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Maintenance of high quality rat precision cut liver slices during culture to study hepatotoxic responses: Acetaminophen as a model compound. Toxicol In Vitro 2017; 42:200-213. [PMID: 28476500 DOI: 10.1016/j.tiv.2017.05.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Revised: 03/13/2017] [Accepted: 05/01/2017] [Indexed: 02/08/2023]
Abstract
Precision cut liver slices (PCLiS) represent a promising tool in reflecting hepatotoxic responses. However, the culture of PCLiS varies considerably between laboratories, which can affect the performance of the liver slices and thus the experimental outcome. In this study, we describe an easily accessible culture method, which ensures optimal slice viability and functionality, in order to set the basis for reproducible and comparable PCLiS studies. The quality of the incubated rat PCLiS was assessed during a 24h culture period using ten readouts, which covered viability (lactate dehydrogenase-, aspartate transaminase- and glutamate dehydrogenase-leakage, ATP content) and functionality parameters (urea, albumin production) as well as histomorphology and other descriptive characteristics (protein content, wet weight, slice thickness). The present culture method resulted in high quality liver slices for 24h. Finally, PCLiS were exposed to increasing concentrations of acetaminophen to assess the suitability of the model for the detection of hepatotoxic responses. Six out of ten readouts revealed a toxic effect and showed an excellent mutual correlation. ATP, albumin and histomorphology measurements were identified as the most sensitive readouts. In conclusion, our results indicate that rat PCLiS are a valuable liver model for hepatotoxicity studies, particularly if they are cultured under optimal standardized conditions.
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Gan J, Zhang H, Humphreys WG. Drug–Protein Adducts: Chemistry, Mechanisms of Toxicity, and Methods of Characterization. Chem Res Toxicol 2016; 29:2040-2057. [DOI: 10.1021/acs.chemrestox.6b00274] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Jinping Gan
- Department of Biotransformation, Bristol-Myers Squibb Pharmaceutical Company, Princeton, New Jersey 08540, United States
| | - Haiying Zhang
- Department of Biotransformation, Bristol-Myers Squibb Pharmaceutical Company, Princeton, New Jersey 08540, United States
| | - W. Griffith Humphreys
- Department of Biotransformation, Bristol-Myers Squibb Pharmaceutical Company, Princeton, New Jersey 08540, United States
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Golizeh M, Geib T, Sleno L. Identification of 4-hydroxynonenal protein targets in rat, mouse and human liver microsomes by two-dimensional liquid chromatography/tandem mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2016; 30:1488-1494. [PMID: 27321836 DOI: 10.1002/rcm.7577] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Revised: 03/30/2016] [Accepted: 04/01/2016] [Indexed: 06/06/2023]
Abstract
RATIONALE 4-Hydroxynonenal (HNE), endogenously generated through peroxidation and breakdown of polyunsaturated fatty acids, has been linked to a number of adverse biological effects through carbonylation of essential biomolecules. Covalent binding of HNE to proteins can alter their structure and functions, causing cell damage as well as adverse immune responses. The liver plays a predominant role in metabolic transformations and hepatic proteins are often targeted by reactive metabolites. METHODS Rat, mouse and human liver microsomes were incubated with HNE, enzymatically digested, and subjected to strong cation-exchange peptide fractionation prior to liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis coupled to electrospray ionization quadrupole time-of-flight (QqTOF) mass spectrometry. HNE-modified peptides were detected by probability-driven peptide spectral matching and comparative analysis between treated and control samples, and confirmed based on accurate mass and high-resolution MS/MS spectra. RESULTS A total of 99, 123 and 51 HNE-modified peptides were identified in rat, mouse and human liver microsomes related to 76, 103 and 44 target proteins, respectively. Eight proteins were found to be adducted by HNE in all three species, including ATP synthase, carbamoyl phosphate synthase, cytochrome P450 1A2, glutamate dehydrogenase 1, protein ERGIC-53, protein disulfide-isomerase, and voltage-dependent anion-selective channel protein 1. These proteins play crucial roles in cellular processes and their covalent modification could potentially alter their function and lead to cytotoxicity. CONCLUSIONS An analytical approach was developed for the identification of in vitro HNE protein targets in rat, mouse and human liver microsomes using two-dimensional (2D) LC/MS/MS. This approach can be applied to study HNE modification of proteins in vitro and in vivo, providing insight into the toxicology of HNE protein adduction. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Makan Golizeh
- Chemistry Department/Pharmaqam, Université du Québec à Montréal (UQÀM), Montréal, QC, Canada
| | - Timon Geib
- Chemistry Department/Pharmaqam, Université du Québec à Montréal (UQÀM), Montréal, QC, Canada
| | - Lekha Sleno
- Chemistry Department/Pharmaqam, Université du Québec à Montréal (UQÀM), Montréal, QC, Canada
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Walker V, Mills GA, Anderson ME, Ingle BL, Jackson JM, Moss CL, Sharrod-Cole H, Skipp PJ. The acetaminophen metabolite N-acetyl-p-benzoquinone imine (NAPQI) inhibits glutathione synthetase in vitro; a clue to the mechanism of 5-oxoprolinuric acidosis? Xenobiotica 2016; 47:164-175. [PMID: 27086508 DOI: 10.3109/00498254.2016.1166533] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
1. Metabolic acidosis due to accumulation of l-5-oxoproline is a rare, poorly understood, disorder associated with acetaminophen treatment in malnourished patients with chronic morbidity. l-5-Oxoprolinuria signals abnormal functioning of the γ-glutamyl cycle, which recycles and synthesises glutathione. Inhibition of glutathione synthetase (GS) by N-acetyl-p-benzoquinone imine (NAPQI) could contribute to 5-oxoprolinuric acidosis in such patients. We investigated the interaction of NAPQI with GS in vitro. 2. Peptide mapping of co-incubated NAPQI and GS using mass spectrometry demonstrated binding of NAPQI with cysteine-422 of GS, which is known to be essential for GS activity. Computational docking shows that NAPQI is properly positioned for covalent bonding with cysteine-422 via Michael addition and hence supports adduct formation. 3. Co-incubation of 0.77 μM of GS with NAPQI (25-400 μM) decreased enzyme activity by 16-89%. Inhibition correlated strongly with the concentration of NAPQI and was irreversible. 4. NAPQI binds covalently to GS causing irreversible enzyme inhibition in vitro. This is an important novel biochemical observation. It is the first indication that NAPQI may inhibit glutathione synthesis, which is pivotal in NAPQI detoxification. Further studies are required to investigate its biological significance and its role in 5-oxoprolinuric acidosis.
