Leonóra Himer

Adenosine A2A receptor activation inhibits T helper 1 and T helper 2 cell development and effector function

Adenosine is an immunosuppressive nucleoside, and adenosine A2A receptors inhibit T‐cell activation. We investigated the role of A2A receptors in regulating T helper (Th)1‐ and Th2‐cell development and effector function. A2A‐receptor stimulation suppressed the development of T‐cell receptor (TCR) ‐stimulated naive T cells into both Th1 and Th2 cells, as indicated by decreased IFN‐γ production by cells developed under Th1‐skewing conditions and decreased interleukin (IL) −4, IL5, and IL10 production by cells developed under Th2‐skewing conditions. Using A2A receptor‐deficient mice, we demonstrate that A2A receptor activation inhibits Th1‐ and Th2‐cell development by decreasing the proliferation and IL2 production of naive T cells, irrespective of whether the cells are expanded under Th1‐ or Th2‐skewing environment. Using in vivo established Th1 and Th2 cells, we further demonstrate the nonselective nature of A2A receptor‐mediated immunosuppressive effects, because A2A receptor activation decreased IFN‐γ and IL4 secretion and mRNA level of TCR‐stimulated effector Th1 and Th2 cells, respectively. A2A receptor mRNA expression in both Th1 and Th2 effector cells increased following TCR stimulation. In summary, these data demonstrate that A2A receptor activation has strong inhibitory actions during early developmental, as well as late effector, stages of Th1‐ and Th2‐cell responses.—Csóka, B., Himer, L., Selmeczy, Z., Vizi, E. S., Pacher, P., Ledent, C., Deitch, E. A., Spolarics, Z., Németh, Z. H., Haskó, G. Adenosine A2A receptor activation inhibits T helper 1 and T helper 2 cell development and effector function. FASEB J. 22, 3491–3499 (2008)

A2B Adenosine Receptors Protect against Sepsis-Induced Mortality by Dampening Excessive Inflammation

Despite intensive research, efforts to reduce the mortality of septic patients have failed. Adenosine is a potent extracellular signaling molecule, and its levels are elevated in sepsis. Adenosine signals through G-protein–coupled receptors and can regulate the host’s response to sepsis. In this study, we studied the role of A2B adenosine receptors in regulating the mortality and inflammatory response of mice following polymicrobial sepsis. Genetic deficiency of A2B receptors increased the mortality of mice suffering from cecal ligation and puncture-induced sepsis. The increased mortality of A2B knockout mice was associated with increased levels of inflammatory cytokines and chemokines and augmented NF-κB and p38 activation in the spleen, heart, and plasma in comparison with wild-type animals. In addition, A2B receptor knockout mice showed increased splenic apoptosis and phosphatase and tensin homolog activation and decreased Akt activation. Experiments using bone-marrow chimeras revealed that it is the lack of A2B receptors on nonhematopoietic cells that is primarily responsible for the increased inflammation of septic A2B receptor-deficient mice. These results indicate that A2B receptor activation may offer a new therapeutic approach for the management of sepsis.

Adenosine receptor activation ameliorates type 1 diabetes

Growing evidence indicates that adenosine receptors could be promising therapeutic targets in autoimmune diseases. Here we studied the role of adenosine receptors in controlling the course of type 1 diabetes. Diabetes in CD‐1 mice was induced by multi‐ple‐low‐dose‐streptozotocin (MLDS) treatment and in nonobese diabetic (NOD) mice by cyclophosphamide injection. The nonselective adenosine receptor agonist 5′‐N‐ethylcarboxamidoadenosine (NECA) prevented diabetes development in both MLDS‐challenged mice and in cyclophosphamide‐treated NOD mice. The effect of NECA was reversed by the selective A2B receptor antagonist N‐(4‐cyanophenyl)‐2‐[4‐(2,3,6,7‐tetrahydro‐2,6‐dioxo‐1,3‐dipropyl‐1H‐purin‐8‐yl)phenoxy]acetamide (MRS 1754). The selective A1 receptor agonist 2‐chloro‐N6‐cyclopentyladenosine (CCPA) and A3 receptor agonist N6 ‐(3‐iodobenzyl)‐adenosine‐5′‐N‐methylu‐ronamide (IB‐MECA) were less efficacious in ameliorating the course of diabetes. NECA inhibited diabetes in A2A receptor KO mice and the selective A2A receptor agonist 2‐P‐(2‐carboxyethyl)phenethyl‐amino‐5′‐N‐ethyl‐carboxamidoadenosine (CGS21680) had no effect in normal mice, indicating a lack of role of A2A receptors. NECA failed to prevent cytokine‐induced β‐cell death in vitro, but NECA strongly suppressed expression of the proinflammatory cytokines TNF‐α, MIP‐1α, IL‐12, and IFN‐γ in pancreata, endotoxin, or anti‐CD3‐stimulated splenic cells, and T helper 1 lymphocytes, indicating that the beneficial effect of NECA was due to immunomodulation. These results demonstrate that adenosine receptor ligands are potential candidates for the treatment of type 1 diabetes.—Nemeth Z. H., Bleich, D., Csóka B., Pacher P., Mabley, J. G., Himer, L., Vizi, E. S., Deitch E. A., Szabo C., Cronstein, B. N., Haskó G. Adenosine receptor activation ameliorates type 1 diabetes. FASEB J. 21, 2379–2388 (2007)

