Paracetamol affects the expression of detoxification- and reproduction-related genes and alters the life traits of Daphnia magna.

Paracetamol (APAP) is a widely used non-steroidal anti-inflammatory drug and has been frequently detected in aquatic environment. However, limited information is provided about the toxic effects and detoxification mechanism of APAP in aquatic invertebrates. In the present study, the change of life traits of Daphnia magna (e.g., body length, growth rate and reproduction) was investigated under the chronic APAP exposure (0-5000 μg/L) for 21 day, and the effects of APAP on the expression of the detoxification- and reproduction-related genes including HR96, CYP360A8, CYP314, MRP4, P-gp, EcR and Vtg in the acute exposure (up to 96 h) were also determined. Results showed that the molting frequency, days to the first brood and days to the first egg production of D. magna were affected under the 50 μg/L concentration of APAP in the chronic exposure test. In the acute test, the transcriptional expression of HR96 was up-regulated under APAP exposure for 24 and 48 h. Similar performances were also observed in the expression of CYP360A8, CYP314, MRP4 and P-gp. However, with exposure time extended to 96 h, the induction of HR96 decreased or even reversed in some cases. It may indicate that the defense system in Daphnia is activated for a short time of exposure or becomes adaptive after longer term of exposure. APAP exposure also affected reproduction-related genes expression, which was related to the exposure time and concentration of APAP. In summary, APAP significantly affected the expression of genes associated with detoxification metabolism and altered some physiological parameters in D. magna.