Discovery and Characterization of 2-Nitro-5-(4-(phenylsulfonyl)piperazin-1-yl)- N-(pyridin-4-ylmethyl)anilines as Novel Inhibitors of the Aedes aegypti Kir1 ( AeKir1) Channel

Molecular Insights into Pharmacological Mechanism of Insect Kir Channels and the Toxicity of Kir Inhibitors on Hemipteran Insects

Inwardly rectifying potassium channels (Kir) play a key role in regulating various physiological processes. However, the structural and pharmacological mechanisms of insect Kir channels remain unclear. In this study, we show that coexpression of different Kir subunits in the same tissue did not affect the rectification properties of strongly rectifying Kir. The Kir inhibitor VU041, along with the insecticide flonicamid and its metabolite flumetnicam, were tested for their inhibitory effects on the homotetrameric Kir1 and Kir2 channels. Both Kir1 and Kir2 channels from the two insect species showed similar pharmacological responses to VU041, flonicamid, and flumetnicam. However, VU041 demonstrated significantly higher inhibitory activity than both insecticides across all four Kir channels, while flumetnicam exhibited the weakest inhibition. Molecular docking analyses indicate that the binding site of VU041 is not the same as that of flonicamid, and flumetnicam. flonicamid, and flumetnicam have binding sites similar to the ATP binding sites in cytoplasmic region of human Kir6.2, whereas VU041 is located in the pore of the ion channel, and serves as a pore blocker that inhibits Kir channels. Mutation analysis confirmed the essential roles of these residues in channel function and binding affinity. Finally, the toxicities of the three inhibitors were evaluated in N. lugens and M. persicae. VU041, a potent inhibitor of the insect Kir channel, showed lower toxicity compared to the other two inhibitors, whereas flumethoxan, which is less active on the Kir1 channel, showed higher toxicity, probably related to the different bioavailability of the different compounds. These findings suggest that the potential of targeting Kir channels as insecticidal strategies requires further evaluation.

Involvement of Inwardly Rectifying Potassium (Kir) Channels in the Toxicity of Flonicamid to Drosophila melanogaster

Inwardly rectifying potassium (Kir) channels regulate essential physiological processes in insects and have been identified as potential targets for developing new insecticides. Flonicamid has been reported to inhibit Kir channels, disrupting the functions of salivary glands and renal tubules. However, the precise molecular target of flonicamid remains debated. It is unclear whether flonicamid directly targets Kir channels or acts on other sites involved in the activation of transient receptor potential vanilloid (TRPV) channels. In this study, we observed that flonicamid is more toxic to flies than its metabolite, flumetnicam. This higher toxicity is difficult to reconcile if nicotinamidase is the active target, as flonicamid does not inhibit nicotinamidase. An alternative explanation is that flonicamid and flumetnicam may have distinct targets or act on multiple targets. Furthermore, reducing the expression of three individual Kir genes in the salivary glands of D. melanogaster significantly decreased the flies' susceptibility to both flonicamid and flumetnicam. The double knockdown of Kir1 with Kir3 or Kir2 with Kir3 further reduced the flies' sensitivity to both compounds. These findings confirm the involvement of Kir channels in mediating the toxic effects of flonicamid on flies. Overall, this study offers new insights into the physiological roles of insect Kir channels and flonicamid toxicity.

The Molecular Physiology and Toxicology of Inward Rectifier Potassium Channels in Insects

Inward rectifier K⁺ (Kir) channels have been studied extensively in mammals, where they play critical roles in health and disease. In insects, Kir channels have recently been found to be key regulators of diverse physiological processes in several tissues. The importance of Kir channels in insects has positioned them to serve as emerging targets for the development of insecticides with novel modes of action. In this article, we provide the first comprehensive review of insect Kir channels, highlighting the rapid progress made in understanding their molecular biology, physiological roles, pharmacology, and toxicology. In addition, we highlight key gaps in our knowledge and suggest directions for future research to advance our understanding of Kir channels and their roles in insect physiology. Further knowledge of their functional roles will also facilitate their exploitation as targets for controlling arthropod pests and vectors of economic, medical, and/or veterinary relevance.

Novel inhibitors of the renal inward rectifier potassium channel of the mosquito vector Aedes aegypti

The mosquito continues to be the most lethal animal to humans due to the devastating diseases that it carries and transmits. Controlling mosquito-borne diseases relies heavily on vector management using neurotoxic insecticides with limited modes of action. This has led to the emergence of resistance to pyrethroids and other neurotoxic insecticides in mosquitoes, which has reduced the efficacy of chemical control agents. Moreover, many neurotoxic insecticides are not selective for mosquitoes and negatively impact beneficial insects such as honeybees. Developing new mosquitocides with novel mechanisms of action is a clear unmet medical need; this review covers the efforts made toward this end by targeting the renal inward rectifier potassium channel (Kir) of the mosquito.

Further SAR on the (Phenylsulfonyl)piperazine Scaffold as Inhibitors of the Aedes aegypti Kir1 (AeKir) Channel and Larvicides

Zika virus (ZIKV), dengue fever (DENV) and chikungunya (CHIKV) are arboviruses that are spread to humans from the bite of an infected adult female Aedes aegypti mosquito. As there are no effective vaccines or therapeutics for these diseases, the primary strategy for controlling the spread of these viruses is to prevent the mosquito from biting humans through the use of insecticides. Unfortunately, the commonly used classes of insecticides have seen a significant increase in resistance, thus complicating control efforts. Inhibiting the renal inward rectifier potassium (Kir) channel of the mosquito vector Aedes aegypti has been shown to be a promising target for the development of novel mosquitocides. We have shown that Kir1 channels play key roles in mosquito diuresis, hemolymph potassium homeostasis, flight, and reproduction. Previous work from our laboratories identified a novel (phenylsulfonyl)piperazine scaffold as potent AeKir channel inhibitors with activity against both adult and larval mosquitoes. Herein, we report further SAR work around this scaffold and have identified additional compounds with improved in vitro potency and mosquito larvae toxicity.