A novel inhibitor of c. elegans glutamate-activated chloride channel with potential anthelmintic activity

TURANI, O.; CASTRO, M.J.; FARAONI, M.B.; GERBINO, D.C.; BOUZAT, C.

Mar del Plata

Congreso; Reunión Anual de Sociedades de Biociencia 2019; 2019

Nematode parasitoses cause mortality and morbidity in humans and considerable losses in livestock, domestic animals and food crops. The acquisition of resistance to current anthelmintic drugs has prompted the search for new compounds. The free-living nematode Caenorhabditis elegans has emerged as a valuable platform for anthelmintic drug discovery. We have previously synthetized a small library of oxygenated tricyclic compounds and tested anthelmintic actions by measuring rapid effects on C.elegans. Exposure to dibenzo[b,e]oxepin-11(6H)-one (C1a) induced paralysis of C. elegans.We here sought to identify its target site and mechanism of action. Given that Cys-loopreceptors are involved in worm locomotion and are targets of classical antiparasitic drugs,we tested the effects of C1a on several C. elegans mutant strains lacking these receptors.We found that a mutant strain that lacks the invertebrate glutamate-gated chlorideselective channel (GluClR), which is the target of the widely used antiparasitic ivermectin,is resistant to C1a. Thus, the paralysis assays revealed that GluClR is the main drug targetof C1a. To unravel the molecular mechanism underlying the paralyzing action, weexpressed in mammalian cells GluClα and β subunits to form GluClRs and evaluated theeffects of C1a by electrophysiological whole-cell recordings. Glutamate elicitedmacroscopic currents from cells expressing GluClα/β heteromeric receptors whereas C1awas not capable of eliciting responses, thus indicating that it is not an agonist of GluClRsand that its mechanism differs from that of ivermectin. We found that C1a acts as aninhibitor of glutamate-responses: Preincubation of the cell with C1a produced astatistically significant decrease of the decay time constant and total charge and a slightdecrease of the peak of currents elicited by glutamate. We here propose C1a as a novelcompound or scaffold with promising antiparasitic activity mediated through inhibition ofGluClRs.