Gut microbiome pattern impacts treatment response in primary biliary cholangitis.

BACKGROUND: Primary biliary cholangitis (PBC) is a progressive autoimmune liver disease. An inadequate response to ursodeoxycholic acid (UDCA) poses a high risk of progression toward end-stage liver disease. Gut dysbiosis has been implicated in PBC. Here, we aimed to investigate microbial signatures that permit risk stratification and provide mechanistic insights into novel therapies for PBC. METHODS: We prospectively recruited UDCA treatment-naive patients with PBC and performed metagenomic sequencing and metabolomic profiling using stool and serum samples obtained before (n = 132) and after (n = 59) treatment. PBC microbiome subtypes were identified using unsupervised machine learning methods and validated in two independent cohorts. FINDINGS: PBC baseline metagenomes clustered into two community subtypes characterized by varying abundances of Clostridia taxa. Compared with Clostridialow microbiomes, Clostridiahigh microbiomes were more similar to healthy controls. Notably, patients in the Clostridialow subtype exhibited a 2-fold higher UDCA non-response rate compared to those in the Clostridiahigh subtype (41% vs. 20%, p = 0.015). Integrative analysis of metagenomic and metabolomic data revealed divergent functional modules and metabolic activities between the two metacommunities. In particular, anaerobic fermentation and the production of bioactive metabolites, including tryptophan derivatives and secondary bile acids, crucial for immune regulation and gut barrier maintenance, were markedly diminished in the Clostridialow subtype. Moreover, UDCA administration reconfigured the fecal microbial and metabolic profiles only in the Clostridiahigh group. Importantly, the microbiome subtypes and their associations with UDCA response were reproducible in two independent treatment-naive PBC cohorts. CONCLUSIONS: Characterizing baseline microbiota patterns may enable the prediction of treatment outcomes in PBC and facilitate personalized treatment strategies. FUNDING: This research was mainly supported by the National Natural Science Foundation of China.

Epidemiologic and genetic associations between primary biliary cholangitis and extrahepatic rheumatic diseases.

Patients with primary biliary cholangitis (PBC) commonly experience extrahepatic rheumatic diseases. However, the epidemiologic and genetic associations as well as causal relationship between PBC and these extrahepatic conditions remain undetermined. In this study, we first conducted systematic review and meta-analyses by analyzing 73 studies comprising 334,963 participants across 17 countries and found strong phenotypic associations between PBC and rheumatic diseases. Next, we utilized large-scale genome-wide association study summary data to define the shared genetic architecture between PBC and rheumatic diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), systemic sclerosis (SSc) and Sjögren's syndrome (SS). We observed significant genetic correlations between PBC and each of the four rheumatic diseases. Pleiotropy and heritability enrichment analysis suggested the involvement of humoral immunity and interferon-associated processes for the comorbidity. Of note, we identified four variants shared between PBC and RA (rs80200208), SLE (rs9843053), and SSc (rs27524, rs3873182) using cross-trait meta-analysis. Additionally, several pleotropic loci for PBC and rheumatic diseases were found to share causal variants with gut microbes possessing immunoregulatory functions. Finally, Mendelian randomization revealed consistent evidence for a causal effect of PBC on RA, SLE, SSc, and SS, but no or inconsistent evidence for a causal effect of extrahepatic rheumatic diseases on PBC. Our study reveals a profound genetic overlap and causal relationships between PBC and extrahepatic rheumatic diseases, thus providing insights into shared biological mechanisms and novel therapeutic interventions.

Gut Microbiota-Derived Butyrate Induces Epigenetic and Metabolic Reprogramming in Myeloid-Derived Suppressor Cells to Alleviate Primary Biliary Cholangitis.

