Discovery could lead to tests for the clinic or battlefield to diagnose ailments with just a few drops of blood

Oct 17 2005

A way to detect fragments of broken brain cells that leak into the bloodstream may help doctors more quickly and precisely treat people with severe head injuries or brain diseases, say researchers at the University of Florida's McKnight Brain Institute.

UF scientists have discovered they can use an approach similar to one commonly used in HIV or pregnancy testing to find bits of axons - nerve fibers that help brain cells communicate - in the blood and spinal fluid of laboratory rats modeling human spinal cord or traumatic brain injuries.

The discovery could lead to tests for the clinic or battlefield to diagnose ailments with just a few drops of blood, bypassing cumbersome and expensive CT or MRI brain scanning equipment. The researchers report their findings in the current online edition of Biochemical and Biophysical Research Communications.

The cellular debris, derived from a protein called NF-H, was not found in the blood or other fluids of healthy animals and humans. That leads researchers to believe it is a biomarker, a substance in blood that signals the presence of disease or injury.

"We could easily see that this particular protein is detectable very soon after a disease starts or an injury occurs," said Gerry Shaw, Ph.D., a professor of neuroscience in the College of Medicine. "A lot more of it is then released in the two or three days following a brain or spinal cord injury, which is interesting because it signals a kind of brain cell death that you could potentially do something about therapeutically."

The test would be helpful in emergency rooms or in combat situations if it could be developed into a simple handheld device that could confirm brain or spinal injury.

"Shaken-soldier syndrome is a traumatic brain injury that shows in veterans who have survived roadside blasts," said Douglas Anderson, Ph.D., chairman of neuroscience at the McKnight Brain Institute who participated in the research. "In patients who are unconscious but with no penetrating head wounds, it would be extremely helpful for emergency medical technicians to test for a marker to see how severe the injuries are. Then perhaps something can be done early on."

Shaw, who, along with UF, has interest in a company to market the biotechnology, said studies already under way will seek to determine whether the protein is detectable in people who have had strokes or who suffer from amyotrophic lateral sclerosis, a debilitating disorder frequently referred to as ALS or Lou Gehrig's disease. Further studies will evaluate patients suffering from Alzheimer's disease and other serious damage and disease states of the nervous system.

Drug researchers can already use the technique to monitor the effectiveness of experimental medicines in animal models of stroke and traumatic brain injury.

"This may become an important clinical marker, but it's also important in terms of experimental work for basic scientists," said Dena Howland, Ph.D., an assistant professor of neuroscience at UF who investigates therapies for spinal cord repair and another of the paper's authors. "It's a way for us to assess whether our interventions are working."

Investigators detect the NF-H protein with a widely used screening method called an ELISA, short for enzyme-linked immunosorbent assay. Versions of it are used to test women for pregnancy and screen patients for HIV. It uses components of the immune system called antibodies, which have a natural affinity to latch onto certain compounds.

In this case, Shaw developed antibodies that react positively to the presence of NF-H. The structure of the molecule lends itself to easy detection, because it contains protein sequences that are repeated dozens of times, each of which can be bound by a detection antibody, increasing the sensitivity of the test. Other potential biomarkers may be identifiable by only one short, non-repeating sequence, making the task more difficult.

"NF-H is a very stable protein; one that does not degrade easily," said Jean-Pierre Julien, Canada research chair in the mechanisms of neurodegeneration at the Université Laval in Quebec, who was not connected with the UF study. "It makes sense that when there is damage to axons this protein would be released and would be detectable."

The next step is for researchers to determine whether the release of NF-H is a universal characteristic of all brain injury and disease.

If so, scientists hope the test will give early warning of disorders such as ALS, Parkinson's disease and Alzheimer's disease, which do much damage before actual symptoms appear in patients.