The red blood cells (RBCs) of fish make up around 95% of the total peripheral blood cells, and the long-held paradigm is that RBCs are mainly responsible for transporting oxygen. Previous studies have showed that the RBCs can be involved in the immune response against bacterial infection; however, this mechanism remains enigmatic. Here, we explored the structure of grass carp RBCs (GcRBCs). The results showed that the GcRBCs released a pseudopodia-like structure when grown in a 24-well plate, and the transmission electron microscopy (TEM) result showed that GcRBCs contained some organelle-like structures. To further verify the organelle-like structures might be the mitochondria and lysosome which similar to other immune cells, a fluorescent labeling assay was used to verify it. To decipher the antibacterial immunity of GcRBCs, transcriptomic profiling of grass carp RBCs after the incubation with E. coli was analyzed. The results showed that there were 4099 differently expressed genes (DEGs) of GcRBCs upon E. coli incubation, including 2041 up-regulated and 2058 down-regulated genes. In addition, to validate our transcriptomic data, we checked the expression of several cytokines, such as CCL4, CCL20, IL4, IL12 and IFN-α, and the results showed that all the selected gens were significantly up-regulated after E. coli incubation. Furthermore, E. coli incubation induced hemoglobin oxidation and increased the heme in GcRBCs, which further activated the expression of heme oxygenase 1 (HO-1), autophagy related genes 5 (ATG5), and ferritin. In contrast, E. coli incubation inhibited the expression of Ferroportin-1 (FPN1), which increased intracellular iron levels, induced Fenton reaction to release reactive oxygen species (ROS), and activated the ferroptosis signaling pathway in GcRBCs. Herein, we demonstrate that E. coli can induce teleost RBCs cell death through an iron-mediated ferroptosis pathway, which sheds new light on the interaction between bacteria and teleost RBCs.

鱼的红细胞占外周血细胞总数的95％左右，长期以来的范例是，红细胞主要负责运输氧气。先前的研究表明，红细胞可以参与针对细菌感染的免疫反应。但是，这种机制仍然是个谜。在这里，我们探讨了草鱼红细胞（Gc RBC）的结构。结果表明，Gc RBCs在24孔板中生长时释放出伪足样结构，而透射电镜（TEM）结果表明，Gc红细胞含有一些细胞器样结构。为了进一步验证细胞器样结构可能是类似于其他免疫细胞的线粒体和溶酶体，使用了荧光标记法对其进行了验证。为了破译GcRBC的抗菌免疫力，分析了与大肠杆菌孵育后草鱼RBC的转录组谱。结果表明，大肠杆菌孵育后存在4099个不同表达的GcRBCs基因（DEGs），包括2041个上调基因和2058个下调基因。此外，为了验证我们的转录组数据，我们检查了几种细胞因子的表达，例如CCL4，CCL20，IL4，IL12和IFN-α，结果表明，大肠杆菌后所有选定的基因均显着上调。孵化。此外，大肠杆菌的孵育诱导了血红蛋白氧化并增加了GcRBC中的血红素，从而进一步激活了血红素加氧酶1（HO-1），自噬相关基因5（ATG5）和铁蛋白的表达。相比之下，大肠杆菌孵育抑制了Ferroportin-1（FPN1）的表达，从而增加了细胞内铁的水平，诱导Fenton反应释放活性氧（ROS），并激活了GcRBCs中的肥大病信号转导途径。在本文中，我们证明了大肠杆菌可以通过铁介导的肥大作用途径诱导硬骨RBC细胞死亡，这为细菌和硬骨RBC之间的相互作用提供了新的思路。