Distinct mPTP activation mechanisms in ischaemia-reperfusion: Contributions of Ca<sup>2+</sup>, ROS, pH, and inorganic polyphosphate

Lea K. Seidlmayer, Vanessa V. Juettner, Sarah Kettlewell, Evgeny Pavlov, Lothar A. Blatter, Elena N. Dedkova

Research output: Contribution to journalArticle

Abstract

Aims The mitochondrial permeability transition pore (mPTP) plays a central role for tissue damage and cell death during ischaemia-reperfusion (I/R). We investigated the contribution of mitochondrial inorganic polyphosphate (polyP), a potent activator of Ca<sup>2+</sup>-induced mPTP opening, towards mPTP activation and cardiac cell death in I/R. Methods and results A significant increase in mitochondrial free calcium concentration ([Ca<sup>2+</sup>]<inf>m</inf>), reactive oxygen species (ROS) generation, mitochondrial membrane potential depolarization (ΔΨ<inf>m</inf>), and mPTP activity, but no cell death, was observed after 20 min of ischaemia. The [Ca<sup>2+</sup>]<inf>m</inf> increase during ischaemia was partially prevented by the mitochondrial Ca<sup>2+</sup> uniporter (MCU) inhibitor Ru360 and completely abolished by the combination of Ru360 and the ryanodine receptor type 1 blocker dantrolene, suggesting two complimentary Ca<sup>2+</sup> uptake mechanisms. In the absence of Ru360 and dantrolene, mPTP closing by polyP depletion or CSA decreased mitochondrial Ca<sup>2+</sup> uptake, suggesting that during ischaemia Ca<sup>2+</sup> can enter mitochondria through mPTP. During reperfusion, a burst of endogenous polyP production coincided with a decrease in [Ca<sup>2+</sup>]<inf>m</inf>, a decline in superoxide generation, and an acceleration of hydrogen peroxide (H<inf>2</inf>O<inf>2</inf>) production. An increase in H<inf>2</inf>O<inf>2</inf> correlated with restoration of mitochondrial pH<inf>m</inf> and an increase in cell death. mPTP opening and cell death on reperfusion were prevented by antioxidants Trolox and MnTBAP [Mn (III) tetrakis (4-benzoic acid) porphyrin chloride]. Enzymatic polyP depletion did not affect mPTP opening during reperfusion, but increased ROS generation and cell death, suggesting that polyP plays a protective role in cellular stress response. Conclusions Transient Ca<sup>2+</sup>/polyP-mediated mPTP opening during ischaemia may serve to protect cells against cytosolic Ca<sup>2+</sup> overload, whereas ROS/pH-mediated sustained mPTP opening on reperfusion induces cell death.

Original languageEnglish (US)
Pages (from-to)237-248
Number of pages12
JournalCardiovascular Research
Volume106
Issue number2
DOIs
Publication statusPublished - May 1 2015

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Keywords

  • Inorganic polyphosphate
  • Ischaemia-reperfusion injury
  • Mitochondrial permeability transition pore
  • Mitochondrial ryanodine receptor
  • Oxidative stress

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)
  • Physiology

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