PGD2 and its mimetic ZK 110.841 are potent inhibitors of receptor-mediated activation of human neutrophils.

The action of PGD2 and its mimetic ZK 110.841 ((5Z,13E)-(9R,11R,15S)-9-chloro-15-cyclohexyl-11,15- dihydroxy-16,17,18,19, 20-pentanor-5,13-prostadienoic acid) was compared to PGE1 in vitro on superoxide anion generation, degranulation, leukotriene (LT) B4 release and Ca++ fluxes in human polymorphonuclear leukocytes (PMN). All compounds were potent inhibitors of formyl-methionyl-leucyl-phenylalanine (FMLP)- and platelet-activating factor (PAF)-induced superoxide anion generation, beta-glucuronidase release and Ca++ influx. The PAF-induced release of LTB4 in the presence of 10 mumoles/l arachidonic acid was significantly attenuated by these prostaglandins. This inhibition of PMN function was paralleled by an increase in cellular cAMP levels. The molar potency of the prostaglandins used was comparable, although the D-type compounds appeared slightly more potent in some PMN function tests. None of the substances affected PMN activation induced by the calcium inophore calcimycin (A23187). The data demonstrate an effective inhibition of receptor-mediated (FMLP, PAF) PMN activation by PGD2 and its mimetic ZK 110.841, suggesting either an inhibitory PGD2 receptor on human PMN or action of PGD2 at the PGE receptor. PGD2 is a labile compound in vivo and is rapidly metabolized into a number of products with different biological properties. Since ZK 110.841 lacks this instability, this compound may serve as an important tool to classify PGD2-mediated reactions.