Figure 3.

The leukotriene biosynthesis and signaling pathway. Leukotrienes derive from arachidonic acid, which is cleaved from membrane phospholipids by phospholipase A2 (PLA2) and further processed by the key enzyme 5-lipoxygenase (5-Lox) and its activator, 5-lipoxygenase activating protein (FLAP). The intermediate product 5-hydroperoxyeicosatetraenoic acid (5-HPETE) gives rise to leukotriene A₄ (LTA₄), which is further converted to leukotriene B₄ (LTB₄) by leukotriene A₄ hydrolase (LTA₄H) or to the cysteinyl leukotrienes leukotriene C₄, D₄ and E₄ (LTC₄, LTD₄ and LTE₄) by leukotriene C₄ synthase (LTC₄S). Leukotrienes evoke inflammatory responses by binding with different affinities to specific receptors on target cells. These include the leukotriene B₄ receptor (BLTR), the G-protein-coupled receptor 17 (GPR17), the cysteinyl leukotriene receptor 1 (CysLT₁R) and cysteinyl leukotriene receptor 2 (CysLT₂R). Created with BioRender.com (last accessed on 4 November 2021).