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Ruijter N, van der Zee M, Katsumiti A, Boyles M, Cassee FR, Braakhuis H. Improving the dichloro-dihydro-fluorescein (DCFH) assay for the assessment of intracellular reactive oxygen species formation by nanomaterials. NANOIMPACT 2024; 35:100521. [PMID: 38901707 DOI: 10.1016/j.impact.2024.100521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 06/03/2024] [Accepted: 06/17/2024] [Indexed: 06/22/2024]
Abstract
To facilitate Safe and Sustainable by Design (SSbD) strategies during the development of nanomaterials (NMs), quick and easy in vitro assays to test for hazard potential at an early stage of NM development are essential. The formation of reactive oxygen species (ROS) and the induction of oxidative stress are considered important mechanisms that can lead to NM toxicity. In vitro assays measuring oxidative stress are therefore commonly included in NM hazard assessment strategies. The fluorescence-based dichloro-dihydro-fluorescein (DCFH) assay for cellular oxidative stress is a simple and cost-effective assay, making it a good candidate assay for SSbD hazard testing strategies. It is however subject to several pitfalls and caveats. Here, we provide further optimizations to the assay using 5-(6)-Chloromethyl-2',7'-dichlorodihydrofluorescein diacetate acetyl ester (CM-H2DCFDA-AE, referred to as DCFH probe), known for its improved cell retention. We measured the release of metabolic products of the DCFH probe from cells to supernatant, direct reactions of CM-H2DCFDA-AE with positive controls, and compared the commonly used plate reader-based DCFH assay protocol with fluorescence microscopy and flow cytometry-based protocols. After loading cells with DCFH probe, translocation of several metabolic products of the DCFH probe to the supernatant was observed in multiple cell types. Translocated DCFH products are then able to react with test substances including positive controls. Our results also indicate that intracellularly oxidized fluorescent DCF is able to translocate from cells to the supernatant. In either way, this will lead to a fluorescent supernatant, making it difficult to discriminate between intra- and extra-cellular ROS production, risking misinterpretation of possible oxidative stress when measuring fluorescence on a plate reader. The use of flow cytometry instead of plate reader-based measurements resolved these issues, and also improved assay sensitivity. Several optimizations of the flow cytometry-based DCFH ISO standard (ISO/TS 19006:2016) were suggested, including loading cells with DCFH probe before incubation with the test materials, and applying an appropriate gating strategy including live-death staining, which was not included in the ISO standard. In conclusion, flow cytometry- and fluorescence microscopy-based read-outs are preferred over the classical plate reader-based read-out to assess the level of intracellular oxidative stress using the cellular DCFH assay.
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Affiliation(s)
- Nienke Ruijter
- National Institute for Public Health & the Environment (RIVM), 3721 MA Bilthoven, the Netherlands
| | - Margriet van der Zee
- National Institute for Public Health & the Environment (RIVM), 3721 MA Bilthoven, the Netherlands; Science Lines, Emmalaan 8, 3451 CT Vleuten, the Netherlands
| | - Alberto Katsumiti
- GAIKER Technology Centre, Basque Research and Technology Alliance (BRTA), 48170 Zamudio, Spain
| | - Matthew Boyles
- Institute of Occupational Medicine (IOM), Edinburgh, EH14 4AP, UK; Centre for Biomedicine and Global Health, School of Applied Sciences, Edinburgh Napier University, Sighthill Campus, Edinburgh EH11 4BN, UK
| | - Flemming R Cassee
- National Institute for Public Health & the Environment (RIVM), 3721 MA Bilthoven, the Netherlands; Institute for Risk Assessment Sciences (IRAS), Utrecht University, 3584 CS Utrecht, the Netherlands.
| | - Hedwig Braakhuis
- National Institute for Public Health & the Environment (RIVM), 3721 MA Bilthoven, the Netherlands; TNO Risk Analysis for Products in Development, 3584 CB Utrecht, the Netherlands
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2
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Belanger-Coast MG, Zhang M, Bugay V, Gutierrez RA, Gregory SR, Yu W, Brenner R. Dequalinium chloride is an antagonists of α7 nicotinic acetylcholine receptors. Eur J Pharmacol 2022; 925:175000. [PMID: 35525312 DOI: 10.1016/j.ejphar.2022.175000] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 04/28/2022] [Accepted: 04/29/2022] [Indexed: 11/29/2022]
Abstract
Dequalinium chloride has been used primarily as antiseptic compounds, but recently has been investigated for its effects on specific targets, including muscarinic acetylcholine receptors. Here we investigated dequalinium chloride as an antagonist to α7 nicotinic acetylcholine receptors. The pharmacological properties of dequalinium were established using cell lines stably co-transfected with the calcium-permeable human α7 nicotinic acetylcholine receptors and its chaperone NACHO, calcium dye fluorescent measurements or a calcium-sensitive protein reporter, and patch clamp recording of ionic currents. Using calcium dye fluorescence plate reader measurements, we find dequalinium chloride is an antagonist of α7 nicotinic acetylcholine receptors with an IC50 of 672 nM in response to activation with 500 μM acetylcholine chloride and positive allosteric modulator PNU-120596. However, using a membrane-tethered GCAMP7s calcium reporter allowed detection of α7-mediated calcium flux in the absence of PNU-120596. Using this approach revealed an IC50 of 157 nM for dequalinium on 300 μM acetylcholine-evoked currents. Using patch clamp recordings with 300 μM acetylcholine chloride and 10 μM PNU-120596, we find lower concentrations are sufficient to block ionic currents, with IC50 of 120 nM for dequalinium chloride and 54 nM for the related UCL 1684 compound. In summary, we find that dequalinium chloride and UCL1684, which are generally used to block SK-type potassium channels, are also highly effective antagonists of α7 nicotinic acetylcholine receptors. This finding, in combination with previous studies of muscarinic acetylcholine receptors, clearly establishes dequalinium compounds within the class of general anti-cholinergic antagonists.
