Delayed differentiation of HL-60 cells following exposure to hypoxia.
OBJECTIVE
Hemorrhagic shock and hypoxia have been shown to alter immune and hematopoietic functions. Cellular hypoxia is thought to be the primary defect and has been shown to induce a variety of biological alterations. In this study, we examined if this defect is at the stage of terminal differentiation with the myelomonocytic cell line HL-60.


METHODS
After hypoxia, HL-60 cells were induced with 1.25% dimethyl sulfoxide (DMSO) to differentiate toward neutrophils (PMN). The ability to differentiate was evaluated by nitroblue tetrazolium staining. The function of the differentiated cells was determined by intracellular calcium levels after exposure to different chemotactic factors, and levels of Id-2 mRNA, a factor associated with terminal differentiation of myeloid cells, were assessed with Northern analysis.


RESULTS
At 48 h following exposure to hypoxia, HL-60 differentiation was significantly blunted (hypoxia 51 +/- 1%, normoxia 69 +/- 1%; P < 0.001). Intracellular calcium levels in DMSO-treated cells stimulated with 1 microM bacterial tripeptide, fMLP, were significantly reduced in the hypoxic cells (381 +/- 11 nM vs 449 +/- 10 nM; P < 0.01). No difference was noted for two other chemotactic factors, C5a and platelet-activating factor. Using Northern analysis to determine the levels of Id-2 mRNA, we demonstrated that hypoxia reduced the levels by 20% over normoxic cells.


CONCLUSIONS
This study demonstrates that hypoxia blunts the differentiation of HL-60 cells to PMN. This altered function of hypoxia appears to be reversible since hypoxia prolonged the time for HL-60 cells to differentiate and this may be partly explained by the premature downregulation of Id-2 expression.
Song
Xiaosong
X
Department of Medicine, University of Medicine and Dentistry of New Jersey--New Jersey Medical School, Newark, 07103, USA.
Mohr
Alicia M
AM
Rameshwar
Pranela
P
Anjaria
Devashish
D
Fekete
Zoltan
Z
Hauser
Carl J
CJ
Livingston
David H
DH
D001692:Biological Transport; D002118:Calcium / Q000378:metabolism; D002454:Cell Differentiation; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D018922:HL-60 Cells / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D000860:Hypoxia / Q000473:pathology* / Q000503:physiopathology*; D007202:Indicators and Reagents; D051797:Inhibitor of Differentiation Protein 2; D009580:Nitroblue Tetrazolium; D012333:RNA, Messenger / Q000378:metabolism; D012016:Reference Values; D012097:Repressor Proteins; D013194:Staining and Labeling; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D004268:DNA-Binding Proteins; C497450:ID2 protein, human; D007202:Indicators and Reagents; D051797:Inhibitor of Differentiation Protein 2; D012333:RNA, Messenger; D012097:Repressor Proteins; D014157:Transcription Factors; D009580:Nitroblue Tetrazolium; D002118:Calcium