Temporal Trends in the Use of Computed Tomographic Pulmonary Angiography for Suspected Pulmonary Embolism in the Emergency Department : A Retrospective Analysis.

BACKGROUND: Recently, validated clinical decision rules have been developed that avoid unnecessary use of computed tomographic pulmonary angiography (CTPA) in patients with suspected pulmonary embolism (PE) in the emergency department (ED). OBJECTIVE: To measure any resulting change in CTPA use for suspected PE. DESIGN: Retrospective analysis. SETTING: 26 European EDs in 6 countries. PATIENTS: Patients with CTPA performed for suspected PE in the ED during the first 7 days of each odd month between January 2015 and December 2019. MEASUREMENTS: The primary end points were the CTPAs done for suspected PE in the ED and the number of PEs diagnosed in the ED each year adjusted to an annual census of 100 000 ED visits. Temporal trends were estimated using generalized linear mixed regression models. RESULTS: 8970 CTPAs were included (median age, 63 years; 56% female). Statistically significant temporal trends for more frequent use of CTPA (836 per 100 000 ED visits in 2015 vs. 1112 in 2019; P < 0.001), more diagnosed PEs (138 per 100 000 in 2015 vs. 164 in 2019; P = 0.028), a higher proportion of low-risk PEs (annual percent change [APC], 13.8% [95% CI, 2.6% to 30.1%]) with more ambulatory management (APC, 19.3% [CI, 4.1% to 45.1%]), and a lower proportion of intensive care unit admissions (APC, -8.9% [CI, -17.1% to -0.3%]) were observed. LIMITATION: Data were limited to 7 days every 2 months. CONCLUSION: Despite the recent validation of clinical decision rules to limit the use of CTPA, an increase in the CTPA rate along with more diagnosed PEs and especially low-risk PEs were instead observed. PRIMARY FUNDING SOURCE: None specific for this study.

Implementation of lung ultrasonography by general practitioners for lower respiratory tract infections: a feasibility study.

OBJECTIVE: To evaluate the feasibility of lung ultrasonography (LUS) performed by novice users' general practitioners (GPs) in diagnosing lower respiratory tract infections (LRTIs) in primary health care settings. DESIGN: A prospective interventional multicenter study (December 2019-March 2020). SETTINGS AND SUBJECTS: Patients aged >3 months, suspected of having LRTI consulting in three different general practices (GPs) (rural, semirural and urban) in France. MAIN OUTCOME MEASURES: Feasibility of LUS by GPs was assessed by (1) the proportion of patients where LUS was not performed, (2) technical breakdowns, (3) interpretability of images by GPs, (4) examination duration and (5) patient perception and acceptability. RESULTS: A total of 151 patients were recruited, and GPs performed LUS for 111 (73.5%) patients (LUS group). In 99.1% (n = 110) of cases, GPs indicated that they were able to interpret images. The median [IQR] exam duration was 4 [3-5] minutes. LRTI was diagnosed in 70.3% and 60% of patients in the LUS and no-LUS groups, respectively (p = .43). After LUS, GPs changed their diagnosis from 'other' to 'LRTI' in six cases (+5.4%, p < .001), prescribed antibiotics for five patients (+4.5%, p = .164) and complementary chest imaging for 10 patients (+9%, p < .001). Patient stress was reported in 1.8% of cases, 81.7% of patients declared that they better understood the diagnosis, and 82% of patients thought that the GP diagnosis was more reliable after LUS. CONCLUSIONS: LUS by GPs using handheld devices is a feasible diagnostic tool in primary health care for LRTI symptoms, demonstrating both effectiveness and positive patient reception. TRIAL REGISTRATION NUMBER: Clinicaltrial.gov: NCT04602234, 20/10/2020.

