Posts tagged medicine

National Institutes of Health researchers used the popular anti-wrinkle agent Botox to discover a new and important role for a group of molecules that nerve cells use to quickly send messages. This novel role for the molecules, called SNARES, may be a missing piece that scientists have been searching for to fully understand how brain cells communicate under normal and disease conditions.

"The results were very surprising," said Ling-Gang Wu, Ph.D., a scientist at NIH’s National Institute of Neurological Disorders and Stroke. "Like many scientists we thought SNAREs were only involved in fusion."

Every day almost 100 billion nerve cells throughout the body send thousands of messages through nearly 100 trillion communication points called synapses. Cell-to-cell communication at synapses controls thoughts, movements, and senses and could provide therapeutic targets for a number of neurological disorders, including epilepsy.

Nerve cells use chemicals, called neurotransmitters, to rapidly send messages at synapses. Like pellets inside shotgun shells, neurotransmitters are stored inside spherical membranes, called synaptic vesicles. Messages are sent when a carrier shell fuses with the nerve cell’s own shell, called the plasma membrane, and releases the neurotransmitter “pellets” into the synapse.

SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) are three proteins known to be critical for fusion between carrier shells and nerve cell membranes during neurotransmitter release.

"Without SNAREs there is no synaptic transmission," said Dr. Wu.

Botulinum toxin, or Botox, disrupts SNAREs. In a study published in Cell Reports, Dr. Wu and his colleagues describe how they used Botox and similar toxins as tools to show that SNAREs may also be involved in retrieving message carrier shells from nerve cell membranes immediately after release.

To study this, the researchers used advanced electrical recording techniques to directly monitor in real time carrier shells being fused with and retrieved from nerve cell membranes while the cells sent messages at synapses. The experiments were performed on a unique synapse involved with hearing called the calyx of Held. As expected, treating the synapses with toxins reduced fusion. However Dr. Wu and his colleagues also noticed that the toxins reduced retrieval.

"The results were very surprising," said Dr. Wu. "Like many scientists we thought SNAREs were only involved in fusion."

For at least a decade scientists have known that carrier shells have to be retrieved before more messages can be sent. Retrieval occurs in two modes: fast and slow. A different group of molecules are known to control the slow mode.

"Until now most scientists thought fusion and retrieval were two separate processes controlled by different sets of molecules", said Dr. Wu.

Nevertheless several studies suggested that one of the SNARE molecules could be involved with both modes.

In this study, Dr. Wu and his colleagues systematically tested this idea to fully understand retrieval. The results showed that all three SNARE proteins may be involved in both fast and slow retrieval.

"Our results suggest that SNAREs link fusion and retrieval," said Dr. Wu.

The results may have broad implications. SNAREs are commonly used by other cells throughout the body to release chemicals. For example, SNAREs help control the release of insulin from pancreas cells, making them a potential target for diabetes treatments. Recent studies suggest that SNAREs may be involved in neurological and psychiatric disorders, such as schizophrenia and spastic ataxia.

"We think SNARES work like this in most nerve cell synapses. This new role could change the way scientists think about how SNAREs are involved in neuronal communication and diseases," said Dr. Wu.

(Source: ninds.nih.gov)

New IBN Peptides May Help Researchers Combat Alzheimer’s, Diabetes and Cancer

Amyloids, or fibrous aggregates of abnormally folded proteins, are a common feature in degenerative diseases such as Alzheimer’s, diabetes and cancer. Amyloids occur naturally in the body, but despite decades of research, their mechanism of formation remains unknown, hampering drug development efforts. Now, a new class of ultrasmall peptides developed by the Institute of Bioengineering and Nanotechnology (IBN) offers scientists a platform for understanding this phenomenon, providing them with the insights required to design more effective treatments for these diseases.

IBN Executive Director Professor Jackie Y. Ying said, “Our researchers have been focusing on creating biomimetic materials for nanomedicine and cell and tissue engineering applications. The novel ultrasmall peptides developed by IBN are not only highly effective as synthetic cell culture substrates, but also as a model for studying the mystery of amyloid formation. Such fundamental understanding could contribute towards advancing medical treatment of amyloid-related disorders.”

First discovered in 2011 by IBN Team Leader and Principal Research Scientist Dr Charlotte Hauser, the peptides were formed from only 3-7 amino acids, making them the smallest ever reported class of self-assembling aliphatic compounds. Peptides perform a wide range of functions in the body, and are distinguished from proteins based on size. Building on this earlier research, IBN researchers have found a striking similarity between the structure of their synthetic peptides and the protein structure of naturally occurring amyloids in the latest study published in Proceedings of the National Academy of Sciences.

