Inhibition of UVB radiation‐induced tissue swelling and immune suppression by nicotinamide riboside and pterostilbene

BackgroundEnvironmental ultraviolet radiation has deleterious effects on humans, including sunburn and immune perturbations. These immune changes are involved in skin carcinogenesis.ObjectivesTo determine whether nicotinamide riboside and/or pterostilbene administered systemically inhibits inflammatory and immune effects of exposure to mid‐range ultraviolet radiation.MethodsTo examine UVB radiation‐induced inflammatory effects, mice were fed standard chow/water, 0.04% pterostilbene in chow and 0.2% nicotinamide riboside in drinking water, diet with nicotinamide riboside alone, or diet with pterostilbene alone. After 4 weeks, mice were exposed to UVB radiation (3500 J/m2), and 24‐/48‐h ear swelling was assessed. We also asked if each agent or the combination inhibits UVB radiation suppression of contact hypersensitivity in two models. Mice were fed standard diet/water or chow containing 0.08% pterostilbene, water with 0.4% nicotinamide riboside, or both for 4 weeks. Low‐dose: Half the mice in each group were exposed on the depilated dorsum to UVB radiation (1700 J/m2) daily for 4 days, whereas half were mock‐irradiated. Mice were immunized on the exposed dorsum to dinitrofluorobenzene 4 h after the last irradiation, challenged 7 days later on the ears with dinitrofluorobenzene, and 24‐h ear swelling assessed. High dose: Mice were treated similarly except that a single dose of 10,000 J/m2 of radiation was administered and immunization was performed on the unirradiated shaved abdomen 3 days later.ResultsNicotinamide riboside and pterostilbene together inhibited UVB‐induced skin swelling more than either alone. Pterostilbene alone and both given together could inhibit UVB‐induced immune suppression in both the low‐dose and high‐dose models while nicotinamide riboside alone was more effective in the low‐dose model than the high‐dose model.ConclusionNicotinamide riboside and pterostilbene have protective effects against UVB radiation‐induced tissue swelling and immune suppression.