Photoprotective effects of green tea polyphenols

Bee venom in cancer therapy

Bee venom (BV) (api-toxin) has been widely used in the treatment of some immune-related diseases, as well as in recent times in treatment of tumors. Several cancer cells, including renal, lung, liver, prostate, bladder, and mammary cancer cells as well as leukemia cells, can be targets of bee venom peptides such as melittin and phospholipase A2. The cell cytotoxic effects through the activation of PLA2 by melittin have been suggested to be the critical mechanism for the anti-cancer activity of BV. The induction of apoptotic cell death through several cancer cell death mechanisms, including the activation of caspase and matrix metalloproteinases, is important for the melittin-induced anti-cancer effects. The conjugation of cell lytic peptide (melittin) with hormone receptors and gene therapy carrying melittin can be useful as a novel targeted therapy for some types of cancer, such as prostate and breast cancer. This review summarizes the current knowledge regarding potential of bee venom and its compounds such as melittin to induce cytotoxic, antitumor, immunomodulatory, and apoptotic effects in different tumor cells in vivo or in vitro. The recent applications of melittin in various cancers and a molecular explanation for the antiproliferative properties of bee venom are discussed.

Green tea polyphenols provide photoprotection, increase microcirculation, and modulate skin properties of women

Dietary constituents including polyphenols and carotenoids contribute to endogenous photoprotection and modulate skin characteristics related to structure and function of the tissue. Animal and in-vitro studies indicate that green tea polyphenols affect skin properties. In a 12-wk, double-blind, placebo-controlled study, 60 female volunteers were randomized to an intervention or control group. Participants consumed either a beverage with green tea polyphenols providing 1402 mg total catechins/d or a control beverage. Skin photoprotection, structure, and function were measured at baseline (wk 0), wk 6, and wk 12. Following exposure of the skin areas to 1.25 minimal erythemal dose of radiation from a solar simulator, UV-induced erythema decreased significantly in the intervention group by 16 and 25% after 6 and 12 wk, respectively. Skin structural characteristics that were positively affected included elasticity, roughness, scaling, density, and water homeostasis. Intake of the green tea polyphenol beverage for 12 wk increased blood flow and oxygen delivery to the skin. Likewise, in a separate, randomized, double-blind, single-dose (0.5, 1.0, and 2.0 g) study of green tea polyphenols, blood flow was maximized at 30 min after ingestion. In summary, green tea polyphenols delivered in a beverage were shown to protect skin against harmful UV radiation and helped to improve overall skin quality of women.

Natural options for the management of hyperpigmentation

Facial hyperpigmented disorders are a common complaint in the adult population of all races. First-line topical treatments are usually hydroquinone or topical retinoids, which can cause irritant reactions. The need for better tolerated, yet effective, skin lightening agents that could be utilized by a wider population has led to the investigation of several potential botanical/natural compounds. There are currently many topical cosmetic formulations claiming skin depigmenting effects. A few of the ingredients (e.g. soy) are supported not only by in vitro results but also by a body of controlled clinical efficacy studies; other ingredients, instead, are backed mostly by in vitro data and a few small uncontrolled clinical studies. In this review, we describe the most common natural ingredients used for skin depigmentation and their major published studies: soy, licorice extracts, kojic acid, arbutin, niacinamide, N-acetylglucosamine, COFFEEBERRY(™) and green tea.

UVB-induced DNA damage, generation of reactive oxygen species, and inflammation are effectively attenuated by the flavonoid luteolin in vitro and in vivo

