High Levels of Glutamate in Brain May Kick-Start Schizophrenia

An excess of the brain neurotransmitter glutamate may cause a transition to psychosis in people who are at risk for schizophrenia, reports a study from investigators at Columbia University Medical Center (CUMC) published in the current issue of Neuron.

The findings suggest 1) a potential diagnostic tool for identifying those at risk for schizophrenia and 2) a possible glutamate-limiting treatment strategy to prevent or slow progression of schizophrenia and related psychotic disorders.

“Previous studies of schizophrenia have shown that hypermetabolism and atrophy of the hippocampus are among the most prominent changes in the patient’s brain,” said senior author Scott Small, MD, Boris and Rose Katz Professor of Neurology at CUMC. “The most recent findings had suggested that these changes occur very early in the disease, which may point to a brain process that could be detected even before the disease begins.”

To locate that process, the Columbia researchers used neuroimaging tools in both patients and a mouse model. First they followed a group of 25 young people at risk for schizophrenia to determine what happens to the brain as patients develop the disorder. In patients who progressed to schizophrenia, they found the following pattern: First, glutamate activity increased in the hippocampus, then hippocampus metabolism increased, and then the hippocampus began to atrophy.

To see if the increase in glutamate led to the other hippocampus changes, the researchers turned to a mouse model of schizophrenia. When the researchers increased glutamate activity in the mouse, they saw the same pattern as in the patients: The hippocampus became hypermetabolic and, if glutamate was raised repeatedly, the hippocampus began to atrophy.

Theoretically, this dysregulation of glutamate and hypermetabolism could be identified through imaging individuals who are either at risk for or in the early stage of disease. For these patients, treatment to control glutamate release might protect the hippocampus and prevent or slow the progression of psychosis.

Strategies to treat schizophrenia by reducing glutamate have been tried before, but with patients in whom the disease is more advanced. “Targeting glutamate may be more useful in high-risk people or in those with early signs of the disorder,” said Jeffrey A. Lieberman, MD, a renowned expert in the field of schizophrenia, Chair of the Department of Psychiatry at CUMC, and president-elect of the American Psychiatric Association. “Early intervention may prevent the debilitating effects of schizophrenia, increasing recovery in one of humankind’s most costly mental disorders.”

In an accompanying commentary, Bita Moghaddam, PhD, professor of neuroscience and of psychiatry, University of Pittsburgh, suggests that if excess glutamate is driving schizophrenia in high-risk individuals, it may also explain why a patient’s first psychotic episodes are often caused by periods of stress, since stress increases glutamate levels in the brain.

First steps of synapse building captured in live zebra fish embryos

Using spinning disk microscopy on barely day-old zebra fish embryos, University of Oregon scientists have gained a new window on how synapse-building components move to worksites in the central nervous system.

What researchers captured in these see-through embryos — in what may be one of the first views of early glutamate-driven synapse formation in a living vertebrate — were orderly movements of protein-carrying packets along axons to a specific site where a synapse would be formed.

Washbourne addresses:

► The basic importance of the findings

► The connection to diseases, including autism

The discovery, in research funded by the National Institutes of Health, is described in a paper placed online ahead of publication in the April 25 issue of the open-access journal Cell Reports. It is noteworthy because most synapses formed in vertebrates use glutamate as a neurotransmitter, and breakdowns in the process have been tied to conditions such as autism, schizophrenia and mental retardation.

The zebra fish has become one of the leading research models for studying early development, in general, and human-disease states.

In this case, researchers used immunofluorescence labeling to highlight the area they put under the microscopes. The embryos they studied were barely 24-hours old and a millimeter in length, but neurons in their spinal cord were already forming connections called synapses. Images were taken every 30 seconds over two hours.

"If we zoom out a bit and look at development in the human, the majority of synapse formation occurs in the cortex after birth and continues for the first two years in a baby’s life," said Philip Washbourne, a professor of biology and member of the UO’s Institute of Neuroscience.

