Proteolytic homeostasis is important at mucosal surfaces, but its actors and their precise role in physiology are poorly understood. Here we report that healthy human and mouse colon epithelia are a ...major source of active thrombin. We show that mucosal thrombin is directly regulated by the presence of commensal microbiota. Specific inhibition of luminal thrombin activity causes macroscopic and microscopic damage as well as transcriptomic alterations of genes involved in host-microbiota interactions. Further, luminal thrombin inhibition impairs the spatial segregation of microbiota biofilms, allowing bacteria to invade the mucus layer and to translocate across the epithelium. Thrombin cleaves the biofilm matrix of reconstituted mucosa-associated human microbiota. Our results indicate that thrombin constrains biofilms at the intestinal mucosa. Further work is needed to test whether thrombin plays similar roles in other mucosal surfaces, given that lung, bladder and skin epithelia also express thrombin.
Urinary tract infections (UTIs) are primarily caused by uropathogenic Escherichia coli (UPEC). This study aims to elucidate the role of the virulence factor HlyF in the epidemiology and ...pathophysiology of UTIs and investigate the dissemination of plasmids carrying the hlyF gene.
An epidemiological analysis was conducted on a representative collection of 225 UPEC strains isolated from community-acquired infections. Selected hlyF+ strains were fully sequenced using a combination of Illumina and Nanopore technologies. To investigate the impact of HlyF, a murine model of UTI was utilized to compare clinical signs, bacterial loads in the bladder, kidney, and spleen, onset of bacteraemia, and inflammation through cytokine quantification among wild-type hlyF+ strains, isogenic mutants, and complemented mutants.
Our findings demonstrate that 20% of UPEC encode the HlyF protein. These hlyF+ UPEC strains exhibited enhanced virulence, frequently leading to pyelonephritis accompanied by bloodstream infections. Unlike typical UPEC strains, hlyF+ UPEC strains demonstrate a broader phylogroup distribution and possess a unique array of virulence factors and antimicrobial resistance genes, primarily carried by ColV-like plasmids. In the murine UTI model, expression of HlyF was linked to the UPECs' capacity to induce urosepsis and elicit an exacerbated inflammatory response, setting them apart from typical UPEC strains.
Overall, our results strongly support the notion that HlyF serves as a significant virulence factor for UPECs, and the dissemination of ColV-like plasmids encoding HlyF warrants further investigation.
Abstract only
Background
Current therapies for Inflammatory Bowel Disease (IBD) are unsatisfactory for proper tissue healing. Serine proteases belong to locally produced host factors that can fuel ...inflammatory processes in tissue from IBD patients, in part through activation of Protease‐Activated Receptors (PAR). We have recently discovered that intestinal epithelium was able to produce active thrombin, suggesting that mucosa itself could be an important source of high thrombin in IBD.
Objectives
We first aimed to determine whether mucosal thrombin was upregulated in animal models of colitis and in tissues from IBD patients. We then determined whether local thrombin upregulation could contribute to local tissue malfunctions. Finally, we evaluated therapeutic feasibility of local delivering of either direct thrombin inhibitors or PAR antagonist in animal models of colitis.
Methods
Colonic tissue samples were obtained from diagnosed IBD patients undergoing colonoscopy at the Toulouse Hospital. Colitis was induced by administering trinitrobenzene sulfonic acid (TNBS) in the colon of Wistar rats or C57Bl6 mice. Human tissue collection and animal procedures received ethical approval from local ethic committees. Thrombin (100 U/ml, 10 days), direct thrombin inhibitor (dabigatran, 1 μg/kg, 4 days) and PAR1 antagonist (Vorapaxar, 2.5 mg/kg, 7 days) were administered in the colon of healthy or TNBS animals under light anesthesia. At time of the sacrifice, colonic tissues were harvested and disease severity was assessed. Thrombin expression was detected using PCR, western blot and immunofluorescence. Thrombin activity was quantified in tissue supernatants using specific enzymatic assays.
Results
We confirmed an increased thrombin protein expression in human mucosal tissue by immunofluorescence and western blots. We found that some, but not all, forms of active thrombin were upregulated, particularly in tissues from Crohn’s disease patients. As observed in human, we found that increased thrombin mRNA expression and activity is also a feature of colitis in animal models of colitis. We demonstrated
in vivo
that colonic exposure to high dose of active thrombin can cause mucosal damage and tissue dysfunctions. Specific inhibition of thrombin activity, and PAR1 antagonists prevent some intestinal damage in TNBS colitis.
Conclusions
In this study, using both animal models and human IBD tissues, we showed that upregulation of mucosal thrombin alone can lead to inflammatory insults. We propose that targeting downstream events from high thrombin activity, rather than inhibiting thrombin directly, might be a better option for IBD because mucosal thrombin at low dose plays an important role on maintaining tissue homeostasis. Considering these promising preclinical results on PAR1 antagonist, future clinical studies in IBD patients could therefore be rapidly envisioned, particularly in patients with the strongest upregulation of thrombin activity.
Abstract
Background and Aims
Thrombin levels in the colon of Crohn’s disease patients have recently been found to be elevated 100-fold compared with healthy controls. Our aim was to determine whether ...and how dysregulated thrombin activity could contribute to local tissue malfunctions associated with Crohn’s disease.
