AH13205, A Selective Prostanoid EP 2 ‐receptor Agonist

1 The aims of this study were to characterize the EP receptor subtype mediating the inhibition of superoxide anion generation by formyl methionyl leucine phenylalanine (FMLP)-stimulated human neutrophils, and to test the hypothesis that adenosine 3':5'-cyclic monophosphate (cyclic AMP) is the second messenger mediating the inhibition of the neutrophil by prostaglandin (PG)E2. 2 PGE2 (0.001-10 ItM) inhibited FMLP (100 nM)-induced 02-generation from human peripheral blood neutrophils in a concentration-dependent manner, with an ECM of 0.15 ± 0.03 AM, and a maximum effect ranging from 36-84% (mean inhibition of 68.7 ± 2.5%, n = 32).3 The EP2-receptor agonists, misoprostol, l1-deoxy PGE1, AH13205 and butaprost, all at 1OpM, inhibited°2-generation, causing 95.5 ± 2.9%, 56.8 ± 5.2%, 37.1 ± 6.6% and 18.9 ± 4.4% inhibition respectively, the latter two being much less effective than PGE2. Similarly, the EPI-receptor agonist, 17-phenyl PGE2 (101sM), and the EP3/EPI-receptor agonist, sulprostone (10I1M), also inhibited 02-generation, causing 32.2 ± 7.0% and 15.3 ± 3.4% inhibition respectively. 4 The non-selective phosphodiesterase inhibitor, isobutyl methylxanthine (IBMX, 0.25 mM) inhibited the FMLP response by 54.5 ± 5.0%. In addition, IBMX shifted concentration-effect curves for PGE2, misoprostol, I 1-deoxy PGEI, butaprost, and AH 13205 to the left, to give ECms of 0.04 ± 0.03 (n = 13), 0.07 ± 0.03 (n = 4), 0.08 ± 0.03 (n = 4), 0.33 ± 0.13 (n = 4) and 0.41 ± 0.2 gM (n = 3) respectively, allowing equieffective concentration-ratios -(EECs, PGE2 = 1) of 11.5, 5.3, 50.7 and 12.7 to be calculated. This agrees well with the relative potencies of these agonists at EP2 receptors. 5 By contrast, even in the presence of IBMX (0.25 mM), sulprostone and 17-phenyl PGE2 were only effective at the highest concentration (10 gM), and gave EECs of > 700 and 486 respectively, suggesting that EP1 or EP3 receptors are not involved. 6 The selective type IV phosphodiesterase inhibitor, rolipram at 2 and 10 nM did not inhibit the FMLP response, but at the higher concentration of 50 nM, it decreased the FMLP response by 46.6 7.3%.However, rolipram shifted concentration-effect curves for PGE2 to the left to give EC50s of 0.06 0.022, 0.015 + 0.0, 0.012 ± 0.006 tM at 2, 10 and 50 nM respectively, compared to the control EC50 of 0.27 ± 0.09 pM for PGE2. 7 The EP4/TP receptor blocking drug, AH 23848B (10 AM, 10 min) did not inhibit 02-generation by PGE2, but was found to potentiate significantly the effect of PGE2 at the lower concentrations of PGE2 tested (0.001-0.1 M). 8 The adenylate cyclase inhibitor, SQ 22,536 (0.1 mM, 2 min) reduced PGE2-induced inhibition of 02-production, giving an EC50 in the absence of SQ 22,536 of 0.24 ± 0.1, and 1.9± 1.1 AM in its presence.9 These results suggest that inhibition of superoxide generation by PGE2 is mediated by stimulation of EP2 receptors and activation of adenylate cyclase, leading to the elevation of intracellular levels of cyclic AMP.

