Researchers develop strategy to combat genetic ALS, FTD

A team of researchers at Mayo Clinic and The Scripps Research Institute in Florida have developed a new therapeutic strategy to combat the most common genetic risk factor for the neurodegenerative disorders amyotrophic lateral sclerosis (ALS or Lou Gehrig’s disease) and frontotemporal dementia (FTD). In the Aug. 14 issue of Neuron, they also report discovery of a potential biomarker to track disease progression and the efficacy of therapies.

The scientists developed a small-molecule drug compound to prevent abnormal cellular processes caused by a mutation in the C9ORF72 gene. The findings come on the heels of previous discoveries by Mayo investigators that the C9ORF72 mutation produces an unusual repetitive genetic sequence that causes the buildup of abnormal RNA in brain cells and spinal cord.

While toxic protein clumps have long been implicated in neurodegeneration, this new strategy takes aim at abnormal RNA, which forms before toxic proteins in C9ORF72-related disorders (c9FTD/ALS). “Our study shows that toxic RNA produced in people with the c9FTD/ALS mutation is indeed a viable drug target,” says the study’s co-senior investigator, Leonard Petrucelli, Ph.D., a molecular neuroscientist at Mayo Clinic in Florida.

The compound, which was tested in cell culture models of c9FTD/ALS, bound to and blocked RNA’s ability to interact with other key proteins, thereby preventing the formation of toxic RNA clumps and “c9RAN proteins” that results from a process called repeat-associated non-ATG (RAN) translation.

The researchers also discovered that c9RAN proteins produced by the abnormal RNA can be measured in the spinal fluid of ALS patients. They are now evaluating whether these proteins are also present in spinal fluid of patients diagnosed with FTD. Although ALS primarily affects motor neurons leading to impaired mobility, speech, swallowing, and respiratory function and FTD affects brain regions that support higher cognitive function, some patients have symptoms of both disorders.

“Development of a readily accessible biomarker for the c9FTD/ALS mutation may aid not only diagnosis of these disorders and allow for tracking disease course in patients, but it could provide a more direct way to evaluate the response to experimental treatments,” says co-author Kevin Boylan, M.D., medical director of the Mayo Jacksonville ALS Center, the only ALS Certified Center of Excellence in Florida.

For example, a decrease in the levels of c9RAN proteins in response to treatment would suggest that a drug is having a desired effect. “The potential of this biomarker discovery is very exciting — even if we are in early days of development of such a test,” he says.

Since ALS is usually fatal two to five years after diagnosis and there is currently no effective treatment for FTD, these landmark findings offer the possibility of both improved diagnosis and treatment for up to 40 percent of all patients with familial (inherited) ALS and up to 25 percent of patients with familial FTD, says Dr. Boylan.

“One of the most exciting aspects of these studies has, in my opinion, been the seamless collaboration of our Florida biosciences institutes — Scripps and Mayo. Our collective biological and chemical expertise made this research possible,” says the other co-senior investigator, Mathew Disney, Ph.D., a professor of chemistry at Scripps Florida.

Dr. Disney and his group studied the structure of the RNA that resulted from the C9ORF72 mutation, and then designed the lead small-molecules. The Mayo team developed the patient-derived cell models to test the compounds in. Both teams then worked together to show that the lead agent’s mode of action was targeting the toxic RNA.

Scientists use lasers to control mouse brain switchboard

Ever wonder why it’s hard to focus after a bad night’s sleep? Using mice and flashes of light, scientists show that just a few nerve cells in the brain may control the switch between internal thoughts and external distractions. The study, partly funded by the National Institutes of Health, may be a breakthrough in understanding how a critical part of the brain, called the thalamic reticular nucleus (TRN), influences consciousness.

“Now we may have a handle on how this tiny part of the brain exerts tremendous control over our thoughts and perceptions,” said Michael Halassa, M.D., Ph.D., assistant professor at New York University’s Langone Medical Center and a lead investigator of the study. “These results may be a gateway into understanding the circuitry that underlies neuropsychiatric disorders.”

