College of Fisheries, Henan Normal University, Xinxiang, 453007, PR China; Department of Biological and Environmental Engineering, Changsha University, Changsha, 410003, PR China.
College of Fisheries, Henan Normal University, Xinxiang, 453007, PR China.
Fish Shellfish Immunol. 2020 Mar;98:324-333. doi: 10.1016/j.fsi.2020.01.037. Epub 2020 Jan 22.
Microbial exopolysaccharides (EPS) from Lactococcus have been found to have an important role in the probiotic activity of this bacterium; however, the immunomodulatory and antioxidant activities have not been fully explored in aquaculture. In the present study, we investigated EPS-2 from Lactococcus lactis Z-2, isolated from healthy common carp, for its immunomodulatory and antioxidant effects and disease resistance against Aeromonas hydrophila in Cyprinus carpio L. We found that the molecular weight of EPS-2 was 18.65 KDa. The monosaccharide composition of this polymer was rhamnose, xylose, mannose, glucose, and galactose at a molar percentage of 13.3%, 14.1%, 18.5%, 27.4%, and 26.7%, respectively. EPS-2 treatment could modulate the immune responses in vitro and in vivo. In vitro tests showed that EPS-2 could significantly enhance the proliferation and phagocytosis activities (P < 0.05) as well as induce the production of nitic oxide (NO), pro-inflammatory cytokines (TNF-α, IL-1β, IL-6), and anti-inflammatory cytokines (IL-10, TGF-β) (P < 0.05) in head kidney cells. When the fish were gavaged with three different concentrations of EPS-2 (250, 500, 1000 μg/mL) for 7 days and infected with A. hydrophila, different expression patterns of the NO, cytokines, lysozyme (LZM), and alkaline phosphatase (AKP) in the serum and of antioxidants (T-AOC, SOD, CAT, GSH, GSH-Px and MDA) in hepatopancreas were observed. Before infection with A. hydrophila, EPS-2 supplementation significantly up-regulated the NO production, protein levels of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6), LZM and AKP activities, and levels of antioxidant molecules compared to those in the negative (G1) group (P < 0.05), whereas levels of NO and pro-inflammatory cytokines and LZM and AKP activities were significantly lower than those in the positive (G2) group after infection (P < 0.05). However, whether infected or not, the expression levels of anti-inflammatory cytokines (IL-10, TGF-β) were significantly increased in the EPS-2 treatment groups (P < 0.05). These results indicate that EPS-2 has immunomodulatory and antioxidant effects on common carp, both in vitro and/or in vivo, and can be applied as a common carp feed supplement to enhance fish immunity and disease resistance against A. hydrophila.
乳球菌的微生物胞外多糖 (EPS) 已被发现对该细菌的益生菌活性具有重要作用; 然而，其在水产养殖中的免疫调节和抗氧化活性尚未得到充分探索。在本研究中，我们研究了从健康鲤鱼中分离出的乳球菌 Lactococcus lactis Z-2 的 EPS-2 的免疫调节和抗氧化作用以及对鲤鱼的嗜水气单胞菌的抗病能力。我们发现 EPS-2 的分子量为 18.65 kDa。该聚合物的单糖组成为鼠李糖、木糖、甘露糖、葡萄糖和半乳糖，摩尔百分比分别为 13.3%、14.1%、18.5%、27.4%和 26.7%。EPS-2 处理可在体外和体内调节免疫反应。体外试验表明，EPS-2 可显著增强头肾细胞的增殖和吞噬活性 (P < 0.05)，并诱导一氧化氮 (NO)、促炎细胞因子 (TNF-α、IL-1β、IL-6) 和抗炎细胞因子 (IL-10、TGF-β) 的产生 (P < 0.05)。当鱼用三种不同浓度的 EPS-2 (250、500 和 1000μg/mL) 灌胃 7 天并感染嗜水气单胞菌时，观察到血清中 NO、细胞因子、溶菌酶 (LZM) 和碱性磷酸酶 (AKP) 的不同表达模式以及肝胰腺中的抗氧化剂 (T-AOC、SOD、CAT、GSH、GSH-Px 和 MDA)。在感染嗜水气单胞菌之前，与阴性 (G1) 组相比，EPS-2 补充剂可显著上调 NO 产生、促炎细胞因子 (TNF-α、IL-1β、IL-6)、LZM 和 AKP 活性以及抗氧化分子的蛋白水平 (P < 0.05)，而感染后 NO 和促炎细胞因子以及 LZM 和 AKP 活性均显著低于阳性 (G2) 组 (P < 0.05)。然而，无论是否感染，EPS-2 处理组的抗炎细胞因子 (IL-10、TGF-β) 的表达水平均显著升高 (P < 0.05)。这些结果表明，EPS-2 对鲤鱼具有免疫调节和抗氧化作用，无论是在体外还是体内，均可作为鲤鱼饲料添加剂使用，以增强鱼类对嗜水气单胞菌的免疫力和抗病能力。
