Posts tagged neurodegenerative disorders
Articles and news from the latest research reports.
Image caption: New details about how motor neurons die in ALS have been uncovered by a new cell-culture system that combines spinal cord or brain cells from ALS patients with human motor neurons. The culture system shows that patient astrocytes (shown here with a blue-stained nucleus) release a toxin that kills motor neurons via a recently discovered process described as a “controlled cellular explosion.” Image: Diane Re.
Toxin from Brain Cells Triggers Neuron Loss in Human ALS Model
In most cases of amyotrophic lateral sclerosis (ALS), or Lou Gehrig’s disease, a toxin released by cells that normally nurture neurons in the brain and spinal cord can trigger loss of the nerve cells affected in the disease, Columbia researchers reported today in the online edition of the journal Neuron.
The toxin is produced by star-shaped cells called astrocytes and kills nearby motor neurons. In ALS, the death of motor neurons causes a loss of control over muscles required for movement, breathing, and swallowing. Paralysis and death usually occur within 3 years of the appearance of first symptoms.
The report follows the researchers’ previous study, which found similar results in mice with a rare, genetic form of the disease, as well as in a separate study from another group that used astrocytes derived from patient neural progenitor cells. The current study shows that the toxins are also present in astrocytes taken directly from ALS patients.
“I think this is probably the best evidence we can get that what we see in mouse models of the disease is also happening in human patients,” said the study’s senior author, Serge Przedborski, MD, PhD, the Page and William Black Professor of Neurology (in Pathology and Cell Biology), Vice Chair for Research in the department of Neurology, and co-director of Columbia’s Motor Neuron Center.
The findings also are significant because they apply to the most common form of ALS, which affects about 90 percent of patients. Scientists do not know why ALS develops in these patients; the other 10 percent of patients carry one of 27 genes known to cause the disease.
“Now that we know that the toxin is common to most patients, it gives us an impetus to track down this factor and learn how it kills the motor neurons,” Dr. Przedborski said. “Its identification has the potential to reveal new ways to slow down or stop the destruction of the motor neurons.”
In the study, Dr. Przedborski and study co-authors Diane Re, PhD, and Virginia Le Verche, PhD, associate research scientists, removed astrocytes from the brain and spinal cords of six ALS patients shortly after death and placed the cells in petri dishes next to healthy motor neurons. Because motor neurons cannot be removed from human subjects, they had been generated from human embryonic stem cells in the Project A.L.S./Jenifer Estess Laboratory for Stem Cell Research, also at CUMC.
Within two weeks, many of the motor neurons had shrunk and their cell membranes had disintegrated; about half of the motor neurons in the dish had died. Astrocytes removed from people who died from causes other than ALS had no effect on the motor neurons. Nor did other types of cells taken from ALS patients.
The researchers confirmed that the cause of the motor neurons’ death was a toxin released into the environment by immersing healthy motor neurons in the astrocytes’ culture media. The presence of the media, even without astrocytes, killed the motor neurons.
How the Toxin Triggers Motor Neuron Death
The researchers have not yet identified the toxin released by the astrocytes. But they did discover the nature of the neuronal death process triggered by the toxin.The toxin triggers a biochemical cascade in the motor neurons that essentially causes them to undergo a controlled cellular explosion.
Drs. Przedborski, Re, and Le Verche found that they could prevent astrocyte-triggered motor neuron death by inhibiting one of the key components of this molecular cascade.
These findings may lead to a way to prevent motor neuron death in patients and potentially prolong life. But the therapeutic potential of such inhibition is far from clear. “For example, we don’t know if this would leave patients with living but dysfunctional neurons,” Dr. Przedborski said. The researchers are now testing the idea of inhibition in animal models of ALS.
New Human Cell Model of ALS Will Speed Identification of Potential Therapies
The development of new therapies for ALS has been disappointing, with more than 30 clinical trials ending with no new treatments since the 1995 FDA approval of riluzole.
The lack of progress may be partly because animal models used to study ALS do not completely recreate the human disease. The new all-human cell model of ALS created for the current study may improve scientists’ ability to identify useful drug targets, particularly for the most common form of the disease.
“Although there are many neurodegenerative disorders, only for a handful do we have access to a simplified model that is relevant to the disease and can therefore potentially be used for high-throughput drug screening. So this model is quite special,” Dr. Przedborski said. “Here we have a spontaneous disease phenotype triggered by the relevant tissue that causes human illness. That’s one important thing. The other important thing is that this model is derived entirely from human elements. This is probably the closest, most natural model of human ALS that we can get in a dish.”
