Brain organoid model shows molecular signs of Alzheimer’s before birth

In a model of human fetal brain development, Emory researchers can see perturbations of epigenetic markers in cells derived from people with familial early-onset Alzheimer’s disease, which takes decades to appear. This suggests that in people who inherit mutations linked to early-onset Alzheimer’s, it would be possible to detect molecular changes in their brains before birth. The results were published in the journal Cell Reports. “The beauty of using organoids is that they allow us to Read more

The earliest spot for Alzheimer's blues

How the most common genetic risk factor in AD interacts with the earliest site of neurodegeneration Read more

Make ‘em fight: redirecting neutrophils in CF

Why do people with cystic fibrosis (CF) have such trouble with lung infections? The conventional view is that people with CF are at greater risk for lung infections because thick, sticky mucus builds up in their lungs, allowing bacteria to thrive. CF is caused by a mutation that affects the composition of the mucus. Rabindra Tirouvanziam, an immunologist at Emory, says a better question is: what type of cell is supposed to be fighting the Read more

drug discovery

Steer microglia toward the angels – with a drug based on sea anemone venom

Researchers interested in Alzheimer’s and other neurodegenerative diseases are focusing their attention on microglia, cells that are part of the immune system in the brain.

Author Donna Jackson Nakazawa titled her recent book on microglia “The Angel and the Assassin,” based on the cells’ dual nature; they can be benign or malevolent, either supporting neuronal health or driving harmful inflammation. Microglia resemble macrophages in their dual nature, but microglia are renewed within the brain, unlike macrophages, which are white blood cells that infiltrate into the brain from outside.

At Emory, neurologist Srikant Rangaraju’s lab recently published a paper in PNAS on a promising drug target on microglia: Kv1.3 potassium channels. Overall, the results strengthen the case for targeting Kv1.3 potassium channels as a therapeutic approach for Alzheimer’s.

Kv1.3 potassium channels have also been investigated as potential therapeutic targets in autoimmune disorders, since they are expressed on T cells as well as microglia. The peptide dalazatide, based on a toxin from the venom of the Caribbean sea anemone Stichodactyla helianthus, is being developed by the Ohio-based startup TEKv Therapeutics. The original venom peptide needed to be modified to make it more selective toward the right potassium channels  – more about that here.

Kv1.3 potassium channels are potential therapeutic targets in autoimmune disorders and Alzheimer’s — blockable with peptides based on venom of the sea anemone Stichodactyla helianthus

It appears that Kv1.3 levels on microglia increase in response to exposure to amyloid-beta, the toxic protein fragment that accumulates in the brain in Alzheimer’s, and Kv1.3 may be an indicator that microglia are turning to the malevolent side.

In the Emory paper, researchers showed that Kv1.3 potassium channels are present on a subset of microglia isolated from Alzheimer’s patients’ brains. They also used bone marrow transplant experiments to show that the immune cells in mouse brain that express Kv1.3 channels are microglia (internal brain origin), not macrophages (transplantable w/ bone marrow).

Read more

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Fixing Humpty Dumpty in cancer cells

As Star Trek’s Spock once observed: “As a matter of cosmic history, it has always been easier to destroy than to create.”

The same is true inside human cells, explaining why Emory researchers’ recent accomplishment – finding a small-molecule compound that corrects a defective protein-protein interaction – is so significant for cancer research. It’s like putting Humpty Dumpty back together again.

Xiulei Mo, Haian Fu and colleagues have identified what they call a “mutation-directed molecular glue”. The glue restores a regulatory circuit that when defective, is responsible for acceleration of colorectal and pancreatic cancer. The results are reported in Cell Chemical Biology.

Restoring protein-protein interactions disrupted by an oncogenic mutation is like putting Humpty Dumpty back together again

“It is very exciting, because this is a clear example of a protein-protein interaction stabilizer that can reactivate the lost function and reestablish tumor-suppressive activity,” says Fu, who is chair of Emory’s Pharmacology and Chemical Biology department and leader of Winship Cancer Institute’s Discovery & Developmental Therapeutics program.

Scientists are very good at finding inhibitors for enzymes that are overactive. But they have meager results as far as strengthening interactions that are weak or absent. There are existing examples of drugs that stabilize protein-protein interactions (transplant drugs rapamycin and cyclosporine), but they inhibit the function of the proteins they target, as intended.

