Abstract:

Dexamethasone is a glucocorticoid drug with various pharmacological effects such as anti-inflammatory and immunosuppressive effects. It is widely used in multiple departments to treat multiple autoimmune diseases. Dexamethasone is often used during pregnancy to promote lung maturation in preterm infants and prevent fetal respiratory distress syndrome. Current epidemiological and experimental studies have shown that dexamethasone exposure during pregnancy could lead to an increased risk of cartilage and kidney damage in the offspring. This study investigated the effects of prenatal dexamethasone exposure （PDE） on the proliferation of fetal hippocampal neurons and the formation of synaptic plasticity in the fetal hippocampus. Wistar rats were injected subcutaneously with dexamethasone （0.2 mg·kg^-1·d^-1） at mid-to-late gestation， and the control group was treated with isodose 0.9% sodium chloride solution. The hippocampus of GD20 offspring was collected and examined for morphology and functions related to hippocampal neuron proliferation and synaptic plasticity formation by real-time fluorescence quantitative PCR and Western blot. We further examined adaptor protein containing pH domain， PTB domain， and leucine zipper motif 1 （APPL1）. Restlts showed that， compared with the blank control group， the specific indexes of Ki67， proliferating cell nuclear antigen （PCNA）， synaptic fusion protein （syntaxin）， and 25 kD synaptic-associated protein （SNAP25） in PDE fetal hippocampus were significantly reduced， suggesting that PDE inhibited neural proliferation， synaptic development， and other functions in the fetal hippocampus. Western blot showed significant downregulation of postsynaptic dense protein 95 （PSD95） in the PDE group， confirming that PDE could lead to impaired synaptic plasticity in the offspring hippocampus. APPL1 results showed that APPL1 expression was down-regulated in the hippocampus of PDE offspring， so it was hypothesized that PDE might affect hippocampal synaptic plasticity in offspring by regulating APPL1 expression. The study suggested that PDE is developmentally toxic to the hippocampus and can reduce hippocampal neurons' proliferation and impaired synaptic plasticity. This study provided the experimental and theoretical basis for guiding the rational use of drugs during pregnancy and effectively assessing the risk of hippocampal developmental toxicity in fetuses.

Key words: drug safety during pregnancy, dexamethasone, hippocampus, neuron, synaptic injury

摘要：

地塞米松是一种糖皮质激素药物，具有抗炎、抑制免疫等多种药理作用，广泛应用于治疗多种疾病。临床上常使用地塞米松来促进早产儿的肺成熟以及预防胎儿呼吸窘迫综合征。目前的流行病学以及试验研究表明，地塞米松孕期暴露会增加子代患软骨病、肾脏损伤等疾病的风险。为了探究孕期地塞米松暴露（prenatal dexamethasone exposure, PDE）对大鼠子代胎鼠海马神经元增殖发育以及胎鼠海马突触可塑性形成的影响，对孕中晚期Wistar大鼠皮下注射地塞米松(0.2 mg·kg^-1·d^-1)，对照组注射等剂量0.9%氯化钠溶液。收集GD20子代海马，采用实时荧光定量PCR以及Western blot法对海马神经增殖、突触可塑性形成和APPL1(adaptor protein containing pH domain, PTB domain and leucine zipper motif 1)进行相关功能检测,并进一步使用投射电镜观察海马突触超微结构。结果显示，与空白对照组相比，PDE胎海马Ki67、增殖细胞核抗原（proliferating cell nuclear antigen, PCNA）、突触融合蛋白(syntaxin)、25 kD突触相关蛋白（SNAP25）等特异性指标显著降低，提示PDE对胎海马神经增殖、突触发育具有不同程度的抑制作用。Western blot 结果显示，PDE组突触后致密蛋白95（PSD95）显著下调，进一步电镜结果证实PDE可导致子代海马突触可塑性受损。APPL1检测结果显示，PDE子代海马APPL1表达水平下调，故而推测PDE可能是通过调节APPL1表达改变子代海马突触可塑性。研究结果揭示PDE具有海马发育毒性并可导致海马神经元增殖减少以及突触可塑性发育损伤。研究结果为指导孕期合理用药和有效评估胎儿海马发育毒性风险提供了实验与理论依据。

关键词: 孕期用药安全, 地塞米松, 海马, 神经元, 突触损伤