The TRN is a thin layer of nerve cells on the surface of the thalamus, a center located deep inside the brain that relays information from the body to the cerebral cortex. The cortex is the outer, multi-folded layer of the brain that controls numerous functions, including one’s thoughts, movements, language, emotions, memories, and visual perceptions. TRN cells are thought to act as switchboard operators that control the flow of information relayed from the thalamus to the cortex.

“The future of brain research is in studying circuits that are critical for brain health and these results may take us a step further,” said James Gnadt, Ph.D., program director at NIH’s National Institute Neurological Disorders and Stroke (NINDS), which helped fund the study. “Understanding brain circuits at the level of detail attained in this study is a goal of the President’s Brain Research through Advancing Innovative Neurotechnologies (BRAIN) Initiative.”

To study the circuits, the researchers identified TRN cells that send inhibitory signals to parts of the thalamus known to relay visual information to the cortex. Using a technique known as multi-electrode recordings, they showed that sleep and concentration affected these cells in opposite ways.

They fired often when the mice were asleep, especially during short bursts of simultaneous brain cell activity called sleep spindles. These activity bursts briefly widen electrical brain wave traces making them look like spindles, the straight spikes with rounded bottoms used to make yarn. In contrast, the cells fired infrequently when the mice were tasked with using visual cues to find food. The results suggested that these cells blocked visual information from reaching the cortex during sleep and allowed its transmission when the mice were awake and attentive.

For Dr. Halassa, a practicing psychiatrist who treats schizophrenia, these surprising results may provide fundamental insights into how the brain controls information transmission, a process that is disrupted in patients with neuropsychiatric disorders. Previous studies suggested that people who experienced more spindles while sleeping were less susceptible to being disturbed by outside noises. Moreover, people with schizophrenia and autism spectrum disorder may experience fewer spindles.

“Spindles may be peepholes into the mysteries of these disorders,” said Dr. Halassa.

To test this idea, the researchers used optogenetics, a technique that introduces light-sensitive molecules into nerve cells. This allowed them to precisely control the firing patterns of visual TRN cells with flashes of laser light. The experiments were performed in well-rested as well as sleep-deprived mice. Similar to what is seen in humans, sleep deprivation can disrupt the ability of mice to focus and block out external distractions.

Well-rested mice needed just a second or two to find the food whereas sleep-deprived mice took longer, suggesting that lack of sleep had detrimental effects on their ability to focus. When the researchers used flashes of laser light to inhibit the firing of optogenetically engineered visual TRN cells in sleep-deprived mice, the mice found the food faster. In contrast, if they used optogenetics to induce sleep-like firing patterns in well-rested mice, then the mice took longer to find food.

“It’s as if with a flick of a switch we could alter the mental states of the mice and either mimic or cure their drowsiness,” said Dr. Halassa.

In a parallel set of experiments the researchers found neighbors of the visual TRN cells had very different characteristics. These neighboring cells control the flow of information to the cortex from limbic brain regions, which are involved with memory formation, emotions and arousal. The cells fired very little during sleep and instead were active when the mice were awake. Dr. Halassa thinks that their firing pattern may be important for the strengthening of new memories that often occurs during sleep. Combined, the results suggest that the TRN is divided into sub-networks that oversee discrete mental states. The researchers think understanding the sub-networks is an initial step in thoroughly exploring the role of the TRN in brain disorders.

Memories of Errors Foster Faster Learning

Using a deceptively simple set of experiments, researchers at Johns Hopkins have learned why people learn an identical or similar task faster the second, third and subsequent time around. The reason: They are aided not only by memories of how to perform the task, but also by memories of the errors made the first time.

“In learning a new motor task, there appear to be two processes happening at once,” says Reza Shadmehr, Ph.D., a professor in the Department of Biomedical Engineering at the Johns Hopkins University School of Medicine. “One is the learning of the motor commands in the task, and the other is critiquing the learning, much the way a ‘coach’ behaves. Learning the next similar task goes faster, because the coach knows which errors are most worthy of attention. In effect, this second process leaves a memory of the errors that were experienced during the training, so the re-experience of those errors makes the learning go faster.”

Shadmehr says scientists who study motor control — how the brain pilots body movement — have long known that as people perform a task, like opening a door, their brains note small differences between how they expected the door to move and how it actually moved, and they use this information to perform the task more smoothly next time. Those small differences are scientifically termed “prediction errors,” and the process of learning from them is largely unconscious.

