Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada.
J Exp Biol. 2011 Feb 1;214(Pt 3):462-8. doi: 10.1242/jeb.048884.
Insects have long been known to excrete toxins via the Malpighian (renal) tubules. In addition, exposure to natural or synthetic toxins is commonly associated with increases in the activity of detoxification enzymes such as the P450 monoxygenases (P450s) and the glutathione-S-transferases (GSTs). We examined the links between mechanisms for detoxification and excretion in adult Drosophila melanogaster using functional assays and measurements of changes in gene expression by quantitative reverse transcriptase PCR in response to dietary exposure to compounds known to alter activity or gene expression of P450s and GSTs. Dietary exposure to phenol, which alters gene expression for multiple GSTs after seven to 10 generations, was also associated with an increase (more than twofold) in secretion of the organic anion methotrexate (MTX) by isolated tubules. Dietary exposure to the insecticide synergist piperonyl butoxide (PBO) was associated with reduced expression of two P450 genes (Cyp4e2, Cyp4p1) and two GST genes (GstD1, GstD5) in the tubules, as well as increased expression of Cyp12d1 and GstE1. Thin layer chromatographic analysis of fluid secreted by isolated tubules indicated that dietary exposure to PBO resulted in increased levels of an MTX metabolite. In addition, exposure to PBO altered the expression of transporter genes in the tubules, including a Drosophila multidrug resistance-associated protein, and was associated with a 73% increase in MTX secretion by isolated tubules. The results suggest that exposure of Drosophila to toxins evokes a coordinated response by the Malpighian tubules, involving both alterations in detoxification pathways as well as enhanced transport.
昆虫通过马尔皮基（renal）小管排泄毒素早已为人所知。此外，接触天然或合成毒素通常与解毒酶如 P450 单加氧酶（P450s）和谷胱甘肽-S-转移酶（GSTs）的活性增加有关。我们使用功能测定和定量逆转录聚合酶链反应测量基因表达的变化，研究了成年黑腹果蝇体内解毒和排泄机制之间的联系，这些变化是对已知改变 P450s 和 GSTs 活性或基因表达的化合物进行膳食暴露的结果。膳食暴露于苯酚会导致 GSTs 的基因表达发生变化，经过 7 到 10 代后，分离的小管对有机阴离子氨甲喋呤（MTX）的分泌也增加了两倍以上。膳食暴露于杀虫剂增效剂胡椒基丁醚（PBO）与小管中两个 P450 基因（Cyp4e2，Cyp4p1）和两个 GST 基因（GstD1，GstD5）的表达减少以及 Cyp12d1 和 GstE1 的表达增加有关。分离的小管分泌的流体的薄层色谱分析表明，膳食暴露于 PBO 导致 MTX 代谢物水平升高。此外，PBO 的暴露改变了小管中的转运体基因的表达，包括果蝇多药耐药相关蛋白，并与分离的小管中 MTX 分泌增加 73%有关。结果表明，果蝇暴露于毒素会引起马尔皮基小管的协调反应，涉及解毒途径的改变以及增强的转运。
