Leaky Gut Driven by Dysbiosis Augments Activation and Accumulation of Liver Macrophages via RIP3 Signaling Pathway in Autoimmune Hepatitis.

The gut-liver axis has been increasingly recognized as a major autoimmunity modulator. However, the implications of intestinal barrier in the pathogenesis of autoimmune hepatitis (AIH) remain elusive. Here, we investigated the functional role of gut barrier and intestinal microbiota for hepatic innate immune response in AIH patients and murine models. In this study, we found that AIH patients displayed increased intestinal permeability and pronounced RIP3 activation of liver macrophages. In mice models, intestinal barrier dysfunction increased intestinal bacterial translocation, thus amplifying the hepatic RIP3-mediated innate immune response. Furthermore, GSK872 dampened RIP3 activation and ameliorated the activation and accumulation of liver macrophages in vitro and in vivo experiments. Strikingly, broad-spectrum antibiotic ablation significantly alleviated RIP3 activation and liver injury, highlighting the causal role of intestinal microbiota for disease progression. Our results provided a potentially novel mechanism of immune tolerance breakage in the liver via the gut-liver axis. In addition, we also explored the therapeutic and research potentials of regulating the intestinal microbiota for the therapy of AIH.

Overlap of concurrent extrahepatic autoimmune diseases is associated with milder disease severity of newly diagnosed autoimmune hepatitis.

BACKGROUND: Concurrent extrahepatic autoimmune disorders (CEHAID) are frequently observed in autoimmune hepatitis (AIH). It is not clear whether there is any prognostic significance of CEHAID on AIH. The aim of this study was to examine the prognostic impact of CEHAID and the correlation with the disease severity of AIH. METHODS: This study included 65 hospitalized subjects who fulfilled the accepted criteria for AIH during an 8-year period (2009-2016). All records were manually screened for presence of associated autoimmune diseases. Disease severity of AIH was assessed by liver laboratory tests including the ratio of aspartate aminotransferase to alanine aminotransferase (AST/ALT) and liver histology. RESULTS: Among the enrolled patients, 52 (80%) were female (median age 61 years, IQR 45-75). Fifty-six (86.2%) were classified as type-1 AIH. In 26 (40%) patients at least one additional extrahepatic autoimmune disease was diagnosed. Thirty-four subjects were referred to our hospital because of acute presentation of AIH (supposed by an acute elevation of hepatic enzymes) for subsequent liver biopsy resulting in initial diagnosis of AIH. This group was stratified into 3 subgroups: (A) AIH alone (n = 14); (B) overlap with primary biliary cirrhosis (PBC) / primary sclerosing cholangitis (PSC) (n = 11); and (C) with CEHAID (n = 9). AST/ALT ratio was the lowest in subgroup C (median 0.64, IQR 0.51-0.94; P = 0.023), compared to subgroup A (median 0.91, IQR 0.66-1.10) and subgroup B (median 1.10, IQR 0.89-1.36). Patients with AIH alone showed a trend to the highest grade of fibrosis (mean 2.3; 95% CI: 1.5-3.0) with no statistical significance compared to subjects with CEHAID (lowest grade of fibrosis; mean 1.5; 95% CI: 0.2-2.8; P = 0.380) whereas the ongoing inflammation was comparable. CONCLUSIONS: AST/ALT ratio and extent of fibrosis were lower in subjects with AIH and CEHAID, compared to subjects with only AIH. Therefore, the occurrence of CEHAID might be a predictor for lower disease severity of newly diagnosed acute onset AIH, possibly caused by an earlier diagnosis or different modes of damage.

Ectonucleotidases in Intestinal and Hepatic Inflammation.

Purinergic signaling modulates systemic and local inflammatory responses. Extracellular nucleotides, including eATP, promote inflammation, at least in part via the inflammasome upon engagement of P2 purinergic receptors. In contrast, adenosine generated during eATP phosphohydrolysis by ectonucleotidases, triggers immunosuppressive/anti-inflammatory pathways. Mounting evidence supports the role of ectonucleotidases, especially ENTPD1/CD39 and CD73, in the control of several inflammatory conditions, ranging from infectious disease, organ fibrosis to oncogenesis. Our experimental data generated over the years have indicated both CD39 and CD73 serve as pivotal regulators of intestinal and hepatic inflammation. In this context, immune cell responses are regulated by the balance between eATP and adenosine, potentially impacting disease outcomes as in gastrointestinal infection, inflammatory bowel disease, ischemia reperfusion injury of the bowel and liver, autoimmune or viral hepatitis and other inflammatory conditions, such as cancer. In this review, we report the most recent discoveries on the role of ENTPD1/CD39, CD73, and other ectonucleotidases in the regulation of intestinal and hepatic inflammation. We discuss the present knowledge, highlight the most intriguing and promising experimental data and comment on important aspects that still need to be addressed to develop purinergic-based therapies for these important illnesses.

