1
|
Richard K, Schonhofer C, Giron LB, Rivera-Ortiz J, Read S, Kannan T, Kinloch NN, Shahid A, Feilcke R, Wappler S, Imming P, Harris M, Brumme ZL, Brockman MA, Mounzer K, Kossenkov AV, Abdel-Mohsen M, Andrae-Marobela K, Montaner LJ, Tietjen I. The African natural product knipholone anthrone and its analogue anthralin (dithranol) enhance HIV-1 latency reversal. J Biol Chem 2020; 295:14084-14099. [PMID: 32788215 DOI: 10.1074/jbc.ra120.013031] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 08/06/2020] [Indexed: 12/12/2022] Open
Abstract
A sterilizing or functional cure for HIV is currently precluded by resting CD4+ T cells that harbor latent but replication-competent provirus. The "shock-and-kill" pharmacological ap-proach aims to reactivate provirus expression in the presence of antiretroviral therapy and target virus-expressing cells for elimination. However, no latency reversal agent (LRA) to date effectively clears viral reservoirs in humans, suggesting a need for new LRAs and LRA combinations. Here, we screened 216 compounds from the pan-African Natural Product Library and identified knipholone anthrone (KA) and its basic building block anthralin (dithranol) as novel LRAs that reverse viral latency at low micromolar concentrations in multiple cell lines. Neither agent's activity depends on protein kinase C; nor do they inhibit class I/II histone deacetylases. However, they are differentially modulated by oxidative stress and metal ions and induce distinct patterns of global gene expression from established LRAs. When applied in combination, both KA and anthralin synergize with LRAs representing multiple functional classes. Finally, KA induces both HIV RNA and protein in primary cells from HIV-infected donors. Taken together, we describe two novel LRAs that enhance the activities of multiple "shock-and-kill" agents, which in turn may inform ongoing LRA combination therapy efforts.
Collapse
Affiliation(s)
- Khumoekae Richard
- Faculty of Health Sciences, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Cole Schonhofer
- Faculty of Health Sciences, Simon Fraser University, Burnaby, British Columbia, Canada
| | | | | | - Silven Read
- Faculty of Health Sciences, Simon Fraser University, Burnaby, British Columbia, Canada
| | | | - Natalie N Kinloch
- Faculty of Health Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.,British Columbia Centre for Excellence in HIV/AIDS, Vancouver, British Columbia, Canada
| | - Aniqa Shahid
- Faculty of Health Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.,British Columbia Centre for Excellence in HIV/AIDS, Vancouver, British Columbia, Canada
| | - Ruth Feilcke
- Institut für Pharmazie, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany
| | - Simone Wappler
- Institut für Pharmazie, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany
| | - Peter Imming
- Institut für Pharmazie, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany
| | - Marianne Harris
- British Columbia Centre for Excellence in HIV/AIDS, Vancouver, British Columbia, Canada
| | - Zabrina L Brumme
- Faculty of Health Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.,British Columbia Centre for Excellence in HIV/AIDS, Vancouver, British Columbia, Canada
| | - Mark A Brockman
- Faculty of Health Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.,British Columbia Centre for Excellence in HIV/AIDS, Vancouver, British Columbia, Canada.,Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Karam Mounzer
- Jonathan Lax Immune Disorders Treatment Center, Philadelphia Field Initiating Group for HIV-1 Trials, Philadelphia, Pennsylvania, USA
| | | | | | | | | | - Ian Tietjen
- Faculty of Health Sciences, Simon Fraser University, Burnaby, British Columbia, Canada .,Wistar Institute, Philadelphia, Pennsylvania, USA
| |
Collapse
|
2
|
Ellis ES, MacHale LT, Szilagyi RK, DuBois JL. How Chemical Environment Activates Anthralin and Molecular Oxygen for Direct Reaction. J Org Chem 2020; 85:1315-1321. [PMID: 31830417 DOI: 10.1021/acs.joc.9b03133] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The role of the chemical environment in promoting anthralin/O2 reactions was discovered using neat solvents to model the amino acids of a cofactor-independent oxygenase. Experimental and computational results highlight the importance of the substrate-enolate, which is accessed via energetically small, escalating steps in which the ground-state keto-isomer is tautomerized to an enol and then ionized by solvent. The resulting ion-pair is poised for spontaneous electron transfer to O2. Similar activation may be exploited in biological/nonbiological oxidations involving O2.
