Molecular cloning and functional characterization of NQO1 in Nile tilapia (Oreochromis niloticus): a quinone oxidoreductase mitigating ammonia-induced oxidative stress.

NAD(P)H dehydrogenase [quinone] 1 (NQO1) is a mammalian quinone oxidoreductase, which can react with cell antioxidants and nucleophiles and reduce cell damage. Although NQO1 has been widely studied in mammals, its research in aquatic animals is relatively limited, especially in Nile tilapia (Oreochromis niloticus). In this study, we successfully cloned NQO1 (OnNQO1) of O. niloticus and studied its role in oxidative stress induced by ammonia exposure. The results showed that the open reading frame (ORF) of OnNQO1 was 882 bp, encoding 293 amino acids, and its protein had NAD(P)H dehydrogenase [quinone] domain. The results of multi-sequence alignment, phylogenetic tree and motifs showed that OnNQO1 was clustered with Maylandia zebra and Pelmatolapia mariae. NQO1 was highly conserved in teleost and even mammals, but it was quite different from NQO1 in arthropods (crustaceans). OnNQO1 could be detected in 10 tissues of tilapia, with higher expression in liver and gill and lower expression in spleen. Ammonia exposure could significantly induce the expression of OnNQO1 in liver, gill, muscle, intestine, skin and head kidney of tilapia. Overexpression of OnNQO1 could significantly attenuate MDA accumulation triggered by ammonia exposure. Moreover, the overexpression of OnNQO1 could mitigate ammonia-induced oxidative stress by reducing inflammation-related genes, upregulating antioxidant-, autophagy-, and immune-related genes, and decreasing apoptosis. Therefore, the present findings are instrumental in enhancing our understanding of the role of NQO1 in teleost.