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Vuerich M, Nguyen DH, Ferrari D, Longhi MS. Adenosine-mediated immune responses in inflammatory bowel disease. Front Cell Dev Biol 2024; 12:1429736. [PMID: 39188525 PMCID: PMC11345147 DOI: 10.3389/fcell.2024.1429736] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2024] [Accepted: 07/16/2024] [Indexed: 08/28/2024] Open
Abstract
Extracellular ATP and its derivates mediate a signaling pathway that might be pharmacologically targeted to treat inflammatory conditions. Extracellular adenosine, the product of ATP hydrolysis by ectonucleotidase enzymes, plays a key role in halting inflammation while promoting immune tolerance. The rate-limiting ectoenzyme ENTPD1/CD39 and the ecto-5'-nucleotidase/CD73 are the prototype members of the ectonucleotidase family, being responsible for ATP degradation into immunosuppressive adenosine. The biological effects of adenosine are mediated via adenosine receptors, a family of G protein-coupled receptors largely expressed on immune cells where they modulate innate and adaptive immune responses. Inflammatory bowel disease (IBD) is a serious inflammatory condition of the gastrointestinal tract, associated with substantial morbidity and often refractory to currently available medications. IBD is linked to altered interactions between the gut microbiota and the immune system in genetically predisposed individuals. A wealth of studies conducted in patients and animal models highlighted the role of various adenosine receptors in the modulation of chronic inflammatory diseases like IBD. In this review, we will discuss the most recent findings on adenosine-mediated immune responses in different cell types, with a focus on IBD and its most common manifestations, Crohn's disease and ulcerative colitis.
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Affiliation(s)
- Marta Vuerich
- Biomedical Research, Novartis Pharma AG, Basel, Switzerland
| | - Du Hanh Nguyen
- Department of Anesthesia, Critical Care & Pain Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, United States
- Department of Immunology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Davide Ferrari
- Department of Life Science and Biotechnology, University of Ferrara, Ferrara, Italy
| | - Maria Serena Longhi
- Department of Anesthesia, Critical Care & Pain Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, United States
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Gao ZG, Auchampach JA, Jacobson KA. Species dependence of A 3 adenosine receptor pharmacology and function. Purinergic Signal 2023; 19:523-550. [PMID: 36538251 PMCID: PMC9763816 DOI: 10.1007/s11302-022-09910-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Accepted: 11/26/2022] [Indexed: 12/24/2022] Open
Abstract
Efforts to fully understand pharmacological differences between G protein-coupled receptor (GPCR) species homologues are generally not pursued in detail during the drug development process. To date, many GPCRs that have been successfully targeted are relatively well-conserved across species in amino acid sequence and display minimal variability of biological effects. However, the A3 adenosine receptor (AR), an exciting drug target for a multitude of diseases associated with tissue injury, ischemia, and inflammation, displays as little as 70% sequence identity among mammalian species (e.g., rodent vs. primate) commonly used in drug development. Consequently, the pharmacological properties of synthetic A3AR ligands vary widely, not only in binding affinity, selectivity, and signaling efficacy, but to the extent that some function as agonists in some species and antagonists in others. Numerous heterocyclic antagonists that have nM affinity at the human A3AR are inactive or weakly active at the rat and mouse A3ARs. Positive allosteric modulators, including the imidazo [4,5-c]quinolin-4-amine derivative LUF6000, are only active at human and some larger animal species that have been evaluated (rabbit and dog), but not rodents. A3AR agonists evoke systemic degranulation of rodent, but not human mast cells. The rat A3AR undergoes desensitization faster than the human A3AR, but the human homologue can be completely re-sensitized and recycled back to the cell surface. Thus, comprehensive pharmacological evaluation and awareness of potential A3AR species differences are critical in studies to further understand the basic biological functions of this unique AR subtype. Recombinant A3ARs from eight different species have been pharmacologically characterized thus far. In this review, we describe in detail current knowledge of species differences in genetic identity, G protein-coupling, receptor regulation, and both orthosteric and allosteric A3AR pharmacology.
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Affiliation(s)
- Zhan-Guo Gao
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892-0810, USA.
| | - John A Auchampach
- Department of Pharmacology and Toxicology, and the Cardiovascular Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA
| | - Kenneth A Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892-0810, USA.
