Vitek M P, Bhattacharya K, Glendening J M, Stopa E, Vlassara H, Bucala R, Manogue K, Cerami A
Picower Institute for Medical Research, Manhasset, NY 11030.
Proc Natl Acad Sci U S A. 1994 May 24;91(11):4766-70. doi: 10.1073/pnas.91.11.4766.
Alzheimer disease (AD) is characterized by deposits of an aggregated 42-amino-acid beta-amyloid peptide (beta AP) in the brain and cerebrovasculature. After a concentration-dependent lag period during in vitro incubations, soluble preparations of synthetic beta AP slowly form fibrillar aggregates that resemble natural amyloid and are measurable by sedimentation and thioflavin T-based fluorescence. Aggregation of soluble beta AP in these in vitro assays is enhanced by addition of small amounts of pre-aggregated beta-amyloid "seed" material. We also have prepared these seeds by using a naturally occurring reaction between glucose and protein amino groups resulting in the formation of advanced "glycosylation" end products (AGEs) which chemically crosslink proteins. AGE-modified beta AP-nucleation seeds further accelerated aggregation of soluble beta AP compared to non-modified "seed" material. Over time, nonenzymatic advanced glycation also results in the gradual accumulation of a set of posttranslational covalent adducts on long-lived proteins in vivo. In a standardized competitive ELISA, plaque fractions of AD brains were found to contain about 3-fold more AGE adducts per mg of protein than preparations from healthy, age-matched controls. These results suggest that the in vivo half-life of beta-amyloid is prolonged in AD, resulting in greater accumulation of AGE modifications which in turn may act to promote accumulation of additional amyloid.
阿尔茨海默病（AD）的特征是大脑和脑血管系统中存在由42个氨基酸组成的β-淀粉样肽（β-AP）聚集体沉积。在体外孵育过程中经过浓度依赖性的延迟期后，合成β-AP的可溶性制剂会缓慢形成类似于天然淀粉样蛋白的纤维状聚集体，可通过沉降和硫黄素T荧光法进行检测。在这些体外试验中，添加少量预聚集的β-淀粉样“种子”物质可增强可溶性β-AP的聚集。我们还通过利用葡萄糖与蛋白质氨基之间的天然反应制备了这些种子，该反应导致形成可化学交联蛋白质的晚期“糖基化”终产物（AGEs）。与未修饰的“种子”物质相比，AGE修饰的β-AP成核种子进一步加速了可溶性β-AP的聚集。随着时间的推移，非酶促晚期糖基化还会导致体内长寿蛋白质上一组翻译后共价加合物的逐渐积累。在标准化的竞争性酶联免疫吸附测定（ELISA）中，发现AD脑的斑块部分每毫克蛋白质中含有的AGE加合物比来自健康的、年龄匹配的对照的制剂多约3倍。这些结果表明，β-淀粉样蛋白在AD中的体内半衰期延长，导致AGE修饰的积累增加，这反过来可能会促进更多淀粉样蛋白的积累。
