Publications by authors named "Roland Stocker"

156 Publications

Bilirubin deficiency renders mice susceptible to hepatic steatosis in the absence of insulin resistance.

Redox Biol 2021 Sep 27;47:102152. Epub 2021 Sep 27.

Heart Research Institute, The University of Sydney, Sydney, Australia; Victor Chang Cardiac Research Institute, Sydney, Australia; School of Life and Environmental Sciences, The University of Sydney, Sydney, Australia. Electronic address:

Background & Aims: Plasma concentrations of bilirubin, a product of heme catabolism formed by biliverdin reductase A (BVRA), inversely associate with the risk of metabolic diseases including hepatic steatosis and diabetes mellitus in humans. Bilirubin has antioxidant and anti-inflammatory activities and may also regulate insulin signaling and peroxisome proliferator-activated receptor alpha (PPARα) activity. However, a causal link between bilirubin and metabolic diseases remains to be established. Here, we used the global Bvra gene knockout (Bvra) mouse as a model of deficiency in bilirubin to assess its role in metabolic diseases.

Approach & Results: We fed mice fat-rich diets to induce hepatic steatosis and insulin resistance. Bile pigments were measured by LC-MS/MS, and hepatic lipids by LC-MS/MS (non-targeted lipidomics), HPLC-UV and Oil-Red-O staining. Oxidative stress was evaluated measuring F-isoprostanes by GC-MS. Glucose metabolism and insulin sensitivity were verified by glucose and insulin tolerance tests, ex vivo and in vivo glucose uptake, and Western blotting for insulin signaling. Compared with wild type littermates, Bvra mice contained negligible bilirubin in plasma and liver, and they had comparable glucose metabolism and insulin sensitivity. However, Bvra mice exhibited an inflamed and fatty liver phenotype, accompanied by hepatic accumulation of oxidized triacylglycerols and F-isoprostanes, in association with depletion of α-tocopherol. α-Tocopherol supplementation reversed the hepatic phenotype and observed biochemical changes in Bvra mice.

Conclusions: Our data suggests that BVRA deficiency renders mice susceptible to oxidative stress-induced hepatic steatosis in the absence of insulin resistance.
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http://dx.doi.org/10.1016/j.redox.2021.102152DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8498001PMC
September 2021

Haem oxygenase limits Mycobacterium marinum infection-induced detrimental ferrostatin-sensitive cell death in zebrafish.

FEBS J 2021 Sep 20. Epub 2021 Sep 20.

Tuberculosis Research Program at the Centenary Institute, The University of Sydney, Camperdown, NSW, Australia.

Iron homeostasis is essential for both sides of the host-pathogen interface. Restricting access of iron slows bacterial growth while iron is also a necessary cofactor for host immunity. Haem oxygenase 1 (HMOX1) is a critical regulator of iron homeostasis that catalyses the liberation of iron during degradation of haem. It is also a stress-responsive protein that can be rapidly upregulated and confers protection to the host. Although a protective role of HMOX1 has been demonstrated in a variety of diseases, the role of HMOX1 in Mycobacterium tuberculosis infection is equivocal across experiments with different host-pathogen combinations. Here, we use the natural host-pathogen pairing of the zebrafish-Mycobacterium marinum infection platform to study the role of zebrafish haem oxygenase in mycobacterial infection. We identify zebrafish Hmox1a as the relevant functional paralog of mammalian HMOX1 and demonstrate a conserved role for Hmox1a in protecting the host from M. marinum infection. Using genetic and chemical tools, we show zebrafish Hmox1a protects the host against M. marinum infection by reducing infection-induced iron accumulation and ferrostatin-sensitive cell death.
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http://dx.doi.org/10.1111/febs.16209DOI Listing
September 2021

Genetic screening reveals phospholipid metabolism as a key regulator of the biosynthesis of the redox-active lipid coenzyme Q.

Redox Biol 2021 Oct 8;46:102127. Epub 2021 Sep 8.

Heart Research Institute, The University of Sydney, Sydney, New South Wales, Australia; Victor Chang Cardiac Research Institute, Sydney, Australia; St Vincent's Clinical School, University of New South Wales, Sydney, Australia; School of Life and Environmental Sciences, The University of Sydney, Sydney, Australia. Electronic address:

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.
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http://dx.doi.org/10.1016/j.redox.2021.102127DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8435697PMC
October 2021

Preparation, validation and use of a vasoactive tryptophan-derived hydroperoxide and relevant control compounds.

Nat Protoc 2021 07 11;16(7):3382-3418. Epub 2021 Jun 11.

Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia.

The L-tryptophan-derived tricyclic hydroperoxide cis-WOOH was recently identified as a novel and biologically important factor for regulating vascular tone and blood pressure under inflammatory conditions and potentially other cellular redox signaling events. cis-WOOH is highly labile and currently not available commercially. In this protocol, we provide procedures for the synthesis, purification, quantification and characterization of cis-WOOH, its epimer trans-WOOH and their respective alcohols (cis-WOH and trans-WOH). Photo-oxidation of L-tryptophan (L-Trp) results in a mixture containing cis-WOOH and trans-WOOH, which are separated and purified by semi-preparative HPLC. cis-WOH and trans-WOH are then produced by sodium borohydride reduction and purified by semi-preparative HPLC. Characterization of cis-WOOH and trans-WOOH and the reduced alcohol variants is achieved using HPLC, fluorescence, NMR and liquid chromatography-tandem mass spectrometry. The protocol provides instructions for storage and quantification, as well as ways to test the stability of these hydroperoxides in commonly used buffers and media. Finally, we describe examples of how to monitor the formation of cis-WOOH in biological samples. The protocol ensures reasonable yield (11%) and purity (>99%) of cis-WOOH and control compounds in 5-6 d and outlines conditions under which cis-WOOH is stable for several months.
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http://dx.doi.org/10.1038/s41596-021-00541-1DOI Listing
July 2021

Highly Efficient Activatable MRI Probe to Sense Myeloperoxidase Activity.