Role of age in presentation, response to therapy and outcome of autoimmune hepatitis.

BACKGROUND: Few studies with diverging results and a small sample size have compared autoimmune hepatitis (AIH) in the elderly to younger patients. AIM: To unbiasedly investigate the role of age in behaviour and treatment outcome of AIH. METHODS: All patients with probable or definite AIH type 1 in four tertiary academic centres were included in this retrospective-and since 2006 prospective-cohort study. Influence of age on presentation, remission and outcome of AIH were investigated. RESULTS: 359 patients were included. Presence of cirrhosis at AIH diagnosis around 30% was independent of age. ALAT was higher at age 30-60 years on AIH diagnosis, and above age 60 there were less acute onset, less jaundice and more concurrent autoimmune disease. Remission was reached in 80.2%, incomplete remission in 18.7%, only 1.1% (all aged 50-65) was treatment-refractory. Age was not an independent predictor of remission, while cirrhosis was. Above age 45 there was more diabetes, above age 60 more loss of remission. Rate of progression to cirrhosis was 10% in the 10 years after diagnosis and unrelated to age at AIH diagnosis. With onset below age 30, there was more development of decompensated cirrhosis over time. With higher age at AIH diagnosis there was a lower survival free of liver-related death or liver transplantation. CONCLUSIONS: AIH presents at all ages. Age influences features at diagnosis, but not response to treatment, while survival without liver-related death or liver transplantation decreases with higher age at diagnosis.

The Activity of Alcohol Dehydrogenase Isoenzymes and Aldehyde Dehydrogenase in the Sera of Patients with Autoimmune Hepatitis.

BACKGROUND: Autoimmune hepatitis (AIH) is a progressive inflammatory hepatopathy and an important cause of end-stage liver. The liver cells' destruction is reflected by increased activity of different enzymes in the serum. These enzymes include alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), which play a significant role in the metabolism of many biological substances and exist mainly in the liver. In this study we investigated the activity of alcohol dehydrogenase and its isoenzymes and the total activity of ALDH in the sera of patients with autoimmune hepatitis. METHODS: Serum samples were taken for routine biochemical investigation from 32 patients with autoimmune hepatitis and from 40 healthy subjects. Class I and II of ADH and ALDH activity was measured by the spectrofluorometric method. For measurement of class III ADH and total ADH activity we employed the photometric methods. RESULTS: The activity of the class I ADH isoenzyme was significantly higher in the sera of patients with autoimmune hepatitis. The median activity of this isoenzyme in the patients group was approximately 63% (3.94 mU/L) higher than the control level (1.46 mU/L). For this reason, the total ADH activity was also significantly increased. The activities of other ADH isoenzymes and ALDH tested were unchanged. CONCLUSIONS: The activity of total ADH and class I isoenzymes in the sera of patients with autoimmune hepatitis is increased, and it seems to be caused by the release of alcohol dehydrogenase from damaged liver cells.

The pseudokinase MLKL mediates programmed hepatocellular necrosis independently of RIPK3 during hepatitis.

Although necrosis and necroinflammation are central features of many liver diseases, the role of programmed necrosis in the context of inflammation-dependent hepatocellular death remains to be fully determined. Here, we have demonstrated that the pseudokinase mixed lineage kinase domain-like protein (MLKL), which plays a key role in the execution of receptor-interacting protein (RIP) kinase-dependent necroptosis, is upregulated and activated in human autoimmune hepatitis and in a murine model of inflammation-dependent hepatitis. Using genetic and pharmacologic approaches, we determined that hepatocellular necrosis in experimental hepatitis is driven by an MLKL-dependent pathway that occurs independently of RIPK3. Moreover, we have provided evidence that the cytotoxic activity of the proinflammatory cytokine IFN-γ in hepatic inflammation is strongly connected to induction of MLKL expression via activation of the transcription factor STAT1. In summary, our results reveal a pathway for MLKL-dependent programmed necrosis that is executed in the absence of RIPK3 and potentially drives the pathogenesis of severe liver diseases.

