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Peters MM, Brister JK, Tang EM, Zhang FW, Lucian VM, Trackey PD, Bone Z, Zimmerman JF, Jin Q, Burpo FJ, Parker KK. Self-organizing behaviors of cardiovascular cells on synthetic nanofiber scaffolds. APL Bioeng 2023; 7:046114. [PMID: 38046543 PMCID: PMC10693444 DOI: 10.1063/5.0172423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Accepted: 11/16/2023] [Indexed: 12/05/2023] Open
Abstract
In tissues and organs, the extracellular matrix (ECM) helps maintain inter- and intracellular architectures that sustain the structure-function relationships defining physiological homeostasis. Combining fiber scaffolds and cells to form engineered tissues is a means of replicating these relationships. Engineered tissues' fiber scaffolds are designed to mimic the topology and chemical composition of the ECM network. Here, we asked how cells found in the heart compare in their propensity to align their cytoskeleton and self-organize in response to topological cues in fibrous scaffolds. We studied cardiomyocytes, valvular interstitial cells, and vascular endothelial cells as they adapted their inter- and intracellular architectures to the extracellular space. We used focused rotary jet spinning to manufacture aligned fibrous scaffolds to mimic the length scale and three-dimensional (3D) nature of the native ECM in the muscular, valvular, and vascular tissues of the heart. The representative cardiovascular cell types were seeded onto fiber scaffolds and infiltrated the fibrous network. We measured different cell types' propensity for cytoskeletal alignment in response to fiber scaffolds with differing levels of anisotropy. The results indicated that valvular interstitial cells on moderately anisotropic substrates have a higher propensity for cytoskeletal alignment than cardiomyocytes and vascular endothelial cells. However, all cell types displayed similar levels of alignment on more extreme (isotropic and highly anisotropic) fiber scaffold organizations. These data suggest that in the hierarchy of signals that dictate the spatiotemporal organization of a tissue, geometric cues within the ECM and cellular networks may homogenize behaviors across cell populations and demographics.
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Affiliation(s)
- Michael M. Peters
- Disease Biophysics Group, Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, Massachusetts 02134, USA
| | - Jackson K. Brister
- Disease Biophysics Group, Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, Massachusetts 02134, USA
| | - Edward M. Tang
- Department of Chemistry and Life Science, United States Military Academy, West Point, New York 10996, USA
| | - Felita W. Zhang
- Department of Chemistry and Life Science, United States Military Academy, West Point, New York 10996, USA
| | - Veronica M. Lucian
- Department of Chemistry and Life Science, United States Military Academy, West Point, New York 10996, USA
| | - Paul D. Trackey
- Department of Chemistry and Life Science, United States Military Academy, West Point, New York 10996, USA
| | - Zachary Bone
- Department of Chemistry and Life Science, United States Military Academy, West Point, New York 10996, USA
| | - John F. Zimmerman
- Disease Biophysics Group, Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, Massachusetts 02134, USA
| | - Qianru Jin
- Disease Biophysics Group, Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, Massachusetts 02134, USA
| | - F. John Burpo
- Department of Chemistry and Life Science, United States Military Academy, West Point, New York 10996, USA
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Choi S, Lee KY, Kim SL, MacQueen LA, Chang H, Zimmerman JF, Jin Q, Peters MM, Ardoña HAM, Liu X, Heiler AC, Gabardi R, Richardson C, Pu WT, Bausch AR, Parker KK. Fibre-infused gel scaffolds guide cardiomyocyte alignment in 3D-printed ventricles. Nat Mater 2023; 22:1039-1046. [PMID: 37500957 PMCID: PMC10686196 DOI: 10.1038/s41563-023-01611-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 06/19/2023] [Indexed: 07/29/2023]
Abstract
Hydrogels are attractive materials for tissue engineering, but efforts to date have shown limited ability to produce the microstructural features necessary to promote cellular self-organization into hierarchical three-dimensional (3D) organ models. Here we develop a hydrogel ink containing prefabricated gelatin fibres to print 3D organ-level scaffolds that recapitulate the intra- and intercellular organization of the heart. The addition of prefabricated gelatin fibres to hydrogels enables the tailoring of the ink rheology, allowing for a controlled sol-gel transition to achieve precise printing of free-standing 3D structures without additional supporting materials. Shear-induced alignment of fibres during ink extrusion provides microscale geometric cues that promote the self-organization of cultured human cardiomyocytes into anisotropic muscular tissues in vitro. The resulting 3D-printed ventricle in vitro model exhibited biomimetic anisotropic electrophysiological and contractile properties.
