Search

Much writing on Donor Advised Funds (DAFs) relates to whether they ‘unduly’ delay the direct application of donated funds to achieve public benefit. However, the discussion rarely touches on a normative basis for determining what is ‘undue’ or that can be used to shape potential reforms, which are typically framed with reference to a private foundation payout rate or time limit for expending contributions. Research on charity accumulation conducted across the United States, United Kingdom, Canada, Australia and New Zealand, suggests that the normative principle of intergenerational justice is helpful for grounding such discussions (Murray, I. 2021. Charity Law and Accumulation: Maintaining an Intergenerational Balance. Cambridge: Cambridge University Press). This article considers intergenerational justice in the context of DAFs and considers whether the principle can be implemented in ways that support DAF sponsor independence and flexibility. One way that this could be achieved is by imposing (or enforcing existing) procedural obligations on decision-makers to give genuine consideration to intergenerational justice when making decisions about how much to spend and retain.

Discrimination by charities raises questions about the appropriate extent of equality regulation and has implications for government outsourcing through charities and for the provision of tax concessions. Professor Parachin has recently provided a justification for denying the application of public equality norms to charities through the public policy test of charity law. This paper builds on that work by considering whether liberal societies might, however, have good grounds to apply public equality norms to charities in circumstances such as the provision of outsourced government services, state enforcement of egoistic giving, or where doing so is a proportionate means to prevent harm.

The isotope-production cross sections in p- and d-induced reactions on 93Zr at approximately 50 MeV/nucleon were measured by using the inverse-kinematics method at RIKEN RI Beam Factory. The measured data were compared with the previous experimental 93Zr + p, d at 105 and 209 MeV/nucleon data. This comparison represents that the isotopic distribution of production cross sections at 51 MeV p-induced reaction is appreciably different from those at 105 and 209 MeV. On the other hand, these three data sets show that the shape of isotopic distribution is similar in the case of the d-induced reaction. Also, the measured production cross sections were compared with the theoretical model calculations with Particle and Heavy Ion Transport code System (PHITS) version 3.10 in order to investigate the reproducibility of the models implemented in PHITS. The calculations well reproduced the experimental data even in such low incident energy, while several discrepancies were still seen as in the p- and d-induced reactions at 105 and 209 MeV/nucleon.

Many experimental evidences suggest that desiccation cracks in clay initiate as a result of the mobilization of soil tensile strength. However this mechanical approach disregards the cohesionless and effective stress-dependent behaviour of fine-grained soil. On the other hand recent findings in the literature suggest that effective stress-dependent shear failure criteria would be appropriate to explain the mechanisms of desiccation cracking for tensile total stress states. This work aims at assessing the validity of a shear failure criterion to predict the onset of cracking in clay forms exposed to air drying. Clay forms of various geometries were experimentally subjected to non-uniform hydraulic and mechanical boundary conditions. Time and location for crack initiation are monitored using a digital camera. Cracking experiments are then modelled in a hydro-mechanical framework using an effective-stress shear failure criterion. The comparison of simulations with experimental results for both the time and the location of cracking allows assuming that cracking occurs due to failure in shearing.

The article presents information on a case of a 53-year old female suffering with a very refractory celiac disease. She was presented with a six month history of alternating bowel habit, post-prandial abdominal bloating and rapid weight loss. She also had a history of alpha-antitrypsin deficiency and endometriosis. Gluten free diet along with oral prednisone and oral metronidazole was prescribed to her.

Sphingolipids play vital roles in metabolism and regulation. Previously, the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor, was reported to directly regulate ceramide synthesis genes by binding to their promoters. Herein, sphingosine kinase 2 (SPHK2), responsible for producing sphingosine-1-phosphate (S1P), was found to interact with AHR through LXXLL motifs, influencing AHR nuclear localization. Through mutagenesis and co-transfection studies, AHR activation and subsequent nuclear translocation was hindered by SPHK2 LXXLL mutants or SPHK2 lacking a nuclear localization signal (NLS). Similarly, an NLS-deficient AHR mutant impaired SPHK2 nuclear translocation. Silencing SPHK2 reduced AHR expression and its target gene CYP1A1, while SPHK2 overexpression enhanced AHR activity. SPHK2 was found enriched on the CYP1A1 promoter, underscoring its role in AHR target gene activation. Additionally, S1P rapidly increased AHR expression at both the mRNA and protein levels and promoted AHR recruitment to the CYP1A1 promoter. Using mouse models, AHR deficiency compromised SPHK2 nuclear translocation, illustrating a critical interaction where SPHK2 facilitates AHR nuclear localization and supports a positive feedback loop between AHR and sphingolipid enzyme activity in the nucleus. These findings highlight a novel function of SPHK2 in regulating AHR activity and gene expression., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.)

