The skin is located at the most outer layer of the body as a barrier against environmental stimuli and shows various changes to adjust to them. Among these changes, the chronic sun exposure to the skin accelerates appearances of solar lentigo and wrinkles, which are symptoms of photoaging. In this article, acute and delayed changes caused by single and chronic sun exposure are summarized.

View full abstract

We examined the effects of scalp massage in reducing stress and augmenting comfort by using physiological and psychological indices. Scalp massage was found to significantly decrease the cortisol level in saliva and significantly increase the level of secretory immunoglobulin A (sIgA). In a test that used the Visual Analogue Scale (VAS), scalp massage was found to lower physical fatigue scores while increasing relaxation scores. Scalp massage also lowered the scores related to negative feelings in the Profile of Mood States-Short Form (POMS-SF). The salivary stress biomarkers and VAS and POMS-SF tests suggested that scalp massage is effective for improving comfort and reducing stress.

View full abstract

The most important characteristics of an effective and safe UV absorber used as a UV-blocking compound in cosmetic sunscreens is photochemical stability. The most widely used organic UV-A absorber is 4-tert-butyl-4'-methoxydibenzoylmethane (BMDBM). However, BMDBM is well-known for its photoinstability under actual conditions of use. The commonly employed method for improving the photostablity of BMDBM is based on the addition of another UV absorber. Octocrylene (OCR) has been found to be most effective at stabilizing BMDBM. In some sunscreen formulations, octyl 4-methoxycinnamate (OMC), the most widely used representative UV-B absorber, is added to the mixture of BMDBM and OCR to provide effective protection throughout the whole UV range of solar radiation because the molar absorption coefficients of OCR are small in the UV-B region. In the present study, we have shown that the observed photostablity of BMDBM in the BMDBM-OCR-OMC combination is lower than that in the BMDBM-OCR combination. To eliminate this problem, we have designed a new UV-B absorber, dioctyl 4-methoxybenzylidenemalonate (DOMBM), which does not undergo cis-trans photoisomerization owing to its molecular structure. We tested the effect of the addition of DOMBM on the photostability of BMDBM in the BMDBM-OCR-DOMBM combination. The photostablity of BMDBM in the BMDBM-OCR-DOMBM combination is higher than those in the BMDBM-OCR and BMDBM-OCR-OMC combinations. It is suggested that intermolecular triplet-triplet energy transfer from BMDBM to DOMBM and the photostable filter effect of DOMBM on BMDBM are possible mechanisms to explain the photostability of BMDBM in the combination of UV-A and UV-B absorbers.

View full abstract

Filaggrin is completely degraded in the uppermost layer of the stratum corneum, affording a mixture of free and modified hygroscopic amino acids known as natural moisturizing factor (NMF),which serves to maintain skin hydration. Recently, we purified a novel aminopeptidase based on its citrulline-cleavage activity and identified it as a neutral cysteine protease, bleomycin hydrolase (BH). BH generated free amino acids from filaggrin-derived peptides but not from filaggrin monomer itself. For NMF synthesis, it is necessary that filaggrin monomer be degraded into smaller peptides. We tested caspase-14, an up-stream enzyme in the NMF generation pathway. Caspase-14 showed limited hydrolysis on filaggrin monomer, liberating three peptide fragments. We examined whether BH is involved in NMF generation in human epidermis. We also examined age-related changes of BH in women in their forties and sixties. We found that BH activity was significantly down-regulated in corneocyte extract from the skin of women in their sixties, compared to women in their forties. The content of free amino acids in the extract was also significantly decreased. Skin of subjects self-reported to be hypersensitive showed markedly decreased BH activity. Lastly, we examined BH expression in patients with atopic dermatitis (AD). BH activity and expression were markedly decreased in lesional skin, suggesting a defect of the filaggrin degradation pathway. Our results support the idea that BH plays a major role in NMF generation. BH may be a novel target for treatment of dry skin as well as skin diseases, such as AD.

View full abstract

Human skin color mainly depends on the quantity and quality of the pigment melanin, which occurs in two types, namely black to brown eumelanin and yellow to reddish pheomelanin. For developing skin whitening cosmetics which lighten the skin tone to the original skin color, it is important to quantitatively analyze not only the total amount of melanin but also eumelanin and pheomelanin, separately. Pyrrole-2, 3, 5-tricarboxylic acid (PTCA) as a marker for eumelanin and aminohydroxyphenylalanines (AHPs) as markers for pheomelanin can be analyzed and quantitated by high performance liquid chromatography (HPLC). In this study, we improved the chromatographic methodology by using reverse phase ion-pair liquid chromatography, and expanded its versatility. The calibration curves were linear (r>0.99) and all relative standard deviations (RSD) of accuracy were between 0.13-0.16%.

View full abstract