Department of Medical Entomology, National Institute of Infectious Diseases, Tokyo, Japan.
Environmental Health Institute, National Environmental Agency, Singapore.
PLoS Negl Trop Dis. 2014 Jun 19;8(6):e2948. doi: 10.1371/journal.pntd.0002948. eCollection 2014 Jun.
Aedes aegypti is the major vector of yellow and dengue fevers. After 10 generations of adult selection, an A. aegypti strain (SP) developed 1650-fold resistance to permethrin, which is one of the most widely used pyrethroid insecticides for mosquito control. SP larvae also developed 8790-fold resistance following selection of the adults. Prior to the selections, the frequencies of V1016G and F1534C mutations in domains II and III, respectively, of voltage-sensitive sodium channel (Vssc, the target site of pyrethroid insecticide) were 0.44 and 0.56, respectively. In contrast, only G1016 alleles were present after two permethrin selections, indicating that G1016 can more contribute to the insensitivity of Vssc than C1534. In vivo metabolism studies showed that the SP strain excreted permethrin metabolites more rapidly than a susceptible SMK strain. Pretreatment with piperonyl butoxide caused strong inhibition of excretion of permethrin metabolites, suggesting that cytochrome P450 monooxygenases (P450s) play an important role in resistance development. In vitro metabolism studies also indicated an association of P450s with resistance. Microarray analysis showed that multiple P450 genes were over expressed during the larval and adult stages in the SP strain. Following quantitative real time PCR, we focused on two P450 isoforms, CYP9M6 and CYP6BB2. Transcription levels of these P450s were well correlated with the rate of permethrin excretion and they were certainly capable of detoxifying permethrin to 4'-HO-permethrin. Over expression of CYP9M6 was partially due to gene amplification. There was no significant difference in the rate of permethrin reduction from cuticle between SP and SMK strains.
埃及伊蚊是黄热病和登革热的主要传播媒介。经过 10 代成虫选择，一种埃及伊蚊品系（SP）对拟除虫菊酯杀虫剂氯菊酯产生了 1650 倍的抗性，氯菊酯是用于控制蚊虫的最广泛使用的拟除虫菊酯杀虫剂之一。SP 幼虫在选择成虫后也产生了 8790 倍的抗性。在选择之前，电压敏感钠通道（Vssc，拟除虫菊酯杀虫剂的靶标）的 II 区和 III 区的 V1016G 和 F1534C 突变的频率分别为 0.44 和 0.56。相比之下，在经过两次氯菊酯选择后，仅存在 G1016 等位基因，这表明 G1016 比 C1534 更能导致 Vssc 不敏感。体内代谢研究表明，SP 品系比敏感的 SMK 品系更快地排泄氯菊酯代谢物。用增效醚预处理可强烈抑制氯菊酯代谢物的排泄，表明细胞色素 P450 单加氧酶（P450s）在抗性发展中起着重要作用。体外代谢研究也表明 P450s 与抗性有关。微阵列分析表明，在 SP 品系的幼虫和成虫阶段，多个 P450 基因过度表达。通过定量实时 PCR，我们关注了两种 P450 同工型 CYP9M6 和 CYP6BB2。这些 P450 的转录水平与氯菊酯排泄率密切相关，它们肯定能够将氯菊酯解毒为 4'-HO-氯菊酯。CYP9M6 的过度表达部分归因于基因扩增。SP 和 SMK 品系之间从表皮层还原氯菊酯的速率没有显著差异。
