Human gestational N‐methyl‐d‐aspartate receptor autoantibodies impair neonatal murine brain function

Objective: Maternal autoantibodies are a risk factor for impaired brain development in offspring. Antibodies (ABs) against the NR1 (GluN1) subunit of the N-methyl-d-aspartate receptor (NMDAR) are among the most frequently diagnosed anti-neuronal surface ABs, yet little is known about effects on fetal development during pregnancy. Methods: We established a murine model of in utero exposure to human recombinant NR1 and isotype-matched nonreactive control ABs. Pregnant C57BL/6J mice were intraperitoneally injected on embryonic days 13 and 17 each with 240μg of human monoclonal ABs. Offspring were investigated for acute and chronic effects on NMDAR function, brain development, and behavior. Results: Transferred NR1 ABs enriched in the fetus and bound to synaptic structures in the fetal brain. Density of NMDAR was considerably reduced (up to -49.2%) and electrophysiological properties were altered, reflected by decreased amplitudes of spontaneous excitatory postsynaptic currents in young neonates (-34.4%). NR1 AB-treated animals displayed increased early postnatal mortality (+27.2%), impaired neurodevelopmental reflexes, altered blood pH, and reduced bodyweight. During adolescence and adulthood, animals showed hyperactivity (+27.8% median activity over 14 days), lower anxiety, and impaired sensorimotor gating. NR1 ABs caused long-lasting neuropathological effects also in aged mice (10 months), such as reduced volumes of cerebellum, midbrain, and brainstem. Interpretation: The data collectively support a model in which asymptomatic mothers can harbor low-level pathogenic human NR1 ABs that are diaplacentally transferred, causing neurotoxic effects on neonatal development. Thus, AB-mediated network changes may represent a potentially treatable neurodevelopmental congenital brain disorder contributing to lifelong neuropsychiatric morbidity in affected children

Der Einfluss maternaler GluN1-Antikörper auf die Nachkommen im Mausmodell

Autoantibodies (AB) against the essential GluN1 subunit of the glutamatergic N-methyl-D-aspartate receptor (NMDAR) are among commonly diagnosed neuronal AB also in healthy individuals creating a considerable subgroup of pregnant women potentially transferring these AB during pregnancy to their fetus. In this study, we established a murine model of maternal AB transfer in order to investigate the effects of human GluN1 AB on the development of the offspring. Therefore, 240 µg of patient-derived, monoclonal GluN1 AB or an isotype-matched non-reactive control (CTL) AB was injected into pregnant C57BL/6J dams at gestational days E13 and E17. Physiological, developmental and behavioral parameters in the offspring were investigated for AB-mediated effects at different developmental stages (E19, P0-P14, adulthood and old age). Indeed, GluN1 AB were enriched in neonatal circulation and brain parenchyma, leading to considerably reduced NMDAR densities (up to 49.2%) in early neonatal life and reducing amplitudes of spontaneous excitatory postsynaptic currents in acute slices. Exposure to GluN1 AB increased mortality (+27%) within the first postnatal days, impaired establishment of neonatal reflexes and reduced bodyweight during neonatal life and adolescence. AB interaction also caused profound changes persisting into adulthood as GluN1 AB-treated offspring displayed significantly decreased brain volumes (total brain, cerebral cortex, cerebellum, and brain stem) and had altered behavioral profiles of hyperactivity, reduced anxiety and impaired pre-pulse inhibition. This murine model proves the pathogenicity of maternally transferred GluN1 AB by causing developmental deficits in early life with long-lasting changes persisting into late adulthood. It might offer an explanation for various features of unclear developmental abnormalities also in humans and builds the basis for further evaluation of prevalence and relevance of GluN1 AB in pregnant women.Autoantikörper (AK) gegen die essentielle Untereinheit GluN1 des glutamatergen N-Methyl-D-Aspartat-Rezeptors (NMDAR) zählen zu den häufig diagnostizierten anti-neuronalen AK auch in der gesunden Bevölkerung. Damit besteht eine große Wahrscheinlichkeit, dass auch schwangere Frauen diesen AK tragen und ihn während der Schwangerschaft auf ihren Fötus über die Plazenta transferieren. Um das Potenzial dieser GluN1 AK zu evaluieren, entwickelten wir ein Mausmodell des maternalen GluN1-AK-Transfers. Dabei wurden je 240 μg eines humanen, monoklonalen GluN1-AK oder eines entsprechenden nicht-reaktiven Kontrollantikörpers in trächtige C57BL/6J Mäuse am 13. und 17. Tag der Trächtigkeit injiziert und die Auswirkungen auf die Nachkommen hinsichtlich Physiologie, Entwicklung und Verhalten zu unterschiedlichen Zeitpunkten ihrer Entwicklung (E19, P0-P14, Erwachsenenalter und fortgeschrittenes Alter) untersucht. Dabei zeigte sich nicht nur, dass der AK in hoher Konzentration übertragen wurde, sondern sogar eine Anreicherung der AK im neonatalen Blutkreislauf und Hirngewebe erfolgte, was zur einer ausgeprägten Reduktion von NMDAR (bis zu 49,2%) führte und die Amplituden von spontanen exzitatorischen postsynaptischen Strömen verringerte. Zudem erhöhten GluN1-AK die Mortalität (+27%), verzögerten die Ausbildung neonataler Reflexe und verringerten das Körpergewicht der murinen Nachkommen bis zum Erwachsenenalter. Die von dem Muttertier übertragenen AK führten nicht nur zu Einschränkungen in der Postnatalphase der Nachkommen, sondern verursachten auch weitreichende Änderungen im Erwachsenenalter, da sie zu einer Reduktion der Hirnvolumina (Gesamthirnvolumen, zerebraler Cortex, Kleinhirn und Hirnstamm) und einem veränderten Verhaltensprofil mit Hyperaktivität, reduziertem Angstverhalten und Störungen des sensomotorischen Gatings führten. Mit diesem Tiermodell konnte die Pathogenität maternaler GluN1 AK nachgewiesen werden, die nicht nur die frühe Entwicklung der Nachkommen schädigten, sondern auch zu langanhaltenden Veränderungen bis ins Erwachsenenalter führten. Diese Arbeit bietet eine mögliche Erklärung für vielgestaltige entwicklungsbedingte Störungen beim Menschen und bildet die Basis für weitere Untersuchungen, um die Häufigkeit und die Relevanz von AK gegen GluN1 in schwangeren Frauen zu untersuchen

