Brain bleeding after stroke may be healed by immune cells

A study funded by the National Institutes of Health suggests that immune cells called neutrophils play a critical role in protecting the brain after a stroke.


Intracerebral hemorrhages account for 10 to 15 percent of all strokes, and occur when blood vessels rupture and leak blood into the brain.
Researchers conducted tests on mice and found that instead of attacking germs, certain neurtrophils help the brain heal after an intracerebral hemorrhage.

“Intracerebral hemorrhage is a damaging and often fatal form of stroke for which there are no effective medicines,” Dr. Jaroslaw Aronowski, professor in the department of neurology, at the University of Texas Health Science Center at Houston, said in a press release. “Our results are a hopeful first step towards developing a treatment for this devastating form of stroke.”

Prior research showed that neutrophils can potentially harm and heal the brain as they are the first immune cells to respond to a hemorrhage.

For this study, researchers found that a protein that controls the activity of immune cells, known as interleukin-27, or IL-27, can alter the role of neutrophils from harming to helping the brain recover from a stroke.

Experiments showed that after a hemorrhagic stroke, the brain secretes high levels of IL-27, leading to a second release of neutrophils with granules filled with higher amounts of healing molecules.

Researchers found that IL-27 levels increased in the brain and blood of mice an hour after hemorrhage and stayed elevated for up to three days. IL-27 molecules travel to the bones of the mice in the experiments and infiltrated their bone marrow, changing the role newborn neutrophils play in response to a stroke.

“Our results suggested that IL-27 links the brain to the bones,” Aronowski said. “We can use these results as a source for ideas for developing potential treatments for hemorrhagic stroke.”

Researchers also discovered that the iron building protein lactoferrin can protect the brain from intracerebral hemorrhagic strokes. Rodents injected with lactoferrin 30 minutes after hemorrhages recovered faster and had less brain damage as a result.

By Amy Wallace