Breach of tolerance versus burden of bile acids: Resolving the conundrum in the immunopathogenesis and natural history of primary biliary cholangitis

Primary biliary cholangitis (PBC) is a classic autoimmune disease due to the loss of tolerance to self-antigens. Bile acids (BA) reportedly play a major role in biliary inflammation and/or in the modulation of dysregulated immune responses in PBC. Several murine models have indicated that molecular mimicry plays a role in autoimmune cholangitis; however, they have all been limited by the relative failure to develop hepatic fibrosis. We hypothesized that species-specific differences in the BA composition between mice and humans were the primary reason for this limited pathology. Here, we aimed to study the impact of human-like hydrophobic BA composition on the development of autoimmune cholangitis and hepatic fibrosis. We took advantage of a unique construct, Cyp2c70/Cyp2a12 double knockout (DKO) mice, which have human-like BA composition, and immunized them with a well-defined mimic of the major mitochondrial autoantigen of PBC, namely 2-octynoic acid (2OA). 2OA-treated DKO mice were significantly exacerbated portal inflammation and bile duct damage with increased Th1 cytokines/chemokines at 8 weeks post-initial immunization. Most importantly, there was clear progression of hepatic fibrosis and increased expression of hepatic fibrosis-related genes. Interestingly, these mice demonstrated increased serum BA concentrations and decreased biliary BA concentrations; hepatic BA levels did not increase because of the upregulation of transporters responsible for the basolateral efflux of BA. Furthermore, cholangitis and hepatic fibrosis were more advanced at 24 weeks post-initial immunization. These results indicate that both the loss of tolerance and the effect of hydrophobic BA are essential for the progression of PBC.

The myristoylated alanine-rich C-kinase substrates (MARCKS): A membrane-anchored mediator of the cell function

The myristoylated alanine-rich C-kinase substrate (MARCKS) and the MARCKS-related protein (MARCKSL1) are ubiquitous, highly conserved membrane-associated proteins involved in the structural modulation of the actin cytoskeleton, chemotaxis, motility, cell adhesion, phagocytosis, and exocytosis. MARCKS includes an N-terminal myristoylated domain for membrane binding, a highly conserved MARCKS Homology 2 (MH2) domain, and an effector domain (which is the phosphorylation site). MARCKS can sequester phosphatidylinositol-4, 5-diphosphate (PIP2) at lipid rafts in the plasma membrane of quiescent cells, an action reversed by protein kinase C (PKC), ultimately modulating the immune function. Being expressed mostly in innate immune cells, MARCKS promotes the inflammation-driven migration and adhesion of cells and the secretion of cytokines such as tumor necrosis factor (TNF). From a clinical point of view, MARCKS is overexpressed in patients with schizophrenia and bipolar disorders, while the brain level of MARCKS phosphorylation is associated with Alzheimer's disease. Furthermore, MARCKS is associated with the development and progression of numerous types of cancers. Data in autoimmune diseases are limited to rheumatoid arthritis models in which a connection between MARCKS and the JAK-STAT pathway is mediated by miRNAs. We provide a comprehensive overview of the structure of MARCKS, its molecular characteristics and functions from a biological and pathogenetic standpoint, and will discuss the clinical implications of this pathway.

Autoimmunity affecting the biliary tract fuels the immunosurveillance of cholangiocarcinoma

Cholangiocarcinoma (CCA) results from the malignant transformation of cholangiocytes. Primary sclerosing cholangitis (PSC) and primary biliary cholangitis (PBC) are chronic diseases in which cholangiocytes are primarily damaged. Although PSC is an inflammatory condition predisposing to CCA, CCA is almost never found in the autoimmune context of PBC. Here, we hypothesized that PBC might favor CCA immunosurveillance. In preclinical murine models of cholangitis challenged with syngeneic CCA, PBC (but not PSC) reduced the frequency of CCA development and delayed tumor growth kinetics. This PBC-related effect appeared specific to CCA as it was not observed against other cancers, including hepatocellular carcinoma. The protective effect of PBC was relying on type 1 and type 2 T cell responses and, to a lesser extent, on B cells. Single-cell TCR/RNA sequencing revealed the existence of TCR clonotypes shared between the liver and CCA tumor of a PBC host. Altogether, these results evidence a mechanistic overlapping between autoimmunity and cancer immunosurveillance in the biliary tract.

Single Cell RNA Sequencing of Human Liver Infiltrating B Cells in Primary Biliary Cholangitis (PBC)

Increasing evidence supports the concept that dysregulated B cell differentiation and activation are pivotal in the initiation and progression of autoimmune disorders, in both antibody (Ab)-dependent and Ab-independent mechanisms. Antimitochondrial antibodies (AMA), the serologic hallmark of PBC, are present in greater than 95% of patients with PBC, with a long latency period between the detection of autoantibodies and the onset of clinical disease. However, the mechanisms involved in the role of B cells in the pathogenesis of PBC have remained enigmatic. Herein, we have applied scRNA sequencing to simultaneously characterize B cell repertoire and transcriptome status in blood-liver paired samples from patients with PBC. Our data reveal that there is a dramatic increase in the heterogeneity of the blood CD27− B-cell population in PBC as compared to control. Strikingly, this overwhelmingly expanded naïve-like population were IgM+/IgD+, and encoded by germline sequences. In contrast with blood B cells, the dominant liver CD27− B-cell population is comprised of a high frequency of class-switched clonal B cells, which strongly express MHC class II genes. Upon stimulation with CpG (a surrogate TI-antigen), PBC CD27− B-cell populations markedly expanded and were accompanied by a significantly reduced expression of MARCKS, a newly identified molecule that suppresses active BCR signaling, as compared to healthy controls. Our data indicate that PBC CD27− B-cells exhibit abnormalities and heterogeneity, which may arise from a consistent exposure to TI-antigens. Our findings underscore the significance of B cells in PBC and suggest that more efforts should be placed on PBC B cell immunobiology and as potential therapeutic targets.

Overcoming Shellfish Allergy: How Far Have We Come?

Shellfish allergy caused by undesirable immunological responses upon ingestion of crustaceans and mollusks is a common cause of food allergy, especially in the Asia-Pacific region. While the prevalence of shellfish allergy is increasing, the mainstay of clinical diagnosis for these patients includes extract-based skin prick test and specific IgE measurement while clinical management consists of food avoidance and as-needed use of adrenaline autoinjector should they develop severe allergic reactions. Such a standard of care is unsatisfactory to both patients and healthcare practitioners. There is a pressing need to introduce more specific diagnostic methods, as well as effective and safe therapies for patients with shellfish allergy. Knowledge gained on the identifications and defining the immuno-molecular features of different shellfish allergens over the past two decades have gradually translated into the design of new diagnostic and treatment options for shellfish allergy. In this review, we will discuss the epidemiology, the molecular identification of shellfish allergens, recent progress in various diagnostic methods, as well as current development in immunotherapeutic approaches including the use of unmodified allergens, hypoallergens, immunoregulatory peptides and DNA vaccines for the prevention and treatment of shellfish allergy. The prospect of a “cure “for shellfish allergy is within reach.

The Glycosylation and Glycoprotein Signature of Immunoglobulins in Patients with Autoimmune Liver Diseases

Glycosylation of antibodies, particularly in the Fc domain, critically modulate the ability of antibodies to bind to FcRs, maintaining immune quiescence and marshaling appropriate immune response to achieve a finely orchestrated immune response. Alterations in the glycosylation profile of immunoglobulin (Ig) have been implicated in various autoimmune conditions, which may arise prior to symptoms and have been considered diagnostic for autoimmune disease. We applied QqQ mass spectroscopy with subsequent multiple reaction monitoring (MRM) to elucidate the overall profile, composition and linkage of the sugar residues of plasma IgG, IgM and IgA glycans in 225 serum samples from healthy donors (HD; n=50), PBC (n=100) and PSC (n=75) with or without IBD, using an Agilent 6490 triple quadruple (QqQ) mass spectrometer. Our data demonstrate that most of IgA 1 and 2 glycopeptides significantly distinguish PBC from PSC, which are associated with lower level of Bi anterary glycoforms and elevated HexNac containing glycoforms in PBC samples as compared to both controls and PSC. HexNac terminated IgG1 glycoforms are enriched in both PBC and PSC. The levels of IgM glycopeptide, IgM_439_5200, IgM_439_6200 and J chain distinguish among three categories of samples. Most importantly, a distinct pattern of glycoforms exists in PSC patients with IBD. Neu5Ac terminated IgA and IgM are enriched, while the galactosylated forms are lower in PSC with IBD. Ig glycosylation pattern can be a novel serological marker to distinguish between PBC and PSC. This novel technology highlights the importance of glycan biology in the immune response and as a potential mechanism in the loss of tolerance and/or a disease specific chronic signal of inflammation.

