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Amyloid plaques consist of deposits of aluminum silicate and amyloid peptides in nervous tissue. The sticky plaque builds up around nerve cells in the brain and disrupts normal brain activity. Amyloid plaques are associated with several diseases, including Creutzfeldt-Jakob disease, but are most commonly associated with Alzheimer's disease. Along with neurofibrillary tangles, amyloid plaques are considered to be a major contributor to the symptoms of Alzheimer's disease.
This type of plague is one of the two brain abnormalities most commonly associated with Alzheimer's disease. The presence of amyloid plaques and neurofibrillary tangles typically is required to confirm an Alzheimer's diagnosis. In fact, the presence of amyloid plaques often precede the behavioral symptoms Alzheimer's patients experience.
Amyloid plaques are located on the outside of neurons, while neurofibrillary tangles are located on the inside of them. Both actually can be found in the brains of people who don't have Alzheimer's, however. It's not their presence that is the issue, rather it is the sheer number of them that creates problems.
Amyloid is a protein. It's normally found throughout the body. In people with Alzheimer's disease, the amyloid protein improperly divides. It creates a form that is referred to as beta amyloid. This beta amyloid is toxic to the neurons that are in the brain.
Beta amyloids have also been known to form tiny holes in neuron membranes. This causes an influx of calcium to enter. Too much calcium kills neurons. Due to these degenerating neurons, plaque begins to form. The body cannot properly break down the plaque, so it begins to build up in the brain.
The gene ApoE4, often referred to as the "Alzheimer's gene," is a genetic abnormality that has been solidly linked to the risk of developing Alzheimer's disease. Scientists now think that it may be involved in the formation of amyloid plaques. It's thought that the ApoE4 gene produces protein that latches onto the beta amyloid. This then makes it even harder for the body to dissolve it, allowing more plaque to accumulate around the brain.
Molecules called free radicals play a role in the damage that leads to Alzheimer's as well. Some studies have suggested that the damage caused by oxidation and inflammation not only comes from the build-up of amyloid plaques, but may actually be preceded by damage caused by free radicals. Though scientists know that the amyloid beta proteins that make up the plaque are capable of producing free radicals and causing other healthy cells to do so, some studies are now suggesting that free radicals may be causing damage even before the plaque starts building up.