Background: Exposure to persistent organic pollutants (POPs) and disruptions in the gastrointestinal microbiota have been positively correlated with a predisposition to factors such as obesity, metabolic syndrome, and type 2 diabetes; however, it is unclear how the microbiome contributes to this relationship., Objective: This study aimed to explore the association between early life exposure to a potent aryl hydrocarbon receptor (AHR) agonist and persistent disruptions in the microbiota, leading to impaired metabolic homeostasis later in life., Methods: This study used metagenomics, nuclear magnetic resonance (NMR)- and mass spectrometry (MS)-based metabolomics, and biochemical assays to analyze the gut microbiome composition and function, as well as the physiological and metabolic effects of early life exposure to 2,3,7,8-tetrachlorodibenzofuran (TCDF) in conventional, germ-free (GF), and Ahr -null mice. The impact of TCDF on Akkermansia muciniphila ( A. muciniphila ) in vitro was assessed using optical density (OD 600), flow cytometry, transcriptomics, and MS-based metabolomics., Results: TCDF-exposed mice exhibited lower abundances of A. muciniphila , lower levels of cecal short-chain fatty acids (SCFAs) and indole-3-lactic acid (ILA), as well as lower levels of the gut hormones glucagon-like peptide 1 (GLP-1) and peptide YY (PYY), findings suggestive of disruption in the gut microbiome community structure and function. Importantly, microbial and metabolic phenotypes associated with early life POP exposure were transferable to GF recipients in the absence of POP carry-over. In addition, AHR-independent interactions between POPs and the microbiota were observed, and they were significantly associated with growth, physiology, gene expression, and metabolic activity outcomes of A. muciniphila , supporting suppressed activity along the ILA pathway., Conclusions: These data obtained in a mouse model point to the complex effects of POPs on the host and microbiota, providing strong evidence that early life, short-term, and self-limiting POP exposure can adversely impact the microbiome, with effects persisting into later life with associated health implications. https://doi.org/10.1289/EHP13356.

The intestinal epithelial layer is susceptible to damage by chemical, physiological and mechanical stress. While it is essential to maintain the integrity of epithelium, the biochemical pathways that contribute to the barrier function have not been completely investigated. Here we demonstrate an aryl hydrocarbon receptor (AHR)-dependent mechanism facilitating the production of the antimicrobial peptide AMP regenerating islet-derived protein 3 gamma (REG3G), which is essential for intestinal homeostasis. Genetic ablation of AHR in mice impairs pSTAT3-mediated REG3G expression and increases bacterial numbers of Segmented filamentous bacteria (SFB) and Akkermansia muciniphila in the small intestine. Studies with tissue-specific conditional knockout mice revealed that the presence of AHR in the epithelial cells of the small intestine is not required for the production of REG3G through the phosphorylated STAT3-mediated pathway. However, immune-cell-specific AHR activity is necessary for normal expression of REG3G in all regions of the small intestine. A diet rich in broccoli, capable of inducing AHR activity, increases REG3G production when compared to a semi-purified diet that is devoid of ligands that can potentially activate the AHR, thus highlighting the importance of AHR in antimicrobial function. Overall, these data suggest that homeostatic antimicrobial REG3G production is increased by an AHR pathway intrinsic to the immune cells in the small intestine., (© 2024 The Authors. The FASEB Journal published by Wiley Periodicals LLC on behalf of Federation of American Societies for Experimental Biology.)

