Abstract 1151: Delivery of Angiotensin II Type 2 Receptor cDNA with Adeno-Associated Virus Type 2 by Intravenous Route Decreases Atherosclerosis in the LDLR Knockout Mice Fed with High Cholesterol Diet
Background: Angiotensin II (Ang II) type 1 receptor (AT1R) is upregulated in atherosclerosis and plays a major role in its genesis in both animals and humans. Since Ang II type 2 receptor (AT2R) counter-regulates the activity of AT1R (oxidant stress and pro-inflammatory pathways), we hypothesized that AT2R delivery (upregulation) may inhibit atherogenesis. This study was performed to examine this hypothesis.
Methods: We studied 4 groups of mice, wild-type C57BL/6J mice, LDLR KO mice, LDLR KO mice given AT2R cDNA with adeno-associated virus (AAV2), and LDLR KO mice given AAV2/Neo (n=10–12 mice in each group). AAV2/AT2R and AAV/Neo were given by tail vein injection at 8 –10 weeks of age. All animals were fed with high cholesterol diet (4% cholesterol in vegetable oil) for 18 weeks. Extent of atherosclerosis was determined by Sudan IV staining of the aorta as well as by cross-section analysis of aortic sections.
Results: Plasma LDL levels were markedly and similarly elevated in all LDLR KO mice. AT2R upregulation in the AAV2/AT2R-treated mice was confirmed by semi-quantitative RT-PCR. AT2R mRNA was upregulated (P2 fold) in all LDLR KO mice and was unaffected by AT2R treatment. Atherosclerosis covered 61±2% of the aorta in the LDLR KO mice, and 31±2% of the aorta of LDLR KO mice given AAV/AT2R (P<0.001 vs. LDLR KO mice). Treatment with AAV2/Neo did not affect the extent of atherosclerosis (51±4%), indicating that AAV2 by itself did not affect atherogenesis. Expression of P67 phox NADPH oxidase and NF-κB was upregulated in the LDLR KO mice (P<0.01 vs. wild-type C57BL/6J mice) and reduced by AAV2/AT2R treatment (P<0.02).
Conclusion: These data show that AT2R cDNA delivered with AAV2 results in sustained AT2R over-expression in the mice. Further, AT2R upregulation can limit oxidant stress and atherogenesis, independent of alterations in AT1R expression.