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Affiliation(s)
- Suji Choi
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA
| | - Keel Yong Lee
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA
- Department of Integrative Bioscience and Biotechnology, Sejong University, Seoul, Republic of Korea
| | - Sean L Kim
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA
| | - Luke A MacQueen
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA
| | - Huibin Chang
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA
| | - John F Zimmerman
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA
| | - Qianru Jin
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA
| | - Michael M Peters
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA
| | - Herdeline Ann M Ardoña
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA
- Department of Chemical and Biomolecular Engineering, Samueli School of Engineering, University of California, Irvine, CA, USA
| | - Xujie Liu
- Department of Cardiology, Boston Children's Hospital, Boston, MA, USA
- Fuwai Hospital Chinese Academy of Medical Sciences, Shenzhen, China
| | - Ann-Caroline Heiler
- Department of Bioscience, TUM School of Natural Sciences, Technische Universität München, Garching, Germany
- Center for Functional Protein Assemblies, Technische Universität München, Garching, Germany
- Center for Organoid Systems (COS), Technische Universität München, Garching, Germany
| | - Rudy Gabardi
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA
| | - Collin Richardson
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA
| | - William T Pu
- Department of Cardiology, Boston Children's Hospital, Boston, MA, USA
- Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA
| | - Andreas R Bausch
- Department of Bioscience, TUM School of Natural Sciences, Technische Universität München, Garching, Germany
- Center for Functional Protein Assemblies, Technische Universität München, Garching, Germany
- Center for Organoid Systems (COS), Technische Universität München, Garching, Germany
- Max Planck School Matter to Life, Max Planck Schools, Heidelberg, Germany
| | - Kevin Kit Parker
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA.
- Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA.
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA.
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Chang H, Liu Q, Zimmerman JF, Lee KY, Jin Q, Peters MM, Rosnach M, Choi S, Kim SL, Ardoña HAM, MacQueen LA, Chantre CO, Motta SE, Cordoves EM, Parker KK. Recreating the heart's helical structure-function relationship with focused rotary jet spinning. Science 2022; 377:180-185. [PMID: 35857545 PMCID: PMC10077766 DOI: 10.1126/science.abl6395] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Helical alignments within the heart's musculature have been speculated to be important in achieving physiological pumping efficiencies. Testing this possibility is difficult, however, because it is challenging to reproduce the fine spatial features and complex structures of the heart's musculature using current techniques. Here we report focused rotary jet spinning (FRJS), an additive manufacturing approach that enables rapid fabrication of micro/nanofiber scaffolds with programmable alignments in three-dimensional geometries. Seeding these scaffolds with cardiomyocytes enabled the biofabrication of tissue-engineered ventricles, with helically aligned models displaying more uniform deformations, greater apical shortening, and increased ejection fractions compared with circumferential alignments. The ability of FRJS to control fiber arrangements in three dimensions offers a streamlined approach to fabricating tissues and organs, with this work demonstrating how helical architectures contribute to cardiac performance.
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Affiliation(s)
- Huibin Chang
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Science, Harvard University, Boston, MA 02134, USA
| | - Qihan Liu
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Science, Harvard University, Boston, MA 02134, USA
- Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - John F. Zimmerman
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Science, Harvard University, Boston, MA 02134, USA
| | - Keel Yong Lee
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Science, Harvard University, Boston, MA 02134, USA
| | - Qianru Jin
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Science, Harvard University, Boston, MA 02134, USA
| | - Michael M. Peters
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Science, Harvard University, Boston, MA 02134, USA
| | - Michael Rosnach
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Science, Harvard University, Boston, MA 02134, USA
| | - Suji Choi
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Science, Harvard University, Boston, MA 02134, USA
| | - Sean L. Kim
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Science, Harvard University, Boston, MA 02134, USA
| | - Herdeline Ann M. Ardoña
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Science, Harvard University, Boston, MA 02134, USA
- Department of Chemical and Biomolecular Engineering, Samueli School of Engineering, University of California, Irvine, CA 92697, USA
| | - Luke A. MacQueen
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Science, Harvard University, Boston, MA 02134, USA
| | - Christophe O. Chantre
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Science, Harvard University, Boston, MA 02134, USA
| | - Sarah E. Motta
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Science, Harvard University, Boston, MA 02134, USA
- Institute for Regenerative Medicine, University of Zurich, Zurich, Switzerland
| | - Elizabeth M. Cordoves
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Science, Harvard University, Boston, MA 02134, USA
| | - Kevin Kit Parker
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Science, Harvard University, Boston, MA 02134, USA
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Chang H, Xu J, Macqueen LA, Aytac Z, Peters MM, Zimmerman JF, Xu T, Demokritou P, Parker KK. High-throughput coating with biodegradable antimicrobial pullulan fibres extends shelf life and reduces weight loss in an avocado model. Nat Food 2022; 3:428-436. [PMID: 37118042 DOI: 10.1038/s43016-022-00523-w] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 04/28/2022] [Indexed: 11/09/2022]
Abstract
Food waste and food safety motivate the need for improved food packaging solutions. However, current films/coatings addressing these issues are often limited by inefficient release dynamics that require large quantities of active ingredients. Here we developed antimicrobial pullulan fibre (APF)-based packaging that is biodegradable and capable of wrapping food substrates, increasing their longevity and enhancing their safety. APFs were spun using a high-throughput system, termed focused rotary jet spinning, with water as the only solvent, allowing the incorporation of naturally derived antimicrobial agents. Using avocados as a representative example, we demonstrate that APF-coated samples had their shelf life extended by inhibited proliferation of natural microflora, and lost less weight than uncoated control samples. This work offers a promising technique to produce scalable, low-cost and environmentally friendly biodegradable antimicrobial packaging systems.