Collapse
Affiliation(s)
- Emerald S Ellis
- Department of Chemistry and Biochemistry , Montana State University , P.O. Box 173400, Bozeman , Montana 59717 , United States
| | - Luke T MacHale
- Department of Chemistry and Biochemistry , Montana State University , P.O. Box 173400, Bozeman , Montana 59717 , United States
| | - Robert K Szilagyi
- Department of Chemistry and Biochemistry , Montana State University , P.O. Box 173400, Bozeman , Montana 59717 , United States
| | - Jennifer L DuBois
- Department of Chemistry and Biochemistry , Montana State University , P.O. Box 173400, Bozeman , Montana 59717 , United States
| |
Collapse
|
3
|
Ding W, Ho CC, Yoshikai N. Photosensitized, Energy-Transfer-Mediated Cyclization of 2-(1-Arylvinyl)benzaldehydes to Anthracen-9-(10H)-ones. Org Lett 2019; 21:1202-1206. [DOI: 10.1021/acs.orglett.9b00182] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Wei Ding
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Chang Chin Ho
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Naohiko Yoshikai
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| |
Collapse
|
4
|
Machovina MM, Usselman RJ, DuBois JL. Monooxygenase Substrates Mimic Flavin to Catalyze Cofactorless Oxygenations. J Biol Chem 2016; 291:17816-28. [PMID: 27307041 DOI: 10.1074/jbc.m116.730051] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Indexed: 01/16/2023] Open
Abstract
Members of the antibiotic biosynthesis monooxygenase family catalyze O2-dependent oxidations and oxygenations in the absence of any metallo- or organic cofactor. How these enzymes surmount the kinetic barrier to reactions between singlet substrates and triplet O2 is unclear, but the reactions have been proposed to occur via a flavin-like mechanism, where the substrate acts in lieu of a flavin cofactor. To test this model, we monitored the uncatalyzed and enzymatic reactions of dithranol, a substrate for the nogalamycin monooxygenase (NMO) from Streptomyces nogalater As with flavin, dithranol oxidation was faster at a higher pH, although the reaction did not appear to be base-catalyzed. Rather, conserved asparagines contributed to suppression of the substrate pKa The same residues were critical for enzymatic catalysis that, consistent with the flavoenzyme model, occurred via an O2-dependent slow step. Evidence for a superoxide/substrate radical pair intermediate came from detection of enzyme-bound superoxide during turnover. Small molecule and enzymatic superoxide traps suppressed formation of the oxygenation product under uncatalyzed conditions, whereas only the small molecule trap had an effect in the presence of NMO. This suggested that NMO both accelerated the formation and directed the recombination of a superoxide/dithranyl radical pair. These catalytic strategies are in some ways flavin-like and stand in contrast to the mechanisms of urate oxidase and (1H)-3-hydroxy-4-oxoquinaldine 2,4-dioxygenase, both cofactor-independent enzymes that surmount the barriers to direct substrate/O2 reactivity via markedly different means.
Collapse
Affiliation(s)
- Melodie M Machovina
- From the Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59715-3400
| | - Robert J Usselman
- From the Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59715-3400
| | - Jennifer L DuBois
- From the Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59715-3400
| |
Collapse
|
5
|
Loh CCJ, Fang X, Peters B, Lautens M. Benzylic Functionalization of Anthrones via the Asymmetric Ring Opening of Oxabicycles Utilizing a Fourth-Generation Rhodium Catalytic System. Chemistry 2015; 21:13883-7. [PMID: 26310604 DOI: 10.1002/chem.201502718] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Indexed: 11/08/2022]
Abstract
While anthrones exist as privileged scaffolds in bioactive molecules, the enantioselective functionalization of anthrones is surprisingly scarce in the literature, with no asymmetric transition metal catalyzed example to date. Herein, we report the first asymmetric transition metal catalyzed benzylic functionalization of anthrones through the rhodium(I) catalyzed desymmetrization of oxabicycles. As previously developed rhodium(I) systems were found to be unsuitable for this substrate, a new robust fourth-generation [Rh(cod)OH]2 based catalytic system was developed to address synthetic challenges in this protocol.
Collapse
Affiliation(s)
- Charles C J Loh
- Department of Chemistry, Davenport Chemical Laboratories, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6 (Canada)
| | - Xiang Fang
- Department of Chemistry, Davenport Chemical Laboratories, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6 (Canada).,Laboratory for Advanced Material and Institute of Fine Chemicals, School of Chemistry and Molecular Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (P. R. China)
| | - Brendan Peters
- Department of Chemistry, Davenport Chemical Laboratories, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6 (Canada)
| | - Mark Lautens
- Department of Chemistry, Davenport Chemical Laboratories, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6 (Canada).
| |
Collapse
|
6
|
Benković ET, Kreft S. Fagopyrins and Protofagopyrins: Detection, Analysis, and Potential Phototoxicity in Buckwheat. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2015; 63:5715-5724. [PMID: 26024291 DOI: 10.1021/acs.jafc.5b01163] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Buckwheat contains many healthy nutrients, and its consumption is therefore increasing. Buckwheat also contains fluorescent phototoxic fagopyrins. A systematic review of fagopyrins and the phototoxicity of buckwheat found that reliable quantitative data on fagopyrin toxicity are not yet available. Generally, buckwheat seeds, flour, and teas are safe in normal amounts. Diets extensively composed of buckwheat sprouts, herbs, and particularly flowers or of fagopyrin-rich buckwheat extracts may cause fagopyrism. A reference standard is needed, as it would enable the accurate evaluation of fagopyrin content in buckwheat products and would allow proper testing of their as yet unknown physical, chemical, and biological characteristics.
