Natural killer T cells play a necessary role in modulating of immune-mediated liver injury by gut microbiota

Microbiota-derived H2S induces c-kit+ cDC1 autophagic cell death and liver inflammation in metabolic dysfunction-associated steatohepatitis

Immune dysregulation-induced inflammation serves as a driving force in the progression of metabolic dysfunction-associated steatohepatitis (MASH), while the underlying cellular and molecular mechanisms remain largely uncharted. A Western diet (WD) is employed to construct mouse models of metabolic dysfunction associated steatotic liver disease (MASLD) or MASH. Mass cytometry identifies a c-kit+ cDC1 subset whose frequency is reduced in the livers of mice and patients with MASH compared with healthy controls. Adoptive cell transfer of c-kit+ cDC1 protects the progression of MASH. Moreover, analysis of gut microbe sequence shows that WD-fed mice and MASLD/MASH patients exhibit gut microbiota dysbiosis, with an elevated abundance of H2S-producing Desulfovibrio_sp. Transplanting of MASH-derived fecal flora, Desulfovibrio_sp., or injecting H2S intraperitoneally into MASLD mice decreases the c-kit+cDC1 population and exacerbates liver inflammation. Mechanistically, H2S induces autophagic cell death of cDC1 in a c-kit-dependent manner in cDC-specific c-kit-/- and Atg5-/- mice. We thus uncover that microbiota-derived H2S triggers the autophagic cell death of c-kit+ cDC1 and ignites the liver inflammatory cascade in MASH.

Impacts of gut microbiota alteration on age-related chronic liver diseases

The gut microbiome and its metabolites are involved in developing and progressing liver disease. Various liver illnesses, such as non-alcoholic fatty liver disease, alcoholic liver disease, hepatitis C, and hepatocellular carcinoma, are made worse and have worse prognoses with aging. Dysbiosis, which occurs when the symbiosis between the microbiota and the host is disrupted, can significantly negatively impact health. Liver disease is linked to qualitative changes, such as an increase in hazardous bacteria and a decrease in good bacteria, as well as quantitative changes in the overall amount of bacteria (overgrowth). Intestinal gut microbiota and their metabolites may lead to chronic liver disease development through various mechanisms, such as increasing gut permeability, persistent systemic inflammation, production of SCFA, bile acids, and alteration in metabolism. Age-related gut dysbiosis can disrupt the communication between gut microbiota and the host, impacting the host's health and lifespan. With aging, a gradual loss of the ability to maintain homeostasis because of structural alteration and gut dysbiosis leads to the disease progression in end-stage liver disease. Recently chronic liver disease has been identified as a global problem. A large number of patients are receiving liver transplants yearly. Thereby gut microbiome ecology is changing in the patients of the gut due to the changes in pathophysiology during the preoperative stage. The present review summarises the age-associated dysbiosis of gut microbial composition and its contribution to chronic liver disease. This review also provides information about the impact of liver transplant on the gut microbiome and possible disadvantageous effects of alteration in gut microbiota.

Gut microbiota and metabolite interface-mediated hepatic inflammation

Immunologic and metabolic signals regulated by gut microbiota and relevant metabolites mediate bidirectional interaction between the gut and liver. Gut microbiota dysbiosis, due to diet, lifestyle, bile acids, and genetic and environmental factors, can advance the progression of chronic liver disease. Commensal gut bacteria have both pro- and anti-inflammatory effects depending on their species and relative abundance in the intestine. Components and metabolites derived from gut microbiota-diet interaction can regulate hepatic innate and adaptive immune cells, as well as liver parenchymal cells, significantly impacting liver inflammation. In this mini review, recent findings of specific bacterial species and metabolites with functions in regulating liver inflammation are first reviewed. In addition, socioeconomic and environmental factors, hormones, and genetics that shape the profile of gut microbiota and microbial metabolites and components with the function of priming or dampening liver inflammation are discussed. Finally, current clinical trials evaluating the factors that manipulate gut microbiota to treat liver inflammation and chronic liver disease are reviewed. Overall, the discussion of microbial and metabolic mediators contributing to liver inflammation will help direct our future studies on liver disease.

Immune modulation of gut microbiota and its metabolites in chronic hepatitis B

The gut microbiota is a diverse ecosystem consisting of 100 trillion microbiomes. The interaction between the host's gut and distal organs profoundly impacts various functions such as metabolism, immunity, neurology, and nutrition within the human body. The liver, as the primary immune organ, plays a crucial role in maintaining immune homeostasis by receiving a significant influx of gut-derived components and toxins. Perturbations in gut microbiota homeostasis have been linked to a range of liver diseases. The advancements in sequencing technologies, such as 16S rRNA and metagenomics, have opened up new avenues for comprehending the intricate physiological interplay between the liver and the intestine. Metabolites produced by the gut microbiota function as signaling molecules and substrates, influencing both pathological and physiological processes. Establishing a comprehensive host-bacterium-metabolism axis holds tremendous potential for investigating the mechanisms underlying liver diseases. In this review, we have provided a summary of the detrimental effects of the gut-liver axis in chronic liver diseases, primarily focusing on hepatitis B virus-related chronic liver diseases. Moreover, we have explored the potential mechanisms through which the gut microbiota and its derivatives interact with liver immunity, with implications for future clinical therapies.

Gut microbiota affects sensitivity to immune-mediated isoniazid-induced liver injury

Isoniazid (INH) is a highly effective single and/or combined first-line anti-tuberculosis (anti-TB) therapy drug, and the hepatotoxicity greatly limits its clinical application. INH-induced liver injury (INH-DILI) is a typical immune-mediated idiosyncratic drug-induced liver injury. Existing mechanisms including genetic variations in drug metabolism and immune responses cannot fully explain the differences in susceptibility and sensitivity to INH-DILI, suggesting that other factors may be involved. Accumulating evidence indicates that the development and severity of immune-mediated liver injury is related to gut microbiota. In this study, INH exposure caused liver damage, immune disregulation and microbiota profile alteration. Depletion of gut microbiota ameliorated INH-DILI, and improved INH-DILI-associated immune disorder and inflammatory response. Moreover, hepatotoxicity of INH was ameliorated by fecal microbiota transplantation (FMT) from INH-treated mice. Notably, Bifidobacterium abundance was significantly associated with transaminase levels. In conclusion, our results suggested that the effect of gut microbiota on INH-DILI was related to immunity, and the difference in INH-DILI sensitivity was related to the structure of gut microbiota. Changes in the structure of gut microbiota by continuous exposure of INH resulted in the tolerance to liver injury, and probiotics such as Bifidobacterium might play an important role in INH-DILI and its "adaptation" phenomenon. This work provides novel evidence for elucidating the underlying mechanism of difference in individual's response to INH-DILI and potential approach for intervening anti-TB drug liver injury by modulating gut microbiota.

A Synbiotic Ameliorates Con A-Induced Autoimmune Hepatitis in Mice through Modulation of Gut Microbiota and Immune Imbalance

SCOPE

Changes in the intestinal flora are related to autoimmune hepatitis (AIH) development. The aim of this study is to investigate the synergistic effects of probiotics and prebiotics on liver injury induced by concanavalin A (Con A).

