Komlodi 2018b EBEC2018
|Endogenous quinones sustain NADH oxidation by complex I during anoxia, supporting substrate-level phosphorylation in mouse liver mitochondria.|
Anoxia leads to over-reduction of mitochondrial coenzyme Q (Q, quinone) pools rendering Complex I unable to oxidize NADH, leading to a profound decrease in the matrix NAD+/NADH ratio. As a consequence, the function of matrix dehydrogenases is impaired. Yet, under certain anoxic conditions catabolism of metabolites converging through the α-ketoglutarate dehydrogenase Complex (KGDHC) is known to occur, yielding succinyl-CoA, in turn supporting substrate-level phosphorylation substantiated by succinate-CoA ligase .
Mitochondrial respiration and NADH autofluorescence were measured simultaneously with the NextGen-O2k (Oroboros Instruments, Innsbruck, Austria), and the redox state of the Q-pool was detected with a three-electrode system implanted into the O2k (Oroboros Q2k).
We show that in isolated mouse liver mitochondria Complex I utilizes endogenous quinones oxidizing NADH during anoxia. Untargeted metabolomic analysis of matrix metabolites of mitochondria subjected to respiratory arrest due to anoxia and in the presence of specific inhibitors of respiratory complexes infer showed that NAD+ arising from Complex I is utilized by KGDHC yielding succinyl-CoA for succinate-CoA ligase, thus maintaining substrate-level phosphorylation during anoxia. Finally, by using custom-made 3D-printed plugs designed for standard fluorometric cuvettes, we show that under no conditions of respiratory arrest due to anoxia and/or pharmacological inhibition of the complexes did the mitochondria undergo swelling, which could potentially confound matrix metabolite estimations or bioenergetic parameters due to permeability transition. Our results highlight the importance of the availability of quinones in conjunction with the operation of Complex I in maintaining substrate-level phosphorylation during anoxia.
Labels: MiParea: Respiration
Stress:Permeability transition, Oxidative stress;RONS Organism: Mouse Tissue;cell: Liver Preparation: Isolated mitochondria
Pathway: N HRR: Oxygraph-2k, O2k-Fluorometer
Komlódi T(4), Ravasz D(1), Kitayev A(2), Hill C, Kiebish M(2), Doerrier C(4), Moore AL(3), Gnaiger E(4,5), Narain N(2), Seyfried TN(6), Adam-Vizi V(1), Chinopoulos C(1)
- Dept Medical Biochem, Semmelweis Univ, Budapest, Hungary
- BERG LLC, Framingham, MA, USA
- Dept Biochemistry Molecular Biology, School Life Sciences, Univ Sussex, Brighton, UK
- Oroboros Instruments, Innsbruck, Austria
- D. Swarovski Research Lab, Mitochondrial Physiology, Dept Visceral, Transplant Thoracic Surgery, Medical Univ Innsbruck, Austria
- Biology Dept, Boston College, Chestnut Hill, Boston, MA, USA
- Kiss G, Konrad C, Doczi J, Starkov AA, Kawamata H, Manfredi G, Zhang SF, Gibson GE, Beal MF, Adam-Vizi V, Chinopoulos C (2013) The negative impact of α-ketoglutarate dehydrogenase complex deficiency on matrix substrate-level phosphorylation. FASEB J 27:2392-406.