A novel C(28)-hydroxylated lupeolic acid suppresses the biosynthesis of eicosanoids through inhibition of cytosolic phospholipase A(2).
Eicosanoids are potent lipid mediators derived from phospholipase (PL)-released arachidonic acid (AA) coupled to subsequent metabolism by cyclooxygenase (COX)-1/2 or lipoxygenases (LO) which are involved in a variety of homeostatic biological functions and inflammation. We have investigated three lupeolic acids (LA) from the gum resin of Boswellia carterii for their ability to interfere with eicosanoid biosynthesis in human blood cells. A novel, yet unknown C(28)-hydroxylated LA, that is, 3α-acetoxy-28-hydroxylup-20(29)-en-4β-oic acid (Ac-OH-LA) was found to inhibit the biosynthesis of COX-, 5-LO- and 12-LO-derived eicosanoids from endogenous AA in activated platelets, neutrophils, and monocytes from human blood with consistent IC(50) values of 2.3-6.9 μM. In contrast, two other LAs lacking the C(28)-OH moiety were essentially inactive in this respect. Inhibition of eicosanoids by Ac-OH-LA correlated with reduced release of AA in intact cells. When AA was exogenously provided as substrate for cellular eicosanoid biosynthesis the inhibitory effects of Ac-OH-LA were essentially reversed, even though some inhibition of 5-LO and COX-1 product formation still remained. Finally, by means of a cell-free phospholipid hydrolysis assay using human recombinant cytosolic PLA(2)α, we show that Ac-OH-LA may directly interfere with cPLA(2)α activity (IC(50) = 3.6 μM). Together, we identified a novel, naturally occuring C(28)-hydroxylated LA which acts as efficient inhibitor of cPLA(2)α and consequently suppresses eicosanoid biosynthesis in intact cells.
Department for Pharmaceutical Analytics, Pharmaceutical Institute, University of Tuebingen, Auf der Morgenstelle 8, D-72076 Tuebingen, Germany. mzverhoff@googl.com
Moritz
M
Verhoff
Stefanie
S
Seitz
Hinnak
H
Northoff
Johann
J
Jauch
Anja M
AM
Schaible
Oliver
O
Werz
D016718:Arachidonic Acid / Q000097:blood; D002478:Cells, Cultured; D003600:Cytosol / Q000201:enzymology*; D015777:Eicosanoids / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D006801:Humans; D006900:Hydroxylation; D009682:Magnetic Resonance Spectroscopy; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism; D064801:Phospholipase A2 Inhibitors; D014315:Triterpenes / Q000737:chemistry / Q000494:pharmacology*; D000094042:Lupanes
D016718:Arachidonic Acid; D015777:Eicosanoids; D064801:Phospholipase A2 Inhibitors; D014315:Triterpenes; C482140:lupeolic acid; D000094042:Lupanes