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O’Connor BB, Pope BD, Peters MM, Ris-Stalpers C, Parker KK. The role of extracellular matrix in normal and pathological pregnancy: Future applications of microphysiological systems in reproductive medicine. Exp Biol Med (Maywood) 2020; 245:1163-1174. [PMID: 32640894 PMCID: PMC7400725 DOI: 10.1177/1535370220938741] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
IMPACT STATEMENT Extracellular matrix in the womb regulates the initiation, progression, and completion of a healthy pregnancy. The composition and physical properties of extracellular matrix in the uterus and at the maternal-fetal interface are remodeled at each gestational stage, while maladaptive matrix remodeling results in obstetric disease. As in vitro models of uterine and placental tissues, including micro-and milli-scale versions of these organs on chips, are developed to overcome the inherent limitations of studying human development in vivo, we can isolate the influence of cellular and extracellular components in healthy and pathological pregnancies. By understanding and recreating key aspects of the extracellular microenvironment at the maternal-fetal interface, we can engineer microphysiological systems to improve assisted reproduction, obstetric disease treatment, and prenatal drug safety.
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Affiliation(s)
- Blakely B O’Connor
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering; Harvard John A. Paulson School of Engineering and Applied Sciences; Harvard University, Cambridge, MA 02138, USA
| | - Benjamin D Pope
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering; Harvard John A. Paulson School of Engineering and Applied Sciences; Harvard University, Cambridge, MA 02138, USA
| | - Michael M Peters
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering; Harvard John A. Paulson School of Engineering and Applied Sciences; Harvard University, Cambridge, MA 02138, USA
| | - Carrie Ris-Stalpers
- Department of Gynecology and Obstetrics, Academic Reproduction and Development, Amsterdam UMC, University of Amsterdam, Amsterdam 1105, The Netherlands
| | - Kevin K Parker
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering; Harvard John A. Paulson School of Engineering and Applied Sciences; Harvard University, Cambridge, MA 02138, USA
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Berg EL, Pride MC, Petkova SP, Lee RD, Copping NA, Shen Y, Adhikari A, Fenton TA, Pedersen LR, Noakes LS, Nieman BJ, Lerch JP, Harris S, Born HA, Peters MM, Deng P, Cameron DL, Fink KD, Beitnere U, O'Geen H, Anderson AE, Dindot SV, Nash KR, Weeber EJ, Wöhr M, Ellegood J, Segal DJ, Silverman JL. Translational outcomes in a full gene deletion of ubiquitin protein ligase E3A rat model of Angelman syndrome. Transl Psychiatry 2020; 10:39. [PMID: 32066685 PMCID: PMC7026078 DOI: 10.1038/s41398-020-0720-2] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 12/17/2019] [Accepted: 01/02/2020] [Indexed: 12/17/2022] Open
Abstract
Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by developmental delay, impaired communication, motor deficits and ataxia, intellectual disabilities, microcephaly, and seizures. The genetic cause of AS is the loss of expression of UBE3A (ubiquitin protein ligase E6-AP) in the brain, typically due to a deletion of the maternal 15q11-q13 region. Previous studies have been performed using a mouse model with a deletion of a single exon of Ube3a. Since three splice variants of Ube3a exist, this has led to a lack of consistent reports and the theory that perhaps not all mouse studies were assessing the effects of an absence of all functional UBE3A. Herein, we report the generation and functional characterization of a novel model of Angelman syndrome by deleting the entire Ube3a gene in the rat. We validated that this resulted in the first comprehensive gene deletion rodent model. Ultrasonic vocalizations from newborn Ube3am-/p+ were reduced in the maternal inherited deletion group with no observable change in the Ube3am+/p- paternal transmission cohort. We also discovered Ube3am-/p+ exhibited delayed reflex development, motor deficits in rearing and fine motor skills, aberrant social communication, and impaired touchscreen learning and memory in young adults. These behavioral deficits were large in effect size and easily apparent in the larger rodent species. Low social communication was detected using a playback task that is unique to rats. Structural imaging illustrated decreased brain volume in Ube3am-/p+ and a variety of intriguing neuroanatomical phenotypes while Ube3am+/p- did not exhibit altered neuroanatomy. Our report identifies, for the first time, unique AS relevant functional phenotypes and anatomical markers as preclinical outcomes to test various strategies for gene and molecular therapies in AS.
