IN-VITRO INVESTIGATIONS ON IMMUNOSUPPRESS ION WITH VERAPAMIL

Aims of the Investigation: It is known that Verapamil and other calciu m channel blockers possess immunosuppressive properties. It has been s uggested that they exert their effects by antagonising protein kinase C (PKC) or calmodulin. Our aim was to investigate whether the adhesion of lymphocytes to allogenic endothelial cells and lymphocyte migratio n are impaired in the presence of Verapamil. The role of PKC and calmo dulin during expression of adhesion molecules, the expression of adhes ion molecules under the influence of Verapamil and lymphocyte motility on endothelial cell monolayers were investigated. Methods: Human endo thelial cells (EC) were obtained from umbilical chord veins and incuba ted as dissociate primary cultures. Expression of adhesion molecules o n EC was determined by quantitative immunofluorescence using the CytoF luor 2300-system. Studies on lymphocyte motility were performed by pha se contrast microscopy using video scope analysis. Results: Expression of Intercellular Adhesion Molecule 1 (ICAM-1), Vascular Cell Adhesion Molecule (VCAM-1) and Endothelial Leukocyte Adhesion Molecule I (ELAM -1) was dose-dependently reduced by the application of PKC-inhibitor H 7. Expression of ICAM-1 and VCAM-1 was also inhibited by the calmoduli n-antagonist W7. Surprisingly, neither R- nor S-Verapamil inhibited ad hesion molecule expression, we even observed significant enhancement o f ELAM-1- and ICAM-1- expression. Nevertheless, lymphocyte motility on allogenic EC monolayers was impaired in the presence of R-verapamil, the enantiomer that is inactive as a calcium channel blocker. Conclusi on: Verapamil reduces lymphocyte motility and is therefore effective i n impairing lymphocyte-endothelial cell-interactions. These effects se em to be independent of calcium channel blockade and are probably not due to inhibition of PKC or calmodulin.