Sulfation through the looking glass--recent advances in sulfotransferase research for the curious

Inhibition of Cancer Cell Migration and Invasion In Vitro by Recombinant Tyrosine-Sulfated Haemathrin, A Thrombin Inhibitor

Thrombin, a key enzyme in the regulation of hemostasis, has been implicated in cancer progression. This study explored the effect of recombinant tyrosine-sulfated haemathrin on cancer cell behavior and signaling pathways compared to wild-type (WT) haemathrin 2. The recombinant proteins, tyrosine-sulfated haemathrin 2 (haemathrin 2S), and WT haemathrin 2 were produced in Escherichia coli and subsequently purified and applied to SKOV3 and MDA-MB-231 cells with and without thrombin stimulation. Cell migration and invasion were assessed using wound healing and Transwell assays, respectively. Haemathrin 2S treatment significantly diminished cell migration and invasion promoted by thrombin in both SKOV3 and MDA-MB-231 cells (p < 0.05). Additionally, haemathrin 2S effectively inhibited thrombin-induced phosphorylation of serine/threonine kinase (Akt) in both cell lines (p < 0.05), while WT haemathrin 2 had this effect only in MDA-MB-231 cells. Furthermore, haemathrin 2S significantly reduced thrombin-activated phosphorylation of extracellular signal-regulated kinases (ERK) and p38 in both cell lines (p < 0.05) and reversed E/N-cadherin expression in thrombin-treated MDA-MB-231 cells (p < 0.05), which were not observed with WT haemathrin 2. Overall, haemathrin 2S was more effective than WT haemathrin 2 in reducing cancer cell migration and invasion, indicating that targeting thrombin with sulfated haemathrin is a promising strategy for cancer therapy. However, further in vivo studies are needed to confirm these results.

Sulfotransferase 4A1 Coding Sequence and Protein Structure Are Highly Conserved in Vertebrates

Cytosolic sulfotransferases (SULTs) are Phase 2 drug-metabolizing enzymes that catalyze the conjugation of sulfonate to endogenous and xenobiotic compounds, increasing their hydrophilicity and excretion from cells. To date, 13 human SULTs have been identified and classified into five families. SULT4A1 mRNA encodes two variants: (1) the wild type, encoding a 284 amino acid, ~33 kDa protein, and (2) an alternative spliced variant resulting from a 126 bp insert between exon 6 and 7, which introduces a premature stop codon that enhances nonsense-mediated decay. SULT4A1 is classified as an SULT based on sequence and structural similarities, including PAPS-domains, active-site His, and the dimerization domain; however, the catalytic pocket lid 'Loop 3' size is not conserved. SULT4A1 is uniquely expressed in the brain and localized in the cytosol and mitochondria. SULT4A1 is highly conserved, with rare intronic polymorphisms that have no outward manifestations. However, the SULT4A1 haplotype is correlated with Phelan-McDermid syndrome and schizophrenia. SULT4A1 knockdown revealed potential SULT4A1 functions in photoreceptor signaling and knockout mice display hampered neuronal development and behavior. Mouse and yeast models revealed that SULT4A1 protects the mitochondria from endogenously and exogenously induced oxidative stress and stimulates cell division, promoting dendritic spines' formation and synaptic transmission. To date, no physiological enzymatic activity has been associated with SULT4A1.

A new type of sulfation reaction: C-sulfonation for α,β-unsaturated carbonyl groups by a novel sulfotransferase SULT7A1

Cytosolic sulfotransferases (SULTs) are cytosolic enzymes that catalyze the transfer of sulfonate group to key endogenous compounds, altering the physiological functions of their substrates. SULT enzymes catalyze the O-sulfonation of hydroxy groups or N-sulfonation of amino groups of substrate compounds. In this study, we report the discovery of C-sulfonation of α,β-unsaturated carbonyl groups mediated by a new SULT enzyme, SULT7A1, and human SULT1C4. Enzymatic assays revealed that SULT7A1 is capable of transferring the sulfonate group from 3'-phosphoadenosine 5'-phosphosulfate to the α-carbon of α,β-unsaturated carbonyl-containing compounds, including cyclopentenone prostaglandins as representative endogenous substrates. Structural analyses of SULT7A1 suggest that the C-sulfonation reaction is catalyzed by a novel mechanism mediated by His and Cys residues in the active site. Ligand-activity assays demonstrated that sulfonated 15-deoxy prostaglandin J2 exhibits antagonist activity against the prostaglandin receptor EP2 and the prostacyclin receptor IP. Modification of α,β-unsaturated carbonyl groups via the new prostaglandin-sulfonating enzyme, SULT7A1, may regulate the physiological function of prostaglandins in the gut. Discovery of C-sulfonation of α,β-unsaturated carbonyl groups will broaden the spectrum of potential substrates and physiological functions of SULTs.

Alterations in the Serum Proteome Following Electroconvulsive Therapy for a Major Depressive Episode: A Longitudinal Multicenter Study

Background

Electroconvulsive therapy (ECT) is the most effective treatment for severe depression, but the biological changes induced by ECT remain poorly understood.

Methods

This study investigated alterations in blood serum proteins in 309 patients receiving ECT for a major depressive episode. We analyzed 201 proteins in samples collected at 3 time points (T): just before the first ECT treatment session (T0), within 30 minutes after the first ECT session (T1), and just before the sixth ECT session (T2).

Results

Using statistical models to account for repeated sampling, we identified 152 and 70 significantly (<5% false discovery rate) altered proteins at T1 and T2, respectively. The most pronounced alterations at T1 were transiently increased levels of prolactin, myoglobin, and kallikrein-6. However, most proteins had decreased levels at T1, with the largest effects observed for pro-epidermal growth factor, proto-oncogene tyrosine-protein kinase Src, tumor necrosis factor ligand superfamily member 14, sulfotransferase 1A1, early activation antigen CD69, and CD40 ligand. The change of several acutely altered proteins correlated with electric current and pulse frequency in a dose-response-like manner. Over a 5-session course of ECT, some acutely altered levels were sustained while others increased, e.g., serine protease 8 and chitinase-3-like protein 1. None of the studied protein biomarkers were associated with clinical response to ECT.

Conclusions

We report experimental data on alterations in the circulating proteome triggered by ECT in a clinical setting. The findings implicate hormonal signaling, immune response, apoptotic processes, and more. None of the findings were associated with clinical response to ECT.

The importance of selecting crystal form for triazole fungicide tebuconazole to enhance its botryticidal activity

The growing evidences of resistant fungi stimulate fully understanding tebuconazole regarding its crystal structure on fungicidal activity. In this study, the crystal structures of six technical tebuconazoles (BX, HH, JP, QZ, SJ, and YT) were characterized by using high-resolution X-ray powder diffraction and three-dimensional crystal structure modeling. A structure-activity relationship of the tebuconazoles on the susceptible (HLS and YJS) or resistant (XHR) Botrytis cinerea isolates was analyzed, the differential tricarboxylic acid (TCA) cycle metabolism was determined, and molecular docking with sterol 14α-demethylase (CYP51) was performed. The results showed that tebuconazole existed in three types of crystal forms: an overlapping-pair conformation, a side-by-side-pair conformation, and a parallel-pair conformation. QZ with the parallel-pair conformation and the minimum crystal cell volume exhibited a higher activity and a lower resistant level. XHR possessed a higher content of TCA cycle metabolites and phosphate than YJS, but the exposure to QZ significantly reduced the contents of citrate, isocitrate, α-ketoglutarate and oxaloacetate in XHR, as did the exposure to other technical tebuconazoles. Moreover, the point mutations F487L, G464S, and G443S altered the binding properties of chiral stereoscopic R-QZ with CYP51 protein. Especially the G443S mutation promoted a weak linking of R-QZ with LEU380 and TYR126, and greatly slashed the binding action at lower docking score. In conclusion, our results evidenced an efficient crystal conformation of tebuconazole to improve botryticidal activity and a potential adaptability of B. cinerea to tebuconazole inhibition in TCA cycle metabolism and CYP51 protein mutation.

