Effects of mistletoe lectin I on human blood cell lines and peripheral blood cells. Cytotoxicity, apoptosis and induction of cytokines.
The effects of mistletoe lectin I (ML I) on the human T-cell leukemia line MOLT-4, the monocytic line THP-1 and on human peripheral blood mononuclear cells (PBMC) were investigated with regard to general cell viability and induction of apoptosis. Using a sensitive serum-free cytotoxicity assay, the time- and concentration-dependent direct toxicity towards MOLT-4 cells was determined with IC50-values ranging from 20-40 pg/ml (300-600 fmol/l). Investigations on the time course of the toxic effect using selected concentrations of ML I revealed distinct response curves for concentrations of high, low and intermediate toxicity, respectively. The ratio of apoptotic to viable MOLT-4 cells was determined after treatment with ML I for 24 h. Apoptosis and cytotoxicity were correlated at low and intermediate concentrations, whereas at long intervals and high concentrations of ML I mostly necrotic effects were observed. The data showed that in the concentration range of low cytotoxicity ML I-induced cell death is quantitatively due to apoptotic processes. The immunomodulatory activity of ML I was investigated in vitro by measuring cytokine release. At concentrations of low cytotoxicity ML I showed immunostimulatory activity on PBMC and THP-1. RT-PCR with THP-1 cells confirmed that cytokine induction by ML I is regulated on the transcriptional level. These findings suggest that in the blood cells investigated both apoptosis and cellular signalling are induced by the same concentration range of ML I.
Möckel
B
B
BRAIN GmbH, Zwingenberg, Germany.
Schwarz
T
T
Zinke
H
H
Eck
J
J
Langer
M
M
Lentzen
H
H
D017209:Apoptosis / Q000187:drug effects*; D001773:Blood Cells / Q000187:drug effects* / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D016207:Cytokines / Q000096:biosynthesis*; D053938:DNA Fragmentation / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D037102:Lectins; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism; D028321:Plant Preparations; D010940:Plant Proteins; D016133:Polymerase Chain Reaction; D054790:Ribosome Inactivating Proteins, Type 2; D014118:Toxins, Biological / Q000494:pharmacology*
D016207:Cytokines; D037102:Lectins; D028321:Plant Preparations; D010940:Plant Proteins; D054790:Ribosome Inactivating Proteins, Type 2; D014118:Toxins, Biological; C488862:mistletoe lectin I; C009674:ribosome inactivating protein, Viscum