Richier Sophie, Furla Paola, Plantivaux Amandine, Merle Pierre-Laurent, Allemand Denis
Université de Nice Sophia-Antipolis, BP 71, F-06108 Nice Cedex 02, France.
J Exp Biol. 2005 Jan;208(Pt 2):277-85. doi: 10.1242/jeb.01368.
Cnidarians in symbiosis with photosynthetic protists must withstand daily hyperoxic/anoxic transitions within their host cells. Comparative studies between symbiotic (Anemonia viridis) and non-symbiotic (Actinia schmidti) sea anemones show striking differences in their response to oxidative stress. First, the basal expression of SOD is very different. Symbiotic animal cells have a higher isoform diversity (number and classes) and a higher activity than the non-symbiotic cells. Second, the symbiotic animal cells of A. viridis also maintain unaltered basal values for cellular damage when exposed to experimental hyperoxia (100% O(2)) or to experimental thermal stress (elevated temperature +7 degrees C above ambient). Under such conditions, A. schmidti modifies its SOD activity significantly. Electrophoretic patterns diversify, global activities diminish and cell damage biomarkers increase. These data suggest symbiotic cells adapt to stress while non-symbiotic cells remain acutely sensitive. In addition to being toxic, high O(2) partial pressure (P(O(2))) may also constitute a preconditioning step for symbiotic animal cells, leading to an adaptation to the hyperoxic condition and, thus, to oxidative stress. Furthermore, in aposymbiotic animal cells of A. viridis, repression of some animal SOD isoforms is observed. Meanwhile, in cultured symbionts, new activity bands are induced, suggesting that the host might protect its zooxanthellae in hospite. Similar results have been observed in other symbiotic organisms, such as the sea anemone Aiptasia pulchella and the scleractinian coral Stylophora pistillata. Molecular or physical interactions between the two symbiotic partners may explain such variations in SOD activity and might confer oxidative stress tolerance to the animal host.
与光合原生生物共生的刺胞动物必须耐受宿主细胞内每日的高氧/缺氧转变。共生海葵（绿色海葵）和非共生海葵（施氏海葵）之间的比较研究表明，它们对氧化应激的反应存在显著差异。首先，超氧化物歧化酶（SOD）的基础表达差异很大。共生动物细胞比非共生细胞具有更高的同工型多样性（数量和类别）和更高的活性。其次，当暴露于实验性高氧环境（100% O₂）或实验性热应激（温度比环境温度升高7摄氏度）时，绿色海葵的共生动物细胞的细胞损伤基础值也保持不变。在这种条件下，施氏海葵会显著改变其SOD活性。电泳图谱多样化，总体活性降低，细胞损伤生物标志物增加。这些数据表明共生细胞能够适应压力，而非共生细胞仍然极其敏感。除了具有毒性外，高氧分压（P(O₂)）也可能是共生动物细胞的一个预处理步骤，导致其适应高氧条件，从而适应氧化应激。此外，在绿色海葵的无共生动物细胞中，观察到一些动物SOD同工型受到抑制。同时，在培养的共生体中，会诱导出新的活性条带，这表明宿主可能在体内保护其虫黄藻。在其他共生生物中也观察到了类似的结果，如美丽艾氏海葵和石珊瑚状珊瑚细指鹿角珊瑚。两个共生伙伴之间的分子或物理相互作用可能解释了SOD活性的这种变化，并可能赋予动物宿主氧化应激耐受性。
