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Bhuktar H, Shukla S, Kakularam KR, Battu S, Srikanth M, Srivastava S, Medishetti R, Ram P, Jagadish PC, Rasool M, Chakraborty S, Khan N, Reddanna P, Oruganti S, Pal M. Design, synthesis and evaluation of 2-aryl quinoline derivatives against 12R-lipoxygenase (12R-LOX): Discovery of first inhibitor of 12R-LOX. Bioorg Chem 2023; 138:106606. [PMID: 37210826 DOI: 10.1016/j.bioorg.2023.106606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 04/12/2023] [Accepted: 05/08/2023] [Indexed: 05/23/2023]
Abstract
The 12R-lipoxygenase (12R-LOX), a (non-heme) iron-containing metalloenzyme belonging to the lipoxygenase (LOX) family catalyzes the conversion of arachidonic acid (AA) to its key metabolites. Studies suggested that 12R-LOX plays a critical role in immune modulation for the maintenance of skin homeostasis and therefore can be considered as a potential drug target for psoriasis and other skin related inflammatory diseases. However, unlike 12-LOX (or 12S-LOX) the enzyme 12R-LOX did not receive much attention till date. In our effort, the 2-aryl quinoline derivatives were designed, synthesized and evaluated for the identification of potential inhibitors of 12R-hLOX. The merit of selection of 2-aryl quinolines was assessed by in silico docking studies of a representative compound (4a) using the homology model of 12R-LOX. Indeed, in addition to participating in H-bonding with THR628 and LEU635 the molecule formed a hydrophobic interaction with VAL631. The desired 2-aryl quinolines were synthesized either via the Claisen-Schmidt condensation followed by one-pot reduction-cyclization or via the AlCl3 induced heteroarylation or via the O-alkylation approach in good to high (82-95%) yield. When screened against human 12R-LOX (12R-hLOX) in vitro four compounds (e.g. 4a, 4d, 4e and 7b) showed encouraging (>45%) inhibition at 100 μM among which 7b and 4a emerged as the initial hits. Both the compounds showed selectivity towards 12R-hLOX over 12S-hLOX, 15-hLOX and 15-hLOXB and concentration dependent inhibition of 12R-hLOX with IC50 = 12.48 ± 2.06 and 28.25 ± 1.63 μM, respectively. The selectivity of 4a and 7b towards 12R-LOX over 12S-LOX was rationalized with the help of molecular dynamics simulations. The SAR (Structure-Activity Relationship) within the present series of compounds suggested the need of a o-hydroxyl group on the C-2 phenyl ring for the activity. The compound 4a and 7b (at 10 and 20 µM) reduced the hyper-proliferative state and colony forming potential of IMQ-induced psoriatic keratinocytes in a concentration dependent manner. Further, both compounds decreased the protein levels of Ki67 and the mRNA expression of IL-17A in the IMQ-induced psoriatic-like keratinocytes. Notably, 4a but not 7b inhibited the production of IL-6 and TNF-α in the keratinocyte cells. In the preliminary toxicity studies (i.e. teratogenicity, hepatotoxicity and heart rate assays) in zebrafish both the compounds showed low safety (<30 µM) margin. Overall, being the first identified inhibitors of 12R-LOX both 4a and 7b deserve further investigations.
