Abstract
Background:
The mechanisms of blood pressure (BP) regulation by endothelin (ET)-1 produced by endothelial cells are complex and remain unclear. Recently, we developed a transgenic mouse with tamoxifen-inducible endothelium-restricted human ET-1 overexpression (ieET-1) using Cre/loxP technology. ieET-1 mice exhibited BP rise after three weeks of induction in an ET type A (ET
A
) receptor-dependent manner, in absence of vascular and kidney injury. It is unknown whether long-term exposure to ET-1 overexpression results in sustained BP elevation and vascular injury.
Design and methods:
Nine to 12-week old male ieET-1 mice and control ieCre mice expressing a tamoxifen-inducible Cre recombinase under the control of endothelium-specific
Tie2
promoter, were treated with tamoxifen (1 mg/kg/day, s.c.) for 5 days and studied 3 months later. ieET-1 mice were treated or not with ET
A
receptor blocker, atrasentan (10 mg/kg/day, PO) in the last 2 weeks of the study. BP by telemetry, endothelial function and vascular remodeling by pressurized myography and reactive oxygen species (ROS) generation using dihydroethidium staining in mesenteric artery (MA) or perivascular fat (PVAT) and renal artery flow (RAF) by ultrasonography were determined.
Results:
Systolic BP was increased in ieET-1 and normalized by atrasentan compared to ieCre mice (141±0 and 124±4 vs 120±0 mm Hg,
P
<0.001). Endothelium-dependent relaxation responses to acetylcholine were impaired in ieET-1 and uncorrected by atrasentan compared to ieCre (35±4 and 32±4 vs 65±8%,
P
<0.01). Media/lumen and media cross-sectional area were unchanged, but stiffness was increased in ieET-1 and normalized by atrasentan compared to ieCre mice (strain at 140 mm Hg: 0.6±0.0 and 0.7±0.0 vs 0.7±0.0 ΔD/D,
P
<0.05). ROS generation was enhanced in PVAT of ieET-1 and normalized with atrasentan when compared to ieCre mice (1.4±0.1 and 0.9±0.1 and vs 1.0±0.1 relative fluorescence units/μm
2
,
P
<0.05). RAF was decreased in ieET-1 and unchanged by atrasentan compared with control (1.8±0.2 and 2.0±0.2 vs 3.0±0.3 mL/min,
P
<0.01).
Conclusions:
Long-term exposure to endothelial human ET-1 overexpression caused sustained BP elevation, endothelial dysfunction and vascular stiffening and oxidative stress.