Isodon eriocalyx and its bioactive component Eriocalyxin B enhance cytotoxic and apoptotic effects of gemcitabine in pancreatic cancer

BACKGROUND

Pancreatic cancer, associated with poor prognosis and low survival rate, has been the fourth leading cause of cancer-related death in the US. Although gemcitabine (Gem) is the first-line chemotherapeutic drug in the management of pancreatic cancer, the median survival extension is only 1.5 months, indicating unsatisfactory clinical results. Therefore, exploring agents that can enhance the anti-cancer activity of Gem would be an attractive strategy.

PURPOSE

Our previous studies have demonstrated that eriocalyxin b (EriB), an ent‑kaurane diterpenoid isolated from Isodon eriocalyx (Dunn.) Hara, possesses anti-pancreatic cancer effects, thus acting as a potential therapeutic agent. In this study, we further investigated whether EriB or the ethanol extract of I. eriocalyx (Isodon) could potentiate the cytotoxic activity of Gem in human pancreatic adenocarcinoma cells. In addition, the mechanism associated with their effects was also studied.

METHODS

The anti-proliferation effect was assessed by MTT assay and Ki-67 immunostaining. The combination effect (addition, synergism and antagonism) of various agents was calculated by the Calcusyn software (Biosoft), utilizing the T.C. Chou Method. Apoptosis was detected using Annexin V and PI double staining followed by quantitative flow cytometry. Protein expression regulated by various treatments was analyzed by western blotting.

RESULTS

The combination index revealed that Gem and EriB (or Isodon extract) had synergistic anti-proliferative effect. Both cellular apoptotic and anti-proliferative effects of Gem were significantly increased after combination with EriB (or Isodon extract). The underlying mechanisms involved in the combination effects were elucidated, which include: (1) increased activation of the caspase cascade; (2) reduction of PDK1 and AKT phosphorylation; (3) induction of JNK phosphorylation by Isodon and Gem combination.

CONCLUSION

Gem and EriB (or Isodon extract) taken together in combination regulated PDK1/AKT1/caspase and JNK signaling and promoted apoptosis synergistically, which may contribute to the much increased anti-proliferative activity compared to either agent alone.

The interplay of type I and type II interferons in murine autoimmune cholangitis as a basis for sex-biased autoimmunity

We have reported on a murine model of autoimmune cholangitis, generated by altering the AU-rich element (ARE) by deletion of the interferon gamma (IFN-γ) 3' untranslated region (coined ARE-Del^-/- ), that has striking similarities to human primary biliary cholangitis (PBC) with female predominance. Previously, we suggested that the sex bias of autoimmune cholangitis was secondary to intense and sustained type I and II IFN signaling. Based on this thesis, and to define the mechanisms that lead to portal inflammation, we specifically addressed the hypothesis that type I IFNs are the driver of this disease. To accomplish these goals, we crossed ARE-Del^-/- mice with IFN type I receptor alpha chain (Ifnar1) knockout mice. We report herein that loss of type I IFN receptor signaling in the double construct of ARE-Del^-/- Ifnar1^-/- mice dramatically reduces liver pathology and abrogated sex bias. More importantly, female ARE-Del^-/- mice have an increased number of germinal center (GC) B cells as well as abnormal follicular formation, sites which have been implicated in loss of tolerance. Deletion of type I IFN signaling in ARE-Del^-/- Ifnar1^-/- mice corrects these GC abnormalities, including abnormal follicular structure.

CONCLUSION

Our data implicate type I IFN signaling as a necessary component of the sex bias of this murine model of autoimmune cholangitis. Importantly these data suggest that drugs that target the type I IFN signaling pathway would have potential benefit in the earlier stages of PBC. (Hepatology 2018;67:1408-1419).

The fingerprint of antimitochondrial antibodies and the etiology of primary biliary cholangitis

The identification of environmental factors that lead to loss of tolerance has been coined the holy grail of autoimmunity. Our work has focused on the reactivity of antimitochondrial autoantibodies (AMA) to chemical xenobiotics and has hypothesized that a modified peptide within PDC-E2, the major mitochondrial autoantigen, will have been immunologically recognized at the time of loss of tolerance. Herein, we successfully applied intein technology to construct a PDC-E2 protein fragment containing amino acid residues 177-314 of PDC-E2 by joining a recombinant peptide spanning residues 177-252 (PDC-228) with a 62-residue synthetic peptide from 253 to 314 (PP), which encompasses PDC-E2 inner lipoyl domain (ILD). We named this intein-constructed fragment PPL. Importantly, PPL, as well as lipoic acid conjugated PPL (LA-PPL) and xenobiotic 2-octynoic acid conjugated PPL (2OA-PPL), are recognized by AMA. Of great importance, AMA has specificity for the 2OA-modified PDC-E2 ILD peptide backbone distinct from antibodies that react with native lipoylated PDC-E2 peptide. Interestingly, this unique AMA subfraction is of the immunoglobulin M isotype and more dominant in early-stage primary biliary cholangitis (PBC), suggesting that exposure to 2OA-PPL-like compounds occurs early in the generation of AMA. To understand the structural basis of this differential recognition, we analyzed PPL, LA-PPL, and 2OA-PPL using electron paramagnetic resonance spectroscopy, with confirmations by enzyme-linked immunosorbent assay, immunoblotting, and affinity antibody analysis. We demonstrate that the conformation of PDC-E2 ILD is altered when conjugated with 2OA, compared to conjugation with lipoic acid.

CONCLUSION

A molecular understanding of the conformation of xenobiotic-modified PDC-E2 is critical for understanding xenobiotic modification and loss of tolerance in PBC with widespread implications for a role of environmental chemicals in the induction of autoimmunity. (Hepatology 2017;65:1670-1682).

Chronic expression of interferon-gamma leads to murine autoimmune cholangitis with a female predominance

In most autoimmune diseases the serologic hallmarks of disease precede clinical pathology by years. Therefore, the use of animal models in defining early disease events becomes critical. We took advantage of a "designer" mouse with dysregulation of interferon gamma (IFNγ) characterized by prolonged and chronic expression of IFNγ through deletion of the IFNγ 3'-untranslated region adenylate uridylate-rich element (ARE). The ARE-Del(-/-) mice develop primary biliary cholangitis (PBC) with a female predominance that mimics human PBC that is characterized by up-regulation of total bile acids, spontaneous production of anti-mitochondrial antibodies, and portal duct inflammation. Transfer of CD4 T cells from ARE-Del(-/-) to B6/Rag1(-/-) mice induced moderate portal inflammation and parenchymal inflammation, and RNA sequencing of liver gene expression revealed that up-regulated genes potentially define early stages of cholangitis. Interestingly, up-regulated genes specifically overlap with the gene expression signature of biliary epithelial cells in PBC, implying that IFNγ may play a pathogenic role in biliary epithelial cells in the initiation stage of PBC. Moreover, differentially expressed genes in female mice have stronger type 1 and type 2 IFN signaling and lymphocyte-mediated immune responses and thus may drive the female bias of the disease.

CONCLUSION

Changes in IFNγ expression are critical for the pathogenesis of PBC. (Hepatology 2016;64:1189-1201).

Transgenic Overexpression of Aryl Hydrocarbon Receptor Repressor (AhRR) and AhR-Mediated Induction of CYP1A1, Cytokines, and Acute Toxicity

BACKGROUND

The aryl hydrocarbon receptor repressor (AhRR) is known to repress aryl hydrocarbon receptor (AhR) signaling, but very little is known regarding the role of the AhRR in vivo.

OBJECTIVE

This study tested the role of AhRR in vivo in AhRR overexpressing mice on molecular and toxic end points mediated through a prototypical AhR ligand.

