Photoprotective effect of black tea extracts against UVB-induced phototoxicity in skin

Loss of hairless confers susceptibility to UVB-induced tumorigenesis via disruption of NF-kappaB signaling

In order to model squamous cell carcinoma development in vivo, researchers have long preferred hairless mouse models such as SKH-1 mice that have traditionally been classified as ‘wild-type’ mice irrespective of the genetic factors underlying their hairless phenotype. The work presented here shows that mutations in the Hairless (Hr) gene not only result in the hairless phenotype of the SKH-1 and Hr^−/− mouse lines but also cause aberrant activation of NFκB and its downstream effectors. We show that in the epidermis, Hr is an early UVB response gene that regulates NFκB activation and thereby controls cellular responses to irradiation. Therefore, when Hr expression is decreased in Hr mutant animals there is a corresponding increase in NFκB activity that is augmented by UVB irradiation. This constitutive activation of NFκB in the Hr mutant epidermis leads to the stimulation a large variety of downstream effectors including the cell cycle regulators cyclin D1 and cyclin E, the anti-apoptosis protein Bcl-2, and the pro-inflammatory protein Cox-2. Therefore, Hr loss results in a state of uncontrolled epidermal proliferation that promotes tumor development, and Hr mutant mice should no longer be considered merely hairless 'wild-type' mice. Instead, Hr is a crucial UVB response gene and its loss creates a permissive environment that potentiates increased tumorigenesis.

Black tea extract prevents lipopolysaccharide-induced NF-κB signaling and attenuates dextran sulfate sodium-induced experimental colitis

Background

Black tea has been shown to elicit anti-oxidant, anti-carcinogenic, anti-inflammatory and anti-mutagenic properties. In this study, we investigated the impact of black tea extract (BTE) on lipopolysaccharide (LPS)-induced NF-κB signaling in bone marrow derived-macrophages (BMM) and determined the therapeutic efficacy of this extract on colon inflammation.

Methods

The effect of BTE on LPS-induced NF-κB signaling and pro-inflammatory gene expression was evaluated by RT-PCR, Western blotting, immunofluorescence and electrophoretic mobility shift assay (EMSA). The in vivo efficacy of BTE was assessed in mice with 3% dextran sulfate sodium (DSS)-induced colitis. The severity of colitis was measured by weight loss, colon length and histologic scores.

Results

LPS-induced IL-12p40, IL-23p19, IL-6 and IL-1β mRNA expressions were inhibited by BTE. LPS-induced IκBα phosphorylation/degradation and nuclear translocation of NF-κB/p65 were blocked by BTE. BTE treatment blocked LPS-induced DNA-binding activity of NF-κB. BTE-fed, DSS-exposed mice showed the less weight loss, longer colon length and lower histologic score compared to control diet-fed, DSS-exposed mice. DSS-induced IκBα phosphorylation/degradation and phosphorylation of NF-κB/p65 were blocked by BTE. An increase of cleaved caspase-3 and poly (ADP-ribose) polymerase (PARP) in DSS-exposed mice was blocked by BTE.

Conclusions

These results indicate that BTE attenuates colon inflammation through the blockage of NF-κB signaling and apoptosis in DSS-induced experimental colitis model.

Natural agents: cellular and molecular mechanisms of photoprotection

The skin is the largest organ of the body that produces a flexible and self-repairing barrier and protects the body from most common potentially harmful physical, environmental, and biological insults. Solar ultraviolet (UV) radiation is one of the major environmental insults to the skin and causes multi-tiered cellular and molecular events eventually leading to skin cancer. The past decade has seen a surge in the incidence of skin cancer due to changes in life style patterns that have led to a significant increase in the amount of UV radiation that people receive. Reducing excessive exposure to UV radiation is desirable; nevertheless this approach is not easy to implement. Therefore, there is an urgent need to develop novel strategies to reduce the adverse biological effects of UV radiation on the skin. A wide variety of natural agents have been reported to possess substantial skin photoprotective effects. Numerous preclinical and clinical studies have elucidated that natural agents act by several cellular and molecular mechanisms to delay or prevent skin cancer. In this review article, we have summarized and discussed some of the selected natural agents for skin photoprotection.

