GABA-谷氨酸系统、糖皮质激素受体相关基因与自杀行为的关联研究

发布时间：2017-12-28 02:35

本文关键词：GABA-谷氨酸系统、糖皮质激素受体相关基因与自杀行为的关联研究　出处：《南方医科大学》2017年博士论文　论文类型：学位论文

【摘要】：自杀是世界性的重大公共卫生问题。在美国,每年大约有30,000人死于自杀,而全世界范围来看,每年大约有100万人死于自杀。自杀行为是一种自主的、以死亡为目的的复杂行为障碍,它的预测、评估、治疗及预防不仅仅是精神疾病学界,也是全社会的难题之一。自杀的主要风险因素是精神障碍。据估计,90%的自杀行为与某种形式的精神障碍相关联。而在这些精神障碍中,大约60%为抑郁症,抑郁症与双相情感障碍出现自杀行为的终生风险相似。由于自杀行为是多因素影响的行为障碍,除精神障碍以外,许多其他的危险因素如心理因素,都与自杀有关。虽然大部分自杀行为发生在有精神障碍的个体,但是有精神障碍的病人中却只有少数人出现过自杀未遂,出现自杀死亡的更少。抑郁症患者中仅有不足10%有自杀未遂史,而10%的自杀死亡者从未诊断过精神障碍。精神病学家认为,自杀行为并不是精神疾病的一种症状,而是某种独立的特质,当有这种特质的人群患有某些精神科疾病或受到重大刺激时,才会出现自杀行为。目前自杀行为仅能通过量表来评估,而高危人群由于害怕受到歧视、或被强制住院、或怕自己的自杀计划被别人阻碍等原因,而不愿意将自杀意念或计划透露出来,导致评估结果不可靠,故而将内在的、主观的量表评估和外在的、客观的生物检测结合在一起才能准确评估自杀行为。最初对自杀的研究主要针对有自杀行为人群的流行病学调查以及对最终出现自杀死亡患者的跟踪报导,这些研究提供了重要的初始数据。随后的研究采用死亡患者脑组织分析有自杀行为人群大脑的共同异常表现。脑组织收藏方法的改进为研究大脑的详细的神经生物学参数提供了机会,脑组织研究为自杀行为的发病机制提供了重要的神经生物学数据。目前,许多研究认为自杀与血清素能系统、神经内分泌系统和其它神经递质系统的异常有关,其中涉及基因多态性、基因表达及表观遗传机制等各方面。研究最多的是血清素系统,自杀人群的血清素及其信号传递水平改变,且有独特的基因型和表达模式。总的看来,虽然目前已经取得很多研究成果,但是由于靶器官活体组织无法取得、缺乏有用的动物模型以及伦理道德等方面的制约,导致自杀行为的分子机制还不明确。近年来,γ-氨基丁酸(γ-aminobutyricacid,GABA)-谷氨酸系统和糖皮质激素受体(Glucocorticoid receptor,GR)系统在自杀行为分子机制中的作用逐渐受到重视,出现了许多有意义的发现,但目前还缺乏系统的研究综合分析基因多态性、基因表达等与自杀行为的关系。GABA和谷氨酸分别是哺乳动物中枢神经系统中主要的抑制性和兴奋性神经递质,GABA-谷氨酸通路是保证中枢神经系统里有足够的神经递质谷氨酸的一系列生化过程。神经元不能直接通过葡萄糖合成GABA或谷氨酸,突触前神经元释放GABA或谷氨酸,吸收进入星形胶质细胞,然后星形胶质细胞再释放谷氨酰胺作为前体在神经元内合成GABA或谷氨酸,这就是常见的谷氨酰胺-谷氨酸/GABA循环。在神经元中,谷氨酰胺不仅能产生能源和合成蛋白质,而且是氨基酸类神经递质生物合成的必需前体。既往许多研究提示,GABA-谷氨酸系统与自杀行为有紧密联系。精神分裂症自杀死亡患者听觉皮层的GABA神经元密度降低。绝大部分GABA-谷氨酸系统的组成成分都与自杀行为有某种形式的关联。除此之外,几乎自杀行为的所有候选内表型(冲动-攻击特质、神经认知功能损害、应激下的皮质醇改变等)均与GABA能系统有密切的关系。许多研究表明,冲动及攻击特质与脑内特定区域的GABA水平有关;也有许多研究发现,GABA能系统功能受损会导致神经认知功能损害包括工作记忆、决策能力及反应抑制等;还有一系列研究表明,GABA能系统可调节HPA轴,改变机体的应激反应。因此GABA-谷氨酸系统基因可能会参与自杀行为的形成机制。应激反应系统也和自杀行为有紧密的联系,研究发现HPA轴相关基因与自杀行为有关。应激引起儿茶酚胺和糖皮质激素的分泌,进而激活GR或盐皮质激素受体。GR通常位于细胞质中,但与配体结合后能被转运到细胞核,参与炎症反应、细胞增殖和靶组织分化。GR激活以后可以快速调控转录、活化下丘脑-垂体-肾上腺轴(HPA),以及当皮质醇水平在压力刺激下升高时,介导HPA轴的负反馈调节。GR受多种调控因素的调节,其中基因单核苷酸多态性、分子伴侣是两个重要因素。目前已有研究结果显示糖皮质激素受体基因(nuclear receptor subfamily 3 group C member 1,NR3C1)的单核苷酸多态性、分子伴侣FK506结合蛋白5(FK506 binding protein 5,FKBP5)等导致GR功能障碍的机制包括改变GR的表达、GR与糖皮质激素的结合力、GR的转核活性、GR与目标基因DNA的结合能力、糖皮质激素受体α亚型和糖皮质激素受体β亚型的比率等,从而影响HPA轴功能、神经可塑性和抑郁行为。FKBP5基因位于人类6号染色体(6p21.31),是GR活动的一个重要的负调控因子。它是调节GR灵敏度的热休克蛋白90的分子伴侣。FKBP5过度表达可以降低皮质醇与GR的亲和力,并影响GR的核转运。作为反馈回路的一部分,GR的激活将会增加FKBP5的转录和蛋白表达。此外,FKBP5可以通过促进GR的非活性β-异构体的核转运而进一步降低GR信号。总体而言,FKBP5是应激反应的重要基因调节器,并能抑制GR活性。近年来,有丝分裂相关蛋白 2(Spindle and kinetochore-associated protein 2,SKA2;又名 Family with sequence similarity 33,member A,FAM33A)对糖皮质激素受体功能的影响也有初步报导。SKA2位于17q22,是一个最近发现的SKA复合物成分,是染色体正确分离所必需的成分。SKA2的过度表达可导致GR转录增加,而降低SKA2的表达将显著抑制GR转录,提示了这两种蛋白之间的功能性相互作用。由于自杀行为和应激之间存在密切关系,而FKBP5、SKA2以及NR3C1是应激反应体系的重要调节剂,因此上述基因在自杀行为中也可能起到重要作用。目前有很多研究发现GABA-谷氨酸系统及糖皮质激素受体系统相关基因的多态性及表达水平与自杀行为有关,但基因多态性是否通过调节基因表达影响自杀行为还不清楚。