家蚕添食纳米TiO_2后体内解毒酶活性及相关基因转录水平的变化

Variation of Activities and Related-gene Transcription of Detoxification Enzymes in Bombyx mori After Administration of TiO_2 Nanoparticles

给5龄起蚕连续3 d添食纳米TiO2,检测家蚕体内的解毒酶活性及相关基因转录水平,探究低浓度纳米TiO2增强家蚕抗逆性的代谢调控机制。添食5 mg/L纳米TiO2溶液浸泡处理的桑叶后,家蚕幼虫中肠与脂肪体中的细胞色素P450氧化酶(P450s)、谷胱甘肽-S-转移酶(GSTs)和非专一性酯酶(ESTs)的活性均呈现上升趋势,试验组家蚕幼虫中肠中以上3种酶的活性分别上升至对照组家蚕的1.99倍、1.44倍和2.33倍,脂肪体中3种酶的活性分别上升至对照组家蚕的8.17倍、2.07倍和1.51倍。实时荧光定量PCR检测家蚕添食低浓度纳米TiO2后3种解毒酶基因家族成员BmCYP6ae22、BmGSTο1和Bmcce的转录水平,在中肠中的转录水平分别是对照组家蚕的2.240倍、1.627倍和2.094倍,在脂肪体中的转录水平分别是对照组家蚕的3.438倍、2.357倍和1.835倍,与解毒酶活性变化趋势一致。研究结果表明,低浓度纳米TiO2可以诱导家蚕解毒酶基因上调表达,使蚕体内3大解毒酶系的活性上升,从而可增强对进入体内有毒物质的降解能力。

To explore the metabolic regulatory mechanism of how low concentration TiO2 nanoparticles （NPs） enhance the resistance in silkworm （ Bombyx mori）, activities and transcription of the relative detoxification enzymes were moni- tored after continuous feeding silkworm larvae of the 5th instar with TiO2 NPs for three days. The results showed that the activity of cytochrome P450 monooxygenases （P450s）, glutathione-S-transferases （GSTs） and carboxylesterases （ESTs） were increased in the midgut and fat body of silkworm after TiO2 NPs feeding. Compared to that of control, the activities of P450s, GSTs, and ESTs were up-regulated by 1.99, 1.44 and 2.33 folds in the midgut, and by 8. 17, 2.07 and 1.51 folds in the fat body, respectively. At the same time, the expression of detoxification enzyme-related genes BmCYP6ae22, BmGSTol and Bmcce were also determined by real-time quantitative PCR. The results showed that the expression of these three genes were increased by 2. 240, 1. 627 and 2.094 folds in the midgut and by 3. 438, 2. 357 and 1. 835 folds in the fat body respectively after TiO2 NPs feeding. Transcriptional changes of these three detoxificationenzyme-related genes were in accordance with their activity changes. These results suggest that low concentration TiO2 could up-regutate the transcription of detoxilication enzyme-related genes, leading to activity increase of three detoxification enzymes, thus enhancing the degradation of toxic substances inside silkworm body.