Collapse
Affiliation(s)
- Eva Tavčar Benković
- Faculty of Pharmacy, University of Ljubljana, Aškerčeva 7, 1000 Ljubljana, Slovenia
| | - Samo Kreft
- Faculty of Pharmacy, University of Ljubljana, Aškerčeva 7, 1000 Ljubljana, Slovenia
| |
Collapse
|
7
|
Savian AL, Rodrigues D, Weber J, Ribeiro RF, Motta MH, Schaffazick SR, Adams AIH, de Andrade DF, Beck RCR, da Silva CB. Dithranol-loaded lipid-core nanocapsules improve the photostability and reduce the in vitro irritation potential of this drug. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2014; 46:69-76. [PMID: 25491961 DOI: 10.1016/j.msec.2014.10.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Revised: 08/26/2014] [Accepted: 10/02/2014] [Indexed: 11/26/2022]
Abstract
Dithranol is a very effective drug for the topical treatment of psoriasis. However, it has some adverse effects such as irritation and stain in the skin that make its application and patient adherence to treatment difficult. The aims of this work were to prepare and characterize dithranol-loaded nanocapsules as well as to evaluate the photostability and the irritation potential of these nanocarriers. Lipid-core nanocapsules containing dithranol (0.5 mg/mL) were prepared by interfacial deposition of preformed polymer. EDTA (0.05%) or ascorbic acid (0.02%) was used as antioxidants. After preparation, dithranol-loaded lipid-core nanocapsules showed satisfactory characteristics: drug content close to the theoretical concentration, encapsulation efficiency of about 100%, nanometric mean size (230-250 nm), polydispersity index below 0.25, negative zeta potential, and pH values from 4.3 to 5.6. In the photodegradation study against UVA light, we observed a higher stability of the dithranol-loaded lipid-core nanocapsules comparing to the solution containing the free drug (half-life times around 4 and 1h for the dithranol-loaded lipid-core nanocapsules and free drug solution containing EDTA, respectively; half-life times around 17 and 7h for the dithranol-loaded lipid-core nanocapsules and free drug solution containing ascorbic acid, respectively). Irritation test by HET-CAM method was conducted to evaluate the safety of the formulations. From the results it was found that the nanoencapsulation of the drug decreased its toxicity compared to the effects observed for the free drug.
Collapse
Affiliation(s)
- Ana L Savian
- Programa de Pós-Graduação em Ciências Farmacêuticas, Universidade Federal de Santa Maria, Av. Roraima, 1000, Santa Maria, RS 97105-900, Brazil
| | - Daiane Rodrigues
- Curso de Farmácia, Centro de Ciências da Saúde, Universidade Federal de Santa Maria, Av. Roraima, 1000, Santa Maria, RS 97105-900, Brazil
| | - Julia Weber
- Programa de Pós-Graduação em Ciências Farmacêuticas, Universidade Federal de Santa Maria, Av. Roraima, 1000, Santa Maria, RS 97105-900, Brazil
| | - Roseane F Ribeiro
- Programa de Pós-Graduação em Ciências Farmacêuticas, Universidade Federal de Santa Maria, Av. Roraima, 1000, Santa Maria, RS 97105-900, Brazil
| | - Mariana H Motta
- Curso de Farmácia, Centro de Ciências da Saúde, Universidade Federal de Santa Maria, Av. Roraima, 1000, Santa Maria, RS 97105-900, Brazil
| | - Scheila R Schaffazick
- Programa de Pós-Graduação em Ciências Farmacêuticas, Universidade Federal de Santa Maria, Av. Roraima, 1000, Santa Maria, RS 97105-900, Brazil
| | - Andréa I H Adams
- Programa de Pós-Graduação em Ciências Farmacêuticas, Universidade Federal de Santa Maria, Av. Roraima, 1000, Santa Maria, RS 97105-900, Brazil
| | - Diego F de Andrade
- Programa de Pós-Graduação em Ciências Farmacêuticas, Universidade Federal do Rio Grande do Sul, Av. Ipiranga, 2752, Porto Alegre, RS 90610-000, Brazil
| | - Ruy C R Beck
- Programa de Pós-Graduação em Ciências Farmacêuticas, Universidade Federal do Rio Grande do Sul, Av. Ipiranga, 2752, Porto Alegre, RS 90610-000, Brazil
| | - Cristiane B da Silva
- Programa de Pós-Graduação em Ciências Farmacêuticas, Universidade Federal de Santa Maria, Av. Roraima, 1000, Santa Maria, RS 97105-900, Brazil.
| |
Collapse
|
8
|
Thierbach S, Bui N, Zapp J, Chhabra SR, Kappl R, Fetzner S. Substrate-assisted O2 activation in a cofactor-independent dioxygenase. ACTA ACUST UNITED AC 2014; 21:217-25. [PMID: 24388758 DOI: 10.1016/j.chembiol.2013.11.013] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 11/22/2013] [Accepted: 11/27/2013] [Indexed: 11/29/2022]
Abstract
In contrast to the majority of O2-activating enzymes, which depend on an organic cofactor or a metal ion for catalysis, a particular group of structurally unrelated oxygenases is functional without any cofactor. In this study, we characterized the mechanism of O2 activation in the reaction pathway of a cofactor-independent dioxygenase with an α/β-hydrolase fold, which catalyzes the oxygenolytic cleavage of 2-alkyl-3-hydroxy-4(1H)-quinolones. Chemical analysis and electron paramagnetic resonance spectroscopic data revealed that O2 activation in the enzyme's active site is substrate-assisted, relying on single electron transfer from the bound substrate anion to O2 to form a radical pair, which recombines to a C2-peroxide intermediate. Thus, an oxygenase can function without a cofactor, if the organic substrate itself, after activation to a (carb)anion by an active-site base, is intrinsically reactive toward molecular oxygen.
