Monthly Archives: Duben 2016

A new study published in Proceedings of the National Academy of Sciences has discovered that a protein called IL-33 can reverse Alzheimer’s disease-like pathology and cognitive decline in mice.

“IL-33 is a protein produced by various cell types in the body and is particularly abundant in the central nervous system (brain and spinal cord),“ explained Professor Eddy Liew, Fellow of the Royal Society, who co-directed the research. “We found that injection of IL-33 into aged APP/PS1 mice rapidly improved their memory and cognitive function to that of the age-matched normal mice within a week.”

The hallmarks of Alzheimer’s include the presence of extracellular amyloid plaque deposits and the formation of neurofibrillary tangles in the brain. During the course of the disease, ‘plaques’ and ‘tangles’ build up, leading to the loss of connections between nerve cells, and eventually to nerve cell death and loss of brain tissue.‌

IL-33 appears to work by mobilising microglia (immune cells in the brain) to surround the amyloid plagues, take them up and digest them and reduces the number and size of the plaques. IL-33 does so by inducing an enzyme called neprilysin, which is known to degrade soluble amyloid.

In addition, the IL-33 treatment worked by inhibiting the inflammation in the brain tissue, which has been shown earlier to potentiate plaque and tangle formation. Therefore IL-33 not only helps to clear the amyloid plague already formed but also prevent the deposition of the plaques and tangles in the first place.‌‌

Professor Liew added: “The relevance of this finding to human Alzheimer’s is at present unclear. But there are encouraging hints. For example, previous genetic studies have shown an association between IL-33 mutations and Alzheimer’s disease in European and Chinese populations. Furthermore, the brain of patients with Alzheimer’s disease contains less IL-33 than the brain from non-Alzheimer’s patients.

“Exciting as it is, there is some distance between laboratory findings and clinical applications. There have been enough false ‘breakthroughs’ in the medical field to caution us not to hold our breath until rigorous clinical trials have been done. We are just about entering Phase I clinical trial to test the toxicity of IL-33 at the doses used. Nevertheless, this is a good start.”

 

Source: Reprinted from materials provided by the University of Glasgow.

Paper: „IL-33 ameliorates Alzheimer’s disease-like pathology and cognitive decline„

While research has identified hundreds of genes required for normal memory formation, genes that suppress memory are of special interest because they offer insights into how the brain prioritizes and manages all of the information, including memories, that it takes in every day. These genes also provide clues for how scientists might develop new treatments for cognitive disorders such as Alzheimer’s disease.

Scientists have identified a unique memory suppressor gene in the brain cells of Drosophila, the common fruit fly, in a study published in the journal Neuron.

The researchers screened approximately 3,500 Drosophila genes and identified several dozen new memory suppressor genes that the brain has to help filter information and store only important parts. One of these suppressor genes, in particular, caught their attention.

“When we knocked out this gene, the flies had a better memory—a nearly two-fold better memory,” said Ron Davis, chair of the Department of Neuroscience at The Scripps Research Institute and leader of the study. “The fact that this gene is active in the same pathway as several cognitive enhancers currently used for the treatment of Alzheimer’s disease suggests it could be a potential new therapeutic target.”

When the scientists disabled this gene, known as DmSLC22A, flies’ memory of smells (the most widely studied form of memory in this model) was enhanced—while overexpression of the gene inhibited that same memory function.

“Memory processes and the genes that make the brain proteins required for memory are evolutionarily conserved between mammals and fruit flies,” said Research Associate Ze Liu, co-first author of the study. “The majority of human cognitive disease-causing genes have the same functional genetic counterparts in flies.”

The gene in question belongs to a family of “plasma membrane transporters,” which produce proteins that move molecules, large and small, across cell walls. In the case of DmSLC22A, the new study indicates that the gene makes a protein involved in moving neurotransmitter molecules from the synaptic space between neurons back into the neurons. When DmSLC22A functions normally, the protein removes the neurotransmitter acetylcholine from the synapse, helping to terminate the synaptic signal. When the protein is missing, more acetylcholine persists in the synapse, making the synaptic signal stronger and more persistent, leading to enhanced memory.

“DmSLC22A serves as a bottleneck in memory formation,” said Research Associate Yunchao Gai, the study’s other co-first author. “Considering the fact that plasma transporters are ideal pharmacological targets, drugs that inhibit this protein may provide a practical way to enhance memory in individuals with memory disorders.”

The next step, Davis added, is to develop a screen for inhibitors of this pathway that, independently or in concert with other treatments, may offer a more effective way to deal with the problems of memory loss due to Alzheimer’s and other neurodegenerative diseases.

“One of the major reasons for working with the fly initially is to identify brain proteins that may be suitable targets for the development of cognitive enhancers in humans,” said Davis. “Otherwise, we would be guessing in the dark as to which of the more than 23,000 human proteins might be appropriate targets.”

Source: Reprinted from materials provided by Eric Sauter at The Scripps Research Institute.

Paper: „Drosophila SLC22A Transporter Is a Memory Suppressor Gene that Influences Cholinergic Neurotransmission to the Mushroom Bodies.“

A study appearing in the journal Neuron suggests there may be a new way to change the damaging course of Huntington’s disease.

Neurobiologists have shown that reducing the aberrant accumulation of a particular form of the mutant Huntingtin protein corresponds to improvement in symptoms and neuroinflammation in HD mice.

They showed this by targeting and modulating levels of PIAS1 — a protein implicated in cancer and other diseases — which they found led to the reduction of the mutant Huntington protein. The work suggests that changing levels of the PIAS1 protein and targeting this pathway could have a benefit to disease.

Source: Reprinted from materials provided by the University of California, Irvine.

Paper: „PIAS1 Regulates Mutant Huntingtin Accumulation and Huntington’s Disease-Associated Phenotypes In Vivo“

The Lancet Neurology Conference: Preclinical neurodegenerative disease — towards prevention and early diagnosis is now accepting abstracts for poster presentation at its 2016 meeting, which will take place October 19-21, 2016, in London, UK.

Abstracts can be submitted on the following topics:

  • Genetic factors, cellular pathways, and neuronal vulnerability
  • Environmental factors, epidemiology, and primary prevention
  • Biomarkers and early diagnosis
  • Prevention through therapeutics
  • Trials; regulatory and ethical considerations

The deadline to submit is June 3, 2016. For more information, visit The Lancet Neurology Conference website.

Researchers have shown how brain connections, or synapses, are lost early in Alzheimer’s disease and demonstrated that the process starts — and could potentially be halted — before telltale plaques accumulate in the brain. Their work, published online by Science, suggests new therapeutic targets to preserve cognitive function early in Alzheimer’s disease.

The researchers show in multiple Alzheimer’s mouse models that mechanisms similar to those used to „prune“ excess synapses in the healthy developing brain are wrongly activated later in life. By blocking these mechanisms, they were able to reduce synapse loss in the mice.

Currently, there are five FDA-approved drugs for Alzheimer’s, but these only boost cognition temporarily and do not address the root causes of cognitive impairment in Alzheimer’s. Many newer drugs in the pipeline seek to eliminate amyloid plaque deposits or reduce inflammation in the brain, but the new research from Boston Children’s suggests that Alzheimer’s could be targeted much earlier, before these pathologic changes occur.

„Synapse loss is a strong correlate of cognitive decline,“ says Beth Stevens, assistant professor in the Department of Neurology at Boston Children’s, senior investigator on the study and a recent recipient of the MacArthur „genius“ grant. „We’re trying to go back to the very beginning and see how synapse loss starts.“

The researchers looked at Alzheimer’s — a disease of aging — through an unusual lens: normal brain development in infancy and childhood. Through years of research, the Stevens lab has shown that normal developing brains have a process to „prune“ synapses that aren’t needed as they build their circuitry.

„Understanding a normal developmental process deeply has provided us with novel insight into how to protect synapses in Alzheimer’s and potentially a host of other diseases,“ says Stevens, noting that synapse loss also occurs in frontotemporal dementia, Huntington’s disease, schizophrenia, glaucoma and other conditions.

In the Alzheimer’s mouse models, the team showed that synapse loss requires the activation of a protein called C1q, which „tags“ synapses for elimination. Immune cells in the brain called microglia then „eat“ the synapses — similar to what occurs during normal brain development. In the mice, C1q became more abundant around vulnerable synapses before amyloid plaque deposits could be observed.

When Stevens and colleagues blocked C1q, a downstream protein called C3, or the C3 receptor on microglia, synapse loss did not occur.

„Microglia and complement are already known to be involved in Alzheimer’s disease, but they have been largely regarded as a secondary event related to plaque-related neuroinflammation, a prominent feature in progressed stages of Alzheimer’s,“ notes Soyon Hong, the Science paper’s first author. „Our study challenges this view and provides evidence that complement and microglia are involved much earlier in the disease process, when synapses are already vulnerable, and could potentially be targeted to preserve synaptic health.“

A human form of the antibody Stevens and Hong used to block C1q, known as ANX-005, is in early therapeutic development with Annexon Biosciences (San Francisco) and is being advanced into the clinic. The researchers believe it has potential to be used someday to protect against synapse loss in a variety of neurodegenerative diseases.

„One of the things this study highlights is the need to look for biomarkers for synapse loss and dysfunction,“ says Hong. „As in cancer, if you treat people at a later stage of Alzheimer’s, it may already be too late.“

The researchers also found that the beta-amyloid protein, C1q and microglia work together to cause synapse loss in the early stages of Alzheimer’s. The oligomeric form of beta-amyloid (multiple units of beta-amyloid strung together) is already known to be toxic to synapses even before it forms plaque deposits, but the study showed that C1q is necessary for this effect. The converse was also true: microglia engulfed synapses only when oligomeric beta-amyloid was present.

Source: Reprinted from materials provided by Boston Children’s Hospital
Paper: „Complement and microglia mediate early synapse loss in Alzheimer mouse models“