β-Adrenergic regulation of renin expression in differentiated U-937 monocytic cells

Previous studies from our laboratories demonstrated that human decidual macrophages and peripheral mononuclear cells express renin. In the present study, we found that U-937 monocytes, induced to differentiate into macrophage-like cells by treatment with phorbol dibutyrate (PDBU), express renin mRNA and release renin (95%, of which is in the form of prorenin). Treatment of these PDBU-exposed cells with dibutyryl-cAMP (1 mM) caused a 20-fold increase in renin mRNA and a 10-fold increase in prorenin release. Forskolin (10 microM), an activator of adenylyl cyclase, and terbutaline (100 microM), a beta2-adrenergic agonist known to increase cAMP levels, also increased renin mRNA and prorenin release. The secretory response to terbutaline was potentiated by the type IV cyclic AMP-phosphodiesterase (PDE) inhibitor Ro 20-1724 (50 microM). Angiotensin II agonist inhibited the stimulatory effect of terbutaline on renin secretion as did the cytokines tumor necrosis factor-alpha and lipopolysaccharide plus interferon-gamma. Since other studies have shown that U-937 cells possess beta2-adrenergic receptors and express mainly the type IV PDE, the present findings strongly suggest that beta-adrenergic receptors in mononuclear cells are coupled to renin expression via the cAMP transduction pathway. The results support a possible role for the renin-angiotensin system in macrophage function and suggest potential autocrine regulatory mechanisms in prorenin expression.