The role of diacylglyceride generation by phospholipase D and phosphatidic acid phosphatase in the activation of 5-lipoxygenase in polymorphonuclear leukocytes.

Diacylglycerides (DAGs) such as 1-oleoyl-2-acetyl-sn-glycerol (OAG) stimulate 5-lipoxygenase (5-LO) enzyme activity and function as agonists for human polymorphonuclear leukocytes (PMNL) to induce 5-LO product synthesis. Here, we addressed the role of endogenous DAG generation in agonist-induced 5-LO activation in human PMNL. Preincubation of PMNL with the phospholipase D (PLD) inhibitor 1-butanol potently suppressed 5-LO product synthesis induced by the Ca(2)(+) ionophore A23187 or thapsigargin (TG) and blocked A23187-evoked translocation of 5-LO from the cytosol to the nuclear membrane, analyzed by subcellular fractionation as well as by indirect immunofluorescence microscopy.

Evaluation of hyperforin analogues for inhibition of 5-lipoxygenase.

The acylphloroglucinol hyperforin, a constituent of the herb Hypericum perforatum (St. John's wort), was recently identified as potent and direct inhibitor of 5-lipoxygenase (5-LO), the key enzyme in the biosynthesis of proinflammatory leukotrienes. In this study, naturally occurring analogues of hyperforin, isolated from H.

1-Oleoyl-2-acetylglycerol stimulates 5-lipoxygenase activity via a putative (phospho)lipid binding site within the N-terminal C2-like domain.

5-Lipoxygenase (5-LO) catalysis is positively regulated by Ca2+ ions and phospholipids that both act via the N-terminal C2-like domain of 5-LO. Previously, we have shown that 1-oleoyl-2-acetylglycerol (OAG) functions as an agonist for human polymorphonuclear leukocytes (PMNL) in stimulating 5-LO product formation. Here we have demonstrated that OAG directly stimulates 5-LO catalysis in vitro.

The aminosteroid phospholipase C antagonist U-73122 (1-[6-[[17-beta-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione) potently inhibits human 5-lipoxygenase in vivo and in vitro.

U-73122 (1-[6-[[17-beta-3-methoxyestra-1,3,5(10)-trien-17-yl]amino] hexyl]-1H-pyrrole-2,5-dione) is a widely used antagonist of phosphoinositide-specific phospholipase C (PLC) and is frequently used to define a role of PLC in receptor-mediated elevation of intracellular calcium concentration ([Ca2+]i). In human polymorphonuclear leukocytes (PMNLs), U-73122 inhibited increases in [Ca2+]i induced by G protein-coupled receptor (GPCR) agonists (N-formyl-methionyl-leucyl-phenylalanine or platelet-activating factor; IC50 of approximately 2 to 4 microM), but it failed to suppress responses induced by ionomycin or thapsigargin. 5-Lipoxygenase (5-LO) is a Ca(2+)-regulated enzyme that can be activated in leukocytes by stimuli that elevate [Ca2+]i.

Induction of 5-lipoxygenase activation in polymorphonuclear leukocytes by 1-oleoyl-2-acetylglycerol.

1,2-Diacylglycerols (DAGs) can prime polymorphonuclear leukocytes (PMNL) for enhanced release of arachidonic acid (AA) and generation of 5-lipoxygenase (5-LO) products upon subsequent agonist stimulation. Here, we demonstrate that in isolated human PMNL, 1-oleoyl-2-acetylglycerol (OAG) functions as a direct agonist stimulating 5-LO product formation (up to 42-fold). OAG caused no release of endogenous AA, but in the presence of exogenous AA, the magnitude of 5-LO product synthesis induced by OAG was comparable to that obtained with the Ca(2+)-ionophore A23187.

Hyperforin is a dual inhibitor of cyclooxygenase-1 and 5-lipoxygenase.

The acylphloroglucinol derivative hyperforin is the major lipophilic constituent in the herb Hypericum perforatum (St. John's wort). The aim of the present study was to investigate if hyperforin as well as extracts of H.