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Lau EY, Enright HA, Lao V, Malfatti MA, Mayer BP, Williams AM, Valdez CA. Evaluation of 6-OxP-CD, an Oxime-based cyclodextrin as a viable medical countermeasure against nerve agent poisoning: Experimental and molecular dynamic simulation studies on its inclusion complexes with cyclosarin, soman and VX. PLoS One 2023; 18:e0283181. [PMID: 36996021 PMCID: PMC10062596 DOI: 10.1371/journal.pone.0283181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 03/04/2023] [Indexed: 03/31/2023] Open
Abstract
The ability of the cyclodextrin-oxime construct 6-OxP-CD to bind and degrade the nerve agents Cyclosarin (GF), Soman (GD) and S-[2-[Di(propan-2-yl)amino]ethyl] O-ethyl methylphosphonothioate (VX) has been studied using 31P-nuclear magnetic resonance (NMR) under physiological conditions. While 6-OxP-CD was found to degrade GF instantaneously under these conditions, it was found to form an inclusion complex with GD and significantly improve its degradation (t1/2 ~ 2 hrs) relative over background (t1/2 ~ 22 hrs). Consequently, effective formation of the 6-OxP-CD:GD inclusion complex results in the immediate neutralization of GD and thus preventing it from inhibiting its biological target. In contrast, NMR experiments did not find evidence for an inclusion complex between 6-OxP-CD and VX, and the agent's degradation profile was identical to that of background degradation (t1/2 ~ 24 hrs). As a complement to this experimental work, molecular dynamics (MD) simulations coupled with Molecular Mechanics-Generalized Born Surface Area (MM-GBSA) calculations have been applied to the study of inclusion complexes between 6-OxP-CD and the three nerve agents. These studies provide data that informs the understanding of the different degradative interactions exhibited by 6-OxP-CD with each nerve agent as it is introduced in the CD cavity in two different orientations (up and down). For its complex with GF, it was found that the oxime in 6-OxP-CD lies in very close proximity (PGF⋯OOxime ~ 4-5 Å) to the phosphorus center of GF in the 'downGF' orientation for most of the simulation accurately describing the ability of 6-OxP-CD to degrade this nerve agent rapidly and efficiently. Further computational studies involving the center of masses (COMs) for both components (GF and 6-OxP-CD) also provided some insight on the nature of this inclusion complex. Distances between the COMs (ΔCOM) lie closer in space in the 'downGF' orientation than in the 'upGF' orientation; a correlation that seems to hold true not only for GF but also for its congener, GD. In the case of GD, calculations for the 'downGD' orientation showed that the oxime functional group in 6-OxP-CD although lying in close proximity (PGD⋯OOxime ~ 4-5 Å) to the phosphorus center of the nerve agent for most of the simulation, adopts another stable conformation that increase this distance to ~ 12-14 Å, thus explaining the ability of 6-OxP-CD to bind and degrade GD but with less efficiency as observed experimentally (t1/2 ~ 4 hr. vs. immediate). Lastly, studies on the VX:6-OxP-CD system demonstrated that VX does not form a stable inclusion complex with the oxime-bearing cyclodextrin and as such does not interact in a way that is conducive to an accelerated degradation scenario. Collectively, these studies serve as a basic platform from which the development of new cyclodextrin scaffolds based on 6-OxP-CD can be designed in the development of medical countermeasures against these highly toxic chemical warfare agents.
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Affiliation(s)
- Edmond Y Lau
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
| | - Heather A Enright
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
| | - Victoria Lao
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
| | - Michael A Malfatti
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
| | - Brian P Mayer
- Global Security Directorate, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
- Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
- Forensic Science Center, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
| | - Audrey M Williams
- Global Security Directorate, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
- Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
- Forensic Science Center, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
| | - Carlos A Valdez
- Global Security Directorate, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
- Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
- Forensic Science Center, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
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2
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Bennion BJ, Malfatti MA, Be NA, Enright HA, Hok S, Cadieux CL, Carpenter TS, Lao V, Kuhn EA, McNerney MW, Lightstone FC, Nguyen TH, Valdez CA. Development of a CNS-permeable reactivator for nerve agent exposure: an iterative, multi-disciplinary approach. Sci Rep 2021; 11:15567. [PMID: 34330964 PMCID: PMC8324913 DOI: 10.1038/s41598-021-94963-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 07/19/2021] [Indexed: 11/09/2022] Open
Abstract
Nerve agents have experienced a resurgence in recent times with their use against civilian targets during the attacks in Syria (2012), the poisoning of Sergei and Yulia Skripal in the United Kingdom (2018) and Alexei Navalny in Russia (2020), strongly renewing the importance of antidote development against these lethal substances. The current standard treatment against their effects relies on the use of small molecule-based oximes that can efficiently restore acetylcholinesterase (AChE) activity. Despite their efficacy in reactivating AChE, the action of drugs like 2-pralidoxime (2-PAM) is primarily limited to the peripheral nervous system (PNS) and, thus, provides no significant protection to the central nervous system (CNS). This lack of action in the CNS stems from their ionic nature that, on one end makes them very powerful reactivators and on the other renders them ineffective at crossing the Blood Brain Barrier (BBB) to reach the CNS. In this report, we describe the use of an iterative approach composed of parallel chemical and in silico syntheses, computational modeling, and a battery of detailed in vitro and in vivo assays that resulted in the identification of a promising, novel CNS-permeable oxime reactivator. Additional experiments to determine acute and chronic toxicity are ongoing.
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Affiliation(s)
- Brian J Bennion
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - Michael A Malfatti
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - Nicholas A Be
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - Heather A Enright
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - Saphon Hok
- Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
- Forensic Science Center, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - C Linn Cadieux
- United States Army Medical Research Institute of Chemical Defense, Aberdeen, MD, 21010, USA
| | - Timothy S Carpenter
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - Victoria Lao
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - Edward A Kuhn
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - M Windy McNerney
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
- Affiliation: Mental Illness Research, Education and Clinical Center, Veterans Affairs, Palo Alto, CA, 94304, USA
- Affiliation: Department of Psychiatry, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Felice C Lightstone
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - Tuan H Nguyen
- Global Security Directorate, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - Carlos A Valdez
- Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA.
- Forensic Science Center, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA.
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3
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France CP, Ahern GP, Averick S, Disney A, Enright HA, Esmaeli-Azad B, Federico A, Gerak LR, Husbands SM, Kolber B, Lau EY, Lao V, Maguire DR, Malfatti MA, Martinez G, Mayer BP, Pravetoni M, Sahibzada N, Skolnick P, Snyder EY, Tomycz N, Valdez CA, Zapf J. Countermeasures for Preventing and Treating Opioid Overdose. Clin Pharmacol Ther 2020; 109:578-590. [PMID: 33113208 DOI: 10.1002/cpt.2098] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 10/15/2020] [Indexed: 02/06/2023]
Abstract
The only medication available currently to prevent and treat opioid overdose (naloxone) was approved by the US Food and Drug Administration (FDA) nearly 50 years ago. Because of its pharmacokinetic and pharmacodynamic properties, naloxone has limited utility under some conditions and would not be effective to counteract mass casualties involving large-scale deployment of weaponized synthetic opioids. To address shortcomings of current medical countermeasures for opioid toxicity, a trans-agency scientific meeting was convened by the US National Institute of Allergy and Infectious Diseases/National Institutes of Health (NIAID/NIH) on August 6 and 7, 2019, to explore emerging alternative approaches for treating opioid overdose in the event of weaponization of synthetic opioids. The meeting was initiated by the Chemical Countermeasures Research Program (CCRP), was organized by NIAID, and was a collaboration with the National Institute on Drug Abuse/NIH (NIDA/NIH), the FDA, the Defense Threat Reduction Agency (DTRA), and the Biomedical Advanced Research and Development Authority (BARDA). This paper provides an overview of several presentations at that meeting that discussed emerging new approaches for treating opioid overdose, including the following: (1) intranasal nalmefene, a competitive, reversible opioid receptor antagonist with a longer duration of action than naloxone; (2) methocinnamox, a novel opioid receptor antagonist; (3) covalent naloxone nanoparticles; (4) serotonin (5-HT)1A receptor agonists; (5) fentanyl-binding cyclodextrin scaffolds; (6) detoxifying biomimetic "nanosponge" decoy receptors; and (7) antibody-based strategies. These approaches could also be applied to treat opioid use disorder.
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Affiliation(s)
- Charles P France
- Department of Pharmacology, Addiction Research, Treatment and Training Center of Excellence, University of Texas Health Science Center, San Antonio, Texas, USA
| | | | - Saadyah Averick
- Neuroscience Institute, Allegheny Health Network, Pittsburgh, Pennsylvania, USA
| | - Alex Disney
- Department of Pharmacy and Pharmacology, University of Bath, Bath, UK
| | | | - Babak Esmaeli-Azad
- CellCure (Stem Cell Division of CiBots, Inc.), San Diego, California, USA
| | - Arianna Federico
- CellCure (Stem Cell Division of CiBots, Inc.), San Diego, California, USA
| | - Lisa R Gerak
- Department of Pharmacology, Addiction Research, Treatment and Training Center of Excellence, University of Texas Health Science Center, San Antonio, Texas, USA
| | | | | | - Edmond Y Lau
- Lawrence Livermore National Laboratory, Livermore, California, USA
| | - Victoria Lao
- Lawrence Livermore National Laboratory, Livermore, California, USA
| | - David R Maguire
- Department of Pharmacology, Addiction Research, Treatment and Training Center of Excellence, University of Texas Health Science Center, San Antonio, Texas, USA
| | | | - Girardo Martinez
- CellCure (Stem Cell Division of CiBots, Inc.), San Diego, California, USA
| | - Brian P Mayer
- Lawrence Livermore National Laboratory, Livermore, California, USA
| | - Marco Pravetoni
- Department of Pharmacology, Center for Immunology, University of Minnesota Medical School, Minneapolis, Minnesota, USA
| | | | - Phil Skolnick
- Opiant Pharmaceuticals, Inc., Santa Monica, California, USA
| | - Evan Y Snyder
- Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Nestor Tomycz
- Neuroscience Institute, Allegheny Health Network, Pittsburgh, Pennsylvania, USA
| | - Carlos A Valdez
- Lawrence Livermore National Laboratory, Livermore, California, USA
| | - Jim Zapf
- CellCure (Stem Cell Division of CiBots, Inc.), San Diego, California, USA
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4
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Malfatti MA, Kuhn EA, Murugesh DK, Mendez ME, Hum N, Thissen JB, Jaing CJ, Loots GG. Manipulation of the Gut Microbiome Alters Acetaminophen Biodisposition in Mice. Sci Rep 2020; 10:4571. [PMID: 32165665 PMCID: PMC7067795 DOI: 10.1038/s41598-020-60982-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 02/19/2020] [Indexed: 12/30/2022] Open
Abstract
The gut microbiota is a vast and diverse microbial community that has co-evolved with its host to perform a variety of essential functions involved in the utilization of nutrients and the processing of xenobiotics. Shifts in the composition of gut microbiota can disturb the balance of organisms which can influence the biodisposition of orally administered drugs. To determine how changes in the gut microbiome can alter drug disposition, the pharmacokinetics (PK), and biodistribution of acetaminophen were assessed in C57Bl/6 mice after treatment with the antibiotics ciprofloxacin, amoxicillin, or a cocktail of ampicillin/neomycin. Altered PK, and excretion profiles of acetaminophen were observed in antibiotic exposed animals. Plasma Cmax was significantly decreased in antibiotic treated animals suggesting decreased bioavailability. Urinary metabolite profiles revealed decreases in acetaminophen-sulfate metabolite levels in both the amoxicillin and ampicillin/neomycin treated animals. The ratio between urinary and fecal excretion was also altered in antibiotic treated animals. Analysis of gut microbe composition revealed that changes in microbe content in antibiotic treated animals was associated with changes in acetaminophen biodisposition. These results suggest that exposure to amoxicillin or ampicillin/neomycin can alter the biodisposition of acetaminophen and that these alterations could be due to changes in gut microbiome composition.
