Genetic Animal Models for the Study of Serotonin Function and Behavior

用于研究血清素功能和行为的遗传动物模型

• 批准号: 7969259
• 负责人: DENNIS L MURPHY
• 金额: $ 94.51万
• 依托单位: NATIONAL INSTITUTE OF MENTAL HEALTH
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/7969259
• 关键词: 5-Hydroxytryptophan; Absence of pain sensation; Adverse effects; Affect; Affinity; Alleles; Animal Model; Anti-Anxiety Agents; Antidepressive Agents; Antipsychotic Agents; Anxiety; Autistic Disorder; Behavior; Behavioral; Binding Sites; Bipolar Disorder; Blood Platelets; Brain; Brain region; Case Study; Clozapine; Data; Development; Disease; Dopamine; Drug usage; Emotional; Environment; Extracellular Fluid; Female; Financial compensation; Foxes; Genes; Genetic; Genetic Models; Genetic Polymorphism; Genetic Predisposition to Disease; Genetic Variation; Genotype; Hallucinogens; Head; Homeostasis; Human; Human Development; Image; Individual; Integrins; Internet; Investigation; Knockout Mice; Laboratories; Lead; Life; Measures; Mediator of activation protein; Meperidine; Metabolic; Modeling; Monoamine Oxidase; Mood Disorders; Morphine; Mus; Neurosecretory Systems; Neurotransmitters; Norepinephrine; Opioid; Organic Cation Transporter; Other Genetics; POU2F1 gene; Patients; Personality; Pharmaceutical Preparations; Phenotype; Physiological; Plasma; Promoter Regions; Proxy; Public Health; Reporting; Rodent; Role; Schizophrenia; Selective Serotonin Reuptake Inhibitor; Series; Serotonin; Serotonin Agents; Serotonin Antagonists; Serotonin Receptor 5-HT1A; Serotonin Syndrome; Site; Social Interaction; Stimulus; Stress; Substance abuse problem; Symptoms; Synapses; Syndrome; System; Temperature; Therapeutic; Time; Tissues; Tramadol; Tranylcypromine; Treatment Efficacy; Variant; base; depression; depressive symptoms; dietary supplements; gene interaction; high risk; human disease; inhibitor/antagonist; insight; male; monoamine; mouse model; neurochemistry; neuropsychiatry; neurotoxicity; receptor; response; serotonin 5 receptor; serotonin 7 receptor; serotonin receptor; serotonin transporter; tool; trait

As recently reviewed, SERT-deficient Slc6a4 +/- and -/- mice have gene-proportionate increases in extracellular fluid serotonin (5-HT) concentrations. i.e., 3- or 6-fold excesses respectively over +/+ mice (Murphy et al., 2008; Murphy & Lesch 2008; Fox et al., 2007). At the same time, the Slc6a4 -/- mice have a marked deficit of intracellular, releasable 5-HT. These mice also have significantly increased 5-HT synthesis and turnover across all five brain regions investigated in Slc6a4 -/- mice, and this increase is significantly greater in female Slc6a4 -/- mice. Expression of the organic cation transporters, OCT1 and OCT3, which are low affinity transporters of monoamines, is increased--indicative of some partial but inefficient attempts at compensation via heterologous transporters. Slc6a4 +/- mice manifest decreased 5-HT clearance and elevated extracellular fluid 5-HT but nonetheless have unchanged tissue 5-HT concentrations in the brain and periphery and unchanged brain 5-HT synthesis and turnover. Thus, a single copy of Slc6a4 is adequate to maintain overall 5-HT tissue homeostasis. The resulting data are: (1). Continuing advances have been made in our studies of the serotonin syndrome. Most commonly, this syndrome occurs as a side effect in humans treated with certain antidepressant and anti-anxiety drugs. Importantly, its occurrence contributes to reduced therapeutic efficacy or a requirement to interrupt treatment in some individuals. Our earlier studies exploring this behavioral and temperature-related syndrome in SERT-deficient mice had discovered that genetic vulnerability to a markedly exaggerated serotonin syndrome was present when these mice were exposed to the metabolic precursor of serotonin, 5-HTP, or to other serotonergic drugs such as the monoamine oxidase inhibiting (MAOI) antidepressant, tranylcypromine. Tranylcypromine is a clinically available antidepressant drug, and 5-HTP is readily available on more than 100 internet sites and sold over-the-counter as a dietary supplement. Spontaneous mild serotonin-syndrome behaviors were also observed in untreated Slc6a4 -/- mice (Fox et al., 2007; Fox et al., 2008). To better define the mechanisms underlying the serotonin syndrome, brain levels of serotonin and its metabolites were measured. In parallel with the greater behavioral changes, SERT -/- mice had 5 to 12-fold increases in serotonin, with smaller 2 to 5-fold increases in SERT +/+ and +/- mice following 5-HTP treatment (Fox et al., 2008). Exaggerated changes in temperature were also found in SERT -/- mice. Different serotonin receptor mechanisms were discovered to be involved with temperature responses by studies with different selective serotonin antagonists. In SERT +/+ and +/- mice, the 5-HT1A auto receptor was