METHODS AND RESULTS

C57BL/6 mice are fed probiotics (Pro), prebiotics (Pre), synbiotic (Syn) for 7 days and then Con A is injected via tail veins to induce AIH. Additionally, methylprednisolone (MP) is gavaged 0.5 h after the Con A injection. It is found that both Pro, Pre, Syn, and MP decrease the levels of serum transaminase, liver F4/80+ macrophage cells, and hepatocellular apoptosis. Pro, Pre, and Syn decrease proinflammatory cytokines, elevate levels of anti-inflammatory as well as restored immune imbalance in AIH. Besides, Pro, Pre, and Syn not only reshape the perturbed gut microbiota, but also maintain intestinal barrier integrity, block the activation of lipopolysaccharide (LPS)/TLR4/NF-κB pathway in the liver. Interestingly, the effects of Syn are superior to Pro or Pre alone in Con A-induced acute liver injury.

CONCLUSIONS

Syn obviously facilitates AIH remission. The combined use of Pro and Pre is effective in improving Pro and Pre efficacy and can be an important tool for preventing and adjuvant treating patients for AIH.

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

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

The gut–liver axis in sepsis: interaction mechanisms and therapeutic potential

Sepsis is a potentially fatal condition caused by dysregulation of the body's immune response to an infection. Sepsis-induced liver injury is considered a strong independent prognosticator of death in the critical care unit, and there is anatomic and accumulating epidemiologic evidence that demonstrates intimate cross talk between the gut and the liver. Intestinal barrier disruption and gut microbiota dysbiosis during sepsis result in translocation of intestinal pathogen-associated molecular patterns and damage-associated molecular patterns into the liver and systemic circulation. The liver is essential for regulating immune defense during systemic infections via mechanisms such as bacterial clearance, lipopolysaccharide detoxification, cytokine and acute-phase protein release, and inflammation metabolic regulation. When an inappropriate immune response or overwhelming inflammation occurs in the liver, the impaired capacity for pathogen clearance and hepatic metabolic disturbance can result in further impairment of the intestinal barrier and increased disruption of the composition and diversity of the gut microbiota. Therefore, interaction between the gut and liver is a potential therapeutic target. This review outlines the intimate gut–liver cross talk (gut–liver axis) in sepsis.

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

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

Role of Intestinal Microbes in Chronic Liver Diseases

With the recent availability and upgrading of many emerging intestinal microbes sequencing technologies, our research on intestinal microbes is changing rapidly. A variety of investigations have found that intestinal microbes are essential for immune system regulation and energy metabolism homeostasis, which impacts many critical organs. The liver is the first organ to be traversed by the intestinal portal vein, and there is a strong bidirectional link between the liver and intestine. Many intestinal factors, such as intestinal microbes, bacterial composition, and intestinal bacterial metabolites, are deeply involved in liver homeostasis. Intestinal microbial dysbiosis and increased intestinal permeability are associated with the pathogenesis of many chronic liver diseases, such as alcoholic fatty liver disease (AFLD), non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), chronic hepatitis B (CHB), chronic hepatitis C (CHC), autoimmune liver disease (AIH) and the development of hepatocellular carcinoma (HCC). Intestinal permeability and dysbacteriosis often lead to Lipopolysaccharide (LPS) and metabolites entering in serum. Then, Toll-like receptors activation in the liver induces the exposure of the intestine and liver to many small molecules with pro-inflammatory properties. And all of these eventually result in various liver diseases. In this paper, we have discussed the current evidence on the role of various intestinal microbes in different chronic liver diseases. As well as potential new therapeutic approaches are proposed in this review, such as antibiotics, probiotics, and prebiotics, which may have an improvement in liver diseases.

Phospholipid metabolites of the gut microbiota promote hypoxia-induced intestinal injury via CD1d-dependent γδ T cells

Gastrointestinal dysfunction is a common symptom of acute mountain sickness (AMS). The gut microbiota and γδ T cells play critical roles in intestinal disease. However, the mechanistic link between the microbiota and γδ T cells in hypoxia-induced intestinal injury remains unclear. Here, we show that hypoxia-induced intestinal damage was significantly alleviated after microbiota depletion with antibiotics. Hypoxia modulated gut microbiota composition by promoting antimicrobial peptides angiogenin-4 secretions. The abundance of Clostridium in the gut of mice after hypoxia significantly decreased, while the abundance of Desulfovibrio significantly increased. Furthermore, Desulfovibrio-derived phosphatidylethanolamine and phosphatidylcholine promoted γδ T cell activation. In CD1d-deficient mice, the levels of intraepithelial IL-17A and γδ T cells and intestinal damage were significantly decreased compared with those in wild-type mice under hypoxia. Mechanistically, phospholipid metabolites from Desulfovibrio are presented by intestinal epithelial CD1d to induce the proliferation of IL-17A-producing γδ T cells, which aggravates intestinal injury. Gut microbiota-derived metabolites promote hypoxia-induced intestinal injury via CD1d-dependent γδ T cells, suggesting that phospholipid metabolites and γδ T cells can be targets for AMS therapy.

Intestinal homeostasis in autoimmune liver diseases

ABSTRACT

Intestinal homeostasis depends on complex interactions between the gut microbiota and host immune system. Emerging evidence indicates that the intestinal microbiota is a key player in autoimmune liver disease (AILD). Autoimmune hepatitis, primary biliary cholangitis, primary sclerosing cholangitis, and IgG4-related sclerosing cholangitis have been linked to gut dysbiosis. Diverse mechanisms contribute to disturbances in intestinal homeostasis in AILD. Bacterial translocation and molecular mimicry can lead to hepatic inflammation and immune activation. Additionally, the gut and liver are continuously exposed to microbial metabolic products, mediating variable effects on liver immune pathologies. Importantly, microbiota-specific or associated immune responses, either hepatic or systemic, are abnormal in AILD. Comprehensive knowledge about host-microbiota interactions, included but not limited to this review, facilitates novel clinical practice from a microbiome-based perspective. However, many challenges and controversies remain in the microbiota field of AILD, and there is an urgent need for future investigations.

The Role of Gut Microbiota in Some Liver Diseases: From an Immunological Perspective

Gut microbiota is a microecosystem composed of various microorganisms. It plays an important role in human metabolism, and its metabolites affect different tissues and organs. Intestinal flora maintains the intestinal mucosal barrier and interacts with the immune system. The liver is closely linked to the intestine by the gut-liver axis. As the first organ that comes into contact with blood from the intestine, the liver will be deeply influenced by the gut microbiota and its metabolites, and the intestinal leakage and the imbalance of the flora are the trigger of the pathological reaction of the liver. In this paper, we discuss the role of gut microbiota and its metabolites in the pathogenesis and development of autoimmune liver diseases((including autoimmune hepatitis, primary biliary cirrhosis, primary sclerosing cholangitis), metabolic liver disease such as non-alcoholic fatty liver disease, cirrhosisits and its complications, and liver cancer from the perspective of immune mechanism. And the recent progress in the treatment of these diseases was reviewed from the perspective of gut microbiota.

