In vitro effects of methylmercury on ascidian (Styela plicata) immunocyte responses

Abstract

This study shows that high methylmercury concentrations are cytotoxic for Styela plicata hemocytes, whereas sublethal concentrations affect immunocyte responses. Moreover, hemocytes exposed to the xenobiotic present a significantly enhanced phenoloxidase activity as revealed in the hemocyte lysate supernatant compared with the control. Although the cytotoxic activity of S. plicata hemocytes toward rabbit erythrocytes is a PO-dependent cell-target reaction due to quinone products, it was significantly decreased by suitable methylmercury concentrations in the medium. The same xenobiotic concentrations decreased the hemocyte phagocytic activity toward yeast. In both the responses celltarget contacts could be affected by methylmercury, whereas the releasing capacity appeared to be unchanged, as indicated by hemocyte PO-release in the medium. Finally, changes in hemocyte shape and spreading capacity were shown. On the basis of the present results, Styela plicata hemocyte responses could be an additional immunotoxicology test using a microplate method that reveals cell morphological changes and spreading capacity.

The ascidian Styela plicata hemocytes as a potential biomarker of marine pollution: In vitro effects of seawater and organic mercury

“…Particularly, our observations suggest that MeHg contamination induces a reduced capability of cell attachment, spreading ability and changes in cell morphology. Changes in spreading ability have been previously observed in S. plicata hemocytes after treatment with increasing MeHg concentrations (from 10 -7 to 10 -4 M) (Cammarata et al, 2007). These findings are congruent with the already known effects of MeHg on phenoloxidase, cytotoxicity and phagocytosis activities of hemocytes.…”

“…3, a significant increase in mortality was observed in hemocytes of S. plicata after treatment with 10-4 M MeHg, the lower methylmercury concentrations we used for examining the effect on immunocytes were not toxic, as indicated by Trypan blue dead cell exclusion test, while viability was not affected by the treatment, as shown by the neutral red test. In general terms, 95% hemocytes maintained their main viable properties, whereas immune functions were affected by the xenobiotic compound (Cammarata et al, 2007).…”

“…In a previous paper, we reported that methylmercury sublethal concentrations quickly affect in vitro Styela plicata hemocyte innate immune activities such as phenoloxidase activity, cytotoxicity and phagocytosis, suggesting an immunosuppressive effect (Cammarata et al, 2007). Exposure to pollutants can also affect the number and the morpho-functional properties of these cells (Radford et al, 2000).…”

“…Styela plicata hemocytes showed several crucial immune reactions including cytotoxic activity (Cammarata et al, 1995(Cammarata et al, , 1997Lipari et al, 1995), phagocytosis (Cammarata et al, 2007), allograft rejection (Raftos et al, 1990) and phenoloxidase-dependent cytotoxicity (Cammarata et al, 1997).…”

Rare earths, zirconium and hafnium distribution in coastal areas: The example of Sabella spallanzanii (Gmelin, 1791)

“…This organism accumulates, owing also to the presence of vanadocytes, various substances in its tissues including heavy metals and hydrocarbons (Cammarata et al, 2007(Cammarata et al, , 2008. In biogeochemical analyses of S. plicata, tests are conducted on the hepatopancreas because it modulates the basic metabolic processes for the organism's life cycle, accumulation of foreign substances and production of molecules involved in its defence.…”