Background: The quinoline-3-carboxamide, Tasquinimod (TasQ), is orally active as a maintenance therapy with an on-target mechanism-of-action via allosteric binding to HDAC4. This prevents formation of the HDAC4/NCoR1/HDAC3 complex, disrupting HIF-1α transcriptional activation and repressing MEF-2 target genes needed for adaptive survival signaling in the compromised tumor micro environment. In phase 3 clinical testing against metastatic castration-resistant prostate cancer(mCRPC), TasQ (1 mg/day) increased time-to-progression, but not overall survival., Methods: TasQ analogs were chemically synthesized and tested for activity compared to the parental compound. These included HDAC4 enzymatic assays, qRT-PCR and western blot analyses of gene and protein expression following treatment, in vitro and in vivo efficacy against multiple prostate cancer models including PDXs, pharmacokinetic analyses,AHR binding and agonist assays, SPR analyses of binding to HDAC4 and NCoR1, RNAseq analysis of in vivo tumors, 3D endothelial sprouting assays, and a targeted kinase screen. Genetic knockout or knockdown controls were used when appropriate., Results: Here, we document that, on this regimen (1 mg/day), TasQ blood levels are 10-fold lower than the optimal concentration (≥2 μM) needed for anticancer activity, suggesting higher daily doses are needed. Unfortunately, we also demonstrate that TasQ is an arylhydrocarbon receptor (AHR) agonist, which binds with an EC50 of 1 μM to produce unwanted off-target side effects. Therefore, we screened a library of TasQ analogsto maximize on-target versus off-target activity. Using this approach, we identified ESATA-20, which has ~10-fold lower AHR agonism and 5-fold greater potency against prostate cancer patient-derived xenografts., Conclusion: This increased therapeuticindex nominates ESATA-20 as a lead candidate forclinical development as an orally active third generation quinoline-3-carboxamide analog thatretains its on-target ability to disrupt HDAC4/HIF-1α/MEF-2-dependent adaptive survival signaling in the compromisedtumor microenvironment found in mCRPC., (© 2023 Wiley Periodicals LLC.)

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that plays an important role in gastrointestinal barrier function, tumorigenesis, and is an emerging drug target. The resident microbiota is capable of metabolizing tryptophan to metabolites that are AHR ligands (e.g., indole-3-acetate). Recently, a novel set of mutagenic tryptophan metabolites named indolimines have been identified that are produced by M. morganii in the gastrointestinal tract. Here, we determined that indolimine-200, -214, and -248 are direct AHR ligands that can induce Cyp1a1 transcription and subsequent CYP1A1 enzymatic activity capable of metabolizing the carcinogen benzo(a)pyrene in microsomal assays. In addition, indolimines enhance IL6 expression in a colonic tumor cell line in combination with cytokine treatment. The concentration of indolimine-248 that induces AHR transcriptional activity failed to increase DNA damage. These observations reveal an additional aspect of how indolimines may alter colonic tumorigenesis beyond mutagenic activity.

The aryl hydrocarbon receptor (AHR) exerts major roles in xenobiotic metabolism, and in immune and barrier tissue homeostasis. How AHR activity is regulated by the availability of endogenous ligands is poorly understood. Potent AHR ligands have been shown to exhibit a negative feedback loop through induction of CYP1A1, leading to metabolism of the ligand. Our recent study identified and quantified 6 tryptophan metabolites (eg, indole-3-propionic acid, and indole-3-acetic acid) in mouse and human serum, generated by the host and gut microbiome, that are present in sufficient concentrations to individually activate the AHR. Here, these metabolites are not significantly metabolized by CYP1A1/1B1 in an in vitro metabolism assay. In contrast, CYP1A1/1B metabolizes the potent endogenous AHR ligand 6-formylindolo[3,2b]carbazole. Furthermore, molecular modeling of these 6 AHR activating tryptophan metabolites within the active site of CYP1A1/1B1 reveal metabolically unfavorable docking profiles with regard to orientation with the catalytic heme center. In contrast, docking studies confirmed that 6-formylindolo[3,2b]carbazole would be a potent substrate. The lack of CYP1A1 expression in mice fails to influence serum levels of the tryptophan metabolites examined. In addition, marked induction of CYP1A1 by PCB126 exposure in mice failed to alter the serum concentrations of these tryptophan metabolites. These results suggest that certain circulating tryptophan metabolites are not susceptible to an AHR negative feedback loop and are likely important factors that mediate constitutive but low level systemic human AHR activity., Competing Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2023.)

