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Cartus AT, Lachenmeier DW, Guth S, Roth A, Baum M, Diel P, Eisenbrand G, Engeli B, Hellwig M, Humpf HU, Joost HG, Kulling SE, Lampen A, Marko D, Steinberg P, Wätjen W, Hengstler JG, Mally A. Acetaldehyde as a Food Flavoring Substance: Aspects of Risk Assessment. Mol Nutr Food Res 2023; 67:e2200661. [PMID: 37840378 DOI: 10.1002/mnfr.202200661] [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: 09/28/2022] [Revised: 05/31/2023] [Indexed: 10/17/2023]
Abstract
The Senate Commission on Food Safety (SKLM) of the German Research Foundation (DFG) has reviewed the currently available data in order to assess the health risks associated with the use of acetaldehyde as a flavoring substance in foods. Acetaldehyde is genotoxic in vitro. Following oral intake of ethanol or inhalation exposure to acetaldehyde, systemic genotoxic effects of acetaldehyde in vivo cannot be ruled out (induction of DNA adducts and micronuclei). At present, the key question of whether acetaldehyde is genotoxic and mutagenic in vivo after oral exposure cannot be answered conclusively. There is also insufficient data on human exposure. Consequently, it is currently not possible to reliably assess the health risk associated with the use of acetaldehyde as a flavoring substance. However, considering the genotoxic potential of acetaldehyde as well as numerous data gaps that need to be filled to allow a comprehensive risk assessment, the SKLM considers that the use of acetaldehyde as a flavoring may pose a safety concern. For reasons of precautionary consumer protection, the SKLM recommends that the scientific base for approval of the intentional addition of acetaldehyde to foods as a flavoring substance should be reassessed.
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Affiliation(s)
| | - Dirk W Lachenmeier
- Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe, Weißenburger Str. 3, 76187, Karlsruhe, Germany
| | - Sabine Guth
- Leibniz Research Centre for Working Environment and Human Factors (IfADo), Ardeystr, 67, 44139, Dortmund, Germany
| | - Angelika Roth
- Leibniz Research Centre for Working Environment and Human Factors (IfADo), Ardeystr, 67, 44139, Dortmund, Germany
| | - Matthias Baum
- Solenis Germany Industries GmbH, Fütingsweg 20, 47805, Krefeld, Germany
| | - Patrick Diel
- Department of Molecular and Cellular Sports Medicine, Institute of Cardiovascular Research and Sports Medicine, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany
| | | | - Barbara Engeli
- Federal Food Safety and Veterinary Office (FSVO), Risk Assessment Division, Schwarzenburgstrasse 155, Bern, 3003, Switzerland
| | - Michael Hellwig
- Chair of Special Food Chemistry, Technische Universität Dresden, Bergstraße 66, 01062, Dresden, Germany
| | - Hans-Ulrich Humpf
- Institute of Food Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstraße 45, 48149, Münster, Germany
| | - Hans-Georg Joost
- Department of Experimental Diabetology, German Institute of Human Nutrition (DIfE), Arthur-Scheunert-Allee 114-116, 14558, Nuthetal, Germany
| | - Sabine E Kulling
- Department of Safety and Quality of Fruit and Vegetables, Max Rubner-Institut, Federal Research Institute of Nutrition and Food, Haid-und-Neu-Straße 9, 76131, Karlsruhe, Germany
| | - Alfonso Lampen
- Risk Assessment Strategies, Bundesinstitut für Risikobewertung (BfR), Max-Dohrn-Straße 8-10, Berlin, Germany
| | - Doris Marko
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Währinger Straße 38, Vienna, 1090, Austria
| | - Pablo Steinberg
- Max Rubner-Institut, Federal Research Institute of Nutrition and Food, Haid-und-Neu-Str. 9, 76131, Karlsruhe, Germany
| | - Wim Wätjen
- Institut für Agrar- und Ernährungswissenschaften, Martin-Luther-Universität Halle-Wittenberg, Weinbergweg 22, 06120, Halle (Saale), Germany
| | - Jan G Hengstler
- Leibniz Research Centre for Working Environment and Human Factors (IfADo), Ardeystr, 67, 44139, Dortmund, Germany
| | - Angela Mally
- Department of Toxicology, University of Würzburg, Versbacher Str. 9, 97078, Würzburg, Germany
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Rietjens IMCM, Michael A, Bolt HM, Siméon B, Andrea H, Nils H, Christine K, Angela M, Gloria P, Daniel R, Natalie T, Gerhard E. The role of endogenous versus exogenous sources in the exposome of putative genotoxins and consequences for risk assessment. Arch Toxicol 2022; 96:1297-1352. [PMID: 35249149 PMCID: PMC9013691 DOI: 10.1007/s00204-022-03242-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 02/01/2022] [Indexed: 12/21/2022]
Abstract
