A new study says that proteins associated with Alzheimer's may worsen the symptoms of Parkinson's disease and vice versa, and understanding this interaction could improve treatments for these conditions, say US researchers. Although both diseases are distinct neurological disorders, up to one-third of Alzheimer's patients develop Parkinson's and some Parkinson's patients develop signs of Alzheimer's.
To research a possible link between the two diseases, neurology experts from the University of California and Gladstone developed strains of transgenic mice that produce two human proteins - human amyloid precursor protein (hAPP) and human alpha-synuclein (hSYN).Of the two proteins, hAPP is linked with Alzheimer's and hSYN with Parkinson's; and mice that produce one of these proteins develop the symptoms of the associated disease.
The researchers discovered that both Alzheimer's and Parkinson's symptoms were worse in the mice that had both conditions than in the mice that had just one of the diseases.
Alzheimer-like symptoms - degeneration of particular classes of brain cells and impaired ability to learn - were enhanced by the production of hSYN (the protein associated with Parkinson's), said the team.
They also found that Abeta - a metabolite of the Alzheimer's protein hAPP - increased the build-up of hSYN in brain cells. This, said the researchers, shows a possible mechanism for the synergistic effects of one of the proteins on the other.The scientists suggest the interaction between the hAPP and hSYN means that drugs blocking these proteins could have broader benefits than previously thought. The study also helps explain the underlying mechanisms that destroy the cognitive and motor functions of Alzheimer's patients who go on to develop Parkinson's, they said.