ABSTRACT
Mitochondria have originated in eukaryotic cells by endosymbiosis of a specialized prokaryote approximately 2 billion years ago. They are essential for normal cell function by providing energy through their role in oxidizing carbon substrates. Glutathione (GSH) is a major thiol-disulfide redox buffer of the cell including the mitochondrial matrix and intermembrane space. We have generated cardiomyocyte-specific Grx1-roGFP2 GSH redox potential (EGSH) biosensor mice in the past, in which the sensor is targeted to the mitochondrial matrix. Using this mouse model a distinct EGSH of the mitochondrial matrix (-278.9⯱â¯0.4â¯mV) in isolated cardiomyocytes is observed. When analyzing the EGSH in isolated mitochondria from the transgenic hearts, however, the EGSH in the mitochondrial matrix is significantly oxidized (-247.7⯱â¯8.7â¯mV). This is prevented by adding N-Ethylmaleimide during the mitochondria isolation procedure, which precludes disulfide bond formation. A similar reducing effect is observed by isolating mitochondria in hypoxic (0.1-3% O2) conditions that mimics mitochondrial pO2 levels in cellulo. The reduced EGSH is accompanied by lower ROS production, reduced complex III activity but increased ATP levels produced at baseline and after stimulation with succinate/ADP. Altogether, we demonstrate that oxygenation is an essential factor that needs to be considered when analyzing mitochondrial function ex vivo.
Subject(s)
Mitochondria/metabolism , Oxygen/metabolism , Adenosine Triphosphate/metabolism , Animals , Electron Transport Complex III/metabolism , Hydrogen Peroxide/metabolism , Hyperoxia/metabolism , Mice , Mitochondria, Heart/metabolism , Myocytes, Cardiac/metabolism , Oxidation-Reduction , Superoxides/metabolismABSTRACT
Macrophages are essential for the inflammatory response after an ischemic insult and thereby influence tissue recovery. For the oxygen sensing prolyl-4-hydroxylase domain enzyme (PHD) 2 a clear impact on the macrophage-mediated arteriogenic response after hind-limb ischemia has been demonstrated previously, which involves fine tuning a M2-like macrophage population. To analyze the role of PHD3 in macrophages, we performed hind-limb ischemia (ligation and excision of the femoral artery) in myeloid-specific PHD3 knockout mice (PHD3-/-) and analyzed the inflammatory cell invasion, reperfusion recovery and fibrosis in the ischemic muscle post-surgery. In contrast to PHD2, reperfusion recovery and angiogenesis was unaltered in PHD3-/- compared to WT mice. Macrophages from PHD3-/- mice showed, however, a dampened inflammatory reaction in the affected skeletal muscle tissues compared to WT controls. This was associated with a decrease in fibrosis and an anti-inflammatory phenotype of the PHD3-/- macrophages, as well as decreased expression of Cyp2s1 and increased PGE2-secretion, which could be mimicked by PHD3-/- bone marrow-derived macrophages in serum starvation.
Subject(s)
Fibrosis/enzymology , Fibrosis/physiopathology , Hypoxia-Inducible Factor-Proline Dioxygenases/metabolism , Inflammation/enzymology , Inflammation/physiopathology , Ischemia/enzymology , Ischemia/physiopathology , Animals , Cytochrome P-450 Enzyme System/genetics , Cytochrome P-450 Enzyme System/metabolism , Disease Models, Animal , Fibrosis/metabolism , Hindlimb , Hypoxia-Inducible Factor-Proline Dioxygenases/genetics , Inflammation/metabolism , Ischemia/metabolism , Macrophages/metabolism , Mice , Mice, KnockoutABSTRACT
On a molecular level, cells sense changes in oxygen availability through the PHDs, which regulate the protein stability of the α-subunit of the transcription factor HIF. Especially, PHD3 has been additionally associated with apoptotic cell death. We hypothesized that PHD3 plays a role in cell-fate decisions in macrophages. Therefore, myeloid-specific PHD3(-/-) mice were created and analyzed. PHD3(-/-) BMDM showed no altered HIF-1α or HIF-2α stabilization or increased HIF target gene expression in normoxia or hypoxia. Macrophage M1 and M2 polarization was unchanged likewise. Compared with macrophages from WT littermates, PHD3(-/-) BMDM exhibited a significant reduction in TUNEL-positive cells after serum withdrawal or treatment with stauro and SNAP. Under the same conditions, PHD3(-/-) BMDM also showed less Annexin V staining, which is representative for membrane disruption, and indicated a reduced early apoptosis. In an unbiased transcriptome screen, we found that Angptl2 expression was reduced in PHD3(-/-) BMDM under stress conditions. Addition of rAngptl2 rescued the antiapoptotic phenotype, demonstrating that it is involved in the PHD3-mediated response toward apoptotic stimuli in macrophages.