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Affiliation(s)
- Matthieu G Belanger-Coast
- Department of Cellular and Integrative Physiology, University of Texas Health San Antonio, San Antonio, TX, USA
| | - Mei Zhang
- Sophion Bioscience, Inc, 400 Trade Center Drive, Suite, 6900, Woburn, MA, USA
| | - Vladislav Bugay
- Department of Cellular and Integrative Physiology, University of Texas Health San Antonio, San Antonio, TX, USA
| | - Raul A Gutierrez
- Department of Cellular and Integrative Physiology, University of Texas Health San Antonio, San Antonio, TX, USA
| | - Summer R Gregory
- Department of Cellular and Integrative Physiology, University of Texas Health San Antonio, San Antonio, TX, USA
| | - Weifeng Yu
- Sophion Bioscience, Inc, 400 Trade Center Drive, Suite, 6900, Woburn, MA, USA
| | - Robert Brenner
- Department of Cellular and Integrative Physiology, University of Texas Health San Antonio, San Antonio, TX, USA.
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3
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Tukker AM, Westerink RHS. Novel test strategies for in vitro seizure liability assessment. Expert Opin Drug Metab Toxicol 2021; 17:923-936. [PMID: 33595380 PMCID: PMC8367052 DOI: 10.1080/17425255.2021.1876026] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Accepted: 01/11/2021] [Indexed: 12/18/2022]
Abstract
INTRODUCTION The increasing incidence of mental illnesses and neurodegenerative diseases results in a high demand for drugs targeting the central nervous system (CNS). These drugs easily reach the CNS, have a high affinity for CNS targets, and are prone to cause seizures as an adverse drug reaction. Current seizure liability assessment heavily depends on in vivo or ex vivo animal models and is therefore ethically debated, labor intensive, expensive, and not always predictive for human risk. AREAS COVERED The demand for CNS drugs urges the development of alternative safety assessment strategies. Yet, the complexity of the CNS hampers reliable detection of compound-induced seizures. This review provides an overview of the requirements of in vitro seizure liability assays and highlights recent advances, including micro-electrode array (MEA) recordings using rodent and human cell models. EXPERT OPINION Successful and cost-effective replacement of in vivo and ex vivo models for seizure liability screening can reduce animal use for drug development, while increasing the predictive value of the assays, particularly if human cell models are used. However, these novel test strategies require further validation and standardization as well as additional refinements to better mimic the human in vivo situation and increase their predictive value.
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Affiliation(s)
- Anke M. Tukker
- School of Health Sciences, Purdue University, Hall for Discovery and Learning Research (DLR 339), INUSA
| | - Remco H. S. Westerink
- Neurotoxicology Research Group, Toxicology Division, Institute for Risk Assessment Sciences (IRAS), Faculty of Veterinary Medicine, Utrecht University, TD Utrecht, The Netherlands
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4
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Kumar SS, Ward ML, Mountjoy KG. Quantitative high-throughput assay to measure MC4R-induced intracellular calcium. J Mol Endocrinol 2021; 66:285-297. [PMID: 33739935 PMCID: PMC8111326 DOI: 10.1530/jme-20-0285] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 03/19/2021] [Indexed: 12/17/2022]
Abstract
The melanocortin-4 receptor (MC4R), a critical G-protein-coupled receptor (GPCR) regulating energy homeostasis, activates multiple signalling pathways, including mobilisation of intracellular calcium ([Ca2+]i). However, very little is known about the physiological significance of MC4R-induced [Ca2+]i since few studies measure MC4R-induced [Ca2+]i. High-throughput, read-out assays for [Ca2+]i have proven unreliable for overexpressed GPCRs like MC4R, which exhibit low sensitivity mobilising [Ca2+]i. Therefore, we developed, optimised, and validated a robust quantitative high-throughput assay using Fura-2 ratio-metric calcium dye and HEK293 cells stably transfected with MC4R. The quantitation enables direct comparisons between assays and even between different research laboratories. Assay conditions were optimised step-by-step to eliminate interference from stretch-activated receptor increases in [Ca2+]i and to maximise ligand-activated MC4R-induced [Ca2+]i. Calcium imaging was performed using a PheraStar FS multi-well plate reader. Probenecid, included in the buffers to prevent extrusion of Fura-2 dye from cells, was found to interfere with the EGTA-chelation of calcium, required to determine Rmin for quantitation of [Ca2+]i. Therefore, we developed a method to determine Rmin in specific wells without probenecid, which was run in parallel with each assay. The validation of the assay was shown by reproducible α-melanocyte-stimulating hormone (α-MSH) concentration-dependent activation of the stably expressed human MC4R (hMC4R) and mouse MC4R (mMC4R), inducing increases in [Ca2+]i, for three independent experiments. This robust, reproducible, high-throughput assay that quantitatively measures MC4R-induced mobilisation of [Ca2+]i in vitro has potential to advance the development of therapeutic drugs and understanding of MC4R signalling associated with human obesity.
