Lionel Velly

Differential dynamic of action on cortical and subcortical structures of anesthetic agents during induction of anesthesia.

Background: Dynamic action of anesthetic agents was compared at cortical and subcortical levels during induction of anesthesia. Unconsciousness involved the cortical brain but suppression of movement in response to noxious stimuli was mediated through subcortical structures. Methods: Twenty-five patients with Parkinson disease, previously implanted with a deep-brain stimulation electrode, were enrolled during the implantation of the definitive pulse generator. During induction of anesthesia with propofol (n = 13) or sevoflurane (n = 12) alone, cortical (EEG) and subcortical (ESCoG) electrogenesis were obtained, respectively, from a frontal montage (F3–C3) and through the deep-brain electrode (p0–p3). In EEG and ESCoG spectral analysis, spectral edge (90%) frequency, median power frequency, and nonlinear analysis dimensional activation calculations were determined. Results: Sevoflurane and propofol decreased EEG and ESCoG activity in a dose-related fashion. EEG values decreased dramatically at loss of consciousness, whereas there was little change in ESCoG values. Quantitative parameters derived from EEG but not from ESCoG were able to predict consciousness versus unconsciousness. Conversely, quantitative parameters derived from ESCoG but not from EEG were able to predict movement in response to laryngoscopy. Conclusion: These data suggest that in humans, unconsciousness mainly involves the cortical brain, but that suppression of movement in response to noxious stimuli is mediated through the effect of anesthetic agents on subcortical structures.

Neuroprotective Effects of Propofol in a Model of Ischemic Cortical Cell Cultures Role of Glutamate and Its Transporters

Background During cerebral ischemia, excess of glutamate release and dysfunction of its high affinity transport induce an accumulation of extracellular glutamate, which plays an important role in neuronal death. The authors studied the relationship among propofol neuroprotection, glutamate extracellular concentrations, and glutamate transporter activity in a model of ischemic cortical cell cultures. Methods Thirteen-day-old primary cortical neuronal-glial cultures were exposed to a 90-min combined oxygen–glucose deprivation (OGD) in an anaerobic chamber, followed by reoxygenation. Propofol was added only during the OGD period, and its effect was compared to that of the N-methyl-d-aspartate receptor antagonist dizocilpine (MK-801). Twenty-four hours after the injury, cell death was quantified by lactate dehydrogenase release and cell viability by reduction of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT). Extracellular concentrations of glutamate in culture supernatants and glutamate uptake were performed at the end of OGD period by high-performance liquid chromatography and incorporation of l-[3H]glutamate into cells, respectively. Results At clinically relevant concentrations (0.05–10 &mgr;m), propofol offered protection equivalent to that of MK-801. It significantly reduced lactate dehydrogenase release and increased the reduction of MTT. At the end of the ischemic injury, propofol was able to reverse the OGD-induced increase in glutamate extracellular concentrations and decrease of glutamate uptake. The inhibition of the glial GLT1 transporter by 3-methyl-glutamate did not further modify the effect of propofol on glutamate uptake, suggesting that GLT1 was not the major target of propofol. Conclusion Propofol showed a neuroprotective effect in this in vitro model of OGD, which was apparently mediated by a GLT1-independent restoration of the glutamate uptake impaired during the injury.

Sevoflurane preconditioning against focal cerebral ischemia: inhibition of apoptosis in the face of transient improvement of neurological outcome.