Previous studies, done in vitro, contradicted each other, with one, in 2000, identifying a single packet of building blocks arriving at a pre-synaptic terminal. The other, in 2004, identified two protein packets. After watching the process unfold live, with imaging over long time spans, Washbourne said: “We now see at least three, and maybe more, such deliveries.”

"Axons are long processes — think of them as highways — of neurons. In humans, these can be a meter long, from spinal cord to your big toe," he said. It’s in the cell body where all the proteins are made, and they have to be transported out. Is it done by a single bus or by several cars? These results point to additional layers of complexity in the established mechanisms of synaptogenesis."

The new research also showed that sequence also is crucial. Two different pre-synaptic packages of molecules repeatedly arrived in the same order. A key building block — the protein synapsin — always arrived third. As these delivery vehicles traveled the axonal highway, another protein, a cyclin-dependent kinase known as Cdk5, acts as a stoplight at the synapse-construction site, where phosphorylation occurs. More research is needed on Cdk5, Washbourne said.

"Understanding how all this happens will inform us to what’s going wrong in neurodevelopment that leads to diseases," Washbourne said. "We have indications that the glue that gets all this going includes a gene that has been linked to autism, so knowing how these molecules start the process of synapse formation — and what goes wrong in people with mutations in these genes — might allow for a therapeutic targeting to correct the mutations and manipulate the stop signs."

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 Confirm Multiple Genes Robustly Contribute to Schizophrenia Risk in Replication

Multiple genes contribute to risk for schizophrenia and appear to function in pathways related to transmission of signals in the brain and immunity, according to an international study led by Virginia Commonwealth University School of Pharmacy researchers.

By better understanding the molecular and biological mechanisms involved with schizophrenia, scientists hope to use this new genetic information to one day develop and design drugs that are more efficacious and have fewer side effects.

In a study published online in the April issue of JAMA Psychiatry, the JAMA Network journal, researchers used a comprehensive and unique approach to robustly identify genes and biological processes conferring risk for schizophrenia.

The researchers first used 21,953 subjects to examine over a million genetic markers. They then systematically collected results from other kinds of biological schizophrenia studies and combined all these results using a novel data integration approach.

The most promising genetic markers were tested again in a large collection of families with schizophrenia patients, a design that avoids pitfalls that have plagued genetic studies of schizophrenia in the past. The genes they identified after this comprehensive approach were found to have involvement in brain function, nerve cell development and immune response.

“Now that we have genes that are robustly associated with schizophrenia, we can begin to design much more specific experiments to understand how disruption of these genes may affect brain development and function,” said principal investigator Edwin van den Oord, Ph.D., professor and director of the Center for Biomarker Research and Personalized Medicine in the Department of Pharmacotherapy and Outcomes Science at the VCU School of Pharmacy.

“Also, some of these genes provide excellent targets for the development of new drugs,” he said.

One specific laboratory experiment currently underway at VCU to better understand the function of one of these genes, TCF4, is being led by Joseph McClay, Ph.D., a co-author on the study and assistant professor and laboratory director in the VCU Center for Biomarker Research and Personalized Medicine. TCF4 works by switching on other genes in the brain. McClay and colleagues are conducting a National Institutes of Health-funded study to determine all genes that are under the control of TCF4. By mapping the entire network, they aim to better understand how disruptions to TCF4 increase risk for schizophrenia.

“Our results also suggest that the novel data integration approach used in this study is a promising tool that potentially can be of great value in studies of a large variety of complex genetic disorders,” said lead author Karolina A. Aberg, Ph.D., research assistant professor and laboratory co-director of the Center for Biomarker Research and Personalized Medicine in the VCU School of Pharmacy.

(Image: iStockphoto)

Either mad and bad or Jekyll and Hyde: media portrayals of schizophrenia

Stigma can take a heavy toll on people who suffer from mental illness. Being shunned, feared, devalued and discriminated against can impair recovery and deepen social isolation and distress. Many sufferers judge stigma to be more difficult to cope with than the symptoms of their illness.