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Affiliation(s)
- Michael A Malfatti
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA.
| | - Edward A Kuhn
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - Deepa K Murugesh
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - Melanie E Mendez
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA.,School of Natural Sciences, University of California Merced, Merced, CA, 95343, USA
| | - Nicholas Hum
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA.,School of Natural Sciences, University of California Merced, Merced, CA, 95343, USA
| | - James B Thissen
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - Crystal J Jaing
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - Gabriela G Loots
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA.,School of Natural Sciences, University of California Merced, Merced, CA, 95343, USA
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5
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Wang S, Scharadin TM, Zimmermann M, Malfatti MA, Turteltaub KW, de Vere White R, Pan CX, Henderson PT. Correlation of Platinum Cytotoxicity to Drug-DNA Adduct Levels in a Breast Cancer Cell Line Panel. Chem Res Toxicol 2018; 31:1293-1304. [PMID: 30381944 DOI: 10.1021/acs.chemrestox.8b00170] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Platinum drugs, including carboplatin and oxaliplatin, are commonly used chemotherapy drugs that kill cancer cells by forming toxic drug-DNA adducts. These drugs have a proven, but modest, efficacy against several aggressive subtypes of breast cancer but also cause several side effects that can lead to the cessation of treatment. There is a clinical need to identify patients who will respond to platinum drugs in order to better inform clinical decision making. Diagnostic microdosing involves dosing patients or patient samples with subtherapeutic doses of radiolabeled platinum followed by measurement of platinum-DNA adducts in blood or tumor tissue and may be used to predict patient response. We exposed a panel of six breast cancer cell lines to 14C-labeled carboplatin or oxaliplatin at therapeutic and microdose (1% therapeutic dose) concentrations for a range of exposure lengths and isolated DNA from the cells. The DNA was converted to graphite, and measurement of radiocarbon due to platinum-DNA adduction was quantified via accelerator mass spectrometry (AMS). We observed a linear correlation in adduct levels between the microdose and therapeutic dose, and the level of platinum-DNA adducts corresponded to cell line drug sensitivity for both carboplatin and oxaliplatin. These results showed a clear separation in adduct levels between the sensitive and resistant groups of cell lines that could not be fully explained or predicted by changes in DNA repair rates or mutations in DNA repair genes. Further, we were able to quantitate oxaliplatin-DNA adducts in the blood and tumor tissue of a metastatic breast cancer patient. Together, these data support the use of diagnostic microdosing for predicting patient sensitivity to platinum. Future studies will be aimed at replicating this data in a clinical feasibility trial.
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Affiliation(s)
- Sisi Wang
- Department of Internal Medicine, Division of Hematology and Oncology , University of California Davis , Sacramento , California 95817 , United States
| | - Tiffany M Scharadin
- Department of Internal Medicine, Division of Hematology and Oncology , University of California Davis , Sacramento , California 95817 , United States.,Accelerated Medical Diagnostics Incorporated , Berkeley , California 95618 , United States
| | - Maike Zimmermann
- Department of Internal Medicine, Division of Hematology and Oncology , University of California Davis , Sacramento , California 95817 , United States.,Accelerated Medical Diagnostics Incorporated , Berkeley , California 95618 , United States
| | - Michael A Malfatti
- Lawrence Livermore National Laboratory , Livermore , California 94550 , United States
| | - Kenneth W Turteltaub
- Lawrence Livermore National Laboratory , Livermore , California 94550 , United States
| | - Ralph de Vere White
- Lawrence Livermore National Laboratory , Livermore , California 94550 , United States
| | - Chong-Xian Pan
- Department of Internal Medicine, Division of Hematology and Oncology , University of California Davis , Sacramento , California 95817 , United States.,Department of Urology , University of California Davis Medical Center , Sacramento , California 95817 , United States.,VA Northern California Health Care System , Mather , California 95655 , United States
| | - Paul T Henderson
- Department of Internal Medicine, Division of Hematology and Oncology , University of California Davis , Sacramento , California 95817 , United States.,Accelerated Medical Diagnostics Incorporated , Berkeley , California 95618 , United States
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6
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Hum NR, Martin KA, Malfatti MA, Haack K, Buchholz BA, Loots GG. Tracking Tumor Colonization in Xenograft Mouse Models Using Accelerator Mass Spectrometry. Sci Rep 2018; 8:15013. [PMID: 30302019 PMCID: PMC6178347 DOI: 10.1038/s41598-018-33368-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 09/24/2018] [Indexed: 12/12/2022] Open
Abstract
Here we introduce an Accelerator Mass Spectrometry (AMS)-based high precision method for quantifying the number of cancer cells that initiate metastatic tumors, in xenograft mice. Quantification of 14C per cell prior to injection into animals, and quantification of 14C in whole organs allows us to extrapolate the number of cancer cells available to initiate metastatic tumors. The 14C labeling was optimized such that 1 cancer cell was detected among 1 million normal cells. We show that ~1–5% of human cancer cells injected into immunodeficient mice form subcutaneous tumors, and even fewer cells initiate metastatic tumors. Comparisons of metastatic site colonization between a highly metastatic (PC3) and a non-metastatic (LnCap) cell line showed that PC3 cells colonize target tissues in greater quantities at 2 weeks post-delivery, and by 12 weeks post-delivery no 14C was detected in LnCap xenografts, suggesting that all metastatic cells were cleared. The 14C-signal correlated with the presence and the severity of metastatic tumors. AMS measurements of 14C-labeled cells provides a highly-sensitive, quantitative assay to experimentally evaluate metastasis and colonization of target tissues in xenograft mouse models. This approach can potentially be used to evaluate tumor aggressiveness and assist in making informed decisions regarding treatment.
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Affiliation(s)
- Nicholas R Hum
- Lawrence Livermore National Laboratory, Physical and Life Sciences Directorate, Livermore, CA, USA
| | - Kelly A Martin
- Lawrence Livermore National Laboratory, Physical and Life Sciences Directorate, Livermore, CA, USA.,Georgetown University, Department of Biochemistry & Molecular Biology, Washington, DC, USA
| | - Michael A Malfatti
- Lawrence Livermore National Laboratory, Physical and Life Sciences Directorate, Livermore, CA, USA
| | - Kurt Haack
- Lawrence Livermore National Laboratory, Physical and Life Sciences Directorate, Livermore, CA, USA
| | - Bruce A Buchholz
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA, USA
| | - Gabriela G Loots
- Lawrence Livermore National Laboratory, Physical and Life Sciences Directorate, Livermore, CA, USA. .,UC Merced, School of Natural Sciences, Merced, CA, USA.
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7
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Schafer R, Ognibene TJ, Malfatti MA, Turteltaub KW, Barnett JB. Comparative Pharmacokinetics of High and Low Doses of the Herbicide Propanil in Mice. Chem Res Toxicol 2018; 31:1080-1085. [PMID: 30230318 DOI: 10.1021/acs.chemrestox.8b00151] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have documented that the herbicide propanil is immunotoxic in mice, and our in vitro tissue culture experiments largely recapitulate the in vivo studies. Laboratory studies on environmental contaminants are the most meaningful when these studies are conducted using concentrations that approximate levels in the environment. Many techniques to measure the distribution and pharmacokinetics (PK) on compounds rely on techniques, such as liquid scintillation counting (LSC) of radio-labeled starting compound, that require concentrations higher than environmental levels. The aim of this study was to compare tissue PK after exposure to propanil concentrations more relevant to levels of exposure to agricultural workers and the general population to concentrations previously reported for laboratory studies. To this end, we conducted a study to measure propanil distribution in three immune organs, using ultrasensitive accelerator mass spectrometry (AMS). We used two doses: the lower dose modeled levels expected in the environment or long-term occupational exposure to low doses, while the higher dose was to model the effects of an accidental exposure. Our results showed that the distribution and PK profiles from these two different concentrations was markedly different. The profile of the high dose (concentration) exposure was indicative of saturation of the detoxifying capability of the animal. In contrast, at the lower environmentally relevant concentration, in vivo concentrations of propanil in spleen, liver, and blood dropped to a very low level by 720 min. In conclusion, these studies highlight the differences in PK of propanil at these two doses, which suggests that the toxicity of this chemical should be re-investigated to obtain better data on toxic effects at doses relevant for humans.
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Affiliation(s)
- Rosana Schafer
- Department of Microbiology, Immunology, and Cell Biology , West Virginia University , Morgantown , West Virginia 26506-9177 , United States
| | - Ted J Ognibene
- Center for Accelerator Mass Spectrometry , Lawrence Livermore National Laboratory , Livermore , California 94551-0808 , United States
| | - Michael A Malfatti
- Center for Accelerator Mass Spectrometry , Lawrence Livermore National Laboratory , Livermore , California 94551-0808 , United States
| | - Kenneth W Turteltaub
- Center for Accelerator Mass Spectrometry , Lawrence Livermore National Laboratory , Livermore , California 94551-0808 , United States
| | - John B Barnett
- Department of Microbiology, Immunology, and Cell Biology , West Virginia University , Morgantown , West Virginia 26506-9177 , United States
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Scharadin TM, Malfatti MA, Haack K, Turteltaub KW, Pan CX, Henderson PT, Jonas BA. Toward Predicting Acute Myeloid Leukemia Patient Response to 7 + 3 Induction Chemotherapy via Diagnostic Microdosing. Chem Res Toxicol 2018; 31:1042-1051. [PMID: 30152692 DOI: 10.1021/acs.chemrestox.8b00107] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Acute myeloid leukemia (AML) is a rare yet deadly cancer of the blood and bone marrow. Presently, induction chemotherapy with the DNA damaging drugs cytarabine (ARA-C) and idarubicin (IDA), known as 7 + 3, is the standard of care for most AML patients. However, 7 + 3 is a relatively ineffective therapy, particularly in older patients, and has serious therapy-related toxicities. Therefore, a diagnostic test to predict which patients will respond to 7 + 3 is a critical unmet medical need. We hypothesize that a threshold level of therapy-induced 7 + 3 drug-DNA adducts determines cytotoxicity and clinical response. We further hypothesize that in vitro exposure of AML cells to nontoxic diagnostic microdoses enables prediction of the ability of AML cells to achieve that threshold during treatment. Our test involves dosing cells with very low levels of 14C-labeled drug followed by DNA isolation and quantification of drug-DNA adducts via accelerator mass spectrometry. Here, we have shown proof of principle by correlating ARA-C- and DOX-DNA adduct levels with cellular IC50 values of paired sensitive and resistant cancer cell lines and AML cell lines. Moreover, we have completed a pilot retrospective trial of diagnostic microdosing for 10 viably cryopreserved primary AML samples and observed higher ARA-C- and DOX-DNA adducts in the 7 + 3 responders than nonresponders. These initial results suggest that diagnostic microdosing may be a feasible and useful test for predicting patient response to 7 + 3 induction chemotherapy, leading to improved outcomes for AML patients and reduced treatment-related morbidity and mortality.
