Environmentally relevant concentrations of tris (2-chloroethyl) phosphate (TCEP) induce hepatotoxicity in zebrafish (Danio rerio): a whole life-cycle assessment.

Tris (2-chloroethyl) phosphate (TCEP), a typical organophosphate flame retardant, is of increasingly great concern considering their ubiquitous presence in aquatic environments and potential ecotoxicity. The present work was aimed to investigate the potential growth inhibition and hepatic stress induced by whole life-cycle exposure to TCEP (0.8, 4, 20 and 100 µg/L) in zebrafish. The results revealed that the body length, body mass and hepatic-somatic index (HSI) of zebrafish were significantly declined after exposure to TCEP for 120 days. GPx activity and GSH content were increased in the liver of zebrafish treated with low concentrations (0.8 and 4 µg/L) of TCEP, while exposure to high concentrations (20 and 100 µg/L) of TCEP reduced antioxidative capacity and elevated lipid peroxidation (LPO) levels. Gene transcription analysis demonstrated that the mRNA levels of nrf2 were altered in a similar manner to the transcription of the downstream genes nqo1 and hmox1, suggesting that Nrf2-Keap1 pathway mediated TCEP-induced oxidative stress in zebrafish liver. In addition, TCEP exposure might alleviate inflammatory response through down-regulating transcription of inflammatory cytokines (il-1ß, il-6 and inos), and induce apoptosis via activating the p53-Bax pathway. Moreover, whole life-cycle exposure to TCEP caused a series of histopathological anomalies in zebrafish liver. Overall, our results revealed that lifetime exposure to environmentally relevant concentrations of TCEP could result in growth retardation and induce significant hepatotoxicity in zebrafish.