Mechanistic study and potential therapeutic targets of synucleinopathies

Mon projet de thèse s’inscrit dans l’étude des synucléinopathies, une famille de maladies neurodégénératives. Les trois principales synucléinopathies sont la maladie de Parkinson, l’atrophie multisystématisée et la démence à corps de Lewy. Ces maladies sont caractérisées par une perte de neurones dans des régions cérébrales spécifiques et la présence d’inclusions intra-cytoplasmiques positives pour l’α-synucléine dans les neurones (Corps de Lewy) ou dans les oligodendrocytes (Inclusions gliales cytoplasmiques). Les causes d’induction de ces maladies restent encore inconnues et les traitements curatifs sont inexistants. L’objectif de mon travail de thèse visait à étudier les mécanismes neurodégénératifs et de potentielles cibles thérapeutiques dans le contexte des synucléinopathies. Je me suis tout d’abord intéressée aux mécanismes impliqués dans la transmission de l’α-synucléine issue de patients atteints de l’atrophie multisystématisée. Ce travail nous a permis de développer un potentiel nouveau modèle de l’atrophie multisystématisée chez la souris et le primate non-humain, par la transmission de l’α-synucléine dans le cerveau. Dans un deuxième temps, nous nous sommes intéressés à des cibles thérapeutiques éventuelles pour la maladie de Parkinson dans un même modèle animal de la pathologie. Nous avons pu vérifier l’efficacité et la pertinence de trois différentes stratégies ciblant plusieurs mécanismes affectés dans la maladie de Parkinson dans le but d’induire une protection des neurones dopaminergiques de la substance noire des souris. Nous avons pu démontrer une dérégulation des niveaux de zinc au cours de la pathologie qui a suscité l’intérêt de cibler son homéostasie dans le cerveau à travers une molécule chélatrice du zinc. Ensuite, la surexpression d’un facteur de transcription impliqué dans la survie des neurones dopaminergiques ainsi que dans le stress oxydatif et le protéasome a montré son intérêt comme cible thérapeutique de la maladie de Parkinson. Enfin, une molécule anti-agrégative a aussi démontré sa capacité à induire une neuroprotection. En résumé, ces travaux montrent d’abord l’importance de l’α-synucléine dans la mise en place et la progression des synucléinopathies, mais aussi la nécessité de cibler d’autres mécanismes dérégulés dans ces pathologies pour proposer des nouvelles stratégies thérapeutiques.My thesis focused on the study of synucleinopathies, a family of neurodegenerative diseases. The three main synucleinopathies are Parkinson’s disease, multiple system atrophy, and dementia with Lewy bodies. These diseases are characterized by the loss of neurons in various brain regions and the presence of intracytoplasmic α-synuclein-positive inclusions. These inclusions are located either in neurons (Lewy bodies) or in oligodendrocytes (Glial cytoplasmic inclusions). The trigger and cause for the formation of these inclusions remain unknown, and no curative treatments currently exist. The objective of my thesis was to study the neurodegenerative mechanisms and potential therapeutic strategies of these synucleinopathies. For this, I was first interested in the mechanisms implicated in the transmission of α-synuclein from multiple system atrophy patients. This allowed us to develop a potential new model to study multiple system atrophy in both mice and non-human primates by spreading of α-synuclein within the brain. In the second part, we wanted to investigate potential therapeutic targets in the same model of Parkinson’s disease. This study confirmed the efficacy and pertinence of three different strategies that target various mechanisms of Parkinson’s disease to induce the protection of dopaminergic neurons of the substantia nigra in a mouse model. By modulating zinc levels, we demonstrated the importance of zinc concentrations in the brain and the therapeutic interest in targeting metal homeostasis via specific chelators. We then used viral vectors to overexpress a transcription factor implicated in dopaminergic neuron survival, oxidative stress and proteasome activity in the substantia nigra of a mouse model of Parkinson’s disease. Finally, we used an anti-aggregative molecule to determine its efficacy in protecting neurons in the same mouse model. Altogether, this thesis work showed the implication of α-synuclein in triggering and propagating synucleinopathies, the importance of targeting this protein, and other dysregulated cellular mechanisms to discover potential therapies

Etude des mécanismes et cibles thérapeutiques des synucléinopathies

My thesis focused on the study of synucleinopathies, a family of neurodegenerative diseases. The three main synucleinopathies are Parkinson’s disease, multiple system atrophy, and dementia with Lewy bodies. These diseases are characterized by the loss of neurons in various brain regions and the presence of intracytoplasmic α-synuclein-positive inclusions. These inclusions are located either in neurons (Lewy bodies) or in oligodendrocytes (Glial cytoplasmic inclusions). The trigger and cause for the formation of these inclusions remain unknown, and no curative treatments currently exist. The objective of my thesis was to study the neurodegenerative mechanisms and potential therapeutic strategies of these synucleinopathies. For this, I was first interested in the mechanisms implicated in the transmission of α-synuclein from multiple system atrophy patients. This allowed us to develop a potential new model to study multiple system atrophy in both mice and non-human primates by spreading of α-synuclein within the brain. In the second part, we wanted to investigate potential therapeutic targets in the same model of Parkinson’s disease. This study confirmed the efficacy and pertinence of three different strategies that target various mechanisms of Parkinson’s disease to induce the protection of dopaminergic neurons of the substantia nigra in a mouse model. By modulating zinc levels, we demonstrated the importance of zinc concentrations in the brain and the therapeutic interest in targeting metal homeostasis via specific chelators. We then used viral vectors to overexpress a transcription factor implicated in dopaminergic neuron survival, oxidative stress and proteasome activity in the substantia nigra of a mouse model of Parkinson’s disease. Finally, we used an anti-aggregative molecule to determine its efficacy in protecting neurons in the same mouse model. Altogether, this thesis work showed the implication of α-synuclein in triggering and propagating synucleinopathies, the importance of targeting this protein, and other dysregulated cellular mechanisms to discover potential therapies.Mon projet de thèse s’inscrit dans l’étude des synucléinopathies, une famille de maladies neurodégénératives. Les trois principales synucléinopathies sont la maladie de Parkinson, l’atrophie multisystématisée et la démence à corps de Lewy. Ces maladies sont caractérisées par une perte de neurones dans des régions cérébrales spécifiques et la présence d’inclusions intra-cytoplasmiques positives pour l’α-synucléine dans les neurones (Corps de Lewy) ou dans les oligodendrocytes (Inclusions gliales cytoplasmiques). Les causes d’induction de ces maladies restent encore inconnues et les traitements curatifs sont inexistants. L’objectif de mon travail de thèse visait à étudier les mécanismes neurodégénératifs et de potentielles cibles thérapeutiques dans le contexte des synucléinopathies. Je me suis tout d’abord intéressée aux mécanismes impliqués dans la transmission de l’α-synucléine issue de patients atteints de l’atrophie multisystématisée. Ce travail nous a permis de développer un potentiel nouveau modèle de l’atrophie multisystématisée chez la souris et le primate non-humain, par la transmission de l’α-synucléine dans le cerveau. Dans un deuxième temps, nous nous sommes intéressés à des cibles thérapeutiques éventuelles pour la maladie de Parkinson dans un même modèle animal de la pathologie. Nous avons pu vérifier l’efficacité et la pertinence de trois différentes stratégies ciblant plusieurs mécanismes affectés dans la maladie de Parkinson dans le but d’induire une protection des neurones dopaminergiques de la substance noire des souris. Nous avons pu démontrer une dérégulation des niveaux de zinc au cours de la pathologie qui a suscité l’intérêt de cibler son homéostasie dans le cerveau à travers une molécule chélatrice du zinc. Ensuite, la surexpression d’un facteur de transcription impliqué dans la survie des neurones dopaminergiques ainsi que dans le stress oxydatif et le protéasome a montré son intérêt comme cible thérapeutique de la maladie de Parkinson. Enfin, une molécule anti-agrégative a aussi démontré sa capacité à induire une neuroprotection. En résumé, ces travaux montrent d’abord l’importance de l’α-synucléine dans la mise en place et la progression des synucléinopathies, mais aussi la nécessité de cibler d’autres mécanismes dérégulés dans ces pathologies pour proposer des nouvelles stratégies thérapeutiques

