A protein injection protected neurons in the brains of mice with prion disease, according to new research that could offer hope to patients with neurodegenerative diseases like Alzheimer’s and Parkinson’s.

In what was described as a “major breakthrough in understanding what kills neurons,” the latest study, published in the journal Nature, has for the first time found a pathway leading to neuron death in mice with prion disease, the mouse equivalent of Creutzfeldt-Jakob Disease (CJD), which is currently an incurable, neurodegenerative and fatal condition that causes the brain to slowly die.

In neurodegenerative diseases like Alzheimer's, Parkinson's and CJD, proteins often “mis-fold” in different ways, leading to an accumulation of abnormally shaped proteins that form plaques in the brain, obstructing normal brain activity in patients with Alzheimer's and the Lewy bodies found in Parkinson's disease.

Researchers explain that as the build-up of misshapen proteins increase in the brain, the body reacts by switching off the production of new and healthy proteins and limiting the levels of health protein in the body, which leads to further mental and physical deterioration in patients.

After finding the pathway, scientists then found a way to block it and to prevent brain cells from dying, helping the diseased mice live longer by injecting a protein that blocks the “off” switch to the pathway, where there are key proteins that are essential to making new healthy nerve cells.

By injecting the diseased mice with the protein, scientists were able to restore the production of the survival proteins and stop brain deterioration in mice. The brain cells in mice were protected, healthy protein levels were restored and synaptic transmission, the way neurons communicate to each other, was re-established.

Researchers also believe that a common mechanism may exist in brain diseases like Alzheimer's, Parkinson's and CJD that damage nerve cells, and therefore be blocked in the same way.

“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,” said Giovanna Mallucci, who led the research at the University of Leicester's toxicology unit said in a statement about the study.

"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," Mallucci said.

Eric Karran, director of research at the charity Alzheimer's Research UK, said while the research was still at an early stage, the results were promising because it suggested that one drug could benefit a range of brain diseases.

“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; however the idea is in its early stages. The research focuses on the effects of the prion protein and we would need to see the same results confirmed in Alzheimer’s and Parkinson’s to really strengthen the evidence,” Karran said in a statement released by the organization.

“Understanding more about what goes so wrong in neurodegenerative diseases is vital for the development of effective new treatments. With diseases such as Alzheimer’s and Parkinson’s affecting huge numbers of people across the world, we must invest in research now,” he added.

The World Health Organization estimates that around 18 million people in the world suffer from Alzheimer's disease, and one in 100 people over the age of 60 are thought to have Parkinson’s. Both these diseases kill neurons in the brain by destroying brain tissue from the inside.

Around 5.1 Americans have Alzheimer’s disease, and the U.S. Department of Health and Human Services estimates that in 2050, the number of patients affected with the mental disease will double, and scientists have not been able to pinpoint the cause of the condition and there is no cure.