鱼腥草对无乳链球菌引起吉富罗非鱼肝脏损伤的修复作用

为探讨池塘种植鱼腥草对无乳链球菌引起吉富罗非鱼肝脏损伤的修复作用,在养殖池塘中分别种植0%(对照组)、5%、10%和15%池塘面积的鱼腥草,养殖90 d后进行无乳链球菌人工感染,分别在感染后0、24、48和72 h采集吉富罗非鱼肝脏,进行肝脏生化、抗氧化性能、组织病理和热休克蛋白70基因(HSP 70)表达研究。结果显示,感染后48和72 h对照组肝脏谷丙转氨酶(ALT)和谷草转氨酶(AST)活性最高,种植鱼腥草各组吉富罗非鱼肝脏ALT活性在感染前后均无显著性变化,感染后72 h,10%组吉富罗非鱼肝脏AST活性已恢复到感染前水平。抗氧化指标显示,种植鱼腥草能减缓链球菌感染引起吉富罗非鱼肝脏总抗氧化能力(T-AOC)下降,显著提高肝脏中超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)、过氧化氢酶(CAT)和一氧化氮合酶(NOS)等抗氧化酶的活性,增加自由基清除能力,减少脂质过氧化丙二醛(MDA)的产生。组织病理学观察显示,对照组吉富罗非鱼感染后48 h肝窦明显淤血,肝索排列紊乱,肝细胞脂肪变性,而各种植鱼腥草组吉富罗非鱼在感染后仅表现为肝细胞明显嗜酸,肝窦轻度扩张。定量PCR结果显示,每组吉富罗非鱼肝脏HSP 70表达量在感染后都显著升高,感染后各时间点对照组吉富罗非鱼肝脏的HSP 70表达量均显著高于鱼腥草种植组。研究表明,种植鱼腥草能显著改善链球菌感染所造成的吉富罗非鱼肝脏AST和ALT上升,提高抗氧化应激能力,减轻链球菌感染引起的病理损伤;吉富罗非鱼通过肝脏HSP 70高表达促进受损蛋白质的早期修复与降解,种植鱼腥草具有抗炎作用和提高鱼体抵御病原菌的能力。

Protective effects from Houttuynia cordata against Streptococcus agalactiae-induced liver injury of GIFT Oreochromis niloticus strain

The present study was conducted to investigate the effects of pond-planted houttuynia cordata levels on hepatic antioxidative status, histopathology and HSP70 expression in Oreochromis spp. infected by streptococcus agalactiae. Four groups of different proportions of Houttuynia cordatah were set. They were 0%(as control), 5%, 10% and 15% area of ponds. After 90 days cultivation, All fish were challenged by S. agalactiae. Liver samples were collected at 0, 24, 48 and 72 hour post injection(hpi). The results showed that hepatic alanine transaminase(ALT) and aspartate aminotransferase(AST) activity reached the peak in the control group at 48 and 72 hpi respectively, and there was no significant change in ALT activity before and after infection in houttuynia cordata-planted groups. The AST activity recovered to the pre-infection level at 72 hpi in 10% group. Antioxidant indexes showed that the activity of glutathione peroxidase (GSH-PX) and catalase (CAT) in houttuynia cordata-planted groups increased significantly after infection. Hepatic NOS activity increased significantly at 48 hpi in 10% group, while hepatic superoxide dismutase (SOD) activity raised significantly at 48 hpi in 15% group. Hepatic malonyldialdehyde (MDA) decreased significantly with the increase of planting area of houttuynia cordata before infection. The hepatic total antioxidative capacity(T-AOC) in the control group reduced significantly at 48 hpi, while there was no significant change in houttuynia cordata-planted groups. Histopathology showed that hepatic sinusoid congested obviously, hepatic cord arranged irregularly, hepatocyte macrovesicular steatosis at 48 hpi in the control group, while the tilapia in houttuynia cordata-planted groups showed only obvious eosinophilic and the hepatic sinus is slightly dilated. There were no obvious inflammatory reaction or tissue necrosis. Quantitative PCR results showed that the expression level of HSP70 mRNA in the liver of each group increased significantly after infection. The expression level of HSP70 in the control group at each time point was significantly higher than that in the houttuynia-planted groups after infection. And HSP70 expression level in the 10% group was significantly higher than that in the 5% and 15% groups at 72 hpi. The results of this study suggest that planting houttuynia cordate can significantly alleviate hepatic AST, ALT rising, increased activity of antioxidant enzymes, reduce hepatic MDA level, and maintain activity of T-AOC. And it alleviated the pathological damage caused by streptococcus infection. The expression of HSP70 can reduce the inflammatory response and maintain the balance of inflammation. The paper preliminarily elucidated the mechanism of planting houttuynia cordata to reduce the death of tilapia challenged by S. agalactiae.