In this work, we describe the identification of the 1,2,4-triazolo[4,3-a]pyrazin-3-one as a new versatile scaffold for the development of adenosine human (h) receptor antagonists. The new chemotype ensued from a molecular simplification approach applied to our previously reported 1,2,4-triazolo[4,3-a]quinoxalin-1-one series. Hence, a set of novel 8-amino-2-aryl-1,2,4-triazolopyrazin-3-one derivatives, featured by different substituents on the 2-phenyl ring (R) and at position 6 (R), was synthesized with the main purpose of targeting the hA adenosine receptor (AR). Several compounds possessed nanomolar affinity for the hA AR (K = 2.9-10 nM) and some, very interestingly, also showed high selectivity for the target. One selected potent hA AR antagonist (12, R = H, R = 4-methoxyphenyl) demonstrated some ability to counteract MPP-induced neurotoxicity in cultured human neuroblastoma SH-SY5Y cells, a widely used in vitro Parkinson's disease model. Docking studies at hAR structures were performed to rationalize the observed affinity data.
In this work, an innovative and non-radioactive functional cAMP assay was validated at the GPR17 receptor. This assay provides a simple and powerful new system to monitor G protein-coupled receptor activity through change in the intracellular cAMP concentration by using a mutant form of Photinus pyralis luciferase into which a cAMP-binding protein moiety has been inserted. Results, expressed as EC 50 or IC 50 values for agonists and antagonists, respectively, showed a strong correlation with those obtained with [ 35 S]GTPγS binding assay, thus confirming the validity of this approach in the study of new ligands for GPR17. Moreover, this method allowed confirming that GPR17 is coupled with a G αi .
A new series of 2-aralkynyl-N(6)-methyl-MECAs 10-13 were synthesized and evaluated in radioligand binding studies and in a new Eu-GTP functional assay that provides a powerful alternative to radioisotope use. The new compounds possess high affinity and selectivity for the AA(3)R with N(6)-methyl-2-phenylethynylMECA (10) showing a subnanomolar affinity and about 100000-fold selectivity vs AA(1)R and AA(2A)R. Furthermore, the new nucleosides showed to be full agonists, the N(6)-methyl-2-(2-pyridinyl)ethynylMECA (13) being the most potent in the series.
A series of aralkylphenoxyethylamine and aralkylmethoxyphenylpiperazine compounds was synthesized and their in vitro pharmacological profile at both 5-HT(1A) receptors and α(1)-adrenoceptor subtypes was measured by binding assay and functional studies. The results showed that the replacement of the 1,3-dioxolane ring by a tetrahydrofuran, cyclopentanone, or cyclopentanol moiety leads to an overall reduction of in vitro affinity at the α(1)-adrenoceptor while both potency and efficacy were increased at the 5-HT(1A) receptor. A significant improvement of 5-HT(1A)/α(1) selectivity was observed in some of the cyclopentanol derivatives synthesized (4acis, 4ccis and trans). Compounds 2a and 4ccis emerged as novel and interesting 5-HT(1A) receptor antagonist (pK(i) = 8.70) and a 5-HT(1A) receptor partial agonist (pK(i) = 9.25, pD(2) = 9.03, E(max) = 47%, 5-HT(1A)/α(1a) = 69), respectively. Docking studies were performed at support of the biological data and to elucidate the molecular basis for 5-HT(1A) agonism/antagonism activity.
Guanosine, released extracellularly from neurons and glial cells, plays important roles in the central nervous system, including neuroprotection. The innovative DELFIA Eu-GTP binding assay was optimized for characterization of the putative guanosine receptor binding site at rat brain membranes by using a series of novel and known guanosine derivatives. These nucleosides were prepared by modifying the purine and sugar moieties of guanosine at the 6- and 5'-positions, respectively. Results of these experiments prove that guanosine, 6-thioguanosine, and their derivatives activate a G protein-coupled receptor that is different from the well-characterized adenosine receptors.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.