title: Oxidative stress induces cytotoxicity during rejection reaction in the compound ascidian Botryllus schlosseri.
abstract: 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.
authors.affiliation: Dipartimento di Biologia, Università di Padova, Via U. Bassi 58/B, I-35121 Padova, Italy. ballarin@civ.bio.unipd.it
authors.forename: Loriano
authors.initials: L
authors.lastname: Ballarin
authors.forename: Francesca
authors.initials: F
authors.lastname: Cima
authors.forename: Maura
authors.initials: M
authors.lastname: Floreani
authors.forename: Armando
authors.initials: A
authors.lastname: Sabbadin
mesh_terms: D000818:Animals; D002374:Catalase / Q000494:pharmacology; D002452:Cell Count; D003602:Cytotoxicity, Immunologic; D004305:Dose-Response Relationship, Drug; D016166:Free Radical Scavengers / Q000494:pharmacology; D005978:Glutathione / Q000378:metabolism; D006084:Graft Rejection / Q000276:immunology*; D006434:Hemocytes / Q000187:drug effects / Q000201:enzymology / Q000276:immunology; D014442:Monophenol Monooxygenase / Q000378:metabolism; D018384:Oxidative Stress; D013012:Sorbitol / Q000494:pharmacology; D013045:Species Specificity; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013482:Superoxide Dismutase / Q000494:pharmacology; D014561:Urochordata / Q000187:drug effects / Q000201:enzymology / Q000276:immunology*
chemical_list: D016166:Free Radical Scavengers; D013438:Sulfhydryl Compounds; D013012:Sorbitol; D002374:Catalase; D014442:Monophenol Monooxygenase; D013482:Superoxide Dismutase; D005978:Glutathione