Black tea polyphenol theaflavin suppresses LPS-induced ICAM-1 and VCAM-1 expression via blockage of NF-κB and JNK activation in intestinal epithelial cells

OBJECTIVE

The aim of this study was to determine the impact of the black tea polyphenol, theaflavin, on the expression of adhesion molecules and activation of lipopolysaccharide (LPS)-induced innate signaling in rat intestinal epithelial (RIE) cells.

METHODS

The effect of theaflavin on neutrophil adhesion, expression of intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1, LPS-induced nuclear factor-kappa B (NF-κB), and mitogen-activated protein kinase (MAPK) signaling was examined by neutrophil adhesion assay, RT-PCR, Western blotting, immunofluorescence, and electrophoretic mobility shift assay (EMSA).

RESULTS

Theaflavin suppressed adhesion of neutrophils to LPS-stimulated RIE cells. LPS-induced ICAM-1 and VCAM-1 expressions were inhibited by theaflavin. LPS-induced IκBα phosphorylation/degradation and nuclear translocation of NF-κB/p65 were blocked by theaflavin. Also, theaflavin blocked NF-κB DNA-binding activity in EMSA. LPS-induced phosphorylation of JNK was inhibited by theaflavin. Bay11-7082 (a NF-κB inhibitor) and SP600125 (a JNK inhibitor) suppressed the LPS-induced ICAM-1 and VCAM-1 mRNA accumulations.

CONCLUSIONS

These results indicate that black tea polyphenol theaflavin suppresses LPS-induced ICAM-1 and VCAM-1 expressions through blockage of NF-κB and JNK activation in intestinal epithelial cells.

Anti-wrinkling effects of the mixture of vitamin C, vitamin E, pycnogenol and evening primrose oil, and molecular mechanisms on hairless mouse skin caused by chronic ultraviolet B irradiation

BACKGROUND

Naturally occurring antioxidants were used to regulate the skin damage caused by ultraviolet (UV) radiation because several antioxidants have demonstrated that they can inhibit wrinkle formation through prevention of matrix metalloproteinases (MMPs) and/or increase of collagen synthesis.

OBJECTIVE

We examined the effect of oral administration of the antioxidant mixture of vitamin C, vitamin E, pycnogenol, and evening primrose oil on UVB-induced wrinkle formation. In addition, we investigated the possible molecular mechanism of photoprotection against UVB through inhibition of collagen-degrading MMP activity or through enhancement of procollagen synthesis in mouse dorsal skin.

METHODS

Female SKH-1 hairless mice were orally administrated the antioxidant mixture (test group) or vehicle (control group) for 10 weeks with UVB irradiation three times a week. The intensity of irradiation was gradually increased from 30 to 180 mJ/cm2. Microtopographic and histological assessment of the dorsal skins was carried out at the end of 10 weeks to evaluate wrinkle formation. Western blot analysis and EMSA were also carried out to investigate the changes in the balance of collagen synthesis and collagen degradation.

RESULTS

Our antioxidant mixture significantly reduced UVB-induced wrinkle formation, accompanied by significant reduction of epidermal thickness, and UVB-induced hyperplasia, acanthosis, and hyperkeratosis. This antioxidant mixture significantly prevented the UVB-induced expressions of MMPs, mitogen-activated protein (MAP) kinase, and activation of activator protein (AP)-1 transcriptional factor in addition to enhanced type I procollagen and transforming growth factor-beta2 (TGF-beta2) expression.

CONCLUSION

Oral administration of the antioxidant mixture significantly inhibited wrinkle formation caused by chronic UVB irradiation through significant inhibition of UVB-induced MMP activity accompanied by enhancement of collagen synthesis.

Molecular aetiology and pathogenesis of basal cell carcinoma

Recent insights into the cell biology of the epidermis and its appendages are transforming our understanding of the pathogenesis of basal cell carcinoma (BCC). The significant progress that has been made warrants a comprehensive review of the molecular and cellular pathology of BCC. The items addressed include environmental and genetic risk factors, the biology of the putative precursor cell(s), and the contribution of aberrations in processes such as apoptosis, cell proliferation, differentiation and signalling to carcinogenesis. Furthermore, established and novel treatment modalities are discussed with particular attention to future biological approaches.

