Aluminum induces a stress response in zebrafish gills by influencing metabolic parameters, morphology, and redox...

Environmental air pollution and resulting acid rain have the effect of increasing aluminum levels in water bodies. We studied the effects of aluminum on fish gills, the tissue most exposed to aluminum, using zebrafish as an experimental model. Adult zebrafish were exposed to an aluminum concentration found in polluted environments (11 mg/L) for 10, 15 and 20 days and the effects on gill morphology, redox homeostasis (ROS content, NADPH oxidase, NOX, activity, oxidative damage, antioxidant enzymes, total antioxidant capacity, in vitro susceptibility to oxidants) and on behavioural and metabolic parameters (routine respiratory oxygen consumption rMO₂, tail-beating frequency, cytochrome oxidase activity and muscle lactate content) were evaluated. Exposure to aluminum affects branchial histology, inducing alterations in primary and secondary lamellae and redox homeostasis, modifying ROS levels, NOX activity, lipid and protein oxidative damage, antioxidant enzymes, and total antioxidant capacities, and increases rMO₂. The effects exhibited a time-dependent behaviour, suggesting the activation of an adaptive response. These changes are associated with a transition of muscle metabolism from aerobic to anaerobic, as suggested by the increase in muscle lactate content, which is probably functional to preserve locomotor performance. Overall, the results here reported provide new insights into the toxicity mechanisms of Al exposure on gill tissue and the subsequent adaptive response of aquatic species.