Disorders of Copper Transport

我们的翻译研究专注于铜代谢紊乱的诊断、治疗和理解，铜代谢紊乱是一种最近扩大的人类疾病集合，影响中枢和外周神经系统的不同组成部分。后天和遗传形式的异常铜稳态与神经功能障碍有关。门克斯病(MD)是一种典型的铜转运缺陷遗传综合征，以脑内铜含量低、婴儿期神经变性和过早死亡为特征。MD是由X连锁铜转运蛋白基因ATP7A突变引起的。枕角综合征(OHS)是一种较轻微的等位基因变异，与泄漏的ATP7A剪接连接突变相关，其中自主神经功能障碍占主导地位。最近，我们发现了几个运动神经元疾病家族，类似于Charcot-Marie-Tooth病和肌萎缩侧索硬化症，这些疾病是由ATP7A羧基一半的几个新的错义突变引起的。这些都是轻微的功能丧失缺陷，似乎会影响ATP7A的细胞内运输。因此，ATP7A突变的表型谱已扩大；这些新的等位基因变异的发现表明，ATP7A在运动神经元维持和功能方面发挥了以前未被认识到的作用。 目前对MD的治疗仅限于皮下注射铜，对突变等位基因不完全消除ATP7A功能的患者有效，并且在出生时被确认(N Engl J Med 2008；358：605-614)。然而，对于功能完全丧失突变的患者，外周输送的铜不能有效地穿过血脑屏障，需要替代的治疗方法。在我们最近对治疗方案的探索中，我们使用联合脑导向疗法拯救了一种严重门克斯病的小鼠模型：重组腺相关病毒血清型5(AAV5)载体表达尺寸缩小的人ATP7A加上铜。单独治疗都不是有效的，但联合治疗显著改变了卡普兰-迈尔生存曲线，16个联合治疗的突变中有5个(31%)存活超过110日龄(p&lt；0.0002)。联合治疗的mo-br小鼠体重高于未治疗的mo-br小鼠(9日龄时分别为5.2克和4.2克，p&lt；0.02)，低于野生型对照组(27日龄时为11.9克和15.1克，p&lt；0.01)。接受联合治疗的幸存者看起来健康、活跃和生育能力强。这种显著的协同效应背后的机制有助于阐明铜在脑内的正常转运过程，以及ATP7A在神经元和神经胶质细胞中的作用。此外，这一进展可能对具有严重ATP7A突变的门克斯病患者以及与ATP7A相关的运动神经元疾病患者具有未来的临床意义。 合成氨基酸L-苏氨酸-3，4-二羟基苯丝氨酸(L-DOPS)能有效逆转常染色体隐性遗传性多巴胺-β-羟基酶缺乏症患者的神经源性直立性低血压，纠正神经化学异常。L-DOPS被DOPA脱羧酶代谢产生去甲肾上腺素，从而绕过了DBH酶的缺陷。枕角综合征(OHS)的个体存在部分DBH缺乏，这是铜依赖的，表现出明显的神经化学异常，并经常出现自主神经功能障碍的症状，如晕厥、头晕、直立性低血压、窦房传导异常、夜间心动过缓和肠道或膀胱功能障碍。就像先天性缺乏胸腺激素的患者一样，这些自主神经系统功能的问题似乎潜在地对恢复正常的神经化学水平做出了反应。我们假设，L-DOPS治疗OHS患者自主神经功能障碍将纠正或改善血液神经化学水平，并产生同步的症状改善。最近IRB批准的一项初步研究将在6名有自主神经症状的患者中验证这一假设，方法是在接受研究药物的8周期间，提供L-DOPS治疗(5 mg/kg/d，po，qd)，并评估神经化学反应(医院内血浆儿茶酚水平)和对症状的长期影响(受试者和/或父母每周完成的医院外自主神经症状问卷)。

Our translational research focuses on the diagnosis, treatment, and understanding of copper metabolism disorders, a recently expanded collection of human diseases that impact varied components of the central and peripheral nervous systems. Acquired as well as inherited forms of abnormal copper homeostasis are implicated in neurologic dysfunction. Menkes disease (MD), a prototypical genetic syndrome of defective copper transport, is characterized by low brain copper, infantile neurodegeneration, and premature death. MD is caused by mutations in an X-linked copper transporter gene, ATP7A. The occipital horn syndrome (OHS) is a milder allelic variant associated with leaky ATP7A splice junction mutations, in which autonomic dysfunction predominates. Recently, we identified several families with motor neuron disease resembling Charcot-Marie-Tooth disease and amyotrophic lateral sclerosis, that are caused by several novel missense mutations in the carboxyl half of ATP7A. These are mild loss-of- function defects that appear to affect intracellular trafficking of ATP7A. Thus, the phenotypic spectrum of ATP7A mutations has expanded; discovery of these new allelic variants indicates a previously unappreciated role for the ATP7A in motor neuron maintenance and function. Current treatment for MD is limited to subcutaneous copper injections and is effective in patients with mutant alleles that do not completely abrogate ATP7A function, and who are identified near birth (N Engl J Med 2008;358:605-614). For patients with complete loss-of-function mutations, however, copper delivered peripherally does not cross the blood-brain barrier efficiently, and alternative treatment approaches are needed. In our recent exploration of treatment alternatives, we rescued a mouse model of severe Menkes disease using combination brain-directed therapies: recombinant adeno-associated virus serotype 5 (AAV5) vector expressing a reduced size human ATP7A, plus copper. Neither treatment alone was effective, but combination therapy dramatically shifted the Kaplan-Meier survival curve, with 5 of 16 (31%) combination-treated mutants surviving beyond 110 days of age (p<0.0002). Combination-treated mo-br mice weighed more than untreated mo-br mice (5.2 g vs. 4.2 g at 9 days of age, p<0.02) and less than wild type controls (11.9 g vs. 15.1 grams at 27 days of age, p<0.01). The combination-treated survivors appear healthy, active, and fertile. The mechanisms underlying this pronounced synergistic effect help to illuminate the normal processes of copper transport in brain, and the role of ATP7A in neuronal and neuroglial cells. In addition, this advance may hold future clinical implications for Menkes disease patients with severe ATP7A mutations, as well as for patients with ATP7A-related motor neuron disease. The synthetic amino acid L-threo-3,4-dihydroxyphenylserine (L-DOPS) is highly effective in reversing neurogenic orthostatic hypotension and correcting neurochemical abnormalities in patients with autosomal recessive congenital absence of dopamine-beta-hydroxylase (DBH). L-DOPS is metabolized by the enzyme DOPA decarboxylase to produce norepinephrine, thus bypassing the DBH enzymatic defect. Individuals occipital horn syndrome (OHS), have partial deficiency of DBH, which is copper-dependent, and show distinctive neurochemical abnormalities and often symptoms of dysautonomia, such as syncope, dizziness, orthostatic hypotension, abnormal sinoatrial conduction, nocturnal bradycardia, and bowel or bladder dysfunction. As in patients with congenital absence of DBH, these problems in autonomic nervous system function seem potentially responsive to restoration of normal neurochemical levels. We hypothesize that L-DOPS treatment in OHS patients with dysautonomia will correct or improve blood neurochemical levels, and produce concurrent symptomatic improvement. A recently IRB-approved pilot study will test this hypothesis in six patients with dysautonomic symptoms, by providing L-DOPS treatment (5mg/kg/d po qd) and assessing the neurochemical response (in-hospital plasma catechol levels) and the longer-term effect on symptoms (out-of-hospital autonomic symptom questionnaire completed weekly by subject and/or parent), during an eight-week period while receiving the study drug.