Hunan Provincial Key Laboratory of Nutrition and Quality Control of Aquatic Animals, Department of Biological and Chemical Engineering, Changsha University, Changsha, 410022, China; State Key Laboratory of Developmental Biology of Freshwater Fish, Department of Life Sciences, Hunan Normal University, Changsha, 410081, China.
Hunan Provincial Key Laboratory of Nutrition and Quality Control of Aquatic Animals, Department of Biological and Chemical Engineering, Changsha University, Changsha, 410022, China.
Fish Shellfish Immunol. 2024 Oct;153:109790. doi: 10.1016/j.fsi.2024.109790. Epub 2024 Jul 24.
Grass carp (Ctenopharyngodon idella) is an intensively cultured and economically important herbivorous fish species in China, but its culture is often impacted by Aeromonas pathogens such as Aeromonas hydrophila and Aeromonas veronii. In this study, healthy grass carp were separately infected with A. hydrophila or A. veronii for 12, 24, 48 or 72 h. The results showed that the mRNA expression levels of intestinal inflammatory factors (tnf-α, il-1β and il-8), complement factors (c3 and c4), antimicrobial peptides (hepcidin, nk-lysin and β-defensin-1), immunoglobulins (igm and igt), and immune pathway-related signaling molecules (tlr1, tlr2, tlr4, myd88, irak4, irak1, traf6, nf-κb p65 and ap-1) were differentially upregulated in response to A. hydrophila and A. veronii challenge. Additionally, the expression levels of the intestinal pro-apoptotic genes tnfr1, tnfr2, tradd, caspase-8, caspase-3 and bax were significantly increased, whereas the expression of the inhibitory factor bcl-2 was significantly downregulated, indicating that Aeromonas infection significantly induced apoptosis in the intestine of grass carp. Moreover, the expression of intestinal tight junction proteins (occludin, zo-1, claudin b and claudin c) was significantly decreased after infection with Aeromonas. Histopathological analysis indicated the Aeromonas challenge caused severe damage to the intestinal villi with adhesions and detachment of intestinal villi accompanied by severe inflammatory cell infiltration at 12 h and 72 h. The 16S rRNA sequencing results showed that Aeromonas infection significantly altered the structure of the intestinal microflora of the grass carp at the phylum (Proteobacteria, Fusobacteria, Bacteroidetes and Firmicutes) and genus (Proteus, Cetobacterium, Bacteroides, and Aeromonas) levels. Take together, the findings of this study revealed that Aeromonas infection induces an intestinal immune response, triggers cell apoptosis, destroys physical barriers and alters microflora structure in the intestine of juvenile grass carp; the results will help to reveal the pathogenesis of intestinal bacterial diseases in grass carp.
草鱼（Ctenopharyngodon idella）是中国一种集约化养殖且经济重要的草食性鱼类，但它的养殖经常受到气单胞菌病原体（如嗜水气单胞菌和维氏气单胞菌）的影响。在本研究中，健康草鱼分别被嗜水气单胞菌或维氏气单胞菌感染 12、24、48 或 72 小时。结果表明，肠道炎症因子（tnf-α、il-1β 和 il-8）、补体因子（c3 和 c4）、抗菌肽（hepcidin、nk-lysine 和 β-防御素-1）、免疫球蛋白（igm 和 igt）和免疫途径相关信号分子（tlr1、tlr2、tlr4、myd88、irak4、irak1、traff6、nf-κb p65 和 ap-1）的 mRNA 表达水平在受到嗜水气单胞菌和维氏气单胞菌的挑战时被差异上调。此外，肠道促凋亡基因 tnfr1、tnfr2、tradd、caspase-8、caspase-3 和 bax 的表达水平显著增加，而抑制因子 bcl-2 的表达水平显著下调，表明气单胞菌感染显著诱导草鱼肠道细胞凋亡。此外，感染气单胞菌后肠道紧密连接蛋白（occludin、zo-1、claudin b 和 claudin c）的表达显著降低。组织病理学分析表明，气单胞菌攻毒在 12 小时和 72 小时时引起肠道绒毛严重损伤，伴有肠道绒毛黏附和脱落，严重的炎症细胞浸润。16S rRNA 测序结果显示，气单胞菌感染显著改变了草鱼肠道微生物群落的结构，在门（变形菌门、梭杆菌门、拟杆菌门和厚壁菌门）和属（变形杆菌属、鲸杆菌属、拟杆菌属和气单胞菌属）水平上均有改变。综上所述，本研究结果揭示了气单胞菌感染诱导草鱼肠道免疫反应，触发细胞凋亡，破坏肠道物理屏障，并改变其肠道微生物群落结构；这些结果将有助于揭示草鱼肠道细菌性疾病的发病机制。
