March 19, 2012 — Vol. 28 No. 11
Idaho State University researchers in the Bearden Vascular Health Laboratory are finding clues on how to block the effects of a chemical in the brain that contributes to dementia and strokes.
Shawn Bearden, an associate professor of physiology in the ISU Department of Biological Sciences, said that his laboratory has documented that the drug, memantine, can counter the effects that the chemical homocysteine has in disrupting the blood-brain barrier. Disruption of this barrier is believed to contribute to vascular cognitive impairment diseases such as dementia and stroke.
In brief, molecules in the bloodstream can cause leakiness in tiny blood vessels of the brain. Normally, our brains have a tight barrier from the blood because elements in the blood can be toxic to the brain. It has also been shown that people who have an abnormally high level of homocysteine, which can result from vitamin deficiencies as well as genetic differences, have a higher risk of stroke and dementia.
Bearden tested mice that had mildly elevated levels of homocysteine. As expected, these mice had leaky blood-brain-barriers. "When the mice were administered the drug we were able to rescue the leakiness," Bearden said. "Then we did the same experiment using cultures of blood vessel cells, treating them with homocysteine and then rescuing leakiness using the drug."
These studies confirm both that the presence of homocysteine can cause the brain microvascular leakiness and that the drug memantine, in some instances, can help "rescue" that problem.
"This is an important advance," continued Bearden, "because we have potentially found a completely different approach for treating homocysteine-related dementia. We must caution that these are preliminary findings, but the results are encouraging."
Bearden's group published their findings in the American Society of Hematology Journal, Blood, one of the premier scientific journals in its field. The group also has published three more papers that further dissect the mechanism causing the blood-brain-barrier leak caused by homocysteine. Bearden has received several grants to study the microcirculation, including a new National Institutes of Health grant titled, "Microvascular Dysfunction in Hyperhomocysteinemia."
"There are a lot of details to work out concerning our findings," Bearden said. "We think that treatment with this drug might be applicable to some subsets of people suffering from dementia, specifically in patients with homocysteine-related vascular dementia, but there is plenty more we need to know, this study is just the beginning. A focused clinical trial would be needed next."
For his research on the microcirculation, Bearden was elected as a Fellow to the American Heart Association. He is very active with the AHA, including serving on several committees that decide on grant funding policies and complete grant reviews.