A novel modulator of the glutamate-activated chloride channel with potential anthelmintic effect

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

La Plata

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Biofísica; 2018

Sociedad Argentina de Biofísica (SAB)

Parasitic nematodes affect human health and livestock. The acquisition ofresistance to current anthelmintic drugs has prompted the search for newcompounds. The use of parasitic worms for drug testing is costly and difficult. The free-living nematode Caenorhabditis elegans has therefore emerged as a valuable platform for anthelmintic drug discovery. We have previously synthetized a small library of oxygenated tricyclic compounds and tested their anthelmintic activity by measuring rapid effects on C. elegans. The exposure todibenzo[b,e]oxepin-11(6H)-one (Compound 1a) rapidly induced paralysis of C.elegans (IC50 = 389 ± 50 mM). Given that Cys-loop receptors are involved in wormlocomotion and are targets of antiparasitic drugs, in this work we tested the effect of Compound 1a on C. elegans mutant strains lacking different Cys-loop receptors. We found that a mutant strain that lacks the invertebrate glutamate-gated chloride-selective channel (GluCl), which is the main target of the antiparasitic drug ivermectin, is resistant to Compound 1a, revealing that GluCl is the drug target. To unravel the molecular mechanism underlying the paralyzing action, we transfected mammalian cells with GluClα and β subunits and evaluated the effect of Compound 1a on whole cell currents. Glutamate elicited macroscopic currents on cells expressing GluClα/β heteromeric receptors. At -60 mV, macroscopic currents showed an onset of 89 ± 29 ms and amplitude-voltage relationships indicated no significant rectification. Preincubation with 0.5 mM Compound 1a (1 min) led to a ~80% decrease of the glutamate-evoked current, but the original peak current could not be fully recovered after 2 min wash. Moreover, the glutamate-activated current decreased with repeated exposure to the drug. These results indicate that Compound 1a acts as novel modulator of invertebrate GluCl receptors. In conclusion, we propose Compound 1a as a promising antiparasitic drug acting through GluCl receptors.