Mechanism of autoimmune hepatic fibrogenesis induced by an adenovirus encoding the human liver autoantigen cytochrome P450 2D6

B and T cells: (Still) the dominant orchestrators in autoimmune hepatitis

Autoimmune hepatitis (AIH) is a severe hepatopathy characterized by hypergammaglobulinemia, presence of serum autoantibodies and histological appearance of interface hepatitis. Liver damage in AIH is initiated by the presentation of a liver autoantigen to uncommitted Th0 lymphocytes, followed by a cascade of effector immune responses culminating with the production of inflammatory cytokines, activation of cytotoxic cells and subsequent hepatocyte injury. B cells actively participate in AIH liver damage by presenting autoantigens to uncommitted T lymphocytes. B cells also undergo maturation into plasma cells that are responsible for production of immunoglobulin G and autoantibodies, which mediate antibody dependent cell cytotoxicity. Perpetuation of effector immunity with consequent progression of liver damage is permitted by impairment in regulatory T cells (Tregs), a lymphocyte subset central to the maintenance of immune homeostasis. Treg impairment in AIH is multifactorial, deriving from numerical decrease, reduced suppressive function, poor response to IL-2 and less stable phenotype. In this review, we discuss the role of B and T lymphocytes in the pathogenesis of AIH. Immunotherapeutic strategies that could limit inflammation and halt disease progression while reconstituting tolerance to liver autoantigens are also reviewed and discussed.

Autoimmune Hepatitis: Pathophysiology

Genome-wide association analyses suggest that HLA genes including HLA-DRB*0301, HLA-DRB*0401, and HLA-B*3501 as well as non-HLA genes including CD28/CTLA4/ICOS and SYNPR increased AIH susceptibility. The destruction of hepatocytes is the result of the imbalance between proinflammatory cells and immunosuppressive cells, especially the imbalance between Tregs and Th17 cells. The microbiome in patients with AIH is decreased in diversity with a specific decline in Bifidobacterium and enrichment in Veillonella and Faecalibacterium. Recent evidence has demonstrated the pathogenic role of E. gallinarum and L.reuteri in inducing autoimmunity in the liver.

Incorporating the Molecular Mimicry of Environmental Antigens into the Causality of Autoimmune Hepatitis

Molecular mimicry between foreign and self-antigens has been implicated as a cause of autoimmune hepatitis in experimental models and cross-reacting antibodies in patients. This review describes the experimental and clinical evidence for molecular mimicry as a cause of autoimmune hepatitis, indicates the limitations and uncertainties of this premise, and encourages investigations that assess diverse environmental antigens as sources of disease-relevant molecular mimics. Pertinent articles were identified in PubMed using multiple search phrases. Several pathogens have linear or conformational epitopes that mimic the self-antigens of autoimmune hepatitis. The occurrence of an acute immune-mediated hepatitis after vaccination for severe acute respiratory syndrome (SARS)-associated coronavirus 2 (SARS-CoV-2) has suggested that vaccine-induced peptides may mimic disease-relevant tissue antigens. The intestinal microbiome is an under-evaluated source of gut-derived antigens that could also engage in molecular mimicry. Chaperone molecules may enhance the pathogenicity of molecular mimics, and they warrant investigation. Molecular mimics of immune dominant epitopes within cytochrome P450 IID6, the autoantigen most closely associated with autoimmune hepatitis, should be sought in diverse environmental antigens and assessed for pathogenicity. Avoidance strategies, dietary adjustments, vaccine improvement, and targeted manipulation of the intestinal microbiota may emerge as therapeutic possibilities. In conclusion, molecular mimicry may be a missing causality of autoimmune hepatitis. Molecular mimics of key immune dominant epitopes of disease-specific antigens must be sought in diverse environmental antigens. The ubiquity of molecular mimicry compels rigorous assessments of peptide mimics for immunogenicity and pathogenicity in experimental models. Molecular mimicry may complement epigenetic modifications as causative mechanisms of autoimmune hepatitis.

Animal Models for Autoimmune Hepatitis: Are Current Models Good Enough?

