Norepinephrine regulates TNF expression via the A1AR-p38 MAPK-Relish pathway in granulocytes of oyster Crassostrea gigas.

Norepinephrine (NE) is involved in regulating cytokine expression and phagocytosis of immune cells in the innate immunity of vertebrates. In the present study, the modulation mechanism of NE on the biosynthesis of TNFs in oyster granulocytes was explored. The transcripts of Cg TNF-1, Cg TNF-2 and Cg TNF-3 were highly expressed in granulocytes, and they were significantly up-regulated after LPS stimulation, while down-regulated after NE treatment. The phagocytic rate and apoptosis index of oyster granulocytes were also triggered by LPS stimulation and suppressed by NE treatment. The mRNA expressions of Cg MAPK14 and Cg Relish were significantly induced after NE treatment, and the translocation of Cg Relish from cytoplasm to nucleus was observed. The concentration of intracellular Ca2+ in granulocytes was significantly up-regulated upon NE incubation, and this trend reverted after the treatment with DOX (specific antagonist for NE receptor, Cg A1AR-1). No obvious significance was observed in intracellular cAMP concentrations in the PBS, NE and NE + DOX groups. Once Cg A1AR-1 was blocked by DOX, the mRNA expressions of Cg MAPK14 and Cg Relish were significantly inhibited, and the translocation of Cg Relish from cytoplasm to nucleus was also dramatically suppressed, while the mRNA expression of Cg TNF-1 and the apoptosis index increased significantly to the same level with those in LPS group, respectively. These results collectively suggested that NE modulated TNF expression in oyster granulocyte through A1AR-p38 MAPK-Relish signaling pathway. • Granulocytes were the main sub-population of haecmocytes to synthesize TNFs in response to LPS stimulation. • NE could regulate phagocytosis, apoptosis and TNFs expression in oyster granulocyte. • NE modulated phagocytosis, apoptosis and TNFs expression in granulocyte through A1AR-p38 MAPK-Relish signaling pathway. [ABSTRACT FROM AUTHOR]