Brandon University, Department of Biology, Brandon, Manitoba, R7A 6A9, Canada.
Vet Parasitol. 2013 Jan 31;191(3-4):264-75. doi: 10.1016/j.vetpar.2012.09.021. Epub 2012 Sep 23.
In vertebrates, the function of P-glycoprotein (PGP) is to protect against toxic compounds through active efflux of the toxin from target tissues. In clinical oncology, the overexpression of PGP confers drug resistance. The function(s) of PGP in nematode physiology or in conferring drug resistance is less understood. The objective of this study was to determine the role of PGP in drug resistance in nematodes using Caenorhabditis elegans and ivermectin (IVM) as the model system. The IVM sensitive wild-type Bristol N2 strain, seven PGP deletion strains and a triple IVM receptor (avr-14/avr-15/glc-1) knock-out strain showing synthetic resistance to IVM (IVM-R) were used to (1) compare the gene expression signatures of 15 PGPs in the wild-type and resistant strains following treatment; (2) measure motility and pharyngeal pumping phenotypes in the wild-type, IVM-R and PGP deletion strains before and after treatment; and (3) quantify the phenotypic responses of the wild-type and IVM-R strains to IVM or IVM co-administered with 12 chemosensitizers that interfere with PGP function. IVM induced changes in both amplitude and timing of gene expression for the 15 PGP genes. Following IVM treatment, the most significant effects were observed in the IVM-R strain for those PGP genes expressed in the neurons, pharynx and intestine. Inactivation of pgp-2, pgp-5, pgp-6, pgp-7, pgp-12 and pgp-13 resulted in increased sensitivity to IVM compared with the wild-type. The phenotypic responses of the IVM-R strain differed from those of the wild-type strain when exposed to IVM alone, or IVM co-administered with chemosensitizers. The phenotypic responses to the co-administration of chemosensitizers varied with the concentration of IVM used, suggesting that the action of PGP's is influenced by the concentration of IVM. Verapamil restored sensitivity to IVM in the IVM-R strain. Our results demonstrate that PGPs play a role in protecting C. elegans from IVM toxicity and inhibition of PGP enhances susceptibility to IVM. PGP may be a mechanism for multidrug resistance (MDR) in parasitic nematodes.
在脊椎动物中，P-糖蛋白（PGP）的功能是通过将毒素从靶组织主动排出来保护机体免受有毒化合物的侵害。在临床肿瘤学中，PGP 的过度表达会导致药物耐药性。PGP 在线虫生理学中的功能或在赋予药物耐药性方面的了解较少。本研究的目的是使用秀丽隐杆线虫和伊维菌素（IVM）作为模型系统，确定 PGP 在线虫药物耐药性中的作用。使用伊维菌素敏感的野生型 Bristol N2 菌株、七个 PGP 缺失菌株和一个三重 IVM 受体（avr-14/avr-15/glc-1）敲除菌株（对 IVM 表现出合成耐药性，即 IVM-R）来：（1）比较野生型和耐药型菌株在治疗后 15 个 PGP 基因的基因表达特征；（2）在治疗前后测量野生型、IVM-R 和 PGP 缺失菌株的运动和咽部抽吸表型；（3）量化野生型和 IVM-R 菌株对 IVM 或 IVM 与 12 种干扰 PGP 功能的化学增敏剂联合治疗的表型反应。IVM 诱导了 15 个 PGP 基因的表达幅度和时间发生变化。在 IVM 治疗后，在神经元、咽和肠中表达的那些 PGP 基因在 IVM-R 菌株中观察到最显著的影响。与野生型相比，pgp-2、pgp-5、pgp-6、pgp-7、pgp-12 和 pgp-13 的失活导致对 IVM 的敏感性增加。当单独暴露于 IVM 或与化学增敏剂联合使用时，IVM-R 菌株的表型反应与野生型菌株不同。对化学增敏剂联合使用的表型反应随 IVM 浓度的变化而变化，这表明 PGP 的作用受到 IVM 浓度的影响。维拉帕米使 IVM-R 菌株对 IVM 的敏感性恢复。我们的结果表明，PGP 在保护秀丽隐杆线虫免受 IVM 毒性和抑制 PGP 方面发挥作用，增强了对 IVM 的敏感性。PGP 可能是寄生线虫多药耐药（MDR）的一种机制。
