Sasaki H, Akamatsu H, Horio T
Department of Dermatology, Kansai Medical University, Osaka, Japan.
Photochem Photobiol. 1997 Apr;65(4):707-13. doi: 10.1111/j.1751-1097.1997.tb01914.x.
Ultraviolet B irradiation has been believed to decrease or impair the activity of reactive oxygen species (ROS) scavenging enzymes such as superoxide dismutase (SOD) in the skin. It has been recently reported that two isozymes of SOD, namely copper-zinc SOD (Cu-Zn SOD) and manganese SOD (Mn SOD), exist in mammalian cells and that the two enzymes play different roles in living systems. The aim of this study was to investigate changes in SOD activities and protein levels in cultured human keratinocytes after acute UVB irradiation. In addition, the protein levels of Cu-Zn SOD and Mn SOD were quantified separately. A single exposure to UVB irradiation produced an increase in SOD activity and protein level that peaked immediately after UVB irradiation, after which a decline was observed, with subsequent recovery to baseline levels 24 h after irradiation. In individual assays of Mn SOD and Cu-Zn SOD, the amount of Mn SOD protein decreased and then gradually recovered 24 h after irradiation. In contrast, the amount of Cu-Zn SOD protein increased immediately after UVB irradiation, and then gradually declined. To evaluate the mechanisms of these changes, we examined the effects of the cytokines, interleukin-1 alpha (IL-1 alpha) and tumor necrosis factor-alpha (TNF-alpha), which can be secreted from keratinocytes after UVB irradiation, on the SOD activity and protein levels in keratinocytes. Interleukin-1 alpha and TNF-alpha enhanced both the SOD activity and protein level of Mn SOD, while these cytokines had no effect on Cu-Zn SOD protein levels in cultured human keratinocytes after incubation for 24 h. Furthermore, when neutralizing antibodies against IL-1 alpha and TNF-alpha were added separately or together to the culture medium before UVB irradiation, the recovery of total SOD activity and Mn SOD protein level were markedly inhibited 24 h after irradiation. Our results suggest that significant increases in SOD activity and protein level occur as a cutaneous antioxidant defense mechanism that protects against the cytotoxicity as a result of UVB irradiation, and that this increase in SOD is attributed to Cu-Zn SOD. The Cu-Zn SOD and Mn SOD protein levels changed in a different manner after UVB irradiation. The former may participate in an early phase and the latter in a late phase defense mechanism directed against oxidant cytotoxicity through UVB irradiation. In addition, the recovery of Mn SOD to baseline levels 24 h after UVB irradiation seems to be mediated through cytokines such as IL-1 alpha and TNF-alpha, which are secreted from keratinocytes.
紫外线B辐射被认为会降低或损害皮肤中活性氧（ROS）清除酶如超氧化物歧化酶（SOD）的活性。最近有报道称，哺乳动物细胞中存在两种SOD同工酶，即铜锌SOD（Cu-Zn SOD）和锰SOD（Mn SOD），且这两种酶在生命系统中发挥不同作用。本研究的目的是调查急性紫外线B辐射后培养的人角质形成细胞中SOD活性和蛋白质水平的变化。此外，还分别对Cu-Zn SOD和Mn SOD的蛋白质水平进行了定量分析。单次紫外线B辐射会使SOD活性和蛋白质水平升高，在紫外线B辐射后立即达到峰值，之后出现下降，辐射后24小时恢复到基线水平。在对Mn SOD和Cu-Zn SOD的单独检测中，Mn SOD蛋白量在辐射后减少，然后在24小时后逐渐恢复。相比之下，Cu-Zn SOD蛋白量在紫外线B辐射后立即增加，然后逐渐下降。为了评估这些变化的机制，我们检测了紫外线B辐射后可由角质形成细胞分泌的细胞因子白细胞介素-1α（IL-1α）和肿瘤坏死因子-α（TNF-α）对角质形成细胞中SOD活性和蛋白质水平的影响。白细胞介素-1α和TNF-α增强了Mn SOD的SOD活性和蛋白质水平，而在培养的人角质形成细胞中孵育24小时后，这些细胞因子对Cu-Zn SOD蛋白水平没有影响。此外，在紫外线B辐射前将抗IL-1α和TNF-α的中和抗体单独或一起添加到培养基中，辐射后24小时总SOD活性和Mn SOD蛋白水平的恢复受到明显抑制。我们的结果表明，SOD活性和蛋白质水平显著升高是一种皮肤抗氧化防御机制，可保护免受紫外线B辐射导致的细胞毒性，且这种SOD的增加归因于Cu-Zn SOD。紫外线B辐射后，Cu-Zn SOD和Mn SOD的蛋白质水平变化方式不同。前者可能参与早期阶段，而后者参与针对紫外线B辐射引起的氧化细胞毒性的晚期防御机制。此外，紫外线B辐射后24小时Mn SOD恢复到基线水平似乎是由角质形成细胞分泌的IL-1α和TNF-α等细胞因子介导的。