Thankfully, there are grounds for hope. Australian researchers have shown that mental illness stigma, such as the unwillingness to interact with affected people, generally declined from 2003 to 2011. Some credit for this improvement must go to media campaigns by beyondblue and SANE, and to the willingness of many people to speak publicly about experiences that would once have been shamefully private.

The dark cloud inside this silver lining is schizophrenia, a serious condition that impairs thinking, emotion and motivation. While Australians’ attitudes towards depression have become more accepting, the stigma of schizophrenia has remained largely unchanged.

Misusing and misunderstanding

People with schizophrenia are still perceived as dangerous and unpredictable, and these perceptions have increased in recent years. Attitudes to people with schizophrenia have also worsened in the United States at the same time as attitudes to depressed people have improved.

Just as the media can take some credit for the declining stigma of other conditions, it must take some of the blame for the continuing stigma of schizophrenia. Media portrayals commonly associate it with violence and danger.

Schizophrenia is also often misused to refer to split personality or incoherence. This Jekyll-and-Hyde misconception persists despite countless corrections. One study of Italian newspapers, for instance, found that the term was employed in this way almost three times as often it was used correctly to refer to people with the diagnosis or their illness.

But just how negative are current media depictions of schizophrenia? My students and I recently examined this question in a study that we published in the academic journal Psychosis. We located every story published in major national, state and territory online and print news media outlets in the year ending August 2012 that cited schizophrenia or schizophrenic.

We then counted how many stories misused these terms and coded how often the condition was linked to violence or presented in a stigmatising way.

Our results were striking. Almost half (47%) of stories linked schizophrenia to some form of violence, and 28% of these associated it with attempted or completed homicide. The schizophrenic person was identified as a perpetrator of violence six times more frequently than as its victim.

Schizophrenia was misused as a split metaphor in 13% of stories. And fully 46% of stories were coded as stigmatising.

It’s hardly surprising that the public’s views of the condition continue to be laced with fear and loathing if they usually find schizophrenia presented in the context of violent aggression or as a metaphor for internal contradiction.

Better ways

What can be done about all of this? For one thing, journalists and the general public need to become aware that schizophrenia doesn’t mean split personality and it bears no resemblance to caricatures of craziness. This mistaken usage should be retired not because the police say it’s offensive, but because it perpetuates a misunderstanding that hurts real people.

Journalists and editors also need to think carefully before linking schizophrenia to violent behaviour. Often the proposed link is dubious and speculative, and adds nothing important to the story. Just as violence supposedly committed by people experiencing mental illness is over-reported – producing an exaggerated sense of their dangerousness – their victimisation is often under-reported.

An equally important corrective would be to publish more stories that feature people with schizophrenia living well, present their everyday struggles and adversities or showcase promising treatments and research findings.

Coverage can be improved. Our study found that stories from broadsheet newspapers were less stigmatising than tabloid stories, and longer, more developed stories were less stigmatising than briefer ones.

This is not a matter of white-washing the news. People with schizophrenia are indeed at a somewhat increased risk of committing violent offences (and of being their victims). They can behave in challenging ways. But the media landscape that our study surveyed is so tilted towards depicting schizophrenia as dangerous that it’s seriously unbalanced.

The news media can do better and, if they do, the stigma of schizophrenia may start to erode.

Brain cell signal network genes linked to schizophrenia risk in families

New genetic factors that predispose to schizophrenia have been uncovered in five families with several affected relatives. The psychiatric disorder can disrupt thinking, feeling, and acting, and blur the border between reality and imagination.

Dr. Debby W. Tsuang, professor of psychiatry and behavioral sciences, and Dr. Marshall S. Horwitz, professor of pathology, both at the University of Washington in Seattle, led the multi-institutional study. Tsuang is also a staff physician at the Puget Sound Veterans Administration Health Care System.