Collapse
Affiliation(s)
- Sven Thierbach
- Institute of Molecular Microbiology and Biotechnology, University of Münster, Corrensstrasse 3, 48149 Münster, Germany
| | - Nguyen Bui
- Department of Biophysics, School of Medicine, Saarland University, Clinical Center, Building 76, 66421 Homburg, Germany
| | - Josef Zapp
- Pharmaceutical Biology, Saarland University, Campus, Building C2, 66123 Saarbrücken, Germany
| | - Siri Ram Chhabra
- School of Life Sciences, Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
| | - Reinhard Kappl
- Department of Biophysics, School of Medicine, Saarland University, Clinical Center, Building 76, 66421 Homburg, Germany
| | - Susanne Fetzner
- Institute of Molecular Microbiology and Biotechnology, University of Münster, Corrensstrasse 3, 48149 Münster, Germany.
| |
Collapse
|
9
|
Korth HG, Mulder P. Anthrone and related hydroxyarenes: tautomerization and hydrogen bonding. J Org Chem 2013; 78:7674-82. [PMID: 23815684 DOI: 10.1021/jo401243b] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The keto-enolization of hydroxyl-substituted naphthols and 9-anthrols has been investigated by means of CBS-QB3 calculations. An excellent agreement between experiment and theory is found for the energetics for the anthrone (5) ⇌ anthrol (6) equilibrium, with an enthalpy of tautomerization, Δ(t)H, of 3.8 kcal mol(-1). In contrast, 1-naphthol is the preferred tautomer with a Δ(t)H = -9.0 kcal mol(-1). Substitution of the hydrogens at the adjacent carbons by hydroxyl groups leads to the formation of strong intramolecular hydrogen bonds within a six-membered ring in the enones and the enols. Due to the difference in the intramolecular hydrogen bond enthalpy, Δ(HB)H(intra), the equilibrium shifts further to the enone. Thus, for 1,8-dihydroxy-anthrone (anthralin, dithranol) Δ(t)H increases to 12.7 kcal mol(-1) with an enol/enone ratio of 10(-10). The solvent effect on the 5 ⇌ 6 equilibrium has been quantified by considering the formation of intermolecular hydrogen bond(s), leading to an acidity parameter α₂(H) for anthrol of 0.42. It is shown that the hydrogen bond donating ability of bulk methanol is greatly attenuated through the formation of cyclic oligomers. The benzylic and phenolic bond dissociation enthalpies for anthrone up to anthralin suggest some antioxidant potency but the precise (radical) mechanism of action remains uncertain.
Collapse
Affiliation(s)
- Hans-Gert Korth
- Institut für Organische Chemie, Universität Duisburg-Essen, D-45117 Essen, Germany.
| | | |
Collapse
|
10
|
Grocholski T, Koskiniemi H, Lindqvist Y, Mäntsälä P, Niemi J, Schneider G. Crystal structure of the cofactor-independent monooxygenase SnoaB from Streptomyces nogalater: implications for the reaction mechanism. Biochemistry 2010; 49:934-44. [PMID: 20052967 DOI: 10.1021/bi901985b] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
SnoaB is a cofactor-independent monooxygenase that catalyzes the conversion of 12-deoxynogalonic acid to nogalonic acid in the biosynthesis of the aromatic polyketide nogalamycin in Streptomyces nogalater. In vitro (18)O(2) experiments establish that the oxygen atom incorporated into the substrate is derived from molecular oxygen. The crystal structure of the enzyme was determined in two different space groups to 1.7 and 1.9 A resolution, respectively. The enzyme displays the ferredoxin fold, with the characteristic beta-strand exchange at the dimer interface. The crystal structures reveal a putative catalytic triad involving two asparagine residues, Asn18 and Asn63, and a water molecule, which may play important roles in the enzymatic reaction. Site-directed mutagenesis experiments, replacing the two asparagines individually by alanine, led to a 100-fold drop in enzymatic activity. Replacement of an invariant tryptophan residue in the active site of the enzyme by phenylalanine also resulted in an enzyme variant with about 1% residual activity. Taken together, our findings are most consistent with a carbanion mechanism where the deprotonated substrate reacts with molecular oxygen via one electron transfer and formation of a caged radical.
Collapse
Affiliation(s)
- Thadee Grocholski
- Department of Biochemistry and Food Chemistry, University of Turku, FIN-20014 Turku, Finland
| | | | | | | | | | | |
Collapse
|
11
|
Krpetić Z, Scarì G, Caneva E, Speranza G, Porta F. Gold nanoparticles prepared using cape aloe active components. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:7217-7221. [PMID: 19505092 DOI: 10.1021/la9009674] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A novel use of two components of Cape aloe, aloin A and aloesin, acting as stabilizers in the preparation of gold and silver nanoparticles, is reported. Stable water-soluble particles of different size and shape are prepared by varying the reaction conditions, temperature, reaction time, and reducing agents. Characterization of the obtained particles is performed using UV-visible, attenuated total reflection Fourier transform infrared (ATR-FTIR), and 1H NMR spectroscopies and transmission electron microscopy (TEM). The efficient cellular uptake of 50 nm sized aloin A and aloesin stabilized gold particles into macrophages and HeLa cells was investigated, proposing these particles as nanovehicles.
Collapse
Affiliation(s)
- Zeljka Krpetić
- Dipartimento di Chimica Inorganica Metallorganica Analitica Lamberto Malatesta, University of Milan, Via Venezian 21, Milan, Italy
| | | | | | | | | |
Collapse
|
12
|
Czerwinska M, Sikora A, Szajerski P, Zielonka J, Adamus J, Marcinek A, Piech K, Bednarek P, Bally T. Anthralin: Primary Products of Its Redox Reactions. J Org Chem 2006; 71:5312-9. [PMID: 16808521 DOI: 10.1021/jo060622o] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
One-electron reduction significantly enhances the ability of anthralin, 1, to act as a hydrogen atom donor. On annealing of an MTHF glass in which the radical anion of anthralin, 1*-, is generated radiolytically, this species decays mainly by loss of H* to give the anthralyl anion, 2- . On the other hand, radicals formed on radiolysis of matrices that are suitable for the generation of radical anions or cations are capable to abstract H* from anthralin to give the anthralyl radical, 2* . Both 2- and 2* are obtained simultaneously by mesolytic cleavage of the radical anion of the anthralin dimer. Contrary to general assumptions, the anthralyl radical is found to be much more reactive toward oxygen than the anion. All intermediates are characterized spectroscopically and by reference to quantum chemical calculations. Attempts to generate the radical cation of anthralin by X-irradiation of an Ar matrix containing anthralin led also to significant formation of its radical anion, i.e., anthralin acts apparently as an efficient electron trap in such experiments.