Genetic Association of PTPN22 Polymorphisms with Autoimmune Hepatitis and Primary Biliary Cholangitis in Japan.

Autoimmune hepatitis (AIH) and primary biliary cholangitis (PBC) are liver-specific autoimmune conditions that are characterized by chronic hepatic damage and often lead to cirrhosis and hepatic failure. Specifically, the protein tyrosine phosphatase N22 (PTPN22) gene encodes the lymphoid protein tyrosine phosphatase, which acts as a negative regulator of T-cell receptor signaling. A missense single nucleotide polymorphism (SNP) (rs2476601) in PTPN22 has been linked to numerous autoimmune diseases in Caucasians. In the present series, nine SNPs in the PTPN22 gene were analyzed in 166 patients with AIH, 262 patients with PBC, and 322 healthy controls in the Japanese population using TaqMan assays. Although the functional rs3996649 and rs2476601 were non-polymorphic in all subject groups, the frequencies of the minor alleles at rs1217412, rs1217388, rs1217407, and rs2488458 were significantly decreased in AIH patients as compared with controls (all Pc < 0.05). There were no significant relationships with PTPN22 SNPs in PBC patients. Interestingly, the AAGTCCC haplotype was significantly associated with resistance to both AIH (odds ratio [OR] = 0.58, P = 0.0067) and PBC (OR = 0.58, P = 0.0048). SNPs in the PTPN22 gene may therefore play key roles in the genetic resistance to autoimmune liver disease in the Japanese.

Angiotensin-converting enzyme for noninvasive assessment of liver fibrosis in autoimmune hepatitis.

BACKGROUND AND AIM: There are no validated noninvasive markers of liver fibrosis in autoimmune hepatitis (AIH). An activated renin-angiotensin system (RAS) and its key element angiotensin-converting enzyme (ACE) have been implicated in the pathogenesis of hepatic fibrogenesis. We aimed to study the assumed role of activated RAS in the fibrogenic process and whether the serum concentration of ACE can predict different fibrosis stages in AIH. PATIENTS AND METHODS: Serum samples of 73 consecutive patients who were diagnosed with AIH were analysed for ACE concentration. All patients underwent a liver biopsy. RESULTS: Serum ACE levels increased significantly for each fibrosis score. The median ACE was 45 U/l in patients with fibrosis score I, 54 U/l in patients with fibrosis score II, 68 U/l in patients with fibrosis score III and 87 U/l in patients with fibrosis score IV. For significant fibrosis (≤F2), a 56 U/l cut-off value of ACE had 95.5% sensitivity and 74.5% specificity, and receiver-operating characteristic curves showed an area under the curve (AUC) of 0.89. For advanced fibrosis (≤F3), a 64 U/l cut-off level of ACE had 85.2% sensitivity and 94.8% specificity, and AUC was 0.91. For cirrhosis, a 68 U/l cut-off level of ACE had 100% sensitivity and 84.4% specificity, and AUC was 0.95. CONCLUSION: Our results suggest that activated RAS may sustain hepatic fibrogenesis in AIH. Measurement of serum ACE offers an easy, accurate and inexpensive noninvasive method that differentiates significant from nonsignificant liver fibrosis in AIH. Blockade of RAS may exert beneficial effects on fibrosis progression in AIH.

Protective effects of astaxanthin on ConA-induced autoimmune hepatitis by the JNK/p-JNK pathway-mediated inhibition of autophagy and apoptosis.

