Department of Neurological Sciences, Division of Epilepsy, University of Nebraska Medical Center, Omaha, NE, United States of America.
Department of Neurological Sciences, Division of Epilepsy, University of Nebraska Medical Center, Omaha, NE, United States of America.
Exp Neurol. 2024 Aug;378:114838. doi: 10.1016/j.expneurol.2024.114838. Epub 2024 May 25.
Anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis results in chronic epilepsy and permanent cognitive impairment. One of the possible causes of cognitive impairment in anti-NMDAR could be aberrant neurogenesis, an established contributor to memory loss in idiopathic drug-resistant epilepsy. We developed a mouse model of anti-NMDAR encephalitis and showed that mice exposed to patient anti-NMDAR antibodies for 2 weeks developed seizures and memory loss. In the present study, we assessed the delayed effects of patient-derived antibodies on cognitive phenotype and examined the corresponding changes in hippocampal neurogenesis.
Monoclonal anti-NMDAR antibodies or control antibodies were continuously infused into the lateral ventricle of male C56BL/6J mice (8-12 weeks) via osmotic minipumps for 2 weeks. The motor and anxiety phenotypes were assessed using the open field paradigm, and hippocampal memory and learning were assessed using the object location, Y maze, and Barnes maze paradigms during weeks 1 and 3-4 of antibody washout. The numbers of newly matured granule neurons (Prox-1+) and immature progenitor cells (DCX+) as well as their spatial distribution within the hippocampus were assessed at these time points. Bromodeoxyuridine (BrdU, 50 mg/kg, i.p., daily) was injected on days 2-12 of the infusion, and proliferating cell immunoreactivity was compared in antibody-treated mice and control mice during week 4 of the washout.
Mice infused with anti-NMDAR antibodies demonstrated spatial memory impairment during week 1 of antibody washout (p = 0.02, t-test; n = 9-11). Histological analysis of hippocampal sections from these mice revealed an increased ectopic displacement of Prox-1+ cells in the dentate hilus compared to the control-antibody-treated mice (p = 0.01; t-test). Mice exposed to anti-NMDAR antibodies also had an impairment of spatial memory and learning during weeks 3-4 of antibody washout (object location: p = 0.009; t-test; Y maze: p = 0.006, t-test; Barnes maze: p = 0.008, ANOVA; n = 8-10). These mice showed increased ratios of the low proliferating (bright) to fast proliferating (faint) BrdU+ cell counts and decreased number of DCX+ cells in the hippocampal dentate gyrus (p = 0.006 and p = 0.04, respectively; t-tests) suggesting ectopic migration and delayed cell proliferation.
These findings suggest that memory and learning impairments induced by patient anti-NMDAR antibodies are sustained upon removal of antibodies and are accompanied by aberrant hippocampal neurogenesis. Interventions directed at the manipulation of neuronal plasticity in patients with encephalitis and cognitive loss may be protective and therapeutically relevant.
抗 N-甲基-D-天冬氨酸受体（抗 NMDAR）脑炎可导致慢性癫痫和永久性认知障碍。抗 NMDAR 导致认知障碍的一个可能原因是神经发生异常，这是特发性耐药性癫痫导致记忆丧失的一个既定因素。我们建立了抗 NMDAR 脑炎的小鼠模型，并表明暴露于患者抗 NMDAR 抗体 2 周的小鼠会出现癫痫发作和记忆丧失。在本研究中，我们评估了患者来源的抗体对认知表型的延迟影响，并检查了海马神经发生的相应变化。
通过渗透微泵连续向雄性 C56BL/6J 小鼠（8-12 周龄）的侧脑室输注单克隆抗 NMDAR 抗体或对照抗体 2 周。使用旷场范式评估运动和焦虑表型，在抗体洗脱的第 1 周和第 3-4 周使用物体位置、Y 迷宫和 Barnes 迷宫范式评估海马记忆和学习。在这些时间点评估新成熟的颗粒神经元（Prox-1+）和未成熟祖细胞（DCX+）的数量及其在海马内的空间分布。在输注的第 2-12 天每天注射溴脱氧尿苷（BrdU，50mg/kg，腹腔注射），并在洗脱的第 4 周比较抗体处理组小鼠和对照组小鼠的增殖细胞免疫反应性。
输注抗 NMDAR 抗体的小鼠在抗体洗脱的第 1 周表现出空间记忆障碍（p=0.02，t 检验；n=9-11）。这些小鼠海马切片的组织学分析显示，与对照组相比，Prox-1+细胞在齿状回的异位迁移增加（p=0.01；t 检验）。暴露于抗 NMDAR 抗体的小鼠在抗体洗脱的第 3-4 周也表现出空间记忆和学习障碍（物体位置：p=0.009；t 检验；Y 迷宫：p=0.006，t 检验；Barnes 迷宫：p=0.008，ANOVA；n=8-10）。这些小鼠的 BrdU+细胞的低增殖（明亮）与快速增殖（暗淡）比例增加，海马齿状回的 DCX+细胞数量减少（p=0.006 和 p=0.04，分别为 t 检验），表明异位迁移和细胞增殖延迟。
这些发现表明，患者抗 NMDAR 抗体引起的记忆和学习障碍在抗体去除后仍然存在，并伴有异常的海马神经发生。针对脑炎和认知丧失患者神经元可塑性的干预措施可能具有保护作用和治疗相关性。
