Lack of endothelial nitric oxide synthase promotes endothelin-induced hypertension: lessons from endothelin-1 transgenic/endothelial nitric oxide synthase knockout mice

J Am Soc Nephrol. 2007 Mar;18(3):730-40. doi: 10.1681/ASN.2006050541. Epub 2007 Feb 7.

Abstract

Endothelin-1 (ET-1) is one of the most potent biologic vasoconstrictors. Nevertheless, transgenic mice that overexpress ET-1 exhibit normal BP. It was hypothesized that vascular effects of ET-1 may be antagonized by an increase of the endothelial counterpart of ET-1, nitric oxide (NO), which is produced by the endothelial NO synthase (eNOS). Therefore, cross-bred animals of ET transgenic mice (ET+/+) and eNOS knockout (eNOS-/-) mice and were generated, and BP and endothelial function were evaluated in these animals. Endothelium-dependent and -independent vascular function was assessed as relaxation/contraction of isolated preconstricted aortic rings. The tissue ET and NO system was determined in aortic rings by quantitative real-time PCR and Western blotting. Systolic BP was similar in ET+/+ and wild-type (WT) mice but was significantly elevated in eNOS-/- mice (117 +/- 4 mmHg versus 94 +/- 6 mmHg in WT mice; P < 0.001) and even more elevated in ET+/+ eNOS-/- cross-bred mice (130 +/- 4 mmHg; P < 0.05 versus eNOS-/-). Maximum endothelium-dependent relaxation was enhanced in ET+/+ mice (103 +/- 6 versus 87 +/- 4% of preconstriction in WT littermates; P < 0.05) and was completely blunted in eNOS-/- (-3 +/- 4%) and ET+/+ eNOS-/- mice (-4 +/- 4%), respectively. Endothelium-independent relaxation was comparable among all groups. Quantitative real-time PCR as well as Western blotting revealed an upregulation of the aortic ET(A) and ET(B) receptors in ET+/+ eNOS-/-, whereas eNOS was absent in aortic rings of eNOS-/- and ET+/+ eNOS-/- mice. ET-1 aortic tissue concentrations were similar in WT mice and ET+/+ eNOS-/- mice most probably as a result of an enhanced clearance of ET-1 by the upregulated ET(B) receptor. These data show for the first time that in transgenic mice that overexpress human ET-1, additional knockout of eNOS results in a further enhancement of BP as compared with eNOS-/- mice. The human ET+/+ eNOS-/- mice therefore represent a novel model of hypertension as a result of an imbalance between the vascular ET-1 and NO systems.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcholine / pharmacology
  • Animals
  • Aorta / drug effects
  • Blood Pressure / physiology*
  • Body Weight
  • Endothelin-1 / genetics
  • Endothelin-1 / metabolism*
  • Endothelium / metabolism*
  • Hypertension / etiology*
  • Mice
  • Mice, Knockout
  • Mice, Transgenic
  • Nitric Oxide / metabolism
  • Nitric Oxide Synthase Type II / metabolism
  • Nitric Oxide Synthase Type III / genetics
  • Nitric Oxide Synthase Type III / metabolism*
  • Organ Size
  • RNA, Messenger / metabolism

Substances

  • Endothelin-1
  • RNA, Messenger
  • Nitric Oxide
  • Nitric Oxide Synthase Type II
  • Nitric Oxide Synthase Type III
  • Acetylcholine