The Role of Sulfotransferases in Liver Diseases

Cell-specific AHR-driven differential gene expression in the mouse liver cell following acute TCDD exposure

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a persistent environmental contaminant that disrupts hepatic function leading to steatotic liver disease (SLD)-like pathologies, such as steatosis, steatohepatitis, and fibrosis. These effects are mediated by the aryl hydrocarbon receptor following changes in gene expression. Although diverse cell types are involved, initial cell-specific changes in gene expression have not been reported. In this study, differential gene expression in hepatic cell types was examined in male C57BL/6 mice gavaged with 30 µg/kg of TCDD using single-nuclei RNA-sequencing. Ten liver cell types were identified with the proportions of most cell types remaining unchanged, except for neutrophils which increased at 72 h. Gene expression suggests TCDD induced genes related to oxidative stress in hepatocytes as early as 2 h. Lipid homeostasis was disrupted in hepatocytes, macrophages, B cells, and T cells, characterized by the induction of genes associated with lipid transport, steroid hormone biosynthesis, and the suppression of β-oxidation, while linoleic acid metabolism was altered in hepatic stellate cells (HSCs), B cells, portal fibroblasts, and plasmacytoid dendritic cells. Pro-fibrogenic processes were also enriched, including the induction retinol metabolism genes in HSCs and the early induction of anti-fibrolysis genes in hepatocytes, endothelial cells, HSCs, and macrophages. Hepatocytes also had gene expression changes consistent with hepatocellular carcinoma. Collectively, these findings underscore the effects of TCDD in initiating SLD-like phenotypes and identified cell-specific gene expression changes related to oxidative stress, steatosis, fibrosis, cell proliferation and the development of HCC.

The HuMet Repository: Watching human metabolism at work

Metabolism oscillates between catabolic and anabolic states depending on food intake, exercise, or stresses that change a multitude of metabolic pathways simultaneously. We present the HuMet Repository for exploring dynamic metabolic responses to oral glucose/lipid loads, mixed meals, 36-h fasting, exercise, and cold stress in healthy subjects. Metabolomics data from blood, urine, and breath of 15 young, healthy men at up to 56 time points are integrated and embedded within an interactive web application, enabling researchers with and without computational expertise to search, visualize, analyze, and contextualize the dynamic metabolite profiles of 2,656 metabolites acquired on multiple platforms. With examples, we demonstrate the utility of the resource for research into the dynamics of human metabolism, highlighting differences and similarities in systemic metabolic responses across challenges and the complementarity of metabolomics platforms. The repository, providing a reference for healthy metabolite changes to six standardized physiological challenges, is freely accessible through a web portal.

An integrated investigation of sulfotransferases (SULTs) in hepatocellular carcinoma and identification of the role of SULT2A1 on stemness

The cytosolic sulfotransferases (SULTs) are phase II conjugating enzymes, which are widely expressed in the liver and mainly mediate the sulfation of numerous xenobiotics and endogenous compounds. However, the role of various SULTs genes has not been reported in hepatocellular carcinoma (HCC). This study aims to analyze the expression and potential functional roles of SULTs genes in HCC and to identify the role of SULT2A1 in HCC stemness as well as the possible mechanism. We found that all of the 12 SULTs genes were differentially expressed in HCC. Moreover, clinicopathological features and survival rates were also investigated. Multivariate regression analysis showed that SULT2A1 and SULT1C2 could be used as independent prognostic factors in HCC. SULT1C4, SULT1E1, and SULT2A1 were significantly associated with immune infiltration. SULT2A1 deficiency in HCC promoted chemotherapy resistance and stemness maintenance. Mechanistically, silencing of SULT2A1 activated the AKT signaling pathway, on the one hand, promoted the expression of downstream stemness gene c-Myc, on the other hand, facilitated the NRF2 expression to reduce the accumulation of ROS, and jointly increased HCC stemness. Moreover, knockdown NR1I3 was involved in the transcriptional regulation of SULT2A1 in stemness maintenance. In addition, SULT2A1 knockdown HCC cells promoted the proliferation and activation of hepatic stellate cells (HSCs), thereby exerting a potential stroma remodeling effect. Our study revealed the expression and role of SULTs genes in HCC and identified the contribution of SULT2A1 to the initiation and progression of HCC.