Development by "simple consensus" of a tool to assist the activation of the helicopter at SAMU 14 / Élaboration par méthode du consensus simple d'un outil d'aide au déclenchement d'un hélicoptère au SAMU 14

The main objective of this work was to develop a tool to assist the activation of a helicopter emergency medical service (HEMS) for the SAMU 14. We opted for a methodology based on "guidelines of good professional practice." Simple consensus was used. A multidisciplinary working group (pilots, medical regulation assistants, doctors) was created. Subgroup meetings (pilots, medical regulation assistants, doctors) developed subparts of the tool. The assembly of the tool's subparts was reviewed by the working group and then by an independent reading group. This work enabled the consensual creation of a tool to support the use of the helicopter emergency medical service (HEMS) for the SAMU 14. It is composed of maps, a protocol, and a written procedure of activation. This methodology by "simple consensus" allowed the development of a tool rationalizing the activation of the helicopter emergency medical service (HEMS) for the SAMU 14. It was the first work of this type within the SAMU 14. This simple and transposable methodology could be used in other emergency centers or for other multidisciplinary protocols.

L'objectif principal de ce travail était la création d'un outil d'aide au déclenchement d'un SMUR héliporté au SAMU 14. Nous avons opté pour une méthodologie type « recommandations de bonnes pratiques professionnelles ¼ (RBPP). Le consensus simple a été utilisé. Un groupe de travail multidisciplinaire (pilotes, assistant de régulation médicale [ARM], médecins) a été créé. Des réunions en sous-groupe (pilote, ARM et médecins) ont permis d'élaborer des sous-parties de l'outil. L'assemblage des sous-parties de l'outil a été relu par le groupe de travail puis par un groupe de lecture autonome et validé en réunion de service. Ce travail a permis la création consensuelle d'un outil d'aide à l'emploi du vecteur héliporté en SMUR primaire au sein du SAMU 14. Il est composé de cartes, d'une fiche réflexe et d'une procédure écrite de déclenchement. Cette méthodologie par consensus simple a permis la création d'un outil rationalisant le déclenchement du vecteur héliporté pour le SAMU 14. Il s'agissait du premier travail de ce type au SAMU 14. Cette méthodologie simple et transposable pourrait être utilisée dans d'autres centres 15 ou pour d'autres protocoles multidisciplinaires.

Effect of Noninvasive Airway Management of Comatose Patients With Acute Poisoning: A Randomized Clinical Trial.

Importance: Tracheal intubation is recommended for coma patients and those with severe brain injury, but its use in patients with decreased levels of consciousness from acute poisoning is uncertain. Objective: To determine the effect of intubation withholding vs routine practice on clinical outcomes of comatose patients with acute poisoning and a Glasgow Coma Scale score less than 9. Design, Setting, and Participants: This was a multicenter, randomized trial conducted in 20 emergency departments and 1 intensive care unit (ICU) that included comatose patients with suspected acute poisoning and a Glasgow Coma Scale score less than 9 in France between May 16, 2021, and April 12, 2023, and followed up until May 12, 2023. Intervention: Patients were randomized to undergo conservative airway strategy of intubation withholding vs routine practice. Main Outcomes and Measures: The primary outcome was a hierarchical composite end point of in-hospital death, length of ICU stay, and length of hospital stay. Key secondary outcomes included adverse events resulting from intubation as well as pneumonia within 48 hours. Results: Among the 225 included patients (mean age, 33 years; 38% female), 116 were in the intervention group and 109 in the control group, with respective proportions of intubations of 16% and 58%. No patients died during the in-hospital stay. There was a significant clinical benefit for the primary end point in the intervention group, with a win ratio of 1.85 (95% CI, 1.33 to 2.58). In the intervention group, there was a lower proportion with any adverse event (6% vs 14.7%; absolute risk difference, 8.6% [95% CI, -16.6% to -0.7%]) compared with the control group, and pneumonia occurred in 8 (6.9%) and 16 (14.7%) patients, respectively (absolute risk difference, -7.8% [95% CI, -15.9% to 0.3%]). Conclusions and Relevance: Among comatose patients with suspected acute poisoning, a conservative strategy of withholding intubation was associated with a greater clinical benefit for the composite end point of in-hospital death, length of ICU stay, and length of hospital stay. Trial Registration: ClinicalTrials.gov Identifier: NCT04653597.

