1
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Zeppilli D, Madabeni A, Nogara PA, Rocha JBT, Orian L. Reactivity of Zinc Fingers in Oxidizing Environments: Insight from Molecular Models Through Activation Strain Analysis. Chempluschem 2024:e202400252. [PMID: 38842473 DOI: 10.1002/cplu.202400252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Revised: 06/06/2024] [Accepted: 06/06/2024] [Indexed: 06/07/2024]
Abstract
The reactivity of Zn2+ tetrahedral complexes with H2O2 was investigated in silico, as a first step in their disruption process. The substrates were chosen to represent the cores of three different zinc finger protein motifs, i. e., a Zn2+ ion coordinated to four cysteines (CCCC), to three cysteines and one histidine (CCCH), and to two cysteines and two histidines (CCHH). The cysteine and histidine ligands were further simplified to methyl thiolate and imidazole, respectively. H2O2 was chosen as an oxidizing agent due to its biological role as a metabolic product and species involved in signaling processes. The mechanism of oxidation of a coordinated cysteinate to sulfenate-κS and the trends for the different substrates were rationalized through activation strain analysis and energy decomposition analysis in the framework of scalar relativistic Density Functional Theory (DFT) calculations at ZORA-M06/TZ2P ae // ZORA-BLYP-D3(BJ)/TZ2P. CCCC is oxidized most easily, an outcome explained considering both electrostatic and orbital interactions. The isomerization to sulfenate-κO was attempted to assess whether this step may affect the ligand dissociation; however, it was found to introduce a kinetic barrier without improving the energetics of the dissociation. Lastly, ligand exchange with free thiolates and selenolates was investigated as a trigger for ligand dissociation, possibly leading to metal ejection; molecular docking simulations also support this hypothesis.
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Affiliation(s)
- Davide Zeppilli
- Dipartimento di Scienze Chimiche Università degli Studi di Padova, Via Marzolo 1, 35131, Padova, Italy
| | - Andrea Madabeni
- Dipartimento di Scienze Chimiche Università degli Studi di Padova, Via Marzolo 1, 35131, Padova, Italy
| | - Pablo A Nogara
- Departamento de Bioquímica e Biologia Molecolar, Universidade Federal de Santa Maria (UFSM), 97105-900, Santa Maria, RS, Brazil
- Instituto Federal de Educação, Ciência e Tecnologia Sul-rio-grandense (IFSul), Av. Leonel de Moura Brizola, 2501, 96418-400, Bagé, RS, Brasil
| | - João B T Rocha
- Departamento de Bioquímica e Biologia Molecolar, Universidade Federal de Santa Maria (UFSM), 97105-900, Santa Maria, RS, Brazil
| | - Laura Orian
- Dipartimento di Scienze Chimiche Università degli Studi di Padova, Via Marzolo 1, 35131, Padova, Italy
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2
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Barbosa NV, Aschner M, Tinkov AA, Farina M, da Rocha JBT. Should ebselen be considered for the treatment of mercury intoxication? A minireview. Toxicol Mech Methods 2024; 34:1-12. [PMID: 37731353 PMCID: PMC10841883 DOI: 10.1080/15376516.2023.2258958] [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: 04/13/2023] [Accepted: 09/09/2023] [Indexed: 09/22/2023]
Abstract
Mercury is a ubiquitous environmental contaminant and can be found in inorganic (Hg0, Hg+ and Hg2+) and organic forms (chiefly CH3Hg+ or MeHg+). The main route of human, mammals and bird exposure occurs via predatory fish ingestion. Occupational exposure to Hg0 (and Hg2+) can also occur; furthermore, in gold mining areas the exposure to inorganic Hg can also be high. The toxicity of electrophilic forms of Hg (E+Hg) is mediated by disruption of thiol (-SH)- or selenol (-SeH)-containing proteins. The therapeutic approaches to treat methylmercury (MeHg+), Hg0 and Hg2+ are limited. Here we discuss the potential use of ebselen as a potential therapeutic agent to lower the body burden of Hg in man. Ebselen is a safe drug for humans and has been tested in clinical trials (for instance, brain ischemia, noise-induce hearing loss, diabetes complications, bipolar disorders) at doses varying from 400 to 3600 mg per day. Two clinical trials with ebselen in moderate and severe COVID are also approved. Ebselen can be metabolized to an intermediate with -SeH (selenol) functional group, which has a greater affinity to electrophilic Hg (E+Hg) forms than the available thiol-containing therapeutic agents. Accordingly, as observed in vitro and rodent models in vivo, Ebselen exhibited protective effects against MeHg+, indicating its potential as a therapeutic agent to treat MeHg+ overexposure. The combined use of ebselen with thiol-containing molecules (e.g. N-acetylcysteine and enaramide)) is also commented, because they can have synergistic protective effects against MeHg+.
