Retina protein that may help conquer blindness discovered

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Posted on 10th August 2015 by Pacific ClearVision Institute in General |Retina

Research led by Nicolas Bazan, MD, PhD, Boyd Professor and Director of the LSU Health New Orleans Neuroscience Center of Excellence, discovered a protein in the retina that is crucial for vision. The paper reports, for the first time, the key molecular mechanisms leading to visual degeneration and blindness. The research reveals events that may be harnessed for prevention, as well as to slow down progression of retinal degenerative diseases. The paper is published in the March 4, 2015, issue of Nature Communications.

There is growing evidence of the significance of the essential omega-3 fatty acid family member, docosahexaenoic acid (DHA), for photoreceptor function and in retinal degenerative diseases, but not much understanding about what governs it. The research team found that the protein receptor for adiponectin, a hormone that promotes insulin sensitivity and is involved in the metabolic syndrome, has a heretofore unrecognized function. The receptor also regulates DHA retention and conservation in cells in the eye and is necessary for photoreceptor cell function.

“This is the first time that such an integral membrane protein has been localized in the photoreceptor cells and shown to have the capacity to support sight,” notes Dr. Bazan, the paper’s corresponding author.

Working with a novel genetic mouse model they developed with the adiponectin receptor gene deleted, the researchers found that total and free retinal DHA were diminished in the gene-deficient mice. When they incubated normal retinas with labeled DHA, they measured abundant levels of it, demonstrating that a functional AdipoR1 gene must be present for DHA uptake and retention. Additionally, when cultured human Retinal Pigment Epithelial (RPE) cells were incubated with labeled DHA, DHA within the medium decreased with time while increasing within the cells. Also, when the AdipoR1 gene activity was ramped up in these cultured RPE cells, much more labeled DHA was taken up and incorporated. But when silenced, labeled DHA was diminished, indicating that human RPE cells can also take up DHA and that the AdipoR1 gene plays a significant role in this activity, too.

DHA in brain and retinal cells also builds reservoirs for molecules called into action when normal functions are disrupted, resulting in such conditions as retinal degeneration, Parkinson’s or Alzheimer’s disease. Dr. Bazan and his colleagues previously discovered neuroprotectin D1 (NPD1), one such molecule made from DHA when cell survival is compromised. Loss of, or diminished, retinal DHA leads to visual impairment and may play an important role in the development of blindness from retinitis pigmentosa and other retinal degenerative diseases, as well as age-related macular degeneration (AMD), the foremost cause of blindness in people older than 50 years.

“Our model and newly discovered molecular mechanism allow therapies to be tested more rapidly,” notes Dr. Bazan. “We feel an urgency to address blindness and cognition impairments of dementias because of their heavy burden on patients, families, care givers and the health care system.”

DHA, found in fish oil, is an essential omega-3 fatty acid and is vital for proper brain function. It is also necessary for the development of the nervous system, including vision. Dr. Bazan has been a pioneer in the understanding of the biology and impact of DHA in medicine.

Receptor that helps protect brain cells has important role in support cells for the retina

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Posted on 10th August 2015 by Pacific ClearVision Institute in General |Retina

A receptor that is already a target for treating neurodegenerative disease also appears to play a key role in supporting the retina, scientists report.

Without sigma 1 receptor, the Müller cells that support the retina can’t seem to control their own levels of destructive oxidative stress, and consequently can’t properly support the millions of specialized neurons that enable us to transform light into images, scientists report in the journal Free Radical Biology and Medicine.

Without support, well-organized layers of retinal cells begin to disintegrate and vision is lost to diseases such as retinitis pigmentosa, diabetic retinopathy and glaucoma, said Dr. Sylvia Smith, retinal cell biologist and Chairwoman of the Department of Cellular Biology and Anatomy at the Medical College of Georgia at Georgia Regents University

The surprising finding makes the sigma 1 receptor a logical treatment target for these typically progressive and blinding retinal diseases, said Smith, the study’s corresponding author. It has implications as well for other major diseases, such as cardiovascular disease and cancer as well as neurodegenerative disease, where oxidative stress plays a role.

