Angelé-Martínez Carlos, Goncalves Leticia Christina Pires, Premi Sanjay, Augusto Felipe A, Palmatier Meg A, Amar Saroj K, Brash Douglas E
Department of Therapeutic Radiology, Yale School of Medicine, New Haven, CT 06520-8040, USA.
Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, São Paulo 05508-900, SP, Brazil.
Antioxidants (Basel). 2022 Feb 11;11(2):357. doi: 10.3390/antiox11020357.
UV-like DNA damage is created in the dark by chemiexcitation, in which UV-activated enzymes generate reactive oxygen and nitrogen species that create a dioxetane on melanin. Thermal cleavage creates an electronically excited triplet-state carbonyl whose high energy transfers to DNA. Screening natural compounds for the ability to quench this energy identified polyenes, polyphenols, mycosporine-like amino acids, and related compounds better known as antioxidants. To eliminate false positives such as ROS and RNS scavengers, we then used the generator of triplet-state acetone, tetramethyl-1,2-dioxetane (TMD), to excite the triplet-energy reporter 9,10-dibromoanthracene-2-sulfonate (DBAS). Quenching measured as reduction in DBAS luminescence revealed three clusters of 50% inhibitory concentration, ~50 μM, 200-500 μM, and >600 μM, with the former including sorbate, ferulic acid, and resveratrol. Representative triplet-state quenchers prevented chemiexcitation-induced "dark" cyclobutane pyrimidine dimers (dCPD) in DNA and in UVA-irradiated melanocytes. We conclude that (i) the delocalized pi electron cloud that stabilizes the electron-donating activity of many common antioxidants allows the same molecule to prevent an electronically excited species from transferring its triplet-state energy to targets such as DNA and (ii) the most effective class of triplet-state quenchers appear to operate by energy diversion instead of electron donation and dissipate that energy by isomerization.
在黑暗中，通过化学激发可产生类似紫外线的DNA损伤，其中紫外线激活的酶会产生活性氧和氮物种，这些物质会在黑色素上形成二氧杂环丁烷。热裂解会产生电子激发的三重态羰基，其高能量会转移到DNA上。通过筛选天然化合物淬灭这种能量的能力，确定了多烯、多酚、类菌孢素氨基酸以及更为人熟知的抗氧化剂相关化合物。为了消除诸如活性氧和氮清除剂等假阳性物质，我们随后使用三重态丙酮发生器四甲基-1,2-二氧杂环丁烷（TMD）来激发三重态能量报告分子9,10-二溴蒽-2-磺酸盐（DBAS）。以DBAS发光的降低来衡量的淬灭显示出三个50%抑制浓度簇，分别约为50 μM、200 - 500 μM和>600 μM，前者包括山梨酸盐、阿魏酸和白藜芦醇。代表性的三重态淬灭剂可防止DNA和紫外线照射的黑素细胞中化学激发诱导的“暗”环丁烷嘧啶二聚体（dCPD）形成。我们得出结论：（i）稳定许多常见抗氧化剂供电子活性的离域π电子云，使得同一分子能够阻止电子激发物种将其三重态能量转移至DNA等靶标；（ii）最有效的一类三重态淬灭剂似乎是通过能量转移而非电子供体作用来发挥作用，并通过异构化耗散该能量。
