Fas (CD95)-induced regeneration of dopaminergic neurons

帕金森氏症的特征是大脑黑质中产生多巴胺的神经元退化。由此导致的多巴胺丢失导致帕金森病(PD)的主要症状，即震颤、运动迟缓、姿势不稳定和僵硬。这种疾病不断发展，最终导致几乎完全残疾的状态。虽然目前的治疗方案可以延缓帕金森病的发生，但目前还不能治愈或预防。我们最近发现，刺激周围感觉神经元上的细胞表面分子Fas(CD95)可以在体外诱导快速、广泛的轴突生长，并能促进坐骨神经挤压伤后体内功能的恢复。与传统的认为Fas是“死亡受体”的观点相反，我们认为Fas参与可以诱导多巴胺能神经元的再生。支持这一观点的是，帕金森病患者在实质黑质中的可溶性Fas水平升高。可溶性Fas作为诱骗受体，阻止细胞表面Fas结合。此外，Fas表达降低的小鼠会发生进行性神经退化，并表现出神经和认知缺陷。我们建议通过以下特定目的来研究Fas表达与帕金森病之间的因果关系：1.确定Fas参与对多巴胺能神经元的生理影响以及触发的信号通路(S)。2.确定Fas表达缺失是否导致多巴胺能神经元变性和/或MPTP毒性(帕金森病模型)。3.确定抗Fas抗体是否能促进体内多巴胺能神经元的恢复。为了实现这些目标，我们将使用三种模型：酪氨酸羟化酶阳性(TH+)细胞系；通过流式细胞仪分选富含TH+神经元的小鼠胚胎腹侧中脑细胞的体外培养；以及MPTP诱导的小鼠黑质纹状体变性作为PD的体内模型。我们将设计我们的实验来测试Fas能够诱导中枢神经系统神经元再生这一新概念。这些目标的成功完成将在帕金森病和神经退行性疾病的研究中产生一个概念上的新方向，并为创新的治疗策略提供一个新的目标。

Parkinson's disease is characterized by the degeneration of dopamine- producing neurons in the substantial nigra of the brain. The resulting loss of dopamine leads to the cardinal symptoms of Parkinson's disease (PD), namely tremor, bradykinesia, postural instability, and rigidity. The disease is relentlessly progressive, ultimately resulting in a state of almost complete disability. Although PD can be slowed by current treatment protocols, it cannot be cured nor prevented at present. We have recently found that stimulating the cell surface molecule (Fas (CD95) on peripheral sensory neurons induces rapid, extensive neurite outgrowth in vitro, and can accelerate functional recovery in vivo after sciatic nerve crush injury. Contrary to the traditional view of Fas as a "death receptor", we propose that Fas engagement may induce regeneration of the dopaminergic neurons. In support of this notion, PD patients have elevated levels of soluble Fas in the substantial nigra. Soluble Fas acts as decoy receptor to prevent cell surface Fas from being engaged. Furthermore, mice with reduced Fas expression undergo progressive neural degeneration, and exhibit neurological and cognitive deficits. We propose to investigate the causal relationship between Fas expression and PD through the following specific aims: 1. To determine the physiological effects, and the signaling pathway(s) triggered, by Fas engagement on dopaminergic neurons. 2. To determine whether lack of Fas expression predisposes dopaminergic neurons to degeneration and/or MPTP toxicity (a model for PD). 3. To establish if anti-Fas antibody can stimulate dopaminergic neuron recovery in vivo. To accomplish these aims, we will use three models: tyrosine hydroxylase-positive (TH+) cell lines; in vitro cultures of embryonic mouse ventral mesencephalon cells enriched for TH+ neurons by flow cytometric sorting; and MPTP- induced nigrostriatal degeneration in the mouse as an in vivo model of PD. We will design our experiments to test the novel concept that Fas is able to induce regeneration in CNS neurons. The successful completion of these aims would yield a conceptually novel direction in the study of PD and neurodegenerative diseases in general, and a new target for innovative treatment strategies.