Polymorphisms in drug-metabolizing genes and urinary bladder cancer susceptibility and prognosis: Possible impacts and future management

Epidemiological studies have shown the association of genetic variants with risks of occupational and environmentally induced cancers, including bladder (BC). The current review summarizes the effects of variants in genes encoding phase I and II enzymes in well-designed studies to highlight their contribution to BC susceptibility and prognosis. Polymorphisms in genes codifying drug-metabolizing proteins are of particular interest because of their involvement in the metabolism of exogenous genotoxic compounds, such as tobacco and agrochemicals. The prognosis between muscle-invasive and non-muscle-invasive diseases is very different, and it is difficult to predict which will progress worse. Web of Science, PubMed, and Medline were searched to identify studies published between January 1, 2010, and February 2023. We included 73 eligible studies, more than 300 polymorphisms, and 46 genes/loci. The most studied candidate genes/loci of phase I metabolism were CYP1B1, CYP1A1, CYP1A2, CYP3A4, CYP2D6, CYP2A6, CYP3E1, and ALDH2, and those in phase II were GSTM1, GSTT1, NAT2, GSTP1, GSTA1, GSTO1, and UGT1A1. We used the 46 genes to construct a network of proteins and to evaluate their biological functions based on the Reactome and KEGG databases. Lastly, we assessed their expression in different tissues, including normal bladder and BC samples. The drug-metabolizing pathway plays a relevant role in BC, and our review discusses a list of genes that could provide clues for further exploration of susceptibility and prognostic biomarkers.

Cytosolic sulfotransferases in endocrine disruption

The mammalian cytosolic sulfotransferases (SULTs) catalyze the sulfation of endocrine hormones as well as a broad array of drugs, environmental chemicals, and other xenobiotics. Many endocrine-disrupting chemicals (EDCs) interact with these SULTs as substrates and inhibitors, and thereby alter sulfation reactions responsible for metabolism and regulation of endocrine hormones such as estrogens and thyroid hormones. EDCs or their metabolites may also regulate expression of SULTs through direct interaction with nuclear receptors and other transcription factors. Moreover, some sulfate esters derived from EDCs (EDC-sulfates) may serve as ligands for endocrine hormone receptors. While the sulfation of an EDC can lead to its excretion in the urine or bile, it may also result in retention of the EDC-sulfate through its reversible binding to serum proteins and thereby enable transport to other tissues for intracellular hydrolysis and subsequent endocrine disruption. This mini-review outlines the potential roles of SULTs and sulfation in the effects of EDCs and our evolving understanding of these processes.

Complex roles for sulfation in the toxicities of polychlorinated biphenyls

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.

Oleacein: A comprehensive review of its extraction, purification, absorption, metabolism, and health effects

Extra virgin olive oil (EVOO) consumption reduces the risk of cardiovascular disease in high-risk groups and the polyphenols in EVOO play an important health effect on it. As one of the most abundant polyphenols in EVOO, oleacein (OLEA) has many health benefits. However, there is no review article that focus comprehensively on OLEA, and most articles have limited data and information on OLEA. The purpose of this review is to summarize the results of all available studies, to present and compare the main traditional and novel techniques for the extraction and isolation and purification of OLEA, to elucidate the absorption and metabolic pathways of OLEA, and finally, to illustrate the health-promoting properties. Hopefully, this review can promote the use of OLEA in functional foods and therapeutic fields.

