Study finds novel relationship between blood brain barrier, stroke

Stroke is the fourth leading cause of death in the United States. Fortunately, a recent study from UC Irvine provides new insights on the relationship of the blood brain barrier and stroke. Assistant professors Dr. Dritan Agalliu and Dr. Axel Nimmerjahn from Salk Institute collaborated on this study to observe the changes that occur in the brain during and after a stroke in living animals.

The blood brain barrier (BBB) functions as a cushion which separates circulating blood from entering the brain. It does however allow for water, particular gases and other soluble molecules to pass through. It is also one of the first areas to become severely damaged during a stroke. Damage to the BBB can often cause permanent deficits in cognition, as well as motor functions.

This study developed a novel mouse strain and used fluorescent tags to tag them in order to see the BBB junctions. The researchers discovered that the BBB becomes severely impaired after six hours after the onset of a stroke.

Interestingly, they also discovered that BBB failure was not due to the breakdown of the tight junctions as previously hypothesized. This breakdown actually didn’t occur until two days after the incident.

“Serum albumin is a large protein present in the blood. During BBB breakdown after stroke, albumin enters the brain to trigger an inflammatory response that exacerbates the disease,” Agalliu said in an email.

The study found that these proteins lead to the initial failure of the BBB, which then leads to the leaking of circulating blood in the brain immediately after a stroke.

“The goal of the research is to identify drugs that would block such pathways,” Agalliu said.

The research team is continuing to use genetic techniques to block degradation of the junctions in order to examine the effect on stroke progression.

“This is an early study that brings people from various backgrounds to visualize the potential effects of regulating the carrier proteins,” Nimmerjahn said in an email.

Although research is ongoing to find more effective treatments for stroke patients, current therapies do exist. According to Elisabeth D’Angelo, a doctoral candidate in the human development program at UC Davis, lecturer and speech-language pathologist, early administration of tissue plasminogen activator (tPA), a protein which aides in the breaking down of clots, can be helpful.

This is a viable treatment for only ischemic strokes, which are caused by an obstruction within a blood vessel that supplies blood to the brain. Another caveat is that the injection must be made within no more than 3 to 4.5 hours of the stroke to effectively break up the clots.

Since 80 percent of strokes are preventable, it is important to be mindful of healthy life strategies.

“Prevention involves healthy lifestyle choices, including not smoking, physical activity and healthy weight. Taking anti-hypertensive and anti-coagulants if needed is also good prevention,” D’Angelo said.

Anti-hypertensive drugs are often used to control blood pressure. Anti-coagulants drugs help to thin blood. Medical research and treatments along with therapies continue to be hopeful avenues for stroke patients and their families.

JASBIR KAUR can be reached at science@theaggie.org.

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