What Is a Beta Amyloid?

-amyloid -protein (A) has a molecular weight of about 4 kDa, is hydrolyzed from -amyloid precursor protein (APP), is secreted by cells, and has a strong strength after the cell matrix precipitates and accumulates. Neurotoxic effects.

beta-amyloid

Under normal physiological conditions,

Neurotoxicity of A The neurotoxicity of A plays a major role in the progression of Alzheimer's disease. In 1991, Kowall et al. Injected A into the cerebral cortex of rats or monkeys and found that tissue necrosis, loss of peripheral neurons and neurokeratosis occurred at the injection site, and there was a significant correlation with the dose. The toxic effect of A on the nervous system is that amyloidosis of the blood vessel wall directly leads to vascular sclerosis, poor elasticity, even rupture or formation of thrombus, and induces premature apoptosis of nerve cells. Animal experiments have shown that the effect of A on neurons is related to its state. Dissolved A can promote neurite growth and improve the survival rate of neurons in a short time, while deposited A has opposite effects on neurons, causing pathological changes similar to Alzheimer's disease --- neurites Withdrawal and neuronal degeneration, the most significant changes occur in the aging mammalian brain ^[1] .

Effects on vascular morphology and vascular function A is first deposited on the basement membrane of the outer layer of blood vessels, and then infiltrates into the smooth muscle cell layer. A deposition reduces the adhesion of arterial smooth muscle cells to the basement membrane, the middle layer of blood vessels is replaced by A, and smooth muscle cells degenerate. Vinters et al. And Yamaguchi et al. Found that A was deposited in the basement membrane of capillaries and protruded into the nerve felt in a plate shape. Capillary A40 / A42 ratio is significantly smaller than arteries. Therefore, A40 is mainly deposited on the arterial wall, while A42 is deposited on the capillaries. A promotes the deposition of fibers around blood vessels, leading to amyloid angiopathy. The possible mechanism has the following two points ^[1] .

Decreasing the expression of fibroblast growth factor 2 A acts on vascular endothelial cells via the fibroblast growth factors 2 pathway through the autocrine / paracrine pathway. A blocks the effect of the FGF-2 axis by interacting with the cell membrane receptors of FGF-2. The point mutation of APP caused a mutation in amino acids 21 to 23 of A. These mutants are closely related to the different genetic phenotypes of amyloid angiopathy, the degree of cerebral vascular tropism, the remodeling of damaged microvessels, and angiogenesis ^[1] .