Production of nitric oxide by murine bone marrow cells: Inverse correlation with cellular proliferation

The present studies were designed to assess the ability of primary cultures of bone marrow cells to produce nitric oxide. We found that two inflammatory stimuli, IFN-γ and LPS, were potent inducers of nitric oxide production by bone marrow cells. In addition, the CSF granulocyte-macrophage (GM)-CSF and IL-3 as well as TNF-α, while inactive by themselves, were synergistic with LPS and IFN-γ in inducing nitric oxide production. Maximal effects were observed with combinations of GM-CSF and LPS. Nitric oxide production by bone marrow cells was found to be dependent on the presence of L-arginine in the culture medium and inhibitable by N(G)-monomethyl-L- arginine and L-canavanine, two nitric oxide synthase inhibitors. Nitric oxide produced by the cells was also suppressed by TGF-β1 and the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate. Separation of bone marrow cells by density gradient centrifugation and flow cytometry revealed that the granulocyte-containing fraction was largely responsible for nitric oxide production. In additional experiments we found that treatment of bone marrow cells with GM-CSF significantly stimulated bone marrow cell growth. In contrast, the combination of GM-CSF and LPS or IFN-γ markedly suppressed cellular proliferation. This suppression was completely reversed by treatment of the cells with N(G)-monomethyl-L-arginine. Taken together, these data demonstrate that various inflammatory stimuli and cytokines induce nitric oxide production by primary cultures of bone marrow cells and that this mediator may play a role in the regulation of bone marrow cell growth and development.