Dr Hauser elaborated, “This is the first proof-of-concept that our peptides self-assemble in the same way as naturally occurring amyloid sequences. Knowing that the process of amyloid formation is common across various chronic degenerative diseases, our goal is to identify the specific trigger so that we can design the appropriate drugs to inhibit and control the aggregate formation.”

The IBN team collaborated with researchers from the Institute of High Performance Computing and the European Synchrotron Radiation Facility to validate their peptides with the core protein sequences of three diseases: Alzheimer’s, diabetes and thyroid cancer.

The results revealed that the mechanism behind the self-assembly of amyloids from smaller intermediate structures into larger amyloid structures was similar to how the IBN peptides were formed. In addition, this study supports the growing evidence that early intermediates are more toxic than the final amyloid fibers, and may even be the driving force behind amyloid formation.

Patent applications have been filed on this research, and the next step of this project is pre-clinical evaluation of ultrasmall peptide therapeutics. IBN will also investigate other amyloid disorders such as corneal dystrophy, which can result in blindness.

(Source: a-star.edu.sg)

Using a new, stem cell-based, drug-screening technology that could reinvent and greatly reduce the cost of developing pharmaceuticals, researchers at the Harvard Stem Cell Institute (HSCI) have found a compound that is more effective in protecting the neurons killed in amyotrophic lateral sclerosis (ALS) than are two drugs that failed in human clinical trials after large sums were invested in them.

The new screening technique developed by Lee Rubin, a member of HSCI’s executive committee and a professor in Harvard’s Department of Stem Cell and Regenerative Biology (SCRB), had predicted that the two drugs that eventually failed in the third and final stage of human testing would do just that.

“It’s a deep, dark secret of drug discovery that very few drugs have been tested on human-diseased cells before being tested in a live person,” said Rubin, who heads HSCI’s program in translational medicine. “We were interested in the notion that we can use stem cells to correct that situation.”

Rubin’s model is built on an earlier proof of concept developed by HSCI principal faculty member Kevin Eggan, who demonstrated that it was possible to move a neuron-based disease into a laboratory dish using stem cells carrying the genes of patients with the disease.

In a paper published today in the journal Cell Stem Cell, Rubin laid out how he and his colleagues applied their new method of stem cell-based drug discovery to ALS, also known as Lou Gehrig’s disease. The illness is associated with the progressive death of motor neurons, which pass information between the brain and the muscles. As cells die, people with ALS experience weakness in their limbs, followed by rapid paralysis and respiratory failure. The disease typically strikes later in life. Ten percent of cases are genetically predisposed, but for most patients there is no known trigger.

Rubin’s lab began by studying the disease in mice, growing billions of motor neurons from mouse embryonic stem cells, half normal and half with a genetic mutation known to cause ALS. Investigators starved the cells of nutrients and then screened 5,000 druglike molecules to find any that would keep the motor neurons alive.

Several hits were identified, but the molecule that best prolonged the life of both normal and ALS motor neurons was kenpaullone, previously known for blocking the action of an enzyme (GSK-3) that switches on and off several cellular processes, including cell growth and death. “Shockingly, this molecule keeps cells alive better than the standard culture medium that everybody keeps motor neurons in,” Rubin said.

Kenpaullone proved effective in several follow-up experiments that put mouse motor neurons in situations of certain death. Neuron survival increased in the presence of the molecule whether the cells were programmed to die or were placed in a toxic environment.

After further investigation, Rubin’s lab discovered that kenpaullone’s potency came from its ability also to inhibit HGK, an enzyme that sets off a chain of reactions that leads to motor neuron death. This enzyme was not previously known to be important in motor neurons or associated with ALS, marking the discovery of a new drug target for the disease.

“I think that stem cell screens will discover new compounds that have never been discovered before by other methods,” Rubin said. “I’m excited to think that someday one of them might actually be good enough to go into the clinic.”

To find out if kenpaullone worked in diseased human cells, Rubin’s lab exposed patient motor neurons and motor neurons grown from human embryonic stem cells to the molecule, as well as two drugs that did well in mice but failed in phase III human clinical trials for ALS. Once again, kenpaullone increased the rate of neuron survival, while one drug saw little response, and the other drug failed to keep any cells alive.

