title: Reduced transcript levels of the heat shock protein 70 gene in diminazene aceturate-resistant Babesia gibsoni variants under low concentrations of diminazene aceturate.
abstract: In our previous report, we developed a diminazene aceturate (DA)-resistant Babesia gibsoni strain that was maintained in culture with 200 ng/ml DA. While developing this strain, we also obtained DA-resistant B. gibsoni variants, which were maintained in culture with DA from 1 to 175 ng/ml for more than 8 weeks. Because heat shock protein 70 (Hsp70) seems to play important roles in adaptation to a stress environment in protozoan parasites, in the present study, we examined the copy number of B. gibsoni Hsp70 (BgHsp70) transcripts of those DA-resistant variants using quantitative real-time reverse transcription-polymerase chain reaction. We found that when wild-type B. gibsoni was exposed to 1 ng/ml DA, the level of BgHsp70 transcripts was decreased at day 14. The copy number of BgHsp70 transcripts in the DA-resistant variant cultured with 1 ng/ml DA was significantly lower than in wild-type B. gibsoni, while those in DA-resistant variants increased with escalating doses of DA from 1 to 75 ng/ml, although they were lower than in wild-type B. gibsoni. However, those in DA-resistant variants cultured with >125 ng/ml DA were almost the same as wild-type B. gibsoni. These results indicated that the transcript levels of the BgHsp70 gene might be reduced when the parasites are exposed to a low concentration of DA, and then might recover to the normal level after achieving resistance against DA. We expect that further study of the function of BgHsp70 will elucidate the mechanism of drug resistance against DA in B. gibsoni.
authors.affiliation: Laboratory of Veterinary Internal Medicine, Department of Veterinary Clinical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan.
authors.forename: Shiang-Jyi
authors.initials: SJ
authors.lastname: Hwang
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamasaki
authors.forename: Kensuke
authors.initials: K
authors.lastname: Nakamura
authors.forename: Noboru
authors.initials: N
authors.lastname: Sasaki
authors.forename: Masahiro
authors.initials: M
authors.lastname: Murakami
authors.forename: Bandula
authors.initials: B
authors.lastname: Kumara
authors.forename: Wickramasekara
authors.initials: W
authors.lastname: Rajapakshage
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ohta
authors.forename: Yoshimitsu
authors.initials: Y
authors.lastname: Maede
authors.forename: Mitsuyoshi
authors.initials: M
authors.lastname: Takiguchi
mesh_terms: D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology*; D001403:Babesia / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D001404:Babesiosis / Q000662:veterinary; D004133:Diminazene / Q000031:analogs & derivatives* / Q000494:pharmacology; D004283:Dog Diseases / Q000469:parasitology; D004285:Dogs / Q000469:parasitology; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D000981:Antiprotozoal Agents; D018840:HSP70 Heat-Shock Proteins; C003915:diminazene aceturate; D004133:Diminazene