Immunomodulatory effect of thymoquinone on atopic dermatitis

Background: Atopic dermatitis (AD) or atopic eczema is a skin disease characterized with itching, increased serum level of immunoglobulin E, and peripheral eosinophilia. Thymoquinone (TQ) is an important ingredient of Nigella sativa seeds having antioxidant and anti-inflammatory effects. Objective: Present study investigates the immunomodulatory effects of Thymoquinone (TQ) in mice model of atopic dermatitis. Methods: Ear pinnas of mice were sensitized and challenged with DNCB (2-4 di nitro chloro benzene) to induce AD-like lesions. The mice were then treated with TQ and tacrolimus, both orally and topically. Ear thickness and weight were measured along with gross changes. Total and differential leukocyte counts were measured in blood. Total serum IgE levels were measured by enzyme linked immunosorbent assay (ELISA). The mRNA expression levels of IL-4, IL-5, and IFN-gamma in ear tissue were measured using reverse transcription polymerase chain reaction (RT-PCR). Results: Both oral and topical thymoquinone showed the potential to improve atopic dermatitis by significantly reducing the inflammatory cells infiltration in the blood (p < 0.001) and improving the dermatitis score (p < 0.001). Significant reduction in ear thickness (p < 0.001) and IgE levels (p < 0.001) were also observed. TQ and tacrolimus also significantly attenuated mRNA expression levels of IL-4, IL-5 and IFN-gamma (p < 0.001). Conclusions & clinical relevance: Taken together, our results showed that oral and topical application of thymoquinone exerts immunomodulatory effects in animal model of atopic dermatitis, suggesting further studies and clinical trials to establish it as a candidate nutraceutical for the treatment of AD.