120589 research outputs found
Sort by
A Story of mRNA Caps: Investigating the Physiological Role of the Cap-specific Methyltransferase PCIF1 and the Decapping Enzyme NUDT2
No full textThe epitranscriptome represents an additional layer of gene regulation by modifying RNA molecules, influencing processes such as RNA stability, translation, and localization. The first part of this thesis focuses on the importance of messenger RNA (mRNA) modifications, especially those occurring at the 5′ end of the molecule. Eukaryotic mRNAs are capped at their 5' end with a modified guanine nucleotide usually referred to as the m7G canonical cap structure, which is essential for mRNA stability and translation. While many organisms incorporate a ribose methylation (Nm) on the first transcribed nucleotide, mammals and other vertebrates introduce an additional modification: N6-methyladenosine (m6Am) catalyzed by the cap-specific methyltransferase PCIF1. In this first project we showed that despite the prevalence of m6Am, Pcif1-depleted mice exhibited normal development and fertility, although they displayed reduced body weight compared to the wild-type controls. Gene expression analysis on several tissues of Pcif1 mutant mice supported a positive correlation between m6Am and transcript stability. We then performed a study across different organisms having a homologue of PCIF1. Interestingly, Drosophila Pcif1 lacks methyltransferase activity but maintains the ability to interact with RNA polymerase II, as does the mammalian counterpart. In contrast, in trypanosomes PCIF1 functions as a methyltransferase, contributing to a more complex cap modification N6,N6,2′-O-trimethyladenosine (m62Am) characteristic of these parasites, highlighting the evolutionary adaptability of PCIF1 and its diverse roles across species.
Beyond the canonical cap structure, RNAs can acquire non-canonical caps (NCCs) at their 5' end, often incorporated by RNA polymerase using nucleotide-like precursors. The second part of this thesis explores the role of one of these RNAs in vivo and the enzymes responsible for their turnover. The innate immune system employs a surveillance mechanism to distinguish between self and non-self nucleic acids, activating the interferon pathway in response to foreign genetic material. Cellular mRNAs, marked by a specific methylation on the first nucleotide, evade this immune detection. Our study identified a class of NNC-capped RNAs, Ap4A-capped RNAs, which accumulate in mice lacking the Nudt2 decapping enzyme. Moreover, we showed that NUDT2 is essential for their turnover, as it functions both as a hydrolase for Ap4A metabolite and as a decapping enzyme for Ap4A-capped RNAs. These RNAs lacks the immune-evading methylation on the first nucleotide and trigger the interferon response through RIG-I activation, mimicking pathogen infection. However, when we artificially installed this methylation, these Ap4A-RNAs were not immunogenic. Consequently, Nudt2-deficient mice phenocopy a rare human disease characterized by mutations on NUDT2; these phenotypes are similar to those observed in the interferonopathies, a condition characterized by excessive and uncontrolled interferon activation. Furthermore, we showed that suppressing the interferon pathway in Nudt2 mutant mice can rescue some of these phenotypes, suggesting a potential therapeutic approach for this disease.</p
The Pro ‐ Office Mindset . Anticorruption Beyond Legal Instruments
No full textThe article builds on how current legal punitive and regulatory anticorruption instruments miss ethically troublesome, but not necessarily unlawful, practices rooted in a corrupt institutional culture that normalizes nepotism, lobbying influence and other legally grey practices. It develops an analytical and normative philosophical toolkit centered on the corrupt dispositional sets—the mindset—of public officeholders, and reframes anticorruption initiatives as the promotion of a pro‑office mindset within an institutional ethics of office. The article discusses the limits and prospects of existing instruments, introduces the notion of the mindset, reconsiders anticorruption through the lenses of the mindset of public officeholders, and illustrates anticorruption measures that the approach justifies.</p
Metabolic interactions between the host and the gut microbiota in the entero-hepatic cycle
No full textThe enterohepatic cycle describes the recycling and exchange of compounds between the liver, gallbladder, and gastrointestinal (GI) tract. The GI tract harbors the gut microbiota—a complex community of microorganisms essential for host health. These microbes help extract energy from food and produce a wide array of metabolites, some of which participate in enterohepatic circulation. This cycle thus represents a metabolic handshake between host and microbiota, shaped by intestinal absorption, liver metabolism, and microbial activity.