The "totality" of the human exposure is conceived to encompass life-associated endogenous and exogenous aggregate exposures. Process-related contaminants (PRCs) are not only formed in foods by heat processing, but also occur endogenously in the organism as physiological components of energy metabolism, potentially also generated by the human microbiome. To arrive at a comprehensive risk assessment, it is necessary to understand the contribution of in vivo background occurrence as compared to the ingestion from exogenous sources. Hence, this review provides an overview of the knowledge on the contribution of endogenous exposure to the overall exposure to putative genotoxic food contaminants, namely ethanol, acetaldehyde, formaldehyde, acrylamide, acrolein, α,β-unsaturated alkenals, glycation compounds, N-nitroso compounds, ethylene oxide, furans, 2- and 3-MCPD, and glycidyl esters. The evidence discussed herein allows to conclude that endogenous formation of some contaminants appears to contribute substantially to the exposome. This is of critical importance for risk assessment in the cases where endogenous exposure is suspected to outweigh the exogenous one (e.g. formaldehyde and acrolein).
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Affiliation(s)
- Ivonne M C M Rietjens
- Division of Toxicology, Wageningen University, Stippeneng 4, 6708 WE, Wageningen, The Netherlands.
| | - Arand Michael
- Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstr. 190, 8057, Zurich, Switzerland
| | - Hermann M Bolt
- Department of Toxicology, Leibniz Research Centre for Working Environment and Human Factors at TU Dortmund (IfADo), Ardeystr. 67, 44139, Dortmund, Germany
| | | | - Hartwig Andrea
- Department of Food Chemistry and Toxicology, Institute of Applied Biosciences (IAB), Karlsruhe Institute of Technology (KIT), Adenauerring 20a, 76131, Karlsruhe, Germany
| | - Hinrichsen Nils
- Food Oils and Fats Research, ADM Hamburg AG, Research, Seehafenstraße 24, 21079, Hamburg, Germany
| | - Kalisch Christine
- Department of Toxicology, University of Würzburg, Versbacher Straße 9, 97078, Wurzburg, Germany
| | - Mally Angela
- Department of Toxicology, University of Würzburg, Versbacher Straße 9, 97078, Wurzburg, Germany
| | - Pellegrino Gloria
- Scientific Affairs and Research, Luigi Lavazza SpA, Strada Settimo, 410, 10156, Turin, Italy
| | - Ribera Daniel
- Regulatory and Scientific Affairs EMEA, Cargill R&D, Havenstraat 84, 1800, Vivoorde, Belgium
| | - Thatcher Natalie
- Food Safety, Mondelez International, Bournville Lane, Birmingham, B30 2LU, UK
| | - Eisenbrand Gerhard
- Department of Toxicology and Food Chemistry, University of Kaiserslautern, Kühler Grund 48/1, 69126, Heidelberg, Germany
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Pugsley K, Scherer SW, Bellgrove MA, Hawi Z. Environmental exposures associated with elevated risk for autism spectrum disorder may augment the burden of deleterious de novo mutations among probands. Mol Psychiatry 2022; 27:710-730. [PMID: 34002022 PMCID: PMC8960415 DOI: 10.1038/s41380-021-01142-w] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 04/16/2021] [Accepted: 04/21/2021] [Indexed: 12/11/2022]
Abstract
Although the full aetiology of autism spectrum disorder (ASD) is unknown, familial and twin studies demonstrate high heritability of 60-90%, indicating a predominant role of genetics in the development of the disorder. The genetic architecture of ASD consists of a complex array of rare and common variants of all classes of genetic variation usually acting additively to augment individual risk. The relative contribution of heredity in ASD persists despite selective pressures against the classic autistic phenotype; a phenomenon thought to be explained, in part, by the incidence of spontaneous (or de novo) mutations. Notably, environmental exposures attributed as salient risk factors for ASD may play a causal role in the emergence of deleterious de novo variations, with several ASD-associated agents having significant mutagenic potential. To explore this hypothesis, this review article assesses published epidemiological data with evidence derived from assays of mutagenicity, both in vivo and in vitro, to determine the likely role such agents may play in augmenting the genetic liability in ASD. Broadly, these exposures were observed to elicit genomic alterations through one or a combination of: (1) direct interaction with genetic material; (2) impaired DNA repair; or (3) oxidative DNA damage. However, the direct contribution of these factors to the ASD phenotype cannot be determined without further analysis. The development of comprehensive prospective birth cohorts in combination with genome sequencing is essential to forming a causal, mechanistic account of de novo mutations in ASD that links exposure, genotypic alterations, and phenotypic consequences.