BACKGROUND & AIMS: Gut dysbiosis and myeloid-derived suppressor cells (MDSCs) are implicated in primary biliary cholangitis (PBC) pathogenesis. However, it remains unknown whether gut microbiota or their metabolites can modulate MDSCs homeostasis to rectify immune dysregulation in PBC. METHODS: We measured fecal short-chain fatty acids levels using targeted gas chromatography-mass spectrometry and analyzed circulating MDSCs using flow cytometry in 2 independent PBC cohorts. Human and murine MDSCs were differentiated in vitro in the presence of butyrate, followed by transcriptomic, epigenetic (CUT&Tag-seq and chromatin immunoprecipitation-quantitative polymerase chain reaction), and metabolic (untargeted liquid chromatography-mass spectrometry, mitochondrial stress test, and isotope tracing) analyses. The in vivo role of butyrate-MDSCs was evaluated in a 2-octynoic acid-bovine serum albumin-induced cholangitis murine model. RESULTS: Decreased butyrate levels and defective MDSC function were found in patients with incomplete response to ursodeoxycholic acid, compared with those with adequate response. Butyrate induced expansion and suppressive activity of MDSCs in a manner dependent on PPARD-driven fatty acid ß-oxidation (FAO). Pharmaceutical inhibition or genetic knockdown of the FAO rate-limiting gene CPT1A abolished the effect of butyrate. Furthermore, butyrate inhibited HDAC3 function, leading to enhanced acetylation of lysine 27 on histone H3 at promoter regions of PPARD and FAO genes in MDSCs. Therapeutically, butyrate administration alleviated immune-mediated cholangitis in mice via MDSCs, and adoptive transfer of butyrate-treated MDSCs also displayed protective efficacy. Importantly, reduced expression of FAO genes and impaired mitochondrial physiology were detected in MDSCs from ursodeoxycholic acid nonresponders, and their impaired suppressive function was restored by butyrate. CONCLUSIONS: We identify a critical role for butyrate in modulation of MDSC homeostasis by orchestrating epigenetic and metabolic crosstalk, proposing a novel therapeutic strategy for treating PBC.

A spatiotemporal atlas of cholestatic injury and repair in mice.

Cholestatic liver injuries, characterized by regional damage around the bile ductular region, lack curative therapies and cause considerable mortality. Here we generated a high-definition spatiotemporal atlas of gene expression during cholestatic injury and repair in mice by integrating spatial enhanced resolution omics sequencing and single-cell transcriptomics. Spatiotemporal analyses revealed a key role of cholangiocyte-driven signaling correlating with the periportal damage-repair response. Cholangiocytes express genes related to recruitment and differentiation of lipid-associated macrophages, which generate feedback signals enhancing ductular reaction. Moreover, cholangiocytes express high TGFß in association with the conversion of liver progenitor-like cells into cholangiocytes during injury and the dampened proliferation of periportal hepatocytes during recovery. Notably, Atoh8 restricts hepatocyte proliferation during 3,5-diethoxycarbonyl-1,4-dihydro-collidin damage and is quickly downregulated after injury withdrawal, allowing hepatocytes to respond to growth signals. Our findings lay a keystone for in-depth studies of cellular dynamics and molecular mechanisms of cholestatic injuries, which may further develop into therapies for cholangiopathies.

Osteoporosis and Primary Biliary Cholangitis: A Trans-ethnic Mendelian Randomization Analysis.

Osteoporosis is a major clinical problem in many autoimmune diseases, including primary biliary cholangitis (PBC), the most common autoimmune liver disease. Osteoporosis is a major cause of fracture and related mortality. However, it remains unclear whether PBC confers a causally risk-increasing effect on osteoporosis. Herein, we aimed to investigate the causal relationship between PBC and osteoporosis and whether the relationship is independent of potential confounders. We performed bidirectional Mendelian randomization (MR) analyses to investigate the association between PBC (8021 cases and 16,489 controls) and osteoporosis in Europeans (the UK Biobank and FinnGen Consortium: 12,787 cases and 726,996 controls). The direct effect of PBC on osteoporosis was estimated using multivariable MR analyses. An independent replication was conducted in East Asians (PBC: 2495 cases and 4283 controls; osteoporosis: 9794 cases and 168,932 controls). Trans-ethnic meta-analysis was performed by pooling the MR estimates of Europeans and East Asians. Inverse-variance weighted analyses revealed that genetic liability to PBC was associated with a higher risk of osteoporosis in Europeans (OR, 1.040; 95% CI, 1.016-1.064; P = 0.001). Furthermore, the causal effect of PBC on osteoporosis persisted after adjusting for BMI, calcium, lipidemic traits, and sex hormones. The causal relationship was further validated in the East Asians (OR, 1.059; 95% CI, 1.023-1.096; P = 0.001). Trans-ethnic meta-analysis confirmed that PBC conferred increased risk on osteoporosis (OR, 1.045; 95% CI, 1.025-1.067; P = 8.17 × 10-6). Our data supports a causal effect of PBC on osteoporosis, and the causality is independent of BMI, calcium, triglycerides, and several sex hormones.