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Affiliation(s)
- E L Berg
- MIND Institute and Department of Psychiatry and Behavioral Sciences, University of California Davis School of Medicine, Sacramento, CA, USA
| | - M C Pride
- MIND Institute and Department of Psychiatry and Behavioral Sciences, University of California Davis School of Medicine, Sacramento, CA, USA
| | - S P Petkova
- MIND Institute and Department of Psychiatry and Behavioral Sciences, University of California Davis School of Medicine, Sacramento, CA, USA
| | - R D Lee
- MIND Institute and Department of Psychiatry and Behavioral Sciences, University of California Davis School of Medicine, Sacramento, CA, USA
| | - N A Copping
- MIND Institute and Department of Psychiatry and Behavioral Sciences, University of California Davis School of Medicine, Sacramento, CA, USA
| | - Y Shen
- MIND Institute and Department of Psychiatry and Behavioral Sciences, University of California Davis School of Medicine, Sacramento, CA, USA
| | - A Adhikari
- MIND Institute and Department of Psychiatry and Behavioral Sciences, University of California Davis School of Medicine, Sacramento, CA, USA
| | - T A Fenton
- MIND Institute and Department of Psychiatry and Behavioral Sciences, University of California Davis School of Medicine, Sacramento, CA, USA
| | - L R Pedersen
- MIND Institute and Department of Psychiatry and Behavioral Sciences, University of California Davis School of Medicine, Sacramento, CA, USA
| | - L S Noakes
- Mouse Imaging Centre, Toronto Centre for Phenogenomics, The Hospital for Sick Children, Toronto, ON, Canada
| | - B J Nieman
- Mouse Imaging Centre, Toronto Centre for Phenogenomics, The Hospital for Sick Children, Toronto, ON, Canada
| | - J P Lerch
- Wellcome Centre for Integrative Neuroimaging, The University of Oxford, Oxford, UK
| | - S Harris
- Department of Pediatrics and Neurology, Baylor College of Medicine, Houston, TX, USA
| | - H A Born
- Department of Pediatrics and Neurology, Baylor College of Medicine, Houston, TX, USA
| | - M M Peters
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, FL, USA
| | - P Deng
- Stem Cell Program, Institute for Regenerative Cures, and Department of Neurology, University of California Davis School of Medicine, Sacramento, CA, USA
| | - D L Cameron
- Stem Cell Program, Institute for Regenerative Cures, and Department of Neurology, University of California Davis School of Medicine, Sacramento, CA, USA
| | - K D Fink
- Stem Cell Program, Institute for Regenerative Cures, and Department of Neurology, University of California Davis School of Medicine, Sacramento, CA, USA
| | - U Beitnere
- MIND Institute, Genome Center, and Department of Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
| | - H O'Geen
- MIND Institute, Genome Center, and Department of Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
| | - A E Anderson
- Department of Pediatrics and Neurology, Baylor College of Medicine, Houston, TX, USA
| | - S V Dindot
- Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, USA
| | - K R Nash
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, FL, USA
| | - E J Weeber
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, FL, USA
| | - M Wöhr
- Behavioral Neuroscience, Experimental and Biological Psychology, Philipps-University of Marburg, Marburg, Germany
| | - J Ellegood
- Mouse Imaging Centre, Toronto Centre for Phenogenomics, The Hospital for Sick Children, Toronto, ON, Canada
| | - D J Segal
- MIND Institute, Genome Center, and Department of Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
| | - J L Silverman
- MIND Institute and Department of Psychiatry and Behavioral Sciences, University of California Davis School of Medicine, Sacramento, CA, USA.
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Abstract
BACKGROUND Studies examining the physiological interactions of oxygen (O(2)) and bronchodilators (BD) during exercise in chronic obstructive pulmonary disease (COPD) should provide new insights into mechanisms of exercise intolerance. We examined the effects of O(2) and BD, alone and in combination, on dyspnoea, ventilation (e), breathing pattern, operating lung volumes, and exercise endurance. METHODS In a randomised, double blind, crossover study, 16 patients with COPD (mean (SE) FEV(1) 43(3)% predicted) performed pulmonary function tests and an incremental exercise test, then completed four visits in which they received either nebulised BD (ipratropium 0.5 mg + salbutamol 2.5 mg) or placebo (PL) with either 50% O(2) or room air (RA). After 90-105 minutes the patients performed pulmonary function tests, then breathed RA or O(2) during symptom limited constant load exercise at 75% peak work rate. RESULTS With BD the mean (SE) increase in inspiratory capacity (IC) was 0.3 (0.1) l (p<0.05) at rest and during exercise, permitting greater tidal volume (Vt) expansion during exercise and a greater peak e. With O(2), e decreased during exercise as a result of decreased breathing frequency (F), with no significant change in IC. During exercise with BD+O(2), IC and Vt increased, F decreased, and e did not change. Dyspnoea decreased with all interventions at a standardised time during exercise compared with PL+RA (p<0.05). Endurance time was significantly (p<0.05) greater with BD+O(2) (10.4 (1.6) min) than with O(2) (8.5 (1.4) min), BD (7.1 (1.3) min) and PL+RA (5.4 (0.9) min). CONCLUSION By combining the benefits of BD (reduced hyperinflation) and O(2) (reduced ventilatory drive), additive effects on exercise endurance were observed in patients with normoxic COPD.
