Endothelial overexpression of endothelin-1 modulates aortic, carotid, iliac and renal arterial responses in obese mice

Abstract

Endothelin-1 (ET-1) is essential for mammalian development and life, but it has also been implicated in increased cardiovascular risk under pathophysiological conditions. The aim of this study was to determine the impact of endothelial overexpression of the prepro-endothelin-1 gene on endothelium-dependent and endothelium-independent responses in the conduit and renal arteries of lean and obese mice. Obesity was induced by high-fat-diet (HFD) consumption in mice with Tie-1 promoter-driven, endothelium-specific overexpression of the prepro-endothelin-1 gene (TET) and in wild-type (WT) littermates on a C57BL/6N background. Isometric tension was measured in rings (with endothelium) of the aorta (A), carotid (CA) and iliac (IA) arteries as well as the main (MRA) and segmental renal (SRA) arteries; all experiments were conducted in the absence or presence of L-NAME and/or the COX inhibitor meclofenamate. The release of prostacyclin and thromboxane A2 was measured by ELISA. In the MRA, TET per se increased contractions to endothelin-1, but the response was decreased in SRA in response to serotonin; there were also improved relaxations to acetylcholine but not insulin in the SRA in the presence of L-NAME. HFD per se augmented the contractions to endothelin-1 (MRA) and to the thromboxane prostanoid (TP) receptor agonist U46619 (CA, MRA) as well as facilitated relaxations to isoproterenol (A). The combination of HFD and TET overexpression increased the contractions of MRA and SRA to vasoconstrictors but not in the presence of meclofenamate; this combination also augmented further relaxations to isoproterenol in the A. Contractions to endothelin-1 in the IA were prevented by endothelin-A receptor antagonist BQ-123 but only attenuated in obese mice by BQ-788. The COX-1 inhibitor FR122047 abolished the contractions of CA to acetylcholine. The release of prostacyclin during the latter condition was augmented in samples from obese TET mice and abolished by FR122047. These findings suggest that endothelial TET overexpression in lean animals has minimal effects on vascular responsiveness. However, if comorbid with obesity, endothelin-1-modulated, prostanoid-mediated renal arterial dysfunction becomes apparent.

No Protective Effect of Constitutive Activation of AMPK in Endothelial Cells on Vascular Function in Aged Obese Mice but Augmented α1-Adrenergic Contractions in Renal Arteries Reversible by Weight Loss

“…On the day of final experiments, the overnight-fasted animals were anesthetized with an intraperitoneal injection of pentobarbital sodium (70 mg/kg; Alfasan, Woerden, The Netherlands) and sacrificed by exsanguination via cardiac puncture. Blood was collected into chilled EDTA tubes, centrifuged at 2,000 rpm at 4 ° C for 20 min, and 100-µL plasma aliquots were stored at -80 ° C. Vascular tissues (carotid arteries, thoracic aortae, main and segmental renal arteries) were harvested for isometric tension recording experiments with preparations thoroughly cleaned from adherent adipose and connective tissues, and prostanoid levels in solution samples from some of these experiments were determined by ELISA as described [3,14]. …”

“…Thereby, renal arteries can serve to investigate both endothelium-dependent NO-and hyperpolarization (EDH)-mediated relaxations to acetylcholine [3,15] with up to four segmental rings from each animal. Besides endothelium-dependent NO-mediated relaxations, the murine thoracic aorta exhibits cyclooxygenase-dependent contractions at the higher concentrations of the muscarinic agonist [3,5,16]. In the mouse, such prostanoid-mediated contractions are prominent in carotid arteries [3,5,14,17].…”

“…Besides endothelium-dependent NO-mediated relaxations, the murine thoracic aorta exhibits cyclooxygenase-dependent contractions at the higher concentrations of the muscarinic agonist [3,5,16]. In the mouse, such prostanoid-mediated contractions are prominent in carotid arteries [3,5,14,17]. To test the smooth muscle responsiveness to activation of thromboxane (TP) receptors, carotid and thoracic aortic preparations were exposed to the full TP receptor agonist U46619; this was also re-examined in main renal arteries where augmented responses have been observed with obesity [3,18].…”

“…In the mouse, such prostanoid-mediated contractions are prominent in carotid arteries [3,5,14,17]. To test the smooth muscle responsiveness to activation of thromboxane (TP) receptors, carotid and thoracic aortic preparations were exposed to the full TP receptor agonist U46619; this was also re-examined in main renal arteries where augmented responses have been observed with obesity [3,18]. To ensure proper comparisons between preparations in the performed longitudinal study, each arterial ring was put individually at its optimal point of tension by stimulations with an equimolar high K + solution (60 mmol/L potassium chloride, with equimolar substitution of sodium by potassium) following each increase in passive tension.…”

“…DOI: 10.1159/000489959 relevant increases in arterial blood pressure or fasting glucose levels [3][4][5]. However, as regards life expectancy in both humans and mice [6], these and most other functional studies were carried out in arteries of relatively young subjects.…”