Inflammatory mediators and mechanisms during central nervous system infection

描述(申请人提供)：炎症是中枢神经系统(CNS)感染期间大脑损伤的基本原因，也是在脑膜炎等感染期间抗炎治疗与抗生素一起使用的原因。皮质类固醇是目前唯一被批准用于中枢神经系统细菌感染的抗炎治疗。然而，皮质类固醇是次优的，因为它们的益处仅限于高收入国家的个人，对某些细菌的感染，最终不会改善长期的神经结果。因此，需要新的治疗方法来改善炎症病理，并提供更积极的患者结果。MicroRNA(MiR)是一种在髓系细胞中表达的短小、非编码的RNA，在先天性和获得性免疫反应中起着关键的调节作用。我们的数据表明，几种miR，例如miR-155，在细菌性脑膜炎患者的脑脊液(CSF)以及感染了单核细胞增生性乳杆菌(LM)的小鼠的大脑中上调。MIR-155的上调与促炎细胞因子的上调和炎性白细胞进入大脑的募集相一致。值得注意的是，这里提供的初步数据显示，miR-155-/-小鼠比正常小鼠招募更多的Ly-6 Chigh单核细胞和中性粒细胞到大脑，这表明miR-155限制了感染期间的炎症。这项提案的目标是建立miR-155在减少感染期间脑部炎症方面的新发现，并确定 感染诱导脑内miR表达的机制在脑膜炎患者和实验性小鼠感染中均可发现。该建议的具体目的包括：目的1.阐明在LM感染过程中导致miR-155-/-小鼠脑内炎性细胞增加的机制。我们的工作假设是，在中枢神经系统感染期间，miR-155的丢失导致大脑中单核细胞和吸引中性粒细胞的趋化因子的产生增加。目的2.确定在中枢神经系统感染过程中上调脑内miR表达的关键生物刺激。我们的工作假设是，大脑中最初的miR上调是由LM感染过程中产生的细胞因子驱动的。实验将部分使用LM感染的小鼠模型以及包括骨髓嵌合体和器官型脑片培养在内的新技术进行。这些目标的成功完成将首次确立特定的miR影响细菌感染期间的脑部炎症，并将评估靶向miRs或特定miR表达的炎症细胞作为治疗中枢神经系统感染的新型辅助治疗的潜在益处。这是发现调控中枢神经系统炎症的新分子靶点的必要的第一步。

DESCRIPTION (provided by applicant): Inflammation is a foundational cause of brain injury during central nervous system (CNS) infections and the reason why anti-inflammatory therapy is used along with antibiotics during infections such as meningitis. Corticosteroids are the only anti-inflammatory treatment currently approved for bacterial infections of the CNS. However, corticosteroids are sub-optimal as their benefit is restricted to individuals in high-income countries, to infections with certain bacteria, and ultimately do not improve long-term neurological outcomes. Thus, new therapies are needed that will ameliorate inflammatory pathology and deliver more positive patient outcomes. MicroRNA (miR) are short, non-coding RNA expressed in myeloid cells that have key roles as modulators of innate and adaptive immune responses. Our data suggest several miR, e.g. miR-155, are up-regulated in cerebrospinal fluid (CSF) of patients with bacterial meningitis as well as in the brains of mice infected with the neurotropic bacterium, L. monocytogenes (Lm). miR-155 up-regulation coincides with up-regulation of pro-inflammatory cytokines and recruitment of inflammatory leukocytes into the brain. Notably, preliminary data presented here show miR-155-/- mice recruit more Ly-6Chigh monocytes and neutrophils to the brain than do normal mice suggesting miR-155 limits inflammation during infection. The goals of this proposal are to establish the novel finding that miR-155 has a role in reducing brain inflammation during infection and to identify the mechanisms by which infection induces brain expression of miR that are found both in patients with meningitis and in experimental mouse infection. Specific Aims of this proposal include: Aim 1. Elucidate the mechanisms leading to increased inflammatory cell influxes in the brains of miR-155-/- mice during Lm infection. Our working hypothesis is that loss of miR-155 leads to increased production of monocyte and neutrophil-attracting chemokines in the brain during CNS infection. Aim 2. To identify key biological stimuli that up-regulate miR expression in the brain during CNS infection. Our working hypothesis is that the initial miR up-regulation in the brain is driven by cytokines produced during Lm infection. Experiments will be performed in part using the mouse model of Lm infection as well as with novel techniques including bone marrow chimeras and organotypic brain slice cultures. Successful completion of these aims will establish for the first time that a specific miR influences brain inflammation during bacterial infection and will gauge the potential benefit of targeting miRs or specific miR-expressing inflammatory cells as novel adjunctive treatment for CNS infections. This is a necessary first step towards discovering new molecular targets for modulating CNS inflammation.