Gastrointestinal stability and cytotoxicity of bacteriocins from gram-positive and gram-negative bacteria : a comparative in vitro study

Bacteriocins are receiving increased attention as potent candidates in food preservation and medicine. Although the inhibitory activity of bacteriocins has been studied widely, little is known about their gastrointestinal stability and toxicity toward normal human cell lines. The aim of this study was to evaluate the gastrointestinal stability and activity of microcin J25, pediocin PA-1, bactofencin A and nisin using in vitro models. In addition cytotoxicity and hemolytic activity of these bacteriocins were investigated on human epithelial colorectal adenocarcinoma cells (Caco-2) and rat erythrocytes, respectively. Pediocin PA-1, bactofencin A, and nisin were observed to lose their stability while passing through the gastrointestinal tract, while microcin J25 is only partially degraded. Besides, selected bacteriocins were not toxic to Caco-2 cells, and integrity of cell membrane was observed to remain unaffected in presence of these bacteriocins at concentrations up to 400 µg/mL. In hemolysis study, pediocin PA-1, bactofencin A, and nisin were observed to lyse rat erythrocytes at concentrations higher than 50 µg/mL, while microcin J25 showed no effect on these cells. According to data indicating gastrointestinal degradation and the absence of toxicity of pediocin PA-1, bactofencin A, and microcin J25 they could potentially be used in food or clinical applications

Fate and Biological Activity of the Antimicrobial Lasso Peptide Microcin J25 Under Gastrointestinal Tract Conditions

The bacteriocin microcin J25 (MccJ25) inhibits the growth of Gram-negative pathogens including Salmonella and Shigella species, and Escherichia coli. This 21-amino acid peptide has remarkable stability to heat and extreme pH values and resistance to many proteases, thanks to a characteristic lasso structure. In this study, we used the dynamic simulator TIM-1 as gastro-intestinal tract model to evaluate the stability and antibacterial activity of MccJ25 during passage through the proximal portion of the human gastrointestinal tract. MccJ25 concentration was measured in the different simulator sections by HPLC, and inhibition of Salmonella enterica serotype Enteritidis was evaluated using qualitative and quantitative assays. LC-MS/MS analysis and subsequent molecular networking analysis on the Global Natural Product Social Molecular Networking platform (GNPS) and analysis of the peptide degradation in the presence of proteolytic enzymes mimicking the gastro-intestinal conditions permitted to delineate the fate of MccJ25 through identification of the main degradation products. MccJ25 was relatively stable under gastric conditions, but degraded rapidly in the compartment mimicking the duodenum, notably in the presence of pancreatin. Among pancreatin components, elastase I appeared primarily responsible for MccJ25 breakdown, while α-chymotrypsin was less efficient

Design of a hydraulic riveter

Thesis (B.S.)--University of Illinois, 1910

A top-down systems biology view of microbiome-mammalian metabolic interactions in a mouse model

Symbiotic gut microorganisms (microbiome) interact closely with the mammalian host's metabolism and are important determinants of human health. Here, we decipher the complex metabolic effects of microbial manipulation, by comparing germfree mice colonized by a human baby flora (HBF) or a normal flora to conventional mice. We perform parallel microbiological profiling, metabolic profiling by 1H nuclear magnetic resonance of liver, plasma, urine and ileal flushes, and targeted profiling of bile acids by ultra performance liquid chromatography–mass spectrometry and short-chain fatty acids in cecum by GC-FID. Top-down multivariate analysis of metabolic profiles reveals a significant association of specific metabotypes with the resident microbiome. We derive a transgenomic graph model showing that HBF flora has a remarkably simple microbiome/metabolome correlation network, impacting directly on the host's ability to metabolize lipids: HBF mice present higher ileal concentrations of tauro-conjugated bile acids, reduced plasma levels of lipoproteins but higher hepatic triglyceride content associated with depletion of glutathione. These data indicate that the microbiome modulates absorption, storage and the energy harvest from the diet at the systems level

Rôle de la région N-terminale 1-16 du peptide amyloïde Abeta dans la deposition amyloïde associée à la maladie d'Alzheimer : Plasticité conformationnelle, modifications liées au vieillissement protéique et interaction avec les ions Zn2+