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Affiliation(s)
- Harshavardhan Bhuktar
- Dr. Reddy's Institute of Life Sciences, University of Hyderabad Campus, Gachibowli, Hyderabad 500046, Telangana, India; Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Madhav Nagar, Manipal 576 104, Karnataka, India
| | - Sharda Shukla
- Dr. Reddy's Institute of Life Sciences, University of Hyderabad Campus, Gachibowli, Hyderabad 500046, Telangana, India; Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Madhav Nagar, Manipal 576 104, Karnataka, India
| | - Kumar Reddy Kakularam
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad 500046, Telangana, India
| | - Srikanth Battu
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad 500046, Telangana, India
| | - Manupati Srikanth
- Immunopathology Lab, School of Biosciences and Technology, Vellore Institute of Technology (VIT), Vellore 632014, Tamil Nadu, India
| | - Susmita Srivastava
- Immunopathology Lab, School of Biosciences and Technology, Vellore Institute of Technology (VIT), Vellore 632014, Tamil Nadu, India
| | - Raghavender Medishetti
- Dr. Reddy's Institute of Life Sciences, University of Hyderabad Campus, Gachibowli, Hyderabad 500046, Telangana, India; Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Madhav Nagar, Manipal 576 104, Karnataka, India
| | - Pooja Ram
- Dr. Reddy's Institute of Life Sciences, University of Hyderabad Campus, Gachibowli, Hyderabad 500046, Telangana, India
| | - P C Jagadish
- Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Madhav Nagar, Manipal 576 104, Karnataka, India
| | - Mahaboobkhan Rasool
- Immunopathology Lab, School of Biosciences and Technology, Vellore Institute of Technology (VIT), Vellore 632014, Tamil Nadu, India
| | - Sandipan Chakraborty
- Dr. Reddy's Institute of Life Sciences, University of Hyderabad Campus, Gachibowli, Hyderabad 500046, Telangana, India
| | - Nooruddin Khan
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad 500046, Telangana, India
| | - Pallu Reddanna
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad 500046, Telangana, India
| | - Srinivas Oruganti
- Dr. Reddy's Institute of Life Sciences, University of Hyderabad Campus, Gachibowli, Hyderabad 500046, Telangana, India
| | - Manojit Pal
- Dr. Reddy's Institute of Life Sciences, University of Hyderabad Campus, Gachibowli, Hyderabad 500046, Telangana, India; Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Madhav Nagar, Manipal 576 104, Karnataka, India.
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Wisastra R, Dekker FJ. Inflammation, Cancer and Oxidative Lipoxygenase Activity are Intimately Linked. Cancers (Basel) 2014; 6:1500-21. [PMID: 25037020 PMCID: PMC4190552 DOI: 10.3390/cancers6031500] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 06/27/2014] [Accepted: 07/02/2014] [Indexed: 02/06/2023] Open
Abstract
Cancer and inflammation are intimately linked due to specific oxidative processes in the tumor microenvironment. Lipoxygenases are a versatile class of oxidative enzymes involved in arachidonic acid metabolism. An increasing number of arachidonic acid metabolites is being discovered and apart from their classically recognized pro-inflammatory effects, anti-inflammatory effects are also being described in recent years. Interestingly, these lipid mediators are involved in activation of pro-inflammatory signal transduction pathways such as the nuclear factor κB (NF-κB) pathway, which illustrates the intimate link between lipid signaling and transcription factor activation. The identification of the role of arachidonic acid metabolites in several inflammatory diseases led to a significant drug discovery effort around arachidonic acid metabolizing enzymes. However, to date success in this area has been limited. This might be attributed to the lack of selectivity of the developed inhibitors and to a lack of detailed understanding of the functional roles of arachidonic acid metabolites in inflammatory responses and cancer. This calls for a more detailed investigation of the activity of arachidonic acid metabolizing enzymes and development of more selective inhibitors.
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Affiliation(s)
- Rosalina Wisastra
- Pharmaceutical Gene Modulation, Groningen Research Institute of Pharmacy, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
| | - Frank J Dekker
- Pharmaceutical Gene Modulation, Groningen Research Institute of Pharmacy, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
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Gaffney BJ, Bradshaw MD, Frausto SD, Wu F, Freed JH, Borbat P. Locating a lipid at the portal to the lipoxygenase active site. Biophys J 2012; 103:2134-44. [PMID: 23200047 PMCID: PMC3512035 DOI: 10.1016/j.bpj.2012.10.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Revised: 10/01/2012] [Accepted: 10/05/2012] [Indexed: 11/28/2022] Open
Abstract
Lipoxygenase enzymes initiate diverse signaling pathways by specifically directing oxygen to different carbons of arachidonate and other polyunsaturated acyl chains, but structural origins of this specificity have remained unclear. We therefore determined the nature of the lipoxygenase interaction with the polar-end of a paramagnetic lipid by electron paramagnetic resonance spectroscopy. Distances between selected grid points on soybean seed lipoxygenase-1 (SBL1) and a lysolecithin spin-labeled on choline were measured by pulsed (electron) dipolar spectroscopy. The protein grid was designed by structure-based modeling so that five natural side chains were replaced with spin labels. Pairwise distances in 10 doubly spin-labeled mutants were examined by pulsed dipolar spectroscopy, and a fit to the model was optimized. Finally, experimental distances between the lysolecithin spin and each single spin site on SBL1 were also obtained. With these 15 distances, distance geometry localized the polar-end and the spin of the lysolecithin to the region between the two domains in the SBL1 structure, nearest to E236, K260, Q264, and Q544. Mutation of a nearby residue, E256A, relieved the high pH requirement for enzyme activity of SBL1 and allowed lipid binding at pH 7.2. This general approach could be used to locate other flexible molecules in macromolecular complexes.