Collapse
|
13
|
Alexandrova AY, Kopnin PB, Vasiliev JM, Kopnin BP. ROS up-regulation mediates Ras-induced changes of cell morphology and motility. Exp Cell Res 2006; 312:2066-73. [PMID: 16624288 DOI: 10.1016/j.yexcr.2006.03.004] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2005] [Revised: 03/06/2006] [Accepted: 03/08/2006] [Indexed: 12/31/2022]
Abstract
Expression of activated Ras causes an increase in intracellular content of reactive oxygen species (ROS). To determine the role of ROS up-regulation in mediation of Ras-induced morphological transformation and increased cell motility, we studied the effects of hydrogen peroxide and antioxidant NAC on morphology of REF52 rat fibroblasts and their ability to migrate into the wound in vitro. Treatment with low dosages of hydrogen peroxide leading to 1.5- to 2-fold increase in intracellular ROS levels induced changes of cell shape, actin cytoskeleton organization, cell adhesions and migration resembling those in Ras-transformed cells. On the other hand, treatment with NAC attenuating ROS up-regulation in cells with conditional or constitutive expression of activated Ras led to partial reversion of morphological transformation and decreased cell motility. The effect of ROS on cell morphology and motility probably results from modulation of activity of Rac1, Rho, and cofilin proteins playing a key role in regulation of actin dynamics. The obtained data are consistent with the idea that ROS up-regulation mediates two key events in Ras-induced morphological transformation and cell motility: it is responsible for Rac1 activation and is necessary (though insufficient) for realization of Ras-induced cofilin dephosphorylation.
Collapse
Affiliation(s)
- Antonina Y Alexandrova
- Institute of Carcinogenesis, Blokhin Memorial Russian Cancer Research Center, Kashirskoye shosse 24, 115478 Moscow, Russia
| | | | | | | |
Collapse
|
14
|
|
15
|
Amigó M, Terencio MC, Mitova M, Iodice C, Payá M, De Rosa S. Potential antipsoriatic avarol derivatives as antioxidants and inhibitors of PGE(2) generation and proliferation in the HaCaT cell line. JOURNAL OF NATURAL PRODUCTS 2004; 67:1459-1463. [PMID: 15387642 DOI: 10.1021/np049873n] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The synthesis and structure-activity relationships for a series of 14 new avarol derivatives as antioxidants and inhibitors of cell proliferation and PGE(2) generation in human keratinocytes are described. Compound 6 (thiosalicylic derivative) was the most potent inhibitor of superoxide generation in human neutrophils and also potently inhibited PGE(2) generation in the human keratinocyte HaCaT cell line. Compound 7(3'-methylaminoavarone) presented the best antiproliferative profile, by the inhibition of (3)H-thymidine incorporation in HaCaT cells, with potency similar to the reference compound anthralin. None of the avarol derivatives showed any sign of cytotoxicity measured as LDH release in treated keratinocytes. The potency and pharmacological profile of derivatives are also discussed.
Collapse
Affiliation(s)
- Maria Amigó
- Departament de Farmacologia, Facultat de Farmàcia, Universitat de València, Av. V. Andrés Estellés s/n, 46100, Burjassot, Valencia, Spain
| | | | | | | | | | | |
Collapse
|
16
|
Liang DWM, Du CJ. Potent Antipsoriatic Agents: A Facile Preparation of Acylated Derivatives from Dithranol in a Mild Basic Reaction. J CHIN CHEM SOC-TAIP 2004. [DOI: 10.1002/jccs.200400018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
17
|
Sciara G, Kendrew SG, Miele AE, Marsh NG, Federici L, Malatesta F, Schimperna G, Savino C, Vallone B. The structure of ActVA-Orf6, a novel type of monooxygenase involved in actinorhodin biosynthesis. EMBO J 2003; 22:205-15. [PMID: 12514126 PMCID: PMC140106 DOI: 10.1093/emboj/cdg031] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
ActVA-Orf6 monooxygenase from Streptomyces coelicolor that catalyses the oxidation of an aromatic intermediate of the actinorhodin biosynthetic pathway is a member of a class of small monooxygenases that carry out oxygenation without the assistance of any of the prosthetic groups, metal ions or cofactors normally associated with activation of molecular oxygen. The overall structure is a ferredoxin-like fold with a novel dimeric assembly, indicating that the widely represented ferredoxin fold may sustain yet another functionality. The resolution (1.3 A) of the enzyme structure and its complex with substrate and product analogues allows us to visualize the mechanism of binding and activation of the substrate for attack by molecular oxygen, and utilization of two gates for the reaction components including a proton gate and an O(2)/H(2)O gate with a putative protein channel. This is the first crystal structure of an enzyme involved in the tailoring of a type II aromatic polyketide and illustrates some of the enzyme-substrate recognition features that may apply to a range of other enzymes involved in modifying a polyketide core structure.