primarily involved. However, in SERT -/- mice, the 5-HT7 receptor was the primary mediator of these temperature changes (Fox et al., 2008). As roles for 5-HT7 receptors in anxiety and depression were recently established and contributions of 5-HT1A receptors to therapeutic responses to serotonergic drugs have been well-established, the current findings have implications for understanding the high anxiety-like and depressive-like phenotype of SERT-deficient mice relevant to the treatment of human anxiety and affective disorders. In another series of studies based on case reports implicating the clinically-used atypical opioid, tramadol and another opioid that is an abused substance, meperidine, in the development of the human serotonin syndrome, we examined tramadol and meperidine as possible causative drugs in our SERT genetic mouse model. Comparisons were also made with SERT mice treated with morphine, an opioid not implicated in the serotonin syndrome in humans. We found that tramadol and meperidine, but not morphine, induced serotonin syndrome behaviors in mice, and that this response was exaggerated in SERT -/- and +/- mice (Fox et al., 2009). The exaggerated response to tramadol in SERT -/- mice was blocked by pretreatment with a serotonin receptor 5-HT1A antagonist. Further, we found that morphine-, meperidine- and tramadol-induced analgesia was markedly decreased in SERT -/- mice. These studies suggest that caution seems warranted in prescribing or not warning patients receiving SRIs or MAOIs that dangerous side-effects may occur during concurrent use of tramadol and similar agents. These findings in this mouse genetic model raise the possibility that humans with lower-expressing SLC6A4 SS genotypes or other SERT variants that lead to 50-80% decreases in SERT binding sites or transport function may be at higher risk to develop serotonin syndrome neurotoxicity. This is based on highly congruent data from imaging, neuroendocrine and other studies that have compared SERT-deficient mice to humans with SERT gene variants. Of special note, it is likely that relatively mild serotonin syndrome occurrence may contribute to early discontinuation of SRIs and other side effects during SRI treatment that are strongly associated with the lower-expressing SLC6A4 SS genotypes and S alleles as well as other newly discovered lower-expressing variants in this gene, as described in our other report, MH000336-30 LCS. (2). Another behavioral abnormality in SERT-deficient mice is reduced head twitch responses to serotonergic agents. This response is considered a pharmacologic proxy for hallucinogenic-like behaviors, as most of the drugs that induce this response in rodents are hallucinogens in humans, and these responses can be blocked by anti-psychotic drugs. In exploring mechanisms underlying this response, we found this year that reducing excess brain serotonin in SERT-deficient mice by using a serotonin synthesis inhibitor restored the deficient head twitch state in SERT -/- mice to levels of SERT control +/+ mice (Basselin et al., 2009). These findings provide a more comprehensive understanding of mechanisms in this genetic mouse model that eventually may provide insights into human disorders with genetic contributions that include hallucinogenic phenomena such as schizophrenia and bipolar disorders as well as the consequences of certain types of substance abuse disorders, all of major public health concern. (3). SERT-deficient mice were also compared to mice with gene-based deficiencies in other neurotransmitters, those for dopamine and norepinephrine, as well as to mice with other genetic deficiencies that interact with SERT, such as the integrin alphaIIbeta3 gene, as well as other types of environmental stimuli. Differences in brain, platelet and gut responses to multiple agents were observed. These findings serve as further illustrations of earlier data accumulated by our Lab that support the use of these mice as vulnerability models for humans with SERT gene variants with regard to gene-environment and gene-gene interactions that contribute to human diseases. (4). In other new studies of SERT-deficient mice, these mice were examined for possible autism-related traits, as some studies have identified associations of SLC6A4 polymorphisms as well as plasma serotonin levels with the occurrence of autism. In a three-chambered choice task, male SERT-deficient mice displayed significantly reduced social interaction behaviors with other mice compared to SERT +/+ mice (Moy et al., 2009). Thus, together with increased anxiety-like behaviors plus increased startle responses and increased behavioral and physiological responses to various types of stress, these mice show a series of features highly relevant to symptoms in several neuropsychiatric disorders of important public health concern.

