Description
Background: The diverse immunomodulatory effects of vitamin D are increasingly being recognized. However, the ability of oral vitamin D to modulate immune responses in vivo has not been established in humans. Methods: Twenty healthy adults were randomized to receive placebo or a single high dose of vitamin D3 (cholecalciferol) one hour after localized skin irradiation with an erythemogenic dose of ultraviolet radiation. Primary outcomes included skin redness, skin thickness, and tissue expression of inflammatory mediators (TNF- and iNOS). Secondary outcomes included microarray analyses. Results: As compared to placebo, subjects receiving vitamin D3 (200,000 IU) demonstrated reduced expression of TNF- (p=0.04) and iNOS (p=0.02) in skin biopsies 48 hours after ultraviolet light exposure. Demonstrated trends included reduced skin redness (p=0.17), and reduced skin thickness (p=0.09) in subjects receiving vitamin D3 (200,000 IU). Unsupervised clustering of individuals based on global gene expression revealed that subjects with enhanced skin barrier repair expression profiles had higher serum vitamin D3 levels (p=0.007), increased arginase expression (p=0.005), and a sustained reduction in skin redness (p=0.02) after treatment, as compared to subjects with enhanced inflammatory gene expression profiles.