Transcutaneous Auricular Vagal Nerve Stimulation and Disorders of Consciousness: A Hypothesis for Mechanisms of Action

Disorders of consciousness (DoC) are the hallmark of severe acquired brain injuries characterized by abnormal activity in important brain areas and disruption within and between brain networks. As DoC's therapeutic arsenal is limited, new potential therapies such as transcutaneous auricular vagal nerve stimulation (taVNS) have recently been explored. The potential of taVNS in the process of consciousness recovery has been highlighted in recent studies with DoC patients. However, it is not clear how taVNS plays a role in the recovery of consciousness. In this article, we first describe the neural correlates of consciousness, the vagus nerve anatomy and functions, along with the results of functional magnetic resonance imaging studies using taVNS. Based on consciousness recovery and taVNS mechanisms, we propose the Vagal Cortical Pathways model. This model highlights four consecutive pathways (A. Lower brainstem activation, B. Upper brainstem activation, C. Norepinephrine pathway, and D. Serotonin pathway) likely to have an impact on patients with a brain injury and DoC. Additionally, we suggest six different mechanisms of action: (1) Activation of the ascending reticular activating system; (2) Activation of the thalamus; (3) Re-establishment of the cortico-striatal-thalamic-cortical loop; (4) Promotion of negative connectivity between external and default mode networks by the activation of the salience network; (5) Increase in activity and connectivity within the external network through the norepinephrine pathway; and (6) Increase in activity within the default mode network through the serotonin pathway. This model aims to explain the potential therapeutic effects that taVNS has on brain activity in the process of consciousness recovery. © Copyright © 2020 Briand, Gosseries, Staumont, Laureys and Thibaut

Physiological map to study kidney toxicity in the ONTOX project

editorial reviewedBackground and Objectives: Continuous improvements of computational approaches also increase the predictive performances of toxicological in silico models [1]. However, being mainly based on animal test data, these computational models lack a good correlation with human toxicity, and, being often based uniquely on chemical structures, they are unable to explain toxicological processes. To overcome these limitations, we have developed a new semi-automated strategy to build a Physiological Map (PM), a framework to study human toxicological mechanisms. Materials and Methods: Our method is useful to build a PM or to validate an existing PM. To retrieve information, a manual literature review was accompanied by computational interrogation of ontologies (e.g. Gene Ontology), thus creating a network of genes, proteins, molecules and phenotypes [2]. The network was converted manually into a PM using the CellDesigner software and visualized on the web using the MINERVA platform. The entire procedure was supported and revised by field experts. Results: We present here the human kidney PM, developed in the framework of ONTOX, a European project aimed at improving risk assessment avoiding the use of animal tests [3]. With the purpose to better understand tubular necrosis and nephrolithiasis, the PM represents the normal physiology in proximal tubule, the loop of Henle, distal tubule, and collecting duct cells, displaying the vitamin D metabolism and the urine production processes: filtration, reabsorption and secretion. Discussion and Conclusions: Our method assists the user to build a PM even starting from limited data. The PM is initially a static representation of physiological processes, also useful to study and develop new adverse outcome pathways. Subsequently, we could add kinetic parameters, transforming the PM into a dynamic model able to represent cellular perturbations. This approach presents an opportunity to investigate human toxicities, improving the toxicological predictions from a qualitative and quantitative perspective. References: [1] Manganelli S, Gamba A, Colombo E, Benfenati E (2022) 'Using VEGAHUB Within a Weight-of-Evidence Strategy'. In: Benfenati E. (eds) In Silico Methods for Predicting Drug Toxicity. Methods in Molecular Biology, vol 2425. Humana, New York, NY. https://doi.org/10.1007/978-1-0716-1960-5_18 [2] Gamba A, Salmona M, Bazzoni G (2020) 'Quantitative analysis of proteins which are members of the same protein complex but cause locus heterogeneity in disease', Sci Rep 10, 10423. https://doi.org/10.1038/s41598-020-66836-7 [3] Vinken M., et al. (2021) 'Safer chemicals using less animals: kick-off of the European ONTOX project', Toxicology 458, 152846. https://doi.org/10.1016/j.tox.2021.15284