The Gut Microbiota: A Novel Player in Autoimmune Hepatitis

Autoimmune hepatitis (AIH) is a chronic immune-mediated liver disease distributed globally in all ethnicities with increasing prevalence. If left untreated, the disease will lead to cirrhosis, liver failure, or death. The intestinal microbiota is a complex ecosystem located in the human intestine, which extensively affects the human physiological and pathological processes. With more and more in-depth understandings of intestinal microbiota, a substantial body of studies have verified that the intestinal microbiota plays a crucial role in a variety of digestive system diseases, including alcohol-associated liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD). However, only a few studies have paid attention to evaluate the relationship between AIH and the intestinal microbiota. While AIH pathogenesis is not fully elucidated yet, some studies have indicated that intestinal microbiota putatively made significant contributions to the occurrence and the development of AIH by triggering several specific signaling pathways, altering the metabolism of intestinal microbiota, as well as modulating the immune response in the intestine and liver. By collecting the latest related literatures, this review summarized the increasing trend of the aerobic bacteria abundance in both AIH patients and AIH mice models. Moreover, the combination of specific bacteria species was found distinct to AIH patients, which could be a promising tool for diagnosing AIH. In addition, there were alterations of luminal metabolites and immune responses, including decreased short-chain fatty acids (SCFAs), increased pathogen associated molecular patterns (PAMPs), imbalanced regulatory T (Treg)/Th17 cells, follicular regulatory T (TFR)/follicular helper T (TFH) cells, and activated natural killer T (NKT) cells. These alterations participate in the onset and the progression of AIH via multiple mechanisms. Therefore, some therapeutic methods based on restoration of intestinal microbiota composition, including probiotics and fecal microbiota transplantation (FMT), as well as targeted intestinal microbiota-associated signaling pathways, confer novel insights into the treatment for AIH patients.

Lamina propria interleukin 17 A aggravates natural killer T-cell activation in autoimmune hepatitis

Autoimmune hepatitis is an interface hepatitis characterized by the progressive destruction of the liver parenchyma, the cause of which is still obscure. Interleukin (IL)-17A is a major driver of autoimmunity, which can be produced by innate immune cells against several intracellular pathogens. Here, we investigated the involvement of IL-17A in a mice model of immune-mediated hepatitis with the intestine exposed to Salmonella typhimurium. Our results showed more severe Concanavalin (Con) A-induced liver injury and gut microbiome dysbiosis when the mice were treated with a gavage of S. typhimurium. Then, the natural killer (NK) T cells were overactivated by the accumulated IL-17A in the liver in the Con A and S. typhimurium administration group. IL-17A could activate NKT cells by inducing CD178 expression via IL-4/STAT6 signaling. Furthermore, via the portal tract, the laminae propria mucosal-associated invariant T (MAIT)-cell-derived IL-17A could be the original driver of NKT cell overactivation in intragastric administration of S. typhimurium and Con A injection. In IL-17A-deficient mice, Con A-induced liver injury and NKT cell activation were alleviated. However, when AAV-sh-mIL-17a was used to specifically knock down IL-17A in liver, it seemed that hepatic IL-17a knock down did not significantly influence the liver injury. Our results suggested that, under Con A-induction, laminae propria MAIT-derived IL-17A activated hepatic NKT, and this axis could be a therapeutic target in autoimmune liver disease.

Gut microbiota and immunity relevance in eubiosis and dysbiosis

Human gut is colonized by numerous microorganisms, in which bacteria present the highest proportion of this colonization that live in a symbiotic relationship with the host. This microbial collection is commonly known as the microbiota. The gut microbiota can mediate gut epithelial and immune cells interaction through vitamins synthesis or metabolic products. The microbiota plays a vital role in growth and development of the main components of human’s adaptive and innate immune system, while the immune system regulates host-microbe symbiosis. On the other hand, negative alteration in gut microbiota composition or gut dysbiosis, can disturb immune responses. This review highlights the gut microbiota-immune system cross-talk in both eubiosis and dysbiosis.

The immunotoxicity, but not anti-tumor efficacy, of anti-CD40 and anti-CD137 immunotherapies is dependent on the gut microbiota

Immune agonist antibodies (IAAs) are promising immunotherapies that target co-stimulatory receptors to induce potent anti-tumor immune responses, particularly when combined with checkpoint inhibitors. Unfortunately, their clinical translation is hampered by serious dose-limiting, immune-mediated toxicities, including high-grade and sometimes fatal liver damage, cytokine release syndrome (CRS), and colitis. We show that the immunotoxicity, induced by the IAAs anti-CD40 and anti-CD137, is dependent on the gut microbiota. Germ-free or antibiotic-treated mice have significantly reduced colitis, CRS, and liver damage following IAA treatment compared with conventional mice or germ-free mice recolonized via fecal microbiota transplant. MyD88 signaling is required for IAA-induced CRS and for anti-CD137-induced, but not anti-CD40-induced, liver damage. Importantly, antibiotic treatment does not impair IAA anti-tumor efficacy, alone or in combination with anti-PD1. Our results suggest that microbiota-targeted therapies could overcome the toxicity induced by IAAs without impairing their anti-tumor activity.

The Immune System through the Lens of Alcohol Intake and Gut Microbiota

The human gut is the largest organ with immune function in our body, responsible for regulating the homeostasis of the intestinal barrier. A diverse, complex and dynamic population of microorganisms, called microbiota, which exert a significant impact on the host during homeostasis and disease, supports this role. In fact, intestinal bacteria maintain immune and metabolic homeostasis, protecting our organism against pathogens. The development of numerous inflammatory disorders and infections has been linked to altered gut bacterial composition or dysbiosis. Multiple factors contribute to the establishment of the human gut microbiota. For instance, diet is considered as one of the many drivers in shaping the gut microbiota across the lifetime. By contrast, alcohol is one of the many factors that disrupt the proper functioning of the gut, leading to a disruption of the intestinal barrier integrity that increases the permeability of the mucosa, with the final result of a disrupted mucosal immunity. This damage to the permeability of the intestinal membrane allows bacteria and their components to enter the blood tissue, reaching other organs such as the liver or the brain. Although chronic heavy drinking has harmful effects on the immune system cells at the systemic level, this review focuses on the effect produced on gut, brain and liver, because of their significance in the link between alcohol consumption, gut microbiota and the immune system.