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Fishman P, Stemmer SM, Bareket-Samish A, Silverman MH, Kerns WD. Targeting the A3 adenosine receptor to treat hepatocellular carcinoma: anti-cancer and hepatoprotective effects. Purinergic Signal 2023; 19:513-522. [PMID: 36781824 PMCID: PMC10539266 DOI: 10.1007/s11302-023-09925-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 01/31/2023] [Indexed: 02/15/2023] Open
Abstract
The A3 adenosine receptor (A3AR) is over-expressed in human hepatocellular carcinoma (HCC) cells. Namodenoson, an A3AR agonist, induces de-regulation of the Wnt and NF-kB signaling pathways resulting in apoptosis of HCC cells. In a phase I healthy volunteer study and in a phase I/II study in patients with advanced HCC, namodenoson was safe and well tolerated. Preliminary evidence of antitumor activity was observed in the phase I/II trial in a subset of patients with advanced disease, namely patients with Child-Pugh B (CPB) hepatic dysfunction, whose median overall survival (OS) on namodenoson was 8.1 months. A phase II blinded, randomized, placebo-controlled trial was subsequently conducted in patients with advanced HCC and CPB cirrhosis. The primary endpoint of OS superiority over placebo was not met. However, subgroup analysis of CPB7 patients (34 namodenoson-treated, 22 placebo-treated) showed nonsignificant differences in OS/progression-free survival and a significant difference in 12-month OS (44% vs 18%, p = 0.028). Partial response was achieved in 9% of namodenoson-treated patients vs 0% in placebo-treated patients. Based on the positive efficacy signal in HCC CPB7 patients and the favorable safety profile of namodenoson, a phase III study is underway.
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Affiliation(s)
- Pnina Fishman
- Can-Fite BioPharma Ltd., 10 Bareket St., 49170, Petah Tikva, Israel.
| | - Salomon M Stemmer
- Davidoff Cancer Center, Petah Tikva and Sackler Faculty of Medicine, Rabin Medical Center-Beilinson Hospital, Tel Aviv, Israel
| | | | | | - William D Kerns
- Can-Fite BioPharma Ltd., 10 Bareket St., 49170, Petah Tikva, Israel
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Pharmacological characterization of DPTN and other selective A 3 adenosine receptor antagonists. Purinergic Signal 2021; 17:737-746. [PMID: 34713378 DOI: 10.1007/s11302-021-09823-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 10/19/2021] [Indexed: 10/20/2022] Open
Abstract
The A3 adenosine receptor (AR) is emerging as an attractive drug target. Antagonists are proposed for the potential treatment of glaucoma and asthma. However, currently available A3AR antagonists are potent in human and some large animals, but weak or inactive in mouse and rat. In this study, we re-synthesized a previously reported A3AR antagonist, DPTN, and evaluated its affinity and selectivity at human, mouse, and rat ARs. We showed that DPTN, indeed, is a potent A3AR antagonist for all three species tested, albeit a little less selective for mouse and rat A3AR in comparison to the human A3AR. DPTN's Ki values at respective A1, A2A, A2B, and A3 receptors were (nM) 162, 121, 230, and 1.65 (human); 411, 830, 189, and 9.61 (mouse); and 333, 1147, 163, and 8.53 (rat). Its antagonist activity at both human and mouse A3ARs was confirmed in a cyclic AMP functional assay. Considering controversial use of currently commercially available A3AR antagonists in rats and mice, we also re-examined other commonly used and selective A3AR antagonists under the same experimental conditions. The Ki values of MRS1523 were shown to be 43.9, 349, and 216 nM at human, mouse, and rat A3ARs, respectively. MRS1191 and MRS1334 showed incomplete inhibition of [125I]I-AB-MECA binding to mouse and rat A3ARs, while potent human A3AR antagonists, MRS1220, MRE3008F20, PSB10, PSB-11, and VUF5574 were largely inactive. Thus, we demonstrated that DPTN and MRS1523 are among the only validated A3AR antagonists that can be possibly used (at an appropriate concentration) in mouse or rat to confirm an A3AR-related mechanism or function.
