Identifying novel natural sources from the marine environment with unique immunomodulatory and antioxidant efficacies is of interest in intensive fish farming. In this sense, marine sponge extract derived from Smenospongia (SS-extract) was tested for its potential anti-inflammatory, antioxidant and antimicrobial activities during the concurrent infection with Trichodina sp. and Flavobacterium columnare in Nile tilapia. A total of 625 Nile tilapia fingerlings were distributed into five groups: the control group (with no additives) and four groups fed the control diet fortified with SS-extract at 50, 100, 150, and 200 mg/kg, respectively, for 60 days. The parasitic challenge with Trichodina sp was done at the endpoint of the feeding trial and at 7 days post-infection (dpi); the fish were coinfected with F. columnare. A significant improvement in growth-related parameters of Nile tilapia was detected in the groups that received SS-extract at the levels of 150 and 200 mg/kg. The scavenging ability for free radicals (2,2′-azino-bis-3-ethylbenzthiazoline-6-sulfonic acid (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH)) was maximized with higher SS-extract supplementation levels. Simultaneously, the antioxidant defense of the Nile tilapia fed 150 and 200 mg/kg was augmented with a decline in oxidation-associated indicators [reactive oxygen species (ROS), hydrogen peroxide (H2O2), and malondialdehyde (MDA)]. The higher concentrations of SS-extract in the feed potentiated the immune response of Nile tilapia before infection and even after coinfection and was paralleled by a subsiding in the exaggerated inflammatory response after concurrent infection. Concurrently, the mRNA expression of autophagy-encountered genes (Atg5 and 12, LC3-II and BCLN1) had its highest expression in the fish fed the 200 mg/kg diet with the lowest expression of the mTOR gene in the same fish. The lowest infection intensity and rate and mucus score were displayed in fish fed 200 mg/kg SS-extract at 20 dpi. Interestingly, higher levels of SS-extract triggered antimicrobial peptides (upregulation of Hepcidin and β-defensin-1). In contrast, excessive expression of endoplasmic reticulum genes (atf4, JAK1, PERK, and eif2α) in the control infected group was downregulated by 200 mg/kg of SS-extract. The quantification of F. columnare indicated that columnaris coinfection severity displayed its lowest rate in the group supplemented with 200 mg/kg of SS-extract. In conclusion, a strategic siting based on fortification of the diet of Nile tilapia with SS-extract was elucidated to reinforce its immune and antioxidant defenses during a concurrent infection.

中文翻译：

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海洋 Smenospongia 提取物减轻尼罗罗非鱼中与 Trichodina sp. 和 Flavobacterium columnare 的混合感染：关于促进生长性能、免疫、抗氧化和自噬防御以及抑制内质网应激相关基因的见解


从海洋环境中鉴定具有独特免疫调节和抗氧化功效的新型天然来源是集约化养鱼的兴趣所在。从这个意义上说，在尼罗罗非鱼同时感染 Trichodina sp. 和 Flavobacterium columnare 期间，测试了源自 Smenospongia 的海洋海绵提取物（SS 提取物）的潜在抗炎、抗氧化和抗菌活性。共将 625 尾尼罗罗非鱼鱼种分为 5 组：对照组（无添加剂）和 4 组分别饲喂以 50、100、150 和 200 mg/kg SS 提取物强化的对照饲料，持续 60 天。毛滴虫属 sp 的寄生虫攻击在喂养试验的终点和感染后 7 天 （dpi） 进行;鱼与 F. columnare 共感染。在接受 150 和 200 mg/kg 水平的 SS 提取物的组中检测到尼罗罗非鱼生长相关参数的显着改善。SS 提取物添加水平较高，对自由基（2,2′-联氮-双-3-乙基苯并噻唑啉-6-磺酸 （ABTS） 和 2,2-二苯基-1-三硝基苯肼 （DPPH））的清除能力最高。同时，喂食 150 和 200 mg/kg 的尼罗罗非鱼的抗氧化防御能力增强，氧化相关指标 [活性氧 （ROS）、过氧化氢 （H2O2） 和丙二醛 （MDA）] 下降。饲料中较高浓度的 SS 提取物增强了尼罗罗非鱼在感染前甚至混合感染后的免疫反应，并且与并发感染后夸张的炎症反应的消退平行。 同时，自噬遭遇基因 （Atg5 和 12、LC3-II 和 BCLN1） 的 mRNA 表达在喂食 200 mg/kg 饮食的鱼中表达最高，而在同一条鱼中 mTOR 基因的表达最低。在 20 dpi 时喂食 200 mg/kg SS 提取物的鱼的感染强度和发生率以及粘液评分最低。有趣的是，更高水平的 SS 提取物触发了抗菌肽（铁调素和 β-防御素-1 的上调）。相比之下，200 mg/kg SS 提取物下调了对照组内质网基因 （atf4 、 JAK1 、 PERK 和 eif2α） 的过表达。F. column的定量表明，柱状菌共感染严重程度在补充 200 mg/kg SS 提取物的组中表现出最低的发生率。总之，阐明了一种基于用 SS 提取物强化尼罗罗非鱼饮食的战略选址，以加强其在并发感染期间的免疫和抗氧化防御。