Stephane Vinit - Academia.edu (original) (raw)
Papers by Stephane Vinit
Following central nervous system lesion, the ability of injured axons to regrowth may depend on t... more Following central nervous system lesion, the ability of injured axons to regrowth may depend on the level and duration of the injured cell body response (CBR). Therefore, in order to investigate whether axotomized brainstem neurons maintain a durable growth-competent state after spinal cord injury, we studied the effect of a chronic C2 hemisection in rats on the expression of various CBR markers involved in axon regeneration, such as c-Jun, ATF-3, HSP27, NO synthase (NOS), and also of the neural mature phenotype marker NeuN, in the bulbospinal respiratory neurons as compared to the Gigantocellularis nucleus. Both at 7 and 30 days post-lesion (DPL), c-Jun and HSP27 were present in respectively ~60% and ~20% of the axotomized respiratory neurons, whereas the apoptotic factor caspase 3 was not detected in these cells. NOS appeared belatedly and it was detected in ~20% of the axotomized respiratory neurons at 30DPL. At 30DPL, these different CBR markers were strongly colocalized in a su...
European Journal …, 2008
Vinit, S., Darlot, F., Stamegna, J.-C., Sanchez, P., Gauthier, P. and Kastner, A.(2008), Long-ter... more Vinit, S., Darlot, F., Stamegna, J.-C., Sanchez, P., Gauthier, P. and Kastner, A.(2008), Long-term reorganization of respiratory pathways after partial cervical spinal cord injury. European Journal of Neuroscience, 27: 897908. doi: 10.1111/j. 1460-9568.2008. 06072. x
International Journal of Molecular Medicine
Macrophages are active contributors to the innate immune defense system. As macrophage activation... more Macrophages are active contributors to the innate immune defense system. As macrophage activation is clearly affected by the surrounding microenvironment, the present study investigated the effect of sulforaphane (SFN) on the bactericidal activity of macrophages and the underlying molecular mechanisms involved in this process. Human THP-1-derived macrophages, primary human peripheral blood mononuclear cell-derived macrophages, and primary mouse bone marrow derived-macrophages (BMdMs) pretreated with SFN or dMSO were utilized in a model of Staphylococcus aureus infection. The results suggested that SFN pretreatment of macrophages effectively repressed the intracellular survival of S. aureus through modulation of p38/JNK signaling and decreased S. aureus-induced caspases-3/7-dependent cell apoptosis, potentially through downregulation of microRNA (miR)-142-5p and miR-146a-5p. As SFN is a well-known activator of nuclear factor erythroid 2-related factor 2 (Nrf2), Nrf2 -/-BMdMs were used to demonstrate that the SFN-mediated inhibitory effect was independent of Nrf2. Nevertheless, an increase in intracellular bacterial survival in Nrf2-deficient macrophages was observed. In addition, SFN pretreatment suppressed S. aureus-induced transcriptional expression of genes coding for the proinflammatory cytokines interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α), as well as for the M1 markers c-c motif chemokine receptor 7, IL-23 and inducible nitric oxide synthase (iNOS). Western blot analysis indicated that S. aureus challenge activated p38 mitogen-activated protein kinase (MAPK) (p38) and c-Jun N-terminal kinase (JNK) MAPK signaling pathways, while SFN pretreatment prevented p38 and JNK phosphorylation. Pretreatment with 2 specific inhibitors of p38 and JNK, SB203580 and SP600125, respectively, resulted in a decrease in S. aureus-induced proinflammatory gene expression levels compared with those observed in the SFN-pretreated macrophages. Furthermore, THP-1-derived macrophages pretreated with SB203580 or SP600125 prior to bacterial infection exhibited a significant inhibition in intracellular S. aureus survival.
The European journal of neuroscience, 2017
Following central nervous system lesion, the ability of injured axons to regrowth may depend on t... more Following central nervous system lesion, the ability of injured axons to regrowth may depend on the level and duration of the injured cell body response (CBR). Therefore, to investigate whether axotomized brainstem neurons maintain a durable growth-competent state after spinal cord injury, we studied the effect of a chronic C2 hemisection in rats on the expression of various CBR markers involved in axon regeneration, such as c-Jun, ATF-3, HSP27, NO synthase (NOS), and also of the neural mature phenotype marker NeuN, in the bulbospinal respiratory neurons as compared to the gigantocellularis nucleus. Both at 7 and 30 days post-lesion (DPL), c-Jun and HSP27 were present in, respectively, ~60 and ~20% of the axotomized respiratory neurons, whereas the apoptotic factor caspase 3 was not detected in these cells. NOS appeared belatedly, and it was detected in ~20% of the axotomized respiratory neurons at 30DPL. At 30DPL, these different CBR markers were strongly colocalized in a sub-popul...
Journal of neuromuscular diseases, 2018
Respiratory muscles are classically involved in neuromuscular disorders, leading to a restrictive... more Respiratory muscles are classically involved in neuromuscular disorders, leading to a restrictive respiratory pattern. The diaphragm is the main respiratory muscle involved during inspiration. Ultrasound imaging is a noninvasive, radiation-free, accurate and safe technique allowing assessment of diaphragm anatomy and function. The authors review the pathophysiology of diaphragm in neuromuscular disorders, the methodology and indications of diaphragm ultrasound imaging as well as possible pitfalls in the interpretation of results.
American journal of physiology. Regulatory, integrative and comparative physiology, Jan 11, 2017
Moderate acute intermittent hypoxia (mAIH) elicits a form of respiratory motor plasticity known a... more Moderate acute intermittent hypoxia (mAIH) elicits a form of respiratory motor plasticity known as phrenic long-term facilitation (pLTF). Preconditioning with modest protocols of chronic intermittent hypoxia enhances pLTF, demonstrating pLTF metaplasticity. Since "low dose" protocols of repetitive acute intermittent hypoxia show promise as a therapeutic modality to restore respiratory (and non-respiratory) motor function in clinical disorders with compromised breathing, we tested the hypothesis that preconditioning with a mild repetitive AIH (rAIH) protocol enhances pLTF and hypoglossal (XII) LTF, and whether the enhancement is regulated by glycolytic flux. In anesthetized, paralyzed and ventilated adult, male Lewis rats, mAIH (3, 5 minute episodes of 10% O2) elicited pLTF (pLTF at 60 min post-mAIH: 49 ± 5% baseline). rAIH pre-conditioning (10, 5 minute episodes of 11% O2/day, 5 min normoxic intervals, 3x per week, 4 weeks) significantly enhanced pLTF (100 ± 16% baseline)....
Résumé : Ce travail doctoral a permis d’étudier les phénomènes de plasticité anatomo-fonctionnell... more Résumé : Ce travail doctoral a permis d’étudier les phénomènes de plasticité anatomo-fonctionnelle et moléculaire survenant après lésion unilatérale cervicale de la moelle épinière. Une section latérale cervicale est suffisante pour abolir l’activité de l’hémidiaphragme ipsilatéral. Néanmoins, après un délai post-lésionnel court (7 jours), une activité phrénique ipsilatérale peut être détectée. Celle-ci dépend de voies descendantes contralatérales croisées, situées latéralement, et de voies afférentes ipsilatérales. A 3 mois post-lésionnels, cette activité est renforcée par des « nouvelles » voies descendantes spinales médianes. Au niveau moléculaire, les neurones respiratoires axotomisés (et d’autres neurones bulbaires non axotomisés) expriment c-Jun en réponse à une hémisection spinale cervicale, ce qui traduit un potentiel de plasticité intrinsèque. Dans la zone lésionnelle, les taux de certains effecteurs de plasticité (GAP-43, BDNF) sont cependant diminués. Ces résultats dans l...
The Faseb Journal, Apr 1, 2014
ABSTRACT Intermittent hypoxia exerts pathologic and beneficial effects in the CNS, depending on t... more ABSTRACT Intermittent hypoxia exerts pathologic and beneficial effects in the CNS, depending on the dose and duration. Whereas hundreds of hypoxic episodes per day mimic sleep apnea and promote neuroinflammation, low dose protocols, such as repetitive acute intermittent hypoxia (rAIH; 10 episodes of 10.5% O2 per day, 3 days/week for 4 weeks), upregulate growth/trophic factors and promote spinal motor plasticity. Because rAIH increases protein levels of key molecules associated with spinal respiratory motor plasticity, we hypothesized that the mRNAs for these and other molecules contributing to neuronal plasticity would be similarly increased. Nimblegen neuronal gene microarrays were used to profile transcript levels in the spinal ventral horn (C4-C6) of male Lewis rats exposed to normoxia or rAIH (n=3 arrays/condition). Surprisingly, there was little evidence of increased mRNA levels of pro-plasticity genes, and these results were confirmed with qRT-PCR for specific genes of interest. Instead, there were signifi
PloS one, 2016
High cervical spinal cord injuries lead to permanent respiratory deficits. One preclinical model ... more High cervical spinal cord injuries lead to permanent respiratory deficits. One preclinical model of respiratory insufficiency in adult rats is the C2 partial injury which causes unilateral diaphragm paralysis. This model allows the investigation of a particular population of respiratory bulbospinal axons which cross the midline at C3-C6 spinal segment, namely the crossed phrenic pathway. Transcranial magnetic stimulation (TMS) is a non-invasive technique that can be used to study supraspinal descending respiratory pathways in the rat. Interestingly, a lateral C2 injury does not affect the amplitude and latency of the largest motor-evoked potential recorded from the diaphragm (MEPdia) ipsilateral to the injury in response to a single TMS pulse, compared to a sham animal. Although the rhythmic respiratory activity on the contralateral diaphragm is preserved at 7 days post-injury, no diaphragm activity can be recorded on the injured side. However, a profound reorganization of the MEPdi...
