Reactive oxygen species augment contractile responses of saphenous artery in 10-15-day-old but not adult rats: Substantial role of NADPH oxidases.

Reactive oxygen species (ROS) produced by NADPH oxidases (NOX, a key source of ROS in vascular cells) are involved in the regulation of vascular tone, but this has been explored mainly for adult organisms. Importantly, the mechanisms of vascular tone regulation differ significantly in early postnatal ontogenesis and adulthood, while the vasomotor role of ROS in immature systemic arteries is poorly understood. We tested the hypothesis that the functional contribution of NADPH oxidase-derived ROS to the regulation of peripheral arterial tone is higher in the early postnatal period than in adulthood. We studied saphenous arteries from 10- to 15-day-old ("young") and 3- to 4-month-old ("adult") male rats using lucigenin-enhanced chemiluminescence, quantitative PCR, Western blotting, and isometric myography. We demonstrated that both basal and NADPH-stimulated superoxide anion radical (O2•-) production was significantly higher in the arteries from young in comparison to adult rats. Importantly, pan-inhibitor of NADPH oxidase VAS2870 (10 µM) reduced NADPH-induced O2•- production in arteries of young rats. Saphenous arteries of both young and adult rats demonstrated high levels of Nox2 and Nox4 mRNAs, while Nox1 and Nox3 mRNAs were not detected. The protein contents of NOX2 and NOX4 were significantly higher in arterial tissue of young compared to adult animals. Moreover, VAS2870 (10 µM) had no effect on methoxamine-induced contractile responses of adult arteries but decreased them significantly in young arteries; such effect of VAS2870 persisted after removal of the endothelium. Finally, NOX2 inhibitor GSK2795039 (10 µM), but not NOX1/4 inhibitor GKT137831 (10 µM) weakened methoxamine-induced contractile responses of arteries from young rats. Thus, ROS produced by NOX2 have a pronounced contractile influence in saphenous artery smooth muscle cells of young, but not adult rats, which is associated with the increased vascular content of NOX2 protein at this age.

Perinatal hypoxia weakens anticontractile influence of NO in rat arteries during early postnatal period.

BACKGROUND: Perinatal hypoxia affects a lot of neonates worldwide every year, however its effects on the functioning of systemic circulation are not clear yet. We aimed at investigation the effects of perinatal hypoxia on the second day of life on the functioning of the rat systemic vasculature in early postnatal period. METHODS: 2-day-old male rat pups were exposed to normobaric hypoxia (8% O2, 92% N2) for 2 hours. At the 11-14 days cutaneous (saphenous) arteries were isolated and studied by wire myography and Western blotting. RESULTS: Hypoxia weakened the contribution of anticontractile influence of NO, but did not affect the contribution of Rho-kinase or Kv7 channels to the contraction to α1-adrenergic agonist methoxamine. The content of eNOS and protein kinase G were not altered by hypoxic conditions. CONCLUSION: Perinatal hypoxia in rats at the second day of life leads to the decrease of anticontractile effect of NO in the systemic arteries in early postnatal ontogenesis (at the age of 11-14 days). Decreased anticontractile effect of NO can be the reason for insufficient blood supply and represent a risk factor for the development of cardiovascular disorders. IMPACT: The mechanisms of perinatal hypoxia influences on systemic circulation are almost unknown. We have shown that perinatal hypoxia weakens anticontractile influence of nitric oxide in early postnatal period. The influence of perinatal hypoxia on systemic circulation should be taken into account during treatment of newborns suffered from the lack of oxygen.