MICHIGAN STATE (US) — The discovery of a second molecular receptor in mosquitoes could make insecticides used to fend off malaria and dengue fever more effective.
For many years, pyrethroid insecticides have been deployed in developing countries to fend off diseases. They’re so effective that they are the only insecticides the World Health Organization uses with their mosquito nets they distribute around the globe.
“Pyrethroids are effective because they eliminate mosquitoes while having few if any side effects on humans,” says Yuzhe Du, a Michigan State electrophysiologist and one of the lead authors of the study published in the Proceedings of the National Academy of Sciences.
“Our discovery of a second receptor in the mosquitoes’ sodium channel gives us a better understanding of how the insecticide works at a molecular level as well as could lead to ways to stem mosquitoes’ resistance to pyrethroids.”
Receptors on sodium channels act as doorways. Pyrethroids work by propping open the sodium channel. Mosquitoes don’t die from the toxin, per se. They die from sodium overdose.
With the door jammed wide open, their cells gulp down sodium, which overexcites their nervous system and eventually leads to paralysis and death.
In the last decade, growing resistance in mosquitoes has been detected in many countries. At the molecular level, resistance appears as mutations in the primary receptor in the sodium channel that allow mosquitoes to survive exposure to the insecticide.
The discovery of the second receptor in the sodium channel, however, opens up more avenues to increase pyrethroids’ effectiveness.
“One of the keys to the success of this research was our cloning of a mosquito sodium channel for the first time,” says Ke Dong, insect toxicologist and neurobiologist and the paper’s senior author. “Another lead author of this study, Yoshiko Nomura, dedicated nearly one year to make this happen, which allowed Dr. Du to perform electrophysiological experiments with the clone.”
The team then spent nearly two years to discover the new pyrethroid-binding site, she adds.
The revelation not only explains much of pyrethroid resistance found in mosquito populations worldwide, but also helps answer why they affect insects but not humans and other mammals.
Since this is a growing issue with cockroaches, bedbugs, fleas, potato beetles, and other crop pests, the discovery could lead to benefits for the pest-control industry and farming.
“Our finding may ultimately improve global prediction and monitoring of pyrethroid resistance in mosquitoes and other arthropod pests,” Dong says. “It could have broad impacts in agriculture and medicine that affect people’s lives, especially in developing countries.”
Additional co-authors include researchers from McMaster University (Canada), the Russian Academy of Sciences, and Bayer CropScience (Germany).
The National Institutes of Health provided partial funding for the study.
Source: Michigan State University