Potential biomarkers for the diagnosis of Alzheimer’s disease
Drugs that modify DNA structure may be beneficial for treating Alzheimer’s Disease
In a study published this week in Nature Neuroscience, Bess Frost, PhD, and co-authors, identify abnormal expression of genes, resulting from DNA relaxation, that can be detected in the brain and blood of Alzheimer’s patients.
The protein tau is involved in a number of neurodegenerative disorders, including Alzheimer’s disease. Previous studies have implicated DNA damage as a cause of neuron, or cell, death in Alzheimer’s patients. Given that DNA damage can change the structure of DNA within cells, the researchers examined changes in DNA structure in tau-induced neurodegeneration. They used transgenic flies and mice expressing human tau to show that DNA is more relaxed in tauopathy. They then identified that the relaxation of tightly wound DNA and resulting abnormal gene expression are central events that cause neurons to die in Alzheimer’s disease.
The authors write, “Our work suggests that drugs that modify DNA structure may be beneficial for treating Alzheimer’s Disease.” The authors recommend, “A greater understanding of the pathway of DNA relaxation in tauopathies will allow us to identify the optimal target and explore the therapeutic potential of epigenetic-based drugs.”
(Source: eurekalert.org)
Detrimental effect of obesity on lesions associated with Alzheimer’s disease
Researchers from Inserm and the Université Lille/Université Lille Nord de France have recently used a neurodegeneration model of Alzheimer’s disease to provide experimental evidence of the relationship between obesity and disorders linked to the tau protein. This research was conducted on mice and is published in the Diabetes review: it corroborates the theory that metabolic anomalies contribute massively to the development of dementia.
In France, more than 860,000 people suffer from Alzheimer’s disease and related disorders, making them the largest cause of age-related loss of intellectual function. Cognitive impairments observed in Alzheimer’s disease result from the accumulation of abnormal tau proteins in nerve cells undergoing degeneration (see the picture below). We know that obesity, a major risk factor in the development of insulin resistance and type 2 diabetes, increases the risk of dementia during the aging process. However, the effects of obesity on ‘Taupathies’ (i.e. tau protein-related disorders), including Alzheimer’s disease, were not clearly understood. In particular, researchers assumed that insulin resistance played a major role in terms of the effects of obesity.
The “Alzheimer & Tauopathies” team from mixed research unit 837 (Inserm/Université Lille 2/Université Lille Nord de France) directed by Dr. Luc Buée, in collaboration with mixed research unit 1011 “Nuclear receptors, cardiovascular diseases and diabetes”, have just demonstrated, in mice, that obese subjects develop aggravated disorders. To achieve this result, young transgenic mice, who develop tau-related neurodegeneration progressively with age, were put on a high-fat diet for five months, leading to progressive obesity.
“At the end of this diet, the obese mice had developed an aggravated disorder both from the point of view of memory and modifications to the Tau protein”, explains David Blum, in charge of research at Inserm.
This study uses a neurodenegeneration model of Alzheimer’s disease to provide experimental evidence of the relationship between obesity and disorders linked to the tau protein. Furthermore, it indicates that insulin resistance is not the aggravating factor, as was suggested in previous studies.
“Our research supports the theory that environmental factors contribute massively to the development of this neurodegenerative disorder” underlines the researcher. “Our work is now focussing on identifying the factors responsible for this aggravation” he adds.
Stony Brook Researchers Look Back on Scientific Advances Made as a Result of a 50-Year Old Puzzle
Fifty years after scientists first posed a question about protein folding, the search for answers has led to the creation of a full-fledged field of research that led to major advances in supercomputers, new materials and drug discovery, and shaped our understanding of the basic processes of life, including so-called “protein-folding diseases” such as Alzheimer’s, Parkinson’s and type II diabetes.
In a review article published in the Nov. 23, 2012 issue of the journal Science, Stony Brook University researchers reviewed the progress on a 50-year-old puzzle called the Protein Folding Problem. Ken Dill and Justin MacCallum of Stony Brook’s Louis and Beatrice Laufer Center for Physical and Quantitative Biology show how a community of scientific researchers rose to tackle a grand-challenge problem of very basic science that had no obvious payoff at the time.
“Protein folding is a quintessential basic science. There has been no specific commercial target, yet the collateral payoffs have been broad and deep,” the researchers said in their paper, The Protein Folding Problem, 50 Years On.
