Angiotensin II Type-2 Receptors Modulate Inflammation Through Signal Transducer and Activator of Transcription Proteins 3 Phosphorylation and TNFα Production

Angiotensin subtype-1 receptor (AT(1)R) influences inflammatory processes through enhancing signal transducer and activator of transcription proteins 3 (STAT3) signal transduction, resulting in increased tumor necrosis factor-a (TNF-alpha) production. Although angiotensin subtype-2 receptor (AT(2)R), in general, antagonizes AT(1)R-stimulated activity, it is not known if AT(2)R has any anti-inflammatory effects. In this study, we tested the hypothesis that AT(2)R activation plays an anti-inflammatory role by reducing STAT3 phosphorylation and TNF-alpha production. Changes in AT(2)R expression, TNF-alpha production, and STAT3 phosphorylation were quantified by Western blotting, Bio-Plex cytokine, and phosphoprotein cellular signaling assays in PC12W cells that express AT(2)R but not AT(1)R, in response to the AT(2)R agonist, CGP-42112 (CGP, 100 nm), or AT(2)R antagonist PD-123319 (PD, 1 mm). A 100% increase in AT2R expression in response to stimulation with its agonist CGP was observed. Further, AT(2)R activation reduced TNF-alpha production by 39% and STAT3 phosphorylation by 83%. In contrast, PD decreased AT(2)R expression by 76%, increased TNF-alpha production by 84%, and increased STAT3 phosphorylation by 67%. These findings suggest that increased AT(2)R expression may play a role in the observed decrease in inflammatory pathway activation through decreased TNF-alpha production and STAT3 signaling. Restoration of AT(2)R expression and/or its activation constitute a potentially novel therapeutic target for the management of inflammatory processes.