34 research outputs found
La présence intrigante de la myéloperoxydase dans les cellules épithéliales de la prostate, serait-elle impliquée dans les lésions prostatiques ?
La myĂ©loperoxydase (MPO) est une enzyme pro-oxydante qui est capable de causer des dommages aux biomolĂ©cules, comme les acides nuclĂ©iques, en les chlorant spĂ©cifiquement par le biais de lâacide hypochloreux (HClO) quâelle produit. La MPO Ă©tant prĂ©sente au sein de tissus prostatiques et impliquĂ©e dans divers mĂ©canismes physiopathologiques (incluant les cancers), il nous semblait important dâĂ©valuer dans ce travail lâimpact de sa prĂ©sence dans le dĂ©veloppement de lĂ©sions prostatiques ainsi que celui de la prĂ©sence de nuclĂ©osides spĂ©cifiquement modifiĂ©s par la MPO sur la rĂ©plication, la transcription et la traduction.Dans un premier temps, des mĂ©thodes ont Ă©tĂ© dĂ©veloppĂ©es afin de permettre lâanalyse quantitative des nuclĂ©osides de lâADN, de lâARN, du pool cytoplasmique et du plasma. Des protocoles dâextraction et dâhydrolyse de lâADN et de lâARN ainsi que des protocoles de purification et de dĂ©phoshorylation des nuclĂ©osides libres (pool cytoplasmique et plasma) ont Ă©tĂ© dĂ©veloppĂ©s ou adaptĂ©s afin de pouvoir ensuite sĂ©parer et quantifier les nuclĂ©osides par chromatographie liquide Ă ultra haute performance couplĂ©e Ă un spectromĂštre de masse Triple QuadupĂŽle (LC/MSMS). La mĂ©thode analytique LC/MSMS a Ă©tĂ© dĂ©veloppĂ©e et validĂ©e pour lâĂ©tude de six rĂ©sidus modifiĂ©s :les 5âchloro-(2â-dĂ©soxy)cytidines, les 8-chloro-(2â-dĂ©soxy)guanosines et les 8-oxo-(2â-dĂ©soxy)guanosines. Les quatre premiers Ă©tant des marqueurs spĂ©cifiques de la MPO et la formation des oxoguanosines pouvant ĂȘtre catalysĂ©e par lâenzyme (marqueur du stress oxydatif). Cette mĂ©thode a notamment lâavantage de prĂ©senter des limites de quantification plus faibles que dans la littĂ©rature, abaissant de 4 Ă 25 fois la sensibilitĂ© de la mĂ©thode selon le nuclĂ©oside.DeuxiĂšmement, nous nous sommes attardĂ©s sur lâimplication de la MPO dans le dĂ©veloppement de lĂ©sions prostatiques, en recherchant la prĂ©sence de ces nuclĂ©osides modifiĂ©s au sein de biopsies prostatiques de patients et de cultures cellulaires prostatiques traitĂ©es in vitro par la MPO, Ă lâaide des mĂ©thodes dĂ©veloppĂ©es prĂ©cĂ©demment. NĂ©anmoins, il sâest avĂ©rĂ© quâaucun chloronuclĂ©oside nâa Ă©tĂ© dĂ©tectĂ© dans ces cas de figure. Une mĂ©thode dâimmunomarquage par fluorescence a Ă©galement Ă©tĂ© dĂ©veloppĂ©e afin dâessayer de colocaliser la prĂ©sence de la MPO et son activitĂ© au sein de tissus prostatiques de patients souffrant de lĂ©sions prostatiques. Ce marquage avait pour but dâestimer lâactivitĂ© rĂ©elle de la prĂ©sence de MPO, et donc son rĂŽle au sein de ces lĂ©sions prostatiques mais un phĂ©nomĂšne dâautofluorescence nâa pas permis dâaboutir Ă des rĂ©sultats.Finalement, lâĂ©tude du plasma de patients hĂ©modialysĂ©s et de la pĂ©nĂ©tration intracellulaire de nuclĂ©osides modifiĂ©s depuis les liquides extracellulaires, tel que le plasma, vers le compartiment cellulaire ont Ă©tĂ© abordĂ©es. Ces expĂ©riences ont Ă©galement Ă©tĂ© rendues possibles grĂące aux mĂ©thodes dĂ©veloppĂ©es et validĂ©s prĂ©cĂ©demment. Puisquâil sâavĂšre que les Ă©chantillons de plasma de donneurs sains et de patients contiennent de la 5-chlorocytidine et que cette derniĂšre est capable de pĂ©nĂ©trer in vitro dans les cellules prostatiques, lâaspect de lâincorporation de ces nuclĂ©osides au sein de lâADN et lâARN a Ă©galement Ă©tĂ© approfondi. Il en rĂ©sulte que seule la 5-chlorocytidine sâincorpore dans lâARN lors de la transcription en prĂ©sence de nuclĂ©osides modifiĂ©s dans le milieu alors quâaucun nuclĂ©oside modifiĂ© ne sâincorpore dans lâADN lors de sa rĂ©plication. Ce dernier point est probablement dĂ» Ă une perte partielle ou complĂšte de lâactivitĂ© de certaines enzymes impliquĂ©es dans la rĂ©plication face aux chloronuclĂ©osides. De plus, lâĂ©tude du rendement de la traduction a montrĂ© que cette incorporation spĂ©cifique Ă©tait accompagnĂ©e dâune importante rĂ©duction de la traduction de lâARN en protĂ©ines.En conclusion, bien que ce travail ait permis dâĂ©tablir une mĂ©thode LC/MSMS