Bright light can cause damage to retinal tissue and cause vision loss or blindness. Scientists from Case Western Reserve University have found that a combination of FDA-approved drugs could protect against retinal damage and ward off some vision-impairing conditions, including macular degeneration.
The team genetically modified mice to be more susceptible to retinal damage and exposed them to 30 minutes of bright light, according to a statement. Some of the mice’s photoreceptor cells died, leaving behind a thinner retina. The surviving photoreceptors were damaged, mimicking human retinal degeneration.
The researchers, led by Krzysztof Palczewski, selected drugs known to act on G protein-coupled receptors--which ferry signals in and out of cells--that activate specific proteins linked to retinopathy, or retinal disease that causes vision loss. They then pre-treated mice with 16 different drugs in a bid to shield them from retinal damage. It worked: The pre-treated mice escaped photoreceptor damage caused by bright light.
With a shortlist of four drugs, the team tested low-dose combinations to find the most effective regimen to ward off bright light-caused photoreceptor damage. While metoprolol, used to treat several cardiovascular conditions, worked best individually, the researchers ultimately found that a combo of metoprolol, bromocriptine and doxazosin or tamsulosin all at “sub-therapeutic” doses, did better than any drug alone. Bromocriptine treats a range of conditions brought on by pituitary problems, as well as Type 2 diabetes, while the latter two drugs are both urinary retention meds used in the treatment of prostate cancer.
“This project is ready for clinical tests assessing effectiveness in age-related macular degeneration and Stargardt disease,” Palczewski said in the statement. And the systems pharmacology method--which seeks to understand how drugs work on different systems of the body--could be applied to conditions beyond retinopathy: “All chronic illnesses and aging diseases should be tested using similar approaches to those developed in our study,” Palczewski said.