Integrated biomarkers induced by chlorpyrifos in two different life stages of zebrafish ( Danio rerio ) for environmental risk assessment

This study was performed to understand how chlorpyrifos (CHL) affects zebrafish ( Danio rerio ) embryos and adults, by exposing this model organism to various concentrations of the insecticide. The 96-h acute toxicity test to determine the effect of CHL on adult zebrafish yielded a LC 50 of 709.43 μg/L −1. Small molecular weight proteins less than 25 kDa and phospholipids were analyzed with MALDI-TOF MS/MS in order to compare expression patterns, revealing that some peaks were dramatically altered after CHL treatment. Whereas no acute toxicity was detected in the embryo toxicity test, malformation of zebrafish larvae was observed, with many individuals harboring curved spines. In an angiogenesis test on larvae of transgenic zebrafish, CHL did not have an inhibitory effect. Relative gene expression analyses using real-time polymerase chain reaction (RT-PCR) of DNA from zebrafish embryos revealed that different subtypes of cytochrome P450 (CYP450), such as CYP1A and CYP3A, were significantly up-regulated in response to CHL at a concentration of 400 μg/L −1 compared to the control. The expression level of NR1I2, a CYP gene transcriptional regulator, UGT1a1, and MDR1 were all up-regulated in the CHL-treated embryos. Finally, the expression level of acetylcholinesterase (AChE) and catalase (CAT) decreased, whereas that of superoxide dismutase (SOD) did not differ significantly. Our results suggest that the up-regulation of metabolic enzymes including CYP450 and MDR1 may be involved in CHL resistance in zebrafish.