Physiological maps and chemical-induced disease ontologies: tools to support NAMs development for next-generation risk assessment

editorial reviewedPhysiological maps (PM) can be defined as a graphical representation of cellular and molecular processes associated to specific organ functions (Vinken et al. 2021). Within the ONTOX project, we designed a total of 6 PMs describing physiological processes in the liver, the kidney and the brain. These PMs are then used as a tool to assess relevant mechanistic coverage and linkage between a specific organ function and a toxicological endpoint. Based on the Disease Maps project (Mazein et al. 2018) pipeline, we developed the first version of 6 PMs describing the following physiological processes: bile secretion & lipid metabolism (liver), vitamin D metabolism & urine composition (kidney), neural tube closure (update of the work of Heusinkveld et al. 2021) & brain development (brain). Our workflow included: (i) data collection from expert curated literature (ii) identification of the relevant biological mechanisms, (iii) screening of online databases (e.g. Wikipathways, Reactome, and KEGG) for previously described pathways, (iv) manual curation and integration of the data into a PM using CellDesigner, and (v) visualization on the MINERVA platform (Hoksza et al. 2019). These qualitative PMs represent an important tool for exploring curated literature, analyzing networks and benchmarking the development of new adverse outcome pathways (AOPs). These PMs provide the basis for developing quantitative disease ontologies, integrating different layers of pathological and toxicological information, chemical information (drug-induced pathways) and kinetic data. The resulting chemical-induced disease ontologies will provide a multi-layered platform for integration and visualization of such information. The ontologies will contribute to improving understanding of organ/disease related pathways in response to chemicals, visualize omics datasets, develop quantitative methods for computational disease modeling and for predicting toxicity, set up an in vitro & in silico test battery to detect a specific type of toxicity, and develop new animal-free approaches for next generation risk assessment

BernardStaumont/New_website: test2

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Nouvelles approches thérapeutiques du mésothéliome pleural malin ciblées sur la réparation de l'ADN et le facteur de croissance transformant TGF-alpha

