Iron Seen as Target in Curing Eye Diseases

From “an eye for an eye” to “Old Blue Eyes,” the windows to the soul have been contemplated and celebrated for centuries by everyone from singers to poets to legal scholars. Although scientists generally understand how eyes function, some of the fundamental biology remains a mystery, says Dr. Chris McGahan, head of the Department of Molecular Biomedical Sciences in the College of Veterinary Medicine. She has devoted her career to unraveling these mysteries with the hope that age-related diseases like cataracts and macular degeneration can be slowed or cured altogether.

The $12 billion spent on cataract surgeries in the U.S. is the biggest single piece of the annual Medicare budget.

Using cultures of lens and retinal cells as well as tissue sections from eyes of humans and dogs, McGahan studies the role iron plays in damaging cells in the eye. Too much iron can cause oxidative reactions, while too little can lead to dysfunction in the cell. “We don’t understand very well how cells regulate iron stores,” she says. “But that’s important if we’re going to control eye disease.”

Cataracts, for example, form when proteins in the lens oxidize and aggregate, blocking light and clouding vision. McGahan’s research has shown that lenses secrete glutamate, an amino acid and neurotransmitter that is regulated by iron. Although that might appear unusual because lenses have no nerves, her studies have determined that glutamate is needed for a reaction that boosts the level of glutathione, an antioxidant that could
act as a protective mechanism against the oxidative reactions that lead to cataracts.

McGahan believes that iron also could play a role in macular degeneration since it regulates the production of vascular endothelial growth factor (VEGF), which has been linked to the disease. VEGF is a chemical signal that spurs the growth of blood vessels, but excess blood vessels or leakage from them behind the retina can warp and buckle the smooth surface needed to transfer light and images to the brain.

“Slowing the onset or progression of these degenerative problems will give people better quality of life and save millions in medical costs.”

Controlling cataracts and macular degeneration is as important to McGahan as curing the two vision problems. Cataracts are the world’s leading cause of blindness, and the $12 billion spent on surgeries in the U.S. to replace clouded lenses is the biggest single piece of the annual Medicare budget. Furthermore, almost a third of people are at risk for macular degeneration by age 75. “With the increasing average age of the population, this will become a bigger issue over time,” McGahan says. “Slowing the onset or progression of these degenerative problems will give people better quality of life and will save millions in medical costs.”

 

Dr. Chris McGahan, left, and research specialist Marilyn Lall examine the results of tests in which a signaling pathway in ocular cells was activated.

Cataracts form when proteins in the eye lens oxidize and aggregate, blocking light and clouding vision.