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Ogawa A, Nagiri C, Shihoya W, Inoue A, Kawakami K, Hiratsuka S, Aoki J, Ito Y, Suzuki T, Suzuki T, Inoue T, Nureki O, Tanihara H, Tomizawa K, Wei FY. N 6-methyladenosine (m 6A) is an endogenous A3 adenosine receptor ligand. Mol Cell 2021; 81:659-674.e7. [PMID: 33472058 DOI: 10.1016/j.molcel.2020.12.038] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 09/15/2020] [Accepted: 12/24/2020] [Indexed: 02/06/2023]
Abstract
About 150 post-transcriptional RNA modifications have been identified in all kingdoms of life. During RNA catabolism, most modified nucleosides are resistant to degradation and are released into the extracellular space. In this study, we explored the physiological role of these extracellular modified nucleosides and found that N6-methyladenosine (m6A), widely recognized as an epigenetic mark in RNA, acts as a ligand for the human adenosine A3 receptor, for which it has greater affinity than unmodified adenosine. We used structural modeling to define the amino acids required for specific binding of m6A to the human A3 receptor. We also demonstrated that m6A was dynamically released in response to cytotoxic stimuli and facilitated type I allergy in vivo. Our findings implicate m6A as a signaling molecule capable of activating G protein-coupled receptors (GPCRs) and triggering pathophysiological responses, a previously unreported property of RNA modifications.
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Affiliation(s)
- Akiko Ogawa
- Department of Modomics Biology and Medicine, Institute of Development, Aging and Cancer (IDAC), Tohoku University, Sendai 980-8575, Japan; Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan; Department of Ophthalmology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Chisae Nagiri
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo, Japan
| | - Wataru Shihoya
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo, Japan
| | - Asuka Inoue
- Laboratory of Molecular and Cellular Biochemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan; Advanced Research and Development Programs for Medical Innovation (PRIME), Japan Agency for Medical Research and Development (AMED), Tokyo, Japan; Advanced Research and Development Programs for Medical Innovation (LEAP), AMED, Tokyo, Japan
| | - Kouki Kawakami
- Laboratory of Molecular and Cellular Biochemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Suzune Hiratsuka
- Laboratory of Molecular and Cellular Biochemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Junken Aoki
- Advanced Research and Development Programs for Medical Innovation (LEAP), AMED, Tokyo, Japan; Department of Health Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan
| | - Yasuhiro Ito
- Department of Ophthalmology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Takeo Suzuki
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo, Japan
| | - Tsutomu Suzuki
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo, Japan
| | - Toshihiro Inoue
- Department of Ophthalmology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Osamu Nureki
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo, Japan
| | | | - Kazuhito Tomizawa
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan; Center for Metabolic Regulation of Healthy Aging, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Fan-Yan Wei
- Department of Modomics Biology and Medicine, Institute of Development, Aging and Cancer (IDAC), Tohoku University, Sendai 980-8575, Japan; Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan; Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Kawaguchi, Japan.
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Sluyter R, Watson D. Use of Humanized Mouse Models to Investigate the Roles of Purinergic Signaling in Inflammation and Immunity. Front Pharmacol 2020; 11:596357. [PMID: 33123018 PMCID: PMC7566314 DOI: 10.3389/fphar.2020.596357] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 09/18/2020] [Indexed: 12/31/2022] Open
Affiliation(s)
- Ronald Sluyter
- Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia.,Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
| | - Debbie Watson
- Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia.,Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
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Arizmendi N, Kulka M. Adenosine activates Gα s proteins and inhibits C3a-induced activation of human mast cells. Biochem Pharmacol 2018; 156:157-167. [PMID: 30099007 DOI: 10.1016/j.bcp.2018.08.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 08/08/2018] [Indexed: 01/14/2023]
Abstract
Anaphylatoxin C3a and adenosine receptors (AR) are implicated in the inflammatory process associated with allergic rhinitis and asthma by modifying mast cell (MC) responses. Possible interactions between these G-protein coupled receptor (GPCR) pathways in MCs have not yet been demonstrated. LAD2 human MC were stimulated with C3a in the presence or absence of AR agonists and antagonists and their adhesion, chemotaxis and mediator release were measured. The pan-specific AR agonist, 5'-N-Ethylcarboxamidoadenosine (NECA) inhibited C3a-induced LAD2 cell migration, adhesion, degranulation, production of CCL2, and ERK1/2 phosphorylation. The selective A2A receptor agonist CGS 21680 inhibited C3a-mediated degranulation, while the A2B and A3 receptor agonists BAY 60-6583 and IB-MECA, respectively, had no effect. Moreover, an A2A receptor antagonist SCH 58261 blocked the inhibitory effect of NECA on C3a-induced degranulation, suggesting that inhibition of degranulation was mediated through the A2A receptor. NECA increased intracellular cAMP in C3a-activated mast cells, suggesting that Gαs protein signals are required for adenosine-induced inhibition of C3a-mediated human mast cell activation. The adenylyl cyclase inhibitor SQ 22536 attenuated the inhibitory effect of NECA on C3a-activated degranulation, and the A2A agonist CSG 21680 potentiated the inhibition of mast cell activation mediated by the A2A receptor. Our results suggest that adenosine inhibits C3a-mediated activation of human mast cells, possibly through a Gαs protein-dependent pathway.
