The role of CD36 in ischemic inflammation and injury

描述（由申请人提供）：卒中诱导的脑损伤主要从神经中心的角度进行观察，主要关注原发损伤部位及其半暗带。然而，从最近的研究中，包括我们自己的研究，得出了一个重要的观点，即外周炎症状态影响原发性损伤的结果。本研究的目的是研究脑缺血对外周免疫的调节机制，以及脑缺血对脑卒中中枢神经系统损害的影响。具体而言，我们提出，脾单核细胞通过一种新的CD 36机制在卒中介导的损伤中发挥关键作用。中风诱导外周血单核细胞浸润到原发性损伤部位。单核细胞运输是严格控制的事件，其涉及表达或不表达促炎趋化因子受体CCR 2的单核细胞亚群的顺序募集。高血压扩大了脾脏中的CCR 2+单核细胞亚群，加速了心脑血管疾病的进展。我们最近做出了一个令人兴奋的观察，将脾脏与中风病理联系起来;与高脂血症相关的损伤越大，脾脏重量的减少越大，并且缺血后脑中CCR 2的表达越高。这使我们假设，脾CCR 2+单核细胞有助于中风诱导的脑损伤在高血压条件。此外，我们确定了CD 36作为一种炎症介质，有助于中风引起的脑损伤。在小鼠中，CD 36缺陷逆转了高血压相关的表型，并导致脑中CCR 2表达减少和梗死范围缩小。这些观察结果导致了随后的假设，即CD 36调节脾CCR 2+单核细胞向梗死的动员。因此，靶向CD 36具有神经保护作用。目的1探讨脾CCR 2+单核细胞在脑卒中后损伤中的作用。我们将建立中风后脑和脾中CCR 2+单核细胞亚群的时间变化。将在已接受脾切除术的小鼠和已通过过继转移接受外源性脾单核细胞的脾切除小鼠中研究脾单核细胞的必要性和充分性。目的2将确定CD 36是否调节CCR 2单核细胞向梗死的运输。我们将评估CCR 2+单核细胞在脾脏和脑中的CD 36表达和缺陷的小鼠中风后。将通过过继转移的GFP+单核细胞在体内评价单核细胞运输。另外的体外研究将确定CD 36缺乏对CCR 2+单核细胞亚群的影响及其在循环中获得CCR 2+表型的能力。目的3将利用几种方法来抑制CD 36。为了选择性地抑制单核细胞CD 36，将使用CD 36缺陷型单核细胞。使用CD 36抑制剂进行急性缺血后治疗和慢性预防性治疗的其他药理学方法将补充基于遗传细胞的方法。了解外周血单核细胞对原发性损伤的影响，可能为神经免疫调节在中风和许多炎症性疾病中的治疗应用打开大门。

DESCRIPTION (provided by applicant): Stroke-induced brain injury has been viewed mainly from a neurocentric perspective, with much attention given to the primary injury site and its penumbra. However, an important notion derived from recent studies, including our own, favor a view that the peripheral inflammatory state influences the outcome of primary injury. The goal of this proposal is to investigate the mechanism(s) by which peripheral immunity may be regulated by cerebral ischemia and how this contributes to CNS damage in stroke. Specifically, we propose that spleen monocytes play a critical role in stroke-mediated injury through a novel CD36 mechanism. Stroke induces infiltration of peripheral monocytes into primary injury sites. The monocyte trafficking is a tightly controlled event that involves sequential recruitment of monocyte subsets that either express or do not express the pro-inflammatory chemokine receptor CCR2. Hyperlipidemia expands the CCR2+ monocyte subset in the spleen and accelerates the progression of cardio- and cerebrovascular diseases. We recently made an exciting observation that links the spleen to stroke pathology; the larger the injury associated with hyperlipidemia, the greater the reduction in spleen weight, and the higher the expression of CCR2 in the post- ischemic brain. This led us to hypothesize that the spleen CCR2+ monocytes contribute to stroke-induced brain injury in hyperlipidemic conditions. Furthermore, we identified CD36 as an inflammatory mediator that contributes to stroke induced brain injury. CD36 deficiency in mice reversed the hyperlipidemia-associated phenotype and resulted in reduced CCR2 expression in the brain and a smaller infarct. These observations led to the subsequent hypotheses that CD36 regulates the mobilization of spleen CCR2+ monocytes to the infarct. Therefore, targeting CD36 is neuroprotective. Aim 1 will determine the role of spleen CCR2+ monocytes in injury following stroke. We will establish temporal changes of CCR2+ monocyte subsets in the brain and spleen following stroke. The necessity and sufficiency of spleen monocytes will be investigated in mice that have undergone a splenectomy and in splenectomized mice that have received exogenous spleen monocytes via adoptive transfer. Aim 2 will determine if CD36 regulates CCR2 monocyte trafficking to infarct. We will assess CCR2+ monocytes in the spleen and brain of CD36-expressing and -deficient mice after stroke. Monocyte trafficking will be evaluated in vivo by adoptively transferred GFP+ monocytes. Additional in vitro study will determine the effect of CD36 deficiency on CCR2+ monocyte subsets and their ability to acquire the CCR2+ phenotype in circulation. Aim 3 will utilize several approaches to inhibit CD36. To selectively inhibit monocyte CD36, CD36-deficient monocytes will used. Additional pharmacological approaches using a CD36 inhibitor for acute post-ischemic treatment and chronic preventive treatment will complement the genetic cell- based approach. Understanding of peripheral monocyte influence on the primary injury may open the door to the therapeutic application of neuro-immune modulation for stroke and a host of inflammatory diseases.