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Affiliation(s)
- Tiffany M Scharadin
- Department of Internal Medicine, Division of Hematology and Oncology , University of California Davis School of Medicine , Sacramento , California 95817 , United States
| | - Michael A Malfatti
- Lawrence Livermore National Laboratory , Livermore , California 94551 , United States
| | - Kurt Haack
- Lawrence Livermore National Laboratory , Livermore , California 94551 , United States
| | - Kenneth W Turteltaub
- Lawrence Livermore National Laboratory , Livermore , California 94551 , United States
| | - Chong-Xian Pan
- Department of Internal Medicine, Division of Hematology and Oncology , University of California Davis School of Medicine , Sacramento , California 95817 , United States.,Accelerated Medical Diagnostics Incorporated , Berkeley , California 95618 , United States.,VA Northern California Health Care System , 10535 Hospital Way , Mather , California 95655 , United States
| | - Paul T Henderson
- Department of Internal Medicine, Division of Hematology and Oncology , University of California Davis School of Medicine , Sacramento , California 95817 , United States.,Accelerated Medical Diagnostics Incorporated , Berkeley , California 95618 , United States
| | - Brian A Jonas
- Department of Internal Medicine, Division of Hematology and Oncology , University of California Davis School of Medicine , Sacramento , California 95817 , United States.,VA Northern California Health Care System , 10535 Hospital Way , Mather , California 95655 , United States
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9
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Malfatti MA, Enright HA, Be NA, Kuhn EA, Hok S, McNerney MW, Lao V, Nguyen TH, Lightstone FC, Carpenter TS, Bennion BJ, Valdez CA. The biodistribution and pharmacokinetics of the oxime acetylcholinesterase reactivator RS194B in guinea pigs. Chem Biol Interact 2017; 277:159-167. [PMID: 28941624 DOI: 10.1016/j.cbi.2017.09.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 09/13/2017] [Accepted: 09/19/2017] [Indexed: 01/09/2023]
Abstract
Organophosphorus-based (OP) nerve agents represent some of the most toxic substances known to mankind. The current standard of care for exposure has changed very little in the past decades, and relies on a combination of atropine to block receptor activity and oxime-type acetylcholinesterase (AChE) reactivators to reverse the OP binding to AChE. Although these oximes can block the effects of nerve agents, their overall efficacy is reduced by their limited capacity to cross the blood-brain barrier (BBB). RS194B, a new oxime developed by Radic et al. (J. Biol. Chem., 2012) has shown promise for enhanced ability to cross the BBB. To fully assess the potential of this compound as an effective treatment for nerve agent poisoning, a comprehensive evaluation of its pharmacokinetic (PK) and biodistribution profiles was performed using both intravenous and intramuscular exposure routes. The ultra-sensitive technique of accelerator mass spectrometry was used to quantify the compound's PK profile, tissue distribution, and brain/plasma ratio at four dose concentrations in guinea pigs. PK analysis revealed a rapid distribution of the oxime with a plasma t1/2 of ∼1 h. Kidney and liver had the highest concentrations per gram of tissue followed by lung, spleen, heart and brain for all dose concentrations tested. The Cmax in the brain ranged between 0.03 and 0.18% of the administered dose, and the brain-to-plasma ratio ranged from 0.04 at the 10 mg/kg dose to 0.18 at the 200 mg/kg dose demonstrating dose dependent differences in brain and plasma concentrations. In vitro studies show that both passive diffusion and active transport contribute little to RS194B traversal of the BBB. These results indicate that biodistribution is widespread, but very low quantities accumulate in the guinea pig brain, indicating this compound may not be suitable as a centrally active reactivator.
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Affiliation(s)
- Michael A Malfatti
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA; Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.
| | - Heather A Enright
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA; Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
| | - Nicholas A Be
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA; Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
| | - Edward A Kuhn
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA; Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
| | - Saphon Hok
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA; Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA; Forensic Science Center, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
| | - M Windy McNerney
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA; War Related Illness and Injury Study Center, Veterans Affairs, Palo Alto, CA 94304, USA
| | - Victoria Lao
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA; Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
| | - Tuan H Nguyen
- Global Security Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
| | - Felice C Lightstone
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA; Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
| | - Timothy S Carpenter
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA; Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
| | - Brian J Bennion
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA; Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
| | - Carlos A Valdez
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA; Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA; Forensic Science Center, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
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10
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Enright HA, Falso MJS, Malfatti MA, Lao V, Kuhn EA, Hum N, Shi Y, Sales AP, Haack KW, Kulp KS, Buchholz BA, Loots GG, Bench G, Turteltaub KW. Maternal exposure to an environmentally relevant dose of triclocarban results in perinatal exposure and potential alterations in offspring development in the mouse model. PLoS One 2017; 12:e0181996. [PMID: 28792966 PMCID: PMC5549899 DOI: 10.1371/journal.pone.0181996] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 07/11/2017] [Indexed: 12/31/2022] Open
Abstract
Triclocarban (TCC) is among the top 10 most commonly detected wastewater contaminants in both concentration and frequency. Its presence in water, as well as its propensity to bioaccumulate, has raised numerous questions about potential endocrine and developmental effects. Here, we investigated whether exposure to an environmentally relevant concentration of TCC could result in transfer from mother to offspring in CD-1 mice during gestation and lactation using accelerator mass spectrometry (AMS). 14C-TCC (100 nM) was administered to dams through drinking water up to gestation day 18, or from birth to post-natal day 10. AMS was used to quantify 14C-concentrations in offspring and dams after exposure. We demonstrated that TCC does effectively transfer from mother to offspring, both trans-placentally and via lactation. TCC-related compounds were detected in the tissues of offspring with significantly higher concentrations in the brain, heart and fat. In addition to transfer from mother to offspring, exposed offspring were heavier in weight than unexposed controls demonstrating an 11% and 8.5% increase in body weight for females and males, respectively. Quantitative real-time polymerase chain reaction (qPCR) was used to examine changes in gene expression in liver and adipose tissue in exposed offspring. qPCR suggested alterations in genes involved in lipid metabolism in exposed female offspring, which was consistent with the observed increased fat pad weights and hepatic triglycerides. This study represents the first report to quantify the transfer of an environmentally relevant concentration of TCC from mother to offspring in the mouse model and evaluate bio-distribution after exposure using AMS. Our findings suggest that early-life exposure to TCC may interfere with lipid metabolism and could have implications for human health.
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Affiliation(s)
- Heather A. Enright
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
- * E-mail:
| | - Miranda J. S. Falso
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
| | - Michael A. Malfatti
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
| | - Victoria Lao
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
| | - Edward A. Kuhn
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
| | - Nicholas Hum
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
| | - Yilan Shi
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
| | - Ana Paula Sales
- Data Analytics and Decision Sciences, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
| | - Kurt W. Haack
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
| | - Kristen S. Kulp
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
| | - Bruce A. Buchholz
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
| | - Gabriela G. Loots
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
| | - Graham Bench
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
| | - Kenneth W. Turteltaub
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
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11
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Bennion BJ, Be NA, McNerney MW, Lao V, Carlson EM, Valdez CA, Malfatti MA, Enright HA, Nguyen TH, Lightstone FC, Carpenter TS. Predicting a Drug's Membrane Permeability: A Computational Model Validated With in Vitro Permeability Assay Data. J Phys Chem B 2017; 121:5228-5237. [PMID: 28453293 DOI: 10.1021/acs.jpcb.7b02914] [Citation(s) in RCA: 154] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Membrane permeability is a key property to consider during the drug design process, and particularly vital when dealing with small molecules that have intracellular targets as their efficacy highly depends on their ability to cross the membrane. In this work, we describe the use of umbrella sampling molecular dynamics (MD) computational modeling to comprehensively assess the passive permeability profile of a range of compounds through a lipid bilayer. The model was initially calibrated through in vitro validation studies employing a parallel artificial membrane permeability assay (PAMPA). The model was subsequently evaluated for its quantitative prediction of permeability profiles for a series of custom synthesized and closely related compounds. The results exhibited substantially improved agreement with the PAMPA data, relative to alternative existing methods. Our work introduces a computational model that underwent progressive molding and fine-tuning as a result of its synergistic collaboration with numerous in vitro PAMPA permeability assays. The presented computational model introduces itself as a useful, predictive tool for permeability prediction.
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Affiliation(s)
- Brian J Bennion
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory , Livermore, California 94550, United States
| | - Nicholas A Be
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory , Livermore, California 94550, United States
| | - M Windy McNerney
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory , Livermore, California 94550, United States.,War Related Illness and Injury Study Center, Veterans Affairs , Palo Alto, California 94304, United States
| | - Victoria Lao
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory , Livermore, California 94550, United States
| | - Emma M Carlson
- U.S. Naval Academy , Annapolis, Maryland 21402, United States
| | - Carlos A Valdez
- Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory , Livermore, California 94550, United States
| | - Michael A Malfatti
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory , Livermore, California 94550, United States
| | - Heather A Enright
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory , Livermore, California 94550, United States
| | - Tuan H Nguyen
- Global Security Directorate, Lawrence Livermore National Laboratory , Livermore, California 94550, United States
| | - Felice C Lightstone
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory , Livermore, California 94550, United States
| | - Timothy S Carpenter
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory , Livermore, California 94550, United States
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12
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Wang Y, Villalta PW, Peng L, Dingley K, Malfatti MA, Turteltaub KW, Turesky RJ. Mass Spectrometric Characterization of an Acid-Labile Adduct Formed with 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine and Albumin in Humans. Chem Res Toxicol 2017; 30:705-714. [PMID: 27984695 DOI: 10.1021/acs.chemrestox.6b00426] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a carcinogenic heterocyclic aromatic amine formed during the high-temperature cooking of meats. The cytochrome P450-mediated N-hydroxylation of the exocyclic amine group of PhIP produces 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine, an electrophilic metabolite that forms adducts with DNA and proteins. Previous studies conducted by our laboratory showed that the reaction of N-oxidized PhIP metabolites with human albumin in vitro primarily occurs at the Cys34 residue, to produce an acid-labile linked sulfinamide adduct. On the basis of these findings, we developed a sensitive ultraperformance liquid chromatography-mass spectrometry method to measure acid-labile albumin-PhIP adducts in human volunteers administered a dietary-relevant dose of 14C-labeled PhIP [Dingley, K. H., et al. (1999) Cancer Epidemiol., Biomarkers Prev. 8, 507-512]. Mild acid treatment of albumin (0.1 N HCl, 37 °C for 1 h) or proteolytic digestion with Pronase [50 mM ammonium bicarbonate buffer (pH 8.5) at 37 °C for 18 h] released similar amounts of covalently bound PhIP, which was characterized by multistage scanning and quantified by Orbitrap mass spectrometry. The amount of [14C]PhIP recovered by acid treatment of albumin 24 h following dosing accounted for 7.2-21.3% of the [14C]PhIP bound to albumin based on accelerator mass spectrometry measurements. 2-Amino-1-methyl-6-(5-hydroxy)phenylimidazo[4,5-b]pyridine, a hydrolysis product of the Cys34 S-N linked sulfenamide adduct of PhIP, was not detected in either acid-treated or protease-treated samples. These findings suggest that a portion of the PhIP bound to albumin in vivo probably occurs as an acid-labile sulfinamide adduct formed at the Cys34 residue.
