Ozone is perhaps best known for its role in protecting the earth from solar radiation. But scientists recently discovered that the extremely reactive form of oxygen is produced by the human immune system as part of its defense strategy. New findings published in the journal Science suggest that such ozone production could contribute to atherosclerosis, the disease commonly known as hardening of the arteries that increases the risk of heart attacks and strokes.

As atherosclerosis develops, inflammation fuels the growth of plaques in the arteries. Paul Wentworth, Jr. and Richard Lerner of the Scripps Research Institute and their colleagues theorized that the fat-laden deposits that are hallmarks of the disease have all the necessary ingredients to manufacture ozone. "Ozone is damaging, and it is really a problem that we are going to have to think about in the next few years," Wentworth notes. "There may be a whole slew of molecules that ozone generates that we have never thought about before." The researchers analyzed plaque samples removed from patients suffering from coronary artery disease and found two compounds--dubbed atheronals by the authors--that are signature byproducts of ozone's interaction with cholesterol, forms of which have long been associated with atherosclerosis. The team writes that "it seems likely that ozone is generated throughout the evolution of the disease."

The researchers also detected one of the atheronal compounds in blood taken from patients suffering from late-stage atherosclerosis. Because the molecule is not present in healthy individuals, the scientists suggest that it could one day form the basis of a new diagnostic test for coronary artery disease.