IL4I1抑制脑缺血后血脑屏障破坏对白质损伤的作用及机制研究

Acute ischemic stroke leads to high risks of disability and death in adults, which has no efficient drug treatment except for tPA. Angioedema and demyelination caused by blood-brain barrier breakdown may be the main reason of disability and death. Interleukin-4 induced one (IL4I1) may promote remyelination in focal inflammation of central nervous system in mice. IL4I1 may also lead to collagen deposition in lung and kidney, affecting the role of vascular barrier. However, it remains unclear that whether and how IL4I1 plays a role in blood-brain barrier injury and neuron demyelination after acute cerebral ischemia. .Recently, we have found that brain tissue loss and neurons demyelination were aggravated in IL4I1-/- mice. After cerebral ischemia, demyelination of neurons resulted in walking pattern changes in mice. We already found that tight junctions disrupted and angioedema increased, with blood-brain barrier opened after cerebral ischemia..In this study, cerebral ischemia model using knockout mice was used to evaluate the role of IL4I1 in blood-brain barrier injury and demyelination of neurons in vivo as well as in vitro by MRI detection, primary cell co-culture and electron microscopy, to evaluate the protective effect of IL4I1 on blood-brain barrier, including basement membrane and endothelial cell junctions integrity, and to evaluate its promoting effect on demyelination and remyelination of neurons, so as to provide a new perspective for elucidating the role of blood-brain barrier in white matter injury after cerebral ischemia, and to provide novel experimental evidence and new ideas in vivo and in vitro for clinical treatment.

缺血性脑卒中是成人致残、致死的高发原因，除tPA外尚无有效治疗药物，血脑屏障损伤引起血管性水肿、神经元脱髓鞘，是致死致残的重要原因。白细胞介素4诱导蛋白1（IL4I1）在小鼠中枢局灶性炎症中促进再髓鞘化，还可能导致肺、肾血管胶原沉积，影响血管屏障作用。但IL4I1对脑缺血后血脑屏障损伤和神经元再髓鞘化的作用尚不清晰。我们目前研究发现，IL4I1-/-小鼠脑组织丢失加重、神经元再髓鞘化受损；脑缺血后，小鼠神经元脱髓鞘导致步态失调。我们以往研究发现，脑缺血后血脑屏障打开、紧密连接受损、血管性水肿增加。本研究通过基因敲除小鼠脑缺血模型，应用磁共振、原代细胞共培养、电镜和步态等方法在体内外研究中，评价IL4I1对血脑屏障，包括基底膜和内皮细胞连接蛋白完整性的保护作用，评价对神经元脱髓鞘抑制和再髓鞘化促进作用，为阐释脑缺血后血脑屏障在白质损伤中的作用提供新角度，为临床治疗提供体内外研究证据和新思路。

急性缺血性脑卒中后的血脑屏障通透性增加和神经元脱髓鞘加重了脑组织损伤。白细胞介素4 诱导蛋白1 (interleukin-four induced one, IL4I1)是一种分泌型氨基酸氧化酶。本研究发现急性大脑中动脉栓塞术后，IL4I1-/-小鼠七天生存率、感觉运动神经学评分差于野生型小鼠。且急性脑缺血再灌注后，IL4I1-/-小鼠，相比于野生型小鼠，出现明显的脑组织缺失和梗死现象，小胶质细胞活化，神经元损伤加重、神经元轴突脱髓鞘程度加剧。氧糖剥夺的体外实验得到类似的结果。另外，在体外细胞培养中，神经元和原代少突胶质细胞在受到氧糖剥夺刺激后，给予外源性IL4I1补充治疗，均可以提升细胞的增殖代谢能力。.本项目研究提示IL4I1对神经元损伤修复、神经元轴突形态的维持有积极作用，有助于保护血脑屏障完整性。IL4I1的存在能够一定程度上发挥对神经元脱髓鞘抑制和再髓鞘化促进作用。该作用与脑缺血后血脑屏障中紧密连接蛋白，线粒体呼吸链特别是氨基酸代谢有密切关系。损伤修复期间不同类型小胶质细胞也发挥了重要作用。IL4I1缺位在白质损伤中有一定的关键作用。本研究提示外源性IL4I1可能对缺氧后脑组织损伤有治疗作用，该关键分子或其相关上下游分子有望成为缓解神经损伤的新型药物，为临床转化提供了潜在可治疗缺血缺氧脑病的药物靶点，探明了神经元和轴突损伤修复的部分关键病理调控机制。