Plasmacytoid dendritic cells protect against immune-mediated acute liver injury via IL-35

Activation of α7 Nicotinic Acetylcholine Receptors Inhibits Hepatic Necroptosis and Ameliorates Acute Liver Injury in Mice

BACKGROUND

Acute liver injury is a disease characterized by severe liver dysfunction, caused by significant infiltration of immune cells and extensive cell death with a high mortality. Previous studies demonstrated that the α7 nicotinic acetylcholine receptor (α7nAChR) played a crucial role in various liver diseases. The hypothesis of this study was that activating α7nAChR could alleviate acute liver injury and investigate its possible mechanisms.

METHODS

Acute liver injury was induced by intraperitoneal injection of lipopolysaccharide (LPS)/D-galactosamine (D-Gal) in wild type, α7nAChR knockout (α7nAChR-/-) and stimulator of interferon gene (STING) mutation (Stinggt/gt) mice in the presence or absence of a pharmacologic selective α7nAChR agonist (PNU-282987). The effects of α7nAChR on hepatic injury, inflammatory response, mitochondrial damage, necroptosis, and infiltration of immune cells during acute liver injury were assessed.

RESULTS

The expression of α7nAChR in liver tissue was increased in LPS/D-Gal-induced acute liver injury mice. Compared to the age-matched wild-type mice, α7nAChR deficiency decreased the survival rate, exacerbated the hepatic injury accompanied with enhanced inflammatory response and oxidative stress, and aggravated hepatic mitochondrial damage and necroptosis. Conversely, pharmacologic activation of α7nAChR by PNU-282987 displayed the opposite trends. Furthermore, PNU-282987 significantly reduced the proportion of infiltrating monocyte-derived macrophages (CD45+CD11bhiF4/80int), M1 macrophages (CD45+CD11b+F4/80+CD86hiCD163low), and Ly6Chi monocytes (CD45+CD11b+MHC [major histocompatibility complex] ⅡlowLy6Chi), but increased the resident Kupffer cells (CD45+CD11bintF4/80hiTIM4hi) in the damaged hepatic tissues caused by LPS/D-Gal. Interestingly, α7nAChR deficiency promoted the STING signaling pathway under LPS/D-Gal stimulation, while PNU-282987 treatment significantly prevented its activation. Finally, it was found that Sting mutation abolished the protective effects against hepatic injury by activating α7nAChR.

CONCLUSIONS

The authors' study revealed that activating α7nAChR could protect against LPS/D-Gal-induced acute liver injury by inhibiting hepatic inflammation and necroptosis possibly via regulating immune cells infiltration and inhibiting STING signaling pathway.

EDITOR’S PERSPECTIVE

A genome-wide association study identified PTPN2 as a population-specific susceptibility gene locus for primary biliary cholangitis

BACKGROUND AND AIMS

Previous genome-wide association studies (GWAS) have indicated the involvement of shared (population-nonspecific) and nonshared (population-specific) susceptibility genes in the pathogenesis of primary biliary cholangitis (PBC) among European and East-Asian populations. Although a meta-analysis of these distinct populations has recently identified more than 20 novel PBC susceptibility loci, analyses of population-specific genetic architecture are still needed for a more comprehensive search for genetic factors in PBC.

APPROACH AND RESULTS

Protein tyrosine phosphatase nonreceptor type 2 ( PTPN2) was identified as a novel PBC susceptibility gene locus through GWAS and subsequent genome-wide meta-analysis involving 2181 cases and 2699 controls from the Japanese population (GWAS-lead variant: rs8098858, p = 2.6 × 10 -8 ). In silico and in vitro functional analyses indicated that the risk allele of rs2292758, which is a primary functional variant, decreases PTPN2 expression by disrupting Sp1 binding to the PTPN2 promoter in T follicular helper cells and plasmacytoid dendritic cells. Infiltration of PTPN2-positive T-cells and plasmacytoid dendritic cells was confirmed in the portal area of the PBC liver by immunohistochemistry. Furthermore, transcriptomic analysis of PBC-liver samples indicated the presence of a compromised negative feedback loop in vivo between PTPN2 and IFNG in patients carrying the risk allele of rs2292758.

CONCLUSIONS

PTPN2 , a novel susceptibility gene for PBC in the Japanese population, may be involved in the pathogenesis of PBC through an insufficient negative feedback loop caused by the risk allele of rs2292758 in IFN-γ signaling. This suggests that PTPN2 could be a potential molecular target for PBC treatment.