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Affiliation(s)
- Shree Senthil Kumar
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Marie-Louise Ward
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Kathleen Grace Mountjoy
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
- Department of Molecular Medicine and Pathology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, Auckland, New Zealand
- Correspondence should be addressed to K G Mountjoy:
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5
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Barczyk A, Bauderlique‐Le Roy H, Jouy N, Renault N, Hottin A, Millet R, Vouret‐Craviari V, Adriouch S, Idziorek T, Dezitter X. Flow cytometry: An accurate tool for screening
P2RX7
modulators. Cytometry A 2020. [DOI: 10.1002/cyto.a.24287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Amélie Barczyk
- Univ. Lille, Inserm, CHU Lille, U1286 – Infinite – Institute for Translational Research in Inflammation Lille France
| | - Hélène Bauderlique‐Le Roy
- Univ. Lille, UMS 2014‐US 41 PLBS BICel, Flow Cytometry Core Facility, Institut Pasteur de Lille Lille cedex France
| | - Nathalie Jouy
- Univ. Lille, UMS 2014‐US 41 PLBS BICel, Flow Cytometry Core Facility, IRCL, 1 place de Verdun Lille cedex France
| | - Nicolas Renault
- Univ. Lille, Inserm, CHU Lille, U1286 – Infinite – Institute for Translational Research in Inflammation Lille France
| | - Audrey Hottin
- Univ. Lille, Inserm, CHU Lille, U1286 – Infinite – Institute for Translational Research in Inflammation Lille France
| | - Régis Millet
- Univ. Lille, Inserm, CHU Lille, U1286 – Infinite – Institute for Translational Research in Inflammation Lille France
| | - Valérie Vouret‐Craviari
- University Cote d'Azur, Institute for Research on Cancer and Aging, IRCAN U1081 UMR CNRS 7284 Nice France
| | - Sahil Adriouch
- Normandie University, UNIROUEN, INSERM, U1234, Pathophysiology, Autoimmunity, Neuromuscular Diseases and Regenerative THERapies (PANTHER) Rouen France
| | - Thierry Idziorek
- Univ. Lille, UMS 2014‐US 41 PLBS BICel, Flow Cytometry Core Facility, IRCL, 1 place de Verdun Lille cedex France
- Univ. Lille, CNRS, Inserm, CHU Lille, Institut de Recherche contre le Cancer de Lille, UMR9020 – UMR‐S 1277 ‐ Canther – Cancer Heterogeneity, Plasticity and Resistance to Therapies Lille France
| | - Xavier Dezitter
- Univ. Lille, Inserm, CHU Lille, U1286 – Infinite – Institute for Translational Research in Inflammation Lille France
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Grosshans HK, Fischer TT, Steinle JA, Brill AL, Ehrlich BE. Neuronal Calcium Sensor 1 is up-regulated in response to stress to promote cell survival and motility in cancer cells. Mol Oncol 2020; 14:1134-1151. [PMID: 32239615 PMCID: PMC7266285 DOI: 10.1002/1878-0261.12678] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 02/08/2020] [Accepted: 03/25/2020] [Indexed: 12/13/2022] Open
Abstract
Changes in intracellular calcium (Ca2+) signaling can modulate cellular machinery required for cancer progression. Neuronal calcium sensor 1 (NCS1) is a ubiquitously expressed Ca2+‐binding protein that promotes tumor aggressiveness by enhancing cell survival and metastasis. However, the underlying mechanism by which NCS1 contributes to increased tumor aggressiveness has yet to be identified. In this study, we aimed to determine (a) whether NCS1 expression changes in response to external stimuli, (b) the importance of NCS1 for cell survival and migration, and (c) the cellular mechanism(s) through which NSC1 modulates these outcomes. We found that NCS1 abundance increases under conditions of stress, most prominently after stimulation with the pro‐inflammatory cytokine tumor necrosis factor α, in a manner dependent on nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NFκB). We found that NFκB signaling is activated in human breast cancer tissue, which was accompanied by an increase in NCS1 mRNA expression. Further exploration into the relevance of NCS1 in breast cancer progression showed that knockout of NCS1 (NCS1 KO) caused decreased cell survival and motility, increased baseline intracellular Ca2+ levels, and decreased inositol 1,4,5‐trisphosphate‐mediated Ca2+ responses. Protein kinase B (Akt) activity was decreased in NCS1 KO cells, which could be rescued by buffering intracellular Ca2+. Conversely, Akt activity was increased in cells overexpressing NCS1 (NCS1 OE). We therefore conclude that NCS1 acts as cellular stress response protein up‐regulated by stress‐induced NFκB signaling and that NCS1 influences cell survival and motility through effects on Ca2+ signaling and Akt pathway activation.
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Affiliation(s)
- Henrike K Grosshans
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT, USA
| | - Tom T Fischer
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT, USA.,Institute of Pharmacology, Heidelberg University, Germany
| | - Julia A Steinle
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT, USA
| | - Allison L Brill
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, USA
| | - Barbara E Ehrlich
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT, USA.,Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, USA
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7
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Sophocleous RA, Berg T, Finol-Urdaneta RK, Sluyter V, Keshiya S, Bell L, Curtis SJ, Curtis BL, Seavers A, Bartlett R, Dowton M, Stokes L, Ooi L, Sluyter R. Pharmacological and genetic characterisation of the canine P2X4 receptor. Br J Pharmacol 2020; 177:2812-2829. [PMID: 32017039 DOI: 10.1111/bph.15009] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 01/16/2020] [Accepted: 01/17/2020] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND AND PURPOSE P2X4 receptors are emerging therapeutic targets for treating chronic pain and cardiovascular disease. Dogs are well-recognised natural models of human disease, but information regarding P2X4 receptors in dogs is lacking. To aid the development and validation of P2X4 receptor ligands, we have characterised and compared canine and human P2X4 receptors. EXPERIMENTAL APPROACH Genomic DNA was extracted from whole blood samples from 101 randomly selected dogs and sequenced across the P2RX4 gene to identify potential missense variants. Recombinant canine and human P2X4 receptors tagged with Emerald GFP were expressed in 1321N1 and HEK293 cells and analysed by immunoblotting and confocal microscopy. In these cells, receptor pharmacology was characterised using nucleotide-induced Fura-2 AM measurements of intracellular Ca2+ and known P2X4 receptor antagonists. P2X4 receptor-mediated inward currents in HEK293 cells were assessed by automated patch clamp. KEY RESULTS No P2RX4 missense variants were identified in any canine samples. Canine and human P2X4 receptors were localised primarily to lysosomal compartments. ATP was the primary agonist of canine P2X4 receptors with near identical efficacy and potency at human receptors. 2'(3')-O-(4-benzoylbenzoyl)-ATP, but not ADP, was a partial agonist with reduced potency for canine P2X4 receptors compared to the human orthologues. Five antagonists inhibited canine P2X4 receptors, with 1-(2,6-dibromo-4-isopropyl-phenyl)-3-(3-pyridyl)urea displaying reduced sensitivity and potency at canine P2X4 receptors. CONCLUSION AND IMPLICATIONS P2X4 receptors are highly conserved across dog pedigrees and display expression patterns and pharmacological profiles similar to human receptors, supporting validation and use of therapeutic agents for P2X4 receptor-related disease onset and management in dogs and humans.
