19 November 2012

Contagious Parkinson's disease

Parkinson's disease is transmitted from diseased neurons to healthy ones

Kirill Stasevich, CompulentaThe assumption that Parkinson's disease can be transmitted from neuron to neuron first arose in 2008.

It turned out that the nerve tissue taken from the embryo and transplanted into the diseased brain also begins to deteriorate and show all the symptoms of Parkinsonism. It was then that scientists first thought that the cell itself does not need to be initially sick: it may well "get infected" with a bad protein from its neighbors.

A bad protein in the case of Parkinson's disease is alpha-synuclein. Taking the wrong spatial conformation, it forms protein deposits and causes the death of neurons. First of all, this concerns dopamine nerve cells responsible for motor signals, therefore, the motor apparatus primarily suffers from the disease. Researchers from the Perelman School of Medicine at the University of Pennsylvania (USA) have shown how alpha-synuclein can spoil quite healthy brains. Scientists injected a bad protein into rats in areas of the brain, especially those rich in dopamine neurons. Soon after, the so-called Levi corpuscles began to form at the injection site, and the cells themselves died after that. Everything happened as in the usual Parkinson's syndrome.

Rat brain in the third month after the introduction of pathogenic alpha-synuclein.
Dopamine neurons are colored green, and protein deposits in them are red.
(Photo by Kelvin C. Luk / Perelman School of Medicine, University of Pennsylvania)Moreover, a few months after the injection, the rats' coordination of movements, balance, and grip strength weakened.

That is, the effect of the protein expanded, capturing all new cells, not just those that were in direct contact with the injection site. Similar experiments have already been conducted, but so far researchers have used mice genetically predisposed to Parkinson's disease. The main feature of the new work is that Parkinsonism infected absolutely healthy, normal, unmodified mice. However, the question still remains, what is the initial meaning for the disease. After all, Parkinson's syndrome does not occur because of an injection of a bad protein into the brain.

It is worth noting that similar results were obtained not so long ago for Alzheimer's disease, but in this case genetically modified animals were used, so it is impossible to say who is more to blame, the protein or the cell itself.

An article with the results of experiments (Luk et al., Pathological alfa-Synuclein Transmission Initiates Parkinson-like Neurodegeneration in Nontransgenic Mice) is published in the journal Science.

Prepared based on the materials of the Perelman Medical School at the University of Pennsylvania:
Parkinson's Disease Protein Causes Disease Spread and Neuron Death in Healthy Animals.

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