Mitochondrial complex I, aconitase, and succinate dehydrogenase during hypoxia-reoxygenation: Modulation of enzyme activities by MnSOD

Charles S. Powell, Robert M. Jackson

Research output: Contribution to journalArticle

91 Scopus citations

Abstract

Both NADH dehydrogenase (complex I) and aconitase are inactivated partially in vitro by superoxide (O2-·) and other oxidants that cause loss of iron from enzyme cubane (4Fe-4S) centers. We tested whether hypoxiareoxygenation (H-R) by itself would decrease lung epithelial cell NADH dehydrogenase, aconitase, and succinate dehydrogenase (SDH) activities and whether transfection with adenoviral vectors expressing MnSOD (Ad.MnSOD) would inhibit oxidative enzyme inactivation and thus confirm a mechanism involving O2-·. Human lung carcinoma cells with alveolar epithelial cell characteristics (A549 cells) were exposed to <1% O2-5% CO2 (hypoxia) for 24 h followed by air-5% CO2 for 24 h (reoxygenation). NADH dehydrogenase activity was assayed in submitochondrial particles; aconitase and SDH activities were measured in cell lysates. H-R significantly decreased NADH dehydrogenase, aconitase, and SDH activities. Ad MnSOD increased mitochondrial MnSOD substantially and prevented the inhibitory effects of H-R on enzyme activities. Addition of α-ketoglutarate plus aspartate, but not succinate, to medium prevented cytotoxicity due to 2,3-dimethoxy-1,4-naphthoquinone. After hypoxia, cells displayed significantly increased dihydrorhodamine fluorescence, indicating increased mitochondrial oxidant production. Inhibition of NADH dehydrogenase, aconitase, and SDH activities during reoxygenation are due to excess O2-· produced in mitochondria, because enzyme inactivation can be prevented by overexpression of MnSOD.

Original languageEnglish (US)
Pages (from-to)L189-L198
JournalAmerican Journal of Physiology - Lung Cellular and Molecular Physiology
Volume285
Issue number1 29-1
DOIs
StatePublished - Jul 1 2003
Externally publishedYes

Keywords

  • Alveolar epithelium
  • Manganese superoxide dismutase
  • Mitochondria
  • NADH dehydrogenase

ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine
  • Cell Biology
  • Physiology

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