Parkinson’s disease is well-known for impairing movement and causing tremors, but many patients also develop other serious problems, including sleep disturbances and significant losses in cognitive function known as dementia.

Now researchers at Washington University School of Medicine in St. Louis have modeled Parkinson’s-associated dementia for the first time. Scientists showed that a single night of sleep loss in genetically altered fruit flies caused long-lasting disruptions in the flies’ cognitive abilities comparable to aspects of Parkinson’s-associated dementia. They then blocked this effect by feeding the flies large doses of the spice curcumin.

“Clinical trials of curcumin to reduce risk of Parkinson’s disease are a future possibility, but for now we are using the flies to learn how curcumin works,” says author James Galvin, M.D., a Washington University associate professor of neurology who treats patients at Barnes-Jewish Hospital. “This should help us find other compounds that can mimic curcumin’s protective effects but are more specific.”

Galvin and senior author Paul Shaw, Ph.D., assistant professor of neurobiology, publish their results in the journal Sleep on Aug. 1.

Galvin is an expert in cognitive impairments in human Parkinson’s disease; Shaw studies sleep and the brain in fruit flies. The researchers decided collaborate based in part on evidence that increased sleep loss in Parkinson’s patients can precede or coincide with increased severity in other Parkinsonian symptoms.

More than 74 percent of Parkinson’s patients have trouble sleeping, and up to 80 percent of patients 65 and older who have Parkinson’s disease for seven years will develop dementia, according to Galvin.

Shaw’s lab has linked sleep loss to changes in the dopaminergic system of the brain, the part of the brain that produces the neurotransmitter dopamine and is at the center of the damage caused by Parkinson’s.

“In healthy flies, sleep deprivation decreases dopamine receptor production and causes temporary learning impairments that are fully restored after a two-hour nap,” Shaw says.

Shaw and Galvin studied fruit flies genetically modified to make a human protein called alpha-synuclein in their brains. Scientists don’t yet know what alpha-synuclein does, nor have they found a fly counterpart for it. But they have shown that it aggregates in the brains of Parkinson’s disease patients and believe the processes that cause the aggregations are harming dopamine-producing cells.

Prior studies of fruit flies with human alpha-synuclein in their brains showed that the flies, like human Parkinson’s patients, also lose dopamine-producing neurons, have movement-related problems and develop alpha-synuclein aggregations. But scientists had yet to evaluate the flies for signs of dementia.

Lead author Laurent Seugnet, Ph.D., research associate at L’Ecole Suprieure de Physique Chimie Industrielles in France, first tested the flies’ learning ability using a procedure he helped develop in Shaw’s lab. For the test, Seugnet placed flies in a vial with two branches: one lighted branch containing quinine, a bitter-tasting substance flies prefer to avoid; and a darkened but quinine-free branch. After a few trials, normal flies learn to suppress their natural attraction to the light and fly into the darkened vial instead to avoid the quinine.

Flies with alpha-synuclein in their brains could still learn when they were middle-aged, or about 16 to 20 days old. But when Seugnet deprived them of sleep for 12 hours, he found that their ability to remember was more severely impaired than that of young healthy flies that had also been sleep-deprived.

“This was still true even 10 days later, so it seemed to be a lasting effect,” says Seugnet.

Galvin had earlier found that curcumin, a derivative of the spice turmeric, blocks alpha-synuclein aggregation in cell models of Parkinson’s disease. Based on this, Seugnet fed curcumin to a new batch of flies, repeated the tests and found middle-aged flies with alpha-synuclein retained their ability to learn as well as normal young flies.

“Thanks to this model our labs have created, Dr. Galvin and I can not only quickly test potential new treatments for these symptoms of Parkinson’s, we can also move up our treatments in terms of the timeline along which the disorder develops,” says Shaw. “That may give us a real chance to change the course of the disease.”

Seugnet L, Galvin JE, Suzuki Y, Gottschalk L, Shaw PJ. Persistent short-term memory defects following sleep deprivation in a Drosophila model of Parkinson disease. Sleep, Aug. 1, 2009

Washington University School of Medicine’s 2,100 employed and volunteer faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children’s hospitals. The School of Medicine is one of the leading medical research, teaching and patient care institutions in the nation, currently ranked third in the nation by U.S. News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children’s hospitals, the School of Medicine is linked to BJC HealthCare.