Adenosine Augments IL-10 Production by Microglial Cells through an A2B Adenosine Receptor-Mediated Process

Microglia are activated by pathogen-associated molecular patterns and produce proinflammatory cytokines, such as TNF-α, IL-6, and IL-12, and the anti-inflammatory cytokine IL-10. Adenosine is an endogenous purine nucleoside and a ligand of four G protein-coupled adenosine receptors (ARs), which are the A1AR, A2AAR, A2BAR, and A3AR. ARs have been shown to suppress TNF-α production by microglia, but their role in regulating IL-10 production has not been studied. In this study, we demonstrate that adenosine augments IL-10 production by activated murine microglia while suppressing the production of proinflammatory cytokines. Because the order of potency of selective AR agonists in inducing IL-10 production was NECA > IB-MECA > CCPA ≥ CGS21680, and the A2BAR antagonist MRS1754 prevented the effect of NECA, we conclude that the stimulatory effect of adenosine on IL-10 production is mediated by the A2BAR. Mechanistically, adenosine augmented IL-10 mRNA accumulation by a transcriptional process. Using mutant IL-10 promoter constructs we showed that a CREB-binding region in the promoter mediated the augmenting effect of adenosine on IL-10 transcription. Chromatin immunoprecipitation analysis demonstrated that adenosine induced CREB phosphorylation at the IL-10 promoter. Silencing CREB using lentivirally delivered short hairpin RNA blocked the enhancing effect of adenosine on IL-10 production, confirming a role for CREB in mediating the stimulatory effect of adenosine on IL-10 production. In addition, adenosine augmented IL-10 production by stimulating p38 MAPK. Collectively, our results establish that A2BARs augment IL-10 production by activated murine microglia.

Adenosine A2A receptor activation protects CD4+ T lymphocytes against activation-induced cell death

Activation‐induced cell death (AICD) is initiated by T‐cell receptor (TCR) restimulation of already activated and expanded peripheral T cells and is mediated through Fas/Fas ligand (FasL) interactions. Adenosine is a purine nucleoside signaling molecule, and its immunomodulatory effects are mediated by 4 G‐protein‐coupled receptors: A1,A2A, A2B, and A3. In this study, we investigated the role of A2A receptors in regulating CD4+ T lymphocyte AICD. Our results showed that the selective A2A receptor agonist CGS21680 (EC50 = 15.2–32.6 nM) rescued mouse CD4+ hybridomas and human Jurkat cells from AICD and that this effect was reversed by the selective A2A receptor antagonist ZM241385 (EC50 = 2.3 nM). CGS21680 decreased phosphatidylserine exposure on the membrane, as well as the cleavage of caspase‐3, caspase‐8 and poly(ADP‐ribose) polymerase indicating that A2A receptor stimulation blocks the extrinsic apoptotic pathway. In addition, CGS21680 attenuated both Fas and FasL mRNA expression. This decrease in FasL expression was associated with decreased activation of the transcription factor systems NF‐κB, NF‐ATp, early growth response (Egr)‐1, and Egr‐3. The antiapoptotic effect of A2A receptor stimulation was mediated by protein kinase A. Together, these results demonstrate that A2A receptor activation suppresses the AICD of peripheral T cells.—Himer, L., Csóka, B., Selmeczy, Z., Koscsó, B., Pócza, T., Pacher, P., Németh, Z. H., Deitch, E. A., Vizi, E. S., Cronstein, B. N., Haskó, G. Adenosine A2A receptor activation protects CD4+ T lymphocytes against activation‐induced cell death. FASEB J. 24, 2631–2640 (2010). www.fasebj.org

