Neuropharmacology and analgesiaComparative functional properties of two structurally similar selective nonpeptide drug-like ligands for the angiotensin II type-2 (AT2) receptor. Effects on neurite outgrowth in NG108-15 cells

There is increasing evidence that angiotensin II (Ang II), through binding to the type 2 (AT2) receptor may have beneficial effects in various physiological and pathological situations. However, specific action presumably mediated by the angiotensin AT2 receptor has been hampered by the absence of appropriate selective ligands. The aim of this study was to compare the biological properties of two related and selective drug-like nonpeptide AT2 ligands, namely an agonist called M024 (also known as Compound 21) and a new ligand, presumably an antagonist, C38/M132, (originally called C38). Properties of the compounds were investigated in NG108-15 cells expressing angiotensin AT2 receptor and known to develop neurite outgrowth upon Ang II stimulation. NG108-15 cells stimulated for three days with C21/M024 (0.1 or 100 nM) exhibited the same neurite outgrowth as cells stimulated with Ang II (100 nM) while co-incubation of Ang II or C21/M024 with C38/M132 (10 or 100 nM) inhibited their effects, similarly to the angiotensin AT2 receptor antagonist, PD123319 (10 μM). As Ang II, C21/M024 induced a Rap1-dependent activation of p42/p44mapk whereas preincubation of cells with C38/M132 inhibited p42/p44mapk and Rap1 activation induced by Ang II. Three-day treatment with C21/M024 or Ang II decreased cell number in culture, an effect that was rescued by preincubation with C38/M132. Taken together, these results indicate that the nonpeptide ligand C21/M024 is a potent angiotensin AT2 receptor agonist while C38/M132 acts as an antagonist. These selective nonpeptide angiotensin AT2 ligands may represent unique and long-awaited tools for the pursuit of in vivo studies.