Intracellular Mg 2+ protects mitochondria from oxidative stress in human keratinocytes

Reactive oxygen species (ROS) are harmful for the human body, and exposure to ultraviolet irradiation triggers ROS generation. Previous studies have demonstrated that ROS decrease mitochondrial membrane potential (MMP) and that Mg 2+ protects mitochondria from oxidative stress. Therefore, we visualized the spatio-temporal dynamics of Mg 2+ in keratinocytes (a skin component) in response to H 2 O 2 (a type of ROS) and found that it increased cytosolic Mg 2+ levels. H 2 O 2 -induced responses in both Mg 2+ and ATP were larger in keratinocytes derived from adults than in keratinocytes derived from newborns, and inhibition of mitochondrial ATP synthesis enhanced the H 2 O 2 -induced Mg 2+ response, indicating that a major source of Mg 2+ was dissociation from ATP. Simultaneous imaging of Mg 2+ and MMP revealed that larger Mg 2+ responses corresponded to lower decreases in MMP in response to H 2 O 2 . Moreover, Mg 2+ supplementation attenuated H 2 O 2 -induced cell death. These suggest the potential of Mg 2+ as an active ingredient to protect skin from oxidative stress.