Skin inflammation and dryness are the features of surfactant-induced irritant
contact dermatitis, a common skin disorder. In Japan, Coix seed (CS, Coix
lacryma-jobi L. var. ma-yuen Stapf) is widely used as a
traditional medicine and functional supplement to treat skin inflammation and
dry skin. However, the efficacy of CS against surfactant-induced skin disorders
has not been reported. Here, we investigated the effect of CS on inflammatory
dry skin disorders induced by multiple topical applications of sodium dodecyl
sulfate (SDS), a representative anionic surfactant. Male HR-1 hairless mice
received a water extract of CS for four weeks. Three weeks after CS
administration, the dorsal skin of the mice was exposed once daily to
10% SDS for five days. CS efficacy was then evaluated by measuring
epidermal water content; erythema index; severity of skin scaling; epidermal
thickness; inflammatory cell infiltration; production of pro-inflammatory
mediators, such as interleukin-1α (IL-1α) and prostaglandin E2
(PGE2); and protein expression of cyclooxygenase 2 (COX-2), in the dorsal skin.
Administration of CS markedly attenuated the SDS-induced reduction in epidermal
water content, elevated erythema index, and severity of skin scaling.
Histological analysis demonstrated that CS suppressed epidermal hyperplasia and
macrophage infiltration in SDS-exposed skin. Furthermore, CS significantly
prevented SDS-induced production of IL-1α and PGE2, as well as COX-2
upregulation. These results indicate that CS prevents SDS-induced
inflammation-mediated skin dryness by inhibiting the production of
pro-inflammatory mediators.