Itaconate inhibits CD103 + T RM cells and alleviates hepatobiliary injury in mouse models of primary sclerosing cholangitis.

BACKGROUND AND AIMS: Primary sclerosing cholangitis (PSC) is a chronic progressive liver disease characterized by the infiltration of intrahepatic tissue-resident memory CD8 + T cells (T RM ). Itaconate has demonstrated therapeutic potential in modulating inflammation. An unmet need for PSC is the reduction of biliary inflammation, and we hypothesized that itaconate may directly modulate pathogenic T RM . APPROACH AND RESULTS: The numbers of intrahepatic CD103 + T RM were evaluated by immunofluorescence in PSC (n = 32), and the serum levels of itaconate in PSC (n = 64), primary biliary cholangitis (PBC) (n = 60), autoimmune hepatitis (AIH) (n = 49), and healthy controls (n = 109) were determined by LC-MS/MS. In addition, the frequencies and immunophenotypes of intrahepatic T RM using explants from PSC (n = 5) and healthy donors (n = 6) were quantitated by flow cytometry. The immunomodulatory properties of 4-octyl itaconate (4-OI, a cell-permeable itaconate derivative) on CD103 + T RM were studied in vitro. Finally, the therapeutic potential of itaconate was studied by the administration of 4-OI and deficiency of immune-responsive gene 1 (encodes the aconitate decarboxylase producing itaconate) in murine models of PSC. Intrahepatic CD103 + T RM was significantly expanded in PSC and was positively correlated with disease severity. Serum itaconate levels decreased in PSC. Importantly, 4-OI inhibited the induction and effector functions of CD103 + T RM in vitro. Mechanistically, 4-OI blocked DNA demethylation of RUNX3 in CD8 + T cells. Moreover, 4-OI reduced intrahepatic CD103 + T RM and ameliorated liver injury in murine models of PSC. CONCLUSIONS: Itaconate exerted immunomodulatory activity on CD103 + T RM in both in vitro and murine PSC models. Our study suggests that targeting pathogenic CD103 + T RM with itaconate has therapeutic potential in PSC.

Fibrinogen-like protein 1 promotes liver-resident memory T-cell exhaustion in hepatocellular carcinoma.

Background and aims: The key role of tissue-resident memory T (TRM) cells in the immune regulation of hepatocellular carcinoma (HCC) has been investigated and reported, but the regulatory mechanism of tumor microenvironment on TRM cells is still unclear. Lymphocyte activating gene 3 (LAG-3) is a promising next-generation immune checkpoint that is continuously expressed due to persistent antigen exposure in the tumor microenvironment. Fibrinogen-like protein 1 (FGL1) is a classical ligand of LAG-3 and can promote T cell exhaustion in tumors. Here, we excavated the effect of FGL1-LAG3 regulatory axis on TRM cells in HCC. Methods: The function and phenotype of intrahepatic CD8+ TRM cells in 35 HCC patients were analyzed using multicolor flow cytometry. Using a tissue microarray of 80 HCC patients, we performed the prognosis analysis. Moreover, we investigated the suppressive effect of FGL1 on CD8+ TRM cells both in in vitro induction model and in vivo orthotopic HCC mouse model. Results: There was an increase in LAG3 expression in CD8+ TRM cells in end-stage HCC; moreover, FGL1 levels were negatively correlated with CD103 expression and related to poor outcomes in HCC. Patients with high CD8+ TRM cell proportions have better outcomes, and FGL1-LAG3 binding could lead to the exhaustion of CD8+ TRM cells in tumors, indicating its potential as a target for immune checkpoint therapy of HCC. Increased FGL1 expression in HCC may result in CD8+ TRM cell exhaustion, causing tumor immune escape. Conclusions: We identified CD8+TRM cells as a potential immunotherapeutic target and reported the effect of FGL1-LAG3 binding on CD8+ TRM cell function in HCC.

