Figure 1.

Synthesis of lipoxin. Three major lipoxygenases (LO) such as 5-LO, 15-LO, and 12-LO are involved in lipoxin synthesis from arachidonic acid.

Notes: In the first route of lipoxin synthesis LTA4 is acted upon by 12-LO, and is converted to lipoxins. The second route of synthesis of lipoxins involves the action of a series of lipoxygenase (5-LO in neutrophils and 15-LO in erythrocytes) activities on arachidonic acid which then gets converted to 15-HEPTE. Lipoxins are formed from 15-HEPTE by the action of either 5-LO or 12-LO. The third route is the formation of epi-lipoxin A4 or aspirin-triggered lipoxin (ATL) and epi-lipoxin B4 whose generation is aspirin dependent. No fill represent enzymes whereas the gray filled represent the metabolites or end products.

Abbreviations: 15-HPETE, 15-hydroxyperoxyeicosatetraenoic acid; COX-2, cyclooxygenase-2; FLAP, 5-lipoxygenase-activating protein; LTA4, leukotriene A4.