Background:Preconditioning the brain with volatile anesthetics seems to be a viable option for reducing ischemic cerebral injury. However, it is uncertain whether this preconditioning effect extends over a longer period of time. The purpose of this study was to determine if sevoflurane preconditioning offers durable neuroprotection against cerebral ischemia. Methods:Rats (Sprague-Dawley) were randomly allocated to two groups: nonpreconditioned control group (n = 44) and preconditioned group (n = 45) exposed to 2.7 vol% sevoflurane (45 min) 60 min before surgery. Animals in both groups were anesthetized with 3.0vol% sevoflurane and subjected to transient middle cerebral artery occlusion. After 60 min of awake focal ischemia, the filament was removed. Functional neurologic outcome (range 0–18; 0 = no deficit), cerebral infarct size (Nissl staining), and apoptosis (Terminal deoxynucleotidyl transferase-mediated 2′-deoxyuridine 5′-triphosphate nick-end labeling; cleaved caspase-3 staining) were evaluated at 3, 7, and 14 days after ischemia. Results:Sevoflurane preconditioning significantly improved functional outcome and reduced infarct volume (109 ± 43 vs. 148 ± 56 mm3) 3 days after ischemia compared to the control group. However, after 7- and 14-day recovery periods, no significant differences were observed between groups. The number of apoptotic cells was significantly lower in the preconditioned group than in the control group after 3- and 7-day recovery periods. Fourteen days after ischemia, no differences were observed between groups. Conclusion:In this model of transient focal cerebral ischemia, sevoflurane preconditioning induced effective but transient neuroprotective effects. Sevoflurane preconditioning also decreased ischemia-induced apoptosis in a more sustained way because it was observed up to 7 days after injury.

Sevoflurane Protects Rat Mixed Cerebrocortical Neuronal–glial Cell Cultures against Transient Oxygen–glucose Deprivation: Involvement of Glutamate Uptake and Reactive Oxygen Species

Background:The purpose of this study was to clarify the role of glutamate and reactive oxygen species in sevoflurane-mediated neuroprotection on an in vitro model of ischemia–reoxygenation. Methods:Mature mixed cerebrocortical neuronal–glial cell cultures, treated or not with increasing concentrations of sevoflurane, were exposed to 90 min combined oxygen–glucose deprivation (OGD) in an anaerobic chamber followed by reoxygenation. Cell death was quantified by lactate dehydrogenase release into the media and cell viability by reduction of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium by mitochondrial succinate dehydrogenase. Extracellular concentrations of glutamate and glutamate uptake were assessed at the end of the ischemic injury by high-performance liquid chromatography and incorporation of L-[3H]glutamate into cells, respectively. Free radical generation in cells was assessed 6 h after OGD during the reoxygenation period using 2′,7′-dichlorofluorescin diacetate, which reacts with intracellular radicals to be converted to its fluorescent product, 2′,7′-dichlorofluorescin, in cell cytosol. Results:Twenty-four hours after OGD, sevoflurane, in a concentration-dependent manner, significantly reduced lactate dehydrogenase release and increased cell viability. At the end of OGD, sevoflurane was able to reduce the OGD-induced decrease in glutamate uptake. This effect was impaired in the presence of threo-3-methyl glutamate, a specific inhibitor of the glial transporter GLT1. Sevoflurane counteracted the increase in extracellular level of glutamate during OGD and the generation of reactive oxygen species during reoxygenation. Conclusion:Sevoflurane had a neuroprotective effect in this in vitro model of ischemia–reoxygenation. This beneficial effect may be explained, at least in part, by sevoflurane-induced antiexcitotoxic properties during OGD, probably depending on GLT1, and by sevoflurane-induced decrease of reactive oxygen species generation during reoxygenation.

Priming of late endothelial progenitor cells with erythropoietin before transplantation requires the CD131 receptor subunit and enhances their angiogenic potential

Summary.  Background:  Endothelial colony‐forming cells (ECFCs) are promising candidates for cell therapy of ischemic diseases. Erythropoietin (EPO) is a cytokine that promotes angiogenesis after ischemic injury. EPO receptors (EPORs) classically include two EPOR subunits, but may also associate with the β‐common chain (CD131) in a newly identified receptor involved in EPO cytoprotective effects.

