The initial forgetfulness and eventual bizarre behavior that typify Alzheimer's disease may be caused by brain cells that commit suicide by a built-in killer molecule.
That discovery by scientists in California may help clarify work under way that seeks to explain why the brain cells -- or neurons -- die in Alzheimer's patients.
"What we found is the first example of a hit man in your neurons," said Dr. Dale Bredesen, a neurobiologist at the University of California at Los Angeles.
"This is an unusual phenomenon, and we're excited about it because it explains a lot of things that we didn't understand before," he said. "The neurons that are affected earliest and most severely in Alzheimer's appear to be those that contribute to the confusion and forgetfulness."
Dr. Bredesen, working with a team at UCLA and the Stanford Research Institute, writes in today's edition of the journal Science that neurons in the cerebral cortex, where memory and learning occur, tend to be those most likely to commit suicide.
Researchers working on the project say the suicide molecule first becomes active long before birth, during life's embryonic stage. It is needed by a vast range of tissues during the embryonic period, as a signal for the cells to stop growing before birth.
In the adult brain, these molecules apparently switch on again -- and kill the cell -- when they detect the absence of a vital neurochemical called nerve growth factor, or NGF. The amount of NGF in the brain declines with age; in Alzheimer's patients, it virtually disappears.