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King DE, Sparling AC, Joyce AS, Ryde IT, DeSouza B, Ferguson PL, Murphy SK, Meyer JN. Lack of detectable sex differences in the mitochondrial function of Caenorhabditis elegans. BMC Ecol Evol 2024; 24:55. [PMID: 38664688 PMCID: PMC11046947 DOI: 10.1186/s12862-024-02238-x] [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: 03/05/2023] [Accepted: 04/09/2024] [Indexed: 04/28/2024] Open
Abstract
BACKGROUND Sex differences in mitochondrial function have been reported in multiple tissue and cell types. Additionally, sex-variable responses to stressors including environmental pollutants and drugs that cause mitochondrial toxicity have been observed. The mechanisms that establish these differences are thought to include hormonal modulation, epigenetic regulation, double dosing of X-linked genes, and the maternal inheritance of mtDNA. Understanding the drivers of sex differences in mitochondrial function and being able to model them in vitro is important for identifying toxic compounds with sex-variable effects. Additionally, understanding how sex differences in mitochondrial function compare across species may permit insight into the drivers of these differences, which is important for basic biology research. This study explored whether Caenorhabditis elegans, a model organism commonly used to study stress biology and toxicology, exhibits sex differences in mitochondrial function and toxicant susceptibility. To assess sex differences in mitochondrial function, we utilized four male enriched populations (N2 wild-type male enriched, fog-2(q71), him-5(e1490), and him-8(e1498)). We performed whole worm respirometry and determined whole worm ATP levels and mtDNA copy number. To probe whether sex differences manifest only after stress and inform the growing use of C. elegans as a mitochondrial health and toxicologic model, we also assessed susceptibility to a classic mitochondrial toxicant, rotenone. RESULTS We detected few to no large differences in mitochondrial function between C. elegans sexes. Though we saw no sex differences in vulnerability to rotenone, we did observe sex differences in the uptake of this lipophilic compound, which may be of interest to those utilizing C. elegans as a model organism for toxicologic studies. Additionally, we observed altered non-mitochondrial respiration in two him strains, which may be of interest to other researchers utilizing these strains. CONCLUSIONS Basal mitochondrial parameters in male and hermaphrodite C. elegans are similar, at least at the whole-organism level, as is toxicity associated with a mitochondrial Complex I inhibitor, rotenone. Our data highlights the limitation of using C. elegans as a model to study sex-variable mitochondrial function and toxicological responses.
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Affiliation(s)
- Dillon E King
- Nicholas School of Environment, Duke University, 308 Research Drive, A304, Durham, NC, 27708, USA
- Department of Obstetrics and Gynecology, Duke University Medical Center, Durham, NC, USA
| | - A Clare Sparling
- Nicholas School of Environment, Duke University, 308 Research Drive, A304, Durham, NC, 27708, USA
| | - Abigail S Joyce
- Pratt School of Engineering, Duke University, Durham, NC, USA
| | - Ian T Ryde
- Nicholas School of Environment, Duke University, 308 Research Drive, A304, Durham, NC, 27708, USA
| | - Beverly DeSouza
- Department of Pharmacology and Cancer Biology, Duke University, Durham, NC, USA
| | - P Lee Ferguson
- Pratt School of Engineering, Duke University, Durham, NC, USA
| | - Susan K Murphy
- Nicholas School of Environment, Duke University, 308 Research Drive, A304, Durham, NC, 27708, USA
- Department of Obstetrics and Gynecology, Duke University Medical Center, Durham, NC, USA
| | - Joel N Meyer
- Nicholas School of Environment, Duke University, 308 Research Drive, A304, Durham, NC, 27708, USA.
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Wlodkowic D, Jansen M. High-throughput screening paradigms in ecotoxicity testing: Emerging prospects and ongoing challenges. CHEMOSPHERE 2022; 307:135929. [PMID: 35944679 DOI: 10.1016/j.chemosphere.2022.135929] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Revised: 06/09/2022] [Accepted: 07/31/2022] [Indexed: 06/15/2023]
Abstract
The rapidly increasing number of new production chemicals coupled with stringent implementation of global chemical management programs necessities a paradigm shift towards boarder uses of low-cost and high-throughput ecotoxicity testing strategies as well as deeper understanding of cellular and sub-cellular mechanisms of ecotoxicity that can be used in effective risk assessment. The latter will require automated acquisition of biological data, new capabilities for big data analysis as well as computational simulations capable of translating new data into in vivo relevance. However, very few efforts have been so far devoted into the development of automated bioanalytical systems in ecotoxicology. This is in stark contrast to standardized and high-throughput chemical screening and prioritization routines found in modern drug discovery pipelines. As a result, the high-throughput and high-content data acquisition in ecotoxicology is still in its infancy with limited examples focused on cell-free and cell-based assays. In this work we outline recent developments and emerging prospects of high-throughput bioanalytical approaches in ecotoxicology that reach beyond in vitro biotests. We discuss future importance of automated quantitative data acquisition for cell-free, cell-based as well as developments in phytotoxicity and in vivo biotests utilizing small aquatic model organisms. We also discuss recent innovations such as organs-on-a-chip technologies and existing challenges for emerging high-throughput ecotoxicity testing strategies. Lastly, we provide seminal examples of the small number of successful high-throughput implementations that have been employed in prioritization of chemicals and accelerated environmental risk assessment.
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Affiliation(s)
- Donald Wlodkowic
- The Neurotox Lab, School of Science, RMIT University, Melbourne, VIC, 3083, Australia.
| | - Marcus Jansen
- LemnaTec GmbH, Nerscheider Weg 170, 52076, Aachen, Germany
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Markovich ZR, Hartman JH, Ryde IT, Hershberger KA, Joyce AS, Ferguson PL, Meyer JN. Mild pentachlorophenol-mediated uncoupling of mitochondria depletes ATP but does not cause an oxidized redox state or dopaminergic neurodegeneration in Caenorhabditis elegans. Curr Res Toxicol 2022; 3:100084. [PMID: 35957653 PMCID: PMC9361317 DOI: 10.1016/j.crtox.2022.100084] [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: 03/03/2022] [Revised: 07/22/2022] [Accepted: 07/28/2022] [Indexed: 11/25/2022] Open
Abstract
Aims Mitochondrial dysfunction is implicated in several diseases, including neurological disorders such as Parkinson's disease. However, there is uncertainty about which of the many mechanisms by which mitochondrial function can be disrupted may lead to neurodegeneration. Pentachlorophenol (PCP) is an organic pollutant reported to cause mitochondrial dysfunction including oxidative stress and mitochondrial uncoupling. We investigated the effects of PCP exposure in Caenorhabditis elegans, including effects on mitochondria and dopaminergic neurons. We hypothesized that mild mitochondrial uncoupling by PCP would impair bioenergetics while decreasing oxidative stress, and therefore would not cause dopaminergic neurodegeneration. Results A 48-hour developmental exposure to PCP causing mild growth delay (∼10 % decrease in growth during 48 h, covering all larval stages) reduced whole-organism ATP content > 50 %, and spare respiratory capacity ∼ 30 %. Proton leak was also markedly increased. These findings suggest a main toxic mechanism of mitochondrial uncoupling rather than oxidative stress, which was further supported by a concomitant shift toward a more reduced cellular redox state measured at the whole organism level. However, exposure to PCP did not cause dopaminergic neurodegeneration, nor did it sensitize animals to a neurotoxic challenge with 6-hydroxydopamine. Whole-organism uptake and PCP metabolism measurements revealed low overall uptake of PCP in our experimental conditions (50 μM PCP in the liquid exposure medium resulted in organismal concentrations of < 0.25 μM), and no measurable production of the oxidative metabolites tetra-1,4-benzoquinone and tetrachloro-p-hydroquinone. Innovation This study provides new insights into the mechanistic interplay between mitochondrial uncoupling, oxidative stress, and neurodegeneration in C. elegans. These findings support the premise of mild uncoupling-mediated neuroprotection, but are inconsistent with proposed broad "mitochondrial dysfunction"-mediated neurodegeneration models, and highlight the utility of the C. elegans model for studying mitochondrial and neurotoxicity. Conclusions Developmental exposure to pentachlorophenol causes gross toxicological effects (growth delay and arrest) at high levels. At a lower level of exposure, still causing mild growth delay, we observed mitochondrial dysfunction including uncoupling and decreased ATP levels. However, this was associated with a more-reduced cellular redox tone and did not exacerbate dopaminergic neurotoxicity of 6-hydroxydopamine, instead trending toward protection. These findings may be informative of efforts to define nuanced mitochondrial dysfunction-related adverse outcome pathways that will differ depending on the form of initial mitochondrial toxicity.
