Tumor necrosis factor alpha is an autocrine growth regulator during macrophage differentiation.
Previous experiments have revealed the expression of tumor necrosis factor alpha (TNF-alpha) transcripts in all murine bone marrow-derived macrophage colonies isolated from days 5 through 9 of differentiation in vitro. These results implicated a role for TNF-alpha gene expression during macrophage differentiation. Antisense oligomers to the initiation region of the TNF-alpha message were used to inhibit its expression, thus allowing the role of TNF-alpha gene expression in controlling the differentiation of macrophages to be determined. Results showed that TNF-alpha regulated the proliferation of macrophages during differentiation. Cells isolated on day 3 were exclusively vulnerable to the effects of blocking TNF-alpha gene expression, displaying a 30% increase in proliferation over control cells or sense oligomer-treated cells. Thus, in the absence of TNF-alpha gene expression, cells maintained proliferation instead of undergoing terminal differentiation. Exogenous TNF-alpha was capable of rescuing day 3 antisense-treated cells, therefore maintaining normal levels of proliferation. In contrast, blocking interleukin 1 beta gene expression by antisense oligonucleotide treatment had no effect on proliferation. Addition of exogenous recombinant murine or human TNF-alpha decreased the total cell number 25-50% regardless of whether cells were grown in medium containing colony-stimulating factor 1 (CSF-1) or granulocyte-macrophage colony-stimulating factor (GM-CSF). These results suggested that exogenous TNF-alpha suppressed proliferation of early hematopoietic progenitors, whereas endogenous TNF-alpha regulated proliferation of macrophage progenitors. The number of differentiated, adherent macrophages on day 5 of differentiation in vitro was increased by TNF-alpha treatment of GM-CSF-induced macrophages but was suppressed in CSF-1-induced macrophages. These findings suggest that distinct TNF receptor expression and/or signaling is induced in differentiating macrophages stimulated with either growth factor.
Witsell
A L
AL
Department of Animal Sciences, University of Illinois, Urbana 61801.
Schook
L B
LB
D000818:Animals; D001483:Base Sequence; D001854:Bone Marrow Cells; D002454:Cell Differentiation / Q000187:drug effects* / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006133:Growth Substances / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects; D007700:Kinetics; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology*; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D011994:Recombinant Proteins / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*
D006133:Growth Substances; D009838:Oligodeoxyribonucleotides; D016376:Oligonucleotides, Antisense; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D012313:RNA; D016173:Macrophage Colony-Stimulating Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor