The Role of Metabolism in the Estrogenic Activity of Endocrine-Disrupting Chemicals

Exposure to several natural and synthetic chemicals can disrupt the endocrine system and thus present a threat to human health. In vivo, such chemicals can be metabolized, which can change the endocrine activity of the parent chemical. Metabolism is usually considered to be a detoxification process, as it generally appears to reduce the estrogenic activity of a chemical and accelerate its elimination from the body. This is seen for bisphenol A (BPA), a known agonist of the estrogen receptor, whereby BPA glucuronide has no effects on this receptor. In contrast, numerous metabolites that show significantly greater estrogenic activities from their parent chemicals have been described in the literature. An example is the ipso metabolite of BPA, 4-methyl-2,4-bis(p-hydroxyphenyl)pent-1-ene, which shows >100-fold estrogenic activity compared to BPA. Consideration of metabolic pathways in in vitro models is therefore of great importance for reliable analysis and correct in vitro to in vivo correlations. The inclusion of metabolic aspects in these assays will reduce false-positive data for chemicals that are detoxified in vivo and false-negative data for proestrogens. Different approaches for this incorporation of metabolic systems for determination of estrogenic activities are already in use and are described in the present chapter

Data on biosynthesis of BPAF glucuronide, enzyme kinetics of BPAF glucuronidation, and molecular modeling

Bisphenol AF (BPAF) is in the body mainly metabolized to the corresponding bisphenol AF glucuronide (BPAF-G). While BPAF-G is not commercially available, enzyme-assisted synthesis of BPAF-G using the human recombinant enzyme UGT2A1, purification of BPAF-G by solid phase extraction and semi-preparative HPLC and chemical characterization of BPAF-G by NMR and LC-MS/MS were performed and are described here. Furthermore, BPAF glucuronidation kinetics with the UGT enzymes that showed the highest glucuronidation activity in previous studies (i.e hepatic UGTs 1A3, 2B7, and 2B17, intestinal UGT 1A10 and UGT 2A1 that is present in airways) was performed and data is presented. Hepatic enzymes exhibited high affinities toward BPAF, while extrahepatic UGTs 2A1 and 1A10 showed the high v(max), values (3.3 and 3.0 nmol/min/mg, respectively). To understand molecular interactions of BPA, BPAF and BPAF-G with ligand biding sites of several nuclear receptors, molecular modeling was performed and data on the binding modes of BPAF, BPA, and BPAF-G in the ligand-binding sites of nuclear receptors are presented. This article is related to "Endocrine activities and adipogenic effects of bisphenol AF and its main metabolite" (Skledar et al., 2019). (C) 2018 The Authors. Published by Elsevier Inc.Peer reviewe

Endocrine activities and adipogenic effects of bisphenol AF and its main metabolite

Bisphenol AF (BPAF) is a fluorinated analog of bisphenol A (BPA), and it is a more potent estrogen receptor (ER) agonist. BPAF is mainly metabolized to BPAF-glucuronide (BPAF-G), which has been reported to lack ER agonist activity and is believed to be biologically inactive. The main goal of the current study was to examine the influence of the metabolism of BPAF via glucuronidation on its ER activity and adipogenesis. Also, as metabolites can have different biological activities, the effects of BPAF-G on other nuclear receptors were evaluated. First, in-vitro BPAF glucuronidation was investigated using recombinant human enzymes. Specific reporter-gene assays were used to determine BPAF and BPAF-G effects on estrogen, androgen, glucocorticoid, and thyroid receptor pathways, and on PXR, FXR, and PPAR gamma pathways. Their effects on lipid accumulation and differentiation were determined in murine 3T3L1 preadipocytes using Nile Red, with mRNA expression analysis of the adipogenic markers adiponectin, Fabp4, Cebp alpha, and PPAR gamma. BPAF showed strong agonistic activity for hER alpha and moderate antagonistic activities for androgen and thyroid receptors, and for PXR. BPAF-G was antagonistic for PXR and PPAR gamma. BPAF (0.1 mu M) and BPAF-G (1.0 mu M) induced lipid accumulation and increased expression of key adipogenic markers in murine preadipocytes. BPAF-G is therefore not an inactive metabolite of BPAF. Further toxicological and epidemiological investigations of BPAF effects on human health are warranted, to provide better understanding of the metabolic end-elimination of BPAF. (C) 2018 Elsevier Ltd. All rights reserved.Peer reviewe

New dual ATP-competitive inhibitors of bacterial DNA gyrase and topoisomerase IV active against ESKAPE pathogens

The rise in multidrug-resistant bacteria defines the need for identification of new antibacterial agents that are less prone to resistance acquisition. Compounds that simultaneously inhibit multiple bacterial targets are more likely to suppress the evolution of target-based resistance than monotargeting compounds. The structurally similar ATP binding sites of DNA gyrase and topoisomerase. offer an opportunity to accomplish this goal. Here we present the design and structure-activity relationship analysis of balanced, low nanomolar inhibitors of bacterial DNA gyrase and topoisomerase IV that show potent antibacterial activities against the ESKAPE pathogens. For inhibitor 31c, a crystal structure in complex with Staphylococcus aureus DNA gyrase B was obtained that confirms the mode of action of these compounds. The best inhibitor, 31h, does not show any in vitro cytotoxicity and has excellent potency against Gram-positive (MICs: range, 0.0078-0.0625 mg/mL) and Gram-negative pathogens (MICs: range, 1-2 mg/mL). Furthermore, 31h inhibits GyrB mutants that can develop resistance to other drugs. Based on these data, we expect that structural derivatives of 31h will represent a step toward clinically efficacious multitargeting antimicrobials that are not impacted by existing antimicrobial resistance. (C) 2021 Elsevier Masson SAS. All rights reserved.Peer reviewe

New Dual ATP-Competitive Inhibitors of Bacterial DNA Gyrase and Topoisomerase IV Active Against ESKAPE Pathogens

The rise in multidrug-resistant bacteria defines the need for identification of new antibacterial agents that are less prone to resistance acquisition. Compounds that simultaneously inhibit multiple bacterial targets are more likely to suppress the evolution of target-based resistance than monotargeting compounds. The structurally similar ATP binding sites of DNA gyrase and topoisomerase IV offer an opportunity to accomplish this goal. Here we present the design and structure-activity relationship analysis of balanced, low nanomolar inhibitors of bacterial DNA gyrase and topoisomerase IV that show potent antibacterial activities against the ESKAPE pathogens. For inhibitor 31c, a crystal structure in complex with Staphylococcus aureus DNA gyrase B was obtained that confirms the mode of action of these compounds. The best inhibitor, 31h, does not show any in vitro cytotoxicity and has excellent potency against Gram-positive (MICs: range, 0.0078–0.0625 μg/mL) and Gram-negative pathogens (MICs: range, 1–2 μg/mL). Furthermore, 31h inhibits GyrB mutants that can develop resistance to other drugs. Based on these data, we expect that structural derivatives of 31h will represent a step toward clinically efficacious multitargeting antimicrobials that are not impacted by existing antimicrobial resistance