The aryl hydrocarbon receptor (AHR) is a ligand activated transcription factor that plays an integral role in homeostatic maintenance by regulating cellular functions such as cellular differentiation, metabolism, barrier function, and immune response. An important but poorly understood class of AHR activators are compounds derived from host and bacterial metabolism of tryptophan. The commensal bacteria of the gut microbiome are major producers of tryptophan metabolites known to activate the AHR, while the host also produces AHR activators through tryptophan metabolism. We used targeted mass spectrometry-based metabolite profiling to determine the presence and metabolic source of these metabolites in the sera of conventional mice, germ-free mice, and humans. Surprisingly, sera concentrations of many tryptophan metabolites are comparable between germ-free and conventional mice. Therefore, many major AHR-activating tryptophan metabolites in mouse sera are produced by the host, despite their presence in feces and mouse cecal contents. Here we present an investigation of AHR activation using a complex mixture of tryptophan metabolites to examine the biological relevance of circulating tryptophan metabolites. AHR activation is rarely studied in the context of a mixture at relevant concentrations, as we present here. The AHR activation potentials of individual and pooled metabolites were explored using cell-based assays, while ligand binding competition assays and ligand docking simulations were used to assess the detected metabolites as AHR agonists. The physiological and biomedical relevance of the identified metabolites was investigated in the context of a cell-based model for rheumatoid arthritis. We present data that reframe AHR biology to include the presence of a mixture of ubiquitous tryptophan metabolites, improving our understanding of homeostatic AHR activity and models of AHR-linked diseases., Competing Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2023.)

Diet-derived aryl hydrocarbon receptor (AHR) ligands have potential to maintain gut health. However, among the myriad bioactive compounds from foods, identifying novel functional ligands which would significantly impact gastrointestinal health is a challenge. In this study, a novel AHR modulator is predicted, identified, and characterized in the white button mushroom ( Agaricus bisporus ). Using a molecular networking approach, a methylated analog to benzothiazole was indicated in white button mushrooms, which was subsequently isolated and identified as 2-amino-4-methyl-benzothiazole(2A4). Cell-based AHR transcriptional assays revealed that 2-amino-4-methyl-benzothiazole possesses agonistic activity and upregulated CYP1A1 expression. This contrasts with previous findings that whole white button mushroom extract has overall antagonistic activity in vivo , underscoring the importance of studying the roles each chemical component plays in a whole food. The findings suggest that 2-amino-4-methyl-benzothiazole is a previously unidentified AHR modulator from white button mushroom and demonstrate that molecular networking has potential to identify novel receptor modulators from natural products., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Joshua Kellogg reports financial support was provided by National Institute of Food and Agriculture. Gary Perdew reports financial support was provided by National Institute of General Medical Sciences. Gary Perdew reports financial support was provided by National Institute of Environmental Health Sciences. Andrew Patterson reports financial support was provided by National Institute of Environmental Health Sciences.

The aryl hydrocarbon receptor (AHR) mediates intestinal barrier homeostasis. Many AHR ligands are also CYP1A1/1B1 substrates, which can result in rapid clearance within the intestinal tract, limiting systemic exposure and subsequent AHR activation. This led us to the hypothesis that there are dietary substrates of CYP1A1/1B1 that functionally increase the half-life of potent AHR ligands. We examined the potential of urolithin A (UroA), a gut bacterial metabolite of ellagitannins, as a CYP1A1/1B1 substrate to enhance AHR activity in vivo. UroA is a competitive substrate for CYP1A1/1B1 in an in vitro competition assay. A broccoli-containing diet promotes the gastric formation of the potent hydrophobic AHR ligand and CYP1A1/1B1 substrate, 5,11-dihydroindolo[3,2-b]carbazole (ICZ). In mice, dietary exposure to UroA in a 10% broccoli diet led to a coordinated increase in duodenal, cardiac, and pulmonary AHR activity, but no increase in activity in the liver. Thus, CYP1A1 dietary competitive substrates can lead to enhanced systemic AHR ligand distribution from the gut, likely through the lymphatic system, increasing AHR activation in key barrier tissues. Finally, this report will lead to a reassessment of the dynamics of distribution of other hydrophobic chemicals present in the diet., (© 2023 The Authors. The FASEB Journal published by Wiley Periodicals LLC on behalf of Federation of American Societies for Experimental Biology.)

In the face of mechanical, chemical, microbial, and immunologic pressure, intestinal homeostasis is maintained through balanced cellular turnover, proliferation, differentiation, and self-renewal. Here, we present evidence supporting the role of the aryl hydrocarbon receptor (AHR) in the adaptive reprogramming of small intestinal gene expression, leading to altered proliferation, lineage commitment, and remodeling of the cellular repertoire that comprises the intestinal epithelium to promote intestinal resilience. Ahr gene/protein expression and transcriptional activity exhibit marked proximal HI to distal LO and crypt HI to villi LO gradients. Genetic ablation of Ahr impairs commitment/differentiation of the secretory Paneth and goblet cell lineages and associated mucin production, restricts expression of secretory/enterocyte differentiation markers, and increases crypt-associated proliferation and villi-associated enterocyte luminal exfoliation. Ahr -/- mice display a decrease in intestinal barrier function. Ahr +/+ mice that maintain a diet devoid of AHR ligands intestinally phenocopy Ahr -/- mice. In contrast, Ahr +/+ mice exposed to AHR ligands reverse these phenotypes. Ligand-induced AHR transcriptional activity positively correlates with gene expression (Math1, Klf4, Tff3) associated with differentiation of the goblet cell secretory lineage. Math1 was identified as a direct target gene of AHR, a transcription factor critical to the development of goblet cells. These data suggest that dietary cues, relayed through the transcriptional activity of AHR, can reshape the cellular repertoire of the gastrointestinal tract., (Copyright © 2022 United States & Canadian Academy of Pathology. Published by Elsevier Inc. All rights reserved.)

