1
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Wang Q, Wang X, Liu B, Ma S, Zhang F, Sun S, Jing Y, Fan Y, Ding Y, Xiong M, Li J, Zhai Q, Zheng Y, Liu C, Xu G, Yang J, Wang S, Ye J, Izpisua Belmonte JC, Qu J, Liu GH, Zhang W. Aging induces region-specific dysregulation of hormone synthesis in the primate adrenal gland. NATURE AGING 2024; 4:396-413. [PMID: 38503993 DOI: 10.1038/s43587-024-00588-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 02/05/2024] [Indexed: 03/21/2024]
Abstract
Adrenal glands, vital for steroid secretion and the regulation of metabolism, stress responses and immune activation, experience age-related decline, impacting systemic health. However, the regulatory mechanisms underlying adrenal aging remain largely uninvestigated. Here we established a single-nucleus transcriptomic atlas of both young and aged primate suprarenal glands, identifying lipid metabolism and steroidogenic pathways as core processes impacted by aging. We found dysregulation in centripetal adrenocortical differentiation in aged adrenal tissues and cells in the zona reticularis region, responsible for producing dehydroepiandrosterone sulfate (DHEA-S), were highly susceptible to aging, reflected by senescence, exhaustion and disturbed hormone production. Remarkably, LDLR was downregulated in all cell types of the outer cortex, and its targeted inactivation in human adrenal cells compromised cholesterol uptake and secretion of dehydroepiandrosterone sulfate, as observed in aged primate adrenal glands. Our study provides crucial insights into endocrine physiology, holding therapeutic promise for addressing aging-related adrenal insufficiency and delaying systemic aging.
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Affiliation(s)
- Qiaoran Wang
- CAS Key Laboratory of Genomic and Precision Medicine, Beijing Institute of Genomics, Chinese Academy of Sciences and China National Center for Bioinformation, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xuebao Wang
- University of Chinese Academy of Sciences, Beijing, China
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
- Beijing Institute for Stem Cell and Regenerative Medicine, Beijing, China
| | - Beibei Liu
- CAS Key Laboratory of Genomic and Precision Medicine, Beijing Institute of Genomics, Chinese Academy of Sciences and China National Center for Bioinformation, Beijing, China
| | - Shuai Ma
- Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
- Beijing Institute for Stem Cell and Regenerative Medicine, Beijing, China
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Feng Zhang
- Division of Endocrinology, Quzhou Affiliated Hospital of Wenzhou Medical University, Quzhou, China
- The Joint Innovation Center for Engineering in Medicine, Quzhou Affiliated Hospital of Wenzhou Medical University, Quzhou, China
| | - Shuhui Sun
- Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
- Beijing Institute for Stem Cell and Regenerative Medicine, Beijing, China
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Yaobin Jing
- Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- International Center for Aging and Cancer, Hainan Medical University, Haikou, China
| | - Yanling Fan
- CAS Key Laboratory of Genomic and Precision Medicine, Beijing Institute of Genomics, Chinese Academy of Sciences and China National Center for Bioinformation, Beijing, China
| | - Yingjie Ding
- CAS Key Laboratory of Genomic and Precision Medicine, Beijing Institute of Genomics, Chinese Academy of Sciences and China National Center for Bioinformation, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Muzhao Xiong
- CAS Key Laboratory of Genomic and Precision Medicine, Beijing Institute of Genomics, Chinese Academy of Sciences and China National Center for Bioinformation, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Jiaming Li
- CAS Key Laboratory of Genomic and Precision Medicine, Beijing Institute of Genomics, Chinese Academy of Sciences and China National Center for Bioinformation, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Qiaocheng Zhai
- Division of Endocrinology, Quzhou Affiliated Hospital of Wenzhou Medical University, Quzhou, China
- The Joint Innovation Center for Engineering in Medicine, Quzhou Affiliated Hospital of Wenzhou Medical University, Quzhou, China
| | - Yandong Zheng
- University of Chinese Academy of Sciences, Beijing, China
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
- Beijing Institute for Stem Cell and Regenerative Medicine, Beijing, China
| | - Chengyu Liu
- University of Chinese Academy of Sciences, Beijing, China
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
- Beijing Institute for Stem Cell and Regenerative Medicine, Beijing, China
| | - Gang Xu
- Liver Transplant Center, Organ Transplant Center, West China Hospital of Sichuan University, Chengdu, China
- Laboratory of Liver Transplantation, Key Laboratory of Transplant Engineering and Immunology, NHC, West China Hospital of Sichuan University, Chengdu, China
| | - Jiayin Yang
- Liver Transplant Center, Organ Transplant Center, West China Hospital of Sichuan University, Chengdu, China
- Laboratory of Liver Transplantation, Key Laboratory of Transplant Engineering and Immunology, NHC, West China Hospital of Sichuan University, Chengdu, China
| | - Si Wang
- Aging Translational Medicine Center, International Center for Aging and Cancer, Xuanwu Hospital, Capital Medical University, Beijing, China
- Advanced Innovation Center for Human Brain Protection, National Clinical Research Center for Geriatric Disorders, Xuanwu Hospital Capital Medical University, Beijing, China
- The Fifth People's Hospital of Chongqing, Chongqing, China
- Aging Biomarker Consortium, Beijing, China
| | - Jinlin Ye
- The Joint Innovation Center for Engineering in Medicine, Quzhou Affiliated Hospital of Wenzhou Medical University, Quzhou, China
| | | | - Jing Qu
- University of Chinese Academy of Sciences, Beijing, China.
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
- Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China.
- Beijing Institute for Stem Cell and Regenerative Medicine, Beijing, China.
- Aging Biomarker Consortium, Beijing, China.
| | - Guang-Hui Liu
- University of Chinese Academy of Sciences, Beijing, China.
- Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China.
- Beijing Institute for Stem Cell and Regenerative Medicine, Beijing, China.
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
- International Center for Aging and Cancer, Hainan Medical University, Haikou, China.
- Aging Translational Medicine Center, International Center for Aging and Cancer, Xuanwu Hospital, Capital Medical University, Beijing, China.
- Advanced Innovation Center for Human Brain Protection, National Clinical Research Center for Geriatric Disorders, Xuanwu Hospital Capital Medical University, Beijing, China.
- Aging Biomarker Consortium, Beijing, China.
| | - Weiqi Zhang
- CAS Key Laboratory of Genomic and Precision Medicine, Beijing Institute of Genomics, Chinese Academy of Sciences and China National Center for Bioinformation, Beijing, China.
- University of Chinese Academy of Sciences, Beijing, China.
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China.
- Aging Biomarker Consortium, Beijing, China.
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2
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Duffel MW, Lehmler HJ. Complex roles for sulfation in the toxicities of polychlorinated biphenyls. Crit Rev Toxicol 2024; 54:92-122. [PMID: 38363552 PMCID: PMC11067068 DOI: 10.1080/10408444.2024.2311270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Accepted: 01/23/2024] [Indexed: 02/17/2024]
Abstract
Polychlorinated biphenyls (PCBs) are persistent organic toxicants derived from legacy pollution sources and their formation as inadvertent byproducts of some current manufacturing processes. Metabolism of PCBs is often a critical component in their toxicity, and relevant metabolic pathways usually include their initial oxidation to form hydroxylated polychlorinated biphenyls (OH-PCBs). Subsequent sulfation of OH-PCBs was originally thought to be primarily a means of detoxication; however, there is strong evidence that it may also contribute to toxicities associated with PCBs and OH-PCBs. These contributions include either the direct interaction of PCB sulfates with receptors or their serving as a localized precursor for OH-PCBs. The formation of PCB sulfates is catalyzed by cytosolic sulfotransferases, and, when transported into the serum, these metabolites may be retained, taken up by other tissues, and subjected to hydrolysis catalyzed by intracellular sulfatase(s) to regenerate OH-PCBs. Dynamic cycling between PCB sulfates and OH-PCBs may lead to further metabolic activation of the resulting OH-PCBs. Ultimate toxic endpoints of such processes may include endocrine disruption, neurotoxicities, and many others that are associated with exposures to PCBs and OH-PCBs. This review highlights the current understanding of the complex roles that PCB sulfates can have in the toxicities of PCBs and OH-PCBs and research on the varied mechanisms that control these roles.
