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.

Immunosuppression induces regression of fibrosis in primary biliary cholangitis with moderate-to-severe interface hepatitis.

BACKGROUND: In patients with primary biliary cholangitis (PBC) treated with ursodeoxycholic acid (UDCA), the presence of moderate-to-severe interface hepatitis is associated with a higher risk of liver transplantation and death. This highlights the need for novel treatment approaches. In this study, we aimed to investigate whether combination therapy of UDCA and immunosuppressant (IS) was more effective than UDCA monotherapy. METHODS: We conducted a multicenter study involving PBC patients with moderate-to-severe interface hepatitis who underwent paired liver biopsies. Firstly, we compared the efficacy of the combination therapy with UDCA monotherapy on improving biochemistry, histology, survival rates, and prognosis. Subsequently we investigated the predictors of a beneficial response. RESULTS: This retrospective cohort study with prospectively collected data was conducted in China from January 2009 to April 2023. Of the 198 enrolled patients, 32 underwent UDCA monotherapy, while 166 received combination therapy, consisting of UDCA combined with prednisolone, prednisolone plus mycophenolate mofetil (MMF), or prednisolone plus azathioprine (AZA). The monotherapy group was treated for a median duration of 37.6 months (IQR 27.5-58.1), and the combination therapy group had a median treatment duration of 39.3 months (IQR 34.5-48.8). The combination therapy showed a significantly greater efficacy in reducing fibrosis compared to UDCA monotherapy, with an 8.3-fold increase in the regression rate (from 6.3% to 52.4%, P < 0.001). Other parameters, including biochemistry, survival rates, and prognosis, supported its effectiveness. Baseline IgG >1.3 × ULN and ALP <2.4 × ULN were identified as predictors of regression following the combination therapy. A predictive score named FRS, combining these variables, accurately identified individuals achieving fibrosis regression with a cut-off point of ≥ -0.163. The predictive value was validated internally and externally. CONCLUSION: Combination therapy with IS improves outcomes in PBC patients with moderate-to-severe interface hepatitis compared to UDCA monotherapy. Baseline IgG and ALP are the most significant predictors of fibrosis regression. The new predictive score, FRS, incorporating baseline IgG and ALP, can effectively identify individuals who would benefit from the combination therapy.

MGAT5/TMEM163 variant is associated with prognosis in ursodeoxycholic acid-treated patients with primary biliary cholangitis.

BACKGROUND: Primary biliary cholangitis (PBC) is a chronic immune-mediated liver disease. Previous genome-wide meta-analysis has identified the association between variants in TMEM163 with PBC. Here we aimed to evaluate the association between variants near the reported risk loci of TMEM163 at 2q21.3 and prognosis of PBC patients. METHODS: We performed a retrospective analysis of 347 PBC patients treated with ursodeoxycholic acid (UDCA) for at least 1 year. We collected clinical data at diagnosis and 1 year after UDCA treatment. SNPs within 200 kb upstream and downstream of the lead variant were genotyped and screened. RESULTS: We identified that rs661899 near MGAT5 and TMEM163 showed the strongest association with prognosis in PBC patients. Patients carrying the rs661899 T allele tended to respond incompletely to UDCA treatment and had worse performances in laboratory values including aspartate aminotransferase (53.5 vs 32 vs 28.5 U/L, p = 0.001), alkaline phosphate (157.25 vs 125 vs 113 U/L, p = 0.001), albumin (41.5 vs 42.3 vs 43.7 g/L, p = 0.008) and bilirubin (19.2 vs 14.9 vs 12.85 µmol/L, p = 0.001). GLOBE scores (p = 4.8 × 10-5) and UK-PBC risk scores (p = 4.6 × 10-4) were strongly correlated with rs661899 genotype. Patients with TT genotype had a higher risk for adverse events compared with CC genotype (p = 0.039) during the 1-year follow-up. Results were also verified in an independent cohort. CONCLUSIONS: PBC patients carrying the rs661899 T allele are associated with poor prognosis and adverse outcomes after 1-year UDCA therapy.

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.

