Abstract 394: Chronic Knockdown of the NTS AT1R Increases Circulating Inflammatory-Endothelial Progenitor Cells Ratio and Exacerbates Hypertension in the SHR

Abstract

AT1R expression is increased in the nucleus of solitary tract (NTS) of many animal models of hypertension. However, the impact of its chronic regulation on cardiovascular control is not well understood. In this study, we investigated the hypothesis that NTS AT1R is involved in peripheral inflammatory status and hypertension-linked cardiovascular pathophysiology. AAV2- mediated expression of a shRNA targeted the AT1R in the NTS has been used to test the hypothesis. First,the efficacy of the AAV2-AR1R-shRNA was established with the use of neuronal cells in primary culture. Transduction of these cultures by AAV2-AT1R-shRNA resulted in a 72% decrease in AT1R mRNA compared with the AAV2- Sc-shRNA transduced control. This was accompanied by complete attenuation of AngII-induced increase in ERK1/2 phosphorylation and neuronal action potential frequency (control: 2.2±0.4 vs. AT1R-shRNA: 0.5±0.3 hz). We then microinjected AAV2-AT1R-shRNA or control vector, AAV2-Scrambled (Sc)-shRNA into the NTS of 8-week-old SHR and WKY rats. Nine weeks following microinjection, AAV2-AT1R-shRNA group of SHRs showed a 29 mmHg increase in mean arterial pressure (MAP) (control: 154.2±4.7; shRNA: 183.0±10.2 mmHg), insignificant effects on the MAP of WKY rats was observed. The increase in MAP in the SHR by AAV2-AT1R-shRNA was associated with a 42% decrease in baroreflex bradycardia (control: 0.57±0.02; shRNA: 0.33±0.06 ms/mmHg), profound cardiac hypertrophy, and significant increase in the plasma norepinephrine (control: 6.36±0.39, shRNA: 13.0±4.13 ng/mL). In addition, AAV2-AT1R-shRNA rats showed significant increases in water intake (control: 32.5±1.5; shRNA: 12.5±2.5 ml/16h) and urine output (control: 1.6 ±0.5; shRNA: 9.3±2.5 ml/16h). Furthermore, AAV2-AT1R-shRNA treated SHR exhibited 74% decrease in circulating endothelial progenitor cells (EPC, CD90+, CD4/5/8-), and ∼300% increases in inflammatory cells (IC) including CD4/8+, T lymphocytes (CD45/3+) and macrophages (CD68+) . As a result, EPC/IC ratio was decreased by 8∼15 fold in AT1R-shRNA treated SHR. These observations suggest that increased AT1R in the NTS of SHR may present a counter-hypertensive mechanism involving inflammatory/angiogenic cells.