Powerful enzyme that tamps down inflammation holds promise for protecting the eyes in diabetes, premature birth

An enzyme under study to treat certain cancers is also showing promise in reducing the significant vision damage that can result from diabetes and premature birth, scientists report.

Inflammation is considered a hallmark of cancer. It’s pervasive as well in both of these potentially blinding eye conditions, in which inadequate oxygen to the eyes prompts growth of new blood vessels to better deliver oxygen, but which instead often obstruct the vision pathway and become leaky, which causes swelling, further hindering vision.

Scientists at the Medical College of Georgia report in newly published studies in the journals Cell Death and Disease and Cells, increasing evidence that making more of the enzyme arginase 1, or A1, available helps alleviate these unhealthy responses and interrupt a natural body response that promotes destructive ongoing, high levels of inflammation in both diabetic retinopathy and retinopathy of prematurity.

Key to the process is making less of the amino acid L-arginine available. With diabetes, for example, high blood sugar and lipid levels as well as oxidative stress increase expression of inducible nitric oxide synthase, or iNOS, which uses the L-arginine to help produce even more inflammation and promote disease progression. The way it’s supposed to work is iNOS goes up in response to an infection then high-expressing A1 cells move in to turn iNOS off and inflammation down.

That’s because A1 competes with iNOS for L-arginine. They theorized that more A1, which actually breaks down L-arginine into two products, would make less L-arginine available to “feed this (unhealthy) iNOS explosion,” and help tamp down the vicious cycle of inflammation and related damage, says Dr. William Caldwell, pharmacologist and chair emeritus of the MCG Department of Pharmacology and Toxicology.

“If you reduce L-arginine levels, iNOS cannot work. This will make things better,” Caldwell says.

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