Six-day selenium supplementation led to either UVA-photoprotection or toxic effects in human fibroblasts depending on the chemical form and dose of Se.

Selenium (Se) is an essential trace element with a narrow safety zone and unclear effects on skin photoageing. The aim of this work was to investigate the photoageing properties of sodium selenite or selenomethionine (SeMet) after a long term (6 days) Se supplementation in normal human skin fibroblasts (NHSF) subjected to ultraviolet-A (UVA) irradiation inducing 30% cell death. The uptake, toxicity and antioxidant effects of sodium selenite and SeMet were compared to better understand their photoageing properties. SeMet uptake was better than sodium selenite and their uptake by fibroblasts was not via an actively transport process. Sodium selenite induced a higher toxicity than SeMet. At 5 μM, sodium selenite inhibited cell proliferation associated with a blockage in the G2 phase and induced DNA fragmentation leading to caspase-3-dependent apoptosis cell death. At low doses (<1 μM), SeMet and sodium selenite induced glutathione peroxidase-1 (GPX1) activity and selenoproteinW1 (SEPW1) transcript expression but metalloproteinase (MMP)-1 was only induced by sodium selenite. SeMet and sodium selenite did not protect NHSFs from UVA-induced cell death. However, SeMet decreased malondialdehyde (MDA) and protected NHSFs from UVA-induced MMP1 and MMP3. We then observed a large difference in terms of photoprotection according to selenium forms. SeMet may be a potential agent for the prevention and treatment of skin photoageing.