The results are published in the April 3 online edition of the JAMA Psychiatry.

Loss of brain nerve cell integrity occurs in schizophrenia, but scientists have not worked out the details of when and how this happens. In all five families in the present study, the researchers found rare variants in genes tied to the networking of certain signal receptors on nerve cells distributed throughout the brain. These N-methyl-D-aspartate, or NMDA, receptors are widespread molecular control towers in the brain. They regulate the release of chemical messages that influence the strength of brain cell connections and the ongoing remodeling of the networks.

These receptors respond to glutamate, one of the most common nerve-signaling chemicals in the brain, and they are also found on brain circuits that manage dopamine release. Dopamine is a nerve signal associated with reward-seeking, movement and emotions. Deficits in glutamate and dopamine function have both been implicated in schizophrenia but most of the medications that have been developed to treat schizophrenia have targeted dopamine receptors.

Tsuang and her groups’ discovery of gene variations that disturb N-methyl-D-aspartate receptor networking functions supports the hypothesis that decreased NMDA receptor-mediated nerve-signal transmissions contributes to some cases of schizophrenia.

Tsuang pointed out that several hallucinogenic drugs, such as ketamine and phencyclidine (PCP, or angel dust), block N-methyl-D-aspartate receptors and can produce symptoms similar to schizophrenia. These are the strongest evidence implicating these receptors in schizophrenia. The drugs sometimes induce psychosis and terrifying sensory detachment. Reports of such effects in recreational drug users fingered faulty NMDA receptor networks as suspects in schizophrenia.

In all five of their study families, Tsuang’s team detected rare protein-altering variants in one of three genes involved with the N-methyl-D-aspartate receptor network. One of the genes, GRM5, is directly linked with glutamate signaling. In the other two genes, the links are indirect and connected through other proteins synthesized in brain cells. One of these proteins, PPEF2, appears to affect the levels of certain brain nerve-cell signaling mediators, and the other altered protein, LRP1B, may compete with a normal protein for a binding spot on a subunit of the NMDA receptor.

These discoveries provide additional clues to the molecular disarray that might occur in the brain nerve cells of some patients with schizophrenia, and suggest new targets for therapy for certain patients. In a disease occurring in about 1 percent of the population, the picture of how and why schizophrenia arises in all these people is far from complete.

“Disorders like schizophrenia are likely to have many underlying causes,” Tsuang noted. She added that it might eventually make sense to divide schizophrenia into categories based, for example, on which biochemical pathways in the brain are disrupted. Treatments might be developed to correct the exact malfunctioning mechanisms underlying various forms of the disease.

Tsuang gave an example: Agents that stimulate N-methyl-D-aspartate receptor-mediated nerve-signal transmissions include glycine-site blockers and glycine-transport inhibitors have shown some encouraging results in pre-clinical drug trials, but mostly in adjunctive treatment in addition to standard antipsychotic therapy.

“But perhaps the data we have generated will help pharmaceutical companies target specific subunits of the NMDA receptors and pathways,” Tsuang said. She added, however, that effective treatments may lag by many years after these kinds of discoveries. Someday it may make sense to initiate such treatments in people at high genetic risk when early symptoms, such as apathy and lack of motivation, appear, and before brain dysfunction is severe.

Also, possessing the newly discovered gene mutations does not always mean that a person will become schizophrenic. In the recent family study, three of the five families had relatives with the protein-altering variants who did not have schizophrenia.

“This isn’t surprising,” Tsuang observed, “Given that schizophrenia is such a complex disorder, we would expect that not everyone who carries the variants would develop the disease.” In the future, researchers will be seeking what triggers the gene variants into causing problems, other mutations within affected individuals’ genetic profile that might promote or protect against disease, as well as non-genetic factors in the onset of the illness in genetically susceptible people.

