apyrase and Hepatitis--Autoimmune

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

Topics: 5'-Nucleotidase; Adenosine Triphosphate; Animals; Apyrase; GPI-Linked Proteins; Hepatitis, Autoimmune; Hepatitis, Viral, Human; Humans; Inflammatory Bowel Diseases; Intestines; Liver; Receptors, Purinergic P2; Reperfusion Injury; Signal Transduction

In autoimmune hepatitis (AIH), the imbalance between regulatory T cells (Tregs) and T-helper type 17 (Th17) cells has been linked to low levels of CD39, an ectoenzyme that hydrolyses ATP, ultimately generating immunosuppressive adenosine. Upregulation of CD39 results from activation of aryl hydrocarbon receptor (AHR), which mediates toxin responses to modulate T-cell immunity. In this study, we investigated whether altered AHR signalling underlies defective CD39 expression and function in AIH Tregs and Th17 cells, therefore contributing to regulatory/effector cell imbalance.. Tregs and Th17 cells, obtained from the peripheral blood of 49 patients with AIH and 21 healthy individuals (HI), were tested for response to endogenous and exogenous AHR ligands.. When compared to those of HI, AIH-derived Tregs and Th17 cells displayed impaired responses to AHR activation, reflected by impaired upregulation of CD39, delayed increase in ectoenzymatic activity, and defective Treg suppressive function. These impairments resulted, at least in part, from heightened levels of AHRR and Erα in Tregs and high HIF-1α in Th17 cells, and were reverted upon molecular blockade. Importantly, in AIH-derived Tregs, the binding affinity of AHR was higher for Erα than ARNT.. In AIH, high levels of AHRR and HIF-1α inhibit AHR signalling in Tregs and Th17 cells. AHR non-canonical binding to Erα further amplifies the lack of effective CD39 upregulation. Blockade of these inhibitory and/or non-canonical activation pathways represents a potential therapeutic approach to restore CD39 and immunohomeostasis in AIH.. In patients with autoimmune hepatitis, the imbalance between regulatory T cells and T helper type-17 cells is linked to dysfunction of the aryl hydrocarbon receptor pathway, resulting from aberrant inhibition or non-canonical activation. These alterations impair Treg- and Th17 cell-induced upregulation of CD39, an ectoenzyme key to immunoregulation. Blockade of excessive inhibition or non-canonical activation of the aryl hydrocarbon receptor pathway might represent a novel therapeutic strategy to control inflammation while restoring immune balance in autoimmune hepatitis.

Topics: Apyrase; Basic Helix-Loop-Helix Transcription Factors; Cells, Cultured; Drug Discovery; Hepatitis, Autoimmune; Humans; Immunity, Cellular; Immunomodulation; Ligands; Liver; Receptors, Aryl Hydrocarbon; Signal Transduction; T-Lymphocytes, Regulatory; Th17 Cells; Up-Regulation

T-helper-type 17 (Th17) cells are involved in autoimmune tissue damage. CD39 is an ectonucleotidase that catalyzes extracellular ATP/ADP hydrolysis, culminating in the generation of immunosuppressive adenosine. Functional CD39 expression confers immunosuppressive properties upon immune cells. As the proportion of CD39 lymphocytes is decreased in juvenile autoimmune liver disease (AILD), we have explored whether decreased CD39 expression is present on Th17 cells and whether this phenomenon is associated with heightened effector function and inflammation.. Thirty-eight patients with juvenile AILD (22 autoimmune hepatitis and 16 autoimmune sclerosing cholangitis), 8 disease controls (DC) and 16 healthy subjects (HS) were studied. Peripheral blood cell phenotype was determined by flow cytometry; ability to suppress by inhibition of cell proliferation/effector cytokine production; ectoenzymatic activity by thin layer chromatography; expression of adenosine receptor, adenosine deaminase (ADA) and phosphodiesterases (PDE) by quantitative real-time PCR or by Western Blot.. CD39(+) Th17 (Th17(CD39+)) cells from HS appear activated and contain high frequencies of lymphocytes producing regulatory cytokines. In AILD, however, Th17(CD39+) cells are markedly diminished and fail to generate AMP/adenosine, thereby limiting control of both target cell proliferation and IL-17 production. When compared to HS, Th17 cells from AILD patients also show lower A2A adenosine receptor expression while displaying similar levels of PDE4A, PDE4B and ADA. Only rare Th17(CD39+) cells are observed by liver immunohistochemistry.. Th17(CD39+) cells in juvenile AILD are both quantitatively decreased and qualitatively deficient. Low levels CD39 and A2A expression may contribute to the perpetuation of Th17 cell effector properties and unfettered inflammation in this disease.

Topics: Adenosine Deaminase; Adolescent; Adult; Antigens, CD; Apyrase; Blotting, Western; Cell Proliferation; Child; Child, Preschool; Cholangitis, Sclerosing; Female; Flow Cytometry; Gene Expression; Hepatitis, Autoimmune; Humans; Immunohistochemistry; Infant; Interleukin-17; Male; Phosphoric Diester Hydrolases; Receptor, Adenosine A2A; Reverse Transcriptase Polymerase Chain Reaction; Th17 Cells; Young Adult

Topics: Antigens, CD; Apyrase; Female; Hepatitis, Autoimmune; Humans; Male; T-Lymphocytes, Regulatory; Th17 Cells

Topics: Antigens, CD; Apyrase; Female; Hepatitis, Autoimmune; Humans; Male; T-Lymphocytes, Regulatory; Th17 Cells

Autoimmune hepatitis (AIH) is an important cause of severe liver disease and is associated with both quantitative and qualitative regulatory T-cell (Treg) impairments. Tregs express CD39, an ectonucleotidase responsible for extracellular nucleotide hydrolysis, culminating in the production of immunosuppressive adenosine. Here, we describe multiple CD39(pos) Treg defects that potentially contribute to the impaired immunoregulation that is characteristic of AIH. We have examined the frequency and phenotype of CD39(pos) Tregs by flow cytometry and measured their ectonucleotidase activity. The capacity of CD4(pos) CD25(high) , CD4(pos) CD25(high) CD39(pos) , and CD4(pos) CD25(high) CD39(neg) subsets to suppress both proliferation of effector T cells and interleukin (IL)-17 production was evaluated. In AIH, CD39(pos) Tregs are decreased in frequency, exhibit limited adenosine triphosphate/adenosine diphosphate hydrolysis activity, and fail to suppress IL-17 production by effector CD4 T cells. Moreover, these CD39(pos) Tregs display a more proinflammatory profile in AIH, which is characterized by elevated CD127 positivity, and a greater propensity to produce interferon-gamma or IL-17 upon challenge with proinflammatory stimuli.. In AIH, CD39(pos) Tregs are decreased in number, fail to adequately hydrolyze proinflammatory nucleotides and do not efficiently suppress IL-17 production by effector CD4 T cells. CD39(pos) Tregs show plasticity and are unstable upon proinflammatory challenge, suggesting that defective immunoregulation in AIH might result not only from reduced Treg number and function, but also from increased conversion of Tregs into effector cells.

Topics: Adolescent; Adoptive Transfer; Adult; Antigens, CD; Apyrase; CD24 Antigen; CD4 Antigens; Child; Female; Flow Cytometry; Hepatitis, Autoimmune; Humans; Immune Tolerance; Immunophenotyping; Male; T-Lymphocytes, Regulatory; Th17 Cells; Young Adult

Topics: Antigens, CD; Apyrase; Female; Hepatitis, Autoimmune; Humans; Male; T-Lymphocytes, Regulatory; Th17 Cells