Abstract 603: Sequences Proximate to the Renin Cleavage Site in Angiotensinogen Do Not Affect Angiotensin II-mediated Functions

Abstract

Objective: Angiotensinogen (AGT) cleavage by renin is the rate limiting step to produce angiotensin (Ang)II, a critical contributor to hypertension and atherosclerosis. Human AGT can not be cleaved by mouse renin as demonstrated by a transgenic mouse model expressing human AGT. Amino acids at positions 11 and 12, adjacent to the renin cleavage site in AGT, have been proposed to regulate renin cleavage between human and mouse. This study determined whether these two residues affect renin cleavage and the consequent AngII-mediated functions. Methods and Results: Hepatocyte-specific AGT deficient (hepAGT-/-) mice have low plasma AGT but high renin concentrations. This mouse model injected with adeno-associated viral vectors (AAV) encoding AGT was used to repopulate AGT. We first determined whether repopulation of human AGT using AAV recapitulate phenotypes of human AGT transgenic mice. HepAGT-/- mice were injected with AAV having a null insert or encoding human AGT, while wild type littermates (hepAGT+/+) were injected with the null AAV. Administration of AAV encoding human AGT led to high plasma human AGT concentrations without affecting plasma mouse renin concentrations, and had no effect on blood pressure and atherosclerosis. In a subsequent study, AAV encoding mutated mouse AGT with Leu11Val and Tyr12Ile that were same as the two residues in human were injected into hepAGT-/- mice. Repopulation of the mutated mouse AGT resulted in increased plasma mouse AGT concentrations and reduced renin concentrations that were comparable to their concentrations in hepAGT+/+ mice injected with the null AAV. Consequently, AAV-driven expression of mutated mouse AGT increased blood pressure and atherosclerosis in hepAGT-/- mice that were comparable to their magnitudes in hepAGT+/+ mice injected with the null AAV. Conclusion: The two amino acids proximate to renin cleavage site do not affect AngII-mediated effects.