酸后处理对缺血性脑卒中的保护作用及与酸敏感通道ASIC1a的相关性研究

Cerebral ischemic postconditioning has emerged recently as a kind of endogenous strategy for neuroprotection, which was defined as a sub-threshold ischemic insult applied to the brain after ischemia/reperfusion. It can mobilize the brain's own endogenous protective mechanisms against severe cerebral ischemia/reperfusion. However, the poor feasibility implied a faint future of its clinical applications. Therefore, it is quite necessary to develop another postconditioning form of non-surgical treatment which is easy to carry out. Acidosis is an important factor in ischemic postconditioning. In the preliminary experiment, we for the first time found that acidic postconditioning has neuroprotective effects against ischemia. In corticostriatal slices and cultured cortical neurons, acidic postconditioning improved the neuronal viability after oxygen-glucose deprivation/reperfusion. Postconditioning with acidosis by inhaling 20% CO2 for 5 min at 5 or 50 min after reperfusion significantly improved neurological function and decreased infarct size induced by middle cerebral artery occlusion in mice. And compared with ischemic postconditioning, acidic postconditioning has a wider time window. These results imply that acidic postconditioning is a novel therapeutic strategy which has practical value in clinic. However, its detailed effect and mechanism are quite unclear. This project will further investigate the action characteristics of acidic postconditioning in vivo and in vitro. And using the acid-sensing ion channel-1a (ASIC1a) knock-out mice and RNA interference, its neuroprotective mechanisms can be partly clarified by investigating the effect of ASIC1a in this process. The achievement of this project will provide a novel therapeutic strategy for ischemic stroke.

缺血后处理作为一种新的内源性保护策略，通过调动多种自身保护机制来减轻严重缺血再灌注造成的损伤，为缺血性脑卒中的治疗提供了新途径，但缺血后处理手术在临床应用上仍存在一定困难，至今尚未形成有效可行的治疗方案，因此寻找其他非手术形式的后处理手段显得尤为必要。组织酸化是脑缺血后处理的重要因素之一，课题组的前期实验在整体、脑片及细胞模型上均发现酸后处理具有显著的神经保护作用，同时与缺血后处理相比，其有效时间窗更宽，提示酸后处理可能是一种具有实际应用价值的新治疗策略，但其具体作用及机制尚不清楚。因此，本课题首先拟在整体、脑片及细胞水平进一步明确酸后处理的作用及特点；并利用酸敏感通道ASIC1a基因敲除小鼠及RNA干扰等手段，探讨ASIC1a在该过程中发挥的作用，进而阐明酸后处理保护作用与ASIC1a的相关性。本项目的完成将为缺血性脑卒中提供新的治疗策略和治疗靶点。

缺血后处理作为一种新的内源性保护策略，通过调动多种自身保护机制来减轻严重缺血再灌注造成的损伤，为缺血性脑卒中的治疗提供了新的途径，但缺血后处理手术在临床应用上仍存在一定困难，因此需寻找其他非手术形式的后处理手段显得尤为必要。组织酸化是缺血后处理的重要因素之一，我们推测，在脑缺血再灌后给予短暂的酸化处理，可能减轻脑损伤。因此，本研究着重探索了两个科学问题：（1）明确酸后处理对脑缺血/复灌损伤的调节作用及特点。（2）阐明ASIC1a和线粒体自噬是否参与了酸后处理诱导的神经保护机制。通过本课题的实施，课题组首次发现了酸后处理可抑制脑缺血/复灌诱发的神经损伤，并且其保护作用具有时间、时程和浓度依赖性。与缺血后处理相比，酸后处理具有更宽的治疗时间窗，操作更便捷安全等优势，有利于其应用于临床治疗脑缺血再灌注损伤。利用药理学方法、基因敲除小鼠及RNA干扰技术等手段，课题组进一步对其保护机制进行了探索。结果发现，ASIC1a/GABA/GABA(A)receptor及Parkin依赖的线粒体自噬是酸后处理在脑缺血后的复灌过程中发挥了神经保护作用的重要机制。这些研究结果为酸后处理治疗缺血性脑卒中提供了重要的理论依据，并为脑缺血的治疗提供了新的潜在治疗靶点。