Characterization of Cerebellum-Specific Ribosomal DNA Epigenetic Modifications in Alzheimer's Disease: Should the Cerebellum Serve as a Control Tissue After All?
阿尔茨海默病小脑特异性核糖体 DNA 表观遗传修饰的表征: 小脑到底应该作为对照组织吗？
- 作者列表："Faria TC","Maldonado HL","Santos LC","DeLabio R","Payao SLM","Turecki G","Mechawar N","Santana DA","Gigek CO","Lemos B","Smith MAC","Chen ES
:Alzheimer's disease (AD) is a neurodegenerative disease, known as the most common form of dementia. In AD onset, abnormal rRNA expression has been reported to be linked in pathogenesis. Although region-specific expression patterns have previously been reported in AD, it is not until recently that the cerebellum has come under the spotlight. Specifically, it is unclear whether DNA methylation is the mechanism involved in rRNA expression regulation in AD. Hence, we sought to explore the rDNA methylation pattern of two different brain regions - auditory cortex and cerebellum - from AD and age-/sex-matched controls. Our results showed differential hypermethylation at an upstream CpG region to the rDNA promoter when comparing cerebellum controls to auditory cortex controls. This suggests a possible regulatory region from rDNA expression regulation. Moreover, when comparing between AD and control cerebellum samples, we observed hypermethylation of the rDNA promoter region as well as an increase in rDNA content. In addition, we also observed increased rRNA levels in AD compared to control cerebellum. Although still considered a pathology-free brain region, there are growing findings that continue to suggest otherwise. Indeed, cerebellum from AD has been recently described as affected by the disease, presenting a unique pattern of molecular alterations. Given that we observed that increased rDNA promoter methylation did not silence rDNA gene expression, we suggest that rDNA promoter hypermethylation is playing a protective role in rDNA genomic stability and, therefore, increasing rRNA levels in AD cerebellum.
: 阿尔茨海默病 (AD) 是一种神经退行性疾病，被称为痴呆的最常见形式。在 AD 发病中，异常 rRNA 表达已被报道与发病机制有关。虽然以前在 AD 中报道过区域特异性表达模式，但直到最近小脑才受到关注。具体而言，目前还不清楚 DNA 甲基化是否是参与 AD 中 rRNA 表达调控的机制。因此，我们试图探索 AD 和年龄/性别匹配对照中两个不同脑区-听觉皮层和小脑的 rDNA 甲基化模式。我们的结果显示，当比较小脑控制和听觉皮层控制时，rDNA 启动子上游 CpG 区域存在差异高甲基化。这提示一个可能的调控区域来自 rDNA 表达调控。此外，当在 AD 和对照小脑样本之间进行比较时，我们观察到 rDNA 启动子区域的高甲基化以及 rDNA 含量的增加。此外，我们还观察到与对照小脑相比，AD 中的 rRNA 水平增加。尽管仍然被认为是无病理的大脑区域，但越来越多的发现继续提示其他情况。事实上，来自 AD 的小脑最近被描述为受该疾病的影响，呈现了独特的分子改变模式。鉴于我们观察到 rDNA 启动子甲基化增加并不能沉默 rDNA 基因表达，我们认为 rDNA 启动子高甲基化在 rDNA 基因组稳定性中发挥保护作用，因此,增加 AD 小脑的 rRNA 水平。
METHODS::Identifying disease-causing pathways and drugs that target them in Parkinson's disease (PD) has remained challenging. We uncovered a PD-relevant pathway in which the stress-regulated heterodimeric transcription complex CHOP/ATF4 induces the neuron prodeath protein Trib3 that in turn depletes the neuronal survival protein Parkin. Here we sought to determine whether the drug adaptaquin, which inhibits ATF4-dependent transcription, could suppress Trib3 induction and neuronal death in cellular and animal models of PD. Neuronal PC12 cells and ventral midbrain dopaminergic neurons were assessed in vitro for survival, transcription factor levels and Trib3 or Parkin expression after exposure to 6-hydroxydopamine or 1-methyl-4-phenylpyridinium with or without adaptaquin co-treatment. 6-hydroxydopamine injection into the medial forebrain bundle was used to examine the effects of systemic adaptaquin on signaling, substantia nigra dopaminergic neuron survival and striatal projections as well as motor behavior. In both culture and animal models, adaptaquin suppressed elevation of ATF4 and/or CHOP and induction of Trib3 in response to 1-methyl-4-phenylpyridinium and/or 6-hydroxydopamine. In culture, adaptaquin preserved Parkin levels, provided neuroprotection and preserved morphology. In the mouse model, adaptaquin treatment enhanced survival of dopaminergic neurons and substantially protected their striatal projections. It also significantly enhanced retention of nigrostriatal function. These findings define a novel pharmacological approach involving the drug adaptaquin, a selective modulator of hypoxic adaptation, for suppressing Parkin loss and neurodegeneration in toxin models of PD. As adaptaquin possesses an oxyquinoline backbone with known safety in humans, these findings provide a firm rationale for advancing it towards clinical evaluation in PD.
