Putting the brakes on Parkinson’s

The earliest signs of Parkinson’s disease can be deceptively mild. The first thing that movie star Michael J. Fox noticed was twitching of the little finger of his left hand. For years, he made light of the apparently harmless tic. But such tremors typically spread, while muscles stiffen up and directed movements take longer to carry out. Research groups led by Armin Giese of LMU Munich and Christian Griesinger at the Max Planck Institute for Biophysical Chemistry in Göttingen have developed a chemical compound that slows down the onset and progression of Parkinson’s disease in mice. The scientists hope that this approach will give them a way to treat the cause of Parkinson’s and so arrest its progress.

The disease usually becomes manifest between the ages of 50 and 60, and results from the loss of dopamine-producing nerve cells in the substantia nigra, which is part of the midbrain. Under the microscope, the affected cells are seen to contain insoluble precipitates made up of a protein called alpha-synuclein. As an early step in the pathological cascade, this protein forms so-called oligomers, tiny aggregates consisting of small numbers of alpha-synuclein molecules, which are apparently highly neurotoxic. By the time the first overt symptoms appear in humans, more than half of the vulnerable cells have already been lost. Many researchers therefore focus on developing methods for early diagnosis of the condition. However, current therapies only alleviate symptoms, so the research teams led by Armin Giese and Christian Griesinger set out to address the underlying cause of nerve-cell death.

Together, the scientists have developed a substance which, in mouse models of the disease, reduces the rate of growth of the protein deposits and delays nerve cell degeneration to a yet unprecedented degree. As a consequence, mice treated with this agent remain disease-free for longer than non-medicated controls. “The most striking feature of the new compound is that it is the first that directly targets oligomers and interferes with their formation,” explains Christian Griesinger, head of the Department of NMR-based Structural Biology and Director at the Max Planck Institute for Biophysical Chemistry. The discovery is the result of years of hard work. “Combining skills from a range of disciplines has been the key to our success. Biologists, chemists, clinicians, physicists, and veterinarians have all contributed to the development of the therapeutic compound,” adds Armin Giese, who leads a research group at LMU’s Center for Neuropathology and Prion Research.

Giese and his colleagues systematically tested 20,000 candidate substances for the ability to block formation of the protein deposits that are typical for the disease. The screen made use of an extremely sensitive laser-based assay developed by Giese years ago when he was working together with Nobel Laureate Manfred Eigen at the Max Planck Institute for Biophysical Chemistry in Göttingen. Some interesting lead compounds identified during the very first phase of the screening program served as starting point for further optimization. Ultimately, one substance proved to be particularly active. Andrei Leonov a chemist in Griesinger’s team, finally succeeded in synthesizing a pharmaceutically promising derivative. This is well tolerated at dosage levels with significant therapeutic effects, can be administered with the food, and penetrates the blood-brain barrier, reaching high levels in the brain. The two teams have already applied for a patent on the compound which they called Anle138b – an abbreviation of Andrei Leonov’s first name and surname.

A complex series of experiments has provided encouraging indications that Anle138b could also be of therapeutic use in humans. These tests involved not only biochemical and structural investigations of Anle138b’s mode of action but also employed several animal models of Parkinson’s which are under study in Munich and in laboratories of the Excellence Cluster “Nanoscale Microscopy and Molecular Physiology of the Brain” in Göttingen. Mice exposed to Anle138b were found to display better motor coordination than their untreated siblings. “We use a kind of fitness test to evaluate muscle coordination,” Giese explains. “The mice are placed on a rotating rod and we measure how long the animals can keep their balance.”

Generally speaking, the earlier the onset of treatment, the longer the animals remained disease free. What’s more, the beneficial effects of Anle138b are not restricted to animals with Parkinson’s disease. “Creutzfeldt-Jakob disease is caused by toxic aggregates of the prion protein,” Griesinger points out. “And here too, Anle138b effectively inhibits clumping and significantly increases survival times.” These findings hint that Anle138b might also prevent the formation of insoluble deposits formed by other proteins, such as the tau protein that is associated with Alzheimer’s disease. Further experiments will address this issue. Anle138b will therefore be a useful research tool in medicine, as it will enable scientists to study the process of oligomer formation in the test-tube and to determine how their assembly is inhibited. The researchers hope ultimately to gain new insights into the mechanisms into how neurodegenerative disorders develop.

