Laboratoire Signalisation Fonctionnelle des Canaux Ioniques et des Récepteurs (SiFCIR), UPRES EA 2647, USC INRA 1330, SFR QUASAV 4207, Université Bretagne Loire, Univ. Angers, UFR Sciences, Angers Cedex, France.
Laboratoire Signalisation Fonctionnelle des Canaux Ioniques et des Récepteurs (SiFCIR), UPRES EA 2647, USC INRA 1330, SFR QUASAV 4207, Université Bretagne Loire, Univ. Angers, UFR Sciences, Angers Cedex, France; Plant Protection Department, Faculty of Agriculture, Assiut University, 71526 Assiut, Egypt.
Neurotoxicology. 2017 Sep;62:239-247. doi: 10.1016/j.neuro.2017.08.001. Epub 2017 Aug 12.
Neonicotinoids are the most important class of insecticides used in agriculture over the last decade. They act as selective agonists of insect nicotinic acetylcholine receptors (nAChRs). The emergence of insect resistance to these insecticides is one of the major problems, which limit the use of neonicotinoids. The aim of our study is to better understand physiological changes appearing after subchronic exposure to sublethal doses of insecticide using complementary approaches that include toxicology, electrophysiology, molecular biology and calcium imaging. We used cockroach neurosecretory cells identified as dorsal unpaired median (DUM) neurons, known to express two α-bungarotoxin-insensitive (α-bgt-insensitive) nAChR subtypes, nAChR1 and nAChR2, which differ in their sensitivity to imidacloprid. Although nAChR1 is sensitive to imidacloprid, nAChR2 is insensitive to this insecticide. In this study, we demonstrate that subchronic exposure to sublethal dose of imidacloprid differentially changes physiological and molecular properties of nAChR1 and nAChR2. Our findings reported that this treatment decreased the sensitivity of nAChR1 to imidacloprid, reduced current density flowing through this nAChR subtype but did not affect its subunit composition (α3, α8 and β1). Subchronic exposure to sublethal dose of imidacloprid also affected nAChR2 functions. However, these effects were different from those reported on nAChR1. We observed changes in nAChR2 conformational state, which could be related to modification of the subunit composition (α1, α2 and β1). Finally, the subchronic exposure affecting both nAChR1 and nAChR2 seemed to be linked to the elevation of the steady-state resting intracellular calcium level. In conclusion, under subchronic exposure to sublethal dose of imidacloprid, cockroaches are capable of triggering adaptive mechanisms by reducing the participation of imidacloprid-sensitive nAChR1 and by optimizing functional properties of nAChR2, which is insensitive to this insecticide.
新烟碱类杀虫剂是过去十年农业中使用的最重要的杀虫剂类别。它们作为昆虫烟碱型乙酰胆碱受体（nAChRs）的选择性激动剂。昆虫对这些杀虫剂产生抗药性是限制新烟碱类杀虫剂使用的主要问题之一。我们研究的目的是通过包括毒理学、电生理学、分子生物学和钙成像在内的互补方法，更好地了解亚慢性暴露于亚致死剂量杀虫剂后出现的生理变化。我们使用已鉴定为背侧未配对中神经分泌细胞（DUM）的蟑螂神经元，这些神经元已知表达两种α-银环蛇毒素不敏感（α-bgt-insensitive）的 nAChR 亚型，nAChR1 和 nAChR2，它们对吡虫啉的敏感性不同。尽管 nAChR1 对吡虫啉敏感，但 nAChR2 对这种杀虫剂不敏感。在这项研究中，我们证明亚慢性暴露于亚致死剂量的吡虫啉会使 nAChR1 和 nAChR2 的生理和分子特性发生差异变化。我们的研究结果表明，这种处理降低了 nAChR1 对吡虫啉的敏感性，减少了流经这种 nAChR 亚型的电流密度，但不影响其亚基组成（α3、α8 和 β1）。亚慢性暴露于亚致死剂量的吡虫啉也影响 nAChR2 的功能。然而，这些影响与 nAChR1 上报道的不同。我们观察到 nAChR2 构象状态的变化，这可能与亚基组成（α1、α2 和 β1）的修饰有关。最后，影响 nAChR1 和 nAChR2 的亚慢性暴露似乎与稳态静息细胞内钙水平的升高有关。总之，在亚慢性暴露于亚致死剂量的吡虫啉下，蟑螂能够通过减少对吡虫啉敏感的 nAChR1 的参与和优化对这种杀虫剂不敏感的 nAChR2 的功能特性来触发适应机制。
