Gingko May Prevent Brain Cell Damage
10/09/2008
Working with genetically engineered mice, researchers at Johns Hopkins have shown that daily doses of a standardized extract from the leaves of the ginkgo tree can prevent or reduce brain damage after an induced stroke.
The scientists, in a report published in Stroke, said their work lends support to other evidence that ginkgo biloba triggers a cascade of events that neutralizes free radicals known to cause cell death.
"It's still a large leap from rodent brains to human brains but these results strongly suggest further research into the protective effects of ginkgo is warranted," said lead researcher Sylvain Doré, Ph.D., an associate professor in the department of anesthesiology and critical care medicine.
"If further work confirms what we've seen, we could theoretically recommend a daily regimen of ginkgo to people at high risk of stroke as a preventive measure against brain damage."
Researchers gave ginkgo biloba EGb 761, a lab-quality form of the extract to normal mice and HO-1 knockout mice, mice lacking the gene that produces the enzyme heme oxygenase-1(HO-1). Doré and his team gave 100 mg/kg/d of EGb 761 extract orally for seven days before inducing stroke in the mice by briefly blocking an artery to one side of the brain.
After stroke induction, the mice were tested for brain function and brain damage. One such test, for example, involves running patterns, another tests reaction to an external stimulus. Similar tests were conducted on mice that did not receive the ginkgo extract.
Neurobehavioral function was evaluated before the study and at 1, 2 and 22 hours after stroke using a four-point scale: (1) no deficit, (2) forelimb weakness, (3) inability to bear weight on the affected side, (4) no spontaneous motor activity.
Results showed normal pretreated mice had 50.9 percent less neurological dysfunction and 48.2 percent smaller areas of brain damage than untreated mice. These positive effects did not exist in the HO-1 knockout mice.
"Our results suggest that some element or elements in ginkgo actually protect brain cells during stroke," said Doré.
According to Doré and his team, ginkgo increases HO-1 levels, and the antioxidant properties of this enzyme eliminate free radicals at the surrounding regions of the stroke site.
The only current treatment for ischemic stroke is to clear the clot with tissue plasminogen activator (tPA) or other means. This, however, offers no real protection against the cell damage that occurs when blood flow is restored.
"Ginkgo has long been touted for its positive effects on the brain and is even prescribed in Europe and Asia for memory loss," said Doré. "Now we have a possible understanding for how ginkgo actually works to protect neurons from damage."
Additional researchers include Sofiyan Saleem, Ph.D.; and Hean Zhuang, M.D., of the Department of Anesthesiology and Critical Care Medicine; and Shyam Biswal, Ph.D., of the Department of Environmental Health Sciences, all from Johns Hopkins.
