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Seeger DR, Schofield B, Besch D, Golovko SA, Kotha P, Parmer M, Solaymani-Mohammadi S, Golovko MY. Exogenous oxygen is required for prostanoid induction under brain ischemia as evidence for a novel regulatory mechanism. J Lipid Res 2023; 64:100452. [PMID: 37783389 PMCID: PMC10630775 DOI: 10.1016/j.jlr.2023.100452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 09/25/2023] [Accepted: 09/28/2023] [Indexed: 10/04/2023] Open
Abstract
Previously, we and others reported a rapid and dramatic increase in brain prostanoids (PG), including prostaglandins, prostacyclins, and thromboxanes, under ischemia that is traditionally explained through the activation of esterified arachidonic acid (20:4n6) release by phospholipases as a substrate for cyclooxygenases (COX). However, the availability of another required COX substrate, oxygen, has not been considered in this mechanism. To address this mechanism for PG upregulation through oxygen availability, we analyzed mouse brain PG, free 20:4n6, and oxygen levels at different time points after ischemic onset using head-focused microwave irradiation (MW) to inactivate enzymes in situ before craniotomy. The oxygen half-life in the ischemic brain was 5.32 ± 0.45 s and dropped to undetectable levels within 12 s of ischemia onset, while there were no significant free 20:4n6 or PG changes at 30 s of ischemia. Furthermore, there was no significant PG increase at 2 and 10 min after ischemia onset compared to basal levels, while free 20:4n6 was increased ∼50 and ∼100 fold, respectively. However, PG increased ∼30-fold when ischemia was followed by craniotomy of nonMW tissue that provided oxygen for active enzymes. Moreover, craniotomy performed under anoxic conditions without MW did not result in PG induction, while exposure of these brains to atmospheric oxygen significantly induced PG. Our results indicate, for the first time, that oxygen availability is another important regulatory factor for PG production under ischemia. Further studies are required to investigate the physiological role of COX/PG regulation through tissue oxygen concentration.
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Affiliation(s)
- Drew R Seeger
- Department of Biomedical Sciences, School of Medicine and Health Science, University of North Dakota, Grand Forks, ND, USA
| | - Brennon Schofield
- Department of Biomedical Sciences, School of Medicine and Health Science, University of North Dakota, Grand Forks, ND, USA
| | - Derek Besch
- Department of Biomedical Sciences, School of Medicine and Health Science, University of North Dakota, Grand Forks, ND, USA
| | - Svetlana A Golovko
- Department of Biomedical Sciences, School of Medicine and Health Science, University of North Dakota, Grand Forks, ND, USA
| | - Peddanna Kotha
- Department of Biomedical Sciences, School of Medicine and Health Science, University of North Dakota, Grand Forks, ND, USA
| | - Meredith Parmer
- Department of Biomedical Sciences, School of Medicine and Health Science, University of North Dakota, Grand Forks, ND, USA
| | - Shahram Solaymani-Mohammadi
- Department of Biomedical Sciences, School of Medicine and Health Science, University of North Dakota, Grand Forks, ND, USA
| | - Mikhail Y Golovko
- Department of Biomedical Sciences, School of Medicine and Health Science, University of North Dakota, Grand Forks, ND, USA.
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Li L, Shen S, Bickler P, Jacobson MP, Wu LF, Altschuler SJ. Searching for molecular hypoxia sensors among oxygen-dependent enzymes. eLife 2023; 12:e87705. [PMID: 37494095 PMCID: PMC10371230 DOI: 10.7554/elife.87705] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 07/09/2023] [Indexed: 07/27/2023] Open
Abstract
The ability to sense and respond to changes in cellular oxygen levels is critical for aerobic organisms and requires a molecular oxygen sensor. The prototypical sensor is the oxygen-dependent enzyme PHD: hypoxia inhibits its ability to hydroxylate the transcription factor HIF, causing HIF to accumulate and trigger the classic HIF-dependent hypoxia response. A small handful of other oxygen sensors are known, all of which are oxygen-dependent enzymes. However, hundreds of oxygen-dependent enzymes exist among aerobic organisms, raising the possibility that additional sensors remain to be discovered. This review summarizes known and potential hypoxia sensors among human O2-dependent enzymes and highlights their possible roles in hypoxia-related adaptation and diseases.
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Affiliation(s)
- Li Li
- Department of Pharmaceutical Chemistry, University of California San Francisco, San FranciscoSan FranciscoUnited States
| | - Susan Shen
- Department of Pharmaceutical Chemistry, University of California San Francisco, San FranciscoSan FranciscoUnited States
- Department of Psychiatry, University of California, San FranciscoSan FranciscoUnited States
| | - Philip Bickler
- Hypoxia Research Laboratory, University of California San Francisco, San FranciscoSan FranciscoUnited States
- Center for Health Equity in Surgery and Anesthesia, University of California San Francisco, San FranciscoSan FranciscoUnited States
- Anesthesia and Perioperative Care, University of California San Francisco, San FranciscoSan FranciscoUnited States
| | - Matthew P Jacobson
- Department of Pharmaceutical Chemistry, University of California San Francisco, San FranciscoSan FranciscoUnited States
| | - Lani F Wu
- Department of Pharmaceutical Chemistry, University of California San Francisco, San FranciscoSan FranciscoUnited States
| | - Steven J Altschuler
- Department of Pharmaceutical Chemistry, University of California San Francisco, San FranciscoSan FranciscoUnited States
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Functional Characterization of Novel Bony Fish Lipoxygenase Isoforms and Their Possible Involvement in Inflammation. Int J Mol Sci 2022; 23:ijms232416026. [PMID: 36555666 PMCID: PMC9787790 DOI: 10.3390/ijms232416026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 12/10/2022] [Accepted: 12/12/2022] [Indexed: 12/23/2022] Open
Abstract
Eicosanoids and related compounds are pleiotropic lipid mediators, which are biosynthesized in mammals via three distinct metabolic pathways (cyclooxygenase pathway, lipoxygenase pathway, epoxygenase pathway). These mediators have been implicated in the pathogenesis of inflammatory diseases and drugs interfering with eicosanoid signaling are currently available as antiphlogistics. Eicosanoid biosynthesis has well been explored in mammals including men, but much less detailed information is currently available on eicosanoid biosynthesis in other vertebrates including bony fish. There are a few reports in the literature describing the expression of arachidonic acid lipoxygenases (ALOX isoforms) in several bony fish species but except for two zebrafish ALOX-isoforms (zfALOX1 and zfALOX2) bony fish eicosanoid biosynthesizing enzymes have not been characterized. To fill this gap and to explore the possible roles of ALOX15 orthologs in bony fish inflammation we cloned and expressed putative ALOX15 orthologs from three different bony fish species (N. furzeri, P. nyererei, S. formosus) as recombinant N-terminal his-tag fusion proteins and characterized the corresponding enzymes with respect to their catalytic properties (temperature-dependence, activation energy, pH-dependence, substrate affinity and substrate specificity with different polyenoic fatty acids). Furthermore, we identified the chemical structure of the dominant oxygenation products formed by the recombinant enzymes from different free fatty acids and from more complex lipid substrates. Taken together, our data indicate that functional ALOX isoforms occur in bony fish but that their catalytic properties are different from those of mammalian enzymes. The possible roles of these ALOX-isoforms in bony fish inflammation are discussed.
