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和 血脑屏障的折衷，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。尸检研究是唯一适合做 这是因为它们捕捉到了自杀行为发生时的大脑状态。 我们的实验室和其他机构的研究结果表明，自杀的易感性包括炎症性 大脑和全身的激活，伴随着血脑屏障的完整性受损：(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密度的增加。 自杀者额叶背侧白质中的血管，在扣带回也有类似的结果。 白色物质。(2)自杀者的脑研究和活体血液和脑脊液的研究 之前曾试图自杀的人发现炎性细胞因子升高。(3)各种 传染病与自杀风险的增加有关，任何人的住院史也是如此 感染。(4)暴露在压力下的实验动物表现出炎性细胞因子水平升高， 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 报道了一种与自杀有关的基因多态以及额叶和扣带回基因转录减少 CD44参与血脑屏障的正常功能。(6)生化指标提示血脑屏障 据报道，精神障碍与自杀未遂和自杀念头有关。(7)MDD受试者 与非精神病非自杀病例相比，我们发现差异甲基化 与细胞死亡相关的基因，在整个皮质匀浆和纯化的神经元部分中都是如此。我们 还发现该基因启动子中的甲基化水平明显降低，为CCL3，一种强大的炎症 由小胶质细胞和星形胶质细胞合成的细胞因子，是小胶质细胞和白血球的引诱剂，但这 纯化后的神经元组分无差异。 综上所述，这些发现引导我们假设一种以血脑屏障受损为特征的自杀状态 促炎症细胞因子的功能、升高和刺激基因的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 已经收集到的特定目标，每个目标都使用了相同的90个尸检大脑。为了区分 从精神疾病患者的自杀特征出发，我们采用三组设计，共30例精神病患者。 疾病和自杀，30例精神疾病而不自杀，30例既不是精神疾病 疾病或自杀，都来自一次尸检的单一收集方案的良好特征收集 服务。为了优化我们区分自杀和精神疾病的特征的能力，除了 在按年龄和性别分组之间寻找最佳匹配，我们试图将所有精神病病例限制在 单一临床组，以精神分裂症谱系障碍效果最好。我们的具体目标是 我们将分析背侧和腹侧前额叶区域的大脑皮层和白质，其中每一个都是： (1)通过对血管周围纤维连接蛋白沉积的体视学评价来评价功能性血脑屏障损害。 (2)量化一组细胞因子，并通过分析分离的BBB损伤寻找结构证据 血管紧密连接蛋白和基质金属蛋白酶的微血管部分。(3)鉴定 血脑屏障改变的转录与全基因组微血管部分甲基化调查的相关性 每个区域的皮质和白质，使用Illumina Infinium甲基EPIC微阵列。这些数据 将使我们能够建立潜在的异常情况，以更好地、识别和 治疗有自杀风险的退伍军人。了解和应用此配置文件将通过确定 新的临床干预措施的潜在目标。

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.