Atopic dermatitis is a chronic inflammatory skin disease. Topical glucocorticoids, calcineurin inhibitors and emollients have limited efficacy for severe atopic dermatitis. Urocanic acid (UCA) is an epidermal chromophore that undergoes trans to cis isomerization after UVB irradiation.  cis-UCA is a potent inhibitor of cutaneous acquired immunity. To search a new therapeutic approach for atopic dermatitis, we first explored the genes which are up-regulated by cis-UCA in normal human epidermal keratinocytes (NHEK) by DNA microarray analysis and investigated its role in vitro and in vivo using T lymphocyte cell line, Jurkat cells, mouse bone marrow derived dendritic cells and an atopic dermatitis mouse model. DNA microarray experiment revealed that cis-UCA increased the expression of a gene encoding a beta-galactoside-binding lectin, galectin-7, LGALS7B. Quantitative real-time RT-PCR analysis showed that the expression of galectin-7 was enhanced by cis-UCA and UVB irradiation, but not by trans-UCA. To elucidate a role of galectin-7 in the control of cytokine production by T lymphocytes, we cultured Jurkat cells with galetin-7. Galectin-7 administration inhibited the expression of interleukin-2 (IL2) and interferon-gamma (IFNG) mRNA by Jurkat cells. Enzyme linked immunosorbent assay revealed that the IL-2 concentration of culture sup of Jurkat cells was down-regulated by galectin-7. FACS analysis revealed the down-modulation of the MHC molecules in bone marrow derived dendritic cells by the addition of galectin-7.  
Atopic dermatitis-like skin lesion was induced in the dorsal skin of NC/Nga mice by repeated topical application of Dermatophagoides farniae body ointment. Local injections of galectin-7 into erythematous regions in NC/Nga mice ameliorated erythema.  Histological examination revealed a decrease in the number of infiltrating lymphocytes into the dermis by galectin-7. Quantitative real-time RT-PCR analysis showed that expression of Il4 mRNA, Il17 mRNA, Ifng mRNA in the skin was suppressed by the injections of galectin-7. Taken together, these data suggested that galectin-7 may play important roles in down-regulation of cutaneous immune system both in vitro and in vivo and can be developed into novel immunosuppressive therapies for atopic dermatitis.

Galectin-7 suppresses the erythema and cytokine productions in Nc/Nga mice, an atopic dermatitis model