Newswise, March 18, 2016--A new study published in Physiological
Genomics suggests that the brain shows signs of aging earlier than old
age. The study found that the microglia cells—the immune cells of the brain—in
middle-aged mice already showed altered activity seen in microglia from older
mice.
Parkinson’s, Alzheimer’s and other aging-related
neurodegenerative disorders are associated with excessive inflammation in the
brain. Scientists believe that overactive microglia cells contribute to the
excess inflammation. Normally, microglia protect the brain from infection and
ensure the brain functions properly. Their immune response is tightly
controlled.
Microglia produce pro-inflammatory molecules to turn the
inflammation process on, followed by anti-inflammatory molecules to turn
inflammation off. With aging, microglial cells can overreact, and their immune
activity can become less controlled—they turn inflammation on too quickly or
turn it off too slowly. The prolonged or constant inflammation that results can
damage the brain.
While it is known that microglia immune activity changes with
aging, which response is affected first—the pro-inflammatory or the
anti-inflammatory—or, more importantly, when microglial aging begins is not
clear, says Jyoti Watters of the University of Wisconsin-Madison and lead
investigator of the study. “We show in a mouse model that it may begin earlier
than we thought,” Watters says.
The research team at the University of Wisconsin-Madison
studied the microglia activity of young (two months old) and middle-aged (nine
to 10 months old) mice. The researchers injected the mice with lipopolysaccharide,
a molecule found in bacteria that strongly activates the immune system and
causes inflammation. The mice were injected twice to assess the microglia’s
ability to reset their immune activity and respond to another bout of
inflammation.
The researchers found that middle-aged mice displayed
exaggerated pro-inflammatory responses after the first injection. However,
anti-inflammatory responses were normal. After the second injection, both
pro-inflammatory and anti-inflammatory responses were normal.
The data suggest that at middle age, the microglia already
showed signs of an altered immune response. But not everything is impaired: The
microglia of the middle-aged mice still responded normally to the second
injection.
“At this time, age-related alterations may only be beginning
since other critical capacities have not begun to deteriorate yet,” according
to Watters. “Of course, it is not known when aging-associated changes in
microglial activities begin in the human brain, but these results in mice suggest
that it may be earlier than we had previously appreciated,” Watters says.
The article “Age-dependent differences in microglial responses
to systemic inflammation are evident as early as middle age” is published ahead-of-print in Physiological
Genomics.
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About the American Physiological Society
Physiology is the study of how molecules, cells, tissues and organs function in health and disease. Established in 1887, the American Physiological Society (APS) was the first U.S. society in the biomedical sciences field. The Society represents more than 10,000 members and publishes 15 peer-reviewed journals with a worldwide readership.
Physiology is the study of how molecules, cells, tissues and organs function in health and disease. Established in 1887, the American Physiological Society (APS) was the first U.S. society in the biomedical sciences field. The Society represents more than 10,000 members and publishes 15 peer-reviewed journals with a worldwide readership.
