Abstract 131: Insulin Regulated Aminopeptidase Inhibitors are More Effective Than the ACE Inhibitor, Perindopril in Preventing Unilateral Ureteral Obstruction-Induced Renal Fibrosis in Mice

Abstract

New strategies are needed to combat pathological organ fibrosis that leads to end stage organ failure. We have identified the enzyme insulin regulated aminopeptidase (IRAP) as one such promising new target, with IRAP KO mice completely protected, and pharmacological inhibition of IRAP reversing, age-induced cardiac fibrosis. However, the effect of IRAP inhibition in renal fibrosis is unknown. Therefore the objective of this study was to: (1) compare anti-fibrotic efficacy of 2 chemically distinct IRAP inhibitors, HFI-419 and SJM4-164 to the ACE inhibitor, perindopril (PER) in a murine model of unilateral ureteral obstructive (UUO)-induced renal fibrosis; and (2) investigate role of IRAP substrates in mediating ant-fibrotic effect of IRAP inhibitors. Male C57Bl/6J mice (8 weeks old) were assigned to one of the following 7 day protocols (n=6/gp): sham, UUO+Veh, UUO+HFI (0.72mg/kg/d), UUO+SJM (0.72mg/kg/d), or UUO+PER (1mg/kg/d). IRAP substrate involvement was determined using specific receptor blockers for the oxytocin receptor (OTR; Atosiban; 0.6mg/kg/d) or the AT2 receptor (AT2R; PD123319; 10mg/kg/d). Interstitial fibrosis was significantly increased in UUO+Veh-injured kidneys compared to sham (% positive staining: UUO=5.9±0.7 vs Sham=1.2±0.3; p<0.05). HFI and SJM treatment were equally effective in preventing UUO-induced increase in interstitial renal fibrosis (% positive staining: HFI=2.5±0.3, SJM=2.8±0.3, all p<0.05 vs UUO). PER had no effect on UUO-induced increase in interstitial renal fibrosis (PER=6.6±0.7), however it was as effective as the IRAP inhibitors in reducing markers of inflammation, including NFκB activation and macrophage infiltration. The anti-fibrotic effects produced with IRAP inhibition were prevented by OTR or AT2R blockade (% positive staining: OTR=5.0±0.55, AT2R=6±0.8). Overall, this study demonstrated greater reno-protection with IRAP inhibition compared to that achieved using an ACE inhibitor, with IRAP inhibitors exhibiting potent anti-fibrotic and anti-inflammatory effects. Moreover, for the first time we show that the anti-fibrotic effects of IRAP inhibition involve activation of receptors associated with endogenous IRAP substrates.