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Affiliation(s)
| | | | - Lijuan Peng
- School of Food Science and Engineering, Wuhan Polytechnic University , ChangQing Garden, Hankou, Wuhan 430023, P. R. China
| | - Karen Dingley
- Biosciences and Biotechnology Division, Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory , Livermore, California 94550, United States
| | - Michael A Malfatti
- Biosciences and Biotechnology Division, Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory , Livermore, California 94550, United States
| | - K W Turteltaub
- Biosciences and Biotechnology Division, Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory , Livermore, California 94550, United States
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13
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Enright HA, Malfatti MA, Zimmermann M, Ognibene T, Henderson P, Turteltaub KW. Use of Accelerator Mass Spectrometry in Human Health and Molecular Toxicology. Chem Res Toxicol 2016; 29:1976-1986. [PMID: 27726383 PMCID: PMC5203773 DOI: 10.1021/acs.chemrestox.6b00234] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [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: 12/13/2022]
Abstract
Accelerator mass spectrometry (AMS) has been adopted as a powerful bioanalytical method for human studies in the areas of pharmacology and toxicology. The exquisite sensitivity (10-18 mol) of AMS has facilitated studies of toxins and drugs at environmentally and physiologically relevant concentrations in humans. Such studies include risk assessment of environmental toxicants, drug candidate selection, absolute bioavailability determination, and more recently, assessment of drug-target binding as a biomarker of response to chemotherapy. Combining AMS with complementary capabilities such as high performance liquid chromatography (HPLC) can maximize data within a single experiment and provide additional insight when assessing drugs and toxins, such as metabolic profiling. Recent advances in the AMS technology at Lawrence Livermore National Laboratory have allowed for direct coupling of AMS with complementary capabilities such as HPLC via a liquid sample moving wire interface, offering greater sensitivity compared to that of graphite-based analysis, therefore enabling the use of lower 14C and chemical doses, which are imperative for clinical testing. The aim of this review is to highlight the recent efforts in human studies using AMS, including technological advancements and discussion of the continued promise of AMS for innovative clinical based research.
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Affiliation(s)
- Heather A. Enright
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA USA
| | - Michael A. Malfatti
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA USA
| | - Maike Zimmermann
- Department of Internal Medicine, Division of Hematology and Oncology, UC Davis Medical Center, Sacramento, CA USA
- Accelerated Medical Diagnostics Incorporated, Berkeley, CA USA
| | - Ted Ognibene
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA USA
| | - Paul Henderson
- Department of Internal Medicine, Division of Hematology and Oncology, UC Davis Medical Center, Sacramento, CA USA
- Accelerated Medical Diagnostics Incorporated, Berkeley, CA USA
| | - Kenneth W. Turteltaub
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA USA
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14
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Scharadin TM, Zhang H, Zimmermann M, Wang S, Malfatti MA, Cimino GD, Turteltaub K, de Vere White R, Pan CX, Henderson PT. Diagnostic Microdosing Approach to Study Gemcitabine Resistance. Chem Res Toxicol 2016; 29:1843-1848. [PMID: 27657672 DOI: 10.1021/acs.chemrestox.6b00247] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Gemcitabine metabolites cause the termination of DNA replication and induction of apoptosis. We determined whether subtherapeutic "microdoses" of gemcitabine are incorporated into DNA at levels that correlate to drug cytotoxicity. A pair of nearly isogenic bladder cancer cell lines differing in resistance to several chemotherapy drugs were treated with various concentrations of 14C-labeled gemcitabine for 4-24 h. Drug incorporation into DNA was determined by accelerator mass spectrometry. A mechanistic analysis determined that RRM2, a DNA synthesis protein and a known resistance factor, substantially mediated gemcitabine toxicity. These results support gemcitabine levels in DNA as a potential biomarker of drug cytotoxicity.
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Affiliation(s)
- Tiffany M Scharadin
- Department of Internal Medicine, Division of Hematology and Oncology, University of California Davis , Sacramento, California 95817, United States
| | - Hongyong Zhang
- Department of Internal Medicine, Division of Hematology and Oncology, University of California Davis , Sacramento, California 95817, United States
| | - Maike Zimmermann
- Department of Internal Medicine, Division of Hematology and Oncology, University of California Davis , Sacramento, California 95817, United States.,Accelerated Medical Diagnostics Incorporated , Berkeley, California 95618, United States
| | - Sisi Wang
- Department of Internal Medicine, Division of Hematology and Oncology, University of California Davis , Sacramento, California 95817, United States
| | - Michael A Malfatti
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory , Livermore, California 94550, United States
| | - George D Cimino
- Accelerated Medical Diagnostics Incorporated , Berkeley, California 95618, United States
| | - Kenneth Turteltaub
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory , Livermore, California 94550, United States
| | - Ralph de Vere White
- Department of Urology, University of California Davis Medical Center , Sacramento, California 95817, United States
| | - Chong-Xian Pan
- Department of Internal Medicine, Division of Hematology and Oncology, University of California Davis , Sacramento, California 95817, United States.,Accelerated Medical Diagnostics Incorporated , Berkeley, California 95618, United States
| | - Paul T Henderson
- Department of Internal Medicine, Division of Hematology and Oncology, University of California Davis , Sacramento, California 95817, United States.,Accelerated Medical Diagnostics Incorporated , Berkeley, California 95618, United States
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15
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Malfatti MA, Kuhn EA, Turteltaub KW, Vickers SM, Jensen EH, Strayer L, Anderson KE. Disposition of the Dietary Mutagen 2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline in Healthy and Pancreatic Cancer Compromised Humans. Chem Res Toxicol 2016; 29:352-8. [PMID: 26918625 DOI: 10.1021/acs.chemrestox.5b00495] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Pancreatic cancer is the fourth leading cause of cancer death in the U.S. Once diagnosed, prognosis is poor with a 5-year survival rate of less than 5%. Exposure to carcinogenic heterocyclic amines (HCAs) derived from cooked meat has been shown to be positively associated with pancreatic cancer risk. To evaluate the processes that determine the carcinogenic potential of HCAs for human pancreas, 14-carbon labeled 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), a putative human carcinogenic HCA found in well-done cooked meat, was administered at a dietary relevant dose to human volunteers diagnosed with pancreatic cancer undergoing partial pancreatectomy and healthy control volunteers. After (14)C-MeIQx exposure, blood and urine were collected for pharmacokinetic and metabolite analysis. MeIQx-DNA adducts levels were quantified by accelerator mass spectrometry from pancreatic tissue excised during surgery from the cancer patient group. Pharmacokinetic analysis of plasma revealed a rapid distribution of MeIQx with a plasma elimination half-life of approximately 3.5 h in 50% of the cancer patients and all of the control volunteers. In 2 of the 4 cancer patients, very low levels of MeIQx were detected in plasma and urine suggesting low absorption from the gut into the plasma. Urinary metabolite analysis revealed five MeIQx metabolites with 2-amino-3-methylimidazo[4,5-f]quinoxaline-8-carboxylic acid being the most abundant accounting for 25%-50% of the recovered 14-carbon/mL urine. There was no discernible difference in metabolite levels between the cancer patient volunteers and the control group. MeIQx-DNA adduct analysis of pancreas and duodenum tissue revealed adduct levels indistinguishable from background levels. Although other meat-derived HCA mutagens have been shown to bind DNA in pancreatic tissue, indicating that exposure to HCAs from cooked meat cannot be discounted as a risk factor for pancreatic cancer, the results from this current study show that exposure to a single dietary dose of MeIQx does not readily form measurable DNA adducts under the conditions of the experiment.
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Affiliation(s)
- Michael A Malfatti
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory , 7000 East Avenue, L-452, Livermore, California 94550, United States
| | - Edward A Kuhn
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory , 7000 East Avenue, L-452, Livermore, California 94550, United States
| | - Kenneth W Turteltaub
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory , 7000 East Avenue, L-452, Livermore, California 94550, United States
| | - Selwyn M Vickers
- University of Alabama , 1720 2nd Avenue South, Birmingham, Alabama 35233, United States
| | - Eric H Jensen
- University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Lori Strayer
- University of Minnesota , Minneapolis, Minnesota 55455, United States
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16
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Dingley KH, Ubick EA, Vogel JS, Ognibene TJ, Malfatti MA, Kulp K, Haack KW. DNA isolation and sample preparation for quantification of adduct levels by accelerator mass spectrometry. Methods Mol Biol 2014; 1105:147-57. [PMID: 24623226 DOI: 10.1007/978-1-62703-739-6_12] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Accelerator mass spectrometry (AMS) is a highly sensitive technique used for the quantification of adducts following exposure to carbon-14- or tritium-labeled chemicals, with detection limits in the range of one adduct per 10(11)-10(12) nucleotides. The protocol described in this chapter provides an optimal method for isolating and preparing DNA samples to measure isotope-labeled DNA adducts by AMS. When preparing samples, special precautions must be taken to avoid cross-contamination of isotope among samples and produce a sample that is compatible with AMS. The DNA isolation method described is based upon digestion of tissue with proteinase K, followed by extraction of DNA using Qiagen isolation columns. The extracted DNA is precipitated with isopropanol, washed repeatedly with 70 % ethanol to remove salt, and then dissolved in water. DNA samples are then converted to graphite or titanium hydride and the isotope content measured by AMS to quantify adduct levels. This method has been used to reliably generate good yields of uncontaminated, pure DNA from animal and human tissues for analysis of adduct levels.
