Inhibition of nitric oxide-dependent activation of soluble guanylyl cyclase by the antimalarial drug, artemisinin

The influence of artemisinin on the activity of human platelet soluble guanylyl cyclase was investigated. Artemisinin (0.1-100 microM) had no effect on the basal activity of the enzyme. Artemisinin inhibited in a concentration-dependent manner the sodium nitroprusside-induced activation of human platelet guanylyl cyclase with an IC(50) value 5.6 microM. Artemisinin (10 microM) also inhibited (by 71+/-4.0%) the activation of the enzyme by the thiol-dependent nitric oxide (NO) donor, the derivative of furoxan, 3,4-dicyano-1,2,5-oxadiazole 2-oxide (10 microM), but did not influence the stimulation of soluble guanylyl cyclase by protoporphyrin 1X. Inhibition of guanylyl cyclase activation by NO donors but not by protoporphyrin 1X represents a possible additional mechanism of the pharmacological action of this drug.