The definition of Amyloid β-protein

Amyloid β-protein is a polypeptide of 39-43 amino acids which is produced by the proteolysis of Amyloid precursor protein (APP) via β-and γ-secretase. It can be produced by a variety of cells, circulating in the blood, cerebrospinal fluid and brain interstitial fluid, mostly with the chaperone protein molecules, a small number of free state exists. The most common subtypes of Amyloid β-protein in the human body are Amyloid β-protein 1-40 and Amyloid β-protein 1-42. In human cerebrospinal fluid and blood, Amyloid β-protein1 ~ 40, respectively, than Amyloid β-protein1 ~ 42 levels of 10 times higher and 1. 5 times, Amyloid β-protein1 ~ 42 with more toxic, and more easily gathered to form the core of Amyloid β-protein precipitation, triggering neurotoxicity. 

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1、Neurotoxicity of Amyloid β-protein     In 1991, Kowall injected Amyloid β-protein into the cerebral cortex of rats and monkeys and found that tissue necrosis, peripheral neuron deletion and keratinocyte proliferation occurred at the injection site. Amyloid β-protein make vascular wall starch changes, a direct result of hardening of the arteries, elastic deterioration, or even easy to rupture or thrombosis, but also to induce premature apoptosis of nerve cells. Animal experiments show that Amyloid β-protein on the role of neurons and their state. Amyloid β-protein in a dissociative state promotes neurite outgrowth and neuron survival in a short period of time, whereas deposition of Amyloid β-protein has the opposite effect on neurons, leading to pathological changes similar to those of Alzheimer's disease, most notably occurs in the aging mammalian brain.

2、 Affect the shape and function of blood vessels     Amyloid β-protein is first deposited on the extravascular basement membrane and then infiltrates into the smooth muscle cell layer. Amyloid β-protein deposition reduces the adhesion of small artery smooth muscle cells to the basement membrane, the middle layer of blood vessels is replaced by Amyloid β-protein, and the smooth muscle cells degeneration. Vinters, etc. and Yamaguchi study found that Amyloid β-protein deposition in the capillary basement membrane, and was a plate into the neural mat. Capillary Amyloid β-protein40 / Amyloid β-protein42 ratio was significantly lower than arteries. Therefore, Amyloid β-protein40 deposition mainly in the arterial wall, and Amyloid β-protein42 is deposited in the capillaries. Amyloid β-protein causes deposition of vascular fibers around the blood vessels, leading to Amyloid angiopathy.

3、Reduced the expression of fibroblast growth factor 2     Amyloid β-protein via the fibroblast growth factor 2 pathway on the vascular endothelial cells through the autocrine / paracrine pathway. Amyloid β-protein blocks the action of the FGF-2 axis by interacting with the cell membrane receptors of FGF-2. The point mutations of APP lead to the mutations of Amyloid β-protein21 ~ 23 amino acids. These mutants are closely related to the different genetic phenotypes of Amyloid angiopathy, the degree of cerebral vascular tropism, the reconstruction of damaged microvessels, and the proliferation of blood vessels.