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Affiliation(s)
- Nilda V. Barbosa
- Departamento de Bioquímica e Biologia Molecular, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, Brazil
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Alexey A. Tinkov
- Yaroslavl State University, Yaroslavl, Russia
- Center of Bioelementology and Human Ecology, IM Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia
| | - Marcelo Farina
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, Brazil
| | - João Batista Teixeira da Rocha
- Departamento de Bioquímica e Biologia Molecular, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, Brazil
- Departamento de Bioquímica, Instituto Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
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3
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Zeppilli D, Madabeni A, Sancineto L, Bagnoli L, Santi C, Orian L. Role of Group 12 Metals in the Reduction of H 2O 2 by Santi's Reagent: A Computational Mechanistic Investigation. Inorg Chem 2023; 62:17288-17298. [PMID: 37769326 PMCID: PMC10598800 DOI: 10.1021/acs.inorgchem.3c02568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Indexed: 09/30/2023]
Abstract
PhSeZnCl, which is also known as Santi's reagent, can catalyze the reduction of hydrogen peroxide by thiols with a GPx-like mechanism. In this work, the first step of this catalytic cycle, i.e., the reduction of H2O2 by PhSeZnCl, is investigated in silico using state-of-the-art density functional theory calculations. Then, the role of the metal is evaluated by replacing Zn with its group 12 siblings (Cd and Hg). The thermodynamic and kinetic factors favoring Zn are elucidated. Furthermore, the role of the halogen is considered by replacing Cl with Br in all three metal compounds, and this turns out to be negligible. Finally, the overall GPx-like mechanism of PhSeZnCl and PhSeZnBr is discussed by evaluating the energetics of the mechanistic path leading to the disulfide product.
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Affiliation(s)
- Davide Zeppilli
- Dipartimento
di Scienze Chimiche, Università degli
Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Andrea Madabeni
- Dipartimento
di Scienze Chimiche, Università degli
Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Luca Sancineto
- Gruppo
di Catalisi Sintesi e Chimica Organica Verde Dipartimento di Scienze
Farmaceutiche, Università degli Studi
di Perugia, Via del Liceo 1, 06122 Perugia, Italy
| | - Luana Bagnoli
- Gruppo
di Catalisi Sintesi e Chimica Organica Verde Dipartimento di Scienze
Farmaceutiche, Università degli Studi
di Perugia, Via del Liceo 1, 06122 Perugia, Italy
| | - Claudio Santi
- Gruppo
di Catalisi Sintesi e Chimica Organica Verde Dipartimento di Scienze
Farmaceutiche, Università degli Studi
di Perugia, Via del Liceo 1, 06122 Perugia, Italy
| | - Laura Orian
- Dipartimento
di Scienze Chimiche, Università degli
Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
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4
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Delgado CP, Rocha JBT, Orian L, Bortoli M, Nogara PA. In silico studies of M pro and PL pro from SARS-CoV-2 and a new class of cephalosporin drugs containing 1,2,4-thiadiazole. Struct Chem 2022; 33:2205-2220. [PMID: 36106095 PMCID: PMC9463509 DOI: 10.1007/s11224-022-02036-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 08/09/2022] [Indexed: 11/29/2022]
Abstract
