Posts tagged neurological disorders
Articles and news from the latest research reports.
Suited for treatment of brain damage
For those with brain damage or neurological disorders, treatment could be as close as the wardrobe.
An alternative to painful treatments and surgery for brain damage may now be available with a specially-designed elastic body suit fitted with electrodes, which was designed at KTH Royal Institute of Technology in collaboration with health care and business partners.
The Mollii garment could improve range of motion and reduce pain for people with brain injuries and neurological disorders such as MS and cerebral palsy.
The garment provides the body with electrical stimulation to ease tension and spasms. The result is reduced pain perception and increased mobility.
The idea originated with a Swedish chiropractor, Fredrik Lundqvist, who worked with rehabilitation of brain-damaged patients. Lundqvist struck upon the idea of sewing electrical stimuli – similar to TENS (transcutaneous electrical nerve stimulation) electrodes – into garments that the patient can wear.
He turned to KTH researchers Johan Gawell and Jonas Wistrand at the Department of Machine Design. “They produced a prototype of the product, and today they are working full time on the development of Mollii,” Lundqvist says.
“We need more engineers in care,” Lundqvist says. “I believe that dedicated, young people who are passionate about the future should be given a free hand to develop innovations.”
Designed with ordinary swimsuit material, the body suit has conductive elastic sewn into it, with electrodes located at the major muscles.
Battery-powered light current is conducted via silver wires to 58 electrodes attached to the inside of the garment, which in turn stimulate as many as distinct 42 muscles, according to the patient’s needs.
Batteries are placed in a small control box fitted at the waistband.
“The idea is that the clothes should be used for a few hours, three times a week, and the effect is expected to last for up to two days,” Lundqvist says.
Users are advised engage in movement through training and stretching during the treatment.
“To enhance the quality of life the patient may choose to use Mollii before it’s time to go to work, school or to a social event. That enables the body to function as well as possible when it is really needed,” he says.
The garment has been shown to be highly effective in patient examinations performed in collaboration with a PhD student Stockholm’s Karolinska Institute, Lundvist says. “One-hundred percent of the participants in the survey say they have experienced improvements in existing function or quality of life,” he says.
Stroke patients with paralysis on one side have been found to gain increased mobility in spastic limbs, in that they had improved gait and their arms and hands worked better after treatment.
“As a bonus, the patients often sleep better, and their pharyngeal motor skills and speech improved after using Mollii,” Lundqvist says.
The treatment of patients with movement difficulties and pain due to neurological damage can often require surgery, injections of botolinumtoxin (neurotoxin) or strong medications.
“These treatments mean high costs and side effects, while our clothes are simple and safe to use,” Lundqvist says. “You can reduce the number of hospital visits because the therapy can be performed at home. And when the mobility increases, there is less need for walkers or wheelchairs.”
Mollii is an approved CE marked medical device, but independent clinical tests have yet been performed. But the company behind the treatment, Inerventions, has launched a scientific study of the clinical effectiveness of the garment, in partnership with Rehab Medical clinics in Linköping and Borås. Lundqvist says the results should come next year.
Today, Mollii is available through the Swedish health care system as a personal tool prescribed by physical or occupational therapists. And the garment can also be purchased directly from Inerventions.
The price is about EUR 5,600 for two years guaranteed spasticity treatment. If the suit during that time becomes too small, the patient can switch to a new, tested garment at no additional cost.
In Denmark, the garment is already subsidized with municipal funds for treatment of nerve damage, based on recommendations from a physiotherapist.
Inerventions’ goal is to establish Mollii in Europe, the U.S. and Japan. The garment can in the future be used to help patients with chronic pain and people with Restless Legs Syndrome (RLS).
“It can also help children with physical disabilities or motor difficulties in the feet, such as constantly walking on toes or with their feet at inward angles,” Lundqvist says.
Sheep’s mucosa shows the way to more effective medicine for severe neurological diseases
New Danish/Italian research shows how medicine for the brain can be absorbed through the nose. This paves the way to more effective treatment of neurological diseases like Alzheimer’s and tumors in the brain.
A big challenge in medical science is to get medicine into the brain when treating patients with neurological diseases. The brain will do everything to keep foreign substances out and therefore the brains of neurological patients fight a constant, daily battle to throw out the medicine prescribed to help the patients.
The problem is the so-called blood-brain barrier, which prevents the active substances in medicine from travelling from the blood into the brain.