Concanavalin-A-Induced Acute Liver Injury in Mice

Acute liver injury is a life-threatening disease. Although immune responses are involved in the development and exacerbation of acute liver injury, the cellular and molecular mechanisms are not fully understood. Intravenous administration of the plant lectin concanavalin A (ConA) is widely used as a model of acute liver injury. ConA triggers T cell activation and cytokine production by crosslinking glycoproteins, including the T cell receptor, leading to the infiltration of myeloid cells into the liver and the subsequent amplification of inflammation in the liver. Thus, the pathogenesis of ConA-induced acute liver injury is considered a model of immune-mediated acute liver injury or autoimmune hepatitis in humans. However, the severity of the liver injury and the analyses of immune cells and non-hematopoietic cells in the liver following ConA injection are significantly influenced by the experimental conditions. This article outlines protocols for ConA-induced acute liver injury in mice and evaluation methods for liver injury, immune cells, and non-hematopoietic cells in the liver. © 2024 Wiley Periodicals LLC. Basic Protocol 1: Induction of acute liver injury by ConA injection Basic Protocol 2: Evaluation of inflammatory cytokines in mouse plasma Basic Protocol 3: Preparation of liver sections and histological analysis of liver injury Basic Protocol 4: Preparation of liver immune cells Basic Protocol 5: Preparation of hepatocytes, endothelial cells, and hepatic stellate cells Basic Protocol 6: Flow cytometry of immune and non-hematopoietic liver cells Basic Protocol 7: Flow cytometric sorting of endothelial cells and hepatic stellate cells Basic Protocol 8: Quantitative reverse transcription polymerase chain reaction.

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

BACKGROUND & AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The presence of CpGs in AAV gene therapy vectors induces a plasmacytoid dendritic cell-like population very early after administration

AAV-mediated gene transfer is a promising platform still plagued by potential host-derived, antagonistic immune responses to therapeutic components. CpG-mediated TLR9 stimulation activates innate immune cells and leads to cognate T cell activation and suppression of transgene expression. Here, we demonstrate that CpG depletion increased expression of an antibody transgene product by 2-3-fold as early as 24 h post-vector administration in mice. No significant differences were noted in anti-transgene product/ anti-AAV capsid antibody production or cytotoxic gene induction. Instead, CpG depletion significantly reduced the presence of a pDC-like myeloid cell population, which was able to directly bind the antibody transgene product via Fc-FcγR interactions. Thus, we extend the mechanisms of TLR9-mediated antagonism of transgene expression in AAV gene therapy to include the actions of a previously unreported pDC-like cell population.

Characterizing the impact of simvastatin co-treatment of cell specific TCDD-induced gene expression and systemic toxicity

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is associated with metabolic syndrome (MetS) in humans and elicits pathologies in rodents that resemble non-alcoholic fatty liver disease (NAFLD) in humans through activation of the aryl hydrocarbon receptor (AHR) pathway. Dysregulation of cholesterol homeostasis, an aspect of MetS, is linked to NAFLD pathogenesis. TCDD exposure is also linked to the suppression of genes that encode key cholesterol biosynthesis steps and changes in serum cholesterol levels. In a previous experiment, treating mice with TCDD in the presence of simvastatin, a 3-Hydroxy-3-Methylglutaryl-CoA Reductase competitive inhibitor, altered lipid and glycogen levels, AHR-battery gene expression, and liver injury in male mice compared to TCDD alone. The aim of this study was to deduce a possible mechanism(s) for the metabolic changes and increased injury using single-nuclei RNA sequencing in mouse liver. We demonstrated that co-treated mice experienced wasting and increased AHR activation compared to TCDD alone. Furthermore, relative proportions of cell (sub)types were different between TCDD alone and co-treated mice including important mediators of NAFLD progression like hepatocytes and immune cell populations. Analysis of non-overlapping differentially expressed genes identified several pathways where simvastatin co-treatment significantly impacted TCDD-induced changes, which may explain the differences between treatments. Overall, these results demonstrate a connection between dysregulation of cholesterol homeostasis and toxicant-induced metabolic changes.

Effects of different allo-Treg/allo-NK ratios on graft-versus-host disease in transplanted mice

To investigate the effects of allo-Treg cells, allo-NK cells, and their mixtures in different proportions on Graft-versus-host disease (GVHD) in bone marrow transplant mouse model. In this study, C57BL/6 mice were used as donors, and 6 Gy dose of 60Co γ was used as the receptor of BALB/c mice. The recipient mice were divided into NC (normal saline), CON (bone marrow cells), NK (bone marrow cells + NK cells), Treg (bone marrow cells + Treg cells), NK+ Treg (1:1) (bone marrow cells +1:1 ratio of Treg cells, NK cells), and NK+ Treg (6:1) (bone marrow cells +1:6 ratio of Treg cells, NK cells), according to the different injection mode through the tail vein. The differences of white blood cell (WBC), platelet (PLT), clinical manifestations, and GVHD score of target organs (liver, lung, small intestine) in each group after transplantation were observed, and the differences of chimerism rate and survival rate in each group at 28 days after transplantation were compared. The interaction between Treg cells and NK cells in different proportions (1:1, 1:2, 1:6, 1:12) was investigated in vitro in mouse erythroleukemia (MEL) cells of mouse erythroleukemia. The results showed that at the 28th day of transplantation, the clinical manifestations and GVHD scores of target organs of mice in NK+ Treg (1:1) group and NK+ Treg (6:1) group were significantly lower than other groups (P < 0.05); the WBC and PLT counts were significantly higher than other groups (P < 0.05), and the survival time was significantly longer than other groups (P < 0.05); the clinical manifestations and GVHD scores of each target organ in NK+ Treg (1:1) group were significantly lower than those in NK+ Treg (6:1) group (P < 0.05); the chimerism rate of each group was >90% on day 28 after transplantation. In vitro experiments showed that the inhibition of Treg cells on NK cell killing activity was dose-dependent, and the proportion of 1:6 and 1:12, killing activity of NK cell was significantly lower than that of groups 1:1 and 1:2 (P < 0.05), which showed that allo-NK and allo-Treg alone had a significant effect on the improvement of GVHD after transplantation, and Treg cells inhibited the killing activity of NK cells by direct contact and showed a dose-dependent effect.