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Affiliation(s)
| | - Jessica H. Hartman
- Nicholas School of the Environment, Duke University, Durham, NC 27708-0328, USA
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Ian T. Ryde
- Nicholas School of the Environment, Duke University, Durham, NC 27708-0328, USA
| | | | - Abigail S. Joyce
- Pratt School of Engineering, Duke University, Durham, NC 27708, USA
| | - Patrick L. Ferguson
- Nicholas School of the Environment, Duke University, Durham, NC 27708-0328, USA
- Pratt School of Engineering, Duke University, Durham, NC 27708, USA
| | - Joel N. Meyer
- Nicholas School of the Environment, Duke University, Durham, NC 27708-0328, USA
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Assessing Drug-Induced Mitochondrial Toxicity in Cardiomyocytes: Implications for Preclinical Cardiac Safety Evaluation. Pharmaceutics 2022; 14:pharmaceutics14071313. [PMID: 35890211 PMCID: PMC9319223 DOI: 10.3390/pharmaceutics14071313] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 06/09/2022] [Accepted: 06/14/2022] [Indexed: 02/07/2023] Open
Abstract
Drug-induced cardiotoxicity not only leads to the attrition of drugs during development, but also contributes to the high morbidity and mortality rates of cardiovascular diseases. Comprehensive testing for proarrhythmic risks of drugs has been applied in preclinical cardiac safety assessment for over 15 years. However, other mechanisms of cardiac toxicity have not received such attention. Of them, mitochondrial impairment is a common form of cardiotoxicity and is known to account for over half of cardiovascular adverse-event-related black box warnings imposed by the U.S. Food and Drug Administration. Although it has been studied in great depth, mitochondrial toxicity assessment has not yet been incorporated into routine safety tests for cardiotoxicity at the preclinical stage. This review discusses the main characteristics of mitochondria in cardiomyocytes, drug-induced mitochondrial toxicities, and high-throughput screening strategies for cardiomyocytes, as well as their proposed integration into preclinical safety pharmacology. We emphasize the advantages of using adult human primary cardiomyocytes for the evaluation of mitochondrial morphology and function, and the need for a novel cardiac safety testing platform integrating mitochondrial toxicity and proarrhythmic risk assessments in cardiac safety evaluation.
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Tang W, Liu W, Wang Z, Hong H, Chen J. Machine learning models on chemical inhibitors of mitochondrial electron transport chain. JOURNAL OF HAZARDOUS MATERIALS 2022; 426:128067. [PMID: 34920224 DOI: 10.1016/j.jhazmat.2021.128067] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 12/05/2021] [Accepted: 12/08/2021] [Indexed: 06/14/2023]
Abstract
Chemicals can induce adverse effects in humans by inhibiting mitochondrial electron transport chain (ETC) such as disrupting mitochondrial membrane potential, enhancing oxidative stress and causing some diseases. Thus, identifying ETC inhibitors (ETCi) is important to chemical risk assessment and protecting the public health. However, it is not feasible to identify all ETCi with experimental methods. Quantitative structure-activity relationship (QSAR) modeling is a promising method to rapidly and effectively identify ETCi. In this study, QSAR models for predicting ETCi were developed using machine learning methods. A clustering-based under-sampling (CBUS) method was developed to handle the imbalance issue in training sets. Structure-activity landscapes were generated and analyzed for training sets generated by the CBUS method. The consensus QSAR models constructed with CBUS achieved satisfactory performances (balanced accuracy = 0.852) in 100 iterations of five-fold cross validations, indicating the models can effectively classify ETCi. The classification model was further employed to screen chemicals in the Inventory of Existing Chemical Substances of China and 13 chemicals were identified as ETCi. Fifteen structural alerts for ETCi were identified in this study. These results demonstrated that the model and structural alerts are useful to screen ETCi.
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Affiliation(s)
- Weihao Tang
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), Dalian Key Laboratory on Chemicals Risk Control and Pollution Prevention Technology, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Wenjia Liu
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), Dalian Key Laboratory on Chemicals Risk Control and Pollution Prevention Technology, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Zhongyu Wang
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), Dalian Key Laboratory on Chemicals Risk Control and Pollution Prevention Technology, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Huixiao Hong
- National Center for Toxicological Research, US Food and Drug Administration, 3900 NCTR Rd, Jefferson, AR 72079, USA
| | - Jingwen Chen
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), Dalian Key Laboratory on Chemicals Risk Control and Pollution Prevention Technology, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
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van der Stel W, Yang H, Vrijenhoek NG, Schimming JP, Callegaro G, Carta G, Darici S, Delp J, Forsby A, White A, le Dévédec S, Leist M, Jennings P, Beltman JB, van de Water B, Danen EHJ. Mapping the cellular response to electron transport chain inhibitors reveals selective signaling networks triggered by mitochondrial perturbation. Arch Toxicol 2021; 96:259-285. [PMID: 34642769 PMCID: PMC8748354 DOI: 10.1007/s00204-021-03160-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 09/09/2021] [Indexed: 12/24/2022]
Abstract
Mitochondrial perturbation is a key event in chemical-induced organ toxicities that is incompletely understood. Here, we studied how electron transport chain (ETC) complex I, II, or III (CI, CII and CIII) inhibitors affect mitochondrial functionality, stress response activation, and cell viability using a combination of high-content imaging and TempO-Seq in HepG2 hepatocyte cells. CI and CIII inhibitors perturbed mitochondrial membrane potential (MMP) and mitochondrial and cellular ATP levels in a concentration- and time-dependent fashion and, under conditions preventing a switch to glycolysis attenuated cell viability, whereas CII inhibitors had no effect. TempO-Seq analysis of changes in mRNA expression pointed to a shared cellular response to CI and CIII inhibition. First, to define specific ETC inhibition responses, a gene set responsive toward ETC inhibition (and not to genotoxic, oxidative, or endoplasmic reticulum stress) was identified using targeted TempO-Seq in HepG2. Silencing of one of these genes, NOS3, exacerbated the impact of CI and CIII inhibitors on cell viability, indicating its functional implication in cellular responses to mitochondrial stress. Then by monitoring dynamic responses to ETC inhibition using a HepG2 GFP reporter panel for different classes of stress response pathways and applying pathway and gene network analysis to TempO-Seq data, we looked for downstream cellular events of ETC inhibition and identified the amino acid response (AAR) as being triggered in HepG2 by ETC inhibition. Through in silico approaches we provide evidence indicating that a similar AAR is associated with exposure to mitochondrial toxicants in primary human hepatocytes. Altogether, we (i) unravel quantitative, time- and concentration-resolved cellular responses to mitochondrial perturbation, (ii) identify a gene set associated with adaptation to exposure to active ETC inhibitors, and (iii) show that ER stress and an AAR accompany ETC inhibition in HepG2 and primary hepatocytes.