Malignant pleural mesothelioma (MPM) is an aggressive cancer of the pleura mainly caused by asbestos fibers exposure. MPM is notably characterized by a very poor prognosis and current treatments, including radiation and chemotherapy, are unsatisfactory. As genomic analyzes show that the major mutations occurring in MPM cells pertain to checkpoint control and DNA repair, a first part of this thesis addresses the DNA damage response and the mechanisms of DNA repair in several MPM cell lines. In this study, we show that gamma ionizing radiation (IR) induces cell cycle arrest of MPM cells at the G2-M checkpoint. We also demonstrate that MPM cells are driven prematurely towards mitosis following the abrogation of IR-induced G2 arrest by the checkpoint inhibitor UCN-01, however without a significant induction of cell death. To avoid excessive genomic instability, DNA repair mechanisms are likely to play a key role in such DNA-damaging conditions. We therefore evaluate here the efficiencies of the two main DNA double-strand break repair mechanisms, non-homologous end-joining (NHEJ) and homologous recombination (HR) and highlight differences in such repair activities among MPM cell lines and in comparison to control mesothelial cells. We underline an efficient HR repair in MPM cells, opening the door to additional investigations that might reveal an addiction to activated DNA repair pathways and thereby render MPM cells hypersensitive to targeted combination therapies. In the second part of this thesis, we perform a pre-clinical study investigating the resistance of MPM to a particular epigenetic-based therapy associating the histone deacetylase (HDAC) inhibitor valproic acid (VPA) and doxorubicin. By comparing MPM cell lines with a differential sensitivity to this combination chemotherapy, this study suggests a correlation between transforming growth factor-alpha (TGF-α) expression and resistance to treatment. We further confirm the role of TGF-α in chemoresistance by modulating its expression in highly- and poorly responsive MPM cell lines. In addition, pharmacological inhibition of TGF-α’s receptor (EGFR or epidermal growth factor receptor) by tyrosine kinase inhibitors gefitinib and erlotinib improves the efficacy of VPA+doxorubicin in vitro. Dual HDAC-EGFR inhibitor CUDC-101 furthermore synergizes with doxorubicin to induce apoptosis in vitro and to slow down tumor growth in two different MPM mouse models, emphasizing its therapeutic potential and opening new prospects for combination therapies associating HDAC and EGFR inhibition against MPM. With two different approaches, this thesis provides a better understanding of MPM resistance to chemo- and radiotherapies and offers clues for new therapeutic strategies based on DNA repair pathways and dual HDAC-EGFR/TGF-α inhibition.Le mésothéliome pleural malin (MPM) est un cancer agressif de la plèvre principalement provoqué par une exposition aux fibres d’amiante. Le MPM se caractérise notamment par un faible pronostic et les traitements actuels, incluant radiation et chimiothérapies, ne sont pas satisfaisants. Alors que des analyses génomiques montrent que les principales mutations du MPM se rencontrent au niveau des gènes impliqués dans les points de contrôle du cycle cellulaire et dans la réparation de l’ADN, la première partie de cette thèse évalue la réponse aux dommages à l’ADN (DNA damage response) et les mécanismes de réparation de l’ADN au sein de plusieurs lignées cellulaires de MPM. Au travers de cette étude, nous montrons que les radiations ionisantes gamma induisent l’arrêt des cellules de MPM au point de contrôle (checkpoint) G2-M du cycle cellulaire. Nous démontrons également que les cellules de MPM sont poussées prématurément vers la phase de mitose suite à l’inhibition de cet arrêt en G2 radio-induit par l’inhibiteur de point de contrôle UCN-01, et ce, sans une augmentation significative de mort cellulaire. Afin d’éviter une instabilité génomique excessive, les mécanismes de réparation de l’ADN sont susceptibles de jouer un rôle déterminant dans de telles conditions de dommages. Nous évaluons ici l’efficacité des deux principaux mécanismes de réparation des cassures doubles brins de l’ADN, à savoir NHEJ (jonction d’extrémités non homologues) et HR (recombinaison homologue), et soulignons des différences en terme d’efficacité de réparation parmi les différentes lignées de mésothéliome et en comparaison aux cellules mésothéliales. Nous mettons en évidence une réparation efficace par HR au sein des cellules de MPM, ouvrant la porte à des études complémentaires susceptibles de révéler une addiction à certains mécanismes de réparation et de sensibiliser les cellules de MPM à des thérapies combinées et ciblées. Dans la seconde partie de cette étude, nous étudions la résistance du MPM envers une thérapie épigénétique associant l’acide valproïque (VPA), inhibiteur d’histone désacétylases (HDAC), et la doxorubicine. Suite à une comparaison entre des lignées de MPM présentant des sensibilités différentes au traitement, ce travail révèle une corrélation entre l’expression du facteur de croissance TGF-α et la résistance à cette thérapie combinée. Nous confirmons également le rôle de TGF-α dans cette chimiorésistance en modulant son expression dans des lignées de MPM hautement ou faiblement sensibles au traitement. L’inhibition pharmacologique du récepteur de TGF-α (EGFR) par les inhibiteurs de tyrosine kinase gefitinib et erlotinib a de plus permis d’améliorer l’efficacité du traitement VPA + doxorubicine in vitro. En outre, CUDC-101, double inhibiteur ciblant HDAC et EGFR, démontre une synergie avec la doxorubicine induisant l’apoptose des cellules de MPM in vitro et ralentissant la croissance tumorale dans deux modèles murins, mettant en avant son potentiel thérapeutique et ouvrant de nouvelles perspectives quant aux thérapies combinées associant les inhibitions de HDAC et EGFR contre le MPM. Avec deux approches distinctes, cette thèse fournit une meilleure compréhension de la résistance du MPM aux chimio- et radiothérapies et présente des pistes pour de nouvelles stratégies thérapeutiques basées sur les mécanismes de réparation de l’ADN et la double inhibition HDAC-EGFR/TGF-α.The role of TGF-alpha in the resistance to malignant pleural mesothelioma chemotherap