Structural requirements in hydroxyeicosanoids for the activation of the 5-lipoxygenase in PT-18 mast/basophil cells

We have previously reported that 15-hydroxyeicosatetraenoic acid (15-HETE) stimulated the 5-lipoxygenase in the murine PT-18 mast/basophil cell line to produce leukotriene B4 and 5-HETE from exogenously added arachidonic acid. In order to determine the structural requirements in the HETE molecule that are necessary for the activation of this 5-lipoxygenase, various isomeric HETEs, derivatives and analogs were prepared, purified and tested. The order of stimulatory potencies was: 15-HETE acetate greater than 15-HETE = 15-hydroperoxyeicosatetraenoic acid (15-HPETE) greater than 5-HPETE = 12-HPETE greater than 5-HETE. 15-HETE methyl ester, 12-HETE and prostaglandin E2 were ineffective over the concentration range tested. Several diHETEs were also tested. 5S,15S-DiHETE was somewhat less potent than 15-HETE, whereas both 8S,15S-diHETE and leukotriene B4 were inactive. The calcium ionophore A23187 was much less effective than 15-HETE. These structure-activity studies indicate the importance of the nature, position and location of the various functional groups in the HETE molecule and suggest that a specific recognition site is involved in the activation of the 5-lipoxygenase in PT-18 cells.