The systematic regulation of oyster CgIL17-1 and CgIL17-5 in response to air exposure

As a proinflammatory cytokine, vertebrate interleukin 17 (IL17) plays a vital role in the balance of inflammation and homeostasis, and is involved in a systemic regulation of glucose homeostasis. In the present study, a remarkable increase of glucose concentration was observed in oyster serum after 2 d air exposure, which was followed by a rapid up-regulation of CgIL17-1 and CgIL17-5. After oysters was received an injection of extra glucose, the mRNA expressions of CgIL17-1 and CgIL17-5 were also significantly up-regulated. The histopathological changes of hepatopancreas were observed after the oysters were treated by the recombinant proteins of CgIL17-1 and CgIL17-5 in vivo or subjected to air exposure. A significant decrease of GSK3β (Glycogen synthase kinase-3β) protein was also observed after the injection of CgIL17-1 and CgIL17-5 recombinant proteins in vivo. When the oysters with CgIL17-1 and CgIL17-5 genes knocked down were subjected to air exposure, the decline of GSK3β concentration was slowed down and it could still be obviously detected after 7 d compared with that in the control. Meanwhile, the expression of CgDefensin and CgDFFA was inhibited, while CgIAP was up-regulated when CgIL17-1 and CgIL17-5 genes were knocked down, and the oysters exhibited higher mortality (p < 0.05) at 3 d, whereas lower at the late stage of air exposure compared with that in the controls. The results collectively suggested that once oysters were exposed to air, the synthesis of proinflammatory cytokines CgIL17-1 and CgIL17-5 was induced by the up-regulated glucose concentration in oyster serum, which would be not only a negative feedback to the high glucose concentration through mediating the regulation of GSK3β, but also an inducer on tissue damage and immunocompetence as well as the adaptability to stresses.