Simvastatin as an emerging pollutant on non-target aquatic invertebrates: effects on antioxidant-related genes in Daphnia magna.

Abstract

Simvastatin (SIM) is one of the most widely used lipid-lowering drugs and consequently has been frequently detected in various waters. However, its potential adverse effects and toxic mechanisms on non-target organisms such as Daphnia magna (D. magna) remain still unclear. In the present study, the expressions of Nrf2 and antioxidant genes including Keap1, HO-1, GCLC, GST, SOD, CAT, GPx5, GPx7, GRx, TRX, TrxR, and Prx1 in D. magna exposed to SIM for 24h, 48h, and 96h were investigated. The changes of SOD, CAT, GST, and GPx enzymatic activities, and the GSH and MDA content under SIM for 48-h exposure were also addressed. Results showed that the expression of Nrf2 was inhibited at 24h but induced at 96h, displaying a time- and/or dose-dependent relationship under SIM exposure. In contrast, Keap1 exhibited induction at 24h. HO-1 showed significant induction under SIM exposure for different time. SOD generally displayed an induction trend under SIM exposure for different periods. GPX5 expression showed significant induction under SIM exposure, particularly at 24h in 5µg L-1 increasing 15 folds of the control. But GPX7 expression generally displayed inhibition except in 5µg L-1. Trx and TrxR showed different induction or inhibition, which was depended on the exposure time and concentration. Prx1 displayed significant induction in most SIM groups. In addition, the decreasing GSH and increasing MDA content also indicated oxidative stress of SIM exposure. Overall, SIM exposure affected the expression of Nrf2 and antioxidant-related genes and altered the redox homeostasis of D. magna, even may cause the morphological changes such as shorten spine and abnormal development eye.