AGING, AMYLOID B PEPTIDE AND MIGRATION OF MONOCYTES ACROSS THE VASCULAR WALL

淀粉样β-肽(Abeta)的血管沉积在正常衰老过程中发生，并在阿尔茨海默病(AD)和相关疾病中加速，如遗传性脑出血伴淀粉样变性荷兰型(HCHWA-D)，一种脑淀粉样血管病(CAA)。在CAA中，HCHWA-D和AD的血管沉积增加与血管壁单核/巨噬细胞的侵袭和实质小胶质细胞的激活有关。对于脑血管系统中可能在Abeta介导的外周炎性细胞聚集中起作用的细胞和分子机制，人们知之甚少。最近的研究表明，外周血造血细胞(即单核细胞)可以穿越血脑屏障(BBB)。我们的研究表明，Abeta可增加白细胞跨血管内皮细胞的滞留，并诱导单核细胞在体外跨人血脑屏障迁移，这一作用可被抗PECAM-1(细胞连接分子)和RAGE(可能的Aβ受体)抗体所阻断。中心假说是Abeta与其在脑血管内皮细胞中可能的受体(S)相互作用，产生细胞信号，从而导致PECAM-1的调节，从而允许单核细胞跨血脑屏障迁移。进一步的假设是，在AD和老年非人类灵长类动物中，单核细胞在脑血管系统中的迁移被夸大，可能是由于Abeta受体在血脑屏障的表达和/或重新分布。为了验证这一假说，我们将确定(1)Abeta对单核细胞在人脑微血管内皮细胞(HBMVEC)的黏附和迁移的影响；(2)Abeta是否能引起老年和AD患者HBMVEC中单核细胞迁移的增加；(3)p21/ras、MAP激酶、NF-kappaB、RAGE和PAF在Abeta诱导的细胞信号转导中的作用；(3)药物抑制剂的使用和通过HBMVEC的过度表达或敲除基因来敲除基因的作用；以及(4)Abeta诱导的白细胞跨血管壁黏附和迁移的机制。所提出的研究将为Aβ诱导的造血细胞跨血管壁和BB迁移的机制提供新的见解，并将为改变Aβ在衰老脑中诱导的炎症反应以改善神经元损伤的治疗原理提供分子基础。

Vascular deposition of amyloid-beta-peptide (Abeta) occurs during normal aging and is accelerated in Alzheimer's Disease (AD) and related disorders such as hereditary cerebral hemorrhage with amyloidosis Dutch type (HCHWA-D), a form of cerebral amyloid angiopathy (CAA). In CAA, HCHWA-D and AD increased vascular deposition of Abeta is associated with invasion of monocyte/macrophages in the vessel wall and activated microglial cells in the parenchyma. Relatively little is known about the cellular and molecular mechanisms in cerebral vasculature that may play a role in Abeta-mediated accumulation of peripheral inflammatory cells. Recent studies indicated that peripheral hematopoietic cells (i.e., monocytes) can cross the blood-brain barrier (BBB). Our studies shown that Abeta increases diapedesis of leukocytes across the vascular endothelium, and induces migration of monocytes across the human BBB in vitro, blocked by antibodies to PECAM-1 ( a cell junction molecule ) and RAGE (putative receptor for A beta). The central hypothesis is that interaction of Abeta with its putative receptor(s) in the brain vascular endothelium brings about cellular signaling which results in the modulation of PECAM-1 to allow migration of monocytes across the BBB. It is further hypothesized, that migration of monocytes is exaggerated across cerebral vasculature in AD and aged non-human primates, presumably due to increased expression and/or redistribution of Abeta receptors at the BBB. To test this hypothesis we will determine (1) the effect of Abeta on adhesion and migration of monocytes across monolayer of human brain microvascular endothelial cells (HBMVEC); (2) whether Abeta causes increased migration of monocytes in HBMVEC from geriatric and AD cases; (3) the role of p21/ras, MAP kinase, NF-kappaB,, RAGE and PAF in Abeta induced cellular signaling, using pharmacological inhibitors and over-expressing or knocking out genes by transfection of HBMVEC, and (4) the mechanisms of Abeta-induced adhesion and diapedesis of leukocytes across the vessel wall in transgenic (Tg) CC HCHWA-D mice and Tg vascular RAGE mice. Proposed studies will provide a novel insight into the mechanisms of Abeta-induced migration of hematopoietic cells across the vessel wall and the BB and will provide a molecular basis for the therapeutic rationale to modify Abeta- induced inflammatory reactions in the aging brain to ameliorate the neuronal injury.