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Affiliation(s)
- Reece A Sophocleous
- Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia.,Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
| | - Tracey Berg
- Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia.,Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
| | - Rocio K Finol-Urdaneta
- Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia.,Electrophysiology Facility for Cell Phenotyping and Drug Discovery, Wollongong, NSW, Australia
| | - Vanessa Sluyter
- Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia.,Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
| | - Shikara Keshiya
- Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia.,Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
| | - Lachlan Bell
- Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia.,Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
| | | | | | - Aine Seavers
- Oak Flats Veterinary Clinic, Oak Flats, NSW, Australia
| | - Rachael Bartlett
- Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia.,Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
| | - Mark Dowton
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
| | - Leanne Stokes
- School of Pharmacy, University of East Anglia, Norwich, UK
| | - Lezanne Ooi
- Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia.,Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
| | - Ronald Sluyter
- Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia.,Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
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8
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Effects of environmental pollutants on calcium release and uptake by rat cortical microsomes. Neurotoxicology 2018; 69:266-277. [DOI: 10.1016/j.neuro.2018.07.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 06/26/2018] [Accepted: 07/25/2018] [Indexed: 12/11/2022]
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9
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Reduced calcium influx in the hypoxia-tolerant Spalax: The role of the erythropoietin receptor. Cell Calcium 2018; 74:123-130. [DOI: 10.1016/j.ceca.2018.07.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 07/15/2018] [Accepted: 07/15/2018] [Indexed: 12/13/2022]
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10
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Ghanian Z, Konduri GG, Audi SH, Camara AKS, Ranji M. Quantitative optical measurement of mitochondrial superoxide dynamics in pulmonary artery endothelial cells. JOURNAL OF INNOVATIVE OPTICAL HEALTH SCIENCES 2018; 11:1750018. [PMID: 30123329 PMCID: PMC6097638 DOI: 10.1142/s1793545817500183] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Reactive oxygen species (ROS) play a vital role in cell signaling and redox regulation, but when present in excess, lead to numerous pathologies. Detailed quantitative characterization of mitochondrial superoxide anion ( O2•- ) production in fetal pulmonary artery endothelia cells (PAECs) has never been reported. The aim of this study is to assess mitochondrial O2•- production in cultured PAECs over time using a novel quantitative optical approach. The rate, the sources, and the dynamics of O2•- production were assessed using targeted metabolic modulators of the mitochondrial electron transport chain (ETC) complexes, specifically an uncoupler and inhibitors of the various ETC complexes, and inhibitors of extra-mitochondrial sources of O2•- . After stabilization, the cells were loaded with nanomolar mitochondrial-targeted hydroethidine (Mito-HE, MitoSOX) online during the experiment without washout of the residual dye. Time-lapse fluorescence microscopy was used to monitor the dynamic changes in O2•- fluorescence intensity over time in PAECs. The transient behaviors of the fluorescence time course showed exponential increases in the rate of O2•- production in the presence of the ETC uncoupler or inhibitors. The most dramatic and the fastest increase in O2•- production was observed when the cells were treated with the uncoupling agent, PCP. We also showed that only the complex IV inhibitor, KCN, attenuated the marked surge in O2•- production induced by PCP. The results showed that mitochondrial respiratory complexes I, III and IV are sources of O2•- production in PAECs, and a new observation that ROS production during uncoupling of mitochondrial respiration is mediated in part via complex IV. This novel method can be applied in other studies that examine ROS production under stress condition and during ROS-mediated injuries in vitro.
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Affiliation(s)
- Zahra Ghanian
- Department of Electrical Engineering, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, USA
| | - Girija Ganesh Konduri
- Department of Pediatrics, Division of Neonatology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Said Halim Audi
- Department of Biomedical Engineering, Marquette University, Milwaukee, Wisconsin, USA
| | - Amadou K. S. Camara
- Department of Anesthesiology and Anesthesia Research, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Mahsa Ranji
- Department of Electrical Engineering, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, USA
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11
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Zieminska E, Lenart J, Diamandakis D, Lazarewicz JW. The Role of Ca 2+ Imbalance in the Induction of Acute Oxidative Stress and Cytotoxicity in Cultured Rat Cerebellar Granule Cells Challenged with Tetrabromobisphenol A. Neurochem Res 2016; 42:777-787. [PMID: 27718046 PMCID: PMC5357503 DOI: 10.1007/s11064-016-2075-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 09/26/2016] [Accepted: 09/27/2016] [Indexed: 12/31/2022]
Abstract
Using primary cultures of rat cerebellar granule cells (CGC) we examined the role of calcium transients induced by tetrabromobisphenol A (TBBPA) in triggering oxidative stress and cytotoxicity. CGC were exposed for 30 min to 10 or 25 µM TBBPA. Changes in intracellular calcium concentration ([Ca2+]i), in the production of reactive oxygen species (ROS), and in the potential of mitochondria (∆Ψm) were measured fluorometrically during the exposure. The intracellular glutathione (GSH) and catalase activity were determined after the incubation; cell viability was evaluated 24 h later. TBBPA concentration-dependently increased [Ca2+]i and ROS production, and reduced GSH content, catalase activity, ∆Ψm and neuronal viability. The combination of NMDA and ryanodine receptor antagonists, MK-801 and bastadin 12 with ryanodine, respectively, prevented Ca2+ transients and partially reduced cytotoxicity induced by TBBPA at both concentrations. The antagonists also completely inhibited oxidative stress and depolarization of mitochondria evoked by 10 µM TBBPA, whereas these effects were only partially reduced in the 25 µM TBBPA treatment. Free radical scavengers prevented TBBPA-induced development of oxidative stress and improved CGC viability without having any effect on the rises in Ca2+ and drop in ∆Ψm. The co-administration of scavengers with NMDA and ryanodine receptor antagonists provided almost complete neuroprotection. These results indicate that Ca2+ imbalance and oxidative stress both mediate acute toxicity of TBBPA in CGC. At 10 µM TBBPA Ca2+ imbalance is a primary event, inducing oxidative stress, depolarization of mitochondria and cytotoxicity, whilst at a concentration of 25 µM TBBPA an additional Ca2+-independent portion of oxidative stress and cytotoxicity emerges.
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Affiliation(s)
- Elzbieta Zieminska
- Department of Neurochemistry, Mossakowski Medical Research Centre, Polish Academy of Sciences, Pawinskiego 5, 02-106, Warsaw, Poland
| | - Jacek Lenart
- Department of Neurochemistry, Mossakowski Medical Research Centre, Polish Academy of Sciences, Pawinskiego 5, 02-106, Warsaw, Poland
| | - Dominik Diamandakis
- Department of Neurochemistry, Mossakowski Medical Research Centre, Polish Academy of Sciences, Pawinskiego 5, 02-106, Warsaw, Poland
| | - Jerzy W Lazarewicz
- Department of Neurochemistry, Mossakowski Medical Research Centre, Polish Academy of Sciences, Pawinskiego 5, 02-106, Warsaw, Poland.
