Carruthers Lauren V, Munday Jane C, Ebiloma Godwin U, Steketee Pieter, Jayaraman Siddharth, Campagnaro Gustavo D, Ungogo Marzuq A, Lemgruber Leandro, Donachie Anne-Marie, Rowan Tim G, Peter Rose, Morrison Liam J, Barrett Michael P, De Koning Harry P
Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.
School of Health and Life Sciences, Teesside University, Middlesbrough, UK.
Mol Microbiol. 2021 Aug;116(2):564-588. doi: 10.1111/mmi.14733. Epub 2021 May 18.
Trypanosoma congolense is a principal agent causing livestock trypanosomiasis in Africa, costing developing economies billions of dollars and undermining food security. Only the diamidine diminazene and the phenanthridine isometamidium are regularly used, and resistance is widespread but poorly understood. We induced stable diminazene resistance in T. congolense strain IL3000 in vitro. There was no cross-resistance with the phenanthridine drugs, melaminophenyl arsenicals, oxaborole trypanocides, or with diamidine trypanocides, except the close analogs DB829 and DB75. Fluorescence microscopy showed that accumulation of DB75 was inhibited by folate. Uptake of [ H]-diminazene was slow with low affinity and partly but reciprocally inhibited by folate and by competing diamidines. Expression of T. congolense folate transporters in diminazene-resistant Trypanosoma brucei brucei significantly sensitized the cells to diminazene and DB829, but not to oxaborole AN7973. However, [ H]-diminazene transport studies, whole-genome sequencing, and RNA-seq found no major changes in diminazene uptake, folate transporter sequence, or expression. Instead, all resistant clones displayed a moderate reduction in the mitochondrial membrane potential Ψm. We conclude that diminazene uptake in T. congolense proceed via multiple low affinity mechanisms including folate transporters; while resistance is associated with a reduction in Ψm it is unclear whether this is the primary cause of the resistance.
刚果锥虫是非洲家畜锥虫病的主要病原体，给发展中经济体造成了数十亿美元的损失，并破坏了粮食安全。目前仅定期使用双脒类药物二脒那秦和菲啶类药物异甲基锥虫胂胺，耐药性普遍存在但了解甚少。我们在体外诱导刚果锥虫IL3000菌株产生了稳定的二脒那秦耐药性。除了结构类似的DB829和DB75外，该耐药性与菲啶类药物、氨基苯基胂制剂、氧硼杂环类锥虫杀虫剂或双脒类锥虫杀虫剂均无交叉耐药性。荧光显微镜检查显示，叶酸可抑制DB75的积累。[H] - 二脒那秦的摄取缓慢，亲和力低，部分但相互地受到叶酸和竞争性双脒的抑制。在耐二脒那秦的布氏布氏锥虫中表达刚果锥虫叶酸转运蛋白，可使细胞对二脒那秦和DB829显著敏感，但对氧硼杂环类药物AN7973不敏感。然而，[H] - 二脒那秦转运研究、全基因组测序和RNA测序发现，二脒那秦摄取、叶酸转运蛋白序列或表达均无重大变化。相反，所有耐药克隆的线粒体膜电位Ψm均有适度降低。我们得出结论，刚果锥虫中二脒那秦的摄取通过多种低亲和力机制进行，包括叶酸转运蛋白；虽然耐药性与Ψm降低有关，但尚不清楚这是否是耐药性的主要原因。
