Sundier 2015 Abstract MiPschool London 2015

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Mitochondrial ROS generation in cardiomyocyte reperfusion injury is modulated by succinate accumulation during ischaemia.

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Sundier SY, Chouchani ET, VPell VR, Gaude E, Frezza C, Krieg T, Davidson SM, Duchen MR, Murphy MP (2015)

Event: MiPschool London 2015

Cardiac ischaemia and reperfusion (I/R) injury contributes heavily to adverse outcomes following a heart attack. Although ischaemia restricts blood flow and starves the infarcted region of nutrient and oxygen delivery, further cellular dysfunction and death occur, paradoxically, during the transition to reperfusion [1]. The increase of mitochondrial production of reactive oxygen species (ROS) during reperfusion has previously been thought to be a non-specific consequence of reoxygenation [2]. However, in vivo metabolomic analysis revealed that specific mitochondrial pathways result in the accumulation of succinate, an intermediate of the citric acid cycle, during the ischaemic period. We have used dihydroethidium to measure ROS generation in isolated rat ventricular cardiomyocytes during a period of anoxia and at reperfusion, and our data show that succinate accumulation during the anoxic period drives increased ROS generation particularly at reoxygenation and determines cell fate. In control conditions, ROS generation was seen at the early stages of reperfusion. However, ROS generation was significantly decreased by exposing cells to dimethylmalonate during ischaemia to inhibit the oxidation of succinate at complex II at reperfusion, an effect also achieved by the independent ischaemic additions of the complex I inhibitors mitoSNO3 or rotenone. Conversely, increasing succinate by exposing cells to dimethylsuccinate (membrane permeant succinate) increased ROS generation at reoxygenation and increased cell death. Further in vivo experiments showed a reduction of reperfusion injury in mouse hearts by malonate and by mitoSNO. Together, these data strongly suggest that ROS generation at reperfusion is specifically driven by the accumulation of succinate during ischaemia and its oxidation at complex II at reperfusion, generating ROS through reverse electron flow to complex I. Notably, further metabolomic analysis showed that succinate accumulation during ischaemia is conserved across I/R-sensitive tissues, implying that the metabolic pathways responsible for ischaemic succinate accumulation - and the mechanism driving mitochondrial ROS production - are highly conserved. These findings pave the way to novel therapeutic strategies and new potential targets to reduce damage by reperfusion injury across a broad spectrum of tissues.


O2k-Network Lab: UK London Duchen MR


Labels: MiParea: Patients  Pathology: Cardiovascular  Stress:Ischemia-reperfusion, Oxidative stress;RONS  Organism: Mouse, Rat  Tissue;cell: Heart  Preparation: Intact cells 


Pathway: N, S 



Affiliations

1-Dept Cell Developm Biol and UCL Consortium for Mitoch Biol, Univ College London, UK. - s.sundier@ucl.ac.uk

2-MRC Mitoch Biol Unit, Univ Cambridge, UK

3-Dept Med, Univ Cambridge, Addenbrooke's Hospital, UK.

4-MRC Cancer Unit, Univ Cambridge, Hutchison/MRC Research Centre, Cambridge Biomed Campus, UK

5-Hatter Cardiovascular Inst, Univ College London, UK

References

  1. Piper HM, D. Garcña-Dorado D, Ovize M (1998) A fresh look at reperfusion injury. Cardiovasc Res 38:291-300.
  2. Turrens JF (2003) Mitochondrial formation of reactive oxygen species. J Physiol 552:335-44.
  3. Chouchani ET, Methner C, Nadtochiy SM, Logan A, Pell VR, Ding S, James AM, Cochemé HM, Reinhold J, Lilley KS, Partridge L, Fearnley IM, Robinson AJ, Hartley RC, Smith RA, Krieg T, Brookes PS, Murphy MP (2013) Cardioprotection by S-nitrosation of a cysteine switch on mitochondrial complex I. Nat Med 19:753-59.