Oxygen treatment after experimental hypoxia-ischemia in neonatal rats alters the expression of HIF-1α and its downstream target genes

Oxygen treatment after experimental hypoxia-ischemia in neonatal rats alters the expression of HIF-1 alpha and its downstream target genes. J Appl Physiol 101: 853-865, 2006. First published May 25, 2006; doi: 10.1152/japplphysiol.00268.2006.-Recently, mounting evidence has emerged to suggest that hyperbaric oxygenation (HBOT)-induced neuroprotection after experimental global ischemia and subarachnoid hemorrhage entails a decrease in the expression of hypoxia-inducible factor-1 alpha (HIF-1 alpha). Therefore, the purpose of this study was to test the hypothesis that oxygen-induced neuroprotection after neonatal hypoxia-ischemia involves alterations in the expression of HIF-1 alpha. Seven-day-old rat pups were subjected to unilateral carotid artery ligation followed by 2 h of hypoxia (8% O-2 at 37 degrees C). Pups were then treated with HBOT (2.5 ATA) or normobaric oxygenation treatment (NBOT) for 2 h. The expression and phosphorylation status of HIF-1 alpha was evaluated at intervals up to 24 h after the insult, as was the expression of glucose transporter (GLUT)-1, GLUT-3, lactate dehydrogenase (LDH), aldolase (Ald), and p53. The protein-protein interaction of HIF-1 alpha and p53 was also examined. An elevated expression of HIF-1 alpha, GLUT-1, GLUT-3, Ald, and LDH was observed after the insult. An increase in the dephosphorylated form of HIF-1 alpha was followed by an increase in the association of HIF-1 alpha with p53 and an increase in p53 levels. Both HBOT and NBOT reduced the elevated expression of HIF-1 alpha and decreased its dephosphorylated form. Furthermore, both treatments promoted a transient increase in the expression of GLUT-1, GLUT-3, LDH, and Ald, while decreasing the HIF-1 alpha-p53 interaction and decreasing the expression of p53. Therefore, the alteration of the HIF-1 alpha phenotype by a single oxygen treatment may be one of the underlying mechanisms for the observed oxygen-induced neuroprotection seen when oxygen is administered after a neonatal hypoxic-ischemic insult.