ABCA1 regulates white matter remodeling and oligodendrogenesis after stroke

 描述（由申请人提供）：中风是白色物质（WM）损伤的主要原因，可导致长期残疾。成年人的大脑中存在有限的WM-重塑。许多脑卒中的神经保护治疗在临床试验中失败，因为它们不能保护WM。因此，迫切需要研究成年脑的WM重塑和少突胶质细胞生成的机制，并开发有效的长期中风治疗。细胞胆固醇调节轴突和树突的生长，是髓鞘形成所必需的。高密度脂蛋白胆固醇水平与脑卒中患者的病情进展和恢复有关。ATP结合盒转运蛋白A1（ABCA 1）是一种主要的胆固醇转运蛋白，在中枢神经系统中对HDL-胆固醇和ApoE的合成和代谢起着重要的调节作用。脑特异性ABCA 1缺陷（ABCA 1-B/-B）小鼠脑HDL-胆固醇/ApoE水平极低，并表现出神经元超微结构改变和功能缺陷。在培养条件下，HDL-胆固醇和ApoE均增加神经突生长。我们的初步研究表明，ABCA 1-B/-B小鼠表现出增加的WM损伤和减少少突神经元的生成，并加重脑卒中后的神经功能缺损。来源于ABCA 1-B/-B小鼠的原代培养的神经元显示出减少的神经突生长，这可以通过HDL处理来减弱。ABCA 1-B/-B星形胶质细胞条件培养基也减少缺氧缺血后野生型神经突生长。因此，我们提出了以下三个具体目标：目的1研究脑ABCA 1缺陷是否表现出减少WM重塑和轴突生长中风后。将ABCA 1-B/-B和去势对照小鼠进行中风，测量WM变化和少突细胞生成。目的2研究ABCA 1是否调节脑HDL和ApoE水平，以及脑HDL和ApoE水平是否介导脑卒中后ABCA 1诱导的WM重塑和少突胶质细胞生成，探讨ABCA 1调控脑卒中后WM重塑和少突胶质细胞生成的分子机制。目的3为了研究ABCA 1在调节WM重塑和少突胶质细胞发生中的细胞机制，我们将在体外和体内研究神经元和少突胶质细胞以及星形胶质细胞与神经元和少突胶质细胞对ABCA 1诱导的WM重塑和少突胶质细胞发生的相互作用。我们预期ABCA 1缺陷的脑将表现出HDL和ApoE水平的显著降低，并且减少WM重塑和少突胶质细胞生成以及卒中后功能结果的降低。脑或脑脊液中HDL/ApoE的水平将至少部分介导中风后缺血脑中ABCA 1诱导的WM重塑和少突胶质细胞生成。据我们所知，还没有人研究过ABCA 1对少突胶质细胞生成和脑卒中后WM-重塑恢复的功能作用，尤其是使用ABCA 1-B/-B小鼠.从这项研究中收集到的新见解将有助于我们理解ABCA 1/HDL-C/ApoE在脑可塑性中的有益作用，这将影响合理恢复方法的发展，以改善卒中患者的神经功能结局。

 DESCRIPTION (provided by applicant): Stroke is a major cause of white matter (WM) damage which induces long-term disability. There is limited WM- remodeling in the adult brain. Many neuroprotective treatments of stroke have failed in clinical trials because they cannot protect WM. Therefore, there is a compelling need to investigate the mechanism underlying WM- remodeling and oligodendrogenesis of the adult brain and to develop effective long-term stroke therapy. Cellular cholesterol modulates axonal and dendritic outgrowth and is required for myelination. The level of HDL-cholesterol is related to the progression and recovery of stroke patients. ATP-binding cassette transporter A 1 (ABCA1) is a major cholesterol transporter and plays critical roles in regulation of HDL-cholesterol and ApoE synthesis and metabolism in the central nervous system. Brain specific-ABCA1 deficient (ABCA1-B/-B) mice have very low brain HDL-cholesterol/ApoE level, and exhibit neuronal ultrastructure changes and functional deficits. Both HDL-cholesterol and ApoE increase neurite outgrowth in culture conditions. Our preliminary study shows that ABCA1-B/-B mice exhibited increased WM damage and reduced oligodendrogenesis and exacerbated neurological functional deficits after stroke. Primary cultured neurons derived from ABCA1-B/-B mice show decreased neurite outgrowth, which can be attenuated by HDL treatment. ABCA1-B/-B astrocyte-conditioned media also decreased wild type neurite outgrowth after hypoxic ischemia. Therefore, we propose the following three specific aims: Aim1 To investigate whether brain-deficient in ABCA1 exhibits decreases in WM-remodeling and axonal growth after stroke. ABCA1 -B/-B and floxed-control mice will be subjected to stroke, WM-changes and oligodendrogenesis will be measured. Aim2 To investigate molecular mechanism underlying ABCA1 in regulation of WM-remodeling and oligodendrogenesis after stroke, we will examine whether ABCA1 regulates brain HDL and ApoE level, and whether brain HDL and ApoE levels mediate ABCA1-induced WM-remodeling and oligodendrogenesis after stroke. Aim3 To investigate cellular mechanisms of ABCA1 in regulation of WM-remodeling and oligodendrogenesis, we will examine neurons and oligodendrocytes and the cross talk of astrocytes with neurons and oligodendrocytes on ABCA1-induced WM- remodeling and oligodendrogenesis in vitro and in vivo. We expect that ABCA1 deficient brain will exhibit significant decreases in HDL and ApoE level, and decreases WM-remodeling and oligodendrogenesis as well as reduced functional outcome after stroke. The level of HDL/ApoE in brain or cerebrospinal fluid will, at least partially, mediate ABCA1-induced WM-remodeling and oligodendrogenesis in the ischemic brain after stroke. To our knowledge, no one has investigated the functional effect of ABCA1 on oligodendrogenesis and WM- remodeling post-stroke recovery, especially by using ABCA1-B/-B mice. The new insights gleaned from this study will contribute to our understanding of the beneficial role of ABCA1/HDL-C/ApoE in brain plasticity which will impact development of rational restorative approaches to improve neurological outcome for stroke patients.