The drugs so far available for treatment of Parkinson’s disease only control its symptoms by enhancing the function of the surviving nerve cells in the substantia nigra. “With Anle138b, we may have the first representative of a new class of neuroprotective agents allowing to retard or even halt the progression of conditions such as Parkinson’s or Creutzfeldt-Jakob disease,” Griesinger says. However, he warns that the findings in mice cannot immediately be applied to humans. The next step will be to carry out toxicity tests in non-rodent species. Only if these are successful will clinical trials in patients become a realistic possibility. As clinician Giese emphasizes: “To successfully establish a novel therapeutic agent for treatment of real patients is a laborious task that requires a lot of work as well as serendipity.”

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Fight Control: Researchers link individual neurons to regulation of aggressive behavior in flies

Scientists have long pondered the roots of aggression—and ways to temper it. Now, new research is beginning to illuminate the cellular-level circuitry responsible for modulating aggression in fruit flies, with the hope of someday translating the findings to humans.

Researchers at Harvard Medical School have identified two pairs of dopamine-producing neurons, also called dopaminergic neurons, and traced their aggression-modulating action to a common structure in the fly brain called the central complex, suggesting that important components of aggression-related behaviors may be processed there.

“This is the first research to identify single dopaminergic neurons that modulate a complex behavior—aggression—in fruit flies,” said Edward Kravitz, George Packer Berry Professor of Neurobiology at HMS and lead author of the study.

“We don’t know how complex this modulatory circuit is, but we now have a key element of it. If we eliminate or increase the function of that dopaminergic neuron, it affects the circuit of the brain responsible for controlling aggression,” Kravitz said.

The findings were published last week in PNAS.

Flies are an ideal animal model for neurological research because genetic methods allow scientists to manipulate neurons and simultaneously observe the resulting behaviors. Many fundamental nervous system mechanisms in flies are similar to those in humans. In fact, both flies and humans share the same neurohormones.

Dopamine is one such neurohormone, and across species it affects a range of behaviors, from learning and memory to motivation and movement. In humans, neurohormones are associated with conditions such as Parkinson’s disease and psychiatric disorders.

Dopaminergic neurons are found in small numbers in particular parts of nervous systems. In humans, there are about 200,000 to 400,000 of these neurons; in fruit flies there are about 100. While their numbers are few, these neurons influence a vast array of behaviors.

Kravitz, along with Olga Alekseyenko, a postdoctoral fellow in the Kravitz lab and first author on the paper, set out to discover how these few dopaminergic neurons can influence such a wide range of behaviors.

To do this, study co-first author, Yick-Bun Chan, HMS research associate in neurobiology, genetically engineered 200 lines of fruit flies. He then used them to target select dopaminergic neurons that could be activated or silenced while the flies engaged in various behaviors.

The team detected two pairs of dopaminergic neurons that affected aggressive behavior in the flies. Interestingly, aggression was increased in the flies either by augmenting the function of these cells or by deactivating them.

In fruit flies, males fight for territory and form stable hierarchical relationships. Using previous observations and analysis of more than 20,000 interactions in fly fights, the team established quantitative measures of aggressive behavior, such as lunging, that allowed them to compare aggression levels in different fly attacks.

“When we turned off the pairs of dopaminergic neurons, the flies fought with more lunging; when we turned them on, they also fought at higher intensity levels. Apparently normal levels of aggression require a precise amount of dopamine released at a specific time and place in the nervous system. These results suggest that these neurons ordinarily hold aggression in check,” said Alekseyenko.

Also significant was the finding that while the two sets of dopaminergic neurons modulated aggression, they did not influence other behaviors.

The first pair of neurons are found in the PPM3 cluster of neurons in the fly brain and the second are within the T1 cluster. Both pairs innervate different parts of the central complex, an important structure in the fly brain.

“We already knew that dopamine receptors are present in the central complex, but we didn’t know which dopamine neurons connected to the receptors or what behaviors those neurons affected,” said Alekseyenko.