The surprise finding in the current study, described in Science Express on Aug. 14, is that not only do such errors train the brain to better perform a specific task, but they also teach it how to learn faster from errors, even when those errors are encountered in a completely different task. In this way, the brain can generalize from one task to another by keeping a memory of the errors.

To study errors and learning, Shadmehr’s team put volunteers in front of a joystick that was under a screen. Volunteers couldn’t see the joystick, but it was represented on the screen as a blue dot. A target was represented by a red dot, and as volunteers moved the joystick toward it, the blue dot could be programmed to move slightly off-kilter from where they pointed it, creating an error. Participants then adjusted their movement to compensate for the off-kilter movement and, after a few more trials, smoothly guided the joystick to its target.

In the study, the movement of the blue dot was rotated to the left or the right by larger or smaller amounts until it was a full 30 degrees off from the joystick’s movement. The research team found that volunteers responded more quickly to smaller errors that pushed them consistently in one direction and less to larger errors and those that went in the opposite direction of other feedback. “They learned to give the frequent errors more weight as learning cues, while discounting those that seemed like flukes,” says David Herzfeld, a graduate student in Shadmehr’s laboratory who led the study.

The results also have given Shadmehr a new perspective on his after-work tennis hobby. “I’m much better in my second five minutes of playing tennis than in my first five minutes, and I always assumed that was because my muscles had warmed up,” he says. “But now I wonder if warming up is really a chance for our brains to re-experience error.”

“This study represents a significant step toward understanding how we learn a motor skill,” says Daofen Chen, Ph.D., a program director at the National Institute of Neurological Disorders and Stroke. “The results may improve movement rehabilitation strategies for the many who have suffered strokes and other neuromotor injuries.”

The next step in the research, Shadmehr says, will be to find out which part of the brain is responsible for the “coaching” job of assigning weight to different types of error.

(Image caption: A cancer cell containing the nanoparticles. The nanoparticles are coloured green, and have entered the nucleus, which is the area in blue. Credit: M Welland)

“Trojan horse” treatment could beat brain tumours

A smart technology which involves smuggling gold nanoparticles into brain cancer cells has proven highly effective in lab-based tests.

A “Trojan horse” treatment for an aggressive form of brain cancer, which involves using tiny nanoparticles of gold to kill tumour cells, has been successfully tested by scientists.

The ground-breaking technique could eventually be used to treat glioblastoma multiforme, which is the most common and aggressive brain tumour in adults, and notoriously difficult to treat. Many sufferers die within a few months of diagnosis, and just six in every 100 patients with the condition are alive after five years.

The research involved engineering nanostructures containing both gold and cisplatin, a conventional chemotherapy drug. These were released into tumour cells that had been taken from glioblastoma patients and grown in the lab.

Once inside, these “nanospheres” were exposed to radiotherapy. This caused the gold to release electrons which damaged the cancer cell’s DNA and its overall structure, thereby enhancing the impact of the chemotherapy drug.

The process was so effective that 20 days later, the cell culture showed no evidence of any revival, suggesting that the tumour cells had been destroyed.

While further work needs to be done before the same technology can be used to treat people with glioblastoma, the results offer a highly promising foundation for future therapies. Importantly, the research was carried out on cell lines derived directly from glioblastoma patients, enabling the team to test the approach on evolving, drug-resistant tumours.

The study was led by Mark Welland, Professor of Nanotechnology at the Department of Engineering and a Fellow of St John’s College, University of Cambridge, and Dr Colin Watts, a clinician scientist and honorary consultant neurosurgeon at the Department of Clinical Neurosciences. Their work is reported in the Royal Society of Chemistry journal, Nanoscale.

“The combined therapy that we have devised appears to be incredibly effective in the live cell culture,” Professor Welland said. “This is not a cure, but it does demonstrate what nanotechnology can achieve in fighting these aggressive cancers. By combining this strategy with cancer cell-targeting materials, we should be able to develop a therapy for glioblastoma and other challenging cancers in the future.”

To date, glioblastoma multiforme (GBM) has proven very resistant to treatments. One reason for this is that the tumour cells invade surrounding, healthy brain tissue, which makes the surgical removal of the tumour virtually impossible.

