Stress hormone could trigger mechanism for the onset of Alzheimer's

June 21, 2013 by Preston Moretz, Temple University

(Medical Xpress)—A chemical hormone released in the body as a reaction to stress could be a key trigger of the mechanism for the late onset of Alzheimer's disease, according to a study by researchers at Temple University.

Previous studies have shown that the chemical hormone , which is released into the body's blood as a , is found at levels two to three times higher in Alzheimer's patients than non-Alzheimer's patients.

"Stress is an that looks like it may play a very important role in the onset of Alzheimer's disease," said Domenico Praticò, professor of pharmacology and microbiology and immunology in Temple's School of Medicine, who led the study. "When the levels of corticosteroid are too high for too long, they can damage or cause the death of , which are very important for learning and memory."

In their study, "Knockout of 5-lipoxygenase prevents -induced tau pathology in 3xTg mice," published in the journal Aging Cell, the Temple researchers set up a series of experiments to examine the mechanisms by which stress can be responsible for the Alzheimer's pathology in the brain.

Using triple , which develop amyloid beta and the tau protein, two major signatures for Alzheimer's, the Temple researchers injected one group with high levels of corticosteroid each day for a week in order to mimic stress

While they found no significant difference in the mice's memory ability at the end of the week, they did find that the tau protein was significantly increased in the group that received the corticosteroid. In addition, they found that the synapses, which allow neuronal cells to communicate and play a key role in , were either damaged or destroyed.

"This was surprising because we didn't see any significant , but the pathology for memory and learning impairment was definitely visible," said Pratico. "So we believe we have identified the earliest type of damage that precedes memory deficit in Alzheimer's patients."

Pratico said another surprising outcome was that a third group of mice that were genetically altered to be devoid of the brain enzyme 5-lipoxygenase appeared to be immune and showed no neuronal damage from the corticosteroid.

In previous studies, Pratico and his team have shown that elevated levels of 5-lipoxygenase cause an increase in tau protein levels in regions of the brain controlling memory and cognition, disrupting neuronal communications and contributing to Alzheimer's disease. It also increases the levels of amyloid beta, which is thought to be the cause for neuronal death and forms plaques in the brain.

Pratico said the corticosteroid causes the 5-lipoxygenase to over-express and increase its levels, which in turn increases the levels of the and amyloid beta.

"The question has always been what up-regulates or increases 5-lipoxygenase, and now we have evidence that it is the stress hormone," he said. "We have identified a mechanism by which the risk factor—having high levels of corticosteroid—could put you at risk for the disease.

"Corticosteroid uses the 5-lipoxygenase as a mechanism to damage the synapse, which results in memory and learning impairment, both key symptoms for Alzheimer's," said Pratico. "So that is strong support for the hypothesis that if you block 5-lipoxygenase, you can probably block the negative effects of corticosteroid in the brain."

Explore further: Protein in the brain could be a key target in controlling Alzheimer's

More information: onlinelibrary.wiley.com/doi/10 … /acel.12096/abstract

Related Stories

Protein in the brain could be a key target in controlling Alzheimer's

January 25, 2012
A protein recently discovered in the brain could play a key role in regulating the creation of amyloid beta, the major component of plaques implicated in the development of Alzheimer's disease, according to researchers at ...

New Alzheimer's research suggests possible cause: The interaction of proteins in the brain

June 19, 2013
For years, Alzheimer's researchers have focused on two proteins that accumulate in the brains of people with Alzheimer's and may contribute to the disease: plaques made up of the protein amyloid-beta, and tangles of another ...

Understanding the molecular mechanisms underlying Alzheimer's disease

June 10, 2013
The accumulation of amyloid-β (Aβ) in the brains of Alzheimer's disease (AD) patients is known to be associated with memory loss and neuronal degeneration, but the mechanism of Aβ pathogenesis is not fully understood.

Blocking overactive receptor in Alzheimer's recovers memory loss and more

June 17, 2013
A new study shows that memory pathology in older mice with Alzheimer's disease can be reversed with treatment. The study by researchers from the Montreal Neurological Institute and Hospital - The Neuro, at McGill University ...

Recommended for you

Pregnancy history may be tied to Alzheimer's disease

July 18, 2018
A woman's history of pregnancy may affect her risk of Alzheimer's disease decades later, according to a study published in the July 18, 2018, online issue of Neurology, the medical journal of the American Academy of Neurology. ...

Molecular tracer, seen with PET scan, shows concentrations of abnormal proteins

July 17, 2018
In a small study of military personnel who had suffered head trauma and had reported memory and mood problems, UCLA researchers found brain changes similar to those seen in retired football players with suspected chronic ...

Yale-developed test for Alzheimer's disease directly measures synaptic loss

July 16, 2018
Yale researchers have tested a new method for directly measuring synaptic loss in individuals with Alzheimer's disease. The method, which uses PET imaging technology to scan for a specific protein in the brain linked to synapses, ...

New study highlights Alzheimer's herpes link, experts say

July 12, 2018
A new commentary by scientists at the Universities of Manchester and Edinburgh on a study by Taiwanese epidemiologists supports the viability of a potential way to reduce the risk of Alzheimer's disease.

Practice imperfect—repeated cognitive testing can obscure early signs of dementia

July 12, 2018
Alzheimer's disease (AD) is a progressive, neurodegenerative condition that often begins with mild cognitive impairment or MCI, making early and repeated assessments of cognitive change crucial to diagnosis and treatment.

The 'Big Bang' of Alzheimer's: Scientists ID genesis of disease, focus efforts on shape-shifting tau

July 10, 2018
Scientists have discovered a "Big Bang" of Alzheimer's disease – the precise point at which a healthy protein becomes toxic but has not yet formed deadly tangles in the brain.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.