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 Good preparation is half the digestion
15.11.2018 | Max-Planck-Institut für Stoffwechselforschung

nachricht How the gut ‘talks’ to brown fat
16.11.2018 | Technische Universität München

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

Im Focus: Coping with errors in the quantum age

Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly

The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

Massive impact crater from a kilometer-wide iron meteorite discovered in Greenland

15.11.2018 | Earth Sciences

When electric fields make spins swirl

15.11.2018 | Physics and Astronomy

Discovery of a cool super-Earth

15.11.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>