Élaboration par méthode du consensus simple d'un outil d'aide au déclenchement d'un hélicoptère au SAMU 14.

The main objective of this work was to develop a tool to assist the activation of a helicopter emergency medical service (HEMS) for the SAMU 14. We opted for a methodology based on "guidelines of good professional practice." Simple consensus was used. A multidisciplinary working group (pilots, medical regulation assistants, doctors) was created. Subgroup meetings (pilots, medical regulation assistants, doctors) developed subparts of the tool. The assembly of the tool's subparts was reviewed by the working group and then by an independent reading group. This work enabled the consensual creation of a tool to support the use of the helicopter emergency medical service (HEMS) for the SAMU 14. It is composed of maps, a protocol, and a written procedure of activation. This methodology by "simple consensus" allowed the development of a tool rationalizing the activation of the helicopter emergency medical service (HEMS) for the SAMU 14. It was the first work of this type within the SAMU 14. This simple and transposable methodology could be used in other emergency centers or for other multidisciplinary protocols.

FRENCH versus ESI: comparison between two nurse triage emergency scales with referent scenarios.

OBJECTIVES: Acute triage is needed to prioritize care and achieve optimal resource allocation in busy emergency departments. The main objective is to compare the FRench Emergency Nurse Classification in Hospital scale (FRENCH) to the American scale Emergency Severity Index (ESI). Secondary objectives are to compare for each scale the over and under-triage, the triage matching to the gold standard and the inter-individual sorting reproducibility between the nurses. METHODS: This is a prospective observational study conducting among the nursing staffs and nursing students, selected from Caen University College Hospital and Lisieux Hospital Center emergency departments between two months. Each group individually rank 60 referent clinical cases composed by scales designers. An assessment of scale practicality is collected after for each tool. The collected parameters are analyzed by a Cohen kappa concordance test (κ). RESULTS: With 8151 triage results of gold standard scenarios sorting in two scales by the same nurses, the FRENCH scale seems to give better triage results than the US ESI scale (nurse: FRENCH 60% and ESI 53%, p = 0.003 ; nursing students: FRENCH 49% and ESI 42%, p < 0.001). In the two groups ESI has also a big tendency to under-sort (p = 0.01), particularly for the most severe patients (p < 0.01). The interobserver sorting concordance for any experience gives good results for the FRENCH and the ESI without any difference (nurses : FRENCH KPQ=0.72 ESI KPQ=0.78; p = 0.32 ; students KPQ=0.44 KPQ=0.55; p = 0.22). CONCLUSION: The ESI and FRENCH scales comparison on 8151 sorting results shows direct validity in favor of FRENCH one and similar interobserver agreement for both scales.

Nonionotropic Action of Endothelial NMDA Receptors on Blood-Brain Barrier Permeability via Rho/ROCK-Mediated Phosphorylation of Myosin.

Increase in blood-brain barrier (BBB) permeability is a crucial step in neuroinflammatory processes. We previously showed that N Methyl D Aspartate Receptor (NMDARs), expressed on cerebral endothelial cells forming the BBB, regulate immune cell infiltration across this barrier in the mouse. Here, we describe the mechanism responsible for the action of NMDARs on BBB permeabilization. We report that mouse CNS endothelial NMDARs display the regulatory GluN3A subunit. This composition confers to NMDARs' unconventional properties: these receptors do not induce Ca2+ influx but rather show nonionotropic properties. In inflammatory conditions, costimulation of human brain endothelial cells by NMDA agonists (NMDA or glycine) and the serine protease tissue plasminogen activator, previously shown to potentiate NMDAR activity, induces metabotropic signaling via the Rho/ROCK pathway. This pathway leads to an increase in permeability via phosphorylation of myosin light chain and subsequent shrinkage of human brain endothelial cells. Together, these data draw a link between NMDARs and the cytoskeleton in brain endothelial cells that regulates BBB permeability in inflammatory conditions.SIGNIFICANCE STATEMENT The authors describe how NMDARs expressed on endothelial cells regulate blood-brain barrier function via myosin light chain phosphorylation and increase in permeability. They report that these non-neuronal NMDARs display distinct structural, functional, and pharmacological features than their neuronal counterparts.