"The barrier is created because there is extremely little space between the cells in the brain’s capillar walls. Only very small molecules can enter through these openings and become active in the brain. And for the substances which finally get in, a new problem arises: The brain will do anything to throw them out again", explains assistant professor, Massimiliano di Cagno from in the Department of Physics, Chemistry and Pharmacy.
On this background science is looking for alternative pathways to the brain - and the nose is a candidate receiving much attention. From cocaine abusers it is well known that a substance can be absorbed through the nose and reach the brain extremely effective.
"It is very interesting to investigate if medical drugs can do the same", says di Cagno.
In recent years research has shown that it can be a very good idea to send medicine to the brain via the nose. The medicine can be sprayed into the nose and absorbed through the olfactory bulb, which is positioned at the front of the underside of the brain. Once the medicine passes the olfactory bulb there is direct access to the brain.
But there are many challenges to be solved before patients can be prescribed medication to be taken nasally.
"One of the biggest challenges is getting the olfactory bulb to absorb the substances aimed for the brain", explains di Cagno.
Together with Barbara Luppi from the University of Bologna in Italy he therefore investigated how to improve access to the olfactory bulb.
"It’s all done at nano-level, and the challenge is to find the vehicles that can transport the required medicine to the brain. In our attempts to come up with efficient vehicles we now point at some special liposomes and polymers that can bring an active substance to the olfactory bulb more than 2-3 times more efficiently than when using the standard techniques", explains di Cagno.
Liposomes are small spheres of fat, which is often used to protect active substance and carry them into the body. Polymers are long molecules that can be attached to the liposomes so that they can be made to look like water and thus not be rejected by the body’s immune system.
The improved efficiency is very important for the development of future medicines for neurological diseases. Today a pill has to contain millions of times more active ingredients than the brain needs to fight the disease. But because the blood-brain barrier is so effective and the brain so good at throwing foreign substances out, you have to send an extreme amount of active substances towards the brain.
"In a pill patients receive extremely more medicine than they need, and when we talk about medicines with severe and unpleasant side effects, it is not good. It is therefore very important that we get better at delivering exactly the amount of active substances needed - and no more", says di Cagno.
The new liposomes and polymers from his and Barbara Luppi’s work can not only carry the active ingredients efficiently through the slimy mucosa of a nose, so that they can reach the olfactory bulb. They can also do it over a longer time.
"We want to develop a vehicle that can release the active ingredients over a long time, over many hours, so the patients do not have to spray their nose too many times a day. In our experiments we still saw active substances being released after three hours, and we are very happy with that. One must remember that the nasal mucosa is constantly working to remove foreign objects and substances", says di Cagno.
The researchers performed their tests on the mucous membranes (mucosa) of sheep. Sheep and human mucosa and the mucinous secretions it produces in the nose are very similar. The sheep’s mucosa were cleaned, distributed on a tissue and then stretched over a container. In the container the researchers placed an active substance, hydrocortisone, that had been put inside different kinds of vehicles. After this the researchers observed how effectively and for how long time the various vehicles transported the hydrocortisone through the mucosa.
(Source: sdu.dk)
Creating a ‘Window to the Brain’
A team of University of California, Riverside researchers have developed a novel transparent skull implant that literally provides a “window to the brain”, which they hope will eventually open new treatment options for patients with life-threatening neurological disorders, such as brain cancer and traumatic brain injury.
The team’s implant is made of the same ceramic material currently used in hip implants and dental crowns, yttria-stabilized zirconia (YSZ). However, the key difference is that their material has been processed in a unique way to make it transparent.
Since YSZ has already proven itself to be well-tolerated by the body in other applications, the team’s advancement now allows use of YSZ as a permanent window through which doctors can aim laser-based treatments for the brain, importantly, without having to perform repeated craniectomies, which involve removing a portion of the skull to access the brain.
The work also dovetails with President Obama’s recently-announced BRAIN (Brain Research through Advancing Innovative Neurotechnologies) Initiative, which aims to revolutionize the understanding of the human mind and uncover new ways to treat, prevent, and cure brain disorders. The team envisions potential for their YSZ windows to facilitate the clinical translation of promising brain imaging and neuromodulation technologies being developed under this initiative.
“This is a case of a science fiction sounding idea becoming science fact, with strong potential for positive impact on patients,” said Guillermo Aguilar, a professor of mechanical engineering at UC Riverside’s Bourns College of Engineering (BCOE).