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Affiliation(s)
- Valerie Walker
- a Department of Clinical Biochemistry , University Hospital Southampton NHS Foundation Trust , Southampton , UK
| | - Graham A Mills
- b School of Pharmacy and Biomedical Sciences, University of Portsmouth , Portsmouth , UK
| | - Mary E Anderson
- c Department of Chemistry and Biochemistry , Texas Woman's University , Denton , TX , USA
| | - Brandall L Ingle
- d Department of Chemistry , Center for Advanced Scientific Computing and Modeling, University of North Texas , Denton , TX , USA
| | - John M Jackson
- e NIHR Southampton Biomedical Research Centre, Southampton General Hospital , Southampton , UK , and
| | - Charlotte L Moss
- f Centre for Proteomic Research and Biological Sciences, University of Southampton , Southampton , UK
| | - Hayley Sharrod-Cole
- a Department of Clinical Biochemistry , University Hospital Southampton NHS Foundation Trust , Southampton , UK
| | - Paul J Skipp
- f Centre for Proteomic Research and Biological Sciences, University of Southampton , Southampton , UK
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Comparative metabonomic analysis of hepatotoxicity induced by acetaminophen and its less toxic meta-isomer. Arch Toxicol 2016; 90:3073-3085. [PMID: 26746206 PMCID: PMC5104807 DOI: 10.1007/s00204-015-1655-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 11/23/2015] [Indexed: 01/31/2023]
Abstract
The leading cause of drug-induced liver injury in the developed world is overdose with N-acetyl-p-aminophenol (APAP). A comparative metabonomic approach was applied to the study of both xenobiotic and endogenous metabolic profiles reflective of in vivo exposure to APAP (300 mg/kg) and its structural isomer N-acetyl-m-aminophenol (AMAP; 300 mg/kg) in C57BL/6J mice, which was anchored with histopathology. Liver and urine samples were collected at 1 h, 3 h and 6 h post-treatment and analyzed by 1H nuclear magnetic resonance (NMR) spectroscopy and gas chromatography–mass spectrometry (liver only). Histopathology revealed the presence of centrilobular necrosis from 3 h post-APAP treatment, while an AMAP-mediated necrotic endpoint was not observed within the timescale of this study, yet two of five treated mice showed minimal centrilobular eosinophilia. The 1H-NMR xenobiotic metabolic profile of APAP-treated animals comprised of mercapturate (urine and liver) and glutathionyl (liver) conjugates detected at 1 h post-treatment. This finding corroborated the hepatic endogenous metabolic profile which showed depletion of glutathione from 1 h onwards. In contrast, AMAP glutathionyl conjugates were not detected, nor was AMAP-induced depletion of hepatic glutathione observed. APAP administration induced significant endogenous hepatic metabolic perturbations, primarily linked to oxidative and energetic stress, and perturbation of amino acid metabolism. Early depletion of glutathione was followed by depletion of additional sulfur-containing metabolites, while altered levels of mitochondrial and glycolytic metabolites indicated a disruption of energy homeostasis. In contrast, AMAP administration caused minimal, transient, distinct metabolic perturbations and by 6 h the metabolic profiles of AMAP-treated mice were indistinguishable from those of controls.
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Zhang H, Gan J, Shu YZ, Humphreys WG. High-Resolution Mass Spectrometry-Based Background Subtraction for Identifying Protein Modifications in a Complex Biological System: Detection of Acetaminophen-Bound Microsomal Proteins Including Argininosuccinate Synthetase. Chem Res Toxicol 2015; 28:775-81. [DOI: 10.1021/tx500526s] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Haiying Zhang
- Biotransformation, Bristol-Myers Squibb Research and Development, Princeton, New Jersey 08543, United States
| | - Jinping Gan
- Biotransformation, Bristol-Myers Squibb Research and Development, Princeton, New Jersey 08543, United States
| | - Yue-Zhong Shu
- Biotransformation, Bristol-Myers Squibb Research and Development, Princeton, New Jersey 08543, United States
| | - W. Griffith Humphreys
- Biotransformation, Bristol-Myers Squibb Research and Development, Princeton, New Jersey 08543, United States
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Stamper BD, Mohar I, Kavanagh TJ, Nelson SD. Proteomic analysis of acetaminophen-induced changes in mitochondrial protein expression using spectral counting. Chem Res Toxicol 2011; 24:549-58. [PMID: 21329376 DOI: 10.1021/tx1004198] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Comparative proteomic analysis following treatment with acetaminophen (APAP) was performed on two different models of APAP-mediated hepatocellular injury in order to both identify common targets for adduct formation and track drug-induced changes in protein expression. Male C57BL/6 mice were used as a model for APAP-mediated liver injury in vivo, and TAMH cells were used as a model for APAP-mediated cytotoxicity in vitro. SEQUEST was unable to identify the precise location of sites of adduction following treatment with APAP in either system. However, semiquantitative analysis of the proteomic data sets using spectral counting revealed a downregulation of P450 isoforms associated with APAP bioactivation and an upregulation of proteins related to the electron transport chain by APAP compared to the control. Both mechanisms are likely compensatory in nature as decreased P450 expression is likely to attenuate toxicity associated with N-acetyl-p-quinoneimine (NAPQI) formation, whereas APAP-induced electron transport chain component upregulation may be an attempt to promote cellular bioenergetics.
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Affiliation(s)
- Brendan D Stamper
- Departments of Medicinal Chemistry and Environmental and Occupational Health Sciences, University of Washington, Seattle, WA 98195, United States
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Gutiérrez-Correa J. Trypanosoma cruzi dihydrolipoamide dehydrogenase as target of reactive metabolites generated by cytochrome c/hydrogen peroxide (or linoleic acid hydroperoxide)/phenol systems. Free Radic Res 2011; 44:1345-58. [PMID: 20815787 DOI: 10.3109/10715762.2010.507669] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
This study determines that cytochrome c (cyt c) catalyses the oxidation of phenol compounds (Phen) in the presence of H2O2 or linoleic acid hydroperoxide (LOOH), generating Phen-derived free radicals or other reactive metabolites. These products irreversibly inactivated the dihydrolipoamide dehydrogenase from Trypanosoma cruzi (T cruzi LADH), depending on: the Phen structure, peroxide type, activated cyt c, incubation time and presence of an antioxidant. Nordihydroguaiaretic acid (NDGA) and caffeic acid (CAFF) with cyt c/H2O2 or cyt c/LOOH were the most effective inhibitors of T cruzi LADH. The comparison of inactivation values for T cruzi and mammalian heart enzymes demonstrated a greater sensitivity of T cruzi LADH to Phen. GSH, N-acetylcysteine, NAD(P)H, ascorbate and trolox, prevented T cruzi LADH inactivation by acetaminophen. The role of the Phen as potential trypanocidal systems is discussed.
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Affiliation(s)
- José Gutiérrez-Correa
- Instituto de Medicina Tropical Daniel A Carrión, Universidad Nacional Mayor de San Marcos, Lima, Perú.
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Abstract
Of the estimated 10,000 documented human drugs, more than 1000 have been associated with drug-induced liver injury (DILI), although causality has not always been established clearly. Numerous biomarkers for DILI have been explored, but less than ten are adopted or qualified as valid by the US FDA. The biomarkers for DILI are individual or a panel of proteins, nucleic acids or metabolites from various sources, such as the liver, blood and urine. While most DILI biomarkers are drug independent, some possibly 'drug-specific' DILIs have been explored, but specificity and sensitivity of both types need to be improved for the diagnosis of DILI during drug development and in clinical practice. Novel approaches for DILI biomarkers have been actively investigated recently, but produced mainly animal-based biomarkers, which are possibly useful for drug development, but are not suitable or have not been validated for clinical applications. This review summarizes the current practice and future perspectives for DILI biomarkers.
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Affiliation(s)
- Qiang Shi
- Center for Toxicoinformatics, Division of Systems Toxicology, National Center for Toxicological Research, US Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079, USA
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Mattow J, Demuth I, Haeselbarth G, Jungblut PR, Klose J. Selenium-binding protein 2, the major hepatic target for acetaminophen, shows sex differences in protein abundance. Electrophoresis 2006; 27:1683-91. [PMID: 16532517 DOI: 10.1002/elps.200500703] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Liver samples from female and male mice of two subspecies, Mus musculus musculus and Mus musculus domesticus, were investigated by a combination of 2-DE and MALDI-MS. The image analysis of the generated 2-DE patterns revealed several protein spots with significant differences in intensity/abundance between the sexes. Seven protein spots, which were prominent in 2-DE patterns of male mice, but which showed very low intensities in females, were identified as selenium-binding protein 2 (SBP2) also known as 56-kDa acetaminophen-binding protein. Edman degradation indicated that at least three of these protein spots represent N-terminally truncated SBP2 variants. Furthermore, it was shown that the observed differences in SBP2 abundance correlate with sex differences in transcription of the gene encoding SBP2, selenbp2, as revealed by RT-PCR and restriction digest as well as sequence analysis of the products. Since SBP2 has been described as the major target for acetaminophen in mouse liver cytosol, these findings are discussed with respect to their possible relevance for sex differences in acetaminophen-mediated toxicity, which have been described in a variety of mammals including mice and rats.
