Recherche de molécules impliquées dans l'inhibition de la régénération axonale dans le colliculus inférieur

Des cultures organotypiques de colliculus inférieur (CI) prélevées sur des animaux âgés de 6 jours (P6) sont capables de régénérer leurs axones commissuraux après lésion. Les mêmes axones sont incapables de traverser le site de lésion si le CI est prélevé sur des animaux au stade P10. L'objectif de ce travail de thèse était d'identifier des molécules pouvant participer à l'inhibition de la régénération axonale dans le CI au stade P10. Dans ce but, des banques enrichies en molécules du stade P6 ou du stade P10 ont été construites par hybridation soustractive suppressive. Après criblage par dot-bot, six clones ont été sélectionnés. Quatre clones du stade P10 correspondaient à des molécules connues : la neuroleukine (NLK), la calmoduline, Rho7/Rnd2 et la cortactine. Deux autres étaient de fonction inconnue : A11 et SSTM (short seven transmembrane protein). L'étude de la localisation des messagers de ces molécules par hybridation in situ révélé une expression préférentiellement neuronale dans le cerveau. De plus, leur niveau d'expression augmente dans le cerveau au cours du développement post-natal. Par immunohistochimie, des profils différents sont obtenus. La NLK est observée dans les soma neuronaux et dans les axones. La calmoduline est présente dans le corps cellulaire des neurones et dans les dendrites. Rho7/Rhd2 est détecté dans les axones et les cellules gliales de Bergmann du cervelet. La cortactine se localise au niveau de la région juxta-membranaire intracellulaire du soma des neurones et des dendrites. A11 et SSTM sont observés dans les neurones au niveau de la membrane cytoplasmique somatique et dendritique, où elles se localisent dans les contacts post-synaptiques, ainsi que dans les prolongements gliaux. Après une lésion du cortex cérébral, la NLK, la cortactine, A11 et SSTM sont surexprimés par les astrocytes réactifs. La NLK est en plus observée dans les axones lésés. La calmoduline et le Rho7/Rhd2 ne semblent pas être surexprimés après lésion. L'ensemble de ces travaux apporte de nouvelles données sur l'expression cérébrale des six molécules étudiées et suggère l'implication de certaines d'entre elles dans le processus de régénération axonale dans le système nerveux central.Sectionned commissural axons of inferior colliculus (IC) organotypique cultures from 6-day old animals (P6) are able to regenerate. In similar conditions, injured axons of IC from P10 are unable to cross through the lesion site. The purpose of this thesis work was to identify molecules potentially involved in the inhibition of axonal regeneration observed in the IC by P10. In this aim, suppression substractive hybridization was used to construct libraries enriched in P6 and P10 molecules. After a dot-blot screening, six clon,es were selected. Four of them, from P10 library, were known molecules, i.e. neuroleukin (NLK), calmodulin, Rho7/Rnd2 and cortactin. Two others were of unknown function i.e. A11 and SSTM (short seven transmembrane protein). In situ hybridization experiments have revealed that these molecule messengers are preferentially expressed by neurons in the brain. In addition, their level of expression increases in the brain during post-natal development. Immunohistochemistry showsdifferent patterns of distribution. NLK is observed in axons and neuronal somata. Calmodulin is present in the cell body and dendrites of neurons. Rho7/Rnd2 is detected in axons and in the cerebellar Bergmann glial cells. Cortactin is localized at the intracellular juxta-membrane level in the neuronal somata and dendrites. A11 and SSTM are present both at the cell body plasma membrane level and in dendrites, where they are localized in post-synaptic contacts, and in glial processes. After a mechanical trauma in the cerebral cortex region, NLK, cortactin, A11 and SSTM are overexpressed by reactive astrocytes. Moreover, NLK is observed in the regenerating axons. Calmodulin and Rho7/Rnd2 were not found to be overexpressed after the injury.All these works expend the knowledge of the cerebral expression of the six studied molecules and suggest the implication of some of them in the axonal regeneration process in the central nervous system.BORDEAUX2-BU Santé (330632101) / SudocSudocFranceF

BACE1 as a potential biomarker for Alzheimer\u27s disease

The diagnosis of Alzheimer\u27s disease (AD) relies principally on clinical criteria for probable and possible AD as defined by the NINCDS-ADRDRA. The field is desperately lacking of biological markers to assist with AD diagnosis and verification of treatment efficacy. According to the Consensus Report of the Working Group on Molecular and Biochemical Markers of Alzheimer\u27s Disease, in order to qualify as a biomarker the sample in question must adhere to certain basic requirements, including the ability to: reflect AD pathology and differentiate it from other dementia with an 80% sensitivity; be reliable and reproducible; be easy to perform and analyze; remain relatively inexpensive. Beta secretases are crucial enzymes in the pathogenesis of AD. Given its primary role in brain amyloidogenesis and its ubiquitous expression, one may consider measuring peripheral BACE1 levels and activity as biomarkers of AD, like performed in the brain and cerebrospinal fluid. However, very little is known about the periphery and whether peripheral BACE1 is involved in AD pathogenesis or mirrors AD progression. Moreover, no investigation has focused on the possibility of monitoring peripheral BACE1 to assess the efficiency of BACE1 inhibitors during the course of clinical trials. Part of the problem may be attributed to the lack of sensitive molecular tools which are absolutely necessary to use BACE1 as a biomarker. In this review we evaluate the progress and feasibility of developing BACE1 as a biomarker for AD in different tissues