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Affiliation(s)
- Michael W. Duffel
- Department of Pharmaceutical Sciences & Experimental Therapeutics, College of Pharmacy, The University of Iowa, Iowa City, Iowa, 52242, United States
| | - Hans-Joachim Lehmler
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, Iowa, 52242, United States
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Sun MZ, Lyu LS, Zheng QC. How does multiple substrate binding lead to substrate inhibition of CYP2D6 metabolizing dextromethorphan? A theoretical study. Phys Chem Chem Phys 2023; 25:5164-5173. [PMID: 36723118 DOI: 10.1039/d2cp05634h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
CYP2D6 is one of the most important metalloenzymes involved in the biodegradation of many drug molecules in the human body. It has been found that multiple substrate binding can lead to substrate inhibition of CYP2D6 metabolizing dextromethorphan (DM), but the corresponding theoretical mechanism is rarely reported. Therefore, we chose DM as the probe and performed molecular dynamics simulations and quantum mechanical calculations on CYP2D6-DM systems to investigate the mechanism of how the multiple substrate binding leads to the substrate inhibition of CYP2D6 metabolizing substrates. According to our results, three gate residues (Arg221, Val374, and Phe483) for the catalytic pocket are determined. We also found that the multiple substrate binding can lead to substrate inhibition by reducing the stability of CYP2D6 binding DM and increasing the reactive activation energy of the rate-determining step. Our findings would help to understand the substrate inhibition of CYP2D6 metabolizing the DM and enrich the knowledge of the drug-drug interactions for the cytochrome P450 superfamily.
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Affiliation(s)
- Min-Zhang Sun
- Institute of Theoretical Chemistry, College of Chemistry, Jilin University, Changchun, 130023, China
| | - Ling-Shan Lyu
- Institute of Theoretical Chemistry, College of Chemistry, Jilin University, Changchun, 130023, China
| | - Qing-Chuan Zheng
- School of Pharmaceutical Sciences, Jilin University, Changchun, 130023, China. .,Institute of Theoretical Chemistry, College of Chemistry, Jilin University, Changchun, 130023, China
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4
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Jia RY, Zhang ZP, Qin GQ, Zhang W, Yang K, Liu YZ, Jiang C, Fang ZZ. Inhibition of hydroxylated polychlorinated biphenyls (OH-PCBs) on sulfotransferases (SULTs). ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 291:118214. [PMID: 34740292 DOI: 10.1016/j.envpol.2021.118214] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 09/17/2021] [Accepted: 09/19/2021] [Indexed: 06/13/2023]
Abstract
Polychlorinated biphenyls (PCBs) have been demonstrated as a kind of the persistent organic pollutants (POPs) that could exert complicated influences towards metabolism in human bodies. Since hydroxylated polychlorinated biphenyls (OH-PCBs) are important metabolites of PCBs, our study focuses on investigating the potential inhibitory capability of OH-PCBs on four human sulfotransferase (SULT) isoforms. P-nitrophenol (PNP) was utilized as nonselective probe substrate for this study, and recombinant SULT isoforms were utilized as the enzyme resources. Ultra-performance liquid chromatography (UPLC)-UV detecting system was used to analyze PNP and its metabolite PNP-sulfate. As result, 100 μM of most tested OH-PCBs significantly inhibited the activity of four SULT isoforms. Concentration-dependent inhibition of OH-PCBs towards SULTs was found, and half inhibition concentration values (IC50) of some inhibition processes were determined. Inhibition kinetics (inhibition kinetic type and parameters) were determined using 4'-OH-PCB106 as the representative OH-PCB, SULT1B1 and SULT1E1 as representative SULT isoforms. The inhibition kinetic parameters (Ki) were 1.73 μM and 1.81 μM for the inhibition of 4'-OH-PCB106 towards SULT1B1 and SULT1E1, respectively. In silico docking simulation was utilized to analyze the inhibition capability of 2'-OH-PCB5, 4'-OH-PCB9, 2'-OH-PCB12 towards SULT1A3.All these results obtained in this study are helpful for further understanding the toxicity of PCBs.
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Affiliation(s)
- Ruo-Yong Jia
- Department of Toxicology and Sanitary Chemistry, School of Public Health, Tianjin Medical University, Tianjin, 300070, China
| | - Zhi-Peng Zhang
- Department of Surgery, Peking University Third Hospital, Beijing, China
| | - Guo-Qiang Qin
- Department of Toxicology and Sanitary Chemistry, School of Public Health, Tianjin Medical University, Tianjin, 300070, China
| | - Wei Zhang
- Department of Toxicology and Sanitary Chemistry, School of Public Health, Tianjin Medical University, Tianjin, 300070, China
| | - Kun Yang
- Department of Toxicology and Sanitary Chemistry, School of Public Health, Tianjin Medical University, Tianjin, 300070, China
| | - Yong-Zhe Liu
- Department of Toxicology and Sanitary Chemistry, School of Public Health, Tianjin Medical University, Tianjin, 300070, China
| | - Changtao Jiang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Key Laboratory of Molecular Cardiovascular Science, Ministry of Education, Peking University, Beijing, China
| | - Zhong-Ze Fang
- Department of Toxicology and Sanitary Chemistry, School of Public Health, Tianjin Medical University, Tianjin, 300070, China; Tianjin Key Laboratory of Environment, Nutrition and Public Health, Tianjin, China; National Demonstration Center for Experimental Preventive Medicine Education, Tianjin Medical University, Tianjin, 300070, China; Tianjin Center for International Collaborative Research in Environment, Nutrition and Public Health, Tianjin, China.
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5
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Foster PA, Mueller JW. SULFATION PATHWAYS: Insights into steroid sulfation and desulfation pathways. J Mol Endocrinol 2018; 61:T271-T283. [PMID: 29764919 DOI: 10.1530/jme-18-0086] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 05/15/2018] [Indexed: 12/18/2022]
Abstract
Sulfation and desulfation pathways represent highly dynamic ways of shuttling, repressing and re-activating steroid hormones, thus controlling their immense biological potency at the very heart of endocrinology. This theme currently experiences growing research interest from various sides, including, but not limited to, novel insights about phospho-adenosine-5'-phosphosulfate synthase and sulfotransferase function and regulation, novel analytics for steroid conjugate detection and quantification. Within this review, we will also define how sulfation pathways are ripe for drug development strategies, which have translational potential to treat a number of conditions, including chronic inflammatory diseases and steroid-dependent cancers.
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Affiliation(s)
- Paul A Foster
- Institute of Metabolism and Systems Research (IMSR)University of Birmingham, Birmingham, UK
- Centre for EndocrinologyDiabetes and Metabolism (CEDAM), Birmingham Health Partners, Birmingham, UK
| | - Jonathan Wolf Mueller
- Institute of Metabolism and Systems Research (IMSR)University of Birmingham, Birmingham, UK
- Centre for EndocrinologyDiabetes and Metabolism (CEDAM), Birmingham Health Partners, Birmingham, UK
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6
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Abunnaja MS, Alherz FA, El Daibani AA, Bairam AF, Rasool MI, Gohal SA, Kurogi K, Suiko M, Sakakibara Y, Liu MC. Effects of genetic polymorphisms on the sulfation of dehydroepiandrosterone and pregnenolone by human cytosolic sulfotransferase SULT2A1. Biochem Cell Biol 2018; 96:655-662. [PMID: 29671343 DOI: 10.1139/bcb-2017-0341] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The cytosolic sulfotransferase (SULT) SULT2A1 is known to mediate the sulfation of DHEA as well as some other hydroxysteroids such as pregnenolone. The present study was designed to investigate how genetic polymorphisms of the human SULT2A1 gene may affect the sulfation of DHEA and pregnenolone. Online databases were systematically searched to identify human SULT2A1 single nucleotide polymorphisms (SNPs). Of the 98 SULT2A1 non-synonymous coding SNPs identified, seven were selected for further investigation. Site-directed mutagenesis was used to generate cDNAs encoding these seven SULT2A1 allozymes, which were expressed in BL21 Escherichia coli cells and purified by glutathione-Sepharose affinity chromatography. Enzymatic assays revealed that purified SULT2A1 allozymes displayed differential sulfating activity toward both DHEA and pregnenolone. Kinetic analyses showed further differential catalytic efficiency and substrate affinity of the SULT2A1 allozymes, in comparison with wild-type SULT2A1. These findings provided useful information concerning the effects of genetic polymorphisms on the sulfating activity of SULT2A1 allozymes.
