Polyphenolic C-glucosidic ellagitannins present in oak-aged wine inhibit HIV-1 nucleocapsid protein

HIV-1 nucleocapsid protein (NC) is a nucleic acid chaperone implicated in several steps of the virus replication cycle and an attractive new target for drug development. In reverse transcription, NC destabilizes nucleic acid secondary structures and catalyzes the annealing of HIV-1 TAR RNA to its DNA copy (cTAR) to form the heteroduplex TAR/cTAR. A screening program led to the identification of the plant polyphenols acutissimins A and B as potent inhibitors of NC in different assays. These two flavano-ellagitannins, which are found in wine aged in oak barrels, exhibited different mechanisms of protein inhibition and higher potency relatively to their epimers, epiacutissimins A and B, and to simpler structures notably representing hydrolytic fragments and metabolites therefrom

Développement de sondes moléculaires appliquées à l'étude de la biosynthèse des flavonoïdes

Les flavonoïdes sont des substances naturelles connues pour leurs propriétés anti-inflammatoires, anti-cancéreuses ou anti-virales chez l'homme. Chez les végétaux, ils participent notamment à leur protection vis-à-vis d'organismes pathogènes. La voie de biosynthèse des flavonoïdes est l'une des plus étudiées chez les plantes et notamment chez la vigne : Vitis vinifera. Cependant, la ou les enzymes impliquées dans les dernières étapes de biosynthèse conduisant aux anthocyanes et aux proanthocyanidines restent, à ce jour, peu ou pas connues. L étude que nous proposons a pour but de concevoir des sondes moléculaires d affinité susceptibles d interagir avec une ou plusieurs enzymes impliquées dans ces dernières étapes de biosynthèse. Ces sondes, basées sur la technologie émergeante de protéomique chimique : Activity- and affininity Based Protein Profiling (ABPP), ont été validées à l aide d une enzyme modèle : la leucoanthocyanidine dioxygénase (LDOX). Elles ont ensuite été appliquées à des extraits complexes de protéines issus de Vitis vinifera.Flavonoids are natural substances known for their anti-inflammatory, anti-cancerous and anti-virals properties in humans. In plants, they are one of the molecules responsible for fighting pathogens. The flavonoid biosynthesis pathway as been greatly studied in plants, especially in that of the grapevine: Vitis vinifera. However, detailed studies of the exact function of the enzymes involved in the last steps of the biosynthesis of anthocyanins and proanthocyanidins remains largely lacking.The study that we propose is to synthesize molecular probes designed to specifically interact with enzymes involved in the last stages of flavonoids biosynthesis. Our probes, based on the emerging chemical proteomic technology, activity- and affinity based protein profiling (ABPP), were validated with a model enzyme: leucoanthocyanidin dioxygenase (LDOX). After which, they were used with complex protein mixtures from Vitis vinifera.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Toward Whole-Brain Minimally-Invasive Vascular Imaging

Imaging the brain vasculature can be critical for cerebral perfusion monitoring in the context of neurocritical care. Although ultrasensitive Doppler (UD) can provide good sensitivity to cerebral blood volume (CBV) in a large field of view, it remains difficult to perform through the skull. In this work, we investigate how a minimally invasive burr hole, performed for intracranial pressure (ICP) monitoring, could be used to map the entire brain vascular tree. We explored the use of a small motorized phased array probe with a non-implantable preclinical prototype in pigs. The scan duration (18 min) and coverage (62 $\pm$ 12 % of the brain) obtained allowed global CBV variations detection (relative in brain Dopplerdecrease =-3[-4-+16]% \& Dopplerincrease. = +1[-3-+15]%, n = 6 \& 5) and stroke detection (relative in core Dopplerstroke. =-25%, n = 1). This technology could one day be miniaturized to be implanted for brain perfusion monitoring in neurocritical care

Rapid Screening of Ellagitannins in Natural Sources via Targeted Reporter Ion Triggered Tandem Mass Spectrometry

Complex biomolecules present in their natural sources have been difficult to analyze using traditional analytical approaches. Ultrahigh-performance liquid chromatography (UHPLC-MS/MS) methods have the potential to enhance the discovery of a less well characterized and challenging class of biomolecules in plants, the ellagitannins. We present an approach that allows for the screening of ellagitannins by employing higher energy collision dissociation (HCD) to generate reporter ions for classification and collision-induced dissociation (CID) to generate unique fragmentation spectra for isomeric variants of previously unreported species. Ellagitannin anions efficiently form three characteristic reporter ions after HCD fragmentation that allows for the classification of unknown precursors that we call targeted reporter ion triggering (TRT). We demonstrate how a tandem HCD-CID experiment might be used to screen natural sources using UHPLC-MS/MS by application of 22 method conditions from which an optimized data-dependent acquisition (DDA) emerged. The method was verified not to yield false-positive results in complex plant matrices. We were able to identify 154 non-isomeric ellagitannins from strawberry leaves, which is 17 times higher than previously reported in the same matrix. The systematic inclusion of CID spectra for isomers of each species classified as an ellagitannin has never been possible before the development of this approach

Leptomeningeal collaterals regulate reperfusion in ischemic stroke

Recanalization is the mainstay of ischemic stroke treatment. However, even with timely clot removal, many stroke patients recover poorly. Leptomeningeal collaterals (LMCs) are pial anastomotic vessels with yet unknown functions. Utilizing a thrombin-based mouse model of stroke and the gold standard fibrinolytic treatment rt-PA, we here show that LMCs play a critical role in preserving vascular function in ischemic territories. We applied laser speckle contrast imaging, ultrafast ultrasound, and two-photon microscopy, to show that after thrombolysis, LMCs allow for gradual reperfusion resulting in small infarcts. On the contrary, in mice with poor LMCs, distal segments of recanalized arteries collapse and deleterious hyperemia causes hemorrhage and mortality. Accordingly, in stroke patients with poor collaterals undergoing thrombectomy, rapid reperfusion resulted in hemorrhagic transformation and unfavorable recovery. Thus, we identify LMCs as key components regulating reperfusion after stroke. Future therapeutic interventions should aim to enhance collateral function, allowing for gradual reperfusion of ischemic tissues after stroke

Leptomeningeal collaterals regulate reperfusion in ischemic stroke and rescue the brain from futile recanalization.