J Med Chem 2021 05 4;64(9):5874-5885. Epub 2021 May 4.

Institute for Innovation in Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts 02129, United States.

Myeloperoxidase (MPO) is a key component of innate immunity but can damage tissues when secreted abnormally. We developed a new generation of a highly efficient MPO-activatable MRI probe (heMAMP) to report MPO activity. heMAMP has improved Gd stability compared to bis-5-HT-Gd-DTPA (MPO-Gd) and demonstrates no significant cytotoxicity. Importantly, heMAMP is more efficiently activated by MPO compared to MPO-Gd, 5HT-DOTA(Gd), and 5HT-DOTAGA-Gd. Molecular docking simulations revealed that heMAMP has increased rigidity via hydrogen bonding intramolecularly and improved binding affinity to the active site of MPO. In animals with subcutaneous inflammation, activated heMAMP showed a 2-3-fold increased contrast-to-noise ratio (CNR) compared to activated MPO-Gd and 4-10 times higher CNR compared to conventional DOTA-Gd. This increased efficacy was further confirmed in a model of unstable atherosclerotic plaque where heMAMP demonstrated a comparable signal increase and responsiveness to MPO inhibition at a 3-fold lower dosage compared to MPO-Gd, further underscoring heMAMP as a potential translational candidate.
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http://dx.doi.org/10.1021/acs.jmedchem.1c00038DOI Listing
May 2021

Methylene blue and ascorbate interfere with the accurate determination of the kinetic properties of IDO2.

FEBS J 2021 08 26;288(16):4892-4904. Epub 2021 Mar 26.

Arterial Inflammation and Redox Biology Group, Heart Research Institute, Newtown, NSW, Australia.

Indoleamine 2,3-dioxygenases (IDOs) catalyze the oxidative cleavage of L-tryptophan (Trp) to N-formylkynurenine. Two IDOs, IDO1 and IDO2, are present in vertebrates. IDO1 is a high-affinity Trp-degrading enzyme involved in several physiological processes. By comparison, IDO2 generally has been reported to have low affinity (high K -value) for Trp, and the enzyme's in vivo function remains unclear. Using IDOs from different species, we show that compared with ferrous-oxy (Fe -O ) IDO1, Fe -O IDO2 is substantially more stable and engages in multiple turnovers of the reaction in the absence of a reductant. Without reductant, Fe -O IDO2 showed K -values in the range of 80-356 μM, that is, values substantially lower than reported previously and close to the physiological concentrations of Trp. Methylene blue and ascorbate (Asc), used commonly as the reducing system for IDO activity determination, significantly affected the enzymatic activity of IDO2: In combination, the two reductants increased the apparent K - and k -values 8- to 117-fold and 2-fold, respectively. Asc alone both activated and inhibited IDO2 by acting as a source of electrons and as a weak competitive inhibitor, respectively. In addition, ferric (Fe ) IDO1 and IDO2 exhibited weak dioxygenase activity, similar to tryptophan 2,3-dioxygenase. Our results shed new light in the enzymatic activity of IDO2, and they support the view that this isoform of IDO also participates in the metabolism of Trp in vivo.
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http://dx.doi.org/10.1111/febs.15806DOI Listing
August 2021

Regulation of vascular tone and blood pressure by singlet molecular oxygen in inflammation.

Curr Opin Nephrol Hypertens 2021 03;30(2):145-150

Heart Research Institute, Newtown.

Purpose Of Review: The principle aim of this review is to prompt vascular researchers interested in vascular inflammation and oxidative stress to consider singlet molecular oxygen (1O2) as a potentially relevant contributor. A secondary goal is to propose novel treatment strategies to address haemodynamic complications associated with septic shock.

Recent Findings: Increased inflammation and oxidative stress are hallmarks of a range of vascular diseases. We recently showed that in systemic inflammation and oxidative stress associated with models of inflammation including sepsis, the tryptophan catabolizing enzyme indoleamine 2,3-dioxygenase-1 (Ido1) contributes to hypotension and decreased blood pressure through production of singlet molecular oxygen (1O2). Once formed, 1O2 converts tryptophan bound to Ido1 to a vasoactive hydroperoxide which decreases arterial tone and blood pressure via oxidation of a specific cysteine residue of protein kinase G1α.

Summary: These works show, for the first time, that 1O2 contributes to arterial redox signalling and that Ido1 contributes to the regulation of blood pressure through production of a novel tryptophan-derived hydroperoxide, thus presenting a new signalling pathway as novel target in the treatment of blood pressure disorders such as sepsis.
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http://dx.doi.org/10.1097/MNH.0000000000000679DOI Listing
March 2021

Hmox1 (Heme Oxygenase-1) Protects Against Ischemia-Mediated Injury via Stabilization of HIF-1α (Hypoxia-Inducible Factor-1α).

Arterioscler Thromb Vasc Biol 2021 01 19;41(1):317-330. Epub 2020 Nov 19.

The Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia (L.L.D., S.M.Y.K., S.T., W.C., A.A., G.J.M., R.S.).