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Affiliation(s)
- Maryam S Abunnaja
- a Department of Pharmacology, College of Pharmacy and Pharmaceutical Sciences, University of Toledo Health Science Campus, Toledo, OH 43614, USA
| | - Fatemah A Alherz
- a Department of Pharmacology, College of Pharmacy and Pharmaceutical Sciences, University of Toledo Health Science Campus, Toledo, OH 43614, USA
| | - Amal A El Daibani
- a Department of Pharmacology, College of Pharmacy and Pharmaceutical Sciences, University of Toledo Health Science Campus, Toledo, OH 43614, USA
| | - Ahsan F Bairam
- a Department of Pharmacology, College of Pharmacy and Pharmaceutical Sciences, University of Toledo Health Science Campus, Toledo, OH 43614, USA.,b Department of Pharmacology, College of Pharmacy, University of Kufa, Najaf, Iraq
| | - Mohammed I Rasool
- a Department of Pharmacology, College of Pharmacy and Pharmaceutical Sciences, University of Toledo Health Science Campus, Toledo, OH 43614, USA.,c Department of Pharmacology, College of Pharmacy, University of Karbala, Karbala, Iraq
| | - Saud A Gohal
- a Department of Pharmacology, College of Pharmacy and Pharmaceutical Sciences, University of Toledo Health Science Campus, Toledo, OH 43614, USA
| | - Katsuhisa Kurogi
- a Department of Pharmacology, College of Pharmacy and Pharmaceutical Sciences, University of Toledo Health Science Campus, Toledo, OH 43614, USA.,d Biochemistry and Applied Biosciences, University of Miyazaki, Miyazaki 889-2192 Japan
| | - Masahito Suiko
- d Biochemistry and Applied Biosciences, University of Miyazaki, Miyazaki 889-2192 Japan
| | - Yoichi Sakakibara
- d Biochemistry and Applied Biosciences, University of Miyazaki, Miyazaki 889-2192 Japan
| | - Ming-Cheh Liu
- a Department of Pharmacology, College of Pharmacy and Pharmaceutical Sciences, University of Toledo Health Science Campus, Toledo, OH 43614, USA
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7
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Parker VS, Squirewell EJ, Lehmler HJ, Robertson LW, Duffel MW. Hydroxylated and sulfated metabolites of commonly occurring airborne polychlorinated biphenyls inhibit human steroid sulfotransferases SULT1E1 and SULT2A1. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2018; 58:196-201. [PMID: 29408762 PMCID: PMC6078096 DOI: 10.1016/j.etap.2018.01.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 01/24/2018] [Indexed: 05/20/2023]
Abstract
Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants that are associated with varied adverse health effects. Lower chlorinated PCBs are prevalent in indoor and outdoor air and can be metabolized to their hydroxylated derivatives (OH-PCBs) followed by sulfation to form PCB sulfates. Sulfation is also a means of signal termination for steroid hormones. The human estrogen sulfotransferase (SULT1E1) and alcohol/hydroxysteroid sulfotransferase (SULT2A1) catalyze the formation of steroid sulfates that are inactive at steroid hormone receptors. We investigated the inhibition of SULT1E1 (IC50s ranging from 7.2 nM to greater than 10 μM) and SULT2A1 (IC50s from 1.3 μM to over 100 μM) by five lower-chlorinated OH-PCBs and their corresponding PCB sulfates relevant to airborne PCB-exposure. Several congeners of lower chlorinated OH-PCBs relevant to airborne PCB exposures were potent inhibitors of SULT1E1 and SULT2A1 and thus have the potential to disrupt regulation of intracellular concentrations of the receptor-active steroid substrates for these enzymes.
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Affiliation(s)
- Victoria S Parker
- Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, The University of Iowa, Iowa City, IA, United States
| | - Edwin J Squirewell
- Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, The University of Iowa, Iowa City, IA, United States
| | - Hans-Joachim Lehmler
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, IA, United States
| | - Larry W Robertson
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, IA, United States
| | - Michael W Duffel
- Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, The University of Iowa, Iowa City, IA, United States.
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8
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Kurogi K, Sakakibara Y, Suiko M, Liu MC. Sulfation of vitamin D3-related compounds-identification and characterization of the responsible human cytosolic sulfotransferases. FEBS Lett 2017; 591:2417-2425. [DOI: 10.1002/1873-3468.12767] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 07/20/2017] [Accepted: 07/24/2017] [Indexed: 11/09/2022]
Affiliation(s)
- Katsuhisa Kurogi
- Department of Pharmacology; College of Pharmacy and Pharmaceutical Sciences; University of Toledo Health Science Campus; OH USA
- Department of Biochemistry and Applied Biosciences; University of Miyazaki; Japan
| | - Yoichi Sakakibara
- Department of Biochemistry and Applied Biosciences; University of Miyazaki; Japan
| | - Masahito Suiko
- Department of Biochemistry and Applied Biosciences; University of Miyazaki; Japan
| | - Ming-Cheh Liu
- Department of Pharmacology; College of Pharmacy and Pharmaceutical Sciences; University of Toledo Health Science Campus; OH USA
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9
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Δ 4-3-ketosteroids as a new class of substrates for the cytosolic sulfotransferases. Biochim Biophys Acta Gen Subj 2017; 1861:2883-2890. [PMID: 28782626 DOI: 10.1016/j.bbagen.2017.08.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 07/08/2017] [Accepted: 08/02/2017] [Indexed: 01/08/2023]
Abstract
Cytosolic sulfotransferase (SULT)-mediated sulfation is generally known to involve the transfer of a sulfonate group from the active sulfate, 3'-phosphoadenosine 5'-phosphosulfate (PAPS), to a hydroxyl group or an amino group of a substrate compound. We report here that human SULT2A1, in addition to being able to sulfate dehydroepiandrosterone (DHEA) and other hydroxysteroids, could also catalyze the sulfation of Δ4-3-ketosteroids, which carry no hydroxyl groups in their chemical structure. Among a panel of Δ4-3-ketosteroids tested as substrates, 4-androstene-3,17-dione and progesterone were found to be sulfated by SULT2A1. Mass spectrometry analysis and structural modeling supported a reaction mechanism which involves the isomerization of Δ4-3-ketosteroids from the keto form to an enol form, prior to being subjected to sulfation. Results derived from this study suggested a potential role of SULT2A1 as a Δ4-3-ketosteroid sulfotransferase in steroid metabolism.
