Chronic propranolol treatment affects expression of adrenoceptors on peritoneal macrophages and their ability to produce hydrogen peroxide and nitric oxide

Using both immunocytochemical and flow cytometric analyses of rat peritoneal exudate cells constitutive expression of tyrosine hydroxylase and both β2- and α1- adrenoceptors on macrophages was revealed. Furthermore, according to the characteristic assemblage of tyrosine hydroxylase and adrenoceptor subtype expression different macrophage subsets were identified. In vitro treatment of macrophages with the non-selective α,β-adrenoceptor agonist arterenol and/or the β-adrenoceptor antagonist propranolol indicated that β-adrenoceptors potentiated nitric oxide (NO) production and suggested α-adrenoceptor-mediated suppression of hydrogen peroxide (H2O2) production. An increase in H2O2 production in the presence of the α1-adrenoceptor antagonist ebrantil provided support for this. Chronic propranolol treatment in vivo led to increased NO and H2O2 production by peritoneal macrophages. Furthermore, this treatment resulted in opposing effects on the expression of β2- and α1-adrenoceptors on peritoneal macrophages (a stimulatory effect on β2-adrenoceptors and a suppressive effect on α1-adrenoceptors). In conclusion, a subset of resident peritoneal macrophages synthesizes catecholamines, which may exert differential effects on H2O2 and NO production via distinct adrenoceptors. Finally, chronic propranolol treatment affected adrenoceptor expression on peritoneal macrophages and altered their capacity to generate NO and H2O2.