Neuroscience, Jan 31, 2011
Acute intermittent hypoxia (AIH) facilitates phrenic motor output by a mechanism that requires sp... more Acute intermittent hypoxia (AIH) facilitates phrenic motor output by a mechanism that requires spinal serotonin (type 2) receptor activation, NADPH oxidase activity and formation of reactive oxygen species (ROS). Episodic spinal serotonin (5-HT) receptor activation alone, without changes in oxygenation, is sufficient to elicit NADPH oxidase-dependent phrenic motor facilitation (pMF). Here we investigated: (1) whether serotonin 2A and/or 2B (5-HT2A/B) receptors are expressed in identified phrenic motor neurons, and (2) which receptor subtype is capable of eliciting NADPH-oxidase-dependent pMF. In anesthetized, artificially ventilated adult rats, episodic C4 intrathecal injections (3×6 μl injections, 5 min intervals) of a 5-HT2A (DOI) or 5-HT2B (BW723C86) receptor agonist elicited progressive and sustained increases in integrated phrenic nerve burst amplitude (i.e. pMF), an effect lasting at least 90 min post-injection for both receptor subtypes. 5-HT2A and 5-HT2B receptor agonist-ind...
Experimental neurology, Jan 2, 2014
Amyotrophic lateral sclerosis (ALS) causes progressive motor neuron degeneration, paralysis and d... more Amyotrophic lateral sclerosis (ALS) causes progressive motor neuron degeneration, paralysis and death by ventilatory failure. In rodent ALS models: 1) breathing capacity is preserved until late in disease progression despite major respiratory motor neuron death, suggesting unknown forms of compensatory respiratory plasticity; and 2) spinal microglia become activated in association with motor neuron cell death. Here, we report a novel experimental model to study the impact of respiratory motor neuron death on compensatory responses without many complications attendant to spontaneous motor neuron disease. In specific, we used intrapleural injections of cholera toxin B fragment conjugated to saporin (CTB-SAP) to selectively kill motor neurons with access to the pleural space. Motor neuron survival, CD11b labeling (microglia), ventilatory capacity and phrenic motor output were assessed in rats 3-28days after intrapleural injections of: 1) CTB-SAP (25 and 50μg), or 2) unconjugated CTB an...
Neural Regeneration Research, 2014
A cervical spinal cord injury induces permanent paralysis, and often leads to respiratory distres... more A cervical spinal cord injury induces permanent paralysis, and often leads to respiratory distress. To date, no efficient therapeutics have been developed to improve/ameliorate the respiratory failure following high cervical spinal cord injury (SCI). Here we propose a murine pre-clinical model of high SCI at the cervical 2 (C2) metameric level to study diverse post-lesional respiratory neuroplasticity. The technique consists of a surgical partial injury at the C2 level, which will induce a hemiparalysis of the diaphragm due to a deafferentation of the phrenic motoneurons from the respiratory centers located in the brainstem. The contralateral side of the injury remains intact and allows the animal recovery. Unlike other SCIs which affect the locomotor function (at the thoracic and lumbar level), the respiratory function does not require animal motivation and the quantification of the deficit/recovery can be easily performed (diaphragm and phrenic nerve recordings, whole body ventilation). This pre-clinical C2 SCI model is a powerful, useful, and reliable pre-clinical model to study various respiratory and non-respiratory neuroplasticity events at different levels (molecular to physiology) and to test diverse putative therapeutic strategies which might improve the respiration in SCI patients.
PLoS ONE, 2014
Respiratory related diseases associated with the neuronal control of breathing represent life-thr... more Respiratory related diseases associated with the neuronal control of breathing represent life-threatening issues and to date, no effective therapeutics are available to enhance the impaired function. The aim of this study was to determine whether a preclinical respiratory model could be used for further studies to develop a non-invasive therapeutic tool applied to rat diaphragmatic neuronal circuitry. Transcranial magnetic stimulation (TMS) was performed on adult male Sprague-Dawley rats using a human figure-of-eight coil. The largest diaphragmatic motor evoked potentials (MEPdia) were recorded when the center of the coil was positioned 6 mm caudal from Bregma, involving a stimulation of respiratory supraspinal pathways. Magnetic shielding of the coil with mu metal reduced magnetic field intensities and improved focality with increased motor threshold and lower amplitude recruitment curve. Moreover, transynaptic neuroanatomical tracing with pseudorabies virus (applied to the diaphragm) suggest that connections exist between the motor cortex, the periaqueductal grey cell regions, several brainstem neurons and spinal phrenic motoneurons (distributed in the C3-4 spinal cord). These results reveal the anatomical substrate through which supraspinal stimulation can convey descending action potential volleys to the spinal motoneurons (directly or indirectly). We conclude that MEPdia following a single pulse of TMS can be successfully recorded in the rat and may be used in the assessment of respiratory supraspinal plasticity. Supraspinal non-invasive stimulations aimed to neuromodulate respiratory circuitry will enable new avenues of research into neuroplasticity and the development of therapies for respiratory dysfunction associated with neural injury and disease (e.g. spinal cord injury, amyotrophic lateral sclerosis).