Neuroprotective effects of tacrolimus (FK506) in a model of ischemic cortical cell cultures : Role of glutamate uptake and FK506 binding protein 12 kDa

BACKGROUND The mechanisms underlying the neuroprotective effects of the immunosuppressant tacrolimus, observed in vivo, remain unclear. Here we quantify these effects in vitro, and evaluate the potential involvement of the glutamate and/or immunophilin FK506 binding protein 12 kDa in tacrolimus-induced neuroprotection. METHODS Primary cultures of neurons and astrocytes from rat cerebral cortex were subjected to transient oxygen-glucose deprivation. Neuronal injury was evaluated by cell counting after immunostaining experiments, lactate dehydrogenase release and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide reduction. The involvement of the immunophilin FK506 binding protein 12 kDa was explored using an anti-FK506 binding protein 12 kDa antibody, (3-3-pyridyl)-1-propyl(2 s)-1-(3,3-dimethyl-1,2-dioxopentyl)-2-pyrrolidine carboxylate and rapamycin. Extracellular glutamate and glutamate uptake were respectively measured by high performance liquid chromatography and l-[3H]glutamate incorporation. RESULTS When added during either oxygen-glucose deprivation or reoxygenation, FK506 (50-500 pM) offered significant neuroprotection. During oxygen-glucose deprivation, it was able to reverse the oxygen-glucose deprivation-induced increase in extracellular glutamate and decrease in glutamate uptake and this effect was reversed in the presence of threo-3-methyl glutamate, a specific inhibitor of glutamate transporter-1. Blocking FK506 binding protein 12 kDa inhibited the neuroprotection induced by tacrolimus added during either oxygen-glucose deprivation or reoxygenation. Tacrolimus-induced neuroprotection was also reversed in the presence of rapamycin, an immunosuppressant FK506 binding protein 12 kDa ligand devoid of neuroprotective properties and (3-3-pyridyl)-1-propyl(2 s)-1-(3,3-dimethyl-1,2-dioxopentyl)-2-pyrrolidine carboxylate, a non-immunosuppressant ligand of FK506 binding protein 12 kDa, exerteing neuroprotective effects. CONCLUSION The beneficial effects of tacrolimus during in vitro ischemia/reperfusion seem to indicate the restoration of a glutamate transporter-1-mediated activity and could be mediated by a FK506 binding protein 12 kDa pathway.

Early anesthetic preconditioning in mixed cortical neuronal-glial cell cultures subjected to oxygen-glucose deprivation: the role of adenosine triphosphate dependent potassium channels and reactive oxygen species in sevoflurane-induced neuroprotection.

BACKGROUND: The purpose of the present study, on mixed cortical neuronal-glial cell cultures subjected to transient oxygen-glucose deprivation (OGD) was: i) to compare the neuroprotection afforded by sevoflurane added either before (preconditioning) or during (direct neuroprotection) the OGD and ii) to explore the possible involvement of adenosine triphosphate-sensitive potassium (KATP) channels and intracellular reactive oxygen species (ROS) levels in the mechanism of the early preconditioning effect of sevoflurane. METHODS: Mature mixed cortical neuronal-glial cell cultures were exposed to 90-min OGD in an anaerobic chamber followed by reoxygenation. Sevoflurane (0.03–3.4 mM) was randomly administered for 90 min and discontinued 60 min before OGD (early preconditioning) or during the 90-min OGD (direct neuroprotection). Cell death was quantified 24 h after the OGD by lactate dehydrogenase release into the bathing medium. Intracellular ROS generation was assessed at the end of sevoflurane preconditioning using 2′,7′-dichlorofluorescin diacetate. RESULTS: Sevoflurane preconditioning elicited a potent threshold-dependent neuroprotective effect at concentrations higher than 0.07 mM and sevoflurane added during OGD elicited a dose dependent neuroprotective effect. Blockers of KATP channels (glibenclamide 0.3 &mgr;M and 5 hydroxydecanoic acid 50 &mgr;M), or ROS-scavengers (N-2-mercaptopropionyl glycine 100 &mgr;M and N-acetylcysteine 50 &mgr;M), although they did not affect cell viability, counteracted the neuroprotection produced by early sevoflurane preconditioning. Sevoflurane exposure during preconditioning induced a significant increase in ROS levels which was prevented by both ROS scavengers and blockers of KATP channels. CONCLUSION: Early sevoflurane preconditioning induced a threshold-dependent protection of mixed cortical neuronal-glial cell cultures against OGD by mechanisms that seem to involve opening KATP channels, thereby leading to generation of ROS.

