By Jessica Tobacman, Special to the Tribune
December 5, 2012
Researchers at the University of Illinois at Chicago and the University of California at Los Angeles recently created a light-sensitive molecule that they say could help restore vision lost in degenerative eye diseases, such as macular degeneration, and reduce epileptic seizures.
The scientists said they took cells inside the retina and found a way to chemically alter the cells so they could take in light. This breakthrough could help people who suffer from the loss of vision caused by macular degeneration by introducing molecules that can recognize light, the scientists said. Macular degeneration is a leading cause of loss of vision for people age 50 or older.
Even after retinal diseases kill photoreceptor cells that usually take in light in the eye, other cells within the retina remain healthy, said David Pepperberg, professor of ophthalmology and visual sciences at the UIC College of Medicine and a principal investigator of the study. The results of the study were published in Oct. 2 in the Nature Communications journal.
"They remain physiologically capable of receiving signals," Pepperberg said. "We asked, 'Could we make other cells responsive to light and bypass dead photoreceptor cells? Could those other cells function as neurons and become light-sensitive?' We're trying to restore vision that's lost in macular degeneration, by making the inner cells of the retina receptive to light."
In a healthy eye, a neurotransmitter known as GABA activates a receptor protein that emits a signal to the nerve cells to take in light, Pepperberg said. The UIC and UCLA scientists found a way to modify molecules in the retina to help the GABA neurotransmitter activate the receptor proteins, he said.
"We set out with the idea to design a molecule sensitive to light, which can transition toward two possible shapes, one of which can activate the GABA receptor and the other which cannot," Pepperberg said.
Different wavelengths of light are absorbed by the light-sensitive molecule, causing it to change its shape, Pepperberg said.
"When the light-sensitive molecule is present and in active shape, it can bind to the receptor and help activate it. It (also) has the ability to illuminate and not activate or activate the GABA receptors in the inner retinal cells, and the ability to interact and make the inner cells light-sensitive," he said.
"Making the GABA receptors responsive to light is an important step toward the ultimate objective of being able to have the semblance of vision."
The therapy could also lead to a new epilepsy treatment, Pepperberg said. There's a possibility of using light-sensitive molecules to illuminate the part of the brain where epileptic seizures begin and regulate the compound that causes them, he said.
"This potentially could be a way of shutting down seizure activity as it's starting," Pepperberg said.
John Dowling, a professor of neuroscience at Harvard University, called the study a "promising approach, in terms of making the retina light-sensitive again."
"This is a very good tool for scientific studies," Dowling said. "It's potentially very important for dealing with retinal diseases. You can get light into the eye with no problem at all and can target molecules to specific synapses."
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