Suppression of YTHDF2 attenuates autoimmune hepatitis by expansion of myeloid-derived suppressor cells.

BACKGROUND & AIMS: The N6-methyladenosine (m6A) reader YTH domain-containing family protein 2 (YTHDF2) is critically involved in a multiplicity of biological processes by mediating the degradation of m6A modified mRNAs. Based on our current understanding of this process, we hypothesized that YTHDF2 will play a role in the natural history and function of myeloid-derived suppressor cells (MDSC) and in particular in AIH. APPROACH & RESULTS: We took advantage of YTHDF2 conditional knock-out mice to first address the phenotype and function of MDSCs by flow cytometry. Importantly, the loss of YTHDF2 resulted in a gradual elevation of MDSCs including PMN-MDSCs both in liver and ultimately in the BM. Notably, YTHDF2 deficiency in myeloid cells attenuated concanavalin (ConA)-induced liver injury, with enhanced expansion and chemotaxis to liver. Furthermore, MDSCs from Ythdf2CKO mice had a greater suppressive ability to inhibit the proliferation of T cells. Using multi-omic analysis of m6A RNA immunoprecipitation (RIP) and mRNA sequencing, we noted RXRα as potential target of YTHDF2. Indeed YTHDF2-RIP-qPCR confirmed that YTHDF2 directly binds RXRα mRNA thus promoting degradation and decreasing gene expression. Finally, by IHC and immunofluorescence, YTHDF2 expression was significantly upregulated in the liver of patients with AIH which correlated with the degree of inflammation. CONCLUSION: Suppression of YTHDF2 enhances the expansion, chemotaxis and suppressive function of MDSCs and our data reveals a unique therapeutical target in immune mediated hepatitis.

Implications of gut microbiota in autoimmune liver diseases.

Autoimmune liver diseases (AILD) are a group of immune-mediated liver inflammatory diseases with three major forms including autoimmune hepatitis (AIH), primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). Interaction of both genetic and environmental factors leads to the breakdown of self-tolerance, hence resulting in hyper-responsive of autoantibodies and aggressive autoreactive immune cells. Genetic studies have identified dozens of risk loci associated with initiation and development of AILD. However, the role of exogenous factors remains unclear. Recently, both infectious and inflammatory diseases have been associated with microbiota, which colonizes multiple mucosal surfaces and participates in human physiological process and function in immune system, particularly influencing liver, and biliary system via gut-liver axis. Emerging evidence on the role of gut microbiota has expanded our knowledge of AILD in both pathogenesis and potential therapeutic targets, along with putative diagnosis biomarkers. Herein we review the relationship between host and gut microbiota, discuss their potential roles in disease onset and progression, and summarize the compositional and functional alterations of the microbiota in AILD. We also highlighted the microbiota-based therapeutics such as antibiotics and fecal microbiota transplantation (FMT).

Intrahepatic activated leukocyte cell adhesion molecule induces CD6highCD4+ T cell infiltration in autoimmune hepatitis.