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Reisch F, Kakularam KR, Stehling S, Heydeck D, Kuhn H. Eicosanoid biosynthesis in marine mammals. FEBS J 2020; 288:1387-1406. [PMID: 32627384 DOI: 10.1111/febs.15469] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 05/19/2020] [Accepted: 06/22/2020] [Indexed: 01/09/2023]
Abstract
After 300 million years of evolution, the first land-living mammals reentered the marine environment some 50 million years ago. The driving forces for this dramatic lifestyle change are still a matter of discussion but the struggle for food resources and the opportunity to escape predators probably contributed. Reentering the oceans requires metabolic adaption putting evolutionary pressure on a number of genes. To explore whether eicosanoid signaling has been part of this adaptive response, we first explored whether the genomes of marine mammals involve functional genes encoding for key enzymes of eicosanoid biosynthesis. Cyclooxygenase (COX) and lipoxygenase (ALOX) genes are present in the genome of all marine mammals tested. Interestingly, ALOX12B, which has been implicated in skin development of land-living mammals, is lacking in whales and dolphins and genes encoding for its sister enzyme (ALOXE3) involve premature stop codons and/or frameshifting point mutations, which interrupt the open reading frames. ALOX15 orthologs have been detected in all marine mammals, and the recombinant enzymes exhibit similar catalytic properties as those of land-living species. All marine mammals express arachidonic acid 12-lipoxygenating ALOX15 orthologs, and these data are consistent with the Evolutionary Hypothesis of ALOX15 specificity. These enzymes exhibit membrane oxygenase activity and introduction of big amino acids at the triad positions altered the reaction specificity in favor of arachidonic acid 15-lipoxygenation. Thus, the ALOX15 orthologs of marine mammals follow the Triad concept explaining their catalytic specificity.
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Affiliation(s)
- Florian Reisch
- Institute of Biochemistry, Charité - University Medicine Berlin, Corporate member of Free University Berlin, Humboldt University Berlin and Berlin Institute of Health, Berlin, Germany
| | - Kumar Reddy Kakularam
- Institute of Biochemistry, Charité - University Medicine Berlin, Corporate member of Free University Berlin, Humboldt University Berlin and Berlin Institute of Health, Berlin, Germany
| | - Sabine Stehling
- Institute of Biochemistry, Charité - University Medicine Berlin, Corporate member of Free University Berlin, Humboldt University Berlin and Berlin Institute of Health, Berlin, Germany
| | - Dagmar Heydeck
- Institute of Biochemistry, Charité - University Medicine Berlin, Corporate member of Free University Berlin, Humboldt University Berlin and Berlin Institute of Health, Berlin, Germany
| | - Hartmut Kuhn
- Institute of Biochemistry, Charité - University Medicine Berlin, Corporate member of Free University Berlin, Humboldt University Berlin and Berlin Institute of Health, Berlin, Germany
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Schäfer M, Fan Y, Gu T, Heydeck D, Stehling S, Ivanov I, Yao YG, Kuhn H. The lipoxygenase pathway of Tupaia belangeri representing Scandentia. Genomic multiplicity and functional characterization of the ALOX15 orthologs in the tree shrew. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1865:158550. [PMID: 31676437 DOI: 10.1016/j.bbalip.2019.158550] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 09/10/2019] [Accepted: 09/22/2019] [Indexed: 12/31/2022]
Abstract
The tree shrew (Tupaia belangeri) is a rat-sized mammal, which is more closely related to humans than mice and rats. However, the use of tree shrew to explore the patho-mechanisms of human inflammatory disorders has been limited since nothing is known about eicosanoid metabolism in this mammalian species. Eicosanoids are important lipid mediators exhibiting pro- and anti-inflammatory activities, which are biosynthesized via lipoxygenase and cyclooxygenase pathways. When we searched the tree shrew genome for the presence of cyclooxygenase and lipoxygenase isoforms we found copies of functional COX1, COX2 and LOX genes. Interestingly, we identified four copies of ALOX15 genes, which encode for four structurally distinct ALOX15 orthologs (tupALOX15a-d). To explore the catalytic properties of these enzymes we expressed tupALOX15a and tupALOX15c as catalytically active proteins and characterized their enzymatic properties. As predicted by the Evolutionary Hypothesis of ALOX15 specificity we found that the two enzymes converted arachidonic acid predominantly to 12S-HETE and they also exhibited membrane oxygenase activities. However, their reaction kinetic properties (KM for arachidonic acid and oxygen, T- and pH-dependence) and their substrate specificities were remarkably different. In contrast to mice and humans, tree shrew ALOX15 isoforms are highly expressed in the brain suggesting a role of these enzymes in cerebral function. The genomic multiplicity and the tissue expression patterns of tree shrew ALOX15 isoforms need to be considered when the results of in vivo inflammation studies obtained in this animal are translated into the human situation.
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Affiliation(s)
- Marjann Schäfer
- Institute of Biochemistry, Charité - University Medicine Berlin, Corporate member of Free University Berlin, Humboldt University Berlin and Berlin Institute of Health, Charitéplatz 1, D-10117 Berlin, Germany
| | - Yu Fan
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Kunming, Yunnan 650223, China
| | - Tianle Gu
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Kunming, Yunnan 650223, China; Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming, Yunnan 650204, China
| | - Dagmar Heydeck
- Institute of Biochemistry, Charité - University Medicine Berlin, Corporate member of Free University Berlin, Humboldt University Berlin and Berlin Institute of Health, Charitéplatz 1, D-10117 Berlin, Germany
| | - Sabine Stehling
- Institute of Biochemistry, Charité - University Medicine Berlin, Corporate member of Free University Berlin, Humboldt University Berlin and Berlin Institute of Health, Charitéplatz 1, D-10117 Berlin, Germany
| | - Igor Ivanov
- Lomonosov Institute of Fine Chemical Technologies, MIREA - Russian Technological University, Vernadskogo pr. 86, 119571 Moscow, Russia
| | - Yong-Gang Yao
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Kunming, Yunnan 650223, China; Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming, Yunnan 650204, China
| | - Hartmut Kuhn
- Institute of Biochemistry, Charité - University Medicine Berlin, Corporate member of Free University Berlin, Humboldt University Berlin and Berlin Institute of Health, Charitéplatz 1, D-10117 Berlin, Germany.
