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Sepsis is characterized by a dysregulated host response to an infection, potentially leading to fatal organ dysfunctions. Among these organs, the central nervous system (CNS) is particularly affected with encephalopathies associated or not with chronic disabling pain. These symptoms are caused by broad neuroinflammation with activation of resident microglia cells and infiltration of leukocytes, especially neutrophils. These immune cells have the ability to produce extracellular traps (ETs) in blood and tissues. These components are composed of chromatins and various antimicrobial proteins, and its role is to capture and destroy pathogens. However, in case of excessive production, deleterious effects occur such as tissue damage and reduction of neuronal excitability.In this study, the objectives were: 1) to determine whether in a model of endotoxemic shock, neutrophils and microglia form ETs in the CNS; 2) and to determine if a modulation of ETs production was beneficial on neuromuscular disorders associated with endotoxemic shock.We observed an infiltration of neutrophils in the SNC, an activation of microglia and a production of ETs following intraperitoneal lipopolyssacharide (LPS) administration in mice (adult Swiss male, 30-45g). Atenolol, a β1-adrenergic blocker with intrinsic immunomodulatory properties, significantly decreases the production of ETs associated in both microglia and neutrophils (citrullinated histone H3: 279.1 ± 101.9 MFI versus 117.1 ± 77.21 MFI, p This work was supported by funding from the Chancellerie des Universites de Paris (Legs Poix), INSERM and Paris-Saclay University-UVSQ. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Spinal cord injuries involve a primary injury that can lead to permanent loss of function and a secondary injury associated with pathologic and inflammatory processes. Extracellular traps are extracellular structures expressed by immune cells that are primarily composed of chromatin, granular enzymes and histones. Extracellular traps are known to induce tissue damage when overexpressed, and could be associated in the occurrence of secondary damage. In the present study, we used flow cytometry to demonstrate that at 1-day following a C2 spinal cord lateral hemisection in male Swiss mice, resident microglia form vital microglia extracellular traps, and infiltrating neutrophils form vital neutrophil extracellular traps. We also used immunolabelling to show that microglia near the lesion area are most likely to form these microglia extracellular traps. As expected, infiltrating neutrophils are located at the site of injury, though only some of them engage in post-injury extracellular traps formation. We also observed the formation of microglia and neutrophil extracellular traps in our sham animal models of durotomy, but formation was less frequent than following the C2 hemisection. Our results demonstrate for the first time that microglia form extracellular traps in the spinal cord following injury and durotomy. It remains however to determine the mechanisms and kinetics of neutrophil and microglia extracellular traps formation following spinal cord injury. This information would allow to better mitigate this inflammatory process that may contribute to secondary injury, and to effectively target extracellular traps to improve functional outcomes following spinal cord injury.

Spinal cord injuries induce motor and sensory deficits. The development of therapies aimed to improve these functions after spinal cord injury is therefore necessary. Repeated magnetic stimulation (rMS) is an innovative and non-invasive technique which has been used to modulate the activity of neuronal networks in various diseases such as bipolar disorder or Parkinson's disease. rMS could therefore display beneficial functional effects in people with spinal cord injury. Studies carried out in vitro, in vivo and ex vivo have made it possible to partly understand the mechanisms underlying the modulation of neuronal activity induced by rMS protocols. Its use in preclinical models of spinal cord injury has also shown beneficial functional effects. Thus, rMS seems to be a promising therapy in the recovery of lost functions after spinal cord injury.La stimulation magnétique répétée pour le traitement des traumas spinaux.Les traumas spinaux induisent des déficits moteurs et sensoriels. La mise au point de thérapies visant à rétablir les fonctions altérées à la suite d’une lésion de la moelle épinière est donc nécessaire. La stimulation magnétique répétée (SMr) est une thérapie innovante et non invasive utilisée pour moduler l’activité de réseaux neuronaux dans diverses maladies neurologiques, telles que la maladie de Parkinson, ou psychiatriques, telles que le trouble bipolaire. Son utilisation chez les personnes atteintes de traumas spinaux pourrait avoir des effets fonctionnels bénéfiques. Des études réalisées in vitro, in vivo et ex vivo ont permis de comprendre en partie les mécanismes sous-jacents à la modulation de l’activité neuronale induite par les protocoles de SMr. Son utilisation dans des modèles précliniques de lésion médullaire a de plus montré des effets bénéfiques fonctionnels. Ainsi, la SMr pourrait potentialiser la récupération des fonctions perdues après un trauma spinal.

