Institute of Parasitology, McGill University, Montreal, Canada.
Vet Parasitol. 2012 Dec 21;190(3-4):519-29. doi: 10.1016/j.vetpar.2012.06.038. Epub 2012 Jul 4.
The functions of nine ATP-binding cassette (ABC) transporter genes, mrp-1, mrp-4, mrp-6, pgp-2, pgp-3, pgp-4, pgp-5, haf-2 and haf-9, in an ivermectin (IVM) resistant strain of Caenorhabditis elegans were screened by comparing transcription levels between the resistant (IVR10) and wild-type (Bristol N2) strains, and by measuring the effects of RNA interference (RNAi) on the IVM resistant strain, on motility, pharyngeal pumping, egg production and death in the presence or varying concentrations of IVM (0-20 ng/ml). mRNA levels of mrp-1, 2, 4, 5, 6, 7, pgp-1, 2, 4, 12, 14, haf-1, 2 and 3 were significantly increased in IVR10 compared with the N2 strain. At 15 or 20 ng/ml IVM, down regulation of mrp-1, pgp-4, haf-2 and haf-9 significantly increased the effect of IVM to reduce egg production. At low to moderate IVM concentrations, down regulation of mrp-1 and haf-2 reduced the motility of C. elegans. However, at high IVM concentrations motility was increased by down regulation of transcription of pgp-3, pgp-4 and haf-9. Down regulation of expression of mrp-1, pgp-2 and pgp-5 resulted in reduced pharyngeal pumping in the presence of varying concentrations of IVM, while down regulation of mrp-6 and haf-2 increased pharyngeal pumping of the resistant strain irrespective of the IVM concentration used. Although the IVR10 strain was markedly resistant to IVM, compared with the unselected N2 strain, IVM led to the death of the C. elegans in a concentration dependent manner. However, differences in the IVM induced death rate, following RNAi, were not significantly different from the IVR10 strain without RNAi. The study shows that different ABC transporter genes may play a role in modulating the effects of IVM on pharyngeal pumping, motility and egg production, with down regulation of mrp-1 and haf-2 perhaps having the greatest effects. However, down regulation of expression of no individual ABC transporter gene profoundly affected the effect of IVM on mortality in the IVR10 strain. This suggests that some of these ABC transporter genes and their products may play a role in modulating the effects of IVM, but are not, individually, the critical gene responsible for IVM resistance. This study provides a model that may help to understand drug resistance in parasitic nematodes.
在伊维菌素（IVM）耐药的秀丽隐杆线虫（Caenorhabditis elegans）株中，通过比较耐药株（IVR10）和野生型株（Bristol N2）之间的转录水平，以及通过测量 RNA 干扰（RNAi）对 IVM 耐药株的运动性、咽泵、产卵和死亡率的影响，筛选了九个 ATP 结合盒（ABC）转运体基因 mrp-1、mrp-4、mrp-6、pgp-2、pgp-3、pgp-4、pgp-5、haf-2 和 haf-9 的功能。在 IVR10 中，mrp-1、2、4、5、6、7、pgp-1、2、4、12、14、haf-1、2 和 3 的 mRNA 水平与 N2 株相比显著升高。在 15 或 20ng/ml IVM 时，mrp-1、pgp-4、haf-2 和 haf-9 的下调显著增加了 IVM 降低产卵的效果。在低至中等 IVM 浓度下，mrp-1 和 haf-2 的下调降低了线虫的运动性。然而，在高 IVM 浓度下，pgp-3、pgp-4 和 haf-9 的转录下调增加了线虫的运动性。mrp-1、pgp-2 和 pgp-5 的表达下调导致在不同 IVM 浓度下咽泵的减少，而 mrp-6 和 haf-2 的下调增加了耐药株的咽泵，而与使用的 IVM 浓度无关。尽管与未选择的 N2 株相比，IVR10 株对 IVM 表现出明显的耐药性，但 IVM 以浓度依赖的方式导致线虫死亡。然而，RNAi 后 IVM 诱导死亡率的差异与未进行 RNAi 的 IVR10 株没有显著差异。该研究表明，不同的 ABC 转运体基因可能在调节 IVM 对咽泵、运动性和产卵的影响方面发挥作用，下调 mrp-1 和 haf-2 的作用可能最大。然而，下调表达没有一个 ABC 转运体基因对 IVR10 株中 IVM 对死亡率的影响有显著影响。这表明这些 ABC 转运体基因及其产物可能在调节 IVM 的作用，但不是单独的，是对 IVM 耐药性负责的关键基因。本研究提供了一个模型，可能有助于理解寄生线虫的耐药性。