Read more

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More NMDA but less excitotoxicity? Now possible

Emory pharmacologists have discovered a new class of potential drugs that might allow them to have their cake and eat it too — with reference to NMDA receptors, important control sites in the brain for learning and memory.

Many researchers have wanted to enhance NMDA receptor signals to treat disorders such as schizophrenia. But at the same time, they need to avoid killing neurons with “excitotoxicity”, which comes from excess calcium entering the cell. Excitotoxicity is thought to be a major mechanism of cell death in stroke and traumatic brain injury.

Usually more sensitivity to NMDA activation and excess calcium go hand in hand. In a new Nature Chemical Biology paper, pharmacologist Stephen Traynelis and colleagues have identified a group of compounds that allow them to separate those two aspects of NMDA signaling.

These compounds appear to selectively decrease how much calcium (as opposed to sodium) flows through the NMDA ion channel. Traynelis says that the discovery opens up pharmacological possibilities for NMDA receptors similar to those for other receptor classes that are prominent drug targets, such as G-protein coupled receptors and acetylcholine receptors. With such receptors, the drugs are called “biased agonists” or “biased modulators” because they shift the balance of how the ion channel responds.

For NMDA receptors, how these newly identified compounds work on a molecular level needs to be explored, and could lead to the long-standing goal of NMDA-based neuroprotection for treatment of stroke/TBI, the authors note. Postdoc Riley Perszyk is first author, with cell biologist Gary Bassell and chemists Dennis Liotta and Lanny Liebeskind as co-authors.

Traynelis discussed this research in his Hodgkin Huxley Katz Prize Lecture to the Physiology 2019 conference in Scotland in December 2019 (the part about the new class of NMDA modulators starts at about 20 minutes).

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Biochemists grab slippery target: LRH-1

To fight fat, scientists had to figure out how to pin down a greasy, slippery target. Researchers at Emory University and Baylor College of Medicine have identified compounds that potently activate LRH-1, a liver protein that regulates the metabolism of fat and sugar. These compounds have potential for treating diabetes, fatty liver disease and inflammatory bowel disease.

Their findings were recently published online in Journal of Medicinal Chemistry.

LRH-1 is thought to sense metabolic state by binding a still-undetermined group of greasy molecules: lipids or phospholipids. It is a nuclear receptor, a type of protein that turns on genes in response to hormones or vitamins. The challenge scientists faced was in designing drugs that fit into the same slot occupied by the lipids.

“Phospholipids are typically big, greasy molecules that are hard to deliver as drugs, since they are quickly taken apart by the digestive system,” says Eric Ortlund, PhD, associate professor of biochemistry at Emory University School of Medicine. “We designed some substitutes that don’t fall apart, and they’re highly effective – 100 times more potent that what’s been found already.”

Previous attempts to design drugs that target LRH-1 ran into trouble because of the grease. Two very similar molecules might bind LRH-1 in opposite orientations. Ortlund’s lab worked with Emory chemist Nathan Jui, PhD and his colleagues to synthesize a large number of compounds, designing a “hook” that kept them in place. Based on previous structural studies, the hook could stop potential drugs from rotating around unpredictably. Read more

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Fighting cancer with combinatorial imagination

In his undergraduate days, Winship Cancer Institute dermatologist and cancer researcher Jack Arbiser was an organic chemist. That may be why he recognized an organic synthesis reagent based on the metal palladium as a potential anti-cancer drug.

We’re talking about Tris-DBA-palladium. Arbiser and colleagues showed in a 2008 Clinical Cancer Research paper that this deep purple stuff (see photo) is active against melanoma, and since then, against other types of cancer such as pancreatic cancer, multiple myeloma, and CLL leukemia.

Tris-DBA-PD has a deep purple color. The palladium atoms can be seen in the diagram as two blue balls at the center. From Wikipedia.

Since it’s used in organic synthesis, you might expect Tris-DBA-palladium not to be very soluble in water. A new paper in Scientific Reports demonstrates that this issue can be addressed by hooking up the reagent to nanoparticles made of hyaluronic acid, which targets tumor cells. They are effective against melanoma in mice, the paper shows.