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10
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Weththasinghe SA, Waller CC, Fam HL, Stevenson BJ, Cawley AT, McLeod MD. Replacing PAPS: In vitro phase II sulfation of steroids with the liver S9 fraction employing ATP and sodium sulfate. Drug Test Anal 2017. [PMID: 28635171 DOI: 10.1002/dta.2224] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In vitro technologies provide the capacity to study drug metabolism where in vivo studies are precluded due to ethical or financial constraints. The metabolites generated by in vitro studies can assist anti-doping laboratories to develop protocols for the detection of novel substances that would otherwise evade routine screening efforts. In addition, professional bodies such as the Association of Official Racing Chemists (AORC) currently permit the use of in-vitro-derived reference materials for confirmation purposes providing additional impetus for the development of cost effective in vitro metabolism platforms. In this work, alternative conditions for in vitro phase II sulfation using human, equine or canine liver S9 fraction were developed, with adenosine triphosphate (ATP) and sodium sulfate in place of the expensive and unstable co-factor 3'-phosphoadenosine-5'-phosphosulfate (PAPS), and employed for the generation of six representative steroidal sulfates. Using these conditions, the equine in vitro phase II metabolism of the synthetic or so-called designer steroid furazadrol ([1',2']isoxazolo[4',5':2,3]-5α-androstan-17β-ol) was investigated, with ATP and Na2 SO4 providing comparable metabolism to reactions using PAPS. The major in vitro metabolites of furazadrol matched those observed in a previously reported equine in vivo study. Finally, the equine in vitro phase II metabolism of the synthetic steroid superdrol (methasterone, 17β-hydroxy-2α,17α-dimethyl-5α-androstan-3-one) was performed as a prediction of the in vivo metabolic profile.
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Affiliation(s)
- Sumudu A Weththasinghe
- Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Christopher C Waller
- Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Han Ling Fam
- Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Bradley J Stevenson
- Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Adam T Cawley
- Australian Racing Forensic Laboratory, Racing NSW, Sydney, New South Wales, Australia
| | - Malcolm D McLeod
- Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory, Australia
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11
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Taylor AB, Roberts KM, Cao X, Clark NE, Holloway SP, Donati E, Polcaro CM, Pica-Mattoccia L, Tarpley RS, McHardy SF, Cioli D, LoVerde PT, Fitzpatrick PF, Hart PJ. Structural and enzymatic insights into species-specific resistance to schistosome parasite drug therapy. J Biol Chem 2017; 292:11154-11164. [PMID: 28536265 PMCID: PMC5500785 DOI: 10.1074/jbc.m116.766527] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 05/17/2017] [Indexed: 02/05/2023] Open
Abstract
The antischistosomal prodrug oxamniquine is activated by a sulfotransferase (SULT) in the parasitic flatworm Schistosoma mansoni. Of the three main human schistosome species, only S. mansoni is sensitive to oxamniquine therapy despite the presence of SULT orthologs in Schistosoma hematobium and Schistosoma japonicum The reason for this species-specific drug action has remained a mystery for decades. Here we present the crystal structures of S. hematobium and S. japonicum SULTs, including S. hematobium SULT in complex with oxamniquine. We also examined the activity of the three enzymes in vitro; surprisingly, all three are active toward oxamniquine, yet we observed differences in catalytic efficiency that implicate kinetics as the determinant for species-specific toxicity. These results provide guidance for designing oxamniquine derivatives to treat infection caused by all species of schistosome to combat emerging resistance to current therapy.
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Affiliation(s)
- Alexander B Taylor
- From the Departments of Biochemistry and Structural Biology and
- the X-ray Crystallography Core Laboratory, University of Texas Health Science Center, San Antonio, Texas 78229
| | - Kenneth M Roberts
- Department of Chemistry and Physics, University of South Carolina, Aiken, South Carolina 29801
| | - Xiaohang Cao
- From the Departments of Biochemistry and Structural Biology and
| | | | | | - Enrica Donati
- Institute of Chemical Methodologies, Consiglio Nazionale delle Ricerche, Via Salaria Km 29.500, 00015 Monterotondo, Rome, Italy
| | - Chiara M Polcaro
- Institute of Chemical Methodologies, Consiglio Nazionale delle Ricerche, Via Salaria Km 29.500, 00015 Monterotondo, Rome, Italy
| | - Livia Pica-Mattoccia
- Institute of Cell Biology and Neurobiology, Consiglio Nazionale delle Ricerche, Via E. Ramarini 32, 00015 Monterotondo, Rome, Italy
| | - Reid S Tarpley
- Center for Innovative Drug Discovery, Department of Chemistry, University of Texas, San Antonio, Texas 78249, and
| | - Stanton F McHardy
- Center for Innovative Drug Discovery, Department of Chemistry, University of Texas, San Antonio, Texas 78249, and
| | - Donato Cioli
- Institute of Chemical Methodologies, Consiglio Nazionale delle Ricerche, Via Salaria Km 29.500, 00015 Monterotondo, Rome, Italy
| | - Philip T LoVerde
- From the Departments of Biochemistry and Structural Biology and
- Pathology and
| | | | - P John Hart
- From the Departments of Biochemistry and Structural Biology and
- the X-ray Crystallography Core Laboratory, University of Texas Health Science Center, San Antonio, Texas 78229
- Department of Veterans Affairs, South Texas Veterans Health Care System, San Antonio, Texas 78229
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12
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Feng L, Yuen YL, Xu J, Liu X, Chan MYC, Wang K, Fong WP, Cheung WT, Lee SST. Identification and characterization of a novel PPARα-regulated and 7α-hydroxyl bile acid-preferring cytosolic sulfotransferase mL-STL (Sult2a8). J Lipid Res 2017; 58:1114-1131. [PMID: 28442498 DOI: 10.1194/jlr.m074302] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2016] [Revised: 04/19/2017] [Indexed: 12/25/2022] Open
Abstract
PPARα has been known to play a pivotal role in orchestrating lipid, glucose, and amino acid metabolism via transcriptional regulation of its target gene expression during energy deprivation. Recent evidence has also suggested that PPARα is involved in bile acid metabolism, but how PPARα modulates the homeostasis of bile acids during fasting is still not clear. In a mechanistic study aiming to dissect the spectrum of PPARα target genes involved in metabolic response to fasting, we identified a novel mouse gene (herein named mL-STL for mouse liver-sulfotransferase-like) that shared extensive homology with the Sult2a subfamily of a superfamily of cytosolic sulfotransferases, implying its potential function in sulfonation. The mL-STL gene expressed predominantly in liver in fed state, but PPARα was required to sustain its expression during fasting, suggesting a critical role of PPARα in regulating the mL-STL-mediated sulfonation during fasting. Functional studies using recombinant His-tagged mL-STL protein revealed its narrow sulfonating activities toward 7α-hydroxyl primary bile acids, including cholic acid, chenodeoxycholic acid, and α-muricholic acid, and thus suggesting that mL-STL may be the major hepatic bile acid sulfonating enzyme in mice. Together, these studies identified a novel PPARα-dependent gene and uncovered a new role of PPARα as being an essential regulator in bile acid biotransformation via sulfonation during fasting.
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Affiliation(s)
- Lu Feng
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR
| | - Yee-Lok Yuen
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR
| | - Jian Xu
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR
| | - Xing Liu
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR
| | - Martin Yan-Chun Chan
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR
| | - Kai Wang
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR
| | - Wing-Ping Fong
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR
| | - Wing-Tai Cheung
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR
| | - Susanna Sau-Tuen Lee
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR
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13
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Bansal S, Lau AJ. Human liver cytosolic sulfotransferase 2A1-dependent dehydroepiandrosterone sulfation assay by ultra-high performance liquid chromatography–tandem mass spectrometry. J Pharm Biomed Anal 2016; 120:261-9. [DOI: 10.1016/j.jpba.2015.12.029] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Revised: 12/03/2015] [Accepted: 12/17/2015] [Indexed: 01/23/2023]
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14
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Ekuase EJ, van 't Erve TJ, Rahaman A, Robertson LW, Duffel MW, Luthe G. Mechanistic insights into the specificity of human cytosolic sulfotransferase 2A1 (hSULT2A1) for hydroxylated polychlorinated biphenyls through the use of fluoro-tagged probes. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2016; 23:2119-2127. [PMID: 26165989 PMCID: PMC4713379 DOI: 10.1007/s11356-015-4886-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 06/15/2015] [Indexed: 06/04/2023]
Abstract
Determining the relationships between the structures of substrates and inhibitors and their interactions with drug-metabolizing enzymes is of prime importance in predicting the toxic potential of new and legacy xenobiotics. Traditionally, quantitative structure activity relationship (QSAR) studies are performed with many distinct compounds. Based on the chemical properties of the tested compounds, complex relationships can be established so that models can be developed to predict toxicity of novel compounds. In this study, the use of fluorinated analogues as supplemental QSAR compounds was investigated. Substituting fluorine induces changes in electronic and steric properties of the substrate without substantially changing the chemical backbone of the substrate. In vitro assays were performed using purified human cytosolic sulfotransferase hSULT2A1 as a model enzyme. A mono-hydroxylated polychlorinated biphenyl (4-OH PCB 14) and its four possible mono-fluoro analogues were used as test compounds. Remarkable similarities were found between this approach and previously published QSAR studies for hSULT2A1. Both studies implicate the importance of dipole moment and dihedral angle as being important to PCB structure in respect to being substrates for hSULT2A1. We conclude that mono-fluorinated analogues of a target substrate can be a useful tool to study the structure activity relationships for enzyme specificity.
