Ferroptosis preceded the onset of oxidative stress under acute ammonia exposure and quercetin relieved ammonia-induced ferroptosis of yellow catfish (Pelteobagrus fulvidraco)

Ammonia is the most common pollutant and stressor in the aquaculture environment and can cause massive fish mortality. Its toxicity in fish is mainly related to the generation of oxidative stress, but the mechanisms are not well understood. Ferroptosis is a unique cell death pathway characterized by iron-dependent lipid peroxidation. However, little information is available regarding the association between oxidative stress and ferroptosis under ammonia stress and mitigation measures in fish. This study was divided into two parts. In the first part of the study, yellow catfish were exposed to three levels of ammonia (0 mg L-1, 5.7 mg L-1, 28.5 mg L-1) for 96 h. Results showed that ammonia poisoning could result in a decrease in survival rates, elevation of blood ammonia levels, ferroptosis activation (iron accumulation, reduced glutathione depletion, upregulation of transferrin receptor 1 and 15B-lipoxygenase, first increased then a decreased expression of glutamate/cystine antiporter system xc- and glutathione peroxidase 4) and oxidative stress (first increased and then decreased expression of superoxide dismutase and catalase). In the second part of the study, primary head-kidney macrophages were used for investigating the underlying mechanism of quercetin in protecting against ammonia-induced ferroptosis in vitro. Results showed that quercetin could decrease the production of reactive oxygen species, increase GSH contents, suppress the expression of TFR1 and LOX-15B, and upregulate the expression levels of FER, system xc- as well as GPX4. The results of this study suggested that oxidative stress induced by ferroptosis might be a prominent mechanism behind ammonia-induced cytotoxicity and quercetin exhibited good protective effects against macrophage ferroptosis under ammonia stress.