Jezek 2013 Abstract MiP2013
|Ježek P, Ježek J, Zelenka J, Dlasková A, Jabůrek M (2013) Antioxidant synergy of mitochondrial uncoupling protein UCP2 and phospholipase iPLA2γ. Mitochondr Physiol Network 18.08.|
Recently, a modified mechanism  of originally suggested fatty acid cycling for mitochondrial uncoupling protein-1 (UCP1) confirmed all our original findings , including the necessity of fatty acid to approach UCP after its cleavage from membrane phospholipids . We now tested a hypothesis that ubiquitous UCP2 provides feedback downregulation of oxidative stress in vivo via synergy with an H2O2–activated mitochondrial calcium–independent phospholipase A2 (mt-iPLA2), which cleaves off free fatty acids required for UCP2 as cycling substrates. We demonstrated UCP2 activation by free fatty acids (detected by gas chromatography/mass spectrometry) while observing that bovine serum albumin or GTP inhibit the tert-butylhydroperoxide– or H2O2–induced increase in respiration and decrease in membrane potential in lung and spleen mitochondria from control but not UCP2-knockout mice . Upon induction of uncoupling, mitochondrial superoxide formation decreased instantly, but not when mt-iPLA2γ was blocked by R-bromoenol lactone (R-BEL). mt-iPLA2γ was alternatively activated by H2O2 produced in conjunction with the electron–transferring flavoprotein:ubiquinone oxidoreductase (ETFQOR), acting in fatty acid β-oxidation. We have also obtained similar findings in insulinoma INS-1E cells silenced for either UCP2 or iPLA2γ. Preliminary data showed that mt-iPLA2γ is directly activated by H2O2. The evidence that this cytoprotective mechanism also exists in vivo stems from the observed increases in protein carbonylation in lung and spleen tissues and mitochondria, potentiated by R-BEL in wild-type but not in UCP2-knockout mice. We thus demonstrate for the first time a synergic antioxidant role between H2O2–activated mt-iPLA2γ and UCP2, because ablation of either mt-iPLA2γ or UCP2 prevented such a role. Our in vitro simulations also show for the first time that UCP2, functional due to fatty acids released by redox–activated mt-iPLA2γ, can suppress mitochondrial superoxide production by its uncoupling action.
H2O2–activated mt-iPLA2γ and UCP2 act in concert to protect against oxidative stress in vivo (cf. Figure).
• O2k-Network Lab: CZ Prague Jezek P
Labels: MiParea: Respiration
Stress:Oxidative stress;RONS Organism: Mouse Tissue;cell: Lung;gill, Islet cell;pancreas;thymus Preparation: Intact cells, Isolated mitochondria Enzyme: Adenine nucleotide translocase, Uncoupling protein Regulation: ATP production, Coupling efficiency;uncoupling, mt-Membrane potential, Redox state, Uncoupler, Fatty acid Coupling state: LEAK, ROUTINE, OXPHOS, ET Pathway: N, S, ROX HRR: Oxygraph-2k, O2k-Fluorometer
Institute of Physiology, Academy of Sciences, Prague, Czech Republic. - Email: email@example.com
Supported by GACR grants P302/10/0346 (PJ), P304/10/P204 (AD) and P303/11/P320 (JJ).
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