Autoimmune encephalitis mediated by B-cell response against N-methyl-d-aspartate receptor.

Anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis is a neuropsychiatric disease characterized by an antibody-mediated autoimmune response against NMDAR. Recent studies have shown that anti-NMDAR antibodies are involved in the pathophysiology of the disease. However, the upstream immune and inflammatory processes responsible for this pathogenic response are still poorly understood. Here, we immunized mice against the region of NMDA receptor containing the N368/G369 amino acids, previously implicated in a pathogenic response. This paradigm induced encephalopathy characterized by blood-brain barrier opening, periventricular T2-MRI hyperintensities and IgG deposits into the brain parenchyma. Two weeks after immunization, mice developed clinical symptoms reminiscent of encephalitis: anxiety- and depressive-like behaviours, spatial memory impairment (without motor disorders) and increased sensitivity to seizures. This response occurred independently of overt T-cell recruitment. However, it was associated with B220+ (B cell) infiltration towards the ventricles, where they differentiated into CD138+ cells (plasmocytes). Interestingly, these B cells originated from peripheral lymphoid organs (spleen and cervical lymphoid nodes). Finally, blocking the B-cell response using a depleting cocktail of antibodies reduced the severity of symptoms in encephalitis mice. This study demonstrates that the B-cell response can lead to an autoimmune reaction against NMDAR that drives encephalitis-like behavioural impairments. It also provides a relevant platform for dissecting encephalitogenic mechanisms in an animal model, and enables the testing of therapeutic strategies targeting the immune system in anti-NMDAR encephalitis.

Prediction of disease activity in models of multiple sclerosis by molecular magnetic resonance imaging of P-selectin.

New strategies for detecting disease activity in multiple sclerosis are being investigated to ameliorate diagnosis and follow-up of patients. Today, although magnetic resonance imaging (MRI) is widely used to diagnose and monitor multiple sclerosis, no imaging tools exist to predict the evolution of disease and the efficacy of therapeutic strategies. Here, we show that molecular MRI targeting the endothelial adhesion molecule P-selectin unmasks the pathological events that take place in the spinal cord of mice subjected to chronic or relapsing experimental autoimmune encephalomyelitis. This approach provides a quantitative spatiotemporal follow-up of disease course in relation to clinical manifestations. Moreover, it predicts relapse in asymptomatic mice and remission in symptomatic animals. Future molecular MRI targeting P-selectin may be used to improve diagnosis, follow-up of treatment, and management of relapse/remission cycles in multiple sclerosis patients by providing information currently inaccessible through conventional MRI techniques.

Neuroendothelial NMDA receptors as therapeutic targets in experimental autoimmune encephalomyelitis.

Multiple sclerosis is among the most common causes of neurological disability in young adults. Here we provide the preclinical proof of concept of the benefit of a novel strategy of treatment for multiple sclerosis targeting neuroendothelial N-methyl-D-aspartate glutamate receptors. We designed a monoclonal antibody against N-methyl-D-aspartate receptors, which targets a regulatory site of the GluN1 subunit of N-methyl-D-aspartate receptor sensitive to the protease tissue plasminogen activator. This antibody reverted the effect of tissue plasminogen activator on N-methyl-D-aspartate receptor function without affecting basal N-methyl-D-aspartate receptor activity (n = 21, P < 0.01). This antibody bound N-methyl-D-aspartate receptors on the luminal surface of neurovascular endothelium in human tissues and in mouse, at the vicinity of tight junctions of the blood-spinal cord barrier. Noteworthy, it reduced human leucocyte transmigration in an in vitro model of the blood-brain barrier (n = 12, P < 0.05). When injected during the effector phase of MOG-induced experimental autoimmune encephalomyelitis (n = 24), it blocked the progression of neurological impairments, reducing cumulative clinical score (P < 0.001) and mean peak score (P < 0.001). This effect was observed in wild-type animals but not in tissue plasminogen activator knock-out animals (n = 10). This therapeutic effect was associated to a preservation of the blood-spinal cord barrier (n = 6, P < 0.001), leading to reduced leucocyte infiltration (n = 6, P < 0.001). Overall, this study unveils a critical function of endothelial N-methyl-D-aspartate receptor in multiple sclerosis, and highlights the therapeutic potential of strategies targeting the protease-regulated site of N-methyl-D-aspartate receptor.