基于自杀行为的国内外研究现状,本研究从分子遗传学角度对GABA-谷氨酸系统及糖皮质激素受体系统相关基因与自杀行为的关系进行了初步分析,并分析基因表达在基因多态性影响自杀行为中的中介作用,同时筛选与自杀行为有关的平行证据最多的基因,并拟在后续研究中将这些生物标记物与临床评定量表相结合,用于预测及评估精神科患者的自杀行为、筛查自杀高危人群,并为药物治疗提供生物靶标。目的:探索GABA能和谷氨酸能信号系统的24种基因及与糖皮质激素受体相关的3个基因FKBP5、SKA2及NR3C1的基因型、基因表达与自杀行为的关系,分析是否存在表达数量性状位点(Expression quantitative trait locus,eQTL),初步筛查自杀行为的生物标记物。方法:第一部分,在276例活体样本(86例自杀未遂、190非自杀未遂)及209例死亡样本(121例自杀死亡、88例非自杀死亡)中,采用Logistic回归分析探索GABA-谷氨酸系统的24种基因(4种转运体、4种酶、16种受体)的119个候选单核苷酸多态性(SNP)以及糖皮质激素受体相关基因FKBP5、SKA2和NR3C1的98个SNP的基因型与自杀行为之间的关系,均经年龄和性别调整;第二部分,在59例死亡样本(21例抑郁症+自杀、9例抑郁症及29例对照)的脑组织背外侧前额叶皮层,采用Robust回归分析探索每个基因的RNA表达水平在自杀vs非自杀的差异,均经年龄、性别和RNA完整性(RNA Integrity Number,RIN)调整;第三部分,在网上数据(脑eQTL年鉴)中(www.braineac.org),查找本研究第一部分中与自杀行为有关的SNP与相应基因的前额叶皮层RNA表达水平之间的关系。结果:1、在GABA-谷氨酸系统及糖皮质激素受体系统中,7个基因的8个多态性位点与自杀死亡相关。分别为:rs6447520(GABRA4)、rs2808536(GABBR2)、rs424740(GABRG2)、rs6849345(GRIA2)、rs4780886(GRIN2A)、rs1062246(SLC6A1)、rs8082544(SKA2)及 rs7502947(SKA2)。2、在GABA-谷氨酸系统及糖皮质激素受体系统中,8个基因的15个多态性位点与自杀未遂相关。分别为:rs6447520(GABRA4)、rs10836356(SLC1A2)、rs1529461(SLC1A3)、rs13035504(GLS)、rs2236418(GAD2)、rs9296158(FKBP5)、rs3777747(FKBP5)、rs4713902(FKBP5)、rs7757037(FKBP5)、rs737054(FKBP5)、rs12945875(SKA2)、rs8067682(SKA2)、rs9380529(FKBP5)、rs9911583(SKA2)及rs9324924(NR3C1)。3、因样本量受限,本研究未能采用mediation analysis证明eQTL的存在。但是,GABRG2基因的转录本表达降低(P = 0.01)及其SNPrs424740AA基因型(P = 0.03)均与自杀死亡有关,同时其AA基因型携带者前额皮层的基因表达降低(p = 0.016、0.04)。该结论强烈提示了 rs424740是eQTL的可能,也反映了 GABRG2基因与自杀行为的关系,有必要在更大的样本中进一步研究。4、3种GABAA受体亚型的RNA转录本在自杀死亡组表达降低,分别为:GABRB1-001、GABRB3-006、GABRG2-003。5、FKBP5单倍型(结构:rs3800373、rs7757037;频率=47%)与自杀未遂风险增加有关(OR=1.58,T = 6.03,p值=0.014),携带单倍型AA的个体有更高的自杀未遂风险。6、NR3C1基因的mRNA转录本ENST00000394466(NR3C1-006)在自杀死亡脑组织中低表达(B =-0.48,SE = 0.12,T =-4.02,多重检验调整后P值=0.004)。结论:本研究发现了 GABA-谷氨酸系统及糖皮质激素受体系统相关基因中与自杀行为相关的许多独立证据,证实了 GABA-谷氨酸系统及糖皮质激素受体系统在自杀行为中的重要作用,本研究的初步结论反映了 GABRG2基因与自杀行为的关系,而且明确了 FKBP5单倍型与自杀未遂风险有关,还发现NR3C1基因前额皮层表达与自杀有关,进一步证实了自杀行为的HPA轴功能紊乱。
[Abstract]:Suicide is a major public health problem in the world. In the United States, about 30000 people die a year from suicide, and around the world, about 1 million people die a year from suicide. Suicidal behavior is an autonomous and complex behavioral disorder with the purpose of death. Its prediction, evaluation, treatment and prevention are not only the academic field of mental disease, but also one of the difficult problems of the whole society. The main risk factor for suicide is mental disorder. It is estimated that 90% of suicides are associated with some form of mental disorder. Of these mental disorders, about 60% of them are depression, and depression is similar to the lifetime risk of suicide in bipolar disorder. In addition to mental disorders, many other risk factors, such as psychological factors, are associated with suicide because of the multiple