红景天苷类似物SalA对脑缺血损伤的保护及机制研究

Extending the time window for thrombolytic therapy by promotion of glucose uptake in ischemic brain tissue and improvement of brain energy metabolism has become an ideal target for development of a new generation of neuroprotective agents. Studies have shown that salidroside, a traditional Tibetan medicine, has a protective effect on hypoxic-ischemic injury of neurons. However, it is difficult to cross the blood brain barrier and penetrate into the brain due to its large molecular polarity and small fat-soluble character. Therefore, our research group members have synthesized the salidroside analogue-SalA. Previous studies have shown that this compound has a significant neuroprotective effect against cerebral ischemia in rats, meanwhile, the oil-water partition coefficient and the brain distribution of SalA is significantly higher than that of salidroside. On the above basis, our research group attempts to analyze the distribution of SalA in various organs of rats and its pharmacokinetic model by high performance liquid chromatography, investigate the therapeutic window of SalA against cerebral ischemia in rats, and explore the protective mechanism of SalA against cerebral ischemia through a series of methods such as glucose uptake, the expression and translocation of neuronal GLUT-3 and glial GLUT-1, and the detection of PKA/CREB/GLUT-3 and MEK/ERK/HIF-1α/GLUT-1 signaling pathways. Our research will provide an important experimental basis for the development of SalA as a potential neuroprotective agent used in clinical treatment of ischemic cerebrovascular disease.

促进缺血脑组织葡萄糖摄取，改善脑能量代谢以延长溶栓治疗的有效时限，已经成为研发新一代神经保护剂的理想靶标。研究表明传统藏药红景天苷对缺血缺氧神经元具有一定的保护作用，但其极性较大而脂溶性较小，难以透过血脑屏障进入脑内。为此，本课题组合成了红景天苷类似物-SalA。前期研究表明，该化合物不但对大鼠脑缺血损伤具有显著保护作用，其油水分配系数和脑内分布显著高于红景天苷。本课题以此为基础，采用高效液相色谱法分析SalA在大鼠体内各脏器分布以及药代动力学模式；探讨SalA对大鼠脑缺血损伤治疗时间窗；通过SalA对缺血脑细胞葡萄糖摄取、神经元GLUT-3和胶质细胞GLUT-1表达和转位以及相关信号通路PKA/CREB/GLUT-3和MEK/ERK/HIF-1α/GLUT-1检测，探讨SalA的脑缺血保护作用机制。通过研究为将其开发为一种潜在的神经保护剂应用于临床防治缺血性脑血管病提供重要的理论基础。

研究表明传统藏药红景天苷分子极性较大而脂溶性较小，难以透过血脑屏障。为此，我们通过结构改造合成了红景天苷类似物（SalA-4g）。本课题采用高效液相色谱法分析SalA-4g在大鼠体内各脏器分布以及药代动力学模式，发现SalA-4g经结构修饰改造后疏水性增加、亲油性增高，与红景天苷相比更易透过血脑屏障进入中枢而发挥脑保护作用；建立SD大鼠大脑中动脉栓塞（middle cerebral artery occlusion, MCAO）模型，发现SalA-4g对MCAO模型鼠脑缺血损伤具有显著的保护作用，且该种作用呈剂量依赖性，治疗时间窗达到3小时；建立了SD大鼠海马神经元以及星形胶质细胞氧糖剥夺（oxygen and glucose deprivation, OGD）损伤模型，发现SalA-4g对OGD损伤海马神经元以及星形胶质细胞具有显著的保护作用，其神经保护作用与拮抗神经元凋亡、促进星形胶质细胞增殖迁移和细胞因子释放、增强受损脑细胞的葡萄糖摄取能力相关；建立SD大鼠栓子法MCAO损伤模型，发现SalA-4g与组织型纤溶酶原激活剂（tissue plasminogen activator, tPA）联合治疗能明显延长脑缺血后溶栓治疗的有效时限，减轻溶栓治疗所带来的副作用，包括脑出血、脑水肿以及细胞毒性，且该神经保护作用与增强缺血脑组织的葡萄糖摄取能力相关。通过研究为将SalA-4g开发为一种神经保护剂应用于临床防治缺血性脑血管病提供重要的理论基础。