Augmenting effect of methionine-enkephalin on interleukin-6 production by cytokine-stimulated murine macrophages

The effects of methionine-enkephalin on the production of interleukin-6 by activated peritoneal murine macrophages were studied. Macrophage were activ ated with interleukin-1 beta or interferon-gamma in the presence or absence of graded concentrations of methionine-enkephalin. Methionine-enkephalin c ombined with interleukin-lp or interferon-gamma caused an increase in IL-6 release from cultured macrophages. The opioid receptor antagonist naloxone did not change the stimulatory effect of methionine-enkephalin on IL-6 prod uction by stimulated macrophages. Methionine-enkephalin added to the cultur e medium of resting macrophages increased IL-6 release from macrophages whi ch were later induced with interleukin-1 beta or interferon-gamma. The resu lts of this study suggest that methionine-enkephalin can modulate the proin flammatory cytokine response by controlling, via non-opioid receptor mechan ism, the production of IL-6. (C) 2000 Harcourt Publishers Ltd.