Efficacy of Alteplase in a Mouse Model of Acute Ischemic Stroke: A Retrospective Pooled Analysis.

BACKGROUND AND PURPOSE: The debate over the fact that experimental drugs proposed for the treatment of stroke fail in the translation to the clinical situation has attracted considerable attention in the literature. In this context, we present a retrospective pooled analysis of a large data set from preclinical studies, to examine the effects of early versus late administration of intravenous recombinant tissue-type plasminogen activator. METHODS: We collected data from 26 individual studies from 9 international centers (13 researchers; 716 animals) that compared recombinant tissue-type plasminogen activator with controls, in a unique mouse model of thromboembolic stroke induced by an in situ injection of thrombin into the middle cerebral artery. Studies were classified into early (<3 hours) versus late (≥3 hours) drug administration. Final infarct volumes, assessed by histology or magnetic resonance imaging, were compared in each study, and the absolute differences were pooled in a random-effect meta-analysis. The influence of time of administration was tested. RESULTS: When compared with saline controls, early recombinant tissue-type plasminogen activator administration was associated with a significant benefit (absolute difference, -6.63 mm(3); 95% confidence interval, -9.08 to -4.17; I(2)=76%), whereas late recombinant tissue-type plasminogen activator treatment showed a deleterious effect (+5.06 mm(3); 95% confidence interval, +2.78 to +7.34; I(2)=42%; Pint<0.00001). Results remained unchanged after subgroup analyses. CONCLUSIONS: Our results provide the basis needed for the design of future preclinical studies on recanalization therapies using this model of thromboembolic stroke in mice. The power analysis reveals that a multicenter trial would require 123 animals per group instead of 40 for a single-center trial.

Effect of the 1-h bundle on mortality in patients with suspected sepsis in the emergency department: a stepped wedge cluster randomized clinical trial.

PURPOSE: The efficacy of the 1-h bundle for emergency department (ED) patients with suspected sepsis, which includes lactate measurement, blood culture, broad-spectrum antibiotics administration, administration of 30 mL/kg crystalloid fluid for hypotension or lactate ≥ 4 mmol/L, remains controversial. METHODS: We carried out a pragmatic stepped-wedge cluster-randomized trial in 23 EDs in France and Spain. Adult patients with Sepsis-3 criteria or a quick sequential organ failure assessment (SOFA) score ≥ 2 or a lactate > 2 mmol/L were eligible. The intervention was the implementation of the 1-h sepsis bundle. The primary outcome was in-hospital mortality truncated at 28 days. Secondary outcomes included volume of fluid resuscitation at 24 h, acute heart failure at 24 h, SOFA score at 72 h, intensive care unit (ICU) length of stay, number of days on mechanical ventilation or renal replacement therapy, vasopressor free days, unnecessary antibiotic administration, and mortality at 28 days. 1148 patients were planned to be analysed; the study period ended after 873 patients were included. RESULTS: 872 patients (mean age 66, 42% female) were analyzed: 387 (44.4%) in the intervention group and 485 (55.6%) in the control group. Median SOFA score was 3 [1-5]. Median time to antibiotic administration was 40 min in the intervention group vs 113 min in the control group (difference - 73 [95% confidence interval (CI) - 93 to - 53]). There was a significantly higher rate, volume, and shorter time to fluid resuscitation within 3 h in the intervention group. There were 47 (12.1%) in-hospital deaths in the intervention group compared to 61 (12.6%) in the control group (difference in percentage - 0.4 [95% CI - 5.1 to 4.2], adjusted relative risk (aRR) 0.81 [95% CI 0.48 to 1.39]). There were no differences between groups for other secondary endpoints. CONCLUSIONS: Among patients with suspected sepsis in the ED, the implementation of the 1-h sepsis bundle was not associated with significant difference in in-hospital mortality. However, this study may be underpowered to report a statistically significant difference between groups.