The gut microbiota-induced kynurenic acid recruits GPR35-positive macrophages to promote experimental encephalitis

The intricate interplay between gut microbes and the onset of experimental autoimmune encephalomyelitis (EAE) remains poorly understood. Here, we uncover remarkable similarities between CD4+ T cells in the spinal cord and their counterparts in the small intestine. Furthermore, we unveil a synergistic relationship between the microbiota, particularly enriched with the tryptophan metabolism gene EC:1.13.11.11, and intestinal cells. This symbiotic collaboration results in the biosynthesis of kynurenic acid (KYNA), which modulates the recruitment and aggregation of GPR35-positive macrophages. Subsequently, a robust T helper 17 (Th17) immune response is activated, ultimately triggering the onset of EAE. Conversely, modulating the KYNA-mediated GPR35 signaling in Cx3cr1+ macrophages leads to a remarkable amelioration of EAE. These findings shed light on the crucial role of microbial-derived tryptophan metabolites in regulating immune responses within extraintestinal tissues.

A General and Efficient Strategy for Gene Delivery Based on Tea Polyphenols Intercalation and Self-Polymerization

Gene therapy that employs therapeutic nucleic acids to modulate gene expression has shown great promise for diseases therapy, and its clinical application relies on the development of effective gene vector. Herein a novel gene delivery strategy by just using natural polyphenol (-)-epigallocatechin-3-O-gallate (EGCG) as raw material is reported. EGCG first intercalates into nucleic acids to yield a complex, which then oxidizes and self-polymerizes to form tea polyphenols nanoparticles (TPNs) for effective nucleic acids encapsulation. This is a general method to load any types of nucleic acids with single or double strands and short or long sequences. Such TPNs-based vector achieves comparable gene loading capacity to commonly used cationic materials, but showing lower cytotoxicity. TPNs can effectively penetrate inside cells, escape from endo/lysosomes, and release nucleic acids in response to intracellular glutathione to exert biological functions. To demonstrate the in vivo application, an anti-caspase-3 small interfering ribonucleic acid is loaded into TPNs to treat concanavalin A-induced acute hepatitis, and excellent therapeutic efficacy is obtained in combination with the intrinsic activities of TPNs vector. This work provides a simple, versatile, and cost-effective gene delivery strategy. Given the biocompatibility and intrinsic biofunctions, this TPNs-based gene vector holds great potential to treat various diseases.

Single-cell transcriptome analysis uncovers underlying mechanisms of acute liver injury induced by tripterygium glycosides tablet in mice

Tripterygium glycosides tablet (TGT), the classical commercial drug of Tripterygium wilfordii Hook. F. has been effectively used in the treatment of rheumatoid arthritis, nephrotic syndrome, leprosy, Behcet's syndrome, leprosy reaction and autoimmune hepatitis. However, due to its narrow and limited treatment window, TGT-induced organ toxicity (among which liver injury accounts for about 40% of clinical reports) has gained increasing attention. The present study aimed to clarify the cellular and molecular events underlying TGT-induced acute liver injury using single-cell RNA sequencing (scRNA-seq) technology. The TGT-induced acute liver injury mouse model was constructed through short-term TGT exposure and further verified by hematoxylin-eosin staining and liver function-related serum indicators, including alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and total bilirubin. Using the mouse model, we identified 15 specific subtypes of cells in the liver tissue, including endothelial cells, hepatocytes, cholangiocytes, and hepatic stellate cells. Further analysis indicated that TGT caused a significant inflammatory response in liver endothelial cells at different spatial locations; led to marked inflammatory response, apoptosis and fatty acid metabolism dysfunction in hepatocytes; activated hepatic stellate cells; brought about the activation, inflammation, and phagocytosis of liver capsular macrophages cells; resulted in immune dysfunction of liver lymphocytes; disturbed the intercellular crosstalk in liver microenvironment by regulating various signaling pathways. Thus, these findings elaborate the mechanism underlying TGT-induced acute liver injury, provide new insights into the safe and rational applications in the clinic, and complement the identification of new biomarkers and therapeutic targets for liver protection.

