Two facets of geotextiles in coastal ecosystems: Anti- or profouling effects?

Nonwoven geotextile fabrics have physical, mechanical and hydraulic properties useful in coastal protection as an alternative to natural stone, slag, and concrete. In a 10-month experiment, the colonisation of macrofouling organisms on different substrata based on polypropylene (PP), polyester (PET) or high density polyethylene (HDPE) fibres was investigated in the Lagoon of Venice, Italy - an environment with temperate transitional waters with high biodiversity - and compared with the colonisation on wood as a reference substratum, because of its occurrence in artificial structures at the study location, until a stable stage was reached in the development of the macrofouling community. Geotextile fabrics showed implications for community development. They affected both ecological succession in different ways by disturbing biofouling settlement and growth (HDPE fabrics) or favouring species which become dominant (PP fabrics). For these two-faceted aspects that potentially cause different long-term impacts on the biodiversity of resident communities, the use of geotextile fabrics as antifouling or as profouling systems for restoration of degraded ecosystems is discussed. In all cases, the communities displayed unique properties, such as differences in the settlement of pioneer species, an initial disturbance to serpulid settlement, absence of barnacles, selection of dominant taxa (ascidians), and changes in the percentages of various taxa forming the community structure. Given the increasing interest in geotextile materials for employment in various marine developments and industries, these results could represent first lines of evidence to inform decision-making to minimise/modify biofouling, and/or predict the use of artificial substrata as habitats by marine organisms.

An intracellular adrenomedullin system reduces IL-6 release via a NF-kB-mediated, cAMP-independent transcriptional mechanism in rat thymic epithelial cells.

Thymic epithelial cells (TECs) play a key role in the regulation of central immune tolerance by expressing autoantigens and eliminating self-reactive T cells. In a previous paper we reported that adrenomedullin (ADM) and its co-receptor protein RAMP2 are located intracellularly in newborn human thymic epithelial cells (TECs). This work has two main aims: (1) to examine the cellular localization of ADM and its receptor in TECs of adult Wistar rats to validate this animal model for the study of the ADM system and its function(s) in thymus; (2) to investigate the potential modulating effect of ADM on the NF-kB pathway, which is involved through the production of cytokines such as IL-6, in the maturation of T-lymphocytes and immunological tolerance. Our results show that, similarly to human newborn TECs, ADM is localized to the cytoplasm of adult rat TECs, and RAMP2 is expressed in the nucleus but not in the plasma membrane. Pretreatment of TECs for 4h with ADM significantly reduced lipopolysaccharide (LPS)-induced release of IL-6 (P<0.001) and expression of the p65 subunit of NF-kB, while doubled the expression of IkBα (P<0.001), the physiological inhibitor of NF-kB nuclear translocation. These effects were not mediated by activation of the cAMP pathway, a signalling cascade that is rapidly activated by ADM in cells that express plasma membrane RAMP2, but were the consequence of a reduction in the transcription of p65 (P<0.001) and an increase in the transcription of IkBα (P<0.05). On the basis of these findings we propose that in rat TECs ADM reduces IL-6 secretion by modulating NF-kB genes transcription through an interaction with a receptor localized to the nucleus. This may partly explain the protective effects of ADM in autoimmune diseases and points to the ADM system of TECs as a novel potential target for immunomodulating drugs.

TCMS inhibits ATP synthesis in mitochondria: a systematic analysis of the inhibitory mechanism.

The interactions of the antifouling compound TCMS (2,3,5,6-tetrachloro-4-methylsulphonyl pyridine) with rat liver mitochondria have been investigated. The results indicate that the compound inhibits ATP synthesis. Further investigations regarding the ATP synthesis mechanism suggest that TCMS inhibits succinic dehydrogenase of the mitochondrial respiratory chain. As the respiratory chain is similar in all living organisms, it can be concluded that the toxic effect of TCMS most likely depend on the different bioavailability of the compound and on the different importance of mitochondria in the ATP production in the animal species.

