title: Analysis of the synergistic stimulation of mouse macrophage proliferation by macrophage colony-stimulating factor (CSF-1) and tumor necrosis factor alpha (TNF-alpha).
abstract: Tumor necrosis factor alpha (TNF-alpha) more than doubles tritiated thymidine ([3H]TdR) uptake in mouse macrophages stimulated by macrophage colony-stimulating factor (CSF-1). However, nothing is known of how TNF-alpha affects this increase or even whether it is manifested by increased cellular proliferation. Here we characterize the effects of TNF-alpha on CSF-1-stimulated proliferation of both primary cells (bone marrow-derived macrophages, BMMs) and a cloned growth factor-dependent macrophage cell line (S1). We show that the TNF-alpha-induced increase in [3H]TdR uptake of CSF-1-stimulated macrophages is directly proportional to an increase in the DNA content of the culture and that the effects of TNF-alpha are direct and independent of cell number. TNF-alpha decreases the population doubling time of log-phase growing macrophages having quite different growth rates to the same (approximately 30%) extent: the doubling time of BMMs decreases from 24 to 17 h and that of S1 cells from 17 to 13 h. TNF-alpha exerts its effects on log-phase growth by increasing to the same proportion CSF-1-stimulated proliferation at all concentrations of CSF-1; that is, TNF-alpha does not shift, but rather amplifies, the CSF-1 dose-response curve. Although TNF-alpha alone does not stimulate macrophage proliferation, its presence in S1 cell cultures coming to quiescence after withdrawal of CSF-1 greatly increases subsequent CSF-1-stimulated [3H]TdR uptake as the cells reenter the cycle. Finally, we show that both human and mouse TNF-alpha increase CSF-1-stimulated log-phase growth and reentry of quiescent cells into the cycle equally on a molar basis (half-maximal stimulation of approximately 0.3 nM). The latter observation argues that the growth-stimulatory effects of TNF-alpha are mediated via the 55-60-kd TNF receptor. We conclude that TNF-alpha acts directly on growth-competent macrophages to decrease significantly the population doubling time in a manner that enhances the mitogenic effects of CSF-1.
authors.affiliation: Department of Immunology, University of Alberta, Edmonton, Canada.
authors.forename: L J
authors.initials: LJ
authors.lastname: Guilbert
authors.forename: B
authors.initials: B
authors.lastname: Winkler-Lowen
authors.forename: A
authors.initials: A
authors.lastname: Smith
authors.forename: D R
authors.initials: DR
authors.lastname: Branch
authors.forename: M
authors.initials: M
authors.lastname: Garcia-Lloret
mesh_terms: D000818:Animals; D002452:Cell Count; D002453:Cell Cycle / Q000502:physiology; D002455:Cell Division / Q000187:drug effects; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D004357:Drug Synergism; D005260:Female; D006133:Growth Substances / Q000494:pharmacology / Q000502:physiology; D006801:Humans; D007700:Kinetics; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D008264:Macrophages / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H; D008934:Mitogens / Q000494:pharmacology; D013268:Stimulation, Chemical; D013936:Thymidine / Q000378:metabolism / Q000493:pharmacokinetics; D014316:Tritium; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000494:pharmacology*
chemical_list: D006133:Growth Substances; D008934:Mitogens; D014409:Tumor Necrosis Factor-alpha; D014316:Tritium; D016173:Macrophage Colony-Stimulating Factor; D004247:DNA; D013936:Thymidine