Oxidative targets in the stratum corneum. A new basis for antioxidative strategies

As the outermost layer of skin, the stratum corneum (SC) is continuously exposed to an oxidative environment, including air pollutants, ultraviolet radiation, chemical oxidants, and aerobic microorganisms. Human SC reveals characteristic antioxidant and protein oxidation gradients with increasing antioxidant depletion and protein oxidation towards the outer layers. SC antioxidants, lipids, and proteins are oxidatively modified upon treatments with ultraviolet A/ultraviolet B, ozone, and benzoyl peroxide. alpha-Tocopherol represents the predominating SC antioxidant with respect to its concentration and its unique susceptibility to the various oxidative challenges tested. In sites rich in sebaceous glands, alpha-tocopherol is physiologically delivered to the surface via secretion of sebum. Oxidative damage in the human SC represents an early pathophysiological event preceding barrier disruption and inflammation in environmentally challenged skin. Furthermore, oxidative gradients in SC proteins may have implications for the process of desquamation in human skin.