COR388 (atuzaginstat): an investigational gingipain inhibitor for the treatment of Alzheimer disease

INTRODUCTION: Evidence from in vitro and in vivo studies demonstrates that amyloid beta (Aβ) oligomers have potent, broad-spectrum antimicrobial properties created by fibrils that entrap pathogens and disrupt their membranes. Data suggest that Aβ may play a protective role in the innate immune response to microbial infections and that Aβ in the brain plays a damaging role when the inflammatory response is not well controlled. AREAS COVERED: This paper describes the relationship between periodontal disease and Alzheimer disease (AD), the role of and its secreted gingipains in AD, and the potential of the gingipain inhibitor atuzaginstat (COR388) to modulate AD neuropathologies. EXPERT OPINION: is opsonized by Aβ42, is capable of entering the brain, and is an accelerant of neuropathologies in rodent models of AD. Thus, in our opinion, this bacteria is highly likely to be a pathogen capable of initiating or precipitating the progression of AD, which agrees with the pathogen hypothesis of clinical AD development

Lecanemab (BAN2401): an anti-beta-amyloid monoclonal antibody for the treatment of Alzheimer disease

INTRODUCTION: Nearly a dozen monoclonal antibodies (mAbs) directed against beta-amyloid (Aβ) have been developed for the treatment of Alzheimer disease (AD), and most of these mAbs are undergoing clinical trials. Newer mAbs have targeted more specific Aβ types. Lecanemab Eisai has a high affinity for large and soluble Aβ protofibrils. Data from phase 2 clinical trials have suggested the possibility of a robust efficacy signal and manageable risk of amyloid-related imaging abnormalities (ARIAs). Lecanemab is currently being studied in phase 3 trials. AREAS COVERED: This article briefly reviews mAbs that target Aβ in AD and discusses the biology, mechanism of action, and targets of lecanemab. EXPERT OPINION: mAbs that target Aβ are an important focus of therapeutic development for AD, with several soon to be considered for US Food and Drug Administration approval. The experience of aducanumab informs the development of other mAbs, such as lecanemab. One consideration is the conformation of Aβ targets. Targeting monomeric species has not resulted in robust clinical efficacy, whereas targeting Aβ in the form of oligomers, protofibrils, and plaques has shown evidence of slowing clinical decline. Another consideration is that mAbs will require safety monitoring for ARIAs

Targeting tumor necrosis factor alpha for Alzheimer’s disease

Alzheimer’s disease (AD) affects an estimated 44 million individuals worldwide, yet no therapeutic intervention is available to stop the progression of the dementia. Neuropathological hall-marks of AD are extracellular deposits of amyloid beta (Aβ) peptides assembled in plaques, intraneuronal accumulation of hyperphosphorylated tau protein forming tangles, and chronic inflammation. A pivotal molecule in inflammation is the pro-inflammatory cytokine TNF-α. Several lines of evidence using genetic and pharmacological manipulations indicate that TNF-α signaling exacerbates both Aβ and tau pathologies in vivo. Interestingly, preventive and intervention anti-inflammatory strategies demonstrated a reduction in brain pathology and an amelioration of cognitive function in rodent models of AD. Phase I and IIa clinical trials suggest that TNF-α inhibitors might slow down cognitive decline and improve daily activities in AD patients. In the present review, we summarize the evidence pointing towards a beneficial role of anti-TNF-α therapies to prevent or slow the progression of AD. We also present possible physical and pharmacological interventions to modulate TNF-α signaling in AD subjects along with their limitations

Neuronal Cell Cultures from Aplysia for High-Resolution Imaging of Growth Cones

Neuronal growth cones are the highly motile structures at the tip of axons that can detect guidance cues in the environment and transduce this information into directional movement towards the appropriate target cell. To fully understand how guidance information is transmitted from the cell surface to the underlying dynamic cytoskeletal networks, one needs a model system suitable for live cell imaging of protein dynamics at high temporal and spatial resolution. Typical vertebrate growth cones are too small to quantitatively analyze F-actin and microtubule dynamics. Neurons from the sea hare Aplysia californica are 5-10 times larger than vertebrate neurons, can easily be kept at room temperature and are very robust cells for micromanipulation and biophysical measurements. Their growth cones have very defined cytoplasmic regions and a well-described cytoskeletal system. The neuronal cell bodies can be microinjected with a variety of probes for studying growth cone motility and guidance. In the present protocol we demonstrate a procedure for dissection of the abdominal ganglion, culture of bag cell neurons and setting up an imaging chamber for live cell imaging of growth cones