1. Uncoupling of eNOS causes superoxide anion production and impairs NO signaling in the cerebral microvessels of hph-1 mice.
- Author
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Santhanam AV, d'Uscio LV, Smith LA, and Katusic ZS
- Subjects
- Animals, Brain enzymology, Cyclic GMP antagonists & inhibitors, Cyclic GMP physiology, Female, Male, Mice, Mice, Inbred C57BL, Mice, Mutant Strains, Oxidative Stress physiology, Brain blood supply, Microvessels enzymology, Nitric Oxide antagonists & inhibitors, Nitric Oxide physiology, Nitric Oxide Synthase Type III antagonists & inhibitors, Nitric Oxide Synthase Type III metabolism, Nitric Oxide Synthase Type III physiology, Phenylalanine Hydroxylase deficiency, Signal Transduction physiology, Superoxides metabolism
- Abstract
In this study, we used the GTP cyclohydrolase I-deficient mice, i.e., hyperphenylalaninemic (hph-1) mice, to test the hypothesis that the loss of tetrahydrobiopterin (BH(4)) in cerebral microvessels causes endothelial nitric oxide synthase (eNOS) uncoupling, resulting in increased superoxide anion production and inhibition of endothelial nitric oxide signaling. Both homozygous mutant (hph-1(-/-)) and heterozygous mutant (hph-1(+/-) mice) demonstrated reduction in GTP cyclohydrolase I activity and reduced bioavailability of BH(4). In the cerebral microvessels of hph-1(+/-) and hph-1(-/-) mice, increased superoxide anion production was inhibited by supplementation of BH(4) or NOS inhibitor- L- N(G) -nitro arginine-methyl ester, indicative of eNOS uncoupling. Expression of 3-nitrotyrosine was significantly increased, whereas NO production and cGMP levels were significantly reduced. Expressions of antioxidant enzymes namely copper and zinc superoxide dismutase, manganese superoxide dismutase, and catalase were not affected by uncoupling of eNOS. Reduced levels of BH(4), increased superoxide anion production, as well as inhibition of NO signaling were not different between the microvessels of male and female mice. The results of our study are the first to demonstrate that, regardless of gender, reduced BH(4) bioavailability causes eNOS uncoupling, increases superoxide anion production, inhibits eNOS/cGMP signaling, and imposes significant oxidative stress in the cerebral microvasculature., (© 2012 The Authors. Journal of Neurochemistry © 2012 International Society for Neurochemistry.)
- Published
- 2012
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