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Affiliation(s)
- Jens Mattow
- Institute of Human Genetics, Charité, Berlin, Germany.
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Lee YS, Wan J, Kim BJ, Bae MA, Song BJ. Ubiquitin-dependent degradation of p53 protein despite phosphorylation at its N terminus by acetaminophen. J Pharmacol Exp Ther 2005; 317:202-8. [PMID: 16330492 PMCID: PMC1409809 DOI: 10.1124/jpet.105.096719] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We previously reported that acetaminophen (APAP, 4-hydroxyacetanilide) caused apoptosis of C6 glioma cells. Therefore, we hypothesized that the level of p53, which usually stimulates apoptosis, might be increased after APAP exposure. However, APAP exposure for 24 h markedly decreased the p53 content and its downstream target p21 in a concentration-dependent manner. Reduction of p53 was not accompanied by a decrease in p53 mRNA in C6 glioma cells, suggesting that p53 was mainly affected at the protein level. Unexpectedly, APAP stimulated phosphorylation of p53 at Ser15, Ser20, and Ser37, which usually elevates p53 content. However, phosphorylation of these residues did not prevent APAP-induced decrease in p53. The p53 reduction was independent from the level of phospho-Akt, which is known to promote p53 degradation. Immunoblot analysis of the immunoprecipitated p53 revealed that increased amounts of murine double minute 2 (mdm2) and ubiquitin were bound to p53 during its degradation. Lactacystin and N-benzoyloxycarbonyl (Z)-Leu-Leu-leucinal (MG132), inhibitors of proteasomal proteolysis, prevented the decrease, supporting the proteasomal degradation of p53 upon APAP exposure. Pretreatment with chlormethiazole, an inhibitor of ethanol-inducible CYP2E1, significantly lowered the CYP2E1 enzyme activity and the rate of APAP-induced cell death while it prevented the reduction of p53 and p21 in C6 glioma cells. A nontoxic analog of APAP, 3-hydroxyacetanilde, did not reduce p53 and p21 contents in C6 glioma cells and LLC-PK1 porcine kidney cells. Taken together, our results show that APAP or its reactive metabolite(s) can directly reduce the p53 content through mdm2-mediated ubiquitin conjugation, despite phosphorylation of p53 at its N terminus.
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Affiliation(s)
| | | | | | | | - Byoung J. Song
- Corresponding author: Dr. B. J. Song, Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, 9000 Rockville Pike, Bethesda, Maryland, USA. (Phone) 301-496-3985; (FAX) 301-594-3113; (e-mail)
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Isbell MA, Morin D, Boland B, Buckpitt A, Salemi M, Presley J. Identification of proteins adducted by reactive naphthalene metabolitesin vitro. Proteomics 2005; 5:4197-204. [PMID: 16206326 DOI: 10.1002/pmic.200401278] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Metabolic activation of inert chemicals to electrophilic intermediates has been correlated with the incidence and severity of cytotoxicity. The current studies have identified several proteins adducted by reactive metabolites of the lung toxicant, naphthalene. Proteins isolated from microsomal incubations of (14)C-naphthalene were separated by 2-DE, proteins were blotted to PVDF membranes and radioactive proteins were localized by storage phosphor analysis. Adducted proteins were isolated from complimentary gels and identified by peptide mass mapping. A total of 18 adducted proteins were identified including: protein disulfide isomerase precursor, ER-60 protease, alpha actin, mouse urinary proteins, and cytochrome b5 reductase. In supernatant fractions, protein disulfide isomerase, heat shock protein 70, and alpha-actin were key proteins to which reactive naphthalene metabolites were bound. All of the proteins adducted, with the exception of cytochrome b5 reductase were sulfhydryl rich. Although several of the proteins found to be adducted in these studies have also been shown to be adducted by other electrophiles, several others have not been reported as common targets of reactive metabolites. These studies provide a basis for both in situ and in vivo work designed to follow the fate and formation of reactive metabolite protein adducts.
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Affiliation(s)
- Margaret A Isbell
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
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Yang XX, Hu ZP, Chan SY, Zhou SF. Monitoring drug-protein interaction. Clin Chim Acta 2005; 365:9-29. [PMID: 16199025 DOI: 10.1016/j.cca.2005.08.021] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2005] [Revised: 08/16/2005] [Accepted: 08/23/2005] [Indexed: 11/25/2022]
Abstract
A variety of therapeutic drugs can undergo biotransformation via Phase I and Phase II enzymes to reactive metabolites that have intrinsic chemical reactivity toward proteins and cause potential organ toxicity. A drug-protein adduct is a protein complex that forms when electrophilic drugs or their reactive metabolite(s) covalently bind to a protein molecule. Formation of such drug-protein adducts eliciting cellular damages and immune responses has been a major hypothesis for the mechanism of toxicity caused by numerous drugs. The monitoring of protein-drug adducts is important in the kinetic and mechanistic studies of drug-protein adducts and establishment of dose-toxicity relationships. The determination of drug-protein adducts can also provide supportive evidence for diagnosis of drug-induced diseases associated with protein-drug adduct formation in patients. The plasma is the most commonly used matrix for monitoring drug-protein adducts due to its convenience and safety. Measurement of circulating antibodies against drug-protein adducts may be used as a useful surrogate marker in the monitoring of drug-protein adducts. The determination of plasma protein adducts and/or relevant antibodies following administration of several drugs including acetaminophen, dapsone, diclofenac and halothane has been conducted in clinical settings for characterizing drug toxicity associated with drug-protein adduct formation. The monitoring of drug-protein adducts often involves multi-step laboratory procedure including sample collection and preliminary preparation, separation to isolate or extract the target compound from a mixture, identification and determination. However, the monitoring of drug-protein adducts is often difficult because of short half-lives of the protein adducts, sampling problem and lack of sensitive analytical techniques for the protein adducts. Currently, chromatographic (e.g. high performance liquid chromatography) and immunological methods (e.g. enzyme-linked immunosorbent assay) are two major techniques used to determine protein adducts of drugs in patients. The present review highlights the importance for clinical monitoring of drug-protein adducts, with an emphasis on methodology and with a further discussion of the application of these techniques to individual drugs and their target proteins.