Objective: Hmox1 (heme oxygenase-1) is a stress-induced enzyme that catalyzes the degradation of heme to carbon monoxide, iron, and biliverdin. Induction of Hmox1 and its products protect against cardiovascular disease, including ischemic injury. Hmox1 is also a downstream target of the transcription factor HIF-1α (hypoxia-inducible factor-1α), a key regulator of the body's response to hypoxia. However, the mechanisms by which Hmox1 confers protection against ischemia-mediated injury remain to be fully understood. Approach and Results: Hmox1 deficient () mice had impaired blood flow recovery with severe tissue necrosis and autoamputation following unilateral hindlimb ischemia. Autoamputation preceded the return of blood flow, and bone marrow transfer from littermate wild-type mice failed to prevent tissue injury and autoamputation. In wild-type mice, ischemia-induced expression of Hmox1 in skeletal muscle occurred before stabilization of HIF-1α. Moreover, HIF-1α stabilization and glucose utilization were impaired in mice compared with wild-type mice. Experiments exposing dermal fibroblasts to hypoxia (1% O) recapitulated these key findings. Metabolomics analyses indicated a failure of mice to adapt cellular energy reprogramming in response to ischemia. Prolyl-4-hydroxylase inhibition stabilized HIF-1α in fibroblasts and ischemic skeletal muscle, decreased tissue necrosis and autoamputation, and restored cellular metabolism to that of wild-type mice. Mechanistic studies showed that carbon monoxide stabilized HIF-1α in fibroblasts in response to hypoxia.

Conclusions: Our findings suggest that Hmox1 acts both downstream and upstream of HIF-1α, and that stabilization of HIF-1α contributes to Hmox1's protection against ischemic injury independent of neovascularization.
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http://dx.doi.org/10.1161/ATVBAHA.120.315393DOI Listing
January 2021

Finite element models can reproduce the effect of nucleotomy on the multi-axial compliance of human intervertebral discs.

Comput Methods Biomech Biomed Engin 2020 Oct 16;23(13):934-944. Epub 2020 Jun 16.

Department of Orthopedic Surgery, Bern University Hospital, Bern, Switzerland.

Finite element (FE) models can unravel the link between intervertebral disc (IVD) degeneration and its mechanical behaviour. Nucleotomy may provide the data required for model verification. Three human IVDs were scanned with MRI and tested in multiple loading scenarios, prior and post nucleotomy. The resulting data was used to generate, calibrate, and verify the FE models. Nucleotomy increased the experimental range of motion by 26%, a result reproduced by the FE simulation within a 5% error. This work demonstrates the ability of FE models to reproduce the mechanical compliance of human IVDs prior and post nucleotomy.
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http://dx.doi.org/10.1080/10255842.2020.1773808DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7735477PMC
October 2020

deletion mitigates respiratory deficiency caused by mutations in the gene encoding the coenzyme Q chaperone protein Coq10.

J Biol Chem 2020 05 23;295(18):6023-6042. Epub 2020 Mar 23.

Department of Chemistry and Biochemistry, Molecular Biology Institute, UCLA, Los Angeles, California 90095-1569. Electronic address:

Coenzyme Q (Q ) is a vital lipid component of the electron transport chain that functions in cellular energy metabolism and as a membrane antioxidant. In the yeast , deletion mutants are respiratory-incompetent, sensitive to lipid peroxidation stress, and unable to synthesize Q The yeast deletion mutant is also respiratory-deficient and sensitive to lipid peroxidation, yet it continues to produce Q at an impaired rate. Thus, Coq10 is required for the function of Q in respiration and as an antioxidant and is believed to chaperone Q from its site of synthesis to the respiratory complexes. In several fungi, Coq10 is encoded as a fusion polypeptide with Coq11, a recently identified protein of unknown function required for efficient Q biosynthesis. Because "fused" proteins are often involved in similar biochemical pathways, here we examined the putative functional relationship between Coq10 and Coq11 in yeast. We used plate growth and Seahorse assays and LC-MS/MS analysis to show that deletion rescues respiratory deficiency, sensitivity to lipid peroxidation, and decreased Q biosynthesis of the Δ mutant. Additionally, immunoblotting indicated that yeast Δ mutants accumulate increased amounts of certain Coq polypeptides and display a stabilized CoQ synthome. These effects suggest that Coq11 modulates Q biosynthesis and that its absence increases mitochondrial Q content in the ΔΔ double mutant. This augmented mitochondrial Q content counteracts the respiratory deficiency and lipid peroxidation sensitivity phenotypes of the Δ mutant. This study further clarifies the intricate connection between Q biosynthesis, trafficking, and function in mitochondrial metabolism.
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http://dx.doi.org/10.1074/jbc.RA119.012420DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7196636PMC
May 2020

Cultivation at high osmotic pressure confers ubiquinone 8-independent protection of respiration on .

J Biol Chem 2020 01 11;295(4):981-993. Epub 2019 Dec 11.

Department of Molecular and Cellular Biology, University of Guelph, 488 Gordon Street, Guelph, Ontario N1G 2W1, Canada

Ubiquinone 8 (coenzyme Q8 or Q8) mediates electron transfer within the aerobic respiratory chain, mitigates oxidative stress, and contributes to gene expression in In addition, Q8 was proposed to confer bacterial osmotolerance by accumulating during growth at high osmotic pressure and altering membrane stability. The osmolyte trehalose and membrane lipid cardiolipin accumulate in cells cultivated at high osmotic pressure. Here, Q8 deficiency impaired growth at low osmotic pressure and rendered growth osmotically sensitive. The Q8 deficiency impeded cellular O uptake and also inhibited the activities of two proton symporters, the osmosensing transporter ProP and the lactose transporter LacY. Q8 supplementation decreased membrane fluidity in liposomes, but did not affect ProP activity in proteoliposomes, which is respiration-independent. Liposomes and proteoliposomes prepared with lipids were used for these experiments. Similar oxygen uptake rates were observed for bacteria cultivated at low and high osmotic pressures. In contrast, respiration was dramatically inhibited when bacteria grown at the same low osmotic pressure were shifted to high osmotic pressure. Thus, respiration was restored during prolonged growth of at high osmotic pressure. Of note, bacteria cultivated at low and high osmotic pressures had similar Q8 concentrations. The protection of respiration was neither diminished by cardiolipin deficiency nor conferred by trehalose overproduction during growth at low osmotic pressure, but rather might be achieved by Q8-independent respiratory chain remodeling. We conclude that osmotolerance is conferred through Q8-independent protection of respiration, not by altering physical properties of the membrane.
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http://dx.doi.org/10.1074/jbc.RA119.011549DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6983841PMC
January 2020

Transition to 37°C reveals importance of NADPH in mitigating oxidative stress in stored RBCs.