An enzyme that naturally occurs in the brain helps destroy the mutated protein that is the most common cause of inherited Parkinsons disease, researchers at UT Southwestern Medical Center have found.

Their study, using human cells, provides a focus for further research into halting the action of the mutated protein. One of the most famous carriers of the mutation is Google co-founder Sergey Brin, who wrote about it on his blog in 2008.

There are currently enormous efforts to identify potential therapies based on inhibiting this mutated protein, said Dr. Matthew Goldberg, assistant professor of neurology and psychiatry and senior author of the paper, which appears online in the journal Public Library of Science.

Our paper is a major advance because we identify a protein that binds to the mutated protein and promotes its breakdown, he said.

The particular mutation that they studied affects a protein whose function is not well understood. In its normal form, it appears to have multiple sites where other molecules can attach themselves, like a space station with many docking areas.

Several mutations can affect the protein, which is named LRRK2. Some of the mutations cause Parkinsons disease.

The current theory is that the mutation leads to increased function of LRRK2 and to the formation of abnormal clumps of proteins inside brain nerve cells. The cells eventually die from these effects.

In the current study, the researchers used cultured human kidney cells and found that LRRK2 and a protein called CHIP robustly associated with each other.

Further testing showed that CHIP and LRRK2 could bind to each other in two different ways, either directly or indirectly by a third molecule that acted as a bridge.

When CHIP bound to either the normal or mutant form of LRRK2, levels of LRRK2 in the cell decreased, the researchers found. This occurred because the cells increased the rate at which they destroyed LRRK2.

CHIP may be a useful therapeutic target for treatments to break down LRRK2 in people with Parkinsons, Dr. Goldberg said.

Our next step is to identify cellular mechanisms that signal LRRK2 to be degraded by CHIP or by other mechanisms, he said. Because LRRK2 mutations are believed to cause Parkinsonism by increasing the activity of LRRK2, enhancing the normal mechanisms that target LRRK2 for degradation by CHIP may be therapeutically beneficial.

Lead author Xiaodong Ding, senior research associate in neurology at UT Southwestern, also contributed to the study.

The study was funded in part by the David M. Crowley Foundation.

Visit www.utsouthwestern.org/neurosciences to learn more about UT Southwesterns clinical services in the neurosciences.

Mouse Model Offers Scientists a Powerful New Way to Understand the Disease and Evaluate Treatments

NEW YORK (June 7, 2009) — Scientists at Weill Cornell Medical College have developed a new mouse model of Parkinson’s disease (PD) that successfully reproduces the impairments of movement and the degenerative brain changes that occur in the human disease. Their research, performed in collaboration with investigators at Columbia University Medical Center, appears in the June 7 issue of the journal Nature Neuroscience.

Weill Cornell Medical College
Weill Cornell Medical College, Cornell University’s medical school located in New York City, is committed to excellence in research, teaching, patient care and the advancement of the art and science of medicine, locally, nationally and globally. Weill Cornell, which is a principal academic affiliate of NewYork-Presbyterian Hospital, offers an innovative curriculum that integrates the teaching of basic and clinical sciences, problem-based learning, office-based preceptorships, and primary care and doctoring courses. Physicians and scientists of Weill Cornell Medical College are engaged in cutting-edge research in areas such as stem cells, genetics and gene therapy, geriatrics, neuroscience, structural biology, cardiovascular medicine, transplantation medicine, infectious disease, obesity, cancer, psychiatry and public health — and continue to delve ever deeper into the molecular basis of disease and social determinants of health in an effort to unlock the mysteries of the human body in health and sickness. In its commitment to global health and education, the Medical College has a strong presence in places such as Qatar, Tanzania, Haiti, Brazil, Austria and Turkey. Through the historic Weill Cornell Medical College in Qatar, the Medical College is the first in the U.S. to offer its M.D. degree overseas. Weill Cornell is the birthplace of many medical advances — including the development of the Pap test for cervical cancer, the synthesis of penicillin, the first successful embryo-biopsy pregnancy and birth in the U.S., the first clinical trial of gene therapy for Parkinson’s disease, the first indication of bone marrow’s critical role in tumor growth, and most recently, the world’s first successful use of deep brain stimulation to treat a minimally conscious brain-injured patient. For more information, visit www.med.cornell.edu.

