| Neuroendocrine-immune regulatory network plays crucial role in the immunomodulation and homeostasis maintenance in vertebrate, in which catecholaminergic neuroendocrine-immune regulatory network is one of the most important components. The knowledge about catecholaminergic neuroendocrine-immune regulatory network is mainly from vertebrates, while it is quite meagre in invertebrates so far. In the present study, the molecular features of catecholaminergic neuroendocrine system, and its activation mechanism and immunomodulation in immune response were investigated preliminarily to understand the catecholaminergic neuroendocrine-immune regulatory network in scallop Chlamys farreri.Four crucial catecholamine-metabolism related enzymes and one adrenoceptor genes including phenylalanine hydroxylase (PAH), dopa decarboxylase (DDC), dopamine beta hydroxylase (DBH), monoamine oxidase (MAO) and adrenoceptor (ADR) were cloned and characterized from C. farreri. The full length cDNA of these five genes were of 1573, 2348, 2302, 1560 and 1462 bp, and their deduced protein contained BiopterinH, PyridoxaldeC, Cu2monooxygen, Aminooxidase and 7tm1 characteristic domains, respectively. Their mRNA transcripts were ubiquitously detectable in all the tested tissues including haemocytes, hepatopancreas, kidney, adductor muscle, gonad, gill and mantle. The recombinant proteins of CfPAH, CfDDC and CfMAO could catalyze the synthesis of tyrosine and dopamine, and the deamination of catecholamines, respectively. Furthermore, rCfDDC could modulate the encapsulation and ROS level of haemocytes. After bacteria Vibrio anguillarum challenge, immune-related enzyme (SOD, CAT and LYZ) activities and catecholamine (norepinephrine, epinephrine and dopamine) concentration in haemolymph were all increased significantly. Meanwhile, the mRNA expression level of CfPAH, CfDDC, CfDBH,CfMAO and CfADR in haemocytes was also increased significantly. At 4 h after the incubation of the haemolymph with LPS, the concentration of TNF-α-like molecule was increased significantly to 2.975±0.034 pg mL-1. When human TNF-αwas employed to treat scallops, the mRNA expression level of the immune-related enzyme (CfSOD, CfCAT and CfLYZ) and catecholamine-anabolism related enzyme (CfPAH, CfDDC and CfDBH) genes was all increased significantly. In those scallops with CfDDC interfered, the mRNA expression level of CfSOD, CfCAT and CfLYZ was all down-regulated. The expression level of CfSOD mRNA was also down-regulatd after the interference of CfMAO. The stimulation of norepinephrine and epinephrine decreased the activities of SOD, CAT and LYZ in haemolymph. The blocking ofα- andβ-adrenoceptor by antagonist decreased the LYZ activities significantly, while no significant effects were observed on the SOD and CAT activities.All the results suggested the existence of important functional catecholaminergic neuroendocrine-immune regulatory network in scallop C. farreri. In this network, the cytokine-like molecules produced in immune response could activate catecholaminergic neuroendocrine system, including haemocyte-derived catecholaminergic system. Once the activation was provoked, the catecholaminergic neuroendocrine system could release catecholamines to modulate the immune response of scallop through the catecholamine receptor located in the immunocytes. It would contribute to the further knowlege of the neuroendocrine-immune regulatory network in marine inveterbrate, and be helpful for better understanding of immune defense system in invertebrates as well.
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