Amyloid deposits are extracellular fibrillar lesions associated with Alzheimer's disease that are mainly composed of the amyloid peptide, Aβ. The transition of Aβ helical or random secondary structure towards a β-sheet conformation, with concomitant peptide fibrillization, is a proposed mechanism of plaque formation. Amyloid deposits contain a high content of zinc ions, and display an important heterogeneity of the N-terminal part of Aβ, with troncated, isomerized and racemized forms. These modifications as well as the interaction with Zn2+ have been suggested to take part in Aβ fibrillogenesis, or to occur after the amyloid deposition, given the accessibility of the N-terminal region of Aβ within amyloid fibrils.Our study was mainly focused on the 1-16 N-terminal region of Aβ, Aβ(1-16), which is suggested to be implicated in Zn2+ binding and displays several sites that are able to undergo protein-aging related modifications. Our aim was to characterize the different molecular mechanisms which alter Aβ and could inhibit the recognition of this potential therapeutic target, by anti-Aβ antibodies in particular.We showed by circular dichroism (CD) and NMR spectroscopy the conformational plasticity of Aβ(1-16), and characterized the structures displayed by the peptide in aqueous medium and in membrane-mimicking medium. Furthermore, we examined the in vitro aging of Aβ(1-16) and identified the modified peptides. The Aβ(1-16)/Zn2+ complex was studied by CD, NMR and ESI-MS, allowing to propose a model for zinc binding to Aβ(1-16). Aβ(1-16) binds to zinc in a tetrahedral geometry, with H6, E11, H13 et H14 as zinc ligands. Furthermore, we showed that this binding modifies the in vitro aging profile of Aβ(1-16) and induces an agonist effect on the recognition of this region of Aβ by cognate antibodies. Two of the modified peptides produced upon in vitro aging, Aβ(1-16)-L-IsoAsp7 and Aβ(1-16)-D-Asp7, were characterized by NMR, illustrating a local change of the conformation in the H6-S8 region, as compared to Aβ(1-16), but no major conformational rearrangement. Zn2+ binding to Aβ(1-16)-L-IsoAsp7 appears to result from a different coordination motif, the IsoAsp residue being involved.Finally, a complementary investigation undertaken on Aβ(1-40) indicates that the presence of Zn2+ or of anti-Aβ antibodies raised against the N-terminal part of Aβ prevents Aβ fibrillogenesis and rather leads to the production of different types of aggregates. Our results suggest that the above mentioned interactions between the 1-16 N-terminal region of Aβ and either Zn2+ or anti-Aβ antibodies inhibit the fibrillogenesis of the full-length amyloid peptide.Les dépôts amyloïdes sont des dépôts fibrillaires extracellulaires associés à la maladie d'Alzheimer, dont le constituant principal est le peptide amyloïde (Aβ). La fibrillogenèse d'Aβ s'accompagne d'une transconformation du peptide, depuis une structure secondaire principalement en hélice au voisinage des membranes ou non structurée en milieu aqueux vers une structure en feuillet β. Cette transconformation est couplée à une oligomérisation. Les plaques amyloïdes renferment une quantité importante de cations métalliques, en particulier Zn2+, et le peptide amyloïde y est caractérisé par une grande hétérogénéité de sa partie N-terminale qui présente des troncations et des isomérisations/racémisations. Ces modifications et l'interaction d'Aβ avec les cations ont été proposées comme des facteurs contribuant à la déposition amyloïde.Afin de caractériser ces différents mécanismes moléculaires, nous avons examiné la région N-terminale 1-16 du peptide amyloïde, Aβ(1-16), qui apparaît impliquée dans l'interaction du peptide avec les cations métalliques et renferme plusieurs sites susceptibles de subir des modifications liées au vieillissement protéique. Du fait de son accessibilité au sein des fibrilles amyloïdes, ce domaine d'Aβ constitue une cible thérapeutique potentielle, notamment pour un traitement immunologique.Au cours de ce travail, nous avons mis en évidence la plasticité conformationnelle d'Aβ(1-16) par dichroïsme circulaire (DC) et RMN et nous avons caractérisé la structure qu'adopte ce peptide en milieu aqueux et en milieu mimant un environnement membranaire. Nous avons également identifié les formes produites par vieillissement in vitro. Le complexe Aβ(1-16)/Zn2+ a été examiné par DC, RMN et ESI-MS, ce qui a conduit à établir un modèle d'attachement du cation Zn(II) au peptide Aβ(1-16). Ce modèle implique une coordination tétraédrique de Zn(II), les résidus H6, E11, H13 et H14 étant identifiés comme ligands. Nous avons de plus montré que l'interaction Aβ(1-16)/Zn2+ modifie le profil de vieillissement protéique et exerce un effet agoniste sur la reconnaissance de la région 1-16 d'Aβ par des anticorps spécifiques. La conformation de deux peptides isomères issus du vieillissement d'Aβ(1-16), Aβ(1-16)-L-IsoAsp7 et Aβ(1-16)-D-Asp7 a été examinée par RMN. Un changement conformationnel local est observé dans la région H6-S8 par rapport à Aβ(1-16), mais pas de remaniement conformationnel global. L'étude de l'interaction Aβ(1-16)-L-IsoAsp7/Zn2+ par RMN a suggéré la participation du résidu IsoAsp7 à la coordination du cation Zn(II).Enfin, une étude complémentaire entreprise sur Aβ(1-40) a mis en évidence l'absence de fibrillogenèse du peptide en présence d'ions Zn2+ ou d'anticorps ciblant la région N-terminale d'Aβ, au profit de la formation de différents types d'agrégats. Ces résultats suggèrent que les différentes interactions établies entre la région N-terminale 1-16 d'Aβ et Zn2+ ou des anticorps anti-Aβ inhiberaient la fibrillogenèse du peptide amyloïde pleine longueur

Vers l'obtention d'ions multichargés en UV-MALDI-TOF

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Toward a versatile protocol for radiocarbon and proteomics analysis of ancient collagen

International audienc

Analyse par spectrométrie de masse du pont thio-ester intramoléculaire de la protéine C3 du système du complément et de ses adduits covalents avec des composés inhibiteurs

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Analyse directe par UV-MALDI-TOF de la matrice extra-cellulaire de cellules cultivées sur membrane polyester

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