Regulation of macrophage-derived tumor necrosis factor production by modification of adrenergic receptor sensitivity

Catecholamines and prostaglandins are among the many diverse mediators which participate in an interactive communication between the nervous and immune systems. We have examined the response of murine peritoneal macrophages (M ø) to prostaglandin-E₂ (PGE₂) and the β-adrenergic agonist isoproterenol. In the present study we found a relationship between the response elicited by PGE₂ and a β-adrenergic agonist, which in a fashion similar to the response of PGE₂ on Møs suppresses lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF) production. It has been established that exposure of Møs to PGE₂ desensitizes the suppressive function of PGE₂. In this study, prior exposure of Møs to a β-adrenergic agonist and the effects on subsequent β-adrenergic responses, as well as the relationship to PGE₂ sensitivity was determined. Complete Freund's adjuvant-elicited Møs were incubated with or without either a β-adrenergic agonist or antagonist. All groups of cells were then extensively washed, followed by incubation with LPS (100 ng/ml) with or without graded concentrations of PGE₂ or the β-adrenergic agonist isoproterenol. Supernatants were collected to determine TNF concentrations by a fibroblast cytolytic assay, and Northern blot analysis was used to determine changes in the regulation of TNF mRNA accumulation. Both isoproterenol and PGE₂ inhibited LPS-stimulated TNF release and TNF mRNA accumulation. We have established Møs regulation of sensitivity to isoproterenol-induced suppression of TNF production. The isoproterenol concentration-effect curve was shifted to the right after pre-exposure of Mø to the β-agonist, suggesting a desensitized β-adrenergic receptor population. Further studies demonstrated that Møs pre-exposed to the β-adrenergic antagonist, ICI 118.551, washed, and then challenged with LPS show an increased sensitivity for isoproterenol-induced suppression of TNF production. In addition, a decreased sensitivity of Møs to exogenous PGE₂ was observed during the desensitization to the β-adrenergic agonist. Although concomitant addition of isoproterenol increased PGE₂-induced suppression of LPS - stimulated TNF production, Møs pre-exposed to isoproterenol (10^-+ M) demonstrated a decreased sensitivity for PGE₂-induced suppression of LPS-stimulated TNF production and TNF mRNA accumulation. Our results show that the effects observed after acute administration of a mediator may be different when Møs have been previously exposed to that or other mediators. These investigations support a role for mediators released from the nervous system to regulate the release of a cytokine needed to maintain inflammatory responses.