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

我们提出了一系列研究，重点关注自杀与神经炎症和 血脑屏障的损害，目的是确定一种可量化的异常模式， 可以作为退伍军人迫在眉睫的自杀风险的生物标志物。尸检研究特别适合做 这是因为它们捕获了自杀行为时的大脑状态。 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 大脑和全身的激活，伴随着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 自杀者背侧前额叶白质中的血管，扣带回也有类似的结果 白色物质。 (2) 对自杀者大脑的研究以及活体血液和脑脊液的研究 曾试图自杀的人发现炎症细胞因子升高。 (3) 各种 传染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表现出炎症细胞因子水平升高， 血脑屏障的通透性、行为异常和小胶质细胞的激活。 (5) 我们有 报道自杀与多态性以及额叶和扣带回转录本减少有关 CD44，参与血脑屏障的正常功能。 (6) 生化指标提示BBB 据报道，损害与自杀未遂和自杀意念有关。 (7) MDD 科目 与非精神病非自杀病例相比，我们发现自杀死亡的病例有差异甲基化 与细胞死亡相关的基因，包括整个皮质匀浆和纯化的神经元部分。我们 还发现 CCL3 基因启动子的甲基化显着降低，CCL3 是一种强大的炎症因子。 由小胶质细胞和星形胶质细胞合成的细胞因子，也是小胶质细胞和白细胞的引诱剂，但这 纯化的神经元部分不存在差异。 综上所述，这些发现使我们推测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刺激基因的 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。为了证实这一表型，我们提出了三个 具体目标，每个目标都使用已收集的同一套 90 个尸检大脑。为了区分 为了区分自杀与精神疾病的特征，我们采用了 3 组设计，包括 30 名精神疾病患者 疾病与自杀，有精神疾病但无自杀的 30 例，无精神疾病的 30 例 疾病或自杀，全部来自于一次尸检时采用单一采集方案的特征明确的采集 服务。为了优化我们区分自杀特征和精神疾病特征的能力，除了 为了找到按年龄和性别分组之间的最佳匹配，我们试图将所有精神病病例限制在 单一临床组，最好是在精神分裂症谱系障碍中实现。我们的具体目标是 我们将检测背侧和腹侧前额叶区域的大脑皮层和白质，分别是： (1)通过体视学评估纤连蛋白血管周围沉积物来评估功能性血脑屏障损伤。 (2) 量化一组细胞因子，并通过分析分离的细胞因子来寻找 BBB 损伤的结构证据 血管紧密连接蛋白和基质金属蛋白酶的微血管组分。(3) 鉴定 BBB 改变的转录相关性与微血管部分的全基因组甲基化调查 使用 Illumina Infinium MmethylationEPIC 微阵列分析每个区域的皮层和白质。这些数据 将使我们能够确定自杀倾向发展的潜在异常，以便更好地识别和 治疗有自杀风险的退伍军人。了解并应用此概况将通过识别来挽救退伍军人的生命 新型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.