title: Studies on the mechanism of omega-hydroxylation of platelet 12-hydroxyeicosatetraenoic acid (12-HETE) by unstimulated neutrophils.
abstract: Stimulated platelets, in the presence or absence of aspirin, synthesize significant quantities of 12-hydroxyeicosatetraenoic acid (12-HETE), which is chemotactic and chemokinetic, and enhances mononuclear cell procoagulant activity. During a cell-cell interaction between stimulated platelets and unstimulated neutrophils, platelet 12-HETE is metabolized to 12,20-dihydroxyeicosatetraenoic acid (12,20-DiHETE) by neutrophils. Characteristics of the enzyme system in unstimulated neutrophils responsible for this omega-hydroxylation were investigated. A broad range of cytochrome P-450 inhibitors, as well as leukotriene B4, blocked formation of 12,20-DiHETE. Owing largely to released proteases, neutrophil homogenization abolished activity. Pretreatment with diisopropylfluorophosphate preserved activity in neutrophil homogenates. omega-Hydroxylation of 12-HETE was confined solely to the microsomal fraction. Specific activity increased 6.6-fold compared with neutrophil sonicates. The electron donor NADPH was a required cofactor. These results indicate that the enzyme in unstimulated human neutrophils, which metabolizes 12-HETE from stimulated platelets to 12,20-DiHETE in this cell-cell interaction, is a cytochrome P-450 monooxygenase.
mesh_terms: D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; D001571:Benzoflavones / Q000494:pharmacology; D001792:Blood Platelets / Q000378:metabolism*; D002248:Carbon Monoxide / Q000494:pharmacology; D003577:Cytochrome P-450 Enzyme System / Q000097:blood*; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000097:blood*; D066298:In Vitro Techniques; D007975:Leukotriene B4 / Q000378:metabolism; D008861:Microsomes / Q000201:enzymology; D009249:NADP / Q000378:metabolism; D009504:Neutrophils / Q000201:enzymology*; D013347:Subcellular Fractions / Q000201:enzymology
chemical_list: D001571:Benzoflavones; D006893:Hydroxyeicosatetraenoic Acids; D007975:Leukotriene B4; D009249:NADP; D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; C011512:alpha-naphthoflavone; D002248:Carbon Monoxide; D003577:Cytochrome P-450 Enzyme System