Effects of cyclophosphamide on antioxidative and immune functions of Nile tilapia (Oreochromis Niloticus) via the TLR-NF-κB signaling pathway

• Published in: Aquatic toxicology 2021-10, Vol.239, p.105956-105956, Article 105956
• Main Authors: Cao, Li-ping, Du, Jin-liang, Jia, Rui, Ding, Wei-dong, Xu, Pao, Yin, Guo-jun, Zhang, Ting
• Format: Article
• Language: English
• Subjects: Cyclophosphamide; Immunosuppression; Oreochromis niloticus; TLR-NF-κB signaling pathway
• ISSN: 0166-445X; 1879-1514
• DOI: 10.1016/j.aquatox.2021.105956

•CTX treatment induces immunosuppression in Nile tilapia•CTX treatment reduces antioxidant ability and promotes lipid peroxidation.•TLR-NF-κB pathway is involved in immunosuppression induced by CTX. Intensive aquaculture often results in immunosuppression in fish, which may cause a series of diseases. In this study, to investigate the immunosuppressive mechanisms in fish, tilapia were intrapleural injected cyclophosphamide (CTX) at the doses of 10, 25, 50, 75 and 100 mg·kg−1 to induce immunosuppression. We determined the viability of immune cells, the content of lysozyme (LZM) and immunoglobulin M (IgM), the levels of nitric oxide (NO) and antioxidant parameters. Meanwhile, the mRNA levels of complement C3 (c3), igm and the genes associated with the TLR-NF-κB signaling pathway in the head kidney (HK) and spleen were also determined. The results showed that CTX had a significant cytotoxic effect on peripheral blood leukocytes, HK macrophages and spleen cells in a dose-dependent manner. The protein and mRNA levels of C3 and IgM were down-regulated with the increase of CTX concentrations in serum, HK and/or spleen. The NO and LZM contents decreased significantly in HK and spleen after CTX treatments with 75 and 100 mg·kg−1. CTX treatments with 50, 75 and/or 100 mg·kg−1 markedly decreased the antioxidant ability and enhanced lipid peroxidation in HK and spleen. Furthermore, qPCR data showed that CTX treatments with 50-100 mg·kg−1 clearly down-regulated the mRNA levels of tlr2, myd88, irak1, traf6, nfκb1, nfκb2, il-6, il-10 and tnf-α in the HK and/or spleen. Overall results suggested that CTX treatment had a cytotoxic effect on immune cells, induced lipid peroxidation, decreased the antioxidant capacity and inhibited immune function. The immunosuppressive mechanisms of CTX may be associated with the TLR-NF-κB signaling pathway.