Postischemic hyperoxia reduces hippocampal pyruvate dehydrogenase activity

Erica M. Richards, Robert E. Rosenthal, Tibor Kristian, Gary Fiskum

Research output: Contribution to journalArticlepeer-review

Abstract

The pyruvate dehydrogenase complex (PDHC) is a mitochondrial matrix enzyme that catalyzes the oxidative decarboxylation of pyruvate and represents the sole bridge between anaerobic and aerobic cerebral energy metabolism. Previous studies demonstrating loss of PDHC enzyme activity and immunoreactivity during reperfusion after cerebral ischemia suggest that oxidative modifications are involved. This study tested the hypothesis that hyperoxic reperfusion exacerbates loss of PDHC enzyme activity, possibly due to tyrosine nitration or S-nitrosation. We used a clinically relevant canine ventricular fibrillation cardiac arrest model in which, after resuscitation and ventilation on either 100% O2 (hyperoxic) or 21-30% O2 (normoxic), animals were sacrificed at 2 h reperfusion and the brains removed for enzyme activity and immunoreactivity measurements. Animals resuscitated under hyperoxic conditions exhibited decreased PDHC activity and elevated 3-nitrotyrosine immunoreactivity in the hippocampus but not the cortex, compared to nonischemic controls. These measures were unchanged in normoxic animals. In vitro exposure of purified PDHC to peroxynitrite resulted in a dose-dependent loss of activity and increased nitrotyrosine immunoreactivity. These results support the hypothesis that oxidative stress contributes to loss of hippocampal PDHC activity during cerebral ischemia and reperfusion and suggest that PDHC is a target of peroxynitrite.

Original languageEnglish (US)
Pages (from-to)1960-1970
Number of pages11
JournalFree Radical Biology and Medicine
Volume40
Issue number11
DOIs
StatePublished - Jun 1 2006

Keywords

  • Free radicals
  • Global ischemia
  • Hyperoxia
  • Mitochondria
  • Nitrotyrosine
  • Normoxia
  • Oxidative stress
  • Selective vulnerability

ASJC Scopus subject areas

  • Biochemistry
  • Physiology (medical)

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