Protecting Neurons from Parkinson's
New insights into the disease's protein culprit
By Katherine Bourzac, SM '04

MIT researchers led by Susan Lindquist, a biology professor and member of the Whitehead Institute for Biomedical Research, have developed a way to protect neurons from degeneration and death in animal studies of Parkinson's disease. The research, which focused on a protein called alpha-synuclein, could lead to therapies for human Parkinson's.

The disease's characteristic tremors and muscle rigidity are caused by damage to and the death of neurons that use the neurotransmitter dopamine to communicate with neighboring neurons. Alpha-synuclein was known to be one of the main causes of that damage; large clumps of it, in a misfolded form, are found in the brains of Parkinson's patients. But researchers did not know what alpha-synuclein's normal role is, why Parkinson's neurons accumulate too much of it, or how it causes disease. Lindquist's team used a yeast model of Parkinson's to study these questions.

Their research suggests that alpha-synuclein plays a role in the process cells use to shuttle proteins between two internal compartments in which critical refinements to proteins are made. Before being shipped off to different parts of the cell, protein strings often need to be cut or folded into three-dimensional shapes, and sometimes groups such as carbohydrates must be added to them.

During these processes, the young proteins are sheltered within protective lipid bubbles. The bubbles also protect the neurons that produce dopamine from damage that can occur if too much dopamine leaks out.

"Dopamine must be packaged in these membranes and sequestered from [the insides of the cell], where it can cause oxidative damage," says Aaron Gitler, a postdoc in Lindquist's lab.

The researchers aren't sure exactly how buildup of misfolded alpha- synuclein disrupts protein trafficking but suspect it disturbs these lipid bubbles. Gitler and Lindquist suggest that as a result, neurons in Parkinson's patients are unprotected from their own dopamine, which thus becomes toxic.

The scientists searched for a way to interfere with this effect. Gene screening showed that activating the gene ypt1, which makes a protein that helps shepherd other, freshly made proteins from one part of the cell to another, did the job: the Parkinson's yeast lived. Rab1, the equivalent shepherding protein in nematode, fly, and rat neurons, also countered alpha-synuclein's toxicity. Rab1 did not completely eliminate neuron death in some of these higher organisms, but it was protective.

Much remains to be done, validation in tests on mice being the most important step. But the Whitehead results have left researchers optimistic about getting at the molecular details of Parkinson's. A complex disease with few treatment options, Parkinson's affects about a million people in the United States. This research represents an important step toward understanding and curing it.

Copyright Technology Review 2006.

This paper is a bit hard to digest, but it reminded me of the whole idea of "oxidative damage" of molecules that can be oxidized to form highly reactive intermediates. There has been (as you know) a lot of investigation of why the nigral neurons are dark in coloration. It's because thhey are pigmented by melanin. An intermediate in the polymerization reactions to form melanin is 5,6-Dihydroxyindole, or 5,6-dihydroxyindole -2- carboxylic acid. These molecules are formed from dopamine or dopa by catalytic oxidation reactions. Now the 5,6- dihydroxy part of the molecule is really an "ortho quinone" which is the reactive precursor to melanin formation. Just one little paper of a search on "5,6-dihydroxyindole toxicity" reveals that this molecule in itself is cytotoxic and biochemistry around it may be responsible for cellular damage of dopamine producing cells. The whole idea relates to what you have posted because "dopamine is easily oxidized and must be protected from the rest of the cellular organelles". Thus, it seems that dopamine must be "packaged by heavy duty vesicles" or it leaks out and causes dirty things to happen.
http://www.ncbi.nlm.nih.gov/entrez/q...&dopt=Citation

Is just one paper that outlines the research and thinking along these lines. ONe can do a lot of searching to find good work that may illuminate what is going on in dopamine producing cells. There is an answer yet to all the speculations of the etiology of PD in the research community. I think they are barking up a possible tree of the "how" of PD on this one. There is much chemisry going on that we have hits but no cigar as of yet. cs