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.

Migration inhibitory factor and cluster of differentiation 74-mediated dendritic cell apoptosis exacerbates acute acetaminophen-induced liver injury

INTRODUCTION

We investigated the role of macrophage migration inhibitory factor (MIF) on dendritic cells (DC) during acetaminophen (APAP)-induced acute liver injury (ALI) in mice.

METHODS

First, we randomly divided the mice into experimental (ALI model) and control groups, then intraperitoneally injected 600 mg/kg of APAP or phosphate-buffered saline, respectively. Then, we collected liver tissue and serum samples to evaluate liver inflammation using serum alanine aminotransferase level and hematoxylin and eosin (H&E) staining of liver tissues. Flow cytometry was used to identify changes in the quantity and percentage of DCs, as well as the expression of cluster of differentiation (CD) 74 and other apoptosis-related markers in the liver. Next, we randomly divided the mice into APAP-vehicles, APAP-bone marrow-derived dendritic cells (BMDCs), APAP-MIF, APAP-IgG (isotype immunoglobin G antibody) groups (four mice per group), after APAP injection, we injected control extracts, BMDCs, mouse recombinant MIF antibodies, or IgG antibodies into the tail vein. Lastly, the severity of the liver injury and the number of DCs were assessed.

RESULTS

The APAP-induced ALI mice had increased hepatic MIF expression but significantly lower amounts of hepatic DCs and apoptotic DCs than healthy mice; CD74 expression on the HDCs also increased markedly. Supplementing APAP-induced ALI mice with BMDCs or MIF antibodies significantly increased the number of hepatic DCs compared with the control mice, alleviating liver damage.

CONCLUSION

The MIF/CD74 signaling pathway may mediate hepatic DC apoptosis and promote liver damage.

Regulation of Progression and Resolution of Liver Fibrosis by Immune Cells

The excessive accumulation of extracellular matrix proteins results in fibrosis-a condition implicated in several diseased conditions, such as nonalcoholic steatohepatitis, viral hepatitis, and autoimmune hepatitis. Despite its prevalence, direct and effective treatments for fibrosis are lacking, warranting the development of better therapeutic strategies. Accumulating evidence has shown that liver fibrosis-a condition previously considered irreversible-is reversible in specific conditions. Immune cells residing in or infiltrating the liver (e.g., macrophages) are crucial in the pathogenesis of fibrosis. Given this background, the roles and action mechanisms of various immune cells and their subsets in the progression and recovery of liver fibrosis, particularly concerning nonalcoholic steatohepatitis, are discussed in this review. Furthermore, the development of better therapeutic strategies based on stage-specific properties and using advanced techniques as well as the mechanisms underlying recovery are elaborated. In conclusion, we consider the review comprehensively provides the present achievements and future possibilities revolving around fibrosis treatment.

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

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

CCR9 axis inhibition enhances hepatic migration of plasmacytoid dendritic cells and protects against liver injury

Plasmacytoid dendritic cells (pDCs) perform dual proinflammatory and immunosuppressive roles. We recently reported the potential of pDC therapy for treatment of intractable acute liver failure. However, establishment of efficient methods to deliver pDCs to the liver is essential for future clinical therapeutic applications. The present study demonstrates a higher abundance of liver and peripheral blood pDCs in mice lacking the C-C motif chemokine receptor 9 (CCR9), a pDC gut-homing receptor, than that in wild-type (WT) mice. Adoptive pDC transfer resulted in a higher efficiency of Ccr9-/- pDC migration to the liver than that to the original target organ, the small intestine, compared with that of WT pDCs. Further, Ccr9-/- pDCs consistently migrated efficiently to the concanavalin A-induced inflamed liver, and exerted a more effective immunosuppressive effect, resulting in better protection against acute liver inflammation than that demonstrated by WT pDCs. These findings highlight the therapeutic potential of the manipulation of CCR9 axis as a novel approach to improve migration of immunosuppressive pDCs to the liver in order to exploit their beneficial effects in acute liver disease.

Interleukin-35 Prevents the Elevation of the M1/M2 Ratio of Macrophages in Experimental Type 1 Diabetes

Macrophages play an important role in the early development of type 1 diabetes (T1D). Based on the phenotype, macrophages can be classified into pro-inflammatory (M1) and anti-inflammatory (M2) macrophages. Despite intensive research in the field of macrophages and T1D, the kinetic response of M1/M2 ratio has not been studied in T1D. Thus, herein, we studied the M1 and M2 macrophages in the early development of T1D using the multiple low dose streptozotocin (MLDSTZ) mouse model. We determined the proportions of M1 and M2 macrophages in thymic glands, pancreatic lymph nodes and spleens on days 3, 7 and 10 after the first injection of STZ. In addition, we investigated the effect of IL-35 in vivo on the M1/M2 ratio and IL-35⁺ plasmacytoid dendritic cells in diabetic mice and in vitro on the sorted macrophages. Our results revealed that the M1/M2 ratio is higher in STZ-treated mice but this was lowered upon the treatment with IL-35. Furthermore, IL-35 treated mice had lower blood glucose levels and a higher proportion of IL-35⁺ cells among pDCs. Macrophages treated with IL-35 in vitro also had a higher proportion of M2 macrophages. Together, our data indicate that, under diabetic conditions, pro-inflammatory macrophages increased, but IL-35 treatment decreased the pro-inflammatory macrophages and increased anti-inflammatory macrophages, further suggesting that IL-35 prevents hyperglycemia by maintaining the anti-inflammatory phenotype of macrophages and other immune cells. Thus, IL-35 should be further investigated for the treatment of T1D and other autoimmune disorders.

