leukotriene

Leukotrienes are lipid signaling molecules derived from arachidonic acid through the 5-lipoxygenase pathway. In leukocytes and other cells, 5-LOX in concert with 5-LOX–activating protein converts arachidonic acid to leukotriene A4 (LTA4). LTA4 can be converted to leukotriene B4 (LTB4) by LTA4 hydrolase, or to the cysteinyl leukotrienes LTC4, LTD4, and LTE4 via LTC synthase and subsequent extracellular processing. These mediators are part of the broader inflammatory cascade and act locally where they are produced.

The leukotriene family includes two main groups: LTB4 and the cysteinyl leukotrienes (LTC4, LTD4, LTE4). LTB4 binds to receptors BLT1 and BLT2, producing neutrophil chemotaxis and activation. The cysteinyl leukotrienes exert their effects primarily through CysLT1 and CysLT2 receptors, promoting bronchoconstriction, increased vascular permeability, mucus secretion, and recruitment of eosinophils and other inflammatory cells. LTB4 and cysteinyl leukotrienes play complementary roles in coordinating inflammatory responses, especially in the airways and at sites of tissue injury.

Clinical relevance centers on their role in asthma and allergic diseases, where leukotrienes contribute to bronchoconstriction, airway edema, and mucus hypersecretion. Therapeutic strategies include leukotriene receptor antagonists (montelukast, zafirlukast, pranlukast), which block CysLT1, and 5-LOX inhibitors (zileuton), which reduce synthesis of all leukotrienes. These agents are used as anti-inflammatory options in chronic asthma and allergic rhinitis, rather than for acute bronchospasm. Potential adverse effects and drug interactions necessitate appropriate patient monitoring.