Protective effect of a topical sunscreen formulation fortified with melatonin against UV-induced photodermatitis: an immunomodulatory effect via NF-κB suppression.

Melatonin and pumpkin seed oil, along with US FDA approved UV filters were incorporated into a formulation for enhancement of UV protection by exerting an antioxidant effect. The objective of this study was to assess the protective effect of this formulation against ultraviolet (UV) radiation-induced photo dermatitis in rats, which is an established model to study the aetiopathogenic mechanisms in psoriasis vulgaris, as the former exhibits the same features to those of clinical psoriasis vulgaris in humans. The animals were segregated into five groups (6/group) and all received their respective formulations dermally prior to chronic UV irradiation for 28 days. The test, placebo, and standard groups; received the test, placebo, and standard formulations respectively; whereas the positive control group received only UV radiation. A normal control group was also maintained. Disease and treatment status were analyzed using various techniques by euthanizing the rats after 28 days. The test formulation was able to ameliorate the UV-induced increase in skin fold, epidermal thickness, and skin edema; inhibit the reduction of hydroxyproline content and incidence of LPO within the skin tissues of exposed animals. The formulation was also able to inhibit the release of proinflammatory cytokines; IFN-γ, IL-1β, IL-6, and TNF-α; and upregulation of NF-κB and COX-2 genes caused by chronic UV exposure. It can be stated that melatonin included in the newly formulated sunscreen was able to inhibit the induction of photodermatitis via immunoregulation of inflammatory cytokines along with NF-κB and COX-2 genes.