In this video, we're going to talk about our 3rd class of eicosanoids, which are the leukotrienes. And so, leukotrienes, of course, are eicosanoids, and as their name implies, the 'tri' indicates that there are 3, and the 'enes' are indicating the presence of double bonds. And so indeed, leukotrienes are eicosanoids that have 3 conjugated double bonds. And, of course, because these are eicosanoids and the Greek word 'eikosi' means 20, leukotrienes are derived from C₂₀ leukotriene D₄ whose structure we're showing you here. And again, leukotrienes as the name implies, they have 3 conjugated double bonds. And so when you take a look at the structure here, you can see that these 3 double bonds right here are conjugated double bonds. And so there are 3 conjugated double bonds. Now by conjugated, really what we mean is that they're just appearing back to back here, in this particular fashion. Now notice that this double bond down here is not conjugated because it's being separated from the others by a CH₂ group.

And so the reason that leukotrienes are called leukotrienes is because they're predominantly expressed by leukocytes, which is really just the scientific name for white blood cells. And so our white blood cells produce these leukotrienes. Now, the leukotrienes actually have variable functions, but they predominantly act as powerful biosignals. For example, leukotriene D₄ will actually induce strong smooth muscle contractions of our lungs. And of course, in some people, allergic reactions can trigger leukotriene synthesis. And so if leukotriene D₄ is being synthesized, or overexpressed, it's going to induce strong smooth muscle contractions of the lungs. And that could lead to an asthma attack. And so, if you know people that have asthma, it's really because of the allergic reactions are causing them to over create leukotrienes, specifically leukotriene D₄. And so, down below in our image, notice that we've got this guy right here, who is having an asthma attack because of the overproduction of leukotriene D₄. And, notice that he's using this inhaler here and the inhalers will actually have specific molecules that block receptors for leukotriene D₄. And so that's just something interesting, to note.

But really this here concludes our introduction to leukotrienes and moving forward we'll be able to apply these concepts that we've learned in our practice problem. So I'll see you guys there.