The role of selenium-dependent glutathione peroxidase (Se-GPx) against oxidative and genotoxic effects of mercury in haemocytes of mussel Mytilus galloprovincialis (Lmk.)

This study investigated whether mercury (Hg) oxidative and genotoxic effects are related with its ability to inhibit selenium-dependent glutathione peroxidase (Se-GPx) activity in haemocytes of mussel Mytilus galloprovincialis. Se-GPx activity was measured both in Se-free cells’ cytosolic fraction and in Se-treated cells, pre-treated with 4 μg/l of Se (as sodium selenite), before the exposure to the metal. Hg at concentrations ranged within 10 or 20 μg/l, thus representing the onset of Hg toxic effects, showed to inhibit Se-GPx activity in Se-free cells, followed by increased levels of superoxide anions (O2-) and nitric oxide (NO) generation, lipid peroxidation and DNA damage as well. On the other hand, increased enzymatic activity and a significant attenuation of Hg toxicity were measured in Se-treated cells exposed to Hg in all cases. The results of the present study showed that inhibition of Se-GPx activity by Hg could promote a shift in the balance between oxidants and antioxidants in favor of oxidants, resulted in the enhancement of Hg-induced oxidative and genotoxic effects. In addition, Se bioavailability within phagocytic cells, such as haemocytes, could regulate the antioxidant role of Se-GPx, thus reinforcing haemocytes’ immune system against toxic effects induced by pro-oxidants, such as Hg.