Abstract 1264: Oxidative Stress Induces Endothelial Progenitor Cell Dysfunction Through the ET-1/ETA/NADPH Oxidase in Low Renin Hypertension
Introduction: The circulating endothelial progenitor cells (EPC) is reduced in hypertension that correlates inversely with its mortality, but the mechanisms are not understood. DOCA-salt hypertension has increased ET-1 level and oxidative stress, and we hypothesized that ET-1-induced oxidative stress contributes to EPC reduction.
Methods: Rat EPC, cultured in EGM-2 and double-positive for DiI-acLDL and lectin, were counted. Intracellular ROS level was assessed by DCF fluorescence microscopy. The effects of ET-1 and ROS generator LY83583 on apoptosis and telomerase activity were assayed by TUNEL and telomeric repeat amplification, respectively.
Results: EPC number was significantly reduced in DOCA-salt vs. Sham rats (3.94±0.30 vs. 10.32±0.25 cells/high power field, n=3– 6, p<0.01), which was rescued by in vivo treatment with ETA receptor antagonist ABT-627 (5 mg/kg/d, 9.42±0.92 cells/hpf) or NADPH oxidase inhibitor apocynin (1.5 mmol/L, 9.02±1.70 cells/hpf). ROS level in EPC of DOCA-salt rats was markedly higher upon treatment with LY83583 (10 μM, 18 hrs) (212.4±8.3% vs. Sham), with a concomitant increase in apoptosis (180.0±3.9% vs. Sham) that was rescued by in vivo treatment with ABT-627 or apocynin (108.1±11.82% and 108.1±5.37%, respectively, all n=3, p<0.05). The telomerase activity of EPC was blunted in DOCA-salt vs. Sham rats (6.15±3.10%, n=3, p<0.05). EPC number was also reduced in ETB receptor-deficient rats (6.27±0.58 cells/hpf), paralleled with a suppressed telomerase activity (21.11±10.61% vs. Sham, n=3– 4, p<0.05). In normal rats, in vitro treatment with ET-1 (10 nM, 48 hrs) significantly reduced EPC number (6.91±0.11 vs. 10.32±0.25 cells/hpf, n=3– 6, p<0.01), restored by ABT-627, apocynin, or adenoviral gene transfer of dominant-negative Rac1 that inhibits NADPH oxidase subunit Rac1 (9.85±0.28, 10.48±0.38, and 9.13±0.38 cells/hpf, respectively, n=3– 6, p<0.01). ET-1 also augmented ROS level (212.4±8.3% vs. Sham) and apoptosis (166.3±0.15) (n=3, p<0.05), both were blunted by ABT-627 and apocynin.
Conclusion: These results indicate that EPC in DOCA-salt hypertension exhibit reduced number and telomerase activity, increased oxidative stress and apoptosis, mediated at least in part, via an ETA-NADPH oxidase pathway.