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Goloshchapova K, Stehling S, Heydeck D, Blum M, Kuhn H. Functional characterization of a novel arachidonic acid 12S-lipoxygenase in the halotolerant bacterium Myxococcus fulvus exhibiting complex social living patterns. Microbiologyopen 2018; 8:e00775. [PMID: 30560563 PMCID: PMC6612559 DOI: 10.1002/mbo3.775] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 10/24/2018] [Accepted: 11/07/2018] [Indexed: 01/24/2023] Open
Abstract
Lipoxygenases are lipid peroxidizing enzymes, which frequently occur in higher plants and mammals. These enzymes are also expressed in lower multicellular organisms but here they are not widely distributed. In bacteria, lipoxygenases rarely occur and evaluation of the currently available bacterial genomes suggested that <0.5% of all sequenced bacterial species carry putative lipoxygenase genes. We recently rescreened the public bacterial genome databases for lipoxygenase-like sequences and identified two novel lipoxygenase isoforms (MF-LOX1 and MF-LOX2) in the halotolerant Myxococcus fulvus. Both enzymes share a low degree of amino acid conservation with well-characterized eukaryotic lipoxygenase isoforms but they involve the catalytically essential iron cluster. Here, we cloned the MF-LOX1 cDNA, expressed the corresponding enzyme as N-terminal hexa-his-tag fusion protein, purified the recombinant enzyme to electrophoretic homogeneity, and characterized it with respect to its protein-chemical and enzymatic properties. We found that M. fulvus expresses a catalytically active intracellular lipoxygenase that converts arachidonic acid and other polyunsaturated fatty acids enantioselectively to the corresponding n-9 hydroperoxy derivatives. The enzyme prefers C20 - and C22 -polyenoic fatty acids but does not exhibit significant membrane oxygenase activity. The possible biological relevance of MF-LOX1 will be discussed in the context of the suggested concepts of other bacterial lipoxygenases.
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Affiliation(s)
- Kateryna Goloshchapova
- Institute of BiochemistryCharité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt‐Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - Sabine Stehling
- Institute of BiochemistryCharité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt‐Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - Dagmar Heydeck
- Institute of BiochemistryCharité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt‐Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | | | - Hartmut Kuhn
- Institute of BiochemistryCharité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt‐Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
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How Supraphysiological Oxygen Levels in Standard Cell Culture Affect Oxygen-Consuming Reactions. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2018; 2018:8238459. [PMID: 30363917 PMCID: PMC6186316 DOI: 10.1155/2018/8238459] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 08/01/2018] [Indexed: 12/31/2022]
Abstract
Most mammalian tissue cells experience oxygen partial pressures in vivo equivalent to 1–6% O2 (i.e., physioxia). In standard cell culture, however, headspace O2 levels are usually not actively regulated and under these conditions are ~18%. This drives hyperoxia in cell culture media that can affect a wide variety of cellular activities and may compromise the ability of in vitro models to reproduce in vivo biology. Here, we review and discuss some specific O2-consuming organelles and enzymes, including mitochondria, NADPH oxidases, the transplasma membrane redox system, nitric oxide synthases, xanthine oxidase, and monoamine oxidase with respect to their sensitivities to O2 levels. Many of these produce reactive oxygen and/or nitrogen species (ROS/RNS) as either primary end products or byproducts and are acutely sensitive to O2 levels in the range from 1% to 18%. Interestingly, many of them are also transcriptional targets of hypoxia-inducible factors (HIFs) and chronic cell growth at physioxia versus 18% O2 may alter their expression. Aquaporins, which facilitate hydrogen peroxide diffusion into and out of cells, are also regulated by HIFs, indicating that O2 levels may affect intercellular communication via hydrogen peroxide. The O2 sensitivities of these important activities emphasize the importance of maintaining physioxia in culture.
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Aldrovandi M, Banthiya S, Meckelmann S, Zhou Y, Heydeck D, O'Donnell VB, Kuhn H. Specific oxygenation of plasma membrane phospholipids by Pseudomonas aeruginosa lipoxygenase induces structural and functional alterations in mammalian cells. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1863:152-164. [PMID: 29146531 PMCID: PMC5764228 DOI: 10.1016/j.bbalip.2017.11.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 10/20/2017] [Accepted: 11/11/2017] [Indexed: 01/18/2023]
Abstract
Pseudomonas aeruginosa is a gram-negative pathogen, which causes life-threatening infections in immunocompromized patients. These bacteria express a secreted lipoxygenase (PA-LOX), which oxygenates free arachidonic acid to 15S-hydro(pero)xyeicosatetraenoic acid. It binds phospholipids at its active site and physically interacts with lipid vesicles. When incubated with red blood cells membrane lipids are oxidized and hemolysis is induced but the structures of the oxygenated membrane lipids have not been determined. Using a lipidomic approach, we analyzed the formation of oxidized phospholipids generated during the in vitro incubation of recombinant PA-LOX with human erythrocytes and cultured human lung epithelial cells. Precursor scanning of lipid extracts prepared from these cells followed by multiple reaction monitoring and MS/MS analysis revealed a complex mixture of oxidation products. For human red blood cells this mixture comprised forty different phosphatidylethanolamine and phosphatidylcholine species carrying oxidized fatty acid residues, such as hydroxy-octadecadienoic acids, hydroxy- and keto-eicosatetraenoic acid, hydroxy-docosahexaenoic acid as well as oxygenated derivatives of less frequently occurring polyenoic fatty acids. Similar oxygenation products were also detected when cultured lung epithelial cells were employed but here the amounts of oxygenated lipids were smaller and under identical experimental conditions we did not detect major signs of cell lysis. However, live imaging indicated an impaired capacity for trypan blue exclusion and an augmented mitosis rate. Taken together these data indicate that PA-LOX can oxidize the membrane lipids of eukaryotic cells and that the functional consequences of this reaction strongly depend on the cell type.
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Affiliation(s)
- Maceler Aldrovandi
- Systems Immunity Research Institute, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
| | - Swathi Banthiya
- Institute of Biochemistry, Charite - University Medicine Berlin, Charitéplatz 1, D-10117 Berlin, Germany
| | - Sven Meckelmann
- Systems Immunity Research Institute, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
| | - You Zhou
- Systems Immunity Research Institute, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
| | - Dagmar Heydeck
- Institute of Biochemistry, Charite - University Medicine Berlin, Charitéplatz 1, D-10117 Berlin, Germany
| | - Valerie B O'Donnell
- Systems Immunity Research Institute, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK.
| | - Hartmut Kuhn
- Institute of Biochemistry, Charite - University Medicine Berlin, Charitéplatz 1, D-10117 Berlin, Germany.
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Kalms J, Banthiya S, Galemou Yoga E, Hamberg M, Holzhutter HG, Kuhn H, Scheerer P. The crystal structure of Pseudomonas aeruginosa lipoxygenase Ala420Gly mutant explains the improved oxygen affinity and the altered reaction specificity. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:463-473. [PMID: 28093240 DOI: 10.1016/j.bbalip.2017.01.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 01/03/2017] [Accepted: 01/12/2017] [Indexed: 12/30/2022]
Abstract
Secreted LOX from Pseudomonas aeruginosa (PA-LOX) has previously been identified as arachidonic acid 15S-lipoxygenating enzyme. Here we report that the substitution of Ala420Gly in PA-LOX leads to an enzyme variant with pronounced dual specificity favoring arachidonic acid 11R-oxygenation. When compared with other LOX-isoforms the molecular oxygen affinity of wild-type PA-LOX is 1-2 orders of magnitude lower (Km O2 of 0.4mM) but Ala420Gly exchange improved the molecular oxygen affinity (Km O2 of 0.2mM). Experiments with stereo-specifically deuterated linoleic acid indicated that the formation of both 13S- and 9R-HpODE involves abstraction of the proS-hydrogen from C11 of the fatty acid backbone. To explore the structural basis for the observed functional changes (altered specificity, improved molecular oxygen affinity) we solved the crystal structure of the Ala420Gly mutant of PA-LOX at 1.8Å resolution and compared it with the wild-type enzyme. Modeling of fatty acid alignment at the catalytic center suggested that in the wild-type enzyme dioxygen is directed to C15 of arachidonic acid by a protein tunnel, which interconnects the catalytic center with the protein surface. Ala420Gly exchange redirects intra-enzyme O2 diffusion by bifurcating this tunnel so that C11 of arachidonic acid also becomes accessible for O2 insertion.
