Lipoxins and aspirin-triggered lipoxins in resolution of inflammation.

The resolution of the inflammatory response is highly regulated by the timely biosynthesis of a number of endogenous lipid mediators. Among these, lipoxins (LX) and their 15-epimers, aspirin triggered lipoxins (ATL) derived by the lipoxygenase (LO) route of arachidonic acid metabolism. In particular, they are formed and released by cells expressing 5-, 12- and 15-LO such as leukocytes, platelets, vascular endothelium and epithelium, alone or during transcellular interactions. ATL biosynthesis requires cyclooxygenase-2 acetylation by aspirin. LX and ATL exert potent bioactions on leukocytes, vascular and epithelial cells to stop inflammation and promote resolution. They have shown to be beneficial in a broad spectrum of preclinical models of disease as well as in some clinical trials. Counter-regulatory signaling by LXA4 and 15-epi-LXA4 follows the activation of a G protein-coupled receptor, termed ALX/FPR2, which is emerging as a key anti-inflammatory receptor.