Ontogeny of Scaling Factors for Pediatric Physiologically Based Pharmacokinetic Modeling and Simulation: Cytosolic Protein Per Gram of Liver

Scaling factors are necessary for translating in vitro drug biotransformation data to in vivo clearance values in physiologically-based pharmacokinetic modeling and simulation. Values for microsomal protein per gram of liver are available from several sources for use as a scaling factor to estimate hepatic clearance from microsomal drug biotransformation data. However, data regarding the distribution of cytosolic protein per gram of liver (CPPGL) values across the lifespan are limited, and sparse pediatric data have been published to date. Thus, CPPGL was determined in 160 liver samples from pediatric (n = 129) and adult (n = 31) donors obtained from multiple sources: the University of Maryland Brain and Tissue Bank, tissue retrieval services at the University of Minnesota and University of Pittsburgh, and Sekisui-XenoTech. Tissues were homogenized and subjected to differential centrifugation to isolate cytosolic fractions. Cytosolic protein content was determined by BCA assay. CPPGL varied from two- to sixfold within each age group/developmental stage. Tissue source and sex did not contribute substantially to variability in protein content. Regression analyses revealed minimal change in CPPGL over the first two decades of life (logCPPGL increases 0.1 mg/g per decade). A mean ± S.D. CPPGL value of 44.4 ± 17.4 mg/g or median 41.0 mg/g is representative of values observed between birth and early adulthood (0-18 years, n = 129). SIGNIFICANCE STATEMENT: Cytosolic protein per gram of liver (CPPGL) is a scaling factor required for physiologically based pharmacokinetic modeling and simulation of drug biotransformation by cytosolic enzymes, but pediatric data are limited. Although CPPGL varies from two- to sixfold within developmental stages, a value of 44.4 ± 17.4 mg/g (mean ± S.D.) is representative of the pediatric period (0-18 years, n = 129).

Corticosteroid-Binding Globulin (SERPINA6) Consolidates Sexual Dimorphism of Adult Rat Liver

Produced by the liver, corticosteroid-binding globulin (CBG) regulates the plasma distribution and actions of glucocorticoids. A sex difference in pituitary growth hormone secretion patterns established during puberty in rats results in increased hepatic CBG production and 2-fold higher plasma corticosterone levels in females. Glucocorticoids control hepatic development and metabolic activities, and we have therefore examined how disrupting the SerpinA6 gene encoding CBG influences plasma corticosterone dynamics, as well as liver gene expression in male and female rats before and after puberty. Comparisons of corticosterone plasma clearance and hepatic uptake in adult rats, with or without CBG, indicated that CBG limits corticosterone clearance by reducing its hepatic uptake. Hepatic transcriptomic profiling revealed minor sex differences (207 differentially expressed genes) and minimal effect of CBG deficiency in 30-day-old rats before puberty. While liver transcriptomes in 60-day-old males lacking CBG remained essentially unchanged, 2710 genes were differentially expressed in wild-type female vs male livers at this age. Importantly, ∼10% of these genes lost their sexually dimorphic expression in adult females lacking CBG, including those related to cholesterol biosynthesis, inflammation, and lipid and amino acid catabolism. Another 203 genes were altered by the loss of CBG specifically in adult females, including those related to xenobiotic metabolism, circadian rhythm, and gluconeogenesis. Our findings reveal that CBG consolidates the sexual dimorphism of the rat liver initiated by sex differences in growth hormone secretion patterns and provide insight into how CBG deficiencies are linked to glucocorticoid-dependent diseases.

Farnesoid X receptor represses human sulfotransferase 1A3 expression through direct binding to the promoter

Human sulfotransferases 1A3 (SULT1A3) has received particular interest, due to their functions of catalyzing the sulfonation of numerous phenolic substrates, including bioactive endogenous molecules and therapeutic agents. However, the regulation of SULT1A3 expression and the underlying mechanism remain unclear. Here, we aimed to investigate the regulation effects of bile acid-activated farnesoid X receptor (FXR) on SULT1A3 expression, and to shed light on the mechanism thereof. Our results demonstrated that FXR agonists (CDCA and GW4064) significantly inhibit the expression of SULT1A3 at mRNA and protein levels. In addition, overexpression of FXR led to decrease in SULT1A3 expression and knockdown of FXR significantly induced the expression of SULT1A3 in protein and mRNA levels, confirming that FXR expression manifestly showed negative regulatory effect on basal SULT1A3 expression. Furthermore, a combination of luciferase reporter gene and CHIP assays showed that FXR repressed SULT1A3 transcription through direct binding to the region at base pair positions -664 to -654. In conclusion, this study for the first time confirmed FXR was a negative transcriptional regulator of human SULT1A3 enzyme.