Aguilar is part of 10-person team, comprised of faculty, graduate students and researchers from UC Riverside’s Bourns College of Engineering and School of Medicine, who recently published a paper “Transparent Nanocrystalline Yttria-Stabilized-Zirconia Calvarium Prosthesis” about their findings online in the journal Nanomedicine: Nanotechnology, Biology and Medicine.
Laser-based treatments have shown significant promise for many brain disorders. However, realization of this promise has been constrained by the need for performing a craniectomy to access the brain since most medical lasers are unable to penetrate the skull. The transparent YSZ implants developed by the UC Riverside team address this issue by providing a permanently implanted view port through the skull.
“This is a crucial first step towards an innovative new concept that would provide a clinically-viable means for optically accessing the brain, on-demand, over large areas, and on a chronically-recurring basis, without need for repeated craniectomies,” said team member Dr. Devin Binder, a clinician and an associate professor of biomedical sciences at UC Riverside.
Although the team’s YSZ windows are not the first transparent skull implants to be reported, they are the first that could be conceivably used in humans, which is a crucial distinction. This is due to the inherent toughness of YSZ, which makes it far more resistant to shock and impact than the glass-based implants previously demonstrated by others. This not only enhances safety, but it may also reduce patient self-consciousness, since the reduced vulnerability of the implant could minimize the need for conspicuous protective headgear.
First Pre-Clinical Gene Therapy Study to Reverse Rett Symptoms
The concept behind gene therapy is simple: deliver a healthy gene to compensate for one that is mutated. New research published today in the Journal of Neuroscience suggests this approach may eventually be a feasible option to treat Rett Syndrome, the most disabling of the autism spectrum disorders. Gail Mandel, Ph.D., a Howard Hughes Investigator at Oregon Health and Sciences University, led the study. The Rett Syndrome Research Trust, with generous support from the Rett Syndrome Research Trust UK and Rett Syndrome Research & Treatment Foundation, funded this work through the MECP2 Consortium.
In 2007, co-author Adrian Bird, Ph.D., at the University of Edinburgh astonished the scientific community with proof-of-concept that Rett is curable, by reversing symptoms in adult mice. His unexpected results catalyzed labs around the world to pursue a multitude of strategies to extend the pre-clinical findings to people.
Today’s study is the first to show reversal of symptoms in fully symptomatic mice using techniques of gene therapy that have potential for clinical application.
Rett Syndrome is an X-linked neurological disorder primarily affecting girls; in the US, about 1 in 10,000 children a year are born with Rett. In most cases symptoms begin to manifest between 6 and 18 months of age, as developmental milestones are missed or lost. The regression that follows is characterized by loss of speech, mobility, and functional hand use, which is often replaced by Rett’s signature gesture: hand-wringing, sometimes so intense that it is a constant during every waking hour. Other symptoms include seizures, tremors, orthopedic and digestive problems, disordered breathing and other autonomic impairments, sensory issues and anxiety. Most children live into adulthood and require round-the-clock care.
The cause of Rett Syndrome’s terrible constellation of symptoms lies in mutations of an X-linked gene called MECP2 (methyl CpG-binding protein). MECP2 is a master gene that regulates the activity of many other genes, switching them on or off.
“Gene therapy is well suited for this disorder,” Dr. Mandel explains. “Because MECP2 binds to DNA throughout the genome, there is no single gene currently that we can point to and target with a drug. Therefore the best chance of having a major impact on the disorder is to correct the underlying defect in as many cells throughout the body as possible. Gene therapy allows us to do that.”
Healthy genes can be delivered into cells aboard a virus, which acts as a Trojan horse. Many different types of these Trojan horses exist. Dr. Mandel used adeno-associated virus serotype 9 (AAV9), which has the unusual and attractive ability to cross the blood-brain barrier. This allows the virus and its cargo to be administered intravenously, instead of employing more invasive direct brain delivery systems that require drilling burr holes into the skull.
Because the virus has limited cargo space, it cannot carry the entire MECP2 gene. Co-author Brian Kaspar of Nationwide Children’s Hospital collaborated with the Mandel lab to package only the gene’s most critical segments. After being injected into the Rett mice, the virus made its way to cells throughout the body and brain, distributing the modified gene, which then started to produce the MeCP2 protein.
As in human females with Rett Syndrome, only approximately 50% of the mouse cells have a healthy copy of MECP2. After the gene therapy treatment 65% of cells now had a functioning MECP2 gene.
