Expression of mitochondrial Apo2.7 molecules and caspase-3 activation in human lymphocytes treated with the ribosome-inhibiting mistletoe lectins and the cell membrane permeabilizing viscotoxins.
BACKGROUND
It is unclear whether expression of newly described mitochondrial Apo2.7 molecules (7A6 antigen) is specific for apoptosis or may also occur in necrosis.


METHODS
We incubated human lymphocytes with the apoptosis-inducing mistletoe lectin (ML) I and the cell membrane-permeabilizing viscotoxins (VT), and measured cell death-associated changes by flow cytometry.


RESULTS
In ML I-treated lymphocytes, Apo2.7 expression and caspase-3 activation was recognized within 24 h. In VT-treated cells, we observed an Apo2.7 expression with low fluorescence level, while active caspase-3 and DNA fragments (TUNEL) were not detected within 24 h. In these cells, caspase-3 activation was recognized 48 h later. As a major subset of ML-treated cells expressing Apo2.7 molecules did not activated caspase-3, while all caspase-3(+) cells did express Apo2.7, one may suggest that the caspase pathway is activated secondarily to mitochondrial events.


CONCLUSIONS
Expression of Apo2.7 is sensitive marker of cell death but may not be specific for apoptosis alone as it can be detected also in cells treated with cell membrane-permeabilizing toxins. On the other hand, this expression may be the consequence of an induction of distinct "death signals" resulting in apoptosis later on.
Büssing
A
A
Krebsforschung Herdecke, Department of Applied Immunology, University Witten/Herdecke, Communal Hospital, Herdecke, Germany. ArBuess@t-online.de
Vervecken
W
W
Wagner
M
M
Wagner
B
B
Pfüller
U
U
Schietzel
M
M
D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D002478:Cells, Cultured; D004789:Enzyme Activation; D005434:Flow Cytometry; D006801:Humans; D020287:In Situ Nick-End Labeling; D037102:Lectins / Q000494:pharmacology*; D008214:Lymphocytes / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D008565:Membrane Proteins / Q000378:metabolism*; D008854:Microscopy, Electron; D014784:Mistletoe; D037121:Plant Lectins; D028321:Plant Preparations; D010940:Plant Proteins; D010946:Plants, Medicinal; D054790:Ribosome Inactivating Proteins, Type 2; D013997:Time Factors; D014118:Toxins, Biological / Q000494:pharmacology*
D037102:Lectins; D008565:Membrane Proteins; D037121:Plant Lectins; D028321:Plant Preparations; D010940:Plant Proteins; D054790:Ribosome Inactivating Proteins, Type 2; D014118:Toxins, Biological; C102086:antigen 7A6; C488862:mistletoe lectin I; C009674:ribosome inactivating protein, Viscum; C488038:viscotoxin; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases