloride or Zymosan Treatment

Kupffer cells are professional phagocytes of the liver clearing bacteria from portal blood. Their clearance capacity, however, can be overwhelmed, transforming them into critical mediators of hepatic-injury. We investigated the consequences of selective Kupffer cell-overload by intraperitoneally administering pyrogen-free gadolinium chloride (GdCl₃) or Zymosan into rats and into endotoxin-resistant mice (C3H/HeJ). The number of myeloperoxidase-positive (MPO⁺) cells increased at 3 h mainly around the portal vessel after both GdCl₃ and Zymosan treatment. Simultaneously, GdCl₃ administration reduced detectability of ED-1⁺ (but not ED-2) cells near the portal vessel. Serum chemokine (C-X-C motif) ligand 1 (CXCL-1), CXCL-2 and chemokine (C-C motif) ligand 2 (CCL-2) showed a peak at 3 h after both treatment regimens although at a higher extent after Zymosan administration. Accordingly, CXCL-1, CXCL-5 and CCL-2 gene expression in the liver was up-regulated after GdCl₃ treatment at 3 h. After Zymosan administration a significant up-regulation of CXCL-1, CXCL-2, CXCL-10, CCL-2, CCL-3 and CCL-20 gene expression in liver at 3 h was observed. After Zymosan administration intracellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) gene expression was up-regulated in rat liver tissue. In C3H/HeJ mice both treatment regimens up-regulated CCL-2 and ICAM-1 gene expression after 3 h and down-regulated platelet endothelial cell adhesion molecule 1 (PECAM-1) gene expression. In conclusion, phagocytosis overload of Kupffer cells causes induction of several CXC, CC-chemokines, upregulation of "positive" adhesion molecule gene expression, down-regulation of the "negative" adhesion molecule PECAM-1 and a recruitment of neutrophil granulocytes in the portal area of the liver of treated rats and mice mainly in close contact to the liver macrophages.

RAMP1 in Kupffer cells is a critical regulator in immune-mediated hepatitis

The significance of the relationship between the nervous and immune systems with respect to disease course is increasingly apparent. Immune cells in the liver and spleen are responsible for the development of acute liver injury, yet the regulatory mechanisms of the interactions remain elusive. Calcitonin gene-related peptide (CGRP), which is released from the sensory nervous system, regulates innate immune activation via receptor activity-modifying protein 1 (RAMP1), a subunit of the CGRP receptor. Here, we show that RAMP1 in Kupffer cells (KCs) plays a critical role in the etiology of immune-mediated hepatitis. RAMP1-deficient mice with concanavalin A (ConA)-mediated hepatitis, characterized by severe liver injury accompanied by infiltration of immune cells and increased secretion of pro-inflammatory cytokines by KCs and splenic T cells, showed poor survival. Removing KCs ameliorated liver damage, while depleting T cells or splenectomy led to partial amelioration. Adoptive transfer of splenic T cells from RAMP1-deficient mice led to a modest increase in liver injury. Co-culture of KCs with splenic T cells led to increased cytokine expression by both cells in a RAMP1-dependent manner. Thus, immune-mediated hepatitis develops via crosstalk between immune cells. RAMP1 in KCs is a key regulator of immune responses.

Development of Kupffer cell targeting type-I interferon for the treatment of hepatitis via inducing anti-inflammatory and immunomodulatory actions

Because of its multifaceted anti-inflammatory and immunomodulatory effects, delivering type-I interferon to Kupffer cells has the potential to function as a novel type of therapy for the treatment of various types of hepatitis. We report herein on the preparation of a Kupffer cell targeting type-I interferon, an albumin-IFNα2b fusion protein that contains highly mannosylated N-linked oligosaccharide chains, Man-HSA(D494N)-IFNα2b, attached by combining albumin fusion technology and site-directed mutagenesis. The presence of this unique oligosaccharide permits the protein to be efficiently, rapidly and preferentially distributed to Kupffer cells. Likewise IFNα2b, Man-HSA(D494N)-IFNα2b caused a significant induction in the mRNA levels of IL-10, IL-1Ra, PD-L1 in RAW264.7 cells and mouse isolated Kupffer cells, and these inductions were largely inhibited by blocking the interferon receptor. These data indicate that Man-HSA(D494N)-IFNα2b retained the biological activities of type-I interferon. Man-HSA(D494N)-IFNα2b significantly inhibited liver injury in Concanavalin A (Con-A)-induced hepatitis model mice, and consequently improved their survival rate. Moreover, the post-administration of Man-HSA(D494N)-IFNα2b at 2 h after the Con-A challenge also exerted hepato-protective effects. In conclusion, this proof-of-concept study demonstrates the therapeutic effectiveness and utility of Kupffer cell targeting type-I interferon against hepatitis via its anti-inflammatory and immunomodulatory actions.