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Affiliation(s)
- Kealan Pugsley
- grid.1002.30000 0004 1936 7857Turner Institute for Brain and Mental Health, School of Psychological Sciences, Monash University, Melbourne, VIC Australia
| | - Stephen W. Scherer
- grid.42327.300000 0004 0473 9646The Centre for Applied Genomics and Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON Canada ,grid.17063.330000 0001 2157 2938McLaughlin Centre and Department of Molecular Genetics, University of Toronto, Toronto, ON Canada
| | - Mark A. Bellgrove
- grid.1002.30000 0004 1936 7857Turner Institute for Brain and Mental Health, School of Psychological Sciences, Monash University, Melbourne, VIC Australia
| | - Ziarih Hawi
- Turner Institute for Brain and Mental Health, School of Psychological Sciences, Monash University, Melbourne, VIC, Australia.
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Identification of New Markers of Alcohol-Derived DNA Damage in Humans. Biomolecules 2021; 11:biom11030366. [PMID: 33673538 PMCID: PMC7997542 DOI: 10.3390/biom11030366] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 02/16/2021] [Accepted: 02/21/2021] [Indexed: 12/13/2022] Open
Abstract
Alcohol consumption is a risk factor for the development of several cancers, including those of the head and neck and the esophagus. The underlying mechanisms of alcohol-induced carcinogenesis remain unclear; however, at these sites, alcohol-derived acetaldehyde seems to play a major role. By reacting with DNA, acetaldehyde generates covalent modifications (adducts) that can lead to mutations. Previous studies have shown a dose dependence between levels of a major acetaldehyde-derived DNA adduct and alcohol exposure in oral-cell DNA. The goal of this study was to optimize a mass spectrometry (MS)-based DNA adductomic approach to screen for all acetaldehyde-derived DNA adducts to more comprehensively characterize the genotoxic effects of acetaldehyde in humans. A high-resolution/-accurate-mass data-dependent constant-neutral-loss-MS3 methodology was developed to profile acetaldehyde-DNA adducts in purified DNA. This resulted in the identification of 22 DNA adducts. In addition to the expected N2-ethyldeoxyguanosine (after NaBH3CN reduction), two previously unreported adducts showed prominent signals in the mass spectra. MSn fragmentation spectra and accurate mass were used to hypothesize the structure of the two new adducts, which were then identified as N6-ethyldeoxyadenosine and N4-ethyldeoxycytidine by comparison with synthesized standards. These adducts were quantified in DNA isolated from oral cells collected from volunteers exposed to alcohol, revealing a significant increase after the exposure. In addition, 17 of the adducts identified in vitro were detected in these samples confirming our ability to more comprehensively characterize the DNA damage deriving from alcohol exposures.