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Affiliation(s)
- Wanda van der Stel
- Division of Drug Discovery and Safety, Leiden Academic Centre of Drug Research, Leiden University, Leiden, The Netherlands
| | - Huan Yang
- Division of Drug Discovery and Safety, Leiden Academic Centre of Drug Research, Leiden University, Leiden, The Netherlands
| | - Nanette G Vrijenhoek
- Division of Drug Discovery and Safety, Leiden Academic Centre of Drug Research, Leiden University, Leiden, The Netherlands
| | - Johannes P Schimming
- Division of Drug Discovery and Safety, Leiden Academic Centre of Drug Research, Leiden University, Leiden, The Netherlands
| | - Giulia Callegaro
- Division of Drug Discovery and Safety, Leiden Academic Centre of Drug Research, Leiden University, Leiden, The Netherlands
| | - Giada Carta
- Division Molecular and Computational Toxicology, Vrije University Amsterdam, Amsterdam, The Netherlands
| | - Salihanur Darici
- Division of Drug Discovery and Safety, Leiden Academic Centre of Drug Research, Leiden University, Leiden, The Netherlands
| | - Johannes Delp
- Chair for In Vitro Toxicology and Biomedicine, Department Inaugurated by the Doerenkamp-Zbinden Foundation, University of Konstanz, Konstanz, Germany
| | - Anna Forsby
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | | | - Sylvia le Dévédec
- Division of Drug Discovery and Safety, Leiden Academic Centre of Drug Research, Leiden University, Leiden, The Netherlands
| | - Marcel Leist
- Chair for In Vitro Toxicology and Biomedicine, Department Inaugurated by the Doerenkamp-Zbinden Foundation, University of Konstanz, Konstanz, Germany
| | - Paul Jennings
- Division Molecular and Computational Toxicology, Vrije University Amsterdam, Amsterdam, The Netherlands
| | - Joost B Beltman
- Division of Drug Discovery and Safety, Leiden Academic Centre of Drug Research, Leiden University, Leiden, The Netherlands
| | - Bob van de Water
- Division of Drug Discovery and Safety, Leiden Academic Centre of Drug Research, Leiden University, Leiden, The Netherlands.
| | - Erik H J Danen
- Division of Drug Discovery and Safety, Leiden Academic Centre of Drug Research, Leiden University, Leiden, The Netherlands.
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Perron NR, Nasarre C, Bandyopadhyay M, Beeson CC, Rohrer B. SAHA is neuroprotective in in vitro and in situ models of retinitis pigmentosa. Mol Vis 2021; 27:151-160. [PMID: 33907370 PMCID: PMC8056468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 03/31/2021] [Indexed: 10/25/2022] Open
Abstract
PURPOSE Recent reports linking HDAC6 to mitochondrial turnover and neurodegeneration led us to hypothesize that an inhibitor such as Vorinostat (suberoylanilide hydroxamic acid, SAHA) may reduce mitochondrial damage found in retinitis pigmentosa (RP), a progressive neurodegenerative disease of the eye. Here we tested the efficacy of SAHA for its ability to protect photoreceptors in in-vitro and in-situ models of RP. As the stressor, we focused on calcium overload. Calcium is one of the main drivers of cell death, and is associated with rod loss in the rd1 mouse retina, which harbors a mutation in the Pde6b gene similar to that found in human patients suffering from autosomal recessive RP. METHOD Murine photoreceptor cell line (661W) were exposed to agents that led to calcium stress. Cell survival and redox capacity were measured using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, real-time changes in cellular metabolism were assessed using the Seahorse Biosciences XF24 analyzer, and mitochondrial fission-fusion using imaging. In-situ, neuroprotection was assessed in RPE/retina organ cultures of the rd1 mouse. SAHA effects on cell survival were compared in 661W cells with those of the specific HDAC6 inhibitor tubastatin A, and those on protein acetylation by Western blotting. RESULTS In stressed 661W cells, SAHA was found to increase cell survival that was associated with improved mitochondrial respiration and reduced mitochondrial fission. The protective effects of SAHA were also observed on photoreceptor cell survival in whole retinal organ explants of the rd1 mouse. Even though tubastatin A was ineffective in increasing cell survival in 661W cells, HDAC6 activity was confirmed in 661W cells after SAHA treatment with protein acetylation specific for HDAC6, defined by an increase in tubulin, but not histone acetylation. CONCLUSIONS SAHA was found to protect mitochondria from damage, and concomitantly reduced photoreceptor cell death in cell and organ cultures. The lack of activity of tubastatin A suggests that there must be an additional mechanism of action involved in the protective mechanism of SAHA that is responsible for its neuroprotection. Overall, SAHA may be a useful treatment for the prevention of photoreceptor degeneration associated with human RP. The results are discussed in the context of the effects of inhibitors that target different classes and members of the HDAC family and their effects on rod versus cone survival.
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Affiliation(s)
- Nathan R. Perron
- Department of Drug Discovery and Biomedical Sciences, Medical University of South Carolina, Charleston, SC
| | - Cécile Nasarre
- Department of Ophthalmology, Medical University of South Carolina, Charleston, SC
| | | | - Craig C. Beeson
- Department of Drug Discovery and Biomedical Sciences, Medical University of South Carolina, Charleston, SC
| | - Baerbel Rohrer
- Department of Ophthalmology, Medical University of South Carolina, Charleston, SC,Research Service, Ralph H Johnson VA Medical Center, Charleston, SC
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Jaiquel Baron S, King MS, Kunji ER, Schirris TJ. Characterization of drug-induced human mitochondrial ADP/ATP carrier inhibition. Am J Cancer Res 2021; 11:5077-5091. [PMID: 33859735 PMCID: PMC8039944 DOI: 10.7150/thno.54936] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2020] [Accepted: 01/18/2021] [Indexed: 01/10/2023] Open
Abstract
An increasing number of commonly prescribed drugs are known to interfere with mitochondrial function, causing cellular toxicity, but the underlying mechanisms are largely unknown. Although often not considered, mitochondrial transport proteins form a significant class of potential mitochondrial off-targets. So far, most drug interactions have been reported for the mitochondrial ADP/ATP carrier (AAC), which exchanges cytosolic ADP for mitochondrial ATP. Here, we show inhibition of cellular respiratory capacity by only a subset of the 18 published AAC inhibitors, which questions whether all compound do indeed inhibit such a central metabolic process. This could be explained by the lack of a simple, direct model system to evaluate and compare drug-induced AAC inhibition. Methods: For its development, we have expressed and purified human AAC1 (hAAC1) and applied two approaches. In the first, thermostability shift assays were carried out to investigate the binding of these compounds to human AAC1. In the second, the effect of these compounds on transport was assessed in proteoliposomes with reconstituted human AAC1, enabling characterization of their inhibition kinetics. Results: Of the proposed inhibitors, chebulinic acid, CD-437 and suramin are the most potent with IC50-values in the low micromolar range, whereas another six are effective at a concentration of 100 μM. Remarkably, half of all previously published AAC inhibitors do not show significant inhibition in our assays, indicating that they are false positives. Finally, we show that inhibitor strength correlates with a negatively charged surface area of the inhibitor, matching the positively charged surface of the substrate binding site. Conclusion: Consequently, we have provided a straightforward model system to investigate AAC inhibition and have gained new insights into the chemical compound features important for inhibition. Better evaluation methods of drug-induced inhibition of mitochondrial transport proteins will contribute to the development of drugs with an enhanced safety profile.
