TORONTO (CP) July 13, 2000 - Conventional thinking on the way neurodegenerative diseases like Parkinson's and Huntington's kill brain cells is wrong, researchers from the University of Toronto and the Hospital for Sick Children reported in the prestigious journal Nature.
Their findings could help unlock the mysteries of a raft of neurodegenerative diseases including ALS (Lou Gehrig's disease) and Alzheimer's and may point researchers towards ways of preventing such diseases or at least halting their progression.
"I really think this is a very exciting paradigm shift, that it is important as to how human disease occurs and at what stage program cell death . . . occurs in the game," said Dr. Alex MacKenzie, a geneticist and pediatrician at the University of Ottawa who was not involved in the study. The study disputes the long-held belief that neurons - cells of the central nervous system that carry information to and from the brain - deteriorate and die over time, in much the same way as people die from old age.
Neurons cannot be replaced or repaired. People can only lose so many before they begin to show symptoms of the neurodegenerative disease they have, such as the tremors of Parkinson's.
The team found that neurons die randomly but remain healthy and functioning right up to the time of their death, like a world class athlete who keels over and dies during a sporting event from an undiagnosed heart problem.
The new model of cell death offers promise because it means that if researchers can find a way to stop the neurons from dying, the neurons will continue to operate properly. That could mean, for instance, that doctors could halt the progression of a case of Retinitis pigmentosa (tunnel vision).
"The cells that haven't died yet are not sick. . .they're just at increased risk of death," explained Dr. Roderick McInnes, senior author and professor of medical genetics at the University of Toronto and Sick Kids.
"That means that if you can do anything to save them - put a copy of the normal gene back in or give a drug that corrects the chemical imbalance that's conferring the increased risk of death - then you can save that cell completely."
Eventually, genetic testing might allow doctors to treat an individual programmed to develop a neurodegenerative disease early enough so that he or she would never develop symptoms. "You can identify the people very early in life, before symptoms actually develop, and treat them and stop symptoms from ever developing," said Geoff Clarke, the study's lead author and a graduate student in molecular and medical genetics at the University of Toronto.
It could also mean that treating neurodegenerative diseases could be easier than has been thought up to now, said Clarke. "It changes the thinking around treatments by saying: If we're only dealing with one event, that's going to be easier than if we're, say, dealing with 10 events. You only have to give one drug or one sort of therapy to help the patients."
While the new model for cell death is promising, the question of why cells that appear perfectly healthy just up and die remains. But McInnes insisted that recognizing how cells die will help scientists figure out why it happens - and eventually how to stop it.
"If your basic assumptions of what's going on are completely wrong, you're not going to get to the cause of the disease," he said.
"This is a definite positive step to ultimate effective treatment of these disorders."