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12
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In vitro neurotoxic hazard characterisation of dinitrophenolic herbicides. Toxicol Lett 2016; 252:62-9. [DOI: 10.1016/j.toxlet.2016.04.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 04/14/2016] [Accepted: 04/18/2016] [Indexed: 11/23/2022]
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13
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Nicolas J, Bovee TF, Kamelia L, Rietjens IM, Hendriksen PJ. Exploration of new functional endpoints in neuro-2a cells for the detection of the marine biotoxins saxitoxin, palytoxin and tetrodotoxin. Toxicol In Vitro 2015; 30:341-7. [DOI: 10.1016/j.tiv.2015.10.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Revised: 09/28/2015] [Accepted: 10/01/2015] [Indexed: 11/28/2022]
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Pratico ED, Feger BJ, Watson MJ, Sullenger BA, Bowles DE, Milano CA, Nair SK. RNA-Mediated Reprogramming of Primary Adult Human Dermal Fibroblasts into c-kit(+) Cardiac Progenitor Cells. Stem Cells Dev 2015; 24:2622-33. [PMID: 26176491 DOI: 10.1089/scd.2015.0073] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Cardiovascular disease is the leading cause of death in the United States. Heart failure is a common, costly, and potentially fatal condition that is inadequately managed by pharmaceuticals. Cardiac repair therapies are promising alternative options. A potential cardiac repair therapy involves reprogramming human fibroblasts toward an induced cardiac progenitor-like state. We developed a clinically useful and safer reprogramming method by nonintegrative delivery of a cocktail of cardiac transcription factor-encoding mRNAs into autologous human dermal fibroblasts obtained from skin biopsies. Using this method, adult and neonatal dermal fibroblasts were reprogrammed into cardiac progenitor cells (CPCs) that expressed c-kit, Isl-1, and Nkx2.5. Furthermore, these reprogrammed CPCs differentiated into cardiomyocytes (CMs) in vitro as judged by increased expression of cardiac troponin T, α-sarcomeric actinin, RyR2, and SERCA2 and displayed enhanced caffeine-sensitive calcium release. The ability to reprogram patient-derived dermal fibroblasts into c-kit(+) CPCs and differentiate them into functional CMs provides clinicians with a potential new source of CPCs for cardiac repair from a renewable source and an alternative therapy in the treatment of heart failure.
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Affiliation(s)
- Elizabeth D Pratico
- Department of Surgery, Duke University Medical Center , Durham, North Carolina
| | - Bryan J Feger
- Department of Surgery, Duke University Medical Center , Durham, North Carolina
| | - Michael J Watson
- Department of Surgery, Duke University Medical Center , Durham, North Carolina
| | - Bruce A Sullenger
- Department of Surgery, Duke University Medical Center , Durham, North Carolina
| | - Dawn E Bowles
- Department of Surgery, Duke University Medical Center , Durham, North Carolina
| | - Carmelo A Milano
- Department of Surgery, Duke University Medical Center , Durham, North Carolina
| | - Smita K Nair
- Department of Surgery, Duke University Medical Center , Durham, North Carolina
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15
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Heusinkveld HJ, van den Berg M, Westerink RHS. In vitro dopaminergic neurotoxicity of pesticides: a link with neurodegeneration? Vet Q 2015; 34:120-31. [PMID: 25506807 DOI: 10.1080/01652176.2014.980934] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Around the globe, chemical compounds are used to treat or repel pests and plagues that pose a threat to food and feed production. From epidemiological studies, it is known that there is a link between exposure to certain chemical classes of these so-called pesticides and the prevalence of neurodegenerative disorders such as Parkinson's disease in humans. However, which particular compound(s) account for this link or what underlying mechanisms are involved is still largely unresolved. The degenerative process in Parkinson's disease is largely limited to the dopaminergic neurons in the basal ganglia. Cellular mechanisms that are implicated in parkinsonian neurodegeneration include mitochondrial dysfunction, oxidative stress, disturbance of intracellular calcium homeostasis and endoplasmic reticulum (ER) stress. A major characteristic that distinguishes the dopaminergic neurons in the basal ganglia from other dopaminergic neurons is a particular reliance on intracellular calcium for spontaneous activity. Considering the energy consuming nature of maintenance of the intracellular calcium homeostasis and its involvement in life and death of a neuron, this may explain the specific vulnerability of this neuronal population. Despite a large variation in primary mechanism of action it has been demonstrated that pesticides from different classes disturb intracellular calcium homeostasis, thus interfering with intracellular calcium signalling. This relates to altered dopaminergic signalling, disturbed protein homeostasis and increased oxidative stress. Therefore, effects of (mixtures of) pesticides on the intracellular calcium homeostasis may play a role in the development of Parkinson's disease in humans. Although human exposure to pesticides via e.g. food often occurs in complex mixtures, (human) risk assessment is largely based on the assessment of single compounds. The discovery of common modes of action across different classes of pesticides therefore underpins the urgency of development of new models and approaches in risk assessment.
