Adhesion of neutrophils to cultured human endothelial cells is enhanced bystimulation of adenosine A(1)-receptors

Adenosine exerts a variety of partly divergent effects during postischemic reperfusion. Since the intravascular retention of neutrophils (PMN) is a cr ucial step in the development of organ reperfusion injury, we tested whethe r stimulation of human endothelial adenosine A(1)-receptors enhances adhesi on of PMN, as described previously for guinea pig coronary and feline coron ary and pulmonary endothelium. Cultured human umbilical vein endothelial ce lls (HUVECs) were stimulated with different concentrations (0.01-10 mu M) o f the A(1)-receptor agonist N-6-cyclopentyladenosine (CPA), thrombin (1U/ml ) serving as control stimulus. Adhesion of isolated human PMN on HUVECs was studied by photometrically determining the amount of the phagocyte-specifi c enzyme myeloperoxidase in culture plate lysates alter sedimentation of PM N and removal of nonadherent PMN. The expression of CD11b, a PMN adhesion m olecule and activation marker, was measured flow cytometrically on nonadher ent PMN. The presence of the endothelial adhesion molecule P-selectin was a lso quantified by flow cytometry. Adhesion rose concentration-dependently a fter stimulation with CPA, reaching a maximum (55% increase vs, control) at 1 mu M, then declining to 18% below control at 10 mu M. Thrombin increased adhesion by 69%. CD11b on neutrophils rose after contact with the supernat ant of stimulated endothelial cells, with a maximum increase of 136% at 1 m u M CPA (thrombin: + 54%). P-selectin was upregulated on HUVECs upon stimul ation: 25, 46, 159, and 29%, respectively, for 0.01, 0.1, 1, and 10 mu M CP A (thrombin: 73%). Thus, activation of human endothelial adenosine Al-recep tors, e.g., by CPA, causes increased adhesion and activation of PMN, and en hances expression of endothelial P-selectin. CPA partially reverses its pro inflammatory actions due to a loss of specificity at high concentrations (1 0 mu M). Drug Dev. Res. 35:350-355, 1998. (C) 1998 Wiley-Liss, Inc.