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Affiliation(s)
- E J Ekuase
- Department of Pharmaceutical Sciences and Experimental Therapeutics, The University of Iowa, Iowa City, IA, USA
| | - T J van 't Erve
- Department of Occupational and Environmental Health, The University of Iowa, Iowa City, IA, USA.
- Institute of Life Sciences, Saxion University of Applied Sciences, Enschede, The Netherlands.
- Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, Iowa City, IA, USA.
- Immunity, Inflammation and Disease Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, 27709, NC, USA.
| | - A Rahaman
- Department of Chemistry, The University of Iowa, Iowa City, IA, USA
| | - L W Robertson
- Department of Occupational and Environmental Health, The University of Iowa, Iowa City, IA, USA
- Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, Iowa City, IA, USA
| | - M W Duffel
- Department of Pharmaceutical Sciences and Experimental Therapeutics, The University of Iowa, Iowa City, IA, USA
- Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, Iowa City, IA, USA
| | - G Luthe
- Department of Occupational and Environmental Health, The University of Iowa, Iowa City, IA, USA
- Institute of Life Sciences, Saxion University of Applied Sciences, Enschede, The Netherlands
- Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, Iowa City, IA, USA
- LuthePharma, Fabrikstrasse 2, 48599, Gronau, Germany
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15
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Wang T, Cook I, Leyh TS. Design and Interpretation of Human Sulfotransferase 1A1 Assays. ACTA ACUST UNITED AC 2015; 44:481-4. [PMID: 26658224 DOI: 10.1124/dmd.115.068205] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 12/07/2015] [Indexed: 11/22/2022]
Abstract
The human sulfotransferases (SULTs) regulate the activities of hundreds, if not thousands, of small molecule metabolites via transfer of the sulfuryl-moiety (-SO3) from the nucleotide donor, 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to the hydroxyls and amines of the recipients. Our understanding of the molecular basis of SULT catalysis has expanded considerably in recent years. The basic kinetic mechanism of these enzymes, previously thought to be ordered, has been redefined as random for SULT2A1, a representative member of the superfamily. An active-site cap whose structure and dynamics are highly responsive to nucleotides was discovered and shown to be critical in determining SULT selectivity, a topic of longstanding interest to the field. We now realize that a given SULT can operate in two specificity modes-broad and narrow-depending on the disposition of the cap. More recent work has revealed that the caps of the SULT1A1 are controlled by homotropic allosteric interactions between PAPS molecules bound at the dimer's active sites. These interactions cause the catalytic efficiency of SULT1A1 to vary in a substrate-dependent fashion by as much as two orders of magnitude over a range of PAPS concentrations that spans those found in human tissues. SULT catalysis is further complicated by the fact that these enzymes are frequently inhibited by their substrates. This review provides an overview of the mechanistic features of SULT1A1 that are important for the design and interpretation of SULT1A1 assays.
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Affiliation(s)
- Ting Wang
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York
| | - Ian Cook
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York
| | - Thomas S Leyh
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York
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16
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Mueller JW, Gilligan LC, Idkowiak J, Arlt W, Foster PA. The Regulation of Steroid Action by Sulfation and Desulfation. Endocr Rev 2015; 36:526-63. [PMID: 26213785 PMCID: PMC4591525 DOI: 10.1210/er.2015-1036] [Citation(s) in RCA: 265] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 07/21/2015] [Indexed: 12/14/2022]
Abstract
Steroid sulfation and desulfation are fundamental pathways vital for a functional vertebrate endocrine system. After biosynthesis, hydrophobic steroids are sulfated to expedite circulatory transit. Target cells express transmembrane organic anion-transporting polypeptides that facilitate cellular uptake of sulfated steroids. Once intracellular, sulfatases hydrolyze these steroid sulfate esters to their unconjugated, and usually active, forms. Because most steroids can be sulfated, including cholesterol, pregnenolone, dehydroepiandrosterone, and estrone, understanding the function, tissue distribution, and regulation of sulfation and desulfation processes provides significant insights into normal endocrine function. Not surprisingly, dysregulation of these pathways is associated with numerous pathologies, including steroid-dependent cancers, polycystic ovary syndrome, and X-linked ichthyosis. Here we provide a comprehensive examination of our current knowledge of endocrine-related sulfation and desulfation pathways. We describe the interplay between sulfatases and sulfotransferases, showing how their expression and regulation influences steroid action. Furthermore, we address the role that organic anion-transporting polypeptides play in regulating intracellular steroid concentrations and how their expression patterns influence many pathologies, especially cancer. Finally, the recent advances in pharmacologically targeting steroidogenic pathways will be examined.
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Affiliation(s)
- Jonathan W Mueller
- Centre for Endocrinology, Diabetes, and Metabolism, Institute of Metabolism and Systems Research, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Lorna C Gilligan
- Centre for Endocrinology, Diabetes, and Metabolism, Institute of Metabolism and Systems Research, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Jan Idkowiak
- Centre for Endocrinology, Diabetes, and Metabolism, Institute of Metabolism and Systems Research, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Wiebke Arlt
- Centre for Endocrinology, Diabetes, and Metabolism, Institute of Metabolism and Systems Research, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Paul A Foster
- Centre for Endocrinology, Diabetes, and Metabolism, Institute of Metabolism and Systems Research, University of Birmingham, Birmingham B15 2TT, United Kingdom
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17
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Chen BH, Wang CC, Hou YH, Mao YC, Yang YS. Mechanism of sulfotransferase pharmacogenetics in altered xenobiotic metabolism. Expert Opin Drug Metab Toxicol 2015; 11:1053-71. [DOI: 10.1517/17425255.2015.1045486] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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18
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Tibbs ZE, Falany CN. Dimeric human sulfotransferase 1B1 displays cofactor-dependent subunit communication. Pharmacol Res Perspect 2015; 3:e00147. [PMID: 26236487 PMCID: PMC4492763 DOI: 10.1002/prp2.147] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Revised: 03/05/2015] [Accepted: 03/22/2015] [Indexed: 01/27/2023] Open
Abstract
The cytosolic sulfotransferases (SULTs) are dimeric enzymes that catalyze the transformation of hydrophobic drugs and hormones into hydrophilic sulfate esters thereby providing the body with an important pathway for regulating small molecule activity and excretion. While SULT dimerization is highly conserved, the necessity for the interaction has not been established. To perform its function, a SULT must efficiently bind the universal sulfate donor, 3'-phosphoadenosine-5'-phosphosulfate (PAPS), and release the byproduct, 3', 5'-diphosphoadenosine (PAP), following catalysis. We hypothesize this efficient binding and release of PAPS/PAP may be connected to SULT dimerization. To allow for the visualization of dynamic protein interactions critical for addressing this hypothesis and to generate kinetically testable hypotheses, molecular dynamic simulations (MDS) of hSULT1B1 were performed with PAPS and PAP bound to each dimer subunit in various combinations. The results suggest the dimer subunits may possess the capability of communicating with one another in a manner dependent on the presence of the cofactor. PAP or PAPS binding to a single side of the dimer results in decreased backbone flexibility of both the bound and unbound subunits, implying the dimer subunits may not act independently. Further, binding of PAP to one subunit of the dimer and PAPS to the other caused increased flexibility in the subunit bound to the inactive cofactor (PAP). These results suggest SULT dimerization may be important in maintaining cofactor binding/release properties of SULTs and provide hypothetical explanations for SULT half-site reactivity and substrate inhibition, which can be analyzed in vitro.
