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

Abstract

Background: Environmental ultraviolet radiation has deleterious effects on humans, including sunburn and immune perturbations. These immune changes are involved in skin carcinogenesis.

Objectives: To determine whether nicotinamide riboside and/or pterostilbene administered systemically inhibits inflammatory and immune effects of exposure to mid-range ultraviolet radiation.

Methods: To 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.

Results: Nicotinamide 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.

Conclusion: Nicotinamide riboside and pterostilbene have protective effects against UVB radiation-induced tissue swelling and immune suppression.

Keywords: animal model; immunity; inflammation; ultraviolet radiation.