TSPO ligand residence time influences human glioblastoma multiforme cell death/life balance

Abstract Ligands addressed to the mitochondrial Translocator Protein (TSPO) have been suggested as cell death/life and steroidogenesis modulators. Thus, TSPO ligands have been proposed as drug candidates in several diseases; nevertheless, a correlation between their binding affinity and in vitro efficacy has not been demonstrated yet, questioning the specificity of the observed effects. Since drug-target residence time is an emerging parameter able to influence drug pharmacological features, herein, the interaction between TSPO and irDE-MPIGA, a covalent TSPO ligand, was investigated in order to explore TSPO control on death/life processes in a standardized glioblastoma cell setting. After 90 min irDE-MPIGA cell treatment, 25 nM ligand concentration saturated irreversibly all TSPO binding sites; after 24 h, TSPO de-novo synthesis occurred and about 40 % TSPO binding sites resulted covalently bound to irDE-MPIGA. During cell culture treatments, several dynamic events were observed: (a) early apoptotic markers appeared, such as mitochondrial membrane potential collapse (at 3 h) and externalization of phosphatidylserine (at 6 h); (b) cell viability was reduced (at 6 h), without cell cycle arrest. After digitonin-permeabilized cell suspension treatment, a modulation of mitochondrial permeability transition pore was evidenced. Similar effects were elicited by the reversible TSPO ligand PIGA only when applied at micromolar dose. Interestingly, after 6 h, irDE-MPIGA cell exposure restored cell survival parameters. These results highlighted the ligand-target residence time and the cellular setting are crucial parameters that should be taken into account to understand the drug binding affinity and efficacy correlation and, above all, to translate efficiently cellular drug responses from bench to bedside

Involvment of Cytosolic and Mitochondrial GSK-3β in Mitochondrial Dysfunction and Neuronal Cell Death of MPTP/MPP+-Treated Neurons

Aberrant mitochondrial function appears to play a central role in dopaminergic neuronal loss in Parkinson's disease (PD). 1-methyl-4-phenylpyridinium iodide (MPP+), the active metabolite of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), is a selective inhibitor of mitochondrial complex I and is widely used in rodent and cell models to elicit neurochemical alterations associated with PD. Recent findings suggest that Glycogen Synthase Kinase-3β (GSK-3β), a critical activator of neuronal apoptosis, is involved in the dopaminergic cell death. In this study, the role of GSK-3β in modulating MPP+-induced mitochondrial dysfunction and neuronal death was examined in vivo, and in two neuronal cell models namely primary cultured and immortalized neurons. In both cell models, MPTP/MPP+ treatment caused cell death associated with time- and concentration-dependent activation of GSK-3β, evidenced by the increased level of the active form of the kinase, i.e. GSK-3β phosphorylated at tyrosine 216 residue. Using immunocytochemistry and subcellular fractionation techniques, we showed that GSK-3β partially localized within mitochondria in both neuronal cell models. Moreover, MPP+ treatment induced a significant decrease of the specific phospho-Tyr216-GSK-3β labeling in mitochondria concomitantly with an increase into the cytosol. Using two distinct fluorescent probes, we showed that MPP+ induced cell death through the depolarization of mitochondrial membrane potential. Inhibition of GSK-3β activity using well-characterized inhibitors, LiCl and kenpaullone, and RNA interference, prevented MPP+-induced cell death by blocking mitochondrial membrane potential changes and subsequent caspase-9 and -3 activation. These results indicate that GSK-3β is a critical mediator of MPTP/MPP+-induced neurotoxicity through its ability to regulate mitochondrial functions. Inhibition of GSK-3β activity might provide protection against mitochondrial stress-induced cell death

Etude des arcs électriques à l'ouverture et de la résistance de contact pour des contacts AgNi dans leurs appareillages.

