A new study raises the intriguing possibility that drugs prescribed
to lower cholesterol may be effective against macular degeneration, a
blinding eye disease.
Researchers at Washington University School of Medicine in St. Louis have found that age-related macular degeneration, the leading cause of vision loss in Americans over 50, shares a common link with atherosclerosis. Both problems have the same underlying defect: the inability to remove a buildup of fat and cholesterol.
The new study is published online in the journal Cell Metabolism.
When the eyes of patients with macular degeneration are examined,
small light dots appear against the orange background beneath the
retina. The dots are cholesterol deposits, and as cholesterol builds up,
the area becomes inflamed. Inflammation spurs the development of
abnormal blood vessels that can lead to loss of vision.
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Patients who have atherosclerosis often are prescribed medications
to lower cholesterol and keep arteries clear. This study, which worked
with both mice and human cells, suggests that some of those same drugs
could help patients with macular degeneration.
“Based on our findings, we need to investigate whether vision loss
caused by macular degeneration could be prevented with
cholesterol-lowering eye drops or other medications that might prevent
the buildup of lipids beneath the retina,” says senior investigator
Rajendra S. Apte, MD, PhD.
The new research centers on macrophages, key immune cells that
remove cholesterol and fats from tissues. In macular degeneration, the
excessive buildup of cholesterol begins to occur as we age, and our
macrophages begin to malfunction.
In the “dry” form of age-related macular degeneration, doctors
examining the eye can see lipid deposits beneath the retina. As those
deposits become larger and more numerous, they slowly begin to destroy
the central part of the eye, interfering with the vision needed to read a
book or drive a car.
As microphages age, they clear fewer fat deposits beneath the
retina. They also become bloated with cholesterol, creating an
inflammatory process that leads to the formation of new blood vessels
that can cause further damage. Those vessels are characteristic of the
later “wet” form of the disease.
“Most of the vision loss from ‘wet’ macular degeneration is the
result of bleeding and scar-tissue formation related to abnormal vessel
growth,” Apte explains.
As part of their research, the scientists identified a protein that
macrophages need to clear fats and cholesterol. As mice and humans age,
they make less of the protein, and macrophages become less effective at
engulfing and removing fat and cholesterol.
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