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Affiliation(s)
- Harm J Heusinkveld
- a Neurotoxicology Research Group, Division of Toxicology, Institute for Risk Assessment Sciences, Faculty of Veterinary Medicine , Utrecht University , 3508 TD Utrecht , The Netherlands
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16
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Zieminska E, Stafiej A, Toczylowska B, Albrecht J, Lazarewicz JW. Role of Ryanodine and NMDA Receptors in Tetrabromobisphenol A-Induced Calcium Imbalance and Cytotoxicity in Primary Cultures of Rat Cerebellar Granule Cells. Neurotox Res 2015. [PMID: 26215658 PMCID: PMC4556744 DOI: 10.1007/s12640-015-9546-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The study assessed the role of ryanodine receptors (RyRs) and NMDA receptors (NMDARs) in the Ca2+ transients and cytotoxicity induced in neurons by the brominated flame retardant tetrabromobisphenol A (TBBPA). Primary cultures of rat cerebellar granule cells (CGC) were exposed to 7.5, 10, or 25 µM TBBPA for 30 min, and cell viability was assessed after 24 h. Moreover, 45Ca uptake was measured, and changes in the intracellular Ca2+ concentration ([Ca2+]i) were studied using the fluo-3 probe. The involvement of NMDARs and RyRs was verified using the pertinent receptor antagonists, 0.5 µM MK-801 and 2.5 µM bastadin 12, which was co-applied with 200 µM ryanodine, respectively. The results show that TBBPA concentration-dependently induces an increase in [Ca2+]i. This effect was partly suppressed by the inhibitors of RyRs and NMDARs when administered separately, and completely abrogated by their combined application. A concentration-dependent activation of 45Ca uptake by TBBPA was prevented by MK-801 but not by RyR inhibitors. Application of ≥10 µM TBBPA concentration-dependently reduced neuronal viability, and this effect was only partially and to an equal degree reduced by NMDAR and RyR antagonists given either separately or in combination. Our results directly demonstrate that both the RyR-mediated release of intracellular Ca2+ and the NMDAR-mediated influx of Ca2+ into neurons participate in the mechanism of TBBPA-induced Ca2+ imbalance in CGC and play a significant, albeit not exclusive, role in the mechanisms of TBBPA cytotoxicity.
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Affiliation(s)
- Elzbieta Zieminska
- Department of Neurochemistry, Mossakowski Medical Research Centre, Polish Academy of Sciences, Pawinskiego 5, 02-106, Warsaw, Poland,
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17
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Comparison of plate reader-based methods with fluorescence microscopy for measurements of intracellular calcium levels for the assessment of in vitro neurotoxicity. Neurotoxicology 2014; 45:31-7. [PMID: 25224521 DOI: 10.1016/j.neuro.2014.09.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 08/29/2014] [Accepted: 09/06/2014] [Indexed: 01/01/2023]
Abstract
The intracellular calcium concentration ([Ca(2+)]i) is an important readout for in vitro neurotoxicity since calcium is critically involved in many essential neurobiological processes, including neurotransmission, neurodegeneration and neurodevelopment. [Ca(2+)]i is often measured with considerable throughput at the level of cell populations with plate reader-based assays or with lower throughput at the level of individual cells with fluorescence microscopy. However, these methodologies yield different quantitative and qualitative results. In recent years, we demonstrated that the resolution and sensitivity of fluorescence microscopy is superior compared to plate reader-based assays. However, it is currently unclear if the use of plate reader-based assays results in more 'false negatives' or 'false positives' in neurotoxicity screening studies. In the present study, we therefore compared a plate reader-based assay with fluorescence microscopy using a small test set of environmental pollutants consisting of dieldrin, lindane, polychlorinated biphenyl 53 (PCB53) and tetrabromobisphenol-A (TBBPA). Using single-cell fluorescence microscopy, we demonstrate that all test chemicals reduce the depolarization-evoked increase in [Ca(2+)]i, whereas lindane, PCB53 and TBBPA also increase basal [Ca(2+)]i, though via different mechanisms. Importantly, none of these effects were confirmed with the plate reader-based assay. We therefore conclude that standard plate reader-based methods are not sufficiently sensitive and reliable to measure the highly dynamic and transient changes in [Ca(2+)]i that occur during chemical exposure.
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18
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de Groot MW, Westerink RH. Chemically-induced oxidative stress increases the vulnerability of PC12 cells to rotenone-induced toxicity. Neurotoxicology 2014; 43:102-109. [DOI: 10.1016/j.neuro.2014.02.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Revised: 02/20/2014] [Accepted: 02/28/2014] [Indexed: 10/25/2022]
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Westerink RHS. Modulation of cell viability, oxidative stress, calcium homeostasis, and voltage- and ligand-gated ion channels as common mechanisms of action of (mixtures of) non-dioxin-like polychlorinated biphenyls and polybrominated diphenyl ethers. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2014; 21:6373-6383. [PMID: 23686757 DOI: 10.1007/s11356-013-1759-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Accepted: 04/22/2013] [Indexed: 06/02/2023]
Abstract
Non-dioxin-like polychlorinated biphenyls (NDL-PCBs) and polybrominated diphenyl ethers (PBDEs) are environmental pollutants that exert neurodevelopmental and neurobehavioral effects in vivo in humans and animals. Acute in vitro neurotoxic effects include changes in cell viability, oxidative stress, and basal intracellular calcium levels. Though these acute cellular effects could partly explain the observed in vivo effects, other mechanisms, such as effects on calcium influx and neurotransmitter receptor function, likely contribute to the disturbance in neurotransmission. This concise review combines in vitro data on cell viability, oxidative stress and basal calcium levels with recent data that clearly demonstrate that (hydroxylated) PCBs and (hydroxylated) PBDEs can exert acute effects on voltage-gated Ca(2+) channels as well as on excitatory and inhibitory neurotransmitter receptors in vitro. These novel mechanisms of action are shared by NDL-PCBs, OH-PBDEs, and some other persistent organic pollutants, such as tetrabromobisphenol-A, and could have profound effects on neurodevelopment, neurotransmission, and neurobehavior in vivo.
