Originally Published June 22, 2023:
Authors: , , , , , , , , , , ,
Abstract
Background: Angiotensinogen (AGT) is an essential component in the renin-angiotensin system. AGT has highly conserved sequences in the loop and 尾-sheet regions among species; however, their functions have not been studied.
Methods: Adeno-associated viral vector (AAV) serotype 2/8 encoding mouse AGT with mutations of conserved sequences in the loop (AAV.loop-Mut), 尾-sheet (AAV.尾sheet-Mut), or both regions (AAV.loop/尾sheet-Mut) was injected into male hepatocyte-specific AGT-deficient (hepAGT-/-) mice in an LDL (low-density lipoprotein) receptor-deficient background. AAV containing mouse wild-type AGT (AAV.mAGT) or a null vector (AAV.null) were used as controls. Two weeks after AAV administration, all mice were fed a western diet for 12 weeks. To determine how AGT secretion is regulated in hepatocytes, AAVs containing the above mutations were transducted into HepG2 cells.
Results: In hepAGT-/- mice infected with AAV.loop-Mut or 尾sheet-Mut, plasma AGT concentrations, systolic blood pressure, and atherosclerosis were comparable to those in AAV.mAGT-infected mice. Interestingly, plasma AGT concentrations, systolic blood pressure, and atherosclerotic lesion size in hepAGT-/- mice infected with AAV.loop/尾sheet-Mut were not different from mice infected with AAV.null. In contrast, hepatic Agt mRNA abundance was elevated to a comparable magnitude as AAV.mAGT-infected mice. Immunostaining showed that AGT protein was accumulated in hepatocytes of mice infected with AAV.loop/尾sheet-Mut or HepG2 cells transducted with AAV.loop/尾sheet-Mut. Accumulated AGT was not located in the endoplasmic reticulum.
Conclusions: The conserved sequences in either the loop or 尾-sheet region individually have no effect on AGT regulation, but the conserved sequences in both regions synergistically contribute to the secretion of AGT from hepatocytes.