METHODS

We generated AhRR-transgenic mice (AhRR Tg) based on the genetic background of C57BL/6J wild type (wt) mice. We tested the effect of the prototypical AhR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the expression of cytochrome P450 (CYP)1A1 and cytokines in various tissues of mice. We next analyzed the infiltration of immune cells in adipose tissue of mice after treatment with TCDD using flow cytometry.

RESULTS

AhRR Tg mice express significantly higher levels of AhRR compared to wt mice. Activation of AhR by TCDD caused a significant increase of the inflammatory cytokines Interleukin (IL)-1β, IL-6 and IL-10, and CXCL chemokines in white epididymal adipose tissue from both wt and AhRR Tg mice. However, the expression of IL-1β, CXCL2 and CXCL3 were significantly lower in AhRR Tg versus wt mice following TCDD treatment. Exposure to TCDD caused a rapid accumulation of neutrophils and macrophages in white adipose tissue of wt and AhRR Tg mice. Furthermore we found that male AhRR Tg mice were protected from high-dose TCDD-induced lethality associated with a reduced inflammatory response and liver damage as indicated by lower levels of TCDD-induced alanine aminotransferase and hepatic triglycerides. Females from both wt and AhRR Tg mice were less sensitive than male mice to acute toxicity induced by TCDD.

CONCLUSION

In conclusion, the current study identifies AhRR as a previously uncharacterized regulator of specific inflammatory cytokines, which may protect from acute toxicity induced by TCDD.

CITATION

Vogel CF, Chang WL, Kado S, McCulloh K, Vogel H, Wu D, Haarmann-Stemmann T, Yang GX, Leung PS, Matsumura F, Gershwin ME. 2016. Transgenic overexpression of aryl hydrocarbon receptor repressor (AhRR) and AhR-mediated induction of CYP1A1, cytokines, and acute toxicity. Environ Health Perspect 124:1071-1083; http://dx.doi.org/10.1289/ehp.1510194.

Anti-kelch-like 12 and anti-hexokinase 1: novel autoantibodies in primary biliary cirrhosis

BACKGROUND & AIMS

Using high-density human recombinant protein microarrays, we identified two potential biomarkers, kelch-like 12 (KLHL12) and hexokinase-1 (HK1), in primary biliary cirrhosis (PBC). The objective of this study was to determine the diagnostic value of anti-KLHL12/HK1 autoantibodies in PBC. Initial discovery used sera from 22 patients with PBC and 62 non-PBC controls. KLHL12 and HK1 proteins were then analysed for immunoglobulin reactivity by immunoblot and enzyme-linked immunosorbent assay (ELISA) in two independent cohorts of PBC and disease/healthy control patients.

METHODS

Serum samples from 100 patients with PBC and 165 non-PBC disease controls were analysed by immunoblot and samples from 366 patients with PBC, 174 disease controls, and 80 healthy donors were tested by ELISA.

RESULTS

Anti-KLHL12 and anti-HK1 antibodies were each detected more frequently in PBC compared with non-PBC disease controls (P < 0.001). Not only are both markers highly specific for PBC (≥95%) but they also yielded higher sensitivity than anti-gp210 and anti-sp100 antibodies. Combining anti-HK1 and anti-KLHL12 with available markers (MIT3, gp210 and sp100), increased the diagnostic sensitivity for PBC. Most importantly, anti-KLHL12 and anti-HK1 antibodies were present in 10-35% of anti-mitochondrial antibody (AMA)-negative PBC patients and adding these two biomarkers to conventional PBC assays dramatically improved the serological sensitivity in AMA-negative PBC from 55% to 75% in immunoblot and 48.3% to 68.5% in ELISA.

CONCLUSIONS

The addition of tests for highly specific anti-KLHL12 and anti-HK1 antibodies to AMA and ANA serological assays significantly improves efficacy in the clinical detection and diagnosis of PBC, especially for AMA-negative subjects.

Ongoing activation of autoantigen-specific B cells in primary biliary cirrhosis

The serologic hallmark of primary biliary cirrhosis (PBC), the antimitochondrial response to the E2 component of the pyruvate dehydrogenase complex (PDC-E2), has unique features, including continuous high titers of immunoglobulin M (IgM) and IgG reactivity throughout all stages of disease, capable not only of target enzyme inhibition, but also crossreactive with chemical xenobiotics that share molecular homology with the inner lipoyl domain of PDC-E2; such chemicals have been proposed as potential etiological agents. We used flow cytometry and enzyme-linked immunospot assay (ELISPOT) to examine B-cell subsets in 59 subjects, including 28 with PBC, 13 with primary sclerosing cholangitis (PSC), and 18 healthy controls. Strikingly, in PBC, although there were no significant differences in B-cell phenotype subpopulations, 10% of the total IgG and IgA plasmablast population and 23% of the IgM plasmablast population were uniquely reactive with PDC-E2, detected in the CXCR7+ CCR10low plasmablast population. In contrast, plasmablast reactivity to a control antigen, tetanus toxoid, was minimal and similar in all groups. Additionally, we isolated plasmablast-derived polyclonal antibodies and compared reactivity with plasma-derived antibodies and noted a distinct noncirculating tissue source of xenobiotic crossreacting antibodies. The high levels of autoantigen specific peripheral plasmablasts indicate recent activation of naive or memory B cells and a continuous and robust activation. The presence of CXCR7+ CCR10low PDC-E2-specific ASCs suggests a mechanistic basis for the migration of circulating antigen specific plasmablasts to the mucosal epithelial ligands CXCL12 and CCL28.

CONCLUSION

Our findings suggest a sustained rigorous B-cell response in PBC, likely activated and perpetuated by cognate autoantigen.

Shotgun proteomics: identification of unique protein profiles of apoptotic bodies from biliary epithelial cells

Shotgun proteomics is a powerful analytic method to characterize complex protein mixtures in combination with multidimensional liquid chromatography-tandem mass spectrometry (LC-MS/MS). We used this platform for proteomic characterization of apoptotic bodies in an effort to define the complex protein mixtures found in primary cultures of human intrahepatic biliary epithelial cells (HiBEC), human renal proximal tubular epithelial cells, human bronchial epithelial cells, isolated intrahepatic biliary epithelial cells from explanted primary biliary cirrhosis (PBC), and control liver using a total of 24 individual samples. Further, as additional controls and for purposes of comparison, proteomic signatures were also obtained from intact cells and apoptotic bodies. The data obtained from LC-MS/MS, combined with database searches and protein assembly algorithms, allowed us to address significant differences in protein spectral counts and identify unique pathways that may be a component of the induction of the signature inflammatory cytokine response against BECs, including the Notch signaling pathway, interleukin (IL)8, IL6, CXCR2, and integrin signaling. Indeed, there are 11 proteins that localize specifically to apoptotic bodies of HiBEC and eight proteins that were specifically absent in HiBEC apoptotic bodies.

CONCLUSION

Proteomic analysis of BECs from PBC liver compared to normal liver are significantly different, suggesting that an immunological attack affects the repertoire of proteins expressed and that such cells should be thought of as living in an environment undergoing continuous selection secondary to an innate and adaptive immune response, reflecting an almost "Darwinian" bias.

IL-12/Th1 and IL-23/Th17 biliary microenvironment in primary biliary cirrhosis: implications for therapy

The interleukin (IL)-12/IL-23-mediated Th1/Th17 signaling pathway has been associated with the etiopathogenesis of primary biliary cirrhosis (PBC). To address the cytokine microenvironment specifically in the liver, we examined the localized expression of cytokine subunits and their corresponding receptors using previously optimized immunohistochemistry with an extensive panel of antibodies directed at IL-12p70, IL-12p35, interferon-gamma (IFN-γ), IL-12RB2, IL-23p40, IL-23p19, IL-17, and IL-23R using liver from PBC (n = 51) and non-PBC (n = 80) control liver disease patients. Multiple portal tracts in each patient were blindly evaluated and individually scored. We report herein that although IL-12/Th1 and IL-23/Th17 staining was detected in all of the liver sections, they were primarily localized around the damaged interlobular bile ducts in PBC. Most important, Th17 skewing was prominent in advanced PBC patients with intensive secretion of IL-23p19 by inflamed hepatocytes around IL-23R, IL-12RB2, and IFN-γ expressing degenerated cholangiocytes. Our novel finding on the direct association of Th17 skewing and disease severity illustrates the significance of the IL-23/Th17 pathway in the perpetuation of IL-12/Th1-mediated immunopathology in PBC. Furthermore, localized IL-23p19 production by hepatocytes may enhance profibrotic Th17 signaling and proinflammatory IFN-γ production that contribute to PBC pathology.

CONCLUSION

Our data emphasize the pathogenic relevance of IL-12/Th1 and IL-23/Th17 in the evolution of PBC. Of significance, however, the shift from a Th1 to a Th17 imbalance at advanced stages of the disease suggests the necessity to consider modulation of the IL-23/Th17 pathway as a potential target for therapeutic intervention.

Eriocalyxin B-induced apoptosis in pancreatic adenocarcinoma cells through thiol-containing antioxidant systems and downstream signalling pathways

Thiol-containing antioxidant systems play an important role in regulating cellular redox homeostasis. Several anti-cancer agents act by targeting these systems by inducing the production of reactive oxygen species (ROS). Our earlier studies have shown that Eriocalyxin B (EriB), a diterpenoid isolated from Isodon eriocalyx, possesses anti-pancreatic tumour activities in vitro and in vivo. The present study further demonstrated that only thiol-containing antioxidants, N-acetylcysteine (NAC) or dithiothreitol (DTT), inhibited EriB-induced cytotoxicity and apoptosis. EriB suppressed the glutathione and thioredoxin antioxidant systems, thus increasing the intracellular ROS levels and regulating the MAPK, NFκB pathways. Treatment with EriB depleted the intracellular thiol-containing proteins in CAPAN-2 cells. In vivo studies also showed that EriB treatment (2.5 mg/kg) reduced the pancreatic tumour weights significantly in nude mice with increased superoxide levels. Taken together, our results shed important new light on the molecular mechanisms of EriB acting as an apoptogenic agent and its therapeutic potential for pancreatic cancer.

Current progress in stem cell research and its potential for islet cell transplantation

Diabetes is characterized by insulin deficiency concomitant with hyperglycemia due to reduced islet cell mass and/or dysfunction. Currently, insulin replacement is the first-line treatment option for patients with type 1 and a severe form of type 2 diabetes. Treatment by insulin injection is generally effective but nonphysiological, and has the potential of producing chronic complications. On the other hand, islet transplantation can maintain normoglycemia without hypoglycemic side effects, potentially freeing diabetic patients of insulin dependence. In practice, islet transplantation remains hindered by the lack of organ donors and transplant rejection concerns. Recent advances in stem cell research and regenerative medicine, however, offer promise for the clinical application of islet cell transplantation. This review article offers a critical appraisal of current molecular induction approaches, such as directed differentiation, microenvironment induction, and genetic modification, which mimic islet cell development by inducing a variety of stem cells; they include embryonic stem cells, induced pluripotent stem cells, and various tissue-derived stem cells to become functional and transplantable insulin-producing islet cells. Despite good progress, several obstacles remain to be overcome before islet transplantation can be translated into a therapy for human patients, including, but are not limited to, immunogenicity and risk of tumorogenesis.

Clonality, activated antigen-specific CD8(+) T cells, and development of autoimmune cholangitis in dnTGFβRII mice

There are several murine models described with features similar to human primary biliary cirrhosis (PBC). Among these models, the one which has the closest serologic features to PBC is a mouse with a T-cell-restricted expression of the dominant negative transforming growth factor β receptor type II (dnTGFβRII). Our work has demonstrated that CD8(+) T cells from dnTGFβRII mice transfer autoimmune cholangitis to Rag1(-/-) recipients. However, it remained unclear whether the autoimmune cholangitis was secondary to an intrinsic function within CD8(+) T cells or due to the abnormal TGFβR environment within which CD8(+) T cells were generated. To address this mechanistic issue, we used our dnTGFβRII, OT-I/Rag1(-/-) , OT-II/Rag1(-/-) mice and in addition generated OT-I/dnTGFβRII/Rag1(-/-) , and OT-II/dnTGFβRII/Rag1(-/-) mice in which the entire T-cell repertoire was replaced with ovalbumin (OVA)-specific CD8(+) or CD4(+) T cells, respectively. Importantly, neither the parental OT-I/dnTGFβRII/Rag1(-/-) mice and/or OT-II/dnTGFβRII/Rag1(-/-) mice developed cholangitis. However, adoptive transfer demonstrated that only transfer of CD8(+) T cells from dnTGFβRII mice but not CD8(+) T cells from OT-I/Rag1(-/-) mice or from OT-I/dnTGFβRII/Rag1(-/-) mice transferred disease. These data were not secondary to an absence of CD4(+) T cell help since a combination of CD8(+) T cells from OT-I/dnTGFβRII/Rag1(-/-) and CD4(+) T cells from OT II/dnTGFβRII/Rag1(-/-) or CD8(+) T cells from OT-I/dnTGFβRII/Rag1(-/-) with CD4(+) T cells from OT-II/Rag1(-/-) mice failed to transfer disease.

CONCLUSION

Defective TGFβRII signaling, in addition to clonal CD8(+) T cells that target biliary cells, are required for induction of autoimmune cholangitis.

Inhibition of the sodium glucose co-transporter-2: its beneficial action and potential combination therapy for type 2 diabetes mellitus

Sodium glucose co-transporter-2 (SGLT2) inhibitors are an emerging class of glucose-lowering drugs in the management of type 2 diabetes mellitus (T2DM). In this context, SGLT2 is a low-affinity, high-capacity transporter that is expressed predominantly in the proximal renal tubules. The rationale for using SGLT2 inhibition as a drug for T2DM is derived from early evidence obtained from individuals with familial renal glycosuria, due to a SGLT2 mutation, which exhibits decreased renal tubular reabsorption of glucose in the absence of hyperglycaemia or any other signs of dysfunction. Thus, reduction of glucose reabsorption by SGLT2 inhibition represents a novel T2DM treatment approach. In light of the emerging role of SGLT2 inhibition in controlling glucose homeostasis, the current review provides a critical appraisal of the rationale, overviews of structural differences between SGLT2 inhibitors and summarizes recent preclinical and clinical studies. The physiological actions of SGLT2 inhibition in relation to insulin sensitivity, islet morphology, inflammation, body weight and blood pressure are reviewed. Finally, the safety and tolerability of SGLT2 inhibitors are also discussed in relation to their potential to provide insulin independence and enhance β-cell function, as well as their potential for synergistic/additive effects if used in combination with other antidiabetic drugs.

Antimitochondrial antibody heterogeneity and the xenobiotic etiology of primary biliary cirrhosis

Antimitochondrial antibodies (AMAs) directed against the lipoyl domain of the E2 subunit of pyruvate dehydrogenase (PDC-E2) are detected in 95% of patients with primary biliary cirrhosis (PBC) and are present before the onset of clinical disease. The recent demonstration that AMAs recognize xenobiotic modified PDC-E2 with higher titers than native PDC-E2 raises the possibility that the earliest events involved in loss of tolerance are related to xenobiotic modification. We hypothesized that reactivity to such xenobiotics would be predominantly immunoglobulin M (IgM) and using sera from a large cohort of PBC patients and controls (n = 516), we examined in detail sera reactivity against either 6,8-bis(acetylthio) octanoic acid (SAc)-conjugated bovine serum albumin (BSA), recombinant PDC-E2 (rPDC-E2) or BSA alone. Further, we also defined the relative specificity to the SAc moiety using inhibition enzyme-linked immunosorbent assay (ELISA); SAc conjugate and rPDC-E2-specific affinity-purified antibodies were also examined for antigen specificity, isotype, and crossreactivity. Reactivity to SAc conjugates is predominantly IgM; such reactivity reflects a footprint of previous xenobiotic exposure. Indeed, this observation is supported by both direct binding, crossreactivity, and inhibition studies. In both early and late-stage PBC, the predominant Ig isotype to SAc is IgM, with titers higher with advanced stage disease. We also note that there was a higher level of IgM reactivity to SAc than to rPDC-E2 in early-stage versus late-stage PBC. Interestingly, this finding is particularly significant in light of the structural similarity between SAc and the reduced form of lipoic acid, a step which is similar to the normal physiological oxidation of lipoic acid.

CONCLUSION

Specific modifications of the disulfide bond within the lipoic-acid-conjugated PDC-E2 moiety, i.e., by an electrophilic agent renders PDC-E2 immunogenic in a genetically susceptible host.

Modulation of hypovitaminosis D-induced islet dysfunction and insulin resistance through direct suppression of the pancreatic islet renin-angiotensin system in mice

AIMS/HYPOTHESIS

Vitamin D is necessary for normal insulin action and suppresses renin production. Increased renin-angiotensin system (RAS) activity causes islet damage, including reduced insulin secretion. We therefore sought to determine whether hypovitaminosis D-induced upregulation of islet RAS in vivo impairs islet cell function and increases insulin resistance, and whether pharmacological suppression of the RAS during continuing vitamin D deficiency might correct this.

METHODS

C57BL/6 mice were rendered vitamin D-deficient by diet, and glucose and insulin tolerance was assessed. The expression and translation of islet functional, and islet RAS, genes were measured and the effects of pharmacological renin suppression examined.

RESULTS

Mice with diet-induced hypovitaminosis D developed impaired glucose tolerance, increased RAS component expression and impaired islet function gene transcription. Treatment with pharmacological renin inhibition (aliskiren), without vitamin D status correction, reduced islet RAS over-reactivity, islet dysfunction and insulin resistance, and improved glucose tolerance.

CONCLUSIONS/INTERPRETATION

Upregulation of islet RAS genes can contribute to hypovitaminosis D-induced impairment of islet function and increase insulin resistance independently of vitamin D status. Thus, our findings support the use of RAS inhibitors in impaired glucose homeostasis or early diabetes. They also suggest that combining RAS inhibition with correction of hypovitaminosis D might be useful in treating impaired glycaemic control and also in type 2 diabetes prevention. However, the use of aliskiren in established diabetes is contraindicated due to the increased risk of side effects such as hyperkalaemia, so other more suitable RAS blockers need to be identified.

Deletion of interleukin (IL)-12p35 induces liver fibrosis in dominant-negative TGFβ receptor type II mice

Mice with a dominant-negative transforming growth factor β receptor restricted to T cells (dnTGFβRII mice) develop an inflammatory biliary ductular disease that strongly resembles human primary biliary cirrhosis (PBC). Furthermore, deletion of the gene encoding interleukin (IL)-12p40 resulted in a strain (IL-12p40(-/-) dnTGFβRII) with dramatically reduced autoimmune cholangitis. To further investigate the role of the IL-12 cytokine family in dnTGFβRII autoimmune biliary disease, we deleted the gene encoding the IL-12p35 subunit from dnTGFβRII mice, resulting in an IL-12p35(-/-) dnTGFβRII strain which is deficient in two members of the IL-12 family, IL-12 and IL-35. In contrast to IL-12p40(-/-) mice, the IL-12p35(-/-) mice developed liver inflammation and bile duct damage with similar severity but delayed onset as the parental dnTGFβRII mice. The p35(-/-) mice also demonstrated a distinct cytokine profile characterized by a shift from a T-helper 1 (Th1) to a Th17 response. Strikingly, liver fibrosis was frequently observed in IL-12p35(-/-) mice. In conclusion, IL-12p35(-/-) dnTGFβRII mice, histologically and immunologically, reflect key features of PBC, providing a useful generic model to understand the immunopathology of human PBC.

Effects of combining linagliptin treatment with BI-38335, a novel SGLT2 inhibitor, on pancreatic islet function and inflammation in db/db mice

Dipeptidyl peptidase-4 (DPP-4) inhibitors enhance incretin actions and beta-cell function. Concurrently, sodium-glucose co-transporter 2 (SGLT2) inhibitors block renal glucose reabsorption promoting excretion. In this study, we investigated the effects of linagliptin (a DPP-4 inhibitor) and BI-38335 (an SGLT2 inhibitor), individually and in combination, on glucose homeostasis, islet function, and pancreatic islet morphology in db/db mice. Diabetic and non-diabetic mice received linagliptin (3 mg/kg), BI-38335 (1 mg/kg), the two drugs in combination or control once daily for 8 weeks. Blood glucose homeostasis and insulin sensitivity were assessed. Pancreatic islet function and morphology as well as inflammatory factors and toll like receptor 2 (TLR2) pathways involved in islet inflammation were investigated. Active treatments markedly reduced blood glucose and glycated hemoglobin A1c (HbA(1c)) levels, with the combined treatment showing the greater effects. Insulin resistance was improved in the BI-38335 and combination groups with the enhancement of insulin sensitivity and significant increase of serum adiponectin levels. The combined treatment exhibited greater effects on enhanced islet glucose-stimulated insulin secretion and improved glucose tolerance. Moreover, the combination restored the islet beta-/alpha-cell ratio, reduced beta-cell apoptosis, decreased expression of islet immune cell markers, and suppressed factors related to the TLR2 pathway. In addition, all active treatments reduced serum lipid profiles, though the combination produced more robust effects. Collectively, our data show that combined treatment with BI-38335 and linagliptin work, at least in part, synergistically to benefit islet cell function/architecture and insulin resistance, thus improving glycemic control.

Lymphoma-like T cell infiltration in liver is associated with increased copy number of dominant negative form of TGFβ receptor II

Hepatosplenic T cell lymphoma (HSTCL) is a distinct and lethal subtype of peripheral T cell lymphoma with an aggressive course and poor outcome despite multiagent chemotherapy. Contradictory literature, an unknown etiology, and poor response to treatment highlight the need to define the malignant process and identify molecular targets with potential for successful therapeutic interventions. Herein, we report that mice homozygously expressing a dominant negative TGFβRII (dnTGFβRII) under the control of the CD4 promoter spontaneously develop lymphoma-like T cell infiltration involving both spleen and liver. Splenomegaly, hepatomegaly and liver dysfunction were observed in homozygous dnTGFβRII mice between 10 weeks and 10 months of age associated with a predominant infiltration of CD4⁻CD8⁻TCRβ⁺NK1.1⁺ or CD8⁺TCRβ⁺NK1.1⁻ T cell subsets. Notch 1 and c-Myc expression at the mRNA levels were significantly increased and positively correlated with the cell number of lymphoid infiltrates in the liver of dnTGFβRII homozygous compared to hemizygous mice. Further, 2×10⁴ isolated lymphoma-like cells transplant disease by adoptive cell transfers. Collectively, our data demonstrate that increased copy number of dnTGFβRII is critical for development of lymphoma-like T cell infiltration.

Combined treatment with a dipeptidyl peptidase-IV inhibitor (sitagliptin) and an angiotensin II type 1 receptor blocker (losartan) promotes islet regeneration via enhanced differentiation of pancreatic progenitor cells

AIM

The existence of pancreatic progenitor cells (PPCs) with differentiation capacity in the adult pancreas has rendered that promotion of islet regeneration is feasible. The dipeptidyl peptidase-IV inhibitor sitagliptin and the angiotensin II type 1 receptor (AT(1) receptor) blocker losartan have a common target action in the pancreata. Thus, we evaluated the synergistic/additive effects of these two drugs on the differentiation of islet progenitors.

METHODS

The acute and chronic effects of sitagliptin and losartan, individually or in combination, on islet regeneration in vivo were investigated by using a streptozotocin-induced type 1 diabetes mouse model. Their effects were also examined on an in vitro PPCs model derived from human foetal pancreas.

RESULTS

A chronic combination treatment enhanced glucose tolerance in diabetic mice associated with an increased ratio of β cells to islet; an acute combination treatment resulted in a marked increase in the production of neurogenin 3 (NGN3(+)) cells in proximity to CK7(+) ductal cell and an increased presence of insulin(+) /CK7(+) cells. The in vitro study revealed that a combination treatment significantly enhanced mRNA expression of NGN3, NKX6.1 and PDX-1 during PPCs differentiation into human islet-like cell clusters (ICCs). Despite no apparent changes in insulin release, the combined treatment resulted in increasing production of peroxisome proliferator-activated receptor γ (PPARγ) during PPC differentiation.

CONCLUSIONS

These data indicate that combined sitagliptin-losartan treatment can improve islet function by promoting the differentiation of PPCs into ICCs, perhaps via a mechanism involving PPARγ production, and could thereby, contribute to islet regeneration.

