Shamsi F A, Lin K, Sady C, Nagaraj R H
Department of Ophthalmology, Center for Vision Research, Case Western Reserve University and University Hospitals of Cleveland, Ohio 44106, USA.
Invest Ophthalmol Vis Sci. 1998 Nov;39(12):2355-64.
To determine whether the Maillard reaction of methylglyoxal is associated with human lens aging and cataractogenesis and to investigate how glutathione depletion affects methylglyoxal-derived modifications in organ-cultured lenses.
Antibodies against methylglyoxal-derived modifications were developed in rabbits and purified by immunoaffinity chromatography. A competitive enzyme-linked immunosorbent assay (ELISA) measured methylglyoxal-derived products in human lens proteins. Lenses of galactosemic rats grown in organ culture were used to assess the role of glutathione-dependent pathways in methylglyoxal metabolism and Maillard reactions.
Methylglyoxal-derived modifications in the human lens were age dependent, and brunescent lenses had the highest levels of these modifications. Immunofluorescence staining identified antigens distributed throughout the lens, with higher levels in old lenses than in younger ones. Experiments with normal or galactosemic rat lenses grown in organ culture showed that lens proteins do not have an increase in methylglyoxal-modified proteins when cultured in medium containing 500 microM methylglyoxal alone, but they accumulate modified proteins when cultured with DL-glyceraldehyde. Inclusion of 30 mM glucose in the medium marginally increased methylglyoxal-derived products, but there was no correlation between lens glutathione content and methylglyoxal-derived modifications.
Methylglyoxal-mediated Maillard reactions that occur in the human lens may play a role in lens aging and cataract formation. Methylglyoxal is probably derived from metabolic pathways within the lens. Decreased glutathione in organ-cultured rat lenses does not significantly influence methylglyoxal-mediated Maillard reactions.
确定甲基乙二醛的美拉德反应是否与人类晶状体老化及白内障形成有关，并研究谷胱甘肽耗竭如何影响器官培养晶状体中甲基乙二醛衍生的修饰。
在兔体内制备针对甲基乙二醛衍生修饰的抗体，并通过免疫亲和层析进行纯化。采用竞争性酶联免疫吸附测定（ELISA）法检测人类晶状体蛋白中甲基乙二醛衍生的产物。利用器官培养的半乳糖血症大鼠的晶状体来评估谷胱甘肽依赖性途径在甲基乙二醛代谢和美拉德反应中的作用。
人类晶状体中甲基乙二醛衍生的修饰与年龄相关，棕色晶状体中这些修饰的水平最高。免疫荧光染色显示抗原分布于整个晶状体，老年晶状体中的水平高于年轻晶状体。对正常或半乳糖血症大鼠的器官培养晶状体进行的实验表明，当仅在含有500微摩尔甲基乙二醛的培养基中培养时，晶状体蛋白中甲基乙二醛修饰的蛋白没有增加，但与DL-甘油醛一起培养时会积累修饰蛋白。培养基中加入30毫摩尔葡萄糖会使甲基乙二醛衍生的产物略有增加，但晶状体谷胱甘肽含量与甲基乙二醛衍生的修饰之间没有相关性。
人类晶状体中发生的甲基乙二醛介导的美拉德反应可能在晶状体老化和白内障形成中起作用。甲基乙二醛可能源自晶状体内部的代谢途径。器官培养的大鼠晶状体中谷胱甘肽减少不会显著影响甲基乙二醛介导的美拉德反应。