Autoimmune liver diseases like autoimmune hepatitis, primary biliary cholangitis, primary sclerosing cholangitis, and IgG4-related cholangitis are chronic inflammatory diseases of the liver with an autoimmune background. The therapy of autoimmune hepatitis targets the autoreactive immune system and is largely dependent on the use of glucocorticoids and cytostatic drugs. In contrast, the treatment of cholestatic autoimmune liver diseases is restricted to the use of secondary or semi-synthetic bile acids, like ursodeoxycholic acid or obeticholic acid. Although the management of the disease using such drugs works well for the majority of patients, many individuals do not respond to standard therapy. In addition, chronic treatment with glucocorticoids results in well-known side effects. Further, the use of bile acids is a symptomatic therapy that has no direct immunomodulatory effect. Thus, there is still a lot of room for improvement. The use of animal models has facilitated to elucidate the pathogenesis of autoimmune liver diseases and many potential target structures for immunomodulatory therapies have been identified. In this review, we will focus on autoimmune hepatitis for which the first animal models have been established five decades ago, but still a precise treatment for autoimmune hepatitis, as obtainable for other autoimmune diseases such as rheumatoid arthritis or multiple sclerosis has yet to be introduced. Thus, the question arises if our animal models are too far from the patient reality and thus findings from the models cannot be reliably translated to the patient. Several factors might be involved in this discrepancy. There is first and foremost the genetic background and the inbred status of the animals that is different from human patients. Here the use of humanized animals, such as transgenic mice, might reduce some of the differences. However, there are other factors, such as housing conditions, nutrition, and the microbiome that might also play an important role. This review will predominantly focus on the current status of animal models for autoimmune hepatitis and the possible ways to overcome discrepancies between model and patient.

Pathogenesis of Autoimmune Hepatitis-Cellular and Molecular Mechanisms

Pediatric autoimmune liver disorders include autoimmune hepatitis (AIH), autoimmune sclerosing cholangitis (ASC), and de novo AIH after liver transplantation. AIH is an idiopathic disease characterized by immune-mediated hepatocyte injury associated with the destruction of liver cells, causing inflammation, liver failure, and fibrosis, typically associated with autoantibodies. The etiology of AIH is not entirely unraveled, but evidence supports an intricate interaction among genetic variants, environmental factors, and epigenetic modifications. The pathogenesis of AIH comprises the interaction between specific genetic traits and molecular mimicry for disease development, impaired immunoregulatory mechanisms, including CD4+ T cell population and Treg cells, alongside other contributory roles played by CD8+ cytotoxicity and autoantibody production by B cells. These findings delineate an intricate pathway that includes gene to gene and gene to environment interactions with various drugs, viral infections, and the complex microbiome. Epigenetics emphasizes gene expression through hereditary and reversible modifications of the chromatin architecture without interfering with the DNA sequence. These alterations comprise DNA methylation, histone transformations, and non-coding small (miRNA) and long (lncRNA) RNA transcriptions. The current first-line therapy comprises prednisolone plus azathioprine to induce clinical and biochemical remission. Further understanding of the cellular and molecular mechanisms encountered in AIH may depict their impact on clinical aspects, detect biomarkers, and guide toward novel, effective, and better-targeted therapies with fewer side effects.

Dysfunctional Immune Regulation in Autoimmune Hepatitis: From Pathogenesis to Novel Therapies

Autoimmune hepatitis (AIH) is a chronic inflammatory disorder characterized by hypergammaglobulinemia, presence of serum autoantibodies and histological features of interface hepatitis. AIH therapeutic management still relies on the administration of corticosteroids, azathioprine and other immunosuppressants like calcineurin inhibitors and mycophenolate mofetil. Withdrawal of immunosuppression often results in disease relapse, and, in some cases, therapy is ineffective or associated with serious side effects. Understanding the mechanisms underlying AIH pathogenesis is therefore of paramount importance to develop more effective and well tolerated agents capable of restoring immunotolerance to liver autoantigens. Imbalance between effector and regulatory cells permits liver damage perpetuation and progression in AIH. Impaired expression and regulation of CD39, an ectoenzyme key to immunotolerance maintenance, have been reported in Tregs and effector Th17-cells derived from AIH patients. Interference with these altered immunoregulatory pathways may open new therapeutic avenues that, in addition to limiting aberrant inflammatory responses, would also reconstitute immune homeostasis. In this review, we highlight the most recent findings in AIH immunopathogenesis and discuss how these could inform and direct the development of novel therapeutic tools.