JCI Insight 2019 11 1;4(21). Epub 2019 Nov 1.

University of Lausanne, Lausanne, Switzerland.

The RBC storage lesion is a multiparametric response that occurs during storage at 4°C, but its impact on transfused patients remains unclear. In studies of the RBC storage lesion, the temperature transition from cold storage to normal body temperature that occurs during transfusion has received limited attention. We hypothesized that multiple deleterious events might occur in this period of increasing temperature. We show dramatic alterations in several properties of therapeutic blood units stored at 4°C after warming them to normal body temperature (37°C), as well as febrile temperature (40°C). In particular, the intracellular content and redox state of NADP(H) were directly affected by post-storage incubation at 37°C, as well as by pro-oxidant storage conditions. Modulation of the NADPH-producing pentose phosphate pathway, but not the prevention of hemoglobin autoxidation by conversion of oxyhemoglobin to carboxyhemoglobin, provided protection against storage-induced alterations in RBCs, demonstrating the central role of NADPH in mitigating increased susceptibility of stored RBCs to oxidative stress. We propose that assessing RBC oxidative status after restoration of body temperature constitutes a sensitive method for detecting storage-related alterations that has the potential to improve the quality of stored RBCs for transfusion.
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http://dx.doi.org/10.1172/jci.insight.126376DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6948768PMC
November 2019

Barocycler-Based Concurrent Multiomics Method To Assess Molecular Changes Associated with Atherosclerosis Using Small Amounts of Arterial Tissue from a Single Mouse.

Anal Chem 2019 10 25;91(20):12670-12679. Epub 2019 Sep 25.

Vascular Biology Division , Victor Chang Cardiac Research Institute , Lowy Packer Building, 405 Liverpool Street , Darlinghurst , New South Wales 2010 , Australia.

Atherosclerosis is a complex, multifactorial disease characterized by the buildup of plaque in the arterial wall. Apolipoprotein E gene deficient () mice serve as a commonly used tool to elucidate the pathophysiology of atherosclerosis because of their propensity to spontaneously develop arterial lesions. To date, however, an integrated omics assessment of atherosclerotic lesions in individual mice has been challenging because of the small amount of diseased and nondiseased tissue available. To address this current limitation, we developed a multiomics method (Multi-ABLE) based on the proteomic method called accelerated Barocycler lysis and extraction (ABLE) to assess the depth of information that can be obtained from arterial tissue derived from a single mouse by splitting ABLE to allow for a combined proteomics-metabolomics-lipidomics analysis (Multi-ABLE). The new method includes tissue lysis via pressure cycling technology (PCT) in a Barocycler, followed by proteomic analysis of half the sample by nanoLC-MS and sequential extraction of lipids (organic extract) and metabolites (aqueous extract) combined with HILIC and reversed phase chromatography and time-of-flight mass spectrometry on the other half. Proteomic analysis identified 845 proteins, 93 of which were significantly altered in lesion-containing arteries. Lipidomic and metabolomic analyses detected 851 lipid and 362 metabolite features, which included 215 and 65 identified lipids and metabolites, respectively. The Multi-ABLE method is the first to apply a concurrent multiomics pipeline to cardiovascular disease using small (<5 mg) tissue samples, and it is applicable to other diseases where limited size samples are available at specific points during disease progression.
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http://dx.doi.org/10.1021/acs.analchem.9b01842DOI Listing
October 2019

Pharmacological characterization of the seven human NOX isoforms and their inhibitors.

Redox Biol 2019 09 11;26:101272. Epub 2019 Jul 11.

Department of Pathology and Immunology, Centre Médical Universitaire, Geneva, Switzerland. Electronic address:

Background: NADPH oxidases (NOX) are a family of flavoenzymes that catalyze the formation of superoxide anion radical (O) and/or hydrogen peroxide (HO). As major oxidant generators, NOX are associated with oxidative damage in numerous diseases and represent promising drug targets for several pathologies. Various small molecule NOX inhibitors are used in the literature, but their pharmacological characterization is often incomplete in terms of potency, specificity and mode of action.

Experimental Approach: We used cell lines expressing high levels of human NOX isoforms (NOX1-5, DUOX1 and 2) to detect NOX-derived O or HO using a variety of specific probes. NOX inhibitory activity of diphenylene iodonium (DPI), apocynin, diapocynin, ebselen, GKT136901 and VAS2870 was tested on NOX isoforms in cellular and membrane assays. Additional assays were used to identify potential off target effects, such as antioxidant activity, interference with assays or acute cytotoxicity.

Key Results: Cells expressing active NOX isoforms formed O, except for DUOX1 and 2, and in all cases activation of NOX isoforms was associated with the detection of extracellular HO. Among all molecules tested, DPI elicited dose-dependent inhibition of all isoforms in all assays, however all other molecules tested displayed interesting pharmacological characteristics, but did not meet criteria for bona fide NOX inhibitors.

Conclusion: Our findings indicate that experimental results obtained with widely used NOX inhibitors must be carefully interpreted and highlight the challenge of developing reliable pharmacological inhibitors of these key molecular targets.
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http://dx.doi.org/10.1016/j.redox.2019.101272DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6658998PMC
September 2019

Inhibition of MPO (Myeloperoxidase) Attenuates Endothelial Dysfunction in Mouse Models of Vascular Inflammation and Atherosclerosis.

Arterioscler Thromb Vasc Biol 2019 07 2;39(7):1448-1457. Epub 2019 May 2.

From the Vascular Biology Division, Victor Chang Cardiac Research Institute, NSW, Australia (D.C., J.T., C.P.S., I.R., G.J.M., R.S.).

