Hematophagous insects are important in public health, as they are vectors of highly prevalent diseases. One of the main strategies developed to reduce the cases of these diseases is based on the control of vector population. In insects, many physiological events are regulated by the hormones ecdysone and juvenile hormone (JH). JH levels are well regulated and the pharmacological intervention, through administration of several JH analogs, have already been used as insecticide strategies. These effects are mediated by a nuclear receptor known as ultraspiracle, USP, which regulates gene expression. Retinoids are molecules derived from retinol, which are similar to JH, and their functions are partially modulated through interaction to their nuclear receptors. Therefore, the main objective of this work is to investigate the effects of retinoids and terpenoids on several physiological parameters in the Chagas’ disease vector Rhodnius prolixus. Injection of 120 pmols of all-trans retinoic acid, 9cis retinoic acid (9cis RA) or all-trans retinol (at-ROH) in the hemocoel of adult females of R. prolixus caused no changes on oogenesis and embryogenesis. However, injection of 9cis RA and at-ROH in 4th instar nymphs led to remarkable changes in the external morphology upon moult, suggesting that these two retinoids may be acting as morphogens. Also, injection of 120 pmols of retinoids and terpenoids significantly decreased hemolymphatic phenoloxidase activity in adult insects. The R. prolixus USP was recently cloned by our group and may be involved in the retinoids/terpenoid physiological changes since its expression is up-regulated 3h after injection in both 9cis RA or JH treted insects. Taken together, these data indicate that putative USP ligands, such as retinoids/terpenoids, seems to regulate important physiological events in this insect.
Financial support: FAPERJ, CNPq, FUJB, TWAS.