Specific signal pathway inhibition reduces ecdysteroid production and follicle cell proliferation in Aedes aegypti ovaries

Insecticides remain a prominent means of mosquito population control, but the spread of resistance to these chemicals necessitates the development of alternative control measures. By hindering essential reproductive processes in the female mosquito, vector populations may be decreased, and subsequently, so may disease transmission.   Here we explore the strategy of using potent chemical inhibitors to disrupt the convergent insulin and target of rapamycin (TOR) pathways, which stimulate and enhance different processes required for female reproduction in Ae. aegypti.  After the female takes a blood meal, insulin like peptides (ILPs) are released by the brain that activate ecdysteroid production through insulin signaling.  Additionally, digestion of the blood meal releases amino acids, which are key activators of the TOR pathway.  Inhibition of insulin and TOR signaling was previously shown to reduce ovary ecdysteroid production.  Ovaries of non-blood fed female mosquitoes were incubated in an amino acid rich media with ILP3 and either OSI906, an inhibitor of insulin receptor activation, or Torin 2, an inhibitor of the TOR protein.  After incubation, media was assayed for ecdysteroid hormone production, and ovaries were stained for EdU as a marker of follicle cell proliferation.  We observed a dose-responsive reduction in ecdysteroid production and follicle cell proliferation in the ovaries with both OSI906 and Torin 2, suggesting a possible correlation between ovary ecdysteroid production and follicle cell proliferation.