正如最近综述的那样，缺乏SERT缺乏的SLC6A4 +/-和 - / - 小鼠在细胞外液血清素（5-HT）浓度中具有基因形式增加。即分别超过 +/ +小鼠的3倍或6倍（Murphy等，2008; Murphy＆Lesch 2008; Fox等，2007）。 同时，SLC6A4 - / - 小鼠具有明显的细胞内，可释放的5-HT。 这些小鼠在SLC6A4 - / - 小鼠中研究的所有五个大脑区域中还显着增加了5-HT合成和周转，并且在雌性SLC6A4-/ - 小鼠中，这种增加明显更大。 有机阳离子转运蛋白的表达OCT1和OCT3（单胺的亲和力转运蛋白）的表达增加了 - 指出了通过异源转运蛋白进行补偿的某些部分但效率低下的尝试。 SLC6A4 +/-小鼠显现降低了5-HT清除率，细胞外液的5-HT升高，但仍具有脑部和外围的5-HT浓度不变，外围和不变的脑5-HT合成和失误。因此，SLC6A4的单个副本足以维持总体5-HT组织稳态。 结果数据是： （1）。在我们对5-羟色胺综合征的研究中，已经取得了持续的进步。 最常见的是，该综合征是用某些抗抑郁药和抗焦虑药治疗的人类的副作用。 重要的是，它的发生有助于降低治疗功效或中断某些个体的治疗的要求。 我们较早的研究探索了缺乏菌的小鼠中这种行为和温度相关综合征的研究，发现这些小鼠暴露于5- HTP的代谢前体时，存在明显夸张的5-羟色胺综合征的遗传脆弱性，或者是其他同素氧酶氧化酶（MAOAMINAMINE氧化剂）的代谢前体时，存在。 tranylcypromine是一种临床上可用的抗抑郁药，5-HTP在100多个互联网站点上很容易获得，并作为饮食补充剂出售。 在未处理的SLC6A4 - / - 小鼠中也观察到了自发的轻度5-羟色胺合成组的行为（Fox等，2007； Fox等，2008）。 为了更好地定义5-羟色胺综合征的基础机制，测量了5-羟色胺及其代谢产物的大脑水平。 与更大的行为变化同时，SERT - / - 小鼠在5-羟色胺中的增加5至12倍，在5-HTP治疗后，SERT +/ +和+/-小鼠的2至5倍增加了2至5倍（Fox等人，2008年）。 在SERT - / - 小鼠中也发现了温度的夸大变化。 发现不同选择性5-羟色胺拮抗剂的研究发现不同的5-羟色胺受体机制与温度反应有关。 在SERT +/ +和+/-小鼠中，5-HT1A自动受体主要涉及。 但是，在SERT - / - 小鼠中，5-HT7受体是这些温度变化的主要介体（Fox等，2008）。 由于最近确定了5-HT7受体在焦虑和抑郁中的作用，并且已经确立了5-HT1A受体对血清素能药物的治疗反应的贡献，目前的发现对了解与人类焦虑症和情感障碍者的治疗相关的高焦虑症状和抑郁样表型具有影响。 在基于病例报告的另一系列研究中，涉及临床中使用的非典型阿片类药物，曲马多和另一种是滥用物质的阿片类药物，它是一种在人类血清素综合征的发展中，我们在我们的Sert Genetic小鼠模型中检查了曲马多和肠植物的曲马多和肠植物。 还与用吗啡治疗的SERT小鼠进行了比较，这是人类中5-羟色胺综合征的阿片类药物。 