Objective- Inflammation-driven endothelial dysfunction initiates and contributes to the progression of atherosclerosis, and MPO (myeloperoxidase) has been implicated as a potential culprit. On release by circulating phagocytes, MPO is thought to contribute to endothelial dysfunction by limiting NO bioavailability via formation of reactive oxidants including hypochlorous acid. However, it remains largely untested whether specific pharmacological inhibition of MPO attenuates endothelial dysfunction. We, therefore, tested the ability of a mechanism-based MPO inhibitor, AZM198, to inhibit endothelial dysfunction in models of vascular inflammation. Approach and Results- Three models of inflammation were used: femoral cuff, the tandem stenosis model of plaque rupture in Apoe mice, and C57BL/6J mice fed a high-fat, high-carbohydrate diet as a model of insulin resistance. Endothelial dysfunction was observed in all 3 models, and oral administration of AZM198 significantly improved endothelial function in the femoral cuff and tandem stenosis models only. Improvement in endothelial function was associated with decreased arterial MPO activity, determined by the in vivo conversion of hydroethidine to 2-chloroethidium, without affecting circulating inflammatory cytokines or arterial MPO content. Mechanistic studies in Mpo mice confirmed the contribution of MPO to endothelial dysfunction and revealed oxidation of sGC (soluble guanylyl cyclase) as the underlying cause of the observed limited NO bioavailability. Conclusions- Pharmacological inhibition of MPO is a potential strategy to limit endothelial dysfunction in vascular inflammation. Visual Overview- An online visual overview is available for this article.
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http://dx.doi.org/10.1161/ATVBAHA.119.312725DOI Listing
July 2019

Cryo-EM reveals distinct conformations of ATP synthase on exposure to ATP.

Elife 2019 03 26;8. Epub 2019 Mar 26.

Molecular, Structural and Computational Biology Division, The Victor Chang Cardiac Research Institute, Darlinghurst, Australia.

ATP synthase produces the majority of cellular energy in most cells. We have previously reported cryo-EM maps of autoinhibited ATP synthase imaged without addition of nucleotide (Sobti et al. 2016), indicating that the subunit ε engages the α, β and γ subunits to lock the enzyme and prevent functional rotation. Here we present multiple cryo-EM reconstructions of the enzyme frozen after the addition of MgATP to identify the changes that occur when this ε inhibition is removed. The maps generated show that, after exposure to MgATP, ATP synthase adopts a different conformation with a catalytic subunit changing conformation substantially and the ε C-terminal domain transitioning via an intermediate 'half-up' state to a condensed 'down' state. This work provides direct evidence for unique conformational states that occur in ATP synthase when ATP binding prevents the ε C-terminal domain from entering the inhibitory 'up' state.
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http://dx.doi.org/10.7554/eLife.43864DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6449082PMC
March 2019

Singlet molecular oxygen regulates vascular tone and blood pressure in inflammation.

Nature 2019 02 13;566(7745):548-552. Epub 2019 Feb 13.

Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia.

Singlet molecular oxygen (O) has well-established roles in photosynthetic plants, bacteria and fungi, but not in mammals. Chemically generated O oxidizes the amino acid tryptophan to precursors of a key metabolite called N-formylkynurenine, whereas enzymatic oxidation of tryptophan to N-formylkynurenine is catalysed by a family of dioxygenases, including indoleamine 2,3-dioxygenase 1. Under inflammatory conditions, this haem-containing enzyme is expressed in arterial endothelial cells, where it contributes to the regulation of blood pressure. However, whether indoleamine 2,3-dioxygenase 1 forms O and whether this contributes to blood pressure control have remained unknown. Here we show that arterial indoleamine 2,3-dioxygenase 1 regulates blood pressure via formation of O. We observed that in the presence of hydrogen peroxide, the enzyme generates O and that this is associated with the stereoselective oxidation of L-tryptophan to a tricyclic hydroperoxide via a previously unrecognized oxidative activation of the dioxygenase activity. The tryptophan-derived hydroperoxide acts in vivo as a signalling molecule, inducing arterial relaxation and decreasing blood pressure; this activity is dependent on Cys42 of protein kinase G1α. Our findings demonstrate a pathophysiological role for O in mammals through formation of an amino acid-derived hydroperoxide that regulates vascular tone and blood pressure under inflammatory conditions.
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http://dx.doi.org/10.1038/s41586-019-0947-3DOI Listing
February 2019

Reactivation of Dihydroorotate Dehydrogenase-Driven Pyrimidine Biosynthesis Restores Tumor Growth of Respiration-Deficient Cancer Cells.

Cell Metab 2019 02 15;29(2):399-416.e10. Epub 2018 Nov 15.

Eunice Kennedy Shriver Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.

Cancer cells without mitochondrial DNA (mtDNA) do not form tumors unless they reconstitute oxidative phosphorylation (OXPHOS) by mitochondria acquired from host stroma. To understand why functional respiration is crucial for tumorigenesis, we used time-resolved analysis of tumor formation by mtDNA-depleted cells and genetic manipulations of OXPHOS. We show that pyrimidine biosynthesis dependent on respiration-linked dihydroorotate dehydrogenase (DHODH) is required to overcome cell-cycle arrest, while mitochondrial ATP generation is dispensable for tumorigenesis. Latent DHODH in mtDNA-deficient cells is fully activated with restoration of complex III/IV activity and coenzyme Q redox-cycling after mitochondrial transfer, or by introduction of an alternative oxidase. Further, deletion of DHODH interferes with tumor formation in cells with fully functional OXPHOS, while disruption of mitochondrial ATP synthase has little effect. Our results show that DHODH-driven pyrimidine biosynthesis is an essential pathway linking respiration to tumorigenesis, pointing to inhibitors of DHODH as potential anti-cancer agents.
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http://dx.doi.org/10.1016/j.cmet.2018.10.014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7484595PMC
February 2019

Myeloperoxidase is a potential molecular imaging and therapeutic target for the identification and stabilization of high-risk atherosclerotic plaque.

