Charité - Universitätsmedizin Berlin, corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Dermatology, Venerology and Allergology, Center of Experimental and Applied Cutaneous Physiology, Berlin, Germany.
Charité - Universitätsmedizin Berlin, corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Dermatology, Venerology and Allergology, Center of Experimental and Applied Cutaneous Physiology, Berlin, Germany.
Free Radic Biol Med. 2021 Jan;162:401-411. doi: 10.1016/j.freeradbiomed.2020.10.319. Epub 2020 Nov 1.
Ultraviolet (UV) radiation leads to the formation of free radicals, which may cause immunological modulations, skin aging or skin cancer. Sunlight exposure in the UVA region according to CIE 85 promotes almost 46% of radical formation in skin. A critical radical concentration characterized by the inversion of the domination of primary ROS (reactive oxygen species) to an excess of secondary LOS (lipid oxygen species) is proven for the spectral regions UV and or VIS light and is intended to be a marker for an imbalance in the redox system, which can no longer compensate harmful effects. To investigate whether this transition point is also universally valid for one spectral region, the radical formation during and after targeted UVA in situ-irradiation at 365 ± 5 nm and three different irradiances (31, 94 and 244 mW/cm) was investigated in ex vivo porcine skin using x-band electron paramagnetic resonance (EPR) spectroscopy. The quantification was performed with the spin probe 3-(carboxy)-2,2,5,5-tetramethylpyrrolidin-1-oxyl (PCA), the spin trap 5,5-Dimethyl-1-Pyrroline-N-Oxide (DMPO) was used to characterize the radical species. Furthermore, the viability of the skin cells after irradiation was controlled by an MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay, skin integrity was examined by histological analysis. A significant dose dependence in the radical formation is given at higher irradiance. The transition point was detected in the range of 0.5 MED after irradiation with the highest irradiance. From this point on the proportion of LOS increases with increasing dose and the proportion of ROS decreases. After switching off the UVA irradiation no further quantitative changes were detected, but rapid changes in the radical pattern were observed demonstrating the importance of in situ irradiation during the use of spin traps. Heat-pre-stressed skin showed more LOS than ROS already at the beginning of the irradiation, leading to the assumption that the transition point to the distress-level has already been reached. In summary, a postulated transition point could be verified for the UVA spectral region using only one spin trap combined with in-situ irradiation. A certain degree of stress is necessary to detect an inversion of the ratio of ROS to LOS. This reversal indicates an imbalance in the redox status. However, at low intensities no changes at all in radical pattern appeared over time (dose), probably it can be compensated by adaptation processes of the skin.
紫外线（UV）辐射会导致自由基的形成，这可能会引起免疫调节、皮肤老化或皮肤癌。根据 CIE 85，UVA 区域的阳光照射几乎会导致皮肤中自由基形成的 46%。已经证明，在 UV 和/或 VIS 光的光谱区域中，自由基浓度的临界值会发生反转，即主要活性氧（ROS）的优势转变为过量的脂质氧（LOS），这被认为是氧化还原系统失衡的标志，这种失衡已经无法再补偿有害影响。为了研究这个转折点是否在一个光谱区域也普遍适用，我们使用 X 波段电子顺磁共振（EPR）光谱法，在离体猪皮中研究了靶向 UVA 在 365±5nm 时的原位辐照过程中和辐照后的自由基形成，以及三种不同辐照度（31、94 和 244mW/cm）。通过自旋探针 3-（羧基）-2,2,5,5-四甲基吡咯啉-1-氧（PCA）进行定量，使用自旋捕获剂 5,5-二甲基-1-吡咯啉-N-氧化物（DMPO）来表征自由基种类。此外，通过 MTT[3-（4,5-二甲基噻唑-2-基）-2,5-二苯基四氮唑溴化物]测定法控制照射后的皮肤细胞活力，通过组织学分析检查皮肤完整性。在较高的辐照度下，自由基的形成呈显著的剂量依赖性。在最高辐照度照射后的 0.5MED 后检测到了转折点。从这一点开始，随着剂量的增加，LOS 的比例增加，而 ROS 的比例减少。关闭 UVA 辐射后，没有检测到进一步的定量变化，但观察到自由基模式的快速变化，这表明在使用自旋捕获剂时原位辐照的重要性。热预应激的皮肤在辐照开始时已经显示出比 ROS 更多的 LOS，这导致假设已经达到了向应激水平的转折点。总之，仅使用一种自旋捕获剂结合原位辐照，就可以验证 UVA 光谱区域的假设转折点。需要一定程度的应激才能检测到 ROS 与 LOS 比值的反转。这种反转表明氧化还原状态失衡。然而，在低强度下，随着时间的推移（剂量），自由基模式没有出现任何变化，这可能是由于皮肤的适应过程造成的。