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Sanchez AB, Garcia CCM, Di Mascio P, Medeiros MHG. Detection of DNA Adduct Formation in Rat Lungs by a Micro-HPLC/MS/MS Approach. Methods Mol Biol 2021; 2279:225-239. [PMID: 33683698 DOI: 10.1007/978-1-0716-1278-1_18] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/16/2023]
Abstract
Aldehydes are abundantly present in tobacco smoke and in urban air pollution and are endogenously generated as products of the lipid peroxidation process. These molecules can react with DNA bases forming mutagenic exocyclic adducts, which have been used as biomarkers of aldehyde exposure and as potential tools for the study of inflammation, metal storage diseases, neurodegenerative disorders, and cancer. High-performance liquid chromatography-tandem mass spectrometry (HPLC/MS/MS) provides a highly precise, specific and ultrasensitive method for the detection of exocyclic DNA adducts. Here we present and describe a validated micro-HPLC-Electro Spray Ionization (ESI)-MS/MS method for the quantification of 1,N2-propanodGuo, an adduct produced following the reaction between 2'-deoxyguanosine and acetaldehyde or crotonaldehyde.
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Affiliation(s)
- Angélica B Sanchez
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, SP, Brazil
- Núcleo de Pesquisas em Ciências Biológicas & Departamento de Ciências Biológicas, Instituto de Ciências Exatas e Biológicas, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil
| | - Camila C M Garcia
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, SP, Brazil
- Núcleo de Pesquisas em Ciências Biológicas & Departamento de Ciências Biológicas, Instituto de Ciências Exatas e Biológicas, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil
| | - Paolo Di Mascio
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, SP, Brazil
| | - Marisa H G Medeiros
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, SP, Brazil.
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Hartwig A, Arand M, Epe B, Guth S, Jahnke G, Lampen A, Martus HJ, Monien B, Rietjens IMCM, Schmitz-Spanke S, Schriever-Schwemmer G, Steinberg P, Eisenbrand G. Mode of action-based risk assessment of genotoxic carcinogens. Arch Toxicol 2020; 94:1787-1877. [PMID: 32542409 PMCID: PMC7303094 DOI: 10.1007/s00204-020-02733-2] [Citation(s) in RCA: 79] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 03/31/2020] [Indexed: 12/16/2022]
Abstract
The risk assessment of chemical carcinogens is one major task in toxicology. Even though exposure has been mitigated effectively during the last decades, low levels of carcinogenic substances in food and at the workplace are still present and often not completely avoidable. The distinction between genotoxic and non-genotoxic carcinogens has traditionally been regarded as particularly relevant for risk assessment, with the assumption of the existence of no-effect concentrations (threshold levels) in case of the latter group. In contrast, genotoxic carcinogens, their metabolic precursors and DNA reactive metabolites are considered to represent risk factors at all concentrations since even one or a few DNA lesions may in principle result in mutations and, thus, increase tumour risk. Within the current document, an updated risk evaluation for genotoxic carcinogens is proposed, based on mechanistic knowledge regarding the substance (group) under investigation, and taking into account recent improvements in analytical techniques used to quantify DNA lesions and mutations as well as "omics" approaches. Furthermore, wherever possible and appropriate, special attention is given to the integration of background levels of the same or comparable DNA lesions. Within part A, fundamental considerations highlight the terms hazard and risk with respect to DNA reactivity of genotoxic agents, as compared to non-genotoxic agents. Also, current methodologies used in genetic toxicology as well as in dosimetry of exposure are described. Special focus is given on the elucidation of modes of action (MOA) and on the relation between DNA damage and cancer risk. Part B addresses specific examples of genotoxic carcinogens, including those humans are exposed to exogenously and endogenously, such as formaldehyde, acetaldehyde and the corresponding alcohols as well as some alkylating agents, ethylene oxide, and acrylamide, but also examples resulting from exogenous sources like aflatoxin B1, allylalkoxybenzenes, 2-amino-3,8-dimethylimidazo[4,5-f] quinoxaline (MeIQx), benzo[a]pyrene and pyrrolizidine alkaloids. Additionally, special attention is given to some carcinogenic metal compounds, which are considered indirect genotoxins, by accelerating mutagenicity via interactions with the cellular response to DNA damage even at low exposure conditions. Part C finally encompasses conclusions and perspectives, suggesting a refined strategy for the assessment of the carcinogenic risk associated with an exposure to genotoxic compounds and addressing research needs.
