Abstract
Allergic contact dermatitis (ACD) and atopic dermatitis (AD) are inflammatory eczematous skin diseases caused by various factors. Here, we report that topical application of the dipeptide, L-glutamic acid-L-tryptophan (L-Glu-L-Trp), improved symptoms in both ACD and AD in mice. Using a mouse model of ACD induced by repeated application of 2,4-dinitorofluorbenzene (DNFB), we demonstrated that L-Glu-L-Trp attenuated DNFB-induced skin thickening. In addition, quantification of cytokines in serum revealed that L-Glu-L-Trp suppressed the DNFB-induced increase in the interleukin (IL)-22 level. Moreover, L-Glu-L-Trp attenuated mite antigen extract-induced AD model symptoms such as the increase of skin thickening and elevation of serum IL-22. We also confirmed that the dipeptide structure rather than the individual amino acid components was important for the therapeutic effects of L-Glu-L-Trp. Furthermore, we showed that IL-22 decreased the expression level of filaggrin mRNA in human epidermal keratinocytes, and L-Glu-L-Trp attenuated that effect. These results suggested that the topical application of the dipeptide, L-Glu-L-Trp, to the skin may be useful for treating ACD and AD.