title: Modulation of dendritic cell differentiation by colony-stimulating factor-1: role of phosphatidylinositol 3'-kinase and delayed caspase activation.
abstract: Monocytes acquire a dendritic cell (DC) phenotype when cultured with GM-CSF and IL-4. By contrast, CSF-1 is a potent inducer of monocyte-to-macrophage differentiation. Increasing evidence indicates that DC development is impaired in conditions characterized by CSF-1 overproduction, including pregnancy, trauma, and diverse malignancies. To study this, we have exposed newly established monocyte-derived DC cultures to conditions of CSF-1 excess. As a consequence, differentiation is skewed toward a unique intermediate phenotype, which we have termed DC-M. Such cells exhibit macrophage-like morphology with impaired allostimulatory capacity, altered cytokine production, and a distinctive cell surface immunophenotype. In light of the emerging role of caspase activation during macrophage differentiation, the activity of caspases 3, 8, and 9 was examined in DC and DC-M cultures. It is striking that DC-M cultures exhibit a delayed and progressive increase in activation of all three caspases, associated with depolarization of mitochondrial membrane potential. Furthermore, when DC-M cultures were supplemented with an inhibitor of caspase 8 or caspase 9, impairment of DC differentiation by CSF-1 was counteracted. To investigate upstream regulators of caspase activation in DC-M cultures, experiments were performed using inhibitors of proximal CSF-1 receptor signaling. These studies demonstrated that the PI-3K inhibitors, wortmannin and LY294002, antagonize the ability of CSF-1 to inhibit DC differentiation and to promote caspase activation. Together, these data identify a novel, PI-3K-dependent pathway by which CSF-1 directs delayed caspase activation in monocytes and thereby modulates DC differentiation.
authors.affiliation: Department of Allergy and Clinical Immunology, King's College Hospital NHS Foundation Trust, London, United Kingdom. agnes_lo@dfci.harvard.edu
authors.forename: Agnes S
authors.initials: AS
authors.lastname: Lo
authors.forename: Patricia
authors.initials: P
authors.lastname: Gorak-Stolinska
authors.forename: Véronique
authors.initials: V
authors.lastname: Bachy
authors.forename: Mohammad A
authors.initials: MA
authors.lastname: Ibrahim
authors.forename: David M
authors.initials: DM
authors.lastname: Kemeny
authors.forename: John
authors.initials: J
authors.lastname: Maher
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D018949:Antigens, CD1 / Q000378:metabolism; D020169:Caspases / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D016207:Cytokines / Q000096:biosynthesis; D003713:Dendritic Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D053222:Fas Ligand Protein / Q000378:metabolism; D006801:Humans; D016130:Immunophenotyping; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D000077191:Wortmannin; D019014:fas Receptor / Q000378:metabolism
chemical_list: D000730:Androstadienes; D018949:Antigens, CD1; C419393:CD1a antigen; D016207:Cytokines; C491901:FAS protein, human; D053222:Fas Ligand Protein; D014409:Tumor Necrosis Factor-alpha; D019014:fas Receptor; D016173:Macrophage Colony-Stimulating Factor; D019869:Phosphatidylinositol 3-Kinases; D020169:Caspases; D000077191:Wortmannin