Alzheimer's breakthrough as memory loss drug in sight
A drug to prevent the memory loss associated with Alzheimer's disease is a step closer after scientists discovered why people with dementia cannot form new memories.
It was previously thought that Alzheimer's was primarily caused by the build-up of plaques in the brain that stop neurons from firing.
But drugs to clear the plaques have so far failed to bring any improvement to sufferers.
Many scientists believe that the plaques trigger a "cascade effect" of other symptoms, meaning that by the time they are disvovered it is already too late.
Researchers at Penn State University have now discovered that the plaques may be triggering overproduction of a chemical – known as GABA neurotransmitter – that causes memory loss by preventing a key part of the brain from functioning.
They believe a drug that deactivates the chemical could halt memory loss in sufferers.
"Billions of dollars were invested in years of research leading up to the clinical trials of those [plaque-clearing] Alzheimer's drugs, but they failed the test after they unexpectedly worsened the patients' symptoms," said Professor Gong Chen, a biologist who led the work at Penn State University.
"The research behind those drugs had targeted the long-recognised feature of Alzheimer's brains: the sticky build-up of the amyloid protein known as plaques, which can cause neurons in the brain to die.
"The research of our lab, and others, now has focused on finding new drug targets and on developing new approaches for diagnosing and treating Alzheimer's disease."
Prof Chen's team found that in Alzheimer's sufferers, the GABA neurotransmitter was drastically increased in deformed brain cells that, in a healthy individual, surround and support individual neurons in the brain. Those deformed cells were found in an area of the brain that is critical for learning and memory.
The team found that in mice with excess GABA neurotransmitter, neurons were not firing when the mouse was learning something new, or remembering something already learnt, as they normally would in a healthy subject.
"We recently discovered an abnormally high concentration of one inhibitory neurotransmitter in the brains of deceased Alzheimer's patients," said Prof Chen.
"After we inhibited the [chemical] in the brains of the mice, we found that they showed better memory capability.
"We are very excited and encouraged by this result, because it might explain why previous clinical trials failed by targeting amyloid plaques alone.
"An ultimate successful therapy may be a cocktail of compounds acting on several drug targets simultaneously." (© The Daily Telegraph, London)