“We have already demonstrated that Tris DBA palladium by itself has activity against melanoma in mice,” Arbiser writes (in his VA grant summary). “However, we believe that we can make Tris DBA palladium into an even more powerful drug by adding it to nanoparticles that are guided to the tumor.”

In an email to Lab Land, Arbiser says he arrived at Tris-DBA-palladium by using his chemist’s imagination, in a “your chocolate landed in my peanut butter” kind of way.

“I got the idea for looking at this compound because it is a complex of Pd with a curcumin-like structure, and I figured it might have the characteristics of platinum and curcumin together,” he says. Read more

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Fragile X: preclinical portfolio for PI3k drug strategy

Research in mice shows that a pharmacological strategy can alleviate multiple behavioral and cellular deficiencies in a mouse model of fragile X syndrome (FXS), the most common inherited form of intellectual disability and a major single-gene cause of autism spectrum disorders.

The results were published online last week by Neuropsychopharmacology, and were presented at the NFXF International Fragile X Conference in Cincinnati.

When the compound GSK6A was given to mice lacking the Fmr1 gene, an established animal model of fragile X syndrome, it relieved symptomatic behaviors, such as impaired social interactions and inflexible decision making, which can be displayed by humans with fragile X syndrome.

The findings indicate that treatment with GSK6A or a similar compound could be a viable strategy for addressing cognitive and behavioral problems in fragile X syndrome; this would need to be tested directly in clinical trials. GSK6A inhibits one particular form of a cellular signaling enzyme: the p110β form of PI3 (phosphoinositide-3) kinase. A closely related p110β inhibitor is already in clinical trials for cancer.

Video from the iBook “Basic Science Breakthroughs: Fragile X Syndrome”. Narration by Emory genetics chair Stephen Warren, whose team identified the gene responsible for fragile X.

“Our results suggest that p110β inhibitors can be repurposed for fragile X syndrome, and they have implications for other subtypes of autism spectrum disorders that are characterized by similar alterations of this pathway,” says Gary Bassell, PhD, professor and chair of cell biology at Emory University School of Medicine.

“Right now, no proven efficient treatments are available for fragile X syndrome that are targeted to the disease mechanism,” says Christina Gross, PhD, from Cincinnati Children’s. “We think that p110β is an appropriate target because it is directly regulated by FMRP, and it is overactivated in both mouse models and patient cell lines.”

The paper represents a collaboration between three laboratories: two at Emory led by Bassell and Shannon Gourley, PhD, and one at Cincinnati Children’s, led by Gross. Gourley is based at Yerkes National Primate Research Center; see this earlier item on her collaboration with Bassell here.

While the researchers are discussing clinical trials of p110β inhibitors in fragile X syndrome, they say that long-term studies in animals are needed to ensure that undesirable side effects do not appear. More here.

With respect to clinical trials, the fragile X community has been disappointed before. Based on encouraging studies in mouse models, drugs targeting mGluR5 glutamate receptors were tested in adolescents and adults. mGluR5 drugs did not show clear benefits; recent re-evaluation suggests the choice of outcome measures, the ages of study participants and drug tolerance may have played a role.

Warren played a major role in developing the mGluR5 approach and Emory investigators were part of those studies. More recently, clinical trials for one of the mGluR5 medications were revived in younger children and Emory is a participating site. Also, see this 2016 discussion in Spectrum with Elizabeth Berry-Kravis on the fragile X mouse model; Bassell, Gross and Gourley have made some inroads on the limitations Berry-Kravis describes.

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Complexity of NMDA receptor drug discovery target revealed

Know your target. Especially if your target is coming into focus for treating diseases such as schizophrenia and treatment-resistant depression.

NMDA receptors, critical for learning and memory, are sensors in the brain. Studying them in molecular detail is challenging, because they usually come in four parts, and the parts aren’t all the same.

Researchers at Emory have been probing one variety of NMDA receptor assembly found in the cerebellum, and also in the thalamus, a central gateway for sensory inputs, important for cognition, movement and sleep. This variety includes a subunit called GluN2C – together with two partners, GluN1 and GluN2A.

The results were published Thursday, June 28 in Neuron.

Outside of a living brain, NMDA receptor assemblies are typically studied with either two copies of GluN2C or two of GluN2A, but not with one of each, says senior author Stephen Traynelis, PhD, professor of pharmacology at Emory University School of Medicine

“Our data suggest that GluN2C is rarely by itself,” Traynelis says. “It’s typically paired up with another GluN2 subunit. This means we really don’t know what the properties of the main NMDA receptor in the cerebellum or the thalamus are.”

