The potential role of the macrophage colony-stimulating factor, CSF-1, in inflammatory responses: characterization of macrophage cytokine gene expression

Abstract
In this report we report that recombinant human monocyte-macrophage colony-stimulating factor-1 (CSF-1) induces resident murine peritoneal cells (PCs) to transcribe several inflammatory cytokine genes, including interleukin (IL)-1α, IL-1β, IL-6, and granulocyte-macrophage CSF in a dose-dependent and time-related manner. Peak mRNA levels were seen between 4 and 6 h. CSF-1 did not modulate the expression of tumor necrosis factor-α mRNA. The serum content of the culture medium appeared to regulate both the extent of CSF-1-induced gene transcription and the adherence properties of the cells. Decreasing the serum concentration significantly reduced CSF-1-induced transcription and was associated with the rapid spreading of the majority of the adherent cells. This reduced sensitivity to CSF-1 was paralleled by a markedly lower levels of c-fms mRNA encoding the CSF-1 receptor. Induced gene transcription was followed by the release of large quantities of IL-6 only. IL-1 activity remained associated with the cells. Neither supernatant nor cell lysate granulocyte-macrophage CSF activity was inducible above the low levels associated with control cultures. Evidence that the mononuclear phagocytes, as opposed to B or T cells, were the targets of CSF-1 was obtained in two ways: (1) PCs from B6 scid/scid and NOD scid/scid mice consisting of 78–86% MAC-1+, F4/80+ cells and few B or T cells, as shown by flow cytometry analysis, released 5- to 10-fold more IL-4 in response to CSF-1 stimulation than B6 PCs, which contained 30% double-positive cells, and (2) pretreatment of B6 PCs with antibodies to the CSF-1 receptor blocked the CSF-1-induced secretion of IL-6. These data suggest that CSF-1 primes noninflammatory mononuclear phagocytes for a role in inflammatory responses but does not provide the necessary signals for either secretion or translation of all cytokines equally. J. Leukoc. Biol. 58: 99–107; 1995.

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