2005 Pilot Study Grants
Funding from The Parkinson Alliance helped to finance the following Parkinson’s research. Grantees were selected by scientific review committees of participating organizations. Updates will be posted, when available.
1. Alpha-synuclein (@-synuclein) is a small protein that has been found in the brain tissue (in Lewy bodies, the hallmark of Parkinson’s disease) of patients dying with PD. Altered or mutated @-synuclein is seen in tissue from some familial parkinsonisms, leading scientists to ask how the protein affects neurodegeneration. Dr. Mel Feany (Harvard) created transgenic fruit flies (drosophila) with human @-synuclein as animal models of such disorders and she and her group are using these inexpensive creatures to study genetic manipulation of the protein. Dr. Li Chen of this laboratory will use the grant award to try to find other proteins that interact with @-synuclein, hoping to delineate the pathways that lead to dopaminergic cell death. Learning more of the pathogenesis of human PD could lead to better knowledge of genes that cause susceptibility to parkinsonism, possibly even classic PD, as well as culling out possible targets for future therapy.
2. Direct and indirect pathways are the terms used by scientists to describe how the brain’s neurons send neurotransmitters via their axons. Some transmitters inhibit (slow) movement, others excite (speed up). The depletion of the neurotransmitter dopamine (DA) due to degeneration results in loss of movements and is thought to involve the biggest neural component of the striatum, medium spiny neurons that project the chemical GABA. Dr. Francois Gonon of Bordeaux (France) and his group will use his grant to record the activities of these neurons in anesthetized parkinsonian rodents in an attempt to determine the effects of various compounds on these pathways. They hope to show that drugs that enhance GABA transmission might prove useful as symptomatic therapy in human Parkinson’s disease patients.
3. Numerous groups have shown that amantadine hydrochloride (Symmetrel) is mildly helpful in relieving levodopa-induced dyskinesias (LIDs), probably due to its antagonism to NMDA receptors. Stronger such agents, however, cause somnolence, even psychoses. In an attempt to get around these problems, Dr. Penelope J. Hallett and her Harvard (Cambridge, Massachusetts) colleagues are using the awarded grant to examine the effects of inhibiting a specific phosphatase (an enzyme) in 6-OHDA-lesioned rat brain slices after administering a dopamine (DA) agonist. Their work will involve transfecting a new protein into the slices, using the new RNAi (interference) function to knock out a specified protein and fluorescence lifetime imaging (FLIM) to detect protein-protein interactions in neurons. Dyskinesias have been a limiting effect in a majority of patients’ receiving sufficient DA drug dosages to provide better mobility and it is thought that better understanding of the interplay between the DA system and the NMDA receptor system could lead to the discovery of compounds that would preclude them.
4. Several recent studies have shown that mutations in the gene LRRK2 appear to cause more cases of autosomal-dominant parkinsonism than has any other gene discovered to date. The LRRK2 gene encodes a protein called dardarin (so named by the Spanish group that first described it; the Basque word means tremor), and it is thought that dardarin may function as a protein kinase. These are enzymes that regulate a large variety of cellular processes. Dr. Sabine N. Hilfiker and her colleagues in Granada (Spain) will use their grant funds to explore the localization and enzymatic activity (dardarin is also thought to be present in Lewy bodies) of the protein and test their hypothesis that it may have a function in the survival of dopaminergic neurons, acting to promote the accumulation and aggregation of unfolded or mutated proteins such as alpha-synuclein and tau. Their work will be done in both human and animal tissues.
5. Two of the environmental toxins that are used to create animal models of parkinsonism, rotenone and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), are thought to work by inhibiting complex 1 of the mitochondria that, in turn, promotes oxidative stress and loss of dopaminergic (DA) neurons. Several groups have described a similar effect caused by a drug, metformin, presently approved to treat diabetes. Dr. Kari R. Hoyt and her associates at Ohio State University (Columbus) will use their grant funds to advance their work in mice that have been exposed to metformin via their drinking water. Reproducing the pathological effects of the compound (followed by behavioral effects) could provide the field with a new and inexpensive animal model of parkinsonism that would be useful in testing putative medications that might decrease the vulnerability of DA neurons to toxins that affect the mitochondria.
