丙酮酸乙酯通过PTEN/AKT轴调节小胶质细胞极性促进TBI后白质重塑

Traumatic brain injury (TBI) is the leading cause of death and disability in young adults worldwide, however, there is no evident effective method or medicine to decrease the disability after TBI. Extensive white matter injury (WMI) has been documented in patients with TBI. This WMI correlates with the long-term deficits in motor and cognitive function. Neuroinflammation, including the activation of resident microglia, is thought to have an important role in pathophysiological process of WMI and finally leads to demyelination and axonal degeneration. Latest findings showed that microglial phenotypic switching modulated white matter repair and axonal remyelination. And the phenotopic swich of microglia to M2 is associated with neighboring oligodendrocyte progenitor cells (OPCs). Our previous study has demonstrated for the first time that ethyl pyruvate (EP) confers neuroprotective effect in rats after TBI by inhibiting microglia activation and releasing inflammatory mediators. Furthermore, we found that EP improved white matter plasticity which may be associated with microglia activation. We thus intent to identify the hypothesis that whether EP has the ability to improve OPCs differentiation by adjusting microglia polarization towards a more specific titration of the inflammatory response away from the destructive M1 phenotype. Finally, we will use the Pten and PI3K inhibitors to find out whether Pten/Akt signaling is the key molecular mechanism in EP-mediated microglia phenotypic switching.

创伤性颅脑损伤（TBI）是45岁以下人群的主要死亡和致残原因，如何促进TBI后的神经功能康复是临床上亟待解决的问题。TBI后的白质损伤程度与神经功能预后紧密相关，机制涉及神经炎症反应。我们发现丙酮酸乙酯（EP）能促进TBI大鼠神经功能恢复，机制与抑制小胶质细胞的过度激活和促进白质重塑相关，但具体机制尚不清楚。我们推测EP可能调节小胶质细胞的极性转化，进而促进少突胶质细胞前体细胞（OPCs）分化和白质重塑。我们将采用已建立的大鼠TBI模型、小胶质细胞和OPCs细胞离体培养，验证EP能够调节TBI后小胶质细胞的M1/M2极性转化，促进动物的白质重塑和神经功能恢复；并确认EP是否通过调节小胶质细胞极性转化促进OPCs分化；最后分别采用Pten和PI3K的抑制剂作用于小胶质细胞，来探讨Pten/Akt轴是否是EP调节小胶质细胞极性转化的分子机制，为脑保护药物开发提供新思路和作用靶点。

背景：严重创伤性脑损伤(TBI)会导致与白质损伤(WMI)相关的长期神经功能缺损。丙酮酸乙酯(EP)是内源性能量底物丙酮酸的简单衍生物，具有神经保护作用，但其在WMI康复中的作用尚不清楚。本研究通过行为测试和脑白质组织学分析，研究EP治疗对大鼠脑外伤后28天的影响。.主要方法：将成年大鼠麻醉后进行控制性皮质撞击导致颅脑损伤。分别于手术后15min，12，24，36，48，60小时，腹腔内注射EP或林格氏溶液(RS)。通过四个独立的测试评估TBI后至第21天的感觉运动缺陷。免疫荧光和透射电子显微镜(TEM)观察脑白质损伤(WMI)的情况。用免疫组化或实时荧光定量PCR检测小胶质细胞活化及相关炎症分子的表达。.研究数据：我们发现，EP改善了大鼠TBI后的感觉运动功能，并改善了TBI后28天的脑白质预后，如减少髓鞘丢失。此外，在TBI急性期给予EP，可以使小胶质细胞极化向抗炎M2表型转变，调节相关炎症因子的释放。因此，EP可能通过调节小胶质细胞向M2的极化，来保护TBI导致的WMI。.局限性：缺乏支持EP诱导的小胶质细胞极化转变机制的体外数据。