A New Rise of Non-Human Primate Models of Synucleinopathies

International audienceSynucleinopathies are neurodegenerative diseases characterized by the presence of α-synuclein-positive intracytoplasmic inclusions in the central nervous system. Multiple experimental models have been extensively used to understand better the mechanisms involved in the pathogenesis of synucleinopathy. Non-human primate (NHP) models are of interest in neurodegenerative diseases as they constitute the highest relevant preclinical model in translational research. They also contribute to bringing new insights into synucleinopathy’s pathogenicity and help in the quest and validation of therapeutical strategies. Here, we reviewed the different NHP models that have recapitulated key characteristics of synucleinopathy, and we aimed to highlight the contribution of NHP in mechanistic and translational approaches for synucleinopathies

Targeting α-synuclein for PD Therapeutics: A Pursuit on All Fronts

International audienceParkinson's Disease (PD) is characterized both by the loss of dopaminergic neurons in the substantia nigra and the presence of cytoplasmic inclusions called Lewy Bodies. These Lewy Bodies contain the aggregated α-synuclein (α-syn) protein, which has been shown to be able to propagate from cell to cell and throughout different regions in the brain. Due to its central role in the pathology and the lack of a curative treatment for PD, an increasing number of studies have aimed at targeting this protein for therapeutics. Here, we reviewed and discussed the many different approaches that have been studied to inhibit α-syn accumulation via direct and indirect targeting. These analyses have led to the generation of multiple clinical trials that are either completed or currently active. These clinical trials and the current preclinical studies must still face obstacles ahead, but give hope of finding a therapy for PD with time

The Zinc Ionophore Clioquinol Reduces Parkinson’s Disease Patient-Derived Brain Extracts-Induced Neurodegeneration

International audienceParkinson's disease (PD) is pathologically characterized by intracellular α-synuclein-rich protein aggregates, named Lewy bodies (LB), and by the progressive loss of dopaminergic neurons in the substantia nigra. Several heavy metals, including zinc (Zn), have been suggested to play a role in PD progression, although the exact role of Zn in neurodegeneration remains to be fully elucidated. To address this gap, we investigated the effects of Zn modulation on the progression of degeneration in mice injected with PD patient-derived LB-extracts carrying toxic α-synuclein aggregates. Zn modulation was achieved using either a clioquinol-enriched diet, a Zn ionophore that redistributes cellular Zn, or a Zn-enriched diet that increases Zn levels. Clioquinol treatment significantly prevented dopaminergic neurodegeneration and reduced α-synuclein-associated pathology in LB-injected mice, while no differences were observed with Zn supplementation. Biochemical analyses further demonstrate that the expression levels of vesicle-specific Zn transporter ZnT3 in the striatum of LB-injected mice treated with clioquinol were decreased, suggesting an intracellular redistribution of Zn. Additionally, we found that clioquinol modulates the autophagy-lysosomal pathway by enhancing lysosomal redistribution within the neuronal compartments. Collectively, we found that in vivo pharmacological chelation of Zn, by dampening Zn-mediated cytotoxicity, can result in an overall attenuation of PD-linked lysosomal alterations and dopaminergic neurodegeneration. The results support zinc chelation as a disease-modifying strategy for treating PD

