Paradoxical Alzheimer's finding linking memory loss

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Do you remember the seventh song that played on your radio on the way to work yesterday? Most of us dont, thanks to a normal forgetting process that is constantly cleaning house culling inconsequential information from our brains. Scientists at the Buck Institute now think that this normal memory loss is hyper-activated in Alzheimers disease (AD) and that this effect is key to the profound memory loss linked to the incurable neurodegenerative disorder.

Last year, this same group of scientists observed that they could completely prevent Alzheimers disease in mice genetically engineered with a human Alzheimers geneMouzheimersby blocking a single site of cleavage of one molecule, called APP for amyloid precursor protein. Normally, this site on APP is attacked by molecular scissors called caspases, but blocking that process prevented the disease. Now they have studied human brain tissue and observed that, just as expected, patients suffering from AD clearly show more of this cleavage process than people of the same age who do not have the disease. However, when they extended their studies to much younger people without Alzheimers disease, they were astonished to find an apparent paradox: these younger people displayed as much as ten times the amount of the same cleavage event as the AD patients. The scientists now believe they know why.

The Buck Institute study implicates a biochemical switch linked to that cleavage of APP, causing AD brains to become stuck in the process of breaking memories, and points to AD as a syndrome affecting the plasticity or malleability of the brain. The study, due would be reported in the March 7 issue of the Journal of Alzheimers Disease, provides new insight into a molecular event resulting in decreased brain plasticity, a central feature of AD.

Young brains operate like Ferraris shifting between forward and reverse, making and breaking memories with a facility that surpasses that of older brains, which are less plastic, said Dale Bredesen, MD, Buck Institute faculty member and leader of the research group. We think that in aging brains, AD occurs when the molecular shifting switch gets stuck in the reverse position, throwing the balance of making and breaking memories seriously off kilter.

In prior research, lead author Veronica Galvan, PhD, prevented this cleavage in mice genetically engineered to develop the amyloid plaques and deposits linked to AD. These surprising mice had normal memories and showed no signs of brain shrinkage or nerve cell damage, despite the fact that their brains were loaded with the sticky A-beta plaques that are otherwise linked to Alzheimers disease.

A-beta is produced throughout the brain throughout life; we think that it is a normal regulator of the synapses, the connections between neurons, said Galvan, who added that AD, like cancer, is a disease in which imbalanced cell signaling plays an important role.

The fact that a number of people develop A-beta plaques yet show no symptoms of AD tells us that the downstream signaling of A-betanot just A-beta itselfis critical, said Bredesen, and these pathways can be targeted therapeutically. Simply put, we can restore the balance. Continuing research at the Buck Institute focuses on nerve signaling and efforts to disconnect the molecular mechanism that throws memory-making in the reverse direction, as well as understanding mechanisms that support brain cell connections that are crucial to the process of memory making.


Posted by: Daniel    Source