Animal Models of Autoimmune Liver Diseases: a Comprehensive Review

Autoimmune liver diseases (AILDs) are potentially life-threatening chronic liver diseases which include autoimmune hepatitis, primary biliary cholangitis, primary sclerosing cholangitis, and recently characterized IgG4-related sclerosing cholangitis. They are caused by immune attack on hepatocytes or bile ducts, with different mechanisms and clinical manifestations. The etiologies of AILDs include a susceptible genetic background, environment insults, infections, and changes of commensal microbiota, but remain complicated. Understanding of the underlying mechanisms of AILDs is mandatory for early diagnosis and intervention, which is of great importance for better prognosis. Thus, animal models are developed to mimic the pathogenesis, find biomarkers for early diagnosis, and for therapeutic attempts of AILDs. However, no animal models can fully recapitulate features of certain AILD, especially the late stages of diseases. Certain limitations include different living condition, cell composition, and time frame of disease development and resolution. Moreover, there is no IgG4 in rodents which exists in human. Nevertheless, the understanding and therapy of AILDs have been greatly advanced by the development and mechanistic investigation of animal models. This review will provide a comprehensive overview of traditional and new animal models that recapitulate different features and etiologies of distinct AILDs.

Effects of adenovirus-induced hepatocyte damage on chronic bile duct inflammation in a sclerosing cholangitis mouse model

BACKGROUND & AIMS

Four major autoimmune diseases target the liver. They develop because of bile duct destruction, leading to chronic cholestasis or result from hepatocyte damage like autoimmune hepatitis (AIH). Interestingly, some patients simultaneously show features of both cholangitis and AIH. Our goal was to mimic such concurrent characteristics in a mouse model that would help deciphering mechanisms possibly involved in an inflammatory crosstalk between cholestatic disease and hepatitis.

METHODS

Mdr2^-/- mice, which spontaneously develop sclerosing cholangitis because of accumulation of toxic bile salts, were infected with adenovirus (Ad) encoding human Cytochrome P4502D6 (hCYP2D6), the major target autoantigen in type-2 AIH, to trigger hepatocyte injury. Wild type FVB mice were controls.

RESULTS

Resulting Ad-Mdr2^-/- mice presented with cholangitis, fibrosis and cellular infiltrations that were higher than in Mdr2^-/- or Ad-FVB mice. Increased levels of anti-neutrophil cytoplasmic antibodies but similar anti-hCYP2D6 antibody titres were detected in Ad-Mdr2^-/- compared to Mdr2^-/- and Ad-FVB mice respectively. IFNγ-expressing hCYP2D6-specific CD4 T cells declined, whereas hCYP2D6-specific CD8 T cells increased in Ad-Mdr2^-/- compared to Ad-FVB mice. The overall T cell balance in Ad-Mdr2^-/- mice was a combination of a type 17 T cell response typically found in Mdr2^-/- mice with a type 1 dominated T cell response characteristic for Ad-FVB mice. Simultaneously, the type 2 T cell compartment was markedly reduced.

CONCLUSIONS

Experimental hepatitis induction in a mouse with sclerosing cholangitis results in a disorder which represents not simply the sum of the individual characteristics but depicts a more complex entity which urges on further analysis.

The JAK inhibitor tofacitinib ameliorates immune‑mediated liver injury in mice

The prevalence of immune-mediated liver diseases such as autoimmune liver disease or viral hepatitis has increased in recent years, and the side effects of pre-existing treatments are a worldwide problem. Regulatory T cells (Tregs) and T helper 17 (Th17) cells play important roles in the development of immune-mediated hepatitis and may serve as potential therapeutic targets. Tofacitinib, a new Janus kinase (JAK) inhibitor, is under investigation for the treatment of rheumatoid arthritis; it is also helpful in treating ulcerative colitis and psoriasis. The roles of tofacitinib were investigated in conferring protection against immune-mediated liver injury in mice. T cell-mediated hepatitis was induced by concanavalin A (ConA). The mice in the treatment groups were administered with tofacitinib intragastrically before the ConA injection. Histopathological examination was performed by hematoxylin and eosin (H&E) staining, and the serum transaminase and inflammatory cytokine levels were determined using an automatic biochemistry analysis apparatus or cytometric bead array (CBA) kits. Flow cytometric analysis was used to detect Tregs and Th17 cells. Tofacitinib significantly decreased the hepatic injury induced by ConA and prominently decreased the liver transaminase level. The secretion of several anti-inflammatory cytokines such as interleukin (IL)-10 was upregulated in mice from the treatment group, compared to that in mice treated with ConA alone, while the expression of interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) decreased. Tofacitinib treatment increased the number of Tregs and reduced the number of Th17 cells. Furthermore, tofacitinib could relieve liver fibrosis under conditions of autoimmune hepatitis (AIH). The present results indicated that tofacitinib improved immune-mediated hepatitis and restored the impaired Treg/Th17 cell ratio, which suggests that it may serve as a novel treatment approach for immune-mediated liver diseases.