Background and objectives: Autoimmune hepatitis (AIH) is characterized by the expansion and accumulation of pathogenic T cells in liver. Although CD6 and its ligand activated leukocyte cell adhesion molecule (ALCAM) are involved in the evolution of multiple inflammatory diseases, their roles in the pathogenesis of AIH remain unknown. Herein, we aimed to investigate ALCAM-CD6 axis in AIH development. Methods: Immunohistochemistry was performed to examine hepatic expression of CD6 and ALCAM. The concentration of serum ALCAM was evaluated by ELISA. The phenotypes of liver infiltrating T cells were determined by flow cytometry. Primary human CD4+ T cells were used for functional studies. Results: Our data showed that patients with AIH exhibited significantly higher expression of CD6 in the liver as compared to primary biliary cholangitis (PBC), chronic hepatitis B (CHB), non-alcoholic liver disease (NAFLD), and healthy controls (HC). In addition, hepatic CD6 expression was strongly correlated with disease severity of AIH. CD6 was mainly expressed on CD4+ T cells in the liver and intrahepatic CD6highCD4+ T cells demonstrated stronger proinflammatory response and proliferation features than CD6low counterparts in both AIH and HC. ALCAM, the ligand of CD6, was highly expressed in the hepatocytes of AIH and serum ALCAM was strongly associated with clinical indices of AIH. Interestingly, close spatial location between CD6+CD4+ T cells and ALCAM+ hepatocytes was observed. Finally, we found that CD6highCD4+ T cells showed enhanced capacity of trans-endothelial migration in vitro, which could be promoted by recombinant ALCAM. Conclusions: Our study found that ALCAM-CD6 axis was upregulated in the AIH liver, suggesting a potential target for alleviating AIH.

NUDT1 promotes the accumulation and longevity of CD103+ TRM cells in primary biliary cholangitis.

BACKGROUND & AIMS: Pyruvate dehydrogenase (PDC)-E2 specific CD8+ T cells play a leading role in biliary destruction in PBC. However, there are limited data on the characterization of these autoantigen-specific CD8+ T cells, particularly in the liver. Herein, we aimed to identify pathogenic intrahepatic CD8+ T-cell subpopulations and investigate their immunobiology in PBC. METHODS: Phenotypic and functional analysis of intrahepatic T-cell subsets were performed by flow cytometry. CD103+ TRM cell frequency was evaluated by histological staining. The transcriptome and metabolome were analyzed by RNA-seq and liquid chromatography-mass spectrometry, respectively. Cytotoxicity of TRM cells against cholangiocytes was assayed in a 3D organoid co-culture system. Moreover, the longevity (long-term survival) of TRM cells in vivo was studied by 2-octynoic acid-BSA (2OA-BSA) immunization, Nudt1 conditional knock-out and adoptive co-transfer in a murine model. RESULTS: Intrahepatic CD103+ TRM (CD69+CD103+CD8+) cells were significantly expanded, hyperactivated, and potentially specifically reactive to PDC-E2 in patients with PBC. CD103+ TRM cell frequencies correlated with clinical and histological indices of PBC and predicted poor ursodeoxycholic acid response. NUDT1 blockade suppressed the cytotoxic effector functions of CD103+ TRM cells upon PDC-E2 re-stimulation. NUDT1 overexpression in CD8+ T cells promoted tissue-residence programming in vitro; inhibition or knockdown of NUDT1 had the opposite effect. Pharmacological blockade or genetic deletion of NUDT1 eliminated CD103+ TRM cells and alleviated cholangitis in mice immunized with 2OA-BSA. Significantly, NUDT1-dependent DNA damage resistance potentiates CD8+ T-cell tissue-residency via the PARP1-TGFßR axis in vitro. Consistently, PARP1 inhibition restored NUDT1-deficient CD103+ TRM cell durable survival and TGFß-Smad signaling. CONCLUSIONS: CD103+ TRM cells are the dominant population of PDC-E2-specific CD8+ T lymphocytes in the livers of patients with PBC. The role of NUDT1 in promoting pathogenic CD103+ TRM cell accumulation and longevity represents a novel therapeutic target in PBC. LAY SUMMARY: Primary biliary cholangitis (PBC) is a rare inflammatory condition of the bile ducts. It can be treated with ursodeoxycholic acid, but a large percentage of patients respond poorly to this treatment. Liver-infiltrating memory CD8+ T cells recognizing the PDC-E2 immunodominant epitope are critical in the pathogenesis of PBC. We identifed the key pathogenic CD8+ T cell subset, and worked out the mechanisms of its hyperactivation and longevity, which could be exploited therapeutically.

Serum Biomarkers for Autoimmune Hepatitis Type 1: the Case for CD48 and a Review of the Literature.

