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Mitochondrial energy production and function rely on optimal concentrations of the essential redox-active lipid, coenzyme Q (CoQ). CoQ deficiency results in mitochondrial dysfunction associated with increased mitochondrial oxidative stress and a range of pathologies. What drives CoQ deficiency in many of these pathologies is unknown, just as there currently is no effective therapeutic strategy to overcome CoQ deficiency in humans. To date, large-scale studies aimed at systematically interrogating endogenous systems that control CoQ biosynthesis and their potential utility to treat disease have not been carried out. Therefore, we developed a quantitative high-throughput method to determine CoQ concentrations in yeast cells. Applying this method to the Yeast Deletion Collection as a genome-wide screen, 30 genes not known previously to regulate cellular concentrations of CoQ were discovered. In combination with untargeted lipidomics and metabolomics, phosphatidylethanolamine N-methyltransferase (PEMT) deficiency was confirmed as a positive regulator of CoQ synthesis, the first identified to date. Mechanistically, PEMT deficiency alters mitochondrial concentrations of one-carbon metabolites, characterized by an increase in the S-adenosylmethionine to S-adenosylhomocysteine (SAM-to-SAH) ratio that reflects mitochondrial methylation capacity, drives CoQ synthesis, and is associated with a decrease in mitochondrial oxidative stress. The newly described regulatory pathway appears evolutionary conserved, as ablation of PEMT using antisense oligonucleotides increases mitochondrial CoQ in mouse-derived adipocytes that translates to improved glucose utilization by these cells, and protection of mice from high-fat diet-induced insulin resistance. Our studies reveal a previously unrecognized relationship between two spatially distinct lipid pathways with potential implications for the treatment of CoQ deficiencies, mitochondrial oxidative stress/dysfunction, and associated diseases.

Atherosclerosis is a major cause of mortality and morbidity, which is mainly driven by complications such as myocardial infarction and stroke. These complications are caused by thrombotic arterial occlusion localized at the site of high-risk atherosclerotic plaques, of which early detection and therapeutic stabilization are urgently needed. Here we show that near-infrared autofluorescence is associated with the presence of intraplaque hemorrhage and heme degradation products, particularly bilirubin by using our recently created mouse model, which uniquely reflects plaque instability as seen in humans, and human carotid endarterectomy samples. Fluorescence emission computed tomography detecting near-infrared autofluorescence allows in vivo monitoring of intraplaque hemorrhage, establishing a preclinical technology to assess and monitor plaque instability and thereby test potential plaque-stabilizing drugs. We suggest that near-infrared autofluorescence imaging is a novel technology that allows identification of atherosclerotic plaques with intraplaque hemorrhage and ultimately holds promise for detection of high-risk plaques in patients. [ABSTRACT FROM AUTHOR]

Atherosclerosis is the main pathophysiological process underlying coronary artery disease (CAD). Acute complications of atherosclerosis, such as myocardial infarction, are caused by the rupture of vulnerable atherosclerotic plaques, which are characterized by thin, highly inflamed, and collagen-poor fibrous caps. Several lines of evidence mechanistically link the heme peroxidase myeloperoxidase (MPO), inflammation as well as acute and chronic manifestations of atherosclerosis. MPO and MPO-derived oxidants have been shown to contribute to the formation of foam cells, endothelial dysfunction and apoptosis, the activation of latent matrix metalloproteinases, and the expression of tissue factor that can promote the development of vulnerable plaque. As such, detection, quantification and imaging of MPO mass and activity have become useful in cardiac risk stratification, both for disease assessment and in the identification of patients at risk of plaque rupture. This review summarizes the current knowledge about the role of MPO in CAD with a focus on its possible roles in plaque rupture and recent advances to quantify and image MPO in plasma and atherosclerotic plaques. [ABSTRACT FROM AUTHOR]

The lipocalin α1-microglobulin (α1m) is a 26-kDa glycoprotein present in plasma and in interstitial fluids of all tissues. The protein was recently shown to have reductase properties, reducing heme-proteins and other substrates, and was also reported to be involved in binding and scavenging of heme and tryptophan metabolites. To investigate its possible role as a reductant of organic radicals, we have studied the interaction of γ1m with the synthetic radical, 2,2′-azino-bis-(3-ethylbenzthiazoline-6- sulfonic acid) (ABTS radical). The lipocalin readily reacted with the ABTS radical forming reduced ABTS. The apparent rate constant for this reaction was 6.3 ± 2.5 × 10³ M-1 s-1. A second reaction product with an intense purple color and an absorbance maximum at 550 nm was formed at a similar rate. This was shown by liquid chromatography/mass spectrometry to be derived from covalent attachment of a portion of ABTS radical to tyrosine residues on α1m. The relative yields of reduced ABTS and the purple ABTS derivative bound to α1m were ∼2:1. Both reactions were dependent on the thiolate group of the cysteine residue in position 34 of the α1m polypeptide. Our results indicate that α1m is involved in a sequential reduction of ABTS radicals followed by trapping of these radicals by covalent attachment. In combination with the reported physiological properties of the protein, our results suggest that α1m may be a radical reductant and scavenger in vivo. [ABSTRACT FROM AUTHOR]