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Affiliation(s)
- Xiao-Xia Yang
- Department of Pharmacy, Faculty of Science, National University of Singapore, Science Drive 4, Singapore 117543, Singapore
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Jaeschke H, Bajt ML. Intracellular signaling mechanisms of acetaminophen-induced liver cell death. Toxicol Sci 2005; 89:31-41. [PMID: 16177235 DOI: 10.1093/toxsci/kfi336] [Citation(s) in RCA: 374] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Acetaminophen hepatotoxicity is the leading cause of drug-induced liver failure. Despite substantial efforts in the past, the mechanisms of acetaminophen-induced liver cell injury are still incompletely understood. Recent advances suggest that reactive metabolite formation, glutathione depletion, and alkylation of proteins, especially mitochondrial proteins, are critical initiating events for the toxicity. Bcl-2 family members Bax and Bid then form pores in the outer mitochondrial membrane and release intermembrane proteins, e.g., apoptosis-inducing factor (AIF) and endonuclease G, which then translocate to the nucleus and initiate chromatin condensation and DNA fragmentation, respectively. Mitochondrial dysfunction, due to covalent binding, leads to formation of reactive oxygen and peroxynitrite, which trigger the membrane permeability transition and the collapse of the mitochondrial membrane potential. In addition to the diminishing capacity to synthesize ATP, endonuclease G and AIF are further released. Endonuclease G, together with an activated nuclear Ca2+,Mg2+-dependent endonuclease, cause DNA degradation, thereby preventing cell recovery and regeneration. Disruption of the Ca2+ homeostasis also leads to activation of intracellular proteases, e.g., calpains, which can proteolytically cleave structural proteins. Thus, multiple events including massive mitochondrial dysfunction and ATP depletion, extensive DNA fragmentation, and modification of intracellular proteins contribute to the development of oncotic necrotic cell death in the liver after acetaminophen overdose. Based on the recognition of the temporal sequence and interdependency of these mechanisms, it appears most promising to therapeutically target either the initiating event (metabolic activation) or the central propagating event (mitochondrial dysfunction and peroxynitrite formation) to prevent acetaminophen-induced liver cell death.
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Affiliation(s)
- Hartmut Jaeschke
- Liver Research Institute, University of Arizona, College of Medicine, Tucson, Arizona 85737, USA.
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Zhou S, Chan E, Duan W, Huang M, Chen YZ. Drug bioactivation, covalent binding to target proteins and toxicity relevance. Drug Metab Rev 2005; 37:41-213. [PMID: 15747500 DOI: 10.1081/dmr-200028812] [Citation(s) in RCA: 197] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
A number of therapeutic drugs with different structures and mechanisms of action have been reported to undergo metabolic activation by Phase I or Phase II drug-metabolizing enzymes. The bioactivation gives rise to reactive metabolites/intermediates, which readily confer covalent binding to various target proteins by nucleophilic substitution and/or Schiff's base mechanism. These drugs include analgesics (e.g., acetaminophen), antibacterial agents (e.g., sulfonamides and macrolide antibiotics), anticancer drugs (e.g., irinotecan), antiepileptic drugs (e.g., carbamazepine), anti-HIV agents (e.g., ritonavir), antipsychotics (e.g., clozapine), cardiovascular drugs (e.g., procainamide and hydralazine), immunosupressants (e.g., cyclosporine A), inhalational anesthetics (e.g., halothane), nonsteroidal anti-inflammatory drugs (NSAIDSs) (e.g., diclofenac), and steroids and their receptor modulators (e.g., estrogens and tamoxifen). Some herbal and dietary constituents are also bioactivated to reactive metabolites capable of binding covalently and inactivating cytochrome P450s (CYPs). A number of important target proteins of drugs have been identified by mass spectrometric techniques and proteomic approaches. The covalent binding and formation of drug-protein adducts are generally considered to be related to drug toxicity, and selective protein covalent binding by drug metabolites may lead to selective organ toxicity. However, the mechanisms involved in the protein adduct-induced toxicity are largely undefined, although it has been suggested that drug-protein adducts may cause toxicity either through impairing physiological functions of the modified proteins or through immune-mediated mechanisms. In addition, mechanism-based inhibition of CYPs may result in toxic drug-drug interactions. The clinical consequences of drug bioactivation and covalent binding to proteins are unpredictable, depending on many factors that are associated with the administered drugs and patients. Further studies using proteomic and genomic approaches with high throughput capacity are needed to identify the protein targets of reactive drug metabolites, and to elucidate the structure-activity relationships of drug's covalent binding to proteins and their clinical outcomes.
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Affiliation(s)
- Shufeng Zhou
- Department of Pharmacy, Faculty of Science, National University of Singapore, Singapore.
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Park BK, Kitteringham NR, Maggs JL, Pirmohamed M, Williams DP. The role of metabolic activation in drug-induced hepatotoxicity. Annu Rev Pharmacol Toxicol 2005; 45:177-202. [PMID: 15822174 DOI: 10.1146/annurev.pharmtox.45.120403.100058] [Citation(s) in RCA: 288] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The importance of reactive metabolites in the pathogenesis of drug-induced toxicity has been a focus of research interest since pioneering investigations in the 1950s revealed the link between toxic metabolites and chemical carcinogenesis. There is now a great deal of evidence that shows that reactive metabolites are formed from drugs known to cause hepatotoxicity, but how these toxic species initiate and propagate tissue damage is still poorly understood. This review summarizes the evidence for reactive metabolite formation from hepatotoxic drugs, such as acetaminophen, tamoxifen, diclofenac, and troglitazone, and the current hypotheses of how this leads to liver injury. Several hepatic proteins can be modified by reactive metabolites, but this in general equates poorly with the extent of toxicity. Much more important may be the identification of the critical proteins modified by these toxic species and how this alters their function. It is also important to note that the toxicity of reactive metabolites may be mediated by noncovalent binding mechanisms, which may also have profound effects on normal liver physiology. Technological developments in the wake of the genomic revolution now provide unprecedented power to characterize and quantify covalent modification of individual target proteins and their functional consequences; such information should dramatically improve our understanding of drug-induced hepatotoxic reactions.
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Affiliation(s)
- B Kevin Park
- Department of Pharmacology and Therapeutics, University of Liverpool, Sherrington Buildings, Liverpool, Merseyside L69 3GE, United Kingdom.
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Hinson JA, Reid AB, McCullough SS, James LP. Acetaminophen-induced hepatotoxicity: role of metabolic activation, reactive oxygen/nitrogen species, and mitochondrial permeability transition. Drug Metab Rev 2005; 36:805-22. [PMID: 15554248 DOI: 10.1081/dmr-200033494] [Citation(s) in RCA: 198] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Large doses of the analgesic acetaminophen cause centrilobular hepatic necrosis in man and in experimental animals. It has been previously shown that acetaminophen is metabolically activated by CYP enzymes to N-acetyl-p-benzoquinone imine. This species is normally detoxified by GSH, but following a toxic dose GSH is depleted and the metabolite covalently binds to a number of different proteins. Covalent binding occurs only to the cells developing necrosis. Recently we showed that these cells also contain nitrated tyrosine residues. Nitrotyrosine is mediated by peroxynitrite, a reactive nitrogen species formed by rapid reaction between nitric oxide and superoxide and is normally detoxified by GSH. Thus, acetaminophen toxicity occurs with increased oxygen/nitrogen stress. This manuscript will review current data on acetaminophen covalent binding, increased oxygen/nitrogen stress, and mitochondrial permeability transition, a toxic mechanism that is both mediated by and leads to increased oxygen/nitrogen stress.
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Affiliation(s)
- Jack A Hinson
- Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA.
