A team of scientists from the University of California, Irvine has discovered a surprising new clue about how some brain hemorrhages may begin.
For many years, doctors believed that bleeding inside the brain was mainly caused by weak, damaged, or broken blood vessels. The new study suggests that this is not always the full story.
In some cases, the first step toward bleeding may begin with old and damaged red blood cells instead of injured blood vessels. This discovery gives researchers a fresh way to think about brain health and could lead to better ways to prevent serious brain diseases in the future.
A brain hemorrhage happens when blood leaks into the brain. The leaked blood can damage nearby brain cells because brain tissue is very delicate.
Depending on where the bleeding occurs, a person may suddenly develop a severe headache, weakness, confusion, trouble speaking, vision problems, or difficulty walking. Large brain hemorrhages can be life-threatening and need emergency medical care. Even very small areas of bleeding can become important if they happen many times over many years.
Doctors already know that high blood pressure, head injuries, certain medicines that affect blood clotting, and diseases that weaken blood vessels can increase the risk of brain bleeding. Tiny areas of bleeding, called cerebral microbleeds, are often found in older adults and in people living with stroke or Alzheimer’s disease.
Until now, these small bleeds were generally believed to happen because blood vessels became weak with age or disease. The new findings suggest that aging red blood cells may also play an important part.
The research was led by Dr. Mark Fisher and Dr. Xiangmin Xu. The scientists wanted to understand what happens when aging red blood cells travel through the smallest blood vessels in the brain, called capillaries. These tiny vessels are so narrow that red blood cells often have to squeeze through them one at a time.
Red blood cells are best known for carrying oxygen from the lungs to every part of the body. They are made to be soft and flexible so they can move through very small blood vessels. As these cells grow older, however, they slowly become weaker and less flexible. They can also be damaged by normal chemical changes that happen inside the body over time.
To study this process, the researchers created older-looking red blood cells in the laboratory. They treated healthy red blood cells with a chemical called tert-butyl hydroperoxide, which causes a type of damage known as oxidative stress.
Oxidative stress is a natural process that increases with aging and many diseases. The scientists then attached a glowing marker to the damaged blood cells so they could follow the cells inside the brain with powerful microscopes.
The marked red blood cells were injected into mice, allowing the research team to watch exactly what happened as the cells moved through the brain. The scientists expected the cells to continue flowing through the capillaries. Instead, they made an unexpected discovery.
Some of the older red blood cells became trapped inside the tiny capillaries instead of passing through them. These trapped cells blocked normal blood flow.
Soon afterward, special immune cells in the brain called microglia surrounded and removed the stuck blood cells. Microglia normally help keep the brain healthy by clearing away damaged cells and other waste. They are an important part of the brain’s natural cleaning system.
During this cleaning process, however, the scientists observed that tiny amounts of blood leaked into nearby brain tissue. These small leaks formed cerebral microbleeds. This suggested that the act of clearing trapped, damaged red blood cells may itself help trigger tiny brain hemorrhages.
The findings are important because cerebral microbleeds have been linked with memory problems, thinking changes, stroke, and Alzheimer’s disease. If damaged red blood cells can help start these tiny bleeds, future treatments may need to focus on keeping blood cells healthy as well as protecting blood vessels.
Dr. Fisher explained that understanding this newly discovered process could change the way scientists study brain diseases. Instead of looking only at blood vessel damage, researchers may also need to study how aging blood cells behave inside the brain.
This new idea could eventually help doctors find better ways to lower the risk of brain bleeding, especially in older adults or people whose red blood cells are easily damaged.
The researchers plan to continue studying how the brain removes damaged blood cells and whether this process also plays a role in different types of stroke and other brain disorders. As people age, both blood vessels and blood cells change.
Understanding how these changes work together may help scientists develop new treatments that protect memory, thinking, and movement later in life.
Although more research is still needed before these findings can be applied to patients, the study offers an important new direction for brain research. It reminds us that even very small cells can have a major effect on health.
By learning more about how aging red blood cells interact with tiny brain blood vessels, scientists hope to reduce the risk of brain hemorrhages and improve the lives of millions of people around the world.
If you care about stroke, please read studies about how to eat to prevent stroke, and diets high in flavonoids could help reduce stroke risk.
For more health information, please see recent studies about how Mediterranean diet could protect your brain health, and wild blueberries can benefit your heart and brain.
The full study was published in the Journal of Neuroinflammation.
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