factors affected by suicide. Although most suicidal behaviors occur in individuals with mental disorders, only a few people with mental disorders have attempted suicide and fewer suicide cases. Only less than 10% of the patients with depression had a history of attempted suicide, while 10% of those who died of suicide had never diagnosed mental disorders. Psychiatrists believe that suicidal behavior is not a symptom of mental illness, but rather an independent trait. When a person with this trait suffers from certain psychiatric disorders or is subject to major stimulation, suicidal behavior will occur. At present can only be evaluated by Dutch act behavior scale, and high risk population because of fear of discrimination, or forced hospitalization, or if their plan was obstructing others Dutch act reasons, rather than ideas or plans Dutch act revealed, the evaluation result is not reliable, so the internal and subjective scale biological evaluation external, objective and accurate assessment of behavior detection based on Dutch act together to. The research on suicide is mainly focused on the epidemiological survey of suicidal behavior and the follow-up reports of the final suicide deaths. These studies provide important initial data. The subsequent study used the brain tissue analysis of death patients to identify the common abnormal manifestations of the brain in the people who had committed suicide. The improvement of brain tissue collection provides an opportunity to study the detailed neurobiological parameters of brain. Brain tissue research provides important neurobiological data for the pathogenesis of suicidal behavior. At present, many studies believe that suicide is related to the abnormality of serotonin system, neuroendocrine system and other neurotransmitter systems, including gene polymorphism, gene expression and epigenetic mechanism. The most research is the serotonin system, the serotonin and its signal transmission level in the suicide population, and the unique genotypes and expression patterns. Generally speaking, although many research achievements have been achieved, the molecular mechanism of suicidal behavior is not clear due to the fact that target organ organ can not be acquired, lack of useful animal models and ethics. In recent years, GABA (gamma -aminobutyricacid, GABA) - glutamate system and glucocorticoid receptor (Glucocorticoid receptor GR) system in Dutch act behavior of the molecular mechanism for increasing attention, there are many interesting discoveries, but there is still a lack of systematic comprehensive analysis of gene polymorphism and gene expression the relationship between behavior and Dutch act. GABA and glutamate are the major inhibitory and excitatory