Therapeutic aryl hydrocarbon receptor (AHR) modulating agents gained attention in dermatology as non-steroidal anti-inflammatory drugs that improve skin barrier properties. By exploiting AHR's known ligand promiscuity, we generated novel AHR modulating agents by lead optimization of a selective AHR modulator (SAhRM; SGA360). Twenty-two newly synthesized compounds were screened yielding two novel derivatives, SGA360f and SGA388, in which agonist activity led to enhanced keratinocyte terminal differentiation. SGA388 showed the highest agonist activity with potent normalization of keratinocyte hyperproliferation, restored expression of skin barrier proteins and dampening of chemokine expression by keratinocytes upon Th2-mediated inflammation in vitro. The topical application of SGA360f and SGA388 reduced acute skin inflammation in vivo by reducing cyclooxygenase levels, resulting in less neutrophilic dermal infiltrates. The minimal induction of cytochrome P450 enzyme activity, lack of cellular toxicity and mutagenicity classifies SGA360f and SGA388 as novel potential therapeutic AHR ligands and illustrates the potential of medicinal chemistry to fine-tune AHR signaling for the development of targeted therapies in dermatology and beyond., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Background and Aims: SARS-CoV-2 and consequent pandemic has presented unique challenges. Beyond the direct COVID-related mortality in those with liver disease, we sought to determine the effect of lockdown on people with liver disease in Scotland. The effect of lockdown on those with alcohol-related disease is of interest; and whether there were associated implications for a change in alcohol intake and consequent presentations with decompensated disease., Methods: We performed a retrospective analysis of patients admitted to seven Scottish hospitals with a history of liver disease between 1 April and 30 April 2020 and compared across the same time in 2017, 2018 and 2019. We also repeated an intermediate assessment based on a single centre to examine for delayed effects between 1 April and 31 July 2020., Results: We found that results and outcomes for patients admitted in 2020 were similar to those in previous years in terms of morbidity, mortality, and length of stay. In the Scotland-wide cohort: admission MELD (Model for End-stage Liver Disease) (16 (12-22) vs 15 (12-19); p=0.141), inpatient mortality ((10.9% vs 8.6%); p=0.499) and length of stay (8 days (4-15) vs 7 days (4-13); p=0.140). In the Edinburgh cohort: admission MELD (17 (12-23) vs 17 (13-21); p=0.805), inpatient mortality ((13.7% vs 10.1%; p=0.373) and length of stay (7 days (4-14) vs 7 days (3.5-14); p=0.525))., Conclusion: This assessment of immediate and medium-term lockdown impacts on those with chronic liver disease suggested a minimal effect on the presentation of decompensated liver disease to secondary care., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY. Published by BMJ.)

Competing Interests: Competing interests: None declared.