“Now we know that two pairs of aggression-mediating dopaminergic neurons terminate in different regions of the central complex, and we know that those regions have different types of dopamine receptors. Our study shows that aggression is one of the behaviors coordinated in these regions of the brain, but we still don’t fully understand the process,” he said.

In a third group of flies, a neuron pair that projected into a different part of the brain was identified. These neurons affected locomotion and sleep, but did not influence aggression.

Kravitz said the next phase of the research will be to use genetic tools to allow his team to identify the subsequent steps in the brain circuitry—which neurons are pre- and post-synaptic to the T1 and PPM3 neurons and how that affects neuronal network function.

The goal will be to establish fundamental principles for how dopaminergic neurons work in the fruit fly system, with the hope that the research will one day translate to how these neurons work in higher species. This may ultimately aid in the development of new dopamine-targeted medications for humans.

“We can now relate these two pairs of neurons specifically to one behavior, and that is aggression,” Kravitz said. “That means we have one piece of the puzzle.”

Scientists reverse memory loss in animal brain cells

Neuroscientists at The University of Texas Health Science Center at Houston (UTHealth) have taken a major step in their efforts to help people with memory loss tied to brain disorders such as Alzheimer’s disease.

Using sea snail nerve cells, the scientists reversed memory loss by determining when the cells were primed for learning. The scientists were able to help the cells compensate for memory loss by retraining them through the use of optimized training schedules. Findings of this proof-of-principle study appear in the April 17 issue of The Journal of Neuroscience.

“Although much works remains to be done, we have demonstrated the feasibility of our new strategy to help overcome memory deficits,” said John “Jack” Byrne, Ph.D., the study’s senior author, as well as director of the W.M. Keck Center for the Neurobiology of Learning and Memory and chairman of the Department of Neurobiology and Anatomy at the UTHealth Medical School.

This latest study builds on Byrne’s 2012 investigation that pioneered this memory enhancement strategy. The 2012 study showed a significant increase in long-term memory in healthy sea snails called Aplysia californica, an animal that has a simple nervous system, but with cells having properties similar to other more advanced species including humans.

Yili Zhang, Ph.D., the study’s co-lead author and a research scientist at the UTHealth Medical School, has developed a sophisticated mathematical model that can predict when the biochemical processes in the snail’s brain are primed for learning.

Her model is based on five training sessions scheduled at different time intervals ranging from 5 to 50 minutes. It can generate 10,000 different schedules and identify the schedule most attuned to optimum learning.

“The logical follow-up question was whether you could use the same strategy to overcome a deficit in memory,” Byrne said. “Memory is due to a change in the strength of the connections among neurons. In many diseases associated with memory deficits, the change is blocked.”

To test whether their strategy would help with memory loss, Rong-Yu Liu, Ph.D., co-lead author and senior research scientist at the UTHealth Medical School, simulated a brain disorder in a cell culture by taking sensory cells from the sea snails and blocking the activity of a gene that produces a memory protein. This resulted in a significant impairment in the strength of the neurons’ connections, which is responsible for long-term memory.

To mimic training sessions, cells were administered a chemical at intervals prescribed by the mathematical model. After five training sessions, which like the earlier study were at irregular intervals, the strength of the connections returned to near normal in the impaired cells.

“This methodology may apply to humans if we can identify the same biochemical processes in humans. Our results suggest a new strategy for treatments of cognitive impairment.  Mathematical models might help design therapies that optimize the combination of training protocols with traditional drug treatments,” Byrne said.

He added, “Combining these two could enhance the effectiveness of the latter while compensating at least in part for any limitations or undesirable side effects of drugs. These two approaches are likely to be more effective together than separately and may have broad generalities in treating individuals with learning and memory deficits.”

(Image courtesy: UC Berkeley)

‘Revealing the scientific secrets of why people can’t stop after eating one potato chip

The scientific secrets underpinning that awful reality about potato chips — eat one and you’re apt to scarf ’em all down — began coming out of the bag today in research presented at the 245^th National Meeting & Exposition of the American Chemical Society, the world’s largest scientific society. The meeting, which news media have termed “The World Series of Science,” features almost 12,000 presentations on new discoveries and other topics. It continues here through today.