What most surprised the scientists was that simply removing sigma 1 receptor from Müller cells significantly increased levels of reactive oxygen species, or ROS, indicating the receptor’s direct role in the oxidative stress response, Smith said. They expected it would take them giving an oxidative stressor to increase ROS levels.

So they looked further at the sigma 1 receptor knockouts compared with normal mice, and found significantly decreased expression in the knockouts of several, well-known antioxidant genes and their proteins. Further examination showed a change in the usual stress response.

These genes that make natural antioxidants contain antioxidant response element, or ARE which, in the face of oxidative stress, gets activated by NRF2, a transcription factor that usually stays in the fluid part of the cell, or cytoplasm. NRF2 is considered one of the most important regulators of the expression of antioxidant molecules. Normally the protein KEAP1 keeps it essentially inactive in the cytoplasm until needed, then it moves to the cell nucleus where it can help mount a defense. “When you have oxidative stress, you want this,” Smith said of the stress response, which works the same throughout the body.

Deleting the sigma receptor in the Müller cells altered the desired response: NRF2 expression decreased while KEAP1 expression increased. The unhealthy bottom line was that ROS levels increased as well.

The study is believed to provide the first evidence of the direct impact of the sigma 1 receptor on the levels of NRF2 and KEAP1, the researchers write.

“We think we are beginning to understand the mechanism by which sigma 1 receptor may work and it may work because of its action on releasing antioxidant genes,” Smith said.

While the ubiquitous receptor was known to help protect neurons in the brain and eye, its impact on Müller cell function was previously unknown. The significant impact the MCG scientists have now found helps explain the dramatic change they documented after using pentazocine, a narcotic already used for pain relief, in animal models of both retinitis pigmentosa and diabetic retinopathy. Pentazocine, which binds to and activates the sigma 1 receptor, seems to preserve functional vision in these disease models by enabling many of the well-stratified layers of photoreceptor cells to survive.

Next steps include clarifying whether it’s actually preservation or regeneration of the essential cell layers and how long the effect lasts. “We do see some retention of function, that is clear and that I am very excited about,” Smith said.

Müller cells are major support cells for the retina, helping stabilize its complex, multi-layer structure, both horizontally and vertically; eliminating debris; and supporting the function and metabolism of its neurons and blood vessels. Typically bustling Müller cells can become even more activated when there is an insult to the eye, such as increased oxidative stress, and start forming scar tissue, which hinders rather than supports vision. Problems such as diabetes, can increase ROS levels.

ROS are molecules produced through normal body function such as breathing and cells using energy. The body needs a limited amount of ROS to carry out additional functions, such as cell signaling. Problems, from eye disease to cancer, result when the body’s natural system for eliminating excess ROS can’t keep up and ROS start to do harm, such as cell destruction.

Normally humans have about 125 million night-vision enabling rods intermingled with about 6 million cones that enable us to respond to light and see color.

Microtubule ‘roadway’ in the retina helps provide energy for vision

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Posted on 10th August 2015 by Pacific ClearVision Institute in General |Retina

Researchers have discovered a thick band of microtubules in certain neurons in the retina that they believe acts as a transport road for mitochondria that help provide energy required for visual processing. The findings appear in the July issue of The Journal of General Physiology.

The retina is a layer of tissue in the back of the eye that converts light into nerve impulses. The retina contains small, specialized neurons called bipolar cells that transmit information from light-sensitive photoreceptor cells to ganglion neurons, which send information to the brain for interpretation as images.

Bipolar cells are continuously active, a characteristic few other neurons share. They require a constant supply of energy to mediate the sustained release of the contents of an enormous number of synaptic vesicles, which store the transmitters that convey information between neurons. An intriguing new study of their subcellular structure could help explain how bipolar synaptic terminals meet such excessive energy demands.

Using cutting-edge 3D microscopy, researchers from the National Heart, Lung, and Blood Institute and Yale University examined the subcellular architecture of presynaptic terminals in retinal bipolar cells of live goldfish. Goldfish retinal bipolar cells have giant presynaptic terminals that make them especially amenable for investigation. Unexpectedly, the team discovered a thick band of microtubules, a component of the cell’s cytoskeleton, that extended from the axon of the neuron into the synaptic terminal and then looped around the interior periphery of the terminal.