According to Rubin, before kenpaullone could be used as a drug, it would need a substantial molecular makeover to make it better able to target cells and find its way into the spinal cord so it can access motor neurons.

“This is kind of a proof of principle on the do-ability of the whole thing,” he said. “I think it’s possible to use this method to discover new drug targets and to prevalidate compounds on real human disease cells before putting them in the clinic.”

Rubin’s next steps will be to continue searching for better druglike compounds that can inhibit HGK and thus enhance motor neuron survival. He believes that the new information that comes out of this research will be useful to academia and the pharmaceutical industry.

“These kinds of exploratory screens are hard to fund, so being part of the HSCI” — which provided some of the funding — “has been absolutely essential,” Rubin said.

(Source: news.harvard.edu)

Scientists at CWRU School of Medicine Discover New Technique that Holds Promise for the Treatment of Multiple Sclerosis and Cerebral Palsy

Researchers at Case Western Reserve School of Medicine have discovered a technique that directly converts skin cells to the type of brain cells destroyed in patients with multiple sclerosis, cerebral palsy and other so-called myelin disorders.

This discovery appears today in the journal Nature Biotechnology.

This breakthrough now enables “on demand” production of myelinating cells, which provide a vital sheath of insulation that protects neurons and enables the delivery of brain impulses to the rest of the body. In patients with multiple sclerosis (MS), cerebral palsy (CP), and rare genetic disorders called leukodystrophies, myelinating cells are destroyed and cannot be replaced.

The new technique involves directly converting fibroblasts - an abundant structural cell present in the skin and most organs - into oligodendrocytes, the type of cell responsible for myelinating the neurons of the brain.

“Its ‘cellular alchemy,’” explained Paul Tesar, PhD, assistant professor of genetics and genome sciences at Case Western Reserve School of Medicine and senior author of the study. “We are taking a readily accessible and abundant cell and completely switching its identity to become a highly valuable cell for therapy.”

In a process termed “cellular reprogramming,” researchers manipulated the levels of three naturally occurring proteins to induce fibroblast cells to become precursors to oligodendrocytes (called oligodendrocyte progenitor cells, or OPCs).

Tesar’s team, led by Case Western Reserve researchers and co-first authors Fadi Najm and Angela Lager, rapidly generated billions of these induced OPCs (called iOPCs). Even more important, they showed that iOPCs could regenerate new myelin coatings around nerves after being transplanted to mice—a result that offers hope the technique might be used to treat human myelin disorders.

When oligodendrocytes are damaged or become dysfunctional in myelinating diseases, the insulating myelin coating that normally coats nerves is lost. A cure requires the myelin coating to be regenerated by replacement oligodendrocytes.

Until now, OPCs and oligodendrocytes could only be obtained from fetal tissue or pluripotent stem cells. These techniques have been valuable, but with limitations.
“The myelin repair field has been hampered by an inability to rapidly generate safe and effective sources of functional oligodendrocytes,” explained co-author and myelin expert Robert Miller, PhD, professor of neurosciences at the Case Western Reserve School of Medicine and the university’s vice president for research. “The new technique may overcome all of these issues by providing a rapid and streamlined way to directly generate functional myelin producing cells.”

This initial study used mouse cells. The critical next step is to demonstrate feasibility and safety using human cells in a lab setting. If successful, the technique could have widespread therapeutic application to human myelin disorders.
“The progression of stem cell biology is providing opportunities for clinical translation that a decade ago would not have been possible,” said Stanton Gerson, MD, professor of Medicine-Hematology/Oncology at the School of Medicine and director of the National Center for Regenerative Medicine and the UH Case Medical Center Seidman Cancer Center. “It is a real breakthrough.”

(Source: newswise.com)

The St. Jude Children’s Research Hospital – Washington University Pediatric Cancer Genome Project has identified mutations responsible for more than half of a subtype of childhood brain tumor that takes a high toll on patients. Researchers also found evidence the tumors are susceptible to drugs already in development.

The study focused on a family of brain tumors known as low-grade gliomas (LGGs). These slow-growing cancers are found in about 700 children annually in the U.S., making them the most common childhood tumors of the brain and spinal cord. For patients whose tumors cannot be surgically removed, the long-term outlook remains bleak due to complications from the disease and its ongoing treatment. Nationwide, surgery alone cures only about one-third of patients.