Aryl hydrocarbon receptor signals in epithelial cells govern the recruitment and location of Helios+ Tregs in the gut

CD4⁺Foxp3⁺ regulatory T cells (Tregs) are essential for homeostasis in the colon, but the mechanism by which local environmental cues determine the localization of colonic Tregs is unclear. Here, we administer indigo naturalis (IN), a nontoxic phytochemical aryl hydrocarbon receptor (AhR) agonist used for treating patients with ulcerative colitis (UC) in Asia, and we show that IN increases Helios⁺ Tregs and MHC class II⁺ epithelial cells (ECs) in the colon. Interactions between Tregs and MHC class II⁺ ECs occur mainly near the crypt bottom in the steady state, whereas Tregs dramatically increase and shift toward the crypt top following IN treatment. Moreover, the number of CD25⁺ T cells is increased near the surface of ECs in IN-treated UC patients compared with that in patients treated with other therapies. We also highlight additional AhR-signaling mechanisms in intestinal ECs that determine the accumulation and localization of Helios⁺ Tregs in the colon.

Patients with treated autoimmune hepatitis and persistent suppression of plasmacytoid dendritic cells: A different point of view

Objectives: Plasmacytoid dendritic cells (pDCs) have been shown to have a role in autoimmune diseases, but their role in Autoimmune Hepatitis (AIH) is not completely clear. In the present study, we assessed the frequency of pDCs in peripheral blood of AIH patients under long-term standard immunosuppressive therapy. Methods: This cross-sectional analysis enrolled 27 AIH patients and 27 healthy controls. We analyzed and compared their proportion of pDCs, CD4⁺, CD8⁺, γδ T cells, CD25⁺ regulatory T (Treg) cells, FoxP3⁺, Foxp3⁺CD39⁺ Treg cells, total B (CD19⁺) cells, and plasma cells (CD38⁺) in peripheral blood using flow cytometry immunophenotyping. Results: AIH patients had a lower percentage of pDCs (median frequencies of 0.2% vs. 0.4%; p = .002) and higher expression of CD8 T cells (32.5% vs 28.6%; p = 0.008) in peripheral blood, when compared to healthy controls. We did not find statistically significant differences between the groups regarding the other cell subtypes.Conclusion: Our data suggest a persistent suppression of pDCs in AIH patients, along with increased CD8 T cell activity, years after AIH diagnosis and despite of good clinical response to treatment, thus pointing to a role of pDCs in the AIH pathogenesis.

Interleukin-35 Promotes Th9 Cell Differentiation in IgG4-Related Disorders: Experimental Data and Review of the Literature

IgG4-related disease (IgG4-RD) is characterized by intense infiltration of IgG4-positive plasma cells in affected organs. However, the mechanisms acting in the immune responses in IgG4-RD are not fully understood. The aim of this study was to dissect the mechanism underlying the immunoglobulin class switch in IgG4-RD by addressing the crosstalk between IL-35-producing and Th9 cells. The expression level of IL-35 was examined in plasma samples from patients with hepatobiliary and/or pancreatic manifestations of IgG4-RD. Our data demonstrate that IgG4-RD patients exhibit significantly high-level productions of IL-35 as compared to disease and healthy controls. We detected the two subunits of IL-35, EBI3 and IL-12p35, in the two major affected organs, liver and pancreatic tissue, from IgG4-RD. The EBI3- and IL-12p35-positive cells were significantly higher in affected organs in IgG4-RD as compared to disease controls. The colocalization of EBI3 with CD19 and CD38, markers for B cells, suggest the presence of IL-35-producing B cells in affected organs in IgG4-RD. The effects of IL-35 in Th9 differentiation and IL-9 in production of immunoglobulin were then assessed. Surprisingly, IL-35 treatment promoted naïve CD4 T cell differentiating towards Th9 cells through IRF4 signaling. As a consequence, IL-9 secreted by Th9 cells promoted the differentiation of plasma cells and production of IgG1 and IgG4, predominantly IgG4. In conclusion, our data demonstrate that IL-35 actively participates in the process of inflammation and plays an important role in Th9 differentiation resulting in an immunoglobulin class switch towards IgG4.