neurotransmitters in the mammalian central nervous system, respectively. The GABA- glutamate pathway is a series of biochemical processes that ensure enough neurotransmitters in the central nervous system. Neurons can not directly through the synthesis of glucose GABA or glutamate release from the presynaptic neuron GABA or glutamate, absorbed into astrocytes, and astrocytes to release glutamine as a precursor in the synthesis of GABA or glutamate neurons, which is a common glutamine glutamate /GABA cycle. In neurons, glutamine not only produces energy and synthetic proteins, but also is a necessary precursor for the biosynthesis of amino acid neurotransmitters. Many previous studies have suggested that the GABA- glutamate system is closely associated with suicide. The density of GABA neurons in the auditory cortex was reduced in patients with schizophrenic suicide deaths. Most of the components of the GABA- glutamic acid system are associated with some form of suicide. Besides, almost all candidate phenotypes, including impulse attack trait, neurocognitive impairment, cortisol changes under stress, are closely related to GABA energy system. Many studies show that the specific characteristics and regional brain impulses and attack within the GABA level; many studies have also found that GABA can cause system impaired neurocognitive impairment including working memory, decision-making ability and response inhibition; and a series of studies show that GABA system can regulate the HPA axis, change the body's stress response. Therefore, the gene of GABA- glutamate system may be involved in the formation mechanism of suicidal behavior. The stress response system is also closely related to suicidal behavior, and the study found that the HPA axis related genes are associated with suicide. Stress causes the secretion of catecholamine and glucocorticoid, and then activates GR or corticosteroid receptor. GR is usually located in the cytoplasm, but it can be transported to the nucleus after binding with the ligand and participates in the inflammatory response, cell proliferation and target tissue differentiation. GR activation can regulate transcription and activation of hypothalamus pituitary adrenal axis (HPA) rapidly, and mediate the negative feedback regulation of HPA axis when cortisol level increases under pressure stimulation. GR is regulated by a variety of regulatory factors, in which the single nucleotide polymorphisms of genes and molecular chaperone are two important factors. At present, the results of the study show the glucocorticoid receptor gene (nuclear receptor subfamily 3 group C member)
【学位授予单位】：南方医科大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：R749

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