Role of glucocorticoid on interleukin-6-induced cellular functions in the mouse macrophage cell line (Mm 1)

To discover a role of glucocorticoid on interleukin-6 (IL-6)-induced responses of a macrophage, we investigated the effect of IL-6 and/or dexamethasone (Dex) on cellular functions of a mouse macrophage cell line (Mm1 cells). The results obtained were as follows. (1) Dex decreased the accumulation of tumor necrosis factor-alpha induced by IL-6, whereas nitric oxide production was enhanced by Dex. Moreover, the enhancement of nitric oxide production could be demonstrated to be associated with stimulation of iNOS mRNA expression by the Dex treatment. (2) Cytotoxic activity of Mm1 cells on mouse B16 melanoma cells was much more enhanced by the co-treatment of IL-6 with Dex than IL-6 treatment alone. (3) Dex promoted further the suppression of proliferation induced by IL-6. (4) DNA fragmentation, introduced by the treatment of cells with IL-6, was further enhanced in the presence of Dex.