Rosemary Protects Against Age-Related Macular Degeneration

LA JOLLA, Calif.Carnosic acid, a compound found in the herb rosemary, may have clinical applications for diseases affecting the outer retina, including age-related macular degeneration, the most common eye disease in the United States, according to a new study published in the journal Investigative Ophthalmology & Visual Science.

Age-related macular degeneration likely has many underlying causes, yet previous studies suggest that the disease might be slowed or improved by chemicals that fight free radicalsreactive compounds related to oxygen and nitrogen that damage membranes and other cell processes.

Researchers at Sanford-Burnham Medical Research Institute (Sanford-Burnham) found carnosic acid protects retinas from degeneration and toxicity in cell culture and in rodent models of light-induced retinal damage. Their findings suggest that carnosic acid may have clinical applications for diseases affecting the outer retina, including age-related macular degeneration.

A few years ago, the researchers first discovered carnosic acid fights off free radical damage in the brain. In this current study, the team initially investigated carnosic acid's protective mechanism in laboratory cultures of retinal cells.

The researchers exposed the cells growing in the dish to hydrogen peroxide in order to induce oxidative stress, a factor thought to contribute to disease progression in eye conditions such as macular degeneration and retinitis pigmentosa. They found that cells treated with carnosic acid triggered antioxidant enzyme production in the cells, which in turn lowered levels of reactive oxygen and nitrogen species (cell-damaging free radicals and peroxides).

The researchers tested carnosic acid in an animal model of light-induced damage to photoreceptorsthe part of the eye that converts light to electrical signals, enabling visual perception. As compared to the untreated group, rodents pre-treated with carnosic acid retained a thicker outer nuclear layer in the eye, indicating that their photoreceptors were protected. The carnosic acid-treated rodents also exhibited better electroretinogram activity, a measure of healthy photoreceptor function.

The researchers now are in the process of developing improved derivatives of carnosic acid and related compounds to protect the retina and other brain areas from a number of degenerative conditions, including age-related macular degeneration and various forms of dementia.