Piper nigrum Fruit Extract Prevents TMA-Induced Allergic Contact Dermatitis by Regulating Th2 Cytokine Production

Allergic contact dermatitis (ACD) remains a leading skin disease in many countries. In this study, we investigated the preventive effect of Piper nigrum fruit extract (PFE) on trimellitic anhydride (TMA)-induced dermatitis and its potential mechanism of action. Oral administration of PFE and prednisolone (PS) significantly suppressed TMA-induced increases in ear, epidermal thickness, and infiltration of CD4 cells, while abnormal expression of IgE, mMCP-1, IL-1β and IL-1β mRNA was also significantly counteracted by oral administration of PFE. PFE also significantly suppresses TMA-induced IL-4 and IL-5 production and IL-4 mRNA expression in vivo, as well as OVA-induced IL-4, IL-5, and IL-13 production and GATA3 mRNA expression ex vivo, and IL-4 induced STAT6 phosphorylation in primary cultured splenocytes and HaCaT cells. Interestingly, the PFE component piperine significantly suppressed OVA-induced IL-4, IL-5, and IL-13 secretion ex vivo. Taken together, these results suggest that PFE could be useful in suppressing allergic contact dermatitis.