Influence of hepatic fibrosis and inflammation: Correlation between histopathological changes and Gd-EOB-DTPA-enhanced MR imaging

Objective

To evaluate the influence of an active inflammatory process in the liver on Gd-EOB-DTPA-enhanced MR imaging in patients with different degrees of fibrosis/cirrhosis.

Material and methods

Overall, a number of 91 patients (61 men and 30 women; mean age 58 years) were included in this retrospective study. The inclusion criteria for this study were Gd-EOB-DTPA-enhanced MRI of the liver and histopathological evaluation of fibrotic and inflammatory changes. T1-weighted VIBE sequences of the liver with fat suppression were evaluated to determine the relative signal change (RE) between native and hepatobiliary phase (20min). In simple and multiple linear regression analyses, the influence of liver fibrosis/cirrhosis (Ishak score) and the histopathological degree of hepatitis (Modified Hepatic Activity Index, mHAI) on RE were evaluated.

Results

RE decreased significantly with increasing liver fibrosis/cirrhosis (p < 0.001) and inflammation (mHAI, p = 0.004). In particular, a correlation between RE and periportal or periseptal boundary zone hepatitis (moth feeding necrosis, mHAI A, p = 0.001) and portal inflammation (mHAI D, p < 0.001) was observed. In multiple linear regression analysis, both the degree of inflammation and the degree of fibrosis were significant predictors for RE (p < 0.01).

Conclusion

The results of this study suggest that the MR-based hepatic enhancement index RE is not only influenced by the degree of fibrosis, but also by the degree of inflammation.

Dexamethasone Conjugation to Biodegradable Avidin-Nucleic-Acid-Nano-Assemblies Promotes Selective Liver Targeting and Improves Therapeutic Efficacy in an Autoimmune Hepatitis Murine Model

Steroids are the standard therapy for autoimmune hepatitis (AIH) but the long-lasting administration is hampered by severe side effects. Methods to improve the tropism of the drug toward the liver are therefore required. Among them, conjugation to nanoparticles represents one possible strategy. In this study, we exploited the natural liver tropism of Avidin-Nucleic-Acid-Nano-Assemblies (ANANAS) to carry dexamethasone selectively to the liver in an AIH animal model. An acid-labile biotin-hydrazone linker was developed for reversible dexamethasone loading onto ANANAS. The biodistribution, pharmacokinetics and efficacy of free and ANANAS-linked dexamethasone (ANANAS-Hz-Dex) in healthy and AIH mice were investigated upon intraperitoneal administration. In ANANAS-treated animals, the free drug was detected only in the liver. Super-resolution microscopy showed that nanoparticles segregate inside lysosomes of liver immunocompetent cells, mainly involved in AIH progression. In agreement with these observational results, chronic low-dose treatment with ANANAS-Hz-Dex reduced the expression of liver inflammation markers and, in contrast to the free drug, also the levels of circulating AIH-specific autoantibodies. These data suggest that the ANANAS carrier attenuates AIH-related liver damage without drug accumulation in off-site tissues. The safety and biodegradability of the ANANAS carrier make this formulation a promising tool for the treatment of autoimmune liver disorders.

In vivo confirmation of altered hepatic glucose metabolism in patients with liver fibrosis/cirrhosis by 18F-FDG PET/CT

OBJECTIVE

The aim of this study was to assess the value of ¹⁸F-FDG PET/CT for quantitative assessment of hepatic metabolism in patients with different stages of liver fibrosis/cirrhosis.

MATERIALS AND METHODS

¹⁸F-FDG PET/CT scans of 37 patients either with or without liver fibrosis/cirrhosis, classified according to the METAVIR score (F0-F4) obtained from histopathological analysis of liver specimen, were analyzed retrospectively and classified as follows: no liver fibrosis (F0, n = 6), mild liver fibrosis (F1, n = 11), advanced liver fibrosis (F2, n = 6), severe liver fibrosis (F3, n = 5), and liver cirrhosis (F4, n = 11). The liver-to-blood ratio (LBR, scan time corrected for a reference time of 75 min) was compared between patient groups.