CD8+ tissue-resident memory T cells promote liver fibrosis resolution by inducing apoptosis of hepatic stellate cells

Non-alcoholic steatohepatitis (NASH) is a leading cause of chronic liver disease that can progress to liver fibrosis. Recent clinical advance suggests a reversibility of liver fibrosis, but the cellular and molecular mechanisms underlying NASH resolution remain unclarified. Here, using a murine diet-induced NASH and the subsequent resolution model, we demonstrate direct roles of CD8⁺ tissue-resident memory CD8⁺ T (CD8⁺ Trm) cells in resolving liver fibrosis. Single-cell transcriptome analysis and FACS analysis revealed CD69⁺CD103⁻CD8⁺ Trm cell enrichment in NASH resolution livers. The reduction of liver CD8⁺ Trm cells, maintained by tissue IL-15, significantly delayed fibrosis resolution, while adoptive transfer of these cells protected mice from fibrosis progression. During resolution, CD8⁺ Trm cells attracted hepatic stellate cells (HSCs) in a CCR5-dependent manner, and predisposed activated HSCs to FasL-Fas-mediated apoptosis. Histological assessment of patients with NASH revealed CD69⁺CD8⁺ Trm abundance in fibrotic areas, further supporting their roles in humans. These results highlight the undefined role of liver CD8⁺ Trm in fibrosis resolution.

The cellular and molecular mechanisms underlying the resolution of non-alcoholic steatohepatitis remain incompletely understood. Here the authors report a single cell-based analysis that identified CD8 + tissue-resident memory T cells, which contribute to resolution of liver fibrosis potentially via elimination of hepatic stellate cells through Fas-mediated cytotoxicity.

Tregs-derived interleukin 35 attenuates endothelial proliferation through STAT1 in pulmonary hypertension

Background

To explore the source, the role and the specific mechanism of IL-35 and its downstream molecules in the development of pulmonary hypertension.

Methods

8–10 weeks male mice were undergoing hypoxia combined with SU5416 (HySu) to establish a pulmonary hypertension (PH) model. The phenotype of PH mice was measured by immunohistochemistry and immunofluorescence staining. The levels of two subunits (EBI3 and p35 subunits) in lung tissue were measured by real-time PCR and western blotting. EBI3 monoclonal antibody was administrated as IL-35 neutralization to offset systemic IL-35 expression. Fludarabine, an inhibitor of STAT1 (signal transducer and activator of transcription 1) was used to clarify the role of STAT1 under IL-35 treatment.

Results

After pulmonary hypertension, the expression of IL-35 and its two subunits (EBI3 and p35 subunits) in lung tissue were significantly increased. And the two subunits of IL-35 are highly expressed in Treg cells. Compared with the controlled PH mice, the IL-35 neutralization PH mice showed aggravated pulmonary hypertension phenotype. The specific manifestations are the increase of right ventricular systolic pressure (RVSP), the growing proportion of right heart [RV/(LV+S)], and the remodeling of pulmonary blood vessels increases. The expression of pulmonary vascular endothelium (CD31) in PH mice increased, and the proliferation ability of vascular endothelium enhanced after IL-35 was inhibited. IL-35 phosphorylates STAT1 through the receptor GP130 on pulmonary vascular endothelial cells, which in turn inhibits endothelial cell proliferation. IL-35 recombinant protein can reduce the expression of CD31 in lung tissues of PH mice. But the administration of STAT1 inhibitor made it invalid from the IL-35 effect of reversing pulmonary hypertension.

Conclusions

Tregs-derived IL-35 can reverse the remodeling of pulmonary blood vessels and alleviate the progression of pulmonary hypertension by reducing the proliferation of endothelial cells.

A Low Level of Plasmacytoid Dendritic Cells at Engraftment Is a Valuable Prognostic Indicator in Children Receiving Allogeneic Hematopoietic Stem Cell Transplantation

Early prediction and intervention are known to be critical for acute graft-versus-host disease (aGVHD) prevention and treatment. Significant progress has been made in the development of human plasma biomarkers for the risk stratification of aGVHD severity. Whether donor-derived immune cells may predict the occurrence of severe aGVHD early after allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains poorly understood. The objective of this retrospective study was to evaluate the results of allo-HSCT in pediatric patients with different counts and frequencies of dendritic cell (DC) subsets at engraftment in pediatric patients at the Children's Hospital of Soochow University. A total of 45 patients as a discovery cohort were enrolled from March 2018 to December 2018 at the hospital. The validation cohort (30 patients) was enrolled from December 2019 to May 2020. Plasma samples collected from 2016 to 2018 were used for testing ST2 and Reg3α in pediatric patients undergoing allo-HSCT. Patients with grade II-IV aGVHD (n = 18; termed severe aGVHD) showed 3- and 6-fold fewer frequency and numbers, respectively, of plasmacytoid dendritic cells (pDCs) in the peripheral blood (PB) at the engraftment time than patients with grade 0-I aGVHD (n = 27; termed no/mild aGVHD). Using a receiver operating characteristic curve analysis, we identified the threshold of pDC level at 0.3 cell/μL as a cutoff to evaluate the difference in patients with high (>0.3 cell/μL) versus low (<0.3 cell/μL) pDC counts. Of these 45 patients, 21 (46.7%) had a high number of pDCs and 24 (53.3%) had low pDCs. The patients with low pDCs at the time of engraftment had a significantly higher probability of developing severe aGVHD (P < .05). The sensitivity of distinguishing severe aGVHD from no/mild aGVHD was 75%, and the specificity was 94%. In addition, the low pDC patients had higher transplantation-related mortality compared with the high pDC patients (12.5% versus 0%). Using an additional cohort of 30 allo-HSCT patients, we validated this observation. Our findings demonstrate that donor pDC count in PB at the time of engraftment is a valuable biomarker for predicting severe aGVHD in pediatric patients undergoing allo-HSCT.