Ultraviolet (UV) radiation induces DNA damage, oxidative stress, and inflammatory processes in human keratinocytes resulting in skin inflammation, photoaging, and photocarcinogenesis. The flavonoid luteolin is one of the most potent antioxidative plant polyphenols. We investigated the UV protective and antioxidant properties of luteolin in human keratinocytes in vitro, ex vivo, and in vivo. Spectrophotometric measurements revealed extinction maxima of luteolin in the UVB and UVA range. UV transmission below 370 nm was <10%. In human skin, luteolin effectively reduced the formation of UVB-induced cyclobutane pyrimidine dimers. The free radical scavenging activity of luteolin was assessed in various cell-free and cell-based assays. In the cell-free DPPH assay the half-maximal effective concentration (EC₅₀) of luteolin (12 μg/ml) was comparable to those of Trolox (25 μg/ml) and N-acetylcysteine (32 μg/ml). In contrast, in the H₂DCFDA assay performed with UVB-irradiated keratinocytes, luteolin (EC₅₀ 3 μg/ml) was much more effective compared to Trolox (EC₅₀ 12 μg/ml) and N-acetylcysteine (EC₅₀ 847 μg/ml). Luteolin also inhibited both UVB-induced skin erythema and the upregulation of cyclooxygenase-2 and prostaglandin E₂ production in human skin via interference with the MAPK pathway. These data suggest that luteolin may protect human skin from UVB-induced damage by a combination of UV-absorbing, DNA-protective, antioxidant, and anti-inflammatory properties.

Photoprotective effects of two natural products on ultraviolet B-induced oxidative stress and apoptosis in SKH-1 mouse skin

Solar ultraviolet radiation (UV) is the major cause of nonmelanoma skin cancer in humans. Photochemoprevention with natural products represents a simple but very effective strategy for the management of cutaneous neoplasia. We studied the photoprotective activity of Calluna vulgaris and red grape seed (Vitis vinifera L, Burgund Mare variety [BM]) extracts in vivo in an SKH-1 hairless mice skin model. Fifty 8-week-old female SKH-1 hairless mice were randomly divided into 5 groups (n = 10 each): controls, UVB-irradiated, C. vulgaris plus UVB-irradiated, BM plus UVB-irradiated, and epigallocatechin gallate (EGCG) plus UVB-irradiated. A dose of 4 mg/mouse per cm² of skin area for both extracts was topically applied to the mice 30 minutes before a single-dose (240 mJ/cm²) UVB exposure. EGCG dissolved in phosphate-buffered saline (pH 6.6; 0.067 M) was administered at 2 mg/mouse per cm². Glutathione peroxidase and catalase activities, reduced glutathione (GSH), malondialdehyde, nitric oxide, and caspase 3 activity were determined in skin homogenates 24 hours after irradiation. A single dose of UVB increased GSH levels and glutathione peroxidase activity in the exposed skin. C. vulgaris and BM pretreatment significantly decreased GSH formation and glutathione peroxidase activity (P < .001) and inhibited UVB-induced lipid peroxidation (P < .0001) and nitric oxide production (C. vulgaris: P < .06). Topical treatments with C. vulgaris and particularly BM extracts (P < .002) significantly reduced caspase 3 activity, indicating that the cells were protected against apoptosis. These results suggest that C. vulgaris and BM extracts might be chemopreventive candidates for reducing UV-induced risk for skin cancer.