Respiratory Physiology & Neurobiology, 2011
Lipopolysaccharide (LPS) induces inflammatory responses, including microglial activation in the c... more Lipopolysaccharide (LPS) induces inflammatory responses, including microglial activation in the central nervous system. Since LPS impairs certain forms of hippocampal and spinal neuroplasticity, we hypothesized that LPS would impair phrenic long-term facilitation (pLTF) following acute intermittent hypoxia (AIH) in outbred Sprague-Dawley (SD) and inbred Lewis (L) rats. Approximately 3h following a single LPS injection (i.p.), the phrenic response during hypoxic episodes is reduced in both rat strains versus vehicle treated, control rats (SD: 84 ± 7% vs. 128 ± 14% baseline for control, p < 0.05; L: 62 ± 10% vs. 90 ± 9% baseline for control, p < 0.05). At 60 min post-AIH, pLTF is also diminished by LPS in both strains: (SD: 22 ± 5% vs. 73.5 ± 14% baseline for control, p < 0.05; L: 18 ± 15% vs. 56 ± 8% baseline for control, p < 0.05). LPS alone does not affect phrenic burst frequency in either rat strain, suggesting that acute LPS injection has minimal effect on brainstem respiratory rhythm generation. Thus, systemic LPS injections and (presumptive) inflammation impair pLTF, a form of spinal neuroplasticity in respiratory motor control. These results suggest that ongoing infection or inflammation must be carefully considered in studies of respiratory plasticity, or during attempts to harness spinal plasticity as a therapeutic tool in the treatment of respiratory insufficiency, such as spinal cord injury.
Respiratory Physiology & Neurobiology, 2009
The rodent respiratory system is a relevant model for study of the intrinsic post-lesion mechanis... more The rodent respiratory system is a relevant model for study of the intrinsic post-lesion mechanisms of neuronal plasticity and resulting recovery after high cervical spinal cord injury. An unilateral cervical injury (hemisection, lateral section or contusion) interrupts unilaterally bulbospinal respiratory pathways to phrenic motor neurons innervating the diaphragm and leads to important respiratory defects on the injured side. However, the ipsilateral phrenic nerve exhibits a spontaneous and progressive recovery with post-lesion time. Shortly after a lateral injury, this partial recovery depends on the activation of contralateral pathways that cross the spinal midline caudal to the injury. Activation of these crossed phrenic pathways after the injury depends on the integrity of phrenic sensory afferents. These pathways are located principally in the lateral part of the spinal cord and involve 30% of the medullary respiratory neurons. By contrast, in chronic post-lesion conditions, the medial part of the spinal cord becomes sufficient to trigger substantial ipsilateral respiratory drive. Thus, after unilateral cervical spinal cord injury, respiratory reactivation is associated with a time-dependent anatomo-functional reorganization of the bulbospinal respiratory descending pathways, which represents an adaptative strategy for functional compensation.
Respiratory Physiology & Neurobiology, 2009
Respiratory-related complications are the leading cause of death in spinal cord injury (SCI) pati... more Respiratory-related complications are the leading cause of death in spinal cord injury (SCI) patients. Few effective SCI treatments are available after therapeutic interventions are performed in the period shortly after injury (e.g. spine stabilization and prevention of further spinal damage). In this review we explore the capacity to harness endogenous spinal plasticity induced by intermittent hypoxia to optimize function of surviving (spared) neural pathways associated with breathing. Two primary questions are addressed: 1) does intermittent hypoxia induce plasticity in spinal synaptic pathways to respiratory motor neurons following experimental SCI? and 2) can this plasticity improve respiratory function? In normal rats, intermittent hypoxia induces serotonin-dependent plasticity in spinal pathways to respiratory motor neurons. Early experiments suggest that intermittent hypoxia also enhances respiratory motor output in experimental models of cervical SCI, (cervical hemisection) and that the capacity to induce functional recovery is greater with longer durations postinjury. Available evidence suggests that intermittent hypoxia-induced spinal plasticity has considerable therapeutic potential to treat respiratory insufficiency following chronic cervical spinal injury.