The SARS-CoV-2 proteases Mpro and PLpro are important targets for the development of antivirals against COVID-19. The functional group 1,2,4-thiadiazole has been indicated to inhibit cysteinyl proteases, such as papain and cathepsins. Of note, the 1,2,4-thiadiazole moiety is found in a new class of cephalosporin FDA-approved antibiotics: ceftaroline fosamil, ceftobiprole, and ceftobiprole medocaril. Here we investigated the interaction of these new antibiotics and their main metabolites with the SARS-CoV-2 proteases by molecular docking, molecular dynamics (MD), and density functional theory (DFT) calculations. Our results indicated the PLpro enzyme as a better in silico target for the new antibacterial cephalosporins. The results with ceftaroline fosamil and the dephosphorylate metabolite compounds should be tested as potential inhibitor of PLpro, Mpro, and SARS-CoV-2 replication in vitro. In addition, the data here reported can help in the design of new potential drugs against COVID-19 by exploiting the S atom reactivity in the 1,2,4-thiadiazole moiety. Supplementary Information The online version contains supplementary material available at 10.1007/s11224-022-02036-5.
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Affiliation(s)
- Cássia Pereira Delgado
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Santa Maria (UFSM), Santa Maria, RS 97105-900 Brazil
| | - João Batista Teixeira Rocha
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Santa Maria (UFSM), Santa Maria, RS 97105-900 Brazil
| | - Laura Orian
- Dipartimento di Scuenze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padua, Italy
| | - Marco Bortoli
- Institut de Química Computacionali Catàlisi (IQCC), Departament de Química, Facultat de Ciències, Universitat de Girona, C/M. A. Capmany 69, 17003 Girona, Spain
| | - Pablo Andrei Nogara
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Santa Maria (UFSM), Santa Maria, RS 97105-900 Brazil
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5
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Pérez-Barcia Á, Montero-Campillo MM, Lamsabhi AM, Salpin JY, Yáñez M. Open questions on toxic heavy metals Cd, Hg and Pb binding small components of DNA and nucleobases. Are there any predictable trends? Phys Chem Chem Phys 2022; 24:20624-20637. [PMID: 36043513 DOI: 10.1039/d2cp02459d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this perspective article, we provide a bibliographic compilation of experimental and theoretical work on Cd, Hg, and Pb, and analyze in detail the bonding of M2+ and CH3M+ (M = Zn, Cd, Hg, Pb) with urea and thiourea as suitable models for larger biochemical bases. Through the use of DFT calculations, we have found that although in principle binding energies decrease according to ionic size (Zn2+ > Cd2+ > Pb2+), Hg2+ largely breaks the trend. Through the use of EDA (Energy Decomposition Analysis) it is possible to explain this behavior, which is essentially due to the strong contribution of polarization to the binding. This conclusion is ratified by the NEDA (Natural Energy Decomposition Analysis) formalism, showing that the charge transfer term is very large in all cases, but particularly in the case of the mercury-thiourea system. The general trends observed for the interactions with CH3M+ monocations show however CH3Hg+ binding energies systematically smaller than the CH3Zn+ ones, likely because the relativistic contraction of the Hg orbitals is very much attenuated by the attachment to the methyl group. Finally, we have investigated the gas-phase reactivity between EtHg+ and uracil to compare it with that exhibited by CH3Hg+ and n-ButHg+ previously described in the literature. This comparison gathers new information that highlights the importance of the length of the alkyl chain attached to the metal on the mechanisms of these reactions. For methyl mercury, only the alkyl transfer process is allowed; for butyl mercury, protonation is clearly favored, and for ethyl mercury, both paths are competitive experimentally.