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Abstract
The analgesic acetaminophen causes a potentially fatal, hepatic centrilobular necrosis when taken in overdose. The initial phases of toxicity were described in Dr. Gillette's laboratory in the 1970s. These findings indicated that acetaminophen was metabolically activated by cytochrome P450 enzymes to a reactive metabolite that depleted glutathione (GSH) and covalently bound to protein. It was shown that repletion of GSH prevented the toxicity. This finding led to the development of the currently used antidote N-acetylcysteine. The reactive metabolite was subsequently identified to be N-acetyl-p-benzoquinone imine (NAPQI). Although covalent binding has been shown to be an excellent correlate of toxicity, a number of other events have been shown to occur and are likely important in the initiation and repair of toxicity. Recent data have shown that nitrated tyrosine residues as well as acetaminophen adducts occur in the necrotic cells following toxic doses of acetaminophen. Nitrotyrosine was postulated to be mediated by peroxynitrite, a reactive nitrogen species formed by the very rapid reaction of superoxide and nitric oxide (NO). Peroxynitrite is normally detoxified by GSH, which is depleted in acetaminophen toxicity. NO synthesis (serum nitrate plus nitrite) was dramatically increased following acetaminophen. In inducible nitric oxide synthase (iNOS) knockout mice, acetaminophen did not increase NO synthesis or tyrosine nitration; however, histological evidence indicated no difference in toxicity. Acetaminophen did not cause hepatic lipid peroxidation in wild-type mice but did cause lipid peroxidation in iNOS knockout mice. These data suggest that NO may play a role in controlling lipid peroxidation and that reactive nitrogen/oxygen species may be important in toxicity. The source of the superoxide has not been identified, but our recent finding that NADPH oxidase knockout mice were equally sensitive to acetaminophen and had equal nitration of tyrosine suggests that the superoxide is not from the activation of Kupffer cells. It was postulated that NAPQI-mediated mitochondrial injury may be the source of the superoxide. In addition, the significance of cytokines and chemokines in the development of toxicity and repair processes has been demonstrated by several recent studies. IL-1beta is increased early in acetaminophen toxicity and may be important in iNOS induction. Other cytokines, such as IL-10, macrophage inhibitory protein-2 (MIP-2), and monocyte chemoattractant protein-1 (MCP-1), appear to be involved in hepatocyte repair and the regulation of proinflammatory cytokines.
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Affiliation(s)
- Laura P James
- Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
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Zhou S. Separation and detection methods for covalent drug–protein adducts. J Chromatogr B Analyt Technol Biomed Life Sci 2003; 797:63-90. [PMID: 14630144 DOI: 10.1016/s1570-0232(03)00399-4] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Covalent binding of reactive metabolites of drugs to proteins has been a predominant hypothesis for the mechanism of toxicity caused by numerous drugs. The development of efficient and sensitive analytical methods for the separation, identification, quantification of drug-protein adducts have important clinical and toxicological implications. In the last few decades, continuous progress in analytical methodology has been achieved with substantial increase in the number of new, more specific and more sensitive methods for drug-protein adducts. The methods used for drug-protein adduct studies include those for separation and for subsequent detection and identification. Various chromatographic (e.g., affinity chromatography, ion-exchange chromatography, and high-performance liquid chromatography) and electrophoretic techniques [e.g., sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), two-dimensional SDS-PAGE, and capillary electrophoresis], used alone or in combination, offer an opportunity to purify proteins adducted by reactive drug metabolites. Conventionally, mass spectrometric (MS), nuclear magnetic resonance, and immunological and radioisotope methods are used to detect and identify protein targets for reactive drug metabolites. However, these methods are labor-intensive, and have provided very limited sequence information on the target proteins adducted, and thus the identities of the protein targets are usually unknown. Moreover, the antibody-based methods are limited by the availability, quality, and specificity of antibodies to protein adducts, which greatly hindered the identification of specific protein targets of drugs and their clinical applications. Recently, the use of powerful MS technologies (e.g., matrix-assisted laser desorption/ionization time-of-flight) together with analytical proteomics have enabled one to separate, identify unknown protein adducts, and establish the sequence context of specific adducts by offering the opportunity to search for adducts in proteomes containing a large number of proteins with protein adducts and unmodified proteins. The present review highlights the separation and detection technologies for drug-protein adducts, with an emphasis on methodology, advantages and limitations to these techniques. Furthermore, a brief discussion of the application of these techniques to individual drugs and their target proteins will be outlined.
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Affiliation(s)
- Shufeng Zhou
- Department of Pharmacy, Faculty of Science, National University of Singapore, Science Drive 4, Singapore 117543, Singapore.
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Abstract
The currently recommended dosing scheme for treating acetaminophen overdose in the United States consists of a loading dose of oral N-acetylcysteine 140 mg/kg, followed by 70 mg/kg every 4 hours for 17 doses, for a total of 72 hours of oral N-acetylcysteine therapy. This protocol has been both effective and safe. We critically evaluated the evidence that supports reducing the course of N-acetylcysteine therapy from 72 hours to 24 or 36 hours. This shorter regimen offers important benefits for both the patient and the patient's family, such as increased drug tolerability and reduced hospital stay. Patients who intentionally ingested acetaminophen with harmful intent could receive appropriate psychosocial treatment more quickly. In addition, shorter courses of N-acetylcysteine therapy have positive financial ramifications by reducing the hospital stay by 1 or 2 days. Clearly, a shorter treatment regimen would not be appropriate for all patients, particularly those who seek treatment late (> 24 hrs after ingestion) and those with evidence of organ toxicity. In order to provide the necessary evidence to support a change in accepted clinical practice, further investigation on the safety and efficacy of a shorter N-acetylcysteine regimen should be conducted by clinical researchers in a controlled manner.
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Affiliation(s)
- Todd Kociancic
- Division of Pediatric Pharmacology and Critical Care, Rainbow Babies and Children's Hospital, Cleveland, Ohio 44106-6010, USA
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James LP, Farrar HC, Sullivan JE, Givens TG, Kearns GL, Wasserman GS, Walson PD, Hinson JA, Pumford NR. Measurement of acetaminophen-protein adducts in children and adolescents with acetaminophen overdoses. . J Clin Pharmacol 2001; 41:846-51. [PMID: 11504272 DOI: 10.1177/00912700122010744] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Acetaminophen-protein adducts are biomarkers of acetaminophen toxicity present in the centrilobular region of the liver of laboratory animals following the administration of toxic doses of acetaminophen. These biomarkers are highly specific for acetaminophen-induced hepatic injury and correlate with hepatic transaminase elevation. The objective of this prospective, multicenter study was to evaluate the clinical application of the measurement of acetaminophen-protein adducts in pediatric acetaminophen overdose patients. Serum samples were obtained from 51 children and adolescents with acetaminophen overdose at the time of routine blood sampling for clinical monitoring. Six subjects developed "severe" hepatotoxicity (transaminase elevation > 1,000 IU/L), and 6 subjects had transaminase elevation of 100 to 1,000 IU/L. Acetaminophen-protein adducts were detected in the serum of only 1 study subject, a patient with marked transaminase elevation (> 6,000 IU/L) and high risk for the development of hepatotoxicity according to the Rumack nomogram. While this study provides further support for the occurrence of covalent binding of acetaminophen to hepatic protein in humans following acetaminophen overdose, the detection of acetaminophen-protein adducts in serum with the current methodology requires significant biochemical evidence of hepatocellular injury.
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Affiliation(s)
- L P James
- Department of Pediatrics, University of Arkansas for Medical Sciences and Arkansas Children's Hospital, Little Rock 72202, USA
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Bessems JG, Vermeulen NP. Paracetamol (acetaminophen)-induced toxicity: molecular and biochemical mechanisms, analogues and protective approaches. Crit Rev Toxicol 2001; 31:55-138. [PMID: 11215692 DOI: 10.1080/20014091111677] [Citation(s) in RCA: 509] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
An overview is presented on the molecular aspects of toxicity due to paracetamol (acetaminophen) and structural analogues. The emphasis is on four main topics, that is, bioactivation, detoxication, chemoprevention, and chemoprotection. In addition, some pharmacological and clinical aspects are discussed briefly. A general introduction is presented on the biokinetics, biotransformation, and structural modification of paracetamol. Phase II biotransformation in relation to marked species differences and interorgan transport of metabolites are described in detail, as are bioactivation by cytochrome P450 and peroxidases, two important phase I enzyme families. Hepatotoxicity is described in depth, as it is the most frequent clinical observation after paracetamol-intoxication. In this context, covalent protein binding and oxidative stress are two important initial (Stage I) events highlighted. In addition, the more recently reported nuclear effects are discussed as well as secondary events (Stage II) that spread over the whole liver and may be relevant targets for clinical treatment. The second most frequent clinical observation, renal toxicity, is described with respect to the involvement of prostaglandin synthase, N-deacetylase, cytochrome P450 and glutathione S-transferase. Lastly, mechanism-based developments of chemoprotective agents and progress in the development of structural analogues with an improved therapeutic index are outlined.