Following central nervous system lesion, the ability of injured axons to regrowth may depend on t... more Following central nervous system lesion, the ability of injured axons to regrowth may depend on the level and duration of the injured cell body response (CBR). Therefore, in order to investigate whether axotomized brainstem neurons maintain a durable growth-competent state after spinal cord injury, we studied the effect of a chronic C2 hemisection in rats on the expression of various CBR markers involved in axon regeneration, such as c-Jun, ATF-3, HSP27, NO synthase (NOS), and also of the neural mature phenotype marker NeuN, in the bulbospinal respiratory neurons as compared to the Gigantocellularis nucleus. Both at 7 and 30 days post-lesion (DPL), c-Jun and HSP27 were present in respectively ~60% and ~20% of the axotomized respiratory neurons, whereas the apoptotic factor caspase 3 was not detected in these cells. NOS appeared belatedly and it was detected in ~20% of the axotomized respiratory neurons at 30DPL. At 30DPL, these different CBR markers were strongly colocalized in a su...
European Journal …, 2008
Vinit, S., Darlot, F., Stamegna, J.-C., Sanchez, P., Gauthier, P. and Kastner, A.(2008), Long-ter... more Vinit, S., Darlot, F., Stamegna, J.-C., Sanchez, P., Gauthier, P. and Kastner, A.(2008), Long-term reorganization of respiratory pathways after partial cervical spinal cord injury. European Journal of Neuroscience, 27: 897908. doi: 10.1111/j. 1460-9568.2008. 06072. x
International Journal of Molecular Medicine
Macrophages are active contributors to the innate immune defense system. As macrophage activation... more Macrophages are active contributors to the innate immune defense system. As macrophage activation is clearly affected by the surrounding microenvironment, the present study investigated the effect of sulforaphane (SFN) on the bactericidal activity of macrophages and the underlying molecular mechanisms involved in this process. Human THP-1-derived macrophages, primary human peripheral blood mononuclear cell-derived macrophages, and primary mouse bone marrow derived-macrophages (BMdMs) pretreated with SFN or dMSO were utilized in a model of Staphylococcus aureus infection. The results suggested that SFN pretreatment of macrophages effectively repressed the intracellular survival of S. aureus through modulation of p38/JNK signaling and decreased S. aureus-induced caspases-3/7-dependent cell apoptosis, potentially through downregulation of microRNA (miR)-142-5p and miR-146a-5p. As SFN is a well-known activator of nuclear factor erythroid 2-related factor 2 (Nrf2), Nrf2 -/-BMdMs were used to demonstrate that the SFN-mediated inhibitory effect was independent of Nrf2. Nevertheless, an increase in intracellular bacterial survival in Nrf2-deficient macrophages was observed. In addition, SFN pretreatment suppressed S. aureus-induced transcriptional expression of genes coding for the proinflammatory cytokines interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α), as well as for the M1 markers c-c motif chemokine receptor 7, IL-23 and inducible nitric oxide synthase (iNOS). Western blot analysis indicated that S. aureus challenge activated p38 mitogen-activated protein kinase (MAPK) (p38) and c-Jun N-terminal kinase (JNK) MAPK signaling pathways, while SFN pretreatment prevented p38 and JNK phosphorylation. Pretreatment with 2 specific inhibitors of p38 and JNK, SB203580 and SP600125, respectively, resulted in a decrease in S. aureus-induced proinflammatory gene expression levels compared with those observed in the SFN-pretreated macrophages. Furthermore, THP-1-derived macrophages pretreated with SB203580 or SP600125 prior to bacterial infection exhibited a significant inhibition in intracellular S. aureus survival.
The European journal of neuroscience, 2017
Following central nervous system lesion, the ability of injured axons to regrowth may depend on t... more Following central nervous system lesion, the ability of injured axons to regrowth may depend on the level and duration of the injured cell body response (CBR). Therefore, to investigate whether axotomized brainstem neurons maintain a durable growth-competent state after spinal cord injury, we studied the effect of a chronic C2 hemisection in rats on the expression of various CBR markers involved in axon regeneration, such as c-Jun, ATF-3, HSP27, NO synthase (NOS), and also of the neural mature phenotype marker NeuN, in the bulbospinal respiratory neurons as compared to the gigantocellularis nucleus. Both at 7 and 30 days post-lesion (DPL), c-Jun and HSP27 were present in, respectively, ~60 and ~20% of the axotomized respiratory neurons, whereas the apoptotic factor caspase 3 was not detected in these cells. NOS appeared belatedly, and it was detected in ~20% of the axotomized respiratory neurons at 30DPL. At 30DPL, these different CBR markers were strongly colocalized in a sub-popul...
