Abstract 277: Diminazene Aceturate, an ACE2 Activator, Decreases AngII-Induced Atherosclerosis in Low-Density Lipoprotein Receptor--Deficient Mice

Abstract

Objectives: Diminazene aceturate (DIZE) activates angiotensin converting enzyme 2 (ACE2) both in vitro and in vivo. ACE2 limits angiotensin II (AngII)/angiotensin type 1 receptor (AT1R) signaling through cleavage of AngII to form angiotensin-(1-7) (Ang-(1-7)). Previous studies in our laboratory demonstrated that whole body ACE2 deficiency increased diet-induced atherosclerosis in low density lipoprotein receptor (LDLr) deficient mice. The purpose of this study was to determine if administration of DIZE to LDLr-/- mice activates ACE2 to decrease AngII-induced atherosclerosis. Materials and Methods: Initial dose ranging studies determined the effects of 7.5, 15, or 30 mg/kg/day of DIZE infused subcutaneously by osmotic minipump for 7 days into male LDLr-/- mice. DIZE dose-dependently increased plasma Ang-(1-7) concentrations with significant elevations at 30 mg/kg/day (vehicle, 5.9 ± 0.6; DIZE, 7.9 ± 0.5 ng/mL, p<0.05). Moreover, kidney ACE2 activity increased in mice administered DIZE (30 mg/kg/day) compared to vehicle-injected controls (vehicle, 208 ± 87; DIZE, 1716 ± 424 fmol/mg/min, p<0.05). For optimal dosing, ACE2 wildtype (Ace2+/y) and deficient (Ace2-/y) LDLr-/- mice were administered either vehicle or DIZE by intramuscular injection for a total of 5 weeks. Seven days after initiation of DIZE administration, mice were infused with AngII (1,000 ng/kg/min for 28 days) to induce atherosclerosis. Compared to vehicle, administration of DIZE resulted in significant reductions in atherosclerotic lesion formation in aortic arches of AngII-infused Ace2+/y , but not Ace2-/y mice (vehicle Ace2+/y, 9.8 ± 1.2; DIZE Ace2+/y, 5.8 ± 1.2; DIZE Ace2-/y, 9.2 ± 1.8, p<0.05). Interestingly, compared to vehicle, DIZE lowered serum cholesterol concentrations in Ace2+/y but not Ace2-/y mice (vehicle Ace2+/y, 837 ± 69; DIZE Ace2+/y, 571 ± 41; DIZE Ace2-/y, 774 ± 113 mg/dl, p<0.05). Conclusions: These studies demonstrate that DIZE decreased AngII-induced atherosclerosis through an ACE2-dependent mechanism. Mechanisms for DIZE-induced reductions in AngII-induced atherosclerosis may include reductions in serum cholesterol concentrations.