Antioxidant and immunomodulatory effects of spermidine and spermine in pearl oysters Pinctada fucata martensii

Abstract

Sperdimine (Spd) and spermine (Spm) play an important role in control of innate immune responses in vertebrates and invertebrates. However, little is known about their functions in mollusks. In this study, we identified two Spd synthase and two Spm synthase genes from the genome of the pearl oyster Pinctada fucata martensii. Spd content gradually reduced in serum after lipopolysaccharide (LPS) stimulation, whereas Spm content increased. In addition, Spd/Spm treatment can significantly up-regulate the activities of superoxide dismutase, catalase, and glutathione peroxidase, and inhibit the activity of inducible nitric oxide synthase. We also found that the content of TNF-α was significantly inhibited in the Spm group, while it was significantly induced at 48 h in the Spd group. IL-17 content was down-regulated at 6, 24 and 48 h in the Spm group, while IL-17 showed no significant change in the Spd group. The expression levels of NF-κB, IKK, STAT, and JAK genes were significantly suppressed at 6 h and induced at 48 h after Spm treatment. However, the expression levels of NF-κB, IKK, and JAK were remarkably upregulated at 12, 24 and 6 h after Spd treatment. STAT gene was suppressed at 6 h and then induced at 12 h in the Spd group. Finally, compared with that in the control group, the growth of Pseudomonas aeruginosa was promoted after being incubated with serum from the Spm group at 6 h but inhibited after being incubated with serum from the Spd group at 12 and 24 h. Collectively, these results indicate that Spm and Spd will be disordered after LPS stimulation, which may be important immune regulatory molecules in pearl oysters. These results provide references for in-depth study of the functions of polyamines in mollusks.