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Affiliation(s)
- Álvaro Pérez-Barcia
- Departamento de Química Física, Universidad de Vigo, Lagoas-Marcosende s/n, 36310 Vigo, Spain
| | - M Merced Montero-Campillo
- Departamento de Química, Módulo 13, Facultad de Ciencias, and Institute of Advanced Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, Campus de Excelencia UAM-CSIC, Cantoblanco, 28049 Madrid, Spain.
| | - Al Mokhtar Lamsabhi
- Departamento de Química, Módulo 13, Facultad de Ciencias, and Institute of Advanced Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, Campus de Excelencia UAM-CSIC, Cantoblanco, 28049 Madrid, Spain.
| | - Jean-Yves Salpin
- Université Paris-Saclay, Univ. Evry, CNRS, LAMBE, 91025, Evry-Courcouronnes, France.,LAMBE, CY Cergy Paris Université, CNRS, 95000 Cergy, France.
| | - Manuel Yáñez
- Departamento de Química, Módulo 13, Facultad de Ciencias, and Institute of Advanced Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, Campus de Excelencia UAM-CSIC, Cantoblanco, 28049 Madrid, Spain.
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6
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Banerjee M, Chakravarty D, Kalwani P, Ballal A. Voyage of selenium from environment to life: Beneficial or toxic? J Biochem Mol Toxicol 2022; 36:e23195. [PMID: 35976011 DOI: 10.1002/jbt.23195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 06/22/2022] [Accepted: 07/21/2022] [Indexed: 11/08/2022]
Abstract
Selenium (Se), a naturally occurring metalloid, is an essential micronutrient for life as it is incorporated as selenocysteine in proteins. Although beneficial at low doses, Se is hazardous at high concentrations and poses a serious threat to various ecosystems. Due to this contrasting 'dual' nature, Se has garnered the attention of researchers wishing to unravel its puzzling properties. In this review, we describe the impact of selenium's journey from environment to diverse biological systems, with an emphasis on its chemical advantage. We describe the uneven distribution of Se and how this affects the bioavailability of this element, which, in turn, profoundly affects the habitat of a region. Once taken up, the subsequent incorporation of Se into proteins as selenocysteine and its antioxidant functions are detailed here. The causes of improved protein function due to the incorporation of redox-active Se atom (instead of S) are examined. Subsequently, the reasons for the deleterious effects of Se, which depend on its chemical form (organo-selenium or the inorganic forms) in different organisms are elaborated. Although Se is vital for the function of many antioxidant enzymes, how the pro-oxidant nature of Se can be potentially exploited in different therapies is highlighted. Furthermore, we succinctly explain how the presence of Se in biological systems offsets the toxic effects of heavy metal mercury. Finally, the different avenues of research that are fundamental to expand our understanding of selenium biology are suggested.
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Affiliation(s)
- Manisha Banerjee
- Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai, India.,Homi Bhabha National Institute, Mumbai, India
| | - Dhiman Chakravarty
- Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai, India
| | - Prakash Kalwani
- Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai, India.,Homi Bhabha National Institute, Mumbai, India
| | - Anand Ballal
- Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai, India.,Homi Bhabha National Institute, Mumbai, India
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7
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A Novel Diselenide-Probucol-Analogue Protects Against Methylmercury-Induced Toxicity in HT22 Cells by Upregulating Peroxide Detoxification Systems: a Comparison with Diphenyl Diselenide. Neurotox Res 2022; 40:127-139. [PMID: 35043379 DOI: 10.1007/s12640-021-00466-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 11/24/2021] [Accepted: 12/20/2021] [Indexed: 10/19/2022]
