Ballarin Loriano, Cima Francesca, Floreani Maura, Sabbadin Armando
Dipartimento di Biologia, Università di Padova, Via U. Bassi 58/B, I-35121 Padova, Italy.
Comp Biochem Physiol C Toxicol Pharmacol. 2002 Nov;133(3):411-8. doi: 10.1016/s1532-0456(02)00123-0.
When genetically incompatible colonies of the compound ascidian Botryllus schlosseri contact each other, a rejection reaction occurs, characterised by the appearance of cytotoxic foci along the touching borders. In the course of this reaction, morula cells, a common haemocyte-type in ascidians, release their vacuolar content, mainly phenoloxidase and its polyphenol substrata, upon the recognition of soluble factors diffusing from the alien colony through the partially fused tunic. In a previous paper, we demonstrated the relationship between phenoloxidase and cytotoxicity. Here, we investigated the effects of superoxide dismutase, catalase and sorbitol (scavengers of superoxide anions, peroxides and hydroxyl radicals, respectively) on the cytotoxicity observed in haemocyte cultures incubated with heterologous blood plasma. Although the above compounds have no effects on morula cell degranulation and phenoloxidase activity, they suppress cell death, suggesting that oxidative stress plays a key role in in vitro cytotoxicity. In addition, sorbitol reduces the extent of the cytotoxicity occurring in the rejection reaction between incompatible colonies, which stresses the important role of hydroxyl radicals in this process. The observation of a decrease in total and non-protein thiols in haemocytes previously incubated with heterologous blood plasma fits the hypothesis of oxidative stress as the main cause of phenoloxidase-related cytotoxicity.
当复合海鞘Botryllus schlosseri的基因不相容群体相互接触时，会发生排斥反应，其特征是在接触边界处出现细胞毒性病灶。在这个反应过程中，桑椹细胞（海鞘中一种常见的血细胞类型）在识别从异体群体通过部分融合的被囊扩散而来的可溶性因子后，释放其液泡内容物，主要是酚氧化酶及其多酚底物。在之前的一篇论文中，我们证明了酚氧化酶与细胞毒性之间的关系。在这里，我们研究了超氧化物歧化酶、过氧化氢酶和山梨醇（分别是超氧阴离子、过氧化物和羟基自由基的清除剂）对在用异源血浆培养的血细胞中观察到的细胞毒性的影响。尽管上述化合物对桑椹细胞脱颗粒和酚氧化酶活性没有影响，但它们抑制细胞死亡，这表明氧化应激在体外细胞毒性中起关键作用。此外，山梨醇降低了不相容群体之间排斥反应中发生的细胞毒性程度，这突出了羟基自由基在这个过程中的重要作用。在用异源血浆预孵育的血细胞中观察到总硫醇和非蛋白质硫醇减少，这符合氧化应激是酚氧化酶相关细胞毒性主要原因的假设。
