Scientists have long believed that brain bleeds mainly happen when blood vessels become weak, damaged, or break apart.
These bleeds can be extremely dangerous because they damage brain tissue and increase the risk of memory loss, strokes, and other serious neurological problems.
But now, researchers from the University of California, Irvine, have discovered another possible cause of brain bleeding that does not begin with damaged blood vessels.
The new research suggests that old or damaged red blood cells themselves may trigger tiny brain bleeds, especially in aging brains. The findings could change the way scientists understand several brain diseases linked to aging, including Alzheimer’s disease, stroke, and high blood pressure-related brain damage.
The study was published in the Journal of Neuroinflammation and was led by Dr. Mark Fisher and Dr. Xiangmin Xu.
The researchers focused on a problem called cerebral microbleeds. These are tiny areas of bleeding in the brain that are often too small to notice immediately but can still harm brain tissue over time.
Cerebral microbleeds are commonly found in older adults and are linked to memory problems, dementia, strokes, and poor brain function.
Doctors have seen these microbleeds for years in brain scans, but scientists still do not fully understand why they happen. Traditionally, researchers believed the bleeding mainly occurred because blood vessel walls became fragile and leaked blood into nearby brain tissue.
However, the new study points to a different process that may also contribute to the problem.
To investigate this, the researchers carried out experiments using mice. They first created damaged red blood cells by exposing them to a chemical called tert-butyl hydroperoxide. This chemical creates oxidative stress, a harmful process that damages cells and is strongly linked to aging and disease.
Oxidative stress happens naturally in the body over time. It occurs when harmful molecules called free radicals build up faster than the body can remove them. Scientists believe oxidative stress plays a major role in aging, heart disease, cancer, and brain disorders like Alzheimer’s disease.
After damaging the red blood cells, the researchers attached glowing markers to the cells so they could track where they traveled inside the body. The cells were then injected into mice, and the scientists closely watched what happened inside the brain.
What they discovered surprised them.
The damaged red blood cells became trapped inside tiny brain blood vessels called capillaries. Capillaries are extremely small vessels responsible for delivering oxygen and nutrients to brain tissue.
Once the damaged cells became stuck, special immune cells in the brain called microglia moved toward them. Microglia act as the brain’s cleanup crew. Their job is to remove waste, dead cells, and harmful materials to help keep the brain healthy.
The microglia swallowed the damaged red blood cells in a process called phagocytosis. But during this process, bleeding appeared in the surrounding brain tissue.
This finding suggests that tiny brain bleeds may happen not only because blood vessels break but also because aging or damaged red blood cells interact with brain immune cells in unexpected ways.
The discovery could have major importance for understanding diseases linked to aging. Cerebral microbleeds are very common in people with Alzheimer’s disease, high blood pressure, and stroke-related brain damage. Scientists now think damaged blood cells and inflammation may play a bigger role in these diseases than previously understood.
The findings may also help explain why aging brains become more vulnerable to bleeding and injury over time. As people age, oxidative stress increases, and red blood cells may become more easily damaged. If these damaged cells collect in brain capillaries, they could trigger harmful immune responses and tiny bleeding events.
Even though cerebral microbleeds are small, they can build up over time and contribute to memory decline, confusion, difficulty thinking, and reduced brain function.
The researchers believe their work could eventually lead to new ways to protect the brain. If scientists can find methods to reduce oxidative stress, improve the removal of damaged red blood cells, or calm harmful immune responses in the brain, it may be possible to lower the risk of tiny brain bleeds before they occur.
The team plans to continue studying how the brain clears damaged blood cells and how this process may connect to other types of strokes and neurological diseases.
The research is still in its early stages, and much more work is needed before new treatments become available for patients. However, the findings open an important new direction in brain research and suggest that blood cells themselves may be more involved in brain disease than scientists once believed.
As researchers continue learning about the hidden causes of brain damage, discoveries like this may help create better ways to protect memory, brain function, and healthy aging in the future.
If you care about Alzheimer’s disease, please read studies that bad lifestyle habits can cause Alzheimer’s disease, and strawberries can be good defence against Alzheimer’s.
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