Quercetin Attenuates Environmental Avermectin-induced ROS Accumulation and Alleviates Gill Damage in Carp Through Activation of the Nrf2 Pathway.

Avermectin (AVM) is one of the most often used insecticides which is toxic to aquatic organisms, and cause oxidative-induced damages to the fish respiratory organ, the "gills". To better understand the mechanism by which an antioxidant reduces AVM-induced gill damage, we investigated the effects of Quercetin (Que) on AVM induction of oxidative stress to inhibit damages to the gills using common carp as a model organism. The Que is a fruit and vegetable rich flavonoid with antioxidant activity. In this study, four groups were created: the Control group, the Que group (400 mg/kg), the AVM group (2.404 μg/L), and the Que plus AVM group. The analytical methods were pathological structure examination, qPCR, Reactive Oxygen Species (ROS) and Western blot. The results showed that Que alleviated AVM-induced oxidative stress, inflammatory damage and apoptosis in the carp gills by activating the Nrf2 pathway. The mechanism was that Que alleviated the accumulation of ROS, reduced the balance between oxidation and antioxidant disrupted by AVM exposure, lowered the content of lipid peroxidation produced malondialdehyde (MDA), and increased the content of antioxidant enzymes including glutathione (GSH) and catalase (CAT). Nrf2 pathway was activated. Meanwhile, Que inhibited gill apoptosis in carp by decreasing the levels of Bax, Cytochrome C, Caspase9, Cleaved-Caspase3 and reduced Bcl2. This has important implications for future studies on Que and AVM. New suggestions are provided to reduce the threat of aquatic environmental pollution.