Visually Indicating Wipe Efficacy and Other Topics: Literature Findings

By: Charles Fox, Independent Consultant

Posted: December 30, 2009, from the January 2010 issue of Cosmetics & Toiletries.

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Caffeine for UVB protection: Kerzendorfer et al. report on the ability of caffeine to protect against the adverse effects of UVB.² Studies using mice have indicated that caffeine, administered orally or topically, promotes apoptosis of UVB-irradiated keratinocytes. These authors identified the pathway targeted by caffeine and suggest that inhibiting the DNA damage response could prevent skin cancer. This could represent an important protective or therapeutic benefit from the most unlikely of sources—one’s daily cup of coffee.

 MMPs in photoaging: Taihao et al. have published on matrix-degrading metalloproteinases that cause photoaging.³ Photoaging is among the most well-known harmful effects of chronic exposure to solar UV radiation, and extensive damage to the dermal connective tissue is a hallmark in photoaged skin. UV irradiation induces the expression of certain members of the matrix metalloproteinase (MMP) family, which degrade collagen and other extracellular matrix proteins that comprise the dermal connective tissue. This disruption of the normal architecture of connective tissue impairs skin function and causes it to look aged.

Although the critical role of MMPs in photoaging is undeniable, important questions remain. These authors have summarized the current understanding of the role of MMPs in photoaging and presented new data that describes the expression and regulation by UV irradiation of all members of the MMP family in human skin in vivo. The article also quantifies the relative contributions of epidermis and dermis to the expression of UV irradiation-induced MMPs in human skin in vivo.

The basement membrane and skin health: Amano et al. have published on aging in sun-exposed skin and its acceleration by three major environmental factors: UV radiation, dryness and oxidation. Since exposure to UV radiation is the most influential factor in photoaging,⁴ researchers studied internal changes of sun-exposed skin and compared them with sun-protected skin to identify ways to protect against damage from UV exposure to delay photoaging.

The researchers observed that the basement membrane (BM) at the dermal-epidermal junction (DEJ) of sun-exposed skin became damaged, multilayered and partly disrupted. The BM plays important roles in maintaining a healthy epidermis and dermis but repeated damage to it destabilizes the skin and accelerates aging. MMPs and urinary plasminogen activators are increased in UV-irradiated skin. In this study, MMPs were detected in the cornified layer in skin-equivalent models in sun-exposed skin but not in protected skin. The researchers found that while MMPs and plasmin damage the BM, its reconstruction is enhanced by inhibiting these proteinases and by increasing the synthesis of BM components. Enhancement of BM repair mechanisms may be a useful strategy in retarding photoaging.