L‐DOPA regulates α‐synuclein accumulation in experimental parkinsonism

International audienceAimsWidespread accumulation of misfolded α‐synuclein aggregates is a key feature of Parkinson’s disease (PD). Although the pattern and extent of α‐synuclein accumulation through PD brains is known, the impact of chronic dopamine‐replacement therapy (the gold‐standard pharmacological treatment of PD) on the fate of α‐synuclein is still unknown. Here, we investigated the distribution and accumulation of α‐synuclein in the 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) non‐human primate of PD and determined the effect of chronic L‐DOPA treatment on MPTP‐induced α‐synuclein pathology.MethodsWe measured the density of α‐synuclein and tau immuno‐positive neurons in the substantia nigra, putamen, hippocampal CA1 region, temporal cortex and dentate nucleus of control, MPTP and MPTP+L‐DOPA‐treated monkeys. Moreover, we also extracted and quantified Triton‐X (TX) soluble and insoluble α‐synuclein in putamen and hippocampus samples from a separate cohort of control, MPTP and MPTP+L‐DOPA‐treated monkeys.ResultsMPTP‐induced α‐synuclein accumulation in NHP model of PD was not limited to the substantia nigra but also occurred in the putamen, hippocampal CA1 region and temporal cortex. Tau was increased only in the temporal cortex. Moreover, increased intraneuronal TX insoluble α‐synuclein was truncated, but not in the structural form of Lewy bodies. The MPTP‐induced increase in α‐synuclein levels was abolished in animals having received L‐DOPA in all the brain regions, except in the substantia nigra.ConclusionsDopamine replacement therapy can dramatically ameliorate α‐synuclein pathology in the MPTP NHP model of PD. Therefore, patient’s dopaminergic medication should be systematically considered when assessing α‐synuclein as a biomarker for diagnosis, monitoring disease progression and response to disease‐modifying treatments

p53-dependent programmed necrosis controls germ cell homeostasis during spermatogenesis

International audienceThe importance of regulated necrosis in pathologies such as cerebral stroke and myocardial infarction is now fully recognized. However, the physiological relevance of regulated necrosis remains unclear. Here, we report a conserved role for p53 in regulating necrosis in Drosophila and mammalian spermatogenesis. We found that Drosophila p53 is required for the programmed necrosis that occurs spontaneously in mitotic germ cells during spermatogenesis. This form of necrosis involved an atypical function of the initiator caspase Dronc/Caspase 9, independent of its catalytic activity. Prevention of p53-dependent necrosis resulted in testicular hyperplasia, which was reversed by restoring necrosis in spermatogonia. In mouse testes, p53 was required for heat-induced germ cell necrosis, indicating that regulation of necrosis is a primordial function of p53 conserved from invertebrates to vertebrates. Drosophila and mouse spermatogenesis will thus be useful models to identify inducers of necrosis to treat cancers that are refractory to apoptosis

Cortical Lewy body injections induce long-distance pathogenic alterations in the non-human primate brain

International audienceAbstract Aggregation of α-synuclein (α-syn) is the cornerstone of neurodegenerative diseases termed synucleinopathies, which include Parkinson’s Disease (PD), Dementia with Lewy Bodies (DLB), and Multiple System Atrophy (MSA). These synucleinopathies are characterized by the deposit of aggregated α-syn in intracellular inclusions observable in neurons and glial cells. In PD and DLB, these aggregates, predominantly located in neurons, are called Lewy Bodies (LBs). These LBs are one of the pathological hallmarks of PD and DLB, alongside dopaminergic neuron loss in the substantia nigra. Previous studies have demonstrated the ability of PD patient-derived LB fractions to induce nigrostriatal neurodegeneration and α-syn pathology when injected into the striatum or the enteric nervous system of non-human primates. Here, we report the pathological consequences of injecting these LB fractions into the cortex of non-human primates. To this end, we inoculated mesencephalic PD patient-derived LB fractions into the prefrontal cortex of baboon monkeys terminated one year later. Extensive analyses were performed to evaluate pathological markers known to be affected in LB pathologies. We first assessed the hypothesized presence of phosphorylated α-syn at S129 (pSyn) in the prefrontal cortices. Second, we quantified the neuronal, microglial, and astrocytic cell survival in the same cortices. Third, we characterized these cortical LB injections’ putative impact on the integrity of the nigrostriatal system. Overall, we observed pSyn accumulation around the injection site in the dorsal prefrontal cortex, in connected cortical regions, and further towards the striatum, suggesting α-syn pathological propagation. The pathology was also accompanied by neuronal loss in these prefrontal cortical regions and the caudate nucleus, without, however, loss of nigral dopamine neurons. In conclusion, this pilot study provides novel data demonstrating the toxicity of patient-derived extracts, their potential to propagate from the cortex to the striatum in non-human primates, and a possible primate model of DLB