Abstract
Methylmercury (MeHg) is a ubiquitous environmental neurotoxicant whose mechanisms of action involve oxidation of endogenous nucleophilic groups (mainly thiols and selenols), depletion of antioxidant defenses, and disruption of neurotransmitter homeostasis. Diphenyl diselenide-(PhSe)2-a model diaryl diselenide, has been reported to display significant protective effects against MeHg-induced neurotoxicity under both in vitro and in vivo experimental conditions. In this study, we compared the protective effects of (PhSe)2 with those of RC513 (4,4'-diselanediylbis(2,6-di-tert-butylphenol), a novel diselenide-probucol-analog) against MeHg-induced toxicity in the neuronal (hippocampal) cell line HT22. Although both (PhSe)2 and RC513 significantly mitigated MeHg- and tert-butylhydroperoxide (t-BuOOH)-cytotoxicity, the probucol analog exhibited superior protective effects, which were observed earlier and at lower concentrations compared to (PhSe)2. RC513 treatment (at either 0.5 µM or 2 µM) significantly increased glutathione peroxidase (GPx) activity, which has been reported to counteract MeHg-toxicity. (PhSe)2 was also able to increase GPx activity, but only at 2 µM. Although both compounds increased the Gpx1 transcripts at 6 h after treatments, only RC513 was able to increase mRNA levels of Prx2, Prx3, Prx5, and Txn2, which are also involved in peroxide detoxification. RC513 (at 2 µM) significantly increased GPx-1 protein expression in HT22 cells, although (PhSe)2 displayed a minor (nonsignificant) effect in this parameter. In agreement, RC513 induced a faster and superior capability to cope with exogenously-added peroxide (t-BuOOH). In summary, when compared to the prototypical organic diaryl diselenide [(PhSe)2], RC513 displayed superior protective properties against MeHg-toxicity in vitro; this was paralleled by a more pronounced upregulation of defenses related to detoxification of peroxides, which are well-known MeHg-derived intermediate oxidant species.
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8
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Nogara PA, Omage FB, Bolzan GR, Delgado CP, Aschner M, Orian L, Teixeira Rocha JB. In silico Studies on the Interaction between Mpro and PLpro From SARS-CoV-2 and Ebselen, its Metabolites and Derivatives. Mol Inform 2021; 40:e2100028. [PMID: 34018687 PMCID: PMC8236915 DOI: 10.1002/minf.202100028] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 04/11/2021] [Indexed: 12/20/2022]
Abstract
The COVID-19 pandemic caused by the SARS-CoV-2 has mobilized scientific attention in search of a treatment. The cysteine-proteases, main protease (Mpro) and papain-like protease (PLpro) are important targets for antiviral drugs. In this work, we simulate the interactions between the Mpro and PLpro with Ebselen, its metabolites and derivatives with the aim of finding molecules that can potentially inhibit these enzymes. The docking data demonstrate that there are two main interactions between the thiol (-SH) group of Cys (from the protease active sites) and the electrophilic centers of the organoselenium molecules, i. e. the interaction with the carbonyl group (O=C… SH) and the interaction with the Se moiety (Se… SH). Both interactions may lead to an adduct formation and enzyme inhibition. Density Functional Theory (DFT) calculations with Ebselen indicate that the energetics of the thiol nucleophilic attack is more favorable on Se than on the carbonyl group, which is in accordance with experimental data (Jin et al. Nature, 2020, 582, 289-293). Therefore, organoselenium molecules should be further explored as inhibitors of the SARS-CoV-2 proteases. Furthermore, we suggest that some metabolites of Ebselen (e. g. Ebselen diselenide and methylebselenoxide) and derivatives ethaselen and ebsulfur should be tested in vitro as inhibitors of virus replication and its proteases.
