Morphine up-regulates expression of substance P and its receptor in human blood mononuclear phagocytes and lymphocytes

In vitro and in vivo studies have indicated that there is an important rela tionship between morphine and neuropeptide substance P (SP). We therefore i nvestigated the interaction of morphine and cultured human immune cells on the expression of SP, a neuropeptide which we have recently demonstrated to be produced by human monocytes and lymphocytes. Morphine up-regulated SP p roduction in human mononuclear phagocytes and lymphocytes at both the mRNA and the protein level. In addition, morphine induced SP receptor (NK-1R) ex pression in human lymphocytes. The specific morphine receptor antagonist. ( naltrexone) blocked morphine-induced SP expression in I human mononuclear p hagocytes, supporting the concept of authentic morphine receptor-mediated r egulation. Since SP modulates neurogenic inflammation and immunologic event s, these data suggest that morphine-induced SP expression in cells of the i mmune system may be of importance in the pathogenesis of immune-mediated di seases, including neuroimmunologic diseases and AIDS. (C) 2000 Academic Pre ss.