The human health effects of ozone depletion and interactions with climate change

Depletion of the stratospheric ozone layer has led to increased solar UV-B radiation (280-315 nm) at the surface of the Earth. This change is likely to have had an impact on human exposure to UV-B radiation with consequential detrimental and beneficial effects on health, although behavioural changes in society over the past 60 years or so with regard to sun exposure are of considerable importance. The present report concentrates on information published since our previous report in 2007. The adverse effects of UV radiation are primarily on the eye and the skin. While solar UV radiation is a recognised risk factor for some types of cataract and for pterygium, the evidence is less strong, although increasing, for ocular melanoma, and is equivocal at present for age-related macular degeneration. For the skin, the most common harmful outcome is skin cancer, including melanoma and the non-melanoma skin cancers, basal cell carcinoma and squamous cell carcinoma. The incidence of all three of these tumours has risen significantly over the past five decades, particularly in people with fair skin, and is projected to continue to increase, thus posing a significant world-wide health burden. Overexposure to the sun is the major identified environmental risk factor in skin cancer, in association with various genetic risk factors and immune effects. Suppression of some aspects of immunity follows exposure to UV radiation and the consequences of this modulation for the immune control of infectious diseases, for vaccination and for tumours, are additional concerns. In a common sun allergy (polymorphic light eruption), there is an imbalance in the immune response to UV radiation, resulting in a sun-evoked rash. The major health benefit of exposure to solar UV-B radiation is the production of vitamin D. Vitamin D plays a crucial role in bone metabolism and is also implicated in protection against a wide range of diseases. Although there is some evidence supporting protective effects for a range of internal cancers, this is not yet conclusive, but strongest for colorectal cancer, at present. A role for vitamin D in protection against several autoimmune diseases has been studied, with the most convincing results to date for multiple sclerosis. Vitamin D is starting to be assessed for its protective properties against several infectious and coronary diseases. Current methods for protecting the eye and the skin from the adverse effects of solar UV radiation are evaluated, including seeking shade, wearing protective clothing and sunglasses, and using sunscreens. Newer possibilities are considered such as creams that repair UV-induced DNA damage, and substances applied topically to the skin or eaten in the diet that protect against some of the detrimental effects of sun exposure. It is difficult to provide easily understandable public health messages regarding "safe" sun exposure, so that the positive effects of vitamin D production are balanced against the negative effects of excessive exposure. The international response to ozone depletion has included the development and deployment of replacement technologies and chemicals. To date, limited evidence suggests that substitutes for the ozone-depleting substances do not have significant effects on human health. In addition to stratospheric ozone depletion, climate change is predicted to affect human health, and potential interactions between these two parameters are considered. These include altering the risk of developing skin tumours, infectious diseases and various skin diseases, in addition to altering the efficiency by which pathogenic microorganisms are inactivated in the environment.

(-)-Epigallocatechin-3-gallate reactivates silenced tumor suppressor genes, Cip1/p21 and p16INK4a, by reducing DNA methylation and increasing histones acetylation in human skin cancer cells

The anti-skin carcinogenic effects of green tea catechins have been studied extensively in vitro and in vivo models but the precise epigenetic molecular mechanisms are still unclear. Accumulating data suggest that dietary phytochemicals may alter cancer risk by modifications of epigenetic processes in the cells. The present study was designed to investigate whether tea catechins, particularly (-)-epigallocatechin-3-gallate (EGCG), would modify epigenetic events to regulate DNA methylation-silenced tumor suppressor genes in skin cancer cells. DNA methylation, histone modifications and tumor suppressor gene expressions were studied in detail using human epidermoid carcinoma A431 cells as an in vitro model after EGCG treatment using cytostaining, western blotting, dot blot analysis, real-time polymerase chain reaction and enzymatic activity assays. Our study shows that EGCG treatment decreased global DNA methylation levels in A431 cells in a dose-dependent manner. EGCG decreased the levels of 5-methylcytosine, DNA methyltransferase (DNMT) activity, messenger RNA (mRNA) and protein levels of DNMT1, DNMT3a and DNMT3b. EGCG decreased histone deacetylase activity and increased levels of acetylated lysine 9 and 14 on histone H3 (H3-Lys 9 and 14) and acetylated lysine 5, 12 and 16 on histone H4 but decreased levels of methylated H3-Lys 9. Additionally, EGCG treatment resulted in re-expression of the mRNA and proteins of silenced tumor suppressor genes, p16INK4a and Cip1/p21. Together, our study provides new insight into the epigenetic mechanism of action of EGCG that may contribute to the chemoprevention of skin cancer and may have important implications for epigenetic therapy.

