The Aging Brain and the Role of Blood
A blood-borne immune factor present in elderly mice contributes to signs of mental decline when injected into young mice. By inhibiting this blood-born immune factor, youthfulness is restored in old mice, implying that it may be possible to change some of the symptoms of aging in the brain by altering the levels of immune factors in the blood.
The hippocampus, an important sea-horse shaped component of the brain that plays a role in memory, spatial memory, and navigation, loses function and ceases to produce new neurons as it ages. Though this deterioration can be partially reversed when animals regularly exercise thereby stimulating circulation and releasing chemicals and metabolites into the blood, Tony Wyss-Coray of Stanford University School of Medicine wondered if there was a blood-borne element that might contribute to these changes.
Published in August 31, 2011 in Nature, his study implies that it may be possible to change some of the aging symptoms of the brain by altering the levels of immune factors in the blood.
By stitching the flank of a young mouse to the flank of an old one, Wyss-Coray and colleagues formed a conjoined-twin effect, allowing the blood of both mice to mingle. They found that the young animals showed a decline in neurogenesis while the old ones showed new growth as compared to young and old stitched to partners of similar age.
"There seemed to be rejuvenation in the old brain," said Wyss-Coray.
So the researchers extracted only blood plasma devoid of the cells of old mice and injected into the young mice. They saw a similar decline in neurogenesis. It appeared as though an extracellular blood protein was responsible. These mice were then administered a battery of memory tests and mazes. The mice with old blood plasma did not form as robust memories and did not remember the solution to a maze as well as normal young mice--similar impairments found in old mice.
In order to identify the element in the plasma that caused this effect, comparisons were made on the concentrations of blood proteins in the conjoined animal; of six candidate proteins whose levels that changed after the mice were stitched together, CCL11 or eotaxin, a chemokine, demonstrated the most significant change.
"The factor [CCL11] is a surprising character," said Richard Ransohoff from the Cleveland Clinic Lerner College of Medicine. "It's a chemokine that has zero prior neurobiology," he added. Known only for its role in attracting eosinophils or immune cells that play a major role in allergy and asthma, when the researchers injected this chemokine into young mice, a decrease in new neuron formation was observed. This effect was then reversed with an injection of a CCL11-blocking antibody! Observing too how CCL11 fluctuates with age, Wyss-Coray and researchers saw that its blood-levels elevated in mice and in humans with age.
Wyss-Coray agrees that this study opens a floodgate of new questions. But he's encouraged by the possibilities. For example, "if we could rejuvenate or maintain the brain in general," he said, it might delay some of the detrimental effects that cause dementia or Alzheimer's.
References:
S. A. Villeda et al., "The ageing systemic milieu negatively regulates neurogenesis and cognitive function," Nature, 477:90-96, doi:10.1038/nature10357, 2011.
Comments
Recent study showed that diet which is containing 3 fatty acids (found mainly in fish) can stop brain shrinking.
The positive effects of vitamin B, C, D and E with harmful effects of trans fats (which are common in processed foods, including cakes, biscuits and fried foods) about brain shrinkage typical of Alzheimer's emphasized in this work.
Source: http://www.bbc.co.uk/news/health-16344228
Greetings
Murat
www.kulakburunbogaz.info
Posted by: Murat | December 31, 2011 6:39 AM
It's good to see ongoing research in this area. Some days I feel I was born too soon to benefit from all the great medical advances that are being researched.
Posted by: Marie at AgingBodies | January 5, 2012 4:51 PM