Adaptation of zebrafish gills after aluminium exposure

Aluminum is considered a dangerous pollutant, especially for aquatic organisms, since the phenomenon of acid rain increases its availability in water bodies. This study aims to obtain preliminary data on the effects of aluminum exposure on the fish gills, the first organ interacting with the metal in water bodies. Zebrafish, a widely used species in ecotoxicological studies, has been chosen as an experimental model. Adult specimens were exposed to 11 mg/L for 10, 15, and 20 days. We evaluated the in vivo oxygen consumption and tail beats, as well as gill's homogenate COX activity, ROS content, relative ability to scavenge ABTS, antioxidant enzyme activity, oxidative damage to lipids, and in vitro susceptibility to oxidative stress was evaluated. The results indicate that aluminum alters both animals' wellness and oxidative state, disrupting redox homeostasis and impairing oxygen consumption and spontaneous activity. However, after 20 days of exposure the antioxidant system efficiency increases, suggesting an adaptive mechanism that makes the animal less susceptible to aluminum-induced oxidative stress. Furthermore, after 20 days of exposure, oxygen consumption is reduced, while the tail beats increase, suggesting the onset of anaerobic metabolism as an adaptive mechanism. Overall, the results provide an essential starting point for assessing the toxicity induced by aluminum on the gills of aquatic organisms, the effects of which are still poorly understood.