Collapse
Affiliation(s)
- Giuliano Sciara
- Dipartimento di Scienze Biochimiche and CNR, Centro di Studi sulla Biologia Molecolare, c/o Dipartimento di Scienze Biochimiche, Università di Roma ‘La Sapienza’, Piazzale A.Moro, 5, 00185 Roma, Dipartimento di Biologia di Base ed Applicata, Università di L’Aquila, 67100 L’Aquila, Istituto G.Donegani, 28100 Novara, Italy, Biotica Technology Ltd, 181A Huntingdon Road, Cambridge CB3 0DJ, UK and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA Corresponding author e-mail:
| | - Steven G. Kendrew
- Dipartimento di Scienze Biochimiche and CNR, Centro di Studi sulla Biologia Molecolare, c/o Dipartimento di Scienze Biochimiche, Università di Roma ‘La Sapienza’, Piazzale A.Moro, 5, 00185 Roma, Dipartimento di Biologia di Base ed Applicata, Università di L’Aquila, 67100 L’Aquila, Istituto G.Donegani, 28100 Novara, Italy, Biotica Technology Ltd, 181A Huntingdon Road, Cambridge CB3 0DJ, UK and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA Corresponding author e-mail:
| | - Adriana E. Miele
- Dipartimento di Scienze Biochimiche and CNR, Centro di Studi sulla Biologia Molecolare, c/o Dipartimento di Scienze Biochimiche, Università di Roma ‘La Sapienza’, Piazzale A.Moro, 5, 00185 Roma, Dipartimento di Biologia di Base ed Applicata, Università di L’Aquila, 67100 L’Aquila, Istituto G.Donegani, 28100 Novara, Italy, Biotica Technology Ltd, 181A Huntingdon Road, Cambridge CB3 0DJ, UK and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA Corresponding author e-mail:
| | - Neil G. Marsh
- Dipartimento di Scienze Biochimiche and CNR, Centro di Studi sulla Biologia Molecolare, c/o Dipartimento di Scienze Biochimiche, Università di Roma ‘La Sapienza’, Piazzale A.Moro, 5, 00185 Roma, Dipartimento di Biologia di Base ed Applicata, Università di L’Aquila, 67100 L’Aquila, Istituto G.Donegani, 28100 Novara, Italy, Biotica Technology Ltd, 181A Huntingdon Road, Cambridge CB3 0DJ, UK and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA Corresponding author e-mail:
| | - Luca Federici
- Dipartimento di Scienze Biochimiche and CNR, Centro di Studi sulla Biologia Molecolare, c/o Dipartimento di Scienze Biochimiche, Università di Roma ‘La Sapienza’, Piazzale A.Moro, 5, 00185 Roma, Dipartimento di Biologia di Base ed Applicata, Università di L’Aquila, 67100 L’Aquila, Istituto G.Donegani, 28100 Novara, Italy, Biotica Technology Ltd, 181A Huntingdon Road, Cambridge CB3 0DJ, UK and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA Corresponding author e-mail:
| | - Francesco Malatesta
- Dipartimento di Scienze Biochimiche and CNR, Centro di Studi sulla Biologia Molecolare, c/o Dipartimento di Scienze Biochimiche, Università di Roma ‘La Sapienza’, Piazzale A.Moro, 5, 00185 Roma, Dipartimento di Biologia di Base ed Applicata, Università di L’Aquila, 67100 L’Aquila, Istituto G.Donegani, 28100 Novara, Italy, Biotica Technology Ltd, 181A Huntingdon Road, Cambridge CB3 0DJ, UK and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA Corresponding author e-mail:
| | - Giuliana Schimperna
- Dipartimento di Scienze Biochimiche and CNR, Centro di Studi sulla Biologia Molecolare, c/o Dipartimento di Scienze Biochimiche, Università di Roma ‘La Sapienza’, Piazzale A.Moro, 5, 00185 Roma, Dipartimento di Biologia di Base ed Applicata, Università di L’Aquila, 67100 L’Aquila, Istituto G.Donegani, 28100 Novara, Italy, Biotica Technology Ltd, 181A Huntingdon Road, Cambridge CB3 0DJ, UK and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA Corresponding author e-mail:
| | - Carmelinda Savino
- Dipartimento di Scienze Biochimiche and CNR, Centro di Studi sulla Biologia Molecolare, c/o Dipartimento di Scienze Biochimiche, Università di Roma ‘La Sapienza’, Piazzale A.Moro, 5, 00185 Roma, Dipartimento di Biologia di Base ed Applicata, Università di L’Aquila, 67100 L’Aquila, Istituto G.Donegani, 28100 Novara, Italy, Biotica Technology Ltd, 181A Huntingdon Road, Cambridge CB3 0DJ, UK and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA Corresponding author e-mail:
| | - Beatrice Vallone
- Dipartimento di Scienze Biochimiche and CNR, Centro di Studi sulla Biologia Molecolare, c/o Dipartimento di Scienze Biochimiche, Università di Roma ‘La Sapienza’, Piazzale A.Moro, 5, 00185 Roma, Dipartimento di Biologia di Base ed Applicata, Università di L’Aquila, 67100 L’Aquila, Istituto G.Donegani, 28100 Novara, Italy, Biotica Technology Ltd, 181A Huntingdon Road, Cambridge CB3 0DJ, UK and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA Corresponding author e-mail:
| |
Collapse
|
18
|
Kemény L, Farkas A, Dobozy A. Low-dose dithranol treatment and tape stripping induce tolerance to dithranol in a mouse ear oedema model. Br J Dermatol 2002; 146:764-9. [PMID: 12000371 DOI: 10.1046/j.1365-2133.2002.04663.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND It is well known from clinical practice that repeated treatment with dithranol leads to the development of tolerance. OBJECTIVES To investigate the characteristics and mechanism of such dithranol tolerance. METHODS The mouse ear was pretreated with a low dose of dithranol or croton oil or, in previously sensitized animals, with dinitrofluorobenzene (DNFB). Twenty-four hours later irritant dermatitis was elicited by painting the mouse ear with a high dose of dithranol, croton oil or DNFB, and the dermatitis was characterized by measurement of ear thickness. RESULTS Low-dose dithranol significantly suppressed dithranol-induced oedema, whereas it had no effect on croton oil- or DNFB-induced dermatitis, suggesting that dithranol-induced tolerance is specific. Tolerance to dithranol could not be induced by pretreatment of the mouse ear with a low dose of croton oil or DNFB. Mild tape stripping of the mouse ear also inhibited the inflammatory effect of dithranol applied 24 h later. Superoxide dismutase treatment abolished the tolerance-inducing effect of low-dose dithranol or stripping. CONCLUSIONS These results suggest that superoxide anion radicals are involved not only in the inflammatory effect of dithranol, but also in the induction of tolerance.