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Affiliation(s)
- Karen H Dingley
- Biology and Biotechnology Research Program, Center for Accelerator Mass Spectroscopy, Lawrence Livermore National Laboratory, Livermore, CA, 94551, USA,
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17
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Malfatti MA, Palko HA, Kuhn EA, Turteltaub KW. Determining the pharmacokinetics and long-term biodistribution of SiO2 nanoparticles in vivo using accelerator mass spectrometry. Nano Lett 2012; 12:5532-8. [PMID: 23075393 PMCID: PMC3499105 DOI: 10.1021/nl302412f] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Biodistribution is an important factor in better understanding silica dioxide nanoparticle (SiNP) safety. Currently, comprehensive studies on biodistribution are lacking, most likely due to the lack of suitable analytical methods. Accelerator mass spectrometry was used to investigate the relationship between administered dose, pharmacokinetics (PK), and long-term biodistribution of (14)C-SiNPs in vivo. PK analysis showed that SiNPs were rapidly cleared from the central compartment, were distributed to tissues of the reticuloendothelial system, and persisted in the tissue over the 8 week time course, raising questions about the potential for bioaccumulation and associated long-term effects.
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Affiliation(s)
- Michael A Malfatti
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, USA. malfatti1@llnlgov
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18
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Chen C, Ma X, Malfatti MA, Krausz KW, Kimura S, Felton JS, Idle JR, Gonzalez FJ. A comprehensive investigation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) metabolism in the mouse using a multivariate data analysis approach. Chem Res Toxicol 2007; 20:531-42. [PMID: 17279779 PMCID: PMC1850849 DOI: 10.1021/tx600320w] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [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: 11/29/2022]
Abstract
2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a potent rodent carcinogen and a potential human carcinogen because of its existence in the normal human diet. N2-OH-PhIP, a major PhIP metabolite, has been identified as a precursor of genotoxic species. In vitro data supported the view that CYP1A2 is the major enzyme responsible for the formation of N2-OH-PhIP. However, disruption of the CYP1A2 gene in mouse failed to inhibit PhIP-induced carcinogenesis. To investigate the mechanism underlying this observation, the metabolism of PhIP in wild-type, Cyp1a2-null, and CYP1A2-humanized mice was examined in detail using a metabolomic approach. Following data acquisition in a high-resolution LC-MS system, urinary metabolomes of the control and PhIP-treated mice were characterized in a principal component analysis (PCA) model. Comprehensive metabolite profiles of PhIP in high dose (10 mg/kg) and low dose (100 microg/kg) were established through analyzing urinary ions contributing to the separation of three mouse lines in the multivariate model and by measuring radiolabled PhIP metabolite in a radio-HPLC assay, respectively. The genotoxicity of PhIP to three mouse lines was evaluated by measuring DNA adduction levels in liver, lung, colon, and mammary gland. On the basis of the chemical identities of 17 urinary PhIP metabolites, including eight novel metabolites, multivariate data analysis revealed the role of CYP1A2 in PhIP metabolism and a human-mouse interspecies difference in the catalytic activity of CYP1A2. In addition, the results also showed that Cyp1a2-null mice still possess significant N2-hydroxylation and DNA adduction activities, which may be partially attributed to mouse CYP2C enzymes according to the results from in vitro microsome and Supersome incubations and antibody inhibition experiments.
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Affiliation(s)
- Chi Chen
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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Chen C, Ma X, Malfatti MA, Krausz KW, Kimura S, Felton JS, Idle JR, Gonzalez FJ. A Metabolomic Investigation of 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) Metabolism in the Mouse. FASEB J 2007. [DOI: 10.1096/fasebj.21.6.a813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Chi Chen
- Laboratory of MetabolismNCINIH37 Convent Drive, Rm3112BethesdaMD20892
| | - Xiaochao Ma
- Laboratory of MetabolismNCINIH37 Convent Drive, Rm3112BethesdaMD20892
| | - Michael A Malfatti
- Biosciences DirectorateLawrence Livermore National LaboratoryP.O. Box 808, L‐452LivermoreCA94551
| | | | - Shioko Kimura
- Laboratory of MetabolismNCINIH37 Convent Drive, Rm3112BethesdaMD20892
| | - James S Felton
- Biosciences DirectorateLawrence Livermore National LaboratoryP.O. Box 808, L‐452LivermoreCA94551
| | - Jeffery R Idle
- Laboratory of MetabolismNCINIH37 Convent Drive, Rm3112BethesdaMD20892
| | - Frank J Gonzalez
- Laboratory of MetabolismNCINIH37 Convent Drive, Rm3112BethesdaMD20892
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Abstract
The understanding of mutagenic potency has been primarily approached using "quantitative structure-activity relationships" (QSAR). Often this method allows the prediction of mutagenic potency of the compound based on its structure. But it does not give the underlying reason why the mutagenic activities differ. We have taken a set of heterocyclic amine structures and used molecular dynamic calculations to dock these molecules into the active site of a computational model of the cytochrome P4501A2 enzyme. The calculated binding strength using Boltzman distribution constants was then compared to the QSAR value (HF/6-31G* optimized structures) and the Ames/Salmonella mutagenic potency. Further understanding will only come from knowing the complete set of mutagenic determinants. These include the nitrenium ion half-life, DNA adduct half-life, efficiency of repair of the adduct, and ultimately fixation of the mutation through cellular processes. For two isomers, PhIP and 3-Me-PhIP, we showed that for the 100-fold difference in the mutagenic potency a 5-fold difference can be accounted for by differences in the P450 oxidation. The other factor of 20 is not clearly understood but is downstream from the oxidation step. The application of QSAR (chemical characteristics) to biological principles related to mutagenesis is explored in this report.
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Affiliation(s)
- James S Felton
- Chemistry, Materials and Life Sciences Directorate, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94551, USA.
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Malfatti MA, Dingley KH, Nowell-Kadlubar S, Ubick EA, Mulakken N, Nelson D, Lang NP, Felton JS, Turteltaub KW. The Urinary Metabolite Profile of the Dietary Carcinogen 2-Amino-1-Methyl-6-Phenylimidazo[4,5-b]Pyridine Is Predictive of Colon DNA Adducts after a Low-Dose Exposure in Humans. Cancer Res 2006; 66:10541-7. [PMID: 17079477 DOI: 10.1158/0008-5472.can-06-1573] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [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: 11/16/2022]
Abstract
Epidemiologic evidence indicates that exposure to heterocyclic amines in the diet is an important risk factor for the development of colon cancer. Well-done cooked meats contain significant levels of heterocyclic amines, which have been shown to cause cancer in laboratory animals. To better understand the mechanisms of heterocyclic amine bioactivation in humans, the most mass abundant heterocyclic amine, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), was used to assess the relationship between PhIP metabolism and DNA adduct formation. Ten human volunteers where administered a dietary relevant dose of [(14)C]PhIP 48 to 72 hours before surgery to remove colon tumors. Urine was collected for 24 hours after dosing for metabolite analysis, and DNA was extracted from colon tissue and analyzed by accelerator mass spectrometry for DNA adducts. All 10 subjects were phenotyped for cytochrome P4501A2 (CYP1A2), N-acetyltransferase 2, and sulfotransferase 1A1 enzyme activity. Twelve PhIP metabolites were detected in the urine samples. The most abundant metabolite in all volunteers was N-hydroxy-PhIP-N(2)-glucuronide. Metabolite levels varied significantly between the volunteers. Interindividual differences in colon DNA adducts levels were observed between each individual. The data showed that individuals with a rapid CYP1A2 phenotype and high levels of urinary N-hydroxy-PhIP-N(2)-glucuronide had the lowest level of colon PhIP-DNA adducts. This suggests that glucuronidation plays a significant role in detoxifying N-hydroxy-PhIP. The levels of urinary N-hydroxy-PhIP-N(2)-glucuronide were negatively correlated to colon DNA adduct levels. Although it is difficult to make definite conclusions from a small data set, the results from this pilot study have encouraged further investigations using a much larger study group.
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Affiliation(s)
- Michael A Malfatti
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
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Ma X, Idle JR, Malfatti MA, Krausz KW, Nebert DW, Chen CS, Felton JS, Waxman DJ, Gonzalez FJ. Mouse lung CYP1A1 catalyzes the metabolic activation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). Carcinogenesis 2006; 28:732-7. [PMID: 17052995 PMCID: PMC1829392 DOI: 10.1093/carcin/bgl184] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [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: 11/14/2022] Open
Abstract
2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) carcinogenesis is initiated by N(2)-hydroxylation, mediated by several cytochromes P450, including CYP1A1. However, the role of CYP1A1 in PhIP metabolic activation in vivo is unclear. In this study, Cyp1a1-null and wild-type (WT) mice were used to investigate the potential role of CYP1A1 in PhIP metabolic activation in vivo. PhIP N(2)-hydroxylation was actively catalyzed by lung homogenates of WT mice, at a rate of 14.9 +/- 5.0 pmol/min/g tissue, but <1 pmol/min/g tissue in stomach and small intestine, and almost undetectable in mammary gland and colon. PhIP N(2)-hydroxylation catalyzed by lung homogenates of Cyp1a1-null mice was approximately 10-fold lower than that of WT mice. In contrast, PhIP N(2)-hydroxylation activity in lung homogenates of Cyp1a2-null versus WT mice was not decreased. Pretreatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin increased lung Cyp1a1 mRNA and lung homogenate PhIP N(2)-hydroxylase activity approximately 50-fold in WT mice, where the activity was substantially inhibited (70%) by monoclonal antibodies against CYP1A1. In vivo, 30 min after oral treatment with PhIP, PhIP levels in lung were similar to those in liver. After a single dose of 0.1 mg/kg [(14)C]PhIP, lung PhIP-DNA adduct levels in Cyp1a1-null mice, but not in Cyp1a2-null mice, were significantly lower (P = 0.0028) than in WT mice. These results reveal that mouse lung has basal and inducible PhIP N(2)-hydroxylase activity predominantly catalyzed by CYP1A1. Because of the high inducibility of human CYP1A1, especially in cigarette smokers, the role of lung CYP1A1 in PhIP carcinogenesis should be considered. (237 words).
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Affiliation(s)
- Xiaochao Ma
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Jeffrey R. Idle
- Institute of Pharmacology, 1 Faculty of Medicine, Charles University, 128 00 Praha 2, Czech Republic
| | - Michael A. Malfatti
- Biosciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94551
| | - Kristopher W. Krausz
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Daniel W. Nebert
- Department of Environmental Health, University of Cincinnati Medical Center, Cincinnati, OH 45267
| | | | - James S. Felton
- Biosciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94551
| | | | - Frank J. Gonzalez
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
- *Corresponding author: Frank J. Gonzalez, Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, Building 37, Room 3106, Bethesda, MD 20892. Tel: +301 496 9067. Fax: +301 496 8419.
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Affiliation(s)
- James S Felton
- Lawrence Livermore National Laboratory, Livermore, CA 94551, USA.
