Conception, synthèse et étude de nouveaux analogues de nucléosides (application dans le domaine des antiviraux et antitumoraux)

Malgré des progrès importants réalisés ces dernières années, la lutte contre les infections virales et les cancers demeure un problème de santé mondiale. Ce bref bilan met en évidence la nécessité de développer de nouvelles molécules pour contourner les limites des traitements disponibles actuellement. Il est donc nécessaire de développer de nouvelles méthodes de synthèse pour accéder à ces composés afin d évaluer leur activité biologique, et de nouveaux outils d analyse pour étudier les interactions mises en jeu. Cette thèse, articulée autour de trois grands thèmes, s inscrit dans ce contexte. Nous avons tout d abord mis au point une méthode de synthèse de 1,2,3-triazolyl-nucléosides substitués en positions 4 et 5, par une réaction tandem clic/addition électrophile. Des tests biologiques ont montré la forte activité anticancéreuse de ces composés contre la LMC. Nous avons ensuite développé une stratégie de modification post-synthétique d oligonucléotides par réaction clic. Elle permet de modifier de manière site-spécifique des oligonucléotides portant un groupement azide. Cette méthode présente plusieurs avantages et peut être utilisée pour de nombreuses applications, principalement pour le marquage spécifique des acides nucléiques. Enfin, nous avons conçu une nouvelle famille de ligands de l ARN TAR du VIH-1 capables de se lier sélectivement à certaines structures secondaires de type tige-boucle ou tige-renflement, via l action coopérative de plusieurs motifs de reconnaissance dont une nucléobase qui se lie spécifiquement à une paire de base UA. Parallèlement, une nouvelle méthode de criblage de triplet de bases par spectrométrie de masse est actuellement à l étude.Despite significant progress made in recent years, the fight against viral infections and cancer remains a global health problem. This brief summary underlines the need for new compounds in order to overcome the limits of the drugs currently available. Therefore, there is a significant need to develop new methodologies for the synthesis of new bioactive molecules, and new analytical tools for the study of the involved drug/biological target interactions. To this end, the main objective of this thesis is to address these issues following the investigation of three major themes. We first developed a strategy for the synthesis of 1,2,3-triazolyl-nucleosides substituted at positions 4 and 5, using a tandem click/electrophilic addition reaction. Biological tests showed strong anticancer activity against CML for these compounds. We then developed a strategy for post-synthetic modification of oligonucleotides by click chemistry. This reaction allows post-synthetic transformation of oligonucleotides bearing an azide group in a site-specific manner. Therefore, this strategy has a great potential in various applications such as specific labelling of nucleic acids. Finally, we designed a new family of HIV-1 TAR RNA ligands that selectively bind to secondary structures such as stem-loop or stem-bulge, through a cooperative action of several recognition patterns. Among them, we used a modified nucleobase that can specifically recognize an AU base pair. Meanwhile, a new method of screening for this type of base triplets by mass spectrometry is being investigated.NICE-BU Sciences (060882101) / SudocSudocFranceF

Mechanical ventilation and Streptococcus pneumoniae pneumonia alter mitochondrial homeostasis

Required mechanical ventilation (MV) may contribute to bacterial dissemination in patients with Streptococcus pneumoniae pneumonia. Significant variations in plasma mitochondrial DNA (mtDNA) have been reported in sepsis according to the outcome. The impact of lung stretch during MV was addressed in a model of pneumonia. Healthy or S. pneumoniae infected rabbits were submitted to MV or kept spontaneously breathing (SB). Bacterial burden, cytokines release, mitochondrial DNA levels, integrity and transcription were assessed along with 48-hour mortality. Compared with infected SB rabbits, MV rabbits developed more severe pneumonia with greater concentrations of bacteria in the lungs, higher rates of systemic dissemination, higher levels of circulating inflammatory mediators and decreased survival. Pulmonary mtDNA levels were significantly lower in infected animals as compared to non-infected ones, whenever they were SB or MV. After a significant early drop, circulating mtDNA levels returned to baseline values in the infected SB rabbits, but remained low until death in the MV ones. Whole blood ex-vivo stimulation with Streptococcus pneumoniae resulted in a reduction of polymorphonuclear leukocytes mitochondrial density and plasma mtDNA concentrations. Thus, persistent mitochondrial depletion and dysfunction in the infected animals submitted to MV could account for their less efficient immune response against S. pneumoniae