Diisopropylphenyl-imidazole (DII): a new compound that exerts anthelmintic activity through novel molecular mechanisms

Abstract

Nematode parasites cause infections that affect approximately one-third of the world ́s population and considerable losses in livestock and food crops. Paradoxically, the repertoire of effective anthelmintics for treating these parasitoses is very limited, as drug development has been delayed for decades. Moreover, resistance to currently available drugs is a global concern in livestock parasites and is an emerging issue for human helminthiasis. Therefore, anthelmintics with novel mechanisms of action are urgently needed. Taking advantage of Caenorhabditis elegans as an established model system for developing agents, in this project we synthesized and screened the anthelmintic potential of novel imidazolium and imidazole derivatives. We found that one of these derivatives, diisopropylphenyl-imidazole (DII), is lethal to C. elegans at both mature and immature stages. Toxicity appears to be specific because DII concentrations which are lethal to C. elegans do not induce significant lethality on bacteria, Drosophila melanogaster,and HEK-293 cells. Our analysis of DII action on C. elegans mutant strains determined that, in the adult stage, null mutants of unc-29 are resistant to the drug. Muscle expression of this gene completely restores DII sensitivity. UNC-29 was reported as an essential constituent of the levamisole-sensitive muscle nicotinic receptor (L-AChR). Nevertheless, null mutants in unc-63 and lev-8 (essential and non-essential subunits of L-AChRs, respectively) are as sensitive to DII as the wild-type strain. Therefore, our results suggest that DII effects on adult nematodes rely on a previously undescribed AChR. This novel AChR is composed by UNC-29 (a non-alfa subunit incapable of forming homomeric receptors) and other unidentified subunits. To completely elucidate its stoichiometry, we are analyzing DII resistance in different strains containing null mutations in AChR subunits. Since DII mechanism is different from those of currently used anthelmintics, it could constitute a therapeutic option when traditional anthelmintic agents fail. Interestingly, DII targets appear to be different between larvae and adults, as unc-29 null mutant larvae are sensitive to the drug. The existence of more than one target could delay resistance development. The specificity and novel mode of action of DII, which includes differential targeting in larvae and adult nematodes, support its potential as a promising drug candidate to treat helminthiasis.