Green Tea Phenol Extracts Reduce UVB‐induced DNA Damage in Human Cells via Interleukin‐12†

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Abstract
Green tea chemoprevention has been a focus of recent research, as a polyphenolic fraction from green tea (GTP) has been suggested to prevent UV radiation‐induced skin cancer. Recently, it was demonstrated that GTP reduced the risk for skin cancer in a murine photocarcinogenesis model. This was accompanied by a reduction in UV‐induced DNA damage. These effects appeared to be mediated via interleukin (IL)‐12, which was previously shown to induce DNA repair. Therefore, we studied whether GTP induction of IL‐12 and DNA repair could also be observed in human cells. KB cells and normal human keratinocytes were exposed to GTP 5 h before and after UVB. UVB‐induced apoptosis was reduced in UVB‐exposed cells treated with GTP. GTP induced the secretion of IL‐12 in keratinocytes. The reduction in UV‐induced cell death by GTP was almost completely reversed upon addition of an anti‐IL‐12‐antibody, indicating that the reduction of UV‐induced cell death by GTP is mediated via IL‐12. The ability of IL‐12 to reduce DNA damage and sunburn cells was confirmed in “human living skin equivalent” models. Hence the previously reported UV‐protective effects of GTP appear to be mediated in human cells via IL‐12, most likely through induction of DNA repair.
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