A new target in fight against dementia
The body’s immune system can turn against itself: What evolved as a protective mechanism can, under different circumstances, actually cause harm.
Scientists have discovered that there is, in fact, something in the brain that plays an immensely important protective and beneficial role but can also, under certain circumstances, cause damage — and they have linked it, possibly, to Alzheimer’s.
This new culprit in the search for the cause of Alzheimer’s is astrocytes. These star-shaped cells (hence their name) constitute an essential part of the central nervous system and are the most abundant cells in the brain.
They perform a number of important functions, including:
—creating and maintaining synapses (links between brain cells),
—serving as gatekeepers of the blood-brain barrier (which prevents toxins and other harmful elements from entering the brain through the blood supply),
—maintaining chemical balance,
—producing antioxidants (to counteract oxidative stress), and
—controlling immune system responses to injury in the central nervous system.
Astrocytes also release chemicals into the brain that are associated with memory and learning and the establishment of new connections between brain cells.
The role of glutamate
One of the key functions of astrocytes is the control of the amount of glutamate around brain cells. Glutamate is a chemical that excites brain cells into communicating with each other.
Too much glutamate and excessive excitation can be harmful to the brain cells, and it is the job of the astrocytes to keep glutamate at the right level and convert the excess glutamate to glutamine.
When amyloid-B plaques accumulate in the brains of Alzheimer’s patients, an inflammatory response is triggered. The inflammation causes the astrocytes to clear the amyloid plaques from the brain.
In the process of reacting to the buildup of amyloid plaques, the astrocytes undergo various changes.
One of these changes is that the astrocytes become less efficient at controlling the amount of glutamate around the brain cells.
What is more damaging, the amyloid plaques can actually cause the astrocytes to release glutamate that they had already taken in for reprocessing into glutamine.
High levels of glutamate surrounding the brain cells cause overactivation of the cells, and this results in cell damage and even cell death.
It is this damage and death of brain cells that is responsible for the memory loss and other cognitive impairments experienced by Alzheimer’s patients.
Researchers are now looking into the possibility of developing drugs that will target astrocytes — and, in particular, their mechanisms for controlling glutamate levels.
Of the more than 1,000 drugs approved by the FDA, more than 20 have been shown to be effective in stimulating the astrocyte mechanism to control glutamate levels.
This is a new approach to the treatment of Alzheimer’s. It shifts the focus away from the amyloid plaques and tau tangles to astrocytes.
Early findings of this approach look extremely promising.
Veena J. Alfred, Ph.D., is a certified dementia practitioner and CEO/Administrator of AlfredHouse.