Monitoring oxidative stress, immune response, Nrf2/NF-κB signaling molecules of Rhynchocypris lagowski living in BFT system and exposed to waterborne ammonia

The present study was implemented to evaluate oxidative stress, immune response, Nrf2 and NF-kappa B signaling molecules related genes expression of Rhynchocypris lagowski living in biofloc technology (BFT) system and exposed to waterborne ammonia. According to the differences of C:N ratios, the experiment was divided into four groups: C:N 10.8:1 (control group), C:N 15:1, C:N 20: 1 and C:N 25:1. The results demonstrated that BFT can effectively regulate water quality and promote growth, and the C:N 20:1 group has the most significant effect (P < 0.05). Besides, significant increases in immune enzymes (lysozyme, complement C3, C4, immunoglobulin M and nitric oxide synthase) and anti-inflammatory factor (IL-2) activity of R. lagowski were emerged in the treatment C:N 20:1 after the 56-d growth experiment and the challenging trial (P < 0.05). Comparing the antioxidant status of R. lagowski in liver and gut before and after ammonia stress: superoxide dismutase, total antioxidant capacity and catalase activity in treatments C:N 20:1 were significant increased (P < 0.05), while the level of malondialdehyde was marked lower than that in control. Meanwhile, treatment C:N 20:1 considerably upregulated Nrf2 signaling molecules related genes and significantly down-regulated the expression of pro-inflammatory factor gene in NF-kappa B signaling pathway compared with the control (P < 0.05). These results indicated that BFT could enhance growth, antioxidant and immune response and regulate Nrf2 and NF-kappa B related genes expression in R. lagowski, with most excellent effects in fish given C:N 20:1 group.