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Affiliation(s)
- Betty J Gaffney
- Department of Biological Science Department, Florida State University, Tallahassee, FL, USA.
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4
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Xu S, Mueser TC, Marnett LJ, Funk MO. Crystal structure of 12-lipoxygenase catalytic-domain-inhibitor complex identifies a substrate-binding channel for catalysis. Structure 2012; 20:1490-7. [PMID: 22795085 DOI: 10.1016/j.str.2012.06.003] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Revised: 06/01/2012] [Accepted: 06/02/2012] [Indexed: 10/28/2022]
Abstract
Lipoxygenases are critical enzymes in the biosynthesis of families of bioactive lipids including compounds with important roles in the initiation and resolution of inflammation and in associated diseases such as diabetes, cardiovascular disease, and cancer. Crystals diffracting to high resolution (1.9 Å) were obtained for a complex between the catalytic domain of leukocyte 12-lipoxygenase and the isoform-specific inhibitor, 4-(2-oxapentadeca-4-yne)phenylpropanoic acid (OPP). In the three-dimensional structure of the complex, the inhibitor occupied a new U-shaped channel open at one end to the surface of the protein and extending past the redox-active iron site that is essential for catalysis. In models, the channel accommodated arachidonic acid, defining the binding site for the substrate of the catalyzed reaction. There was a void adjacent to the OPP binding site connecting to the surface of the enzyme and providing a plausible access channel for the other substrate, oxygen.
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Affiliation(s)
- Shu Xu
- Department of Chemistry, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606, USA
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Rapp J, Xu S, Sharp AM, Griffith WP, Kim YW, Funk MO. EPR spectroscopy and electrospray ionization mass spectrometry reveal distinctive features of the iron site in leukocyte 12-lipoxygenase. Arch Biochem Biophys 2009; 490:50-6. [PMID: 19683507 DOI: 10.1016/j.abb.2009.08.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2009] [Revised: 08/05/2009] [Accepted: 08/11/2009] [Indexed: 11/17/2022]
Abstract
The procedure for the expression and purification of recombinant porcine leukocyte 12-lipoxygenase using Escherichia coli [K.M. Richards, L.J. Marnett, Biochemistry 36 (1997) 6692-6699] was updated to make it possible to produce enough protein for physical measurements. Electrospray ionization tandem mass spectrometry confirmed the amino acid sequence. The redox properties of the cofactor iron site were examined by EPR spectroscopy at 25K following treatment with a variety of fatty acid hydroperoxides. Combination of the enzyme in a stoichiometric ratio with the hydroperoxides led to a g4.3 signal in EPR spectra instead of the g6 signal characteristic of similarly treated soybean lipoxygenase-1. Native 12-lipoxygenase was also subjected to electrospray ionization mass spectrometry. There was evidence for loss of the mass of an iron atom from the protein as the pH was lowered from 5 to 4. Native ions in these samples indicated that iron was lost without the protein completely unfolding.
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Affiliation(s)
- Johanna Rapp
- Department of Chemistry, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606, USA
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Nigam S, Zafiriou MP, Deva R, Ciccoli R, Roux-Van der Merwe R. Structure, biochemistry and biology of hepoxilins. FEBS J 2007; 274:3503-3512. [PMID: 17608719 DOI: 10.1111/j.1742-4658.2007.05910.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hepoxilins are biologically relevant epoxy-hydroxy eicosanoids synthesized through the 12S-lipoxygenase (12S-LOX) pathway of the arachidonic acid (AA) metabolism. The pathway is bifurcated at the level of 12S-hydroperoxy-eicosatetraenoic acid (12S-HpETE), which can either be reduced to 12S-hydro-eicosatetraenoic acid (12S-HETE) or converted to hepoxilins. The present review gives an update on the biochemistry, biology and clinical aspects of hepoxilin-based drug development. The isolation, cloning and characterization of a rat leukocyte-type 12S-LOX from rat insulinoma RINm5F cells revealed a 12S-LOX possessing an intrinsic 8S/R-hydroxy-11,12-epoxyeicosa-5Z,9E,14Z-trienoic acid (HXA(3)) synthase activity. Site-directed mutagenesis studies on rat 12S-LOX showed that the HXA(3) synthase activity was impaired when the positional specificity of AA was altered. Interestingly, amino acid Leu353, and not conventional sequence determinants Met419 and Ile418, was found to be a crucial sequence determinant for AA oxygenation. The regulation of HXA(3) formation is dependent on the cellular overall peroxide tone. Cellular glutathione peroxidases (cGPxs) compete with HXA(3) synthase for 12S-HpETE as substrate either to reduce to 12S-HETE or to convert to HXA(3), respectively. Therefore, RINm5F cells, which are devoid of GPxs, are capable of converting AA or 12S-HpETE to HXA(3) under basal conditions, whereas cells overexpressing cGPx are unable to do so. HXA(3) exhibits a myriad of biological effects, most of which are associated with the stimulation of intracellular calcium or the transport of calcium across the membrane. The activation of HXA(3)-G-protein-coupled receptors explains many of the extracellular effects of HXA(3), including AA- and diacylglycerol (DAG) release in human neutrophils, insulin secretion in rat pancreatic beta-cells or islets, and synaptic actions in the brain. The availability of stable analogs of HXA(3), termed 10-hydroxy-11,12-cyclopropyl-eicosa-5Z,8Z,14Z-trienoic acid derivatives (PBTs), recently made several animal studies possible and explored the role of HXA(3) as a therapeutic in treatment of diseases. Thus, PBT-3 induced apoptosis in K562 tumour cells and inhibited growth of K562 CML solid tumours in nude mice. HXA(3) inhibited bleomycin-evoked lung fibrosis and inflammation in mice and the raised insulin level in the circulation of rats. At low glucose concentrations (0-3 mm), HXA(3) also stimulated insulin secretion in RINm5F cells through the activation of IRE1alpha, an endoplasmic reticulum-resident kinase. The latter regulates the protein folding for insulin biosynthesis. In conclusion, HXA(3)-mediated signaling may be involved in normal physiological functions, and hepoxilin-based drugs may serve as therapeutics in diseases such as type II diabetes and idiopathic lung fibrosis.
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Affiliation(s)
- Santosh Nigam
- Eicosanoid & Lipid Research Division and Centre for Experimental Gynecology & Breast Research, Charité- University Medical Centre Benjamin Franklin, Berlin, Germany
| | - Maria-Patapia Zafiriou
- Eicosanoid & Lipid Research Division and Centre for Experimental Gynecology & Breast Research, Charité- University Medical Centre Benjamin Franklin, Berlin, Germany
| | - Rupal Deva
- Eicosanoid & Lipid Research Division and Centre for Experimental Gynecology & Breast Research, Charité- University Medical Centre Benjamin Franklin, Berlin, Germany
| | - Roberto Ciccoli
- Eicosanoid & Lipid Research Division and Centre for Experimental Gynecology & Breast Research, Charité- University Medical Centre Benjamin Franklin, Berlin, Germany
| | - Renate Roux-Van der Merwe
- Eicosanoid & Lipid Research Division and Centre for Experimental Gynecology & Breast Research, Charité- University Medical Centre Benjamin Franklin, Berlin, Germany
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Wu F, Gaffney BJ. Dynamic behavior of fatty acid spin labels within a binding site of soybean lipoxygenase-1. Biochemistry 2006; 45:12510-8. [PMID: 17029406 PMCID: PMC2515559 DOI: 10.1021/bi061415l] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The putative substrate-binding site in lipoxygenases is long and internal. There is little direct evidence about how the unsaturated fatty acid substrates enter and move within the cavity to position themselves correctly for electron transfer reactions with the catalytic non-heme iron. An EPR spectroscopy approach, with spin-labeled fatty acids, is taken here to investigate dynamic behavior of fatty acids bound to soybean lipoxygenase-1. The probes are labeled on C5, C8, C10, C12, and C16 of stearic acid. The EPR-determined affinity for the enzyme increases as the length of the alkyl end of the probe increases, with a DeltaDeltaG of -190 cal/methylene. The probes in the series exhibit similar enhanced paramagnetic relaxation by the iron center. These results indicate that the members of the series have a common binding site. All of the bound probes undergo considerable local mobility. The stearate spin-labeled at C5 has the highest affinity for the lipoxygenase, and it is a competitive inhibitor, with a K(i) of 9 muM. Surprisingly, this stearate labeled near the carboxyl end undergoes more local motion than those labeled in the middle of the chain, when it is bound. This shows that the carboxyl end of the fatty-acid spin label is not rigidly docked on the protein. During catalysis, repositioning of the substrate carboxyl on the protein surface may be coupled to motion of portions of the chain undergoing reaction.