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Affiliation(s)
- Jacqueline Kalms
- Institute of Medical Physics and Biophysics (CC2), Group Protein X-ray Crystallography and Signal Transduction, Charité - University Medicine Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Swathi Banthiya
- Institute for Biochemistry (CC2), Charité - University Medicine Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Etienne Galemou Yoga
- Institute of Medical Physics and Biophysics (CC2), Group Protein X-ray Crystallography and Signal Transduction, Charité - University Medicine Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Mats Hamberg
- Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden
| | - Hermann-Georg Holzhutter
- Institute for Biochemistry (CC2), Charité - University Medicine Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Hartmut Kuhn
- Institute for Biochemistry (CC2), Charité - University Medicine Berlin, Charitéplatz 1, 10117 Berlin, Germany.
| | - Patrick Scheerer
- Institute of Medical Physics and Biophysics (CC2), Group Protein X-ray Crystallography and Signal Transduction, Charité - University Medicine Berlin, Charitéplatz 1, 10117 Berlin, Germany.
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Juránek I, Nikitovic D, Kouretas D, Hayes AW, Tsatsakis AM. Biological importance of reactive oxygen species in relation to difficulties of treating pathologies involving oxidative stress by exogenous antioxidants. Food Chem Toxicol 2013; 61:240-7. [PMID: 24025685 DOI: 10.1016/j.fct.2013.08.074] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 08/21/2013] [Accepted: 08/22/2013] [Indexed: 02/07/2023]
Abstract
Findings about involvement of reactive oxygen species (ROS) not only in defense processes, but also in a number of pathologies, stimulated discussion about their role in etiopathogenesis of various diseases. Yet questions regarding the role of ROS in tissue injury, whether ROS may serve as a common cause of different disorders or whether their uncontrolled production is just a manifestation of the processes involved, remain unexplained. Dogmatically, increased ROS formation is considered to be responsible for development of the so-called free-radical diseases. The present review discusses importance of ROS in various biological processes, including origin of life, evolution, genome plasticity, maintaining homeostasis and organism protection. This may be a reason why no significant benefit was found when exogenous antioxidants were used to treat free-radical diseases, even though their causality was primarily attributed to ROS. Here, we postulate that ROS unlikely play a causal role in tissue damage, but may readily be involved in signaling processes and as such in mediating tissue healing rather than injuring. This concept is thus in a contradiction to traditional understanding of ROS as deleterious agents. Nonetheless, under conditions of failing autoregulation, ROS may attack integral cellular components, cause cell death and deteriorate the evolving injury.
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Affiliation(s)
- Ivo Juránek
- Institute of Experimental Pharmacology & Toxicology, Slovak Academy of Sciences, Bratislava, Slovakia.
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11
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Stobart JL, Anderson CM. Multifunctional role of astrocytes as gatekeepers of neuronal energy supply. Front Cell Neurosci 2013; 7:38. [PMID: 23596393 PMCID: PMC3622037 DOI: 10.3389/fncel.2013.00038] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 03/26/2013] [Indexed: 01/01/2023] Open
Abstract
Dynamic adjustments to neuronal energy supply in response to synaptic activity are critical for neuronal function. Glial cells known as astrocytes have processes that ensheath most central synapses and express G-protein-coupled neurotransmitter receptors and transporters that respond to neuronal activity. Astrocytes also release substrates for neuronal oxidative phosphorylation and have processes that terminate on the surface of brain arterioles and can influence vascular smooth muscle tone and local blood flow. Membrane receptor or transporter-mediated effects of glutamate represent a convergence point of astrocyte influence on neuronal bioenergetics. Astrocytic glutamate uptake drives glycolysis and subsequent shuttling of lactate from astrocytes to neurons for oxidative metabolism. Astrocytes also convert synaptically reclaimed glutamate to glutamine, which is returned to neurons for glutamate salvage or oxidation. Finally, astrocytes store brain energy currency in the form of glycogen, which can be mobilized to produce lactate for neuronal oxidative phosphorylation in response to glutamatergic neurotransmission. These mechanisms couple synaptically driven astrocytic responses to glutamate with release of energy substrates back to neurons to match demand with supply. In addition, astrocytes directly influence the tone of penetrating brain arterioles in response to glutamatergic neurotransmission, coordinating dynamic regulation of local blood flow. We will describe the role of astrocytes in neurometabolic and neurovascular coupling in detail and discuss, in turn, how astrocyte dysfunction may contribute to neuronal bioenergetic deficit and neurodegeneration. Understanding the role of astrocytes as a hub for neurometabolic and neurovascular coupling mechanisms is a critical underpinning for therapeutic development in a broad range of neurodegenerative disorders characterized by chronic generalized brain ischemia and brain microvascular dysfunction.
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Affiliation(s)
- Jillian L Stobart
- Division of Neurodegenerative Disorders, Department of Pharmacology and Therapeutics, St. Boniface Hospital Research, University of Manitoba Winnipeg, MB, Canada ; Department of Nuclear Medicine, Institute of Pharmacology and Toxicology, University of Zürich Zürich, Switzerland
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Abstract
Neurovascular coupling is a process through which neuronal activity leads to local increases in blood flow in the central nervous system. In brain slices, 100% O(2) has been shown to alter neurovascular coupling, suppressing activity-dependent vasodilation. However, in vivo, hyperoxia reportedly has no effect on blood flow. Resolving these conflicting findings is important, given that hyperoxia is often used in the clinic in the treatment of both adults and neonates, and a reduction in neurovascular coupling could deprive active neurons of adequate nutrients. Here we address this issue by examining neurovascular coupling in both ex vivo and in vivo rat retina preparations. In the ex vivo retina, 100% O(2) reduced light-evoked arteriole vasodilations by 3.9-fold and increased vasoconstrictions by 2.6-fold. In vivo, however, hyperoxia had no effect on light-evoked arteriole dilations or blood velocity. Oxygen electrode measurements showed that 100% O(2) raised pO(2) in the ex vivo retina from 34 to 548 mm Hg, whereas hyperoxia has been reported to increase retinal pO(2) in vivo to only ~53 mm Hg [Yu DY, Cringle SJ, Alder VA, Su EN (1994) Am J Physiol 267:H2498-H2507]. Replicating the hyperoxic in vivo pO(2) of 53 mm Hg in the ex vivo retina did not alter vasomotor responses, indicating that although O(2) can modulate neurovascular coupling when raised sufficiently high, the hyperoxia-induced rise in retinal pO(2) in vivo is not sufficient to produce a modulatory effect. Our findings demonstrate that hyperoxia does not alter neurovascular coupling in vivo, ensuring that active neurons receive an adequate supply of nutrients.
