INDUCIBLE NITRIC-OXIDE SYNTHASE (INOS) EXPRESSION IN HUMAN MONOCYTES TRIGGERED BY BETA-ENDORPHIN THROUGH AN INCREASE IN CAMP

Evidence suggesting a relationship between neuroendocrine and immune s ystems is steadily growing. We demonstrate now that inducible nitric o xide synthase (iNOS) is expressed in human peripheral blood monocytes after incubation of lymphomononuclear cells in the presence of beta-en dorphin, a neuropeptide released by the pituitary in response to menta l or physical stress or by activated lymphocytes. beta-endorphin raise d cAMP level in monocytes. The possible relationship between cAMP and iNOS expression on monocytes was investigated. Immunostaining for iNOS decreased, when besides beta-endorphin an inhibitor of protein kinase A (H-89) was added to the medium at the beginning of the incubation. The cAMP level raised by beta-endorphin was lowered by naloxone, which also reduced slightly iNOS expression. These results clearly point to the monocyte as a link between neuroendocrine and immune systems, an observation of potential relevance in our understanding of how stress and autoimmunity could be interconnected. (C) 1998 Academic Press.