In autoimmune hepatitis (AIH), the persisting inflammation contributes to fibrosis progression, for which conventional biochemical markers manifest relatively unsatisfactory prediction. Herein, we assessed the value of serum CD48 (sCD48) as an indicator for inflammation and fibrosis in AIH type 1. The levels of sCD48 were detected first in an exploratory cohort using ELISA. In this cohort, compared with healthy controls (4.90 ng/mL, P < 0.0001), primary biliary cholangitis (7.32 ng/mL, P < 0.0001), and non-alcoholic fatty liver disease (7.76 ng/mL, P < 0.0001), sCD48 levels were elevated in AIH (12.81 ng/mL) and correlated with histological inflammation and fibrosis. Further using multivariate logistic regression analysis, sCD48 was identified as an independent predictor for both significant inflammation (G3-4) and advanced fibrosis (S3-4). Two predictive scores, based on sCD48, were constructed for diagnosing significant inflammation and advanced fibrosis (sCD48-AIH-SI and sCD48-AIH-AF, respectively). Using these data as a premise, predictive abilities were subsequently evaluated and verified in a validation cohort. In the exploratory cohort, the area under the receiver operating characteristic curve of sCD48 and sCD48-AIH-SI, for significant inflammation, were 0.748 and 0.813, respectively. Besides, during treatment follow-up, sCD48 levels gradually decreased from immunosuppression initiation to re-evaluation biopsy, in parallel with aspartate transaminase, total sera IgG, and fibrosis-4 score. For AIH patients in a re-evaluation biopsy cohort, sCD48 could predict significant fibrosis (S2-4). Further using immunohistochemistry, hepatic CD48 expression was elevated in AIH patients and decreased after treatment. In conclusion, sCD48 and sCD48-based predictive scores predict histological inflammation and fibrosis in AIH-1. Detecting sCD48 might help in the clinical management of AIH.

Methylcobalamin Alleviates Neuronal Apoptosis and Cognitive Decline Induced by PM2.5 Exposure in Mice.

BACKGROUND: Fine particulate matter (particulate matter 2.5, PM2.5) is considered one of the harmful factors to neuronal functions. Apoptosis is one of the mechanisms of neuronal injury induced by PM2.5. Methylcobalamine (MeCbl) has been shown to have anti-apoptotic and neuroprotective effects. OBJECTIVE: The current work tried to explore the neuroprotective effects and mechanisms that MeCbl protects mice against cognitive impairment and neuronal apoptosis induced by chronic real-time PM2.5 exposure. METHODS: Twenty-four 6-week-old male C57BL/6 mice were exposed to ambient PM2.5 and fed with MeCbl for 6 months. Morris water maze was used to evaluate the changes of spatial learning and memory ability in mice. PC12 cells and primary hippocampal neurons were applied as the in vitro model. Cell viability, cellular reactive oxygen species (ROS) and the expressions of apoptosis-related proteins were examined. And cells were stained with JC-1 and mitochondrial membrane potential was evaluated. RESULTS: In C57BL/6 mice, MeCbl supplementation alleviated cognitive impairment and apoptosis-related protein expression induced by PM2.5 exposure. In in vitro cell model, MeCbl supplementation could effectively rescue the downregulation of cell viability induced by PM2.5, and inhibited the increased levels of ROS, cellular apoptosis, and the expressions of apoptosis related proteins related to PM2.5 treatment, which may be associated with modulation of mitochondrial function. CONCLUSION: MeCbl treatment alleviated cognitive impairment and neuronal apoptosis induced by PM2.5 both in vivo and in vitro. The mechanism for the neuroprotective effects of MeCbl may at least be partially dependent on the regulation of mitochondrial apoptosis.

The immunological characteristics of TSPAN1 expressing B cells in autoimmune hepatitis.