The treated mice showed profound improvements in motor function, tremors, seizures and hind limb clasping. At the cellular level the smaller body size of neurons seen in mutant cells was restored to normal. Biochemical experiments proved that the gene had found its way into the nuclei of cells and was functioning as expected, binding to DNA.
One Rett symptom that was not ameliorated was abnormal respiration. Researchers hypothesize that correcting this may require targeting a greater number of cells than the 15% that had been achieved in the brainstem.
“We learned a critical and encouraging point with these experiments – that we don’t have to correct every cell in order to reverse symptoms. Going from 50% to 65% of the cells having a functioning gene resulted in significant improvements,” said co-author Saurabh Garg.
One of the potential challenges of gene therapy in Rett is the possibility of delivering multiple copies of the gene to a cell. We know from the MECP2 Duplication Syndrome that too much of this protein is detrimental. “Our results show that after gene therapy treatment the correct amount of MeCP2 protein was being expressed. At least in our hands, with these methods, overexpression of MeCP2 was not an issue,” said co-author Daniel Lioy.
Dr. Mandel cautioned that key steps remain before clinical trials can begin. “Our study is an important first step in highlighting the potential for AAV9 to treating the neurological symptoms in Rett. We are now working on improving the packaging of MeCP2 in the virus to see if we can target a larger percentage of cells and therefore improve symptoms even further,” said Mandel. Collaborators Hélène Cheval and Adrian Bird see this as a promising follow up to the 2007 work showing symptom reversal in Rett mice. “That study used genetic tricks that could not be directly applicable to humans, but the AAV9 vector used here could in principle deliver a gene therapeutically. This is an important step forward, but there is a way to go yet.”
“Gene therapy has had a tumultuous road in the past few decades but is undergoing a renaissance due to recent technological advances. Europe and Asia have gene therapy treatments already in the clinic and it’s likely that the US will follow suit. Our goal now is to prioritize the next key experiments and facilitate their execution as quickly as possible. Gene therapy, especially to the brain, is a tricky undertaking but I’m cautiously optimistic that with the right team we can lay out a plan for clinical development. I congratulate the Mandel and Bird labs on today’s publication, which is the third to be generated from the MECP2 Consortium in a short period of time,” said Monica Coenraads, Executive Director of the Rett Syndrome Research Trust and mother of a teenaged daughter with the disorder.
(Source: rsrt.org)
A ‘Rocking’ Receptor: Crucial Brain-Signaling Molecule Requires Coordinated Motion to Turn On
Study could help yield new drugs for brain disorders
Johns Hopkins biophysicists have discovered that full activation of a protein ensemble essential for communication between nerve cells in the brain and spinal cord requires a lot of organized back-and-forth motion of some of the ensemble’s segments. Their research, they say, may reveal multiple sites within the protein ensemble that could be used as drug targets to normalize its activity in such neurological disorders as epilepsy, schizophrenia, Parkinson’s and Alzheimer’s disease.
The glutamate-binding segments (blue, yellow) of ionotropic glutamate receptors undergo a “rocking” motion during activation by glutamate (red). (The dotted line provides a point of reference.)
A summary of the results, published online in the journal Neuron on Aug. 7, shows that full activation of so-called ionotropic glutamate receptors is more complex than previously envisioned. In addition to the expected shape changes that occur when the receptor “receives” and clamps down on glutamate messenger molecules, the four segments of the protein ensemble also rock back and forth in relation to each other when fewer than four glutamates are bound.
“We believe that our study is the first to show the molecular architecture and behavior of a prominent neural receptor protein ensemble in a state of partial activation,” says Albert Lau, Ph.D., assistant professor of biophysics and biophysical chemistry at the Johns Hopkins University School of Medicine.
Glutamate receptors reside in the outer envelope of every nerve cell in the brain and spinal cord, Lau notes, and are responsible for changing chemical information — the release of glutamate molecules from a neighboring nerve cell — into electrical information, the flow of charged particles into the receiving nerve cell. There would be sharply reduced communication between nerve cells in our brains if these receptors were disabled, he added, and thought and normal brain function in general would be severely compromised. Malfunctioning receptors, says Lau, have been linked with numerous neurological disorders and are therefore potential targets for drug therapies.
Lau explained that each glutamate receptor is a united group of four protein segments that has a pocket for clamping down on glutamate like a Venus fly trap snaring a bug. Below the glutamate-binding segments are four other segments embedded in the cell’s outer envelope to form a channel for charged particles to flow through. When no glutamates are bound to the receptor, the channel is closed; full activation of the receptor and full opening of the channel occur when four glutamates are bound, each to a difference pocket.
Previously, Lau says, investigators thought that the level of receptor activation simply corresponded to the degree to which each glutamate-binding segment changed shape during the glutamate-binding process. Using a combination of computer modeling, biophysical “imaging” of molecular structure, biochemical analysis and electrical monitoring of individual cells, the researchers teased apart some of the steps in between zero activation and full activation. They were able to show that the four glutamate-binding segments, in addition to clamping down on glutamate, also rock back and forth in pairs when fewer than four glutamates are bound.
“It isn’t clear yet how this rocking motion affects receptor function, but we now know that activation depends on more than how much each glutamate-binding segment clamps down,” says Lau. Previous development of drugs targeting the receptor focused on the four glutamate-binding pockets. “Our discovery of this molecular motion could aid the development of drugs by revealing additional drug-binding sites on the receptor,” he adds.
(Source: hopkinsmedicine.org)
The Present and Future of Neurogenomics
Support the BRAIN Initiative, but don’t overlook the neurogenomic diagnostics that are already driving breakthroughs in brain and rare neurological disorders.
On April 2nd, 2013, President Obama proposed a forward-thinking, $100 million research program designed to unlock the mysteries of the human brain. The BRAIN (Brain Research through Advancing Innovative Neurotechnologies) Initiative seeks to identify how brain cells and neural circuits interact in order to inform the development of future treatments for brain disorders, including Alzheimer’s disease, epilepsy, and traumatic brain injury.
This Initiative could favorably contribute to medical practice years from now. It should not, however, overshadow the potential of neurogenomic advances to improve the diagnosis, treatment and management of neurological disorders right now.
Most of my career has focused on neurogenomics. During the Human Genome Project era, I managed a clinical neurogenomics program at the National Institutes of Health to further understanding the genetic underpinnings of neurological disorders to help diagnose, treat, cure, and even prevent disease. Today, I oversee the development of neurodiagnostics for the neurology business of Quest Diagnostics, with an emphasis on rare neurological disorders, autism, and dementias.
Over the years, I’ve come to identify certain obstacles that prevent the translation of neurogenomic science into effective clinical management. These obstacles are surmountable, but they require a fundamental shift in how care is delivered to patients with neurological disorders.
Our current healthcare system groups healthcare professionals into two categories: generalists, such as primary care physicians and internists, and specialists, including neurologists. We assume that the former have the knowledge to reliably refer patients, when appropriate, to the latter. This may have been a fair assumption in the past, but in the age of genomic medicine, is it still valid?
In the case of neurogenomic disorders, such as genetic forms of epilepsy, neuromuscular disorders, dementia, and developmental disabilities overlapping clinical signs and symptoms often present a diagnostic challenge for neurologists, and even more so for generalists. A dearth of clinical information available on rare disorders, and the infrequency with which primary care physicians come in contact with effected patients, makes diagnosis even more difficult.
Dravet syndrome, for example, is a rare and catastrophic form of infantile epilepsy that is associated with a high incidence of developmental delays and even SUDEP (sudden unexplained death in epilepsy). Dravet is caused by a genetic defect in the SCN1A gene-affecting sodium channel. While not curable, the condition can be managed if diagnosed—but only if treating physicians are aware of the disorder, treatment options, and the detrimental effects of certain anticonvulsants.
Through advances in laboratory diagnostics, physicians are increasingly equipped to pinpoint the molecular causes of these diseases—some of which are amenable to treatment. But too often, the only clinicians who know about the tests and treatment options are specialists.
We must work more closely with medical societies and advocacy groups to educate primary care professionals and even patients in the value of, and tools for, diagnosing and treating neurological disorders.
Neurogenomic research is revealing that some rare disorders share similar molecular markers and mechanisms. By categorizing these rare disorders into clinical areas, we potentially reduce an otherwise lengthy diagnostic process for the patient and advance the development of new treatment options. Greater investment in new diagnostics that pinpoint molecular markers for disease will help remove the mystery that clouds the diagnosis of many disorders.
Too few clinicians, including neurologists, can keep on top of the rapid evolution of genomic science and diagnostics. As a result, patients are often referred from physician to physician, and administered test after test, in a protracted process to diagnose and treat. This wastes healthcare dollars. More importantly, it creates terrible anxiety and frustration for patients.