Inverse Molecular Docking Elucidating the Anticarcinogenic Potential of the Hop Natural Product Xanthohumol and Its Metabolites

Natural products from plants exert a promising potential to act as antioxidants, antimicrobials, anti-inflammatory, and anticarcinogenic agents. Xanthohumol, a natural compound from hops, is indeed known for its anticarcinogenic properties. Xanthohumol is converted into three metabolites: isoxanthohumol (non-enzymatically) as well as 8- and 6-prenylnaringenin (enzymatically). An inverse molecular docking approach was applied to xanthohumol and its three metabolites to discern their potential protein targets. The aim of our study was to disclose the potential protein targets of xanthohumol and its metabolites in order to expound on the potential anticarcinogenic mechanisms of xanthohumol based on the found target proteins. The investigated compounds were docked into the predicted binding sites of all human protein structures from the Protein Data Bank, and the best docking poses were examined. Top scoring human protein targets with successfully docked compounds were identified, and their experimental connection with the anticarcinogenic function or cancer was investigated. The obtained results were carefully checked against the existing experimental findings from the scientific literature as well as further validated using retrospective metrics. More than half of the human protein targets of xanthohumol with the highest docking scores have already been connected with the anticarcinogenic function, and four of them (including two important representatives of the matrix metalloproteinase family, MMP-2 and MMP-9) also have a known experimental correlation with xanthohumol. Another important protein target is acyl-protein thioesterase 2, to which xanthohumol, isoxanthohumol, and 6-prenylnaringenin were successfully docked with the lowest docking scores. Moreover, the results for the metabolites show that their most promising protein targets are connected with the anticarcinogenic function as well. We firmly believe that our study can help to elucidate the anticarcinogenic mechanisms of xanthohumol and its metabolites as after consumption, all four compounds can be simultaneously present in the organism.

What If Not All Metabolites from the Uremic Toxin Generating Pathways Are Toxic? A Hypothesis

The topic of uremic toxicity has received broad attention from the nephrological community over the past few decades. An aspect that is much less often considered is the possibility that the metabolic pathways that generate uremic toxins also may produce molecules that benefit body functions. Here, we discuss this dualism based on the example of tryptophan-derived metabolites, which comprise elements that are mainly toxic, such as indoxyl sulfate, kynurenine and kynurenic acid, but also beneficial compounds, such as indole, melatonin and indole-3-propionic acid, and ambivalent (beneficial for some aspects and harmful for others) compounds such as serotonin. This dualism can also be perceived at the level of the main receptor of the tryptophan-derived metabolites, the aryl hydrocarbon receptor (AHR), which has also been linked to both harm and benefit. We hypothesize that these beneficial effects are the reason why uremic toxin generation remained preserved throughout evolution. This duality is also not unique for the tryptophan-derived metabolites, and in this broader context we discuss the remote sensing and signaling theory (RSST). The RSST proposes that transporters (e.g., organic anion transporter 1—OAT1; ATP-binding cassette transporter G—ABCG2) and drug metabolizing enzymes form a large network of proteins interacting to promote small molecule remote communication at the inter-organ (e.g., gut–liver–heart–brain–kidney) and inter-organismal (e.g., gut microbe–host) levels. These small molecules include gut microbe-derived uremic toxins as well as beneficial molecules such as those discussed here. We emphasize that this positive side of uremic metabolite production needs more attention, and that this dualism especially needs to be considered when assessing and conceiving of therapeutic interventions. These homeostatic considerations are central to the RSST and suggest that interventions be aimed at preserving or restoring the balance between positive and negative components rather than eliminating them all without distinction.

Association of CHEK2 I157T and SULT1A1 R213H genetic variants with risk of sporadic colorectal cancer in a sample of Egyptian patients

Background

Recent research proposed an association between functional defects involving CHEK2 I157T and SULT1A1 R213H variants and increased incidence of several types of cancer. A total of 86 unrelated colorectal cancer patients attending the Surgical Oncology Department were recruited in the study. The second group of 152 healthy age- and sex-matched volunteers were included as controls. Polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) was applied for genotyping. Chi-square test was applied to compare genotype and allele frequencies in the studied groups. The purpose of the present study was to evaluate the association between CHEK2 I157T and SULT1A1 R213H polymorphisms and colorectal cancer.

Results

No significant differences in genotypes were detected between cases and controls in the present study for both CHEK2 I157T and SULT1A1 R213H polymorphisms (χ2 = 1.839; P = 0.399/χ2 = 2.831; P = 0.243), respectively. Likewise, discrepancies in allele frequency for the wild-type or mutant alleles were non-statistically significant in CHEK2 I157T and SULT1A1 R213H (χ2 = 1.231; P = 0.267/χ2 = 0.180; P = 0.671), respectively.

Conclusions

Results of the current study propose that CHEK2 I157T and SULT1A1 R213H polymorphisms are not associated with CRC development in Egyptian population. Further future studies on the functional implications of these polymorphisms are strongly recommended.

The Role of Chirality of [18F]SMBT-1 in Imaging of Monoamine Oxidase-B

(S)-(2-Methylpyrid-5-yl)-6-[(3-[¹⁸F]fluoro-2-hydroxy)propoxy]quinoline ([¹⁸F]SMBT-1) was recently developed as a novel class of selective and reversible monoamine oxidase-B (MAO-B) tracers for in vivo imaging of reactive astrogliosis via positron emission tomography. To investigate the effect of the chirality of [¹⁸F]SMBT-1 on tracer performance, we synthesized (S)-[¹⁸F]6 ([¹⁸F]SMBT-1) and (R)-[¹⁸F]6 and compared their binding properties, pharmacokinetics, and metabolism. (S)-6 showed higher binding affinity to MAO-B and lower binding affinity to MAO-A than (R)-6, demonstrating a higher selectivity ratio (MAO-B/MAO-A). A pharmacokinetic study in mice demonstrated that both (S)-[¹⁸F]6 and (R)-[¹⁸F]6 showed sufficient initial brain uptake. However, (S)-[¹⁸F]6 was cleared significantly faster from the body. An abundant sulfoconjugate metabolite M2 was observed in plasma for (S)-[¹⁸F]6 but not for (R)-[¹⁸F]6. In vitro sulfation assays confirmed that (S)-6 was more reactive than (R)-6, consistent with the in vivo findings. Mefenamic acid, a selective sulfotransferase 1A1 (SULT1A1) inhibitor, strongly inhibited the in vitro sulfation of (S)-6 by mouse liver fractions, human liver cytosol fractions, and human recombinant SULT1A1 enzyme. Genetic polymorphisms of SULT1A1 did not affect the sulfation of (S)-6 in vitro. In conclusion, (S)-[¹⁸F]6 had a more favorable binding affinity and binding selectivity for MAO-B than (R)-[¹⁸F]6. Additionally, (S)-[¹⁸F]6 also possessed better pharmacological and metabolic properties than (R)-[¹⁸F]6. These results suggest that (S)-[¹⁸F]6 ([¹⁸F]SMBT-1) is a promising candidate for application in the imaging of MAO-B in vivo.

Simultaneous determination of melatonin and 6-hydroxymelatonin in human overnight urine by LC-MS/MS

For the quantification of the pineal hormone melatonin and its metabolite, 6-hydroxymelatonin, in human overnight urine, a single accurate method by liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed. Urine samples were deconjugated using β-glucuronidase/arylsulfatase from Helix pomatia before solid phase extraction (SPE) purification. Chromatographic separation was performed using a reverse phase C18 column with a 7-minute gradient elution. Water was used as matrix to prepare the calibration standards, and deuterated analogues of melatonin and 6-hydroxymelatonin were used as internal standards. This newly developed method was validated in terms of linearity, accuracy, repeatability, intermediate precision, recovery, matrix effect, and stability according to the guidelines of the European Medicines Agency. The method was successfully applied to the analysis of overnight urine samples from 12 healthy volunteers, showing significant correlations of urinary melatonin and 6-hydroxymelatonin excretion rates with age. The urinary 6-hydroxymelatonin to melatonin ratio was also established and will be assessed in further studies as a potential endogenous metric of CYP1A2 activity.

SULT genetic polymorphisms: physiological, pharmacological and clinical implications

INTRODUCTION

Cytosolic sulfotransferases (SULTs)-mediated sulfation is critically involved in the metabolism of key endogenous compounds, such as catecholamines and thyroid/steroid hormones, as well as a variety of drugs and other xenobiotics. Studies performed in the past three decades have yielded a good understanding about the enzymology of the SULTs and their structural biology, phylogenetic relationships, tissue/organ-specific/developmental expression, as well as the regulation of the SULT gene expression. An emerging area is related to the functional impact of the SULT genetic polymorphisms.

AREAS COVERED

The current review aims to summarize our current knowledge about the above-mentioned aspects of the SULT research. An emphasis is on the information concerning the effects of the polymorphisms of the SULT genes on the functional activity of the SULT allozymes and the associated physiological, pharmacological, and clinical implications.

