The authors have previously shown that neonatal hyperoxic stress leads to
high blood pressure, impaired endothelium-mediated vasodilatation, and increased vascular production of
superoxide anion by
NAD(P)H oxidase in adulthood. However, it is unknown whether changes in
nitric oxide (NO) production and/or bioinactivation prevail and whether
NO synthase (NOS) is also a source of
superoxide. The purpose of this study was to evaluate whether adult animals exposed to neonatal hyperoxic stress have impaired vascular NO production associated with NOS uncoupling participating to vascular
superoxide production and vascular dysfunction. In adult male rats exposed to 80%
oxygen from day 3 to 10 of life (H, n = 6) versus room air controls (CTRL, n = 6), vascular (aorta) NO production is decreased at baseline (CTRL: 21 ± 1 vs. H: 16 ± 2 4,5-diaminofluorescein diacetate fluorescence intensity arbitrary units; P < 0.05) and after
carbachol stimulation (
acetylcholine analog; CTRL: 26 ± 2 vs. H: 18±2; P < 0.05). Pretreatment with
L-arginine (CTRL: 32 ± 4 vs. H: 31 ± 5) and L-
sepiapterine [analog of key NOS cofactor tetrahydro-
L-biopterin (BH4)] (CTRL: 30 ± 3 vs. H: 29 ± 3) normalizes NO production after
carbachol. L-
Sepiapterine also normalizes impaired vasodilatation to
carbachol. Vascular endothelial
NO synthase (eNOS) immunostaining is reduced, whereas total eNOS
protein expression is increased in H (CTRL: 0.76 ± 0.08 vs. H: 1.76± 0.21; P < 0.01). The significantly higher
superoxide generation (CTRL: 20 ± 2 vs. H: 28 ± 3
hydroethidine fluorescence intensity arbitrary units; P < 0.05) is prevented by pretreatment with the eNOS inhibitor N-nitro-
L-arginine methyl ester (CTRL: 21 ± 4 vs. H: 22 ± 4). Taken together, the current data indicate a role for eNOS uncoupling in enhanced vascular
superoxide, impaired endothelium-mediated vasodilatation, and decreased NO production in adult animals with programmed elevated blood pressure after a brief neonatal
oxygen exposure.