The present study reported the first pathogenic Aeromonas salmonicida (SRW-OG1) isolated from the warm water fish orange-spotted grouper (Epinephelus coioides), and investigated the function of Aryl hydrocarbon receptor (AhR), a ligand-dependent transcriptional factor which has been recently found to be closely associated with immune response in mammals and E. coioides. Our results showed that AhR was activated by an unknown ligand in the spleen, intestine and macrophages. Meanwhile, ahr1a and ahr1b were significantly increased in the spleen, intestine and macrophages, whereas ahr2 was only increased in the intestine, which indicated that the contribution of AhR2 to the immune response may be less than that of AhR1a and AhR1b. Some key genes involved in the macrophage inflammatory response, bacterial recognition, and intestinal immunity were significantly up-regulated in the SRW-OG1 infected E. coioides. Nevertheless, declining macrophage ROS production and down-regulation of related genes were also observed, suggesting that SRW-OG1 utilized its virulence mechanisms to prevent macrophage ROS production. Furthermore, AhR inhibitor 3′, 4′-DMF and the silence of ahr1a or ahr1b significantly rescued the increased IL-1β and IL-8 induced by SRW-OG1 infection, which proved that the induction of IL-1β and IL-8 in E. coioides macrophages was mediated by AhR. However, BPI/LBP, ROS production and related genes were not affected by AhR. The survival rate and immune escape rate of SRW-OG1 in the ahr1a/ahr1b knocked-down and 3′, 4′-DMF treated macrophages were significantly increased compared with those in wild type macrophages. Taken together, it was preliminarily confirmed that ahr1a and ahr1b played an important role in the immune response against A. salmonicida SRW-OG1.

本研究报道了从温水鱼橙斑石斑鱼（Epinephelus coioides）中分离出的第一个致病性杀鲑气单胞菌（SRW-OG1），并研究了芳基烃受体（AhR）的功能，该受体是一种配体依赖性转录因子最近发现与哺乳动物和E. coioides 的免疫反应密切相关。我们的结果表明，AhR 被脾脏、肠和巨噬细胞中的未知配体激活。同时，ahr1a和ahr1b在脾脏、肠道和巨噬细胞中显着增加，而ahr2仅在肠道中增加，这表明 AhR2 对免疫反应的贡献可能小于 AhR1a 和 AhR1b。一些参与巨噬细胞炎症反应、细菌识别和肠道免疫的关键基因在 SRW-OG1 感染的大肠杆菌中显着上调。尽管如此，也观察到巨噬细胞ROS产生的下降和相关基因的下调，表明SRW-OG1利用其毒力机制来阻止巨噬细胞ROS的产生。此外，AhR 抑制剂 3'、4'-DMF 和ahr1a或ahr1b的沉默显着挽救了增加的IL-1β和IL-8通过SRW-OG1感染，这证明的诱导诱导IL-1β和IL-8在E.带石斑鱼的巨噬细胞通过的AhR介导的。然而，BPI/LBP、ROS 产生和相关基因不受 AhR 的影响。与野生型巨噬细胞相比，SRW-OG1 在ahr1a / ahr1b敲低和 3', 4'-DMF 处理的巨噬细胞中的存活率和免疫逃逸率显着增加。综合起来，初步证实ahr1a和ahr1b在针对杀鲑鱼SRW-OG1的免疫反应中起重要作用。