We report a new subgroup of Type III Restriction-Modification systems that use m4C methylation for host protection. Recognition specificities for six such systems, each recognizing a novel motif, have been determined using single molecule real-time DNA sequencing. In contrast to all previously characterized Type III systems which modify adenine to m6A, protective methylation of the host genome in these new systems is achieved by the N4-methylation of a cytosine base in one strand of an asymmetric 4 to 6 base pair recognition motif. Type III systems are heterotrimeric enzyme complexes containing a single copy of an ATP-dependent restriction endonuclease-helicase (Res) and a dimeric DNA methyltransferase (Mod). The Type III Mods are beta-class amino-methyltransferases, examples of which form either N6-methyl adenine or N4-methyl cytosine in Type II RM systems. The Type III m4C Mod and Res proteins are diverged, suggesting ancient origin or that m4C modification has arisen from m6A MTases multiple times in diverged lineages. Two of the systems, from thermophilic organisms, required expression of both Mod and Res to efficiently methylate an E. coli host, unlike previous findings that Mod alone is proficient at modification, suggesting that the division of labor between protective methylation and restriction activities is atypical in these systems. Two of the characterized systems, and many homologous putative systems, appear to include a third protein; a conserved putative helicase/ATPase subunit of unknown function and located 5' of the mod gene. The function of this additional ATPase is not yet known, but close homologs co-localize with the typical Mod and Res genes in hundreds of putative Type III systems. Our findings demonstrate a rich diversity within Type III RM systems., Competing Interests: Iain A. Murray, Richard D. Morgan, Yvette A. Luyten, Alexey Fomenkov, Ivan R. Corrêa Jr, Nan Dai, and Richard J. Roberts are full-time employees of New England Biolabs. There are no patents, products in development or marketed products to declare. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Aryl hydrocarbon receptor (AHR) activation via 2,3,7,8-tetrachlorodibenzofuran (TCDF) induces the accumulation of hepatic lipids. Here we report that AHR activation by TCDF (24  μg/kg body weight given orally for five days) induced significant elevation of hepatic lipids including ceramides in mice, was associated with increased expression of key ceramide biosynthetic genes, and increased activity of their respective enzymes. Results from chromatin immunoprecipitation (ChIP), electrophoretic mobility shift assay (EMSA) and cell-based reporter luciferase assays indicated that AHR directly activated the serine palmitoyltransferase long chain base subunit 2 (Sptlc2, encodes serine palmitoyltransferase 2 (SPT2)) gene whose product catalyzes the initial rate-limiting step in de novo sphingolipid biosynthesis. Hepatic ceramide accumulation was further confirmed by mass spectrometry-based lipidomics. Taken together, our results revealed that AHR activation results in the up-regulation of Sptlc2, leading to ceramide accumulation, thus promoting lipogenesis, which can induce hepatic lipid accumulation., (Copyright © 2021. Published by Elsevier B.V.)

Objectives: Existing scores are not accurate at predicting mortality in upper (UGIB) and lower (LGIB) gastrointestinal bleeding. We aimed to develop and validate a new pre-endoscopy score for predicting mortality in both UGIB and LGIB., Design and Setting: International cohort study. Patients presenting to hospital with UGIB at six international centres were used to develop a risk score for predicting mortality using regression analyses. The score's performance in UGIB and LGIB was externally validated and compared with existing scores using four international datasets. We calculated areas under receiver operating characteristics curves (AUROCs), sensitivities, specificities and outcome among patients classified as low risk and high risk., Participants and Results: We included 3012 UGIB patients in the development cohort, and 4019 UGIB and 2336 LGIB patients in the validation cohorts. Age, Blood tests and Comorbidities (ABC) score was closer associated with mortality in UGIB and LGIB (AUROCs: 0.81-84) than existing scores (AUROCs: 0.65-0.75; p≤0.02). In UGIB, patients with low ABC score (≤3), medium ABC score (4-7) and high ABC score (≥8) had 30-day mortality rates of 1.0%, 7.0% and 25%, respectively. Patients classified low risk using ABC score had lower mortality than those classified low risk with AIMS65 (threshold ≤1) (1.0 vs 4.5%; p<0.001). In LGIB, patients with low, medium and high ABC scores had in-hospital mortality rates of 0.6%, 6.3% and 18%, respectively., Conclusions: In contrast to previous scores, ABC score has good performance for predicting mortality in both UGIB and LGIB, allowing early identification and targeted management of patients at high or low risk of death., Competing Interests: Competing interests: IG is a consultant, has a financial interest and is a member of the Medical Advisory Board of MOTUS GI. IG is a consultant for Boston Scientific, Symbionix and GI View. KO has received editorial fees for reviews on the same topic., (© Author(s) (or their employer(s)) 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

Increasingly, the aryl hydrocarbon receptor (AHR) is being recognized as a sensor for endogenous and pseudo-endogenous metabolites, and in particular microbiota and host generated tryptophan metabolites. One proposed explanation for this is the role of the AHR in innate immune signaling within barrier tissues in response to the presence of microorganisms. A number of cytokine/chemokine genes exhibit a combinatorial increase in transcription upon toll-like receptors and AHR activation, supporting this concept. The AHR also plays a role in the enhanced differentiation of intestinal and dermal epithelium leading to improved barrier function. Importantly, from an evolutionary perspective many of these tryptophan metabolites exhibit greater activation potential for the human AHR when compared to the rodent AHR. These observations underscore the importance of the AHR in barrier tissues and may lead to pharmacologic therapeutic intervention.

