Prostaglandin D2 (PGD2) together with its positional isomer PGE2 is a direct metabolite of PGH2 arising from the dioxygenation of arachidonic acid (1). More than 15 years ago, PGJ2, the 9-deoxy derivative of PGD2 via dehydration, was identified and described as a mitogen (2). Later, the 12 isomer of PGJ2 was found in human urine (3).

A new dehydration product of PGJ2, 15-deoxy-12, 14-PGJ2 (15dPGJ2), has been described as a specific ligand of peroxisome proliferator-activated receptor, which is associated with adipocyte differentiation (4, 5). Considerable interest has arisen in cyclopentenone derivatives of prostaglandins (6), particularly 15dPGJ2, which has been described as an active compound in cancer (7, 8) and in cell apoptosis (9, 10), in addition to adipogenesis (11). 15dPGJ2 has recently been reported to have antiinflammatory activity (12). Indeed, it prevents cytokine-and endotoxin-stimulated activation of peripheral and resident tissue macrophages and cytokine-induced inducible nitric oxide synthase expression in B cells by inhibition of transcriptional activation and induction of the heat-shock response.