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In Vitro Exposure of Leukocytes to HIV Preexposure Prophylaxis Decreases Mitochondrial Function and Alters Gene Expression Profiles. Antimicrob Agents Chemother 2020; 65:AAC.01755-20. [PMID: 33020165 PMCID: PMC7927818 DOI: 10.1128/aac.01755-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Accepted: 10/01/2020] [Indexed: 12/21/2022] Open
Abstract
The use of antiretroviral therapy (ART) as preexposure prophylaxis (PrEP) is an effective strategy for preventing HIV acquisition. The cellular consequences of PrEP exposure, however, have not been sufficiently explored to determine potential effects on health in individuals without HIV. In this study, peripheral blood mononuclear cells (PBMCs) from people without HIV were exposed to tenofovir disoproxil fumarate (TDF) or emtricitabine (FTC) overnight. Mitochondrial mass and function were measured by flow cytometry and an Agilent XFp analyzer. The use of antiretroviral therapy (ART) as preexposure prophylaxis (PrEP) is an effective strategy for preventing HIV acquisition. The cellular consequences of PrEP exposure, however, have not been sufficiently explored to determine potential effects on health in individuals without HIV. In this study, peripheral blood mononuclear cells (PBMCs) from people without HIV were exposed to tenofovir disoproxil fumarate (TDF) or emtricitabine (FTC) overnight. Mitochondrial mass and function were measured by flow cytometry and an Agilent XFp analyzer. Monocyte-derived macrophages (MDMs) were differentiated in 20% autologous serum for 5 days in the presence or absence of TDF or FTC, and surface markers, lipid uptake, and efferocytosis were measured by flow cytometry. MDM gene expression was measured using transcriptome sequencing (RNA-seq). Plasma lipids were measured using mass spectrometry. PBMCs exposed to TDF or FTC had decreased maximal oxygen consumption rate (OCR) and reduced mitochondrial mass. Exposure to PrEP also increased reactive oxygen species (ROS) production from monocyte subsets. Compared to MDMs cultured in medium alone, cells differentiated in the presence of TDF (829 genes) or FTC (888 genes) had significant changes in gene expression. Further, PrEP-exposed MDMs had decreased mitochondrial mass and displayed increased lipid uptake and reduced efferocytosis. Plasma biomarkers and lipid levels were also altered in vivo in individuals receiving a PrEP regimen. In conclusion, exposure of leukocytes to TDF or FTC resulted in decreased mitochondrial function and altered functional and transcriptional profiles. These findings may have important implications for the metabolic and immunologic consequences of PrEP in populations at risk for HIV acquisition.
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Hallinger DR, Lindsay HB, Friedman KP, Suarez DA, Simmons SO. Respirometric Screening and Characterization of Mitochondrial Toxicants Within the ToxCast Phase I and II Chemical Libraries. Toxicol Sci 2020; 176:175-192. [PMID: 32374859 PMCID: PMC10626520 DOI: 10.1093/toxsci/kfaa059] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Mitochondrial toxicity drives several adverse health outcomes. Current high-throughput screening assays for chemically induced mitochondrial toxicity typically measure changes to mitochondrial structure and may not detect known mitochondrial toxicants. We adapted a respirometric screening assay (RSA) measuring mitochondrial function to screen ToxCast chemicals in HepG2 cells using a tiered testing strategy. Of 1042 chemicals initially screened at a singlemaximal concentration, 243 actives were identified and rescreened at 7 concentrations. Concentration-response data for 3 respiration phases confirmed activity and indicated a mechanism for 193 mitochondrial toxicants: 149 electron transport chain inhibitors (ETCi), 15 uncouplers and 29 adenosine triphosphate synthase inhibitors. Subsequently, an electron flow assay was used to identify the target complex for 84 of the 149 ETCi. Sixty reference chemicals were used to compare the RSA to existing ToxCast and Tox21 mitochondrial toxicity assays. The RSA was most predictive (accuracy = 90%) of mitochondrial toxicity. The Tox21 mitochondrial membrane potential assay was also highly predictive (accuracy = 87%) of bioactivity but underestimated the potency of well-known ETCi and provided no mechanistic information. The tiered RSA approach accurately identifies and characterizes mitochondrial toxicants acting through diverse mechanisms and at a throughput sufficient to screen large chemical inventories. The electron flow assay provides additional confirmation and detailed mechanistic understanding for ETCi, the most common type of mitochondrial toxicants among ToxCast chemicals. The mitochondrial toxicity screening approach described herein may inform hazard assessment and the in vitro bioactive concentrations used to derive relevant doses for screening level chemical assessment using new approach methodologies.
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Affiliation(s)
| | | | | | - Danielle A. Suarez
- Center for Public Health and Environmental Assessment, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
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11
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Acetoacetate enhances oxidative metabolism and response to toxicants of cultured kidney cells. Toxicol Lett 2020; 323:19-24. [DOI: 10.1016/j.toxlet.2020.01.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 01/16/2020] [Accepted: 01/17/2020] [Indexed: 01/16/2023]
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Pandya JD, Valdez M, Royland JE, MacPhail RC, Sullivan PG, Kodavanti PRS. Age- and Organ-Specific Differences in Mitochondrial Bioenergetics in Brown Norway Rats. J Aging Res 2020; 2020:7232614. [PMID: 32318291 PMCID: PMC7152959 DOI: 10.1155/2020/7232614] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 01/22/2020] [Accepted: 02/13/2020] [Indexed: 12/27/2022] Open
Abstract
Mitochondria play a central role in energy homeostasis and act as regulatory checkpoints for downstream metabolic responses and cell senescence processes during an entire life span. Acute or chronic environmental toxicant exposures have shown deleterious organ-specific human health issues at various life stages. Since mitochondria are a prime target for ensuing cellular bioenergetics responses and senescence, it is essential to understand mitochondrial bioenergetic responses in different organs over multiple life stages. Therefore, in the present study, we evaluated mitochondrial bioenergetic parameters in the liver, lung, and heart in four diverse age groups (young: 1 month; adult: 4 months; middle-aged: 12 months; old-aged: 24 month) using male Brown Norway rats as a model of aging (n = 5 sample size/organ/age group) and compared them with our previously published results on brain. Real-time mitochondrial bioenergetic parameters (i.e., State III, State IV, and State V) were measured using the Seahorse Extracellular Flux Analyzer. Additionally, mitochondrial enzyme pyruvate dehydrogenase complex (PDHC), Complex I, Complex II, and Complex IV activities were measured using Synergy HT plate reader. Our results indicated that nearly in all parameters, significant age- and organ-specific interactions were observed. We observed age-specific declines in State III (i.e., ATP synthesis rate) responses in both the heart and lung, where opposite was observed in the liver as age advances. Across the age, the heart has highest enzyme activities than the liver and lung. Interestingly, heart and liver mitochondrial bioenergetic rates and enzyme activities remain higher than the lung, which specifies their higher metabolic capabilities than the lung. Amongst all, bioenergetic rates and enzyme activities in the lung remain lowest suggesting the lung may display higher vulnerability and lower resilience to environmental toxicants during aging than other organs tested here. Overall, these age- and organ-specific findings may facilitate a more contextualized understanding of mitochondrial bioenergetic outcomes when considering the interactions of age-related sensitivities with exposure to chemical stressors from the environment.