New theory of Parkinson’s disease gives researchers fresh ideas for treatments

Parkinson’s: Neurons destroyed by 3 simultaneous strikesIn a study that reveals the clearest picture to date of neuron death in Parkinson’s disease, researchers at Columbia University Medical Center have found that a trio of culprits acting in concert is responsible for killing the brain cells.

The study, published in the April 30 issue of Neuron, showed that three molecules the neurotransmitter dopamine, a calcium channel, and a protein called alpha-synuclein act together to kill the neurons.

The discovery gives researchers a new understanding of how to save the neurons, say the study’s authors, Eugene Mosharov, Ph.D., associate research scientist, and David Sulzer, Ph.D., professor of neurology & psychiatry at Columbia University Medical Center.

“Though the interactions among the three molecules are complex, the flip side is that we now see that there are many options available to rescue the cells,” says Dr. Mosharov.

The symptoms of Parkinson’s including uncontrollable tremors and difficulty in moving arms and legs are blamed on the loss of neurons from the substantia nigra region of the brain.

Researchers had previously suspected dopamine, alpha-synuclein and calcium channels were involved in killing the neurons, but could not pin the deaths on any single molecule.

The new paper, along with previous studies with Dr. Ana Maria Cuervo at Albert Einstein College of Medicine, shows that it is the combination of all three factors that kills the neurons.

The studies found that neurons die because calcium channels lead to an increase of dopamine inside the cell; excess dopamine then reacts with alpha-synuclein to form inactive complexes; and then the complexes gum up the cell’s ability to dispose of toxic waste that builds up in the cell over time. The waste eventually kills the cell.

The neurons will survive if just one of the three factors is missing, Drs. Sulzer and Mosharov also found. “It may be possible to save neurons and stop Parkinson’s disease by interfering with just one of the three factors,” Dr. Mosharov says.

That means that one drug already in clinical trials which blocks the culprit calcium channel may work to slow or stop the progression of the disease, an achievement none of the current treatments for Parkinson’s disease can accomplish.

Good Dopamine; Bad Dopamine

The idea that dopamine contributes to the death of neurons may seem paradoxical, since most Parkinson’s patients take L-DOPA to increase the amount of dopamine inside the cells.

The new study shows that it’s the location of the dopamine inside the neurons that determines its toxicity.

Most of dopamine inside the neurons is packaged into compartments that are shipped to the edge of the cell where the dopamine is released. The motor symptoms of Parkinson’s arise when the amount of dopamine released by the cells declines. L-DOPA improves symptoms by boosting the amount of dopamine released by the cells. As long as dopamine is confined inside the compartments before it is released, it is safe.

Outside the compartments in the cell’s cytoplasm, however, Drs. Sulzer and Mosharov found that dopamine - in concert with calcium and alpha-synuclein is toxic.

New Idea for Treatment

A better treatment, the researchers say, may be to push more dopamine into the compartments where it has no toxic effect on the cell.

“That would be a magic treatment,” Dr. Mosharov says. “Not only would it stop cells from dying and the disease from progressing, it would improve the patient’s symptoms at the same time by giving their neurons more dopamine to release.”

Drs. Sulzer and Mosharov are currently working on genetic therapies that could accomplish this feat, but caution that it will be years before any such treatment is ready for clinical trials, if ever.

Columbia University Medical Center

Columbia University Medical Center provides international leadership in basic, pre-clinical and clinical research, in medical and health sciences education, and in patient care. The Medical Center trains future leaders and includes the dedicated work of many physicians, scientists, public health professionals, dentists, and nurses at the College of Physicians & Surgeons, the Mailman School of Public Health, the College of Dental Medicine, the School of Nursing, the biomedical departments of the Graduate School of Arts and Sciences, and allied research centers and institutions. Established in 1767, Columbia’s College of Physicians and Surgeons was the first institution in the country to grant the M.D. degree and is now among the most selective medical schools in the country. Columbia University Medical Center is home to the most comprehensive medical research enterprise in New York City and state and one of the largest in the United States and is affiliated with NewYork-Presbyterian Hospital. For more information, please visit www.cumc.columbia.edu.

