Resistance to the nitric oxide/cyclic guanosine 5'-monophosphate/protein kinase G pathway in vascular smooth muscle cells from the obese Zucker rat, a classical animal model of insulin resistance: role of oxidative stress

Endocrinology. 2008 Apr;149(4):1480-9. doi: 10.1210/en.2007-0920. Epub 2007 Dec 13.


Some in vivo and ex vivo studies demonstrated a resistance to the vasodilating effects of nitric oxide (NO) in insulin-resistant states and, in particular, obese Zucker rats (OZR). To evaluate the biochemical basis of this phenomenon, we aimed to identify defects of the NO/cGMP/cGMP-dependent protein kinase (PKG) pathway in cultured vascular smooth muscle cells (VSMCs) from OZR and lean Zucker rats (LZR) by measuring: 1) NO donor ability to increase cGMP in the absence and presence of inhibitors of soluble guanylate cyclase (sGC) and phosphodiesterases (PDEs); 2) NO and cGMP ability to induce, via PKG, vasodilator-stimulated phosphoprotein (VASP) phosphorylation at serine 239 and PDE5 activity; 3) protein expression of sGC, PKG, total VASP, and PDE5; 4) superoxide anion concentrations and ability of antioxidants (superoxide dismutase+catalase and amifostine) to influence the NO/cGMP/PKG pathway activation; and 5) hydrogen peroxide influence on PDE5 activity and VASP phosphorylation. VSMCs from OZR vs. LZR showed: 1) baseline cGMP concentrations higher, at least in part owing to reduced catabolism by PDEs; 2) impairment of NO donor ability to increase cGMP, even in the presence of PDE inhibitors, suggesting a defect in the NO-induced sGC activation; 3) reduction of NO and cGMP ability to activate PKG, indicated by the impaired ability to phosphorylate VASP at serine 239 and to increase PDE5 activity via PKG; 4) similar baseline protein expression of sGC, PKG, total VASP, and PDE5; and 5) higher levels of superoxide anion. Antioxidants partially prevented the defects of the NO/cGMP/PKG pathway observed in VSMCs from OZR, which were reproduced by hydrogen peroxide in VSMCs from LZR, suggesting the pivotal role of oxidative stress.

MeSH terms

  • Animals
  • Cell Adhesion Molecules / metabolism
  • Cells, Cultured
  • Cyclic GMP / physiology*
  • Cyclic GMP-Dependent Protein Kinases / physiology*
  • Cyclic Nucleotide Phosphodiesterases, Type 5 / metabolism
  • Disease Models, Animal
  • Insulin Resistance*
  • Male
  • Microfilament Proteins / metabolism
  • Muscle, Smooth, Vascular / cytology
  • Muscle, Smooth, Vascular / metabolism*
  • Myocytes, Smooth Muscle / metabolism*
  • Nitric Oxide / physiology*
  • Oxidative Stress*
  • Phosphodiesterase Inhibitors / pharmacology
  • Phosphoproteins / metabolism
  • Phosphorylation
  • Rats
  • Rats, Zucker
  • Signal Transduction / physiology*


  • Cell Adhesion Molecules
  • Microfilament Proteins
  • Phosphodiesterase Inhibitors
  • Phosphoproteins
  • vasodilator-stimulated phosphoprotein
  • Nitric Oxide
  • Cyclic GMP-Dependent Protein Kinases
  • Cyclic Nucleotide Phosphodiesterases, Type 5
  • Cyclic GMP