This interplay is particularly relevant in drug metabolism. Most drugs are administered orally, making them subject to interaction with the gut microbiota before entering systemic circulation. These interactions are bidirectional: drugs can alter microbial composition and activity, while microbes can biotransform drugs, modifying their bioavailability, efficacy, or toxicity. Once absorbed, both parent drugs and their microbial metabolites undergo liver metabolism and may be excreted into bile, re-entering the cycle. The enterohepatic circulation thus critically influences drug pharmacokinetics.
In this thesis, we investigate metabolic host-microbiota interactions through intestinal permeability assays, liver metabolism studies, and microbiome profiling. We developed a novel in vitro workflow to assess absorption of bacterial (drug) metabolites across a monolayer of intestinal epithelial cells. Using this system, we screened 482 drugs and 170 bacterial drug metabolites. We observed that, in most cases, bacterial biotransformation did not significantly alter permeability. Complementing this, untargeted metabolomics of 7,240 compounds revealed that most bacterial metabolites do not cross the intestinal barrier unchanged, emphasizing the role of the gut barrier in shaping host-microbe metabolic exchange.
To study microbial effects on liver metabolism, we used gnotobiotic mouse models colonized with stool samples from three human donors. Liver transcriptomics and metabolomics analyses revealed microbiota-induced changes in key metabolic pathways, particularly lipid and drug metabolism. Notably, a significant fraction of drug-metabolizing enzymes and transporter genes were differentially expressed. By integrating transcriptomic and metabolomic data within metabolic networks, we identified four Cyp-gene–associated reactions consistently altered across all donor groups, along with 37 donor-specific metabolic neighborhoods—highlighting the influence of microbiome composition on liver metabolism and interindividual variability. Together, these findings deepen our understanding of the molecular dialogue between host and microbiota and underscore its importance in drug disposition, metabolic individuality, and personalized medicine.</p
Early and concomitant administration of norepinephrine and ilomedin improves microcirculatory perfusion without impairing macrocirculation in an intestinal ischemia-reperfusion injury swine model : a randomized experimental trial
No full textBackground: Intestinal ischemia-reperfusion injury is associated with both macrocirculatory and microcirculatory failure. Association of a vasoconstrictor in combination with a vasodilator such as ilomedin may improve macrocirculation parameters, microcirculation perfusion and reduce endothelial dysfunction. The primary objective was to demonstrate a difference in mean arterial pressure (MAP) after intestinal reperfusion with the concomitant administration of norepinephrine and ilomedin during ischemia compared with traditional hemodynamic treatment strategies (fluid resuscitation and vasopressors only). Secondary objectives were to demonstrate an improvement in peripheral and intestinal microcirculatory perfusion and endothelial dysfunction after intestinal reperfusion using this association.
Methods: We conducted a randomized preclinical trial in 21 large white pigs, in which a 2-h small bowel ischemia was performed using a segmental mesenteric occlusion model, followed by a 2-h reperfusion. Pigs were randomized into the following three groups: goal-directed fluid therapy, early administration of norepinephrine before reperfusion and early administration of ilomedin and norepinephrine before reperfusion. Macrocirculatory (MAP and Cardiac Index (CI), microcirculatory (Sublingual with SideStream Dark Field system and intestinal hemoglobin oxygen saturation with hyperspectral imaging) measurements and biological analysis (biomarkers of endothelial dysfunction) were performed.
Results: There were no significant differences in the MAP ( P = 0.499) and the CI ( P = 0.659) between the three groups. Perfused vessel density in sublingual microcirculation was significantly higher immediately after reperfusion and 2 h after reperfusion in the early administration of ilomedin and norepinephrine group compared with the other two groups ( P < 0.05). Hemoglobin oxygen saturation measured at the intestinal level was significantly higher immediately after reperfusion in the early administration of ilomedin and norepinephrine group compared with the other two groups ( P < 0.01). There were no significant differences in biomarkers of endothelial dysfunction between the three groups. Creatinine, AST and alkaline phosphatases increased significantly 2 h after reperfusion in the early administration of ilomedin and norepinephrine group compared with baseline ( P < 0.05).
