Corrigendum: A Click Chemistry-Based Proteomic Approach Reveals that 1,2,4-Trioxolane and Artemisinin Antimalarials Share a Common Protein Alkylation Profile

A Class of Valuable (Pro-)Activity-Based Protein Profiling Probes: Application to the Redox-Active Antiplasmodial Agent, Plasmodione

Plasmodione (PD) is a potent antimalarial redox-active drug acting at low nM range concentrations on different malaria parasite stages. In this study, in order to determine the precise PD protein interactome in parasites, we developed a class of (pro-)activity-based protein profiling probes (ABPP) as precursors of photoreactive benzophenone-like probes based on the skeleton of PD metabolites (PDO) generated in a cascade of redox reactions. Under UV-photoirradiation, we clearly demonstrate that benzylic oxidation of 3-benzylmenadione 11 produces the 3-benzoylmenadione probe 7, allowing investigation of the proof-of-concept of the ABPP strategy with 3-benzoylmenadiones 7-10. The synthesized 3-benzoylmenadiones, probe 7 with an alkyne group or probe 9 with -NO₂ in para position of the benzoyl chain, were found to be the most efficient photoreactive and clickable probes. In the presence of various H-donor partners, the UV-irradiation of the photoreactive ABPP probes generates different adducts, the expected "benzophenone-like" adducts (pathway 1) in addition to "benzoxanthone" adducts (via two other pathways, 2 and 3). Using both human and Plasmodium falciparum glutathione reductases, three protein ligand binding sites were identified following photolabeling with probes 7 or 9. The photoreduction of 3-benzoylmenadiones (PDO and probe 9) promoting the formation of both the corresponding benzoxanthone and the derived enone could be replaced by the glutathione reductase-catalyzed reduction step. In particular, the electrophilic character of the benzoxanthone was evidenced by its ability to alkylate heme, as a relevant event supporting the antimalarial mode of action of PD. This work provides a proof-of-principle that (pro-)ABPP probes can generate benzophenone-like metabolites enabling optimized activity-based protein profiling conditions that will be instrumental to analyze the interactome of early lead antiplasmodial 3-benzylmenadiones displaying an original and innovative mode of action.

Increasing the Strength and Production of Artemisinin and Its Derivatives

Artemisinin is a natural sesquiterpene lactone obtained from the Artemisia annua herb. It is widely used for the treatment of malaria. In this article, we have reviewed the role of artemisinin in controlling malaria, spread of resistance to artemisinin and the different methods used for its large scale production. The highest amount of artemisinin gene expression in tobacco leaf chloroplast leads to the production of 0.8 mg/g of the dry weight of the plant. This will revolutionize the treatment and control of malaria in third world countries. Furthermore, the generations of novel derivatives of artemisinin- and trioxane ring structure-inspired compounds are important for the treatment of malaria caused by resistant plasmodial species. Synthetic endoperoxide-like artefenomel and its derivatives are crucial for the control of malaria and such synthetic compounds should be further explored.

In vitro activity of anti-malarial ozonides against an artemisinin-resistant isolate

BACKGROUND

Recently published data suggest that artemisinin derivatives and synthetic peroxides, such as the ozonides OZ277 and OZ439, have a similar mode of action. Here the cross-resistance of OZ277 and OZ439 and four additional next-generation ozonides was probed against the artemisinin-resistant clinical isolate Plasmodium falciparum Cam3.I, which carries the K13-propeller mutation R539T (Cam3.IR539T).

METHODS

The previously described in vitro ring-stage survival assay (RSA0-3h) was employed and a simplified variation of the original protocol was developed.

RESULTS

At the pharmacologically relevant concentration of 700 nM, all six ozonides were highly effective against the dihydroartemisinin-resistant P. falciparum Cam3.IR539T parasites, showing a per cent survival ranging from <0.01 to 1.83%. A simplified version of the original RSA0-3h method was developed and gave similar results, thus providing a practical drug discovery tool for further optimization of next-generation anti-malarial peroxides.

CONCLUSION

The absence of in vitro cross-resistance against the artemisinin-resistant clinical isolate Cam3.IR539T suggests that ozonides could be effective against artemisinin-resistant P. falciparum. How this will translate to the human situation in clinical settings remains to be investigated.