Arteries affected by atherosclerosis become inflexible and inflamed. In the current study, the researchers had hypothesized that aspirin might protect against such inflammation.

"Aspirin is widely used to prevent heart attacks and strokes, but it is assumed that its effects are solely attributable to its blood-thinning actions. But our research turns the clock back on aspirin, and suggests that some of aspirin's effects really are due to its anti-inflammatory properties, which people have known about for 100 years or more," says Patrick J. T. Vallance, M.D., study author.

The British researchers used typhoid vaccine to cause inflammation in 17 healthy volunteers to determine if aspirin would prevent changes in arterial function. Of the 17 volunteers, 12 subjects randomly received either 1.2 grams of aspirin or placebo two hours before vaccination. The remaining 5 patients received aspirin after the vaccination.

The researchers measured Interluekin-1 to determine level of inflammation. In the placebo group, the interleukin level peaked at three hours and remained elevated until 8 hours after vaccination, corresponding with a 30-fold increase in baseline values. In the group treated with a single oral dose of aspirin before the vaccine, the concentration of Interleukin-1 did not change from baseline.

In a second test, researchers measured endothelial function by infusing drugs that affect the endothelium into the artery of one arm and measuring blood flow in that arm. The 6 participants who received placebo had decreased forearm blood flow eight hours after vaccination compared with baseline value, indicating temporary stiffening. However, the 6 subjects who received aspirin before vaccination showed an increase in forearm blood flow eight hours after vaccination, indicating a protective effect from aspirin.

"There is an exciting opportunity to rethink how we use aspirin and whether there are situations in which we should be giving aspirin to reduce cardiovascular risk," Vallance says.