Journal of neuromuscular diseases, 2018
Respiratory muscles are classically involved in neuromuscular disorders, leading to a restrictive... more Respiratory muscles are classically involved in neuromuscular disorders, leading to a restrictive respiratory pattern. The diaphragm is the main respiratory muscle involved during inspiration. Ultrasound imaging is a noninvasive, radiation-free, accurate and safe technique allowing assessment of diaphragm anatomy and function. The authors review the pathophysiology of diaphragm in neuromuscular disorders, the methodology and indications of diaphragm ultrasound imaging as well as possible pitfalls in the interpretation of results.
American journal of physiology. Regulatory, integrative and comparative physiology, Jan 11, 2017
Moderate acute intermittent hypoxia (mAIH) elicits a form of respiratory motor plasticity known a... more Moderate acute intermittent hypoxia (mAIH) elicits a form of respiratory motor plasticity known as phrenic long-term facilitation (pLTF). Preconditioning with modest protocols of chronic intermittent hypoxia enhances pLTF, demonstrating pLTF metaplasticity. Since "low dose" protocols of repetitive acute intermittent hypoxia show promise as a therapeutic modality to restore respiratory (and non-respiratory) motor function in clinical disorders with compromised breathing, we tested the hypothesis that preconditioning with a mild repetitive AIH (rAIH) protocol enhances pLTF and hypoglossal (XII) LTF, and whether the enhancement is regulated by glycolytic flux. In anesthetized, paralyzed and ventilated adult, male Lewis rats, mAIH (3, 5 minute episodes of 10% O2) elicited pLTF (pLTF at 60 min post-mAIH: 49 ± 5% baseline). rAIH pre-conditioning (10, 5 minute episodes of 11% O2/day, 5 min normoxic intervals, 3x per week, 4 weeks) significantly enhanced pLTF (100 ± 16% baseline)....
Résumé : Ce travail doctoral a permis d’étudier les phénomènes de plasticité anatomo-fonctionnell... more Résumé : Ce travail doctoral a permis d’étudier les phénomènes de plasticité anatomo-fonctionnelle et moléculaire survenant après lésion unilatérale cervicale de la moelle épinière. Une section latérale cervicale est suffisante pour abolir l’activité de l’hémidiaphragme ipsilatéral. Néanmoins, après un délai post-lésionnel court (7 jours), une activité phrénique ipsilatérale peut être détectée. Celle-ci dépend de voies descendantes contralatérales croisées, situées latéralement, et de voies afférentes ipsilatérales. A 3 mois post-lésionnels, cette activité est renforcée par des « nouvelles » voies descendantes spinales médianes. Au niveau moléculaire, les neurones respiratoires axotomisés (et d’autres neurones bulbaires non axotomisés) expriment c-Jun en réponse à une hémisection spinale cervicale, ce qui traduit un potentiel de plasticité intrinsèque. Dans la zone lésionnelle, les taux de certains effecteurs de plasticité (GAP-43, BDNF) sont cependant diminués. Ces résultats dans l...
The Faseb Journal, Apr 1, 2014
ABSTRACT Intermittent hypoxia exerts pathologic and beneficial effects in the CNS, depending on t... more ABSTRACT Intermittent hypoxia exerts pathologic and beneficial effects in the CNS, depending on the dose and duration. Whereas hundreds of hypoxic episodes per day mimic sleep apnea and promote neuroinflammation, low dose protocols, such as repetitive acute intermittent hypoxia (rAIH; 10 episodes of 10.5% O2 per day, 3 days/week for 4 weeks), upregulate growth/trophic factors and promote spinal motor plasticity. Because rAIH increases protein levels of key molecules associated with spinal respiratory motor plasticity, we hypothesized that the mRNAs for these and other molecules contributing to neuronal plasticity would be similarly increased. Nimblegen neuronal gene microarrays were used to profile transcript levels in the spinal ventral horn (C4-C6) of male Lewis rats exposed to normoxia or rAIH (n=3 arrays/condition). Surprisingly, there was little evidence of increased mRNA levels of pro-plasticity genes, and these results were confirmed with qRT-PCR for specific genes of interest. Instead, there were signifi
PloS one, 2016
High cervical spinal cord injuries lead to permanent respiratory deficits. One preclinical model ... more High cervical spinal cord injuries lead to permanent respiratory deficits. One preclinical model of respiratory insufficiency in adult rats is the C2 partial injury which causes unilateral diaphragm paralysis. This model allows the investigation of a particular population of respiratory bulbospinal axons which cross the midline at C3-C6 spinal segment, namely the crossed phrenic pathway. Transcranial magnetic stimulation (TMS) is a non-invasive technique that can be used to study supraspinal descending respiratory pathways in the rat. Interestingly, a lateral C2 injury does not affect the amplitude and latency of the largest motor-evoked potential recorded from the diaphragm (MEPdia) ipsilateral to the injury in response to a single TMS pulse, compared to a sham animal. Although the rhythmic respiratory activity on the contralateral diaphragm is preserved at 7 days post-injury, no diaphragm activity can be recorded on the injured side. However, a profound reorganization of the MEPdi...