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Affiliation(s)
- Narcy Arizmendi
- Nanotechnology Research Centre, National Research Council Canada, Edmonton, AB, Canada
| | - Marianna Kulka
- Nanotechnology Research Centre, National Research Council Canada, Edmonton, AB, Canada; Department of Medical Microbiology and Immunology, Faculty of Medicine, University of Alberta, Edmonton, AB, Canada.
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8
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Gao ZG, Jacobson KA. Purinergic Signaling in Mast Cell Degranulation and Asthma. Front Pharmacol 2017; 8:947. [PMID: 29311944 PMCID: PMC5744008 DOI: 10.3389/fphar.2017.00947] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 12/14/2017] [Indexed: 11/13/2022] Open
Abstract
Mast cells are responsible for the majority of allergic conditions. It was originally thought that almost all allergic events were mediated directly only via the high-affinity immunoglobulin E receptors. However, recent evidence showed that many other receptors, such as G protein-coupled receptors and ligand-gated ion channels, are also directly involved in mast cell degranulation, the release of inflammatory mediators such as histamine, serine proteases, leukotrienes, heparin, and serotonin. These mediators are responsible for the symptoms in allergic conditions such as allergic asthma. In recent years, it has been realized that purinergic signaling, induced via the activation of G protein-coupled adenosine receptors and P2Y nucleotide receptors, as well as by ATP-gated P2X receptors, plays a significant role in mast cell degranulation. Both adenosine and ATP can induce degranulation and bronchoconstriction on their own and synergistically with allergens. All three classes of receptors, adenosine, P2X and P2Y are involved in tracheal mucus secretion. This review will summarize the currently available knowledge on the role of purinergic signaling in mast cell degranulation and its most relevant disease, asthma.
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Affiliation(s)
- Zhan-Guo Gao
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Kenneth A Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
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9
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Kim TH, Kim YK, Woo JS. The adenosine A3 receptor agonist Cl-IB-MECA induces cell death through Ca²⁺/ROS-dependent down regulation of ERK and Akt in A172 human glioma cells. Neurochem Res 2012; 37:2667-77. [PMID: 22878643 DOI: 10.1007/s11064-012-0855-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2012] [Revised: 07/19/2012] [Accepted: 07/25/2012] [Indexed: 02/06/2023]
Abstract
Adenosine A(3) receptor (A3AR) is coupled to G proteins that are involved in a variety of intracellular signaling pathways and physiological functions. 2-Chloro-N(6)-(3-iodobenzyl) adenosine-5'-N-methylcarboxamide (Cl-IB-MECA), an agonist of A3AR, has been reported to induce cell death in various cancer cells. However, the effect of CI-IB-MECA on glioma cell growth is not clear. This study was undertaken to examine the effect of CI-IB-MECA on glioma cell viability and to determine its molecular mechanism. CI-IB-MECA inhibited cell proliferation and induced cell death in a dose- and time-dependent manner. Treatment of CI-IB-MECA resulted in an increase in intracellular Ca(2+) followed by enhanced reactive oxygen species (ROS) generation. EGTA and N-acetylcysteine (NAC) blocked the cell death induced by CI-IB-MECA, suggesting that Ca(2+) and ROS are involved in the Cl-IB-MECA-induced cell death. Western blot analysis showed that CI-IB-MECA induced the down-regulation of extracellular signal-regulated kinases (ERK) and Akt, which was prevented by EGTA, NAC, and the A3AR antagonist MRS1191. Transfection of constitutively active forms of MEK, the upstream kinase of ERK, and Akt prevented the cell death. CI-IB-MECA induced caspase-3 activation and the CI-IB-MECA-induced cell death was blocked by the caspase inhibitors DEVD-CHO and z-VAD-FMK. In addition, expression of XIAP and Survivin were decreased in cells treated with Cl-IB-MECA. Collectively, these findings demonstrate that CI-IB-MECA induce a caspase-dependent cell death through suppression of ERK and Akt mediated by an increase in intracellular Ca(2+) and ROS generation in human glioma cells. These suggest that A3AR agonists may be a potential therapeutic agent for induction of apoptosis in human glioma cells.