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Affiliation(s)
- J G Bessems
- Leiden/Amsterdam Center for Drug Research, Department of Pharmacochemistry, Vrije Universiteit, Amsterdam, The Netherlands
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Casper D, Yaparpalvi U, Rempel N, Werner P. Ibuprofen protects dopaminergic neurons against glutamate toxicity in vitro. Neurosci Lett 2000; 289:201-4. [PMID: 10961664 DOI: 10.1016/s0304-3940(00)01294-5] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Non-steroidal anti-inflammatory drugs (NSAIDs) reduce the risk of Alzheimer's disease, although the underlying mechanisms are unknown. Glutamate excitotoxicity has been implicated in Alzheimer's disease, Parkinson's disease, and others. We examined the effects of aspirin, acetaminophen, and ibuprofen on cultured primary rat embryonic neurons from mesencephalon, the area primarily affected in Parkinson's disease. We evaluated whether these drugs protect dopaminergic neurons against excitotoxicity. All three NSAIDs significantly attenuated the decrease in dopamine uptake caused by glutamate, indicating preservation of neuronal integrity. One hundred micro-moles ibuprofen protected both dopaminergic neurons and neurons overall against glutamate toxicity. In addition, ibuprofen alone increased the relative number of dopaminergic neurons by 47%. Thus, NSAIDs protected neurons against glutamate excitotoxicity in vitro, and deserve further consideration as neuroprotective agents in Parkinson's disease.
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Affiliation(s)
- D Casper
- Department of Neurological Surgery, Neurosurgery Lab, Montefiore Medical Center, The Bronx, New York 10467, USA.
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Abstract
Our study investigated the effects of Corylus avellana extract on acetaminophen and carbon tetrachloride intoxicated liver of young rats. Hepatocytolysis was determined by measuring the level of serum transaminases (GPT and GOT), steatosis by Sudan black staining, histological structures by hamatoxylineosin staining and the activity of enzymes such as SDH, GtDH, G-6-Pase and ATPase. Comparatively, the most serious lesions appeared in CCl4 intoxication. Corylus avellana extract had some beneficial effects in CCl4 toxicosis: it reduced hepatocytolysis as well as histological lesions and returned the activity of some enzymes to normal values.
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Affiliation(s)
- M A Rusu
- Biological Research Institute, Cluj-Napoca, Romania
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26
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Bruno MK, Khairallah EA, Cohen SD. Inhibition of protein phosphatase activity and changes in protein phosphorylation following acetaminophen exposure in cultured mouse hepatocytes. Toxicol Appl Pharmacol 1998; 153:119-32. [PMID: 9875306 DOI: 10.1006/taap.1998.8512] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Protein phosphorylation was determined in cultured mouse hepatocytes exposed to an hepatotoxic concentration of acetaminophen (APAP) for selected times up to 12 h. Cultures were radiolabled with 32P-orthophosphoric acid and the cell extracts were analyzed by 2D gel electrophoresis and autoradiography. APAP exposure selectively increased the phosphorylation state of proteins of molecular weight 22, 25, 28, and 59 kDa and decreased the phosphorylation of a 26-kDa protein. Evidence is presented that these changes (1) are dependent on cytochrome P-450 activation of APAP; (2) occur well before enzyme leakage in this in vitro model; (3) are not likely attributed to GSH depletion alone; (4) are in part mimicked by okadaic acid, calyculin A, and cantharidic acid, three structurally distinct inhibitors of protein phosphatases 1 and 2A; and (5) are paralleled by a decline in protein phosphatase activity. The physiological consequences of protein phosphatase inactivation could be significant in APAP overdose since these enzymes are involved in the dephosphorylation of regulatory proteins that control many cell functions. This study also provides the first evidence for disruption in signal transduction pathways as a response to or component of APAP-induced hepatic injury.
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Affiliation(s)
- M K Bruno
- Department of Molecular and Cell Biology, University of Connecticut, Storrs 06269, USA
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27
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Tonge RP, Kelly EJ, Bruschi SA, Kalhorn T, Eaton DL, Nebert DW, Nelson SD. Role of CYP1A2 in the hepatotoxicity of acetaminophen: investigations using Cyp1a2 null mice. Toxicol Appl Pharmacol 1998; 153:102-8. [PMID: 9875304 DOI: 10.1006/taap.1998.8543] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Acetaminophen (APAP) is known to cause centrilobular hepatic necrosis under overdose conditions. This is thought to be mediated via the P450-generated reactive intermediate N-acetyl-p-benzoquinone imine (NAPQI). Initially, NAPQI is detoxified by conjugation with glutathione (GSH), but once GSH is depleted, NAPQI reacts more extensively with hepatic proteins leading to hepatocellular damage. The P450 isoforms thought to be responsible for APAP hepatotoxicity in humans are CYP2E1, CYP1A2, and CYP3A4, and thus, we have investigated the effect of murine Cyp1a2 on APAP hepatotoxicity using Cyp1a2 knockout mice (Liang et al., Proc. Natl. Acad. Sci. USA 93, 1671-1676, 1996). Doses of 250 mg/kg were markedly hepatotoxic in these mice, and surprisingly, deaths only occurred in the knock-out and heterozygote mice over a 24-h period after dosing. Furthermore, there were no significant differences among survivors of any genotype in serum ALT concentrations, a well correlated indicator of APAP hepatotoxicity in mice. Finally, no differences were observed in the urinary metabolites excreted ove the 24-h period, including those derived from GSH conjugation of the major reactive metabolite NAPQI. Consistent with the effects on hepatotoxicity and metabolism, 2 h after hepatotoxic doses (500 mg/kg, i.p.) of APAP no significant differences were observed in total whole liver homogenate nonprotein thiol concentrations among the three genotypes even though hepatic thiols were decreased compared to control animals (> 90%). In addition, when the liver cytosol and microsome samples were examined by immunoblotting for the presence of APAP-protein adducts using a specific antiserum, there were no observable differences in either the intensity of staining or in the spectrum of adducts formed between APAP-dosed mice of any genotype. The cumulative data suggest that Cyp1a2 doses not play a significant role in APAP hepatotoxicity in these mice.
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Affiliation(s)
- R P Tonge
- Department of Medicinal Chemistry, University of Washington, Seattle 98195-7631, USA
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28
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Qiu Y, Benet LZ, Burlingame AL. Identification of the hepatic protein targets of reactive metabolites of acetaminophen in vivo in mice using two-dimensional gel electrophoresis and mass spectrometry. J Biol Chem 1998; 273:17940-53. [PMID: 9651401 DOI: 10.1074/jbc.273.28.17940] [Citation(s) in RCA: 224] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Liver toxicity following an overdose of acetaminophen is frequently considered a model for drug-induced hepatotoxicity. Extensive studies over many years have established that such toxicity is well correlated with liver protein arylation by acetaminophen metabolites. Identification of protein targets for covalent modifications is a challenging but necessary step in understanding how covalent binding could lead to liver toxicity. Previous approaches suffered from technical limitations, and thus over the last 10 years heroic efforts were required to determine the identity of only a few target proteins. We present a new mass spectrometry-based strategy for identification of all target proteins that now provides a comprehensive survey of the suite of liver proteins modified. After administration of radiolabeled acetaminophen to mice, the proteins in the liver tissue lysate were separated by two-dimensional polyacrylamide gel electrophoresis. In-gel digestion of the radiolabeled gel spots gave a set of tryptic peptides, which were analyzed by matrix-assisted laser desorption ionization mass spectrometry. Interrogation of data bases based on experimentally determined molecular weights of peptides and product ion tags from postsource decay mass spectra was employed for the determination of the identities of modified liver proteins. Using this method, more than 20 new drug-labeled proteins have been identified.