sensible, prĂ©cise et exacte pour lâanalyse de nuclĂ©osides modifiĂ©s (chlorĂ©s et oxydĂ©s) dans diffĂ©rentes matrices, il nâa pas permis de mettre en Ă©vidence des chloronuclĂ©osides dans les tissus prostatiques de patients et d'impliquer la MPO dans le dĂ©veloppement de lĂ©sions prostatiques. Le rĂŽle de la MPO dans les tissus prostatiques reste donc encore Ă Ă©lucider. De plus, ce travail a mis pour la premiĂšre fois en Ă©vidence la prĂ©sence de 5-chlorocytidine dans le plasma humain ;ce mĂȘme nuclĂ©oside est capable de sâincorporer spĂ©cifiquement dans lâARN, influençant fortement le rendement de la production de protĂ©ines, ce qui soulĂšve encore des questions quant Ă son impact sur les fonctions et la viabilitĂ© des cellules en prĂ©sence de 5-chlorocytidine dans le milieu extracellulaire.Doctorat en Sciences biomĂ©dicales et pharmaceutiques (Pharmacie)info:eu-repo/semantics/nonPublishe
Syndrome dépressif : modalités et difficultés de sa prise en charge pour le médecin généraliste. Une étude qualitative menée en région PACA
Objectif : comprendre et analyser la prise en charge du syndrome dĂ©pressif par le mĂ©decin gĂ©nĂ©raliste et entendre son ressenti et ses apprĂ©hensions.MĂ©thode : Ă©tude qualitative menĂ©e auprĂšs de mĂ©decins gĂ©nĂ©ralistes installĂ©s en rĂ©gion PACA. Le recueil de donnĂ©es eÌtait effectueÌ lors dâentretiens individuels semi-dirigĂ©s aÌ lâaide dâun guide dâentretien. Les verbatims Ă©taient Ă©tudiĂ©s selon une analyse phĂ©nomĂ©nologique thĂ©matique Ă lâaide du logiciel NVivo. Les rĂ©sultats ont Ă©tĂ© recueillis, dĂ©crits puis interprĂ©tĂ©s par la mĂȘme personne.RĂ©sultats : les mĂ©decins rencontrent de plus en plus souvent des patients qui prĂ©sentent les symptĂŽmes dâun Ă©pisode dĂ©pressif caractĂ©risĂ© en consultation. LâĂ©tude rĂ©vĂšle la difficultĂ© de poser le diagnostic, mais aussi de le faire entendre au patient. La prise en charge, complexe et pluridimensionnelle, consiste le plus souvent en lâintroduction de traitements mĂ©dicamenteux, associĂ©e Ă la mise en place dâune psychothĂ©rapie. La gestion de la crise suicidaire paraĂźt ĂȘtre la plus laborieuse et reprĂ©sente une source dâinquiĂ©tude pour le praticien. La coordination entre les diffĂ©rents acteurs de soins pourrait ĂȘtre amĂ©liorĂ©e, notamment dans le dialogue avec le psychiatre et les autres acteurs de la santĂ© mentale comme le psychologue. Les mĂ©decins exprimaient plusieurs Ă©motions, satisfaction ou anxiĂ©tĂ© dans la gestion de la pathologie, agacement voire colĂšre envers le systĂšme de santĂ© dont ils dĂ©pendent, et paraissaient trĂšs impliquĂ©s vis-Ă -vis de leur patient jusquâĂ basculer dans la sympathie et la compassion. Conclusion : le syndrome dĂ©pressif est une entitĂ© complexe que le mĂ©decin gĂ©nĂ©raliste est de plus en plus amenĂ© Ă rencontrer dans sa pratique courante puisque sa prĂ©valence explose, câest une tendance qui sâaggrave chaque annĂ©e, avec un rebond particuliĂšrement prĂ©occupant Ă la suite de la pandĂ©mie du COVID-19.La place du mĂ©decin gĂ©nĂ©raliste semble centrale dans cette prise en charge de par sa disponibilitĂ©, sa proximitĂ© avec le patient et sa capacitĂ© Ă organiser une prise en charge adaptĂ©e Ă celui-ci. Le diagnostic reste difficile et lâutilisation dâoutils standardisĂ©s, notamment le score PHQ-9, paraĂźt intĂ©ressant pour dĂ©pister et dĂ©finir la gravitĂ© dâun Ă©pisode dĂ©pressif caractĂ©risĂ© dans la pratique courante. La prescription des mĂ©dicaments nâest pas obligatoire mais souvent nĂ©cessaire dans les cas dâĂ©pisodes dĂ©pressifs majeurs, leur utilisation semble pouvoir ĂȘtre optimisĂ©e afin de limiter la prescription « empathique » de benzodiazĂ©pines et maximiser lâutilisation des antidĂ©presseurs. La mise en place dâune psychothĂ©rapie est couramment proposĂ©e au patient, souvent associĂ©e au traitement mĂ©dicamenteux; les Ă©tudes tendent Ă la proposer comme seul traitement des Ă©pisodes dĂ©pressifs mineurs Ă modĂ©rĂ©s. La coordination entre les diffĂ©rents soignants de la maladie psychiatrique peut ĂȘtre amĂ©liorĂ©e, dâune part avec le psychiatre de ville, pour simplifier lâaccĂšs Ă ses consultations, mais aussi avec le psychologue qui est amenĂ© Ă prendre une place plus importante dans la prise en charge du patient dĂ©pressif Ă lâavenir.Le mĂ©decin gĂ©nĂ©raliste qui pratique lâĂ©coute active et/ou la psychothĂ©rapie se voit endosser les souffrances et traumatismes de ces patients, ce qui Ă terme semble avoir des consĂ©quences sur son propre Ă©tat Ă©motionnel, câest une rĂ©alitĂ© dont nous devons avoir conscience afin de prĂ©venir lâapparition de phĂ©nomĂšnes dâĂ©vitement et dâĂ©puisement
Phosphatidylethanolamine is a Key Regulator of Membrane Fluidity in Eukaryotic Cells
Adequate membrane fluidity is required for a variety of key cellular processes and in particular for proper function of membrane proteins. In most eukaryotic cells membrane fluidity is known to be regulated by fatty acids desaturation and cholesterol although some cells, such insect cells, are almost devoid of sterols synthesis. We show here that insect and mammalian cells present similar microviscosity at their respective physiological temperature. In order to investigate how both sterols and phospholipids control fluidity homeostasis we quantified the lipidic composition of insect SF9b and mammalian HEK 293T cells under normal or sterol-modified condition. As expected, insect cells show minimal sterols compared to mammalian cells. A major difference is also observed in phospholipid content as the ratio of phosphatidylethanolamine (PE) to phosphatidylcholine (PC) is inverted (four times higher in SF9 cells). In vitro studies in liposomes confirm that both cholesterol and PE can increase rigidity of the bilayer, suggesting that both can be used by cells to maintain membrane fluidity. We then show that exogenously increasing the cholesterol amount in SF9 membranes leads to a significant decrease in PE/PC ratio while decreasing cholesterol in HEK 293T cells using statin treatment leads to an increase in the PE/PC ratio. In all cases the membrane fluidity is maintained, indicating that both cell types combine regulation by sterols and phospholipids to control proper membrane fluidity.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Glycobiology analysis of Myeloperoxidase
Carbohydrates of glycoproteins, such as myleoperoxidase (MPO), play an important role in biosynthesis and influence properties of the mature protein such as solubility, stability, immunogenicity, or molecular recognition. In the case of MPO, five N-glycans sites were described in the literature (P. Van Antwerpen, J. Biol. Chem. 2010) and the activity of deglycosylated enzyme was decreased significantly by comparison with native enzyme. Indeed, at least 3 of the five glycosylation sites were able to interact with receptors or others membranes proteins; the others ones, localized at interface, contributes to dimer stabilization. Moreover, N-glycosylation of MPO could modulate the enzyme activity and could change in some pathologies. For example, a high mannose and a complex glycan structures were presented on residue N485 of MPO in samples from a leukemia patient (T. Ravnsborg, Bioch. Biophys. Acta, 2010). In this context, the development of mass spectrometry coupled to liquid chromatography that could quantify modifications sustained by the carbohydrate moiety of MPO, is of interest. After digestion by PNGase F from glycoproteins and a eventual permethylation, glycans analysis using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was carried out with different sources (ESI and APCI) and chromatographic systems.info:eu-repo/semantics/nonPublishe
Optimisation of parameters to improve protein sequence recovery by LC-MS/MS: application to apolipoprotein B-1000 and myeloperoxidase
info:eu-repo/semantics/nonPublishe
Oxidation of Apolipoprotein-B-100: a Proteomic Approach of Atherosclerosis