To alleviate this problem, medical societies need to do more to cultivate sub-specialists in neurogenomics—clinicians who have deep specialized expertise in specific neurological diseases, particularly rare disorders. With such experience, these experts can more efficiently and reliably diagnose the patient’s disorder.
While the BRAIN Initiative may yield clinically valuable insights in the future, scientists and physicians can do a great deal now with current technologies to translate genomic knowledge into effective diagnosis, management and, in some cases, treatment. With greater genomics education and collaboration, we can help improve the quality of life for patients with neurological disorders—and that, ultimately, is the most meaningful measurement of success.
(Source: the-scientist.com)
Scientists advance understanding of brain receptor; may help fight neurological disorders
For several years, the pharmaceutical industry has tried to develop drugs that target a specific neurotransmitter receptor in the brain, the NMDA receptor. This receptor is present on almost every neuron in the human brain and is involved in learning and memory. NMDA receptors also have been implicated in several neurological and psychiatric conditions such as Alzheimer’s disease, Parkinson’s disease, schizophrenia and depression.
But drug companies have had little success developing clinically effective drugs that target this receptor.
Now, researchers at Oregon Health & Science University’s Vollum Institute believe they may understand why. And what they’ve discovered may help in the development of new therapies for these conditions.
In a paper published in the current issue of the Journal of Neuroscience, OHSU scientists describe their work on NMDA receptors. There are various types of NMDA receptors, resulting from differences in the protein components that make up the receptor. These differences in the protein components produce receptors with varying properties.
As drug companies have worked to develop compounds that manipulate the activity of these receptors, the focus of much of this drug discovery effort has been on a specific NMDA receptor subtype. In their Journal of Neuroscience paper, the OHSU scientists describe their discovery — that the specific receptor subtype that drug companies have seen as a target is an almost nonexistent contributor of NMDA receptor action.
What does exist, the OHSU scientists found, was a different kind of NMDA receptor subtype — one containing two specific protein components, called GluN2A and GluN2B. NMDA receptors containing these two components were not thought to be very common. The OHSU study found that not only was this NMDA receptor subtype more common than previously believed, it was the most common subtype at synapses. And it was far more common than the receptor subtype that has been the target of drug development efforts.
"What our paper shows is that one reason no drugs have worked well to this point may be because that particular NMDA receptor subtype isn’t there in high quantities. The target they’ve been looking for isn’t the target that’s there," said Ken Tovar, Ph.D., a senior postdoctoral fellow at the Vollum Institute. Tovar’s co-authors on the paper were Gary Westbrook, M.D., senior scientist and co-director of the Vollum Institute, and Matthew McGinley, Ph.D., a former graduate student in the Westbrook laboratory.
Tovar said these findings could provide a new target for drug development.
"If you know what’s there, then you know what to go after — you just have to figure out how to do it," Tovar said.
The OHSU study also provides clues into how the function of this most common NMDA receptor subtype might be manipulated. Highly specific drugs interact with either GluN2A or GluN2B. Tovar and colleagues demonstrated that when GluN2A and GluN2B coexist in the same receptor, molecules that targeted GluN2A change the behavior of the receptor in ways that could be clinically beneficial.
"NMDA receptors have been implicated in a diverse list of neurological and psychiatric conditions. Thus, the more we know about how to modulate the behavior of the receptors that are there — at synapses — the greater chance we have of finding drugs to treat these conditions," Tovar said.
"From the perspective of drug development, knowing the nature of your target is one way to keep drug development costs down," said Tovar. "Spending resources investigating a target that turns out to be unimportant means those costs get passed on to the drugs that are effective."
(Image: iStockphoto)
The Secret Lives (and Deaths) of Neurons
As the human body fine-tunes its neurological wiring, nerve cells often must fix a faulty connection by amputating an axon — the “business end” of the neuron that sends electrical impulses to tissues or other neurons. It is a dance with death, however, because the molecular poison the neuron deploys to sever an axon could, if uncontained, kill the entire cell.
Researchers from the University of North Carolina School of Medicine have uncovered some surprising insights about the process of axon amputation, or “pruning,” in a study published May 21 in the journal Nature Communications. Axon pruning has mystified scientists curious to know how a neuron can unleash a self-destruct mechanism within its axon, but keep it from spreading to the rest of the cell. The researchers’ findings could offer clues about the processes underlying some neurological disorders.