Methods
Thrombin activity was studied in tissues from Crohn’s disease patients and healthy controls. Intracolonic administration of thrombin to wild-type or protease-activated receptor-deficient mice was used to assess the effects and mechanisms of local thrombin upregulation. Colitis was induced in rats and mice by the intracolonic administration of trinitrobenzene sulphonic acid.
Results
Active forms of thrombin were increased in Crohn’s disease patient tissues. Elevated thrombin expression and activity were associated with intestinal epithelial cells. Increased thrombin activity and expression were also a feature of experimental colitis in rats. Colonic exposure to doses of active thrombin comparable to what is found in inflammatory bowel disease tissues caused mucosal damage and tissue dysfunctions in mice, through a mechanism involving both protease-activated receptors -1 and -4. Intracolonic administration of the thrombin inhibitor dabigatran, as well as inhibition of protease-activated receptor-1, prevented trinitrobenzene sulphonic acid-induced colitis in rodent models.
Conclusions
Our data demonstrated that increased local thrombin activity, as it occurs in the colon of patients with inflammatory bowel disease, causes mucosal damage and inflammation. Colonic thrombin and protease-activated receptor-1 appear as possible mechanisms involved in mucosal damage and loss of function and therefore represent potential therapeutic targets for treating inflammatory bowel disease.
A series of homoleptic copper(I), silver(I), and gold(I) complexes of two bisphosphine ligands {1,2‐bis(diphenylphosphino)benzene, dppb; bis2‐(diphenylphosphino)phenylether, POP} have been prepared. ...Whilst all three M(dppb)2BF4 complexes are tetracoordinate, this geometry is found only for the silver(I) complex with POP. Instead, Cu(POP)2+ and Au(POP)2+ adopt a trigonal coordination geometry with an uncoordinated phosphorus atom. A close inspection of the P–M bond lengths reveals an interesting trend. From the copper to silver and gold complexes, a substantial elongation is found. On the other hand, from the silver to gold compounds, a decrease in the M–P bond length is found. Indeed, gold(I) has a smaller van der Waals radius than silver(I) as a result of its peculiar relativistic effects. Electrochemical investigations revealed two oxidation processes for all of the M(dppb)2BF4 and M(POP)2BF4 complexes. The first oxidation is likely metal‐centered, whereas the second one corresponds to ligand‐centered processes in all cases. The emission properties of these compounds in solution, in frozen rigid matrices at 77 K, and in the solid state at room temperature have been systematically investigated. Although all of them are weak emitters in solution, remarkably high emission quantum yields were found in the solid state, in particular for Cu(dppb)2BF4 and Ag(dppb)2BF4. Finally, these two compounds were used for the fabrication of light‐emitting devices. Interestingly, both the copper(I) and the silver(I) complex afford quite broad electroluminescence spectra with white light emission.
Copper(I), silver(I), and gold(I) M(PP)2BF4 complexes have been prepared from two bisphosphine ligands, namely, 1,2‐bis(diphenylphosphino)benzene (dppb) and bis2‐(diphenylphosphino)phenylether (POP). Their electronic properties have been systematically investigated and rationalized as a combination of steric and electronic effects as well as by differences in their coordination geometries.
Homo- and heteroleptic copper(I) complexes obtained from various chelating bis-phosphine ligands and Cu(CH3CN)4BF4 have been used for the preparation of light emitting devices.
Le texte médiéval est soumis, dans sa construction et sa diffusion, à un travail éditorial qui en modifie nécessairement la nature et la réception. Face à la mouvance du texte au Moyen Âge et devant ...l’hétérogénéité des pratiques éditoriales médiévales, quels ont été les partis-pris scientifiques de l’édition de ces trente dernières années ? Depuis le XIXe siècle, la philologie a connu de nombreuses évolutions : comment le travail éditorial a-t-il intégré, adapté ou rejeté les acquis de ses prédécesseurs ? Par ailleurs, Internet est depuis ces quinze dernières années l’un des principaux vecteurs de transformation de l’édition de textes médiévaux et les enjeux de cette révolution éditoriale n’ont pas encore fait l’objet d’un bilan. La dématérialisation du livre suppose nécessairement une construction et une transmission différente du texte. On pourra notamment se demander dans quelle mesure cet outil parvient ou non à pallier les limites techniques du livre imprimé et à renouveler l’approche de l’objet manuscrit dans ce qu’il a de plus singulier. Cependant, l’édition sur Internet, la numérisation du patrimoine manuscrit et tous les outils électroniques de ressources textuelles qui se développent aujourd’hui n’imposent-ils pas un nouveau mirage ? Le sentiment d’un accès apparemment illimité et sans contrainte à l’objet manuscrit ne produit-il pas de nouveaux écarts interprétatifs entre le texte édité et le manuscrit ? Les contribution qui forment la partie « Études et travaux » de ce premier numéro en ligne de Perspectives médiévales apportent des éléments de réponse et des éclairages à ces questionnement qui traversent l’histoire et les pratiques contemporaines de l’édition des textes médiévaux. Sébastien Douchet
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