Proximal tubule ACE2 mediates early responses to hypertension by regulating intrarenal RAS and sodium homeostasis.

Abstract

ACE2 is a membrane-bound monocarboxypeptidase strongly expressed in the renal proximal tubule (PT) with high affinity to degrade the vasopressor angiotensin II (AngII). We employed a mouse model of PT-specific ACE2 deletion (PT ACE2-KO) to demonstrate that the renal PT is a critical site for ACE2 regulation of blood pressure (BP) via modulation of the intrarenal renin-angiotensin system (RAS). While deletion of ACE2 from the PT had a minimal effect on baseline physiology, PT ACE2-KO mice were more susceptible to AngII hypertension than control mice. At day 5 of AngII infusion, the enhanced BP response was associated with cardiac hypertrophy, increased renal AngII levels, failure to suppress epithelial sodium channel (ENaC) γ cleavage, and increased sodium pump activity in PT ACE2-KO mice. Control mice instead increased renal ACE2 expression to reduce renal AngII accumulation and suppress intrarenal RAS activation, which offered protection from hypertension and complications. Transcriptional analysis corroborated changes in intrarenal RAS components and revealed alterations in distinct physiological pathways during AngII hypertension in PT ACE2-KO mice. Our studies provide evidence for alterations in ENaC regulation to contribute to the development of AngII hypertension and support PT-derived ACE2 as an integral member of the intrarenal RAS.