The researchers also utilized a strategy and selected more distant relatives of affected individuals for genetic sequencing. Distant kin share, a smaller proportion of genes compared to closely related family members. For example,siblings typically on the average share about 50 percent of their genes whereas cousins on the average share 12.5 percent of their genes. The researhers also hypothesized that the causative mutation within each family would be the same variant.

This strategy helped the researchers decrease the number of genetic variants that were detected by sequencing and thereby concentrate only on the remaining strongest candidates. The researchers also filtered their results against the many publicly available sequencing databases. This allowed them to pick out genetic variants not seen in individuals without psychiatric illness.

According to Tsuang, the research team was excited by recent advances in technology enabled them to uncover unknown, rare genetic variants not previously found in large populations without psychiatric condition. The ability to rapidly sequence only those portions of the genome that code for proteins made this experiment possible.

The next step for the researchers will be to screen for the newly discovered genetic variants in a large sample of unrelated cases of schizophrenia compared to controls. They want to determine if the variants are statistically associated with the disease.

Alterations in brain activity in children at risk of schizophrenia predate onset of symptoms

Research from the University of North Carolina has shown that children at risk of developing schizophrenia have brains that function differently than those not at risk.

Brain scans of children who have parents or siblings with the illness reveal a neural circuitry that is hyperactivated or stressed by tasks that peers with no family history of the illness seem to handle with ease.

Because these differences in brain functioning appear before neuropsychiatric symptoms such as trouble focusing, paranoid beliefs, or hallucinations, the scientists believe that the finding could point to early warning signs or “vulnerability markers” for schizophrenia.

“The downside is saying that anyone with a first degree relative with schizophrenia is doomed. Instead, we want to use our findings to identify those individuals with differences in brain function that indicate they are particularly vulnerable, so we can intervene to minimize that risk,” said senior study author Aysenil Belger, PhD, associate professor of psychiatry at the UNC School of Medicine.

The UNC study, published online on March 6, 2013, in the journal Psychiatry Research: Neuroimaging, is one of the first to look for alterations in brain activity associated with mental illness in individuals as young as nine years of age.

Individuals who have a first degree family member with schizophrenia have an 8-fold to 12-fold increased risk of developing the disease. However, there is no way of knowing for certain who will become schizophrenic until symptoms arise and a diagnosis is reached. Some of the earliest signs of schizophrenia are a decline in verbal memory, IQ, and other mental functions, which researchers believe stem from an inefficiency in cortical processing – the brain’s waning ability to tackle complex tasks.

In this study, Belger and her colleagues sought to identify what if any functional changes occur in the brains of adolescents at high risk of developing schizophrenia. She performed functional magnetic resonance imaging (fMRI) on 42 children and adolescents ages 9 to 18, half of which had relatives with schizophrenia and half of which did not. Study participants each spent an hour and a half playing a game where they had to identify a specific image – a simple circle – out of a lineup of emotionally evocative images, such as cute or scary animals. At the same time, the MRI machine scanned for changes in brain activity associated with each target detection task.

Belger found that the circuitry involved in emotion and higher order decision making was hyperactivated in individuals with a family history of schizophrenia, suggesting that the task was stressing out these areas of the brain in the study subjects.

“This finding shows that these regions are not activating normally,” she says. “We think that this hyperactivation eventually damages these specific areas in the brain to the point that they become hypoactivated in patients, meaning that when the brain is asked to go into high gear it no longer can.”

Belger is currently exploring what kind of role stress plays in the changing mental capacity of adolescents at high risk of developing schizophrenia. Though only a fraction of these individuals will be diagnosed with schizophrenia, Belger thinks it is important to pinpoint the most vulnerable people early to explore interventions that may stave off the mental illness.

“It may be as simple as understanding that people are different in how they cope with stress,” says Belger. “Teaching strategies to handle stress could make these individuals less vulnerable to not just schizophrenia but also other neuropsychiatric disorders.”