Effects of sulfamethoxazole on the growth, oxidative stress and inflammatory response in the liver of juvenile Nile tilapia (Oreochromis niloticus)

Due to its ubiquitous occurrence and potential toxicity to aquatic animals, sulfamethoxazole (SMZ) is of increasing concern. The purpose of this study is to investigate the adverse effects of SMZ on juvenile fish. To this end, juvenile Nile tilapia were exposed to 0, 1, 10 and 100 μg/L SMZ for 7 and 30 days, respectively. The results showed that SMZ had no significant effect on growth of Nile tilapia at both 7 and 30 d. In fish liver, 1 and 10 μg/L SMZ significantly increased the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) and the content of glutathione (GSH), meanwhile significantly reduced malondialdehyde (MDA) content, whereas 100 μg/L SMZ significantly suppressed SOD activity and GSH content, and enhanced lipid peroxidation (LPO) at both 7 and 30 d. Besides, the transcriptional changes of CAT and GPx were consistent with the changes of enzyme activities. Exposure to 100 μg/L SMZ significantly up-regulated the mRNA levels of heat shock protein 70 (HSP-70), Kelch-like ECH-associated protein 1 (Keap1), nuclear factor κB (NF-κB) and interleukin-1 beta (IL-1β), but down-regulated the transcriptions of nuclear erythroid 2-related factor 2 (Nrf2), NAD(P)H: quinone oxidoreductase 1 (NQO1), heme oxygenase-1 (HO-1), interleukin 10 (IL-10) and GST at both 7 and 30 d. Moreover, 100 μg/L SMZ significantly up-regulated tumor necrosis factor α (TNF-α) and interleukin 8 (IL-8) only at 7 d. In conclusion, exposure to SMZ could not inhibit the growth of Nile tilapia, but high concentration (100 μg/L) of SMZ exposure could increase oxidative damage and induce inflammatory response.