Dr. Nicolas Bazan, Director of the Neuroscience Center of Excellence, Boyd Professor, and Ernest C. and Yvette C. Villere Chair of Retinal Degenerative Diseases Research at LSU Health Sciences Center New Orleans, will present new research findings showing that an omega three fatty acid in the diet protects brain cells by preventing the misfolding of a protein resulting from a gene mutation in neurodegenerative diseases like Parkinson’s and Huntington’s. He will present these findings for the first time on Sunday, April 19, 2009 at 10:30 a.m. at the Ernest N. Morial Convention Center, Nouvelle C Room, at the American Society for Nutrition, Experimental Biology 2009 Annual Meeting.

With funding from the National Eye Institute of the National Institutes of Health, Dr. Bazan and his colleagues developed a cell model with a mutation of the Ataxin-1 gene. The defective Ataxin-1 gene induces the misfolding of the protein produced by the gene. These misshapened proteins cannot be properly processed by the cell machinery, resulting in tangled clumps of toxic protein that eventually kill the cell. Spinocerebellar Ataxia, a disabling disorder that affects speech, eye movement, and hand coordination at early ages of life, is one disorder resulting from the Ataxin-1 misfolding defect. The research team led by Dr. Bazan found that the omega three fatty acid, docosahexaenoic acid (DHA), protects cells from this defect.

Dr. Bazan’s laboratory discovered earlier that neuroprotectin D1 (NPD1), a naturally-occurring molecule in the human brain that is derived from DHA also promotes brain cell survival. In this system NPD1 is capable of rescue the dying cells with the pathological type of Ataxin-1, keeping their integrity intact.

“These experiments provide proof of principle that neuroprotectin D1 can be applied therapeutically to combat various neurodegenerative diseases,” says Dr. Bazan. “Furthermore, this study provides the basis of new therapeutic approaches to manipulate retinal pigment epithelial cells to be used as a source of NPD1 to treat patients with disorders characterized by this mutation like Parkinson’s, Retinitis Pigmentosa and some forms of Alzheimer’s Disease.”

LSU Health Sciences Center New Orleans educates the majority of Louisiana’s health care professionals. The state’s academic health leader, LSUHSC comprises a School of Medicine, the state’s only School of Dentistry, Louisiana’s only public School of Public Health, Schools of Allied Health Professions and Graduate Studies, as well as the only School of Nursing in Louisiana within an academic health center. LSUHSC faculty take care of patients in public and private hospitals and clinics throughout Louisiana. In the vanguard of biosciences research in a number of areas worldwide, LSUHSC faculty have made lifesaving discoveries and continue to work to prevent, treat, or cure disease. LSUHSC outreach programs span the state.

Louisiana State University Health Sciences Center

A novel stimulation method, the first potential therapy to target the spinal cord instead of the brain, may offer an effective and less invasive approach for Parkinson’s disease treatment, according to pre-clinical data published in the journal Science by researchers at Duke University Medical Center.

Researchers developed a prosthetic device that applies electrical stimulation to the dorsal column in the spinal cord, which is a main sensory pathway carrying tactile information from the body to the brain. The device was attached to the surface of the spinal cord in mice and rats with depleted levels of the chemical dopamine mimicking the biologic characteristics of someone with Parkinson’s disease along with the impaired motor skills seen in advanced stages of the disease.

When the device was turned on, the dopamine-depleted animals’ slow, stiff movements were replaced with the active behaviors of healthy mice and rats. Improved movement was typically observed within 3.35 seconds after stimulation.

“We see an almost immediate and dramatic change in the animal’s ability to function when the device stimulates the spinal cord,” says senior study investigator Miguel Nicolelis, M.D., Ph.D., the Anne W. Deane Professor of Neuroscience at Duke. “Moreover, it is easy to use, significantly less invasive than other alternatives to medication, such as deep brain stimulation, and has the potential for widespread use in conjunction with medications typically used to treat Parkinson’s disease.”

Researchers tested mice and rats with acute and chronic dopamine deficit using varying levels of electrical stimulation and in combination with different doses of dopamine replacement therapy, also known as 3,4-dihydroxy-L-phenylalanine or L-DOPA, to determine the most effective pairing.