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13
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Trushkin NA, Filimonov IS, Vrzheshch PV. Inhibition of cyclooxygenase activity of prostaglandin-H-synthase by excess substrate (molecular oxygen). BIOCHEMISTRY (MOSCOW) 2011; 75:1368-73. [PMID: 21314604 DOI: 10.1134/s0006297910110088] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
For the cyclooxygenase reaction of prostaglandin-H-synthase isolated from ram vesicular glands, dependences of the initial reaction rate, the maximal yield of the product, and the rate constant of enzyme inactivation in the course of reaction on oxygen concentration were studied in the absence and in the presence of electron donor in the reaction medium. It is shown that in the absence of electron donor the cyclooxygenase reaction is strictly governed by Michaelis-Menten kinetics over a wide range of oxygen concentrations (5-800 µM). In the presence of electron donor in the reaction medium it was found that cyclooxygenase reaction is inhibited by an excess of dissolved oxygen: the maximal values of the initial reaction rate and yield of the product are attained at oxygen concentration 50 µM, and its increase to 500 µM causes twofold decrease in the initial rate and maximal yield. The rate constant of enzyme inactivation in the course of reaction increases on increase in oxygen concentration both in the presence and in the absence of electron donor.
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Affiliation(s)
- N A Trushkin
- International Research Center for Biochemical Technology, Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow 119992, Russia
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14
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Attwell D, Buchan AM, Charpak S, Lauritzen M, Macvicar BA, Newman EA. Glial and neuronal control of brain blood flow. Nature 2010; 468:232-43. [PMID: 21068832 PMCID: PMC3206737 DOI: 10.1038/nature09613] [Citation(s) in RCA: 1641] [Impact Index Per Article: 117.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Blood flow in the brain is regulated by neurons and astrocytes. Knowledge of how these cells control blood flow is crucial for understanding how neural computation is powered, for interpreting functional imaging scans of brains, and for developing treatments for neurological disorders. It is now recognized that neurotransmitter-mediated signalling has a key role in regulating cerebral blood flow, that much of this control is mediated by astrocytes, that oxygen modulates blood flow regulation, and that blood flow may be controlled by capillaries as well as by arterioles. These conceptual shifts in our understanding of cerebral blood flow control have important implications for the development of new therapeutic approaches.
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Affiliation(s)
- David Attwell
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
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15
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Kominsky DJ, Campbell EL, Colgan SP. Metabolic shifts in immunity and inflammation. THE JOURNAL OF IMMUNOLOGY 2010; 184:4062-8. [PMID: 20368286 DOI: 10.4049/jimmunol.0903002] [Citation(s) in RCA: 297] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Sites of ongoing inflammation and triggered immune responses are characterized by significant changes in metabolic activity. Recent studies have indicated that such shifts in tissue metabolism result from a combination of profound recruitment of inflammatory cells (neutrophils and monocytes) and high proliferation rates among lymphocyte populations. The resultant shifts in energy supply and demand can result in metabolic acidosis and diminished delivery and/or availability of oxygen, leading to hypoxia extensive enough to trigger transcriptional and translation changes in tissue phenotype. Such phenotypic shifts can imprint fundamental changes to tissue metabolism. In this study, we review recent work addressing metabolic changes and metabolic control of inflammation and immunity.
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Affiliation(s)
- Douglas J Kominsky
- Department of Anesthesiology, University of Colorado Denver Health Sciences Center, Aurora, CO 80045, USA
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16
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Prostaglandin H synthase: resolved and unresolved mechanistic issues. Arch Biochem Biophys 2009; 493:103-24. [PMID: 19728984 DOI: 10.1016/j.abb.2009.08.019] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Revised: 08/25/2009] [Accepted: 08/26/2009] [Indexed: 11/20/2022]
Abstract
The cyclooxygenase and peroxidase activities of prostaglandin H synthase (PGHS)-1 and -2 have complex kinetics, with the cyclooxygenase exhibiting feedback activation by product peroxide and irreversible self-inactivation, and the peroxidase undergoing an independent self-inactivation process. The mechanistic bases for these complex, non-linear steady-state kinetics have been gradually elucidated by a combination of structure/function, spectroscopic and transient kinetic analyses. It is now apparent that most aspects of PGHS-1 and -2 catalysis can be accounted for by a branched chain radical mechanism involving a classic heme-based peroxidase cycle and a radical-based cyclooxygenase cycle. The two cycles are linked by the Tyr385 radical, which originates from an oxidized peroxidase intermediate and begins the cyclooxygenase cycle by abstracting a hydrogen atom from the fatty acid substrate. Peroxidase cycle intermediates have been well characterized, and peroxidase self-inactivation has been kinetically linked to a damaging side reaction involving the oxyferryl heme oxidant in an intermediate that also contains the Tyr385 radical. The cyclooxygenase cycle intermediates are poorly characterized, with the exception of the Tyr385 radical and the initial arachidonate radical, which has a pentadiene structure involving C11-C15 of the fatty acid. Oxygen isotope effect studies suggest that formation of the arachidonate radical is reversible, a conclusion consistent with electron paramagnetic resonance spectroscopic observations, radical trapping by NO, and thermodynamic calculations, although moderate isotope selectivity was found for the H-abstraction step as well. Reaction with peroxide also produces an alternate radical at Tyr504 that is linked to cyclooxygenase activation efficiency and may serve as a reservoir of oxidizing equivalent. The interconversions among radicals on Tyr385, on Tyr504, and on arachidonate, and their relationships to regulation and inactivation of the cyclooxygenase, are still under active investigation for both PGHS isozymes.
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17
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Filimonov IS, Vrzheshch PV. Molecular oxygen (a substrate of the cyclooxygenase reaction) in the kinetic mechanism of the bifunctional enzyme prostaglandin-H-synthase. BIOCHEMISTRY (MOSCOW) 2007; 72:944-53. [PMID: 17922652 DOI: 10.1134/s0006297907090040] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Prostaglandin-H-synthase is a bifunctional enzyme catalyzing conversion of arachidonic acid into prostaglandin H2 as a result of cyclooxygenase and peroxidase reactions. The dependence of the rate of the cyclooxygenase reaction on oxygen concentration in the absence and in the presence of electron donor was determined. A two-dimensional kinetic scheme accounting for independent proceeding and mutual influence of the cyclooxygenase and peroxidase reactions and also for hierarchy of the rates of these reactions was used as a model. In the context of this model, it was shown that there are irreversible stages in the mechanism of the cyclooxygenase reaction between points of substrate donation (between donation of arachidonic acid and the first oxygen molecule and also between donation of two oxygen molecules).