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Affiliation(s)
- Fayi Wu
- Department of Biological Sciences, BIO Unit I, Florida State University, Tallahassee, FL 32306-4370.
| | - Betty J. Gaffney
- Department of Biological Sciences, BIO Unit I, Florida State University, Tallahassee, FL 32306-4370.
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Schurink M, van Berkel WJH, Wichers HJ, Boeriu CG. Identification of Lipoxygenase Inhibitory Peptides from β-Casein by Using SPOT Synthesis. Chembiochem 2006; 7:743-7. [PMID: 16628755 DOI: 10.1002/cbic.200500461] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Marloes Schurink
- Agrotechnology and Food Innovations, P.O. Box 17, 6700AA Wageningen, The Netherlands.
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Abe M, Yoshimoto T. [Leukotriene-lipoxygenase pathway and drug discovery]. Nihon Yakurigaku Zasshi 2005; 124:415-25. [PMID: 15572846 DOI: 10.1254/fpj.124.415] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The first drugs affecting the leukotriene-lipoxygenase pathway, which have been introduced in clinical application, inhibit effects of slow reacting substance of anaphylaxis (SRS-A). Although, a 5-lipoxygenase inhibitor was first used in clinical practice as an anti-asthma drug, cysteinyl-leukotriene type 1 receptor (cysLT(1)R) antagonists are preferred as anti-asthma and anti-rhinitis drugs because they are almost as effective as the 5-lipoxygenase inhibitors but have fewer side effects. The cloning of genes related to lipoxygenase-leukotriene metabolism prompted us to try to elucidate the role of leukotrienes in various inflammations. There are at least two types of cysLTRs known: cysLT(1)R and cysLT(2)R. CysLT(1)R plays an important role in the pathophysiology of asthma; however, the role of the cysLT(2)R remains unknown. The abundant distribution of cysLT(2)R in heart and brain tissues suggests that cysLTs play an important role in the pathophysiology of ischemic heart diseases or arrhythmias and through this receptor (cysLT(2)R), psychoneurological disorders. The use of a selective cysLT(2)R antagonist may clarify these questions. Since the 5-lipoxygenase pathway is abundantly expressed in atherosclerotic lesions, and 12/15-lipoxygenase is able to oxygenate polyunsaturated fatty acid esterified in the membranous phospholipids, 5-lipoxygenase or 12/15-lipoxygenase inhibitors may prevent progression of atherosclerosis. In addition, it has been reported that 15-lipoxygenase participates in suppression of prostate cancer. In conclusion, the leukotriene-lipoxygenase metabolism may be involved in the pathophysiology of acute inflammatory to chronic progressive disorders. We think that more drugs modifying leukotriene-lipoxygenase metabolism will be introduced into clinical practice in the future.