Conclusions: Early administration of norepinephrine and ilomedin during ischemia improved short-term postreperfusion sublingual and intestinal microcirculation without worsening macrocirculatory parameters in an intestinal ischemia-reperfusion injury model. However, use of this strategy seemed to worsen both liver and kidney function.</p
L’action civile adhésive et la réforme du CPP : ça colle !
No full textL’action civile au pénale apparait comme le sujet évident qui fait la synthèse entre la procédure civile et la procédure pénale. Il s’agira de mener une brève réflexion sur l’action civile adhésive et les conséquences induites par la réforme du CPP entrée en vigueur le 1er janvier 2024.</p
Advancing Radical-Driven Ionization and Fragmentation Techniques for Isomer-Resolved Mass Spectrometry-Based Metabolomics and Lipidomics
No full textMass spectrometry has emerged as a key technology for both untargeted and targeted analysis of molecules in nature, including metabolites, lipids, proteins, pollutants, and synthetic chemicals. However, conventional tandem mass spectrometry with collision-induced dissociation (CID) is challenged by the unambiguous identification of isomers. To overcome this challenge, radical-driven fragmentation techniques, such as ultraviolet photodissociation (UVPD) and electron activated dissociation (EAD), have become essential tools for the structural elucidation of biomolecules, revealing structural features, such as double bond positions, that are inaccessible through CID of even-electron precursor ions. While the fragmentation of odd-electron radical cation precursors, often observed in EAD and UVPD, has been shown to access orthogonal structural features, little effort has been made to enhance radical cation formation within the ion source for subsequent MS2 experiments. Atmospheric pressure photoionization (APPI) is well suited for the generation of radical cations through charge-exchange reactions. To maintain radical cations, it is necessary to limit proton-transfer reactions with and ionization of solvent constituents in the gas phase. APPI avoids ionization of typical LC solvents and is less affected by undesired gas-phase reactions than other ionization techniques. To further reduce undesired gas-phase reactions and enable adaptive ion formation, it is necessary to decouple ionization conditions from chromatographic conditions. This can be achieved through µLC or supercritical-fluid chromatography (SFC) with post‑column addition of methanol and with chlorobenzene as a dopant allows radical cation formation for a wide range of analytes, including lipids, amino acids, and drug molecules. Notably, the CID of radical cations with a collision energy spread from 10 to 70 eV produces spectra that are orthogonal to [M+H]+ CID and closely resemble those of electron ionization (EI). This allows the use of radical cation CID spectra for EI library searches and in-silico structural elucidation tools based on electron ionization using liquid chromatography. Altogether, this enables the comprehensive screening of xenobiotics in biological samples, with identical retention times between electrospray ionization (ESI) and APPI with SFC facilitating feature cross-validation of putative molecules. The ability to fine-tune collision energies enhances the signal of ions related to structural features, such as methyl and double bond positions, and provides access to structural features absent in EI and [M+H]+ CID spectra. This enables the differentiation of isomeric metabolites, steroids and lipids through low-energy CID. For lipids, this permits rule-based de novo annotation of double bonds. The analysis can be automated by rule-based approaches using the R package MsRadaR using both high- and low-resolution instrumentation in targeted and untargeted experiments. Moreover, differential mobility spectrometry (DMS) of radical cations and protonated molecules exhibits different selectivity and allows the separation of electronic isomers of the same molecule as well as cannabinoid isomers. This illustrates that APPI is not only a complementary ionization technique to electrospray, but also an excellent option for the structural elucidation of isomers, metabolites, and lipids.</p
Dinuclear Heteroleptic Erbium Complexes for Improving Molecular-Based Light Upconversion in Solution?
