Vienna, Austria – The destructive cellular pathways activated in Alzheimer’s disease are also triggered following traumatic brain injury, say researchers from Georgetown University Medical Center (GUMC). They say this finding suggests that novel therapy might successfully target both conditions.
In an oral presentation at the Alzheimer’s Association 2009 International Conference on Alzheimer’s Disease, the scientists will show that deactivating these pathways in part by using a gamma secretase inhibitor - a class of Alzheimer’s disease drugs currently being tested - reduced loss of neurons in animal models of traumatic brain injury and protected the animals against motor and cognitive deficits.
“The goal for both diseases is to prevent neuronal cell death, and this study suggests that one therapy could possibly work for both,” says the study’s lead author, neuroscientist Mark Burns, PhD, an assistant professor at GUMC.
Both disorders are associated with build-up of beta amyloid, a toxic brain peptide. This substance is commonly found in the brains of elderly patients who died from Alzheimer’s disease, but has also been found in a third of traumatic brain injury victims, some of whom are children, Burns says. It is also known that people who experience such a brain injury have a 400 percent increased risk of developing Alzheimer’s disease.
Burns says that buildup of beta amyloid occurs in a second wave of damage that follows immediate “necrotic” death of nerve cells after traumatic brain injury. This secondary injury can last months, if not years, resulting in large holes within brain tissue.
Amyloid peptides are produced when a long brain protein known as the amyloid precursor protein (APP) is cut in two by the enzyme beta secretase, and then cut once again by a second enzyme known as gamma secretase. Agents that inhibit the activity of gamma secretase are now being studied as treatment for Alzheimer’s disease.
In this study, researchers used mice that were either treated with DAPT, an experimental gamma secretase inhibitor, or mice which were “BACE knock-outs” – so called because they were genetically altered in such a way that they could not produce beta secretase. In unaltered and untreated “normal” mice, brain injury resulted in a rapid accumulation of beta amyloid, along with cognitive and motor deficits. But DAPT and BACE knock-out mice had brain lesions that were as much as 70 percent smaller than control animals and they experienced minimal impairment.
The findings further cement the connection between Alzheimer’s disease and traumatic brain injury, Burns says, and show that “modulation of beta and gamma secretase may provide novel therapeutic targets for the treatment of traumatic brain injury.”
The study was funded by grants from the National Institutes of Health and by the Klingel Family Foundation. Burns is one of three Georgetown University faculty members who are inventors on a patent application filed by the University related to the technology involved in this paper.
About Georgetown University Medical Center
Georgetown University Medical Center is an internationally recognized academic medical center with a three-part mission of research, teaching and patient care (through Georgetown’s affiliation with MedStar Health). GUMC’s mission is carried out with a strong emphasis on public service and a dedication to the Catholic, Jesuit principle of cura personalis -- or "care of the whole person." The Medical Center includes the School of Medicine and the School of Nursing and Health Studies, both nationally ranked, the world-renowned Lombardi Comprehensive Cancer Center and the Biomedical Graduate Research Organization (BGRO), home to 60 percent of the university’s sponsored research funding.