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Affiliation(s)
- M M Peters
- Department of Medicine, Respiratory Investigation Unit, Queen's University, Kingston, Ontario, Canada
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Richardson KA, Peters MM, Wong BA, Megens RH, van Elburg PA, Booth ED, Boogaard PJ, Bond JA, Medinsky MA, Watson WP, van Sittert NJ. Quantitative and qualitative differences in the metabolism of 14C-1,3-butadiene in rats and mice: relevance to cancer susceptibility. Toxicol Sci 1999; 49:186-201. [PMID: 10416264 DOI: 10.1093/toxsci/49.2.186] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
1,3-Butadiene (butadiene) is a potent carcinogen in mice, but not in rats. Metabolic studies may provide an explanation of these species differences and their relevance to humans. Male Sprague-Dawley rats and B6C3F1 mice were exposed for 6 h to 200 ppm [2,3-14C]-butadiene (specific radioactivity [sa] 20 mCi/mmol) in a Cannon nose-only system. Radioactivity in urine, feces, exhaled volatiles and 14C-CO2 were measured during and up to 42 h after exposure. The total uptake of butadiene by rats and mice under these experimental conditions was 0.19 and 0.38 mmol (equivalent to 3.8 and 7.5 mCi) per kg body weight, respectively. In the rat, 40% of the recovered radioactivity was exhaled as 14C-CO2, 70% of which was trapped during the 6-h exposure period. In contrast, only 6% was exhaled as 14C-CO2 by mice, 3% during the 6-h exposure and 97% in the 42 h following cessation of exposure. The formation of 14C-CO2 from [2,3-14C]-labeled butadiene indicated a ready biodegradability of butadiene. Radioactivity excreted in urine accounted for 42% of the recovered radioactivity from rats and 71% from mice. Small amounts of radioactivity were recovered in feces, exhaled volatiles and carcasses. Although there was a large measure of commonality, the exposure to butadiene also led to the formation of different metabolites in rats and mice. These metabolites were not found after administration of [4-14C]-1,2-epoxy-3-butene to animals by i.p. injection. The results show that the species differences in the metabolism of butadiene are not simply confined to the quantitative formation of epoxides, but also reflect a species-dependent selection of metabolic pathways. No metabolites other than those formed via an epoxide intermediate were identified in the urine of rats or mice after exposure to 14C-butadiene. These findings may have relevance for the prediction of butadiene toxicity and provide a basis for a revision of the existing physiologically based pharmacokinetic models.
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Affiliation(s)
- K A Richardson
- Shell International Chemicals, Toxicology Department, Shell Research and Technology Centre Amsterdam, The Netherlands
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Richardson KA, Peters MM, Megens RH, van Elburg PA, Golding BT, Boogaard PJ, Watson WP, van Sittert NJ. Identification of novel metabolites of butadiene monoepoxide in rats and mice. Chem Res Toxicol 1998; 11:1543-55. [PMID: 9860500 DOI: 10.1021/tx970175v] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Differences in the metabolism of 1,3-butadiene (Bd) in rats and mice may account for the observed species difference in carcinogenicity. Previous studies of the metabolic fate of Bd have identified epoxide formation as a key metabolic transformation which gives 1, 2-epoxy-3-butene (BMO), although some evidence of aldehyde metabolites is reported. In this study, male Sprague-Dawley rats and male B6C3F1 mice received single doses of [4-14C]BMO at 1, 5, 20, and 50 mg/kg of body weight (0.014, 0.071, 0.286, and 0.714 mmol/kg of body weight). Analysis of urinary metabolites indicated that both species preferentially metabolize BMO by direct reaction with GSH when given by ip administration. The excretion of (R)-2-(N-acetyl-L-cystein-S-yl)-1-hydroxybut-3-ene (IIa), 1-(N-acetyl-L-cystein-S-yl)-2-(S)-hydroxybut-3-ene (IIb), 1-(N-acetyl-L-cystein-S-yl)-2-(R)-hydroxybut-3-ene (IIc), and (S)-2-(N-acetyl-L-cystein-S-yl)-1-hydroxybut-3-ene (IId) accounted for 48-64% of urinary radioactivity in rats and 46-54% in mice. The metabolites originating from the R-stereoisomer of BMO (IIc and IId) predominated over those arising from the S-stereoisomer (IIa and IIb) in both species. IIc was formed preferentially in mice and IId in rats. The corresponding mercaptoacetic acids, S-(1-hydroxybut-3-en-2-yl)mercaptoacetic acid (IIf) and S-(2-hydroxybut-3-en-1-yl)mercaptoacetic acid (IIg), were identified only in mouse urine (ca. 20% of the recovered radioactivity). 4-(N-Acetyl-L-cystein-S-yl)-1,2-dihydroxybutane (Ia), a metabolite derived from hydrolysis of BMO, accounted for 10-17% of the radioactivity in rat and 6-10% in mouse urine. 4-(N-Acetyl-L-cystein-S-yl)-2-hydroxybutanoic acid (Ib), 3-(N-acetyl-L-cystein-S-yl)propan-1-ol (Ic), and 3-(N-acetyl-L-cystein-S-yl)propanoic acid (Id), also derived from the hydrolysis of BMO, were only present in the rat. Metabolites of 1,2,3,4-diepoxybutane (DEB) were not detected after administration of BMO in rat or mouse urine. This study showed both quantitative and qualitative differences in the metabolism of BMO with varying doses and between species. The data aid in the safety evaluation of Bd and contribute to the interpretation of mathematical models developed for quantitative risk assessment and extrapolation of animals to humans.
