Green Tea Prevents UV-Induced Immunosuppression

BIRMINGHAM, Ala.Results from a study at the University of Alabama found drinking green tea polyphenols (GTP) prevented UV-induced immunosuppression, possibly underlying the chemopreventive activity of GTPs against photocarcinogenesis (Cancer Prev Res. 2010;3(2):17989). UV radiationinduced immunosuppression, which causes a reduction in the activation or efficacy of the immune system, has been implicated in the development of skin cancers. Researchers studied whether GTPs in drinking water (0.1 to 0.5 percent, w/v) prevent UV-induced immunosuppression and, if so, the potential mechanisms of this effect in mice. GTPs (0.2 percent and 0.5 percent, w/v) reduced UV-induced suppression of contact hypersensitivity (CHS) in response to a contact sensitizer in local (58 to 62 percent reductions) and systemic (51 to 55 percent reductions) models of CHS.

Compared with untreated mice, GTP-treated mice (0.2 percent, w/v) had a reduced number of cyclobutane pyrimidine dimerpositive (CPD+) cells (59 percent) in the skin, showing faster repair of UV-induced DNA damage, and had a reduced (twofold) migration of CPD+ cells from the skin to draining lymph nodes, which was associated with elevated levels of nucleotide excision repair (NER) genes. GTPs did not prevent UV-induced immunosuppression in NER-deficient mice, but significantly prevented it in NER-proficient mice; immunohistochemical analysis of CPD+ cells indicated GTPs reduced the numbers of UV-induced CPD+ cells in NER-proficient mice, but not in NER-deficient mice. GTPs repaired UV-induced CPDs in xeroderma pigmentosum complementation group A (XPA)proficient cells of a healthy person, but did not in XPA-deficient cells obtained from XPA patients, indicating an NER mechanism is involved in DNA repair.