“We have learned that proteins fold rapidly because random thermal motions cause conformational changes leading energetically downhill toward the native structure, a principle that is captured in funnel-shaped energy landscapes. And thanks in part to the large Protein Data Bank of known structures, predicting protein structures is now far more successful than was thought possible in the early days. What began as three questions of basic science one half-century ago has now grown into the full-fledged research field of protein physical science.”
Researchers define key events early in the process of cellular aging
For the first time, scientists at Fred Hutchinson Cancer Research Center have defined key events that take place early in the process of cellular aging.
Together the discoveries, made through a series of experiments in yeast, bring unprecedented clarity to the complex cascade of events that comprise the aging process and pave the way to understanding how genetics and environmental factors like diet interact to influence lifespan, aging and age-related diseases such as cancer and neurodegenerative disorders.
The findings, including unexpected results that link aspects of aging and lifespan to a mechanism cells use to store nutrients, are described in the Nov. 21 issue of Nature by co-authors Daniel Gottschling, Ph.D., a member of the Hutchinson Center’s Basic Sciences Division, and Adam Hughes, Ph.D., a postdoctoral fellow in the Gottschling Lab.
The work began with Hughes and Gottschling searching for the source of age-related damage in mitochondria.
“Normally, mitochondria are beautiful, long tubes, but as cells get older, the mitochondria become fragmented and chunky,” said Gottschling, also an affiliate professor in the Department of Genome Sciences at the University of Washington. “The changes in shape seen in aging yeast cells are also observed in certain human cells, such as neurons and pancreatic cells, and those changes have been associated with a number of age-related diseases in humans.”
What causes mitochondria to become distorted and dysfunctional as cells age had long been a mystery, but Gottschling and Hughes have discovered that specific changes in the vacuole lead directly to their malfunctioning.The researchers found the acidity of a structure in yeast cells known as the vacuole is critical to aging and the functioning of mitochondria – the power plants of the cell. They also describe a novel mechanism, which may have parallels in human cells, by which calorie restriction extends lifespan.
LSUHSC research identifies new therapeutic target for Alzheimer’s disease
Research led by Chu Chen, PhD, Associate Professor of Neuroscience at LSU Health Sciences Center New Orleans, has identified an enzyme called Monoacylglycerol lipase (MAGL) as a new therapeutic target to treat or prevent Alzheimer’s disease. The study was published online November 1, 2012 in the Online Now section of the journal Cell Reports.
The research team found that inactivation of MAGL, best known for its role in degrading a cannabinoid produced in the brain, reduced the production and accumulation of beta amyloid plaques, a pathological hallmark of Alzheimer’s disease. Inhibition of this enzyme also decreased neuroinflammation and neurodegeneration, and improved plasticity of the brain, learning and memory.
"Our results suggest that MAGL contributes to the cause and development of Alzheimer’s disease and that blocking MAGL represents a promising therapeutic target," notes Dr. Chu Chen, who is also a member of the Department of Otolaryngology at LSU Health Sciences Center New Orleans.
The researchers blocked MAGL with a highly selective and potent inhibitor in mice using different dosing regimens and found that inactivation of MAGL for eight weeks was sufficient to decrease production and deposition of beta amyloid plaques and the function of a gene involved in making beta amyloid toxic to brain cells. They also measured indicators of neuroinflammation and neurodegeneration and found them suppressed when MAGL was inhibited. The team discovered that not only did the integrity of the structure and function of synapses associated with cognition remain intact in treated mice, but MAGL inactivation appeared to promote spatial learning and memory, measured with behavioral testing.
Alzheimer’s disease is a neurodegenerative disorder characterized by accumulation and deposition of amyloid plaques and neurofibrillary tangles, neuroinflammation, synaptic dysfunction, progressive deterioration of cognitive function and loss of memory in association with widespread nerve cell death. The most common cause of dementia among older people, more than 5.4 million people in the United States and 36 million people worldwide suffer with Alzheimer’s disease in its various stages. Unfortunately, the few drugs that are currently approved by the Food and Drug Administration have demonstrated only modest effects in modifying the clinical symptoms for relatively short periods, and none has shown a clear effect on disease progression or prevention.
"There is a great public health need to discover new therapies to prevent and treat this devastating disorder," Dr. Chen concludes. The research was supported by grants from the National Institutes of Health. In addition to scientists from LSU Health Sciences Center New Orleans, the research team also included investigators from the Massachusetts Institute of Technology.
(Source: eurekalert.org)
Berkeley Lab Scientists Help Develop Promising Therapy for Huntington’s Disease
There’s new hope in the fight against Huntington’s disease. A group of researchers that includes scientists from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have designed a compound that suppresses symptoms of the devastating disease in mice.