Ornithine decarboxylase is a target for chemoprevention of basal and squamous cell carcinomas in Ptch1+/- mice

Solar ultraviolet B (UVB) radiation induces cutaneous ornithine decarboxylase (ODC), the first enzyme in the polyamine-biosynthesis pathway, which drives continued proliferation and clonal expansion of initiated (mutated) cells, leading to tumorigenesis. Therefore ODC is a potentially important target for chemoprevention of basal cell carcinomas (BCCs), the majority of which have mutations in the tumor-suppressor gene known as patched (PTCH). To assess this possibility, we first overexpressed ODC in the skin of Ptch1+/- mice using a keratin 6 (K6) promoter that directs constitutive ODC expression in the outer root sheath of the hair follicle. UVB irradiation of these mice accelerated induction of BCCs as compared with their Ptch1+/- littermates. To further verify the role of ODC in BCC tumorigenesis, we used an antizyme (AZ) approach to inhibit ODC activity in the Ptch1+/- mice. Ptch1+/- mice with AZ overexpression driven by the K6 promoter were resistant to the induction of BCCs by UVB. Furthermore, oral administration of the suicidal ODC inhibitor alpha-difluoromethylornithine reduced UVB-induced BCCs in Ptch1+/- mice. These results demonstrate the crucial importance of ODC for the induction of BCCs and indicate that chemopreventive strategies directed at inhibiting this enzyme may be useful in reducing BCCs in human populations.

Topical and systemic photoprotection

Sunscreens are a valuable method of sun protection. Several new compounds are now available. It is important to remember, however, that photoprotection includes more than the use of sunscreens. There are a number of sun-protective behaviors that people can use to decrease their exposure to ultraviolet (UV) radiation. Dermatologists and other health professionals can work toward changing public policy, greatly increasing the ability of people to access shade. In addition, there is growing evidence about the effectiveness of other sun-protective agents. The only systemic medication for sun protection is beta-carotene, which is effective in erythropoietic protoporphyria (EPP).

Topical vitamins, minerals and botanical ingredients as modulators of environmental and chronological skin damage

Ageing skin is characterized by fine lines, wrinkles, lentigines, dyspigmentation and increased coarseness. Topical preparations alleged to combat these changes abound in the over-the-counter market. Some of the most popular ingredients used in these products are vitamins, minerals and botanical extracts. Proposed mechanisms for antiageing effects on skin range from antioxidant properties to improved collagen synthesis or protection from collagen breakdown. Despite the media attention and consumer popularity that these ingredients have generated, there have been few scientific studies to support these claims. In this report, we review recent published studies on the most common of these ingredients for the topical photoprotection and the treatment of ageing skin.

Suppression of tumorigenesis in the Apc(min) mouse: down-regulation of beta-catenin signaling by a combination of tea plus sulindac

Epidemiological and animal studies suggest that tea may be protective towards cancers of the GI tract. White tea, the least processed form of tea, contains high levels of polyphenols and, like green tea, is chemopreventive towards heterocyclic amine-initiated colonic aberrant crypt formation in male F344 rats. We examined for the first time the relative effectiveness of white and green tea in suppressing intestinal tumorigenesis in C57BL/6J-Apc(Min/+) (Apc(min)) mice. Each tea was also compared with sulindac, a non-steroidal anti-inflammatory drug known to be highly effective in Apc(min) mice. Male C57BL/6J (+/+) (wild-type) and Apc(min) mice were treated in the drinking water with white tea or green tea (1.5% w/v, 2 min brew-time), 80 p.p.m. sulindac, a combination of 80 p.p.m. sulindac in 1.5% white tea, or pH buffered water. After 12 weeks of treatment, Apc(min) mice given white tea, green tea, or sulindac had significantly fewer tumors than controls (P < 0.05). The protection provided by 1.5% green or white tea was comparable to that provided by 80 p.p.m. sulindac. Mice treated with a combination of white tea plus sulindac had significantly fewer tumors than either treatment alone (P < 0.05). beta-catenin and beta-catenin/Tcf-4 regulated proteins Cyclin D(1) and c-Jun were readily detected in polyps, but markedly reduced in normal-looking intestines of mice treated with both tea and sulindac. This research provides evidence that teas, particularly when administered in combination with sulindac, are highly effective at inhibiting intestinal neoplasia in male Apc(min) mice via direct or indirect effects on the beta-catenin/APC pathway.