Atherosclerosis is an inflammatory disease characterized by the accumulation of lipids in the subendothelial space. Among the proatherogenic factors, the oxidative modifications of low-density lipoproteins (LDLs) are frequently mentioned. Apolipoprotein-B-100 (ApoB100) is the major protein of LDLs which stabilizes the particle, binds to the LDL receptor and plays a key role in lipoprotein metabolism. It is also a huge protein (550kDa) containing 4536 amino acids. Although many experiments have been done on copper-oxidized LDLs, other more physiological pathways of oxidation are known and myeloperoxidase (MPO) is one of them (1). MPO is indeed able to oxidize ApoB100 by catalysing the synthesis of hypochlorous acid (HOCl), a powerful oxidant, in the presence of hydrogen peroxide (H2O2) and chloride ions (2). However, the oxidative modifications of ApoB100 are still unclear. In order to determine characteristics of the specific MPO-dependent oxidation, we analyzed in vitro modifications of ApoB100 under 2 oxidative conditions: the oxidation of native-LDLs with (i) HOCl (to mimic MPO-oxidation), and (ii) the MPO/H2O2/Cl- system. ApoB100 was isolated from LDLs, digested using trypsin and the resulting peptides were analyzed by LC-autoMS/MS. As ApoB100 is a large protein, we optimized numbers of parameters involved in the analytical method and the data analyses, in order to increase the sequence coverage (79% instead of 50% in the literature) and to detect a maximum of modifications(3). The three major residues targeted by oxidative species were methionine, tryptophan and tyrosine, forming methionine sulfoxide, hydroxy-tryptophan and chloro-tyrosine, respectively. Although similar oxidized residues were detected in both conditions, several amino acids were specifically oxidized by MPO: 2 tyrosine residues (Y76 and Y1901) and some methionine residues (M723, M727, M1080, M1715, M1716 and M3986). ApoB100 modifications are therefore different under both experimental conditions, revealing important characteristics of the specific MPO-dependent oxidation, a physiologically relevant process. The MPO site-specific oxidations will be further examined in patients who present different clinical situations. (1) Daugherty and Roselaar, Cardiovascular Research 29 (1995). (2) Klebanoff, J Leukoc Biol 77 (2005). (3) Delporte et al. J. Anal. Biochem. 411 (2011).info:eu-repo/semantics/nonPublishe
In vitro effects of myeloperoxidase activity on DNA transcription and RNA translation
info:eu-repo/semantics/nonPublishe
Advancement in stationary phase for peptide separation helps in protein identification: Application to atheroma plaque proteomics using nano-chip liquid chromatography and mass spectrometry
In the last decades, proteomics has largely progressed. Mass spectrometry and liquid chromatography (LC) are generally used in proteomics. These techniques enable proper separation of peptides and good identification and/or quantification of them. Later, nano-scaled liquid chromatography, improvements of mass spectrometry resolution and sensitivity brought huge advancements. Enhancements in chemistry of chromatographic columns also brought interesting results. In the present work, the potency of identification of proteins by different nano-chip columns was studied and compared with classical LC column. The present study was applied to cardiovascular field where proteomics has shown to be highly helpful in research of new biomarkers. Protein extracts from atheroma plaques were used and proteomics data were compared. Results show that fewer spectra were acquired by the mass spectrometer when nano-chip columns were used instead of the classical ones. However, approximately 40% more unique peptides were identified by the recently optimized chip named Polaris-HR-chip-3C18 column, and 20% more proteins were identified. This fact leads to the identification of more low-abundance proteins. Many of them are involved in atheroma plaque development such as apolipoproteins, ceruloplasmin, etc. In conclusion, present data shows that recent developments of nanoLC column chemistry and dimensions enabled the improved detection and identification of low-abundance proteins in atheroma plaques. Several of them are of major interest in the field of cardiovascular disease.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Penetration of modified nucleosides in cultured cells and incorporation in RNA and DNA in cultured cells and incorporation in RNA and DNA
info:eu-repo/semantics/nonPublishe
DEVELOPMENT OF AN ANALYTICAL METHOD USING LC/MSMS TO QUANTIFY OXO(d)GUANOSINE AND CHLOROGUANOSINE IN URINE
info:eu-repo/semantics/nonPublishe