Ubiquitin proteasomal pathway mediated degradation of p53 in melanoma

Ubiquitin proteasomal pathway (UPP) is the principle mechanism for protein catabolism and affects cellular processes critical for survival and proliferation. Levels of tumor suppressor protein p53 are very low in cells due to its rapid turnover by UPP-mediated degradation. While p53 is mutated in human cancers, most human melanomas maintain wild-type conformation. In this study, to investigate the effects of UPP inhibitor invitro and in vivo, we used a genetically-engineered mouse model (GEMM) that has the same genetic alterations as those of human melanomas. Melanoma cells were established from mouse tumors and named 8B20 cells. Treatment of 8B20 cells with the UPP inhibitors, MG132 and clasto-lactacystin-β-lactone, led to an increase in levels of p53 while treatment with non-proteasomal inhibitors did not alter p53 levels. UPP inhibitors induced formation of heavy molecular weight ubiquitinated proteins, a hallmark of UPP inhibition, and p53-specific poly-ubiquitinated products in 8B20 cells. To further decipher the mechanism of p53 stabilization, we investigated half-life of p53 in cells treated with cycloheximide to block de novo protein synthesis. Treatment of 8B20 cells with MG132 led to an increase in the half-life of p53. Further analysis revealed that p53 stabilization was not mediated by phosphorylation of Ser-15 and Ser-20 residues. In vivo studies showed that MG132 induced p53 overexpression and reduced tumor growth, suggesting an important role of p53 stabilization in controlling melanoma. Taken together, our studies provide a proof of principle for using a GEMM to address the mechanisms of action and efficacy of melanoma treatment.

The role of phytonutrients in skin health

Photodamage is known to occur in skin with exposure to sunlight, specifically ultraviolet (UV) radiation. Such damage includes inflammation, oxidative stress, breakdown of the extracellular matrix, and development of cancer in the skin. Sun exposure is considered to be one of the most important risk factors for both nonmelanoma and melanoma skin cancers. Many phytonutrients have shown promise as photoprotectants in clinical, animal and cell culture studies. In part, the actions of these phytonutrients are thought to be through their actions as antioxidants. In regard to skin health, phytonutrients of interest include vitamin E, certain flavonoids, and the carotenoids, β-carotene, lycopene and lutein.

Potentiation of Bleomycin Lethality in HeLa and V79 Cells by Bee Venom

This study investigated possible growth-inhibiting effects of bee venom applied alone or in combination with a cytotoxic drug bleomycin on HeLa and V79 cells in vitro based on clone formation, cell counting, and apoptosis. Melittin, the key component of bee venom, is a potent inhibitor of calmodulin activity, and also a potent inhibitor cell growth and clonogenicity. Intracellular accumulation of melittin correlates with the cytotoxicity of antitumour agents. Previous studies indicated that some calcium antagonists and calmodulin inhibitors enhanced intracellular levels of antitumor agents by inhibiting their outward transport. In this study, treatment of exponentially growing HeLa and V79 cells with bleomycin caused a dose-dependent decrease in cell survival due to DNA damage. This lethal effect was potentiated by adding a non-lethal dose of the bee venom. By preventing repair of damaged DNA, bee venom inhibited recovery from potentially lethal damage induced by bleomycin in V79 and HeLa cells. Apoptosis, necrosis, and lysis were presumed as possible mechanisms by which bee venom inhibited growth and clonogenicity of V79 cells. HeLa cells, on the other hand, showed greater resistance to bee venom. Our findings suggest that bee venom might find a therapeutic use in enhancing cytotoxicity of antitumour agent bleomycin.

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.

Development of a whole-organism model to screen new compounds for sun protection

We used zebrafish as a whole-organism model to screen new compounds for sun protection activity. First of all, we designed a series of UVB exposure experiments and recorded the phenotypic changes of zebrafish embryos. Results showed that 100 mJ/cm(2) of UVB given six times separated by 30 min intervals is the best condition. Fin malformation (reduced and/or absent fin) phenotypes are the most evident consequences after exposure to UVB. Each fin was affected by UVB, including pelvic, ventral, caudal, and dorsal fin, but pelvic fin seemed to be the most sensitive target after UVB exposure. We furthermore carried out "prevention" and "treatment" experiments using green tea extract and/or (-)-epigallocatechin (EGCG) to test this whole-organism model by observing the morphological changes of all fins (especially pelvic fin) after UVB exposure. Effects of UVB, green tea extract and EGCG on fin development were assessed using the Kaplan-Meier analysis, log-rank test and Cox proportional hazards regression. Results showed that a zebrafish pelvic fin in the UVB + green tea (treatment) group is 5.51 (range from 2.39 to 14.90) times, one in the UVB + green tea (prevention) group is 7.04 (range from 3.11 to 18.92) times, and one in the 25 ppm of EGCG (prevention) group is 22.19 (range from 9.40 to 61.50) times more likely to return to normal fin than one in the UVB only group. On the basis of these observations, we believe this model is effective for screening the higher stability and lower toxicity of new compounds, such as small chemicals which are derivative from EGCG or other dietary agents for sun protection.

