Generation of reactive oxygen intermediates (ROI) by the thionins from Viscum album L.
BACKGROUND
Extracts from Viscum album L. are widely used as an adjuvant in complementary cancer therapy. While the mechanisms of mistletoe lectin (ML) cytotoxicity are well described, the viscotoxin (VT) effects are unclear at present. Thus, we treated human lymphocytes with VT and measured cell death-associated changes by flow cytometry.


RESULTS
Treatment of lymphocytes with VT for 2 hours resulted in the binding of Annexin-V, permeabilisation of cell membranes, and generation of ROI. Apart from interindividual differences in response to VT, the number of intracellulary Bcl-2 proteins increased only marginally. The VT A1, A2, A3 and 1-PS were similar in their ROI-inducing potencies, while other cationic and/or amphipathic substances such protamine sulfate, VT B, purothionin or wasp venom peptides mastoparan I and II were less effective. However, the cytotoxic properties of VT-rich whole plant extracts from mistletoe grown on different host trees (Iscador), correlated with the content of ML rather than VT.


CONCLUSIONS
Permeabilisation of lymphocytes cell membranes by VT was associated with generation of ROI within 2 hours indicating accidental cell death. VT cannot be ignored any longer as they posses both immunomodulating and cytotoxic properties, which both might be of clinical relevance.
Büssing
A
A
Department of Applied Immunology, University Witten/Herdecke, Communal Hospital Herdecke, Germany. ArBuess@t-online.dt
Schaller
G
G
Pfüller
U
U
D023181:Antimicrobial Cationic Peptides; D002463:Cell Membrane Permeability; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D000529:Complementary Therapies; D005434:Flow Cytometry; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D008214:Lymphocytes / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D014784:Mistletoe; D010455:Peptides; D008517:Phytotherapy; D028321:Plant Preparations; D010940:Plant Proteins / Q000494:pharmacology*; D010946:Plants, Medicinal; D011479:Protamines / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D017382:Reactive Oxygen Species / Q000378:metabolism*; D054790:Ribosome Inactivating Proteins, Type 2; D014118:Toxins, Biological / Q000494:pharmacology; D014197:Trees; D014862:Wasp Venoms / Q000494:pharmacology
D023181:Antimicrobial Cationic Peptides; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D028321:Plant Preparations; D010940:Plant Proteins; D011479:Protamines; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D054790:Ribosome Inactivating Proteins, Type 2; D014118:Toxins, Biological; D014862:Wasp Venoms; C009674:ribosome inactivating protein, Viscum; C037500:mastoparan; C016085:purothionin; C488038:viscotoxin