Marine organisms are highly sensitive to many environmental pressures, and consequently, the analysis of their bio-molecular responses to different stress agents is very important for the understanding of putative repair mechanisms and for application in environmental studies. A research line of activities has been recently pursued by researchers of the Section "Biologia dello Sviluppo", concerning the use of cells and embryos of an aquatic invertebrate as sentinels of the health state of marine habitats. The organism chosen for the purpose, the sea urchin, has been enormously useful since it represents a simple though significant model system where to test: 1) the impact on the biology of development in association with gene expression on embryos, and 2) the effects on gene expression and DNA damage on adult immuno-competent cells. The latter are cells contained in the coelomic cavity of the adult sea urchin, generically called coelomocytes, studied since many decades, but only recently used in our laboratories as bio-indicators of stress. Due to their capability to respond to injuries, host invasion and cytotoxic agents, coelomocytes have been regarded as the immune effectors of the sea urchin, although the molecular basis of their functioning is not yet well studied and understood.
The Institute has recently taken part to an International Project, in the frame of the 5th European Commission R&D Programme, titled: "Development and field validation of biosensor methods for the assessment of the effects of pollution and solar UV radiation on commercially and ecologically important marine invertebrates". One of the goals of the multidisciplinary project, which involved research laboratories in Germany, France and Hungary, was to identify those molecular markers which are elicited by physical and chemical stress, to be used for the estimate of the health state of marine invertebrates in their natural habitats (sponges and sea urchins) or in aquaculture (bivalves). To this purpose embryos and cells from marine invertebrates have been challenged in laboratory experiments in exposure to heavy metals and/or UV radiations. In short, during the last 4 years in our laboratories, a number of coding sequences of genes specific for stress proteins, repair enzymes, differentiation antigens, growth and transcription factors, ECM molecules have been cloned and sequenced. By means of these tools it was found that ceolomocytes exposed to heavy metals and/or UV-B radiation express high levels of stress markers, quantified by WB, 2-D gel electrophoresis, RT-PCR. In embryos the variation in expression levels, found by genomic and proteomic analyses, is directly correlated to the amount of developmental abnormalities found upon exposure to heavy metals and/or UV-B radiation. Interestingly, although microscopical inspection revealed the occurrence of abnormalities only after 24 hours of exposure to the pollutant, Northern blot and RT-PCR analyses revealed significant increases in stress gene expression levels already after 12 and 6 hours of exposure, respectively. In this case, this provides early molecular markers of stress that can be used for their application to determine hazardous effects of physical and chemical impacts in contaminated marine habitats.
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