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Inhibition of UVB-induced skin tumor development by drinking green tea polyphenols is mediated through DNA repair and subsequent inhibition of inflammation.

ABSTRACT: Consumption of green tea polyphenols (GTPs) in drinking water prevents photocarcinogenesis in mice; however, the molecular mechanisms underlying this effect have not been fully elucidated. Using IL-12p40 knockout (KO) mice and their wild-type counterparts and an established photocarcinogenesis protocol, we found that although administration of GTPs (0.2%, w/v) in drinking water significantly reduced UVB-induced tumor development in wild-type mice, this treatment had a nonsignificant effect in IL-12-KO mice. GTPs resulted in reduction in the levels of markers of inflammation (cyclooxygenase-2, prostaglandin E(2), proliferating cell nuclear antigen, and cyclin D1) and proinflammatory cytokines (tumor necrosis factor-alpha, IL-6, and IL-1beta) in chronically UVB-exposed skin and skin tumors of wild-type mice but less effective in IL-12p40-KO mice. UVB-induced DNA damage (cyclobutane pyrimidine dimers) was resolved rapidly in GTPs-treated wild-type mice than untreated wild-type mice and this resolution followed the same time course as the GTPs-induced reduction in the levels of inflammatory responses. This effect of GTPs was less pronounced in IL-12-KO mice. The above results were confirmed by treatment of IL-12-KO mice with murine recombinant IL-12 and treatment of wild-type mice with neutralizing anti-IL-12 antibody. To our knowledge, it is previously unreported that prevention of photocarcinogenesis by GTPs is mediated through IL-12-dependent DNA repair and a subsequent reduction in skin inflammation.

SUBMITTER: Meeran SM

PROVIDER: S-EPMC2669839 | biostudies-literature | 2009 May

REPOSITORIES: biostudies-literature

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Inhibition of UVB-induced skin tumor development by drinking green tea polyphenols is mediated through DNA repair and subsequent inhibition of inflammation.

Meeran Syed M SM Akhtar Suhail S Katiyar Santosh K SK

The Journal of investigative dermatology 20081120 5

Consumption of green tea polyphenols (GTPs) in drinking water prevents photocarcinogenesis in mice; however, the molecular mechanisms underlying this effect have not been fully elucidated. Using IL-12p40 knockout (KO) mice and their wild-type counterparts and an established photocarcinogenesis protocol, we found that although administration of GTPs (0.2%, w/v) in drinking water significantly reduced UVB-induced tumor development in wild-type mice, this treatment had a nonsignificant effect in IL ...[more]

PMID: 19020550

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Project description:Previously, we and others have shown that the regular intake of green tea polyphenols (GTPs) reduces ultraviolet B (UVB) radiation-induced skin cancer by targeting multiple signaling pathways, including DNA damage, DNA repair, immunosuppression, and inflammation. Here, we determine the effect of GTPs on UVB-induced epigenetic changes, emphasizing DNA hypermethylation in UV-exposed skin and tumors and their association with miR-29, a key regulator of DNA methyltransferases (DNMTs). Skin cancer was induced in SKH-1 hairless mice following repeated exposures of UVB radiation (180 mJ/cm2, three times/week, 24 weeks) with or without GTPs supplementation (0.2%) in drinking water. Regular intake of GTPs inhibited tumor growth by hindering the cascade of DNA hypermethylation events. GTPs supplementation significantly blocked UVB-induced DNA hypermethylation in the skin (up to 35%; p < 0.0001) and in tumors (up to 50%; p < 0.0001). Experimental results showed that the levels of DNA hypermethylation were higher in GTPs-treated mice than in the control group. The expressions of miR-29a, miR-29b, and miR-29c were markedly decreased in UV-induced skin tumors, and GTPs administration blocked UVB-induced miR-29s depletion. Furthermore, these observations were verified using the in vitro approach in human skin cancer cells (A431) followed by treatment with GTPs or mimics of miR-29c. Increased levels of miR-29 were observed in GTPs-treated A431 cells, resulting in increased TET activity and decreased DNA hypermethylation. In conclusion, UVB-mediated miR-29 depletion promotes DNA hypermethylation and leads to enhanced tumor growth by silencing tumor suppressors. Regular intake of GTPs rescued UVB-induced miR-29 depletion and prevented tumor growth by maintaining reduced DNA hypermethylation and activating tumor suppressors. Our observations suggest that miR-based strategies and regular consumption of GTPs could minimize the risk of UVB-induced skin cancers and contribute to better management of NMSCs.

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Inhibition of UVB-induced skin tumor development by drinking green tea polyphenols is mediated through DNA repair and subsequent inhibition of inflammation.

Publications

Inhibition of UVB-induced skin tumor development by drinking green tea polyphenols is mediated through DNA repair and subsequent inhibition of inflammation.

Similar Datasets

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