“Aberrant axon pruning is thought to underlie some of the causes for neurodevelopmental disorders, such as schizophrenia and autism,” said Mohanish Deshmukh, PhD, professor of cell biology and physiology at UNC and the study’s senior author. “This study sheds light on some of the mechanisms by which neurons are able to regulate axon pruning.”
Axon pruning is part of normal development and plays a key role in learning and memory. Another important process, apoptosis — the purposeful death of an entire cell — is also crucial because it allows the body to cull broken or incorrectly placed neurons. But both processes have been linked with disease when improperly regulated.
The research team placed mouse neurons in special devices called microfluidic chambers that allowed the researchers to independently manipulate the environments surrounding the axon and cell body to induce axon pruning or apoptosis.
They found that although the nerve cell uses the same poison — a group of molecules known as Caspases — whether it intends to kill the whole cell or just the axon, it deploys the Caspases in a different way depending on the context.
“People had assumed that the mechanism was the same regardless of whether the context was axon pruning or apoptosis, but we found that it’s actually quite distinct,” said Deshmukh. “The neuron essentially uses the same components for both cases, but tweaks them in a very elegant way so the neuron knows whether it needs to undergo apoptosis or axon pruning.”
In apoptosis, the neuron deploys the deadly Caspases using an activator known as Apaf-1. In the case of axon pruning, Apaf-1 was simply not involved, despite the presence of Caspases. “This is really going to take the field by surprise,” said Deshmukh. “There’s very little precedent of Caspases being activated without Apaf-1. We just didn’t know they could be activated through a different mechanism.”
In addition, the team discovered that neurons employ other molecules as safety brakes to keep the “kill” signal contained to the axon alone. “Having this brake keeps that signal from spreading to the rest of the body,” said Deshmukh. “Remarkably, just removing one brake makes the neurons more vulnerable.”
Deshmukh said the findings offer a glimpse into how nerve cells reconfigure themselves during development and beyond. Enhancing our understanding of these basic processes could help illuminate what has gone wrong in the case of some neurological disorders.
Finding a family for a pair of orphan receptors in the brain
Researchers at Emory University have identified a protein that stimulates a pair of “orphan receptors” found in the brain, solving a long-standing biological puzzle and possibly leading to future treatments for neurological diseases.
The results are published in the Proceedings of the National Academy of Sciences, Early Edition.
The human genome is littered with orphans: proteins that look like they will bind and respond to a hormone or a brain chemical, based on the similarity of their sequences to other proteins. However, scientists haven’t figured out what each orphan’s partner chemical is yet.
Orphans that look like GPCRs (G protein-coupled receptors) currently number about 100. GPCRs are the targets of many drugs and are involved in vision, smell and brain cells’ responses to a host of hormones and neurotransmitters. One orphan GPCR, called GPR37, has attracted interest from researchers because it is connected with an inherited form of Parkinson’s disease. It is abundant in the dopamine-producing neurons that degenerate in Parkinson’s. But its partner chemical, or “ligand,” has not been found.
"We reasoned that GPR37 had to be doing something important, besides becoming misfolded in some forms of Parkinson’s," says senior author Randy Hall, PhD, professor of pharmacology at Emory University School of Medicine.
Working with Hall, graduate student Rebecca Meyer devised a way to detect when cells producing GPR37 were reacting with GPR37’s ligand.
"Usually, cells remove GPCRs from their surfaces when they encounter their ligand," Meyer says. "So we set things up so that GPR37 would be labeled red on the surface of the cell, but would appear green once internalized."
They discovered that cells producing GPR37 – and also a close relative, GPR37L1 — respond to a protein known as prosaposin, which was discovered by John O’Brien of University of California San Diego in the 1990s.
Prosaposin is a growth factor for brain cells and protects them from stress. Scientists studying it had worked out that it stimulates cells via a GPCR – but which one was unclear until now. In animal models, prosaposin has shown potential for treating conditions such as stroke, Parkinson’s and neuropathic pain. An artificial fragment of prosaposin called prosaptide has been tested in clinical studies, but it quickly breaks down in the body.
"That’s the reason why it was so important to find the receptor," Hall says. "Then we can actually do some pharmacology."
Now, Hall’s laboratory is planning to look for other compounds that can activate GPR37 as well. These could be more stable in the body than the previously studied protein fragment and thus better potential drugs.