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Affiliation(s)
- Jignesh D Pandya
- Spinal Cord and Brain Injury Research Center, Department of Neuroscience, University of Kentucky, Lexington, KY 40536, USA
| | - Matthew Valdez
- Oak Ridge Institute for Science and Education, U.S. Department of Energy, Oak Ridge, TN 37831, USA
- Neurological and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, CPHEA/ORD, U.S. Environmental Protection Agency, Research Triangle Park, Durham, NC 27711, USA
| | - Joyce E Royland
- Neurological and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, CPHEA/ORD, U.S. Environmental Protection Agency, Research Triangle Park, Durham, NC 27711, USA
| | - Robert C MacPhail
- Neurological and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, CPHEA/ORD, U.S. Environmental Protection Agency, Research Triangle Park, Durham, NC 27711, USA
| | - Patrick G Sullivan
- Spinal Cord and Brain Injury Research Center, Department of Neuroscience, University of Kentucky, Lexington, KY 40536, USA
| | - Prasada Rao S Kodavanti
- Neurological and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, CPHEA/ORD, U.S. Environmental Protection Agency, Research Triangle Park, Durham, NC 27711, USA
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13
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Contreras-Baeza Y, Ceballo S, Arce-Molina R, Sandoval PY, Alegría K, Barros LF, San Martín A. MitoToxy assay: A novel cell-based method for the assessment of metabolic toxicity in a multiwell plate format using a lactate FRET nanosensor, Laconic. PLoS One 2019; 14:e0224527. [PMID: 31671132 PMCID: PMC6822764 DOI: 10.1371/journal.pone.0224527] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 10/15/2019] [Indexed: 12/13/2022] Open
Abstract
Mitochondrial toxicity is a primary source of pre-clinical drug attrition, black box warning and post-market drug withdrawal. Methods that detect mitochondrial toxicity as early as possible during the drug development process are required. Here we introduce a new method for detecting mitochondrial toxicity based on MDA-MB-231 cells stably expressing the genetically encoded FRET lactate indicator, Laconic. The method takes advantage of the high cytosolic lactate accumulation observed during mitochondrial stress, regardless of the specific toxicity mechanism, explained by compensatory glycolytic activation. Using a standard multi-well plate reader, dose-response curve experiments allowed the sensitivity of the methodology to detect metabolic toxicity induced by classical mitochondrial toxicants. Suitability for high-throughput screening applications was evaluated resulting in a Z’-factor > 0.5 and CV% < 20 inter-assay variability. A pilot screening allowed sensitive detection of commercial drugs that were previously withdrawn from the market due to liver/cardiac toxicity issues, such as camptothecin, ciglitazone, troglitazone, rosiglitazone, and terfenadine, in ten minutes. We envisage that the availability of this technology, based on a fluorescent genetically encoded indicator, will allow direct assessment of mitochondrial metabolism, and will make the early detection of mitochondrial toxicity in the drug development process possible, saving time and resources.
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Affiliation(s)
| | | | - Robinson Arce-Molina
- Centro de Estudios Científicos (CECs), Valdivia, Chile
- Universidad Austral de Chile (UACh), Valdivia, Chile
| | | | - Karin Alegría
- Centro de Estudios Científicos (CECs), Valdivia, Chile
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14
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Leung MCK, Meyer JN. Mitochondria as a target of organophosphate and carbamate pesticides: Revisiting common mechanisms of action with new approach methodologies. Reprod Toxicol 2019; 89:83-92. [PMID: 31315019 PMCID: PMC6766410 DOI: 10.1016/j.reprotox.2019.07.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 06/19/2019] [Accepted: 07/09/2019] [Indexed: 01/01/2023]
Abstract
Mitochondrial toxicity has been proposed as a potential cause of developmental defects in humans. We evaluated 51 organophosphate and carbamate pesticides using the U.S. EPA ToxCast and Tox21 databases. Only a small number of them bind directly to cholinesterases in the parent form. The hydrophobicity of organophosphate pesticides is correlated significantly to TSPO binding affinity, mitochondrial membrane potential reduction in HepG2 cells, and developmental toxicity in Caenorhabditis elegans and Danio rerio (p < 0.05). Structural analysis suggests that in some cases the Krebs cycle is a potential target of organophosphate and carbamate exposure at early life stages. The results support the hypothesis that mitochondrial effects of some organophosphate pesticides-particularly those that require enzymatic activation to the oxon form-may augment the documented effects of disruption of acetylcholine signaling. This study provides a proof of concept for applying new approach methodologies to interrogate mechanisms of action for cumulative risk assessment.
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Affiliation(s)
- Maxwell C K Leung
- Department of Environmental Toxicology, University of California, Davis, CA, United States; Nicholas School of the Environment, Duke University, Durham, NC, United States.
| | - Joel N Meyer
- Nicholas School of the Environment, Duke University, Durham, NC, United States
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15
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Dreier DA, Mello D, Meyer J, Martyniuk CJ. Linking Mitochondrial Dysfunction to Organismal and Population Health in the Context of Environmental Pollutants: Progress and Considerations for Mitochondrial Adverse Outcome Pathways. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2019; 38:1625-1634. [PMID: 31034624 PMCID: PMC6961808 DOI: 10.1002/etc.4453] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 04/10/2019] [Accepted: 04/24/2019] [Indexed: 05/19/2023]
Abstract
Mitochondria are key targets of many environmental contaminants, because specific chemicals can interact directly with mitochondrial proteins, lipids, and ribonucleic acids. These direct interactions serve as molecular initiating events that impede adenosine triphosphate production and other critical functions that mitochondria serve within the cell (e.g., calcium and metal homeostasis, apoptosis, immune signaling, redox balance). A limited but growing number of adverse outcome pathways (AOPs) have been proposed to associate mitochondrial dysfunction with effects at organismal and population levels. These pathways involve key events such as altered membrane potential, mitochondrial fission/fusion, and mitochondrial DNA damage, among others. The present critical review and analysis reveals current progress on AOPs involving mitochondrial dysfunction, and, using a network-based computational approach, identifies the localization of mitochondrial molecular initiating events and key events within multiple existing AOPs. We also present 2 case studies, the first examining the interaction between mitochondria and immunotoxicity, and the second examining the role of early mitochondrial dysfunction in the context of behavior (i.e., locomotor activity). We discuss limitations in our current understanding of mitochondrial AOPs and highlight opportunities for clarifying their details. Advancing our knowledge of key event relationships within the AOP framework will require high-throughput datasets that permit the development and testing of chemical-agnostic AOPs, as well as high-resolution research that will enhance the mechanistic testing and validation of these key event relationships. Given the wide range of chemicals that affect mitochondria, and the centrality of energy production and signaling to ecologically important outcomes such as pathogen defense, homeostasis, growth, and reproduction, a better understanding of mitochondrial AOPs is expected to play a significant, if not central, role in environmental toxicology. Environ Toxicol Chem 2019;38:1625-1634. © 2019 SETAC.
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Affiliation(s)
- David A. Dreier
- Center for Environmental and Human Toxicology, Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, 32611 USA
| | - Danielle Mello
- Nicholas School of the Environment, Duke University, Durham, NC, 27708-0328 USA
| | - Joel Meyer
- Nicholas School of the Environment, Duke University, Durham, NC, 27708-0328 USA
| | - Christopher J. Martyniuk
- Center for Environmental and Human Toxicology, Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, 32611 USA
- University of Florida Genetics Institute, Interdisciplinary Program in Biomedical Sciences Neuroscience, University of Florida, Gainesville, FL, 32611 USA
- Address correspondence to
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16
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Thomas RS, Bahadori T, Buckley TJ, Cowden J, Deisenroth C, Dionisio KL, Frithsen JB, Grulke CM, Gwinn MR, Harrill JA, Higuchi M, Houck KA, Hughes MF, Hunter ES, Isaacs KK, Judson RS, Knudsen TB, Lambert JC, Linnenbrink M, Martin TM, Newton SR, Padilla S, Patlewicz G, Paul-Friedman K, Phillips KA, Richard AM, Sams R, Shafer TJ, Setzer RW, Shah I, Simmons JE, Simmons SO, Singh A, Sobus JR, Strynar M, Swank A, Tornero-Valez R, Ulrich EM, Villeneuve DL, Wambaugh JF, Wetmore BA, Williams AJ. The Next Generation Blueprint of Computational Toxicology at the U.S. Environmental Protection Agency. Toxicol Sci 2019; 169:317-332. [PMID: 30835285 PMCID: PMC6542711 DOI: 10.1093/toxsci/kfz058] [Citation(s) in RCA: 211] [Impact Index Per Article: 42.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The U.S. Environmental Protection Agency (EPA) is faced with the challenge of efficiently and credibly evaluating chemical safety often with limited or no available toxicity data. The expanding number of chemicals found in commerce and the environment, coupled with time and resource requirements for traditional toxicity testing and exposure characterization, continue to underscore the need for new approaches. In 2005, EPA charted a new course to address this challenge by embracing computational toxicology (CompTox) and investing in the technologies and capabilities to push the field forward. The return on this investment has been demonstrated through results and applications across a range of human and environmental health problems, as well as initial application to regulatory decision-making within programs such as the EPA's Endocrine Disruptor Screening Program. The CompTox initiative at EPA is more than a decade old. This manuscript presents a blueprint to guide the strategic and operational direction over the next 5 years. The primary goal is to obtain broader acceptance of the CompTox approaches for application to higher tier regulatory decisions, such as chemical assessments. To achieve this goal, the blueprint expands and refines the use of high-throughput and computational modeling approaches to transform the components in chemical risk assessment, while systematically addressing key challenges that have hindered progress. In addition, the blueprint outlines additional investments in cross-cutting efforts to characterize uncertainty and variability, develop software and information technology tools, provide outreach and training, and establish scientific confidence for application to different public health and environmental regulatory decisions.
