The NQO1 of Nile tilapia (Oreochromis niloticus) is involved in the oxidative stress induced by copper exposure.

NAD(P)H dehydrogenase [quinone] 1 (NQO1) is a key antioxidant enzyme involved in cellular defense against oxidative stress; however, its role in Nile tilapia (Oreochromis niloticus) remains poorly understood. In this study, we aimed to investigate whether the Nile tilapia NQO1 gene (OnNQO1) protects cells against CuSO4·5H2O-induced oxidative damage. We hypothesized that OnNQO1 overexpression would alleviate oxidative injury and modulate inflammation-, autophagy-, and apoptosis-related responses. To test this, a eukaryotic expression plasmid, pCDNA3.1-OnNQO1, was constructed and transfected into TSE-04 cells, a Nile tilapia skin epithelial cell line, followed by CuSO4·5H2O exposure. Cell morphology, malondialdehyde (MDA) content, catalase (CAT) activity, the expression of related genes under induction and apoptosis were then evaluated. The results showed that OnNQO1 overexpression significantly reduced CuSO4·5H2O-induced morphological damage and MDA accumulation, while increasing CAT activity. After overexpression with pCDNA3.1-OnNQO1, the TSE-04 cells were exposed to CuSO4·5H2O, the expression of the antioxidant gene sod was significantly upregulated, whereas trx and hsp70 were downregulated. The expression levels of inflammation-related genes (tgfβ and il-1β), the autophagy-related gene p62, and the immune-related gene p65 first decreased and then increased. In addition, OnNQO1 overexpression resulted in substantial inhibition of CuSO4 5H2O-induced apoptotic processes in TSE-04 cells, and the normal cells increased slightly. This discovery indicates that OnNQO1 may have the function of regulating antioxidation, inflammation and apoptosis in Nile tilapia under CuSO4 5H2O exposure.