PARKINSON’S disease could soon be prevented – after scientists found evidence to challenge what many previously believed caused the disease.
Scientists used to believe inherited forms of early-onset Parkinson’s disease – the condition which affected the later Muhammad Ali – have been blamed on poorly function mitchondria – which are found in human cells.
Mitochondria are often described as the ‘powerhouses of cells’ and without reliable sources of energy, neurons – which transmit nerve impulses – wither and die.
But Medical Research Council researchers at University of Leicester found this may not be the complete picture for Parkinson’s sufferers.
Instead neurodegeneration was the result of stress on the endoplasmic reticulum (ER) – part of the outer skin of the cell – rather than failure of the mitochondria as previously thought.
The death of neurons associated with the disease was prevented when chemicals that block the effects of endoplasmic reticulum stress were used, scientists have revealed.
Dr Miguel Martins said: “This research challenges the current held belief the Parkinson’s disease is a result of malfunctioning mitochondria.
“By identifying and preventing ER stress in a model of the disease it was possible for us to prevent neurodegeneration.
“Lab experiments, like this, allow us to see what effect ER stress has on Parkinson’s disease.
“While the finding so far only applies to fruit flies, we believe further research could find that a similar intervention in people might help treat certain forms of Parkinson’s.”
Parkinson’s disease is a degenerative disorder of the central nervous system mainly affecting the motor system.
The study by Leicester’s MRC Toxicology Unit used a ‘mutant’ common fruit fly to investigate this further as they provide a good genetic model for humans.
It was found that the bulk of the damage to neurons with damaged mitochondria stems from a related but different source – the neighbouring maze-like endoplasmic reticulum (ER).
The ER has the important job of folding proteins so that they can do the vast majority of work within cells.
Misfolded proteins are recognised by the cell as being dangerous and as a result, cells halt protein production if there are too many of these harmful proteins.
While this system is protective, it also stalls the manufacture of vital proteins, and this eventually results in the death of neurons.
To find out if ER stress might be at play in Parkinson’s, scientists analysed fruit flies with mutant forms of the pink1 or parkin genes.
These genes are also mutated in humans and result in hereditary versions of the disease causing shaking, trembling and difficulty walking.
Scientists found fruit flies with either mutation moved more slowly and have weakened muscles.
The insects in the study struggled to fly and they lost dopaminergic neurons in their brains – a classic feature of Parkinson’s.
The mutants experienced large amounts of ER stress and did not manufacture proteins as quickly as the non-mutants.
They also had elevated levels of the protein-folding molecule BiP, a telltale sign of stress.
The study, published in the journal Cell Death and Disease, showed that the neurodegeneration seen in Parkinson’s is a result of ER stress rather than a general failure of the mitochondria.