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Affiliation(s)
- Remco H S Westerink
- Neurotoxicology Research Group, Toxicology Division, Institute for Risk Assessment Sciences (IRAS), Faculty of Veterinary Medicine, Utrecht University, P.O. Box 80.177, 3508 TD, Utrecht, The Netherlands,
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20
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Munro TA, Huang XP, Inglese C, Perrone MG, Van't Veer A, Carroll FI, Béguin C, Carlezon WA, Colabufo NA, Cohen BM, Roth BL. Selective κ opioid antagonists nor-BNI, GNTI and JDTic have low affinities for non-opioid receptors and transporters. PLoS One 2013; 8:e70701. [PMID: 23976952 PMCID: PMC3747596 DOI: 10.1371/journal.pone.0070701] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 06/21/2013] [Indexed: 01/16/2023] Open
Abstract
Background Nor-BNI, GNTI and JDTic induce selective κ opioid antagonism that is delayed and extremely prolonged, but some other effects are of rapid onset and brief duration. The transient effects of these compounds differ, suggesting that some of them may be mediated by other targets. Results In binding assays, the three antagonists showed no detectable affinity (Ki≥10 µM) for most non-opioid receptors and transporters (26 of 43 tested). There was no non-opioid target for which all three compounds shared detectable affinity, or for which any two shared sub-micromolar affinity. All three compounds showed low nanomolar affinity for κ opioid receptors, with moderate selectivity over μ and δ (3 to 44-fold). Nor-BNI bound weakly to the α2C-adrenoceptor (Ki = 630 nM). GNTI enhanced calcium mobilization by noradrenaline at the α1A-adrenoceptor (EC50 = 41 nM), but did not activate the receptor, displace radioligands, or enhance PI hydrolysis. This suggests that it is a functionally-selective allosteric enhancer. GNTI was also a weak M1 receptor antagonist (KB = 3.7 µM). JDTic bound to the noradrenaline transporter (Ki = 54 nM), but only weakly inhibited transport (IC50 = 1.1 µM). JDTic also bound to the opioid-like receptor NOP (Ki = 12 nM), but gave little antagonism even at 30 µM. All three compounds exhibited rapid permeation and active efflux across Caco-2 cell monolayers. Conclusions Across 43 non-opioid CNS targets, only GNTI exhibited a potent functional effect (allosteric enhancement of α1A-adrenoceptors). This may contribute to GNTI's severe transient effects. Plasma concentrations of nor-BNI and GNTI may be high enough to affect some peripheral non-opioid targets. Nonetheless, κ opioid antagonism persists for weeks or months after these transient effects dissipate. With an adequate pre-administration interval, our results therefore strengthen the evidence that nor-BNI, GNTI and JDTic are highly selective κ opioid antagonists.
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MESH Headings
- Allosteric Regulation
- Biological Transport
- Caco-2 Cells
- Calcium/metabolism
- Guanidines/metabolism
- Guanidines/pharmacology
- Humans
- Kinetics
- Morphinans/metabolism
- Morphinans/pharmacology
- Naltrexone/analogs & derivatives
- Naltrexone/metabolism
- Naltrexone/pharmacology
- Narcotic Antagonists/metabolism
- Narcotic Antagonists/pharmacology
- Norepinephrine/metabolism
- Norepinephrine Plasma Membrane Transport Proteins/metabolism
- Piperidines/metabolism
- Piperidines/pharmacology
- Protein Binding
- Receptors, Adrenergic, alpha/metabolism
- Receptors, Opioid, delta/metabolism
- Receptors, Opioid, kappa/antagonists & inhibitors
- Receptors, Opioid, kappa/metabolism
- Receptors, Opioid, mu/metabolism
- Tetrahydroisoquinolines/metabolism
- Tetrahydroisoquinolines/pharmacology
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Affiliation(s)
- Thomas A. Munro
- McLean Hospital, Belmont, Massachusetts, United States of America
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, United States of America
- School of Chemistry and Bio21 Institute, University of Melbourne, Parkville, Australia
- * E-mail:
| | - Xi-Ping Huang
- National Institute of Mental Health Psychoactive Drug Screening Program and Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, United States of America
| | - Carmela Inglese
- Dipartimento di Farmacia-Scienze del Farmaco, Università degli Studi di Bari, Bari, Italy
| | - Maria Grazia Perrone
- Dipartimento di Farmacia-Scienze del Farmaco, Università degli Studi di Bari, Bari, Italy
| | - Ashlee Van't Veer
- McLean Hospital, Belmont, Massachusetts, United States of America
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, United States of America
| | - F. Ivy Carroll
- Center for Organic and Medicinal Chemistry, Research Triangle Institute, Research Triangle Park, North Carolina, United States of America
| | - Cécile Béguin
- McLean Hospital, Belmont, Massachusetts, United States of America
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, United States of America
| | - William A. Carlezon
- McLean Hospital, Belmont, Massachusetts, United States of America
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Nicola A. Colabufo
- Dipartimento di Farmacia-Scienze del Farmaco, Università degli Studi di Bari, Bari, Italy
| | - Bruce M. Cohen
- McLean Hospital, Belmont, Massachusetts, United States of America
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Bryan L. Roth
- National Institute of Mental Health Psychoactive Drug Screening Program and Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, United States of America
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Heusinkveld HJ, Molendijk J, van den Berg M, Westerink RHS. Azole fungicides disturb intracellular Ca2+ in an additive manner in dopaminergic PC12 cells. Toxicol Sci 2013; 134:374-81. [PMID: 23708404 DOI: 10.1093/toxsci/kft119] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Humans are exposed to complex mixtures of pesticides and other compounds, mainly via food. Azole fungicides are broad spectrum antifungal compounds used in agriculture and in human and veterinary medicine. The mechanism of antifungal action relies on inhibition of CYP51, resulting in inhibition of fungal cell growth. Known adverse health effects of azole fungicides are mainly linked to CYP inhibition. Additionally, azole fungicide-induced neurotoxicity has been reported, though the underlying mechanism(s) are largely unknown. We therefore investigated the effects of a group of six azole fungicides (imazalil, flusilazole, fluconazole, tebuconazole, triadimefon, and cyproconazole) on cell viability using a combined alamar Blue/CFDA-AM assay and on oxidative stress using a H2-DCFDA fluorescent assay. As calcium plays a pivotal role in neuronal survival and functioning, effects of these six azole fungicides and binary and quaternary mixtures of azole fungicides on the intracellular calcium concentration ([Ca(2+)]i) were investigated using single-cell fluorescence microscopy in dopaminergic PC12 cells loaded with the calcium-sensitive fluorescent dye Fura-2. Only modest changes in cell viability and ROS production were observed. However, five out of six azole fungicides induced a nonspecific inhibition of voltage-gated calcium channels (VGCCs), though with varying potency. Experiments using binary IC20 and quaternary IC10 mixtures indicated that the inhibitory effects on VGCCs are additive. The combined findings demonstrate modulation of intracellular Ca(2+) via inhibition of VGCCs as a novel mode of action of azole fungicides. Furthermore, mixtures of azole fungicides display additivity, illustrating the need to take mixture effects into account in human risk assessment.
