NRG1-ErbB4信号介导的NMDA受体紊乱在七氟醚神经毒性中的作用和机制研究

GABA mimetic sevoflurane is a commonly used anaesthetic for pregnant women. It can damage fetal brain development. Previous studies including ours found that sevoflurane exposure in the embryonic period can cause abnormal NMDA receptor and the anchor protein PSD95 expression, and impair the dendritic development in the brain after birth. How sevoflurane affects NMDA receptor expression and formation at embryonic period remains unknown although our preliminary data showed that sevoflurane exposure can cause downregulation of GABA synthase GAD67 and upregulation of its regulatory factor neuregulin 1(NRG1) in fetal brain. Furthermore, NRG1-ErbB4 signaling was reported to be involved in NMDA receptor regulation and the PSD95/Kalirin-7 is considered to an important downstream signaling regulation for dendritic development. Accordingly, we proposed that sevoflurane may modulate GABA coupled with NMDA receptor function through NRG1-ErbB4 signaling, cause downstream PSD95/Kalirin-7 signal abnormality and then impaire dendritic development. We will treat conditional ErbB4 knockout animals with sevoflurane and assess their behavioral and its associated molecular changes to address the role of of NRG1-ErbB4 signal mediated NMDA receptors’ abnormality in sevoflurane induced abnormal dendritic development. The outcome from the proposed application is likely to provide the theoretical basis for the anesthetic-induced neurotoxicity for identifying therapeutic targets.

GABA受体激动剂七氟醚是临床常用的全麻药，已报道其可损害胎儿大脑发育。我们及前人的研究发现，胚胎期七氟醚暴露致出生后大脑NMDA受体及PSD95表达异常，树突发育障碍。但胚胎期NMDA受体表达和组配尚不完善，是什么机制介导了七氟醚对出生后NMDA受体的调控尚不清楚。我们进一步发现，胎脑GABA合成酶GAD67的下调及其调控因子NRG1的上调，有报道NRG1-ErbB4信号也参与调控NMDA受体,其下游PSD95/Kalirin-7是树突发育的重要调节信号。据此我们推测：七氟醚可能通过NRG1-ErbB4信号调控NMDA受体功能，致下游PSD95/Kalirin-7信号异常阻碍树突发育。为此，我们将用ErbB4条件性敲除动物模型、行为学、分子生物学等方法验证NRG1-ErbB4信号介导的NMDA受体紊乱及树突发育异常是七氟醚神经毒性的重要分子机制。为全麻药毒性机制及干预靶点提供理论依据。

项目的背景：据报道，每年约1%～2%的孕妇因急性胆囊炎或阑尾炎、肿瘤、外伤等需在妊娠期行非产科手术。这类手术必须维持较深的麻醉使子宫松弛，避免子宫收缩所导致胎盘早剥及流产。七氟醚能够抑制子宫收缩，是妊娠期非产科手术首选的全麻药。值得注意的是，最近大量研究表明全麻药可损伤发育的大脑，影响远期神经功能，但具体机制不明，也无有效的防治措施。.主要研究内容：观察和分析出生前（G14.5）七氟醚暴露对出生后远期行为学的影响；出生后前额皮质（PFC）兴奋性神经递质系统和抑制性神经递质系统的变化；出生后前额皮质（PFC）神经元树突、树突棘、突触的形态学变化；证实胚胎期七氟醚暴露通过NRG1–ErbB4信号通路调控NMDA受体亚基组配和功能；探讨 NR2B/PSD95/Kalirin-7 通路对树突发育的调控。.重要结果和关键数据：出生前七氟醚暴露致PFC区Ⅱ-Ⅲ层抑制性PV阳性的中间能神经元提前发育，密度显著增加，抑制性神经递质GABA,囊泡转运蛋白（VGAT）、合成限速酶谷氨酸脱羧酶GAD67显著增加；兴奋性神经递质谷氨酸浓度及谷氨酸转运蛋白1（VGLUT1）显著下降。锥体神经元基底树突总分支长度显著下降，总分支数目减少，树突棘密度显著下降。电生理的结果表明PSE导致锥体神经元微小兴奋性突触后电流（mEPSCs）的平均频率显著下降及代偿性平均幅度上升。微小抑制性突触后电流（mIPSCs）的幅度和频率显著上升，兴奋/抑制（E/I）比例显著下调。NRG1、ErbB4显著上调；NMDA受体亚基NR1、NR2A、NR2B紊乱及突触后密度蛋白95（PSD95）、Kalirin-7显著下调。.科学意义：本研究为全麻药发育早期神经毒性提供理论依据及干预靶点。所属基础研究，正在进行成果转化。我们利用研七氟醚可以调控E/I平衡，将该结果用于精神分裂症、双相障碍和重性抑郁的治疗，取得了很的临床疗效。