EXPERT OPINION

Elucidation of how SULT SNPs may influence the drug-sulfating activity of SULT allozymes will help understand the differential drug metabolism and eventually aid in formulating personalized drug regimens. Moreover, the information concerning the differential sulfating activities of SULT allozymes toward endogenous compounds may allow for the development of strategies for mitigating anomalies in the metabolism of these endogenous compounds in individuals with certain SULT genotypes.

Characterization of a commercially available line of iPSC hepatocytes as models of hepatocyte function and toxicity for regulatory purposes

It has recently become possible to produce hepatocytes from human induced pluripotent stem cells (iPSC-heps), which may offer some advantages over primary human hepatocytes (Prim-heps) in the regulatory environment. The aim of this research was to assess similarities and differences between commercially available iPSC-heps and Prim-heps in preliminary assays of drug metabolism, hepatotoxicity, and drug transport. Hepatocytes were either cultured in collagen-coated 96-well plates (Prim-heps and 2d-iPSC-heps) or in ultra-low adhesion plates as spheroids (3d-iPSC-heps). 3d-iPSC-heps were used to enhance physiological cell-cell contacts, which is essential to maintain the phenotype of mature hepatocytes. Cytochrome P450 (CYP) 3A4, CYP1A2, and CYP2B6 activity levels were evaluated using fluorescent assays. Phase II metabolism was assessed by HPLC measurement of formation of glucuronides and sulfates of 4-methylumbelliferone, 1-naphthol, and estradiol. The toxicity of acetaminophen, amiodarone, aspirin, clozapine, tacrine, tamoxifen, and troglitazone was monitored using a luminescent cell viability assay. Canaliculi formation was monitored by following the fluorescence of 5,6-carboxy-2',7'-dichlorofluorescein diacetate. All culture models showed similar levels of basal CYP3A4, CYP1A2 and CYP2B6 activity. However, while Prim-heps showed a vigorous response to CYP inducing agents, 2d-iPSC-heps showed no response and 3d-iPSC-heps displayed an inconclusive response. 2d-iPSC-heps showed reduced, yet appreciable, glucuronide and sulfate formation compared to Prim-heps. All culture models showed similar activity in tests of hepatotoxicity, with Prim-heps generally being more sensitive. All models formed canaliculi capable of transporting carboxy-2',7'-dichlorofluorescein. The iPSC-heps appear to be useful for toxicity and transport studies, but metabolic activity is not optimum, and metabolism studies would benefit from a more mature model.

Effects of Genetic Polymorphisms on the Sulfation of Doxorubicin by Human SULT1C4 Allozymes

Doxorubicin is a chemotherapeutic drug widely utilized in cancer treatment. An enzyme critical to doxorubicin metabolism is the cytosolic sulfotransferase (SULT) SULT1C4. This study investigated the functional impact of SULT1C4 single nucleotide polymorphisms (SNPs) on the sulfation of doxorubicin by SULT1C4 allozymes. A comprehensive database search was performed to identify various SULT1C4 SNPs. Ten nonsynonymous SULT1C4 SNPs were selected, and the corresponding cDNAs, packaged in pGEX-2TK expression vector, were generated via site-directed mutagenesis. Respective SULT1C4 allozymes were bacterially expressed and purified by affinity chromatography. Purified SULT1C4 allozymes, in comparison with the wild-type enzyme, were analyzed for sulfating activities toward doxorubicin and 4-nitrophenol, a prototype substrate. Results obtained showed clearly differential doxorubicin-sulfating activity of SULT1C4 allozymes, implying differential metabolism of doxorubicin through sulfation in individuals with distinct SULT1C4 genotypes.

A simple method to measure sulfonation in man using paracetamol as probe drug

Sulfotransferase enzymes (SULT) catalyse sulfoconjugation of drugs, as well as endogenous mediators, gut microbiota metabolites and environmental xenobiotics. To address the limited evidence on sulfonation activity from clinical research, we developed a clinical metabolic phenotyping method using paracetamol as a probe substrate. Our aim was to estimate sulfonation capability of phenolic compounds and study its intraindividual variability in man. A total of 36 healthy adult volunteers (12 men, 12 women and 12 women on oral contraceptives) received paracetamol in a 1 g-tablet formulation on three separate occasions. Paracetamol and its metabolites were measured in plasma and spot urine samples using liquid chromatography-high resolution mass spectrometry. A metabolic ratio (Paracetamol Sulfonation Index—PSI) was used to estimate phenol SULT activity. PSI showed low intraindividual variability, with a good correlation between values in plasma and spot urine samples. Urinary PSI was independent of factors not related to SULT activity, such as urine pH or eGFR. Gender and oral contraceptive intake had no impact on PSI. Our SULT phenotyping method is a simple non-invasive procedure requiring urine spot samples, using the safe and convenient drug paracetamol as a probe substrate, and with low intraindividual coefficient of variation. Although it will not give us mechanistic information, it will provide us an empirical measure of an individual’s sulfonator status. To the best of our knowledge, our method provides the first standardised in vivo empirical measure of an individual’s phenol sulfonation capability and of its intraindividual variability. EUDRA-CT 2016-001395-29, NCT03182595 June 9, 2017.

Structure of mouse cytosolic sulfotransferase SULT2A8 provides insight into sulfonation of 7α-hydroxyl bile acids

Cytosolic sulfotransferases (SULTs) catalyze the transfer of a sulfonate group from the cofactor 3'-phosphoadenosine 5'-phosphosulfate to a hydroxyl (OH) containing substrate and play a critical role in the homeostasis of endogenous compounds, including hormones, neurotransmitters, and bile acids. In human, SULT2A1 sulfonates the 3-OH of bile acids; however, bile acid metabolism in mouse is dependent on a 7α-OH sulfonating SULT2A8 via unknown molecular mechanisms. In this study, the crystal structure of SULT2A8 in complex with adenosine 3',5'-diphosphate and cholic acid was resolved at a resolution of 2.5 Å. Structural comparison with human SULT2A1 reveals different conformations of substrate binding loops. In addition, SULT2A8 possesses a unique substrate binding mode that positions the target 7α-OH of the bile acid close to the catalytic site. Furthermore, mapping of the critical residues by mutagenesis and enzyme activity assays further highlighted the importance of Lys44 and His48 for enzyme catalysis and Glu237 in loop 3 on substrate binding and stabilization. In addition, limited proteolysis and thermal shift assays suggested that the cofactor and substrates have protective roles in stabilizing SULT2A8 protein. Together, the findings unveil the structural basis of bile acid sulfonation targeting 7α-OH and shed light on the functional diversity of bile acid metabolism across species.

An activity-based fluorescent sensor for the detection of the phenol sulfotransferase SULT1A1 in living cells

Human phenol sulfotransferases mediate the transfer of a sulfuryl moiety from the activated sulfate donor PAPS to hydroxy-containing substrates, altering substrate solubility and charge to affect phase II metabolism and cell signaling. Here, we present the development, computational modeling, in vitro enzymology, and biological application of STS-3, an activity-based fluorescent sensor for the SULT1A1 isoform.

Insights into the metabolic characteristics of aminopropanediol analogues of SYLs as S1P1 modulators: from structure to metabolism

SYL927 and SYL930, two aminopropanediol analogues, are novel Sphingosine-1-phosphate receptor 1 (S1P₁) modulators with higher selectivity and pharmacological activity compared with FTY720. Although the immunosuppressive activity of SYLs has been well demonstrated, information regarding the metabolic fates of the two chemicals is limited except for the CYP-catalyzed hydroxylation of SYL930. In this study, the biotransformation schemes of the two promising chemicals were investigated and compared using liver microsomes, S9 fractions and recombinant enzymes, and relevant molecular mechanism was primarily demonstrated by ligand-enzyme docking analysis (CDOCKER). As a result, the hydroxylation at alkyl chain on oxazole ring by the action of CYPs was found for both SYLs in vivo. The SULT-catalyzed sulfonation of the hydroxide was observed for SYL927 while the ADH/ALDH-catalyzed oxidation was only discovered for SYL930. The docking analysis suggested that specific non-covalent forces and/or bonding conformations of the hydroxides with biomacromolecules might be involved in the disparate metabolism of SYLs. Exploring the metabolic characteristics will help clarify the substance base for efficacy and safety of the two drugs. The uncovered structure-metabolism relationship in this study may provide an implication for the design and optimization for other S1P modulators.

Evaluation of a conserved tryptophanyl residue in donor substrate binding and catalysis by a phenol sulfotransferase (SULT1A1)

Structural determinations of members of the sulfotransferase (SULT) family suggest a direct interaction between a conserved tryptophanyl side chain and bound 3'-phosphoadenosine-5'-phosphate (PAP). We have prepared and purified mutants of the bovine SULT1A1, a very conserved homolog to the human SULT1A1, in which tryptophanyl-53 was sequentially trimmed to tyrosine, leucine, and alanine. Differential scanning fluorimetry indicated structural stabilities of the mutant proteins comparable to the wild type SULT1A1; however, less thermal stabilizations by PAP plus pentachlorophenol were observed with the mutants, suggesting weakened ligand binding. Protein fluorescence of the wild type enzyme decreased 6.5% upon binding PAP, whereas no changes occurred with the mutant enzymes. This reveals that W53, or its positional counterpart, has been the source of emission intensity changes used in previous investigations of other SULTs. Fluorescence resonance energy transfer from excited tryptophans to bound 7-hydroxycoumarin, as induced by PAP, indicated weakened binding of ligands to the mutant SULTs. This was also encountered and quantified in initial rate kinetic analyses. Ablation of the PAPS adenine-to-W53 ring interaction, shown by the W53A mutant enzyme, resulted in a 6.4-fold increase in K_PAPS and a 92% decrease in k_cat/K_PAPS. Measured K_PAPS values reveal the W53 indole ring contribution to PAPS binding to be 1.1 kcal/mol (4.6 kJ/mol). These results verify the structurally-inferred role for the π-π stacking interaction between PAP(S) and the conserved tryptophanyl residue in SULT1A1 and other members of the SULT family.

Impact of SULT1A3/SULT1A4 genetic polymorphisms on the sulfation of phenylephrine and salbutamol by human SULT1A3 allozymes

OBJECTIVES

Phenylephrine and salbutamol are drugs that are used widely to treat diseases/disorders, such as nasal congestion, hypotension, and asthma, in individuals of different age groups. Human cytosolic sulfotransferase (SULT) SULT1A3 has been shown to be critically involved in the metabolism of these therapeutic agents. This study was carried out to investigate the effects of single nucleotide polymorphisms of human SULT1A3 and SULT1A4 genes on the sulfation of phenylephrine and salbutamol by SULT1A3 allozymes.

MATERIALS AND METHODS

Wild-type and SULT1A3 allozymes, prepared previously by site-directed mutagenesis in conjunction with bacterial expression and affinity purification, were analyzed for sulfating activity using an established assay procedure.

RESULTS

Purified SULT1A3 allozymes, in comparison with the wild-type enzyme, showed differential sulfating activities toward phenylephrine and salbutamol. Kinetic studies showed further significant variations in their substrate-binding affinity and catalytic activity toward phenylephrine and salbutamol.

CONCLUSION

The results obtained showed clearly the differential enzymatic characteristics of SULT1A3 allozymes in mediating the sulfation of phenylephrine and salbutamol. This information may contribute toward a better understanding of the pharmacokinetics of these two drugs in individuals with distinct SULT1A3 and/or SULT1A4 genotypes.

Estrogen Formation and Inactivation Following TBI: What we Know and Where we Could go

Traumatic brain injury (TBI) is responsible for various neuronal and cognitive deficits as well as psychosocial dysfunction. Characterized by damage inducing neuroinflammation, this response can cause an acute secondary injury that leads to widespread neurodegeneration and loss of neurological function. Estrogens decrease injury induced neuroinflammation and increase cell survival and neuroprotection and thus are a potential target for use following TBI. While much is known about the role of estrogens as a neuroprotective agent following TBI, less is known regarding their formation and inactivation following damage to the brain. Specifically, very little is known surrounding the majority of enzymes responsible for the production of estrogens. These estrogen metabolizing enzymes (EME) include aromatase, steroid sulfatase (STS), estrogen sulfotransferase (EST/SULT1E1), and some forms of 17β-hydroxysteroid dehydrogenase (HSD17B) and are involved in both the initial conversion and interconversion of estrogens from precursors. This article will review and offer new prospective and ideas on the expression of EMEs following TBI.

Structural and Dynamic Characterizations Highlight the Deleterious Role of SULT1A1 R213H Polymorphism in Substrate Binding

Sulfotransferase 1A1 (SULT1A1) is responsible for catalyzing various types of endogenous and exogenous compounds. Accumulating data indicates that the polymorphism rs9282861 (R213H) is responsible for inefficient enzymatic activity and associated with cancer progression. To characterize the detailed functional consequences of this mutation behind the loss-of-function of SULT1A1, the present study deployed molecular dynamics simulation to get insights into changes in the conformation and binding energy. The dynamics scenario of SULT1A1 in both wild and mutated types as well as with and without ligand showed that R213H induced local conformational changes, especially in the substrate-binding loop rather than impairing overall stability of the protein structure. The higher conformational changes were observed in the loop3 (residues, 235-263), turning loop conformation to A-helix and B-bridge, which ultimately disrupted the plasticity of the active site. This alteration reduced the binding site volume and hydrophobicity to decrease the binding affinity of the enzyme to substrates, which was highlighted by the MM-PBSA binding energy analysis. These findings highlight the key insights of structural consequences caused by R213H mutation, which would enrich the understanding regarding the role of SULT1A1 mutation in cancer development and also xenobiotics management to individuals in the different treatment stages.

Ontogeny of Hepatic Sulfotransferases and Prediction of Age-Dependent Fractional Contribution of Sulfation in Acetaminophen Metabolism

Cytosolic sulfotransferases (SULTs), including SULT1A, SULT1B, SULT1E, and SULT2A isoforms, play noteworthy roles in xenobiotic and endobiotic metabolism. We quantified the protein abundances of SULT1A1, SULT1A3, SULT1B1, and SULT2A1 in human liver cytosol samples (n = 194) by liquid chromatography-tandem mass spectrometry proteomics. The data were analyzed for their associations by age, sex, genotype, and ethnicity of the donors. SULT1A1, SULT1B1, and SULT2A1 showed significant age-dependent protein abundance, whereas SULT1A3 was invariable across 0-70 years. The respective mean abundances of SULT1A1, SULT1B1, and SULT2A1 in neonatal samples was 24%, 19%, and 38% of the adult levels. Interestingly, unlike UDP-glucuronosyltransferases and cytochrome P450 enzymes, SULT1A1 and SULT2A1 showed the highest abundance during early childhood (1 to <6 years), which gradually decreased by approx. 40% in adolescents and adults. SULT1A3 and SULT1B1 abundances were significantly lower in African Americans compared with Caucasians. Multiple linear regression analysis further confirmed the association of SULT abundances by age, ethnicity, and genotype. To demonstrate clinical application of the characteristic SULT ontogeny profiles, we developed and validated a proteomics-informed physiologically based pharmacokinetic model of acetaminophen. The latter confirmed the higher fractional contribution of sulfation over glucuronidation in the metabolism of acetaminophen in children. The study thus highlights that the ontogeny-based age-dependent fractional contribution (fm) of individual drug-metabolizing enzymes has better potential in prediction of drug-drug interactions and the effect of genetic polymorphisms in the pediatric population.

Estrogen sulfotransferase in the metabolism of estrogenic drugs and in the pathogenesis of diseases

INTRODUCTION

Biotransformation is important in the metabolism of endobiotics and xenobiotics. This process comprises the activity of phase I and phase II enzymes. Estrogen sulfotransferase (SULT1E1 or EST) is a phase II conjugating enzyme that belongs to the family of cytosolic sulfotransferases. The expression of SULT1E1 can be detected in many tissues, including the liver. SULT1E1 catalyzes the transfer of a sulfate group from 3'-phosphoadenosine-5'-phosphosulfate (PAPS) to any available hydroxyl group in estrogenic molecules. The substrates of SULT1E1 include the endogenous and synthetic estrogens. Upon SULT1E1-mediated sulfation, the hydrosolubility of estrogens increases, preventing the binding between the sulfated estrogens and the estrogen receptor (ER). This sulfated state of the estrogens is not irreversible, as the steroid sulfatase (STS) can convert sulfoconjugated estrogens to free estrogens. The expression of SULT1E1 is inducible by several diseases that involve tissue inflammation, such as type 2 diabetes, sepsis, and ischemia-reperfusion injury. Areas covered: This systematic literature review aims to summarize the role of SULT1E1 in the metabolism of estrogenic drugs and xenobiotics, and the role of SULT1E1 in the pathogenesis of several diseases, including cancer, metabolic disease, sepsis, liver injury, and cystic fibrosis. Meanwhile, ablation or pharmacological inhibition of SULT1E1 can affect the outcomes of the aforementioned diseases. Expert opinion: In addition to its role in metabolizing estrogenic drugs, SULT1E1 is unexpectedly being unveiled as a mediator for the disease effect on estrogen metabolism and homeostasis. Meanwhile, because the expression and activity of SULT1E1 can affect the outcome of diseases, the same sulfotransferase and the reversing enzymes STS can be potential therapeutic targets to prevent or manage diseases. Accumulating evidence suggest that the physiological and pathophysiological effects of SULT1E1 can be estrogen-independent and it is necessary to elucidate what other possible substrates may be recognized by the enzyme. Moreover, human studies are paramount to confirm the human relevance of the animal studies.

Effects of the human SULT1A1 polymorphisms on the sulfation of acetaminophen,O-desmethylnaproxen, and tapentadol

BACKGROUND

Non-opioid and opioid analgesics, as over-the-counter or prescribed medications, are widely used for the management of a diverse array of pathophysiological conditions. Previous studies have demonstrated the involvement of human cytosolic sulfotransferase (SULT) SULT1A1 in the sulfation of acetaminophen, O-desmethylnaproxen (O-DMN), and tapentadol. The current study was designed to investigate the impact of single nucleotide polymorphisms (SNPs) of the human SULT1A1 gene on the sulfation of these analgesic compounds by SULT1A1 allozymes.

METHODS

Human SULT1A1 genotypes were identified by database search. cDNAs corresponding to nine SULT1A1 nonsynonymous missense coding SNPs (cSNPs) were generated by site-directed mutagenesis. Recombinant wild-type and SULT1A1 allozymes were bacterially expressed and affinity-purified. Purified SULT1A1 allozymes were analyzed for sulfation activity using an established assay procedure.

RESULTS

Compared with the wild-type enzyme, SULT1A1 allozymes were shown to display differential sulfating activities toward three analgesic compounds, acetaminophen, O-desmethylnaproxen (O-DMN), and tapentadol, as well as the prototype substrate 4NP.

CONCLUSION

Results obtained indicated clearly the impact of genetic polymorphisms on the drug-sulfation activity of SULT1A1 allozymes. Such information may contribute to a better understanding about the differential metabolism of acetaminophen, O-DMN, and tapentadol in individuals with different SULT1A1 genotypes.

Bio-artificial bone formation model with a radial-flow bioreactor for implant therapy-comparison between two cell culture carriers: porous hydroxyapatite and β-tricalcium phosphate beads

Bone grafting is necessary before dental implant treatment in patients with jaw bone defects. Currently, autologous bone grafting is a major burden on the patient. However, it is impossible to form a sufficient foundation for the implant with a bone-filling agent alone. It is, therefore, necessary to prepare hybrid artificial bone tissue containing osteoblasts and osteoclasts. In this study, mouse MC3T3-E1 pre-osteoblast cells and human embryonic-derived osteoblastic cell line hFOB1.19 were cultured in radial-flow bioreactors (RFB) to form three-dimensional artificial bone filled with porous beads of β-tricalcium phosphate (β-TCP) or hydroxyapatite (HA)—which are clinically used as bone-filling agents—as cell culture carriers. When circulation culturing was performed in the growth medium for the first 10–12 days, glucose consumption was increased in the cultures with HA beads in comparison to the cultures with β-TCP beads. When cultured in the differentiation culture medium during the second half of the culture period, the glucose consumption decreased in the culture with HA beads. A DNA microarray analysis suggested that osteogenesis progressed fast in three-dimensional culture filled with HA beads and that partly differentiation into osteoblasts was prominent in cultures with β-TCP beads. In the growth process of MC3T3-E1 cells, the vitamin A metabolism was also activated, the synthesis and degradation of retinoic acid was enhanced, and the metabolism of the same process decreased at the end of differentiation in three-dimensional cultures. Three-dimensional circulation culture in RFB is considered to be useful for the formation of hybrid bio-artificial bone tissue.

Hydroxylated and sulfated metabolites of commonly observed airborne polychlorinated biphenyls display selective uptake and toxicity in N27, SH-SY5Y, and HepG2 cells

Although neurotoxicity and hepatotoxicity have long been associated with exposure to polychlorinated biphenyls (PCBs), less is known about the selective toxicity of those hydroxylated PCBs (OH-PCBs) and PCB sulfates that are metabolites derived from exposure to PCBs found in indoor air. We have examined the toxicity of OH-PCBs and PCB sulfates derived from PCBs 3, 8, 11, and 52 in two neural cell lines (N27 and SH-SY5Y) and an hepatic cell line (HepG2). With the exception of a similar toxicity seen for N27 cells exposed to either OH-PCB 52 or PCB 52 sulfate, these OH-PCBs were more toxic to all three cell-types than their corresponding PCB or PCB sulfate congeners. Differences in the distribution of individual OH-PCB and PCB sulfate congeners between the cells and media, and the ability of cells to interconvert PCB sulfates and OH-PCBs, were important components of cellular sensitivity to these toxicants.

Effects of human SULT1A3/SULT1A4 genetic polymorphisms on the sulfation of acetaminophen and opioid drugs by the cytosolic sulfotransferase SULT1A3

Sulfoconjugation has been shown to be critically involved in the metabolism of acetaminophen (APAP), morphine, tapentadol and O-desmethyl tramadol (O-DMT). The objective of this study was to investigate the effects of single nucleotide polymorphisms (SNPs) of human SULT1A3 and SULT1A4 genes on the sulfating activity of SULT1A3 allozymes toward these analgesic compounds. Twelve non-synonymous coding SNPs (cSNPs) of SULT1A3/SULT1A4 were investigated, and the corresponding cDNAs were generated by site-directed mutagenesis. SULT1A3 allozymes, bacterially expressed and purified, exhibited differential sulfating activity toward each of the four analgesic compounds tested as substrates. Kinetic analyses of SULT1A3 allozymes further revealed significant differences in binding affinity and catalytic activity toward the four analgesic compounds. Collectively, the results derived from the current study showed clearly the impact of cSNPs of the coding genes, SULT1A3 and SULT1A4, on the sulfating activity of the coded SULT1A3 allozymes toward the tested analgesic compounds. These findings may have implications in the pharmacokinetics as well as the toxicity profiles of these analgesics administered in individuals with distinct SULT1A3 and/or SULT1A4 genotypes.

Disruption of thyroid hormone sulfotransferase activity by brominated flame retardant chemicals in the human choriocarcinoma placenta cell line, BeWo

Brominated flame retardants (BFRs) have been shown to disrupt thyroid hormone (TH) homeostasis through multiple mechanisms, including inhibition of enzymes that regulate intracellular levels of THs, such as sulfotransferases (SULTs). The placenta plays a critical role in helping to maintain TH levels during fetal development and expresses SULTs. This is concerning given that disruption of TH regulation within the placenta could potentially harm the developing fetus. In this study, we investigated the effects of two polybrominated diphenyl ethers (PBDEs), two hydroxylated PBDEs, and 2,4,6-tribromophenol (2,4,6-TBP) on TH SULT activity in a choriocarcinoma placenta cell line (BeWo). BeWo cells were exposed to BFR concentrations up to 1 μM for 1-24 h to investigate changes in basal SULT activity and in mRNA expression of several TH regulating genes. 2,4,6-TBP was the most potent inhibitor of basal 3,3'-T2 SULT activity at all exposure durations, decreasing activity by as much as 86% after 24 h of exposure. BDE-99, 3-OH BDE-47, and 6-OH BDE-47 also decreased 3,3'-T2 SULT activity by 23-42% at concentrations of 0.5 μM and 1.0 μM following 24 h exposures. BDE-47 had no effect on SULT activity, and there was no observed effect of any BFR exposure on expression of SULT1A1, or thyroid nuclear receptors alpha or beta. This research demonstrates that total TH SULT activity in placental cells are sensitive to BFR exposure; however, the mechanisms and consequences have yet to be fully elucidated.

