Among various hypothetical mechanisms for the in vivo production of
reactive oxygen species, transition
metal-catalyzed reactions in cooperation with a biologic
reducing agent like
ascorbic acid or
superoxide may be some of the most important. In the present study, we retrospectively examined the existence of non-
protein-bound
metal ions, an essentially hazardous
pro-oxidant form of various transition metals, and the occurrence of
metal-catalyzed
reactive oxygen species production in cerebrospinal fluid (CSF) of 10 infants with
hypoxic ischemic encephalopathy (HIE) subsequent to perinatal
asphyxia and 12 control infants within 72 h of birth. Non-
protein-bound
iron was detected in eight out of 10 CSF samples from the HIE infants and its level was significantly correlated with Sarnat's clinical stage, whereas none of the control infants had detectable non-
protein-bound
iron levels. Non-
protein-bound
copper was below the detection limit in all CSF samples from both groups.
Ascorbic acid was significantly increased in the CSF of HIE infants when compared with that of controls (means, 664.9 versus 449.4 microM, p = 0.008).
ortho-Tyrosine and
meta-tyrosine, which are highly specific and sensitive markers of
protein oxidation induced by
hydroxyl radicals, were significantly higher in HIE infants than in controls when evaluated by the ratio relative to their source
amino acid,
phenylalanine [means, 110.5 versus 75.4, p = 0.018 for
ortho-tyrosine/
phenylalanine; 104.6 versus 67.7 (nM/microM x 10(2)), p = 0.048 for
meta-tyrosine/
phenylalanine]. Both ratios were significantly correlated with non-
protein-bound
iron, but not with
ascorbic acid. Our preliminary observations provide direct evidence that
hydroxyl radicals are generated in the CNS during asphyxiation.
Iron chelation therapy could be worth developing as a neuroprotective strategy for perinatal
asphyxia.