In vivo activity of a phospholipase C inhibitor, 1-(6-((17β-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122), in acute and chronic inflammatory reactions

To investigate the role of phospholipase C (PLC) in inflammatory processes, we tested 1-(6-((17beta-3-methoxyestra-1,3,5(10-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122), a widely used PLC inhibitor, in several in vitro and in vivo assays. We first examined the effects of U73122 significantly inhibited recombinant human PLC-beta2, with an IC50 of similar to6 muM. U73122 had little effect on PLC-beta1, PLC-beta3, or PLC-beta4. Consistent with its ability to inhibit PLC-beta2 enzymatic activity, U73122 reduced interleukin-8 and leukotriene B-4-induced Ca2+ flux and chemotaxis in human neutrophils in a concentration-dependent manner. In vivo, U73122 blocked carrageenan-induced hind paw edema in rats, carrageenan-induced macrophage and lymphocyte accumulation into subcutaneous chambers in dogs, lipopolysaccharide-induced macrophage, lymphocyte infiltration and prostaglandin E-2 production in a mouse peritonitis model, and 12-O-tetradecanoyl-phorbal-13-acetate-induced ear edema in mice. These results implicate PLC-dependent signaling pathways in the development of acute and chronic inflammatory responses in vivo.