Xu Zhanning, Wei Yujie, Wang Guizhong, Ye Haihui
College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361102, China.
College of Fisheries, Jimei University, Xiamen, 361021, China.
Dev Comp Immunol. 2021 Jul;120:104050. doi: 10.1016/j.dci.2021.104050. Epub 2021 Feb 22.
B-type allatostatins (AST-B) are neuropeptides that have important physiological roles in arthropods, they have also been identified in a number of crustacean species. Recent research on neuroendocrine-immune (NEI) regulatory system in invertebrates has exploded, it reveals that the NEI network plays an indispensable role in optimizing the immune response and maintaining homeostasis. Herein, mud crab Scylla paramamosain provides a primitive and ancient model to study crosstalk between the neuroendocrine and immune systems. In this study, qRT-PCR analysis showed that the nervous system was the main production site for Sp-AST-B mRNA in S. paramamosain, while its receptor gene (Sp-AST-BR) mRNA could be detected in all the analyzed tissues including hemocytes. This reveals that AST-B might act as a pleiotropic neuropeptide. In situ hybridization further confirmed that granular cells of hemocyte subpopulations express Sp-AST-BR. Time-course analysis revealed that bacteria-analog LPS or virus-analog Poly (I:C) challenge significantly induced Sp-AST-B expression in the thoracic ganglion, and the expression of Sp-AST-BR in hemocytes were also positively changed. Furthermore, mud crabs treated with a synthetic AST-B peptide significantly increased the mRNA levels of AST-BR, nuclear factor-κB (NF-κB) transcription factor (Dorsal and Relish), pro-inflammatory cytokine (IL-16) and immune-effector molecules, and also dramatically enhanced the nitric oxide (NO) production and phagocytic activity in hemocytes. Meanwhile dsRNA-mediated knockdown of Sp-AST-B remarkably suppressed the NO concentrations, phagocytic activity and the expression of immune related genes, resulting in markedly impaired ability of crabs to inhibit bacterial proliferation in vivo. Combined, these data demonstrate that AST-B induced innate immune in the mud crab.
B型咽侧体抑制素（AST-B）是在节肢动物中具有重要生理作用的神经肽，在许多甲壳类动物中也已被鉴定出来。最近对无脊椎动物神经内分泌-免疫（NEI）调节系统的研究激增，结果显示NEI网络在优化免疫反应和维持体内平衡方面发挥着不可或缺的作用。在此，拟穴青蟹为研究神经内分泌系统与免疫系统之间的相互作用提供了一个原始而古老的模型。在本研究中，qRT-PCR分析表明，神经系统是拟穴青蟹中Sp-AST-B mRNA的主要产生部位，而其受体基因（Sp-AST-BR）mRNA可在包括血细胞在内的所有分析组织中检测到。这表明AST-B可能作为一种多效性神经肽发挥作用。原位杂交进一步证实血细胞亚群的颗粒细胞表达Sp-AST-BR。时间进程分析显示，细菌类似物脂多糖（LPS）或病毒类似物聚肌胞苷酸（Poly (I:C)）刺激显著诱导胸神经节中Sp-AST-B的表达，血细胞中Sp-AST-BR的表达也呈正向变化。此外，用合成的AST-B肽处理拟穴青蟹可显著提高AST-BR、核因子-κB（NF-κB）转录因子（Dorsal和Relish）、促炎细胞因子（IL-16）和免疫效应分子的mRNA水平，还能显著增强血细胞中的一氧化氮（NO）产生和吞噬活性。同时，dsRNA介导的Sp-AST-B敲低显著抑制了NO浓度、吞噬活性以及免疫相关基因的表达，导致螃蟹体内抑制细菌增殖的能力明显受损。综合这些数据表明，AST-B可诱导拟穴青蟹的先天免疫。
