Neurodegenerative diseases like Alzheimer's and Parkinson's may be linked to defective brain cells disposing toxic proteins, making neighbouring cells sick, scientists say.

The findings showed that although healthy neurons should be able to sort out and rid brain cells of toxic proteins and damaged cell structures, they are unable to do so always.

"Normally the process of throwing out this trash would be a good thing," said Monica Driscoll, professor at Rutgers University in New Jersey.

"But we think with neurodegenerative diseases like Alzheimer's and Parkinson's there might be a mismanagement of this very important process that is supposed to protect neurons but, instead, is doing harm to neighbour cells," Driscoll added, in the paper published in Nature.

To understand how the mechanism of eliminating toxic cellular substances works externally, the team conducted experiments on the transparent roundworm, known as the C. elegans, which are similar in molecular form, function and genetics to those of humans.

The researchers discovered that the worms -- which have a lifespan of about three weeks -- had an external garbage removal mechanism and were disposing these toxic proteins outside the cell as well.

However, the roundworms engineered to produce human disease proteins associated with Huntington's disease and Alzheimer's, were found to throw out more trash consisting of these neurodegenerative toxic materials.

While neighbouring cells degraded some of the material, more distant cells scavenged other portions of the diseased proteins.

"These finding are significant. The work in the little worm may open the door to much needed approaches to addressing neurodegeneration and diseases like Alzheimer's and Parkinson's," Driscoll said.

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