Prostaglandins and Eicosanoids

Key points

• • Eicosanoids (prostaglandins, thromboxanes and leukotrienes) are local signalling molecules made from arachidonic acid, a fatty acid released from cell membranes.
• • They act close to where they are made and are quickly broken down, so they work as local rather than circulating hormones.
• • The enzyme cyclo-oxygenase (COX) turns arachidonic acid into prostaglandins and thromboxanes, while lipoxygenase makes the leukotrienes.
• • Prostaglandins drive mainly the redness (vasodilation), pain and fever of inflammation (swelling also involves other mediators such as histamine), which is why blocking their production eases these symptoms.
• • Thromboxane (TXA2), made by platelets, promotes platelet aggregation and narrows vessels, while prostacyclin from vessel walls does the opposite.
• • Leukotrienes cause the airways to tighten and drive allergic and asthmatic responses.