Sea urchin embryos as an in vivo model for the assessment of manganese toxicity: developmental and stress response effects.

In the marine environment increasing concentrationsof bio-available compounds often result fromanthropogenic activities. Among metal ions, manganeserepresents a new emergent factor in environmental contamination.Here, we studied the effects of manganese onParacentrotus lividus sea urchin embryos using biologicaland biochemical approaches for the analysis of impact ondevelopment, tissue accumulation and stress markers.Embryos were continuously exposed from fertilization tomanganese at concentrations ranging from 1.0 to61.6 mg l-1, monitored for developmental abnormalities at48 h after fertilization, and used for atomic spectrometricanalysis at various times from 6 to 72 h. We found thatconcentration- and time-dependent increases in morphologicalabnormalities were directly correlated to manganeseaccumulation, with major defects in skeletonformation at 48 h. Concurrently, we found an upregulationof the hsc70 and hsc60 stress proteins detected by immunoblotting,whereas no induction of apoptosis or ROSproduction was observed by TUNEL and live tests,respectively. Taken together, our findings demonstrate thatthe observed manganese embryo-toxicity is related to bothits intracellular accumulation and misregulated homeostasis,and confirm the importance of stress proteins as protectiveagents in the acquisition of tolerance and resistanceto apoptosis.