Colony-stimulating factor-1 (CSF-1) rescues osteoblast attachment, survival and sorting of beta-actin mRNA in the toothless (tl-osteopetrotic) mutation in the rat.
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We have shown that in the osteopetrotic rat mutation toothless (tl) osteoblasts are absent from older bone surfaces in mutants and that mutant osteoblasts in vivo lack the prominent stress fiber bundles polarized along bone surfaces in osteoblasts from normal littermates. Our recent data demonstrate that in normal osteoblasts in vitro beta- and gamma-actin mRNAs have different, characteristic intracellular distributions and that tl (mutant) osteoblasts fail to differentially sort these mRNAs. Because bone resorption and formation are highly interdependent and injections of CSF-1, a growth factor, increase bone resorption and growth in tl rats, we examined the effects of CSF-1 treatment on osteoblast survival and ultrastructure in vivo and ability to sort actin mRNAs in vitro. Neonatal CSF-1 treatment of mutants restores osteoblasts on older bone surfaces, normalizes the intracellular distribution of stress fibers in osteoblasts in vivo and promotes normal sorting of beta-actin mRNA in mutant osteoblasts in vitro without normalizing gamma-actin distribution. These data suggest the beta- and gamma-actin mRNAs in osteoblasts are sorted by different mechanisms and that the differential sorting of beta-actin mRNA is related to the characteristic polarization of stress fibers in osteoblasts and their survival on bone surfaces. This experimental system can be used to explore the relationships and regulation of these aspects of cell and tissue biology. (+info)
Induction of potent antitumor response by vaccination with tumor lysate-pulsed macrophages engineered to secrete macrophage colony-stimulating factor and interferon-gamma.
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Adoptive transfer of activated macrophages, being both effector cells and antigen-presenting cells, represents a promising approach to immunotherapy of cancer. In order to get activated macrophages with increased antitumor potential, in the present study, murine peritoneal macrophages were transduced with human macrophage colony-stimulating factor (M-CSF) and murine interferon-gamma (IFNgamma) by recombinant adenovirus infection. The results demonstrate that M-CSF and IFNgamma gene-modified macrophages exhibited higher expression of MHC-II, B7.1 and ICAM-1, increased antigen-presenting activity and cytotoxicity. It was also shown that they secreted more tumor necrosis factor, interleukin-1 and nitric oxide. In vivo experiments showed that in previously initiated murine pulmonary metastatic melanoma, tumor lysate-pulsed, M-CSF and IFNgamma gene-modified macrophages elicited more potent antitumor effects than tumor lysate pulsed M-CSF or IFNgamma gene-modified macrophages. Cytotoxic T lymphocyte (CTL) activity, IFNgamma and tumor-necrosis factor production of the splenocytes increased significantly in mice after intravenous injection of the gene-modified macrophages. M-CSF and IFNgamma gene-modified macrophages may act as activated effector and antigen-presenting cells, thus eliciting a more potent antitumor response. (+info)
Postnatal mammary gland development requires macrophages and eosinophils.
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Interactions between mammary epithelial and mesenchymal cells including fibroblasts and adipocytes are crucial for the proper postnatal development of the mammary ductal tree. Often overlooked, however, are the migrant cells that enter tissues at different stages of development. In this paper we identify two such cell types, macrophages and eosinophils, that are recruited around the growing terminal end buds (TEBs) during postnatal development. An important role for leukocytes in mammary gland ductal outgrowth is first demonstrated by depleting mice of leukocytes using sub-lethal (gamma)-irradiation. This treatment results in a curtailment of mammary gland epithelial development that is completely rescued by bone-marrow transplantation, concurrent with a restoration of macrophage and eosinophil recruitment around the growing ducts. Using mice homozygous for a null mutation in the gene for CSF1 (Csfm(op)/Csfm(op)), the major growth factor for macrophages, we show that in the absence of CSF1, the population of macrophages in mammary glands is depleted. In this mutant, the formation of TEBs, their outgrowth into the fat pad and the branching of the resultant ducts are all impaired. Similarly, by using mice homozygous for a null mutation in the gene for eotaxin, a major chemokine for local recruitment of eosinophils in tissue, we identify eotaxin as the necessary and sufficient chemokine responsible for eosinophil recruitment around TEBs. In the absence of eosinophils, mammary gland branch formation and to a lesser extent TEB formation are reduced. Our data show that CSF1-regulated macrophages, in collaboration with eotaxin-regulated eosinophils, have essential and complementary functions in regulating the branching morphogenesis of the mammary gland. (+info)
Mechanical strain inhibits expression of osteoclast differentiation factor by murine stromal cells.
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Normal dynamic loading prevents bone resorption; however, the means whereby biophysical factors reduce osteoclast activity are not understood. We show here that mechanical strain (2% at 10 cycles per minute) applied to murine marrow cultures reduced 1, 25(OH)(2)D(3)-stimulated osteoclast formation by 50%. This was preceded by decreased expression of osteoclast differentiation factor (ODF/TRANCE). RT-PCR for ODF/TRANCE revealed that ODF/TRANCE mRNA in strained cultures was 59 +/- 3% of that seen in control cultures. No significant effects on total cell count, thymidine uptake, or alkaline phosphatase activity were induced by strain. To isolate the cell targeted by strain, primary stromal cells were cultured from marrow. Mechanical strain also reduced mRNA for ODF/TRANCE to 60% that of control in these cells. In contrast, mRNA for membrane-bound macrophage colony-stimulating factor was not significantly affected. Soluble ODF ( approximately 2 ng/ml) was able to reverse the effect of strain, returning osteoclast numbers to control. Because osteoclast formation is dependent upon ODF/TRANCE expression, strain-induced reductions in this factor may contribute to the accompanying reduction in osteoclastogenesis. (+info)
Cell cycle-independent induction of D1 and D2 cyclin expression, but not cyclin-Cdk complex formation or Rb phosphorylation, by IFNgamma in macrophages.