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Affiliation(s)
- Zachary E Tibbs
- The Department of Pharmacology and Toxicology, The University of Alabama at Birmingham Birmingham, Alabama, 35294-0019
| | - Charles N Falany
- The Department of Pharmacology and Toxicology, The University of Alabama at Birmingham Birmingham, Alabama, 35294-0019
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19
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Tibbs ZE, Rohn-Glowacki KJ, Crittenden F, Guidry AL, Falany CN. Structural plasticity in the human cytosolic sulfotransferase dimer and its role in substrate selectivity and catalysis. Drug Metab Pharmacokinet 2015; 30:3-20. [DOI: 10.1016/j.dmpk.2014.10.004] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 10/02/2014] [Accepted: 10/08/2014] [Indexed: 10/24/2022]
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20
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Choughule KV, Locuson CW, Coughtrie MWH. Characterization of bovine phenol sulfotransferases: evidence of a major role for SULT1B1 in the liver. Xenobiotica 2014; 45:495-502. [PMID: 25539458 DOI: 10.3109/00498254.2014.997325] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
1. Cattle are an important component of the human food chain. Drugs used either legally or illegally in cattle may therefore enter the food chain and it is thus important to understand pathways of drug metabolism in this species, including sulfation catalyzed by the sulfotransferases (SULTs). 2. In this study, we have analyzed the sulfation of 4-nitrophenol and other compounds in male and female bovine liver and characterized recombinant bovine SULT isoforms 1A1 and 1B1 expressed in Escherichia coli. 3. We found that, in contrast to most other mammalian species, the major phenol sulfotransferase SULT1A1 is not expressed in bovine liver. Rather SULT1B1 seems to be a major form in both male and female bovine liver. 4. We also identified kinetic differences between bovine and human SULT1A1 and, using the human SULT1A1 crystal structure, identified two amino acid positions in the active site of bovine SULT1A1 (Ile89Val and Phe247Val) that may be responsible for these differences.
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Affiliation(s)
- Kanika V Choughule
- Medical Research Institute, Ninewells Hospital & Medical School, University of Dundee , Dundee , UK
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21
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van der Horst MA, Hartog AF, El Morabet R, Marais A, Kircz M, Wever R. Enzymatic Sulfation of Phenolic Hydroxy Groups of Various Plant Metabolites by an Arylsulfotransferase. European J Org Chem 2014. [DOI: 10.1002/ejoc.201402875] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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22
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Squirewell EJ, Qin X, Duffel MW. Endoxifen and other metabolites of tamoxifen inhibit human hydroxysteroid sulfotransferase 2A1 (hSULT2A1). Drug Metab Dispos 2014; 42:1843-50. [PMID: 25157097 PMCID: PMC4201133 DOI: 10.1124/dmd.114.059709] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 08/25/2014] [Indexed: 01/07/2023] Open
Abstract
Although tamoxifen is a successful agent for treatment and prevention of estrogen-dependent breast cancer, its use has been limited by the low incidence of endometrial cancer. Human hydroxysteroid sulfotransferase 2A1 (hSULT2A1) catalyzes the formation of an α-sulfooxy metabolite of tamoxifen that is reactive toward DNA, and this has been implicated in its carcinogenicity. Also, hSULT2A1 functions in the metabolism of steroid hormones such as dehydroepiandrosterone (DHEA) and pregnenolone (PREG). These roles of hSULT2A1 in steroid hormone metabolism and in generating a reactive metabolite of tamoxifen led us to examine its interactions with tamoxifen and several of its major metabolites. We hypothesized that metabolites of tamoxifen may regulate the catalytic activity of hSULT2A1, either through direct inhibition or through serving as alternate substrates for the enzyme. We found that 4-hydroxy-N-desmethyltamoxifen (endoxifen) is a potent inhibitor of hSULT2A1-catalyzed sulfation of PREG and DHEA, with Ki values of 3.5 and 2.8 μM, respectively. In the hSULT2A1-catalyzed sulfation of PREG, 4-hydroxytamoxifen (4-OHTAM) and N-desmethyltamoxifen (N-desTAM) exhibited Ki values of 12.7 and 9.8 μM, respectively, whereas corresponding Ki values of 19.4 and 17.2 μM were observed with DHEA as substrate. A Ki value of 9.1 μM was observed for tamoxifen-N-oxide with DHEA as substrate, and this increased to 16.9 μM for the hSULT2A1-catalyzed sulfation of PREG. Three metabolites were substrates for hSULT2A1, with relative sulfation rates of 4-OHTAM > N-desTAM > > endoxifen. These results may be useful in interpreting ongoing clinical trials of endoxifen and in improving the design of related molecules.
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Affiliation(s)
- Edwin J Squirewell
- Division of Medicinal and Natural Products Chemistry, Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, University of Iowa, Iowa City, Iowa
| | - Xiaoyan Qin
- Division of Medicinal and Natural Products Chemistry, Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, University of Iowa, Iowa City, Iowa
| | - Michael W Duffel
- Division of Medicinal and Natural Products Chemistry, Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, University of Iowa, Iowa City, Iowa
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Abstract
The sulfotransferase (SULT) enzymes catalyze the formation of sulfate esters or sulfamates from substrates that contain hydroxy or amine groups, utilizing 3'-phosphoadenosyl-5'-phosphosulfate (PAPS) as the donor of the sulfonic group. The rate of product formation depends on the concentrations of PAPS and substrate as well as the sulfotransferase enzyme; thus, if PAPS is held constant while varying substrate concentration (or vice versa), the kinetic constants derived are apparent constants. When studied over a narrow range of substrate concentrations, classic Michaelis-Menten kinetics can be observed with many SULT enzymes and most substrates. Some SULT enzymes exhibit positive or negative cooperativity during conversion of substrate to product, and the kinetics fit the Hill plot. A characteristic feature of most sulfotransferase-catalyzed reactions is that, when studied over a wide range of substrate concentrations, the rate of product formation initially increases as substrate concentration increases, then decreases at high substrate concentrations, i.e., they exhibit substrate inhibition or partial substrate inhibition. This chapter gives an introduction to sulfotransferases, including a historical note, the nomenclature, a description of the function of SULTs with different types of substrates, presentation of examples of enzyme kinetics with SULTs, and a discussion of what is known about mechanisms of substrate inhibition in the sulfotransferases.
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24
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Wang T, Cook I, Falany CN, Leyh TS. Paradigms of sulfotransferase catalysis: the mechanism of SULT2A1. J Biol Chem 2014; 289:26474-26480. [PMID: 25056952 DOI: 10.1074/jbc.m114.573501] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Human cytosolic sulfotransferases (SULTs) regulate the activities of thousands of signaling small molecules via transfer of the sulfuryl moiety (-SO3) from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to the hydroxyls and primary amines of acceptors. Sulfonation controls the affinities of ligands for their targets, and thereby regulates numerous receptors, which, in turn, regulate complex cellular responses. Despite their biological and medical relevance, basic SULT mechanism issues remain unresolved. To settle these issues, and to create an in-depth model of SULT catalysis, the complete kinetic mechanism of a representative member of the human SULT family, SULT2A1, was determined. The mechanism is composed of eight enzyme forms that interconvert via 22 rate constants, each of which was determined independently. The result is a complete quantitative description of the mechanism that accurately predicts complex enzymatic behavior. This is the first description of a SULT mechanism at this resolution, and it reveals numerous principles of SULT catalysis and resolves previously ambiguous issues. The structures and catalytic behaviors SULTs are highly conserved; hence, the mechanism presented here should prove paradigmatic for the family.
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Affiliation(s)
- Ting Wang
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461-1926
| | - Ian Cook
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461-1926
| | - Charles N Falany
- Departments of Pharmacology and Toxicology, University of Alabama School of Medicine at Birmingham, Birmingham, Alabama 35294-0019 and
| | - Thomas S Leyh
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461-1926.
