Topical Nicotinamide Prevents UV Immunosuppression

1Department of Dermatology and Cutaneous Surgery, University of Miami Miller School of Medicine, Miami, Florida, USA UV light is a major risk factor for skin cancer development (Essen and Klar, 2006). The mechanisms by which UV leads to cancer formation are complex and appear not to be limited solely to UV-induced DNA damage. UV induces immune suppression, which is associated with increased skin cancer formation, as evidenced by the increased cancer risk in immunosuppressed transplant patients (Bergstresser, 1983; Ulrich and Stockfleth, 2007). Therefore, protection against UV-induced immune suppression may have clinical benefits. In this issue, Damian et al. (2008) explore the potential role of topical nicotinamide in preventing UV immunosuppression in humans, based on animal models to prevent UV-induced immune suppression. Using volunteers with a positive Mantoux test (purified protein derivative positive from Bacille Calmette-Guerin vaccination), the authors studied the ability of topical nicotinamide to prevent UVB immune suppression and the mechanisms by which this occurred. They found that when nicotinamide was applied either before or after UV exposure (simulating normal sunlight exposure), the typically encountered immune suppression was reduced. Additionally, men were more sensitive to UV-light-induced immune suppression, which the investigators concluded may account, in part, for the greater incidence of skin cancer and skin cancer mortality in men. Nicotinamide did not work as a sunscreen but rather, as suggested by microarray analysis, as a mechanism that may include alterations in complement, energy metabolism, and apoptosis. Through the following questions we will delve into this paper in greater detail. For brief answers, please refer to http://network.nature.com/group/jidclub.