Molecular cloning of glutathione peroxidase cDNAs from Seriola lalandi and analysis of changes in expression in cultured fibroblast-like cells in response to tert-butyl hydroquinone

Glutathione peroxidases (GPxs) protect cells against oxidative damage by catalyzing the reduction of hydroperoxides. In mammals, GPx1 is expressed in most tissues and has a wide substrate range, while GPx4 plays an important role in the reduction of complex lipid hydroperoxides in cell membranes and has been shown to be important for male fertility. These enzymes have not been well studied in marine teleosts, which accumulate large quantities of polyunsaturated fatty acids that are prone to oxidation. To better understand GPx expression and regulation in marine teleosts, we have cloned and characterized GPx cDNAs from yellowtail kingfish (YTK; Seriola lalandi) and investigated changes in gene expression in response to tert-butyl hydroquinone (t-BHQ), a redox-cycling metabolite of the common aquaculture feed additive, butylated hydroxyanisole. The putative GPx1 from YTK displayed a high degree of homology with GPx1 sequences from other vertebrates. Two putative GPx4 transcript variants were obtained from YTK liver. The GPx4 variants differed only in the amino terminal region of the predicted amino acid sequences, suggesting that the variants may be encoded from a single gene with alternative first exons. Computational analysis indicated a high probability of YTK GPx4 secretion. In cultured YTK fibroblast-like cells, t-BHQ treatment significantly induced the expression of GPx1 but not GPx4. The expression of glutamyl cysteine ligase, catalytic subunit (GCLC) was also significantly induced by t-BHQ, while the expression of the antioxidant enzymes peroxiredoxin 1 (Prx1) and Prx4 remained unchanged. The induction of GPx1 and GCLC by t-BHQ suggests that the conserved redox-sensing gene regulatory pathway known as the Keap1/Nrf2/ARE axis may be involved in regulating the expression of these genes in YTK. This work contributes towards a better understanding of the regulation of glutathione peroxidases in marine fish.