When the device was used without additional medication, Parkinsonian animals were 26 times more active. When stimulation was coupled with medication, only two L-DOPA doses were needed to produce movement compared to five doses when the medication was used by itself.

“This work addresses an important need because people living with Parkinson’s disease face a difficult reality L-Dopa will eventually stop managing the symptoms,” explains Romulo Fuentes, a postdoctoral fellow at Duke University and lead author of the study. “Patients are left with few options for treatment, including electrical stimulation of the brain, which is appropriate for only a subset of patients.”

While deep brain stimulation (DBS) and other experimental treatments attack the disease at its origin in the brain Nicolelis and team took a different approach. The concept for the device began when researchers made a surprising connection with another neurological condition.

“It was a moment of sudden insight,” explains Nicolelis. “We were analyzing the brain activity of mice with Parkinson’s disease and suddenly it reminded me of some research I’d done in the epilepsy field a decade earlier. The ideas began to flow from there.”

The rhythmic brain activity in the animals with Parkinson’s disease resembled the mild, continuous, low-frequency seizures that are seen in those with epilepsy. One effective therapy for treating epilepsy involves stimulating the peripheral nerves, which facilitate communication between the spinal cord and the body. Researchers took that concept and developed a modified approach for a Parkinson’s disease model.

Nicolelis says that the low frequency seizures, or oscillations, seen in the animal model of Parkinson’s disease have been observed in humans with the condition. Stimulating the dorsal column of the spinal cord reduces these oscillations, which researchers believe creates the ability to produce motor function.

In a healthy body, neurons fire at varying rates as information is transmitted between the brain and the body to initiate normal movement. This process breaks down in someone with Parkinson’s disease.

“Our device works as an interface with the brain to produce a neural state permissive for locomotion, facilitating immediate and dramatic recovery of movement,” says Per Petersson, co-author of the study. “Following stimulation, the neurons desynchronize, similar to the firing pattern that you would see when a healthy mouse is continuously moving.”

Nicolelis says that if the device is proven safe and effective through further research, he imagines it mirroring similar spinal cord stimulator technology currently used to treat chronic pain. Small leads are implanted over the spinal cord and then connected to a portable generator, a small device capable of producing mild electrical currents. During the trial period, the generator is external, while for permanent treatment it would be implanted below the skin.

“If we can demonstrate that the device is safe and effective over the long term in primates and then humans, virtually every patient could be eligible for this treatment in the near future,” Nicolelis said.

The Duke team is collaborating with neuroscientists at the Edmond and Lily Safra International Institute of Neuroscience in Natal, Brazil, to test the new procedure in primate models of Parkinson’s disease prior to initiating clinical studies. Neuroscientists from the Brain and Mind Institute at the Swiss Institute of Technology (EPFL), in Lausanne, Switzerland, will also participate in this international research effort to translate these new findings into clinical practice.

Study co-authors include William Siesser and Marc Caron.

Funding for this research was provided by grants from the National Institutes of Neurological Disorders and Stroke (NINDS), International Neuroscience Network Foundation (INNF) and the Anne W. Deane Endowed Chair.

Duke University Medical Center

Doctors may be able to tailor a specialized form of brain surgery to more closely match the needs of Parkinson patients, according to results from the first large-scale effort to compare the two current target areas of deep brain stimulation surgery, or DBS.

Called the COMPARE Trial, the National Institutes of Health-funded study conducted at the University of Florida evaluated 45 patients for mood and cognitive changes related to DBS.

UF investigators found that DBS in either brain target effectively treated motor symptoms such as tremors, stiffness and slowness.

However, DBS also produced unique effects depending on the target location, especially in patients’ moods and mental sharpness.

The discoveries, in today’s (March 13, 2009) Annals of Neurology, may have an impact on the selection of DBS patients, especially those with pre-existing memory, cognitive or mood disabilities.

“Both targets are FDA-approved and provide excellent outcomes for motor function in Parkinson patients,” said Michael S. Okun, M.D., the principal investigator of the study and a co-director of the Movement Disorders Center at UF’s McKnight Brain Institute. “But there were differences in cognitive function and verbal fluency seven months after the surgery, and that is something that should be considered when trying to tailor therapy to an individual patient’s condition.”