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Affiliation(s)
- Russell S. Thomas
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Tina Bahadori
- National Center for Environmental Assessment, Office of Research and Development, US Environmental Protection Agency
| | - Timothy J. Buckley
- National Exposure Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - John Cowden
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Chad Deisenroth
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Kathie L. Dionisio
- National Exposure Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - Jeffrey B. Frithsen
- Chemical Safety for Sustainability National Research Program, Office of Research and Development, US Environmental Protection Agency
| | - Christopher M. Grulke
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Maureen R. Gwinn
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Joshua A. Harrill
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Mark Higuchi
- National Health and Environmental Effects Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - Keith A. Houck
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Michael F. Hughes
- National Health and Environmental Effects Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - E. Sidney Hunter
- National Health and Environmental Effects Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - Kristin K. Isaacs
- National Exposure Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - Richard S. Judson
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Thomas B. Knudsen
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Jason C. Lambert
- National Center for Environmental Assessment, Office of Research and Development, US Environmental Protection Agency
| | - Monica Linnenbrink
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Todd M. Martin
- National Risk Management Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - Seth R. Newton
- National Exposure Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - Stephanie Padilla
- National Health and Environmental Effects Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - Grace Patlewicz
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Katie Paul-Friedman
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Katherine A. Phillips
- National Exposure Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - Ann M. Richard
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Reeder Sams
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Timothy J. Shafer
- National Health and Environmental Effects Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - R. Woodrow Setzer
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Imran Shah
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Jane E. Simmons
- National Health and Environmental Effects Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - Steven O. Simmons
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Amar Singh
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Jon R. Sobus
- National Exposure Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - Mark Strynar
- National Exposure Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - Adam Swank
- National Exposure Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - Rogelio Tornero-Valez
- National Exposure Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - Elin M. Ulrich
- National Exposure Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - Daniel L Villeneuve
- National Health and Environmental Effects Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - John F. Wambaugh
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
| | - Barbara A. Wetmore
- National Exposure Research Laboratory, Office of Research and Development, US Environmental Protection Agency
| | - Antony J. Williams
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency
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17
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Affiliation(s)
- Kendall B Wallace
- Department of Biomedical Sciences, University of Minnesota Medical School, Room 259, 1035 University Avenue, Duluth, Minnesota 55812
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18
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Dreier DA, Denslow ND, Martyniuk CJ. Computational in Vitro Toxicology Uncovers Chemical Structures Impairing Mitochondrial Membrane Potential. J Chem Inf Model 2019; 59:702-712. [PMID: 30645939 DOI: 10.1021/acs.jcim.8b00433] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Technological advances in molecular biology have enabled high-throughput screening (HTS) of large chemical libraries. These approaches have provided valuable toxicity data for many physiological responses, including mitochondrial dysfunction. While several quantitative structure-activity relationship (QSAR) models have been developed for mitochondrial dysfunction, there remains a need to identify specific chemical features associated with this response. Thus, the objective of this study was to identify chemical structures associated with altered mitochondrial membrane potential (MMP). To achieve this, we developed computational models to examine the relationship between specific chemotypes (e.g., ToxPrints) and bioactivity in ToxCast/Tox21 HTS assays for altered MMP. The analysis revealed that the "bond:COH_alcohol_aromatic", "bond:COH_alcohol_aromatic_phenol", and "ring:aromatic_benzene" ToxPrints had the highest average correlations (phi coefficient) with ToxCast/Tox21 assay component endpoints for decreased MMP. These structures also constituted a "core" group of ToxPrints for decreased MMP in a force-directed network model and were the most important chemotypes in a random forest (RF) classification model for the "TOX21_MMP_ratio_down" assay component endpoint. Based on multiple lines of evidence, these structures, which are present in numerous chemicals (e.g., aromatic hydrocarbons, pesticides, and industrial chemicals) are likely involved in mitochondrial dysfunction. Because of the hierarchical structure of ToxPrints, these chemotypes were highly convergent and, when excluded from training data, had limited effects on the classification performance as related structures compensated for predictor loss. These results highlight the flexibility of the RF algorithm and ToxPrints for QSAR modeling, which is useful to identify chemicals affecting mitochondrial function.
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Affiliation(s)
- David A Dreier
- Center for Environmental & Human Toxicology, Department of Physiological Sciences, College of Veterinary Medicine , University of Florida , Gainesville , Florida 32611 , United States
| | - Nancy D Denslow
- Center for Environmental & Human Toxicology, Department of Physiological Sciences, College of Veterinary Medicine , University of Florida , Gainesville , Florida 32611 , United States
| | - Christopher J Martyniuk
- Center for Environmental & Human Toxicology, Department of Physiological Sciences, College of Veterinary Medicine , University of Florida , Gainesville , Florida 32611 , United States
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19
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Chandrasekharan A, Varadarajan SN, Lekshmi A, Lupitha SS, Darvin P, Chandrasekhar L, Pillai PR, Santhoshkumar TR, Pillai MR. A high-throughput real-time in vitro assay using mitochondrial targeted roGFP for screening of drugs targeting mitochondria. Redox Biol 2018; 20:379-389. [PMID: 30408753 PMCID: PMC6222140 DOI: 10.1016/j.redox.2018.10.013] [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: 08/28/2018] [Revised: 10/14/2018] [Accepted: 10/15/2018] [Indexed: 12/28/2022] Open
Abstract
Most toxic compounds including cancer drugs target mitochondria culminating in its permeabilization. Cancer drug-screening and toxicological testing of compounds require cost-effective and sensitive high-throughput methods to detect mitochondrial damage. Real-time methods for detection of mitochondrial damage are less toxic, allow kinetic measurements with good spatial resolution and are preferred over end-stage assays. Cancer cell lines stably expressing genetically encoded mitochondrial-targeted redox-GFP2 (mt-roGFP) were developed and validated for its suitability as a mitochondrial damage sensor. Diverse imaging platforms and flow-cytometry were utilized for ratiometric analysis of redox changes with known toxic and cancer drugs. Key events of cell death and mitochondrial damage were studied at single-cell level coupled with mt-roGFP. Cells stably expressing mt-roGFP and H2B-mCherry were developed for high-throughput screening (HTS) application. Most cancer drugs while inducing mitochondrial permeabilization trigger mitochondrial-oxidation that can be detected at single-cell level with mt-roGFP. The image-based assay using mt-roGFP outperformed other quantitative methods of apoptosis in ease of screening. Incorporation of H2B-mCherry ensures accurate and complete automated segmentation with excellent Z value. The results substantiate that most cancer drugs and known plant-derived antioxidants trigger cell-death through mitochondrial redox alterations with pronounced ratio change in the mt-roGFP probe. Real-time analysis of mitochondrial oxidation and mitochondrial permeabilization reveal a biphasic ratio change in dying cells, with an initial redox surge before mitochondrial permeabilization followed by a drastic increase in ratio after complete mitochondrial permeabilization. Overall, the results prove that mitochondrial oxidation is a reliable indicator of mitochondrial damage, which can be readily determined in live cells using mt-roGFP employing diverse imaging techniques. The assay described is highly sensitive, easy to adapt to HTS platforms and is a valuable resource for identifying cytotoxic agents that target mitochondria and also for dissecting cell signaling events relevant to redox biology. Mitochondrial oxidation is an universal marker for mitochondrial damage and mitochondrial permeabilization. Ratiometric imaging of mt-roGFP in high-throughput mode allows rapid screening of compounds that target mitochondria. Real-time ratiometric imaging of mt-roGFP and mitochondrial permeabilization reveals a biphasic redox alteration in cells undergoing mitochondrial permeabilization.