RESULTS

Patients with liver fibrosis or cirrhosis (≥ F1; LBR 1.53 ± 0.35) showed a significant higher LBR than patients with normal liver parenchyma (F0, 1.08 ± 0.23; P = 0.004). In direct comparison, LBR increased up to the advanced stage of liver fibrosis (F2; 2.00 ± 0.40) and decreased until liver cirrhosis is reached (F4, 1.32 ± 0.14).

CONCLUSION

Functional changes in liver parenchyma during liver fibrosis/cirrhosis affect hepatic glucose metabolism and significantly differ between stages of liver fibrosis/cirrhosis, classified according to the METAVIR scoring system, as demonstrated by LBR quantification by ¹⁸F-FDG PET/CT.

Pathogens and autoimmune hepatitis

Autoimmune hepatitis (AIH) is a severe form of hepatitis resulting in the autoimmune-mediated destruction of the liver parenchyma. Whereas many of the immunopathogenic events have been elucidated and some of the drivers of the disease have been identified, little is known about the aetiology of the disease. There are certain risk factors, such as particular human leucocyte antigen (HLA) haplotypes, that enhance the susceptibility for AIH or influence the severity of the disease. However, as for many other autoimmune diseases, the mere presence of such risk factors does not warrant the occurrence of the disease. Not all individuals carrying risk factors develop AIH, and not all patients with AIH are carriers of high-risk alleles. Thus, additional environmental factors need to be considered as triggers for AIH. Environmental factors include diet, sunlight exposure, stress, medication and hygiene, as well as pathogen infections and vaccinations. This review discusses if pathogens should be considered as triggers for the initiation and/or propagation of AIH.

Animal models of autoimmune hepatitis

Many animal models for autoimmune hepatitis (AIH) have been described in the past. Most models had to deal with the relative immunosuppressive environment of the liver. Therefore, some models used a combination of several triggering factors often on a susceptible background to generate an aggressive immune response that targets the liver. In addition, in order to be able to track the immune response the models used specific model autoantigens as targets that are either not present or have not been identified as a natural autoantigen in AIH patients. Thereby the feasibility of such models is somewhat questionable. Although many historic approaches included challenges of experimental animals with liver homogenates it was only in the last decade that natural occurring liver autoantigens have been used in animal models. This article reflects on the requirements for breaking liver tolerance and on how an ideal experimental model for AIH would look like. In addition, it discusses historic as well as recent animal models in the context of feasibility of induction, similarity of the clinical outcome to human AIH, and gain of knowledge for possible future therapies.

Junctional adhesion molecules JAM-B and JAM-C promote autoimmune-mediated liver fibrosis in mice

Fibrosis remains a serious health concern in patients with chronic liver disease. We recently reported that chemically induced chronic murine liver injury triggers increased expression of junctional adhesion molecules (JAMs) JAM-B and JAM-C by endothelial cells and de novo synthesis of JAM-C by hepatic stellate cells (HSCs). Here, we demonstrate that biopsies of patients suffering from primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC) or autoimmune hepatitis (AIH) display elevated levels of JAM-C on portal fibroblasts (PFs), HSCs, endothelial cells and cholangiocytes, whereas smooth muscle cells expressed JAM-C constitutively. Therefore, localization and function of JAM-B and JAM-C were investigated in three mouse models of autoimmune-driven liver inflammation. A PBC-like disease was induced by immunization with 2-octynoic acid-BSA conjugate, which resulted in the upregulation of both JAMs in fibrotic portal triads. Analysis of a murine model of PSC revealed a role of JAM-C in PF cell-cell adhesion and contractility. In mice suffering from AIH, endothelial cells increased JAM-B level and HSCs and capsular fibroblasts became JAM-C-positive. Most importantly, AIH-mediated liver fibrosis was reduced in JAM-B^-/- mice or when JAM-C was blocked by soluble recombinant JAM-C. Interestingly, loss of JAM-B/JAM-C function had no effect on leukocyte infiltration, suggesting that the well-documented function of JAMs in leukocyte recruitment to inflamed tissue was not effective in the tested chronic models. This might be different in patients and may even be complicated by the fact that human leukocytes express JAM-C. Our findings delineate JAM-C as a mediator of myofibroblast-operated contraction of the liver capsule, intrahepatic vasoconstriction and bile duct stricture. Due to its potential to interact heterophilically with endothelial JAM-B, JAM-C supports also HSC/PF mural cell function. Together, these properties allow JAM-B and JAM-C to actively participate in vascular remodeling associated with liver/biliary fibrosis and suggest them as valuable targets for anti-fibrosis therapies.

