Comparison of AMP579 and adenosine in inhibition of cell-cell interaction between human neutrophil and vascular endothelial cell

The purpose of the present study was to compare inhibitory effects between AMP579 (a new adenosine analog) and adenosine (Ado) in attenuating an inter action between human neutrophils (PMNs) and cultured human umbilical vein e ndothelial cells (HUVECs). PMN activation was determined by superoxide anio n (O-2(-)) production and degranulation (myeloperoxidase release). Cell-cel l interaction was quantitated by adherence of fluorescent labeled PMNs to H UVECs. AMP579 inhibited O-2(-) (nM/5 x 10(6) PMN) from fMLP-activated human PMNs (55.3 +/- 3.1) in a concentration-dependent manner ranging from 31.1 +/- 2.9 at 10 nM to 11.7 +/- 0.9 at 10 +/- mu M, all P < 0.01 vs, fMLP grou p. In the same dose range, however, Ado showed significant inhibition only at 1 mu M (30.3 +/- 4.1) and 10 +/- mu M (27.5 +/- 4.3) vs, the fMLP group. The calculated IC50 value (0.11 +/- 0.05 mu M) in AMP579 group was signifi cantly less than that in the Ado group (4.1 +/- 1.2 mu M). Although there w as no group difference on PMN myeloperoxidase release (percent inhibition f rom fMLP) between AMP579 and Ado at concentrations greater than 1 mu M (52. 9 +/- 5,2 vs. 46.4 +/- 5.9), AMPS 79 showed significant attenuation of degr anulation compared with Ado at 10 nM (31.7 +/- 2.5 vs. 11.6 +/- 1.9) and 10 0 nM (48.2 +/- 4.6 vs. 25.6 +/- 3.8), respectively, suggesting that AMP579 is more potent in inhibiting PMN activation. AMP579 reduced PMN adherence t o TNF alpha-stimulated HUVEC (fluorescent units/well) in a concentration-de pendent manner from 472 +/- 32 at 10 nM to 214 +/- 15 at 10 mu M vs. 675 +/ - 54 in the TNF alpha group. At 10 nM and 100 nM, adenosine did not attenua te PMN adherence, while it showed significant inhibition at 1 (504 +/- 45) and 10 mu M (435 +/- 50), respectively. The IC50 value (2.8 +/- 1 mu M) for AMP579 was significantly lower than that (41 +/- 8 mu M) in the Ado group. The results from the present study suggest that 1) AMP579 directly inhibit s adherence-independent superoxide radical generation and degranulation fro m activated PMNs and attenuates cell-cell interaction between PMNs and vasc ular endothelial cells by preventing damage on endothelial cells. 2) AMP579 exerts more potent protective effect compared with adenosine at a lower do se range, indicating its prospect for clinical application. (C) 2000 Wiley- Liss, Inc.