College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China.
Fisheries College, Jimei University, Xiamen, 361021, China.
Dev Comp Immunol. 2020 Sep;110:103725. doi: 10.1016/j.dci.2020.103725. Epub 2020 May 4.
B-type allatostatin (AST-B) is a pleiotropic neuropeptide, widely found in arthropods. However, the information about its immune effect in crustaceans is unknown. In this study, we identified the nervous tissue as the main site for Sp-AST-B expression, while its receptor gene (Sp-AST-BR) is widely expressed in various tissues, including the hepatopancreas. This suggests the peptide's potential role in diverse physiological processes in the mud crab Scylla paramamosain. In situ hybridization revealed that Sp-AST-BR is mainly localized in the F-cell of hepatopancreas. Furthermore, we found a significant up-regulation of Sp-AST-BR transcripts in the hepatopancreas following exposure to lipopolysaccharide (LPS) or polyriboinosinic polyribocytidylic acid (Poly (I:C)). Results from in vitro and in vivo experiments revealed that treatment with a synthetic AST-B peptide mediated significant upregulation in expression of AST-BR, nuclear factor-κB (NF-κB) pathway components (Dorsal and Relish), pro-inflammatory cytokine (IL-16) and antimicrobial peptides (AMPs) in the hepatopancreas. In addition, AST-B treatment mediated significant elevation of nitric oxide (NO) production and enhanced the bacteriostasis capacity of the hepatopancreas tissue in vitro. Taken together, these findings reveal the existence of a basic neuroendocrine-immune (NEI) network in crabs, and indicate that AST-B could couple with its receptor to trigger downstream signaling pathways and induce immune responses in the hepatopancreas.
B 型脑肠肽（AST-B）是一种多功能神经肽，广泛存在于节肢动物中。然而，甲壳动物中关于其免疫作用的信息尚不清楚。在本研究中，我们鉴定出神经组织是 Sp-AST-B 表达的主要部位，而其受体基因（Sp-AST-BR）广泛表达于包括肝胰腺在内的各种组织中。这表明该肽在泥蟹 Scylla paramamosain 中可能具有多种生理功能。原位杂交结果显示，Sp-AST-BR 主要定位于肝胰腺的 F 细胞中。此外，我们发现 LPS 或聚肌胞苷酸（Poly（I:C））处理后肝胰腺中 Sp-AST-BR 转录本显著上调。体外和体内实验结果表明，合成的 AST-B 肽处理可介导肝胰腺中 AST-BR、核因子-κB（NF-κB）途径组成部分（Dorsal 和 Relish）、促炎细胞因子（IL-16）和抗菌肽（AMPs）的表达显著上调。此外，AST-B 处理可显著提高肝胰腺组织中一氧化氮（NO）的产生，并增强其体外抑菌能力。综上所述，这些发现揭示了甲壳动物中存在基本的神经内分泌免疫（NEI）网络，并表明 AST-B 可以与其受体结合，触发下游信号通路，并在肝胰腺中诱导免疫反应。