Collapse
Affiliation(s)
- L Kemény
- Department of Dermatology, Faculty of General Medicine, University of Szeged, Szeged, Hungary.
| | | | | |
Collapse
|
19
|
Abstract
Inflammatory skin diseases account for a large proportion of all skin disorders and constitute a major health problem worldwide. Contact dermatitis, atopic dermatitis, and psoriasis represent the most prevalent inflammatory skin disorders and share a common efferent T-lymphocyte mediated response. Oxidative stress and inflammation have recently been linked to cutaneous damage in T-lymphocyte mediated skin diseases, particularly in contact dermatitis. Insights into the pathophysiology responsible for contact dermatitis can be used to better understand the mechanism of other T-lymphocyte mediated inflammatory skin diseases, and may help to develop novel therapeutic approaches. This review focuses on redox sensitive events in the inflammatory scenario of contact dermatitis, which comprise for example, several kinases, transcription factors, cytokines, adhesion molecules, dendritic cell surface markers, the T-lymphocyte receptor, and the cutaneous lymphocyte-associated antigen (CLA). In vitro and animal studies clearly point to a central role of several distinct but interconnected redox-sensitive pathways in the pathogenesis of contact dermatitis. However, clinical evidence that modulation of the skin's redox state can be used therapeutically to modulate the inflammatory response in contact dermatitis is presently not convincing. The rational for this discrepancy seems to be multi-faceted and complex and will be discussed.
Collapse
Affiliation(s)
- J Fuchs
- Department of Dermatology, Medical School, J. W. Goethe University, Frankfurt, Germany
| | | | | | | |
Collapse
|
20
|
10-Hydrocinnamoyl- and 10-cinnamoyl-1,8-dihydroxy-9(10H)-anthracenones as inhibitors of leukotriene B4 biosynthesis and HaCaT cell growth. Eur J Med Chem 1998. [DOI: 10.1016/s0223-5234(99)80021-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
21
|
Sellmer A, Terpetschnig E, Wiegrebe W, Wolfbeis OS. UV/Vis and fluorescence study on anthralin and its alkylated derivatives. J Photochem Photobiol A Chem 1998. [DOI: 10.1016/s1010-6030(98)00277-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
22
|
Müller K, Altmann R, Prinz H. 10-Benzoyl-1,8-dihydroxy-9(10H)-anthracenones: Synthesis and biological properties. Eur J Med Chem 1998. [DOI: 10.1016/s0223-5234(98)80010-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
23
|
Müller K, Prinz H, Gawlik I, Ziereis K, Huang HS. Simple analogues of anthralin: unusual specificity of structure and antiproliferative activity. J Med Chem 1997; 40:3773-80. [PMID: 9371243 DOI: 10.1021/jm970292n] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Fifty-nine simple analogues of the antipsoriatic agent, anthralin, have been prepared by modifying the positions of the 1,8-hydroxyl groups, replacement of the hydroxyl groups, substitution at the oxygen functions, introduction of additional functional groups into various positions of the anthracenone nucleus, or removal of particular structural elements. The compounds were evaluated for their antiproliferative action against human keratinocytes and inhibition of the generation of leukotriene B4 in polymorphonuclear leukocytes, which may be useful to resolve the proliferative and inflammatory aspects of psoriasis, respectively. Even though many anthracenones were more potent inhibitors of leukotriene biosynthesis than anthralin, none of the compounds was substantially more effective as this drug in suppressing keratinocyte cell growth. There is an absolute requirement for two hydroxyl groups peri to a hydrogen bond acceptor such as a keto or an imino group for high potency. In addition to further delineating the nature of the pharmacophore for this class of compounds, also naphthalenedione with a peri hydroxyl group was identified as a pharmacophore with antiproliferative activity against keratinocyte growth.