Eur Heart J 2018 09;39(35):3301-3310

Vascular Biology Division, Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool Street, Darlinghurst NSW, Australia.

Aims: As the inflammatory enzyme myeloperoxidase (MPO) is abundant in ruptured human atherosclerotic plaques, we aimed to investigate the role of MPO as a potential diagnostic and therapeutic target for high-risk plaque.

Methods And Results: We employed the tandem stenosis model of atherosclerotic plaque instability in apolipoprotein E gene knockout (Apoe-/-) mice. To test the role of MPO, we used Mpo-/-Apoe-/- mice and the 2-thioxanthine MPO inhibitor AZM198. In vivo MPO activity was assessed by liquid chromatography-tandem mass spectrometry detection of 2-chloroethidium generation from hydroethidine and by bis-5HT-DTPA-Gd (MPO-Gd) molecular magnetic resonance imaging (MRI), while plaque phenotype was verified histologically. Myeloperoxidase activity was two-fold greater in plaque with unstable compared with stable phenotype. Genetic deletion of MPO significantly increased fibrous cap thickness, and decreased plaque fibrin and haemosiderin content in plaque with unstable phenotype. AZM198 inhibited MPO activity and it also increased fibrous cap thickness and decreased fibrin and haemosiderin in plaque with unstable phenotype, without affecting lesion monocytes and red blood cell markers or circulating leukocytes and lipids. MPO-Gd MRI demonstrated sustained enhancement of plaque with unstable phenotype on T1-weighted imaging that was two-fold greater than stable plaque and was significantly attenuated by both AZM198 treatment and deletion of the Mpo gene.

Conclusion: Our data implicate MPO in atherosclerotic plaque instability and suggest that non-invasive imaging and pharmacological inhibition of plaque MPO activity hold promise for clinical translation in the management of high-risk coronary artery disease.
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http://dx.doi.org/10.1093/eurheartj/ehy419DOI Listing
September 2018

Endothelial indoleamine 2,3-dioxygenase-1 regulates the placental vascular tone and is deficient in intrauterine growth restriction and pre-eclampsia.

Sci Rep 2018 04 3;8(1):5488. Epub 2018 Apr 3.

Gottfried Schatz Research Centre for Cell Signalling, Metabolism and Ageing, Department of Cell Biology, Histology and Embryology, Medical University of Graz, Graz, 8010, Austria.

Indoleamine 2,3-dioxygenase-1 (IDO1) mediates the degradation of L-tryptophan (L-Trp) and is constitutively expressed in the chorionic vascular endothelium of the human placenta with highest levels in the microvasculature. Given that endothelial expression of IDO1 has been shown to regulate vascular tone and blood pressure in mice under the condition of systemic inflammation, we asked whether IDO1 is also involved in the regulation of placental blood flow and if yes, whether this function is potentially impaired in intrauterine growth restriction (IUGR) and pre-eclampsia (PE). In the large arteries of the chorionic plate L-Trp induced relaxation only after upregulation of IDO1 using interferon gamma and tumor necrosis factor alpha. However, ex vivo placental perfusion of pre-constricted cotyledonic vasculature with L-Trp decreases the vessel back pressure without prior IDO1 induction. Further to this finding, IDO1 protein expression and activity is reduced in IUGR and PE when compared to gestational age-matched control tissue. These data suggest that L-Trp catabolism plays a role in the regulation of placental vascular tone, a finding which is potentially linked to placental and fetal growth. In this context our data suggest that IDO1 deficiency is related to the pathogenesis of IUGR and PE.
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http://dx.doi.org/10.1038/s41598-018-23896-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5883010PMC
April 2018

Mitochondrial oxidative stress causes insulin resistance without disrupting oxidative phosphorylation.

J Biol Chem 2018 05 29;293(19):7315-7328. Epub 2018 Mar 29.

Charles Perkins Centre, School of Life and Environmental Sciences, Camperdown, New South Wales 2006, Australia; Charles Perkins Centre, Sydney Medical School, University of Sydney, Camperdown, New South Wales 2006, Australia. Electronic address:

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 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.
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http://dx.doi.org/10.1074/jbc.RA117.001254DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5950018PMC
May 2018

Mitochondrial CoQ deficiency is a common driver of mitochondrial oxidants and insulin resistance.

Elife 2018 02 6;7. Epub 2018 Feb 6.

Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia.

Insulin resistance in muscle, adipocytes and liver is a gateway to a number of metabolic diseases. Here, we show a selective deficiency in mitochondrial coenzyme Q (CoQ) in insulin-resistant adipose and muscle tissue. This defect was observed in a range of in vitro insulin resistance models and adipose tissue from insulin-resistant humans and was concomitant with lower expression of mevalonate/CoQ biosynthesis pathway proteins in most models. Pharmacologic or genetic manipulations that decreased mitochondrial CoQ triggered mitochondrial oxidants and insulin resistance while CoQ supplementation in either insulin-resistant cell models or mice restored normal insulin sensitivity. Specifically, lowering of mitochondrial CoQ caused insulin resistance in adipocytes as a result of increased superoxide/hydrogen peroxide production via complex II. These data suggest that mitochondrial CoQ is a proximal driver of mitochondrial oxidants and insulin resistance, and that mechanisms that restore mitochondrial CoQ may be effective therapeutic targets for treating insulin resistance.
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http://dx.doi.org/10.7554/eLife.32111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5800848PMC
February 2018

Absence of the biliverdin reductase-a gene is associated with increased endogenous oxidative stress.

Free Radic Biol Med 2018 02 1;115:156-165. Epub 2017 Dec 1.