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Malfatti MA, Ubick EA, Felton JS. The impact of glucuronidation on the bioactivation and DNA adduction of the cooked-food carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine in vivo. Carcinogenesis 2005; 26:2019-28. [PMID: 15944213 DOI: 10.1093/carcin/bgi151] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [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: 12/13/2022] Open
Abstract
UDP-glucuronosyltransferases (UGTs) catalyze the glucuronidation of many different chemicals. Glucuronidation is especially important for detoxifying reactive intermediates from metabolic reactions, which otherwise can be biotransformed into highly reactive cytotoxic or carcinogenic species. Detoxification of certain food-borne-carcinogenic heterocyclic amines (HAs) is highly dependent on UGT1A-mediated glucuronidation. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), the most mass abundant carcinogenic HA found in well-done cooked meat, is extensively glucuronidated by UGT1A proteins. In humans, CYP1A2 catalyzed N-hydroxylation and subsequent UGT1A-mediated glucuronidation is a dominant pathway in the metabolism of PhIP. Therefore, changes in glucuronidation rates could significantly alter PhIP metabolism. To determine the importance of UGT1A-mediated glucuronidation in the biotransformation of PhIP, hepatic UGT1A deficient Gunn and UGT1A proficient Wistar rats were exposed to a 100 microg/kg oral dose of [(14)C]PhIP. Urine was collected over 24 h and the PhIP urinary metabolite profiles were compared between the two strains. After the 24 h exposure, livers and colons were removed and analyzed for DNA adduct formation by accelerator mass spectrometry. Wistar rats produced several PhIP and N-hydroxy-PhIP glucuronides that accounted for approximately 25% of the total amount of recovered urinary metabolites. In the Gunn rats, PhIP and N-hydroxy-PhIP glucuronides were reduced by 68-92%, compared with the Wistar rats. PhIP-DNA adduct analysis from the Gunn rats revealed a correlation between reduced urinary PhIP and N-hydroxy-PhIP glucuronide levels and increased hepatic DNA adducts, compared with the Wistar rats. In the colon, DNA adduct levels were lower in the Gunn rats compared with the Wistar rats, suggesting deficient hepatic UGT1A activity provides protection against DNA adduct formation in peripheral tissue. Due to differences in PhIP metabolism between humans and rodents, extrapolation of these results to the human situation must be done with caution. These results indicate that UGT1A-mediated glucuronidation of PhIP and N-hydroxy-PhIP is an important pathway for PhIP detoxification, and demonstrate the importance of tissue-specific metabolism. Tissues with reduced UGT1A activity can have a higher rate of PhIP activation and be more inclined to form DNA adducts compared with tissues with normal UGT1A activity.
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Affiliation(s)
- Michael A Malfatti
- Biosciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94551, USA
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Malfatti MA, Wu RW, Felton JS. The effect of UDP-glucuronosyltransferase 1A1 expression on the mutagenicity and metabolism of the cooked-food carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine in CHO cells. Mutat Res 2005; 570:205-14. [PMID: 15708579 DOI: 10.1016/j.mrfmmm.2004.11.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [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] [Received: 08/30/2004] [Revised: 11/03/2004] [Accepted: 11/15/2004] [Indexed: 05/01/2023]
Abstract
UDP-glucuronosyltransferase proteins (UGT) catalyze the glucuronidation of both endogenous and xenobiotic compounds. In previous studies, UGT1A1 has been implicated in the detoxification of certain food-borne carcinogenic-heterocyclic amines. To determine the importance of UDP-glucuronosyltransferase 1A1 (UGT1A1) in the biotransformation of the cooked-food carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), genetically modified CHO cells that are nucleotide excision repair-deficient, and express cytochrome P4501A2 (UV5P3 cell line) were transfected with a cDNA plasmid of human UGT1A1 to establish the UDP-glucuronosyltransferase 1A1 expressing 5P3hUGT1A1 cell line. Expression of the UGT1A1 gene was verified by screening neo gene expressing clonal isolates (G-418 resistant) for their sensitivity to cell killing from PhIP exposure. Five of 11 clones were chosen for further analysis due to their resistance to cell killing. Western blot analysis was used to confirm the presence of the UGT1A1 and CYP1A2 proteins. All five clones displayed a 52-kDa protein band, which corresponded to a UGT1A1 control protein. Only four of the clones had a protein band that corresponded to the CYP1A2 control protein. Correct fragment size of the cDNAs in the remaining four clones was confirmed by RT-PCR and quantification of the mRNA product was accomplished by real-time RT-PCR. Expression of UGT1A1 in the transfected cells was 10(4)-10(5)-fold higher relative to the UV5P3 parental cells. One clone (#14) had a 10-fold higher increase in expression at 1.47 x 10(5) over the other three clones. This clone was also the most active in converting N-hydroxy-PhIP to N-hydroxy-PhIP glucuronide conjugates in microsomal metabolism assays. Based on the D50 values, the cytotoxic effect of PhIP was decreased approximately 350-fold in the 5P3hUGT1A1 cells compared to the UV5P3 control cells. In addition, no significant increase in mutation frequency was observed in the transfected cells. These results clearly indicate that UGT1A1 plays a critical role in PhIP biotransformation, providing protection against PhIP-mediated cytotoxicity and mutagenicity.
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Affiliation(s)
- Michael A Malfatti
- Biology and Biotechnology Research Program, Lawrence Livermore National Laboratory, P.O. Box 808, L-452, Livermore, CA 94551-9900, USA
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Malfatti MA, Felton JS. Human UDP-Glucuronosyltransferase 1A1 Is the Primary Enzyme Responsible for the N-Glucuronidation of N-Hydroxy-PhIP in Vitro. Chem Res Toxicol 2004; 17:1137-44. [PMID: 15310245 DOI: 10.1021/tx049898m] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [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: 11/30/2022]
Abstract
UDP-glucuronosyltransferase 1A proteins (UGT1A) catalyze the glucuronidation of many endogenous and xenobiotic compounds including heterocyclic amines and their hydroxylated metabolites. Studies have shown that in humans UGT1A-mediated glucuronidation is an important pathway in the detoxification of food-borne carcinogenic heterocyclic amines. The biotransformation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), the most mass abundant heterocyclic amine found in cooked meats, is highly dependent on cytochrome P4501A2 hydroxylation followed by UGT-catalyzed glucuronidation of the N-hydroxy-PhIP reactive intermediate. To determine which UGT1A proteins are involved in the glucuronidation of N-hydroxy-PhIP, microsomal preparations from baculovirus-infected insect cells that express all of the known functional human UGT1A isozymes (UGT1A1, -1A3, -1A4, -1A6, -1A7, -1A8, -1A9, and -1A10) were exposed to N-hydroxy-PhIP and the reaction products were isolated by HPLC. All UGT1A proteins except UGT1A6 showed some degree of activity toward N-hydroxy-PhIP. The formation of both N-hydroxy-PhIP-N(2)-glucuronide and N-hydroxy-PhIP-N3-glucuronide was both time- and substrate concentration-dependent. UGT1A1 was the most efficient in converting N-hydroxy-PhIP to both conjugates producing five times more of the N(2)-conjugate than UGT1A4, the next most active UGT, and 286 times more than UGT1A7, the least active UGT. With an apparent K(m) of 52 microM and a K(cat) of 114 min(-)(1), UGT1A1 was also the most catalytically efficient in forming N-hydroxy-PhIP-N(2)-glucuronide. The catalytic efficiency for N-hydroxy-PhIP-N3-glucuronide formation was 8, 10, and 6 times lower for UGT1A1, -1A4, and -1A8, respectively, when compared to the K(cat) values for N-hydroxy-PhIP-N(2)-glucuronide formation. These results clearly show that UGT1A1 has the highest specificity for glucuronidating N-hydroxy-PhIP. Polymorphic expression resulting in decreased UGT1A1 activity in humans can cause reduced rates of glucuronidation, which can change the metabolic ratio between bioactivation and detoxification to favor bioactivation. This change will increase the susceptibility to the deleterious effects from PhIP exposure because the capacity to form nontoxic N-hydroxy-PhIP glucuronide conjugates will be diminished.
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Affiliation(s)
- Michael A Malfatti
- Biology and Biotechnology Research Program, Lawrence Livermore National Laboratory, P.O. Box 808, L-452, Livermore, California 94551, USA
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Felton JS, Knize MG, Bennett LM, Malfatti MA, Colvin ME, Kulp KS. Impact of environmental exposures on the mutagenicity/carcinogenicity of heterocyclic amines. Toxicology 2004; 198:135-45. [PMID: 15138037 DOI: 10.1016/j.tox.2004.01.024] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [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: 01/30/2023]
Abstract
Carcinogenic heterocyclic amines are produced from overcooked foods and are highly mutagenic in most short-term test systems. One of the most abundant of these amines, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), induces breast, colon and prostate tumors in rats. Human dietary epidemiology studies suggest a strong correlation between either meat consumption or well-done muscle meat consumption and cancers of the colon, breast, stomach, lung and esophagus. For over 20 years our laboratory has helped define the human exposure to these dietary carcinogens. In this report we describe how various environmental exposures may modulate the risk from exposure to heterocyclic amines, especially PhIP. To assess the impact of foods on PhIP metabolism in humans, we developed an LC/MS/MS method to analyze the four major PhIP urinary metabolites following the consumption of a single portion of grilled chicken. Adding broccoli to the volunteers' diet altered the kinetics of PhIP metabolism. At the cellular level we have found that PhIP itself stimulates a significant estrogenic response in MCF-7 cells, but even more interestingly, co-incubation of the cells with herbal teas appear to enhance the response. Numerous environmental chemicals found in food or the atmosphere can impact the exposure, metabolism, and cell proliferation response of heterocyclic amines.
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Affiliation(s)
- James S Felton
- Biology and Biotechnology Research Program, L-452, Lawrence Livermore National Laboratory, Livermore, CA 94551, USA.
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Felton JS, Knize MG, Salmon CP, Malfatti MA, Kulp KS. Human exposure to heterocyclic amine food mutagens/carcinogens: relevance to breast cancer. Environ Mol Mutagen 2002; 39:112-118. [PMID: 11921178 DOI: 10.1002/em.10070] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Heterocyclic amines produced from overcooked foods are extremely mutagenic in numerous in vitro and in vivo test systems. One of these mutagens, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), induces breast tumors in rats and has been implicated in dietary epidemiology studies as raising the risk of breast cancer in humans. Efforts in our laboratory and others have centered on defining the exposure to PhIP and other dietary mutagens derived from cooked food. We accomplish this by analyzing the foods with a series of solid-phase extractions and HPLC. We have developed an LC/MS/MS method to analyze the four major human PhIP metabolites (sulfates and glucuronides) following a single meal containing 27 microg of cooking-produced PhIP in 200 g of grilled meat. Although the intake of PhIP was similar for each of eight women, the total amount excreted in the urine and the metabolite profiles differed among the subjects. It appears that adsorption (digestion) from the meat matrix, other foods in the diet, and genetic differences in metabolism may contribute to the variation. The four major metabolites that can be routinely assayed in the urine are N(2)-OH-PhIP-N(2)-glucuronide, PhIP-N(2)-glucuronide, 4'-PhIP-glucuronide, and N(2)-OH-PhIP-N3-glucuronide. This work is suited to investigate individual exposure and risk, especially for breast cancer, from these potent dietary mutagens.
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Affiliation(s)
- James S Felton
- Molecular and Structural Biology Division, Lawrence Livermore National Laboratory, Livermore, California 94551, USA.
