McLellan Megan E, Kajdasz Stephen T, Hyman Bradley T, Bacskai Brian J
Massachusetts General Hospital, Department of Neurology/Alzheimer's Disease Research Laboratory, Charlestown, Massachusetts 02129, USA.
J Neurosci. 2003 Mar 15;23(6):2212-7. doi: 10.1523/JNEUROSCI.23-06-02212.2003.
Amyloid-beta, the primary constituent of senile plaques in Alzheimer's disease, is hypothesized to cause neuronal damage and cognitive failure, but the mechanisms are unknown. Using multiphoton imaging, we show a direct association between amyloid-beta deposits and free radical production in vivo in live, transgenic mouse models of Alzheimer's disease and in analogous ex vivo experiments in human Alzheimer tissue. We applied two fluorogenic compounds, which become fluorescent only after oxidation, before imaging with a near infrared laser. We observed fluorescence associated with dense core plaques, but not diffuse plaques, as determined by subsequent addition of thioflavine S and immunohistochemistry for amyloid-beta. Systemic administration of N-tert-butyl-alpha-phenylnitrone, a free radical spin trap, greatly reduced oxidation of the probes. These data show directly that a subset of amyloid plaques produces free radicals in living, Alzheimer's models and in human Alzheimer tissue. Antioxidant therapy neutralizes these highly reactive molecules and may therefore be of therapeutic value in Alzheimer's disease.
β-淀粉样蛋白是阿尔茨海默病中淀粉样斑块的主要成分，据推测它会导致神经元损伤和认知功能衰退，但其机制尚不清楚。利用多光子成像技术，我们在活体转基因阿尔茨海默病小鼠模型中以及在人类阿尔茨海默病组织的类似体外实验中，展示了β-淀粉样蛋白沉积物与体内自由基产生之间的直接关联。在用近红外激光成像之前，我们应用了两种仅在氧化后才会发出荧光的荧光化合物。我们观察到与致密核心斑块相关的荧光，而弥漫性斑块则没有，这是通过随后添加硫黄素S和β-淀粉样蛋白免疫组织化学确定的。自由基自旋捕获剂N-叔丁基-α-苯基硝酮的全身给药大大减少了探针的氧化。这些数据直接表明，在活体阿尔茨海默病模型和人类阿尔茨海默病组织中，一部分淀粉样斑块会产生自由基。抗氧化疗法可中和这些高活性分子，因此可能对阿尔茨海默病具有治疗价值。
