Background:
Circulating endothelial progenitor cells (EPCs) are reduced in hypertension that correlates inversely with its mortality, but the mechanisms are poorly understood. DOCA-salt and ET
B
receptor deficiency rats (ET
B
−/ −) have salt-sensitive hypertension, characterized by increased ET-1 and oxidative stress levels. We hypothesized that ET
A
receptor activation and ET
B
receptor deficiency reduce circulating EPCs in adult male DOCA-salt rats.
Methods and Results:
Systolic blood pressure (SBP) was higher in DOCA-salt (4-wk regimen) vs. Sham rats (199.3 ± 4.8 vs. 133.4 ± 4.6 mmHg, n =8 –15, p<.05), which was significantly reduced by in vivo treatment with ET
A
antagonist ABT-627 (5 mg/kg/d) or NADPH oxidase inhibitor apocynin (1.5 mmol/L) (167.8 ± 6.8 and 156.9 ± 16.6 mmHg, respectively). Flow cytometry showed that circulating CD34- and Flk-1-positive EPCs were significantly lower in DOCA vs. Sham rats (31.5 ± 0.2 vs. 18.3 ± 0.8% and 21.1 ± 0.9 vs. 16.3 ± 0.7%, respectively, n=7– 8, p<.05). Dil-acLDL and isolectin double-stainings also showed reduced EPCs in DOCA vs. Sham rats (4.5 ± 0.4 vs. 10.2 ± 0.3 cells/hpf, n=5–15, p<.01), which was rescued by in vivo treatment with ABT-627 (10.1 ± 1.7) or apocynin (8.9 ± 0.8). Real-time RT-PCR and fluorescence confocal microscopy showed that ET
A
and ET
B
receptor mRNA and proteins were present in EPCs of SD rats. Intracellular ROS level was increased by >50% in EPCs of DOCA vs. Sham rats (DCF fluorescence, n = 9 –11, p<.05). Apoptosis was increased by >80% in EPCs of DOCA vs. Sham rats, which was reversed by ABT-627 or apocynin (TUNEL assay, n=5– 6, p<.05). EPCs were significantly lower in ET
B
−/ − vs. ET
B
+/+ rats (6.3 ± 0.6 cells/hpf, n =7– 8), paralleled with higher SBP (telemetry 151 ± 1.2 vs. 129 ± 0.9 mmHg, n = 6), plasma ET-1 level (5.2 ± 0.3 vs. 3.6 ± 0.1 pg/ml, n = 5–12), and suppressed telomerase activity (354.6 ± 105.5 vs. 83.3 ± 26.2%, n = 3) (all p<.05). ET-1 treatment (10 nM, 48 hrs) also reduced EPCs of normal rats (6.9 ± 0.1 vs. 10.3 ± 0.3 cells/hpf, n = 5– 6, p<.05), which was rescued by ABT-627 (9.9 ± 0.3), but not by ET
B
antagonist BQ788 (7.6 ± 0.4).
Conclusion:
ET
A
activation and ET
B
deficiency reduce circulating EPCs in DOCA-salt and ET
B
−/ − rats, in part, due to NADPH oxidase-induced oxidative stress, apoptosis, and telomerase inactivation.
Effects of ACE inhibition on circulating endothelial progenitor cells, vascular damage, and oxidative stress in hypertensive patients
