Impact of reactive oxygen species on keratinocyte signaling pathways

Human epidermal keratinocytes are located on the body surface, which is a specialized location for component cells of human skin tissue. Those cells are always exposed to external stimuli, which constantly generate reactive oxygen species (ROS) in the cells. Regulation of the redox state is a key for maintaining intracellular homeostasis. Originally, each cell type has defensive systems against oxidative stress, thus keratinocytes may have a unique system for regulating ROS levels. Intracellular signaling appropriately reacts to changes of ROS in cooperation with intra- and extra-cellular antioxidant agents, and is sometimes affected by excessive ROS generated by various stresses. We review in this paper the impact of ROS on keratinocytes based on published data and focus on related signaling pathways involved in inflammation and oncogenesis.