Activated natural killer T cells in mice induce acute kidney injury with hematuria through possibly common mechanisms shared by human CD56+ T cells

Although activation of mouse natural killer T (NKT) cells by α-galactosylceramide (α-GalCer) causes failure of multiple organs, including the kidneys, the precise mechanisms underlying kidney injury remain unclear. Here, we showed that α-GalCer-activated mouse NKT cells injured both kidney vascular endothelial cells and tubular epithelial cells in vitro, causing acute kidney injury (AKI) with hematuria in middle-aged mice. The perforin-mediated pathway was mainly involved in glomerular endothelial cell injury, whereas the TNF-α/Fas ligand pathway played an important role in the injury of tubular epithelial cells. Kidney injury in young mice was mild but could be significantly exacerbated if NKT cells were strongly activated by NK cell depletion alone or in combination with IL-12 pretreatment. When stimulated by a combination of IL-2 and IL-12, human CD56⁺ T cells, a functional counterpart of mouse NKT cells, also damaged both glomerular endothelial cells and tubular epithelial cells, with the former being affected in a perforin-dependent manner. These data suggest that both mouse NKT cells and human CD56⁺ T cells are integral to the processes that mediate AKI. Targeting CD56⁺ T cells may, therefore, be a promising approach to treat AKI.

CD36 deficiency attenuates immune-mediated hepatitis in mice by modulating the proapoptotic effects of CXC chemokine ligand 10

The scavenger receptor CD36 recognizes a diverse set of ligands and has been implicated in a wide variety of normal and pathological processes, including lipid metabolism, angiogenesis, atherosclerosis, and phagocytosis. In particular, recent findings have demonstrated its crucial functions in sterile inflammation and tumor metastasis. However, the role of CD36 in immune-mediated hepatitis remains unclear. Concanavalin A (ConA)-induced liver injury is a well-established experimental T cell-mediated hepatitis. To understand the role of CD36 in hepatitis, we tested the susceptibility of CD36-deficient (CD36^-/- ) mice to this model, evaluated by a liver enzyme test, terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay, histological analysis, mononuclear cell (MNC) infiltration, and hepatic proinflammatory factor production. CD36^-/- mice were less sensitive to ConA-induced hepatitis and had a significantly lower number of liver MNCs (LMNCs), including CD4⁺ cells, CD8⁺ T cells, natural killer cells, natural killer T cells, infiltrating macrophages, and neutrophils, as well as reduced expression of inflammatory mediators (tumor necrosis factor α, CXC chemokine ligand (CXCL) 10, interleukin (IL)-1α, monocyte chemotactic protein 1, and IL-6) compared with controls. Notably, we used bone marrow chimeric mice to demonstrate that CD36 expression on nonhematopoietic cells was required to drive ConA-induced liver injury. Furthermore, our data show that the CD36 receptor was essential for CXCL10-induced hepatocyte apoptosis and activation of IκB kinase, Akt, and Jun N-terminal kinase. Moreover, treatment of wild-type mice with genistein, a tyrosine kinase inhibitor that blocks CD36-Lyn signaling, attenuated ConA-induced liver injury and reduced the number of MNCs.

CONCLUSIONS

Our findings suggest that CD36 plays an important proinflammatory role in ConA-induced liver injury by promoting hepatic inflammation and mediating the proapoptotic effect of chemokine CXCL10, and therefore, may be a potential therapeutic target for immune-mediated hepatitis. (Hepatology 2018;67:1943-1955).

Neoboutonia melleri var velutina Prain: in vitro and in vivo hepatoprotective effects of the aqueous stem bark extract on acute hepatitis models

BACKGROUND

Hepatitis is a liver inflammation caused by different agents and remains a public health problem worldwide. Medicinal plants are an important source of new molecules being considered for treatment of this disease. Our work aims at evaluating the hepatoprotective properties of Neoboutonia velutina, a Cameroonian medicinal plant.