6. Drs. Daniel Levesque (and Claude Rouillard Laval University, Quebec City) will continue the work funded by their prior grant, last year, of using retinoic ligands (substances allied to retinoic acids) to modify levodopa-induced abnormal movements (LIDs) in MPTP-intoxicated monkeys. Having accomplished these modifications, the group will use this year’s funding to determine the pathways involved since it is thought that LIDs such as dyskinesias, so common in advancing PD patients, are influenced by potential chemical “partners” known as Nur 77 and Nurr 1. These, along with Nor-1, are identified as proteins that regulate the expression of numerous target genes that are involved in the dopaminergic (DA) system. This year’s work is the next step toward determining the appropriate compound to decrease or even preclude the LIDs that so greatly affect the quality of life of human patients.
7. Dr. Gil Levkowitz (Weizmann Institute, Israel) received a grant last year to study zebrafish as an alternate vertebrate model, since brain physiology and embryonic development are quite similar among this species, rodents and humans. He cited as an advantage of using zebrafish to study neural development is that their embryos are visually transparent and thus dopaminergic (DA) cells can be monitored in the brains of living specimens. He and his colleagues have identified several novel candidate neuropeptides (brain-specific proteins) that may have a role in the development of DA neurons and will use this year’s funding in an attempt to identify the assembly of extrinsic (from without) and intrinsic (innate) signals that govern DA cell fate and position in the vertebrate brain. In order to one day succeed in cell replacement and neuroprotective mechanisms for PD patients, we must better understand the functions of the molecules that control neural specification during development as well as why DA neurons are vulnerable in several degenerative disorders.
8. Oxidative stress of multiple causes has been shown by many scientists to be involved in the pathogenesis of Parkinson’s disease. While the DATATOP study was not able to determine benefits from the antioxidant vitamin E alone or in combination with a monoamine-oxidase inhibitor, basic scientists have seen moderate benefits in animal cells and animal models of parkinsonism with the use of such compounds. Nor do we yet have data showing Lewy body or oxidative damage protection. Dr. LiPing Liang will use his grant to study yet another type of catalytic antioxidant, metalloporphyrins, in MPTP-parkinsonian mice and also in rat mitochondria slices. This class of antioxidants has been shown to have high lipid solubility and is thus better able to cross the blood-brain barrier resulting in more bioavailability. (One of the problems with vitamin E is that very little of a dose can cross the relatively intact barrier of the patient with PD.) His work will be done at the University of Colorado in Denver. Should his hypothesis prove out, the results could lead to development of candidate drugs for human clinical trials.
9. Mitochondria are considered the “powerhouse” or energy-producers of neuronal cells. In Parkinson’s disease, a large protein complex (Complex 1) has been found to be damaged, resulting in mitochondrial dysfunction. Numerous groups have shown that toxins that produce parkinsonisms in animal models do so by inhibiting Complex 1, resulting in oxidative stress and loss of dopaminergic (DA) neurons. Dr. Srinivas B.M. Mukunda and colleagues at the Buck Institute (Novato, California) are approved for grant funding to continue their work with DA rodent PC12 cells with induced depletion of glutathione. This is a tripeptide compound that is depleted in the parkinsonian brain and parallels disease severity. Molecular data indicate that oxidative stress plays a major role in neurodegeneration, with glutathione depletion being one of the early triggering events. More detailed knowledge of how Complex 1 is targeted for damage and how extensively that damage occurs, as well as how it leads to mitochondrial and blood-brain barrier defects, would provide the field with important information as to disease cause(s). In turn, such data could provide valuable insight as to terms of designs for neuroprotective as well as symptomatic therapy.
10. Should Dr. Meir Plotnik and his colleagues at Tel Aviv University (Israel) accomplish their grant funded goal of determining the basis of freezing of gait (FOG) in patients with Parkinson’s disease, it probably wouldn’t be long before appropriate therapy were devised. FOG is only too common in advancing patients; resistant in most patients to symptomatic medications and surgical procedures and a major handicap to patients who wish to live independently. His group, after some years of studying FOG, now wants to attempt to explain the mechanisms as a manifestation of uncoordinated bilateral motor performance of gait. They will compare PD patients experiencing FOG with patients who do not experience FOG and with a control group of age-matched healthy people. Computerized systems will be used to record and time both leg and hand movements, separately and together, during various novel motor tasks. They hope to finally determine if there is deterioration of the coordination between and among limbs during gait prior to the occurrence of a FOG episode. Identifying the pathophysiology of the symptom could lead to development of therapeutic counter-measures such as more appropriate physical therapy.
