Non-enzymatic NO production in human skin: effect of UVA on cutaneous NO stores.

Nitric oxide (NO(*)) in human skin has been under investigation since first reports of NOS expression in skin tissue in 1992. NO(*) plays a key role in the dermal response to external stimuli such as heat, ultraviolet (UV) light, or infection, and in healing of abrasions, lesions or burns. Recently, a range of non-enzymatic pathways for NO(*) release has been identified, mostly in the context of systemic blood flow. In this article we consider the non-enzymatic formation of NO(*) in human skin tissues. Significant quantities of NO() are continuously released from human skin into the ambient air. This release can be significantly enhanced by photolysis of endogenous NO() stores under UVA. In addition, we give the first estimate of the basal enzymatic NO(*) production in healthy human skin.