UVA ユウドウ ヒフ ヒカリロウカ ニオケル シシツ カサンカブツ ノ ヤクワリ ト コウサンカ ブッシツ セッシュ ノ エイキョウ

Role of ultraviolet A（UVA）on oxidative damage has attracted much attention in relation to skin photoaging process. In this study, we investigated effect of cholesterol hydroperoxides（Chol- OOHs）, stable products of reactive oxygen species（ROS）-induced lipid peroxidation, on matrix metalloproteinase（MMP）activation responsible for wrinkle formation in hairless mouse skin and then estimated the inhibition of UVA-induced MMP activation by dietary β-carotene. Hairless mice were exposed to UVA irradiation for 8 weeks. Chol-OOHs content in the skin was found to increase significantly by the exposure of UVA. In addition, the activity of MMP-9 and its protein expression were elevated with wrinkle formation. This activation was also induced by intracutaneous injection of Chol-OOHs. Interestingly, dietary β-carotene（500 mg/kg diet） and α-tocopherol （100 mg/kg diet）suppressed the accumulation of Chol-OOH as well as MMP activation. These results suggest that Chol-OOHs formed by the exposure of UVA to skin contribute to the activation of MMPs resulting in skin photoaging. Dietary antioxidants may prevent skin photoaging through, at least partly, the suppression of MMP activation due to UVA-induced lipid peroxidation

Neutralino Warm Dark Matter

In the supersymmetric (SUSY) standard model, the lightest neutralino may be the lightest SUSY particle (LSP), and it is is a candidate of the dark matter in the universe. The LSP dark matter might be produced by the non-thermal process such as heavy particle decay after decoupling of the thermal relic LSP. If the produced LSP is relativistic, and does not scatter enough in the thermal bath, the neutralino LSP may contribute as the warm dark matter (WDM) to wash out the small scale structure of O(0.1) Mpc. In this letter we calculate the energy reduction of the neutralino LSP in the thermal bath and study whether the LSP can be the WDM. If temperature of the production time T_I is smaller than 5MeV, the bino-like LSP can be the WDM and may contribute to the small-scale structure of O(0.1) Mpc. The Higgsino-like LSP might also work as the WDM if T_I< 2MeV. The wino-like LSP cannot be the WDM in the favoured parameter region.Comment: 13 pages. Some references are added in revised versio