11. Among the compounds being tested as possible antiparkinson medications are those called A2A (adenosine) and NMDA (glutamate) receptor antagonists. These are two neurotransmitters that are thought to interact with the dopaminergic (DA) system and may have a role in the motor complications such as dyskinesias (LIDs) that affect so many symptomatically treated PD patients. Grant funds have been awarded to Dr. Alexia E. Pollack at the University of Massachusetts (Boston) so that she and her students can use the 6-hydroxydopamine (6-OHDA) rat model of parkinsonism to continue their attempts at determining how each of these neurotransmitters affects the ability of DA drugs to produce LIDs. It is their theory that the animals exhibit rotational behavior caused by “priming,” or repeated administration of DA drugs and that this known behavior suggests the cause of the motor complications seen in human patients. They will use numerous approved and experimental compounds in combinations, hoping that blocking behavioral sensitization in these animals will lead to a treatment strategy that is better tolerated by human patients who obviously will require DA replacement therapy over many years.
12. A large body of evidence has shown, over the past few years that the alpha-synuclein (@-synuclein) protein plays a major role in Parkinson’s disease, indeed, has caused a new delineation in the field of movement disorders: synucleinopathies. These disorders are characterized by accumulations of the protein that the healthy brain would break down and excrete. What is not known is how this key element is deposited and whether it is a cause or effect, in normal or mutated form and in what amount(s). It is known to form fibers that become fibrils (found in cell bodies and axons of neurons) and accumulate in clusters. Dr. Dean L. Pountney (Griffith University, Australia) has grant funds to prove his hypothesis that this protein, in cluster form (bodies) is potentially the initiating agent leading to neurodegeneration in PD and the other synucleinopathies. He will use cultured neuronal cells in his attempt to determine how @-synuclein clusters become toxic to neurons as well as how they can be stabilized. Knowledge of the mechanism of neurotoxicity should single out targets for developing “a new generation of therapeutics effective in halting the pathogenic process.”
13. The end-products of a specific enzymatic action called glycation are called AGEs. These are oxidized sugar residues and are indicators of the oxidative stress that is thought to play a role in the development of Parkinson’s disease (and diabetes as well). AGEs are ligands for a receptor known as RAGE and are known to accumulate in Lewy bodies in the brains of patients with PD. Dr. Peter Teismann of Georg-August University (Gottingen, Germany) theorizes that AGEs are increased in PD and may thus contribute to the pathogenesis of the disorder. He will use his grant to study mice, half of which are intoxicated with MPTP, the other littermates used as healthy controls, to try to determine how the receptor RAGE is activated. If he is successful in ablating RAGE, therefore providing beneficial neuroprotection in this mouse model of parkinsonism, such mediation could help determine a potential target for neuroprotection or neuroregeneration in human Parkinson’s disease.
14. A grant was awarded last year to Drs. Philip J. Thomas (University of Pennsylvania and Chang-Wei Liu University of Texas at Dallas) to collaborate on a project to define the proteasomal pathway(s) of degradation effected by alpha-synuclein (@-synuclein) in the brains of PD patients and how this degradation produces fragments of the protein that causes or worsens neurodegeneration. They did, indeed accomplish their goals, delineating two pathways: a processive one that clears potentially toxic forms of the protein (good) and a second, non-processive one that leads to the fragment production (bad). In this next year of grant support, they will advance their work by showing how residual aggregates of @-synuclein accumulate and create a “vicious cycle” of cytotoxicity. They hope to investigate the mechanisms by which excessive or mutated forms of the protein act on neurons that may be already vulnerable due to aging, another major risk for PD. It is their theory that inhibiting a specific part of the proteasome would lead to the ability to create neuroprotective compounds to be used to benefit human patients.
15. One of the three groups who have done extensive work to date on the LRRK2 gene (called “dardarin” by the Spanish group) is that at the Norwegian University of Science and Technology in Trondheim. One of this team is Dr. Mathias Toft, who is being funded by a grant this year to use haplotype-tagging “snips” and coding variants in their PD population in an attempt to determine any association among the seven large Norwegian families they have been following. They will also further their genealogic research of the original families and include these patients and healthy family members in a prospective clinicogenetic study. While prospective studies take years to complete, they are considered more definitive than are retrospective studies; the latter rely on participants’ memories and data are not as reliable. The importance of this work is partially based on the fact that mutations in the LRRK2 gene are not confined to familial parkinsonism, but have been seen in classic PD patients as well.
