Skin inflammation: reactive oxygen species and the role of iron.

Superoxide and hydrogen peroxide are reactive oxygen species (ROS) primarily produced by phagocytic cells as a consequence of the process of phagocytosis. This defensive role, may, however, become one of attack when production of ROS is excessive and overwhelms cellular scavenging systems. This happens in situations such as acute inflammation and results in host cell membrane damage, which is particularly prevalent in the presence of transition metal catalysts such as iron and copper. The skin is uniquely vulnerable to this attack being rich in polyunsaturated fatty acids and exposed to high oxygen tensions and ultraviolet light, both of which promote production of ROS. Additionally, the respiratory burst of infiltrating polymorphonuclear leukocytes and macrophages in inflamed skin will produce high local levels of superoxide that can release "catalytic iron" from storage proteins such as ferritin. The role of iron and ROS in the pathogenesis of inflammatory skin disease is discussed as is the possibility of novel therapeutic strategies based on their removal.