METHODS::Huntington's disease (HD) is an inherited progressive neurodegenerative disease characterized by brain atrophy particularly in the striatum that produces motor impairment, and cognitive and psychiatric disturbances. Multiple pathogenic mechanisms have been proposed including dysfunctions in neurotrophic support and calpain-overactivation, among others. Kinase D-interacting substrate of 220 kDa (Kidins220), also known as ankyrin repeat-rich membrane spanning (ARMS), is an essential mediator of neurotrophin signaling. In adult brain, Kidins220 presents two main isoforms that differ in their carboxy-terminal length and critical protein-protein interaction domains. These variants are generated through alternative terminal exon splicing of the conventional exon 32 (Kidins220-C32) and the recently identified exon 33 (Kidins220-C33). The lack of domains encoded by exon 32 involved in key neuronal functions, including those controlling neurotrophin pathways, pointed to Kidins220-C33 as a form detrimental for neurons. However, the functional role of Kidins220-C33 in neurodegeneration or other pathologies, including HD, has not been explored. In the present work, we discover an unexpected selective downregulation of Kidins220-C33, in the striatum of HD patients, as well as in the R6/1 HD mouse model starting at early symptomatic stages. These changes are C33-specific as Kidins220-C32 variant remains unchanged. We also find the early decrease in Kidins220-C33 levels takes place in neurons, suggesting an unanticipated neuroprotective role for this isoform. Finally, using ex vivo assays and primary neurons, we demonstrate that Kidins220-C33 is downregulated by mechanisms that depend on the activation of the protease calpain. Altogether, these results strongly suggest that calpain-mediated Kidins220-C33 proteolysis modulates onset and/or progression of HD.
METHODS:BACKGROUND:Neuroinflammation has been recognized as an important factor in the pathogenesis of Alzheimer's disease (AD). One of the most recognized pathways in mediating neuroinflammation is the prostaglandin E2-EP1 receptor pathway. OBJECTIVE:Here, we examined the efficacy of the selective EP1 antagonist ONO-8713 in limiting amyloid-β (Aβ), lesion volumes, and behavioral indexes in AD mouse models after ischemic stroke. METHODS:Transgenic APP/PS1, 3xTgAD, and wildtype (WT) mice were subjected to permanent distal middle cerebral artery occlusion (pdMCAO) and sham surgeries. Functional outcomes, memory, anatomical outcomes, and Aβ concentrations were assessed 14 days after surgery. RESULTS:pdMCAO resulted in significant deterioration in functional and anatomical outcomes in the transgenic mice compared with the WT mice. No relevant differences were observed in the behavioral tests when comparing the ONO-8713 and vehicle-treated groups. Significantly lower cavitation (p = 0.0373) and percent tissue loss (p = 0.0247) were observed in APP/PS1 + ONO-8713 mice compared with the WT + ONO-8713 mice. However, the percent tissue injury was significantly higher in APP/PS1 + ONO-8713 mice compared with WT + ONO-8713 group (p = 0.0373). Percent tissue loss was also significantly lower in the 3xTgAD + ONO-8713 mice than in the WT + ONO-8713 mice (p = 0.0185). ONO-8713 treatment also attenuated cortical microgliosis in APP/PS1 mice as compared with the vehicle (p = 0.0079); however, no differences were observed in astrogliosis across the groups. Finally, APP/PS1 mice presented characteristic Aβ load in the cortex while 3xTgAD mice exhibited very low Aβ levels. CONCLUSION:In conclusion, under the experimental conditions, EP1 receptor antagonist ONO-8713 showed modest benefits on anatomical outcomes after stroke, mainly in APP/PS1 mice.