Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Avenida Bento Gonçalves, 9500, Prédio 43421, Porto Alegre 91501-970, RS, Brazil.
Int J Parasitol. 2011 Nov;41(13-14):1323-33. doi: 10.1016/j.ijpara.2011.08.004. Epub 2011 Oct 14.
ATP-binding cassette (ABC) transporters are efflux transporters found in all organisms. These proteins are responsible for pumping xenobiotic and endogenous metabolites through extra- and intracellular membranes, thereby reducing cellular concentrations of toxic compounds. ABC transporters have been associated with drug resistance in several nematodes and parasitic arthropods. Here, the ability of ABC transporter inhibitors to enhance ivermectin (IVM) sensitivity was tested in larvae and adult females of Rhipicephalus (Boophilus) microplus. Larvae of susceptible and IVM-resistant tick populations were pre-exposed to sub-lethal doses of the ABC transporter inhibitors Cyclosporin A (CsA) and MK571, and subsequently treated with IVM in a Larval Packet Test (LPT). ABC transporter inhibition by both drugs significantly reduced the concentration for 50% lethality (LC(50)) values of four IVM-resistant populations but IVM sensitivity of a susceptible population remained unchanged. IVM sensitivity in adults was assessed through an artificial feeding assay. The addition of CsA to a blood meal substantially affected IVM toxicity in adult female ticks from a resistant population by reducing oviposition and egg viability, although it did not alter IVM toxicity in susceptible females. Three partial nucleotide sequences with similarity to ABC transporters were retrieved from the DFCI Boophilus microplus Gene Index (http://compbio.dfci.harvard.edu/index.html). Their transcriptional levels in the midgut of resistant and susceptible females were determined by quantitative PCR, showing that one of these sequences was significantly up-regulated in IVM-resistant females and suggesting its participation in IVM detoxification. We believe this work reports the first known evidence for the participation of ABC transporters in IVM resistance in R. microplus.
三磷酸腺苷结合盒（ABC）转运蛋白是一种在所有生物体中都存在的外排转运蛋白。这些蛋白质负责将外源性和内源性代谢物泵过细胞内外膜，从而降低细胞内有毒化合物的浓度。ABC 转运蛋白与几种线虫和寄生节肢动物的药物耐药性有关。在这里，测试了 ABC 转运蛋白抑制剂对伊维菌素（IVM）敏感性的影响，方法是在 Rhipicephalus（Boophilus）microplus 的幼虫和成年雌性中进行。敏感和 IVM 耐药蜱种群的幼虫预先暴露于亚致死剂量的 ABC 转运蛋白抑制剂环孢菌素 A（CsA）和 MK571，随后在幼虫包测试（LPT）中用 IVM 处理。两种药物对 ABC 转运蛋白的抑制显著降低了四种 IVM 耐药群体的 50%致死浓度（LC50）值，但敏感群体对 IVM 的敏感性保持不变。通过人工喂养试验评估了成虫对 IVM 的敏感性。CsA 加入到血液餐中，通过降低产卵和卵的活力，对来自耐药群体的成年雌性蜱的 IVM 毒性有很大影响，尽管它没有改变敏感雌性对 IVM 的毒性。从 DFCI Boophilus microplus Gene Index（http://compbio.dfci.harvard.edu/index.html）中检索到与 ABC 转运蛋白具有相似性的三个部分核苷酸序列。通过定量 PCR 确定了它们在敏感和耐药雌性的中肠中的转录水平，表明其中一个序列在 IVM 耐药雌性中显著上调，表明其参与 IVM 解毒。我们认为这项工作首次报道了 ABC 转运蛋白参与 R. microplus 中 IVM 耐药性的已知证据。