Background and aims: Tetraspanin proteins are closely related to the functional changes of B cells, including antigen presentation, production of cytokines, and transduction. We aim to explore the potential role of Tetraspanin 1 (TSPAN1) in the biological activities of B cells in AIH. Methods and results: Herein, this study found that numbers of cells expressing TSPAN1 were significantly increased in AIH patients compared to PBC, chronic hepatitis B, and healthy control (P < 0.0001). Moreover, there was a positive correlation between numbers of TSPAN1+ cells and AIH disease severity (P < 0.0001). Immunofluorescence staining further confirmed that TSPAN1 was primarily expressed on CD19+ B cells. Flow-cytometric analysis showed that TSPAN1+ B cells secreted more inflammatory cytokines and expressed higher level of CD86 than TSPAN1- B cells. Furthermore, compared with TSAPN1- cells, the expression of CXCR3 on TSPAN1+ cells was also higher. Meanwhile, CXCL10, the ligand of CXCR3, was significantly elevated in the liver of AIH (P < 0.01) and had positive correlation with the quantities of TSPAN1 (P < 0.05). Interestingly, the numbers of TSPAN1+ B cells were decreased in AIH patients after immunosuppressive therapy. Conclusions: TSPAN1+ B cells in the liver may promote the progression of AIH via secreting cytokines and presenting antigens. The chemotactic movement of TSPAN1+ B cells toward the liver of AIH was possibly due to CXCR3 - CXCL10 interaction.

Altered faecal microbiome and metabolome in IgG4-related sclerosing cholangitis and primary sclerosing cholangitis.

OBJECTIVE: Multiple clinical similarities exist between IgG4-related sclerosing cholangitis (IgG4-SC) and primary sclerosing cholangitis (PSC), and while gut dysbiosis has been extensively studied in PSC, the role of the gut microbiota in IgG4-SC remains unknown. Herein, we aimed to evaluate alterations of the gut microbiome and metabolome in IgG4-SC and PSC. DESIGN: We performed 16S rRNA gene amplicon sequencing of faecal samples from 135 subjects with IgG4-SC (n=34), PSC (n=37) and healthy controls (n=64). A subset of the samples (31 IgG4-SC, 37 PSC and 45 controls) also underwent untargeted metabolomic profiling. RESULTS: Compared with controls, reduced alpha-diversity and shifted microbial community were observed in IgG4-SC and PSC. These changes were accompanied by differences in stool metabolomes. Importantly, despite some common variations in the microbiota composition and metabolic activity, integrative analyses identified distinct host-microbe associations in IgG4-SC and PSC. The disease-associated genera and metabolites tended to associate with the transaminases in IgG4-SC. Notable depletion of Blautia and elevated succinic acid may underlie hepatic inflammation in IgG4-SC. In comparison, potential links between the microbial or metabolic signatures and cholestatic parameters were detected in PSC. Particularly, concordant decrease of Eubacterium and microbiota-derived metabolites, including secondary bile acids, implicated novel host-microbial metabolic pathways involving cholestasis of PSC. Interestingly, the predictive models based on metabolites were more effective in discriminating disease status than those based on microbes. CONCLUSIONS: Our data reveal that IgG4-SC and PSC possess divergent host-microbe interplays that may be involved in disease pathogenesis. These data emphasise the uniqueness of IgG4-SC.

Myeloid-Derived Suppressive Cells Deficient in Liver X Receptor α Protected From Autoimmune Hepatitis.

Myeloid-derived suppressor cells (MDSCs) emerge as a promising candidate for the immunotherapy of autoimmune hepatitis (AIH). However, targets for modulating MDSC in AIH are still being searched. Liver X receptors (LXRs) are important nuclear receptors linking lipid metabolism and immune responses. Despite the extensive studies of LXR in myeloid compartment, its role in MDSCs is currently less understood. Herein, expression of LXRα was found to be upregulated in AIH patients and colocalized with hepatic MDSCs. In ConA-induced hepatitis, deletion of LXRα led to increased expansion of MDSCs in the liver and alleviated the hepatic injury. MDSCs in LXRα-/- mice exhibited enhanced proliferation and survival comparing with WT mice. T-cell proliferation assay and adoptive cell transfer experiment validated the potent immunoregulatory role of MDSCs in vitro and in vivo. Mechanistically, MDSCs from LXRα-/- mice possessed significantly lower expression of interferon regulatory factor 8 (IRF-8), a key negative regulator of MDSC differentiation. Transcriptional activation of IRF-8 by LXRα was further demonstrated. Conclusion: We reported that abrogation of LXRα facilitated the expansion of MDSCs via downregulating IRF-8, and thereby ameliorated hepatic immune injury profoundly. Our work highlights the therapeutic potential of targeting LXRα in AIH.

