MTA Centre for Ecological Research, Balaton Limnological Institute, Tihany, Hungary.
MTA Centre for Ecological Research, Balaton Limnological Institute, Tihany, Hungary.
Aquat Toxicol. 2018 Dec;205:148-155. doi: 10.1016/j.aquatox.2018.10.013. Epub 2018 Oct 23.
Mussels are among the most frequently used invertebrate animals in aquatic toxicology to detect toxic exposure in the environment. The presence and activity of a cellular defence system, the multixenobiotic resistance (MXR) mechanism, was also established in these organisms. In isolated gill tissues of dreissenid mussels (D. bugensis) the MXR activity was assayed after treatment by commercially available insecticides (formulated products) which contain neonicotinoids as their active ingredients: Actara (thiamethoxam), Apacs (clothianidin), Calypso (thiacloprid) and Kohinor (imidacloprid), respectively. While applying the accumulation assay method, 0.5 μM rhodamine B was used as model substrate and 20 μM verapamil as model inhibitor of the MXR mechanism. In acute (in vitro) experiments when isolated gills were co-incubated in graded concentrations of insecticides and rhodamine B simultaneously, Calypso and Kohinor treatment resulted increasing rhodamine accumulation. Chemical analysis of gills in vitro incubated in insecticides demonstrated higher tissue concentrations of thiamethoxam, clothianidin and thiacloprid in the presence of verapamil suggesting that the active ingredients of Actara, Apacs and Calypso are potential substrates of the MXR mediated cellular efflux. In contrast, verapamil did significantly alter the accumulated imidacloprid concentrations in gills, suggesting that the active component of Kohinor is not transported by the MXR mechanism. Chronic (in vivo) exposures of the intact animals in lower, 1, 10 mg/L concentration of neonicotinoid products, resulted in a decreased level of both rhodamine accumulation and verapamil inhibition by the 12th-14th days of treatment. These results suggest an enhancement of MXR activity (chemostimulation), building up gradually in the animals exposed to Actara, Apacs and Kohinor, respectively. Neonicotinoid-type insecticides are generally considered as selective neurotoxins for insects, targeting the nicotinic type acetylcholine receptors (nAChRs) in their central nervous system. Our present results provide the first evidences that neonicotinoid insecticides are also able to alter the transmembrane transport mechanisms related to the MXR system.
贻贝是水生毒理学中最常被用于检测环境中有毒暴露的无脊椎动物之一。在这些生物体中，还建立了细胞防御系统——多药耐药（MXR）机制的存在和活性。在分离的贻贝（D. bugensis）鳃组织中，在用市售杀虫剂（含有新烟碱类作为其有效成分的配方产品）处理后，测定了 MXR 活性：Actara（噻虫嗪）、Apacs（氯虫腈）、Calypso（噻虫啉）和 Kohinor（吡虫啉）。在应用累积测定法时，将 0.5μM 罗丹明 B 用作模型底物，将 20μM 维拉帕米用作 MXR 机制的模型抑制剂。在急性（体外）实验中，当分离的鳃同时在不同浓度的杀虫剂和罗丹明 B 中共同孵育时，Calypso 和 Kohinor 处理导致罗丹明积累增加。在体外孵育于杀虫剂的鳃中的化学分析表明，维拉帕米存在时，噻虫嗪、氯虫腈和噻虫啉的组织浓度更高，这表明 Actara、Apacs 和 Calypso 的有效成分是 MXR 介导的细胞外排的潜在底物。相比之下，维拉帕米并未显著改变鳃中积累的吡虫啉浓度，这表明 Kohinor 的活性成分不是通过 MXR 机制转运的。在较低的 1、10mg/L 浓度的新烟碱类产品中对完整动物进行慢性（体内）暴露，在第 12-14 天的处理中，罗丹明积累和维拉帕米抑制的水平均降低。这些结果表明，在分别暴露于 Actara、Apacs 和 Kohinor 的动物中，MXR 活性（化学刺激）逐渐增强。新烟碱类杀虫剂通常被认为是对昆虫具有选择性神经毒素，作用于其中枢神经系统中的烟碱型乙酰胆碱受体（nAChRs）。我们目前的结果首次提供了证据，表明新烟碱类杀虫剂也能够改变与 MXR 系统相关的跨膜转运机制。
