Tian Jinzhou, Shi Jing, Zhang Leiming, Yin Junxiang, Hu Quan, Xu Yi, Sheng Shuli, Wang Pengwen, Ren Ying, Wang Rong, Wang Yongyan
BUCM Neurology Centre, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China.
Curr Alzheimer Res. 2009 Apr;6(2):118-31. doi: 10.2174/156720509787602942.
Accumulation of beta-amyloid peptide (Abeta) in the brain is a primary influence driving Alzheimer's disease (AD) pathogenesis. The disease process, including formation of neurofibrillary tangles containing tau protein, is proposed to result from an imbalance between production and clearance of Abeta. A major therapeutic strategy for AD should be to decrease deposition of Abeta by the inhibition of its production and the facilitation of its degradation. Hence, the primary aim of this study was to investigate effects of GEPT, a combination of herbal extracts, on Abeta levels, beta- and gamma-secretases substrate (BACE1 and PS1, respectively) associated with production of Abeta, and insulin-degrading enzyme (IDE) and neprilysin (NEP) related to degradation of Abeta in the brain.
Three-month-old-male APPV717I mice were randomly divided into five groups (n=6 per group): (i) APP mice alone were given distilled water, (ii) APP donepezil mice were treated with donepezil (0.92 mg/kg/d), and (iii-v) APP mice treated with GEPT low dose (0.75 g/kg/d), middle dose (1.5 g/kg/d), and large dose (3.0 g/kg/d) for 8 months. Three-month-old-male C57BL/6J mice (n=6) for vehicle were given distilled water for 8 months. Immunohistochemistry and Western blot analysis were used in determining amyloid precursor protein (APP), Abeta1-42, BACE1, PS1, IDE and NEP in hippocampal CA1 region and hippocampal tissue homogenates.
Expression level of Abeta1-42 in the large GEPT dose was significantly lower than those in APP alone or APP treated with donepezil, and decreased to the level of vehicle mice. Similarly, a ratio calculated from the densitometric measures of Abeta1-42 protein/beta-actin in the large dose also was significantly lower than those in APP mice alone or APP mice treated with donepezil, and even reduced to the level of vehicle mice. Expression of PS1 in the large GEPT dose was significantly lower than that of APP mice alone and decreased to those in vehicle mice as well. A decreased level of BACE1 appeared, respectively, in APP mice treated with the large GEPT dose or donepezil but was still much greater than the level of vehicle mice. In contrast, NEP and IDE showed a significantly higher expression in APP mice treated with either the large dose or the middle dose of GEPT compared to APP mice alone or donepezil, and were even increased in level compared to vehicle mice.
The combination of GEPT extracts can reduce levels of endogenous Abeta peptide in APPV717I transgenic mice through the inhibition of PS1 activity rather than BACE1 and the promotion of IDE and NEP activity. Lower-expression of PS1 and over-expression of IDE or NEP may be helpful in potentially lowering brain Abeta levels in subjects with AD, and hence GEPT appears to offer potential that should be explored in AD.
大脑中β-淀粉样肽（Aβ）的积累是驱动阿尔茨海默病（AD）发病机制的主要因素。包括含有tau蛋白的神经原纤维缠结形成在内的疾病过程，被认为是由Aβ产生与清除之间的失衡所致。AD的主要治疗策略应是通过抑制Aβ的产生和促进其降解来减少Aβ的沉积。因此，本研究的主要目的是探讨中药复方提取物（GEPT）对Aβ水平、与Aβ产生相关的β-和γ-分泌酶底物（分别为BACE1和PS1）以及与大脑中Aβ降解相关的胰岛素降解酶（IDE）和中性内肽酶（NEP）的影响。
将3月龄雄性APPV717I小鼠随机分为五组（每组n = 6）：（i）单独给予APP小鼠蒸馏水，（ii）APP多奈哌齐小鼠用多奈哌齐（0.92 mg/kg/d）治疗，以及（iii - v）用GEPT低剂量（0.75 g/kg/d）、中剂量（1.5 g/kg/d）和高剂量（3.0 g/kg/d）治疗的APP小鼠，持续8个月。给予3月龄雄性C57BL/6J小鼠（n = 6）作为对照，给予蒸馏水8个月。采用免疫组织化学和蛋白质印迹分析来测定海马CA1区和海马组织匀浆中的淀粉样前体蛋白（APP）、Aβ1 - 42、BACE1、PS1、IDE和NEP。
GEPT高剂量组中Aβ1 - 42的表达水平显著低于单独的APP组或用多奈哌齐治疗的APP组，并降至对照小鼠水平。同样，高剂量组中Aβ1 - 42蛋白与β-肌动蛋白光密度测量值计算出的比值也显著低于单独的APP小鼠或用多奈哌齐治疗的APP小鼠，甚至降至对照小鼠水平。GEPT高剂量组中PS1的表达显著低于单独的APP小鼠，也降至对照小鼠水平。GEPT高剂量组或多奈哌齐治疗的APP小鼠中BACE1水平均有所降低，但仍远高于对照小鼠水平。相比之下，与单独的APP小鼠或多奈哌齐治疗组相比，GEPT高剂量或中剂量治疗的APP小鼠中NEP和IDE的表达显著更高，甚至高于对照小鼠水平。
GEPT提取物组合可通过抑制PS1活性而非BACE1，并促进IDE和NEP活性，降低APPV717I转基因小鼠内源性Aβ肽水平。PS1的低表达以及IDE或NEP的过表达可能有助于潜在降低AD患者大脑中的Aβ水平，因此GEPT似乎具有在AD研究中值得探索的潜力。
