Saturday, June 1, 2013

Research aims for insecticide that targets malaria mosquitoes

Acetylcholinesterase helps regulate nervous system activity by stopping electrical signaling in nerve cells. If the enzyme can't do its job, the mosquito begins convulsing and dies. The research team's goal is to develop compounds perfectly matched to the acetylcholinesterase molecules in malaria-transmitting mosquitoes, he said.

"A simple analogy would be that we're trying to make a key that fits perfectly into a lock," Bloomquist said. "We want to shut down the enzyme, but only in target species."

Bloomquist and colleagues at Virginia Tech, where the project is based, are trying to perfect mosquito-specific compounds that can be manufactured on a large scale and applied to mosquito netting and surfaces where the pests might land.

It will take at least four to five years before the team has developed and tested a compound enough that it's ready to be submitted for federal approval, Bloomquist said.

As per the claims by the researchers, conventional insecticides targeting acetylcholinesterase (AChE) typically show high mammalian toxicities and because there is resistance to these compounds in many insect species, alternatives to established AChE inhibitors used for pest control are needed. Here researchers  used a fluorescence method to monitor interactions between various AChE inhibitors and the AChE peripheral anionic site, which is a novel target for new insecticides acting on this enzyme. The assay uses thioflavin-T as a probe, which binds to the peripheral anionic site of AChE and yields an increase in fluorescent signal. Three types of AChE inhibitors were studied: catalytic site inhibitors (carbamate insecticides, edrophonium, and benzylpiperidine), peripheral site inhibitors (tubocurarine, ethidium bromide, and propidium iodide), and bivalent inhibitors (donepezil, BW284C51, and a series of bis(n)-tacrines). All were screened on murine AChE to compare and contrast changes of peripheral site conformation in the TFT assay with catalytic inhibition. All the inhibitors reduced thioflavin-T fluorescence in a concentration-dependent manner with potencies (IC50) ranging from 8 nM for bis(6)-tacrine to 159 μM for benzylpiperidine. Potencies in the fluorescence assay were correlated well with their potencies for enzyme inhibition (R2 = 0.884). Efficacies for reducing thioflavin-T fluorescence ranged from 23–36% for catalytic site inhibitors and tubocurarine to near 100% for ethidium bromide and propidium iodide. Maximal efficacies could be reconciled with known mechanisms of interaction of the inhibitors with AChE. When extended to pest species, we anticipate these findings will assist in the discovery and development of novel, selective bivalent insecticides acting on AChE....

 Ref :

Research aims for insecticide that targets malaria mosquitoes

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