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Affiliation(s)
- K A Richardson
- Toxicology Department, Shell Research and Technology Centre, Shell International Chemicals, P.O. Box 38000, 1030 BN Amsterdam, The Netherlands
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Peters MM, Jones TW, Monks TJ, Lau SS. Cytotoxicity and cell-proliferation induced by the nephrocarcinogen hydroquinone and its nephrotoxic metabolite 2,3,5-(tris-glutathion-S-yl)hydroquinone. Carcinogenesis 1997; 18:2393-401. [PMID: 9450487 DOI: 10.1093/carcin/18.12.2393] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Hydroquinone, an intermediate used in the chemical industry and a metabolite of benzene, is a nephrocarcinogen in the 2-year National Toxicology Program bioassay in male Fischer 344 rats. Current evidence suggests that certain chemicals may induce carcinogenesis by a mechanism involving cytotoxicity, followed by sustained regenerative hyperplasia and ultimately tumor formation. Glutathione (GSH) conjugates of a variety of hydroquinones are potent nephrotoxicants, and we now report on the effect of hydroquinone and 2,3,5-(tris-glutathion-S-yl)hydroquinone, on site-selective cytotoxicity and cell proliferation in rat kidney. Male Fischer 344 rats (160-200 g) were treated with hydroquinone (1.8 mmol/kg or 4.5 mmol/kg, p.o.) or 2,3,5-(tris-glutathion-S-yl)hydroquinone (7.5 micromol/kg; 1.2-1.5 micromol/rat, i.v.), and blood urea nitrogen (BUN), urinary gamma-glutamyl transpeptidase (gamma-GT), alkaline phosphatase (ALP), glutathione-S-transferase (GST) and glucose were measured as indices of nephrotoxicity. Hydroquinone (1.8 mmol/kg, p.o.) is nephrotoxic in some rats, but not others, but cell proliferation (BrDU incorporation) in proximal tubular cells of the S3M region correlates with the degree of toxicity in individual rats. At 4.5 mmol/kg, hydroquinone causes significant increases in the urinary excretion of gamma-GT, ALP and GST. Pretreatment of rats with acivicin prevents hydroquinone-mediated nephrotoxicity, indicating that toxicity is dependent on the formation of metabolites that require processing by gamma-GT. Consistent with this view, 2,3,5-(tris-glutathion-S-yl)hydroquinone, a metabolite of hydroquinone, causes increases in BUN, urinary gamma-GT and ALP, all of which are maximal 12 h after administration of 2,3,5-(tris-glutathion-S-yl)hydroquinone. In contrast, the maximal excretion of GST and glucose occurs after 24 h. By 72 h, BUN and glucose concentrations return to control levels, while gamma-GT, ALP and GST remain slightly elevated. Examination of kidney slices by light microscopy revealed the presence of tubular necrosis in the S3M segment of the proximal tubule, extending into the medullary rays. Cell proliferation rates in this region were 2.4, 6.9, 15.3 and 14.3% after 12, 24, 48 and 72 h, respectively, compared to 0.8-2.4% in vehicle controls. Together with the metabolic data, the results indicate a role for hydroquinone-thioether metabolites in hydroquinone toxicity and carcinogenicity.
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Affiliation(s)
- M M Peters
- Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin, 78712, USA
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Peters MM, Rivera MI, Jones TW, Monks TJ, Lau SS. Glutathione conjugates of tert-butyl-hydroquinone, a metabolite of the urinary tract tumor promoter 3-tert-butyl-hydroxyanisole, are toxic to kidney and bladder. Cancer Res 1996; 56:1006-11. [PMID: 8640754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
3-tert-Butyl-4-hydroxyanisole and tert-butyl-hydroquinone (TBHQ) are antioxidants known to promote renal and bladder carcinogenesis in the rat, although the mechanisms of these effects are unclear. Because glutathione (GSH) conjugates of a variety of hydroquinones are nephrotoxic, and because 2-tert-butyl-5-(glutathion-S-yl)hydroquinone [5-(GSyl)TBHQ], 2-tert-butyl-6-(glutathion-S-yl)hydroquinone [6-(GSyl)TBHQ], and 2-tert-butyl-3,6-bis-(glutathion-S-yl)hydroquinone [3,6-bis-(GSyl)-TBHQ] have been identified recently as metabolites of TBHQ in the male rat, we investigated the effects of these metabolites in the male rat. At the highest dose tested (400 micromol/kg,i.v.) 5-(Gsyl)TBHQ and 6-(GSyl)TBHQ caused 2-fold increases in the urinary excretion of gamma-glutamyl transpeptidase and alkaline phosphatase, and pigments arising from the polymerization of metabolites were deposited in the kidney. 3,6-bis-(GSyl)TBHQ (200 micromol/kg) was the most potent of the GSH conjugates tested and produced significant increases in the urinary excretion of gamma-glutamyl transpeptidase, alkaline phosphatase, lactate dehydrogenase, and glucose (2-, 2-, 22-, and 11-fold increases, respectively). Alterations in the biochemical parameters correlated with the degree of single cell and tubular necrosis in the S(3)-M segment of the proximal tubule, as observed by light microscopy. In addition to nephrotoxicity, 3,6-bis-(GSyl)TBHQ increased the bladder wet weight 2-fold and caused severe hemorrhaging of the bladder. The half-wave oxidation potentials of 5-(Gsyl)TBHQ and 6-(GSyl)TBHQ were similar to that of TBHQ, whereas the half-wave oxidation potential of 3,6-bis-(Gsyl)TBHQ was approximately 100 mV higher than that of TBHQ. The TBHQ-GSH conjugates also catalyzed the formation of 8- hydroxydeoxyguanosine, indicating that GSH conjugation does not impair the redox activity of TBHQ. Because some chemicals may induce carcinogenesis by a mechanism involving cytotoxicity followed by sustained regenerative hyperplasia, our results suggest that the toxicity of GSH conjugates of TBHQ to kidney and bladder may contribute to the promoting effect of 3-tert-butyl-4-hydroxyanisole and TBHQ in these tissues.
