Topical application of green and white tea extracts provides protection from solar-simulated ultraviolet light in human skin.

BACKGROUND: Tea polyphenols have been found to exert beneficial effects on the skin via their antioxidant properties. AIMS: We sought to determine whether topical application of green tea or white tea extracts would prevent simulated solar radiation-induced oxidative damages to DNA and Langerhans cells that may lead to immune suppression and carcinogenesis. METHODS: Skin samples were analysed from volunteers or skin explants treated with white tea or green tea after UV irradiation. In another group of patients, the in vivo immune protective effects of green and white tea were evaluated using contact hypersensitivity to dinitrochlorobenzene. RESULTS: Topical application of green and white tea offered protection against detrimental effects of UV on cutaneous immunity. Such protection is not because of direct UV absorption or sunscreen effects as both products showed a sun protection factor of 1. There was no significant difference in the levels of protection afforded by the two agents. Hence, both green tea and white tea are potential photoprotective agents that may be used in conjunction with established methods of sun protection.

UV protective effects of DNA repair enzymes and RNA lotion.

Solar UV radiation is known to cause immune suppression, believed to be a critical factor in cutaneous carcinogenesis. Although the mechanism is not entirely understood, DNA damage is clearly involved. Sunscreens function by attenuating the UV radiation that reaches the epidermis. However, once DNA damage ensues, repair mechanisms become essential for prevention of malignant transformation. DNA repair enzymes have shown efficacy in reducing cutaneous neoplasms among xeroderma pigmentosum patients. In vitro studies suggest that RNA fragments increase the resistance of human keratinocytes to UVB damage and enhance DNA repair but in vivo data are lacking. This study aimed to determine the effect of topical formulations containing either DNA repair enzymes (Micrococcus luteus) or RNA fragments (UVC-irradiated rabbit globin mRNA) on UV-induced local contact hypersensitivity (CHS) suppression in humans as measured in vivo using the contact allergen dinitrochlorobenzene. Immunohistochemistry was also employed in skin biopsies to evaluate the level of thymine dimers after UV. Eighty volunteers completed the CHS portion. A single 0.75 minimum erythema dose (MED) simulated solar radiation exposure resulted in 64% CHS suppression in unprotected subjects compared with unirradiated sensitized controls. In contrast, UV-induced CHS suppression was reduced to 19% with DNA repair enzymes, and 7% with RNA fragments. Sun protection factor (SPF) testing revealed an SPF of 1 for both formulations, indicating that the observed immune protection cannot be attributed to sunscreen effects. Biopsies from an additional nine volunteers showed an 18% decrease in thymine dimers by both DNA repair enzymes and RNA fragments, relative to unprotected UV-irradiated skin. These results suggest that RNA fragments may be useful as a photoprotective agent with in vivo effects comparable to DNA repair enzymes.

Anti-angiogenic effects of epigallocatechin-3-gallate in human skin.

Epigallocatechin-3-gallate (EGCG) is the main polyphenol component of green tea. This compound exhibits antioxidant, immunomodulatory, photoprotective, anti-angiogenic, and anti-inflammatory properties. We conducted a small randomized, double blind, split face trial using a cream containing 2.5% w/w of EGCG. Four healthy volunteers with significant erythema and telangiectasia on the face applied EGCG cream to one side of the face, and vehicle control cream to the other, twice daily for six weeks. After six weeks, biopsies were taken from EGCG and vehicle treated sites. Immunohistochemistry was used to measure VEGF and HIF-1 α. HIF-1 α expression was decreased in EGCG treated sites, such that 28.4% of the epidermis showed positive staining in vehicle treated vs. 13.8% in EGCG treated sites (p<0.001). A similar decrease in VEGF expression was found (6.7% in EGCG vs. 11.0%in in vehicle-treated skin (p<0.005). EGCG topical treatments influence HIF-1 α induction and VEGF expression and may serve as a potential agent in the prevention of telangiectasias.

Determination of in vivo dose response and allergen-specific T cells in subjects contact-sensitized to squaric acid dibutyl ester.

BACKGROUND: Squaric acid dibutyl ester (SADBE) is a known contact sensitizer, but dose-response data are not defined. OBJECTIVE: To determine the relationship between sensitization dose and contact hypersensitivity (CHS) response to SADBE in human volunteers. The study also aimed to investigate whether SADBE-reactive blood T cells could be detected using ex vivo mature dendritic cells (DCs) as antigen-presenting cells. METHOD: Forty healthy volunteers were sensitized to either 12.5, 25, 50, or 250 microg of SADBE in a 48 microL volume. This was followed by elicitation 2 weeks later with five doses (0, 0.2, 2, 20, and 200 microg in 20 microL). An additional 10 subjects received the elicitation doses without prior sensitization. Blood samples obtained after sensitization were purified into T cells and mature DCs. RESULTS: A direct relationship between sensitization dose and in vivo CHS response was observed. The SADBE dose that effectively sensitized 50% of the population (ED50) was 22 microg/cm2. Significant SADBE-specific T-cell proliferation in vitro was not observed 2 weeks after sensitization but became evident after elicitation. CONCLUSION: This study establishes the in vivo dose-response characteristics of immune reactivity to SADBE and antigen-specific T-cell reactivity.

Protective effects of tea polyphenols and caffeine.

Compounds derived from botanical sources, such as polyphenols from tea, have been of interest as possible therapeutic agents. Their benefits in terms of cancer chemoprevention have also been investigated primarily through in vitro and animal in vivo studies. Ultraviolet light from solar radiation has been proven to initiate and promote skin cancer, which is the most common malignancy in light-skinned populations. This review discusses the effects of tea polyphenols in preventing cutaneous carcinogenesis. Although many of the mechanisms and pathways discussed may be applicable to other carcinogens, this review focuses mainly on those related to ultraviolet light-induced processes and potential action sites for tea polyphenols. Since caffeine is a component of tea, and has also been suggested as a possible chemoprotective agent, it is included in this review. Based on data from numerous studies published in the scientific literature, tea polyphenols are promising chemopreventive agents against ultraviolet-induced skin cancers. Their antioxidant properties, inhibitory effects on signal transduction pathways, cell proliferation, angiogenesis and capacity for apoptosis induction, as well as possible immune protective effects, are among the mechanisms that contribute to skin cancer prevention.