FREE RADICAL AND ENZYMATIC OXIDATION OF RETINOIDS

所有反式维甲酸(RA)和13-顺式维甲酸(13-CIS)用于 治疗痤疮，光老化，并代表主要代谢物 维生素A。我们已经证明了13-维生素A的氧化依赖于过氧基。 顺式病毒在小鼠皮肤中。此外，我们还证明了RA和13-CIS的功能 作为抗氧化剂，抑制脂质体和微生物体的过氧化。在……里面 相反，RA在洗涤剂胶束中发挥促氧化作用 刺激自由基的传播反应。我们建议澄清 抗氧化剂和促氧化剂的作用机制 通过鉴定主要的RA和13-CIS氧化产物获得维甲酸 在磷脂双层和洗涤剂胶束中通过反应生成 在化学上或在碳氢化合物中产生的过氧基 自氧化作用。此外，氧张力、视黄醇的影响 浓度，通过维甲酸5，6-双键的环氧化反应，以及 磷脂对溶剂笼效应的相对贡献 双层与胶束相比，对抗氧化剂和促氧化作用的影响 被调查。 我们还表明，RA和13-CIS经历了过氧化氢--和 前列腺素H合成酶对花生四烯酸的依赖氧化 涉及过氧化物酶和过氧化氢自由基化学的混合机制。 RA和13-CIS与PGH合成酶过氧化物酶的反应 C4位的羟基化(这也是一种主要的细胞色素P-450 代谢物)和其他氧化产物的形成。PGH合成酶- RA和13-CIS的催化氧化可能代表着一种重要的代谢 高环氧合酶在多种肝外组织中的途径 活性低，细胞色素P-450活性低。我们建议确定 PGH合成酶产生的主要RA和13-CIS氧化产物 过氧化物酶催化的体外氧化，测定区域和 氢原子抽提的立体化学和氢原子的立体化学 羟化反应，测量氢原子的动力学同位素效应 提取反应，确定氧化产物中氧的来源， 并证实了维甲酸衍生的碳中心，过氧基， 和烷氧基。我们还将研究细胞色素P-450- 催化的与动力学同位素的氢化反应 氢原子抽提和羟化的作用和立体化学。 最后，我们将研究RA和13-CIS在培养的人体内的氧化 角质形成细胞和犬肾来源的MDCK细胞系 测定过氧基、POH合酶、 和细胞色素P-450依赖的氧化机制在这些生物中 系统。

All trans-retinoic acid (RA) and 13-cis-retinoic acid (13-CIS) are used in the treatment of acne, photoaging, and represent major metabolites of vitamin A. We have demonstrated peroxyl radical-dependent oxidation of 13- CIS in mouse skin. In addition, we have shown that RA and 13-CIS function as antioxidants and inhibit peroxidation of liposomes and microsomes. In contrast, RA exerts prooxidant effects in detergent micelles where it stimulates free radical propagation reactions. We propose to elucidate the mechanisms involved in the antioxidant and prooxidant properties of these retinoids by identifying the major RA and 13-CIS oxidation products generated, in phospholipid bilayers and detergent micelles, by reaction with peroxyl radicals generated chemically or during hydrocarbon autoxidation. In addition, the effects of dioxygen tension, retinoid concentration, epoxidation across the retinoid 5,6-double bonds, and the relative contributions of solvent cage effects, imposed by phospholipid bilayers versus micelles, on the antioxidant and prooxidant effects will be investigated. We have also shown that RA and 13-CIS undergo hydroperoxide- and arachidonic acid-dependent oxidation by prostagalndin H (PGH) synthase by mechanisms involving a hybrid of peroxidase and peroxyl radical chemistry. Reaction of RA and 13-CIS with PGH synthase peroxidase results in hydroxylation at the C4 position (which is also a major cytochrome P-450 metabolite) and the formation of other oxidation products. PGH synthase- catalyzed oxidation of RA and 13-CIS may represent a significant metabolic pathway in various extrahepatic tissues containing high cyclooxygenase activity and low cytochrome P-450 activity. We propose to identify the major RA and 13-CIS oxidation products generated during PGH synthase peroxidase-catalyzed oxidation in vitro, determine the regio- and stereochemistry of H-atom abstraction and the stereochemistry of hydroxylation, measure deuterium kinetic isotope effects of the H-atom abstraction reaction, determine the source of oxygen in oxidized products, and confirm the intermediacy of retinoid-derived carbon-centered, peroxyl, and alkoxyl radicals. We will also investigate the cytochrome P-450- catalyzed hydroxylation reaction with respect to deuterium kinetic isotope effects and stereochemistry of H-atom abstraction and hydroxylation. Finally we will investigate oxidation of RA and 13-CIS in cultured human keratinocytes and in the canine kidney-derived MDCK cell line in order to determine the relative contributions of peroxyl radical-, POH synthase-, and cytochrome P-450-dependent mechanisms of oxidation in these biological systems.