Alteration of Gut Microbiota and Its Impact on Immune Response in Patients with Chronic HBV Infection: A Review

Chronic hepatitis B virus infection is a source of substantial global health problems, particularly in economically underdeveloped and/or developing countries. It is the primary cause of severe liver disorders such as liver fibrosis, cirrhosis, and hepatocellular carcinoma. The liver is connected by the bile duct to the small intestine that carries bile produced in the liver to the intestine. The liver is the initial organ exposed to materials originating from the gut including dietary compounds, bacteria, and their products. Human intestines harbor a wide diversity of the community of microbes which are collectively termed as gut microbiota. In chronic infection with the hepatitis B virus, microbial alteration of the gut is a source of systemic immune activation. Besides, gut permeability is altered in hepatitis B virus-infected patients with an increased bacterial translocation and endotoxin load in the portal vein that caused toll-like receptor activation in the liver, which facilitates immune-mediated liver injury. Toll-like receptors further triggered the host-wide inflammatory response by inducing signaling cascades such as nuclear factor-kappa B-linked pathways and by accelerating cytokine secretion like tumor necrosis factor-alpha, which evokes chronic inflammation and leads to liver lesion formation, fibrosis progression, and cirrhosis and hepatocellular carcinoma development. In conclusion, changes in intestinal flora play an important role in encouraging the production of chronic infection with the hepatitis B virus. Therefore, careful attention should be given to the maintenance of intestinal microecology of patients which can provide a sound foundation for the treatment of chronic infection with the hepatitis B virus.

Gut Microbiota and Chemical-Induced Acute Liver Injury

Background: Drug overdose or chemical exposures are the main causes of acute liver injury (ALI). Severe liver injury can develop into liver failure that is an important cause of liver-related mortality in intensive care units in most countries. Pharmacological studies have utilized a variety of comprehensive chemical induction models that recapitulate the natural pathogenesis of acute liver injury. Their mechanism is always based on redox imbalance-induced direct hepatotoxicity and massive hepatocyte cell death, which can trigger immune cell activation and recruitment to the liver. However, the pathogenesis of these models has not been fully stated. Many studies showed that gut microbiota plays a crucial role in chemical-induced liver injury. Hepatotoxicity is likely induced by imbalanced microbiota homeostasis, gut mucosal barrier damage, systemic immune activation, microbial-associated molecular patterns, and bacterial metabolites. Meanwhile, many preclinical studies have shown that supplementation with probiotics can improve chemical-induced liver injury. In this review, we highlight the pathogenesis of gut microorganisms in chemical-induced acute liver injury animal models and explore the protective mechanism of exogenous microbial supplements on acute liver injury.

Chromatin assembly factor 1B critically controls the early development but not function acquisition of invariant natural killer T cells in mice

CD4⁺ CD8⁺ double-positive thymocytes give rise to both conventional TCRαβ⁺ T cells and invariant natural killer T cells (iNKT cells), but these two kinds of cells display different characteristics. The molecular mechanism underlying iNKT cell lineage development and function acquisition remain to be elucidated. We show that the loss of chromatin assembly factor 1B (CHAF1b) maintains the normal development of conventional TCRαβ⁺ T cells but severely impairs early development of iNKT cells. This dysregulation is accompanied by the impairment in chromatin activation and gene transcription at Vα14-Jα18 locus. Notably, ectopic expression of a Vα14-Jα18 TCR rescues Chaf1b-deficient iNKT cell developmental defects. Moreover, cytokine secretion and antitumor activity are substantially maintained in Vα14-Jα18 TCR transgene-rescued Chaf1b-deficient iNKT cells. Our study identifies CHAF1b as a critical factor that controls the early development but not function acquisition of iNKT cells via lineage- and stage-specific regulation.

An Unconventional View of T Cell Reconstitution After Allogeneic Hematopoietic Cell Transplantation

Allogeneic hematopoietic cell transplantation (allo-HCT) is performed as curative-intent therapy for hematologic malignancies and non-malignant hematologic, immunological and metabolic disorders, however, its broader implementation is limited by high rates of transplantation-related complications and a 2-year mortality that approaches 50%. Robust reconstitution of a functioning innate and adaptive immune system is a critical contributor to good long-term patient outcomes, primarily to prevent and overcome post-transplantation infectious complications and ensure adequate graft-versus-leukemia effects. There is increasing evidence that unconventional T cells may have an important immunomodulatory role after allo-HCT, which may be at least partially dependent on the post-transplantation intestinal microbiome. Here we discuss the role of immune reconstitution in allo-HCT outcome, focusing on unconventional T cells, specifically mucosal-associated invariant T (MAIT) cells, γδ (gd) T cells, and invariant NK T (iNKT) cells. We provide an overview of the mechanistic preclinical and associative clinical studies that have been performed. We also discuss the emerging role of the intestinal microbiome with regard to hematopoietic function and overall immune reconstitution.

Natural Killer T Cells in Various Mouse Models of Hepatitis

Natural killer T (NKT) cells are a key component of innate immunity. Importantly, a growing body of evidence indicates that NKT cells play an integral role in various acute and chronic liver injuries. NKT cells participate in the progression of an injury through the secretion of cytokines, which promote neutrophil infiltration and enhance Fas ligand (FasL) and granzyme-mediated NKT cytotoxic activity. Therefore, examining the role of NKT cells in hepatic disease is critical for a comprehensive understanding of disease pathogenesis and may provide insight into novel approaches for treatment. For more than a century, mouse models that imitate the physiopathological conditions of human disease have served as a critical tool in biological and medical basic research, including studies of liver disease. Here, we review the role of NKT cells in various mouse models of hepatitis.

Gut microbiome, liver immunology, and liver diseases

The gut microbiota is a complex and plastic consortium of microorganisms that are intricately connected with human physiology. The liver is a central immunological organ that is particularly enriched in innate immune cells and constantly exposed to circulating nutrients and endotoxins derived from the gut microbiota. The delicate interaction between the gut and liver prevents accidental immune activation against otherwise harmless antigens. Work on the interplay between the gut microbiota and liver has assisted in understanding the pathophysiology of various liver diseases. Of immense importance is the step from high-throughput sequencing (correlation) to mechanistic studies (causality) and therapeutic intervention. Here, we review the gut microbiota, liver immunology, and the interaction between the gut and liver. In addition, the impairment in the gut-liver axis found in various liver diseases is reviewed here, with an emphasis on alcohol-associated liver disease (ALD), nonalcoholic fatty liver disease (NAFLD), and autoimmune liver disease (AILD). On the basis of growing evidence from these preclinical studies, we propose that the gut-liver axis paves the way for targeted therapeutic modalities for liver diseases.

Gut Microbiota Participates in Antithyroid Drug Induced Liver Injury Through the Lipopolysaccharide Related Signaling Pathway

Background: Drugs can alter the gut microbiota structure, and gut microbiota dysbiosis in turn is correlated with drug side effects through the intestinal endotoxemia hypothesis. Whether antithyroid drugs (including methimazole and propylthiouracil) cause gut microbiota dysbiosis and whether the gut microbiota is correlated with antithyroid drugs induced liver injury is unknown.

Methods: Initial Graves’ disease patients were randomly divided into the methimazole group (n = 20) and the propylthiouracil group (n = 20) and were followed up every 2 weeks; 50 healthy controls were also included. The structure and function of gut microbiota were compared from the cross sectional and longitudinal levels. The correlation between the gut microbiota and clinical parameters was also determined. In addition, Sprague-Dawley rats were randomly allotted into six groups, including four drug groups, which received daily doses of methimazole (1.5 mg/kg/day; 2.5 mg/kg/day) or propylthiouracil (7.5 mg/kg/day; 12.5 mg/kg/day) by oral gavage, and two control groups received the vehicle. In addition to the indexes mentioned above, intestinal barrier-related indexes were also performed.

