History of Aspirin - Investigating How Aspirin Works

Investigating How Aspirin Works

The mechanism of aspirin's analgesic, anti-inflammatory and antipyretic properties was unknown through the drug's heyday in the early- to mid-twentieth century; Heinrich Dreser's explanation, widely accepted since the drug was first brought to market, was that aspirin relieved pain by acting on the central nervous system. In 1958 Harry Collier, a biochemist in the London laboratory of pharmaceutical company Parke Davis, began investigating the relationship between kinins and the effects of aspirin. In tests on guinea pigs, Collier found that aspirin, if given beforehand, inhibited the bronchoconstriction effects of bradykinin. He found that cutting the guinea pigs' vagus nerve did not affect the action of bradykinin or the inhibitory effect of aspirin—evidence that aspirin worked locally to combat pain and inflammation, rather than on the central nervous system. In 1963, Collier began working with University of London pharmacology graduate student Priscilla Piper to determine the precise mechanism of aspirin's effects. However, it was difficult to pin down the precise biochemical goings-on in live research animals, and in vitro tests on removed animal tissues did not behave like in vivo tests.

After five years of collaboration, Collier arranged for Piper to work with pharmacologist John Vane at the Royal College of Surgeons of England, in order to learn Vane's new bioassay methods, which seemed like a possible solution to the in vitro testing failures. Vane and Piper tested the biochemical cascade associated with anaphylactic shock (in extracts from guinea pig lungs, applied to tissue from rabbit aortas). They found that aspirin inhibited the release of an unidentified chemical generated by guinea pig lungs, a chemical that caused rabbit tissue to contract. By 1971, Vane identified the chemical (which they called "rabbit-aorta contracting substance," or RCS) as a prostaglandin. In a June 23, 1971 paper in the journal Nature, Vane and Piper suggested that aspirin and similar drugs (the non-steroidal anti-inflammatory drugs or NSAIDs) worked by blocking the production of prostaglandins. Later research showed that NSAIDs such as aspirin worked by inhibiting cyclooxygenase, the enzyme responsible for converting arachidonic acid into a prostaglandin.