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Affiliation(s)
- M M Peters
- Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin, 78712 USA
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Peters MM, Lau SS, Dulik D, Murphy D, van Ommen B, van Bladeren PJ, Monks TJ. Metabolism of tert-butylhydroquinone to S-substituted conjugates in the male Fischer 344 rat. Chem Res Toxicol 1996; 9:133-9. [PMID: 8924582 DOI: 10.1021/tx950122i] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
tert-Butyl-4-hydroxyanisole (BHA) and its demethylated analog, tert-butyl-hydroquinone (TBHQ), are antioxidants used in food. Both BHA and TBHQ have been shown to promote kidney and bladder carcinogenesis in the rat. We have previously demonstrated that glutathione (GSH) conjugates of a variety of hydroquinones are nephrotoxic and proposed that GSH conjugation serves to target these compounds to the kidney. In the present study, we examined the metabolism of TBHQ, focusing on the formation of potentially nephrotoxic sulfur-containing metabolites. 2-tert-Butyl-5-glutathion-S-ylhydroquinone, 2-tert-butyl-6-glutathion-S-ylhydroquinone, and 2-tert-butyl-3,6-bisglutathion-S-ylhydroquinone were identified as biliary metabolites of TBHQ (1.0 mmol/kg, ip) in male F344 rats, accounting for 2.2% of the dose. Liquid chromatography/mass spectroscopic analysis of urine also revealed the presence of additional sulfur-containing metabolites, tentatively identified as 2,5-dihydroxy-3-tert-butyl-thiophenol, 2,5-dihydroxy-4-tert-butylthiophenol, and their S-methyl derivatives. No mercapturic acids of TBHQ were found in the urine. The major biliary and urinary metabolites were TBHQ-glucuronide and TBHQ-sulfate, with a trace of TBHQ excreted unchanged. The results indicate that TBHQ undergoes oxidation and GSH conjugation in vivo in the male F344 rat. These conjugates are excreted into bile and undergo further metabolism prior to excretion in urine. Formation of the S-containing metabolites of TBHQ may occur in amounts sufficient to play a role in the toxicity of TBHQ to kidney and bladder.
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Affiliation(s)
- M M Peters
- Division of Pharmacology and Toxicology, University of Texas at Austin 78712, USA
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Lau SS, Peters MM, Kleiner HE, Canales PL, Monks TJ. Linking the metabolism of hydroquinone to its nephrotoxicity and nephrocarcinogenicity. Adv Exp Med Biol 1996; 387:267-73. [PMID: 8794221 DOI: 10.1007/978-1-4757-9480-9_35] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- S S Lau
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, 78712, USA
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Monks TJ, Rivera MI, Mertens JJ, Peters MM, Lau SS. The kidney as a target for biological reactive metabolites: linking metabolism to toxicity. Adv Exp Med Biol 1996; 387:203-12. [PMID: 8794214 DOI: 10.1007/978-1-4757-9480-9_28] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- T J Monks
- Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin, USA
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Abstract
The metabolism of trans-[3-14C]cinnamaldehyde was investigated in male and female Fischer 344 rats and CD1 mice at doses of 2 and 250 mg/kg body weight given by ip injection and in males at 250 mg/kg by oral gavage. Some 94% of the administered dose was recovered in the excreta in 72 hr in both species with most (75-81%) present in the 0-24-hr urine. Less than 2% of the administered dose was found in the carcasses at 72 hr after dosing. Urinary metabolites were identified by their chromatographic characteristics. In both species the major urinary metabolite was hippuric acid accompanied by 3-hydroxy-3-phenylpropionic acid, benzoic acid and benzoyl glucuronide. The glycine conjugate of cinnamic acid was formed to a considerable extent only in the mouse. The oxidative metabolism of cinnamaldehyde essentially follows that of cinnamic acid, by beta-oxidation analogous to that of fatty acids. Apart from the metabolites common to cinnamic acid and cinnamaldehyde, 7% of 0-24-hr urinary 14C was accounted for by two new metabolites in the rat and three in the mouse, which have been shown in other work to arise from a second pathway of cinnamaldehyde metabolism involving conjugation with glutathione. The excretion pattern and metabolic profile of cinnamaldehyde in rats and mice are not systematically affected by sex, dose size and route of administration. The data are discussed in terms of their relevance to the safety evaluation of trans-cinnamaldehyde, particularly the validity or otherwise of extrapolation of toxicity data from high to low dose.
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Affiliation(s)
- M M Peters
- Department of Pharmacology and Toxicology, St Mary's Hospital Medical School, Imperial College of Science, Technology and Medicine, London
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Petrek JA, Peters MM, Cirrincione C, Thaler HT. A prospective randomized trial of single versus multiple drains in the axilla after lymphadenectomy. Surg Gynecol Obstet 1992; 175:405-9. [PMID: 1440167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Increasing duration and amount of postoperative fluid formation after axillary lymphadenectomy delays final healing. We postulated that multiple drains (instead of a single drain) might decrease postoperative fluid accumulation by their greater proximity to points of leakage. We randomized 65 women with clinical stage I or II carcinoma of the breast to single or multiple drains. They were stratified for axillary dissection or modified radical mastectomy. For axillary dissection, randomization to multiple drains meant placement of four catheters in the axilla, and randomized to the single drain, one catheter in the axilla. For modified radical mastectomy, the patients randomized to multiple drains received four catheters in the axilla and one catheter under the inferior flap; the patients randomized to single drains had one catheter in the axilla and one catheter under the inferior flap. All catheters exited separately. The two arms (single versus multiple drains) were determined to be homogeneous in other variables that may affect postoperative fluid formation--age, size of the breast, weight, height, obesity, presence of previous surgical biopsy, excision of pectoralis minor muscle, excision of thoracodorsal complex, level of axillary dissection, number of lymph nodes, number and proportion of positive lymph nodes and whether or not the dominant hand was on the side operated upon. Single versus multiple drains had no clinically significant effect on the amount or duration of drainage, as an inpatient or outpatient, or total. We recommend a single drain to the axilla after lymphadenectomy.
