溶栓酶tPA是FDA批准治疗急性脑缺血的唯一药物，但因其显著增加脑出血风险而使临床应用受限。血脑屏障（BBB）损伤是脑出血的主要原因，维持BBB的完整性能减少脑出血。临床研究发现，吸烟患者tPA溶栓后脑出血率显著下降，但机制尚不清楚。本实验室的前期研究显示，急性脑缺血引起BBB损伤并伴有miR-21降低及Pdlim5升高，而慢性尼古丁暴露则引起miR-21升高及Pdlim5下降。因此我们提出假说：慢性尼古丁暴露通过调控miR-21/Pdlim5从而减轻急性脑缺血引起的BBB损伤。本项目将采用qPCR、免疫荧光、siRNA干扰、荧光素酶等技术，在动物、细胞和分子水平以miR-21/Pdlim5为靶点，研究其在减轻急性脑缺血BBB损伤中的作用及慢性尼古丁暴露对其调控机制，阐明慢性尼古丁暴露减轻急性脑缺血BBB损伤的分子机制，从而为降低tPA溶栓后的脑出血率、为tPA的临床应用提供新策略和靶点。

Thrombolysis with tPA remains the only FDA approved drug for acute cerebral ischemia, but the clinic application of tPA is limited because of the most feared neurovascular complication of hemorrhagic transformation (HT). The blood brain barrier (BBB) integrity disruption plays a central role in HT. Therefore, HT could be reduced by maintaining the integrity of BBB. A study from NIH tPA trial has shown that cigarette smoking protects tPA-treated patients from cerebral hemorrhage. The prevalence of intracerebral hemorrhage among smokers receiving tPA was significantly decreased, as compared with the patients who did not smoke. So far the mechanism is not clear. Our preliminary data showed that acute ischemia disrupted BBB accompanied by miR-21 decrease and Pdlim5 increase. Of note, chronic nicotine exposure could significantly increase miR-21 and decrease Pdlim5. Our hypothesis is that chronic nicotine exposure prevents acute ischemia-induced BBB damage by regulating miR-21/Pdlim5. In this study, using in vivo and in vitro ischemia model, we will investigate the roles of miR-21/Pdlim5 in acute ischemia-induced BBB damage as well as the effect of chronic nicotine exposure on miR-21/Pdlim5 expression. Our aim is to clarify the mechanism underlying BBB damage that is induced by acute ischemia, provide new strategy to decrease tPA-induced HT and improve tPA application in clinic.