GluN2D subunit-containing NMDA receptors control tissue plasminogen activator-mediated spatial memory.

Tissue plasminogen activator (tPA) is a serine protease with pleiotropic actions in the CNS, such as synaptic plasticity and neuronal death. Some effects of tPA require its interaction with the GluN1 subunit of the NMDA receptor (NMDAR), leading to a potentiation of NMDAR signaling. We have reported previously that the pro-neurotoxic effect of tPA is mediated through GluN2D subunit-containing NMDARs. Thus, the aim of the present study was to determine whether GluN2D subunit-containing NMDARs drive tPA-mediated cognitive functions. To address this issue, a strategy of immunization designed to prevent the in vivo interaction of tPA with NMDARs and GluN2D-deficient mice were used in a set of behavioral tasks. Altogether, our data provide the first evidence that tPA influences spatial memory through its preferential interaction with GluN2D subunit-containing NMDARs.

High t-PA release by neonate brain microvascular endothelial cells under glutamate exposure affects neuronal fate.

Glutamate excitotoxicity is a consolidated hypothesis in neonatal brain injuries and tissue plasminogen activator (t-PA) participates in the processes through proteolytic and receptor mediated effects. In brain microvascular endothelial cell (nBMEC) cultures from neonates, t-PA content and release upon glutamate are higher than in adult (aBMECs) cultures. Owing to the variety of t-PA substrates and receptor targets, the study was aimed at determining the putative roles of endothelial t-PA in the neonatal brain parenchyma under glutamate challenge. Basal t-PA release was 4.4 fold higher in nBMECs vs aBMECs and glutamate was 20 fold more potent to allow Evans blue vascular permeability in neonate microvessels indicating that, under noxious glutamate (50 µM) exposure, high amounts of endothelial t-PA stores may be mobilized and may access the nervous parenchyma. Culture media from nBMECS or aBMECs challenged by excitotoxic glutamate were applied to neuron cultures at DIV 11. While media from adult cells did not evoke more LDH release in neuronal cultures that under glutamate alone, media from nBMECs enhanced 2.2 fold LDH release. This effect was not observed with media from t-PA(-/-) nBMECs and was inhibited by hr-PAI-1. In Cortical slices from 10 day-old mice, hrt-PA associated with glutamate evoked neuronal necrosis in deeper (more mature) layers, an effect reversed by NMDA receptor GluN1 amino-terminal domain antibody capable of inhibiting t-PA potentiation of the receptor. In superficial layers (less mature), hrt-PA alone inhibited apoptosis, an effect reversed by the EGF receptor antagonist AG1478. Applied to immature neurons in culture (DIV5), media from nBMEC rescued 85.1% of neurons from cell death induced by serum deprivation. In cortical slices, the anti-apoptotic effect of t-PA fitted with age dependent localization of less mature neurons. These data suggest that in the immature brain, propensity of vessels to release high amounts of t-PA may not only impact vascular integrity but may also influence neuronal fate, via regulation of apoptosis in immature cells and, as in adult by potentiating glutamate toxicity in mature neurons. The data point out putative implication of microvessels in glutamate neurotoxicity in the development, and justify research towards vessel oriented neuroprotection strategies in neonates.

Ultra-sensitive molecular MRI of cerebrovascular cell activation enables early detection of chronic central nervous system disorders.

