Editor's Note: Prevention of Ultraviolet Radiation-Induced Immunosuppression by (-)-Epigallocatechin-3-Gallate in Mice Is Mediated through Interleukin 12-Dependent DNA Repair.

Abstract

Purpose: Solar UV radiation–induced immunosuppression is considered to be a risk factor for melanoma and nonmelanoma skin cancers. We previously have shown that topical application of (−)-epigallocatechin-3-gallate (EGCG) prevents UV-induced immunosuppression in mice. We studied whether prevention of UV-induced immunosuppression by EGCG is mediated through interleukin 12 (IL-12)–dependent DNA repair. Experimental Design: IL-12 knockout (KO) mice on C3H/HeN background and DNA repair–deficient cells from xeroderma pigmentosum complementation group A ( XPA ) patients were used in this study. The effect of EGCG was determined on UV-induced suppression of contact hypersensitivity and UV-induced DNA damage in the form of cyclobutane pyrimidine dimers (CPD) in mice and XPA -deficient cells using immunohistochemistry and dot-blot analysis. Results: Topical treatment with EGCG prevented UV-induced suppression of the contact hypersensitivity in wild-type (WT) mice but did not prevent it in IL-12 KO mice. Injection of anti-IL-12 monoclonal antibody to WT mice blocked the preventive effect of EGCG on UV-induced immunosuppression. EGCG reduced or repaired UV-induced DNA damage in skin faster in WT mice as shown by reduced number of CPDs + cells and reduced the migration of CPD + antigen-presenting cells from the skin to draining lymph nodes. In contrast, this effect of EGCG was not seen in IL-12 KO mice. Further, EGCG was able to repair UV-induced CPDs in XPA -proficient cells obtained from healthy person but did not repair in XPA -deficient cells, indicating that nucleotide excision repair mechanism is involved in DNA repair. Conclusions: These data identify a new mechanism by which EGCG prevents UV-induced immunosuppression, and this may contribute to the chemopreventive activity of EGCG in prevention of photocarcinogenesis.