Best not read if you aren't into technoblurb

In my "old life", I did a lot of research on Alzheimers disease. The current "schtick" about the cause of ALZ still implicates the formation of "plaques and tangles made out of "beta folded sheets" of a 41-42(?) amino acid chain called beta protein, which is just a small peptide cut from a larger transmembrane protein called beta precursor protein. Like alpha synuclein, if it doesn't fold into Beta sheets, it can be eliminated from the body. If it does fold into the very configurationally stable sheets, it can't be eliminated and builds up because, once it forms a sheet, others of its kind are then more eisily "crystallized" epitaxiallly to form the gummed up plaque and tangles that are the undoing of a neuron because this "junk" chokes off neuronal axons and thus kills the cellular functions and the cells die off.
Well, it's a long shot, but serotonergic neurons are present in the cerebral cortex as are a lot of serotonergic axons projecting into the cortex. Serotonin is just 5-hydroxytryptamine, derived from tryptophan (an indole amino acid found in most foods), and, if enzymatically turned into 5,6-dihydroxytrypamine, this is closely related to the Dopamine oxidative cytotoxic 5,6- dihydroxyindole discussed above. You see what i'm getting at? If serotonergic neurons also try to protect 5HT from oxidation and get killed off by producing and using alpha synuclein, then get rid of alpha synuclein protein (a by-product of the vesicles that hold or protect 5-HT neurotransmitter from leaking out into the cytosol where oxidative processes occur) and alpha synuclein is ejected from the cell and misfolds into junk plaques (also found in ALZ patients brains), then the reason why cortical neurons produce beta protein is because the cortical neuron is put in "apoptotic mode" because the serotonergic neurons are dying. Since serotonergic neurons no longer ennervate cortical neurons, then a lot of beta protein is formed as a result of "clipping of the beta precursor protein as part of getting rid of the dying cell.
Thus, protection of serotoneric neurons by stopping the misfolding of alpha synuclein by product, may help protect cortical neurons from dying and clogging up the cortex with plaques and tangles formed by beta protein, which just keeps on forming and killing more cortical neurons. IN essence a cascade effect caused by other junk proteins far from the actual cortical neurons.
I may be dreaming, but that is what science is all about; to think of possibilities and then prove them wrong or right. cs

There has been some discussion here on how people with PD lose dopamine producing neurons. And some believe that these neurons have gone dormant.
Inflammation has been increasingly recognized to contribute to the pathogenesis of Parkinson’s disease. Several compounds are neuroprotective at femtomolar concentrations through the inhibition of inflammation. However, the mechanisms mediating femtomolar-acting compounds are poorly understood. Here we show that both gly-gly-phe (GGF), a tri-peptide contained in the dynorphin opioid peptide, and naloxone are neuroprotective at femtomolar concentrations against LPS-induced dopaminergic neurotoxicity through the reduction of microglial activation. Mechanistic studies demonstrated the critical role of NADPH oxidase in the GGF and naloxone inhibition of microglial activation and associated DA neurotoxicity. Pharmacophore analysis of the neuroprotective dynorphin peptides and naloxone revealed common chemical properties (hydrogen bond acceptor, hydrogen bond donor, positive ionizable, hydrophobic) of these femtomolar-acting compounds. These results support a common high-affinity site of action for several femtomolar-acting compounds, where NADPH oxidase is the critical mechanism governing neuroprotection, suggesting a novel avenue of anti-inflammatory and neuroprotective therapy.—Qin, L., Block, M. L., Liu, Y., Bienstock, R. J., Pei, Z., Zhang, W., Wu, X., Wilson, B., Burka, T., Hong, J.-S. Microglial NADPH oxidase is a novel target for femtomolar neuroprotection against oxidative stress.
Parkinson’s disease (PD) is characterized by the specific and progressive death of dopaminergic neurons in the substantia nigra (SN); other neuronal cell types are much less affected. Recent reports have linked inflammation to neurodegenerative disease, where microglia, cells of myeloid lineage responsible for innate immunity in the brain, are considered to be the major cell type underlying the inflammation-mediated neurotoxicity (7 8 9) . The activation of microglia is a complex process involving the release of several soluble proinflammatory factors [tumor necrosis factor {alpha} (TNF-{alpha}), PGE2, IL-1] and free radicals (nitric oxide, superoxide) (7) . Current replacement therapy with L-dopa is able to alleviate disease symptoms, but is unable to alter the disease course. Thus, therapeutic interventions designed to inhibit the microglial inflammatory response offer hope for attenuation of the neurodegenerative disease process. The current anti-inflammatory treatments available, including steroids and nonsteroidal anti-inflammatory drugs, are limited by the ability to influence only a small portion of the microglial response (10) . Thus, identification of compounds acting on novel targets to inhibit the release of a wide range of proinflammatory factors from overactivated microglia is of paramount importance. In the ensuing study, we report that femtomolar concentrations of naloxone and the peptide fragment glycine-glycine-phenylalanine (GGF) attenuate a broad spectrum of the microglia inflammatory response (reactive oxygen species (ROS) and proinflammatory factors) and are neuroprotective with extremely potent efficacy through the inhibition of microglial NADPH oxidase.
http://www.fasebj.org/cgi/content/full/19/6/550

