Abstract
Introduction:
Endothelium-derived endothelin (ET)-1 has been implicated in hypertension and renal disease but the mechanisms are complex and remain unclear. We have shown that tamoxifen-inducible endothelium-restricted human ET-1 overexpressing (ieET-1) mice exhibited BP rise after 3 weeks of induction in an ET type A receptor (ET
A
R)-dependent manner, in absence of renal injury. It is unknown whether long-term exposure to ET-1 overexpression results in sustained BP elevation and renal injury.
Methods:
Adult male ieET-1 and control tamoxifen-inducible endothelium-restricted Cre recombinase (ieCre) mice were treated with tamoxifen (1 mg/kg/day, SC) for 5 days and 2.5 months later were treated or not with an ET
A
R blocker, atrasentan (10 mg/kg/day, PO) for 2 weeks. Blood pressure (BP) by telemetry, renal artery flow (RAF) by ultrasonography, immune cell infiltration by flow cytometry, kidney injury molecule (KIM)-1 expression by immunofluorescence, 24h urinary albumin by ELISA and creatinine by alkaline picrate method were determined at the end of the study.
Results:
Induction of ET-1 overexpression for 3 months resulted in greater systolic BP (135±4 vs 114±2 mmHg,
P
<0.001) and reduced RAF (1.7±0.2 vs 3±0.3 mL/min,
P
<0.05). ieET-1 mice presented increased myeloid (21255±5294 vs 5146±1987 CD11b
+
cells/kidney,
P
<0.001) and myeloid-derived suppressor cells (5332±1463 vs 1126±507 CD11b
+
Gr-1
+
cells/kidney,
P
<0.01) renal infiltration associated with greater frequency of CD11b
+
(23.2±1.8 vs 7.5±1.6 % of CD45
+
cells,
P
<0.001) and non-immune renal cells (CD45
-
, 5.7±0.8 vs 3.2±0.6 % of CD45
-
cells,
P
<0.001) expressing a pro-inflammatory maker, CD36. Early renal injury was demonstrated in ieET-1 by increased KIM-1 expression in proximal tubules (4.0±0.7 vs 1.0±0.2 % of renal cortex,
P
<0.05) and unchanged albumin/creatinine ratio (327±74 vs 173±36 μg/mg, P=0.215). Atrasentan reversed or reduced all of the above except the decreased RAF (
P
<0.05).
Conclusions:
Long-term exposure to endothelial ET-1 overexpression caused sustained BP elevation and renal injury via ET
A
R.