4,5-Dimethylangelicin effects on lymphocytes with and without UV-radiation

Compared to the linear derivative 8-methoxypsoralen (8-MOP) the angular structured furocoumarin 4,5'-dimethylangelicin (4,5'-DMA) causes smaller photosensitization effects (loss of viability, inhibition of phytohemagglutinin (PHA)-induced transformation rate and E-rosette formation of T-cells, respectively) on cultured human lymphocytes. When 4,5'-DMA or 8-MOP are added to the cultures without additional UV-irradiation, increased or decreased PHA-stimulation rates are observed, respectively. In addition, 4,5'-DMA is able to reduce the binding of sheep erythrocytes to lymphocytes in a higher degree than 8-MOP. These findings suggest different action mechanisms on cytoplasma membranes and intracellular structures of lymphocytes by different furocoumarins.