Analysis of genomic DNA from pathogenic strains of Burkholderia cenocepacia J2315 and Escherichia coli O104:H4 revealed the presence of two unusual MTase genes. Both are plasmid-borne ORFs, carried by pBCA072 for B. cenocepacia J2315 and pESBL for E. coli O104:H4. Pacific Biosciences SMRT sequencing was used to investigate DNA methyltransferases M.BceJIII and M.EcoGIX, using artificial constructs. Mating properties of engineered pESBL derivatives were also investigated. Both MTases yield promiscuous m6A modification of single strands, in the context SAY (where S = C or G and Y = C or T). Strikingly, this methylation is asymmetric in vivo, detected almost exclusively on one DNA strand, and is incomplete: typically, around 40% of susceptible motifs are modified. Genetic and biochemical studies suggest that enzyme action depends on replication mode: DNA Polymerase I (PolI)-dependent ColE1 and p15A origins support asymmetric modification, while the PolI-independent pSC101 origin does not. An MTase-PolI complex may enable discrimination of PolI-dependent and independent plasmid origins. M.EcoGIX helps to establish pESBL in new hosts by blocking the action of restriction enzymes, in an orientation-dependent fashion. Expression and action appear to occur on the entering single strand in the recipient, early in conjugal transfer, until lagging-strand replication creates the double-stranded form., (© The Author(s) 2020. Published by Oxford University Press on behalf of Nucleic Acids Research.)

Commensal microbiota-dependent tryptophan catabolism within the gastrointestinal tract is known to exert profound effects upon host physiology, including the maintenance of epithelial barrier and immune function. A number of abundant microbiota-derived tryptophan metabolites exhibit activation potential for the aryl hydrocarbon receptor (AHR). Gene expression facilitated by AHR activation through the presence of dietary or microbiota-generated metabolites can influence gastrointestinal homeostasis and confer protection from intestinal challenges. Utilizing untargeted mass spectrometry-based metabolomics profiling, combined with AHR activity screening assays, we identify four previously unrecognized tryptophan metabolites, present in mouse cecal contents and human stool, with the capacity to activate AHR. Using GC/MS and LC/MS platforms, quantification of these novel AHR activators, along with previously established AHR-activating tryptophan metabolites, was achieved, providing a relative order of abundance. Using physiologically relevant concentrations and quantitative gene expression analyses, the relative efficacy of these tryptophan metabolites with regard to mouse or human AHR activation potential is examined. These data reveal indole, 2-oxindole, indole-3-acetic acid and kynurenic acid as the dominant AHR activators in mouse cecal contents and human stool from participants on a controlled diet. Here we provide the first documentation of the relative abundance and AHR activation potential of a panel of microbiota-derived tryptophan metabolites. Furthermore, these data reveal the human AHR to be more sensitive, at physiologically relevant concentrations, to tryptophan metabolite activation than mouse AHR. Additionally, correlation analyses indicate a relationship linking major tryptophan metabolite abundance with AHR activity, suggesting these cecal/fecal metabolites represent biomarkers of intestinal AHR activity.

The human PXR (pregnane X receptor), a master regulator of drug metabolism, has essential roles in intestinal homeostasis and abrogating inflammation. Existing PXR ligands have substantial off-target toxicity. Based on prior work that established microbial (indole) metabolites as PXR ligands, we proposed microbial metabolite mimicry as a novel strategy for drug discovery that allows exploiting previously unexplored parts of chemical space. Here, we report functionalized indole derivatives as first-in-class non-cytotoxic PXR agonists as a proof of concept for microbial metabolite mimicry. The lead compound, FKK6 (Felix Kopp Kortagere 6), binds directly to PXR protein in solution, induces PXR-specific target gene expression in cells, human organoids, and mice. FKK6 significantly represses pro-inflammatory cytokine production cells and abrogates inflammation in mice expressing the human PXR gene. The development of FKK6 demonstrates for the first time that microbial metabolite mimicry is a viable strategy for drug discovery and opens the door to underexploited regions of chemical space., (© 2020 The Authors. Published under the terms of the CC BY 4.0 license.)