DBS received Food and Drug Administration approval in 2002 as a therapy for movement-related problems associated with essential tremor and Parkinson’s disease. It uses a medical device surgically implanted in a patient’s brain and connected to a power pack in the shoulder region. DBS delivers electrical pulses to targeted areas of the brain via very thin wires, known as “leads.” Each lead ends with four distinct electrical “contacts.”

Currently, in almost all cases worldwide, the leads are implanted in a brain region known as the subthalamic nucleus. But the nearby globus pallidus interna, or GPi, may again emerge as a viable target, especially for patients with mood and cognitive issues, researchers say.

Forty-five volunteers with moderate to advanced Parkinson’s disease completed the prospective, randomized study. Twenty-three received leads to the GPi and 22 to the subthalamic nucleus.

Before surgery, scientists at UF’s Cognitive Neuroscience Laboratory evaluated the patients’ verbal fluency, memory, attention and cognitive processing. Patients were retested about seven months later during four conditions with stimulation at the optimal contact point on the lead as determined during previous programming sessions, with stimulation at contact points adjacent to the optimal one, and with stimulation turned off. Examiners and patients were blind to the conditions as well as to the brain target.

Generally, the target choice produced no major differences in motor function, mood or cognition in the patients. However, patients whose leads were implanted in the subthalamic nucleus, the most common surgery target, did have increased problems with verbal fluency and mood and they tended to be more angry and irritable.

“We think it will be important to tailor the therapy to the patient,” said Kelly D. Foote, M.D., an associate professor of neurosurgery at the College of Medicine and a co-director of the UF Movement Disorders Center. “Targeting the traditional location the subthalamic nucleus might be better for someone who is younger and healthier. But for someone who is older with memory problems, or perhaps in the early stages of dementia, it would be important to consider the alternative.”

The traditional target does have unique advantages, Foote said. It seems to be more effective at reducing a patient’s medications, which may lead to an improved quality of life and cost savings. In addition, because it is relatively smaller about a third the size of a pea less electricity was required to stimulate this area, which is an important consideration because more surgery is required to replace DBS batteries.

More study will be necessary to determine whether DBS target choice can be tailored to meet individual patient needs. However, in considering the surgery, potential patients need to weigh the benefits of DBS against risks such as mild cognitive decline.

“It is unclear whether these mild cognitive changes are clinically significant in terms of the patient’s everyday life,” said Dawn Bowers, Ph.D., a professor in the department of clinical and health psychology in the College of Public Health and Health Professions and the director of the Cognitive Neuroscience Laboratory where the patients were assessed. “Though important, they pale in comparison to the tremendous boost these patients receive in motor behavior.”

In the meantime, scientists say uses for DBS technology will continue to move beyond the movements disorders field.

“It is vitally important that we take the opportunities afforded to us by deep brain stimulation technology to better understand what underpins mood and cognitive circuitry in the brain,” said Okun, who is also an associate professor of neurology and neurosurgery at the UF College of Medicine and the national medical director of the National Parkinson Foundation. “What we have learned from Parkinson’s disease we are now taking into other areas, and as we unlock the circuitry, we can apply new technologies to ultimately improve quality of life.”

The sweet spot? UF doctors test targets for Parkinson surgeryUniversity of Florida

A connection between genetic and environmental causes of Parkinson’s disease has been discovered by a research team led by Aaron D. Gitler, PhD, Assistant Professor in the Department of Cell and Developmental Biology at the University of Pennsylvania School of Medicine. Gitler and colleagues found a genetic interaction between two Parkinson’s disease genes (alpha-synuclein and PARK9) and determined that the PARK9 protein can protect cells from manganese poisoning, which is an environmental risk factor for a Parkinson’s disease-like syndrome. The findings appear online this week in Nature Genetics.

Manganism, or manganese poisoning, is prevalent in such occupations as mining, welding, and steel manufacturing. It is caused by exposure to excessive levels of the metal manganese, which attacks the central nervous system, producing motor and dementia symptoms that resemble Parkinson’s disease.

In Parkinson’s patients, the alpha-synuclein protein normally found in the brain misfolds, forming clumps. Yeast cells, the model system in which Gitler studies disease proteins, also form clumps and die when this protein is expressed at high levels. These are the same yeast cells that bakers and brewers use to make bread, beer, and wine.