Used on their own, chemotherapy drugs can cause a dip in the rate at which the tumour spreads. In many cases, however, this is temporary, as the cell population then recovers.

“We need to be able to hit the cancer cells directly with more than one treatment at the same time” Dr Watts said. “This is important because some cancer cells are more resistant to one type of treatment than another. Nanotechnology provides the opportunity to give the cancer cells this ‘double whammy’ and open up new treatment options in the future.”

In an effort to beat tumours more comprehensively, scientists have been researching ways in which gold nanoparticles might be used in treatments for some time. Gold is a benign material which in itself poses no threat to the patient, and the size and shape of the particles can be controlled very accurately.

When exposed to radiotherapy, the particles emit a type of low energy electron, known as Auger electrons, capable of damaging the diseased cell’s DNA and other intracellular molecules. This low energy emission means that they only have an impact at short range, so they do not cause any serious damage to healthy cells that are nearby.

In the new study, the researchers first wrapped gold nanoparticles inside a positively charged polymer, polyethylenimine. This interacted with proteins on the cell surface called proteoglycans which led to the nanoparticles being ingested by the cell.

Once there, it was possible to excite it using standard radiotherapy, which many GBM patients undergo as a matter of course. This released the electrons to attack the cell DNA.

While gold nanospheres, without any accompanying drug, were found to cause significant cell damage, treatment-resistant cell populations did eventually recover several days after the radiotherapy. As a result, the researchers then engineered a second nanostructure which was suffused with cisplatin.

The chemotherapeutic effect of cisplatin combined with the radiosensitizing effect of gold nanoparticles resulted in enhanced synergy enabling a more effective cellular damage. Subsequent tests revealed that the treatment had reduced the visible cell population by a factor of 100 thousand, compared with an untreated cell culture, within the space of just 20 days. No population renewal was detected.

The researchers believe that similar models could eventually be used to treat other types of challenging cancers. First, however, the method itself needs to be turned into an applicable treatment for GBM patients. This process, which will be the focus of much of the group’s forthcoming research, will necessarily involve extensive trials. Further work needs to be done, too, in determining how best to deliver the treatment and in other areas, such as modifying the size and surface chemistry of the nanomedicine so that the body can accommodate it safely.

Sonali Setua, a PhD student who worked on the project, said: “It was hugely satisfying to chase such a challenging goal and to be able to target and destroy these aggressive cancer cells. This finding has enormous potential to be tested in a clinical trial in the near future and developed into a novel treatment to overcome therapeutic resistance of glioblastoma.”

Welland added that the significance of the group’s results to date was partly due to the direct collaboration between nanoscientists and clinicians. “It made a huge difference, as by working with surgeons we were able to ensure that the nanoscience was clinically relevant,” he said. “That optimises our chances of taking this beyond the lab stage, and actually having a clinical impact.”

Researchers reveal weakness in defenses of deadly brain tumor

Glioblastoma is a complex, deadly, and hard-to-treat brain cancer, but Yale School of Medicine researchers may have found the tumor’s Achilles heel.

The researchers report in the Aug. 12 issue of the journal Science Signaling that targeting a protein crucial in the early development of the brain can block multiple signaling pathways implicated in glioblastoma growth. The approach also reduced human tumors in mouse models of the disease.

“In neurodevelopment, this protein (atyptical protein kinase or aPKC) helps regulate proliferation and migration of cells but when active in adults, can cause formation and spread of cancer,” said Sourav Ghosh, assistant professor of neurology and co-senior author of the paper.

About 13,000 people die of primary malignant brain tumors annually in the United States. Glioblastomas are particularly hard to treat because these tumors grow rapidly, spread quickly, and respond poorly to current anti-tumor therapies.

The new study shows that targeting this protein works in several ways. Inhibiting aPKC blocks a signal pathway that is the target of existing glioblastoma therapy. But it also blocks the action of some immune system cells called macrophages, which instead of attacking tumors, actively promote their growth.

“This is exciting because it ends up targeting multiple pathways involved in cancer,” said Carla Rothlin, assistant professor of immunobiology and co-senior author of the paper.

