5-Lipoxygenase: a target for antiinflammatory drugs revisited

Arachidonate 5-lipoxygenase is the key enzyme in leukotriene biosynthesis and catalyzes the initial steps in the conversion of arachidonic acid to biologically active leukotrienes. Leukotrienes are considered as potent potent mediators of inflammatory and allergic reactions which are locally released by leukocytes and other 5-LO expressing cells and exert their effects via binding to specific membrane receptors and, as suggested recently, the nuclear receptor PPARa. Because of the proinflammatory profile of leukotrienes it was assumed that leukotriene biosynthesis inhibitors and leukotriene receptor antagonists have a therapeutical potential in a variety of inflammatory diseases. Clinical studies confirmed the therapeutic value of the antileukotriene therapy in asthma but the results with leukotriene biosynthesis inhibitors in psoriasis, arthritis and inflammatory bowel disease were more or less disappointing. This review summarizes the biochemistry of the 5-lipoxygenase pathway, the pharmacology of FLAP and 5 lipoxygenase inhibitors and discusses possible criteria for the development of these drugs.