Tobias Hoch, Ph.D., who conducted the study, said the results shed light on the causes of a condition called “hedonic hyperphagia” that plagues hundreds of millions of people around the world.

“That’s the scientific term for ‘eating to excess for pleasure, rather than hunger,’” Hoch said. “It’s recreational over-eating that may occur in almost everyone at some time in life. And the chronic form is a key factor in the epidemic of overweight and obesity that here in the United States threatens health problems for two out of every three people.”

The team at FAU Erlangen-Nuremberg, in Erlangen, Germany, probed the condition with an ingenious study in which scientists allowed one group of laboratory rats to feast on potato chips. Another group got bland old rat chow. Scientists then used high-tech magnetic resonance imaging (MRI) devices to peer into the rats’ brains, seeking differences in activity between the rats-on-chips and the rats-on-chow.

With recent studies showing that two-thirds of Americans are obese or overweight, this kind of recreational over-eating continues to be a major problem, health care officials say.

Among the reasons why people are attracted to these foods, even on a full stomach, was suspected to be the high ratio of fats and carbohydrates, which send a pleasing message to the brain, according to the team. In the study, while rats also were fed the same mixture of fat and carbohydrates found in the chips, the animals’ brains reacted much more positively to the chips.

“The effect of potato chips on brain activity, as well as feeding behavior, can only partially be explained by its fat and carbohydrate content,” explained Tobias Hoch, Ph.D. “There must be something else in the chips that make them so desirable,” he said.

In the study, rats were offered one out of three test foods in addition to their standard chow pellets: powdered standard animal chow, a mixture of fat and carbs, or potato chips. They ate similar amounts of the chow as well as the chips and the mixture, but the rats more actively pursued the potato chips, which can be explained only partly by the high energy content of this snack, he said. And, in fact, they were most active in general after eating the snack food.

Although carbohydrates and fats also were a source of high energy, the rats pursued the chips most actively and the standard chow least actively. This was further evidence that some ingredient in the chips was sparking more interest in the rats than the carbs and fats mixture, Hoch said.

Hoch explained that the team mapped the rats’ brains using Manganese-Enhanced Magnetic Resonance Imaging (MEMRI) to monitor brain activity. They found that the reward and addiction centers in the brain recorded the most activity. But the food intake, sleep, activity and motion areas also were stimulated significantly differently by eating the potato chips.

“By contrast, significant differences in the brain activity comparing the standard chow and the fat carbohydrate group only appeared to a minor degree and matched only partly with the significant differences in the brain activities of the standard chow and potato chips group,” he added.

Since chips and other foods affect the reward center in the brain, an explanation of why some people do not like snacks is that “possibly, the extent to which the brain reward system is activated in different individuals can vary depending on individual taste preferences,” according to Hoch. “In some cases maybe the reward signal from the food is not strong enough to overrule the individual taste.” And some people may simply have more willpower than others in choosing not to eat large quantities of snacks, he suggested.

If scientists can pinpoint the molecular triggers in snacks that stimulate the reward center in the brain, it may be possible to develop drugs or nutrients to add to foods that will help block this attraction to snacks and sweets, he said. The next project for the team, he added, is to identify these triggers. He added that MRI studies with humans are on the research agenda for the group.

On the other hand, Hoch said there is no evidence at this time that there might be a way to add ingredients to healthful, albeit rather unpopular, foods like Brussels sprouts to affect the rewards center in the brain positively.

Imaging Patients with Psychosis and a Mouse Model Establishes a Spreading Pattern of Hippocampal Dysfunction and Implicates Glutamate as a Driver

The hippocampus in schizophrenia is characterized by both hypermetabolism and reduced size. It remains unknown whether these abnormalities are mechanistically linked. Here we addressed this question by using MRI tools that can map hippocampal metabolism and structure in patients and mouse models. In at-risk patients, hypermetabolism was found to begin in CA1 and spread to the subiculum after psychosis onset. CA1 hypermetabolism at baseline predicted hippocampal atrophy, which occurred during progression to psychosis, most prominently in similar regions. Next, we used ketamine to model conditions of acute psychosis in mice. Acute ketamine reproduced a similar regional pattern of hypermetabolism, while repeated exposure shifted the hippocampus to a hypermetabolic basal state with concurrent atrophy and pathology in parvalbumin-expressing interneurons. Parallel in vivo experiments using the glutamate-reducing drug LY379268 and direct measurements of extracellular glutamate showed that glutamate drives both neuroimaging abnormalities. These findings show that hippocampal hypermetabolism leads to atrophy in psychotic disorder and suggest glutamate as a pathogenic driver.

