The Inhibitory Effect of Premature Citrus unshiu Extract on Atopic Dermatitis In Vitro and In Vivo

Atopic dermatitis (AD) is a chronic, recurrent inflammatory skin disease that is associated with Th2 cell-mediated allergy. The process that leads to infiltration of inflammatory cells into an AD lesion is remarkably dependent on various chemokines, especially TARC (thymus and activation-regulated chemokine/CCL17) and MDC (macrophage-derived chemokine/CCL22). Serum levels of these chemokines are over-expressed in AD patients. Citrus unshiu, which is known as Satsuma mandarin, has anti-oxidative, anti-inflammation, and anti-microviral activity. Therefore, we investigated the effect of EtOH extract of premature C. unshiu on AD. We did this using a DNCB-induced AD mouse model. We also tried to confirm an inhibitory effect for premature C. unshiu on the expression of inflammatory chemokines in IFN-γ and TNF-α stimulated HaCaT human keratinocytes. We found that extract of premature C. unshiu reduced DNCB-induced symptoms such as hyperkeratosis, increased skin thickness, and infiltrated mast cells, in our AD-like animal model. The extract decreased levels of IFN-γ and IL-4 in ConA-stimulated splenocytes isolated from DNCB-treated mice. Also, extract of premature C. unshiu inhibited mRNA expression and protein production of TARC and MDC through the inhibition of STAT1 phosphorylation. These results suggest that C. unshiu has anti-atopic activity by regulating inflammatory chemokines such as TARC and MDC.