The ability of the aryl hydrocarbon receptor (AHR) to alter hepatic expression of cholesterol synthesis genes in a DRE-independent manner in mice and humans has been reported. We have examined the influence of functionally distinct classes of AHR ligands on the levels of Niemann-Pick C1-like intracellular cholesterol transporter (NPC1L1) and enzymes involved in the cholesterol synthesis pathway. NPC1L1 is known to mediate the intestinal absorption of dietary cholesterol and is clinically targeted. AHR ligands were capable of attenuating cholesterol uptake through repression of NPC1L1 expression. Through mutagenesis experiments targeting the two DRE sequences present in the promoter region of the NPC1L1 gene, we provide evidence that the repression does not require functional DRE sequences; while knockdown experiments demonstrated that this regulation is dependent on AHR and sterol-regulatory element-binding protein-2 (SREBP-2). Furthermore, upon ligand activation of AHR, the human intestinal Caco-2 cell line revealed coordinate repression of both mRNA and protein levels for a number of the cholesterol biosynthetic enzymes. Transcription of NPC1L1 and genes of the cholesterol synthesis pathway is predominantly regulated by SREBP-2, especially after treatment with a statin. Immunoblot analyses revealed a significant decrease in transcriptionally active SREBP-2 levels upon ligand treatment, whereas the precursor form of SREBP-2 was modestly increased by AHR activation. Mechanistic insights indicate that AHR induces proteolytic degradation of mature SREBP-2 in a calcium-dependent manner, which correlates with the AHR ligand-mediated upregulation of the transient receptor potential cation channel subfamily V member 6 (TRPV6) gene encoding for a membrane calcium channel. These observations emphasize a role for AHR in the systemic homeostatic regulation of cholesterol synthesis and absorption, indicating the potential use of this receptor as a target for the treatment of hyperlipidosis-associated metabolic diseases.

Persistent organic pollutants (POPs) are important environmental chemicals and continued study of their mechanism of action remains a high priority. POPs, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,7,8-tetrachlorodibenzofuran (TCDF), and polychlorinated biphenyls (PCBs), are widespread environmental contaminants that are agonists for the aryl hydrocarbon receptor (AHR). Activation of the AHR modulates the gut microbiome community structure and function, host immunity, and the host metabolome. In the current study, male C57BL6/J mice were exposed, via the diet, to 5 µg/kg body weight (BW) TCDF or 24 µg/kg BW of TCDF every day for 5 days. The functional and structural changes imparted by TCDF exposure to the gut microbiome and host metabolome were explored via 16S rRNA gene amplicon sequencing, metabolomics, and bacterial metatranscriptomics. Significant changes included increases in lipopolysaccharide (LPS) biosynthesis gene expression after exposure to 24 µg/kg BW of TCDF. Increases in LPS biosynthesis were confirmed with metabolomics and LPS assays using serum obtained from TCDF-treated mice. Significant increases in gene expression within aspartate and glutamate metabolism were noted after exposure to 24 µg/kg BW of TCDF. Together, these results suggest that after exposure to 24 µg/kg BW of TCDF, the gut microbiome increases the production of LPS and glutamate to promote localized gut inflammation, potentially using glutamate as a stress response.

The aryl hydrocarbon receptor (AHR) mediates 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced toxicity that can lead to chloracne in humans. A characteristic of chloracne, in contrast to acne vulgaris, is shrinkage or loss of sebaceous glands. Acne vulgaris, on the other hand, is often accompanied by excessive sebum production. Here, we examined the role of AHR in lipid synthesis in human sebocytes using distinct classes of AHR ligands. Modulation of AHR activity attenuated the expression of lipogenic genes and key proinflammatory markers in the absence of canonical DRE-driven transcription of the AHR target gene CYP1A1. Furthermore, topical treatment with TCDD, which mediates DRE-dependent activity, and SGA360, which fails to induce DRE-mediated responses, both exhibited a decrease in the size of sebaceous glands and the number of sebocytes within each gland in the skin. To elucidate the mechanism of AHR-mediated repression of lipid synthesis, we demonstrated that selective AHR modulators, SGA360 and SGA315 increased the protein turnover of the mature sterol regulatory element-binding protein (mSREBP-1), the principal transcriptional regulator of the fatty acid synthesis pathway. Interestingly, selective AHR ligand treatment significantly activated the AMPK-dependent kinase (AMPK) in sebocytes. Moreover, we demonstrated an inverse correlation between the active AMPK and the mSREBP-1 protein, which is consistent with the previously reported role of AMPK in inhibiting cleavage of SREBP-1. Overall, our findings indicate a DRE-independent function of selective AHR ligands in modulating lipid synthesis in human sebocytes, which might raise the possibility of using AHR as a therapeutic target for treatment of acne., (© The Author(s) 2019. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)