School of BioSciences, The University of Melbourne, Melbourne, Victoria, Australia.
Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA.
Pest Manag Sci. 2023 Oct;79(10):3913-3925. doi: 10.1002/ps.7585. Epub 2023 Jun 11.
The insecticides spinosad and imidacloprid are neurotoxins with distinct modes of action. Both target nicotinic acetylcholine receptors (nAChRs), albeit different subunits. Spinosad is an allosteric modulator, that upon binding initiates endocytosis of its target, nAChRα6. Imidacloprid binding triggers excessive neuronal ion influx. Despite these differences, low-dose effects converge downstream in the precipitation of oxidative stress and neurodegeneration.
Using RNA-sequencing, we compared the transcriptional signatures of spinosad and imidacloprid, at low-dose exposures. Both insecticides cause up-regulation of glutathione S-transferase and cytochrome P450 genes in the brain and down-regulation in the fat body, whereas reduced expression of immune-related genes is observed in both tissues. Spinosad shows unique impacts on genes involved in lysosomal function, protein folding, and reproduction. Co-expression analyses revealed little to no correlation between genes affected by spinosad and nAChRα6 expressing neurons, but a positive correlation with glial cell markers. We also detected and experimentally confirmed nAChRα6 expression in fat body cells and male germline cells. This led us to uncover lysosomal dysfunction in the fat body following spinosad exposure, and a fitness cost in spinosad-resistant (nAChRα6 null) males - oxidative stress in testes, and reduced fertility.
Spinosad and imidacloprid share transcriptional perturbations in immunity-, energy homeostasis-, and oxidative stress-related genes. Low doses of other neurotoxic insecticides should be investigated for similar impacts. While target-site spinosad resistance mutation has evolved in the field, this may have a fitness cost. Our findings demonstrate the power of tissue-specific transcriptomics approach and the use of single-cell transcriptome data. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
杀虫剂多杀菌素和吡虫啉是具有不同作用模式的神经毒素。两者都靶向烟碱型乙酰胆碱受体（nAChRs），尽管是不同的亚基。多杀菌素是一种变构调节剂，与靶标 nAChRα6 结合后会引发内吞作用。吡虫啉结合会引发神经元离子过度内流。尽管存在这些差异，但低剂量效应会在氧化应激和神经退行性变的加剧中汇聚。
我们使用 RNA 测序比较了低剂量暴露下多杀菌素和吡虫啉的转录特征。两种杀虫剂都会导致大脑中谷胱甘肽 S-转移酶和细胞色素 P450 基因的上调，以及脂肪体中基因的下调，而两种组织中免疫相关基因的表达都减少。多杀菌素对涉及溶酶体功能、蛋白质折叠和生殖的基因有独特的影响。共表达分析显示，受多杀菌素影响的基因与表达 nAChRα6 的神经元之间几乎没有相关性，但与神经胶质细胞标记物呈正相关。我们还检测到并实验证实了脂肪体细胞和雄性生殖细胞中 nAChRα6 的表达。这导致我们发现多杀菌素暴露后脂肪体中的溶酶体功能障碍，以及在多杀菌素抗性（nAChRα6 缺失）雄性中出现的生殖力下降和氧化应激，即睾丸中的氧化应激和生育力下降。
多杀菌素和吡虫啉在免疫、能量稳态和氧化应激相关基因方面存在转录扰动。其他神经毒性杀虫剂的低剂量也应该进行类似的影响调查。尽管田间已经出现了靶标位点多杀菌素抗性突变，但这可能会带来适应性成本。我们的研究结果证明了组织特异性转录组学方法和使用单细胞转录组数据的力量。© 2023 作者。害虫管理科学由 John Wiley & Sons Ltd 代表化学工业协会出版。