Chemopreventive effects of sarcophine-diol on ultraviolet B-induced skin tumor development in SKH-1 hairless mice

Sarcophine-diol (SD), one of the structural modifications of sarcophine, has shown chemopreventive effects on 12-dimethylbenz(a)anthracene-initiated and 12-O-tetradecanoylphorbol-13-acetate-promoted skin tumor development in female CD-1 mice. The objective of this study was to determine the chemopreventive effects of SD on UVB-induced skin tumor development in hairless SKH-1 mice, a model more relevant to human skin cancer, and to determine the possible mechanisms of action. Carcinogenesis was initiated and promoted by UVB radiation. Female hairless SKH-1 mice were divided into two groups having 27 mice in each group: control and SD treatment. The control group was topically treated with 100 μL acetone and SD treatment group was topically treated with SD (30 μg/100 μL in acetone) 1 hour before each UVB radiation for 32 weeks. Tumor counts were recorded on a weekly basis for 30 weeks. Effects of SD on the expression of caspases were investigated to elucidate the possible mechanism of action. The proteins from epidermal homogenates of experimental mice were used for SDS-PAGE and Western blotting using specific antibodies against caspase-3, caspase-8 and caspase-9 respectively. TUNEL assay was used for determining DNA fragmented apoptotic cells in situ. Results showed that at the end of experiment, tumor multiplicity in control and SD treatment groups was 25.8 and 16.5 tumors per mouse respectively. Furthermore, Topical treatment of SD induced DNA fragmented apoptotic cells by upgrading the expressions of cleaved caspase-3 and caspase-8. This study clearly suggested that SD could be an effective chemopreventive agent for UVB-induced skin cancer by inducing caspase dependent apoptosis.

Sarcophine-diol, a Chemopreventive Agent of Skin Cancer, Inhibits Cell Growth and Induces Apoptosis through Extrinsic Pathway in Human Epidermoid Carcinoma A431 Cells

Sarcophine-diol (SD), a structural modifications of sarcophine, has shown chemopreventive effects on 7,12-dimethylbenz(a)anthracene-initiated and 12-O-tetradecanoylphorbol-13-acetate-promoted skin tumor developments in mice. Tumorigenesis is associated with uncontrolled cell growth and loss of apoptosis. In the present study, the effects of SD on cell growth and apoptosis in human epidermoid carcinoma A431 cells were determined to assess whether SD could inhibit cell growth and/or induce apoptosis, thus elucidating possible mechanism of action. MTT assay was used for cell viability; bromodeoxyuridine incorporation assay was used for cell proliferation; fluorescence-activated cell sorting analysis of annexin V/propidium iodide staining and TUNEL assay were used for determining apoptotic cells; Western blot analysis was used for determining the expression of caspase-3 and colorimetric caspase activity assays were used for determination of caspase-3, -8, and -9 activity. The results showed that SD treatment at concentration of 200 to 600 microM resulted in a concentration-dependent decrease in cell viability and cell proliferation in A431 cells, which largely inhibited cell growth. Sarcophine-diol treatment induced a strong apoptosis and significantly (P < .05) increased DNA fragmentation in A431 cells. Furthermore, SD treatment significantly (P < .05) increased the activity and expression of caspase-3 through activation of upstream caspase-8 in A431 cells rather than the activation of caspase 9. Sarcophine-diol treatment is relatively much less cytotoxic in monkey kidney normal CV-1 cells. These results suggest that SD decreases cell growth and induces apoptosis through caspase-dependent extrinsic pathway in A431 cells, and this may contribute to its overall chemopreventive effects in mouse skin cancer models.

