PubMed1987
Both interleukin 3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF) induce increased histamine production by murine hemopoietic cells. Histidine-free culture conditions or addition of alpha-fluoromethylhistidine, an irreversible inhibitor of histidine decarboxylase, completely abrogate this phenomenon, indicating that increased histamine levels result from an augmentation of the rate of its synthesis. L-Histidine decarboxylase (HDC) (EC 4.1.1.22) activity is detected in normal bone marrow cell lysates. It is markedly increased following incubation of the cells with IL-3 or GM-CSF. The cells responding by the most important enhancement of HDC activity are located in the less dense layers of a discontinuous Ficoll gradient containing the majority of the hemopoietic progenitor cell types, such as colony-forming units (spleen), granulocyte-macrophage colony-forming cells, and mast cell precursors. In comparison with other HDC-containing cell populations tested, the enzymatic activity contained in these cells is particularly high after IL-3 or GM-CSF treatment and similar to the HDC levels observed in murine fetal liver. The time course of IL-3 and GM-CSF-induced HDC activation at comparable concentrations is slightly different. In response to GM-CSF, HDC activation is more rapid, with a significant enhancement after 4 hr of incubation, as compared with IL-3-induced HDC activation. Moreover, in the latter case the activation increases more progressively up to 48 hr of incubation, whereas GM-CSF-induced increase of HDC activity reaches a plateau more rapidly. In addition, maximal increase in histamine production in response to IL-3 is always higher than in response to GM-CSF. Moreover, the simultaneous presence of both factors at optimal concentration induces only a partially cumulative effect. These results suggest that IL-3 and GM-CSF induce HDC activation in two distinct ways, possibly reflecting the involvement of distinct target cells. However, both mediators act by inducing the transcription of the HDC gene and de novo synthesis of this enzyme since actinomycin D or cycloheximide abolish GM-CSF-or IL-3-induced histamine-producing cell-stimulating activity. This synthesis is independent from cell proliferation as demonstrated by the lack of effect of bone marrow cell irradiation. Finally, the observation that cholera toxin, prostaglandin E2, and N6,2'-O-dibutyryl adenosine 3',5'-cyclic monophosphate mimic the effects of IL-3 and GM-CSF on bone marrow cell HDC suggests an involvement of cyclic adenosine monophosphate in factor-induced histamine-producing cell-stimulating activity.