Fine mapping identifies independent HLA associations in autoimmune hepatitis type 1.

Background & Aims: Association studies have greatly refined the important role of the major histocompatibility complex (MHC) region in autoimmune hepatitis (AIH). However, the effects of human leucocyte antigen (HLA) polymorphisms on AIH are not well established. The aim of this study is to systematically characterise the association of MHC variants with AIH in our well-defined cohort of patients. Methods: We performed an imputation-based analysis on the extensive association observed within the MHC region using the Han-MHC reference panel, and tested the comprehensive associations of HLA polymorphisms with AIH in 1622 Chinese AIH type 1 patients and 10,466 population controls. Results: A total of 588 HLA variants were significantly associated with AIH, with HLA-B∗35:01 (p = 8.17 × 10-304; odds ratio [OR] = 7.32) contributing the strongest signal. Stepwise conditional analysis revealed additional independent signals at HLA-B∗08:01 (p = 1.35 × 10-33; OR = 4.26) and rs7765379 (p = 5.08 × 10-18; OR = 1.66). A strong link between the lead HLA variant and clinical phenotypes of AIH was observed: patients with HLA-B∗35:01 were less frequently positive for ANA and tended to have higher serum AST and ALT levels at diagnosis, but lower serum IgG levels. Conclusions: Our study reveals three novel and independent variants at HLA-B∗35:01, HLA-B∗08:01, and rs7765379 associated with AIH across the whole MHC region in the Han Chinese population. The findings illustrate the value of the MHC region in AIH and provide a new perspective for the immunogenetics of AIH. Impact and implications: This study revealed three novel and independent variants associated with autoimmune hepatitis across the whole major histocompatibility complex region in the Han Chinese population. These findings are significant in identifying autoantigens, providing insights into the activation of the autoimmune processes, and further advancing our understanding of the immunogenetic basis underlying autoimmune hepatitis.

A+T rich interaction domain protein 3a (Arid3a) impairs Mertk-mediated efferocytosis in cholestasis.

BACKGROUND & AIMS: Macrophages are key elements in the pathogenesis of cholestatic liver diseases. Arid3a plays a prominent role in the biologic properties of hematopoietic stem cells, B lymphocytes and tumor cells, but its ability to modulate macrophage function during cholestasis remains unknown. METHODS: Gene and protein expression and cellular localization were assessed by q-PCR, immunohistochemistry, immunofluorescence staining and flow cytometry. We generated myeloid-specific Arid3a knockout mice and established three cholestatic murine models. The transcriptome was analyzed by RNA-seq. A specific inhibitor of the Mertk receptor was used in vitro and in vivo. Promoter activity was determined by chromatin immunoprecipitation-seq against Arid3a and a luciferase reporter assay. RESULTS: In cholestatic murine models, myeloid-specific deletion of Arid3a alleviated cholestatic liver injury (accompanied by decreased accumulation of macrophages). Arid3a-deficient macrophages manifested a more reparative phenotype, which was eliminated by in vitro treatment with UNC2025, a specific inhibitor of the efferocytosis receptor Mertk. Efferocytosis of apoptotic cholangiocytes was enhanced in Arid3a-deficient macrophages via upregulation of Mertk. Arid3a negatively regulated Mertk transcription by directly binding to its promoter. Targeting Mertk in vivo effectively reversed the protective phenotype of Arid3a deficiency in macrophages. Arid3a was upregulated in hepatic macrophages and circulating monocytes in primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). Mertk was correspondingly upregulated and negatively correlated with Arid3a expression in PBC and PSC. Mertk+ cells were located in close proximity to cholangiocytes, while Arid3a+ cells were scattered among immune cells with greater spatial distances to hyperplastic cholangiocytes in PBC and PSC. CONCLUSIONS: Arid3a promotes cholestatic liver injury by impairing Mertk-mediated efferocytosis of apoptotic cholangiocytes by macrophages during cholestasis. The Arid3a-Mertk axis is a promising novel therapeutic target for cholestatic liver diseases. IMPACT AND IMPLICATIONS: Macrophages play an important role in the pathogenesis of cholestatic liver diseases. This study reveals that macrophages with Arid3a upregulation manifest a pro-inflammatory phenotype and promote cholestatic liver injury by impairing Mertk-mediated efferocytosis of apoptotic cholangiocytes during cholestasis. Although we now offer a new paradigm to explain how efferocytosis is regulated in a myeloid cell autonomous manner, the regulatory effects of Arid3a on chronic liver diseases remain to be further elucidated.

A regulatory variant at 19p13.3 is associated with primary biliary cholangitis risk and ARID3A expression.

Genome-wide association studies have identified 19p13.3 locus associated with primary biliary cholangitis (PBC). Here we aim to identify causative variant(s) and initiate efforts to define the mechanism by which the 19p13.3 locus variant(s) contributes to the pathogenesis of PBC. A genome-wide meta-analysis of 1931 PBC subjects and 7852 controls in two Han Chinese cohorts confirms the strong association between 19p13.3 locus and PBC. By integrating functional annotations, luciferase reporter assay and allele-specific chromatin immunoprecipitation, we prioritize rs2238574, an AT-Rich Interaction Domain 3A (ARID3A) intronic variant, as a potential causal variant at 19p13.3 locus. The risk allele of rs2238574 shows higher binding affinity of transcription factors, leading to an increased enhancer activity in myeloid cells. Genome-editing demonstrates the regulatory effect of rs2238574 on ARID3A expression through allele-specific enhancer activity. Furthermore, knock-down of ARID3A inhibits myeloid differentiation and activation pathway, and overexpression of the gene has the opposite effect. Finally, we find ARID3A expression and rs2238574 genotypes linked to disease severity in PBC. Our work provides several lines of evidence that a non-coding variant regulates ARID3A expression, presenting a mechanistic basis for association of 19p13.3 locus with the susceptibility to PBC.

P4HA2 induces hepatic ductular reaction and biliary fibrosis in chronic cholestatic liver diseases.

BACKGROUNDS: Prolyl-4-hydroxylases (P4Hs) are key enzymes in collagen synthesis. The P4HA subunit (P4HA1, P4HA2, and P4HA3) contains a substrate binding and catalyzation domain. We postulated that P4HA2 would play a key role in the cholangiocyte pathology of cholestatic liver diseases. METHODS: We studied humans with primary biliary cholangitis (PBC) and Primary sclerosing cholangitis (PSC), P4HA2 -/- mice injured by DDC, and P4HA2 -/- /MDR2 -/- double knockout mice. A parallel study was performed in patients with PBC, PSC, and controls using immunohistochemistry and immunofluorescence. In the murine model, the level of ductular reaction and biliary fibrosis were monitored by histology, qPCR, immunohistochemistry, and Western blotting. Expression of Yes1 Associated Transcriptional Regulator (YAP) phosphorylation was measured in isolated mouse cholangiocytes. The mechanism of P4HA2 was explored in RBE and 293T cell lines by using qPCR, Western blot, immunofluorescence, and co-immunoprecipitation. RESULTS: The hepatic expression level of P4HA2 was highly elevated in patients with PBC or PSC. Ductular reactive cholangiocytes predominantly expressed P4HA2. Cholestatic patients with more severe liver injury correlated with levels of P4HA2 in the liver. In P4HA2 -/- mice, there was a significantly reduced level of ductular reaction and fibrosis compared with controls in the DDC-induced chronic cholestasis. Decreased liver fibrosis and ductular reaction were observed in P4HA2 -/- /MDR2 -/- mice compared with MDR2 -/- mice. Cholangiocytes isolated from P4HA2 -/- /MDR2 -/- mice displayed a higher level of YAP phosphorylation, resulting in cholangiocytes proliferation inhibition. In vitro studies showed that P4HA2 promotes RBE cell proliferation by inducing SAV1 degradation, eventually resulting in the activation of YAP. CONCLUSIONS: P4HA2 promotes hepatic ductular reaction and biliary fibrosis by regulating the SAV1-mediated Hippo signaling pathway. P4HA2 is a potential therapeutic target for PBC and PSC.

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).

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.

Immunologic Responses and the Pathophysiology of Primary Biliary Cholangitis.

Primary biliary cholangitis (PBC) is an autoimmune liver disease with a female predisposition and selective destruction of intrahepatic small bile ducts leading to nonsuppurative destructive cholangitis. It is characterized by seropositivity of antimitochondrial antibodies or PBC-specific antinuclear antibodies, progressive cholestasis, and typical liver histologic manifestations. Destruction of the protective bicarbonate-rich umbrella is attributed to the decreased expression of membrane transporters in biliary epithelial cells (BECs), leading to the accumulation of hydrophobic bile acids and sensitizing BECs to apoptosis. A recent X-wide association study reveals a novel risk locus on the X chromosome, which reiterates the importance of Treg cells.

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.

Tissue-resident memory T cells in chronic liver diseases: Phenotype, development and function.

Tissue-resident memory (TRM) T cells are a unique subset of memory T cells that are critical for the first line of defense against pathogens or antigens in peripheral non-lymphoid tissues such as liver, gut, and skin. Generally, TRM cells are well adapted to the local environment in a tissue-specific manner and typically do not circulate but persist in tissues, distinguishing them from other memory T cell lineages. There is strong evidence that liver TRM cells provide a robust adaptive immune response to potential threats. Indeed, the potent effector function of hepatic TRM cells makes it essential for chronic liver diseases, including viral and parasite infection, autoimmune liver diseases (AILD), nonalcoholic fatty liver disease (NAFLD), hepatocellular carcinoma (HCC) and liver transplantation. Manipulation of hepatic TRM cells might provide novel promising strategies for precision immunotherapy of chronic liver diseases. Here, we provide insights into the phenotype of hepatic TRM cells through surface markers, transcriptional profiles and effector functions, discuss the development of hepatic TRM cells in terms of cellular origin and factors affecting their development, analyze the role of hepatic TRM cells in chronic liver diseases, as well as share our perspectives on the current status of hepatic TRM cell research.

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.

Genome-wide meta-analysis identifies susceptibility loci for autoimmune hepatitis type 1.

BACKGROUND AND AIMS: Autoimmune hepatitis (AIH) is a rare and chronic autoimmune liver disease. While genetic factors are believed to play a crucial role in the etiopathogenesis of AIH, our understanding of these genetic risk factors is still limited. In this study, we aimed to identify susceptibility loci to further understand the pathogenesis of this disease. APPROACH AND RESULTS: We conducted a case-control association study of 1,622 Chinese patients with AIH type 1 and 10,466 population controls from two independent cohorts. A meta-analysis was performed to ascertain variants associated with AIH type 1. A single-nucleotide polymorphism within the human leukocyte antigen (HLA) region showed the strongest association with AIH (rs6932730: OR = 2.32; p = 9.21 × 10-73 ). The meta-analysis also identified two non-HLA loci significantly associated with AIH: CD28/CTLA4/ICOS on 2q33.3 (rs72929257: OR = 1.31; p = 2.92 × 10-9 ) and SYNPR on 3p14.2 (rs6809477: OR = 1.25; p = 5.48 × 10-9 ). In silico annotation, reporter gene assays, and CRISPR activation experiments identified a distal enhancer at 2q33.3 that regulated expression of CTLA4. In addition, variants near STAT1/STAT4 (rs11889341: OR = 1.24; p = 1.34 × 10-7 ), LINC00392 (rs9564997: OR = 0.81; p = 2.53 × 10-7 ), IRF8 (rs11117432: OR = 0.72; p = 6.10 × 10-6 ), and LILRA4/LILRA5 (rs11084330: OR = 0.65; p = 5.19 × 10-6 ) had suggestive association signals with AIH. CONCLUSIONS: Our study identifies two novel loci (CD28/CTLA4/ICOS and SYNPR) exceeding genome-wide significance and suggests four loci as potential risk factors. These findings highlight the importance of costimulatory signaling and neuro-immune interaction in the pathogenesis of AIH.