New Molecule Could Save Brain Cells from Neurodegeneration, Stroke

ScienceDaily (Jan. 18, 2011) — Researchers at the University of North Carolina at Chapel Hill have discovered a molecule that can make brain cells resistant to programmed cell death or apoptosis.

A fluorescently labeled neuron in which the apoptosis pathway is inhibited

This molecule, a tiny strand of nucleotides called microRNA-29 or miR-29, has already been shown to be in short supply in certain neurodegenerative illnesses such as Alzheimer's disease and Huntington's disease. Thus, the discovery could herald a new treatment to prompt brain cells to survive in the wake of neurodegeneration or acute injury like stroke.

"There is the real possibility that this molecule could be used to block the cascade of events known as apoptosis that eventually causes brain cells to break down and die," said senior study author Mohanish Deshmukh, PhD, associate professor of cell and developmental biology.

The study, published online Jan. 18, 2011, in the journal Genes & Development, is the first to find a mammalian microRNA capable of stopping neuronal apoptosis.

Remarkably, a large number of the neurons we are born with end up dying during the normal development of our bodies. Our nerve cells must span great distances to ultimately innervate our limbs, muscles and vital organs. Because not all nerve cells manage to reach their target tissues, the body overcompensates by sending out twice as many neurons as required. The first ones to reach their target get the prize, a cocktail of factors needed for them to survive, while the ones left behind die off. Once that brutal developmental phase is over, the remaining neurons become impervious to apoptosis and live long term.

But exactly what happens to suddenly keep these cells from dying has been a mystery. Deshmukh thought the key might lie in microRNAs, tiny but powerful molecules that silence the activity of as many as two-thirds of all human genes. Though microRNAs have been a hotbed of research in recent years, there have been relatively few studies showing that they play a role in apoptosis. So Deshmukh and his colleagues decided to look at all of the known microRNAs and see if there were any differences in young mouse neurons versus mature mouse neurons.

One microRNA jumped out at them, an entity called miR-29, which at that time had never before been implicated in preventing apoptosis. When the researchers injected their new molecule into young neurons, which are able to die if instructed, they found that the cells became resistant to apoptosis, even in the face of multiple death signals.

They then decided to pinpoint where exactly this molecule played a role in the series of biochemical events leading to cell death. The researchers looked at a number of steps in apoptosis and found that miR-29 acts at a key point in the initiation of apoptosis by interacting with a group of genes called the BH3-only family. Interestingly, the microRNA appears to interact with not just one but as many as five members of that family, circumventing a redundancy that existed to allow cell death to continue even if one of them had been blocked.

"People in the field have been perplexed that when they have knocked-out any one of these members it hasn't had a remarkable effect on apoptosis because there are others that can step in and do the job," said Deshmukh. "The fact that this microRNA can target multiple members of this family is very interesting because it shows how a single molecule can basically in one stroke keep apoptosis from happening. Interestingly, it only targets the members that are important for neuronal apoptosis, so it may be a way of specifically preserving cells in the brain without allowing them to grow out of control (and cause cancer) elsewhere in the body."

Deshmukh is currently developing mouse models where miR-29 is either "knocked-out" or overactive and plans to cross them with models of Alzheimer's disease, Parkinson's disease and ALS to see if it can prevent neurodegeneration. He is also actively screening for small molecule compounds that can elevate this microRNA and promote neuronal survival.

The research was funded by the National Institutes of Health. Study co-authors were Adam J. Kole, a graduate student in Deshmukh's lab; Vijay Swahari, research technician; and Scott M. Hammond, PhD, associate professor of cell and developmental biology.

New Hope in Fight Against Huntington's Disease

ScienceDaily (Jan. 18, 2011) — Hope for new ways of treating devastating neurodegenerative disorders such as Huntington's disease has been raised by a trans-Atlantic team of researchers thanks to the use of cutting-edge genetic techniques.

Visualisation of individual baker’s yeast cells 

(Saccharomyces cerevisiae) by scanning electron microscopy.

