Rapid kill of malaria parasites by artemisinin and semi-synthetic endoperoxides involves ROS-dependent depolarization of the membrane potential

Abstract

ObjectivesArtemisinin and artemisinin semi-synthetic derivatives (collectively known as endoperoxides) are first-line antimalarials for the treatment of uncomplicated and severe malaria. Endoperoxides display very fast killing rates and are generally recalcitrant to parasite resistance development. These key pharmacodynamic features are a result of a complex mechanism of action, the details of which lack consensus. Here, we report on the primary physiological events leading to parasite death.MethodsParasite mitochondrial (ΔΨm) and plasma membrane (ΔΨp) electrochemical potentials were measured using real-time single-cell imaging following exposure to pharmacologically relevant concentrations of endoperoxides (artemisinin, dihydroartemisinin, artesunate and the synthetic tetraoxane RKA182). In addition, mitochondrial electron transport chain components NADH:quinone oxidoreductase (alternative complex I), bc1 (complex III) and cytochrome oxidase (complex IV) were investigated to determine their functional sensitivity to the various endoperoxides.ResultsParasite exposure to endoperoxides resulted in rapid depolarization of parasite ΔΨm and ΔΨp. The rate of depolarization was decreased in the presence of a reactive oxygen species (ROS) scavenger and Fe3+ chelators. Depolarization of ΔΨm by endoperoxides is not believed to be through the inhibition of mitochondrial electron transport chain components, owing to the lack of significant inhibition when assayed directly.ConclusionsThe depolarization of ΔΨm and ΔΨp is shown to be mediated via the generation of ROS that are initiated by iron bioactivation of endoperoxides and/or catalysed by iron-dependent oxidative stress. These data are discussed in the context of current hypotheses concerning the mode of action of endoperoxides.

Artemisinin activity-based probes identify multiple molecular targets within the asexual stage of the malaria parasites Plasmodium falciparum 3D7

“…In the parasite, a V-type ATPase generates a proton motive force across the parasite plasma membrane as well as across the digestive food vacuole (49,50). It has previously been shown that ART results in rapid depolarization of the parasite plasma membrane (51). Although the depolarization of the plasma membrane was previously shown to be partially attributed to lipid peroxidation, the ARTABPPs data presented here could be interpreted as showing the potential for a direct inhibition of the V-type ATPase activity by ART.…”

Antimalarial Action of Artesunate Involves DNA Damage Mediated by Reactive Oxygen Species

“…Bioactivated endoperoxides have been shown to generate downstream radical oxygen species, disrupting a number of parasite membranes and enzymes (23). In cancer cells, cytotoxic activity has been shown to arise from ROS-mediated oxidative DNA damage induced by ART (39).…”

“…Recently, artemisinins have been shown to be distributed to the mitochondrial compartment in the parasite, result-ing in impaired mitochondrial functions (22) and ROS-dependent depolarization of plasma and mitochondrial membranes (23). Even though many cellular targets have been identified, the mechanism of action of artemisinin derivatives still remains ambiguous.…”

Mechanism of artemisinin phytotoxicity action: Induction of reactive oxygen species and cell death in lettuce seedlings

“…Characterization of the mode of action of allelochemicals in receptor species is essential for a full understanding of this planteplant interaction. Previous studies demonstrated that allelochemicals could have multiple phytotoxic effects to influence almost every aspect of plant growth and development such as gene expression, phytohormone activity, ion uptake and photosynthetic function (Babula et al, 2009). Therefore, phytotoxic mechanisms of allelochemicals will undoubtedly be complex.…”