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Affiliation(s)
- J A Petrek
- Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, New York 10021
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Peters MM, Walters DG, van Ommen B, van Bladeren PJ, Lake BG. Effect of inducers of cytochrome P-450 on the metabolism of [3-14C]coumarin by rat hepatic microsomes. Xenobiotica 1991; 21:499-514. [PMID: 1897250 DOI: 10.3109/00498259109039490] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
1. The metabolism of [3-14C]coumarin has been studied in rat hepatic microsomes and with two purified cytochrome P-450 isoenzymes. 2. [3-14C]Coumarin was converted by liver microsomes to several polar products including 3- and/or 5-hydroxycoumarin, omicron-hydroxyphenylacetic acid and a major unidentified novel coumarin metabolite. 3. [3-14C]Coumarin was also converted to reactive metabolite(s) as indicated by covalent binding to proteins, and by the depletion of reduced glutathione added to the microsomal incubations. 4. [3-14C]Coumarin metabolism to polar and covalently bound metabolites by rat liver microsomes was induced by pretreatment with phenobarbitone, 3-methylcholanthrene, beta-naphthoflavone, Aroclor 1254 and isosafrole; but not by dexamethasone or nafenopin. 5. The profile of [3-14C]coumarin metabolism to polar products was similar in control and pretreated liver microsomes and in incubations with purified cytochrome P450 IA1 and P450 IIB1 isoenzymes. 6. The results indicate that coumarin is a substrate for isoenzymes of the cytochrome P450 IA and P450 IIB subfamilies. The bioactivation of coumarin by rat hepatic microsomes is postulated to result in the formation of a coumarin 3,4-epoxide intermediate which may rearrange to 3-hydroxycoumarin, be further metabolized to a coumarin 3,4-dihydrodiol, or form a glutathione conjugate.
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Affiliation(s)
- M M Peters
- Department of Toxicology, Wageningen Agricultural University, The Netherlands
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Petrek JA, Peters MM, Nori S, Knauer C, Kinne DW, Rogatko A. Axillary lymphadenectomy. A prospective, randomized trial of 13 factors influencing drainage, including early or delayed arm mobilization. Arch Surg 1990; 125:378-82. [PMID: 2407228 DOI: 10.1001/archsurg.1990.01410150100018] [Citation(s) in RCA: 88] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Greater amount and duration of postoperative wound drainage after lymphadenectomy impede healing. We evaluated the influence of early vs delayed initiation of shoulder mobilization on postoperative drainage. Fifty-seven women with clinical stage I or II breast cancer were randomized to either early (postoperative day 2) or delayed (postoperative day 5) shoulder motion. Early vs delayed time of exercise initiation had no effect on total amount or duration of drainage, either as an inpatient or outpatient. The two groups were determined to be homogeneous as to age, breast size, weight, height, obesity, previous biopsy, excision of pectoralis minor, excision of thoracodorsal complex, level of axillary dissection, total number of lymph nodes, number of positive lymph nodes, lymphatic vessel invasion (with negative lymph nodes), and whether the dominant hand was on the side operated on. The two factors predicting greater drainage were large numbers of positive lymph nodes and no previous surgical biopsy (as in one-step procedure).
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Affiliation(s)
- J A Petrek
- Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, NY
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den Besten C, Peters MM, van Bladeren PJ. The metabolism of pentachlorobenzene by rat liver microsomes: the nature of the reactive intermediates formed. Biochem Biophys Res Commun 1989; 163:1275-81. [PMID: 2675838 DOI: 10.1016/0006-291x(89)91116-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Metabolism of [14C]-pentachlorobenzene by liver microsomes from dexamethasone-induced rats results in the formation of pentachlorophenol and 2,3,4,6-tetrachlorophenol as major primary metabolites in a ratio of 4:1, with 2,3,4,5- and 2,3,5,6-tetrachlorophenols as minor metabolites. The unsubstituted carbon atom is thus the favourite site of oxidative attack, but the chlorine substituted positions still play a sizable role. As secondary metabolites both para- and ortho-tetrachlorohydroquinone are formed (1.4 and 0.9% of total metabolites respectively). During this cytochrome P450-dependent conversion of pentachlorobenzene, 5-15% of the total amount of metabolites becomes covalently bound to microsomal protein. Ascorbic acid inhibits this binding to a considerable extent, indicating that quinone metabolites play an important role in the binding. However, complete inhibition was never reached by ascorbic acid, nor by glutathione, suggesting that other reactive intermediates, presumably epoxides, are also responsible for covalent binding.
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Affiliation(s)
- C den Besten
- Department of Toxicology, Agricultural University, Wageningen, The Netherlands
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