Mitochondrial oxidative stress, mitochondrial dysfunction, or both have been implicated in insulin resistance. However, disentangling the individual roles of these processes in insulin resistance has been difficult because they often occur in tandem, and tools that selectively increase oxidant production without impairing mitochondrial respiration have been lacking. Using the dimer/monomer status of peroxiredoxin isoforms as an indicator of compartmental hydrogen peroxide burden, we provide evidence that oxidative stress is localized to mitochondria in insulin-resistant 3T3-L1 adipocytes and adipose tissue from mice. To dissociate oxidative stress from impaired oxidative phosphorylation and study whether mitochondrial oxidative stress per se can cause insulin resistance, we used mitochondria-targeted paraquat (MitoPQ) to generate superoxide within mitochondria without directly disrupting the respiratory chain. At ≤10 μm, MitoPQ specifically increased mitochondrial superoxide and hydrogen peroxide without altering mitochondrial respiration in intact cells. Under these conditions, MitoPQ impaired insulin-stimulated glucose uptake and glucose transporter 4 (GLUT4) translocation to the plasma membrane in both adipocytes and myotubes. MitoPQ recapitulated many features of insulin resistance found in other experimental models, including increased oxidants in mitochondria but not cytosol; a more profound effect on glucose transport than on other insulin-regulated processes, such as protein synthesis and lipolysis; an absence of overt defects in insulin signaling; and defective insulin- but not AMP-activated protein kinase (AMPK)-regulated GLUT4 translocation. We conclude that elevated mitochondrial oxidants rapidly impair insulin-regulated GLUT4 translocation and significantly contribute to insulin resistance and that MitoPQ is an ideal tool for studying the link between mitochondrial oxidative stress and regulated GLUT4 trafficking., (© 2018 by The American Society for Biochemistry and Molecular Biology, Inc.)

Objective: We aimed to investigate the role of oxidative stress in the progression of multiple sclerosis (MS)., Methods: We determined by liquid chromatography-tandem mass spectrometry nonenzymatic (F2-isoprostanes) and enzymatic oxidation products of arachidonic acid (prostaglandin F2α [PGF2α]) in plasma and CSF of 45 controls (other neurologic disease [OND] with no signs of inflammation) and 62 patients with MS. Oxidation products were correlated with disease severity and validated biomarkers of inflammation (chemokine ligand 13; matrix metalloproteinase-9; osteopontin) and axonal damage (neurofilament light protein)., Results: Compared with OND controls, plasma concentrations of F2-isoprostanes and PGF2α were significantly lower in patients with progressive disease, and decreased with increasing disability score (Expanded Disability Status Scale). In contrast, CSF concentrations of PGF2α, but not F2-isoprostanes, were significantly higher in patients with progressive disease than OND controls (p < 0.01). The content of PGF2α in CSF increased with disease severity (p = 0.044) and patient age (p = 0.022), although this increase could not be explained by age. CSF PGF2α decreased with natalizumab and methylprednisolone treatment and was unaffected by the use of nonsteroidal anti-inflammatory drug in secondary progressive MS. CSF PGF2α did not associate with validated CSF markers of inflammation and axonal damage that themselves did not associate with the Expanded Disability Status Scale., Conclusions: Our data suggest that MS progression is associated with low systemic oxidative activity. This may contribute to immune dysregulation with CNS inflammation accompanied by increased local cyclooxygenase-dependent lipid oxidation.

Heme oxygenase-1 is critical for iron recycling during red blood cell turnover, whereas its impact on steady-state erythropoiesis and red blood cell lifespan is not known. We show here that in 8- to 14-week old mice, heme oxygenase-1 deficiency adversely affects steady-state erythropoiesis in the bone marrow. This is manifested by a decrease in Ter-119(+)-erythroid cells, abnormal adhesion molecule expression on macrophages and erythroid cells, and a greatly diminished ability to form erythroblastic islands. Compared with wild-type animals, red blood cell size and hemoglobin content are decreased, while the number of circulating red blood cells is increased in heme oxygenase-1 deficient mice, overall leading to microcytic anemia. Heme oxygenase-1 deficiency increases oxidative stress in circulating red blood cells and greatly decreases the frequency of macrophages expressing the phosphatidylserine receptor Tim4 in bone marrow, spleen and liver. Heme oxygenase-1 deficiency increases spleen weight and Ter119(+)-erythroid cells in the spleen, although α4β1-integrin expression by these cells and splenic macrophages positive for vascular cell adhesion molecule 1 are both decreased. Red blood cell lifespan is prolonged in heme oxygenase-1 deficient mice compared with wild-type mice. Our findings suggest that while macrophages and relevant receptors required for red blood cell formation and removal are substantially depleted in heme oxygenase-1 deficient mice, the extent of anemia in these mice may be ameliorated by the prolonged lifespan of their oxidatively stressed erythrocytes., (Copyright© Ferrata Storti Foundation.)

The lipocalin alpha(1)-microglobulin (alpha(1)m) is a 26-kDa glycoprotein present in plasma and in interstitial fluids of all tissues. The protein was recently shown to have reductase properties, reducing heme-proteins and other substrates, and was also reported to be involved in binding and scavenging of heme and tryptophan metabolites. To investigate its possible role as a reductant of organic radicals, we have studied the interaction of alpha(1)m with the synthetic radical, 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS radical). The lipocalin readily reacted with the ABTS radical forming reduced ABTS. The apparent rate constant for this reaction was 6.3 +/- 2.5 x 10(3) M(-1) s(-1). A second reaction product with an intense purple color and an absorbance maximum at 550 nm was formed at a similar rate. This was shown by liquid chromatography/mass spectrometry to be derived from covalent attachment of a portion of ABTS radical to tyrosine residues on alpha(1)m. The relative yields of reduced ABTS and the purple ABTS derivative bound to alpha(1)m were approximately 2:1. Both reactions were dependent on the thiolate group of the cysteine residue in position 34 of the alpha(1)m polypeptide. Our results indicate that alpha(1)m is involved in a sequential reduction of ABTS radicals followed by trapping of these radicals by covalent attachment. In combination with the reported physiological properties of the protein, our results suggest that alpha(1)m may be a radical reductant and scavenger in vivo.