Adverse effects of nitroglycerin treatment on endothelial function, vascular nitrotyrosine levels and cGMP-dependent protein kinase activity in hyperlipidemic Watanabe rabbits.
OBJECTIVE
With the present studies we sought to determine how treatment with nitroglycerin (NTG) affects endothelial function, oxidative stress and nitric oxide (NO)-downstream signaling in Watanabe heritable hyperlipidemic rabbits (WHHL).


BACKGROUND
In vitro experiments have demonstrated potent antiatherosclerotic effects of NO suggesting that treatment with NO-donors such as NTG could compensate for the diminished availability of endothelial NO. Nitric oxide may, however, not only be scavenged by reaction with endothelium-derived superoxide but also form the potent oxidant and inhibitor of vascular function, peroxynitrite (ONOO(-)).


METHODS
Watanabe heritable hyperlipidemic rabbits were treated for three days with NTG patches. Normolipidemic New Zealand White rabbits (NZWR) served as controls. Endothelial function was assessed ex vivo with organ chamber experiments and vascular superoxide was quantified using lucigenin (5 and 250 microM) and CLA-enhanced chemiluminescence. Vascular ONOO(-) formation was determined using nitrotyrosine antibodies. The activity of the cGMP-dependent kinase (cGK-I) was assessed by determining the phosphorylation of vasodilator-stimulated phosphoprotein VASP (P-VASP).


RESULTS
Nitroglycerin treatment caused endothelial dysfunction in NZWR and WHHL, associated with an increase in superoxide and ONOO(-) production and a substantial drop in cGK-I activity. In vivo NTG-treatment decreased lipophilic antioxidants (alpha- and beta-carotene) in NZWR and WHHL. Treatment of NZWR with NTG also decreased plasma extracellular superoxide dismutase (EC-SOD)-activity.


CONCLUSIONS
Nitroglycerin treatment of WHHL with exogenous NO worsens rather than improves endothelial dysfunction secondary to increased formation of superoxide and/or peroxynitrite leading to decreased cGK-I activity. The decrease in plasma levels of alpha- and beta-carotene may be at least in part due to a decrease in EC-SOD activity.
Warnholtz
Ascan
A
Division of Cardiology, University Hospital Eppendorf, Hamburg, Germany.
Mollnau
Hanke
H
Heitzer
Thomas
T
Kontush
Anatol
A
Möller-Bertram
Tobias
T
Lavall
Dirk
D
Giaid
Adel
A
Beisiegel
Ulrike
U
Marklund
Stefan L
SL
Walter
Ulrich
U
Meinertz
Thomas
T
Munzel
Thomas
T
D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D017869:Cyclic GMP-Dependent Protein Kinases / Q000187:drug effects*; D004195:Disease Models, Animal; D004353:Drug Evaluation, Preclinical; D004730:Endothelium, Vascular / Q000187:drug effects*; D005609:Free Radicals / Q000097:blood; D006949:Hyperlipidemias / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D007150:Immunohistochemistry; D008297:Male; D009569:Nitric Oxide / Q000502:physiology; D005996:Nitroglycerin / Q000009:adverse effects*; D018384:Oxidative Stress / Q000187:drug effects; D011817:Rabbits; D017382:Reactive Oxygen Species / Q000097:blood; D013482:Superoxide Dismutase / Q000097:blood / Q000187:drug effects; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000187:drug effects* / Q000276:immunology; D014665:Vasodilator Agents / Q000009:adverse effects*; D019207:beta Carotene / Q000097:blood
D000975:Antioxidants; D005609:Free Radicals; D017382:Reactive Oxygen Species; D014665:Vasodilator Agents; D019207:beta Carotene; D009569:Nitric Oxide; C002744:3-nitrotyrosine; D014443:Tyrosine; D013482:Superoxide Dismutase; D017869:Cyclic GMP-Dependent Protein Kinases; D005996:Nitroglycerin