September 25 2001
Study Offers Proof of Alzheimer-Parkinson Link
By Merritt McKinney
NEW YORK (Reuters Health) - Results of a new study provide evidence
supporting a possible link between Alzheimer's
disease and Parkinson's disease.
The potential connection suggests that experimental drugs designed to
target Alzheimer-linked brain deposits might be
effective against more types of neurological diseases than expected, one
of the study's authors told Reuters Health.
Both Parkinson's and Alzheimer's are progressive neurological diseases,
but the illnesses cause distinct symptoms. Parkinson's
disease causes tremor, muscle rigidity and movement problems. In
contrast, Alzheimer's leads to a gradual decline in mental
abilities.
However, symptoms of both diseases sometimes occur in the same person,
raising the possibility that the diseases are linked,
Dr. Eliezer Masliah, of the University of California, San Diego,
explained to Reuters Health in an interview.
In collaboration with Dr. Lennart Mucke at the University of California,
San Francisco, Masliah and his team genetically
engineered several strains of mice to look for signs of a connection
between the two diseases.
One strain was engineered to accumulate beta-amyloid proteins in the
brain, which have been linked to Alzheimer's disease.
Another strain produced alpha-synuclein, a protein that builds up in the
brain of Parkinson's patients. A third group of mice
accumulated both types of proteins.
Mice that had beta-amyloid and alpha-synuclein proteins developed
symptoms typical of a type of Alzheimer's disease
marked by brain deposits called Lewy bodies. The ability of these mice
to learn deteriorated more rapidly than in mice that
did not have alpha-synuclein proteins.
Having both types of brain proteins also sped the Parkinson's disease
process. Mice with both types of proteins developed
movement problems sooner than animals that only had alpha-synuclein
proteins.
The findings appear in the online Early Edition of the journal
Proceedings of the National Academy of Sciences.
``This is the very first time that we were able to demonstrate
experimentally that Alzheimer's disease and Parkinson's disease
are linked mechanistically,'' Masliah said.
The presence of both diseases in some patients is not just a
coincidence, he added.
The proof of the connection between the diseases could have ''important
therapeutic consequences,'' according to Masliah.
``If amyloid-beta protein is driving the Parkinson's pathology, if we
block the amyloid, we might be able to block the
Parkinson's disease,'' he said.
This would allow doctors ``to kill two birds with one shot,'' according
to the California researcher. He noted that several
amyloid-blocking drugs are in the early stages of development.
Right now, Masliah and his colleagues are continuing to investigate the
connection between the two diseases. They are also
conducting animal research to see whether blocking amyloids also
prevents the development of Parkinson's symptoms, he
said.
SOURCE: Proceedings of the National Academy of Sciences 2001;10.1073.
--
Judith Richards, London, Ontario, Canada
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