Using whole genome sequencing, researchers identified genetic alterations in two genes that occurred almost exclusively in a subtype of LGG termed diffuse LGG. This subtype cannot be cured surgically because the tumor cells invade the healthy brain. Together, the mutations accounted for 53 percent of the diffuse LGG in this study. Researchers also demonstrated that one of the mutations, which had not previously been linked to brain tumors, caused tumors when introduced into the glial brain cells of mice.

The findings appear in the April 14 advance online edition of the scientific journal Nature Genetics.

“This subtype of low-grade glioma can be a nasty chronic disease, yet prior to this study we knew almost nothing about its genetic alterations,” said David Ellison, M.D., Ph.D., chair of the St. Jude Department of Pathology and the study’s corresponding author. The first author is Jinghui Zhang, Ph.D., an associate member of the St. Jude Department of Computational Biology.

The Pediatric Cancer Genome Project is using next-generation whole genome sequencing to determine the complete normal and cancer genomes of children and adolescents with some of the least understood and most difficult to treat cancers. Scientists believe that studying differences in the 3 billion chemical bases that make up the human genome will provide the scientific foundation for the next generation of cancer care.

“We were surprised to find that many of these tumors could be traced to a single genetic alteration,” said co-author Richard K. Wilson, Ph.D., director of The Genome Institute at Washington University School of Medicine in St. Louis. “This is a major pathway through which low-grade gliomas develop and it provides new clues to explore as we search for better treatments.”

The study involved whole genome sequencing of 39 paired tumor and normal tissue samples from 38 children and adolescents with different subtypes of LGG and related tumors called low-grade glioneuronal tumors (LGGNTs). Although many cancers develop following multiple genetic abnormalities, 62 percent of the 39 tumors in this study stemmed from a single genetic alteration.

Previous studies have linked LGGs to abnormal activation of the MAPK/ERK pathway. The pathway is involved in regulating cell division and other processes that are often disrupted in cancer. Until now, however, the genetic alterations involved in driving this pathway were unknown for some types of LGG and LGGNT.

This study linked activation in the pathway to duplication of a key segment of the FGFR1 gene, which investigators discovered in brain tumors for the first time. The segment is called a tyrosine kinase domain. It functions like an on-off switch for several cell signaling pathways, including the MAPK/ERK pathway. Investigators also demonstrated that experimental drugs designed to block activity along two altered pathways worked in cells with theFGFR1 tyrosine kinase domain duplication. “The finding suggests a potential opportunity for using targeted therapies in patients whose tumors cannot be surgically removed,” Ellison said.

Researchers also showed that the FGFR1 abnormality triggered an aggressive brain tumor in glial cells from mice that lacked the tumor suppressor gene Trp53.

Whole-genome sequencing found previously undiscovered rearrangements in the MYB and MYBL1 genes in diffuse LGGs. These newly identified abnormalities were also implicated in switching on the MAPK/ERK pathway.

Researchers checked an additional 100 LGGs and LGGNTs for the same FGFR1, MYB and MYBL1 mutations. Overall, MYB was altered in 25 percent of the diffuse LGGs, and 24 percent had alterations in FGFR1. Researchers also turned up numerous other mutations that occurred in just a few tumors. The affected genes included BRAF, RAF1, H3F3A, ATRX, EP300, WHSC1 and CHD2.

“The Pediatric Cancer Genome Project has provided a remarkable opportunity to look at the genomic landscape of this disease and really put the alterations responsible on the map. We can now account for the genetic errors responsible for more than 90 percent of low-grade gliomas,” Ellison said. “The discovery that FGFR1 and MYB play a central role in childhood diffuse LGG also serves to distinguish the pediatric and adult forms of the disease.”

(Source: stjude.org)

Some breast tumor circulating cells in the bloodstream are marked by a constellation of biomarkers that identify them as those destined to seed the brain with a deadly spread of cancer, said researchers led by those at Baylor College of Medicine in a report that appears online in the journal Science Translational Medicine.

"What prompted us to initiate this study was our desire to understand the characteristics of these cells," said Dr. Dario Marchetti, professor of pathology at BCM, director of the CTC (circulating tumor cell) Core Facility at BCM and a member of the NCI-designated Dan L. Duncan Cancer Center at BCM. Often, he said, circulating tumor cells (CTCs) from breast cancer patients which spread or metastasize to the brain are not identified by the current method for identifying such cells approved by the U.S. Food and Drug Administration (CellSearch® platform).