Psychiatrists have become interested in GluN2C because it appears to decline in the brains of schizophrenia patients. Mice without adequate levels of GluN2C display abnormalities in learning, memory and sensory processing, which together resemble schizophrenia in humans. In addition, GluN2C appears to be important for the mechanism of ketamine, a drug being studied for its rapid anti-depressant effects.

Using drugs that are selective for particular combinations of NMDA receptor subunits, Traynelis’ laboratory showed that an assembly of GluN2A and GluN2C is the dominant form in the mouse cerebellum. When GluN2C is introduced into cortical neurons, it prefers to pair up with GluN2A, the researchers found. This raises the question, in regions such as the thalamus, of whether GluN2C also appears with a partner GluN2 subunit. They also observed that the GluN2A-GluN2C assembly has distinct electrochemical properties. Read more

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A sickly sweet anticancer drug

Cancer cells are well known for liking the simple sugar glucose. Their elevated appetite for glucose is part of the Warburg effect, a metabolic distortion that has them sprinting all the time (glycolysis) despite the presence of oxygen.

A collaboration between researchers at Winship Cancer Institute, Georgia State and University of Mississippi has identified a potential drug that uses cancer cells’ metabolic preferences against them: it encourages the cells to consume so much glucose it makes them sick.

Their findings were published in Oncotarget. Read more

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Drug discovery: selective anti-inflammatory approach to AD

Anyone familiar with Alzheimer’s disease research can say what a challenge drug development has been. In Emory’s Department of Pharmacology, Thota Ganesh is focusing on an anti-inflammatory approach. Ganesh’s work has been supported by the Alzheimer’s Drug Discovery Foundation and more recently by a five-year, $3.6 million grant from the National Institute on Aging.

Medicinal chemist Thota Ganesh, PhD, is focusing on an anti-inflammatory approach to Alzheimer’s disease, targeting the prostaglandin receptor EP2.

An assistant professor at Emory since 2011, he is continuing research he undertook with Ray Dingledine on EP2 antagonists. In animals, they showed that this class of compounds could reduce injury to the brain after a prolonged seizure. Since then, they have shown that EP2 antagonists have similar effects in protecting against organophosphate pesticides/nerve agents.

EP2 is one of the four receptors for prostaglandin E2, a hormone involved in processes such as fever, childbirth, digestion and blood pressure regulation. Before Ganesh and colleagues from the Emory Chemical Biology Discovery Center started looking for them, chemicals that could block EP2 selectively were not available.

Their idea is: blocking EP2 is a better strategy than the more general approach of going after prostaglandins, the targets for non-steroid anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen and celecoxib (Celebrex). Read more

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Nutty stimulant revealed as anticancer tool

Arecoline — the stimulant component of areca nuts — has anticancer properties, researchers at Winship Cancer Institute of Emory University have discovered. The findings were published Thursday, November 17 in Molecular Cell.

areca-nut-and-arecoline

Areca nut and chemical structure of arecoline. From Wikimedia.

Areca nuts are chewed for their stimulant effects in many Asian countries, and evidence links the practice to the development of oral and esophageal cancer. Analogous to nicotine, arecoline was identified as an inhibitor of the enzyme ACAT1, which contributes to the metabolism-distorting Warburg effect in cancer cells.

Observers of health news have complained that coffee, as a widely cited example, is implicated in causing cancer one week and absolved the next. Arecoline is not another instance of the same trend, stresses senior author Jing Chen, PhD, professor of hematology and medical oncology at Emory University School of Medicine and Winship Cancer Institute.

“This is just a proof of principle, showing that ACAT1 is a good anticancer target,” Chen says. “We view arecoline as a lead to other compounds that could be more potent and selective.”

Chen says that arecoline could be compared to arsenic, a form of which is used as a treatment for acute promyelocytic leukemia, but is also linked to several types of cancer. Plus, arecoline’s cancer-promoting effects may be limited if it is not delivered or absorbed orally, he says. When arecoline first arose in a chemical screen, Chen says: “It sounded like a carcinogen to me. But it all depends on the dose and how it is taken into the body.” Read more

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