title: Effect of the P-glycoprotein inhibitor, R(+)-verapamil on the drug susceptibility of a triclabendazole-resistant isolate of Fasciola hepatica.
abstract: A study has been carried out to investigate whether the action of triclabendazole (TCBZ) against Fasciola hepatica is altered by the inhibition of P-glycoprotein (Pgp)-linked drug efflux pumps. The Sligo TCBZ-resistant and Cullompton TCBZ-susceptible fluke isolates were used for these experiments and the Pgp inhibitor selected was R(+)-verapamil [R-VPL]. In the first experiment, flukes were initially incubated for 2 h in R-VPL (100 μM), then incubated for a further 22 h in R-VPL+triclabendazole sulphoxide (TCBZ.SO) (50 μg/ml, or 0.1327 μM). For controls, flukes were incubated for 24 h in R-VPL and TCBZ.SO on their own. In a second experiment, flukes were removed from the incubation media following cessation of movement. In the third experiment, Sligo flukes were incubated in lower concentrations of R-VPL (10 μM) and TCBZ.SO (15 μg/ml, or 0.0398 μM). Morphological changes resulting from drug treatment and following Pgp inhibition were assessed by means of scanning electron microscopy. Incubation in R-VPL alone had minimal effect on either isolate. After treatment with TCBZ.SO alone, there was greater surface disruption to the Cullompton than Sligo isolate. However, combined treatment of R-VPL+TCBZ.SO led to more severe surface changes to the Sligo isolate than with TCBZ.SO on its own; this potentiation of drug activity was not seen with the Cullompton isolate. The phenomenon was evident at both concentrations of TCBZ.SO. Inclusion of R-VPL in the incubation medium also reduced the time taken for the flukes to become inactive; again, this effect was more distinct with the Sligo isolate. The results of this study support the concept of altered drug efflux in TCBZ-resistant flukes and indicate that drug transporters may play a role in the development of drug resistance.
authors.affiliation: Parasite Therapeutics Research Group, School of Biological Sciences, Medical Biology Centre, The Queen's University of Belfast, 97 Lisburn Road, Belfast, BT9 7BL, Northern Ireland, United Kingdom.
authors.forename: J
authors.initials: J
authors.lastname: Savage
authors.forename: M
authors.initials: M
authors.lastname: Meaney
authors.forename: G P
authors.initials: GP
authors.lastname: Brennan
authors.forename: E
authors.initials: E
authors.lastname: Hoey
authors.forename: A
authors.initials: A
authors.lastname: Trudgett
authors.forename: I
authors.initials: I
authors.lastname: Fairweather
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000037:antagonists & inhibitors*; D000818:Animals; D001562:Benzimidazoles / Q000494:pharmacology*; D004351:Drug Resistance; D005210:Fasciola hepatica / Q000166:cytology / Q000187:drug effects*; D005211:Fascioliasis / Q000188:drug therapy / Q000469:parasitology; D008297:Male; D008855:Microscopy, Electron, Scanning; D051381:Rats; D017207:Rats, Sprague-Dawley; D013454:Sulfoxides / Q000494:pharmacology*; D000077682:Triclabendazole; D014700:Verapamil / Q000494:pharmacology*
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D001562:Benzimidazoles; D013454:Sulfoxides; D000077682:Triclabendazole; D014700:Verapamil; C085104:triclabendazole sulfoxide