Ionic mechanism of ouabain-induced concurrent apoptosis and necrosis in individual cultured cortical neurons

Ai Ying Xiao, Ling Wei, Shuli Xia, Steven Rothman, Shan Ping Yu

Research output: Contribution to journalArticlepeer-review

Abstract

Energy deficiency and dysfunction of the Na+, K+-ATPase are common consequences of many pathological insults. The nature and mechanism of cell injury induced by impaired Na+, K+-ATPase, however, are not well defined. We used cultured cortical neurons to examine the hypothesis that blocking the Na+, K+-ATPase induces apoptosis by depleting cellular K+ and, concurrently, induces necrotic injury in the same cells by increasing intracellular Ca2+ and Na+. The Na+, K+-ATPase inhibitor ouabain induced concentration-dependent neuronal death. Ouabain triggered transient neuronal cell swelling followed by cell shrinkage, accompanied by intracellular Ca2+ and Na+ increase, K+ decrease, cytochrome c release, caspase-3 activation, and DNA laddering. Electron microscopy revealed the coexistence of ultrastructural features of both apoptosis and necrosis in individual cells. The caspase inhibitor Z-Val-Ala-Asp(OMe)-fluoromethyl ketone (Z-VAD-FMK) blocked >50% of ouabain-induced neuronal death. Potassium channel blockers or high K+ medium, but not Ca2+ channel blockade, prevented cytochrome c release, caspase activation, and DNA damage. Blocking of K+, Ca2+, or Na+ channels or high K+ medium each attenuated the ouabain-induced cell death; combined inhibition of K+ channels and Ca2+ or Na+ channels resulted in additional protection. Moreover, coapplication of Z-VAD-FMK and nifeclipine produced virtually complete neuroprotection. These results suggest that the neuronal death associated with Na+, K+-pump failure consists of concurrent apoptotic and necrotic components, mediated by intracellular depletion of K+ and accumulation of Ca2+ and Na+, respectively. The ouabain-induced hybrid death may represent a distinct form of cell death related to the brain injury of inadequate energy supply and disrupted ion homeostasis.

Original languageEnglish (US)
Pages (from-to)1350-1362
Number of pages13
JournalJournal of Neuroscience
Volume22
Issue number4
DOIs
StatePublished - Feb 15 2002
Externally publishedYes

Keywords

  • Apoptosis
  • Calcium
  • Caspase
  • Cytochrome c
  • DNA fragmentation
  • Hybrid death
  • Necrosis
  • Ouabain
  • Potassium channel
  • Strophanthidin

ASJC Scopus subject areas

  • Neuroscience(all)

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