title: Role for peroxynitrite in the inhibition of prostacyclin synthase in nitrate tolerance.
abstract: OBJECTIVE
  We tested whether in vivo nitroglycerin (NTG) treatment causes tyrosine nitration of prostacyclin synthase (PGI(2)-S), one of the nitration targets of peroxynitrite, and whether this may contribute to nitrate tolerance.
  
  
  BACKGROUND
  Long-term NTG therapy causes tolerance secondary to increased vasoconstrictor sensitivity and increased vascular formation of reactive oxygen species. Because NTG releases nitric oxide (NO), NTG-induced stimulation of superoxide production should increase vascular nitrotyrosine levels, compatible with increased formation of peroxynitrite, the reaction product from NO and superoxide.
  
  
  METHODS
  New Zealand White rabbits and Wistar rats were treated with NTG (0.4 mg/h for 3 days). Tolerance was assessed with isometric tension studies. Vascular peroxynitrite levels were quantified with luminol-derived chemiluminescence (LDCL) and peroxynitrite scavengers, such as uric acid and ebselen. As a surrogate parameter for the assessment of the activity of cyclic guanosine monophosphate-dependent kinase-I (cGK-I; the final signaling pathway for NO), the phosphorylation of the vasodilator-stimulated phosphoprotein (P-VASP) at serine 239 was analyzed.
  
  
  RESULTS
  Nitroglycerin treatment increased LDCL, and the inhibitory effect of uric acid and ebselen on LDCL was augmented in tolerant rings. Immunoprecipitation of 3-nitrotyrosine-containing proteins and immunohistochemistry analysis identified PGI(2)-S as a tyrosine-nitrated protein. Accordingly, conversion of ((14)C)-PGH(2) into 6-keto-PGF(1 alpha) (=PGI(2)-S activity) was strongly inhibited. In vitro incubation of tolerant rings with ebselen and uric acid markedly increased the depressed P-VASP levels and improved NTG sensitivity of the tolerant vasculature.
  
  
  CONCLUSIONS
  Nitroglycerin-induced vascular peroxynitrite formation inhibits the activity of PGI(2)-S as well as NO, cGMP, and cGK-I signaling, which may contribute to vascular dysfunction in the setting of tolerance.
authors.affiliation: University Hospital Eppendorf, Division of Cardiology, Hamburg, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Hink
authors.forename: Matthias
authors.initials: M
authors.lastname: Oelze
authors.forename: Philip
authors.initials: P
authors.lastname: Kolb
authors.forename: Markus
authors.initials: M
authors.lastname: Bachschmid
authors.forename: Ming-Hui
authors.initials: MH
authors.lastname: Zou
authors.forename: Andreas
authors.initials: A
authors.lastname: Daiber
authors.forename: Hanke
authors.initials: H
authors.lastname: Mollnau
authors.forename: Michael
authors.initials: M
authors.lastname: August
authors.forename: Stefan
authors.initials: S
authors.lastname: Baldus
authors.forename: Nikos
authors.initials: N
authors.lastname: Tsilimingas
authors.forename: Ulrich
authors.initials: U
authors.lastname: Walter
authors.forename: Volker
authors.initials: V
authors.lastname: Ullrich
authors.forename: Thomas
authors.initials: T
authors.lastname: Münzel
mesh_terms: D000818:Animals; D001808:Blood Vessels / Q000378:metabolism; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004361:Drug Tolerance / Q000502:physiology*; D019746:Intramolecular Oxidoreductases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D023421:Models, Animal; D005996:Nitroglycerin / Q000494:pharmacology*; D030421:Peroxynitrous Acid / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D017382:Reactive Oxygen Species; D014665:Vasodilator Agents; D030421:Peroxynitrous Acid; D003577:Cytochrome P-450 Enzyme System; D017869:Cyclic GMP-Dependent Protein Kinases; D019746:Intramolecular Oxidoreductases; C022461:prostacyclin synthetase; D005996:Nitroglycerin