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Affiliation(s)
- Andrea Hartwig
- Department of Food Chemistry and Toxicology, Institute of Applied Biosciences (IAB), Karlsruhe Institute of Technology (KIT), Adenauerring 20a, 76131, Karlsruhe, Germany.
| | - Michael Arand
- Institute of Pharmacology and Toxicology, University of Zurich, 8057, Zurich, Switzerland
| | - Bernd Epe
- Institute of Pharmacy and Biochemistry, University of Mainz, 55099, Mainz, Germany
| | - Sabine Guth
- Department of Toxicology, IfADo-Leibniz Research Centre for Working Environment and Human Factors, TU Dortmund, Ardeystr. 67, 44139, Dortmund, Germany
| | - Gunnar Jahnke
- Department of Food Chemistry and Toxicology, Institute of Applied Biosciences (IAB), Karlsruhe Institute of Technology (KIT), Adenauerring 20a, 76131, Karlsruhe, Germany
| | - Alfonso Lampen
- Department of Food Safety, German Federal Institute for Risk Assessment (BfR), 10589, Berlin, Germany
| | - Hans-Jörg Martus
- Novartis Institutes for BioMedical Research, 4002, Basel, Switzerland
| | - Bernhard Monien
- Department of Food Safety, German Federal Institute for Risk Assessment (BfR), 10589, Berlin, Germany
| | - Ivonne M C M Rietjens
- Division of Toxicology, Wageningen University, Stippeneng 4, 6708 WE, Wageningen, The Netherlands
| | - Simone Schmitz-Spanke
- Institute and Outpatient Clinic of Occupational, Social and Environmental Medicine, University of Erlangen-Nuremberg, Henkestr. 9-11, 91054, Erlangen, Germany
| | - Gerlinde Schriever-Schwemmer
- Department of Food Chemistry and Toxicology, Institute of Applied Biosciences (IAB), Karlsruhe Institute of Technology (KIT), Adenauerring 20a, 76131, Karlsruhe, Germany
| | - Pablo Steinberg
- Max Rubner-Institut, Federal Research Institute of Nutrition and Food, Haid-und-Neu-Str. 9, 76131, Karlsruhe, Germany
| | - Gerhard Eisenbrand
- Retired Senior Professor for Food Chemistry and Toxicology, Kühler Grund 48/1, 69126, Heidelberg, Germany.
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Murakami H, Tomita H, Aoyanagi T, Sugita T, Miki Y, Esaka Y, Inoue Y, Teshima N. Effects of pendant-like hydrophilic monomers on the adsorption properties of reversed-phase-type sorbents for solid-phase extraction. Anal Chim Acta 2019; 1075:106-111. [PMID: 31196415 DOI: 10.1016/j.aca.2019.05.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Revised: 04/26/2019] [Accepted: 05/09/2019] [Indexed: 10/26/2022]
Abstract
Solid-phase extraction (SPE) has been extensively employed as a pretreatment method. In SPE, reversed-phase-type sorbents have been widely applied for the pretreatment of environmental or biological samples. Hydrophilic-lipophilic balance (HLB)-type sorbents, constituting the copolymers used as reversed-phase-type sorbents, have been applied for various sample pretreatment methods. In HLB-type sorbents, the hydrophilic monomer contributes to the improved wettability of sorbents and increase of polar interactions. In this study, three pendant-like hydrophilic monomers, viz. N-vinylpyrrolidone (NVP), 4-acryloylmorpholine (AMO), and 4-vinyl-1,3-dioxolan-2-one (VDO), respectively, exhibiting different Log P values and possibly causing different polar interactions, were selected to improve the adsorption properties of polar compounds, and divinylbenzene (DVB)-based HLB-type sorbents containing each hydrophilic monomer were synthesized and examined. By the optimization of the molar ratio of DVB and the hydrophilic monomer (i.e. HLB), the inert diluent, and the degree of cross-linking, the developed sorbents exhibited higher recoveries for various polar compounds (viz. cytosine, uracil, cytidine, uridine, 2'-deoxycytidine, 2'-deoxyguanosine, adenine, thymidine, adenosine, and 2'-deoxyadenosine) compared to commercially available HLB-type sorbents.