The microtubule band appeared to associate with mitochondria–organelles known for providing energy to cells–in the synaptic terminal. When the researchers administered drugs to inhibit the movement of certain “motor” proteins that transport mitochondria and other cargo within the cell by traveling along microtubules, the mitochondria accumulated in the axon of the neuron and never made it to the synaptic terminal.

The findings suggest that these previously unknown microtubule structures provide a “roadway” for the transport of mitochondria crucial to maintain energy supplies into the synaptic terminals of these highly active neurons associated with vision.

Light in sight: A step towards a potential therapy for acquired blindness

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Posted on 10th August 2015 by Pacific ClearVision Institute in General |Retina

Hereditary blindness caused by a progressive degeneration of the light-sensing cells in the eye, the photoreceptors, affects millions of people worldwide. Although the light-sensing cells are lost, cells in deeper layers of the retina, which normally cannot sense light, remain intact. A promising new therapeutic approach based on a technology termed “optogenetics” is to introduce light-sensing proteins into these surviving retinal cells, turning them into “replacement photoreceptors” and thereby restoring vision. However, several factors limit the feasibility of a clinical optogenetic therapy using traditional light-sensitive proteins, as they require unnaturally high and potentially harmful light intensities and employ a foreign signaling mechanism within the target retinal cells.

New research publishing May 7th in the Open Access journal PLOS Biology from van Wyk and colleagues demonstrates how optogenetic proteins can be tailored to bring this promising technology closer to medical application. “We were asking the question, ‘Can we design light-activatable proteins that gate specific signaling pathways in specific cells?’, in other words, can the natural signaling pathways of the target cells be retained and just modified in a way to be turned on by light instead of a neurotransmitter released from a preceding neuron?” says Dr. Sonja Kleinlogel, corresponding author of the paper (whose research group is based at the University of Berne, Switzerland). The aim of molecular engineering was to achieve maximal compatibility with native signaling whilst retaining all the advantages of traditional optogenetic proteins, such as fast kinetics and resistance to bleaching by light.

The novel light-sensing protein, termed Opto-mGluR6, is a chimeric protein composed of the light-sensing domains of the retinal photopigment melanopsin and the ON-bipolar cell-specific metabotropic glutamate receptor mGluR6, which is naturally activated by glutamate released from the photoreceptors and amplifies the incoming signal through a coupled intracellular enzymatic pathway. Unlike rhodopsin, for example, the “light antenna” of melanopsin is resistant to bleaching. In other words, the response strength of Opto-mGluR6 never attenuates, no matter how often and hard the protein is hit by light. Moreover, since Opto-mGluR6 is a chimeric protein consisting of two “local” retinal proteins it is also likely to be “invisible” to the immune system, another improvement over traditional optogenetic proteins.

In their study van Wyk and colleagues targeted the retinal ON-bipolar cells, which naturally receive direct input from the photoreceptors. Targeting the surviving cells at the top end of the visual cascade has the advantage that signal computation of the retina is maximally utilized. Turning the native chemical receptor (mGluR6) into a light-activated receptor ensures conservation of native signaling within the ON-bipolar cells, conferring high light-sensitivity and fast “normal” responsiveness. In their study they show proof-of-principle that mice suffering from Retinitis pigmentosa can be treated to regain daylight vision. “The new therapy can potentially restore sight in patients suffering from any kind of photoreceptor degeneration” says Dr. Kleinlogel, “for example also those suffering from severe forms of age-related macular degeneration, a very common disease that affects to some degree about one in every 10 people over the age of 65.”

