A Stroke of Luck: Vampire Bat Spit May Yield New Stroke Treatment

By Ellen Kuwana Neuroscience for Kids Staff Writer January 29, 2003 Nature is just enough; but men and women must comprehend and accept her suggestions. -- Antoinette Brown Blackwell (1825 - 1921) Nature does nothing uselessly. -- Aristotle (384 BC - 322 BC) The small vampire bat is proving these quotations correct. The bat's saliva contains an enzyme that allows it to feed on blood without the blood clotting. (Vampire bats feed most often on birds, cattle, horses and pigs.) Researchers hope to use this enzyme to break up clots in blood vessels. Treatments using this enzyme have the potential to help people who suffer from blood clotting disorders or strokes. The enzyme in bat saliva is called DSPA (or "desmodus rotundus salivary plasminogen activator," if you want to impress your friends). It is similar to an enzyme called t-PA (tissue plasminogen activator) that is used currently to treat strokes. In new experiments, researchers used mice with brain damage similar to that caused by a stroke. Some of the mice were injected with DSPA; other mice received injections of t-PA. The mice were then studied to determine which treatment caused the least amount of further brain damage and had the greatest effect in reducing the amount of brain damage that had already occurred. The data showed that the DSPA-treated mice had fewer damaged neurons than the mice that received t-PA. These results suggest that DSPA may offer some advantages over t-PA in the treatment of stroke victims: less bleeding: DSPA seems to cause less bleeding in the brain as it dissolves the clot. One study showed that t-PA caused some bleeding in 6% of patients who received it. DSPA may work better because it is active only when a clot is present. It works by targeting one component of the blood clot, a protein called fibrin. Fibrin forms the scaffold or structure of the clot. timing: t-PA must be given within the first few hours after a stroke. Unfortunately, the quick administration of t-PA within these first few hours occurs in fewer than 5% of stroke patients. If patients do not arrive at the hospital quickly or if they are being evaluated during that critical time when t-PA should be given, t-PA may not be given soon enough to be effective. T-PA is usually not given after the three hour mark because the damage caused by it may be greater than its benefits. Further research is required to determine if the conclusions from the mice studies hold true for humans. Currently, two studies are underway to assess whether stroke patients can benefit from DSPA administered up to 9 hours after a stroke. The results of these studies could be available as soon as the end of 2003. Clotting disorders and strokes are serious health concerns to humans because uncontrolled bleeding can lead to death. The term clotting refers to a process by which your body sends specialized cells called platelets to the site of the injury. Platelets accumulate and form connections with each other to seal the vessel that is bleeding. Once the damage to the blood vessel is repaired, the clot should dissolve. If the clot becomes large enough to block a blood vessel, vital nutrients and oxygen cannot be transported to the area of the body supplied by the blood vessel. As a result, the area may be damaged and its normal function affected. A complicated cascade of enzymes and proteins is involved in the processes of forming and dissolving clots, so there are many steps at which something can go wrong.

Stroke is also called a "brain attack." The effects of a stroke depend on the location and extent of damage. These factors are influenced by the time elapsed before medical treatment (call 911 for emergency medical help immediately at the first symptoms of stroke) and where in the brain the attack occurs. Learn about the risk factors for stroke and changes you can make in your lifestyle to help prevent strokes. The Five Most Common Stroke Symptoms are: Sudden numbness or weakness of face, arm, or leg, especially on one side of the body. Sudden confusion or trouble speaking or understanding speech. Sudden trouble seeing in one or both eyes. Sudden trouble walking, dizziness, or loss of balance or coordination. Sudden severe headache with no known cause. Call 911 if you see or have any of these symptoms. Treatment can be more effective if given quickly. Every minute counts!

Did You Know?

Strokes occur every 53 seconds in the United States. Each year in the US, about 600,000 people will have a stroke, resulting in 160,000 deaths. Stroke is the No. 3 killer in the United States and is a leading cause of severe, long-term disability. (Source: American Stroke Association) Smoking DOUBLES your risk of stroke. Don't worry -- there aren't bats flying around the researchers who study bat saliva. Scientists have been able to make DSPA in the laboratory since the 1990s. Researchers use an artificial version of the DSPA, not actual bat spit.