Led by the University of Leicester, scientists from the University of Lisbon (led by Dr Tiago Outeiro) and University of California at San Francisco (led by Dr Paul Muchowski) collaborated to generate novel approaches for tackling the diseases. Their work, funded by the Medical Research Council, is published in the Journal of Biological Chemistry.

At Leicester, working simply with baker's yeast, a team of biological scientists examined aspects of Huntington's disease. These yeast are extremely well-characterised and have powerful and facile genetics which allow researchers to rapidly interrogate this system at a genome-wide level. Research in recent years has found that baker's yeast can be used to study mechanisms underlying disease pathology, and this simple organism has been used to identify several promising candidate drug targets for neurodegenerative disorders, including Huntington's disease.

Flaviano Giorgini, lead author of the research paper at the University of Leicester, said: "My research group is interested in using genetics and genomics approaches to better understand the fatal neurodegenerative disorders of Huntington's disease and Parkinson's disease.

"By clarifying the genes and cellular pathways involved in these diseases we hope to identify novel strategies for treatment and therapy of these disorders. In our work we use simple, yet powerful genetic organisms such as baker's yeast and fruit flies to model aspects of these devastating diseases.

"In the current study we have used a novel functional genomics profiling approach to identify genes which can protect these simple organisms from disease symptoms. We then used computational approaches to uncover a network of interactions amongst these genes, which has shed light on the mechanisms underlying this disorder."

Using the approach above, the scientists found that many of the protective genes are involved in translation -- a cellular process in which messenger RNA (mRNA) is decoded by the ribosome to produce specific proteins. This is particularly intriguing as this process has not been implicated in Huntington's disease in the past.

This is important because recent work indicates that pharmacological modulation of translation may represent a promising avenue for treatment of Parkinson's disease. Therefore, this new research strongly dovetails with these observations and suggests that similar drug treatment may be beneficial in Huntington's disease.

Dr Giorgini, of the Department of Genetics, said: "Our research has taken advantage of cutting edge genomics approaches using a simple model organism to identify a novel area for potential therapeutic intervention for Huntington's disease.

"If our findings are validated by further studies, it might suggest a novel therapeutic approach for this devastating disorder -- which is critical as currently there are no treatments for onset or progression of symptoms."

New Synthetic Compound Created With HIV-Fighting Promise

ScienceDaily (Jan. 18, 2011) — Using chemical compounds found in a Japanese plant as a lead and the clever application of ultraviolet light, a Scripps Research Institute team has created a unique library of dozens of synthetic compounds to test for biomedical potential. Already, one of the compounds has shown great promise in inhibiting replication of HIV particles and fighting inflammation.

With the report of their work scheduled to appear in the online Early Edition of Proceedings of the National Academy of Sciences this week, the researchers now plan to optimize the compound's pharmaceutical potential so that it can be pursued as a drug candidate.

The plant Hypericum chinense, known in Japan as biyouyanagi, produces beautiful yellow flowers and, as it happens, potent chemical compounds known as biyouyanagins that have already shown promising anti-HIV and anti-tumor activity. That got the attention of K.C. Nicolaou, who holds the titles chair of the Department of Chemistry, Aline W. and L.S. Skaggs Professor of Chemical Biology, and Darlene Shiley Chair in Chemistry at Scripps Research. Nicolaou's interest was also piqued because the plant is from the same family that produces St. John's wort, and the biyouyanagins possess an intriguing molecular architecture.

"It was the perfect recipe for convincing a synthetic chemist to get into the game," said Nicolaou, who spearheaded the project in collaboration with a number of Scripps Research colleagues. "It seemed like there was so much to be discovered."

Best of Both Worlds

Within the biomedical field there are some researchers that argue natural products are the best route to new drug discovery. Others laud the potential of designing completely synthetic drugs. "I belong to both camps," says Nicolaou, because he prefers to start with natural products and then modify them in a variety of ways to create new synthetic products with improved potential. "The power of this method is that it allows us to build on the natural structures to make a whole new and diverse family of compounds."