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25
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Structure-based mutational studies of substrate inhibition of betaine aldehyde dehydrogenase BetB from Staphylococcus aureus. Appl Environ Microbiol 2014; 80:3992-4002. [PMID: 24747910 DOI: 10.1128/aem.00215-14] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Inhibition of enzyme activity by high concentrations of substrate and/or cofactor is a general phenomenon demonstrated in many enzymes, including aldehyde dehydrogenases. Here we show that the uncharacterized protein BetB (SA2613) from Staphylococcus aureus is a highly specific betaine aldehyde dehydrogenase, which exhibits substrate inhibition at concentrations of betaine aldehyde as low as 0.15 mM. In contrast, the aldehyde dehydrogenase YdcW from Escherichia coli, which is also active against betaine aldehyde, shows no inhibition by this substrate. Using the crystal structures of BetB and YdcW, we performed a structure-based mutational analysis of BetB and introduced the YdcW residues into the BetB active site. From a total of 32 mutations, those in five residues located in the substrate binding pocket (Val288, Ser290, His448, Tyr450, and Trp456) greatly reduced the substrate inhibition of BetB, whereas the double mutant protein H448F/Y450L demonstrated a complete loss of substrate inhibition. Substrate inhibition was also reduced by mutations of the semiconserved Gly234 (to Ser, Thr, or Ala) located in the BetB NAD(+) binding site, suggesting some cooperativity between the cofactor and substrate binding sites. Substrate docking analysis of the BetB and YdcW active sites revealed that the wild-type BetB can bind betaine aldehyde in both productive and nonproductive conformations, whereas only the productive binding mode can be modeled in the active sites of YdcW and the BetB mutant proteins with reduced substrate inhibition. Thus, our results suggest that the molecular mechanism of substrate inhibition of BetB is associated with the nonproductive binding of betaine aldehyde.
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26
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Ekuase EJ, Lehmler HJ, Robertson LW, Duffel MW. Binding interactions of hydroxylated polychlorinated biphenyls (OHPCBs) with human hydroxysteroid sulfotransferase hSULT2A1. Chem Biol Interact 2014; 212:56-64. [PMID: 24508592 PMCID: PMC3994546 DOI: 10.1016/j.cbi.2014.01.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 01/15/2014] [Accepted: 01/29/2014] [Indexed: 12/15/2022]
Abstract
Polychlorinated biphenyls (PCBs) are persistent environmental contaminants, and exposure to PCBs and their hydroxylated metabolites (OHPCBs) has been associated with various adverse health effects. The mammalian cytosolic sulfotransferases (SULTs) catalyze the sulfation of OHPCBs, and the interaction of OHPCBs with both the SULT1 and SULT2 families of these enzymes has received attention both with respect to metabolic disposition of these molecules and the potential mechanisms for their roles in endocrine disruption. We have previously shown that OHPCBs interact with human hydroxysteroid sulfotransferase hSULT2A1, an enzyme that catalyzes the sulfation of dehydroepiandrosterone (DHEA), other alcohol-containing steroids, bile acids, and many xenobiotics. The objective of our current studies is to investigate the mechanism of inhibition of hSULT2A1 by OHPCBs by combining inhibition kinetics with determination of equilibrium binding constants and molecular modeling of potential interactions. Examination of the effects of fifteen OHPCBs on the sulfation of DHEA catalyzed by hSULT2A1 showed predominantly noncompetitive inhibition patterns. This was observed for OHPCBs that were substrates for sulfation reactions catalyzed by the enzyme as well as those that solely inhibited the sulfation of DHEA. Equilibrium binding experiments and molecular modeling studies indicated that the OHPCBs bind at the binding site for DHEA on the enzyme, and that the observed noncompetitive patterns of inhibition are consistent with binding in more than one orientation to more than one enzyme complex. These results have implications for the roles of SULTs in the toxicology of OHPCBs, while also providing molecular probes of the complexity of substrate/inhibitor interactions with hSULT2A1.
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Affiliation(s)
- Edugie J Ekuase
- Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, University of Iowa, Iowa City, IA 52242, United States
| | - Hans-Joachim Lehmler
- Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, IA 52242, United States
| | - Larry W Robertson
- Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, IA 52242, United States
| | - Michael W Duffel
- Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, University of Iowa, Iowa City, IA 52242, United States.
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Qin X, Lehmler HJ, Teesch LM, Robertson LW, Duffel MW. Chlorinated biphenyl quinones and phenyl-2,5-benzoquinone differentially modify the catalytic activity of human hydroxysteroid sulfotransferase hSULT2A1. Chem Res Toxicol 2013; 26:1474-85. [PMID: 24059442 DOI: 10.1021/tx400207q] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Human hydroxysteroid sulfotransferase (hSULT2A1) catalyzes the sulfation of a broad range of environmental chemicals, drugs, and other xenobiotics in addition to endogenous compounds that include hydroxysteroids and bile acids. Polychlorinated biphenyls (PCBs) are persistent environmental contaminants, and oxidized metabolites of PCBs may play significant roles in the etiology of their adverse health effects. Quinones derived from the oxidative metabolism of PCBs (PCB-quinones) react with nucleophilic sites in proteins and also undergo redox cycling to generate reactive oxygen species. This, along with the sensitivity of hSULT2A1 to oxidative modification at cysteine residues, led us to hypothesize that electrophilic PCB-quinones react with hSULT2A1 to alter its catalytic function. Thus, we examined the effects of four phenylbenzoquinones on the ability of hSULT2A1 to catalyze the sulfation of the endogenous substrate, dehydroepiandrosterone (DHEA). The quinones studied were 2'-chlorophenyl-2,5-benzoquinone (2'-Cl-BQ), 4'-chlorophenyl-2,5-benzoquinone (4'-Cl-BQ), 4'-chlorophenyl-3,6-dichloro-2,5-benzoquinone (3,6,4'-triCl-BQ), and phenyl-2,5-benzoquinone (PBQ). At all concentrations examined, pretreatment of hSULT2A1 with the PCB-quinones decreased the catalytic activity of hSULT2A1. Pretreatment with low concentrations of PBQ, however, increased the catalytic activity of the enzyme, while higher concentrations inhibited catalysis. A decrease in substrate inhibition with DHEA was seen following preincubation of hSULT2A1 with all of the quinones. Proteolytic digestion of the enzyme followed by LC/MS analysis indicated PCB-quinone- and PBQ-adducts at Cys55 and Cys199, as well as oxidation products at methionines in the protein. Equilibrium binding experiments and molecular modeling suggested that changes due to these modifications may affect the nucleotide binding site and the entrance to the sulfuryl acceptor binding site of hSULT2A1.
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Affiliation(s)
- Xiaoyan Qin
- Interdisciplinary Graduate Program in Human Toxicology, University of Iowa , Iowa City, Iowa 52242, United States
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Leyh TS, Cook I, Wang T. Structure, dynamics and selectivity in the sulfotransferase family. Drug Metab Rev 2013; 45:423-30. [PMID: 24025091 DOI: 10.3109/03602532.2013.835625] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Combined structure, function and molecular dynamics studies of human cytosolic sulfotransferases (SULT1A1 and 2A1) have revealed that these enzymes contain a ≈ 30-residue active-site cap whose structure responds to substrates and mediates their interactions. The binding of 3'-phosphoadenosine 5'-phosphosulfate (PAPS) gates access to the active site by a remodeling of the cap that constricts the pore through which acceptors must pass to enter the active site. While the PAPS-bound enzyme spends the majority (≈ 95%) of its time in the constricted state, the pore isomerizes between the open and closed states when the nucleotide (PAPS) is bound. The dimensions of the open and closed pores place widely different steric constraints on substrate selectivity. Nature appears to have crafted these enzymes with two specificity settings - a closed-pore setting that admits a set of closely related structures, and an open setting that allows a far wider spectrum of acceptor geometries. The specificities of these settings seem well matched to the metabolic demands for homeostatic and defensive SULT functions. The departure of nucleotide requires that the cap open. This isomerization dependent release can explain both the product bursts and substrate inhibition seen in many SULTs. Here, the experimental underpinnings of the cap-mechanism are reviewed, and the advantages of such a mechanism are considered in the context of the cellular and metabolic environment in which these enzymes operate.