Les traumas spinaux induisent des déficits moteurs et sensoriels. La mise au point de thérapies visant à rétablir les fonctions altérées à la suite d’une lésion de la moelle épinière est donc nécessaire. La stimulation magnétique répétée (SMr) est une thérapie innovante et non invasive utilisée pour moduler l’activité de réseaux neuronaux dans diverses maladies neurologiques, telles que la maladie de Parkinson, ou psychiatriques, telles que le trouble bipolaire. Son utilisation chez les personnes atteintes de traumas spinaux pourrait avoir des effets fonctionnels bénéfiques. Des études réalisées in vitro, in vivo et ex vivo ont permis de comprendre en partie les mécanismes sous-jacents à la modulation de l’activité neuronale induite par les protocoles de SMr. Son utilisation dans des modèles précliniques de lésion médullaire a de plus montré des effets bénéfiques fonctionnels. Ainsi, la SMr pourrait potentialiser la récupération des fonctions perdues après un trauma spinal.

High cervical spinal cord injuries induce permanent neuromotor and autonomic deficits. These injuries impact both central respiratory and cardiovascular functions through modulation of the sympathetic nervous system. So far, cardiovascular studies have focused on models of complete contusion or transection at the lower cervical and thoracic levels and diaphragm activity evaluations using invasive methods. The present study aimed to evaluate the impact of C2 hemisection on different parameters representing vital functions (i.e., respiratory function, cardiovascular, and renal filtration parameters) at the moment of injury and 7 days post-injury in rats. No ventilatory parameters evaluated by plethysmography were impacted during quiet breathing after 7 days post-injury, whereas permanent diaphragm hemiplegia was observed by ultrasound and confirmed by diaphragmatic electromyography in anesthetized rats. Interestingly, the mean arterial pressure was reduced immediately after C2 hemisection, with complete compensation at 7 days post-injury. Renal filtration was unaffected at 7 days post-injury; however, remnant systolic dysfunction characterized by a reduced left ventricular ejection fraction persisted at 7 days post-injury. Taken together, these results demonstrated that following C2 hemisection, diaphragm activity and systolic function are impacted up to 7 days post-injury, whereas the respiratory and cardiovascular systems display vast adaptation to maintain ventilatory parameters and blood pressure homeostasis, with the latter likely sustained by the remaining descending sympathetic inputs spared by the initial injury. A better broad characterization of the physiopathology of high cervical spinal cord injuries covering a longer time period post-injury could be beneficial for understanding evaluations of putative therapeutics to further increase cardiorespiratory recovery.

Repetitive transcranial magnetic stimulation (rTMS) is a promising, innovative, and non-invasive therapy used clinically. Efficacy of rTMS has been demonstrated to ameliorate psychiatric disorders and neuropathic pain through neuromodulation of affected neural circuits. However, little is known about the mechanisms and the specific neural circuits via which rTMS facilitates these functional effects. The aim of this study was to begin revealing the mechanisms by which rTMS may tap into existing neural circuits, by using a well characterized spinal motor circuit – the phrenic circuit. Here we hypothesized that rTMS can be used to enhance phrenic motoneuron excitability in anesthetized Sprague Dawley rats. Multiple acute rTMS protocols were used revealing 10 Hz rTMS protocol induced a robust, long-lasting increase in phrenic motoneuron excitability, functionally evaluated by diaphragm motor evoked potentials (59.1 ± 21.1 % of increase compared to baseline 60 min after 10 Hz protocol against 6.0 ± 5.8 % (p = 0.007) for Time Control, −5.8 ± 7.4 % (p < 0.001) for 3 Hz, and 5.2 ± 12.5 % (p = 0.008) for 30 Hz protocols). A deeper analyze allowed to discriminate “responder” and “non-responder” subgroups among 10 Hz rTMS treated animals. Intravenous injections of GABA(A) and GABA(B) receptor agonists prior to 10 Hz rTMS treatment, abolished the enhanced phrenic motoneuron excitability, suggesting GABAergic input plays a mechanistic role in rTMS-induced phrenic excitability. These data demonstrate that a single high frequency rTMS protocol at 10 Hz increases phrenic motoneuron excitability, mediated by a local GABAergic “disinhibition”. By understanding how rTMS can be used to affect neural circuits non-invasively we can begin to harness the therapeutic potential of this neuromodulatory strategy to promote recovery after disease or injury to the central nervous system.

Cervical spinal cord injury (SCI) results in permanent life-altering motor and respiratory deficits. Other than mechanical ventilation for respiratory insufficiency secondary to cervical SCI, effective treatments are lacking and the development of animal models to explore new therapeutic strategies are needed. The aim of this work was to demonstrate the feasibility of using a mouse model of partial cervical spinal hemisection at the second cervical metameric segment (C2) to investigate the impact of 6 weeks training on forced exercise wheel system on locomotor/respiratory plasticity muscles. To measure run capacity locomotor and respiratory functions, incremental exercise tests and diaphragmatic electromyography were done. In addition, muscle fiber type composition and capillary distribution were assessed at 51 days following chronic C2 injury in diaphragm, extensor digitorum communis (EDC), tibialis anterior (TA) and soleus (SOL) muscles. Six-week exercise training increased the running capacity of trained SCI mice. Fiber type composition in EDC, TA and SOL muscles was not modified by our protocol of exercise. The vascularization was increased in all muscle limbs in SCI trained group. No increase in diaphragmatic electromyography amplitude of the diaphragm muscle on the side of SCI was observed, while the contraction duration was significantly decreased in sedentary group compared to trained group. Cross-sectional area of type IIa myofiber in the contralateral diaphragm side of SCI was smaller in trained group. Fiber type distribution between contralateral and ipsilateral diaphragm in SCI sedentary group was affected, while no difference was observed in trained group. In addition, the vascularization of the diaphragm side contralateral to SCI was increased in trained group. All these results suggest an increase in fatigue resistance and a contribution to the running capacity in SCI trained group. Our exercise protocol could be a promising non-invasive strategy to sustain locomotor and respiratory muscle plasticity following SCI.