Researchers create next-generation Alzheimer’s disease model

A new genetically engineered lab rat that has the full array of brain changes associated with Alzheimer’s disease supports the idea that increases in a molecule called beta-amyloid in the brain causes the disease, according to a study, published in the Journal of Neuroscience. The study was supported by the National Institutes of Health.

"We believe the rats will be an excellent, stringent pre-clinical model for testing experimental Alzheimer’s disease therapeutics,” said Terrence Town, Ph.D., the study’s senior author and a professor in the Department of Physiology & Biophysics in the Zilkha Neurogenetic Institute at the University of Southern California Keck School of Medicine, Los Angeles.

Alzheimer’s is an age-related brain disorder that gradually destroys a person’s memory, thinking, and the ability to carry out even the simplest tasks. Affecting at least 5.1 million Americans, the disease is the most common form of dementia in the United States. Pathological hallmarks of Alzheimer’s brains include abnormal levels of beta-amyloid protein that form amyloid plaques; tau proteins that clump together inside neurons and form neurofibrillary tangles; and neuron loss.  

Additionally, glial cells—which normally support, protect, or nourish nerve cells—are overactivated in Alzheimer’s.

Plaque-forming beta-amyloid molecules are derived from a larger protein called amyloid precursor protein (APP). One hypothesis states that increases in beta-amyloid initiate brain degeneration. Genetic studies on familial forms of Alzheimer’s support the hypothesis by linking the disease to mutations in APP, and to presenilin 1, a protein thought to be involved in the production beta-amyloid.

Researchers often use rodents to study diseases. However, previous studies on transgenic mice and rats that have the APP and presenilin 1 mutations only partially reproduce the problems caused by Alzheimer’s. The animals have memory problems and many plaques but none of the other hallmarks, especially neurofibrillary tangles and neuron loss.

To address this issue, Dr. Town and his colleagues decided to work with a certain strain of rats.

“We focused on Fischer 344 rats because their brains develop many of the age-related features seen in humans,” said Dr. Town, who conducted the study while working as a professor of Biomedical Sciences at Cedars-Sinai Medical Center and David Geffen School of Medicine at the University of California, Los Angeles.

The rats were engineered to have the mutant APP and presenilin 1 genes, which are known to play a role in the rare, early-onset form of Alzheimer’s. Behavioral studies showed that the rats developed memory and learning problems with age. As predicted, the presence of beta-amyloid in the brains of the rats increased with age. However, unlike previous rodent studies, the rats also developed neurofibrillary tangles.

“This new rat model more closely represents the brain changes that take place in humans with Alzheimer’s, including tau pathology and extensive neuronal cell death,” said Roderick Corriveau, Ph.D., a program director at NIH’s National Institute of Neurological Disorders and Stroke. “The model will help advance our understanding of the various disease pathways involved in Alzheimer’s onset and progression and assist us in testing promising interventions.”

The researchers performed a variety of experiments confirming the presence of neurofibrillary tangles in brain regions most affected by Alzheimer’s such as the hippocampus and the cingulate cortex, which are involved in learning and memory. Further experiments showed that about 30 percent of neurons in these regions died with age, the largest amount of cell death seen in an Alzheimer’s rodent model, and that some glial cells acquired shapes reminiscent of the activated glia found in patients.

“Our results suggest that beta-amyloid can drive Alzheimer’s in a clear and progressive way,” said Dr. Town.

Activation of glia occurred earlier than amyloid plaque formation, which suggests Dr. Town and his colleagues identified an early degenerative event and new treatment target that scientists studying other rodent models may have missed.

The findings support a prime research objective identified during the May 2012, NIH-supported Alzheimer’s Disease Research Summit 2012: Path to Treatment and Prevention, an international gathering of Alzheimer’s researchers and advocates. Improved animal models were cited as key to advancing understanding of this complex disease.