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Affiliation(s)
- Pablo Andrei Nogara
- Departamento de Bioquímica e Biologia MolecularUniversidade Federal de Santa Maria (UFSM)Santa Maria97105-900RSBrazil
| | - Folorunsho Bright Omage
- Departamento de Bioquímica e Biologia MolecularUniversidade Federal de Santa Maria (UFSM)Santa Maria97105-900RSBrazil
| | - Gustavo Roni Bolzan
- Departamento de Bioquímica e Biologia MolecularUniversidade Federal de Santa Maria (UFSM)Santa Maria97105-900RSBrazil
| | - Cássia Pereira Delgado
- Departamento de Bioquímica e Biologia MolecularUniversidade Federal de Santa Maria (UFSM)Santa Maria97105-900RSBrazil
| | - Michael Aschner
- Department of Molecular PharmacologyAlbert Einstein College of Medicine1300 Morris Park Avenue, BronxNY10461USA
| | - Laura Orian
- Dipartimento di Scienze ChimicheUniversità degli Studi di PadovaVia Marzolo 135131PadovaItaly
| | - João Batista Teixeira Rocha
- Departamento de Bioquímica e Biologia MolecularUniversidade Federal de Santa Maria (UFSM)Santa Maria97105-900RSBrazil
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9
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Nogara PA, Madabeni A, Bortoli M, Teixeira Rocha JB, Orian L. Methylmercury Can Facilitate the Formation of Dehydroalanine in Selenoenzymes: Insight from DFT Molecular Modeling. Chem Res Toxicol 2021; 34:1655-1663. [PMID: 34077192 DOI: 10.1021/acs.chemrestox.1c00073] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Experimental studies have indicated that electrophilic mercury forms (e.g., methylmercury, MeHg+) can accelerate the breakage of selenocysteine in vitro. Particularly, in 2009, Khan et al. (Environ. Toxicol. Chem. 2009, 28, 1567-1577) proposed a mechanism for the degradation of a free methylmercury selenocysteinate complex that was theoretically supported by Asaduzzaman et al. (Inorg. Chem. 2010, 50, 2366-2372). However, little is known about the fate of methylmercury selenocysteinate complexes embedded in an enzyme, especially in conditions of oxidative stress in which methylmercury target enzymes operate. Here, an accurate computational study on molecular models (level of theory: COSMO-ZORA-BLYP-D3(BJ)/TZ2P) was carried out to investigate the formation of dehydroalanine (Dha) in selenoenzymes, which irreversibly impairs their function. Methylselenocysteine as well as methylcysteine and methyltellurocysteine were included to gain insight on the peculiar behavior of selenium. Dha forms in a two-step process, i.e., the oxidation of the chalcogen nucleus followed by a syn-elimination leading to the alkene and the chalcogenic acid. The effect of an excess of hydrogen peroxide, which may lead to the formation of chalcogenones before the elimination, and of MeHg+, a severe toxicant targeting selenoproteins, which leads to the formation of methylmercury selenocysteinate, are also studied with the aim of assessing whether these pathological conditions facilitate the formation of Dha. Indeed, elimination occurs after chalcogen oxidation and MeHg+ facilitates the process. These results indicate a possible mechanism of toxicity of MeHg+ in selenoproteins.
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Affiliation(s)
- Pablo Andrei Nogara
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Santa Maria (UFSM), Santa Maria 97105-900, RS, Brazil.,Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Andrea Madabeni
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Marco Bortoli
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - João Batista Teixeira Rocha
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Santa Maria (UFSM), Santa Maria 97105-900, RS, Brazil
| | - Laura Orian
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
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10
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Madabeni A, Nogara PA, Bortoli M, Rocha JB, Orian L. Effect of Methylmercury Binding on the Peroxide-Reducing Potential of Cysteine and Selenocysteine. Inorg Chem 2021; 60:4646-4656. [PMID: 33587617 PMCID: PMC8763373 DOI: 10.1021/acs.inorgchem.0c03619] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Indexed: 01/09/2023]
Abstract
Methylmercury (CH3Hg+) binding to catalytically fundamental cysteine and selenocysteine of peroxide-reducing enzymes has long been postulated as the origin of its toxicological activity. Only very recently, CH3Hg+ binding to the selenocysteine of thioredoxin reductase has been directly observed [Pickering, I. J. Inorg. Chem., 2020, 59, 2711-2718], but the precise influence of the toxicant on the peroxide-reducing potential of such a residue has never been investigated. In this work, we employ state-of-the-art density functional theory calculations to study the reactivity of molecular models of the free and toxified enzymes. Trends in activation energies are discussed with attention to the biological consequences and are rationalized within the chemically intuitive framework provided by the activation strain model. With respect to the free, protonated amino acids, CH3Hg+ binding promotes oxidation of the S or Se nucleus, suggesting that chalcogenoxide formation might occur in the toxified enzyme, even if the actual rate of peroxide reduction is almost certainly lowered as suggested by comparison with fully deprotonated amino acids models.