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Affiliation(s)
- I S Filimonov
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow 119992, Russia
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18
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Saam J, Ivanov I, Walther M, Holzhütter HG, Kuhn H. Molecular dioxygen enters the active site of 12/15-lipoxygenase via dynamic oxygen access channels. Proc Natl Acad Sci U S A 2007; 104:13319-24. [PMID: 17675410 PMCID: PMC1948941 DOI: 10.1073/pnas.0702401104] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Cells contain numerous enzymes that use molecular oxygen for their reactions. Often, their active sites are buried deeply inside the protein, which raises the question whether there are specific access channels guiding oxygen to the site of catalysis. Choosing 12/15-lipoxygenase as a typical example for such oxygen-dependent enzymes, we determined the oxygen distribution within the protein and defined potential routes for oxygen access. For this purpose, we have applied an integrated strategy of structural modeling, molecular dynamics simulations, site-directed mutagenesis, and kinetic measurements. First, we computed the 3D free-energy distribution for oxygen, which led to identification of four oxygen channels in the protein. All channels connect the protein surface with a region of high oxygen affinity at the active site. This region is localized opposite to the nonheme iron providing a structural explanation for the reaction specificity of this lipoxygenase isoform. The catalytically most relevant path can be obstructed by L367F exchange, which leads to a strongly increased Michaelis constant for oxygen. The blocking mechanism is explained in detail by reordering the hydrogen-bonding network of water molecules. Our results provide strong evidence that the main route for oxygen access to the active site of the enzyme follows a channel formed by transiently interconnected cavities whereby the opening and closure are governed by side chain dynamics.
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Affiliation(s)
- Jan Saam
- Institute of Biochemistry, Charité-Universitätsmedizin Berlin, Monbijoustrasse 2, 10117 Berlin, Germany.
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19
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Prusakiewicz JJ, Turman MV, Vila A, Ball HL, Al-Mestarihi AH, Di Marzo V, Marnett LJ. Oxidative metabolism of lipoamino acids and vanilloids by lipoxygenases and cyclooxygenases. Arch Biochem Biophys 2007; 464:260-8. [PMID: 17493578 PMCID: PMC2774498 DOI: 10.1016/j.abb.2007.04.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2007] [Revised: 03/28/2007] [Accepted: 04/02/2007] [Indexed: 11/25/2022]
Abstract
The lipoamino acids and endovanilloids have multiple roles in nociception, pain, and inflammation, yet their biological reactivity has not been fully characterized. Cyclooxygenases (COXs) and lipoxygenases (LOs) oxygenate polyunsaturated fatty acids to generate signaling molecules. The ability of COXs and LOs to oxygenate arachidonyl-derived lipoamino acids and vanilloids was investigated. COX-1 and COX-2 were able to minimally metabolize many of these species. However, the lipoamino acids were efficiently oxygenated by 12S- and 15S-LOs. The kinetics and products of oxygenation by LOs were characterized. Whereas 15S-LOs retained positional specificity of oxygenation with these novel substrates, platelet-type 12S-LO acted as a 12/15-LO. Fatty acid oxygenases may play an important role in the metabolic inactivation of lipoamino acids or vanilloids or may convert them to bioactive derivatives.
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Affiliation(s)
- Jeffery J. Prusakiewicz
- A. B. Hancock, Jr. Memorial Laboratory for Cancer Research, Departments of Biochemistry and Chemistry, Vanderbilt Institute of Chemical Biology, and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232 USA
| | - Melissa V. Turman
- A. B. Hancock, Jr. Memorial Laboratory for Cancer Research, Departments of Biochemistry and Chemistry, Vanderbilt Institute of Chemical Biology, and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232 USA
| | - Andrew Vila
- A. B. Hancock, Jr. Memorial Laboratory for Cancer Research, Departments of Biochemistry and Chemistry, Vanderbilt Institute of Chemical Biology, and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232 USA
| | - Heather L. Ball
- A. B. Hancock, Jr. Memorial Laboratory for Cancer Research, Departments of Biochemistry and Chemistry, Vanderbilt Institute of Chemical Biology, and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232 USA
| | - Ahmad H. Al-Mestarihi
- A. B. Hancock, Jr. Memorial Laboratory for Cancer Research, Departments of Biochemistry and Chemistry, Vanderbilt Institute of Chemical Biology, and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232 USA
| | - Vincenzo Di Marzo
- Istituto di Chimica Biomolecolare, Consiglio Nazionale delle Ricerche, Pozzuoli (NA) Italy 80078
| | - Lawrence J. Marnett
- A. B. Hancock, Jr. Memorial Laboratory for Cancer Research, Departments of Biochemistry and Chemistry, Vanderbilt Institute of Chemical Biology, and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232 USA
- Corresponding Author Lawrence J. Marnett, Ph.D. Department of Biochemistry Vanderbilt University School of Medicine Nashville, TN 37237-0146 Telephone (615)-343-7329 Fax (615)-343-7534
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20
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Amat-Bronnert A, Castegnaro M, Pfohl-Leszkowicz A. Genotoxic activity and induction of biotransformation enzymes in two human cell lines after treatment by Erika fuel extract. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2007; 23:89-95. [PMID: 21783741 DOI: 10.1016/j.etap.2006.07.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2006] [Revised: 07/11/2006] [Accepted: 07/31/2006] [Indexed: 05/31/2023]
Abstract
On 12 December 1999, the tanker Erika broke in two parts at about 60km from the Brittany French coasts (Point of Penmarc'h, Sud Finistère, France). About 10,000tonnes of heavy oil fuel were released in the sea. DNA adduct have been detected in fish liver and mussels digestive gland exposed to the Erika oil spill. In order to investigate the mechanism by which Erika fuel extract exhibits genotoxic effects the induction of DNA adducts by an Erika fuel extract have been analysed on two cell lines, human epithelial bronchial cells (WI) and human hepatoma cells. DNA adducts, reflected by a diagonal radioactive zone and individual adducts are detected only in hepatoma cells indicating biotransformation via CYP 1A2 and CYP 1B1. In addition, Erika fuel extract induces some metabolizing enzymes such CYP 1A2, COX2 and 5-LOX, the two later are involved in cancer processes. Formation of leucotrienes B4 (LTB(4)), a mediator playing a role in inflammation, is induced in epithelial bronchial cells. Since inhalation is one of the ways of contamination for human, the above results are important for human health and prevention.
