Hoogduijn M J, Cemeli E, Ross K, Anderson D, Thody A J, Wood J M
Department of Biomedical Sciences, University of Bradford, Bradford, UK.
Exp Cell Res. 2004 Mar 10;294(1):60-7. doi: 10.1016/j.yexcr.2003.11.007.
Reactive oxygen species (ROS) such as hydrogen peroxide (H(2)O(2)) are produced in the skin under the influence of UV radiation. These compounds are highly reactive and can induce DNA lesions in epidermal cells. Melanin is considered to protect human skin against DNA damage by absorbing UV radiation. We have investigated whether melanin can, in addition, offer protection against the effects of H(2)O(2) in human melanocytes and HaCaT keratinocytes. In the present study, it was shown that 40 and 100 microM H(2)O(2) increased the number of DNA strand breaks as measured using the comet assay, in melanocytes of Caucasian origin. In melanocytes of the same origin in which melanin levels were increased by culturing in presence of 10 mM NH(4)Cl and elevated l-tyrosine, H(2)O(2)-induced DNA damage was reduced compared to that in control melanocytes. Similarly, HaCaT cells that were loaded with melanin were better protected against H(2)O(2)-induced DNA strand breaks than control HaCaT cells. These protective effects of melanin were mimicked by the intracellular Ca(2+)-chelator BAPTA. Thus, BAPTA reduced the level of H(2)O(2)-induced DNA strand breaks in melanocytes. Like BAPTA, melanin is known to be a potent chelator of Ca(2+) and this was confirmed in the present study. It was shown that melanin levels in melanocytic cells correlated directly with intracellular Ca(2+) binding capacity and, in addition, correlated inversely with H(2)O(2)-induced increases in intracellular Ca(2+). Our results show that melanin may have an important role in regulating intracellular Ca(2+) homeostasis and it is suggested that melanin protects against H(2)O(2)-induced DNA strand breaks in both melanocytes and keratinocytes and through its ability to bind Ca(2+).
诸如过氧化氢（H₂O₂）之类的活性氧物质（ROS）在紫外线辐射的影响下于皮肤中产生。这些化合物具有高度反应性，可在表皮细胞中诱导DNA损伤。黑色素被认为可通过吸收紫外线来保护人体皮肤免受DNA损伤。我们研究了黑色素是否还能保护人类黑素细胞和HaCaT角质形成细胞免受H₂O₂的影响。在本研究中，结果表明，使用彗星试验检测，40和100微摩尔的H₂O₂会增加白种人来源黑素细胞中的DNA链断裂数量。在通过在10毫摩尔氯化铵和升高的L-酪氨酸存在下培养而使黑色素水平升高的相同来源的黑素细胞中，与对照黑素细胞相比，H₂O₂诱导的DNA损伤有所减少。同样，加载了黑色素的HaCaT细胞比对照HaCaT细胞对H₂O₂诱导的DNA链断裂具有更好的保护作用。黑色素的这些保护作用被细胞内钙螯合剂BAPTA模拟。因此，BAPTA降低了黑素细胞中H₂O₂诱导的DNA链断裂水平。与BAPTA一样，已知黑色素是一种有效的钙螯合剂，本研究证实了这一点。结果表明，黑素细胞中的黑色素水平与细胞内钙结合能力直接相关，此外，还与H₂O₂诱导的细胞内钙增加呈负相关。我们的结果表明，黑色素可能在调节细胞内钙稳态中起重要作用，并且表明黑色素通过其结合钙的能力保护黑素细胞和角质形成细胞免受H₂O₂诱导的DNA链断裂。