我们发现曲马多和米胃但不是吗啡，诱导小鼠的5-羟色胺综合征行为，并且这种反应在sert - / - 和+/-小鼠中被夸大了（Fox等，2009）。 用5-羟色胺受体5-HT1A拮抗剂预处理对SERT - / - 小鼠中曲马多的反应被阻断。 此外，我们发现SERT - / - 小鼠中吗啡 - ，甲状腺毒素和曲马多诱导的镇痛显着降低。 这些研究表明，在开处方或不警告接受SRIS或MAOI的患者时，谨慎行事似乎是有必要的，该患者在同时使用Tramadol和类似药物时可能会发生危险的副作用。 在该小鼠遗传模型中的这些发现增加了表达较低的SLC6A4 SS基因型或其他SERT变体的可能性，导致SERT结合位点降低50-80％的其他SERT变体可能会有较高的风险，可能具有较高的风险来发展血清素蛋白综合征综合征神经毒性。 这是基于来自成像，神经内分泌和其他研究的高度一致数据，这些数据已将缺陷小鼠与具有SERT基因变异的人进行了比较。特别值得注意的是，相对温和的5-羟色胺综合征的发生可能会导致SRI和其他副作用在SRI治疗期间的早期停用，这与较低表达的SLC6A4 SS基因型和S等位基因和S等位基因以及其他新发现的较低表达的变体以及我们在我们的其他较低的基因中，如我们的其他报告中所述。 （2）。 SERT缺陷小鼠的另一个行为异常是对血清素能剂的头部抽搐反应减少。 这种反应被认为是幻影症样行为的药理学代理，因为大多数诱导啮齿动物中这种反应的药物是人类的致幻剂，并且这些反应可以被抗精神药物阻止。 在探索这一反应的基础机制时，我们发现，通过使用5-羟色胺合成抑制剂恢复Sert - / - 小鼠中缺陷的头部Twitch状态，将SERT - / - 小鼠的水平恢复到Sert Control +/ +小鼠的水平（Basselin等人，Basselin等，2009）。 这些发现为这种遗传小鼠模型中的机制提供了更全面的理解，最终可能会提供对人类疾病的见解，其中包括幻觉症状现象，例如精神分裂症和双极性疾病，以及某些类型的药物滥用疾病的后果，以及所有主要的公共卫生问题。 （3）。还将缺乏SERT的小鼠与其他神经递质中的基因缺乏的小鼠（用于多巴胺和去甲肾上腺素的小鼠，以及与其他与SERT相互作用的遗传缺陷的小鼠，例如整合蛋白Alphaiibeta3基因，以及其他类型的环境刺激。 观察到大脑，血小板和肠道对多种药物的差异。这些发现是我们实验室积累的早期数据的进一步说明，这些数据支持这些小鼠作为对基因环境和基因 - 基因相互作用的人类的脆弱模型，这些模型和基因 - 基因相互作用有助于人类疾病。 （4）。在其他对SERT缺陷型小鼠的新研究中，检查了这些小鼠的可能与自闭症相关的特征，因为一些研究已经确定了SLC6A4多态性以及血浆5-羟色胺水平与自闭症发生的关联。 与SERT +/ +小鼠相比，在三腔选择任务中，雄性SERT缺陷小鼠与其他小鼠的社交相互作用行为显着降低（Moy等，2009）。 因此，加上焦虑样行为加上增加的惊吓反应以及对各种压力的行为和生理反应的增加，这些小鼠在几种重要的公共卫生关注的几种神经精神疾病中显示了一系列与症状高度相关的特征。