Neuroinflammatory and Epigenetic Mechanisms of Blood-Brain Barrier Compromise in Suicide

我们提出了一系列研究，重点是自杀与神经炎症的关联， 血脑屏障的损害，目的是确定可量化的异常模式， 可以作为退伍军人自杀风险的生物标志物。尸检研究是唯一适合于 这是因为它们捕捉到了自杀行为发生时大脑的状态。 我们的实验室和其他实验室的研究结果表明，自杀的易感性包括炎症， 脑和全身激活，伴随血脑屏障完整性受损：（1） 最直接的是，我们报告了与血液相关的小胶质细胞或其他吞噬细胞的密度增加， 自杀者的背侧前额叶白色物质中的血管，扣带回中也报告了类似的结果 白色物质。(2)对自杀死亡者的大脑进行研究，并对活的人的血液和CSF进行研究。 先前曾试图自杀的个体发现炎性细胞因子升高。(3)各种 感染性疾病与自杀风险增加有关，任何人的住院史也是如此。 感染(4)暴露于压力的实验动物显示炎性细胞因子水平升高， 血脑屏障的渗透性、行为异常和小胶质细胞的激活。(5)我们有 报告了自杀与多态性和额叶和扣带回转录减少的关联， CD44参与BBB的正常功能。(6)生化指标提示BBB 据报道，损伤与自杀未遂和自杀意念有关。(7)MDD受试者中 与非精神病性非自杀病例相比，我们发现， 与细胞死亡相关的基因，无论是在整个皮质匀浆和纯化的神经元组分。我们 还发现CCL3基因启动子的甲基化显著降低，CCL3是一种强有力的炎症因子， 小胶质细胞和星形胶质细胞合成的细胞因子以及小胶质细胞和白色血细胞的引诱剂，但这 在纯化的神经元级分中不存在差异。 综上所述，这些发现使我们假设一种以血脑屏障受损为特征的自杀状态 功能，促炎细胞因子的升高，以及基因刺激的DNA甲基化异常， 炎症，所有这些都可以在活体个体中进行评估。为了证实这种表型，我们提出了三个 每一个都有特定的目标，每一个都使用了相同的90个尸检大脑，已经收集到了。为了区分 为了解精神疾病患者自杀的特点，我们采用三组设计， 30例无自杀的精神疾病患者和30例既无精神疾病也无自杀的患者 疾病或自杀，均来自一次尸检中具有单一采集方案的特征良好的采集 的服务.为了优化我们区分自杀特征和精神疾病特征的能力， 为了找到年龄和性别组之间的最佳匹配，我们试图将所有精神病病例限制在一个 单一临床组，这是最好的实现与精神分裂症谱系障碍。我们的具体目标是， 我们将分析大脑皮层和来自背侧和腹侧前额叶区域的白色物质，分别是： (1)通过纤维连接蛋白血管周围沉积物的体视学评估来评估功能性BBB损伤。 (2)为了定量一组细胞因子，并通过测定分离的细胞因子来寻找BBB损伤的结构证据， 微血管部分的血管紧密连接蛋白和基质金属蛋白酶。(3)以识别 BBB改变的转录相关性，并对微血管组分进行全基因组甲基化调查， 皮质和白色物质从每个区域，使用Illumina Infinium甲基化EPIC微阵列。这些数据 将使我们能够建立潜在的异常发展的自杀档案，以更好地，识别和 治疗有自杀危险的退伍军人了解和应用这一概况将挽救退伍军人的生命， 新的临床干预的潜在目标。

We propose a set of studies focused on the association of suicide with neuroinflammation and compromise of the blood-brain barrier, with the goal of identifying a pattern of quantifiable abnormalities that could serve as a biomarker for imminent suicidal risk in our Veterans. Autopsy studies are uniquely suited to do this, because they capture the state of the brain at the time of the suicidal act. Findings from our laboratories and others indicate that susceptibility to suicide includes inflammatory activation in the brain and systemically, accompanied by compromised integrity of the blood-brain barrier: (1) Most directly, we reported increased densities of microglia or other phagocytic cells associated with blood vessels in dorsal prefrontal white matter of people who died by suicide, Similar results are reported in cingulate white matter. (2) Studies of brains from individuals who died by suicide and studies of blood and CSF from live individuals who had previously attempted suicide found elevations of inflammatory cytokines. (3) Various infectious diseases are associated with increased risk of suicide, as is a history of hospitalization for any infection. (4) Laboratory animals exposed to stress show elevated levels of inflammatory cytokines, increased permeability of the blood-brain barrier, behavioral abnormalities, and activation of microglia. (5) We have reported an association of suicide with a polymorphism and decreased frontal and cingulate transcripts for CD44, which is involved in the normal function of the BBB. (6) Biochemical measures suggesting BBB impairment are reportedly associated with attempted suicide and with suicidal ideation. (7) In MDD subjects who died by suicide, compared with nonpsychiatric non-suicide cases, we found differential methylation of genes associated with cell death, both in whole cortical homogenates and in purified neuronal fractions. We also found significantly lower methylation in the promoter of the gene for CCL3, a powerful inflammatory cytokine synthesized by microglia and astrocytes and an attractant for microglia and white blood cells, but this difference was not present in the purified neuronal fraction. Taken together, these findings lead us to hypothesize a suicidal state characterized by impaired BBB function, elevation of pro-inflammatory cytokines, and abnormalities in DNA methylation of genes stimulating inflammation, all of which can be assessed in live individuals. To confirm this phenotype, we propose three specific aims, each employing the same set of 90 autopsy brains, already collected. In order to distinguish features of suicide from those of psychiatric illness, we employ a 3-group design with 30 cases of psychiatric disease and suicide, 30 cases of psychiatric disease without suicide, and 30 cases with neither psychiatric disease nor suicide, all from a well-characterized collection with a single collection protocol at a single autopsy service. To optimize our ability to distinguish features of suicide from those of psychiatric disease, in addition to finding the best matches between groups by age and sex, we sought to limit all of the psychiatric cases to a single clinical group, which was best achieved with schizophrenia spectrum disorders. Our specific aims, for each of which we will assay cerebral cortex and white matter from dorsal and ventral prefrontal regions, are: (1) To evaluate functional BBB impairment by stereological assessment of perivascular deposits of fibronectin. (2) To quantify a panel of cytokines, and to look for structural evidence of BBB impairment by assaying isolated microvessel fractions for vascular tight junction proteins and matrix metalloproteases.(3) To identify transcriptional correlates of BBB alterations with a genome-wide methylation survey on microvessel fractions of cortex and white matter from each region, using the Illumina Infinium MethylationEPIC microarray .These data will allow us to establish the underlying abnormalities for development of a suicidal profile to better, identify and treat veterans at risk of suicide. Knowledge and application of this profile will save Veterans’ lives by identifying potential targets for novel clinical interventions.