Safer Pesticides? Targeted Control May be Our Best Bet

Pesticides have been earning themselves a pretty bum rap these days. One of the driving factors behind the decline of honeybees and butterflies around the world, these chemicals have even recently been identified as a major water contaminant, harming aquatic life. Now, new research argues that to make pesticides acceptably safe, our best bet is to focus them solely on one target - a goal some experts think they can achieve.

A team of researchers at Purdue University is taking a step in the right direction, after having identified a new class of chemical insecticides that could provide a more selective means for controlling mosquito populations.

"These are sophisticated designer drugs," entomologist Catherine Hill explained in a recent statement. "They're like personalized medicine for mosquitoes - but in this case, the medicine is lethal."

The chemicals in question are known as dopamine receptor antagonists (DRAs) and essentially race dopamine to the protein receptors that the hormone normally occupies. When these DRAs beat dopamine to the punch, they successfully disrupt cell signaling, movement, development, and other complex behaviors in a mosquito - eventually leading to the insect's death.

As most living creatures use dopamine to some extent, this approach hardly sounds targeted, but the researchers are quick to point out that receptors vary heavily between species. That's a huge improvement over many current common insecticides, which can bind with ease to other molecules - becoming contaminants for humans and vulnerable environments.

"Many of the compounds we've identified are selective for mosquito receptors versus human receptors  - some at a more than one hundredfold," researcher Val Watts, a medicinal chemist, added reassuringly. "Also, some of these compounds are already used as treatments for diseases such as schizophrenia and depression. They are safely handled by physicians and pharmacists every day."

And recent tests with these DRAs has already shown that the focused chemicals are effective at killing both larval and adult stages of Aedes aegypti mosquitos, which transmit yellow fever, dengue and chikungunya; and Culex quinquefasciatus, the vector of West Nile virus.

The results were published in PLOS Neglected Tropical Diseases alongside a proof-of-concept trial described in The Journal of Pharmacology and Experimental Therapeutics.

"There's an urgent need for new insecticides," Hill said. "We are seeing a resurgence of infectious diseases that for the last 50 years we had the luxury of controlling with antibiotics and modern medicine."

Past research has revealed that these diseases are becoming increasingly resistant to medication even as their vectors continue to become resistant to the pesticides that normally control them. Finding new effect and safe pesticides, then, is not only a means to protect the environment but people as well.

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