"To fully benefit from this exciting new work, there is a critical need to share the animal model with researchers dedicated to finding ways to delay, prevent or treat Alzheimer’s disease’’ said Neil Buckholtz, Ph.D., of the National Institute on Aging, which leads the NIH effort in Alzheimer’s research. “Accordingly, Dr. Town and his colleagues are working towards making their new rat model easily accessible to the research community.”

Researchers shine light on how stress circuits learn

Researchers at the University of Calgary’s Hotchkiss Brain Institute have discovered that stress circuits in the brain undergo profound learning early in life. Using a number of cutting edge approaches, including optogenetics, Jaideep Bains, PhD, and colleagues have shown stress circuits are capable of self-tuning following a single stress. These findings demonstrate that the brain uses stress experience during early life to prepare and optimize for subsequent challenges.

The team was able to show the existence of unique time windows following brief stress challenges during which learning is either increased or decreased. By manipulating specific cellular pathways, they uncovered the key players responsible for learning in stress circuits in an animal model. These discoveries culminated in the publication of two back-to-back studies in the April 7 online edition of Nature Neuroscience [1, 2], one of the world’s top neuroscience journals.

"These new findings demonstrate that systems thought to be ‘hardwired’ in the brain, are in fact flexible, particularly early in life," says Bains, a professor in the Department of Physiology and Pharmacology. "Using this information, researchers can now ask questions about the precise cellular and molecular links between early life stress and stress vulnerability or resilience later in life."

Stress vulnerability, or increased sensitivity to stress, has been implicated in numerous health conditions including cardiovascular disease, obesity, diabetes and depression. Although these studies used animal models, similar mechanisms mediate disease progression in humans.

"Our observations provide an important foundation for designing more effective preventative and therapeutic strategies that mitigate the effects of stress and meet society’s health challenges," he says.

Brain Cancer Treatment Using Genetic Material from Bone Marrow Cells

In a first-of-its-kind experiment using microvesicles generated from mesenchymal bone marrow cells (MSCs) to treat cancer, neurological researchers at Henry Ford Hospital have discovered a novel approach for treatment of tumors.

Specifically, the research team found that introducing genetic material produced by MSCs significantly reduced a particularly resistant form of malignant brain tumor in living lab rats.

“This is the first foray of its type in experimental cancer therapy, and it represents a highly novel and potentially effective treatment,” says Michael Chopp, Ph.D., scientific director of the Henry Ford Neuroscience Institute and vice chairman of the Department of Neurology at Henry Ford Hospital.

The research is published in the current issue Cancer Letters.

“I think this is an important and very novel approach for the treatment of cancers, and in this particular case the treatment of glioma,” says Dr. Chopp. “We have been at the forefront of developing microRNAs as a means to treat disease, such as cancer and neurological injury.

“This study shows it is effective in the living brain, and may even lend itself to specific cancer therapy, customized for the individual patient,” Chopp adds.

Chopp and his colleagues focused their efforts on glioma, by far the most common type of malignant brain tumor and one with a notably poor prognosis for survival.

Tumor cells were surgically implanted in the brains of anesthetized male lab rats and allowed to grow for five days.

The tumors then were injected with exosomes containing molecules of a microRNA called miR-146b – found in earlier Henry Ford research to have a strong effect on glioma cells.

Exosomes are microscopic “lipid bubbles” that once were thought to carry and get rid of “old” proteins that were no longer needed by the body. After they were more recently found to also carry RNA, whole new fields of study were suggested, including groundbreaking work by Henry Ford researchers.

In the rat study, Dr. Chopp and his colleagues used MSC bone marrow cells to produce the exosomes containing the miR-146b they injected into the cancerous tumors.

Five days after this treatment, the rats were euthanized and their brains were removed, prepared for study and examined. Tumor size was measured using computer software.

“We found that one injection of exosomes containing miR-146b five days after tumor implantation led to a significant reduction in tumor volume at 10 days after implant,” Chopp says. “Our data suggest that miR-146b elicits an anti-tumor effect in the rat brain, and that MSCs can be used as a ‘factory’ to generate exosomes genetically altered to contain miR-146b to effectively treat tumor.”

(Image: iStock)