Results: Cross sectional and longitudinal comparison results from both clinical trials and animal studies indicate that antithyroid drugs altered gut microbiota structure; and the liver function related indexes all increased which correlated with gut microbiota. In addition, lipopolysaccharide-related pathways and the lipopolysaccharide concentration in feces and serum all increased after antithyroid drugs administration. These results consistent with the destroyed intestinal barrier in animal study after antithyroid drugs administration.

Conclusion: We verified that antithyroid drugs altered gut microbiota structure and that the gut microbiota may in turn be correlated with antithyroid drugs-induced liver injury through the intestinal endotoxemia hypothesis.

Atypical immunometabolism and metabolic reprogramming in liver cancer: Deciphering the role of gut microbiome

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related mortality worldwide. Much recent research has delved into understanding the underlying molecular mechanisms of HCC pathogenesis, which has revealed to be heterogenous and complex. Two major hallmarks of HCC include: (i) a hijacked immunometabolism and (ii) a reprogramming in metabolic processes. We posit that the gut microbiota is a third component in an entanglement triangle contributing to HCC progression. Besides metagenomic studies highlighting the diagnostic potential in the gut microbiota profile, recent research is pinpointing the gut microbiota as an instigator, not just a mere bystander, in HCC. In this chapter, we discuss mechanistic insights on atypical immunometabolism and metabolic reprogramming in HCC, including the examination of tumor-associated macrophages and neutrophils, tumor-infiltrating lymphocytes (e.g., T-cell exhaustion, regulatory T-cells, natural killer T-cells), the Warburg effect, rewiring of the tricarboxylic acid cycle, and glutamine addiction. We further discuss the potential involvement of the gut microbiota in these characteristics of hepatocarcinogenesis. An immediate highlight is that microbiota metabolites (e.g., short chain fatty acids, secondary bile acids) can impair anti-tumor responses, which aggravates HCC. Lastly, we describe the rising 'new era' of immunotherapies (e.g., immune checkpoint inhibitors, adoptive T-cell transfer) and discuss for the potential incorporation of gut microbiota targeted therapeutics (e.g., probiotics, fecal microbiota transplantation) to alleviate HCC. Altogether, this chapter invigorates for continuous research to decipher the role of gut microbiome in HCC from its influence on immunometabolism and metabolic reprogramming.

Unveiling the heterogeneity of NKT cells in the liver through single cell RNA sequencing

CD1d-dependent type I NKT cells, which are activated by lipid antigen, are known to play important roles in innate and adaptive immunity, as are a portion of type II NKT cells. However, the heterogeneity of NKT cells, especially NKT-like cells, remains largely unknown. Here, we report the profiling of NKT (NK1.1⁺CD3e⁺) cells in livers from wild type (WT), Jα18-deficient and CD1d-deficient mice by single-cell RNA sequencing. Unbiased transcriptional clustering revealed distinct cell subsets. The transcriptomic profiles identified the well-known CD1d-dependent NKT cells and defined two CD1d-independent NKT cell subsets. In addition, validation of marker genes revealed the differential organ distribution and landscape of NKT cell subsets during liver tumor progression. More importantly, we found that CD1d-independent Sca-1⁻CD62L⁺ NKT cells showed a strong ability to secrete IFN-γ after costimulation with IL-2, IL-12 and IL-18 in vitro. Collectively, our findings provide a comprehensive characterization of NKT cell heterogeneity and unveil a previously undefined functional NKT cell subset.

Intestinal IL-17R Signaling Constrains IL-18-Driven Liver Inflammation by the Regulation of Microbiome-Derived Products

Interleukin (IL)-17 signaling to the intestinal epithelium regulates the intestinal microbiome. Given the reported links between intestinal dysbiosis, bacterial translocation, and liver disease, we hypothesize that intestinal IL-17R signaling plays a critical role in mitigating hepatic inflammation. To test this, we study intestinal epithelium-specific IL-17RA-deficient mice in an immune-driven hepatitis model. At the naive state, these mice exhibit microbiome dysbiosis and increased translocation of bacterial products (CpG DNA), which drives liver IL-18 production. Upon disease induction, absence of enteric IL-17RA signaling exacerbates hepatitis and hepatocyte cell death. IL-18 is necessary for disease exacerbation and is associated with increased activated hepatic lymphocytes based on Ifng and Fasl expression. Thus, intestinal IL-17R regulates translocation of TLR9 ligands and constrains susceptibility to hepatitis. These data connect enteric Th17 signaling and the microbiome in hepatitis, with broader implications on the effects of impaired intestinal immunity and subsequent release of microbial products observed in other extra-intestinal pathologies.

Castillo-dela Cruz et al. describe a unique protective role of intestinal IL-17RA in hepatitis. Disruption of intestinal IL-17RA signaling results in microbiome dysbiosis and translocation of bacterial products, specifically unmethylated CpG DNA, to the liver. This promotes IL-18 production and subsequent lymphocyte activation and cell death to exacerbate liver inflammation.

Sishen Pill Treatment of DSS-Induced Colitis via Regulating Interaction With Inflammatory Dendritic Cells and Gut Microbiota

Sishen Pill (SSP) is a typical prescription in the pharmacopeia of traditional Chinese medicine (TCM), and is usually used to treat inflammatory bowel disease (IBD). It is known that inflammatory dendritic cells (DCs) and imbalance of gut microbiota play significant roles in the pathogenesis of IBD. However, it is not clear whether SSP can treat IBD by regulating interaction of DCs and gut microbiota. In the present study, the levels of inflammatory DCs and gut microbiota were analyzed by flow cytometry and 16S rDNA analysis. SSP relieved the pathological damage to the colon of mice with colitis induced by dextran sodium sulfate (DSS). As typical indicators of inflammatory DCs, the levels of CD11c+CD103+E-cadherin+ cells and pro-inflammatory cytokines [interleukin (IL)-1β, -4, -9, and -17A] were decreased in mice with colitis treated by SSP for 10 days. Simultaneously, the gut microbiota composition was regulated, and beneficial bacteria were increased and pathogenic bacteria were reduced. The results indicated that SSP regulated the interaction between inflammatory DCs and gut microbiota to treat DSS-induced colitis.

License to Kill: When iNKT Cells Are Granted the Use of Lethal Cytotoxicity

Invariant Natural Killer T (iNKT) cells are a non-conventional, innate-like, T cell population that recognize lipid antigens presented by the cluster of differentiation (CD)1d molecule. Although iNKT cells are mostly known for mediating several immune responses due to their massive and diverse cytokine release, these cells also work as effectors in various contexts thanks to their cytotoxic potential. In this Review, we focused on iNKT cell cytotoxicity; we provide an overview of iNKT cell subsets, their activation cues, the mechanisms of iNKT cell cytotoxicity, the specific roles and outcomes of this activity in various contexts, and how iNKT killing functions are currently activated in cancer immunotherapies. Finally, we discuss the future perspectives for the better understanding and potential uses of iNKT cell killing functions in tumor immunosurveillance.

