Functional Characterization of the Oxantel-Sensitive Acetylcholine Receptor from Trichuris muris.

Tina V A Hansen,Mohamed Issouf,Cédric Neveu,Claude L Charvet,Richard K Grencis

doi:10.3390/ph14070698

Abstract

The human whipworm, Trichuris trichiura, is estimated to infect 289.6 million people globally. Control of human trichuriasis is a particular challenge, as most anthelmintics have a limited single-dose efficacy, with the striking exception of the narrow-spectrum anthelmintic, oxantel. We recently identified a novel ACR-16-like subunit from the pig whipworm, T. suis which gave rise to a functional acetylcholine receptor (nAChR) preferentially activated by oxantel. However, there is no ion channel described in the mouse model parasite T. muris so far. Here, we have identified the ACR-16-like and ACR-19 subunits from T. muris, and performed the functional characterization of the receptors in Xenopus laevis oocytes using two-electrode voltage-clamp electrophysiology. We found that the ACR-16-like subunit from T. muris formed a homomeric receptor gated by acetylcholine whereas the ACR-19 failed to create a functional channel. The subsequent pharmacological analysis of the Tmu-ACR-16-like receptor revealed that acetylcholine and oxantel were equally potent. The Tmu-ACR-16-like was more responsive to the toxic agonist epibatidine, but insensitive to pyrantel, in contrast to the Tsu-ACR-16-like receptor. These findings confirm that the ACR-16-like nAChR from Trichuris spp. is a preferential drug target for oxantel, and highlights the pharmacological difference between Trichuris species.

Highlights

The human whipworm, Trichuris trichiura, is a Clade I parasitic nematode [1] and one of the Soil-Transmitted Helminths (STHs) which include the roundworm Ascaris lumbricoides and the hookworms Ancylostoma duodenale and Necator americanus
Oxantel was previously shown to act on the nicotinic acetylcholine receptors (nAChRs) made of ACR-16-like subunits from T. suis [30]
To investigate the ACR-16-like nAChR from T. muris, we identified and cloned the full-length coding sequence of the T. muris acr-16-like subunit cDNA (Tmu-acr-16-like)

Summary

Introduction

The human whipworm, Trichuris trichiura, is a Clade I parasitic nematode [1] and one of the Soil-Transmitted Helminths (STHs) which include the roundworm Ascaris lumbricoides and the hookworms Ancylostoma duodenale and Necator americanus. Control of trichuriasis (and STHs in general) relies on hygiene education, access to appropriate sanitation and periodic mass drug administration of the anthelmintic drugs, albendazole and mebendazole which belong to the benzimidazoles anthelmintic drug class [6]. Trichuriasis has proven notoriously difficult to control using a single-oral-dose treatment regime with these drugs [7,8,9,10,11,12] and there are only a few anthelmintic drugs effective against Trichuris infections. One of these is oxantel, which is a m-oxyphenol of pyrantel which belongs to the tetrahydropyrimidine chemical class. Oxantel was developed in 1972 [13] and marketed in 1974 as a veterinary, narrow-spectrum anthelmintic, for the treatment of

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