Metabolomics reveals that sulfotransferase 1 may regulate colchicine-induced liver injury

Colchicine is widely used to treat gouty arthritis for years. Previous studies showed that colchicine overdose can cause liver damage, yet the mechanism underlying its hepatotoxicity remains unclear. In this study, hepatotoxicity of colchicine was investigated in vivo. Metabolomic analysis of colchicine metabolites and endogenous metabolites was performed using Ultra High Performance Liquid Chromatography (UHPLC) - mass spectrometry (MS). Seventeen metabolites of colchicine were identified, including 3 novel sulfated metabolites. Meanwhile, endogenous sulfated metabolites were found to be decreased by colchicine. Colchicine might regulate sulfotransferase 1 (SULT1) through perixisome proliferation-activated receptor ɑ (PPARα), and inhibition of SULT1 reduced the levels of sulfated metabolites of colchicine. Inhibition of SULT1 aggravated colchicine-induced liver injury, whereas activation of SULT1 attenuated its liver injury. The supplementation of endogenous sulfated metabolites indoxyl sulfate (IS) or p-cresol sulfate (PCS) alleviated colchicine-induced liver injury through modulation of the CASPASE-1-gasdermin D (GSDMD) pathway. These results indicated that colchicine might cause hepatotoxicity through inhibition of SULT1and decreased production of bioactive sulfated endogenous metabolites IS and PCS. Our results provided evidence for potential therapeutic targets and agents to prevent liver injury caused by colchicine. Targeting the SULT1 enzyme and administration of IS and PCS may be useful in alleviating colchicine hepatotoxicity.

4-Ethylphenol-fluxes, metabolism and excretion of a gut microbiome derived neuromodulator implicated in autism

Gut-microbiome-derived metabolites, such as 4-Ethylphenol [4EP], have been shown to modulate neurological health and function. Although the source of such metabolites is becoming better understood, knowledge gaps remain as to the mechanisms by which they enter host circulation, how they are transported in the body, how they are metabolised and excreted, and the way they exert their effects. High blood concentrations of host-modified 4EP, 4-ethylphenol sulfate [4EPS], are associated with an anxiety phenotype in autistic individuals. We have reviewed the existing literature and discuss mechanisms that are proposed to contribute influx from the gut microbiome, metabolism, and excretion of 4EP. We note that increased intestinal permeability is common in autistic individuals, potentially explaining increased flux of 4EP and/or 4EPS across the gut epithelium and the Blood Brain Barrier [BBB]. Similarly, kidney dysfunction, another complication observed in autistic individuals, impacts clearance of 4EP and its derivatives from circulation. Evidence indicates that accumulation of 4EPS in the brain of mice affects connectivity between subregions, particularly those linked to anxiety. However, we found no data on the presence or quantity of 4EP and/or 4EPS in human brains, irrespective of neurological status, likely due to challenges sampling this organ. We argue that the penetrative ability of 4EP is dependent on its form at the BBB and its physicochemical similarity to endogenous metabolites with dedicated active transport mechanisms across the BBB. We conclude that future research should focus on physical (e.g., ingestion of sorbents) or metabolic mechanisms (e.g., conversion to 4EP-glucuronide) that are capable of being used as interventions to reduce the flux of 4EP from the gut into the body, increase the efflux of 4EP and/or 4EPS from the brain, or increase excretion from the kidneys as a means of addressing the neurological impacts of 4EP.

