Jurkiewicz B A, Buettner G R
Radiation Research Laboratory, University of Iowa College of Medicine, Iowa City 52242-1101.
Photochem Photobiol. 1994 Jan;59(1):1-4. doi: 10.1111/j.1751-1097.1994.tb04993.x.
It has been suggested that ultraviolet light induces free radical formation in skin, leading to photoaging and cancer. We have demonstrated by electron paramagnetic resonance that the ascorbate free radical is naturally present in unexposed skin at a very low steady state level. When a section of SKH-1 hairless mouse skin in an EPR cavity is exposed to UV light (4,500 J m-2.s-1, Xe lamp, 305 nm cutoff and IR filters), the ascorbate free radical signal intensity increases. These results indicate that UV light increases free radical oxidative stress, consistent with ascorbate's role as the terminal, small-molecule antioxidant. The initial radicals produced by UV light would have very short lifetimes at room temperature; thus, we have applied EPR spin trapping techniques to detect these radicals. Using alpha-[4-pyridyl 1-oxide]-N-tert-butyl nitrone (POBN), we have for the first time spin trapped a UV light-produced carbon-centered free radical from intact skin. The EPR spectra exhibited hyperfine splittings that are characteristic of POBN/alkyl radicals, aN = 15.56 G and aH = 2.70 G, possibly generated from membrane lipids as a result of beta-scission of lipid alkoxyl radicals. Iron can act as a catalyst for free radical oxidative reactions; chronic exposure of skin to UV radiation causes increased iron deposition. Using our spin trapping system, we have shown that topical application of the iron-chelator, Desferal, to a section of skin reduces the UV light-induced POBN adduct radical signal.(ABSTRACT TRUNCATED AT 250 WORDS)
有人提出，紫外线会诱导皮肤中自由基的形成，从而导致光老化和癌症。我们通过电子顺磁共振证明，抗坏血酸自由基以非常低的稳态水平自然存在于未暴露的皮肤中。当将处于电子顺磁共振腔中的一段SKH-1无毛小鼠皮肤暴露于紫外线（4500 J m-2·s-1，氙灯，305 nm截止和红外滤光片）下时，抗坏血酸自由基信号强度会增加。这些结果表明紫外线会增加自由基氧化应激，这与抗坏血酸作为终端小分子抗氧化剂的作用一致。紫外线产生的初始自由基在室温下寿命会非常短；因此，我们应用电子顺磁共振自旋捕获技术来检测这些自由基。使用α-[4-吡啶基1-氧化物]-N-叔丁基硝酮（POBN），我们首次从完整皮肤中自旋捕获到了紫外线产生的以碳为中心的自由基。电子顺磁共振光谱显示出超精细分裂，这是POBN/烷基自由基的特征，aN = 15.56 G，aH = 2.70 G，可能是由于脂质烷氧基自由基的β-断裂而从膜脂质中产生的。铁可以作为自由基氧化反应的催化剂；皮肤长期暴露于紫外线辐射会导致铁沉积增加。使用我们的自旋捕获系统，我们已经表明，在皮肤的一部分局部应用铁螯合剂去铁胺会降低紫外线诱导的POBN加合物自由基信号。（摘要截短至250字）
