SUPPRESSION OF SISTER-CHROMATID EXCHANGE-INDUCING DNA LESIONS IN CULTURED PERIPHERAL-BLOOD MONONUCLEAR-CELLS BY VISCUM-ALBUM L

Based on recently published data, Viscum album L. (VAL) provides a DNA stabilizing property which seems to be restricted to the mononuclear cells of the peripheral blood (PBMC). To further characterize the anti mutagenic properties of this drug, we investigated the frequency of si ster chromatid exchange (SCE)-inducing DNA lesions in PBMC from health y individuals and leukemic Jurkat T cells cultured for 72 hrs. in the presence of the indirect acting alkylance cyclophosphamide (CP). The a ddition of CP resulted in the induction of an apoptotic cell death in a fraction of cultured cells, while in the surviving cells the number of SCE-inducing DNA lesions severely increased. By the addition of a w hole plant extract from VAL (Helixor A), the number of CP-induced SCE significantly declined. Due to a severe depletion of cultured leukemic Jurkat T cells by the addition of CP and VAL, only 3 M2 metaphases we re detected. VAL did not protect the expression of activation-associat ed surface markers such as IL-2 receptor and transferrin receptor on c ultured B cells from patients with chronic lymphocytic leukemia and on Jurkat T cells, while it was protective in PBMC of healthy individual s. However, in the supernatants of cultured PBMC we were unable to det ect a VAL-mediated induction of protective cytokines such as IFN-alpha and IFN-beta, TNF-alpha or IL-1. Whatever the exact mechanisms are, o ur result indicate that VAL can modify the DNA damaging effect of carc inogens.