ANGⅡ在慢性脑低灌注神经元铁稳态失衡中的作用及分子机制研究

Iron misregulation induced by chronic cerebral hypoperfusion (CHP) plays an important role in the development of neurodegenerative disease and cognitive dysfunction. However, the relevant mechanism is unknown. It has been demonstrated that ANGII could promote inflammation, JAK expression and STAT3 activation, resulting in iron misregulation in VSMC. Our recent study demonstrated that ANGII could reduce iron uptake and release as well as expression of two major iron uptake proteins transferrin receptor 1 (TfR1) and divalent metal transporter 1 (DMT1) and the key iron exporter ferroportin 1 (Fpn1) in cultured neurons. Based on the above, we speculated that CHP might have the ability to affect expression of ANGII and then iron transporter in the brain via the IL-6/JAK2/STAT3 pathway. To test this hypothesis, we will investigate the effects of CHP on expression of ANGII, iron transport proteins, hepcidin and iron contents in the presence of absence of activators or inhibitors of ANG II receptor, JAK2 and STAT3 in the brain. The proposed study is fundamental and critical not only for elucidating the pathophysiological mechanisms responsible for CHP-induced iron misregulation in the brain but also for developing pharmacological interventions that can disrupt the chain of pathological events occurring in CHP.

慢性脑低灌注（CHP）后铁稳态失衡导致的神经元退行性变，与认知减退有关，也在很多神经退行性疾病的发病中起作用，但其具体机制不明确。血管紧张素II（ANGII）可促进炎症、增强JAK表达和STAT3 磷酸化，导致心血管内皮细胞铁稳态失衡。我们前期研究显示原代培养的皮层神经元经ANGII处理后，神经元铁吸收和释放减少，同时铁代谢相关蛋白的表达降低。据此我们假设CHP导致ANGII 高表达，经IL-6/JAK2/STAT3信号通路调节脑内铁调素表达，进而影响脑内铁转运蛋白表达及脑铁水平。本项目拟观察生理和CHP状态下，激活或阻断ANGII受体、靶向干扰JAK2/ STAT3后脑内铁调素、铁代谢相关蛋白表达和脑铁含量的变化，以及对CHP神经元变性、白质脱髓鞘和整体认知功能的影响。旨在验证ANGII/IL-6//JAK2/ STAT3是CHP脑铁稳态失衡的关键信号通路之一，为防治CHP提供新思路。

慢性脑低灌注（CHP）后铁稳态失衡导致的神经元退行性变，与认知减退有关，也在很多神经退行性疾病的发病中起作用，但其具体机制不明确，血管紧张素II（ANGII）在铁稳态失衡中的作用研究备受关注，阐明ANGII在CHP铁稳态失衡中的作用和分子机制意义重大。对40名临床患者的研究表明：慢性低灌注患者的认知功能较对照组差，双侧海马和左侧壳核与其认知功能损害有显著的相关性，而且慢性脑低灌注合并认知障碍的患者双侧的壳核、海马和黑质脑区表现出显著增加的磁化率值，这为脑铁沉积在慢性低灌注患者认知功能障碍中的作用的提供了新证据。体外实验结果表明，ANGII通过升高铁调素Hepcidin的mRNA表达水平以及抑制NRF2降低了排铁蛋白（FPN1）的表达水平，通过抑制IRE/IRP机制降低摄铁蛋白TfR1的表达水平并升高储铁蛋白的表达水平，以上ANGII引起的铁代谢相关变化均被坎地沙坦显著抑制。在体试验发现与假手术组小鼠相比，BCAS小鼠大脑皮层铁相关蛋白和铁调素表达无明显变化，而海马区出现血管紧张素受体1升高、血管紧张素酶原mRNA水平升高、IL-6 mRNA和蛋白水平升高、铁调素Hepcidin mRNA 水平升高、排铁蛋白Ferroportin 1 (Fpn1)表达水平下降、储铁蛋白Ferritin-L和Ferritin-H表达水平升高，同时STAT3磷酸化水平升高。将小鼠随机分为假手术组、颈动脉狭窄（BCAS）组和BCAS+坎地沙坦给药组，结果发现BCAS小鼠皮层和海马均出现IL-6水平升高、STAT3磷酸化水平升高、膜铁转运蛋白表达水平下降、储铁蛋白表达水平升高，而腹腔注射坎地沙坦能够扭转这些变化。临床和基础研究的结果明确了ANGII在脑铁代谢中发挥重要作用，而ANGII/JAK2/STAT3信号是慢性脑低灌注神经元脑铁稳态失衡的关键信号通路之一，阻ANGII/JAK2/STAT3信号可以纠正慢性脑低灌注铁稳态失衡，降低氧化应激，减轻神经元变性坏死，改善慢性脑低灌注相关认知功能。