Doctors have reported a few cases of genetic deficiency in prosaposin, leading to severe neurodegeneration. Mice engineered to lack GPR37 have more subtle brain perturbations, so Hall also plans to test the hypothesis that prosaposin acts by both GPR37 and GPR37L1, by “knocking out” both in mice, potentially duplicating the same severe effects seen in the human cases of prosaposin deficiency.
Researchers develop new pathway to brain for medicine
Stumped for years by a natural filter in the body that allows few substances, including life-saving drugs, to enter the brain through the bloodstream, physicians who treat neurological diseases may soon have a new pathway to the organ via a technique developed by a physicist and an immunologist working together at Florida International University’s Herbert Wertheim College of Medicine.
The FIU researchers developed the technique to deliver and fully release the anti-HIV drug AZTTP into the brain, but their finding has the potential to also help patients who suffer from neurological diseases such as Alzheimer’s, Parkinson’s and epilepsy, as well as cancer.
“Anything where you have trouble getting drugs to the brain and releasing it, this opens so many opportunities,’’ said Madhavan Nair, an FIU professor and chair of the medical school’s immunology department.
In an in vitro laboratory test with HIV-infected cells, Nair and a colleague, Sakhrat Khizroev, a professor of immunology and electrical engineering, attached the antiretroviral drug AZTTP to tiny, magneto-electric nanoparticles. Then, using magnetic energy, they guided the drug across a cell membrane created in the lab to mimic the blood-brain barrier found in the human body.
Once the drug reached its target, researchers triggered its release from the nanoparticle by zapping it with a low-energy electrical current. The drug remained functional and structurally sound after the release, according to the experiment findings.
“We learned to control electrical forces in the brain using magnetics,’’ said Khizroev, who designed, oversaw and supervised the entire project. “We pretty much opened a pathway to the brain.’’
The test findings were published in April in the online peer-reviewed journal, Nature Communications. Researchers believe that using this method will allow physicians to send a higher level of AZTTP — up to 97 percent more — to HIV-infected cells in the brain.
Currently, more than 99 percent of the antiretroviral therapies used to treat HIV, such as AZTTP, are deposited in the liver, lungs and other organs before they reach the brain.
While anti-viral drugs have helped HIV patients live longer by reducing their viral loads, the drugs cannot pass the blood-brain barrier in significant amounts, which allows the virus to lurk unchecked in the brain and can lead to neurological damage, said Dr. Cheryl Holder, a practicing physician and FIU professor who specializes in treating patients with HIV.
“We know that even though the viral load is undetectable in the blood, we don’t know what’s going on in the brain fully,’’ Holder said.
HIV causes constant inflammation, she said, and the virus can pool in areas of the brain where medicine cannot reach, potentially causing damage.
“It’s important to get the drug to the brain,’’ she said, “to help prevent dementia in older patients, and inflammation.’’
But the ability to target drug delivery and release it on demand in the brain has been impossible without opening the skull, Nair and Khizroev said.
Nair, an immunologist who specializes in HIV research, and Khizroev, an electrical engineer and physicist, began collaborating on the project about 18 months ago after winning a National Institutes of Health grant to study the use of magnetic particles.
One of the keys to success was controlling the release of the drug without adversely affecting the brain.
The researchers found their solution in the magneto-electric nanoparticles, which are uniquely suited to deliver and release drugs in the brain, Khizroev said. These nanoparticles can convert magnetic energy into the electrical energy needed to release the drugs without creating heat, which could potentially harm the brain.
The development of a new, less invasive pathway to the brain would open the door to many new medical uses.
Khizroev said he recently returned from a trip to the University of Southern California, where he briefed physicians at the medical school on the technique and its potential for cancer treatment. And Nair said he received a letter recently on behalf of a 91-year-old man suffering from Parkinson’s, asking when the technique might become available for use in people.
That may take a while. With the first phase of testing successfully completed using in vitro experiments, the second will take place at Emory University in Georgia, where researchers will test the technique on monkeys infected with the HIV virus.
If researchers complete the second phase successfully, clinical trials on humans could follow, Nair said. Approval from the Food and Drug Administration would be required before the technique becomes commercially available, he said.
FIU researchers have applied for a patent and would receive royalties, they said, though the university would benefit the most, in part because a successful research project could open opportunities for more grant funding on other topics.
For Khizroev, who had previously done research on quantum computing and information processing, the project has offered a way to put his scientific knowledge to use in a way that could have a direct affect on people’s health.
“I wanted to apply my knowledge of nanoparticles to something important,’’ he said.
(Source: miamiherald.com)