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Malfatti MA, Felton JS. N-glucuronidation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and N_hydroxy-PhIP by specific human UDP-glucuronosyltransferases. Carcinogenesis 2001; 22:1087-93. [PMID: 11408353 DOI: 10.1093/carcin/22.7.1087] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [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: 11/14/2022] Open
Abstract
Glucuronidation is a major metabolic pathway in the biotransformation of many xenobiotics. Recent studies have shown that in humans, UDP-glucuronosyltransferase (UGT)-mediated glucuronidation plays a critical role in the detoxification of food-borne carcinogenic heterocyclic amines. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), the most abundant carcinogenic heterocyclic amine found in well-cooked meats, has been shown to be extensively glucuronidated in humans. To determine which UGT isozymes are involved in the biotransformation of PhIP and the cytochrome P4501A2-mediated reactive intermediate N-hydroxy-PhIP, microsomes expressing human UGT1A1, -1A4, -1A6 or -1A9 were incubated with PhIP and N-hydroxy-PhIP and the reaction products analyzed by HPLC and ESI-MS. Incubations containing N-hydroxy-PhIP and UGT1A1 expressing microsomes, with an apparent Km of 4.58 microM and a Vmax of 4.18 pmol/min/mg protein, had the highest capacity to convert N-hydroxy-PhIP to N-hydroxy-PhIP-N2-glucuronide. Microsomes expressing UGT1A9 produced N-hydroxy-PhIP-N3-glucuronide at the highest rate with an apparent Km and Vmax of 3.73 microM and 4.07 pmol/min/mg, respectively. A third previously undefined glucuronide accounted for 31% of the total glucuronides formed from the UGT1A4 expressing microsomes. No glucuronide conjugates were detected from microsomes expressing UGT1A6. Incubations containing PhIP as substrate formed direct PhIP-glucuronides in microsomes expressing UGT1A1, UGT1A4 and UGT1A9 but at levels averaging 53-fold lower than when N-hydroxy-PhIP was used as the substrate. Knowing the glucuronidation capacity of the specific UGT isozymes involved in PhIP and N-hydroxy-PhIP glucuronidation should help in determining the individual susceptibility to the potential cancer risk from exposure to PhIP.
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Affiliation(s)
- M A Malfatti
- Biology and Biotechnology Research Program, Lawrence Livermore National Laboratory, PO Box 808, L-452, Livermore, CA 94551, USA
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Knize MG, Kulp KS, Malfatti MA, Salmon CP, Felton JS. Liquid chromatography–tandem mass spectrometry method of urine analysis for determining human variation in carcinogen metabolism. J Chromatogr A 2001; 914:95-103. [PMID: 11358237 DOI: 10.1016/s0021-9673(01)00522-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [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: 10/17/2022]
Abstract
We developed a solid-phase extraction LC-MS-MS method for the analysis of the four major metabolites of PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine) in human urine after a meal of well-done chicken. Ten volunteers each ate either 150 or 200 g of well-done chicken breast containing 9-21 microg of PhIP. Among the individual volunteers there is 8-fold variation in the total amount of metabolites and 20-fold variation in the relative amounts of individual metabolites, showing individual differences in carcinogen metabolism. PhIP metabolites were also detected in urine from a subject consuming chicken in a restaurant meal, demonstrating the method's sensitivity after real-life exposures.
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Affiliation(s)
- M G Knize
- Biology and Biotechnology Research Program, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.
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Kulp KS, Knize MG, Malfatti MA, Salmon CP, Felton JS. Identification of urine metabolites of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine following consumption of a single cooked chicken meal in humans. Carcinogenesis 2000; 21:2065-72. [PMID: 11062169 DOI: 10.1093/carcin/21.11.2065] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [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: 11/13/2022] Open
Abstract
Many studies suggest that mutagenic/carcinogenic chemicals in the diet, like 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), may play a role in human cancer initiation. We have developed a method to quantify PhIP metabolites in human urine and have applied it to samples from female volunteers who had eaten a meal of cooked chicken. For this analysis, urine samples (5 ml) were spiked with a deuterium-labeled internal standard, adsorbed to a macroporous polymeric column and then eluted with methanol. After a solvent exchange to 0.01 M HCl, the urine extracts were passed through a filter, applied to a benzenesulfonic acid column, washed with methanol/acid and eluted with ammonium acetate and concentrated on a C(18) column. The metabolites were eluted from the C(18) column and quantified by LC/MS/MS. In our studies of human PhIP metabolism, eight volunteers were fed 200 g of cooked chicken containing a total of 27 microg PhIP. Urine samples were collected for 24 h after the meal, in 6 h aliquots. Although no metabolites could be found in urine collected from volunteers before eating the chicken, four major human PhIP metabolites, N:(2)-OH-PhIP-N:(2)-glucuronide, PhIP-N:(2)-glucuronide, 4'-PhIP-sulfate and N:(2)-OH-PhIP-N:3-glucuronide, were found in the urine after the chicken meal. The volunteers in the study excreted 4-53% of the ingested PhIP dose in the urine. The rate of metabolite excretion varied among the subjects, however, in all of the subjects the majority of the metabolites were excreted in the first 12 h. Very little metabolite was detected in the urine after 18 h. In humans, N:(2)-OH-PhIP-N:(2) glucuronide is the most abundant urinary metabolite, followed by PhIP-N:(2)-glucuronide. The variation seen in the total amount, excretion time and metabolite ratios with our method suggests that individual digestion, metabolism and/or other components of the diet may influence the absorption and amounts of metabolic products produced from PhIP.
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Affiliation(s)
- K S Kulp
- Biology and Biotechnology Research Program, L-452, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.
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Turteltaub KW, Dingley KH, Curtis KD, Malfatti MA, Turesky RJ, Garner RC, Felton JS, Lang NP. Macromolecular adduct formation and metabolism of heterocyclic amines in humans and rodents at low doses. Cancer Lett 1999; 143:149-55. [PMID: 10503895 DOI: 10.1016/s0304-3835(99)00116-0] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.8] [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: 11/26/2022]
Abstract
2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) are heterocyclic amines formed during the cooking of meat and fish. Both are genotoxic in a number of test systems and are carcinogenic in rats and mice. Human exposure to these compounds via dietary sources has been estimated to be under 1 microg/kg body wt. per day, although most laboratory animal studies have been conducted at doses in excess of 10 mg/kg body wt. per day. We are using accelerator mass spectrometry (AMS), a tool for measuring isotopes with attomole sensitivity, to study the dosimetry of protein and DNA adduct formation by low doses of MeIQx and PhIP in rodents and comparing the adduct levels to those formed in humans. The results of these studies show: 1, protein and DNA adduct levels in rodents are dose-dependent; 2, adduct levels in human tissues and blood are generally greater than in rodents administered equivalent doses; and 3, metabolite profiles differ substantially between humans and rodents for both MeIQx and PhIP, with more N-hydroxylation (bioactivation) and less ring oxidation (detoxification) in humans. These data suggest that rodent models do not accurately represent the human response to heterocyclic amine exposure.
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Affiliation(s)
- K W Turteltaub
- Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.
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Lang NP, Nowell S, Malfatti MA, Kulp KS, Knize MG, Davis C, Massengill J, Williams S, MacLeod S, Dingley KH, Felton JS, Turteltaub KW. In vivo human metabolism of [2-14C]2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). Cancer Lett 1999; 143:135-8. [PMID: 10503892 DOI: 10.1016/s0304-3835(99)00142-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [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: 11/29/2022]
Abstract
To better understand the interactions of the pathways of activation and detoxification on the metabolism of the putative carcinogen, PhIP, we administered a dose of 70-84 microg [2-14C] PhIP (17.5 [microCi 14C) 48-72 h before scheduled colon surgery. Blood and urine collected for the next 48-72 h was evaluated by linear accelerator mass spectroscopy (AMS) and scintillation counting LC-MS to identify specific PhIP metabolites. The thermostable phenol sulfotransferase (SULT1A1) phenotype was correlated with the 4'-PhIP-SO4 levels in the urine at 0-4 h (R = 0.86, P = 0.059). The CYP1A2 activity had a negative correlation with PhIP serum levels at 1 h (R = 0.94, P = 0.06) and a positive correlation with urine N-OH-PhIP levels at 0-4 h (R = 0.85, P = 0.15). This low level radioisotope method of determining the influence of phenotype on metabolism will significantly improve our understanding of the interrelationships of these pathways and provide a critical foundation for the development of individual risk assessment.
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Affiliation(s)
- N P Lang
- Surgery Service, Little Rock VA Hospital, Arkansas Cancer Research Center, University of Arkansas for Medical Sciences, 72205, USA
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Malfatti MA, Kulp KS, Knize MG, Davis C, Massengill JP, Williams S, Nowell S, MacLeod S, Dingley KH, Turteltaub KW, Lang NP, Felton JS. The identification of [2-(14)C]2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine metabolites in humans. Carcinogenesis 1999; 20:705-13. [PMID: 10223203 DOI: 10.1093/carcin/20.4.705] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.2] [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: 01/11/2023] Open
Abstract
[2-(14)C]2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine ([14C]PhIP), a putative human carcinogenic heterocyclic amine found in well-done cooked meat, was administered orally to three colon cancer patients undergoing a partial colonectomy. Forty-eight to seventy-two hours prior to surgery, subjects received a 70-84 microg dose of 14C. Urine and blood were analyzed by HPLC for PhIP and PhIP metabolites. Metabolites were identified based on HPLC co-elution with authentic PhIP metabolite standards, mass spectral analysis and susceptibility to enzymatic cleavage. In two subjects, approximately 90% of the administered [14C]PhIP dose was eliminated in the urine, whereas in the other, only 50% of the dose was found in the urine. One subject excreted three times more radioactivity in the first 4 h than did the others. Twelve radioactive peaks associated with PhIP were detected in the urine samples. The relative amount of each metabolite varied by subject, and the amounts of each metabolite within subjects changed over time. In all three subjects the most abundant urinary metabolite was identified as 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine-N2-glucuron ide (N-hydroxy-PhIP-N2-glucuronide), accounting for 47-60% of the recovered counts in 24 h. PhIP accounted for <1% of the excreted radiolabel in all three patients. Other metabolites detected in the urine at significant amounts were 4-(2-amino-1-methylimidazo[4,5-b]pyrid-6-yl)phenyl sulfate, N-hydroxy-PhIP-N3-glucuronide and PhIP-N2-glucuronide. In the plasma, N-hydroxy-PhIP-N2-glucuronide accounted for 60, 18 and 20% of the recovered plasma radioactivity at 1 h post PhIP dose in subjects 1, 2 and 3 respectively. Plasma PhIP was 56-17% of the recovered dose at 1 h post exposure. The relatively high concentration of N-hydroxy-PhIP-N2-glucuronide and the fact that it is an indicator of bioactivation make this metabolite a potential biomarker for PhIP exposure and activation. Determining the relative differences in PhIP metabolites among individuals will indicate metabolic differences that may predict individual susceptibility to carcinogenic risk from this suspected dietary carcinogen.
