Nguyen Thi Mai, Tran Thi Nang Thu, Nguyen Thu Hang, Do Thi Ngoc Anh, Kestemont Patrick
Department of Aquaculture Nutrition and Feed, Faculty of Fisheries, Vietnam National University of Agriculture, Hanoi, Vietnam.
Department of Aquaculture Nutrition and Feed, Faculty of Fisheries, Vietnam National University of Agriculture, Hanoi, Vietnam.
Fish Shellfish Immunol. 2023 Mar;134:108585. doi: 10.1016/j.fsi.2023.108585. Epub 2023 Feb 8.
The D-series resolvins formed from docosahexaenoic acid (DHA) work as anti-inflammatory mediators indicating the role of this long-chain polyunsaturated fatty acid in the immune system of mammals. However, such information is still limited in fish. The current study was conducted to evaluate the immunomodulatory effects of graded levels of DHA in common carp Cyprinus carpio by in vitro and in vivo approaches. In the in vitro experiment, the head kidney leukocytes isolated from common carp (body weight = 120.3 ± 12.4 g) were exposed to DHA at 0, 15, and 75 μM (corresponding to DHA0, DHA15, and DHA75) for 1 h; the cells were then immediately exposed to lipopolysaccharides (LPS) at a dose of 10 μg/ml for 4 or 24 h to stimulate the pro-inflammatory responses. The expression of several target genes involved in the inflammatory response (tlr4, nfkb, il-1, il-6, pge2, pla2, nf-kbi, il-10, and tgf-β1) and cytoprotection (hsp70, gpx1, and prdx3) was then assessed by RT-qPCR. Results showed that the pro-inflammatory response induced by LPS was confirmed through the upregulations of il-1 and il-6 expressions in the DHA0 group after 4 h of LPS exposure. The downregulations of il-6 in DHA15 and DHA75 cells after 4 h of LPS exposure compared to DHA0 indicated that the free DHA supplementation in the cell culture medium induced an anti-inflammatory response. Decreases of il-10 and nf-kbi expression were also observed in DHA-treated groups and the highest expression of hsp70 in DHA75 cells. In the in vivo experiment, common carp juveniles (21.7 ± 0.9 g) were fed to apparent satiation with a diet supplemented with DHA at 0, 6, and 20 g/kg for 8 weeks. After the feeding trial, the fish were challenged with Aeromonas veronii at 2.1 × 10 CFU/ml and the fish mortality was then recorded during 14 days. At the end of the feeding trial and the second day of bacterial infection, fish blood samples were collected for haematological parameters while liver and head kidney were used for assaying different immune variables. Results showed that the DHA supplementation in fish diet did not influence the fish growth and other husbandry parameters. The lowest value of fish mortality was recorded in DHA20-fed fish. The positive effects of DHA-supplemented diets were also found in myeloperoxidase (MPO), glutathione (GSH), and catalase (CAT) activities. In conclusion, the results suggest that DHA is able to modulate the inflammatory response in the immune celsl at a dose of 75 μM/mL and to boost disease resistance in common carp fed on a diet supplemented with DHA at 20 g/kg of feed.
由二十二碳六烯酸（DHA）形成的D系列消退素作为抗炎介质发挥作用，表明这种长链多不饱和脂肪酸在哺乳动物免疫系统中的作用。然而，鱼类中的此类信息仍然有限。本研究通过体外和体内方法，评估了不同水平DHA对鲤鱼（Cyprinus carpio）免疫调节的影响。在体外实验中，从鲤鱼（体重 = 120.3 ± 12.4 g）分离的头肾白细胞分别暴露于0、15和75 μM的DHA（分别对应DHA0、DHA15和DHA75）1小时；然后立即将细胞暴露于剂量为10 μg/ml的脂多糖（LPS）中4或24小时，以刺激促炎反应。随后通过RT-qPCR评估参与炎症反应（tlr4、nfkb、il-1、il-6、pge2、pla2、nf-kbi、il-10和tgf-β1）和细胞保护（hsp70、gpx1和prdx3）的几个靶基因的表达。结果表明，LPS暴露4小时后，DHA0组中il-1和il-6表达上调，证实了LPS诱导的促炎反应。与DHA0相比，LPS暴露4小时后，DHA15和DHA75细胞中il-6表达下调，表明细胞培养基中添加游离DHA诱导了抗炎反应。在DHA处理组中还观察到il-10和nf-kbi表达降低，且DHA75细胞中hsp70表达最高。在体内实验中，将鲤鱼幼鱼（21.7 ± 0.9 g）喂至表观饱足，饲料中分别添加0、6和20 g/kg的DHA，持续8周。饲养试验后，用维氏气单胞菌（Aeromonas veronii）以2.1×10 CFU/ml进行攻毒，然后记录14天内的鱼类死亡率。在饲养试验结束和细菌感染第二天，采集鱼血样本检测血液学参数，同时采集肝脏和头肾检测不同免疫变量。结果表明，饲料中添加DHA不影响鱼类生长和其他养殖参数。DHA20组投喂的鱼死亡率最低。在髓过氧化物酶（MPO）、谷胱甘肽（GSH）和过氧化氢酶（CAT）活性方面也发现了添加DHA饲料的积极作用。总之，结果表明，75 μM/mL剂量的DHA能够调节免疫细胞中的炎症反应，并增强以20 g/kg饲料添加DHA的饮食喂养的鲤鱼的抗病能力。