Neuroscience, Jan 31, 2011
Acute intermittent hypoxia (AIH) facilitates phrenic motor output by a mechanism that requires sp... more Acute intermittent hypoxia (AIH) facilitates phrenic motor output by a mechanism that requires spinal serotonin (type 2) receptor activation, NADPH oxidase activity and formation of reactive oxygen species (ROS). Episodic spinal serotonin (5-HT) receptor activation alone, without changes in oxygenation, is sufficient to elicit NADPH oxidase-dependent phrenic motor facilitation (pMF). Here we investigated: (1) whether serotonin 2A and/or 2B (5-HT2A/B) receptors are expressed in identified phrenic motor neurons, and (2) which receptor subtype is capable of eliciting NADPH-oxidase-dependent pMF. In anesthetized, artificially ventilated adult rats, episodic C4 intrathecal injections (3×6 μl injections, 5 min intervals) of a 5-HT2A (DOI) or 5-HT2B (BW723C86) receptor agonist elicited progressive and sustained increases in integrated phrenic nerve burst amplitude (i.e. pMF), an effect lasting at least 90 min post-injection for both receptor subtypes. 5-HT2A and 5-HT2B receptor agonist-ind...
Experimental neurology, Jan 2, 2014
Amyotrophic lateral sclerosis (ALS) causes progressive motor neuron degeneration, paralysis and d... more Amyotrophic lateral sclerosis (ALS) causes progressive motor neuron degeneration, paralysis and death by ventilatory failure. In rodent ALS models: 1) breathing capacity is preserved until late in disease progression despite major respiratory motor neuron death, suggesting unknown forms of compensatory respiratory plasticity; and 2) spinal microglia become activated in association with motor neuron cell death. Here, we report a novel experimental model to study the impact of respiratory motor neuron death on compensatory responses without many complications attendant to spontaneous motor neuron disease. In specific, we used intrapleural injections of cholera toxin B fragment conjugated to saporin (CTB-SAP) to selectively kill motor neurons with access to the pleural space. Motor neuron survival, CD11b labeling (microglia), ventilatory capacity and phrenic motor output were assessed in rats 3-28days after intrapleural injections of: 1) CTB-SAP (25 and 50μg), or 2) unconjugated CTB an...
Neural Regeneration Research, 2014
A cervical spinal cord injury induces permanent paralysis, and often leads to respiratory distres... more A cervical spinal cord injury induces permanent paralysis, and often leads to respiratory distress. To date, no efficient therapeutics have been developed to improve/ameliorate the respiratory failure following high cervical spinal cord injury (SCI). Here we propose a murine pre-clinical model of high SCI at the cervical 2 (C2) metameric level to study diverse post-lesional respiratory neuroplasticity. The technique consists of a surgical partial injury at the C2 level, which will induce a hemiparalysis of the diaphragm due to a deafferentation of the phrenic motoneurons from the respiratory centers located in the brainstem. The contralateral side of the injury remains intact and allows the animal recovery. Unlike other SCIs which affect the locomotor function (at the thoracic and lumbar level), the respiratory function does not require animal motivation and the quantification of the deficit/recovery can be easily performed (diaphragm and phrenic nerve recordings, whole body ventilation). This pre-clinical C2 SCI model is a powerful, useful, and reliable pre-clinical model to study various respiratory and non-respiratory neuroplasticity events at different levels (molecular to physiology) and to test diverse putative therapeutic strategies which might improve the respiration in SCI patients.
PLoS ONE, 2014
Respiratory related diseases associated with the neuronal control of breathing represent life-thr... more Respiratory related diseases associated with the neuronal control of breathing represent life-threatening issues and to date, no effective therapeutics are available to enhance the impaired function. The aim of this study was to determine whether a preclinical respiratory model could be used for further studies to develop a non-invasive therapeutic tool applied to rat diaphragmatic neuronal circuitry. Transcranial magnetic stimulation (TMS) was performed on adult male Sprague-Dawley rats using a human figure-of-eight coil. The largest diaphragmatic motor evoked potentials (MEPdia) were recorded when the center of the coil was positioned 6 mm caudal from Bregma, involving a stimulation of respiratory supraspinal pathways. Magnetic shielding of the coil with mu metal reduced magnetic field intensities and improved focality with increased motor threshold and lower amplitude recruitment curve. Moreover, transynaptic neuroanatomical tracing with pseudorabies virus (applied to the diaphragm) suggest that connections exist between the motor cortex, the periaqueductal grey cell regions, several brainstem neurons and spinal phrenic motoneurons (distributed in the C3-4 spinal cord). These results reveal the anatomical substrate through which supraspinal stimulation can convey descending action potential volleys to the spinal motoneurons (directly or indirectly). We conclude that MEPdia following a single pulse of TMS can be successfully recorded in the rat and may be used in the assessment of respiratory supraspinal plasticity. Supraspinal non-invasive stimulations aimed to neuromodulate respiratory circuitry will enable new avenues of research into neuroplasticity and the development of therapies for respiratory dysfunction associated with neural injury and disease (e.g. spinal cord injury, amyotrophic lateral sclerosis).
