title: Resistance of bone marrow-derived macrophages to apoptosis is associated with the expression of X-linked inhibitor of apoptosis protein in primary cultures of bone marrow cells.
abstract: In this study we investigated the underlying mechanisms that confer resistance on mature macrophages with the use of macrophage colony-stimulating factor (M-CSF)-induced bone marrow-derived macrophages (BMDM). In the presence of M-CSF, immature precursor cells were induced to undergo proliferation and differentiation into mature macrophages in vitro with cell morphology similar to that of tissue macrophages by day 7-10. Immunoblot analyses showed that bone marrow precursors express appreciable levels of caspase-3 and caspase-9 but no or very low levels of c-fms (M-CSF receptor) and the apoptosis regulators X-linked inhibitor of apoptosis protein (XIAP), c-IAP-1, Bcl-2 and Bax. The differentiation of BMDM is associated with a steady and gradual increase in the levels of c-fms, XIAP, c-IAP-1, Bcl-2 and Bax, reaching maximal levels by day 7. However, the levels of caspase-3 and caspase-9 stayed essentially unchanged even after prolonged incubation (more than 10 days) with M-CSF. Unlike bone marrow precursor cells, mature BMDM (day 7-10) were resistant to apoptosis induced by M-CSF depletion, which includes the activation of caspase-3 and caspase-9 and the degradation of XIAP, Bcl-2 and Bax proteins in the process. Treatment of day 7 BMDM with XIAP anti-sense oligonucleotides (oligos), but not sense oligos, partly abolished their resistance to apoptosis. By using a gel-shift assay and a specific nuclear factor kappaB (NF-kappaB) inhibitor, we demonstrated that NF-kappaB activity is responsible for the up-regulation of XIAP in M-CSF-treated macrophages. In addition, treatment of starved macrophages with M-CSF induced a rapid phosphorylation of Akt kinase before the activation of NF-kappaB. Our results showed that XIAP is one of the anti-apoptotic regulators that confer resistance on mature macrophages by M-CSF.
authors.affiliation: Division of Hematology-Oncology, Department of Internal Medicine, and Barbara Ann Karmanos Cancer Institutes, Wayne State University School of Medicine, Detroit, MI 48201, U.S.A.
authors.forename: H
authors.initials: H
authors.lastname: Lin
authors.forename: C
authors.initials: C
authors.lastname: Chen
authors.forename: B D
authors.initials: BD
authors.lastname: Chen
mesh_terms: D017209:Apoptosis; D001854:Bone Marrow Cells / Q000378:metabolism / Q000502:physiology*; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002454:Cell Differentiation; D004789:Enzyme Activation; D006801:Humans; D016173:Macrophage Colony-Stimulating Factor / Q000172:deficiency / Q000494:pharmacology; D008264:Macrophages / Q000502:physiology*; D016328:NF-kappa B / Q000096:biosynthesis; D014176:Protein Biosynthesis; D011506:Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein
chemical_list: D016328:NF-kappa B; D011506:Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D016173:Macrophage Colony-Stimulating Factor; C505407:CASP3 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases