the interaction of the a1-adenosine receptor with its cognate g proteins (gi/go) disrupted by nf503 and nf449 at concentrations that are >30- fold higher than those required for uncoupling of b-adrenergic receptor/gs tandems; similarly, the compounds barely affected the angiotensin ii type-1 receptor . thus, nf503 and nf449 achieve essential criteria for gsa-selective antagonists. the observations demonstrate that subtype-selective g protein inhibition is feasible[1]. inhibited 5-triphosphate-induced shape change in treatment of washed human platelets with apyrase to abolish desensitization of the p2x1 receptor. the calcium rise mediated by the p2y1 receptor was also antagonized by nf449, but with lower potency. in contrast, nf449 was a very weak antagonist of inhibiting adenylyl cyclase activity mediated by p2y12. selective blockade of the p2x1 receptor with nf449 led to decreased collagen-induced aggregation. therefore, a role of this receptor in platelet activation induced by collagen was confirmed [2]. so far, characterize nf449 as the most potent and selective antagonist of receptors (the p2x1 subunit such as the p2x1 homomer and the p2x1c5 heteromer) [3].
intravenous injection of 10 mg/kg nf449 into mice exhibited selective inhibition of the p2x1 receptor and reduced intravascular platelet aggregation in a model of systemic thromboembolism without prolongation of the bleeding time. at a higher dose (50 mg/kg), nf449 blocked the three platelet p2 receptors. this, compared with mice injected with saline, led to a further reduction in platelet consumption. nf449 also decreased dose-dependently the size of thrombi formed after laser-induced injury of mesenteric arterioles. overall, our results indicate that nf449 constitutes a new agent to investigate the functions of the p2x1 receptor and could be a starting compound in the investigation for new antithrombotic drugs targeting the platelet tp2 receptors [2].
[1] hohenegger m, waldhoer m, beindl w, bing b, kreimeyer a, nickel p, nanoff c, freissmuth m. gsalpha-selective g protein antagonists. proc natl acad sci u s a. 1998 jan 6;95(1):346-51.
[2] hechler b, magnenat s, zighetti ml, kassack mu, ullmann h, cazenave jp, evans r, cattaneo m, gachet c. inhibition of platelet functions and thrombosis through selective or nonselective inhibition of the platelet p2 receptors with increasing doses of nf449 [4,4',4'',4'''-(carbonylbis(imino-5,1,3-benzenetriylbis-(carbonylimino)))tetrakis-benzene-1,3-disulfonic acid octasodium salt]. j pharmacol exp ther. 2005 jul;314(1):232-43. epub 2005 mar 25.
[3]. rettinger j, braun k, hochmann h, kassack mu, ullmann h, nickel p, schmalzing g, lambrecht g. profiling at recombinant homomeric and heteromeric rat p2x receptors identifies the suramin analogue nf449 as a highly potent p2x1 receptor antagonist. neuropharmacology. 2005 mar;48 (3):461-8.
