塔玛亚历山大藻对中国明对虾鳃组织的氧化胁迫和对 Caspase 基因（FcCasp）表达的影响

摘要

Toxic microalgae outbreaks have caused significant economic losses in the Chinese aquaculture industry, including the aquaculture of shrimp. Blooms that involve phycotoxins, especially paralytic shellfish poison(PSP), are dangerous, harm the shrimps and cause losses in marine production. Previous studies mainly focused on the toxic ef-fects on shellfish and fish, rather than shrimp. This study investigated the inductive effect of the toxic dinoflagellate Alexandrium tamarense(ATHK), a producer of PSP, on oxidative stress and the expression of a caspase gene (FcCasp) in the gills of the Chinese shrimp, Fenneropenaeus chinensis, an important mariculture species in China. F. chinensis individuals were exposed to 200 and 1 000 cells/mL of A. tamarense, and F. chinensis individuals cultured with filtered seawater were set as control. Superoxide dismutase (SOD) activity, glutathione S-transferase (GST) activity, malonyldialdehyde (MDA) content and FcCasp expression in the gills were analyzed at 3, 6, 12, 24, 48, 72 and 96 h after exposure. The results showed that SOD activity, GST activity, MDA content and FcCasp expression exposed to 200 cells/mL of A. tamarense generally increased at first and then decreased with increasing exposure time. However, when exposed to 1000 cells/mL of A. tamarense, SOD activity increased and then decreased with increasing exposure time, and was significantly(P<0.05) inhibited between 24 and 96 h. GST activity was significantly(P<0.05) inhibited, except at 3-and 48 h-post treatment. The changes in SOD and GST activities of F. chinensis in this study suggest that these enzymes were actively involved in the detoxification process in gills of F. chinensis. The MDA content and FcCasp expression of F. chinensis exposed to 1 000 cells/mL of A. tamarense increased with increased exposure time, and displayed a time-dependent response relationship. The FcCasp transcript level in the gills of F. chinensis exposed to A. tamarense was positively and linearly correlated with the MDA content. The current study revealed that exposure to A. tamarense influenced the antioxidative status of F. chinensis, causing lipid peroxidation (LPO) and upregulation of FcCasp in gills of the shrimp. The findings from this study demonstrated that SOD, GST and MDA were sensitive and suitable potential oxidative biomarkers of F. chinensis and other aquatic invertebrates exposed to A. tamarense in the short term. Further studies are needed to clarify the mechanism of toxicity of A. tamarense to aquatic invertebrates.%选择在中国分离得到的一株能产生麻痹性贝毒(Paralytic Shellfish Poison, PSP)的赤潮甲藻塔玛亚历山大藻(Alexandrium tamarense) ATHK株,研究其对中国明对虾(Fenneropenaeus chinensis)鳃组织氧化胁迫和Caspase基因(FcCasp)表达的影响。将中国明对虾分别暴露于200 cells/mL 和1000 cells/mL塔玛亚历山大藻中,于胁迫后3、6、12、24、48、72和96 h 测定鳃的超氧化物歧化酶(SOD)活性、谷胱甘肽硫转移酶(GST)活性、丙二醛(MDA)含量和 FcCasp 基因相对表达量,以不加藻的过滤海水作为对照。结果表明,在200 cells/mL 塔玛亚历山大藻胁迫下, SOD活性、GST活性、MDA含量和 FcCasp相对表达量均随取样时间推移表现出先上升后下降的趋势。而在1000 cells/mL 塔玛亚历山大藻胁迫下, SOD 活性随时间增加呈现先升高后降低的趋势,在24~96 h 被显著抑制(P<0.05), GST活性除3和48 h外均被显著抑制(P<0.05), MDA含量和FcCasp相对表达量均整体表现上升的趋势,呈现出一定的时间效应。相关性分析显示,塔玛亚历山大藻胁迫下,中国明对虾鳃的 MDA含量和 FcCasp相对表达量呈正相关(P<0.05)。实验结果表明,塔玛亚历山大藻可破坏中国明对虾氧化-抗氧化系统的平衡,引发对虾鳃组织的脂质过氧化(LPO),造成其氧化损伤,从而导致FcCasp表达的上调。本实验结果为将SOD活性、GST活性和MDA含量作为生物标志物,用于评价塔玛亚历山大藻胁迫提供了依据,同时也为研究塔玛亚历山大藻对中国明对虾的危害机制提供了参考。