Review article: pancreatic renin-angiotensin systems in health and disease

BACKGROUND

In addition to the circulating (endocrine) renin-angiotensin system (RAS), local renin-angiotensin systems are now known to exist in diverse cells and tissues. Amongst these, pancreatic renin-angiotensin systems have recently been identified and may play roles in the physiological regulation of pancreatic function, as well as being implicated in the pathogenesis of pancreatic diseases including diabetes, pancreatitis and pancreatic cancer.

AIM

To review and summarise current knowledge of pancreatic renin-angiotensin systems.

METHODS

We performed an extensive PubMed, Medline and online review of all relevant literature.

RESULTS

Pancreatic RAS appear to play various roles in the regulation of pancreatic physiology and pathophysiology. Ang II may play a role in the development of pancreatic ductal adenocarcinoma, via stimulation of angiogenesis and prevention of chemotherapy toxicity, as well as in the initiation and propagation of acute pancreatitis (AP); whereas, RAS antagonism is capable of preventing new-onset diabetes and improving glycaemic control in diabetic patients. Current evidence for the roles of pancreatic RAS is largely based upon cell and animal models, whilst definitive evidence from human studies remains lacking.

CONCLUSIONS

The therapeutic potential for RAS antagonism, using cheap and widely available agents, and may be untapped and such roles are worthy of active investigation in diverse pancreatic disease states.

Fine phenotypic and functional characterization of effector cluster of differentiation 8 positive T cells in human patients with primary biliary cirrhosis

In primary biliary cirrhosis (PBC), patients develop a multilineage response to a highly restricted peptide of the E2 component of pyruvate dehydrogenase (PDC-E2) involving autoantibody and autoreactive cluster of differentiation (CD)4(+) and CD8(+) T-cell responses. Recent data from murine models have suggested that liver-infiltrating CD8(+) cells play a critical role in biliary destruction in PBC. We hypothesized that chronic antigen stimulation of CD8(+) T cells alters effector memory T cell (T(EM) ) frequency and function similar to that seen with chronic viral infections, including failure to terminally differentiate and relative resistance to apoptosis. We have rigorously phenotyped CD8(+) T-cell subpopulations from 132 subjects, including 76 patients with PBC and 56 controls, and report a higher frequency of T(EM) cells characterized as CD45RO(high) CD57(+) CD8(high), but expressing the gut homing integrin, α4β7, in peripheral blood mononuclear cells of PBC. These CD8(high) T(EM) cells have reduced expression of Annexin V after TCR stimulation. Consistent with a T(EM) phenotype, CD45RO(high) CD57(+) CD8(high) T cells express higher levels of granzyme A, granzyme B, perforin, CCR5 and α4β7, and lower levels of CCR7 and CD28 than other CD8(high) T cells. Furthermore, interleukin (IL)-5 produced by CD8(+) CD57(+) T lymphocytes upon in vitro T-cell receptor stimulation are increased in PBC. Histologically, CD8(+) CD57(+) T cells accumulate around the portal area in PBC. Moreover, CD8(+) CD57(+) T cells respond specifically to the major histocompatibility class I epitope of PDC-E2.

CONCLUSION

In conclusion, our data demonstrate that CD45RO(high) CD57(+) CD8(high) T cells are a subset of terminally differentiated cytotoxic T(EM) cells, which could play a critical role in the progressive destruction of biliary epithelial cells.

A novel role for vitamin D: modulation of expression and function of the local renin-angiotensin system in mouse pancreatic islets

AIMS/HYPOTHESIS

The aim of this study was to demonstrate that hormonal vitamin D (calcitriol) modulates the local pancreatic islet renin-angiotensin system (RAS) whilst improving islet beta cell secretory function.

METHODS

Isolated islets cultured ex vivo under high- or low-glucose conditions and treated with or without calcitriol were examined for changes in RAS component activity and glucose-stimulated insulin secretion (GSIS). Isolated islets from vitamin D receptor knockout (VDR-KO) mice were compared with islets from wild-type (WT) mice for major RAS component expression and RAS protein production.

RESULTS

Isolated islets incubated ex vivo under high-glucose conditions showed increased expression and production of major RAS components; this was prevented and reversed by calcitriol in parallel with increases in GSIS. VDR-KO mice displayed increased RAS component mRNA expression and protein production as compared with WT mice, despite comparable glucose homeostasis.

CONCLUSIONS

Young mice with vitamin D receptor ablation showed abnormal increases in islet RAS components at mRNA and protein levels, despite unaltered glucose homeostasis. Calcitriol prevents and can correct induction of RAS component production under high-glucose conditions in parallel with the well-known effect of calcitriol on increasing islet beta cell secretory responses to glucose.

Epithelial cell specificity and apotope recognition by serum autoantibodies in primary biliary cirrhosis

A major enigma of primary biliary cirrhosis (PBC) is the selective targeting of biliary cells. Our laboratory has reported that after apoptosis, human intrahepatic biliary epithelial cells (HiBECs) translocate the E2 subunit of the pyruvate dehydrogenase complex immunologically intact into apoptotic bodies, forming an apotope. However, the cell type and specificity of this reaction has not been fully defined. To address this issue, we investigated whether the E2 subunit of the pyruvate dehydrogenase complex, the E2 subunit of the branched chain 2-oxo acid dehydrogenase complex, the E2 subunit of the oxo-glutarate dehydrogenase complex, four additional inner mitochondrial enzymes, and four nuclear antigens remain immunologically intact with respect to postapoptotic translocation in HiBECs and three additional control epithelial cells. We report that all three 2-oxo acid dehydrogenase enzymes share the ability to remain intact within the apotope of HiBECs. Interestingly, the E2 subunit of the branched chain 2-oxo acid dehydrogenase complex also remained intact in the other cell types tested. We extended the data, using sera from 95 AMA-positive and 19 AMA-negative patients with PBC and 76 controls, by testing for reactivity against the seven mitochondrial proteins studied herein and also the ability of AMA-negative sera to react with HiBEC apotopes. Sera from 3 of 95 AMA-positive sera, but none of the controls, reacted with 2,4-dienoyl coenzyme A reductase 1, an enzyme also present intact only in the HiBEC apotope, but which has not been previously associated with any autoimmune disease. Finally, the specificity of HiBEC apotope reactivity was confined to AMA-positive sera.

CONCLUSION

We submit that the biliary specificity of PBC is secondary to the unique processes of biliary apoptosis.

Innate immunity and primary biliary cirrhosis: activated invariant natural killer T cells exacerbate murine autoimmune cholangitis and fibrosis

Murine models of autoimmunity allow the study of the earliest events in disease pathogenesis. Our laboratory has developed a xenobiotic induced model of primary biliary cirrhosis (PBC) following immunization of mice with 2-octynoic acid coupled to bovine serum albumin (2-OA-BSA), an antigen selected following quantitative structure-activity relationship analysis of the E2 subunit of the pyruvate dehydrogenase complex (PDC-E2), the immunodominant autoantigen of PBC. Recent data in humans with PBC has suggested that a major component of liver pathology is due to activation of innate immunity. We took advantage of our 2-OA-BSA model and immunized mice with and without the addition of α-galactosylceramide (α-GalCer), an invariant natural killer T cell activator. Importantly, we report herein that 2-OA-BSA-immunized mice exposed to α-GalCer develop a profound exacerbation of their autoimmune cholangitis, including significant increases in CD8(+) T-cell infiltrates, portal inflammation, granuloma formation, and bile duct damage. Furthermore, such mice produce increased levels of antimitochondrial antibodies and have evidence of fibrosis, a feature not previously reported in the murine models of PBC.

CONCLUSION

Our data suggests a primary role of innate immunity in the exacerbation of autoimmune cholangitis and also become a logical explanation for the recurrence of PBC following liver transplantation in the absence of major histocompatability complex compatibility. We submit that PBC begins with loss of tolerance to PDC-E2 and a multilineage antimitochondrial response in which autoreactive CD8(+) T cells are critical. However, the perpetuation of disease and its exacerbation will also be modulated by innate immune mechanisms.