“The major improvement of the new approach is that patients will be able to see under normal daylight conditions without the need for light intensifiers or image converter goggles” Dr. Kleinlogel further notes “and retaining the integrity of the intracellular enzymatic cascade through which native mGluR6 acts ensures consistency of the visual signal, as the enzymatic cascade is intricately modulated at multiple levels.” The mGluR6 receptor of ON-bipolar cells belongs to the large family of so-called G-protein-coupled transmembrane receptors (GPCRs). The novel principle of engineering bleach-resistant chimeric Opto-GPCRs opens a whole palette of new possibilities. For example, as GPCRs are prime targets for pharmaceutical interventions, Opto-GPCRs could potentially be used to treat conditions such as pain, depression and epilepsy.

New nanotechnology drug to control blindness

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Posted on 10th August 2015 by Pacific ClearVision Institute in General |Retina

The Mexican company “Medical and Surgical Center for Retina” created a way to transport drugs, in order to avoid risks and painful treatments in people with secondary blindness due to chronic degenerative blindness such as diabetic retinopathy and degeneration of the eye. The innovative formula results eliminates the need to administrate the drug by intraocular injection.

It is a nanotechnology product, which works with last generation liposomes particles, concentrated in droplets, which function as a conveyor that wraps proteins or antibody fragments and allow its passage into the eye. Once inside, it releases the drugs.

With the nanotechnology product the costs are reduced by 80 to 90 percent and enables the elderly population to make use of it. “With this technology hospitals that have no resources can apply the needed drugs, without requiring a a specialist or a particular facility for the administration. It is necessary to be prescribed by a physician, but it can be administered at home, which lowers the cost. ”

The doctor Juan Carlos Altamirano Vallejo, medical director of the Medical and Surgical Center for Retina, mentions that the conditions that originate in the retina are mostly caused by chronic degenerative diseases such as diabetes (diabetic retinopathy) or macular alteration . Patients with this conditions usually require one injection per month which comes at a very high cost and increases if the procedure is needed for both eyes.

The company, located in Jalisco (central west state of Mexico) won the Mexican National Prize for Technology and Innovation and plans to conclude the Clinical Research regulated by the Federal Commission for Protection Against Health Risks (COFEPRIS) next year. The idea is for the medicine to be distributed in state and private health institutions. So far, the achieved results are the same as the ones obtained with intraocular injection, but without the inherent risks of this procedure, such as infection or retinal detachment.

Current talks are being held with COFEPRIS to conduct a study within several diseases and increase its use for different conditions. In the United States, patients who have followed the treatment have had positive results.

The Medical and Surgical Center for Retina provides medical care and a specialized retina Ophthalmology Clinic provides consultation, which also has an area of ??Biotechnology and Drug Research of Biomedical Engineering, Diagnosis and Treatment Equipment.

Altamirano Vallejo says that receiving the award opens the doors to reach more people and prevent blindness. “It is the most important prize delivered by the Presidency of the Republic in the area of technology and innovation. For us, to have an entity such as the award foundation to guide us and allows us to learn, know skills, strengths and company administration makes us proud, specially the opportunity for a product like this to reach the market and prevent blindness.”

Eye’s motion detection sensors identified

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Posted on 10th August 2015 by Pacific ClearVision Institute in General |Retina

Driving a car at 40 mph, you see a child dart into the street. You hit the brakes. Disaster averted.

But how did your eyes detect that movement? It’s a question that has confounded scientists.

Now, studying mice, researchers at Washington University School of Medicine in St. Louis have an answer: A neural circuit in the retina at the back of the eye carries signals that enable the eye to detect movement. The finding could help in efforts to build artificial retinas for people who have suffered vision loss.

The research is published June 16 in the online journal eLife.

The research team identified specific cell types that form a neural circuit to carry signals from the eye’s photoreceptors — the rods and cones that sense light — to the brain’s visual cortex, where those signals are translated into an image.

“This ability to detect motion is key for animals, allowing them to detect the presence of predators,” said principal investigator Daniel Kerschensteiner, MD, an assistant professor of ophthalmology and visual sciences. “And we know that these same cells are found not only in mice but in rabbits, cats, primates and likely humans, too. The cells look similar in every species, and we would assume they function in a similar manner as well.”

