Rosaria M Ruggeri1,2, Angela D'Ascola3, Teresa M Vicchio4, Salvatore Campo3, Fiorenza Gianì5, Salvatore Giovinazzo4, Francesco Frasca5, Salvatore Cannavò4,6, Alfredo Campennì7, Francesco Trimarchi8. 1. Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy. rmruggeri@unime.it. 2. Endocrine Unit, University Hospital AOU Policlinico G. Martino, Messina, Italy. rmruggeri@unime.it. 3. Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy. 4. Endocrine Unit, University Hospital AOU Policlinico G. Martino, Messina, Italy. 5. Department of Clinical and Experimental Medicine, Endocrinology Unit, University of Catania, Catania, Italy. 6. Department of Human Pathology DETEV, University of Messina, Messina, Italy. 7. Department of Biomedical and Dental Sciences and Morfo-Functional Images, Unit of Nuclear Medicine, University of Messina, Messina, Italy. 8. Accademia Peloritana dei Pericolanti, University of Messina, Messina, Italy.
Abstract
PURPOSE: Selenium, incorporated into specific seleno-enzymes, is essential to proper thyroid function and protect cells from oxidative damage induced by H2O2 during thyroid hormone synthesis. Several studies indicated that low selenium levels are associated with thyroid autoimmunity and related disorders, but real effectiveness of selenium supplementation in such diseases is still controversial. We evaluated the effect of selenium on oxidative damage in human thyrocytes and thyroid fibroblasts in vitro. METHODS: To induce oxidative stress, primary cultures were exposed to H2O2, in the presence or the absence of selenium, as either selenomethionine or selenite. We performed the following assays: cell viability, caspase-3 activity, BCL-2/BAX gene expression, DNA fragmentation, malondialdehyde levels, and glutathione peroxidase (GPx) activity measurements. RESULTS: Thyrocytes and thyroid fibroblasts exposed to H2O2 and preincubated with both selenocompounds displayed a significant dose-dependent increase in cell viability compared to cells incubated with H2O2 alone. Pretreatment with selenomethionine and selenite significantly reduced caspase-3 activity and BAX mRNA levels and increased BCL-2 mRNA levels in a dose-dependent manner. Accordingly, H2O2 induced a diffuse pattern of DNA degradation and an increase in malondialdehyde levels, which was prevented by the pretreatment with both selenomethionine and selenite. Both selenocompounds induced an increase in GPx activity, suggesting that these protective effects may be, almost in part, mediated by these selenoproteins. CONCLUSION: In human thyrocytes and fibroblasts in vitro, selenium exerts protective effects against H2O2 in a dose-dependent manner, being selenite effective at lower doses than selenomethionine.
PURPOSE:Selenium, incorporated into specific seleno-enzymes, is essential to proper thyroid function and protect cells from oxidative damage induced by H2O2 during thyroid hormone synthesis. Several studies indicated that low selenium levels are associated with thyroid autoimmunity and related disorders, but real effectiveness of selenium supplementation in such diseases is still controversial. We evaluated the effect of selenium on oxidative damage in human thyrocytes and thyroid fibroblasts in vitro. METHODS: To induce oxidative stress, primary cultures were exposed to H2O2, in the presence or the absence of selenium, as either selenomethionine or selenite. We performed the following assays: cell viability, caspase-3 activity, BCL-2/BAX gene expression, DNA fragmentation, malondialdehyde levels, and glutathione peroxidase (GPx) activity measurements. RESULTS: Thyrocytes and thyroid fibroblasts exposed to H2O2 and preincubated with both selenocompounds displayed a significant dose-dependent increase in cell viability compared to cells incubated with H2O2 alone. Pretreatment with selenomethionine and selenite significantly reduced caspase-3 activity and BAX mRNA levels and increased BCL-2 mRNA levels in a dose-dependent manner. Accordingly, H2O2 induced a diffuse pattern of DNA degradation and an increase in malondialdehyde levels, which was prevented by the pretreatment with both selenomethionine and selenite. Both selenocompounds induced an increase in GPx activity, suggesting that these protective effects may be, almost in part, mediated by these selenoproteins. CONCLUSION: In human thyrocytes and fibroblasts in vitro, selenium exerts protective effects against H2O2 in a dose-dependent manner, being selenite effective at lower doses than selenomethionine.