There has been some discussion here on how people with PD lose dopamine producing neurons. Some believe that these neurons die off, others believe they have gone dormant. I am not a biochemist as some on this forum are, I find their ideas interesting but hard to follow. I have done internet searches on a drug, naltrexone, which is claimed to be neuroprotective at low doses for many brain diseases such as MS and PD. Most of the research papers I've come across claim that PD and Alzheimers is caused by neuro-inflammation and the neurons die. The researchers work has been with naloxone which they believe is neruo protective. Independantly, a growing number of people with MS believe in low dose naltrexone and they have been taking it over the past few years. Naltrexone is similar to naloxone. I believe there is good reason to look at naloxone/naltrexone, it's possible this drug can stop PD progression and it's available now. I take it.
Ashley

Below is a link to RemedyFind and the people with MS who take LDN.
http://www.remedyfind.com/treatments/21/2165/

Neuropharmacology Section,
{dagger} Laboratory of Structural Biology,
{ddagger} Chemistry Section, Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA;
§ Department of Bioscience and Bioengineering, Dalian University of Technology, Dalian, P.R. China; and
|| Department of Neurology, First Clinical Hospital,

"Inflammation has been increasingly recognized to contribute to the pathogenesis of Parkinson’s disease. Several compounds are neuroprotective at femtomolar concentrations through the inhibition of inflammation. However, the mechanisms mediating femtomolar-acting compounds are poorly understood. Here we show that both gly-gly-phe (GGF), a tri-peptide contained in the dynorphin opioid peptide, and naloxone are neuroprotective at femtomolar concentrations against LPS-induced dopaminergic neurotoxicity through the reduction of microglial activation. Mechanistic studies demonstrated the critical role of NADPH oxidase in the GGF and naloxone inhibition of microglial activation and associated DA neurotoxicity. Pharmacophore analysis of the neuroprotective dynorphin peptides and naloxone revealed common chemical properties (hydrogen bond acceptor, hydrogen bond donor, positive ionizable, hydrophobic) of these femtomolar-acting compounds. These results support a common high-affinity site of action for several femtomolar-acting compounds, where NADPH oxidase is the critical mechanism governing neuroprotection, suggesting a novel avenue of anti-inflammatory and neuroprotective therapy.—Qin, L., Block, M. L., Liu, Y., Bienstock, R. J., Pei, Z., Zhang, W., Wu, X., Wilson, B., Burka, T., Hong, J.-S. Microglial NADPH oxidase is a novel target for femtomolar neuroprotection against oxidative stress.
Parkinson’s disease (PD) is characterized by the specific and progressive death of dopaminergic neurons in the substantia nigra (SN); other neuronal cell types are much less affected. Recent reports have linked inflammation to neurodegenerative disease, where microglia, cells of myeloid lineage responsible for innate immunity in the brain, are considered to be the major cell type underlying the inflammation-mediated neurotoxicity (7 8 9) . The activation of microglia is a complex process involving the release of several soluble proinflammatory factors [tumor necrosis factor {alpha} (TNF-{alpha}), PGE2, IL-1] and free radicals (nitric oxide, superoxide) (7) . Current replacement therapy with L-dopa is able to alleviate disease symptoms, but is unable to alter the disease course. Thus, therapeutic interventions designed to inhibit the microglial inflammatory response offer hope for attenuation of the neurodegenerative disease process. The current anti-inflammatory treatments available, including steroids and nonsteroidal anti-inflammatory drugs, are limited by the ability to influence only a small portion of the microglial response (10) . Thus, identification of compounds acting on novel targets to inhibit the release of a wide range of proinflammatory factors from overactivated microglia is of paramount importance. In the ensuing study, we report that femtomolar concentrations of naloxone and the peptide fragment glycine-glycine-phenylalanine (GGF) attenuate a broad spectrum of the microglia inflammatory response (reactive oxygen species (ROS) and proinflammatory factors) and are neuroprotective with extremely potent efficacy through the inhibition of microglial NADPH oxidase.
http://www.fasebj.org/cgi/content/full/19/6/550

