The effects of heparin on the adhesion of human peripheral blood mononuclear cells to human stimulated umbilical vein endothelial cells.

1. The effects of unfractionated heparin (UH) and a selectively O-desulphated derivative of heparin (ODSH), lacking anticoagulant activity, on the adhesion of human peripheral blood mononuclear cells (HPBMNC) to human stimulated umbilical vein endothelial cells (HUVECs), were investigated. 2. For comparison, the effects of poly-L-glutamic acid (PGA), a large polyanionic molecule without sulphate groups and two different molecular weight sulphated dextrans (DS 5 k and DS 10 k) were studied. 3. UH (50 - 1000 u ml(-1)) significantly (P<0.05) inhibited the adhesion of HPBMNC to HUVECs, stimulated with IL-1beta (100 u ml(-1)), TNF-alpha (1000 u ml(-1)) or LPS (100 microg ml(-1)), when the drugs were added together with stimuli to HUVECs and coincubated for 6 h. Such effects on adhesion occurred with limited influence on expression of relevant endothelial adhesion molecules (ICAM-1 and VCAM-1). 4. UH (100 - 1000 u ml(-1)), when added to prestimulated HUVECs, significantly (P<0.05) increased adhesion of mononuclear cells to endothelium at the higher concentrations tested, without any effect on adhesion molecule expression. In contrast, the opposite effect was observed when human polymorphonuclear leucocyte adhesion was examined, under the same experimental conditions, suggesting that the observed potentiation of HPBMNC adhesion is cell specific. 5. The effects of UH on HPBMNC adhesion were shared by the non-anticoagulant ODSH (600 - 6000 microg ml(-1)) but not by sulphated dextrans or PGA (300 - 6000 microg ml(-1)). 6. Heparin affects the adhesion of HPBMNC to stimulated endothelium, in both an inhibitory and potentiating manner, effects which are unrelated to its anticoagulant activity and not solely dependent on molecular charge characteristics.