Histological and transcriptomic responses of two immune organs, the spleen and head kidney, in Nile tilapia (Oreochromis niloticus) to long-term hypersaline stress. Issue 76 (May 2018)

• Record Type: Journal Article
• Authors: Xu, Chang; Li, Erchao; Suo, Yantong; Su, Yujie; Lu, Minghui; Zhao, Qun; Qin, Jian G.; Chen, Liqiao
• Is Part Of: Fish & shellfish immunology. Issue 76(2018)
• Page Start: 48
• Page End: 57
• Publication Date: 2018-05
• Subjects: Nile tilapia Oreochromis niloticus -- Immune organ -- Hematology -- Phagocytosis -- Transcriptomics -- Spleen -- Head kidney; Fishes -- Immunology -- Periodicals; Shellfish -- Immunology -- Periodicals; Poissons -- Immunologie -- Périodiques; Crustacés -- Immunologie -- Périodiques; 571.9617
• DOI: 10.1016/j.fsi.2018.02.041
• Languages: English
• ISSNs: 1050-4648

Abstract

Abstract: 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. Highlights: Long-term hyperosmotic stress can induce splenomegaly and reduce coagulation function in Nile tilapia Oreochromis niloticus. Hyperosmotic stress can enhance the deposition of pigment and the ability of phagocytic in the spleen and the head kidney. Complement pathway showed significant down-regulation in the spleen under long-term hyperosmotic stress. The spleen is more sensitive organ for immune responses to chronic hyperosmotic stress than the head kidney.