Zhao Beibei, Diao Jing, Li Le, Kondo Hidehiro, Li Lei, Hirono Ikuo
Laboratory of Healthy and Safe Aquaculture, Zhejiang Ocean University, Zhoushan, Zhejiang, 316022, China; Shandong Key Laboratory of Disease Control in Mariculture, Qingdao, 266104, China.
Marine Biology Institute of Shandong Province, Qingdao, 266104, China; Shandong Key Laboratory of Disease Control in Mariculture, Qingdao, 266104, China.
Dev Comp Immunol. 2021 Jul;120:104047. doi: 10.1016/j.dci.2021.104047. Epub 2021 Feb 26.
Chemokines are categorized into five families; one of the families is the CXC chemokines, which are critical in the pro-inflammatory process. CXC chemokines transmit signals and mediate a cell's biological activities by binding to cell surface receptors known as chemokine receptors (CXCRs). In this study, the CXCR2 from Japanese flounder (Paralichthys olivaceus) (JfCXCR2) was identified and characterized at the molecular level. The JfCXCR2 gene has a 1077 bp open reading frame that encodes a protein of 359 amino acid residues with seven transmembrane domains. Phylogenetic analysis of JfCXCR2 revealed that it belonged to the fish CXCR2 subfamily. Furthermore, JfCXCR2 was compared with the previously identified Japanese flounder CXCR1 (JfCXCR1). The expression analysis of uninfected Japanese flounder showed that JfCXCR1 and JfCXCR2 were expressed in all the tissues and organs tested but mainly in immune-related organs, including the kidney and spleen. Infection by Streptococcus iniae significantly increased the level of JfCXCR1 and JfCXCR2 mRNA in the kidney at days 1 and 3 post-infection. On the other hand, VHSV (viral hemorrhagic septicemia virus) and Edwardsiella tarda infection significantly increased JfCXCR2 mRNA levels in the kidney at days 3 and 6 post-infection, respectively. Conversely, JfCXCR1 expression was not significantly changed by either E. tarda or VHSV infection. Additionally, the peripheral blood leukocytes (PBLs) stimulated by recombinant proteins rCXCL8_L1a and rCXCL8_L1b were found to have significantly increased levels of JfCXCR1 and JfCXCR2 mRNA. Interestingly, even higher levels of JfCXCR1 and JfCXCR2 expression were observed in PBLs stimulated with rCXCL8_L1a and rCXCL8_L1b than in PBLs stimulated with either recombinant protein. These data suggest that bacterial infections may activate JfCXCR1. By contrast, JfCXCR2 may be activated by both bacterial and viral infection to mediate the immune response. These data can contribute to further understanding the functions of CXCR1 and CXCR2 in the fish immune system.
趋化因子分为五个家族；其中一个家族是CXC趋化因子，它在促炎过程中至关重要。CXC趋化因子通过与称为趋化因子受体（CXCRs）的细胞表面受体结合来传递信号并介导细胞的生物学活性。在本研究中，对牙鲆（Paralichthys olivaceus）的CXCR2（JfCXCR2）进行了分子水平的鉴定和表征。JfCXCR2基因有一个1077 bp的开放阅读框，编码一个含有7个跨膜结构域的359个氨基酸残基的蛋白质。对JfCXCR2的系统发育分析表明它属于鱼类CXCR2亚家族。此外，还将JfCXCR2与先前鉴定的牙鲆CXCR1（JfCXCR1）进行了比较。未感染牙鲆的表达分析表明，JfCXCR1和JfCXCR2在所检测的所有组织和器官中均有表达，但主要在免疫相关器官，包括肾脏和脾脏中表达。海豚链球菌感染在感染后第1天和第3天显著增加了肾脏中JfCXCR1和JfCXCR2 mRNA的水平。另一方面，病毒性出血性败血症病毒（VHSV）和迟缓爱德华氏菌感染分别在感染后第3天和第6天显著增加了肾脏中JfCXCR2 mRNA的水平。相反，迟缓爱德华氏菌或VHSV感染均未使JfCXCR1表达发生显著变化。此外，发现重组蛋白rCXCL8_L1a和rCXCL8_L1b刺激的外周血白细胞（PBLs）中JfCXCR1和JfCXCR2 mRNA水平显著升高。有趣的是，在用rCXCL8_L1a和rCXCL8_L1b刺激的PBLs中观察到的JfCXCR1和JfCXCR2表达水平甚至高于用任何一种重组蛋白刺激的PBLs。这些数据表明细菌感染可能激活JfCXCR1。相比之下，JfCXCR2可能被细菌和病毒感染激活以介导免疫反应。这些数据有助于进一步了解CXCR1和CXCR2在鱼类免疫系统中的功能。
