Scientists are harnessing the body's natural resources to attack Alzheimer's disease, offering the hope of treatments for the condition.
Gene therapy could be used to attack the protein which clumps together into dangerous plaques in the brains of Alzheimer's patients, researchers say.
Scientists have also identified a type of brain cell which could also prevent the build up of plaques.
"
These are very new ways of addressing the problem
"
Brad Wise, National Institute on Aging
In the first study, researchers an enzyme was used to reduce levels of the protein by up to 50% using gene therapy.
The neprilysin enzyme naturally reduces the accumulation of the protein beta-amyloid which makes up amyloid plaques in the brain.
Mechanisms
Researchers from the Salk Institute and University College of San Diego and the University of Kentucky carried out the study, published in the Journal of Neuroscience.
They used a modified version of the HIV virus to transfer a gene for neprilysin to neurons of genetically modified mice which produced human beta-amyloid.
The researchers concentrated on two areas of the brain, the hippocampus and the frontal cortex, areas where plaque formation occurs in humans.
Plaques which built up close to where neprilysin was injected were found to be smaller and more compact than in other regions of the brains.
In some cases, the so-called plaque "load" was reduced to less than half that found in comparable, untreated areas.
The treatment also eliminated damage linked to the build-up of beta-amyloid.
Dr Fred Gage, of the Saks Institute, said: "What's significant about this is that neprilysin isn't a drug, but a molecule that controls levels of beta-amyloid naturally.
"This study is an example of how understanding the basic mechanisms of protein interaction can lead to new disease treatments."
More research is currently being carried out in mice.
Defects
A second study, published in Nature Medicine, identified cells in the brain called astrocytes, which laboratory tests showed can also attack beta-amyloid plaques.
Researchers from Columbia University, New York, say the finding offers another potential avenue of study.
Astrocyte cells support, nourish and protect neurons in the brain. They are found close to Alzheimer's plaques.
Mice studies showed that the amount of plaque within the hippocampus was reduced by 40% after exposure to astrocyte cells.
The researchers say their findings indicate defects in the normal astrocyte cell clearance of beta amyloid could help the formation of plaques.
Dr Jens Husemann, who led the research, said: "Harnessing the protective function of these cells may be a strategy for AD prevention and treatment."
'Clearing build-ups'
Brad Wise, of the US National Institute on Aging, said: "In recent years, we have been looking at ways to battle amyloid.
"Most studies have focused on blocking the production of proteins that form AD plaques.
"Both of these studies suggest how we might clear amyloid even if it does build up in the brain. These are very new ways of addressing the problem."
Dr Richard Harvey of the UK's Alzheimer's Society, cautioned: "We have to be clear that these are animal studies, and they are a long way off being used in humans."
But he added preventing the build-up of plaques was the focus of Alzheimer's research.
"In the medium to long-term, it is likely that we will come up with an effective treatment for Alzheimer's."
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