Honeybee venom induces calcium-dependent but caspase-independent apoptotic cell death in human melanoma A2058 cells

Honeybee (Apis mellifera) venom (BV) has been reported to exhibit anticancer effects, but its mode of action at the cellular and molecular levels remains largely unknown. We found that honeybee venom induced apoptosis in human melanoma A2058 cells but not in normal skin fibroblast Detroit 551 cells. The BV-induced apoptosis was accompanied by generation of reactive oxygen species and alteration of mitochondrial membrane potential transition. Treatment with antioxidants significantly attenuated BV-induced apoptosis. Although caspase-2 and -3 were slightly activated by BV, inhibitors of caspase-2 and -3 could not block BV-induced apoptosis in A2058 cells. Data from immunostaining indicated that EndoG and AIF were translocated from mitochondria to the cytosol or nucleus, suggesting that BV induces apoptosis in A2058 cells via a caspase-independent pathway. In addition, cJun N-terminal kinases (JNK) and ERK were rapidly activated after a 5 min incubation with BV, while p38 and AKT were inactivated after 30 min administration of BV. Inhibition of JNK significantly attenuated BV-triggered apoptotic death. Moreover, BV induced a rapid and marked increase in cytosolic calcium ion. Incubation of cells under calcium-free conditions effectively diminished BV-induced apoptosis. Furthermore, when the calcium-free treatment was combined with ouabain, the recovery of cellular calcium fluctuation protected A2058 cells against BV-induced apoptosis. Finally, treatment of A2058 cells with melittin, the major component of BV, resulted in similar elevation of calcium levels and cell killing effects, suggesting that melittin is the major determinant in BV-triggered cell death. These observations provide a molecular explanation for the antiproliferative properties of BV, and suggest that this agent may be useful in treating melanoma.

Less-known botanical cosmeceuticals

Complementary and alternative medicine (CAM) has become increasingly popular in the United States during the last 10-15 years. The use of oral and topical supplements falls within this framework. Most oral and topical supplements are based on or include several botanical ingredients, many of which have long histories of traditional or folk medicine usage. Several of the available products derived from botanical sources are touted for their dermatologic benefits. The focus in this discussion will be on a select group of botanical compounds that have been used for dermatologic purposes or show promise for such applications, including: rosemary, polypodium leucotomos, propolis, oatmeal, olive oil, grape seed extract, lavender, mushrooms, and coffeeberry. Other more commonly used products of botanical origin, such as arnica, bromelain, caffeine, chamomile, ferulic acid, feverfew, green tea, licorice, pomegranate, and resveratrol, are also briefly considered.

Differential growth suppression of human melanoma cells by tea (Camellia sinensis) epicatechins (ECG, EGC and EGCG)

We previously reported that catechins of green tea have different antiproliferative effects on cell lines derived from gender-dependent cancers; epicatechin 3-gallate (ECG) had the strongest inhibitory effect. In the present study, we examined the effects of epigallocatechin (EGC), epicatechin-gallate (ECG) and EGC 3-gallate (EGCG) on the viability, density, doubling time and cycle number of cell lines derived from melanoma metastasized to lymph nodes (MB-1133 and SE-0154) or distant organs (CH-0356, JK-0346, SA-1171, GE-0208, NS-1176 and LF-0023). These catechins have been documented to have no growth suppressive or apoptotic effects on normal melanocytes (Nihal et al., Int J Cancer 2005;114:513-21). EGCG (50 muM) showed greater inhibitory potency than EGC (50 muM) in SE-0154, NS-1176, GE-0208 and LF-0023 cell lines but the two catechins produced similar inhibitory effects in CH-0356, JK-0346 and SA-1171 cell lines. The IC(50) (50% inhibitory concentration) was lower for EGC than EGCG in MB-1133 and CH-0356 cells, higher for EGC than EGCG in GE-0208 cells and comparable (11-12 muM) for both the catechins in LF-0023 cells. When compared with EGC, the cytotoxic effect (% dead cell counts) and the suppression of the growth (change in cell number) of all melanoma cell lines tested were pronounced with EGCG. This investigation validates the hypothesis that anticancer action of the various catechins may vary with the type of malignancy and provides a model for tumor cell heterogeneity based on susceptibility and resistance of tumor cells to different green tea catechins. Therefore, this information is critical for undertaking chemopreventive or chemotherapeutic trials against melanoma and gender-based cancers.