Roles of reactive oxygen species in UVA-induced oxidation of 5,6-dihydroxyindole-2-carboxylic acid-melanin as studied by differential spectrophotometric method
Roles of reactive oxygen species in UVA-induced oxidation of 5,6-dihydroxyindole-2-carboxylic acid-melanin as studied by differential spectrophotometric method
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DOI：
10.1111/pcmr.12469
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发表时间：
2016-05-01
影响因子：
4.3
通讯作者：
Wakamatsu, Kazumasa
中科院分区：
文献类型：
--
作者：
Ito, Shosuke;Kikuta, Marina;Wakamatsu, Kazumasa
真黑素可保护色素组织免受紫外线（UV）损伤。然而，UVA诱导的晒黑似乎是由于预先存在的黑色素的光氧化而导致的，并且无助于光保护。我们研究了UVA诱导的5，6-二羟基吲哚-2-羧酸（DHICA）-黑色素的降解机制，利用其在中性缓冲液中的溶解度，并使用差示分光光度法检测其结构的细微变化。我们的方法适用于检查与活性氧（ROS）相互作用的各种试剂的影响，以确定ROS如何参与UVA诱导的氧化修饰。结果表明，UVA辐射诱导DHICA氧化为真黑素中的吲哚-5，6-醌-2-羧酸，然后裂解形成光降解的吡咯部分，最后形成游离的吡咯-2，3，5-三羧酸。超氧自由基和单线态氧可能参与了氧化反应。通过直接测量单线态氧磷光证实了DHICA-黑色素单线态氧的产生和猝灭。
Eumelanin photoprotects pigmented tissues from ultraviolet (UV) damage. However, UVA-induced tanning seems to result from the photooxidation of preexisting melanin and does not contribute to photoprotection. We investigated the mechanism of UVA-induced degradation of 5,6-dihydroxyindole-2-carboxylic acid (DHICA)-melanin taking advantage of its solubility in a neutral buffer and using a differential spectrophotometric method to detect subtle changes in its structure. Our methodology is suitable for examining the effects of various agents that interact with reactive oxygen species (ROS) to determine how ROS is involved in the UVA-induced oxidative modifications. The results show that UVA radiation induces the oxidation of DHICA to indole-5,6-quinone-2-carboxylic acid in eumelanin, which is then cleaved to form a photodegraded, pyrrolic moiety and finally to form free pyrrole-2,3,5-tricarboxylic acid. The possible involvement of superoxide radical and singlet oxygen in the oxidation was suggested. The generation and quenching of singlet oxygen by DHICA-melanin was confirmed by direct measurements of singlet oxygen phosphorescence.