Autoimmune acute liver failure: proposed clinical and histological criteria

Identifying autoimmune hepatitis as the etiology of acute liver failure (ALF) is potentially important, because administering corticosteroids might avoid the need for liver transplantation. However, clinical and histological criteria of autoimmune ALF (AI-ALF) have not been defined. Liver sections (biopsies and explants) from a 72-patient subset of the ALF Study Group Registry with indeterminate ALF were reviewed by a pathologist blinded to all clinical data and were diagnosed with probable AI-ALF based on four features suggestive of an autoimmune pathogenesis: distinctive patterns of massive hepatic necrosis (present in 42% of sections), presence of lymphoid follicles (32%), a plasma cell-enriched inflammatory infiltrate (63%), and central perivenulitis (65%). Forty-two sections (58%) were considered probable for AI-ALF; this group demonstrated higher serum globulins (3.7 ± 0.2 g/dL versus 3.0 ± 0.2 g/dL; P = 0.037) and a higher prevalence of antinuclear and/or anti-smooth muscle antibodies (73% versus 48%; P = 0.034) compared to those without histology suggestive of probable AI-ALF. Thirty patients concordant for autoantibodies and probable AI-ALF upon histological analysis were more likely to have the classical autoimmune hepatitis phenotype (female predominance [72% versus 48%; P < 0.05], higher globulins [3.9 ± 0.2 g/dL versus 3.0 ± 0.2 g/dL; P < 0.005], and higher incidence of chronic hepatitis in long-term follow-up [67% versus 17%, P = 0.019]) compared to the population without concordant AI-ALF histology and autoantibodies.

CONCLUSION

Patients with indeterminate ALF often have features of autoimmune disease by histological analysis, serological testing, and clinical recurrence during follow-up. In contrast to classical autoimmune hepatitis, histological features of AI-ALF predominate in the centrilobular zone.

Increased basal insulin secretion in Pdzd2-deficient mice

Expression of the multi-PDZ protein Pdzd2 (PDZ domain-containing protein 2) is enriched in pancreatic islet beta cells, but not in exocrine or alpha cells, suggesting a role for Pdzd2 in the regulation of pancreatic beta-cell function. To explore the in vivo function of Pdzd2, Pdzd2-deficient mice were generated. Homozygous Pdzd2 mutant mice were viable and their gross morphology appeared normal. Interestingly, Pdzd2-deficient mice showed enhanced glucose tolerance in intraperitoneal glucose tolerance tests and their plasma insulin levels indicated increased basal insulin secretion after fasting. Moreover, insulin release from mutant pancreatic islets was found to be twofold higher than from normal islets. To verify the functional defect in vitro, Pdzd2 was depleted in INS-1E cells using two siRNA duplexes. Pdzd2-depleted INS-1E cells also displayed increased insulin secretion at low concentrations of glucose. Our results provide the first evidence that Pdzd2 is required for normal regulation of basal insulin secretion.

Novel hypoglycemic effects of Ganoderma lucidum water-extract in obese/diabetic (+db/+db) mice

In this study, we evaluated the pharmacological effects of Ganoderma lucidum (G. lucidum) (water-extract) (0.003, 0.03 and 0.3g/kg, 4-week oral gavage) consumption using the lean (+db/+m) and the obese/diabetic (+db/+db) mice. Different physiological parameters (plasma glucose and insulin levels, lipoproteins-cholesterol levels, phosphoenolpyruvate carboxykinase (PEPCK), 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG CoA reductase) and isolated aorta relaxation of both species were measured and compared. G. lucidum (0.03 and 0.3g/kg) lowered the serum glucose level in +db/+db mice after the first week of treatment whereas a reduction was observed in +db/+m mice only fed with 0.3g/kg of G. lucidum at the fourth week. A higher hepatic PEPCK gene expression was found in +db/+db mice. G. lucidum (0.03 and 0.3g/kg) markedly reduced the PEPCK expression in +db/+db mice whereas the expression of PEPCK was attenuated in +db/+m mice (0.3g/kg G. lucidum). HMG CoA reductase protein expression (in both hepatic and extra-hepatic organs) and the serum insulin level were not altered by G. lucidum. These data demonstrate that G. lucidum consumption can provide beneficial effects in treating type 2 diabetes mellitus (T2DM) by lowering the serum glucose levels through the suppression of the hepatic PEPCK gene expression.

Environmental causes of autoimmunity: Clues to the loss of tolerance in primary biliary cirrhosis (137.14)

Primary biliary cirrhosis (PBC) is a human autoimmune disease that destroys small bile ducts and is characterized by antimitochondrial antibodies (AMAs) directed to the inner lipoyl domain of pyruvate dehydrogenase (PDC-E2). Our thesis is that environmental factors trigger the onset of PBC by breaking tolerance to PDC-E2. In particular, we submit that chemical xenobiotic modification of the lipoyl moiety of PDC-E2 results in creation of a neoantigen with a subsequent immune response in genetically predisposed individuals. Our previous work has been focused in two areas: the use of microarrays to identify chemical xenobiotics that react to AMAs as well as or better than native autoantigen and, second, the demonstration that a PBC-like disease can be generated in mice following immunization with our optimal xenobiotic coupled to BSA. Herein, we have focused on fine mapping of the optimal chemical compounds that mimic lipoic acid. We modified the S-S linkage ring structure of lipoic acid and conjugated an array of such chemicals on a PDC-E2 peptide backbone and then analyzed such compounds for reactivity using sera from patients with PBC and a variety of controls. Importantly, by such chemical fine mapping, we now identify 6,8-bis(acetylthio)octanoic acid as an optimal chemical structure. Finally, we note that this compound has striking structural similarity with a variety of drug metabolites.

Antimitochondrial antibodies in acute liver failure: implications for primary biliary cirrhosis

In our previous work, including analysis of more than 10,000 sera from control patients and patients with a variety of liver diseases, we have demonstrated that with the use of recombinant autoantigens, antimitochondrial autoantibodies (AMAs) are only found in primary biliary cirrhosis (PBC) and that a positive AMA is virtually pathognomonic of either PBC or future development of PBC. Although the mechanisms leading to the generation of AMA are enigmatic, we have postulated that xenobiotic-induced and/or oxidative modification of mitochondrial autoantigens is a critical step leading to loss of tolerance. This thesis suggests that a severe liver oxidant injury would lead to AMA production. We analyzed 217 serum samples from 69 patients with acute liver failure (ALF) collected up to 24 months post-ALF, compared with controls, for titer and reactivity with the E2 subunits of pyruvate dehydrogenase, branched chain 2-oxo-acid dehydrogenase, and 2-oxo-glutarate dehydrogenase. AMAs were detected in 28/69 (40.6%) ALF patients with reactivity found against all of the major mitochondrial autoantigens. In addition, and as further controls, sera were analyzed for autoantibodies to gp210, Sp100, centromere, chromatin, soluble liver antigen, tissue transglutaminase, and deaminated gliadin peptides; the most frequently detected nonmitochondrial autoantibody was against tissue transglutaminase (57.1% of ALF patients).

CONCLUSION

The strikingly high frequency of AMAs in ALF supports the thesis that oxidative stress-induced liver damage may lead to AMA induction. The rapid disappearance of AMAs in these patients provides further support for the contention that PBC pathogenesis requires additional factors, including genetic susceptibility.

PGE suppresses excessive anti-IgE induced cysteinyl leucotrienes production in mast cells of patients with aspirin exacerbated respiratory disease

BACKGROUND

Aspirin causes bronchospasm in patients with aspirin exacerbated respiratory disease (AERD). The contribution of mast cells to the increased cysteinyl-leucotrienes (cys-LTs) detected in AERD patients is however not defined.

AIMS OF THE STUDY

Effects of prostaglandin (PG) E(2) and inhibitors of cyclooxygenase (COX) and lipoxygenase (LO) pathways on mediator release from cultured mast cells of normal subjects, aspirin tolerant asthma (ATA) and AERD patients were compared to better define the role of mast cells in AERD.

METHODS

Mast cells were cultured from peripheral blood progenitors and were activated by anti-IgE. Histamine, PGD(2) and cys-LTs released were then determined.

RESULTS

Basal release of all three mediators was similar in all subjects. Although the release of all three mediators was increased by anti-IgE, mast cells from AERD patients produced significantly more cys-LTs (6.9 +/- 2.0 ng/10(6) cells) than normal and ATA subjects (2.3 +/- 0.8 and 1.7 +/- 0.5 ng/10(6) cells, respectively). While COX and LO pathway inhibitors did not affect anti-IgE induced histamine release, they significantly suppressed the production of PGD(2) and cys-LTs, respectively, in all patients. PGE(2) significantly enhanced anti-IgE induced histamine and PGD(2) release from mast cells of normal subjects but not those of ATA and AERD patients. In contrast, PGE(2) suppressed only anti-IgE induced cys-LTs release from mast cells of AERD patients.