National audienc

Analysis of temporal and spatial contact voltage fluctuation during fretting in automotive connectors

International audienceOur study is focused on contact voltage fluctuations during fretting with small amplitudes of a few tens microns which generate damage of the contact of connectors. A contact composed by a pin and a curve female part are submitted to vibration cyclic of 25µm at 100Hz and supplied with current ramp from 0.1mA to 3A in two directions. With the help of fast devices, the voltage and position data acquisition are conjointly made with the common DC contact voltage dur-ing fretting. Some unexpected results state that voltage fluctuation occurs in the different stage of fretting and start at the beginning of test in the insertion direction and located at half of track. These small voltage fluctuations around few mV increased to few hundred millivolts and may reach few volt at ultimate phase of degradation with random distribu-tion along the track. When the motion is stopped the ohmic conduction of such fretting interface is ensured only when the subsequent voltage stay below a sutured value depending on the degradation and current level. It is found that the common three phases of degradation have a different saturation voltage which appears at higher and higher current and induce voltage breakdown. Regarding that symmetric characterises is obtained in two the directions current ramp the semiconducting behaviour effect of oxide layers on debris particle is negligible. As voltage-current experimental data was well fitted to similar equation of granular material conduction we have deduced the fitting parameters (V l and I 0) of interface

Le rôle de l’évolution des paysages holocènes dans le comblement des bas-fonds du Parc national de la Lopé, moyenne vallée de l’Ogooué au Gabon

International audienceSedimentological and geochemical analyses and 14C dating were performed for a sedimentary core sample from the Lopé 2 marsh in the northern zone of Gabon’s Lopé National Park. The results produced a division of the core sample into three main units. The basal part of the core sample was dated to 2,320 years cal BP. At this time, the Lopé 2 marsh was a topographic hollow that flooded sporadically during the rainy season. This unit corresponds to a soil formation of clay, quartz and highly decomposed organic matter. The upper boundary of this unit corresponds to the end of the climatic deterioration that affected central Africa around 2,500 years BP. The second unit represents the period from 2,320 to 585 years cal BP. This shows a gradual decrease in the flow of quartz that reflects the increasing relative density of the marsh vegetation as the climate became more humid. The organic matter in this unit is of mixed origin, relatively abundant and with a high content of refractory material. The third unit, representing the period from 585 years cal BP to the present, shows plant cover associated with developing marshland (whichbegan in unit 2) that was sustained by the humid climate. The organic matter here is rich in biological material.Des analyses sédimentologique et géochimique associées à des datations 14C ont été réalisées sur une carotte sédimentaire prélevée dans le marais Lopé 2 situé dans la zone nord du Parc national de la Lopé au Gabon. L’ensemble des résultats obtenus nous amène à subdiviser cette carotte en trois principales uni- tés. La première unité part de la base de la carotte à 2 320 ans cal BP. Durant cette période, le marais Lopé 2 est une dépres- sion topographique inondée occasionnellement en saison des pluies. Cette unité correspond à une formation pédologique constituée d’argile, de quartz et de matière organique très dégradée. La fin de cette unité correspond à la fin de la péjoration climatique qu’a connue l’Afrique centrale autour de 2 500 ans BP. La deuxième unité va de 2 320 à 585 ans cal BP. Elle montre une diminution pro- gressive du flux de quartz témoignant de la densification relative de la végétation du marais en conséquence d’une humidification du climat. La matière organique de cette unité relativement abondante et riche en constituants réfractaires est d’origine mixte. La troisième unité qui va de 585 ans cal BP à l’actuel connaît un couvert végétal associé au développement du marais (amorcé à l’unité 2), entretenu par l’humidité du climat. Ici, la matière organique est riche en constituants biologiques

Tracking zoonotic pathogens using bloodsucking flies as 'flying syringes'

About 60% of emerging infectious diseases in humans are of zoonotic origin. Their increasing number requires the development of new methods for early detection and monitoring of infectious agents in wildlife. Here, we investigated whether blood meals from hematophagous flies could be used to identify the infectious agents circulating in wild vertebrates. To this aim, 1230 blood-engorged flies were caught in the forests of Gabon. Identified blood meals (30%) were from 20 vertebrate species including mammals, birds and reptiles. Among them, 9% were infected by different extant malaria parasites among which some belonged to known parasite species, others to new parasite species or to parasite lineages for which only the vector was known. This study demonstrates that using hematophagous flies as 'flying syringes' constitutes an interesting approach to investigate blood-borne pathogen diversity in wild vertebrates and could be used as an early detection tool of zoonotic pathogens