The HuMet Repository: Watching human metabolism at work

The human metabolism constantly responds to stimuli such as food intake, fasting, exercise, and stress, triggering adaptive biochemical processes across multiple metabolic pathways. To understand the role of these processes and disruptions thereof in health and disease, detailed documentation of healthy metabolic responses is needed but still scarce on a time-resolved metabolome-wide level. Here, we present the HuMet Repository, a web-based resource for exploring dynamic metabolic responses to six physiological challenges (exercise, 36 h fasting, oral glucose and lipid loads, mixed meal, cold stress) in healthy subjects. For building this resource, we integrated existing and newly derived metabolomics data measured in blood, urine, and breath samples of 15 young healthy men at up to 56 time points during the six highly standardized challenge tests conducted over four days. The data comprise 1.1 million data points acquired on multiple platforms with temporal profiles of 2,656 metabolites from a broad range of biochemical pathways. By embedding the dataset into an interactive web application, we enable users to easily access, search, filter, analyze, and visualize the time-resolved metabolomic readouts and derived results. Users can put metabolites into their larger context by identifying metabolites with similar trajectories or by visualizing metabolites within holistic metabolic networks to pinpoint pathways of interest. In three showcases, we outline the value of the repository for gaining biological insights and generating hypotheses by analyzing the wash-out of dietary markers, the complementarity of metabolomics platforms in dynamic versus cross-sectional data, and similarities and differences in systemic metabolic responses across challenges. With its comprehensive collection of time-resolved metabolomics data, the HuMet Repository, freely accessible at https://humet.org/, is a reference for normal, healthy responses to metabolic challenges in young males. It will enable researchers with and without computational expertise, to flexibly query the data for their own research into the dynamics of human metabolism.

Targeting bladder cancer: A sex sensitive perspective in mutations and outcomes

The incidence of bladder cancer (BC) is more common in males, however, the clinical outcome for females tends to be more unfavorable, as demonstrated by a 21% increase in mortality compared to males within two years of diagnosis. While it was previously believed that the differences in outcome were solely the result of differences in sex chromosomes and hormones, it is now acknowledged that a more intricate interplay of factors is at play. By acquiring a more comprehensive understanding of these sex-specific effects, future efforts in precision medicine can be customized to an individual's biological sex. This narrative review aims to summarize our knowledge of the molecular classification of sex differences in BC by compiling the existing evidence on genetic disparities between males and females and evaluating these disparities in both noninvasive bladder cancer (NMIBC) and muscle invasive bladder cancer (MIBC). Our findings emphasize the significance of considering sex as a factor in future clinical trials and registry studies due to established differences in immune composition, molecular profiling, and genetic mutations between males and females. Further investigation into the molecular processes involved in the evasion or resistance of immune-based therapies, such as Bacillus Calmette-Guérin and other immunotherapies, is essential to identify markers of response or resistance that vary between male and female patients. This will aid in optimizing treatment and promoting equitable outcomes, particularly in NMIBC cases.

Tp53 haploinsufficiency is involved in hotspot mutations and cytoskeletal remodeling in gefitinib-induced drug-resistant EGFRL858R-lung cancer mice

Tumor heterogeneity is the major factor for inducing drug resistance. p53 is the major defender to maintain genomic stability, which is a high proportion mutated in most of the cancer types. In this study, we established in vivo animal models of gefitinib-induced drug-resistant lung cancer containing EGFR^L858R and EGFR^L858R*Tp53^+/- mice to explore the molecular mechanisms of drug resistance by studying the genomic integrity and global gene expression. The cellular morphology of the lung tumors between gefitinib-induced drug-resistant mice and drug-sensitive mice were very different. In addition, in drug-resistant mice, the expression of many cytoskeleton-related genes were changed, accompanied by decreased amounts of actin filaments and increased amounts of microtubule, indicating that significant cytoskeletal remodeling is induced in gefitinib-induced drug-resistant EGFR^L858R and EGFR^L858R*Tp53^+/- lung cancer mice. The gene expression profiles and involved pathways were different in gefitinib-sensitive, gefitinib-resistant and Tp53^+/--mice. Increases in drug resistance and nuclear size (N/C ratio) were found in EGFR^L858R*Tp53^+/- drug-resistant mice. Mutational hotspot regions for drug resistance via Tp53^+/+- and Tp53^+/--mediated pathways are located on chromosome 1 and chromosome 11, respectively, and are related to prognosis of lung cancer cohorts. This study not only builds up a gefitinib-induced drug-resistant EGFR^L858R lung cancer animal model, but also provides a novel mutation profile in a Tp53^+/+- or Tp53^+/--mediated manner and induced cytoskeleton remodeling during drug resistance, which could contribute to the prevention of drug resistance during cancer therapy.

