Endothelin-1 enhances neutrophil adhesion to human coronary artery endothelial cells: role of ETA receptors and platelet-activating factor

1 The potent coronary vasoconstrictor, endothelin-l (ET-1) may also regulat e neutrophil traffic into tissues. The aim of the present study was to char acterize the endothelin receptors responsible and to investigate the underl ying mechanisms. 2 ET-1 (1 nM-1 mu M) markedly enhanced attachment of human neutrophils to l ipopolysaccharide-, and to a lesser extent, to ET-l-activated human coronar y artery endothelial cells (HCAEC). This can partially be blocked by monocl onal antibodies against E-selectin, L-selectin or CD18, whereas combination of the three antibodies inhibited adhesion by similar to 83%. Increases in neutrophil adhesion evoked by ET-1 were also blocked by the platelet-activ ating factor (PAF) antagonists, BN 52021 (50 mu M) and WEB 2086 (10 mu M). 3 ET-I downregulated the expression of L-selectin and upregulated expressio n of CD11b/CD18 and CD45 on the neutrophil surface and induced gelatinase r elease with EC50 values of similar to 2 nM. These actions of ET-1 were almo st completely prevented by the ETA receptor antagonist FR 139317 (1 mu M) a nd the ETA/ETB receptor antagonist bosentan (10 mu M), whereas the ETB rece ptor antagonist BQ 788 (1 mu M) had no effect. ET-1 slightly increased the expression of E-selectin and ICAM-1 on HCAEC, that was prevented by BQ 788, but not by FR 139317. 4 Receptor binding studies indicated the presence of ETB receptors (K-D: 40 pM) on phosphoramidon-treated HCAEC and the predominant expression of ETA receptors (K-D: 38 pM) on neutrophils. 5 These results indicate that promotion by ET-1 of neutrophil adhesion to H CAEC is predominantly mediated through activation of ETA receptors on neutr ophils and subsequent generation of PAF.