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During G1 to S phase transition, D-type cyclins form complexes with cyclin-dependent kinases (Cdk), which in turn phosphorylate retinoblastoma gene product (Rb) and inhibit its growth-inhibitory function, leading ultimately to cell proliferation. We report here a novel finding that D1 and D2 cyclins are induced in macrophages by antiproliferative factor gamma interferon (IFNgamma). The induction appears to be transcriptional activation of the D cyclin genes, since indirect events such as IFNgamma-induced colony-stimulating factor-1 (CSF-1) autocrine stimulation, alteration of D1 and D2 mRNA stability and lipopolysaccharide contamination in commercial IFNgamma preparations play no roles. In contrast to CSF-1, IFNgamma neither induces D1-Cdk4 complex formation and Rb hyperphosphorylation nor interferes with CSF-1-stimulated D1-Cdk4 interaction and Rb phosphorylation, while it completely blocks CSF-1-stimulated cell proliferation. This study suggests that induction of D1 and D2 cyclins is not necessarily associated with cell cycle progression, and D cyclins may have cell cycle-independent functions in response to IFNgamma. (+info)
LPS induces apoptosis in macrophages mostly through the autocrine production of TNF-alpha.
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The deleterious effects of lipopolysaccharide (LPS) during endotoxic shock are associated with the secretion of tumor necrosis factor (TNF) and the production of nitric oxide (NO), both predominantly released by tissue macrophages. We analyzed the mechanism by which LPS induces apoptosis in bone marrow-derived macrophages (BMDM). LPS-induced apoptosis reached a plateau at about 6 hours of stimulation, whereas the production of NO by the inducible NO-synthase (iNOS) required between 12 and 24 hours. Furthermore, LPS-induced early apoptosis was only moderately reduced in the presence of an inhibitor of iNOS or when using macrophages from iNOS -/-mice. In contrast, early apoptosis was paralleled by the rapid secretion of TNF and was almost absent in macrophages from mice deficient for one (p55) or both (p55 and p75) TNF-receptors. During the late phase of apoptosis (12-24 hours) NO significantly contributed to the death of macrophages even in the absence of TNF-receptor signaling. NO-mediated cell death, but not apoptosis induced by TNF, correlated with the induction of p53 and Bax genes. Thus, LPS-induced apoptosis results from 2 independent mechanisms: first and predominantly, through the autocrine secretion of TNF-alpha (early apoptotic events), and second, through the production of NO (late phase of apoptosis). (Blood. 2000;95:3823-3831) (+info)
Constitutive activation of the MAPK pathway mediates v-fes-induced mitogenesis in murine macrophages.
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Fes is a nonreceptor tyrosine kinase expressed at the highest level in macrophages. We previously showed that the overexpression of c-fes in murine macrophages of the BAC-1.2F5 cell line renders these cells independent of macrophage colony-stimulating factor (MCSF) for survival and proliferation, although no direct relationship could be established between tyrosine-phosphorylated substrates of Fes- and MCSF receptor-dependent signaling and mitogenesis. In this study, we investigated whether the mitogen-activated protein kinase (MAPK) pathway is involved in the growth factor-independent growth of v-fes-overexpressing macrophages. We found a constitutively increased phosphorylation of extracellularly regulated kinase (ERK) in v-fes-overexpressing macrophages as compared with mock-infected cells. This finding was associated with activation of mitogen/extracellular signal-regulated kinase (MEK) and with constitutive localization of ERK in the nucleus. Treatment of v-fes-overexpressing cells with the MEK-specific inhibitor PD98059 markedly reduced cell growth, hyperphosphorylation, and nuclear localization of ERK, indicating that the MAPK pathway mediates the mitogenic effect of v-fes. (Blood. 2000;95:3959-3963) (+info)
Involvement of p38 mitogen-activated protein kinase signaling pathway in osteoclastogenesis mediated by receptor activator of NF-kappa B ligand (RANKL).
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The receptor activator of NF-kappaB ligand (RANKL) induces osteoclast differentiation from bone marrow cells in the presence of macrophage colony-stimulating factor. We found that treatment of bone marrow cells with SB203580 inhibited osteoclast differentiation via inhibition of the RANKL-mediated signaling pathway. To elucidate the role of p38 mitogen-activated protein (MAP) kinase pathway in osteoclastogenesis, we employed RAW264 cells which could differentiate into osteoclast-like cells following treatment with RANKL. In a dose-dependent manner, SB203580 but not PD98059, inhibited RANKL-induced differentiation. Among three MAP kinase families tested, this inhibition profile coincided only with the activation of p38 MAP kinase. Expression in RAW264 cells of the dominant negative form of either p38alpha MAP kinase or MAP kinase kinase (MKK) 6 significantly inhibited RANKL-induced differentiation of the cells. These results indicate that activation of the p38 MAP kinase pathway plays an important role in RANKL-induced osteoclast differentiation of precursor bone marrow cells. (+info)