Baba T, Nakano H, Tamai K, Sawamura D, Hanada K, Hashimoto I, Arima Y
Department of Dermatology, Hirosaki University School of Medicine, Japan.
J Invest Dermatol. 1998 Jan;110(1):24-8. doi: 10.1046/j.1523-1747.1998.00078.x.
Sunburn cells are thought to represent ultraviolet B-induced apoptotic keratinocytes. It has been demonstrated that enzymatic and nonenzymatic antioxidants effectively suppress sunburn cell formation, indicating that reactive oxygen species may play a role in the progression of ultraviolet B-induced apoptosis. Metallothionein, a cytosol protein, has antioxidant activity, and overexpression of metallothionein has been reported to reduce the number of sunburn cells in mouse skin. We have also demonstrated that overexpression of metallothionein inhibits ultraviolet B-induced DNA ladder formation in mouse keratinocytes. These findings support the hypothesis that cellular metallothionein may play an important role in the inhibition of ultraviolet B-induced apoptosis in keratinocytes through its antioxidant activity. In the present study, we investigated the effects of beta-thujaplicin, an extract from the woods of Thuja plicata D. Don. and Chamaecyparis obtuse, Sieb. et Zucc., on ultraviolet B-induced apoptosis in keratinocytes and on metallothionein induction. Topical application of beta-thujaplicin decreased the number of ultraviolet B-mediated sunburn cells and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling-positive cells in mouse ear skin. Incubation with beta-thujaplicin suppressed ultraviolet B-induced DNA ladder formation in cultured mouse keratinocytes. Histochemical analysis showed that topical application of beta-thujaplicin induced metallothionein protein in mouse skin. Northern analysis and western blotting revealed significant induction of metallothionein mRNA and metallothionein protein, respectively, in beta-thujaplicin-treated cultured mouse keratinocytes. These findings indicate that beta-thujaplicin inhibits ultraviolet B-induced apoptosis in keratinocytes and strongly suggest that the inhibitory mechanism is due to the antioxidant activity of metallothionein induced by the agent.
晒伤细胞被认为是紫外线B诱导的凋亡角质形成细胞。已经证明，酶促和非酶促抗氧化剂能有效抑制晒伤细胞的形成，这表明活性氧可能在紫外线B诱导的凋亡进程中发挥作用。金属硫蛋白是一种胞质蛋白，具有抗氧化活性，据报道，金属硫蛋白的过表达可减少小鼠皮肤中晒伤细胞的数量。我们还证明，金属硫蛋白的过表达可抑制紫外线B诱导的小鼠角质形成细胞中的DNA梯状条带形成。这些发现支持了这样一种假说，即细胞金属硫蛋白可能通过其抗氧化活性在抑制角质形成细胞中紫外线B诱导的凋亡中发挥重要作用。在本研究中，我们研究了从美国扁柏（Thuja plicata D. Don）和钝叶扁柏（Chamaecyparis obtuse，Sieb. et Zucc.）木材中提取的β-崖柏素对角质形成细胞中紫外线B诱导的凋亡以及金属硫蛋白诱导的影响。局部应用β-崖柏素可减少小鼠耳部皮肤中紫外线B介导的晒伤细胞数量以及末端脱氧核苷酸转移酶（TdT）介导的dUTP-生物素缺口末端标记阳性细胞数量。用β-崖柏素孵育可抑制培养的小鼠角质形成细胞中紫外线B诱导的DNA梯状条带形成。组织化学分析表明，局部应用β-崖柏素可诱导小鼠皮肤中的金属硫蛋白蛋白。Northern分析和Western印迹分别显示，在β-崖柏素处理的培养小鼠角质形成细胞中，金属硫蛋白mRNA和金属硫蛋白蛋白有显著诱导。这些发现表明，β-崖柏素可抑制角质形成细胞中紫外线B诱导的凋亡，并强烈提示其抑制机制是由于该药物诱导的金属硫蛋白的抗氧化活性。
