Magnesium Supplementation Attenuates Ultraviolet-B-Induced Damage Mediated through Elevation of Polyamine Production in Human HaCaT Keratinocytes

Magnesium ions (Mg²⁺) have favorable effects such as the improvement of barrier function and the reduction of inflammation reaction in inflammatory skin diseases. However, its mechanisms have not been fully understood. Microarray analysis has shown that the gene expressions of polyamine synthases are upregulated by MgCl₂ supplementation in human HaCaT keratinocytes. Here, we investigated the mechanism and function of polyamine production. The mRNA and protein levels of polyamine synthases were dose-dependently increased by MgCl₂ supplementation, which were inhibited by U0126, a MEK inhibitor; CHIR-99021, a glycogen synthase kinase-3 (GSK3) inhibitor; and Naphthol AS-E, a cyclic AMP-response-element-binding protein (CREB) inhibitor. Similarly, reporter activities of polyamine synthases were suppressed by these inhibitors, suggesting that MEK, GSK3, and CREB are involved in the transcriptional regulation of polyamine synthases. Cell viability was reduced by ultraviolet B (UVB) exposure, which was rescued by MgCl₂ supplementation. The UVB-induced elevation of reactive oxygen species was attenuated by MgCl₂ supplementation, which was inhibited by cysteamine, a polyamine synthase inhibitor. Our data indicate that the expression levels of polyamine synthases are upregulated by MgCl₂ supplementation mediated through the activation of the MEK/GSK3/CREB pathway. MgCl₂ supplementation may be useful in reducing the UVB-induced oxidative stress in the skin.