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Affiliation(s)
- Aneesh Chandrasekharan
- Cancer Research Program, Rajiv Gandhi Centre for Biotechnology, Poojappura, Thycaud P.O., Thiruvananthapuram, Kerala 695014, India
| | - Shankara Narayanan Varadarajan
- Cancer Research Program, Rajiv Gandhi Centre for Biotechnology, Poojappura, Thycaud P.O., Thiruvananthapuram, Kerala 695014, India
| | - Asha Lekshmi
- Cancer Research Program, Rajiv Gandhi Centre for Biotechnology, Poojappura, Thycaud P.O., Thiruvananthapuram, Kerala 695014, India
| | - Santhik Subhasingh Lupitha
- Cancer Research Program, Rajiv Gandhi Centre for Biotechnology, Poojappura, Thycaud P.O., Thiruvananthapuram, Kerala 695014, India
| | - Pramod Darvin
- Cancer Research Program, Rajiv Gandhi Centre for Biotechnology, Poojappura, Thycaud P.O., Thiruvananthapuram, Kerala 695014, India
| | - Leena Chandrasekhar
- Cancer Research Program, Rajiv Gandhi Centre for Biotechnology, Poojappura, Thycaud P.O., Thiruvananthapuram, Kerala 695014, India
| | - Prakash Rajappan Pillai
- Cancer Research Program, Rajiv Gandhi Centre for Biotechnology, Poojappura, Thycaud P.O., Thiruvananthapuram, Kerala 695014, India
| | - T R Santhoshkumar
- Cancer Research Program, Rajiv Gandhi Centre for Biotechnology, Poojappura, Thycaud P.O., Thiruvananthapuram, Kerala 695014, India.
| | - M Radhakrishna Pillai
- Cancer Research Program, Rajiv Gandhi Centre for Biotechnology, Poojappura, Thycaud P.O., Thiruvananthapuram, Kerala 695014, India
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20
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Swimming Exercise and Transient Food Deprivation in Caenorhabditis elegans Promote Mitochondrial Maintenance and Protect Against Chemical-Induced Mitotoxicity. Sci Rep 2018; 8:8359. [PMID: 29844465 PMCID: PMC5974391 DOI: 10.1038/s41598-018-26552-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2017] [Accepted: 05/14/2018] [Indexed: 12/11/2022] Open
Abstract
Exercise and caloric restriction improve health, including reducing risk of cardiovascular disease, neurological disease, and cancer. However, molecular mechanisms underlying these protections are poorly understood, partly due to the cost and time investment of mammalian long-term diet and exercise intervention studies. We subjected Caenorhabditis elegans nematodes to a 6-day, twice daily swimming exercise regimen, during which time the animals also experienced brief, transient food deprivation. Accordingly, we included a non-exercise group with the same transient food deprivation, a non-exercise control with ad libitum access to food, and a group that exercised in food-containing medium. Following these regimens, we assessed mitochondrial health and sensitivity to mitochondrial toxicants. Exercise protected against age-related decline in mitochondrial morphology in body-wall muscle. Food deprivation increased organismal basal respiration; however, exercise was the sole intervention that increased spare respiratory capacity and proton leak. We observed increased lifespan in exercised animals compared to both control and transiently food-deprived nematodes. Finally, exercised animals (and to a lesser extent, transiently food-deprived animals) were markedly protected against lethality from acute exposures to the mitotoxicants rotenone and arsenic. Thus, swimming exercise and brief food deprivation provide effective intervention in C. elegans, protecting from age-associated mitochondrial decline and providing resistance to mitotoxicant exposures.
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Abstract
Recent decades have seen a rapid increase in reported toxic effects of drugs and pollutants on mitochondria. Researchers have also documented many genetic differences leading to mitochondrial diseases, currently reported to affect ∼1 person in 4,300, creating a large number of potential gene-environment interactions in mitochondrial toxicity. We briefly review this history, and then highlight cutting-edge areas of mitochondrial research including the role of mitochondrial reactive oxygen species in signaling; increased understanding of fundamental biological processes involved in mitochondrial homeostasis (DNA maintenance and mutagenesis, mitochondrial stress response pathways, fusion and fission, autophagy and biogenesis, and exocytosis); systemic effects resulting from mitochondrial stresses in specific cell types; mitochondrial involvement in immune function; the growing evidence of long-term effects of mitochondrial toxicity; mitochondrial-epigenetic cross-talk; and newer approaches to test chemicals for mitochondrial toxicity. We also discuss the potential importance of hormetic effects of mitochondrial stressors. Finally, we comment on future areas of research we consider critical for mitochondrial toxicology, including increased integration of clinical, experimental laboratory, and epidemiological (human and wildlife) studies; improved understanding of biomarkers in the human population; and incorporation of other factors that affect mitochondria, such as diet, exercise, age, and nonchemical stressors.
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Affiliation(s)
- Joel N Meyer
- Nicholas School of the Environment and Integrated Toxicology and Environmental Health Program, Duke University, Durham, North Carolina 27708-0328
| | - Jessica H Hartman
- Nicholas School of the Environment and Integrated Toxicology and Environmental Health Program, Duke University, Durham, North Carolina 27708-0328
| | - Danielle F Mello
- Nicholas School of the Environment and Integrated Toxicology and Environmental Health Program, Duke University, Durham, North Carolina 27708-0328
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22
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The use of high-throughput screening techniques to evaluate mitochondrial toxicity. Toxicology 2017; 391:34-41. [PMID: 28789971 DOI: 10.1016/j.tox.2017.07.020] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 07/28/2017] [Accepted: 07/31/2017] [Indexed: 01/30/2023]
Abstract
Toxicologists and chemical regulators depend on accurate and effective methods to evaluate and predict the toxicity of thousands of current and future compounds. Robust high-throughput screening (HTS) experiments have the potential to efficiently test large numbers of chemical compounds for effects on biological pathways. HTS assays can be utilized to examine chemical toxicity across multiple mechanisms of action, experimental models, concentrations, and lengths of exposure. Many agricultural, industrial, and pharmaceutical chemicals classified as harmful to human and environmental health exert their effects through the mechanism of mitochondrial toxicity. Mitochondrial toxicants are compounds that cause a decrease in the number of mitochondria within a cell, and/or decrease the ability of mitochondria to perform normal functions including producing adenosine triphosphate (ATP) and maintaining cellular homeostasis. Mitochondrial dysfunction can lead to apoptosis, necrosis, altered metabolism, muscle weakness, neurodegeneration, decreased organ function, and eventually disease or death of the whole organism. The development of HTS techniques to identify mitochondrial toxicants will provide extensive databases with essential connections between mechanistic mitochondrial toxicity and chemical structure. Computational and bioinformatics approaches can be used to evaluate compound databases for specific chemical structures associated with toxicity, with the goal of developing quantitative structure-activity relationship (QSAR) models and mitochondrial toxicophores. Ultimately these predictive models will facilitate the identification of mitochondrial liabilities in consumer products, industrial compounds, pharmaceuticals and environmental hazards.
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23
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Meyer JN, Chan SSL. Sources, mechanisms, and consequences of chemical-induced mitochondrial toxicity. Toxicology 2017. [PMID: 28627407 DOI: 10.1016/j.tox.2017.06.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Joel N Meyer
- Nicholas School of the Environment and Integrated Toxicology and Environmental Health Program, Duke University, Durham, NC, 27708-0328, USA.
| | - Sherine S L Chan
- Drug Discovery and Biomedical Sciences, College of Pharmacy, Medical University of South Carolina, Charleston, SC, 29425, USA; Neuroene Therapeutics, Mt. Pleasant, SC 29464, USA.