Sulfation of catecholamines and serotonin by SULT1A3 allozymes

Previous studies have demonstrated the involvement of sulfoconjugation in the metabolism of catecholamines and serotonin. The current study aimed to clarify the effects of single nucleotide polymorphisms (SNPs) of human SULT1A3 and SULT1A4 genes on the enzymatic characteristics of the sulfation of dopamine, epinephrine, norepinephrine and serotonin by SULT1A3 allozymes. Following a comprehensive search of different SULT1A3 and SULT1A4 genotypes, twelve non-synonymous (missense) coding SNPs (cSNPs) of SULT1A3/SULT1A4 were identified. cDNAs encoding the corresponding SULT1A3 allozymes, packaged in pGEX-2T vector were generated by site-directed mutagenesis. SULT1A3 allozymes were expressed, and purified. Purified SULT1A3 allozymes exhibited differential sulfating activity toward catecholamines and serotonin. Kinetic analyses demonstrated differences in both substrate affinity and catalytic efficiency of the SULT1A3 allozymes. Collectively, these findings provide useful information relevant to the differential metabolism of dopamine, epinephrine, norepinephrine and serotonin through sulfoconjugation in individuals having different SULT1A3/SULT1A4 genotypes.

Sulfonation, an underexploited area: from skeletal development to infectious diseases and cancer

Sulfonation is one of the most abundant cellular reactions modifying a wide range of xenobiotics as well as endogenous molecules which regulate important biological processes including blood clotting, formation of connective tissues, and functionality of secreted proteins, hormones, and signaling molecules. Sulfonation is ubiquitous in all tissues and widespread in nature (plants, animals, and microorganisms). Although sulfoconjugates were discovered over a century ago when, in 1875, Baumann isolated phenyl sulfate in the urine of a patient given phenol as an antiseptic, the significance of sulfonation and its roles in human diseases have been underappreciated until recent years. Here, we provide a current overview of the significance of sulfonation reactions in a variety of biological functions and medical conditions (with emphasis on cancer). We also discuss research areas that warrant further attention if we are to fully understand how deficiencies in sulfonation could impact human health which, in turn, could help define treatments to effect improvements in health.

Relationship of SULT1A1 copy number variation with estrogen metabolism and human health

Human cytosolic sulfotransferase 1A1 (SULT1A1) is considered to be one of the most important SULT isoforms for metabolism, detoxification, and carcinogenesis. This theory is driven by observations that SULT1A1 is widely expressed in multiple tissues and acts on a wide range of phenolic substrates. SULT1A1 is subject to functional common copy number variation (CNV) including deletions or duplications. However, it is less clear how SULT1A1 CNV impacts health and disease. To better understand the biological role of SULT1A1 in human health, we genotyped CNV in 14,275 Marshfield Clinic patients linked to an extensive electronic health record. Since SULT1A1 is linked to steroid metabolism, select serum steroid hormones were measured in 100 individuals with a wide spectrum of SULT1A1 CNV genotypes. Furthermore, comprehensive phenome-wide association studies (PheWAS) were conducted using diagnostic codes and clinical text data. For the first time, individuals homozygous null for SULT1A1 were identified in a human population. Thirty-six percent of the population carried >2 copies of SULT1A1 whereas 4% had ≤1 copy. Results indicate SULT1A1 CNV was negatively correlated with estrone-sulfate to estrone ratio predominantly in males (E1S/E1; p=0.03, r=-0.21) and may be associated with increased risk for common allergies. The effect of SULT1A1 CNV on circulating estrogen metabolites was opposite to the predicted CNV-metabolite trend based on enzymatic function. This finding, and the potential association with common allergies reported herein, warrants future studies.

Are some people at increased risk of paracetamol-induced liver injury? A critical review of the literature

Purpose

Paracetamol is one of the world’s most commonly used drugs. In overdose, it is well established to be hepatotoxic. The aim of this review was to identify factors that have been, or actually are, associated with the development of liver injury after paracetamol exposure in humans.

Method

Google Scholar and PubMed were searched on various dates between December 2016 and March 2017. Papers identified had their references analysed for further studies that might be relevant.

Results

At the time of writing, there was little good quality clinical evidence—from studies of paracetamol overdose or therapeutic use—to suggest that any groups of people are relatively protected from, or are at greater risk of, liver injury. The factors that were historically used to indicate higher risk in the UK have no good quality clinical evidence to support their re-introduction into clinical practice. The safe (and still effective) oral dose of paracetamol in patients weighing less than 50 kg has not been established.

Conclusion

There is no patient group that is unequivocally at elevated risk of paracetamol-induced liver toxicity. We propose two clinical scenarios that warrant further research. Firstly, there is a need to establish whether the dose of paracetamol should be reduced in patients with low body weight. Secondly, if or when genomic information regarding individual patients becomes readily available to inform prescribing, we propose the contribution of the genome to paracetamol toxicity should be re-investigated with robustly designed studies. Such studies could enhance the safe use of one of the most frequently taken drugs.

Electronic supplementary material

The online version of this article (10.1007/s00228-017-2356-6) contains supplementary material, which is available to authorized users.

Advanced Approaches to Model Xenobiotic Metabolism in Bacterial Genotoxicology In Vitro

During the past 30 years there has been considerable progress in the development of bacterial test systems for use in genotoxicity testing by the stable introduction of expression vectors (cDNAs) coding for xenobiotic-metabolizing enzymes into bacterial cells. The development not only provides insights into the mechanisms of bioactivation of xenobiotic compounds but also evaluates the roles of enzymes involved in metabolic activation or inactivation in chemical carcinogenesis. This review describes recent advances in bacterial genotoxicity assays and their future prospects, with a focus on the development and application of genetically engineering bacterial cells to incorporate some of the enzymatic activities involved in the bio-activation process of xenobiotics. Various genes have been introduced into bacterial umu tester strains encoding enzymes for genotoxic bioactivation, including bacterial nitroreductase and O-acetyltransferase, human cytochrome P450 monooxygenases, rat glutathione S-transferases, and human N-acetyltransferases and sulfotransferases. Their application has provided new tools for genotoxicity assays and for studying the role of biotransformation in chemical carcinogenesis in humans.

Implications of sulfotransferase activity in interindividual variability in drug response: clinical perspective on current knowledge

The interindividual variability in drug response is a major issue in clinical practice and in drug development. Sulfoconjugation is an important Phase II reaction catalyzed by cytosolic sulfotransferases (SULTs), playing a major role in homeostatic functions, xenobiotic detoxification, and carcinogen bioactivation. SULT display wide interindividual variability, explained only partially by genetic variation, suggesting that other non-genetic, epigenetic, and environmental influences could be major determinants of variability in SULT activity. This review focuses on the factors known to influence SULT variability in expression and activity and the available evidence regarding the impact of SULT variability on drug response.

On the sulfation of O-desmethyltramadol by human cytosolic sulfotransferases

BACKGROUND

Previous studies have demonstrated that sulfate conjugation is involved in the metabolism of the active metabolite of tramadol, O-desmethyltramadol (O-DMT). The current study aimed to systematically identify the human cytosolic sulfotransferases (SULTs) that are capable of mediating the sulfation of O-DMT.

METHODS

The sulfation of O-DMT under metabolic conditions was demonstrated using HepG2 hepatoma cells and Caco-2 human colon carcinoma cells. O-DMT-sulfating activity of thirteen known human SULTs and four human organ specimens was examined using an established sulfotransferase assay. pH-Dependency and kinetic parameters were also analyzed using, respectively, buffers at different pHs and varying O-DMT concentrations in the assays.

RESULTS

Of the thirteen human SULTs tested, only SULT1A3 and SULT1C4 were found to display O-DMT-sulfating activity, with different pH-dependency profiles. Kinetic analysis revealed that SULT1C4 was 60 times more catalytically efficient in mediating the sulfation of O-DMT than SULT1A3 at respective optimal pH. Of the four human organ specimens tested, the cytosol prepared from the small intestine showed much higher O-DMT-sulfating activity than cytosols prepared from liver, lung, and kidney. Both cultured HepG2 and Caco-2 cells were shown to be capable of sulfating O-DMT and releasing sulfated O-DMT into cultured media.

CONCLUSION

SULT1A3 and SULT1C4 were the major SULTs responsible for the sulfation of O-DMT. Collectively, the results obtained provided a molecular basis underlying the sulfation of O-DMT and contributed to a better understanding about the pharmacokinetics and pharmacodynamics of tramadol in humans.

Development and progress for three decades in umu test systems

Umu test have been widely used to predict the detection and assessment of DNA- damaging chemicals in environmental genotoxicity field for three decades. This test system is more useful with respect to simplicity, sensitivity, rapidity, and reproducibility. A review of the literature on the development of the umu test is presented in this article. The contents of this article are included a description of numerous data using the umu test. This test have been fully evaluated and used in many directions. Different genetically engineered umu systems introducing bacterial and rat or human drug metabolizing enzymes into the umu tester strains, have been successfully established and are considered as useful tools for genotoxicity assays to study the mechanisms of biotransformation in chemical carcinogenesis. Actually, we developed that two types of bacterial metabolizing enzymes and 4 types of rat and human metabolizing enzyme DNAs are expressed in these strains such as nitroreductase and O-acetyltransferase, cytochrome P450, N-acetyltransferases, sulfotransferases, and glutathione S-transferases, respectively. Due to increasing numbers of minute environmental samples and new pharmaceuticals, a high-throughput umu test system using Salmonella typhimurium TA1535/pSK1002, NM2009, and NM3009 strains provides a useful for these genotoxicity screening. I also briefly describe the first attempts to incorporate such umu tester strain into photo-genotoxicity test.

The African hedgehog (Atelerix albiventris): Low phase I and phase II metabolism activities

The African hedgehog, Atelerix albiventris, is a spiny mammal that has become popular as an exotic pet in many countries. To elucidate the ability of hedgehogs to metabolize xenobiotics, the animals were exposed to polycyclic aromatic hydrocarbon, pyrene. The in vivo exposure study indicated that pyrene was biotransformed to glucuronide and sulfate conjugates, such as pyrene-1-glucuronide, pyrene-1-sulfate, and pyrenediol-sulfate, and excreted in the urine. Pyrene-1-glucuronide was the main metabolite, and limited sulfate conjugate excretion was observed. The main products excreted in feces were 1-hydroxypyrene and pyrene. Based on the results of the in vivo exposure study, in vitro enzymatic kinetic experiments were performed using various substrates and compared to rats and pigs. The enzyme efficiencies of cytochrome P450 (CYP)-mediated ethoxyresorufin O-deethylase activity and warfarin 4'-, 6-, and 8-hydroxylation activity in hedgehogs were lower than those of rats. Furthermore, UDP-glucuronosyltransferase activity in hedgehogs also had a lower K_m value than that in pigs. Interestingly, the enzyme efficiencies of sulfation activity toward 1-hydroxypyrene and β-estradiol in hedgehogs were significantly lower than those in pigs. These observations suggested that phenol and estrogen sulfotransferases may have limited roles in xenobiotic metabolism in hedgehogs.

From Metabonomics to Pharmacometabonomics: The Role of Metabolic Profiling in Personalized Medicine

Variable patient responses to drugs are a key issue for medicine and for drug discovery and development. Personalized medicine, that is the selection of medicines for subgroups of patients so as to maximize drug efficacy and minimize toxicity, is a key goal of twenty-first century healthcare. Currently, most personalized medicine paradigms rely on clinical judgment based on the patient's history, and on the analysis of the patients' genome to predict drug effects i.e., pharmacogenomics. However, variability in patient responses to drugs is dependent upon many environmental factors to which human genomics is essentially blind. A new paradigm for predicting drug responses based on individual pre-dose metabolite profiles has emerged in the past decade: pharmacometabonomics, which is defined as “the prediction of the outcome (for example, efficacy or toxicity) of a drug or xenobiotic intervention in an individual based on a mathematical model of pre-intervention metabolite signatures.” The new pharmacometabonomics paradigm is complementary to pharmacogenomics but has the advantage of being sensitive to environmental as well as genomic factors. This review will chart the discovery and development of pharmacometabonomics, and provide examples of its current utility and possible future developments.

Function and organization of the human cytosolic sulfotransferase (SULT) family

The sulfuryl transfer reaction is of fundamental biological importance. One of the most important manifestations of this process are the reactions catalyzed by members of the cytosolic sulfotransferase (SULT) superfamily. These enzymes transfer the sulfuryl moiety from the universal donor PAPS (3'-phosphoadenosine 5'-phosphosulfate) to a wide variety of substrates with hydroxyl- or amino-groups. Normally a detoxification reaction this facilitates the elimination of a multitude of xenobiotics, although for some molecules sulfation is a bioactivation step. In addition, sulfation plays a key role in endocrine and other signalling pathways since many steroids, sterols, thyroid hormones and catecholamines exist primarily as sulfate conjugates in humans. This article summarizes much of our current knowledge of the organization and function of the human cytosolic sulfotransferases and highlights some of the important interspecies differences that have implications for, among other things, drug development and chemical safety analysis.

Identification of Human Sulfotransferases Involved in Lorcaserin N-Sulfamate Formation

Lorcaserin [(R)-8-chloro-1-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine] hydrochloride hemihydrate, a selective serotonin 5-hydroxytryptamine (5-HT) 5-HT(2C) receptor agonist, is approved by the U.S. Food and Drug Administration for chronic weight management. Lorcaserin is primarily cleared by metabolism, which involves multiple enzyme systems with various metabolic pathways in humans. The major circulating metabolite is lorcaserin N-sulfamate. Both human liver and renal cytosols catalyze the formation of lorcaserin N-sulfamate, where the liver cytosol showed a higher catalytic efficiency than renal cytosol. Human sulfotransferases (SULTs) SULT1A1, SULT1A2, SULT1E1, and SULT2A1 are involved in the formation of lorcaserin N-sulfamate. The catalytic efficiency of these SULTs for lorcaserin N-sulfamate formation is widely variable, and among the SULT isoforms SULT1A1 was the most efficient. The order of intrinsic clearance for lorcaserin N-sulfamate is SULT1A1 > SULT2A1 > SULT1A2 > SULT1E1. Inhibitory effects of lorcaserin N-sulfamate on major human cytochrome P450 (P450) enzymes were not observed or minimal. Lorcaserin N-sulfamate binds to human plasma protein with high affinity (i.e., >99%). Thus, despite being the major circulating metabolite, the level of free lorcaserin N-sulfamate would be minimal at a lorcaserin therapeutic dose and unlikely be sufficient to cause drug-drug interactions. Considering its formation kinetic parameters, high plasma protein binding affinity, minimal P450 inhibition or induction potential, and stability, the potential for metabolic drug-drug interaction or toxicological effects of lorcaserin N-sulfamate is remote in a normal patient population.

The Important Roles of Steroid Sulfatase and Sulfotransferases in Gynecological Diseases

Gynecological diseases such as endometriosis, adenomyosis and uterine fibroids, and gynecological cancers including endometrial cancer and ovarian cancer, affect a large proportion of women. These diseases are estrogen dependent, and their progression often depends on local estrogen formation. In peripheral tissues, estrogens can be formed from the inactive precursors dehydroepiandrosterone sulfate and estrone sulfate. Sulfatase and sulfotransferases have pivotal roles in these processes, where sulfatase hydrolyzes estrone sulfate to estrone, and dehydroepiandrosterone sulfate to dehydroepiandrosterone, and sulfotransferases catalyze the reverse reactions. Further activation of estrone to the most potent estrogen, estradiol, is catalyzed by 17-ketosteroid reductases, while estradiol can also be formed from dehydroepiandrosterone by the sequential actions of 3β-hydroxysteroid dehydrogenase-Δ⁴-isomerase, aromatase, and 17-ketosteroid reductase. This review introduces the sulfatase and sulfotransferase enzymes, in terms of their structures and reaction mechanisms, and the regulation and different transcripts of their genes, together with the importance of their currently known single nucleotide polymorphisms. Data on expression of sulfatase and sulfotransferases in gynecological diseases are also reviewed. There are often unchanged mRNA and protein levels in diseased tissue, with higher sulfatase activities in cancerous endometrium, ovarian cancer cell lines, and adenomyosis. This can be indicative of a disturbed balance between the sulfatase and sulfotransferases enzymes, defining the potential for sulfatase as a drug target for treatment of gynecological diseases. Finally, clinical trials with sulfatase inhibitors are discussed, where two inhibitors have already concluded phase II trials, although so far with no convincing clinical outcomes for patients with endometrial cancer and endometriosis.