Ashley, your posts on LDN and the published work by Hong's group are the reasons I began using dextromethorphan, assuming it has the same properties in supressing neuroinflammation as naltrexone. So far, it seems to be working.
As I have said before, one can't be sure if this is a true indication of neuroprotection or simply a sinemet "honeymoon".
In addition to sinemet, amantadine, CoQ10 and DM, I am now taking a tsp of tumeric each day, and plan to increase that to 2 tsp next week. I see no reason to not continue this regimen indefinitely.

Cs, I was able to follow what you were saying but I'm too tired to understand it completely. I'll try again later.

I think that the biochemistry of the brain is hard to reduce to simple theories. There's much more than altered dopamine metabolism going on. Also, something that is harmful to the brain may also in some ways protect the brain. Even turmeric raises acetylcholine, which I'm trying to reduce with my artane.

I thought the following articles are very interesting and illuminate my point:

Pathogenic role of glial cells in Parkinson's disease


Parkinson's disease (PD) is a common neurodegenerative disorder characterized by the progressive loss of the dopaminergic neurons in the substantia nigra pars compacta (SNpc). The loss of these neurons is associated with a glial response composed mainly of activated microglial cells and, to a lesser extent, of reactive astrocytes. This glial response may be the source of trophic factors and can protect against reactive oxygen species and glutamate.

Alternatively, this glial response can also mediate a variety of deleterious events related to the production of pro-oxidant reactive species, and pro-inflammatory prostaglandin and cytokines. We discuss the potential protective and deleterious effects of glial cells in the SNpc of PD and examine how those factors may contribute to the pathogenesis of this disease. © 2002 Movement Disorder Society

http://www3.interscience.wiley.com/c...TRY=1&SRETRY=0

Viewpoint
Challenging conventional wisdom: The etiologic role of dopamine oxidative stress in Parkinson's disease
J. Eric Ahlskog, PhD, MD *

Oxidative stress is well documented in Parkinson's disease (PD) and has been attributed to dopamine oxidative metabolism. However, evidence of oxidative stress is found in a variety of neurodegenerative disorders, suggesting that more general factors are responsible or that cytodestructive processes secondarily generate oxyradical products. Increasing evidence points away from dopamine metabolism as an important contributor to PD neurodegeneration. Predictions from the dopamine oxidative stress hypothesis of PD reveal multiple inconsistencies. Although the clinical and therapeutic importance of the nigrostriatal dopaminergic system is undeniable, PD neuropathology is much more widespread. © 2004 Movement Disorder Society

http://www3.interscience.wiley.com/c...3299/HTMLSTART

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