Galectin-7, induced by cis-urocanic acid and ultraviolet B irradiation, down-modulates cytokine production by T lymphocytes.

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. The aim of this study was to explore the genes, which are upregulated by cis-UCA in normal human epidermal keratinocytes (NHEK) and investigated its role in vitro using human T-lymphocyte cell line, Jurkat cells. DNA microarray analysis and real-time PCR investigation revealed that cis-UCA, not trans-UCA, increased the expression of a gene encoding a β-galactoside-binding lectin, galectin-7, LGALS7B. Immunohistochemical study demonstrated that galectin-7 was highly expressed in the epidermis in the patients with actinic keratosis. Galectin-7 administration upregulated apoptosis and inhibited the expression of interleukin-2 (IL2) and interferon-γ (IFNG) mRNA in Jurkat cells. Taken together, galectin-7 may play important roles in downregulating the functions of T lymphocytes after UVB irradiation and can be developed into novel immunosuppressive therapies for inflammatory skin diseases.