Lipoxin A4 is a lipid-derived signaling hormone involved in resolution of inflammation, immune regulation, leukocyte control, and restoration of tissue homeostasis after inflammatory activation. Unlike many inflammatory lipid mediators that amplify immune signaling, lipoxin A4 functions primarily as a pro-resolving mediator that helps limit excessive inflammation and coordinate transition toward tissue recovery.
The hormone reduces neutrophil recruitment, modulates cytokine production, influences macrophage activity, and supports clearance of inflammatory debris. Lipoxin A4 also participates in regulation of endothelial signaling, vascular permeability, and communication between innate immune cells during the later phases of inflammatory responses. Through these actions, it contributes to balancing inflammatory activation with tissue-protective resolution pathways.
Lipoxin A4 is synthesized from arachidonic acid through coordinated lipoxygenase enzyme activity involving multiple cell types. Production commonly occurs through interactions between neutrophils, platelets, macrophages, endothelial cells, and epithelial tissues. Sequential metabolism of arachidonic acid by five-lipoxygenase and twelve- or fifteen-lipoxygenase pathways generates lipoxin intermediates that are converted into lipoxin A4.
Unlike many hormones stored in secretory vesicles, lipoxin A4 is synthesized locally during active inflammatory signaling. Production often increases during later stages of inflammation when tissues begin transitioning toward resolution and repair processes.
Lipoxin A4 synthesis is regulated by inflammatory timing, immune-cell interactions, oxidative signaling, phospholipase pathways, and lipoxygenase enzyme activity. Cytokine signaling, leukocyte activation status, endothelial communication, and tissue injury patterns influence production dynamics.
Lipoxin A4 acts mainly through ALX/FPR2 receptors located on neutrophils, macrophages, endothelial cells, and additional immune-cell populations. Receptor activation modulates cytokine production, leukocyte migration, oxidative signaling, and phagocytic activity. Through these integrated pro-resolving lipid-signaling systems, lipoxin A4 helps coordinate inflammatory termination, tissue stabilization, immune balance, and restoration of physiological homeostasis after inflammatory activation.
LXA₄ is a resolution-phase lipid mediator that tempers leukocyte trafficking and promotes non-phlogistic clearance.
