Angiotensin II stimulation of granuloma macrophage phagocytosis and actin polymerization in murine schistosomiasis mansoni.

In murine schistosomiasis, components of the renin-angiotensin system are present in isolated liver granulomas. Furthermore, granuloma macrophages have receptors for angiotensin II (AII). These observations with other evidence suggest that angiotensins function in immunoregulation. Since AII can stimulate actin-myosin interactions and since macrophages have contractile proteins, it was determined whether AII could alter the phagocytic activity of granuloma macrophages. AII, at concentrations which saturate AII receptors, enhanced phagocytic activity for both unopsonized and opsonized sheep red blood cells (RBC). Using a DNase inhibitory assay, it was also shown that similar concentrations of AII stimulated intracellular actin polymerization. Cytochalasin B, which impedes actin filament interactions, inhibited AII-stimulated phagocytosis. AII analogs, with little-known agonist activity, blocked AII-stimulated actin polymerization and phagocytosis of RBC and RBC opsonized with IgG. These data support the contention that AII binds to AII receptors on the macrophage and stimulates phagocytosis possibly through polymerization of intracellular actin.