Assessment of the early effects of the Diarrhetic Shellfish Toxins in the mussel "Mytilus galloprovincialis" using cellular and molecular biomarkers

Resumo

Diarrhetic shellfish poisoning (DSP) toxins constitute a group of marine toxins displaying wide geographic distribution and involved in frequent toxic episodes (Harmful algal blooms, HABs) in coastal areas. Okadaic acid (OA) and its derivatives the dinophysistoxins (DTXs) are the main toxic compounds of this group. Seafood contamination by DSP toxins, especially bivalve molluscs, constitutes the principal cause of diarrhetic shellfish poisoning syndrome (DSP) in human consumers. In order to reduce its prevalence, efficient pollution control programs are currently conducted in shellfish farming industries, causing collateral economic losses. Despite the toxicity caused by DSP toxins in human and mammalian cell lines, bivalve molluscs show an apparent resistance to these compounds. This thesis evaluates, for the first time, the early effects of DSP toxins in the mussel Mytilus galloprovincialis using cellular and molecular biomarkers. Accordingly, the genotoxic and cytotoxic effects of OA were evaluated in hemolymph and gill cells in vitro. This approach was supplemented with the in vivo assessment of the effects of DSP-toxin-producing dinoflagellate Prorocentrum lima. Additionally, the transcriptional and biochemical responses of several antioxidant enzymes were determined in mussels exposed in vivo to P. lima. The results presented in this thesis increase the general knowledge pertaining the genotoxic and cytotoxic potential of DSP toxins in marine organisms and, more especifically, in the case bivalve molluscs. In addition, this work helps elucidate the connection between the exposure to these toxins and the induction of oxidative stress. Similarly, the results obtained suggest that the resistance of these organisms to DSP toxins is associated with the ability of their antioxidant system to respond immediately to damage. In conclusion, this thesis lays the foundation for the future development of efficient monitoring programs.