METHODS

The aqueous extract has been prepared using phytochemical methods. HepG2 cells were used to assess anti-inflammatory properties of the extract at different concentrations. Acute hepatitis models (Carbon tetrachloride and Concanavalin A) were performed in mice receiving or not receiving, different extract doses by gavage. Liver injury was assessed using histology, transaminases and pro-inflammatory markers. Extract antioxidant and radical scavenging capacities were evaluated.

RESULTS

The extract led to a significant decrease in pro-inflammatory cytokine expression in vitro and to a remarkable protection of mice from carbon tetrachloride-induced liver injury, as shown by a significant decrease in dose-dependent transaminases level. Upon extract treatment, inflammatory markers were significantly decreased and liver injuries were limited as well. In the Concanavalin A model, the extract displayed weak effects.

CONCLUSIONS

Taking into account underlying mechanisms in both hepatitis models, we demonstrate the extract's radical scavenging capacity. Neoboutonia velutina displays a potent hepatoprotective effect mediated through radical scavenging properties.

In vivo Lipopolysaccharide Tolerance Recruits CD11b+ Macrophages to the Liver with Enhanced Bactericidal Activity and Low Tumor Necrosis Factor-Releasing Capability, Resulting in Drastic Resistance to Lethal Septicemia

OBJECTIVES

In vivo lipopolysaccharide (LPS) tolerance on bacterial infection was investigated, focusing on liver macrophages.

METHODS

LPS tolerance was induced by intraperitoneal injections with 5 μg/kg of LPS for 3 consecutive days, and then mice were intravenously infected with Escherichia coli.

RESULTS

All LPS-primed mice survived lethal bacterial infection. Drastic enhancement of bactericidal activity of liver macrophages strongly contributed to bacterial clearance. Although LPS-primed mice produced substantial amounts of tumor necrosis factor (TNF) inside the liver, TNF efflux into the systemic circulation was markedly suppressed. These mice showed a dramatic increase in CD11b+ monocyte- derived macrophages in the liver. The CD11b+ macrophages that increased in LPS-primed mice were those with strong phagocytic/bactericidal activity and an upregulated expression of Fcγ receptor I, but the subfraction with a potent TNF-producing capacity and poor phagocytic activity diminished. The adoptive transfer of CD11b+ macrophages from LPS-primed mice to control mice increased survival after bacterial infection and reduced the elevation of plasma TNF. LPS priming did not affect the CD68+ resident Kupffer cells, and CD68+ Kupffer cell-depleted mice still exhibited LPS tolerance with strong resistance to bacteremia.

CONCLUSIONS

LPS tolerance recruits CD11b+ macrophages to the liver with enhanced bactericidal activity, which plays a central role in resistance to lethal bacteremia.

Deciphering the landscape of host barriers to Listeria monocytogenes infection

Listeria monocytogenes is a common food-borne pathogen that can disseminate from the intestine and infect multiple organs. Here, we used sequence tag-based analysis of microbial populations (STAMP) to investigate Lmonocytogenes population dynamics during infection. We created a genetically barcoded library of murinized Lmonocytogenes and then used deep sequencing to track the pathogen's dissemination routes and quantify its founding population (N_b) sizes in different organs. We found that the pathogen disseminates from the gastrointestinal tract to distal sites through multiple independent routes and that N_b sizes vary greatly among tissues, indicative of diverse host barriers to infection. Unexpectedly, comparative analyses of sequence tags revealed that fecally excreted organisms are largely derived from the very small number of L. monocytogenes cells that colonize the gallbladder. Immune depletion studies suggest that distinct innate immune cells restrict the pathogen's capacity to establish replicative niches in the spleen and liver. Finally, studies in germ-free mice suggest that the microbiota plays a critical role in the development of the splenic, but not the hepatic, barriers that prevent L. monocytogenes from seeding these organs. Collectively, these observations illustrate the potency of the STAMP approach to decipher the impact of host factors on population dynamics of pathogens during infection.