Studying the neural circuit, Tahnbee Kim, a graduate student in Kerschensteiner’s lab, identified a specific type of cell called an amacrine cell that’s key to detecting motion. Amacrine cells are thought to inhibit, or tamp down, the activity of other cells called ganglion cells. This process ensures that the brain doesn’t receive too much visual information, which could distort an image.

Using a technique that combines a powerful microscope with a method that allows researchers to track how often retinal cells fire, the researchers also showed that when there is motion in the visual field, a specific subtype of amacrine cell excites ganglion cells, signaling the brain so it becomes aware that an object is moving.

The discovery that this type of cell transmits object-motion signals is an important step in understanding how the eye senses motion. It also provides a high level of detail that will be needed to design computerized, artificial retinas, which will need to detect motion as well as sense light.

“There are many elements in the retinal circuitry that we haven’t figured out yet,” said Kerschensteiner, also an assistant professor of anatomy and neurobiology. “We know the signals from the rods and cones are transmitted to the retina — where the amacrine and ganglion cells are located — and that’s really where the ‘magic’ happens that allows us to see what we see. Unfortunately, we still have a very limited understanding of what most of the cells in the inner retina actually do.”

Kim T, Soto F, Kerschensteiner D. An excitatory amacrine cell detects object motion and provides feature-selective input to ganglion cells in the mouse retina. eLife, published online June 16, 2015.

Lanosterol revealed clues for cataract prevention and treatment

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Posted on 10th August 2015 by Pacific ClearVision Institute in Cataracts |General

On July 30, 2015, researchers from Sichuan University, Sun Yat-sen University, University of California, BGI, etc, reported the latest study on congenitalcataracts. The finding, published on Nature, identifies lanosterol as a key molecule in the prevention of lens protein aggregation and points to a novel strategy for cataract prevention and treatment.

Cataracts are the most common cause of blindness worldwide, accounting for over half of all cases of blindness worldwide. Currently the only treatment is surgical removal of cataractous lenses. High concentrations of crystallin proteins in lens fibers contribute to lens transparency and refractive properties. Protein aggregation is the single most important factor in cataract formation. Factors that lead to protein aggregation include mutations in crystallin proteins, which are known to cause congenital cataracts, or oxidative stress, which in turn contributes to age-related cataracts. However, the precise mechanisms by which lens proteins both prevent aggregation and maintain lens transparency are largely unknown.

Lanosterol is an amphipathic molecule enriched in the lens. It is synthesized by lanosterol synthase (LSS) in a key cycliza¬tion reaction of a cholesterol synthesis pathway. Previous study showed that the specific combination of hypomorphic mutations on LSS could decrease cholesterol levels in the lens and result in cataracts in rats.

In the study, researchers identified novel homozygous mutations in the LSS gene in two consanguineous families and investigate the ability of lanosterol to alleviate protein aggregation and cataract formation. They found that, treatment by lanosterol significantly decreased preformed protein aggregates both in vitro and in cell-transfection experiments. They further show that lanosterol treatment could reduce cataract severity and increase transparency in animal models.

Dr. Xin Jin, Project Leader of BGI, stated, “This project is aimed to discover casual genes for congenital cataracts. Then we uncovered that gene LSS responsible for two affected families involved in the study. This is extremely exciting when we noticed that the discovery might lead to a novel and simple strategy for the prevention and treatment of cataracts. It encourages us to have more efforts from bench to bed-side.”

Cataract culprits: Genes linked to cataract formation identified

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Posted on 10th August 2015 by Pacific ClearVision Institute in Cataracts |General

When cataracts encroach on the eyes, the only effective remedy is to surgically replace the eyes’ lenses with synthetic substitutes.

But what if scientists found a way to delay or prevent cataracts from forming in the first place?

Researchers at the University of Delaware may have found such an opportunity by identifying the prime suspects in the formation of cataracts — deficiency of two genes that encode regulatory proteins.

When those two genes are unable to do their work, the lenses of the eyes become cloudy and develop cataracts, no aging process or damaging exposure to radiation required.

Cataracts, the leading cause of blindness, can have a genetic basis.

The discoveries emerged in the laboratory of UD biologist Salil Lachke, assistant professor of biological sciences and a Pew Scholar in biomedical sciences.