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Affiliation(s)
- Y Qiu
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143-0446, USA
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Halmes NC, Samokyszyn VM, Hinton TW, Hinson JA, Pumford NR. The acetaminophen regioisomer 3'-hydroxyacetanilide inhibits and covalently binds to cytochrome P450 2E1. Toxicol Lett 1998; 94:65-71. [PMID: 9544700 DOI: 10.1016/s0378-4274(97)00100-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
3'-Hydroxyacetanilide has been previously studied as a nontoxic regioisomer of the analgesic acetaminophen (4'-hydroxyacetanilide). The radiolabeled derivative has been shown to covalently bind to liver proteins at levels similar to that observed with hepatotoxic doses of radiolabeled acetaminophen with no evidence of hepatic damage. Using an anti-arylacetamide antiserum the primary protein adduct detected following administration of 3'-hydroxyacetanilide (300 and 600 mg/kg) to mice was a 50 kDa microsomal protein that co-migrated with cytochrome P450 2E1. Cytochrome P450 2E1 enzyme activity (p-nitrophenol hydroxylase) was decreased by 79% in the mice treated with 3'-hydroxyacetanilide (600 mg/kg). Incubation of 3'-hydroxyacetanilide with hepatic microsomes resulted in a time dependent 47% decrease in cytochrome P450 2E1 activity. Pre-incubation of acetaminophen with microsomes did not result in covalent binding to the cytochrome P450 nor was there a decrease in p-nitrophenol hydroxylase activity. These data suggest that 3'-hydroxyacetanilide covalently binds to cytochrome P450 2E1 with preferential loss of activity.
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Affiliation(s)
- N C Halmes
- Division of Toxicology, University of Arkansas for Medical Sciences, Little Rock 72205-7199, USA
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Ribeiro JM, Agudo A, Costas MJ, Cameselle JC. Rat liver ADP-ribose pyrophosphatase-I as an in vitro target of the acetaminophen metabolite N-acetyl-p-benzoquinoneimine. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1336:403-8. [PMID: 9367167 DOI: 10.1016/s0304-4165(97)00051-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
N-acetyl-p-benzoquinoneimine (NAPQI) is the metabolite responsible for acetaminophen hepatotoxicity. ADP-ribose pyrophosphatase-I (ADPRibase-I; EC 3.6.1.13) hydrolyzes protein-glycating ADP-ribose. The results show NAPQI-dependent alterations of ADPRibase-I leading to strong inhibition: a fast Km increase produced by low concentrations, and a time-dependent Vmax decrease by higher NAPQI concentrations. Both effects were prevented by thiols, but not reverted by them, nor by gel filtration of NAPQI-treated enzyme. Liver ADPRibase-I can be a target of NAPQI-dependent arylation. The inhibition or inactivation of the enzyme would contribute to increasing the free ADP-ribose concentration and nonenzymatic ADP-ribosylation, which is coherent with results linking free ADP-ribose-producing pathways to acetaminophen toxicity.
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Affiliation(s)
- J M Ribeiro
- Unidad de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Extremadura, Badajoz, Spain
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Gupta S, Rogers LK, Taylor SK, Smith CV. Inhibition of carbamyl phosphate synthetase-I and glutamine synthetase by hepatotoxic doses of acetaminophen in mice. Toxicol Appl Pharmacol 1997; 146:317-27. [PMID: 9344900 PMCID: PMC5127704 DOI: 10.1006/taap.1997.8228] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The primary mechanisms proposed for acetaminophen-induced hepatic necrosis should deplete protein thiols, either by covalent binding and thioether formation or by oxidative reactions such as S-thiolations. However, in previous studies we did not detect significant losses of protein thiol contents in response to administration of hepatotoxic doses of acetaminophen in vivo. In the present study we employed derivatization with the thiol-specific agent monobromobimane and separation of proteins by SDS-PAGE to investigate the possible loss of specific protein thiols during the course of acetaminophen-induced hepatic necrosis. Fasted adult male mice were given acetaminophen, and protein thiol status was examined subsequently in subcellular fractions isolated by differential centrifugation. No decreases in protein thiol contents were indicated, with the exception of a marked decrease in the fluorescent intensity, but not of protein content, as indicated by staining with Coomassie blue, of a single band of approximately 130 kDa in the mitochondrial fractions of acetaminophen-treated mice. This protein was identified by isolation and N-terminal sequence analysis as carbamyl phosphate synthetase-I (CPS-I) (EC 6.3.4.16). Hepatic CPS-I activities were decreased in mice given hepatotoxic doses of acetaminophen. In addition, hepatic glutamine synthetase activities were lower, and plasma ammonia levels were elevated in mice given hepatotoxic doses of acetaminophen. The observed hyperammonemia may contribute to the adverse effects of toxic doses of acetaminophen, and elucidation of the specific mechanisms responsible for the hyperammonemia may prove to be useful clinically. However, the preferential depletion of protein thiol content of a mitochondrial protein by chemically reactive metabolites generated in the endoplasmic reticulum presents a challenging and potentially informative mechanistic question.
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Affiliation(s)
- S Gupta
- Department of Pediatrics, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA
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Cohen SD, Pumford NR, Khairallah EA, Boekelheide K, Pohl LR, Amouzadeh HR, Hinson JA. Selective protein covalent binding and target organ toxicity. Toxicol Appl Pharmacol 1997; 143:1-12. [PMID: 9073586 DOI: 10.1006/taap.1996.8074] [Citation(s) in RCA: 239] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Protein covalent binding by xenobiotic metabolites has long been associated with target organ toxicity but mechanistic involvement of such binding has not been widely demonstrated. Modern biochemical, molecular, and immunochemical approaches have facilitated identification of specific protein targets of xenobiotic covalent binding. Such studies have revealed that protein covalent binding is not random, but rather selective with respect to the proteins targeted. Selective binding to specific cellular target proteins may better correlate with toxicity than total protein covalent binding. Current research is directed at characterizing and identifying the targeted proteins and clarifying the effect of such binding on their structure, function, and potential roles in target organ toxicity. The approaches employed to detect and identify the tartgeted proteins are described. Metabolites of acetaminophen, halothane, and 2,5-hexanedione form covalently bound adducts to recently identified protein targets. The selective binding may influence homeostatic or other cellular responses which in turn contribute to drug toxicity, hypersensitivity, or autoimmunity.
