Abstract 636: Angiotensinogen and Megalin Interaction Contribute to Renal Angiotensin II Production and Hypercholesterolemia-induced Atherosclerosis

Objective: Hepatocyte-derived angiotensinogen (AGT) contributes to atherosclerosis through its cleavage to angiotensin II (AngII) by renin and angiotensin-converting enzyme (ACE). Molecular mechanisms of this process and the source of AngII to promote atherosclerosis are unknown. In this study, we used hepatocyte-specific AGT (hepAGT)-/- mice and megalin antisense oligonucleotides (ASO) to determine AGT and megalin interaction and their contributions to renal AngII production and atherosclerosis. Methods and Results: Immunostaining of mouse kidney sections demonstrated that AGT, renin, and ACE co-localized with megalin in proximal tubules. Hepatocyte-specific AGT deficiency diminished AGT protein and AngII production in mouse kidney and increased renal renin abundance without changes in plasma AngII concentrations. Inhibition of megalin by administering an ASO eliminated AGT and renin in proximal convoluted tubules and led to profound augmentations of their concentrations in urine, accompanied by 70% reduction of renal, but not plasma, AngII concentrations. To determine whether megalin contributes to atherosclerosis, male LDL receptor -/- mice were fed Western diet and administered two different sequences of megalin ASOs. Megalin inhibition by either ASO resulted in pronounced reductions of atherosclerosis compared to their control groups. These findings were also confirmed in female mice. LDL receptor -/- mice fed Western diet exhibited extensive vacuolization derived from enlarged lysosomes in proximal convoluted tubules. This pathological characteristic was absent in mice with either hepatocyte-specific AGT depletion or megalin inhibition. Conclusion: Our study demonstrated that megalin regulates AGT homeostasis, and AngII produced in kidney is a contributor to atherosclerosis through AGT and megalin interaction in proximal tubules.