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24
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Thompson RM, Dytfeld D, Reyes L, Robinson RM, Smith B, Manevich Y, Jakubowiak A, Komarnicki M, Przybylowicz-Chalecka A, Szczepaniak T, Mitra AK, Van Ness BG, Luczak M, Dolloff NG. Glutaminase inhibitor CB-839 synergizes with carfilzomib in resistant multiple myeloma cells. Oncotarget 2017; 8:35863-35876. [PMID: 28415782 PMCID: PMC5482623 DOI: 10.18632/oncotarget.16262] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Accepted: 03/01/2017] [Indexed: 01/10/2023] Open
Abstract
Curative responses in the treatment of multiple myeloma (MM) are limited by the emergence of therapeutic resistance. To address this problem, we set out to identify druggable mechanisms that convey resistance to proteasome inhibitors (PIs; e.g., bortezomib), which are cornerstone agents in the treatment of MM. In isogenic pairs of PI sensitive and resistant cells, we observed stark differences in cellular bioenergetics between the divergent phenotypes. PI resistant cells exhibited increased mitochondrial respiration driven by glutamine as the principle fuel source. To target glutamine-induced respiration in PI resistant cells, we utilized the glutaminase-1 inhibitor, CB-839. CB-839 inhibited mitochondrial respiration and was more cytotoxic in PI resistant cells as a single agent. Furthermore, we found that CB-839 synergistically enhanced the activity of multiple PIs with the most dramatic synergy being observed with carfilzomib (Crflz), which was confirmed in a panel of genetically diverse PI sensitive and resistant MM cells. Mechanistically, CB-839 enhanced Crflz-induced ER stress and apoptosis, characterized by a robust induction of ATF4 and CHOP and the activation of caspases. Our findings suggest that the acquisition of PI resistance involves adaptations in cellular bioenergetics, supporting the combination of CB-839 with Crflz for the treatment of refractory MM.
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Affiliation(s)
- Ravyn M. Thompson
- Department of Cell and Molecular Pharmacology & Experimental Therapeutics, Medical University of South Carolina, Charleston, SC, USA
| | - Dominik Dytfeld
- Karol Marcinkowski University of Medical Sciences, Poznan, Poland
| | - Leticia Reyes
- Department of Cell and Molecular Pharmacology & Experimental Therapeutics, Medical University of South Carolina, Charleston, SC, USA
| | - Reeder M. Robinson
- Department of Cell and Molecular Pharmacology & Experimental Therapeutics, Medical University of South Carolina, Charleston, SC, USA
| | - Brittany Smith
- Department of Cell and Molecular Pharmacology & Experimental Therapeutics, Medical University of South Carolina, Charleston, SC, USA
| | - Yefim Manevich
- Department of Cell and Molecular Pharmacology & Experimental Therapeutics, Medical University of South Carolina, Charleston, SC, USA
| | | | | | | | | | | | | | - Magdalena Luczak
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Nathan G. Dolloff
- Department of Cell and Molecular Pharmacology & Experimental Therapeutics, Medical University of South Carolina, Charleston, SC, USA
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25
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Marlatt VL, Martyniuk CJ. Biological responses to phenylurea herbicides in fish and amphibians: New directions for characterizing mechanisms of toxicity. Comp Biochem Physiol C Toxicol Pharmacol 2017; 194:9-21. [PMID: 28109972 DOI: 10.1016/j.cbpc.2017.01.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Revised: 01/11/2017] [Accepted: 01/13/2017] [Indexed: 12/19/2022]
Abstract
Urea-based herbicides are applied in agriculture to control broadleaf and grassy weeds, acting to either inhibit photosynthesis at photosystem II (phenylureas) or to inhibit acetolactate synthase acetohydroxyacid synthase (sulfonylureas). While there are different chemical formulas for urea-based herbicides, the phenylureas are a widely used class in North America and have been detected in aquatic environments due to agricultural run-off. Here, we summarize the current state of the literature, synthesizing data on phenylureas and their biological effects in two non-target animals, fish and amphibians, with a primary focus on diuron and linuron. In fish, although the acutely lethal effects of diuron in early life stages appear to be >1mg/L, recent studies measuring sub-lethal behavioural and developmental endpoints suggest that diuron causes adverse effects at lower concentrations (i.e. <0.1mg/L). Considerably less toxicity data exist for amphibians, and this is a knowledge gap in the literature. In terms of sub-lethal effects and mode of action (MOA), linuron is well documented to have anti-androgenic effects in vertebrates, including fish. However, there are other MOAs that are not adequately assessed in toxicology studies. In order to identify additional potential MOAs, we conducted in silico analyses for linuron and diuron that were based upon transcriptome studies and chemical structure-function relationships (i.e. ToxCast™, Prediction of Activity Spectra of Substances). Based upon these analyses, we suggest that steroid biosynthesis, cholesterol metabolism and pregnane X receptor activation are common targets, and offer some new endpoints for future investigations of phenylurea herbicides in non-target animals.
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Affiliation(s)
- Vicki L Marlatt
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada.
| | - Christopher J Martyniuk
- Department of Physiological Sciences and Center for Environmental and Human Toxicology, UF Genetics Institute, College of Veterinary Medicine, University of Florida, Gainesville, FL 326111, USA; Canadian Rivers Institute, Canada
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26
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Raftery TD, Jayasundara N, Di Giulio RT. A bioenergetics assay for studying the effects of environmental stressors on mitochondrial function in vivo in zebrafish larvae. Comp Biochem Physiol C Toxicol Pharmacol 2017; 192:23-32. [PMID: 27939721 PMCID: PMC5218841 DOI: 10.1016/j.cbpc.2016.12.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 12/01/2016] [Accepted: 12/02/2016] [Indexed: 01/29/2023]
Abstract
Mitochondria, an integral component of cellular energy metabolism and other key functions, are extremely vulnerable to damage by environmental stressors. Although methods to measure mitochondrial function in vitro exist, sensitive, medium- to high-throughput assays that assess respiration within physiologically-relevant whole organisms are needed to identify drugs and/or chemicals that disrupt mitochondrial function, particularly at sensitive early developmental stages. Consequently, we have developed and optimized an assay to measure mitochondrial bioenergetics in zebrafish larvae using the XFe24 Extracellular Flux Analyzer. To prevent larval movement from confounding oxygen consumption measurements, we relied on MS-222-based anesthetization. We obtained stable measurement values in the absence of effects on average oxygen consumption rate and subsequently optimized the use of pharmacological agents for metabolic partitioning. To confirm assay reproducibility we demonstrated that triclosan, a positive control, significantly decreased spare respiratory capacity. We then exposed zebrafish from 5 hours post-fertilization (hpf) to 6days post-fertilization (dpf) to three polycyclic aromatic hydrocarbons (PAHs) - benzo(a)pyrene (BaP), phenanthrene (Phe), and fluoranthene (FL) - and measured various fundamental parameters of mitochondrial respiratory chain function, including maximal respiration, spare respiratory capacity, mitochondrial and non-mitochondrial respiration. Exposure to all three PAHs decreased spare respiratory capacity and maximal respiration. Additionally, Phe exposure increased non-mitochondrial respiration and FL exposure decreased mitochondrial respiration and increased non-mitochondrial respiration. Overall, this whole organism-based assay provides a platform for examining mitochondrial dysfunction in vivo at critical developmental stages. It has important implications in biomedical sciences, toxicology and ecophysiology, particularly to examine the effects of environmental chemicals and/or drugs on mitochondrial bioenergetics.
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Affiliation(s)
- Tara D Raftery
- Nicholas School of the Environment, Duke University, Durham, NC 27708, United States.
| | - Nishad Jayasundara
- Nicholas School of the Environment, Duke University, Durham, NC 27708, United States
| | - Richard T Di Giulio
- Nicholas School of the Environment, Duke University, Durham, NC 27708, United States
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