Department of Aquaculture, College of Marine Sciences, Hainan University, Haikou, Hainan 570228, China; School of Life Sciences, East China Normal University, Shanghai 200241, China.
Department of Aquaculture, College of Marine Sciences, Hainan University, Haikou, Hainan 570228, China.
Fish Shellfish Immunol. 2018 May;76:48-57. doi: 10.1016/j.fsi.2018.02.041. Epub 2018 Feb 24.
Hyperosmotic stress can adversely affect fish immunity, but little is known about the histological and transcriptomic responses of immune organs in fish in a hyperosmotic environment. This study evaluated the effects of long-term hypersaline conditions (16‰) on the growth, histology and transcriptomics of the two main immune organs, the spleen and head kidney, in Nile tilapia Oreochromis niloticus relative to those reared in freshwater for eight weeks. No differences in weight gain and specific growth rate were found between fish reared under these two salinities. Hyperosmotic stress induced a congestive or enlarged spleen. Platelet- and coagulation-related gene expression was significantly decreased in tilapia at 16‰. The red cell distribution width and value of the mean corpuscular hemoglobin were significantly greater in fish at 16‰ salinity than in control fish in freshwater. A large volume of melano-macrophages in the spleen and pigment deposition in both the spleen and head kidney were observed in the histological sections in fish at 16‰ salinity. Transmission electron microscopic results showed abnormal macrophages with deposition granules in the spleen and head kidney and more neutrophils in the head kidney of fish at 16‰ than in control fish. In total, 772 and 502 genes were annotated for significantly different expression in the spleen and head kidney, respectively, and corresponded to five and one significantly changed immune system pathways, respectively. The complement pathway in the spleen was significantly down-regulated at 16‰. This study indicates that long-term exposure of Nile tilapia to a hyperosmotic environment can induce splenomegaly, reduce coagulation function, enhance phagocytic activity and down-regulate the complement pathway in the spleen. The spleen is a more sensitive organ for immune responses to chronic ambient salinity stress than the head kidney in Nile tilapia.
高渗胁迫会对鱼类的免疫产生不利影响，但对于鱼类在高渗环境中免疫器官的组织学和转录组反应知之甚少。本研究评估了长期高盐条件（16‰）对尼罗罗非鱼（Oreochromis niloticus）两个主要免疫器官脾脏和头肾的生长、组织学和转录组的影响，相对于在淡水中饲养 8 周的鱼。在这两种盐度下饲养的鱼的体重增加和特定生长率没有差异。高渗胁迫导致脾脏充血或肿大。在 16‰盐度下，血小板和凝血相关基因的表达显著降低。红细胞分布宽度和平均红细胞血红蛋白值在 16‰盐度下的鱼显著大于淡水对照组。在 16‰盐度下的鱼的脾脏中有大量的黑色素巨噬细胞，在脾脏和头肾中都有色素沉积。透射电镜结果显示，在 16‰盐度下的鱼的脾脏和头肾中，巨噬细胞异常，有沉积颗粒，头肾中有更多的中性粒细胞。总共在脾脏和头肾中分别有 772 个和 502 个基因被注释为差异表达，分别对应于五个和一个显著改变的免疫系统途径。脾脏中的补体途径在 16‰时显著下调。本研究表明，长期暴露于高渗环境会导致尼罗罗非鱼脾肿大、凝血功能降低、吞噬活性增强、脾脏补体途径下调。与头肾相比，脾脏是尼罗罗非鱼对慢性环境盐度胁迫的免疫反应更敏感的器官。