16. Dr. Konstantinos Vekrellis (Academy of Athens, Greece) and his colleagues used last year’s PDF grant to test the effects of various inhibitors of the ubiquitin-proteasomal system, thought to have multiple roles in the brain. They have characterized cell lines and have devised a system to better address the effects of alpha-synuclein (@-synuclein) expression on proteasomal activity. While mutations of this protein have been identified in only a small minority of familial patients with parkinsonism, Dr. Vekrellis feels that it is reasonable to assume that learning the aberrant effects of the mutated protein will give us insight into the pathophysiology of the classic or sporadic disease (PD) by uncovering common mechanisms of neuronal dysfunction and death. He hopes to use this year’s continuing funding to delineate which defect(s) come(s) first and if other defects are causally linked to some such primary defect. The work this year, as in last, will be done in cell cultures.
17. Enhanced Recovery Through Treadmill Exercise in the Mouse Model of Parkinson’s Disease.
Investigator: The Laboratories of Michael Jakowec, PhD, and Giselle Petzinger, MD., Department of Neurology, University of Southern California
In early life our brain goes through a tremendous explosion of learning where we acquire new motor skills such as walking, running, ice-skating, and balance. Other parts of the brain also learn their selective functions including language, musical skills, vision, and problem solving. Until recently, it was assumed that our brains ability to change (a term called neuroplasticity) was permanently fixed once we reached adulthood, and that specific skills are selectively lost if their controlling regions within the brain are damaged through injury or disease. Remarkably, we are learning that the brain’s capacity for recovery from injury is far greater than previously recognized. Recent studies in a number of labs have shown that the intrinsic ability of the injured brain to repair, at any age, can be enhanced through activity-dependent processes including environmental enrichment, exercise, forced-use, and complex skills training. Not only can this approach be applied to clinical conditions like stroke but we are now learning that other phenomenon like Parkinson’s disease (PD) can in fact lead to functional improvement through neuroplasticity.
A primary focus of our lab is to better understand neuroplasticity (and repair) in models of PD. Both the mouse and nonhuman primate, when subjected to the neurotoxicant MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), which selectively destroys nigrostriatal dopaminergic neurons (the same neurons lost in PD), leads to behavioral and biochemical features similar to that seen in human PD. Remarkably, both the MPTP-lesioned mouse and nonhuman primate recover from the effects of MPTP but it takes a period of several months. Our goal is to find ways to enhance this natural recovery and by doing so identify new therapeutic modalities for the treatment of basal ganglia disorders including PD. In addition to pharmacological and molecular intervention strategies we have also found that we are able enhance motor behavior deficits in MPTP-lesioned mice subjected to an intensive treadmill exercise program. Interestingly, our studies indicate that there are remarkable changes in those genes and proteins involved in dopamine neurotransmission as well as another neurotransmitter system that uses glutamate. These results have recently been published in Fisher et al (2004) Journal of Neuroscience Research 77: 378-390. Ongoing studies in the lab are designed to better understand the molecular mechanisms underlying exercise-enhanced recovery in the basal ganglia. For example, we wish to know how precisely the dopamine and glutamate systems are altered, and can we further enhance the benefits of exercise or even block them with pharmacological treatment targeting dopamine and glutamate. In addition, we wish to explore important questions regarding age-related benefits of exercise, how long the benefits persists, and if other tests of motor behavior enhancement are also affected by treadmill exercise.
To accomplish these goals we would like to thank Team Parkinson’s for providing the addition of a new state-of-the-art rodent treadmill to our laboratory. This treadmill will allow us to run mice in an intensive exercise program, more accurately quantify behavioral measures, and allow computer integration of these measures. Understanding the mechanisms by which repair of the injured brain may be enhanced in a mouse model of PD, will provide valuable insights into the development of therapeutic treatments for PD. For example, by understanding the mechanisms responsible for exercise enhanced recovery will permit precise tailoring of exercise programs with specific clinical treatments, disease stages, and may identify new targets for drug discovery.