Th17 cells in rheumatoid arthritis

Th17 cells are the newly described subset of the CD4(+) T lymphocytes. Activated Th17 cells are characterized by their ability to produce IL-17A and other pro-inflammatory cytokines. IL-17A regulates immune function through its cell-surface receptor expressed on epithelial-and endothelial cells, fibroblasts and leukocytes by promoting neutrophil recruitment and releasing further pro-inflammatory mediators. Failures of the susceptible balance of the immunoregulation may lead to unchecked immune response and autoimmune diseases. The central role of Th17 cells and cytokines produced by Th17 cells were confirmed in a wide variety of human autoimmune diseases, including rheumatoid arthritis. Recently Th17 cells and its cytokines come into the focus of immunological research as potential therapeutic targets.A T helper 17 (Th17) populáció a CD4+ T-lymphocyták újonnan felfedezett csoportja. Az aktivált Th17 sejtek az őket leginkább jellemző interleukin (IL) -17A mellett számos más proinfl ammatorikus citokint is termelnek. Az IL-17A epithelés endothelsejteken, fi broblastokon és a leukocytákon található sejtfelszíni receptorán keresztül további gyulladásos mediátorok felszabadításával és neutrophil granulocyták aktiválásával vesz részt az immunválasz szabályozásában. Az immunreguláció érzékeny egyensúlyának megbomlása gyulladásos és autoimmun betegségekhez vezet. A Th17 sejtek és az általuk termelt citokinek kiemelt szerepét számos humán autoimmun kórképben, köztük a rheumatoid arthritisben is igazolták. Terápiás célpontként való felhasználásuk napjaink immunológiai kutatásainak egyik ígéretes területe.

Role of Th17 cells in rheumatoid arthritis

Th17 cells are the newly described subset of the CD4(+) T lymphocytes. Activated Th17 cells are characterized by their ability to produce IL-17A and other pro-inflammatory cytokines. IL-17A regulates immune function through its cell-surface receptor expressed on epithelial-and endothelial cells, fibroblasts and leukocytes by promoting neutrophil recruitment and releasing further pro-inflammatory mediators. Failures of the susceptible balance of the immunoregulation may lead to unchecked immune response and autoimmune diseases. The central role of Th17 cells and cytokines produced by Th17 cells were confirmed in a wide variety of human autoimmune diseases, including rheumatoid arthritis. Recently Th17 cells and its cytokines come into the focus of immunological research as potential therapeutic targets.A T helper 17 (Th17) populáció a CD4+ T-lymphocyták újonnan felfedezett csoportja. Az aktivált Th17 sejtek az őket leginkább jellemző interleukin (IL) -17A mellett számos más proinfl ammatorikus citokint is termelnek. Az IL-17A epithelés endothelsejteken, fi broblastokon és a leukocytákon található sejtfelszíni receptorán keresztül további gyulladásos mediátorok felszabadításával és neutrophil granulocyták aktiválásával vesz részt az immunválasz szabályozásában. Az immunreguláció érzékeny egyensúlyának megbomlása gyulladásos és autoimmun betegségekhez vezet. A Th17 sejtek és az általuk termelt citokinek kiemelt szerepét számos humán autoimmun kórképben, köztük a rheumatoid arthritisben is igazolták. Terápiás célpontként való felhasználásuk napjaink immunológiai kutatásainak egyik ígéretes területe.