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Affiliation(s)
- Thae Hyun Kim
- Department of Physiology, School of Medicine, Pusan National University, Beomeo-ri, Mulgeum-eup, Yangsan 626-870, Gyungsangnam-do, Republic of Korea
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Hüttemann M, Lee I, Gao X, Pecina P, Pecinova A, Liu J, Aras S, Sommer N, Sanderson TH, Tost M, Neff F, Aguilar-Pimentel JA, Becker L, Naton B, Rathkolb B, Rozman J, Favor J, Hans W, Prehn C, Puk O, Schrewe A, Sun M, Höfler H, Adamski J, Bekeredjian R, Graw J, Adler T, Busch DH, Klingenspor M, Klopstock T, Ollert M, Wolf E, Fuchs H, Gailus-Durner V, Hrabě de Angelis M, Weissmann N, Doan JW, Bassett DJP, Grossman LI. Cytochrome c oxidase subunit 4 isoform 2-knockout mice show reduced enzyme activity, airway hyporeactivity, and lung pathology. FASEB J 2012; 26:3916-30. [PMID: 22730437 DOI: 10.1096/fj.11-203273] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Cytochrome c oxidase (COX) is the terminal enzyme of the mitochondrial electron transport chain. The purpose of this study was to analyze the function of lung-specific cytochrome c oxidase subunit 4 isoform 2 (COX4i2) in vitro and in COX4i2-knockout mice in vivo. COX was isolated from cow lung and liver as control and functionally analyzed. COX4i2-knockout mice were generated and the effect of the gene knockout was determined, including COX activity, tissue energy levels, noninvasive and invasive lung function, and lung pathology. These studies were complemented by a comprehensive functional screen performed at the German Mouse Clinic (Neuherberg, Germany). We show that isolated cow lung COX containing COX4i2 is about twice as active (88 and 102% increased activity in the presence of allosteric activator ADP and inhibitor ATP, respectively) as liver COX, which lacks COX4i2. In COX4i2-knockout mice, lung COX activity and cellular ATP levels were significantly reduced (-50 and -29%, respectively). Knockout mice showed decreased airway responsiveness (60% reduced P(enh) and 58% reduced airway resistance upon challenge with 25 and 100 mg methacholine, respectively), and they developed a lung pathology deteriorating with age that included the appearance of Charcot-Leyden crystals. In addition, there was an interesting sex-specific phenotype, in which the knockout females showed reduced lean mass (-12%), reduced total oxygen consumption rate (-8%), improved glucose tolerance, and reduced grip force (-14%) compared to wild-type females. Our data suggest that high activity lung COX is a central determinant of airway function and is required for maximal airway responsiveness and healthy lung function. Since airway constriction requires energy, we propose a model in which reduced tissue ATP levels explain protection from airway hyperresponsiveness, i.e., absence of COX4i2 leads to reduced lung COX activity and ATP levels, which results in impaired airway constriction and thus reduced airway responsiveness; long-term lung pathology develops in the knockout mice due to impairment of energy-costly lung maintenance processes; and therefore, we propose mitochondrial oxidative phosphorylation as a novel target for the treatment of respiratory diseases, such as asthma.
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Affiliation(s)
- Maik Hüttemann
- Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, MI 48201, USA.
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Rudich N, Ravid K, Sagi-Eisenberg R. Mast cell adenosine receptors function: a focus on the a3 adenosine receptor and inflammation. Front Immunol 2012; 3:134. [PMID: 22675325 PMCID: PMC3366457 DOI: 10.3389/fimmu.2012.00134] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2012] [Accepted: 05/09/2012] [Indexed: 12/13/2022] Open
Abstract
Adenosine is a metabolite, which has long been implicated in a variety of inflammatory processes. Inhaled adenosine provokes bronchoconstriction in asthmatics or chronic obstructive pulmonary disease patients, but not in non-asthmatics. This hyper responsiveness to adenosine appears to be mediated by mast cell activation. These observations have marked the receptor that mediates the bronchoconstrictor effect of adenosine on mast cells (MCs), as an attractive drug candidate. Four subtypes (A1, A2a, A2b, and A3) of adenosine receptors have been cloned and shown to display distinct tissue distributions and functions. Animal models have firmly established the ultimate role of the A3 adenosine receptor (A3R) in mediating hyper responsiveness to adenosine in MCs, although the influence of the A2b adenosine receptor was confirmed as well. In contrast, studies of the A3R in humans have been controversial. In this review, we summarize data on the role of different adenosine receptors in mast cell regulation of inflammation and pathology, with a focus on the common and distinct functions of the A3R in rodent and human MCs. The relevance of mouse studies to the human is discussed.
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Affiliation(s)
- Noam Rudich
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University Tel Aviv, Israel
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Internalization and desensitization of adenosine receptors. Purinergic Signal 2007; 4:21-37. [PMID: 18368531 PMCID: PMC2245999 DOI: 10.1007/s11302-007-9086-7] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2007] [Accepted: 10/02/2007] [Indexed: 01/28/2023] Open
Abstract
Until now, more than 800 distinct G protein-coupled receptors (GPCRs) have been identified in the human genome. The four subtypes of the adenosine receptor (A1, A2A, A2B and A3 receptor) belong to this large family of GPCRs that represent the most widely targeted pharmacological protein class. Since adenosine receptors are widespread throughout the body and involved in a variety of physiological processes and diseases, there is great interest in understanding how the different subtypes are regulated, as a basis for designing therapeutic drugs that either avoid or make use of this regulation. The major GPCR regulatory pathway involves phosphorylation of activated receptors by G protein-coupled receptor kinases (GRKs), a process that is followed by binding of arrestin proteins. This prevents receptors from activating downstream heterotrimeric G protein pathways, but at the same time allows activation of arrestin-dependent signalling pathways. Upon agonist treatment, adenosine receptor subtypes are differently regulated. For instance, the A1Rs are not (readily) phosphorylated and internalize slowly, showing a typical half-life of several hours, whereas the A2AR and A2BR undergo much faster downregulation, usually shorter than 1 h. The A3R is subject to even faster downregulation, often a matter of minutes. The fast desensitization of the A3R after agonist exposure may be therapeutically equivalent to antagonist occupancy of the receptor. This review describes the process of desensitization and internalization of the different adenosine subtypes in cell systems, tissues and in vivo studies. In addition, molecular mechanisms involved in adenosine receptor desensitization are discussed.
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Kuehn HS, Gilfillan AM. G protein-coupled receptors and the modification of FcepsilonRI-mediated mast cell activation. Immunol Lett 2007; 113:59-69. [PMID: 17919738 DOI: 10.1016/j.imlet.2007.08.007] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2007] [Accepted: 08/16/2007] [Indexed: 12/17/2022]
Abstract
By releasing multiple pro-inflammatory mediators upon activation, mast cells are critical effector cells in the pathogenesis of allergic inflammation. The traditional viewpoint of antigen-dependent mast cell activation is that of a Th(2)-driven process whereby antigen-specific IgE molecules are produced by B cells followed by binding of the IgE to high affinity IgE receptors (FcepsilonRI) expressed on mast cells. Subsequent antigen-dependent aggregation of the FcepsilonRI initiates an intracellular signalling cascade that culminates in mediator release. Mast cell responses, including cell growth, survival, chemotaxis, and cell adhesion, however, can also be regulated by other receptors expressed on mast cells. Furthermore, FcepsilonRI-mediated mast cell mediator release can be significantly modified by ligation of specific classes of these receptors. One such class of receptors is the G protein-coupled receptors (GPCR). In this review, we describe how sub-populations of GPCRs can either enhance or inhibit FcepsilonRI-mediated mast cell activation depending on the particular G protein utilized for relaying signalling. Furthermore, we discuss the potential mechanisms whereby the signalling responses utilized by the FcepsilonRI for mast cell activation are influenced by those initiated by GPCRs to produce these diverse responses.