Interaction between microbiota and immunity in health and disease

The interplay between the commensal microbiota and the mammalian immune system development and function includes multifold interactions in homeostasis and disease. The microbiome plays critical roles in the training and development of major components of the host's innate and adaptive immune system, while the immune system orchestrates the maintenance of key features of host-microbe symbiosis. In a genetically susceptible host, imbalances in microbiota-immunity interactions under defined environmental contexts are believed to contribute to the pathogenesis of a multitude of immune-mediated disorders. Here, we review features of microbiome-immunity crosstalk and their roles in health and disease, while providing examples of molecular mechanisms orchestrating these interactions in the intestine and extra-intestinal organs. We highlight aspects of the current knowledge, challenges and limitations in achieving causal understanding of host immune-microbiome interactions, as well as their impact on immune-mediated diseases, and discuss how these insights may translate towards future development of microbiome-targeted therapeutic interventions.

Interaction between microbiota and immunity in health and disease

The interplay between the commensal microbiota and the mammalian immune system development and function includes multifold interactions in homeostasis and disease. The microbiome plays critical roles in the training and development of major components of the host's innate and adaptive immune system, while the immune system orchestrates the maintenance of key features of host-microbe symbiosis. In a genetically susceptible host, imbalances in microbiota-immunity interactions under defined environmental contexts are believed to contribute to the pathogenesis of a multitude of immune-mediated disorders. Here, we review features of microbiome-immunity crosstalk and their roles in health and disease, while providing examples of molecular mechanisms orchestrating these interactions in the intestine and extra-intestinal organs. We highlight aspects of the current knowledge, challenges and limitations in achieving causal understanding of host immune-microbiome interactions, as well as their impact on immune-mediated diseases, and discuss how these insights may translate towards future development of microbiome-targeted therapeutic interventions.

Sodium butyrate modulates gut microbiota and immune response in colorectal cancer liver metastatic mice

Colorectal cancer (CRC) liver metastasis (CLM) is the leading death cause of CRC patients, but there is no satisfied approach to treat CLM. Gut microbiota plays a pivotal role in CRC initiation and development. Targeting dysbiosis of the gut microbiota might open up new opportunities for CLM treatment. Here, we investigated the efficacy of sodium butyrate (NaB), a major product of gut microbial fermentation, in modulating gut microbiota in CLM mice. NaB supplement decreased mouse colon cancer CT26 cell liver metastasis in intrasplenic tumor injection model of BALB/c mice. Using 16S rRNA gene sequencing, we found altered microbiota composition in CLM mice, characterized by increases of Firmicutes and Proteobacteria. NaB beneficially changed dysbiosis in CLM mice. Functional analysis of the KEGG pathways showed that NaB changed pathways related to immune system diseases and primary immunodeficiency in CLM mice. In addition, NaB decreased T regulatory cells and increased natural killer T cells and T helper 17 cells, accordingly decreased IL-10 and increased IL-17 secretion in CLM mice liver. In conclusion, NaB beneficially modulated gut microbiota and improved host immune response in CLM mice. These findings demonstrate the therapeutic potential of NaB in CLM treatment.

Evidence-based analysis on the toxicity of disinfection byproducts in vivo and in vitro for disinfection selection

Disinfection is a key step in drinking water treatment process to prevent water-borne infections. However, reactions between chlorine, one of the most common disinfectants, and natural organic matter (NOM) often lead to the formation of hazardous disinfection byproducts (DBPs). However, the cytotoxicity of some DBPs is still poorly understood. Such knowledge is critical for proper selection of disinfection processes. We investigated the effects of DBPs on mouse acute liver injury. The exacerbation of liver damage increased with the DBPs concentrations, likely due to the increased hepatic macrophages. Haloacetonitriles (HANs) and haloketones (HKs) are more toxic to Human Hepatocellular (Hep3B) cells than trihalomethanes (THMs). Cytotoxicity of DBPs were governed by the halogen type (brominated DBPs > chlorinated DBPs) and the numbers of halogen atoms per molecule. Then, we used the pilot-scale WDS to study the best conditions for reducing the formation of DBPs. The result showed that the formation of DBPs followed the order: stainless-steel (SS) > ductile iron (DI) > polyethylene (PE) pipe. Higher flowrate promoted the formation of DBPs in all three pipes. The results suggest that the formation of DBPs in chlorine disinfection can be reduced by using PE pipes and low flow rate in water distribution systems (WDS).

Pretreatment With Bacillus cereus Preserves Against D-Galactosamine-Induced Liver Injury in a Rat Model

Bacillus cereus (B. cereus) functions as a probiotic in animals, but the underlying mechanisms remain unclear. We aim to evaluate the protective effects and definite mechanism by which orally administered B. cereus prevents D-galactosamine (D-GalN)-induced liver injury in rats. Twenty-one Sprague–Dawley rats were equally assigned into three groups (N = 7 animals per group). B. cereus ATCC11778 (2 × 10⁹ colony-forming units/ml) was administered to the B. cereus group via gavage, and phosphate-buffered saline was administered to the positive control (PC) and negative control (NC) groups for 2 weeks. The PC and B. cereus groups received 1.1 g/kg D-GalN via an intraperitoneal injection to induce liver injury. The blood, terminal ileum, liver, kidney and mesenteric lymph nodes (MLNs) were collected for histological examinations and to evaluate bacterial translocation. Liver function was also determined. Fecal samples were collected for deep sequencing of the 16S rRNA on an Illumina MiSeq platform. B. cereus significantly attenuated D-GalN-induced liver injury and improved serum alanine aminotransferase (ALT) and serum cholinesterase levels (P < 0.05 and P < 0.01, respectively). B. cereus modulated cytokine secretion, as indicated by the elevated levels of the anti-inflammatory cytokine interleukin-10 (IL-10) in both the liver and plasma (P < 0.05 and P < 0.01, respectively) and the substantially decreased levels of the cytokine IL-13 in the liver (P < 0.05). Pretreatment with B. cereus attenuated anoxygenic bacterial translocation in the veins (P < 0.05) and liver (P < 0.05) and upregulated the expression of the tight junction protein 1. The gut microbiota from the B. cereus group clustered separately from that of the PC group, with an increase in species of the Ruminococcaceae and Peptococcaceae families and a decrease in those of the Parabacteroides, Paraprevotella, and Desulfovibrio families. The potential probiotic B. cereus attenuated liver injury by restoring the gut flora balance and enhancing the intestinal barrier function.

The role of the gut microbiome in chronic liver disease: the clinical evidence revised

Recent research has suggested a role for the intestinal microbiota in the pathogenesis and potential treatment of a wide range of liver diseases. The intestinal microbiota and bacterial products may contribute to the development of liver diseases through multiple mechanisms including increased intestinal permeability, chronic systemic inflammation, production of short-chain fatty acids and changes in metabolism. This suggests a potential role for pre-, pro- and synbiotic products in the prevention or treatment of some liver diseases. In addition, there is emerging evidence on the effects of faecal microbial transplant. Herein, we discuss the relationship between the intestinal microbiota and liver diseases, as well as reviewing intestinal microbiota-based treatment options that are currently being investigated.