Plant Lectins Activate the NLRP3 Inflammasome To Promote Inflammatory Disorders

Plant-derived dietary lectins have been reported to be involved in the pathogenesis of several inflammatory diseases, including inflammatory bowel disease, diabetes, rheumatoid arthritis, and celiac disease, but little is known about the molecular mechanisms underlying lectin-induced inflammation. In this study, we showed that plant lectins can induce caspase-1 activation and IL-1β secretion via the NLRP3 inflammasome. Lectins were internalized and subsequently escaped from the lysosome and then translocated to the endoplasmic reticulum. Endoplasmic reticulum-loaded plant lectins then triggered Ca²⁺ release and mitochondrial damage, and inhibition of Ca²⁺ release and mitochondrial reactive oxygen species by chemical inhibitors significantly suppressed NLRP3 inflammasome activation. In vivo, plant lectin-induced inflammation and tissue damage also depended on the NLRP3 inflammasome. Our findings indicate that plant lectins can act as an exogenous "danger signal" that can activate the NLRP3 inflammasome and suggest that dietary lectins might promote inflammatory diseases via the NLRP3 inflammasome.

Possible Involvement of Liver Resident Macrophages (Kupffer Cells) in the Pathogenesis of Both Intrahepatic and Extrahepatic Inflammation

Liver resident macrophages designated Kupffer cells (KCs) form the largest subpopulation of tissue macrophages. KCs are involved in the pathogenesis of liver inflammation. However, the role of KCs in the systemic inflammation is still elusive. In this study, we examined whether KCs are involved in not only intrahepatic inflammation but also extrahepatic systemic inflammation. Administration of clodronate liposomes resulted in the KC deletion and in the suppression of liver injury in T cell-mediated hepatitis by ConA as a local acute inflammation model, while the treatment did not influence dextran sulfate sodium- (DSS-) induced colitis featured by weight loss, intestinal shrink, and pathological observation as an ectopic local acute inflammation model. In contrast, KC deletion inhibited collagen-induced arthritis as a model of extrahepatic, systemic chronical inflammation. KC deleted mice showed weaker arthritic scores, less joint swelling, and more joint space compared to arthritis-induced control mice. These results strongly suggest that KCs are involved in not only intrahepatic inflammatory response but also systemic (especially) chronic inflammation.

Activation and increase of radio-sensitive CD11b+ recruited Kupffer cells/macrophages in diet-induced steatohepatitis in FGF5 deficient mice

We have recently reported that Kupffer cells consist of two subsets, radio-resistant resident CD68+ Kupffer cells and radio-sensitive recruited CD11b+ Kupffer cells/macrophages (Mφs). Non-alcoholic steatohepatitis (NASH) is characterized not only by hepatic steatosis but also chronic inflammation and fibrosis. In the present study, we investigated the immunological mechanism of diet-induced steatohepatitis in fibroblast growth factor 5 (FGF5) deficient mice. After consumption of a high fat diet (HFD) for 8 weeks, FGF5 null mice developed severe steatohepatitis and fibrosis resembling human NASH. F4/80+ Mφs which were both CD11b and CD68 positive accumulated in the liver. The production of TNF and FasL indicated that they are the pivotal effectors in this hepatitis. The weak phagocytic activity and lack of CRIg mRNA suggested that they were recruited Mφs. Intermittent exposure to 1 Gy irradiation markedly decreased these Mφs and dramatically inhibited liver inflammation without attenuating steatosis. However, depletion of the resident subset by clodronate liposome (c-lipo) treatment increased the Mφs and tended to exacerbate disease progression. Recruited CD11b+ CD68+ Kupffer cells/Mφs may play an essential role in steatohepatitis and fibrosis in FGF5 null mice fed with a HFD. Recruitment and activation of bone marrow derived Mφs is the key factor to develop steatohepatitis from simple steatosis.

Activated NKT cells facilitated functional switch of myeloid-derived suppressor cells at inflammation sites in fulminant hepatitis mice

Myeloid-derived suppressor cells (MDSCs) confer immunosuppressive properties, but their roles in fulminant hepatitis have not been well defined. In this study, we systematically examined the distribution of MDSCs in bone marrow (BM), liver and spleen, and their functional and differentiation status in an acute fulminant hepatitis mouse model induced by lipopolysaccharide and D-galactosamine (LPS-GalN). Moreover, the interaction between NKT cells and MDSCs was determined. Our study revealed that BM contained the largest pool of MDSCs during pathogenesis of fulminant hepatitis compared with liver and spleen. MDSCs in liver/spleen expressed higher levels of chemokine receptors such as CCR2, CX3CR1 and CXCR2. At inflamed tissues such as liver or spleen, activated NKT cells induced differentiation of MDSCs through cell-cell interaction, which markedly dampened the immunosuppressive effects and promoted MDSCs to produce pro-inflammatory cytokines and activate inflammatory cells. Our findings thus demonstrated an unexpected pro-inflammatory state for MDSCs, which was mediated by the activated NKT cells that precipitated the differentiation and functional evolution of these MDSCs at sites of inflammation.