Molecular programming modulates hepatic lipid metabolism and adult metabolic risk in the offspring of obese mothers in a sex-specific manner

Male and female offspring of obese mothers are known to differ extensively in their metabolic adaptation and later development of complications. We investigate the sex-dependent responses in obese offspring mice with maternal obesity, focusing on changes in liver glucose and lipid metabolism. Here we show that maternal obesity prior to and during gestation leads to hepatic steatosis and inflammation in male offspring, while female offspring are protected. Females from obese mothers display important changes in hepatic transcriptional activity and triglycerides profile which may prevent the damaging effects of maternal obesity compared to males. These differences are sustained later in life, resulting in a better metabolic balance in female offspring. In conclusion, sex and maternal obesity drive differently transcriptional and posttranscriptional regulation of major metabolic processes in offspring liver, explaining the sexual dimorphism in obesity-associated metabolic risk.

Sex and maternal obesity drive differently transcriptional and posttranscriptional regulation of major metabolic processes in the livers of female and male offspring, contributing to the sexual dimorphism in obesity-associated metabolic risk.

O-Sulfation disposition of curcumin and quercetin in SULT1A3 overexpressing HEK293 cells: the role of arylsulfatase B in cellular O-sulfation regulated by transporters

Extensive phase II metabolic reactions (i.e., glucuronidation and sulfation) have resulted in low bioavailability and decreased biological effects of curcumin and quercetin. Compared to glucuronidation, information on the sulfation disposition of curcumin and quercetin is limited. In this study, we identified that BCRP and MRP4 played a critical role in the cellular excretion of curcumin-O-sulfate (C-O-S) and quercetin-O-sulfate (Q-O-S) by integrating chemical inhibition with transporter knock-down experiments. Inhibited excretion of sulfate (C-O-S and Q-O-S) caused significant reductions in cellular O-sulfation of curcumin (a maximal 74.4% reduction) and quercetin (a maximal 76.9% reduction), revealing a strong interplay of sulfation with efflux transport. It was further identified that arylsulfatase B (ARSB) played a crucial role in the regulation of cellular O-sulfation by transporters. ARSB overexpression significantly enhanced the reduction effect of MK-571 on the cellular O-sulfation (f_met) of the model compound (38.8% reduction for curcumin and 44.2% reduction for quercetin). On the contrary, ARSB knockdown could reverse the effect of MK-571 on the O-sulfation disposition of the model compound (29.7% increase for curcumin and 47.3% increase for quercetin). Taken together, ARSB has been proven to be involved in cellular O-sulfation, accounting for transporter-dependent O-sulfation of curcumin and quercetin. A better understanding of the interplay beneath metabolism and transport will contribute to the exact prediction of in vivo drug disposition and drug-drug interactions.

Metabolic Activation of Gemfibrozil Mediated by Cytochrome P450 Enzymes and Sulfotransferases

Gemfibrozil (GEM), a lipid regulator, is a fibric acid derivative widely used in the treatment of hyperlipidemia. It has been reported that GEM can induce acute liver injury in the course of therapy in clinical practice, so it is necessary to elucidate the mechanisms of toxic action. The present study focused on metabolic activation of GEM, possibly participating in GEM-mediated liver injury. A benzylic alcohol metabolite (M1), along with a phenol metabolite (M2), was detected in microsomal incubations, rat primary hepatocyte culturing, and rats given GEM. A GSH conjugate (M3) was detected in cultured rat hepatocytes after exposure to GEM. Formation of M1 was found to be NADPH dependent, and generation of M3 required M1 and 3'-phosphoadenosine-5'-phosphosulfate. It is most likely that GEM was biotransformed to M1, which was further metabolized to a sulfate. The resulting sulfate was reactive to bio-thiols. Cytochrome P450 and sulfotransferases participated in the phase I and phase II reactions, respectively. M1 and M3 were chemically synthesized, and their structures were characterized by mass spectrometry and NMR. The present study has particular value for elucidating the mechanism of liver injury caused by GEM.

Inhibition of p53 Sulfoconjugation Prevents Oxidative Hepatotoxicity and Acute Liver Failure

BACKGROUND & AIMS

Sulfoconjugation of small molecules or protein peptides is a key mechanism to ensure biochemical and functional homeostasis in mammals. The PAPS synthase 2 (PAPSS2) is the primary enzyme to synthesize the universal sulfonate donor 3'-phosphoadenosine 5'-phosphosulfate (PAPS). Acetaminophen (APAP) overdose is the leading cause of acute liver failure (ALF), in which oxidative stress is a key pathogenic event, whereas sulfation of APAP contributes to its detoxification. The goal of this study was to determine whether and how PAPSS2 plays a role in APAP-induced ALF.

METHODS

Gene expression was analyzed in APAP-induced ALF in patients and mice. Liver-specific Papss2-knockout mice using Alb-Cre (Papss2^ΔHC) or AAV8-TBG-Cre (Papss2^iΔHC) were created and subjected to APAP-induced ALF. Primary human and mouse hepatocytes were used for in vitro mechanistic analysis.

RESULTS

The hepatic expression of PAPSS2 was decreased in APAP-induced ALF in patients and mice. Surprisingly, Papss2^ΔHC mice were protected from APAP-induced hepatotoxicity despite having a decreased APAP sulfation, which was accompanied by increased hepatic antioxidative capacity through the activation of the p53-p2-Nrf2 axis. Treatment with a sulfation inhibitor also ameliorated APAP-induced hepatotoxicity. Gene knockdown experiments showed that the hepatoprotective effect of Papss2^ΔHC was Nrf2, p53, and p21 dependent. Mechanistically, we identified p53 as a novel substrate of sulfation. Papss2 ablation led to p53 protein accumulation by preventing p53 sulfation, which disrupts p53-MDM2 interaction and p53 ubiquitination and increases p53 protein stability.

CONCLUSIONS

We have uncovered a previously unrecognized and p53-mediated role of PAPSS2 in controlling oxidative response. Inhibition of p53 sulfation may be explored for the clinical management of APAP overdose.

DHEA Protects Human Cholangiocytes and Hepatocytes against Apoptosis and Oxidative Stress

Primary biliary cholangitis (PBC) is a rare chronic cholestatic and immune-mediated liver disease of unknown aetiology that targets intrahepatic bile duct cells (cholangiocytes) and primarily affects postmenopausal women, when their estrogen levels sharply decrease. An impaired cholangiocyte response to estrogen characterizes the terminal stage of the disease, as this is when an inefficiency of cholangiocyte proliferation, in balancing the loss of intrahepatic bile ducts, is observed. Here, we report that the estrogen precursor dehydroepiandrosterone (DHEA) and its sulfate metabolites, DHEA-S and 17 β-estradiol, enhance the proliferation of cholangiocytes and hepatocytes in vitro. Flow cytometry analysis showed that DHEA and DHEA-S decreased glyco-chenodeoxycholic acid (GCDC)-driven apoptosis in cholangiocytes. Cell viability assay (MTT) indicated that ER-α, -β, and the G-protein-coupled estrogen receptor, are involved in the protection of DHEA against oxidative stress in cholangiocytes. Finally, immunoblot analysis showed an elevated level of steroid sulfatase and a reduced level of sulfotransferase 1E1 enzymes, involved in the desulfation/sulfation process of estrogens in cirrhotic PBC, and primary sclerosis cholangitis (PSC) liver tissues, another type of chronic cholestatic and immune-mediated liver disease. Taken together, these results suggest that DHEA can prevent the deleterious effects of certain potentially toxic bile acids and reactive oxygen species, delaying the onset of liver disease.

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.