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Affiliation(s)
- Agnès Amat-Bronnert
- Laboratoire de Génie Chimique, UMR CNRS/INPT/UPS no. 5503, Department BioSyM, INP/ENSAT 1 avenue Agrobiopôle, BP 32607, 31326 Auzeville-Tolosane, France
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21
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Yu Y, Fan J, Hui Y, Rouzer CA, Marnett LJ, Klein-Szanto AJ, FitzGerald GA, Funk CD. Targeted cyclooxygenase gene (ptgs) exchange reveals discriminant isoform functionality. J Biol Chem 2006; 282:1498-506. [PMID: 17110378 DOI: 10.1074/jbc.m609930200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The prostaglandin G/H synthase enzymes, commonly termed COX-1 and COX-2, differ markedly in their responses to regulatory stimuli and their tissue expression patterns. COX-1 is the dominant source of "housekeeping" prostaglandins, whereas COX-2 synthesizes prostaglandins of relevance to pain, inflammation, and mitogenesis. Despite these distinctions, the two enzymes are remarkably conserved, and their subcellular distributions overlap considerably. To address the functional interchangeability of the two isozymes, mice in which COX-1 is expressed under COX-2 regulatory elements were created by a gene targeting "knock-in" strategy. In macrophages from these mice, COX-1 was shown to be lipopolysaccharide-inducible in a manner analogous to COX-2 in wild-type macrophages. However, COX-1 failed to substitute effectively for COX-2 in lipopolysaccharide-induced prostaglandin E2 synthesis at low concentrations of substrate and in the metabolism of the endocannabinoid 2-arachidonylglycerol. The marked depression of the major urinary metabolite of prostacyclin in COX-2 null mice was only partially rescued by COX-1 knock-in, whereas the main urinary metabolite of prostaglandin E2 was rescued totally. Replacement with COX-1 partially rescued the impact of COX-2 deletion on reproductive function. The renal pathology consequent to COX-2 deletion was delayed but not prevented, whereas the corresponding peritonitis was unaltered. Insertion of COX-1 under the regulatory sequences that drive COX-2 expression indicated that COX-1 can substitute for some COX-2 actions and rescue only some of the consequences of gene disruption. Manipulation of COX-2 also revealed a preference for coupling with distinct downstream prostaglandin synthases in vivo. These mice will provide a valuable reagent with which to elucidate the distinct roles of the COX enzymes in mammalian biology.
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Affiliation(s)
- Ying Yu
- Institute for Translational Medicine and Therapeutics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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22
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Kühn H, O'Donnell VB. Inflammation and immune regulation by 12/15-lipoxygenases. Prog Lipid Res 2006; 45:334-56. [PMID: 16678271 DOI: 10.1016/j.plipres.2006.02.003] [Citation(s) in RCA: 291] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2005] [Revised: 01/19/2006] [Accepted: 02/06/2006] [Indexed: 12/22/2022]
Abstract
12/15-Lipoxygenases (12/15-LOX) are members of the LOX family, which are expressed in mammals by monocytes and macrophages following induction by the T helper type 2 cytokines, interleukins-4 and -13. They oxygenate free polyenoic fatty acids but also ester lipids and even complex lipid-protein assemblies such as biomembranes and lipoproteins. The primary oxidation products are either reduced by glutathione peroxidases to corresponding hydroxy derivatives or metabolized into secondary oxidized lipids including leukotrienes, lipoxins and hepoxilins, which act as lipid mediators. Examination of knockout and transgenic animals revealed important roles for 12/15-LOX in inflammatory diseases, including atherosclerosis, cancer, osteoporosis, angiotension II-dependent hypertension and diabetes. In vitro studies suggested 12/15-LOX products as coactivators of peroxisomal proliferator activating-receptors (PPAR), regulators of cytokine generation, and modulators of gene expression related to inflammation resolution. Despite much work in this area, the biochemical mechanisms by which 12/15-LOX regulates physiological and pathological immune cell function are not fully understood. This review will summarize the biochemistry and tissue expression of 12/15-LOX and will describe the current knowledge regarding its immunobiology and regulation of inflammation.
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Affiliation(s)
- Hartmut Kühn
- Institute of Biochemistry, Monbijoustrasse 2, University Medicine Berlin -- Charité, Germany
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23
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Abstract
Studying the oxygenation kinetics of (19R/S,5Z,8Z,11Z,14Z)-19-hydroxyeicosa-5,8,11,14-tetraenoic acid (19-OH-AA) by rabbit 15-lipoxygenase-1 we observed a pronounced oxygen dependence of the reaction rate, which was not apparent with arachidonic acid as substrate. Moreover, we found that peroxide-dependent activation of the lipoxygenase depended strongly on the oxygen concentration. These data can be described with a kinetic model that extends previous schemes of the lipoxygenase reaction in three essential aspects: (a) the product of 19-OH-AA oxygenation is a less effective lipoxygenase activator than (13S,9Z,11E)-13-hydroperoxyoctadeca-9,11-dienoic acid; (b) molecular dioxygen serves not only as a lipoxygenase substrate, but also impacts peroxide-dependent enzyme activation; (c) there is a leakage of radical intermediates from the catalytic cycle, which leads to the formation of inactive ferrous lipoxygenase. This enzyme inactivation can be reversed by another round of peroxide-dependent activation. Taken together our data indicate that both peroxide activation and the oxygen affinity of lipoxygenases depend strongly on the chemistry of the lipid substrate. These findings are of biological relevance as variations of the reaction conditions may turn the lipoxygenase reaction into an efficient source of free radicals.
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Affiliation(s)
- Igor Ivanov
- Institute of Biochemistry Humboldt University Medical School Charité, Berlin, Germany
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24
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Baines AD, Ho P. O(2) affinity of cross-linked hemoglobins modifies O(2) metabolism in proximal tubules. J Appl Physiol (1985) 2003; 95:563-70. [PMID: 12716868 DOI: 10.1152/japplphysiol.00223.2003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous experiments using cross-linked tetrameric hemoglobins (XLHb) to perfuse isolated rat kidneys showed that high-O2-affinity XLHb improved proximal tubule function more effectively than low-O2-affinity XLHb. To determine how function was improved, proximal tubule fragments were incubated with albumin, Hb34 [half-saturation point (P50) 34 Torr], or Hb13 (P50 13 Torr) with Po2 values ranging from 22 to 147 Torr. ATP content reflected O2 delivery to mitochondria. Both XLHb increased ATP, Hb34 with Po2 >or= 47 Torr and Hb13 with Po2 <or= 47 Torr. XLHb increased Na-K-ATPase activity (86Rb uptake) in similar Po2-dependent patterns. O2 consumption (Qo2) was measured in a closed, well-stirred chamber. Ouabain- and oligomycin-inhibited Qo2, reflecting Na-K-ATPase activity and oxidative phosphorylation, respectively, mirrored the Po2-dependent patterns of ATP and 86Rb uptake. As Po2 fell below the midpoint of XLHb desaturation, Qo2, uncoupled from oxidative phosphorylation, transiently increased. The increase was most pronounced with Hb34. Nitro-l-arginine methyl ester had no effect on Qo2. Inhibitors of NAD(P)H oxidases and diamine oxidase partially prevented the Qo2 surge with Hb34. In conclusion, facilitated diffusion accounts for Po2-dependent XLHb effects on ATP content and Na-K-ATPase and for Hb13's effectiveness in hypoxic perfused kidneys. NO scavenging was not a factor. O2-binding characteristics influence XLHb effects on mitochondria and O2-sensitive enzymes such as oxidases.
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Affiliation(s)
- A D Baines
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada.