As a postdoctoral fellow at the Whitehead Institute in Cambridge, Massachusetts, Gitler and colleagues started looking for genes that could prevent the cell death caused by mis-folded alpha-synuclein in yeast. Eventually they found a few genes to test in animal models and some were able to protect neurons from the toxic effects of alpha-synuclein. “One of the genes that we found was a previously uncharacterized yeast gene called YOR291W. No one knew what it did back in 2006,” he recalls.

In the meantime, researchers in Europe published studies about a family that had an early-onset form of a type of Parkinson’s disease caused by mutations in the PARK9 gene. “When I read about this study, I wondered what the closest yeast gene was to the human PARK9 gene and it turned out to be YOR291W,” explains Gitler. “It was one of the genes that could rescue alpha-synuclein toxicity from our yeast screen. That was the big Eureka! and completely unexpected. It suggested that Parkinson’s disease genes could interact with each other in previously unexpected ways.”

Because of its similarity to the human PARK9 gene, Gitler and colleagues renamed the yeast gene to YPK9 (which stands for Yeast PARK9). Researchers at Purdue University and The University of Alabama teamed up with Gitler and his colleagues to show that the PARK9 gene could also protect neurons from alpha-synuclein’s toxic effects.

Next, the team set out to find the function of YPK9. Study co-first author, postdoctoral fellow Alessandra Chesi, PhD, discovered that YPK9 encodes a metal transporter protein. “Its sequence looks like other proteins that we know transport metals,” says Chesi.

She deleted the YPK9 gene from yeast and the cells were fine. Then she exposed YPK9-deficient yeast cells to an excess of different metals — zinc, copper, manganese, iron, etc. — to determine which metal it might transport. Of all the metals Chesi tested, she found that in the presence of manganese, the YPK9-deficient yeast did not grow as well. They were hypersensitive to manganese.

“This was astonishing, because it was known for years that welders and miners that inhale manganese get a Parkinson’s-like disease called manganese poisoning,” says Chesi. “The specific neurons that are lost in the miners are from the globus pallidus, a brain motor center. The European parkinsonism patients with the PARK9 mutation also lose neurons in this region.”

Gitler then found that the protein made by YPK9, the yeast gene equivalent of PARK9, is localized to the vacuole membrane in the yeast cell. Vacuoles are inner cell components that wall off toxic substances for later disposal. “Our hypothesis is that the vacuole, a bag in the cell that captures toxins, is sitting there and taking in manganese and sequestering it for detoxification, keeping it away from other cell organelles,” explains Gitler. “But, having a mutation in the PARK9 gene causes problems for this process in yeast and possibly in humans”.

“It’s an interesting story that we’ve discovered in yeast and it will be important to see if it holds up in people. What’s new is the connection between genetic and environmental causes of Parkinson’s. How does PARK9 protect against alpha-synuclein toxicity and how does PARK9 help prevent manganese poisoning? This is what we will be investigating next.”

Research on the mechanisms involved in neurodegenerative diseases such as Alzheimer’s, stroke, dementia, Parkinson’s and multiple sclerosis, to name a few, has taken a step forward thanks to the work of biological sciences Ph.D. student Sonia Do Carmo, supervised by Professor ric Rassart of the Universit du Qubec Montreal (UQAM) Biological Sciences Department, in collaboration with researchers at the Armand-Frappier Institute and the University of Valladolid in Spain.

Do Carmo and her collaborators have successfully demonstrated the protective and reparative role of apolipoprotein D, or ApoD, in neurodegenerative diseases. Their discovery suggests interesting avenues for preventing and slowing the progression of this type of illness.

These studies were inspired by work done ten years ago by Professor Rassart’s team, who then discovered increased levels of ApoD in the brains of people with several types of neurodegenerative disorders, including Alzheimer’s. The team hypothesized that this protein might play a protective and restorative role but were unable to demonstrate this at the time.