OBJECTIVE: Astaxanthin, a potent antioxidant, exhibits a wide range of biological activities, including antioxidant, atherosclerosis and antitumor activities. However, its effect on concanavalin A (ConA)-induced autoimmune hepatitis remains unclear. The aim of this study was to investigate the protective effects of astaxanthin on ConA-induced hepatitis in mice, and to elucidate the mechanisms of regulation. MATERIALS AND METHODS: Autoimmune hepatitis was induced in in Balb/C mice using ConA (25 mg/kg), and astaxanthin was orally administered daily at two doses (20 mg/kg and 40 mg/kg) for 14 days before ConA injection. Levels of serum liver enzymes and the histopathology of inflammatory cytokines and other maker proteins were determined at three time points (2, 8 and 24 h). Primary hepatocytes were pretreated with astaxanthin (80 µM) in vitro 24 h before stimulation with TNF-α (10 ng/ml). The apoptosis rate and related protein expression were determined 24 h after the administration of TNF-α. RESULTS: Astaxanthin attenuated serum liver enzymes and pathological damage by reducing the release of inflammatory factors. It performed anti-apoptotic effects via the descending phosphorylation of Bcl-2 through the down-regulation of the JNK/p-JNK pathway. CONCLUSION: This research firstly expounded that astaxanthin reduced immune liver injury in ConA-induced autoimmune hepatitis. The mode of action appears to be downregulation of JNK/p-JNK-mediated apoptosis and autophagy.

Serum superoxide dismutase activity in acute and chronic paediatric liver diseases.

BACKGROUND AND STUDY AIMS: Measuring serum superoxide dismutase (SOD) levels in infants and children having acute or chronic liver disease of different aetiologies, and correlating these levels with disease aetiology in an attempt to clarify the role of SOD as an antioxidant in these diseases. PATIENTS AND METHODS: We prospectively enrolled 58 infants and children and divided them into four groups: Group I, 24 patients with surgical cholestasis; group II, 11 patients with medical cholestasis; group III, nine patients with autoimmune chronic hepatitis; and group IV, 14 patients with viral hepatitis. Forty healthy age- and sex-matched children served as controls. Serum SOD activity was measured in all patients and controls using spectrophotometry. RESULTS: The level of SOD showed a statistically significant increase in patients with medical cholestasis compared to healthy controls (p<0.0001). SOD activity of other groups showed no significant difference compared to controls. CONCLUSIONS: Significantly increased serum SOD in infants and children with medical cholestasis is probably consequent to its increase in liver tissue in response to the liberation of reactive oxygen species. This suggests that products of free radical reactions might be involved in the pathogenesis and/or progression of medical cholestasis, and that SOD might attempt to minimise the liver injury.

Liver enzyme elevations within 3 months of diagnosis of inflammatory bowel disease and likelihood of liver disease.

BACKGROUND: Inflammatory bowel disease-associated liver diseases (IBD-LDs) include autoimmune hepatitis (AIH), primary sclerosing cholangitis (PSC), and an overlap syndrome. Prospective unbiased multicenter data regarding the frequency of IBD-LD in patients with pediatric inflammatory bowel disease (IBD) are lacking. We examined early alanine aminotransferase (ALT) and γ-glutamyl transpeptidase (GGT) elevations in children diagnosed as having IBD and assessed the likelihood of IBD-LD. METHODS: Data collected from the prospective observational Pediatric Inflammatory Bowel Disease Collaborative Research Group Registry enrolling children of age <16 years within 30 days of diagnosis. AIH, PSC, and overlap syndrome were diagnosed using local institutional criteria. RESULTS: A total of 1569 subjects had liver enzymes available. Of the total, 757 had both ALT and GGT, 800 had ALT only (no GGT), and 12 had GGT only (no ALT). Overall, 29 of 1569 patients (1.8%) had IBD-LD. IBD-LD was diagnosed in 1 of 661 (0.15%) of patients with both ALT and GGT ≤ 50 IU/L compared with 21 of 42 (50%) of patients with both ALT and GGT > 50 (odds ratio 660, P < 0.0001). Of the 29 patients with IBD-LD, 21 had PSC, 2 had AIH, and 6 had overlap syndrome. IBD-LD was more common in patients with ulcerative colitis and IBD-unclassified (indeterminate colitis) than in those with Crohn disease (4% vs 0.8%, respectively, P < 0.001). CONCLUSIONS: Elevation of both ALT and GGT within 90 days after the diagnosis of IBD is associated with a markedly increased likelihood of IBD-LD. Both ALT and GGT levels should be measured in all of the pediatric patients newly diagnosed as having IBD.

Paradoxical attenuation of autoimmune hepatitis by oral isoniazid in wild-type and N-acetyltransferase-deficient mice.