Liver Resident Macrophages (Kupffer Cells) Share Several Functional Antigens in Common with Endothelial Cells

The identification and specific functions of Kupffer cells (KCs), a liver resident macrophage subpopulation, are still unclear. We compared KCs with peritoneal macrophages using cDNA microarray analysis and found that these cells share some antigens with endothelial cells. KCs highly express VCAM-1 and VEGF receptors (VEGF-Rs) at transcriptional and protein levels. VCAM-1 mediates the functional binding of KCs with lymphocytes and induces KC activation. Among the VEGF receptors, VEGF-R2 and VEGF-R3 were expressed on the KCs, while VEGF-R1 was expressed on other tissue macrophage subsets. VEGF120, a ligand of both VEGF-R1 and VEGF-R2, transduced strong survival and chemotactic signals through the KCs, when compared to PIGF, a VEGF-R1 ligand, indicating that VEGF-R2 plays significant roles in regulating KC activities. Expression of the VEGF-Rs was regulated by TLR4 signalling. These results suggest that the function of KCs is partly regulated by the common antigens shared with endothelial cells.

Methane-rich saline protects against concanavalin A-induced autoimmune hepatitis in mice through anti-inflammatory and anti-oxidative pathways

Methane is a common gas which has been reported to play a protective role in organ injury and presents an anti-inflammatory property. However, its effects on Concanavalin A (Con A)-induced autoimmune hepatitis (AIH) remain unknown. Thus, the aim of this study was to investigate the effects of methane on Con A-induced autoimmune hepatitis in mice and its underlying mechanism. Autoimmune hepatitis was induced by Con A (15 mg/kg) in healthy C57BL/6 mice and methane-rich saline (MS) (20 ml/kg) was intraperitoneally injected 30 min after the challenge with Con A. We found that methane treatment significantly reduced the elevated serum aminotransferase levels and ameliorated liver pathological damage. Furthermore, methane treatment obviously suppressed the secretion of proinflammatory cytokines including tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-6 (IL-6) and interleukin-1β (IL-1β) and increased anti-inflammatory cytokine interleukin-10 (IL-10). Moreover, we found that the levels of malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) were highly increased while the activities of superoxide dismutase (SOD) and catalase (CAT) were decreased in liver with the injection of Con A, which was reversed by methane. Also, the data demonstrated that the phosphorylated IκB, NF-κB and P38 MAPK in liver were significantly down-regulated by methane. These results suggested that methane protected liver against Con A-induced injury through anti-inflammatory and anti-oxidative pathways.

Allo-transplantation of mesenchymal stem cells attenuates hepatic injury through IL1Ra dependent macrophage switch in a mouse model of liver disease

BACKGROUND & AIMS

Autologous transplantation of mesenchymal stem cells (MSCs) reduces concanavalin A (Con A)-induced hepatic injury in mice. However, the mechanism is unclear and the therapeutic effect of allo-transplantation remains unknown. Our aim was to investigate the effects and mechanisms related to allo-transplantation of MSCs when used to treat Con A hepatic injury.

METHODS

After Con A-induced liver injury was created in C57BL/6J mice, MSCs derived from BALB/c mice or a vehicle control was administered.

RESULTS

Allo-transplantation of MSCs derived from BALB/c mice attenuated hepatic apoptosis in C57BL/6J mice that had undergone Con A-induced liver injury. MSCs increased the level of serum interleukin (IL)-10 and the phosphorylation of hepatic STAT3, but decreased the level of hepatic IFN-γ and phospho-STAT1. Notably, the administered MSCs were trapped mostly in the lungs and promoted the macrophage M2 switch, which contributed to the increased IL10 levels in the lungs and serum. Loss of the therapeutic effect was observed after knock-down of the expression of interleukin 1 receptor antagonist (IL1Ra) in the MSCs. In vitro investigation supported the hypothesis that MSCs are able to switch Con A-stimulated macrophages to the M2 phenotype, which results in an increase in IL10 production.

CONCLUSIONS

Allo-transplantation of MSCs reduces Con A liver injury by increasing IL10 production through an IL1Ra dependent macrophage switch.

Kupffer cell-monocyte communication is essential for initiating murine liver progenitor cell-mediated liver regeneration

Liver progenitor cells (LPCs) are necessary for repair in chronic liver disease because the remaining hepatocytes cannot replicate. However, LPC numbers also correlate with disease severity and hepatocellular carcinoma risk. Thus, the progenitor cell response in diseased liver may be regulated to optimize liver regeneration and minimize the likelihood of tumorigenesis. How this is achieved is currently unknown. Human and mouse diseased liver contain two subpopulations of macrophages with different ontogenetic origins: prenatal yolk sac-derived Kupffer cells and peripheral blood monocyte-derived macrophages. We examined the individual role(s) of Kupffer cells and monocyte-derived macrophages in the induction of LPC proliferation using clodronate liposome deletion of Kupffer cells and adoptive transfer of monocytes, respectively, in the choline-deficient, ethionine-supplemented diet model of liver injury and regeneration. Clodronate liposome treatment reduced initial liver monocyte numbers together with the induction of injury and LPC proliferation. Adoptive transfer of monocytes increased the induction of liver injury, LPC proliferation, and tumor necrosis factor-α production.

CONCLUSION

Kupffer cells control the initial accumulation of monocyte-derived macrophages. These infiltrating monocytes are in turn responsible for the induction of liver injury, the increase in tumor necrosis factor-α, and the subsequent proliferation of LPCs.

Mouse CD11b+Kupffer Cells Recruited from Bone Marrow Accelerate Liver Regeneration after Partial Hepatectomy

TNF and Fas/FasL are vital components, not only in hepatocyte injury, but are also required for hepatocyte regeneration. Liver F4/80⁺Kupffer cells are classified into two subsets; resident radio-resistant CD68⁺cells with phagocytic and bactericidal activity, and recruited radio-sensitive CD11b⁺cells with cytokine-producing capacity. The aim of this study was to investigate the role of these Kupffer cells in the liver regeneration after partial hepatectomy (PHx) in mice. The proportion of Kupffer cell subsets in the remnant liver was examined in C57BL/6 mice by flow cytometry after PHx. To examine the role of CD11b⁺Kupffer cells/Mφ, mice were depleted of these cells before PHx by non-lethal 5 Gy irradiation with or without bone marrow transplantation (BMT) or the injection of a CCR2 (MCP-1 receptor) antagonist, and liver regeneration was evaluated. Although the proportion of CD68⁺Kupffer cells did not significantly change after PHx, the proportion of CD11b⁺Kupffer cells/Mφ and their FasL expression was greatly increased at three days after PHx, when the hepatocytes vigorously proliferate. Serum TNF and MCP-1 levels peaked one day after PHx. Irradiation eliminated the CD11b⁺Kupffer cells/Mφ for approximately two weeks in the liver, while CD68⁺Kupffer cells, NK cells and NKT cells remained, and hepatocyte regeneration was retarded. However, BMT partially restored CD11b⁺Kupffer cells/Mφ and recovered the liver regeneration. Furthermore, CCR2 antagonist treatment decreased the CD11b⁺Kupffer cells/Mφ and significantly inhibited liver regeneration. The CD11b⁺Kupffer cells/Mφ recruited from bone marrow by the MCP-1 produced by CD68⁺Kupffer cells play a pivotal role in liver regeneration via the TNF/FasL/Fas pathway after PHx.

Kupffer-cell-expressed transmembrane TNF-α is a major contributor to lipopolysaccharide and D-galactosamine-induced liver injury

Tumor necrosis factor (TNF)-α exists in two bioactive forms, a 26-kDa transmembrane form (tmTNF-α) and a 17-kDa soluble form (sTNF-α). sTNF-α has been recognized as a key regulator of hepatitis; however, serum sTNF-α disappears in mice during the development of severe liver injury, and high levels of serum sTNF-α do not necessarily result in liver damage. Interestingly, in a mouse model of acute hepatitis, we have found that tmTNF-α expression on Kupffer cells (KCs) significantly increases when mice develop severe liver injury caused by lipopolysaccharide (LPS)/D-galactosamine (D-gal), and the level of tmTNF-α expression is positively related to the activity of serum transaminases. Therefore, we hypothesized that KC-expressed tmTNF-α constitutes a pathomechanism in hepatitis and have explored the role of tmTNF-α in this disease model. Here, we have compared the impact of KCs(tmTNFlow) and KCs(tmTNFhigh) on acute hepatitis in vivo and ex vivo and have further demonstrated that KCs(tmTNFhigh), rather than KCs(tmTNFlow), not only exhibit an imbalance in secretion of pro- and anti-inflammatory cytokines, favoring inflammatory response and exacerbating liver injury, but also induce hepatocellular apoptosis via tmTNF-α and the expression of another pro-apoptotic factor, Fas ligand. Our data suggest that KC(tmTNFhigh) is a major contributor to liver injury in LPS/D-gal-induced hepatitis.