The compound is a synthetic antioxidant that targets mitochondria, an organelle within cells that serves as a cell’s power plant. Oxidative damage to mitochondria is implicated in many neurodegenerative diseases including Alzheimer’s, Parkinson’s, and Huntington’s.
The scientists administered the synthetic antioxidant, called XJB-5-131, to mice that have a genetic mutation that triggers Huntington’s disease. The compound improved mitochondrial function and enhanced the survival of neurons. It also inhibited weight loss and stopped the decline of motor skills, among other benefits. In short, the Huntington’s mice looked and behaved like normal mice.
Based on their findings, the scientists believe that XJB-5-131 is a promising therapeutic compound that deserves further investigation as a way to fight neurodegenerative diseases.
They report their research in a paper that appears online Nov. 1 in the journal Cell Reports.
Caffeine’s effect on the brain’s adenosine receptors visualized for the first time
Scans allow researchers to study the link between caffeine and neurodegenerative disorders.
Molecular imaging with positron emission tomography (PET) has enabled scientists for the first time to visualize binding sites of caffeine in the living human brain to explore possible positive and negative effects of caffeine consumption. According to research published in the November issue of The Journal of Nuclear Medicine, PET imaging with F-18-8-cyclopentyl-3-(3-fluoropropyl)-1-propylxanthine (F-18-CPFPX) shows that repeated intake of caffeinated beverages throughout a day results in up to 50 percent occupancy of the brain’s A1 adenosine receptors.
"The effects of caffeine to the human body are generally attributed to the cerebral adenosine receptors. In the human brain the A1 adenosine receptor is the most abundant," said David Elmenhorst, MD, lead author of "Caffeine Occupancy of Human Cerebral A1 Adenosine Receptors: In Vivo Quantification with F-18-CPFPX and PET." "In vitro studies have shown that commonly consumed quantities of caffeine have led to a high A1 adenosine occupancy. Our study aimed to measure the A1 adenosine receptor occupancy with in vivo imaging."
Stay-at-home transcription factor saves axons
The old saw that local actions can have global consequences holds true for neurons, too. Selvaraj et al. show that a transcription factor remains in the axon to help prevent neurodegeneration.
In neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), neurons usually die in stages, with axons deteriorating first and the cells themselves perishing later. Axon degeneration may represent a turning point for patients, after which so much neuronal damage has accumulated that treatments won’t work. Researchers have tested several proteins for their ability to save axons. One of these molecules, ciliary neurotrophic factor (CNTF), rescues axons in rodents and extends their lives. But it caused severe side effects in patients during clinical trials. “Acting on the same pathway but farther downstream could be an ideal way to improve the situation for motor neuron disease” and possibly for other neurodegenerative diseases, says senior author Michael Sendtner.
To discover how CNTF works, Selvaraj et al. studied pmn mutant mice that mimic ALS. The researchers found that CNTF not only prevented the shrinkage of the rodents’ motor neurons, it also reduced the number of swellings along the axon that are markers of degeneration. Another sign that CNTF was beneficial was the movement of mitochondria, which continually shuttle back and forth along the axons of healthy motor neurons. In axons from pmn mice, stalled mitochondria were prevalent, but treatment with CNTF accelerated the organelles to normal speeds.
Yeast model offers clues to possible drug targets for Lou Gehrig’s disease
Amyotrophic lateral sclerosis, also called Lou Gehrig’s disease, is a devastatingly cruel neurodegenerative disorder that robs sufferers of the ability to move, speak and, finally, breathe. Now researchers at the Stanford University School of Medicine and San Francisco’s Gladstone Institutes have used baker’s yeast — a tiny, one-celled organism — to identify a chink in the armor of the currently incurable disease that may eventually lead to new therapies for human patients.
“Even though yeast and humans are separated by a billion years of evolution, we were able to use the power of yeast genetics to identify an unexpected potential drug target for ALS,” said Aaron Gitler, PhD, an associate professor of genetics at Stanford. “Many neurodegenerative disorders such as ALS, Parkinson’s and Alzheimer’s exhibit protein clumping or misfolding within the neurons that is thought to either cause or contribute to the conditions. We are trying to figure out why these proteins aggregate in neurons in the brain and spinal cord, and what happens when they do.”
In 2008, Gitler received a New Innovator award from the National Institutes of Health to use yeast as a model for understanding human neurodegenerative diseases and as a way to identify new targets for drug development.
(Source: med.stanford.edu)