Mind and body: Scientists identify immune system link to mental illness

Children with high everyday levels of a protein released into the blood in response to infection are at greater risk of developing depression and psychosis in adulthood, according to new research which suggests a role for the immune system in mental illness.

The study, published today in JAMA Psychiatry, indicates that mental illness and chronic physical illness such as coronary heart disease and type 2 diabetes may share common biological mechanisms.

When we are exposed to an infection, for example influenza or a stomach bug, our immune system fights back to control and remove the infection. During this process, immune cells flood the blood stream with proteins such as interleukin-6 (IL-6), a tell-tale marker of infection. However, even when we are healthy, our bodies carry trace levels of these proteins – known as ‘inflammatory markers’ – which rise exponentially in response to infection.

Now, researchers have carried out the first ever longitudinal study – a study that follows the same cohort of people over a long period of time – to examine the link between these markers in childhood and subsequent mental illness.

A team of scientists led by the University of Cambridge studied a sample of 4,500 individuals from the Avon Longitudinal Study of Parents and Children – also known as Children of the 90s – taking blood samples at age 9 and following up at age 18 to see if they had experienced episodes of depression or psychosis. The team divided the individuals into three groups, depending on whether their everyday levels of IL-6 were low, medium or high. They found that those children in the ‘high’ group were nearly two times more likely to have experienced depression or psychosis than those in the ‘low’ group.

Dr Golam Khandaker from the Department of Psychiatry at the University of Cambridge, who led the study, says: “Our immune system acts like a thermostat, turned down low most of the time, but cranked up when we have an infection. In some people, the thermostat is always set slightly higher, behaving as if they have a persistent low level infection – these people appear to be at a higher risk of developing depression and psychosis. It’s too early to say whether this association is causal, and we are carrying out additional studies to examine this association further.”

The research indicates that chronic physical illness such as coronary heart disease and type 2 diabetes may share a common mechanism with mental illness. People with depression and schizophrenia are known to have a much higher risk of developing heart disease and diabetes, and elevated levels of IL-6 have previously been shown to increase the risk of heart disease and type 2 diabetes.

Professor Peter Jones, Head of the Department of Psychiatry and senior author of the study, says: “Inflammation may be a common mechanism that influences both our physical and mental health. It is possible that early life adversity and stress lead to persistent increase in levels of IL-6 and other inflammatory markers in our body, which, in turn, increase the risk of a number of chronic physical and mental illness.”

Indeed, low birth weight, a marker of impaired foetal development, is associated with increased everyday levels of inflammatory markers as well as greater risks of heart disease, diabetes, depression and schizophrenia in adults.

This potential common mechanism could help explain why physical exercise and diet, classic ways of reducing risk of heart disease, for example, are also thought to improve mood and help depression. The group is now planning additional studies to confirm whether inflammation is a common link between chronic physical and mental illness.

The research also hints at interesting ways of potentially treating illnesses such as depression: anti-inflammatory drugs. Treatment with anti-inflammatory agents leads to levels of inflammatory markers falling to normal. Previous research has suggested that anti-inflammatory drugs such as aspirin used in conjunction with antipsychotic treatments may be more effective than just the antipsychotics themselves. A multicentre trial is currently underway, into whether the antibiotic minocycline, used for the treatment of acne, can be used to treat lack of enjoyment, social withdrawal, apathy and other so called negative symptoms in schizophrenia. Minocycline is able to penetrate the ‘blood-brain barrier’, a highly selective permeability barrier which protects the central nervous system from potentially harmful substances circulating in our blood.

The ‘blood-brain barrier’ is also at the centre of a potential puzzle raised by research such as today’s research: how can the immune system have an effect in the brain when many inflammatory markers and antibodies cannot penetrate this barrier? Studies in mice suggest that the answer may lie in the vagus nerve, which connects the brain to the abdomen. When activated by inflammatory markers in the gut, it sends a signal to the brain, where immune cells produce proteins such as IL-6, leading to increased metabolism (and hence decreased levels) of the ‘happiness hormone’ serotonin in the brain. Similarly, the signals trigger an increase in toxic chemicals such as nitric oxide, quinolonic acid, and kynurenic acid, which are bad for the functioning of nerve cells.