Expression of PARK7 is increased in celiac disease

Recently, it has been suggested that the gene called Parkinson’s disease 7 (PARK7) might be an upstream activator of hypoxia-inducible factor (HIF)-1α, which plays a major role in sustaining intestinal barrier integrity. Furthermore, PARK7 has been proposed to participate in the Toll-like receptor (TLR)-dependent regulation of the innate immune system. Our aim was to investigate the involvement of PARK7 in the pathogenesis of coeliac disease (CD). Duodenal biopsy specimens were collected from 19 children with untreated CD, five children with treated CD (maintained on gluten-free diet), and ten children with histologically normal duodenal biopsies. PARK7 mRNA expression and protein level were determined by real-time polymerase chain reaction (PCR) and Western blot, respectively. Localization of PARK7 was visualized by immunofluorescence staining. Protein level of PARK7 increased in the duodenal mucosa of children with untreated CD compared to children with treated CD or to control biopsies (p <0.03). We detected intensive PARK7 staining in the epithelial cells and lamina propria of the duodenal mucosa of children with untreated CD compared with that in control biopsies. Our finding that mucosal expression of PARK7 is increased suggests that PARK7 is involved in the pathogenesis of gastrointestinal diseases, notably CD. Our results suggest that PARK7 may alter processes mediated by HIF-1α and TLR4, which supports a role for PARK7 in the maintenance of epithelial barrier integrity, immune homeostasis, or apoptosis.

Immunological and Molecular Mechanisms Leading to Fibrosis: Origin of Renal Myofibroblasts

There are about quarter of million patients on chronic renal replacement therapy in Europe, and the estimated number of patients with chronic kidney disease, stages 1-4 is about tenfold higher. Interestingly, regardless of the initiating cause (infection, autoimmune response, chemical insult, radiation or tissue injury etc.), the mechanism of fibrosis is similar in the different chronic kidney diseases and characterized by inflammation. In general, the damaged glomerular or tubular cells release danger signals (Anders, 2010; McDonald et al., 2010) and produce chemotactic stimuli, which trigger the rapid recruitment of leukocytes. The infiltrating immune and the damaged renal cells then produce high levels of proinflammatory cytokines, growth factors, chemokines and adhesion molecules which contribute to glomerular/tubular injury, accumulation of further leukocytes and myofibroblasts, which are the effector cells of renal fibrosis. However the origin of the myofibroblasts is still controversial recent hypotheses suggest that myofibroblasts can originate from different renal cells, such as epithelial and endothelial cells, pericytes or the bone marrow derived fibrocytes. The thus generated myofibroblasts then serves as the key cellular mediator of renal fibrosis. Myofibroblasts have migratory capacity, are resistant to apoptosis, produce several growth factors and cytokines and according to our present knowledge these cells are the main source of the collagen-I and collagen-III rich extracellular matrix in the fibrous tissue. Organ fibrosis is characterized by excessive deposit of extracellular matrix (ECM) leading to glomerular sclerosis and renal tubule-interstitium fibrosis. The excessive deposition of fibrous tissue replaces healthy kidney tissue; the nephrons disappear and the kidney function gradually declines. In this chapter we will summarize our knowledge about the role of immune cells and molecular changes leading to generation of renal myofibroblasts.

A Th17 sejtek szerepe rheumatoid arthritisben

Th17 cells are the newly described subset of the CD4(+) T lymphocytes. Activated Th17 cells are characterized by their ability to produce IL-17A and other pro-inflammatory cytokines. IL-17A regulates immune function through its cell-surface receptor expressed on epithelial-and endothelial cells, fibroblasts and leukocytes by promoting neutrophil recruitment and releasing further pro-inflammatory mediators. Failures of the susceptible balance of the immunoregulation may lead to unchecked immune response and autoimmune diseases. The central role of Th17 cells and cytokines produced by Th17 cells were confirmed in a wide variety of human autoimmune diseases, including rheumatoid arthritis. Recently Th17 cells and its cytokines come into the focus of immunological research as potential therapeutic targets.A T helper 17 (Th17) populáció a CD4+ T-lymphocyták újonnan felfedezett csoportja. Az aktivált Th17 sejtek az őket leginkább jellemző interleukin (IL) -17A mellett számos más proinfl ammatorikus citokint is termelnek. Az IL-17A epithelés endothelsejteken, fi broblastokon és a leukocytákon található sejtfelszíni receptorán keresztül további gyulladásos mediátorok felszabadításával és neutrophil granulocyták aktiválásával vesz részt az immunválasz szabályozásában. Az immunreguláció érzékeny egyensúlyának megbomlása gyulladásos és autoimmun betegségekhez vezet. A Th17 sejtek és az általuk termelt citokinek kiemelt szerepét számos humán autoimmun kórképben, köztük a rheumatoid arthritisben is igazolták. Terápiás célpontként való felhasználásuk napjaink immunológiai kutatásainak egyik ígéretes területe.