Regulatory B cells in cancer

Tumorigenesis proceeds through discrete steps where acquisition of genetic lesions and changes in the surrounding microenvironment combine to drive unrestricted neoplastic proliferation and metastasis. The ability of tumor-infiltrating immune cells to promote tumor growth via the provision of signals that enable tumor cell survival and proliferation as well as contribute to immune suppression is an active area of research. Recent efforts have provided us with mechanistic insights into how B cells can positively and negatively regulate immune responses. Negative regulation of immune responses in cancer can be mediated by regulatory B cells and is often a result of increased production of cytokines that can directly and indirectly affect anti-tumor immune function and cancer cell growth. Signals that lead to the expansion of regulatory B cells and the spectrum of their functional roles are not well understood and are the subject of active research by many groups. Here, we elaborate broadly on the history of regulatory B cells in cancer and summarize recent studies that have established genetic models for the study of regulatory B cell function and their potential for therapeutic intervention in the setting of solid cancers.

Interleukin-35: An emerging player in the progression of liver diseases

Interleukin-35(IL-35), a newly identified immunosuppressive cytokine, has recently been shown to play a significant role in the progression of various autoimmune diseases and malignant tumors. The liver is the largest organ in the body and is generally regarded as an important lymphoid organ by an increasing number of immunologists. A number of reports have demonstrated that IL-35 plays essential roles in maintaining the immune homeostasis of the liver microenvironment. This review summarizes the existing studies of IL-35 in liver diseases, including viral hepatitis, immune liver injury, liver cirrhosis and carcinoma. We aimed to provide a comprehensive overview of the vital roles of IL-35 in hepatic damage and explore new alternative therapeutic targets for these diseases.

Inhibition of EZH2 ameliorates bacteria-induced liver injury by repressing RUNX1 in dendritic cells

Fulminant hepatic failure (FHF) is a clinical syndrome characterized by a sudden and severe impairment in liver function. However, the precise mechanism of immune dysregulation that is significant to FHF pathogenesis remains unclear. Enhancer of zeste homolog 2 (EZH2) has been implicated in inflammation as a regulator of immune cell function. In this study, we investigated the role of EZH2 in an animal model of human FHF induced by Propionibacterium acnes (P. acnes) and lipopolysaccharide (LPS). We demonstrated that EZH2 depletion in dendritic cells (DCs) and pharmacological inhibition of EZH2 using GSK126 both significantly ameliorated liver injury and improved the survival rates of mice with P. acnes plus LPS-induced FHF, which could be attributed to the decreased infiltration and activation of CD4⁺ T cells in the liver, inhibition of T helper 1 cells and induction of regulatory T cells. The expression of EZH2 in DCs was increased after P. acnes administration, and EZH2 deficiency in DCs suppressed DC maturation and prevented DCs from efficiently stimulating CD4⁺ T-cell proliferation. Further mechanistic analyses indicated that EZH2 deficiency directly increased the expression of the transcription factor RUNX1 and thereby suppressed the immune functions of DCs. The functional dependence of EZH2 on RUNX1 was further illustrated in DC-specific Ezh2-deficient mice. Taken together, our findings establish that EZH2 exhibits anti-inflammatory effects through inhibition of RUNX1 to regulate DC functions and that inhibition of EZH2 alleviates P. acnes plus LPS-induced FHF, probably by inhibiting DC-induced adaptive immune responses. These results highlight the effect of EZH2 on DCs, serving as a guide for the development of a promising immunotherapeutic strategy for FHF.