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Affiliation(s)
- Andrea Madabeni
- Dipartimento
di Scienze Chimiche, Università degli
Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Pablo A. Nogara
- Dipartimento
di Scienze Chimiche, Università degli
Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
- Departamento
de Bioquímica e Biologia Molecular, Universidade Federal de Santa Maria (UFSM), 97105-900 Santa
Maria, RS, Brazil
| | - Marco Bortoli
- Dipartimento
di Scienze Chimiche, Università degli
Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - João B.
T. Rocha
- Departamento
de Bioquímica e Biologia Molecular, Universidade Federal de Santa Maria (UFSM), 97105-900 Santa
Maria, RS, Brazil
| | - Laura Orian
- Dipartimento
di Scienze Chimiche, Università degli
Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
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11
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Nogueira CW, Barbosa NV, Rocha JBT. Toxicology and pharmacology of synthetic organoselenium compounds: an update. Arch Toxicol 2021; 95:1179-1226. [PMID: 33792762 PMCID: PMC8012418 DOI: 10.1007/s00204-021-03003-5] [Citation(s) in RCA: 103] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 02/10/2021] [Indexed: 12/17/2022]
Abstract
Here, we addressed the pharmacology and toxicology of synthetic organoselenium compounds and some naturally occurring organoselenium amino acids. The use of selenium as a tool in organic synthesis and as a pharmacological agent goes back to the middle of the nineteenth and the beginning of the twentieth centuries. The rediscovery of ebselen and its investigation in clinical trials have motivated the search for new organoselenium molecules with pharmacological properties. Although ebselen and diselenides have some overlapping pharmacological properties, their molecular targets are not identical. However, they have similar anti-inflammatory and antioxidant activities, possibly, via activation of transcription factors, regulating the expression of antioxidant genes. In short, our knowledge about the pharmacological properties of simple organoselenium compounds is still elusive. However, contrary to our early expectations that they could imitate selenoproteins, organoselenium compounds seem to have non-specific modulatory activation of antioxidant pathways and specific inhibitory effects in some thiol-containing proteins. The thiol-oxidizing properties of organoselenium compounds are considered the molecular basis of their chronic toxicity; however, the acute use of organoselenium compounds as inhibitors of specific thiol-containing enzymes can be of therapeutic significance. In summary, the outcomes of the clinical trials of ebselen as a mimetic of lithium or as an inhibitor of SARS-CoV-2 proteases will be important to the field of organoselenium synthesis. The development of computational techniques that could predict rational modifications in the structure of organoselenium compounds to increase their specificity is required to construct a library of thiol-modifying agents with selectivity toward specific target proteins.
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Affiliation(s)
- Cristina W Nogueira
- Laboratório de Síntese, Reatividade e Avaliação Farmacológica E Toxicológica de Organocalcogênios, Centro de Ciências Naturais E Exatas, Universidade Federal de Santa Maria, Santa Maria, RS, CEP 97105-900, Brazil.
| | - Nilda V Barbosa
- Laboratório de Síntese, Reatividade e Avaliação Farmacológica E Toxicológica de Organocalcogênios, Centro de Ciências Naturais E Exatas, Universidade Federal de Santa Maria, Santa Maria, RS, CEP 97105-900, Brazil
| | - João B T Rocha
- Laboratório de Síntese, Reatividade e Avaliação Farmacológica E Toxicológica de Organocalcogênios, Centro de Ciências Naturais E Exatas, Universidade Federal de Santa Maria, Santa Maria, RS, CEP 97105-900, Brazil.
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