title: Study of A(2A) adenosine receptor gene deficient mice reveals that adenosine analogue CGS 21680 possesses no A(2A) receptor-unrelated lymphotoxicity.
abstract: Cell surface A(2A) adenosine receptor (A(2A)R) mediated signalling affects a variety of important processes and adenosine analogues possess promising pharmacological properties. Demonstrating the receptor specificity of potentially lymphotoxic adenosine-based drugs facilitates their development for clinical applications. To distinguish between the receptor-dependent and -independent lymphotoxicity and apoptotic activity of adenosine and its analogues we used lymphocytes from A(2A)R-deficient mice. Comparison of A(2A)R-expressing (+/+) and A(2A)R-deficient (-/-) cells in cyclic AMP accumulation assays confirmed that the A(2A)R agonist CGS 21680 is indeed selective for A(2A) receptors in T-lymphocytes. Incubation of A(2A)R-expressing thymocytes with extracellular adenosine or CGS 21680 in vitro results in the death of about 7-15% of thymocytes. In contrast, no death was induced in parallel assays in cells from A(2A)R-deficient mice, providing genetic evidence that CGS 21680 does not display adenosine receptor-independent intracellular cytotoxicity. The A(2A) receptor-specific lymphotoxicity of CGS 21680 is also demonstrated in a long-term (6-day) in vitro model of thymocyte positive selection where addition of A(2A)R antagonist ZM 241,385 did block the effects of CGS 21680, allowing the survival of T cells. The use of cells from adenosine receptor-deficient animals is proposed as a part of the screening process for potential adenosine-based drugs for their receptor-independent cytotoxicity and lymphotoxicity.
authors.affiliation: Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, MD 20892-1892, USA.
authors.forename: S G
authors.initials: SG
authors.lastname: Apasov
authors.forename: J F
authors.initials: JF
authors.lastname: Chen
authors.forename: P T
authors.initials: PT
authors.lastname: Smith
authors.forename: M A
authors.initials: MA
authors.lastname: Schwarzschild
authors.forename: J S
authors.initials: JS
authors.lastname: Fink
authors.forename: M V
authors.initials: MV
authors.lastname: Sitkovsky
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000633:toxicity; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism; D051379:Mice; D010627:Phenethylamines / Q000633:toxicity*; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D018047:Receptors, Purinergic P1 / Q000172:deficiency / Q000502:physiology*; D013601:T-Lymphocytes / Q000187:drug effects*
chemical_list: D010627:Phenethylamines; D011948:Receptors, Antigen, T-Cell; D018047:Receptors, Purinergic P1; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; D000242:Cyclic AMP; D000241:Adenosine