In vivo treatment with granulocyte colony-stimulating factor does not delay apoptosis in human neutrophils by increasing the expression of the vacuolar proton ATPase.
BACKGROUND
Neutrophils die by apoptosis, and in vivo administration of granulocyte colony-stimulating factor (G-CSF) delays this apoptotic cell death. G-CSF administered in vitro correlates delayed apoptosis with upregulation of the vacuolar proton ATPase (v-ATPase). Because this enzyme requires assembly of membrane and cytosolic domains to function, we hypothesized that in vivo G-CSF would increase synthesis and assembly of v-ATPase components to delay apoptosis.


METHODS
Volunteers received G-CSF for 5 days, and each had a paired control. Neutrophils were isolated from subjects before the first and after the fifth injection. Proteins from cytosol or plasma membrane or from whole cell lysates were resolved by SDS-polyacrylamide gel electrophoresis and immunoblotted with antibody to the 33kDa v-ATPase E subunit. Densitometry quantified immunoreactivity.


RESULTS
No significant increase on the E subunit occurred between treated and control groups.


CONCLUSIONS
In vivo G-CSF does not increase the amount of v-ATPase in neutrophils. Although G-CSF in vivo delays apoptosis, the mechanism(s) by which this occurs is not known.
Zimbelman
Julie
J
Bonfils Blood Center, Department of Pediatrics, University of Colorado School of Medicine, Denver 80230, USA.
Thurman
Gail
G
Leavey
Patrick J
PJ
Ellison
Misoo C
MC
Ambruso
Daniel R
DR
D000328:Adult; D017209:Apoptosis / Q000187:drug effects; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology*; D006801:Humans; D008875:Middle Aged; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D011994:Recombinant Proteins; D025262:Vacuolar Proton-Translocating ATPases / Q000097:blood
D011994:Recombinant Proteins; D016179:Granulocyte Colony-Stimulating Factor; D025262:Vacuolar Proton-Translocating ATPases