Neurofibrillary tangles and amyloid plaques are hallmark features of Alzheimer’s disease. Neurofibrillary tangles consist of microtubules and tau proteins, which become deformed and disrupt transport networks. There is no cure for Alzheimer’s, but drugs can slow the disease’s progression.
Neurofibrillary tangles are found within the brain cells of people with Alzheimer’s disease. They are one of the hallmark features of Alzheimer’s, along with accumulations of proteins known as amyloid plaques. At the microscopic level, a neurofibrillary tangle is seen to consist of a bundle of thread-like structures called microtubules. These are tangled together with proteins known as tau proteins. Tau proteins and microtubules are normally found inside brain cells, but in people without Alzheimer’s disease most microtubules are parallel to each other and tau proteins link them together in an orderly fashion.
Alzheimer’s disease is the most frequent cause of dementia, where there is a slow decline in brain function. It is a common disease, affecting millions of people around the world and there is no cure. The brains of people with Alzheimer’s appear smaller than those of healthy individuals, and the spaces, or ventricles, within the brain are larger. Within the nerve cells of the brain, the classic sign of Alzheimer’s is the presence of neurofibrillary tangles and amyloid plaques, or senile plaques. Senile plaques are made up of a set of proteins found outside the nerve cells of the brain, and although they exist in healthy older adults, they are found in much greater numbers in Alzheimer’s patients.
Inside a healthy nerve cell in the brain, microtubules are arranged in straight rows. They serve as a structural framework for the cell, as well as a transport network along which substances can pass. Tau proteins are part of the connecting structures that hold microtubules together.
In Alzheimer’s disease, tau proteins become deformed and can no longer help support the orderly arrangement of microtubules, resulting in disrupted transport networks. Nerve cells may no longer communicate effectively, and it is thought that the inability to transport substances may also contribute to their death later in the disease. It is possible to see neurofibrillary tangles in the brain of a person without Alzheimer’s because they occur in healthy individuals, but in far fewer numbers.
Since cells normally have efficient mechanisms for clearing out defective proteins, it is not known why in Alzheimer’s disease the brain cell lacks the misshapen tau proteins found within a neurofibrillary tangle. Ongoing research into the function of various proteins involved in removing damaged tau could help develop a cure for Alzheimer’s in the future. There are currently no treatments that can eradicate senile plaques and neurofibrillary tangles, but there are drugs available that can slow the progression of the disease for some people.
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