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Affiliation(s)
- M A Malfatti
- Biology and Biotechnology Research Program, Lawrence Livermore National Laboratory, CA 94551, USA
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Abstract
Common cooking procedures such as broiling, frying, barbecuing (flame-grilling), heat processing and pyrolysis of protein-rich foods induce the formation of potent mutagenic and carcinogenic heterocyclic amines. These same compounds produce tumors at multiple organ sites in both mice and rats. One example of these induced tumors has also been seen in nonhuman primates. Risk assessment for the human population consuming these compounds requires the integration of knowledge of dosimetry, metabolism, carcinogenic potency, and epidemiology. When this integration is done in even a preliminary way as is done here, the range of risk for an individual from these compounds is enormous. Exposure contributes a range of 200-fold or more and metabolism and DNA repair differences among individuals could easily be an additional 10-fold between individuals. This indicates that differences in human cancer risk for heterocyclic amines could range more than a thousandfold between individuals based on exposure and genetic susceptibility.
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Affiliation(s)
- J S Felton
- Biology and Biotechnology Program, Lawrence Livermore National Laboratory, Livermore, CA 94551-9900, USA.
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Malfatti MA, Connors MS, Mauthe RJ, Felton JS. The capability of rat colon tissue slices to metabolize the cooked-food carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine. Cancer Res 1996; 56:2550-5. [PMID: 8653696] [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] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A major target tissue for carcinogenesis from the cooked-food carcinogen 2-amino-l-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in rodents is the colon, yet the role of colon metabolism on the carcinogenicity of PhIP is not clearly understood. The mutagenic potency of PhIP is highly dependent upon cytochrome P450 N-hydroxylation. In the present study, the ability of rat colon tissue to activate PhIP to a mutagen was investigated in Salmonella typhimurium (strains TA98 and YGI024) and rat colon tissue slices. In the Ames/Salmonella assay, using rat colon S9 as the activating system, no mutations were evident from bacteria exposed to PhIP at any concentration tested. However, mutations were observed when bacteria were exposed to 2-aminoanthracene (2AA) and colon S9, indicating sufficient P450 activity in the S9 to activate 2AA but not PhIP. In rat colon slice preparations, the sulfotransferase and acetyltransferase inhibitors pentachlorophenol (PCP) and 2,6-dichloro-4-nitrophenol (DCNP) were used to modulate DNA adduct and metabolite formation. Incubations of 3-methylcholanthrene-induced colon slices dosed with 50 microMolar [(3)H]PhIP produced no detectable metabolites. However, incubations of uninduced slices exposed to 10 microMolar of the reactive intermediate, [(3)H]2-(hydroxyamino)-l-methyl-6-phenylimidazo[4,5-b]pyridine (N-hydroxy-PhIP), produced a single detectable metabolite, a glucuronide conjugate of N-hydroxy-PhIP. This metabolite decreased when PCP or DCNP was added to the incubation medium. DNA adducts were detected in colon slices exposed to N-hydroxy-PhIP at approximately 33 adducts/10(7) nucleotides. Interestingly, when PCP was added to the incubation mixture, an increase in DNA adduct levels was detected, whereas DCNP produced a decrease in adducts. Because these inhibitors are thought to have similar mechanisms with regard to sulfotransferase inhibition, the inverse relationship in DNA adduct levels due to PCP or DCNP treatment is at present unexplainable. The formation of DNA adducts and metabolites from colon slices exposed to N-hydroxy-PhIP but not PhIP implies that there is insufficient P450 activity in the rat colon to activate PhIP to hydroxylated metabolites, suggesting that the rat colon is a site of Phase II metabolism for PhIP and that the liver is the primary source for hydroxylation.
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Affiliation(s)
- M A Malfatti
- Biology and Biotechnology Research Program, Lawrence Livermore NationalLaboratory, Livermore, California 94551, USA
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Malfatti MA, Shen NH, Wu RW, Turteltaub KW, Felton JS. A correlation of Salmonella mutagenicity with DNA adducts induced by the cooked-food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine. Mutagenesis 1995; 10:425-31. [PMID: 8544756 DOI: 10.1093/mutage/10.5.425] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [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: 01/31/2023] Open
Abstract
The correlation of bacterial mutagenicity with DNA adducts from the heterocyclic amine cooked-food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was investigated in Salmonella typhimurium strains TA98 (uvrB deficient) and TA1978 (uvrB proficient). Bacterial cells were exposed to PhIP using a modification of the Ames/Salmonella microsuspension assay. Half of the cells, generated from a 90 min pre-incubation and washing, were plated for revertant formation while the remaining half was subjected to DNA adduct analysis via 32P-postlabeling. In TA98, DNA adducts were detected at an RAL (relative adduct labeling) of 10 x 10(-7) and 21 x 10(-7) at PhIP concentrations of 5.5 and 17 microM, respectively. This corresponded to 28.8 and 20.9 adducts/revertant, respectively. These values were based on the assumption that only four repeating GC bases within a 75 DNA base region is the gene target site for PhIP induced mutations. In TA1978, no revertants above background were detected at any concentration of PhIP tested. DNA adducts, however, were detected at 11 x 10(-7) and 21 x 10(-7) adducts per nucleotide at 223 and 1116 microM PhIP, respectively. The lack of detectable revertants, but the presence of DNA adducts, suggests pre-mutational lesions did occur during the 90 min pre-incubation. Presumably, when the S9 activating system and PhIP were removed (via washing with phosphate buffered saline) prior to plating, the cells containing an intact uvrB repair system repaired the lesions during the incubation time on the plates. In conclusion, the induction of revertants by adducts appears quite efficient, as approximately 25 adducts are required for one mutational event in the excision repair deficient bacteria.
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Affiliation(s)
- M A Malfatti
- Biology and Biotechnology Research Program, Lawrence Livermore National Laboratory, CA 94551, USA
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Connors MS, Malfatti MA, Felton JS. The metabolism and DNA binding of the cooked-food mutagen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in precision-cut rat liver slices. Chem Biol Interact 1995; 96:185-202. [PMID: 7728907 DOI: 10.1016/0009-2797(94)03595-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [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: 01/26/2023]
Abstract
Precision-cut liver slices prepared from Aroclor 1254 pretreated male rats were used to investigate the metabolism of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). The acetyltransferase and sulfotransferase inhibitors, pentachlorophenol (PCP) and 2,6-dichloro-4-nitrophenol (DCNP), and the cytochrome P450 inhibitor, alpha-naphthoflavone (ANF), were used to modulate PhIP metabolism and DNA and protein adduct formation. PCP and DCNP had similar effects on the formation of some PhIP metabolites. PCP and DCNP decreased the formation of 4'-(2-amino-1-methylimidazo[4,5-b]pyrid-6-yl)phenyl sulfate (4'-PhIP-sulfate) and 2-(hydroxyamino)-1-methyl-6-phenylimidazo[4,5-b]pyridine (N-hydroxy-PhIP)-glucuronide to 10% and 55% of controls, respectively. 2-Amino-1-methyl-4'-hydroxy-6-phenylimidazo[4,5-b]pyridine (4'-hydroxy-PhIP) was increased by 50% relative to control levels due to PCP and DCNP treatment. PCP and DCNP had different effects on the formation of other PhIP metabolites. Metabolite formation as percent of control for the uncharacterized metabolite, 'Peak A', was 50% and 100% in incubations with PCP and DCNP, respectively. Formation of 4'-hydroxy-PhIP-glucuronide was decreased to 10% of controls with PCP and increased to 147% of controls with DCNP. PCP and DCNP had no effect on the formation of an unidentified metabolite, 'Peak B'. ANF decreased metabolite formation by 60-95%. None of the enzyme inhibitors had a statistically significant effect on PhIP-DNA binding. Covalent binding of PhIP to protein was slightly decreased in incubations containing DCNP or PCP. The lack of significant changes in covalent binding to either DNA or protein suggests that additional pathways may be important in PhIP bioactivation in rat liver slices. With ANF, there was a significant decrease (35%) in protein binding. These observations on the effects of PCP, DCNP and ANF on PhIP metabolism as well as on covalent binding of PhIP to tissue macromolecules are in close agreement with what was reported earlier in hepatocytes. This indicates that tissue slices from various target tissues for tumorigenesis will be a useful in vitro tool for future studies on heterocyclic amine metabolism. This study provides another important example of the utility of precision-cut tissue slices to investigate xenobiotic metabolism and toxicity.
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Affiliation(s)
- M S Connors
- Department of Biological Sciences, San Jose State University, CA 95192-0100, USA
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Malfatti MA, Buonarati MH, Turteltaub KW, Shen NH, Felton JS. The role of sulfation and/or acetylation in the metabolism of the cooked-food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine in Salmonella typhimurium and isolated rat hepatocytes. Chem Res Toxicol 1994; 7:139-47. [PMID: 8199301 DOI: 10.1021/tx00038a005] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [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: 01/29/2023]
Abstract
Mutagenic activity of the cooked-food mutagen/carcinogen 2-amino-1-methyl-6-phenylimidazo-[4,5-b]pyridine (PhIP) is highly dependent upon cytochrome P450 activation to the N-hydroxylated intermediate. In the present study the bioactivation pathways of PhIP were investigated in Salmonella typhimurium and isolated rat hepatocyte preparations. In the Ames/S. typhimurium assay, the acetyltransferase and sulfotransferase enzyme inhibitors pentachlorophenol (PCP) and 2,6-dichloro-4-nitrophenol (DCNP) were used to modulate mutagenicity. DCNP, but not PCP, produced a concentration-dependent decrease in mutagenic activity of 2-(hydroxyamino)-1-methyl-6-phenylimidazo[4,5-b]pyridine (N-hydroxy-PhIP). In rat hepatocyte preparations, PCP and DCNP, as well as the cytochrome P450 IA1 and IA2 inhibitor alpha-naphthoflavone (ANF), were used to modulate metabolite, protein adduct, and DNA adduct formation. Incubations of [3H]PhIP (100 microM) with Aroclor 1254-induced or uninduced hepatocytes resulted in the formation of several metabolites, including 4'-(2-amino-1-methylimidazo[4,5-b]pyrid-6-yl)phenyl sulfate (4'-PhIP-sulfate), 2-amino-1-methyl-4'-hydroxy-6- phenylimidazo[4,5-b]pyridine (4'-hydroxy-PhIP), a glucuronide conjugate of 2-(hydroxyamino)-1-methyl-6-phenylimidazo[4,5-b]pyridine, and other uncharacterized metabolites. While PCP or DCNP pretreatment produced a significant decline in sulfate-dependent conjugation of 4'-hydroxy-PhIP to 4'-PhIP-sulfate, these inhibitors produced only slight decreases in PhIP-dependent covalent binding to proteins in hepatocytes derived from either Aroclor 1254-induced or uninduced rats. PhIP DNA adduct levels were relatively unchanged by PCP or DCNP pretreatment of Aroclor 1254-induced hepatocytes. DNA adducts from hepatocytes dosed with N-hydroxy-PhIP, however, resulted in a decrease in adduct levels from cells pretreated with PCP or DCNP.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M A Malfatti
- Biology and Biotechnology Research PRogram, Lawrence Livermore National Laboratory, Livermore, California 94550
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