Komlodi 2018 J Bioenerg Biomembr

Komlódi T, Geibl FF, Sassani M, Ambrus A, Tretter L (2018) Membrane potential and delta pH dependency of reverse electron transport-associated hydrogen peroxide production in brain and heart mitochondria. J Bioenerg Biomembr 50:355-365

» PMID: 30116920 Open Access

Komlodi Timea, Geibl F Fanni, Sassani Mathilde, Ambrus Attila, Tretter Laszlo (2018) J Bioenerg Biomembr

Abstract: Succinate-driven reverse electron transport (RET) is one of the main sources of mitochondrial reactive oxygen species (mtROS) in ischemia-reperfusion injury. RET is dependent on mitochondrial membrane potential (Δψm) and transmembrane pH difference (ΔpH), components of the proton motive force (pmf); a decrease in Δψm and/or ΔpH inhibits RET. In this study we aimed to determine which component of the pmf displays the more dominant effect on RET-provoked ROS generation in isolated guinea pig brain and heart mitochondria respiring on succinate or α-glycerophosphate (α-GP). Δψm was detected via safranin fluorescence and a TPP+ electrode, the rate of H₂O₂ formation was measured by Amplex UltraRed, the intramitochondrial pH (pHin) was assessed via BCECF fluorescence. Ionophores were used to dissect the effects of the two components of pmf. The K⁺/H⁺ exchanger, nigericin lowered pHin and ΔpH, followed by a compensatory increase in Δψm that led to an augmented H₂O₂ production. Valinomycin, a K⁺ ionophore, at low [K⁺] increased ΔpH and pHin, decreased Δψm, which resulted in a decline in H₂O₂ formation. It was concluded that Δψm is dominant over ∆pH in modulating the succinate- and α-GP-evoked RET. The elevation of extramitochondrial pH was accompanied by an enhanced H₂O₂ release and a decreased ∆pH. This phenomenon reveals that from the pH component not ∆pH, but rather absolute value of pH has higher impact on the rate of mtROS formation. Minor decrease of Δψm might be applied as a therapeutic strategy to attenuate RET-driven ROS generation in ischemia-reperfusion injury. • Keywords: Alpha-glycerophosphate, Membrane potential, Mitochondria, Nigericin, Proton motive force, Reactive oxygen species, Reverse electron transport, Succinate, Valinomycin • Bioblast editor: Komlodi T • O2k-Network Lab: HU Budapest Tretter L

Cited by

Gnaiger E (2020) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 5^th ed. Bioenerg Commun 2020.2. https://doi.org/10.26124/bec:2020-0002

• Komlodi et al (2022) Hydrogen peroxide production, mitochondrial membrane potential and the coenzyme Q redox state measured at tissue normoxia and experimental hyperoxia in heart mitochondria. MitoFit Preprints 2021 (in prep)
  
• Komlódi et al (2022) The protonmotive force - not merely membrane potential. MitoFit Preprints 2022 (in prep)
  

Labels: MiParea: Respiration, mt-Membrane 

Stress:Oxidative stress;RONS  Organism: Guinea pig  Tissue;cell: Heart, Nervous system  Preparation: Isolated mitochondria  Enzyme: Complex I, Complex II;succinate dehydrogenase  Regulation: mt-Membrane potential, pH  Coupling state: LEAK  Pathway: S, Gp  HRR: Oxygraph-2k, O2k-Fluorometer, O2k-Protocol 

Succinate pathway control state, SUIT-009 AmR mt D021, Nigericin, BEC 2020.2, MitoFit 2021 Tissue normoxia, MitoFit 2022 pmF