An unexpected side result of the group's initial work was the discovery that the structure previously reported for the biyouyanagins was slightly off. With the proper structures in hand, the Nicolaou team recognized it could induce formation of critical bonds that join the two domains of the molecules by bombarding the right chemical building blocks with ultraviolet light.

This technique, known as photocycloaddition, allowed the scientists to synthesize the two known biyouyanagins as well as a third type not yet discovered in nature. The scientists then began combining a variety of different building blocks -- some commercially available and others they produced in the lab -- using the photocycloaddition to build a library of about 50 analogs, compounds similar to the originals but with significant chemical variations.

The resulting compounds then went in groups to various collaborating Scripps Research laboratories. Professor Dennis Burton's lab analyzed the compounds' ability to inhibit replication of HIV. Chair of the Department of Chemical Physiology Ben Cravatt's team looked at anti-inflammatory potential. Professor Juan de la Torre's group examined effects against LCMV, the prototype member of the arenavirus family that includes several causative agents of deadly hemorrhagic fever disease in West Africa and South America.

All of the compounds in the team's new library are, like aspirin, considered small molecules. Nicolaou believes these offer the best biomedical potential. Larger molecules such as proteins are finding new medical applications, but have to be injected and are often short-lived and very expensive.

"If you can discover small molecules that work, they're affordable and they last long enough in the body to do their jobs," he said. "Those are the magic bullets."

A Promising Lead

One compound from the new library, number 53, stood out. One side of its structure is essentially the same as that of a natural biyouyanagin, while the other side is a departure comprising a structural motif like the bases found in DNA. In the HIV testing, it compared favorably with the well-known AIDS drug AZT, though it is not yet as potent. In the anti-inflammatory tests, it was as potent or more so than commercially available products. This particular compound hasn't been tested for its potential against arenaviruses, but Nicolaou is hopeful the team will eventually find interesting activity there as well.

"We were certainly excited to see those results," says Nicolaou. "It's quite a promising lead." Next, the team will tinker with 53's initial structure in search of modifications that will increase its potency. Once its biomedical activities are optimized, the group will consider pushing the compound toward the drug-testing process.

This work was funded by the National Institutes of Health, the Skaggs Institute for Chemical Biology, the Universita degli Studi di Urbino "Carlo Bo," the Japanese Society for the Promotion of Science, the Natural Sciences and Engineering Research Council of Canada, and the National Institute on Drug Abuse.

In addition to Nicolaou, Burton, Cravatt, and de la Torre, authors of the paper, titled "Design, synthesis, and biological evaluation of a biyouyanagin compound library," were Silvano Sanchini, David Sarlah, Gang Lu, T. Robert Wu, Daniel Nomura, Beatrice Cubitt, and Ann Hessell, all from The Scripps Research Institute.

Scientists Bring Cancer Cells Back Under Control

ScienceDaily (Jan. 18, 2011) — Scientists at The University of Nottingham have brought cancer cells back under normal control -- by reactivating their cancer suppressor genes. The discovery could form a powerful new technology platform for the treatment of cancer of the breast and other cancers.

Tumor reduction.

Breast cancer is diagnosed in about 1.4 million women throughout the world every year, with half a million dying from the disease. A common cause of cancer is when cells are altered or mutated and the body's tumour suppressor genes are switched off.

Research, published in the journalMolecular Cancer, reveals how Dr Cinzia Allegrucci from the School of Veterinary Science and Medicine and Dr Andrew Johnson in the Centre for Genetics and Genomics reactivated tumour suppressor genes and stopped the cancer from growing by treating them with Axolotl oocyte extract. After 60 days there was still no evidence of cancerous growth.

Cancers occur when the mechanisms that control normal cell division are mutated. The process of cell division is controlled by specific genes and these are turned "on" or "off" depending on their function. Among the most important of these genes are tumour suppressor genes. These genes repress the development of cancers and normally act as a control point in the cell division cycle. Therefore, the switching off of tumour suppressor genes is a common cause of cancers, including breast cancer.

