Abstract 448: Angiotensin-converting Enzyme In Renal Proximal Tubular Cells Does Not Affect Atherosclerosis In Male And Female Hypercholesterolemic Mice

Abstract

Objective: Angiotensin-converting enzyme (ACE) generates Angiotensin II (AngII), the bioactive angiotensin peptide that contributes to atherosclerosis. ACE is present in proximal tubular cells (PTCs), and AngII concentrations are higher in kidney than in plasma. The purpose of this study was to determine whether ACE in PTCs contributed to atherosclerosis in both male and female mice. Approach and Results: ACE f/f x Ndrg1-Cre ERT2 -/- (PTC-ACE+/+) and ACE f/f x Ndrg1-Cre ERT2+/- (PTC-ACE -/-) mice were generated by breeding female ACE floxed mice (ACE f/f) xNdrg1-Cre ERT2-/- and male ACE f/f x Ndrg1-Cre ERT2+/- transgenic mice. Both male and female littermates in an LDL receptor -/- background were used to study atherosclerosis. PTC-ACE+/+ and PTC-ACE-/- littermates were administered with of tamoxifen (150 mg/kg/day) for 5 consecutive days at the age of 4-6 weeks to ACE deletion in PTCs. Two weeks after the last injection of tamoxifen, mice were fed a Western diet for 12 weeks. Blood pressure was measured using a tail-cuff system during the study. Systolic blood pressure was not different between the two genotypes (PTC-ACE+/+ vs -/-: 124±3 vs 121±2 mmHg in male, P=0.3; and 114±3 vs 115±3 mm Hg in female, P=0.9). All mice were hypercholesterolemic, and plasma cholesterol concentrations were not different between the two genotypes (PTC-ACE +/+ vs -/-: 1524±108 vs 1680±66 mg/dl in male, P=0.2; 1175±47 vs 1210±55 mg/dl in female, P=0.6). ACE mRNA abundance measured by qPCR of ACE in kidneys was less in the PTC-ACE-/- mice (PTC-ACE +/+ vs -/-: 1.03±0.11 vs 0.33±0.04 in male, P=0.001; 1.14±0.21 vs 0.64±0.09 in female, P=0.02). In PTC-ACE-/- mice, immunostaining of ACE in kidney sections showed that ACE was deleted in S1 and S2 PTCs, but remained in S3 of the outer medulla. Atherosclerosis was measured using an en face method. PTC-ACE+/+ and PTC-ACE-/- mice had comparable atherosclerotic lesion size in the ascending and aortic arch regions (PTC-ACE+/+ vs -/-: 11.4±1.4% vs 13.4±1.7% in male, P=0.4; 14.9±2.2% vs 15.7±3.7% in female, P=1.0). Conclusion: PTC-specific ACE deficiency did not affect atherosclerosis in hypercholesterolemic mice.