Abstract
Exposure to pesticides across species has been associated with cognitive and motor impairments. As the problem impacts ecosystem stability, food production and public health, it is urgent to develop multifactorial solutions, from regulatory legislation to pharmacological alternatives that ameliorate the impairments. Fipronil, a commonly used insecticide, acts as a GABAA receptor (GABAAR) antagonist and induces motor impairments in vertebrates and invertebrates. Here, we hypothesized that kaempferol, a secondary metabolite derived from plants, acting as an allosteric modulator of GABAARs, would protect against the negative effects induced by the administration of fipronil in adults of the fruit fly Drosophila melanogaster. We further evaluated our hypothesis via co-administration of flumazenil, a competitive antagonist on the GABAAR, and through in silico analyses. We administered kaempferol prophylactically at three concentrations (10, 30 and 50 µmol l-1) and evaluated its protective effects against motor impairments induced by fipronil. We then used a single dose of kaempferol (50 µmol l-1) to evaluate its protective effect while administering flumazenil. We found that oral administration of fipronil impaired motor control and walking ability. In contrast, kaempferol was innocuous and protected flies from developing the motor-impaired phenotype, whereas the co-administration of flumazenil counteracted these protective effects. These results are supported by the binding of the ligands with the receptor. Together, our results suggest that kaempferol exerts a protective effect against fipronil via positive allosteric modulation of GABAARs, probably within brain areas such as the central complex and the mushroom bodies. These findings further support current attempts to use metabolites derived from plants as protectors against impairments produced by pesticides.