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Affiliation(s)
- Harm J Heusinkveld
- Neurotoxicology Research Group, Division of Toxicology, Institute for Risk Assessment Sciences, Faculty of Veterinary Medicine, Utrecht University, 3508 TD Utrecht, The Netherlands
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22
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de Groot MWGDM, Westerink RHS, Dingemans MML. Don't judge a neuron only by its cover: neuronal function in in vitro developmental neurotoxicity testing. Toxicol Sci 2012; 132:1-7. [PMID: 22961093 DOI: 10.1093/toxsci/kfs269] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Classical cases of developmental neurotoxicity (DNT) in humans and advances in risk assessment methods did not prevent the emergence of new chemicals with (suspected) DNT potential. Exposure to these chemicals may be related to the increased worldwide incidence of learning and neurodevelopmental disorders in children. DNT is often investigated in a traditional manner (in vivo using large numbers of experimental animals), whereas development of in vitro methods for DNT reduces animal use and increases insight into cellular and molecular mechanisms of DNT. Several essential neurodevelopmental processes, including proliferation, migration, differentiation, formation of axons and dendrites, synaptogenesis, and apoptosis, are already being evaluated in vitro using biochemical and morphological endpoints. Yet, investigation of chemical-induced effects on the development of functional neuronal networks, including network formation, inter- and intracellular signaling and neuronal network function, is underrepresented in DNT testing. This view therefore focuses on in vitro models and innovative experimental approaches for functional DNT testing, ranging from optical and electrophysiological measurements of intra- and intercellular signaling in neural stem/progenitor cells to measurements of network activity in neuronal networks using multielectrode arrays. The development of functional DNT assays will strongly support the decision-making process for measures to prevent potential chemical-induced adverse effects on neurodevelopment and cognition in humans. We therefore argue that for risk assessment, biochemical and morphological approaches should be complemented with investigations of neuronal (network) functionality.
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23
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Hendriks HS, van Kleef RGDM, van den Berg M, Westerink RHS. Multiple novel modes of action involved in the in vitro neurotoxic effects of tetrabromobisphenol-A. Toxicol Sci 2012; 128:235-46. [PMID: 22547355 DOI: 10.1093/toxsci/kfs136] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Neurotoxicological data on the widely used brominated flame retardant tetrabromobisphenol-A (TBBPA) is limited. Since recent studies indicated that inhibitory GABA(A) and excitatory α(4)β(2) nicotinic acetylcholine (nACh) receptors are sensitive targets for persistent organic pollutants, we investigated the effects of TBBPA on these receptors, expressed in Xenopus oocytes, using the two-electrode voltage-clamp technique. Our results demonstrate that TBBPA acts as full (≥ 10 μM) and partial (≥ 0.1 μM) agonist on human GABA(A) receptors, whereas it acts as antagonist (≥ 10 μM) on human α(4)β(2) nACh receptors. Next, neuronal B35 cells were used to further study the effects of TBBPA on calcium-permeable nACh receptors using single-cell fluorescent calcium imaging. These results demonstrate that TBBPA (≥ 1 μM) inhibits acetylcholine (ACh) receptors as evidenced by a reduction in the ACh-evoked increases in the intracellular calcium concentration ([Ca(2+)](i)). Additionally, TBBPA (> 1 μM) induced a strong and concentration-dependent increase in basal [Ca(2+)](i) in B35 cells. Similarly, TBBPA (> 1 μM) increases basal [Ca(2+)](i) in dopaminergic PC12 cells. This increase is also evident under calcium-free conditions, indicating it originates from intracellular calcium stores. Moreover, depolarization-evoked increases in [Ca(2+)](i) are strongly reduced by TBBPA (≥ 1 μM), indicating TBBPA-induced inhibition of voltage-gated calcium channels. Our in vitro studies thus demonstrate that TBBPA exerts several adverse effects on functional neurotransmission endpoints with effect concentrations that are only two orders of magnitude below the highest cord serum concentrations. Although epidemiological proof for adverse TBBPA effects is lacking, our data justify the quest for flame retardants with reduced neurotoxic potential.
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Affiliation(s)
- Hester S Hendriks
- Neurotoxicology Research Group, Toxicology Division, Institute for Risk Assessment Sciences (IRAS), Utrecht University, NL-3508 TD Utrecht, The Netherlands
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24
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van Thriel C, Westerink RHS, Beste C, Bale AS, Lein PJ, Leist M. Translating neurobehavioural endpoints of developmental neurotoxicity tests into in vitro assays and readouts. Neurotoxicology 2011; 33:911-24. [PMID: 22008243 DOI: 10.1016/j.neuro.2011.10.002] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Accepted: 10/04/2011] [Indexed: 12/11/2022]
Abstract
The developing nervous system is particularly vulnerable to chemical insults. Exposure to chemicals can result in neurobehavioural alterations, and these have been used as sensitive readouts to assess neurotoxicity in animals and man. Deconstructing neurobehaviour into relevant cellular and molecular components may allow for detection of specific neurotoxic effects in cell-based systems, which in turn may allow an easier examination of neurotoxic pathways and modes of actions and eventually inform the regulatory assessment of chemicals with potential developmental neurotoxicity. Here, current developments towards these goals are reviewed. Imaging genetics (CB) provides new insights into the neurobiological correlates of cognitive function that are being used to delineate neurotoxic mechanisms. The gaps between in vivo neurobehaviour and real-time in vitro measurements of neuronal function are being bridged by ex vivo measurements of synaptic plasticity (RW). An example of solvent neurotoxicity demonstrates how an in vivo neurological defect can be linked via the N-methyl-d-aspartate (NMDA)-glutamate receptor as a common target to in vitro readouts (AB). Axonal and dendritic morphology in vitro proved to be good correlates of neuronal connectivity and neurobehaviour in animals exposed to polychlorinated biphenyls and organophosphorus pesticides (PJL). Similarly, chemically induced changes in neuronal morphology affected the formation of neuronal networks on structured surfaces. Such network formation may become an important readout for developmental neurotoxicity in vitro (CvT), especially when combined with human neurons derived from embryonic stem cells (ML). We envision that future in vitro test systems for developmental neurotoxicity will combine the above approaches with exposure information, and we suggest a strategy for test system development and cell-based risk assessment.
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Affiliation(s)
- Christoph van Thriel
- Neurobehavioural Toxicology and Chemosensation, IfADo - Leibniz Research Centre for Working Environment and Human Factors, Dortmund, Germany.
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