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For over 70 years, aspirin was a medical mystery. Doctors prescribed it to reduce fevers, ease headaches, and bring down swelling, but no one could explain exactly what the drug was doing inside the body. That changed on 23 June 1971, when British pharmacologist John Vane published a paper in *Nature New Biology* titled "Inhibition of prostaglandin synthesis as a mechanism of action for aspirin-like drugs".
Vane's discovery that aspirin shuts down the production of pain-causing chemical signals earned him the 1982 Nobel Prize in Physiology or Medicine. It also launched a new era of drug discovery, shifting pharmacology from testing plant extracts to designing molecules that target specific enzymes.
What are prostaglandins?
Prostaglandins are lipid compounds that act as local messengers. Unlike hormones that are made in a gland and travel through the blood to reach distant organs, prostaglandins are manufactured on demand by nearly all tissues in the body when they are injured or stressed.
Their production begins with arachidonic acid, a fatty acid released from the cell membrane by an enzyme called phospholipase A2. Once the acid is free, another enzyme called cyclooxygenase (COX) takes over. The COX enzyme adds oxygen to the arachidonic acid, converting it into intermediate compounds such as PGH2. These intermediates are quickly turned into specific prostaglandins.
Once released, these prostaglandins bind to receptors on nearby cells. They trigger the classic signs of inflammation: they make blood vessels dilate to cause redness and swelling, they sensitize nerve endings to increase pain, and they act on the brain's thermostat to induce a fever.
If you are trying to learn complex biological pathways like this, following the molecules from start to finish can be difficult. The Fermi Concept Library has a lesson for every concept in physics, chemistry, biology, mathematics and computing, each with its place in the map, helping you see how substrates and enzymes fit together without getting lost.
How does aspirin block the enzyme?
Before Vane's work, researchers had isolated prostaglandins but did not know how standard painkillers interacted with them. Vane proved that aspirin works by interfering directly with the COX enzyme. Aspirin physically blocks the enzyme's active site, stopping its ability to grab arachidonic acid.
Without functioning COX enzymes, the cell cannot produce its local messengers. As the local levels of prostaglandins drop, the pain receptors stop firing as intensely, the blood vessels stop leaking fluid into the tissue (which brings down the swelling), and the brain's temperature control resets to normal. Vane's single mechanism explained aspirin's main effects: as an analgesic (painkiller), an antipyretic (fever reducer), and an anti-inflammatory.
This mechanism also explained the drug's most common side effect. Because the stomach uses a constant baseline of prostaglandins to maintain its protective mucus lining, blocking the COX enzyme leaves the stomach wall vulnerable to its own acid. Vane's insight later allowed scientists to discover distinct COX enzymes: COX-1, which protects the stomach, and COX-2, which causes inflammation. This led to a new class of painkillers designed to block only COX-2.
How to trace a biological pathway
Vane's work is a classic example of tracing a biological pathway to find an intervention point. When you study enzyme cascades in biology or biochemistry, do not just memorize the steps. Build a framework to understand what drives the reaction.
Find the trigger: What starts the cascade? For prostaglandins, it is physical or chemical stress to the cell.
Locate the precursor: Identify the raw material. Here, it is arachidonic acid released from the membrane.
Name the enzyme: What drives the crucial step? Cyclooxygenase (COX) is the rate-limiting enzyme.
Note the product's job: What do the final molecules do? Prostaglandins cause pain, fever, and inflammation.
Identify the inhibitor: Where does a drug or poison step in? Aspirin blocks the COX enzyme, stopping the cascade before the product can be made.
By breaking a pathway into these five parts, you transform a long list of chemical names into a logical sequence of events.
