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Vector-borne diseases such as dengue fever and malaria, which are transmitted by infected female mosquitoes, affect nearly half of the world's population. The emergence of insecticide-resistant mosquito populations is reducing the effectiveness of conventional insecticides and threatening current vector control strategies, which has created an urgent need to identify new molecular targets against which novel classes of insecticides can be developed. We previously demonstrated that small molecule inhibitors of mammalian Kir channels represent promising chemicals for new mosquitocide development. In this study, high-throughput screening of approximately 30,000 chemically diverse small-molecules was employed to discover potent and selective inhibitors of Aedes aegypti Kir1 (AeKir1) channels heterologously expressed in HEK293 cells. Of 283 confirmed screening ‘hits’, the small-molecule inhibitor VU625 was selected for lead optimization and in vivo studies based on its potency and selectivity toward AeKir1, and tractability for medicinal chemistry. In patch clamp electrophysiology experiments of HEK293 cells, VU625 inhibits AeKir1 with an IC50 value of 96.8 nM, making VU625 the most potent inhibitor of AeKir1 described to date. Furthermore, electrophysiology experiments in Xenopus oocytes revealed that VU625 is a weak inhibitor of AeKir2B. Surprisingly, injection of VU625 failed to elicit significant effects on mosquito behavior, urine excretion, or survival. However, when co-injected with probenecid, VU625 inhibited the excretory capacity of mosquitoes and was toxic, suggesting that the compound is a substrate of organic anion and/or ATP-binding cassette (ABC) transporters. The dose-toxicity relationship of VU625 (when co-injected with probenecid) is biphasic, which is consistent with the molecule inhibiting both AeKir1 and AeKir2B with different potencies. This study demonstrates proof-of-concept that potent and highly selective inhibitors of mosquito Kir channels can be developed using conventional drug discovery approaches. Furthermore, it reinforces the notion that the physical and chemical properties that determine a compound's bioavailability in vivo will be critical in determining the efficacy of Kir channel inhibitors as insecticides. [ABSTRACT FROM AUTHOR]

Mosquito-borne diseases such as malaria and dengue fever take a large toll on global health. The primary chemical agents used for controlling mosquitoes are insecticides that target the nervous system. However, the emergence of resistance in mosquito populations is reducing the efficacy of available insecticides. The development of new insecticides is therefore urgent. Here we show that VU573, a small-molecule inhibitor of mammalian inward-rectifying potassium (Kir) channels, inhibits a Kir channel cloned from the renal (Malpighian) tubules of Aedes aegypti (AeKir1). Injection of VU573 into the hemolymph of adult female mosquitoes (Ae. aegypti) disrupts the production and excretion of urine in a manner consistent with channel block of AeKir1 and renders the mosquitoes incapacitated (flightless or dead) within 24 hours. Moreover, the toxicity of VU573 in mosquitoes (Ae. aegypti) is exacerbated when hemolymph potassium levels are elevated, suggesting that Kir channels are essential for maintenance of whole-animal potassium homeostasis. Our study demonstrates that renal failure is a promising mechanism of action for killing mosquitoes, and motivates the discovery of selective small-molecule inhibitors of mosquito Kir channels for use as insecticides. [ABSTRACT FROM AUTHOR]