Scientists 'switch off' brain cell death

British researchers writing in the journal Nature say they have found a major pathway leading to brain cell death in mice with prion disease, the mouse equivalent of Creutzfeld-Jacob Disease (CJD). These misshapen proteins form the plaques found in the brains of patients with Alzheimer's and the Lewy bodies found in Parkinson's disease. The finding, described by one expert as "a major breakthrough in understanding what kills neurons", points to a common mechanism by which brain diseases such as Alzheimer's, Parkinson's and CJD damage the nerve cells. Scientists have figured out how to stop brain cell death in mice with brain disease which could provide a deeper understanding of neurodegenerative diseases such as Alzheimer's and Parkinson's. They then worked out how to block it, and were able to prevent brain cells from dying, helping the mice live longer. In neurodegenerative diseases, proteins "mis-fold" in a various ways, leading to a build up of misshapen proteins, the researchers explain in the study. "What's exciting is the emergence of a common mechanism of brain cell death, across a range of different neurodegenerative disorders, activated by the different mis-folded proteins in each disease," says Professor Giovanna Mallucci, who led the research at the University of Leicester's toxicology unit.

By injecting a protein that blocks the "off" switch, the scientists were able to restore the production of the survival proteins and halt the neurodegeneration. Switching off

Mallucci's team found that the build up of mis-folded proteins in the brains of mice with prion disease activated a natural defence mechanism in cells, which switches off the production of new proteins. This is the trigger point leading to brain cell death, because key proteins essential for cell survival are not made. In these diseases, neurons in the brain die, destroying the brain from the inside. "The fact that in mice with prion disease we were able to manipulate this mechanism and protect the brain cells means we may have a way forward in how we treat other disorders," she says. But why the neurons die has remained an unsolved mystery, presenting an obstacle to developing effective treatments and to being able to diagnose the illnesses at early stages when medicines might work better. An estimated 18 million people worldwide have Alzheimer's, and Parkinson's is thought to affect around one in 100 people over the age of 60. This would normally switch back on again, the researchers explain, but in these ill mice the continued build-up of misshapen proteins keeps the switch turned off. They found the brain cells were protected, protein levels were restored and synaptic transmission - the way brain cells signal to each other - was re-established. Eric Karran, director of research at the charity Alzheimer's Research UK, says while the research was still at an early stage, the results were exciting The mice also lived longer, even though only a very small part of their brains had been treated.

"While neurodegenerative diseases can have many different triggers, this study suggests that they may act through a common mechanism to damage nerve cells. The findings present the appealing concept that one treatment could have benefits for a range of different diseases," he says.

Professor Roger Morris, a molecular neurobiologist at King's College London who was not involved in the work, says the finding is "a major breakthrough in understanding what kills neurons in neurodegenerative disease".

"There are good reasons for believing this response, identified with prion disease, applies also to Alzheimer's and other neurodegenerative diseases," he says.