Isoniazid (INH) treatment can cause serious liver injury and autoimmunity. There are now several lines of evidence that INH-induced liver injury is immune mediated, but this type of liver injury has not been reproduced in animals, possibly because immune tolerance is the dominant response of the liver. In this study, we immunized mice with isonicotinic acid (INA)-modified proteins and Freund's adjuvant, which led to mild experimental autoimmune hepatitis (EAH) with an increase in cells staining positive for F4/80, CD11b, CD8, CD4, CD45R, and KI67. We expected that subsequent treatment of mice with oral INH would lead to more serious immune-mediated liver injury, but paradoxically it markedly attenuated the EAH caused by immunization with INA-modified hepatic proteins. In addition, patients of the slow acetylator phenotype are at increased risk of INH-induced liver injury. Treatment of arylamine N-acetyltransferase-deficient Nat1/2(-/-) mice with INH for up to 5 weeks produced mild increases in glutamate and sorbitol dehydrogenase activities, but not severe liver injury. Female Nat1/2(-/-) mice treated with INH for 1, 3, or 7 days developed steatosis, an increase in Oil Red O staining, and abnormal mitochondrial morphology in the liver. A decrease in M1 and an increase in M2a and M2b macrophages was observed in female Nat1/2(-/-) mice treated with INH for 1, 3, or 7 days; these changes returned to baseline levels by day 35. These data indicate that INH has immunosuppressive effects, even though it is also known to induce autoantibody production and a lupus-like autoimmune syndrome in humans.

Detection of anti-lactoferrin antibodies and anti-myeloperoxidase antibodies in autoimmune hepatitis: a retrospective study.

Anti-lactoferrin antibodies (ALA) and anti-myeloperoxidase antibodies (AMPA) are specific serological markers for autoimmune hepatitis (AIH). The project aimed to detect ALA and AMPA and explore their clinical significances in AIH patients. 59 AIH patients, 217 non AIH patients, and 50 healthy controls were enrolled in this study. ALA and AMPA were detected by ELISA. Antineutropil cytoplasmic antibodies (ANCA) and anti-smooth muscle antibodies (ASMA) were examined by indirect immunofluorescence. Antimitochondrial antibody M2 subtype (AMA-M2), anti-liver kidney microsomal antibody Type 1 (LKM1), anti-liver cytosol antibody Type 1 (LC1), and anti-soluble liver antigen/liver-pancreas antibodies (SLA/LP) were tested by immunoblot. The positivity for ALA was 18.6% in AIH group, only one patient in non-AIH group was positive for ALA; the positivity for AMPA was 59.3% in AIH group, with significant differences (P < 0.01) compared with other groups. The specificities for ALA and AMPA were 99.63% and 97.75%; the sensitivities were 18.64% and 59.32%; and the accuracy rates were 84.97% and 90.80%, respectively. A certain correlation was observed between ALA and SLA/LP, AMPA and ANCA, ASMA in AIH group. ALA and AMPA were associated with AIH, and had high clinical diagnostic value. Co-detection with other relative autoantibodies could play an important role in differential diagnosis of AIH.

Development of a spontaneous liver disease resembling autoimmune hepatitis in mice lacking tyro3, axl and mer receptor tyrosine kinases.

Autoimmune hepatitis (AIH) is a severe type of chronic liver disease. The lack of appropriate animal models has resulted in a limited understanding regarding the etiology of AIH. Here, we demonstrated that mice deficient in Tyro3, Axl and Mer (TAM) receptor tyrosine kinases (RTKs) developed persistent inflammatory liver damage resembling AIH. Tyro3(-/-)Axl(-/-)Mer(-/-) triple mutant (TAM(-/-)) mice exhibited chronic hepatitis, manifested by progressive appearance of interface hepatitis, immune cell infiltrations and elevated inflammatory cytokine levels in the liver. Accordingly, increased levels of transaminases were observed. Moreover, characteristic autoantibodies and high levels of plasma immunoglobulin G for AIH were detected as TAM(-/-) mice aged. Finally, we provided evidence that the liver damage in TAM(-/-) mice mainly result from bone marrow-derived cells and could be rescued by transplantation of WT bone marrow cells. Results suggest that TAM RTKs play an important role in maintaining immune tolerance of the liver.

Predictors of poor outcome in patients w ith autoimmune hepatitis: a population-based study.

