Immunotoxicity in ascidians: antifouling compounds alternative to organotins - II. The case of Diuron and TCMS pyridine.

Using short-term hemocyte cultures of the colonial ascidian Botryllus schlosseri exposed to various sublethal concentrations of Diuron (3-(3,4-diclorophenyl)-1,1-dimethylurea) and TCMS pyridine (2,3,5,6-tetrachloro-4-(metylsulphonyl)pyridine), we evaluated their immunotoxic effects through a series of cytochemical assays previously used for organotin compounds. At concentrations higher than 250 micro M and 10 micro M for Diuron and TCMS pyridine, respectively, both biocides exerted immunosuppressant effects on Botryllus hemocytes, causing i) deep changes in the cytoskeleton that irreversibly affect cell morphology and phagocytosis, ii) induction of DNA damage, iii) leakage of oxidative and hydrolytic enzymes due to membrane alteration. Unlike organotin compounds, Diuron and TCMS pyridine do not inhibit cytochrome-c-oxidase, and only TCMS pyridine triggers oxidative stress.

Immunomodulatory molecules in the compound ascidian Botryllus schlosseri: evidence from conditioned media.

The supernatant from cultures of haemocytes of the compound ascidian Botryllus schlosseri incubated with zymosan (conditioned medium; CM) can enhance yeast phagocytosis by Botryllus blood cells. It contains molecules recognised by antibodies raised against the mammalian pro-inflammatory cytokines IL-1-alpha and TNF-alpha which appear as a single band of 60 kDa in immunoblot analysis. The effects on phagocytosis are abolished by the presence of sugars, such as galactose and rhamnose, sharing the same hydroxyl group configuration at C2 and C4.

Haemocytes and blastogenetic cycle in the colonial ascidian Botryllus schlosseri: a matter of life and death.

A recurrent blastogenetic cycle characterizes colonies of the ascidian Botryllus schlosseri. This cycle starts when a new zooid generation opens its siphons and ends with take-over, when adult zooids cease filtering and are progressively resorbed and replaced by a new generation of buds, reaching functional maturity. During the generation change, massive apoptosis occurs in the colony, mainly in the tissues of old zooids.