Vascular Biology Division, Victor Chang Cardiac Research Institute, Sydney, Australia; St Vincent's Clinical School, University of New South Wales, Sydney, Australia. Electronic address:

Bilirubin, a byproduct of heme catabolism, has been shown to be an effective lipid-soluble antioxidant in vitro. Bilirubin is able to inhibit free radical chain reactions and protects against oxidant-induced damage in vitro and ex vivo. However, direct evidence for bilirubin's antioxidant effects in vivo remains limited. As bilirubin is formed from biliverdin by biliverdin reductase, we generated global biliverdin reductase-a gene knockout (Bvra) mice to assess the contribution of bilirubin as an endogenous antioxidant. Bvra mice appear normal and are born at the expected Mendelian ratio from Bvra x Bvra matings. Compared with corresponding littermate Bvra and Bvra animals, Bvra mice have green gall bladders and their plasma concentrations of biliverdin and bilirubin are approximately 25-fold higher and 100-fold lower, respectively. Naïve Bvra and Bvra mice have comparable plasma lipid profiles and low-molecular weight antioxidants, i.e., ascorbic acid, α-tocopherol and ubiquinol-9. Compared with wild-type littermates, however, plasma from Bvra mice contains higher concentrations of cholesteryl ester hydroperoxides (CE-OOH), and their peroxiredoxin 2 (Prx2) in erythrocytes is more oxidized as assessed by the extent of Prx2 dimerization. These data show that Bvra mice experience higher oxidative stress in blood, implying that plasma bilirubin attenuates endogenous oxidative stress.
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http://dx.doi.org/10.1016/j.freeradbiomed.2017.11.020DOI Listing
February 2018

Flavonoid-Rich Apple Improves Endothelial Function in Individuals at Risk for Cardiovascular Disease: A Randomized Controlled Clinical Trial.

Mol Nutr Food Res 2018 02 19;62(3). Epub 2017 Dec 19.

School of Medicine, University of Western Australia, Royal Perth Hospital, Perth, Western Australia, Australia.

Scope: The cardioprotective effects of apples are primarily attributed to flavonoids, found predominantly in the skin. This study aimed to determine if acute and/or chronic (4 weeks) ingestion of flavonoid-rich apples improves endothelial function, blood pressure (BP), and arterial stiffness in individuals at risk for cardiovascular diseases (CVD).

Methods And Results: In this randomized, controlled cross-over trial, acute and 4 week intake of apple with skin (high flavonoid apple, HFA) is compared to intake of apple flesh only (low flavonoid apple, LFA) in 30 participants. The primary outcome is endothelial function assessed using flow-mediated dilation (FMD) of the brachial artery, while main secondary outcomes are 24 h ambulatory BP and arterial stiffness. Other outcomes include fasting serum glucose and lipoprotein profile, plasma heme oxygenase-1 (Hmox-1), F -isoprostanes, flavonoid metabolites, and plasma and salivary nitrate (NO ) and nitrite (NO ) concentrations. Compared to LFA control, the HFA results in a significant increase in FMD acutely (0.8%, p < 0.001) and after 4 weeks chronic intake (0.5%, p < 0.001), and in plasma flavonoid metabolites (p < 0.0001). Other outcomes are not altered significantly.

Conclusion: A lower risk of CVD with higher apple consumption could be mediated by the beneficial effect of apple skin on endothelial function, both acutely and chronically.
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http://dx.doi.org/10.1002/mnfr.201700674DOI Listing
February 2018

[Late sequelae of a stab injury in the forearm with incorporation of a foreign body].

Handchir Mikrochir Plast Chir 2017 10 17;49(5):352-354. Epub 2017 Oct 17.

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http://dx.doi.org/10.1055/s-0043-118796DOI Listing
October 2017

NADPH oxidases as drug targets and biomarkers in neurodegenerative diseases: What is the evidence?

Free Radic Biol Med 2017 11 12;112:387-396. Epub 2017 Aug 12.

Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, Switzerland. Electronic address:

Neurodegenerative disease are frequently characterized by microglia activation and/or leukocyte infiltration in the parenchyma of the central nervous system and at the molecular level by increased oxidative modifications of proteins, lipids and nucleic acids. NADPH oxidases (NOX) emerged as a novel promising class of pharmacological targets for the treatment of neurodegeneration due to their role in oxidant generation and presumably in regulating microglia activation. The unique function of NOX is the generation of superoxide anion (O) and hydrogen peroxide (HO). However in the context of neuroinflammation, they present paradoxical features since O/HO generated by NOX and/or secondary reactive oxygen species (ROS) derived from O/HO can either lead to neuronal oxidative damage or resolution of inflammation. The role of NOX enzymes has been investigated in many models of neurodegenerative diseases by using either genetic or pharmacological approaches. In the present review we provide a critical assessment of recent findings related to the role of NOX in the CNS as well as how the field has advanced over the last 5 years. In particular, we focus on the data derived from the work of a consortium (Neurinox) funded by the European Commission's Programme 7 (FP7). We discuss the evidence gathered from animal models and human samples linking NOX expression/activity with neuroinflammation in neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS) and Creutzfeldt-Jakob disease as well as autoimmune demyelinating diseases like multiple sclerosis (MS) and chronic inflammatory demyelinating polyneuropathy (CIDP). We address the possibility to use measurement of the activity of the NOX2 isoform in blood samples as biomarker of disease severity and treatment efficacy in neurodegenerative disease. Finally we clarify key controversial aspects in the field of NOX, such as NOX cellular expression in the brain, measurement of NOX activity, impact of genetic deletion of NOX in animal models of neurodegeneration and specificity of NOX inhibitors.
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http://dx.doi.org/10.1016/j.freeradbiomed.2017.08.006DOI Listing
November 2017

NAD Deficiency, Congenital Malformations, and Niacin Supplementation.