Since endothelial cells can be targeted by large contrast-carrying particles, molecular imaging of cerebrovascular cell activation is highly promising to evaluate the underlying inflammation of the central nervous system (CNS). In this study, we aimed to demonstrate that molecular magnetic resonance imaging (MRI) of cerebrovascular cell activation can reveal CNS disorders in the absence of visible lesions and symptoms. To this aim, we optimized contrast carrying particles targeting vascular cell adhesion molecule-1 and MRI protocols through both in vitro and in vivo experiments. Although, pre-contrast MRI images failed to reveal the ongoing pathology, contrast-enhanced MRI revealed hypoperfusion-triggered CNS injury in vascular dementia, unmasked amyloid-induced cerebrovascular activation in Alzheimer's disease and allowed monitoring of disease activity during experimental autoimmune encephalomyelitis. Moreover, contrast-enhanced MRI revealed the cerebrovascular cell activation associated with known risk factors of CNS disorders such as peripheral inflammation, ethanol consumption, hyperglycemia and aging. By providing a dramatically higher sensitivity than previously reported methods and molecular contrast agents, the technology described in the present study opens new avenues of investigation in the field of neuroinflammation.

Antibodies preventing the interaction of tissue-type plasminogen activator with N-methyl-D-aspartate receptors reduce stroke damages and extend the therapeutic window of thrombolysis.

BACKGROUND AND PURPOSE: Tissue-type plasminogen activator (tPA) is the only drug approved for the acute treatment of ischemic stroke but with two faces in the disease: beneficial fibrinolysis in the vasculature and damaging effects on the neurovascular unit and brain parenchyma. To improve this profile, we developed a novel strategy, relying on antibodies targeting the proneurotoxic effects of tPA. METHODS: After production and characterization of antibodies (αATD-NR1) that specifically prevent the interaction of tPA with the ATD-NR1 of N-methyl-d-aspartate receptors, we have evaluated their efficacy in a model of murine thromboembolic stroke with or without recombinant tPA-induced reperfusion, coupled to MRI, near-infrared fluorescence imaging, and behavior assessments. RESULTS: In vitro, αATD-NR1 prevented the proexcitotoxic effect of tPA without altering N-methyl-d-aspartate-induced neurotransmission. In vivo, after a single administration alone or with late recombinant tPA-induced thrombolysis, antibodies dramatically reduced brain injuries and blood-brain barrier leakage, thus improving long-term neurological outcome. CONCLUSIONS: Our strategy limits ischemic damages and extends the therapeutic window of tPA-driven thrombolysis. Thus, the prospect of this immunotherapy is an extension of the range of treatable patients.

Functional occurrence of the interaction of tissue plasminogen activator with the NR1 Subunit of N-methyl-D-aspartate receptors during stroke.

BACKGROUND AND PURPOSE: Despite its fibrinolytic effect, tissue-type plasminogen activator (tPA) displays deleterious effects in the brain, including proexcitotoxicity, that can reduce the overall benefit from thrombolysis during stroke. We have proposed that tPA potentiates excitotoxicity by interacting with and cleaving the aminoterminal end of the NR1 subunit of N-methyl-d-aspartate receptors, leading to an increased calcium influx, Erk1/2 activation, and neurotoxicity. Because this mechanism is debated, our aim was to demonstrate its in vivo occurrence and relevance. Because tPA is released under ischemic conditions, we hypothesized that if it indeed processes NR1, then the released fragment should reactivate the immune system in animals that had been immunized long before with recombinant aminoterminal end of the NR1. This effect should be exacerbated in ischemic animals thrombolysed with recombinant tPA. METHODS: At a time when specific antibodies could not be detected any longer, mice previously vaccinated with recombinant aminoterminal end of the NR1 were subjected to thromboembolic stroke induced by injecting thrombin in the middle cerebral artery alone or with intravenous thrombolysis. RESULTS: Stroke performed 1 year after active immunization induced the reappearance of antibodies against the aminoterminal end of the NR1 in the plasma, an effect significantly increased when ischemia was followed by recombinant tPA-induced reperfusion. Moreover, immunization preventing the interaction of tPA with aminoterminal end of the NR1 reduced ischemic brain damages and extended the therapeutic window of tPA-induced thrombolysis. CONCLUSIONS: We demonstrate that the tPA-dependent interaction and cleavage of the NR1 subunit of N-methyl-d-aspartate receptors occurs in vivo after stroke and that this interaction is a relevant therapeutic target for stroke treatment.