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Oligopeptides in Sensory, Proteins in Winter Skin and Carotenoids: Literature Findings
By: Charles Fox, Independent Consultant
Posted: November 26, 2008, from the December 2008 issue of Cosmetics & Toiletries.
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Carbonyl protein levels in winter skin: Kobayashi et al. have reported on increased carbonyl protein levels during winter in the SC of the face.6 The SC is the interface between the body and the environment and is continuously exposed to oxidative stress that results in carbonyl modification of proteins. The investigators had previously developed a simple and noninvasive method to assess SC carbonyl protein (SCCP) levels. In the present study, they used this method to examine the seasonal changes in the SCCP levels and the relationship between the SCCP level and the physiological condition of the SC.
SC was collected from the faces of only healthy Japanese volunteers by adhesive tape stripping, and its carbonyl groups were determined by reaction with fluorescein-5-thiosemicarbazide. The average fluorescence intensity of the SC was calculated as the SCCP level, and this level was found to be higher in winter than in summer. The SCCP level was negatively correlated with the water content in the SC, measured by the conductance and capacitance, and also negatively correlated with the extensibility of the skin, measured by a cutometer. This suggests that the mechanical properties of the skin can be affected by oxidative modification of the SC. The data suggests the involvement of oxidative modification of SC proteins in the generation of rough skin during winter.
Protein carbonylation and optical properties of the SC: Iwai et al. have published on in vitro changes in the optical properties of the SC, induced by protein carbonylation.7 The skin is the frontier against the external environment and is continuously exposed to environmental oxidative stress such as UV irradiation. Protein carbonyls are the major oxidative products of protein and may be introduced by their reaction with aldehydes derived from lipid peroxide. Acrolein is one of the most reactive aldehydes generated during degradation of lipid peroxides, and protein-acrolein adducts have been found in oxidatively damaged lesions in UV-damaged skin.
Recent studies revealed that protein carbonyls also are detected in the thin outermost layer of the SC. However, the effect of protein carbonylation on the function of SC was unclear. In the described study, researchers treated SC sheets of reconstructed human epidermis and porcine epidermis with acrolein to explore the influence of protein carbonylation on the SC.
Human and porcine SC sheets treated with acrolein showed less transmission at visible light than the untreated SC sheets. Attenuated total reflection-IR spectroscopy with curve fitting analysis of amide I region showed that acrolein induced alterations in protein secondary structure of the porcine SC sheets, which were accompanied by a diminished fibrous keratin structure observed by transmission electron microscopy. These results suggest that carbonylation of the SC caused by environmental influences is one of the factors that alters the fibrous structure of keratin and decreases the light transmission of SC, which changes the quality of the skin’s appearance.