N Engl J Med 2017 08;377(6):544-552

From the Divisions of Developmental and Stem Cell Biology (H.S., A.E., M.R., E.M.M.A.M., R.W., J.M., J.O.S., E.I., K.S., J.H., K.K., G.C., D.B.S., S.L.D.), Vascular Biology (G.J.M., R.S.), and Molecular, Structural, and Computational Biology (D.T.H., J.W.K.H., E.G.), Victor Chang Cardiac Research Institute, the Faculties of Medicine and Science, University of New South Wales (H.S., A.E., J.O.S., E.I., D.T.H., G.J.M., J.W.K.H., K.K., R.S., E.G., G.C., D.B.S., S.L.D.), Liverpool Hospital, Department of Clinical Genetics (A.E., A.C.), the Department of Clinical Genetics (A.E., J.S., F.C., D.O.S.) and the Heart Centre for Children (D.S.W.), Children's Hospital at Westmead, the Discipline of Genetic Medicine (A.E., J.S., F.C., D.O.S.) and the Medical School (D.S.W.), University of Sydney, and the Faculty of Medicine and Health Sciences, Macquarie University (C.K.L., G.J.G.) - all in Sydney, the School of Biological Sciences, University of Adelaide, Adelaide, SA (J.N.H., P.Q.T.), and the Institute of Health and Biomedical Innovation, Queensland University of Technology (A.M.M.-L., P.J.L., M.A.B., E.L.D.), the Translational Research Institute (A.M.M.-L., P.J.L., M.A.B., E.L.D.), the Department of Endocrinology, Royal Brisbane and Women's Hospital (E.L.D.), and the University of Queensland School of Medicine (E.L.D.), Brisbane - all in Australia; and Spectrum Health Medical Group, Medical Genetics, Grand Rapids, MI (P.R.M.).

Background: Congenital malformations can be manifested as combinations of phenotypes that co-occur more often than expected by chance. In many such cases, it has proved difficult to identify a genetic cause. We sought the genetic cause of cardiac, vertebral, and renal defects, among others, in unrelated patients.

Methods: We used genomic sequencing to identify potentially pathogenic gene variants in families in which a person had multiple congenital malformations. We tested the function of the variant by using assays of in vitro enzyme activity and by quantifying metabolites in patient plasma. We engineered mouse models with similar variants using the CRISPR (clustered regularly interspaced short palindromic repeats)-Cas9 system.

Results: Variants were identified in two genes that encode enzymes of the kynurenine pathway, 3-hydroxyanthranilic acid 3,4-dioxygenase (HAAO) and kynureninase (KYNU). Three patients carried homozygous variants predicting loss-of-function changes in the HAAO or KYNU proteins (HAAO p.D162*, HAAO p.W186*, or KYNU p.V57Efs*21). Another patient carried heterozygous KYNU variants (p.Y156* and p.F349Kfs*4). The mutant enzymes had greatly reduced activity in vitro. Nicotinamide adenine dinucleotide (NAD) is synthesized de novo from tryptophan through the kynurenine pathway. The patients had reduced levels of circulating NAD. Defects similar to those in the patients developed in the embryos of Haao-null or Kynu-null mice owing to NAD deficiency. In null mice, the prevention of NAD deficiency during gestation averted defects.

Conclusions: Disruption of NAD synthesis caused a deficiency of NAD and congenital malformations in humans and mice. Niacin supplementation during gestation prevented the malformations in mice. (Funded by the National Health and Medical Research Council of Australia and others.).
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http://dx.doi.org/10.1056/NEJMoa1616361DOI Listing
August 2017

Characterization of plasma labile heme in hemolytic conditions.

FEBS J 2017 10 11;284(19):3278-3301. Epub 2017 Sep 11.

Instituto Gulbenkian da Ciência, Oeiras, Portugal.

Extracellular hemoglobin, a byproduct of hemolysis, can release its prosthetic heme groups upon oxidation. This produces metabolically active heme that is exchangeable between acceptor proteins, macromolecules and low molecular weight ligands, termed here labile heme. As it accumulates in plasma labile heme acts in a pro-oxidant manner and regulates cellular metabolism while exerting pro-inflammatory and cytotoxic effects that foster the pathogenesis of hemolytic diseases. Here, we developed and characterized a panel of heme-specific single domain antibodies (sdAbs) that together with a cellular-based heme reporter assay, allow for quantification and characterization of labile heme in plasma during hemolytic conditions. Using these approaches, we demonstrate that when generated during hemolytic conditions labile heme is bound to plasma molecules with an affinity higher than 10 m and that 2-8% (~ 2-5 μm) of the total amount of heme detected in plasma can be internalized by bystander cells, termed here bioavailable heme. Acute, but not chronic, hemolysis is associated with transient reduction of plasma heme-binding capacity, that is, the ability of plasma molecules to bind labile heme with an affinity higher than 10 m. The heme-specific sdAbs neutralize the pro-oxidant activity of soluble heme in vitro, suggesting that these maybe used to counter the pathologic effects of labile heme during hemolytic conditions. Finally, we show that heme-specific sdAbs can be used to visualize cellular heme. In conclusion, we describe a panel of heme-specific sdAbs that when used with other approaches provide novel insights to the pathophysiology of heme.
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http://dx.doi.org/10.1111/febs.14192DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5978748PMC
October 2017

Near-infrared autofluorescence induced by intraplaque hemorrhage and heme degradation as marker for high-risk atherosclerotic plaques.

Nat Commun 2017 07 13;8(1):75. Epub 2017 Jul 13.

Baker IDI Heart & Diabetes Institute, Melbourne, VIC, Australia.

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.Atherosclerosis diagnosis relies primarily on imaging and early detection of high-risk atherosclerotic plaques is important for risk stratification of patients and stabilization therapies. Here Htun et al. demonstrate that vulnerable atherosclerotic plaques generate near-infrared autofluorescence that can be detected via emission computed tomography.
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http://dx.doi.org/10.1038/s41467-017-00138-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5509677PMC
July 2017
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