Dose- and time-dependent changes in tissue levels of tetrabromobisphenol A (TBBPA) and its sulfate and glucuronide conjugates following repeated administration to female Wistar Han Rats

Tetrabromobisphenol A (TBBPA), a nongenotoxic flame retardant, causes uterine tumors in female rats. A proposed mode of action (MoA) for these tumors involves an increase in the bioavailability of estradiol as a result of TBBPA inhibiting estrogen sulfotransferases (ES), the enzymes responsible for inactivating and enhancing the elimination of estradiol. The objective of this study was to evaluate the effect of dose and repeated administration of TBBPA on the level of TBBPA, TBBPA-glucuronide (GA) and TBBPA-sulfate (S) conjugates in plasma, liver and uterus of female Wistar Han rats administered TBBPA (50, 100, 250, 500 or 1000 mg/kg) for 28 consecutive days. In accordance with this objective, TBBPA sulfation was used as a surrogate for evaluating the potential for estradiol sulfation to be limited at high dose levels of TBBPA. Blood samples were collected at 4 and 8 h post-dosing on study day 7, 14, and 28, while liver and uterus were collected at the same time points following 28 days of dosing. Tissue samples were analyzed for TBBPA, TBBPA-GA and TBBPA-S by LC–MS/MS. A dose-related increase in the concentration of all three analytes occurred in plasma (day 7, 14, and 28) as well as liver and uterus tissue (day 28) at both 4 and 8 h post dose. The plasma concentration of TBBPA-GA and TBBPA-S was higher in animals dosed for 28 days compared to those dosed for 7 or 14 days showing an increase in systemic circulation of these conjugates with repeated administration. The balance of these conjugates was also different in tissues with TBBPA-S > TBBPA-GA at high doses in the liver and TBBPA-GA > TBBPA-S in both plasma and uterus. In all three tissues the ratio of TBBPA-S/TBBPA-GA showed a decreasing trend with dose, suggesting that at high TBBPA dose levels sulfation of TBBPA becomes limited. This effect was most apparent in the liver and plasma at 28 days of administration. Together these data show that administration of high doses of TBBPA associated with the induction of uterine tumors, results in a disruption in the balance of conjugates reflected by a decrease in the TBBPA-S/TBBPA-GA ratio. A limitation in the sulfation of TBBPA in vivo supports in vitro data defining TBBPA as an inhibitor of ES activity, thus providing further support that the proposed MoA occurs under conditions of high dose, chronic TBBPA administration to Wistar Han rats. Given that the uterine tumors observed in rats (250–1000 mg/kg-day) only occur at very high doses that perturb homeostatic control, it is unlikely such effects would occur in humans given that current TBBPA exposure levels are approximately eight orders of magnitude lower than these doses that are associated with exceeding the capacity of conjugation pathways in animal studies.

Characterization of regio- and stereo-selective sulfation of bufadienolides: exploring the mechanism and providing insight into the structure–sulfation relationship by experimentation and molecular docking analysis

Bufadienolides are a major class of bioactive compounds derived from amphibian skin secretion.

Gene-environment interactions in esophageal cancer

Esophageal cancer (EC) is one of the most common malignancies in low- and medium-income countries and represents a disease of public health importance because of its poor prognosis and high mortality rate in these regions. The striking variation in the prevalence of EC among different ethnic groups suggests a significant contribution of population-specific environmental and dietary factors to susceptibility to the disease. Although individuals within a demarcated geographical area are exposed to the same environment and share similar dietary habits, not all of them will develop the disease; thus genetic susceptibility to environmental risk factors may play a key role in the development of EC. A wide range of xenobiotic-metabolizing enzymes are responsible for the metabolism of carcinogens introduced via the diet or inhaled from the environment. Such dietary or environmental carcinogens can bind to DNA, resulting in mutations that may lead to carcinogenesis. Genes involved in the biosynthesis of these enzymes are all subject to genetic polymorphisms that can lead to altered expression or activity of the encoded proteins. Genetic polymorphisms may, therefore, act as molecular biomarkers that can provide important predictive information about carcinogenesis. The aim of this review is to discuss our current knowledge on the genetic risk factors associated with the development of EC in different populations; it addresses mainly the topics of genetic polymorphisms, gene-environment interactions, and carcinogenesis. We have reviewed the published data on genetic polymorphisms of enzymes involved in the metabolism of xenobiotics and discuss some of the potential gene-environment interactions underlying esophageal carcinogenesis. The main enzymes discussed in this review are the glutathione S-transferases (GSTs), N-acetyltransferases (NATs), cytochrome P450s (CYPs), sulfotransferases (SULTs), UDP-glucuronosyltransferases (UGTs), and epoxide hydrolases (EHs), all of which have key roles in the detoxification of environmental and dietary carcinogens. Finally, we discuss recent advances in the study of genetic polymorphisms associated with EC risk, specifically with regard to genome-wide association studies, and examine possible challenges of case-control studies that need to be addressed to better understand the interaction between genetic and environmental factors in esophageal carcinogenesis.

Sulphation of acetaminophen by the human cytosolic sulfotransferases: a systematic analysis

Sulphation is known to be critically involved in the metabolism of acetaminophen in vivo. This study aimed to systematically identify the major human cytosolic sulfotransferase (SULT) enzyme(s) responsible for the sulphation of acetaminophen. A systematic analysis showed that three of the twelve human SULTs, SULT1A1, SULT1A3 and SULT1C4, displayed the strongest sulphating activity towards acetaminophen. The pH dependence of the sulphation of acetaminophen by each of these three SULTs was examined. Kinetic parameters of these three SULTs in catalysing acetaminophen sulphation were determined. Moreover, sulphation of acetaminophen was shown to occur in HepG2 human hepatoma cells and Caco-2 human intestinal epithelial cells under the metabolic setting. Of the four human organ samples tested, liver and intestine cytosols displayed considerably higher acetaminophen-sulphating activity than those of lung and kidney. Collectively, these results provided useful information concerning the biochemical basis underlying the metabolism of acetaminophen in vivo previously reported.

Formation of DNA adducts in wild-type and transgenic mice expressing human sulfotransferases 1A1 and 1A2 after oral exposure to furfuryl alcohol

Furfuryl alcohol (FFA) is present in many heat-treated foods as a result of its formation via dehydration of pentoses. It is also used legally as a flavouring agent. In an inhalation study conducted in the National Toxicology Program, FFA showed some evidence of carcinogenic activity in rats and mice. FFA was generally negative in conventional genotoxicity assays, which suggests that it may be a non-genotoxic carcinogen. However, it was recently found that FFA is mutagenic in Salmonella strains expressing appropriate sulfotransferases (SULTs), such as human or mouse SULT1A1. The same DNA adducts that were formed by FFA in these strains, mainly N (2)-((furan-2-yl)methyl)-2'-deoxyguanosine (N (2)-MF-dG), were also detected in tissues of FFA-exposed mice and even in human lung specimens. In the present study, a single oral dose of FFA (250 mg/kg body weight) or saline was administered to FVB/N mice and transgenic mice expressing human SULT1A1/1A2 on the FVB/N background. The transgenic mice were used, since human and mouse SULT1A1 substantially differ in substrate specificity and tissue distribution. DNA adducts were studied in liver, kidney, proximal and distal small intestine as well as colon, using isotope-dilution ultra performance liquid chromatography (UPLC-MS/MS). Surprisingly, low levels of adducts that may represent N (2)-MF-dG were detected even in tissues of untreated mice. FFA exposure enhanced the adduct levels in colon and liver, but not in the remaining investigated tissues of wild-type (wt) mice. The situation was similar in transgenic mice, except that N (2)-MF-dG levels were also strongly enhanced in the proximal small intestine. These different results between wt and transgenic mice may be attributed to the fact that human SULT1A1, but not the orthologous mouse enzyme, is strongly expressed in the small intestine.

Identification and characterization of in vitro and in vivo metabolites of steroidal alkaloid veratramine

Veratramine, a steroidal alkaloid originating from Veratrum nigrum L., has demonstrated distinct anti-tumor and anti-hypertension effects, however, its metabolism has rarely been explored. The objective of the current study was to provide a comprehensive investigation of its metabolic pathways. The in vitro metabolic profiles of veratramine were evaluated by incubating it with liver microsomes and cytosols. The in vivo metabolic profiles in plasma, bile, urine and feces were monitored by UPLC-MS/MS after oral (20 mg/kg) and i.v. (50 µg/kg) administration in rats. Meanwhile, related P450s inhibitors and recombinant P450s and SULTs were used to identify the isozymes responsible for its metabolism. Eleven metabolites of veratramine, including seven hydroxylated, two sulfated and two glucuronidated metabolites, were characterized. Unlike most alkaloids, the major reactive sites of veratramine were on ring A and B instead of on the amine moiety. CYP2D6 was the major isozyme mediating hydroxylation, and substrate inhibition was observed with a Vmax , Ki and Clint of 2.05 ± 0.53 nmol/min/mg, 33.08 ± 10.13 µ m and 13.58 ± 1.27 µL/min/mg. SULT2A1, with Km , Vmax and Clint values of 19.37 ± 0.87 µ m, 1.51 ± 0.02 nmol/min/mg and 78.19 ± 8.57 µL/min/mg, was identified as the major isozyme contributing to its sulfation. In conclusion, CYP2D6 and SULT2A1 mediating hydroxylation and sulfation were identified as the major biotransformation for veratramine.