González S, Pathak M A
Department of Dermatology, Massachusetts General Hospital, Harvard Medical School, Boston 02114, USA.
Photodermatol Photoimmunol Photomed. 1996 Apr;12(2):45-56. doi: 10.1111/j.1600-0781.1996.tb00175.x.
The acute reactions of human skin to solar ultraviolet radiation (290-400 nm) are recognized as a form of inflammation reactions that are mediated by several possible mechanisms including (a) direct action of photons on DNA, (b) generation of reactive free radicals and reactive oxygen species involving the formation of O2.-, 1O2, H2O2, OH, etc., (c) generation of prostaglandins (PGD2, PGE2, etc.), histamine, leucotrienes, and other inflammatory mediators. It is conceivable that UV-induced reactions represent oxidative stress mediated by the formation of free radicals, reactive oxygen, lipid peroxidation, liberation of membrane phospholipids, and subsequent formation of prostaglandins by cyclo-oxygenase pathway. In this study, we examined the role of reactive oxygen species and lipid peroxidation in in vitro reactions as well as in vivo skin inflammation reactions induced by (a) UVB radiation (290-320 nm), and (b) skin photosensitization reaction by PUVA treatment involving 8-methoxypsoralen and UVA (320-400 nm) radiation and presented data for the generation of superoxide anion O2.-) and lipid peroxides. We have also evaluated, both in vitro as well as in vivo systems, the quenching or the inhibition of O2.- by a plant extract known as Polypodium leucotomos. The P. leucotomos extract was found to exhibit interesting antioxidant and anti-inflammatory as well as photoprotective properties against photo-oxidative stress involving the generation of reactive oxygen, lipid peroxidation under in vitro reactions as well as in vivo experimental conditions. Significant inhibition of UVB-induced erythemal response, and 8-methoxypsoralen plus UVA-induced phototoxic reaction after topical application or oral administration of the photosensitizer could be demonstrated in guinea pig skin and human skin following the topical application of P. leucotomos extract. The photoprotective mechanism of P.leucotomos involving interaction with reactive oxygen species or free radicals appears to have potential clinical usefulness in preventing sunburn and inhibiting phototoxic reaction.
人类皮肤对太阳紫外线辐射（290 - 400纳米）的急性反应被认为是一种炎症反应形式，其由多种可能机制介导，包括：（a）光子对DNA的直接作用；（b）活性自由基和活性氧的产生，涉及超氧阴离子（O2.-）、单线态氧（1O2）、过氧化氢（H2O2）、羟基自由基（OH）等的形成；（c）前列腺素（PGD2、PGE2等）、组胺、白三烯及其他炎症介质的产生。可以想象，紫外线诱导的反应代表由自由基形成、活性氧、脂质过氧化、膜磷脂释放以及随后通过环氧化酶途径形成前列腺素介导的氧化应激。在本研究中，我们研究了活性氧和脂质过氧化在体外反应以及由（a）UVB辐射（290 - 320纳米）和（b）补骨脂素和UVA（320 - 400纳米）辐射的PUVA治疗引起的皮肤光敏反应所诱导的体内皮肤炎症反应中的作用，并给出了超氧阴离子（O2.-）和脂质过氧化物产生的数据。我们还在体外和体内系统中评估了一种名为白藓的植物提取物对O2.-的淬灭或抑制作用。发现白藓提取物在体外反应以及体内实验条件下，对涉及活性氧产生、脂质过氧化的光氧化应激表现出有趣的抗氧化、抗炎以及光保护特性。在豚鼠皮肤和人类皮肤局部应用白藓提取物后，可证明局部应用或口服光敏剂后，UVB诱导的红斑反应以及8 - 甲氧基补骨脂素加UVA诱导的光毒性反应受到显著抑制。白藓的光保护机制涉及与活性氧或自由基的相互作用，在预防晒伤和抑制光毒性反应方面似乎具有潜在的临床应用价值。