Brain injections of glial cytoplasmic inclusions induce a multiple system atrophy-like pathology

International audienceAbstract Synucleinopathies encompass several neurodegenerative diseases, which include Parkinson's disease, dementia with Lewy bodies and multiple system atrophy. These diseases are characterized by the deposit of α-synuclein aggregates in intracellular inclusions in neurons and glial cells. Unlike Parkinson’s disease and dementia with Lewy bodies, where aggregates are predominantly neuronal, multiple system atrophy is associated with α-synuclein cytoplasmic inclusions in oligodendrocytes. Glial cytoplasmic inclusions are the pathological hallmark of multiple system atrophy and are associated with neuroinflammation, modest demyelination and, ultimately, neurodegeneration. To evaluate the possible pathogenic role of glial cytoplasmic inclusions, we inoculated glial cytoplasmic inclusion-containing brain fractions obtained from multiple system atrophy patients into the striatum of non-human primates. After a 2-year in vivo phase, extensive histochemical and biochemical analyses were performed on the whole brain. We found loss of both nigral dopamine neurons and striatal medium spiny neurons, as well as loss of oligodendrocytes in the same regions, which are characteristics of multiple system atrophy. Furthermore, demyelination, neuroinflammation and α-synuclein pathology were also observed. These results show that the α-synuclein species in multiple system atrophy-derived glial cytoplasmic inclusions can induce a pathological process in non-human primates, including nigrostriatal and striatofugal neurodegeneration, oligodendroglial cell loss, synucleinopathy and gliosis. The present data pave the way for using this experimental model for MSA research and therapeutic development

Germ cells in the testes of <i>p53</i>-deficient mice are resistant to heat-induced necrosis.

<p>(<b>A</b>-<b>C”</b>) Sections of heat-shocked testes from 6–8-week-old wild-type (<i>wt</i>, <b>A</b>-<b>A”</b>), <i>p53</i>^<i>+/-</i> (<b>B</b>-<b>B”</b>), and <i>p53</i>^<i>-/-</i> (<b>C</b>-<b>C”</b>) mice, counterstained with HES (<b>A</b>, <b>B</b>, <b>C</b>) and stained with TUNEL (<b>A'</b>, <b>A” B'</b>, <b>B”</b>, <b>C'</b>, <b>C”</b>). Black and blue arrowheads indicate seminiferous tubules fully and partially filled with TUNEL⁺ cells, respectively. Scale bars, 200 μm (<b>A</b>, <b>A', B</b>, <b>B', C</b>, <b>C'</b>) and 50 μm (<b>A”</b>, <b>B”</b>, <b>C”</b>). (<b>D</b>) Quantification of the total fraction of seminiferous tubules containing TUNEL⁺ cells (left) and the fraction of seminiferous tubules partially filled with TUNEL⁺ cells (right) shown in <b>A</b>-<b>C”</b> (mean ± s.e.m. of N testes/genotype). <i>*p <</i> 0.05, *<i>*p <</i> 0.01 by Welch’s two-sample t-test.</p