While this system is based on the detection of antibodies that target the epithelial cell adhesion molecule (EpCAM), the biomarkers identified by Marchetti and his colleagues include human epidermal growth factor receptor 2 (HER2+), epidermal growth factor receptor (EGFR), heparanase (HPSE) and Notch1 - and not EpCAM. Together, said Marchetti, these four proteins, previously known to be associated with cancer metastasis, spell out the signature of circulating tumors cells that travel to the brain.

Marchetti, using sophisticated techniques to test samples provided by Dr. Morris D. Groves of The University of Texas MD Anderson Cancer Center, also found this same pattern of proteins in the tissue taken from brain metastases of animals injected with breast cancer circulating tumor cells (CTCs).

They tested these special circulating tumor cells in laboratory models and found that they are highly invasive and capable of spread in live animals. They also found cells with this signature in the metastatic tumors of animals with breast cancer.

"We were able to grow these cells in vitro (in the laboratory in culture) for the first time ever," said Marchetti.

Circulating tumor cells are a promising method of identifying and monitoring solid tumors and could replace tumor biopsies in some cases. However, the promise is still being studied by experts such as Marchetti. In this case, he has identified a new signature for such cells - one that directs their activities toward spreading cancer to brain - an outcome with frequently fatal consequences.

The study not only identifies a novel signature of circulating tumor cells, it shows the limitations of currently approved platforms used to identify cancer in this way. Understanding such cells can help scientist understand how the disease spreads - an initial step in developing new methods of treating metastatic disease.

"We don’t claim that these biomarkers are the only important ones," said Marchetti. "We hope to find novel markers in brain metastasis that will make diagnosis and monitoring even more targeted."

They are also trying to find ways to link these circulating tumor cells back to the signature of the original or primary tumor.

(Source: bcm.edu)

Obesity, heart disease, and high blood pressure (hypertension) are all related, but understanding the molecular pathways that underlie cause and effect is complicated.

A new University of Iowa study identifies a protein within certain brain cells as a communications hub for controlling blood pressure, and suggests that abnormal activation of this protein may be a mechanism that links cardiovascular disease and obesity to elevated blood pressure.

"Cardiovascular diseases are the leading cause of death worldwide, and hypertension is a major cardiovascular risk factor," says Kamal Rahmouni, UI associate professor of pharmacology and internal medicine, and senior study author. "Our study identifies the protein called mTORC1 in the hypothalamus as a key player in the control of blood pressure. Targeting mTORC1 pathways may, therefore, be a promising strategy for the management of cardiovascular risk factors."

The hypothalamus is a small region of the brain that is responsible for maintaining normal function for numerous bodily processes, including blood pressure, body temperature, and glucose levels. Signaling of mTORC1 protein in the hypothalamus has previously been shown to affect food intake and body weight.

The new study, which was published April 2 in the journal Cell Metabolism, shows that the mTORC1 protein is activated by small molecules and hormones that are associated with obesity and cardiovascular disease, and this activation leads to dramatic increases in blood pressure.

Leucine is an amino acid that we get from food, which is known to activate mTORC1. The UI researchers showed that activating mTORC1 in rat brains with leucine increased activity in the nerves that connect the brain to the kidney, an important organ in blood pressure control. The increased nerve activity was accompanied by a rise in blood pressure. Conversely, blocking this mTORC1 activation significantly blunted leucine’s blood pressure-raising effect.

This finding may have direct clinical relevance as elevated levels of leucine have been correlated with an increased risk of high blood pressure in patients with cardiovascular disease.

"Our new study suggests a mechanism by which leucine in the bloodstream might increase blood pressure,” Rahmouni says.

Previous work has also suggested that mTORC1 is a signaling hub for leptin, a hormone produced by fat cells, which has been implicated in obesity-related hypertension.

Rahmouni and his colleagues showed that leptin activates mTORC1 in a specific part of the hypothalamus causing increased nerve activity and a rise in blood pressure. These effects are blocked by inhibiting activation of mTORC1.

“Our study shows that when this protein is either activated or inhibited in a very specific manner, it can cause dramatic changes in blood pressure,” Rahmouni says. “Given the importance of this protein for the control of blood pressure, any abnormality in its activity might explain the hypertension associated with certain conditions like obesity and cardiovascular disease.”

Rahmouni and his team hope that uncovering the details of the pathways linking mTORC1 activation and high blood pressure might lead to better treatments for high blood pressure in patients with cardiovascular disease and obesity.

(Source: now.uiowa.edu)