NO-independent regulatory site of direct sGC stimulators like YC-1 and BAY 41-2272

BACKGROUND: The most important receptor for nitic oxide is the soluble guanylate cyclase (sGC), a heme containing heterodimer. Recently, a pyrazolopyridine derivative BAY 41-2272, structurally related to YC-1, was identified stimulating soluble guanylate cyclase in an NO-independent manner, which results in vasodilatation and antiplatelet activity. The study described here addresses the identification of the NO-independent site on soluble guanylate cyclase. RESULTS: We developed a photoaffinity label ((3)H-meta-PAL) for the direct and NO-independent soluble guanylate cyclase (sGC) stimulator BAY 41-2272 by introducing an azido-group into the tritium labeled compound. The synthesized photoaffinitylabel directly stimulates the purified sGC and shows in combination with NO a synergistic effect on sGC activity. Irradiation with UV light of (3)H-meta-PAL together with the highly purified sGC leads to a covalent binding to the α(1)-subunit of the enzyme. This binding is blocked by unlabeled meta-PAL, YC-1 and BAY 41-2272. For further identification of the NO-independent regulatory site the (3)H-meta-PAL labeled sGC was fragmented by CNBr digest. The (3)H-meta-PAL binds to a CNBr fragment, consisting of the amino acids 236–290 of the α(1)-subunit. Determination of radioactivity of the single PTH-cycles from the sequencing of this CNBr fragment detected the cysteines 238 and 243 as binding residues of the (3)H-meta-PAL. CONCLUSIONS: Our data demonstrate that the region surrounding the cysteines 238 and 243 in the α(1)-subunit of the sGC could play an important role in regulation of sGC activity and could be the target of this new type of sGC stimulators

Artemisone--a highly active antimalarial drug of the artemisinin class.

Artemisinin - the next generation: Efficacies of artemisone against the malaria parasite are substantially greater than those of the current artemisinin "gold standard", artesunate. Also, in contrast to most current artemisinins it displays low lipophilicity and negligible neuro- and cytotoxicity in in vitro and in vivo assays. Thus, the drug offers promise for use in artemisinin-based combination therapy. (Chemical Equation Presented). © 2006 Wiley-VCH Verlag GmbH & Co. KGaA