The experiments
To establish the protective and reparative role of ApoD, the researchers used two types of genetically modified mice: one type with increased levels of ApoD in the brain and a second type with no ApoD. The mice were then exposed to neurodegenerative agents. A group of the modified mice and a control group (unmodified) were exposed to paraquat, a widely used herbicide that has been shown to increase the risk of Parkinson’s. Then the same type of experiment was performed by injecting two groups with a virus that causes encephalitis. In both cases, the mice modified for increased levels of ApoD had the best outcomes, with a better ability to combat the diseases and a higher survival rate than the unmodified mice. The knockout mice with no ApoD displayed the poorest outcomes. These experiments serve to illustrate the protective and reparative role of this protein.

When can we expect medication?
A number of steps remain before this research can translate into effective drugs against neurodegenerative conditions. The original investigator, Professor ric Rassart, explains, You cannot simply inject ApoD, as it has to enter the brain in order for it to be active. We have successfully demonstrated the role of ApoD, but now we need to understand the action of this protein. Only then will we be able to think about creating a drug to prevent these types of diseases and to slow their progression. All the same, this discovery by Sonia Do Carmo and her collaborators is a significant breakthrough, as we know very little about the mechanisms of neurodegenerative diseases.

The discovery has aroused considerable interest among the molecular biology community. Two major scientific journals have already published the research findings: Aging Cell (Vol. 7: 506-515, 2008) and Journal of Neuroscience (Vol. 28: 10330-10338, 2008).

Source

Neurologists have observed for decades that Lewy bodies, clumps of aggregated proteins inside cells, appear in the brains of patients with Parkinson’s disease and other neurodegenerative diseases.

The presence of Lewy bodies suggests underlying problems in protein recycling and waste disposal, leading to the puzzle: how does disrupting those processes kill brain cells?

One possible answer: by breaking a survival circuit called MEF2D. Researchers at Emory University School of Medicine have discovered that MEF2D is sensitive to the main component of Lewy bodies, a protein called alpha-synuclein.

In cell cultures and animal models of Parkinson’s, an accumulation of alpha-synuclein interferes with the cell’s recycling of MEF2D, leading to cell death. MEF2D is especially abundant in the brains of people with Parkinson’s, the researchers found.

The results are scheduled for publication in the Jan. 2, 2009 issue of Science.

“We’ve identified what could be an important pathway for controlling cell loss and survival in Parkinson’s disease,” says senior author Zixu Mao, PhD, associate professor of pharmacology at Emory University School of Medicine.

Further research could identify drugs that could regulate MEF2D, allowing brain cells to survive toxic stresses that impair protein recycling, he suggests.

Most cases of Parkinson’s disease are termed sporadic, meaning that there is no obvious genetic cause, but there are inherited forms of Parkinson’s. Some of these can be linked to mutations in the gene for alpha-synuclein or triplications of the gene. The mutations and triplications cause the brain to produce either a toxic form of alpha-synuclein or more alpha-synuclein than normal.

“Somehow it’s toxic, but alpha-synuclein isn’t part of the cell’s machinery of death and survival,” Mao says.

He and his colleagues began examining how alpha-synuclein influenced MEF2D after a report from another laboratory on disposal of alpha-synuclein by chaperone-mediated autophagy (CMA).

During CMA, certain selected proteins are funneled into lysosomes, compartments of the cell devoted to chewing up discarded proteins. Mao and colleagues found that lysosomes isolated from cells will absorb MEF2D protein, and interfering with CMA chemically causes MEF2D levels to rise.

MEF2D is a transcription factor, a protein that controls whether several genes are turned on or off. Previous studies have shown MEF2D is needed for proper development and survival of brain cells. To function, MEF2D must be able to bind DNA.

The authors found that when CMA is disrupted, most of the accumulated MEF2D can’t bind DNA. This may indicate that the protein is improperly folded or otherwise modified.

“Even though there’s a lot of it, something is making the MEF2D protein inactive,” Mao says.

Mao and his colleagues found that mice that artificially overproduce alpha-synuclein (a model of Parkinson’s disease) have elevated levels of apparently inactive MEF2D in their brains. In addition, MEF2D protein levels were higher in the brains of Parkinson’s patients than in controls.

Following the influence of alpha-synuclein on MEF2D may be a way to connect the various genetic and environmental risk factors for Parkinson’s, even if CMA is not the sole mechanism, Mao says.

“It may be that various stresses impact MEF2D in different ways,” he says. “We think this work provides an explanation that ties several important observations together.”