pyrrophenone and arachidonyltrifluoromethane

We investigated role(s) of luteal group IVA phospholipase A(2) (GIVA PLA(2)) in prostaglandin (PG) F(2alpha)-induced regression in pseudopregnant rats. Prostaglandin F(2alpha) (PGF(2alpha)) treatment of day 6 pseudopregnant rats stimulated luteal PLA(2) activity, which was sensitive to inhibitors and associated with increased GIVA PLA(2) immunoreactivity. Intra-bursal treatment with the enzyme inhibitor (AACOCF3) prior to PGF(2alpha) failed to prevent the initial decline in progesterone but induced subsequently a persistent rise that was significantly higher than that of vehicle-treated group. TUNEL-positive signals in luteal cells of control group were reduced by AACOCF3 treatment. TUNEL-positive reaction induced in luteal cells in vitro by combined cytokines and agonistic anti-Fas were both reduced by AACOCF3 and another inhibitor pyrrophenone. Overall data show that luteal GIVA PLA(2) activity and expression increased following PGF(2alpha) administration and that acute chemical inhibition of this activity could reverse, at least partly, PGF(2alpha)-induced functional regression and prevent apoptosis induced by PGF(2alpha)in vivo and by cytokines in vitro.

Topics: Animals; Apoptosis; Arachidonic Acids; Dinoprost; Enzyme Inhibitors; Female; Immunohistochemistry; In Situ Nick-End Labeling; Luteolysis; Male; Phospholipases A2; Progesterone; Pseudopregnancy; Pyrrolidines; Rats; Rats, Wistar

The biosynthesis of leukotrienes (LT) and platelet-activating factor (PAF) involves the release of their respective precursors, arachidonic acid (AA) and lyso-PAF by the group IVA PLA2 (cPLA2alpha). This paper aims at characterizing the inhibitory properties of the cPLA2alpha inhibitor pyrrophenone on eicosanoids and PAF in human neutrophils (PMN).. Freshly isolated human PMN were activated with physiological and pharmacological agents (fMLP, PAF, exogenous AA, A23187 and thapsigargin) in presence and absence of the cPLA2alpha inhibitor pyrrophenone and biosynthesis of LT, PAF, and PGE2 was measured.. Pyrrophenone potently inhibited LT, PGE2 and PAF biosynthesis in PMN with IC50s in the range of 1-20 nM. These inhibitory effects of pyrrophenone were specific (the consequence of substrate deprivation), as shown by the reversal of inhibition by exogenous AA and lyso-PAF. Comparative assessment of pyrrophenone, methyl-arachidonoyl-fluoro-phosphonate (MAFP) and arachidonoyl-trifluoromethylketone (AACOCF3) demonstrated that pyrrophenone was more specific and 100-fold more potent than MAFP and AACOCF3 for the inhibition of LT biosynthesis in A23187-activated PMN. The inhibitory effect of pyrrophenone on LT biosynthesis was reversible as LT biosynthesis was recovered when pyrrophenone-treated PMN were washed with autologous plasma. No alteration of phospholipase D (PLD) activity in fMLP-activated PMN was observed with up to 10 microM pyrrophenone, suggesting that the cPLA2alpha inhibitor does not directly inhibit PLD.. Pyrrophenone is a more potent and specific cPLA2alpha inhibitor than MAFP and AACOCF3 and represents an excellent pharmacological tool to investigate the biosynthesis and the biological roles of eicosanoids and PAF.

Topics: Arachidonic Acids; Dinoprostone; Dose-Response Relationship, Drug; Eicosanoids; Enzyme Inhibitors; Group IV Phospholipases A2; Humans; In Vitro Techniques; Leukotrienes; Neutrophils; Organophosphonates; Phospholipase D; Phospholipases A; Phospholipases A2; Platelet Activating Factor; Pyrrolidines