The differential organogenesis and functionality of two liver-draining lymph nodes in mice

The liver is an immunological organ. However, fundamental knowledge concerning liver-draining lymph nodes (LNs), which have been newly identified in mice as the portal and celiac LNs, is still lacking. Here, we revealed that the portal LN and celiac LN drain liver lymph through different lymphatic vessels. Although both the portal LN and celiac LN possess typical structures, they have different cell compositions. Interestingly, these two LNs form at different times during fetal development. Moreover, the organogenesis of the celiac LN, but not the portal LN, is controlled by the transcription factor NFIL3. Furthermore, the portal LN and celiac LN also perform different functions. The celiac LN is the predominant site of liver antiviral immune responses, whereas the portal LN functions in the in situ induction of dietary antigen-specific regulatory T cells. In conclusion, the portal LN and celiac LN are two independent liver-draining LNs with different organogenesis histories and separate functions in maintaining immune homeostasis in the liver.

Immunopathogenic Mechanisms of Autoimmune Hepatitis: How Much Do We Know from Animal Models?

Autoimmune hepatitis (AIH) is characterized by a progressive destruction of the liver parenchyma and a chronic fibrosis. The current treatment of autoimmune hepatitis is still largely dependent on the administration of corticosteroids and cytostatic drugs. For a long time the development of novel therapeutic strategies has been hampered by a lack of understanding the basic immunopathogenic mechanisms of AIH and the absence of valid animal models. However, in the past decade, knowledge from clinical observations in AIH patients and the development of innovative animal models have led to a situation where critical factors driving the disease have been identified and alternative treatments are being evaluated. Here we will review the insight on the immunopathogenesis of AIH as gained from clinical observation and from animal models.

Transgenic animal models of type 2 autoimmune hepatitis

Autoimmune hepatitis (AIH) is a chronic liver disease putatively caused by loss of tolerance to hepatocyte specific autoantigens. It is currently divided into types 1 and 2, based on the expression of autoantibodies. Autoantigenic epitopes have been identified only for the less frequent type 2 AIH. Many type 2 AIH mouse models have been well developed in recent years. This review focuses on some kinds of well-established type 2 AIH mouse models.

Treatment of cholestatic fibrosis by altering gene expression of Cthrc1: Implications for autoimmune and non-autoimmune liver disease

Collagen triple helix repeat containing-1 (Cthrc1) is a documented specific inhibitor of TGF-β signaling. Based on this observation, we developed the hypothesis that knocking in/knocking out the Cthrc1 gene in murine models of cholestasis would alter the natural history of cholestatic fibrosis. To study this thesis, we studied two murine models of fibrosis, first, common bile duct ligation (CBDL) and second, feeding of 3, 5-diethoxy-carbonyl-1, 4-dihydrocollidine (DDC). In both models, we administered well-defined adenoviral vectors that expressed either Cthrc1 or, alternatively, a short hairpin RNA (shRNA)-targeting Cthrc1 either before or after establishment of fibrosis. Importantly, when Cthrc1 gene expression was enhanced, we noted a significant improvement of hepatic fibrosis, both microscopically and by analysis of fibrotic gene expression. In contrast, when Cthrc1 gene expression was deleted, there was a significant exacerbation of fibrosis. To identify the mechanism of action of these significant effects produced by knocking in/knocking out Cthrc gene expression, we thence studied the interaction of Cthrc1 gene expression using hepatic stellate cells (HSCs) and human LX-2 cells. Importantly, we demonstrate that Cthrc1 is induced by TGF-β1 via phospho-Smad3 binding to the promoter with subsequent transcription activation. In addition, we demonstrate that Cthrc1 inhibits TGF-β signaling by accelerating degradation of phospho-Smad3 through a proteosomal pathway. Importantly, the anti-fibrotic effects can be recapitulated with a truncated fragment of Cthrc1. In conclusion, our findings uncover a critical negative feedback regulatory loop in which TGF-β1 induces Cthrc1, which can attenuate fibrosis by accelerating degradation of phospho-Smad3.

