Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL, 32610, USA.
Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL, 32610, USA.
Pestic Biochem Physiol. 2024 May;201:105898. doi: 10.1016/j.pestbp.2024.105898. Epub 2024 Apr 8.
The dinoflagellate Karenia brevis is a causative agent of red tides in the Gulf of Mexico and generates a potent family of structurally related brevetoxins that act via the voltage-sensitive Na channel. This project was undertaken to better understand the neurotoxicology and kdr cross-resistance to brevetoxins in house flies by comparing the susceptible aabys strain to ALkdr (kdr) and JPskdr (super-kdr). When injected directly into the hemocoel, larvae exhibited rigid, non-convulsive paralysis consistent with prolongation of sodium channel currents, the known mechanism of action of brevetoxins. In neurophysiological studies, the firing frequency of susceptible larval house fly central nervous system preparations showed a > 200% increase 10 min after treatment with 1 nM brevetoxin-3. This neuroexcitation is consistent with the spastic paralytic response seen after hemocoel injections. Target site mutations in the voltage-sensitive sodium channel of house flies, known to confer knockdown resistance (kdr and super-kdr) against pyrethroids, attenuated the effect of brevetoxin-3 in baseline firing frequency and toxicity assays. The rank order of sensitivity to brevetoxin-3 in both assays was aabys > ALkdr > JPskdr. At the LD level, resistance ratios for the knockdown resistance strains were 6.9 for the double mutant (super-kdr) and 2.3 for the single mutant (kdr). The data suggest that knockdown resistance mutations may be one mechanism by which flies survive brevetoxin-3 exposure during red tide events.
短沟对甲藻是墨西哥湾赤潮的病原体，产生一系列结构相关的强效膝沟藻毒素，通过电压敏感的钠通道起作用。本项目旨在通过比较易感的 aabys 品系与 ALkdr（kdr）和 JPskdr（超级 kdr），更好地了解对家蝇的神经毒理学和 kdr 对膝沟藻毒素的交叉抗性。当直接注射到家蝇幼虫的血腔时，幼虫表现出僵硬、非惊厥性麻痹，与延长钠通道电流一致，这是膝沟藻毒素的已知作用机制。在神经生理学研究中，易感家蝇幼虫中枢神经系统制剂的放电频率在 1 nM 膝沟藻毒素-3 处理后 10 分钟增加了>200%。这种神经兴奋与血腔注射后出现的痉挛性麻痹反应一致。家蝇电压敏感钠通道中的靶位突变，已知对拟除虫菊酯具有击倒抗性（kdr 和超级 kdr），减弱了膝沟藻毒素-3 对基础放电频率和毒性测定的影响。在这两种测定中，对膝沟藻毒素-3 的敏感性的排序为 aabys > ALkdr > JPskdr。在 LD 水平下，击倒抗性菌株的抗性比分别为双突变体（超级 kdr）的 6.9 和单突变体（kdr）的 2.3。数据表明，击倒抗性突变可能是在赤潮事件中，蝇类在暴露于膝沟藻毒素-3 时存活的一种机制。