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Affiliation(s)
- Hye Sun Kuehn
- Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 10 Center Drive MSC 1881, Bethesda, MD 20892-1881, USA
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Volpini R, Dal Ben D, Lambertucci C, Taffi S, Vittori S, Klotz KN, Cristalli G. N6-methoxy-2-alkynyladenosine derivatives as highly potent and selective ligands at the human A3 adenosine receptor. J Med Chem 2007; 50:1222-30. [PMID: 17309246 DOI: 10.1021/jm060963u] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A new series of N6-methoxy-2-(ar)alkynyladenosine derivatives has been synthesized and tested at the human recombinant adenosine receptors. Binding studies demonstrated that the new compounds possess high affinity and selectivity for the A3 subtype. Among them, compounds bearing an N-methylcarboxamido substituent in the 4'-position showed the highest A3 affinity and selectivity. In particular, the N6-methoxy-2-p-acetylphenylethynylMECA (40; Ki A3 = 2.5 nM, A3 selectivity versus A1 = 21 500 and A2A = 4200) results in one of the most potent and selective agonists at the human A3 adenosine receptor reported so far. Furthermore, functional assay, performed with selected new compounds, revealed that the presence of an alkylcarboxamido group in the 4'-position seems to be essential to obtain full agonists at the A3 subtype. Finally, results of molecular docking analysis were in agreement with binding and functional data and could explain the high affinity and potency of the new compounds.
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Affiliation(s)
- Rosaria Volpini
- Dipartimento di Scienze Chimiche, Università di Camerino, Via S. Agostino, 1, 62032 Camerino, Italy
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Yamano K, Inoue M, Masaki S, Saki M, Ichimura M, Satoh M. Generation of adenosine A3 receptor functionally humanized mice for the evaluation of the human antagonists. Biochem Pharmacol 2005; 71:294-306. [PMID: 16300745 DOI: 10.1016/j.bcp.2005.10.028] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2005] [Revised: 10/17/2005] [Accepted: 10/17/2005] [Indexed: 11/26/2022]
Abstract
Although the adenosine A(3) receptor (A3AR), which is a G(i/o) protein-coupled receptor, has attracted considerable interest as a potential target for drugs against asthma or inflammation, the in vivo evaluation of the antagonists using rodents in the first step of drug development has been hampered by the lack of highly potent antagonists for the rodent A3AR. To evaluate the pharmacological effects of human A3AR antagonists in mice, we previously generated A3AR-humanized mice, in which the mouse A3AR gene was replaced by its human counterpart. However, the human A3AR did not lead to the phosphoinositide 3-kinase (PI3K) gamma-signaling pathway such as IgE/antigen-dependent mast cell degranulation, probably due to the uncoupling of the mouse G(i/o) protein(s). To overcome the uncoupling, we here generated A3AR functionally humanized mice by replacing the mouse A3AR gene with a human/mouse chimeric A3AR sequence in which whole intracellular regions of the human A3AR were substituted for the corresponding regions of the mouse A3AR. The chimeric A3AR led to intracellular Ca(2+) elevation and activation of the PI3Kgamma-signaling pathway, which are equivalent to the actions induced by A3AR in wild-type mice. The human A3AR antagonist had the same binding affinities for the chimeric A3AR as the human A3AR and completely antagonized this potentiation. This is the first direct evidence that the uncoupling of mouse G protein(s) to the human A3AR is due to a sequence difference in the intracellular regions of A3AR. The A3AR functionally humanized mice can be widely employed for pharmacological evaluations of the human A3AR antagonists.
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Affiliation(s)
- Kazuya Yamano
- Tokyo Research Laboratories, Kyowa Hakko Kogyo Co. Ltd., 3-6-6 Asahi-machi, Machida-shi, Tokyo 194-8533, Japan
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