Erythropoietin protects newborn rat against sevoflurane-induced neurotoxicity.

Recent data on newborn animals exposed to anesthetics have raised safety concerns regarding anesthesia practices in young children. Indeed, studies on rodents have demonstrated a widespread increase in brain apoptosis shortly after exposure to sevoflurane, followed by long‐term neurologic impairment. In this context, we aimed to evaluate the protective effect of rh‐EPO, a potent neuroprotective agent, in rat pups exposed to sevoflurane.

Functional Cerebral Venous Outflow in Swine and Baboon: Feasibility of an Intracranial Venous Hypertension Model

Introduction: To evaluate the feasibility of performing a functional cerebral venous outflow blockage in two large animals species, the swine and the baboon, for elaboration of venous hypertension models. Method: Cerebral venous outflow pathways were identified on angiogram and venography of three swine and two baboons, and potential approaches to access these structures were assessed. Practicability of performing functional intracranial dural outflow blockage was tested. Results: The main cerebral venous outflow route was the internal jugular vein in baboons and the paraspinal venous network in swine. Both animals had an additional venous outflow structure, the petrosquamous sinus. Access to intracranial venous sinuses was achieved through a percutaneous retrograde approach in baboon but not in swine, due to the absence of a direct connection between the dural structures and the internal jugular vein. A transcranial approach allowed to access dural venous structures in swine. In both models, partial and progressive venous sinus occlusion increased intracranial pressure, while preserving the animals vital status. At 6 months, all animals are alive with no neurological deficits. Conclusion: Functional venous dural outflow blockage for elaboration of intracranial venous hypertension is feasible in both models. To be effective, the sinus blockage must be performed before the origin of the petrosquamous, an additional venous sinus seen in swine and baboon. The baboon has the greatest advantage of resembling human cerebral venous drainage, which enables an intracranial venous retrograde access. However, the transcranial approach remains a valuable option to access intracranial venous sinuses in swine.

Therapeutic benefit of a combined strategy using erythropoietin and endothelial progenitor cells after transient focal cerebral ischemia in rats

Abstract Objective: Many studies have demonstrated beneficial effects of either erythropoietin (EPO) or endothelial progenitor cell (EPC) treatment in cerebral ischemia. To improve post-ischemic tissue repair, we investigated the effect of systemic administration of endothelial colony-forming cells (ECFCs), considered as relevant endothelial progenitors due to their specific vasculogenic activity, in the presence or absence of EPO, on functional recovery, apoptosis, angiogenesis, and neurogenesis in a transient focal cerebral ischemia model in the adult rat. Design: Experimental study. Intervention: The rats were divided into four groups 24 hours after ischemia,, namely control, ECFCs, EPO, and ECFCs+EPO, and received a single intravenous injection of ECFCs (5×106 cells) and/or intraperitoneal administration of EPO (2500 UI/kg per day for 3 days). Measurement: Infarct volume, functional recovery, apoptosis, angiogenesis, and neurogenesis were assessed at different time points after ischemia. Main results: The combination of EPO and ECFCs was the only treatment that completely restored neurological function. The ECFCs+EPO treatment was also the most effective to decrease apoptosis and to increase angiogenesis and neurogenesis in the ischemic hemisphere compared to controls and to groups receiving ECFCs or EPO alone. Conclusion: These results suggest that EPO could act in a synergistic way with ECFCs to potentiate their therapeutic benefits.