Irgarol inhibits the synthesis of ATP in mitochondria from rat liver.

The interactions of Irgarol with rat liver mithocondrial have been investigated. The results indicate that Irgarol inhibits the ATP synthesis. The analysis of the various steps involved in the ATP synthesis suggests that the inhibition is due to the opening of small-size pores.

External amebocytes guard the pharynx entry in a tunicate (Ascidiacea).

In the present report, we describe the identification of unusual free amebocytes, completely exposed to seawater, which inhabit the inner surface of the oral and atrial siphons of the compound ascidian Botryllus schlosseri (Urochordata). The origin and biological role of these cells were studied by cytochemical and ultrastructural analysis. These amebocytes are mononucleate cells, with numerous round granules, varying in content, and long filopodia, which contact the cuticle protrusions of the tunic in the siphon. Histochemical, histoenzymatic and immunohistochemical assays were carried out under light microscopy on sections and on living and fixed cultured hemocytes. Results showed that the phagocytic blood cells and the free amebocytes of the siphons shared: (i) affinity for the alpha-mannose specific agglutinin of Narcissus pseudonarcissus (NPA), (ii) occurrence of hydrolytic activities of acid phosphatase and non-specific esterases inside lysosomal vesicles and large vacuoles, (iii) membrane labeling with the lipophilic dye PKH26 specific for phagocytic cells, (iv) anti-CD39 immunocytochemical labeling specific for lysosomes of mammalian macrophages. All histochemical data support the hypothesis that these cells are 'sentinel cells' belonging to the hyaline amebocyte population of the phagocytic differentiation line of the immunocytes, since they can also recognize and phagocytize carmine experimentally administered as target particles.

Tributyltin-sulfhydryl interaction as a cause of immunotoxicity in phagocytes of tunicates.

We reported elsewhere that tributyltin (TBT) has detrimental effects on the immune system of the colonial ascidian Botryllus schlosseri, through interaction with calmodulin and alteration of Ca2+ homeostasis. Here, we studied the capability of TBT to react with intracellular thiols. After exposure to 0.1 microM TBT, a significant decrease in B. schlosseri hemocytes stained for total thiols and reduced glutathione (GSH) was detected. Exogenous sulfhydryl and sulfide compounds can prevent TBT-induced cell morphology alterations and decrease the percentage of tin-containing hemocytes, indicating the scavenging ability of thiol peptides. No effects were observed with disulfides, N-acetylcysteine, or the GSH fragment Cys-Gly. No interactions were observed with TBT and carmustine, whereas TBT and N-ethylmaleimide (NEM) showed a combined antagonistic action, suggesting direct interaction of TBT with thiol-containing compounds. Regulation of Ca2+ efflux from internal stores seems to depend on stimulation of the inositol 1,4,5-trisphosphate (InsP3) receptor by oxidized glutathione (GSSG), which results from interactions of both TBT-GSH and TBT-GSH reductase.

Cellular aspects of allorecognition in the compound ascidian Botryllus schlosseri.

We studied changes in the morphology of morula cells, a common haemocyte type in botryllid ascidians, during both the rejection reaction (occurring between contacting, genetically incompatible colonies) and fusion (occurring between compatible colonies), and in short-term cultures of haemocytes incubated with heterologous or autologous blood plasma. In both the rejection reaction and haemocyte cultures in the presence of heterologous blood plasma, we observed alterations in morula cells, consistent with a degranulation event, and their expression of molecules recognised by anti-IL-1-alpha- and anti-TNF-alpha-antibodies. Anti-cytokine-antibodies markedly reduced the extent of the in vitro cytotoxicity, when haemocytes were exposed to heterologous blood plasma. In addition, the increase in the production of nitrite ions and the decrease of the in vitro cytotoxicity by the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester, suggest the role of nitric oxide in cell death. These results provide new clues to understand the process of rejection reaction in botryllid ascidians.

Oxidative stress induces cytotoxicity during rejection reaction in the compound ascidian Botryllus schlosseri.

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.