Lachke and graduate students Smriti Agrawal, Archana Siddam and post-doctoral fellow Deepti Anand study lens development in mice to better understand the genetic mechanisms that lead to cataracts in humans.

Their findings, published in the journal Human Genetics, could contribute to interventions that one day delay or prevent cataract formation, which now afflicts more than half of the U.S. population over 80 years old and costs Medicare an estimated $3 billion in treatment every year.

The study was supported by a grant from the National Institutes of Health (NIH) and a Fight For Sight grant-in-aid award to Lachke.

Lachke compares the lens of the eye to the lens of a camera. A clear lens, free of internal scratches and other damage, transmits a clear image to the retina. Vision is impaired and can be lost completely when lens deterioration is unaddressed.

Lachke and his students wanted to understand the genetic factors involved in keeping the lens transparent and whether disrupting their function allowed cataracts to form.

They found answers in the proteins that regulate expression of genes necessary for transparency, demonstrating that deficiency of two regulatory proteins — called Mafg and Mafk — led to formation of cataracts.

The lens of the eye is made up of several kinds of proteins, Lachke said. Some are essential to transcribing genetic information and promoting healthy development.

To zero in on the genes essential to lens transparency — distinguishing them from normal day-to-day genetic function — Lachke’s lab used the integrated Systems Tool for Eye Gene Discovery (iSyTE), a web-based bioinformatics tool initiated by Lachke during his post-doctoral work at Harvard Medical School and now hosted at UD’s Center for Bioinformatics and Computational Biology.

With iSyTE, Lachke and his fellow researchers were able to identify the genes critical to lens formation and develop a detailed roadmap of the network controlled by the Mafg and Mafk proteins.

When these regulatory proteins were compromised, several genes responsible for lens transparency were “turned down” and cataracts formed about four months after birth.

“The lens pathology in the compound mutants is severe,” said Agrawal, now studying human genetics in a doctoral program at the Baylor College of Medicine in Texas. “The lens appears to be completely opaque and the fiber cells that comprise the tissue lose their structural organization.”

Using a microarray — a collection of thousands of DNA probes on a small chip — researchers can look at the expression of all the genes in the lens, Agrawal said, and bioinformatics allows them to identify the specific targets of regulatory proteins such as Mafg and Mafk.

The discoveries were exciting to be part of, she said.

“When I first found out that the mutant mice exhibited cataract, I ran to Dr. Lachke,” she said.

It was a “eureka!” moment, she said.

The iSyTE tool has many other uses, Lachke said, and it is available to other researchers and to the public.

“In just four years, application of the iSyTE tool has significantly expedited eye disease gene discovery, having led to identification of several new — and often unexpected — genes linked to cataracts,” he said.

The list of iSyTE-identified genes includes a novel post-transcriptional regulator called TDRD7, commonly involved in germ cell development across various animal species, he said. TDRD7 was shown by Lachke to be linked to human cataract in a research article published in Science.

“There are 22,000 protein-coding genes in our genome — and far less than half are characterized,” Lachke said. “Extending the iSyTE approach to other components of the eye and other tissues or organs will greatly expedite disease gene discovery and advance our understanding of the human genome.”

Working with Lachke has been an outstanding experience, his three co-authors said.

“He gives us intellectual freedom,” Siddam said. “We always go back and run our ideas through him, but he will challenge you and make you think outside the box.”

“He likes to include state-of-the-art approaches,” Anand said. “He never says ‘No’ — he tries to understand our ideas.”

“And even if they are almost technically impossible, he would never just say ‘No,’” Siddam said. “He would appreciate the thought process.”

Innovation and discovery happens more freely in such an environment, they said.

“If you want to make breakthroughs, you need to take risks,” Anand said.

Agrawal said working with Lachke on cataract research at UD inspired her to pursue her doctorate research on understanding the genetic basis of other eye diseases. Her research now focuses on retinal diseases.

Siddam said top researchers from around the world approached them at a recent conference to discuss the work of the Lachke Lab.

“The credibility of the research here drives us to do more,” she said.