The challenge of treating orphan disease

Uncommon or orphan diseases are less frequently addressed in mainstream medical journals and, as a consequence, their understanding and clinical recognition may rely on case series or anecdotal data with limited guidelines and management directions. The study of selected underrepresented autoimmune and allergy conditions is the subject of the present issue of Clinical Reviews in Allergy and Immunology to provide peculiar perspectives on common and rare themes. First, allergy remains a major concern for physicians worldwide despite the limited developments over the past years, particularly for antigens such as mite or Alternaria alternata, and due to the increasing incidence of drug hypersensitivity. Second, the female predominance of autoimmune diseases such as systemic sclerosis is well recognized but enigmatic, and a unifying hypothesis remains elusive. Third, the management of conditions triggered by infectious agents as in Guillain-Barre syndrome or mixed cryoglobulinemia is challenging, and clinical guidelines are needed in the setting of infections and autoimmunity. Fourth, gamma-delta T cells represent major players in innate immunity and are the subject of extensive studies in autoimmune diseases to provide new therapeutic targets for disease prevention or modulation in the near future. Ultimately, we acknowledge the major developments in the broad fields of rheumatology and immunology and expect that microbiota definition, epigenetics studies, and microRNA analysis will provide new exciting avenues toward the understanding and treatment of chronic and acute inflammation.

Upregulation of matrilin-2 expression in murine hepatic stellate cells during liver injury has no effect on fibrosis formation and resolution

BACKGROUND & AIMS

Matrilins are a family of four oligomeric adaptor proteins whose functions in extracellular matrix assembly during pathophysiological events still need to be explored in more detail. Matrilin-2 is the largest family member and the only matrilin expressed in the naive liver. Several studies demonstrate that matrilin-2 interacts with collagen I, fibronectin or laminin-111-nidogen-1 complexes. All these matrix components get upregulated during hepatic scar tissue formation. Therefore, we tested whether matrilin-2 has an influence on the formation and/or the resolution of fibrotic tissue in the mouse liver.

METHODS

Fibrosis was induced by infection with an adenovirus encoding cytochrome P450 2D6 (autoimmune liver damage) or by exposure to the hepatotoxin carbon tetrachloride. Fibrosis severity and matrilin-2 expression were assessed by immunohistochemistry. Hepatic stellate cells (HSCs) were isolated and analysed by immunocytochemistry and Transwell migration assays.

RESULTS

Both autoimmune as well as chemically induced liver damage led to simultaneous upregulation of matrilin-2 and collagen I expression. Discontinuation of carbon tetrachloride exposure resulted in concomitant dissolution of both proteins. Activated HSCs were the source of de novo matrilin-2 expression. Comparing wild type and matrilin-2-deficient mice, no differences were detected in fibronectin and collagen I upregulation and resolution kinetics as well as amount or location of fibronectin and collagen I production and degradation.

CONCLUSIONS

Our findings suggest that the absence of matrilin-2 has no effect on HSC activation and regression kinetics, synthetic activity, proliferative capacity, motility, or HSC apoptosis.

Interventional effects of Plumbago zeylanica L. decoction on CCl4-induced hepatic fibrosis in rats

AIM: To investigate the intervention effects of Plumbago zeylanica L. decoction (PZL) on carbon tetrachloride (CCl4)-induced hepatic fibrosis in rats.

METHODS: A model of hepatic fibrosis was established by subcutaneous injection of 40% CCl₄ in rats. SD rats were randomly divided into five groups (10 rats in each group): a model group, a positive control group (colchicines 0.25 mg/kg), high-, medium- and low-dose PZL groups. A blank control group was also established. The levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were tested using a ultraviolet-visible pectrophotometer (UV). Serum levels of total bilirubin (TBIL), direct bilirubin (DBIL) and indirect bilirubin (IBIL) were detected by the method of vanadate oxidation. The contents of hyaluronic acid (HA), laminin (LN), procollagen type Ⅲ (P3NP), and type Ⅳ collagen (CⅣ) were detected by radioimmunoassay. HE staining was used to examine the degree of hepatic fibrosis, and the expression of collagen type Ⅰ and Ⅲ and α-SMA in hepatic tissues was detected by immunohistochemistry.

