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Phosphorylation of endothelial nitric oxide synthase is increased in mouse model of GTP‐cyclohydrolase I deficiency
Author(s) -
d'Uscio Livius V.,
Katusic Zvonimir S.
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.959.8
Subject(s) - enos , tetrahydrobiopterin , medicine , endocrinology , gtp cyclohydrolase i , chemistry , biopterin , nitric oxide , nitric oxide synthase , gtp' , nitric oxide synthase type iii , superoxide , endothelial nos , nitrotyrosine , phosphorylation , biochemistry , biology , enzyme
Tetrahydrobiopterin (BH 4 ) is an essential cofactor for endothelial nitric oxide synthase (eNOS). Suboptimal level of BH 4 reduces formation of nitric oxide leading to uncoupling of eNOS. However, the exact molecular mechanisms underlying the effects of eNOS uncoupling on vascular endothelium in‐vivo are not completely understood. In the present study, we used the hph‐1 mouse, which displays GTP‐cyclohydrolase I deficiency. HPLC analysis revealed that BH 4 levels were significantly reduced in the aortas of hph‐1 mice (3.9±0.5 pmol/mg; P<0.05 vs. wild‐type mice: 5.9±0.6 pmol/mg), while oxidative products of BH 4 , 7,8‐dihydrobiopterin (7,8‐BH 2 ), were unchanged. Consequently, the BH 4 to 7,8‐BH 2 ratio was significantly reduced in the aorta of hph‐1 mice (P<0.05). Expression of eNOS protein was not different between wild‐type and hph‐1 mice. Unexpectedly, protein expressions of phosphorylated Ser 1177 ‐eNOS and Ser 473 ‐Akt1 were significantly increased in hph‐1 mice aortas (P<0.05). Consistent with uncoupling of eNOS, L‐NAME sensitive superoxide anion production and 3‐nitrotyrosine formation were significantly increased in aortas of hph‐1 mice (P<0.05). Protein expressions of CuZnSOD, MnSOD, and EC‐SOD were unaltered in the aortas of hph‐1 mice as compared with wild‐type mice. Our results suggest that uncoupling eNOS increases phosphorylation of Akt1 and eNOS. This effect is most likely mediated by increased formation of eNOS‐derived reactive oxygen species including superoxide anion and hydrogen peroxide.