Arachidonic acid metabolism by peripheral blood cells in psoriasis.

The metabolism of arachidonic acid by mixed suspensions of leukocytes and platelets prepared from peripheral blood has been studied in 20 patients with psoriasis and 21 healthy controls. A lipoxygenase-derived product, identified as 12,20-dihydroxy-5,8,10,14-eicosatetraenoic acid was formed in increased amounts by the cell suspension from the psoriatic patients. This product results from the metabolism of platelet-derived 12-hydroxy-5,8,10,14-eicosatetraenoic acid by the polymorphonuclear leukocyte 20-hydroxylase enzyme. By contrast, synthesis of the cyclo-oxygenase products 12-hydroxy-5,8,10-heptadecatrienoic acid and thromboxane B2 was diminished. Benoxaprofen, which is known to be beneficial in psoriasis, diminished the levels of 12,20-dihydroxy-5,8,10,14-eicosatetraenoic acid formed in vitro.