Respiratory Physiology & Neurobiology, 2011
Lipopolysaccharide (LPS) induces inflammatory responses, including microglial activation in the c... more Lipopolysaccharide (LPS) induces inflammatory responses, including microglial activation in the central nervous system. Since LPS impairs certain forms of hippocampal and spinal neuroplasticity, we hypothesized that LPS would impair phrenic long-term facilitation (pLTF) following acute intermittent hypoxia (AIH) in outbred Sprague-Dawley (SD) and inbred Lewis (L) rats. Approximately 3h following a single LPS injection (i.p.), the phrenic response during hypoxic episodes is reduced in both rat strains versus vehicle treated, control rats (SD: 84 ± 7% vs. 128 ± 14% baseline for control, p < 0.05; L: 62 ± 10% vs. 90 ± 9% baseline for control, p < 0.05). At 60 min post-AIH, pLTF is also diminished by LPS in both strains: (SD: 22 ± 5% vs. 73.5 ± 14% baseline for control, p < 0.05; L: 18 ± 15% vs. 56 ± 8% baseline for control, p < 0.05). LPS alone does not affect phrenic burst frequency in either rat strain, suggesting that acute LPS injection has minimal effect on brainstem respiratory rhythm generation. Thus, systemic LPS injections and (presumptive) inflammation impair pLTF, a form of spinal neuroplasticity in respiratory motor control. These results suggest that ongoing infection or inflammation must be carefully considered in studies of respiratory plasticity, or during attempts to harness spinal plasticity as a therapeutic tool in the treatment of respiratory insufficiency, such as spinal cord injury.
Respiratory Physiology & Neurobiology, 2009
The rodent respiratory system is a relevant model for study of the intrinsic post-lesion mechanis... more The rodent respiratory system is a relevant model for study of the intrinsic post-lesion mechanisms of neuronal plasticity and resulting recovery after high cervical spinal cord injury. An unilateral cervical injury (hemisection, lateral section or contusion) interrupts unilaterally bulbospinal respiratory pathways to phrenic motor neurons innervating the diaphragm and leads to important respiratory defects on the injured side. However, the ipsilateral phrenic nerve exhibits a spontaneous and progressive recovery with post-lesion time. Shortly after a lateral injury, this partial recovery depends on the activation of contralateral pathways that cross the spinal midline caudal to the injury. Activation of these crossed phrenic pathways after the injury depends on the integrity of phrenic sensory afferents. These pathways are located principally in the lateral part of the spinal cord and involve 30% of the medullary respiratory neurons. By contrast, in chronic post-lesion conditions, the medial part of the spinal cord becomes sufficient to trigger substantial ipsilateral respiratory drive. Thus, after unilateral cervical spinal cord injury, respiratory reactivation is associated with a time-dependent anatomo-functional reorganization of the bulbospinal respiratory descending pathways, which represents an adaptative strategy for functional compensation.
Respiratory Physiology & Neurobiology, 2009
Respiratory-related complications are the leading cause of death in spinal cord injury (SCI) pati... more Respiratory-related complications are the leading cause of death in spinal cord injury (SCI) patients. Few effective SCI treatments are available after therapeutic interventions are performed in the period shortly after injury (e.g. spine stabilization and prevention of further spinal damage). In this review we explore the capacity to harness endogenous spinal plasticity induced by intermittent hypoxia to optimize function of surviving (spared) neural pathways associated with breathing. Two primary questions are addressed: 1) does intermittent hypoxia induce plasticity in spinal synaptic pathways to respiratory motor neurons following experimental SCI? and 2) can this plasticity improve respiratory function? In normal rats, intermittent hypoxia induces serotonin-dependent plasticity in spinal pathways to respiratory motor neurons. Early experiments suggest that intermittent hypoxia also enhances respiratory motor output in experimental models of cervical SCI, (cervical hemisection) and that the capacity to induce functional recovery is greater with longer durations postinjury. Available evidence suggests that intermittent hypoxia-induced spinal plasticity has considerable therapeutic potential to treat respiratory insufficiency following chronic cervical spinal injury.