Section: Discussionsupporting

confidence: 78%

Section: Discussionmentioning

confidence: 99%

Characterization of the PGE receptor subtype mediating inhibition of superoxide production in human neutrophils

Talpain

Armstrong

Coleman

et al. 1995

“…The selective EP2-receptor agonists, 1 1-deoxy PGEI (Lawrence et al, 1992), butaprost (Gardiner, 1986) and AH 13205 (Nials et al, 1993) also inhibited chemotaxis, giving maximal inhibitions of 43.8 +7.9% (n=3), 65.2±6.2% (n=5) and 61.9 ± 2.7% (n = 3), respectively at concentrations of 1OyM (Figure 2a). Taking the maximal effect of PGE2 at 10 $M as 100% response, apparent EC5&s of 106.4±63 nM, 140.9±64.7 nM and 1.58±0.73 pM were determined for butaprost, 1 1-deoxy PGEI and AH 13205, respectively.…”

Section: Inhibition Of Chemotaxis By Selective Ep Agonistsmentioning

confidence: 99%

Investigation of the inhibitory effects of PGE₂ and selective EP agonists on chemotaxis of human neutrophils

Armstrong

1995

104

1 The aims of this study were to investigate the inhibitory effects of prostaglandin E2 (PGE2) on chemotaxis of N-formyl-methionyl-leucine-phenylalaiine (FMLP)-stimulated human neutrophils, and to test the hypothesis that cyclic AMP is the second messenger involved. For this purpose, the inhibitory effect of selective EP agonists, and the modulatory effects of the adenylate cyclase inhibitor, SQ 22536, the protein kinase A (PKA) inhibitors H-89 and Rp-cAMPS, and the type IV phosphodiesterase (PDE) inhibitors, rolipram and Ro20-1724 have been examined. 2 Chemotaxis has been measured using blindwell chambers. When human neutrophils were stimulated with FMLP (100 nM), PGE2 inhibited chemotaxis in a concentration-dependent manner (0.01-10 Mm), with an EC50 of 90+24.5 nm, a maximum effect ranging from 45-75% and a mean inhibition of 64.5 ± 2.4%.

“…In human isolated hand veins, the vasorelaxation to PGF2.. was partly endothelium-dependent (Arner et al, 1994). These PGF2,e,-mediated vasorelaxant effects were not attributed to stimulation of the FP-receptor but were suggested to occur by stimulation of the recognized relaxant prostanoid receptors such as the DP, EP2 and IP receptor subtypes (Giles et al, 1989;Nials et al, 1991;Lawrence & Jones, 1992) as well as an endothelium-derived relaxing factor.…”

Section: Introductionmentioning

confidence: 96%

Identification of a prostanoid FP receptor population producing endothelium‐dependent vasorelaxation in the rabbit jugular vein

Chen

Champa‐Rodriguez

Woodward

1995

1 Prostaglandin F2u (PGFu) and its synthetic analogue, fluprostenol, potently relaxed the precontracted isolated jugular vein of the rabbit (RJuV). The vasorelaxant activity of PGFu and fluprostenol was dependent upon an intact vascular endothelium. Although removal of the vascular endothelium abolished activity associated with PGF2-like agonists, it did not significantly alter the relaxant effects of prostaglandin E2 (PGE2). 2 The nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), at 100 4M significantly inhibited the endothelium-dependent relaxations induced by PGFu. Lower doses (1 !M, 10 MM) of L-NAME had little or no effect. The relaxant effects of PGE2 were not affected by L-NAME(1 -100 MM). D-NAME at 100 gM was without effect on the vasorelaxant responses to either PGF2u or PGE2.3 The potassium (K)-channel blockers tetraethylammonium (TEA, 1 mM), barium (1 mM) and quinine (100 gM), each tested in the presence of the inactive enantiomer D-NAME (100 gM) did not significantly affect the response to PGFA. Unexpectedly, both TEA and barium significantly and partially reversed the inhibitory effects of 100 gM L-NAME, whereas quinine had no effect. In similar studies, none of the three potassium channel blockers had any effect on relaxations elicited by PGE2 when given with D-NAME or L-NAME. 4 These results indicate that the PGFu-sensitive prostanoid receptors found in the vascular endothelium of the rabbit jugular vein are of the FP-receptor subtype. Nitric oxide (NO) appears to be the predominant messenger involved in PGFu-induced relaxation of the rabbit jugular vein. Potassium channels may have a minor role in mediating the vasorelaxation response to PGFu. When both NO synthesis and K-channels are simultaneously blocked, inhibition of PGFuA-induced vasorelaxation by L-NAME is opposed by K-channel blockers. This diminution of the inhibitory effect of L-NAME by TEA and barium suggests that K-channels may possibly serve a compensatory role via the NO pathway.