Below is an article in Nature Reviews Neuroscience on the probable disease process for PD and other neurodegenerative diseases. Dr. Jau-Shyong Hong, head of the NeuroPharmocology Dept. at the NIH is one of the authors. While they go into no detail on their ideas on how to slow or stop the progression of these diseases (they may in future articles), Dr. Hong has published previously on testing with rodents using opioid antagonist type drugs like naloxone, naltrexone and dextromethorphan to halt or slow neuroinflamation.
There is an off-label drug, LDN, available now for anyone who is interested.
Ashley

http://www.nature.com/nrn/journal/v8...l/nrn2038.html
Review

Nature Reviews Neuroscience 8, 57-69 (January 2007) | doi:10.1038/nrn2038
Microglia-mediated neurotoxicity: uncovering the molecular mechanisms

Michelle L. Block1, Luigi Zecca2 and Jau-Shyong Hong1 About the authors
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Abstract

Mounting evidence indicates that microglial activation contributes to neuronal damage in neurodegenerative diseases. Recent studies show that in response to certain environmental toxins and endogenous proteins, microglia can enter an overactivated state and release reactive oxygen species (ROS) that cause neurotoxicity. Pattern recognition receptors expressed on the microglial surface seem to be one of the primary, common pathways by which diverse toxin signals are transduced into ROS production. Overactivated microglia can be detected using imaging techniques and therefore this knowledge offers an opportunity not only for early diagnosis but, importantly, for the development of targeted anti-inflammatory therapies that might slow or halt the progression of neurodegenerative disease.

http://www.fasebj.org/cgi/content/full/19/6/550
http://www.lowdosenaltrexone.org/index.htm