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Affiliation(s)
- Thomas S Leyh
- Department of Microbiology and Immunology, Albert Einstein College of Medicine , Bronx, NY , USA
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Qin X, Teesch LM, Duffel MW. Modification of the catalytic function of human hydroxysteroid sulfotransferase hSULT2A1 by formation of disulfide bonds. Drug Metab Dispos 2013; 41:1094-103. [PMID: 23444386 PMCID: PMC3629806 DOI: 10.1124/dmd.112.050534] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 02/26/2013] [Indexed: 01/01/2023] Open
Abstract
The human cytosolic sulfotransferase hSULT2A1 catalyzes the sulfation of a broad range of xenobiotics, as well as endogenous hydroxysteroids and bile acids. Reversible modulation of the catalytic activity of this enzyme could play important roles in its physiologic functions. Whereas other mammalian sulfotransferases are known to be reversibly altered by changes in their redox environment, this has not been previously shown for hSULT2A1. We have examined the hypothesis that the formation of disulfide bonds in hSULT2A1 can reversibly regulate the catalytic function of the enzyme. Three thiol oxidants were used as model compounds to investigate their effects on homogeneous preparations of hSULT2A1: glutathione disulfide, 5,5'-dithiobis(2-nitrobenzoic acid), and 1,1'-azobis(N,N-dimethylformamide) (diamide). Examination of the effects of disulfide bond formation with these agents indicated that the activity of the enzyme is reversibly altered. Studies on the kinetics of the hSULT2A1-catalyzed sulfation of dehydroepiandrosterone (DHEA) showed the effects of disulfide bond formation on the substrate inhibition characteristics of the enzyme. The effects of these agents on the binding of substrates and products, liquid chromatography-mass spectrometry identification of the disulfides formed, and structural modeling of the modified enzyme were examined. Our results indicate that conformational changes at cysteines near the nucleotide binding site affect the binding of both the nucleotide and DHEA to the enzyme, with the specific effects dependent on the structure of the resulting disulfide. Thus, the formation of disulfide bonds in hSULT2A1 is a potentially important reversible mechanism for alterations in the rates of sulfation of both endogenous and xenobiotic substrates.
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Affiliation(s)
- Xiaoyan Qin
- Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, The University of Iowa, Iowa City, Iowa, USA
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Dong D, Ako R, Wu B. Crystal structures of human sulfotransferases: insights into the mechanisms of action and substrate selectivity. Expert Opin Drug Metab Toxicol 2012; 8:635-46. [PMID: 22512672 DOI: 10.1517/17425255.2012.677027] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
INTRODUCTION Cytosolic sulfotransferases (SULTs) are the enzymes that catalyze the sulfonation reaction, an important metabolic pathway for numerous endogenous and exogenous compounds. Human SULTs exhibit complex patterns of broad, differential and overlapping substrate selectivity. Moreover, these enzymes often display substrate inhibition kinetics (i.e., inhibition of the enzyme activity at high substrate concentrations). AREAS COVERED At present, the crystal structures for 12 human SULTs (i.e., SULT1A1, 1A2, 1A3, 1B1, 1C1, 1C2, 1C3, 1E1, 2A1, 2B1a, 2B1b and 4A1) are available, many of which are in complex with a substrate. This review describes the similarities and differences in these structures (particularly the active-site structures) of SULT enzymes. The authors also discuss the structural basis for understanding the catalytic mechanism, the substrate inhibition mechanisms, the cofactor (3'-phosphoadenosine 5'-phosphosulfate or PAPS) binding and the substrate recognition. EXPERT OPINION Correlations of the structural features (including conformational flexibility) in the active sites with the substrate profiles of several SULTs have been well established. One is encouraged to closely integrate in silico approaches with the structural knowledge of the active sites for development of a rationalized and accurate tool that is able to predict metabolism of SULTs toward chemicals and drug candidates.
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Affiliation(s)
- Dong Dong
- University of Houston, College of Pharmacy, Department of Pharmacological and Pharmaceutical Sciences, Houston, TX 77030, USA
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Ekuase EJ, Liu Y, Lehmler HJ, Robertson LW, Duffel MW. Structure-activity relationships for hydroxylated polychlorinated biphenyls as inhibitors of the sulfation of dehydroepiandrosterone catalyzed by human hydroxysteroid sulfotransferase SULT2A1. Chem Res Toxicol 2011; 24:1720-8. [PMID: 21913674 PMCID: PMC3196794 DOI: 10.1021/tx200260h] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Polychlorinated biphenyls (PCBs) are persistent worldwide pollutants that are of concern due to their bioaccumulation and health effects. Metabolic oxidation of PCBs results in the formation of hydroxylated metabolites (OHPCBs). Among their biological effects, OHPCBs have been shown to alter the metabolism of endocrine hormones, including inhibition of mammalian cytosolic sulfotransferases (SULTs) that are responsible for the inactivation of thyroid hormones and phenolic steroids (i.e., hSULT1A1, hSULT1B1, and hSULT1E1). OHPCBs also interact with a human hydroxysteroid sulfotransferase that plays a role in the sulfation of endogenous alcohol-containing steroid hormones and bile acids (i.e., hSULT2A1). The objectives of our current study were to examine the effects of a series of OHPCB congeners on the activity of hSULT2A1 and to develop a three-dimensional quantitative structure-activity relationship (3D-QSAR) model for OHPCBs as inhibitors of the enzyme. A total of 15 OHPCBs were examined, and the sulfation of 1 μM [(3)H] dehydroepiandrosterone (DHEA) was utilized as a model reaction catalyzed by the enzyme. All 15 OHPCBs inhibited the sulfation of DHEA, with IC(50) values ranging from 0.6 μM to 96 μM, and eight of these OHPCBs were also substrates for the enzyme. Comparative molecular field analysis (CoMFA) provided a predictive 3D-QSAR model with a q(2) value of 0.697 and an r(2) value of 0.949. The OHPCBs that had the highest potency as inhibitors of DHEA sulfation were those with a 3, 5-dichloro-4-hydroxy substitution pattern on the biphenyl ring system, and these congeners were also substrates for sulfation catalyzed by hSULT2A1.
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Affiliation(s)
- Edugie J. Ekuase
- Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, The University of Iowa, Iowa City, Iowa 52242
| | - Yungang Liu
- Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, The University of Iowa, Iowa City, Iowa 52242
| | - Hans-Joachim Lehmler
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, Iowa 52242
| | - Larry W. Robertson
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, Iowa 52242
| | - Michael W. Duffel
- Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, The University of Iowa, Iowa City, Iowa 52242
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Abstract
Inhibition of enzyme activity at high substrate concentrations, so-called "substrate inhibition," is commonly observed and has been recognized in drug metabolism reactions since the last decade. Although the importance of such "atypical" kinetics in vivo remains poorly understood, a substrate with substrate inhibition kinetics has been shown to unconventionally alter the metabolism of other substrates. In recent years, it is becoming increasingly evident that the mechanisms for substrate inhibition are highly complex, which are possibly contributed by multiple (at least two) binding sites within the enzyme protein, the formation of a ternary dead-end enzyme complex, and/or the ligand-induced changes in enzyme conformation. This review primarily discusses the mechanisms for substrate inhibition displayed by the important drug-metabolizing enzymes, such as cytochrome p450s, UDP-glucuronyltransferases, and sulfotransferases. Kinetic modeling of substrate inhibition in the absence or presence of a modifier is another central issue in this review because of its importance in the determination of kinetic parameters and in vitro/in vivo predictions.
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Affiliation(s)
- Baojian Wu
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Texas, USA.
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