Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

RPE meets EPR

29.07.2005


Studies shed light on role of melanin in preventing macular degeneration



Two studies from an unusual research partnership at the University of Chicago appear to have resolved a long-standing dispute about the role of melanin in the eye. The studies, one published in the Proceedings of the National Academy of Sciences (PNAS) and one early online in the Journal of the American Chemical Society (JACS), also suggest a new way to prevent a common cause of blindness.

Chemist James Norris, Ph.D., and retina surgeon Kourous Rezai, M.D., combined resources to show that melanin, a pigment found throughout the human body, acts like a neutralizing sponge inside cells in the retina to soak up and destroy reactive oxygen species. Reactive oxygen species, or free radicals, energized by light, are thought to play a major role in macular degeneration, the leading cause of blindness in people over the age of 60.


"We now have the first persuasive evidence that melanin plays an important protective role within the eye," said Norris, professor in the Department of Chemistry and the Institute for Biophysical Dynamics at the University of Chicago and one of the senior authors of both papers. "Although melanin contains its own intrinsic free radical, we found that it absorbs a far more damaging form of free radical, converting its destructive energy into harmless heat before it can hurt the retina."

An estimated 1.75 million Americans have decreased vision from age-related macular degeneration (AMD), with about 200,000 new cases each year. The incidence of AMD is expected to double within the next 25 years as the number of older persons continues to increase. The disorder is far more prevalent among whites than among black persons.

It causes gradual loss of central vision by damaging the retinal pigment epithelial (RPE) cells that lie underneath the macula, the small region of the retina responsible for fine detail at the center of the field of vision. Without RPE cells, the photoreceptors, which are the light detectors, also die. Patients lose the ability to see detail and soon they can’t read.

"This is a devastating disease," said Rezai, director of the vitreoretinal service at the University of Chicago. "We do not have a cure for this disease. We can only treat the secondary complications, such as growth of abnormal blood vessels."

"Since we don’t know how to replace or repair the dead or damaged retinal cells," he said, " we need to find ways to protect them."

Because people stop producing new RPE cells after birth, these cells have to last a lifetime. They live, however, in a toxic environment. Oxygen concentrations at the back of the eye are very high. At the same time the eye is constantly bombarded with light energy, which interacts with oxygen and can lead to the production of harmful free radicals – which can damage cell membranes and DNA. "It’s amazing," noted Norris, "that the eye lasts as long as it does."

"To prevent the damage," Rezai said, "we need to understand exactly how it happens." He grows human RPE cells in culture in his lab, but "until now, we have had no direct way to measure the production of most dangerous free radicals. They are too small and too fast."

Norris studies photosynthesis, in which energy from sunlight is converted into electrochemical energy, a process with many parallels to vision. To study the early steps, he uses a tool called electron paramagnetic resonance (EPR). EPR is similar to magnetic resonance imaging except that it measures the spin of electrons rather than of protons.

Because photochemical reactions happen extremely fast, the Norris laboratory has one of the world’s few high-speed EPR spectroscopy devices, able to record actions that occur in nanoseconds, about 1,000 times faster than standard EPR.

"Free radicals are dangerous chemicals and dangerous chemistry takes place rapidly," said Norris. "This lets us see some of it."

Norris and Rezai have another valuable asset, an ambitious student, interested in chemistry and medicine, experienced with EPR and looking for a project. This was a unique opportunity for Brandon-Luke Seagle, a third-year student in the College at the time. His knowledge of chemistry and medicine enabled him to be the link between Rezai’s cells and Norris’s techniques. He is the first author on both papers.

Using Rezai’s cells, Norris’s technology and Seagle’s leg work, the team was able to capture convincing and dramatic evidence that melanin protects the retinal cells. In the PNAS paper (21 June 2005), they show that increased melanin aggregation and radical migration within melanin aggregates can protect RPE cells from free-radical damage and help prevent cell death. In the JACS paper (17 August 2005, but available online) they demonstrate how melanin actually scavenges the harmful free radicals produced by high-energy blue or ultraviolet light as it flows into the eye, soaking them up and neutralizing their effects.

"We now have molecular-based evidence to support the epidemiologic data that points to the protective effects for melanin," said Rezai, who is testing ways to boost melanin levels, first in cells grown in culture and, if that appears promising, in animal models.

John Easton | EurekAlert!
Further information:
http://www.uchospitals.edu

More articles from Life Sciences:

nachricht A new technique isolates neuronal activity during memory consolidation
22.06.2017 | Spanish National Research Council (CSIC)

nachricht CWRU researchers find a chemical solution to shrink digital data storage
22.06.2017 | Case Western Reserve University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

Im Focus: Optoelectronic Inline Measurement – Accurate to the Nanometer

Germany counts high-precision manufacturing processes among its advantages as a location. It’s not just the aerospace and automotive industries that require almost waste-free, high-precision manufacturing to provide an efficient way of testing the shape and orientation tolerances of products. Since current inline measurement technology not yet provides the required accuracy, the Fraunhofer Institute for Laser Technology ILT is collaborating with four renowned industry partners in the INSPIRE project to develop inline sensors with a new accuracy class. Funded by the German Federal Ministry of Education and Research (BMBF), the project is scheduled to run until the end of 2019.

New Manufacturing Technologies for New Products

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

A new technique isolates neuronal activity during memory consolidation

22.06.2017 | Life Sciences

Plant inspiration could lead to flexible electronics

22.06.2017 | Materials Sciences

A rhodium-based catalyst for making organosilicon using less precious metal

22.06.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>