Topical nicotinamide modulates cellular energy metabolism and provides broad-spectrum protection against ultraviolet radiation-induced immunosuppression in humans

• Published in: British journal of dermatology (1951) Vol. 161; no. 6; pp. 1357 - 1364
• Main Authors: Sivapirabu, G., Yiasemides, E., Halliday, G.M., Park, J., Damian, D.L
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-12-2009
• Subjects: Administration, Topical; Adult; Aged; Animals; Apoptosis - drug effects; Cells, Cultured; delayed type hypersensitivity; Dose-Response Relationship, Drug; Energy Metabolism - drug effects; Female; Gene Expression - drug effects; Humans; Immunosuppression; Male; Mice; Middle Aged; niacin; Niacinamide - administration & dosage; Niacinamide - pharmacology; photoprotection; Reverse Transcriptase Polymerase Chain Reaction; Skin - drug effects; Skin - radiation effects; skin cancer; Skin Neoplasms - prevention & control; Sunscreening Agents - administration & dosage; Sunscreening Agents - pharmacology; Ultraviolet Rays - adverse effects; vitamin B3; Young Adult
• ISSN: 0007-0963; 1365-2133
• DOI: 10.1111/j.1365-2133.2009.09244.x

Summary
Background  Ultraviolet (UV) radiation can profoundly suppress the cutaneous immune system, thus enhancing carcinogenesis. Agents that prevent UV‐induced immunosuppression may thus reduce skin cancer. Nicotinamide (vitamin B3) prevents UV‐induced immunosuppression and carcinogenesis in mice, and solar‐simulated (ss) UV‐induced immunosuppression in humans. Its effectiveness against different UV wavebands and mechanism of action is as yet unknown.
Objectives  To determine the effects and mechanisms of topical nicotinamide on UV‐induced suppression of delayed type hypersensitivity (DTH) responses in humans.
Methods  Healthy Mantoux‐positive volunteers in four randomised, double‐blinded studies were irradiated with solar‐simulated (ss)UV (UVB + UVA) or narrowband UVB (300 nm) or UVA (385 nm). Topical nicotinamide (0·2% or 5%) or its vehicle were applied immediately after each irradiation. Mantoux testing was performed at irradiated sites and adjacent unirradiated control sites 48 h after the first irradiation and measured 72 h later. Immunosuppression was calculated as the difference in Mantoux‐induced erythema and induration at test sites compared to control sites. Human keratinocyte cell cultures, with and without ssUV and nicotinamide, were used for quantitative real‐time reverse transcriptase‐polymerase chain reaction assessment of TP53 and enzymes that regulate oxidative phosphorylation.
Results  Nicotinamide cooperated with ssUV to increase enzymes involved in cellular energy metabolism and p53, and significantly protected against immunosuppression caused by UVB, longwave UVA and single and repeated ssUV exposures.
Conclusions  Longwave UVA, which is poorly filtered by most sunscreens, was highly immune suppressive even at doses equivalent to 20 min of sun exposure. Nicotinamide, which protected against both UVB and UVA, is a promising agent for skin cancer prevention.