Dr Allegrucci, a lecturer in molecular genetics and cell biology, said: "The on/off switch in genes is controlled by the modification of proteins that are bound to the DNA in a cell -- so called epigenetic modifications. Tumour suppressor genes in many breast cancers are switched off by epigenetic marks, which is the underlying cause of tumours. We sought to reverse this process, activating the tumour suppressor genes, in hope of stopping cancerous cell divisions."

Dr Johnson said: "To do this we used novel technology that makes use of the eggs of the axolotl salamander. Over the years Dr Johnson's lab has shown that humans evolved from animals that closely resemble axolotls, and because of this the proteins in axolotls are very similar to those in humans. Axolotl oocytes -- which are the eggs prior to ovulation -- are packed with molecules that have very powerful epigenetic modifying activity. Previously Johnson's lab showed that extracts prepared from these oocytes have powerful capacity to change epigenetic marks on the DNA of human cells.

And, in a breakthrough, they showed it is important to use oocytes from the ovary, because if the oocytes are ovulated these activities are lost. We thought that by treating cancer cells with extracts made from axolotl oocytes we could reverse the epigenetic marks on tumour suppressor genes, causing these genes to reactivate, and thereby stopping the cancerous cell growth."

The identification of the proteins responsible for this tumour reversing activity in axolotl oocytes is a major goal of future research which could form a powerful new technology platform for the treatment of cancers from the breast, and other tissues.

How Progesterone Increases Breast Cancer Risk

ScienceDaily (Jan. 18, 2011) — Researchers have identified how the hormones progesterone and estrogen interact to increase cell growth in normal mammary cells and mammary cancers, a novel finding that may explain why postmenopausal women receiving hormone replacement therapy with estrogen plus progestin are at increased risk of breast cancer.

The discovery that both estrogen and progesterone must be present for the increased production of the protein amphiregulin, which binds to mammary cells and promotes cell growth, could lead to new treatment methods for the disease, said Sandra Haslam, director of Michigan State University's Breast Cancer and the Environment Research Center and lead researcher on the project.

The study, funded by the Department of Defense's Breast Cancer Research Program and published in Hormones and Cancer, looked at why progesterone combined with estrogen may contribute to increased breast cancer risk. In the study, researchers used both the native hormone, progesterone, and a synthetic compound, progestin -- obtaining the same results.

The finding might help explain earlier results from the groundbreaking Women's Health Initiative showing the risk of breast cancer is significantly greater for postmenopausal women who received hormone replacement therapy with combined estrogen plus progestin compared to women receiving estrogen alone.

"Also, breast cancers that develop in women receiving estrogen plus progestin are more invasive and deadlier," Haslam said. "What is the progestin doing to increase the risk of tumor growth?"

Along with co-investigator Anastasia Kariagina, a colleague in the College of Human Medicine and Department of Physiology, Haslam identified the protein amphiregulin and its receptor as one potential culprit.

"Amphiregulin -- acting through its receptor, epidermal growth factor receptor -- along with progesterone leads to the activation of intracellular pathways that regulate cell growth," Haslam said. "When activated, this promotes normal cell growth and the growth of tumors."

The study was performed in rats because breast cancers in rats contain receptors for estrogen and progesterone -- similar to the human breast -- and tumor growth is hormone-dependent, as are the majority of human breast cancers. The research team also confirmed the same phenomenon in human breast cancer cell cultures.

In addition, the research team found that Iressa, a cancer drug that blocks the epidermal growth factor receptor, effectively stopped the proliferation caused by amphiregulin. While those studies were done only in cell cultures and not on tumors growing in animals, the results are promising, Haslam said.

"The results indicate that the interactions between estrogen, progesterone and epidermal growth factor receptor pathways may be considered relevant targets for the treatment of hormone-dependent breast cancers," she said. "This may be especially important in premenopausal breast cancer because women produce their own estrogen and progesterone.

"A combined approach of inhibiting both the hormones and the epidermal growth factor receptor may be beneficial for some women in treating hormone-dependent breast cancer."