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Affiliation(s)
- Masayoshi Abe
- Department of Pharmacology, School of Medicine, Fukuoka University, Fukuoka 814-0180, Japan
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Nigam S, Patabhiraman S, Ciccoli R, Ishdorj G, Schwarz K, Petrucev B, Kühn H, Haeggström JZ. The rat leukocyte-type 12-lipoxygenase exhibits an intrinsic hepoxilin A3 synthase activity. J Biol Chem 2004; 279:29023-30. [PMID: 15123652 DOI: 10.1074/jbc.m307576200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hepoxilins are biologically relevant eicosanoids formed via the 12-lipoxygenase pathway of the arachidonic acid cascade. Although these eicosanoids exhibit a myriad of biological activities, their biosynthetic mechanism has not been investigated in detail. We examined the arachidonic acid metabolism of RINm5F rat insulinoma cells and found that they constitutively express a leukocyte-type 12S-lipoxygenase. Moreover, we observed that RINm5F cells exhibit an active hepoxilin A(3) synthase that converts exogenous 12S-HpETE (12S-5Z,8-Z,10E,14Z-12-hydro(pero)xy-eicosa-5,8,10,14-tetraenoic acid) or arachidonic acid predominantly to hepoxilin A(3). 12S-lipoxygenase and hepoxilin A(3) synthase activities were co-localized in the cytosol; immunoprecipitation with an anti-12S-lipoxygenase antibody co-precipitated the two catalytic activities. These data suggested that hepoxilin A(3) synthase activity may be considered an intrinsic catalytic property of the leukocyte-type 12S-lipoxygenase. To test this hypothesis we cloned the leukocyte-type 12S-LOX from RINm5F cells, expressed it in Pichia pastoris, and found that the recombinant enzyme exhibited both 12S-lipoxygenase and hepoxilin A(3) synthase activities. The recombinant human platelet-type 12S-lipoxygenase and the porcine leukocyte-type 12S-lipoxygenase also exhibited hepoxilin A(3) synthase activity. In contrast, the native rabbit reticulocyte-type 15S-lipoxygenase did not convert 12S-HpETE to hepoxilin isomers. These data suggest that the positional specificity of lipoxygenases may be crucial for this catalytic function. This hypothesis was confirmed by site-directed mutagenesis studies that altered the positional specificity of the rat leukocyte-type 12S- and the rabbit reticulocyte-type 15-lipoxygenase. In summary, it may be concluded that naturally occurring 12S-lipoxygenases exhibit an intrinsic hepoxilin A(3) synthase activity that is minimal in lipoxygenase isoforms with different positional specificity.
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Affiliation(s)
- Santosh Nigam
- Eicosanoid and Lipid Research Division and Centre of Experimental Gynecology and Breast Research, University Medical Centre Berlin, Campus Benjamin Franklin, Free University of Berlin, D-12200 Berlin, Germany.
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Amagata T, Whitman S, Johnson TA, Stessman CC, Loo CP, Lobkovsky E, Clardy J, Crews P, Holman TR. Exploring sponge-derived terpenoids for their potency and selectivity against 12-human, 15-human, and 15-soybean lipoxygenases. JOURNAL OF NATURAL PRODUCTS 2003; 66:230-5. [PMID: 12608855 DOI: 10.1021/np020462l] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
To sharpen the search for new lipoxygenase inhibitors, we designed a screen to probe for both potency and selectivity. The assay utilized 12-human (12-HLO), 15-human (15-HLO), and 15-soybean (15-SLO) lipoxygenases. The IC(50) value data obtained provided new insights about structure-activity relationships (SAR) for redox and nonredox inhibitors. All of the compounds tested were isolated from sponges and consisted of a novel terpenoid, hyrtenone A (1), and 12 known terpenoids. Potent compounds were defined as those having IC(50) values < 1 microM, and selectivity was assessed from the three possible IC(50) value ratios. One of the four terpenoid redox inhibitors studied, puupehenone (2), was equivalent to or better in potency than the well-known redox inhibitor nordihydroguarierate acid (NDGA, 14). However, none of the terpene redox inhibitors exhibited a selectivity ratio on a par with that of 14. Several potent nonredox inhibitors were identified, and one, dimethoxypuupehenol (5), exhibited notable selectivity. The structural elucidation of 1 and the SAR results for 13 natural products are reported. This study suggests that sponge-derived terpenes are a promising source for new lipoxygenase inhibitors.
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Affiliation(s)
- Taro Amagata
- Department of Chemistry, Institute for Marine Sciences, University of California Santa Cruz, Santa Cruz, California 95064, USA
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