Recent Advances on Possible Association Between the Periodontal Infection of Porphyromonas gingivalis and Central Nervous System Injury.

Chronic periodontitis caused by Porphyromonas gingivalis (P. gingivalis) infection generally lasts for a lifetime. The long-term existence and development of P. gingivalis infection gradually aggravate the accumulation of inflammatory signals and toxic substances in the body. Recent evidence has revealed that P. gingivalis infection may be relevant to some central nervous system (CNS) diseases. The current work collects information and tries to explore the possible relationship between P. gingivalis infection and CNS diseases, including the interaction or pathways between peripheral infection and CNS injury, and the underlying neurotoxic mechanisms.

The Clinical Significance of Hepatic CD69+ CD103+ CD8+ Resident-Memory T Cells in Autoimmune Hepatitis.

BACKGROUND AND AIMS: The diverse inflammatory response found in the liver of patients with autoimmune hepatitis (AIH) is well established, but identification of potentially pathogenic subpopulations has proven enigmatic. APPROACH AND RESULTS: We report herein that CD69+ CD103+ CD8+ tissue-resident memory T cells (TRM ) are significantly increased in the liver of patients with AIH compared to chronic hepatitis B, NAFLD, and healthy control tissues. In addition, there was a significant statistical correlation between elevation of CD8+ TRM cells and AIH disease severity. Indeed, in patients with successful responses to immunosuppression, the frequencies of such hepatic CD8+ TRM cells decreased significantly. CD69+ CD8+ and CD69+ CD103+ CD8+ T cells, also known as CD8+ TRM cells, reflect tissue residency and are well known to provide intense immune antigenic responses. Hence, it was particularly interesting that patients with AIH also manifest an elevated expression of IL-15 and TGF-ß on inflammatory cells, and extensive hepatic expression of E-cadherin; these factors likely contribute to the development and localization of CD8+ TRM cells. Based on these data and, in particular, the relationships between disease severity and CD8+ TRM cells, we studied the mechanisms involved with glucocorticoid (GC) modulation of CD8+ TRM cell expansion. Our data reflect that GCs in vitro inhibit the expansion of CD8+ TRM cells induced by IL-15 and TGF-ß and with direct down-regulation of the nuclear factor Blimp1 of CD8+ TRM cells. CONCLUSIONS: Our data suggest that CD8+ TRM cells play a critical role in the pathogenesis of AIH, and GCs attenuate hepatic inflammation through direct inhibition of CD8+ TRM cell expansion.

Ambient PM2.5 chronic exposure leads to cognitive decline in mice: From pulmonary to neuronal inflammation.

Fine particulate matter 2.5 (PM2.5), one of the main components of air pollutants, seriously threatens human health. Possible neuronal dysfunction induced by PM2.5 has received extensive attention. However, there is little evidence for the specific biochemical mechanism of neuronal injury induced by PM2.5. Moreover, the pathway for PM2.5 transport from peripheral circulation to the central nervous system (CNS) is still unclear. In the current work, C57BL/6 mice were chronically exposed to ambient PM2.5 for 3, 6, 9, and 12 months. Exposure to ambient PM2.5 resulted in a significant reduction of cognitive ability in mice by Morris water maze test. PM2.5 exposure induced a neuroinflammatory reaction after cognitive impairment, while inflammation in the hypothalamus and olfactory bulb tissue occurred earlier. The expression levels of integrity tight junction proteins in the blood-brain barrier (BBB) were reduced by PM2.5 exposure. Pulmonary inflammation occurred much earlier and diminished at later stage of PM2.5 exposure. The results indicated that chronic exposure to ambient PM2.5 led to cognitive decline in mice; CNS dysfunction may be due to neuroinflammatory reactions; the reduced integrity of the BBB allowed the influence of pulmonary inflammation to neuronal alterations. The work may provide promising therapeutic or preventive targets for air pollution-induced neurodegenerative disease.