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Affiliation(s)
- Hiroya Murakami
- Department of Applied Chemistry, Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota, 470-0392, Japan
| | - Hiroki Tomita
- Department of Applied Chemistry, Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota, 470-0392, Japan
| | - Takuya Aoyanagi
- Department of Applied Chemistry, Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota, 470-0392, Japan
| | - Takashi Sugita
- Department of Applied Chemistry, Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota, 470-0392, Japan
| | - Yuta Miki
- Department of Applied Chemistry, Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota, 470-0392, Japan
| | - Yukihiro Esaka
- Gifu Pharmaceutical University, Daigaku-nishi, Gifu, 501-1196, Japan
| | - Yoshinori Inoue
- Department of Applied Chemistry, Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota, 470-0392, Japan
| | - Norio Teshima
- Department of Applied Chemistry, Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota, 470-0392, Japan.
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Kroeger AA, Karton A. A computational foray into the mechanism and catalysis of the adduct formation reaction of guanine with crotonaldehyde. J Comput Chem 2018; 40:630-637. [DOI: 10.1002/jcc.25595] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 08/21/2018] [Accepted: 08/23/2018] [Indexed: 01/18/2023]
Affiliation(s)
- Asja A. Kroeger
- School of Molecular Sciences The University of Western Australia Perth Western Australia 6009 Australia
| | - Amir Karton
- School of Molecular Sciences The University of Western Australia Perth Western Australia 6009 Australia
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Leaden L, Silva LG, Ribeiro RA, Dos Santos NM, Lorenzetti APR, Alegria TGP, Schulz ML, Medeiros MHG, Koide T, Marques MV. Iron Deficiency Generates Oxidative Stress and Activation of the SOS Response in Caulobacter crescentus. Front Microbiol 2018; 9:2014. [PMID: 30210482 PMCID: PMC6120978 DOI: 10.3389/fmicb.2018.02014] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2018] [Accepted: 08/09/2018] [Indexed: 01/18/2023] Open
Abstract
In C. crescentus, iron metabolism is mainly controlled by the transcription factor Fur (ferric uptake regulator). Iron-bound Fur represses genes related to iron uptake and can directly activate the expression of genes for iron-containing proteins. In this work, we used total RNA sequencing (RNA-seq) of wild type C. crescentus growing in minimal medium under iron limitation and a fur mutant strain to expand the known Fur regulon, and to identify novel iron-regulated genes. The RNA-seq of cultures treated with the iron chelator 2-2-dypiridyl (DP) allowed identifying 256 upregulated genes and 236 downregulated genes, being 176 and 204 newly identified, respectively. Sixteen transcription factors and seven sRNAs were upregulated in iron limitation, suggesting that the response to low iron triggers a complex regulatory network. Notably, lexA along with most of its target genes were upregulated, suggesting that DP treatment caused DNA damage, and the SOS DNA repair response was activated in a RecA-dependent manner, as confirmed by RT-qPCR. Fluorescence microscopy assays using an oxidation-sensitive dye showed that wild type cells in iron limitation and the fur mutant were under endogenous oxidative stress, and a direct measurement of cellular H2O2 showed that cells in iron-limited media present a higher amount of endogenous H2O2. A mutagenesis assay using the rpoB gene as a reporter showed that iron limitation led to an increase in the mutagenesis rate. These results showed that iron deficiency causes C. crescentus cells to suffer oxidative stress and to activate the SOS response, indicating an increase in DNA damage.
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Affiliation(s)
- Laura Leaden
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Larissa G Silva
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Rodolfo A Ribeiro
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Naara M Dos Santos
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Alan P R Lorenzetti
- Departamento de Bioquímica e Imunologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Thiago G P Alegria
- Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil
| | - Mariane L Schulz
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil
| | - Marisa H G Medeiros
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil
| | - Tie Koide
- Departamento de Bioquímica e Imunologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Marilis V Marques
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
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