CONCLUSION

We speculate that overproduction of cys-LTs is unique to mast cells of AERD patients and is particularly sensitive to suppression by PGE(2). Consequently reduction of PGE(2) production by aspirin removes this endogenous control of cys-LTs overproduction, resulting in asthma attack.

Mechanisms of protective effects induced by blockade of the renin-angiotensin system: novel role of the pancreatic islet angiotensin-generating system in Type 2 diabetes

Large clinical trials have shown that inhibition of the renin-angiotensin system (RAS) can delay and/or prevent the onset of Type 2 diabetes mellitus (T2DM) in high-risk individuals, such as those with hypertension or chronic heart failure. Moreover, a meta-analysis of these randomized clinical studies concluded that the mean weighted relative risk of development of T2DM was reduced by 25% in those patients treated with angiotensin II receptor blockers or angiotensin-converting enzyme inhibitors. In spite of these firm clinical data, the mechanistic pathways mediating the protective activity of RAS blockade have yet to be resolved. Of particular interest is the recently identified local pancreatic RAS and, perhaps more importantly, the finding that it is up-regulated in animal models of T2DM. This putative local RAS may regulate pancreatic islet blood flow, oxygen tension, and islet (pro)insulin biosynthesis. It might also mediate the generation of reactive oxygen species, thereby causing oxidative stress-induced pancreatic beta-cell apoptosis and fibrosis. Moreover, findings that RAS blockade improved beta-cell secretory function and cell mass in experimental animal models of Type 2 diabetes indicate that inhibition of RAS activation may play a pivotal role in protecting islet cell function, and furthermore may prevent the development of overt T2DM. Such data supporting the involvement of the local pancreatic RAS in islet function, as well as a causal relationship between RAS activation and T2DM, and RAS induced beta-cell dysfunction, mandate further investigation into the role of RAS in the pathogenesis of the progressive islet impairment observed in patients with T2DM.

AT1 receptor antagonism ameliorates acute pancreatitis-associated pulmonary injury

Acute pancreatitis (AP) is an inflammatory disease characterized by tissue edema, necrosis and hemorrhage. The mortality rate associated with this disease is particularly high when the inflammation has become systemic. Recently, activation of the pancreatic renin-angiotensin system (RAS) was shown to play a role in AP. The present study investigated whether administering an AT1 receptor antagonist decreases the severity of AP and pancreatitis-induced systemic inflammation, particularly pulmonary injury. Rats with AP-associated lung injury were induced by multiple doses of caerulein, which was demonstrated in the previous studies. Three injections of losartan (200 microg/ kg/h) were given 30 min prior to the first injection of caerulein. The results demonstrated that caerulein injections resulted in significant increases in pancreatic and pulmonary myeloperoxidase (MPO) activities, and losartan treatment attenuates these effects. Lung microvascular permeability was also significantly improved by losartan treatment. Losartan prevented caerulein-induced pancreatic and pulmonary morphological alterations, but not elevations in serum alpha-amylase or pancreas/body weight ratio. These data indicate that losartan treatment can attenuate pancreatic and lung injury. Thus, the implication is that a blockade of AT1 receptors may have a clinical application for the treatment of AP and, perhaps more importantly, subsequent pulmonary complications.

Increased duodenal iron uptake and transfer in a rat model of chronic hypoxia is accompanied by reduced hepcidin expression

BACKGROUND

Despite the requirement for increased iron delivery for erythropoiesis during hypoxia, there is very little information on how duodenal iron uptake and its transfer to the blood adapts to this condition.

AIMS

To assess the effects of 30 days of chronic hypoxia in rats on luminal iron uptake and transfer of the metal to blood, together with gene expression of hepcidin, a proposed negative regulator of iron transport.

METHODS

59-Fe uptake by isolated duodenum and its transfer to blood by in vivo duodenal segments was measured after exposure of rats to room air or 10% oxygen for four weeks. Liver hepcidin expression was measured by real time reverse transcription-polymerase chain reaction. The effects of hypoxia on hepcidin gene expression by HepG2 cells was also determined.

RESULTS

Hypoxia did not affect villus length but enhanced (+192.6%) luminal iron uptake by increasing the rate of uptake by all enterocytes, particularly those on the upper villus. Hypoxia promoted iron transfer to the blood but reduced mucosal iron accumulation in vivo by 66.7%. Hypoxia reduced expression of hepcidin mRNA in both rat liver and HepG2 cells.

CONCLUSIONS

Prolonged hypoxia enhances iron transport from duodenal lumen to blood but the process is unable to fully meet the iron requirement for increased erythropoiesis. Reduced secretion of hepcidin may be pivotal to the changes in iron absorption. The processes responsible for suppression of hepcidin expression are unknown but are likely to involve a direct effect of hypoxia on hepatocytes.

Angiotensin II type 1 receptor inhibition markedly improves the blood perfusion, oxygen tension and first phase of glucose-stimulated insulin secretion in revascularised syngeneic mouse islet grafts

AIMS/HYPOTHESIS

We recently found evidence of an angiotensin-generating system in pancreatic islets. The present study investigated the effect of endogenously produced angiotensin II on microcirculation and function in transplanted islets.

MATERIALS AND METHODS

Losartan, an angiotensin II type 1 receptor inhibitor, was administered either acute intravenously to mice with 4-week-old islet renal subcapsular transplants, or added to the drinking water for the final 14 days or throughout the 4-week post-transplantation period. The graft-bearing kidney was, in some cases, dissected out and perfused in vitro to evaluate the effect of angiotensin II and losartan on glucose-stimulated insulin release from the grafts.

RESULTS

Losartan treatment throughout the 4-week post-transplantation period had negative effects on islet revascularisation as well as on islet graft insulin release. However, administration of losartan, either intravenously or orally, after the formation of a new vascular network, improved islet graft blood perfusion. PO2 in the islet transplants was also effectively improved by the losartan treatment. Graft perfusion experiments showed a markedly better first phase of glucose-stimulated insulin release in transplanted islets when exposed to losartan. In contrast, acute administration of angiotensin II decreased islet graft blood flow, PO2 and glucose-stimulated insulin release.

CONCLUSIONS/INTERPRETATION

This study shows that inhibition of the islet reninangiotensin system may be a feasible strategy to increase the blood perfusion, PO2 and function within islet grafts. Such treatment should not be initiated, however, before the islet vascular system has been formed.

Evidence for a local angiotensin-generating system and dose-dependent inhibition of glucose-stimulated insulin release by angiotensin II in isolated pancreatic islets

AIMS/HYPOTHESIS

A local angiotensin-generating system has been found in the exocrine pancreas. This study aimed, primarily, to investigate the existence of a local angiotensin-generating system in the pancreatic islets and, secondly, to elucidate its role in regulating insulin secretion.

METHODS

Real-time RT-PCR and western blot were used to investigate if angiotensin-generating components are present in the mouse pancreatic islets, which are subject to regulation by islet transplantation. The localisation of AT1-receptors in islets was investigated by immunohistochemistry. Batch-type incubations of isolated islets were applied for studying the influence of angiotensin II on the glucose-stimulated insulin release, glucose oxidation and (pro)insulin, and total protein biosynthesis.

RESULTS

Major components, namely angiotensinogen, ACE, AT1- and AT2-receptors, were expressed in endogenous islets. AT1-receptors were localised to pancreatic beta cells. Exposure of the isolated islets to angiotensin II induced a dose-dependent inhibition of glucose-stimulated insulin release and inhibited (pro)insulin biosynthesis. This inhibitory action was fully preventable by pretreatment of the islets with losartan, an AT1-receptor antagonist. We also investigated if the expression of these components was changed after islet transplantation. Notably, a markedly increased expression of mRNA for the AT1-receptor was observed in islets retrieved from 4-week-old syngeneic islet transplants, a finding that was confirmed at the protein level.

CONCLUSION/INTERPRETATION

These data indicate the existence of an islet angiotensin-generating system of potential importance in the physiological regulation of glucose-induced insulin secretion, thus diabetes mellitus. The increased expression of the AT1-receptor in islet transplants could have relevance to islet-graft function.