UNLABELLED: Autoimmune hepatitis (AIH) can lead to cirrhosis, hepatic failure, and death. We aimed to identify predictors of advanced liver fibrosis at presentation, predictors of incomplete response to initial immunosuppression, and predictors of poor liver-related outcomes in the population-based AIH cohort from Canterbury, New Zealand. Cases diagnosed after 1980 that fulfilled standard diagnostic criteria were included. Cases were censored at death or liver transplantation and had a median follow-up of 9 years. Analyses were performed with Cox proportional hazards regression and logistic binary regression. The times to event outcomes were summarized using Kaplan-Meier curves. A total of 133 AIH patients were included. Predictors for advanced liver fibrosis at diagnosis were age at presentation of ≤20 years or >60 years (P = 0.02), serum albumin <36 g/L (P < 0.01), platelet <150 U/L (P < 0.01), and International Normalized Ratio (INR) >1.2 (P < 0.01). The only independent predictor for incomplete normalization of alanine aminotransferase (ALT) at 6 months was age at presentation ≤20 years. Independent predictors of poor liver-related outcomes were incomplete normalization of ALT at 6 months (P < 0.01), serum albumin <36 g/L (P < 0.01), and age at presentation of ≤20 years or >60 years (P = 0.01). Kaplan-Meier estimates showed that 10-year adverse liver event-free survival was 80% for age at presentation ≤20 years and >60 years, and 93% and 100% for age at presentation between 21-40 years and 41-60 years, respectively. CONCLUSION: Incomplete normalization of ALT at 6 months, low serum albumin concentration at diagnosis, and age at presentation of ≤20 years or >60 years were significant independent predictors of liver-related death or requirement for liver transplantation. Histological cirrhosis at diagnosis was not associated with poor prognosis and did not influence the response to initial immunosuppressive treatment. (HEPATOLOGY 2013;57:2399-2406).

p38 mitogen-activated protein kinase (p38 MAPK)-mediated autoimmunity: lessons to learn from ANCA vasculitis and pemphigus vulgaris.

Evidence is beginning to accumulate that p38 mitogen activated protein kinase (p38 MAPK) signaling pathway plays an important role in the regulation of cellular and humoral autoimmune responses. The exact mechanisms and the degree by which the p38 MAPK pathway participates in the immune-mediated induction of diseases have started to emerge. This review discusses the recent advances in the molecular dissection of the p38 MAPK pathway and the findings generated by reports investigating its role in the pathogenesis of autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, and autoimmune hepatitis. Application of newly-developed protocols based on sensitive flow cytometric detection has proven to be a useful tool in the investigation of the phosphorylation of p38 MAPK within different peripheral blood mononuclear cell populations and may help us to better understand the enigmatic role of this signaling cascade in the induction of autoimmunity as well as its role in immunosuppressive-induced remission. Special attention is paid to reported data proposing a specific role for autoantibody-induced activation of p38 MAPK-mediated immunopathology in the pathogenesis of autoimmune blistering diseases and anti-neutrophilic antibody-mediated vasculitides.

Liver fibrosis and hepatocyte apoptosis are attenuated by GKT137831, a novel NOX4/NOX1 inhibitor in vivo.

Reactive oxygen species (ROS) play a key role in chronic liver injury and fibrosis. Homologs of NADPH oxidases (NOXs) are major sources of ROS, but the exact role of the individual homologs in liver disease is unknown. Our goal was to determine the role of NOX4 in liver fibrosis induced by bile duct ligation (BDL) with the aid of the pharmacological inhibitor GKT137831, and genetic deletion of NOX4 in mice. GKT137831 was either applied for the full term of BDL (preventive arm) or started at 10 day postoperatively (therapeutic arm). Primary hepatic stellate cells (HSC) from control mice with and without BDL were analyzed and the effect of NOX4 inhibition on HSC activation was also studied. FasL or TNFα/actinomycin D-induced apoptosis was studied in wild-type and NOX4(-/-) hepatocytes. NOX4 was upregulated by a TGF-ß/Smad3-dependent mechanism in HSC. Downregulation of NOX4 decreased ROS production and the activation of NOX4(-/-) HSC was attenuated. NOX4(-/-) hepatocytes were more resistant to FasL or TNFα/actinomycin D-induced apoptosis. Similarly, after pharmacological NOX4 inhibition, ROS production, the expression of fibrogenic markers, and hepatocyte apoptosis were reduced. NOX4 was expressed in human livers with stage 2-3 autoimmune hepatitis. Fibrosis was attenuated by the genetic deletion of NOX4. BDL mice gavaged with GKT137831 in the preventive or the therapeutic arm displayed less ROS production, significantly attenuated fibrosis, and decreased hepatocyte apoptosis. In conclusion, NOX4 plays a key role in liver fibrosis. GKT137831 is a potent inhibitor of fibrosis and hepatocyte apoptosis; therefore, it is a promising therapeutic agent for future translational studies.

