Epigallocatechin-3-gallate (EGCG), the major polyphenolic component of green tea, has been demonstrated to possess anti-inflammatory, antioxidant, anti-mutagenic and anti-carcinogenic properties. The anti-melanoma effect of EGCG has been previously suggested, but no clear mechanism of action has been established. In this study, we demonstrated that EGCG inhibits melanoma cell growth at physiological doses (0.1–1 μM). In the search for mechanisms of EGCG-mediated melanoma cell suppression, we found that NF-κB was inhibited, and that reduced NF-κB activity was associated with decreased IL-1β secretion from melanoma cells. Since inflammasomes are involved in IL-1β secretion, we investigated whether IL-1β suppression was mediated by inflammasomes, and found that EGCG treatment led to downregulation of the inflammasome component, NLRP1, and reduced caspase-1 activation. Furthermore, silencing the expression of NLRP1 abolished EGCG-induced inhibition of tumor cell proliferation both in vitro and in vivo, suggesting a key role of inflammasomes in EGCG efficacy. This paper provides a novel mechanism for EGCG-induced melanoma inhibition: inflammasome downregulation → decreased IL-1β secretion → decreased NF-κB activities → decreased cell growth. In addition, it suggests inflammasomes and IL-1β could be potential targets for future melanoma therapeutics.
Apoptosis-associated speck-like protein containing a CARD (ASC) was originally named because it triggered apoptosis in certain tumors. More recently, however, ASC was found to be a central adaptor protein of inflammasome which mediates the secretion of pro-tumorigenic inflammation. Here we examined the role of ASC in tumorigenesis of human melanoma. Compared with primary melanoma, ASC protein expression was generally downregulated in metastatic melanoma. While overexpressing ASC in metastatic melanoma showed no effects on cell viability, silencing ASC with short hairpin RNA induced G1 cell cycle arrest, reduced cell viability and suppressed tumorigenesis in metastatic melanoma. On the other hand, silencing ASC in primary melanoma reduced cell death, increased cell viability and enhanced tumorigenesis. In primary and metastatic melanoma cells, ASC knockdown inhibited inflammasome-mediated caspase-1 activity and IL-1β secretion. However, phosphorylated IKKα/β expression and NF-κB activity were suppressed in metastatic melanoma and enhanced in primary melanoma after ASC knockdown. These findings suggest stage-dependent dual roles of ASC in tumorigenesis. ASC expression in primary melanoma inhibits tumorigenesis, by reducing IKKα/β phosphorylation and inhibiting NF-κB activity. In metastatic melanoma, on the other hand, this inhibitory effect is diminished, and ASC induces tumorigenic pathways through enhanced NF-κB activity and inflammasome-mediated IL-1β secretion.
The link between psychological stress and aging is intuitive although the underlying mechanisms are not well defined. Evidence suggests that chronic psychological stress stimulates the autonomic nervous system, renin-angiotensin system, and the hypothalamic-pituitary-adrenal axis when the body attempts to resolve perceived threats to homeostasis. Prolonged activation of these pathways can result in chronic immune dysfunction, increased production of reactive oxygen species, and DNA damage, which are known to contribute to the again of skin and other tissues.Despite the lack of conclusive evidence directly linking psychological stress to skin aging, mechanisms by which stress leads to immune dysfunction, oxidative radicals, and ultimately DNA damage via neuronal, endocrine, and immune modulation may present a possible intervention for skin aging. In addition to the wide array of anti-oxidant therapies being developed to combat aging, the topical use of beta-blockers such as timolol, angiotensin receptor blockers such as valsartan, glucocorticoid blockers such as mifepristone, and cholinergic modulators including botulinum toxin, might be potential therapeutic strategies to prevent skin aging. Given the current understanding of these pathways, it would be premature to utilize such modalities for prevention of skin aging at this time, but future research into this type of topical pharmacologic anti-aging intervention may be promising.
Patient-centered and professional dermatology organizations use social networking sites; however, academic journals tend to lag behind significantly. Although some journals are active in social media, most have yet to recognize the potential benefits of fully embracing popular social networks.
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