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Affiliation(s)
- S D Cohen
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs 06269-2092, USA
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33
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Pumford NR, Halmes NC, Hinson JA. Covalent binding of xenobiotics to specific proteins in the liver. Drug Metab Rev 1997; 29:39-57. [PMID: 9187510 DOI: 10.3109/03602539709037572] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Chemicals that cause toxicity though a direct mechanism, such as acetaminophen, covalently bind to a select group of proteins prior to the development of toxicity, and these proteins may be important in the initiation of the events that lead to the hepatotoxicity. Disruption of the cell is measured by release of intracellular proteins such as alanine aminotransferase and occurs late in the time course following a hepatotoxic dose of a direct toxin. Prior to this disruption, there appears to be a large number of proteins covalently modified by a reactive metabolite. There are at least two possible mechanisms that may cause the toxicity. First, some critical protein is a target of the reactive metabolite. Disruption of the enzymatic function (or a critical pathway for a regulatory protein) may lead directly to cell death. With the direct hepatotoxin acetaminophen, there is a decrease in the activity of several of the early target proteins, but how this disruption of critical proteins leads to the toxicity is still unclear. The early targets appear to be proteins with accessible nucleophilic sulfhydryl groups, and usually the target has a high concentration of the protein within the cell. It is possible that the binding to some of these proteins represents a detoxification protecting more critical targets within the cell. A second mechanism for the direct toxicity is that more and more proteins become targets in the time course following administration of a direct toxin, and eventually the cells machinery is overwhelmed. The cell can then no longer function, or there is a disruption the redox balance within the cell due to the decreased function of numerous proteins. In contrast to the direct-acting toxins, the chemical-protein conjugates that initiate toxicity through an activation of the immune system appear to have a limited number of target proteins and are localized within one subcellular fraction. Halothane produces adducts almost exclusively in the microsomal fraction, and these adducts appear to be limited to selective proteins with high concentrations in this fraction. The substitution level is an important factor in the development of an immune response. Halothane hepatitis patients' antibodies primarily recognize proteins with a high substitution level. For halothane and diclofenac, the proteins are accessible to the immune system through exposure on the plasma membrane. Trichloroethylene binds primarily to a 50-kDa microsomal protein, and preliminary evidence has been presented which indicates that a trichloroethylene-protein conjugate is released into the blood following exposure, where contact with the immune system can occur. In order to elicit an immune response the immune system requires multiple exposure to the chemical-protein conjugates. With halothane hepatitis and with diclofenac hepatitis, as well as occupational and environmental exposure to trichloroethylene, there are multiple exposures leading to repeat presentation of the protein adducts to the immune system; this situation is not generally found with acetaminophen overdose patients. In summary, direct toxicants such as acetaminophen covalently bind to selected targets which may be critical to the development of hepatotoxicity, and they later form adducts with numerous proteins which may overwhelm the cell's capacity to maintain homeostasis, leading to loss of vital function and cell death (Fig.3). In contrast, indirect toxicants that elicit an immune-mediated toxicity such as halothane, and possibly diclofenac and trichloroethylene, appear to have a limited number of protein targets with a high substitution level, and the immune system is exposed repeatedly to the modified proteins.
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Affiliation(s)
- N R Pumford
- Division of Toxicology, University of Arkansas for Medical Sciences, Little Rock 72205-7199, USA
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Abstract
More than 20 years have passed since the early reports of acute hepatotoxicity with APAP overdose. During that period investigative research to discover the "mechanism" underlying the toxicity has been conducted in many species and strains of intact animals as well as in a variety of in vitro and culture systems. Such work has clarified the primary role of biotransformation and the protective role of GSH. Understanding the former provides explanations for the toxic interactions which may occur with alcohol or other xenobiotics, while understanding of the latter led to the development of antidotes for the treatment of acute poisoning. Acetaminophen (APAP)-induced hepatotoxicity: roles for protein arylation. Initiating events in toxicity require biotransformation of APAP to NAPQI followed by arylation of several important proteins with subsequent alteration of protein structure and function. The immediate consequence of the alterations is detectable in several organelles and these may represent multiple initiating events which are depicted as acting in concert to cause cell injury (large arrowheads). Arylation of cytosolic 58-ABP with subsequent translocation to the nucleus is depicted as a possible signaling mechanism for determining outcome at the cell or organ level (within dotted boundary). For simplicity NAPQI's potentials for oxidizing protein sulfhydryls and direct binding to DNA have been omitted. Significant light has also been shed on the biochemical and cellular events which accompany APAP-induced hepatotoxicity. However, such studies have not identified a unique mechanism of toxicity that is universally accepted. The recent identification of several protein targets which become arylated during toxicity--along with the findings that arylation of some of those target proteins results in loss of protein function--demonstrates that covalent binding does, indeed, have biological consequences and is not merely an indicator of the fleeting presence of reactive electrophiles. These observations further suggest that multiple independent insults to the cell may be involved in toxicity. it is now apparent that the concept of a multistage process that involves both initiation and progression events is appropriate for APAP toxicity, and it is unlikely that a unique initiating event will ever be identified. In light of recent findings it is more likely that a number of such cellular events occur very early after toxic overdosage, and that they collectively set in motion and perpetuate the biochemical, cellular, and molecular processes which will determine outcome. The importance of 58-ABP arylation with early, apparently selective, translocation to the nucleus remains to be elucidated. To date there is nothing to suggest that this represents an initiating event in toxicity. rather it is plausible that the translocation may play a role in signaling electrophile presence and in calling for cellular defense against electrophile insult. This is reflected in the hypothetical model presented in Fig. 3. Critical experimental testing of this model will advance our understanding of the cellular and molecular responses to toxic electrophile insult.
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Affiliation(s)
- S D Cohen
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs 06269, USA
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Halmes NC, Samokyszyn VM, Pumford NR. Covalent binding and inhibition of cytochrome P4502E1 by trichloroethylene. Xenobiotica 1997; 27:101-10. [PMID: 9041682 DOI: 10.1080/004982597240794] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
1. To investigate the effects of trichloroethylene on cytochrome P4502E1 (CYP2E1), an isozyme responsible for its metabolic activation, mice were treated with trichloroethylene and Western blot staining with both anti-dichloroacetyl and anti-CYP2E1 antisera detected a comigrating 50 kDa protein band. There was a dose-dependent increase in the intensity of the 50 kDa protein adduct stained immunochemically with anti-dichloroacetyl. 2. CYP2E1 enzyme activity was decreased from control levels in a dose-dependent manner in mice treated with 250-500 mg/kg TRI. 3. Microsomal incubations with trichloroethylene resulted in covalent binding to several proteins including a 50 kDa adduct, which is in contrast with the selective binding to the 50 kDa protein observed in vivo. 4. CYP2E1 enzyme activity levels were significantly decreased following microsomal incubation with NADPH and trichloroethylene, and additionally there was a time- and NADPH-dependent decrease in enzyme activity indicating that trichloroethylene is a mechanism-based inhibitor of CYP2E1.
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Affiliation(s)
- N C Halmes
- Division of Toxicology, University of Arkansas for Medical Sciences, Little Rock 72205, USA
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Abstract
Many xenobiotics are metabolically activated to electrophilic intermediates that form covalent adducts with proteins; the mechanism of toxicity is either intrinsic or idiosyncratic in nature. Many intrinsic toxins covalently modify cellular proteins and somehow initiate a sequence of events that leads to toxicity. Major protein adducts of several intrinsic toxins have been identified and demonstrate significant decreases in enzymatic activity. The reactivity of intermediates and subcellular localization of major targets may be important in the toxicity. Idiosyncratic toxicities are mediated through either a metabolic or immune-mediated mechanism. Xenobiotics that cause hypersensitivity/autoimmunity appear to have a limited number of protein targets, which are localized within the subcellular fraction where the electrophile is produced, are highly substituted, and are accessible to the immune system. Metabolic idiosyncratic toxins appear to have limited targets and are localized within a specific subcellular fraction. Identification of protein targets has given us insights into mechanisms of xenobiotic toxicity.
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Affiliation(s)
- N R Pumford
- Division of Toxicology, University of Arkansas for Medical Sciences, Little Rock 72205-7199, USA
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Identification of a 54-kDa mitochondrial acetaminophen-binding protein as aldehyde dehydrogenase. Toxicol Appl Pharmacol 1996. [DOI: 10.1016/s0041-008x(96)80036-6] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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