Human Th17 cells express high levels of enzymatically active dipeptidylpeptidase IV (CD26).

Dipeptidylpeptidase IV (CD26) is a multifunctional ectoenzyme involved in T cell activation that has been implicated in autoimmune pathophysiology. Because IL-17-producing CD4(+) T cells (Th17 cells) are important mediators of autoimmune disease, we analyzed the expression of CD26 and its enzymatic function on human Th17 cells. Analysis of CD26 expression on different CD4(+) T helper subsets showed that CD26 expression is highest on CD4(+) T cells producing type 17 cytokines (e.g., IL-22, IL-17, GM-CSF, or TNF) compared with Th1, Th2, and regulatory T cells. Phenotypic analysis revealed that CD26(++)CD4(+) T cells express the type 17 differentiation molecules CD161, CCR6, lL-23R, and retinoic acid-related orphan receptor-γt. Furthermore, sorted CD26(++)CD4(+) T cells contain >90-98% of Th17 cells, indicating that CD26(++) T cells harbor the Th17 lineage. A comparison with CD161 and CCR6 indicated that analysis of CD26 coexpression may improve the phenotypic characterization of Th17 cells. Of note, CD26(++) Th17 cells are enriched in the inflamed tissue of patients with hepatitis and inflammatory bowel disease. Functional analysis in migration assays revealed that CD26 expressed on Th17 cells is enzymatically active. Indeed, CD26 negatively regulates the chemotactic CD4(+) T cell response to the inflammatory chemokines CXCL9-12 that can be restored by pharmacological blockade of the enzymatic center of CD26. In summary, these results strongly suggest that CD26 may contribute to the orchestration of the immune response by Th17 cells in human inflammatory diseases. They also suggest that the phenotypic analysis of Th17 cells may be facilitated by determination of CD26 expression.

The CYP2D6 animal model: how to induce autoimmune hepatitis in mice.

Autoimmune hepatitis is a rare but life threatening autoimmune disease of the liver of unknown etiology(1,2). In the past many attempts have been made to generate an animal model that reflects the characteristics of the human disease (3-5). However, in various models the induction of disease was rather complex and often hepatitis was only transient(3-5). Therefore, we have developed a straightforward mouse model that uses the major human autoantigen in type 2 autoimmune hepatitis (AIH-2), namely hCYP2D6, as a trigger(6). Type 1 liver-kidney microsomal antibodies (LKM-1) antibodies recognizing hCYP2D6 are the hallmark of AIH-2(7,8). Delivery of hCYP2D6 into wildtype FVB or C57BL/6 mice was by an Adenovirus construct (Ad-2D6) that ensures a direct delivery of the triggering antigen to the liver. Thus, the ensuing local inflammation generates a fertile field(9) for the subsequent development of autoimmunity. A combination of intravenous and intraperitoneal injection of Ad-2D6 is the most effective route to induce a long-lasting autoimmune damage to the liver (section 1). Here we provide a detailed protocol on how autoimmune liver disease is induced in the CYP2D6 model and how the different aspects of liver damage can be assessed. First, the serum levels of markers indicating hepatocyte destruction, such as aminotransferases, as well as the titers of hCYP2D6 antibodies are determined by sampling blood retroorbitaly (section 2). Second, the hCYP2D6-specific T cell response is characterized by collecting lymphocytes from the spleen and the liver. In order to obtain pure liver lymphocytes, the livers are perfused by PBS via the portal vein (section 3), digested in collagen and purified over a Percoll gradient (section 4). The frequency of hCYP2D6-specific T cells is analyzed by stimulation with hCYP2D6 peptides and identification of IFNγ-producing cells by flow cytometry (section 5). Third, cellular infiltration and fibrosis is determined by immunohistochemistry of liver sections (section 6). Such analysis regimen has to be conducted at several times after initiation of the disease in order to prove the chronic nature of the model. The magnitude of the immune response characterized by the frequency and activity of hCYP2D6-specific T and/or B cells and the degree of the liver damage and fibrosis have to be assessed for a subsequent evaluation of possible treatments to prevent, delay or abrogate the autodestructive process of the liver.