The In Vitro Secretion of Acetylcholinesterase by Adult Stages of Heligmosomoides polygyrus: the Effects of Broad‐Spectrum Anthelmintics

Abstract

The secretion of acetylcholinesterase (AChE) by female and male Heligmosomoides polygyrus was studied in different in vitro culture media. AChE secretion was increased in the presence of fetal calf serum or bovine serum albumin (BSA). In the absence of crowding effects, specific AChE activity in excretion/secretion products was higher for male (2.41 +/- 0.07 mumol min-1 l-1 mg-1) than for female (0.56 +/- 0.04 mumol min-1 mg-1) worms but on a per nematode basis both sexes showed comparable rates of secretion. Acetylthiocholine iodide was the favoured substrate of the enzyme. When the nematodes were incubated in vitro with albendazole (ABZ), ricobendazole (RBZ), mebendazole (MBZ), levamisole (LVM), morantel (MRT) or ivermectin (IVM), at concentrations from 1 mM to 10 nM, in RPMI medium for 2 or 6 h and then transferred to a drug-free medium (RPMI medium supplemented with 0.5% BSA) for 24 h or continuously exposed to the drugs in supplement-free medium (24 h), the concentration- and time-dependent inhibitory effects on AChE secretion were observed. The continued exposure to the drugs for all incubation periods (with a single exception for LVM 1 mM) produced the highest levels of inhibition. Under these conditions, the concentrations inhibiting the secretion of AChE by 50% (IC50) relative to drug-free controls were estimated. The IC50 values ranged from 0.012 microM (IVM) to 2.96 microM (MRT). The potential of this bioassay for the selective primary evaluation of new compounds with broad-spectrum anti-nematodal activity is discussed.

Nematocidal activity of nitazoxanide in laboratory models

“…It can be used as a parameter for detecting new antiparasitic agents (Rapson et al 1986(Rapson et al , 1987Alonso-Villalobos and Martı´nez-Grueiro 2000) . When comparing in vitro effects of the tested compounds it appears that the secretion of AChE is a much more sensitive test than the release of AcP.…”

In VitroAntiparasitic Activity of Plant Extracts from Panama

“…All the broad-spectrum anthelmintics of known activity -benzimidazoles, imidazothiazoles, tetrahydropyrimidines, and avermectins -inhibit AChE secretion, ranging in IC 50 from 0.012 mM (ivermectin) to 2.96 mM (morantel) (Alonso-Villalobos & Martínez Grueiro, 2000). So, this biochemical parameter appears to be a sensitive indicator of nematocide activity.…”

“…Acetylcholinesterase and acid phosphatase activities were determined by colorimetric assays according to previously described methods (Alonso-Villalobos & Martínez-Grueiro, 2000;Martínez-Grueiro, 2002). The level of activity of each test extract was expressed as the percentage decreased in absorbance in relation to the control wells.…”

When Secretomes Meet Anthelmintics: Lessons for Therapeutic Interventions

“…This will ultimately require that the genetic toolbox for parasitic species continues to improve, along with our abilities to edit parasite nuclear genomes in a heritable manner. An underappreciated characteristic of some anthelmintics, such as ivermectin (IVM) and albendazole, is their ability to block the release of PDMs in culture [22,[32][33][34]. Does this effect contribute to their mechanisms of action, which have focused on paralysis of somatic and pharyngeal muscles and disruption of the tubulin-microtubule equilibrium, respectively?…”