title: Pharmacological characterization of novel A3 adenosine receptor-selective antagonists.
abstract: The effects of putative A3 adenosine receptor antagonists of three diverse chemical classes (the flavonoid MRS 1067, the 6-phenyl-1,4-dihydropyridines MRS 1097 and MRS 1191, and the triazoloquinazoline MRS 1220) were characterized in receptor binding and functional assays. MRS1067, MRS 1191 and MRS 1220 were found to be competitive in saturation binding studies using the agonist radioligand [125I]AB-MECA (N6-(4-amino-3-iodobenzyl)adenosine-5'-N-methyluronamide) at cloned human brain A3 receptors expressed in HEK-293 cells. Antagonism was demonstrated in functional assays consisting of agonist-induced inhibition of adenylate cyclase and the stimulation of binding of [35S]guanosine 5'-O-(3-thiotriphosphate) ([35S]GTP-gamma-S) to the associated G-proteins. MRS 1220 and MRS 1191, with KB values of 1.7 and 92 nM, respectively, proved to be highly selective for human A3 receptor vs human A1 receptor-mediated effects on adenylate cyclase. In addition, MRS 1220 reversed the effect of A3 agonist-elicited inhibition of tumor necrosis factor-alpha formation in the human macrophage U-937 cell line, with an IC50 value of 0.3 microM.
authors.affiliation: Molecular Recognition Section, LBC, NIDDK, National Institutes of Health, Bethesda, MD 20892, USA. kajacobs@helix.nih.gov
authors.forename: K A
authors.initials: KA
authors.lastname: Jacobson
authors.forename: K S
authors.initials: KS
authors.lastname: Park
authors.forename: J L
authors.initials: JL
authors.lastname: Jiang
authors.forename: Y C
authors.initials: YC
authors.lastname: Kim
authors.forename: M E
authors.initials: ME
authors.lastname: Olah
authors.forename: G L
authors.initials: GL
authors.lastname: Stiles
authors.forename: X D
authors.initials: XD
authors.lastname: Ji
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000378:metabolism; D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000166:cytology; D016466:CHO Cells; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D006224:Cricetinae; D004095:Dihydropyridines / Q000378:metabolism / Q000494:pharmacology; D005419:Flavonoids / Q000378:metabolism / Q000494:pharmacology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000166:cytology; D008264:Macrophages / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D058915:Purinergic P1 Receptor Antagonists; D011799:Quinazolines / Q000378:metabolism / Q000494:pharmacology; D011869:Radioligand Assay; D043684:Receptor, Adenosine A3; D018047:Receptors, Purinergic P1 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
chemical_list: C110042:3,6-dichloro-2'-isopropyloxy-4'-methylflavone; D000067956:Adenylyl Cyclase Inhibitors; D004095:Dihydropyridines; D005419:Flavonoids; C100736:MRS 1097; C107728:MRS 1191; D058915:Purinergic P1 Receptor Antagonists; D011799:Quinazolines; D043684:Receptor, Adenosine A3; D018047:Receptors, Purinergic P1; D014409:Tumor Necrosis Factor-alpha; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C089722:N(6)-(4-amino-3-iodobenzyl)adenosine-5'-N-methyluronamide; D000262:Adenylyl Cyclases; D000241:Adenosine