RESULTS: Compared with the model group, the levels of ALT, AST, TBIL, DBIL and IBIL were significantly decreased in the PZL groups. PZL could also significantly reduce the contents of HA, LN, P3NP, and CⅣ. HE staining showed that PZL could significantly reduce the degree of hepatic fibrosis. Immunohistochemistry showed that the expression of collagen type Ⅰ and Ⅲ and α-SMA in hepatic tissues was decreased by PZL (P < 0.05 or P < 0.01), and the effect was dose-dependent.

CONCLUSION: PZL has a protective effect against CCl₄-induced liver fibrosis in rats possibly by improving the liver function, inhibiting liver cell degeneration and necrosis, reducing secretion of collagen by hepatic stellate cells and promoting extracellular matrix degradation.

Hepatitis mouse models: from acute-to-chronic autoimmune hepatitis

Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease associated with interface hepatitis, raised plasma liver enzymes, the presence of autoantibodies and regulatory T-cell (Tregs) dysfunction. The clinical course is heterogeneous, manifested by a fulminant or indolent course. Although genetic predisposition is well accepted, the combination with currently undefined environmental factors is crucial for the development of the disease. Progress in the development of reliable animal models provides added understanding of the pathophysiology of AIH, and these will be very useful in evaluating potential therapeutics. It appears that artificially breaking tolerance in the liver is easy. However, maintaining this state of tolerance breakdown, to get chronic hepatitis, is difficult because liver immune homeostasis is strongly regulated by several immune response inhibitory mechanisms. For example, Tregs are crucial regulators in acute and chronic hepatitis, and C57BL/6 mice are most prone to experimental AIH. Immunization of C57BL/6 mice with liver (AIH) autoantigens (CYP2D6/FTCD or IL-4R) and the disturbance of liver regulatory mechanism(s), leading to experimental AIH, are likely to be most representative of human AIH pathology.

Pathogen infection as a possible cause for autoimmune hepatitis

Autoimmune disorders afflicting the liver comprise the bona fide autoimmune diseases, primary biliary cirrhosis, primary sclerosing cholangitis, and autoimmune hepatitis as well as drug-induced autoimmune-like diseases, such as halothane hepatitis. Whereas drug-induced forms of acute or chronic hepatitis often have a clear triggering factor, the etiology of classical autoimmune liver diseases is only poorly understood. Besides a genetic component present in disease susceptible individuals, environmental triggering factors are likely to play a role in the initiation and/or propagation of the disease. In this article, we will review on current evidence obtained from epidemiological associations, case studies, and findings in animal models for pathogens, to be involved in the etiology of autoimmune liver disease with a special focus on autoimmune hepatitis.

Hepatic inflammation and progressive liver fibrosis in chronic liver disease

Chronic liver inflammation drives hepatic fibrosis, and current immunosuppressive, anti-inflammatory, and anti-viral therapies can weaken this driver. Hepatic fibrosis is reversed, stabilized, or prevented in 57%-79% of patients by conventional treatment regimens, mainly by their anti-inflammatory actions. Responses, however, are commonly incomplete and inconsistently achieved. The fibrotic mechanisms associated with liver inflammation have been clarified, and anti-fibrotic agents promise to improve outcomes as adjunctive therapies. Hepatitis C virus and immune-mediated responses can activate hepatic stellate cells by increasing oxidative stress within hepatocytes. Angiotensin can be synthesized by activated hepatic stellate cells and promote the production of reactive oxygen species. Anti-oxidants (N-acetylcysteine, S-adenosyl-L-methionine, and vitamin E) and angiotensin inhibitors (losartin) have had anti-fibrotic actions in preliminary human studies, and they may emerge as supplemental therapies. Anti-fibrotic agents presage a new era of supplemental treatment for chronic liver disease.

Advances in research of autoimmune hepatitis

Autoimmune hepatitis (AIH) is a chronic inflammatory disease of the liver triggered by an immune-mediated attack, characterized by the presence of hypergammaglobulinemia, serum autoantibodies, interface hepatitis on histological examination, and good response to immunosuppressive therapy. In this article, we will review the role of genetic susceptibility, inducing factors, molecular mimicry, liver injury, and immune regulation imbalance in the pathogenesis of AIH. In addition, this article systematically describes the advances in research of AIH in terms of clinical features, serological characteristics, histologic features, diagnosis and therapy.