Imaging epigenetic dysregulation in the Lewy body dementias with [11C]Martinostat

越来越多的证据表明，表观遗传变化--对基因组的功能性修饰， 改变DNA序列，并提供了一个强大的机制，环境暴露可以影响 基因表达-可能导致路易体痴呆（DLB）和帕金森病（PD）。组蛋白 脱乙酰酶（HDAC）是表观遗传酶家族，其通过化学作用调节基因表达。 改变染色质，染色体结构中的蛋白质和DNA网络，以响应生活经验 和环境保护在DLB和PD尸检中，组蛋白乙酰化明显失调。但 目前尚不清楚组蛋白乙酰化相关的表观遗传学变化是否会随着疾病的进展而积累。 疾病，包括痴呆，例如反映路易体病理学的严重性和地形，也 HDAC的变化是否与运动，认知和行为障碍的积累有关， 疾病还不清楚DLB中HDAC表达的变化是否与DLB中的HDAC表达的变化不同。 帕金森病痴呆症（PDD），在认知和运动障碍的时间上不同。近期 [11 C]Martinostat是第一种标记活体人类HDAC的放射性示踪剂， HDAC在人脑中的水平和分布的死前评估。[11 C]Martinostat显示特异性 HDAC以低纳摩尔亲和力结合，并且正在几个患者群体中积极研究。整体 因此，该建议的目标是：1）评价脑HDAC水平和[11 C]Martinostat的区域分布， 与阿尔茨海默病和年龄匹配的正常人相比， 对照（NC）受试者，和2）随着时间的推移，局部[11 C]Martinostat结合的蓄积与路易体相关 疾病临床特征及其进展以及淀粉样蛋白负荷。DLB、PDD受试者，认知 正常PD、阿尔茨海默病和NC将接受标准化的神经系统检查、神经心理学检查和神经功能检查。 测试，结合[11 C]Martinostat PET-MRI和淀粉样蛋白成像与[11 C]PiB PET，并将在12个月时返回 用于重复[11 C]Martinostat PET-MRI和临床评价。基于初步[11 C]Martinostat PET成像 数据，我们将测试以下假设：（1）HDAC表达的顺序将增加从AD 从NC到认知正常的PD到PDD到DLB;（2）用PET检测局部HDAC表达的变化 将与已知的病理变化的地形相关;（3）皮质和纹状体淀粉样蛋白沉积将 不会对这些结果产生定性影响，但与组内区域HDAC降低相关 （4）HDAC在中脑和壳核的表达与运动障碍的严重程度有关; 扣带回和尾状核的表达与认知功能障碍的严重程度有关; （5）局部HDAC表达随时间的变化将与视觉幻觉有关。 运动、认知和神经精神障碍的进展。总之，这些努力将揭示 在生命过程中基因表达的表观遗传控制失调对PD、PDD和DLB的贡献。

Accumulating evidence suggests that epigenetic changes - functional modifications to the genome that do not change the DNA sequence and that provide a powerful mechanism by which environmental exposure can impact gene expression – may contribute to dementia with Lewy bodies (DLB) and Parkinson disease (PD). Histone deacetylases (HDACs) are a family of epigenetic enzymes that regulate gene expression by chemically modifying chromatin, the network of proteins and DNA in chromosomal structure, in response to life experience and the environment. In DLB and PD at autopsy, histone acetylation is markedly dysregulated. However, it remains unclear whether histone acetylation-associated epigenetic changes accumulate with progression of disease including to dementia, for example reflecting the severity and topography of Lewy body pathology, nor whether HDAC changes relate to the accumulation of motor, cognitive, and behavioral impairments in these diseases. It is also unknown whether HDAC expression changes in life in DLB are distinct from those of Parkinson disease dementia (PDD), which differ in the timing of cognitive and motor impairments. The recent development of [11C]Martinostat, the first radiotracer that labels HDACs in living humans, has enabled the antemortem assessment of HDAC levels and distribution in the human brain. [11C]Martinostat shows specific HDAC binding with low nanomolar affinity and is actively under study in several patient populations. The overall goals of this proposal are thus 1) to evaluate brain HDAC levels and regional distribution with [11C]Martinostat in well-characterized PD, PDD, and DLB subjects, contrasted with Alzheimer’s disease and age-matched normal control (NC) subjects, and 2) to relate accumulation in regional [11C]Martinostat binding over time to Lewy body disease clinical features and their progression as well as to amyloid burden. Subjects with DLB, PDD, cognitively normal PD, Alzheimer’s, and NC will undergo standardized neurological examination, neuropsychological testing, combined [11C]Martinostat PET-MRI, and amyloid imaging with [11C]PiB PET, and will return at 12 months for repeat [11C]Martinostat PET-MRI and clinical evaluation. Building on preliminary [11C]Martinostat PET imaging data, we will test the following hypotheses: (1) The order of global brain HDAC expression will increase from AD to NC to cognitively normal PD to PDD to DLB; (2) Changes in regional HDAC expression detected with PET will correlate with the known topography of pathologic changes; (3) Cortical and striatal amyloid deposition will not qualitatively impact these results but will be associated with within-group reductions in regional HDAC expression; (4) HDAC expression in midbrain and putamen will relate to the severity of motor impairment; anterior cingulate and caudate expression will relate to the severity of cognitive impairment; occipital cortex expression will be associated with visual hallucinations; (5) Changes in regional HDAC expression over time will relate to progression of motor, cognitive, and neuropsychiatric impairments. Together, these efforts will shed light on the contribution of dysregulated epigenetic control of gene expression during life to PD, PDD, and DLB.