Mechanism of neoagarotetraose protects against intense exercise-induced liver injury based on molecular ecological network analysis

Here we have explored the effect of neoagarotetraose (NAT) on liver injury caused by intense exercise. Our results showed that NAT treatment obviously decreased liver weight (p &lt; 0.01), improved the liver morphological structure, decreased ALT level (p &lt; 0.05) and endotoxin (LPS) (p &lt; 0.01). In addition, NAT could regulate bile acid profiles in feces and serum of mice, which indicated the potential of liver function, suggesting that NAT was effective to relieve intense exercise-induced liver injury. NAT could regulate the expression of colon genes. NAT tended to alter the microbial composition of mice under intense exercise. We uncovered the network interactions between liver traits and microbial communities in NAT treatment mice. Interestingly, our data indicated that intense exercise-induced liver injury may be related to Clostridiales. In summary, these results demonstrated that NAT relieved liver injury induced by intense exercise may be related to gut microbiota.

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.

Effect of Intestinal Flora Clearance on Liver Proteomics in Mice

Background:

Intestinal flora dynamically affects the host&#039;s systemic immune system. Liver is one of the organs that may be affected by intestinal microbiota. </P><P> Materials and Methods: In this study, we aimed to identify proteome level differences between liver tissue from mice cleared intestinal flora and control using tandem mass spectrometry (LC-MS/MS) and label free quantification. Additionally, protein-protein interactions were mapped by STRING, and also, the enrichment of inflammation-related signaling pathways and biological processes was identified using GO and IPA network system. RT-PCR and Western blot were used for validation of the proteomics findings.

Results:

Our study demonstrated that mice with cleared intestinal flora exhibited decreased sensitivity to Concanavalin A induced acute hepatitis. 324 Proteins in liver were differently expressed after intestinal flora clearance for one week while 210 proteins were differently expressed after intestinal flora clearance for two weeks. Furthermore, five of the identified proteins were validated by western blotting and further investigated by semi-quantitative RT-PCR.

Conclusion:

Our results showed that intestinal flora clearance in mice could reduce sensitivity to Concanavalin A induced liver injury and influence the expression of proteins in liver, which provides a clue for studying the relationship between gut bacteria and Concanavalin A induced hepatitis.

High salt diet stimulates gut Th17 response and exacerbates TNBS-induced colitis in mice

This study focuses on characterizing the effect of a high salt diet (HSD) on intestinal immunity and the risk of inflammatory bowel diseases (IBD). We found that mice on a HSD had an increased frequency of IL-17A producing cells in the intestinal lamina propria (LP) compared to mice on a normal diet (ND). Furthermore, most intestinal IL-17A producing cells were CD4⁺TCRβ⁺ cells. A HSD increased the LP T helper 17 (Th17) responses in both the small and large intestines but did not increase the Th17 response of other gut-associated lymphoid organ. Although, HSD did not change the percentage of regulatory T (Treg) cells, HSD significantly inhibit secretion of IL-10 and the suppressive function of Treg cells. Moreover, we found that HSD exacerbates trinitrobenzenesulfonic acid (TNBS) induced colitis, and Th17 response was significantly increased in the colonic LP of HSD TNBS-treated mice compared with the ND TNBS-treated mice. This study demonstrates that HSD stimulates the intestinal Th17 response but inhibits the function of Treg cells. Moreover, HSD exacerbates TNBS induced mice colitis, suggesting that HSD disrupts the intestinal immunity and increases the risk of IBD.

The effects of hemocyanin on T cells cultured in vitro

As a broad-spectrum antibiotic, gentamicin is used extensively in T cell culturing in vitro, but preliminary studies have identified that T cell activity is significantly affected by gentamicin. In the present study, the hemocyanin from Litopenaeus vannamei (L. vannamei) was selected as an additive for T cell cultures in vitro. Compared with those in the control group, the cell quantity exhibited no significant difference, and the formation rate of cell colony increased gradually with increases in the hemocyanin concentration. Additionally, flow cytometry assays identified that cluster of differentiation (CD)3⁺CD4⁺ and CD4⁺CD25⁺ T cells in the 0.2 µg/ml hemocyanin (Hem 3) group were all significantly increased. Furthermore, cell cycle analysis demonstrated that T cells in the G0/G1 phase were significantly decreased in the Hem 3 group compared with in the control, 0.05 µg/ml (Hem 1) and 0.1 µg/ml (Hem 2) groups, and cells in the S phase were significantly elevated in the Hem 3 group compared with in the control and Hem 1 groups. In addition, MTT analysis indicated that the cytotoxicity of T cells towards HepG2 cells was significantly increased in the Hem 3 group compared with in the control, Hem 1 and Hem 2 groups. Taken together, the present study identified that hemocyanin may improve the proliferation and cytotoxicity of T cells, and the results supported the use of hemocyanin in T cell adoptive immunotherapy.

The influence of HK2 blood group antigen on human B cell activation for ABOi-KT conditions

Background

It is well known that ABO blood group system incompatible kidney transplantation (ABOi-KT) is an effective strategy for end-stage renal disease. The main barrier for ABOi-KT is how to keep host B cell activation and blood group antibody titer in low levels. Moreover, the mechanism of B cell activation induced by blood group antigen was unclear in ABOi-KT.

Results

In this study, HK2 cells were identified to express blood group B antigen when cocultured with lymphocytes of blood group A. Optical microscope observation demonstrated that HK2 cells in coculture group gradually decreased. Furthermore, flow cytometer assay identified that T cell phenotypes (CD3⁺, CD3⁺CD4⁺ and CD3⁺CD8⁺) had no significant change and B cell phenotypes (CD19⁺ and CD138⁺) were all significantly enhanced (3.07 and 3.02 folds) at day 4. In addition, immunoturbidimetry analysis demonstrated that blood group B antibody was significantly increased to 2.35 fold at day 4, IgG was significantly increased to 3.60 and 2.81 folds at days 4 and 8 respectively, while IgM had no significant change at the measured time points.

Conclusions

Taken together, B cells were activated and secreted blood group B antibody after treatment with HK2 expressing blood group B antigen. The results of this study maybe useful for further determination of the mechanism of B cell activation after ABO incompatible kidney endothelial cells stimulation.

Electronic supplementary material

The online version of this article (10.1186/s12865-017-0233-9) contains supplementary material, which is available to authorized users.