Recanalization is the mainstay of ischemic stroke treatment. However, even with timely clot removal, many stroke patients recover poorly. Leptomeningeal collaterals (LMCs) are pial anastomotic vessels with yet-unknown functions. We applied laser speckle imaging, ultrafast ultrasound, and two-photon microscopy in a thrombin-based mouse model of stroke and fibrinolytic treatment to show that LMCs maintain cerebral autoregulation and allow for gradual reperfusion, resulting in small infarcts. In mice with poor LMCs, distal arterial segments collapse, and deleterious hyperemia causes hemorrhage and mortality after recanalization. In silico analyses confirm the relevance of LMCs for preserving perfusion in the ischemic region. Accordingly, in stroke patients with poor collaterals undergoing thrombectomy, rapid reperfusion resulted in hemorrhagic transformation and unfavorable recovery. Thus, we identify LMCs as key components regulating reperfusion and preventing futile recanalization after stroke. Future therapeutic interventions should aim to enhance collateral function, allowing for beneficial reperfusion after stroke

Désaromatisation oxydante asymétrique de phénols (développements méthodologiques et application à la synthèse de la scyphostatine)

Les réactifs iodés hypervalents (i.e. iodanes) et les complexes métalliques en milieu oxydant sont des outils particulièrement efficaces pour réaliser la réaction de désaromatisation oxydante de phénols et donner ainsi accès à des motifs cyclohexa-2,4-diénone. Ces travaux de thèse ont permis d'étudier le développement de versions asymétriques de cette réaction de désaromatisation contrôlée soit par le substrat dans le cas de l utilisation d iodanes, soit par le réactif lorsqu un complexe métal/ligands chiraux est privilégié. Cette méthodologie a ensuite été appliquée à la synthèse de la (+)-scyphostatine, un inhibiteur naturel de la sphingomyélinase neutre.AbstractBORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Développement d'outils chimiques pour l'élucidation de la biosynthèse des flavonoïdes du raisin (anthocyanes versus proanthocyanidines)

Ces dernières années, des progrès remarquables ont été accomplis afin d élucider la biosynthèse des flavonoïdes. Cependant les dernières étapes menant à la formation des proanthocyanidines ou tannins condensés issus de la vigne, restent à ce jour inconnues. Dans le but de déterminer si une ou plusieurs enzyme(s) spécifique(s) sont impliquées dans cette voie de biosynthèse, nous avons développé une approche de protéomique chimique, impliquant des matrices d affinité constituées de substrats de type flavanols greffés sur un support solide. La validation de ces outils à l aide de LDOX, une enzyme issue de Vitis vinifera a pu être menée à bien dans le cadre de ces travaux de thèse.Remarkable progress toward the complete elucidation of the biosynthesis of flavonoids has been accomplished during the last decade, but the final step leading to proanthocyanidins still remain to be elucidated, in particular, the exact nature of starter and extension units as well as the enzymatic or non enzymatic condensation process. In order to answer whether some specific enzymes are involved in the biosynthesis of grapevine proanthocyanidins, we have developped a chemical proteomics approach, with an affinity chromatography-based tool in which a flavanol type substrate is loaded on an appropriate solid support. The validation of these tools with the LDOX enzyme from Vitis vinifera was developped and performed in this Ph.D work.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Synthèse de dérivés de polyphénols bioactifs pour l'étude de leurs interactions avec des protéines

Ce travaille de thèse concerne la synthèse de dérivés de polyphénols de type flavanol, ellagitannins C-glucosidique et procyanidine, modifiés avec un espaceur comportant une biotine terminale. Cette biotine terminale a permis d immobiliser ces polyphénols modifiés sur des surfaces SPR, permettant ainsi l étude d interactions polyphénol-protéine en temps réel. Ainsi, la topoisomerase II alpha et l'actine fibrilaire ont montré une plus grande affinité pour les polyphenols de type ellagitannins que pour ceux de type flavanol. Nous avons également pu montrer que d autres protéines (BSA, myoglobine, actine globulaire, streptavidine, collagen type I) n avaient pas d interaction avec les flavanols et les ellagitannins.This work concerns the synthesis of derivatives of polyphenols of the type flavanol, C-glucosidic ellagitannin and procyanidin, which are modified to bear a spacer ending with a biotin unit. This biotin ending unit allowed to immobilize these modified polyphenols on to SPR surfaces, which allowed the study of polyphenol-protein interactions in real time. The proteins topoisomerase II alpha and fibrilar actin showed a higher affinity for the polyphenols of the type ellagitannins than for those of the type flavanol. It was also showed that other proteins (BSA, myoglobin, globular actin, streptavidin, collagen type I) did not interact with either the flavanols or the ellagitanninsBORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF