Purinergic signaling as potential target of thiamethoxam-induced neurotoxicity using silver catfish (Rhamdia quelen) as experimental model.

Thiamethoxam is a broad-spectrum pesticide widely used in agricultural practice throughout the world. Worryingly, this pesticide is considered a potential contaminant on the surface and underground water, being a significant risk to aquatic ecosystems and humans. In this sense, we decided to evaluate the activity of enzymes belonging to purinergic system, which is linked with regulation of extracellular nucleotides and nucleosides, as adenosine triphosphate (ATP) and adenosine (Ado) molecules involved in the regulation of immune and inflammatory responses. Such as the neurotoxic effects of thiamethoxam remain poorly understood, the aim of this study was to evaluate whether purinergic signaling may be considered a potential target of thiamethoxam-induced neurotoxicity in silver catfish (Rhamdia quelen). Brain ectonucleoside triphosphate diphosphohydrolase (ATP as substrate) and 5'-nucleotidases activities were inhibited at 3.75 µg L after 24 h of exposure and at 1.125 and 3.75 µg L after 96 h of exposure compared with the control group. On the other hand, brain adenosine deaminase activity was stimulated at 3.75 µg L after 24 h of exposure and at 1.125 and 3.75 µg L after 96 h of exposure compared with the control group. Brain ATP levels increased at 3.75 µg L after 24 h of exposure and at 1.125 and 3.75 µg L after 96 h of exposure compared with the control group, while the Ado levels decreased. The enzymatic activity of the purinergic signaling did not return to control levels after a 48-h recovery period, revealing the potential neurotoxic effects of thiamethoxam. In summary, the brain purinergic signaling may be considered a potential target for thiamethoxam-induced neurotoxicity in silver catfish.