Perivascular nitric oxide and superoxide in neonatal cerebral hypoxia-ischemia

Roderic H. Fabian, J. Regino Perez-Polo, Thomas A. Kent

    Research output: Contribution to journalArticle

    51 Citations (Scopus)

    Abstract

    Decreased cerebral blood flow (CBF) has been observed following the resuscitation from neonatal hypoxic-ischemic injury, but its mechanism is not known. We address the hypothesis that reduced CBF is due to a change in nitric oxide (NO) and superoxide anion O2 - balance secondary to endothelial NO synthase (eNOS) uncoupling with vascular injury. Wistar rats (7 day old) were subjected to cerebral hypoxia-ischemia by unilateral carotid occlusion under isoflurane anesthesia followed by hypoxia with hyperoxic or normoxic resuscitation. Expired CO2 was determined during the period of hyperoxic or normoxic resuscitation. Laser-Doppler flowmetry was used with isoflurane anesthesia to monitor CBF, and cerebral perivascular NO and O 2 - were determined using fluorescent dyes with fluorescence microscopy. The effect of tetrahydrobiopterin supplementation on each of these measurements and the effect of apocynin and Nω- nitro-L-arginine methyl ester (L-NAME) administration on NO and O 2 - were determined. As a result, CBF in the ischemic cortex declined following the onset of resuscitation with 100% O2 (hyperoxic resuscitation) but not room air (normoxic resuscitation). Expired CO2 was decreased at the onset of resuscitation, but recovery was the same in normoxic and hyperoxic resuscitated groups. Perivascular NO-induced fluorescence intensity declined, and O2 --induced fluorescence increased in the ischemic cortex after hyperoxic resuscitation up to 24 h postischemia. L-NAME treatment reduced O2 - relative to the nonischemic cortex. Apocynin treatment increased NO and reduced O2 - relative to the nonischemic cortex. The administration of tetrahydrobiopterin following the injury increased perivascular NO, reduced perivascular O2 -, and increased CBF during hyperoxic resuscitation. These results demonstrate that reduced CBF follows hyperoxic resuscitation but not normoxic resuscitation after neonatal hypoxic-ischemic injury, accompanied by a reduction in perivascular production of NO and an increase in O2 -. The finding that tetrahydrobiopterin, apocynin, and L-NAME normalized radical production suggests that the uncoupling of perivascular NOS, probably eNOS, due to acquired relative tetrahydrobiopterin deficiency occurs after neonatal hypoxic-ischemic brain injury. It appears that both NOS uncoupling and the activation of NADPH oxidase participate in the changes of reactive oxygen concentrations seen in cerebral hypoxic-ischemic injury.

    Original languageEnglish (US)
    JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
    Volume295
    Issue number4
    DOIs
    StatePublished - Oct 2008

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    Brain Hypoxia-Ischemia
    Resuscitation
    Superoxides
    Cerebrovascular Circulation
    Nitric Oxide
    NG-Nitroarginine Methyl Ester
    Isoflurane
    Wounds and Injuries
    Anesthesia
    Fluorescence
    Laser-Doppler Flowmetry
    Phenylketonurias
    Nitric Oxide Synthase Type III
    NADPH Oxidase
    Vascular System Injuries
    Fluorescent Dyes
    Fluorescence Microscopy
    Nitric Oxide Synthase
    Brain Injuries
    Wistar Rats

    Keywords

    • Apocynin
    • N-nitro-L-arginine methyl ester
    • Neonatal rat
    • Vasculature

    ASJC Scopus subject areas

    • Physiology
    • Physiology (medical)
    • Cardiology and Cardiovascular Medicine

    Cite this

    Perivascular nitric oxide and superoxide in neonatal cerebral hypoxia-ischemia. / Fabian, Roderic H.; Perez-Polo, J. Regino; Kent, Thomas A.

    In: American Journal of Physiology - Heart and Circulatory Physiology, Vol. 295, No. 4, 10.2008.

    Research output: Contribution to journalArticle

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