Investigating Neuromelanin-Mediated Locus Coeruleus Neurodegeneration in a Novel Mouse Model of Parkinson's Disease

一种新的帕金森病小鼠模型研究神经黑素介导的蓝斑神经变性 Alexa Iannitelli 摘要 帕金森病是世界范围内第二常见的神经退行性疾病，以运动为特征 和非运动性症状。主要的药物疗法左旋多巴只对引起的运动症状有效。 由多巴胺(DA)神经元变性，而与去甲肾上腺素能功能障碍相关的非运动症状严重 对帕金森病患者生活质量的影响，目前任何可用的治疗方法都不能缓解。 因此，对帕金森病神经病理和治疗的新研究必须考虑主要中枢蓝斑(LC)。 去甲肾上腺素能核。在帕金森病患者中，LC先于DA神经元发展为α-突触核蛋白病变，并且几乎完全 在疾病后期退化，但导致其脆弱性的分子机制尚不清楚。与.一起 黑质DA神经元，LC是大脑中唯一能产生大量神经黑素的结构 (NM)，一种深棕色的细胞质色素。有人提出，这些NM颗粒最初通过以下方式发挥保护作用 隔离有毒的儿茶酚胺代谢物和重金属，但在老化过程中变得有害，尤其是在帕金森病中 它们使细胞机械不堪重负，在神经退化过程中释放出来。因为啮齿动物不会自然产生 NM，对这种色素的研究大多局限于对人类身体的研究，还不可能 实验解决了NM在PD相关LC病理中的作用。然而，我采用了一种病毒中介的方法 为了表达人类酪氨酸酶，这种酶负责皮肤细胞中黑色素的形成，以促进NM 啮齿动物LC神经元的产生。我发现LC中的色素表达概括了内源性NM的关键特征 存在于灵长类动物中，包括真黑素和褐黑素、脂滴和双膜包裹。提前10周 注射后，小鼠表现出严重的LC神经变性和强烈的神经炎性反应，导致星形胶质细胞 神经胶质疤痕。行为后果包括过度唤醒、类似焦虑的行为增加和认知障碍。 这些表型反映了帕金森病的非运动症状，验证了该模型在研究帕金森病后果方面的实用性。 NM在LC中积累，因为它与神经退行性疾病有关。在F99阶段，我建议扩展这些 使用核糖体亲和纯化(TRAP)翻译核糖体标签技术的研究结果 基因转录的变化与NM诱导的LC功能障碍和变性有关，并可能是其潜在的基础。在K00 阶段，我将应用从这些研究中收集的信息来研究潜在的机制和药理学 希望减轻LC和SN中有毒NM积聚和随后的神经变性的干预措施。 这些研究将提供对NM如何导致早期脆弱性的全面了解 在帕金森病的儿茶酚胺神经元，并将有助于确定潜在的分子靶点，以预防和治疗这种情况 衰弱的神经退行性疾病。

Investigating neuromelanin-mediated locus coeruleus neurodegeneration in a novel mouse model of Parkinson’s disease Alexa Iannitelli Summary Parkinson’s disease (PD) is the second most common neurodegenerative disorder worldwide, and is characterized by motor and non-motor symptoms. The leading pharmacotherapy, levodopa, is only effective for treating the motor symptoms caused by dopamine (DA) neuron degeneration, while non-motor symptoms associated with noradrenergic dysfunction have grave consequences for the quality of life experienced by PD patients and are not alleviated by any currently available therapies. Thus, new research on PD neuropathology and treatment must consider the locus coeruleus (LC), the major central noradrenergic nucleus. The LC develops alpha-synuclein pathology prior to DA neurons in PD and is almost completely degenerated in later stage disease, but the molecular mechanisms responsible for its vulnerability are unknown. Along with substantia nigra DA neurons, the LC is the only structure in the brain that produces appreciable amounts of neuromelanin (NM), a dark brown cytoplasmic pigment. It has been proposed that these NM granules initially play a protective role by sequestering toxic catecholamine metabolites and heavy metals, but become harmful during aging and particularly in PD as they overwhelm cellular machinery and get released during neurodegeneration. Because rodents do not naturally produce NM, the study of this pigment has been mostly limited to human postmortem studies, and it has not been possible to experimentally address the role of NM in PD-associated LC pathology. However, I have adapted a viral-mediated approach for expression of human tyrosinase, the enzyme responsible for the development of melanin in skin cells, to promote NM production in rodent LC neurons. I found that pigment expression in the LC recapitulates key features of endogenous NM found in primates, including eumelanin and pheomelanin, lipid droplets, and a double-membrane encasement. By 10-weeks post-injection, mice display severe LC neurodegeneration and a robust neuroinflammatory response, resulting in astrocytic glial scarring. Behavioral consequences include hyperarousal, increased anxiety-like behavior, and cognitive impairment. These phenotypes reflect non-motor symptoms of PD, validating the utility of this model for studying the consequences of NM accumulation in the LC as it relates to neurodegenerative disease. During the F99 phase, I propose to expand these findings by employing the ribo-tagging technique Translating Ribosome Affinity Purification (TRAP) to investigate how changes in gene transcription relate to, and potentially underlie, NM-induced LC dysfunction and degeneration. In the K00 phase, I will apply the information gleaned from these studies to investigate potential mechanistic and pharmacological interventions in the hopes of mitigating toxic NM accumulation and subsequent neurodegeneration, in both the LC and SN. These studies will provide a comprehensive understanding of how NM contributes to the early vulnerability of catecholamine neurons in PD, and will help identify potential molecular targets for the prevention and treatment of this debilitating neurodegenerative disease.