No full textIn an attempt to boost molecular-based excited-state absorption (ESA) via cross-relaxation (CR), the back-to-back ditridentate polyaromatic 2,2',6,6'-tetrakis(1-methyl-1H -benzo[d ]imidazole-2-yl)-4,4'-bipyridine ligand (L4 ) was reacted with neutral [Ln(hfac)3 ] lanthanide cargoes (Ln = Y, Eu, and Er and H-hfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione) to give dinuclear erbium [(hfac)3 LnL4 Ln(hfac)3 ] ≡ [L4 Ln2 (hfac)6 ] adducts. Their crystal structures confirm the formation of dimeric molecular scaffolds made of two nine-coordinated trivalent [LnN3 O6 ] chromophores separated by a 4,4'-bipyridine bridge with Ln···Ln distances within the nanometric range (Eu···Eu = 11.69 Å, Y···Y = 11.65 Å, and Er···Er = 12.12 Å). Thermodynamic studies in dichloromethane provide critical insights into the formation and stability of these adducts. Under near-infrared (NIR) excitation at 801 nm in solution, [L4 Er2 (hfac)6 ] exhibits ESA light upconversion with blueish-green emissions at 525 and 542 nm corresponding to Er(2 H11/2 ,4 S3/2 → 4 I15/2 ) transitions. Thanks to the pertinent speciation in dichloromethane, we could extract a reliable upconversion quantum yield and brightness for the targeted dinuclear [L4 Er2 (hfac)6 ] adduct in solution. They largely overpass by 2 orders of magnitude those of the unsaturated mononuclear [L4 Er(hfac)3 ] intermediate but remain comparable to data reported for related saturated monomeric adducts in the same conditions. No global beneficial cross-relaxation effect could thus be unambiguously identified
Syndromes de Marfan et apparentés
No full textMarfan syndrome and related disorders describe a group of rare genetic diseases affecting connective tissue and characterised by cardiovascular, ocular and musculoskeletal manifestations. Marfan syndrome presents with a marfanoid habitus, ectopia lentis, dilatation of the aorta and typical musculoskeletal features. Other related disorders share similar characteristics. Loeys-Dietz syndrome distinguishes itself with generalized arterial tortuosities and aneurysms as well as, occasionally, hypertelorism and bifid uvula; patients with Beals syndrome have congenital articular contractures and craniofacial anomalies. Lujan-Fryns and Shprintzen-Goldberg syndromes, as well as homocystinuria, are often associated with intellectual disability.Les syndromes de Marfan et apparentés désignent un groupe de maladies génétiques rares affectant le tissu conjonctif et caractérisé par des atteintes cardiovasculaires, oculaires et musculosquelettiques. Le syndrome de Marfan se présente avec un habitus marfanoïde, une ectopie du cristallin, une dilatation de l’aorte et des atteintes musculosquelettiques évocatrices. Les syndromes dits apparentés ont des manifestations similaires. Celui de Loeys-Dietz se différencie par une tortuosité et des anévrismes artériels généralisés et parfois, un hypertélorisme et une luette bifide ; le syndrome de Beals comprend des contractures articulaires congénitales et des anomalies craniofaciales distinctives. Les syndromes de Lujan-Fryns et de Shprintzen Goldberg sont, en revanche, le plus souvent associés à une déficience intellectuelle, tout comme l’homocystinurie
Antibiotics in inflammatory arthritis and background population one year before and after diagnosis : a nationwide drug utilization study
No full textObjectives: To describe antibiotic use in patients with inflammatory arthritis (IA) and in the background population (BP) within one year before and after IA diagnosis.
Methods: Using data from Danish nationwide registries, we identified all adults with a first-time diagnosis of RA, PsA, or AS/spondyloarthritis (AS/SpA) from 2010 through 2018. For each IA patient, we randomly sampled 10 persons from the BP, matched on sex and birthdate. We calculated the prevalence (n [%]) of any antibiotic dispensing and the total antibiotic dispensing in the year before and after diagnosis.
Results: We identified 28 504 new-onset IA patients (RA, n = 16 130; PsA, n = 5988; AS/SpA, n = 6386) and 285 040 BP individuals. Within one year before diagnosis, the total amount of dispensed antibiotics was higher in both RA, PsA and As/SpA compared with the BP (prevalence rate ratios [PRR], 1.48 [1.46; 1.51]; 1.67 [1.62; 1.72]; 1.52 [1.47; 1.56], respectively). The amount increased with 22% in IA patients three months before diagnosis compared with the preceding three-month period. Although the prevalence of any antibiotic dispensing in IA patients decreased in the year following the diagnosis (IA; 40.6%), the total one-year antibiotic dispensing remained constant in RA (PRR 0.99 [0.97; 1.01]), decreased in PsA (0.91 [0.87; 0.94]) and increased in AS/SpA (1.08 [1.04; 1.12]) patients after diagnosis compared with before.
Conclusion: Antibiotics are more frequently dispensed to individuals developing IA compared with the BP. Antibiotic utilization patterns change after IA diagnosis with marked differences among IA subgroups.</p