Regulatory T cells with a defect in inhibition on co-stimulation deteriorated primary biliary cholangitis

Regulatory T cells (Tregs) play an indispensable role in the progression of primary biliary cholangitis (PBC). Although Tregs could normalize costimulation in in vivo and in vitro models, it is obscure whether and how Tregs mediate these effects in PBC. Herein we focused on the quantitative and functional characteristics of Tregs in PBC. The number and proportion of Tregs, and the production of interleukin (IL)-10 were all significantly less in the PBC patients than in the healthy controls (HCs). In addition, compared to the HCs, the costimulatory CD86 of the circulation and liver were significantly higher in the patients with PBC. CD86 expression on CD1c+ cells negatively correlated with the proportion of Tregs. There was also a positive correlation between mayo risk score and the ratio of CD86/Treg. In vitro experiments showed that inhibition of CD86 expression on CD1c+ cells by Tregs was significantly weakened in the PBC patients. Furthermore, the autoantibodies from the PBC patients could promote CD86 expression on CD1c+ cells and transforming growth factor-β production by human hepatic stellate cells. Overall, Tregs declined in inhibition on co-stimulation expression in the presence of autoantibodies, which could be associated to PBC-related bile duct injury and fibrosis. This indicated that maintenance of balance of co-stimulation and Tregs could be beneficial for PBC.

Intestinal microbiome and permeability in patients with autoimmune hepatitis

Autoimmune hepatitis (AIH) is a severe inflammatory liver disease. The underlying mechanisms remain unclear, but recent studies provided new perspectives on altered intestinal microbiome and permeability in AIH animal models and patients, highlighting gut-liver crosstalk in the pathogenesis of AIH. Transgenic AIH mice carrying HLA-DR3 showed reduced diversity and total load of gut microbiota. Germ-free mice are resistant to concanavalin A-induced liver injury, whereas enterogenouss antigens induce the activation of natural killer T cells participating in concanavalin A-induced liver injury, supporting the close relationship between microbiota and AIH. Moreover, 'molecular mimicry' provides a plausible interpretation of the immune reactions between microorganic antigens and liver autoantigens, for instance, cytochrome P4502D6, the target of cross-reactivity between virus and self. Nevertheless, direct evidence for the intestinal microbiome and permeability in AIH is still limited. The relationship between AIH susceptibilities and an intestinal microbiome shaped by drugs, diets or genes needs further study.

Protective Effect of Akkermansia muciniphila against Immune-Mediated Liver Injury in a Mouse Model

Accumulating evidence indicates that gut microbiota participates in the pathogenesis and progression of liver diseases. The severity of immune-mediated liver injury is associated with different microbial communities. Akkermansia muciniphila can regulate immunologic and metabolic functions. However, little is known about its effects on gut microbiota structure and function. This study investigated the effect of A. muciniphila on immune-mediated liver injury and potential underlying mechanisms. Twenty-two C57BL/6 mice were assigned to three groups (N = 7-8 per group) and continuously administrated A. muciniphila Muc^T or PBS by oral gavage for 14 days. Mouse feces were collected for gut microbiota analysis on the 15th day, and acute liver injury was induced by Concanavalin A (Con A, 15 mg/kg) injection through the tail vein. Samples (blood, liver, ileum, colon) were assessed for liver injury, systemic inflammation, and intestinal barrier function. We found that oral administration of A. muciniphila decreased serum ALT and AST and alleviated liver histopathological damage induced by Con A. Serum levels of pro-inflammatory cytokines and chemokines (IL-2, IFN-γ, IL-12p40, MCP-1, MIP-1a, MIP-1b) were substantially attenuated. A. muciniphila significantly decreased hepatocellular apoptosis; Bcl-2 expression increased, but Fas and DR5 decreased. Further investigation showed that A. muciniphila enhanced expression of Occludin and Tjp-1 and inhibited CB1 receptor, which strengthened intestinal barriers and reduced systemic LPS level. Fecal 16S rRNA sequence analysis indicated that A. muciniphila increased microbial richness and diversity. The community structure of the Akk group clustered distinctly from that of mice pretreated with PBS. Relative abundance of Firmicutes increased, and Bacteroidetes abundance decreased. Correlation analysis showed that injury-related factors (IL-12p40, IFN-γ, DR5) were negatively associated with specific genera (Ruminococcaceae_UCG_009, Lachnospiraceae_UCG_001, Akkermansia), which were enriched in mice pretreated with A. muciniphila. Our results suggested that A. muciniphila Muc^T had beneficial effects on immune-mediated liver injury by alleviating inflammation and hepatocellular death. These effects may be driven by the protective profile of the intestinal community induced by the bacteria. The results provide a new perspective on the immune function of gut microbiota in host diseases.

Gut-liver axis: gut microbiota in shaping hepatic innate immunity

Gut microbiota play an essential role in shaping immune cell responses. The liver was continuously exposed to metabolic products of intestinal commensal bacterial through portal vein and alteration of gut commensal bateria was always associated with increased risk of liver inflammation and autoimmune disease. Considered as a unique immunological organ, the liver is enriched with a large number of innate immune cells. Herein, we summarize the available literature of gut microbiota in shaping the response of hepatic innate immune cells including NKT cells, NK cells, γδ T cells and Kupffer cells during health and disease. Such knowledge might help to develop novel and innovative strategies for the prevention and therapy of innate immune cell-related liver disease.

NK1.1+ cells promote sustained tissue injury and inflammation after trauma with hemorrhagic shock

Various cell populations expressing NK1.1 contribute to innate host defense and systemic inflammatory responses, but their role in hemorrhagic shock and trauma remains uncertain. NK1.1⁺ cells were depleted by i.p. administration of anti-NK1.1 (or isotype control) on two consecutive days, followed by hemorrhagic shock with resuscitation and peripheral tissue trauma (HS/T). The plasma levels of IL-6, MCP-1, alanine transaminase (ALT), and aspartate aminotransferase (AST) were measured at 6 and 24 h. Histology in liver and gut were examined at 6 and 24 h. The number of NK cells, NKT cells, neutrophils, and macrophages in liver, as well as intracellular staining for TNF-α, IFN-γ, and MCP-1 in liver cell populations were determined by flow cytometry. Control mice subjected to HS/T exhibited end organ damage manifested by marked increases in circulating ALT, AST, and MCP-1 levels, as well as histologic evidence of hepatic necrosis and gut injury. Although NK1.1⁺ cell-depleted mice exhibited a similar degree of organ damage as nondepleted animals at 6 h, NK1.1⁺ cell depletion resulted in marked suppression of both liver and gut injury by 24 h after HS/T. These findings indicate that NK1.1⁺ cells contribute to the persistence of inflammation leading to end organ damage in the liver and gut.

Cellular Innate Immunity: An Old Game with New Players

Innate immunity is a rapidly evolving field with novel cell types and molecular pathways being discovered and paradigms changing continuously. Innate and adaptive immune responses are traditionally viewed as separate from each other, but emerging evidence suggests that they overlap and mutually interact. Recently discovered cell types, particularly innate lymphoid cells and myeloid-derived suppressor cells, are gaining increasing attention. Here, we summarize and highlight current concepts in the field, focusing on innate immune cells as well as the inflammasome and DNA sensing which appear to be critical for the activation and orchestration of innate immunity, and may provide novel therapeutic opportunities for treating autoimmune, autoinflammatory, and infectious diseases.