title: Effects of in vitro exposure to ivermectin and levamisole on the expression patterns of ABC transporters in Haemonchus contortus larvae.
abstract: This study investigated the interaction of ATP binding cassette (ABC) transport proteins with ivermectin (IVM) and levamisole (LEV) in larvae of susceptible and resistant isolates of Haemonchus contortus in vitro by measuring transcription patterns following exposure to these anthelmintics. Furthermore, we studied the consequences of drug exposure by measuring the sensitivity of L3 to subsequent exposure to higher drug concentrations using larval migration assays. The most highly transcribed transporter genes in both susceptible and resistant L3 were pgp-9.3, abcf-1, mrp-5, abcf-2, pgp-3, and pgp-10. The resistant isolate showed significantly higher transcription of pgp-1, pgp-9.1 and pgp-9.2 compared to the susceptible isolate. Five P-gp genes and the haf-6 gene showed significantly higher transcription (up to 12.6-fold) after 3 h exposure to IVM in the resistant isolate. Similarly, five P-gp genes, haf-6 and abcf-1 were transcribed at significantly higher levels (up to 10.3-fold) following 3 h exposure to LEV in this isolate. On the other hand, there were no significant changes in transcriptional patterns of all transporter genes in the susceptible isolate following 3 and 6 h exposure to IVM or LEV. In contrast to these isolate-specific transcription changes, both isolates showed an increase in R-123 efflux following exposure to the drugs, suggesting that the drugs stimulated activity of existing transporter proteins in both isolates. Exposure of resistant larvae to IVM or LEV resulted, in some instances, in an increase in the proportion of the population able to migrate at the highest IVM concentrations in subsequent migration assays. The significant increase in transcription of some ABC transporter genes following 3 h exposure to both IVM and LEV in the resistant isolate only, suggests that an ability to rapidly upregulate protective pathways in response to drugs may be a component of the resistance displayed by this isolate.
authors.affiliation: CSIRO Agriculture, Queensland Bioscience Precinct, University of Queensland, Brisbane, Australia; School of Veterinary Science, University of Queensland, Gatton, Australia.
authors.forename: Ali
authors.initials: A
authors.lastname: Raza
authors.affiliation: School of Veterinary Science, University of Queensland, Gatton, Australia.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Kopp
authors.affiliation: CSIRO Agriculture, Queensland Bioscience Precinct, University of Queensland, Brisbane, Australia.
authors.forename: Neil H
authors.initials: NH
authors.lastname: Bagnall
authors.affiliation: Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, Victoria, Australia.
authors.forename: Abdul
authors.initials: A
authors.lastname: Jabbar
authors.affiliation: CSIRO Agriculture, Queensland Bioscience Precinct, University of Queensland, Brisbane, Australia. Electronic address: andrew.kotze@csiro.au.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Kotze
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis*; D000818:Animals; D000871:Anthelmintics / Q000494:pharmacology*; D004351:Drug Resistance; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects*; D006189:Haemonchus / Q000187:drug effects* / Q000254:growth & development; D007559:Ivermectin / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects; D007978:Levamisole / Q000494:pharmacology*; D014158:Transcription, Genetic
chemical_list: D018528:ATP-Binding Cassette Transporters; D000871:Anthelmintics; D007978:Levamisole; D007559:Ivermectin
keywords: ABC transporters; Anthelmintics; Haemonchus contortus; P-glycoprotein; Resistance