A Rank-Order Procedure Applied to an Ethoexperimental Behavior Model—The Multivariate Concentric SquareField™ (MCSF) Test

Designing relevant animal models in order to investigate the neurobiological basis for human mental disorders is an important challenge. The need for new tests to be developed and traditional tests to be improved has recently been em-phasized. The authors propose a multivariate test approach, the multivariate concentric square fieldTM (MCSF) test. To measure and evaluate variation in the behavioral traits, we here put forward a statistical procedure of which the working title is “trend analysis”. Low doses of the benzodiazepine agonist diazepam (DZP; 1.0, 1.5, or 2.0 mg/kg) were used for exploring the use of the trend analysis in combination with multivariate data analysis for assessment of MCSF per-formance in rats. The commonly used elevated plus maze (EPM) test was used for comparison. The trend analysis comparing vehicle and the DZP1.5 groups revealed significantly higher general activity and risk-taking behavior in the DZP1.5 rats relative to vehicle rats. This finding was supported by multivariate data analysis procedures. It is concluded that the trend analysis together with multivariate data analysis procedures offers possibilities to extract information and illustrates effects obtained in the MCSF test. Diazepam in doses that have no apparent increase in open arm activity in the EPM was effective to alter the behavior in the MCSF test. The MCSF test and the use of multivariate data analysis and the proposed trend analysis may be useful alternatives to behavioral test batteries and traditionally used tests for the understanding of mechanisms underlying various mental states. Finally, the impact of an ethological reasoning and multivariate measures enabling behavioral profiling of animals may be a useful complementary methodology when phenotyping animals in behavioral neuroscience

Altered paired associative stimulation‐induced plasticity in NMDAR

OBJECTIVE: To determine whether neurophysiological mechanisms indicating cortical excitability, long‐term potentiation (LTP)‐like plasticity, GABAergic and glutamatergic function are altered in patients with anti‐N‐methyl‐d‐aspartate receptor (NMDAR) encephalitis and whether they can be helpful as markers of diagnostic assessment, disease progression, and potentially therapy response. METHODS: Neurophysiological characterizations of patients with NMDAR encephalitis (n = 34, mean age: 28 ± 11 years; 30 females) and age/gender‐matched healthy controls (n = 27, 28.5 ± 10 years; 25 females) were performed using transcranial magnetic stimulation‐derived protocols including resting motor threshold, recruitment curve, intracortical facilitation, short intracortical inhibition, and cortical silent period. Paired associative stimulation (PAS) was applied to assess LTP‐like mechanisms which are mediated through NMDAR. Moreover, resting state functional connectivity was determined using functional magnetic resonance imaging. RESULTS: PAS‐induced plasticity differed significantly between groups (P = 0.0056). Cortical excitability, as assessed via motor‐evoked potentials after PAS, decreased in patients, whereas it increased in controls indicating malfunctioning of NMDAR in encephalitis patients. Lower PAS‐induced plasticity significantly correlated with the modified Rankin Scale (mRS) (r = −0.41; P = 0.0031) and was correlated with lower functional connectivity within the motor network in NMDAR encephalitis patients (P < 0.001, uncorrected). Other neurophysiological parameters were not significantly different between groups. Follow‐up assessments were available in six patients and demonstrated parallel improvement of PAS‐induced plasticity and mRS. INTERPRETATION: Assessment of PAS‐induced plasticity may help to determine NMDAR dysfunction and disease severity in NMDAR encephalitis, and might even aid as a sensitive, noninvasive, and well‐tolerated “electrophysiological biomarker” to monitor therapy response in the future. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov: Identifier: NCT0186557