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25
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Cyclooxygenase isoforms and prostaglandin E2 receptors in the ductus arteriosus. Curr Ther Res Clin Exp 2002. [DOI: 10.1016/s0011-393x(02)80072-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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26
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Kühn H, Borchert A. Regulation of enzymatic lipid peroxidation: the interplay of peroxidizing and peroxide reducing enzymes. Free Radic Biol Med 2002; 33:154-72. [PMID: 12106812 DOI: 10.1016/s0891-5849(02)00855-9] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
For a long time lipid peroxidation has only been considered a deleterious process leading to disruption of biomembranes and thus, to cellular dysfunction. However, when restricted to a certain cellular compartment and tightly regulated, lipid peroxidation may have beneficial effects. Early on during evolution of living organisms special lipid peroxidizing enzymes, called lipoxygenases, appeared and they have been conserved during phylogenesis of plants and animals. In fact, a diverse family of lipoxygenase isoforms has evolved starting from a putative ancient precursor. As with other enzymes, lipoxygenases are regulated on various levels of gene expression and there are endogenous antagonists controlling their cellular activity. Among the currently known mammalian lipoxygenase isoforms only 12/15-lipoxygenases are capable of directly oxygenating ester lipids even when they are bound to membranes and lipoproteins. Thus, these enzymes represent the pro-oxidative part in the cellular metabolism of complex hydroperoxy ester lipids. Its metabolic counterplayer, representing the antioxidative part, appears to be the phospholipid hydroperoxide glutathione peroxidase. This enzyme is unique among glutathione peroxidases because of its capability of reducing ester lipid hydroperoxides. Thus, 12/15-lipoxygenase and phospholipid hydroperoxide glutathione peroxidase constitute a pair of antagonizing enzymes in the metabolism of hydroperoxy ester lipids, and a balanced regulation of the two proteins appears to be of major cell physiological importance. This review is aimed at summarizing the recent developments in the enzymology and molecular biology of 12/15-lipoxygenase and phospholipid hydroperoxide glutathione peroxidase, with emphasis on cytokine-dependent regulation and their regulatory interplay.
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Affiliation(s)
- Hartmut Kühn
- Institute of Biochemistry, University Clinics Charité, Humboldt University, Berlin, Germany.
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27
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Abstract
The prostaglandin endoperoxide H synthases-1 and 2 (PGHS-1 and PGHS-2; also cyclooxygenases-1 and 2, COX-1 and COX-2) catalyze the committed step in prostaglandin synthesis. PGHS-1 and 2 are of particular interest because they are the major targets of nonsteroidal anti-inflammatory drugs (NSAIDs) including aspirin, ibuprofen, and the new COX-2 inhibitors. Inhibition of the PGHSs with NSAIDs acutely reduces inflammation, pain, and fever, and long-term use of these drugs reduces fatal thrombotic events, as well as the development of colon cancer and Alzheimer's disease. In this review, we examine how the structures of these enzymes relate mechanistically to cyclooxygenase and peroxidase catalysis, and how differences in the structure of PGHS-2 confer on this isozyme differential sensitivity to COX-2 inhibitors. We further examine the evidence for independent signaling by PGHS-1 and PGHS-2, and the complex mechanisms for regulation of PGHS-2 gene expression.
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Affiliation(s)
- W L Smith
- Department of Biochemistry, Michigan State University, East Lansing, MI 48824, USA.
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28
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Smith WL, Rieke CJ, Thuresson ED, Mulichak AM, Garavito RM. Fatty-acid substrate interactions with cyclo-oxygenases. ERNST SCHERING RESEARCH FOUNDATION WORKSHOP 2000:53-64. [PMID: 10943327 DOI: 10.1007/978-3-662-04047-8_3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- W L Smith
- Department of Biochemistry, Michigan State University, East Lansing 48824, USA
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29
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Suzuki H, Ueda T, Juránek I, Yamamoto S, Katoh T, Node M, Suzuki T. Hinokitiol, a selective inhibitor of the platelet-type isozyme of arachidonate 12-lipoxygenase. Biochem Biophys Res Commun 2000; 275:885-9. [PMID: 10973816 DOI: 10.1006/bbrc.2000.3390] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hinokitiol (4-isopropyltropolone), a constituent of Japanese cypress, reversibly inhibited platelet-type 12-lipoxygenase with an IC(50) of 0.1 microM, and the enzyme activity was almost lost at 1 microM. The compound was much less active with other lipoxygenase enzymes with higher IC(50) values (leukocyte-type 12-lipoxygenase, 50 microM; soybean lipoxygenase, 17 microM; 15-lipoxygenase-1, >100 microM; 5-lipoxygenase, 17 microM). Hinokitiol up to 100 microM had almost no effect on cyclooxygenases-1 and -2. Their structure-activity relationship examined with various tropolone derivatives indicated the requirements of the 2-hydroxyl group and 4-alkyl group for the potent and selective inhibition of platelet-type 12-lipoxygenase.
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Affiliation(s)
- H Suzuki
- Department of Biochemistry, Tokushima University School of Medicine, Kuramoto-cho, Tokushima, 770-8503, Japan.
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30
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Thuresson ED, Lakkides KM, Smith WL. Different catalytically competent arrangements of arachidonic acid within the cyclooxygenase active site of prostaglandin endoperoxide H synthase-1 lead to the formation of different oxygenated products. J Biol Chem 2000; 275:8501-7. [PMID: 10722687 DOI: 10.1074/jbc.275.12.8501] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Arachidonic acid is converted to prostaglandin G(2) (PGG(2)) by the cyclooxygenase activities of prostaglandin endoperoxide H synthases (PGHSs) 1 and 2. The initial, rate-limiting step is abstraction of the 13-proS hydrogen from arachidonate which, for PGG(2) formation, is followed by insertion of O(2) at C-11, cyclization, and a second O( 2) insertion at C-15. As an accompaniment to ongoing structural studies designed to determine the orientation of arachidonate in the cyclooxygenase site, we analyzed the products formed from arachidonate by (a) solubilized, partially purified ovine (o) PGHS-1; (b) membrane-associated, recombinant oPGHS-1; and (c) a membrane-associated, recombinant active site mutant (V349L oPGHS-1) and determined kinetic values for formation of each product. Native forms of oPGHS-1 produced primarily PGG(2) but also several monohydroxy acids, which, in order of abundance, were 11R-hydroxy-5Z, 8Z,12E,14Z-eicosatetraenoic acid (11R-HETE), 15S-hydroxy-5Z,8Z,11Z, 13E-eicosatetraenoic acid (15S-HETE), and 15R-HETE. V349L oPGHS-1 formed primarily PGG(2), 15S-HETE, and 15R-HETE but only trace amounts of 11R-HETE. With native enzyme, the K(m) values for PGG(2), 11-HETE, and 15-HETE formation were each different (5.5, 12.1, and 19.4 microM, respectively); similarly, the K(m) values for PGG(2) and 15-HETE formation by V349L oPGHS-1 were different (11 and 5 microM, respectively). These results establish that arachidonate can assume at least three catalytically productive arrangements within the cyclooxygenase site of oPGHS-1 leading to PGG(2), 11R-HETE, and 15S-HETE and/or 15R-HETE, respectively. IC(50) values for inhibition of formation of the individual products by the competitive inhibitor, ibuprofen, were determined and found to be the same for a given enzyme form (i.e. 175 microM for oPGHS-1 and 15 microM for V349L oPGHS-1). These latter results are most simply rationalized by a kinetic model in which arachidonate forms various catalytically competent arrangements only after entering the cyclooxygenase active site.
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Affiliation(s)
- E D Thuresson
- Department of Biochemistry, Michigan State University, East Lansing, Michigan 48824, USA
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