AMPK-Drp1介导的线粒体分裂在老年术后认知功能障碍中的作用

Postoperative cognitive dysfunction (POCD) is a common complication among the elderly after surgery, associated with increased life disorder and mortality. Previous studies have assessed that neuroinflammation induced by surgery play an important role in the pathogenesis of POCD, while the underlying mechanism of neuron injury and their difference vulnerability to surgery remained largely to be determined. Recently, mitochondrial dysfunction is found to be a vital feature of aged or degenerated neuron, whereas, its involvement in POCD has not been concerned. We previously have established a POCD model of abdominal surgery under isoflurane anesthesia and found that Drpl, which is a crucial regulator of mitochondrial fission, was activated in the hippocampus of mice at day 1 postoperation, accompanied by a decline of mitochondrial function. Further studies showed that AMPK take part in this process. Inhibition the activity of AMPK blocked the combination of Drpl to mitochondria in the hippocampus at day 1 postoperation, indicating that mitochondrial fission mediated by AMPK-Drpl may be participated in the mitochondrial dysfunction and subsequent cognitive decline after surgery. The aim of this study is to determine the specific changes of mitochondrial function postoperation as well as its duration, and investigate the relation between mitochondrial metabolism and POCD with a focus on the mitochondrial fission mediated by AMPK-Drpl. The implementation of this research may provide fundamental evidence for a viable therapy of POCD.

术后认知功能障碍（POCD）是老年患者术后生活障碍和死亡的重要原因，其发生过程中神经细胞的损伤机制尚不清楚。近年研究发现，线粒体功能障碍是神经细胞自然老化或病理性改变的主要特征之一，而其在POCD中的作用尚未受到关注。我们前期已建立老年小鼠POCD模型，并发现术后1天小鼠海马中线粒体功能显著下降，线粒体融合蛋白2（Mfn-2）水平降低，而动力相关蛋白（Drpl）与线粒体结合增加，提示海马线粒体存在分裂/融合失衡；同时AMPK磷酸化水平明显增多，进一步研究显示：抑制AMPK活化可阻断术后1天海马中Drpl与线粒体结合以及线粒体分裂。本项目拟以小鼠海马和神经细胞为研究对象，明确老年和成年小鼠在麻醉手术前后海马线粒体分裂程度、功能变化的差异，并针对AMPK-Drpl介导的线粒体分裂这一关键环节，探讨海马线粒体在POCD发生过程中的作用，为临床POCD防治提供新的理论和实践基础。

术后认知功能障碍（POCD）是老年患者术后生活障碍和死亡的重要原因，其发生过程中神经细胞的损伤机制尚不清楚。本研究以小鼠海马和神经细胞为研究对象，明确小鼠在手术前后海马线粒体分裂程度和功能变化，并针对Drpl介导线粒体分裂这一关键环节，探讨线粒体在老年POCD发生中的作用。我们的结果显示：①术前线粒体功能障碍是POCD发生的高危因素。老年小鼠海马线粒体的基础和最大耗氧量均显著低于成年小鼠，仅老年小鼠在开腹探查术后出现海马线粒体分裂增多、功能下降和学习记忆能力受损。②Drp1介导POCD发生过程中神经细胞线粒体分裂。老年小鼠术后1天海马中Drp1活化并向线粒体转移，术后7天基本恢复。原代培养的神经细胞经TNF-α处理后，线粒体功能障碍先于Drp1活化出现。Drp1抑制剂Mdivi-1虽能阻断小鼠术后海马和神经细胞经TNF-α处理后Drp1向线粒体转移和线粒体分裂，但不改变p637-Drpl水平，并且恶化线粒体功能和神经棘突形成。在SH-5YSY细胞系中Drpl-siRNA干扰可阻断TNF-α诱导的线粒体分裂。③TNF-α通过激活钙调磷酸酶（CaN）活化Drpl并诱导线粒体分裂。神经细胞经TNF-α处理后，AMPK活化水平降低，AMPK激动剂预处理虽能阻断AMPK活化水平下降，但加重Drpl活化和线粒体分裂。TNF-α处理后神经细胞CaN活性升高，CaN抑制剂FK506预处理阻断TNF-α诱导的Drpl活化、线粒体分裂和功能障碍以及对神经细胞树突棘形成的影响。在老年小鼠中，AMPK激动剂预处理加重而CaN抑制剂预处理减轻老年小鼠术后海马Drpl活化、ATP水平下降、CA1区锥体细胞中线粒体分裂以及学习记忆能力的下降。本课题揭示了线粒体在老年POCD发生过程中的重要作用，以及其中TNF-CaN-Drp1介导的线粒体分裂对线粒体功能的调节机制，为探索POCD临床防治措施提供新的思路与实践依据。