Introduction Les lesions de la moelle epiniere au niveau cervical entrainent une insuffisance respiratoire permanente. Une axotomie des voies respiratoires spinales descendantes induit une deafferentation des motoneurones phreniques innervant le diaphragme (principal muscle inspiratoire) [1] . La stimulation magnetique transcrânienne repetee (rTMS) est un outil therapeutique non-invasif couramment utilise en clinique dont le but est de moduler l’excitabilite neuronale [2] . Le but de cette etude est de tester l’effet chronique d’une application d’un protocole de rTMS a haute frequence sur les processus de plasticite synaptique au niveau du reseau phrenique chez un modele preclinique de lesion medullaire. Methodes Sept jours apres hemisection spinale cervicale laterale, des rats Spragues Dawley mâles ont recu un protocole de rTMS a haute frequence pendant 4 semaines (9 trains de 100 stimulations a 10 Hz, 1 fois par jour, 5 jours par semaine) ou une stimulation sham (animaux non-traites). L’excitabilite et l’activite du muscle diaphragmatique ont ete evaluees par enregistrement des potentiels evoques moteurs (PEM) et electromyographie (EMG). Resultats Une augmentation de l’amplitude des PEM et EMG diaphragmatiques est induite par rTMS du cote intact chez les animaux traites (PEM = 0,55 ± 0,26 μV ; EMG = 0,63 ± 0,15 μV.s.s) compare aux animaux non-traites (PEM = 0,32 ± 0,12 μV, p Conclusions Ce traitement chronique par rTMS a haute frequence conduit a une augmentation robuste de l’excitabilite et de l’activite du cote intact du diaphragme en post-traumatique chez nos animaux. Ce resultat peut etre la consequence d’une amelioration des connexions synaptiques du cote intact du diaphragme qui compenserait la perte d’activite observee du cote lese. Une etude plus approfondie des mecanismes moleculaires sous-jacents est necessaire afin de confirmer cette hypothese.

International audience; Ultrasound imaging is a non-invasive technique to assess organ function. Its potential application in rodents to evaluate respiratory function remains poorly investigated. We aimed to assess and validate ultrasound technique in rats to analyze inspiratory and expiratory muscles. We measured respiratory parameters to provide normal eupneic values. Histological studies and plethysmography were used to validate the technique and assess the physiological implications. A linear relationship was observed between ultrasound and histological data for diaphragm and rectus abdominis (RA) measurement. The tidal volume was significantly correlated with the right + left RA area (r = 0.76, p < 0.001), and the rapid shallow breathing index was significantly and inversely correlated with the right + left RA area (r=-0.53, p < 0.05). In the supine position, the right and left diaphragm expiratory thickness were not associated with tidal volume obtained in the physiological position. Ultrasound imaging is highly accurate and reproducible to assess and follow up diaphragm and RA structure and function in rats.

International audience; High spinal cord injuries (SCI) lead to permanent respiratory insufficiency, and the search for new therapeutics to restore this function is essential. To date, the most documented preclinical model for high SCI is the rat cervical C2 hemisection. However, molecular studies with this SCI model are limited due to the poor availability of genetically modified specimens. The aim of this work was to evaluate the pathophysiology of respiratory activity following a cervical C2 injury at different times post-injury in a C57BL/6 mouse model. No significant spontaneous recovery of diaphragmatic activity was observed up to 30 days post-injury in eupneic condition. However, during a respiratory challenge, i.e. mild asphyxia, a partial restoration of the injured diaphragm was observed at 7 days post-injury, corresponding to the crossed phrenic phenomenon. Interestingly, the diaphragmatic recording between 2 respiratory bursts on the injured side showed an amplitude increase between 1–7 days post-injury, reflecting a change in phrenic motoneuronal excitability. This increase in inter-burst excitability returned to pre-injured values when the crossed phrenic phenomenon started to be effective at 7 days post-injury. Taken together, these results demonstrate the ability of the mouse respiratory system to express long-lasting plasticity following a C2 cervical hemisection and genetically modified animals can be used to study the pathophysiological effects on these plasticity phenomena.