Plasmacytoid dendritic cells in the eye

Plasmacytoid dendritic cells (pDCs) are a unique subpopulation of immune cells, distinct from classical dendritic cells. pDCs are generated in the bone marrow and following development, they typically home to secondary lymphoid tissues. While peripheral tissues are generally devoid of pDCs during steady state, few tissues, including the lung, kidney, vagina, and in particular ocular tissues harbor resident pDCs. pDCs were originally appreciated for their potential to produce large quantities of type I interferons in viral immunity. Subsequent studies have now unraveled their pivotal role in mediating immune responses, in particular in the induction of tolerance. In this review, we summarize our current knowledge on pDCs in ocular tissues in both mice and humans, in particular in the cornea, limbus, conjunctiva, choroid, retina, and lacrimal gland. Further, we will review our current understanding on the significance of pDCs in ameliorating inflammatory responses during herpes simplex virus keratitis, sterile inflammation, and corneal transplantation. Moreover, we describe their novel and pivotal neuroprotective role, their key function in preserving corneal angiogenic privilege, as well as their potential application as a cell-based therapy for ocular diseases.

Nobiletin Protects against Acute Liver Injury via Targeting c-Jun N-Terminal Kinase (JNK)-Induced Apoptosis of Hepatocytes

Acute liver injury resulting from several factors such as medication, food toxins, and herbal supplementation often leads to a severe health condition and makes treatment difficult; thereby, the prevention of acute liver injury remains a critical issue and is of great importance. In this study, we investigated the preventive effects of nobiletin (NOB) on a mouse model of concanavalin A (ConA)-induced acute liver injury. We observed that NOB (10 mg/kg) pretreatment of ConA-treated mice significantly lowered the levels of liver enzymes including alanine aminotransferase (ALT) and aspartate aminotransferase (AST), decreased the intracellular generation of reactive oxygen species (ROS), and suppressed the release of inflammatory cytokines such as tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ). Pathological data suggested that pretreatment with NOB ameliorated ConA-induced liver damage by promoting proliferation and alleviating apoptosis of hepatocytes. Furthermore, significant suppression of the c-Jun-activating kinase (JNK) signal was also observed in NOB-pretreated liver tissues compared with that of ConA treatment only. In addition, an in vitro mechanism study confirmed that the addition of NOB protected hepatocytes via inhibition of JNK activation, manifesting that alleviation of JNK-induced apoptosis of hepatocytes is correlated with NOB protection in acute liver injury.

CLIF-C Organ Failure Score and Liver Volume Predict Prognosis in Steroid-Treated Severe Acute Autoimmune Hepatitis

Controversies and debates remain regarding the best management of severe acute‐onset autoimmune hepatitis (SA‐AIH) due to the lack of useful outcome or complication prediction systems. We conducted this clinical practice‐based observational study to clarify whether Chronic Liver Failure Consortium Organ Failure scores (CLIF‐C OFs) and the computed tomography–derived liver volume to standard liver volume (CTLV/SLV) ratio at admission to a tertiary transplant center can predict outcomes and complications due to infection. Thirty‐four consecutive corticosteroid‐treated patients with SA‐AIH from 2007 to 2018 were included. Severe hepatitis was defined as an international normalized ratio (of prothrombin time) over 1.3 any time before admission. Of the 34 corticosteroid‐treated patients with SA‐AIH inclusive of 25 (73.5%) acute liver failure cases, transplant‐free survival was observed in 24 patients (70.6%). Any infection was noticed in 10 patients (29.4%). CLIF‐C OFs, at the cutoff of 9, significantly predicted survival (P = 0.0002, log‐rank test), outperformed the Model for End‐stage Liver Disease system in predicting outcome (P = 0.0325), and significantly discriminated between liver transplant and death in a competing risk analysis. SA‐AIH was characterized as having decreased CTLV/SLV, which was also predictive of survival (P < 0.0001). Interestingly, CLIF‐C OFs, especially the subscores for respiratory dysfunction, also predicted infection (P = 0.007). Conclusion: In corticosteroid‐treated patients with SA‐AIH, CLIF‐C OFs and CTLV/SLV ratios predicted both survival outcome and complications due to infection. Further investigation is warranted to determine whether making decisions based on CLIF‐C OFs or CTLV/SLV ratios is useful.

Plasmacytoid Dendritic Cells Protect Against Middle Cerebral Artery Occlusion Induced Brain Injury by Priming Regulatory T Cells

Regulatory T cells (Tregs) play an anti-inflammatory effect to protect against ischemic stroke. Plasmacytoid dendritic cells (pDCs) can induce regulatory T cells tolerance in sterile-inflammation conditions. However, whether and how pDCs-mediated Tregs response play a part in the pathology of ischemic stroke remains unclear. In this study, we showed that pDCs were increased in the brain of middle cerebral artery occlusion (MCAO) mice. Depletion of pDCs with 120G8 exacerbated MCAO-induced brain injury, peripheral pro-inflammation response and decreased the systemic Tregs in mice. Furthermore, the data of mixed lymphocyte reaction (MLR) in vitro demonstrate that splenic pDCs from MCAO mice can significantly promote Tregs proliferation, accompanying with the increased expression of indoleamine 2,3-dioxygenase 1 (IDO1) on pDCs. Taken together, the findings here suggested that under the pathologic state of stroke, pDCs protect against MCAO-induced brain injury by priming Tregs, illustrating that pDCs represented as a therapeutic target for the prevention of ischemic brain injury.