A brominated flame retardant 2,2 ',4,4 ' tetrabrominated diphenyl ether (BDE-47) leads to lipogenesis in the copepod Tigriopus japonicus

Abstract

De novo lipogenesis (DNL) is a fatty acid synthesis process that requires several genes, including sterol regulatory element binding protein (SREBP), ATP-citrate lyase (ACLY), and acetyl-CoA carboxylase (ACC). DNL up-regulation is able to induce fat accumulation through an increase in fatty acids. To investigate the relationship between DNL up-regulation and the accumulation of fatty acids and lipid droplets in response to 2,2′,4,4′ tetrabrominated diphenyl ether (BDE-47), we examined DNL in the copepod Tigriopus japonicus. Transcription levels of DNL-related genes were increased after exposure to 2.5 μg/L BDE-47 for 24 h. After exposure to 2.5 μg/L BDE-47, palmitic acid was significantly increased (P < 0.05) at days 1 and 4, along with upregulation of fatty acid synthesis-related genes (e.g., desaturases and elongases). However, docosahexaenoic acid and arachidonic acid were down-regulated at days 1 and 4, showing an antagonistic effect. Lipid droplet area significantly increased in Nile red staining analysis after 24 h of exposure to 2.5 μg/L BDE-47 in T. japonicus, while DNL was down-regulated in response to 500 μM salicylate (a lipogenesis inhibitor), indicating that BDE-47 exposure is closely associated with an increase in fatty acids in this copepod. This study provides a better understanding of the effects of BDE-47 on DNL in copepods.