Collapse
Affiliation(s)
- K Müller
- Institut für Pharmazeutische Chemie, Westfälische Wilhelms-Universität Münster, Germany
| | | | | | | | | |
Collapse
|
24
|
10-Aminomethylene-1,8-dihydroxy-9(10H)-anthracenones: Inhibitory action against 5-lipoxygenase and the growth of HaCaT cells. Eur J Med Chem 1997. [DOI: 10.1016/s0223-5234(97)82775-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
25
|
Müller K, Prinz H. Antipsoriatic anthrones with modulated redox properties. 4. Synthesis and biological activity of novel 9,10-dihydro-1,8-dihydroxy-9-oxo-2-anthracenecarboxylic and -hydroxamic acids. J Med Chem 1997; 40:2780-7. [PMID: 9276024 DOI: 10.1021/jm9701785] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A novel series of carboxylic and hydroxamic acids based on 1,8-dihydroxy-9(10H)-anthracenone were synthesized from 8-hydroxy-1-methoxy-9,10-anthracenedione as the key intermediate and evaluated both in the bovine polymorphonuclear leukocyte 5-lipoxygenase (5-LO) assay and in the HaCaT keratinocyte proliferation assay for their enzyme inhibitory and antiproliferative activity, respectively. The most potent inhibitors in both assays were the N-methylated hydroxamic acids 5d-8d with straight chain alkyl spacers. Incorporation of these structural features on the anthracenone pharmacophore resulted in increased inhibitory activity against 5-LO while the antiproliferative activity was retained. In addition, prooxidant properties as measured by deoxyribose degradation and cytotoxicity as assessed by LDH release were largely reduced as compared with the antipsoriatic anthralin. Contrary to anthralin, antioxidant properties were observed as documented by the reactivity of the novel compounds against free radicals and inhibition of lipid peroxidation in model membranes.
Collapse
Affiliation(s)
- K Müller
- Institut für Pharmazeutische Chemie, Westfälische Wilhelms-Universität Münster, Germany
| | | |
Collapse
|
26
|
Müller K. Antipsoriatic and proinflammatory action of anthralin. Implications for the role of oxygen radicals. Biochem Pharmacol 1997; 53:1215-21. [PMID: 9214681 DOI: 10.1016/s0006-2952(96)00732-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Anthralin is among the most effective agents for the topical treatment of psoriasis. However, this drug causes unpleasant side-effects such as inflammation and staining of the nonaffected skin surrounding a psoriatic lesion. The biochemical basis for the induction of an inflammatory response in the skin and the antipsoriatic effectiveness are uncertain, although several cellular targets of anthralin action have been identified. Because no single mechanism is operative, the view was taken that all the effects exerted by anthralin are caused by its redox activity leading to the generation of anthralin free radicals and oxygen radicals. Clear relationships between oxygen-radical production by anthralin and biological response are evident with respect to chemical lesions in cellular macromolecules such as DNA, lipid membranes, and enzymes, indicating that these species account for the antipsoriatic and proinflammatory effects elicited by anthralin. This poses new challenges for the medicinal chemist and provides impetus for identifying novel compounds having potential for an improved therapeutic index.
Collapse
Affiliation(s)
- K Müller
- Institute of Pharmaceutical Chemistry, University of Münster, Germany
| |
Collapse
|
27
|
Müller K, Gawlik I. Effects of reactive oxygen species on the biosynthesis of 12 (S)-hydroxyeicosatetraenoic acid in mouse epidermal homogenate. Free Radic Biol Med 1997; 23:321-30. [PMID: 9199895 DOI: 10.1016/s0891-5849(97)00092-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Arachidonic acid is converted to 12-hydroxyeicosatetraenoic acid (12-HETE) in a homogenate of mouse epidermal cells. When the epidermal homogenate was preincubated with scavengers of reactive oxygen species (ROS), catalase or superoxide dismutase, significantly larger amounts of 12-HETE were produced as compared to untreated controls, suggesting that 12-lipoxygenase is quite prone to inactivation by ROS and peroxides. Mouse epidermal homogenate was then exposed to nine different ROS-generating systems to study the effects of superoxide, hydrogen peroxide, singlet oxygen, hypochlorite, peroxyl radicals, and alkyl hydroperoxides on the enzyme activity. Analysis by chiral phase high performance liquid chromatography demonstrated that the 12-HETE biosynthesized from arachidonic acid by mouse epidermal homogenate was the 12 (S)-enantiomer and excludes oxidation of arachidonic acid by ROS in a nonspecific free radical mechanism which leads to racemic 12-HETE. ROS generated by the interaction of xanthine with xanthine oxidase strongly inhibited epidermal 12 (S)-HETE biosynthesis. A flux of 0.7 nmol of superoxide/min/ml of reaction medium resulted in more than 50% inhibition of epidermal 12-lipoxygenase activity. The decrease in 12 (S)-HETE biosynthesis appeared to involve both superoxide and hydrogen peroxide. The efficacy of the latter species was also documented by exposure of mouse epidermal 12-lipoxygenase to glucose and glucose oxidase, which resulted in similar inhibitory effects on 12 (S)-HETE biosynthesis. The presence of the iron chelator diethylenetriaminepentaacetic acid during incubation of epidermal 12-lipoxygenase with both the xanthine/xanthine oxidase or the glucose/glucose oxidase systems partially protected the enzyme against inhibition, indicating that hydroxyl radical contributes to the overall inhibitory effect. Also, organic hydroperoxides inhibited epidermal 12-lipoxygenase, whereas singlet oxygen, hypochlorite, and peroxyl radicals were not effective. The results of this study lead to the proposal that 12-lipoxygenase activity may be regulated by ROS such as hydrogen peroxides, superoxide, and hydroxyl radicals.
Collapse
Affiliation(s)
- K Müller
- Institute of Pharmacy, Pharmaceutical Chemistry I, University of Regensburg, Germany
| | | |
Collapse
|