Sensitization to autoimmune hepatitis in group VIA calcium-independent phospholipase A2-null mice led to duodenal villous atrophy with apoptosis, goblet cell hyperplasia and leaked bile acids

Chronic bowel disease can co-exist with severe autoimmune hepatitis (AIH) in an absence of primary sclerosing cholangitis. Genetic background may contribute to this overlap syndrome. We previously have shown that the deficiency of iPLA2β causes an accumulation of hepatocyte apoptosis, and renders susceptibility for acute liver injury. We here tested whether AIH induction in iPLA2β-null mice could result in intestinal injury, and whether bile acid metabolism was altered. Control wild-type (WT) and female iPLA2β-null (iPLA2β(-/-)) mice were intravenously injected with 10mg/kg concanavalinA (ConA) or saline for 24h. ConA treatment of iPLA2β(-/-) mice caused massive liver injury with increased liver enzymes, fibrosis, and necrosis. While not affecting WT mice, ConA treatment of iPLA2β(-/-) mice caused severe duodenal villous atrophy concomitant with increased apoptosis, cell proliferation, globlet cell hyperplasia, and endotoxin leakage into portal vein indicating a disruption of intestinal barrier. With the greater extent than in WT mice, ConA treatment of iPLA2β(-/-) mice increased jejunal expression of innate response cytokines CD14, TNF-α, IL-6, and SOCS3 as well as chemokines CCL2 and the CCL3 receptor CCR5. iPLA2β deficiency in response to ConA-induced AIH caused a significant decrease in hepatic and biliary bile acids, and this was associated with suppression of hepatic Cyp7A1, Ntcp and ABCB11/Bsep and upregulation of intestinal FXR/FGF15 mRNA expression. The suppression of hepatic Ntcp expression together with the loss of intestinal barrier could account for the observed bile acid leakage into peripheral blood. Thus, enteropathy may result from acute AIH in a susceptible host such as iPLA2β deficiency.

Polythiol-containing, recombinant mannosylated-albumin is a superior CD68+/CD206+ Kupffer cell-targeted nanoantioxidant for treatment of two acute hepatitis models

Since reactive oxygen species (ROS) derived from Kupffer cells (KC), especially CD68(+) KC, play a key role in the induction of hepatic oxidative stress and injuries, we developed a polythiolated- and mannosylated human serum albumin (SH-Man-HSA), which functions as a novel nanoantioxidant for delivering thiol to CD68(+) KC. In vitro electron paramagnetic resonance coupled with pharmacokinetics and immunohistochemical studies showed that SH-Man-HSA possessed powerful radical-scavenging activity and rapidly and selectively delivered thiols to the liver via mannose receptor (CD206) on CD68(+) cells. SH-Man-HSA significantly improved the survival rate of concanavalin-A (Con-A)-treated mice. Moreover, SH-Man-HSA exhibited excellent hepatoprotective functions, not by decreasing tumor necrosis factor or interferon-γ production that is closely associated with Con-A-induced hepatitis, but by suppressing ROS production. Interestingly, the protective effect of SH-Man-HSA was superior to N-acetyl cysteine (NAC). This could be attributed to the difference in the inhibition of hepatic oxidative stress between the two antioxidants depending on their potential for thiol delivery to the liver. Similar results were also observed for acetaminophen (APAP)-induced hepatopathy models. Flow cytometric data further confirmed that an increase in F4/80(+)/ROS(+) cells was dramatically decreased by SH-Man-HSA. The administration of SH-Man-HSA at 4 hours following a Con-A or APAP injection also exhibited a profound hepatoprotective action against these hepatitis models, whereas this was not observed for NAC. It can be concluded therefore that SH-Man-HSA has great potential for use in a rescue therapy for hepatopathy as a nanoantioxidant because of its ability to efficiently and rapidly deliver thiols to CD68(+)/CD206(+) KC.