视黄酸受体α通过调控视皮质轴突蛋白1参与维生素A缺乏大鼠孤独症样行为的机制研究

Involvement of retinoic acid receptor α in the autistic-like behavior of rats with vitamin A deficiency by regulating neurexin 1 in the visual cortex: a mechanism study

摘要:

目的 探讨视黄酸受体α（retinoic acid receptor α，RARα）信号变化通过调控视皮质轴突蛋白1（neurexin 1，NRXN1）参与维生素A缺乏（vitamin A deficiency，VAD）大鼠孤独症样行为的机制。 方法 构建孕期开始的维生素A正常（vitamin A normal，VAN）和VAD母鼠模型，并在生后早期对部分VAD母鼠和仔鼠给予维生素A补充（vitamin A supplement，VAS）。各组仔鼠（n=20）于6周龄进行行为学检测，利用三箱和旷场实验检测各组仔鼠社交行为和重复刻板行为；采用高效液相色谱法检测各组仔鼠血清视黄醇水平；采用电生理实验检测各组仔鼠视皮质的长时程增强（long-term potentiation，LTP）水平；采用实时荧光定量PCR法和Western blot法检测RARα、NRXN1和N-甲基-D-天冬氨酸受体1（N-methyl-D-aspartate receptor subunit 1，NMDAR1）的表达水平；采用染色质免疫共沉淀技术检测RARα转录因子在NRXN1基因启动子区的富集量。 结果 VAD组仔鼠出现社会交往障碍、重复刻板等孤独症样行为表现，生后开始的VAS可改善仔鼠大部分行为缺陷。VAD组仔鼠血清视黄醇水平明显低于VAN组和VAS组（P<0.05）。VAD组仔鼠视皮质NMDAR1、RARα和NRXN1的mRNA和蛋白表达水平及LTP水平均较VAN组和VAS组显著降低（P<0.05）。VAD组仔鼠视皮质中RARα转录因子在NRXN1基因启动子区的富集量较VAN组和VAS组显著下降（P<0.05）。 结论 RARα通过调控NRXN1影响VAD大鼠视皮质突触可塑性，从而参与VAD大鼠孤独症样行为的形成。

Abstract:

Objective To study the mechanism of retinoic acid receptor α (RARα) signal change to regulate neurexin 1 (NRXN1) in the visual cortex and participate in the autistic-like behavior in rats with vitamin A deficiency (VAD). Methods The models of vitamin A normal (VAN) and VAD pregnant rats were established, and some VAD maternal and offspring rats were given vitamin A supplement (VAS) in the early postnatal period. Behavioral tests were performed on 20 offspring rats in each group at the age of 6 weeks. The three-chamber test and the open-field test were used to observe social behavior and repetitive stereotyped behavior. High-performance liquid chromatography was used to measure the serum level of retinol in the offspring rats in each group. Electrophysiological experiments were used to measure the long-term potentiation (LTP) level of the visual cortex in the offspring rats. Quantitative real-time PCR and Western blot were used to measure the expression levels of RARα, NRXN1, and N-methyl-D-aspartate receptor 1 (NMDAR1). Chromatin co-immunoprecipitation was used to measure the enrichment of RARα transcription factor in the promoter region of the NRXN1 gene. Results The offspring rats in the VAD group had autistic-like behaviors such as impaired social interactions and repetitive stereotypical behaviors, and VAS started immediately after birth improved most of the behavioral deficits in offspring rats. The offspring rats in the VAD group had a significantly lower serum level of retinol than those in the VAN and VAS groups (P<0.05). Compared with the offspring rats in the VAN and VAS groups, the offspring rats in the VAD group had significant reductions in the mRNA and protein expression levels of NMDAR1, RARα, and NRXN1 and the LTP level of the visual cortex (P<0.05). The offspring rats in the VAD group had a significant reduction in the enrichment of RARα transcription factor in the promoter region of the NRXN1 gene in the visual cortex compared with those in the VAN and VAS groups (P<0.05). Conclusions RARα affects the synaptic plasticity of the visual cortex in VAD rats by regulating NRXN1, thereby participating in the formation of autistic-like behaviors in VAD rats.